JP2010221731A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device ensuring a vehicle mounting layout property, attaining common utilization on a right hand drive vehicle and a left hand drive vehicle and further enhancing reduction of moment vibration and endurance reliability. <P>SOLUTION: An electric motor 11 and a control unit 12 are assembled to a speed-reduction gear box 10, and the speed-reduction gear box 10 has a storage part 104 for storing a speed-reduction mechanism and a steering shaft 3. The electric motor 11 is attached to an outer peripheral part of the storage part 104 while making the axial direction as a direction crossing to the axial direction of the steering shaft 3, and the control unit 12 is attached to a portion neighborhood to the electric motor 11. The electric motor 11 is made to a flat structure that the axial whole length is short relative to an outer diameter of the frame, and thereby, a distance from a central axis of the steering shaft 3 to the most far part of the electric motor 11 is shortened. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electric power steering apparatus that transmits a steering assist force generated by an electric motor to a steering shaft via a reduction mechanism in a reduction gear box.

  In this type of electric power steering apparatus, an electric motor having a built-in resolver is connected to a manual steering gear constituting the steering apparatus via a speed reduction mechanism consisting of a worm and a wheel or a planetary gear. And the resolver built in this and the control apparatus are connected with a harness and a lead wire (for example, refer patent document 1).

  Thus, when the electric motor and the control device are connected by a harness, it is necessary to increase the motor current in order to increase the output of the electric motor that generates the steering assist force. The wiring loss of the motor harness connecting the control unit for driving and controlling the motor and the electric motor increases, and the efficiency decreases. Also, when connecting the resolver and the control device with lead wires, it is easily affected by external noise and strong magnetic field, etc., so there is a concern that the signal reliability will decrease, and an electrical shield to ensure reliability There are unsolved issues such as the need for additional members.

  In order to solve this unresolved problem, an electric motor is applied by applying a motor with a brush and placing the motor with the brush and a controller for driving the motor with the brush close to each other on the reduction gear box. There has been proposed an electric power steering device in which electrical connection between the control device and the control device is performed at the shortest distance without using a harness (see, for example, Patent Document 2).

JP 2008-011661 A JP 2007-276741 A

  However, in the conventional example described in Patent Document 2, since an electric motor with a brush is applied, an angle detector such as a resolver for detecting the rotation angle of the electric motor is not necessary, but the axial direction of the electric motor is not necessary. Therefore, there is an unsolved problem that it becomes an obstacle for ensuring the vehicle mounting layout. Further, when the electric power steering device is to be shared by the right-hand drive vehicle and the left-hand drive vehicle, the protruding amount of the structure such as the rear end portion of the electric motor from the central axis of the steering shaft becomes longer, for example, the left-hand drive vehicle. Even if there is no interference, if you try to install it in a right-hand drive car, it will interfere with the air conditioner unit and audio unit in the center console, resulting in a mirror-reversed configuration for the right-hand drive car. There is an unsolved problem that it is necessary to additionally set the electric power steering device.

In addition, since the heavy electric motor is fixed at a position away from the center axis of the steering shaft, the center of gravity is also located away from the center axis of the steering shaft, resulting in increased moment vibration and durability. There are unresolved issues such as reduced reliability and generation of abnormal noise due to vibration.
Therefore, the present invention has been made paying attention to the above-mentioned unsolved problems of the conventional example, ensuring vehicle mounting layout, enabling sharing between right-hand drive vehicles and left-hand drive vehicles, and moment vibration. An object of the present invention is to provide an electric power steering device capable of reducing the amount of power and improving the reliability of durability.

  In order to achieve the above object, an electric power steering apparatus according to the present invention includes a steering column having a steering shaft to which a steering torque is transmitted, and a steering assist force via a reduction mechanism in a reduction gear box. An electric power steering apparatus comprising: an electric motor for transmitting the power; and a control unit for driving and controlling the electric motor, wherein the electric motor has a flat structure with a short axial total length with respect to the outer diameter of the frame, and The speed reduction gear box is fixed in proximity to the control unit.

  According to this configuration, since the electric motor has a short flat structure with a short axial length, and the electric motor is fixed to the reduction gear box in close proximity to the control unit, the electric motor protrudes from the central axis of the steering shaft. The amount can be shortened and the position of the center of gravity can be brought close to the center axis of the steering shaft, which can be shared by right-hand drive cars and left-hand drive cars, and electrical connection between the electric motor and the control unit Can be performed at the shortest distance.

Further, the electric power steering apparatus according to the present invention includes a farthest portion from the central axis of the steering shaft of the control unit in a circle having a radius from the central axis of the steering shaft to the farthest portion of the electric motor. It is characterized by being configured to fit.
According to this configuration, the farthest part from the central axis of the steering shaft of the control unit can be accommodated in a circle having a radius from the central axis of the steering shaft to the farthest part of the electric motor, and the degree of freedom of the vehicle mounting layout Thus, the right-hand drive vehicle and the left-hand drive vehicle can be reliably shared.

Furthermore, in the electric power steering apparatus according to the present invention, the speed reduction mechanism includes a worm wheel connected to a steering shaft and a worm connected to an output shaft of the electric motor meshing with the worm wheel. It is characterized by that.
According to this configuration, the speed reduction mechanism is constituted by a worm speed reduction mechanism, and the output shaft of the electric motor is connected to the worm that meshes with the worm wheel connected to the steering shaft. Since the electric motor is disposed, the overall configuration of the electric power steering apparatus can be reduced in size.

Furthermore, in the electric power steering apparatus according to the present invention, the control unit is arranged near an intersection of an outer peripheral edge of a worm wheel storage portion for storing the worm wheel of the reduction gear box and a central axis of the worm. It is characterized by being arranged along a plane perpendicular to the central axis of the steering shaft.
According to this configuration, the control unit can be disposed along the plane perpendicular to the central axis of the steering shaft in the vicinity of the intersection between the outer peripheral edge of the worm wheel storage portion and the central axis of the worm, and close to the electric motor. The control unit can be arranged.

In the electric power steering apparatus according to the present invention, the radius from the central axis of the steering shaft to the farthest portion of the electric motor is set to be twice or less the outer diameter of the worm wheel storage portion that stores the worm wheel. It is characterized by being.
According to this configuration, the electric motor and the control unit can be disposed within a range of twice or less the outer diameter of the worm wheel storage portion, and the overall configuration can be reduced in size.

  According to the present invention, since the electric motor having a flat structure with a short axial total length is fixed to the control unit in the vicinity of the control unit, the protrusion length of the electric motor and the control unit with respect to the reduction gear box is suppressed, While improving the degree of freedom of layout when mounted on a vehicle, it is possible to bring the center of gravity of the electric motor closer to the center axis of the steering shaft, thereby reducing moment vibration and improving durability reliability. can get. In addition, even if the steering mechanism is mounted on the left and right cars, such as right-hand drive cars and left-hand drive cars, the same electric power steering device ensures the flexibility of layout without preparing separate electric power steering devices. However, the effect that it can mount | wear to a right-hand drive vehicle and a left-hand drive vehicle is acquired.

  Further, by configuring the farthest part from the central axis of the steering shaft of the control unit within a circle having a radius from the central axis of the steering shaft to the farthest part of the electric motor, The amount of protrusion of the electric motor and the control unit from the reduction gear box can be suppressed to reduce the size, and the degree of freedom of the vehicle mounting layout can be further improved.

1 is a schematic configuration diagram of a steering mechanism equipped with an electric power steering device according to the present invention. It is a front view of the electric power steering apparatus of FIG. It is explanatory drawing which shows the relationship between the farthest part of an electric motor, and a worm wheel storage part. FIG. 3 is a side view of FIG. 2. It is sectional drawing on the AA line of FIG. It is the front view which made the electric motor of an electric power steering device the section. It is a disassembled perspective view of an electric power steering device. It is a perspective view of the state where the electric motor of the reduction gear box was removed. It is a perspective view of an electric motor. It is explanatory drawing with which it uses for description of the layout freedom degree of an electric power steering device. It is explanatory drawing which shows the mounting state of the right-hand drive vehicle and left-hand drive vehicle of an electric power steering device.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing an example in which an embodiment of an electric power steering apparatus according to the present invention is applied to a right-hand drive vehicle.
In FIG. 1, reference numeral 1 denotes a steering mechanism. The steering mechanism 1 includes a steering column 4 that is provided with a steering wheel 2 at an end portion on the rear side of the vehicle, and in which a steering shaft 3 disposed on the right side of the vehicle is rotatably mounted.

The vehicle front side end of the steering shaft 3 is connected to a pinion shaft 5a disposed on the right side of the vehicle of the steering gear mechanism 5 composed of, for example, a rack and pinion mechanism, and the rack shaft 5b of the steering gear mechanism 5 is connected. Are connected to the steered wheels 7 via tie rods 6 respectively.
An electric power steering device 9 is attached to the steering column 4. In the electric power steering device 9, a reduction gear box 10 configured by, for example, a worm gear mechanism is disposed on the steering column 4, and the axial direction of the reduction gear box 10 is orthogonal to the axial direction of the steering column 4. An electric motor 11 constituted by, for example, a brushless motor extended in the left direction is disposed so as to protrude to the left.

As shown in FIG. 2, the electric motor 11 is attached to a gear box flange 107 formed in a tangential direction on the outer peripheral side of a worm wheel storage portion 104 (described later) of the reduction gear box 10. A control unit 12 arranged in series in the axial direction of the electric motor 11 is mounted on the right side of the gear box flange 107 in the reduction gear box 10.
The reduction gear box 10 is formed by die-casting, for example, any one of materials having high thermal conductivity, such as aluminum, aluminum alloy, magnesium, and magnesium alloy.

  As shown in FIGS. 5 and 6, the reduction gear box 10 has a worm housing portion 102 for housing the worm 21, and a worm housing portion 102 having a central axis perpendicular to the central axis below the worm housing portion 102. A worm wheel storage portion 104 that opens the front side of the vehicle that stores the meshing worm wheel 103, and a torque sensor storage portion that stores a torque sensor 105 that is integrally and coaxially connected to the vehicle front side of the worm wheel storage portion 104. 106, a gear box flange 107 for attaching the electric motor 11 formed on the open end surface of the worm storage portion 102, and a cylindrical shape that press-fits the tip of the steering column 4 formed on the vehicle rear side end of the torque sensor storage portion 106. Box cover 1 covering the column mounting portion 108 and the open end surface of the worm wheel storage portion 104 9, is formed in the worm housing unit 102 and the worm wheel housing portion 104 a box shape having an open rear side of the vehicle body straddling a part of, and a control unit housing portion 110 for mounting the control unit 12.

Further, the torque sensor 105 detects the steering torque transmitted to the steering shaft 3 by detecting the torsional state between the input shaft 3a and the output shaft 3c of the steering shaft 3 as shown in FIG. Detection is performed by a pair of detection coils 105a and 105b as elements.
External connection terminals 105c, 105d and 105e, 105f projecting outward in parallel to the direction orthogonal to the central axis of the steering column 4 are connected to the start and end of winding of the pair of detection coils 105a and 105b, respectively. The protrusions of the terminals 105c to 105f are bent at the central portion in parallel with the central axis of the steering column 4, and formed in an L shape, and as shown in FIG. It protrudes upward from an opening 112 formed in a guide surface 111 that guides the lower surface of the unit 12.

The output shaft 3c of the steering shaft is instructed to rotate freely by a rolling bearing 109a fixed to the inner peripheral surface of the box cover 109.
Further, as shown in FIG. 8, the gear box flange 107 to which the connecting portion 11b of the electric motor 11 is attached has a rectangular opening through which a power supply bus bar 13 and a resolver signal terminal 14 to be described later of the electric motor 11 are inserted. A first through hole 107a and a second through hole 107b are formed.

  As shown in FIG. 6, the electric motor 11 includes a bottomed cylindrical motor frame 11 a having an open front end, and a connecting portion 11 b that covers the front end of the motor frame 11 a and is attached to the reduction gear box 10. . A motor stator 11c around which an exciting coil is wound is disposed in the motor frame 11a. The output shaft 11g is rotatably supported by a rear bearing 11d fixed to the bottom of the motor frame 11a and a front bearing 11f fixed to an inlay portion 11e protruding from the connecting portion 11b in the motor stator 11c. . A surface magnet type motor rotor 11i having a permanent magnet 11h formed on the surface is fixed to a position of the output shaft 11g facing the motor stator 11c. A resolver 11j as a rotor rotation angle detector for detecting the rotor rotation angle is disposed at a position facing the connecting portion 11b of the motor rotor 11i.

Here, as shown in FIG.2 and FIG.9, the flange part 11k is formed in the connection part 11b in the position 180 degree apart of the outer peripheral surface in the connection part 11b by the side of an open end.
For example, three motor power supply bus bars 13 that are electrically connected to the coils wound around the motor stator 11c of the electric motor 11 protrude outside the spigot portion 11e of the connecting portion 11b. The motor power supply bus bar 13 is covered with a bus bar insulating portion 13a made of a rectangular parallelepiped synthetic resin at a position in the connecting portion 11b and a base protruding from the connecting portion 11b.

The resolver 11j is inserted into the resolver stator 11v, and a resolver stator 11v fixed to the inner peripheral surface of the cylindrical portion 11u integrally formed extending in the connecting portion 11b opposite to the inlay portion 11e. And a resolver rotor 11w fixed to the output shaft 11g.
When a sine wave excitation signal f (t) = A · sin (ωt) is input from an external signal processing circuit, the resolver stator 11v receives a sine wave and cosine wave resolver signal Ys corresponding to the rotation angle θ of the rotor. (= K · sin (θ) · f (t)) and Yc (= k · sin (θ) · f (t)) are output.

  For this reason, for example, six resolver signal terminals 14 each composed of a pair of excitation signal input terminals and resolver signal output terminals for inputting and outputting the excitation signal f (t) and the resolver signals Ys and Yc are connected to the connecting portion. It protrudes at a predetermined interval from the power supply bus bar 13 so as to be in series in the tangential direction of the power supply bus bar 13 and the inlay part 11e described above outside the inlay part 11e of 11b. The base portion of the protruding portion from the connecting portion 11b and the connecting portion 11b of the resolver signal terminal 14 is covered with a signal terminal insulating portion 14a made of a rectangular parallelepiped synthetic resin.

  Further, as shown in FIG. 6, a worm 21 is integrally formed on the output shaft 11 g of the electric motor 11, and the other end of the worm 21 is disposed at the bottom of the worm storage portion 102 of the reduction gear box 10. The bearing 102a is rotatably supported. After all, the output shaft 11g integrally formed with the worm 21 is supported by the three bearings 11d, 11f and 22a, and when the output shaft 11g and the worm 21 are separated, a total of four output shafts 11g are provided. Since a single bearing is required, the distance of one bearing can be shortened, and the coupling portion for connecting the output shaft 11g and the worm 21 can be omitted, so that the length can be shortened. it can.

  As described above, in the electric motor 11, the front bearing 11f that rotatably supports the output shaft 11g is fixed inside the spigot 11e that protrudes outward from the connecting portion 11b. Therefore, as shown in FIG. A flat structure in which the axial total length Lm from the bottom plate portion of 11a to the contact surface with the gear box flange 107 of the connecting portion 11b is shortened to about 2/3 of the frame outer diameter Df of the motor frame 11a can be obtained. Therefore, as will be described later, with the electric motor 11 mounted on the gear box flange 107 of the reduction gear box 10, a long distance from the central axis of the steering shaft 3 to the farthest part of the electric motor 11 as shown in FIG. When the radius is the radius Rm, the radius Rm can be accommodated within twice the outer diameter Dw of the worm wheel housing portion 104 constituting the reduction gear box 10 described later, and the center axis of the steering shaft 3 is used as a reference. The amount of protrusion can be reduced. Accordingly, since the overall axial length Lm of the relatively heavy electric motor 11 can be shortened, the center of gravity of the entire electric power steering device 9 can be brought closer to the central axis of the steering shaft 3.

Then, when the flange portion 11k of the electric motor 11 is brought into contact with the gear box flange 107, the bus bar insulating portion 13a is inserted into the first through hole 107a, the tip of the power supply bus bar 13 is extended into the control unit 12, and the first The signal terminal insulating part 14 a is inserted and fitted into the two through holes 107 b, and the tip of the resolver signal terminal 14 is extended inside the control unit 12.
As shown in FIG. 7, the control unit 12 includes a circuit board 31 disposed in the control unit housing part 110 of the reduction gear box 10, and is mounted on the control unit housing part 110 so as to cover the entire circuit board 31. And a resin cover 32. Further, as shown in FIG. 4, an external connection connector 39 electrically connected to the circuit board 31 is provided on the rear surface of the end of the control unit housing 110 on the side opposite to the gear box flange 107 of the reduction gear box 10. Is provided. The external connection connector 39 is composed of a power connector 39a and a signal connector 39b. Electrical wiring connected to a battery (not shown) is inserted into the power connector 39a from the front of the vehicle, and the signal connector 39b is connected to the vehicle body. A signal wiring of a network such as CAN for exchanging data with the control device of each part is inserted from the front of the vehicle.

  As shown in FIGS. 4 and 5, the circuit board 31 is a router from the plane side along the belt-like portion 32 so as to leave the belt-like portion 32 at the center portion in the front-rear direction of a single 4-layer epoxy resin rigid board. The power groove substrate portion 36 and the control rigid substrate portion facing each other in a U-shape are formed by bending the cutting groove portions 33 and 34 having a depth corresponding to two layers by 90 degrees to form the bent portions 35. 37 is formed. And the power rigid board | substrate part 36 is stored in the control unit storage part 110 facing the bottom part of the control unit storage part 110, and is screwed. Further, the control rigid board portion 37 is screwed onto a support column 38 formed in the control unit storage portion 110.

  The power rigid board portion 36 is mounted with heat generating circuit components such as a semiconductor switching element, a fail-safe relay circuit, a noise countermeasure coil, and a power supply smoothing electrolytic capacitor. Further, as shown in FIG. 9, the left end portion of the power rigid board portion 36 is electrically connected to the power supply bus bar 13 of the electric motor 11 and on the back surface of the external connection connector 39 shown in FIG. The provided power supply electrode terminals L1 and L2 are electrically connected.

  Although not shown in detail, the control rigid board portion 37 is mounted with a motor current detection IC, a torque calculation IC 42, a calculation processing device, a gate drive IC, and the like. As shown in FIG. 4, the resolver signal terminal 14 of the resolver 11j built in the electric motor 11 is electrically connected to the left end portion of the control rigid board portion 37, and the right end portion is shown in FIG. Signal electrode terminals L3 to L5 provided on the back surface of the external connection connector 39 shown are electrically connected.

  Further, although not shown in the bent portion 35, circuit components such as a semiconductor switching element, a relay circuit, and a coil mounted on the power rigid substrate portion 36, an arithmetic processing device mounted on the control rigid substrate portion 27, and gate drive A wiring pattern is formed to electrically connect circuit components such as a circuit. Further, a circuit component can be mounted on the band-like portion 32 of the bent portion 35.

  Here, as shown in FIG. 2, the control unit 12 includes an outer peripheral edge of the worm wheel storage portion 104 of the reduction gear box 10 as viewed from the front, and a central axis L1 of the worm 21, that is, the output shaft 11 g of the electric motor 11. The control unit 12 can be placed so that the center position of the control unit 12 is substantially present in the vicinity of the intersection position, and is opposed to the connecting portion 11b of the electric motor 11 with the gear box flange 107 interposed therebetween and orthogonal to the center axis of the steering shaft 3. The position Pc, which is the farthest part from the central axis of the steering shaft 3 of the control unit 12, is located from the central axis of the steering shaft 3 to the farthest part of the electric motor 11. Can be contained in a circle having a radius Rm.

Next, the effect of the vehicle provided with the electric power steering device 9 having the above-described configuration will be described.
In the electric power steering apparatus 9 according to the present embodiment, the connecting portion 11b of the electric motor 11 is brought into contact with the gear box flange 107 of the reduction gear box 10 and the spigot portion 11e is in-line coupled to the spigot hole 107c of the gear box flange 107. As a result, the electric motor 11 is mounted on the reduction gear box 10. At this time, the worm 21 integrally connected to the output shaft 11 g of the electric motor 11 is inserted into the worm storage portion 102 of the reduction gear box 10, and stored in the worm wheel storage portion 104 to the output shaft 3 c of the steering shaft 3. It meshes with the connected worm wheel 103.

  At the same time, the power supply bus bar 13 and the resolver signal terminal 14 projecting from the end face of the connecting portion 11b along the output shaft 11g penetrate the first through hole 107a and the second through hole 107b provided in the gear box flange 107, respectively. Thus, the power rigid board portion 36 and the control rigid board portion 37 of the control unit 12 are electrically connected. Therefore, unlike the conventional apparatus, the power supply bus bar and the resolver signal terminal do not protrude radially outward from the outer periphery of the reduction gear box 10 and the electric motor 11, and the motor harness and the connection cord are used. There is no need to connect. Therefore, it is possible to reduce the wiring loss when using the motor harness, and it is possible to ensure good signal reliability without being affected by external noise or a strong magnetic field. Further, even if vehicle-side members and the like are disposed around the electric power steering device 9, the electrical connection portion of the electric power steering device 9 does not interfere with these members, so that the vehicle mounting layout can be improved. it can.

Further, since the power supply bus bar 13 and the resolver signal terminal 14 of the electric motor 11 are not exposed to the outside of the device 9, a member (such as a cover member) for preventing intrusion of conductive foreign matters becomes unnecessary, and the number of components does not increase. Cost can be reduced.
The base portions of the three power supply bus bars 13 are covered with a bus bar insulating portion 13a made of a rectangular parallelepiped synthetic resin, and the base portions of the six resolver signal terminals 14 are also made of a rectangular parallelepiped synthetic resin. Since it is covered with the insulating portion 14a, the bus bar insulating portion 13a and the signal terminal insulating portion 14a are inserted through the first through hole 107a and the second through hole 107b of the gear box flange 107, so that the power supply bus bar 13 and the resolver The insulation between the signal terminal 14 and the reduction gear box 10 can be reliably ensured.

  Further, the spigot portion 11e formed on the connecting portion 11b of the electric motor 11 is simply connected in spigot to the spigot hole 107c formed on the gear box flange 107 of the reduction gear box 10 to the worm wheel 103 disposed in the worm wheel storage portion 104. Since the worm 21 can be easily engaged, assembly is facilitated, and the manufacturing cost can be further reduced.

  The electric motor 11 attached to the reduction gear box 10 has a flat structure in which the axial total length Lm is short with respect to the frame outer diameter Df of the motor frame 11a. The radius Rm, which is the distance to the far portion, can be shortened, and interference with components in the vicinity of the electric power steering device 9 can be suppressed.

  Thus, since the radius Rm, which is the distance from the central axis of the steering shaft 3 to the farthest part of the electric motor 11, can be shortened, the electric power steering device 9 is centered on the central axis of the steering shaft 3 as shown in FIG. As a result, even when rotated clockwise by 120 degrees, there is no change in the amount of protrusion from the central axis of the steer shaft 3 and the layout on the vehicle can be improved.

  Therefore, as shown in FIG. 11, as in the above-described embodiment, even when the electric power steering device 9 is installed for a right-hand drive vehicle or a left-hand drive vehicle, no significant change occurs. Interference with the center console 200 and the left and right inner walls of the vehicle body can be suppressed, and there is no need to distinguish between the right-hand drive vehicle and the left-hand drive vehicle, and the electric power steering device 9 having the same shape can be used in common.

  Further, since a brushless motor is applied as the electric motor 11, the axial length can be shortened as compared with a motor with a brush, and there is no loss due to the contact resistance of the brush, and the wire harness for energizing the motor In combination with the omission of the electric power steering apparatus, it is possible to provide an electric power steering apparatus that realizes high output efficiency that cannot be achieved by only one of the low-loss techniques.

  Further, since the worm 21 is integrally formed on the output shaft 11g of the electric motor 11, the coupling for connecting the two can be omitted, and the number of bearings that are rotatably supported can be reduced to three. Therefore, the electric motor 11 can be mounted close to the worm housing portion 102 of the reduction gear box 10, and the protruding length of the electric motor 11 can be shortened accordingly.

  Further, by setting the radius Rm, which is the distance from the central axis of the steering shaft 3 to the farthest part of the electric motor 11, to be equal to or less than twice the outer diameter Dw of the worm wheel storage portion 104 constituting the reduction gear box 10, The overall configuration of the electric power steering device 9 can be reduced in size, the vehicle mounting layout can be further improved, and the sharing of the right-hand drive vehicle and the left-hand drive vehicle can be promoted.

  Further, since the protruding amount of the heavy electric motor 11 is reduced in the reduction gear box 10 and the control unit 12 is arranged to protrude in the opposite direction to the electric motor 11, the reduction gear box 10 and the electric motor 11 are disposed. In addition, the center of gravity position including the control unit 12 approaches the center axis position of the steering shaft 3. For this reason, the moment for rotating the electric power steering device 9 due to the vibration transmitted to the steering shaft 3 becomes small, and it becomes difficult to be affected by the vibration transmitted to the steering shaft 3. That is, when the electric motor is mounted on one side of the reduction gear box 10 so as to protrude greatly as in the conventional example described above, the position of the center of gravity is greatly separated from the steering shaft 3, so that vibration transmitted to the steering shaft 3 is not transmitted. When transmitted to the electric motor, the moment for rotating the electric power steering device is increased, so that it is easily affected by vibration, and the mechanical strength of the support bracket needs to be increased. However, in the above embodiment, since the position of the center of gravity of the electric power steering device 9 can be brought close to the center axis of the steering shaft, the moment for rotating the electric power steering device 9 due to vibration can be reduced, and the electric power steering device 9 can be mounted on the vehicle body. The mechanical strength of the mounting bracket supported on the side can be reduced to provide a simple configuration.

  When the mounting of the electric power steering device 9 having the above configuration on the vehicle is completed, when an ignition switch (not shown) of the vehicle is turned on to supply power from the battery to the power module board unit 36 and the control rigid board unit 37, the micro A steering assist control process is executed by the control unit (MCU), and a steering assist current command value is calculated based on detection values of the torque sensor 105 and a vehicle speed sensor (not shown). 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 module substrate 36 and controlling the inverter circuit, a three-phase AC drive current flows through the electric motor 11 and the electric motor 11 is required in the forward or reverse direction. Drive to generate steering assist force.

Therefore, a steering assist force corresponding to the steering torque of the steering wheel 2 is generated from the electric motor 11, and this steering assist force is transmitted to the output shaft 3 c of the steering shaft 3 via the worm 21 and the worm wheel 103. The steering wheel 2 can be steered with a light steering force.
In the above-described embodiment, the case where the present invention is applied to a column assist type electric power steering device has been described. However, the present invention is not limited to this, and the present invention is not limited to a pinion assist type or rack assist type electric power steering device. Even if applied, the same effect as described above can be obtained.

  Further, in the above embodiment, the farthest portion Pc of the control unit 12 with respect to the central axis of the steering shaft 3 is contained in a circle having a radius Rm between the central axis of the steering shaft 3 and the farthest portion of the electric motor 11. Although the case has been described, the farthest portion Pc from the central axis of the steering shaft 3 of the control unit 12 may be made to coincide with a circle having a radius Rm. In this case, the position of the center of gravity of the electric power steering device 9 is Since it is closer to the central axis of the steering shaft 3, generation of moments due to vibration can be further suppressed.

  In the above embodiment, the case where the power supply bus bar 13 and the resolver signal terminal 14 of the electric motor 11 are electrically connected to the control unit 12 without being exposed to the outside has been described. However, the present invention is not limited to this. The power supply bus bar 13 and the resolver signal terminal 14 are formed on the outer peripheral side of the connecting portion 11b of the electric motor 11 so as to protrude outward in the radial direction, and the power supply bus bar 13 and the resolver signal terminal are connected to the control unit 12 accordingly. The terminal part electrically connected to 14 may be formed, and both may be contacted and electrically connected.

Furthermore, in the above-described embodiment, the case where the surface magnet type motor rotor 11i is applied as the electric motor 11 has been described. However, the present invention is not limited to this, and an embedded magnet (IPM) brushless motor, an induction motor, or the like. Other types of brushless motors can be applied.
Moreover, in the said embodiment, although the circuit board 31 demonstrated the case where it comprised with one board | substrate of the bending part 35, the power rigid board part 36, and the control rigid board part 37, it is not limited to this. The power rigid board portion 36 and the control rigid board portion 37 may be separated from each other and configured by two circuit boards.

  In the above embodiment, the torque sensor 105 is configured by only the torque detection element, and the signal processing circuit is built in the control unit 12. However, the present invention is not limited to this. The torque detection elements 105a and 105b and the signal processing circuit thereof are provided. The reduction gear box 10 includes the torque detection elements 105a and 105b and a signal processing circuit electrically connected to the torque detection elements 105a and 105b. In this case, the signal processing circuit can be calibrated with the reduction gearbox 10 alone, and the signal processing circuit can be calibrated without being affected by the electric motor. . Then, the electric motor 11 is assembled to the reduction gear box 10 in which the signal processing circuit of the torque sensor 105 has been calibrated, and the electric power between the control unit 12 and the torque detecting element is assembled after or before the control unit 12 is assembled. Connection and electrical connection between the control unit 12 and the electric motor 11 can be performed, the assembly work can be easily performed, and the assembly process can be simplified without degrading the accuracy of the torque sensor. .

  In the above-described embodiment, the case where the electric motor 11 is mounted on the gear box flange 107 with the axial direction orthogonal to the steering shaft 3 has been described. However, the present invention is not limited to this. Any direction that intersects may be used.

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering apparatus, 2 ... Steering wheel, 3 ... Steering shaft, 4 ... Steering column, 10 ... Reduction gear box, 11 ... Electric motor, 11a ... Motor frame, 11b ... Connection part, 11c ... Motor stator, 11e ... Inlay part, 11g ... Output shaft, 11i ... Motor rotor, 11j ... Resolver, 21 ... Worm, 31 ... Circuit board, 35 ... Bending part, 36 ... Power rigid board part, 37 ... Control rigid board part, 39 ... External connection connector, DESCRIPTION OF SYMBOLS 102 ... Worm accommodating part, 103 ... Worm wheel, 104 ... Worm wheel accommodating part, 105 ... Torque sensor, 106 ... Torque sensor accommodating part, 107 ... Gear box flange, 108 ... Column attaching part, 110 ... Control unit accommodating part

Claims (6)

A steering column having a steering shaft to which steering torque is transmitted, an electric motor that transmits a steering assist force to the steering shaft via a reduction mechanism in a reduction gear box, and a control unit that controls the drive of the electric motor. An electric power steering device with
The electric power steering device according to claim 1, wherein the electric motor has a flat structure with a short axial total length with respect to an outer diameter of the frame, and is fixed to the reduction gear box in proximity to the control unit.   The farthest part from the central axis of the steering shaft of the control unit is contained in a circle having a radius from the central axis of the steering shaft to the farthest part of the electric motor. The electric power steering apparatus according to claim 1.   3. The speed reduction mechanism includes a worm wheel connected to a steering shaft and a worm connected to an output shaft of the electric motor meshing with the worm wheel. 4. Electric power steering device.   The control unit is arranged in the vicinity of the intersection between the outer peripheral edge of the worm wheel storage portion for storing the worm wheel of the reduction gear box and the central axis of the worm along a plane orthogonal to the central axis of the steering shaft. The electric power steering apparatus according to claim 3, wherein the electric power steering apparatus is provided.   The radius from the central axis of the steering shaft to the farthest part of the electric motor is set to be not more than twice the outer diameter of the worm wheel storage part that stores the worm wheel. 4. The electric power steering apparatus according to 4.   The electric motor is composed of a brushless motor having a built-in rotation angle detector, and the electric connection between the electric motor and the rotation angle detector and the control unit is directly electrically connected. The electric power steering device according to any one of claims 1 to 5.

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