JPH0299456A - Motor drive device - Google Patents

Abstract

PURPOSE:To prevent the damage of a switching element by a method wherein when an unbalance occurs in a motor current, the current is detected, and when a level exceeds a given value, drive by a motor drive part is stopped, and the feel of a power source is stopped by a relay circuit. CONSTITUTION:A motor drive circuit 4 controls a steering motor 6 according to an output from a torque sensor 2, and a bridge circuit formed with first -fourth switching elements 12-15. In this case, the motor 6 is connected between a common connection point between the first and fourth switching elements 12, 15 and that between the third and second switching elements 14, 13, and a zero phase transformer 16 is mounted to connection lines L1 and L2. An unbalance current flowing when insulation of either end part of the motor 6 from a car body is ruptured and brought into a grounding state is detected through the zero phase transformer 16. When the detecting value attains the threshold of a comparing circuit 19, a drive stop signal is generated, and a relay 21 is energized to release a normally-opened contact.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a power steering motor drive device for driving a steering wheel of a vehicle by a steering motor.

[Conventional technology]

As shown in Japanese Patent Application Laid-Open No. 59-156863, a conventional electric power steering motor drive device has a first motor drive device that is electrically connected when steering in the left and right directions. 2nd and 3rd. A bridge connection is made around the steering motor using a control element such as a fourth transistor. When steering to the right, the first and second control elements are made conductive at the same time based on the detection of the steering torque, and a forward driving current flows through the motor, and when steering to the left, the third control element is made conductive based on the detection of the steering torque. The fourth control element is made conductive at the same time to flow a drive current in the opposite direction to the motor to rotate the motor forward and reverse, respectively, thereby controlling the steering.

[Problem to be solved by the invention]

In such a motor drive device, it is necessary to insulate the lines at both ends of the motor from the vehicle body, but if insulation breakdown occurs, a short circuit will flow and a large current will flow, causing damage to the switching element and sudden battery damage. The drawback was that it was wasted.

The present invention has been made in view of the problems of the conventional motor drive device, and a technical problem is to detect dielectric breakdown of a steering motor and prevent failures due to dielectric breakdown. do.

[Means to solve the problem]

The present invention includes a torque sensor that is connected to a steering shaft and detects its rotational torque, a steering motor that rotates the steering wheel, a first switching element, a fourth switching element, and a third switching element connected to both ends of a power supply. The first switching element, the fourth switching element, and the third switching element are connected in series with the second switching element, respectively.
A bridge circuit configured by connecting a steering motor symmetrically between the common connection ends of the second switching element, and a first switching element of the bridge circuit based on the output from the torque sensor.
2nd or 3rd. A motor drive device comprising: a steering motor drive section that controls the steering motor by driving a fourth switching element; a zero-phase transformer that is attached to a connection line of the steering motor and detects its unbalanced current; A relay circuit that cuts off the power supply to the motor drive unit, and a cutoff that stops control by the motor drive unit and cuts off the power supply via the relay circuit when the unbalanced current detected by the zero-phase transformer exceeds a predetermined level. The invention is characterized in that it has a control means.

[Effect]

According to the present invention having such characteristics, the first, second, or third
．． The fourth switching element is simultaneously opened and closed to rotate the steering motor forward or reverse to realize power steering. A zero-phase transformer is connected to the lines at both ends connected to the steering motor to detect the motor current. Therefore, if an unbalance occurs in the motor current, that current is detected by the zero-phase transformer. If this level exceeds a predetermined value, the drive by the motor drive unit is stopped, and the relay circuit stops the supply of power to the vehicle.

(Effects of the Invention) Therefore, according to the present invention, only the ground fault current can be detected by the zero-phase transformer, and if the ground fault current exceeds a predetermined value, the motor drive device itself can be prevented from operating. This prevents large current from flowing from the power source to the vehicle body and damaging the switching elements.

[Explanation of Examples]

FIG. 2 is a schematic diagram of a power steering mechanism to which the present invention is applied, and FIG. 1 is a block diagram showing the overall configuration of its motor drive circuit. In FIG. 2, a torque sensor 2 and a transmission mechanism 3 for transmitting a steering force from the steering handle 1 are connected to the steering handle 1. The torque sensor 2 detects the torque of the steering wheel l in the left and right direction, and its output is given to the motor drive circuit 4. The motor drive circuit 4 is connected to a battery 5 of the vehicle, and controls a steering motor 6 which is driven in the left and right direction in response to the left and right l/lux signals given from the torque sensor 2. 3, the steering shaft 7 is rotated by a predetermined angle in the left-right direction.

Next, the configuration of the motor drive circuit 4 will be explained with reference to FIG. In this figure, a torque detection signal from a torque sensor 2 is transmitted to a motor drive section 11. Motor drive section 1
Reference numeral 1 determines whether the output of the torque sensor 2 is positive or negative, and drives a switching element, such as a power MO3FET, with a PWM modulated signal having a pulse width corresponding to the level. 1st. Fourth switching element 1
2 and 15 and 3rd. Second switching element 14°13
are connected in series between both ends of the battery 5, respectively. Both ends of the steering motor 6 are symmetrically connected between the common connection points of these switching elements. The first to fourth switching elements 12 to 15 constitute a bridge circuit, and the output of the motor drive section 11 is given to the first to fourth switching elements 12 to 15. Now, as shown in the diagram, the first. The fourth switching element 12.15 and the third switching element 12.15. Second switching element 14.1
A motor 6 is connected between the common connection points of the motors 3 and 3, and a zero-phase transformer 16 is attached to the connection lines LL and L2. The zero-phase transformer 16 detects the unbalanced current flowing through the motor 6, and its output is given to the amplifier 17. The amplifier 17 amplifies the detection signal of the unbalanced current of the motor 6, and the amplified output is given to the full-wave rectifier circuit 18. The full-wave rectifier circuit 18 performs full-wave rectification on the amplified signal, and its output is given to the comparator circuit 19. A predetermined darkness value is set in the comparison circuit 19, and when the level is exceeded, the comparison output is held by the circuit 20.
give to The holding circuit 20 holds the output obtained from the comparison circuit 19 and provides a drive stop signal to the motor drive section 11, and also energizes the relay 21. relay 21
The normally closed contacts are the vehicle's battery 5 and the 1st contact. It is connected between the third switching elements 12 and 14, and cuts off the power supply circuit when energized. Once energized, the relay 21 is configured to open its normally closed contacts even if the power is cut off.

Here, in this figure, the comparison circuit 19 in the motor drive circuit 4
．． The holding circuit 20 and the relay 21 constitute a cutoff control means that cuts off the power when the ground fault current exceeds a predetermined level.

Next, the operation of this embodiment will be explained with reference to the time chart of FIG. The driver uses the steering wheel
When the motor is rotated clockwise, the change in torque is detected by the torque sensor 2 and applied to the motor drive section 11. For example, when a signal from the torque sensor 2 as shown in FIG. 3(a) is transmitted after time t1, the first . The second switching element or the third and fourth switching elements are driven, for example, by pulse width modulation. Therefore, as shown in Fig. 3 (bl), currents 1...1 flow in the two lines Ll and L2 of the motor 6 in symmetrical directions, respectively.
As shown in , even if these currents flow, the zero-phase transformer 16
The output remains at almost zero level.

Now, at time t2, if the insulation of either end of the motor 6 with the vehicle body is broken and a ground fault occurs as shown by the broken line in FIG. 1, the ground fault occurs as shown in FIG. Short circuit current flows. Since this current is an unbalanced current, the zero-phase transformer 16
This signal is amplified by the amplifier 17. Since the amplified output is full-wave rectified and given to the comparison circuit 19, when the dark value of the comparison circuit 19 is reached, a comparison output is obtained as shown in FIG. 3(d) and given to the holding circuit 20. Then, a drive stop signal is given as shown in FIG. At the same time, the relay 21 is energized and the normally closed contacts are opened, as shown in FIG.

Then, power will no longer be supplied from the battery 5 to this motor drive device, and the motor 6 and switching element 12 will no longer be supplied with power.
~14 will be protected.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall configuration of a motor drive device according to an embodiment of the present invention, FIG. 2 is a schematic diagram of an electric power steering mechanism to which the motor drive device according to this embodiment is applied, and FIG. It is a time chart showing the operation. 1・・・・・Steering handle 2・−・−
Torque sensor 3 - - - - Conduction mechanism 4 - - -
- Motor drive circuit 6 - - Steering motor 11 - - Motor drive section 12 - - - - 1st
Switching element 13 - - 1 - - 2nd switching element 14 - - 1 - 3rd switching element 1
5-.-Fourth switching element 16...--
Zero-phase transformer 17... Amplifier 18-... Full wave rectifier circuit 19... Comparison circuit 20--
Holding circuit 21-・-・-Lille Patent applicant Tateishi Electric Co., Ltd. Agent Patent attorney Yoshiki Okamoto (1 other person)

Claims (1)

[Claims] (1) A torque sensor that is connected to the steering shaft and detects its rotational torque; a steering motor that rotates the steering; first and fourth switching elements connected to both ends of the power supply;
and a second switching element connected in series, respectively, and the steering motor is connected symmetrically between common connection terminals of the first and fourth switching elements and the third and second switching elements. a steering motor drive unit that controls a steering motor by driving a first, second, third, or fourth switching element of the bridge circuit based on the output from the torque sensor. The device includes: a zero-phase transformer that is attached to a connection line of the steering motor to detect the unbalanced current; a relay circuit that disconnects power supply to the motor drive device; and an unbalanced current detected by the zero-phase transformer. A motor drive device comprising: a cutoff control means that stops control by the motor drive unit and cuts off power via the relay circuit when a predetermined level is exceeded.