JP2924516B2 - Electric power steering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering device for a vehicle such as an automobile, and more particularly to an electric power steering device.

[0002]

2. Description of the Related Art Conventionally, an electric power steering apparatus for a vehicle such as an automobile generally includes a motor for driving a steering linkage member such as a rack bar via a clutch and a steering gear box, and a control device for controlling the rotation of the motor. The control device is configured to generate a required steering assist force by controlling the motor based on the detection results of various sensors.

[0003] As one of such electric power steering devices, for example, as described in Japanese Patent Application Laid-Open No. 63-215461, a motor is driven in a state in which a clutch is released, and the motor is driven by a no-load current of the motor. 2. Description of the Related Art An electric power steering apparatus configured to determine a motor abnormality has been conventionally known. According to the electric power steering apparatus configured as described above, it is possible to reliably detect an abnormality such as a lock in which the motor cannot rotate when the clutch is released.

[0004]

However, in the conventional electric power steering apparatus as described above, the abnormality of the motor cannot be detected unless the clutch is released. The abnormality cannot be detected, and the abnormality of the motor can be monitored substantially only while the vehicle is stopped. Therefore, the clutch cannot be actively released even if the motor becomes abnormal, such as a lock, and cannot rotate while the vehicle is running, so that the power steering device cannot function promptly as a manual steering device. There is a problem that the driver must steer against excessive frictional force caused by slipping in the clutch.

In view of the above-mentioned problems in the conventional electric power steering apparatus, the present invention can monitor the motor lock at all times during the running of the vehicle, thereby locking the motor during the running of the vehicle. It is an object of the present invention to provide an electric power steering device improved so that the clutch can be immediately released in such a case to function as a manual steering device.

[0006]

SUMMARY OF THE INVENTION According to the present invention, as shown in FIG. 1, a motor M1 for generating a steering assist force, a steering torque detecting means M2,
An electric power steering apparatus having a control means M3 for controlling a steering assist force by controlling the motor at least according to a steering torque, comprising: a steering angular velocity detecting means M4; and a rotation detecting a rotational angular velocity of the motor. The angular velocity detecting means M5 determines that the motor is locked when the steering angular velocity and the steering torque are each equal to or greater than the corresponding reference value and the rotational angular velocity of the motor M1 is equal to or less than the reference value corresponding to the rotational angular velocity of the motor. This is achieved by an electric power steering device having a lock determination unit M6.

[0007]

When the motor is locked, even if the driver turns the steering wheel and the steering angular velocity exceeds a certain value, the motor cannot rotate at all and the steering torque becomes abnormally high. The same phenomenon occurs when the steering wheel tire hits a curb or the like and the turning angle of the tire cannot be changed normally even if the motor is normal, but in this case, due to the elastic deformation of the tire, The turning angle of the tire changes slightly, so that the rotational angular speed of the motor also exceeds a certain value. Therefore, when the steering angular velocity and the steering torque are respectively equal to or more than the corresponding reference values, it is determined whether the motor is locked by determining whether the rotation angular velocity of the motor is equal to or less than the reference value corresponding to the rotation angular velocity of the motor. Can be reliably detected.

According to the above arrangement, when the steering angular velocity and the steering torque detected by the steering angular velocity detecting means M4 and the steering torque detecting means M2 are respectively equal to or more than the corresponding reference values, the rotational angular velocity detecting means is used. M5
Rotation of the motor rotation angular speed of the motor detected by the
When the value is equal to or less than the reference value corresponding to the angular velocity, the motor is determined to be locked by the lock determining means M6, so that the motor lock can be reliably detected even while the vehicle is traveling. In this case, the power steering device can be quickly switched to the manual steering device.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a schematic diagram showing one embodiment of an electric power steering apparatus according to the present invention, and FIG.
FIG. 3 is a block diagram showing the electronic control device shown in FIG.

In FIG. 2, reference numeral 10 denotes a steering wheel. The steering wheel 10 drives a rack bar 16 via a steering shaft 12 and a steering gear box 14. A power unit 20 is drivingly connected to the steering shaft 12 by a gear reduction mechanism 18. The power unit 20 has a motor 22 and an electromagnetic clutch 24 for selectively drivingly connecting the gear reduction mechanism 18 and the motor 22.

In the illustrated embodiment, the steering shaft 12 is provided with a steering angle sensor 26 for detecting the steering angle θ and a torque sensor 28 for detecting the steering torque T, and the output of these sensors is electronic. It is supplied to the control device 32. The electronic control unit 32 also includes a signal indicating the vehicle speed V detected by the vehicle speed sensor 34 and the rotation angle φ of the motor 22 detected by the rotation angle sensor 36.
Is also input.

As shown in detail in FIG. 3, the electronic control unit 32 includes a microcomputer 38, which is a central processing unit (CPU) 40.
A read only memory (ROM) 42, a random access memory (RAM) 44, and an input port device 46
And an output port device 48, which are connected to each other by a bidirectional common bus 50.

The input port device 46 has a steering angle sensor 26
Indicating the steering angle θ detected by the torque sensor 2
8, a signal indicating the steering torque T detected by the controller 8, a signal indicating the vehicle speed V detected by the vehicle speed sensor 34, and a signal indicating the rotation angle φ of the motor detected by the rotation angle sensor 36 are input. . The input port device 46 appropriately processes the signal input thereto, and outputs the processed signal to the CPU and the RAM 44 in accordance with an instruction of the CPU 40 based on a control program stored in the ROM 42.

The ROM 42 stores a control program shown in FIG. 4 and maps corresponding to the graphs shown in FIGS. The CPU 40 performs various calculations and signal processing based on the control program shown in FIG. The output port device 48 outputs a control signal to the motor 22 via the drive circuit 52 according to the instruction of the CPU 40, outputs a control signal to the electromagnetic clutch 24 via the drive circuit 54, and further determines that the motor is locked. The alarm lamp 56 is turned on when the alarm occurs.

Next, the operation of the illustrated embodiment will be described with reference to the flowchart shown in FIG. The control by the electronic control unit 32 is started when an ignition switch (not shown in FIG. 2) is closed. In the flowchart shown in FIG. 4, N indicates the number of times that the motor is locked.

First, in step 10, a control signal is output to the electromagnetic clutch 24 via the drive circuit 54 to connect the clutch. In step 20, the steering angle θ detected by the steering angle sensor 26 is determined. A signal indicating the steering torque T detected by the torque sensor 28,
A signal indicating the vehicle speed V detected by the vehicle speed sensor 34, and the rotation angle φ of the motor detected by the rotation angle sensor 36
Is read.

In step 30, based on the steering torque T read in step 20, a basic assist amount Tab is calculated from a map corresponding to the graph shown in FIG.
In step 40, the vehicle speed coefficient Kv is calculated from the map corresponding to the graph shown in FIG. 6 based on the vehicle speed V read in step 20, and in step 50, the vehicle speed coefficient Kv is calculated in step 30. The assist amount Ta is calculated as the product of the basic assist amount Tab and the vehicle speed coefficient Kv calculated in step 40.

In step 60, the steering angular velocity θd is calculated by differentiating the steering angle θ, and it is determined whether or not the absolute value of the steering angular velocity θd is equal to or more than a reference value θdo (positive constant). Is performed, and when it is determined that | θd | ≧ θdo, that is, when it is determined that the steering wheel 10 is steered, the routine proceeds to step 70, where | θd
When it is determined that | ≧ θdo is not satisfied, that is, when it is determined that the vehicle is substantially in the straight running state or the turning and steering state, the routine proceeds to step 90.

In step 70, it is determined whether or not the absolute value of the steering torque T is equal to or larger than a reference value To (a positive constant).
That is, it is determined whether or not the absolute value of the steering torque is a high value that does not occur during normal steering due to the impossibility of rotation of the motor 22, and when it is determined that | T | ≧ To The routine proceeds to step 80, and if it is determined that | T | ≧ To is not satisfied, the routine proceeds to step 90.

In step 80, the rotational angle φd of the motor is calculated by differentiating the rotational angle φ of the motor, and the absolute value of the rotational angular speed φd is equal to or smaller than a reference value φdo (positive constant). It is determined whether or not there is a situation where it is difficult for the turning angle to be changed by a steered wheel (not shown) abutting on a curb or the like,
When it is determined that | φd | ≦ φdo, the routine proceeds to step 110, and when it is determined that | φd | ≦ φdo, the routine proceeds to step 90.

The determination reference values θdo, To and φdo in steps 60 to 80 described above may be obtained experimentally, for example, so that the corresponding determinations are properly performed.

In step 90, the abnormality determination frequency N is zero.
Is determined, and if it is determined that N = 0, the process proceeds directly to step 130, where N =
When it is determined that the value is not 0, step 100 is executed.
After the number N is reset to 0 in step (1), the routine proceeds to step 130. In step 110, the number N is incremented by one. In step 120, it is determined whether or not the number N is three. When it is determined that N is not three, step 130 is performed. In step (2), a control signal corresponding to the assist amount Ta is output to the motor 22 via the drive circuit 52, so that the steering assist force is controlled to a value corresponding to the assist amount Ta, and then the process returns to step 20, where N = 3.
When it is determined that is the case, the routine proceeds to step 140.

In step 140, the energization of the motor 22 is stopped and the output of the control signal to the electromagnetic clutch 24 is stopped to release the clutch.
In step 150, the control signal is output to the warning lamp 56 to turn on the warning lamp, thereby issuing a warning to the driver of the vehicle that the motor is locked.

Thus, according to the illustrated embodiment, in step 30, the basic assist amount Tab is calculated from a map corresponding to the graph shown in FIG. 5, and in step 40, the vehicle speed coefficient Kv is shown in FIG. In step 50, the assist amount Ta is calculated as the product of the basic assist amount Tab and the vehicle speed coefficient Kv.

If the motor is not locked and is normal, it is difficult to change the turning angle by making a NO determination in step 70 or by the steered wheels coming into contact with a curb or the like. In such a situation, a determination of YES is made in step 70 and a determination of NO is made in step 80, so that a control signal corresponding to the assist amount Ta is output to the motor 22 in step 130. As a result, the steering assist force is controlled so as to correspond to the steering torque and to decrease as the vehicle speed increases, so that light steering at a low vehicle speed range is secured and good steering stability at a high vehicle speed range is ensured. Nature is secured.

On the other hand, when the motor is locked, the motor cannot rotate at all even if the steering wheel 10 is turned, and the absolute value of the steering torque T becomes greater than the reference value To. Is determined. If this determination, that is, the determination that the motor is locked is performed three times in succession, a determination of YES is made in step 120, and in step 140, the power supply to the motor 22 is stopped and the clutch 24 When the output of the control signal is stopped, the clutch is disengaged, whereby the power steering device is switched to the manual steering device. Further, at step 150, the alarm lamp 56 is turned on, and the driver of the vehicle is notified of the motor operation. An alarm is issued to the effect that is locked.

According to the illustrated embodiment, steps 140 and 150 are not executed unless the determination that the motor is locked is performed three times in succession. Therefore, it is erroneously determined that the motor is locked. Although the motor is not actually locked based on the determination result, step 140
And 150 are executed, that is, the alarm lamp 5
6 is reliably prevented from being turned on and the power steering device being switched to the manual steering device.

Although the present invention has been described in detail with reference to specific embodiments, the present invention is not limited to such embodiments, and various other embodiments may be made within the scope of the present invention. The possibilities will be clear to the skilled person.

[0030]

As is apparent from the above description, according to the present invention, the steering angular velocity and the steering torque detected by the steering angular velocity detecting means M4 and the steering torque detecting means M2 are respectively equal to or more than the corresponding reference values. In this case, when the rotation angular velocity of the motor detected by the rotation angular velocity detection means M5 is equal to or less than a reference value corresponding to the rotation angular velocity of the motor , the lock determination means M6 determines that the motor M1 is locked. It is possible to reliably detect the lock of the motor even during the traveling of the vehicle, so that when the motor is locked, the power steering device can be quickly switched to the manual steering device.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of an electric power steering device according to the present invention, corresponding to the description in the claims.

FIG. 2 is a schematic configuration diagram showing one embodiment of an electric power steering device according to the present invention.

FIG. 3 is a block diagram showing the electronic control device shown in FIG. 2;

FIG. 4 is a flowchart showing a control flow achieved by the electronic control device shown in FIGS. 2 and 3.

FIG. 5 is a graph showing a relationship between a steering torque T detected by a torque sensor and a basic assist amount Tab.

FIG. 6 is a graph showing a relationship between a vehicle speed V detected by a vehicle speed sensor and a vehicle speed coefficient Kv.

[Explanation of symbols]

 Reference Signs List 10 steering wheel 12 steering shaft 14 steering gear box 16 rack bar 22 motor 24 electromagnetic clutch 26 steering angle sensor 28 torque sensor 32 electronic control unit 34 vehicle speed sensor 36 rotation angle sensor 56 alarm lamp

Continued on the front page (51) Int.Cl. ⁶ Identification code FI B62D 119: 00

Claims (1)

(57) [Claims] 1. An electric power steering apparatus comprising: a motor for generating a steering assist force; a steering torque detecting unit; and a control unit for controlling the steering assist force by controlling the motor according to at least the steering torque. The steering angular velocity detecting means, the rotational angular velocity detecting means for detecting the rotational angular velocity of the motor, the steering angular velocity and the steering torque are respectively equal to or more than the corresponding reference values, and the rotational angular velocity of the motor is equal to the rotational angular velocity of the motor. An electric power steering device, comprising: a lock determination unit that determines that the motor is locked when the value is equal to or less than a corresponding reference value.