JP3282293B2 - Electric power steering device - Google Patents

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 a vehicle such as an automobile, and more particularly to an electric power steering device.

[0002]

2. Description of the Related Art Conventionally, an electric power steering apparatus for a vehicle such as an automobile generally includes a motor for driving a steering linkage member such as a rack bar via a clutch and a steering gear box, and a control device 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.

[0003] As one of such electric power steering devices, for example, as described in Japanese Patent Application Laid-Open No. 63-215461, a motor is driven in a state in which a clutch is released, and the motor is driven by a no-load current of the motor. 2. Description of the Related Art An electric power steering apparatus configured to determine a motor abnormality has been conventionally known. According to the electric power steering apparatus configured as described above, it is possible to reliably detect an abnormality such as a lock in which the motor cannot rotate when the clutch is released.

[0004]

However, in the conventional electric power steering apparatus as described above, the abnormality of the motor cannot be detected unless the clutch is released. The abnormality cannot be detected, and the abnormality of the motor can be monitored substantially only while the vehicle is stopped. Therefore, the clutch cannot be actively released even if the motor becomes abnormal, such as a lock, and cannot rotate while the vehicle is running, so that the power steering device cannot function promptly as a manual steering device. There is a problem that the driver must steer against excessive frictional force caused by slipping in the clutch.

In view of the above-mentioned problems in the conventional electric power steering apparatus, the present invention can monitor the motor lock at all times during the running of the vehicle, thereby locking the motor during the running of the vehicle. It is an object of the present invention to provide an improved electric power steering device which can be immediately made to function as a manual steering device in such a case.

[0006]

SUMMARY OF THE INVENTION According to the present invention, as shown in FIG. 1, a motor M1 for generating a steering assist force, a steering torque detecting means M2,
An electric power steering apparatus having control means M3 for controlling the steering assist force by controlling the motor at least according to the steering torque, comprising a vehicle speed detecting means M4, a steering angle detecting means M7, A traveling state determining means M5 for determining whether or not the vehicle is in a traveling state in which a lateral acceleration equal to or greater than a predetermined value is obtained. a steering torque detected by the steering torque detecting means determines that the motor lock when it is out of a predetermined range
In both cases, in a situation where the vehicle speed is less than the reference value and the steering angle is equal to or less than the corresponding reference value, when the steering torque detected by the steering torque detection means is out of a predetermined range, the lock of the motor is disabled. It is achieved by an electric power steering apparatus characterized by having a determining lock determination unit M 6.

[0007]

When the auxiliary steering motor is locked, the driver cannot turn the motor at all even if the driver turns the steering wheel (steering wheel) and the steering angular speed exceeds a certain value. High value. In addition, even if the motor is normal, (a) at the time of stationary steering (when steering is performed at an extremely low vehicle speed), (b) at the end of the steering wheel (when the steering wheel is steered beyond its turning range) ,
(C) The steering torque is also high during a severe turn (when the vehicle body is turned with high lateral acceleration). Therefore, when the vehicle is not in any of the above-mentioned states (a) to (c), it can be determined whether or not the motor has locked based on whether or not the steering torque is out of the predetermined range.

According to configuration described above, the vehicle speed is detected by the vehicle speed detecting means M4, the steering angle by the steering angle detection means M7
Is detected by the traveling state determination means M5 to determine whether or not the vehicle is in a traveling state in which a lateral acceleration equal to or more than a predetermined value is generated. In this situation, when the steering torque detected by the steering torque detection means M2 is out of the predetermined range, the lock determination means M6 determines that the motor is locked, and the vehicle speed is less than the reference value and the steering angle Is smaller than the corresponding reference value, the steering torque detecting means M
Since the steering torque detected by 2 is determined as the lock of the motor by the lock determining unit M 6 when it is out of the predetermined range, it is possible to reliably detect the lock of a motor even during running of the vehicle Thus, when the motor is locked, the power steering device can be quickly switched to the manual steering device.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an embodiment of the present invention.

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

In FIG. 2, reference numeral 10 denotes a steering wheel. 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 is provided with a steering angle sensor 26 for detecting the steering angle θ and a torque sensor 28 for detecting the steering torque T, and the output of these sensors is electronic. It is supplied to the control device 32. Further, a signal indicating the vehicle speed V detected by the vehicle speed sensor 34 and a signal indicating the lateral acceleration G of the vehicle body detected by the lateral acceleration sensor 36 are also input to the electronic control unit 32.

As shown in detail in FIG. 3, the electronic control unit 32 includes a microcomputer 38, which is a central processing unit (CPU) 40.
A read only memory (ROM) 42, a random access memory (RAM) 44, and an 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
Indicating the steering angle θ detected by the torque sensor 2
8, a signal indicating the steering torque T detected by the control unit 8, a signal indicating the vehicle speed V detected by the vehicle speed sensor 34, and a signal indicating the lateral acceleration G of the vehicle body detected by the lateral acceleration sensor 36 are input. . Input port device 46
Is configured to appropriately process a signal input thereto and output the processed signal to the CPU and the RAM 44 in accordance with an instruction of the CPU 40 based on a control program stored in the ROM 42.

The ROM 42 stores a control program shown in FIG. 4 and maps corresponding to the graphs shown in FIGS. The CPU 40 performs various calculations and signal processing based on the control program shown in FIG. The output port device 48 outputs a control signal to the motor 22 via the drive circuit 52 according to the instruction of the CPU 40, outputs a control signal to the electromagnetic clutch 24 via the drive circuit 54, and further determines that the motor is locked. The alarm lamp 56 is turned on when the alarm occurs.

Next, the operation of the illustrated embodiment will be described with reference to the flowchart shown in FIG. The control by the electronic control unit 32 is started when an ignition switch (not shown in FIG. 2) is closed. In the flowchart shown in FIG. 4, N indicates the number of times that the motor is locked.

First, in step 10, a control signal is output to the electromagnetic clutch 24 via the drive circuit 54 to connect the clutch. In step 20, the steering angle θ detected by the steering angle sensor 26 is determined. A signal indicating the steering torque T detected by the torque sensor 28,
A signal indicating the vehicle speed V detected by the vehicle speed sensor 34 and a signal indicating the lateral acceleration G of the vehicle body detected by the lateral acceleration sensor 36 are read.

In step 30, based on the steering torque T read in step 20, a basic assist amount Tab is calculated from a map corresponding to the graph shown in FIG.
In step 40, the vehicle speed coefficient Kv is calculated from the map corresponding to the graph shown in FIG. 6 based on the vehicle speed V read in step 20, and in step 50, the vehicle speed coefficient Kv is calculated in step 30. The assist amount Ta is calculated as the product of the basic assist amount Tab and the vehicle speed coefficient Kv calculated in step 40.

In step 60, it is determined whether or not the absolute value of the steering angle θ is equal to or larger than a reference value θe (a positive constant for judging the steering wheel end), and | θ | ≧ θe. When it is determined that the steering is substantially at the steering end state, the process proceeds to step 110, and it is determined that | θ | ≧ θe is not satisfied, ie, the steering is substantially at the steering end state. When it is determined that there is no such information, the process proceeds to step 70.

In step 70, the vehicle speed V is changed to the reference value Vo.
(Positive constant for determining whether the vehicle is stopped or running at a very low vehicle speed) is determined.
o, that is, when it is determined that the vehicle is stopped or running at an extremely low vehicle speed, the process proceeds to step 110, and it is determined that V ≦ Vo is not satisfied, that is, the vehicle is at a low vehicle speed. When it is determined that the vehicle is traveling at the above speed, the process proceeds to step 80.

In step 80, the vehicle speed V is set to the reference value Vh.
(Positive constant for determining high vehicle speed) is determined, and it is determined whether or not V ≧ Vh, that is, whether the vehicle is running at a low or medium vehicle speed. When the determination is made, the process proceeds to step 90 , and when it is determined that V ≧ Vh, that is, when the vehicle is running at a high vehicle speed, the process proceeds to step 100 .

In step 90, it is determined whether or not the absolute value of the steering angle θ is equal to or less than a reference value θo (a positive constant for determining that the vehicle is in a substantially straight running state). When it is determined that | θ | ≦ θo, that is, when it is determined that the vehicle is substantially in a straight running state, the process proceeds to step 120, and it is determined that | θ | ≦ θo, that is, the vehicle is not. Is determined to be substantially in a turning state, the number of motor lock determinations N is reset to 0 in step 110.

In step 100, it is determined whether or not the absolute value of the lateral acceleration G is equal to or smaller than a reference value Go (positive constant).
That is, it is determined whether or not the vehicle is in a running state in which substantially no lateral acceleration occurs in the vehicle body. When it is determined that | G | ≦ Go is not satisfied, the process proceeds to step 110,
When it is determined that | G | ≦ Go, the routine proceeds to step 120.

In step 120, it is determined whether or not the absolute value of the steering torque T is greater than or equal to a reference value Tc (a positive constant for determining whether the motor is locked).
If it is determined that it is not c, step 110
When it is determined that | T | ≧ Tc, the number N is incremented by one in step 130.

It should be noted that the reference values θe, Vo, Vh, θo,
Go and Tc may be experimentally determined, for example, so that the corresponding determination is properly performed.

In step 140, it is determined whether or not the number N is three. If it is determined that N is not three, in step 150, a control signal corresponding to the assist amount Ta is determined. Is output to the motor 22 through the drive circuit 52, so that the steering assist force is controlled to a value corresponding to the assist amount Ta, and then the process returns to step 20, where N = 3
When it is determined that the condition is true, the process proceeds to step 160.

In step 160, the energization of the motor 22 is stopped and the output of the control signal to the electromagnetic clutch 24 is stopped to release the clutch.
In step 170, the control signal is output to the warning lamp 56 to turn on the warning lamp, whereby a warning that the motor is locked is issued to the driver of the vehicle.

Thus, according to the illustrated embodiment, in step 30, the basic assist amount Tab is calculated from a map corresponding to the graph shown in FIG. 5, and in step 40, the vehicle speed coefficient Kv is shown in FIG. In step 50, the assist amount Ta is calculated as the product of the basic assist amount Tab and the vehicle speed coefficient Kv.

In a situation where the motor is not locked and is operating normally, the steering is not at the time of stationary steering, at the end of the steering wheel, or at the time of severe turning, that is, at step 60.
No is determined in steps 70 and 70 and step 90 or 1
Even in the case where the determination of "00" is made, the determination of "No" is always made in step 120, so that the control signal corresponding to the assist amount Ta is output to the motor 22 in step 150, and As a result, the steering assist force is controlled to correspond to the steering torque and become lower as the vehicle speed increases, so that light steering at low vehicle speeds and good steering stability at high vehicle speeds are ensured. Is done.

On the other hand, when the motor is locked, the motor cannot rotate at all even if the steering wheel 10 is turned, and the absolute value of the steering torque T becomes greater than the reference value Tc. Is determined. When this determination, that is, the determination that the motor is locked is performed three times in succession, a determination of YES is made in step 140, and in step 160, the power supply to the motor 22 is stopped and the clutch 24 The clutch is released by stopping the output of the control signal to
As a result, the power steering device is switched to the manual steering device, and in step 170, the alarm lamp 56 is turned on, and the driver of the vehicle is warned that the motor is locked.

According to the illustrated embodiment, steps 160 and 170 are not executed unless the determination that the motor is locked is performed three times in succession. Therefore, it is erroneously determined that the motor is locked. Although the motor is not actually locked based on the determination result, step 160
And 170 are executed, that is, the alarm lamp 5
6 is reliably prevented from being turned on and the power steering device being switched to the manual steering device.

In the illustrated embodiment, the torque sensor 2
Since it is not determined whether or not the motor 8 is normal, if an abnormality such as disconnection or short-circuit occurs in the torque sensor, a determination of YES is made in step 120, thereby determining whether or not the motor is locked. Regardless, the power steering device is switched to the manual steering device. However, if an abnormality such as disconnection or short circuit occurs in the torque sensor, the assist amount Ta becomes an inappropriate value. Therefore, it is preferable not to continue the power assist control even in this case. Therefore, according to the illustrated embodiment, Even when an abnormality occurs, inappropriate power assist is reliably prevented from being performed.

Although the present invention has been described in detail with reference to specific embodiments, the present invention is not limited to such embodiments, and various other embodiments may be made within the scope of the present invention. The possibilities will be clear to the skilled person.

For example, in the above-described embodiment, it is determined whether or not the vehicle is in a running state in which a lateral acceleration of a predetermined value or more does not occur. It is determined whether or not the vehicle is in a running state in which the vehicle does not generate a lateral acceleration exceeding a predetermined value. However, the absolute value of the yaw rate of the vehicle is equal to or less than a reference value. May be performed depending on whether
Alternatively, the determination may be performed based on whether the vehicle speed V and the steering angle θ are in a region other than the hatched region of the graph shown in FIG.

In the control routine shown in FIG. 4, prior to step 60, it is determined whether or not the torque sensor 28 is normal. If it is determined that the torque sensor 28 is abnormal, the process proceeds to step 130. The process may be modified to proceed to step 60 when the torque sensor is normal. In this case, whether the torque sensor is normal or not can be determined, for example, by the method described in the specification and drawings of Japanese Patent Application No. 4-276616 filed by the same applicant as the present applicant, or by using the torque sensor. The determination may be performed by determining whether the difference between the detected values is equal to or greater than a predetermined value.

[0036]

As is clear from the above description, according to the present invention, the vehicle speed is equal to or greater than the reference value且車body steering At a situation is a running state does not occur lateral acceleration equal to or greater than a predetermined value in the torque When the steering torque detected by the detection means M2 is out of the predetermined range, the lock determination means M6 determines that the motor is locked, and the vehicle speed is less than the reference value.
Motor M by the lock determining unit M 6 when 且操 steering torque steering angle is detected At a situation is less than the corresponding reference value by the steering torque detection means M2 is outside a predetermined range
Since it is determined 1 of the lock and, to a wide range of driving situations vehicle
In this case, the lock of the motor can be reliably detected, whereby the power steering device can be quickly switched to the manual steering device even when the motor is locked while the vehicle is running .

[0037]

[Brief description of the drawings]

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

FIG. 5 is a graph showing a relationship between a steering torque T detected by a torque sensor and a basic assist amount Tab.

FIG. 6 is a graph showing a relationship between a vehicle speed V detected by a vehicle speed sensor and a vehicle speed coefficient Kv.

FIG. 7 is a graph showing a region where a lateral acceleration equal to or more than a predetermined value occurs in a vehicle body as a function of a vehicle speed V and a steering angle θ.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Steering wheel 12 ... Steering shaft 14 ... Steering gear box 16 ... Rack bar 22 ... Motor 24 ... Electromagnetic clutch 26 ... Steering angle sensor 28 ... Torque sensor 32 ... Electronic control unit 34 ... Vehicle speed sensor 36 ... Lateral acceleration sensor 56 ... Warning lamp

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI B62D 119: 00 B62D 119: 00 (72) Inventor Masaaki Tsuboi 1st Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Watanabe Tomoyuki 1st Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) References JP-A-4-138965 (JP, A) JP-A-4-232179 (JP, A) JP-A-63-173759 (JP) , A) JP-A-64-4572 (JP, A) JP-A-63-215461 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B62D 5/04 B62D 6/00- 6/06

Claims (1)

(57) [Claims] 1. An electric power steering apparatus comprising: a motor for generating a steering assist force; a steering torque detecting unit; and a control unit for controlling the steering assist force by controlling the motor according to at least the steering torque. A vehicle speed detecting means, a steering angle detecting means, a running state determining means for determining whether or not the vehicle body is in a running state in which a lateral acceleration exceeding a predetermined value occurs, and a vehicle speed being equal to or higher than a reference value and the vehicle body having a predetermined value. When the steering torque detected by the steering torque detecting means is out of a predetermined range in a running state in which the lateral acceleration does not occur, it is determined that the motor is locked, and the vehicle speed is lower than the reference value. And the steering angle corresponds
The steering torque detection
If the steering torque detected by the gear is out of the predetermined range
An electric power steering apparatus , comprising: a lock determination unit that determines that the motor is locked when the motor is locked .