JP2009120093A - Power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power steering device capable of facilitating backlash control by suppressing fluctuation of backlash in a speed reducing mechanism and reducing rattling noise due to backlash. <P>SOLUTION: A housing H of the power steering device is equipped with a gear case 14, a gear box 15, and a stub case 16 adjacently disposed in the vertical direction. A worm wheel 12 and a worm 13 constituting the speed reducing mechanism 8 are supported by the single gear case 14. A portion near a lower end of a pinion shaft 6 engaged with a rack shaft 9 is rotatably supported by the gear case 14 via a first ball bearing 23. An outer ring 23A of the first ball bearing 23 is press-fitted and fixed in an annular bearing receiving part 22 provided to the gear case 14, and the pinion shaft 6 is press-fitted and fixed in an inner ring 23B of the first ball bearing 23. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a power steering apparatus that transmits a steering force of a steering wheel to a steered system while adding a steering assist force generated by a steering assist force generating means.

  As shown in FIG. 9, a conventional power steering apparatus 100 includes a housing 101 including a gear box 102 as a lower housing body and a gear case 103 as an upper housing body. In the housing 101, an input shaft 104 to which a steering force from the steering wheel is input, a pinion shaft 105 coaxially connected to the input shaft 104, and a rotational motion of the pinion shaft 105 are converted into a linear motion to be covered. A rack shaft 106 that transmits to the steering system and a speed reduction mechanism 107 that transmits a steering assist force from a steering assist force generating means (not shown) such as an electric motor to the pinion shaft 105 are supported. The speed reduction mechanism 107 includes a worm wheel 108 that is connected to the pinion shaft 105 so as to be integrally rotatable, and a worm 109 that transmits the power of the steering assist force generating means to the worm wheel 108.

  In the conventional apparatus of FIG. 9, the coaxial coupling body of the input shaft 104 and the pinion shaft 105 is rotatably supported by the housing 101 by three lower, middle and upper ball bearings (111 to 113). ing. In particular, the pinion shaft 105 that supports the worm wheel 108 is rotatably supported by two lower and middle ball bearings 111 and 112. In the lower ball bearing 111 located near the lower end of the pinion shaft 105, the pinion shaft 105 is fitted into the inner ring 111a with a gap, and the outer ring 111b is also spaced from the annular bearing portion 121 under the gear box 102. It is fitted. The inner ring 111 a of the lower ball bearing is pressed and fixed to the pinion shaft 105 by a nut 114, and the outer ring 111 b of the lower ball bearing is pressed and fixed to the gear box 102 by a plug 115.

  On the other hand, in the middle ball bearing 112 located in the middle of the pinion shaft 105, the pinion shaft 105 is fitted into the inner ring 112a with a gap, and the outer ring 112b is press-fitted into the annular bearing portion 122 above the gear box 102. It is fixed. Further, in the upper ball bearing 113 positioned in the middle of the input shaft 104, the input shaft 104 is fitted into the inner ring 113a with a clearance, and the outer ring 113b is press-fitted and fixed to the annular bearing portion 123 on the upper side of the gear case 103. ing. The worm wheel 108 is rotatably supported by the gear box 102 via the pinion shaft 105, while the worm 109 is rotatably supported by the gear case 103.

  However, in the conventional apparatus shown in FIG. 9, the worm wheel 108 and the worm 109 constituting the speed reduction mechanism 107 are supported by separate housing bodies (102, 103). In addition, the pinion shaft 105 is fitted into both the lower and middle ball bearings 111 and 112 with a gap. For this reason, the backlash between the worm 109 and the worm wheel 108 is not uniquely determined due to the joining accuracy of the two housing bodies (102, 103) and the gap due to the gap fitting, and the control of the backlash is very difficult. There was a problem that it was difficult. Further, the fact that the pinion shaft 105 can be displaced in the radial direction within the range of the gap due to the gap fitting not only causes fluctuation of the backlash, but also causes fluctuation of the operating resistance. Furthermore, excessive backlash and the presence of a gap due to the above-described gap fitting have caused the rattle noise resulting from these to be annoyingly loud.

Patent Document 1 is an example of a prior art in which a rack-and-pinion type steering device reduces the hitting sound and the like by eliminating rattling of the pinion shaft relative to the bearing.
JP 2002-67986 A

  An object of the present invention is to provide a power steering device capable of facilitating backlash control by suppressing fluctuations in backlash in a speed reduction mechanism and reducing the occurrence of rattle noise caused by the backlash of the speed reduction mechanism and the bearing structure. There is.

  The present invention is a power steering device that transmits a steering force of a steering wheel to a steered system while adding a steering assist force generated by a steering assist force generating means. A power steering device according to the present invention includes a housing constituted by a plurality of cases and / or boxes, an input shaft that is rotatably supported by the housing and receives a steering force from the handle, and the input shaft. A pinion shaft rotatably supported by the housing in a coaxially connected state, a speed reduction mechanism for transmitting a steering assist force from the steering assist force generating means to the pinion shaft, and a rotational motion of the pinion shaft. And a rack shaft that converts to linear motion and transmits the linear motion to the steered system. The speed reduction mechanism includes a worm wheel coupled to the pinion shaft so as to be integrally rotatable, and a worm cooperating with the worm wheel. The housing has a single gear case that supports both the worm and the worm wheel. The pinion shaft is configured such that a part of the pinion shaft is press-fitted and fixed to the inner ring of the first ball bearing and the outer ring of the first ball bearing is press-fitted and fixed to the annular bearing portion of the gear case. It is supported so as to be rotatable with respect to the gear case via a ball bearing.

  In the present invention, the worm and the worm wheel constituting the speed reduction mechanism are supported by the same single gear case. Further, a part of the pinion shaft is press-fitted and fixed to the inner ring of the first ball bearing, and the outer ring of the first ball bearing is press-fitted and fixed to the annular bearing portion of the gear case. An inner ring and an outer ring of the bearing are concentrically fixed to the pinion shaft and the gear case. As a result, the bearing structure of the pinion shaft is excluded from the main fluctuation factors of the backlash between the worm and the worm wheel, and the main fluctuation factors of the backlash are the machining accuracy of the gear case itself and the component machining accuracy of the worm and the worm wheel. It is almost limited to. Therefore, according to the present invention, the backlash control can be facilitated by suppressing the fluctuation of the backlash in the speed reduction mechanism as compared with the conventional case. Moreover, the fluctuation | variation of the operating resistance of a deceleration mechanism can be suppressed.

  According to the present invention, the backlash of the speed reduction mechanism can be made as small as possible, and the inner ring and the outer ring of the first ball bearing employ press-fitting to eliminate the gap fit, resulting in the backlash or the bearing structure of the speed reduction mechanism. The occurrence of rattle noise can be reduced as compared with the prior art.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1 and FIG. 2, the power steering apparatus 1 is coaxially connected to an input shaft 5 for inputting a steering force from a handle 2 via a steering column 3 and an intermediate shaft 4, and the input shaft 5. The pinion shaft 6, the steering force detection sensor means 7 for detecting the steering force of the handle 2, the electric motor M as a steering auxiliary force generating means for generating the steering auxiliary force corresponding to the steering force of the handle 2, and the electric A reduction mechanism 8 that transmits a steering assist force from the motor M to the pinion shaft 6, a rack shaft 9 that converts the rotational motion of the pinion shaft 6 into a linear motion and transmits the linear motion to the steered system 60, and a housing H are provided. Yes.

  As shown in FIG. 2, the pinion shaft 6 is formed in a substantially rod shape, and a pinion portion 11 is set at a substantially central portion of the pinion shaft 6. The upper part of the pinion shaft 6 above the pinion part 11 is formed in a slightly enlarged diameter, and an annular relief recess 10 is formed in the upper part. A worm wheel 12 is provided at the lower end portion of the pinion shaft 6 so as to be rotatable integrally with the pinion shaft 6. The pinion portion 11 of the pinion shaft 6 meshes with the rack teeth 9 </ b> A of the rack shaft 9. The worm wheel 12 meshes with a worm 13 operatively connected to the electric motor M. The speed reduction mechanism 8 is configured by the worm wheel 12 and the worm 13.

  The housing H includes a gear case 14, a gear box 15, and a stub case 16 that are disposed adjacent to each other along the vertical direction. The gear case 14 is located at the lowest position, the stub case 16 is located at the uppermost position, and the gear box 15 is located at the middle position between the cases 14 and 16.

  The lower surface side of the gear case 14 is opened and can be closed by the lid body 19, and a shaft insertion hole 21 through which the pinion shaft 6 is inserted is opened on the upper surface side. A worm wheel 12 is accommodated in the gear case 14, and both the worm wheel 12 and the worm 13 are supported by the same single gear case 14. An annular bearing portion 22 is erected on the upper surface side of the gear case 14 with the shaft insertion hole 21 as the center. An outer ring 23A of the first ball bearing 23 is press-fitted and fixed to the bearing portion 22, and a pinion shaft 6 is press-fitted and fixed to the inner ring 23B of the first ball bearing 23. A spacer S is provided between the first ball bearing 23 and the worm wheel 12, and the spacer S and the worm wheel 12 are fastened and fixed between the inner ring 23 </ b> B and the nut 61 by a tightening nut 61. . The pinion shaft 6 is press-fitted into the central hole of the worm wheel 12.

  The gear box 15 is formed in a cylindrical shape so that the pinion shaft 6 can pass therethrough, and shaft insertion holes 24 and 25 are provided in the upper part and the lower part thereof. The internal space of the gear box 15 provides a pinion shaft housing chamber 26, and the pinion portion 11 of the pinion shaft 6 and the rack teeth 9 </ b> A of the rack shaft 9 mesh with each other in the pinion shaft housing chamber 26.

  An annular bearing fitting portion 27 is provided at the periphery of the shaft insertion hole 24 on the lower side of the gear box 15, and an annular bearing portion 28 is provided on the periphery of the shaft insertion hole 25 on the upper side of the gear box 15. It has been. The outer ring 23 </ b> A of the first ball bearing 23 is fitted into the bearing fitting portion 27 of the gear box 15. An outer ring 29A of the second ball bearing 29 is press-fitted and fixed to the bearing portion 28 of the gear box 15, and the pinion shaft 6 is fitted into the inner ring 29B of the second ball bearing 29 with a gap. However, an O-ring 30 as an annular elastic body is interposed between the inner ring 29B and the pinion shaft 6.

  3A is a perspective view of the gear box 15 as viewed from above, and FIG. 3B shows a cross section taken along the line BB in FIG. 3A. As shown in FIG. 3A, the bearing portion 28 at the top of the gear box is formed in an annular shape. The pinion shaft housing chamber 26 that connects the upper and lower shaft insertion holes 24 and 25 is formed so that the cross-sectional shape in a direction orthogonal to the insertion direction of the pinion shaft 6 is substantially oval. Therefore, the pinion shaft 6 temporarily arranged in the pinion shaft housing chamber 26 in the assembly process of the apparatus can be moved or displaced along the major axis direction of the oval shape.

  As shown in FIG. 2, an opening 31 is provided on the side surface of the gear box 15, and a rack shaft pressing mechanism 32 is disposed in the opening 31. The rack shaft pressing mechanism 32 presses the rack shaft 9 toward the pinion shaft 6 to mesh the rack teeth 9A with the pinion portion 11.

  As shown in FIG. 2, the stub case 16 is formed in a cylindrical shape, and circular shaft insertion holes 33 and 34 through which the input shaft 5 is inserted are provided at the upper and lower portions thereof. A sensor mounting hole 38 is provided on the side surface of the stub case 16.

  An annular bearing fitting portion 35 is provided at the periphery of the shaft insertion hole 33 on the lower side of the stub case 16, and an annular bearing receiving portion 36 is provided in the vicinity of the shaft insertion hole 34 on the upper side of the stub case 16. ing.

  An outer ring 29 </ b> A of the second ball bearing 29 is fitted into the bearing fitting portion 35 of the stub case 16. On the other hand, the outer ring 37A of the third ball bearing 37 is press-fitted and fixed to the bearing portion 36 of the stub case 16, and the input shaft 5 is fitted into the inner ring 37B of the third ball bearing 37 with a gap. However, an O-ring 39 as an annular elastic body is interposed between the inner ring 37 </ b> B and the input shaft 5. An annular oil seal 40 is provided in the shaft insertion hole 34 of the stub case 16.

  As shown in FIG. 4, the rack shaft 9 is provided with a plurality of rack teeth 9 </ b> A and a relief portion 9 </ b> B formed as a flat portion or a recessed portion without rack teeth on one side of the rack tooth 9 </ b> A group. . The escape portion 9B functions as a portion for temporarily avoiding interference with the pinion portion 11 of the pinion shaft 6 when the apparatus is assembled.

  Next, the steering force detection sensor means 7 for detecting the steering force from the handle 2 will be described. As shown in FIG. 2, the input shaft 5 is formed in a hollow shape, and a torsion bar 41 is inserted therein. The torsion bar 41 has an upper end attached to the input shaft 5 by a pin 42 and a lower end projecting downward from the input shaft 5.

  The lower end portions of the input shaft 5 and the torsion bar 41 are inserted into the bottomed recess formed at the upper end portion of the pinion shaft 6, and the lower end portion of the torsion bar 41 is connected to the pinion shaft via the serration 43. 6 is connected. Note that, due to the presence of the torsion bar 41, the input shaft 5 and the pinion shaft 6 are connected so as to be able to transmit torque to each other and to be able to swing with respect to each other.

  A sleeve 44 is attached to the outer periphery of the lower end portion of the input shaft 5 and the outer periphery of the upper end portion of the pinion shaft 6. A female helical spline 45 is formed on the inner peripheral surface of the sleeve 44, while a male helical spline 46 is formed on the outer periphery of the input shaft 5. The helical spline 45 of the sleeve 44 and the helical spline 46 of the input shaft 5 are meshed with each other. The sleeve 44 is formed with an axial groove 47 having a long hole shape along the axial direction. In the axial groove 47, the tip of a pin 48 that is horizontally held at the upper end of the pinion shaft 6 is inserted.

  According to the steering force detection sensor means 7 configured in this way, the input shaft 5 rotates according to the steering force of the handle 2 and the torsion bar 41 is twisted, whereby the sleeve 44 is removed from the helical splines 45 and 46. It moves in the axial direction (vertical direction) along the spiral orbit of the cam mechanism.

  Further, a concave portion 49 is formed on the outer peripheral portion of the sleeve 44, and the detection lever 51 of the potentiometer 50 is inserted into the concave portion 49. The potentiometer 50 can detect the amount of movement of the sleeve 44 in the axial direction by inserting the detection lever 51 into the recess 49. That is, when the sleeve 44 moves in the axial direction as described above, the potentiometer 50 detects this movement, whereby the steering force of the handle 2 is detected.

  The electric motor M generates a rotational driving force corresponding to the steering force of the handle 2 detected by the potentiometer 50. This rotational driving force is transmitted to the pinion shaft 6 through the worm 13 and the worm wheel 12, and is transmitted from the pinion shaft 6 to the rack shaft 9 as a steering assist force.

  Next, the assembly procedure of the power steering device 1 of this embodiment will be described. The assembly procedure mainly includes the four steps shown in FIGS.

  FIG. 5 shows a first step until the primary assembly 52 is formed. In the first step, first, the torsion bar 41, the input shaft 5 and the sleeve 44 are assembled to the upper end portion of the pinion shaft 6 to form the coaxial coupling body (5, 6) of the input shaft 5 and the pinion shaft 6. Next, the lower end portion of the pinion shaft 6 is press-fitted into the inner ring 23 </ b> B of the first ball bearing 23, and the first ball bearing 23 is integrated with the pinion shaft 6.

  Subsequently, the outer ring 23A of the first ball bearing 23 integrated with the pinion shaft 6 is press-fitted into the annular bearing portion 22 of the gear case 14 which is the lowest housing, and the coaxial coupling body (5, 6). Is placed upright on the gear case 14. Thereafter, the spacer S is fitted around the lower end portion of the pinion shaft 6 in the gear case 14, and the worm wheel 12 is press-fitted into the lower end portion of the pinion shaft 6. Then, the spacer S and the worm wheel 12 are fastened and fixed by the fastening nut 61. The worm 13 is supported by the gear case 14 while meshing with the worm wheel 12. Then, a lid 19 is attached to the lower surface side of the gear case 14. Thus, the primary assembly 52 in which the coaxial coupling bodies (5, 6), the gear case 14, and the speed reduction mechanism 8 are integrated is configured.

  6 and 7 show the second process and the third process from the primary assembly 52 to the construction of the secondary assembly 53. FIG.

  In the second step shown in FIG. 6, first, the outer ring 29 </ b> A of the second ball bearing 29 is press-fitted into the annular bearing portion 28 at the top of the gear box 15, and the second ball bearing 29 is inserted into the gear box 15 in advance. Keep it integrated. Next, the gear box 15 is externally fitted to the primary assembly 52 from above the primary assembly 52. At this time, as shown in FIG. 6, while the second ball bearing 29 integrated with the gear box 15 is temporarily retracted in the relief recess 10 of the pinion shaft 6, the pinion shaft 6 of the primary assembly 52 is The gear box 15 in the floating state is assembled to the primary assembly so as to be offset toward one end side (left side in FIG. 6) in the major axis direction of the pinion shaft accommodating chamber 26 (substantially oval in cross section) of the gear box 15. Position relative to 52.

  In the relative positioning state shown in FIG. 6, there is a relatively large space between the other end (right side in FIG. 6) of the pinion shaft accommodating chamber 26 in the major axis direction and the pinion portion 11 of the pinion shaft 6 that is offset. Secured. Therefore, the rack shaft 9 can be easily inserted into this relatively large space in the pinion shaft accommodating chamber 26. 3A indicates a position where the pinion shaft 6 of the primary assembly 52 is disposed so as to be offset toward one end of the pinion shaft housing chamber 26 in the major axis direction. The second step is completed by inserting the rack shaft 9 into the pinion shaft housing chamber 26 of the gear box 15.

  In the third step shown in FIG. 7, first, the position of the rack shaft 9 is adjusted so that the escape portion 9 </ b> B of the rack shaft 9 inserted in the pinion shaft housing chamber 26 faces the pinion portion 11 of the pinion shaft 6. Then, the position of the gear box 15 is adjusted while maintaining the facing relationship between the relief portion 9B of the rack shaft 9 and the pinion portion 11 of the pinion shaft 6, whereby the pinion shaft 6 of the primary assembly 52 is moved to the pinion shaft. Relative positioning is performed at a specified position in the storage chamber 26. 3A indicates the specified position of the pinion shaft 6 in the pinion shaft housing chamber 26.

  At this time, the second ball bearing 29 is detached from the relief recess 10 of the pinion shaft 6. Then, the second ball bearing 29 is mounted on the top of the pinion shaft 6 while the O-ring 30 is interposed between the inner ring 29 </ b> B of the second ball bearing 29 and the top of the pinion shaft 6.

  In synchronization with this, the first ball bearing 23 fixed to the gear case 14 is fitted into the bearing fitting portion 27 at the lower part of the gear box 15, and the gear box 15 is connected to the gear case 14. As a result, the pinion shaft 6 of the coaxial coupling body (5, 6) is rotatably supported with respect to the gear case 14 and the gear box 15 via the first ball bearing 23 and the second ball bearing 29.

  Finally, as shown in FIG. 7, the gear box 15 is fastened to the gear case 14 with a plurality of connecting bolts 18 (only one is shown). Thus, the secondary assembly 53 in which the coaxial connector (5, 6), the speed reduction mechanism 8, the gear case 14, and the gear box 15 are integrated is configured.

  Next, in the fourth step shown in FIG. 8, first, the rack shaft pressing mechanism that presses the rack shaft 9 against the pinion shaft 6 after meshing the rack teeth 9 </ b> A of the rack shaft 9 and the pinion portion 11 of the pinion shaft 6. 32 is assembled to the gear box 15. On the other hand, the oil seal 40 is attached to the stub case 16 and the outer ring 37A of the third ball bearing 37 is press-fitted and fixed to the annular bearing portion 36 at the top of the stub case 16 to thereby fix the third ball bearing 37. It is integrated with the stub case 16 in advance. Then, the stub case 16 is put on the input shaft 5 of the secondary assembly 53 from above.

  At this time, the third ball bearing 37 is mounted on the input shaft 5 while the O-ring 39 is interposed between the inner ring 37 </ b> B of the third ball bearing 37 and the input shaft 5. In synchronism with this, the second ball bearing 29 fixed to the gear box 15 is fitted into the bearing fitting portion 35 below the stub case 16, and the stub case 16 is connected to the gear box 15. Is done. As a result, the coaxially connected body (5, 6) rotates with respect to the housing H including the gear case 14, the gear box 15, and the stub case 16 via the first, second and third ball bearings 23, 29 and 37. Supported as possible.

  Finally, as shown in FIG. 8, the basic structure of the power steering apparatus as shown in FIG. 8 is completed by fastening the stub case 16 to the gear box 15 with a plurality of connecting bolts 17 (only one is shown). . Thereafter, the electric steering device 1 shown in FIG. 2 is completed by assembling electric components such as the potentiometer 50 and the electric motor M, tie rod ends (not shown), and the like.

[Effect of the embodiment]
In this embodiment, the worm wheel 12 and the worm 13 constituting the speed reduction mechanism 8 are supported by the same single gear case 14. Further, the pinion shaft 6 is press-fitted and fixed to the inner ring 23B of the first ball bearing 23, and the outer ring 23A of the first ball bearing 23 is press-fitted and fixed to the annular bearing portion 22 of the gear case 14, thereby The inner and outer rings of the ball bearing 23 are concentrically fixed to the pinion shaft 6 and the gear case 14. As a result, the bearing structure of the pinion shaft 6 is excluded from the main fluctuation factors of the backlash between the worm wheel 12 and the worm 13, and the main fluctuation factors of the backlash are the machining accuracy of the gear case 14 itself, the worm wheel 12 and the worm. 13 parts machining accuracy is almost limited. Therefore, the backlash control can be facilitated by suppressing the fluctuation of the backlash in the speed reduction mechanism 8 as compared with the prior art. In addition, fluctuations in the operating resistance (rotational resistance) of the speed reduction mechanism 8 can be suppressed.

  Further, the backlash in the speed reduction mechanism 8 can be reduced as much as possible, and the outer ring 23A and the inner ring 23B of the first ball bearing are fixed by press-fitting to eliminate the gap fit, thereby reducing the backlash and the second speed of the speed reduction mechanism 8. The generation of rattle noise caused by the mounting structure of one ball bearing 23 can be reduced as compared with the prior art.

  In the present embodiment, for the second ball bearing 29 that rotatably supports the pinion shaft 6 on the gear box 15, the outer ring 29 </ b> A of the second ball bearing is press-fitted and fixed to the annular bearing portion 28 of the gear box 15. In addition, the pinion shaft 6 is elastically supported by interposing an O-ring 30 as an annular elastic body between the inner ring 29B of the second ball bearing and the pinion shaft 6. The pinion shaft 6 is aligned by the action of the O-ring 30 and is not easily affected by vibration or the like. As described above, the pinion shaft 6 is elastically supported by the second ball bearing 29 and the O-ring 30, thereby reducing the operating resistance (rotational resistance) of the pinion shaft 6 and reducing the rattle noise caused by the clearance between the bearings. Can be planned.

  In the present embodiment, with respect to the third ball bearing 37 that rotatably supports the input shaft 5 on the stub case 16, the outer ring 37 </ b> A of the third ball bearing is press-fitted and fixed to the annular bearing portion 36 of the stub case 16. At the same time, the input shaft 5 is elastically supported by interposing an O-ring 39 as an annular elastic body between the inner ring 37B of the third ball bearing and the input shaft 5. The input shaft 5 is aligned by the action of the O-ring 39 and is not easily affected by vibration or the like. As described above, the input shaft 5 is elastically supported by the third ball bearing 37 and the O-ring 39, thereby reducing the operating resistance (rotational resistance) of the input shaft 5 and reducing the rattle noise caused by the clearance between the bearings. Can be planned.

  In the power steering apparatus 1 of the present embodiment, the housing H is configured by the gear case 14, the gear box 15, and the stub case 16, and the pinion portion 11 of the rack shaft 9 and the pinion shaft 6 sandwiched between the gear case 14 and the stub case 16. A cross-sectional shape in a direction (horizontal direction in FIG. 2) that passes through the gear box 15 in the insertion direction of the pinion shaft 6 (vertical direction in FIG. 2) and is orthogonal to the insertion direction (in the horizontal direction in FIG. 2). Is provided with a pinion shaft accommodating chamber 26 having a substantially oval shape. Therefore, in the second step shown in FIG. 2, the pinion shaft 6 is disposed so as to be offset toward one end in the major axis direction of the pinion shaft accommodating chamber 26 having a substantially elliptical cross section, and the offset arrangement state thereof. The assembly procedure is adopted in which the rack shaft 9 is inserted into the pinion shaft housing chamber 26, the pinion shaft 6 is then positioned at a specified position in the pinion shaft housing chamber 26, and the pinion shaft 6 and the rack shaft 9 are engaged with each other. be able to. Therefore, according to the present embodiment, the pinion shaft 6 and the rack shaft 9 can be assembled smoothly and efficiently even when the dimensions of the gear box 15 are kept relatively small.

  In the present embodiment, the rack shaft 9 is provided with an escape portion 9B at one end of the rack teeth 9A group for temporarily avoiding interference with the pinion shaft 6 during assembly. For this reason, in the above-mentioned offset arrangement state of the pinion shaft 6, not only can the escape portion 9B of the rack shaft 9 face the pinion portion 11 of the pinion shaft 6, but also the gear box 15 maintains the facing state. The operation of adjusting the position and repositioning the pinion shaft 6 and the rack shaft 9 to the specified positions in the pinion shaft housing chamber 26 can be performed very smoothly. Then, after the repositioning of the pinion shaft 6 and the rack shaft 9 is completed, the pinion shaft 6 and the rack shaft 9 can be engaged with each other.

  In the present embodiment, since the power steering device 1 is assembled through the first to fourth steps as described above, the input shaft 5 and the pinion shaft can be obtained without increasing the size of the gear box 15 occupying the middle of the housing H. 6. The parts such as the rack shaft 9 and the speed reduction mechanism 8 can be assembled smoothly and efficiently. In particular, as in this embodiment, the diameter near the upper end portion of the pinion shaft 6 is slightly larger than the diameter of the pinion portion 11 and the diameter dimension of the worm wheel 12 connected to the lower end portion of the pinion shaft 6 is very large. In this case, the usefulness of the present invention is greatly enhanced.

[Example of change]
The position of the O-ring 30 adjacent to the second ball bearing 29 may be changed. That is, the pinion shaft 6 is press-fitted and fixed to the inner ring 29B of the second ball bearing 29, and the outer ring 29A of the second ball bearing 29 is fitted into the bearing portion 28 of the gear box 15 so that the bearings of the outer ring 29A and the bearing are supported. An O-ring 30 may be interposed between the part 28.

  The position of the O-ring 39 adjacent to the third ball bearing 37 may be changed. In other words, the input shaft 5 is press-fitted and fixed to the inner ring 37B of the third ball bearing 37, and the outer ring 37A of the third ball bearing 37 is fitted into the bearing receiving part 36 of the stub case 16 so that the bearing is connected to the outer ring 37A. An O-ring 39 may be interposed between the portion 36.

The figure which shows the outline of a power steering apparatus and its peripheral mechanism. FIG. 2 is a longitudinal sectional view of a power steering device corresponding to a cross section in the direction of arrows II-II in FIG. (A) is the perspective view which looked at the gearbox from the upper side, (B) is BB arrow direction sectional drawing of (A). The front view which shows the whole rack axis | shaft. Sectional drawing which shows the 1st process of the assembly procedure of a power steering device. Sectional drawing which shows the 2nd process of the assembly procedure of a power steering device. Sectional drawing which shows the 3rd process of the assembly procedure of a power steering apparatus. Sectional drawing which shows the 4th process of the assembly procedure of a power steering apparatus. The longitudinal cross-sectional view of the conventional power steering apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Power steering apparatus 2 Handle 5 Input shaft 6 Pinion shaft 8 Deceleration mechanism 9 Rack shaft 9A Rack tooth 9B Relief part 11 Pinion part 12 of pinion shaft Warm wheel (a part of reduction mechanism)
13 Worm (part of deceleration mechanism)
14 Gear case (part of housing)
15 Gearbox (part of housing)
16 Stub case (part of housing)
22 Bearing receiving portion 23 First ball bearing 26 Pinion shaft accommodating chamber 28 Bearing receiving portion 29 Second ball bearing 30 O-ring (annular elastic body)
36 Bearing receiving portion 37 Third ball bearing 39 O-ring (annular elastic body)
60 Steered system H Housing M Electric motor (steering assist force generating means)

Claims (3)

A power steering device for transmitting a steering force of a steering wheel to a steered system while adding a steering assist force generated by a steering assist force generating means,
A housing constituted by a plurality of cases and / or boxes;
An input shaft that is rotatably supported by the housing and receives a steering force from the handle;
A pinion shaft rotatably supported by the housing in a state of being coaxially connected to the input shaft;
A speed reduction mechanism for transmitting a steering assist force from the steering assist force generating means to the pinion shaft;
A rack shaft that converts the rotational motion of the pinion shaft into a linear motion and transmits the linear motion to the steered system,
The speed reduction mechanism comprises a worm wheel coupled to the pinion shaft so as to be integrally rotatable, and a worm cooperating with the worm wheel;
The housing has a single gear case that supports both the worm and the worm wheel;
The pinion shaft is configured such that a part of the pinion shaft is press-fitted and fixed to the inner ring of the first ball bearing and the outer ring of the first ball bearing is press-fitted and fixed to the annular bearing portion of the gear case. A power steering device, wherein the power steering device is supported by the gear case via a ball bearing. The housing has a gear box that is adjacent to the gear case and that houses the rack shaft and the pinion portion of the pinion shaft that meshes with the rack shaft;
The pinion shaft is rotatably supported by the gear box via a second ball bearing, and one of the outer ring and the inner ring of the second ball bearing is an annular bearing of the gear box. And the other one of the outer ring and the inner ring of the second ball bearing is connected to the ring bearing part of the gear box or the pinion shaft via an elastic body. The power steering apparatus according to claim 1, wherein the power steering apparatus is elastically connected to a part. The housing has a stub case adjacent to the gear box and accommodating the input shaft;
The input shaft is rotatably supported by the stub case via a third ball bearing, and one of an outer ring and an inner ring of the third ball bearing is an annular bearing of the stub case. And the other one of the outer ring and the inner ring of the third ball bearing is fixed to the part of the stub case or the input shaft via the elastic body. The power steering apparatus according to claim 2, wherein the power steering apparatus is elastically connected to a part.

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