JP2002249059A - Power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power steering device capable of excellently starting an electric motor even under the environment at very low temperature. SOLUTION: After applying the starting voltage to the electric motor 27, the state that the rotational speed of the electric motor 27 is <=500 rpm is continued, and if the temperature of a drive element of the electric motor 27 is below -35 deg.C, application of the starting voltage to the electric motor 27 is interrupted, and the electric motor 27 is driven alternately in the forward and reverse directions for the predetermined time. Then, application of the starting voltage to the electric motor 27 is re-started.

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 that generates a steering assist force for assisting steering by a hydraulic pressure generated by a pump driven by an electric motor.

[0002]

2. Description of the Related Art Conventionally, a power steering apparatus has been used in which hydraulic oil is supplied to a power cylinder connected to a steering mechanism, thereby generating a steering assist force from the power cylinder. Some of such power steering devices include, for example, a gear pump driven by an electric motor, and supply hydraulic oil pumped from a reservoir tank by the gear pump to a power cylinder.

[0003] The gear pump has a drive gear into which a rotational force of an electric motor is input and a driven gear meshed with the drive gear in a cavity formed in the pump housing. A suction chamber and a discharge chamber are formed on both sides of the meshing position of the drive gear and the driven gear so as to communicate with the cavity. The driven gear rotates following the rotation, and the hydraulic oil that has flowed into the suction chamber is conveyed toward the discharge chamber in a state of being sealed between the teeth of the drive gear and the driven gear and the inner wall surface of the cavity. This achieves a pumping action.

[0004]

However, in the power steering apparatus provided with the gear pump as described above, the electric motor cannot be started in an extremely low temperature environment (for example, about -40 degrees or less), and the power cylinder is not driven by the gear pump. In some cases, hydraulic fluid is not supplied toward That is, in an extremely low temperature environment, the hydraulic motor in the cavity of the gear pump is fixed to the drive gear and the driven gear, so that even when power is supplied to the electric motor, the electric motor is not started (the drive gear rotates. Do not start).

It is an object of the present invention to solve the above-mentioned technical problems and to provide a power steering device capable of satisfactorily starting an electric motor even in an extremely low temperature environment.

[0006]

Means for Solving the Problems and Effects of the Invention According to the first aspect of the present invention, the steering is assisted by a hydraulic pressure generated by a pump (23) driven by an electric motor (27). A power steering device for generating a steering assist force for performing a steering condition, and a condition satisfaction determining means (3, S
2, S3; T2, T3, T4) and forward / reverse alternating rotation means for rotating the electric motor alternately forward / reverse in response to the condition satisfaction determination means determining that the predetermined condition is satisfied. (3, S5, T5).

[0007] Alphanumeric characters in parentheses indicate corresponding components in the embodiment described later. According to the present invention, when the predetermined condition is satisfied, the electric motor is rotated alternately in the forward and reverse directions. Thus, if the above-described predetermined conditions are appropriately set, even if the hydraulic oil is stuck to a drive gear or the like in the pump due to the extremely low temperature environment, the fixed state of the hydraulic oil can be eliminated. In addition, the electric motor can be started well even in an extremely low temperature environment.

The predetermined condition may include a condition that the rotation speed of the electric motor is kept at a predetermined speed or less after the start of application of a voltage for starting the electric motor. Good (claim 2). When this condition is included, the forward / reverse alternating rotation means repeats the control of rotating the electric motor forward / reverse alternately for a predetermined time within a predetermined time when the condition is satisfied. It is preferable that the power steering device further includes a lock failure means (3, S7) for stopping rotation of the electric motor as a motor lock failure after the predetermined time has passed.

Further, in place of or in addition to the condition described in claim 2, a condition that a motor current of a predetermined value or more continuously flows through the electric motor for a predetermined time or more is included. (Claim 3).

[0010]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a conceptual diagram showing a basic configuration of a power steering device according to an embodiment of the present invention. This power steering device is provided in association with a steering mechanism 1 of a vehicle, and is for applying a steering assist force to the steering mechanism 1.

The steering mechanism 1 includes a steering wheel 11 operated by a driver, a steering shaft 12 connected to the steering wheel 11, and a pinion gear 1 provided at the tip of the steering shaft 12.
3 and a rack shaft 14 extending in the left-right direction of the vehicle. A rack gear portion 14a is formed on the rack shaft 14, and a pinion gear 13a is formed on the rack gear portion 14a.
Are engaged. Tie rods 15 are respectively connected to both ends of the rack shaft 14.
Numerals 5 are respectively connected to a knuckle arm 16 that supports a front left wheel FL and a front right wheel FR as steering wheels. The knuckle arm 16 is provided rotatably around the king pin 17. With this configuration, when the steering wheel 11 is operated and the steering shaft 12 is rotated, the rotation is converted by the pinion gear 13 and the rack shaft 14 into linear motion along the left-right direction of the vehicle, and this linear motion is converted to the knuckle arm 16. Kingpin 1
The rotation of the front left wheel FL and the front right wheel FR is achieved by being converted into a rotation around 7.

A torsion bar 21 which twists in the middle of the steering shaft 12 according to the direction and magnitude of the steering torque applied to the steering wheel 11,
A hydraulic control valve 22 whose opening changes in accordance with the direction and size of the twist of the torsion bar 21 is interposed. The hydraulic control valve 22 has four ports 221, 22
2, 223 and 224 are provided, and the operating oil pumped from the reservoir tank 24 by the oil pump 23 is supplied to the port 221 through the oil pipe 251. The port 222 communicates with the reservoir tank 24 via an oil pipe 252. Port 22
The oil chambers 2 and 3 of the power cylinder 26 that generate a steering assist force via oil pipes 253 and 254, respectively.
61 and 262. A piston 263 is provided between the oil chambers 261 and 262 of the power cylinder 26 to move in the vehicle width direction due to a difference in oil pressure in the oil chambers 261 and 262. This piston 263 is configured integrally with the rack shaft 14.

When the steering wheel 11 is rotated leftward or rightward, the torsion bar 21 is twisted. 26
Hydraulic oil is supplied to one of the first and second 262. As a result, a hydraulic pressure difference is generated between the oil chambers 261 and 262, and the piston 263 of the power cylinder 26 moves according to the hydraulic pressure difference, whereby the steering assist force is applied to the rack shaft 14. At this time, the excess hydraulic oil is returned from the hydraulic control valve 22 to the reservoir tank 24 via the oil pipe 252. When the torsion bar 21 is hardly twisted, the hydraulic control valve 22 is in an equilibrium state, and the hydraulic oil supplied from the oil pump 23 to the hydraulic control valve 22 is not supplied to the power cylinder 26 , Oil pipe 2
It is returned to the reservoir tank 24 via 52.

The oil pump 23 is a gear pump that performs a pumping operation by the rotation of a drive gear and a driven gear (not shown). The rotational force of the electric motor 27 is input to the drive gear. The electric motor 27 is driven and controlled by an electronic control unit 3 including a microcomputer. The electronic control unit 3 includes a steering angle sensor 4 for detecting the steering angle of the steering wheel 11, a vehicle speed sensor 5 for detecting the speed of the vehicle, and a current flowing through the electric motor 27 (motor current).
And an output signal of a motor rotation speed sensor 7 for detecting a rotation speed of the electric motor 27.

The electronic control unit 3 turns on an ignition key switch of the vehicle, for example, based on signals given from the steering angle sensor 4, the vehicle speed sensor 5, the motor current detection circuit 6, the motor speed sensor 7, and the like. In response to this, the electric motor 27 is started, and after the electric motor 27 is started, the drive of the electric motor 27 is controlled such that an appropriate steering assist force according to the operation of the steering wheel 11 is applied to the steering mechanism 1. .

FIG. 2 is a flowchart for explaining a process performed when the electric motor 27 is started.
First, a driving voltage (starting voltage) for starting is applied to the electric motor 27 (motor voltage initial application) (step S).
1). Then, when a predetermined time has elapsed since the start of the application of the starting voltage to the electric motor 27, it is determined whether or not the rotation speed of the electric motor 27 (motor rotation speed) is 500 rpm or less (step S2).

If the motor rotation speed is 500 rpm or less, the state where the motor rotation speed is 500 rpm or less is maintained for a predetermined time (for example, the motor drive element) corresponding to the temperature of the motor drive element measured from the initial application of the motor voltage. 20 seconds if the temperature is lower than -35 ° C, 0 to -35 ° C or higher
15 ° C for less than 0 ° C and 5 seconds for 0 ° C or more and less than 80 ° C
Second, if it is 80 ° C. or more, it is determined whether or not it has continued for more than 2 seconds (step S3). When the state where the motor rotation speed is 500 rpm or less does not continue for a predetermined time or more, that is, when 20 seconds have not elapsed from the initial application of the motor voltage, the temperature of the drive element (FET) of the electric motor 27 further decreases. It is determined whether the temperature is lower than −35 ° C. (step S4). The temperature of the drive element (motor drive element) of electric motor 27 is detected, for example, by a temperature sensor (not shown) provided in association with the drive element.

The temperature of the driving element of the electric motor 27 is -35.
If the temperature is lower than ° C, the application of the voltage for starting to the electric motor 27 is interrupted, and the electric motor 27 is alternately rotated forward and backward for a predetermined time (for example, one second) (step S5). Accordingly, even if the hydraulic oil is stuck to the drive gear and the driven gear because the ambient temperature around the electric motor 27 is extremely low, it is possible to eliminate the stuck state of the hydraulic oil. When the electric motor 27 is alternately rotated forward and backward for a predetermined time, a voltage for starting is again applied to the electric motor 27 (step S6), and after an appropriate time has elapsed, the motor rotation speed is reduced. 500rpm
It is determined again whether or not the following is true (step S2).
If the motor speed is below 500rpm,
It is determined again whether the state has continued for a predetermined time or more (step S3). If the state has not continued for a predetermined time or more, it is determined again whether the temperature of the driving element is lower than −35 ° C. Is performed (step S4). If the temperature of the driving element is lower than −35 ° C., the voltage application for starting the electric motor 27 is interrupted, and the electric motor 27
Are alternately rotated forward and backward by the predetermined time (step S5). Thus, the motor rotation speed 500r
pm or less and the electric motor 27
While the condition that the temperature of the driving element is less than −35 ° C. is satisfied, the forward / reverse alternating rotation of the electric motor 27 continues until the state of the motor rotation speed of 500 rpm or less is continuously detected for a predetermined time or more. The application of the starting voltage to the electric motor 27 is alternately repeated.

If the state where the motor rotation speed is 500 rpm or less is continuously detected for 20 seconds or more, that is, even if 20 seconds elapse after the start-up voltage application to the electric motor 27 is restarted, the motor rotation speed is not changed. If the speed does not increase to 500 rpm or more, it is determined that the motor lock fail condition has been satisfied (the electric motor 27 has an abnormality) (step S7), and the application of the starting voltage to the electric motor 27 is stopped. , This process ends. In this case, drive control of the electric motor 27 for assisting steering is not performed, and
After the end of the process shown in FIG. 2, no voltage is applied to the electric motor 27.

On the other hand, before the elapse of 20 seconds from the application of the starting voltage to the electric motor 27, the motor rotation speed becomes 500 rpm.
If it has reached m or more, it is determined that the electric motor 27 has been started normally. Then, this process is ended, and subsequently, the drive control of the electric motor 27 for giving the steering mechanism 1 an appropriate steering assist force according to the operation of the steering wheel 11 is started. As mentioned above,
According to this embodiment, after the start of application of the starting voltage to the electric motor 27, the rotation speed of the electric motor 27 becomes 500 rpm.
When the following condition is continued and the temperature of the drive element is lower than −35 ° C., the electric motor 27 is rotated alternately in the forward and reverse directions. Thereby, even if the hydraulic oil is fixed to the drive gear and the driven gear, the fixed state of the hydraulic oil can be eliminated. Therefore, the electric motor 27 can be started well even in an extremely low temperature environment.

FIG. 3 is a flowchart for explaining another embodiment of the present invention. The process shown in FIG. 3 is a process performed when the electric motor 27 is started (for example, when the ignition key switch of the vehicle is turned on) instead of the process shown in FIG. 2 described above. . First, a drive voltage for starting is applied to the electric motor 27 (step T1). Then, it is determined whether the temperature of the drive element of the electric motor 27 is lower than 0 ° C. (step T2).

If the temperature of the drive element is lower than 0 ° C., it is determined whether the motor current detected by the motor current detection circuit 6 is 50 A (ampere) or more (step T3). . Furthermore, if the motor current is 5
If it is 0 A or more, it is determined whether the state of the motor current of 50 A or more has continued for 3 seconds or more (step T4). If the motor current drops to less than 50 A within three seconds after the state where the motor current is 50 A or more is detected, the determination whether the motor current is 50 A or more is denied in step T3, and the electric motor 27 Is determined to have been started normally, and this process ends. After the end of this process, the drive control of the electric motor 27 for giving the steering mechanism 1 an appropriate steering assist force according to the operation of the steering wheel 11 is started.

On the other hand, if the state of the motor current of 50 A or more continues for 3 seconds or more, the voltage application for starting to the electric motor 27 is interrupted, and the electric motor 27 is stopped for a predetermined time (for example, 1 second). Are rotated alternately forward and backward (step T5). After the forward / reverse alternating rotation of the electric motor 27 is performed, the voltage application for starting the electric motor 27 is restarted. Thereafter, it is determined whether or not the motor current is 50 A or more (step T6). If the motor current is 50 A or more, a predetermined time corresponding to the temperature of the motor drive element measured from the initial application of the motor voltage (step T6). For example, if the temperature of the motor drive element is less than -35 ° C, it is 20 seconds; if it is -35 ° C or more and less than 0 ° C, it is 15 seconds; if it is 0 ° C or more and less than 80 ° C, it is 5 seconds; Seconds)
It is determined whether the above has elapsed (step T7).
If the predetermined time has not elapsed from the initial application of the motor voltage, the process returns to step T6, and it is determined again whether the motor current is 50 A or more.

If the motor current drops to less than 50 A before the predetermined time elapses from the initial application of the motor voltage, the determination as to whether the motor current is 50 A or more is denied in step T6, and the electric motor 27 Is determined to have been started normally, and this process ends. Then, following this processing, the drive control of the electric motor 27 for giving the steering mechanism 1 an appropriate steering assist force according to the operation of the steering wheel 11 is started.

On the other hand, if the motor current remains at 50 A or more even after the predetermined time has elapsed from the initial application of the motor voltage, it is determined that an abnormality has occurred in the electric motor 27 (motor lock failure) ( Step T8). And
After the application of the voltage to the electric motor 27 is stopped, the process is terminated. In this case, the drive control of the electric motor 27 for assisting the steering is not performed, and the voltage application to the electric motor 27 is not performed even after the processing illustrated in FIG.

When the temperature of the driving element is equal to or higher than 0 ° C., the above-described steps T3 to T5 are skipped, and
The processing after step T6 is performed. That is, if the motor current has decreased to less than 50 A before 20 seconds have elapsed from the initial application of the motor voltage, the determination as to whether or not the motor current is 50 A or more is denied in step T6,
It is determined that the electric motor 27 has been started normally. On the other hand, if the motor current remains at 50 A or more even after 20 seconds from the initial application of the motor voltage, it is determined that the electric motor 27 is abnormal (step T).
8) According to this embodiment, when the state where the motor current is 50 A or more continues for 3 seconds or more when the electric motor 27 is started and the temperature of the driving element is less than 0 ° C., the electric motor 27 It is rotated only forward and reverse alternately. As a result, similarly to the first embodiment, even if the hydraulic oil is fixed to the driving gear and the driven gear, the fixed state of the hydraulic oil can be eliminated. Thus, the electric motor 27 can be started well.

Further, in the processing according to this embodiment, since means for detecting the rotation speed of the electric motor 27 is not required, the motor rotation speed sensor provided in the configuration according to the first embodiment described above. 7 can be omitted,
There is an advantage that the configuration of the power steering device can be simplified. As described above, the two embodiments of the present invention have been described, but the present invention can be embodied in modes other than the above-described embodiments. For example, the specific values shown in FIGS. 2 and 3 (0 ° C., 500 rpm, 5
0A, 3 seconds) are merely examples, and may be appropriately changed according to the characteristics of the vehicle.

In addition, various design changes can be made within the scope of the matters described in the claims.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a basic configuration of a power steering device according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a process performed when the electric motor is started.

FIG. 3 is a flowchart illustrating another process performed when the electric motor is started.

[Explanation of symbols]

 Reference Signs List 1 steering mechanism 3 electronic control unit 7 motor rotation speed sensor 23 oil pump 26 power cylinder 27 electric motor

Claims (3)

[Claims] 1. A power steering apparatus for generating a steering assist force for assisting steering by a hydraulic pressure generated by a pump driven by an electric motor, wherein a condition for determining whether a predetermined condition is satisfied is satisfied. Determining means; and, in response to the condition satisfaction determining means determining that the predetermined condition is satisfied, forward / reverse alternating rotation means for alternately rotating the electric motor in the forward / reverse direction. Power steering device. 2. The method according to claim 1, wherein the predetermined condition includes a condition that a rotation speed of the electric motor is kept at a predetermined speed or less after a voltage for starting is applied to the electric motor. The power steering apparatus according to claim 1, wherein 3. The power steering apparatus according to claim 1, wherein the predetermined condition includes a condition that a motor current of a predetermined value or more continuously flows through the electric motor for a predetermined time or more. .