JP2009227176A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device, integrally provided with a motor and a control device for that, so that heat of both the motor and the control device are efficiently eliminated. <P>SOLUTION: The control device 13 in the electric power steering device 11 houses an electric circuit inside a cylindrical circuit case 40 that is open at one end. The motor 12 as a drive source has a cylindrical rear end part 12R as an open rear end surface, and an opening part of the cylindrical rear end part 12R and an opening part of the cylindrical circuit case 40 are faced to each other to be engaged. Between a motor support wall 30A projected from a side surface of a cylindrical rack housing 22 and a circuit case support wall 35, the motor 12 and the control device 13 are disposed. While the motor 12 is fixed to the motor support wall 30A, the control device 13 is fixed to the circuit case support wall 35. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  According to the present invention, a ball screw is formed on a part of a rack shaft passed between a pair of steered wheels in a vehicle, and a ball nut screwed to the ball screw is driven by a motor arranged in parallel with the rack shaft. The present invention relates to an electric power steering apparatus.

Conventionally, in this type of electric power steering apparatus, a side bulge is protruded laterally from a cylindrical rack housing that covers the rack shaft, and a motor is fixed to the side bulge (for example, Patent Document 1). Further, in this type of electric power steering apparatus, an apparatus in which a motor and its control device are integrated is also known.
JP 2004-314770 A (FIG. 2, paragraphs [0010] to [0012])

  However, in the conventional electric power steering device in which the motor and the control device are integrally provided, the control device is disposed on the side surface or the rear surface of the motor. Could not be removed efficiently.

  The present invention has been made in view of the above circumstances, and provides an electric power steering device that includes a motor and its control device as one body, and that can efficiently remove both the heat of the motor and the control device. Objective.

  An electric power steering device (11) according to the invention of claim 1 made to achieve the above object includes a rack shaft (21) passed between a pair of steered wheels (24) in a vehicle (10). A ball screw portion (25) formed in a part of the rack shaft (21) in the axial direction, a cylindrical rack housing (22) covering the rack shaft (21), and a cylindrical rack housing (22) A ball nut (28) screwed into the ball screw portion (25), a motor (12) disposed in parallel with the cylindrical rack housing (22), and a motor (12 ) And a motor support wall (30A) having an output shaft insertion hole (30B) through which the output shaft (12S) of the motor (12) is inserted, 12) A power transmission mechanism (29, 32, 33) in which the output shaft (12S) of 12) is connected to the ball nut (28), and a control device (13) for controlling the drive of the motor (12) according to the operating conditions. In the electric power steering device (11) that assists the turning of the steered wheels (24) by directly moving the rack shaft (21) with the power of the motor (12), one end of the control device (13) is opened. The electric circuit including the motor drive circuit (55) is housed in the cylindrical circuit case (40) whose other end is closed, and the rear end surface of the motor (12) is opened to form a cylindrical rear end ( 12R), and the opening of the cylindrical rear end (12R) and the opening of the cylindrical circuit case (40) face each other so as to be capable of linear movement, and the fitting gap is formed into an annular seal member. Sealed with (45), cylindrical rack housing 22) is provided with a circuit case support wall (35) projecting from the side surface and facing the motor support wall (30A), and the bottom wall (43) of the cylindrical circuit case (40) is pressed against the circuit case support wall (35). It is characterized by being fixed.

  According to a second aspect of the present invention, in the electric power steering apparatus (11) according to the first aspect, the motor (12) is an AC motor, and the motor drive circuit (55) is a direct current mounted on the vehicle (10). This is an inverter circuit having a plurality of FETs (52) for converting the output of the power source into an alternating current, and the plurality of FETs (52) are fixed by pressing against the inner surface of the bottom wall (43) of the cylindrical circuit case (40). It has the characteristics in that place.

[Invention of Claim 1]
In the electric power steering device according to the first aspect, the cylindrical rear end portion of the motor and the cylindrical circuit case of the control device are fitted, and the fitting gap is closed by the annular seal member. As a result, the motor and the control device are integrated, and in the communication space between the cylindrical rear end portion and the cylindrical circuit case, the electric circuits of the motor and the control device are connected to each other with an inexpensive structure without worrying about dust and water resistance. Can be connected. The motor and the control device are arranged between the motor support wall protruding from the cylindrical rack housing and the circuit case support wall, and the motor is fixed to the motor support wall, while the control device supports the circuit case. Fixed to the wall. Thereby, the heat of both the motor and the control device can be efficiently removed, and both ends of the integrated motor and control device are supported, thereby improving the support strength. Further, since the cylindrical rear end portion and the cylindrical circuit case can be moved directly, the thermal expansion and processing error of the cylindrical rack housing can be absorbed by the change in the fitting depth.

[Invention of claim 2]
According to the configuration of the second aspect, since the FET that generates the most heat in the motor drive circuit is pressed against the inner surface of the bottom wall fixed to the circuit case support wall in the cylindrical circuit case, the heat of the FET is efficiently removed. can do.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. The vehicle 10 shown in FIG. 1 includes a vehicle speed sensor 17 for detecting a vehicle speed, a torque sensor 16 for detecting a load torque applied to the handle 18, and a handle 18 together with the electric power steering apparatus 11 according to the present invention. And a steering angle sensor 15 for detecting the steering angle. And the control apparatus 13 takes in the detection result of each sensor 16-17, and drive-controls the motor 12 which is a drive source of the electric power steering apparatus 11, The assist force according to a driving | running condition is from the electric power steering apparatus 11. As a result, steering of the handle 18 is assisted.

  FIG. 2 shows the internal structure of the electric power steering apparatus 11. As shown in the figure, the electric power steering apparatus 11 includes a rack shaft 21 housed in a cylindrical rack housing 22. A guide groove (not shown) formed in the rack shaft 21 and a guide projection (not shown) protruding inward from the cylindrical rack housing 22 are in sliding engagement, and the rack shaft 21 is linearly moved in the cylindrical rack housing 22. It is pivotally supported so that it cannot rotate. As shown in FIG. 1, both ends of the rack shaft 21 are connected to a pair of steered wheels 24 and 24 via tie rods 23 and 23. In addition, bellows-cylindrical rubber boots 39 and 39 are attached to both ends of the cylindrical rack housing 22 to prevent foreign matter from entering. The cylindrical rack housing 22 is made of aluminum including a side bulging portion 30 and a circuit case support wall 35 which will be described later.

  As shown in FIG. 2, a ball screw portion 25 is formed at a position near one end of the rack shaft 21 in the axial direction, and a rack gear portion 26 is formed at a position near the other end. The rack gear portion 26 is engaged with a pinion 27 penetrating the cylindrical rack housing 22 from the side. The pinion 27 is connected to a lower end portion of a steering shaft 19 extending downward from the handle 18 (see FIG. 1) so as to be integrally rotatable. Thereby, the rack shaft 21 moves linearly with the steering of the handle 18, and the steered wheels 24, 24 are steered.

  A ball nut 28 is pivotally supported in a portion of the cylindrical rack housing 22 corresponding to the ball screw portion 25 so that the ball nut 28 can rotate but cannot move directly. Then, the ball nut 28 is screwed into the ball screw portion 25 to form a ball screw mechanism, and the rotation of the ball nut 28 is converted into a linear motion of the ball screw portion 25 by this ball screw mechanism.

  A first pulley 29 is fitted and fixed to the outer surface of the ball nut 28. A side bulging portion 30 that protrudes laterally from the side surface of the cylindrical rack housing 22 is formed in a portion of the cylindrical rack housing 22 corresponding to the first pulley 29. The side bulging portion 30 has a bag structure communicating with the accommodation space of the first pulley 29 in the cylindrical rack housing 22.

  A wall portion facing the pinion 27 side of the side bulging portion 30 is a motor support wall 30A according to the present invention. An output shaft insertion hole 30 </ b> B is formed through the motor support wall 30 </ b> A in a direction parallel to the rack shaft 21. Then, the output shaft 12S of the motor 12 is inserted into the output shaft insertion hole 30B, and the front end surface 12F of the motor 12 is pressed against the outer surface of the motor support wall 30A and fixed by the bolt B1. More specifically, a flange portion 12A protrudes laterally from the front end portion of the motor 12, and a bolt B1 passing through the flange portion 12A is screwed into a screw hole (not shown) formed in the motor support wall 30A. In addition, the motor 12 is fixed to the motor support wall 30A. As a result, the motor 12 is arranged in parallel with the rack shaft 21 on the side of the cylindrical rack housing 22. A portion of the lateral bulging portion 30 that faces the motor support wall 30A is a detachable lid 30F.

  A second pulley 32 is fixed to a portion of the output shaft 12S of the motor 12 that passes through the motor support wall 30A and is positioned in the side bulging portion 30 so as to be integrally rotatable. And the belt 33 is spanned between the 1st and 2nd 2nd pulleys 29 and 32, and the "power transmission mechanism" concerning this invention is comprised. Thereby, the ball nut 28 is rotationally driven by the power of the motor 12.

  Now, the motor 12 of the present embodiment is a three-phase AC motor and incorporates a rotational position sensor (not shown). Further, as shown in FIG. 3, a control device 13 is integrally assembled with the rear end portion of the motor 12. Specifically, the rear end portion of the motor 12 is a cylindrical rear end portion 12R having a cylindrical shape whose rear end surface is open. A connector (not shown) at the end of each of U, V, W windings of the motor 12 and a connector (not shown) at the output terminal of the rotational position sensor are arranged at the back of the cylindrical rear end 12R. Is housed.

  On the other hand, the control device 13 is configured by housing an electric circuit in a cylindrical circuit case 40. The cylindrical circuit case 40 is made of aluminum and has a cylindrical shape with one end open and the other end closed by a bottom wall 43. Then, the opening of the cylindrical circuit case 40 and the opening of the cylindrical rear end portion 12R face each other, and the cylindrical rear end portion 12R and the cylindrical circuit case 40 are fitted to each other. The device 13 and the motor 12 are integrated.

  Specifically, the cylindrical circuit case 40 has a large-diameter cylindrical portion 41 having an outer diameter substantially the same as the cylindrical rear end portion 12R on the bottom wall 43 side, and an open port side directly on the inner side of the cylindrical rear end portion 12R. The small-diameter cylindrical portion 42 is movably fitted. Further, an O-ring groove 44 is formed on the outer side surface of the small-diameter cylindrical portion 42, and an O-ring 45 (corresponding to the “annular seal member” of the present invention) mounted in the O-ring groove 44 is formed after the cylindrical shape. The fitting gap between the cylindrical rear end 12R and the cylindrical circuit case 40 is closed by being in close contact with the inner surface of the end 12R.

  The cylindrical circuit case 40 is accommodated in a pair of circuit boards 50 and 51. These circuit boards 50 and 51 are formed in, for example, a substantially disk shape, and have electric wire insertion holes 50A and 51A for inserting electric wires. Further, the inner diameter of the inner portion of the cylindrical circuit case 40 is slightly reduced, for example, in a stepped shape. Then, one circuit board 50 is fitted into the cylindrical circuit case 40 and abutted against the step surface on the back side, and the first cylindrical spacer 46B, the other circuit board 51, and the second cylindrical spacer 46C. The second cylindrical spacer 46C inserted last is fixed to the cylindrical circuit case 40 with an adhesive, whereby the pair of circuit boards 50 and 51 are connected to the cylindrical circuit case 40. It is fixed inside.

  For example, a plurality of FETs 52 are fixed to the inner surface of the bottom wall 43 of the cylindrical circuit case 40. The motor drive circuit 55 shown in FIG. 4 is configured by wiring between the FETs 52. The motor drive circuit 55 is an inverter circuit that converts direct current into three-phase alternating current, and includes U, V, and W phases between a positive electrode (Vcc) and a negative electrode (GND) of a battery mounted on the vehicle 10. Circuits 53U, 53V, and 53W are connected in parallel, and a pair of FETs 52 and 52 are connected in series for each of the phase circuits 53U, 53V, and 53W.

  Further, U, V, and W feed lines 54U, 54V, and 54W extend from a common connection point of the pair of FETs 52 and 52 in the phase circuits 53U, 53V, and 53W. Then, a total of six FETs 52 for each pair of U, V, and W phases are fixed as described above with screws, for example, while pressed against the inner surface of the bottom wall 43. The power supply lines 54U, 54V, 54W extend to the cylindrical rear end 12R side through the wire through holes 50A, 51A (see FIG. 3) of the circuit boards 50, 51, for example, and each phase winding of the motor 12 Are connected by a connector (not shown). Further, the output terminal of the rotational position sensor of the motor 12 is connected to a signal line extending from one of the circuit boards 50 and 51 by a connector (not shown). The large-diameter cylindrical portion 41 of the cylindrical circuit case 40 is provided with a cable insertion hole (not shown) through which the signal lines of the sensors 15 to 17 and the power line from the battery are inserted, and the cable insertion hole. The gap is filled with a sealing agent.

  As shown in FIG. 3, female screw holes 43 </ b> N are formed in the bottom wall 43 of the cylindrical circuit case 40 at a plurality of positions (for example, four positions) shifted from the FET. These female screw holes 43 </ b> N are bottomed holes and do not penetrate into the control device 13.

  The cylindrical rack housing 22 is provided with a circuit case support wall 35 so as to face the motor support wall 30A with the motor 12 and the control device 13 interposed therebetween. The circuit case support wall 35 has a flat plate shape standing upright from the side surface of the cylindrical rack housing 22. Further, a reinforcing triangular rib 36 is integrally formed on a surface of the circuit case support wall 35 facing the side opposite to the motor support wall 30A. The circuit case support wall 35 is formed with bolt insertion holes 35A penetratingly formed at positions corresponding to the plurality of female screw holes 43N in the bottom wall 43 of the cylindrical circuit case 40, and the plurality of bolt insertion holes 35A inserted therethrough. The bolt B2 is tightened in the female screw hole 43N, and the bottom wall 43 of the cylindrical circuit case 40 is fixed to the circuit case support wall 35.

  When the motor 12 is assembled between the motor support wall 30A and the circuit case support wall 35, the cylindrical circuit case 40 is moved to the cylindrical rear end 12R side within a range in which the motor 12 can be linearly moved, and the output shaft 12S is inserted into the output shaft insertion hole 30B obliquely from above in FIG. Thus, when the motor 12 and the control device 13 are disposed between the motor support wall 30A and the circuit case support wall 35, the motor 12 is fixed to the motor support wall 30A, and the lid 30F of the side bulging portion 30 is attached. In the removed state, the second pulley 32 and the belt 33 are attached to the output shaft 12S of the motor 12, and the lid 30F is closed. Then, the control device 13 is moved directly to the circuit case support wall 35 side, and the bolt B2 passed through the bolt insertion hole 35A of the circuit case support wall 35 may be tightened into the female screw hole 43N of the cylindrical circuit case 40.

  This completes the description of the configuration of the electric power steering device 11 of the present embodiment. Next, the effect of the electric power steering apparatus 11 will be described.

  When an ignition key (not shown) of the vehicle 10 is turned on, detection results of the rudder angle sensor 15, torque sensor 16 and vehicle speed sensor 17 are taken into the control device 13. When the steering wheel 18 is steered, a current command value is determined according to the steering angle, the steering resistance, and the vehicle speed detected by the sensors 15 to 17, and the three-phase alternating current corresponding to the current command value is converted into a motor of the control device 13. Generated by the drive circuit 55 and energizes the motor 12. As a result, an assist force corresponding to the driving situation is output from the electric power steering device 11 and the steering of the handle 18 is assisted.

  Now, in the electric power steering apparatus 11 of this embodiment, the cylindrical rear end portion 12R of the motor 12 and the cylindrical circuit case 40 of the control apparatus 13 are fitted, and the fitting gap is closed by the 0 ring 45. ing. As a result, the motor 12 and the control device 13 are integrated, and the motor 12 and the control are controlled in an inexpensive structure without worrying about dust and water resistance in the communication space between the cylindrical rear end 12R and the cylindrical circuit case 40. The electrical circuits of the device 13 can be connected to each other. The motor 12 and the control device 13 are disposed between the motor support wall 30A protruding from the cylindrical rack housing 22 and the circuit case support wall 35, and the motor 12 is fixed to the motor support wall 30A. The control device 13 (in detail, the cylindrical circuit case 40) is fixed to the circuit case support wall 35. In addition, the FET 52 of the motor drive circuit 55 that generates the most heat in the control device 13 is pressed against the inner surface of the bottom wall 43 of the cylindrical circuit case 40. Thereby, the heat of both the motor 12 and the control device 13 can be efficiently removed. Moreover, the both ends of the integrated body of the motor 12 and the control device 13 are supported, and the support strength is also improved. Furthermore, since the cylindrical rear end portion 12R and the cylindrical circuit case 40 can move linearly, thermal expansion and processing errors of the cylindrical rack housing 22 can be absorbed by changes in the fitting depth.

[Other Embodiments]
The present invention is not limited to the above-described embodiment. For example, the embodiments described below are also included in the technical scope of the present invention, and various other than the following can be made without departing from the scope of the invention. It can be changed and implemented.

  (1) In the above embodiment, the cylindrical rear end 12R and the cylindrical circuit case 40 are cylindrical, but may be rectangular.

  (2) In the above embodiment, the cylindrical circuit case 40 is fixed to the circuit case support wall 35 with the bolts B2. However, the cylindrical circuit case may be fixed to the circuit case support wall with an adhesive.

The conceptual diagram of the vehicle which concerns on one Embodiment of this invention. Side sectional view of electric power steering device Enlarged side sectional view of the electric power steering device Circuit diagram of motor drive circuit

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Vehicle 11 Electric power steering apparatus 12 Motor 12R Cylindrical rear end part 12S Output shaft 13 Control apparatus 21 Rack shaft 22 Cylindrical rack housing 24 Steering wheel 25 Ball screw part 28 Ball nut 29 First pulley (power transmission mechanism)
30 Side bulging portion 30A Motor support wall 30B Output shaft insertion hole 30F Lid 32 Second pulley (power transmission mechanism)
33 Belt (Power transmission mechanism)
35 Circuit case support wall 40 Cylindrical circuit case 43 Bottom wall 45 O-ring (annular seal member)
55 Motor drive circuit 52 FET

Claims (2)

A rack shaft passed between a pair of steered wheels in a vehicle;
A ball screw portion formed in a part of the rack shaft in the axial direction;
A cylindrical rack housing covering the rack shaft;
A ball nut screwed into the ball screw portion in the cylindrical rack housing;
A motor disposed in parallel with the cylindrical rack housing;
A motor support wall that protrudes from a side surface of the cylindrical rack housing and has an output shaft insertion hole through which the output shaft of the motor is inserted, and the front end surface of the motor is pressed and fixed;
A power transmission mechanism that connects the output shaft of the motor to the ball nut;
An electric power steering device that includes a control device that drives and controls the motor according to an operating situation, and that directly drives the rack shaft with the power of the motor to assist the turning of the steered wheels;
The control device accommodates an electric circuit including a motor drive circuit inside a cylindrical circuit case with one end open and the other end closed.
A rear end surface of the motor is opened to form a cylindrical rear end portion, and an open port of the cylindrical rear end portion and an open port of the cylindrical circuit case are opposed to each other so as to be directly movable and Close the fitting gap with an annular seal member,
An electric power characterized by providing a circuit case support wall protruding from a side surface of the cylindrical rack housing and facing the motor support wall, and pressing and fixing the bottom wall of the cylindrical circuit case to the circuit case support wall Steering device.   The motor is an AC motor, and the motor driving circuit is an inverter circuit including a plurality of FETs for converting an output of a DC power source mounted on the vehicle into an AC, and the plurality of FETs are connected to the cylinder. The electric power steering apparatus according to claim 1, wherein the electric power steering apparatus is fixed by being pressed against an inner surface of a bottom wall of the circuit case.

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