JPS62139756A - Four wheel steering apparatus for automobile - Google Patents

Abstract

PURPOSE:To enhance the running stability of a vehicle, by stopping the operation of an actuator for steering rear wheels when an abnormality in sensors, a drive system for the actuator or the like is detected, and by fixing the steering angle of the rear wheels at a value which is set when the abnormality occurs. CONSTITUTION:In a four wheel steering apparatus, a control circuit 11 determines a steering angle for rear wheels in accordance with a front wheel steering signal (a) from a control wheel steering angle sensor 13 and a vehicle speed signal (b) from a vehicle speed sensor 14, and a drive circuit 12 operates an actuator 7 such as a motor in accordance with the thus determined steering angle to steer the rear wheels 10. In the above-mentioned arrangement, the control circuit 11 is provided with an abnormality detecting section for detecting an abnormality in sensors such as front and rear wheel steering angle sensors 13, 15, a vehicle speed sensor or the like and a drive system for the actuator 7. Further, control is made such that the operation of the actuator 7 is stopped when the abnormality detecting section detects an abnormality, and the steering angle of the rear wheels is held at a value which is set at that time.

Description

[Detailed description of the invention] Utilization field of Sanmata-1- The invention relates to a four-wheel steering system for automobiles.

Conventional technology In automobiles, by turning the steering device,
The controller is configured so that not only the front wheels but also the rear wheels are steered, and the controller controls the steering angle of the rear wheels based on the Φ-speed sensor's jlt-velocity and the front wheel steering angle of the front wheel steering angle sensor (5). Various four-wheel steering devices have been developed in the past, in which a predetermined output is determined and an actuator consisting of an electric motor or the like is actuated by the output to steer the rear wheels. No. 42161--Already published in the publication.

Problems to be Solved by the Invention In the four-wheel steering system as described in 1-1, if an abnormality such as a disconnection occurs in the sensor system or actuator drive circuit cap, the rear wheels will be 1. This is extremely dangerous as the vehicle will be steered abnormally.

In order to solve this problem, in the conventional four-wheel steering system, the front wheel steering angle detected by the front wheel steering angle sensor is 11
(When the critical front wheel steering angle exceeds the allowable critical front wheel steering angle at the speed, the front wheel steering angle sensor or 1 (t) determines that an abnormality has occurred in the sensor system such as the speed sensor. One stage of safety control is provided to return the steering angle to zero, that is, to the straight-ahead state.

However, as described above, with the conventional device that returns the rear wheels to zero steering angle when an abnormality occurs in the rear wheel steering angle control system, the system does not operate until the rear wheels return to zero steering angle after the abnormality occurs. During this period, only the rear wheels are steered, completely unrelated to the front wheel steering angle controlled by the driver's steering wheel operation, and therefore regardless of the driver's intention. The problem is that the behavior of 1 changes regardless of the situation, which is extremely dangerous, especially when driving at high speed.

The present invention is primarily intended to deal with the problems of the conventional device as described in 1-.

A first step of the present invention to solve the problem is to detect a front wheel steering angle and to generate a front wheel steering angle signal according to the front wheel steering angle;
A control circuit is provided which determines the rear wheel steering angle based on the vehicle speed signal of the vehicle speed sensor which detects the vehicle speed and issues a speed signal corresponding to the vehicle speed. In a four-wheel steering system for an automobile equipped with an actuator that operates a steering wheel, a front wheel steering angle sensor;
An abnormality detection section is provided to detect an abnormality in the drive system that should operate sensors such as a vehicle speed sensor or an actuator, and when the abnormality detection section detects an abnormality, the operation of the actuator is stopped and the rear wheel steering angle is abnormally adjusted. , 51 is characterized in that it is provided with a rear wheel steering angle fixing means that fixes and maintains the steering angle as it was at the time of birth.

When a failure such as a disconnection occurs in the sensors or actuator drive system 1' in the operation J pair, and the abnormality detection section detects an abnormality, a signal is issued and the actuator operation is stopped.
At the same time, the rear wheel steering angle is fixed and held at the steering angle at the time the abnormality was detected, and from then on, the front wheel It! Only the 7i rudder controls the behavior of ``1 movement + 1.''

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

FIG. 1 is a cross-sectional explanatory diagram showing an example of a four-wheel steering system to which the present invention is applied, where l is a steering handle, 2 is a steering shaft, 3 is a steering gear box, By rotating the gear in the steering gear box 3, the tie rod 4.4 is actuated in the axial direction, and the 1111 wheels 6, 6 are rotated around the king pin via the knuckle arms 5, 5, and the front wheels are steered. will be held.

Reference numeral 7 denotes a 7 actuator such as an electric motor, and when the first actuator 7 operates, a tie rod 8.8 is actuated in the axial direction, and the tie rod 8.8 is actuated via a knuckle arm 9.9 to the rear wheel 10.1.
0 rotates around the kingpin to perform rear wheel steering.

Reference numeral 11 denotes a control circuit, which detects the steering angle of the steering wheel l or the actual steering angle of the front wheels 6.6, and outputs a front wheel steering angle signal a corresponding to the front wheel steering angle. The steering angle signals a and lj are detected, and a vehicle speed signal corresponding to the speed is generated. 'The characteristics of the front and rear wheel steering angle ratio with respect to the heavy speed predetermined by the input of No. 1 a and b), (duki, rear wheel 1
A steering angle of 0.10 is determined, and an output signal d to obtain the rear wheel steering angle is issued to the drive circuit 12.

An actuator 7 such as an electric motor is actuated by the output of the drive circuit 12, and the rear wheels TO and IO are steered. Reference numeral 15 is a rear wheel steering angle sensor that detects the rear wheel steering angle of 10°lO and starts from the rear wheel steering angle (j C), and the rear wheel steering angle is fed back by the rear wheel steering angle property L'iC. controlled.

In the four-wheel steering system as described above, in the present invention, the front wheel steering angle sensor 13. The control circuit 11 is provided with an abnormality detection unit that detects abnormalities such as disconnection of the rear wheel steering angle sensor 15, the IiL speed sensor 14, and the circuit from the drive circuit 12 to the actuator 7, and the abnormality detection unit detects abnormalities. The present invention is characterized in that a rear wheel steering angle fixing means is provided which stops the operation of the actuator 7 when detected, and fixes the rear wheel steering angle at the current steering angle.

Hereinafter, an embodiment of the present invention in which an electric motor 71 is used as the actuator 7 will be described in detail with reference to FIGS. 2 to 5.

Both the front wheel steering angle sensor 13 and the rear wheel steering angle sensor 15 are
As shown in the figure, the voltage division point of the resistance changes according to the change in the steering angle, and the output power according to the steering angle changes depending on the change in the voltage division point.
3X'i, that is, an output voltage, which is A/D converted and sent to the control circuit 11.
At the same time, the output voltage of the speed sensor 14 is also A/D converted and input to the control circuit 11. The ideal rear wheel steering angle is determined by calculation based on the characteristics of the front and rear wheel steering angle ratio with respect to the current speed, and an output signal t)d is issued to the drive circuit 12.

As shown in FIG. 3, the drive circuit 12 controls the switching element 7-Trl and
r4 or Tr3 and Tr2 to close a circuit for forward or reverse rotation of the electric motor 71, and by 1E rotation or reverse rotation of the electric motor 71, the rear wheel 10 is rotated to the right. Or operate the steering to the left, control circuit 1
When the ideal rear wheel steering angle determined by 1 and the steering angle of the rear wheel 10 detected by the rear wheel steering angle sensor 15 match, the control circuit 11
The output signal d of is stopped and the switching element of the drive circuit is
fTr 1 to 4 are all non-conductive and the electric motor 71
rotation stops, and the rear wheel steering operation is completed.

In L, the front wheel steering angle sensor 13 and the rear wheel steering angle sensor 13
For example, as shown in Fig. 2, the input terminals 15 each have 5 volts, and by dividing the voltage with a resistor, the range from the maximum steering angle on the right side to the maximum steering angle on the left side, that is, the range of low 2, toe, and lock. is configured to correspond to the sensor output voltage in the range of 0.5 volts to 4.5 volts as shown in FIG. In FIG. 4, if the sensor output voltage in the area indicated by the hatched knob is outputted, it can be assumed that some kind of abnormality has occurred in the steering angle sensor.

Also, 11: The change in the output of the speed sensor 14 causes the automatic;
If the deceleration or acceleration is so large that it would never be possible for the brake performance or acceleration performance of the vehicle, it can be assumed that an abnormality such as a wire breakage has occurred in the vehicle speed sensor.

Furthermore, if no change appears in the output of the rear wheel steering angle sensor 15 after a certain period of time has passed since the control circuit 11 issues the output signal d to rotate the electric motor 71, or if the control circuit 1
1 is not emitting the output signal 7) d that should rotate the electric morph 71. The output of the rear wheel steering angle sensor 15 continues to change for more than a certain period of time (beyond the control error range). If so, it can be considered that an abnormality has occurred in the drive system such as the drive circuit 12 and the electric motor 71.

An abnormality in the sensors or the drive system as described in L is detected by an abnormality detection section provided in the control circuit 11, and when the abnormality detection section detects an abnormality, it emits a signal 0gine and causes the electric motor 71 to be activated from the power supply 16. (i.e., the power supply circuit of the electric morph 71)
At the same time, a switch 17 provided on the rear wheel 10 is turned off, and a brake 18 provided on the output shaft side of the electric motor 71 is activated to maintain the steering angle of the rear wheels 10 fixed at the same steering angle as when the abnormality occurred. There is.

The L brake 18 may be, for example, a non-excited brake that is turned off during energization, allowing the electric motor 71 to rotate freely, and turned on and off when the energization is cut, thereby restraining the rotation of the output shaft of the electric motor 71. Ru.

In the above, in the case of a conventional device that is designed to return the rear wheels to zero steering angle, that is, to return to the straight-ahead position if an abnormality occurs in the sensors, for example, the front wheels are steered to the right and the rear wheels are also steered to the right. If an abnormality is detected in the sensors while turning right, the rear wheels will independently steer in the straight-ahead direction, i.e., to the left, regardless of the driver's intention to drive to the right. In a normal situation, the rear wheels tend to sway in the direction of centrifugal force, that is, in the outward direction opposite to the turning center, and especially when driving at high speeds, there is a risk of body spin.
It's dangerous.

In contrast to such conventional devices, in the present invention, if an abnormality is detected in sensors or the drive system during a right turn when both the front and rear wheels are turned to the right, the rear wheels are turned to the right. Since the rudder is fixed in the same state, the turning operation continues without any danger as before the abnormality occurred, and in the case of a four-wheel steering system ξ, the rear wheel steering angle is originally one front and rear wheel when the front and rear wheels are steered in the same phase. In both cases of reverse phase steering, the steering angle is very small (for example, the rear wheel steering angle is within about 3 degrees), so even if the rear wheels are fixed in the steered state, it is difficult to return the vehicle from a turning state to a straight-ahead state. The yaw angle of the Tokiwaka car's east body is such that it can move straight, and it can maintain almost the same driving performance as a conventional two-wheel steering vehicle without rear wheel steering.

FIG. 5 shows a specific example of a rear wheel steering mechanism to which the present invention is applied.

That is, in FIG. 5, reference numeral 19 denotes a cylindrical cross member attached to a vehicle body member. A rack shaft 20 is supported within the cross member 19 so as to be able to move in the axial direction, and the left and right sides of the rack shaft 20 are A cylindrical member 21 is joined to the end of the rack shaft 20 , and as the rack shaft 20 moves in the axial direction, the cylindrical member 21 is attached to the cross member 19 .
It is configured to move and displace in the direction, that is, in the left and right direction.

22 is an outer arm whose front end is rotatably attached to the 1:2 cylinder member 21 and whose rear end is connected to the /X housing of the rear wheel 10; 23 is an outer arm whose front end is rotatably attached to the cross member 19; Installed rear end with king pin 24
The rear wheel 10 is supported by an L outer arm 22 and an inner arm 23 so as to be capable of driving. When the motor 71 rotates once and its rotation is transmitted to the pinion 26 via the reduction mechanism consisting of the worm gear 25, the pinion 26
Rakushaft 20 that matches t4 with the rotation of
The cylindrical member 21 moves to the right or left in the axial direction, and the rear wheel 10 rotates to the right or left around the king pin 24 via the outer arm 22, thereby performing rear wheel steering.

In this 514th specific structural example, the cylindrical member 21 also serves as the tie rod 8 shown in 51, and the rear outer arm 22 serves as the knuckle arm 9 shown in the 1st drawing.

In this example, by using the worm gear 25 as a reduction mechanism, the rotation of the electric motor 71 is controlled by the cheek shaft 2.
However, the load input from the rear wheel lO to the rack shaft 20 is locked by the worm gear 25 so that the predetermined steering angle of the rear wheels 10 can be maintained. The worm gear 25
In addition, a non-excited brake 18 is provided on the output shaft side of the electric motor 71, and if an abnormality occurs in the sensors, drive system, etc., the brake 18 makes the electric motor output shaft unable to rotate, and the rear wheel steering angle is The worm gear 25 and the brake 18 are used to fix the rear wheel steering angle, but the worm gear 25 alone may be used as the first stage to fix the rear wheel steering angle in the event of an abnormality in the J-biped sensors, drive system, etc.
Only 8 is fine.

Note that although FIGS. 2 to 5 show an example in which an electric motor is used as the actuator unit for rear wheel steering, the present invention is also applicable to an arrangement in which a hydraulic actuator is used as the actuator 7. In this case, when an abnormality occurs in the sensors, etc., by blocking the oil passage of the kit that should activate the 4-hour pressure actuator with a valve, the rear wheel steering angle can be fixed in the state at the time of the abnormality. [l]
Able to achieve target.

Effects of the Invention According to the present invention, the control path 1111 determines the ideal rear wheel steering angle based on the front wheel steering angle and the vehicle speed, and generates an output to operate the rear wheel steering actuator. Applicable °
In a four-wheel steering system for an automobile in which the rear wheels are steered by the operation of a steering unit, a control circuit detects the front wheel steering angle and speed and controls the front wheel steering angle signal and the vehicle speed at 9 o'clock. If an abnormality occurs in the front wheel steering angle sensor that inputs to the front wheel steering angle sensor, the sensors in the vehicle speed sensor cap, or the drive system that should operate the 7 actuator, the operation of the L actuator will be stopped and the rear wheel steering angle will be adjusted to the point at which the abnormality occurred. By providing a rear wheel steering angle fixing means that fixes the steering angle as it is, when the abnormality described in -■- occurs, only the rear wheels are fixed at the same angle, regardless of the front wheel steering angle, that is, the driver's steering wheel operation. There is no risk of injury if the steering is activated, and the behavior of the insect can be controlled by the driver's steering wheel operation in almost the same way as in a conventional two-wheel steering vehicle. The practical effect is extremely significant in that it can significantly improve safety in the field.

[Brief explanation of drawings]

Figure 1 shows the automatic application of unreleased tJI! 2 to 5 show embodiments of the present invention, and FIG. 2 shows the block IΔ of the rear wheel steering angle control device, and FIG. 4 is an explanatory diagram of a drive system of a rear wheel steering actuator, FIG. 4 is a sensor output voltage characteristic diagram of a front wheel steering angle sensor or a rear wheel steering angle sensor, and FIG. 5 is a diagram of a rear wheel steering mechanism to which the present invention is applied. FIG. 2 is a cross-sectional view showing a specific example. ■...Steering handle, 6...Front wheel, 7...
・Actuator, lO... Rear wheel, 11... Controller ° road, 12... Drive circuit, 13... Front wheel steering angle sensor, 14... Vehicle speed sensor, 15... Rear wheel steering angle sensor,
16...power supply, 17...switch, 18...brake, 25...two ohm gear. 1- Substitute Me Kiyose Three Parts Same Foot rl-':'-husband γ 1 Closed 2 Mouth 3 Mouth Said 4 Figure Said Figure

Claims (2)

[Claims] (1) The front wheel steering angle signal of the front wheel steering angle sensor which detects the turning angle of the front wheels and issues a front wheel steering angle signal corresponding to the front wheel steering angle, and the front wheel steering angle signal of the front wheel steering angle sensor which detects the vehicle speed and issues a vehicle speed signal corresponding to the vehicle speed. A four-wheel steering system for a motor vehicle, which includes a control circuit that determines a rear wheel steering angle based on the vehicle speed signal and issues an output, and an actuator that operates based on the output of the control circuit to steer the rear wheels, An abnormality detection section is provided to detect an abnormality in the drive system that should operate sensors such as the front wheel steering angle sensor and vehicle speed sensor or the actuator, and when the abnormality detection section detects an abnormality, it stops the operation of the actuator and A four-wheel steering system for an automobile, characterized in that a rear wheel steering angle fixing means is provided for fixing and holding the wheel steering angle at the same steering angle as at the time of occurrence of an abnormality. (2) The actuator is composed of an electric motor, and when the abnormality detection section detects an abnormality, the power supply circuit of the electric motor is cut off, and the output shaft of the electric motor is restrained from rotating by a brake. A four-wheel steering system for an automobile according to claim 1, characterized in that: