JP2001206232A - Electric power steering control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a method of preventing the generation of thermal breakdown of a motor and a circuit device at a low cost in an electric power steering control device. SOLUTION: This electric power steering control device is formed by mounting a bridge circuit, which is formed of plural semiconductor switching elements Q1-Q4 forming a part of a current control means for controlling quantity and direction of the motor current in response to the auxiliary torque, on the same board 65 with a current detecting means 43A for detecting the motor current and formed of a resistor having a positive temperature characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering control device for applying an auxiliary steering force to a steering device of a vehicle by the rotational force of a motor.
In particular, it relates to the configuration of the control circuit.

[0002]

2. Description of the Related Art FIG. 4 is a circuit diagram showing a motor control unit of a general electric power steering control device. In the figure, reference numeral 40 denotes a motor that outputs an auxiliary torque to a steering wheel (not shown) of the vehicle, and 41 denotes a battery that supplies a motor current IM for driving the motor 40.

Reference numeral 42 denotes a large-capacity (about 3600 μF) capacitor for absorbing a ripple component of the motor current IM; 43, a shunt resistor (current detection resistor) for detecting the motor current IM; A bridge circuit including a plurality of semiconductor switching elements (for example, FETs) Q1 to Q4 for switching the magnitude and direction of the motor current IM flowing to the motor 40 according to the magnitude and direction, 49 denotes ON / OFF of the semiconductor switching elements. OF
This is a coil for removing electromagnetic noise generated at the time of F.

L1 is a conductive line connecting one end of the capacitor 42 to the ground, P1 and P2 are bridge connections of the semiconductor switching elements Q1 to Q4, and wiring patterns connecting the shunt resistor 43 and the bridge circuit 44 to the connection points, respectively. , P3 are wiring patterns serving as output terminals of the bridge circuit 44.

Reference numeral 45 denotes a connector comprising a plurality of lead terminals for connecting the motor 40 and the battery 41 to the bridge circuit 44; L2, an external wiring for connecting the motor 40 and the battery 41 to the connector 45; A normally open relay for interrupting the supply of the motor current IM supplied from the controller as required, P4 is a wiring pattern for connecting the relay 46, the capacitor 42 and the shunt resistor 43, and P5 is a wiring pattern for connecting the connector 45 to the ground. It is. A wiring pattern P3 serving as an output terminal of the bridge circuit 44 is connected to an external wiring L via a connector 45.
2 are connected.

Reference numeral 47 denotes a motor 4 via a bridge circuit 44.
A driving circuit that drives the relay 46 while driving 0.
L3 is a conductive line that connects the drive circuit 47 to the exciting coil of the relay 46, L4 is a conductive line that connects the drive circuit 47 to the bridge circuit 44, and 48 is a motor that detects the motor current IM via one end of the shunt resistor 43. A current detector,
The drive circuit 47 and the motor current detector 48 constitute a peripheral circuit element of a microcomputer described later.

Reference numeral 50 denotes a steering torque T of a steering wheel (not shown).
Is a torque sensor for detecting the vehicle speed, and 51 is a vehicle speed sensor for detecting the vehicle speed V of the vehicle. 55 is a steering torque T and a vehicle speed V
The auxiliary torque is calculated based on the motor current IM
(ECU) for generating a drive signal corresponding to an auxiliary torque by inputting the feedback signal from the motor current detection unit 48, and using the rotation direction command D0 for controlling the bridge circuit 44 and the current control amount I0 as the drive signal. Input to the drive circuit 47.

The microcomputer 55 includes a motor 40
A motor current determining unit 56 for generating a motor current command Im corresponding to the rotation direction command D0 and the auxiliary torque, a subtractor 57 for calculating a current difference ΔI between the motor current command Im and the motor current IM, and a current deviation ΔI P (proportional) term,
The correction amounts of the I (integral) and D (differential) terms are calculated and P
A PID calculation unit 58 that generates a current control amount I0 corresponding to the WM duty ratio.

Although not shown, the microcomputer 55 includes a well-known self-diagnosis function in addition to an AD converter, a PWM timer circuit, and the like, and constantly performs self-diagnosis as to whether or not the system is operating normally. When an abnormality occurs, the relay 46 is opened via the drive circuit 47 and the motor current IM
Is to be shut off. L5 is a conductive line for connecting the microcomputer 55 to the drive circuit 47. Further, the microcomputer 55 monitors the motor current command Im with the continuous execution of the steering control.
When it is detected that a motor current of a predetermined value or more has flowed for a predetermined time or more, the motor current command maximum value Im (maximum) is reduced stepwise with the passage of time, so that the motor 40 and circuit elements are thermally destroyed. To prevent

Generally, circuit elements 42 to 44 and 49, wiring patterns P1 to P5, and conductive lines L1 and L2 interposed between the motor 40 and the battery 41 correspond to a large motor current IM. In view of heat dissipation (heat resistance), durability and the like, it is configured to be large.
On the other hand, the peripheral circuit elements including the microcomputer 55, the drive circuit 47, and the motor current detection unit 48 and the conductive lines L3 to L5 are configured to be small in size because they are required to correspond to a small current and have a high density.

FIG. 5 is a plan view showing a structure of a control circuit of a general electric power steering control device. 5, reference numeral 1 denotes a box-shaped metal frame that also functions as a shield plate and a heat radiator plate, 2 denotes an insulated printed circuit board mounted on the bottom surface of the metal frame 1, and 3 denotes one end surface on the inner side surface of the metal frame 1. Is, for example, a heat sink made of aluminum. The semiconductor switching elements Q1 to Q4 constituting the bridge circuit 44 are joined to the other surface of the radiator plate 3 while maintaining insulation from each other. In this case, each of the semiconductor switching elements Q1 to Q4 is a pair of F
It is composed of ET.

Each circuit element 4 is provided on the insulating printed board 2.
2, 43, 46, 49, 55, etc. are placed.
The large-capacity capacitor 42 is constituted by three capacitors, and the microcomputer 55 is constituted by a one-chip IC. Also, to prevent the drawing from being complicated,
Omit peripheral circuit elements, wiring patterns, conductive lines, etc.,
Only typical circuit components are shown.

Reference numerals 4a to 4e denote wiring boards corresponding to the wiring patterns P1 to P5 and the like. In order to cope with a large current exclusively, a conductive board having a large width and a large thickness separately from the wiring patterns on the insulated printed circuit board 2. Is used.

Next, the operation of the conventional electric power steering control device shown in FIG. 5 will be described with reference to FIG. The microcomputer 55 takes in the steering torque T and the vehicle speed V from the torque sensor 50 and the vehicle speed sensor 51, and feeds back the motor current IM from the shunt resistor 43 so that the rotational direction of the power steering is obtained from the steering torque T and the vehicle speed V. Command D0 and a motor current command Im, and a current control amount I0 corresponding to an auxiliary torque amount based on a current deviation ΔI between the motor current command Im and the motor current IM. Is input to the drive circuit 47 via the.

In the steady driving state, the drive circuit 47 closes the normally open relay 46 based on a command via the conductive line L3. When the rotation direction command D0 and the current control amount I0 are input, the drive circuit 47 A PWM drive signal is generated, and the conductive line L
4 is applied to each of the semiconductor switching elements Q1 to Q4 of the bridge circuit 44.

As a result, the motor 40 is
Motor current IM supplied from the external wiring L2, connector 45, coil 49, relay 46, wiring pattern P4, shunt resistor 43, wiring pattern P1, bridge circuit 44, wiring pattern P3, connector 45 and external wiring L2 , And outputs a required amount of auxiliary torque in a required direction.

At this time, the motor current IM is detected via the shunt resistor 43 and the motor current detecting section 48 and is fed back to the subtractor 57 in the microcomputer 55, so that it matches the motor current command Im. Is controlled as follows. The motor current IM is
Although a ripple component is included by the switching operation at the time of PWM driving of the bridge circuit 44, the ripple component is smoothed and suppressed by the large-capacity capacitor 42. further,
The coil 49 prevents the noise generated by the switching operation of the bridge circuit 44 during the PWM driving from being emitted to the outside and becoming radio noise.

By the way, the value of the motor current IM controlled by this type of electric power steering control device is about 25 A even in a light car, and is about 60 A in a small car.
A to about 80A. Therefore, the bridge circuit 44
Of the semiconductor switching elements Q1 to Q4 are increased in size according to the magnitude of the motor current IM, and a plurality of the semiconductor switching elements are connected in parallel as shown in FIG.
It is necessary to suppress heat generation during switching.

Further, the semiconductor switching elements Q1 to Q4
In order to dissipate the heat generation amount, the heat radiating plate 3 is necessary. As the motor current IM increases, the number of the semiconductor switching elements Q1 to Q4 increases, and the heat radiating plate 3 also increases in size.

Further, a wiring pattern P1 from the terminal of the connector 45 to the ground via the coil 49, the relay 46, the shunt resistor 43 and the bridge circuit 44,
The lengths of P2 and P4 and the wiring pattern P3 from the bridge circuit 44 to the motor 40 are determined by the motor current IM.
, And the number of semiconductor switching elements Q1 to Q4 increases, and the size of the heat sink increases in proportion to the physical length.

As a result, if the temperature rise increases due to the amount of heat generated by the voltage drop in each of the wiring patterns P1 to P4, the heat resistance and durability of the wiring patterns P1 to P4 may be impaired. In order to prevent this, wiring boards 4a to 4e having a large width and thickness and dedicated to a large current are used for the wiring patterns P1 to P4 as shown in FIG. Therefore,
This causes an increase in the size of the insulating printed board 2.

The capacitor 42 and the shunt resistor 4
3, the relay 46 and the coil 49 are connected to the motor current IM.
However, if these components are mounted on the insulated printed circuit board 2, the mounting space is increased and the insulated printed circuit board 2 is further increased in size.

In order to solve these problems, for example, one described in JP-A-6-270824 is known. FIG. 6 shows an electric power steering control apparatus described in Japanese Patent Application Laid-Open No. 6-270824. FIG. 6A is a side sectional view of the apparatus (hatching is omitted), and FIG. FIG. 7 is a plan view showing a state where the insulating printed board 2 shown in FIG. still,
4 and 5 indicate the same or corresponding parts. In FIG. 6B, 1A and 3A correspond to the metal frame 1 and the heat sink 3, respectively.

The insulated printed circuit board 2 (not shown) is provided with a microcomputer 55, peripheral circuits of a small current such as an interface circuit, a power supply circuit, a logic circuit, and a signal processing circuit belonging to the microcomputer 55. A sensor signal connector (not shown) connected to the vehicle speed sensor 50 and the vehicle speed sensor 51 (see FIG. 4) is provided.

The heat radiating plate 3A has a function of a shield plate at the lower part of the device, and the metal frame 1A is electrically connected to the heat radiating plate 3A to form a complete shield structure. Is shut off. Reference numeral 2A denotes another insulating printed board mounted on the heat sink 3A, which is divided from the insulating printed board 2 on which the microcomputer 55 is mounted, and on which a driving circuit (peripheral circuit element) 47 composed of an IC chip is mounted. Is placed.

Reference numeral 10 denotes a metal substrate made of, for example, a HITT substrate (trade name) manufactured by Denki Kagaku Kogyo Co., Ltd. The wiring pattern P is a 100 μm copper pattern (20 μm aluminum) on a 3 mm aluminum substrate via an 80 μm insulating layer. Film is coated). The wiring pattern P is a general term for P1 to P5 and the like, and here only a part is shown.

The back surface of the metal substrate 10 is fixed to the heat radiating plate 3A, and the heat radiating function is enhanced. Metal substrate 10
The divided printed circuit boards 2A are arranged in parallel in the horizontal direction.

As shown in the figure, on the wiring pattern P joined and disposed on the metal substrate 10 with the insulating layer interposed therebetween,
The shunt resistor 43 and the bridge circuit 44 are mounted, and the metal substrate 10 also functions as a heat sink.
The wiring pattern P formed on the metal substrate 10 is
A circuit element having a sufficient cross-sectional capacity to cope with a large current and through which the motor current IM flows can be mounted.

The number of the semiconductor switching elements Q1 to Q4 constituting the bridge circuit 44 is, for example, eight (two each).
And is soldered to a primary heat radiating plate (not shown) made of copper or molybdenum.
(P1 to P3, etc.) are connected by soldering and aluminum bonding or the like, and are bridge-connected to the motor 40 in FIG.

As described above, by using bare-chip semiconductor switching elements Q1 to Q4 which are smaller in size than ordinary elements because they are not covered with resin,
The bridge circuit 44 can be arranged in a small space on the metal substrate 10. Therefore, even if three or more semiconductor switching elements Q1 to Q4 are connected in parallel with each other by increasing the motor current IM, compact mounting can be achieved.

Further, the semiconductor switching elements Q1 to Q4
In addition, the amount of heat generated from the wiring pattern P is effectively transmitted to the heat radiating plate 3A via the metal substrate 10 and is radiated to the outside air from the heat radiating plate 3A. it can.

Reference numerals 14a to 14g denote a plurality of leads protruding from the wiring pattern P on the metal substrate 10,
The leads 14a and 14g correspond to the wiring pattern P4 and the conductive line L3 of the relay 46.

Reference numeral 5 denotes an insulating support member interposed between the metal substrate 10 and the insulated printed circuit board 2;
0 and the insulated printed circuit board 2, while maintaining a predetermined distance between the capacitor 42, the connector 45 and the relay 46.
Is attached. The insulating printed board 2 and the metal board 10 sandwich the support member 5 from above and below, and are superposed at a predetermined interval from each other.

The capacitor 42 is soldered to a pattern on the support member 5 via an electrode terminal 42a and a support terminal 42b. The electrode terminal 42a on the ground (-) side of the capacitor 42 is connected to the ground terminal of the connector 45, the electrode terminal 42a on the anode (+) side is connected to the shunt resistor 43 via the lead 14e, and the support terminal 42b
Fix the other end of the capacitor 42 on the support member 5.

The connector 45 is attached to the support member 5 in a frame shape by, for example, integral molding of an insert resin mold, and has an extension terminal portion 45a inside. The extension terminal portion 45a is electrically connected to the leads 14a to 14d projecting in a bar shape from the metal substrate 10.

As shown in FIG. 4, the motor 40 and the battery 41 are connected to the outer terminal of the connector 45 via the external wiring L2. The connector 45 may form a male pin, or may form a screw-type connection terminal.

In the relay 46, the relay contact terminal on the battery 41 side is connected to the battery terminal of the connector 45, and the relay contact terminal on the bridge circuit 44 side is connected to the wiring pattern P4 via the lead 14a.

As described above, the large-capacity capacitor 42, the connector 45, and the relay 46, which require a large mounting space and are difficult to mount on the metal substrate 10, are mounted on the support member 5 located on the intermediate layer. 10
It is electrically connected to the wiring pattern P via the leads 14a to 14g projecting upward.

Accordingly, the wiring pattern P on the metal substrate 10
In this case, the degree of freedom in the structural design between the capacitor 42 and each terminal of the relay 46 and the extension terminal 45a of the connector 45 is increased, so that the wiring length can be reduced compactly and effectively. Further, the insulating printed board 2 and the metal board 10 disposed above and below the support member 5 can also be reduced in size because the use space is effectively omitted.

On the other hand, a drive circuit 47 mounted as a hybrid IC on an alumina thick film substrate of another insulated printed circuit board 2A is connected to a bridge circuit 44 on the metal substrate 10 via a conductive line L4, and a conductive line L5 Is connected to a microcomputer 55 on the insulated printed circuit board 2.

As described above, by using a divided insulating printed board 2A separately from the upper insulating printed board 2 and arranging the insulating printed board 2A on the same plane as the lower metal board 10, The useless space on the substrate 10 side is eliminated, and further downsizing can be realized.
Accordingly, high-density mounting of the microcomputer 55 and its peripheral circuit elements (such as the drive circuit 47) can be realized.

Further, a metal frame 1A serving as a shield plate
Are insulated printed circuit boards 2 and 2 in cooperation with heat sink 3A.
A is completely covered, and electromagnetic noise that can be input to the insulated printed circuit boards 2 and 2A is reliably blocked. Further, in order to solve the above-mentioned problems, Japanese Patent Application Laid-Open No. 7-23
There is an "motor control device" disclosed in Japanese Patent No. 1696. In this device, by using a material having a large temperature coefficient for the shunt resistor 43 shown in FIG. 4, when a large current flows through the shunt resistor, the resistance value increases due to heat generation, and the motor current detection is performed. The output of the circuit becomes a value larger than the current actually flowing to the motor. Thereby, the CP
U determines that an excessive current is flowing through the motor and controls so that the motor current decreases.

[0043]

According to the conventional electric power steering control device configured as described above,
By using a material having a large temperature coefficient for the shunt resistor, when a large current flows through the shunt resistor, heat is generated and the resistance value increases. Since the motor current is detected based on the increased resistance value, a large motor current is detected when the heat generation amount is large, and the microcomputer controls the motor current based on the detected current value. However, in this case, the shunt resistor is only affected by the temperature rise due to the current flowing through itself, and the surrounding elements, for example, FETs forming a bridge circuit
Cannot be protected from elevated temperatures. Another method of protecting the control device from thermal destruction is to prevent the motor and the circuit device from being thermally destructed due to heat generated by an excessive current flowing through the circuit when steering is performed continuously. When it is detected that a motor current equal to or more than a predetermined value has flowed for a predetermined time or more, the motor current command maximum value Im (maximum) is reduced stepwise with the passage of time, so that the current flowing in the bridge circuit gradually decreases with time. Control to prevent more current from flowing. However, in this method, the current control program becomes complicated, and the responsiveness of the current control is affected by the processing speed of the program. In order to ensure control responsiveness, an expensive microcomputer with a high processing speed is required, which leads to an increase in cost.

As another overheat protection method for continuous steering, there is a method of detecting the temperature of a motor or a circuit device and limiting the maximum current at a predetermined temperature or higher.
However, in this method, a temperature detecting element and its peripheral circuit are required, which leads to an increase in cost, and a space for mounting components is required, which causes a problem that the apparatus becomes large. .

An object of the present invention is to solve the above-mentioned problems and to provide an electric power steering control device capable of preventing a motor and circuit elements from being thermally destroyed by an inexpensive method. With the goal.

[0046]

SUMMARY OF THE INVENTION An electric power steering control device according to the present invention includes a motor for generating an auxiliary torque to a steering wheel of a vehicle, a battery for supplying a motor current for driving the motor, and the motor current. Current detection means for detecting the current, the current control means for controlling the amount and direction of the motor current according to the auxiliary torque, a bridge circuit comprising a plurality of semiconductor switching elements constituting a part of this current control means, at least A substrate with good thermal conductivity on which the bridge circuit and the current detecting means are mounted, a heat sink made of a material with good thermal conductivity attached in close contact with the substrate, and a torque sensor for detecting a steering torque of the handle A vehicle speed sensor for detecting a vehicle speed of the vehicle, a steering torque of the steering wheel and a vehicle speed of the vehicle based on the vehicle speed. The electric power steering control system having a microcomputer and a peripheral circuit element for generating a drive signal for controlling the ridge circuit,
The resistance of the current detecting means has a positive temperature characteristic,
Wherein the bridge circuit and the current detecting means are mounted on the same substrate.

The electric power steering control device according to the present invention has a non-linear temperature characteristic in which the resistance of the current detecting means increases in temperature and the rate of increase in the resistance value increases.

[0048] In the electric power steering control device according to the present invention, the electric current detecting means includes a power MOS FE.
It is composed of T and peripheral circuit elements.

[0049] In the electric power steering control device according to the present invention, the current detecting means is constituted by a white plate.

In the electric power steering control device according to the present invention, the substrate on which the bridge circuit and the current detecting means are mounted is formed of a metal substrate with good thermal conductivity.

In the electric power steering control device according to the present invention, the substrate having good heat conductivity is formed of a ceramic substrate.

In the electric power steering control device according to the present invention, the substrate having good thermal conductivity is formed of an aluminum nitride substrate.

In the electric power steering control device according to the present invention, the resistance value of the current detecting means is set to a value equal to or less than the resistance value of the semiconductor switching element.

In the electric power steering control device according to the present invention, the power MOS
The thermal resistance of the FET is set to a value equal to or less than the thermal resistance of each semiconductor switching element forming the bridge circuit.

In the electric power steering control device according to the present invention, the current detecting means is mounted at a distance within a predetermined value from each of the semiconductor switching elements.

In the electric power steering control device according to the present invention, the power MOS
The resistance value of the FET can be adjusted by changing the voltage applied to the gate of the power MOS FET.

In the electric power steering control device according to the present invention, the radiator plate is a metal housing for accommodating the steering mechanism of the steering wheel.

In the electric power steering control device according to the present invention, the radiator plate is a metal housing for housing the motor.

[0059]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, a first embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram illustrating a circuit element constituting a motor-driven power steering control apparatus according to Embodiment 1 of the present invention, a wiring board on which the circuit element is mounted, a heat sink on which the wiring board is mounted, and a case accommodating the circuit element and the wiring board. FIG. 4 is a perspective view showing a shield cover for covering a case in the order of assembly. In addition, in FIG.
6 denote the same or corresponding parts. In FIG. 1, reference numeral 1B denotes a shield cover which, when assembled (not shown), surrounds the wiring board and the electronic circuit attached to the case, and blocks electromagnetic noise from the electronic circuit. Reference numeral 64 denotes a first substrate on which an electronic control unit (ECU) 55 such as a microcomputer and small current components such as peripheral circuits are mounted, and is formed of an insulated printed circuit board. Numeral 65 denotes a power switching element constituting the semiconductor switching elements Q1 to Q4 and the current detecting section 43A.
A second substrate on which a large current component such as an SFET is mounted;
It is composed of a metal substrate having excellent thermal conductivity. In addition, E
The CU 55 is an arithmetic unit, the current detecting unit 43A is a current detecting unit, and the semiconductor switching elements Q1 to Q4 (Q2, Q4
(Not shown) constitute current control means. The circuit configuration of the electric power steering control device according to the present embodiment is the same as that of the conventional electric power steering control device shown in FIG.
3 is provided with a current detector 43A composed of a MOS FET, a resistor, and a DC power supply, which will be described later (see FIG. 3).

A small current component is mounted on an insulated printed circuit board (first substrate) 64, and a large current component is mounted on a metal substrate (second substrate).
By mounting on 65, a two-substrate structure is obtained. As a result, the area of each of the substrates 64 and 65 is reduced, and the first substrate 64 and the second substrate 65 are vertically overlapped with the case 62 interposed therebetween. In addition, heat generated by large current components such as the semiconductor switching elements Q1 to Q4 and the current detection unit 43 is transmitted to a heat radiating plate 3B, which will be described later, through a metal substrate 65 having excellent heat conduction, thereby promoting heat release to the outside. The reliability of the device is improved by minimizing thermal damage to circuit elements.

Reference numeral 62 denotes a case, in which a connector 45 for connection to an external device is integrally formed. In the case 62, the lead terminals of the connector 45 are formed by insert molding, and the lead terminals are extended into the case 62, and the bottom surface 6 of a case recess 66 described later is formed.
A wiring pattern P <b> 6 is formed on 6 </ b> A, and is further extended to form an extension terminal 67 for connecting to the second substrate 65.

Reference numeral 3B denotes a radiator plate, which is attached so as to be in contact with a second substrate 65 constituted by a metal substrate.
The heat generated by the electronic components mounted on the second substrate 65 is released to the outside. The heat sink 3B has
A concave cutout 3C is formed in a portion of the case 62 facing the concave portion 66 (see FIG. 2). When the heat radiating plate 3B is not provided, a protective cover (not shown) for covering the concave portion 66 of the case 62 is provided.

FIG. 2A is a plan view showing the bottom surface of the case 62, and FIG. 2B is a side view of the case 62 viewed from the direction of arrow A. As shown in each figure, a concave portion 66 is provided in a part of a case 62, and a connector 45 is provided on a bottom surface 66A thereof.
A wiring pattern P6 formed by extending the lead terminals is provided. Of the circuit components, large components such as the capacitor 42, the relay 46, and the coil 49 are inserted into the concave portion 66, attached, and connected by the wiring pattern P6.
Large parts can be stored efficiently. Connector 4
The lead terminal No. 5 is thicker than the wiring pattern originally arranged on the insulated printed circuit board or the like, and can be electrically connected by the wiring pattern P6 provided by extending the lead terminal. Need not be wide,
The entire device can be reduced in size.

If the height of the case 62 is reduced to further reduce the size of the device, the capacitor 42 and the relay 4
The height of the coil 6 or the coil 49 becomes higher than the height of the case 62, and the top of the capacitor 42, the relay 46 or the coil 49 projects from the concave portion 66 of the case 62.
In such a case, as shown in FIG. 1, a concave notch 3C is provided on a heat sink 3B attached to face the case 62, and the capacitor 42,
By inserting the relay 46, the coil 49, etc., the capacitor 42, the relay 46, the coil 49, etc.
The device can be further miniaturized without projecting from the device.

The first substrate 64 on which components such as the microcomputer 55 and peripheral circuit elements to which a small current is supplied is mounted.
As shown in FIG. 1, a conductive line L5 connecting the bridge circuit 44 and a second substrate 65 on which a component through which a large current flows, such as a power MOS FET constituting the current detecting unit 43A, is mounted. 62 is provided independently. Therefore, when the conductive line L5 is connected to the second substrate 65, it can be mounted on the substrate as one of simple electric components, and positioning is easy. In addition, the conductive line L5
Is connected to the first substrate 64, since the conductive line L5 is not fixed to the case 62, positioning can be relatively easily performed. As described above, by providing the conductive line L5 independently of the case 62, the first substrate 64 and the second substrate 65 are provided.
Connection to is easy.

As described above, the second heat radiation plate 3B
After the substrate 65, the case 62, and the first substrate 64 are mounted, if the case 62 is screwed to the heat radiating plate 3B with the mounting screw 61, the entire device is surrounded by the shield cover 1B, so that erroneous operation of the device due to electromagnetic noise. Operation can be prevented and the reliability of the device can be improved.

Next, the configuration and operation of the current detector 43A according to the present embodiment will be described in detail with reference to FIG. FIG. 3A shows a power MOS FET having a positive temperature characteristic in which the resistance value increases as the temperature rises, compared to a current detecting shunt resistor conventionally formed of a resistor.
FIG. 4 is a diagram showing a configuration of a current detection unit 43A configured with.

The power M constituting the current detecting section 43A
The OS FET has a drain D connected to a positive terminal of the battery 41 through a relay contact, and a source S connected to a current input terminal of the bridge circuit 44 and a motor current detector 48 through a wiring pattern. The gate G and the source S
A predetermined bias voltage V _GS is applied through the resistor R between them. Drain-source S for case temperature
The resistance between them varies with the bias voltage _VGS .

FIG. 3B shows the temperature characteristics of the resistance between the drain D and the source S of the power MOS FET of the current detection unit 43A, using the bias voltage V _GS between the gate G and the source S of the power MOSFET as a parameter. is there. FIG. 3C shows a change in the temperature of the current detection unit 43 with respect to the energization time, a change in the resistance between the drain D and the source S of the power MOSFET, and a change in the motor current IM during continuous steering of the electric power steering control device. It is a figure which shows various characteristics.

As shown in FIG. 3B, the current detector 4
3, the case temperature of the power MOS FET and the resistance characteristic between the drain D and the source S are represented by the power MOS FE.
When the bias voltage V _GS between the gate G and the source S of T is set to a constant value (for example, V _GS = 1OV), the resistance between the drain (D) and the source (S) increases as the case temperature increases. For this reason, when the power MOSFETs Q1 to Q4 forming the bridge circuit 44 generate heat due to the energization of the motor current IM accompanying the operation of the steering device, this heat is generated.
The power is transmitted to the case of the power MOS FET constituting the current detecting unit 43A mounted on the second substrate 65 having the same thermal conductivity, and the power is changed as shown in the case temperature-resistance change in FIG. The increase in the resistance between the drain D and the source S of the MOS-FET leads to an increase in the resistance value of the current detection unit 43A.

Since the motor current IM is converted into a voltage by the resistance between the drain D and the source S of the power MOS-FET constituting the current detecting section 43A and detected, an increase in the resistance between the drain and the source is equivalent. Then, the voltage drop due to the resistance increases. This voltage drop is detected by the motor current detector 4
8 and is negatively fed back to the subtractor 57 in the microcomputer 55 as the motor current IM. As a result, the microcomputer 55
Controls the motor current IM in a direction to further decrease.

As described above, at the time of continuous steering, as shown in FIG. 3C, the temperature rises with the passage of the energization time, and the resistance between the drain D and the source S also rises. Is reduced in accordance with the decreasing rate that changes with the passage of the energization time, so that the motor 40 and the circuit elements can be protected from being thermally destroyed by heat generated by the motor current IM.

As described above, according to the present embodiment, the power MOSFET forming the current detecting section 43A has the same thermal conductivity as the power MOSFETs Q1 to Q4 forming the bridge circuit 44 having a large temperature rise during continuous steering. Since it is mounted on a good second substrate 65, a power MOS
The temperature can be more accurately detected along with the temperature rise of the FETs Q1 to Q4, and the motor 40 and the circuit can be protected from thermal destruction by suppressing the rise of the motor current IM according to the temperature detection result.

When the motor current IM is gradually decreased at a constant rate from the beginning to protect the circuit from thermal destruction during continuous steering, the steering force of the steering wheel also gradually increases. Become. This gives the driver an unnatural feeling of unnaturalness, which is not preferable in terms of steering performance. As a measure to improve such a situation, the current detection unit 4
By giving the 3A a non-linear temperature characteristic in which the rate of increase of the resistance value increases as the temperature increases, the characteristic can be such that the reduction of the steering force is initially small and the rate of reduction increases with time.

As a result, when the steering is started, the weight does not suddenly become heavy, and the uncomfortable feeling of the steering can be reduced within the actual use time. The power MOS FET constituting the current detector 43 is an element having a non-linear positive temperature characteristic in which the case temperature increases and the rate of increase in the resistance value between the drain D and the source S increases.

Power MOS constituting current detector 43A
The FET itself generates heat when the motor current is supplied. By reducing the effect of this self-heating, the bridge circuit 4
In order to more accurately detect the temperature of each of the power MOS FETs Q1 to Q4 constituting the power MOS FET 4, the resistance between the drain D and the source S is determined by each power MOS FET constituting the bridge circuit.
The resistance is set to be equal to or less than the resistance value of the FET.

As another method for enabling the power MOS FETs constituting the current detecting section 43A to more accurately detect the temperature of each power MOS FET constituting the bridge circuit, the current detecting section 43A is constituted. Reduce the thermal resistance of the power MOS FET. As a result, the case temperature of each of the power MOS FETs Q1 to Q4 depends on the drain D of the power MOS FET constituting the current detection unit 43A.
-It easily appears as a resistance change between the sources S. Or,
There is also a method of arranging a power MOS FET constituting the current detection unit 43A near the bridge circuit 44 to have the same temperature distribution. When it is desired to increase the detection accuracy of the motor current in order to improve the performance of the protection operation, the bias voltage V _GS applied between the gate G and the source S as shown in FIG.
, The current detection resistance (the resistance between the drain D and the source S) is increased, and a large voltage drop is generated, so that the current detection accuracy can be improved.

In this embodiment, the circuit board is the first board 6
4. The second substrate 65 is composed of two sheets, and the second substrate 65 is placed on the heat sink 3B for releasing heat generated in the second substrate 65 on which the large current element is mounted. The configuration is not limited to these. In addition, without specially providing the heat radiating plate 3B, an aluminum column housing or a rack housing for accommodating the steering mechanism is used as a heat radiating plate, and the substrate is placed on the heat radiating plate while maintaining thermal conductivity.
Alternatively, it goes without saying that various embodiments are included within a range compatible with the gist of the present invention, such as using an aluminum housing for housing the motor 40 as a heat sink.

Further, in the present embodiment, the second substrate 65 is a metal substrate, but the same effect can be obtained by using a ceramic substrate or an aluminum nitride substrate. Further, according to the embodiment of the present invention, the power MOS FE having a temperature characteristic whose resistance value is positive with respect to a temperature rise is set in the current detection unit 43A.
The same effect can be obtained by using a T white plate made of a material having a positive temperature characteristic, or a material having similar characteristics or an electronic circuit. Further, when the influence of radio noise generated at the time of the switching operation of the power MOS FET forming the bridge circuit is small, the radio noise removing coil 49 may be omitted.

[0080]

According to the present invention, a motor for generating an auxiliary torque to a steering wheel of a vehicle, a battery for supplying a motor current for driving the motor, a current detecting means for detecting the motor current, Current control means for controlling the amount and direction of the motor current according to auxiliary torque,
A bridge circuit composed of a plurality of semiconductor switching elements constituting a part of the current control means, a substrate having good heat conductivity on which at least the bridge circuit and the current detection means are mounted, and a heat conduction closely attached to the board; A radiator plate made of a material having good performance, a torque sensor for detecting a steering torque of the steering wheel, a vehicle speed sensor for detecting a vehicle speed of the vehicle, and controlling the bridge circuit based on a steering torque of the steering wheel and a vehicle speed of the vehicle. In a motor-driven power steering control device including a microcomputer for generating a drive signal for performing the operation and a peripheral circuit element, the resistance of the current detecting means has a positive temperature characteristic, and the bridge circuit and the current detecting means are the same. By mounting on a substrate, not only heat generation due to the resistance of the current detection means, but also Also it is possible to reduce the motor current in response to heat generated by the circuit, there is an effect that the prevention of thermal destruction of the motor and the circuit can be realized without using an expensive microcomputer.

According to the present invention, the resistance of the current detecting means has a non-linear temperature characteristic in which the rate of increase of the resistance value increases as the temperature increases, thereby preventing thermal destruction of the motor and the circuit. The advantage is that the present invention can be realized without using an expensive microcomputer and without impairing the steering performance.

According to the present invention, the current detecting means includes:
Because it is composed of power MOS FET and peripheral circuit elements,
This has the effect of preventing thermal destruction of the motor and the circuit without using an expensive microcomputer.

According to the present invention, the current detecting means includes:
Since it is made of a white plate, it is possible to prevent the motor and the circuit from being thermally damaged without using an expensive microcomputer.

According to the present invention, since the substrate having good thermal conductivity on which the current control means and the current detection means are mounted is made of a metal substrate, it is possible to prevent the motor and the circuit from being thermally destroyed by using an expensive microcontroller. This has the effect of realizing it without using a computer.

According to the present invention, since the substrate having good thermal conductivity is formed of a ceramic substrate, it is possible to prevent the motor and the circuit from being thermally destroyed without using an expensive microcomputer. Play.

According to the present invention, since the substrate having good thermal conductivity is formed of the aluminum nitride substrate, the motor and the circuit can be prevented from being thermally destroyed without using an expensive microcomputer. To play.

According to the present invention, the current control means includes a plurality of semiconductor switching elements forming a bridge circuit, and the resistance of the current detection means is set to a value equal to or less than the resistance of the semiconductor switching elements. In addition, it is possible to prevent the thermal destruction of the circuit without using an expensive microcomputer and to reduce the influence of the heat generated by the resistance of the current detecting means.

According to the present invention, the thermal resistance of the power MOS FET constituting the current detecting means is set to a value equal to or less than the thermal resistance of each semiconductor switching element constituting the current controlling means. This prevents the thermal destruction of the current detecting means without using an expensive microcomputer and reduces the effect of heat generated by the resistance of the current detecting means.

According to the present invention, the current detecting means includes:
Since it is mounted within a predetermined distance from each of the semiconductor switching elements, it is possible to prevent thermal destruction of the motor and the circuit without using an expensive microcomputer, and to more accurately control the temperature of each of the semiconductor switching elements. This has the effect of being detectable.

According to the present invention, the resistance value of the power MOS FET constituting the current detecting means is changed by the power MOS FET.
Since the adjustment can be performed by changing the gate applied voltage of the FET, the thermal destruction of the motor and the circuit device can be prevented without using an expensive microcomputer, and the gate applied voltage can be reduced to reduce the current. By increasing the resistance value of the detection unit, it is possible to improve the current detection accuracy and improve the performance.

According to the present invention, since the heat radiating plate is a metal housing for accommodating the steering mechanism of the handle, there is no need to provide a separate heat radiating plate, and the apparatus can be constructed at low cost.

According to the present invention, since the heat radiating plate is a metal housing for accommodating the motor, it is not necessary to provide a separate heat radiating plate, so that the apparatus can be constructed at a low cost.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a configuration of an electric power steering control device according to a first embodiment of the present invention;

FIG. 2 is a diagram showing details of a part of the configuration of the electric power steering control device according to the first embodiment of the present invention;

FIG. 3 is a diagram illustrating a part of the configuration of the electric power steering control device according to the first embodiment of the present invention and a description of various characteristics;

FIG. 4 is a circuit diagram showing a circuit configuration of a general electric power steering control device.

FIG. 5 is a configuration diagram showing a configuration of a general electric power steering control device.

FIG. 6 is a configuration diagram showing a configuration of a conventional electric power steering control device.

[Explanation of symbols]

3B heat sink, 42 capacitor, 43A current detector (shunt resistor), 44 bridge circuit, 46 relay, 49 coil, 62 case, 65 second board, 6
7 Extension terminal.

Claims (13)

[Claims] A motor for generating an auxiliary torque to a steering wheel of a vehicle; a battery for supplying a motor current for driving the motor; a current detecting means for detecting the motor current; Current control means for controlling the amount and direction of the motor current, a bridge circuit comprising a plurality of semiconductor switching elements constituting a part of the current control means, and having at least the bridge circuit and the current detection means having good thermal conductivity. A board, a radiator plate made of a material having good thermal conductivity attached in close contact with the board, a torque sensor for detecting a steering torque of the steering wheel, a vehicle speed sensor for detecting a vehicle speed of the vehicle, a steering torque of the steering wheel And a microcomputer for generating a drive signal for controlling the bridge circuit based on a vehicle speed of the vehicle And a resistance of the current detecting means has a positive temperature characteristic, and the bridge circuit and the current detecting means are mounted on the same substrate. Electric power steering control device. 2. The electric power steering control device according to claim 1, wherein the resistance of the current detection means has a non-linear temperature characteristic in which the rate of increase of the resistance value increases as the temperature increases. 3. A power MOS F.
2. The electric power steering control device according to claim 1, wherein the electric power steering control device comprises an ET and peripheral circuit elements. 4. The electric power steering control device according to claim 1, wherein said current detecting means is constituted by a white plate. 5. The electric power steering control device according to claim 1, wherein the substrate having good thermal conductivity on which the bridge circuit and the current detecting means are mounted is formed of a metal substrate. 6. The electric power steering control device according to claim 1, wherein the substrate having good thermal conductivity is formed of a ceramic substrate. 7. The electric power steering control device according to claim 1, wherein the substrate having good thermal conductivity is formed of an aluminum nitride substrate. 8. The electric power steering control device according to claim 1, wherein a resistance value of said current detecting means is set to a value equal to or less than a resistance value of said semiconductor switching element. 9. A power MO constituting said current detecting means.
4. The electric power steering control device according to claim 3, wherein a thermal resistance value of the SFET is equal to or less than a thermal resistance value of each semiconductor switching element included in the bridge circuit. 10. The electric power steering control device according to claim 1, wherein said current detecting means is mounted at a distance within a predetermined value from each of said semiconductor switching elements. 11. A power M constituting said current detecting means.
4. The electric power steering control device according to claim 3, wherein the resistance value of the OS FET can be adjusted by changing a gate application voltage of the power MOS FET. 12. The electric power steering control device according to claim 1, wherein the radiator plate is a metal housing that accommodates a steering mechanism of the steering wheel. 13. The electric power steering control device according to claim 1, wherein the radiator plate is a metal housing for housing the motor.