JPH01182163A - Rear wheel steering device for vehicle - Google Patents

Abstract

PURPOSE:To enable disconnection of connection between a rear wheel steering mechanism and an electric motor, where necessary, when a failure in operation occurs to a device, by a method wherein a clutch to disconnect the connection is mounted between the electric motor and the rear steering mechanism. CONSTITUTION:Right and left front wells are interconnected through a front steering mechanism A, and right and left rear wheels are interconnected through a rear wheel steering mechanism B. The rear wheel steering mechanism B is coupled to a servo motor 20 serving as a drive source to steer rear wheels 2R and 2L. A reduction mechanism 21 containing a gear train and a ball screw, a clutch 22, and a brake mechanism 23 are located, in order named, from the relay rod 12 side in a coupling mechanism between the relay rod 12 and the servo motor 20. When a failure in operation occurs to a device, by means of a signal from a control unit, the clutch 22 is disengaged.

Description

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

(Prior Art) Some i#7 cars have so-called four-wheel steering (4WS) in which both the front wheels and the rear wheels are steered.

In this four-wheel steering, the steering mechanism for the rear wheels is
A mechanical system in which a front wheel steering mechanism and a rear wheel steering mechanism are mechanically connected, and a mechanical system in which an electric motor is linked to the rear wheel steering mechanism as seen in Japanese Utility Model Application Publication No. 62-25275. There are two main types: electric type, which uses driving force to steer the rear wheels. In the latter case, the rear wheel steering is exclusively controlled in an upward manner, so it is necessary to fully consider fail-safe measures such as failures in this control system.

From this point of view, as seen in Japanese Patent Application Laid-Open No. 61-202977, it has been proposed to provide the rear wheel steering mechanism with a neutral holding means that always biases the rear wheel steering mechanism in the neutral direction. This proposal is based on the idea that when some kind of failure occurs in the control system, control of rear wheel steering is stopped and the rear wheels are returned to the neutral position by the above-mentioned intermediate retaining means.

However, as seen in both of the above publications, this type of rear wheel steering device has a motor brake attached to the electric motor to increase the holding torque, and a deceleration mechanism is installed between the electric motor and the rear wheel steering mechanism. It is customary to intervene to reduce the size of the electric motor. For this reason, even if the rear wheels are returned to the neutral position by the biasing force of the neutral holding means, it is necessary to overcome the holding torque of the motor via the deceleration mechanism, and in practice, the neutral position of the rear wheels is secured. That is difficult.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a rear wheel steering system for a vehicle that can ensure a neutral position of the rear wheels even if a failure occurs in the rear wheel steering system for some reason.

(Means and operations for solving the problem) In order to achieve the technical problem described in item 2, in the present invention, in addition to the above-mentioned center retaining means, there is a A clutch is provided to connect and disconnect the rear wheel steering mechanism, so that when a failure occurs in the device, the connection between the rear wheel steering mechanism and the electric motor can be disconnected as necessary.

Specifically, on the premise of a rear wheel steering system for one vehicle, in which an electric motor is linked to the rear wheel steering mechanism and the electric motor is used as a drive source to steer the rear wheels, a neutral holding means attached to the mechanism and always biasing the rear wheel steering mechanism in the middle direction; and a neutral holding means disposed between the rear wheel steering mechanism and the electric motor, and the neutral holding means is provided between the rear wheel steering mechanism and the electric motor. The configuration includes a clutch that connects and disconnects the linkage.

With this configuration, when the clutch is disengaged, the rear wheel steering mechanism is released from the restraint from the electric motor, and the neutral holding means ensures that the rear wheel steering mechanism, that is, the rear wheels 2R12L, is in the neutral position. be done.

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

In Fig. 1, IR is the right front wheel, IL is the left front wheel, 2R is the right rear wheel, and 2L is the left rear wheel.The left and right front wheels IR and IL are linked by a front wheel steering mechanism A, and the left and right rear wheels are 2R1
2L is linked by rear wheel steering mechanism B.

In the embodiment, the front wheel steering device 4XIA includes a pair of left and right knuckle arms 3R13L and a tie rod 4R14, respectively.
L, and a relay rod 5 that connects the pair of left and right tie rods 4R14L. A steering mechanism C is linked to this front wheel steering mechanism A, and the steering mechanism C is of a rack and pinion type in the ' 8, when the handle 8 is turned to the right, the relay rod 5 is displaced to the left in FIG. 1, and the knuckle arm 3
R13L is steered clockwise in the figure by an amount corresponding to the operating displacement of the handle 8, that is, the steering angle, about the rotation centers 3R' and 3L'. Similarly, when the steering wheel 8 is operated to turn left, the left and right front wheels IR, IL are steered to the left in accordance with this operation displacement 4.

Similarly to the front wheel steering mechanism A, the rear wheel steering mechanism B also includes a pair of left and right knuckle arms lOR, 10L and a tie rod IIR1ILL, and a relay rod 12 that connects the tie rods 11R and llL. A neutrality holding means 13 is attached to the. As shown in FIG. 3, the neutral holding means 13 has a casing 15 fixed to the vehicle body 14, and a pair of spring receivers 16a, 16b are loosely fitted into the casing 15. A compression spring 17 is disposed between them. The relay rod 12 extends through the casing 15, and the relay rod 12 has a pair of flanges 12a, 12.
b are formed at intervals, and the spring receivers 16a, 16b are received by the flanges 12a, 12b, so that the relay rod 12 is always biased in the neutral direction by the compression spring 17. Of course, the compression spring 17 is provided with a spring force sufficient to overcome the side force during cornering.

The rear wheel steering mechanism B shown in L is linked to a servo motor 20 as a drive source for steering the rear wheels 2R12L. More basically, in the connection a width between the relay rod 12 and the servo motor 20, from the relay rod 12 side to 11"1, there is a speed reduction mechanism 2 including a gear 21a and a hall gear 21b.
1, 7, 22, and a brake mechanism 23 are interposed. As a result, the flange 22 can mechanically disconnect the servo motor 20 from the rear wheel steering system B as appropriate, and the brake mechanism 23 can mechanically disconnect the servo motor 20 from the rear wheel steering system B.
The rotation of the output shaft can be locked by gripping the output shaft.

With the above configuration, when the clutch 22 is in the connected state, the forward rotation or normal rotation of the servo motor 20 displaces the relay rod 12 to the left or right in FIG. The above servo motor 2 is rotated around the rotation center 10R' and IOL'.
It will be steered in the clockwise direction or in the counterclockwise direction by the amount corresponding to the rotation angle of 0. Other power, the above clutch 22
When the neutral holding means 1 is in the disconnected state, the neutral holding means 1
3, the rear wheels 2R12L are forcibly returned to the neutral position and held at this neutral position. That is, when the clutch 22 is disengaged.

This is a so-called 2WS vehicle in which only the front wheels IR2IL are steered.

Here, the rear wheel steering control is vehicle speed sensitive, and an example of changing 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 steering angle relative to the steering wheel steering angle changes in the same phase direction as the vehicle speed increases. This situation is shown in FIG. In order to perform such control, signals from a steering wheel angle sensor 30, a vehicle speed sensor 31, and an encoder 32 that detects the rotational position of the servo motor 20 are basically input to the control unit U. The unit U calculates a target rear wheel steering angle based on the steering wheel steering angle and vehicle speed, and a control signal corresponding to the required rear wheel steering angle is sent to the servo motor 20.
is output to. The encoder 32 constantly monitors whether or not the servo motor 20 is operating properly.
12L steering is performed.

] - The basic control system has a two-east configuration for fail-safe purposes. In other words, a front wheel steering angle sensor 34 is added to the above-mentioned steering angle sensor 30,
A second vehicle speed sensor 35 is added to the vehicle speed sensor 31, and a rear wheel steering angle sensor 36 is added to the encoder 32 for detecting mechanical displacement of a member closer to the relay rod 12 than the clutch 22. Among these sensors 30 to 36, rear wheel steering is performed only when both corresponding sensors detect the same value.

That is, in the sensors 30 to 36, for example, the first
The vehicle speed detected by the vehicle speed sensor 31 and the 20th east speed sensor 3
If the vehicle speed is different from the vehicle speed detected in step 5, it means that a failure has occurred, and the control of rear wheel steering is turned off and the neutral holding means 13'? The rear wheels 2R12L are maintained in a neutral state by using this.

In addition, to detect various failures, turn-off signals from switches 37 to 40 are input to the control unit U, and a signal indicating the presence or absence of power generation is input from the L terminal 41 of the alternator. Ru. Here, the switch 37
is a neutral clutch switch, switch 38 is an inhibitor switch, switch 39 is a brake switch,
Switch 40 is an engine switch. Here, in a city equipped with a manual transmission, the neutral switch 37 outputs an off signal when the manual transmission is in the shift position or neutral or when the clutch pedal is depressed, and otherwise outputs an on signal. It looks like this.

In a vehicle equipped with an automatic transmission, the inhibitor switch 38 outputs an on signal when the range is in neutral (N) or parking (P).
An off signal is output when the vehicle is in the driving range. The brake switch 39 outputs an on signal when the brake pedal is depressed, and the engine shift switch 40 outputs an on signal when the engine is in operation.

A block diagram of the above control system is shown in FIG. 5. In other words, the microprocessor 5o has two
The microprocessor 50 receives signals from the vehicle speed sensor 31.35, switches 37 to 40, and the L terminal 41 of the alternator via a buffer 51, and also receives signals from the sensors 30.34.36. is A
The signal from the encoder 32 is 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, to the motor brake 23 via a brake drive circuit 55, or to the clutch via a clutch drive circuit 56. 22. This rear wheel steering control is started on the condition that the signal from the L terminal 41 of the alternator becomes high (Hi). In addition, in the figure, reference numeral 57 is a battery, 58 is an ignition key switch, and 59 is a relay.If some kind of failure occurs in the four-wheel steering control system, the relay drive circuit 60 is activated to stop supplying electricity to the coil 61. As a result, the B contact of the relay 59 is closed and the warning lamp 62 is turned on.

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 (FIG. 6) This is a mode in which control of the rear wheel 2R12L and determination of its position are still possible. That is, when the motor 20 can return to neutral, the motor 2
0 returns to neutrality. Specifically, as shown in FIG. 6, the contents of this procedure are as follows: 1. After the warning lamp 62 lights up (step 51), 2. The rear wheels 2R12L are returned to the neutral position by the drive of the servo motor 20 ( Steps S4.S6).

G) After that, the motor brake 23 is engaged (step 37).

Treatment mode B (FIG. 7) This is a mode when the control of the rear wheel 2R12L and its position determination become unbalanced. The contents of this procedure are as shown in FIG.
(7) After that, (?) the flange 22 is turned off and the linkage between the servo motor 20 and the rear wheel steering mechanism B is disconnected (step 511).
, (■ Due to the spring force of the neutral holding means 13, the rear wheels 2R12L
after waiting for it to return to the neutral position (step S1
2), (1) The clutch 22 is connected (step 515).

Note that after disengaging the clutch 22 (step 5)
ll), in step S12, the motor brake 23
The agreement is now set to be concluded. As a result, runaway of the motor 2o is physically prohibited for the time being. Then, the power supply to the motor 20 is cut off (step S13).

Below, the failure modes and their setting conditions are classified into each system, and the corresponding treatment methods will be explained.

When it is determined that a failure has occurred in the main vehicle speed signal system, the above-mentioned mode A is taken.

(1) ffJ, 1 variation error in vehicle speed sensor 31.

This determination is made when the brake switch 39 is off (OFF) and the first vehicle speed sensor 31 is 1dV1/dtl>a.
The condition is that a deceleration of (constant) is detected. Here, Vl represents the heavy speed detected by the first vehicle speed sensor 31. That is, when the vehicle fails to decelerate beyond a predetermined value 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 vehicle speed sensor 31,
The conditions are that the brake switch 39 is off (OFF) and that the H second vehicle speed sensors 35 detect a deceleration of IdV2/dt l>a (constant). Here v
2 represents the vehicle speed detected by the first vehicle speed sensor 31.

(3) Heavy speed mismatch error The condition for this judgment is that the detected values of the first and second vehicle speed sensors 31.35 do not match, as expressed by, for example, IVI −V2 1>b (constant) .

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 31 or 35, it will be determined as a failure, and as described above, , the processing of aspect A is performed.

(4) Simultaneous failure of both vehicle speed sensors 31 and 35.

This determination is based on the fact that the signal from the L terminal 41 of the alternator is high (Hi) and that the first and second vehicle speeds -1=n+t
-31 and 35 are zero (Vt = V2 = 0), and in vehicles with manual transmission, on condition that the neutral switch 37 remains on for a certain period of time, the other automatic In a vehicle with a transmission, simultaneous failure of both sensors 31 and 35 is determined on the condition that the inhibitor switch 38 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 fact that the vehicle speed is zero despite the fact that the engine speed is at which the vehicle can be driven based on the amount of power generated and the vehicle can be considered to be traveling based on the shift position does not mean that some abnormality has occurred in the sensor 31 or 35. It won't happen.

When it is determined that a failure has occurred in the main system of the rear wheel steering mechanism system, the action of aspect B is taken.

(1) Control deviation (Part 1) This judgment is based on the mismatch between the output of the encoder 32 (EN) and the rear wheel steering angle (OR), for example If(EN)-G(OR).
The condition is that I>c (constant).

(2) Control deviation (part 2) This determination is based on the mismatch between the [-1 mark rear wheel steering angle (Or) and the actual rear wheel steering angle (OR) set by the control unit U, e.g. l Or-ORl> The condition is that c (constant).

(3) Rear wheel reference position error The condition for this determination is that the rear wheel center reference cannot be found at the start of control (initialization). Here, initialization is performed on the condition that the engine key is turned on.

When it is determined that a failure has occurred in the main DC servo motor system. The treatment of aspect B is performed.

(1) Rotation amount error This judgment is based on the control amount and the rotation amount of the motor 20 (encoder 3
The condition is that the detected values of 2) do not match.

(2) Motor monitor error This judgment will be made in the case of multiple cases.

([〉Motor coil disconnection or short circuit.

(Run harness disconnection, VAN.

■Failure of motor drive circuit 52.

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

(1) The rotary encoder monitor error tree determination is performed on the condition 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.

When it is determined that a failure has occurred in the main front wheel steering angle sensor system, the measure A 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.

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

(3) Front wheel steering angle mismatch error Unopened/fixed: Handle steering angle sensor 30 and front wheel steering angle sensor 3
The condition is that the difference in output from 4 is greater than a certain value.

Malfunction of disconnection of electromagnetic clutch When it is determined that the disengagement of the electromagnetic clutch 22 is malfunctioning, the action of aspect A is taken.

This determination is made on the condition that the output of the rear wheel steering angle sensor 36 fluctuates by a certain value or more when an off signal is output to the clutch 22 and the servo motor 20 is operated.

When it is determined that a failure has occurred in the control unit 1m, mode B is taken.

(1) RAM error The condition for this determination is that an abnormality is found in the RAM read/write check.

(2) ROM error The condition for this judgment is that an abnormality is found in the ROM dumb thumb check.

(3) FRC error The condition for this judgment is that an abnormality is recognized in the initial change of the free-running counter.

(4) A/D error This determination is made on the condition that an abnormality is recognized in the I10 NAEC of the A/D converter 52.

Microprocessor System (1) Operation Error This determination is made on the condition that the calculation results of the microprocessor system and the calculation results of the microprocessor II do not match.

(2) Communication error The condition for this determination is that mutual communication between microprocessors I and II has become impossible.

With the above configuration, when the rear wheel control becomes impossible, the rear wheel steering mechanism B is released from the electric motor 20 by disengaging the clutch 22, so that the rear wheel steering mechanism B is released from the electric motor 20, so that it is not affected by the biasing force of the center wheel holding means 13. This ensures that the rear wheels 2R and 2L are returned to their neutral positions. Further, according to this embodiment, the motor 2
If neutral return is possible with zero, neutral return is performed under the driving force of the motor 20, so the return speed can be freely controlled. Furthermore,
When the engine key switch is turned off, clutch 2
Since the power supply to the vehicle 2 is turned off and the clutch 22 is automatically disconnected, the rear wheels 2R12L are automatically returned to neutral by the biasing force of the neutral holding means 13 while the vehicle is stopped. Therefore, it is possible to eliminate the need for center positioning at the time of starting. Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and the present invention is not limited to the above embodiment.
When an abnormality occurs in the operation of one clutch 22, the other clutch may be operated. Further, in a vehicle with an automatic transmission, when the shift position is put into the P range, the motor 20 may be used to shift the vehicle to the center. According to this, it is possible to prevent an IS condition in which the rear wheels 2R12L are steered when the vehicle is stopped with the engine running without returning the steering wheel to neutral. As a result, when the vehicle is stopped with the engine rotating, the steering is performed after 1 h, and as a result, it is possible to prevent wasteful consumption of fuel due to the upward shift of the idle rotation.

(Effects of the Invention) As is clear from the description below, according to the present invention, the rear wheel steering mechanism can be operated by disconnecting the clutch provided between the electric motor and the rear wheel steering mechanism as necessary. Since the restraint from the electric motor is released, the rear wheel steering mechanism can reliably return to neutral due to the biasing force of the neutral holding means.
Furthermore, it is possible to reliably hold the neutral position difference.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of the rear wheel control according to the embodiment, FIG. 2 is a configuration diagram of the rear wheel steering mechanism, FIG. 3 is an enlarged cross-sectional view of the middle retaining means, and FIG. 4 is a diagram of the rear wheel steering mechanism.・Example: Vehicle speed sensitive type 1L
jJ control characteristic diagram, Figure 5 is a characteristic diagram showing changes in rear wheel steering angle according to vehicle speed, Force 6 is a block diagram of the control system according to the embodiment, and Figure 7 is an example of troubleshooting E; FIG. 8 is a flowchart showing another example of the failure treatment mode. 1: Front wheel 2; Rear wheel 13; Neutral holding means 17; Compression spring 20, DCC thermotor 21; Reduction mechanism 22; Clutch 23: Motor brake U; Control unit B: Rear wheel steering mechanism Figure 4 Figure 5

Claims (1)

[Claims] (1) In a rear wheel steering device for a vehicle, in which an electric motor is linked to a rear wheel steering mechanism, and the electric motor is used as a drive source to steer the rear wheels, a neutral holding means that always urges the wheel steering mechanism in a neutral direction; a clutch that is disposed between the rear wheel steering mechanism and the electric motor and disconnects and disconnects the rear wheel steering mechanism and the electric motor; A rear wheel steering device for a vehicle, comprising: