JPH03292264A - Rear wheel steering control device for vehicle - Google Patents

Abstract

PURPOSE:To reduce the roll angle of a car body and swing back of a car body by means of a roll during cornering by varying and controlling a target steering angle ratio to a second steering angle ratio having a tendency for iso-phase steering control. CONSTITUTION:A vehicle on which a suspension device 1 having an orientation control means 1a to control orientation of a car body during cornering of a vehicle is mounted is provided with a steering angle ratio setting control means 4 which decides a first steering angle ratio, changed throughout a range of from an opposite phase to an iso-phase with the increase of a car speed detected by a car speed detecting means 3, as a target steering angle ratio, and sets and controls a steering angle ratio, set by a rear wheel steering mechanism 2, to a target steering angle ratio. In a so formed device, abnormality of an orientation control means 1a is detected by an abnormality detecting means 5. A steering angle ratio setting control means 4 is controlled by a correction control means 6 so that, when abnormality of the orientation control means 1a is detected, a second steering angle having a tendency for iso-phase steering control compared with a first steering angle ratio is decided as a target steering angle ratio instead of a first steering angle ratio.

Description

[Detailed description of the invention] [Industrial application field]

The present invention is applied to a vehicle equipped with a suspension device having an attitude control means for controlling the attitude of the vehicle body when the vehicle turns, and controls the steering of the rear wheels from the opposite phase to the front wheels depending on the vehicle speed. The present invention relates to a rear wheel steering control device for a vehicle.

[Prior Art 1] Conventionally, the vehicle has been equipped with a rear wheel steering mechanism that can steer the rear wheels in conjunction with the steering of the front wheels and can change and control the steering angle ratio of the rear wheels with respect to the front wheels from opposite phase to in-phase. A steering angle ratio that changes from the opposite phase to the same phase as the vehicle speed increases is determined as a target steering angle ratio, and the steering angle ratio set by the rear wheel steering mechanism is set to the determined target steering angle ratio. There is a known rear wheel steering control device that controls the same rear wheel steering mechanism to improve the maneuverability and tight turning performance of the vehicle when driving at low speeds, as well as the running stability of the vehicle when driving at high speeds. . (For example, see Japanese Patent Application Laid-open No. 62-8870.) On the other hand, the load sharing of each wheel is controlled according to the front wheel steering angle and the vehicle speed (more load sharing on the outer wheel side of the turning), and the posture of the vehicle body when turning is controlled. There is also known a suspension device that has attitude control means for controlling the . (For example, see Japanese Patent Application Laid-Open No. 11408/1983.) [Problem to be Solved by the Invention 1] However, when the above-mentioned rear wheel steering control is performed in a vehicle equipped with the above-mentioned suspension device, the above-mentioned If the attitude control means in the suspension system is normal, even if the rear wheels tend to steer in a reverse phase relative to the front wheels, the attitude control means will maintain the attitude of the vehicle, so there will be no problem with vehicle rolling. An abnormality occurs in the attitude control means, and the attitude of the vehicle body when the vehicle turns is I1.
1, the following problems occur regarding the rolling. That is, when the vehicle turns, the vehicle body rolls and a roll angle is generated depending on the turning radius and vehicle speed. - On the other hand, if the reverse steering tendency of the rear wheels with respect to the front wheels is increased, the turning performance and small turning performance of the vehicle are improved, and as a result, the turning radius of the vehicle is reduced, and as a result, the roll angle is increased. As a result, the roll of the vehicle causes large alternating left and right rocking of the vehicle body while the vehicle is turning, resulting in a problem that the ride quality of the vehicle is not good. The present invention has been made to solve the above problem, and its purpose is to improve the ride quality of the vehicle even if the posture control means in the suspension device malfunctions and the posture of the vehicle body is no longer controlled when the vehicle turns. To provide a rear wheel steering control device for a vehicle that prevents deterioration of the vehicle's rear wheel steering. [Means for Solving the Problems] In order to achieve the above object, the structural features of the present invention are as follows:
As shown in FIG. 1, it is applied to a vehicle equipped with a suspension device 1 having an attitude control means 1a that controls the attitude of the vehicle body when the vehicle turns, and the rear wheels RW1i: is steered in conjunction with the steering of the front wheels FW. Front wheel F of the rear wheel RW
a rear wheel steering mechanism 2 capable of changing and controlling a steering angle ratio with respect to W from opposite phase to in-phase; vehicle speed detection means 3 for detecting vehicle speed; and changing from opposite phase to in-phase as the detected vehicle speed increases. A steering angle ratio setting control means 4 that determines a steering angle ratio of xi as a target steering angle ratio and controls the steering angle ratio set by the rear wheel steering mechanism 2 to be set to the target steering angle ratio. The rear wheel steering control device includes an abnormality detection means 5 for detecting an abnormality in the attitude control means 1a, and an in-phase steering control in comparison with the first steering angle ratio when the abnormality detection means 5 detects an abnormality in the attitude control means 1a. A correction control means 6 is provided for controlling the steering angle ratio setting control means 4 so as to determine the second steering angle ratio, which is on the trend, as the target steering angle ratio instead of the first steering angle ratio.

[Action of the invention]

In the present invention configured as described above, the attitude control means 1a in the suspension device 1 is operating normally,
When the abnormality detection means 5 does not detect an abnormality in the means 1a, the steering angle ratio setting control means 4 sets the first steering angle which changes from the opposite phase to the same phase in accordance with the increase in the vehicle speed detected by the vehicle speed detection means 3. The ratio is determined as the target steering angle ratio, and the steering angle ratio set in the rear wheel steering mechanism 2 is controlled to be set to the target steering angle ratio. In such a case, the attitude of the vehicle body is determined by the attitude control means 1.
a, the rear wheel steering mechanism 2 steers the rear wheels RW to the set and controlled target steering angle ratio (first steering angle ratio) in conjunction with the steering of the front wheels FW. Even if the reverse phase steering tendency for the front wheels FW increases, that is, even if the turning ability and small turning performance of the vehicle are increased and the turning radius of the vehicle is reduced, the roll angle and rolling of the vehicle body during turning do not increase. On the other hand, when the attitude control means 1a becomes abnormal and the attitude of the vehicle body is no longer controlled when the vehicle turns, the correction control means 6 responds to the abnormality detection by the abnormality detection means 5 and the steering angle ratio setting control means 4 is controlled to change the target steering angle ratio determined by the same steering angle ratio setting control means 4 to a second steering angle ratio that tends to be in phase steering control compared to the first steering angle ratio. The RW is controlled to be steered so that the in-phase tendency increases compared to the above case. As a result, the roll angle of the vehicle body during turning becomes smaller, and the amount of rolling of the vehicle body due to the roll also becomes smaller.

【Effect of the invention】

As can be understood from the above description of the operation, according to the present invention, when the attitude control means 1a is normal, the steering control of the rear wheels RW maintains good turning performance and small turning performance of the vehicle, and at the same time, the attitude control means 1a maintains the vehicle body. The attitude is kept stable, and when the attitude control means 1a is abnormal, the amount of steering of the rear wheels RW by the rear wheel steering mechanism 2 is controlled so that the in-phase tendency increases, thereby preventing rolls and rocking of the vehicle body when the vehicle turns. As a result, the steering function of the rear wheels RW is utilized as much as possible, and the ride comfort of the vehicle is always kept good.

【Example】

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. FIG. 2 schematically shows the entire vehicle according to the present invention. This vehicle has each wheel FWI, FW2. Suspension mechanisms A1 to A4 are provided between RWI, RW2 and the vehicle body BD to support the vehicle body BD. As shown in FIGS. 2 and 3, the suspension eye mechanism A1 for left front wheel FWI is rotatably connected to the vehicle body BD at one end and rotatably connected to the knuckle arm 11 at the other end. The suspension arm 15 connects the left front wheel FWI to the vehicle body BD via the knuckle arm 11. This suspension arm 15 and the upper end of the vehicle body B
A spring 25 is interposed between the supporting member 21 which is rotatably connected to the support member 21, and a piston 35 is fixed to the upper end of the rod 31 whose lower end is rotatably connected to the suspension arm 15. A hydraulic cylinder 41 serving as an actuator is installed, and the vehicle body BD is supported with respect to the suspension arm 15 by the hydraulic pressure within the cylinder 41 and the elastic force of the spring 25. Further, the suspension mechanisms A2 to A4 for the right front wheel FW2 and the left and right rear wheels RWI and RW2 also include knuckle arms 12 to 14, suspension arms 16 to 18, springs 26 to 28, and rods 32 to 32, similarly to the suspension mechanism A1. 34, pistons 36 to 38 and hydraulic cylinder 42
44, respectively, and support the vehicle body BD. A pressure control valve 4 is provided in each oil chamber of the hydraulic cylinders 41 to 44.
5 to 48 are connected respectively, and each valve 45 to 4
8 is connected to a hydraulic pump P1 at each supply boat and to a reservoir R1 at each discharge boat, and maintains and controls the working oil pressure in each of the hydraulic cylinders 41 to 44 at a value corresponding to an input control signal. In addition, each hydraulic cylinder 41
- 44 and each pressure control valve 45-48, and each oil passage communicating with reservoir R1, electromagnetic switching valves 51-54 are interposed, respectively. Each of the electromagnetic switching valves 51 to 54 is set in a first state by a spring in a non-energized state to communicate between the respective oil passages, and is set in a second state (the state shown in the figure) in an energized state to allow communication between the respective oil passages. Prohibit communication between roads. The vehicle also includes a front wheel steering mechanism B1 that steers the left and right front wheels FWI and FW2, and a rear wheel steering mechanism B2 that steers the left and right rear wheels RWI and RW2. The front wheel steering mechanism B1 steers the left and right front wheels via tie rods 55 and 56 and knuckle arms 11 and 12. A rank bar 57 is provided to which the FW 2 is connected in a steerable manner, and the bar 57 is connected to a steering handle SW via a steering shaft 58. A pinion shaft 59a meshes with the rack par 57, and rotary shirts 59b and 59c extending rearward are connected to the shaft 59a so as to rotate together. These pinion shaft 59a and rotating shafts 59b and 59c constitute a mechanical transmission means, and this transmission means controls the left and right front wheels F of the ladle.
The steering amounts of WI and FW2 are transmitted to the rear wheel steering mechanism B2. The rear wheel steering mechanism B2 steers the left and right rear wheels RWI and RW2 in conjunction with the steering of the left and right front wheels FWI and FW2,
! 1211 and Figure 4~! As shown in FIG. 7, a rail rod 62 is disposed within a housing 61 so as to be displaceable in the axial direction and rotatable around the axis. Left and right rear wheels RWI, RW2 are steerably connected to both ends of the relay rondro 2 via tie rods 63, 64 and knuckle arms 13, 14, and the left and right rear wheels RWI, RW2 are steerably connected to both ends of the relay rondro 2 through tie rods 63, 64 and knuckle arms 13, 14. RW2 is now being steered. Such a rear wheel steering mechanism B2 is disclosed in the well-known Japanese Patent Application Laid-Open No. 1986-
It is basically the same as that shown in Publication No. 163064, and at the same time, it is based on the Utility Application No. 1983 related to the earlier application of the same applicant as the present application.
Since it is the same as that shown in the application specification of No. 51096 (Rack Bar Support Mechanism), a detailed explanation will be omitted, but only the parts directly related to the present application will be briefly explained. The relay rod 62 includes an input shaft 65 connected to the rear end of the rotary shaft 59c so as to rotate integrally therewith, and an input shaft 65 connected to the rear end of the rotary shaft 59c so as to rotate integrally therewith.
The first and second supports 66 and 67 rotate according to the rotation of the
and a pin 7 that engages with the second support body 67 via a bush 68 and is integrally formed upright with the relay rod 62.
Power is transmitted from the rotary shaft 59c through the rotary shaft 59c, and the rod 62 is driven in the axial direction in accordance with the rotation of the rotary shaft 59c. In such a case, the second support 67 is connected to the relay rod 62 within the first support 66.
The pin 71 is supported rotatably around the axis of the
The displacement direction and displacement of the relay rod 62 relative to one rotation of the shaft 59c are determined in accordance with the rotational positions of the i12 support 67, the bush 68, and the pin 71. The amount is controlled to change. In this example,
When the bushing 68 and pin 71 are in the lower position in FIGS. 5 and 6, the left and right rear wheels RWI and RW2 are the left and right front wheels FW.
When the left and right rear wheels RWI and RW2 are steered in the same phase as I and FW2 (the steering angle ratio reaches the maximum positive value) and the bush 68 and pin 71 are in the upper position in both figures, the left and right rear wheels RWI and RW2
is front left and right wheels FWI. As FW2 is steered in the opposite phase (the steering angle ratio reaches its maximum negative value) and the bushing 68 and pin 71 move towards the center, the steering amount of the left and right rear wheels RWI and RW2 (absolute steering angle ratio) (
III) decreases, and the left and right rear wheels R at the center position
WI and RW2 will no longer be steered (steering angle ratio will be zero)
, the second support 67, the bush 68 and the pin 7
The rotation of the motor 72 is controlled by an electric motor 72 consisting of a step motor, and the rotation of the motor 72 is controlled by a worm 73 connected to the rotating shaft of the electric motor 72 so as to rotate integrally therewith. The signal is transmitted to the pin 71 via the relay rod 62 and a wheel 74 that meshes with the relay rod 62 and is spline-fitted to the relay rod 62 . Furthermore, the vehicle has an electric control path C that electrically controls each of the suspension mechanisms A1 to A4 and the rear wheel steering mechanism B2.
The control circuit C includes a first microcomputer 81 for suspension control and a rear wheel steering flJfl1.
M 1!2 microcomputers 82 are independently provided. The I11 microcomputer 81 has a ROM 81b, a CPU 81c, a RAM 81d, and an I11 connected to a bus 81a.
1081e. The ROM8 lb stores a suspension control program corresponding to the flowchart in FIG.
s, K+r+ are stored in the form of first and second tables, respectively. The CPU 81c executes the program, and the RAM 81d temporarily stores variables necessary for executing the program. 1081e is for sending and receiving signals with external circuits.
A front wheel steering angle sensor f83, a first vehicle speed sensor 84, and oil pressure sensors 85 to 88 are connected to the same engineer 1081e, respectively. The front wheel steering angle sensor 83 is assembled on the outer periphery of the steering shaft 58, and measures the rotation angle of the same shaft 58 to measure the steering angle δf of the left and right front wheels FW1, FW2 (a positive value indicates right steering of the wheel, and a negative value indicates steering to the left of the wheel). (representing the steering angle) and outputs a detection signal representing the steering angle δf. The first vehicle speed sensor 84 is assembled on the outer periphery of the output shaft (not shown) of the transmission, detects the vehicle speed v1 by measuring the number of rotations per unit time of the same shaft, and outputs a detection signal representing the vehicle speed v1. do. The oil pressure sensors 85 to 88 are attached to the respective output ports of the pressure control valves 45 to 48 toward the respective oil passages communicating with the hydraulic cylinders 41 to 44, respectively, and detect the oil pressures P1 to P4 in the respective oil passages. Same hydraulic pressure P1
- Each detection signal representing P4 is outputted. Furthermore, drive circuits 91a to 91d and an excitation circuit 91f are connected to l1081e. Each drive circuit 91a to 9
1d has a function of storing control data representing each target oil pressure value P1* to P4* supplied from the first micron computer 81, and stores each target oil pressure value P1 to P4* according to each stored control data. A control signal representing P-numbers is supplied to each pressure control valve 45-48. The excitation circuit 91f has a function of storing excitation/de-excitation data supplied from the first microcomputer 81, and simultaneously controls the electromagnetic switching valves 51 to 54 to be energized or de-energized according to each stored data. Furthermore, a rear wheel steering fail signal indicating an abnormality in the control of the rear wheel steering system is inputted to this l1081e from the second microcomputer 82, and a rear wheel steering fail signal indicating an abnormality in the control of the suspension system is inputted from the l1081e. A suspension fail signal representing this is supplied to the second microcomputer 82 and warning lamp 92. A warning lamp 92 is provided near the driver's seat to warn the driver of an abnormality in the suspension system control. The second microcomputer 82 also has a ROM 82b, CPU 82c, RAM 82d and l1 connected to the bus 82a.
It consists of 082e. The ROM 82b stores a rear wheel steering control program corresponding to the flowchart in FIG. 10, and also stores @ and K+ in the first and second tables for the steering angle ratio that changes according to the vehicle speed V, as shown by the solid line and broken line in FIG. They are remembered in the form of The CPU 82c executes the program, and the RAM 82d temporarily stores variables necessary for executing the program. The I/082e sends and receives signals to and from an external circuit, and a second vehicle speed sensor 93 and a steering angle ratio sensor 94 are connected to the I/082e, respectively. The second vehicle speed sensor 93 is configured similarly to the first vehicle speed sensor 84, and has a vehicle speed V2 (the first and second vehicle speed sensors 8
If both speeds 4 and 93 are normal, a detection signal representing the vehicle speed v1 is output. The steering angle ratio sensor 94 detects the steering angle ratio K set in the rear wheel steering mechanism B2 by detecting the rotation angle of the relay rod 62 (the bush 68 and the pin 71), and determines the steering angle ratio K. As shown in FIGS. 4 and 5, the wheel 7
4 and a rotation angle sensor connected to the relay rod 62 via an auxiliary gear 95 press-fitted into the relay rod 62 and a gear 96 meshed with the auxiliary gear 95. Further, a drive circuit 97 is connected to the r/082e. The drive circuit 97 is the second microcomputer 82
It has a function of storing *-K in the steering angle ratio control data supplied from the controller, supplies a control signal corresponding to *-K to the stored control data to the electric motor 72, and feeds back the rotation of the motor 72. Control. In addition, K tree is left and right front wheels FWI,
This is the target steering angle ratio of the left and right rear wheels RWI and RW2 with respect to FW2. Furthermore, a suspension fail signal indicating an abnormality in the control of the suspension system is inputted to this part 1082e from the first microcomputer 81, and a suspension fail signal indicating an abnormality in the control of the rear wheel steering system is input from the same part 1082e. A rear wheel steering fail signal is supplied to the first microcomputer 81 and warning lamp 98. A warning lamp 98 is provided near the driver's seat together with the warning lamp 92 to warn the driver of an abnormality in the control of the rear wheel steering system. Next, the operation of the embodiment configured as described above will be explained. When the ignition switch (not shown) is closed to start the vehicle, the CPU 81c starts executing the suspension control program in step 100 of FIG. 8, and the CPU 82c starts executing the rear wheel steering control program in step 200. Start execution. In executing the suspension control program, excitation data is output to the excitation circuit 91f in step 102. As a result, the excitation circuit 91f excites and controls the electromagnetic switching valves 51 to 54, so that the valves 51 to 54 are respectively set to the second state (state It of tI12wI), and each of the valves 51 to 54 connected to each hydraulic cylinder 41 to 44 is set to the second state (state It of tI12wI). Communication between the oil passage and the oil passage communicating with the reservoir R1 is prohibited. Next, in step 104, after the first to fourth target oil pressure values P10 to P4 are set to the standard oil pressure value Pa, step 1
11 to 114 target oil pressure value P1* set above in 06
Each control data representing ~P4 is connected to each drive circuit 91a to 91.
output to d. Due to this. Each of the drive circuits 91a to 91d is connected to the set first to fourth drive circuits.
Since each control signal representing the target oil pressure value P1* to P4* is supplied to each pressure control valve 45 to 48, the same valve 45 to 4
8 controls the supply and discharge of hydraulic oil to each hydraulic cylinder 41 to 44 to control each hydraulic pressure in the cylinders 41 to 44 as described above.
114 Target oil pressure IP1* to P4 (standard oil pressure value Pa). As a result, the vehicle body BD is supported by the respective oil pressures and the elastic forces of the springs 25-28. In such a case, the springs 25 to 28 bear most of the positive load on the vehicle body BD, and each hydraulic pressure carries the amount of load movement of the vehicle body when the vehicle turns. After the processing in step 106, in step 108, the front wheel steering angle δf and the vehicle speed v1 represented by the detection signals from the front wheel steering angle sensor 83 and the first vehicle speed sensor 84 are determined by I.
/081 e, and the front wheel steering angle δf and vehicle speed v1 thus taken are set as the new front wheel steering angle δ.
The settings are stored as f sEw and new vehicle speed vNE11, and the initial setting processing routine consisting of steps 102 to 108 is completed. After processing this initialization routine, steps 110-1
26 continues to be executed, and the characteristics of the functions of each of the suspension mechanisms A1 to A4 are changed according to the driving state of the vehicle. It will be IIIF. In this circulation process, in step 110 the old front wheel steering angle δf OLD and the old vehicle speed VoLn are updated with the new front wheel steering angle δfNi- and the new vehicle speed vNEII, and in step 112 the current front wheel steering angle is updated by the same process as in step 108 above. The angle δf and the vehicle speed v1 are the new front wheel steering angle δfs
E- and new vehicle speed VNE-, step 11
At 4, each oil pressure value P1 to P4 represented by the detection signal from each oil pressure sensor 85 to 88 is taken in as a set oil pressure value via l1081e. Next, in step 116, it is determined whether or not the operation of the suspension control system is normal, as shown in (1) to (2) below. ■Old front wheel steering angle δf OLD and new front wheel steering angle δfxε−
If the difference between the front wheel steering angle and the new front wheel steering angle δfNE- shows a value that is impossible for the vehicle to run, it is determined that the front wheel steering angle sensor 83 is abnormal. . ■If the difference between the old military speed V OL D and the new vehicle speed vNEiI shows a change that is impossible for the vehicle to run, or if the new vehicle speed VJIE- shows a value that is impossible for the vehicle to run, etc. 1 It is determined that the vehicle speed sensor 84 is abnormal. ■Each set oil pressure value P1~P4 and each target oil pressure value 21*~PA
If the winter wear with books exceeds the allowable control error, it is determined that each of the oil pressure sensors 85 to 88, each of the pressure control valves 45 to 48, or each of the drive circuits 91a to 91d is abnormal. ■If the new front wheel steering angle δfNt\1, the new vehicle speed VNEIJ, the set oil pressure values P1 to P4, and the target oil pressure values P1 to P- have a relationship that is impossible for vehicle running, the first microcomputer 81, each It is determined that any part of the suspension control system including the sensors 83-88, each pressure control valve 45-48, each drive circuit 91a-91d, etc. is abnormal. In the abnormality determination in step 116, rYEs
” In other words, if it is determined that the operation of the suspension control system is normal, the new front fIk! The centrifugal force acting on the vehicle body BD is calculated based on the steering angle δfNE- and the new vehicle speed VNEw, and at the same time, the inside vehicle FWI, RWI (or F
W 2. RW2) to turn outside wheel FW2. R
The amount of load movement ΔM to W2 (or FWI, RWI) is calculated. Note that this load movement amount ΔM indicates the movement direction (left and right) of the load using positive and negative signs. Next, in step 120, a process is performed to determine whether or not the operation of the rear wheel steering control system is normal. In addition, in this determination process, a rear wheel steering fail signal, which will be described later, is transmitted from the second microphone computer 82 to l108.
It is determined whether the input is input to 1e or not. If it is determined in step 120 that the rear wheel steering control system is normal, the table 111 in the ROM 81b is referred to in step 122, and the vehicle speed V
The front and rear load distribution ratio data Kf,s that changes as shown by the solid line in FIG. Set. Next, in step 124, each wheel FW1, FW is
2. Each of the target oil pressure values P1* to P4 corresponding to the shared loads of RWI and RW2 is calculated, and in step 126, each control data representing each of the calculated target oil pressure values P1 to P4 is applied to each drive circuit 91a to 91a. 91d. As a result, each of the drive circuits 91a to 91d stores each of the output control data, and each control signal corresponding to each of the control data, that is, each of the target oil pressure values P++ to
Each control signal representing P4* is supplied to the pressure control pulps 45 to 48, respectively, and each of the valves 45 to 48 controls the supply and discharge of hydraulic oil according to the supply control signal to the hydraulic cylinders 41 to 4.
4 is set to each of the target oil pressure values P1* to P4. In such a case, each of the target oil pressure values P1 to P4 for the hydraulic cylinders 42, 44 (or hydraulic cylinders 41, 43) corresponding to the turning outer wheels becomes higher than the standard oil pressure value P2 according to the load movement amount ΔM, In addition, hydraulic cylinders 41, 43 (or hydraulic cylinders 42, 42, 43, 42, 42, 42, 42, 42, 43, 43, 42, 42, 42, 42, 43, 43, 43, 42, 43, 41, 43, 43, 43, 42, 42, 42, 43, 41, 43, 42, 43, 43, 42, 43, 43, 43, 43, 43, 43, 43, 43, 42, 4, , 43, 43 , 43, 4, , , , , , , , , , , , , , , , , , , , , , , , , , , ,
44) is set to be lower than the standard hydraulic pressure value pH according to the load movement amount ΔM, so the load movement amount ΔM accompanying turning is covered by the hydraulic pressure of the hydraulic cylinders 25 to 28. As a result, the roll of the vehicle body BD during turning is reduced, and the posture of the vehicle is always maintained in a good condition. In addition, the left and right front wheels FWI, FWZ side and the left and right rear wheels RWl, R
Regarding the distribution of the load movement amount ΔM with W2(t!!I), the front-rear load distribution ratio K t = (= K r, ll)
changes as shown in FIG. 9 as the vehicle speed V changes, that is, as the vehicle speed V increases, the left and right front wheels FWI and FW2 bear a larger amount of load movement ΔM. The steering characteristics of the A4 when the vehicle turns tend to understeer as the vehicle speed increases, and the vehicle's tight turning performance at low speeds and the running stability of the vehicle at high speeds are maintained well. This point will be explained using a specific example. When the vehicle is traveling straight as shown in FIG. 12(A), each wheel FWI, FW2 . RWl,R
Assume that the load shared by each of the hydraulic cylinders 41 to 44 corresponding to W2 is "10". In addition,
This number "10" and subsequent numbers related to the shared load indicate the ratio of the load shared by each of the hydraulic cylinders 41 to 44, and do not represent the actual load. Assume that the vehicle starts to turn left from the straight-ahead state, and the load moves by "8" from the left wheels FWI and RWI to the right wheels FW2°RW2. In such a case, when the vehicle is running at a low speed, the left and right front wheels FWI, FW2 share the load movement amount ΔM (=8) with the left and right rear wheels RWI, RW2.
For example, if the ratio is 1:3, the left and right front wheels FWI, FW2 and the left and right rear wheels RWI,
The shared loads of RW2 are "9", "rll", "7", and "13", respectively, as shown in FIG. 12(B). Here, the amount of load movement between the left and right wheels FWI, FW2 (or RWI. RW2) and each wheel FWI, FW2°RWI
, RW2 and the cornering power will be explained using FIG. 13. Each wheel FWI, FW2. RWI,
Since the relationship between each cornering power of RW2 and each load has non-linearity as shown by the solid line in FIG. 13, the total cornering power of the left and right wheels decreases as the amount of load movement increases. (2a>bl+b2>cl+
c2) As a result, as mentioned above, when the vehicle is turning at low speed, the left and right front wheels FWI, FW2 and the left and right rear wheels RW1, RW
The shared loads of 2 are "9" and "11" r7J respectively.
If it is r13J, the cornering power on the rear wheels RWI, RWZ side will be smaller than the cornering power on the front wheels FWI, FW2 side, and the left and right rear wheels RWI, RW2 will become slippery, so when the vehicle turns using the suspension mechanisms A1 to A4. The steering characteristics are controlled to change to the oversteer direction, improving the vehicle's tight turning performance. In addition, when the vehicle is running at a medium speed and the load movement amount ΔM
(=8) left and right front wheels FWI, FW2 and left and right rear wheels R
If the sharing ratio of WI and RW2 is equal, the left and right front wheels FWI
, FW2 and left and right rear wheels RWI. As shown in Fig. 12(C), each shared load of RW2 is as follows:
r8J rl 2J r8J rl 2 respectively
It becomes J. As a result, in this case, front wheels FWI, FW2 side and rear wheels RW1. Each cornering power on the RW2 side becomes equal, and the steering characteristics of the suspension mechanisms A1 to A4 when the vehicle turns are kept neutral. Furthermore, when the vehicle is running at high speed, the load movement amount ΔM
(=8), if the share of left and right front wheels FWI, FW2 is larger than that of left and right rear wheels RWI, RW2, for example, if the ratio is 3:1, then left and right front wheels FWI, FW2
And the respective loads of the left and right rear wheels RWI, RW2 are the 1st
As shown in Figure 2 (D), r7J rl 3, respectively.
J r9” becomes “11”. As a result, the cornering power on the rear wheels RWI, RW2 side becomes larger than the cornering power on the front wheels FWI, FW211, and the cornering power on the left and right rear wheels RW1. Since RW2 becomes difficult to slip, the steering characteristics of the suspension mechanisms A1 to A4 when the vehicle turns are controlled to be changed to the understeer direction, and the turning stability of the vehicle becomes better. Next, a rear wheel steering control program that is executed in parallel with the suspension control program will be described. In executing the rear wheel steering control program, step 2
At 02, the vehicle speed v2 and the steering angle ratio K represented by the respective detection signals from the second vehicle speed sensor 93 and the steering angle ratio sensor 94 are taken in via the device 1082e, and the taken vehicle speed v2 and the steering angle ratio are K is set and stored as a new vehicle speed VNE- and a new steering angle ratio KNE-. Next, step 20
At step 4, the first table in the ROM 82b is referred to, and the steering angle ratio data Ke corresponding to the vehicle speed rOJ is read from the table, and 9 is set as the target steering angle ratio in the same data. After setting * to this target steering angle ratio, in step 206, a steering angle ratio control data file corresponding to the difference between the target steering angle ratio and the new steering angle ratio Kwtw representing the currently set steering angle ratio K is entered. Book-K
NE- is supplied to the drive circuit 97. As a result, the drive circuit 97 applies a control signal corresponding to the supplied steering angle ratio control data to the electric motor 7.
Since the motor 72 outputs the output to the worm 73 (the fifth
and FIG. 7) is rotated by a rotation angle corresponding to *-K based on the control data. This rotation is transmitted to the relay rod 62 via the wheel 74 and the rod 62 rotates, so that the bin 71 rotates integrally with the relay rod 62 while the second support 67 and bush 68 rotate. As a result, the set steering angle ratio K in the rear wheel steering mechanism B2 is set to * as the target steering angle ratio. After the initial setting process routine consisting of steps 202 to 206 ends, the circulation process consisting of steps 208 to 218 continues to be executed, and the steering control of the left and right rear wheels RWI and RW2 by the rear wheel steering mechanism B2 is changed according to the vehicle speed. controlled. In this circulation process, in step 208, the old vehicle speed VOLD and the old steering angle ratio KOLD are changed to the new vehicle speed VNE.
11 and the new steering angle ratio KNEW, step 2
In step 10, the current vehicle speed v2 and steering angle ratio K are changed to the new vehicle speed VNE- and the new steering angle ratio KN by the same process as in step 202 above.
Set as EII. Next, in step 212, a determination is made as to whether or not the operation of the rear wheel steering control system is normal, as shown in (1) to (2) below. ■If the difference between the old military speed VOL 11 and the new vehicle speed vNEII shows a change that is impossible for the vehicle to run, or if the new vehicle speed vNEI+ shows a value that is impossible for the vehicle to run, etc., the second It is determined that the vehicle speed sensor 93 is abnormal. ■If the difference between the old steering angle ratio KoLv and the new steering angle ratio KsEu shows a change that is impossible for the vehicle to run, or if the new steering angle ratio KNE- shows a value that is impossible for the vehicle to run, etc. It is determined that the steering angle ratio sensor 94 is abnormal. ■If the relationship between the new vehicle speed VNE- and the new steering angle ratio KNE11 is impossible for vehicle running, rear wheel steering control including the second microcomputer 82, each sensor 93, 94, electric motor 72, drive circuit 97, etc. It is determined that some part of the system is abnormal. rYE in the abnormality determination in step 212]
That is, if it is determined that the operation of the rear wheel steering control system is normal, a process for determining whether or not the operation of the suspension control system is normal is executed in step 214. In this determination process, a suspension fail signal, which will be described later, is transmitted from the first microcomputer 81 to the factory 1082.
It is determined whether or not it is input to e. If it is determined in step 214 that rYEsJ, that is, the suspension control system is normal, step 216
The first table in the ROM 82b is referred to, and the steering angle ratio data K[1 (see the solid line in Figure 1111) is read from the table based on the new vehicle speed VNE-, and the same data Ks is set to the target steering angle ratio * is set as . and,
In step 218, the steering angle ratio control data Kl-K is transferred to the drive circuit 9 by processing similar to the processing in step 206.
7, and the set steering angle ratio K in the rear wheel steering mechanism B2 is set to the target steering angle ratio. In this state, when the left and right front wheels FWI, FW2 are steered, the displacement of the rack par 57 (front wheel steering amount) is transmitted to the input shaft 65 via the pinion shaft 59a and the rotary shafts 59b, 59c, and the same shaft 65 rotates around the axis. Rotate to . This rotation of the input shaft 65 is transmitted to the first support 66,
The second support 66 rotates around a horizontal axis perpendicular to the axis of the relay rod 13, that is, rotates clockwise or counterclockwise on the paper in FIG. It rotates integrally with the support body 66 in the same direction. At this time, the target steering angle ratio is rQJ, and the steering angle ratio control causes the rotational position of the relay rod 62 to be in the reference state, that is, the rotational position of the pin 71 to be perpendicular to the surface of the paper in FIG. @ (left side in Figure 6), the second support 67 only rotates around the outer circumference of the pin 71 and the relay rod 62 is kept in the standard state, so the left and right rear wheels RW
1. RW2 is not steered to the left or right. Further, if * is negative (reverse phase value) in the target steering angle ratio and the rotational position of the pin 71 is on the upper side in FIG. 5 (and FIG. 6), the second
As the support body 67 rotates clockwise (or counterclockwise) in FIG. Since it is pushed rightward (or leftward) in FIG. 5, the relay rod 62 is displaced in the direction together with the pin 71, and the left and right rear wheels RWI, RW2 are steered rightward (or leftward). Note that the rotation direction of the second support body 67 is clockwise (or counterclockwise) in FIG. 5 when the left and right front wheels FWI, FW2 are steered leftward (or rightward). As a result, the left and right rear wheels R
WI and RW2 are steered in opposite phases to the left and right front wheels FWl and FW2. Further, as the pin 71 moves upward away from the reference position, the left and right rear wheels RWI, RW
2, the amount of anti-phase steering becomes large. On the other hand, when the target steering angle ratio is set to a positive value (in-phase value) and the pin 71 comes to the lower side in FIG. The rotation pushes it in the opposite direction, so
The left and right rear wheels RWI and RW2 are steered in the opposite direction to that in the above case. That is, left and right rear *RW1. RW2 has left and right front wheels FW1. They are steered in the same phase with respect to FW2, and in this case as well, the further the pin 71 moves downward from the reference position, the larger the in-phase steering amount of the left and right rear wheels RWI, RW2 becomes. In this way, the left and right rear wheels RWI, RW2 are steered according to the target steering angle ratio. Since it is set to change from a predetermined negative value toward positive as the vehicle speed V increases, when the vehicle is running at low speed, the left and right rear wheels RWI, RW2 are set to change from a predetermined negative value to a positive value as the vehicle speed V increases.
In proportion to the steering angle of I and FW2, the front wheels FWI and FW2 are steered in the opposite phase, and the rear wheels RWI,
The smaller the vehicle speed V is, the more RW2 is steered. As a result, the smaller the vehicle speed V is, the smaller the turning radius of the vehicle is set, and the better the turning radius of the vehicle is when traveling at low speeds. Also, when the vehicle is running at high speed, the left and right rear wheels RWI, RW2 are the left and right front wheels F.
The same front wheels FWI, FW2 in proportion to the steering angle of WI, FW2.
It is steered in the same phase as the RWI, R
W2 is steered more as the vehicle speed V increases. As a result, as the vehicle speed V increases, the turning radius of the vehicle is set to be larger, and the running stability of the vehicle during high-speed running becomes better. Note that both the rear wheel steering control and the above-mentioned suspension control are set so that the overall dynamic characteristics of the vehicle are optimized. Returning to the explanation of the flowcharts in FIGS. 118 and 1110, if an abnormality occurs in the rear wheel steering control system during the circulation process of the suspension control consisting of steps 110 to 126 and the rear wheel steering control consisting of steps 208 to 218, , the determination in step 212 in FIG. 10 is "NO", and the electric motor 72 is controlled to stop in step 222. As a result, the steering angle ratio change control for the rear wheel steering mechanism B2 is stopped, and the set steering angle ratio in the rear wheel steering mechanism B2 is returned to zero by a neutral return mechanism (not shown). Next, in step 224, the rear wheel steering fail signal is set to I/082.
e to l1081 of the first microcomputer 81
e and the warning lamp 98, and the execution of the rear m steering control program ends in step 226. The warning lamp 98 lights up to warn the driver of an abnormality in the rear wheel steering control system. On the other hand, the CPU 81c, which is executing the cyclic process consisting of steps 110 to 126 in FIG.
J, that is, it is determined that the rear wheel steering control system is not operating normally, and thereafter steps 110 to 120, 128, and 124 are performed.
, 126 is executed. In this # ring process, in step 128, the ROM 73b
1 is read from the table based on the new vehicle speed VNEIJ, and the same data K t is read out from the table based on the new vehicle speed VNEIJ. r + is front and rear load distribution *K
It is set as T. As a result, the front and rear load distribution ratio K
tr is set to a value closer to the rear wheels in a low vehicle speed region and closer to the front wheels in a high vehicle speed region, compared to when no abnormality occurs in the rear wheel steering control system described above. Therefore, when the vehicle is running at low speed, the left and right rear wheels RWI, RW2
At the same time, when the vehicle is running at high speed, the left and right rear wheels RWI and RW2 bear a smaller amount of the load movement ΔM when the vehicle turns. As a result, compared to the case where no abnormality has occurred in the rear wheel steering control system, the steering characteristics of the suspension mechanisms A1 to A4 when the vehicle turns tend to tend to oversteer at low speeds and to understeer at high speeds. Therefore, the change in steering characteristics due to the stop of the rear 111 steering control is compensated for by the steering characteristics control of the suspension control system, and the small turning performance of the vehicle when driving at low speeds and the driving stability of the vehicle when driving at high speeds are improved by the rear wheel steering control. The system is maintained in the state it was in before the abnormality. In addition, even in such a case, the amount of load movement ΔM of the vehicle body when the vehicle turns is the hydraulic cylinder 42.44 (or hydraulic cylinder 41.43) corresponding to the outer turning wheel and the hydraulic cylinder 41.43 corresponding to the inner turning wheel. (or the hydraulic cylinders 42 and 44), the roll of the vehicle body BD during turning is reduced and the posture of the vehicle is always maintained in a good condition. To explain this point using a specific example, when the vehicle is running at a low speed and the ratio of the share of the left and right front wheels FWI, FW2 and the share of the left and right rear wheels RWI, RW2 to the amount of load movement ΔM (=8) is, for example, 1. If the pair becomes 7, the shared loads r9J rllJ r for the left and right front wheels FWI, FW2 and the left and right rear wheels RWI, RW2, which were set before the abnormality, respectively.
7J r13J is hr9. as shown in Figure 112 (E). 5J rlo, 5J r6.5
J r13.5J. As a result, rear wheel RWI, R
The cornering power on the W2 side becomes smaller than before the abnormality, and the rear wheels RW1 and RW2 become more slippery when the vehicle turns, and the left and right front wheels FWI, FW21! The cornering power of I becomes larger than before the abnormality, the front wheels FW1 and FW2 become more difficult to slip when the vehicle turns, and the steering characteristics of the vehicle caused by the suspension control mechanisms A1 to A4 become more prone to oversteer. Also, when the vehicle is running at medium speed, the load movement amount ΔM (=8)
Left and right front wheels FWI, FW2 sharing and left and right rear wheels RW
1. If the ratio with the load shared by RW2 does not change, the shared load of the left and right front wheels FWI, FW2 and the left and right rear wheels RWI, RW2 after the abnormality will be "8", respectively, as shown in Figure 8 (F).
”, “12”, “8”, and “12”, so that the steering characteristics of the suspension mechanisms A1 to A4 when the vehicle turns are maintained at the same neutral state as before the abnormality. Furthermore, the vehicle is traveling at high speed and the amount of load movement ΔM (=
8), if the ratio between the left and right front wheels FWI, FW2 and the left and right rear wheels RWI, RW2 is 7:1, then the left and right front wheels FWI, FW that were set before the abnormality will be reduced.
W2 and each shared load r7J of left and right rear wheels RWl, RW2
r13J r9" and "11" are r6.5J r13.5J r, respectively, as shown in FIG. 12 (G).
9.5J rlo, 5J. As a result, the rear wheel RW
The cornering power on the I and RW2 sides became larger than before the abnormality, and the rear wheels RWI and RW2 became more slippery when the vehicle turned, and the cornering power on the left and right front wheels FWI and FWZ became larger than before the abnormality. Due to the smaller size, the front wheels FWI and FW2 become more slippery when the vehicle turns.
The steering characteristics of the vehicle caused by the suspension control mechanisms A1 to A4 become more likely to understeer. Further, if an abnormality occurs in the suspension control system during the circulation process of the suspension control consisting of steps 110 to 126 and the rear wheel steering control consisting of steps 208 to 218, it is determined to be rNOJ in step 116 of FIG. At step 130, the excitation release data is transferred to the excitation circuit 8.
7. As a result, the excitation circuit 87 de-energizes each of the electromagnetic switching valves 51 to 54, so that the valves 51 to 54 are set to the first state and each hydraulic cylinder 4
The oil chambers 1 to 44 are communicated with the reservoir R1. As a result, the support of the vehicle body BD by each of the hydraulic cylinders 41 to 44 is released, and the vehicle body BD is supported only by the springs 25 to 28, and each suspension eye mechanism A1
~The attitude of the vehicle during turning by A4 is no longer controlled. After the processing in step 130, in step 132, the suspension fail signal is transmitted from l1081e to l1082e of the second microcomputer 82 and the warning lamp 92.
At step 134, the execution of the suspension control program ends. The warning lamp 92 lights up to warn the driver of an abnormality in the suspension control system. On the other hand, the CPU 82c, which is executing the circulation process consisting of steps 208 to 218 in FIG.
○, that is, it is determined that the suspension control system is not operating normally, and thereafter steps 208 to 214 and 220 are performed.
, 218 is executed. In this circulation process, in step 220, the ROM 82b
1 is the new vehicle speed VN.
E- is read from the same table based on E-, and 1 is set in the same data as the target steering angle ratio.As a result, the target steering angle ratio is read out when no abnormality occurs in the above-mentioned suspension control system. In comparison, even if the vehicle speed V is small, it is set to be positive (in-phase I), that is, to increase the in-phase tendency.
The amount of steering of RW2f [to the opposite phase with respect to the left and right front wheels FWI and FW2 will be small. As a result, only when the vehicle is traveling at an extremely low speed, the left and right rear wheels RW
I, RW2 are now steered in the opposite phase to the left and right front wheels FWI, FW2, and the turning radius of the vehicle is not controlled to become smaller at medium speeds or higher, which means oversteer that affects the turning characteristics of the vehicle. Since the tendency is suppressed, the amount of load movement ΔM of the vehicle body also becomes smaller. As a result, as mentioned above, even if the vehicle attitude control function is stopped due to an abnormality in the suspension control, the amount of roll of the vehicle body when the vehicle turns is reduced, and the ride comfort of the vehicle will not deteriorate significantly. . In addition, in the above embodiment, * is used as the target steering angle ratio.
When the suspension control system is operating normally, 6 is used for the steering angle ratio data that changes as shown by the solid line in Figure 11, and when an abnormality occurs in the suspension control system, the value changes as shown by the broken line in Figure 11. 1 is used for the changing steering angle ratio data, but instead of + for these steering angle ratio data Ks, steering angle ratio data K e , which changes as shown by the solid line and broken line in FIG. 14, is used. K+ may also be used. In such a case, 1 is added to the steering angle ratio data.
Its absolute value becomes smaller in the low vehicle speed range, and increases in the high vehicle speed range. Even in this case, if an abnormality occurs in the suspension control system, the same Since the in-phase tendency is controlled more than when the control system is normal, the same effect as the above embodiment is expected. In addition, in the above embodiment, the load distribution ratio K t around 1
By controlling r in accordance with the vehicle speed V, it is also possible to change the steering characteristics of the vehicle when turning by suspension control, but the present invention is also applicable to vehicles in which only the attitude of the vehicle body is controlled by suspension control. can. That is, the present invention is also applicable to a vehicle in which the amount of load movement ΔM when the vehicle turns is always distributed at a constant ratio between the left and right front wheels FWI, FW2 and the left and right rear wheels RWI, RW2. In such a case, in order to compensate for the steering characteristic change control by suspension control, it is preferable that the absolute value IK*1 of the target steering angle ratio be made larger than in the above embodiment. Furthermore, in the above embodiment, the suspension mechanism A
Although various sensors and microcomputers are separately provided to control the rear wheel steering mechanism B2 to A4 and the rear wheel steering mechanism B2, these sensors and microcomputers may be provided together if necessary.

[Brief explanation of drawings]

FIG. 1 is a claim correspondence diagram corresponding to the configuration of the present invention described in the above claims, FIG. 2 is an overall schematic diagram of a vehicle showing an embodiment of the present invention, and 31st! I is a detailed view of the suspension mechanism corresponding to one wheel in Figure 2, Figure 4 is a partially broken new front view of the rear wheel steering mechanism in Figure 1, Figure 5 is a new longitudinal front view of the same mechanism, Figure 6 is a sectional view taken along line VI-VI in Figure 4, Figure 7 is a sectional view taken along line ■-■ in Figure 4, and Figure 8 is a suspension i#II#l program. 9 is a characteristic diagram of changes in the front and rear load distribution ratio with respect to vehicle speed. FIG. 10 is a flow chart corresponding to the rear wheel steering control program. FIG. 11 is a characteristic diagram of changes in steering angle ratio with respect to vehicle speed. Figures (A) to (G) are operation explanatory diagrams for explaining the steering characteristics of the suspension device, Figure 13 is a characteristic diagram of changes in cornering power with respect to the shared load of the wheels, and Figure 14 is a modification of the present invention. FIG. 3 is a characteristic diagram of changes in steering angle ratio with respect to vehicle speed. A1-A4...Suspension mechanism, B1...Front wheel steering mechanism, B2...Rear wheel steering mechanism, C...Electric control circuit, FWI, FW2...Front wheel, RWI, RW2・・・
・Rear wheel, SW... Steering handle, 41-44... Hydraulic cylinder, 45-48... Pressure control valve, 57.
... Rack bar 59a ... Binion shaft, 59b
, 59c...Rotating shaft, 62...Relay iron, 65...Input shaft, 66...First support body, 67...
- Second support, 71... pin, 72... electric motor, 81.82... microcomputer, 83...
Front wheel steering angle sensor, 84, 93...Vehicle speed sensor, 85
~88... Oil pressure sensor, 94... Steering angle ratio sensor.

Claims (1)

[Claims] Applicable to a vehicle equipped with a suspension device having an attitude control means for controlling the attitude of the vehicle body when the vehicle turns, the system steers the rear wheels in conjunction with the steering of the front wheels, and a rear wheel steering mechanism capable of changing and controlling a steering angle ratio from opposite phase to in-phase; vehicle speed detection means for detecting vehicle speed; and a steering angle ratio changing from opposite phase to in-phase as the detected vehicle speed increases 1 steering angle ratio as a target steering angle ratio, and steering angle ratio setting control means for controlling the steering angle ratio set by the rear wheel steering mechanism to be set to the target steering angle ratio. In the steering control device, an abnormality detection means for detecting an abnormality in the attitude control means, and when the abnormality detection means detects an abnormality in the attitude control means, the steering control tends to be in-phase compared to the first steering angle ratio. and correction control means for controlling the steering angle ratio setting control means so as to determine a second steering angle ratio as a target steering angle ratio instead of the first steering angle ratio. Steering control device.