JPH02155875A - Motor driving device - Google Patents

Abstract

PURPOSE:To prevent an obstruction caused by the breakage of insulation in a power steering by comparing the driving signals of first and second or third and fourth switching elements with a motor connecting portion voltage and stopping driving when they fail to conform. CONSTITUTION:Based on the torque signal from a torque sensor 2, the first and second or the third and fourth switching elements 22, 27, 23, 26 of a motor driving circuit 4 are simultaneously opened/closed to normally/reversely rotate a steering motor 6. The outputs of gate circuits 16a, 16b for driving the switching elements are compared with the outputs of the drains of the switching elements (PET) 26, 27 by comparing circuits 29, 30 respectively and, when they fail to conform, a flip-flop 32 is set via an OR circuit 31 to turn off a transistor Tr1 and stop the drive of the motor 6. Thereby, even if a signal is erroneously give at the time of earthing, no large current flows in the motor improving safety.

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 and FIG. 5, a conventional electric power steering motor drive device has two first and second motors that are electrically conductive when steering in the left and right directions. 2nd and 3rd. Control elements 101 to 10 such as fourth transistors
4 is used to connect the steering motor 105 in a bridge manner.

When steering to the right, the first control is performed based on the detection of the steering torque.
The second control element is made conductive at the same time to supply a positive driving current to the motor, and when steering to the left, the third control element is turned on 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. By selectively making the first or third control element conductive, and then making the second or fourth control element intermittently conductive by changing the duty ratio according to the required driving force of the motor, Electric power steering devices that vary the torque of a motor have also been proposed.

[Problem to be solved by the invention]

However, in such a motor drive device, it is necessary to insulate the terminals at both ends of the motor from the vehicle body, but insulation breakdown may occur and, for example, as shown by the broken line in Figure 5, one end of the motor may connect to the vehicle's ground terminal. In the event of a short circuit (hereinafter referred to as a ground fault), a large current flows through the motor 105 in the direction of the arrow while the control element 101 is conducting, causing the handle to be pulled in one direction, which is extremely dangerous. Furthermore, if the control element 103 is conductive during a ground fault, a large current will flow through the control element, resulting in damage to the control element and rapid wear and tear on the battery.

The present invention has been made in view of the problems of the conventional motor drive device, and includes a steering motor! !
1! ! The technical challenge is to detect edge breakdown and to be able to prevent problems associated with dielectric breakdown.

[Means to solve the problem]

The present invention includes a torque sensor connected to a steering shaft to detect its rotation I and torque, a steering motor for rotating the steering wheel, and a first sensor connected to both ends of a power source. a fourth switching element; and a third switching element. the first and fourth switching elements, the third .
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 steering motor drive unit that controls a steering motor by driving a fourth switching element, the motor drive device comprising: a steering motor drive unit that controls a steering motor by driving a fourth switching element;
2nd or 3rd. The drive signal for the fourth switching element and the first . signal comparison means for comparing the voltages of the connection parts between the second, third, and fourth switching elements and the motor; signal holding means for holding the mismatched signals obtained from the signal comparison means; First. 2nd or 3rd. The present invention is characterized in that it has a cutoff control means for stopping driving of the fourth switching element.

[Effect]

According to the present invention having such characteristics, the first, second, third, .
The fourth switching element is simultaneously opened and closed to rotate the steering motor forward or reverse to realize power steering. In the steering motor, a signal comparing means compares a drive signal for driving a switching element with a voltage actually obtained at one end of the motor. If these signals match, it is considered that the motor is being driven by the control signal, but if these signals no longer match, a large current is flowing through the motor due to a ground fault, causing a malfunction. be judged. Therefore, in that case, the comparison output is temporarily held and the power supply to the motor is stopped using that output.

〔Effect of the invention〕

Therefore, according to the present invention, if a ground fault occurs in which one end of the motor is short-circuited to the vehicle, the control signal and the motor voltage do not match, so the signal comparison means immediately determines the mismatch state and starts driving the motor. will be suspended.

Therefore, there is no possibility that a large current will flow through the motor due to the erroneous application of a signal in the event of a ground fault, and the effect that the handle will not be taken off can be achieved. Therefore, it becomes possible to improve the safety of the power steering device.

[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 that drives in the left and right direction in response to a left and right torque signal given from the torque sensor 2. The steering wheel 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 circuit 4. The motor drive circuit 4 current-amplifies the output of the torque sensor 2 using a differential amplifier circuit 11.
differential amplifier 12. The output of the operational amplifier 13 is applied to the other input terminal of the differential amplifier circuit 12, and this differential amplified output is applied to a torque control signal, a PWM circuit 14, and a polarity discrimination circuit 15. The PWM circuit 14 has a sawtooth wave generator and obtains a pulse width modulated signal by comparing it with the torque control signal given from the differential amplifier 12, and its output is sent to the gate circuit 1.
6a, 16b. The polarity determining circuit 15 determines the polarity of the torque signal from the differential amplifier 12, thereby activating one of the gate circuits 16a and 16b and driving a pair of photocouplers 17 and 18. The cathode ends of the photocouplers 17a and 18a on the light emitting side are connected to the collector of the transistor Trl. Light receiving sections 17b and 18b of photocoupler 1718
The outputs of are given to upper FET drivers 20 and 19, respectively. The upper FET driver 19.20 has a drive power supply 2.
1 output is given, and the upper FET drivers 19 and 20 are alternatively driven by this power supply. Upper FET
Drivers 19 and 20 selectively drive upper FETs 22 and 23, respectively. Also, AND circuits 16a, 16
The outputs of b are given to lower FET drivers 24 and 25, respectively, and lower FETs 26 and 27 are driven via these drivers. FET22゜23 and 26.27 are the source of FET22, the drain of FET26, and the FE
The source of T23 and the drain of FET 27 are commonly connected, and the steering motor 6 and current detection resistor 28 are connected between the connection points, and the other end of the FET is connected to both ends of the battery 5, which is a power source, forming a bridge circuit. are doing. Here, the upper FETs 22 and 23 are the first and second transistors, respectively. The third switching elements, FETs 26 and 27 are connected to the fourth switching elements, FETs 26 and 27, respectively. Second
It constitutes a switching element. Now, gate circuit 1
The outputs of FETs 6a and 16b and the drains of FETs 26 and 27 are applied to signal comparison circuits 29 and 30, respectively. The signal comparison circuits 29 and 30 are signal comparison means for determining whether these signals match, and provide an output to the OR circuit 31 when the two input signals do not match.

The OR circuit 31 sets the flip-flop 32 based on the OR signal. flip flop 3
2 is reset when the power is turned on, and the Q output controls the transistor Tri to turn off. Here, the OR circuit 31 and the flip-flop 32 constitute a signal holding means that holds the output of the signal comparison means, and the transistor Tr1 and the photo couplers 17 and 18 act as a cutoff that stops driving the motor based on this holding output. It constitutes a control means.

Next, the detailed configuration of the signal comparison circuit 29 and its peripheral circuits will be explained with reference to FIG. The polarity determination circuit 15 has operational amplifiers 15a and 15b, and uses the output thereof to selectively operate gate circuits 16a and 16b and photocouplers 17a and 18a. The output of the gate circuit 16a is applied to an integrating circuit including a capacitor CI of a signal comparison circuit 29, and the integrated output is applied to a comparator 41. A predetermined threshold value Vrefl is set in the comparator 41, and the integrated output is discriminated based on this output, and the output is given to the NOR circuit 43 via the inverter 42.

Further, the voltage at the drain end of the FET 26 is applied to the l transistor Tr2 via a resistance divider circuit, and its inverted output is applied to an integrating circuit having a capacitor C2. Similarly, the integral output is applied to the input terminal of comparator 44. A predetermined threshold value Vref2 is similarly set in the comparator 44, and a comparison output is given to the NOR circuit 43. The NOR circuit 43 provides its OR output to the aforementioned OR circuit 31. The other signal comparison circuit 30 also has a similar configuration. The signal from the OR circuit 31 is applied to the seven input terminals of the flip-flop 32, and the Q output is connected to the base of the transistor Tri through a diode, thereby simultaneously turning on and off the photocouplers 17 and 18.

Further, both ends of a resistor 28 connected in series with the steering motor 6 are applied to an operational amplifier 13, and its current output is applied to one input end of a differential amplifier 12 as a torque control signal.

Next, the operation of this embodiment will be explained with reference to waveform diagrams. A torque control signal is applied from the differential amplifier 12 to the PWM circuit 14 and the polarity discrimination circuit 15 based on the signal from the torque sensor 2 and the current output flowing to the steering motor 6 shown in FIG. Figure 4(a) shows this P
The motor is in a stopped state before time t1, the motor drive amount gradually increases at time t+'''tz, and after time t2, a pulse width modulation signal with a duty of 100% is a gate I circuit. 16a or 16b to the lower FET drivers 24..25. At this time, the polarity determining circuit 15 drives which photocoupler, for example the photocoupler 18a.

Since the flip-flop 32 is reset when the power is turned on, the transistor Tri is in an on state, and the output of the polarity determination circuit 15 drives the foI coupler 17a, and the power MO3 is outputted via the upper FET driver 2o.
The FET 23 is continuously conductive, and at this time, the lower FET 26 is pulse-driven as shown in FIG. Comparator 41 shown in the figure
As shown in FIG. 4(b), a signal integrated based on the PWM signal is obtained at the input end of the PWM signal. Then, it is determined based on the threshold level Vrefl of the comparator 41, and a signal that becomes the "■" level after time L3 is obtained at the output terminal of the inverter 42 as shown in FIG. 4 (C1).On the other hand, this PWM Depending on the signal, a voltage as shown in FIG. 4 Fdl is obtained at the drain of the FET 26,
This signal is applied to the integrating circuit via the transistor Tr2. Therefore, a signal as shown in FIG. 4 (el) is obtained at the input terminal of the comparator 44, and a signal as shown in FIG.
At time t4 exceeding f2, the output becomes rLJ level. Since this signal is applied to the NOR circuit 43, a signal of r L J level is obtained from the NOR circuit 43 as shown in FIG. 4(g). Also, when the torque control signal is reversed by operating the handle 1 in the opposite direction, the gate circuit 16b is
The FET 22 is continuously driven by the photocoupler 18, and the FET 27 is pulse driven. At this time as well, these signals are compared by the signal comparison circuit 30, and if these signals match, no signal is given to the OR circuit 31. Now, time t.

Thereafter, if one end of the steering motor 6 short-circuits with the vehicle body as shown by the broken line in Fig. 1 and a ground fault occurs, P
Since the motor is short-circuited even when the WM signal is not generated, one terminal of the steering motor 6, that is, the drain voltage of the MO3FET 26 becomes almost zero, as shown in FIG. 4Fdl. Therefore, as shown in FIG.
Both inputs of 3 are at the "■," level. Therefore, a signal of rHJ level is applied from the NOR circuit 43 to the OR circuit 31, and the flip-flop 32 is set. Therefore, the Q output of the flip-flop 32 becomes "L" and the transistor Tr1 is turned off. Therefore, photo coupler 17
Or, the signal is no longer transmitted from 18 to upper FET drivers 19 and 20, and these drivers are not driven and FET
ET22 and 23 remain non-conductive. Therefore, no drive current flows through the steering motor 6. In this way, in a ground fault condition where one end of the steering motor 6 is shorted to the vehicle body, the drive of the steering motor 6 can be immediately stopped and steering assistance can be stopped. .

In this embodiment, when a ground fault is detected, the drive signal to the upper FET driver is stopped.
2 and 23 are in the off state, but the gate circuit 16a
, 16b or the PWM circuit 14, the NOR FETs 26 and 27 may be made non-conductive at the same time.

Further, in this embodiment, the drive signal given to the lower FET driver and the voltage of the switching element at that time are detected, but this method also applies when the switching element is controlled in an analog manner by the gate voltage without pulse driving. A ground fault condition can be similarly detected by comparing the drive signal and the drain voltage.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the 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. 3 is a block diagram showing the configuration of a motor drive device according to an embodiment of the present invention. FIG. 4 is a circuit diagram showing the signal comparison circuit and its peripheral parts in detail, FIG. 4 is a waveform diagram showing waveforms of each part of this embodiment, and FIG. 5 is a diagram showing the main parts of a conventional electric power steering device. . 1--------Handle 2-----) Lux sensor 4--Motor drive circuit 5-----Battery 12-Differential amplifier 14----- P W M
Circuit 15 Polarity discrimination circuit 16 a, 16
b------Gate circuit 17. I8---Photocoupler 1920, 24, 25--
-FET driver 22゜23, 26,
27-------Power MO3FET 29,
30------ Signal comparison circuit 3 k------
-OR circuit 32-1---Flip-flop 41
,44・-1111 Comparator patent applicant Tateishi Electric Co., Ltd. agent Patent attorney Kanki 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. In the apparatus, a signal that compares the drive signal of the first, second, third, or fourth switching element with the voltage of the connection portion between the first, second, third, or fourth switching element and the motor, respectively. a comparison means; a signal holding means for holding a discrepancy signal obtained from the signal comparing means;
A motor drive device comprising: cutoff control means for stopping driving of the fourth switching element.