JP2014231277A - Rear wheel steering device of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a structure which can easily join a metal-made hollow rotating shaft and a synthetic resin-made sun gear, and can surely transmit torque, in a rear wheel steering device which is interposed at a suspension mechanism for supporting a rear wheel of a vehicle, and steers the rear wheel.SOLUTION: A rear wheel steering device comprises a metal-made hollow rotating shaft 20 which is supported to a housing so as to be turnable, penetrates a rod, and constitutes an output shaft of an electric motor. An annular groove 20h is formed at an external peripheral face of the hollow rotating shaft, outer teeth 20i are aligned in the annular groove in parallel with one another, and by integrally molding a synthetic resin so as to include the outer teeth and the annular groove, a gear (sun gear 31) constituting a reduction mechanism is formed integrally with the hollow rotating shaft.

Description

  The present invention relates to a vehicle rear wheel steering apparatus that is interposed in a suspension mechanism that supports a rear wheel of a vehicle and steers the rear wheel.

  Recently, various types of devices have been known as rear wheel steering devices constituting a part of a four-wheel steering system (4WS) of a vehicle. The basic configuration is described in Patent Document 1 below. From a "rod connected to the rear wheel of the vehicle, a housing supporting the rod and fixed to the chassis of the vehicle, and a motor housed in the housing and driving the rod to steer the rear wheel" Become. This apparatus is provided with a speed reduction mechanism that converts the rotational motion of the motor into the linear motion of the rod and transmits it, and a planetary gear mechanism is disclosed as an example. A planetary gear mechanism is also used in a rear wheel steering angle control device described in Patent Document 2 below, and a sun gear and the like constituting the planetary gear mechanism are formed of a resin material.

  Further, in Patent Document 3 below, a planetary gear device is used in a transmission for converting the rotational motion of an electric motor into the translational motion of a push rod, and the ring gear is press-fitted into an outer ring of a ball screw thrust bearing, It is described that the sun gear is a constituent member of the electric motor. In addition, a blocking device that interrupts transmission of driving force from the motor to the push rod is provided, and is supported by the module housing together with the electric motor and the transmission.

Japanese Patent No. 5098242 Japanese Patent No. 3068779 Special table 2012-511465 gazette

  In the devices disclosed in Patent Documents 1 and 3, the cylindrical motor output shaft is connected to the sun gear of the planetary gear mechanism, and spline coupling is adopted as a normal connecting means. For this reason, it is necessary to perform spline processing on the outer peripheral surface of the output shaft (hollow rotary shaft) and the inner peripheral surface of the sun gear, and a holding snap ring is required, so these processing costs and parts costs are costly. It becomes an up factor. If the sun gear is formed of a resin material as described in Patent Document 2, the cost becomes low, but it is not easy to join the steel hollow rotating shaft. Patent Document 2 is characterized in that the resin material of each gear is different, and the connection with the hollow rotating shaft is not clearly shown.

  In either of Patent Documents 1 and 2, the structure for supporting the rod is complicated because it is supported at both ends, and if it is diverted to a cantilevered support structure, the assembly process of other parts is wasted. On the other hand, the device described in Patent Document 3 can be classified as a cantilever support structure. However, since the electric motor, the transmission, and the blocking device are supported by the module housing, high strength is required, and the housing is It becomes large.

  Accordingly, the present invention facilitates the joining of a metal hollow rotating shaft and a synthetic resin sun gear in a vehicle rear wheel steering device that is interposed in a suspension mechanism that supports the rear wheel of the vehicle and steers the rear wheel. It is an object of the present invention to provide a rear wheel steering device that is capable of reliably transmitting torque and that is easy to assemble and that can be reduced in cost and weight.

  In order to achieve the above object, the present invention provides a rear wheel steering device for a vehicle that is interposed in a suspension mechanism that supports a rear wheel of a vehicle and steers the rear wheel. A housing connected through two connecting members, an electric motor housed in the housing, a speed reducing mechanism housed in the housing and decelerating the output of the electric motor, and a nut rotating in conjunction with the speed reducing mechanism A linear motion mechanism that includes a member and a rod that is screwed to the nut member and coupled to the second coupling member, and that converts the rotational motion of the nut member into linear motion of the rod; A cylinder that houses the electric motor and the speed reduction mechanism in series, and a connection cover that has the first connection member and closes the opening of the cylinder on the speed reduction mechanism side. And a hollow hollow shaft made of metal that constitutes an output shaft of the electric motor while supporting the housing rotatably and inserting the rod, and forming an annular groove on an outer peripheral surface of the hollow rotational shaft In addition, external gears are arranged in parallel to the annular groove, and a gear constituting the reduction mechanism is formed integrally with the hollow rotary shaft by integral molding of synthetic resin so as to include the external teeth and the annular groove. It is comprised so that it may do.

  In the above rear wheel steering device, the speed reduction mechanism is a planetary gear mechanism, and the sun gear constituting the planetary gear mechanism is integrally molded with resin so as to include the outer teeth and the annular groove, so that the hollow rotation is performed. It is good to set it as the structure formed integrally with a axis | shaft. Moreover, it is good to set it as the structure which arranges the said external tooth along with the said hollow rotating shaft adjacent to the said annular groove.

  Furthermore, it is preferable that the hollow rotary shaft has a plurality of step portions whose outer diameters are gradually reduced from a portion adjacent to the annular groove to an opening on the electric motor side.

  Since this invention is comprised as mentioned above, there exist the following effects. That is, in the rear wheel steering device of the present invention, an annular groove is formed on the outer peripheral surface of the hollow rotary shaft, and external teeth are arranged in parallel to the annular groove, and the synthetic resin is formed so as to include the external teeth and the annular groove. Since the gear constituting the speed reduction mechanism is formed integrally with the hollow rotary shaft by integral molding, the gear (eg sun gear) constituting the speed reduction mechanism (eg planetary gear mechanism) is the shaft of the hollow rotary shaft. It can be firmly joined in both the direction of rotation and the direction of rotation, easy to assemble, and can be reduced in cost and weight.

  In particular, if the external teeth are arranged in parallel with the hollow rotary shaft adjacent to the annular groove, cutting when forming the hollow rotary shaft can be easily performed continuously.

  If the hollow rotary shaft has a plurality of step portions whose outer diameters gradually decrease from the portion adjacent to the annular groove to the opening on the electric motor side, a gear (integrally formed with the hollow rotary shaft ( For example, components of a speed reduction mechanism (for example, a planetary gear mechanism) other than a sun gear are assembled to a rod to form a subassembly, which is accommodated in a cylindrical body from an opening on the speed reduction mechanism side, and an electric motor is mounted on each step portion of the hollow rotating shaft. In the state where the above components are assembled, the rod is inserted into the hollow portion of the hollow rotary shaft from the opening on the electric motor side, and the gear formed integrally with the hollow rotary shaft is engaged with the speed reduction mechanism. By doing so, it can be assembled easily and the cost can be reduced.

1 is a cross-sectional view illustrating an overall configuration of a rear wheel steering apparatus according to an embodiment of the present invention. It is a cross-sectional view which expands and shows the actuator part in one Embodiment of this invention. It is a cross-sectional view which expands and shows the controller part in one Embodiment of this invention. It is a longitudinal cross-sectional view which expands and shows the controller part in one Embodiment of this invention. It is a cross-sectional view which expands and shows the hollow rotating shaft part which comprises some actuators in one Embodiment of this invention. It is a side view which expands and shows the hollow rotating shaft part which comprises some actuators in one Embodiment of this invention. It is a longitudinal cross-sectional view of the subassembly which comprises a part of actuator in one Embodiment of this invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an overall configuration of a rear wheel steering apparatus according to an embodiment of the present invention. The rear wheel steering device of this embodiment constitutes a part of the four-wheel steering system (4WS), but the front wheel steering device is omitted because it is the same as before. There are various modes of suspension mechanisms for supporting the rear wheels of the vehicle. In this embodiment, the suspension mechanism is configured as shown by a two-dot chain line in FIG. 1, and supports the rear wheels RL and RR of the vehicle. An actuator unit AU constituting the rear wheel steering device of this embodiment is interposed between a support portion RS for the rear axle RA and a link LS that is pivotally supported by the rear axle RA and swings about the swing center C. As a result, the support portion RS and the link LS are telescopically driven, and the rear wheels RL and RR are steered via the tie rods TR and TR according to the swing of the link LS.

  The actuator unit AU is supported by the housing 1 so that the rod 2 can move in the axial direction (linear motion), one end of which is connected to the link LS via the ball joint JL, and the housing 1 is supported by the ball joint JA. It is connected to RS, and the rod 2 is driven by the actuator 3 so that the space between the support portion RS of the rear axle RA and the link LS is expanded and contracted. Specifically, the electric motor 3a constituting the actuator 3 is controlled by the controller 4, and after the rotational output of the electric motor 3a is decelerated by the speed reduction mechanism 3b, it is converted into a linear motion of the rod 2 via the linear motion mechanism 3c. It is configured to be. In the present embodiment, the electric motor 3a is a brushless motor.

  In the present embodiment, the housing 1 is roughly divided into a housing 1a that mainly contains components of the actuator 3 (electric motor 3a and the like) and a housing 1b that mainly contains components of the controller 4 (electronic circuit board 40 and the like). The connecting cover 11 is joined to the cylindrical body 10 constituting the housing 1a, and the housing 12 that constitutes the housing 1b and has openings in the vertical and axial directions is joined to the upper and lower openings of the housing 12. The lids 15 and 16 are configured to be joined. The housing 1 of this embodiment is made of metal, the connection cover 11 and the housing 12 are made of aluminum, and the cylinder 10 and the lids 15 and 16 are made of iron.

  The actuator 3 is configured as shown in an enlarged view in FIG. 2, and is press-fitted and fixed in the cylindrical body 10 with the coil 23 wound around the stator 24. The output shaft of the electric motor 3 a is constituted by a hollow rotary shaft 20, which has an inner diameter portion 25 a of an annular motor cover 25 inserted into the cylindrical body 10 and an annular groove formed in the housing 12. 12a is rotatably supported via bearings 25b and 12b, respectively. A core 21 that constitutes the rotor of the electric motor 3 a is press-fitted and fixed to an intermediate portion in the axial direction of the hollow rotary shaft 20, and permanent magnets 22 are evenly arranged in the circumferential direction of the core 21.

  Further, the rod 2 is coaxially arranged in the hollow rotary shaft 20 and is supported so as to be movable in the axial direction (linear motion) with respect to the housing 1 and non-rotatably supported with respect to the housing 1. The structure will be described later. In addition, bushes 2a and 2b are interposed between the rod 2 and the support portion of the housing 12, but these reduce the sliding resistance in order to smoothly move the rod 2 in the axial direction. is there. That is, since this embodiment is a cantilever-supported expansion / contraction mechanism, the bushes 2a and 2b are not required to function as bearings in the axial movement mechanism supported at both ends.

  The speed reduction mechanism 3b of the present embodiment includes a planetary gear mechanism 30, and a sun gear 31 that is an external gear is integrally coupled to the hollow rotary shaft 20 and is rotatably supported together with the hollow rotary shaft 20. A ring gear 33 as an internal gear is fixed to a holder 34 as a cylindrical holding member, and a planetary gear 32 as an external gear is arranged so as to mesh with the sun gear 31 and the ring gear 33 and rotate around the sun gear 31. . A nut member 36 is rotatably supported by a holder 34 via a bearing 37 as a carrier that rotatably supports the planetary gear 32 via a pin 35. The bearing 37 is a ball bearing, and an inner ring 37a is fitted to the nut member 36, and an outer ring 37b is fitted to the holder 34, and held by the nut member 36 by a C-shaped spacer 37c.

  In the present embodiment, the holder 34 and the pin 35 are made of metal (for example, iron), but the sun gear 31, the planetary gear 32, and the ring gear 33 are made of synthetic resin, and the sun gear 31 is integrally formed with the metal hollow rotary shaft 20. Has been. That is, as shown by the solid line in FIGS. 5 and 6, the hollow rotary shaft 20 of the present embodiment has an annular groove 20h formed on the outer peripheral surface thereof, and external teeth 20i that are adjacent to and parallel to the annular groove 20h. Are arranged side by side. The sun gear 31 is integrally formed with the hollow rotary shaft 20 by integral molding of synthetic resin so as to include the annular groove 20h and the external teeth 20i. As a result, the sun gear 31 is firmly joined in both the axial direction and the rotational direction of the hollow rotary shaft 20.

  The hollow rotary shaft 20 is formed with a hollow portion having two inner diameters, a large diameter and a small diameter, and the outside is formed in step portions 20a to 20g. That is, the outer diameter of the stepped portion 20a is set to be the maximum, the outer diameter of the stepped portion from both sides in the direction of both opening ends is sequentially reduced, and the outer diameter of the stepped portion 20d is set to be gradually reduced. . And each component which comprises the electric motor 3a is assembled | attached to each step part of the hollow rotating shaft 20, as shown with a dashed-two dotted line in FIG.

  The ring gear 33 is supported so as not to rotate with respect to the holder 34, and the holder 34 is supported so as not to rotate with respect to the cylindrical body 10. That is, as shown in FIG. 2, the snap ring 14 is held in an annular groove 10 a formed in the cylindrical body 10, and a bearing 37 is interposed between the annular side surface of the snap ring 14 and the annular opening end surface of the connecting cover 11. In the state where the outer ring 37b and the holder 34 are sandwiched, the annular lock nut 13 is screwed into a screw portion formed at the opening end of the cylinder body 10 on the speed reduction mechanism 3b side (left side in FIG. 2). And the connection cover 11 is fastened. Thus, the outer ring 37b and the holder 34 of the bearing 37 are firmly held between the snap ring 14 and the connecting cover 11 by the axial pressing force generated with the screwing of the lock nut 13, and as a result, the holder 34 is held in a non-rotatable manner with respect to the cylindrical body 10.

  Then, a male screw portion 2 c formed with a trapezoidal screw over a predetermined axial length and a female screw portion 36 c formed on the inner peripheral surface of the nut member 36 are screwed onto the outer peripheral surface of one end portion of the rod 2. The nut member 36 and the rod 2 constitute a linear motion mechanism 3c. In order to prevent the rod 2 from falling off, a nut 2d is screwed to the tip of the male screw portion 2c. Since the rod 2 is supported as described above, the axial load that can be applied to the rod 2 is the cylindrical body 10 and the connecting cover 11 via the nut member 36, the bearing 37, the holder 34, and the snap ring 14. Absorbed in.

  On the other hand, as shown in FIG. 3, as the controller 4, an electronic circuit board 40 constituting an electronic control device (not shown) and a magnet block 50 constituting a displacement detection device 5 are accommodated in a housing 1b. The displacement detection device 5 includes a displacement sensor 5a composed of, for example, a magnetic vector sensor and a permanent magnet 5b composed of, for example, a neodymium magnet. The displacement sensor 5a is supported by the electronic circuit board 40, and the permanent magnet 5b is composed of a magnet block 50. Is held in. The magnet block 50 has a function of detecting axial displacement during linear movement of the rod 2 and a function of preventing the rotation of the rod 2 described above.

  As shown in FIG. 3 and FIG. 4, long grooves (substantially rectangular recesses) 2 r and 2 s that are elongated in the axial direction are formed on both side surfaces of the rod 2, and a magnet block 50 is formed in one long groove 2 r. The bolt 51 is inserted from the long groove 2 s on the opposite side and fixed to the rod 2. The magnet block 50 is formed of a synthetic resin, and as shown in FIG. 3, a holding part 52 that houses the permanent magnet 5 b and a pair of leg parts 53, 53 are formed at both ends, and both leg parts 53, A metal nut 54 is insert-molded between 53. On the other hand, as shown in FIG. 4, a support portion 12 s is formed inside the housing 12, and a pair of standing wall portions 12 w and 12 w are formed in parallel to the axis of the rod 2. The holding portion 52 is assembled so as to be held between the pair of standing wall portions 12 w and 12 w, and the bolt 51 is inserted into the through hole 2 h of the rod 2 and screwed into the nut 54. As a result, the rod 2 is supported by the magnet block 50 so as not to rotate with respect to the standing wall portions 12 w and 12 w of the housing 12 and thus the housing 1.

  Thus, in the actuator 3 of the present embodiment, when the hollow rotary shaft 20 is rotationally driven by the electric motor 3a, the rotational output is decelerated by the speed reduction mechanism 3b of the planetary gear mechanism 30, and the nut member 36 is rotationally driven. Furthermore, the rotational motion of the nut member 36 is converted into the linear motion of the rod 2 by the linear motion mechanism 3c. As a result, the support portion RS of the rear axle RA and the link LS are expanded and contracted as described above, and the steering angle of the rear wheels is adjusted.

  The manufacturing method of the actuator unit AU having the above configuration will be described. First, the stator 24 around which the coil 23 is wound is press-fitted into the cylindrical body 10 by a press-fitting device (not shown), and the predetermined unit shown in FIG. Fixed in position. Further, the motor cover 25 is inserted into the cylindrical body 10, and the snap ring 14 is fixed to the annular groove 10 a in the cylindrical body 10. Separately from this, after the bearing 25b is press-fitted into the hollow rotary shaft 20 in which the sun gear 31 is integrally formed, a resin pressing member 22a for holding the permanent magnet 22 is press-fitted and the core 21 is press-fitted. Fixed. And the permanent magnet 22 is magnetized in the state of the subassembly in which the permanent magnet 22 is accommodated in the core 21 and the pressing member 22b is press-fitted.

  Next, the hollow rotary shaft 20 is inserted into the hollow portion of the stator 24, and the bearing 25 b is held in a state of being fitted into the hollow portion of the motor cover 25. Further, after the support member 26 to which the plastic magnet 6b for the magnetic pole sensor 6 is fixed is press-fitted into the end of the hollow rotary shaft 20 and the plastic magnet 6b is magnetized, the casing 12 is the electric motor 3a of the cylindrical body 10. It is joined to the opening on the side (right side in FIG. 2) and bolted. The outer ring of the bearing 12 b is press-fitted into the annular groove 12 a of the housing 12, and when the housing 12 is joined to the cylindrical body 10, the inner ring of the bearing 12 b is fitted to the hollow rotary shaft 20.

  On the other hand, the inner ring 37 a of the bearing 37 is fitted to the nut member 36 and held by the spacer 37 c, and the outer ring 37 b of the bearing 37 is fitted to the holder 34. Next, when the ring gear 33 is attached to the holder 34 and the planetary gear 32 is supported by the nut member 36 by the pin 35, the state shown in FIG. 7 is obtained, and the locking member 38 is locked to the pin 35. Then, the male screw portion 2c of the rod 2 is screwed to the female screw portion 36c of the nut member 36, and the nut 2d is screwed to the tip of the male screw portion 2c, thereby forming the subassembly SA shown in FIG.

  As a result, the subassembly SA in which the components of the planetary gear mechanism 30 other than the sun gear 31 are assembled to the rod 2 is accommodated in the cylindrical body 10 from the opening on the planetary gear mechanism 30 side (left side in FIG. 1). The rod 2 is accommodated in the cylindrical body 10 through the opening on the electric motor 3a side (the right side in FIG. 1) in a state in which the components of the electric motor 3a are assembled to each step portion of the integrally formed hollow rotary shaft 20. Can be easily assembled by engaging the sun gear 31 with the ring gear 33.

  Thus, the rod 2 of the subassembly SA is inserted into the hollow rotary shaft 20 shown in FIGS. 1 to 3, and the sun gear 31 is assembled so as to mesh with the planetary gear 32 and the ring gear 33. It is pushed in until the end surface comes into contact with the side end surface of the snap ring 14. Subsequently, the connection cover 11 is attached, and the lock nut 13 is screwed into the cylinder 10. As a result, the outer ring 37 b of the bearing 37 and the holder 34 are firmly sandwiched between the snap ring 14 and the connection cover 11. At this time, the rod 2 of the subassembly SA is inserted through the bushes 2 a and 2 b provided in the housing 12 and extends to the outside of the housing 12.

  And in the housing | casing 12, the magnet block 50 is arrange | positioned in the long groove 2r of the rod 2, and it is assembled | attached so that the holding | maintenance part 52 may be hold | maintained between the standing wall parts 12w and 12w. Thus, when the bolt 51 is inserted into the through hole 2 h of the rod 2 and screwed into the nut 54, the rod 2 is supported so as not to rotate with respect to the housing 1.

  Further, the electronic circuit board 40 on which the displacement sensor 5a is mounted is accommodated in the housing 12, and the displacement sensor 5a is fixed at a position facing the permanent magnet 5b. Then, after the wire harness (not shown) is connected, when the lids 15 and 16 are bolted to the housing 12 via the O-ring OR of the sealing member, the inside of the housing 12 becomes a liquid-tight space. . After the assembly as described above, the ball joint JL is connected to the tip of the rod 2 and the rubber boot BT is mounted.

DESCRIPTION OF SYMBOLS 1 Housing 2 Rod 3 Actuator 3a Electric motor 3b Deceleration mechanism 3c Linear motion mechanism 4 Controller 5 Displacement detection apparatus 10 Cylindrical body 11 Connection cover 12 Case 13 Lock nut 14 Snap ring 15, 16 Lid 20 Hollow rotary shaft 20h Annular groove 20i External gear 30 Planetary gear mechanism 31 Sun gear 33 Ring gear 34 Holder (tubular holding member)
36 Nut member 37 Bearing 40 Electronic circuit board 50 Magnet block

Claims (4)

  In a vehicle rear wheel steering apparatus that is interposed in a suspension mechanism that supports a rear wheel of a vehicle and steers the rear wheel, a housing that is coupled to the suspension mechanism via a first coupling member and a second coupling member; An electric motor housed in the housing; a reduction mechanism housed in the housing that decelerates the output of the electric motor; a nut member that rotates in connection with the reduction mechanism; And a linear motion mechanism that converts the rotational motion of the nut member into linear motion of the rod, and the housing includes the electric motor and the speed reduction mechanism arranged in series. And a connecting cover that has the first connecting member and closes the opening of the cylindrical body on the speed reduction mechanism side, and is rotatably supported with respect to the housing. And a metal hollow rotary shaft that constitutes the output shaft of the electric motor, and an annular groove is formed on the outer peripheral surface of the hollow rotary shaft, and external teeth are parallel to the annular groove. The gears constituting the speed reduction mechanism are formed integrally with the hollow rotary shaft by integral molding of synthetic resin so as to include the outer teeth and the annular groove. Steering device.   The speed reduction mechanism is a planetary gear mechanism, and the sun gear constituting the planetary gear mechanism is formed integrally with the hollow rotary shaft by integral molding of resin so as to include the outer teeth and the annular groove. The rear-wheel steering device for a vehicle according to claim 1.   The vehicle rear wheel steering system according to claim 1 or 2, wherein the external teeth are arranged in parallel with the hollow rotary shaft adjacent to the annular groove.   The hollow rotating shaft has a plurality of step portions whose outer diameters are sequentially reduced from a portion adjacent to the annular groove to an opening on the electric motor side. The rear-wheel steering device for a vehicle according to the item.

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