JP5557006B2 - Manufacturing method of electric power steering apparatus - Google Patents

Description

  The present invention relates to a method for manufacturing an electric power steering apparatus.

The electric power steering apparatus includes a steering shaft coupled to a steering member, and a torque sensor that detects a steering torque transmitted through the steering shaft. The control device controls the electric motor based on the detected steering torque, so that a steering assist force is applied to the steering mechanism.
The steering shaft is divided into an input shaft continuous with the steering member and an output shaft continuous with the steering mechanism. The input shaft and the output shaft are connected to each other on the same axis via a torsion bar. When steering torque is input to the input shaft, the torsion bar is elastically torsionally deformed so that the input shaft and the output shaft rotate relative to each other. The torque sensor detects a steering torque based on a relative rotational displacement amount between the input shaft and the output shaft via the torsion bar. The outer periphery of one end of the input shaft is supported by a connecting hole of the output shaft via a winding bush wound in a cylindrical shape. This winding bush is press-fitted into the connecting hole of the output shaft.

  Moreover, the technique of patent document 1 is known as a technique which press-fits a bush.

JP 2002-321125 A

By the way, when the above-described winding bush of the electric power steering apparatus is press-fitted into the connecting hole of the output shaft, the circumferential end of the winding bush may enter radially inward and be deformed into a protrusion shape. As a result, a part of the inner diameter of the wound bush after press-fitting is too small, the roundness is deteriorated, and the defect rate at the time of manufacture is increased. As a result, the manufacturing cost increases.
Therefore, an object of the present invention is to provide a method for manufacturing an electric power steering apparatus that can reduce a defective rate during manufacturing.

  In order to achieve the above object, the inventor of the present application has made extensive studies and as a result, the following knowledge has been obtained as a cause of the circumferential end of the wound bush being deformed into a protruding shape during press-fitting. That is, when the winding bush is press-fitted, the insertion shaft of the press-fitting jig is inserted into the inner periphery of the winding bush. Since the outer diameter of the insertion shaft was made sufficiently smaller than the inner diameter of the wound bush after press-fitting, the above-described protrusion-shaped deformation could not be regulated.

The present invention relates to a torsion bar that passes through a first shaft (17), a second shaft (18), the first shaft and the second shaft, and coaxially connects the first shaft and the second shaft. (19), and one end (171) of the first shaft is supported by the connecting hole (181) of the second shaft through a cylindrically wound bush (35). It is a manufacturing method of a steering device (1). This manufacturing method uses a press-fitting jig (40) including an insertion shaft (41) inserted into the winding bush and a pressing portion (42) that presses an axial end (353) of the winding bush. A step of pressing the winding bush into the connection hole of the second shaft; and a step of inserting the one end of the first shaft into the winding bush after removing the pressing jig. In the press-fitting step, the insertion shaft is configured such that the circumferential end (354) of the winding bush press-fitted into the connection hole of the second shaft is prevented from entering inward by the insertion shaft. The outer diameter (L1) is larger than the inner diameter (L41) of the wound bush press-fitted into the connection hole when the inner diameter (L3) of the connection hole is the lower limit (L31) within the tolerance range, and in which characterized that you have been smaller than the inner diameter (L42) of said winding bush which is pressed into the connecting hole when the upper limit of the inner diameter of the connecting hole is within the tolerance range (L32) .

In the present invention, the insertion shaft of the press-fitting jig can suppress the circumferential end of the winding bush from being deformed in a protruding shape inwardly in the radial direction of the winding bush during press-fitting. As a result, the defective rate during manufacturing can be reduced. As a result, the manufacturing cost can be reduced .
Further, the circumferential ends of the winding the pressure Nyutoki bush is deformed protruding inward is likely to occur to the extent that the inner diameter of the connecting hole is close to the lower limit value within the tolerance range. In the present invention, since the outer diameter of the insertion shaft is made larger than the inner diameter of the winding bush press-fitted into the connection hole at the above-mentioned lower limit value at which protrusion-like deformation is likely to occur, the circumferential end of the winding bush during press-fitting Can be reliably prevented from deforming inwardly into a protruding shape. As a result, the defect rate at the time of manufacturing can be further reduced, and the manufacturing cost can be further reduced.

  In addition, although the alphanumeric characters in the parentheses indicate reference signs of corresponding components in the embodiments described later, the scope of the claims is not limited by these reference signs.

1 is a schematic diagram of a schematic configuration of an electric power steering apparatus to which a manufacturing method according to an embodiment of the present invention is applied. FIG. 2 is a cross-sectional view of the output shaft, worm wheel, and the like of FIG. 1. It is sectional drawing, such as an output shaft, a winding bush, a press-fit jig | tool, when press-fitting a winding bush in the connection hole of an output shaft. FIG. 4A is a cross-sectional view of the output shaft, the winding bush and the press-fitting jig when the winding bush mounted on the press-fitting jig is press-fitted into the connecting hole of the output shaft, and FIG. It is sectional drawing of the IVb-IVb cross section shown to Fig.4 (a). It is sectional drawing of an output shaft, a winding bush, an input shaft, etc. when inserting an input shaft in the inner periphery of the winding bush press-fit in the connection hole of the output shaft. It is a schematic diagram which shows the dimensional relationship of the connection hole of an output shaft, a winding bush, and a press-fitting jig. It is a graph which shows the measurement result of the internal diameter of the winding bush after press-fit, and variation range A1, A2 of the circumscribed circle of the inner periphery of the wound bush after press-fit and the diameter of the inscribed circle in the intermediate for production of the group according to the comparative example And the circumscribed circle on the inner circumference of the wound bush and the variation range B1 and B2 of the diameter of the inscribed circle after press-fitting in the production intermediates of the groups according to Test Examples 1 and 2.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic diagram of a schematic configuration of an electric power steering apparatus (EPS) to which a manufacturing method according to an embodiment of the present invention is applied. Referring to FIG. 1, an electric power steering apparatus 1 includes a steering shaft 3 connected to a steering member 2 such as a steering wheel, and an intermediate shaft 5 connected to the steering shaft 3 via a first universal joint 4. And a pinion shaft 7 connected to the intermediate shaft 5 via a second universal joint 6 and a rack 9 meshing with a pinion 8 provided in the vicinity of the end of the pinion shaft 7 and extending in the left-right direction of the automobile. It has a rack shaft 10 as a turning shaft.

  The pinion shaft 7 and the rack shaft 10 constitute a steering mechanism 11 including a rack and pinion mechanism. The rack shaft 10 is supported in a rack housing 13 fixed to a vehicle body (not shown) so as to be linearly reciprocable via a plurality of bearings (not shown). A pair of tie rods 14 are coupled to the rack shaft 10. Each tie rod 14 is connected to a corresponding steered wheel 16 via a corresponding knuckle arm.

When the steering member 2 is operated and the steering shaft 3 is rotated, this rotation is converted by the pinion 8 and the rack 9 into a linear motion of the rack shaft 10 in the left-right direction of the automobile. Thereby, the turning of the steered wheels 16 is achieved.
The steering shaft 3 is divided into an input shaft 17 as a first axis that is continuous with the steering member 2 and an output shaft 18 as a second axis that is continuous with the pinion shaft 7. The input shaft 17 and the output shaft 18 are connected to each other on the same axis via a torsion bar 19. When steering torque is input to the input shaft 17, the torsion bar 19 is elastically torsionally deformed, whereby the input shaft 17 and the output shaft 18 are rotated relative to each other.

  A torque sensor 20 that detects a steering torque based on the amount of relative rotational displacement between the input shaft 17 and the output shaft 18 via the torsion bar 19 is provided. A vehicle speed sensor 21 for detecting the vehicle speed is also provided. An ECU (Electronic Control Unit) 22 is provided as a control device. Further, an electric motor 23 as an actuator for generating a steering force (steering assist force in the present embodiment) and a speed reducer 24 that decelerates the output rotation of the electric motor 23 are provided.

  Detection signals from the torque sensor 20 and the vehicle speed sensor 21 are input to the ECU 22. The ECU 22 controls the steering assisting electric motor 23 based on the torque detection result, the vehicle speed detection result, and the like. The output rotation of the electric motor 23 is decelerated via the speed reducer 24, transmitted to the pinion shaft 7, and converted into a linear motion of the rack shaft 10, thereby assisting in steering.

The speed reducer 24 includes a worm shaft 26 as a drive gear that is rotationally driven by the electric motor 23, and a worm wheel 27 as a driven gear that meshes with the worm shaft 26. The worm wheel 27 is coupled to the output shaft 18 of the steering shaft 3 so as to be able to rotate together. For example, the worm wheel 27 is press-fitted into the outer periphery of the output shaft 18.
FIG. 2 is a cross-sectional view of the output shaft 18 and the worm wheel 27 shown in FIG. 1 and 2, the electric power steering apparatus 1 includes a steering column 28 that rotatably supports the steering shaft 3. For example, the steering shaft 3 is attached obliquely with respect to the front-rear direction of the vehicle body so that the steering member 2 faces upward.

In addition, the electric power steering apparatus 1 includes a first bearing (not shown), a second bearing (not shown), a third bearing 33, and a fourth bearing for rotatably supporting the steering shaft 3. 34 and a winding bush 35 as a fifth bearing.
The upper end portion of the steering column 28 with respect to the axial direction of the steering shaft 3 holds the first bearing, and supports the upper portion in the axial direction of the input shaft 17 via the first bearing so as to be rotatable. The first bearing is a ball bearing as a rolling bearing.

An intermediate portion of the steering column 28 with respect to the axial direction of the steering shaft 3 holds a second bearing (not shown), and the lower portion in the axial direction of the input shaft 17 can be rotated via the second bearing. I support it. The second bearing is a ball bearing as a rolling bearing.
The lower part of the steering column 28 with respect to the axial direction of the steering shaft 3 holds a third bearing 33 and a fourth bearing 34, and the output shaft 18 is connected via the third bearing 33 and the fourth bearing 34. It is rotatably supported. Each of the third bearing 33 and the fourth bearing 34 is a ball bearing as a rolling bearing. The inner rings of the third bearing 33 and the fourth bearing 34 are, for example, press-fitted into the outer periphery of the output shaft 18.

  As described above, the steering shaft 3 passes through the input shaft 17 as the first shaft, the output shaft 18 as the second shaft, the input shaft 17 and the output shaft 18, and the input shaft 17 and the output shaft 18 are coaxial. And a torsion bar 19 connected to the top. One end 171 of the input shaft 17 is supported by the connecting hole 181 of the output shaft 18 via a winding bush 35 wound in a cylindrical shape.

The connection hole 181 of the output shaft 18 is disposed at an intermediate portion of the output shaft 18 with respect to the axial direction of the steering shaft 3. The inner periphery of the connecting hole 181 forms a cylindrical press-fitting surface. The outer periphery 351 of the winding bush 35 is press-fitted and fixed to the press-fitting surface.
One end 171 of the input shaft 17 is disposed at the lower end portion of the input shaft 17 with respect to the axial direction of the steering shaft 3. The outer periphery of the one end 171 has a fitting surface having a cylindrical shape. This fitting surface is fitted to the inner periphery 352 of the winding bush 35. The outer diameter of the fitting surface is less than the inner diameter of the winding bush 35 press-fitted into the connection hole 181 so that a predetermined amount of clearance can be secured between the inner diameter 352 of the winding bush 35 press-fitted into the connection hole 181. Is set to a value.

The winding bush 35 is interposed between the input shaft 17 and the output shaft 18. The winding bush 35 rotatably supports one end 171 of the input shaft 17. The winding bush 35 is a sliding bearing.
The inner periphery 352 of the winding bush 35 is covered with a fluororesin 37. That is, the winding bush 35 includes a metal cylinder member 38 and a fluororesin 37 that covers the inner periphery of the cylinder member 38. The fluororesin 37 is, for example, polytetrafluoroethylene (PTFE), and forms an inner periphery 352 of the wound bush 35. The fluororesin 37 is elastically deformable and has an effect of reducing friction when sliding relative to the one end 171 of the counterpart input shaft 17. The cylindrical member 38 of the winding bush 35 is formed by winding a metal plate material into a cylindrical shape and abutting a pair of opposite edges of the plate material.

  FIG. 3 is a cross-sectional view of the output shaft 18, the winding bush 35, the press-fitting jig 40 and the like when the winding bush 35 is press-fitted into the output shaft 18. FIG. 4A is a cross-sectional view of the output shaft 18, the winding bush 35, and the press-fitting jig 40 when the winding bush 35 attached to the press-fitting jig 40 is press-fitted into the connection hole 181 of the output shaft 18. FIG. 4B is a cross-sectional view of the IVb-IVb cross section shown in FIG. FIG. 5 is a cross-sectional view of the input shaft 17, the output shaft 18, the winding bush 35, and the like when the input shaft 17 is inserted into the inner periphery 352 of the winding bush 35 press-fitted into the connection hole 181 of the output shaft 18. . FIG. 6 is a schematic diagram exaggeratingly showing the dimensional relationship among the connecting hole 181, the winding bush 35, and the press-fitting jig 40 of the output shaft 18.

  The method for manufacturing the electric power steering apparatus 1 according to the present embodiment includes a step (see FIG. 3) of press-fitting the winding bush 35 into the connection hole 181 of the output shaft 18 using a press-fitting jig 40 described later, and the press-fitting jig 40. And a step of inserting one end 171 of the input shaft 17 into the winding bush 35 after the removal (see FIG. 5). Thereafter, the torsion bar 19 is connected to the input shaft 17 and the output shaft 18 and assembled to the steering column 28 (see FIG. 2).

  Referring to FIG. 3, the press-fitting jig 40 used in the press-fitting step has an insertion shaft 41 inserted into the winding bush 35 and a pressing portion 42 that presses the axial end 353 of the winding bush 35. doing. The insertion shaft 41 has a cylindrical shape. The pressing part 42 is configured by an annular step part. The annular step portion extends outward in the radial direction of the insertion shaft 41 from the end of the insertion shaft 41 in the axial direction of the insertion shaft 41. The press-fitting jig 40 is positioned with respect to the receiving jig 43 and is supported by a guide member (not shown) so as to be movable in the axial direction of the insertion shaft 41 (corresponding to the press-fitting direction of the winding bush 35). And is urged by an urging member (not shown) in the axial direction of the insertion shaft 41.

With reference to FIGS. 3 and 5, for example, the outer diameter L1 of the insertion shaft 41 is equal to or lower than the lower limit value within the tolerance range of the outer diameter L2 of the fitting surface of the one end 171 of the input shaft 171. It has been enlarged. More preferably, it is equal to or larger than the upper limit value within the tolerance range of the outer diameter L2 of the fitting surface of the one end 171 of the input shaft.
Referring to FIG. 3, in the press-fitting process, output shaft 18 to which third bearing 33 and worm wheel 27 are fixed is held by receiving jig 43. The winding bush 35 held by the insertion shaft 41 of the press-fitting jig 40 is press-fitted into the connecting hole 181 of the output shaft 18 held by the receiving jig 43 (see FIG. 4A).

Referring to FIGS. 4A and 4B, in the press-fitting step, the circumferential end 354 of the winding bush 35 press-fitted into the connecting hole 181 of the output shaft 18 may enter the inner side. 41 is suppressed.
As described above, in this embodiment, the insertion shaft 41 of the press-fitting jig 40 can suppress the circumferential end 354 of the winding bush 35 from being deformed in a projecting shape inward in the radial direction of the winding bush 35 during press-fitting. . As a result, the roundness of the inner periphery 352 of the wound bush 35 after press-fitting can be improved, and the defective rate during manufacturing can be reduced. As a result, the manufacturing cost can be reduced.

Moreover, since it can suppress that the circumferential direction edge part 354 of the winding bush 35 deform | transforms inwardly at the time of press-fitting, the tolerance of both the internal diameter of the connection hole 181 of the output shaft 18 and the thickness of the winding bush 35 is made into the present value While maintaining the above, it is possible to reduce the defective rate of roundness during manufacturing.
With reference to FIG. 1 and FIG. 4B, it is possible to prevent the circumferential end portion 354 of the winding bush 35 from being deformed inwardly during press-fitting, so that the input shaft 17 and the output shaft in the electric power steering apparatus 1 can be suppressed. It is suppressed that the friction when 18 and the relative rotation are increased. As a result, a decrease in steering torque detection accuracy can be suppressed. As a result, a decrease in steering feeling can be suppressed.

  Referring to FIGS. 2 and 4 (b), more specifically, the circumferential end 354 of the winding bush 35 can be prevented from being deformed inwardly during press-fitting, so that the connection hole 181 of the output shaft 18 can be prevented. It is also possible to reduce the upper limit value and the median value of the tolerance range of the inner diameter. As a result, the gap amount between the inner periphery 352 of the wound bush 35 after press-fitting and the outer periphery of the one end 171 of the input shaft 17 is set to a value within an appropriate range so that relative rotation can be smoothly performed and rattling does not occur. It is also possible to do.

As a result, in the electric power steering apparatus 1, generation | occurrence | production of abnormal noise can be suppressed. In addition, there is no need to use a part (for example, a backup O-ring disposed in a circumferential groove provided in the inner periphery of the connection hole) for suppressing the generation of abnormal noise. Therefore, the defective rate of abnormal noise generation in the electric power steering apparatus 1 can be reduced, which contributes to a reduction in manufacturing cost.
In this way, by suppressing the circumferential end portion 354 of the winding bush 35 from being deformed inwardly during press-fitting, both the above-described roundness defect rate and abnormal noise occurrence defect rate are reduced. Is possible.

The outer diameter L1 of the insertion shaft 41 may be set according to the dimension of the one end 171 of the input shaft 17 as described above, but is more preferably set as follows.
Referring to FIG. 6, the outer diameter L1 of the insertion shaft 41 is equal to the inner diameter L4 of the winding bush 35 press-fitted into the connection hole 181 when the inner diameter L3 of the connection hole 181 is the lower limit L31 within the tolerance range. It is larger than the value L41 and smaller than the value L42 of the inner diameter L4 of the winding bush 35 press-fitted into the connecting hole 181 when the inner diameter L3 of the connecting hole 181 is the upper limit value L32 within the tolerance range ( L42 ≧ L1 ≧ L41).

  In FIG. 6, the connection hole 181 when the inner diameter L3 of the connection hole 181 is the upper limit value L32 within the tolerance range and the wound bush 35 press-fitted into the connection hole 181 are shown by solid lines. The connecting hole 181 and the winding bush 35 press-fitted into the connecting hole 181 when the inner diameter L3 of the connecting hole 181 is the lower limit L31 within the tolerance range are shown by two-dot chain lines.

Here, when the inner diameter L3 of the connecting hole 181 is the lower limit L31 (for example, 13.970 mm) within the tolerance range, the value L41 of the inner diameter L4 of the winding bush 35 press-fitted into the connecting hole 181 is corresponding to the lower limit value tolerance range of the inner diameter of the winding bush 35 of the. The above-described value L41 is, for example, a value obtained by subtracting a value twice the average value (for example, 0.978 mm before press-fitting) of the thickness L5 of the wound bush 35 from the above-described lower limit value L31 (for example, 12. 014 mm). When obtaining this value L41, the upper limit value of the tolerance range of the thickness L5 may be used instead of the average value of the thickness L5.

When the inner diameter L3 of the connecting hole 181 is the upper limit L32 (for example, 14.018 mm) within the tolerance range, the value L42 of the inner diameter L4 of the winding bush 35 press-fitted into the connecting hole 181 is the wound bush after press-fitting. corresponding to the upper limit value of the tolerance range of the inner diameter of 35. The above-described value L42 is, for example, a value obtained by subtracting a value twice the average value (for example, 0.978 mm before press-fitting) of the thickness L5 of the wound bush 35 from the above-described upper limit value L32 (for example, 12.2. 062 mm). When obtaining this value L42, the lower limit value of the tolerance range of the thickness L5 may be used instead of the average value of the thickness L5.

  With reference to FIG. 6 and FIG. 4 (b), since the tolerance of the thickness L5 of the wound bush 35 between individuals is usually small, the thickness L5 is set when setting the outer diameter L1 of the insertion shaft 41 as described above. There is no problem even if the average value of is used. Further, even when the tolerance of the thickness L5 of the winding bush 35 between the individual is large, when the winding bush 35 includes the fluororesin 37, the thickness of the winding bush 35 is reduced due to elastic deformation of the fluororesin 37. There is no problem because the tolerance is absorbed.

  The circumferential end 354 of the winding bush 35 is deformed inwardly at the time of press-fitting as the inner diameter L3 of the connecting hole 181 approaches the lower limit L31 within the tolerance range. Thus, the outer diameter L1 of the insertion shaft 41 is larger than the value L41 of the inner diameter L4 of the winding bush 35 press-fitted into the connecting hole 181 at the above-described lower limit value L31 where the protrusion-like deformation is likely to occur (L1 ≧ L41). Therefore, it is possible to more reliably prevent the circumferential end portion 354 of the winding bushing 35 from being deformed inwardly during the press-fitting. As a result, the defect rate at the time of manufacturing can be further reduced, and the manufacturing cost can be further reduced.

  On the other hand, the circumferential end 354 of the winding bush 35 is deformed inwardly at the time of press-fitting, so that the inner diameter L3 of the connecting hole 181 is less likely to become closer to the upper limit L32 within the tolerance range. On the other hand, when the outer diameter L1 of the insertion shaft 41 is larger than the value L42 of the inner diameter L4 of the winding bush 35 press-fitted into the connection hole 181 at the upper limit value L32 (L1> L42), it is press-fitted into the connection hole 181. The outer periphery of the insertion shaft 41 is press-fitted into the inner periphery 352 of the wound bush 35. As a result, it is difficult to remove the insertion shaft 41 from the winding bush 35 press-fitted into the connection hole 181. Therefore, the outer diameter L1 of the insertion shaft 41 is made smaller than the value L42 of the inner diameter L4 of the winding bush 35 press-fitted into the coupling hole 181 at the upper limit value L32 (L1 ≦ L42), The insertion shaft 41 of the press-fitting jig 40 can be easily removed. As a result, the manufacturing cost can be further reduced.

The outer diameter L1 of the insertion shaft 41 of the press-fitting jig 40 is determined according to the value L42 and the value L41 of the inner diameter L4 of the winding bush 35 based on the upper limit value L32 and the lower limit value L31 within the tolerance range of the connecting hole 181. In some cases, the insertion shaft 41 of the press-fitting jig 40 may be tightly fitted to the inner periphery 352 of the winding bush 35 press-fitted into the fitting hole 181.
In the present embodiment, the fluororesin 37 coated on the inner periphery 352 of the winding bush 35 is elastically deformable and has low friction characteristics, so that the insertion shaft 41 can be easily pulled out from the winding bush 35 after press-fitting. As a result, it contributes to a reduction in manufacturing cost.

Further, the low friction characteristic of the fluororesin 37 makes it easy to insert the insertion shaft 41 into the winding bush 35 during assembly.
Referring to FIG. 3, since fluororesin 37 can be elastically deformed, a dimensional difference between outer diameter L6 of winding bush 35 held by insertion shaft 41 and inner diameter L3 of connecting hole 181 can be absorbed. As a result, the winding bush 35 can be easily press-fitted into the connecting hole 181.

Moreover, the following modifications can be considered about this embodiment. In the following description, the points different from the above-described embodiment will be mainly described. Since other configurations are the same as those in the above-described embodiment, the description thereof is omitted.
For example, a case where the inner periphery 352 of the winding bush 35 is not covered with the fluororesin 37 is also conceivable.

Further, in the above-described embodiment, the example in which the present invention is applied to the so-called column assist type electric power steering apparatus 1 has been described. However, the present invention is not limited to this, and the so-called pinion assist type electric power steering apparatus or the so-called rack assist. The present invention may be applied to an electric power steering device of the type. In addition, various changes can be made within the scope of the matters described in the claims.
[test]
An intermediate for manufacturing an electric power steering apparatus according to Test Examples 1 and 2 corresponding to the manufacturing method of the embodiment of FIG. 3 of the present invention was manufactured. As shown in FIG. 3, the manufacturing intermediate includes an output shaft 18, a worm wheel 27 press-fitted on the outer periphery of the output shaft 18, a third bearing 33 press-fitted on the outer periphery of the output shaft 18, And a winding bush 35 press-fitted into the connecting hole 181 of the output shaft 18. In the production intermediate, the inner diameter of the winding bush 35 press-fitted into the connection hole 181 of the output shaft 18 was measured.

Similarly, an intermediate for manufacturing an electric power steering apparatus according to a comparative example corresponding to a conventional manufacturing method was manufactured, and the inner diameter of the press-fitted wound bush was measured in the intermediate for manufacturing.
These measurement results are compared with each other to explain that the roundness of the wound bush after press-fitting of the production intermediate according to Test Examples 1 and 2 is better than that of the production intermediate according to the comparative example.
In addition, the tolerance range of each component which comprises these manufacturing intermediates was made the same mutually between the manufacturing intermediate which concerns on Test Examples 1 and 2 and the manufacturing intermediate which concerns on a comparative example. Further, the specific dimensions of the connecting hole of the output shaft and the winding bush of these production intermediates are as described in the above embodiment.
<Test Examples 1 and 2>
In the manufacturing method of Test Example 1, the outer diameter of the insertion shaft of the press-fitting jig is 12.033 mm. In the manufacturing method of Test Example 2, the outer diameter of the insertion shaft of the press-fitting jig is 12.044 mm.

A plurality of (for example, 18) intermediates for production according to Test Examples 1 and 2 were produced. That is, the winding bush is press-fitted into the connecting hole of the output shaft in which the worm wheel and the third bearing are assembled using the press-fitting jigs of the respective production methods of Test Examples 1 and 2 to obtain a production intermediate. It was.
About the winding bush of each intermediate for production of the group according to Test Examples 1 and 2, the inner diameter of each winding bush after press-fitting was measured as follows. That is, the contour shape of the inner periphery of the wound bush press-fitted into the connecting hole is measured, the diameter of the circumscribed circle of the measured contour shape (corresponding to the maximum value of the inner diameter of the wound bush in the individual) and the inscribed circle. (Corresponding to the minimum value of the inner diameter of the wound bush). Note that half the difference between the diameter of the circumscribed circle and the diameter of the inscribed circle corresponds to the roundness.

Upper limit value P11 and lower limit value P12 of the diameter variation range B1 of the circumscribed circle of the inner circumference of the wound bush in the group according to Test Examples 1 and 2, and the diameter of the inscribed circle of the inner circumference of the wound bush in the group The upper limit value P21 and the lower limit value P22 of the variation range B2 are shown in the right half of the graph of FIG. In addition, since there was no significant difference in the measurement results of the production intermediates in the groups according to Test Examples 1 and 2, the measurement results were illustrated without distinguishing Test Examples 1 and 2.
<Comparative example>
The outer diameter of the insertion shaft of the conventional press-fitting jig used in the manufacturing method of the comparative example is 11.970 mm. A plurality of (for example, 30) intermediates for production according to the comparative example were produced.

For the wound bushes into which the intermediates for production in the group according to the comparative example are press-fitted, the upper limit value Q11 and the lower limit value of the variation range A1 of the diameter of the circumscribed circle on the inner circumference in the group, as in Test Examples 1 and 2 Q12 and the upper limit value Q21 and the lower limit value Q22 of the variation range A2 of the diameter of the inscribed circle on the inner circumference within the group were obtained and shown in the left half of the graph of FIG.
<Measurement result of the diameter of the inner circumference of the winding bush of the intermediate for production in the groups according to Test Examples 1 and 2>
Referring to FIG. 7, in the groups according to Test Examples 1 and 2, the diameter of the circumscribed circle on the inner periphery of the winding bush of the production intermediate has an upper limit value P11 (12.052 mm) and a lower limit value P12 (12.041 mm). ). Further, in the group, the diameter of the inscribed circle on the inner periphery of the winding bush of the production intermediate varies between the upper limit value P21 (12.03 mm) and the lower limit value P22 (12.019 mm).
<Measurement result of the diameter of the inner circumference of the winding bush of the intermediate for production in the group according to the comparative example>
In the group according to the comparative example, the diameter of the circumscribed circle on the inner periphery of the winding bush of the production intermediate varies between the upper limit value Q11 (12.005 mm) and the lower limit value Q12 (12.042 mm). Further, in the group, the diameter of the inscribed circle on the inner periphery of the winding bush of the production intermediate varies between the upper limit value Q21 (12.026 mm) and the lower limit value Q22 (12.010 mm).
<Evaluation>
In the production intermediate of the group according to Test Examples 1 and 2, the lower limit P22 of the diameter variation range B2 of the inscribed circle on the inner circumference of the press-fitted wound bush is the production intermediate of the group according to the comparative example. It is larger than the corresponding lower limit value Q22 of the measurement result (P22> Q22). In other words, in the production intermediates of the groups according to Test Examples 1 and 2, even if the deformation in which the circumferential end of the press-fitted winding bush protrudes inward does not occur or has occurred, the protrusion It can be said that the amount is getting smaller.

  Further, the upper limit value P11 of the diameter variation range B1 of the circumscribed circle of the inner periphery of the wound bush after press-fitting in the group production intermediate according to Test Examples 1 and 2 is the same as that in the group production intermediate according to the comparative example. It is smaller than the corresponding upper limit value Q11 of the measurement result (P11 <Q11). From this, for example, when the inner diameter of the coupling hole of the output shaft is the upper limit value of the tolerance range, there is no deformation in which the circumferential end of the press-fitted winding bush protrudes inward, and Test Example 1, The insertion shaft of the press-fitting jig according to No. 2 expands the portion where the radial dimension of the inner circumference of the winding bush is the narrowest (the radial dimension of this part corresponds to the diameter of the inscribed circle of the inner circumference). With this, it is considered that the diameter of the inner circumference of the wound bush becomes the largest (the radial dimension of this portion corresponds to the diameter of the circumscribed circle on the inner circumference).

Therefore, in the production intermediates of the groups according to Test Examples 1 and 2, the roundness of the inner periphery of the wound bush after press-fitting is higher on average than the production intermediates of the group according to the comparative example. It can be said that.
Therefore, it was confirmed that the production of the embodiment of the present invention corresponding to Test Examples 1 and 2 can suppress the occurrence of poor roundness of the wound bush after press-fitting.

DESCRIPTION OF SYMBOLS 1 ... Electric power steering apparatus, 17 ... Input shaft (1st axis), 18 ... Output shaft (2nd axis), 19 ... Torsion bar, 35 ... Winding bush, 37 ... Fluororesin, 41 ... Insertion shaft, 42 ... Press 40, press fitting jig, 171 ... one end of the first shaft, 181 ... coupling hole, 352 ... inner periphery of the winding bush, 353 ... axial end of the winding bush, 354 ... circumferential end of the winding bush, L1 ... outer diameter of insertion shaft, L3 ... inner diameter of connecting hole, L4 ... inner diameter of winding bush, L31 ... lower limit value within tolerance range of inner diameter of connecting hole, L32 ... upper limit value within tolerance range of inner diameter of connecting hole.

Claims (1)

A first shaft; a second shaft; and a torsion bar that passes through the first shaft and the second shaft and coaxially connects the first shaft and the second shaft; One end is a manufacturing method of an electric power steering device supported by a connecting hole of the second shaft through a winding bush wound in a cylindrical shape,
Press-fitting the winding bush into the connection hole of the second shaft using a press-fitting jig including an insertion shaft inserted into the winding bush and a pressing portion that presses an axial end of the winding bush; ,
After removing the press-fitting jig, inserting the one end of the first shaft into the winding bush,
In the press-fitting step, the outer diameter of the insertion shaft is such that the circumferential end of the wound bush press-fitted into the connection hole of the second shaft is prevented from entering inward by the insertion shaft. The inner diameter of the connecting hole is larger than the inner diameter of the wound bush press-fitted into the connecting hole when the inner diameter is the lower limit value within the tolerance range, and the inner diameter of the connecting hole is the upper limit value within the tolerance range. method of manufacturing an electric power steering apparatus characterized that you have been smaller than the inner diameter of the winding bush which is pressed into the connecting hole when there.

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