JP3028883B2 - Vehicle rear wheel steering system - Google Patents

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 apparatus for controlling a rear wheel steering angle based on a steering angle of a front wheel of a vehicle and a vehicle speed.

[0002]

2. Description of the Related Art Conventionally, in this type of rear wheel steering apparatus, a target steering angle of a rear wheel is calculated based on a steering angle of a front wheel of a vehicle and a vehicle speed, and the actual rear wheel steering angle is calculated as the target steering angle. Thus, a drive motor serving as a drive source of the rear wheel steering mechanism is feedback-controlled.

In this type of apparatus, a sensor for detecting the rear wheel steering angle is used to perform such feedback control. If this sensor fails, the rear wheel steering angle greatly deviates from the target steering angle. Since it is extremely dangerous, as disclosed in, for example, Japanese Patent Application Laid-Open No. 1-229768, a sensor for detecting the rear wheel steering angle has been used as a sensor for detecting the rear wheel steering angle from the rotation of the drive motor. An angle sensor and a rear wheel steering angle sensor that directly detects a rear wheel steering angle from a displacement amount of a rear wheel steering mechanism that is displaced by rotation of a drive motor to steer a rear wheel are provided, and an output of each sensor is provided. There is also proposed an apparatus that performs a fault diagnosis of a sensor by monitoring the sensor.

[0004]

However, in the device proposed above, a rotation angle sensor must be mounted on the drive motor, and a rear wheel steering angle sensor is mounted on the rear wheel steering mechanism. When the mechanism cannot mount the rear wheel steering angle sensor due to its shape, there is a problem that the above-mentioned proposal cannot improve the safety.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has been described in an apparatus using one rotation angle sensor or one rear wheel steering angle sensor as a sensor for detecting a rear wheel steering angle. Another object of the present invention is to reliably perform a motor abnormality diagnosis and improve control reliability.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a rear wheel steering mechanism for steering rear wheels of a vehicle, as shown in FIG. 1, and a rear wheel steering mechanism. A driving motor to be driven, a rear wheel steering state detecting means for detecting a rotation angle of the driving motor or a steering angle of the rear wheel, a vehicle speed detecting means for detecting a vehicle speed, and detecting a steering angle of a front wheel of the vehicle by a vehicle driver. And a target steering angle for calculating a target steering angle of the rear wheels based on a steering angle of the front wheels detected by the front wheel steering angle detecting means and a vehicle speed detected by the vehicle speed detecting means. Calculating means, the target steering angle of the rear wheel calculated by the target steering angle calculating means, and the rotation angle of the drive motor or the steering angle of the rear wheel detected by the rear wheel steering state detecting means. Calculating a control amount of the drive motor based on the calculated Control means for controlling the steering angle of the rear wheel to the target steering angle by driving the drive motor in accordance with the result, wherein the target steering angle of the rear wheel changes. After a predetermined time has elapsed, it is determined whether or not a detection signal from the rear wheel steering state detecting means has changed within a determination period until the steering angle of the rear wheel is controlled to the target steering angle. When the control state determination means and the control state determination means determine that the detection signal from the rear wheel steering state detection means has not changed within the determination period, the motor current flowing to the drive motor is determined in advance. It is determined whether or not the motor current is within the set normal range.If the motor current is within the normal range, the rear wheel steering state detecting means is broken. Failure determination means for determining each failure of the drive motor It is characterized by having a.

[0007]

In the rear wheel steering apparatus according to the present invention, the target steering angle calculating means determines the steering angle of the front wheels detected by the front wheel steering angle detecting means and the vehicle speed detected by the vehicle speed detecting means. The control means calculates the target steering angle of the rear wheel based on the calculated target steering angle and the rotation angle of the drive motor or the steering angle of the rear wheel detected by the rear wheel steering state detecting means. And the drive motor is driven according to the calculation result to control the steering angle of the rear wheels to the target steering angle.

In the rear wheel steering device according to the present invention,
After a predetermined period of time has elapsed after the target steering angle of the rear wheel has changed, the control state determining means determines that the rear wheel steering state detecting means has not changed within a determination period until the steering angle of the rear wheel is controlled to the target steering angle. It is determined whether or not the detection signal has changed, and the control state determination means
If it is determined that the detection signal from the rear wheel steering state detection means has not changed within the determination period, the failure determination means determines whether the motor current flowing to the drive motor is within a predetermined normal range. If the motor current is in the normal range, the failure of the rear wheel steering state detecting means is determined, and if the motor current is out of the normal range, the failure of the drive motor is determined.

That is, in the rear wheel steering apparatus of the present invention, when the target steering angle of the rear wheel changes, the drive motor rotates after a lapse of a predetermined time required for starting the drive motor, and the rear wheel steering angle becomes the target wheel steering angle. Because the steering angle is controlled, first, after a predetermined period required for the drive motor to actually rotate by changing the target steering angle of the rear wheel by the operation of the control state determination means,
During the determination period until the rear wheel steering angle is controlled to the target steering angle,
By determining whether or not the detection signal from the rear wheel steering state detecting means has changed, it is determined whether or not the rear wheel steering control has been executed, and within the determination period, the rear wheel steering state detecting means has been determined. If the detection signal does not change, it is determined that either the drive motor or the rear wheel steering state detecting means has failed, and the abnormality is determined by the motor current flowing through the drive motor to indicate that the abnormality is due to the failure of the drive motor. It is determined whether the failure is caused by a failure of the rear wheel steering state detecting means.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 2 is a schematic configuration diagram illustrating a configuration of the entire rear wheel steering device of the present embodiment, and FIG. 3 is an electric circuit diagram illustrating an electrical configuration of a control system thereof.

As shown in FIG. 2, the rear wheel steering apparatus according to the present embodiment includes a rear wheel steering mechanism 10 for steering left and right rear wheels 2RL, 2RR of a vehicle, and a direct current (DC) for driving the rear wheel steering mechanism 10. Driving motor 1 consisting of motor, brushless motor, etc.
2, a rotation angle sensor 14 as a rear wheel steering state detecting means for generating a pulse signal at each predetermined rotation angle of the drive motor 12, and a steering wheel 18 for the vehicle driver to steer the left and right front wheels 2FL, 2FR. And a steering sensor 24 as a front wheel steering angle detecting means for generating a pulse signal at each predetermined rotation angle of the steering shaft 22, and a vehicle speed detecting means for detecting a vehicle speed. A vehicle speed sensor 26, a warning lamp 28 for giving a warning to the vehicle driver when the device is abnormal, and a target rear wheel steering angle are set based on detection signals from these sensors. Drive motor 12
, And an electronic control unit (ECU) 30 that detects an abnormality of the device and turns on a warning lamp 28.

Here, the rotation angle sensor 14 is shown in FIG.
As shown in FIG. 1, a well-known device comprising a slit plate 32 fixed to the rotating shaft 12a of the drive motor 12, and a detection element section 34 disposed so as to sandwich the slit plate 32. That is, the slit plate 32 of the rotation angle sensor 14 is provided with a slit 32a for detecting a rotation angle at every predetermined angle around the rotation axis 12a of the drive motor 12, and a predetermined edge of the periphery of the slit plate 32 is formed. A slit 32b for detecting a reference position is formed at the position. Then, a pair of photointerrupters 34 provided in the detection element unit 34
A and 34B (shown in FIG. 3) detect the slit 32a, and as shown in FIG. 4B, the on / off state is reversed at every predetermined rotation angle of the rotation shaft 12a of the drive motor 12,
Two types (A) whose phases are shifted by half (θ) of the inversion cycle
4B), and a slit 32b is detected by a photo-interrupter 34Z (shown in FIG. 3) provided in the detecting element section 34, and the slit 32b is formed as shown in FIG. A pulse signal (Z phase) which is turned off at a predetermined rotation angle position of the corresponding rotation shaft 12a is generated.

The above-mentioned photo interrupters 34A,
34B and 34Z, as shown in FIG.
And a phototransistor TR that receives light from the light-emitting diode D through the slit plate 32.

Further, the detection element section 34 is provided with the rear wheels 2RL, 2RL.
When the rear wheel steering angle when the RR is not steered: 0 degree, and when the drive motor 12 rotates one or two rotations left or right from this rotation position (rotation angles: ± 360 degrees, ± 7 degrees).
(At 20 degrees), the position is adjusted so that the photointerrupter 34Z detects the slit 32b.

Next, the ECU 30 comprises a CPU, ROM, RA
It is composed of a well-known microcomputer including M and the like. The ECU 30 controls the drive motor 1 as described above.
When the abnormality of the device is detected, the warning lamp 28 is turned on to notify the vehicle driver of the abnormality.
Simply stopping the energization of the drive motor 12 causes the drive motor 12 to rotate by inertia.

Therefore, in this embodiment, as shown in FIG.
The drive motor 12 is provided with a cut relay 36. When the rear wheel steering control is executed, the cut relay 36 is turned on to
The CU 30 controls the current supplied to the drive motor 12. When the rear wheel steering control is stopped in the event of an abnormality or the like, the cut relay 36 is turned off and the drive motor 12 is turned off.
The rotation of the drive motor 12 can be fixed by short-circuiting the positive terminal and the negative terminal.

The ECU 3 is connected to the ECU 3 via a cut relay 36.
A motor current detection circuit 38 for detecting a motor current IM flowing through the drive motor 12 is provided in a current path of the drive motor 12 connected to the motor 0. It can be detected.

Next, the rear wheel steering control executed by the ECU 30 will be described in detail with reference to the flowchart shown in FIG. The rear wheel steering control shown in FIG. 5 is performed by turning on an ignition switch (not shown).
The operation is started when the power is supplied to the CU 30 and the ECU 30 is activated.

As shown in FIG. 5, when the rear wheel steering control is started, first, at step 110, a timer counter for counting time, which is counted up every predetermined time by an internal clock pulse in the ECU 30, is reset. And
In the following step 120, the steering angle and the vehicle speed obtained based on the detection signals from the steering sensor 24 and the vehicle speed sensor 26 are read, and in the following step 130, based on the read steering angle and the vehicle speed,
A process as a target steering angle calculating means for calculating a target value (target steering angle) of the rear wheel steering angle is executed.

After the target steering angle is calculated in step 130, the process proceeds to step 140, in which the target rotation angle of the drive motor 12 for controlling the rear wheel steering angle to the target steering angle is calculated, and then the process proceeds to step 140. In step 150, it is determined whether the calculated target rotation angle has changed from the previously calculated target rotation angle. If the target rotation angle has changed, the process proceeds to step 170 after resetting the timer counter in step 160. If the target rotation angle has not changed, the process directly proceeds to step 170.

In step 170, the rotation angle sensor 1
4 to read the rotation angle of the drive motor 12 obtained based on the detection signal, and in the subsequent step 180, the rotation angle of the drive motor 12 is controlled to the target rotation angle calculated in step 140 (in other words, The control amount of the drive motor 12 (for controlling the wheel steering angle to the target steering angle) is calculated.
Then, in the subsequent step 190, the drive motor 12 is driven by the calculated control amount. Step 1 above
The processing from 40 to 190 corresponds to the control means of the present invention.

Next, as described above, at step 190, the drive motor 1 is controlled to control the rear wheel steering angle to the target steering angle.
2 is driven, the process proceeds to step 200 to determine whether the rotation angle of the drive motor 12 has reached the target rotation angle. If the rotation angle of the drive motor 12 has reached the target rotation angle, Then, the rotation of the drive motor 12 is stopped in step 210, the timer counter is reset in step 220, and the process returns to step 120 again.

On the other hand, in step 200, the drive motor 1
If it is determined that the second rotation angle has not reached the target rotation angle, the process proceeds to step 230 to determine whether or not the value of the timer counter has exceeded a predetermined value K1 that is, After the target rotation angle, that is, the target rear wheel steering angle has changed, it is determined whether or not a predetermined time determined by a predetermined value K1 has elapsed. The predetermined value K1 is set to a value corresponding to a delay time from when the driving of the driving motor 12 is started to when the driving motor 12 actually starts moving when the driving motor 12 is stopped. .

If it is determined in step 230 that the value of the timer counter has not exceeded the predetermined value K1 and that the predetermined time has not elapsed after the change in the target rear wheel steering angle, the routine proceeds to step 240. Then, the motor current IM detected by the motor current detection circuit 38 is read, and
At 0, it is determined whether or not the read motor current IM exceeds a preset short-circuit determination value I1.

If it is determined in step 250 that the motor current IM has exceeded the short-circuit determination value I1, in step 260, it is determined that the drive motor 12 is short-circuited. When the motor current IM is determined to be less than or equal to the short-circuit determination value I1 in step 250, the drive motor 12 is turned on.
Is determined to be operating normally, and step 120 is executed again.
Move to

Next, if it is determined in step 230 that the value of the timer counter has exceeded the predetermined value K1 and that a predetermined time has elapsed after the change in the target rear wheel steering angle, the flow proceeds to step 270. The rotation angle of the drive motor 12 obtained based on the detection signal from the rotation angle sensor 14 is read,
A change in the rotation angle of the drive motor 12 is obtained from the read rotation angle and the rotation angle read in the previous step 170,
This rotation angle change is executed as a control state determination means for determining whether or not the rotation angle is within the minimum rotation angle 1 LSB (= θ) detectable by the rotation angle sensor 14, that is, whether or not the drive motor 12 is rotating. I do.

If it is determined in step 270 that the drive motor 12 is rotating more than the minimum rotation angle 1 LSB, the timer counter is reset in step 280, and the process proceeds to step 120 again. Ni
If it is determined in step 270 that the change in the rotation angle of the drive motor 12 is within the minimum rotation angle 1 LSB, step 29
The process proceeds to 0, and the motor current IM detected by the motor current detection circuit 38 is read.

When the motor current IM is read in step 290, the process proceeds to step 300 to determine whether the read motor current IM is a normal value, that is, whether the read motor current IM is within a predetermined normal range. Determine whether or not. If it is determined in step 300 that the motor current IM is a normal value, the rotation of the drive motor 12 detected by the rotation angle sensor 14 is detected even though the drive motor 12 is rotating normally. Since the angle has not changed,
It is determined that the rotation angle sensor 14 has failed, and the warning lamp 28 is turned on to notify the driver of the failure.

On the other hand, at step 300, the motor current I
If it is determined that M is not a normal value, then step 32
The process proceeds to 0 to determine whether the motor current IM is equal to or less than a preset lock / disconnection determination value I2 (I2 <I1). Then, the motor current IM is equal to the lock / disconnection determination value I2.
If it is below, it is determined that the drive motor 12 is disconnected,
The warning lamp 28 is lit to notify the driver of the fact, and if the motor current IM exceeds the lock / disconnection determination value I2, it is determined that the drive motor 12 is locked, and that fact is determined. The warning lamp 28 is turned on to notify the driver.

As described above, steps 260 and 3
In step 10, step 330 or step 340, a failure of the drive motor 12 or the rotation angle sensor 14 is determined, and the fact is notified to the vehicle driver.
, The rotation of the drive motor 12 is stopped, and the process further proceeds to step 360, where the cut relay 36 is turned off.
By short-circuiting the positive terminal and the negative terminal of the drive motor 12, the drive motor 12 is fixed at the current rotational position, and the rear wheel steering control ends.

As described above, in the rear wheel steering apparatus of this embodiment, every time the target steering angle of the rear wheels 2RL, 2RR changes with the change of the steering angle of the front wheels 2FL, 2FR or the vehicle speed, Until the drive motor 12 is controlled to the target rotation angle, whether or not the rotation of the drive motor 12 is detected by the rotation angle sensor 14 every delay time from the start of energization to the actual rotation. Is determined, and if the rotation of the drive motor 12 is not detected, the drive motor 1
2 and the rotation angle sensor 14 are determined to be malfunctioning, and whether the drive motor 12 or the rotation angle sensor 14 is malfunctioning is identified based on whether or not the motor current IM is a normal value. I have to.

Therefore, according to the rear wheel steering apparatus of the present embodiment, the failure determination of the drive motor 12 and the rotation angle sensor 14
This can be performed with only one rotation angle sensor 14 without separately providing a sensor such as a rear wheel steering angle sensor as in the conventional device. In this embodiment, the motor current IM is equal to the short-circuit determination value I1 except when the failure of the drive motor 12 and the rotation angle sensor 14 is determined based on whether or not the rotation of the drive motor 12 is detected by the rotation angle sensor 14. By judging whether the current exceeds the large current, the short-circuit of the drive motor 12 is determined.
When the failure of the drive motor 12 is identified from the motor current IM after determining the failure of the rotation angle sensor 14, the lock of the drive motor 12 is determined by determining whether the motor current IM is equal to or less than the lock / disconnection determination value I2. And disconnection. Therefore, when the drive motor 12 fails, the details of the failure can also be notified to the vehicle driver.

Further, in this embodiment, the drive motor 12
When the failure of the rotation angle sensor 14 is detected, not only the vehicle driver is notified to that effect and the rotation of the drive motor 12 is stopped, but also the cut relay 36 is turned off, so that the rotation of the drive motor 12 is stopped. It is fixed with. Therefore, the drive motor 12 and the rotation angle sensor 1
In the event of a failure in 4, the rear wheels 2RL, 2RR are not excessively steered by the inertia of the drive motor 12, and the running stability of the vehicle can be ensured.

In the above-described embodiment, the rear wheel steering apparatus in which the drive motor 12 is provided with the rotation angle sensor 14 for detecting the rear wheel steering angle has been described. Also in the rear wheel steering device provided with a rear wheel steering angle sensor for directly detecting the rear wheel steering angle from the displacement amount of the mechanism 10, by executing the rear wheel steering control in the same manner as in the above embodiment, the drive motor 12 and the rear The failure of the wheel steering angle sensor can be determined.

[0035]

As described above in detail, in the rear wheel steering apparatus according to the present invention, after a predetermined period required for the drive motor to actually rotate after the target steering angle of the rear wheel has changed, By determining whether or not the detection signal from the rear wheel steering state detecting means has changed within the determination period until the rear wheel steering angle is controlled to the target steering angle, the rear wheel steering control can be executed. It is determined whether or not the drive motor or the rear wheel steering state detecting means has failed if the detection signal from the rear wheel steering state detecting means has not changed within the determination period. Then, based on the motor current flowing through the drive motor, it is determined whether the abnormality is due to a failure of the drive motor or a failure of the rear wheel steering state detecting means.

For this reason, according to the rear wheel steering apparatus of the present invention, the failure determination of the drive motor and the rear wheel steering state detecting means is performed by:
Unlike the conventional device, the rear wheel steering state detecting means does not need to be composed of two types of sensors, and can be performed by only one sensor. Therefore, a rotation angle sensor for detecting the rotation angle of the drive motor and a rear wheel for directly detecting the rear wheel steering angle from the displacement of the rear wheel steering mechanism as the rear wheel steering state detecting means from the shapes of the drive motor and the rear wheel steering mechanism. Even in a device in which only one of the steering angle sensors can be mounted, the failure diagnosis can be performed accurately and safety can be ensured.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating the configuration of the present invention.

FIG. 2 is a schematic configuration diagram illustrating a configuration of an entire rear wheel steering device according to the embodiment.

FIG. 3 is an electric circuit diagram illustrating a configuration of a control system of the rear wheel steering device according to the embodiment.

FIG. 4 is an explanatory diagram illustrating a configuration of a rotation angle sensor and an output signal thereof according to the embodiment.

FIG. 5 is a flowchart showing a rear wheel steering control executed by the ECU.

[Explanation of symbols]

2FL, 2FR: Front wheel 2RL, 2RR: Rear wheel 1
0 ... rear wheel steering mechanism 12 ... drive motor 14 ... rotation angle sensor 24 ... steering sensor 26 ... vehicle speed sensor 28 ... warning lamp 30 ... electronic control unit (ECU) 36 ... cut relay 38 ... motor current detection circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI B62D 137: 00 (72) Inventor Takashi Inaba 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Japan Denso Co., Ltd. (56) References Special Kaihei 3-227770 (JP, A) JP-A 3-115575 (JP, U) JP-A 4-29472 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B62D 6 / 00 B62D 7/14

Claims (1)

(57) [Claims] 1. A rear wheel steering mechanism for steering rear wheels of a vehicle, a drive motor for driving the rear wheel steering mechanism, and a rear wheel for detecting a rotation angle of the drive motor or a steering angle of the rear wheels. Steering state detecting means, vehicle speed detecting means for detecting a vehicle speed, front wheel steering angle detecting means for detecting a steering angle of a front wheel of a vehicle by a vehicle driver, and steering angle of the front wheels detected by the front wheel steering angle detecting means. A target steering angle calculating unit that calculates a target steering angle of the rear wheel based on the vehicle speed detected by the vehicle speed detecting unit; a target steering angle of the rear wheel calculated by the target steering angle calculating unit; A control amount of the drive motor is calculated based on the rotation angle of the drive motor or the steering angle of the rear wheel detected by the rear wheel steering state detection unit, and the drive motor is driven according to the calculation result. Control the steering angle of the rear wheels to the target steering angle A rear wheel steering device comprising: a determination period after a predetermined time elapses after a change in the target steering angle of the rear wheel until the steering angle of the rear wheel is controlled to the target steering angle. A control state determining means for determining whether or not a detection signal from the rear wheel steering state detecting means has changed; and the control state determining means, wherein the rear wheel steering state detecting means within the determination period. When it is determined that the detection signal has not changed, it is determined whether or not the motor current flowing to the drive motor is within a normal range set in advance. A rear wheel steering state detecting unit, and a failure judging unit for judging a failure of the drive motor when the motor current is out of a normal range. Steering gear.