JPH1076966A - Motor-driven pump type power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the increase of a cost when a motor is driven at a high current. SOLUTION: A relay 3 and a low current capacity electric field effect transistor 2 connected in parallel to the relay 3 are arranged as a drive means for a motor 1, and a current sensor 4 to detect a motor current is provided. A motor controller/drive 7 operates a relay when a motor current is high and operates the transistor 2 when a motor current is low, and the motor 1 is respectively driven. As a result, when the motor is driven at a high current, a need for a high current capacity and high-cost semiconductor switching element is eliminated. Further, since the motor is driven without connecting in parallel a plurality of semiconductor switching elements being low in current capacity, the increase of a cost of a device is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric pump type power steering apparatus for driving a hydraulic pump using a motor.

[0002]

2. Description of the Related Art In an electric pump type power steering apparatus of this type, a hydraulic pump is driven by an electric motor so that a required assist force is obtained by a hydraulic pressure according to a vehicle traveling condition such as a vehicle speed. As an electric motor used in such an electric pump type power steering device, a DC motor is often used.

[0003]

In the case of driving such an electric motor, conventionally, each armature coil in the electric motor is energized by using a semiconductor switching element such as a bipolar transistor or a field effect transistor. However, the voltage of the battery mounted on the vehicle is usually 12 V
(Volts), and when this vehicle-mounted battery is used, it is necessary to apply a current of 100 A (ampere) or more to the electric motor that drives the hydraulic pump.

For this reason, a semiconductor switching element capable of flowing a current of 100 A or more is conventionally used. However, a semiconductor switching element having such a current capacity is expensive, so that the cost of the entire apparatus increases. There was a problem. It is also possible to obtain a required current capacity by connecting a plurality of semiconductor switching elements having a small current capacity in parallel.However, in such a case, a large mounting space is required and the cost of the device is similarly reduced. There is a problem of rising. There is also a problem that a circuit design in consideration of the variation of the switching element is required. Therefore, an object of the present invention is to suppress an increase in the cost of the device when driving an electric motor with a large current.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a motor for driving a hydraulic pump, and a driving means for applying a current to the motor according to the speed and steering angle of the vehicle to rotate the motor. In an electric pump type power steering apparatus that obtains a required assist force by hydraulic pressure of a hydraulic pump based on rotation of a motor, a relay and a semiconductor switching element having a small current capacity and connected in parallel to the relay are provided as the driving means, A current sensor for detecting the current of the motor and control means for operating one of the relay and the semiconductor switching element according to the magnitude of the current of the motor when the motor is driven are provided.
Therefore, when the motor is driven, one of the relay and the semiconductor switching element is operated according to the magnitude of the current of the motor. The control means detects the current of the motor based on the output of the current sensor when the relay operates. Further, the control means activates the relay by operating the relay when the current of the motor is equal to or higher than the predetermined threshold, and deactivates the relay when the state where the motor current is equal to or lower than the predetermined threshold continues for a predetermined time. In operation, the semiconductor switching element is operated so that the motor has a predetermined rotation speed. Further, the control means drives the motor only by the semiconductor switching element when the current of the motor is equal to or less than the rated current capacity of the semiconductor switching element when the vehicle speed is equal to or higher than a predetermined set speed and a required assist force is obtained. .

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a main configuration of the present invention, and shows a configuration of a motor driving device used in an electric pump type power steering device. In FIG. 1, the driving device includes a motor 1 for driving a hydraulic pump, a field effect transistor (hereinafter, transistor) 2 for driving the motor 1, a relay 3 for driving the motor 1,
A current sensor 4 for detecting a current of the motor 1, a vehicle speed sensor 5 for detecting a speed of a vehicle to which the present apparatus is attached, a steering angle sensor 6 for detecting a steering angle of the vehicle, and a motor controller / driver 7 for controlling the above-mentioned components. And a battery 8 which is a power supply of the apparatus.

Here, the motor controller / driver 7
Is to determine whether to use the relay 3 or the transistor 2 based on the magnitude of the current of the motor 1 detected by the current sensor 4 when driving the motor 1. Now, the operation of the motor drive device configured as described above will be described with reference to the timing chart of FIG. FIG.
2 detected at time t0 by the vehicle speed sensor 5.
It is assumed that both the vehicle speed shown in FIG. 2A and the steering angle detected by the steering angle sensor 6 in FIG. 2B are “0”.

Under such conditions, since the load on the motor 1 is small and the motor current is also small, the motor controller / driver 7 performs PWM control on the transistor 2 so that the motor 1 rotates at the set rotational speed M1, and outputs its output. The duty ratio of the pulse is changed (FIG. 2 (f)), and the relay 3 is deactivated (FIG. 2 (e)). This is performed to reduce noise and save energy by rotating the motor 1 at as low a speed as possible when the vehicle is stopped and not being steered.

In this case, the set rotation speed M1 is to prevent the driver from feeling uncomfortable due to the delay of the steering power assist when the steering operation is started. If a motor that does not cause an assist delay is used, the motor may be stopped. Next, at time t1 in FIG. 2, when the steering is started while the speed of the vehicle is “0” (FIG. 2B), the load on the motor 1 increases as the steering angle increases. Here, since the motor 1 is driven such that the rotation speed of the motor 1 becomes M1 even if the load of the motor 1 increases, the current of the motor 1 increases (FIGS. 2C and 2D).

At time t1 'when the current of the motor 1 detected by the current sensor 4 exceeds the threshold value C1, the motor controller / driver 7 turns on the relay 3 and turns off the transistor Q1 (FIG. 2).
(E), (f)). However, the threshold value C1 is set to a value that does not exceed the rating of the transistor Q1 used. After the time t1 ′, the load on the motor 1 increases as the steering angle increases, so that the current of the motor 1 gradually increases (FIG. 2C), and the rotation speed of the motor 1 decreases (FIG. 2C). 2 (d)). Here, the relationship between the current and the rotation speed of the motor 1 is obtained while the relay 3 is kept on, and thus can be determined by the characteristics of the motor 1.

In the meantime, the speed of the vehicle increases as shown in FIG. 2 (a).
However, at this point, the current value of the motor 1 has exceeded the threshold value C1, and therefore the motor 1 is still driven by the relay 3. Here, FIG.
When the steering angle decreases from time t3 as shown in FIG. 2, the load on the motor 1 also decreases, so that the rotation speed of the motor 1 increases (FIG. 2C), and the current value of the motor 1 decreases (FIG. 2 (C)). d)).

At time t4, it is assumed that the current of the motor 1 has become smaller than the threshold value C1 as shown in FIG.
During the time until the current reaches 4 ', the current of the motor 1 reaches the threshold value C1.
If the motor speed remains below the set speed M2, the motor controller / driver 7 turns off the relay 3 (FIG. 2E) and drives the transistor 2 to reduce the motor rotation speed to the set speed M2.
The duty ratio is adjusted so as to be as shown in FIG.
(F)). This is to reduce the rotation speed of the motor 1 within a range where no assist delay occurs at the start of the next steering in a state where there is no steering, similarly to the time from the time t0 to t1 ′. It aims to reduce noise and save energy. In this case, the rotation speed is M
If a motor that does not cause an assist delay with respect to the start of steering even if it is 1 or “0” is used, the motor may be held at the rotation speed M1 or the motor may be stopped. The reason why the set time ΔT is provided is to prevent the steering feeling from deteriorating due to the fluctuation of the assist force, assuming continuous turning steering.

Next, at time t5, the steering is started again, and as the steering angle increases, the current of the motor 1 increases in order to maintain the rotation speed of the motor 1 at M2 (FIG. 2).
(D)). When the current of the motor 1 becomes equal to or more than the threshold value C1 at time t5 ', the motor controller / driver 7
Turns on the relay 3 and turns off the transistor 2 so as to obtain a necessary steering assist force.

As described above, the basic concept of switching the rotation speed of the motor 1 is to prevent a feeling of steering discomfort due to a sudden decrease in the power steering assist force when the rotation speed of the motor 1 is switched to a lower direction. For this purpose, the rotation speed of the motor is reduced after the set time has elapsed. When switching to a direction in which the rotation speed of the motor 1 is increased, control is performed so as to increase the rotation speed of the motor immediately after the steering is determined, in order to prevent a feeling of steering discomfort due to assist delay. Therefore, although not shown in the timing chart of FIG. 2, when the speed of the vehicle is equal to or lower than V1 and the current of the motor becomes smaller than C1, the timing for setting the rotation speed of the motor to the set speed M1 is as follows.
After the condition is satisfied for the set time.

FIG. 3 is a flowchart showing the operation of the motor controller / driver 7 in such a driving device. The operation of the main part of the present invention will be further described according to this flowchart. When the motor controller / driver 7 is started and started, first, in step S1, it is determined whether or not the speed of the vehicle is equal to or higher than V1. If the vehicle speed is equal to or lower than V1, it is determined in step S2 whether the current of the motor 1 is equal to or higher than the threshold C1. 2 is turned off and the process is terminated.

On the other hand, if the motor current is less than the threshold value C1, it is determined in step S4 whether or not the activated internal timer (not shown) has passed a set time (ΔT). If the set time has not elapsed, after confirming that the motor current is equal to or less than C1 during the set time, the relay 3 is turned off in step S5, and the transistor is set so that the motor 1 rotates at the set rotation speed M1. 2 is subjected to PWM control. If the motor current becomes equal to or greater than the threshold value C1 during the set time and the determination in step S2 becomes “Y”,
Go to step S3, turn on relay 3, and set transistor 2
To end the process.

If the vehicle speed is equal to or higher than V1, step S1 is executed.
Is determined to be "Y", it is determined in step S6 whether or not the current of the motor 1 is equal to or more than the threshold value C1, and if it is equal to or more than the threshold value C1, the relay 3 is turned on in step S7. Then, the transistor 2 is turned off, and the process ends.

If the vehicle speed is equal to or higher than V1 and the motor current is equal to or lower than the threshold value C1, the motor controller / driver 7 determines in step S8 whether or not the set time by the activated internal timer has elapsed. During the time, when it is confirmed that the motor current is equal to or less than C1, step S9 is performed.
To turn off the relay 3 and PWM-control the transistor 2 so that the motor 1 rotates at the set rotation speed M2.

In the above example, when the motor 1 is driven, the motor 1 is driven by the relay 3 or the transistor 2 based on the magnitude of the current of the motor 1. In such a case, there is also a method of obtaining the steering stability by performing all the driving of the motor 1 using the transistor 2. In this case, the transistor 2
It is assumed that a sufficient steering assist force can be obtained with a motor current value equal to or less than the rating of. That is, in FIG. 4, when the speed of the vehicle becomes equal to or higher than the set speed V1 at time t2 (see FIG. 4).
(A)) controls the transistor 2 so that the rotation speed of the motor 1 is adjusted at a preset inclination and the set speed becomes M3.

As shown in FIG. 4 between times t4 and t4 ', the speed of the vehicle is equal to or higher than the set speed V1 (FIG. 4A).
And the current value of the motor 1 is equal to or less than the set value C0 (FIG. 4).
If the state of (d)) continues for the set time ΔT, the transistor 2 is controlled so that the rotation speed of the motor 1 becomes the set rotation speed M2 (FIG. 4C). In the example shown in FIG. 4, similarly to the example shown in FIG. 2, when it is determined that the vehicle is not being steered, the rotation speed of the motor 1 is reduced within a range where there is no delay in the steering assist to reduce noise and save energy. Aim. Although a description is omitted in each of the above drawings, since a large current flows when the motor 1 is started, if the current value exceeds the rating of the transistor 2, the motor 1 is started by the relay 3 and the motor is started. When the current value falls below the rating of transistor 2, transistor 2
To drive the motor.

[0021]

As described above, according to the present invention, a relay and a semiconductor switching element connected in parallel to the relay and having a small current capacity are provided as driving means for the motor, and a current sensor for detecting the current of the motor is provided. When driving the motor, one of the relay and the semiconductor switching element is operated in accordance with the magnitude of the motor current. Since the motor can be driven without the need for connecting a plurality of semiconductor switching elements having a small current capacity in parallel, it is possible to suppress an increase in the cost of the apparatus. Further, since the current of the motor is detected based on the output of the current sensor when the relay operates, the current flowing through the motor can be accurately detected. When the current of the motor is equal to or higher than a predetermined threshold, the relay is operated to drive the motor, and when the state of the motor current equal to or lower than the predetermined threshold continues for a predetermined time, the relay is deactivated, In addition, since the semiconductor switching element is operated such that the motor has a predetermined rotational speed, it is possible to prevent a feeling of steering discomfort due to a delay in the steering assist force and a feeling of steering discomfort due to a sharp decrease in the assist force. Also, when the current of the motor when the speed of the vehicle is equal to or higher than a predetermined set speed and a required assist force is obtained is equal to or less than the rated current capacity of the semiconductor switching element, the motor is driven only by the semiconductor switching element. Therefore, the apparatus can be configured at a lower cost.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main configuration of the present invention.

FIG. 2 is a timing chart showing the operation of the device shown in FIG.

FIG. 3 is a flowchart showing an operation of a main part of the apparatus.

FIG. 4 is a timing chart showing another operation example of the device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Motor, 2 ... Transistor (semiconductor switching element), 3 ... Relay, 4 ... Current sensor, 5 ... Vehicle speed sensor, 6 ... Steering angle sensor, 7 ... Motor controller / driver, 8 ... Battery.

Claims (4)

[Claims] 1. A motor for driving a hydraulic pump, driving means for supplying a current corresponding to the speed and steering angle of a vehicle to the motor to rotate the motor, and a hydraulic pressure of the hydraulic pump based on the rotational driving of the motor. An electric pump-type power steering device that obtains the assisting force of: a relay, a semiconductor switching element connected in parallel to the relay and having a small current capacity as the driving unit, and a current sensor for detecting a current of the motor; An electric pump type power steering device, further comprising: control means for operating one of the relay and the semiconductor switching element according to the magnitude of a motor current. 2. The electric pump type power steering device according to claim 1, wherein the control means detects a current of the motor based on an output of the current sensor when the relay operates. 3. The control device according to claim 1, wherein when the current of the motor is equal to or more than a predetermined threshold, the control means activates the relay to drive the motor, and when the current of the motor is equal to or less than a predetermined threshold. An electric pump type power steering device, wherein when the state continues for a predetermined time, the relay is deactivated and the semiconductor switching element is operated so that the motor has a predetermined rotation speed. 4. The motor control device according to claim 1, wherein the control unit is configured to control the motor current when the vehicle speed is equal to or higher than a predetermined set speed and a required assist force is obtained to be equal to or lower than a rated current capacity of the semiconductor switching element. In this case, an electric pump-type power steering device characterized in that the motor is driven only by the semiconductor switching element.