JPH07112666A - Electric power steering device - Google Patents

Abstract

PURPOSE:To prevent the heating damage of an electric motor and resolve the sense of incompatibility on driving by measuring the temperature of the electric motor, and controlling the voltage applied to the electric motor according to the cases that the measured temperature is the warning temperature or below, the warning temperature or above, and the upper limit temperature or above. CONSTITUTION:A power steering device generates the assist torque according to the steering force of a steering device, i.e., a steering wheel with an electric motor 1. The temperature of the electric motor l is measured by a temperature measuring device 2, and the electric motor 1 is controlled by a motor control device 3. The motor control device 3 applies the voltage according to the assist torque with a normal control means 3a when the measured temperature of the electric motor 1 is the warning temperature or below. When the measured temperature of the electric motor 1 is the warning temperature or above, relatively lower voltage is applied to the electric motor 1 by a voltage reducing control means 3b. When the measured temperature of the electric motor 1 is the upper limit temperature or above, the applied voltage is reduced to zero by a motor stopping means 3c, and the electric motor 1 is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering system for an automobile which generates an assist torque by using an electric motor.

[0002]

2. Description of the Related Art Generally, a power steering apparatus for an automobile has a steering shaft and a pinion shaft connected by an elastic member (torsion bar), and is based on the relative rotation of the steering shaft and the pinion shaft caused by the torsion of the elastic member. The supply of the working fluid to the power cylinder that gives the assisting force is controlled by the servo valve that operates in this way. That is, the elastic member is twisted in proportion to the magnitude of the manual torque input from the steering wheel of the automobile to the relative rotation between the steering shaft and the pinion shaft to generate assist torque (auxiliary steering force) for steering. It is a device that reduces the manual torque required for.

The supply of the working fluid to the servo valve is accomplished by rotating the pump using the power of the engine. Here, a car without an engine mounted on the front side (for example, a midship car)
However, since the engine and the steering shaft and the like are considerably separated from each other, it is not appropriate to connect the distance by piping because the configuration becomes complicated.

Therefore, as disclosed in Japanese Unexamined Patent Publication No. 56-99859, it is conceivable to dispose an electric pump in the vicinity of a steering shaft or the like and generate an assist torque by the electric pump. However, if a high current continues to flow through the electric motor that constitutes the pump, as in the case where the steering wheel operation continues at low speed, the electric motor may heat up and eventually cause damage to the electric motor. is there. Therefore, in order to solve this problem, there is an electric pump type power steering device disclosed in Japanese Patent Application Laid-Open No. 3-132473. This monitors the load current flowing through the electric motor, estimates the temperature of the electric motor from the load current, and controls the electric motor according to this temperature. That is, when the estimated temperature of the electric motor is below a certain temperature, the voltage obtained from the map showing the relationship between the motor temperature and the applied voltage applied to the motor is applied to the electric motor by normal control. To control. On the other hand, when the estimated temperature of the electric motor exceeds the predetermined temperature, the voltage applied to the electric motor is set to zero and the electric motor is stopped to avoid damage due to heating of the electric motor.

[0005]

However, the above-mentioned conventional electric pump type power steering apparatus has the following problems. That is, when the estimated temperature of the electric motor reaches a set value during steering of the steering wheel, the electric motor stops at that stage, which causes the driver to feel uncomfortable that the steering wheel suddenly becomes heavy.

Further, since the temperature of the electric motor is estimated from the load current flowing through the electric motor, if the reading accuracy of the load current is poor, the timing of stopping the electric motor may be shifted, or the ambient temperature around the electric motor may change. Nevertheless, the electric motor stop time tended to be earlier in cold places, and the electric motor stop time was delayed in hot places. Therefore,
The present invention has been made to solve the above-described problems, and an object of the present invention is to prevent damage due to heating of an electric motor in a power steering apparatus using the electric motor and to make the driver feel uncomfortable. To provide an electric power steering apparatus that does not provide

[0007]

As shown in FIG. 1, the structure of the invention for solving the above-mentioned problems generates an assist torque corresponding to a steering force of a steering wheel by using an electric motor 1. The power steering apparatus includes a temperature measuring device 2 for measuring the temperature of the electric motor 1 and a motor control device 3 for controlling the electric motor 1, and the motor control device 3 includes the temperature measuring device 2 When the temperature of the electric motor 1 measured by the above is less than or equal to a preset warning temperature, the normal control means 3a for applying a voltage corresponding to the assist torque to be generated to the electric motor 1 and the electric motor 1 When the temperature exceeds the warning temperature, the normal control means 3a causes the electric motor 1 to operate.
When the temperature of the electric motor 1 and the voltage reduction control means 3b for applying a voltage lower than the voltage applied to the electric motor 1 exceeds the upper limit temperature set higher than the warning temperature, the electric motor 1 is applied. Motor stop means 3c for stopping the electric motor 1 by setting the voltage to zero is provided.

[0008]

The temperature of the electric motor 1 is measured by the temperature measuring device 2 and input to the motor control device 3. When the temperature of the electric motor 1 is lower than a preset warning temperature, the normal control means 3a applies a voltage according to the assist torque to be generated to the electric motor 1 to control the electric motor 1. ing.

Further, when the temperature of the electric motor 1 rises and becomes higher than the warning temperature, the voltage reduction control means 3
By b, a voltage lower than the voltage applied to the electric motor 1 by the normal control means 3a is applied, and the electric motor 1 is controlled. When the temperature of the electric motor 1 further rises and becomes higher than the upper limit temperature which is higher than the warning temperature, the voltage applied to the electric motor 1 is made zero by the motor stopping means 3c. It is supposed to stop.

[0010]

EXAMPLES Hereinafter, examples will be described based on the present invention.
FIG. 2 is a configuration diagram showing the configuration of the electric power steering apparatus according to the present invention. Reference numeral 11 is a vehicle speed sensor that detects the vehicle speed of the automobile, and 12 is a steering sensor that is connected to the steering wheel shaft and that detects whether the steering wheel 13 is being steered.

Reference numeral 14 is a control device. The control device 14 is supplied with power from a battery B and receives output signals from the vehicle speed sensor 11 and the steering sensor 12. P is a pump rotated by the electric motor M,
The working fluid sent from the pump P which is arranged integrally with the electric motor M is supplied to the servo valve 16.

Further, the temperature of the electric motor M is measured by the thermistor 15 attached to the electric motor M, and its output signal is inputted to the control device 14. Reference numeral 21 is a gear housing composed of a rack and pinion gear. The supply and discharge of the working fluid to and from the power cylinder 22 for generating the auxiliary steering force is controlled by 22 and the ball joint 25 is operated via the left and right steering rods 24 of the piston 23 of the power cylinder 22 to operate a steering wheel (not shown). Rotate.

Next, the processing procedure of the control device 14 for obtaining the voltage E to be applied to the electric motor M will be described with reference to the flowchart of FIG. First, step 100
Then, the vehicle speed V at that time is read from the speed sensor 11. Next, in step 101, the temperature T of the electric motor M is measured by the thermistor 15 and input to the control device 14.

At step 102, it is judged if T <TH. That is, the temperature T of the electric motor M measured in step 101 and the preset upper limit temperature TH which is the upper limit temperature at which the electric motor M is not damaged.
(Eg 70 ° C.) is compared. If the temperature T of the electric motor M does not exceed the upper limit temperature TH, the electric motor M has not reached a temperature at which it is damaged, so that the inequality in step 102 is established and the process proceeds to step 103. On the other hand, when the temperature T exceeds the upper limit temperature TH, it is determined that the electric motor M has reached a temperature at which it is damaged, the process proceeds to step 107, and the electric motor M is stopped as described later.

If the temperature T of the electric motor M has not reached the upper limit temperature TH, the routine proceeds to step 103, where T <TM.
Is determined. That is, step 101
The temperature T of the electric motor measured in 1 is compared with a warning temperature TM (for example, 60 ° C.) which is an upper limit temperature at which the electric motor M, which is preset, can be normally driven.

If the temperature T of the electric motor M does not exceed the warning temperature TM, it is determined that the electric motor M is at a temperature at which normal driving can be performed, and the routine proceeds to step 104. On the contrary, when the temperature T exceeds the warning temperature TM, it is determined that the temperature of the electric motor M has reached a high temperature without being damaged, and the process proceeds to step 106. Electric motor M
If the temperature T has not reached the warning temperature TM, the process proceeds to step 104 and the electric motor M is driven normally. That is, the voltage to be applied to the electric motor M from the vehicle speed V read in step 100 from the characteristic diagram (map 1) of the vehicle speed V and the voltage E shown in FIG. Calculate E.

Next, in step 105, the voltage E calculated in step 104 is output to the electric motor M,
This program ends. In this way, the assist torque is controlled to increase as the vehicle speed decreases. In step 103, the temperature T of the electric motor M is set to the warning temperature T.
If M is exceeded, at step 106, the vehicle speed V shown in FIG.
Then, the voltage E to be applied to the electric motor M is calculated from the vehicle speed V read in step 100 from the characteristic diagram of the voltage E (map 2). Then, the process proceeds to step 105, and the voltage E calculated in step 104 is output to the electric motor M. That is, when the temperature T of the electric motor M is between the warning temperature TM and the upper limit temperature TH, the voltage E to be applied to the electric motor M is calculated by the map 2 in which the voltage lower than the map 1 is calculated. The low voltage E controls the electric motor M to prevent the temperature rise of the electric motor M.

Further, in step 102, the electric motor M
If the temperature T of exceeds the upper limit temperature TH, step 1
In step 07, the voltage E to be applied to the electric motor M is set to 0, and then in step 105, the electric motor M is stopped. In this way, the temperature T of the electric motor M is equal to the upper limit temperature T.
When it exceeds H, the electric motor M is stopped to prevent the electric motor M from being damaged.

The above steps are executed at any time with a preset cycle time, and control is performed according to the temperature T of the electric motor M. In the embodiment described above, in step 106, the electric motor M
The voltage E to be applied to is calculated according to the map 2 shown in FIG. 5, but for example, a voltage half the voltage E calculated according to the map 1 may be applied. further,
The relationship between the temperature T of the electric motor M and the correction coefficient K shown in FIG. 6 is stored in the memory of the control device 14, and step 101
The correction coefficient K may be obtained from the temperature T of the electric motor measured in step S1, and the voltage E × K applied by multiplying the voltage E calculated from the map 1 may be applied to the electric motor M.

Further, in the above embodiment, as the temperature measurement of the electric motor M, the temperature of the electric motor M is directly measured by the thermistor 15. However, the temperature of the electric motor M is estimated from the load current flowing through the electric motor M. Means may be used. Further, although the electric power steering apparatus of the present embodiment shows the example of the power steering apparatus in which the pump P is driven by the electric motor M, it can be generally used in the power steering apparatus using the electric motor. A power steering device that directly generates assist torque by an electric motor may be used.

[0021]

As described above, the electric power steering apparatus of the present invention measures the temperature of the electric motor, and when the temperature of the electric motor exceeds the warning temperature, the voltage applied normally is higher than the voltage applied. Is applied, and when the upper limit temperature of the electric motor is exceeded, the electric motor is stopped. That is, when the temperature of the electric motor exceeds the warning temperature, the voltage applied to the electric motor by the voltage reduction control means decreases the voltage applied to the electric motor by the normal control means. Hard to rise to temperature. In addition, since the electric motor does not suddenly stop due to the normal rotation of the electric motor, there is no sense of discomfort that the assist force suddenly disappears during steering. further,
Since the steering wheel becomes heavier than that in the normal control due to the voltage reduction control, there is an effect that the driver can be warned that the electric motor is under a heavy load.

When the temperature of the electric motor exceeds the upper limit temperature, the rotation of the electric motor is stopped by the motor stopping means, so that the electric motor can be reliably prevented from being damaged by heating. Further, as in the electric power steering apparatus according to the second aspect, by directly providing the temperature sensor for measuring the temperature of the electric motor on the electric motor, the electric motor temperature can be measured without being influenced by the outside air temperature, If the electric motor is stopped too early due to an error in reading the electric motor temperature,
Not too late.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to a complaint.

FIG. 2 is a configuration diagram of an electric power steering apparatus showing an embodiment of the present invention.

FIG. 3 is a flowchart showing a processing procedure of the control device according to the present embodiment.

FIG. 4 is a characteristic diagram showing a relationship between a vehicle speed V and a voltage E applied to an electric motor according to the present embodiment.

FIG. 5 is a characteristic diagram showing a relationship between a vehicle speed V and a voltage E applied to an electric motor according to the present embodiment.

FIG. 6 is a characteristic diagram showing the relationship between the correction coefficient K and the temperature T of the electric motor according to another embodiment of the present invention.

[Explanation of symbols]

 11 Vehicle speed sensor 13 Handle 14 Control device 15 Thermistor 16 Servo valve 17 Reservoir tank 21 Gear housing 22 Power cylinder 25 Ball joint B Battery M Electric motor P Pump TH Upper limit temperature TM Warning temperature

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Akihiro Ohno 1-1 Asahi-cho, Kariya city, Aichi Toyota Koki Co., Ltd. (72) Inventor Kazumasa Kodama 1-1-chome Asahi-cho, Kariya city Aichi Incorporated (72) Inventor Takashi Shirai 1-1-1 Asahi-cho, Kariya city, Aichi Toyota Koki Co., Ltd.

Claims (2)

[Claims] 1. A power steering apparatus for generating an assist torque according to a steering force of a steering wheel by using an electric motor, wherein a temperature measuring apparatus for measuring a temperature of the electric motor and a control of the electric motor are performed. A motor control device, wherein the motor control device, when the temperature of the electric motor measured by the temperature measuring device is below a preset warning temperature, a voltage according to the assist torque to be generated, Normal control means for applying to the electric motor, and a voltage reduction control means for applying a voltage lower than the voltage applied to the electric motor by the normal control means when the temperature of the electric motor exceeds the warning temperature, When the temperature of the electric motor exceeds the upper limit temperature set higher than the warning temperature, the voltage applied to the electric motor is set to zero. An electric power steering apparatus comprising: a motor stopping unit that stops the electric motor. 2. The electric power steering apparatus according to claim 1, wherein a temperature sensor is provided on the electric motor as the temperature measuring apparatus.