JP3785585B2 - Anomaly detection control device for electric power steering system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an abnormality detection control device for an electric power steering system that improves the operability by adding an assist torque to the steering torque when the steering wheel is operated.
[0002]
[Prior art]
In the conventional electric power steering system, for example, as disclosed in Japanese Patent Application Laid-Open No. 64-56274 or Japanese Patent Application Laid-Open No. 2-293260, the steering torque and the assist torque are converted into electric signals. Is controlled by an electric control unit (hereinafter referred to as ECU).
In addition to these control circuits, the ECU is provided with a failure detection mechanism and an assist prohibition mechanism. That is, when the relationship between the steering torque and the assist torque exceeds the allowable range, they are compared with each other in software to detect a failure, and further, assist prohibition control is performed based on this detection signal.
[0003]
[Problems to be solved by the invention]
However, in the ECU of the conventional electric power steering system described above, a failure detection mechanism and an assist prohibition mechanism that are electrically configured are provided together with a control circuit that calculates the assist torque from the steering torque. Hardware and software to configure are necessary, and there is a problem that the system becomes complicated and expensive.
[0004]
In order to operate the vehicle safely, the assist torque at high speed may be set to be smaller than the assist torque at low speed, and thus two types of assist torque were applied depending on the vehicle speed. There is a need to develop a failure detection mechanism and an assist prohibition mechanism.
[0005]
In addition, when the steering torque increases due to contact with the curbstone or the like, it is effective to add the assist torque in a wide range, and it is desired to expand the range of the power steering control allowable range.
[0006]
The present invention has been made in view of the above circumstances, and its purpose is to directly compare the steering torque and the assist torque as the mechanical displacement amount, to integrate the failure detection mechanism and the assist prohibition mechanism, and to control the allowable range of control. An object of the present invention is to provide an abnormality detection control device for an electric power steering system that can be applied at high speed and low speed with different assist torque while expanding the range.
[0007]
[Means for Solving the Problems]
Means taken by the invention of claim 1 to solve this problem will be described with reference numerals used in the embodiments.
The steering torque of the steering wheel 1 is detected, and the torque of the assist motor 10 is added in a predetermined relationship at low speeds according to the detection signal, and the torque of the assist motor 10 is added at a lower ratio at high speeds than at low speeds. In the electric power steering system
First detection means 20 for detecting the steering torque;
Second detection means 31 connected in series with the assist motor 10 and displaced in accordance with the current;
A low-speed comparison unit 41 and a high-speed comparison unit 42 are provided. When the relationship between the steering torque and the additional torque exceeds a predetermined range, the power-off state is switched and the additional torque is reduced to zero. Means 40;
When the vehicle speed is detected and the vehicle speed is low, a resistor 32 is connected in parallel with the second detector 31 to select the low-speed comparator 41, and when the vehicle is high, the resistor 32 is released from the second detector 31 and the high-speed With vehicle speed detection means 33 and 34 for selecting the comparison unit 42,
The low speed comparison unit 41 is
The first and second electrodes 52 and 53 that are displaced according to the detection signal of the first detection means 20, and the normal detection state of the second detection means 30 when these electrodes are in an energized state at normal times. A low-speed brush 54 that is displaced according to a detection signal and a first stopper 55 that prevents displacement of only the first electrode 52 when the first and second electrodes 52 and 53 are displaced by a predetermined distance in one direction. And a second stopper 56 for preventing the displacement of only the second electrode 53 when the first and second electrodes 52, 53 are displaced by a predetermined distance in the other direction,
The high-speed comparison unit 42
The third and fourth electrodes 59, 60 that are displaced according to the detection signal of the first detection means 20, and the second detection means 30 at high speed when these electrodes are normally energized. The high-speed brush 61 that is displaced according to the detection signal and the third stopper that prevents the displacement of only the third electrode 59 when the third and fourth electrodes 59, 60 are displaced by a predetermined distance in one direction. 62 and a fourth stopper 63 for preventing the displacement of only the fourth electrode 60 when the third and fourth electrodes 59, 60 are displaced by a predetermined distance in the other direction.
[0008]
In the invention of claim 2, the displacement of the high speed brush 61 in the high speed comparison section 42 is increased in inverse proportion to the ratio of the assist torque with respect to the displacement of the low speed brush 54 in the low speed comparison section 41. However, it has characteristics.
[0009]
According to a third aspect of the present invention, the energization range of the third and fourth electrodes 59 and 60 in the high-speed comparison unit 42 is larger than the energization range of the first and second electrodes 52 and 53 in the low-speed comparison unit 41. It is characterized in that it is enlarged in inverse proportion to the ratio of the assist torque.
[0010]
According to a fourth aspect of the present invention, the position at which the first, second electrodes 52, 53 and the third and fourth electrodes 59, 60 are in contact with the brushes 54, 61 is the stopper side where each electrode abuts at the neutral position. It is characterized by being wide and narrow on the opposite side.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
First, an electric power steering system will be described with reference to FIGS.
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 a pinion at the lower end of the output shaft 4. The rack 5 changes the direction of the wheels 7 via the steering link 6.
[0012]
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 ECU) 9. Then, the assist motor 10 is driven based on a signal from the ECU 9. A worm gear 81 is coupled to the motor shaft 10 a of the assist motor 10, and assist torque is transmitted to the rack 5 through a worm wheel 82 meshing with the worm wheel 82 and a pinion (not shown) integrated with the worm wheel 82. Since the rack 5 is driven by the output shaft 14 of the assist motor 10 together with the output shaft 4 of the steering wheel 1, the operability is remarkably improved.
[0013]
Next, a first detection device 20 of a torsion bar type will be described with reference to FIGS. 14 to 16 as first detection means for detecting steering torque.
The input shaft 3 and the output shaft 4 are each rotatably attached to the gear case 2. The torsion bar 21 has an upper end integrated with the input shaft 3 by a pin 22 and a lower end press-fitted into the hole 4 a of the output shaft 4 integrally. Therefore, the torque input to the input shaft 3 is transmitted to the output shaft 4 via the torsion bar 21.
[0014]
On the other hand, a sleeve 23 is fitted to the outside of the input shaft 3. The sleeve 23 is formed with a long groove 24 parallel to the axial direction and an inclined groove 25. A pin 26 fixed to the output shaft 4 is inserted into the long groove 24, and 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.
[0015]
Here, when the steering torque is transmitted from the input shaft 3 to the output shaft 4, a torsion angle is generated in the torsion bar 21, and a circumferential shift occurs between the input shaft 3 and the output shaft 4. Accordingly, the pin 27 fixed to the input shaft 3 moves in the inclined groove 25, and the sleeve 23 rises by a predetermined amount, for example, a dimension H in the axial direction. The first detection device 20 takes out the dimension H as a detection amount, and a groove 28 is formed on the outer peripheral surface of the sleeve 23.
[0016]
On the other hand, a proportional solenoid 31 connected in series to the assist motor 10 is used as the second detection means. The proportional solenoid 31 includes a solenoid through which the circuit current of the assist motor 10 flows and a plunger that moves inside the solenoid.
[0017]
This plunger has a large moving distance when the solenoid current is large, and the moving distance is small even though the solenoid current is small. That is, when the assist torque of the assist motor 10 is large and the current is large, the plunger travel distance is large, and when the assist torque is small and the current is small, the plunger travel distance is also small.
[0018]
Further, a resistor 32 functioning as a low speed comparison unit and a vehicle speed switch 33 as vehicle speed detecting means are connected in parallel with the proportional solenoid 31. The vehicle speed detecting means is composed of a vehicle speed switch 33 and a selection switch 34. The selection switch 34 is switched in conjunction with the vehicle speed switch 33, and either a low speed comparison unit 41 or a high speed comparison unit 42 described later is used. select. A contact 35 is connected between the proportional solenoid 31 and the ECU 9.
[0019]
At high speed, the current of the proportional solenoid 31 is the same as that of the motor 10, and at low speed, a part of the current is shunted to the resistor 32. The displacement amount of the plunger at high speed is set to N times that at low speed.
[0020]
The second detection means is not limited to a proportional solenoid, but may be a motor that operates in association with the circuit current of the assist motor 10. In short, any means that can convert the assist torque of the assist motor 10 into mechanical displacement. If it does not specifically limit.
[0021]
Next, the I / O switch 40 in which the comparison means 40 is mechanically configured will be described with reference to FIGS.
The comparison means 40 is composed of a low speed comparison unit 41 and a high speed comparison unit 42. In these, the vehicle speed switch 33 and the selection switch 34 are switched by a signal from the vehicle speed detection means for detecting the vehicle speed, and either the low speed comparison unit 41 or the high speed comparison unit 42 is selected.
[0022]
Then, assist torque as shown by the control line 44 in FIG. 7 is added to the steering torque at low speed, and assist torque as shown by the control line 45 is added at high speed. The assist torque at high speed is 1 / N of the assist torque at low speed.
[0023]
As shown in FIG. 1, the low-speed comparison unit 41 includes a first electrode 52 attached to the central portion of the insulating substrate 51, a second electrode 53 disposed opposite to the first electrode 52, and these It is composed of a low speed brush 54 and first and second stoppers 55 and 56 that slide on the surfaces of the first and second electrodes 52 and 53.
The lever 57 of the low speed comparison unit 41 is fitted in the groove 28 of the sleeve 23 of the first detection device 20 shown in FIGS. 15 and 16, and the first and second electrodes 52, 53 are displaced by the sleeve 23. A predetermined amount, for example, dimension H is moved in the axial direction according to the amount.
This movement may be linearly slid or may be rotated in the circumferential direction.
[0024]
The first stopper 55 abuts against the insulating substrate 51 to prevent the displacement of the first electrode 52 when the first and second electrodes 52 and 53 move in the direction of arrow A, which is one direction shown in FIG. To do. The second stopper 56 is in contact with the insulating substrate 51 when the first and second electrodes 52 and 53 move in the direction of arrow B, which is the other direction shown in FIG. To prevent.
A spring 58 is interposed between the first and second electrodes 52 and 53 and the lever 57.
[0025]
In the neutral position, the position where the first electrode 52 and the low speed brush 54 are in contact is set such that the first stopper 55 side 52a is wide and the opposite side 52b is narrow. The position where 54 contacts is set such that the second stopper 56 side 53a is wide and the opposite side 53b is narrow.
[0026]
The high-speed comparison unit 42 includes a third electrode 59 attached to the central portion of the insulating substrate 51, a fourth electrode 60 disposed to face the third electrode 59, and the third and fourth electrodes. The high-speed brush 61 and the third and fourth stoppers 62 and 63 sliding on the surfaces of 59 and 60 are configured. These third and fourth electrodes 59 and 60 are displaced by a lever 57 in the same manner as the first and second electrodes 52 and 53.
[0027]
The third stopper 62 abuts against the insulating substrate 51 to prevent displacement of the third electrode 59 when the third and fourth electrodes 59, 60 move in the direction of arrow A, which is one direction shown in FIG. To do. The fourth stopper 63 abuts against the insulating substrate 51 when the third and fourth electrodes 59 and 60 move in the direction of arrow B, which is the other direction shown in FIG. To prevent.
[0028]
In the neutral position, the position where the third electrode 59 contacts the high speed brush 61 is set so that the third stopper 62 side is wide and the opposite side is narrow, and the fourth electrode 60 contacts the high speed brush 61. Is set such that the fourth stopper 63 side is wide and the opposite side is narrow.
The width dimension (energization range) of the third and fourth electrodes 59 and 60 is set to N times the width dimension of the first and second electrodes 52 and 53.
[0029]
The low speed brush 54 and the high speed brush 61 are moved via the push-pull wire 64 according to the amount of displacement of the proportional solenoid 31.
Although the assist torque at high speed is reduced to 1 / N at low speed, the movement distance of the plunger at high speed is set to N times at low speed, so the third and fourth electrodes 59, The relative position between the high speed brush 61 and the high speed brush 61 is maintained in the same manner as at low speed.
[0030]
Here, during low-speed traveling, the detection amount of the first detection device 20 (the movement amount of the electrodes 52 and 53) by the steering torque and the detection amount of the second detection device 30 by the assist torque (the movement amount of the low-speed brush 54). ) Is controlled along the control line 44 shown in FIG. At this time, as will be described later in FIG. 8, the control permissible range surrounded by pqrstp′q′r′s′t ′ is such that the first electrode 52 and the second electrode 53 are the low-speed brush 54 when normal. The low-speed brush 54 is connected to the first and second electrodes 52 and 53 in the hatched portion exceeding the control allowable range. This indicates that the power line is deviated and switched to a power-off state, resulting in an abnormal range (fail area).
[0031]
Further, the detection amount of the first detection device 20 (the amount of movement of the third and fourth electrodes 59 and 60) by the steering torque during high-speed traveling and the detection amount of the second detection device 30 by the assist torque (the high-speed brush) 61 is controlled along the control line 45 shown in FIG. Even in this case, the control allowable range surrounded by pqrstp′q′r′s′t ′ is that the third electrode 59 and the fourth electrode 60 are in contact with each other via the high-speed brush 61 and the power supply line is energized. In the shaded area exceeding the control allowable range, the high-speed brush 61 deviates from the third and fourth electrodes 59 and 60 and the power line is switched to the disconnection state. In other words, it indicates an abnormal range (fail area).
[0032]
Here, the basic operation of the comparison means 40 will be described. Since both the low-speed comparison unit 41 and the high-speed comparison unit 42 are the same, the case of the low-speed comparison unit 41 will be described with reference to FIGS. Note that, when the first and second electrodes 52 and 53 move in the direction of the arrow A and in the direction of the arrow B, the operation is the same, so the case where they move in the direction of the arrow A will be described as an example. To do.
At a low speed when the vehicle is started, the vehicle speed switch 33 is turned on, and the resistor 32 is connected to the proportional solenoid 30 in parallel. The selection switch 34 selects the low speed comparison unit 41 .
[0033]
1, the case where neither the steering torque nor the assist torque is applied (STEP 10 in FIG. 10) corresponds to the point O (control allowable range) in FIG. 8, and as shown in FIG. , 53 is in contact with the low-speed brush 54, and the power supply is energized.
[0034]
2. When steering torque and assist torque are in a normal relationship (moves along control line 44) (STEP 11)
The first and second electrodes 52 and 53 and the low speed brush 54 move while maintaining the relationship shown in FIG. When the insulating substrate 51 comes into contact with the first stopper 55 (point H in FIG. 8, FIG. 2), the movement of the first electrode 52 stops. The second electrode 53 and the low speed brush 54 continue to move while maintaining a predetermined relationship, and the energized state is maintained.
[0035]
When the low-speed brush 54 further moves and exceeds a distance corresponding to the width of the electrode 52a as shown in FIG. 3 (point J shown in FIG. 8, STEP 12), the power supply is switched to a power-off state.
By the way, the width dimension H1 of the control permissible range at the point H increases or decreases corresponding to the width dimension 53a of the second electrode 53, and the width dimension H2 of the control permissible range corresponds to the width dimension 53a of the second electrode 53. Can be changed.
[0036]
3. When the assist torque is too larger than the steering torque (STEP 13, FIG. 4)
Since the low speed brush 54 advances faster than the second electrode 53, when the point K shown in FIG. 8 (fail area) is reached, the low speed brush 54 passes through the second electrode 53 and is on the insulating substrate 51. Moves and the power supply is cut off, and a failure is detected.
[0037]
4. When the assist torque is too small than the steering torque (STEP 13, FIG. 5 and FIG. 6)
If the low speed brush 54 is in contact with the first electrode 52 when the first electrode 52 (insulating substrate 51) is in contact with the first stopper 55, the first electrode 52 is stopped. The brush 54 is continuously energized while moving a distance corresponding to the width of the electrode 52a (points L1 and L2 in FIG. 8 and FIG. 5). When the voltage exceeds, the power supply switches to the power cut state.
Further, when the low speed brush 54 is detached from the first electrode 52 before the first electrode 52 contacts the first stopper 55 (point M1, FIG. 6), the power supply is turned off at that time.
[0038]
5. When assist torque acts in the opposite direction (STEP 14, FIG. 6)
Since the low speed brush 54 moves in the opposite direction, it is located at the point M2 (fail area) shown in FIG. The low speed brush 54 moves onto the insulating substrate 51 and the power supply is cut off.
[0039]
In the above embodiment, the distance between the first electrode 52 (insulating substrate 51) and the first stopper 55 and the distance between the second electrode 53 (insulating substrate 51) and the second stopper 56 are used. If the distance is set to 0, the control allowable range changes as shown in FIG.
[0040]
When the vehicle speed detection means detects high speed travel, the vehicle speed switch 33 is turned off, the selection switch 34 is switched, and the high speed comparison unit 42 is selected.
The high-speed comparison unit 42 also exhibits the same action as that of the low-speed comparison unit 41. In the above description, the first electrode 52 is used as the third electrode 59, and the second electrode 53 is used as the second electrode 53. If the fourth electrode 60, the low speed brush 54 are replaced with the high speed brush 61, the first stopper 55 is replaced with the third stopper 62, and the second stopper 56 is replaced with the fourth stopper 63, the same can be understood. The
[0041]
Note that the amount of movement of the high speed brush 61 is increased by N times that of the low speed brush 54, but the width of the third and fourth electrodes 59, 60 is increased, so that the allowable control range is reached. Can be set in the same way as at low speed.
Further, if the distance between the third electrode 59 (insulating substrate 51) and the third stopper 62 and the distance between the fourth electrode 60 (insulating substrate 51) and the fourth stopper 63 are set to 0, The control allowable range changes as shown in FIG.
[0042]
Next, these control circuits and fail-safe functions will be described with reference to FIGS.
When the ignition switch 71 and the contact 72 of the engine starter interlocking relay are turned on, the DC power source 73 is connected to the circuit. A relay coil 74 is connected in series to the engine starter contact 72, and even if the contact 72 is turned off, the contact 75, the contact 76 and the contact 35 are self-held.
[0043]
Next, in FIG. 18, when the vehicle speed detecting means first detects that the vehicle is traveling at a low speed (STEP 20 in FIG. 18), the vehicle speed switch 33 is turned on, and the resistor 32 is connected in parallel to the proportional solenoid 31 and the vehicle selection switch. 34 is switched to select the low speed comparison unit 41 . When the vehicle speed shifts to a high speed, the vehicle speed switch 33 is turned off, the resistor 32 is opened, and the selection switch 34 is switched to the high speed comparison unit 42 (STEP 21 in FIG. 18).
[0044]
When the steering wheel 1 is operated, the first detection device 20 detects the steering torque, and the proportional solenoid 31 detects the assist torque. Then, the two are compared by the I / O switch 40 (STEP 22 in FIG. 18). If the relationship is within the control allowable range, the I / O switch 40 maintains the energized state and the power assist is continued (STEP 26). ).
[0045]
On the other hand, when the relationship becomes an abnormal range, that is, when a failure area is entered, as described above, the I / O switch 40 is turned off and a failure is detected. Then, since the relay 74 is turned off (STEP 23), the contact 75 and the contact 76 are also turned off simultaneously.
As a result, the assist motor 10 is turned off (STEP 24). Then, since the torque of the assist motor 10 is not transmitted to the gear case 12, the assist torque becomes zero and the assist is prohibited. That is, when an abnormality is detected, the fail safe function is activated to switch to manual steering (STEP 25).
[0046]
In this embodiment, even if the I / O switch 40 is momentarily disconnected due to a sudden handle, vibration, or the like, the contact 75 and the contact 76 are self-held for a time corresponding to the capacity of the capacitor 77. Therefore, the occurrence of an erroneous failure can be prevented in advance.
[0047]
According to the first embodiment described above, the following effects are obtained.
(1) Since the I / O switch 40 as the comparison means is provided with the low speed comparison section 41 and the high speed comparison section 42, and either one is selected according to the vehicle speed, appropriate power steering control is performed even during high speed traveling. Can do.
(2) The I / O switch 40 is composed of the electrodes 52 and 53 and the low speed brush 54 and the electrodes 59 and 60 and the high speed brush 61 that move relative to each other, and the failure detection mechanism and the assist prohibition mechanism are integrated. The structure can be simplified, the cost can be reduced, and the reliability can be improved.
[0048]
(3) Since the fail-safe function is controlled by the I / O switch 40 and provided separately to the ECU 9, fail-safe is possible even if a failure occurs in the ECU 9.
(4) The I / O switch 40 directly compares the mechanical displacements of the first and second electrodes 52, 53 and the low speed brush 54 or the electrodes 59, 60 and the high speed brush 61. By changing the range, the fail-safe adjustment range can be changed.
[0049]
(5) In the I / O switch 40, the first and second electrodes 52 and 53 are provided with stoppers 55 and 56, respectively, and the third and fourth electrodes 59 and 60 are provided with stoppers 62 and 63, respectively. The power steering control allowable range can be set widely.
(6) The third and fourth electrodes 59 and 60 of the high speed comparison unit 42 are set larger than the first and second electrodes 52 and 53 of the low speed comparison unit 41 according to the displacement amount of the high speed brush 61. Therefore, the fail-safe adjustment range at low speed and high speed can be managed with the same control limit.
(7) Since the proportional solenoid 31 detects the assist torque, the number of components in the gear case 12 is reduced, the cost can be reduced, and the mounting position of the assist motor 10 can be freely selected. .
[0050]
【The invention's effect】
As described above in detail, in the first aspect of the invention, the comparison means is provided with the low speed comparison section and the high speed comparison section, and each of them detects the failure by directly comparing the steering torque and the assist torque as mechanical displacements. Simultaneously with this failure detection, control of prohibiting assist is performed by mechanically disabling the power supply.
For this reason, the failure detection mechanism and the assist prohibition mechanism can be integrated, and optimum power steering control can be performed even at low speeds and high speeds. In addition, the reliability can be improved with a simple configuration, the cost can be reduced, and the electric control unit can be simplified.
[0051]
Further, since the mechanical displacement is directly compared by the comparison means, there is an excellent effect that the fail area can be easily changed only by changing the energization range.
Further, since the torque is detected by the second detection means by the current of the assist motor, there is an effect that the components can be easily formed.
[0052]
In the inventions of claims 2 and 3, the failure detection mechanism and the assist prohibition mechanism can be integrated even when the ratio of the assist torque is changed at the low speed and the high speed. With this configuration, the reliability can be improved and the cost can be reduced.
According to the invention of claim 4, there is an effect that the control allowable range can be appropriately changed.
[Brief description of the drawings]
FIG. 1 is a diagram showing a first state of mechanical displacement of a comparison means of the present invention.
FIG. 2 is a diagram showing a second state of mechanical displacement of the comparison means.
FIG. 3 is a diagram showing a third state of mechanical displacement of the comparison means.
FIG. 4 is a diagram showing a fourth state of mechanical displacement of the comparison means.
FIG. 5 is a diagram showing a fifth state of mechanical displacement of the comparison means.
FIG. 6 is a diagram showing a sixth state of mechanical displacement of the comparison means.
FIG. 7 is a diagram showing a relationship between steering torque and assist torque.
FIG. 8 is a graph showing assist characteristics and a fail area at a low speed.
FIG. 9 is a graph showing assist characteristics and a fail area at high speed.
FIG. 10 is a flowchart showing a control mode of the comparison means.
FIG. 11 is a graph showing different fail areas at low speed.
FIG. 12 is a graph showing different fail areas at high speed.
FIG. 13 is a block diagram illustrating a system.
FIG. 14 is a longitudinal front view of the main part.
FIG. 15 is a longitudinal front view.
FIG. 16 is a front view of a sleeve.
FIG. 17 is a control circuit diagram.
FIG. 18 is a flowchart showing control.
[Explanation of symbols]
1 Steering wheel 9 Electric control unit (ECU)
DESCRIPTION OF SYMBOLS 10 Assist motor 20 1st detection apparatus (1st detection means)
31 Proportional solenoid (second detection means)
33 Vehicle speed switch (vehicle speed detection means)
34 Selection switch (vehicle speed detection means)
40 I / 0 switch (comparison means)
41 Low speed comparison section 42 High speed comparison section 52 First electrode 56 Second electrode 54 Low speed brush 55 First stopper 56 Second stopper 59 Third electrode 60 Fourth electrode 61 High speed brush 62 Third Stopper 63 Fourth stopper

Claims (4)

Electric type that detects the steering torque of the steering wheel, adds the assist motor torque in a predetermined relationship at low speeds according to this detection signal, and adds the assist motor torque at a smaller ratio at low speeds than at low speeds A power steering system,
First detecting means for detecting the steering torque;
A second detection means connected in series with the assist motor and displaced in accordance with the current;
Comparing means comprising a low-speed comparison unit and a high-speed comparison unit, which is normally energized and switches to a power-off state when the relationship between the steering torque and the additional torque exceeds a predetermined range, and makes the additional torque zero. ,
When the vehicle speed is detected and a low speed is selected, a resistor is connected in parallel with the second detection means to select the low speed comparison section, and when the speed is high, the resistance is released from the second detection means and the high speed comparison section is selected. With a vehicle speed detecting means,
The low speed comparison unit,
The first and second electrodes that are displaced according to the detection signals of the first detection means, and these electrodes are normally energized in response to the detection signals of the second detection means at low speed. A low-speed brush that displaces, a first stopper that prevents displacement of only the first electrode when the first and second electrodes are displaced by a predetermined distance in one direction, and the first and second electrodes, A second stopper for preventing displacement of only the second electrode when displaced by a predetermined distance in the other direction;
The high-speed comparison unit ;
The third and fourth electrodes that are displaced according to the detection signal of the first detection means, and these electrodes are normally energized and in response to the detection signal of the second detection means at high speed. A high-speed brush that displaces, a third stopper that prevents displacement of only the third electrode when the third and fourth electrodes are displaced by a predetermined distance in one direction, and the third and fourth electrodes An abnormality detection control device for an electric power steering system, comprising: a fourth stopper that prevents displacement of only the fourth electrode when the lens is displaced by a predetermined distance in the other direction. 2. The electric motor according to claim 1, wherein the displacement of the high speed brush in the high speed comparison unit is enlarged in inverse proportion to the ratio of the assist torque with respect to the displacement of the low speed brush in the low speed comparison unit. -Type power steering system abnormality detection control device. The energization range of the third and fourth electrodes in the high speed comparison unit is expanded in inverse proportion to the assist torque ratio with respect to the energization range of the first and second electrodes in the low speed comparison unit. The abnormality detection control device for an electric power steering system according to claim 1 or 2. The position at which the first, second and third and fourth electrodes are in contact with the brush is set so that the stopper side with which each electrode abuts in the neutral position is wide and the opposite side is narrow. An abnormality detection control device for an electric power steering system according to claim 1, 2 or 3.

Images