WO2012026296A1

WO2012026296A1 - Worm gear mechanism and electric power steering device using same

Info

Publication number: WO2012026296A1
Application number: PCT/JP2011/067757
Authority: WO
Inventors: 高大青木; 康夫清水; 岳人白石
Original assignee: 本田技研工業株式会社
Priority date: 2010-08-23
Filing date: 2011-08-03
Publication date: 2012-03-01
Also published as: JP2013249846A; CN102893057A

Abstract

The present invention is a worm gear mechanism (44) that comprises a worm (80), a torque transmission worm wheel (90), and an auxiliary worm wheel (100). The auxiliary worm wheel is positioned at the center line (CL) of rotation of the torque transmission worm wheel, is caused to overlap the torque transmission worm wheel, and is positioned by a positioning section (110). The positioning section comprises a positioning receiving section (111) and a positioning convex section (112) that that can fit into the positioning receiving section. The positioning receiving section is formed on one of either the auxiliary worm wheel or the torque transmission worm wheel, and the positioning convex section is formed on the other of the two.

Description

Worm gear mechanism and electric power steering apparatus using the same

The present invention relates to a worm gear mechanism and an electric power steering apparatus using the same.

The worm gear mechanism mounted on the electric power steering apparatus is constituted by a worm connected to the electric motor and a worm wheel for torque transmission connected to a load. The assist torque generated by the electric motor is transmitted from the worm to the load via the worm wheel. In recent years, in order to enhance the steering feeling (steering feeling) by the electric power steering apparatus, a technology has been developed to reduce the backlash (gap) between the teeth of the worm and the teeth of the worm wheel. A technique for reducing the backlash is known from Patent Document 1.

The worm gear mechanism known in Patent Document 1 includes a worm, a torque transmission worm wheel engaged with the worm, and an auxiliary worm wheel provided on the torque transmission worm wheel. The auxiliary worm wheel is located concentrically with the rotation center line of the torque transmission worm wheel, and is superimposed on the torque transmission worm wheel. The relative rotational displacement of the auxiliary worm wheel with respect to the torque transmission worm wheel is restricted.

Backlash between the worm teeth and the torque transfer worm wheel teeth is reduced by the auxiliary worm wheel. In order to reduce the backlash, it is required to make the relative positional relationship of the teeth of the auxiliary worm wheel with the teeth of the torque transmission worm wheel appropriate.

Japanese Patent Application Publication No. 2005-337489

An object of the present invention is to provide a technique for appropriately setting the relative positions of the teeth of the auxiliary worm wheel with respect to the teeth of the torque transmission worm wheel.

The invention according to claim 1 comprises a worm, a torque transmission worm wheel engaged with the worm, and an auxiliary worm wheel provided on the torque transmission worm wheel, and the teeth of the worm and In a worm gear mechanism for reducing backlash between a plurality of teeth of a torque transmission worm wheel, the auxiliary worm wheel is concentric with a rotation center line of the torque transmission worm wheel, and the torque transmission worm wheel And the positioning portion may be positioned and attached by the positioning portion, and the positioning portion may be a positioning receiving portion formed on any one of the auxiliary worm wheel and the torque transmitting worm wheel, and the auxiliary With the worm wheel The serial torque-transmitting worm wheel, is formed in the other, and the positioning receiving portions can be fitted positioning protrusions, the worm gear mechanism comprising is provided.

In the invention according to claim 2, the positioning receiving portion is formed on any one of the mating surface of the auxiliary worm wheel and the mating surface of the torque transmission worm wheel, and the positioning convex portion is the auxiliary worm. It is formed in the other of the said mating surface of a wheel, and the said mating surface of the said worm wheel for torque transmissions.

In the invention according to claim 3, one of the positioning receiving portion and the positioning convex portion, which is formed on the torque transmitting worm wheel, is integrally formed with a plurality of teeth of the torque transmitting worm wheel. It is done.

In the invention according to claim 4, the mating surface on which the positioning receiving portion is located further has an arc-shaped long groove based on the rotation center line, and the positioning receiving portion is the long groove The positioning convex portion can be guided by the long groove and displaced to the positioning receiving portion by being fitted into the long groove.

In the invention according to claim 5, any one of the torque transmission worm wheel and the auxiliary worm wheel has a hook portion extending along the rotation center line toward the other, and the other is And a hooking portion capable of hooking the hooking portion, wherein the hooking portion is hooked to the hooking portion to restrict displacement in a direction along the rotation center line. The auxiliary worm wheel is attached to the torque transmission worm wheel.

In the invention according to claim 6, the hook portion is an arm extending from the mating surface of the torque transmission worm wheel along the rotation center line toward the auxiliary worm wheel, and a tip of the arm And a claw portion protruding along the mating surface of the torque transmission worm wheel, and the hooking portion penetrates the auxiliary worm wheel along the rotation center line, and the rotation center line The through-hole is formed of a through-hole formed in a circular arc shape as a reference and an inclined surface formed on the non-matching surface of the auxiliary worm wheel along an arc-shaped edge forming the through-hole. A first through hole through which the arm and the claw portion can be simultaneously inserted, and a second through hole connected to the first through hole and through which only the arm can penetrate; The slope has a slope start point at a position deep from the non-matching surface of the auxiliary worm wheel and at the boundary between the first through hole and the second through hole, and from the slope start point to the second through hole Extending along the edge to the non-matching surface, the extended end being the end point of the slope, the claw portion being inserted into the first through hole together with the arm, the claw portion being inserted into the first through hole. By being rotated relative to the rotation center line, it is possible to resiliently latch the non-matching surface when it is positioned on the non-matching surface while being guided by the inclined surface.

In the invention according to claim 7, the positioning receiving portion is disposed at a position where the positioning convex portion can be fitted when the claw portion is latched to the non-matching surface of the auxiliary worm wheel There is.

In the invention according to claim 8, the torque transmission worm wheel, the positioning convex portion, the arm, and the claw portion are an integral product integrally molded of a resin material, and the claw portion is the arm It projects toward the said rotation center line from.

In the invention according to claim 9, a hook portion extending toward the other along the rotation center line is formed on one of the torque transmission worm wheel and the auxiliary worm wheel, and the other is formed on the other The positioning convex portion is constituted by the hooking portion and the positioning receiving portion is constituted by the hooking portion by forming the hooking portion capable of fitting and holding the hooking portion. And the auxiliary worm wheel is mounted on the torque transmission worm wheel by restricting the displacement in the direction along the rotation center line by the hooking portion being fitted and latched in the hooking portion. It is positioned and attached.

In the invention according to claim 10, the auxiliary worm wheel has a plurality of teeth for meshing with the teeth of the worm, and the plurality of teeth have a spring characteristic in the rotational direction of the auxiliary worm wheel. By being configured to be flexible and deformable, at least one of the worm and the torque transmission worm wheel can be rotated by coming into contact with the worm in a state of being flexed in the rotational direction of the auxiliary worm wheel. is there.

In the invention according to claim 11, when none of the plurality of teeth of the torque transmission worm wheel is in contact with the teeth of the worm, at least one of the plurality of teeth of the auxiliary worm wheel is And in contact with the teeth of the worm in a state of being bent in the rotational direction of the auxiliary worm wheel.

In the invention according to claim 12, at least one of the plurality of teeth of the auxiliary worm wheel is always in contact with the teeth of the worm in a state of being bent in the rotational direction of the auxiliary worm wheel.

In the invention according to claim 13, when the rotation direction of the worm is switched from the normal direction to the reverse direction, immediately before the reverse direction is switched among the plurality of teeth of the torque transmission worm wheel. At least one of the plurality of teeth of the auxiliary worm wheel is the auxiliary worm wheel during the period from the first tooth meshing with the teeth of the worm to the second tooth meshing with the first tooth. Contact with the teeth of the worm in a state of bending in the direction of rotation of

In the invention according to claim 14, the auxiliary worm wheel is a molded article integrally molded of resin as a whole including the plurality of teeth.

In the invention according to claim 15, the worm gear mechanism, a steering system extending from the steering wheel of the vehicle to the steered wheels, and an electric motor generating torque and transmitting the torque to the steering system through the worm gear mechanism An electric power steering apparatus using the provided worm gear mechanism is provided.

In the invention according to claim 1, the auxiliary worm wheel is superimposed on the torque transmitting worm wheel, and the positioning convex portion is fitted in the positioning receiving portion, so that the optimum phase preset for the torque transmitting worm wheel is obtained. The auxiliary worm wheel can be reliably positioned. Therefore, the relative position of the teeth of the auxiliary worm wheel to the teeth of the torque transmission worm wheel can be appropriately and easily set to the optimum position. Moreover, the configuration for positioning may be a simple configuration in which only the positioning receiving portion and the positioning convex portion are combined.

In the invention according to claim 2, since the positioning receiving portion and the positioning convex portion are positioned on the respective mating surfaces, it is easy to fit the positioning convex portion into the positioning receiving portion.

In the invention according to claim 3, any one of the positioning receiving portion and the positioning convex portion is integrally formed with the teeth of the torque transmission worm wheel. For this reason, either one of the positioning receiving portion and the positioning convex portion can set the position with respect to the teeth of the torque transmission worm wheel with high accuracy as compared with the case where the teeth are formed as separate members. Therefore, the relative positions of the teeth of the auxiliary worm wheel with respect to the teeth can be reliably set with accuracy.

In the invention which concerns on Claim 4, the positioning recessed part is located in a part of circular arc-shaped long groove on the basis of the rotation center line of an auxiliary worm wheel. For this reason, the positioning concave portion positioned in the long groove is formed by inserting one of the torque transmission worm wheel and the auxiliary worm wheel with respect to the rotation center line after inserting the positioning convex portion into the arc-like long groove. Positioning convex part fits into. The operator can reliably and easily set the relative positions of the teeth of the auxiliary worm wheel to the teeth of the torque transmission worm wheel at the optimum position without visual observation. Therefore, the number of assembling steps can be reduced.

In the invention according to claim 5, the hooking claw portion is hooked on the hooking portion by superposing the auxiliary worm wheel on the torque transmitting worm wheel. As a result, the auxiliary worm wheel can be reliably and easily assembled to the torque transmitting worm wheel. The assembled auxiliary worm wheel maintains a stable assembled state without being axially displaced with respect to the torque transmitting worm wheel.

In the invention according to claim 6, after the arm and the claw portion are inserted into the first through hole, the claw portion is guided to the inclined surface by being rotated relative to the auxiliary worm wheel with respect to the rotation center line. Located on the non-matching surface of the auxiliary worm wheel. As a result, the claws have elasticity on the non-matching surface and stop. As described above, the auxiliary worm wheel can be integrally attached to the torque transmitting worm wheel by the operation of simply superposing the auxiliary worm wheel on the torque transmitting worm wheel and relatively rotating it. Is good.

In the invention according to claim 7, the positioning convex portion is fitted into the positioning concave portion at the same time the hook portion is hooked to the non-matching surface. Attach the auxiliary worm wheel to the torque transmission worm wheel by overlapping the auxiliary worm wheel on the torque transmission worm wheel and simply turning it relatively, and attach the auxiliary worm wheel to the torque transmission worm wheel teeth. The relative position of the teeth can be reliably and easily set to the optimum position. Therefore, the assemblability is good.

In the invention according to claim 8, the torque transmitting worm wheel, the arm and the claw portion are integrally formed of resin. Since the claws project from the arm toward the rotation center line, the molding die for molding the torque transmission worm wheel can be divided into two parts along the rotation center line. Therefore, the productivity of the torque transmission worm wheel can be enhanced.

In the invention according to claim 9, the hooking portion has the function of the positioning convex portion, and the hooking portion has the function of the positioning receiving portion. Therefore, the structure for positioning and attaching the auxiliary worm wheel to the torque transmitting worm wheel can be simplified.

In the invention according to claim 10, the plurality of teeth of the auxiliary worm wheel is configured to be able to be bent and deformed with "spring characteristics" in the rotational direction (both the normal direction and the reverse direction) of the auxiliary worm wheel. The spring characteristics of a tooth have certain characteristics set in advance for the load applied to the tooth and the amount of tooth deflection caused by this load (that is, the tooth itself has a "spring function") Say). The plurality of teeth having spring characteristics and capable of bending and deforming are configured to be able to rotate at least one of the worm and the torque transmission worm wheel by contacting the worm in a state of being bent in the rotational direction. As a result, by rotating the torque transmitting worm wheel or the auxiliary worm wheel, the worm and the torque transmitting worm wheel are brought into contact with each other to reduce backlash between the teeth of the worm and the teeth of the torque transmitting worm wheel. be able to. In this way, the teeth of the auxiliary worm wheel itself are resiliently deformable with spring properties, so that separate parts for reducing backlash are not required. Therefore, the configuration of the worm gear mechanism that reduces backlash can be simplified, the number of parts can be reduced, and the number of assembling steps can be reduced.

In the invention according to claim 11, at least one of the plurality of teeth of the auxiliary worm wheel is bent in the rotation direction of the auxiliary worm wheel at least until the teeth of the worm wheel and the teeth of the torque transmitting worm wheel are in contact with each other. It is in contact with the worm's teeth. That is, at least one of the plurality of teeth bias at least one of the worm and the torque transmission worm wheel in the rotational direction. As a result, it is possible to reliably reduce the influence of backlash between the worm teeth and the torque transmission worm wheel teeth.

In the invention according to claim 12, at least one of the plurality of teeth of the auxiliary worm wheel is in contact with the teeth of the worm in a state of being always bent in the rotational direction of the auxiliary worm wheel. Therefore, when there is no torque transmission between the worm and the torque transmission worm wheel, at least one of the plurality of teeth urges at least one of the worm and the torque transmission worm wheel in the rotational direction. .

For example, when torque is not transmitted from the worm to the torque transmission worm wheel, the torque transmission worm wheel may be reversed by an external force to hit the worm. However, the plurality of teeth of the auxiliary worm wheel are in contact with the teeth of the worm in a state of being bent in the rotational direction of the auxiliary worm wheel. For this reason, the teeth of the reverse torque transmission worm wheel gently engage and mesh without hitting the teeth of the worm. It is possible to prevent the generation of a hitting sound due to the teeth hitting each other. Furthermore, when torque is not being transmitted from the worm to the torque transmission worm wheel, the torque transmission worm wheel is prevented from being reversed by external force by the teeth having the spring characteristics. Therefore, the influence of backlash between the teeth of the worm and the teeth of the worm wheel for torque transmission can be reliably reduced.

Furthermore, by using the worm gear mechanism for a long time, the teeth of the worm and the teeth of the worm wheel for torque transmission are worn away, and even if backlash is going to increase, the teeth of the auxiliary worm wheel And in contact with the teeth of the worm in a state of bending in the direction of rotation of the auxiliary worm wheel. Therefore, there is no need to perform backlash adjustment work.

In the invention according to claim 13, when the rotation direction of the worm is switched from the normal direction to the reverse direction, the teeth of the reverse worm gently contact the teeth of the torque transmission worm wheel. It is possible to suppress the generation of a hitting sound due to the teeth hitting each other.

In the invention according to claim 14, the auxiliary worm wheel is integrally formed of resin as a whole including a plurality of teeth. Therefore, the productivity of the auxiliary worm wheel can be enhanced.

In the invention according to claim 15, in the electric power steering apparatus, a worm gear mechanism from which backlash is removed is adopted as a power transmission mechanism for transmitting the torque generated by the electric motor to the steering system. Therefore, the durability of the power transmission mechanism can be further enhanced. Furthermore, by removing the backlash of the worm gear mechanism, it is possible to further suppress the generation of the hitting sound between the teeth when steering the steering wheel, and as a result, it is possible to further reduce the noise in the passenger compartment. . For example, when the vehicle travels straight, torque is not transmitted from the worm to the torque transmission worm wheel. In this traveling state, it is possible to suppress, as much as possible, that the teeth hit each other under the influence of the traveling vibration of the vehicle and hit noise is generated.

Further, in the invention according to claim 15, by removing the backlash of the worm gear mechanism, it is possible to maintain a good meshing state of the torque transmitting worm wheel with respect to the worm. Therefore, it is possible to suppress the occurrence of time delay in which the assist torque is transmitted from the worm gear mechanism to the steering system when the steering wheel is turned back. Furthermore, since the backlash is removed, when the torque transmission worm wheel is rotated by the worm, the teeth gently engage with each other without hitting each other, so that the steering wheel can be made to have a good turning operation. . Thus, the steering feeling (steering feeling) of the electric power steering apparatus can be further enhanced.

It is a schematic diagram of the electric-power-steering apparatus of Example 1 of this invention. It is a whole block diagram of the electric-power-steering apparatus shown by FIG. FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 2; FIG. 5 is a cross-sectional view taken along line 4-4 of FIG. 2; It is the figure which expanded the worm gear mechanism shown by FIG. FIG. 6 is an exploded cross-sectional view of a torque transmitting worm wheel and an auxiliary worm wheel shown in FIG. 5; FIG. 7 is a perspective view of a torque transmitting worm wheel and an auxiliary worm wheel shown in FIG. 6; It is the figure which looked at the structure which combined the worm wheel for torque transmission and auxiliary | assistant worm wheel which were shown by FIG. 5 from the non-matching surface side of an auxiliary | assistant worm wheel. It is the figure which looked at the auxiliary | assistant worm wheel shown by FIG. 8 from the non-matching surface side. It is the figure which looked at the auxiliary | assistant worm wheel shown by FIG. 9 from the mating surface side. It is explanatory drawing explaining the relationship of the positioning part shown by FIG. 8, a hook part, and a latching part. It is explanatory drawing explaining the assembly | attachment procedure of the positioning part shown by FIG. 11, a hook part, and a latching part. It is explanatory drawing explaining the attachment completion state of the positioning part shown by FIG. 12, a hook part, and a latching part. It is explanatory drawing explaining the procedure which shape | molds the worm wheel for torque transmission shown by FIG. FIG. 5 is an explanatory view for explaining a meshing configuration of each tooth of the worm gear mechanism shown in FIG. 4; FIG. 16 is an explanatory view for explaining the meshing configuration of the teeth of the worm gear mechanism when the teeth of the torque transmission worm wheel are not in contact with the worm shown in FIG. 15. FIG. 16 is an explanatory view for explaining a meshing configuration of each tooth of the worm gear mechanism when the worm shown in FIG. 15 is reversely rotated. It is the figure which expanded the worm gear mechanism of Example 2 of this invention. FIG. 19 is an exploded cross-sectional view of the torque transmitting worm wheel and the auxiliary worm wheel shown in FIG. 18; FIG. 20 is a perspective view of a torque transmitting worm wheel and an auxiliary worm wheel shown in FIG. 19; FIG. 19 is a view of a combination of the torque transmitting worm wheel and the auxiliary worm wheel shown in FIG. 18 as viewed from the non-matching surface side of the torque transmitting worm wheel. It is the figure which expanded the worm gear mechanism of Example 3 of this invention. FIG. 23 is an exploded cross-sectional view of the torque transmitting worm wheel and the auxiliary worm wheel shown in FIG. 22; FIG. 24 is a perspective view of a torque transmitting worm wheel and an auxiliary worm wheel shown in FIG. 23; It is explanatory drawing explaining the relationship of the hook part shown by FIG. 24, and a latching part. FIG. 26 is an explanatory view for explaining a state in which the hooking claw portion and the hooking portion shown in FIG. 25 are completely assembled. It is the figure which expanded the worm gear mechanism of Example 4 of this invention. FIG. 28 is an exploded cross-sectional view of the torque transmitting worm wheel and the auxiliary worm wheel shown in FIG. 27. FIG. 29 is a perspective view of a torque transmitting worm wheel and an auxiliary worm wheel shown in FIG. 28. It is the figure which looked at the auxiliary | assistant worm wheel shown by FIG. 29 from the non-matching surface side. It is the figure which looked at the auxiliary | assistant worm wheel shown by FIG. 29 from the mating surface side.

A mode for carrying out the present invention will be described below based on the attached drawings.

A worm gear mechanism and an electric power steering apparatus using the same according to a first embodiment will be described based on FIGS. 1 to 17.

As shown in FIG. 1, the electric power steering apparatus 10 has a steering system 20 extending from a steering wheel 21 of the vehicle to steering wheels 29 and 29 (for example, front wheels) of the vehicle, and an assist torque for applying assist torque to the steering system 20. And a mechanism 40.

The steering system 20 includes a steering wheel 21, a pinion shaft 24 (input shaft 24) connected to the steering wheel 21 via a steering shaft 22 and universal shaft joints 23 and 23, and a rack and pinion mechanism for the pinion shaft 24. And a left and

right steering wheels

29, 29 connected to the both ends of the rack shaft 26 via left and

right tie rods

27, 27 and

knuckles

28, 28, respectively.

The rack and pinion mechanism 25 comprises a pinion 31 formed on the pinion shaft 24 and a rack 32 formed on the rack shaft 26.

According to the steering system 20, when the driver steers the steering wheel 21, the steering torque steers the left and

right steering wheels

29, 29 via the rack and pinion mechanism 25 and the left and

right tie rods

27, 27. Can.

The assist torque mechanism 40 includes a steering torque sensor 41, a control unit 42, an electric motor 43 and a worm gear mechanism 44. The steering torque sensor 41 detects the steering torque of the steering system 20 applied to the steering wheel 21. That is, the steering torque sensor 41 detects the torque applied to the pinion shaft 24 and outputs it as a torque detection signal, and is constituted by, for example, a magnetostrictive torque sensor or a torsion bar torque sensor. The control unit 42 generates a control signal based on a torque detection signal of the steering torque sensor 41. The electric motor 43 generates a motor torque (auxiliary torque) according to the steering torque based on a control signal of the control unit 42. The worm gear mechanism 44 transmits the assist torque generated by the electric motor 43 to the pinion shaft 24. The auxiliary torque is transmitted from the pinion shaft 24 to the rack and pinion mechanism 25.

According to the electric power steering apparatus 10, the

steering wheels

29, 29 can be steered by the rack shaft 26 by the combined torque obtained by adding the assist torque of the electric motor 43 to the steering torque of the driver.

As shown in FIG. 2, the housing 51 extends in the vehicle width direction (left and right direction in FIG. 2), and slidably accommodates the rack shaft 26 in the axial direction. The rack shaft 26 is connected to tie

rods

27, 27 at both longitudinal ends projecting from the housing 51 via ball joints 52, 52.

As shown in FIG. 3, the electric power steering apparatus 10 accommodates the pinion shaft 24, the rack and pinion mechanism 25, the steering torque sensor 41 and the worm gear mechanism 44 in the housing 51, and the upper opening of the housing 51 is the upper cover portion 53. Blocked by The steering torque sensor 41 is attached to the upper cover portion 53.

The housing 51 rotatably supports the upper portion, the central longitudinal portion, and the lower end of the vertically extending pinion shaft 24 via three bearings 55 to 57, and further includes a rack guide 70.

The rack guide 70 is a pressing means comprising a guide portion 71 which is brought into contact with the rack shaft 26 from the opposite side of the rack 32 and an adjustment bolt 73 which pushes the guide portion 71 via the compression spring 72.

As shown in FIG. 4, the electric motor 43 includes a horizontally oriented motor shaft 43 a and is attached to the housing 51. The motor shaft 43 a extends into the housing 51 and is connected to the worm shaft 46 by a coupling 45. The housing 51 rotatably supports the both ends of the worm shaft 46 extending horizontally via

bearings

47 and 48.

As shown in FIGS. 3 and 4, the worm gear mechanism 44 is an assist torque transmission mechanism that transmits the assist torque generated by the electric motor 43 to the pinion shaft 24, that is, a boosting mechanism. More specifically, the worm gear mechanism 44 comprises a worm 80, a torque transmitting worm wheel 90 engaged with the worm 80, and an auxiliary worm wheel 100 provided on the torque transmitting worm wheel 90. The auxiliary worm wheel 100 is an auxiliary gear provided for removing backlash between the worm 80 and the torque transmitting worm wheel 90. Hereinafter, the torque transmitting worm wheel 90 is appropriately referred to as "transmitting wheel 90", and the auxiliary worm wheel 100 is appropriately referred to as "auxiliary wheel 100".

The worm 80 is integrally formed with the worm shaft 46. The transmission wheel 90 is attached to the pinion shaft 24. By meshing the transmission wheel 90 with the drive-side worm 80, torque can be transmitted from the worm 80 to the load via the transmission wheel 90.

FIG. 5 shows only the left half of the worm gear mechanism 44 corresponding to FIG. As shown in FIGS. 5 to 8, the transmission wheel 90 is a cylindrical boss 91 that can be fitted to the pinion shaft 24, and a disk integrally formed on the outer peripheral portion of the boss 91. And a wheel body 92, and a gear of an integrally formed product. A plurality of teeth 93 are formed on the outer circumferential surface of the wheel main body 92 over the entire circumference. In such a transmission wheel 90, the wheel body 92 is formed of a resin molded product including at least a plurality of teeth 93. For example, the transmission wheel 90 is entirely formed of a resin molded product. Alternatively, in the transmission wheel 90, the boss portion 91 is made of a metal material, and the wheel body 92 is made of a resin molded product. The transmission wheel 90 can be manufactured by a method other than manufacturing with a molding die, for example, cutting with a cutting tool such as a hob.

The transfer wheel 90 is restricted in axial movement relative to the pinion shaft 24 and restricted in relative rotation. For example, the bosses 91 are splined or serrated to the pinion shaft 24. The rotation center line CL of the transmission wheel 90 coincides with the axis of the pinion shaft 24.

As shown in FIGS. 5 to 8, the transmission wheel 90 and the auxiliary wheel 100 are arranged in a line along the rotation center line CL. The rotation center line (center) of the auxiliary wheel 100 is the same as the rotation center line CL of the transmission wheel 90. The auxiliary wheel 100 is superimposed on one surface 94 of the transmission wheel 90 (one surface 94 of the wheel main body 92), and both relative axial movement and relative rotation are restricted and attached. The auxiliary wheel 100 is an annular member thinner than the transmission wheel 90. A plurality of teeth 103 are formed on the outer peripheral surface of the auxiliary wheel 100 over the entire circumference. The number of teeth of the teeth 103 is the same as the number of teeth 93 of the transmission wheel 90.

Furthermore, the auxiliary wheel 100 is integrally formed of resin as a whole including the plurality of teeth 103. For this reason, the productivity of the auxiliary wheel 100 can be enhanced.

Here, it defines as follows. As shown in FIG. 6, one surface 94 of the transmission wheel 90, that is, the surface 94 on which the auxiliary wheel 100 is superimposed, is referred to as "the mating surface 94 of the transmission wheel 90". The surface 104 of the auxiliary wheel 100, that is, the surface 104 superimposed on the transmitting wheel 90, is referred to as "the mating surface 104 of the auxiliary wheel 100". The other surface 105 of the auxiliary wheel 100, that is, the surface opposite to the mating surface 104, is referred to as the "non-coincidence surface 105 of the auxiliary wheel 100".

As shown in FIGS. 5 to 8, at least one, preferably a plurality of auxiliary wheels 100 are superimposed on the transmitting wheel 90 and provided on the mating surfaces 94 and 104 of each other. Components that are positioned and attached by the positioning unit 110). Each positioning portion 110 is composed of a positioning receiving portion 111 and a positioning convex portion 112. The positioning convex portion 112 can be fitted into the positioning receiving portion 111, and is formed of a pin of circular cross section. The positioning receiving portion 111 is configured by a recess. The diameter of the positioning receiving portion 111 is slightly larger than the diameter of the positioning convex portion 112.

The positioning receiving portion 111 is formed on any one of the mating surface 94 of the transmission wheel 90 and the mating surface 104 of the auxiliary wheel 100. The positioning convex portion 112 is formed on the other of the mating surface 94 of the transmission wheel 90 and the mating surface 104 of the auxiliary wheel 100. In the first embodiment, the positioning receiving portion 111 is formed on the mating surface 104 of the auxiliary wheel 100, and the positioning convex portion 112 is formed on the mating surface 94 of the transmission wheel 90.

FIG. 9 shows the auxiliary wheel 100 as viewed from the non-matching surface 105 side. FIG. 10 shows the auxiliary wheel 100 as viewed from the mating surface 104 side. FIG. 11A shows the positioning portion 110, the hooking portion 121 and the hooking portion 131 viewed from above, developed in the circumferential direction with reference to the rotation center line CL. FIG. 11B shows the relationship between the hooking claw 121 and the hooking part 131 shown in FIG. 11A as a cross-sectional view as viewed from the side. FIG.11 (c) represents the positioning part 110 shown by Fig.11 (a) as sectional drawing seen from the side.

As shown in FIGS. 7 to 11, at least one mating surface 104 on which the plurality of positioning receivers 111 are located, that is, the mating surface 104 of the auxiliary wheel 100, is based on the rotation center line CL, Preferably, a plurality of (three in the first embodiment) arcuate long grooves 113 are provided. The long grooves 113 are all arranged concentrically with respect to the rotation center line CL. Each positioning receiving part 111 is located in a part of long slot 113, respectively. The groove width of the long groove 113 is slightly larger than the diameter of the positioning protrusion 112. Each positioning convex portion 112 can be positioned in the positioning receiving portion 111 while being moved along the long groove 113 by being fitted into each long groove 113. Because the positioning convex portion 112 is configured to be guided and displaced by the long groove 113, when the auxiliary wheel 100 is rotated relative to the transmission wheel 90, alignment between the transmission wheel 90 and the auxiliary wheel 100 is easy. is there.

Each positioning protrusion 112 is formed in a tapered shape. That is, each positioning convex portion 112 has a tapered shape whose tip is smaller than the root when viewed in the axial cross section. Each long groove 113 is open facing the mating surface 104, and the surface on the non-combining surface 105 side is a bottom 113a. The groove width of each long groove 113 is set in accordance with the taper of each of the predetermined protrusions 112, and is tapered such that the bottom 113a of the groove is narrowed. That is, each long groove 113 has a tapered shape in which the bottom 113a of the groove is smaller than the tip of the groove when viewed in the axial cross section. Thereby, the positioning convex portion 112 can be easily fitted into the long groove 113, and the positioning becomes easy. Note that at least one of the positioning convex portion 112 and the long groove 113 may be tapered.

As shown in FIG. 6 to FIG. 8, at least one, preferably a plurality of transmission wheels 90 extend from the mating surface 94 along the rotation center line CL toward the auxiliary wheel 100. 3) hook claws 121. The auxiliary wheel 100 has at least one and preferably a plurality of (three in the first embodiment) hooking portions 131 for hooking one or more hooking claws 121. The auxiliary wheel 100 is attached to the transmission wheel 90 by the hooking portions 121 being hooked to the hooking portions 131.

Each hook portion 121 has an arm 122 extending from the mating surface 94 of the transmission wheel 90 toward the auxiliary wheel 100 along the rotation center line CL, and the mating surface of the transmission wheel 90 from the tip of the arm 122 And a claw portion 123 protruding along 94. Each of the claws 123 protrudes from the arm 122 toward the rotation center line CL, as shown in FIGS. 5 to 7.

Each hooking portion 131 includes a through hole 132, an inclined surface 134, and a non-matching surface 105, respectively. The through hole 132 penetrates the auxiliary wheel 100 along the rotation center line CL, and is formed in an arc shape based on the rotation center line CL. The through hole 132 includes a first through hole 135 through which the arm 122 and the claw portion 123 can be inserted simultaneously, and a second through hole 136 which is continuous with the first through hole 135 and through which only the arm 122 can penetrate. The inclined surface 134 is formed on the non-matching surface 105 of the auxiliary wheel 100 and is along the arc-shaped edge 133 (inner peripheral edge 133) of the through hole 132 formed in the auxiliary wheel 100.

As shown in FIG. 9 and FIG. 11 (b), the inclined surface 134 is the boundary 134 a between the first through hole 135 and the second through hole 136, and is the deepest inclined starting point 134 a The inclined end 134b extends from the inclined start point 134a along the second through hole 136 to the non-matching surface 105 of the auxiliary wheel 100, and the extended inclined end 134b is continuous with the non-matching surface 105.

After the claw portion 123 is inserted through the first through hole 135 together with the arm 122, the claw portion 123 is rotated relative to the auxiliary wheel 100 with respect to the rotation center line CL, thereby being guided by the inclined surface 134 and being unaligned. When positioned on the surface 105, as shown in FIG. 5, the non-matching surface 105 is configured to be resiliently latched.

That is, as shown in FIG. 6, the height Hi from the mating surface 94 of the transmission wheel 90 to the lower surface 123 a (the hooking surface 123 a) of the claw portion 123 is from the mating surface 104 of the auxiliary wheel 100 to the non mating surface 105. The thickness Th is set to be slightly smaller than the thickness Th. Therefore, when the claw portion 123 reaches the non-matching surface 105 while being guided by the inclined surface 134, the auxiliary wheel 100 has elasticity toward the mating surface 94 of the transmission wheel 90 while following the second through hole 136. And slightly flex. Therefore, the claw portion 123 is resiliently latched to the non-matching surface 105.

Furthermore, as shown in FIG. 5 and FIG. 8, when the claws 123 (see FIG. 7) of the hooking claws 121 (see FIG. 7) are latched on the non-matching surface 105, the positioning convex portions 112 It is the structure located. Specifically, as shown in FIGS. 8 to 10, the positioning portions 110 are arranged at equal pitches in the circumferential direction with reference to the rotation center line CL. The hooking claws 121 and the hooking parts 131 are also arranged at equal pitches in the circumferential direction with reference to the rotation center line CL. Furthermore, all the hooking claws 121 and all the hooking parts 131 are arranged concentrically with respect to the rotation center line CL, and are located closer to the rotation center line CL than the positioning parts 110.

The center P1 of each of the first through holes 135 (the center P1 in the circumferential direction with reference to the rotation center line CL) is taken as a first reference point P1. Each first reference point P1 is arranged at an equal angle θ1. The circumferential width of each first through hole 135 is set larger than the widths of the arms 122 and the claws 123.

One end of the arcuate long groove 113 is positioned at the first reference point P1, and the other end is positioned at the second reference point P2. All the long grooves 113 extend in the same direction from the first reference point P1. The angle from the first reference point P1 to the second reference point P2 is θ2. That is, the range (length) of the long groove 113 is the angle θ2. The positioning receiving portion 111 is located at the second reference point P2. More preferably, the depth of the positioning receiving portion 111 formed of a recess is set larger than the depth of the long groove 113.

All the through holes 132 extend in the same direction from the first reference point P 1 and are along the long groove 113. The range (length) of the arc-shaped through hole 132 is larger than the angle θ2. The inclination end point 134b of the inclined surface 134 is positioned closer to the first reference point P1 than the second reference point P2.

Next, the procedure for alignment and attachment of the auxiliary wheel 100 to the transmission wheel 90 will be described with reference to FIGS.

First, as shown in FIG. 11B, the auxiliary wheel 100 is aligned on the mating surface 94 of the transmission wheel 90, and the position of the hooking claw 121 is aligned with the first through hole 135. At this time, the positioning convex portion 112, one end of the long groove 113, the hook portion 121, and the first through hole 135 are all located at the first reference point P1.

Although the positioning convex portion 112, one end of the arc-shaped long groove 113, the hooking claw portion 121, and the first through hole 135 are all located at the first reference point P1, the positioning convex portion 112 and the circular arc shape One end of the long groove 113 may be at the same position, and the hooking claw 121 and the first through hole 135 may be at the same position. That is, the hooking portion 121 and the first through hole 135 may not be at the same position as the positioning convex portion 112 and the one end of the arcuate long groove 113.

Next, the auxiliary wheel 100 is turned toward the second reference point P2 while being superimposed on the mating surface 94 of the transmission wheel 90. This intermediate stage is shown in FIG.

FIG. 12 is represented to correspond to FIG. 11, and shows a stage in the middle of assembly. FIG. 12A shows a state in which the positioning convex portion 112 and the hook portion 121 are displaced from the first reference point P1 toward the second reference point P2. FIG. 12B shows the relation between the hooking claw 121 and the hooking part 131 shown in FIG. 12A as a cross-sectional view as viewed from the side. FIG.12 (c) represents the positioning part 110 shown by FIG. 12 (a) as sectional drawing seen from the side.

As shown in FIGS. 12A and 12B, the claws 123 are in contact with the inclined surface 134. From this state, the auxiliary wheel 100 is further rotated toward the second reference point P2 with respect to the transmission wheel 90. As a result, the claws 123 are guided by the inclined surface 134 and displaced toward the non-matching surface 105 of the auxiliary wheel 100. For this reason, the auxiliary wheel 100 approaches the mating surface 94 of the transmission wheel 90 and is finally superimposed on the mating surface 94. Thereafter, the auxiliary wheel 100 is further rotated toward the second reference point P2 with respect to the transmission wheel 90. As a result, the claw portion 123 reaches the second reference point P2. The final stage of this assembly is shown in FIG.

FIG. 13 is drawn to correspond to FIGS. 8 and 12 and shows the final stage of assembly. FIG. 13A shows a state in which the positioning convex portion 112 and the hooking claw portion 121 have reached the second reference point P2. FIG. 13B is a cross-sectional view of the relationship between the hook portion 121 and the hook portion 131 shown in FIG. 13A as viewed from the side. FIG.13 (c) represents the positioning part 110 shown by FIG. 13 (a) as sectional drawing seen from the side.

As shown in FIG. 8 and FIG. 13, the claw portion 123 is hooked to the non-matching surface 105 by reaching the second reference point P2. At this time, the positioning convex portion 112 is fitted into the positioning receiving portion 111 by being positioned at the second reference point P2. At this time, at the moment of being inserted, a vibration or a fitting sound is generated along with the insertion, and the assembling operator can recognize that the assembly is completed without visual observation. This completes the task of aligning and attaching the auxiliary wheel 100 to the transfer wheel 90. That is, by relatively rotating the auxiliary wheel 100 by the angle θ2 (turning angle θ2) with respect to the transmission wheel 90, alignment and assembly of the

wheels

90 and 100 can be performed.

In this manner, the auxiliary wheel 100 can be positioned and attached to the transmission wheel 90 by superposing the auxiliary wheel 100 on the transmission wheel 90 and fitting the positioning convex portion 112 on the positioning receiving portion 111. Therefore, as shown in FIG. 4, the relative position of the teeth 103 of the auxiliary wheel 100 with respect to the teeth 93 of the transmission wheel 90 can be optimized by fitting the positioning convex portion 112 into the positioning receiving portion 111. Can easily be set. By assembling the

wheels

90 and 100 integrated with one another in this manner to the worm 80, at least one of the worm 80 and the transmission wheel 90 is pre-biased in the direction of rotation of the auxiliary wheel 100 (preload Configuration).

Furthermore, the positioning receiving portion 111 is located at a part of the arc-shaped long groove 113 with reference to the rotation center line CL of the auxiliary wheel 100. For this reason, after the positioning convex portion 112 is fitted in the arc-shaped long groove 113, one of the transmission wheel 90 and the auxiliary wheel 100 is positioned on the long groove 113 by rotating the rotation center line CL. The positioning convex portion 112 is fitted in the positioning receiving portion 111 which is located. The operator can reliably and easily set the relative position of the teeth 103 of the auxiliary wheel 100 to the teeth 93 of the transmission wheel 90 at an optimal position without visual observation. Therefore, the number of assembling steps can be reduced.

Furthermore, by overlapping the auxiliary wheel 100 on the transmission wheel 90, the hooking portion 121 is hooked on the hooking portion 131. As a result, the auxiliary wheel 100 can be reliably and easily assembled to the transmission wheel 90. The assembled auxiliary wheel 100 maintains a stable assembled state without being axially displaced with respect to the transmission wheel 90.

Furthermore, after the arm 122 and the claw portion 123 are inserted into the first through hole 135, the claw portion 123 is guided by the inclined surface 134 by rotating relative to the auxiliary wheel 100 with respect to the rotation center line CL. While being positioned on the non-matching surface 105 of the auxiliary wheel 100. As a result, the claws 123 have elasticity and stop on the non-matching surface 105. As described above, the auxiliary wheel 100 can be integrally attached to the transmission wheel 90 by the operation of simply superposing the auxiliary wheel 100 on the transmission wheel 90 and relatively rotating it, so that the assembling property is good. .

Furthermore, the positioning convex portion 112 is fitted into the positioning receiving portion 111 at the same time the hook portion 123 is hooked to the non-matching surface 105. The auxiliary wheel 100 is attached to the transmission wheel 90 by the operation of superposing the auxiliary wheel 100 on the transmission wheel 90 and relatively rotating it, and the teeth 103 of the auxiliary wheel 100 with respect to the teeth 93 of the transmission wheel 90. The relative position of can be set reliably and easily to the optimum position. Therefore, the assemblability is good.

By the way, as shown in FIG. 5 to FIG. 7, the transmitting worm wheel 90, the arm 122 and the claws 123 are molded articles integrally molded of resin. The claw portion 123 protrudes from the arm 122 toward the rotation center line CL. For this reason, as shown in FIG. 14, the molding die 140 for molding the transmission wheel 90 may be divided into two parts along the rotation center line CL, that is, the upper mold 141 and the lower mold 142. it can. Therefore, the productivity of the transmission wheel 90 can be enhanced.

Next, the meshing relationship between the worm 80, the transmission wheel 90, and the auxiliary wheel 100 will be described based on FIG.

15A shows the meshing relationship between the worm 80, the transmitting wheel 90 and the auxiliary wheel 100 shown in FIG. 4 as viewed from the side, that is, from the direction of the arrow line 15 in FIG. In FIG. 15A, the transmission wheel 90 is shown by an imaginary line. Also, only the teeth 103 are shown for the auxiliary wheel 100.

FIG. 15 (b) is a cross-sectional view taken along the line bb in FIG. 15 (a). FIG. 15 (c) is a cross-sectional view taken along the line cc of FIG. 15 (a), and shows a cross-sectional configuration along the widthwise center line Lw of the transmission wheel 90. As shown in FIG. FIG. 15 (d) is a cross-sectional view taken along line dd of FIG. 15 (a), and shows a cross-sectional configuration along the mating surface 94 of the transmission wheel 90. As shown in FIG.

As shown in FIGS. 4 and 15 (a), the axial angle (crossing angle) between the worm 80 and the transmission wheel 90 is not 90 °, but “90 ° ± β °”. Here, the angle β is referred to as “oblique angle β”. For this reason, the meshing action line WL of the worm gear mechanism 44 (the rotation center line WL of the worm 80) is the axial plane of the transmission wheel 90 with respect to a general worm gear mechanism (the center line Lw in the tooth width direction of the transmission wheel 90). ) Has a slope of ± β °. Thus, the respective meshing points of the teeth 93 of the transmission wheel 90 meshing with the worm 80 are not on the same axial plane of the transmission wheel 90. Such a worm gear mechanism 44 is a so-called "oblique worm gear mechanism".

The worm 80 is a metal product, for example, a steel product such as carbon steel material for machine structure (JIS-G-4051). On the other hand, in the transmission wheel 90, the wheel main body 92 including at least a plurality of teeth 93 is a resin product such as nylon resin. The auxiliary wheel 100 is a resin product such as nylon resin. Since the

resin product wheels

90 and 100 are engaged with the metal product worm 80, the engagement can be made relatively smooth and noise can be further reduced. Furthermore, since the worm 80 is a metal product, the rigidity is large and it is difficult to elastically deform. On the other hand, since the

wheels

90 and 100 are resin products, they have relatively low rigidity and are more susceptible to elastic deformation than the worm 80.

The

teeth

93, 103 of the

wheels

90, 100 are "spurs". For this reason, when resin molding is performed, it is possible to easily perform die cutting.

As shown in FIG. 15 (b), the outer diameter Da of the auxiliary wheel 100 is set larger than the outer diameter Dt of the transmission wheel 90. Specifically, the transmission wheel 90 is positioned just beside the worm 80 and engaged therewith. The teeth 103 of the auxiliary wheel 100 extend directly above the worm 80 along the mating surface 94 of the transfer wheel 90 and mesh with one another directly above the worm 80.

The tooth 103 has a tip portion (a portion extending radially outward from the transmission wheel 90) protruding toward the top of the worm shaft 46, and the other portion is recessed, as shown in FIGS. As shown in FIG. 6, the protruding lower end face 103 u coincides with the height of the mating surface 104 of the auxiliary wheel 100. That is, the tooth width of the tip portion of the tooth 103 is the same as the thickness Th from the mating surface 104 of the auxiliary wheel 100 to the non mating surface 105. As described above, since the dented portion 103 d (see FIG. 6) is provided in the tooth 103, when the tooth 103 bends in the rotational direction of the auxiliary wheel 100, the tooth 103 bends smoothly without contacting the mating surface 94 of the transmission wheel 90. You can

As shown in FIG. 15A, in the worm 80, the screw thread 81 (that is, the tooth 81) is set to, for example, one strip, and the pitch of the screw thread 81 is set to be constant. The profile of the teeth 81 of the worm 80 and the profile of the teeth 93 of the transmission wheel 90 are involute or substantially trapezoidal. The tooth shape of the transmitting wheel 90 can be obtained by forming the tooth shape of the transmitting wheel 90 into the same shape and cutting the teeth with respect to the tooth shape of the involute or substantially trapezoidal worm 80. For the pressure angle of the teeth 81 of the worm 80, the pressure angle of the teeth 93 of the transmission wheel 90 is the same.

As shown in FIGS. 7 and 8, the tooth shape of the teeth 103 of the auxiliary wheel 100 is a substantially flat tooth shape having a substantially constant tooth thickness. That is, the teeth 103 of the auxiliary wheel 100 have a slightly thicker tooth thickness than the tooth thickness of the tooth. In addition, the “tooth” of the tooth 103 (the radial distance between the tip circle and the base circle) is larger than the “tooth” of the tooth 93 of the transmission wheel 90. Therefore, the teeth 103 of the auxiliary wheel 100 are more easily elastically deformed in the tooth thickness direction (the rotational direction of the auxiliary wheel 100) than the teeth 93 of the transmission wheel 90. Further, since the tooth form of the teeth 103 of the auxiliary wheel 100 is substantially rectangular when viewed in the radial direction, it is difficult to deform in the axial direction (the rotation center line CL direction), so that the shift of the meshing in the axial direction can be prevented. The meshing becomes stable.

In this manner, all the teeth 103 of the auxiliary wheel 100 are configured to be able to perform bending deformation with "spring characteristics" in the direction of rotation (both forward and reverse directions) of the auxiliary wheel 100. The spring characteristics of the teeth 103 have predetermined characteristics set in advance for the load applied to the teeth 103 and the amount of deflection of the teeth 103 caused by the loads (the teeth 103 themselves have the function of "spring"). Say that). That is, the teeth 103 have the same function as a leaf spring.

Such an auxiliary wheel 100 is as if a large number of leaf springs that can be elastically deformed in the rotational direction of the disc are arranged on the outer peripheral surface of the rotatable disc. The multiple leaf springs play the role of the teeth 103 of the auxiliary wheel 100.

Here, in order to facilitate understanding of the meshing relationship between the worm 80 and the

wheels

90, 100, the thread 81 and the

teeth

93, 103 will be conveniently described as follows.

As shown in FIGS. 15 (a), (c) and (d), the actual thread 81 is a continuous spiral tooth, but for convenience here it meshes with the tooth 93 of the transmission wheel 90 The three teeth 81 are referred to as a first tooth 81a, a second tooth 81b, and a third tooth 81c in order from the right side to the left side of the drawing.

As shown in FIGS. 15 (a) and 15 (c), in the plurality of teeth 93 of the transmission wheel 90, the three teeth 93 meshing with the screw thread 81 are sequentially arranged from the right side to the left side of the drawing as the first teeth 93a. , The second tooth 93b, the third tooth 93c.

Further, as shown in FIGS. 15 (a) and 15 (d), in the plurality of teeth 103 of the auxiliary wheel 100, the three teeth 103 meshing with the screw thread 81 are sequentially ordered from the right to the left in FIG. It is called 103a, the second tooth 103b, and the third tooth 103c. The phase of the first teeth 103 a corresponds to the phase of the first teeth 93 a of the transmission wheel 90. The phase of the second teeth 103 b corresponds to the phase of the second teeth 93 b of the transmission wheel 90. The phase of the third tooth 103c corresponds to the phase of the third tooth 93c of the transmission wheel 90.

The plurality of teeth 103 of the auxiliary wheel 100 are configured to be capable of bending and deforming with "spring characteristics" in the direction of rotation of the auxiliary wheel 100. For this reason, each tooth 103 contacts at least one of the teeth 80 of the worm 80 in a state of bending in the rotational direction of the auxiliary wheel 100, whereby at least one of the worm 80 and the transmission wheel 90 in the rotational direction of the auxiliary wheel 100. It is possible to energize. That is, the plurality of teeth 103 is configured to be able to rotate at least one of the worm 80 and the transmission wheel 90. More specifically, at least one of the plurality of teeth 103 of the auxiliary wheel 100 is in contact with the teeth 81 of the worm 80 while being always bent in the rotational direction of the auxiliary wheel 100.

For example, as shown in FIGS. 15A and 15C, the left tooth surface of the first tooth 93a of the transmission wheel 90 is in contact with the right tooth surface of the first tooth 81a of the worm 80. . At this time, the other teeth 93 of the transmission wheel 90, that is, the second teeth 93 b and the third teeth 93 c are not in contact with the thread 81 of the worm 80.

In this meshing state, as shown in FIGS. 15A and 15D, the right tooth surface of the third tooth 103c of the auxiliary wheel 100 elastically deforms to the left tooth surface of the second tooth 81b of the worm 80. It is touching while doing. At this time, the other teeth 103 of the auxiliary wheel 100, that is, the first teeth 103a and the second teeth 103b are not in contact with the thread 81 of the worm 80.

Thus, the screw thread 81 of the worm 80 is axially sandwiched by the first teeth 93 a of the transmission wheel 90 and the third teeth 103 c of the auxiliary wheel 100. Therefore, the plurality of teeth 103 bias at least one of the worm 80 and the transmission wheel 90 in the rotational direction of the auxiliary wheel 100 by contacting the worm 80 in a state of bending in the rotational direction. As a result, the backlash δ (gap δ) between the first teeth 81 a of the worm 80 and the first teeth 93 a of the transmission wheel 90 can be removed. That is, the backlash δ between the teeth 81 of the worm 80 and the teeth 93 of the transmission wheel 90 can be removed.

In the meshed state shown in FIG. 15, when the worm 80 is rotated forward (rotated in the direction of arrow R1), the

wheels

90, 100 rotate forward (rotated in the direction of arrow Ra). The teeth 81 of the worm 80 and the teeth 93 of the transmission wheel 90 maintain the meshing state without the backlash δ.

FIG. 16 (a) corresponds to FIG. 15 (c). FIG. 16 (b) is shown in correspondence with FIG. 15 (d). FIG. 16A shows the case where the teeth 93 of the transmission wheel 90 are not in contact with the teeth 81 of the worm 80 at all. In this case, between the first teeth 81a of the worm 80 and the first teeth 93a of the transmission wheel 90, and between the first teeth 81a of the worm 80 and the second teeth 93b of the transmission wheel 90, It has backlash δ. However, as shown in FIG. 16 (b), at least one of the plurality of teeth 103 of the auxiliary wheel 100, that is, the third tooth 103 c is bent in the rotational direction of the auxiliary wheel 100 and the second of the worm 80 is It is in contact with the teeth 81 b.

Therefore, at least one of the plurality of teeth 103 of the auxiliary wheel 100 is bent in the rotational direction of the auxiliary wheel 100 until at least the teeth 81 of the transmission wheel 90 contact the teeth 81 of the worm 80. Contact with the teeth 81 of the That is, at least one of the plurality of teeth 103 urges at least one of the worm 80 and the transmission wheel 90 in the rotational direction. As a result, the influence of backlash between the teeth 81 of the worm 80 and the teeth 93 of the transmission wheel 90 can be reliably reduced.

FIG. 17 (a) corresponds to FIG. 15 (c). FIG. 17B corresponds to FIG. 15D. When the worm 80 is switched from the normal rotation state shown in FIG. 15 to the reverse rotation (rotation in the arrow R2 direction) shown in FIG. 17, the

wheels

90 and 100 reverse (rotation in the arrow Rb direction). As a result, the first teeth 81a of the worm 80 mesh with (contact with) the second teeth 93b shown in FIG. 17 (a) from the state of meshing (contacting) the first teeth 93a shown in FIG. ) Switch to the state. However, at this switching point, as shown in FIG. 17B, the third tooth 103c of the auxiliary wheel 100 is still in contact with the second tooth 81b of the worm 80 in a bent state.

Thus, by switching the worm 80 from normal rotation to reverse rotation, the first teeth 93a of the transmission wheel 90 meshing with the worm 80 immediately before switching to the reverse rotation direction are different from the first teeth 93a. Before meshing with the teeth 93 b, the third teeth 103 c of the auxiliary wheel 100 contact the teeth 81 in a state of bending in the rotational direction of the auxiliary wheel 100. Therefore, when the direction of rotation of the worm 80 is switched from the normal direction to the reverse direction, the teeth 81 of the reverse worm 80 gently contact the teeth 93 of the transmission wheel 90. It is possible to suppress the generation of striking sound due to the

teeth

81 and 93 hitting each other.

As apparent from the above description, at least one of the plurality of teeth 103 of the auxiliary wheel 100 is in contact with the teeth 81 of the worm 80 in a state of being always bent in the rotational direction of the auxiliary wheel 100. Therefore, when there is no torque transmission between the worm 80 and the transmission wheel 90, at least one of the plurality of teeth 103 urges at least one of the worm 80 and the transmission wheel 90 in the rotational direction. Do.

For example, when torque is not transmitted from the worm 80 to the transmission wheel 90, the transmission wheel 90 may be reversed by an external force and hit the worm 80. However, the plurality of teeth 103 of the auxiliary wheel 100 are in contact with the teeth 81 of the worm 80 in a state of being bent in the rotational direction of the auxiliary wheel 100. For this reason, the teeth 93 of the transmission wheel 90, which has been reversed, gently hit and mesh without hitting the teeth 81 of the worm 80. It is possible to prevent the generation of striking sound due to the

teeth

81 and 93 hitting each other. Furthermore, when torque is not transmitted from the worm 80 to the transmission wheel 90, the transmission wheel 90 continues to be suppressed by the external force by the tooth 103 having a spring characteristic. Therefore, the influence of backlash between the teeth 81 of the worm 80 and the teeth 93 of the transmission wheel 90 can be reliably reduced.

Furthermore, even if the teeth 81 of the worm 80 and the teeth 93 of the transmission wheel 90 are abraded by using the worm gear mechanism 44 for a long period of time, a plurality of the auxiliary wheels 100 may be increased. The teeth 103 are in contact with the teeth 81 of the worm 80 in a state of being bent in the rotational direction of the auxiliary wheel 100. Therefore, there is no need to perform backlash adjustment work.

The above description is summarized as follows.
The worm gear mechanism 44 reduces backlash between the worm 80, the transmission wheel 90 for transmitting torque between the worm 80 and the load, and the teeth 81 of the worm 80 and the teeth 93 of the transmission wheel 90. And an auxiliary wheel 100. For this reason, since the transmission wheel 90 only needs to have a function of transmitting torque, it can be easily designed to have sufficient strength. As a result, the durability of the worm gear mechanism 44 can be easily enhanced.

Furthermore, the plurality of teeth 103 of the auxiliary wheel 100 are configured to be able to perform bending deformation with “spring characteristics” in the rotational direction of the auxiliary wheel 100. The plurality of teeth 103 having a spring characteristic and capable of bending deformation contact at least one of the worm 80 and the transmission wheel 90 in the rotation direction by contacting the worm 80 in a state of bending in the rotation direction. Energize. As a result, backlash between the teeth 81 of the worm 80 and the teeth 93 of the transmission wheel 90 can be reduced.

In this way, the teeth 103 of the auxiliary wheel 100 themselves are resiliently deformable with spring characteristics, so that separate parts for reducing backlash are not required. Therefore, the configuration of the worm gear mechanism 44 in which the backlash is reduced can be simplified, the number of parts can be reduced, and the number of assembling steps can be reduced.

Furthermore, in the electric power steering apparatus 10, the worm gear mechanism 44 from which the backlash is removed is adopted as a power transmission mechanism for transmitting the torque generated by the electric motor 43 to the steering system 20. It can be raised more.

Furthermore, by removing the backlash of the worm gear mechanism 44, it is possible to further suppress the generation of the striking sound between the

teeth

81 and 93 when the steering wheel 21 is steered. As a result, noise in the passenger compartment can be further reduced. For example, when the vehicle travels straight, no torque is transmitted from the worm 80 to the transmission wheel 90. In this traveling state, it is possible to suppress, as much as possible, that the teeth hit each other under the influence of the traveling vibration of the vehicle and hit noise is generated.

Furthermore, by removing the backlash of the worm gear mechanism 44, the good meshing state of the transmission wheel 90 with respect to the worm 80 can be maintained. Therefore, when the steering wheel 21 is turned back, occurrence of a time delay in which the assist torque is transmitted from the worm gear mechanism 44 to the steering system 20 can be suppressed. Furthermore, since the backlash has been removed, when the transmission wheel 90 is rotated by the worm 80, the

teeth

81 and 93 gently engage with each other without hitting each other, so that the steering wheel 21 has a good turning operation. can do. Because of this, the steering feeling (steering feeling) of the electric power steering apparatus 10 can be further enhanced.

A worm gear mechanism and an electric power steering apparatus using the same according to a second embodiment will be described based on FIGS. 18 to 21. FIG. FIG. 18 corresponds to FIG. 5 described above. FIG. 19 is shown corresponding to FIG. FIG. 20 corresponds to FIG. 7 described above. FIG. 21 corresponds to FIG. 8 described above.

The worm gear mechanism 44A of the second embodiment and the electric power steering apparatus 10A using the same have the arrangement relationship of the positioning portion 110, the hook portion 121, and the hook portion 131 shown in FIGS. The arrangement of the positioning portion 110A, the hooking claw portion 121A, and the hooking portion 131A of the first embodiment shown in FIG. 21 is changed, and the other structures are the same as those shown in FIGS. Since it is the same, the description is omitted.

Specifically, the worm gear mechanism 44A of the second embodiment includes a worm 80, a torque transmission worm wheel 90A engaged with the worm 80, and an auxiliary worm wheel 100A provided on the torque transmission worm wheel 90A. The torque transmission worm wheel 90A (transmission wheel 90A) has substantially the same configuration as the transmission worm wheel 90 of the first embodiment, and is provided on the cylindrical boss portion 91A and the outer peripheral portion of the boss portion 91A. It is a gear of a single-piece product comprising a disk-shaped wheel main body 92A integrally formed. The auxiliary worm wheel 100A (auxiliary wheel 100A) has substantially the same configuration as the auxiliary wheel 100 of the first embodiment.

At least one, preferably a plurality (three in the second embodiment) of the positioning portions 110A have substantially the same configuration as the positioning portions 110 of the first embodiment, and the positioning receiving portion 111A and the positioning convex portion 112A It consists of The plurality of positioning receiving portions 111A have substantially the same configuration as the plurality of positioning receiving portions 111 of the first embodiment, and are formed on the mating surface 94 of the transmission wheel 90A. The plurality of positioning receiving portions 111A are located in a part of the plurality of long grooves 113A. The plurality of long grooves 113A have substantially the same configuration as the plurality of long grooves 113 of the first embodiment, and are formed on the mating surface 94 of the transmission wheel 90A. The plurality of positioning projections 112A have substantially the same configuration as the plurality of positioning projections 112 in the first embodiment, and are formed on the mating surface 104 of the auxiliary wheel 100A.

At least one, preferably a plurality (three in the first embodiment) of hooking claws 121A have substantially the same configuration as that of the hooking claws 121 of the first embodiment, and are used on the mating surface 104 of the auxiliary wheel 100A. It is formed. The claws 123 of the plurality of hook claws 121A project radially outward of the auxiliary wheel 100A from the arm 122.

At least one, preferably a plurality (three in the first embodiment) of the hooking portions 131A have substantially the same configuration as the hooking portion 131 of the first embodiment, and are formed on the transmission wheel 90A. There is. Each inclined surface 134 of the plurality of hooking portions 131A is along the arc-shaped edge 133A (outer peripheral edge 133A) of the through hole 132 formed in the transmission wheel 90A.

Here, it defines as follows. As shown in FIG. 19, one surface 94 of the transmission wheel 90A, that is, the surface 94 on which the auxiliary wheel 100A is superimposed, is referred to as "a mating surface 94 of the transmission wheel 90A". Of the other surface 95A of the transmission wheel 90A, that is, the surface on the opposite side to the mating surface 94, the surface 95A on which the hooking surface 123a of the claw portion 123 is hooked 95A. One surface 104 of the auxiliary wheel 100A, that is, the surface 104 superimposed on the transmitting wheel 90A is referred to as "the mating surface 104 of the auxiliary wheel 100A".

The height HiA from the mating surface 104 of the auxiliary wheel 100A to the lower surface 123a of the claw portion 123 is set slightly smaller than the thickness ThA from the mating surface 94 of the transmission wheel 90A to the non-matching surface 95A.

According to the second embodiment, the same operation and effect as those of the first embodiment are exhibited.

A worm gear mechanism according to a third embodiment and an electric power steering apparatus using the same will be described based on FIGS. 22 to 26. FIG. FIG. 22 corresponds to FIG. 5 described above. FIG. 23 corresponds to FIG. FIG. 24 corresponds to FIG. 7 described above. FIG. 25 corresponds to FIG. FIG. 26 corresponds to FIG. 13 described above.

The worm gear mechanism 44B of the third embodiment and the electric power steering apparatus 10B using the same are the same as the positioning receiving portion 111 and the positioning convex portion 112 of the first embodiment shown in FIGS. 5 to 13 described above. The present embodiment is characterized in that it is changed to the configuration in which the hooking portion 131B and the hooking claw portion 121B are combined, and the other configurations are the same as the configurations shown in FIG. 1 to FIG.

Specifically, the worm gear mechanism 44B of the third embodiment has the same configuration as the worm gear mechanism 44 of the first embodiment. The plurality of hooking claws 121 B have the same configuration as the plurality of hooking claws 121. The plurality of hooking portions 131 B have a plurality of recessed portions 131 a formed in the non-matching surface 105 of the auxiliary wheel 100. All the concave portions 131a are located at the second reference point P2, and the hooking surfaces 123a of the plurality of hooking claws 121B can be fitted, and the bottom surface is formed flat.

As shown in FIG. 23, the height HiB from the mating surface 94 of the transmission wheel 90 to the hooking surface 123a of the claw 123 is slightly greater than the thickness ThB from the mating surface 104 of the auxiliary wheel 100 to the recess 131a. It is set small. Therefore, as shown in FIG. 26, when the claw portion 123 is guided by the inclined surface 134 and reaches the second reference point P2, the concave portion 131a of the non-matching surface 105 is resiliently latched.

Thus, the positioning convex portion 112 of the first embodiment shown in FIG. 6 is configured by the hooking claw portion 121B of the third embodiment. Further, the positioning receiving portion 111 of the first embodiment shown in FIG. 6 is constituted by the hooking portion 131 B of the third embodiment. Therefore, the hooking claw portion 121B is fitted into the hooking portion 131B and held therein, and the displacement in the direction along the rotation center line CL is restricted. Thus, the auxiliary wheel 100 is positioned and attached to the transmitting wheel 90.

According to the third embodiment, the same operation and effect as those of the first embodiment are exhibited. Furthermore, according to the third embodiment, the hook portion 121B has the function of the positioning convex portion, and the hooking portion 131B has the function of the positioning receiving portion. Therefore, the positioning receiving part 111 and the positioning convex part 112 of Example 1 are unnecessary. Therefore, the configuration for positioning and attaching the auxiliary wheel 100 to the transmission wheel 90 can be simplified.

The configuration of the third embodiment can be adopted to the second embodiment. That is, it is possible to form the hooking claw portion 121B on the auxiliary wheel 100A and to form the hooking portion 131B on the transmission wheel 90A.

Fourth Embodiment A worm gear mechanism and an electric power steering apparatus using the same according to a fourth embodiment will be described with reference to FIGS. FIG. 27 corresponds to FIG. 5 described above. FIG. 28 corresponds to FIG. FIG. 29 corresponds to FIG. 7 described above. FIG. 30 is shown corresponding to FIG. FIG. 31 is shown corresponding to FIG.

The worm gear mechanism 44C of the fourth embodiment and the electric power steering apparatus 10C using the same are the same as those of the auxiliary worm wheel 100 shown in FIGS. 27 to 31 except for the auxiliary worm wheel 100 shown in FIGS. The other configurations are the same as the configurations shown in FIGS. 1 to 17 above, and therefore the description will be omitted.

Specifically, the worm gear mechanism 44C according to the fourth embodiment includes a worm 80, a torque transmission worm wheel 90C engaged with the worm 80, and an auxiliary worm wheel 100C provided on the torque transmission worm wheel 90C.

The torque transmission worm wheel 90C (transmission wheel 90C) has substantially the same configuration as that of the transmission worm wheel 90 of the first embodiment, and has a cylindrical boss portion 91C and an outer peripheral portion of the boss portion 91C. It is a gear of a single-piece product comprising a disk-shaped wheel main body 92C integrally formed. A plurality of teeth 93 are formed over the entire circumference of the outer peripheral surface of the wheel main body 92C. In such a transmission wheel 90C, the wheel main body 92C is formed of a resin molded product including at least a plurality of teeth 93.

The auxiliary worm wheel 100C (auxiliary wheel 100C) is an auxiliary gear provided for removing backlash between the worm 80 and the torque transmitting worm wheel 90C. Hereinafter, the thing of auxiliary worm wheel 100C is suitably called "auxiliary wheel 100C."

The transmission wheel 90 and the auxiliary wheel 100C are arranged in a line along the rotation center line CL. The rotation center line (center) of the auxiliary wheel 100C is the same as the rotation center line CL of the transmission wheel 90. The auxiliary wheel 100C is an annular member thinner than the transmission wheel 90C, and is superimposed on one surface 94C (one surface 94C of the wheel main body 92C) of the transmission wheel 90C and has a relative axial direction Both movement and relative rotation are regulated and attached.

The auxiliary wheel 100C includes a disk-shaped boss 101a that is attached to the transmission wheel 90C in an overlapping manner, an annular biasing member 101b integrally formed on an outer peripheral portion of the boss 101a, and the biasing member 101b. And an annular wheel main body 101c integrally formed on the outer peripheral portion, and an integrally molded gear.

Here, it defines as follows. As shown in FIG. 28, one surface 94C of the boss portion 91C of the transmission wheel 90C, that is, the surface 94C on which the auxiliary wheel 100C is superimposed is referred to as "a mating surface 94C of the transmission wheel 90C". The one surface 104C of the boss portion 101a of the auxiliary wheel 100C, that is, the surface 104C superimposed on the transmission wheel 90C is referred to as "a mating surface 104C of the auxiliary wheel 100C". The other surface 105C of the boss portion 101a of the auxiliary wheel 100C, that is, the surface 105C opposite to the mating surface 104C is referred to as a "non-coincidence surface 105C of the auxiliary wheel 100C".

As shown in FIG. 28 to FIG. 31, the auxiliary wheel 100C is superimposed on the transmission wheel 90C, and at least one, preferably a plurality of them (three in the fourth embodiment) provided on the mating surfaces 94C and 104C. Components that are positioned and attached by the positioning unit 110). The positioning unit 110 has the same configuration as the positioning unit 110 of the first embodiment shown in FIGS. 5 to 11, and includes a positioning receiving unit 111 and a positioning protrusion 112.

The positioning receiving portion 111 is formed on any one of the mating surface 94C of the transmission wheel 90C and the mating surface 104C of the auxiliary wheel 100C. The positioning convex portion 112 is formed on one of the mating surface 94C of the transmission wheel 90C and the mating surface 104C of the auxiliary wheel 100C. In the fourth embodiment, the positioning receiving portion 111 is formed on the mating surface 104C of the auxiliary wheel 100C, and the positioning convex portion 112 is formed on the mating surface 94C of the transmission wheel 90C.

As shown in FIGS. 28 to 31, at least one, preferably a plurality of transmission wheels 90C extend from the mating surface 94C toward the auxiliary wheel 100C along the rotation center line CL. 3) hook claws 121. The auxiliary wheel 100C has at least one and preferably a plurality of (three in the fourth embodiment) hooking portions 131 for hooking the one or more hooking claws 121. The hooking claw portion 121 has the same configuration as the positioning portion hooking claw portion 121 of the first embodiment shown in FIG. 5 to FIG. The hooking portion 131 has the same configuration as the hooking portion 131 of the first embodiment shown in FIGS. The auxiliary wheel 100C is attached to the transmission wheel 90C by the respective hooking portions 121 being hooked to the respective hooking portions 131.

The wheel body 101c of the auxiliary wheel 100C is a resin molded product in which a plurality of teeth 103C are integrally formed on the outer peripheral portion, and the biasing member 101b is integrally incorporated by insert molding. The number of teeth of the teeth 103C is the same as the number of teeth 93 of the transmission wheel 90C.

Such an auxiliary wheel 100C is a so-called crown (also referred to as a cap) gear in which a plurality of teeth 103C are extended toward the transmission wheel 90C. The plurality of teeth 103C extend parallel to the rotation center line CL. That is, the auxiliary wheel 100C presenting a crown is engaged with the worm 81 by overlapping the transmission wheel 90C with the teeth 103C surrounding the outer peripheral surface of the transmission wheel 90C.

On the other hand, as shown in FIGS. 27 and 28, the biasing member 101b biases the auxiliary wheel 100C toward the transmission wheel 90C. In other words, the biasing member 101b biases the plurality of teeth 103C of the wheel main body 101c from the tip of the worm 81 toward the bottom in the direction along the rotation center line CL of the auxiliary wheel 100C. It is a configured member. Therefore, the auxiliary wheel 100C meshes with the worm 81 without backlash.

As shown in FIGS. 28 and 29, the biasing member 101b of the auxiliary wheel 100C is smaller in diameter than the inner diameter of the hollow disc-like outer circular portion 107C incorporated in the wheel main body 101c and the outer circular portion 107C. A hollow disk-shaped inner circular portion 108C attached to the transmission wheel 90C, and a flat plate extending radially from the inner circular portion 108C toward the outer circular portion 107C and connected to the outer circular portion 107C. A plurality of elastic arms 109C, which are integrally molded products. The biasing member 101b is an integrally formed product made of a metal plate such as a spring steel material, for example, a pressed product.

The plate thicknesses of the outer circular portion 107C, the inner circular portion 108C and the elastic arm 109C are the same. The outer circular portion 107C and the inner circular portion 108C are the same as the center of the auxiliary wheel 100C, that is, the rotation center CL of the transmission wheel 90C. The position of the outer circular portion 107C is offset from the position of the inner circular portion 108C by a fixed distance Hc (see FIG. 28) along the rotation center line CL of the auxiliary wheel 100C. The fixed distance Hc is referred to as an offset amount Hc. The outer circular portion 107C is substantially parallel to the inner circular portion 108C.

The biasing member 101b having such a configuration is a so-called generally "conical spring" -like elastic member having a truncated cone shape which inclines from the wheel main body 101c toward the central portion. The bottom of the conical shape is an inner circle portion 108C consisting of a horizontal flat surface. The generally disc spring-like biasing member 101b is disposed to be lower toward one surface 94C of the wheel body 92C of the transmission wheel 90C. Since the disc spring-like biasing member 101b is used, the biasing force increases as the offset amount Hc increases. Therefore, by appropriately setting the offset amount Hc, it is possible to set an urging force for urging the teeth 103C of the wheel main body 101c toward the tooth bottom of the worm 81 to an optimal value.

As shown in FIG. 27, in a state where the worm gear mechanism 44C is assembled, at least one tooth 103C of the auxiliary wheel 100C is a tooth of the tooth 81 of the worm 80 by a constant biasing force of the plurality of elastic arms 109C. It is biased toward the bottom, that is, in the direction of the arrow Sp. For this reason, the backlash between the teeth 81 of the worm 80 and the teeth 103C of the auxiliary wheel 100C is zero, and a constant contact pressure, so-called preload (also referred to as "preload") is applied to the contact surfaces of the

teeth

81 and 103C. It has been granted. When the worm 80 is at rest, there is some backlash between the teeth 81 of the worm 80 and the teeth 93 of the transmitting wheel 90C.

Thereafter, when the worm 80 is rotated in the forward direction, the tooth surface of the teeth 103C of the auxiliary wheel 100C is first pushed to try to rotate the auxiliary wheel 100C. At this time, a component of force acts on the teeth 103C of the auxiliary wheel 100C in a direction away from the bottom of the teeth 81 of the worm 80 (in the direction opposite to the arrow Sp) according to the pressure angle of itself. Therefore, the teeth 103C of the auxiliary wheel 100C are displaced in the direction away from the bottom of the teeth 81 of the worm 80 against the biasing force of the plurality of elastic arms 109C. As a result of displacement of the teeth 103C of the auxiliary wheel 100C, backlash occurs between the

teeth

81 and 103C. As a result, the teeth 81 of the worm 80 come in contact with the teeth 93 of the transmission wheel 90C, and the transmission wheel 90C starts to rotate in the forward direction.

Thus, the teeth 81 of the worm 80 can be gently applied to the teeth 93 of the transmission wheel 90C. Therefore, the durability of the worm gear mechanism 44C can be further enhanced. Moreover, since the backlash between the teeth 81 of the worm 80 and the teeth 93 of the transmission wheel 90C can be removed, the generation of hitting noise between the

teeth

81 and 93 can be further suppressed.

According to the fourth embodiment, the same operation and effect as those of the first embodiment are exhibited. Furthermore, according to the fourth embodiment, the backlash between the teeth 81 of the worm 80 and the teeth 103C of the auxiliary wheel 100C is set smaller than the backlash between the teeth 81 of the worm 80 and the teeth 93 of the transmission wheel 90C. The worm gear mechanism has a simple structure in which the auxiliary wheel 100C is superimposed on the transmission wheel 90C and the biasing member 101b biases the teeth 103C of the auxiliary wheel 100C toward the bottom of the teeth 81 of the worm 80. The durability of 44C can be enhanced.

In the present invention, the

worm gear mechanisms

44, 44A to 44C are not limited to the oblique axis worm gear mechanism, and the axial angle between the worm 80 and the

transmission wheels

90, 90A, 90C may be 90 °. .

The

worm gear mechanisms

44 and 44A to 44C according to the present invention detect the steering torque generated by the steering wheel 21 by the steering torque sensor 41, and the electric motor 43 generates an auxiliary torque in accordance with the detection signal of the steering torque sensor 41. The present invention is suitable for an electric

power steering apparatus

10, 10A to 10C for a vehicle which transmits the auxiliary torque to the steering system 20 through the

worm gear mechanisms

44, 44A to 44C.

10, 10A to 10C: electric power steering apparatus, 20: steering system, 21: steering wheel, 29: steering wheel, 43: electric motor, 44, 44A to 44C: worm gear mechanism, 80: worm, 81: tooth, 90, 90A, 90C ... Worm wheel for torque transmission, 93 ... Teeth, 94, 94C ... Matching surface, 100, 100A, 100C ... Auxiliary worm wheel, 103, 103C ... Tooth, 104, 104C ... Matching surface, 105, 105C ... Non-matching Surfaces 110, 110A: positioning

portions

111, 111A: positioning receiving

portions

112, 112A: positioning

convex portions

113, 113A:

long grooves

121, 121A, 121B: hooking claws 122: arms 123: claws, 131, 131A, 131B ... latching portion, 132 ... through hole, 13 , 133A: arc-shaped edge forming a through hole, 134: inclined surface, 134a: inclined start point, 134b: inclined end point, 135: first through hole, 136: second through hole, CL: torque transmission worm wheel Rotation center line (the rotation center line of the auxiliary worm wheel), WL ... rotation center line of the worm.

Claims

A worm, a torque transmission worm wheel meshing with the worm, and an auxiliary worm wheel provided on the torque transmission worm wheel, the auxiliary worm wheel a plurality of teeth of the worm and a plurality of the torque transmission worm wheels In a worm gear mechanism that reduces backlash between teeth,
The auxiliary worm wheel is concentric with the rotation center line of the torque transmission worm wheel, is superimposed on the torque transmission worm wheel, and can be positioned and attached by a positioning unit.
The positioning unit is
A positioning receiving portion formed on any one of the auxiliary worm wheel and the torque transmitting worm wheel;
A worm gear mechanism comprising: a positioning convex portion which is formed on the other of the auxiliary worm wheel and the torque transmitting worm wheel and which can be fitted into the positioning receiving portion.
The positioning receiving portion is formed on one of the mating surface of the auxiliary worm wheel and the mating surface of the torque transmission worm wheel.
The worm gear mechanism according to claim 1, wherein the positioning convex portion is formed on any one of the mating surface of the auxiliary worm wheel and the mating surface of the torque transmission worm wheel.
The worm gear according to claim 2, wherein one of the positioning receiving portion and the positioning convex portion, which is formed on the torque transmitting worm wheel, is integrally formed with a plurality of teeth of the torque transmitting worm wheel. mechanism.
The mating surface on which the positioning receiving portion is located further includes an arc-shaped long groove based on the rotation center line,
The positioning receiving portion is constituted by a recess located at a part of a groove bottom forming the long groove,
The worm gear mechanism according to claim 2 or 3, wherein the positioning convex portion can be guided to the long groove and displaced to the positioning receiving portion by being fitted into the long groove.
One of the torque transmission worm wheel and the auxiliary worm wheel has a hook that extends along the rotation center line toward the other, and the other hooks the hook. Have a hook that can
The auxiliary worm wheel is attached to the torque transmitting worm wheel by the hooking portion being latched on the hooking portion to restrict displacement in a direction along the rotation center line. The worm gear mechanism according to any one of 4.
The hook portion is
An arm extending from the mating surface of the torque transmission worm wheel toward the auxiliary worm wheel along the rotation center line;
And a claw portion protruding from a tip end of the arm along the mating surface of the torque transmission worm wheel,
The hooking portion is
A through hole which penetrates the auxiliary worm wheel along the rotation center line, and is formed in an arc shape based on the rotation center line;
And an inclined surface formed on the non-matching surface of the auxiliary worm wheel, along an arc-shaped edge forming the through hole;
The through hole is
A first through hole through which the arm and the claw can be simultaneously inserted;
And a second through hole connected to the first through hole and through which only the arm can penetrate;
The inclined surface has an inclined start point at a position deep from the non-matching surface of the auxiliary worm wheel and at the boundary between the first through hole and the second through hole, and the second through hole from the inclined start point It extends inclining along the hole to the non-matching surface, and the extended inclined end is an inclined end point,
The claw portion is guided to the inclined surface by being rotated relative to the auxiliary worm wheel with reference to the rotation center line after being passed through the first through hole together with the arm. The worm gear mechanism according to claim 5, wherein the non-matching surface can be resiliently latched when positioned on the non-matching surface.
The worm gear according to claim 6, wherein the positioning receiving portion is disposed at a position where the positioning convex portion can be fitted when the claw portion is latched on the non-matching surface of the auxiliary worm wheel. mechanism.
The torque transmission worm wheel, the positioning convex portion, the arm, and the claw portion are an integral product integrally molded of a resin material,
The worm gear mechanism according to claim 6, wherein the claw portion protrudes from the arm toward the rotation center line.
A hooking portion extending toward the other along the rotation center line is formed on one of the torque transmission worm wheel and the auxiliary worm wheel, and the hooking portion can be fitted to the other. And by forming a latchable portion that can be latched,
The positioning convex portion is constituted by the hooking portion, and the positioning receiving portion is constituted by the hooking portion,
The auxiliary worm wheel is positioned on the torque transmission worm wheel by the hooking portion being fitted in and latched to the hooking portion to restrict displacement in a direction along the rotation center line. The worm gear mechanism according to claim 1 mounted.
The auxiliary worm wheel has a plurality of teeth for meshing with the teeth of the worm,
The plurality of teeth are configured to be capable of bending and deforming with spring characteristics in the rotational direction of the auxiliary worm wheel, so that the plurality of teeth contact the worm in a state of bending in the rotational direction of the auxiliary worm wheel The worm gear mechanism according to any one of claims 1 to 9, wherein at least one of the worm and the torque transmission worm wheel can be rotated.
When none of the plurality of teeth of the torque transmission worm wheel is in contact with the teeth of the worm, at least one of the plurality of teeth of the auxiliary worm wheel is in the rotational direction of the auxiliary worm wheel 11. The worm gear mechanism according to claim 10, wherein the worm gear mechanism contacts the teeth of the worm in a bent state.
The worm gear mechanism according to claim 10, wherein at least one of the plurality of teeth of the auxiliary worm wheel is in contact with the teeth of the worm in a state of being always bent in the rotational direction of the auxiliary worm wheel.
When the direction of rotation of the worm is switched from the normal direction to the reverse direction, the teeth of the worm gear are engaged with the teeth of the torque transmitting worm wheel immediately before the reverse direction is switched. Between the first tooth and the second tooth different from the first tooth, at least one of the plurality of teeth of the auxiliary worm wheel is bent in the rotational direction of the auxiliary worm wheel The worm gear mechanism according to claim 10, wherein the gear is in contact with the teeth of the worm.
The worm gear mechanism according to any one of claims 10 to 13, wherein the auxiliary worm wheel is a molded product integrally formed of resin as a whole including the plurality of teeth.
A worm gear mechanism according to any one of claims 1 to 14, a steering system from a steering wheel of a vehicle to steering wheels, an electric motor generating torque and transmitting the torque to the steering system through the worm gear mechanism And an electric power steering apparatus using a worm gear mechanism.