JPS62139763A - Four wheel steering device for vehicle - Google Patents

Abstract

PURPOSE:To make it possible to shift the steering mode of a vehicle into the two wheel steering mode while the steering characteristic of the vehicle is prevented from abruptly changing, by gradually communicating both pressure chambers in a power cylinder with each other when a control means fails to control the turn angle of rear wheels so that the latter is finally locked and held at zero angle. CONSTITUTION:In a power steering mechanism 16 in which a rear wheel steering mechanism 12 for turning rear wheels 2L, 2R is driven in association with the operation of an actuator 50 controlled by a control means 117, there is provided a communication passage 53 for communicating between both pressure chambers 17b, 17c of a power cylinder 17. The communication passage 53 is disposed therein with a valve means 54 for variably adjusting the passage area thereof. Further, a valve control means 118 controls the valve means 54 in such a way that the passage area of the communication passage 53 is gradually increased to its maximum area when the control means 110 malfunctions due to coupler disconnection and harness breakage.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention provides a four-wheel steering i! that steers the front and rear wheels of a vehicle. ! The present invention relates to devices, and in particular to measures to increase safety in the event of abnormalities in control systems.

(Prior Art) In recent years, this type of four-wheel steering system for vehicles has attracted attention as a device that can greatly change the driving characteristics of the vehicle. At $I speed, the steering ratios of the front and rear wheels are controlled to be in opposite phases,
The steering characteristics are set to oversteer characteristics to improve the vehicle's ability to turn, while at high vehicle speeds, the steering ratio is kept in the same phase and the steering characteristics are changed to understeer characteristics to ensure vehicle running stability. .

As an example of this four-wheel steering device, the applicant has:
Previously, we have proposed a system in which the steering ratio of the front and rear wheels is variably controlled by changing the inclination angle of a swinging arm called a swash plate (Japanese Patent Application No. 59-48054 Specification J3). and drawings).

That is, this proposal includes a moving member that is connected to a rear wheel steering mechanism that steers the rear wheels of a vehicle and is movable in a predetermined movement axis direction, and a swing center located on the movement axis of the moving member. A swinging member b that swings slightly, a connecting member that connects the swinging arm and the movable member, and a front wheel steering mechanism that steers the front wheels of the vehicle, and movement of the movable member that is the connecting member. and a rotation imparting arm that rotates around an axis, and the steering ratio of the front and rear wheels is changed by changing the inclination angle of the swing center line of the swing arm with respect to the movement axis of the moving member using an actuator. This is what I did.

Furthermore, for example, Japanese Patent Laid-Open No. 58-22757 discloses a system in which a power steering mechanism having a power cylinder is linked to a rear wheel steering mechanism, and the output of the power cylinder assists the steering of the rear wheels. Disclosed.

(Problem to be Solved by the Invention) By the way, it is not limited to changing the steering ratio of the front and rear wheels as in the above proposed example. In a four-wheel steering system, including Nishichino, when the power supply to the control system is cut off due to a broken coupler or a disconnected harness, or when the control to the actuator becomes abnormal, the vehicle's four-wheel steering control is disabled. It will not work properly. Therefore, in order to ensure a higher level of driving safety, it is desirable to establish a safety system in case of an abnormality in the control system.

The main purpose of the present invention is to actively utilize the conventional power steering mechanism and its attached mechanisms, and when the control system malfunctions as described above, the power steering mechanism controls both pressure chambers of the power cylinder in J3. The control system is controlled by communicating with the valve means to stop its function, and at the same time locking and holding the rear wheels of the vehicle in a state where the steering angle is zero by the rear wheel steering angle biasing means of the attached mechanism. The purpose is to automatically switch the vehicle to the normal two-wheel steering state even if the vehicle becomes inoperable, thereby ensuring a higher level of driving safety.

However, in that case, if the valve means is immediately opened to communicate the two pressure chambers of the power cylinder as soon as an abnormality occurs, the steering characteristics of the vehicle will suddenly switch from a four-wheel steering state to a two-wheel steering state. This sudden change in the steering characteristics may cause the occupants to feel uncomfortable.

Therefore, it is conceivable to connect an orifice in series with the above valve means to extend the communication time. If the angle changes, VJ fluid may be supplied to the pressure chamber and the power steering mechanism may operate, so this cannot be an essential solution.

The present invention has been made in view of the above points, and further advances the above idea by adjusting the speed of communication between the two pressure chambers of the power cylinder using the valve means itself, thereby adjusting the steering characteristics of the vehicle to the occupant. The purpose of this is to enable the driver to gradually switch from a four-wheel steering state to a two-wheel steering state without causing any discomfort.

(Means for Solving the Problems) In order to achieve this object, the solving means taken in the present invention is as shown in FIG. , 2R as a four-wheel steering system for a vehicle that steers the front wheels of both vehicles.
, 1R, a rear wheel steering mechanism 12 that steers the rear wheels 2L and 2R, and the rear wheel steering mechanism 12.
an actuator 5o for controlling the rear wheel steering angle θR via the actuator 5o, an actuator control means 117 for controlling the operation of the actuator 50, and an actuator control means 117 that controls the operation of the rear wheel steering mechanism 12, and is linked to the rear wheel steering mechanism 12 to control the rear wheels 2L, 2R at their steering angles. 8th is θ
Rear wheel steering angle biasing means 17 that biases R so that R=O.
d, and the power cylinder 1 linked to the rear wheel steering mechanism 12.
7, and the power cylinder 17 connects the rear wheels 2L, 2+
It is assumed that the present invention is equipped with a power steering mechanism 16 that assists the steering of t against the urging force of the rear wheel turning angle urging means 17d.

In addition to the four-wheel steering system having the above configuration, the power steering mechanism 16 has a communication passage 53 that communicates both pressure chambers 17b and 17C of the power cylinder 17, and a passage area of the communication passage 53 is variable. valve means 54 for regulating;
Valve control means 1 that controls the valve means 54 so that the passage area of the communication passage 53 gradually increases toward the maximum area when the actuator control means 117 malfunctions.
18 is provided.

(Function) Therefore, in the present invention, with the above configuration, when the actuator control means 117 is operating normally while the vehicle is driving, both pressure chambers 17b and 17c of the power cylinder 17 are closed due to the non-operation of the valve means 54. Without communication, the rear wheels 2L and 2R of the vehicle are steered while being assisted by the output of the power cylinder 17, thereby performing four-wheel steering.

On the other hand, if the actuator control means 117 does not operate normally due to a disconnection of the cover or a disconnection of the harness, the valve control means 118
An actuation signal is output to the valve opening operation th of the valve means 54.
Both pressure chambers 17b, 17 of the power cylinder 17 are
C communicate with each other via the communication path 53, and the assist 1- function disappears, thereby substantially reducing the rear wheels 2L and 2+.
? is the steering angle θR due to the urging force of the rear wheel steering angle urging means 17d.
is fixed at a neutral position where θR-0, and the vehicle is maintained in a two-wheel steering state. Therefore, unstable four-wheel steering conditions are avoided, and driving safety can be further improved accordingly.

At that time, the valve means 54 is controlled by the valve control means 11.
8, the passage area of the communication passage 53 is adjusted to the maximum value in a R-regular manner while gradually opening the valve. For this reason, the transition from the four-wheel steering state to the two-wheel steering state of the vehicle is performed gradually, thereby eliminating the discomfort felt by the occupant.

(Example) Hereinafter, an example of the present invention will be described based on the drawings from FIG. 2 onwards.

In Figures 2 and 3, IL, IR, 2L, 2R
has four heavy wheels, and the left and right front wheels IL and 1R are controlled by 1) 0-wheel steering mechanism 3, and the left and right rear wheels 2L and 2R
are linked to each other by a rear wheel steering mechanism 12.

The front wheel steering mechanism 3 includes a pair of left and right knuckle arms 4L.
, 4R and tie rods 5L, 5R, and a relay rod 6 that connects the left and right tie rods 5L, 5R.
It consists of Further, a steering wheel 10 is linked to the front wheel steering mechanism 3 via a rack and pinion type steering mechanism 7. That is, the relay rod 6 is formed with a recess 8, while the lower end of the steering shaft 11, which is connected to the steering wheel 10 at its upper end, is fitted with a pinion 9 that engages with the rack 8. In response to the operation of the wheel 10, the left and right front wheels 1 are turned and the IR is steered.

On the other hand, similar to the front wheel steering mechanism 3, the above-mentioned 1st steering modification 12 includes left and right knuckle arms 13'L, 13th and ties 14L, 14R, the tie rod 14L,
It has a relay rod 15 that connects the '14Rs together, and is further provided with a hydraulic power steering mechanism 16. The power steering mechanism 16 includes a power cylinder 17 that is fixed in the middle and has the relay rod 15 as a screw-on rod, and inside the power cylinder 7 is a piston 17a that is integrally attached to the relay rod 15. The hydraulic pressure chambers 17b and 17C in the cylinder 17 are respectively connected to the control valve 2o via passages 18.19. Further, two passages, an oil supply passage 22 and an oil discharge passage 23, leading to a reserve tank 21 are connected to the expansion control valve 20, and the oil supply passage 22 is connected to a hydraulic pump 2 driven by an on-vehicle engine (not shown).
4 are arranged. The control valve 20 is
The valve casing 20a, which is a known spool valve type, has a cylindrical shape and is integrally attached to the relay rod 15 via a connecting member 25, and the valve casing 20a shown in the figure is fitted into the valve casing 2Oa. According to the movement of the spool valve, pressure oil from the hydraulic pump 24 is supplied to one hydraulic chamber 17b (17c) of the power cylinder 17, and the relay rod 15
This assists the driving force for the vehicle. In addition, the relay rod 15 is placed in the power cylinder 17 at the neutral position (the position where the steering angle θR of the rear wheels 2L and 2R is zero).
A return spring 176.17d attached to the rear wheel steering angle biasing means 9A is compressed.

The relay rod 6 of the front wheel steering mechanism 3 is equipped with a rack 2 other than the rack 8 constituting the steering mechanism 7.
6 is formed, and a binion 27 attached to the front end of a rotating shaft 28 extending in the longitudinal direction of the vehicle body is engaged with the rack 26, and the rear end of the rotating shaft 28 is connected to the rear wheel steering via a steering ratio control mechanism 29. It is linked to mechanism 12.

As shown in FIG. 4, the steering ratio control mechanism 29 includes a control rod 30 that is slidably held on a movement axis 91 in the vehicle width direction with respect to the vehicle body.
One end of the roll rod 30 is connected to the control valve 20.
is connected to the spool valve. Further, the steering ratio control mechanism 29 has a base end attached to a U-chamber-shaped boulder 31 and a support bin 32.
A swing arm 33 is swingably supported via the swing arm 33,
The holder 31 is rotatably supported by a casing 34 fixed to the vehicle body via a support shaft 35 having a rotation axis 92 orthogonal to the movement axis It of the control rod 30. The support pin 32 of the swing arm 33 is located at the intersection of the two axes U+ and 92, and the pivot axis Jl! '
extends in the direction perpendicular to Iz, and by rotating the holder 31 around the support shaft 35 (rotation axis 92), the inclination between the support pin 32 at its tip and the movement axis IQ+ of the control rod 30 The corner, that is, the swing locus plane of the swing arm 33 centered on the support pin 32 is the movement axis Q1.
The angle of inclination made with respect to a plane perpendicular to the plane (hereinafter referred to as a reference plane) is changed.

Further, one end of a connecting rod 37 is connected to the distal end of the 1ffl moving arm 33 via a ball joint 36, and the other end of the connecting rod 37 is connected to the control rod 30 via a ball joint 38. The control rod 30 is connected to the other end, and the control rod 30
is adapted to be displaced in the left and right direction.

The connecting rod 37 is slidably supported by the rotation imparting arm 40 via the ball joints 1 to 41 at a portion thereof close to the ball joint 36 .

This rotation imparting arm 40 includes a large-diameter heavy arm lI43 rotatably supported on the movement axis 9+ via a support shaft 42.
It is provided integrally with the umbrella 6N! As shown in FIG. 3, a bevel gear 44 attached to the rear end of the rotating shaft 28 is meshed with the bevel gear 43, so that rotation of the steering wheel 10 is transmitted to the rotation imparting arm 40. Therefore, the suspension rotation imparting arm 40 and the connecting rod 37 rotate around the movement axis R+ according to the rotation angle of the steering wheel 10, and accordingly, the swing arm 3
3 is swung around the support pin 32, the bottle 3
When the axis 2 coincides with the movement axis 91 of the control rod 30, the ball joint 36 at the tip of the swing arm 33 only swings along the axis 1i described above, and the control rod 30 is held stationary. If the axis of the bin 32 is inclined with respect to the movement axis 91 and the swing locus plane of the 3ffi swing arm 33 deviates from the reference plane, the ball joint will move as the swing arm 33 swings around the bin 32. The control rod 36 is displaced in the left-right direction in FIG.
and the control rod 30 moves along the movement axis 91.
The control valve 20 is configured to move along the control valve 20 to operate the spool valve of the control valve 20. That is,
Even if the swing angle of the swing arm 33 about the axis of the bin 32 is the same, the left-right displacement of the control arm 30 is the same as the tilt angle of the bin 32, that is, the rotation angle of the holder 310. Change with change.

In order to change the inclination angle of the support pin 32 with respect to the movement axis 91, that is, the inclination angle of the holder 31 with respect to the reference plane, the support shaft 35 of the holder 31 is equipped with a worm wheel as shown in FIG. A sector gear 45 is attached, and an A-mugia 47 on the rotating shaft 46 is meshed with this sector gear A745. Further, a bevel gear 48 is attached to the rotating shaft 46, a bevel gear 49 is meshed with the bevel gear 48, and the bevel gear 49 is connected to the rear wheel 2L.
, 2R is mounted on the output shaft 50a of a stepping motor 50 as an actuator for controlling the steering angle θR, and by operating the stepping motor 50 and rotating the sector gear 45, the steering angle θR of the holder 31 is The tilt angle is changed to control the steering angle 0 of the rear wheels 2L and 2R, and the sector gear 45 is adjusted so that its center line is aligned with the worm gear 4.
Neutral position e perpendicular to the center line of the rotating shaft 46 of No. 7 (at this time, the pole join i to 36 at the tip of the swing arm
rotates on the reference plane, and the steering angle θR of rear wheels 2L and 2R is θR.
= 0) in the clockwise direction in Figure 5, the steering ratio between the front and rear wheels 1L and 2L (IR, 2R> (rear wheel steering angle OR/front wheel steering angle θF) 2 L l
2R is controlled in the opposite phase so that it points in the opposite direction to the front wheels IL and IR, but when the wheels are rotated counterclockwise, the steering ratio is controlled so that the rear wheels 2L and 2R are in the same direction as the front wheels 1L and IR. The configuration is such that control is performed so that they are in the same phase as each other.

Furthermore, the casing 34 that supports the holder 31 includes:
Stopper members 51 and 52 on the opposite phase side and the same phase side, which are made of pins that restrict the rotation range of the sector gear 745, are attached to the left and right sides of the sector gear 45, as shown in the lower part of FIG. When the sector gear 45 rotates toward the opposite phase side, when the rotation angle from the neutral position reaches, for example, -17°5', the sector gear 45 comes into contact with the opposite phase side stopper member 51 and is prevented from rotating further. On the other hand, when the sector f V45 rotates toward the same phase side, when the rotation angle from the neutral position reaches, for example, 20 degrees, the sector gear 45 comes into contact with the stopper member 52 on the same phase side and the movement is restricted. It is made to be done. The control position of the stepping motor 50 when the sector pin t45 comes into contact with the stopper member 51 on the opposite phase side is set as its initial position.

On the other hand, both independent pressure chambers 17b and 17C of the power cylinder 17 in the power steering mechanism 16 are connected to the hydraulic chamber 17.
Connecting path 5 in the middle of the path 18゜19 connected to b, 17c
3, and the communication passage 53 is provided with both internal pressure chambers 1 of the power cylinder 17 by variably adjusting the passage area of the communication passage 53.
A proportional solenoid valve 54 is provided as a valve means for controlling communication or blocking of 7b and 17c.

This proportional solenoid valve 54 has a plunger 54a (valve body') whose movement stroke (valve opening period) changes depending on the ON duty ratio change of the input rectangular wave signal,
When the ON duty ratio of the input signal is 100%, the plunger stroke is zero to fully close the communication passage 53, but when the ON duty ratio decreases toward 0%,
Accordingly, the stroke of the plunger 11 is increased to gradually open the communication passage 53. In addition, in FIG. 3, 39 is a rod stopper that restricts the maximum movement range of the relay rod 15 in the rear wheel steering mechanism 12.

As shown in FIG. 6, the stepping motor 50 and the proportional solenoid valve 54 are equipped with a built-in microcomputer that operates using battery power supplied as a system power supply when the vehicle's ignition key switch (not shown) is turned on. The operation is controlled by a control unit 100, and a detection signal from a vehicle speed sensor 101 that detects the traveling speed of the vehicle +ffi S PD is input to the control unit 100.

The internal configuration of the control unit 100 will be described with reference to FIG. 7. The control unit 100 includes a CPL 1102 as a control section and a ROM 103 that stores predetermined control data. Constant voltage circuit 10 that maintains voltage
C)) U
CPU running detection section 105 that detects the tightening of 102, output voltage detection section 106 that detects that the output voltage Vcc has decreased to 4.5V or less, and power-on section that outputs a relet signal when the ignition key switch 117 starts to be turned on. It is reset in response to each output from the reset unit 107.

Further, the output signal of the vehicle speed sensor 101 is input to an integral filter 109 via an interface 108, and after chattering is removed by the filter 109, the signal waveform is shaped by a waveform shaping circuit 110 and then supplied to the CPU 102. .

Furthermore, the control unit 100 includes a CPU 102
It has a stepping motor driver 111 that drives the stepping motor 50 based on the output of the driver 111, and an operating state detection interface 112 that detects the operating states of the driver 111 and the motor 50 based on the output of the driver 111. , in response to a current down command signal from the CPU 102, the output current from the battery power supply to the stepping motor 50 is set to 100IIIA for each phase during non-ti control of the motor 50 (when the rotation of the motor output @ 50a is stopped). It has a curve 1 to a down part 113 that limit the flow.

The control unit 100 also includes the CPU 1
02; A lamp driver 115 is provided that receives an output from the CPU 102 and turns on a warning lamp 116 when an open failure, short circuit failure in the motor control system, harness breakage, cover removal, etc. occur.

Here, further, C of the control unit 100 is
The signal processing procedure performed in the PU 102 will be explained based on FIGS. 8 to 11.

FIG. 8 shows the main routine of the signal processing program. After starting by turning on the ignition key switch 117, first, the system is initialized in step s1, and a system check is performed in the next step s2. This system check is performed using the stepping motor 50 mentioned above.
This is to check whether the control system is in a normal state or not, and is processed according to the subroutine shown in FIG.

That is, in the first step S3, the output of the current down command signal to the current down section 113 is canceled, and the motor failure determination flag F2ws is set to FzWS.
=Reset to O. This motor failure determination flag F2W
S is reset to F2WS=O when the control system for the stepping motor 50 is in a normal state, but when an abnormality occurs in the control system due to a failure of the motor 50, in other words, the proportional solenoid valve 54 17 internal pressure chambers 17b, 17c are communicated with each other to connect the rear wheels 21-. When it is necessary to maintain 2R in a state where the steering angle θR is θR=O and maintain the vehicle in a normal two-wheel steering state, F2WS=1 is set. After that, in step S4, a signal is output to keep all the excitation phases of the stepping motor 50 in the ON state (excitation state),
Next, after a certain period of time has elapsed in step S5, the excitation state of the motor excitation phase is monitored by the operating state detection ink face 112 in step s6, and it is determined in the next step S7 whether all the excitation phases are at Lo level or not. . If this determination is YES, all excitation phases for the stepping motor 5o are turned off in step 866.
Outputs a signal to maintain the FF state (excitation release state), waits for a certain period of time to pass in step S, and then returns to step S.
At +o, the excitation state is monitored in the same manner as in step S6 above, and at step So, it is determined whether all the excitation phases are at the 1-1i level. When this determination is YES, it is assumed that the control system is in a normal state, and after resetting the excitation state and current down command state for the stepping motor 5o in step S12, the next step S +s of the above main routine is performed. to return to.

On the other hand, if the determination in step S7 is NO, it is assumed that there is an open failure of the drive transistor in the stamping motor driver 111, and if the determination in step Sn is NO, the motor 50 and the control unit 100 are In any case, it is determined that the control system is abnormal, and the process proceeds to step S13, where the current number of steps MP of the stepping motor 50 is set to the target step C.
P, the operation of the motor 50 is stopped, the warning lamp 116 is turned on, and the next step S
In step 14, the flag F2ws@F2ws=1 is set to communicate the two internal pressure chambers 17b and 17c of the power cylinder 17, and thereafter steps S+a and SI4 are repeated. The above target step number CP is determined by the stepping motor 5
The control initial position of 0, that is, the position where the sector gear 45 is in contact with the opposite phase side stopper member 51 and the steering ratio is the maximum steering ratio on the opposite phase side, is set as CP=0, and from there the motor 5
0 indicates the number of steps of the pulse signal input to the motor 50 when controlling the target control position, and the current step aMP indicates the number of steps of the current control position of the motor 50 from the control initial position. This shows that.

After completing such a system check, the main routine proceeds to step S+s in J3, where the current step number MP of the stepping motor 50 is set to MP=O.
The target step number CP is set to CP=-580, and the flag F1 is set to F1=1, indicating that the motor position initialization control mode is not executed. Above flag E
1 is set to F1=1 after the motor position initialization control mode in which the motor 50 is controlled to initialize its control position; When tll'E-do, F1 is reset to 0.

After that, proceed to step S + c, perform a system check in the same manner as step S2 above, and then proceed to step S + y.
It is determined whether the flag F1 is F+=1 or not. When this determination/J'FI=1 is YES, that is, when performing the position initialization control mode of the motor 50, the process advances to step S+s to determine whether the target number of steps CP for the motor 50 is equal to the current number of steps MP. If the determination is No for CPf-MP, the process directly returns to step S+6. Also, the judgment is CP-M
When the initialization of the control position of the motor 50 is completed by YES in P, the process advances to step S+s, and the target step number CP and current step number MP of the sweater 50 are set to CP-M.
P-0, reset the flag F1 to 1-O, and set the flag F2 to F2-1 to identify that the initialization of the control position of the motor 50 has been completed once. Return to step S+s above.

On the other hand, the determination in step S17 is F+ -0.
When the motor 50 is controlled to change the steering ratio at step O, the process proceeds to step Si, where it is determined whether the vehicle speed SPD detected by the vehicle speed hinter 101 is in a stopped state fi of 5PD-0, and this determination is made. is YES, step 8
At 2+, it is further determined whether the flag F2 is F2-0.

Then, the determination in step S21 is that N of F2=1
If the determination is 0, the process returns to step S+6, but if the determination is YES (F2=0) and the initialization of the control position of the motor 50 is not being executed when the vehicle is stopped, the flag F1 is set to F1 in step 822. = 1, and in the next step 823, the target step number C of the motor 50 is set.
After setting P to CP--580 corresponding to the initial control position, the process returns to step S+s.

Also, if the determination in step 820 is 5PD-^O, then
If it is O, the process proceeds to step S24, where the detected vehicle speed SPD is set in advance according to the vehicle speed and stored in the ROM 103.
The target step number CP of the motor 50 is set to the target step number CP=f (SPD) corresponding to the actual vehicle speed SPD, and both of the above flags F+ are set in the next step Sδ. , F2 are both reset to F+ = F2 = 0, and then the above step S
Return to +a.

The control data table stored in the ROM 103 shows that the steering ratios of the front and rear wheels 1L, 2L (IR, 2R) change according to the vehicle speed SPD, as shown in FIG.
When the speed SPD is low, the rear wheels 2L and 2R are steered in the opposite direction and in the opposite phase to the front wheels IL and IR in order to improve the lateral direction of the vehicle, thereby increasing the steering ratio. On the other hand, when the vehicle speed SPD reaches approximately 67 km/h, for example, the steering ratio becomes zero, and the steering angle θR of the rear wheels 2L and 2R becomes θR=O regardless of the steering of the front wheels IL, IR. is maintained, and the vehicle enters the normal two-wheel steering state. Furthermore, when driving at high speeds, the rear wheels 2L and 2R are rotated in the same direction as the front wheels IL and 1R, that is, in the same phase, in order to improve the vlip force of the rear wheels 2L and 2R during cornering and increase driving stability. The steering ratio is set to be positive.

Further, FIG. 10 shows a first interwoven routine that interrupts the main routine when the time set in the timer built in the CPU 102 has elapsed. In the first step S30, it is determined that the target step number CP of the motor 50 is equal to the current step number MP. When this determination is YES for CP-MP, that is, when the output of the pulse signal to the motor 50 is unnecessary and the motor 50 can be maintained at its controlled position, the process advances to step S31 and the control signal 1-
By outputting a down command signal to the current down unit 113, the voltage applied to the motor 50 is lowered to suppress the amount of heat generated, and then, in step SI, the above-mentioned timer is set to prevent the next interrupt processing from occurring, and then the above-mentioned main routine is executed. Return to the step after the interrupt in .

Also, if the determination in step 830 is NO for CP+MP,
If so, the process proceeds to step 832 to cancel the output of the current down command signal to the current down section 113, and then proceeds to step 833 to cancel the output of the current down command signal to the current down section 113.
The magnitude relationship between the target number of steps CP of 0 and the current number of steps MP is determined. If this determination is YES (CP>MP), the process proceeds to step 834, where the excitation phase is switched so that the motor 50 moves by one step in the same phase direction of the steering ratio, and then, in step 835, the current step aMP
After updating to MP4-MP+1, perform the above step 83+
Move to 1. On the other hand, the determination in step SfJ above is CP<
If MP is No, the process proceeds to step 5-13, where the excitation phase is switched so that the motor 50 moves by one step in the opposite phase direction of the steering ratio, and in step 837, the current step number MP is changed to MP(MP- After updating to 1, the process moves to step 8311 described above.

Furthermore, similarly to the first included routine, FIG. 11 shows a valve control program that interrupts the main routine when the time T set in the timer built in the CPU 102 has elapsed. 3 shows a second included routine.

In this routine, in the first step Sao, it is determined whether the morph failure determination flag F2WS is F2WS=1, that is, whether or not there is an abnormality in the control system that should maintain the vehicle in a two-wheel steering state. This judgment is N of F2WS-0
o, the process proceeds to step S41, outputs an ON signal to the proportional solenoid valve 5/I, resets the counter CNT to CNT=0, and further sets the time T to T.
= 10,000 .mu. seconds, the timer is set to the time T (.mu. seconds) in step 85G, and then the process returns to the step after the interruption of the main routine.

On the other hand, the determination in step Sao is YES for FzWS-1.
In step S42, the counter CNT
It is determined whether or not CNT<100, and the determination is Y.
In the case of ES, it is further determined in step S43 whether or not the proportional solenoid valve 54 is in the ON state. If this determination is YES, the process proceeds to step S44, where an OFF signal is output to the proportional solenoid valve 54,
Next, in step S46, "1" is added to the counter CNT to update it to CNT+1, and then in step S846
The coefficient 1 for time conversion to that new counter CNT with
Multiply by 00 and get 1 in the above case! ? The IT-CNTX 100 is operated, and then the process moves to step Sso, where the timer is set to the time T (=CNTx100) μ seconds.

If the determination in step S4:I is No due to the OFF state of the proportional solenoid valve 54, the process proceeds to step S47, where an ON signal is output to the valve 54, and the counter CN is turned on in the next step S48. constant 10
Add the above time conversion coefficient 10 to the value 10O-CNT subtracted from 0.
The time T=100x (100-CNT) is calculated by multiplying by 0, and then the process moves to step Sso described above.

That is, by repeating steps S43 to S48 and sSO, 1 is output to the proportional solenoid valve 54.
The ON duty ratio of the square wave signal of 001-12 is 100.
% to 0%. and,
Through this process, the counter CN number becomes CNT-10.
If the determination at step 842 is NO, the process proceeds to step 841, where the above time T is set to T == 1000.
Set it to 0 μs and turn the proportional solenoid valve 54 to O.
After outputting a signal that maintains the FF state, that is, the fully open state, the process proceeds to step 5riJ, and thereafter, step 8
Repeat ao, 5cSu, Sso.

Therefore, step S+ in the above main routine! J
, S24 and steps 830 to $30 in the first included routine, the stepping motor 50 as an actuator is adjusted based on its control initial position i(
Motor control means 11 configured to stop and actuate 911
7 is composed.

In addition, in steps 8@, 842 to 850 in the second interaction 1-routine, when the motor control means 117 operates abnormally (motor failure determination flag F2WS
A valve control means 118 is configured to control the proportional solenoid valve 54 so that the passage area of the communication passage 53 gradually increases toward the maximum area when ``1'' is set.

Next, the operation of the above embodiment will be explained.

First, when an ignition key switch is turned on to drive a vehicle that is out of service, a system check is performed accordingly.

P When the control system for the stepping motor 50 is in a normal state, the control unit 100 outputs a 580-step pulse signal to the stepping motor 50 to operate the motor 50, and the operation of the motor 50 reverses the sector gear ψ45. The sector gear 1745 rotates in the phase direction (clockwise direction in Figure 5).
The motor 50 is brought into contact with the stopper member 51 on the opposite phase side.
The control initial position of is determined.

After such positioning of the motor 50, when the vehicle shifts to a running state, the next vehicle speed SPD is detected by the vehicle speed sensor 101.
A detection signal is output from the vehicle speed sensor 101 to the control unit 100, and the CPU 102 outputs a steering ratio corresponding to the vehicle speed SPD. The pulse signal is output to the motor 50 and the motor 50
is activated. Due to the operation of this motor 50, the sector gear r4
5 is rotated, and the rocking locus plane of the rocking arm 33 connected to the sector gear 45 is tilted with respect to the reference plane, and this change is linked to the operation of the steering wheel 10, that is, the steering of the front wheels IL and IR. and move 4111 jlQ
J) The moving direction and moving distance of the control rod 30 change with respect to the movement of the connecting rod 37 that rotates in the + direction, and according to the movement of the control rod 30, the rear wheels 2L and 2R change the above calculation with respect to the front wheels IL and IR. The vehicle is steered while being assisted by the power cylinder 17 of the power steering mechanism 16 so that the predetermined steering ratio is achieved. As a result, the four wheels of the vehicle, 1st wheel, 1st wheel
, 2L, and 2R are controlled so that the steering ratios are in opposite phases when the speeds are low and medium, and the steering ratios are in the same phase when the vehicle speeds are high.

On the other hand, as a result of the system check, if the control system for the motor 50 is in an abnormal state due to a failure or short circuit failure in the stepping motor driver 111, control of the motor 50 is stopped, and the warning lamp 116 is turned on instead. At the same time, an ON duty ratio control signal is output to the proportional pressure valve 54, and the valve 54 is finally switched to the quantity valve state, thereby reducing both oil pressures of the power cylinder 17! 17b, 17cIfi communication path 5
3. Therefore, the assist force for rear wheel steering of the power cylinder 17 is lost, and the rear wheels 2L, 2
R is a return spring 17d without being substantially steered;
The biasing force 17d holds the steering angle θR at the neutral position where 0R=O. As a result, the vehicle has its front wheels IL, I
The vehicle is fixed in a normal two-wheel steering state in which only R is steered, and the running safety of the vehicle can be improved.

Also, at this time, the proportional solenoid valve 54 gradually opens over time due to the gradual decrease in the ON duty ratio of the control signal to the valve 54, so that the vehicle can be switched from a four-wheel steering state to a two-wheel steering state! This will be done on one ship at a time, so the crew will not feel any discomfort.

Further, while driving the vehicle as described in E, when the vehicle stops running and the vehicle speed S P D /) (S P D = 0), the system is checked and the motor 50 is returned to the initial control position in the same manner as described above. positioning is performed.

In the above embodiment, the front and rear wheels 1L and 1R of the vehicle.

Although the case where the present invention is applied to a four-wheel steering system in which the steering ratios of 2L and 2R are variably controlled according to the vehicle speed SPD has been exemplified,
The present invention has a rear wheel! The present invention can also be applied to a four-wheel steering system in which the actuator directly drives the vehicle according to the vehicle speed and the front wheel steering angle.

(Effects of the Invention) As explained above, according to the present invention, four wheels of a vehicle are provided, in which the steered wheels are steered by operating the steering wheel, and the steering of the rear wheels is assisted by the power steering mechanism. In a wheel steering system, when the actuator control means that controls the steering angle of the rear wheels is malfunctioning, both pressure chambers of the power cylinder in the power steering mechanism are gradually brought into communication with each other, and the rear wheel steering angle is finally brought to zero. By locking and holding the two wheels, when the control means malfunctions, the vehicle can be automatically locked into the normal two-wheel steering state without giving the occupants a sense of discomfort due to a sudden change in steering characteristics. Safety can be further improved.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of the present invention. 2 to 12 show embodiments of the present invention, in which FIG. 2 is a plan view showing a schematic configuration of a four-wheel steering system, FIG. 3 is a schematic perspective view of the same, and FIG.
The figure is a vertical view of the steering ratio III control mechanism, and FIG. 5 is an explanatory diagram showing the sector gear V rotation range regulated by the stopper member. Fig. 6 is an explanatory diagram showing the connection status of each device to the control unit, Fig. 7 is a block diagram showing the internal configuration of the control unit, and Fig. 8 is a diagram showing the connection status of each device to the control unit. Figure 9 shows a flowchart p-1 showing the main routine for checking the same system.
- Figure 10 is a flowchart showing the included routine for controlling the motor, Figure 11 is a flowchart showing the included routine for controlling the valve, and Figure 12 is stored in the ROM. FIG. 3 is a characteristic diagram showing a control data table in which IL, IR...Front wheel, 2L, 2R...Rear wheel, 3...
・Front wheel steering mechanism, 7... Steering mechanism, 10...
・Steering wheel, 12... Rear wheel steering mechanism, 1
6... Power steering mechanism, 17... Power cylinder, 17b, 170... Hydraulic chamber, 17d... Return spring, 20... Control valve, 2
9... Steering ratio control mechanism, 30... Control rod, 33... Swinging arm, 37... Connecting rod, 40... Rotation imparting arm, 50... Stepping motor, 53...・Communication path, 54...Proportional solenoid valve, 100...Control, 1 nit,
1o1...Vehicle speed sensor, 102...CPU1103
...ROM1117...Motor control means, 118.
...Valve control means. -2~ Patent application person Mazda Motor Corporation agent
1) Hiroshi--' 1st Zuden (Ken Iiv!r) 2nd drawing 3rd figure 5 glossy figure 8th figure 9th figure 1o figure 11th! ¥1

Claims (1)

[Claims] (1) A four-wheel steering device for a vehicle that steers the front and rear wheels according to the operation of a steering wheel, including a front wheel steering mechanism that steers the front wheels and a rear wheel steering mechanism that steers the rear wheels. an actuator that controls a rear wheel steering angle via the rear wheel steering mechanism; an actuator control means that controls the operation of the actuator; and an actuator that is linked to the rear wheel steering mechanism so that the rear wheel steering angle becomes zero. It has a rear wheel steering angle biasing means for biasing the rear wheel steering angle as shown in FIG. a power steering mechanism that assists against the pressure, and a communication path that communicates both pressure chambers of the power cylinder in the power steering mechanism;
A valve means for variably adjusting the passage area of the communication passage; and a valve control means for controlling the valve means so that the passage area of the communication passage gradually increases toward a maximum area when the actuator control means malfunctions. A four-wheel steering device for a vehicle, characterized by comprising: