JPH1169881A - Motor drive unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor drive unit in which a relay can be subjected to error free check for short circuit. SOLUTION: The motor drive 10 comprises a circuit 2 for driving a motor 1, a capacitor 3 for smoothing the driving current of the motor 1 connected with the driving circuit 2, a relay 4 interposed between a power supply 5 and the driving circuit 2, and a section 7 for controlling the driving circuit 2 to discharge the smoothing capacitor 3 before a decision is made whether the relay 4 is short-circuited or not, wherein the driving circuit 2 discharges the smoothing capacitor 3 by driving the motor 1 at a predetermined duty or below.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric motor driving device, and more particularly to an electric motor driving device having a function of determining whether a relay provided in a circuit for supplying a current to an electric motor is short-circuited.

[0002]

2. Description of the Related Art Japanese Patent Laying-Open No. 8-108589 discloses a technique in which an abnormality detecting device is provided in a control device of an electric power steering device and a short-circuit check of a fail-safe relay is performed.

In this type of electric motor driving device,
Usually, a smoothing capacitor for smoothing a current supplied to the drive circuit for PWM control is provided between the drive circuit of the electric motor and the relay.

[0004]

The above-described conventional electric motor driving apparatus has the following problems.

When performing a relay short check,
The control unit detects a voltage (hereinafter, referred to as a PIG voltage) between the driving circuit of the electric motor and the smoothing capacitor from a terminal provided between the driving circuit of the electric motor and the smoothing capacitor. The control unit determines that the relay is short-circuited if the PIG voltage is close to the power supply voltage even though the relay is off (open).

Here, the ignition switch is turned on again within a relatively short time (for example, about 30 seconds) after the ignition switch is turned off.
When the switch is turned on, electric charges still remain in the smoothing capacitor. For this reason, since the PIG voltage becomes a high value near the power supply voltage, there is a problem that an erroneous determination that the relay is short-circuited is made even when the relay is not short-circuited.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problem, and an object of the present invention is to turn on the ignition again within a relatively short time (for example, about 30 seconds) after the ignition is turned off. An object of the present invention is to provide an electric motor drive device that can reliably perform a short-circuit check of a relay without erroneous determination even when electric charges remain in a smoothing capacitor that smoothes a current for PWM control.

Another object of the present invention is to provide an electric motor driving device that protects a circuit of an electric motor driving device without damaging the circuit of the electric motor driving device by an excessive current when discharging a capacitor, and erroneously determines a short-circuit check of a relay. It is an object of the present invention to provide an electric motor driving device that can perform the operation without any problem.

[0009]

An electric motor driving apparatus according to the present invention comprises: a driving circuit for driving a motor; a capacitor connected to the driving circuit for smoothing a current for driving the motor;
A relay provided between a power supply and the drive circuit, and a control for controlling the drive circuit so as to discharge the charge stored in the capacitor before determining whether the relay is short-circuited. Section.

According to the electric motor driving device of the present invention, the control unit controls the driving circuit so as to discharge the electric charge stored in the capacity before determining whether or not the relay is short-circuited.

As described above, the short check of the relay is executed after the electric charge stored in the capacitor is discharged. Therefore, even if the ignition is turned on again within a relatively short time (for example, about 30 seconds) after the ignition is turned off, and the electric charge remains in the capacitor for smoothing the current for driving the motor, the relay is turned on. Can be reliably performed without erroneous determination.

In order to discharge the electric charge stored in the capacitor, a method of discharging the smoothing capacitor by simultaneously turning on the upper MOS and the lower MOS of the drive circuit of the electric motor can be considered. I do.

That is, when a short-circuit fault occurs in a relay, a through current flows through the power supply, the short-circuited relay, and the upper and lower MOS transistors of the drive circuit. For this reason, there is a problem that a fatal mode such as a failure of the MOS or a blown fuse is caused.

On the other hand, when the relay is normal (open), the current is increased because the smoothing capacitor is discharged with an impedance of almost 0 ohms (about the ON resistance and the pattern resistance of the MOS). For this reason, there arises a problem that the repetition of such discharge may damage the smoothing capacitor.

Therefore, in one embodiment of the present invention,
The drive circuit may discharge the electric charge stored in the capacitor by driving the motor with a duty value equal to or less than a predetermined duty value.

As described above, since the motor is driven with a low duty value at the time of discharging, the current value flowing through the circuit of the electric motor driving device is limited. For this reason, when discharging the capacity for smoothing the current for driving the motor, the short-circuit check of the relay is reliably performed without erroneous determination while protecting the circuit without damaging the circuit of the electric motor driving device due to excessive current. be able to.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an electric motor driving device according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a configuration of an electric motor driving device 10 according to the present embodiment. The electric motor driving device 10 includes:
It can be used in an electric power steering device and a control device for an electric rear wheel steering device.

The electric motor driving device 10 includes a driving circuit 2 for driving the motor 1, a smoothing capacitor 3, and a relay 4
, A power supply 5, a terminal 6, and a control unit 7.

The drive circuit 2 receives a current from the power supply 5 via the relay 4 and outputs the current to the upper-stage MOSs 151, 152, and 1
53 and the lower MOSs 154, 155, and 156 are PW
M control is performed to control the rotation of the motor 1.

The smoothing capacitor 3 is connected to the drive circuit 2. The smoothing capacitor 3 smoothes the current supplied from the power supply 5 to the drive circuit 2 via the relay 4.

The drive circuit 2 uses the motor coil 21 to turn on the upper MOS 151, turn off the upper MOSs 152 and 153, turn off the lower MOSs 154 and 156, and turn off the lower MOS 15
5 is subjected to PWM control, so that the electric current stored in the smoothing capacitor 3 is discharged by flowing the current from the U phase to the V phase while limiting the current.

The reason why the current is limited in this way is to prevent the circuit of the electric motor driving device 10 from being damaged by an excessive current flowing when the smoothing capacitor 3 is discharged. This current limitation is performed by setting the PWM to a low duty (for example, 10%).

The motor coil 21 to be energized has a U-phase,
Any of the V phase and the W phase may be used. Preferably, from two arbitrary phases to another one, for example, two terminals of V phase and W phase (upper MOSs 152 and 153 corresponding to terminals V and W are turned on) to U phase (lower MOS 154 corresponding to terminal U) Is controlled by PWM.). With such an energizing method, it is possible to discharge the electric charge stored in the smoothing capacitor 3 even when one of the two terminals of the V terminal and the W terminal is disconnected. in this way,
The control unit 7 controls the drive circuit 2 so that the drive circuit 2 discharges the electric charge stored in the smoothing capacitor 3 before determining whether or not the relay 4 is short-circuited.

The control unit 7 is connected to a terminal 6 provided between the drive circuit 2 and the smoothing capacitor 3 and to the power supply 5.
The control unit 7 controls the PIG voltage detected from the terminal 6 and the power supply 5
It is determined whether or not the relay 4 is short-circuited based on the VIG voltage received from.

In determining whether or not the relay 4 is short-circuited, the controller 7 compares the VIG voltage (ECU power supply) with the PIG voltage from the start of discharging of the smoothing capacitor 3. The controller 7 determines that the relay 4 is normal when the PIG voltage becomes lower than the VIG voltage by a predetermined voltage value or more.

On the other hand, even if discharging is continued for a predetermined time, the PIG voltage does not become lower than the VIG voltage by a predetermined voltage value or more.
When the condition that the VIG voltage is equal to or higher than a predetermined voltage (for example, 9 V) is satisfied, the control unit 7 determines that the relay 4 is abnormal.

Note that the VIG voltage is a predetermined voltage (for example,
If it is smaller than 9 V), it is not determined whether the relay 4 is short-circuited. This is because the reliability of the determination result is low because the power supply voltage supplied from the power supply 5 is low.

FIG. 2 shows a procedure of a relay short check process according to the present embodiment. Hereinafter, the procedure will be described step by step.

The drive circuit 2 starts discharging the smoothing capacitor 3 (S31). The control unit 7 determines that the PIG voltage is VIG
It is determined whether the voltage is lower than the voltage by a predetermined voltage value (for example, 4 V or more) (S32).

When the control unit 7 determines that the PIG voltage has become lower than the VIG voltage by a predetermined voltage value or more (for example, 4 V or more), the control unit 7 determines that the relay 4 is normal (S33). ) Then, the process ends (S38).

On the other hand, when the controller 7 determines that the PIG voltage is not lower than the VIG voltage by a predetermined voltage value or more (for example, 4 V or more), after the discharging of the smoothing capacitor 3 is started, The control unit 7 determines whether a predetermined time (for example, 2 seconds) has elapsed (S34).

If the control unit 7 determines that the predetermined time (for example, 2 seconds) has not elapsed, the process returns to S32, and the control unit 7 again determines that the PIG voltage is higher than the VIG voltage by a predetermined voltage (for example, 4 V). It is determined whether or not it has become lower.

On the other hand, if the control unit 7 determines that a predetermined time (for example, 2 seconds) has elapsed, the control unit 7 determines whether the VIG voltage is equal to or higher than a predetermined voltage (eg, 9 V or higher) ( S35).

The VIG voltage is equal to or higher than a predetermined voltage (for example, 9 V
If the control unit 7 determines that
Determines that the relay 4 is abnormal (S36).

On the other hand, when the control unit 7 determines that the VIG voltage is not higher than the predetermined voltage (for example, 9 V or higher), or when the control unit 7 determines that the relay 4 is abnormal (S36), the control unit 7 turns on the lamp. Is turned on (S37), and then the process ends (S38).

The above-mentioned predetermined voltage and predetermined time are values experimentally obtained in consideration of low voltage / high voltage, low temperature / high temperature, cranking, variation in capacitor capacitance, and the like. In the electric motor driving device according to the present embodiment, the predetermined voltage and the predetermined time are 4 V and 2 seconds, respectively, but these numerical values are not limited to these, and these numerical values are If the constants and the like are different, different values can be obtained.

In the present embodiment, the PIG voltage is set to VIG
Although an example in which the relay is compared with the voltage has been described, the present invention is not limited to this, and it is determined whether the relay is normal based on the absolute value of the PIG voltage, for example, based on a criterion for determining whether the PIG voltage is 3 V or less. It is also possible to do Note that P
The reason why the IG voltage is compared with the VIG voltage is to make it possible to more reliably determine the fluctuation of the power supply voltage.

As described above, according to the present embodiment, PW
After the electric charge stored in the smoothing capacitor 3 for smoothing the current for the M control is discharged, a short check of the relay 4 is performed.

Therefore, within a relatively short time (for example, about 30 seconds) after the ignition is turned off, the ignition is turned on again.
Even if the charge is turned on and the charge remains in the smoothing capacitor 3, the relay 4 is short-checked after the charge is discharged. Therefore, the short check of the relay 4 can be reliably performed without erroneous determination.

The drive circuit 2 uses the motor coil 21 to perform PWM control on the lower MOSs 154, 155, and 156 from the U-phase to the V-phase, for example, with a duty value equal to or less than a predetermined duty value. By driving 1, the charge stored in the smoothing capacitor 3 is discharged.

As described above, by driving the motor 1 with a low duty value at the time of discharging, the current value flowing through the circuit of the electric motor driving device 10 is limited. For this reason,
Even if the relay 4 is short-circuited, the MO
A fatal mode such as failure of S or blown fuse will not occur. Further, even when the relay 4 is normal (open), the short check of the relay 4 can be reliably performed without erroneous determination without damaging the smoothing capacitor 3.

[0043]

According to the electric motor driving device of the present invention, the short-circuit check of the relay is performed after the capacity for smoothing the current for the PWM control is discharged.

As a result, even if the ignition is turned on again within a relatively short time (for example, about 30 seconds) after the ignition is turned off and a charge remains in the capacitor, the relay short-circuit check is erroneously determined. Without fail.

According to the electric motor driving device according to the second aspect of the present invention, the motor is driven with a low duty value at the time of discharging, so that the current value flowing through the circuit of the electric motor driving device is limited.

Thus, during discharging of the capacity, an excessive current does not flow to damage the circuit of the electric motor driving device, and the short-circuit check of the relay can be reliably performed without erroneous judgment while protecting the circuit. .

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an electric motor drive device according to the present embodiment.

FIG. 2 is a flowchart illustrating a procedure of a relay short check process according to the present embodiment.

[Explanation of symbols]

 Reference Signs List 1 motor 2 drive circuit 3 smoothing capacitor 4 relay 5 power supply 6 terminal 7 control unit

Claims (2)

[Claims] A driving circuit for driving the motor; a capacitor connected to the driving circuit for smoothing a current for driving the motor; a relay provided between a power supply and the driving circuit; A control unit that controls the drive circuit so as to discharge the electric charge stored in the capacitor before determining whether or not is short-circuited. 2. The electric motor drive device according to claim 1, wherein the drive circuit discharges the electric charge stored in the capacity by driving the motor with a duty value equal to or less than a predetermined duty value.