JP5321489B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering apparatus including an electric motor that applies a steering assist force to a steering system, and a control unit that controls an energization state of the electric motor according to a steering torque of the steering system.

An electromechanical integrated electric power steering device in which an electric motor and a control unit are mounted on a reduction gear box is known. The control unit includes a control board on which a control circuit for driving and controlling an electric motor that transmits steering assist force is mounted. They are stored (for example, Patent Document 1 and Patent Document 2).
The control unit includes a unit cover that is attached to the outer periphery of the reduction gear box and covers the board surface on which the control circuit of the control board is mounted. The unit cover of Patent Document 1 is made of resin.
However, even if the resin unit cover of Patent Document 1 is a member having a large thickness, resistance to impact force is weak. May have an impact.

  Therefore, the unit cover of Patent Document 2 is a metal unit cover, and an impact reinforcement portion (reinforcement rib) is provided on a protective plate portion that covers the substrate surface on which the control circuit of the control board is mounted. Increases resistance to power. The metal unit cover has a function of preventing electromagnetic waves generated inside the control unit from being released to the outside or preventing electromagnetic waves from entering the control unit from the outside.

JP 2001-196770 A JP 2009-23458 A

By the way, the vehicle vibration transmitted from the vehicle to the reduction gearbox or the motor vibration transmitted from the electric motor is transmitted to the unit cover of the control unit. An unpleasant sound is generated.
The unit cover of Patent Document 2 has impact resistance by providing an impact reinforcing portion (reinforcing rib), but the effect until the vehicle vibration and motor vibration are attenuated cannot be expected, and unpleasant noise such as chatter noise is expected. Sound may be generated.

  Therefore, the present invention has been made paying attention to the unsolved problems of the above-mentioned conventional example, and electromagnetic waves generated inside the control unit are emitted to the outside, or electromagnetic waves enter the inside of the control unit from the outside. It has a unit cover that can be prevented, is excellent in impact resistance even when impact force is applied, and can securely protect the control board that is housed, and even if vehicle vibration or motor vibration is transmitted, An object of the present invention is to provide an electric power steering device that can suppress unpleasant sounds such as chatter noise.

In order to achieve the above object, an electric power steering apparatus according to claim 1 of the present invention is mounted with an electric motor that generates a steering assist force that assists a steering operation, and a control circuit that controls driving of the electric motor. In the electric power steering apparatus in which the control unit including the control board is mounted on the outer periphery of the housing,
The control unit includes a unit cover that houses the control board, a cover edge is fixed to the housing, and a protection plate part faces a board surface on which the control circuit of the control board is mounted, The surface central portion of the protection plate portion is fixed to the housing via a vibration suppression portion, and the vibration suppression portion is disposed inside the protection plate portion and fixed to the housing while being fixed to the housing. And a connecting portion that integrally connects the inner cover portion and the central portion of the surface of the protective plate portion.

According to the present invention, when vehicle vibration is transmitted from the vehicle to the housing or motor vibration is transmitted from the electric motor, the surface center portion of the protective plate portion of the unit cover is fixed to the housing via the vibration damping portion. As a result, the transmitted vibration is easily attenuated when the protective plate vibrates with a small amplitude. For this reason, the unit cover has a structure in which unpleasant sound is unlikely to occur even when vehicle vibrations and motor vibrations are transmitted.
Further, according to the present invention, the inner cover fixed to the housing and the connecting portion that connects the inner cover and the surface center portion of the protection plate portion securely hold the surface center portion of the protection plate portion of the unit cover. Further, since the inner cover covers the board surface of the control board, the protection effect of the control circuit in the event of a collision can be enhanced.

According to a second aspect of the present invention, in the electric power steering apparatus according to the first aspect, the unit cover is a metal member.
According to the present invention, by providing the metal unit cover, it is possible to improve the resistance against impact force, and prevent the electromagnetic wave generated inside the control unit from being released to the outside. The function of preventing electromagnetic waves from entering the inside can be improved.

According to a third aspect of the present invention, in the electric power steering apparatus according to the first or second aspect , the inner cover is a member made of synthetic resin.
According to the present invention, the dual structure of the unit cover and the synthetic resin inner cover can further improve the resistance to impact force, and further improve the function of electromagnetic wave emission and intrusion prevention. Can do. In addition, vibration can be attenuated.

According to a fourth aspect of the present invention, in the electric power steering apparatus according to any one of the first to third aspects, a torque sensor is disposed inside the housing, and a plurality of external devices connected to the torque sensor are arranged. A connection terminal protrudes outside from the housing, and each of the plurality of external connection terminals is electrically connected to a plurality of through holes provided in the control board by soldering, and the inner cover includes the control It was made to function as a member that prevents solder from splashing into the circuit.
According to the present invention, it is possible to improve the efficiency of the assembly work of the electric power steering apparatus.

Further, the invention according to claim 5 is the electric power steering apparatus according to any one of claims 1 to 4 , wherein the housing transmits a steering assist force generated by the electric motor to a steering system. This is a reduction gearbox with a built-in mechanism.
According to the present invention, the electric motor and the reduction gear box can be easily assembled.

  According to the electric power steering apparatus according to the present invention, even if vehicle vibration is transmitted from the vehicle to the housing or motor vibration is transmitted from the electric motor, the central portion of the surface of the protection plate portion of the unit cover is interposed via the vibration damping portion. Since it is fixed to the housing, the protection plate portion vibrates with a small amplitude, and the transmitted vibration is easily attenuated. For this reason, even if vehicle vibration and motor vibration are transmitted, it is possible to provide an electric power steering device with improved silence.

1 is a perspective view showing an embodiment of an electric power steering apparatus according to the present invention. It is a longitudinal cross-sectional view which shows the principal part of the reduction gear box which comprises an electric power steering apparatus. It is a disassembled perspective view of the control unit which comprises an electric power steering device. It is the schematic which compared the structure of the control unit which concerns on this invention, and the control unit of the conventional structure,

Hereinafter, the best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described in detail with reference to the drawings.
FIG. 1 is a perspective view showing an electric power steering apparatus according to the present invention from the front of a vehicle.
Reference numeral 1 in FIG. 1 denotes a column-type electric power steering device. A reduction gear box 4 is connected to a steering column 3 that rotatably houses a steering shaft 2 connected to a steering wheel (not shown). The reduction gear box 4 is provided with an electric motor 5 whose axial direction is extended in a direction perpendicular to the axial direction of the steering column 3.

The steering column 3 has a double tube structure of an inner tube 3a and an outer tube 3b. The inner tube 3 a and the reduction gear box 4 of the steering column 3 are attached to the vehicle body side by an upper mounting bracket 6 and a lower mounting bracket 7.
The lower mounting bracket 7 is formed of a mounting plate portion 7a attached to the vehicle body side member, and a pair of support plate portions 7b extending in parallel from the lower surface of the mounting plate portion 7a in the left-right direction with a predetermined interval. . And the lower end of the support plate part 7b is rotatably connected to the support part 4b integrally formed in the vehicle body front side of the reduction gear box 4 via the pivot 7c.

  The upper mounting bracket 6 is formed on a pair of flanges 6a, a pair of support plate portions 6c fixed to the lower ends of the flanges 6a and spaced apart in the left-right (vehicle width) direction, and the pair of support plate portions 6c. And a tilt mechanism 6 d that supports the outer tube 3 b of the steering column 3. A slit 6a1 is formed in the flange 6a, and a release capsule 6b is fitted in the slit 6a1. A bolt through hole 6b1 is formed in the release capsule 6b, and a fixing bolt (not shown) that penetrates the bolt through hole 6b1 from below the release capsule 6b is screwed into a vehicle body side member (not shown). The flange 6a is attached to the vehicle body side member.

Then, by tilting the tilt lever 6g of the tilt mechanism 6d and releasing the support state of the outer tube 3b, the tilt position of the steering column 3 can be adjusted up and down around the pivot 7c of the lower mounting bracket 7. .
As shown in FIG. 2, the steering shaft 2 has an input shaft 2a whose upper end is connected to the steering wheel, and an output shaft 2c that covers the torsion bar 2b connected to the lower end of the input shaft 2a via the torsion bar 2b. It consists of

  As shown in FIGS. 1 and 2, the reduction gear box 4 includes a worm storage portion 12 that stores a worm 11 connected to an output shaft (not shown) of the electric motor 5, and a lower portion of the worm storage portion 12. A worm wheel housing part 14 for housing a worm wheel 13 having a central axis perpendicular to the central axis and meshing with the worm 11, and a torque sensor integrally and coaxially connected to the rear side of the vehicle body of the worm wheel housing part 14 15, a torque sensor housing portion 16 for housing 15, a motor mounting portion 17 for attaching the electric motor 5 formed on the open end surface of the worm housing portion 12, and a cylindrical column formed at the rear end of the vehicle body of the torque sensor housing portion 16. A control unit device for mounting a mounting unit 18 and a control unit 19 formed over part of the worm storage unit 12 and the worm wheel storage unit 14. And a part 20. The front end portion of the vehicle body of the steering column 3 is externally fitted and connected to the column mounting portion 18 of the reduction gear box 4.

  Here, as shown in FIG. 2, the torque sensor 15 magnetically detects the twisted state between the input shaft 2a and the output shaft 2c of the steering shaft 2 and detects a pair of steering torques transmitted to the steering shaft 2. The coils 15a and 15b are configured to detect the external connection terminals 15c projecting outward in parallel to the direction perpendicular to the central axis of the steering column 3 at the start and end of winding of the pair of detection coils 15a and 15b, respectively. 15d and 15e, 15f are connected, and the protruding portions of these external connection terminals 15c to 15f are bent in parallel with the central axis of the steering column 3 at the central portion to form an L shape.

  As shown in FIG. 1, the electric motor 5 has a connection terminal (not shown) at a position close to and facing the control unit 19 mounted on the control unit mounting portion 20 at a position close to the mounting flange 5b. Although not specifically shown, each of the connection terminals is insulated from each other in a synthetic resin brush support body having an armature insertion hole at the bottom center, and is individually connected to two sets of brushes. The arc-shaped connection terminals are integrally formed at opposite ends.

Although not specifically shown, the control unit mounting portion 20 formed in the reduction gear box 4 is formed to face the vehicle body rear side with the worm storage portion 12 and the upper side of the worm wheel storage portion 14 below the worm storage portion 12. And a flat unit mounting surface orthogonal to the flat mounting surface and the flat mounting surface formed on the upper surface of the torque sensor housing 16 and extending in the left-right direction in the longitudinal direction. It is formed in an L shape when viewed from the left-right direction.
Here, an opening (not shown) that communicates with the internal space of the torque sensor storage unit 16 that stores the torque sensor 15 is formed at the center in the left-right direction of the unit mounting surface of the control unit mounting unit 20. The external connection terminals 15c to 15f of the torque sensor 15 are provided so as to protrude above the unit mounting surface through the opening.

Further, a frame mounting surface (not shown) having a narrow width at a position on the rear side of the vehicle body parallel to the flat mounting surface formed on the rear end surface of the vehicle mounting portion 17 so as to face the rear side of the vehicle body. Is formed.
As shown in FIG. 3, the control unit 19 mounted on the control unit mounting unit 20 includes a heat radiating plate 21, a power board 22, a rectangular frame 23, a control board 24, an inner cover 25, and an outer side. And a cover 26.

  The heat radiating plate 21 is directly fixed to the flat mounting surface of the control unit mounting portion 20 via heat radiating grease. The power board 22 is a discrete component 22a, 22b such as an H bridge circuit composed of a power switching element such as a field effect transistor that drives and controls the electric motor 5, and a pulse width modulation circuit that drives the power switching element of the H bridge circuit. Is implemented.

  The control board 24 is attached to the front surface of the frame 23, and has through holes 24a to 24d that are directly inserted through the external connection terminals 15c to 15f of the torque sensor 15. A torque detection value from the torque sensor 15 or a vehicle speed sensor (not shown) is provided. The steering assist current command value is calculated based on the detected vehicle speed value from the vehicle, and the current feedback control is performed based on the steering assist current command value and the detected value of the motor current output to the electric motor 5 to perform the pulse of the power board 22. By calculating a voltage command value to the width modulation circuit, a discrete part 24e such as a micro control unit (MCU) for controlling a steering assist force generated by the electric motor 5 and its peripheral devices is mounted.

The frame 23 is a member that surrounds the power board 22, and includes a rectangular frame-shaped frame body 23 a and a mounting plate portion 23 b that is formed at the left end of the frame body 23 a and is fixed to the frame mounting surface of the reduction gear box 4. A terminal block 23c fixed on the mounting plate 23b and electrically connected to a connection terminal of the electric motor 5 and a female connector 45 fixed to the right end of the frame body 23a are provided. Although not shown, the female connector 45 includes a power connector 45a that is connected to a battery via a male connector for power supply, and a signal connector 45b that is connected to a network such as a CAN that transmits and receives data to / from a control device in each part of the vehicle body. And. The power board 22 and the control board 24 are connected via a connection terminal 22c.
The inner cover 25 is a resin member, and is fixed to a rectangular flat plate portion 25a, a screw insertion hole 25b formed in an edge of the flat plate portion 25a, and a lower surface of the flat plate portion 25a corresponding to the screw insertion hole 25b. This is a member provided with a plurality of hollow cylindrical leg portions 25c and a connecting cylinder portion 25d which is fixed to the center of the upper surface of the flat plate portion 25a and has a screw hole 25d1.

Then, the inner cover 25 is screwed into the screw holes 41 for fixing the inner cover formed in the frame 23 by screwing the fixing screws 40 inserted through the screw insertion holes 25b and the screw insertion holes of the leg portions 25c from above the flat plate portion 25a. Is fixed to the frame 23 while covering the power board 22 and the control board 24.
The outer cover 26 is a metal member, and extends perpendicularly from a rectangular first protective plate portion 28 that covers the inner cover 25 and an edge portion in the longitudinal direction of the first protective plate portion 28. Second and third protective plate portions 29, 30 and fourth and fourth portions extending in the same direction as the second and third protective plate portions 29, 30 from the edge in the short direction of the first protective plate portion 28. A plurality of screw insertion holes formed in the direction orthogonal to the outside of the cover from the end portions of the fifth protection plate portions 31, 32, the second protection plate portion 29, the fourth protection plate portion 31, and the fifth protection plate portions 31, 32. And a fixed piece 34.

The fourth protective plate portion 31 is formed with a notch 31 a surrounding the outer periphery of the female connector 45.
Here, a screw insertion hole 28 a is formed in the central portion of the first protection plate portion 28, and a connection screw 42 inserted into the screw insertion hole 28 a is connected to the connecting cylinder portion of the inner cover 25 fixed to the frame 23. Screw into the 25d screw hole 25d1. As a result, the first protective plate portion 28 of the outer cover 26 is integrated with the flat plate portion 25 a of the inner cover 25 via the connecting screw 42.

  Then, the heat radiating plate 21 and the frame 23 of the control unit 19 are fixed to the control unit mounting portion 20 of the reduction gear box 4, and the outer cover 26 is also fixed by being inserted into the screw insertion holes of the fixing piece 34 as shown in FIG. By screwing the screw 43 into a screw hole (not shown) of the control unit mounting part 20, the control unit 19 is mounted on the control unit mounting part 20 of the reduction gear box 4. Further, the terminal block 23 c fixed to the mounting plate portion 23 b of the frame 23 and the connection terminal of the electric motor 5 are electrically connected. The electrically connected terminal block 23c and the connection terminal of the electric motor 5 are covered with a synthetic resin terminal cover denoted by reference numeral 27 in FIG.

Next, the operation of the above embodiment will be described.
When power is supplied from the battery to the power board 22 and the control board 24 by turning on an ignition switch (not shown) of the vehicle body, a steering assist control process is executed by the micro control unit (MCU), and the torque sensor 15 and the vehicle speed sensor (not shown) are A steering assist current command value is calculated based on the detected value. A current feedback process is executed based on the steering assist current command value and the motor current detected by the motor current detection unit to calculate a voltage command value. By supplying this voltage command value to the gate drive circuit of the power board 22 and controlling the H bridge circuit, a motor drive current flows through the electric motor 5 and the electric motor 5 needs to be operated in the forward or reverse direction. Drive to generate force.
Therefore, a steering assist force corresponding to the steering torque of the steering wheel is generated from the electric motor 5, and this steering assist force is transmitted to the output of the steering shaft 2 via the worm 11 and the worm wheel 13, whereby the steering wheel Can be steered with a light steering force.

Next, the effect of this embodiment is demonstrated with reference to FIG.
FIG. 4A schematically shows a single unit cover provided in a conventional control unit (for example, Patent Documents 1 and 2). When vehicle vibration is transmitted from the vehicle to the reduction gear box 4 or motor vibration is transmitted from the electric motor 5, the single unit cover of the conventional device is deformed only at the edge of the protective plate covering the control board. Therefore, as shown in the figure, it vibrates and resonates with a large amplitude, and an unpleasant sound such as a chatter sound is likely to be generated.

  On the other hand, as shown in FIG. 4B, in the control unit 19 of this embodiment, the central portion of the first protective plate portion 28 of the outer cover 26 is connected via the connecting cylinder portion 25d and the connecting screw 42. Since it is connected to the inner cover 25, even if vehicle vibration or motor vibration is transmitted, it vibrates with a small amplitude, and the transmitted vibration is easily attenuated. Therefore, the outer cover 26 of the present embodiment has a structure in which unpleasant noise is unlikely to be generated even when vehicle vibrations and motor vibrations are transmitted, so that the electric power steering apparatus 1 with improved silence can be provided.

Further, in the control unit 19 of the present embodiment, the double-layered outer cover 26 and inner cover that are integrated via the connecting cylinder portion 25d and the connecting screw 42 are configured to receive impact force from the rear of the vehicle. Thus, the resistance against impact force can be improved and the mounted components such as the control board 24 can be reliably protected.
Further, since the outer cover 26 is formed of a metal member and the inner cover 25 is formed of a synthetic resin member, the inner cover 25 is formed inside the control unit 19 as compared with a conventional device configured with a single unit cover. The function of preventing the generated electromagnetic wave from being released to the outside and preventing the electromagnetic wave from entering the control unit 19 from the outside can be improved.

Further, since the inner cover 25 is disposed so as to cover the control board 24, when connecting the external connection terminals 15c to 15f to the detection coils 15a and 15b of the torque sensor 15 shown in FIG. Since it is possible to prevent the solder from being scattered on the control board 24, it is possible to improve the efficiency of the assembly work of the electric power steering apparatus 1.
In the above embodiment, the first protective plate portion 28 of the outer cover 26 is connected to the inner cover 25 via the connecting cylinder portion 25d and the connecting screw 42. However, the present invention is not limited to this. Instead, if the first protective plate portion 28 and the inner cover 25 are connected by a connecting means such as a clip, fitting of a concavo-convex portion, caulking fixing, adhesion, or the like, the same effect can be obtained.

Further, in the above embodiment, the connecting cylinder portion 25 d of the inner cover 25 is provided as a protrusion toward the outer cover 26, but the same effect can be obtained even when protruding toward the control board 24.
Further, in the above embodiment, the outer cover 26 is fixed to the reduction gear box 4, but the same effect can be obtained even if it is fixed to the mounting plate portion 23 b of the frame 23.
In the above embodiment, the case where the electric motor 5, the control unit 19, and the female connector 45 are arranged in a straight line along a line orthogonal to the central axis of the steering column 3 has been described. However, the present invention is not limited to this. Instead of this, they may be arranged in a straight line along a line intersecting the central axis of the steering column 3.

  Moreover, in the said embodiment, although the case where a brush motor was applied as the electric motor 5 was demonstrated, it is not limited to this, You may make it apply a brushless motor, In this case, a connection terminal Is connected to the power supply side of the excitation coil of each phase and drives the brushless motor on the power board 23, for example, an inverter circuit having a field effect transistor (FET) and the gate of the field effect transistor of the inverter circuit is driven by a pulse width modulation signal And a gate driving circuit to be mounted.

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering device, 2 ... Steering shaft, 2a ... Input shaft, 2b ... Torsion bar, 2c ... Output shaft, 3 ... Steering column, 3a ... Inner tube, 3b ... Outer tube, 4 ... Reduction gear box (housing) 4b ... support portion, 5 ... electric motor, 5b ... mounting flange, 6 ... upper mounting bracket, 6a ... flange, 6a1 ... slit, 6b ... detaching capsule, 6b1 ... bolt through hole, 6c ... support plate portion, 6d ... Tilt mechanism, 6g ... tilt lever, 7 ... lower mounting bracket, 7a ... mounting plate, 7b ... support plate, 7c ... pivot, 11 ... worm, 12 ... worm storage, 13 ... worm wheel, 14 ... worm wheel storage 15, torque sensors, 15 a, 15 b, detection coils, 15 c to 15 f, external connection terminals, 16, torque sensor , 17 ... Motor mounting portion, 18 ... Column mounting portion, 19 ... Control unit, 20 ... Control unit mounting portion, 21 ... Heat dissipating plate, 22 ... Power substrate, 22a, 22b ... Discrete parts, 22c ... Connection terminal, 23 ... Frame, 23a ... Frame body, 23b ... Mounting plate, 23c ... Terminal block, 24 ... Control board, 24a-24d ... Through hole, 24e ... Discrete parts, 25 ... Inner cover, 25a ... Flat plate, 25b ... Screw insertion hole 25c ... Legs, 25d ... Connection cylinder (connection), 25d1 ... Screw hole, 26 ... Outer cover (unit cover), 28 ... First protection plate (protection plate), 28a ... Screw insertion hole (connection) Part), 29 ... second protective plate part, 30 ... third protective plate part, 31 ... fourth protective plate part, 32 ... fifth protective plate part, 34 ... fixing piece, 40 ... fixing screw, 41 ... ne Hole, 42 ... connecting screw (connecting portion), 43 ... fixing screws, 45 ... female connector, 45a ... power connector, 45b ... signal connector

Claims (5)

In an electric power steering apparatus in which an electric motor that generates a steering assist force for assisting a steering operation and a control unit including a control board on which a control circuit for driving and controlling the electric motor is mounted are mounted on the outer periphery of the housing.
The control unit includes a unit cover that houses the control board, a cover edge is fixed to the housing, and a protection plate part faces a board surface on which the control circuit of the control board is mounted, The surface central portion of the protection plate portion is fixed to the housing via a vibration damping portion ,
The vibration damping portion is disposed inside the protective plate portion, and an inner cover that covers the substrate surface while being fixed to the housing, and the inner cover portion and the central portion of the surface of the protective plate portion are integrated. An electric power steering device comprising a connecting portion to be connected .   The electric power steering apparatus according to claim 1, wherein the unit cover is a metal member. The electric power steering apparatus according to claim 1 or 2 , wherein the inner cover is a member made of synthetic resin . A torque sensor is disposed inside the housing, and a plurality of external connection terminals connected to the torque sensor are projected outward from the housing, and each of the plurality of external connection terminals is provided on the control board. 4. The structure according to claim 1, wherein the inner cover is configured to be electrically connected to the through hole by soldering, and the inner cover functions as a member that prevents the solder from scattering to the control circuit. The electric power steering device according to the item . The electric power according to any one of claims 1 to 4, wherein the housing is a reduction gear box including a worm reduction mechanism that transmits a steering assist force generated by the electric motor to a steering system. Steering device.

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