JP5801170B2 - Worm gear device manufacturing method - Google Patents

Description

  The present invention relates to a method of manufacturing a worm gear device including a worm shaft and a rolling bearing for rotatably supporting the worm shaft.

  2. Description of the Related Art Conventionally, electric power steering devices that assist a driver's steering by transmitting a rotational driving force of an electric motor to a pinion shaft have been widely used.

  This type of electric power steering device includes a reduction mechanism (worm gear device) that reduces the rotational driving force of the electric motor and transmits it to the pinion shaft.

  As shown in FIG. 11, the worm gear device 300 is generally provided so as to be integrally rotatable with a worm shaft 302 that rotates by driving of an electric motor and a pinion shaft 304, and meshes with a helical tooth 306 of the worm shaft 302. A worm wheel 310 having teeth 308 and a rolling bearing 314 that rotatably supports the worm shaft 302 in a state of being provided in the gear housing 312.

  In the worm gear device 300 configured as described above, the rolling bearing 314 is mounted on the worm shaft 302 in a preassembled state (with the rolling element 320 mounted between the inner ring 316 and the outer ring 318). Lightly press-fitted into the portion 322.

  However, in this case, since the coupling force between the inner ring 316 of the rolling bearing 314 and the mounting portion 322 is relatively weak, the rotational driving force of the electric motor is transmitted to the pinion shaft 304 via the worm shaft 302 and the worm wheel 310. At this time, a reaction force along the axial direction of the worm shaft 302 from the worm wheel 310 acts on the worm shaft 302, and the rolling bearing 314 is displaced relative to the worm shaft 302 along the axial direction. Sometimes. Then, the rolling bearing 314 may come off from the mounting portion 322 of the worm shaft 302.

  As a method for eliminating such inconvenience, there is a method of increasing the coupling force between the rolling bearing 314 and the mounting portion 322 by setting a large press-fitting allowance between the rolling bearing 314 and the mounting portion 322. It is done.

  However, in this case, since the mounting portion 322 and the rolling bearing 314 have appropriate dimensional tolerances, the inner ring 316 of the rolling bearing 314 is excessively radially outward in a state where the rolling bearing 314 is press-fitted into the mounting portion 322. May be spread. Then, there is no gap between the rolling element 320 and the outer ring 318 (inner ring 316) in the radial direction of the rolling bearing 314, and the rolling element 320 contacts both the inner ring 316 and the outer ring 318, so that the preload of the rolling bearing 314 is large. Too much. As a result, the frictional force generated in the rolling element 320 increases, and the life of the rolling bearing 314 (worm gear device 300) is shortened.

  As another method, as shown in FIG. 12, for example, an annular groove 324 is formed at the end of the mounting portion 322 of the worm shaft 302, and the rolling bearing 314 is lightly press-fitted into the mounting portion 322. A method of preventing the rolling bearing 314 from being relatively displaced along the axial direction with respect to the worm shaft 302 by placing a retaining ring 326 in the groove 324 and caulking is cited. However, in this case, although it is possible to suppress a decrease in the life of the rolling bearing 314, the number of parts and the number of manufacturing steps of the worm gear device 300 are increased.

  In order to reduce the number of parts of the worm gear device, raceway grooves along the circumferential direction are formed at both ends of the worm shaft so that the rolling elements can roll freely between the outer ring press-fitted into the casing and the raceway grooves. A technical idea is known in which the inner ring of the rolling bearing is omitted by interposing it (see, for example, Patent Document 1).

JP 2003-112737 A

  However, in the worm gear device described in Patent Document 1 described above, it is necessary to form a raceway groove on the worm shaft, and the worm shaft becomes a special product, so that the manufacturing cost of the worm gear device increases.

  The present invention has been made in consideration of such problems, and can reduce the life of the worm gear device, increase the number of parts, and increase the manufacturing cost, and the rolling bearing is less than the worm shaft. It is an object of the present invention to provide a method of manufacturing a worm gear device that can suitably prevent relative displacement along the axial direction.

A method of manufacturing a worm gear device according to the present invention is a method of manufacturing a worm gear device including a worm shaft and a rolling bearing for rotatably supporting the worm shaft, wherein an inner ring of the rolling bearing is press-fitted directly into the worm shaft. The dimension of the inner ring acquired in the dimension acquisition process, the dimension acquisition process of acquiring the dimension along the radial direction of the inner ring expanded by press-fitting into the worm shaft, and the dimension of the inner ring acquired in the dimension acquisition process. Based on this, the rolling element and the outer ring are selected so that the distance between the rolling element of the rolling bearing and the outer ring in the radial direction of the inner ring is a predetermined value, and assembled to the inner ring press-fitted into the worm shaft. And an assembly process .

  According to the worm gear device manufacturing method of the present invention, after the press-fitting step of press-fitting the inner ring of the rolling bearing into the worm shaft, the assembly step of assembling the rolling elements and the outer ring to the inner ring is performed. Even if the inner ring is press-fitted into the worm shaft with a large press-fitting allowance between the inner ring and the worm shaft, the rolling elements and the outer ring can be easily assembled to the inner ring according to the degree of diameter expansion of the inner ring. Can be changed. As a result, it is possible to suppress the press-fitted rolling bearing from being displaced relative to the worm shaft in the axial direction, and the preload of the rolling bearing becomes too large (the frictional force generated in the rolling element is reduced). Increase more than necessary). Therefore, the life of the worm gear device is not shortened.

  In the worm gear device manufactured in this way, the coupling force between the inner ring and the worm shaft can be increased, and the retaining ring for preventing the rolling bearing from being displaced along the axial direction with respect to the worm shaft. Therefore, the number of parts does not increase. Further, in the worm gear device, since it is not necessary to form a raceway groove on the worm shaft, an increase in manufacturing cost can be suppressed.

Further , a dimension along the radial direction of the inner ring expanded by press-fitting into the worm shaft is acquired, and the distance between the rolling element of the rolling bearing and the outer ring in the radial direction of the inner ring based on the acquired dimension of the inner ring. Since the rolling element and the outer ring are selected and assembled to the inner ring, the rolling bearing has a predetermined clearance between the rolling element and the outer ring (inner ring) in the radial direction of the rolling bearing. Can be of any size.

  As described above, according to the present invention, since the rolling element and the outer ring are assembled to the inner ring after the inner ring of the rolling bearing is press-fitted into the worm shaft, the life of the worm gear device is reduced, the number of parts is increased, and An increase in manufacturing cost can be suppressed, and the rolling bearing can be suitably prevented from being displaced relative to the worm shaft in the axial direction.

It is a schematic diagram of the electric steering device incorporating the worm gear device manufactured by the manufacturing method according to the present invention. It is sectional drawing along the II-II line of FIG. It is an expanded sectional view of the 1st bearing shown in Drawing 2, and its peripheral part. It is a partially broken perspective view of the 1st bearing shown in FIG. It is a flowchart for demonstrating the manufacturing method of the worm gear apparatus which concerns on one Embodiment of this invention. FIG. 10 is a partially omitted cross-sectional view for explaining a process of press-fitting only the inner ring of the first bearing into the first mounting portion of the worm shaft. FIG. 7A is a partially omitted cross-sectional view for explaining the raceway diameter d3 of the inner ring press-fitted into the first mounting portion, and FIG. 7B is a partially omitted illustration for explaining how to obtain the raceway d4 by the overpin method. FIG. 7C is a partially omitted cross-sectional view for explaining the outer diameter d5 of the inner ring press-fitted into the first mounting portion. It is a perspective view for demonstrating a mode that a some rolling element and an outer ring | wheel are assembled | attached to the inner ring press-fit in the 1st mounting part. It is sectional drawing which shows the state with which the several rolling element and the outer ring | wheel were assembled | attached to the inner ring press-fit in the 1st mounting part. It is a perspective view for demonstrating assembly | attachment of a pair of holder | retainer and a pair of shield member. It is a partially abbreviated sectional view for explaining a configuration of a worm gear device according to the prior art. FIG. 12 is a partially omitted cross-sectional view for explaining an example in which a retaining ring is attached to the worm shaft shown in FIG. 11.

  Hereinafter, preferred embodiments of a method for manufacturing a worm gear device according to the present invention will be described with reference to the accompanying drawings.

  First, an electric power steering device (hereinafter simply referred to as a steering device 12) incorporating a worm gear device 10 manufactured by a method of manufacturing a worm gear device according to an embodiment of the present invention will be described.

  As shown in FIG. 1, the steering device 12 is configured as a so-called pinion assist type steering device, and a steering handle (steering wheel) 14 operated by a driver, and a steering connected to the steering handle 14. A shaft 16, a steering gear mechanism 18 connected to the steering shaft 16, a steering assist unit 20 for assisting the driver's steering, and a pair of left and right steerings connected to the steering gear mechanism 18 Wheels 22L and 22R, a vehicle speed sensor 24, an electronic control unit (ECU) 26, and a battery 28 are provided.

  The steering shaft portion 16 includes a first steering shaft 30 connected to the steering handle 14, an intermediate steering shaft 34 connected to the first steering shaft 30 via a universal joint (universal joint) 32, and the intermediate steering. A second steering shaft 38 is connected to the shaft 34 via a universal joint (universal joint) 36.

  The second steering shaft 38 is rotatably supported by a bearing 42 fixed to the steering column 40. The second steering shaft 38 is provided with a torque sensor 44 that detects a steering torque acting on the second steering shaft 38. A detection signal from the torque sensor 44 is output to the electronic control unit 26. As the torque sensor 44, for example, a magnetostrictive torque sensor is used.

  The steering gear mechanism 18 includes a pinion shaft 46 connected so as to be coaxial with the second steering shaft 38, a pinion gear 48 provided on the tip side of the pinion shaft 46, and a rack gear 50 that meshes with the pinion gear 48. , A pair of left and right tie rods 54L, 54R that connect the rack 52 and each of the steering wheels 22L, 22R, and a gear box 56 that houses the pinion gear 48 and the rack 52. The pinion shaft 46 is rotatably supported by a bearing 58 fixed to the steering column 40 and a bearing 60 fixed to the gear box 56.

  As shown in FIG. 2, the steering assist unit 20 includes a motor unit 62 and a worm gear device 10 for transmitting the rotational driving force of the motor unit 62 to the pinion shaft 46. The motor unit 62 includes a motor case 64, an annular stator 66 disposed in the motor case 64, a rotor 68 disposed in the stator 66, and a support member 70 to which the motor case 64 is attached. Have

  The stator 66 includes a laminated iron core 72, an insulator 74 provided on the laminated iron core 72, and a coil 76 wound around the laminated iron core 72 via the insulator 74. The coil 76 is electrically connected to the electronic control unit 26 (see FIG. 1) via a cable harness 78.

  The rotor 68 is rotatably supported by a bearing 80 fixed to the motor case 64 and a bearing 82 fixed to the support member 70. A plurality of magnets 84 are disposed on the outer peripheral surface of the rotor 68 that faces the stator 66.

  The other end of the motor case 64 is attached to one end of the support member 70 with the O-ring 86 attached. The support member 70 is provided with a rotation speed sensor 88 that detects the rotation speed of the rotor 68 in the vicinity of the bearing 82. The detection signal of the rotation speed sensor 88 is output to the electronic control unit 26 via the cable harness 90. One end of a gear housing 94 (described later) is fastened to the other end of the support member 70 with a plurality of fastening screws (fastening members) 93 with the O-ring 92 attached.

  The worm gear device 10 includes a gear housing 94, a worm wheel 98 having a cored bar portion 96 fixed to the pinion shaft 46 so as to be integrally rotatable, and a tooth 100 of the worm wheel 98. And a first bearing 106 and a second bearing 108 which are provided on the inner wall surface of the gear housing 94 and rotatably support the worm shaft 104.

  The gear housing 94, the steering column 40, and the gear box 56 are integrally configured (see FIG. 1). One end of the worm shaft 104 is serrated to the other end of the rotor 68 with the axis of the worm shaft 104 positioned on the axis of the rotor 68. Thereby, the rotational driving force of the rotor 68 can be smoothly and reliably transmitted to the worm shaft 104.

  The worm shaft 104 includes a first mounting portion 110 having a constant outer diameter formed on one end side of the worm shaft 104, a first flange 112 formed between the first mounting portion 110 and the helical teeth 102, A second flange 114 formed on the other end of the helical tooth 102 and a second mounting portion 116 having a constant outer diameter formed on the other end side of the second flange 114 are included.

  As shown in FIGS. 3 and 4, the first bearing 106 is configured as a rolling bearing, and is arranged between the inner ring 118, the outer ring 120 surrounding the inner ring 118, and the inner ring 118 and the outer ring 120. A plurality of rolling elements 122 provided, a pair of retainers 124 that hold the rolling elements 122 in a state of being spaced apart at equal intervals along the circumferential direction of the inner ring 118, the inner ring 118, and the outer ring 120. And a pair of shield members 126 for preventing foreign matters and the like from being mixed into the space between them.

  The inner ring 118 is press-fitted and fixed to the first mounting portion 110 in a state where the inner ring 118 is in contact with the first flange 112. An arc-shaped raceway groove (rolling surface) 128 is formed on the outer circumferential surface of the inner ring 118 along the circumferential direction, and an arc-shaped raceway groove (rolling surface) 128 is formed on the inner circumferential surface of the outer ring 120 along the circumferential direction. A rolling surface) 130 is formed, and a plurality of rolling elements 122 are arranged in the raceway grooves 128 and 130 so as to be able to roll. The outer ring 120 is fixed to the gear housing 94 by a fixing screw (fixing member) 132. Specifically, the outer ring 120 is fixed to the gear housing 94 by tightening the fixing screw 132 in a state where the other end surface of the outer ring 120 is in contact with a stepped portion 134 formed in the gear housing 94. For example, the fixing screw 132 is screwed into the inner wall surface of the gear housing 94 (tightened), and one end of the fixing screw 132 is tightened to prevent rotation.

  Thus, since the inner ring 118 of the first bearing 106 is press-fitted and fixed to the first mounting portion 110 of the worm shaft 104 and the outer ring 120 is fixed to the gear housing 94 by the fixing screw 132, for example, the rotor 68 Even when the reaction force along the axial direction acts on the worm shaft 104 from the worm wheel 98 when the rotation direction is switched, the worm shaft 104 does not move along the axial direction. Therefore, it is possible to suitably suppress the occurrence of fluctuations in the transmission torque and the generation of impact sound due to the movement of the worm shaft 104. In addition, since there is no gap between the inner ring 118 and the first mounting portion 110, it is possible to prevent the worm shaft 104 from vibrating and generating operating noise.

  The second bearing 108 is configured as a rolling bearing, and is fixed by being lightly press-fitted into the inner ring 136 provided in the second mounting portion 116 and in contact with the second flange 114 and the inner wall surface of the gear housing 94. An outer ring 138, and a plurality of rolling elements 140 disposed between the inner ring 136 and the outer ring 138.

  The electronic control unit 26 calculates a target motor current based on the output signal of the torque sensor 44, the output signal of the rotation speed sensor 88, and the output signal of the vehicle speed sensor 24, and uses the target motor current to the coil 76 of the motor unit 62. A drive voltage (PWM signal) for energizing is applied to the motor unit 62.

  Further, the electronic control unit 26 detects the actual motor current that is actually energized in the coil 76 by a current sensor (not shown) provided in the electronic control unit 26, and the actual motor current detected by the current sensor. Power is generated in the motor unit 62 by performing PI control so that the target motor current matches. The battery 28 supplies power to the electronic control unit 26.

  In the steering device 12 configured as described above, when the electronic control unit 26 drives and controls the motor unit 62 to rotationally drive the rotor 68, the rotational driving force of the rotor 68 is transmitted via the worm shaft 104 and the worm wheel 98. Thus, the vehicle is transmitted to the pinion shaft 46 in a decelerated state, so that the driver's steering load can be reduced.

  Next, a method for manufacturing the worm gear device 10 will be described with reference mainly to FIGS. As shown in FIG. 5, first, in a state where the second bearing 108 is assembled in advance (a plurality of rolling elements 140 are mounted between the inner ring 136 and the outer ring 138), the outer ring 138 of the second bearing 108 is geared. The housing 94 is lightly press-fitted and fixed to the inner wall surface on the other end side (step S1).

  Subsequently, the worm wheel 98 fixed to the pinion shaft 46 so as to be integrally rotatable is disposed in the gear housing 94 (step S2).

  Thereafter, as shown in FIG. 6, the first mounting portion 110 of the worm shaft 104 formed with the first mounting portion 110, the first flange 112, the spiral tooth 102, the second flange 114, and the second mounting portion 116 is first connected to the first mounting portion 110. Only the inner ring 118 constituting one bearing 106 is press-fitted and fixed (step S3).

  At this time, the press-fit tightening allowance is set to be relatively large. For example, even when a reaction force is applied from the worm wheel 98 during rotation of the worm shaft 104, the inner ring 118 moves along the axial direction of the worm shaft. The size is set so as not to be displaced relative to the shaft 104.

  Thus, even when an impact load due to motor inertia force acts between the worm wheel 98 and the worm shaft 104 when the steering handle 14 is rotated to the handle lock end, the inner ring 118 is applied to the worm shaft 104 along the axial direction. On the other hand, it is possible to prevent relative displacement.

  Here, when the press-fit tightening allowance is δ, the outer diameter of the first mounting portion 110 is d1, and the inner diameter of the inner ring 118 is d2, δ = d1-d2 (d1> d2) is obtained. It means the value to be obtained.

  Thereafter, the raceway diameter d3 of the inner ring 118 that has been expanded (expanded) radially outward by being press-fitted into the first mounting portion 110 is acquired (step S4, see FIG. 7A). In this step S4, for example, the track diameter d3 of the inner ring 118 may be directly measured using a predetermined measuring device, or the measurement reference is inserted into the track groove 128 of the inner ring 118 press-fitted into the first mounting portion 110. A pin (cylindrical member or ball member) 142 may be disposed, and the orbit diameter d3 may be calculated by measuring the overpin diameter d4 by a so-called overpin method (see FIG. 7B).

  In step S4, as shown in FIG. 7C, the outer diameter d5 of the inner ring 118 that is press-fitted into the first mounting portion 110 may be measured. In short, it is only necessary to obtain the dimension along the radial direction of the inner ring 118 that has been expanded by press-fitting.

  Next, as shown in FIG. 8, a plurality of rolling elements 122 having an outer diameter corresponding to the track diameter d3 (outer diameter d5) of the inner ring 118 acquired in step S4, and the track diameter d3 (outer diameter d5). ) Is attached to the inner ring 118 (step S5).

  Specifically, as shown in FIG. 9, the distance L between the rolling elements 122 and the outer ring 120 (inner ring 118) in the radial direction of the inner ring 118 in a state where the plurality of rolling elements 122 and the outer ring 120 are assembled to the inner ring 118. A plurality of rolling elements 122 having a predetermined outer diameter and an outer ring 120 having a predetermined raceway diameter (outer diameter) are selected and assembled to the inner ring 118 so that becomes a predetermined value.

  Then, as shown in FIG. 10, after the pair of retainers 124 are assembled to the plurality of rolling elements 122, the pair of shield members 126 are assembled to the inner ring 118 and the outer ring 120 (step S6). Thereby, the assembly | attachment to the 1st mounting part 110 of the worm shaft 104 of the 1st bearing 106 is completed.

  Subsequently, the other end portion of the worm shaft 104 into which the first bearing 106 is press-fitted is inserted into the inner ring 136 of the second bearing 108 that is lightly press-fitted into the inner wall surface on the other end side of the gear housing 94, The second mounting portion 116 of the worm shaft 104 is disposed on the inner ring 136 of the second bearing 108 (step S7). At this time, the other end surface of the outer ring 120 constituting the first bearing 106 contacts the stepped portion 134 of the gear housing 94. A slight gap is formed between the inner ring 136 constituting the second bearing 108 and the second mounting portion 116.

  Thereafter, the outer ring 120 of the first bearing 106 is fixed to the gear housing 94 by tightening the fixing screw 132 to the gear housing 94 (step S8). Then, one end portion of the worm shaft 104 disposed in the gear housing 94 is serrated to the other end portion of the rotor 68 of the motor portion 62, and the gear housing 94 and the support member 70 are fastened by the fastening screw 93. (Step S9). At this stage, the manufacture of the worm gear device 10 according to the present embodiment is completed.

  According to the present embodiment, a press-fitting process (step S3) in which only the inner ring 118 of the first bearing 106 is press-fitted and fixed to the first mounting part 110 of the worm shaft 104, and the inner ring press-fitted into the first mounting part 110. The worm gear device 10 is manufactured by performing an assembly process (step S5) for assembling the plurality of rolling elements 122 and the outer ring 120 with respect to 118.

  Therefore, in the press-fitting process, even when the inner ring 118 is press-fitted into the first mounting part 110 in a state where the press-fitting tightening margin between the inner ring 118 and the first mounting part 110 is set large, the diameter of the inner ring 118 is increased. The plurality of rolling elements 122 and the outer ring 120 assembled to the inner ring 118 can be easily changed according to the degree. As a result, it is possible to prevent the press-fitted inner ring 118 (first bearing 106) from being displaced relative to the worm shaft 104 in the axial direction, and the preload of the first bearing 106 becomes too large. (The frictional force generated in the rolling element 122 is increased more than necessary). Therefore, the life of the worm gear device 10 is not shortened.

  Further, in the worm gear device 10 manufactured as described above, the coupling force between the inner ring 118 and the first mounting portion 110 can be increased, and the first bearing 106 is displaced along the axial direction with respect to the worm shaft 104. Since there is no need to provide a retaining ring or the like for preventing this, the number of parts does not increase. Furthermore, unlike the prior art, since it is not necessary to form a raceway groove in the worm shaft 104, an increase in manufacturing cost can be suppressed.

  According to the present embodiment, after the press-fitting step, a dimension acquisition step (step S4) of acquiring a dimension (track diameter d3 or outer diameter d5) along the radial direction of the inner ring 118 press-fitted into the first mounting portion 110. A plurality of rolling elements 122 having an outer diameter corresponding to the dimension and an outer ring 120 having a dimension (track diameter or outer diameter) along the radial direction corresponding to the dimension are assembled to the inner ring 118. Therefore, a predetermined gap can be provided between the rolling element 122 and the outer ring 120 (inner ring 118) in the radial direction of the first bearing 106, so that the preload of the first bearing 106 can be appropriately set.

  The present invention is not limited to the above-described embodiment, and it is naturally possible to adopt various configurations without departing from the gist of the present invention.

  For example, the worm gear device 10 may be attached to the steering shaft portion 16. That is, for example, the cored bar 96 of the worm wheel 98 may be fixed to the first steering shaft 30 so as to be integrally rotatable.

  Moreover, the manufacturing method of the worm gear apparatus according to the present invention is not limited to the manufacturing method of the worm gear apparatus incorporated in the electric power steering apparatus, and can be used for manufacturing various worm gear apparatuses.

DESCRIPTION OF SYMBOLS 10 ... Worm gear apparatus 12 ... Electric power steering apparatus 62 ... Motor part 68 ... Rotor 94 ... Gear housing 96 ... Core metal part 98 ... Worm wheel 102 ... Spiral tooth 104 ... Worm shaft 106 ... 1st bearing (rolling bearing)
DESCRIPTION OF SYMBOLS 108 ... 2nd bearing 110 ... 1st mounting part 116 ... 2nd mounting part 118 ... Inner ring 120 ... Outer ring 122 ... Rolling body 124 ... Cage 126 ... Shield member 132 ... Fixing screw

Claims (1)

In a method of manufacturing a worm gear device comprising a worm shaft and a rolling bearing for rotatably supporting the worm shaft,
A press-fitting step of press-fitting and fixing the inner ring of the rolling bearing directly into the worm shaft;
A dimension acquisition step of acquiring a dimension along the radial direction of the inner ring that has been expanded by press-fitting into the worm shaft;
Based on the dimension of the inner ring acquired in the dimension acquisition step, the rolling element and the outer ring such that the distance between the rolling element of the rolling bearing and the outer ring in the radial direction of the inner ring is a predetermined value. An assembling step for selecting and assembling the inner ring press-fitted into the worm shaft;
A method for manufacturing a worm gear device.

Images