JPH05193511A - Rear wheel steering device for vehicle - Google Patents

Abstract

PURPOSE:To steer rear wheels by a mechanical operating means such as an electric motor and carry out fail-safe treatment without applying a large load to the mechanical operating means. CONSTITUTION:When an anomaly is generated in a main control circuit 25 or a main motor 23 is put inoperative by disconnection, an auxiliary control circuit 26 operates an auxiliary steering unit 100, and rear wheels are returned to the vicinity of a neutral position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear wheel steering device for a vehicle having a so-called fail-safe function, which enhances stability and safety of steering when an abnormality occurs in a rear wheel steering mechanism.

[0002]

2. Description of the Related Art Conventionally, as a rear wheel steering device having a fail-safe function, for example, a device disclosed in Japanese Patent Application Laid-Open No. 62-218282 has been proposed. With this device,
A rear wheel steering mechanism that uses hydraulic pressure is provided for normal rear wheel steering, and when the actuator can be driven due to an abnormality in the device, hydraulic pressure is used to set the rear wheel steering ratio. There are provided a first fail mode for fixing the value to a value and a second fail mode for fixing the steering ratio of the rear wheels to a predetermined value by a biasing means such as a spring when the actuator cannot be driven. And when an abnormality occurs,
When the drive power of the actuator is sufficient, the rear wheel steering position is slowly returned to the predetermined position using the first fail mode, and the second fail mode is used only when the drive power of the actuator is insufficient. Comparatively slowly, the rear wheel steering position is returned to a predetermined position.

[0003]

However, in the above-mentioned conventional apparatus, since the hydraulic pressure is used in the normal rear wheel steering, the hydraulic pump must be constantly rotated, resulting in large energy consumption and poor fuel efficiency. Further operation,
(Actuator for controlling hydraulic pressure or pressure direction) →
(Increase in hydraulic pressure by the pump) → (Rear wheel steering by the power cylinder) is transmitted, resulting in poor responsiveness of the device. Therefore, in the rear wheel steering process, it is desired that the rear wheels be directly steered by a mechanical operation of an electric motor or the like without using hydraulic pressure. Therefore, a rear wheel steering device using an electric motor is provided with a biasing means such as a spring as in the above-mentioned conventional device, and a method of fixing the steering ratio or the steering angle of the rear wheels to a predetermined value by this biasing force is used. An apparatus for performing fail-safe processing is disclosed in JP-A-1-266067 and JP-A-2-26067.
It is disclosed in Japanese Patent No. 270679. However,
This method requires a steering force larger than the biasing force of the spring during normal rear wheel steering, which causes a problem that a large load is generated on the electric motor that drives the rear wheel steering device.

Therefore, the present invention has been made in view of the above problems, in which the rear wheels are steered by a mechanical actuating means such as an electric motor, and a fail-safe operation is performed without giving a large load to the mechanical actuating means. An object of the present invention is to provide a rear wheel steering device for a vehicle that can perform processing.

[0005]

To achieve the above object, a vehicle rear wheel steering apparatus according to the present invention comprises a traveling state detecting means for detecting a traveling state of a vehicle, and a rear wheel steering means for steering a rear wheel. A first operating means for mechanically operating the rear wheel steering means, a second operating means for mechanically operating the rear wheel steering means, and a first operating means connected to the traveling state. A first control means for controlling the first operating means according to the traveling state of the vehicle detected by the detecting means, and a vehicle connected to the second operating means and detected by the traveling state detecting means. A second control unit that controls the second operation unit according to a traveling state and an abnormality detection unit that detects an abnormality of the first control unit are provided. When an abnormality of the control means is detected, the second Control means actuates the rear wheel turning means with said second actuating means, and its gist that steers rear wheels in a predetermined turning angle inside.

Further, the first control means determines whether or not there is a disconnection between the first control means and the first actuation means, and the first control means causes the first control means. When it is determined that there is a disconnection between the first operating device and the first operating device, the second control device operates the rear wheel steering device by using the second operating device to move the rear wheel within a predetermined steering angle. You may make it steer to.

The first operating means may be a first electric motor and the second operating means may be a second electric motor. Further, the first operating means and the second operating means are built in a motor housing of one electric motor, and the abnormality detecting means detects an abnormality of the first control means and the second operating means. When the abnormality of the control means is detected and the abnormality of the first abnormality detection means and the second abnormality detection means is not detected by the abnormality detection means, the first control means causes the first operation means to operate. And the second control means actuates the second actuating means to drive the electric motor, thereby mechanically actuating the rear wheel steering means.

A clutch may be provided between the second electric motor and the rear wheel steering means, and the second electric motor may mechanically operate the rear wheel steering means via the clutch. Good.

[0009]

In the vehicle rear wheel steering apparatus of the present invention having the above structure, when the abnormality detecting means detects the abnormality of the first control means, the second control means uses the second actuating means to perform the rear operation. The wheel steering means is mechanically operated to return the rear wheels to within a predetermined steering angle. That is, even if an abnormality occurs in the first control means, since the second actuating means and the second control means are provided, these can be used to return the rear wheel to the predetermined position. Therefore, the fail-safe process can be performed without requiring a biasing force such as a spring and without giving a large load to the electric motor.

[0010]

The present invention will be described in detail below with reference to the embodiments shown in the drawings. FIG. 1 is a block diagram of the first embodiment. The present embodiment is characterized in that in addition to the main motor that steers the rear wheels during normal four-wheel steering control, an auxiliary motor for fail safe is provided.

The main motor 23 is a known electric motor for steering the rear wheels during normal operation, and the main control circuit 2
Controlled by 5. A rear wheel steering unit 1 is fixed to a vehicle body (not shown). Reference numeral 2 denotes a rigid rod which penetrates through the inside of the rear wheel steering unit 1 and is installed so as to be linearly movable substantially vertically to the center line of the vehicle and in the left-right direction in the figure. The left rear wheel 41 and the right rear wheel 42 are connected via link mechanisms 31 and 32. Then, when the rod 2 swings to the left or right by the force given from the rear wheel steering unit 1, the rear wheel 4 is accordingly moved.
1, 42 are attached so as to be steered to the left and right at a certain ratio to the movement amount of the rod 2. The movement amount of the rod 2 is limited to a predetermined amount by a mechanical stopper (not shown).

In the rear wheel steering unit 1, the worm 5,
A stroke sensor 9, a worm wheel 13, a pinion gear 14, and a rack 15 are provided. When the main motor 23 is energized by the main control circuit 25 and the motor shaft 22 rotates, the worm 5 inserted into the motor shaft 22 and assembled so that the relative rotation with the motor shaft 22 is restricted by a key or the like is the motor shaft 22. And the worm wheel 13 that is meshed with the worm wheel 13 is rotated. The worm wheel 13 is integrally assembled with the pinion gear 14, and both rotate at the same angular velocity. Therefore, the rack 15 that meshes with the pinion gear 14 and the rod 2 that is connected to the rack 15
Moves linearly in the right or left direction in FIG. 1 depending on the rotation direction of the pinion gear 14. At this time, the stroke of the rod 2 is detected by measuring the rotation amount of the pinion gear 14 with the stroke sensor 9, and the main motor 23
The rotation angle of the motor shaft 22 (that is, the motor shaft 22) is detected by the rotation angle sensor 24.

The auxiliary steering unit 100 performs an operation of returning the rear wheels to the neutral position by the control of the auxiliary control circuit 26 when the main control device 25 is abnormal or when the main motor 23 is not driven due to the disconnection. is there. A detailed configuration diagram of the auxiliary steering unit 100 is shown in FIG.

The auxiliary steering unit 100 includes an auxiliary motor 2
7. A reduction mechanism (a worm gear 28, a worm wheel gear 29, a small diameter spur gear 33, a large diameter spur gear 30, etc.) that reduces the rotation of the shaft of the auxiliary motor 27 to an appropriate rotation speed.
And a clutch 34. The clutch 34 is normally disengaged in order to avoid becoming a load on the main motor 23, and is a mechanism that is automatically connected when the auxiliary motor 27 starts to rotate. The feature is that it automatically connects when rotated in either the left or right direction. In the case of the electromagnetic clutch, the electromagnetic clutch is likely to increase in failure modes such as failure of the control circuit for the electromagnetic clutch, disconnection of the connector, peeling of solder, and the like. It is a formula clutch. On the other hand, the auxiliary motor 27 is a small DC motor so as to generate the required torque by using a speed reduction mechanism in order to keep the device size small.

Next, the operating principle of the clutch 34 will be described with reference to FIG. If the main controller 25 is abnormal, or if the main motor 23 does not drive due to disconnection,
As shown in FIG. 3 (a), the auxiliary motor 2 is attached to the clutch 34.
The rotation from 7 is transmitted, and the projection of the large diameter spur gear 30 pushes and pushes the push cam 52 through the pin 51, so that the push cam 52 rides on the slope of the ring cam 53. The pushed push cam 52 urges the cam 55 toward the worm 5 via the push spring 54. The biased cam 55 contracts the spring 57 and fits into the groove of the clutch plate 56 attached to the end surface of the worm 5, and transmits the rotation.

Main controller 25 and main motor 2
3 returns to the normal state, the clutch 34 is rotated by the main motor 23 and the cam 55 moves as shown in FIG.
It is released by returning the push cam 52 to the groove of the ring cam 53 via.

The clutch 34 is used not only as a clutch for the auxiliary motor of the mechanical rear wheel steering apparatus of the present embodiment but also as a clutch for the auxiliary motor for throttle control, as a countermeasure against failure. It can be widely adopted as a clutch attached to an auxiliary motor used.

The main control circuit 25 inputs signals output from a vehicle speed sensor 3 for detecting a vehicle speed, a yaw rate sensor 4 for detecting a yaw rate, a rotation angle sensor 24, and a stroke sensor 9, which are provided in the vehicle. 23 is an electronic control circuit including a CPU for controlling 23. Further, in the main control circuit 25, a monitoring circuit 21 including a CPU that detects an abnormality of the main control circuit 25 is built in.

The auxiliary control circuit 26 is a CP of the monitoring circuit 21.
This is a circuit for inputting a signal output from the stroke sensor 9 and controlling the auxiliary motor 27 when U detects an abnormality of the CPU of the main control circuit 25.

The fail-safe processing executed by the main control circuit 25 and the auxiliary control circuit 26 in the present embodiment having the above-described structure will be described with reference to the flow chart shown in FIG.

The control starts when the ignition switch is turned on. First, in step S10, the CPU of the main control circuit 25 resets the circuit, and at the same time, the CPU of the main control circuit 25 initializes the stroke sensor 9 and the rotation angle sensor 24 such as zero point check.

In the next step S20, the main control circuit 2
The CPU 5 causes the main motor 23 to rotate a predetermined number of times at a predetermined speed to release the clutch 34, and the auxiliary motor 27
Does not become a load.

In step S40, the main control circuit 25
Signals are passed between the CPU of the CPU and the CPU of the monitoring circuit 21, and it is determined whether or not there is an abnormality in each signal. If there is an abnormality, YES is determined and the operation proceeds to step S80, and if there is no abnormality, NO is determined and the operation proceeds to step S50.
Proceed to.

In step S50, the main control circuit 25
CPU determines whether or not the drive system is broken. Specifically, a drive signal for driving the main motor 23 in the CPU of the main control circuit 25 and the main control circuit 25.
From the current actually output to the main motor 23. If the wire is broken, no current flows from the main control circuit 25 to the main motor 23, so that the determination is YES, and the process proceeds to step S80. If the wire is not broken, it is determined as NO and the process proceeds to step S60.

In step S60, the CPU of the main control circuit 25 detects whether or not the position sensor is normal.
That is, the signals from the stroke sensor 9 and the rotation angle sensor 24 are taken in and it is detected which one is broken or whether there is a discrepancy between the outputs of both. If there is an abnormality, the process proceeds to step S11011. If there is no abnormality, the process proceeds to step S70.

In step S70, the CPU of the main control circuit 25 controls the steering angle proportional to the front wheels, the yaw rate feedback control for controlling the yaw rate of the vehicle to the target value by using the yaw rate sensor, and so-called rear wheel steering. A known control known as control is performed.

On the other hand, step S40 or step S
In step S80, which is performed when YES is determined in 50, the main control circuit 25 and the monitoring circuit 21 set an abnormality occurrence flag in the CPU provided in each circuit, and the main control circuit 25 stops the CPU. That is, when it is determined to be YES in step S40, it cannot be determined which CPU is abnormal.
At 0, both CPUs are flagged as abnormal and the control by the main control circuit 25 is stopped. As a result, the main motor 23 is no longer driven.

In step S90, the auxiliary control circuit 26 inputs the signal from the stroke sensor 9 and compares the signal from the stroke sensor 9 with a reference value to determine whether the rear wheel steering angle is within 1 °. judge.
If the rear wheel steering angle is within 1 °, it is determined as YES. Then, when the steering angle is fixed within 1 °, the control is terminated because the traveling stability is not significantly affected. If the rear-wheel steering angle is larger than 1 °, NO is determined and step S10 is performed.
Go to 0.

In step S100, the auxiliary control circuit 26
Outputs a drive signal to the auxiliary motor 27 to operate the auxiliary steering unit 100 to return the rear wheels to the neutral position.

In step S110, which is executed when it is determined in step S60 that there is an abnormality, the main control circuit 2
The CPU of 5 inputs the output signal from the vehicle speed sensor 3 to determine whether the vehicle speed is equal to or higher than a predetermined speed. If the vehicle speed is equal to or higher than the predetermined speed, YES is determined and the control ends. That is, the rear wheel steering angle is fixed in order to prevent the rear wheels from being largely steered when traveling at high speed. If the vehicle speed is less than the predetermined speed, NO is determined and step S120 is performed.
Proceed to.

In step S120, the main control circuit 2
When the CPU of 5 drives the main motor 23,
Steer the rear wheel to the left or right until the rear wheel is prevented from being steered by a mechanical stopper, and use the position sensor that accurately indicates the steered angle of the rear wheel to return the rear wheel to the neutral position. ..

As described above, in the present embodiment, the auxiliary control circuit 26 operates the auxiliary steering unit 100 when an abnormality occurs in the main control circuit 25 or when the main motor 23 becomes inoperable due to disconnection. Since the rear wheels are returned to the neutral position by doing so, fail-safe processing can be performed without utilizing hydraulic pressure and without requiring a large electric motor.

In this embodiment, the vehicle speed sensor 3 and the yaw rate sensor 4 correspond to the traveling state detecting means, the rear wheel steering unit 1 corresponds to the rear wheel steering means, and the main motor 23 corresponds to the first operating means. However, the auxiliary steering unit 100 corresponds to the second actuation means, the main control circuit 25 corresponds to the first control means, the auxiliary control circuit 26 corresponds to the second control means, and the monitoring circuit 21 corresponds to the second control means. 1 corresponds to the abnormality detecting means.

Next, the second embodiment will be described. FIG. 5 shows the configuration of the second embodiment. The structure of the second embodiment is partly the same as the structure of the first embodiment, and the same components will be assigned the same reference numerals and explanations thereof will be omitted.

Reference numeral 5 denotes a special motor (hereinafter referred to as "tandem motor") which is a drive source of this apparatus, and its detailed configuration diagram is shown in FIG. This tandem motor 5
It is characterized in that two motor mechanisms 5a and 5b sharing a rotary shaft are built in one motor housing. More specifically, it is a kind of brushless motor in which a permanent magnet rotates and a coil is fixed, and the permanent magnets (or an assembly thereof) 7a, 7b are arranged along the rotation axis of the rotor 11 back and forth.
2 are arranged, and the coil is also divided into two accordingly.
The two motor mechanisms 5a and 5b have independent wirings, the motor mechanism 5a is controlled by the control circuit 71, and the motor mechanism 5b is controlled by the control circuit 72.

The tandem motor 5 of this embodiment is set so that the rear wheels 41, 42 can be steered even when only one of the two motor mechanisms 5a, 5b is driven. Under normal conditions, the two motor mechanisms 5a and 5b are driven jointly so that 100% of the performance of the rear wheel steering device is exhibited. As a result, this tandem motor 5 requires less parts such as bearings and couplings, as compared with the case where only two motors having the same structure are arranged, and the labor for assembling such as rotation axis alignment can be saved. In addition to being advantageous in terms of reliability, even if one of the control circuits and the motor mechanism becomes inoperable due to a failure, safe rear wheel steering can be realized without becoming inoperable.

As the structure of the tandem motor 5, in addition to the example shown in the figure, the coil is wound not by one but by two or more wires to make the wiring a multiple system, and it looks like one motor. Although visible, a structure that forms two or more motors on the circuit is conceivable. Further, in this embodiment, the brushless motor is used, but it is also possible to adopt a structure (a kind of DC motor) in which two or more brushes are used to rotate the coil.

Further, in the present embodiment, two lines are connected in series on the same rotary shaft.
Although this is a configuration example in which one or more motors are formed, the motors may be formed in parallel on the same rotation shaft as shown in FIG. 7. The tandem motor 5 described in detail above is widely applicable not only to the rear wheel steering device but also to a motor for a throttle control of an automatic drive, a motor for an electric pump of an anti-skid control, or the like, which is highly reliable in safety. ..
Further, in the case of ensuring the operation at the time of failure like the rear wheel steering system of this embodiment, one of the motor mechanisms having two or more is configured.
Although it is possible to operate with two motors, but when it is necessary to reliably stop at the time of failure, the torque generated by each motor mechanism is set to a movable torque or less and it operates when two or more operate together. By setting in this way, it is possible to prevent runaway at the time of failure and to ensure a reliable stop without a failure determination circuit.

Reference numeral 10 is a rotation angle sensor for detecting the rotor rotation angle of the tandem motor 5. The control circuits 71 and 72 are C
An electronic control circuit including a PU, which receives signals output from the vehicle speed sensor 3, the yaw rate sensor 4, the rotation angle sensor 24, and the stroke sensor 9 to input the control circuit 71 to the motor mechanism 5a and the control circuit 72 to the motor mechanism. 5b is controlled. Further, the control circuit 71 includes a monitoring circuit 81 that detects an abnormality in the control circuit 72, and the control circuit 72 includes a monitoring circuit 82 that detects an abnormality in the control circuit 71. The monitoring circuits 81 and 82 have a built-in 1-bit CPU.

Next, the fail-safe processing executed by the control circuit 71 and the control circuit 72 in the present embodiment configured as described above will be described with reference to the flow chart shown in FIG.

The fail-safe process is started when the ignition switch is turned on. First, step S0
In 5, the CPU of the control circuit 71 and the CPU of the control circuit 72
Resets each circuit including the monitoring circuit and initializes the apparatus such as checking the zero points of the stroke sensor 9 and the rotation angle sensor 10.

In the following step S25, signals are transferred between the CPU of the control circuit 71 and the CPU of the monitoring circuit 81, and between the CPU of the control circuit 72 and the CPU of the monitoring circuit 82 to check whether each signal is normal. judge. If an abnormality is detected in either control device, the determination is YES and the process proceeds to step S65. If no abnormality is detected in either control device, it is determined as NO and a step S3.
Go to 5.

In step S35, the CP of the control circuit 71 is
U, the CPU of the control circuit 72 determines whether or not the drive system is broken. Specifically, C of the control circuits 71 and 72
The determination is made by comparing the respective drive signals for driving the motor mechanisms 5a and 5b in the PU with the respective currents actually output from the control circuits 71 and 72 to the motor mechanisms 5a and 5b. If it is broken, the control circuit 7
Since no signal is output from the motor mechanisms 1 and 72 to the motor mechanisms 5a and 5b, YES is determined and the process proceeds to step S65. If the wire is not broken, the determination is NO, and the process proceeds to step S45.

In step S45, the CP of the control circuit 71 is
U, the CPU of the control circuit 72 detects whether or not there is any abnormality in the position sensor. That is, the signals from the stroke sensor 9 and the rotation angle sensor 24 are fetched, and it is detected which of the stroke sensor 9 and the rotation angle sensor 10 is broken or whether there is a discrepancy between their outputs. If there is an abnormality, the process proceeds to step S115, and if there is no abnormality, the process proceeds to step S55.

In step S55, the CP of the control circuit 71
U, the CPU of the control circuit 72 controls the steering angle proportional to the front wheels by using both the motor mechanisms 5a and 5b, and the yaw rate feedback control that controls the yaw rate of the vehicle to match the target value by using the yaw rate sensor, etc. Well-known control known as so-called rear wheel steering control is performed.

On the other hand, step S25 or step S
In step S65 which is proceeded when YES is determined in 35, the CPU of the control circuit and the monitoring circuit determined to be abnormal in step 25 sets an abnormality occurrence flag, and the control circuit stops the CPU. As a result, the tandem motor 5 is not driven by the control circuit that sets the abnormality occurrence flag.

In step S75, the CPU of the normal control circuit determines whether the rear wheel turning angle is within 1 °.
If the rear wheel steering angle is within 1 °, it is determined as YES and 1 °
When the steering angle is fixed within the range, the control is terminated because the running stability is not significantly affected. If the rear wheel turning angle is greater than 1 °, the determination is NO and the process proceeds to step S85.

In step S85, the CPU of the normal control circuit outputs a drive signal to the motor mechanism to drive the tandem motor 5, and the loop between step S75 is repeated to set the rear wheel to the neutral position within 1 °. Return to. At this time, 1
Since the tandem motor 5 is driven by two motor mechanisms, the maximum output of the tandem motor 5 is smaller than that under normal conditions, but it is sufficient to operate at a predetermined rear wheel steering angular velocity for ensuring safety. Output is obtained.

In step S95, the CP of the control circuit 71
U, the CPU of the control circuit 72 determines whether the vehicle speed is equal to or higher than a predetermined speed. If the vehicle speed is equal to or higher than the predetermined speed, Y
It is judged as ES and the control is ended. That is, the rear wheel steering angle is fixed in order to prevent the rear wheels from being largely steered when traveling at high speed. If the vehicle speed is less than the predetermined speed, NO is determined and the process proceeds to step S105.

In step S105, C of the control circuit 71
The CPU of the PU and the control circuit 72 has the motor mechanisms 5a and 5b.
To steer the rear wheels to the left or right until the mechanical stopper prevents the rear wheels from being steered. If the steering of the rear wheels is disturbed, a large current will flow through the tandem motor 5. Therefore, using this position as either the left or right end, the position sensor that accurately indicates the steering angle of the rear wheels at this time is used. To the neutral position.

As described above, in this embodiment, when an abnormality occurs in one of the CPUs of the control circuits 71 and 72,
Alternatively, when one of the motor mechanisms 5a and 5b becomes inoperable due to disconnection, the normal control circuit can be used to return the rear wheels to the neutral position, so that hydraulic pressure is not used and a large electric motor is used. Fail-safe processing can be performed without the need for.

Further, in this embodiment, a fail-safe mechanism can be added although it is almost the same as the conventional one in terms of the physical constitution of the apparatus, and two motor mechanisms are used instead of simply using two motors having the same structure. By configuring it in one housing, it is possible to reduce the number of parts and the number of assembling steps without increasing the load on the motor.

In this embodiment, the vehicle speed sensor 3 and the yaw rate sensor 4 correspond to the traveling state detecting means, the rear wheel steering unit 1 corresponds to the rear wheel steering means, and the motor mechanism 5a corresponds to the first operating means. However, the motor mechanism 5b corresponds to the second actuation means, the control circuit 71 corresponds to the first control means,
The control circuit 72 corresponds to the second control means, and the monitoring circuit 81
Corresponds to the first abnormality detecting means, and the monitoring circuit 82 corresponds to the second abnormality detecting means.

Next, the third embodiment will be described. FIG. 9 shows the configuration of the third embodiment. The structure of the third embodiment is also partly the same as the structure of the first embodiment, and the same components will be assigned the same reference numerals and explanations thereof will be omitted.

When the main motor 23, which is an electric motor, is energized by an electronic control unit (ECU) 62, its rotation is reduced by a speed reducer 63 by a worm gear, and then linear motion is made via a pinion gear 64 and a rack 65. It is converted and transmitted to the rod 66.
The sub motor 67, which is an electric motor, is the main motor 23.
When an abnormality occurs in the rear wheel steering due to the
Instead of 3, the rear wheels are steered, and the rotation thereof is transmitted to the pinion gear 64 via a mechanical clutch 68.

FIG. 10 shows the internal structure of the ECU 62. E
The CU 62 inputs signals from the steering sensor 4, the vehicle speed sensor 3, the stroke sensor 9, and the motor rotation angle sensor 24, and executes a calculation process based on these input signals. The CPU 70 controls the main relay 75 based on the output from the CPU 70. A main relay drive unit 77 for driving, a main motor drive unit 78 for driving the main motor 23, a sub relay drive unit 73 for driving the sub relay 76, a sub motor drive unit 74 for driving the sub motor 67, and a plurality of logic circuits. .. Further, the warning lamp 69 blinks when there is an abnormality.

Of these, the processing by the CPU 70 will be described with reference to FIG. 11. First, in S2, the CPU 70 initializes. This initialization is performed by setting the neutral point of the rear wheel from the stroke sensor 9 and determining the current angle of the motor. When the initialization is completed, steps S12 and S22
At, the rear wheel steering angle target value is calculated based on the inputs from the steering sensor 4 and the vehicle speed sensor 3. And step S3
In step 2, the current motor rotation angle is input from the motor rotation angle sensor 24, and in step S42 it is determined whether the current motor rotation angle and the rear wheel steering angle target value match. Here, if the current motor rotation angle and the rear wheel steering angle target value do not match, the process proceeds to step S52. At this time, the CPU 70
Is a main motor drive unit 78 and a main relay drive unit 77.
The motor ON / OFF signal is output high and the abnormality signal is output low, and the logical product of the motor ON / OFF signal and the inversion signal of the abnormality signal is high. Therefore, the main relay drive unit 77 and the main motor drive unit 78 can operate. On the other hand, the sub-relay drive unit 73 and the sub-motor drive unit 74 are in a stopped state because low is input.

In step S52, the CPU 70 outputs to the main motor drive unit 78 a command for the motor rotation direction and motor speed calculated from the rear wheel steering angle target value and the current motor rotation angle. Based on this command value, the main motor drive unit 78
Will drive the main motor 23 to steer the rear wheels to the target position. On the other hand, if the current motor rotation angle and the rear wheel steering angle target value match in step S42, it is not necessary to drive the main motor 23, so the process of step S52 is not executed.

Thereafter, the CPU 70 checks in step S62 whether or not there is an abnormality in the main motor 23, the main motor drive unit 78 or the like from the motor disconnection, short circuit or motor operating state. Here, if there is no abnormality, the control is ended and the process returns to step S12. However, if an abnormality has occurred, the process proceeds to step S82 below to output an abnormality signal (high) and turn on the warning lamp 69. ..

When the CPU 70 outputs a high abnormality signal, the logical product input to the main relay drive unit 77 and the main motor drive unit 78 becomes low, so that the main relay 75 and the main motor 23 are turned off. It becomes a state. On the other hand, the inputs to the sub-relay drive unit 73 and the sub-motor drive unit 74 become high, and these drive units become operable.

Now, the fail-safe processing of the sub motor drive unit 74 will be described with reference to FIG. When a high abnormality signal is output from the CPU 70 in step S3, the rear wheel steering angle is input from the stroke sensor 9 in steps S13 and S23, and the input rear wheel steering angle value matches the neutral value. It is determined whether or not there is. If the value of the rear wheel steering angle does not match the neutral value, the process proceeds to step S33 and the sub motor 6
Drive 7 slowly and gradually return the rear wheels to the neutral position (speed that does not make the driver feel uncomfortable). When the sub motor is driven, the clutch 68 operates in conjunction with the sub motor 67, and the rotation of the sub motor 67 is transmitted to the speed reducer 63. Further, the main motor 23 is connected to the sub motor 67 to rotate.

Then, steps S13 to S33 are performed until the rear wheel returns to the neutral position, and when the rear wheel returns to the neutral position, an affirmative decision is made in step S23, and the operation proceeds to step S43 to drive the sub motor. Stop.

As described above, in this embodiment, even if the main motor 23 cannot be driven, the rear wheels can be returned to the neutral position by the sub-motor 74, so that the rear wheels are fixed at a large steering angle or larger. It will no longer be steered to the rudder angle. Moreover, since the worm gear having the non-reciprocal characteristic is used as the speed reducer, the rear wheels are not steered after the rear wheels are returned to the neutral position by the sub motor 67, and the fail-safe reliability is improved. Furthermore, when returning the rear wheel to the neutral position, the sub-motor 67 is used to gradually return to the neutral position at a speed that does not cause the driver to feel uncomfortable, instead of abruptly returning to the neutral position with a spring or the like.
The maneuverability can be maintained.

In this embodiment, the speed reducer 63 and the pinion 6
4, the rack 65 corresponds to the rear wheel steering means, the main motor 23 corresponds to the first operating means, and the sub motor 67 is the second.
The main motor drive unit 78 corresponds to the first control unit, the sub motor drive unit 74 corresponds to the second control unit, and the CPU 70 corresponds to the abnormality detection unit.

The main motor and sub motor of this embodiment may be DC motors, brushless motors or step motors. Further, the clutch 68 may be an electromagnetic type. Further, the abnormality detection of the main motor 23, the main motor drive unit 78 and the like may be performed by the detection means provided separately from the CPU.

When an abnormality other than the main motor 23 and the main motor drive section 78 is detected, the rear wheels are gradually moved to the neutral position by using the main motor 23 and the main relay 77 instead of using the sub relay 76 and the sub motor 67. You can bring it back.

[0067]

As described in detail above, in the vehicle rear wheel steering system according to the present invention, when the abnormality detecting means detects an abnormality in the first control means, the second control means sets the rear wheel to a predetermined position. Since the failsafe process is performed by mechanically operating the rear wheel steering means by controlling the second operating means so as to return to the position, the biasing force of the spring or the like is applied when an abnormality occurs in the rear wheel steering mechanism. There is an excellent effect that the fail-safe processing can be performed mechanically without need and without giving a large load to the mechanical operating means.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of a first embodiment.

FIG. 2 is a detailed configuration diagram showing an example of an auxiliary steering unit 100.

FIG. 3 is an explanatory diagram illustrating an operating principle of a clutch 34.

FIG. 4 is a flowchart showing a fail-safe process of the first embodiment.

FIG. 5 is a configuration diagram showing a configuration of a second embodiment.

FIG. 6 is a detailed configuration diagram of the tandem motor 5.

FIG. 7 is a configuration diagram showing an example of a tandem motor.

FIG. 8 is a flowchart showing a fail-safe process of the second embodiment.

FIG. 9 is a configuration diagram showing a configuration of a third embodiment.

FIG. 10 is a circuit diagram showing the internal configuration of the ECU 62 of the third embodiment.

FIG. 11 is a flowchart showing the processing of the CPU of the third embodiment.

FIG. 12 is a flowchart showing a process of a sub motor drive unit of the third embodiment.

[Explanation of symbols]

 1 Rear Wheel Steering Unit 5 Tandem Motor 5a Motor Mechanism 5b Motor Mechanism 23 Main Motor 25 Main Controller 26 Auxiliary Controller 27 Auxiliary Motor 63 Reducer 64 Pinion 65 Rack 67 Sub Motor 70 CPU 71 Control Circuit 72 Control Circuit 74 Sub Motor Drive 78 Main motor drive unit 100 Auxiliary steering unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiro Shimizu 1-1, Showa-machi, Kariya city, Aichi Prefecture Nihon Denso Co., Ltd. (72) Inventor Satoshi Haseda 1-1-chome, Showa town, Kariya city, Aichi prefecture Co., Ltd. (72) Inventor Yoshihiko Tsuzuki, 1-1, Showa-machi, Kariya, Aichi Prefecture, Nippon Denso Co., Ltd. (72) Inventor, Masatoshi Kuroyanagi, 1-1, Showa-cho, Kariya, Aichi Prefecture, Nihondenso Co., Ltd. (72) Inventor Ryuji Murakawa 1-1, Showa-cho, Kariya city, Aichi prefecture, Nihon Denso Co., Ltd.

Claims (5)

[Claims] 1. A traveling state detecting means for detecting a traveling state of a vehicle, a rear wheel steering means for steering rear wheels, a first operating means for mechanically operating the rear wheel steering means, and a second Operating means, first control means connected to the first operating means, and controlling the first operating means in accordance with the traveling state of the vehicle detected by the traveling state detecting means; Second control means for controlling the second operation means according to the traveling state of the vehicle detected by the traveling state detection means, and detecting an abnormality of the first control means. Abnormality detecting means, and when the abnormality detecting means detects an abnormality in the first control means, the second control means causes the second control means to operate as the second control means.
A rear-wheel steering device for a vehicle, characterized in that the rear-wheel steering means is operated by using the above-mentioned operating means to steer the rear wheels within a predetermined steering angle. 2. The first control means determines whether or not there is a disconnection between the first control means and the first actuation means, and the first control means determines the first control means. If it is determined that there is a disconnection between the first operating means and the second operating means, the second
2. The vehicle rear wheel steering system according to claim 1, wherein the control means operates the rear wheel steering means using the second operation means to steer the rear wheels within a predetermined steering angle. apparatus. 3. The vehicle according to claim 1, wherein the first operating means is a first electric motor, and the second operating means is a second electric motor. Rear wheel steering device for use. 4. The first operating means and the second operating means are built in a motor housing of one electric motor, and the abnormality detecting means detects an abnormality of the first control means. When the abnormality of the second control means is detected, and the abnormality of the first abnormality detection means and the second abnormality detection means is not detected by the abnormality detection means, the first control means is operated by the first control means. And the second control means actuates the second actuating means to drive the electric motor to mechanically actuate the rear wheel steering means. The rear wheel steering device for a vehicle according to claim 1 or 2. 5. A clutch is provided between the second electric motor and the rear wheel steering means, and the second electric motor mechanically operates the rear wheel steering means via the clutch. The rear wheel steering device for a vehicle according to claim 3.