JP2012245848A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device capable of reducing the torque ripple and the radio noise.SOLUTION: In an ECU 12, a power board 104 and a capacitor 108 are concentrically disposed relative to an insertion hole 107 of a control board 103, a buss bar 1-105 and a buss bar 2-106, through which a motor shaft is inserted. Further, power source connection parts PIG, PGND and the power board 104 are connected to each other by the circular buss bar 1-105 and 2-206 to eliminate a difference of the wiring resistance to be caused by a difference of the wiring length of each phase of U, V and W.

Description

  The present invention relates to an electric power steering apparatus.

2. Description of the Related Art Conventionally, there is a motor control device that converts a DC voltage supplied from a DC power source into three-phase (U, V, W) driving power by a PWM inverter and supplies the driving power to a brushless motor.
A PWM inverter (not shown) is configured by connecting three arms corresponding to each phase in parallel, with an arm composed of a pair of switching elements (such as MOS-FETs) connected in series as a basic unit. . Then, the motor control device supplies three-phase driving power to the motor by alternately turning on and off the high-order switching elements and the low-order switching elements of each arm at a predetermined timing.

  By the way, in such a motor control device, a capacitor is usually provided in the power supply line of the inverter in order to reduce power noise generated in the inverter. For example, a circuit system, a component arrangement, and a wiring method in which a plurality of capacitors are connected in parallel are employed so that this capacitor functions effectively. (For example, see Patent Document 1)

JP 2001-23849 A

  However, in the motor control device configured as described above, the wiring for supplying the driving power from the power source to the inverter has a different wiring length from each phase arm to each phase arm. Variations and noise may occur. In general, even in a control device for an electric power steering device, a motor torque ripple or radio noise from the control device may be generated due to a difference in wiring resistance from a ripple absorbing electrolytic capacitor to a switching element of an inverter.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide an electric power steering apparatus capable of reducing torque ripple and radio noise.

  In order to solve the above-mentioned problems, a first aspect of the present invention provides a motor that applies a steering assist force to a steering mechanism of a vehicle, motor driving means that outputs driving power to the motor, and power supply voltage to the motor driving means. The motor driving means is formed integrally with the motor so that the rotating shaft of the motor is inserted in the axial direction of the motor, and a plurality of the motor driving means are arranged on the input side In an electric power steering apparatus including a capacitor, a drive circuit that controls the drive of the motor, and a power supply line that connects the capacitor and the drive circuit, the drive circuit and the drive circuit are arranged in the vicinity of the drive circuit. The capacitor is arranged concentrically with respect to the rotation shaft of the motor to be inserted and divided for each phase of the motor, and the drive circuit As each phase of the wiring resistance becomes equal to, and summarized in that were provided with the power supply line.

  According to the above configuration, the drive circuit and the capacitor of each phase of the motor drive means are arranged at an equidistant position with respect to the rotation axis center of the motor, and the power supply is made so that the wiring resistance of the drive power supply from the battery is equal Arrange the lines. Thereby, the dispersion | variation in resistance by the difference in the wiring length of the power supply line of each phase is suppressed, and the radio noise resulting from a motor torque ripple and a control apparatus can be reduced. Also, since the capacitor is divided and arranged near each phase drive circuit, it can absorb the ripple equally for each phase

  An electric power steering device that can reduce torque ripple and radio noise can be provided.

1 is a schematic diagram showing a schematic configuration of an electric power steering apparatus as a vehicle steering apparatus according to an embodiment of the present invention. The circuit diagram of the control circuit of the electric power steering device concerning one embodiment of the present invention. 1 is a side view of an electric power steering apparatus according to an embodiment of the present invention. The top view which looked at the control apparatus except the motor of the electric power steering apparatus of FIG. 3 from the A direction.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
FIG. 1 is a schematic diagram showing a schematic configuration of an electric power steering apparatus 1 as a vehicle steering apparatus according to an embodiment of the present invention.
Referring to FIG. 1, an electric power steering apparatus 1 includes a steering wheel 2 as a steering member, a steering mechanism 4 that steers a steered wheel 3 in conjunction with rotation of the steering wheel 2, and steering of a driver. And a steering assist mechanism 5 for assisting. The steering wheel 2 and the steering mechanism 4 are mechanically coupled via a steering shaft 6 and an intermediate shaft 7.

In the present embodiment, the steering assist mechanism 5 will be described based on an example in which an assist force (steering assist force) is applied to the steering shaft 3, but the present invention is applied to the pinion shaft described later. The present invention can be applied to a structure for giving or an assisting mechanism 5 for giving assist force to a rack shaft, which will be described later.
The steering shaft 6 extends linearly. Steering shaft 6 includes an input shaft 8 connected to steering wheel 2 and an output shaft 9 connected to intermediate shaft 7. The input shaft 8 and the output shaft 9 are connected via a torsion bar 10 so as to be relatively rotatable on the same axis. That is, when a steering torque greater than a certain value is input to the steering wheel 2, the input shaft 8 and the output shaft 9 rotate in the same direction while rotating relative to each other.

  A torque sensor 11 disposed around the steering shaft 6 detects the steering torque input to the steering wheel 2 based on the relative rotational displacement amounts of the input shaft 8 and the output shaft 9. The torque detection result of the torque sensor 11 is input to an ECU 12 (Electronic Control Unit) as a control device. Further, the vehicle speed detection result from the vehicle speed sensor 23 is input to the ECU 12. The intermediate shaft 7 connects the steering shaft 6 and the steering mechanism 4.

The steered mechanism 4 includes a rack and pinion mechanism including a pinion shaft 13 and a rack shaft 14 as a steered shaft. A steered wheel 3 is connected to each end of the rack shaft 14 via a tie rod 15 and a knuckle arm (not shown).
The pinion shaft 13 is connected to the intermediate shaft 7. The pinion shaft 13 rotates in conjunction with the steering of the steering wheel 2. A pinion 16 is connected to the tip of the pinion shaft 13 (the lower end in FIG. 1).

  The rack shaft 14 extends linearly along the left-right direction of the vehicle. A rack 17 that meshes with the pinion 16 is formed in the middle of the rack shaft 14 in the axial direction. By the pinion 16 and the rack 17, the rotation of the pinion shaft 13 is converted into the axial movement of the rack shaft 14. The steered wheel 3 can be steered by moving the rack shaft 14 in the axial direction.

When the steering wheel 2 is steered (rotated), this rotation is transmitted to the pinion shaft 13 via the steering shaft 6 and the intermediate shaft 7. The rotation of the pinion shaft 13 is converted into an axial movement of the rack shaft 14 by the pinion 16 and the rack 17. Thereby, the steered wheel 3 is steered.
The steering assist mechanism 5 includes a steering assist motor 18 and a speed reduction mechanism 19 as a transmission mechanism for transmitting the output torque of the motor 18 to the steering mechanism 4. As the speed reduction mechanism 19, for example, a staggered shaft gear mechanism such as a worm gear mechanism, a parallel shaft gear mechanism including a spur gear mechanism and a helical gear mechanism, or the like can be used. In the present embodiment, a worm gear mechanism is used as the speed reduction mechanism 19. That is, the speed reduction mechanism 19 includes a worm shaft 20 as a drive gear (drive-side member of the transmission mechanism) and a worm wheel 21 as a driven gear (driven-side member of the transmission mechanism) that meshes with the worm shaft 20. The speed reduction mechanism 19 is accommodated in a gear housing 22 as a transmission housing.

The worm shaft 20 is rotationally driven by the motor 18. The worm wheel 21 is connected to the steering shaft 6 so as to be able to rotate together. The worm wheel 21 is rotationally driven by the worm shaft 20.
When the motor 18 rotationally drives the worm shaft 20, the worm wheel 21 is rotationally driven by the worm shaft 20, and the worm wheel 21 and the steering shaft 6 rotate together. The rotation of the steering shaft 6 is transmitted to the pinion shaft 13 via the intermediate shaft 7. The rotation of the pinion shaft 13 is converted into the axial movement of the rack shaft 14. Thereby, the steered wheel 3 is steered. In other words, the steered wheels 3 are steered by rotating the worm shaft 20 by the motor 18.

  The motor 18 is controlled by the ECU 12. The ECU 12 controls the motor 18 based on the torque detection result from the torque sensor 11, the vehicle speed detection result from the vehicle speed sensor 23, and the like. Specifically, the ECU 12 determines a target assist amount using a map in which the relationship between the torque and the target assist amount is stored for each vehicle speed, and controls the assist force generated by the motor 18 to approach the target assist amount. .

  FIG. 2 is a circuit diagram of a control circuit included in the ECU 12 of the electric power steering apparatus 1 according to the embodiment of the present invention. The control circuit shown in FIG. 2 includes a capacitor 108 and a motor drive circuit 101. This control circuit is provided in the ECU 12, and is connected to the power connection portions PIG and PGND via the power relay 102 from the battery 100 as a power source.

  The motor drive circuit 101 includes six MOS-FETs (U1, U2, V1, V2, W1, W2) as switching elements. As shown in FIG. 2, MOS-FET.U1 and MOS-FET.U2 are connected in series, MOS-FET.V1 and MOS-FET.V2 are connected in series, and MOS-FET.W1 and MOS-FET. W2 is connected in series. This is a known inverter formed by connecting three circuits (arms) formed by connecting six MOS-FETs in series two by two in parallel, between the two power supply lines L1 and L2. Provided in parallel. A connection point between the MOS-FET · U1 and the MOS-FET · U2 is connected to one end of the U-phase coil of the motor 18. A connection point between the MOS-FET · V1 and the MOS-FET · V2 is connected to one end of the V-phase coil of the motor 18. A connection point between the MOS-FET · W1 and the MOS-FET · W2 is directly connected to one end of the W-phase coil of the motor 18. The other ends of the three-phase coils of the motor 18 are connected to a common connection point. The motor 18 is a three-phase brushless motor having a three-phase coil.

  The three capacitors 108 are provided between the two power supply lines L1 and L2. Each capacitor 108 accumulates electric charge from the battery 100 and discharges the accumulated electric charge when the current flowing from the battery 100 to the motor drive circuit 101 is insufficient. Thus, the capacitor 108 functions as a capacitor for absorbing current ripple. The capacitor 108 is divided and arranged in the vicinity of each phase drive circuit.

  The wiring between the power supply connection portion PIG and the MOS-FETs U1, V1, W1 and between the current detecting shunt resistors Ru, Rv, Rw and the power supply connection portion PGND are bus bars 1 and 105 and bus bars 2 and 106, respectively. Connected at.

  FIG. 3 is a side view of the motor and ECU of the electric power steering apparatus according to the embodiment of the present invention. As shown in FIG. 3, the electric power steering apparatus 1 includes a motor 18 and an ECU 12.

  Next, FIG. 4 is a plan view seen from the motor side showing the structure of the ECU 12 according to the present embodiment. The ECU 12 is disposed in the axial direction of the motor 18 between the motor 18 and a speed reduction mechanism 19 (see FIG. 1) of an electric power steering device (not shown).

  The ECU housing case accommodates and holds three power boards 104 and a control board 103 that constitute a part of the ECU 12. At least a part of a power circuit for driving the motor 18 (for example, a switching element such as a MOS-FET) is mounted on the power substrate 103. Each power board 104 forming each phase of U, V, and W is arranged on a concentric circle with the shaft of the motor 18 as the axis center. Further, it is connected to the power board 104 via a terminal of a bus bar connected to each phase coil of the motor 18. Further, the three capacitors 108 are arranged in the vicinity of the power board 104 on concentric circles centering on the rotation axis (hereinafter referred to as a shaft) of the motor 18.

  A power circuit for driving the motor 18 is mounted on the power board 104. The power circuit mounted on the power board 104 includes two MOS-FETs and one shunt resistor as heating elements. The power substrate 104 is composed of a multilayer substrate on which a circuit is mounted on one side, and the multilayer substrate includes a high thermal conductive plate (not shown) made of, for example, an aluminum plate that is in surface contact with a thick portion serving as a heat sink. Yes.

  Further, the control board 103 shown in FIG. 4 has a circular shape similar to the motor shape and is arranged around the shaft of the motor 18. The control board 103 is formed with a through hole 107 through which the shaft of the motor 18 is inserted.

  A control circuit for controlling the power circuit is mounted on the control board 103. The control circuit includes a driver (not shown) for controlling the MOS-FETs U1, U2, V1, V2, W1, W2 (see FIG. 2) of the power circuit and a CPU (not shown) for controlling the driver. Z). The ECU 12 includes a plurality of capacitors 108 for removing ripples of current flowing through the motor 18, a relay (not shown) for cutting off current flowing through the motor 18 as necessary, and other non-heating elements. Yes. The capacitor 108, the relay, and the like as non-heat generating elements constitute a subassembly supported by an annular synthetic resin holder (not shown), and can be collectively attached to the ECU housing case. Yes.

  The bus bars 1 and 105 are wiring members that connect between the power connection portion PIG and the MOS-FETs U1, V1, and W1 (see FIG. 2) of each power substrate 104 and function as a power supply pattern. The bus bars 2 and 106 are wiring members that connect between the power supply connecting portion PGND and the shunt resistors Ru, Rv, and Rw (see FIG. 2) of each power board 104 and function as a ground pattern. The bus bars 1 and 105 and the bus bars 2 and 106 each have a circular shape and are arranged around the shaft of the motor 18. Here, since the terminals of the power connection portions PIG and PGND are arranged not at the center position but away from the shaft of the motor 18, the wiring lengths between the power connection portions PIG and PGND of each phase and the power board 104 are different. For this reason, the bus lengths and wiring paths are matched by the bus bars 1 and 105 and the bus bars 2 and 106 so that the wiring resistance of each phase becomes equal. That is, the resistance difference between the power supply connection portion of each phase and the MOS-FET (PIG-U1, PIG-V1, and PIG-W1) can be reduced by the wiring path of the bus bars 1 and 105 indicated by the broken line in FIG. The same applies to the wiring between the power connection portion PGND of the bus bars 2 and 106 and the shunt resistor.

  The bus bars 1 and 105 and the bus bars 2 and 106 are formed with through holes 107 through which the shaft of the motor 18 is inserted in the same manner as the control board 103. The bus bars 1 and 105 and the bus bars 2 and 106 which are lead wires are three protruding bus bars (not shown) for supplying drive current to the coil portions of the U, V and W phases of the coil of the motor 18. 2), MOS-FETs U1, U2, V1, V2, W1, W2, and electrically connected parts such as a capacitor 108, and the above-described holder made of resin or the like, are fixed to the ECU housing case.

  As shown in FIG. 4, a power board 104 for each phase, a capacitor 108, bus bars 1 and 105, and bus bars 2 and 106 are mounted on a control board 103. Furthermore, the accommodation space formed between the motor 18 and the control board 103 in the ECU housing case has a sufficient height with respect to the axial direction of the motor 18. In this accommodation space, the capacitor 108 shown in FIG. 4 and tall parts such as a relay are accommodated as required, so that the space of the ECU housing case is effectively used.

  As described above, in the electric power steering apparatus 1 according to the present embodiment, the power board 104 and the capacitor 108 are concentrically arranged with respect to the shaft of the motor 18 in the ECU 12, and further, the power connection portions PIG, PGND and the power By connecting the substrates 104 with circular bus bars 1 and 105 and bus bars 2 and 106, it is possible to eliminate a difference in wiring resistance caused by a difference in wiring length of each phase.

Next, operations and effects of the electric power steering apparatus 1 of the present embodiment configured as described above will be described.
As described above, according to the present embodiment, the ECU 12 is formed in a circular shape in accordance with the shape of the motor 18, and circuit components are arranged radially with respect to the central axis, thereby suppressing resistance variation between the phases. However, since the shaft of the motor 18 passes through the center of the ECU 12, the wiring length of the power supply line to each phase is different. On the other hand, the power supply connection portions PIG and PGND and the respective phase circuit components are connected by the circular busbars 1 and 15 and the busbars 2 and 16, and the power is supplied from the battery 100. The wiring length and the wiring path can be matched so that the wiring resistance to each phase driving circuit becomes equal. As a result, it is possible to reduce current detection error particularly when the current is large, improve detection accuracy, and reduce torque ripple of the motor 18 and radio noise caused by the ECU 12. Capacitor 108 can absorb the ripple equally for each phase by being divided and arranged in the vicinity of each phase power substrate 104.
In addition, when the mounting position of the ECU 12 is changed by the vehicle, it is possible to easily change the wiring extraction position and the like by rotating the circuit unit around the shaft of the motor 18 without changing the component arrangement inside the ECU 12. Become.

In addition, you may change this embodiment as follows.
If the motor shaft does not penetrate the ECU board, the present invention can be applied to a bus bar having a different shape other than a circle by disposing the power supply connecting portion in the center of the ECU.
Although the present invention has been described with reference to an example using an electric power steering apparatus, the present invention is not limited to the above-described embodiment, and various applications are possible.
Further, the present invention can be applied not only to the above-described column assist type electric power steering apparatus but also to a pinion assist type or rack assist type electric power steering apparatus.

1: electric power steering device, 2: steering wheel, 3: steered wheel,
4: steering mechanism, 5: steering assist mechanism, 6: steering shaft, 11: torque sensor,
12: ECU, 13: Pinion shaft, 14: Rack shaft, 18: Motor, 19: Reduction mechanism,
23: Vehicle speed sensor, 100: Battery, 101: Motor drive circuit, 102: Power supply relay,
103: Control board, 104: Power board, 105: Bus bar 1, 106: Bus bar 2,
107: insertion hole, 108: capacitor,
L1, L2: power supply line, PIG, PGND: power supply connection part,
U1, U2, V1, V2, W1, W2: MOS-FET,
Ru, Rv, Rw: Shunt resistance

Claims (1)

A motor for providing a steering assist force to the steering mechanism of the vehicle;
Motor drive means for outputting drive power to the motor;
A battery for supplying a power supply voltage to the motor driving means,
The motor driving means is formed integrally with the motor so that the rotation shaft of the motor is inserted in the axial direction of the motor,
A plurality of capacitors on the input side;
A drive circuit for driving and controlling the motor;
In the electric power steering apparatus comprising the power supply line connecting the capacitor and the drive circuit,
The drive circuit and the capacitor disposed in the vicinity of the drive circuit are arranged separately for each phase of the motor on a concentric circle with respect to the rotation shaft of the motor to be inserted,
The electric power steering apparatus, wherein the power supply line is arranged so that the wiring resistance of each phase of the drive circuit becomes equal.

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