JPS6215174A - Four wheel steering device for automobile - Google Patents

Abstract

PURPOSE:To aim at saving electrical power and at enhancing the durability of a steering device, by providing a no signal transmitting range setting section for variably controlling the no signal transmitting range of a front wheel steering sensor so that no useless current is fed to a rear wheel steering actuator. CONSTITUTION:A control circuit 11 receives a vehicle speed signal (a) from a vehicle speed sensor 12 and a front wheel steering angle signal (b) from a front wheel steering sensor 13, and computes the steering angle of rear wheels 10 in accordance with the characteristic of the steering ratio between front and rear wheels which is previously obtained corresponding to the vehicle speed. Further, there is provided a no signal transmitting range setting section 15 for changing the no signal transmitting range of the front wheel steering angle sensor 13 in accordance with the vehicle speed, and the front wheel steering angle signal from the front wheel steering angle sensor 13 is compared with the vehicle speed signal from the vehicle speed sensor 12 so that no front wheel steering signal is delivered to the control circuit 11 in accordance with a play and the condition of the road surface, thereby no useless current is fed to an actuator 7.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a four-wheel steering system for an automobile.

Conventional Technology Steering OperationIn a vehicle in which the rear wheels are also steered at the same time as the front wheels are steered, the ratio k (=θtiny >) of the rear wheel steered angle θr to the front wheel steered angle θf is Front and rear wheel steering angle ratio characteristics that change according to vehicle speed are set in advance, and the rear wheel turning angle relative to the front wheel turning angle when the driver operates the steering wheel is controlled based on the front and rear wheel steering angle ratio characteristics. Various four-wheel steering devices have been developed in the past, and have already been disclosed, for example, in Japanese Patent Laid-Open No. 11173/1983.

Problems to be Solved by the Invention As mentioned above, a four-wheel steering system for an automobile that changes the ratio of the rear wheel steering angle to the front wheel steering angle, that is, the front and rear wheel steering angle ratio k, according to the vehicle speed is, for example, is a front wheel steering angle sensor that detects the steering angle of the front wheels based on the rotation angle of the steering handle or steering shaft, or the pinion, or the axial movement amount of the rack shaft in the case of a rack-type steering device, and the A vehicle speed sensor that detects vehicle speed from the rotational speed is provided, and the steering angle of the rear wheels is determined based on the front and rear wheel steering angle ratio characteristics set in advance from the signals of both sensors, that is, the front wheel steering angle signal and the vehicle speed signal. However, the front wheel steering angle sensor described above is generally designed to have a non-emission region, or dead zone, in which it does not emit a steering angle signal within a certain angular range left and right from the neutral point, that is, when the vehicle is traveling straight. When the vehicle is traveling straight while turning the steering wheel, it is normal to avoid applying force so that the wheels are steered unnecessarily.

However, when driving at low speeds, there is play in the front wheel steering mechanism from the steering wheel to the front wheels, and the slip resistance between the tires and the road surface is large, making it easy for the steering wheel to turn due to input from the road surface. Despite this, there are many situations in which the steering wheel is constantly turned to the left or right, and each time the front wheel steering angle sensor issues a signal, for example, rear wheel steering is caused by an electric device such as a motor. It is not preferable to drive the rear wheel steering actuator in terms of power consumption and durability of the rear wheel steering actuator. Therefore, when driving at low speeds, it is preferable to set the non-transmission range of the front wheel steering angle sensor to be large.

On the other hand, when driving at reverse speed, it is desirable to minimize the area where the front wheel steering angle sensor does not transmit signals so that the vehicle can accurately turn with a slight rotation of the steering wheel. If the area is fixedly set within a certain angular range, it is not possible to fully satisfy both the above-mentioned requirements during low-speed running and high-speed running.

Means for Solving the Problems The present invention provides a method that is set in advance based on the input of a front wheel steering angle signal from a front wheel steering angle sensor that detects the front wheel steering angle, and a vehicle speed signal from a vehicle speed sensor that detects the vehicle speed. An faI control circuit is provided which determines the optimum rear wheel steering angle at that time based on the front and rear wheel steering angle ratio characteristics, and generates an output to drive a rear wheel turning marine actuator to steer the rear wheels to the above-mentioned optimum rear wheel turning angle. In the four-wheel steering system aVC of a car, the front wheel steering angle sensor has a non-transmission area in which the front wheel steering angle signal is not emitted from the front wheel steering angle 0 to the left and right predetermined angle range control circuit, which is large at low vehicle speeds and small at high vehicle speeds. The present invention is characterized in that it includes a non-transmission area setting section that variably controls according to the vehicle speed.

Function In the above description, when the vehicle is running at low speed, the non-signal area of the front wheel steering angle sensor is set by the non-signal area setting section to, for example, about 6 degrees left and right as the steering wheel rotation angle from the straight-ahead state. When driving straight while turning the steering wheel to the right or left due to play or input from the road surface to the front wheel steering mechanism, almost all of the steering wheel steering angle is within the above-mentioned non-sensing region of the front wheel steering angle sensor. Within this range, the front wheel steering angle signal is not input to the control circuit, the output that should drive the rear wheel steering actuator is not generated, and unnecessary rear wheel steering is often performed.

When driving at high speeds, the non-radiation area setting section sets the non-radiation area of the wheel steering angle sensor, for example, the steering wheel rotation angle, which is set to about 2 degrees to the left and right from the straight-ahead state, and even when the steering wheel is slightly operated. Even at a corner, the front wheel steering angle signal is input to the control circuit, and the control circuit issues an output to steer the rear wheels based on the preset front and rear wheel steering angle ratio characteristics, and the rear wheel steering actuator is driven. This system steers the rear wheels to ensure responsive maneuverability.

Example Embodiments of the present invention will be described below with reference to the accompanying drawings.

In Fig. 1, 1 is a steering handle, 2 is a steering shaft, and 3 is a steering gear box.When the steering handle 1 is rotated, the gear in the steering gear box 3 is rotated, and the tie rod is rotated by 4 degrees. Or move to the right and knuckle arm 5
, 5, the front wheels 6, 6 are rotated around the kingpin, and the front wheels are steered.

7 is an actuator such as an electric motor, and the operation of the actuator T moves the tie rods 8, 8 to the left or right, and connects the rear wheel io via the knuckle arms 9, 9.
, to rotates as the kingpin turns, and rear wheels are steered.

Reference numeral 11 denotes a control circuit υ, which detects the vehicle speed and outputs a vehicle speed signal α corresponding to the vehicle speed, and the vehicle speed signal α of the vehicle speed sensor 12, the steering angle of the steering wheel 1, or the actual steering of the front wheels 6.6. The front wheel steering angle signal from the front wheel steering angle sensor 13, which detects the front wheel steering angle and issues a front wheel steering angle signal corresponding to the front wheel turning angle, is input to the control circuit 11, and the control circuit 11 receives both the signals α. , b determines the steering angle of the rear wheels 10, 10 based on the characteristics of the front and rear wheel steering angle ratio with respect to the vehicle speed predetermined by the inputs of inputs, and issues an output to the actuator 7 to obtain the rear wheel steering angle; By operating the actuator 7, the rear wheels 10, 10 are steered. Reference numeral 14 denotes a rear wheel steering angle sensor that detects the steering angle of the rear wheels 10.degree. 10 and generates a rear wheel steering angle signal C, and the rear wheel steering angle is feedback-controlled by the rear wheel steering angle signal C.

The characteristics of the front and rear wheel steering angle ratios include, for example, in a low vehicle speed range, the rear wheels are slightly steered in the opposite direction to the front wheel steering direction (front and rear wheel reverse phase steering), and as the vehicle speed increases, the front wheel steering angle θfVc The ratio of the rear wheel steering angle θr (=θt−/f)f) changes from 0 to front and rear wheels being steered in the same phase, and as the vehicle speed increases, the front and rear wheel steering angle ratio k gradually increases toward 1. However, the above-mentioned front and rear wheel anti-phase steering range is eliminated, and the front and rear wheels are steered in the same phase over the entire vehicle speed range, and the vehicle speed is zero.
The front and rear wheel steering angle ratio k may be set to gradually increase from 0 to 1 as the vehicle speed increases, or any other front and rear wheel steering angle ratio characteristics may be adopted.

In the above, the front wheel steering angle sensor 13 is a non-transmission area (where the front wheel steering angle sensor 13 does not emit a front wheel steering angle signal within a predetermined angle range left and right from the neutral point (θ = 0), that is, from the straight-ahead driving state, for example, as the rotational operation angle θ of the steering handle 1. Normally, a dead zone (sb) is set, and in the past, the non-transmission area was constant regardless of the vehicle speed, as shown by ■ in Fig. 3.

In the present invention, as shown in the block diagrams of FIGS. 1 and 2, a non-transmission region setting section 15 is provided that changes the non-transmission region of the front wheel steering angle sensor 13 depending on the vehicle speed.

That is, the non-transmission area setting unit 15 compares, for example, the front wheel steering angle signal of the front wheel steering angle sensor 13 and the vehicle speed signal of the vehicle speed sensor 12, and as shown by the symbol ■ in FIG. The front wheel steering angle signal is not output until the steering angle θ becomes a fairly large angle (for example, about 6 degrees left or right from the neutral point as the steering wheel operation angle), and the front wheel steering angle signal is not output until the steering angle θ becomes a considerably large angle (for example, about 6 degrees left or right from the neutral point as the steering wheel operation angle). It is constituted by a comparison circuit that outputs a front wheel steering angle signal to the control circuit 11 at a steering wheel operation angle of about 2 degrees left and right from the neutral point.

In the above, the non-transmission area of the lllI wheel steering angle signal input from the front wheel steering angle sensor 13 to the control circuit 11 is as follows:
At low vehicle speeds, the control circuit 1 becomes more stable than before, and when driving in a straight line while turning the steering handle 1 left and right.
No front wheel steering angle signal is input to the actuator 1, and the inconvenience that wasteful current repeatedly flows through the actuator 7 is almost eliminated.

On the other hand, when driving at high speeds, the area in which the front wheel steering angle signal is not transmitted is much smaller than that of the conventional system, and the front wheel steering angle signal is immediately input to the control circuit 11 when the steering wheel 1 is turned slightly. When the actuator 7 is actuated by the output of the control circuit 11 and the steering wheel 10 is operated to initiate a turn, extremely responsive handling can be obtained.

The non-transmission area setting 8515 may be configured to be incorporated into the control circuit 11, and the non-transmission area characteristics controlled by the non-transmission area setting section 15 are not limited to the characteristics shown in FIG. , it is possible to adopt any characteristic in which the non-signal area is large at low vehicle speeds and small at high vehicle speeds.

Effects of the Invention As described above, according to the present invention, in the 4Q & steering system equipped with a control circuit that controls the rear wheel steering angle from the front wheel steering angle signal from the front wheel steering angle sensor and the vehicle speed signal from the vehicle speed sensor, the front wheel steering angle can be adjusted. By providing a non-emission area setting section that variably controls the sensor's non-emission area according to the vehicle speed so that the area where the sensor does not emit is large at low vehicle speeds and small at high vehicle speeds, it is possible to repeatedly turn the steering wheel left and right at low vehicle speeds. This eliminates unnecessary current flow to the rear wheel steering actuator when the vehicle is traveling straight ahead, thereby conserving power and improving durability as well as improving maneuverability when traveling straight at low speed. In addition, when driving at high speeds, the rear wheels will be steered immediately even with the slightest steering operation.
It is possible to obtain maneuvering characteristics with good responsiveness,
This can bring about great practical effects.

[Brief explanation of the drawing]

FIG. 1 is an explanatory plan view showing an embodiment of the present invention, FIG. 2 is a block diagram showing a control system Z of the device shown in FIG. DESCRIPTION OF SYMBOLS 1... Steering handle, 7... Rear wheel rotation marine actuator, 11... Control circuit, 12... Vehicle speed sensor, 13... Front wheel steering angle sensor, 15... Non-radiation area setting unit. that's all

Claims (1)

[Claims] a front wheel steering angle signal from a front wheel steering angle sensor that detects the front wheel steering angle;
In a four-wheel steering system for an automobile, which is equipped with a control circuit that generates an output to operate a rear wheel steering actuator based on the input of a vehicle speed signal from a vehicle speed sensor that detects the vehicle speed, the front wheel steering angle sensor's front wheel steering angle is 0, and the left and right steering angles are 0. The predetermined angle range control circuit is provided with a non-transmission region setting section that variably controls the non-transmission region in accordance with the vehicle speed so that the non-transmission region in which the front wheel steering angle signal is not generated is large at low vehicle speeds and small at high vehicle speeds. A four-wheel steering system for automobiles.