JPH10203392A - Control device of motor-driven power steering - Google Patents

Abstract

PROBLEM TO BE SOLVED: To largely relieve a sense of incompatibility felt by a driver until control of an electric motor is stopped when abnormality of steering torque sensors is caused. SOLUTION: Abnormality of steering torque detecting values TM and TS of main and sub-steering torque sensors is detected (Step S2 to S14), and control is finished when an abnormal condition continues for a prescribed time, but until the prescribed time passes after being put in the abnormal condition, a small absolute value is selected as a steering torque detecting value T when the directions of both steering torque detecting values TM and TS coincide with each other, and when the directions do not coincide with each other, the control is continued while restricting the steering torque value T to an allowable range noninfluential on steering, for example, '0'.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light steering system in which a steering torque applied to a steering system is detected by a plurality of steering torque detecting means, and a steering assist force generated by an electric motor is controlled in accordance with the detected values. The present invention relates to a control device for an electric power steering that performs the above-mentioned operation, particularly in order to prevent a driver from feeling uncomfortable when an abnormal steering torque detection value occurs.

[0002]

2. Description of the Related Art A conventional electric power steering control apparatus is disclosed in, for example, Japanese Patent Application Laid-Open No. 2-120179 (hereinafter simply referred to as a conventional example).

In this conventional example, first and second torque sensors for detecting a steering torque of a steering system are provided, and the abnormality of these torque sensors is continued for a predetermined time while the value of the second torque sensor is an abnormal value. Whether or not to do the first and second
It is determined whether or not the state in which the absolute value of the difference value of the torque sensor exceeds a predetermined value continues for a predetermined time.If both sensors are normal or abnormal, this abnormal state is continued for a predetermined time. If not, a torque detection value having a small absolute value among the two sensors is selected, and the drive current of the electric motor that assists the steering torque is controlled based on this.
When any one of the torque sensors becomes abnormal, the assist by the electric motor is stopped to extend the predetermined time of the abnormality determination, thereby preventing an erroneous abnormality determination due to the influence of noise included in the torque detection value of the torque sensor. Also, there is disclosed a control method of an electric power steering apparatus in which assist control is always performed on the safe side regardless of an abnormality in any aspect of the torque sensor.

[0004]

However, in the above-mentioned conventional electric power steering control device,
In order to eliminate the influence of noise, it is determined that the torque sensor is abnormal only when the abnormal state of the torque sensor continues for a relatively long predetermined time. If an abnormality occurs in which the absolute value is smaller than the absolute value of the torque sensor but the torque detection direction is reversed, the electric motor is controlled based on the detected value of the second torque sensor. Therefore, there is an unsolved problem of giving a sense of incongruity to the driver.

Accordingly, the present invention has been made in view of the above-mentioned unsolved problems of the prior art, and is intended to prevent the driver from feeling uncomfortable when an abnormality occurs in the steering torque detecting means. An object of the present invention is to provide a control device for a steering device.

[0006]

To achieve the above object, a control device for an electric power steering apparatus according to claim 1 comprises a plurality of steering torque detecting means for detecting a steering torque applied to a steering system; An electric power steering control device, comprising: an electric motor that applies a steering assist force to the steering system; and a control unit that controls the electric motor based on steering torque detection values of the plurality of steering torque detection units. Means for selecting a steering torque detection value having a small absolute value of the steering torque detection values of the plurality of steering torque detection means; and a steering torque detection value selected by the torque selection means and another steering torque detection value. Torque detection value limiting means for limiting the steering torque detection value selected when the value is in a different direction to a value within an allowable range that does not affect steering. It is characterized by comprising.

According to a second aspect of the present invention, there is provided a control device for an electric power steering device, wherein a plurality of steering torque detecting means for detecting a steering torque applied to a steering system, and a steering assist force is applied to the steering system. An electric power steering control device comprising: an electric motor; and a control unit that controls the electric motor based on steering torque detection values of the plurality of steering torque detection units, wherein the control unit includes an abnormality of the plurality of steering torque detection units. Abnormality detection means for detecting abnormality of the steering torque detection means when the state continues for a predetermined time;
A torque selection unit that selects a steering torque detection value having a small absolute value of the steering torque detection values of the plurality of steering torque detection units when no abnormality is detected by the abnormality detection unit; Torque detection value limiting means for limiting the selected steering torque detection value to a value within an allowable range that does not affect steering when the steering torque detection value and the other steering torque detection values are in different directions. It is characterized by:

According to a third aspect of the present invention, in the control device for an electric power steering apparatus according to the second aspect, when the abnormality detecting means includes two sets of steering torque detecting means, the difference value between the two sets is determined. Is characterized in that the steering torque detecting means is determined to be abnormal when a state in which the absolute value is equal to or more than the set value continues for a predetermined time.

According to a fourth aspect of the present invention, in the control apparatus for an electric power steering apparatus according to any one of the first to third aspects, the torque detection value control means is provided within an allowable range which does not affect steering. As a value, the selected steering torque detection value is limited to zero.

[0010]

According to the first aspect of the present invention, a steering torque detection value having a small absolute value is always selected from a plurality of steering torque detection means, and the selected steering torque detection value is set to another steering torque detection value. When the direction is reversed, the selected steering torque detection value is limited to a value within an allowable range that does not affect the steering. When an abnormality occurs in which the absolute value is smaller than the detected steering torque value and the direction is reversed, the control of the electric motor based on the selected detected steering torque value is limited to a state in which the steering is not affected. An effect is obtained that it is possible to reliably prevent a person from feeling uncomfortable.

According to the second aspect of the present invention, it is preferable that the abnormality detecting means removes the influence of noise and detects the abnormality of the steering torque detecting means until a predetermined time elapses. Similarly, when the direction of the detected abnormal steering torque is different from that of the other steering torques, the control of the electric motor is limited to a state in which the steering is not affected, so that the driver may feel uncomfortable. The effect that the prevention can be surely obtained is obtained.

Further, according to the invention according to claim 3, 2
When the steering torque is detected by the set of steering torque detecting means, it is determined that the state is an abnormal state when the state in which the absolute value of the difference between the two is equal to or more than the predetermined value continues for a predetermined time,
Even when the detected steering torque value of the abnormal steering torque detection means is substantially the same as the absolute value of the other steering torque detection values and is in the opposite direction, it is possible to recognize the abnormal state. .

Still further, according to the invention, when the selected steering torque detection value has a direction opposite to that of another steering torque detection value, the value of the selected steering torque detection value is changed to the value of the steering operation. The state is limited to a state where the torque is zero, that is, a state where steering is not performed, and an effect is obtained that the driver can be more reliably prevented from feeling uncomfortable.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing one embodiment of the present invention. A steering wheel 1 is connected to an upper end of a steering shaft 2, and the steering shaft 2 is supported by a fixed portion and extends downward. The pinion 3 is mounted on the section.

The pinion 3 meshes with a rack 4 extending horizontally in the vehicle width direction to form a steering gear, and the rotational movement from the steering wheel 1 to the steering shaft 2 is a linear movement (translational movement) of the rack 4. Is converted to

The two ends of the horizontally extending rack 4 are connected to knuckles and steered wheels 6 via tie rods 5, respectively, and the rack 4 moves horizontally (translational movement), so that the left and right steered wheels 6 are moved. Is steered.

A ring gear 11 constituting a speed reducer is provided above the pinion 3 in the steering shaft 2.
Is fixed coaxially, a ring gear 10 connected to a drive shaft 9 of a steering assist motor 8 meshes with the ring gear 11, and the steering assist motor 8 is steered by a duty controlled pulse current output from a control unit 7 described later. Control is performed so as to generate a steering assist force according to the torque.

Further, a torque detecting mechanism 12 is provided above the ring gear 11 in the steering shaft 2. The torque detecting mechanism 12 includes a torsion bar (not shown) connecting the lower end of the steering shaft 2 and the upper end of the pinion 3, and a main steering torque sensor 13M and a sub steering torque sensor 13 arranged on the outer periphery thereof.
S.

These steering torque sensors 13M and 13S
Detects a steering torque from the torsion amount of the torsion bar, and sets a positive value according to the magnitude of the steering torque and a right turn of the steering wheel 1 (counterclockwise with respect to an input from the pinion 3). The torque detection values TM and TS, which are negative left voltage signals at the left turn of 1 (clockwise with respect to the input from the pinion 3), are supplied to the control unit 7 described later.

The vehicle is provided with a vehicle speed sensor 14 for detecting a vehicle speed. The vehicle speed sensor 14 detects a vehicle speed in the front-rear direction of the vehicle, and a vehicle speed detection value V which is a voltage signal corresponding to the magnitude of the vehicle speed. Is supplied to the control unit 7 described later. Further, a current detector 16 constituting a current detecting means is attached to the steering assist motor 8, and the current detector 16 detects an actual current flowing through the steering assist motor 8, and outputs a current signal corresponding to the magnitude thereof. Is supplied to the control unit 7.

As shown in FIG. 2, the control unit 7 includes main and sub steering torque sensors 13M and 13M.
Steering torque detection value T output from S and current detector 1
A microcontroller for inputting the actual current detection value i output from the control unit 6 and outputting a duty control signal for duty-controlling the drive current to the steering assist motor 8 for controlling the rotation direction and rotation speed of the steering assist motor 8; Computer 15
And a motor drive circuit 19 for supplying a duty control current pulse output from the microcomputer 15 and controlling the rotation direction and rotation speed of the steering assist motor 8 based on the duty control current pulse.

In this case, the microcomputer 15
Input / output interface circuit 15a having an A / D conversion function and an A / D conversion function, an arithmetic processing unit (CPU) 15b including a microprocessor unit and the like, and a RAM and a ROM
And the like and an output-side interface circuit 15d. And the input interface circuit 1
5a, steering torque detection values TM and T of the main steering torque sensor 13M and the sub steering torque sensor 13S are shown.
S and the actual current detection value i from the current detector 16 are input,
From the output interface circuit 15d, a left-turn direction signal LD and a right-turn direction signal RD indicating the steering assist force generation direction are output.
A left-turning duty control current pulse LP and a right-turning duty control current pulse RP for duty-controlling the current supplied to the steering assist motor 8;
9 to the motor drive circuit 19.

The arithmetic processing unit 15b executes the arithmetic processing of FIG. 5 to be described later for a predetermined sampling time ΔT (for example, 5 m
sec), the two steering torque sensors 13M
When the abnormal state continues for a predetermined time or longer based on the detected steering torque values TM and TS of 13S and 13S, it is determined that the state is abnormal and the steering assist force control is stopped. It is determined whether or not the signs of the values TM and TS, that is, the directions, coincide with each other. If they match, a steering torque detection value having a small absolute value is set as the steering torque detection value T. If they do not match, the steering torque detection value T is set to “ 0 ", and forms left / right turning direction signals LD, RD and left / right turning duty control current pulses LP, RP so as to generate a steering assist force in accordance with the set steering torque detection value T. Circuit 15d
To send to.

Further, the storage device 15c stores in advance control maps and arithmetic expressions necessary for the arithmetic processing of the arithmetic processing device 15b,
In addition to storing programs and the like, the arithmetic processing unit 1
The calculation results required in the calculation process of 5b are sequentially stored.

On the other hand, the motor drive circuit 19 has four MOs.
Two switching elements T1 to T4 such as SFETs are connected in series to form two sets of series circuits, and the steering assist motor 8 is connected between the switching elements T1 and T2 and between T3 and T4 of these series circuits. The input sides of the switching elements T1 and T3 are connected to each other, and the negative side is connected to the positive side of the grounded battery 22 via the motor relay 20 and the key switch 21.
The output sides of T2 and T4 are connected to each other and grounded via a current detector 16 composed of a current detection resistor, thereby forming a so-called H-bridge circuit.

The left-turning direction signal LD and right-turning direction signal RD output from the output side interface circuit 15d of the microcomputer 15 are supplied to the switching elements T1 and T3, respectively. A left-turn duty control current pulse LP and a right-turn duty control current pulse RP output from the side interface circuit 15d are supplied, respectively, and one end of a relay coil of the motor relay 20 is keyed via an NPN transistor 23 as a switching element. The energization control signal CS output from the output side interface circuit 15d of the microcomputer 15 is supplied to the transistor 23 while being connected to the switch 21 and the other end is grounded.
6 is connected to the input side interface circuit 15 a of the microcomputer 15.

Next, the operation of the above embodiment will be described with reference to FIGS. 3 and 4, which show a steering assist control processing procedure executed by the arithmetic processing unit 15b in the microcomputer 15.

The steering assist control process shown in FIG. 3 is executed as a main program. First, in step S0, an energization control signal CS for turning on a motor relay 20 for starting energization of the motor drive circuit 19 is set to an on state. The process proceeds to S1 to read the steering torque detection value T selected in the steering torque detection value selection process of FIG. 4 described later and stored in the steering torque detection value storage area of the storage device 15c, and then to step S2. After reading the vehicle speed detection value V of the vehicle speed sensor 14, the process proceeds to step S3.

In step S3, one of the control maps representing the relationship between the detected steering torque T and the motor target drive current i ^* is selected by using the vehicle speed shown in FIG. 5 as a parameter based on the read vehicle speed detected value V. After performing the control map selection process, the process proceeds to step S4.

In this step S4, the target drive current i ^* of the steering assist motor is calculated by referring to the control map selected in step S3 based on the detected steering torque value T selected in step S1, and then the step Move to S5
The actual current detection value i of the current detector 16 is read, and then the process proceeds to step S6 to calculate the duty ratio D by performing the calculation of the following equation (1).

D = K (i ^* −i) (1) where K is a control gain, and an allowable error range between the target drive current i ^* and the actual current detection value i, for example, about several A Is set to a value of about ten to several tens in anticipation of

Next, the routine proceeds to step S7, where it is determined whether or not the detected steering torque value T selected in step S1 is positive including zero. When T ≧ 0, it is determined that the vehicle is in a left-turn state. The process proceeds to step S8, in which the left-turn direction signal LD is turned on, the right-turn direction signal RD is turned off, and the left-turn duty control current pulse LP having the duty ratio D calculated in step S6. Is output and the right-turn duty control current pulse RP in the off state is output, and then the process proceeds to step S10a, where T
If <0, it is determined that the vehicle is in the right-turning state, and the process proceeds to step S9, where the right-turning direction signal RD is turned on.
In addition, the left turn direction signal LD is turned off, the right turn duty control current pulse RP having the duty ratio D calculated in step S6 is output, and the left turn duty control current pulse LP in the off state is output. Then, the process proceeds to step S10a.

In step S10a, it is determined whether or not to end the steering assist control processing. This determination is made based on whether or not the control end flag F has been set to “1” in the steering torque detection value selection processing of FIG. 4 described later. When the control end flag F has been reset to “0”, the control is performed. And returns to the step S1.
When the control end flag F is set to "1", it is determined that an abnormality has occurred in at least one of the steering torque sensors 13M and 13S, and the process proceeds to step S10b, where the energization control signal C for the motor drive circuit 19 is controlled.
After turning S off, the steering assist control process ends.

The arithmetic processing unit 15b executes the steering torque detection value selection processing of FIG. 4 for a predetermined time (for example, 10 msec.).
c) Execute as a timer interrupt process for each. In this steering torque detection value selection process, first, in step S11, the steering torque detection values TM and TS of the main and sub steering torque sensors 13M and 13S are read, and then in step S12
Then, it is determined whether the main steering torque detection value TM is within a normal range defined by a preset maximum value T _MAX and minimum value −T _MIN , and −T _MIN <TM <T _MAX
, It is determined that it is normal, and step S1
Move to 3.

[0035] In step S13, it is determined whether or not within the normal range sub steering torque detection value TS is defined similarly the maximum value T _MAX and the minimum value -T _MIN, -T _MIN
If <TS < _TMAX , it is determined that the operation is normal, and the process proceeds to step S14.

In step S14, it is determined whether or not the absolute value | TM-TS | of the difference between the main steering torque detection value TM and the sub steering torque detection value TS is equal to or less than a predetermined allowable value ΔT. , | TM-TS | ≦ ΔT, it is determined that both the main steering torque sensor 13M and the sub steering torque sensor 13S are normal, and the process proceeds to step S15.

In step S15, a timer value t for measuring the duration of the abnormal state, which will be described later, is cleared to "0", and the process proceeds to step S16, where the main and sub steering torque detection values TM and TS are set to one direction. It is determined whether or not they are in compliance. This determination is based on the detected steering torque values TM and TS.
Is determined by whether or not the sign of
If the directions match, it is determined that the state is normal, and the process proceeds to step S17.

In this step S17, it is determined whether or not the absolute value of the main steering torque detection value TM is equal to or smaller than the absolute value of the sub steering torque detection value TS. When | TM | ≦ | TS | Since the torque detection value TM is smaller than the sub steering torque detection value TS, the process proceeds to step S18, and the main steering torque detection value TM is updated and stored as the steering torque detection value T in the steering torque detection value storage area of the storage device 15c. From step S2 in FIG.
When | TM |> | TS |, the sub-steering torque detection value TS becomes a small value. Therefore, the process proceeds to step S19, where the sub-steering torque detection value TS is set as the steering torque detection value T and the steering torque detection value storage area is set. Then, the process proceeds to step S2 in FIG.

On the other hand, the result of the determination in step S16 is
Main steering torque detection value TM and sub steering torque detection value T
If the direction does not match S, it is determined that there is a possibility that an abnormality has occurred in any of the steering torque sensors, and the process proceeds to step S20, where "0" is set as the steering torque detection value T to the steering torque. After the updated value is stored in the detected value storage area, the process proceeds to step S2 in FIG.

The result of the determination in step S12 is TM
If ≦ −T _MIN or TM ≧ T _MAX , step S1
Third determination result, the determination result of and S14 when a TS ≦ -T _MIN or TS ≧ T _MAX is | TM-TS |
If> ΔT, it is determined that at least one of the main and sub steering torque sensors 13M and 13S has become an abnormal state, and the process proceeds to step S21, where the timer value t for measuring the duration of the abnormal state is set to “1”. Then, the process proceeds to step S22.

In this step S22, it is determined whether or not the timer value t has reached a preset time t _{S at} which the influence of noise set in advance can be reliably removed. If t <t _S , the possibility of noise is determined. It is determined that there is
6, when t ≧ t _S , it is determined that at least one of the main and sub steering torque sensors 13M and 13S is abnormal, the process proceeds to step S23, and the control end flag F is set to “1”. To end the process.

Therefore, assuming that the key switch 21 is off and the vehicle is in a stopped state, in this state, the power supply of the control unit 7 is cut off,
The motor relay 20 of the motor drive circuit 19 is also turned off, and the power supply to the electric motor 8 is cut off.

When the key switch 21 is turned on in this stopped state, the power of each part of the control unit 7 is turned on, and the microcomputer 15 starts processing. At this time, the arithmetic processing unit 15b starts execution of the steering assist control process of FIG. 3, and outputs an on-state energization control signal CS to the transistor 23 of the motor drive circuit 19 in step S0.

Therefore, the transistor 23 is turned on, the motor relay 20 is turned on, and the supply of the DC power from the battery 22 to the H-bridge circuit is started. At this time, when the steering wheel 1 is not being steered, the steering torque detection values TM and TS of the main and sub steering torque sensors 13M and 13S are substantially “0” as shown in FIG. It is assumed that the main steering torque detection value TM is “0” due to an error or the like, but the sub steering torque detection value TS is a small negative value.

In this state, when the steering torque detection value selection process of FIG. 4 is executed, it is determined in steps S12 to S14 that the main and sub steering torque detection values TM and TS are normal, and the process proceeds to step S15. After the timer value t representing the duration of the abnormal state is cleared to "0", the process proceeds to step S16, and since the main steering torque detection value TM is "0", the main and sub steering torque sensors 1
It is determined that the directions of the steering torques detected in 3M and 13S match, and the flow shifts to step S17. Since the absolute value of the main steering torque detection value TM is smaller, the flow shifts to step S18 to “0”. Is updated and stored in the steering torque detection value storage area as the steering torque detection value T.

For this reason, in the steering assist control processing of FIG.
In step S1, the steering torque detection value T stored in the steering torque detection value storage area is read, and then in step S2
Reads the vehicle speed detection value V. Since this time the vehicle is in a stopped state, a vehicle speed detecting value V is "0", the corresponding control map on the inner slope best characteristic line large characteristic line L ₁ shown in FIG. 5 is selected in step S3 Is the steering torque detection value T
Is “0”, the motor target drive current value i ^* calculated in step S4 is also “0”.

On the other hand, since the electric motor 8 is also stopped,
Since the actual current detection value i detected by the current detector 16 is also "0", the duty ratio D calculated in step S6 is also "0", and the left direction signal LD is turned on in step S8, and the right direction signal RD is turned off, the duty ratio control current pulse LP is maintained at the duty ratio "0", that is, the off state, and the right turn duty control current pulse RP is maintained in the off state.

Therefore, in the motor drive circuit 19, only the switching element T1 is turned on and the other switching elements T2 to T4 are turned off, so that no current flows through the H-type bridge circuit and the electric motor 8 The non-energized state is maintained, the steering assist torque generated by the electric motor 8 maintains "0", and the non-steering state is continued.

In this stopped state, when the so-called stationary steering for turning the steering wheel 1 to the left at time t ₁ is performed, the main and sub steering torque sensors 13 M and 13
The steering torque detection values TM and TS detected in S both increase in the negative direction while maintaining a predetermined error as shown in FIG.

At this time, the absolute value of the main steering torque detection value TM is always smaller than the absolute value of the sub steering torque detection value TS in the steering torque detection value selection processing of FIG. It is updated and stored in the steering torque detection value storage area as the torque detection value T.

Therefore, in the steering assist control processing of FIG.
The motor target drive current i ^* is calculated based on the selected steering torque detection value T, and the duty ratio D is calculated based on the difference between this and the actual current detection value i detected by the current detector 16.
Is calculated (step S6). Then, since the steering torque detection value T is negative, steps S7 to S8
And the left signal LD is turned on and the right signal R
D is turned off, the left-turn duty control current pulse LD is set to an on / off ratio corresponding to the calculated duty ratio D, and the right-turn duty control current pulse RD is maintained in the off state.

For this reason, the switching element T1 of the motor drive circuit 19 continues to be in the ON state, and in addition, the switching element T4 is turned on and off at the duty ratio D, so that the electric motor 8 is shown in FIG. As described above, the drive current i for turning left in accordance with the duty ratio D flows, and the electric motor 8 is driven to rotate to detect the steering torque detection value T.
By generating the left-turn steering assist torque according to the above, light steering can be performed.

[0053] Thereafter, upon completion of cut laid at time t _2, the main and sub steering torque detection value TM and TS returns to the initial state of substantially "0". From this state, when the vehicle is driven straight ahead and the steering wheel 1 is turned right at time t ₃ to make a steady circular turning state, the main and sub steering torque detection values TM and TS are correspondingly changed as shown in FIG. As shown in (1), both of them increase in the positive direction, then become a constant value, and a control map according to the vehicle speed is selected to control the drive current of the electric motor 8.

At this time, in the initial state of the right turn, the main steering torque detection value TM increases in the positive direction, and the sub steering torque detection value TS goes from a negative value to zero. In the steering torque detection value selection processing of No. 4, the process proceeds from step S16 to step S20, where the steering torque detection value T is set to "0", and this is updated and stored in the steering torque detection value storage area. Therefore, the motor drive current i also maintains the state of “0” as shown in FIG.

Thereafter, at time t ₄ , the main steering torque detection value TM continues to increase in the positive direction, and the sub steering torque detection value TS becomes “0”. In step S16, it is determined that they are in the same direction, and the process proceeds to step S17. At this time, since the sub steering torque detection value TS is smaller,
In step S19, the sub steering torque detection value TS of "0" is updated and stored in the steering torque detection value storage area as the steering torque detection value T. Therefore, the motor drive current i also maintains the state of “0” as shown in FIG.

Thereafter, as the sub-steering torque detection value TS increases in the positive direction, the motor target driving current i ^* is calculated based on the sub-steering torque detection value TS, and based on this and the actual driving current i. Since the steering torque detection value T is positive in step S7, the process proceeds to step S9, where the right direction signal RD is turned on, the left direction signal LD is turned off, and the right turn duty control is performed. By controlling the current pulse RP to an on / off ratio corresponding to the duty ratio D and turning off the left-turn duty control current pulse LP, the electric motor 8 is driven in reverse, for example, to generate a right-turn steering torque. By doing so, light steering can be performed.

[0057] In this right turn steady circular turning state, abnormality is generated in the time t _5, for example, the sub steering torque sensor 13S,
When the steering torque detection value TS instantaneously changes from a positive value to a relatively small value on the negative side, the main steering torque detection value TM and the sub steering torque detection value TS are determined in the steering torque detection value selection process of FIG. When the absolute value of the difference value exceeds the set value ΔT, it is determined in step S14 that the sensor is abnormal, and the process proceeds to step S21, where the timer value t representing the abnormal continuation time is incremented.

However, until the timer value t reaches the set value t _S set as the noise judgment period,
The process shifts from step S22 to step S16, and the same processing as in the normal state is performed.

However, the sub steering torque detection value TS
Is greater than "0" and becomes negative, step S16
Therefore, it is determined that the directions of the main steering torque detection value TM and the sub steering torque detection value TS do not match, so the process proceeds to step S20, and "0" is set to the steering torque detection value T. .

For this reason, the control is continued with the steering torque input to the steering wheel 1 being "0". During this time, when the abnormal state of the sub-steering torque sensor 13S is eliminated and the sub-steering torque sensor 13S returns to the normal state, the influence of the noise is exerted. Is returned to the normal control state as it is, but when the abnormal state of the sub steering torque sensor 13S is continued and the timer value t becomes equal to or more than the set value t _S , the process proceeds from step S22 to step S23. Then, after the control end flag F is set to "1", the timer interrupt processing ends.

For this reason, in the steering assist control processing of FIG. 3, since the control end flag F is set to "1" in step S10a, the process proceeds to step S10b.
The control is ended after the energization control signal CS is turned off.

When the energization control signal CS is turned off, the transistor 23 of the motor drive circuit 10 is turned off, and the motor relay 20 is turned off accordingly. Is interrupted, the energization to the electric motor 8 is stopped, and the generation of the steering assist torque by the electric motor 8 is stopped.

Conversely, when an abnormality occurs in the main steering torque sensor 13M and the detected steering torque TM becomes a negative value, the same operation as described above is performed, and the left-turn steering state is further reduced. The main or sub steering torque sensor 13
When an abnormality occurs in the M or 13S and the steering torque detection value TM or TS becomes a positive value, the directions of the main and sub steering torque detection values TM and TS are different. Processing is performed.

As described above, according to the above embodiment, when an abnormality occurs in one of the main and sub steering torque sensors 13M and 13S and changes to a sign different from the sign before the occurrence of the abnormality, the steering torque detection value By limiting T to "0", the control is continued as a state where the steering torque is not input, so that it is possible to reliably prevent the generation of the steering assist force in the direction opposite to the previous steering state. As a result, the sense of incongruity felt by the driver can be greatly reduced.

When the detected steering torque T is not restricted, the sub-steering torque sensor 13S becomes abnormal in the right-turn steady turning state as shown in FIG. When the absolute value of the TS is smaller than the detected value of the main steering torque TM in the negative direction, the absolute value of the detected value of the sub steering torque TS is smaller than the absolute value of the detected value of the main steering torque TM. By performing the steering assist control based on the value TS, a current in the reverse direction flows through the electric motor 8 as shown in FIG. 7B, which gives a great sense of discomfort to the driver.
This state continues for a predetermined time and continues until the steering assist control ends.

In the above embodiment, when the directions of the detected steering torques TM and TS of the main and sub steering torque sensors 13M and 13S are different, the detected steering torque T is limited to "0". Although the case has been described, the present invention is not limited to this, and the abnormal steering torque detection value TM or TS may be limited to a value close to “0” and not to generate the steering assist torque. Good.

In the above embodiment, the case where the control unit 7 is constituted by using the microcomputer 15 has been described. However, the present invention is not limited to this. For example, a function generator, a subtractor, a multiplier, a pulse width modulation circuit, etc. Can be configured by combining an electronic circuit. Furthermore, it is possible to omit forming the duty control current pulses LP and RP in the arithmetic processing unit 15b of the microcomputer 15 and provide an external pulse width modulation circuit. It may be.

Further, the motor drive circuit 19 is not limited to the above configuration, and any other switching element such as a transistor or a relay can be applied to the switching element forming the H-type bridge circuit.

Further, in the above embodiment, 2
The case where two steering torque sensors 13M and 13S are applied has been described, but the present invention is not limited to this.
Three or more steering torque sensors are applied, and a minimum value or a value close to the minimum value among them is selected as a steering torque detection value T for calculating a target drive current, and one or more of these are detected. The steering torque detection value T may be limited to "0" or a value in the vicinity thereof when the direction of the remaining sensors is reversed.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing a specific example of the control unit of FIG.

FIG. 3 is a flowchart illustrating an example of a steering assist control process of a microcomputer in a control unit.

FIG. 4 is a flowchart illustrating an example of a steering torque detection value selection process of a microcomputer in a control unit.

FIG. 5 is a characteristic diagram showing a control map representing a relationship between a detected steering torque value using a vehicle speed as a parameter and a motor target drive current.

FIG. 6 is a time chart for explaining the operation of the embodiment of the present invention.

FIG. 7 is a time chart for explaining the operation of the conventional example.

[Explanation of symbols]

 Reference Signs List 1 steering wheel 2 steering shaft 7 control unit 8 electric motor 13M main steering torque sensor 13S sub steering torque sensor 14 vehicle speed sensor 15 microcomputer 16 current detector 19 motor drive circuit

Claims (4)

[Claims] 1. A plurality of steering torque detecting means for detecting a steering torque applied to a steering system; an electric motor for applying a steering assist force to the steering system; and a steering torque detection value of the plurality of steering torque detecting means. And a control unit for controlling the electric motor based on the control signal, wherein the control unit selects a steering torque detection value having a small absolute value of the steering torque detection values of the plurality of steering torque detection units. A torque selection unit, and a steering torque detection value selected when the steering torque detection value selected by the torque selection unit and another steering torque detection value are in different directions within an allowable range that does not affect steering. A control device for an electric power steering, comprising: a torque detection value limiting means for limiting the torque to a value. 2. A plurality of steering torque detecting means for detecting a steering torque applied to a steering system, an electric motor for applying a steering assist force to the steering system, and a steering torque detection value of the plurality of steering torque detecting means. Control means for controlling the electric motor based on the control of the electric power steering, the control means, when the abnormal state of the plurality of steering torque detection means continued for a predetermined time, the abnormality of the steering torque detection means Abnormality detection means for detecting, and torque selection means for selecting a steering torque detection value having a small absolute value of the steering torque detection values of the plurality of steering torque detection means when no abnormality is detected by the abnormality detection means; The steering torque detection value selected when the steering torque detection value selected by the torque selection means and the other steering torque detection values are in different directions affects the steering. And a torque detection value limiter that limits the torque to a value within an allowable range that does not provide the control. 3. The steering torque detecting device according to claim 1, wherein when the steering torque detecting device includes two sets of steering torque detecting devices, the state where the absolute value of the difference between the two is equal to or greater than a set value continues for a predetermined time. The electric power steering control device according to claim 2, wherein the control device is configured to determine that: 4. The apparatus according to claim 1, wherein the torque detection value control means limits the selected steering torque detection value to zero as a value within an allowable range that does not affect steering. A control device for an electric power steering device according to any one of claims 1 to 3.