JPH02159476A - Continuously variable transmission speed change control device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a device for controlling the gear ratio of a continuously variable transmission used for vehicles and the like.

(Prior Art) As a speed change control method for continuously variable transmissions used in vehicles, etc., the speed change control method is based on driver input such as engine throttle opening, etc.
A method is known in which a target engine speed is set in accordance with an index indicating the intention to decelerate, and the gear ratio is controlled so that the actual engine speed matches the target engine speed (for example, Publication No. 82-237164).

On the other hand, in a vehicle equipped with such a continuously variable transmission,
A manual lever operated by the driver is provided,
This lever operation often allows setting of a plurality of travel ranges (eg, D range, L range, etc.). In this case, in the high-speed driving range (D range),
The gear ratio is changed from the maximum value (LOW) to the minimum value (TOP), but the lower speed range (L range)
In this system, the gears are changed between the maximum gear ratio and a predetermined gear ratio (this gear ratio is larger than the minimum gear ratio) to satisfy the driver's demand for driving force.

(Problem to be Solved by the Invention) However, when such speed change control is performed, for example, when the gear ratio is changed to the L range while driving at high speed in the D range, the gear ratio changes from the minimum gear ratio to the above-mentioned predetermined gear ratio. Since the engine speed is increased by that amount, there is a problem that the engine speed is increased by that amount, which may lead to overspeeding.
When the vehicle speed increases while driving downhill in the L range, the gear ratio does not become smaller than the predetermined gear ratio in the L range, so there is a problem that the engine rotation may enter an overspeed range.

Therefore, it is an object of the present invention to provide a speed change control device that can perform speed change control corresponding to a plurality of driving ranges and can suppress the occurrence of engine overspeed as described above. shall be.

1. Configuration of the Invention (Means for Solving the Problems) As a means for achieving the above object, the transmission control device of the present invention includes range selection means for setting at least two types of travel ranges according to the driver's operation. and a top side gear change prohibiting means for prohibiting the setting of a gear ratio smaller than a predetermined gear ratio set between the maximum gear ratio and the minimum gear ratio in the low speed side running range; The engine overspeed prevention means sometimes stops the operation of the top side gear change prohibition means and allows the setting of a gear ratio smaller than the predetermined gear ratio. A target rotational speed is set, and the gear ratio is controlled so that the input rotational speed matches the target rotational speed.

(Function) When the above-mentioned speed change control device is used, when the high-speed running range (for example, D range) is selected by the range selection means,
The speed change ratio is controlled within the entire range from the minimum speed change ratio to the maximum speed change ratio, but when the low speed range (for example, L range) is selected, the top speed change prohibition means prevents the minimum speed change from occurring. The gear ratio is controlled within a range from the gear ratio to a predetermined range, and is smaller than the predetermined gear ratio (T.

P side) The gear ratio is not set. Therefore, driving force is ensured in the low speed range, and the driver's demand for driving force is satisfied. However, even if the low-speed driving range is selected, if the vehicle speed becomes high and the engine rotation exceeds a predetermined number of revolutions, the engine overspeed prevention means is activated, allowing the setting of a gear ratio smaller than the above-mentioned predetermined gear ratio. This prevents the engine speed from becoming too high.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 is a hydraulic circuit diagram of a continuously variable transmission equipped with a speed change control device according to the present invention. It includes a variable displacement swash plate axial plunger type hydraulic pump P and a variable displacement swash plate axial plunger type hydraulic motor M that drives wheels (not shown) via a forward/reverse switching device 20. The hydraulic pump P and the hydraulic motor M are connected to a first circuit oil passage La that communicates the discharge port of the pump P and the suction port of the motor M, and the suction port of the pump P and the motor M.
The two oil passages constitute a hydraulic closed circuit and are connected to the second circuit oil passage Lb which communicates the discharge ports of the two oil passages. These 2
Of the main oil passages La and Lb, the first circuit oil passage La is used when the pump P is driven by the engine E and the motor M is rotationally driven by the oil pressure from the pump P to drive the wheels, that is, the engine E When the wheels are driven via the continuously variable transmission T, the pressure becomes high (at this time, the second circuit oil path Lb is at low pressure), while the second circuit oil path Lb becomes high pressure when the vehicle decelerates, etc. The pressure becomes high when the driving force is received from the wheels and the engine brake is applied (at this time, the pressure in the first circuit oil passage La is low).

A direct coupling clutch valve DC that can connect and disconnect the oil passage La is disposed within the first circuit oil passage La.

A discharge port of a charge pump (replenishment pump) 10 driven by the engine E via a pair of gear sets 9a+9b is
It is connected to the regulator valve 12 via a pump discharge oil passage Lj, and a first control oil passage L+ branches from this discharge oil passage Lj. The regulator valve 12 operates according to the oil pressure in the discharge oil passage Lj, sets the oil pressure in the discharge oil passage Lj and the first control oil passage to a predetermined control line pressure PL, and sets this line pressure Pt. The hydraulic oil contained therein is supplied from the first control oil path to the control valves and the like, which will be described later.

The amount of oil supplied from this first control oil path to the control valves, etc. is small compared to the discharge amount of the charge pump 10, so the remaining oil is supplied to the first control oil path by the operation of the regulator valve 12.
It is sent to charge oil path Lk. In addition, when there is still an excess amount of oil even after sending it to the first charge oil path Lk, it is returned to the sump 17 from the drain oil path Lm. In this way the first
The oil sent to the charge oil path Lk passes through the centrifugal oil filter 4 and is purified, and then passes through the second charge oil path Ln to the third circuit oil path La, which has a pair of check valves 3, 3. By the action of the check valves 3, 3, the oil is supplied to the low pressure side oil path of the first and second circuit oil paths La+Lb.

Note that a first lubricating oil passage Lp that connects to the internal space of the motor cylinder 70 that constitutes the pump case branches from the second charge oil passage Ln, and a portion of the oil supplied to the second charging oil passage Ln is The oil passes through a check valve 6a disposed in the first lubricating oil passage Lp and is supplied into the internal space via this oil passage Lp. The oil supplied to this internal space lubricates the pump parts and is sent to the outside from the second lubricating oil path LQ for lubrication. Note that when the rotation of the motor cylinder 70 is extremely small, that is, when the engine is stopped, the check valve 6b is opened and the hydraulic oil in this internal space is directly discharged into the sump 17.

A governor valve 8 is attached coaxially with the charge pump 10. Hydraulic oil at a predetermined pressure is supplied to this governor valve 8 from a control valve (not shown), and the governor valve 8 converts the pressure of this hydraulic oil into governor oil pressure corresponding to the rotational speed of the engine E. Note that the input and output oil passages connected to the governor valve 8 will be described later.

A fourth circuit oil path La having a shuttle valve 110 is connected to the closed circuit. A fifth circuit oil passage La having a low pressure relief valve 7 and connected to the oil sump 17 is connected to the shuttle valve 110. The shuttle valve 110 operates according to the oil pressure difference between the first and second circuit oil passages La, Lb, and operates between the first and second circuit oil passages La, Lb.
b, the low pressure side oil passage is communicated with the fifth circuit oil passage La. As a result, the relief oil pressure in the oil passage on the low pressure side is regulated by the low pressure relief valve 7.

Between the first and second circuit oil passages L a + L and b,
A first circuit oil passage La that short-circuits both passages is also provided, and a main clutch valve CL consisting of a variable throttle valve that controls the opening degree of this oil passage is provided in this sixth circuit oil passage Lf. has been done.

Further, the seventh circuit oil passage Lg having the engine brake control valve 120 is connected to the first and O second circuit oil passages La.
, Lb.

Furthermore, the first and second branch oil passages 1. al, Lb
l is branched. These two branch oil paths Lal, Lbl
are connected to the high pressure oil path Lh via check valves 5a + 5b, and are connected to the first and second circuit oil paths Lh.
The higher oil pressure PH of a +Lb is this high pressure oil path L
h.

An output shaft 28 is arranged parallel to the rotating shaft 2 of the hydraulic motor M, and a forward/reverse switching device 20 is provided between both shafts 2 and 28. This device 20 includes first and second drive gears 21 and 22 disposed on a rotating shaft 2 with a spacing in the axial direction, and rotatably supported by an output shaft 28 and a first drive gear 2
1, a second driven gear 25 that meshes with the second drive gear 22 via an intermediate gear 24 and is rotatably supported on the output shaft 28, and the first and second driven gears. A clutch hub 26 is fixed to the output shaft 28 between 23.25 and a clutch gear 23a or 25a which is slidable in the axial direction and formed on the side surfaces of the clutch hub 26 and the driven gears 23 and 25, respectively. A sleeve 27 that is selectively connected is provided, and this sleeve 27 is moved left and right by a shift fork 29. The specific structure of this forward/reverse switching device 20 is shown in FIG. In this forward/reverse switching device 20, when the sleeve 27 is slid leftward in the drawing by the shift fork 29 and the clutch gear 23a of the first wave gear 23 and the clutch hub 26 are connected as shown in the drawing, the output is The shaft 28 is rotated in the opposite direction to the rotating shaft 2, and the wheels are rotated in the forward direction as the continuously variable transmission T is driven. On the other hand, when the sleeve 27 is slid to the right by the shift fork 29 and the clutch gear 25a of the second driven gear 25 and the clutch hub 26 are connected, the output shaft 28 is rotated in the same direction as the rotating shaft 2, The wheels are rotated in the reverse direction.

Next, the concrete structure of the continuously variable transmission T will be briefly explained using FIG. 2.

This continuously variable transmission T has first to fourth cases 15a to 15d.
A hydraulic pump P and a hydraulic motor M are arranged intermittently in a space surrounded by. An input shaft 1 of the hydraulic pump P is coupled to a crankshaft Es of the engine E via a flywheel 1a. This flywheel 1
A centrifugal filter 4 is disposed within the inner circumferential recess of a.

Further, a drive gear 9a is connected to the input shaft 1 by a spline, and a driven gear 9b meshes with the drive gear 9a. The driven gear 9b is coaxially connected to the drive shaft 11 of the charge pump 10, and the rotation of the engine E is transmitted to the drive shaft 11 of the charge pump 10 via the pair of gears 9a and 9b, and the charge pump 10 is driven. 1tl
J-surureru. This drive shaft 11 passes through the charge pump 10 and protrudes to the side opposite to the gear 9b, and is also connected to the governor valve 8. Therefore, the rotation of the engine E is also transmitted to the governor valve 8, and the governor oil pressure P corresponding to the rotation of the engine E is generated by the governor valve 8. is made.

The hydraulic pump P includes a pump cylinder 60 spline-coupled to the input shaft 1, and a plurality of pump plungers 62 slidably engaged with a plurality of cylinder holes 61 formed in the pump cylinder 60 at equal intervals on the circumference. It is rotationally driven by the power of the engine E transmitted through the input shaft 1.

The hydraulic motor M includes a motor cylinder 70 provided surrounding the pump cylinder 60, and a plurality of motor plungers 72 that slide into a plurality of cylinder holes 71 formed in the motor cylinder 70 at equal intervals on the circumference. It is designed to be able to rotate relative to the pump cylinder 60 coaxially.

The motor cylinder 70 is composed of first to fourth parts 70a to 70d that are aligned in the axial direction and are integrally coupled.

The first portion 70a has a bearing 7 at its left end outer periphery.
The pump swash plate ring 63 is rotatably supported by the case 15b via the pump 9a, and the right inner surface is inclined with respect to the input shaft 1 to form a pump swash plate member. is provided. second part 70
The plurality of cylinder holes 71 are formed in b, and the third portion 70c has a distribution plate 80 in which oil passages to each cylinder hole 81.71 are formed. A gear member having the first and second drive gears 21 and 22 is press-fitted into the fourth portion 70d, and is connected to the case 1 through a bearing 79b.
It is rotatably supported by 5c.

An annular pump shoe 64 is rotatably and slidably attached on the pump swash plate ring 63, and the pump shoe 64 and the pump plunger 62 are connected to each other via a connecting rod 65 so as to be able to swing freely to some extent. pump shoe 6
4 and the pump cylinder 6o are bevel gears 68 that mesh with each other.
a and 68b are formed. Therefore, when the pump cylinder 60 is rotationally driven from the input shaft 1, the pump shoe 64
The pump plunger 62 is reciprocated in accordance with the inclination of the pump swash plate ring 63 to suck oil from the suction port and discharge oil to the discharge port.

Also, a swash plate member 73 facing each motor plunger 72
However, the second case 15
It is swingably supported by b. A motor swash plate ring 73b is disposed on the surface of the swash plate member facing the motor plunger 72, and a motor shoe 74 is mounted on the motor swash plate ring 73b by a sliding fluid. The motor shoe 74 is swingably connected to the end of each motor plunger 72. This swash plate member 73 is connected to the piston rod 32 of the first shift servo unit 30 via a link member 39 at a position away from the trunnion shaft 73a.
When the piston rod 32 is moved in the axial direction,
The swash plate member 73 is configured to swing around a trunnion shaft 73a.

The fourth portion 70d of the motor cylinder 70 is formed hollow, and a fixed shaft 91 fixed to the pressure distribution board 18 is inserted into the center thereof. A distribution ring 92 is fluid-tightly fitted to the left end of the fixed shaft 91, and the left end surface of the distribution ring 92 in the axial direction is eccentric so that it can come into sliding contact with the distribution plate 80.

This distribution ring 92 divides the hollow portion formed within the fourth portion 70d into an inner oil chamber and an outer oil chamber, with the inner oil chamber forming the first circuit oil passage La and the outer oil chamber forming the first circuit oil passage La. A second circuit oil path Lb is configured. Note that the pressure distribution panel 18 has a shuttle valve 1101, a low pressure relief valve 7, etc.
Attached to the right side of the third case 15C,
It is covered by a fourth case 15d.

A pump discharge port and a pump suction port are bored in the distribution board 80, and the cylinder hole 61 of the pump plunger 62 in the discharge stroke and the inner oil chamber are connected through the discharge boat and the discharge passage connected thereto. The second circuit oil passage Lb, which is made up of the cylinder hole 61 of the pump plunger 62 in the suction stroke and the outer oil chamber, is communicated with the first circuit oil passage La, and via the pump suction boat and the suction passage connected thereto. communicated. Furthermore, a communication path communicating with the cylinder hole (cylinder chamber) 71 of each motor plunger 72 is formed in the distribution board 80, and the opening of this communication path is
Due to the action of the distribution ring 92, it is communicated with the first circuit oil passage La or the second circuit oil passage Lb according to the rotation of the motor cylinder 70. Therefore, the cylinder hole 71 of the motor plunger 72 in the expansion stroke and the first circuit oil passage La are different from the cylinder hole 71 of the motor plunger 72 in the contraction stroke and the second circuit oil passage La.
The circuit oil passages Lb are communicated with each other via communication passages.

In this way, a hydraulic closed circuit is formed between the hydraulic pump P and the hydraulic motor M via the distribution panel 80 and the distribution ring 92. Therefore, when the pump cylinder 60 is driven from the input shaft 1, the high-pressure hydraulic oil generated by the discharge stroke of the pump plunger 62 is transferred from the pump discharge port to the pump discharge passage, the first circuit oil passage La (inner oil chamber), and the like. It flows into the cylinder hole 71 of the motor plunger 72 which is in the expansion stroke through the first communication path which is in communication with the
A thrust is applied to the motor plunger 72. On the other hand, the hydraulic oil discharged by the motor plunger 72 in the contraction stroke is in the suction stroke via the second communication path communicating with the second circuit oil path Lb (outer oil chamber), the pump suction path, and the pump suction boat. It flows into the cylinder hole 61 of the pump plunger 62.

Due to this circulation of hydraulic oil, the reaction torque that the pump plunger 62 in the discharge stroke applies to the motor cylinder 70 via the pump swash plate ring 63, and the reaction torque that the motor plunger 72 in the expansion stroke receives from the motor swash plate member 73. The motor cylinder 70 is rotationally driven by the sum of .

The gear ratio of the motor cylinder 70 to the pump cylinder 60 is given by the following equation.

Rotation speed of motor cylinder 70 Capacity of hydraulic motor MAs can be seen from the above equation, if the swash plate member 73 is oscillated by the gear shifting servo unit 30 and the capacity of the hydraulic motor M is changed from 0 to a certain value, the gear ratio can be changed. can vary from 1 (minimum value) to some desired value (maximum value).

On the other hand, as described above, a gear member having first and second drive gears is press-fitted and fixed into the fourth portion 70d of the motor cylinder 70. For this reason, the motor cylinder 70
The rotational driving force is transmitted to the output shaft 2 via the forward/reverse switching device 20.
8.

This output shaft 28 is connected to a differential device 100 via a final gear set 28a, 28b.
The rotational driving force of the output shaft 28 is provided by the differential device 10.
0. And the differential device 100
The rotational driving force divided between the left and right drive shafts 105 and 108 is transmitted to left and right wheels (not shown) to drive the vehicle.

A short-circuit path between the first circuit oil passage La and the second circuit oil passage Lb is formed in the fixed shaft 91 inserted into the hollow portion of the fourth portion 70d, and this short-circuit path can be changed from fully closed to fully opened. A main clutch valve CL1 that can control up to 100 degrees and a direct clutch valve DC that can control the first circuit oil passage La on and off are provided.

First, the main clutch valve CL will be explained. A first circuit oil passage La and a second circuit oil passage Lb are provided on the peripheral wall of the fixed shaft 91.
A cylindrical main clutch valve body 95 is inserted into the hollow portion of the fixed shaft 91. This valve body 95 is rotatable relative to the fixed shaft 91, and has a short-circuit hole that can be aligned with the short-circuit boat. By rotating an arm 95a formed at the right end of the valve body 95, the valve body 95 can be rotated to adjust the alignment (overlap) fi between the short circuit boat and the short circuit hole. The size of this matching part becomes the opening degree of the short-circuit passage between the first circuit oil passage La and the second circuit oil passage Lb, and therefore, by controlling the rotation of the valve body 95, the opening degree of the short-circuit passage is changed from fully open to fully open. Can be controlled when fully closed. If the opening degree of the short circuit passage is fully open, the hydraulic oil discharged from the pump discharge boat to the first circuit oil passage La flows directly from the short circuit boat and the short circuit hole into the second circuit oil passage Lb, and also flows into the pump suction boat. Since the fluid flows in, the hydraulic motor M becomes inactive and the clutch becomes OFF. Naturally,
Conversely, if the opening degree of the short-circuit passage is fully open, a clutch ON state in which the hydraulic motor M operates is realized.

A direct coupling clutch valve DC is disposed within the hollow portion of this main clutch valve body 95. This direct-coupled Clara valve DC includes a piston shaft 85 that is fitted within the valve body 95 so as to be movable in the axial direction, a shoe 86 that is attached to the tip of the piston shaft 85, and a shoe 86 that is inserted into the piston shaft 85. The pilot spool 84 is composed of a pilot spool 84.
By moving in the axial direction, the piston shaft 85 can be moved in the axial direction to follow this movement. Therefore, the pilot spool 84 is moved to the left, the piston shaft 85 is moved to the left, and the shoe 86 at the tip of the pilot spool 84 is moved to the left to block the discharge path of the pump that opens to the end face of the distribution board 80, thereby blocking the first circuit oil path La. It is now possible to do so. In this state where the pump discharge passage is closed, the pump plunger 62 is hydraulically locked, and the hydraulic pump P and the hydraulic motor M are directly connected.

Next, the control device for the continuously variable transmission T having the above configuration will be explained using the circuit diagrams shown in FIGS. 3 and 4.

The control device includes a clutch servo unit 130 that controls the main clutch CL, a forward/reverse servo unit 140 that controls the operation of the forward/reverse switching device 20, and a swash plate member 73 that swings to control the gear ratio. There are first and second shift servo units 30, 50, which are operated appropriately by the illustrated hydraulic valves to perform various controls.

First, the configuration and operation of each device will be explained.

The clutch servo unit 130 has a fixed cylinder 131
The piston member 132 is fitted into the cylinder 131 so as to be slidable in the axial direction, and a spring 133 biases the piston member 132 to the right in the figure. The cylinder 13 is divided into two parts by the piston of the piston member 132.
The left and right cylinder chambers 134 and 135 formed in 1 include
Two sixths connected to the clutch control valve 220
and seventh control oil passages La and L7, respectively. Therefore, the piston member 132 is moved left and right in the figure by the hydraulic pressure of the hydraulic oil that is selectively supplied to and discharged from the left and right cylinder chambers 134 and 135 by the clutch control valve 220.

The left end of the piston member 132 is connected to a cam member 97 via a link 96a. The cam member 97 has its cam surface 97
a is the right spool 2 of the clutch control valve 220
23 end face, and is fixed to the shaft 98a at one end. A link arm 98b is also fixed to the shaft 98a. The tip of this link arm 98b is a link 96
It is connected to an arm 95a integrally formed with the main clutch valve body 95 described above through b. Therefore, when the piston member 132 is moved left and right, the cam member 97 and the link arm 98b are rotated together around the shaft 98a, and the main clutch valve body 95 is accordingly moved to the OFF position shown in the figure. (open position) to ON position (closed position)
It is rotated between. Note that at this time, the cam surface 97a
is adapted to push the right spool 223 to the right in response to the rotation of the cam member 97.

The clutch control valve 220 includes a left spool 221 and a right spool 223 that are movable in the axial direction, and a spring 222 disposed between the spools 221 and 223.
The spring 224 biases the left spool 221 to the right. Furthermore, the space in which this spring 224 is arranged (
In the left side space of the left spool 221, there is a governor valve 8.
The 17th control oil passage L communicates with the 16th control oil passage L1e through the clutch-on valve 230 and communicates with the discharge port of
17 is in communication with the governor pressure P corresponding to the rotation speed of the engine E in this left side space. is supplied. In addition, the space where the spring 222 is arranged (the left and right spools 221
．． 223), the throttle valve 240
Throttle pressure Pro corresponding to the throttle opening is transmitted from
is supplied.

Therefore, the left spool 221 has a governor pressure P.

It is moved to the right or left in response to a rightward pushing force by the spring 224 and a leftward pushing force by the throttle pressure pro and the spring 222. In response to this movement, the line pressure PL sent from the first control oil path to the fifth control oil path L6 is supplied to one of the sixth and seventh control oil paths Le=L7, and the other is activated. Drain the oil to the drain. As a result, the piston member 132 of the clutch servo unit 130 is actuated, and the operation of the main clutch CL is controlled. However, at this time, the right spool 223 is pushed by the cam member 97 in accordance with the movement of the piston member 132, and the pushing force of the spring 222 can be changed, so that the main clutch is opened and closed according to desired characteristics. It looks like this.

In addition, when discharging the hydraulic oil in the left cylinder chamber 134 from the sixth control oil passage L8 in order to operate the clutch CL from OFF to ON, the clutch control valve 22
0 to 8th, 9th and 10th control oil passages La+La+L
1o. This 10th control oil passage Lso is
It is connected to the drain via the first orifice 274 and also via the orifice change valve 270 and the second orifice 272, and these orifices 272 and 274 limit the discharge speed of the hydraulic oil.
The connection speed (speed from OFF to ON) of clutch CL is adjusted.

The connection speed of the clutch CL is required to be faster when the throttle opening of the engine E is small than when it is large. For this reason, the throttle pressure PTH is introduced from the throttle valve 240 to the right end of the orifice change valve 270 via the 25th control oil passage L25, and the throttle opening becomes large, causing the throttle pressure P7
．． (When the pressure exceeds a predetermined value, the orifice change valve 270 is moved to the left by this hydraulic pressure, and this valve 27
0 is closed. In this way, the throttle opening is small and the orifice change valve 27
When 0 is open, the above-mentioned hydraulic oil discharge is 2
However, when the throttle opening is large and the orifice change valve 270 is closed, the discharge is performed only through one of the orifices 274, and the throttle opening is large. , ), the connection speed of the main clutch CL becomes slow.

As described above, the discharge speed of hydraulic oil from the left cylinder chamber 134 of the clutch servo unit 130 is changed in accordance with the throttle opening degree, and the connection speed of the clutch CL is adjusted to a desired value.

However, since this adjustment is performed using fixed orifices 272 and 274, the discharge speed is affected by changes in the viscosity of the hydraulic oil. There is a problem in that the clutch CL is engaged slowly and the connection speed of the clutch CL becomes extremely slow.

In order to solve this problem, in this example, an eleventh control oil passage L11 having a relief valve 280 is branched from the tenth control oil passage L+o. This is done in consideration of the fact that when the discharge of hydraulic oil from the fixed orifices 272 and 274 is slow at low temperatures, the oil pressure in the oil passage upstream from these becomes higher than normal. Therefore, the relief valve 260 is set to open when the oil pressure in the oil passage Lll becomes higher than the oil pressure generated at the normal operating temperature (for example, 80° C.).

Therefore, the orifice is 272°274° when the hydraulic oil temperature is low.
When the flow resistance is large and the oil pressure in the oil passage Lit is high, this relief valve 260 is opened, and even if the amount of oil discharged from the fixed orifices 272, 274 is small, it is compensated for by the discharge from the relief valve 260, To smoothly connect a clutch CL. This allows the clutch CL to be connected without delay even when starting at a low temperature, making it possible to start the vehicle smoothly.

The servo unit 140 for forward and backward movement has a fixed cylinder 141
The piston member 142 is fitted into the cylinder 141 so as to be movable in the axial direction (up and down in the figure), and a spring 143 urges the piston member 142 downward. The space inside the cylinder 141 covered by the cover 146 is
This space is divided into upper and lower cylinder chambers 144 and 145 by the piston of the piston member 142 fitted into this space, and the 31st and 33rd control oil passages L311 and L33 communicate with both cylinder chambers 144 and 145, respectively. ing.

Both passages and L12 are each connected to the manual valve 210 directly or via the clutch-on valve 230 and the 32nd control oil passage L3□. When the manual valve 210 is in the R, L2, L1 position 1 (in the figure, the line pressure Pt from the control oil passage L2 is supplied to the 31st control oil passage L31), and the 33rd control oil When the path L G3 is in communication with the drain and is in the R position, the 33rd control oil path L31
A line pressure Pi is supplied to the drain, and the 31st control oil passage L3K is communicated with the drain. For this reason, the manual valve 210 allows L2. When Lt position is selected, the piston member 142 is moved down as shown in the figure, and the shift fork 2 fixed to the tip of the piston member 142 is moved downward.
9 is located in the forward position.

On the other hand, when the R position is selected, the piston member 142 is moved upward and the shift fork 29 is located in the reverse position. In addition, other positrons, that is, N
And in P-Posisilon, the above-mentioned re-control oil passage L11
and L33 are both connected to the drain,
In this case, the piston member 1 is biased by the spring 143.
42 is held at the lower movement position, and the shift fork 29 is placed at the forward position.

Furthermore, when the line pressure Pt is supplied to the upper cylinder chamber 144 and the piston member 142 is moved downward, this line pressure Pt is introduced into the fifteenth control oil passage L15 via the outer circumferential groove 142a of the piston member 142, When the line pressure PL is supplied to the lower cylinder chamber 145 and the piston member 142 is moved upward, the through hole 1 in the piston member 142
42b, this line pressure Pt is applied to the 15th control oil path L.
Introduced in I5.

Next, the shift servo unit 30.50 shown in FIG. 4 will be explained. Both units) 30.50 is link mechanism 4
Connected via 0.

The first speed change servo unit 30 includes a fixed cylinder 31, a piston rod 32 fitted into the cylinder 31 so as to be movable up and down in the figure, a valve member 33 fixedly held within the rod 32, and this valve. The spool member 34 is inserted into the member 33 so as to be movable up and down in the figure. The internal space of the cylinder 31 is covered at the upper part of the figure by a cover (not shown), and is divided into two parts by the piston portion 32a of the piston rod 32 to form upper and lower cylinder chambers 35 and 36. Further, the lower end of the piston rod 32 projects outward from the cylinder 31, and is connected to a swash plate member 73 of the motor M via a link member 39, as shown in FIG.

A high pressure oil passage Lh is connected to the cylinder 31, and a high pressure introduction hole 31a that communicates this with the lower cylinder chamber 36
is formed, and hydraulic oil having a hydraulic pressure P□ on the high pressure side in the hydraulic closed circuit of the transmission T is introduced into the lower cylinder chamber 36. This hydraulic oil with high pressure PH further
It is guided to the groove 33a of the valve member 33 through the communication hole 32b of the piston rod 32, and the groove 33a is also guided to the spool member insertion hole (not shown) in the valve member 33 through the communication hole 33b.

When the spool member 34 inserted into this insertion hole is moved upward relative to the valve member 33 in the figure, it closes the communication hole 33b of the valve member 33 and opens the upper cylinder chamber 35 inside the piston rod 32. When it is discharged to the drain through the through hole 32c and is relatively moved downward,
The communication hole 33b of the valve member 33 is communicated with the upper cylinder chamber 35. For this reason, the spool member 3
4, the high pressure P acting on the lower cylinder chamber 36 increases.
The piston rod 32 is moved to the spool member 3 by the hydraulic pressure of
It will be moved up following 4. Also, when the spool member 34 is moved downward, high pressure P is applied to the upper and lower cylinder chambers 35 and 38.
, and the piston rod 32 is moved downward following the spool member due to the difference in pressure receiving area in the piston portion 32a (the pressure receiving area on the upper cylinder chamber 35 side is larger). Note that when the spool member 34 is stationary, the piston rod 32 is also held stationary at a position where the forces applied to the piston portion 32a from the upper and lower cylinder chambers 35, 36 are balanced.

That is, when the spool member 34 is moved up and down, the piston rod 32 is moved up and down following this. At this time, since the piston rod 32 is connected to the swash plate member 73 of the motor M, the swash plate angle can be controlled by moving the spool member 34, that is, the gear ratio of the transmission T can be controlled.

The upper end of the spool member 34 is connected to the second link via the first link 41.
It is connected to one end of the link 42. The second link 42 is integrally connected to the shaft 43 and is rotatable about the shaft 43. A third link 44 is also integrally connected to the shaft 43, and the third link 44 is connected to a piston member 52 of a second speed change servo unit 50 via a fourth link 45. Therefore, when the piston member 52 is moved up and down in the drawing, the spool member 34 of the first gear shifting servo unit 30 is moved up and down via the link mechanism 40 constituted by the links 41 to 45.

The second speed change servo unit 50 is constructed by fitting the piston member 52 into a fixed cylinder 51 so as to be movable in the axial direction (in the vertical direction in the figure). The internal space of the fixed cylinder 51 is covered by the plug member 53 and divided into two by the piston portion of the piston member 52 to form upper and lower cylinder chambers 54 and 55. The upper cylinder chamber 54 includes a 44th control oil passage L44 having an orifice 57a and a 45th control oil passage L44 having a check valve 57b.
A 42nd control oil passage L4° communicates with the control oil passage L45, and a 40th control oil passage L4° communicates with the lower cylinder chamber 55. The 42nd control oil path L4□ is the clutch off valve 23
5 and the 41st control oil passage L41, and the 40th control oil passage L40 is directly connected to the shift control valve 2.
It communicates with 50.

Therefore, due to the action of the shift control valve 250, the upper cylinder chamber 54 and the lower cylinder chamber 55 are
Supply of line pressure Pt from control oil path L15, or
The hydraulic oil in the cylinder chamber is drained. The piston member 52 is moved up and down in response to the supply and discharge of the hydraulic oil, and this is transmitted to the first shift servo unit 30 via the link mechanism 40 to perform shift control. Specifically, by moving the piston member 52 of the second shift servo unit 50 upward and moving the piston member 32 of the first shift servo unit 30 downward, the gear ratio is increased (L
OW side), and conversely, the piston member 52
By moving the piston member 32 downward and moving the piston member 32 upward, the gear ratio can be decreased (shifted to the TOP side).

In this case, the line pressure PL is gradually supplied to the upper cylinder chamber 54 by the action of the orifice 57a, but the hydraulic oil is discharged from the upper cylinder chamber 54 by the check valve 5.
7b is opened and done rapidly. Therefore, when moving the piston member 52 upward to increase the gear ratio (LOW
This is done rapidly when shifting to the side), but when the piston member 52 is moved downward to reduce the gear ratio (
When shifting to the TOP side), this is done slowly. However, the piston member 52 has a first
A groove 52a is formed, and the 43rd control oil path 41 communicating with the hole formed in the cylinder 51 is connected to this groove when the gear ratio is large (when the piston member 52 is moving upward by a predetermined amount or more). It communicates with the upper cylinder chamber 54 via. For this reason, the line pressure Pt is supplied via this 43rd control oil passage L4G until the piston member moves downward by a predetermined amount or more and the gear ratio becomes below a certain value, and during this period, a rapid gear change is performed.

Note that the lower end of the piston member 52 is formed with a tapered surface 52d, and the end surface of the spool 151 of the throttle cam mechanism 150 is in contact with this tapered surface 52d.
The throttle cam mechanism 160 is configured to operate in accordance with the gear ratio.

Further, in the upper part of the cylinder 51, through holes 56a and 58b are formed which are connected to the insertion hole of the piston member 52, and the both passage holes 56a and 58b have the 46th and 47th control oil passages L481L4?, respectively. communicate.

A groove 52 is provided in the upper part of the piston member 52 to connect the through holes 56a and 56b to the drain when the piston member 52 is moved upward by a predetermined amount or more.
b, 52c are formed. Therefore, the piston member 52 is moved upward, and the gear ratio becomes smaller (TOP
When the piston member 52 is moved upward, the 47th control oil passage L47 is first communicated with the drain via the groove 52C and the through hole 56b, and when the piston member 52 is further moved upward, the 47th control oil passage L47 is communicated with the drain through the groove 52b and the through hole 58a. The 46th control oil passage Lag is communicated with the drain.

The spool 211 of the manual valve 210 is operated in response to operation of the shift lever at the driver's seat, and the operation of the forward/reverse servo unit 140 is controlled as described above.

Note that when the spool 211 is located at the "2" position (L2 position), the 48th control oil passage L48 having governor pressure is communicated with the 46th control oil passage L4G, and the '1'
“When you are in position (L□ position),
The 48th control oil passage L48 is communicated with the 47th control oil passage L47. Therefore, the spool 211 is 162" or "
1" position, when the gear ratio falls below a predetermined value, the governor pressure in the 48th control oil passage L48 is drained, the governor pressure acting on the shift control valve 250 becomes zero, and the gear ratio becomes lower than this. Small (toward the TOP side)
be prevented from becoming.

To explain this operation, shift control valve 25
0 will be explained. shift control valve 250
is the pressing force of the second cam 171 of the throttle cam mechanism 150 transmitted via the spring 252 and the 49th control oil path L.
It has a spool 251 that receives pressing force from governor pressure P0 from 49. The left and right movement of the spool 251 controls the supply and discharge of the line pressure PL to and from the upper and lower cylinder chambers 54 and 55 of the second shift servo unit 50, thereby controlling the gear ratio.

The pressing force of the second cam 171 changes according to the depression of the accelerator pedal, and is the governor pressure P. changes depending on the engine speed. Therefore, if the pressing force of the governor pressure Pa corresponding to the engine speed is greater than the pressing force of the second cam 171 corresponding to the depression of the accelerator pedal, the spool 251 is moved to the left and the 41st and 42nd control oil Road L4
Supply line pressure PL to □+L4□ to reduce the gear ratio
(TOP side) to lower the engine speed. Conversely, governor pressure P. If the pressing force is smaller, the spool 251 is moved to the right to supply line pressure P1 to the 40th control oil passage L40, increasing the gear ratio (to the LOW side) and increasing the engine speed. In other words, the gear ratio is controlled so that the engine speed corresponding to the pressing force of the second cam 171 is obtained, and as can be seen from this, the driver's acceleration and
The pressing force of the second cam 171, which indicates an index indicating the intention to decelerate (accelerator pedal depression amount, throttle opening, etc.), represents the target engine speed, and the actual engine speed matches the target engine speed set in this way. The gear ratio is controlled so as to.

In this case, the spool 211 of the manual valve 210 is located at the D position and is in the D range (high-speed travel range).
is set, the piston member 52 of the second shift servo unit 50 moves from its highest moving position to its lowest moving position, and the gear ratio changes from the maximum (LOW) to the minimum (TO).
P). However, when the spool 211 is located at the 2nd or 1st position and the L2 or 2 range (low speed running range) is set,
As mentioned above, the 48th control oil passage L48 is connected to the 46th or 47th control oil passage L411 via the groove of the spool 211.
1 Connected to L47. Therefore, the gear ratio is maximum (
When the predetermined gear ratio (RL2 or RLI) is reached, the governor pressure in the 48th control oil passage L4B is drained. For this reason, shift control valve 2
The spool 251 of No. 50 is moved to the right, and the piston member 52 of the second shift servo unit 50 is not moved upward any further.
The gear ratio will never be smaller than this.

Note that when the L2 range is selected by the manual valve 210, the groove 52 on the left side of the piston member 52
The governor pressure is drained through the groove 52c on the right side when the L lunge is selected. Therefore, the predetermined gear ratio RL2 in the %L2 range is smaller than the predetermined gear ratio RLI in the LI range. That is, RL2 has a gear ratio closer to the TOP side than RLI.

This control device is provided with an engine rotation inhibitor valve 265 that serves as engine overspeed prevention means. Is this an engine rotation inhibitor valve? -65 is the governor pressure P when the engine rotation exceeds a predetermined rotation. This is a valve that is activated when the 48th control oil passage L48 and the 49th control oil passage L49 are disconnected from each other when the 48th control oil passage L48 becomes a predetermined value or more. 48th control oil passage L4g and 49th control oil passage L4. When the communication with the 49th control oil passage L49 is cut off, even if the 48th control oil passage L4B is connected to the drain, the 18th control oil passage Lea to the 49th control oil passage L49
governor pressure P to the shift control valve 250 through
. acts. Therefore, in this case, that is, when the engine speed exceeds a predetermined speed, even if the low-speed driving range (L2 range or L lunge) is selected, the gear ratio will be set to the minimum gear ratio (TOP). It can be shifted up to. This prevents the engine speed from becoming too high in the low speed range.

The above operation control will be specifically explained using the graph of FIG. In the case of the D range, for example, when a target engine speed N1 is set according to the depression of the accelerator pedal, the gear ratio is changed from the maximum gear ratio LOW so that the actual engine speed matches the target engine speed N1. The gear ratio is controlled and changes as shown by the line a → 1)-I-C, and after reaching the minimum gear ratio TOP, the speed is increased along the line of the minimum gear ratio (TOP) in response to further depression of the accelerator pedal. (line cl+e).

On the other hand, if the L2 range is selected,
The gear is shifted from the maximum gear ratio (LOW) so that the actual engine speed matches the target rotation speed N1 (line a+b), but the gear ratio is the predetermined gear ratio R for the L2 range.
When L2 is reached, the governor pressure P acting on the shift control valve 250 is drained, so no further gear shifting is performed, and when the accelerator pedal is further depressed, the gear ratio increases along the predetermined gear ratio line (RL2). speeded up (
line f). However, when the engine rotation speed reaches the predetermined rotation speed N2, the engine rotation inhibitor valve 265 is activated and draining of the governor pressure Pa is stopped. Therefore, if the target engine speed at this time is N2, the shift control is performed so that the actual engine speed matches this (
Line g).

Then, the gear ratio is controlled up to the minimum gear ratio (TOP).

Even when the L□ range is selected, the maximum gear ratio (L
OW), gear changes are made to match the actual engine speed to the target engine speed N1 (line a), but if the gear ratio increases and reaches the predetermined gear ratio RLI for the range, no further gear changes are performed. First, when the accelerator pedal is further depressed, the speed is increased along the predetermined speed ratio line (RLl) (line h). Then, when the engine rotation speed reaches a predetermined rotation speed NQ, the engine rotation inhibitor valve 265
is activated, and if the target engine speed at this time is NQ, shift control is performed so that the actual engine speed matches this (line i+g).

Then, the gear ratio is controlled up to the minimum gear ratio (TOP). Note that in the figure, line j indicates the maximum target engine speed in the D range.

If such control is performed, even if the vehicle speed increases while driving in Ll or L2, the engine rotation will be suppressed to the predetermined rotation speed N2 until the gear ratio becomes the minimum, and even if the gear ratio becomes the minimum, D Since the rotation is kept to the same level as when using the range, overspeeding of the engine is prevented. Also, for example,
Conventionally, when the vehicle is shifted to the L2 range or the HI range while driving at the vehicle speed Vt in the D range, the engine speed increases to N5 or N8 corresponding to the predetermined gear ratio RL2 or RLl of each range, resulting in overspeed. However, in this example, the speed change control is performed so that the engine rotation becomes the predetermined rotation N2, thereby preventing the engine from over-speeding.

The other illustrated valves will be briefly described below.

The clutch-on valve 230 is normally connected to its spool 23.
1 has been moved to the left by the pushing force of the spring 232 as shown in the figure. However, the controller 100
When it is detected that the vehicle speed has become equal to or higher than a predetermined vehicle speed, the normally open type first solenoid valve 280 is operated and closed, and the flow of water from the third control oil path L3 into the 51st control oil path L□ is activated. Line pressure PL is generated, and the spool 232 is moved to the right by this hydraulic pressure. As a result, the 17th
Line pressure Pt from the 34th control oil passage L34 is supplied to the control oil passage LI7, and the clutch control valve 220
The left spool 221 of the main clutch CL is moved to the right.
is set to ON state (connected state) regardless of its state. At the same time, line pressure P is also supplied from the 60th control oil passage L6° to the engine brake control valve 120 shown in FIG. Note that at this time, the 33rd cylinder connected to the lower cylinder chamber 144 of the forward/reverse servo unit 140
The control oil passage L33 communicates with the drain, and even if the manual valve 210 is switched to reverse (R) while the vehicle is running in this state, the servo unit 140 is prevented from operating, thereby improving safety. There is.

Clutch off valve 235 is manual valve 210
In cases other than when is N, P body, spool 2
38 is moved to the left as shown in the figure by the line pressure PL from the 15th control oil passage L+ct acting on its right end, and when the manual valve 210 is switched to the N (or P) position, it is moved to the right by the spring 237. Ru. When the spool 236 is moved to the right, the line pressure Pt from the fourth control oil passage L4 is supplied to the 24th control oil passage L24, the clutch control valve 21 is moved to the left, and the main clutch CL is turned off. At the same time, the 42nd control oil passage L4□ is closed, the piston member 52 of the second speed change servo unit 50 is held as it is, and the speed change ratio is held as it is.

The throttle modulator valve 245 reduces the line pressure PL supplied to the 20th control oil passage L2G to create a predetermined modulator pressure PH, and supplies this to the throttle valve 240 via the 21st control oil passage L21.

The throttle valve 240 is actuated in response to the pressure of the first cam 161 of the throttle cam mechanism 150, which is actuated in accordance with the accelerator pedal or throttle valve opening, and the throttle opening (or accelerator A throttle pressure PTH corresponding to the opening degree) is supplied.

The kickdown control valve 258 is activated by the 42nd control oil path L4 when the accelerator pedal is suddenly depressed while driving. Drain the hydraulic oil from the and widen the gear ratio (
This is a valve for switching to the LOW side.

The second solenoid valve 285 is a normally closed type valve, and is opened when the controller 100 detects sudden braking. For this reason, line pressure PL is normally supplied to the right end of the shift control valve 250, but in the event of sudden braking, this is released, the spool 251 of the shift control valve 250 is moved to the right, and the gear ratio is shifted to the LOW side. controlled so that

Next, another embodiment of the present invention will be described based on the circuit diagram of FIG. 6. In this example, in place of the shift control valve 250 shown in FIG. 3, a second throttle valve 350 that generates oil pressure (second throttle pressure Pt, I2) corresponding to the throttle opening (or the amount of depression of the accelerator pedal) is arranged. However, the method of controlling the operation of the second shift servo unit 50 is different. Components that are the same as those in FIG. 3 are given the same numbers.

Here, the 41st control oil passage L41, which communicates with the upper cylinder chamber 54 of the second shift servo unit 50 via the 42nd control oil passage L42 and the clutch off valve 235, is at the governor pressure P. The upper cylinder chamber 54 has a governor pressure P. is supplied. The 40th control oil passage L4o communicating with the lower cylinder chamber 55 is the second
It is connected to the throttle valve 350. The second throttle valve 350 includes a 71st control oil path L711, a kickdown control valve 358, and a 72nd control oil path L711.
? 2, the line pressure PL supplied from the 15th control oil passage LI5 is regulated to the second throttle pressure PTH2 corresponding to the pushing force of the second cam 171, and this is adjusted to the 40th control oil passage L4.
Supply to 0.

Therefore, the second shift servo unit 50 controls the governor pressure P0 acting on the upper cylinder chamber 54 and the lower cylinder chamber 55.
It is operated according to the difference between the second throttle pressure PTH2 and the second throttle pressure PTH2. That is, the governor pressure P corresponding to the second throttle pressure P TFI2. As can be seen from this, the second throttle pressure (PT) 12 corresponds to the target engine speed, and the governor pressure P corresponds to the actual engine speed. The gear ratio is controlled so that the second throttle pressure PTH2 (that is, the target engine speed) coincides with the second throttle pressure PTH2.

The 73rd control oil passage L? has an orifice 355 on the right side of the spool 351 of the second throttle valve 350. A second throttle pressure P'112 acts through G. Further, the 73rd control oil passage L7CI communicates with the 49th and 48th control oil passages L491L48. Therefore, when the low-speed running range (L2 or range) is selected, when the gear ratio reaches the predetermined gear ratio (RL2 or RLl), the spool 35
The second throttle pressure PTH□ acting on the right side of
It is drained from the control oil path L48. As a result, in the case of the low-speed running range, the gear ratio is smaller than the predetermined gear ratio (TOP
side) The gear ratio will no longer be set.

Further, in this example as well, an engine rotation inhibitor valve 265 is provided which operates when the engine rotation speed reaches a predetermined rotation speed or higher to cut off communication between the 49th control oil passage L411 and the 48th control oil passage L48. ing. Therefore, when the engine speed exceeds a predetermined speed in the low speed range, the minimum speed ratio (T
OP) can be controlled.

As described in detail of the invention, according to the invention, the transmission control device
Range selection means for setting at least two types of driving ranges; Top side gear change prohibiting means for prohibiting setting of a gear ratio smaller than a predetermined gear ratio in the low speed side running range; The engine overspeed prevention means stops the operation of the side shift prohibition means and also allows the setting of a gear ratio smaller than the predetermined gear ratio, and sets the target rotation speed based on an index indicating the driver's intention to accelerate or decelerate. Since the speed ratio is controlled so that the input rotation speed matches the target rotation speed, the range selection means selects the high-speed running range (for example, D range).
When the gear ratio is selected, the gear ratio is controlled within the entire range from the minimum gear ratio to the maximum gear ratio, but when the low speed range (for example, L range) is selected, the top gear ratio is controlled. The inhibiting means controls the gear ratio within a range from the minimum gear ratio to a predetermined range, and a gear ratio smaller than the predetermined gear ratio (TOP side) is not set. Therefore, sufficient driving force can be ensured in the low speed range, and the driver's demand for driving force can be met. However, even if the low-speed driving range is selected, if the vehicle speed becomes high and the engine rotation exceeds the predetermined number of revolutions, the engine overspeed prevention means is activated, allowing the setting of a gear ratio smaller than the above-mentioned predetermined gear ratio. This prevents the engine speed from becoming too high.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic circuit diagram of a continuously variable transmission equipped with a speed change control device according to the present invention, FIG. 2 is a sectional view of the continuously variable transmission, and FIGS. 3 and 4 are a diagram of the continuously variable transmission. FIG. 5 is a graph showing the running characteristics of a vehicle equipped with the above continuously variable transmission; FIG. 6 is a control circuit of a continuously variable transmission equipped with a speed change control device according to a different embodiment of the present invention. It is a diagram. 1... Input shaft 8... Governor valve 10
...Charge pump 20...Forward/forward switching device 30
．． 50... Servo unit for speed change 95... Clutch valve body 97... Cam member 110... Shuttle valve 130... Clutch servo unit 140... Servo unit for forward and backward movement 210... Manual valve

Claims (1)

[Scope of Claims] 1) A speed change control device that variably controls the speed ratio of a continuously variable transmission that continuously changes input rotation input to an input shaft and transmits the same to an output shaft, the speed change control device - In a transmission control device that sets a target rotation speed based on an index indicating an intention to decelerate, and controls the gear ratio so that the input rotation driven by a driving power source matches the target rotation speed, the driver a range selection means for setting at least two types of driving ranges according to the operation of the driving range; and in a lower speed driving range of the driving ranges,
a top side gear change prohibiting means for prohibiting setting of a gear ratio smaller than a predetermined gear ratio set between a maximum gear ratio and a minimum gear ratio; A speed change control device for a continuously variable transmission, comprising engine overspeed prevention means for stopping the operation of the means and allowing setting of a speed ratio smaller than the predetermined speed ratio.