JP2006082610A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device capable of considerably improving the assembly workability without increasing cost. <P>SOLUTION: When assembling the electric power steering device, an output shaft 4 (a pinion shaft) with a worm wheel 11 being not fitted is inserted in a lower gear box 1. Next, an outer wheel of an upper bearing 6 is fixed by screwing a ring nut 41 to a screw hole 40 formed in the lower gear box 1. After the upper bearing 6 is fixed by the ring nut 41, the worm wheel 11 is fitted to the output shaft 4 via a slip ring 42. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electric power steering apparatus in which the support structure is improved and the assemblability is improved.

  As a conventional example of an electric power steering apparatus, as shown in Patent Document 1, a worm wheel is press-fitted into an output shaft (pinion shaft) in advance.

  Further, the bearing that supports the pinion shaft in the radial direction and the thrust direction is disposed substantially directly below the worm wheel. Thereby, the relative shift | offset | difference of the pinion axial direction of the meshing position of a worm wheel and a worm by a temperature change is made small.

  That is, FIG. 4 is a longitudinal sectional view of a conventional pinion-assisted electric power steering device.

  The electric power steering device 51 is a pinion assist type electric power steering device. A cored bar 78 of a worm wheel 77 that meshes with a worm 79 of a worm reducer 76 is press-fitted into the upper end portion of the output shaft 52. The upper end surface of the metal core 78 is in contact with the step portion 55 of the output shaft 52, and restricts the metal core 78 from moving upward with respect to the output shaft 52. The worm 79 is connected to an output shaft of a steering assist electric motor (not shown).

  The output shaft 52 is pivotally supported by the lower gear box 69 by a four-point contact type bearing 65 substantially directly below the worm wheel 77. The caulking ring 56 that has been crimped by being mounted in the groove 57 of the output shaft 52 sandwiches the inner ring of the bearing 65 with the lower end surface of the boss 80 of the core metal 78. Further, the outer ring of the bearing 65 is press-fitted into a bearing hole 73 formed directly in the lower gear box 69 and is pressed in the axial direction by a ring nut 67 screwed into the female screw 74 of the bearing hole 45, thereby lower gear. It is fixed to the box 69.

  The lower end portion of the output shaft 52 is supported by the lower gear box 69 only in the radial direction by a needle bearing 66. Thus, since the output shaft 52 is supported by the bearing 65 in the thrust direction and the radial direction, the support reference of the output shaft 52 with respect to the lower gear box 69 is the bearing 65 that supports the upper end portion of the output shaft 52. It has become.

  An upper gear box 72 is fixed to the upper end surface of the lower gear box 69 by bolts (not shown). An input shaft 82 is rotatably supported on the upper gear box 72 by a bearing 83. The input shaft 82 is connected to the steering wheel via a steering shaft (not shown). The torsion bar 85 whose upper end is connected to the input shaft 82 by a pin 84 is pivotally supported by the bush 86 at the lower end, and is press-fitted to the upper end of the output shaft 52 below the bush 86.

  A torque sensor 87 that detects torque acting on the torsion bar 85 includes a sensor shaft portion 88, detection coils 90 and 91, and a cylindrical member 92. The sensor shaft portion 88 is formed at the lower end of the input shaft 82, and the detection coils 90 and 91 are disposed in a yoke 89 press-fitted inside the upper gear box 72. The cylindrical member 92 is disposed between the sensor shaft portion 88 and the detection coils 90 and 91.

  The cylindrical member 92 is fixed to the upper end of the output shaft 52, and a plurality of ridges extending in the axial direction on the sensor shaft portion 88 are formed at equal intervals in the circumferential direction. In the cylindrical member 92, a plurality of rectangular windows are formed at equal intervals in the circumferential direction at positions facing the detection coils 90 and 91.

  When the input shaft 82 is rotated by operating the steering wheel, the rotational force is transmitted to the output shaft 52 via the torsion bar 85. At this time, the torsion bar 63 connecting the input shaft 82 and the output shaft 52 is twisted due to the resistance on the steering wheel side, and relative rotation is caused between the protrusion on the surface of the sensor shaft portion 88 and the window of the cylindrical member 92. Arise. With this relative rotation, the magnetic flux generated in the sensor shaft portion 88 increases and decreases, and the increase and decrease of the magnetic flux is detected by the detection coils 90 and 91 as a change in inductance. From this detection result, torque acting on the torsion bar 85 is detected, and the electric motor is driven to rotate the worm 79 with a required steering assist force. The rotation of the worm 79 is transmitted to the rack 54 via the worm wheel 77, the output shaft 52, and the pinion 53, and the direction of the steering wheel is changed via a tie rod (not shown) connected to the rack 54.

  The rack guide 93 always presses the roller 96 against the back surface of the rack 54 with an adjustment cover 97. The roller 96 is rotatably supported on a shaft 94 by a needle bearing 95. The adjustment cover 97 presses the roller 96 against the back surface of the rack 54 via a disc spring. As a result, the backlash at the meshing portion between the pinion 53 and the rack 54 is eliminated, and the rack 54 moves smoothly.

  In the electric power steering apparatus 51, a bearing 65 serving as a support reference for the output shaft 52 is provided almost directly below the worm wheel 77.

  Therefore, even if there is a temperature change around the electric power steering device, the amount by which the meshing position between the worm wheel 77 and the worm 79 is shifted in the axial direction of the output shaft 52 is small. Accordingly, a normal meshing state is always maintained, and no noise is generated at the meshing portion and tooth surface wear does not occur.

  Further, a bearing hole 75 into which the outer ring of the lower needle bearing 66 is press-fitted and a bearing hole 73 into which the outer ring of the upper bearing 65 is press-fitted are formed in the same lower gear box 69, and from the bearing hole 73 side. Therefore, the processing time is short and the concentricity between the bearing holes is improved. Therefore, the vibration of the worm wheel 77 is small, and noise at the meshing portion and wear on the tooth surface can be suppressed.

  Further, since the bearing hole 73 into which the outer ring of the upper bearing 65 is press-fitted is directly formed in the lower gear box 69, the processing error of the bearing hole does not accumulate and the concentricity between the bearing holes is improved. The worm wheel shake can be kept small.

  The ring nut 67 is tightened by the following method. A plurality of engaging recesses (grooves or holes) 68 are formed on the same circumference on the upper end surface of the ring nut 67, and the core metal 78 of the worm wheel 77 is engaged on the same circumference as the engaging recesses 68. A plurality of tool insertion holes 81 are formed at the same angular position as the joint recess 68.

If a bifurcated tightening tool is inserted into the engaging recess 68 through the tool insertion hole 81 and the tightening tool is turned, the ring nut 67 rotates and the outer ring of the bearing 65 can be tightened. In synchronization with the tightening operation of the ring nut 67, the metal core 78 having the tool insertion hole 81 and the worm wheel 77 are rotated by the tightening tool. Therefore, the output shaft 52 and the pinion 53 to which the worm wheel 77 is fixed rotate, and as a result, the rack 54 that meshes with the pinion 53 moves.
Japanese Patent Application No. 2004-073398

  However, the bearing 65 almost directly below the worm wheel 77 is fixed using a ring nut 67, and a bifurcated tightening tool is inserted from above the worm wheel 77. It is necessary to provide the tool insertion hole 81.

  However, depending on conditions for ensuring the strength of the worm wheel 77, the tool insertion hole 81 may not be provided. For this reason as well, the worm wheel 77 needs to be assembled later, and the output shaft 52 (pinion shaft). ) Is inserted into the lower gear box 69, and the worm wheel 77 is preferably attached to the output shaft 52 (pinion shaft).

  Further, when the ring nut 67 is tightened, it is necessary to form a relief portion outside the stroke end of the gear teeth of the rack 54 so that the rack 54 does not move even if the output shaft 52 (pinion shaft) rotates. There is. As a result, these processes may increase costs.

  Furthermore, in the case of a steering device in which the core of the worm wheel of the worm speed reducer is press-fitted into the output shaft (pinion shaft) in advance, the bearing 65 that supports the output shaft (pinion shaft) at the time of the press-fitting, High load is applied and there is a risk of damage.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an electric power steering device capable of remarkably improving assembly workability without causing an increase in cost.

In order to achieve the above object, an electric power steering apparatus according to claim 1 of the present invention generates an auxiliary steering torque from an electric motor in accordance with a steering torque applied to a steering wheel, and decelerates by a worm reducer. In the electric power steering device that transmits to the output shaft of the steering mechanism
The worm wheel of the worm speed reducer is fitted to the output shaft via a slip ring.

  The electric power steering apparatus according to claim 2 of the present invention is characterized in that the vehicle upper bearing that supports the output shaft is fixed to the gear box by a fixing member that is press-fitted in the axial direction.

  In the electric power steering apparatus according to a third aspect of the present invention, the fixing member is a retaining ring, a snap ring, or a push nut.

  According to the present invention, since the worm wheel of the worm reduction gear is fitted to the output shaft via the slip ring, the output shaft (pinion shaft) is mounted after the output shaft (pinion shaft) is attached to the gear box. A worm wheel can be attached to the shaft. Therefore, it is possible to eliminate the need for worm wheel press-fitting and eliminate the possibility of damage to the worm wheel, and it is necessary to provide a tool insertion hole for the core metal of the worm wheel or a relief part outside the stroke end of the rack gear teeth. In addition, even when the ring nut is tightened, it is possible to eliminate co-rotation of the output shaft (pinion shaft). Therefore, the assembly workability of the electric power steering apparatus can be remarkably improved without causing an increase in cost.

  The bearing on the upper side of the vehicle that supports the output shaft is fixed to the gear box by a fixing member that is press-fitted in the axial direction, and the fixing member is, for example, a retaining ring, a snap ring, or a push nut. Therefore, it is possible to greatly facilitate the mounting workability.

  Hereinafter, an electric power steering apparatus according to an embodiment of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a longitudinal sectional view of a pinion-assisted electric power steering device according to a first embodiment of the present invention.

  In the present embodiment, the gear box includes a lower gear box 1 on the vehicle lower side and an upper gear box 2 on the vehicle upper side.

  In the lower gear box 1, the lower part of the output shaft 4 (pinion shaft) is rotatably supported by the lower bearing 5 (needle bearing), and the upper part thereof is the upper bearing 6 (four-point contact type bearing). ) Is supported rotatably.

  A worm reduction gear 10 is housed in the lower gear box 1, and the core metal 11 a of the worm wheel 11 is connected to the output shaft 4 via a slip ring 42, as will be described in detail later. 4 is fitted.

  The worm wheel 11 has resin gear teeth 11b. A worm 12 is meshed with the worm wheel 11, and the worm 12 is driven by an electric motor (not shown).

  A rack 21 is engaged with the pinion 20 of the output shaft 4. In the rack guide 22, a roller 23 is always pressed against the back surface of the rack 21 by an adjustment cover 24. The roller 23 is rotatably supported on a shaft 25 by a needle bearing 26.

  The adjustment cover 24 has a roller 23 pressed against the back surface of the rack 21 via a disc spring. As a result, the backlash of the meshing portion between the pinion 20 and the rack 21 is eliminated, and the rack 21 moves smoothly.

  An input shaft 30 is rotatably supported in the upper gear box 2 via a bearing 31.

  The input shaft 30 is connected to the steering wheel via a steering shaft (not shown). The torsion bar 33 whose upper end is connected to the input shaft 30 by a pin 32 is connected to the upper end portion of the output shaft 4 by press fitting.

  A torque sensor 34 that detects torque acting on the torsion bar 33 includes a sensor shaft portion 35, detection coils 36 and 37, and a cylindrical member 38. The sensor shaft portion 35 is formed at the lower end of the input shaft 30, and detection coils 36 and 37 are arranged in a yoke 39 press-fitted inside the upper gear box 2. The cylindrical member 38 is disposed between the sensor shaft portion 35 and the detection coils 36 and 37.

  The cylindrical member 38 is fixed to the output shaft 4, and a plurality of ridges extending in the axial direction on the sensor shaft portion 35 are formed at equal intervals in the circumferential direction. In the cylindrical member 38, a plurality of rectangular windows are formed at equal intervals in the circumferential direction at positions facing the detection coils 36 and 37.

  When the input shaft 30 is rotated by operating the steering wheel, the rotational force is transmitted to the output shaft 4 via the torsion bar 33. At this time, the torsion bar 33 that connects the input shaft 30 and the output shaft 4 is twisted due to the resistance on the steering wheel side, and relative rotation occurs between the protrusion on the surface of the sensor shaft portion 35 and the window of the cylindrical member 38. . With this relative rotation, the magnetic flux generated in the sensor shaft portion 35 increases and decreases, and the increase and decrease of the magnetic flux is detected by the detection coils 36 and 37 as a change in inductance. From this detection result, the torque acting on the torsion bar 33 is detected, and the electric motor is driven to rotate the worm 12 with a required steering assist force. The rotation of the worm 12 is transmitted to the rack 21 via the worm wheel 11, the output shaft 4, and the pinion 20, and the direction of the steering wheel is changed via a tie rod (not shown) connected to the rack 21.

  In the present embodiment, when the electric power steering apparatus is assembled, the output shaft 4 (pinion shaft) with the worm wheel 11 not attached is inserted into the lower gear box 1.

  Next, the outer ring of the upper bearing 6 is fixed by screwing a ring nut 41 into a screw hole 40 formed in the lower gear box 1.

  After the upper bearing 6 is fixed by the ring nut 41, the worm wheel 11 is fitted to the output shaft 4 via the slip ring 42.

  Thus, in this embodiment, after the output shaft 4 (pinion shaft) is attached to the lower gear box 1, the worm wheel 11 can be attached to the output shaft 4 (pinion shaft).

  Therefore, it is possible to eliminate the need for press-fitting the worm wheel 11 to eliminate the possibility of damage to the upper bearing 6 and to release the tool insert hole in the core metal of the worm wheel 11 or the outer side of the stroke end of the gear teeth of the rack 21. It is not necessary to provide a portion, and the rotation of the output shaft 4 (pinion shaft) can be eliminated even when the ring nut 41 is tightened.

  From the above, the assembly workability of the electric power steering apparatus can be remarkably improved without causing an increase in cost.

(Second Embodiment)
FIG. 2 is a longitudinal sectional view of a pinion-assisted electric power steering device according to the second embodiment of the present invention.

  As is apparent from the drawings, this embodiment has the same basic structure as the first embodiment described above, and only differences will be described.

  In this embodiment, a snap ring (retaining ring) 44 is used instead of the ring nut 41 described above.

  That is, the outer ring of the upper bearing 6 is fixed by fitting the snap ring (retaining ring) 44 into the recess 43 formed in the lower gear box 1.

  From the above, in the present embodiment, when the electric power steering apparatus is assembled, the output shaft 4 (pinion shaft) with the worm wheel 11 not attached is inserted into the lower gear box 1.

  Next, the outer ring of the upper bearing 6 is fixed by fitting a snap ring (retaining ring) 44 into a recess 43 formed in the lower gear box 1.

  After the upper bearing 6 is fixed by a snap ring (retaining ring) 44, the worm wheel 11 is fitted to the output shaft 4 via the slip ring 42.

  Thus, in this embodiment, after the output shaft 4 (pinion shaft) is attached to the lower gear box 1, the worm wheel 11 can be attached to the output shaft 4 (pinion shaft).

  Accordingly, it is possible to eliminate the need for press-fitting of the worm wheel 11 and to eliminate the possibility of damage to the worm wheel 11, and to release the outer side of the stroke end of the gear teeth of the rack 21 or the tool insertion hole of the core metal of the worm wheel 11. It is not necessary to provide a portion, and the rotation of the output shaft 4 (pinion shaft) can be eliminated even when the ring nut 41 is tightened.

  From the above, also in the present embodiment, the assembly workability of the electric power steering device can be remarkably improved without causing an increase in cost.

  Further, since the upper bearing 6 is fixed by a snap ring (retaining ring) 44, compared to the ring nut 41, the mounting workability can be greatly facilitated.

  The snap ring (retaining ring) 44 is preferably tapered. Thereby, backlash can also be prevented.

(Third embodiment)
FIG. 3 is a longitudinal sectional view of a pinion-assisted electric power steering apparatus according to the third embodiment of the present invention.

  As is apparent from the drawings, this embodiment has the same basic structure as the first embodiment described above, and only differences will be described.

  In this embodiment, a push nut 46 is used in place of the ring nut 41 or the snap ring (retaining ring) 44 described above.

  That is, the outer ring of the upper bearing 6 is fixed by fitting the push nut 46 into the recess 45 formed in the lower gear box 1.

  From the above, in the present embodiment, when the electric power steering apparatus is assembled, the output shaft 4 (pinion shaft) with the worm wheel 11 not attached is inserted into the lower gear box 1.

  Next, the outer ring of the upper bearing 6 is fixed by fitting a push nut 46 into a recess 45 formed in the lower gear box 1.

  After the upper bearing 6 is fixed by the push nut 46, the worm wheel 11 is fitted to the output shaft 4 via the slip ring 42.

  Thus, in this embodiment, after the output shaft 4 (pinion shaft) is attached to the lower gear box 1, the worm wheel 11 can be attached to the output shaft 4 (pinion shaft).

  Therefore, it is possible to eliminate the need for press-fitting the worm wheel 11 to eliminate the possibility of damage to the upper bearing 6 and to release the tool insert hole in the core metal of the worm wheel 11 or the outer side of the stroke end of the gear teeth of the rack 21. It is not necessary to provide a portion, and since no ring nut is used to fix the upper bearing 6, it is possible to eliminate co-rotation of the output shaft 4 (pinion shaft).

  From the above, also in the present embodiment, the assembly workability of the electric power steering device can be remarkably improved without causing an increase in cost.

  Further, since the upper bearing 6 is fixed by the push nut 46, the mounting workability can be greatly facilitated as compared with the ring nut 41.

  In addition, this invention is not limited to embodiment mentioned above, A various deformation | transformation is possible.

1 is a longitudinal sectional view of a pinion-assisted electric power steering device according to a first embodiment of the present invention. It is a longitudinal cross-sectional view of the pinion assist type electric power steering device according to the second embodiment of the present invention. It is a longitudinal cross-sectional view of the pinion assist type electric power steering device which concerns on 3rd Embodiment of this invention. It is a longitudinal cross-sectional view of the pinion assist type electric power steering device according to the conventional example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lower gear box 2 Upper gear box 4 Output shaft 5 Lower bearing 6 Upper bearing 10 Worm speed reducer 11 Worm wheel 11a Core metal 11b Gear tooth 12 Worm 20 Pinion 21 Rack 22 Rack guide 23 Roller 24 Adjustment cover 25 Shaft 26 Needle Bearing 27 Upper bearing 30 Input shaft 31 Bearing 32 Pin 33 Torsion bar 34 Torque sensor 35 Sensor shaft portion 36, 37 Detection coil 38 Cylindrical member 39 Yoke 40 Screw hole 41 Ring nut 42 Slip ring 43 Concave portion 44 Snap ring (Retaining ring)
45 recess 46 push nut 51 electric power steering device 52 output shaft 53 pinion 54 rack 55 step 56 caulking 57 groove 65 bearing 66 needle bearing 67 ring nut 68 engagement recess 69 lower gear box 72 upper gear box 73 bearing hole 74 female Screw 75 Bearing hole 76 Worm speed reducer 77 Worm wheel 78 Core metal 79 Worm 80 Boss part 81 Tool insertion hole 82 Input shaft 83 Bearing 84 Pin 85 Torsion bar 86 Bush 87 Torque sensor 88 Sensor shaft part 89 Yoke 90, 91 Detection coil 92 Cylindrical member 93 Rack guide 94 Shaft 95 Needle bearing 96 Roller 97 Adjust cover

Claims (3)

In an electric power steering device that generates an auxiliary steering torque from an electric motor according to a steering torque applied to a steering wheel, decelerates it by a worm reducer, and transmits it to an output shaft of a steering mechanism.
An electric power steering apparatus, wherein a worm wheel of the worm reducer is fitted to the output shaft through a slip ring.   2. The electric power steering apparatus according to claim 1, wherein the bearing on the upper side of the vehicle that supports the output shaft is fixed to the gear box by a fixing member that is press-fitted in the axial direction.   The electric power steering apparatus according to claim 2, wherein the fixing member is a retaining ring, a snap ring, or a push nut.

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