JP2007074831A - Motor controller and steering unit for vehicle using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the size and cost of a construction for motor current detection and reduce a power loss resulting from motor current detection. <P>SOLUTION: An electronic control unit 10 includes: a motor drive circuit 12 connected to an electric motor M; a microcomputer 11 that controls the circuit; and a motor current detection circuit 13 for monitoring a motor current. The motor drive circuit 12 includes six power MOSICs 21 to 26 each provided with a current detecting function in bridge connection. These MOSICs 21 to 26 include: a power MOSFET that is turned on/off according to a PWM signal from the microcomputer 11; and a shunt FET for shunting a current passed through the power MOSFET. The current passed through the shunt FET is detected by the motor current detection circuit 13. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a motor control device for controlling an electric motor. The present invention also relates to a vehicle steering apparatus that drives an electric motor in response to an operation of an operation member such as a steering wheel and applies a turning force to a steered wheel using the electric motor as a drive source. Such a vehicle steering device includes an electric power steering device that applies a steering assist force to the steering mechanism by an electric motor, and an electric pump type power that assists steering by transmitting the generated hydraulic pressure of a pump driven by the electric motor to the steering mechanism. A steering device, a steer-by-wire system that eliminates the mechanical link between the operation member and the steering mechanism, and steers the steered wheels exclusively by the driving force of the electric motor are included.

Conventionally, an electric power steering device that assists steering by transmitting torque generated by an electric motor to a steering mechanism of a vehicle has been used. The electric motor is driven and controlled based on a target current value determined in accordance with a steering torque applied to the steering wheel and a vehicle speed.
An electronic control unit (ECU) for driving and controlling an electric motor includes a motor drive circuit that supplies electric power to the electric motor, a current detection circuit that detects a motor current flowing through the electric motor, a target current, and a motor current And a control circuit that feedback-controls the motor drive circuit so as to approach the target current value.

  The motor drive circuit is configured, for example, by connecting a plurality of power MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) in a bridge connection. For example, when using a three-phase brushless motor, the motor drive circuit connects three series circuits of a high-side power MOSFET and a low-side power MOSFET connected in parallel to the high potential side and the low potential side of the power supply, respectively. Configured.

  The current detection circuit includes a shunt resistor interposed in series with each of the three series circuits, and a monitor circuit that detects and amplifies a current drop in the shunt resistor and inputs the voltage drop to the control circuit as a voltage signal. . As another configuration, there may be a configuration in which one shunt resistor is interposed in series with the motor drive circuit and a voltage drop at the shunt resistor is detected (Patent Document 1).

For fail-safe processing at the time of failure, a fail-safe relay may be interposed between the in-vehicle battery as a power source and the motor drive circuit. When the control circuit detects an abnormality (fail) in the system, the control circuit cuts off the fail-safe relay and stops the power supply to the electric motor. An FET may be applied instead of the fail-safe relay (Patent Document 1).
JP-A-10-167085

  In the conventional configuration, a large current for driving the motor flows through the shunt resistor. For this reason, the shunt resistor inevitably becomes a large size and its cost increases. As a result, there is a problem that the electronic control unit for electric power steering becomes large and its cost is high. Moreover, the power loss in the shunt resistor cannot be ignored.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a motor control device that can contribute to overall size reduction and cost reduction by reducing the size and cost of the configuration for motor current detection, and a vehicle using the same. It is providing the steering device for a vehicle.
Another object of the present invention is to provide a motor control device that can reduce power loss due to motor current detection and a vehicle steering device using the motor control device.

  In order to achieve the above object, an invention according to claim 1 is a motor control device (10) having a motor drive circuit (12, 12A) connected to an electric motor (M), which flows to the electric motor. Field effect transistor elements (41, 51) through which current passes and motor current detection means (13, 42 to 46, 46) for detecting the motor current flowing in the electric motor by dividing the current flowing in the field effect transistor elements. 52 to 56, 66, 68, r1, r2). The alphanumeric characters in parentheses indicate corresponding components in the embodiments described later. The same applies hereinafter.

  According to this configuration, the shunt resistor is not connected in series with the field effect transistor element through which the current flowing through the electric motor passes, but the motor current is detected by dividing the current flowing through the field effect transistor element. I am doing so. Therefore, the motor current detecting means does not need to detect a large current for driving the motor, and only needs to detect a small divided current. Therefore, it is not necessary to use a large and expensive shunt resistor, and the current detecting means It is also possible to suppress power loss caused by. The motor current can be obtained based on the detected shunt current and the shunt ratio.

Preferably, the motor control device further includes a control circuit (11) for controlling the motor drive circuit based on the motor current detected by the motor current detection means.
A second aspect of the present invention is the motor control apparatus according to the first aspect, wherein the field effect transistor element constitutes a part of the motor drive circuit.
According to this configuration, the field effect transistor element forms part of the motor drive circuit. For example, the motor drive circuit can be configured by bridge-connecting a plurality of field effect transistor elements. More specifically, assuming that the electric motor is a three-phase motor, a series circuit of a pair of field effect transistor elements respectively connected to a high potential side and a low potential side of a power source (for example, an in-vehicle battery) is connected in parallel. A motor drive circuit may be configured by connecting three. In this case, the motor current (phase current) of each phase can be obtained by diverting and detecting the current flowing through the field effect transistor element for at least two of the three series circuits.

A third aspect of the present invention is the motor control apparatus according to the first aspect, wherein the field effect transistor element is interposed between the motor drive circuit and a power source (8).
In this configuration, since a field effect transistor element is interposed between the motor drive circuit and the power supply, this field effect transistor element serves as a fail-safe switching means for stopping power supply to the electric motor in the event of a failure. Can be used. And the electric current which flows into an electric motor is detectable by detecting the electric current shunted from such a field effect type transistor element.

  According to a fourth aspect of the present invention, the motor current detecting means is connected in parallel to the field effect transistor element and is turned on / off by a control signal common to the field effect transistor element (42). 52, preferably having an on-resistance larger than that of the field effect transistor element), and a series circuit connected between the shunting transistor element and the power source, and connecting the electric resistance element and the current adjusting transistor element in series. (43, 44; 53, 54; 66; 68) and one end of each of the shunting transistor element and the field effect transistor element (more specifically, one end on the same side as the power source. More specifically, Is the potential of one end of the shunt transistor on the series circuit side and the corresponding one end of the field effect transistor). A motor control device according to any one of claims 1 to 3, characterized in that it comprises an operational amplifier (46, 56) for controlling the current regulating transistor to be properly.

  According to this configuration, a current is shunted to the shunting transistor element connected in parallel to the field effect transistor element, and this current flows to the electric resistance element and the current adjusting transistor element. On the other hand, the current adjusting transistor element is controlled by the operation of the operational amplifier so that the potentials of the corresponding one ends of the field effect transistor element and the shunting transistor element become equal. As a result, a current corresponding to the reciprocal of the on-resistance ratio of the field-effect transistor element and the shunt transistor element (that is, the shunt ratio) flows through the electric resistance element connected in series with the current adjusting transistor element. Accordingly, by detecting the current flowing through the electric resistance element (specifically, the voltage drop in the electric resistance element), the current flowing through the field effect transistor element can be accurately detected.

  The shunting transistor element preferably has an on-resistance much higher (eg, 1000 times) than that of the field effect transistor element. Thus, a large current flowing through the field effect transistor element can be detected by detecting a small current. As a result, since only a small current flows through the electric resistance element, a small-sized inexpensive electric resistance element can be applied, and power loss can be remarkably suppressed.

  According to a fifth aspect of the present invention, the motor current detecting means is connected in parallel to the field effect transistor element, and is turned on / off by a control signal common to the field effect transistor element (52). : Preferably having an on-resistance larger than that of the field-effect transistor element) and the shunting transistor element and the high-potential portion of the power source, and the high-potential side electric resistance element (R1) and the high-potential side A high potential side series circuit (66) in which current adjusting transistor elements (65) are connected in series, and the shunting transistor element and a low potential portion of a power source are connected, and a low potential side electric resistance element (R2) and A low potential side series circuit (68) in which low potential side current adjusting transistor elements (67) are connected in series, the shunting transistor element, and the electric field effect Corresponding one ends of the type transistor elements (more specifically, each one end on the same side with respect to the power source. More specifically, one end connected to the high potential side and low potential side series circuit of the shunting transistor; 2. An operational amplifier (56) for controlling the high-potential-side and low-potential-side current adjusting transistors so that the potentials of the corresponding one end of the field effect transistor are equal to each other. 4. The motor control device according to any one of items 3 to 3.

  According to this configuration, the push-pull circuit is configured by the high-potential-side and low-potential-side current adjustment transistor elements, and when the current flows from the high-potential side of the power source to the field effect transistor element, When current flows and current is drawn into the field effect transistor element from the low potential side of the power supply, the current flows through the low potential side series circuit. Thus, even when a current flows in any direction through the field effect transistor element, the current can be detected by being shunted.

  According to a sixth aspect of the present invention, the high potential side current adjustment transistor and the low potential side current adjustment transistor are connected to a high potential portion and a low potential portion of the power source, respectively, The high potential side electric resistance element and the low potential side electric resistance element are connected to each other between the side current adjustment transistors, and the high potential side electric resistance element is connected between the high potential side and the low potential side current adjustment transistor. 6. The motor according to claim 5, further comprising a series circuit of a first resistance element (r1) and a second resistance element (r2) connected in parallel to a series circuit of the side and low potential side electric resistance elements. It is a control device.

According to this configuration, the connection point between the first and second resistance elements is the reference potential point (81), and the connection point between the high potential side and low potential side electrical resistance elements is the measurement potential point (82). By obtaining the potential difference between the measured potential point and the measured potential point, the current shunted to the shunting transistor element can be detected.
Therefore, in order to detect a voltage drop in the high potential side and low potential side electric resistance elements, two monitor circuits (one that detects and amplifies the voltage drop and generates a voltage signal) are required. With the configuration of 6, the current in both directions flowing through the field effect transistor element can be monitored by one monitor circuit.

At least a part of the motor current detection means and the field effect transistor element may be integrated as a power IC (21-26, 21A, 22A, 24A, 26A, 100) with a current detection function.
According to this configuration, further miniaturization can be achieved by integrating at least a part of the motor current detection means and the field effect transistor element into one IC.

According to a seventh aspect of the present invention, the field effect transistor element and the shunting transistor element are configured by assigning a plurality of integrated cells at a predetermined ratio. It is a motor control device given in any 1 paragraph.
More specifically, the field effect transistor element and the shunting transistor element can be configured using a transistor IC chip in which a plurality (for example, about several tens of millions) of MOSFET cells are integrated. That is, a plurality (large number) of cells are divided into A: B (where A> B, preferably A >> B, for example, A: B = 1000: 1), and cells with a ratio A are divided into field effect transistor elements (main ) And a cell having the ratio B is assigned to the shunt transistor element (sub). Thus, a field effect transistor element and a shunting transistor element having an on-resistance ratio of B: A (a shunt ratio is A: B) are obtained.

The invention according to claim 8 is provided with the motor control device according to any one of claims 1 to 7, and is connected to the motor drive circuit in accordance with an operation of the operation member (1) for steering the vehicle. This is a vehicle steering apparatus that drives the electric motor and applies a steering force to the steered wheels (7).
With this configuration, it is possible to reduce the size and cost of the motor control device for the vehicle steering device and to suppress power loss.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a block diagram showing an electrical configuration of an electric power steering apparatus according to an embodiment of the present invention. Steering torque applied to the steering wheel 1 as an operation member for steering the vehicle is mechanically transmitted via the steering shaft 2 to the steering mechanism 3 that gives a steering force to the left and right front wheels 7 as the steered wheels. Is done. A steering assist force from an electric motor M (for example, a three-phase brushless motor) is transmitted to the steering mechanism 3 via a speed reduction mechanism (not shown) or by a direct drive system.

  The steering shaft 2 is divided into an input shaft 2A coupled to the steering wheel 1 side and an output shaft 2B coupled to the steering mechanism 3 side. The input shaft 2A and the output shaft 2B are connected to the torsion bar 4. Are connected to each other. The torsion bar 4 is twisted according to the steering torque, and the direction and amount of the twist are detected by the torque sensor 5.

For example, the torque sensor 5 is configured by a magnetic sensor that detects a magnetic resistance that changes in accordance with a change in the positional relationship between the input shaft 2A and the output shaft 2B in the rotational direction. The output signal of the torque sensor 5 is input to an electronic control unit (ECU) 10 as a motor control device.
In addition to the output signal of the torque sensor 5, a vehicle speed signal output from the vehicle speed sensor 6 is input to the electronic control unit 10. The electronic control unit 10 determines a target current value according to the steering torque detected by the torque sensor 5 and the vehicle speed detected by the vehicle speed sensor 6, and a steering assist force according to the steering torque and the vehicle speed is given to the steering mechanism 3. Thus, the electric motor M is drive-controlled.

  The electronic control unit 10 includes a microcomputer 11, a motor drive circuit 12, and a motor current detection circuit 13 that monitors a motor current flowing through the electric motor M. The microcomputer 11 determines a target current value based on the steering torque detected by the torque sensor 5 and the vehicle speed detected by the vehicle speed sensor 6. The microcomputer 11 feedback-controls the motor drive circuit 12 so that the motor current detected by the motor current detection circuit 13 matches the target current value. More specifically, the microcomputer 11 provides the motor drive circuit 12 with a PWM (pulse width modulation) signal having a duty set in accordance with the deviation between the target current value and the motor current. Thereby, the motor drive circuit 12 supplies the electric motor M with a current corresponding to the PWM signal. Then, the driving force generated by the electric motor M is transmitted to the steering mechanism 3 as a steering assist force.

  The motor drive circuit 12 is connected to an in-vehicle battery 8 as a power source. A fail-safe relay 9 that is opened and closed by the microcomputer 11 is interposed between the motor drive circuit 12 and the in-vehicle battery 8. The microcomputer 11 normally holds the fail safe relay 9 in a closed state. However, when a predetermined abnormality is detected, the microcomputer 11 opens the fail safe relay 9 and stops power supply to the motor drive circuit 12.

  FIG. 2 is an electric circuit diagram for explaining a specific configuration of the motor drive circuit 12. The motor drive circuit 12 includes six power MOSICs (IC = integrated circuit elements) 21 to 26 having a current detection function and a capacitor 27 that are bridge-connected. Two of the six power MOSICs 21 to 26 are connected in series to form a series circuit, and the other two power MOSICs 23 and 24 are also connected in series to form a series circuit. Two other power MOSICs 25 and 26 are similarly connected in series to form a series circuit. These three series circuits and the capacitor 27 are connected in parallel to the in-vehicle battery 8. In each series circuit, the power MOSICs 21, 23, 25 connected to the high potential side (+ side, high side) of the in-vehicle battery 8 and the low potential (ground) side (− side, low side) of the in-vehicle battery 8 are connected. Connection points 28, 29, 30 between the power MOSICs 22, 24, 26 are connected to the U-phase lead 31, the V-phase lead 32 and the W-phase lead 33 of the electric motor M, respectively.

  The power MOSICs 21, 23, 25 on the high potential side have a high potential side terminal (drain terminal) a 1 connected to the high potential side of the in-vehicle battery 8 and a control input to which the PWM signal of each phase from the microcomputer 11 is input. A terminal (gate terminal) b 1, a low potential side terminal (source terminal) c 1 connected to the connection points 28, 29, and 30 side, and a current monitor terminal d 1 connected to the motor current detection circuit 13 are provided.

  On the other hand, the power MOSICs 22, 24, 26 on the low potential side receive the high potential side terminal (drain terminal) a 2 connected to the connection points 28, 29, 30 side and the PWM signal of each phase from the microcomputer 11. A control input terminal (gate terminal) b 2, a low potential side terminal (source terminal) c 2 connected to the low potential side of the in-vehicle battery 8, and a current monitor terminal d 2 connected to the motor current detection circuit 13. Yes.

The motor current detection circuit 13 includes monitor circuits 35, 36, 37, and 38 connected to current monitor terminals d1 and d2 of the power MOSICs 21, 22, 23, and 24, respectively. The monitor circuits 35 and 36 detect and amplify signals from the current monitor terminals d1 and d2 of the power MOSICs 21 and 22 to thereby a voltage signal (U-phase current detected by the current detection function of the power MOSICs 21 and 22). U-phase current signal) is generated and input to the microcomputer 11. Similarly, the monitor circuits 37 and 38 represent the V-phase current detected by the current detection function of the power MOSICs 21 and 22 by detecting and amplifying signals from the current monitor terminals d1 and d2 of the power MOSICs 23 and 24, respectively. A voltage signal (V-phase current signal) is generated and input to the microcomputer 11. The microcomputer 11 obtains a W-phase current I _W (= − (I _U + I _V )) by calculation based on the input two-phase (U-phase and V-phase) current signals I _U and I _V. The microcomputer 11 generates a PWM signal to be supplied to the power MOSICs 21 to 26 based on the three-phase motor current values of U, V, and W.

The W-phase current may be detected by providing a monitor circuit corresponding to the power MOSICs 25 and 26 instead of being obtained by calculation by the microcomputer 11.
FIG. 3 is an electric circuit diagram for explaining a common configuration example of the power MOSICs 21, 23, 25 on the high potential side. A power MOSFET 41 as a field effect transistor element is connected between the high potential side terminal a1 and the low potential side terminal c1, and a control signal is input to the gate of the power MOSFET 41 from the control input terminal b1. ing. On the other hand, a series circuit of a shunting FET 42, a current adjusting NPN transistor 43, and a current detecting resistor 44 is connected between the high potential side terminal a1 and the ground potential portion (the low potential side of the in-vehicle battery 8). . This series circuit is connected to the high potential side terminal a1 in parallel with the power MOSFET 41. A control signal from the control input terminal b1 is input to the gate of the shunting FET 42. The shunting FET 42 is turned on / off in the same manner as the power MOSFET 41, and shunts the current flowing into the power MOSFET 41. .

Further, the connection point 45 between the shunting FET 42 and the current adjusting NPN transistor 43 and the low potential side (low potential side terminal c1) of the power MOSFET 41 are respectively connected to a pair of input terminals of the operational amplifier 46. Has been. The output terminal of the operational amplifier 46 is connected to the base of the current adjusting NPN transistor 43.
When the power MOSFET 41 is turned on, the shunting FET 42 is simultaneously turned on to shunt the current from the high potential side terminal a1 to the low potential side terminal c1 to the current adjusting NPN transistor 43 and the current detecting resistor 44. On the other hand, the operational amplifier 46 controls the current adjusting NPN transistor 43 so that the potential between the pair of input terminals becomes equal. As a result, a current corresponding to the ratio of the on resistances of the power MOSFET 41 and the shunting FET 42 (reciprocal of the shunt ratio) flows through the current detection resistor 44.

  More specifically, the motor current flowing in the power MOSFET 41 is Im, the current shunted to the current detection resistor 44 side is Is, and the ratio between the on-resistance of the power MOSFET 41 and the on-resistance of the shunt FET 42 is B: A. If (for example, B: A = 1: 1000), the relationship Im: Is = A: B is established. Therefore, when the current Is is detected, the motor current Im can be obtained by Im = (A / B) · Is.

The current Is is obtained by detecting a voltage drop in the current detection resistor 44 by the monitor circuits 35 and 37 provided in the motor current detection circuit 13. The monitor circuits 35 and 37 amplify the voltage drop to create a voltage signal, and input this voltage signal to the microcomputer 11.
The power MOSFET 41 and the diversion FET 42 divide the cell of the power MOS transistor IC having a number of MOSFET cells into an A: B ratio, assign the ratio A cell to the power MOSFET 41, and assign the ratio B cell to the diversion FET 42. You may make it comprise.

  FIG. 4 is an electric circuit diagram for explaining a common configuration example of the power MOSICs 22, 24, 26 on the low potential side. A power MOSFET 51 as a field effect transistor element is connected between the high potential side terminal a2 and the low potential side terminal c2. A control signal is input to the gate of the power MOSFET 51 from the control input terminal b2. ing. On the other hand, a series circuit of a shunting FET 52, a current adjusting PNP transistor 53, and a current detecting resistor 54 is connected between the low potential side terminal c2 and the high potential side (voltage + B) of the in-vehicle battery 8. This series circuit is connected to the low potential side terminal c <b> 2 in parallel with the power MOSFET 51. A control signal from the control input terminal b2 is input to the gate of the shunting FET 52. The shunting FET 52 is turned on / off in the same manner as the power MOSFET 51, and shunts the current flowing into the power MOSFET 51. .

Further, the connection point 55 between the shunting FET 52 and the current adjusting PNP transistor 53 and the high potential side (high potential side terminal a2) of the power MOSFET 51 are respectively connected to a pair of input terminals of the operational amplifier 56. Has been. The output terminal of the operational amplifier 56 is connected to the base of the current adjusting PNP transistor 53.
When the power MOSFET 51 is turned on, the shunting FET 52 is turned on at the same time, a current flows through the power MOSFET 51 from the high potential side terminal a2 to the low potential side terminal c2, and the shunting FET 52 includes a current adjusting PNP transistor 53 and a current. A current is supplied from the detection resistor 54. On the other hand, the operational amplifier 56 controls the current adjusting PNP transistor 53 so that the potential between the pair of input terminals becomes equal. As a result, a current corresponding to the ratio of the on resistances of the power MOSFET 51 and the shunting FET 52 (reciprocal of the non-shunting ratio) flows through the current detection resistor 54.

  As in the case described above, the motor current flowing in the power MOSFET 51 is Im, the current flowing in the current detection resistor 54 is Is, and the ratio between the on-resistance of the power MOSFET 51 and the on-resistance of the shunting FET 52 is B: A (for example, , B: A = 1: 1000), the following relationship is established: Im: Is = A: B. Therefore, when the current Is is detected, the motor current Im can be obtained by Im = (A / B) · Is.

The current Is is obtained by detecting a voltage drop in the current detection resistor 54 by the monitor circuits 36 and 38 provided in the motor current detection circuit 13. The monitor circuits 36 and 38 amplify the voltage drop to create a voltage signal, and input this voltage signal to the microcomputer 11.
In the power MOSFET 51 and the shunting FET 52, the cells of the power MOS transistor IC having a number of MOSFET cells are divided into A: B ratios, the cells of the ratio A are allocated to the power MOSFETs 51, and the cells of the ratio B are allocated to the shunting FETs 52. You may make it comprise.

  As shown in FIG. 2, the motor leads 31, 32, and 33 have a current I1 flowing from the high potential side power MOSICs 21, 23, 25 and a current I2 flowing from the low potential side power MOSICs 22, 24, 26, respectively. Flows. The current I1 is detected using the current detection function of the power MOSICs 21 and 23 on the high potential side, and the current I2 is detected using the current detection function of the power MOSICs 22 and 24 on the low potential side.

  As described above, according to this embodiment, the current of each phase is detected using the current detection function of the power MOSICs 21 to 26 with a current detection function. As a result, it is not necessary to provide a shunt resistor through which a large current for driving the motor flows as in the prior art, so that the electronic control unit 10 can be downsized and its cost can be reduced. Furthermore, the problem of large power loss in the shunt resistor can also be avoided.

  In the power MOSICs 21 to 26 with a current detection function, a slight current is supplied to the current detection resistors 44 and 54 via the shunt FETs 42 and 52 as compared with the motor driving current flowing in the power MOSFETs 41 and 51. It has become. Accordingly, since only a small current flows through the current detection resistors 44 and 54, the size of the current detection resistors 44 and 54 may be small, an expensive configuration is not required, and power loss is also small.

FIG. 5 is a diagram for explaining another embodiment of the present invention. The configuration of an electronic control unit 10 that can be applied to the electric power steering apparatus of FIG. 1 in place of the configuration shown in FIG. It is shown. In FIG. 5, parts corresponding to those shown in FIG. 2 are given the same reference numerals as in FIG.
In this embodiment, instead of the power MOSICs 21, 23, 25 having a current detection function on the high potential side, normal power MOSFETs 61, 62, 63 having no current detection function are used. In place of the power MOSICs 22, 24, 26 with current detection function on the low potential side, further improved power MOSICs 22A, 24A, 26A with current detection function are applied.

  The power MOSICs 22A, 24A, and 26A include a high potential side terminal a2 connected to the connection points 28, 29, and 30 side, a control input terminal b2 to which each phase PWM signal from the microcomputer 11 is input, and the in-vehicle battery 8 And a pair of current monitor terminals d21, d22 connected to the motor current detection circuit 13. As will be described below, the power MOSICs 22A, 24A, and 26A have a configuration capable of detecting both the current I11 flowing in the electric motor M and the current I12 flowing in the electric motor M.

FIG. 6 is an electric circuit diagram for explaining a common configuration example of the power MOSICs 22A, 24A, and 26A. In FIG. 6, the same reference numerals as those in FIG. 4 are attached to the same parts as those in FIG.
A power MOSFET 51 as a field effect transistor element is connected between the high potential side terminal a2 and the low potential side terminal c2. A control signal is input to the gate of the power MOSFET 51 from the control input terminal b2. ing. On the other hand, one end of the shunting FET 52 is connected to the low potential side terminal c2. A series circuit (high potential side series circuit) 66 of a current adjusting NPN transistor 65 and a current detection resistor R1 is provided between the other end of the shunt FET 52 and the high potential side (voltage + B) of the in-vehicle battery 8. A series circuit (low potential side series circuit) 68 of a current adjusting PNP transistor 67 and a current detection resistor R2 is connected between the low voltage side (ground side) of the in-vehicle battery 8. The emitters and bases of the current adjusting NPN transistor 65 and the current adjusting PNP transistor 67 are connected in common to form a push-pull circuit. The shunt FET 52 is connected in parallel to the power MOSFET 51 to the low potential side terminal c2. A control signal from the control input terminal b2 is input to the gate of the shunting FET 52. The shunting FET 52 is turned on / off in the same manner as the power MOSFET 51, and shunts the current flowing into the power MOSFET 51. .

  Further, a connection line 69 between the shunt FET 52 and the current adjusting transistors 65 and 67 is connected to the non-inverting input terminal of the operational amplifier 56, and the high potential side (high potential side terminal a 2) of the power MOSFET 51 is connected to the operational amplifier 56. Is connected to the inverting input terminal. The output of the operational amplifier 56 is divided by resistors 71 and 72 and is commonly input to the bases of the current adjusting transistors 65 and 67.

  When the power MOSFET 51 is turned on, the shunt FET 52 is simultaneously turned on. In this case, when the current I11 flowing in the direction of flowing into the electric motor M flows, the current adjustment PNP transistor 67 on the low potential side is turned on, and the current directed from the low potential side terminal c2 to the high potential side terminal a2 flows. From the current through the current adjusting PNP transistor 67 to the current detecting resistor R2. As a result, a current corresponding to the ratio of the on resistances of the power MOSFET 51 and the shunting FET 52 flows through the current detection resistor R2.

  On the other hand, when the current I12 in the direction flowing out of the electric motor M flows when the power MOSFET 51 is turned on, the high potential side current adjusting NPN transistor 65 is turned on. As a result, a current flows into the shunting FET 52 through the current detecting resistor R1 and the current adjusting NPN transistor 65. At this time, a current corresponding to the ratio of the on-resistance of the power MOSFET 51 and the shunting FET 52 flows through the current detection resistor R1. That is, the current flowing through the power MOSFET 51 is shunted according to the on-resistance ratio between the power MOSFET 51 and the shunting FET 52.

Voltage drops generated in the current detection resistors R1 and R2 are detected by the monitor circuits 35 and 37; 36 and 38 provided in the motor current detection circuit 13 through the current monitor terminals d21 and d22, respectively.
As understood from FIG. 5, the monitor circuits 35 and 36 generate a U-phase current signal, and the monitor circuits 37 and 38 generate a V-phase current signal. In response to these signals, the microcomputer 11 calculates the W-phase current by calculation.

As described above, according to this embodiment, it is only necessary to provide one power MOSFET with a current detection function for each of at least two of the three phases of U, V, and W. Compared to the embodiment, the configuration can be simplified and further cost reduction can be achieved.
FIG. 7 is an electric circuit diagram for explaining a modification of the embodiment shown in FIGS. 5 and 6. The power MOSIC 21 A with a current detection function is applied to the high potential side, and the normal power is applied to the low potential side. A U-phase configuration when the MOSFET 64 is applied is shown. In FIG. 7, portions corresponding to the respective portions shown in FIG. 6 are denoted by the same reference numerals as those in FIG.

  A power MOSFET 51 as a field effect transistor element is connected between the high potential side terminal a1 and the low potential side terminal c1, and a control signal is input to the gate of the power MOSFET 51 from the control input terminal b1. ing. On the other hand, one end of the shunt FET 52 is connected to the high potential side terminal a1. A series circuit (high potential side series circuit) 66 of a current adjusting NPN transistor 65 and a current detection resistor R1 is provided between the other end of the shunt FET 52 and the high potential side (voltage + B) of the in-vehicle battery 8. A series circuit (low potential side series circuit) 68 of a current adjusting PNP transistor 67 and a current detection resistor R2 is connected between the low voltage side (ground side) of the in-vehicle battery 8. The emitters and bases of the current adjusting NPN transistor 65 and the current adjusting PNP transistor 67 are connected in common to form a push-pull circuit. The shunt FET 52 is connected in parallel to the power MOSFET 51 to the high potential side terminal a1. A control signal from the control input terminal b1 is inputted to the gate of the shunting FET 52. This shunting FET 52 is turned on / off in the same manner as the power MOSFET 51, and shunts the current flowing into the power MOSFET 51. .

Further, the connection line 69 between the shunt FET 52 and the current adjusting transistors 65 and 67 is connected to the inverting input terminal of the operational amplifier 56, and the low potential side (low potential side terminal c 1) of the power MOSFET 51 is connected to the operational amplifier 56. Connected to non-inverting input terminal. The output of the operational amplifier 56 is commonly input to the bases of the current adjusting transistors 65 and 67.
With this configuration, it is possible to detect both the current flowing into the electric motor M and the current flowing out of the electric motor M by an operation similar to the case of the configuration of FIG.

  FIG. 8 is a view for explaining still another embodiment of the present invention. In FIG. 8, parts corresponding to the parts shown in FIG. 7 are given the same reference numerals. In this embodiment, the current detection resistors R1 and R2 are respectively connected to the shunt FET 52, and the current adjustment transistors 65 and 67 are connected to the in-vehicle battery 8 side than the current detection resistor R1. On the other hand, a series circuit of reference potential generating resistors r1 and r2 is connected in parallel to a series circuit of current detecting resistors R1 and R2, and a bridge circuit of resistors R1, R2, r1, and r2 is formed. Yes. The reference potential generating resistors r1 and r2 have a resistance value (for example, about 100 times) much larger than the current detection resistors R1 and R2, and the following relational expression (1 ) Is established.

r1 / r2 = R1 / R2 (1)
For example, if the resistance values R1 and R2 are equal, the resistance values r1 and r2 are set equal.
The monitor circuit 35A of the motor current detection circuit 13 detects the potential difference between the potential of the reference potential point 81 that is the connection point of the resistors r1 and r2 and the potential of the measurement point 82 that is the connection point of the resistors R1 and R2. Is input to the microcomputer 11 as a corresponding voltage signal (U-phase current signal).

  When the power MOSFET 51 is in the on state and the current I21 directed to the electric motor M flows, the current adjustment PNP transistor 67 on the low potential side is turned on. At this time, the current from the shunting MOSFET 52 flows from the measurement point 82 to the ground potential side through the current detection resistor R2, and from the measurement point 82 to the ground potential side through the resistors R1, r1, and r2 in order. At this time, if the potential at the measurement point 82 is Vs, the potential at the reference potential point 81 is as shown in the following equation.

Vs · r2 / (R1 + r1 + r2) ≈Vs · r2 / (r1 + r2) (2)
∵R1 << r1, r2
Therefore, the difference Δ between the potential at the measurement point 82 and the potential at the reference potential point 81 is Δ = r1 · Vs / (r1 + r2). Since Vs = R2 · Is, the current Is flowing in the shunting MOSFET 52 is obtained by the following equation.

Is = (r1 + r2) · Δ / r1 · R2 (3)
On the other hand, when the power MOSFET 51 is in the ON state and the current I22 in the direction drawn from the electric motor M to the power MOSFET 51 flows, the high potential side current adjusting NPN transistor 65 is turned on. At this time, the current from the current adjusting NPN transistor 65 is supplied to the shunting MOSFET 52 through the resistor R1 and the measuring point 82, and reaches the measuring point 82 through the resistors r1, r2, and R2 in order. At this time, if the potential at the measurement point 82 is Vs, the potential at the reference potential point 81 is given by the following equation.

Vs + (B−Vs) × (r2 + R2) / (r1 + r2 + R2)
≒ Vs + (B-Vs) x r2 / (r1 + r2) (4)
∵R2 << r1, r2
Therefore, the difference Δ between the potential at the measurement point 82 and the potential at the reference potential point 81 is Δ = (B−Vs) × r2 / (r1 + r2). Since B−Vs = R1 · Is, the current Is flowing through the shunting MOSFET 52 is obtained by the following equation.

Is = (r1 + r2) · Δ / R1 · r2 (5)
However, from the above relational expression (1), r1 · R2 = R1 · r2, and r1 + r2 is constant, so that (r1 + r2) / r1 · R2 = (r1 + r2) / R1 · r2 = α (constant) In any case, the current Is flowing in the shunting FET 52 is determined as Is = α · Δ. The motor current Im is obtained based on this current Is.

Thus, according to this embodiment, the current flowing through the power MOSFET 51 can be detected by one monitor circuit 35A regardless of the direction. Thereby, the structure of the electronic control unit 10 can be further simplified.
Of course, this embodiment can be modified to have a configuration in which current detection is performed on the low potential side.

  FIG. 9 is a block diagram for explaining the configuration of an electric power steering apparatus according to still another embodiment of the present invention. 9, parts corresponding to the respective parts shown in FIG. 2 are given the same reference numerals as those in FIG. In this embodiment, the motor drive circuit 12A is configured by bridge-connecting ordinary power MOSFETs 91 to 96 that do not have a current detection function.

  On the other hand, a power MOSIC 100 with a current detection function is interposed in series between the in-vehicle battery 8 and the motor drive circuit 12A. The power MOSIC 100 has the same configuration as that shown in FIG. The high potential side terminal a1 is connected to the motor drive circuit 12A, the low potential side terminal c1 is connected to the low potential side of the in-vehicle battery 8, the control input terminal b1 is connected to the MOSIC drive circuit 101, and the current monitor terminal d1 is connected to the motor current detection circuit 13.

  The MOSIC drive circuit 101 is controlled by the microcomputer 11. When the microcomputer 11 detects a predetermined abnormality, the MOSIC driving circuit 101 cuts off the power MOSFET 41 (see FIG. 3) in the power MOSIC 100 and stops the power supply to the electric motor M. Of course, during normal operation, the microcomputer 11 controls the power MOSFET 41 in the power MOSIC 100 to be conductive by the MOSIC drive circuit 101 and allows the electric motor M to be energized. That is, the power MOSIC 100 functions in the same manner as the fail safe relay 9 in the above-described embodiment.

Thus, in this embodiment, the motor current can be detected without requiring a large and expensive shunt resistor by the configuration in which the power MOSIC 100 with a current detection function is connected in series to the motor drive circuit 12A.
Note that this embodiment may be modified so that a power MOSIC with a current detection function is interposed in series between the high potential side of the in-vehicle battery 8 and the motor drive circuit 12A.

As mentioned above, although four embodiment of this invention was described, this invention can also be implemented with another form. For example, in the above-described embodiment, the configuration in the case of using a three-phase brushless motor as the electric motor M has been described. However, the motor drive circuit may be a so-called H-bridge circuit by using a single-phase motor.
Furthermore, in the above-described embodiment, the configuration in which the power MOSFET and the shunting FET are integrated into the IC has been described. However, these may be configured as individual elements. Furthermore, a current adjusting transistor, an electric resistance element, and the like provided in association with the shunt FET may be configured by individual elements different from the power MOSFET.

  In the above-described embodiment, the example in which the present invention is applied to the electric power steering apparatus has been described. However, the present invention generates a hydraulic pressure by a pump driven by an electric motor and uses the hydraulic pressure as a drive source. Thus, the present invention can also be applied to an electric pump type power steering apparatus configured to apply a steering assist force to the steering mechanism. Furthermore, the present invention eliminates the mechanical link between the steering wheel and the steering mechanism, electrically detects the operation of the steering wheel, and drives the electric motor according to the detection result, and the electric motor steers the steering. It can also be applied to a so-called steer-by-wire system that drives the mechanism.

Furthermore, the present invention is not limited to the vehicle steering device as described above, and can be widely applied to a motor control device for controlling an electric motor while detecting a motor current.
In addition, various design changes can be made within the scope of matters described in the claims.

1 is a block diagram showing an electrical configuration of an electric power steering apparatus according to an embodiment of the present invention. It is an electric circuit diagram for demonstrating the specific structure of a motor drive circuit. It is an electric circuit diagram for demonstrating the structural example of power MOSIC of a high electric potential side. It is an electric circuit diagram for demonstrating the structural example of power MOSIC by the side of a low electric potential. It is a block diagram which shows the structure of the electronic control unit which concerns on other embodiment of this invention. FIG. 6 is an electric circuit diagram for explaining a configuration example of a power MOSIC used in the configuration of FIG. 5. It is an electric circuit diagram for demonstrating the modification of embodiment shown by FIG. 5 and FIG. It is an electric circuit diagram for demonstrating other embodiment of this invention. It is a block diagram for demonstrating the structure of the electric power steering apparatus which concerns on further another embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Steering wheel, 7 ... Front left and right wheel, 8 ... In-vehicle battery, 9 ... Fail safe relay, 10 ... Electronic control unit, 21-26 ... Power MOSIC with current detection function, 41, 51 ... Power MOSFET, 42, 52 ... min Current application FET, 43, 53 ... Current adjustment transistor, 44, 54 ... Current detection resistor, 46, 56 ... Operational amplifier, 65, 67 ... Current adjustment transistor, 66 ... High potential side series circuit, 81 ... Reference potential point , 82 ... Measurement points, 100 ... Power MOSIC, 101 ... MOSIC drive circuit, R1, R2 ... Current detection resistors, r1, r2 ... Reference potential generation resistors

Claims (8)

A motor control device having a motor drive circuit connected to an electric motor,
A field effect transistor element through which a current flowing through the electric motor passes;
A motor control device comprising: motor current detection means for detecting a motor current flowing in the electric motor by dividing a current flowing in the field effect transistor element.   2. The motor control device according to claim 1, wherein the field effect transistor element constitutes a part of the motor drive circuit.   The motor control device according to claim 1, wherein the field effect transistor element is interposed between the motor drive circuit and a power source. The motor current detection means is
A shunting transistor element connected in parallel to the field effect transistor element and turned on / off by a control signal common to the field effect transistor element;
A series circuit connected between the shunting transistor element and the power source, and connecting the electric resistance element and the current adjusting transistor element in series;
4. An operational amplifier that controls the current adjusting transistor so that potentials at corresponding ends of the shunting transistor element and the field effect transistor element are equal to each other. The motor control apparatus of Claim 1. The motor current detection means is
A shunting transistor element connected in parallel to the field effect transistor element and turned on / off by a control signal common to the field effect transistor element;
A high-potential-side series circuit connected between the shunting transistor element and the high-potential portion of the power supply, the high-potential-side electric resistance element and the high-potential-side current adjusting transistor element connected in series;
A low-potential-side series circuit connected between the shunting transistor element and the low-potential portion of the power supply, and having a low-potential-side electric resistance element and a low-potential-side current adjusting transistor element connected in series;
And an operational amplifier that controls the high-potential side and low-potential side current adjustment transistors so that potentials at corresponding ends of the shunting transistor element and the field effect transistor element are equal to each other. Item 4. The motor control device according to any one of Items 1 to 3. The high-potential-side current adjustment transistor and the low-potential-side current adjustment transistor are respectively connected to the high-potential portion and the low-potential portion of the power supply;
Between the high potential side and low potential side current adjustment transistor, the high potential side electric resistance element and the low potential side electric resistance element are connected to each other,
A series circuit of a first resistance element and a second resistance element connected in parallel to the series circuit of the high potential side and low potential side electric resistance elements between the high potential side and low potential side current adjusting transistors. The motor control device according to claim 5, further comprising:   7. The device according to claim 4, wherein the field effect transistor element and the shunting transistor element are configured by assigning a plurality of integrated cells at a predetermined ratio. 8. Motor control device.   A motor control device according to any one of claims 1 to 7, wherein the electric motor connected to the motor drive circuit is driven in accordance with an operation of an operation member for steering the vehicle to perform a rotation. A vehicle steering device that applies a steering force to a steering wheel.

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