JP2003033082A - Motor drive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor drive of a motor power steering system in which the assist direction of an assist motor 8 can be determined through simple circuitry and a decision can be made that the motor drive is abnormal upon occurrence of reverse assist. SOLUTION: A relay circuit 12a, a current detection resistor 21, and a bridge circuit 22 of FETs 22a-22d are connected sequentially in series between the positive electrode of a battery 13 and the earth and the assist motor 8 is connected between common joints P1 and P2 . Voltages at the joints P1 and P2 are detected by voltage monitor circuits 23a and 23b and taken into a sub- microcomputer 24S. The sub-microcomputer 24S estimates the direction of motor current (i.e., the assist direction of the assist motor 8) from the magnitude of a voltage detected across the motor and makes a decision that reverse assist has occurred (an abnormality is present) when the assist direction is different from the direction of steering torque detected by a torque sensor 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive device for an electric motor capable of discriminating the driving direction of the electric motor with a simple circuit structure, and for example, an assist motor for generating a steering assist force to a steering system of a vehicle. The present invention relates to an electric power steering device that has a device that can determine the assist direction of an assist motor.

[0002]

2. Description of the Related Art Generally, an electric power steering apparatus is constructed as shown in FIG. In FIG. 5, the steering wheel 1 is the first steering shaft 2
It is connected to the second steering shaft 2b via a and the universal joint 3.

The second steering shaft 2b is
It is connected to a tie rod 6 of a steering wheel via a pinion 4 and a rack 5. Second steering shaft 2
A torque sensor 7 for detecting the steering torque of the steering wheel 1 is provided at b, and an assist motor (DC electric motor) 8 for assisting the steering force of the steering wheel 1 is coupled to the second steering shaft 2b via a reduction gear 9. Has been done. Reference numeral 10 denotes a vehicle state detection device that detects a running state of the vehicle such as engine speed, vehicle speed, and steering wheel load by a sensor.

Reference numeral 11 denotes a motor drive current (target current command value) from the detection output of the vehicle state detection device 10, the detection torque of the torque sensor 7, the detection current obtained from a current detector (not shown), a voltage detector, detection voltage, etc. ) Is obtained and the current supplied to the assist motor 8 is controlled based on the target current command value, and is composed of, for example, a microcomputer.

Reference numeral 12 is a relay which is turned on by turning on a key switch of an ignition key and is turned off, for example, in case of a malfunction. The controller 11 and the assist motor 8 are driven by the power source of the battery 13 supplied via the relay 12.

In the apparatus constructed as described above, the motor drive control section of the controller 11 drives the assist motor 8 to add the assist torque to the steering torque to improve the operability of the steering wheel 1.

At this time, in order to prevent the assist motor 8 from being driven (that is, reverse assist) in the direction opposite to the steering assist direction (steering torque detection direction of the torque sensor 7) due to the influence of external force or the like. It is necessary to determine the assist direction of the assist motor 8.

In order to determine the assist direction of the assist motor, for example, as disclosed in Japanese Patent Laid-Open No. 10-264842, the direction of rotation of the assist motor is determined by the detected current value of the assist motor and the terminal voltage of the motor. There is a method of estimating.

For example, as disclosed in JP-A-2-246870 and JP-A-3-186477, a bridge is connected to a motor drive circuit (bridge circuit in which semiconductor control elements such as FETs are bridge-connected). There is a method in which a resistor for detecting the generated current is provided and the terminal voltage of the resistor is input to the differential amplifier to detect the rotation direction of the motor.

[0010]

However, in the assist direction determination method disclosed in the above-mentioned Japanese Patent Laid-Open No. 10-264842, in addition to the motor terminal voltage detection means, the motor drive circuit for obtaining the motor current detection value. There is a problem that a shunt resistor or the like bridged to the (bridge circuit) is required, which causes an increase in cost.

Further, there is a drawback that the control must be performed in consideration of the current detection value due to the shunt resistance, and the parameters increase correspondingly and the circuit configuration becomes complicated.

Further, the assist direction determining method disclosed in Japanese Patent Laid-Open No. 2-246870 and Japanese Patent Laid-Open No. 3-186477 requires not only a resistor bridged in a motor drive circuit (bridge circuit). However, there is a problem that the circuit configuration including the differential amplifier becomes complicated.

The present invention has been made in view of the above points, and an object thereof is to be able to determine the driving direction of an electric motor with a simple circuit configuration, and to determine the driving direction indicated by the driving direction instruction signal of the electric motor and the electric motor. If the driving direction is opposite,
For example, it is an object of the present invention to provide a drive device for an electric motor that can determine an abnormality of the device when reverse assist occurs.

[0014]

A drive device for an electric motor according to the present invention for solving the above-mentioned problems includes a bridge circuit which is connected between positive and negative power source buses of a DC power source and bridge-connects semiconductor control elements. , A motor connected between a common connection point of the positive side arm and the negative side arm of the bridge circuit, a voltage value detecting means for detecting a voltage value of both terminals of the electric motor, and a magnitude judgment of the voltage value of both terminals. It is characterized by having a voltage magnitude discriminating means and a drive direction discriminating means for discriminating the drive direction of the electric motor based on the magnitude relation of the terminal voltages discriminated by the voltage magnitude discriminating means.

Further, when the drive direction of the electric motor discriminated by the drive direction discriminating means is different from the drive direction instruction signal of the control section for controlling the driving of the semiconductor control element of the bridge circuit, it is judged that the apparatus is abnormal. It is characterized by having a judging means.

Further, the electric motor is composed of an assist motor in an electric power steering apparatus, and the drive direction discriminating means is composed of an assist direction discriminating means for discriminating an assist direction based on a drive direction of the assist motor, and a steering shaft is provided. When the steering assist direction detected by the provided steering assist direction detecting unit and the assist direction of the assist motor discriminated by the assist direction discriminating unit are different from each other, an abnormality judging unit for judging that the apparatus is abnormal is provided. I am trying.

[0017]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment in which the present invention is applied to the electric power steering apparatus of FIG. 1, the same parts as those in FIG. 5 are designated by the same reference numerals.

In FIG. 1, the positive electrode side of the battery 13 has a field effect transistor (hereinafter referred to as FET) 22a through a relay circuit 12a and a current detecting resistor 21.
It is connected to a bridge circuit 22 formed by connecting 22d in a bridge.

A common connection point P of the FETs 22a and 22c
_The assist motor 8 is connected between ₁ and the common connection point P ₂ of the FETs 22b and 22d. FET 22c
The common connection point of 22 and 22d is grounded (connected to the negative electrode side of the battery 13).

The voltage at the common connection point P ₁ on one terminal side of the assist motor 8 is detected by the voltage monitor circuit 23a (voltage value detecting means of the present invention), and the detected voltage value signal is obtained by the sub-microcomputer 24 _S. Will be introduced to.

The voltage at the common connection point P ₂ on the other terminal side of the assist motor 8 is detected by the voltage monitor circuit 23b (voltage value detecting means of the present invention), and the detected voltage value signal is obtained by the sub-microcomputer 24 _S. Will be introduced to.

This sub-microcomputer 24 _S is
A voltage magnitude discriminating function for discriminating the magnitude of the voltage value of both terminals (P ₁ , P ₂ ) of the assist motor 8 guided from the voltage monitor circuits 23a, 23b, and the assist motor depending on the magnitude relation of the discriminated terminal voltages. 8, the assist direction determination function for determining the rotation direction, that is, the assist direction, the detection assist torque direction of the torque sensor 7, and the steering assist direction obtained from the detected torque signal are different from the assist direction of the assist motor 8. In this case, it has an abnormality judging function for judging that the apparatus is abnormal.

The voltage magnitude discriminating function and the assist direction discriminating function of the sub-microcomputer 24 _{S use} the detected voltage values (equivalent to the voltages at both terminals P ₁ and P ₂ of the assist motor 8) from the voltage monitor circuits 23a and 23b. By comparison, it is executed by estimating the motor current direction by utilizing the fact that the motor current flows from the terminal side having a high voltage to the terminal side having a low voltage.

The abnormality determining function is used when the steering assist direction by the detected torque is different from the estimated motor current direction (assist direction of the assist motor 8), that is, in the steering torque-motor current characteristic diagram of FIG. When it is in the reverse assist determination area shown, it is determined that there is an abnormality, and in that case, control is performed to cut off the power supply to the assist motor 8.

Reference numeral 24 _M is a main microcomputer, which takes in the voltage detected by the current flowing through the current detecting resistor 21 via the operational amplifier 25, the torque detection signal of the torque sensor 7 and the like, and outputs the motor drive current (target). It has a function of calculating a current command value) and controlling a current supplied to the assist motor 8 based on the target current command value.

26 is a main microcomputer 24 _M
And a relay that excites the coil of the relay circuit 12a to turn on its contact, or turns off the contact by deactivating the coil based on a control signal introduced from the sub-microcomputer 24 _S via the AND gate 27a. It is a drive circuit.

A control signal for an enable signal is input to the AND gate 27b from the main microcomputer 24 _M and the sub microcomputer 24 _S , and the gate output (enable signal) of the AND gate 27b is supplied to each of the AND gates 27c and 27d. It is input to one of the input terminals.

The target current command signal from the main microcomputer 24 _M is supplied to the other input terminal of each of the AND gates 27c and 27d, and each output terminal is connected to the predrivers 28a and 28b.

The pre-driver 28a, 28b is a pulse width modulation duty ratio is determined based on the target current command value calculated by the main microcomputer 24 _M (PW
M) signal is transferred to the FETs 22a, 2 of the bridge circuit 22.
It is a pre-driver that supplies each gate of 2b to control the FET on and off.

[0030] 28c, 28d is a control signal from the main microcomputer 24 _M, the period bridge circuit 22 for driving the assist motor 8 FET22c, 2
Continuous drive signal (ON control signal) to each 2d gate
Is a pre-driver to supply.

The voltage monitor circuits 23a and 23b are constructed, for example, as shown in FIG. That is, the resistor 31 connected in series between _one terminal P ₁ of the assist motor 8 and the ground.
a and 32a and a noise removing capacitor 33a connected in parallel to the resistor 32a constitute a voltage monitor circuit 23a, and resistors 31b and 32b connected in series between the other terminal P ₂ of the assist motor 8 and the ground and the resistor A voltage monitor circuit 23b is configured with a noise removing capacitor 33b connected in parallel with 32b.

The common connection point (voltage division point) potential of the resistors 31a and 32a and the common connection point (voltage division point) potential of the resistors 31b and 32b are set to the sub-microcomputer 2
Introduced in 4 _S. The capacitors 33a and 33b
Is set to a capacitance that does not affect the PWM control of the FETs 22a and 22b.

Signals are exchanged between the main microcomputer 24 _M , the sub microcomputer 24 _S and its peripheral circuits via an interface not shown.

Next, the operation of the apparatus configured as described above will be described with reference to the reverse assist detection flowchart of FIG. First, during normal operation of the device, for example, a high-level signal is supplied from the main microcomputer 24 _M and the sub-microcomputer 24 _S to the AND gate 27a, and the relay drive signal output from the relay drive circuit 26 causes the relay circuit 12a to operate. The coil is energized, its contact is turned on, and power is supplied from the battery 13 to the bridge circuit 22.

A high level signal is supplied from the main microcomputer 24 _M and the sub microcomputer 24 _S to the AND gate 27b, and the AND gates 27c and 27d are output by the output signal (high level enable signal) of the AND gate 27b. A high level signal is input to one of the input gates.

The FET 22a or 22 of the bridge circuit 22
b is subjected to pulse width modulation control by the pre-driver 28a or 28b, and the FET 22c or 22d is continuously turned on by the pre-driver 28c or 28d.

Therefore, from the battery 13 to the relay circuit 12
bridge circuit 22 via a and the current detection resistor 21.
The current supplied to the FET flows in a path of FET 22a (or 22b) → assist motor 8 → FET 22d (or 22c) → ground, and the assist motor 8 rotates to the right (or to the left). As a result, the steering wheel 1 rotates in the direction in which the steering operation is performed, and assists the steering force.

At this time, the sub-microcomputer 24 _S
Reads the voltages at both terminals P ₁ and P ₂ of the assist motor 8 introduced via the voltage monitor circuits 23a and 23b (step S _{1 in} FIG. 4). Then, the magnitudes of the voltage values at the terminals P ₁ and P ₂ are compared (step S ₂ ), and the motor current direction is estimated based on the magnitude of the voltage value (step S ₃ ).

For example, in the bridge circuit 22, FE
T22a → When the assist motor 8 → FET22d comprising current path flows becomes a voltage> the voltage at the terminal P ₂ of the terminal P _1, for example, is estimated as the right rotation direction, FET2
When a current is flowing through the route of 2b → assist motor 8 → FET 22c, the voltage of the terminal P ₂ > the voltage of the terminal P ₁ , which is presumed to be the left rotation direction, for example.

Next, in step S ₄ , the torque detection signal of the torque sensor 7 is fetched. That is, the steering torque is obtained by subjecting the torsion bar torque to low-pass filter processing (reduction of high frequency components) for reducing steering wheel vibration.

Next, in steps S ₅ and S ₆ , it is determined whether or not the steering torque direction and the motor current direction match.
If they do not match, that is, in the case of the reverse assist region in FIG. 2, it is determined that there is an abnormality (reverse assist detection flag:
1).

In this case, fail-safe processing is performed in step S ₇ to stop the operation of the apparatus. Specifically, the control signal level supplied from the sub-microcomputer 24 _S to the AND gate 27a switches from the high level to the low level, the AND condition is not satisfied, and the operation of the relay drive circuit 26 is turned off.
The exciting current no longer flows through the coil and its contact is turned off. Therefore, no current is supplied to the bridge circuit 22.

Further, the control signal level supplied from the sub-microcomputer 24 _S to the AND gate 27b switches from the high level to the low level, the AND condition is not satisfied (the enable signal changes from the high level to the low level), and the AND Since the output gate signals of the gates 27c and 27d also become low level, the predrivers 28a and 2d
The drive of 8b is stopped and the FETs 22a and 22b are turned off.

If it is determined in step S ₆ in FIG. 4 that there is no abnormality (reverse assist detection flag: 0), the processes of steps S _{1 to} S ₆ are repeated.

The current detection signal introduced from the current detection resistor 21 to the sub-microcomputer 24 _S via the operational amplifier 25 is also used to stop the operation of the device when an overcurrent is detected.

As described above, the rotation direction of the assist motor 8, that is, the assist direction can be easily determined only by determining the magnitude relationship between the voltage values of the terminal voltages P ₁ and P ₂ . Therefore, in order to determine the rotation direction of the assist motor 8, it is not necessary to specially provide an expensive shunt resistor or the like.

Since the abnormality can be determined with a simpler structure, it is possible to reliably prevent reverse assist in the electric power steering system.

Incidentally, the main microcomputer 24
_{The M} and the sub-microcomputer 24 _S may be combined to form a single unit.

Further, the FET 22a of the bridge circuit 22.
22d are not limited to the PWM control of the FET 22a or 22b and the ON control of the FET 22c or 22d continuously as described above, and may be controlled by other control methods.

The semiconductor control element forming the bridge circuit is not limited to the FET, but may be another semiconductor control element.

The present invention is not limited to the electric power steering device as in the above-described embodiment, but may be applied to another device, for example, a device for monitoring and displaying the rotating direction of the electric motor. The abnormality determining means in this case is configured by means for determining an abnormality of the device when the determined drive direction of the electric motor and the drive direction instruction signal of the control unit for controlling the drive of the semiconductor control element of the bridge circuit are different. To be done.

Also in the case of such a configuration, the driving direction (rotational direction) of the electric motor can be easily discriminated by simply discriminating the magnitude relation between the voltage values of the both terminals of the electric motor as described above. Therefore, the circuit configuration for determining the driving direction of the electric motor and determining the abnormality is extremely simplified.

[0053]

As described above, according to the present invention, the driving direction (rotational direction) of the electric motor can be easily determined only by determining the magnitude relationship between the voltage values of both terminals of the electric motor. Therefore, the circuit configuration for determining the driving direction of the electric motor and determining the abnormality is extremely simplified.

Especially when the present invention is applied to the electric power steering apparatus, the rotation direction of the assist motor, that is, the assist direction can be easily determined only by determining the magnitude relationship between the voltage values of the two terminals of the assist motor. be able to. Therefore, in order to determine the rotation direction of the assist motor, it is not necessary to specially provide an expensive shunt resistor or the like, and the cost can be suppressed. Since the abnormality can be determined with a simpler configuration, it is possible to reliably prevent reverse assist in the electric power steering device.

[Brief description of drawings]

FIG. 1 is a motor control block diagram showing an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a steering torque and a motor current in the electric power steering device.

FIG. 3 is a circuit diagram of a main part of an embodiment of the present invention.

FIG. 4 is a flowchart of reverse assist detection according to the embodiment of the present invention.

FIG. 5 is a configuration diagram showing an example of an electric power steering device.

[Explanation of symbols]

1 ... steering wheel 7 ... torque sensor 8 ... assist motor 12a ... relay circuit 13 ... Battery 21 ... current detection resistor 22 ... bridge circuit 22a to 22d ... FET 23a, 23b ... voltage monitor circuit 24 _M ... main microcomputer 24 _S ... Sub-microcomputer 25 ... Operational amplifier 26 ... Relay drive circuits 27a-27d ... AND gates 28a-28d ... Pre-drivers 31a, 31b, 32a, 32b ... Resistors 33a, 33b ... Capacitors

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 3D033 CA03 CA16 CA21 CA33                 5H571 AA03 BB10 CC04 EE02 GG04                       HA09 HC01 HD02 JJ04 LL22                       LL23 MM08 MM20

Claims (3)

[Claims] 1. A bridge circuit which is connected between positive and negative power supply buses of a DC power supply and which is formed by connecting semiconductor control elements in a bridge, and is connected between a common connection point of a positive side arm and a negative side arm of the bridge circuit. An electric motor, a voltage value detecting means for detecting both terminal voltage values of the electric motor, a voltage magnitude discriminating means for discriminating the magnitude of the both terminal voltage values, and a terminal voltage magnitude relation discriminated by the voltage magnitude discriminating means. And a driving direction discriminating means for discriminating the driving direction of the electric motor. 2. When the drive direction of the electric motor discriminated by the drive direction discriminating means is different from the drive direction instruction signal of the control section for driving and controlling the semiconductor control element of the bridge circuit, the abnormality is judged to be an abnormality of the device. The drive device for an electric motor according to claim 1, further comprising a determination unit. 3. The electric motor is composed of an assist motor in an electric power steering apparatus, and the drive direction discrimination means is composed of assist direction discrimination means for discriminating an assist direction based on a drive direction of the assist motor. When the steering assist direction detected by the provided steering assist direction detecting unit and the assist direction of the assist motor discriminated by the assist direction discriminating unit are different from each other, an abnormality judging unit for judging that the apparatus is abnormal is provided. The drive device for the electric motor according to claim 1.