JPH071346Y2 - Rear wheel steering system - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rear wheel steering system for a vehicle.

2. Description of the Related Art Conventionally known rear wheel steering devices are, for example, the actual open sho 61
As disclosed in Japanese Laid-Open Patent Publication No. 199476, the amount of oil supplied from the pump to the rear wheel steering cylinder is adjusted by a single solenoid valve to obtain a desired rear wheel steering angle.

Therefore, if a malfunction occurs due to foreign matter being caught in the valve operating part of the solenoid valve, the rear-wheel steering cylinder will operate regardless of the rear-wheel steering control signal. There was a risk of it getting lost.

Therefore, the present invention has been devised for the purpose of solving the above-mentioned problems of the prior art.

Means for Solving the Problems That is, a rear wheel steering system according to the present invention is attached to the left and right oil chambers of a rear wheel steering cylinder defined by a piston, and is supplied from a pump to the rear wheel steering cylinder. The difference control value between the rear wheel steering angle value calculated based on the signal from the pair of solenoid valves that adjust the oil amount and the sensor that detects the running state of the vehicle and the input value from the rear wheel steering angle sensor is The excitation signal is output to the solenoid valve so as to be zero, and the differential pressure value and the difference obtained from the detection signals from the pair of hydraulic pressure sensors that respectively detect the hydraulic pressures of the left and right oil chambers of the rear wheel steering cylinder. When the control value does not match, the controller is provided with a controller that outputs an excitation signal to a solenoid valve attached to an oil chamber having a lower pressure so that the differential pressure value becomes zero.

Effect As a result of the present invention having the above-mentioned characteristic configuration, when one solenoid valve fails and the pressure in one oil chamber of the rear wheel steering cylinder abnormally rises, this pressure fluctuation is detected by the hydraulic sensor, and The detection signal is input to the controller. Then, the controller obtains the differential pressure value between the oil chambers from the detection signals of these hydraulic pressure sensors, and the differential pressure value,
The difference control value between the desired rear wheel turning angle value and the actual rear wheel turning angle is compared.

Here, when one solenoid valve is out of order, even if the steering angle of the rear wheels matches the desired rear wheel steering angle value and the difference control value becomes zero, the pressure between the oil chambers is reduced. Is not balanced and the pressure on the one side of the failure is high.

Therefore, since the differential pressure value and the differential control value do not match at the time of failure, the controller controls the differential pressure value to be zero.
An excitation signal is output to the solenoid valve attached to the oil chamber having the lower pressure, that is, the other normal solenoid valve, and the other solenoid valve is operated. As a result, the pressures in the left and right oil chambers of the rear-wheel steering cylinder are balanced, the rear-wheel steering cylinder returns to the neutral position, and the rear wheel is held straight.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a vehicle control system diagram showing an embodiment of the present invention. In the figure, reference numeral 1 denotes a handle, and by rotating the handle 1, the front wheels 4 can be steered via the steering gear 2 and the front wheel side link mechanism 3. Reference numeral 5 is a rear wheel steering cylinder, and the rear wheel steering cylinder 5 includes left and right oil chambers 7a, 7b partitioned by a piston 6.
The rear wheel 9 is steered via the rear wheel side link mechanism 8 by operating due to the pressure difference. And this rear wheel steering cylinder 5
The oil discharged from the pump 11 is supplied to the valve 11 via the valve mechanism 10. The valve mechanism 10 is the second
As shown in the figure, a pair of left and right solenoid valves 12 are provided. The solenoid valve 12 includes a solenoid portion 14 fixed to a body 13 and a spool valve portion 15 housed in the body 13. The spool valve section 15
Spool 17 reciprocally housed in spool hole 16
And a spring 18 that is housed in the bottom of the spool hole 16 and constantly presses the spool 17 toward the solenoid portion 14 side.The variable orifices 20a, 20b, 20c and 20d are formed. Then, the first formed in the spool hole 16
The annular passage 21 is communicated with the pump 11 via passages 22 and 23,
The second annular passage 24 is connected to the reservoir tank 27 via the passages 25 and 26.
Is in communication with. And one spool valve part 15
The spool hole 16 between the first annular passage 21 and the second annular passage 24 on the side of the second annular passage 24 on the other side of the second annular passage 24 on the side of the other spool valve portion 15 is provided with a passage 28. And the one oil chamber 7a of the rear wheel steering cylinder 5 or the other oil chamber 7b of the rear wheel steering cylinder 5, respectively. The upper spool hole 16 in the figure of the first annular passage 21 and the lower spool hole 16 in the figure of the second annular passage 24 are connected to the reservoir tank 27 via the passages 30 and 26. Therefore, for example, when the solenoid valve 12 on the left side of the drawing is actuated and the variable orifices 20a, 20b are throttled, the oil discharged from the pump 11 passes from the opened variable orifice 20c through the passage 28 and the branch passage 29 to the rear wheel. The oil is supplied to one oil chamber 7a of the steering cylinder 5, and the rear wheel steering cylinder 5 operates. As a result, the rear wheels 9 are steered by the rear wheel steering cylinder 5 via the link mechanism 8 (see FIG. 1).

In FIG. 1, reference numeral 31 is a controller, which is based on input signals from the front wheel steering angle sensor 32, the vehicle speed sensor 33, the yaw angular velocity sensor 34, and the rear wheel steering angle sensor 35. Is output. As shown in detail in FIG. 3, the controller 31 includes a front wheel steering angle processing circuit 36, a yaw angular velocity processing circuit 37, and a vehicle speed processing circuit 38.
The steering angle of the rear wheel 9 is calculated by the arithmetic circuit 39 based on the input signals V1, V2, V3 from the front wheel steering angle sensor 32, the yaw angular velocity sensor 34 and the vehicle speed sensor 33 processed by the calculation result V5. And the input signal V4 from the rear wheel turning angle sensor 35 processed by the rear wheel turning angle processing circuit 40 are compared by the differential control circuit 41, and the excitation signal V6 'corresponding to the difference control value V6 is supplied to the solenoid drive circuit. Output to the solenoid valve 12 via 42. Further, the controller 31 is obtained by comparing the signals V9 and V10 from the pair of hydraulic pressure sensors 43, which detect the hydraulic pressures of the left and right oil chambers 7a and 7b of the rear wheel steering cylinder 5, with an adding circuit 45 described later. The differential pressure value V7 and the differential control value V6 output from the differential control circuit 41 are compared in the judgment circuit 44, and this comparison value
An excitation signal V6 'corresponding to V8 is output to the solenoid valve 12 via the solenoid drive circuit 42. Reference numeral 45 denotes an adder circuit. As shown in FIG. 3, the adder circuit 45 compares the detection signals V9 and V10 output from the respective hydraulic pressure sensors 43 to obtain a differential pressure value V7. The differential pressure value V7 is input to the determination circuit 44.

According to the above-described structure of the embodiment, when the steering wheel 1 is operated and the front wheels 4 are steered, the front wheel steering angle sensor 32 and the vehicle speed sensor 3
3 and the input signals V1, V2, V3 from the yaw angular velocity sensor 34 are input to the controller 31.

Then, by the controller 31, these various sensors 32, 3
Based on the input signals V1, V2, V3 from 3, 34, the rear wheel turning angle is calculated according to the running condition of the vehicle, and the excitation signal V6 'according to the calculation result V5 is output to the valve mechanism 10. As a result, the flow of oil supplied from the pump 11 to the rear wheel steering cylinder 5 is adjusted by the valve mechanism 10, and a pressure difference is generated between the left and right oil chambers 7a, 7b of the rear wheel steering cylinder 5, and the rear wheel steering is performed. The cylinder 5 is activated. Therefore, the rear wheels 9 are steered by the rear wheel steering cylinder 5 via the link mechanism 8. The turning amount of the rear wheels 9 is detected by the rear wheel turning angle sensor 35, and is input to the controller 31 as an input signal V4.

Then, until the steering amount of the rear wheel 9 reaches a desired steering angle, that is, the rear wheel steering angle sensor compared by the operation control circuit 41.
From the controller 31 to the valve mechanism 10 until the input signal V4 from 35 and the calculation result V5 match and the difference control value V6 becomes zero.
An excitation signal V6 'is output to.

Here, while the excitation signal V6 'is being output, that is, when the difference control value V6 is not zero, the rear wheel steering cylinder 5
Since there is a pressure difference between the oil chambers 7a and 7b, a non-zero differential pressure value V7 is output from the addition circuit 45 and input to the determination circuit 44.

On the other hand, the determination circuit 44 indicates that the differential control value V6
Has been entered. Therefore, at the time of normal steering, this differential pressure value V7 and the difference control value V6 are matched, and the comparison value that is the difference between the two
V8 is not input to the solenoid drive circuit 42. The front wheel 4
When the valve is returned to the straight traveling state, the output of the excitation signal V6 'from the controller 31 to the valve mechanism 10 is stopped, and the spool 17 of the solenoid valve 12 is returned to the neutral position (see FIG. 2). Therefore, the rear wheel steering cylinder 5 also returns to the neutral position, and the rear wheels 9 return to the straight traveling state.

As shown in FIG. 4, when one solenoid valve 12 fails, for example, when the spool 17 on the left side in the figure becomes inoperable due to foreign matter being caught, that is, the solenoid valve 12 on the left side in the figure operates. After moving the spool 17 from the neutral position to the lower side, the spool 17 bites foreign matter, and even if the solenoid valve 12 stops operating, the spring force of the spring 17 cannot return to the original position. In this case, one of the variable orifices 20a, 20b is throttled, so that the high pressure oil discharged from the pump 11 is passed through the passages 23, 21, 28, 2
The oil flows into the oil chamber 7a on one side (the left side in the figure) of the rear wheel steering cylinder 5 through 9 to increase the pressure in the one oil chamber 7a. The pressure fluctuation in the oil chamber 7a and the pressure in the other oil chamber 7b are respectively detected by the hydraulic pressure sensors 43, and these detection signals V9, V10 are input to the adding circuit 45 in the controller 31. As a result, the adder circuit 45 compares the two signals V9 and V10 and outputs the differential pressure value V7 to the determination circuit 44. Next, the determination circuit 44 compares the differential pressure value V7 with the differential control value V6 input from the differential control circuit 41.

Here, as described above, when the rear wheels 9 reach the desired turning angle, the differential control value V6 becomes zero, the spool 17 returns to the neutral position, and the pressure between the oil chambers 7a, 7b is balanced. However, the differential pressure value V7 should be zero. However, when the spool 17 cannot be returned to the neutral position due to the foreign matter being caught, the differential control value V6 becomes zero, whereas the differential pressure value V7 does not become zero and does not conform to the differential control value V6. The judgment circuit 44 outputs a comparison value V8 which is the difference between the two.

As a result, the solenoid drive circuit 42 outputs the excitation signal V6 'to the solenoid valve 12 having the lower pressure, that is, the normal solenoid valve 12 (the right side in the figure).
As a result, as shown in FIG. 5, the other solenoid valve 12 is actuated, and the variable orifices 20c, 20d are throttled in the same manner as the variable orifices 20a, 20b of the one solenoid valve 12 (on the left side in the figure), so that the rear wheel The pressure in the left and right oil chambers 7a, 7b of the steering cylinder 5 is balanced. Therefore, even if one solenoid valve 12 fails, the rear wheel steering cylinder 5 does not operate independently of the excitation signal V6 '.

As described above, the rear wheel steering system of the present invention is attached to the left and right oil chambers of the rear wheel steering cylinder defined by the piston, and the oil supplied from the pump to the rear wheel steering cylinder is provided. The solenoid valves are energized so that the difference control value between the pair of solenoid valves for adjusting the amount and the calculated value of the signal from the sensor that detects the running state of the vehicle and the input value from the rear wheel steering angle sensor becomes zero. A signal is output, and when the differential pressure value obtained by the detection signals from the pair of hydraulic pressure sensors that detect the hydraulic pressures of the left and right oil chambers of the rear wheel steering cylinder and the differential control value do not match, Since a controller that outputs an excitation signal to a solenoid valve attached to an oil chamber with a lower pressure so that the differential pressure value becomes zero is provided, one of the solenoid valves fails and the rear wheel steering is performed. If one of the oil chambers in the rear cylinder has an abnormal pressure rise, the abnormality is detected and the other solenoid valve is activated to balance the pressures in the left and right oil chambers of the rear wheel steering cylinder, It is possible to hold the working cylinder in the neutral position and improve the reliability of the rear wheel steering device, which is a great practical effect.

[Brief description of drawings]

FIG. 1 is a vehicle control system diagram showing an embodiment of the present invention, FIG. 2 is a detailed diagram of the valve mechanism, FIG. 3 is a detailed diagram of the controller, and FIG. 4 is an explanatory diagram of a failure state of the valve mechanism. ,
FIG. 5 is an explanatory diagram of a failure correction state of the valve mechanism. 5 ... Rear wheel steering cylinder, 6 ... Piston, 7a, 7b ...
… Oil chamber, 11… Pump, 12… Solenoid valve, 31…
… Controller, 32 …… Front wheel steering angle sensor, 33 …… Vehicle speed sensor, 34 …… Yaw angular velocity sensor, 35 …… Rear wheel steering angle sensor, 43 …… Hydraulic pressure sensor.

Claims (1)

[Scope of utility model registration request] 1. A pair of solenoid valves attached to right and left oil chambers of a rear-wheel steering cylinder defined by pistons for adjusting the amount of oil supplied from a pump to the rear-wheel steering cylinder; An excitation signal is output to the solenoid valve so that the difference control value between the rear wheel steering angle value calculated based on the signal from the sensor that detects the running state and the input value from the rear wheel steering angle sensor becomes zero. In addition, when the differential pressure value obtained by the detection signals from the pair of hydraulic pressure sensors that respectively detect the hydraulic pressures of the left and right oil chambers of the rear wheel steering cylinder and the differential control value do not match, the differential pressure value A rear wheel steering system including: a controller that outputs an excitation signal to a solenoid valve attached to an oil chamber having a lower pressure so that the pressure becomes zero.