JPH06346811A - Fuel injection pump - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a fuel injection pump, and an object of the present invention is to prevent a decrease in the amount of fuel pumped due to a decrease in the bulk modulus of the fuel at a high engine temperature. A spill ring position changing means 26 for changing the position of the spill ring 25 so as to obtain a required fuel pressure feed amount according to each engine operating state, and a housing 15 supporting the spill ring position changing means 26 are provided. The pressure chamber 1 is made of a second material having a larger linear expansion coefficient than that of the first material forming the plunger 14, and the engine temperature becomes high.
When the amount of compressed fuel of No. 7 becomes large, the spill ring position changing means 26 due to the difference in thermal expansion between the first and second materials at this time.
The diameter of the plunger 14 and the support position 28 of the spill ring position changing means 26 to the housing 15 are set so that the increase in the fuel pumping amount caused by the displacement of the spill ring through the valve offsets the increase in the fuel compression amount. To decide.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a fuel injection pump for a diesel engine, for example.

[0002]

2. Description of the Related Art Fuel injection pumps of this type are generally
Having a plunger that reciprocates along the axis while rotating around the axis in the cylinder, fuel is sucked into the pressure chamber from the pump chamber when the volume of the pressure chamber formed by the plunger tip and the cylinder increases. When the volume of the pressure chamber is reduced, the fuel in the pressure chamber is pumped to the fuel injection valve of each cylinder through the fuel supply passage formed inside the plunger and the delivery passage formed in the cylinder wall. This pumping of fuel is carried out only when the spill passage, which connects the fuel supply passage and the outer wall surface of the plunger in the pump chamber, is closed by the spill ring fitted in the outer wall surface of the plunger in the pump chamber, whereby spill By moving the ring in the axial direction, the amount of fuel pumped can be changed.

Since a gap having a predetermined size is provided between the outer wall surface of the plunger and the inner wall surface of the cylinder and the spill ring, a small amount of the fuel inside the fuel is fed at the time of pumping the fuel. A leak occurs. Therefore, the position control of the spill ring that determines the fuel pumping amount is executed in consideration of the occurrence of a predetermined amount of internal leakage. However, since the viscosity of the fuel decreases as the temperature rises, the internal leak amount of the fuel passing through the gap of a predetermined size increases considerably at high engine temperature, and the desired amount of fuel is pumped under each engine operating condition. However, there is a problem that the fuel temperature must be taken into consideration in the position control of the spill ring, which complicates the control.

[0004] In order to solve this problem, actual Kaihei 1-9
3364 describes a distributed fuel injection pump in which the plunger is formed from a material having a coefficient of linear expansion greater than that of the cylinder and spill ring. This is to reduce the gap between the two due to the difference in coefficient of linear expansion at high engine temperature, thereby maintaining the internal leakage of fuel whose viscosity decreases at a predetermined amount and without complicating the position control of the spill ring. It is intended to realize a desired fuel pumping amount according to each engine operating state.

[0005]

When the engine temperature becomes high and the fuel temperature rises, not only does the viscosity decrease, but also
The volume modulus of elasticity becomes small and the amount of compression of the fuel at the time of pressure feeding is increased, which causes a substantial decrease in the amount of fuel pressure feeding. In the above-mentioned conventional technique, it is impossible to prevent the reduction of the fuel pumping amount when the engine temperature is high.

Therefore, an object of the present invention is to provide a fuel injection pump capable of preventing a decrease in the fuel pumping amount due to a decrease in the bulk modulus of the fuel at a high engine temperature, without complicating the position control of the spill ring. Is to provide.

[0007]

A fuel injection pump according to the present invention includes a cylinder, a plunger, and the plunger for pressurizing and pumping fuel in a pressure chamber formed by the cylinder and the plunger into a combustion chamber. A plunger reciprocating means for at least reciprocating motion with respect to the cylinder, a spill ring that closes the spill passage of the plunger and changes the fuel pumping amount according to its position, and a required fuel pumping amount according to each engine operating state. And a spill ring position changing means for changing the position of the spill ring so that
The housing of the fuel injection pump that supports the spill ring position changing means is made of a second material having a larger linear expansion coefficient than the first material that forms the plunger, and when the engine temperature is high, the fuel in the pressure chamber is compressed. When the amount becomes large, the increase in the fuel pumping amount caused by the displacement of the spill ring through the spill ring position changing means due to the difference in thermal expansion between the first and second materials at this time is equal to the compression amount of the fuel. It is characterized in that the diameter of the plunger and the supporting position of the spill ring position changing means on the housing are determined so as to cancel the increase of

[0008]

In the fuel injection pump described above, the housing of the fuel injection pump that supports the spill ring position changing means is formed of the second material having a larger linear expansion coefficient than the first material forming the plunger. The support position of the diameter and spill ring position changing means to the housing is
When the amount of fuel compressed in the pressure chamber becomes large at high engine temperature, the amount of fuel pumped by displacement of the spill ring via the spill ring position changing means due to the difference in thermal expansion between the first and second materials at this time Is determined so as to offset the increase in the amount of fuel compression in the pressure chamber.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a fuel injection pump to which the present invention is applied. Reference numeral 11 is a feed pump (developed by 90 degrees), which is rotationally driven by the drive shaft 12 and supplies fuel to the pump chamber 13 through the fuel filter as shown by an arrow A. Reference numeral 14 denotes a plunger, which is a cylinder 16 formed in the housing 15.
Is inserted in the bore 16a. The plunger 14 is also rotationally driven by the drive shaft 12.

A face cam 21 is attached to the plunger 14, and the cam surface of the face cam 21 and the roller 21 provided in the housing 15 form a face cam 2.
A compression spring 23 provided between the surface on the opposite side of 1 and the inner wall of the housing 15 always abuts. As a result, the plunger 14 reciprocates left and right while rotating.

As the plunger 14 reciprocates, the pressure chamber 17 formed by the tip of the plunger 14 and the cylinder bore 16a expands and contracts. Plunger 14
A notch 14a corresponding to the number of cylinders is provided at the tip of the notch 14a. When the pressure chamber 17 is expanded, one notch 14a communicates with the suction passage 18 communicating with the pump chamber 13 as the plunger 14 rotates. As a result, the fuel is sucked into the pressure chamber 17. When the pressure chamber 17 is contracted, the notch 14a and the suction passage 18 do not communicate with each other as the plunger 14 rotates, and the fuel supply passage 14b formed in the plunger 14 and the side wall of the cylinder 16 and the housing 15 are formed. The delivery passage 19 is communicated with the delivery passage 19, and the fuel is pressure-fed to the combustion chamber via the delivery valve 20. The delivery valve 20 is opened when the pressure reaches a predetermined pressure, and this pressure is the fuel pumping pressure. The delval passage 19 and the delivery valve 20 are formed around the plunger 14 by the number of cylinders and enable fuel supply to each cylinder.

A spill passage 24 extending in the diametrical direction is formed in the portion of the plunger 14 that does not enter the cylinder 16, and the spill passage 24 and the fuel supply passage 14b are in communication with each other. . A cylindrical spill ring 25 is fitted into the plunger 14 so that the spill passage 24 can be opened and closed. When the pressure chamber 17 is contracted by the plunger 14, the fuel is pumped only when the spill passage 24 is closed by the spill ring 25, and the spill passage 24 moves as the plunger 14 moves.
Is released from the spill ring 25 and released, the pressure chamber 1
Since the fuel in 7 escapes to the pump chamber 13 through the spill passage 24, the pressure feeding of the fuel is stopped.

Therefore, by changing the position of the spill ring 25, it is possible to control the amount of fuel pumped into each combustion chamber. Spill ring 25 is control lever 2
The position of the control lever 26 is changed by engaging the protrusion 27 fixed to the lower portion of 6 and rotating the control lever 26 around the pin 28. The control lever 26 is
When the tension lever 30 is rotationally displaced by being pressed by a governor sleeve 41, which will be described later, the governor sleeve 41 is pressed by a leaf spring 29 to rotate.

That is, the control lever 26 stands still at a position where the forces received from the governor sleeve 41 and the tension lever 30 are balanced. The tension lever 30 is connected to an adjusting lever 32 via a control spring 31, and is rotationally displaced according to the rotational position of the adjusting lever 32. The governor sleeve 41 is guided by the governor shaft 42 and moves left and right. The governor shaft 42 is rotatably supported around the axis by the housing 15, and a gear 43 fixed to the shaft 42 meshes with a gear 44 fixed to the drive shaft 12 to rotate to be driven to rotate. In a holder 45 provided on the governor shaft 42, a flyweight 46 that expands outward by a centrifugal force generated by the rotation of the shaft 42 is accommodated, and the governor sleeve 41 engages with the flyweight 46. Then, when the governor shaft 42 rotates and the flyweight 46 expands, the governor sleeve 41 is displaced along with this, and the control lever 26 is pressed.

In this way, the position of the spill ring 25 is changed and the fuel pressure feed amount, that is, the fuel injection amount is controlled, while the timer piston 61 is displaced according to the pressure in the pump chamber 13 and the fuel pressure feed timing, That is, the fuel injection timing is controlled. The timer piston 61 is slidably accommodated in a bore 62 formed below the housing 15. The pressure receiving chamber 63 formed between the right end surface of the timer piston 61 and the bore 62 is constantly communicated with the pump chamber 13 via the passage 64, and is provided between the left end surface of the timer piston 61 and the end surface of the bore 62. A timer spring 65 is provided. The timer piston 61 is connected to the roller 22 via a lever 66, and stops at a position where the pressure in the pressure receiving chamber 63 and the elastic force of the timer spring 65 are balanced to determine the position of the roller 22. That is, the timer piston 61 is displaced according to the pressure in the pump chamber 13, and when the pressure in the pump chamber 13 becomes low, for example, it is displaced by the timer spring 65 toward the pressure receiving chamber 63 side, whereby the roller 22 injects fuel. It is displaced in the direction of delaying the time. The pressure in the pump chamber 13 is controlled by the governor sleeve 41.

By the way, as the temperature of the fuel increases, the viscosity decreases and the bulk modulus K decreases. The decrease in viscosity increases the amount of internal leakage of fuel that passes through the gap formed around the plunger 14 with respect to the cylinder 16 and the spill ring 25, and reduces the amount of fuel pumped. Further, as shown in the graph of FIG. 2, the bulk modulus K becomes smaller as the pressure P acting on the fuel is lower and the fuel temperature is higher, and the fuel compression amount V in the pressure chamber 17 at the time of fuel pressure feeding is expressed by the following equation ( 1)
Given by. V = dP / K * V1 (1) Here, dP is a pressure change acting on the fuel, and specifically, the valve opening fuel pressure of the delivery valve 20 and the pump chamber 13
It is the pressure difference with the fuel pressure inside. V1 is the plunger 1
4 is the dead volume of the pressure chamber 17 at the rightmost position of 4.

It can be considered that dP and V1 are substantially constant with respect to the temperature change, and the fuel compression amount dV is the bulk modulus K.
Becomes smaller, that is, the higher the fuel temperature is, the larger the value becomes, and the fuel injection amount is reduced.

By making the material forming the plunger 14 have a linear expansion coefficient larger than that of the material forming the cylinder 16 and the spill ring 25, the clearance around the plunger at the time of high engine temperature is reduced, and the viscosity of the fuel is reduced. It is possible to maintain the internal leakage of the fuel cell at a predetermined amount, and it is possible to prevent a decrease in the fuel pumping amount by this amount. However, this alone cannot prevent a decrease in the amount of fuel pumped due to a decrease in bulk modulus.

In the fuel injection pump shown in FIG. 1, the housing 15 is made of cast aluminum to reduce the manufacturing cost and reduce the weight, and the plunger 14 is made of a steel material to obtain a predetermined strength. When the engine temperature becomes high, both of them thermally expand. As a result, the position of the pin 28, which serves as the rotation axis of the control lever 26, and the spill passage 24 of the plunger 14.
Is displaced away from the feed pump 11. The displacement of the pin 28 depends on the housing 15 in which it is mounted.
Is made of aluminum and has a larger linear expansion coefficient than the steel material forming the plunger 14, so that it is larger than the displacement of the spill passage 24. This results in shifting the position of the spill ring 25 relative to the spill passage 24, which is determined by the required fuel pumping amount in the current engine operating state, to the right, that is, toward the side where the fuel pumping amount increases.

Therefore, the increase in the amount of fuel pumped by the displacement of the spill ring 25 is taken into consideration by the pressure chamber 17 at the time of high fuel temperature.
It is possible to maintain a desired fuel pressure feed amount by offsetting the increase in the fuel compression amount in the above. The calculation formula will be specifically described below.

Assuming that the temperature at the engine normal temperature is t1, the temperature at the engine high temperature is t2, and the fuel temperature and the engine temperature are equal, the increase dV of the fuel compression amount in the pressure chamber 17 at the engine high temperature is as described above. Using equation (1) is given by equation (2) below. dV = (1 / K2-1 / K1) * dPV1 (2) Here, K1 and K2 are the bulk modulus of the fuel at each temperature.

On the other hand, the increment dV 'of the fuel pressure feed amount due to the displacement of the spill ring 25 is given by the following equation (3). dV ′ = π / 4 * D _p ² * (ε ₂ −ε ₁ ) * L · Δt (3) where D _P is the diameter of the plunger 14, ε ₂ is the linear expansion coefficient of the material of the housing 15, and ε ₁ Is plunger 1
The linear expansion coefficient, Δt, of the material of No. 4 is the temperature difference t2-t1.
Is. In addition, L is a reference of the displacement of the pin 28 and the spill passage 24, from the cover of the feed pump 11 to the pin 28.
Is the length up to the mounting position.

The following equation (4) can be obtained by making both equal. Dp ² · L = 4dP · V1 / πΔt (ε ₂ −ε ₁ ) * (1 / K2-1 / K1) (4) The diameter D _{P of the} plunger 14 and the feed pump are set so that this expression (4) is satisfied. By determining the length L from the cover of 11 to the mounting position of the pin 28, the engine high temperature t2
In the above, it is possible to prevent a decrease in the amount of fuel pumped due to a decrease in the bulk modulus of the fuel. Further, the engine temperature t1 to t2
Even during the period, the temperature change of the bulk elastic modulus K is not peculiar and gradually decreases, so that the desired fuel pumping amount is maintained.

The fuel injection pump according to the present invention does not require addition of new parts as compared with general ones, only the dimensions of specific parts are set, and no increase in cost is required.

[0025]

As described above, according to the fuel injection pump of the present invention, the housing of the fuel injection pump supporting the spill ring position changing means forms the plunger.
When the plunger diameter and the support position of the spill ring position changing means on the housing are made of a second material having a larger linear expansion coefficient than the material, when the engine temperature is high and the compression amount of fuel in the pressure chamber is large, First and second at this time
The increase in the amount of fuel pumped by the displacement of the spill ring through the spill ring position changing means due to the difference in the thermal expansion of the material is determined so as to cancel the increase in the amount of compression of the fuel. The reduction of the fuel pumping amount due to the increase of the compression amount of the fuel is prevented without requiring the complicated control of changing the spill ring position according to the above.

[Brief description of drawings]

FIG. 1 is a sectional view of a fuel injection pump according to the present invention.

FIG. 2 is a graph showing changes in bulk modulus of fuel with respect to fuel temperature and working pressure.

[Explanation of symbols]

 11 ... Feed pump 13 ... Pump chamber 14 ... Plunger 15 ... Housing 16 ... Cylinder 17 ... Pressure chamber 24 ... Spill passage 25 ... Spill ring 26 ... Control lever 28 ... Pin

Claims (1)

[Claims] 1. A plunger, a plunger, and a plunger reciprocating motion for at least reciprocating the plunger with respect to the cylinder in order to pressurize fuel in a pressure chamber formed by the cylinder and the plunger into a combustion chamber. And a spill ring that closes the spill passage of the plunger and changes the fuel pumping amount according to its position, and changes the position of the spill ring so as to obtain the required fuel pumping amount according to each engine operating state. And a spill ring position changing means for causing the spill ring position changing means to support the spill ring position changing means. The fuel injection pump housing is formed of a second material having a linear expansion coefficient larger than that of the first material forming the plunger. Is
When the amount of fuel compressed in the pressure chamber becomes large due to high engine temperature, displacement of the spill ring through the spill ring position changing means due to the difference in thermal expansion between the first and second materials at this time occurs. Fuel injection, characterized in that the diameter of the plunger and the support position of the spill ring position changing means to the housing are determined so that the increase in the amount of fuel pumped cancels the increase in the amount of compression of the fuel. pump.