JP6780434B2 - Warm reducer - Google Patents

Description

The present invention relates to a worm reducer including a worm wheel including an inner wheel element serving as a core material and an outer wheel element made of synthetic resin having tooth portions.

FIGS. 10 to 15 show an example of an electric power steering device described in Patent Document 1 and the like and conventionally known. The front end portion of the steering shaft 2 to which the steering wheel 1 is attached to the rear end portion is rotatably supported in the housing 3, and the worm wheel 4 is fixed to the portion rotationally driven by the steering shaft 2. .. On the other hand, a worm shaft 6 is connected to the output shaft of the electric motor 5. Then, the electric motor 5 is formed by engaging the worm tooth portion 18 provided on the outer peripheral surface of the axially intermediate portion of the worm shaft 6 with the worm wheel tooth portion 19 provided on the outer peripheral surface of the worm wheel 4. It is possible to apply an auxiliary torque (auxiliary power) of a predetermined amount in a predetermined direction to the worm wheel 4.

The worm wheel 4 is externally fitted and fixed to an axially intermediate portion of an output shaft 7 which is an output portion of auxiliary torque, and rotates together with the output shaft 7. The output shaft 7 is supported by a pair of rolling bearings 8a and 8b in the housing 3 near both ends in the axial direction, and is supported by a pair of rolling bearings 8a and 8b through the torsion bar 9. It is connected to the front end of 2. The electric motor 5 rotationally drives the worm shaft 6 according to the direction and magnitude of the steering torque applied from the steering wheel 1 to the steering shaft 2 detected by the torque sensor 10, and assists the output shaft 7. Apply torque. The rotation of the output shaft 7 is transmitted to the pinion shaft 14 which is the input portion of the steering gear unit 13 via the pair of universal joints 11a and 11b and the intermediate shaft 12, and a desired steering angle is given to the steering wheels. Rudder.

Further, in the case of the illustrated example, the worm wheel 4 is formed by combining a metal inner wheel element 15 as a core material and an outer wheel element 16 made of synthetic resin. That is, in the worm wheel 4, the portion that is externally fitted and fixed to the output shaft 7 is the inner wheel element 15 that is made of metal and has a circular ring shape, and the portion that includes the worm wheel tooth portion 19 is made of synthetic resin. The outer wheel element 16 is used. By making the outer wheel element 16 made of synthetic resin in this way, the work of forming the worm wheel tooth portion 19 on the outer peripheral surface of the worm wheel 4 is facilitated (cost reduction), and the worm shaft 6 is The tooth striking noise generated at the meshing portion between the worm tooth portion 18 and the worm wheel tooth portion 19 of the worm wheel 4 can be reduced.

Further, the outer wheel element 16 is made of synthetic resin, and the radial outer end portion of the inner wheel element 15 is embedded over the entire circumference by injection molding (by insert molding). Further, the outer peripheral surface of the inner wheel element 15 is provided with a (gear-shaped) uneven portion 17 in the circumferential direction, and the outer wheel element 16 is formed in a plurality of concave portions constituting the uneven portion 17. By incorporating a part of the synthetic resin, the holding force of the outer wheel element 16 with respect to the inner wheel element 15 in the rotation direction is enhanced.

In the case of the conventional structure as described above, there is room for improvement from the viewpoint of reducing the manufacturing error of the worm wheel tooth portion 19 provided on the outer peripheral surface of the outer wheel element 16.
That is, in the case of the above-mentioned conventional structure, the outer peripheral surface of the inner wheel element 15 is provided with the concave-convex portion 17 in the circumferential direction, and the outer wheel element 16 is formed in the plurality of concave portions constituting the concave-convex portion 17. A part of synthetic resin is included. Therefore, in the outer wheel element 16, the plurality of teeth 20 and 20 constituting the worm wheel tooth portion 19 are positioned as the radial wall thickness of the portion that overlaps the uneven portion 17 in the radial direction. Each part may have a different size (see FIGS. 14 to 15). In such a case, the amount of molding shrinkage at the time of injection molding is different for each portion where the plurality of teeth 20 and 20 are located {the portion having a large wall thickness in the radial direction (for example, the α portion in FIG. 15) becomes large. Since the wall thickness in the radial direction is small (for example, the β part in FIG. 15)}, there is a difference in the size of the plurality of teeth 20 and 20 after molding, and due to this, the worm There is a possibility that a manufacturing error such as a pitch error may occur in the wheel tooth portion 19.

Special Table 2013-084613

In view of the above circumstances, the present invention secures the holding force of the outer wheel element made of synthetic resin with respect to the inner wheel element serving as the core material, and provides the worm wheel tooth portion provided on the outer peripheral surface of the outer wheel element. Of these, it was invented to realize a structure that can suppress manufacturing errors in the portion that meshes with the worm tooth portion.

The worm reducer of the present invention includes a worm wheel having a worm wheel tooth portion on the outer peripheral surface, and a worm shaft having a worm tooth portion on the outer peripheral surface and engaging the worm tooth portion with the worm wheel tooth portion. .. Of these, the worm shaft is rotatably supported by, for example, a housing, and the worm wheel is externally fitted and fixed to, for example, a rotating shaft rotatably supported by the housing.
The worm wheel has an inner wheel element and an outer wheel element.
Of these, the inner wheel element is formed in an annular shape, and has an annular recess provided in a state of being recessed in the axial direction over the entire circumference in a portion of the axial side surface located radially inside the outer peripheral edge, and an outer circumference. It has a concavo-convex portion provided in a portion sandwiched between the surface and the annular recess, and the entire axial range of the outer peripheral surface deviating from the concavo-convex portion in the axial direction (axial direction of the outer peripheral surface). If a chamfered portion is provided on the edge portion, this chamfered portion is excluded) is a cylindrical surface portion. The annular recess can be provided, for example, in the radial intermediate portion of the axial side surface of the inner wheel element, or in the radial intermediate portion or the inner end portion of the axial side surface of the inner wheel element.
Further, the outer wheel element is made of synthetic resin and is formed in an annular shape, has the worm wheel tooth portion on the outer peripheral surface, and embeds the radial outer end portion of the inner wheel element all around. At the same time, a part of the synthetic resin has entered the annular recess and the recess forming the uneven portion.
Further, the entire meshing portion between the worm wheel tooth portion and the worm tooth portion overlaps with the cylindrical surface portion in the radial direction of the worm wheel. In other words, the width dimension of the cylindrical surface portion with respect to the axial direction is equal to or greater than the width dimension of the meshing portion with respect to the axial direction of the worm wheel, and the meshing portion is located with respect to the axial direction of the worm wheel. The range is within the range where the cylindrical surface portion is located.
Further, the worm wheel in a region where the width dimension of the cylindrical surface portion in the axial direction overlaps the worm wheel tooth portion and the worm tooth portion in the axial direction of the worm shaft (region including the meshing portion). It is equal to or larger than the width dimension in the axial direction of the worm wheel, and the range where the region is located is within the range where the cylindrical surface portion is located in the axial direction of the worm wheel.

In carrying out the present invention, a metal can be used as the material of the inner wheel element, and for example, it is superior in heat resistance to the material of the outer wheel element, and when the outer wheel element is injection-molded, for example. Use a synthetic resin that is not easily affected by heat (for example, the synthetic resin that constitutes the outer wheel element is a thermoplastic resin, while the synthetic resin that constitutes the inner wheel element is a thermosetting resin). You can also.

When implementing the worm reducer of the present invention, for example, the uneven portion is provided in a portion of the axial side surface of the inner wheel element sandwiched between the outer peripheral surface and the annular recess in the radial direction. It is possible to adopt a configuration that is an uneven portion in the circumferential direction.
In this case, for example, it is possible to adopt a configuration in which the axial depth of the concave portion constituting the concave-convex portion decreases toward the inner side in the radial direction.

When the worm reducer of the present invention is implemented, for example, a portion of the synthetic resin constituting the outer wheel element that has entered the annular recess is formed from an outer diameter side peripheral surface that constitutes the inner surface of the annular recess. It is possible to adopt a configuration that covers a continuous range up to the inner peripheral side peripheral surface that constitutes the inner surface.

When implementing the worm reducer of the present invention, for example, it is possible to adopt a configuration in which the annular recess and the uneven portion are provided on both side surfaces in the axial direction of the inner wheel element.

When the worm reducer of the present invention is implemented, for example, at least a part of the surface of the inner wheel element covered with the synthetic resin constituting the outer wheel element (for example, the cylindrical surface portion, the inner side). The entire surface of the wheel element) is formed by various processes such as knurling, graining (processing to transfer fine irregularities formed on the surface of hard metal to the surface of the molded product), and shot blasting. It is possible to adopt a configuration having an uneven surface.
If such a configuration is adopted, a part of the synthetic resin constituting the outer wheel element enters the recess forming the fine uneven surface, so that the holding force (adhesion) of the outer wheel element with respect to the inner wheel element ) Can be increased.
The depth of the recesses forming the fine uneven surface is 1/10 or less (preferably 1/20 or less, more preferably 1/30 or less) of the radial height of the teeth constituting the worm wheel tooth portion. ), It is preferable that the volume of the synthetic resin constituting the outer wheel element is not significantly affected.

According to the worm reducer of the present invention having the above-described configuration, the worm wheel tooth portion provided on the outer peripheral surface of the outer wheel element while ensuring the holding force of the outer wheel element made of synthetic resin with respect to the inner wheel element. Of these, the manufacturing error of the part that meshes with the worm tooth part can be suppressed.

FIG. 12 is a sectional view similar to FIG. 12 regarding a first example of a reference example related to the present invention. Similarly, only the worm shaft and the worm wheel are taken out and viewed from the axial direction of the worm wheel. Similarly, a sectional view taken along the line AA of FIG. Similarly, a sectional view taken along line BB of FIG. 3 regarding the worm wheel. Similarly, an enlarged view of part C in FIG. For the second example of the reference example associated with the present invention, similar to FIG. 3. The same figure as FIG. 3 regarding the 3rd example of the reference example which concerns on this invention. The same figure as FIG. 3 regarding the 4th example of the reference example related to this invention. The same figure as FIG. 3 regarding the 1st example of the Embodiment of this invention. A partially cut side view showing an example of a conventional structure of an electric power steering device. Enlarged DD cross-sectional view of FIG. Enlarged EE sectional view of FIG. Sectional view of the worm wheel. FIG. 13 is a sectional view taken along line FF of FIG. FIG. 14 is an enlarged view of part G in FIG.

[First example of reference example ]
A first example of a reference example related to the present invention will be described with reference to FIGS. 1 to 5.
In the following description of this reference example, "one side" in the axial direction means the left side of FIGS. 1 and 3, and "the other side" in the axial direction means the right side of FIGS. 1 and 3.
Further, the front-rear direction means the front-rear direction of the automobile.

FIG. 1 shows an electric power steering device incorporating the worm reducer of this reference example. The front end portion of the steering shaft 2 to which the steering wheel 1 (see FIG. 10) is attached to the rear end portion is rotatably supported in the housing 3, and the worm wheel 4a is rotatably driven by the steering shaft 2. Is fixed. On the other hand, a worm shaft 6 is connected to the output shaft of the electric motor 5 (see FIGS. 10 to 12). Then, the electric motor 5 is formed by engaging the worm tooth portion 18 provided on the outer peripheral surface of the axially intermediate portion of the worm shaft 6 with the worm wheel tooth portion 19a provided on the outer peripheral surface of the worm wheel 4a. It is possible to apply an auxiliary torque (auxiliary power) of a predetermined amount in a predetermined direction to the worm wheel 4a.

The worm wheel 4a is externally fitted and fixed to an axially intermediate portion of an output shaft 7 which is an output portion of auxiliary torque, which is a rotation shaft, and rotates together with the output shaft 7. The output shaft 7 is supported by a pair of rolling bearings 8a and 8b in the housing 3 near both ends in the axial direction, and is supported by a pair of rolling bearings 8a and 8b through the torsion bar 9. It is connected to the front end of 2. The electric motor 5 rotationally drives the worm shaft 6 according to the direction and magnitude of the steering torque applied from the steering wheel 1 to the steering shaft 2 detected by the torque sensor 10, and assists the output shaft 7. Apply torque. The rotation of the output shaft 7 is transmitted to the pinion shaft 14 (see FIG. 10) which is the input portion of the steering gear unit 13 via the pair of universal joints 11a and 11b and the intermediate shaft 12, and is desired for the steering wheel. The steering angle is given.

The worm wheel 4a is formed by combining an inner wheel element 15a and an outer wheel element 16a.

The inner wheel element 15a is made of metal and is formed in an annular shape (substantially circular ring shape) having a U-shaped cross section. Such an inner wheel element 15a has a fitting hole 21 at the central portion in the radial direction for internally fitting and fixing the axial intermediate portion of the output shaft 7 so as to enable torque transmission. Further, in the radial intermediate portion of one side surface in the axial direction of the inner wheel element 15a, an annular recess 22 is provided in a state of being recessed in the axial direction over the entire circumference. The outer diameter side peripheral surface 23 and the inner diameter side peripheral surface 25 constituting the inner surface of the annular recess 22 are each formed in a cylindrical surface shape that is not inclined with respect to the central axis of the inner wheel element 15a. The bottom surface 24 forming the inner surface of the annular recess 22 is formed in a circular ring surface shape orthogonal to the central axis of the inner wheel element 15a. Further, a sub-recess 26 is provided in a portion of the outer diameter side peripheral surface 23 near the other end in the axial direction so as to extend over the entire circumference and to be recessed outward in the radial direction.

Further, an annular recess 22a is provided over the entire circumference of the inner wheel element 15a at a portion near the outer end in the radial direction on the other side surface in the axial direction. The width dimension in the radial direction and the depth dimension in the axial direction of the annular recess 22a are smaller than those of the annular recess 22 provided on one side surface in the axial direction of the inner wheel element 15a, respectively. Further, the outer diameter side peripheral surface 23a forming the inner surface of the annular recess 22a is formed in a cylindrical surface shape that is not inclined with respect to the central axis of the inner wheel element 15a. Further, the inner diameter side peripheral surface 25a constituting the inner surface of the annular recess 22a becomes larger in the radial direction of the annular recess 22a toward the other side in the axial direction, which is the axial opening side of the annular recess 22a. It is formed in the shape of a partial cone that is inclined inward in the radial direction, which is the direction. The bottom surface 24a forming the inner surface of the annular recess 22a is formed in a circular ring surface shape orthogonal to the central axis of the inner wheel element 15a.

Further, on one side surface of the inner wheel element 15a in the axial direction, the portion sandwiched between the outer peripheral surface and the annular recess 22 in the radial direction extends over the entire circumference and is convex with the recess 28 in the circumferential direction. Concavo-convex portions 27 (in the shape of side gears) in the circumferential direction are provided, which are formed by arranging the portions 29 alternately (and at equal pitches). The bottom surface of each recess 28 constituting the uneven portion 27 is formed in a direction (radial direction) orthogonal to the central axis of the inner wheel element 15a. Further, each recess 28 constituting the uneven portion 27 is open on one side surface in the axial direction of the inner wheel element 15a, and also on the outer peripheral surface of the inner wheel element 15a and the annular recess 22. The outer diameter side peripheral surface 23 that constitutes the inner surface is also open.

Further, in the outer peripheral surface, the inner wheel element 15a has a chamfered portion on the entire axial range (axial intermediate portion and other end portion) deviating from the uneven portion 27 in the axial direction (axial end edge portion). If provided, the chamfered portion) is a cylindrical surface portion 30 in which the radial distance from the central axis of the inner wheel element 15a does not substantially change over the entire circumference. In the case of this reference example, the cylindrical surface portion 30 has a bus line parallel to the central axis of the worm wheel 4a, and is formed in a single cylindrical surface shape whose diameter does not change in the axial direction.

Further, in the case of this reference example, in other words, the inner wheel element 15a has an inner diameter side annular portion 31 and an outer diameter side annular portion 32 arranged concentrically with each other, and an outer circumference of these inner diameter side annular portions 31. A ring-shaped connecting portion 33 for connecting the surface and the inner peripheral surface of the outer diameter side annular portion 32 is provided. The annular recess 22 is a portion surrounded on three sides by one side surface of the connecting portion 33 in the axial direction, the outer peripheral surface of the inner diameter side annular portion 31, and the inner peripheral surface of the outer diameter side annular portion 32. The annular recess 22a is provided at a position straddling the axial other side surface of the outer diameter side annular portion 32 and the axial other side surface of the connecting portion 33. Further, one side surface of the outer diameter side annular portion 32 in the axial direction is the uneven portion 27, and the axial intermediate portion and the other end portion of the outer peripheral surface of the outer diameter side annular portion 32 are the cylindrical surface portion 30. ing.

As the metal constituting the inner wheel element 15a, various metals such as copper alloys, aluminum alloys, magnesium alloys and the like can be adopted in addition to iron alloys such as steel. Further, as the processing for molding the inner wheel element 15a, various cutting processing and plastic working can be adopted. However, in order to form with good yield and low cost, it is preferable to adopt plastic working (forging, pressing, flow forming, etc.).

The outer wheel element 16a is manufactured by injection molding a synthetic resin, and the radial outer end of the inner wheel element 15a formed into an L-shaped cross section with this injection molding (by insert molding). The part is buried all around. In this state, a part of the synthetic resin is the radial outer end portion of the annular recess 22, the entire auxiliary recess 26, the entire annular recess 22a, and each recess 28 constituting the concave-convex portion 27. It is invading the whole of. The portion of the synthetic resin that has entered the annular recess 22 constitutes the annular holding portion 34. Further, a portion of the synthetic resin that has entered the sub-recess 26 constitutes an annular sub-holding portion 35. Further, a portion of the synthetic resin that has entered the annular recess 22a constitutes an annular holding portion 34a. Further, a portion of the synthetic resin that enters each recess 28 constituting the uneven portion 27 and covers the entire surface of the concave-convex portion 27 engages with the concave-convex portion 27 (matches with the uneven portion 27). It constitutes a rotation holding portion 36 (having a shape).

Further, a worm wheel tooth portion 19a is formed on the outer peripheral surface of the outer wheel element 16a. The axially intermediate portion of the worm wheel tooth portion 19a overlaps with the cylindrical surface portion 30 in the radial direction. Although not shown, the forming directions of the plurality of teeth 20a and 20a constituting the worm wheel tooth portion 19a are inclined with respect to the axial direction of the worm wheel 4a. Further, in the case of this reference example, the diameter of the tooth tip circle and the diameter of the tooth bottom circle of the worm wheel tooth portion 19a do not change in the axial direction, respectively.

In the case of this reference example, when the outer wheel element 16a is manufactured by injection molding and at the same time the outer wheel element 16a is coupled to the inner wheel element 15a, insert molding is performed, for example, the inner side. By setting the wheel element 15a in the mold, an annular cavity (a space in which the outer wheel element 16a is formed) is formed between the radial outer end of the inner wheel element 15a and the inner surface of the mold. At the same time, the radial outer end of the disc gate is positioned at the radial inner end on the other side of the cavity in the axial direction. Then, the outer wheel element 16a can be molded by feeding the synthetic resin into the cavity through the disc gate.

As the synthetic resin constituting the outer wheel element 16a, in addition to polyamide 66 (PA66), polyamide 46 (PA46), polyamide 9T (PA9T), polyphenylene sulfide (PPS), polyethylene terephthalate (PET), and polyacetal (POM). ) And other various synthetic resins can be used. Further, various reinforcing fibers such as glass fiber, polyethylene fiber, carbon fiber, and aramid fiber can be mixed with these synthetic resins, if necessary.

Further, in the case of this reference example, in the state where the worm reducer is assembled, the entire meshing portion 37 (the portion provided with the oblique grid in FIG. 3) between the worm tooth portion 18 and the worm wheel tooth portion 19a. Is radially superimposed on the cylindrical surface portion 30 existing on the outer peripheral surface of the inner wheel element 15a. For this reason, the axial width dimension T of the cylindrical surface portion 30 is set to be equal to or greater than the axial width dimension S of the meshing portion 37 {T ≧ S (T> S in the example shown in FIG. 3)}, and the meshing is performed. The axial range in which the portion 37 is located is contained within the axial range in which the cylindrical surface portion 30 is located. In other words, in the case of this reference example, of the outer peripheral surface of the inner wheel element 15a, at least the axial range that overlaps with the entire meshing portion 37 in the radial direction is the cylindrical surface portion 30. ing.

According to the worm reducer of this reference example configured as described above, the outer peripheral surface of the outer wheel element 16a is covered with the holding force of the outer wheel element 16a made of synthetic resin with respect to the metal inner wheel element 15a. Of the worm wheel tooth portions 19a provided, the manufacturing error of the portion that meshes with the worm tooth portion 18 can be suppressed. This point will be described below.

When an auxiliary torque is applied to the output shaft 7 through the worm wheel 4a, the meshing reaction force acting on the meshing portion 37 between the worm wheel tooth portion 19a of the worm wheel 4a and the worm tooth portion 18 of the worm shaft 6 As shown by the arrow in FIG. 3, a moment M in the tilting direction is applied to the worm wheel 4a based on the axial component of.

On the other hand, in the case of this reference example, annular recesses 22 and 22a are provided on both side surfaces of the inner wheel element 15a in the axial direction over the entire circumference. At the same time, the outer diameter side peripheral surface 23 forming the inner surface of the annular recess 22 is provided with the sub-recess 26 over the entire circumference. The outer wheel element 16a embeds the radial outer end of the inner wheel element 15a over the entire circumference, and a part of the synthetic resin constituting the outer wheel element 16a is an annular recess. The radial outer end portion of 22, the entire annular recess 22a, and the entire sub-recess 26 are inserted, and the portions that have entered each of these portions form the annular holding portions 34, 34a and the sub-holding portion 35, respectively. It is configured. Therefore, in the case of this reference example, the holding force of the outer wheel element 16a with respect to the inner wheel element 15a in the moment M direction can be secured.

In the case of this reference example, the inner diameter side peripheral surface 25a constituting the inner surface of the annular recess 22a is formed in the above-mentioned partial conical surface shape, and the outer diameter side peripheral surface 23a constituting the inner surface is formed into a cylindrical surface. It is formed in a shape. Therefore, as described above, when the outer wheel element 16a is injection-molded, the synthetic resin sent from the disc gate into the cavity is not disturbed by the flow, and the inner diameter side peripheral surface (partial conical surface). It can enter the annular recess 22a along the 25a. At the same time, the engagement strength between the holding portion 34a constituting the outer wheel element 16a and the outer diameter side peripheral surface (cylindrical surface) 23a can be increased to increase the holding force in the moment M direction.

Further, in the case of this reference example, a concave-convex portion 27 in the circumferential direction is provided at the radial outer end portion of one side surface in the axial direction of the inner wheel element 15a, and a composite constituting the outer wheel element 16a. A part of the resin enters the entire surface of each concave portion 28 constituting the uneven portion 27 and covers the entire surface of the concave-convex portion 27 to form a rotation holding portion 36 that engages with the uneven portion 27. There is. Therefore, in the case of this reference example, the holding force of the outer wheel element 16a in the rotational direction with respect to the inner wheel element 15a can be secured.

Further, in the case of this reference example, of the outer peripheral surface of the inner wheel element 15a, at least a portion that overlaps with the entire meshing portion 37 in the radial direction is the cylindrical surface portion 30. Therefore, in the outer wheel element 16a, the plurality of teeth 20a and 20a constituting the worm wheel tooth portion 19a are positioned as the radial wall thickness of the portion that overlaps the cylindrical surface portion 30 in the radial direction. They are almost (substantially) equal to each other.

Further, in the case of this reference example, the diameter of the tooth tip circle and the diameter of the tooth bottom circle of the worm wheel tooth portion 19a provided on the outer peripheral surface of the outer wheel element 16a do not change in the axial direction, respectively. Therefore, in the case of this reference example, the thickness of the portion of the outer wheel element 16a that overlaps the cylindrical surface portion 30 provided on the outer peripheral surface of the inner wheel element 15a in the radial direction. Is a portion where a plurality of teeth 20a, 20a constituting the worm wheel tooth portion 19a are located over the entire length in the axial direction, and is substantially equal to each other.

Therefore, in the case of this reference example, of the outer wheel element 16a, at least the portion overlapping the cylindrical surface portion 30 provided on the outer peripheral surface of the inner wheel element 15a in the radial direction is as shown in FIG. In addition, the molding shrinkage amount at the time of injection molding of the portion where the plurality of teeth 20a and 20a are located can be made substantially equal to each other. As a result, the sizes (diameter thickness) of the plurality of teeth 20a and 20a after molding can be made substantially equal, and due to this, the pitch error and the like related to the worm wheel tooth portion 19a can be manufactured. The error can be suppressed.

Further, in the case of this reference example, in the state where the worm reducer is assembled, the entire meshing portion 37 between the worm tooth portion 18 and the worm wheel tooth portion 19a is superposed on the cylindrical surface portion 30 in the radial direction. I'm letting you. That is, in the case of this reference example, the manufacturing error of the portion of the worm wheel tooth portion 19a that meshes with the worm tooth portion 18 can be suppressed. Therefore, the meshing state of the meshing portion 37 can be improved.

[Second example of reference example ]
A second example of a reference example related to the present invention will be described with reference to FIG.
This reference example is a modification of the first example of the reference example shown in FIGS. 1 to 5 described above.

In the case of this reference example, the configuration of the other side surface in the axial direction of the inner wheel element 15b constituting the worm wheel 4b is different from that of the first example of the above-mentioned reference example . That is, in the case of this reference example, the same as the annular recess 22 and the uneven portion 27 existing on one side surface of the inner wheel element 15b in the axial direction on the other side surface in the axial direction of the inner wheel element 15b constituting the worm wheel 4b. An annular recess 22b (outer diameter side peripheral surface 23b, bottom surface 24b, inner diameter side peripheral surface 25b) and uneven portion 27a (a plurality of concave portions 28a, convex portions 29a) are provided.

Then, a part of the synthetic resin constituting the outer wheel element 16b is inserted into the radial outer end portion of the annular recess 22b, and the portion entering the annular recess 22b is used as an annular holding portion 34b. At the same time, a part of the synthetic resin constituting the outer wheel element 16b is allowed to enter the entire surface of each recess 28a constituting the uneven portion 27a to cover the entire surface of the concave-convex portion 27a. It is a rotation holding portion 36a that engages with 27a. By adopting such a configuration, the holding force of the outer wheel element 16b with respect to the inner wheel element 15b in the moment M direction and the rotation direction is increased.

In the case of this reference example, the sub-recess is not provided on the inner surface of the annular recess 22. However, in the case of carrying out this reference example, the sub-recess is also provided on the inner surface of the annular recess 22 (22b). , A part of the synthetic resin can be put into this sub-recess.
Other configurations and operations are the same as in the case of the first example of the above-mentioned reference example .

[Third example of reference example ]
A third example of a reference example related to the present invention will be described with reference to FIG.
This reference example is a modification of the second example of the reference example shown in FIG. 6 above.

In the case of this reference example, the configuration of the uneven portions 27b and 27c provided on the radial outer ends of the axially both side surfaces of the inner wheel element 15c constituting the worm wheel 4c is the second example of the above-mentioned reference example . Different from the case of. That is, in the case of this reference example, the axial depths (axial heights of the convex portions 29a and 29b) of the concave portions 28b and 28c constituting both the concave-convex portions 27b and 27c are directed inward in the radial direction. It is made smaller according to. As a result, the axial depths of the concave portions 28b and 28c (the axial heights of the convex portions 29a and 29b) are set to the same size as in the second example of the above-mentioned reference example at the radial outer edge portion. On the other hand, the radial inner edge is smaller (zero in the illustrated example) than in the second example of the above-mentioned reference example .

By adopting such a configuration, the volumes of the recesses 28b and 28c can be reduced so that the molding load when the both concave and convex portions 27b and 27c are molded by plastic working can be suppressed to a low level. We are trying to reduce the manufacturing cost. Further, the opening area of the radial inner ends of the recesses 28b and 28c with respect to the outer diameter side peripheral surfaces 23 and 23b forming the inner surfaces of the pair of annular recesses 22 and 22b is determined by the second example of the above-mentioned reference example . By making it smaller than the case (zero in the illustrated example), the engagement area between the peripheral surfaces 23 and 23b on both outer diameter sides and the pair of holding portions 34 and 34b constituting the outer wheel element 16c is increased. As a result, the holding force of the outer wheel element 16c with respect to the inner wheel element 15c in the moment M direction is increased.
Other configurations and operations are the same as in the second example of the above-mentioned reference example .

[Fourth example of reference example ]
A fourth example of a reference example related to the present invention will be described with reference to FIG.
This reference example is a modification of the second example of the reference example shown in FIG. 6 above.

In the case of this reference example, the configuration of the outer wheel element 16d constituting the worm wheel 4d is different from the case of the second example of the above-mentioned reference example .
That is, in the case of this reference example, the pair of holding portions 34c and 34d constituting the outer wheel element 16d constitutes the inner surface of the pair of annular recesses 22 and 22b provided in the inner wheel element 15d. It covers a continuous range (the entire inner surface thereof) from the radial side peripheral surfaces 23 and 23b to the inner diameter side peripheral surfaces 25 and 25b constituting these inner surfaces. By adopting such a configuration, the holding force of the outer wheel element 16d with respect to the inner wheel element 15d in the moment M direction is increased.
Other configurations and operations are the same as in the second example of the above-mentioned reference example .

[ First Example of Embodiment]
A first example of the embodiment of the present invention will be described with reference to FIG.
This example is a modification of the second example of the reference example shown in FIG. 6 above.

In the case of this example, the axial dimensions of the radial outer end portion (outer diameter side annular portion 32a, cylindrical surface portion 30a) of the inner wheel element 15e constituting the worm wheel 4e are determined by the second example of the above-mentioned reference example . It is larger than the case. As a result, in the assembled state of the worm reducer, the width dimension T with respect to the axial direction of the cylindrical surface portion 30a existing on the outer peripheral surface of the inner wheel element 15e becomes the worm tooth portion 18 and the worm wheel tooth with respect to the axial direction of the worm shaft 6. The region 38 on which the portion 19a overlaps (the region including the meshing portion 37, and is surrounded by the straight line represented by the upper broken line and the arc curve represented by the lower solid line in FIG. 9). The width dimension U or more {T ≧ U (T> U in the example shown in FIG. 3)} of the bow-shaped region) with respect to the axial direction of the worm wheel 4e, and with respect to the axial direction of the worm wheel 4e. The range where the region 38 is located is set to fit within the range where the cylindrical surface portion 30a is located.

When the meshing portion 37 between the worm tooth portion 18 and the worm wheel tooth portion 19a is worn with the use of the worm reducer, the axial width dimension S of the meshing portion 37 increases. However, since the meshing portion 37 is a portion existing in the region 38, even if the axial width dimension S of the meshing portion 37 increases, the maximum value thereof is the axial width dimension U of the region 38. It stays at the above and does not exceed the axial width dimension U of this region 38. That is, the meshing portion 37 does not protrude outside the region 38 in the axial direction of the worm wheel 4e. Therefore, in the case of this example adopting the above-described configuration, even if the axial width dimension S of the meshing portion 37 increases due to the wear of the meshing portion 37, the meshing portion 37 It is possible to maintain a state in which the entire surface of the cylinder is overlapped with the cylindrical surface portion 30a in the radial direction, and the meshed state of the meshing portion 37 can be maintained in a good condition.
Other configurations and operations are the same as in the second example of the above-mentioned reference example .

In the case of implementing the present invention can be implemented in combination form of implementation described above and the configuration of each reference examples as appropriate.

Further, in the embodiments and reference examples of implementation described above, but the inner wheel element is made of metal, when practicing the present invention, for example, the inner wheel element, than the synthetic resin forming the outer wheel element It can also be made of synthetic resin having excellent heat resistance. In this case, it is possible to obtain the same effects as the embodiments and reference examples of implementation described above.

Further, in the structure of the embodiment and the reference example of implementation described above, of the surface of the inner wheel elements, at least a portion (e.g., the cylindrical surface of the portion covered by the synthetic resin forming the outer wheel element, If the entire surface of the inner wheel element) is a fine concavo-convex surface formed by various processing such as lauret processing, grain processing, shot blasting, etc., the outer wheel element is formed in a recess constituting the fine concavo-convex surface. Since a part of the synthetic resin constituting the above is inserted, the holding force (adhesion) of the outer wheel element with respect to the inner wheel element can be increased. Even when such a configuration is adopted, the depth of the recesses constituting the fine uneven surface is 1/10 or less (for example, 1/20) of the radial height of the teeth constituting the worm wheel tooth portion. If the volume of the synthetic resin constituting the outer wheel element is not significantly affected, the manufacturing error of the portion of the worm wheel tooth portion that meshes with the worm tooth portion can be suppressed.

The worm wheel and worm reducer of the present invention can be used by being incorporated in various mechanical devices such as a wiper device as well as an electric power steering device.

1 Steering wheel 2 Steering shaft 3 Housing 4, 4a-4e Warm wheel 5 Electric motor 6 Warm shaft 7 Output shaft 8a, 8b Rolling bearing 9 Torsion bar 10 Torque sensor 11a, 11b Universal joint 12 Intermediate shaft 13 Steering gear unit 14 Pinion shaft 15, 15a to 15e Inner wheel element 16, 16a to 16e Outer wheel element 17 Concavo-convex part 18 Warm tooth part 19, 19a Warm wheel tooth part 20, 20a Tooth 21 Fitting hole 22, 22a, 22b Annular recess 23, 23a, 23b Outer diameter side peripheral surface 24, 24a, 24b Bottom surface 25, 25a, 25b Inner diameter side peripheral surface 26 Sub-concave part 27, 27a to 27c Concavo-convex part 28, 28a to 28c Recessed part 29, 29a to 29c Convex part 30, 30a Cylindrical surface part 31 Inner diameter Side annular part 32, 32a Outer diameter side annular part 33 Connecting part 34, 34a to 34d Holding part 35 Sub-holding part 36, 36a Rotating holding part 37 Engaging part 38 area

Claims (6)

A worm wheel with worm wheel teeth on the outer peripheral surface,
A worm shaft having worm teeth on the outer peripheral surface and engaging the worm teeth with the worm wheel teeth,
With
The worm wheel has an inner wheel element and an outer wheel element.
The inner wheel element is formed of an annular shape, and has an annular recess formed in a portion of the axial side surface located radially inside the outer peripheral edge in a state of being recessed in the axial direction over the entire circumference, and an outer peripheral surface. It has an uneven portion provided in a portion sandwiched between the annular recess and the outer peripheral surface, and the entire axial range deviated from the concave-convex portion in the axial direction is a cylindrical surface portion.
The outer wheel element is made of synthetic resin and is formed in an annular shape, has the worm wheel tooth portion on the outer peripheral surface, and embeds the radial outer end portion of the inner wheel element all around. A part of the synthetic resin has entered the annular recess and the recess constituting the uneven portion.
The entire meshing portion between the worm wheel tooth portion and the worm tooth portion overlaps with the cylindrical surface portion in the radial direction of the worm wheel .
The width dimension of the cylindrical surface portion in the axial direction is equal to or greater than the width dimension in the axial direction of the worm wheel in the region where the worm wheel tooth portion and the worm tooth portion overlap with respect to the axial direction of the worm shaft. A worm reducer in which the range where the region is located is within the range where the cylindrical surface portion is located with respect to the axial direction of the worm wheel . The first aspect of claim 1, wherein the uneven portion is an uneven portion in the circumferential direction provided in a portion of the axial side surface of the inner wheel element sandwiched between the outer peripheral surface and the annular recess in the radial direction. Warm reducer. The worm reducer according to claim 2, wherein the axial depth of the concave portion constituting the uneven portion becomes smaller toward the inner side in the radial direction. The portion of the synthetic resin constituting the outer wheel element that has entered the annular recess covers a continuous range from the outer diameter side peripheral surface that constitutes the inner surface of the annular recess to the inner diameter side peripheral surface that constitutes this inner surface. The worm reducer according to any one of claims 1 to 3. The worm reducer according to any one of claims 1 to 4 , wherein the annular recess and the uneven portion are provided on both side surfaces in the axial direction of the inner wheel element. In any one of claims 1 to 5 , at least a part of the surface of the inner wheel element covered with the synthetic resin constituting the outer wheel element is a fine uneven surface. Worm reducer described.

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