JPH11180331A - Motor-driven powder steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the motions of a vehicle in good performance even in case a steering motor is locked. SOLUTION: In normal operation, a steering torque sensor 12 senses the steering torque, and a steering motor 60 generates a driving force according to the steering torque, and this force is given to a steering wheel 15 as an assist force. At this time, an electromagnetic clutch 70 is disengaged so that a transition to the manual steering state takes place. If any reason hinderes such clutch releasing, the steering wheel 15 can no more be turned, but even in this case, a brake 54 is controlled so that a braking force according to the steering torque is generated. Thereby the vehicle can be stopped in a safe place in the condition that the motions in the yawing direction are controlled by this braking force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus, and more particularly to an electric power steering apparatus capable of avoiding inappropriate movement of a vehicle even when a steering motor locks.

[0002]

2. Description of the Related Art As is well known, a power steering apparatus is an apparatus for reducing a force of a driver such as an automobile turning a steering wheel. In one example of an electric power steering device, steering information (for example, steering torque) is detected by a steering sensor attached to a steering shaft, a driving force of a steering motor is calculated based on the steering information, and a result of the calculation is calculated. The steering motor is controlled so that a driving force is generated.
The driving force generated by the steering motor is transmitted to the steered wheels (at least one of the front wheels and the rear wheels) as an assist force.

[0003] It has been proposed to provide a clutch in a driving force transmission path between the steering motor and the steered wheels in order to maintain a state in which the movement of the vehicle can be controlled even when the steering motor is locked due to some abnormality. . When the motor lock is detected, the clutch is disengaged, thereby shifting to a manual steering state without power assist.

[0004] This type of apparatus is described in Japanese Patent Application Laid-Open No. 4-163280. The steering torque is detected by a torque sensor attached to the steering shaft, and an assist force is applied to the steering shaft by driving the steering motor according to the detection result. When the differential value of the steering torque exceeds a predetermined value, the steering motor is stopped, and the clutch that couples the steering motor to the steering shaft is turned off.

[0005]

In the power steering apparatus disclosed in the above publication, the differential value of the torque sensor attached to the steering shaft exceeds a predetermined value, and the coupling between the steering motor and the steering shaft is released. And If the clutch cannot be disengaged due to a trouble in the power line energizing the clutch or mechanical sticking, the steered wheels are fixed and maintain the same direction, and therefore, the vehicle moves in the yaw direction. There is a possibility that it cannot be controlled properly.

It is also desirable that a power steering apparatus having no clutch for a steering motor or a mechanism similar thereto can control the vehicle even if a motor lock occurs.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an electric power steering apparatus capable of suitably controlling the movement of a vehicle in a yaw direction, that is, a traveling direction even when a steering motor is locked. Is to do.

[0008]

(1) An electric power steering apparatus according to the present invention comprises: a steering information detecting means for detecting steering information of a steering; and a steering motor for generating a driving force corresponding to the detected steering information. And transmission means for transmitting the driving force of the steering motor to the steering wheel, further comprising: a motor lock detection means for detecting a lock state of the steering motor; and a direction of the steering information when the motor lock is detected. And braking control means for controlling the braking force of the wheels based on the magnitude, and when the steered wheels cannot be steered by the motor lock, by applying a braking force to at least one of the wheels, Controls yaw movement.

According to the present invention, even when the direction of the steered wheels is fixed, the movement in the yaw direction, that is, the traveling direction can be controlled by controlling the braking force of the wheels based on the steering information. Therefore, the speed of the vehicle can be reduced and the vehicle can be stopped at a safe place under the state where the motion of the vehicle is controlled.

In the present invention, the steered wheels may be front wheels, rear wheels, or front and rear wheels. The wheels that apply the braking force when the steering motor locks may be the same as the steered wheels, or may be different from the steered wheels. The braking force is applied to one or both of the left and right wheels. Then, by generating a braking force difference between the left and right wheels, a yaw moment of the vehicle is generated, and the motion of the vehicle can be controlled. A configuration in which one of the front wheels or the rear wheels is provided with a braking force equal to the left and right, and the other has a difference in braking force between the left and right,
Of course, it is included in the present invention.

In the present invention, the steering information is information indicating an operation state of a steering means (for example, a steering wheel) by a driver, for example, a steering torque and a steering angle.

(2) Preferably, in one embodiment of the present invention, the transmission means includes a cutting means for cutting a driving force transmission path between a steering motor and a steered wheel. Then, when the motor lock occurs and the driving force transmission path cannot be cut, a braking force for yaw direction motion control is applied to the steered wheels.

According to this aspect, first, an attempt is made to disconnect the steering motor from the steered wheels by a disconnecting means such as a clutch. Even in the case where the separation is not properly realized, the motion of the vehicle can be controlled by using the braking force of the wheels.

The present invention can be suitably applied to a power steering apparatus in which the above-described disconnection means such as a clutch is not provided.

Further, as shown in a second embodiment described later, the present invention can be suitably applied to a configuration in which the steering wheel and the steered wheels are not directly mechanically connected.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention (hereinafter, referred to as embodiments) will be described below with reference to the drawings.

<First Embodiment> FIG. 1 conceptually shows the configuration of an electric power steering apparatus according to the present invention.
In the steering information detecting means M1, steering information is detected using a steering information detection sensor attached to the steering shaft. In the first embodiment, a steering torque is used as steering information. The detected steering information is used to determine the driving force of the steering motor, to detect whether the steering motor is locked, and to determine the braking force to be applied to the wheels.

[0018] Steering motor driving force calculation device M2
Is based on the detected steering information,
The driving force of a steering motor that assists the steering force of the steered wheels is calculated and obtained. The calculated driving force of the steering motor is calculated by the steering motor driving force generator.
Generated in M3. The motor driving force of the steering may be proportional to the steering information. Further, the steering information and the driving force may be represented by a certain function. In the present invention, the relationship between the steering information and the driving force of the steering motor is not limited.

The motor lock detecting means M4 determines whether the steering motor is locked. The locked state of the steering motor is described in, for example,
As described in JP-A-63280, it is determined based on the differential value of the steering torque in the steering information, and when this differential value exceeds a predetermined value, it is determined that the lock has occurred. Further, for example, as described in JP-A-6-305438, it may be determined that the lock has occurred when the amount of change in the steering torque with respect to the amount of change in the steering angle in the steering information exceeds a predetermined value. In the present invention, the method of determining the lock of the steering motor is not limited, and any method can be applied.

The clutch release device M5 is disclosed in
The electromagnetic clutch provided between the steering motor and the steering shaft is released by the method described in Japanese Patent No. 3280 or JP-A-6-305438. When the steering motor is separated from the steering shaft in this manner, the assist force by the steering motor is not applied to the steered wheels. As a result, the torque for turning the steered wheels is increased, and a manual steering state having no assist force is established. In this state, the function of controlling the movement of the vehicle is maintained.

However, when the clutch connecting the steering motor and the steering shaft is to be released, the clutch may not actually be released properly. This situation occurs due to, for example, an abnormality in the electric system or mechanical fixation as described above. Thus, the clutch release detecting means M7 detects whether the clutch has been actually released based on the assist torque detected by the assist torque detecting means M6.

If the clutch is not actually released even if the clutch release device M5 is actuated, the steered wheels maintain the same direction, so that the yaw direction motion of the vehicle cannot be suitably controlled. Further, in the electric power steering device configured without the clutch mechanism, the same result as in the case where the clutch mechanism is provided and cannot be released as described above is produced.

When the lock of the steering motor occurs and the above-mentioned clutch mechanism cannot be released, the braking force calculating device M9 operates as follows. Further, when the electric power steering device is configured without the clutch mechanism, it operates as follows when the motor lock occurs.

The braking force calculating device M9 includes a steering information detecting means M
An appropriate value of the braking force difference between the left and right wheels is determined based on the steering information detected by step 1. Here, a braking force difference that can produce an appropriate yaw moment corresponding to steering information (steering operation state) is required. The target wheels that provide the left and right braking force differences may be front wheels, rear wheels, or front and rear wheels. The target wheel may be the same as or different from the steered wheel. Braking force generator M8
Generates a braking force difference between the left and right wheels calculated by the braking force calculation device M9, thereby generating a yaw moment of the vehicle. In this way, the movement of the vehicle in the yaw direction is suitably controlled, and the vehicle can be safely stopped.

FIG. 2 shows a specific configuration example of the electric power steering apparatus according to the present embodiment. FIG. 3 shows FIG.
It is a block diagram which shows the structure of the electronic control apparatus shown by.

In FIG. 2, the steering wheel 10
Is connected to the rack bar 14 via the steering shaft 11 and the steering gear box 13, and finally steers the steered wheels 15. The steering shaft 11 is connected to the steering motor 60 via the electromagnetic clutch 70 by the gear reduction mechanism 16. The electromagnetic clutch 70 is selectively driven by the electronic control device 30 to be connected or disconnected. Further, inside the electromagnetic clutch 70, an assist torque sensor 17 for detecting an assist torque between the gear reduction mechanism 16 and the electromagnetic clutch 70 is incorporated.

Also. The steering shaft 11 is provided with a steering torque sensor 12 for detecting a steering torque given by the driver. The output of this sensor is supplied to the electronic control unit 30. In the present embodiment, this steering torque corresponds to the steering information of the present invention.

As shown in FIG. 3, the electronic control unit 30 includes a microcomputer 31. The microcomputer 31 includes a central processing unit (CPU) 34, a read-only memory (ROM) 35, and a random access memory (R).
AM) 36, an input port 32, and an output port 33, which are connected to each other by a bidirectional common bus 37.

The input port 32 has a steering torque sensor 1
2, a steering torque signal detected by the assist torque sensor 17, and a vehicle speed signal detected by the vehicle speed sensor 18 are input.
The input port 32 appropriately processes the input steering torque signal, and outputs a processed signal to the CPU 34 and the RAM 36 in accordance with a command from the CPU 34 based on a control program stored in the ROM 35.

The ROM 35 stores (1) the control program shown in FIG. 4 and (2) data (maps and tables) indicating the relationship between the detected steering torque and the driving torque of the steering motor 60 corresponding to the detected steering torque. (3) logic for determining whether the steering motor 60 is locked, (4) logic for detecting release of the electromagnetic clutch 70 connecting the steering shaft 11 and the steering motor 60, and (5) front wheel or And logic for calculating the braking force of any one or more of the rear wheels.

The CPU 34 performs various calculations and signal processing based on the control program shown in FIG. The output port 33 is connected to the drive circuit 6 according to the instruction of the CPU 34.
1 to output a control signal to the steering motor 60,
Further, it outputs a control signal to the electromagnetic clutch 70 via the drive circuit 71. Further, when it is determined that the steering motor is locked, the CPU 34 sets the alarm speaker 4
1 is sounded, and the warning lamp 42 is turned on. If the electromagnetic clutch 70 has not been released for some reason despite the release command being output to the electromagnetic clutch 70, a control signal is output to the brake control device via the drive circuit 51. Then, the brake-related components including the pressure control device 52, the accumulator 53, and the brake 54 shown in FIG. 1 are operated, whereby the braking force indicated by the control signal is generated. It should be noted that the brake-related configuration of the present invention does not need to be a dedicated one, and may be shared with a brake-related configuration used for other purposes.

Next, a control process of the electric power steering apparatus according to the present embodiment will be described with reference to a flowchart of FIG. The control by the electronic control unit 30 is started when an ignition switch (not shown in FIG. 2) is closed. First, in step 10, the driving circuit 7
The control signal is sent to the electromagnetic clutch 70 via 1 and the electromagnetic clutch 70 is connected. In step 20, the steering torque detected by the steering torque sensor 12, the assist torque detected by the assist torque sensor 17, and the vehicle speed detected by the vehicle speed sensor 18 are input to and read from the input port 32. In step 30, based on the read steering torque, an assist amount (assist torque) to be generated by the steering motor 60 is calculated according to a map corresponding to the graph shown in FIG. In step 40, the steering motor 60 is driven via the drive circuit 61 based on the assist amount calculated in step 30, and the assist amount is given to the steered wheels 15.

In steps 50 and 60, it is determined whether or not the steering motor 60 is locked.
In this determination, as described in, for example, Japanese Patent Application Laid-Open No. 4-163280, it is determined that the lock is established when the differential value of the steering torque exceeds a predetermined value. In addition, for example, see
As described in Japanese Patent Publication No. 305438, locking is determined when the amount of change in steering torque with respect to the amount of change in steering angle exceeds a certain predetermined value. As described above, in the present embodiment,
Any lock determination method can be suitably applied.

If it is determined in steps 50 and 60 that the steering motor 60 is not locked,
Returning to step 20, the steering torque is read. If the motor lock has not occurred, steps 20 to 60 are repeatedly executed, and the power steering apparatus operates normally.

On the other hand, if it is determined that the lock has occurred, the process proceeds to step 70. Then, in response to the result that it is determined that the steering motor 60 is locked, the processing of S70 to S100 is performed. Step 70
Then, the warning speaker 41 is sounded, and in step 80, the warning lamp 42 is turned on. In step 90, the power supply to the steering motor 60 is stopped. Thus, the application of the assist amount from the steering motor 60 to the steered wheels 15 is stopped. In step 100, the control signal to the electromagnetic clutch 70 via the drive circuit 71 is stopped, and thereby the electromagnetic clutch 70 is released.

In step 110, it is determined whether or not the release of the electromagnetic clutch 70 performed in step 100 has been completely performed. This determination is made based on the magnitude of the assist torque detected by the assist torque sensor 17 and input via the input port 32. If the assist torque has a large value equal to or greater than the predetermined threshold even though the electromagnetic clutch release command is issued in step 100, it is determined that the electromagnetic clutch 70 has not been released. If the assist torque is smaller than the predetermined threshold, it is determined that the electromagnetic clutch 70 has been released. It is also preferable that the determination of clutch release be made based on the output of the steering torque sensor 12.

If it is determined in step 110 that the electromagnetic clutch 70 has been released, the process proceeds to step 120, in which the steering force assist control of the electric power steering by the electronic control unit 30 ends. In this case, a normal manual steering state without assist power is set. Therefore, the torque for turning the steered wheels increases, but the steerable state is ensured.

If it is determined in step 110 that the electromagnetic clutch 70 has not been released, the routine proceeds to step 130. Steps 130 to 160 are the processing contents when it is determined in step 110 that the clutch is not released even though it is determined in step 60 that the steering motor 60 is locked.

In step 130, the steering torque sensor 1
2, the steering torque detected by the assist torque sensor 17, the assist torque detected by the assist torque sensor 17, and the vehicle speed detected by the vehicle speed sensor 18 are input to and read from the input port 32. In step 140, based on the read steering torque, the braking force of one or more of the front wheels and the rear wheels is calculated according to a map corresponding to the graph shown in FIG.

For example, it is assumed that the steered wheels are front wheels, and braking force is also applied to the front wheels. The steering torque in the clockwise direction is positive. If the steering torque is positive, the braking force of the right front wheel is set to the braking force corresponding to the steering torque in FIG. 6, and the braking force of the left front wheel is set to 0. Conversely, if the steering torque is negative, the braking force of the right front wheel is set to 0, and the braking force of the left front wheel is set to a braking force (absolute value) corresponding to the steering torque in FIG. Alternatively, a braking force may be applied to the left and right wheels, and the braking force difference between the two wheels may be set to the value shown in FIG.

When the clutch cannot be released, the steering wheel 11 is fixed after the occurrence of the motor lock, and its rotation angle (hereinafter, steering angle) becomes constant.
Then, the steered wheels 15 face the same direction as they were when the motor lock occurred. Step S14 above
At 0, the braking force is adjusted according to such a fixed wheel direction. Here, it is preferable to perform an adjustment process for canceling the yaw direction movement corresponding to the influence of the wheel direction. Here, a plurality of maps each corresponding to a different wheel direction may be prepared, and the map corresponding to the wheel direction at that time may be used for control. The above-mentioned fixed wheel direction can be known from the steering angle at the time of occurrence of the motor lock, but the direction of the steered wheels 15 may be directly detected using another appropriate sensor. In addition, the above-described braking force adjustment processing
It may be performed based on another element corresponding to the wheel direction, for example, the fixed steering angle described above.

In step 150, a control signal is output via the drive circuit 51 based on the braking force calculated in step 140, and the brake 54 is operated in accordance with the control signal, thereby controlling the yaw motion for controlling the yaw motion. A moment is applied to the vehicle.

In step 160, it is determined whether or not the speed of the vehicle input in step 130 is equal to or less than a predetermined threshold speed value. If the detected speed is equal to or higher than the predetermined speed threshold, the process returns to step 130, and the control loop from step 130 to step 160 is repeated. If the speed is less than the predetermined threshold speed value, it is determined that the vehicle has stopped, and the routine proceeds to step 170, where the control of the electric power steering process performed by the electronic control unit 30 ends.

FIG. 7 to FIG. 10 show the results of verification of the effects of the present embodiment by experiments. FIG. 7 shows a traveling locus of a vehicle provided with a conventional power steering device.
The part of the road approaching a curved road from a straight road (part A in the figure)
In the above, the steering motor of the electric power steering device was locked, and the electromagnetic clutch was not released. In this case, steering becomes impossible, and the vehicle deviates to the left of the road with respect to the traveling direction.

FIG. 8 shows a traveling locus of a vehicle equipped with the electric power steering device of this embodiment. FIG.
7, the steering motor of the electric power steering device was locked and the electromagnetic clutch was not released at the portion A approaching the curved road from the straight road, as in the case of FIG. 7. However, since the braking force is controlled based on the steering torque, it can be understood that the vehicle can travel without departing from the road.

FIG. 9 shows a steering angle waveform of the driver from a straight road to a curved road. Locking of the steering motor occurs at the portion A, and the steering angle is fixed thereafter.

FIG. 10 shows the steering torque detected by the steering torque sensor 12 and the pressure waveform of the brake acting on the brake 54. As in FIG. 9, A
The steering motor is locked at the part. After the lock is generated, the steering torque according to the steering operation of the driver is detected, and it can be understood that the brake pressure according to the magnitude of the steering torque is generated. In the brake pressure shown in the figure, the positive pressure indicates the pressure acting on the right side of the front wheel, and the negative pressure indicates the pressure acting on the left side of the front wheel.

As shown in FIGS. 7 to 10, in the electric power steering, even when the steering motor is locked and the clutch cannot be released, the yaw motion of the vehicle can be controlled by the present invention. Therefore, it is easy to safely drive on the road and stop at a safe place.

The present embodiment can be similarly applied to an electric power steering apparatus not equipped with a clutch for releasing the connection between the steering motor and the steering shaft. In this configuration, when the detection that the steering motor is locked is performed, preferably, the calculation of the braking force based on the steering torque is immediately performed, and the braking force of the wheel is controlled. That is, in the control of FIG. 4, steps 100 to 120 are omitted.

<Embodiment 2> Next, an electric power steering apparatus according to Embodiment 2 will be described. In the second embodiment, unlike the first embodiment, the steering wheel and the steered wheels are not mechanically connected. The present invention can be suitably applied to such a type of power steering device as described below. In the following, differences from the first embodiment will be mainly described, and description of parts common to the first embodiment will be appropriately omitted.

FIG. 11 shows the configuration of the electric power steering apparatus according to the second embodiment. Also, FIG.
FIG. 2 is a block diagram showing a configuration of the electronic control device shown in FIG. In FIG. 11, a steering wheel 110 is connected to a steering reaction force generating motor 11 via a steering shaft 111.
9. The steering reaction force generating motor 119 is
An appropriate amount of reaction force is generated so that the driver can easily operate the steering wheel 110. The steering motor 160 is controlled by a gear reduction mechanism 116 via an electromagnetic clutch 170 so that the steering gear box 113
To the steered wheels 11 via a rack bar 114.
5.

In the second embodiment, the steering shaft 111 is not connected to the steering gear box 113.
Therefore, the operation of the steering wheel 110 is not mechanically transmitted to the steered wheels 115. The steering motor 160 generates a driving force according to the steering state of the steering wheel 110, and this driving force is transmitted to the steered wheels 115 as an assist force. Thus, the steered wheels 11
The steering of No. 5 is realized exclusively by the driving force of the steering motor 160.

The steering shaft 111 is provided with a steering information sensor 112.
Detects steering information provided by the driver. In the second embodiment, a steering torque and a steering angle are detected as the steering information.

The electronic control unit 130 shown in FIG.
It has substantially the same configuration as the first embodiment shown in FIG. As a difference from the first embodiment, steering information detected by the steering information sensor 112 is input to the input port 132. The ROM 135 stores a control program for performing the processing shown in FIG.

Next, the operation of the power steering apparatus according to the second embodiment will be described with reference to FIG. Here also, differences from the first embodiment will be mainly described, and description of portions common to the first embodiment will be omitted as appropriate.

In steps 210 to 260,
Steps 10 to 6 in FIG. 4 of the first embodiment
Similarly to 0, control of the power steering device in the normal state is performed. However, in the second embodiment, in step 220, the steering information is read from the steering information sensor 112. The steering information includes a steering torque and a steering angle. In step 230, an assist amount (assist torque) to be generated by the steering motor 160 is calculated based on the steering information in accordance with a map corresponding to the graph shown in FIG. The steering information on the horizontal axis in FIG. 14 is the steering torque as in the first embodiment. The steering motor 160 is controlled based on the assist amount, and the steered wheels 115 are steered.

If it is detected in step 260 that the steering 160 is locked, the process proceeds to step 270. Then, in step 270, the warning speaker 141 is sounded, and in step 280, the warning lamp 142 is turned on. In step 90, the power supply to the steering motor 160 is stopped. In step 300, the control signal to the electromagnetic clutch 170 is stopped, whereby the electromagnetic clutch 170 is released.

In step 310, it is determined whether or not the release of the electromagnetic clutch 170 performed in step 300 has been completely performed. This determination is made based on the detected value of the assist torque, similarly to the first embodiment.

Here, in the second embodiment, since the steering wheel 111 is not mechanically connected to the steered wheels 115, even if the electromagnetic clutch 170 is released, it is not possible to shift to the manual steering state. After disengaging the clutch,
The steered wheels 115 face the neutral direction, and the vehicle goes straight. On the other hand, even when the electromagnetic clutch 170 is not released, the operation does not shift to the manual steering state. At this time, the direction of the steered wheels 115 is fixed to the direction when the motor lock occurs. Therefore, in the second embodiment, regardless of whether the clutch release has been achieved, steps 330 to 330 are performed.
The process of step 360 is performed.

In step 330, the steering torque sensor 1
The steering information detected by the controller 12, the assist torque detected by the assist torque sensor 117, and the speed of the vehicle detected by the vehicle speed sensor 118 are input to and read from the input port 132. In step 140, based on the read steering information, the braking force of one or more of the front wheels and the rear wheels is calculated according to a map corresponding to the graph shown in FIG.

In the second embodiment, the steering information on the horizontal axis in FIG. 14 is the steering angle. The steering angle is the steering wheel 111
The neutral position is 0, the clockwise direction is positive, and the counterclockwise direction is negative. If the steering angle is positive, the braking force of the right front wheel is set to the braking force corresponding to the steering angle in FIG. 14, and the braking force of the left front wheel is set to 0. Conversely, if the steering angle is negative, the braking force of the right front wheel is set to 0, and the braking force of the left front wheel is set to a braking force (absolute value) corresponding to the steering torque in FIG. Alternatively, a braking force may be applied to both the left and right wheels, and the braking force difference between the two wheels may be set to the value shown in FIG.

As described above, when the clutch release has been achieved, the steered wheels 115 face forward of the vehicle. Also, if the clutch release has not been achieved,
The steered wheels 115 face the same direction as they were when the motor lock occurred. In step S340, the braking force is adjusted or determined according to the direction of the steered wheels 115 at that time according to the same principle as in the first embodiment.

In step 350, the brake 54 is controlled so that the braking force calculated in step 340 is generated. Then, the brake 54 operates to apply a yaw moment to the vehicle for controlling the yaw movement. In step 360, it is determined whether or not the vehicle has stopped based on the vehicle speed.
Return to If the vehicle speed drops below the predetermined threshold speed,
Proceeding to step 370, the control ends.

FIGS. 16 to 19 show the results of verification of the effects of this embodiment by experiments. FIG. 16 is a view showing the state of FIG.
5 shows a traveling locus of a vehicle equipped with the conventional device. FIG. 17 corresponds to FIG. 8 of the first embodiment, and shows a traveling locus of a vehicle including the electric power steering device of the present embodiment. In part A of FIG. 17, the steering motor is locked, but it can be understood that the vehicle can travel without departing from the road. As described above, according to the second embodiment, the same effect as that of the first embodiment can be obtained.

FIG. 18 shows the angles of the steered wheels from a straight road to a curved road, and the steering angle waveform of the driver in the portion. Locking of the steering motor occurs in the portion A, and the angle of the steered wheels is fixed thereafter.
However, in the second embodiment, even if the steered wheels are fixed, the steering wheel 111 can be rotated. As described above, the steering wheel 111 and the steered wheels 11
5 is not mechanically connected. Therefore, as shown in the lower part of FIG. 18, the steering angle changes according to the steering operation of the driver even after passing the portion A.
In the present embodiment, based on the steering angle as the steering information,
The braking force of the front wheels is controlled, and thereby the vehicle travel is controlled. FIG. 19 shows a brake pressure waveform acting on the brake 154. After the lock occurs in part A,
It can be understood that the brake pressure according to the magnitude of the steering angle is generated. In the brake pressure shown in the figure, the positive pressure indicates the pressure acting on the right side of the front wheel, and the negative pressure indicates the pressure acting on the left side of the front wheel.

As shown in FIGS. 16 to 19, the yaw motion of the vehicle can be controlled even when the steering motor is locked. Therefore, it is easy to safely drive on the road and stop at a safe place.

In the second embodiment, the same as in the first embodiment,
The present invention is also applicable to an electric power steering device not equipped with the electromagnetic clutch 170. In this case, FIG.
In the above control, steps 300 and 310 are omitted. Further, in step 340, the calculation of the braking force when the clutch release is achieved becomes unnecessary.

In the second embodiment, during normal operation, the steering motor 160 is controlled based on the steering information, that is, the steering angle and the steering torque. On the other hand, when the motor lock occurs, the brake 154 is controlled based on the steering angle. Was done. In the modified example, both motor control and brake control
Both may be performed based on the steering torque. Alternatively, both controls may be performed based on the steering angle. In addition, any steering information can be applied to motor control and brake control within the scope of the present invention. Then, information necessary at that time may be detected as steering information.

[Brief description of the drawings]

FIG. 1 is a diagram conceptually showing a configuration of an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of the electric power steering device according to the first embodiment.

FIG. 3 is a block diagram illustrating a configuration of an electronic control device in FIG. 2;

FIG. 4 is a flowchart showing a control process of the apparatus of FIG. 2;

FIG. 5 is a diagram showing a map for determining a motor driving force based on a steering torque in the processing of FIG. 4;

6 is a diagram showing a map for determining a braking force of a wheel brake based on a steering torque in the processing of FIG. 4;

FIG. 7 is a diagram showing a traveling locus of a vehicle provided with a conventional electric power steering device.

FIG. 8 is a diagram illustrating a traveling locus of a vehicle including the electric power steering device according to the first embodiment.

FIG. 9 is a diagram showing a change in a steering angle before and after the occurrence of a motor lock in the apparatus of FIG. 2;

FIG. 10 is a diagram showing changes in steering torque and brake braking force before and after the occurrence of motor lock in the apparatus of FIG. 2;

FIG. 11 is a block diagram illustrating a configuration of an electric power steering device according to a second embodiment.

FIG. 12 is a block diagram illustrating a configuration of an electronic control device in FIG. 11;

FIG. 13 is a flowchart showing a control process of the apparatus of FIG. 11;

14 is a diagram showing a map for determining a motor driving force based on steering information in the processing of FIG.

FIG. 15 is a diagram showing a map for determining a braking force of a wheel brake based on steering information in the processing of FIG.

FIG. 16 is a diagram illustrating a traveling locus of a vehicle including a conventional electric power steering device.

FIG. 17 is a diagram illustrating a traveling locus of a vehicle including the electric power steering device according to the second embodiment.

FIG. 18 is a diagram showing changes in the rotation angle and the steering angle of the steered wheels before and after the occurrence of a motor lock in the apparatus of FIG. 11;

FIG. 19 is a diagram showing a change in brake braking force before and after the occurrence of a motor lock in the apparatus of FIG. 11;

[Explanation of symbols]

10 steering wheel, 11 steering axis,
Reference Signs List 12 steering torque sensor, 13 steering gear box, 14 rack bar, 15 steered wheels, 17 assist torque sensor, 18 vehicle speed sensor, 30 electronic control unit, 31 microcomputer, 41 warning speaker, 42 warning lamp, 52 pressure control device, 54 Brake, 60 steering motor, 70 electromagnetic clutch.

Claims (1)

[Claims] 1. Steering information detecting means for detecting steering information of a steering, a steering motor for generating a driving force according to the detected steering information, and transmitting means for transmitting the driving force of the steering motor to steered wheels. An electric power steering apparatus comprising: a motor lock detecting means for detecting a lock state of a steering motor; and controlling a wheel braking force based on a direction and a magnitude of the steering information when a motor lock is detected. Braking control means, and when a steered wheel cannot be steered by the motor lock, by applying a braking force to at least one wheel,
An electric power steering device for controlling a movement of a vehicle in a yaw direction.