JPH01229771A - Device for steering rear wheel of vehicle - Google Patents

Abstract

PURPOSE:To return rear wheels to the neutral position by placing a clutch and a brake between a rear wheel steering mechanism and a driving means and disengaging the clutch when rear wheel steering by the driving means is unable due to the failure of the brake. CONSTITUTION:A rear wheel steering mechanism B rotates knuckle arms 10R, 10L clockwise or counterclockwise via a speed reduction mechanism 21, a relay rod 12, etc. by the rotation of a servomotor 20 as a driving source, thereby steering rear wheels 2R, 2L. In this case, in the cooperating mechanism of the relay rod 12 and servomotor 20, the speed reduction mechanism 21, a clutch 22, and a brake mechanism 23 are provided in order from the relay rod 12 side. By holding the output shaft of the servomotor 20 with the brake mechanism 23 to lock the rotation thereof while disengaging the clutch 22, the rear wheels 2R, 2L are forcedly returned to the neutral position by a neutral holding means 13.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rear wheel steering device for steering rear wheels.

(Prior art) Some heavy vehicles have so-called four-wheel steering (4WS) and one
There is a system in which the rear wheels are steered along with the front wheels so that the rear wheels can be steered.2 In this four-wheel steering system, the steering mechanism for the rear wheels is as follows:
A mechanical type in which the 1rj wheel steering mechanism and the rear wheel steering mechanism are mechanically connected, and a mechanical type in which the rear wheel steering mechanism is equipped with an electromagnetic drive means such as an electric motor, as seen in Utility Model Application No. 62-25275. It is roughly divided into an electric type in which the rear wheels are steered by the driving force of this driving means in conjunction with each other. In this electromagnetic type, a speed reduction mechanism is interposed between the drive means and the rear wheel steering mechanism so that the capacity of the drive means can be made as small as possible, and the steering force of the drive means is released. It has also been proposed to provide a brake for maintaining a predetermined rear wheel steering condition (see Japanese Utility Model Application No. 62-25277).

In the case of the electric type, the rear wheel steering is controlled exclusively electrically, so it is necessary to fully consider fail-safe measures such as failure of this control system. From this point of view, as seen in Japanese Unexamined Patent Application Publication No. 61-202977, the rear wheel steering mechanism is always in the middle position,
It has been proposed to provide neutral holding means for biasing in the direction. This proposal is to stop rear wheel steering control when some kind of failure occurs in the control system, and to
This is based on the idea of forcibly returning the rear wheels to the neutral position using a holding stage. 1 (Problems to be Solved by the Invention) By the way, as mentioned above, in the case where the steered state of the rear wheels is maintained by the brake, failure of this brake,
In particular, there are cases where the brakes remain in a braking state due to seizure or the like. If such a brake failure occurs while the rear wheels are being steered, the rear wheels will remain in the steered state they were in when the brake failed. Therefore, some kind of countermeasure will be required.

Therefore, the 171st object of the present invention is to provide a vehicle equipped with a brake for maintaining rear wheel steering, so as to ensure safety especially when the brake fails, especially when the brake remains locked. The purpose of the present invention is to provide a rear wheel steering system for a vehicle that has a rear wheel steering system.

(Means and operations for solving the problem) In order to achieve the above-mentioned objective 1, the present invention has the following configuration.

a rear wheel steering mechanism for steering the rear wheels; and a neutral holding means (11) attached to the rotary wheel steering mechanism to always urge the rear wheel steering mechanism toward the 1"1 position.

[j; Linked to one wheel steering mechanism, [N7 in 111]
．． A drive means as a drive source for displacing the rear wheel steering mechanism against the holding means, 1ii7, L! A clutch that is interposed between the rear wheel steering mechanism and the drive means and connects and disconnects the rear wheel steering mechanism and the drive stage, +i? interposed between the driving hand driving means and the driving hand driving means; 11;
; drive (i); and a brake that locks the operation of the stage. .

As described above, in the present invention, since the brake for maintaining rear wheel steering is interposed between the clutch and the drive means, if this brake fails, the rear wheel cannot be steered by the drive means. In this case, by disengaging the clutch, it becomes possible to return the rear wheels to the neutral position (only the front wheels are steered) by holding the middle η first stage.

(Example) Examples of the present invention will be described below based on the attached drawings.

In Figure 1, IR is the right front wheel, IL is the left [) 11 wheels,
2R is the right rear wheel, 2L is the left rear wheel, and the left and right +iii
The rear wheels 2R and 2L are linked by a front wheel steering mechanism A, and the left and right rear wheels 2R and 2L are linked by a rear wheel steering mechanism B.

In the embodiment, the front wheel steering mechanism includes a pair of left and right knuckle arms 3R131, and a tie rod 4R14, respectively.
1, and a pair of left and right tie rods 4[, 4[, and a relay rod 5 that connects the tie rods 5]. A steering mechanism C is linked to this front wheel steering mechanism A, and the steering mechanism Cj is of a rack-and-binion type in the embodiment, and its component is a pinion 6.
is connected to a handle 8 via a shaft 7.

As a result, when the handle 8 is operated to the right, the relay rod 5 is displaced to the left in FIG.
3 Operation displacement of the above handle 8 centered on +,'':
In other words, the vehicle is steered clockwise in the figure by an amount corresponding to the steering angle. Similarly, when the steering wheel 8 is turned to the left, the left and right + ii 7 x 1 R 1114 will be steered to the left) according to the degree of operation 11:t. , Similar to 1iii wheel steering machine purchase A,
A pair of left and right knuckle arms I(')n, 101, respectively
, and the tie rod llR1111, and the tar rod IR, l11. A relay rod 12 is used to connect the relay rods, and this relay rod 12 has a holding stage 1;
3 is attached. As shown in FIG. 3, the middle i7 holding stage 1:3 holds the casing 15 fixed to the middle rest I4 at f7, and inside the casing 15 there are a pair of spring receivers 16a,
+6b is loosely fitted, and a compression spring 17 is disposed between these spring receivers 16a and 16b. The relay rod 12 extends through the cage jig 15, and a pair of flanges 12a and 12b are formed on the relay rod 12 at an interval.
a, 16b Lt-, and the relay lot I2 is always biased in the η direction by the compression spring 17. Of course, the compression spring 17 is provided with a spring force sufficient to overcome the site force during cornering.

[The rotary wheel steering mechanism L3 is linked to a servo 20 serving as a drive source for steering the rear wheels 21 and 2L. More specifically, relay lot 12 and servo lot 2
In the interlocking mechanism with 0, interposed in order from the relay lot 12 side are a reduction mechanism 21 including a float train 21a and a ball screw 21b, a clutch 22, and a brake mechanism 2:3. This allows the clutch 22 to properly dry the servo.
The servo motor 20 is configured to be able to mechanically disconnect from the rear wheel steering mechanism 13, and the brake mechanism 23 grips the output shaft of the servo motor 20 to lock rotation of the output shaft. has been done.

With the above configuration, when the clutch 22 is in the connected state, the IF rotation or reverse rotation of the servo motor 20 causes the relay rod 12 to move to the left or right in FIG.
The knuckle arm lO[<, 101- rotates clockwise or counterclockwise in the figure by an amount corresponding to the same rotation +H of the servo motor 20 about its rotation center 10R', IOL'. When the clutch 22 is in the disengaged state, the rear wheels 2 R121, which are to be steered, are forcibly returned to the neutral position by the middle holding means 13. 'L position. That is, when the clutch 22 is disengaged.

Only the heavy wheels I, RlI, and L are steered, so-called 2W
It turns out that Koyama from S...

The rear wheel steering control here is medium speed sensitive, and an example of a modification of the steering ratio according to the vehicle speed is as shown in FIG. 3. When the control characteristics shown in FIG. 3 are applied, the rear wheel turning angle relative to the steering angle changes in the same phase direction as the vehicle speed increases.

This situation is shown in Figure 4. In order to achieve such control, the control unit (J basically includes a steering wheel steering angle sensor 30, a medium speed sensor 31, and an encoder 3 that determines the rotational position of the servo controller 20).
Faith from 2 7;° is manually operated and the control unit [
At J, the rear wheel angle is calculated based on the steering wheel angle and the medium speed, and a control signal corresponding to the required rear wheel steering V is output to the servo motor 20. Then, the encoder 3 determines whether or not the servo motor 20 is operating properly.
The rear wheels 21 (21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 22, 22, 22, 22, 4, 4, 4, 3, 3, 3, 3, 3, 3, 4, 3, 5, 4, 5, 4, 5, 4, 3, 3, 3, 3, 3, 4, 2,,,,,,,,,,,,,,,,,,,,,,,,,,,,, t, , steered) While constantly monitoring, that is, under feedback control.

The basic control described above has a 2 in FM control system for fail-safe purposes. In other words, a steering angle sensor (III) is added to the steering wheel angle sensor 30, and a second medium speed sensor 3 is added to the medium speed sensor 31
35 is added, and the clutch 2
Rear wheel steering angle sensor 3 detects mechanical displacement of a member closer to relay rod 12 than sensor 2 (3 is added, and when both corresponding sensors in these sensors 30 to 36 detect the same value, Only the rear wheels are steered.

That is, in the sensors 30 to 36 described in 1-, for example, the vehicle speed at which the first medium speed sensor 31 has started and the medium speed detected by the second medium speed sensor 35 has become +j! When this occurs, it means that a failure has occurred, and the rear wheels 21'<, 21- are held in the middle 1''l state by control during fail mort, which will be described later.

In addition, in order to detect various failures, a control unit (J includes switches 37 to 40) 4;
r injured, and the alternator 1, end r-41
No. 18, which indicates whether or not power is being generated, is entered manually. Here, the above switches: 37 is the neutral clutch f-switch, switch 38 is the inhibitor switch, and switch 3
9 is a press switch, and switch 40 is a J engine switch. Here, the neutral switch 37 outputs an off signal when the shift position of the manual transmission is neutral or the clutch pedal is depressed in a small mountain equipped with a manual transmission, and otherwise outputs an on signal No. 114. It has become. inhibitor switch 3
8 has an automatic transmission (tiii) in the ilj cars,
The range is neutral (N) or park (
1)), an on signal is output, and when the vehicle is in the driving range, an off signal is output. Brake switch: 39 outputs Oshi No. 43 when the brake pedal is depressed, and engine switch 4
0 is set so that the ON 15 bow is output when the engine is in operation.

A block diagram of the L control system is shown in FIG. 5. In other words, the microprocessor 50 has two processes, I and II.
This microprocessor 50 has heavy speed sensors 3 + , 35 and switches 37 to 404 (2
The belief from the L terminal 41 of the alternator is buffer 5.
1, signals from the sensors 30, 34, and 36 are input via the A/D converter 52, and signals from the encoder 32 are input via the interface 53. On the other hand, the signals generated in the microprocessor 50 are sent to the servo motor 29 via a drive circuit 54.
This rear wheel steering control is carried out by the alternator 1, which is also sent to the rear brake 23 via the brake drive circuit 55, or to the clutch 22 via the Kurasochi drive circuit 56. The process is started on condition that the signal from the terminal 41 becomes high (Ili). In addition, in the same figure, numeral 57 is a battery, and 58
is the ignition key switch, 59 is the relay, 4@
When some kind of failure occurs in the steering control system, the relay drive circuit 60 is activated to stop energizing the coil 61, and as a result, the 13 contacts of the relay 59 are closed and the warning lamp 62 is turned on. Ru.

Next, failures and their treatment will be explained.Here, a treatment corresponding to the location where the failure occurs is taken, and there are two modes of treatment as follows.

Treatment mode A (Hill at the time of failure mode)
) This is a case where the control and position determination of the rear wheel 2R52L can still be performed OT. That is, when it is possible to return to the middle position using the dryer 20, the motor 20 will perform the return to the middle position. V-4 Physically, the contents of the one-wheel treatment are as follows. ■ After the warning lamp 62 lights up, ■ The rear wheel 2R12 [, is returned to the neutral position by the drive of the servo motor 20. ■ Then The morph brake 23 is engaged.

place! Control in 2-wheel mode) Rear wheel 2R1
What happens when control of 2L and determination of its position become impossible?
He is like a horse. The contents of this procedure are as follows.

■After the warning lamp 62 flashes, ■The clutch 22 is turned off, and the connection between the servos 20 and the rear wheel steering mechanism 11 is disconnected.
: After waiting for the rear wheel 2R121 to return to the middle position due to the spring force of step 3, the clutch 22 is connected.

Preferably, the dryer brake 23 is engaged after the clutch 22 is disengaged. As a result, steering of the rear wheels 211, 21-4 due to the runaway of the vehicle 20 is physically prohibited for the time being. After that, the power supply to Chiyo 20 is cut off. .

Below, the failed motes and their setting conditions will be classified into each system, and the corresponding treatment modes will be explained.

When it is determined that a failure has occurred in the Konopiku yarn production system, i;1
The treatment described in Aspect A is performed.

(1) 1st f [speed sensor; 31 change meter error.

This judgment is that the brake switch 39 is disabled) (OFl・゛)
, and the 11 first medium speed sensors 31 are 1(1■+/
The condition is that a deceleration of ci L l > a (constant) is detected. Here, V is the first vehicle speed sensor 3
1 represents the detected vehicle speed. That is, when the vehicle exhibits a predetermined deceleration even though the vehicle is not braked, it is determined that the first vehicle speed sensor 31 is malfunctioning.

(2) Error in the amount of change in the second vehicle speed sensor 35.

This determination is made as in the case of the first heavy speed sensor 31,
The conditions are that the brake switch 39 is off (OFF) and the H second vehicle speed sensors 35 detect a deceleration of I (IV2/dt, l>a (constant).Here, ■2
represents the vehicle speed detected by the first vehicle speed sensor 31.

(3) Heavy speed failure/accepted error This judgment is made in the first step. The condition is that the detected values of the second vehicle speed sensor 31.35 do not match, for example, as expressed by IV, -V2 1>b (constant Fi).

In this case, it is considered that an abnormality has occurred in at least one of the vehicle speed sensors, so regardless of whether the abnormality occurs in either sensor 3+ or 35, it is determined to be a failure, and as described above, , processing is performed on the aspect.

(4) Both medium speed sensors 3! , 35 simultaneous failures.

This judgment is based on the fact that the signal from the alternator terminal r-41 is high (lli), and the outputs of the first and second vehicle speed sensors 31.35 are zero (V+ = V2 = 0). For vehicles with a manual transmission, the condition is that the neutral switch 37 remains on for a certain period of time, and for heavy vehicles with an automatic transmission, the inhibitor switch 38 is turned on. Simultaneous failure of both sensors 31 and 35 is determined to be ≧ on the condition that the engine switch 40 is off, the engine switch 40 is on, and the brake switch 39 is off for a certain period of time.

In other words, the RFI speed is 0, even though the engine speed is sufficient for driving based on the power generation ■, and it can be considered that the car is running from the 1st shift position. This means that some abnormality has occurred in the sensors 31 and 35. This is no exception.

17 Rotary Printing Machine System When it is determined that a failure has occurred in the main system, the action of aspect B is taken.

(1) Control deviation (Part 1) This judgment is based on the output (EN) of the encoder 32 and the sensor 36
In other words, the discrepancy with the rear wheel steering angle (OR), for example l
It is assumed that r (EN) - G (eR) l > c (constant).

(2) Control deviation (part 2) This determination is based on the discrepancy 1 between the target rear wheel steering angle (θ'') set by the control unit U and the actual rear wheel steering angle (OR), for example, 1θr−〇Ill>c( Let it be assumed that it is a constant.

(3) Rear wheel reference position error This judgment is made on the condition that the center position of the rear wheel cannot be found at the time of control start (initialization)1.Here, the condition for initialization is that the engine key is turned on. It is now being carried out as

1-) C servo drying-Nini-beggarly control When it is determined that a failure has occurred in this system.

The treatment of aspect B is performed.

(1) Rotation error This determination is made on the condition that the control H, ) and the rotation of the motor 20 (detected value of the encoder 32) do not match.

(2) Motor monitor error This judgment is made in the following cases.

■Motor coil disconnection or short circuit. −■ Harness disconnection or short circuit.

■Failure of motor drive circuit 52.

When it is determined that a failure has occurred in the main system of the sensor system for one wheel, the action of aspect B is taken.

(1) Rotary encoder monitor error The condition for this determination is that an abnormality is recognized in the code output from the encoder 32.

(2) Rear wheel steering angle sensor monitor error The condition for this determination is that the output of the rear wheel steering angle sensor 36 exceeds a set range.

[゛ wo one transport j? When it is determined that a failure has occurred in the main sensor system, action in state IA is taken.

(1) Steering wheel steering angle sensor monitor error This determination is made on the condition that the output of the steering wheel angle sensor 30 exceeds a set range.

(21+iii Steering Angle Sensor Monitor Error The condition for this judgment is that the output of the front wheel steering angle sensor 36 exceeds the set range.

(3) +iiij steering angle mismatch error This judgment is made by the steering wheel steering angle sensor 30 and the heavy wheel steering angle sensor 34.
The condition is that the difference in output from

If it is determined that the disconnection operation of the clutch 22 is defective, the action of mode A is taken.

This establishment is based on the condition that the output of the rear wheel steering angle sensor 36 fluctuates by more than a certain value when the servo motor 20 is operated while outputting an off signal to the clutch 22.

When it is determined that a failure has occurred in the main system of the control i-roll unit system, the action of aspect 13 is taken.

(1) RAM error This establishment is conditional on a 5° error being recognized in the [<AM reading 1-1] check.

(2 + ROM error This judgment is based on the condition that 1 and 1 are recognized in the dumb thumb check of the ROM, (3) l・I
<0 error This judgment is made on the condition that an abnormality is recognized in the initial check of the self-running counter.

(4) △/1) Error The condition for this judgment is that an abnormality is recognized in the I10 check of the △/[) converter 52.

Microprocessor System (1) Calculation Error The condition for this judgment is that the calculation result of Macroprocessor II, I) Calculation 5 and Microprocessor 11 do not match.

(2) Communication error This judgment is based on the phase n between microblock processor I and [I.
1 letter (;1 is required to be disabled.

Brakes When brakes 2 and 3 fail, the procedure of mode F3 is taken. This failure determination of the brake 23 may be performed, for example, as follows.

Auto) When the motor 20 remains locked by the brake 23 4 The motor 20 is controlled to rotate with the brake 23 inactive (unopened/locked), and at this time the outputs of the encoder 32 and sensor 36 are If not (rear wheel 2R12
L is not steered).

(2) When the motor 20 cannot be locked by the brake 23.

When the brake 23 is locked and the motor 20 is rotated, if there is an output from the encoder 32 and sensor 3 F5 (rear wheel 2
21. The ship was steered.

Next, please refer to the flowcharts in Figs. 7 to 9 regarding the control for the 7-coil safety in accordance with the multiple failure modes.
-ru. In addition, in the following explanation, P or S: Maste Tsubu is not indicated.

\ \ \ \ \ \ Full control (Figure 9) First, system initialization is performed at 1]0 in Figure 9. At this time, any malfunctions that may be known at the time of initialization are detected (for example, checking for errors in the rear wheel reference position, ROM of the control unit,
(Error checking of RAM, etc.)

Next, the signals from each sensor or switch are input to the PI, and the above-mentioned failure determination is made (ql(+). In other words, if there is an abnormality in the heavy speed signal state (
(when the determination in P2 is YES), when there is an abnormality in the curvature steering angle sensor system (when the determination in P3 is YES), when there is an abnormality in the clutch 22 (when the determination in P4 is YES), If any one of the conditions applies, proceed to P5 and change the lower device mode △ (braking in the first fail mode) to be described later.
is done in principle.

If all of the above P2 to P4 judgments are No, P6 to pH
A failure determination is made. If there is an abnormality in the rear wheel steering mechanism system in the judgment of P6 to P11 (G) 6 is determined as YES.
S), if there is an abnormality in the motor 20 (1) If the determination in 7 is YES), if there is an abnormality in the rear steering angle sensor system (if the determination in P8 is YES), there is an abnormality in the control unit system. If there is (Y F, S in the judgment on P9
), or if there is an abnormality in the microprocessor system (
If one of the following applies (when the Plo determination is YES), when there is an abnormality in the brake 23 (when the pH determination is YIi, S), the process moves to Y12. In this case, processing mode B (second fail mode control), which will be described later, is performed.

6ij P2 to P4 and P6 to pH determination all N.
When it is O, there is no abnormality, and in this case 1)j
At step 3, normal control is performed. That is, control is performed to realize the steering ratio characteristics shown in FIG. 4.

The details of the control at P5 are shown in FIG. 7.

First, at Sl, the warning lamp 62 is turned on to notify the driver that an abnormality has occurred. Next, in order to check whether rear wheel control and position determination are performed normally,
2. Judgment in S3 is made. In other words, if the rear steering sensor 36 is normal (when the determination in S2 is YES) and the encoder 32 is normal (when the determination in S3 is YES), the steering wheel 20 is controlled in S4. Rear wheel 2R
12L, is gradually returned to the neutral position. After this,
In S5, confirm that the motor 20 itself is normal (if the determination in S5 is YES), then continue to drive the rear wheel 2R.
After confirming that ,2L, is actually in the neutral position (
If the determination in S6 is YES), the brake is operated in S7 to lock the operation of the motor 20 while the backward rotation 2 H1214 is in the neutral position. Of course, at this time, the clutch 22 remains connected, and therefore, the backward rotation 2R12L is caused by the urging force of the medium η holding means 13, the resistance of the motor 20 via the deceleration mechanism 21, and the locking action of the brake 23. is firmly held in the neutral position.

On the other hand, if the determination in S2, SS3, or S5 is No, the motor 2o is activated to drive the rear wheel 2R12[
, it is impossible to accurately return it to the neutral position. In this case, the process moves to S11 in processing mode B in FIG. 8, which will be described later.

Processing mode [3 (Fig. 8) First, after lighting the warning lamp 62 in SIO, S11
At this point, the clutch 22 is disengaged. As a result, the reverse rotation 2R12L is forcibly returned to the neutral position by the neutral holding means 13. After that, in S12, the brake 23 is activated to lock the motor 20, and then in S13, the power supply to the dryer 20 is cut (the motor 2
prevention of runaway). Wait for a predetermined time to elapse in S14, that is, wait for this time to elapse taking into account the time required for the reverse rotation 2R12L to return to the neutral position, and then connect the clutch 2o in S15. (Stay firmly in neutral position). In addition, in the event of a failure in which the brake 23 cannot be locked, the locking by the brake in S12 will not actually be performed, but this does not cause any problem from the viewpoint of returning to the neutral position.

Although the embodiments have been described above, the driving means as the driving source of the rear wheel steering mechanism B may be an electromagnetic hydraulic actuator or the like as appropriate. In this case, a switching valve that supplies and discharges hydraulic pressure to a hydraulic actuator may be used as the braking means. That is, the hydraulic actuator is locked by maintaining the switching valve in a state in which no pressure oil is supplied or discharged from the hydraulic actuator.

(Effects of the Invention) As is clear from the above description, according to the present invention, when the brake is used to maintain rear wheel steering and the brake fails, especially when the brake remains locked, safety can be ensured.

1Titli explanation of 4 diagrams FIG. 1 is an overall system diagram showing one embodiment of the present invention.

Figure 2 is a configuration diagram of the rear wheel steering mechanism.

Figure 3 is an enlarged sectional view of the middle holding stage.

FIG. 4 is a control characteristic diagram of a heavy speed sensitive type, which is an example of rear wheel steering.

FIG. 5 is a characteristic diagram showing changes in rear wheel steering angle according to heavy speed.

Figure 6 is a block diagram of the control system according to the embodiment 3゜Figure 7~
FIG. 9 is a flowchart illustrating a control example of the present invention.

l: Front wheel 2: Rear wheel Iko 3: Medium) 7 Holding means 17: Compression spring 20: Servo motor (drive stage) 22: Cra...lchi 23: Dryer brake IJ, control unit 13: Rear wheel steering mechanism

Claims (1)

[Claims] (1) a rear wheel steering mechanism for steering the rear wheels; a neutral holding means attached to the rear wheel steering mechanism and always biasing the rear wheel steering mechanism toward a neutral position; and the rear wheel steering mechanism. a drive means as a drive source that is linked to the mechanism and displaces the rear wheel steering mechanism against the neutral holding means; and a drive means that is interposed between the rear wheel steering mechanism and the drive means, and is interposed between the rear wheel steering mechanism and the drive means. A rear wheel steering system for a vehicle, comprising: a clutch that connects and disconnects the drive means; and a brake that is interposed between the drive means and the clutch and locks the operation of the drive means.