JPH06305436A - Motor-driven power steering device - Google Patents

Abstract

PURPOSE:To surely detect the abnormality of a steering torque detecting means by one steering torque detecting means so as to enable rapid changeover to p manual steering system. CONSTITUTION:A motor-driven power steering has a motor M1 for generating steering assist force, and a control device M3 for controlling the motor M1 according to at least steering torque detected by a steering torque detecting device M2. A rectilinear travel detecting device M4 detects the rectilinear travel state of a vehicle, and a steering torque deviation computing device M5 computes deviation between the detected steering torque at the time of the vehicle being in the rectilinear travel state and the detected steering torque at the time of the actual steering torque being 0. An abnormality judging device M6 judges whether the steering torque deviation is out of a specified range and judges the steering torque detecting device M2 to be abnormal when the deviation is out of the specified range.

Description

Detailed Description of the Invention

[0001]

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

[0002]

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

As one of such electric power steering devices, for example, as disclosed in Japanese Patent Laid-Open No. 227859/1987, a difference between steering torques detected by two torque sensors provided on a steering shaft is calculated. However, when the difference between the detected steering torques is greater than or equal to the reference value, it is determined that an abnormality such as offset has occurred in the torque sensor, and the motor is de-energized and the electric power is configured to release the clutch. Steering devices have been known for some time. According to the electric power steering device configured as described above, it is possible to reliably prevent the power assist from being stopped and prevent inappropriate power assist when an abnormality occurs in one of the torque sensors. .

[0004]

However, in the conventional electric power steering system as described above, two torque sensors must be used in order to determine whether or not an abnormality has occurred in the torque sensor due to the offset. If the two torque sensors have the same offset such as temperature drift, the difference between the detected steering torques will not exceed the reference value.Thus, even though the torque sensor is actually abnormal, There is a problem that the abnormality cannot be detected.

In view of the above-mentioned problems in the conventional electric power steering apparatus as described above, the present invention can surely detect the abnormality by one steering torque detecting means. It is an object of the present invention to provide an improved electric power steering device that allows the steering device to immediately function as a manual steering device.

[0006]

According to the present invention, as described above, the above-described object is to provide a motor M1 for generating a steering assist force and a detected steering torque as a function of an actual steering torque, as shown in FIG. An electric power steering apparatus having a steering torque detecting means M2 for outputting and a controlling means M3 for controlling the steering assist force by controlling the motor at least in accordance with the detected steering torque is provided, and a straight traveling state of the vehicle is achieved. A straight traveling detection means M4 for detecting, a steering torque deviation calculating means M5 for calculating a deviation between the detected steering torque when the vehicle is in a straight traveling state and the detected steering torque when the actual steering torque is 0, and An abnormality determination means M6 for determining abnormality of the steering torque detection means when the deviation of the steering torque is out of a predetermined range. It is achieved by over steering device.

[0007]

The steering torque detecting means M2 outputs the detected steering torque as a function of the actual steering torque. Since the actual steering torque is 0 when the vehicle is in a straight traveling state, the steering torque detecting means is When normal, the detected steering torque when the vehicle is in a straight running state and the detected steering torque when the actual steering torque is 0 (hereinafter referred to as reference torque) are the same, and their deviation is 0. is there.
On the other hand, if an abnormality occurs in the steering torque detecting means due to offset, disconnection, short circuit, etc., the detected steering torque when the vehicle is in a straight traveling state becomes a value different from the reference torque, and the difference between the two becomes large. Grows larger as you go. Therefore, it is possible to determine whether or not an abnormality has occurred in the steering torque detecting means by determining whether or not the deviation of the steering torque is out of the predetermined range.

According to the above-described structure of the present invention, the straight traveling detection means M4 detects the straight traveling state of the vehicle, and the steering torque deviation calculating means M5 detects the detected steering torque and the actual steering when the vehicle is in the straight traveling state. The deviation from the detected steering torque (reference torque) when the torque is 0 is calculated,
When the deviation of the steering torque is out of the predetermined range, the abnormality determining means M6 determines that the steering torque detecting means M2 is abnormal, so that one steering torque detecting means can reliably detect the abnormality. As a result, when an abnormality occurs in the steering torque detecting means, the power steering device can be quickly switched to the manual steering device.

[0009]

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

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

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

In the illustrated embodiment, the steering shaft 12 has a steering angle sensor 26 for detecting a steering angle .theta. (The right turning direction is positive) and a substantially actual steering angle as shown in FIG. A torque sensor 28 that detects the steering torque as a linear function of the torque Tr and outputs the detected steering torque Tout.
Are provided, and the outputs of these sensors are supplied to the electronic control unit 32. The electronic control unit 32 is also adapted to receive signals indicating the rotational speeds Vwl and Vwr of the left and right wheels detected by the wheel speed sensors 34 and 36.

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

The input port device 46 has a steering angle sensor 26.
A signal indicating the steering angle θ detected by the torque sensor 2
A signal indicating the steering torque Tout detected by 8 and a signal indicating the rotation speeds Vwl and Vwr of the left and right wheels detected by the wheel speed sensors 34 and 36 are input. The input port device 46 appropriately processes the signal input thereto, and in accordance with the instruction of the CPU 40 based on the control program stored in the ROM 42, the CPU and the RAM.
The processed signal is output to 44.

The ROM 42 stores the control programs shown in FIGS. 4 and 5 and maps corresponding to the graphs shown in FIGS. 6 and 7. The CPU 40 is adapted to perform various calculations and signal processing based on the control programs shown in FIGS. 4 and 5, as will be described later. The output port device 48 passes through the drive circuit 52 and the motor 22 according to the instruction of the CPU 40.
A control signal is output to the electromagnetic clutch 24 via the drive circuit 54, and the alarm lamp 56 is turned on when it is determined that the torque sensor 28 is abnormal. There is.

Next, the operation of the illustrated embodiment will be described with reference to the flow charts shown in FIGS. The control by the electronic control unit 32 is started by closing an ignition switch not shown in FIG. Further, in the flowchart shown in FIG. 5, N indicates the number of determinations that abnormality has occurred in the torque sensor 28.

First, in step 10, the control signal is output to the electromagnetic clutch 24 through the drive circuit 54 so that the clutch is engaged, and in step 20, the steering angle θ detected by the steering angle sensor 26 is set. The signal indicating the output steering torque Tout of the torque sensor 28 and the signals indicating the rotation speeds Vwl and Vwr of the left and right wheels detected by the wheel speed sensors 34 and 36 are read.

In step 30, the steering torque T is calculated according to the following equation 1 based on the detected steering torque Tout read in step 20, and the basic assist amount is calculated from the map corresponding to the graph shown in FIG. Tab is calculated. In the equation 1, Tst is the detected steering torque Tout when the actual steering torque Tr is 0 when the torque sensor 28 is normal as shown in FIG.

## EQU1 ## T = Tout-Tst

In step 40, the vehicle speed V is calculated according to the following equation 2 using Kw as a positive constant based on the rotational speeds Vwl and Vwr of the left and right wheels read in step 20, and the vehicle speed V is calculated based on the vehicle speed V. The vehicle speed coefficient Kv is calculated from the map corresponding to the graph shown in FIG. 7, and in step 50 the basic assist amount Tab calculated in step 30 and the vehicle speed coefficient Kv calculated in step 40 are calculated. The assist amount Ta is calculated as the product.

[Formula 2] Vw = Kw (Vwl + Vwr) / 2

In step 60, the difference ΔVw between the rotational speeds Vwl and Vwr of the left and right wheels is calculated according to the following equation 3, and the absolute value of the rotational speed difference ΔVw is less than the reference value Vo (small positive constant). It is determined whether or not the vehicle is substantially in a straight traveling state, and | ΔVw | ≦ V
If it is determined that the vehicle is not o, that is, the vehicle is in the non-straight ahead state, the process proceeds to step 170, where | ΔV
When it is determined that w│≤Vo, that is, the vehicle is substantially in the straight traveling state, the routine proceeds to step 70.

[Formula 3] ΔVw = Vwl−Vwr

In step 70, it is determined whether or not the absolute value of the steering angle θ is less than or equal to θo (a small positive constant), that is, whether or not the steering wheel is substantially in the neutral position. If it is determined that | θ | ≦ θo, that is, the steering wheel is substantially in the neutral position, the process proceeds to step 90, where | θ | ≦ θo
If it is determined that the steering wheel is not in the neutral position, the process proceeds to step 80.

In step 80, it is determined whether or not the steering angle θ is positive, that is, whether or not the steering wheel is in the right-turn position, and it is determined that θ> 0 is not satisfied, that is, When it is determined that the steering wheel is in the left-turn position, the routine proceeds to step 110, where θ> θ
When it is determined that the steering wheel is in the right-turn position, that is, when the determination is “o”, step 100 is performed.
Go to.

In step 90, step 12 described later is executed.
Reference value TH of positive direction offset of steering torque T in 0 to 150 and reference value T of negative direction offset
L is the first reference value TH1 (positive constant) and TL1
(Negative constant), and in step 100, the reference values TH and TL are set to the second reference value TH2 (a positive constant larger than TH1) and the first reference value TL1, respectively.
In step 110, the reference values TH and TL are set to the first reference value TH1 and the second reference value TL2 (negative constants smaller than TL1), respectively.

In step 120, it is judged whether or not the steering torque T calculated according to the equation 1 in step 30 exceeds the reference value TH of the plus direction offset, and it is determined that T> TH. When the determination is made, the torque sensor abnormality determination number N is incremented by 1 in step 180, and when it is determined that T> TH is not established, the routine proceeds to step 130.

In step 130, the coefficient Kt is set to a positive constant smaller than 1 to determine whether or not the steering torque T exceeds TH.Kt, and it is determined that T> TH.Kt. If so, in step 160, the coefficient K is set to a positive constant smaller than 1 and the assist amount Ta is set to T.
When it is determined that the correction is reduced to a · K and T> TH · Kt is not established, the process proceeds to step 140.

In step 140, it is judged whether or not the steering torque T is less than the reference value TL of the minus direction offset, and when it is judged that T <TL, the routine proceeds to step 180. If it is determined that T <TL is not satisfied, the routine proceeds to step 150.

In step 150, the steering torque T is T
It is determined whether or not L is less than Kt, and T <TL.
If it is determined that it is Kt, step 160
When it is determined that T <TL.multidot.Kt is not established, the torque sensor abnormality determination count N is reset to 0 in step 170.

The reference values Vo and θo for the judgments in steps 60 and 70, the reference values TH and TL for the judgments in steps 120 to 150 set in steps 90 to 110, and steps 130 and 150. The coefficient Kt in the above equation may be obtained, for example, experimentally so that the corresponding determination can be properly performed.

In step 190, it is judged whether or not the number of times N is 3, and when it is judged that N = 3 is not satisfied, in step 200, a control signal corresponding to the assist amount Ta is obtained. Is output to the motor 22 via the drive circuit 52, the steering assist force is controlled to a value corresponding to the assist amount Ta, and then the process returns to step 20 and N = 3.
If it is determined that the above condition is true, the process proceeds to step 210.

In step 210, the energization of the motor 22 is stopped and the output of the control signal to the electromagnetic clutch 24 is stopped, so that the clutch is released.
In step 220, the alarm lamp is turned on by outputting the control signal to the alarm lamp 56, and thereby the driver of the vehicle is alerted that an abnormality has occurred in the torque sensor 28.

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

When steering is performed in a state where the torque sensor 28 is operating normally without any abnormality, a negative determination is made in step 60, and thus in step 200. As a result, a control signal corresponding to the assist amount Ta is output to the motor 22, whereby the steering assist force is controlled so as to correspond to the actual steering torque and become lower as the vehicle speed becomes higher. Therefore, a light steering operation in a low vehicle speed range is performed. Is ensured and good steering stability is ensured in the high vehicle speed range.

On the other hand, when the torque sensor 28 has a serious abnormality such as an offset, disconnection, or short circuit exceeding the allowable range, the difference between the output Tout of the torque sensor and the reference torque Tst when the vehicle is in a straight traveling state. Becomes larger, the determination of yes is made in step 120 or 140. If this determination, that is, the determination that a serious abnormality has occurred in the torque sensor is performed three times in succession, a yes determination is made in step 190, and step 21
At 0, the power supply to the motor 22 is stopped and the output of the control signal to the clutch 24 is stopped to release the clutch, whereby the power steering device is switched to the manual steering device, and step 220 At this time, the alarm lamp 56 is turned on, and the driver of the vehicle is warned that a serious abnormality has occurred in the torque sensor 28.

Further, according to the illustrated embodiment, steps 210 and 220 are not executed unless the determination that a serious abnormality has occurred in the torque sensor is made three times in succession.
It is erroneously determined that a serious abnormality has occurred in the torque sensor, and based on the result of the determination, steps 210 and 22 are executed despite the fact that no serious abnormality has occurred in the torque sensor.
It is reliably prevented that 0 is executed, that is, the warning lamp 56 is turned on and the power steering device is switched to the manual steering device.

Also according to the illustrated embodiment, step 12
At 0 to 150, it is determined whether the abnormality that has occurred in the torque sensor is serious or minor, and when it is determined that the abnormality is minor, that is, step 130 or 1
If the determination in step 50 is YES, the power steering device is not switched to the manual steering device by executing steps 210 and 220, but the assist amount Ta is set in step 160.
As the assist force is reduced by the correction of the steering force, the influence of inappropriate steering assist due to the fact that the assist force does not correspond to the actual steering torque is reduced and the driver of the vehicle receives an excessive steering burden. This can be prevented.

Further, when the vehicle travels on a road surface inclined in the traveling direction of the vehicle such as a cant road surface, the steering wheel is slightly turned to the right or left even if the vehicle is in a straight traveling state. The torque sensor outputs steering torque in the right turning direction or the left turning direction even when the vehicle is in a straight traveling state. Therefore, the steering torque T may exceed the reference value depending on the degree of inclination of the road surface. Therefore, it may be erroneously determined that an abnormality has occurred although the torque sensor is not abnormal.

According to the illustrated embodiment, steps 60-8
At 0, it is determined whether the steering wheel is in the right-turn position or the left-turn position when the vehicle is substantially straight ahead, and when the steering wheel is in the right-turn position, that is, the step If the determination in step 80 is YES, the reference value of the offset in the plus direction is increased and corrected in step 100. Conversely, if the steering wheel is in the left-turn position, that is, in step 80, no determination is made. If the determination is made, since the reference value of the minus direction offset is reduced in step 110,
Compared to the case where these reference values are constant, it is possible to reduce the possibility that the torque sensor may be erroneously determined to be abnormal due to the vehicle traveling on a road surface inclined in the lateral direction. Therefore, it is possible to accurately determine whether or not an abnormality has occurred in the torque sensor.

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

For example, in the above-described embodiment, when the vehicle travels straight on a road surface inclined laterally with respect to the traveling direction as described above, the steering torque offset is large or small according to the inclination direction of the road surface. Although the reference values TH and TL for discrimination are increased or decreased, steps 70 to 110 may be omitted. In that case, the absolute values of the positive direction offset reference value TH and the negative direction offset reference value TL may be the same as each other, but considering the general inclination of the traveling road surface Is set so that the reference value TH of the plus direction offset is larger than the absolute value of the reference value TL of the minus direction offset, and the absolute value of the reference value TL is set to be larger than the reference value TH for a vehicle for driving on the right as in the United States. Preferably.

In the above embodiment, step 16
Coefficient K used for correction correction of the assist amount Ta at 0
Is a constant, but the coefficient K may be variably set as a function of the vehicle speed so that it becomes smaller as the vehicle speed V becomes higher.

Further, in the control routine shown in FIG. 5, the steering angle sensor 26 and the wheel speed sensor 3 are preceded to step 60.
If it is determined that any of these sensors is abnormal, the process proceeds to step 170, and only when all of these sensors are normal. It may be modified to proceed to step 60.

[0042]

As is apparent from the above description, according to the present invention, when the straight running state detecting means M4 detects the straight running state of the vehicle and the steering torque deviation calculating means M5 is in the straight running state. The deviation between the detected steering torque and the detected steering torque when the actual steering torque is 0, that is, the reference torque is calculated, and when the deviation of the steering torque is out of a predetermined range, the abnormality determination means M6 causes the steering torque detection means. Since it is determined that M2 is abnormal, one steering torque detecting means can reliably detect the abnormality, and when an abnormality occurs in the steering torque detecting means, the power steering device can be quickly and manually operated. You can switch to the steering system.

[Brief description of drawings]

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

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

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

FIG. 4 is a flowchart showing a part of a power assist control routine achieved by the electronic control device shown in FIGS. 2 and 3.

5 is a flowchart showing the remaining part of the power assist control routine achieved by the electronic control device shown in FIGS. 2 and 3. FIG.

FIG. 6 is a graph showing a relationship between a steering torque T detected by a torque sensor and a basic assist amount Tab.

FIG. 7 is a graph showing a relationship between a vehicle speed V detected by a vehicle speed sensor and a vehicle speed coefficient Kv.

FIG. 8 is a graph showing the relationship between the actual steering torque Tr and the output torque Tout of the torque sensor.

[Explanation of symbols]

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

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical display location B62D 119: 00 (72) Inventor Masaaki Tsuboi 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Corporation ( 72) Inventor Tomoyuki Watanabe 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation

Claims (1)

[Claims] 1. A motor for generating a steering assist force, a steering torque detecting means for outputting a detected steering torque as a function of an actual steering torque, and a steering assist force for controlling the motor according to at least the detected steering torque. An electric power steering device having a control means for controlling the vehicle, a straight traveling detection means for detecting a straight traveling state of the vehicle, and a detected steering torque and an actual steering torque when the vehicle is in the straight traveling state are zero. A steering torque deviation calculating means for calculating a deviation from a detected steering torque at a certain time, and an abnormality judging means for judging an abnormality of the steering torque detecting means when the deviation of the steering torque is out of a predetermined range. An electric power steering device characterized by: