JPH10230859A - Abnormality detection controller of electric power steering system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abnormality detection controller for directly comparing steering torque and assist torque with the mechanical displacement amount and in which a failure detecting mechanism and an assist prohibiting mechanism are integrated with each other. SOLUTION: An electric power steering system is provided with a first detecting means 20 for detecting steering torque, a second detecting means 30 connected to an assist motor 10 in series and to be displaced according to the electric current, a vehicle speed switch 32 for detecting the vehicle speed, to be turned when the speed is low and to be turned off when the speed is high to release a resistor 31, and a comparing means 40 composed of an electrode to be displaced according to the detected signal of the first detecting means 20 and a brush to be in the electrification sate in the normal time in relation to the electrode and to be displaced according to the displacement amount of the second detecting means 30, and to be switched to the shutdown state when the relationship between steering torque and additional torque exceeds the specified range, and for making the additional torque zero.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abnormality detection control device for an electric power steering system which improves the operability by adding an assist torque to a steering torque when a steering wheel is operated.

[0002]

2. Description of the Related Art In a conventional electric power steering system, as disclosed in, for example, Japanese Patent Application Laid-Open No. 64-56274 or Japanese Patent Application Laid-Open No. 2-293260, an electric power steering system uses steering signals and assist torques as electric signals. And convert them into electric control units (hereinafter referred to as ECUs).
Is controlled by The ECU is provided with a failure detection mechanism and an assist prohibition mechanism together with these control circuits. That is, when the relationship between the steering torque and the assist torque exceeds the permissible range, the two are compared by software to detect a failure, and further, the assist inhibition control is performed based on this detection signal.

[0003]

However, in the above-described ECU of the conventional electric power steering system, a control circuit for calculating an assist torque from a steering torque, a failure detection mechanism and an assist prohibition mechanism which are electrically configured. Is provided, hardware and software for configuring these are required, and there is a problem that the system becomes complicated and the cost increases.

In order to operate the vehicle safely, it is conceivable that the assist torque at a high speed is set smaller than the assist torque at a low speed. In this manner, two types of assist torques are set according to the vehicle speed. There is a demand for the development of a failure detection mechanism and an assist prohibition mechanism when applied.

The present invention has been made in view of the above circumstances, and an object of the present invention is to directly compare a steering torque and an assist torque as a mechanical displacement to integrate a failure detection mechanism and an assist prohibition mechanism. Another object of the present invention is to provide an abnormality detection control device for an electric power steering system that can be applied even at high speeds and low speeds.

[0006]

In order to solve this problem, the means adopted by the invention of claim 1 is described with reference numerals used in the embodiment, and the steering torque of the steering wheel 1 is detected. At a low speed, the torque of the assist motor 10 is added in a predetermined relationship according to the detection signal,
Assist motor 1 at higher speeds at a lower rate than at lower speeds
In an electric power steering system for applying a torque of 0, a first detecting means 20 for detecting the steering torque, a second detecting means 30 connected in series with the assist motor 10 and displaced according to a current, When the vehicle speed is detected, the resistor 31 is turned on at a low speed and the resistor 31 is connected in parallel with the second detecting means 30.
A vehicle speed switch 32 for releasing 1 from the second detection means;
An electrode 42 which is displaced in accordance with a detection signal of the first detecting means 20 and a brush 43 which is in a state of being energized when the electrode 42 is normal and is displaced in accordance with the amount of displacement of the second detecting means 30. When the relationship between the steering torque and the additional torque exceeds a predetermined range, there is provided a comparing means 40 which switches to a cut-off state and makes the additional torque zero.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIGS. First, an electric power steering system will be described with reference to FIG. When the steering wheel 1 is operated, the steering torque is transmitted to the input shaft 3 of the gear case 2 and drives the rack 5 via the pinion at the lower end of the output shaft 4. This rack 5
Changes the direction of the wheels 7 via the steering link 6.

On the other hand, a torque sensor 8 attached to the gear case 2 detects a steering torque, and an electric signal thereof is input to an electric control device (hereinafter referred to as an ECU) 9. Then, based on a signal from the ECU 9, the assist motor 10
Is driven. The assist motor 10 has a motor shaft 1
0a and the gear 1 meshing with the pinion 11
The rack 5 is driven via 2. Since the rack 5 is driven by the assist motor 10 together with the output shaft 4 of the steering wheel 1, the operability is significantly improved.

Next, as a first detecting means for detecting the steering torque, a first detecting device 20 of a torsion bar system is used.
Will be described with reference to FIGS. Input shaft 3
The output shaft 4 is rotatably attached to the gear case 2. The upper end of the torsion bar 21 is integrated with the input shaft 3 by the pin 22, and the lower end is integrally press-fitted into the hole 4 a of the output shaft 4. Therefore, the torque input to the input shaft 3 is transmitted to the output shaft 4 via the torsion bar 21.

On the other hand, a sleeve 23 is fitted outside the input shaft 3. The sleeve 23 has a long groove 24 parallel to the axial direction and an inclined groove 25. Then, a pin 26 fixed to the output shaft 4 is inserted into the long groove 24,
A pin 27 fixed to the input shaft 3 is inserted into the inclined groove 25. That is, the sleeve 23 moves in the axial direction with respect to the output shaft 4, but does not rotate in the circumferential direction.

Here, the steering torque is changed from the input shaft 3 to the output shaft 4.
When the torque is transmitted to the torsion bar 21, a torsion angle is generated in the torsion bar 21, and a circumferential displacement occurs between the input shaft 3 and the output shaft 4. Therefore, the pin 27 fixed to the input shaft 3 moves in the inclined groove 25, and the sleeve 23 moves up in the axial direction by a predetermined dimension, for example, the dimension H. First detection device 20
Is for extracting the dimension H as a detection amount, and a groove 28 is formed on the outer peripheral surface of the sleeve 23.

As a second detecting means, a proportional solenoid 30 connected in series to the assist motor 10 is used. The proportional solenoid 30 includes a solenoid through which a circuit current of the assist motor 10 flows, and a plunger that moves inside the solenoid.
Since the torque of the assist motor 10 increases and decreases according to the current, the proportional solenoid 30 that is displaced according to the current is displaced according to the torque of the assist motor 10.

In this plunger, the moving distance increases when the current of the solenoid increases, and the moving distance decreases when the current of the solenoid decreases. That is, the assist motor 10
When the assist torque increases and the current increases, the moving distance of the plunger also increases. When the assist torque decreases and the current decreases, the moving distance of the plunger also decreases.

A series circuit of a resistor 31 and a vehicle speed switch 32 is connected to both ends of the proportional solenoid 30. The vehicle speed switch 32 is operated by a vehicle speed detecting means, and is turned on at a low speed, so that the resistance 31 is connected in parallel with the proportional solenoid 30. Further, at high speed, the resistor 31 is turned off, and the resistor 31 is released from the circuit of the assist motor 10.

The second detecting means is not limited to the proportional solenoid, but may be a motor that operates in association with the circuit current of the assist motor 10. The essential point is that the assist torque of the assist motor 10 can be converted into mechanical displacement. There is no particular limitation as long as it is a means.

Next, the I / O switch 40 in which the comparison means 40 is mechanically constructed will be described with reference to FIGS.
This will be described with reference to FIG. As shown in FIG. 8, the I / O switch 40 includes an electrode 42 attached to a central portion of an insulating substrate 41.
And a brush 43 that slides on the surface of the electrode 42. The electrode 42 has a lever 44 fitted into the groove 28 of the sleeve 23 of the first detection device 20 as shown in FIG.
The sleeve 23 is moved according to the displacement amount. This movement may be slid linearly, or may be rotated in the circumferential direction. The brush 43 includes the proportional solenoid 30
The plunger is connected and moved.

The relationship between the steering torque and the assist torque is as follows:
At a low speed, control is performed according to a predetermined relationship described later, and at a high speed, control is performed at a smaller ratio than at a low speed. FIG. 5 shows the relationship between the amount of movement of the electrode 42 according to the steering torque and the amount of movement of the brush 43 that moves according to the assist torque at a low speed, with a predetermined relationship along the control line 45. Controlled. At this time, in FIG. 5, the operation is performed in a normal state between the predetermined ranges 46, 46 which are the allowable control ranges, and the hatched portion exceeding the ranges 46, 46 becomes the abnormal range (fail area). It shows. These ranges 46, 46 can be appropriately changed by changing the width of the electrode 42.

On the other hand, at the time of high speed, control is performed along a control line 47 shown in FIG. That is, for the same steering torque, the assist torque at high speed is reduced to 1 / N of the assist torque at low speed. In order to control these two types of assist torque with the same I / O switch 40, in the present embodiment, the electric current of the assist motor 10 is directly supplied to the proportional solenoid 30 at the time of high speed, and the assist current is supplied at the time of low speed. The current of the motor 10 is diverted to the resistor 31, and the current of the proportional solenoid 30 is reduced to 1 / N of the current of the assist motor 10 to correspond to the ratio of the assist torque.

Here, the basic operation of the comparing means 40 will be described. Since the relationship between the electrode 42 and the brush 43 is the same at low speeds and at high speeds, the description will be made with reference to the low speeds shown in FIG.

First, in FIG. 5, FIG. 7, and FIG. 8, 1, when neither the steering torque nor the assist torque is applied (STEP 10 in FIG. 7), it corresponds to the point O (permissible control range) in FIG. As shown in FIG.
The brush 43 is in contact with the center of 2. The reference positions of the electrode 42 and the brush 43 are indicated as A1 and A2, respectively.

Next, various cases where the assist torque is varied will be described by taking as an example a case where the steering torque acts rightward and the electrode 42 moves the dimension H1 rightward. 2. When the steering torque and the assist torque are in a normal relationship (STEP 11, FIG. 9) Since the brush 43 moves by the dimension L1, A shown in FIG.
The brush 43 corresponds to the electrode 42
, And the power supply maintains the energized state. The brush 43
Are within the predetermined ranges 46, 46 so that the dimensions La to Lb
(Corresponding to the width dimension of the electrode 42) also keeps the power supply energized.

3. If the assist torque is larger than the steering torque (STEP 12, FIG. 10) The brush 43 moves by the dimension L2 and is located at the point B (fail area) shown in FIG. The brush 43 passes over the electrode 42 and moves onto the insulating substrate 41, the power supply is turned off, and a failure is detected.

4. If the assist torque is smaller than the steering torque (STEP 12, FIG. 11) The brush 43 moves by the dimension L3 and is located at the point C (fail area) shown in FIG. Since the relative movement distance of the electrode 42 with respect to the brush 43 is large, the brush 43 moves on the insulating substrate 41 and the power supply is turned off.

5. When the assist torque acts in the opposite direction (STEP 13, FIG. 12) The brush 43 moves by the dimension L4 in the opposite direction and is located at the point D (fail area) shown in FIG. The brush 43 moves onto the insulating substrate 41, and the power is turned off.

Next, the control circuit and the fail-safe function will be described with reference to FIGS. When the ignition switch 52 is turned on, the contact point 51 of the engine starter interlock relay is turned on, and the DC power supply 5
3 is connected to the circuit. A relay coil 54 is connected in series to the engine starter contact 51, and even when the ignition switch 52 is turned off, the contact 55 and the contact 56 are held by themselves.

The contact 55 is connected to the I / O switch 40 and the relay coil 54 in series. Also, the contact 33
And a circuit of the assist motor 10 and the proportional solenoid 30 is formed via the control unit. A resistance 31 and a vehicle speed switch 32 are connected in parallel to the proportional solenoid 30. Note that a capacitor 57 is connected to the relay 54 in parallel.

When the vehicle starts, in FIG.
The vehicle speed detecting means detects that the vehicle speed is low (STEP 2).
0), the vehicle speed switch 32 is turned on (STEP 2).
1) The current of the assist motor 10 is controlled by the proportional solenoid 3
The current is divided into 0 and the resistor 31.

When the steering wheel 1 is operated, the first detecting device 20 detects the steering torque and the electrode 42 is displaced. In addition, the plunger of the proportional solenoid 30 moves according to the electric current of the assist motor 10 and the proportional solenoid 30 to displace the brush 43. Then, I / O
If the relationship is within the normal range as compared with the O switch 40 (STEP 22), the I / O switch 40 maintains the energized state (STEP 26), and power assist is continued.

When the relationship falls within the abnormal range, the I / O switch 40 is turned off as described above. Then, since the relay 54 is turned off (STEP 23), the contacts 55 and 33 are also turned off at the same time. Accordingly, the assist motor 10 is turned off (STEP 24), and the assist torque becomes zero. That is, when an abnormality is detected, the fail-safe function is activated to switch to manual steering (STEP 25).

Next, when the vehicle speed increases and the vehicle enters a high speed state, the assist torque changes as indicated by a control line 47 in FIG. On the other hand, the vehicle speed switch 32 is turned off by the vehicle speed detecting means, and the current of the assist motor 10 flows through the proportional solenoid 30 (STEP 21). In this case, the amount of displacement of the proportional solenoid 30 is set to be N times the amount of displacement at low speed when the proportional solenoid 30 and the resistor 31 are connected in parallel. Therefore, the assist motor 1
I / O even if the assist torque is reduced to 0/1 / N at low speed
The same control can be performed by the switch 40. Then, the electrode 42 and the brush 43 perform the same relative movement as described above to perform fail-safe.

In the above embodiment, the brush 4 at high speed
Since the movement amount of the control line 3 is larger than the movement amount of the brush 43 at the time of low speed, the width of the control limit of the control lines 48, 48 is managed to be smaller than the control limit of the control lines 46, 46. You. In the above embodiment, the same electrode 42 is used at the time of low speed and at the time of high speed. However, if the energization range of the electrode 42 is appropriately switched, control can be performed at the high speed at the same control limit as at the time of low speed.

In this embodiment, even if the I / O switch 40 is momentarily cut off due to a sudden steering wheel, vibration, or the like, the contact 5 has a duration corresponding to the capacity of the capacitor 57.
Since the contacts 5 and the contacts 56 are held by themselves, the occurrence of erroneous failures can be prevented accordingly.

According to the above-described embodiment, the following effects can be obtained. (1) The vehicle speed switch 32 is operated by the vehicle speed detecting means, and the resistance 31 is connected in parallel with the proportional solenoid 30 in accordance with the vehicle speed.
Is connected or opened, so that appropriate power steering control can be performed even during high-speed running. (2) Since the I / O switch 40 is composed of the electrode 42 and the brush 43 which move relatively to each other, and the failure detection mechanism and the assist prohibition mechanism are integrated, the structure can be simplified and the cost can be reduced. In addition, reliability can be improved. (3) Since the fail-safe function is controlled by the I / O switch 40 and provided separately for the ECU 9, even if a failure occurs in the ECU 9, fail-safe is possible.

(4) Since the I / O switch 40 directly compares the mechanical displacement between the electrode 42 and the brush 43, the fail-safe adjustment range can be changed by changing the size of the electrode. (5) Since the electrode 44c of the high-speed comparison unit 42 is set to be larger than the electrode 42 of the low-speed comparison unit 41 in accordance with the amount of displacement of the brush 45b, the fail-safe adjustment range at low speed and high speed is within the same management limit. Can manage. (6) Since the proportional solenoid 30 is used as the second detection means, the number of components in the gear case 12 is reduced,
Cost reduction can be achieved, and the assist motor 10
Can be freely selected.

[0035]

As described above in detail, according to the present invention, in an electric power steering system in which an assist torque is added at a different ratio to a steering torque according to a vehicle speed, in accordance with a current in series with the assist motor, The second detection means which is displaced by the motor is provided, and the resistors are connected in parallel according to the vehicle speed. Therefore, the optimum power steering control can be performed even at a low speed and at a high speed by one kind of comparison means. It has excellent effects. In addition, the failure detection mechanism and the assist prohibition mechanism can be integrated, and the failure is detected by directly comparing the steering torque and the assist torque as a mechanical displacement. Prohibition control is being performed. For this reason, it is possible to improve the reliability and reduce the cost with a simple configuration, and to simplify the electric control unit.

[0036]

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a system according to an embodiment of the present invention.

FIG. 2 is a vertical sectional front view of a main part.

FIG. 3 is a vertical sectional front view of the first detection device.

FIG. 4 is a front view of a sleeve of the first detection device.

FIG. 5 is a graph showing an assist characteristic and a fail area at a low speed.

FIG. 6 is a graph showing an assist characteristic and a fail area at a high speed.

FIG. 7 is a flowchart illustrating a control mode of a comparing unit.

FIG. 8 is a diagram showing a first state of the mechanical displacement of the comparison means.

FIG. 9 is a diagram showing a second state of the mechanical displacement of the comparison means.

FIG. 10 is a diagram showing a third state of the mechanical displacement of the comparison means.

FIG. 11 is a diagram showing a fourth state of the mechanical displacement of the comparison means.

FIG. 12 is a diagram showing a fifth state of the mechanical displacement of the comparison means.

FIG. 13 is a control circuit diagram of the present invention.

FIG. 14 is a flowchart showing control.

[Explanation of symbols]

 Reference Signs List 1 steering wheel 9 electric control device (ECU) 10 assist motor 20 first detection device (first detection device) 30 proportional solenoid (second detection device) 31 resistance 32 vehicle speed switch 40 I / O switch (comparison device) 42 electrode 43 brush

Claims (1)

[Claims] A steering torque of a steering wheel is detected, and an assist motor torque is added in a predetermined relationship at a low speed in response to the detection signal, and the torque of the assist motor is reduced at a high speed at a lower rate than at a low speed. An electric power steering system, wherein: first detecting means for detecting the steering torque; second detecting means connected in series with the assist motor and displaced in accordance with a current; A vehicle speed switch that turns on at some times and connects the resistance in parallel with the second detection means, and turns off at high speed to release the resistance from the second detection means, and is displaced in response to a detection signal of the first detection means An electrode and a brush which is normally energized with respect to the electrode and is displaced in accordance with the displacement amount of the second detecting means; Abnormality detection control device for an electric power steering system, wherein a relationship between the additional torque is a comparison means for zero switched the additional torque to the deenergized state when exceeding the predetermined range.