JPH06305439A - Motor-driven power steering device - Google Patents

Abstract

PURPOSE:To surely suspend power assist even in the case of grave abnormality being generated during the process of steering assist force being gradually reduced due to the generation of minor abnormality. CONSTITUTION:A motor-driven power steering has a motor M1 for generating steering assist force, a steering torque detecting device M2, and a control device M3 for controlling the motor at a specified assist ratio according to at least the steering torque so as to control the steering assist force. When grave abnormality is generated in the power steering, the control of the motor is stopped by a first abnormality detecting processor M4. When minor abnormality is generated in the power steering, the assist ratio is gradually changed to the specified value by a second abnormality detecting processor M5, and further when grave abnormality is generated during the processing of the second abnormality detecting processor M5, the control of the motor is stopped by a third abnormality detecting processor M6.

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 vehicles such as automobiles, 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 has a motor for driving a steering member such as a rack bar via a steering gear box and a control device for controlling the rotation of the motor. However, the control device generates a required steering assist force by controlling the motor based on the detection results of various sensors such as a torque sensor.

As one of such electric power steering devices, for example, as disclosed in Japanese Patent Laid-Open No. 1-156172, an abnormality detecting means for detecting an abnormality in the power steering device and an abnormality in the power steering device are detected. When it is detected, the steering assist force is switched to a predetermined value and the abnormal time processing means is provided.The abnormal time processing means rotates the motor when the detected abnormality is a serious abnormality such as a motor current abnormality or a power supply voltage abnormality. An electric power steering device configured to gradually reduce the steering assist force when the control is stopped to stop the power assist and the abnormality is a slight abnormality such as an offset of the vehicle speed sensor or the torque sensor is conventionally known. There is.

According to the electric power steering system as described above, when a serious abnormality occurs in the power steering system, the power assist is stopped and the power steering system is switched to the manual steering system, so that the motor is improperly controlled. Improper power assist is reliably prevented, and when a slight abnormality occurs in the power steering device, the steering assist force generated by the motor is gradually reduced to not zero. Therefore, not only the inappropriate power assist is reliably prevented, but also the sudden change in the steering feeling is surely avoided.

[0005]

However, in the conventional electric power steering apparatus as described above, a slight abnormality occurs in the power steering apparatus, and the steering assist force is gradually reduced by the abnormality processing means. When a serious abnormality occurs in the power steering device, the serious abnormality is not detected by the abnormality processing means. Therefore, the power assist is not stopped despite the occurrence of the serious abnormality in the power steering device. There's a problem.

In view of the above-mentioned problems in the conventional electric power steering apparatus, the present invention provides a power steering apparatus in the process in which a slight abnormality occurs in the power steering apparatus and the steering assist force is gradually reduced. It is an object of the present invention to provide an improved electric power steering device that can reliably stop power assist and switch the power steering device to a manual steering device even when a serious abnormality occurs.

[0007]

According to the present invention, as described above, the above object is to provide a motor M1 for generating a steering assist force, a steering torque detecting means M2, and a steering torque detecting means M2.
An electric power steering device having a control means M3 for controlling the steering assist force by controlling the motor at a predetermined assist ratio according to at least the steering torque is provided, and a serious abnormality in the power steering device is detected. A first abnormality detection processing means M4 for detecting and stopping the control of the motor, and a second abnormality detection processing means M5 for detecting a slight abnormality in the power steering device and gradually changing the assist ratio to a predetermined value. And the third abnormality detection processing means M6 for detecting a serious abnormality in the power steering device during the processing by the second abnormality detection processing means and stopping the control of the motor. Achieved by a power steering system.

[0008]

According to the above-mentioned structure, the first abnormality detection processing means M4 for detecting a serious abnormality in the power steering device and stopping the control of the motor and the minor abnormality in the power steering device to detect the assist ratio. In addition to the second abnormality detection processing means M5 for gradually changing the value to a predetermined value, a third abnormality is detected during the processing by the second abnormality detection processing means, and the control of the motor is stopped. Since the abnormality detection processing means M6 is provided, the power steering is performed in the process in which a slight abnormality occurs in the power steering device and the assist ratio is gradually changed to a predetermined value by the second abnormality detection processing means. When a serious abnormality occurs in the device, the serious abnormality is detected by the third abnormality detection processing means, and it is confirmed by stopping the motor control. Power assist is stopped, the power steering system is switched reliably manual steering apparatus.

[0009]

[Supplementary Explanation of Means for Solving the Problem] In the present specification, "serious abnormality" means that continuation of power assist is a serious obstacle in running of the vehicle, and therefore power assist control is immediately stopped. It means an abnormality that requires the power steering device to be switched to the manual steering device. "Minor abnormality" does not cause a serious obstacle to the running of the vehicle, but the optimum power assist is performed. Therefore, it is preferable to gradually change the assist ratio at the time of occurrence of abnormality to a predetermined value (in particular, gradually reduce the assist ratio and finally switch the power steering device to the manual steering device). .

According to one embodiment of the present invention, a pair of torque detecting means is provided, and an abnormality such as an offset of only one of the torque detecting means is treated as a minor abnormality.
Anomalies such as offsets in both torque sensing means are treated the same as significant anomalies. According to this configuration, when an offset abnormality occurs in both torque detecting means,
Even if the abnormality that has occurred in each torque detection means is a minor abnormality, it is processed in the same way as a serious abnormality for the power steering device as a whole, so it is possible to reliably prevent inappropriate power assist control from continuing. It

[0011]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

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

In FIG. 2, reference numeral 10 denotes a steering wheel. The steering wheel 10 is a rack bar 1 as a steering linkage member via a steering shaft 12 and a steering gear box 14.
6 is driven. A power unit 20 is drivingly connected to the steering shaft 12 by a gear reduction mechanism 18. The power unit 20 is 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 a steering angle θ and torque sensors 28 and 30 for detecting steering torques T1 and T2, respectively. The output of the sensor is supplied to the electronic control unit 32.
Further, 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 22 detected by the rotation angle sensor 36 are also input to the electronic control unit 32.

As shown in detail in FIG. 3, the electronic controller 32 includes a microcomputer 38, which is a central processing unit (CPU) 40.
, Read only memory (ROM) 42, random access memory (RAM) 44, and 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.
A signal indicating the steering angle θ detected by the torque sensor 2
A signal indicating the output steering torques T1 and T2 from 8 and 30, 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 22 detected by the rotation angle sensor 36 are input. It has become. The input port device 46 appropriately processes the signal input thereto, and outputs the processed signal to the CPU and the RAM 44 according to the instruction of the CPU 40 based on the control program stored in the ROM 42.

The ROM 42 stores the control program shown in FIG. 4 and maps corresponding to the graphs shown in FIGS. 5 and 6. The CPU 40 is adapted to perform various calculations and signal processing as will be described later 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 an instruction from the CPU 40, and outputs a control signal to the electromagnetic clutch 24 via the drive circuit 54.

Further, the electronic control unit 32 diagnoses whether or not an abnormality has occurred in the power steering device, and when the abnormality is serious, outputs a control signal to the alarm lamp 56 to blink the alarm lamp and to drive the motor. The rotation control is immediately stopped, and when the abnormality is slight, the alarm lamp is turned on and the rotation output of the motor is gradually reduced.

In the illustrated embodiment, the torque sensor 2
When an offset exceeding the allowable range occurs in 8 or 30, the output pulse of the rotation angle sensor 26 for detecting whether or not the motor 22 is rotating at the rotation speed corresponding to the control signal is misaligned, and the electronic control unit 32 is driven. Abnormalities such as the circuit 52 are treated as serious abnormalities, and the torque sensor 28 or 30 is detected.
Disconnection, short circuit, noise superposition, slight offset such as temperature drift, vehicle speed sensor 34 disconnection, short circuit, output pulse misalignment, noise superposition, steering angle sensor 26 disconnection, short circuit, output pulse misalignment, noise superposition The midpoint deviation and the like are treated as minor abnormalities, and if exceptionally abnormalities such as offset occur in both of the two torque sensors 28 and 30, they are treated in the same manner as a serious abnormality.

Further, the diagnosis as to whether or not an abnormality has occurred in the power steering device and the determination as to whether the abnormality is a serious abnormality or a minor abnormality do not form the gist of the present invention. However, the diagnosis and discrimination of the abnormality may be performed by any method conventionally proposed in this technical field.

Next, the operation of the illustrated embodiment will be described with reference to the flow chart shown in FIG. In the flow chart shown in FIG. 4, the flag F relates to whether or not a slight abnormality has occurred in the power steering device, and 1 indicates that a slight abnormality has occurred.

First, at step 10, the control signal is output to the clutch 24 to connect the clutch,
In step 20, the signal indicating the steering angle θ detected by the steering angle sensor 26, the signals indicating the steering torques T1 and T2 detected by the torque sensors 28 and 30, respectively, and the vehicle speed V detected by the vehicle speed sensor 34 are displayed. The read signal and the signal indicating the rotation angle φ of the motor 22 detected by the rotation angle sensor 36 are read.

In step 30, it is judged whether or not a serious abnormality has occurred in the power steering device. When it is judged that a serious abnormality has occurred, the routine proceeds to step 120, where the serious abnormality is detected. If it is determined that no abnormal condition has occurred, the process proceeds to step 40. In step 40, it is determined whether or not the flag F is 1, that is, whether or not a slight abnormality has occurred in the power steering device, and it is determined that F = 1. If so, the process proceeds to step 80, and if it is determined that F = 1 is not satisfied, the process proceeds to step 50.

In step 50, it is determined whether or not a minor abnormality has occurred in the power steering device. If it is determined that no minor abnormality has occurred, then in step 60 the assist is performed. When the numerator K of the ratio is set to A (a positive integer) and it is determined that a slight abnormality has occurred, the alarm lamp 5 is issued in step 70.
6 is turned on, the flag F is set to 1, and the numerator K of the assist ratio is decremented by 1 in step 80.

In step 90, the assist ratio numerator K
Is determined to be 0, and when it is determined that K = 0, in step 100, the output of the control signal to the electromagnetic clutch 24 is stopped to release the clutch. Then, the power assist control by the routine shown in FIG. 4 is terminated, and when it is determined that K = 0 is not satisfied, the routine proceeds to step 110.

In step 110, the torque sensor 28 is used.
It is determined whether or not both of the torque sensors 30 and 30 have failed, that is, whether or not any abnormality such as disconnection or short circuit has occurred in any of the two torque sensors, and at least one of the torque sensors is normal. If the determination is made, step 14
When it is determined that the two torque sensors are out of order, the process proceeds to step 120.

In step 120, the control signal is output to the alarm lamp 56, so that the alarm lamp blinks, and the driver of the vehicle is alerted that a serious abnormality has occurred in the power steering system. In step 130, the energization of the motor 22 is stopped and the output of the control signal to the electromagnetic clutch 24 is stopped, so that the clutch is released, and the power assist control by the routine shown in FIG. 4 is performed. finish.

In step 140, the torque sensor 2
Based on the steering torques T1 and T2 detected by 8 and 30, the average value T of the steering torque is calculated according to the following equation 1, and the map corresponding to the graph shown in FIG. Then, the basic assist amount Tab is calculated, and in step 150, the basic assist amount Tab is corrected according to the following equation 2.

[0029]

[Equation 1] T = (T1 + T2) / 2

[Equation 2] Tab = (K / A) · Tab

In step 160, 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 170, in step 150. The assist amount Ta is calculated as a product of the corrected basic assist amount Tab calculated in step 160 and the vehicle speed coefficient Kv calculated in step 160, and in step 180, a control signal of a voltage corresponding to the assist amount Ta is calculated. Is output to the motor 22 via the drive circuit 52, whereby a required assist force is generated, and then the process returns to step 20.

Thus, according to the illustrated embodiment, in step 140, the basic assist amount Tab is calculated from the map corresponding to the graph shown in FIG. 5 based on the average value T of the steering torque, and in step 150. The basic assist amount Tab is corrected and calculated, and in step 160 the vehicle speed coefficient Kv is calculated from the map corresponding to the graph shown in FIG. 6 based on the vehicle speed V. In step 170, the assist amount Ta is calculated as the basic assist amount Tab. And the vehicle speed coefficient Kv.

If no abnormality has occurred in the power steering device and it is operating normally, a negative determination is made in steps 30, 50 and 110, and the assist operation is performed in step 180. A control signal corresponding to the amount Ta is output to the motor 22, whereby the steering assist force is controlled so as to correspond to the actual steering torque and become lower as the vehicle speed increases, so that light steering is ensured in the low vehicle speed range. At the same time, good driving stability is ensured in the high vehicle speed range.

On the other hand, if a serious abnormality occurs in the power steering device, a yes determination is made in step 30, the alarm lamp 56 is blinked in step 120, and the driver of the vehicle is informed of the power steering device. An alarm is issued indicating that a serious abnormality has occurred, and step 13
At 0, the energization of the motor 22 is stopped and the output of the control signal to the clutch 24 is stopped to release the clutch, whereby the power steering device is switched to the manual steering device.

According to the illustrated embodiment, if a slight abnormality occurs in the power steering device, a yes determination is made in step 50 and the alarm lamp 56 is turned on in step 70 to drive the vehicle. A person is alerted that a slight abnormality has occurred in the power steering device, and the assist ratio K / A is set to 0 in steps 80 and 150.
Steps 140 to 180 are executed while being gradually reduced until. Therefore, in this case, the power steering device is not immediately switched to the manual steering device, but power assist is continued while gradually reducing the assist ratio, and when the assist ratio becomes 0, the power steering device is manually operated. It is switched to the steering device.

Further, according to the illustrated embodiment, if a slight abnormality occurs in the power steering device and a serious abnormality occurs in the power steering device while the power assist is being continued while gradually reducing the assist ratio, Step 3
Since the determination of YES is made in 0 and steps 120 and 130 are always executed, this causes the vehicle to be in the same condition as when a serious abnormality occurs in a situation where a slight abnormality does not occur in the power steering device. The driver is alerted that a serious abnormality has occurred, and the power steering device is reliably switched to the manual steering device.

Further, according to the embodiment shown in the drawing, even if the abnormality occurring in each of the two torque sensors is slight, if the abnormality occurs in both torque sensors, the determination in step 110 is YES. As a result, steps 120 and 130 are executed. In this case as well, an alarm is issued to the driver of the vehicle indicating that a serious abnormality has occurred, and the power steering device is reliably switched to the manual steering device.

Although the present invention has been described in detail above with reference to specific embodiments, the present invention is not limited to such embodiments, and various other embodiments are possible within the scope of the present invention. It will be apparent to those skilled in the art that it is possible.

For example, in the above embodiment, step 1
The basic assist amount Tab in 40 is calculated based on the average value T of the steering torques T1 and T2 detected by the two torque sensors 28 and 30, but the basic assist amount is calculated in the torque sensor 28. It may be calculated based on the steering torque detected by one of
In this case, when it is determined in step 50 that a slight abnormality has occurred in one of the torque sensors, the basic assist amount is calculated based on the steering torque detected by the other normal torque sensor. May be configured as follows.

In the above embodiment, step 90
When it is judged whether the numerator K of the assist ratio is 0 or not and it is judged that K = 0, step 10
At 0, the clutch is disengaged and the power steering device is switched to the manual steering device. The determination at step 90 is whether the numerator K has reached a predetermined value B such as half of the denominator A. When it is determined that K = B, the clutch is not released but step 80 is bypassed, the numerator K is always set to B, and steps 110 and thereafter are executed.
With this, when a slight abnormality occurs in the power steering device, the power assist control may be configured to continue with the reduced assist ratio.

[0040]

As is apparent from the above description, according to the present invention, the first abnormality detection processing means M4 for detecting a serious abnormality in the power steering device and stopping the control of the motor and the power steering device. In addition to the second abnormality detection processing means M5 for gradually changing the assist ratio to a predetermined value, a serious abnormality in the power steering device is detected during the processing by the second abnormality detection processing means. Third abnormality detection processing means M for stopping the control of the motor
6 is provided. Therefore, in the process in which a slight abnormality occurs in the power steering apparatus and the assist ratio is gradually changed to a predetermined value by the second abnormality detection processing means, a serious abnormality is detected in the power steering apparatus. When the occurrence of the above occurs, the serious abnormality is detected by the third abnormality detection processing means, so that it is possible to stop the motor control and surely stop the power assist, thereby ensuring the power steering device. In addition, it can promptly function as a manual steering device.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of an electric power steering device according to the present invention in correspondence with the description of 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 power assist control routine achieved by the electronic control device shown in FIGS. 2 and 3.

FIG. 5 is a graph showing a relationship between an average value T of steering torque 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]

 10 ... Steering wheel 12 ... Steering shaft 14 ... Steering gear box 22 ... Motor 24 ... Electromagnetic clutch 26 ... Steering angle sensor 28, 30 ... Torque sensor 32 ... Electronic control unit 34 ... Vehicle speed sensor 36 ... Rotation angle sensor 56 ... Warning lamp

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaaki Tsuboi, 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Corporation (72) Inventor, Tomoyuki Watanabe 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation

Claims (1)

[Claims] 1. A motor for generating a steering assist force, a steering torque detecting means, and a control means for controlling the steering assist force by controlling the motor at a predetermined assist ratio according to at least the steering torque. An electric power steering apparatus having the above, first abnormality detection processing means for detecting a serious abnormality in the power steering apparatus and stopping control of the motor, and detecting a minor abnormality in the power steering apparatus. Second abnormality detection processing means for gradually changing the assist ratio to a predetermined value, and a serious abnormality in the power steering device is detected during processing by the second abnormality detection processing means, and control of the motor is stopped. An electric power steering apparatus comprising: a third abnormality detection processing means.