JPH06263053A - Motor-driven pump type power steering device - Google Patents

Abstract

PURPOSE:To restrain generation of heat of an electric motor of a motor-driven pump by PWM control by using DC high voltage electric power supply in a motor driven pump type power steering device. CONSTITUTION:An ECU14 to which a battery B being DC high voltage electric power supply carries out PWM control on an electric motor M of a motor driven pump according to output signals from a vehicle speed sensor 11 and a steering sensor 12. Operating fluid sent out from the pump P arranged integrally with the electric motor M is supplied to a servo valve 16, and generates assist torque. A choke coil 18 is connected in series between it and a positive electrode side connecting terminal of the electric motor M connected to the ECU14. Thereby, since voltage impressed upon the electric motor M is smoothed and a rise time inclination of an electric current is leveled moderately, generation of heat in a brush part or the like can be restrained.

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 mounted on an electric vehicle.

[0002]

2. Description of the Related Art Conventionally, there is known an electric vehicle that uses a direct current high voltage of 288 V, for example, as a power supply voltage and directly supplies it to a driving electric motor (main engine). In addition to the drive electric motor for the main engine, the electric pump electric motor is mounted in the electric pump type steering device. In the electric motor of this electric pump or the like, a DC / DC converter (voltage step-down device) is used to convert the power supply voltage of 288 V into a voltage of 12 V and is supplied with power for auxiliary machinery.

[0003]

The above-mentioned DC /
In the voltage conversion using the DC converter, there is a problem that heat generation is large and energy conversion efficiency is low. Therefore, using an electronic control unit (hereinafter referred to as ECU),
It was found that the method of directly applying the power supply voltage of 288 V to the electric motor of the electric pump by PWM control can be applied. However, since the battery voltage (power supply voltage 288 V) is instantaneously applied to the electric motor of the electric pump,
In particular, the heat generation around the brush of the electric motor becomes large, which causes a new problem that the motor may be burned. As a result of intensive studies on the above problems, the inventors have provided a new electric pump type power steering apparatus as follows.

The present invention has been made to solve the above problems, and an object thereof is to suppress heat generation of an electric motor of an electric pump by PWM control using a DC high voltage power supply. It is to provide a possible electric pump type power steering device.

[0005]

The structure of the invention for solving the above problems is an electric pump type power steering system in which an assist torque controlled by fluid pressure by an electric pump mounted in an electric vehicle is applied to a steering device. A device,
A DC high-voltage power supply mounted on the electric vehicle, an electronic control unit that supplies the DC high-voltage power supply to the electric motor of the electric pump by PWM control, and both connections of the electronic control unit and the electric motor of the electric pump At least one of the terminals and the choke coil connected in series is provided.

[0006]

According to the above-mentioned means, the DC high voltage power source outputs the PWM controlled DC high voltage composed of the repetitive voltage in which 0V and the power source voltage alternately appear by the electronic control unit. This sliced DC high voltage PWM output is
The choke coil connected in series with the electric motor of the electric pump provides a smoothed voltage waveform in which a voltage higher than 0 V and a voltage lower than the power supply voltage alternately appear. A PWM output composed of this smoothed voltage waveform is supplied to the electric motor. Therefore, the current due to the smoothed voltage waveform applied to the brush of the electric motor of the electric pump decreases, and the rising slope of the current becomes gentle.

[0007]

EXAMPLES The present invention will be described below based on specific examples. FIG. 1 is a configuration diagram showing an electric pump type power steering apparatus according to the present invention. Electric pump type power steering device (E
HPS: Electro Hydraulic Power Steering) has the following configuration. The vehicle speed sensor 11 detects the vehicle speed V of the electric vehicle, and the steering sensor 12 detects the steering angle θ of the steering wheel 13. E
Output signals from the vehicle speed sensor 11 and the steering sensor 12 are input to the CU 14. In addition, the ECU 14
A battery B, which is a DC high voltage power source (288V), is connected to.

Further, P is a pump rotated by an electric motor M, and an electric pump is composed of the electric motor M and a pump P which is arranged integrally with the electric motor M, and the working fluid sent from the pump P is a servo valve. 16 are supplied. E above
A choke coil 18 is connected in series between the positive electrode side connection terminal of the electric motor M connected to the CU 14.
Further, a flywheel diode 19 for flowing a current when the circuit is disconnected in the ECU 14 is connected in parallel to the electric motor M. The choke coil 18 may be connected in series to the negative electrode side connection terminal side of the electric motor M.

Reference numeral 21 is a gear housing composed of a rack and pinion gear. Reference numeral 22 is a power cylinder that generates an assist torque (auxiliary steering force). As described above, the supply / discharge of the working fluid to / from the power cylinder 22 is controlled by the servo valve 16, and the ball joint 25 is operated via the steering rods 24 on the left and right of the piston 23 of the power cylinder 22 to rotate the steering wheel (not shown). To move. The excess working fluid in the servo valve 16 is returned to the reservoir tank 17 and sent out to the pump P again.

Next, the operation will be described with reference to FIG. 2 showing the waveforms of the PWM output voltage and current at points A and B in FIG. Based on the output signals from the vehicle speed sensor 11 and the steering sensor 12, the ECU 14 calculates a control voltage of the electric motor M so as to obtain a desired rotation speed, and executes PWM control by a known switching element. Then, as shown by the alternate long and short dash line in FIG. 2, a sliced PWM output voltage E _{A in} which 0 V and the maximum peak value 288 V alternately appear is output. The current at this time has a waveform I having a steep rising slope, as indicated by the alternate long and short dash line in FIG.
It becomes _A. This PWM output voltage E _A has its voltage value smoothed by the choke coil 18, and as shown by the solid line in FIG. 2, for example, the minimum peak value 50V and the maximum peak value 100V.
The PWM output voltage E _{B in the} form of a slice appears alternately and is applied to the electric motor M. Then, the current actually flowing through the electric motor M has a smooth waveform I _B with a gentle rising slope, as shown by the solid line in FIG.

As described above, the waveform of the current flowing through the electric motor M has a gentle rising slope and a smooth slope.
A large arc will not fly at the brush part,
In addition, the effective current is reduced and heat generation is suppressed. Therefore, burning of the electric motor M is prevented. If the amount of heat generated by the electric motor M is reduced, the heat sink (radiating plate) in the motor casing can be downsized. Furthermore, the electric capacity for the electric pump type power steering device is set to DC / DC.
Since it is not necessary to make it by the converter, the electric capacity for other auxiliary machines can be small, and as a result, the DC / DC converter can be downsized.

[0012]

As described above, the DC high voltage of the battery PWM-controlled by the ECU is smoothed and applied by the choke coil to the electric motor of the electric pump. Therefore, the current flowing through the electric motor has a gentle rising gradient and is averaged, and heat generation in the brush portion or the like is suppressed as much as possible. Therefore, there is an effect that the electric motor is prevented from being burnt out and the heat sink can be downsized.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an electric pump type power steering apparatus according to a specific embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a difference between a PWM output voltage and a current at points A and B in FIG.

[Explanation of symbols]

 14 ... ECU (electronic control unit) 18 ... Choke coil B ... Battery (DC high voltage power supply) M ... Electric motor P ... Pump

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takuya Okubo 1-1-1, Asahi-cho, Kariya city, Aichi prefecture Toyota Koki Co., Ltd.

Claims (1)

[Claims] 1. An electric pump type power steering apparatus in which an assist torque controlled by a fluid pressure by an electric pump mounted on an electric vehicle is applied to a steering device, the direct current high voltage power source mounted on the electric vehicle. And the DC high voltage power supply to the electric motor of the electric pump.
An electronic control device that is supplied by WM control; and a choke coil that is connected in series to at least one of the electronic control device and both connection terminals of the electric motor of the electric pump. Electric pump-type power steering device that