JP2002263872A - Method for joining sintered member, joining structure for the same, and joining method for ring gear and leaf spring, and gear mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a joining method which is capable of easily and surely joining a ring gear and a leaf spring for axially movably and elastically supporting the ring gear and suppressing the occurrence of shaking, etc., by wear when the leaf spring is bent. SOLUTION: A hypoid gear mechanism includes the inner ring gear 11 and outer ring gear 12 concentrically arranged with the hypoid ring gears to be meshed with hypoid pinion gears respectively, and has an inner ring base 15 which supports the inner ring gear 11 and the leaf spring 13 which is joined to the inner ring base 15 and axially movably and elastically supports the inner ring gear 11. The mechanism is provided with a welding area 21 which grasps and joins the inner ring base 15 and an arm portion 13b of the leaf spring 13 by means of a rivet 20 and welds and joins both on the outer sides of their diametral directions and further the arm portion 13b of the spring member 13 is provided with a local deformation area 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for joining sintered members, a joining structure thereof, a method for joining a ring gear and a leaf spring, and a gear mechanism. More particularly, the present invention relates to a sintered member formed by sintering and other components. And a method of joining the ring gear and a leaf spring for elastically supporting the ring gear movably in the axial direction, and a gear and a ring gear meshing with the gear. The present invention relates to a gear mechanism comprising a leaf spring for elastically supporting the ring gear movably in the axial direction.

[0002]

2. Description of the Related Art For example, in an electric power steering apparatus 1 for a vehicle or the like, as shown in FIG. 1, a gear mechanism 2 such as a hypoid gear mechanism or a bevel gear mechanism is conventionally used. The electric power steering device 1 includes an electric motor 6 according to a rotational torque of an input shaft 4 of a steering shaft 3 that is rotated by manually steering a steering wheel (not shown).
Is applied to the output shaft 5 of the steering shaft 3 and rotated to drive the rack shaft 8 meshed with the pinion gear 7 formed on the output shaft 5 in the axial direction. In general, the electric motor 6 is arranged so that its drive axis is substantially orthogonal to the axis of the steering shaft 3, and changes the direction of the rotational driving force of the electric motor 6 by the gear mechanism 2 and decelerates at a predetermined ratio. To the output shaft 5. In the hypoid gear mechanism 2 of the electric power steering device 1, a hypoid ring gear 9 connected to the output shaft 5 of the steering shaft 3 and a hypoid pinion gear 10 as a predetermined gear provided on a rotation shaft of the electric motor 6. Be engaged.

[0003] The hypoid gear mechanism 2 in such an electric power steering device 1 includes:
Refer to FIG. 2 in order to eliminate the tooth contact noise due to backlash when the electric motor 6 is driven at the time of inputting vibration or the like from the road surface on which the vehicle travels or at the start of steering or when the steering wheel is turned back. The hypoid ring gear 9 includes an inner ring gear 11 and an outer ring gear 12 arranged concentrically, and the inner ring gear 11 and the outer ring gear 12
Is relatively elastically urged in its axial direction to elastically support one of the ring gears 11 and 12 so as to be movable in its axial direction, and a leaf spring 13 is urged to press against the hypoid pinion 10. is there. The tooth profiles 12c, 11c of the outer ring gear 12 and the inner ring gear 11 constitute the tooth profile of a single ring gear that is properly meshed with the pinion gear 10 when the leaf spring 13 flexes and the inner ring gear 11 moves in the axial direction. It is formed as follows. In FIG. 2, the leaf spring 13 urges the tooth surface of the inner ring gear 11 so as to protrude from the tooth surface of the outer ring gear 12 so as to press the hypoid pinion gear 10. In the gear mechanism 2 configured as described above, when the inner ring gear 11 moves in the axial direction against the urging force of the leaf spring 13 due to input of driving of the electric motor 6 and vibration from a road surface at the start of steering, The hypoid pinion gear 10 of the electric motor 6
It meshes with both the inner ring gear 11 and the outer ring gear 12.

Among such gear mechanisms, gears such as the hypoid ring gear 9 are not only formed from a general steel material, but also because they are inexpensive, easy to form, and have little tooth contact noise. In some cases, gears formed of resin have been adopted, and in recent years, gears formed by sintering have been used because they are inexpensive and easy to mold with high precision, and have excellent wear resistance. Is often adopted. As shown in FIGS. 2 and 3, the inner ring base 15 is provided separately from the inner ring gear 11 as a ring gear portion having a tooth surface formed of, for example, resin.
There is also known a gear mechanism 2 which is formed by fitting the inner ring base 15 and supporting the inner ring base 11 so as to be integral with the inner ring gear 11. In such a gear mechanism 2, the inner ring base 15 is formed by a general steel material or sintering.

[0005] As shown in FIG.
Generally, the boss 12 of the outer ring gear 12 as a base material
a ring-shaped portion 13 whose inner side in the radial direction is engaged with and supported by a
a, and a plurality of arms 13b radially extending radially outward from the ring-shaped portion 13a.
The tip of each arm portion 13b is joined to the inner ring gear 11 or the inner ring base 15. In the following description, the case where the inner ring base 15 that supports the inner ring gear 11 and the tip of each arm portion 13b of the leaf spring 13 are joined will be described.

A conventional technique for joining the ends of the inner ring base 15 and the arms 13b of the leaf spring 13 to each other is as follows. Rivet hole 1
3d and 15d are formed so as to correspond to each other, and the rivet 20 is pinched and joined by mechanical fastening means such as inserting the shaft portion of the rivet 20 into the rivet holes 13d and 15d and caulking the tip.

[0007]

However, in the prior art in which the above-mentioned gear mechanism is joined by mechanical fastening means, each arm portion 13b and the inner ring base 15 are caulked and riveted by rivets 20. The fastening is dependent on the frictional force at the interface between the two 13b and 13b. The frictional force at the interface between each arm 13b and the inner ring base 15 varies. A gap is formed between the shaft of the rivet 20 and the rivet holes 13d and 15d. On the other hand, when the inner ring gear 11 moves in the axial direction together with the inner ring base 15 against the bias of the leaf spring 13, the interface between the arm 13 b and the inner ring base 15 is deformed because the arm 13 b of the leaf spring 13 bends. The rivets 13 d and 15 d slide in the radial direction, and the rivet holes 13 d and 15 d abut against the shaft of the rivet 20. Therefore, when the sliding of the interface between the arm portion 13b and the inner ring base 15 and the abutment with the rivet 20 are repeated, the two 13
There has been a problem that the interface between b and 15 and the rivet holes 13d and 15d and the shaft portion of the rivet 20 are mutually worn, and play is caused. Further, since the frictional force varies due to the arm portion 13b, the arm portion 13b repeatedly bends, so that the fastened inner ring base 15
There is a problem that there is a possibility that a gap is generated between the spring 13 and the leaf spring 13.

Further, a member (sintered member) formed by sintering, such as the hypoid ring gear 9 or the inner ring base 15 of the gear mechanism 2, has a lower density than a general steel material, and pores remain. Sometimes. Therefore, the sintering member is replaced with, for example, the arm portion 13b of the leaf spring 13.
When joining with other members such as, for example, joining by general arc welding or gas welding, there is a possibility that the heat-affected zone is large and cracks may occur, so that it cannot be adopted. Also, YA
In the fusion bonding by welding using a G laser, a CO ₂ laser, or the like, as shown in FIG. 7, since the wavelength is long and the reflectance is high (that is, the absorption is low), It is necessary to squeeze the laser beam output with a predetermined energy by an optical system or the like to increase the energy density and irradiate the joint with the energy. However, when sintering members with low density are irradiated with such high energy density laser light,
Since the molten layer of the sintering member may be blown out and blow-out or melted off, good welding cannot be performed. In addition, since a laser beam having a long wavelength and a high reflectance is irradiated, energy efficiency cannot be improved. In addition, the laser beam having a large amount of waste and having the required energy is controlled accurately and easily. Can not. Therefore, in particular, in the conventional technique for joining a sintered member such as the inner ring base 15 formed by sintering to another member as described above, it is inexpensive, reliable and not easily separated as described above. Not only because they can be joined together, but also because they cannot be joined by welding, they have to be joined by mechanical fastening means 20 such as rivets, and there is no other choice as a joining method.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made even in a case where at least one of the members joined and fastened to each other is formed by sintering.
It is an object of the present invention to provide a method of joining sintered members and a joining structure thereof, in which these members can be easily and reliably joined to each other by welding with a simple configuration. Further, the present invention has been made in view of the above-described problems,
The ring gear and a leaf spring for elastically supporting the ring gear so as to be movable in the axial direction can be easily and reliably joined, and furthermore, the occurrence of play due to wear when the leaf spring is bent is suppressed. It is an object of the present invention to provide a bonding method that can perform the bonding. Further, the present invention has been made in view of the above-described problems, and has as its object to provide a method capable of reliably welding and joining to a leaf spring even when a ring gear is formed by sintering. I do.
Further, the present invention has been made in view of the above-mentioned problems, and a gear mechanism including a gear, a ring gear meshing with the gear, and a leaf spring for elastically supporting the ring gear movably in the axial direction. With a simple configuration, the ring gear and the leaf spring for elastically supporting the ring gear so as to be movable in the axial direction are easily and surely joined together, and furthermore, play occurs due to wear when the leaf spring is bent. It is an object of the present invention to provide a gear mechanism capable of suppressing the above.

[0010]

According to the first aspect of the present invention, there is provided a method for joining a sintered member formed by sintering and another member to achieve the above object. A laser beam is irradiated by a semiconductor laser to a joint between a sintered member and another member, and the joint is melt-joined to each other.

According to a second aspect of the present invention, there is provided a method for joining a sintered member formed by sintering to another member, the method comprising: At the joint with the member, the wavelength is 1.0 μm or less so that the reflectance is 0.6 or less, and the converging width is 1.0
It is characterized by irradiating a laser beam of not less than mm and melting and joining the joined portions.

According to a third aspect of the present invention, in order to achieve the above object, in the first or second aspect of the present invention, the sintering member and the sintering member are illuminated prior to irradiating the joint with the laser beam. Another member is fastened by mechanical fastening means.

According to a fourth aspect of the present invention, there is provided a joining structure of a sintered member formed by sintering and another member to achieve the above object. And the member is fused by a semiconductor laser while being fastened by mechanical fastening means.

According to a fifth aspect of the present invention, there is provided a method for joining a ring gear and a leaf spring, wherein the ring gear is joined to a leaf spring for elastically supporting the ring gear so as to be movable in the axial direction. Further, the ring gear and the leaf spring are welded and joined after being clamped and joined by mechanical fastening means.

According to a sixth aspect of the invention relating to a method of joining a ring gear and a leaf spring, in order to achieve the above object, in the fifth aspect of the invention, the leaf spring has a radially inner side supported by a base material. A ring-shaped portion, and an arm portion joined to a plurality of ring gears formed to extend radially outward from the ring-shaped portion in a radial direction. It is characterized by welding.

In order to achieve the above object, the invention according to a seventh aspect of the present invention relates to a method of joining a ring gear and a leaf spring, wherein the ring gear is a ring gear having a tooth surface and supports the ring gear. The base portion is joined to each arm portion of the leaf spring.

The invention according to an eighth aspect of the present invention, which relates to a method of joining a ring gear and a leaf spring, achieves the above object.
In the invention described in any one of the above, the ring gear or its base portion is formed from a sintered member, and the wavelength of the welded joint is 1.0 μm so that the reflectance is 0.6 or less.
The method is performed by irradiating a laser beam having a condensing width of 1.0 mm or more.

The invention according to claim 9 is a gear mechanism,
To achieve the above object, a gear mechanism comprising a gear, a ring gear meshing with the gear, and a leaf spring for elastically supporting the ring gear movably in an axial direction, wherein the ring gear and the leaf spring are It is characterized in that it is sandwiched and joined by a mechanical fastening means and welded.

According to a tenth aspect of the present invention, there is provided a gear mechanism according to the ninth aspect, wherein:
The leaf spring includes a ring-shaped portion whose radial inner side is supported by the base material, and an arm portion joined to a plurality of ring gears formed so as to radially extend radially outward from the ring-shaped portion, The ring gear and the respective arm portions of the leaf spring are welded to each other on the radially outer side.

According to an eleventh aspect of the present invention, in order to achieve the above object, in the invention according to the tenth aspect, the ring gear comprises a ring gear portion having tooth surfaces and a base portion supporting the ring gear portion. Wherein the base portion and each arm portion of the leaf spring are joined.

According to a twelfth aspect of the invention, there is provided a gear mechanism according to the tenth or eleventh aspect, wherein a local deformation portion is provided in each arm portion. .

According to a thirteenth aspect of the invention, there is provided a gear mechanism according to any one of the ninth to twelfth aspects, wherein the ring gear or a base thereof is formed from a sintered member. The ring gear or its base and the leaf spring are welded and joined by a semiconductor laser.

According to the first aspect of the present invention, a laser beam is efficiently output at an output precisely controlled to an appropriate energy by a semiconductor laser at a joint between a sintered member having a low density and a large number of holes remaining and another member. Due to the irradiation, the joints of the sintering members are properly melt-joined to each other without spouting or melting off. In addition, other members to be joined with the sintering member, in addition to members molded by a method other than sintering,
A member formed by sintering is also included.

According to the second aspect of the present invention, the joint between the sintered member having a low density and a large number of pores remaining and another member is
By irradiating a laser beam having a wavelength of 1.0 μm or less and a condensing width of 1.0 mm or more so that the reflectivity becomes 0.6 or less and melting and joining the joints to each other, an appropriate energy can be obtained. Since the output laser light is efficiently irradiated, the joints of the sintering members are appropriately melt-joined to each other without spouting or melting off. The other members joined to the sintering member include members formed by sintering in addition to members formed by a method other than sintering.

According to a third aspect of the present invention, in the first or second aspect, prior to irradiating the joint portion with the laser beam, the sintering member and another member are fastened by mechanical fastening means. Since the sintering member is positioned with respect to the other members, the joints can be easily and accurately welded to each other. In addition, since the sintering member and the other member are fastened by mechanical fastening means and the joining portion is further melt-joined, not only the joining between the sintering member and the other member becomes reliable, but also An external force that separates the joining surfaces can be countered by mechanical fastening means, and an external force that slides the joining surfaces can be countered by a fusion-bonded joint. can do.

According to the fourth aspect of the present invention, the sintering member and the other member are fastened by a mechanical fastening means, and are fused and joined by a semiconductor laser to prevent an external force that separates the joining surfaces from each other. Can be countered by mechanical fastening means, and can be countered by a fusion-bonded joint portion against external force that slides the joint surfaces of each other, so that the sintered member and other members can be opposed. Are securely joined. The other members joined to the sintering member include members formed by sintering in addition to members formed by a method other than sintering.

On the other hand, in the invention of claim 5, since the ring gear and the leaf spring are positioned by first sandwiching and joining the ring gear and the leaf spring by the mechanical fastening means, the ring gear and the leaf spring are easily and accurately welded. Joined. Then, against an external force generated when the ring gear moves in the axial direction and the leaf spring bends and the interface between the ring gear and the leaf spring relatively slides in the radial direction, both are restrained by welding. Oppose by being. Further, an external force such that the interface between the ring gear and the leaf spring is separated from each other is opposed by being constrained by the clamping and joining by the mechanical fastening means.

According to a sixth aspect of the present invention, in the fifth aspect of the invention, a radially intermediate position of the ring gear is sandwiched and joined to the leaf spring by mechanical fastening means, and a radially outer side of the ring gear is each of the leaf springs. It is welded to the arm.
Since the welded portion is located outside the radially intermediate position where the ring gear is mechanically fastened by the mechanical fastening means, cracks and cracks due to bending of the arm portion of the leaf spring are prevented. You.

According to a seventh aspect of the present invention, in the sixth aspect, the base portion of the ring gear integrated with the ring gear portion is joined to each arm portion of the leaf spring. The object to be joined to each arm portion of the leaf spring is applied not only to a single ring gear but also to a ring gear including a ring gear portion and a base portion.

According to an eighth aspect of the present invention, in the invention according to any one of the fifth to seventh aspects, a ring gear formed from a sintered member having a low density and a hole may remain or a base portion thereof and a leaf spring are provided. By irradiating a laser beam having a wavelength of 1.0 μm or less and a converging width of 1.0 mm or more so that the reflectance becomes 0.6 or less, a suitable energy output can be obtained. The laser beam is efficiently radiated, so that the joining portions of the ring gear formed from the sintered member or the joining portion of the base portion thereof are appropriately welded and joined without spouting or melting down.

According to the ninth aspect of the present invention, the ring gear and the leaf spring are clamped and joined by mechanical fastening means and welded, so that the ring gear moves in the axial direction and the leaf spring bends. An external force that sometimes occurs and separates the interface between the ring gear and the leaf spring is countered by restraint by sandwiching and joining using mechanical fastening means.
Further, an external force that slides on the interface between the ring gear and the leaf spring is opposed by restraint by welding.

According to a tenth aspect of the present invention, in the ninth aspect of the present invention, the radially intermediate position of the ring gear is sandwiched and joined to the leaf spring by mechanical fastening means, and the outer side of the ring gear in the radial direction is each arm of the leaf spring. And welded. Such a welded portion is located outside the radially intermediate position sandwiched and joined by the mechanical fastening means of the ring gear, so that cracks and cracks due to bending of the arm portion of the leaf spring are prevented. .

In the eleventh aspect of the present invention, in the tenth aspect of the present invention, the base of the ring gear integrated with the ring gear is joined to each arm of the leaf spring. The object to be joined to each arm portion of the leaf spring is applied not only to a single ring gear, but also to a ring gear including a ring gear portion and a base portion.

According to a twelfth aspect of the present invention, according to the tenth or eleventh aspect of the present invention, the local deformation portion is provided in each arm portion, so that when the arm portion of the leaf spring bends, its elastic deformation is locally reduced. Because the deformed part is securely allowed, an unreasonable load is not applied to the arm of the leaf spring, the axial movement of the ring gear is not hindered, and the length of the radial joint position of the arm to the ring gear is changed. To reduce the load on the mechanical fastening means and the welded part which are sandwiched and joined.

According to a thirteenth aspect of the present invention, in the invention according to any one of the ninth to twelfth aspects, a ring gear formed from a sintered member having a low density and in which pores may remain, or a base portion thereof and a leaf spring. By irradiating a laser beam of an appropriate output with a semiconductor laser to the weld joint portion of the above, the ring layer formed from the sintered member or the molten layer at the joint portion of the base portion thereof does not erupt or melt off In this case, the joint portions are appropriately welded to each other.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an embodiment of a gear mechanism according to the present invention will be described with reference to FIGS. 1 to 4 according to the case of a hypoid gear mechanism 2 used in an electric power steering apparatus 1. FIG.
It will be described in detail based on. In the drawings, the same reference numerals denote the same parts or corresponding parts.

As shown in FIG. 1, the electric power steering apparatus 1 includes an input shaft 4 connected to a manually operated steering wheel (not shown) and driven to rotate around an axis, and a steering wheel ( A steering shaft 3 having an output shaft 5 for moving a rack shaft 8 for driving the shaft (not shown) in the axial direction of the steering shaft 3, and an input shaft 4 arranged so that the drive axis is substantially perpendicular to the axis of the steering shaft 3. An electric motor 6 driven in accordance with the rotational torque; a hypoid gear mechanism 2 that reduces the rotational output of the electric motor 6 and converts the rotational direction to transmit to an output shaft; And a torque detecting means 17 for controlling the electric motor 6. Output shaft 5
Is formed with a pinion gear 7 that meshes with the rack shaft 8. The hypoid gear mechanism 2 includes a hypoid pinion gear 10 provided on a rotary drive shaft of the electric motor 6,
A hypoid ring gear 9 is provided on the output shaft 5 of the steering shaft 3 and meshes with a hypoid pinion gear 10. In the case of this embodiment, an inner ring gear (sometimes called a sub gear) 11 and a outer ring gear (sometimes called a main gear) 12 in which hypoid ring gears 9 are arranged concentrically and mesh with a hypoid pinion gear 10, respectively. And an inner ring base 15 to which the inner ring gear 11 is fitted and which supports the inner ring gear 11, and which is joined to the inner ring base 15 so as to project the inner ring gear 11 relative to the outer ring gear 12 in the axial direction thereof. And a leaf spring 13 that urges against the hypoid pinion gear 10.

The hypoid gear mechanism 2 of the present invention is
The inner ring base 15 and the leaf spring 13 are fastened by a rivet 20 as a mechanical fastening means to be clamped and joined, and are also joined by welding to restrain radial displacement of the leaf spring 13 with respect to the inner ring base 15. In this example, a welding portion 21 is provided. Further, the leaf spring 13 is provided with a locally deformed portion 22. In this embodiment, the inner ring base 15 for supporting the inner ring gear 11 is formed by sintering, and a welding portion 21 is provided by semiconductor laser welding to be welded to the leaf spring 13 as described later. Are joined.

As shown in FIGS. 2 and 3, the outer ring gear 12 has a boss 12a formed at the center thereof so as to be non-rotatably engaged with the output shaft 5 of the steering shaft 3, and is provided around the boss 12a. An annular recess 12b is formed. On the outer circumference of one surface of the outer ring gear 12, a hypoid tooth profile 12c having a predetermined number of teeth meshing with a hypoid pinion gear 10 provided on a rotary drive shaft of the electric motor 6 is formed in an annular array.

The inner ring gear 11 is formed in a substantially annular shape, and on one surface thereof, like the outer ring gear 12, is engaged with a hypoid pinion gear 10 provided on a rotary drive shaft of the electric motor 6. A hypoid tooth profile 11c having a predetermined number of teeth is formed. In the case of this embodiment, when the hypoid gear mechanism 2 is completely assembled, the inner ring gear 11 is press-fitted into the inner ring base 15 and is substantially integrated.

Hypoid tooth profiles 12c, 11 formed on the outer ring gear 12 and the inner ring gear 11.
c is such that when the leaf spring 13 is bent and the inner ring gear 11 moves in the axial direction and meshes with the pinion gear 10, it forms a tooth profile as a single hypoid ring gear that meshes properly with the pinion gear 10. Is formed.

The inner ring base 15 extends in the axial direction and has a support portion 15 into which the inner ring gear 11 is fitted.
a, an outer flange portion 15b extending radially outward, and an inner flange portion 15c extending radially inward, and are integrally formed by sintering.

The leaf spring 13 is formed of spring steel, and has a ring-shaped portion 13a engaged with the boss 12a of the outer ring gear 12, and extends radially outward from the ring-shaped portion 13a. A plurality of arm portions 13b each having a tip joined to the inner ring gear 11 or the inner ring base 15 are provided. In the case of the embodiment shown in FIG. 4, an opening is formed at the center of the ring-shaped portion 13a of the leaf spring 13 so as to be fitted into the boss 12a of the outer ring gear 12 so as not to rotate relatively. The arm portion 13b is formed so as to extend radially from the ring-shaped portion 13a at equal angles around the axis. Radial outer end of each arm 13b and inner ring base 15
The rivet holes 13d and 15d are respectively formed at substantially the center in the radial direction (width direction) of the outer flange 15b so as to correspond to each other. The inner ring gear 1
1. Outer flange 15b of inner ring base 15
Is formed on the other surface opposite to the one surface on which the hypoid tooth profile 11c is formed, so as to retract the head or swaged portion of each rivet 20.
e is formed. Rivets 20 for each arm 13b
As shown in FIG. 3, a locally deformed portion 22 is formed radially inward of the position through which is inserted. The locally deformed portion 22 is formed by bending the arm portion 13b in the plane direction so that the cross section becomes substantially V-shaped or U-shaped.
When the inner ring gear 11 and the outer ring gear 12 form a tooth shape as a single hypoid ring gear, as the inner ring gear 11 descends in the figure, the locally deformed portion 22 bent in the plane direction is elastically deformed.
It is configured to be able to absorb a change in the radial length at the position where the lowered arm 13 b is joined to the inner ring base 15.

In the embodiment shown in FIG.
The upper surface in the vicinity of the radially outer end of each arm portion 13b and the lower surface of the outer flange 15b of the inner ring base 15 are in contact with each other, and the shaft portion of the rivet 20 is inserted into the rivet holes 13d, 15d. The rivet 20 is mechanically fastened by caulking the tip of the shaft portion. Shaft of rivet 20 and rivet holes 13d, 15d
A gap is necessarily formed between the two. On the other hand, a welding portion 21 is formed by a semiconductor laser welding described later on the foremost end of the arm portion 13b of the leaf spring 13 that is further radially outward than the rivet 15 and the outer peripheral edge of the outer flange 15b of the inner ring base 15. Is formed.

Although the present invention is not limited to this embodiment and is not shown, bolts and nuts are used instead of rivets, or the tip of each arm portion 13b of the leaf spring 13 is provided. While forming a screw hole, a female screw hole is formed in the inner ring base 15 so as to correspond to the screw hole, and a screw member such as a screw or a bolt is inserted into the screw hole and fastened to the female screw hole. Alternatively, a configuration in which an engagement portion and an engaged portion are provided on each of the arm portions 13b of the leaf spring 13 and the inner ring base 15 is also included.
In the present specification, a rivet 20, a bolt and a nut, a screw member, or an engaging portion and an engaged portion, which are inserted into holes (13d, 15d) provided in at least one of these members and joined to each other, It is referred to as mechanical fastening means. That is, the mechanical fastening means according to the present invention comprises the respective arm portions 13 b of the leaf spring 13 and the inner ring base 15.
Can be pinched and joined so as not to be separated from each other in the axial direction, but each arm portion 13b of the leaf spring 13 and the inner ring base 15 can be displaced in the radial direction by moving the inner ring gear 12 in the axial direction. Means a fastening means having a certainty.

An opening formed in the ring-shaped portion 13a of the leaf spring 13 is inserted into the boss 12a (base material) of the outer ring gear 12 at a predetermined position in the axial direction via a spacer 23, and is supported. Furthermore, the outer ring gear 1
The second boss 12a is fitted outside the press-fitting rings 25 and 26 so that the plate-shaped pressing spring member 24 is held at a predetermined interval with respect to the leaf spring 13. The outer peripheral edge of the restraining spring member 24 is in contact with the inner flange 15c so as to restrain the inner ring base 15 supported by the leaf spring 13. With this configuration, the inner ring gear 11 integrated with the inner ring base 15 is housed in the annular concave portion 12b of the outer ring gear 12, and is elastically supported so as to be movable in the axial direction. . The protrusion amount of the tooth surface of the inner ring gear 11 from the tooth surface of the outer ring gear 12 is as follows:
It is adjusted by the thickness of the spacer 23 in the axial direction.

The gear mechanism 2 of the present invention is not limited to this embodiment. As shown in FIG. 5, the lower surface of the radially outer end of each arm portion 13b of the leaf spring 13 is connected to the inner ring base. 15 can be brought into contact with the upper surface of the inner flange 15c and mechanically fastened by a rivet 20 or the like. Further, although not shown, the upper surface of the radially outer tip of each arm portion 13b of the leaf spring 13 is omitted. And the lower surface of the inner flange 15 c of the inner ring base 15 can be brought into contact with each other and mechanically fastened by the rivets 20. Further, as shown in FIG. 6, the inner ring gear 11 integrally formed with the flange 11b is formed by sintering without the inner ring gear 11 being fitted to and supported by the inner ring base 15.
The arm portion 13b of the leaf spring 13 can be directly mechanically fastened to the lower surface or the upper surface (not shown) of b.
In any of these cases, the leading end, which is radially outside the rivet hole 13d of each arm portion 13b of the leaf spring 13, is welded to the inner ring base 15 or the inner ring gear 11.

Further, the gear mechanism 2 of the present invention comprises a leaf spring 13.
The inner ring base 15 or the inner ring gear 11 to be fastened is not limited to the one formed by sintering, but may be applied to a metal formed by other than sintering, such as a general metal such as steel. As described above, when the inner ring base 15 or the inner ring gear 11 formed by means other than sintering is welded to the plate spring 13, for example, an electron beam, a YAG laser, a CO ₂ laser, or the like other than the semiconductor laser welding described later. Welding, general arc welding, gas welding, high frequency welding, or the like, the joints of a plurality of members are welded and joined together so as to be continuous, and the inner ring base 15 or the inner ring gear 11 and the leaf spring 13 are joined together. Any method can be used as long as it can restrain movement such that the joint surface (interface) with the slidably slides in the radial direction.

In the electric power steering apparatus 1 configured as described above, by manually steering a steering wheel (not shown), the pinion gear 7 formed on the output shaft 5 of the steering shaft 3 is rotated around the axis. The rack shaft 8 meshed with the pinion gear 7 is moved in the axial direction to drive steered wheels (not shown). At this time, the torque detecting means 17 controls the driving of the electric motor 6 based on the rotational torque of the input shaft 4, and outputs the assisting force of the electric motor 6 as necessary to the output of the steering shaft 3 via the hypoid gear mechanism 2. Rotate in addition to shaft 5.

When the drive of the electric motor 6 is not controlled, the inner ring gear 11 is urged to protrude from the outer ring gear 12 by a leaf spring, so that the hypoid provided on the rotating shaft of the electric motor 6 is provided. The backlash is removed by being engaged with the pinion gear 10 so as to be pressed. Therefore, when the vehicle is running, vibrations from the road surface and the like are generated by the output shaft 5.
, Or when the steering shaft 4 is rotated or turned back to start steering,
Hypoid ring gear 9 and hypoid pinion gear 10
The occurrence of abnormal noise such as rattling noise between the two is suppressed. When the drive of the electric motor 6 is controlled, the leaf spring 1
The inner ring gear 11 meshed with the hypoid pinion gear 10 is urged to protrude from the outer ring gear 12 by 3 to move in the axial direction, and together with the outer ring gear 12, a tooth profile as a single hypoid ring gear is formed. Properly meshed.

When the inner ring gear 11 moves in the axial direction and the arm 13b of the leaf spring 13 bends, the position of the arm 13b in the radial direction to which the inner ring base 15 is joined changes, so that both abutments are brought into contact. Relative displacement occurs between the surfaces, and the rivet 20 and the rivet hole 13d or 15d attempt to abut.

Here, it is assumed that the arm portion 13b of the leaf spring 13 and the inner ring base 15 are joined only by welding. In such a case, the arm 13 b and the inner ring base 15
The periphery of b will be welded. Therefore, when the inner ring gear 11 moves in the axial direction and the arm 13b of the leaf spring 13 bends, the bending of the arm 13b is not mechanically fastened with the rivet 20 or the like. The external force in the direction of separating the interface is directly received by the welding portion 21, and the stress is concentrated on the welding portion 21. Therefore, when the inner ring base 15 is raised by the urging of the leaf spring 13 in a case where the both 13 and 15 are joined as shown in FIG. 3, as shown in FIG. When a crack or a crack K occurs and the inner ring base 15 descends, the leaf spring 13 acts in a leverage manner as shown in FIG.
A crack or a crack K will be generated outside of the element 1.

However, in the present invention, as shown in FIG. 8, the arm portion 13b of the leaf spring 13 and the inner ring base 15 are fastened by the rivets 20 and clamped and joined to restrain bending deformation due to the bending of the leaf spring 13. At the same time, the displacement parallel to the interface is restrained by welding the inner ring base 15 and the inner ring base 15 by welding at the radially outer side, so that an excessive load is not applied to the welding portion 21 and stress is not concentrated. Since the relative displacement of the interface does not occur, the rivet 20 does not collide with the rivet hole 13d or 15d.
Since no friction occurs at the interface between b and 15, the occurrence of backlash due to wear is suppressed. Further, as shown in FIG. 9, when the arm portion 13 b is provided with the locally deformable portion 22 that can be elastically deformed, the load due to the bending of the arm portion 13 b is reduced. There is no need to strongly clamp and join the base 15 to restrain bending deformation.

Next, the joining method of the ring gear and the leaf spring according to the present invention will be described with reference to the outer flange (joining portion of the sintering member) 15b of the inner ring base 15 and the arm of the leaf spring 13 formed by the sintering member as described above. A more detailed description will be given in connection with the case of joining the outermost end of the portion 13b in the radial direction (joining portion of another member).

The method of joining a ring gear and a leaf spring according to the present invention is a method for joining an inner ring base 15 and a leaf spring 13 which elastically supports the inner ring base 15 so as to be movable in the axial direction. Base 1
5 and the arm portion 13b of the leaf spring 13 are sandwiched and joined by mechanical fastening means such as a rivet 20, and also welded. Then, the inner ring base 15 and the arm portion 13b are welded and joined on the radially outer side.

As described above, the inner ring base 15 made of a sintered member has a low density compared with a general steel material and may have holes. Arc welding and gas welding cannot be adopted. In the case of welding with a YAG laser or a CO ₂ laser, as shown in FIG. 7, since the wavelength is long and the reflectance is high, the laser beam is narrowed down by an optical system or the like in order to melt the joint, and the energy density is reduced. It is necessary to irradiate the joint with a high energy and a predetermined energy. However, when the sintering member is to be welded by irradiating the laser beam having such a high energy density, a molten layer is blown out and blowout occurs or burns out. Therefore, good welding cannot be performed.

Therefore, in the method for joining a ring gear and a leaf spring according to the present invention, the reflectance of the inner ring base 15 made of a sintered member and the welded joint portion of the arm portion 13b is set to 0.6 or less. Wavelength is 1.0 μm
In this case, laser light having a condensing width of 1.0 mm or more is irradiated.

As described above, each of the arm portions 13b of the leaf spring 13 has a locally deformed portion 22 located at an intermediate portion thereof.
And a rivet hole 13d located in the vicinity of the tip end are formed in advance. First, each of the arm portions 13b of the leaf spring 13 thus formed is so aligned that the rivet holes 13d are aligned with the rivet holes 15d provided substantially at the center in the radial direction of the outer flange 15b of the inner ring base 15.
The rivet hole 13 is brought into contact with the inner ring base 15.
By inserting the shaft portion of the rivet 20 as a mechanical fastening means into the inner ring base 15 as a sintering member, the shaft portion of the rivet 20 as a mechanical fastening means is inserted into the inner ring base 15. for that reason,
Since the leaf spring 13 and the inner ring base 15 are positioned so as to be relatively immovable relative to each other, there is no need for a jig or the like for positioning when welding and joining by laser light later.

Next, a laser beam is irradiated by a semiconductor laser, and the outermost edge (joining portion) of the outer side of the outer flange 15b of the inner ring base 15 and the outermost edge (joining portion) of the outer portion 15b of the inner ring base 15 are radiated. Fusion bonding. Laser light emitted by a semiconductor laser at a predetermined output is:
The wavelength is set to be 1.0 μm or less, and the light collection width is set to be 1.0 mm or more. By setting the wavelength to 1.0 μm or less, as shown in FIG. 7, the reflectance of the irradiated laser light is 0.6 or less (that is, the absorption is 0.4 or more). Therefore, both joints 13b, 1
In order to melt 5d, it is not necessary to narrow the laser beam to increase the energy density unlike the related art, and the width (condensing width) in the moving direction of the laser beam is 1.0 mm wider than that of the related art. The above can be considered. Therefore, the energy density of the laser beam applied to both of the joints 13b and 15d can be suppressed low, so that even when the sintered member having a low density is applied, the molten layer is blown out to cause blowout or melting. Good welding can be performed without dropping. According to the present invention, when the sintering member 15 and the other member 13 are joined to each other, there is no choice but to use only the mechanical fastening means 20 in the prior art. In addition to the pinching and joining by the temporary fastening means 20, welding joining can be performed. In addition, since the absorption rate can be increased by irradiating a laser beam having a short wavelength with a semiconductor laser, the energy efficiency can be improved, and the laser beam having the required energy can be stably and accurately output at a predetermined output. Irradiation can be easily controlled. Note that the converging width can be rephrased as the converging diameter when the irradiated laser beam is substantially circular.

The joining method of the present invention is not limited to the above-described embodiment, and the member to be joined to the leaf spring 13 is made of a material other than the sintered member, such as a general metal such as steel. The present invention is also applicable to a case in which sintered members are joined together, or a sintered member is joined to another member formed by means other than sintering, such as a case where the inner ring base 15 is an inner ring gear 11 made of a sintered member or a non-sintered member. Can be.

Further, the bonding method of the present invention is not limited to the above-described embodiment, and a laser beam applied to a bonding portion is irradiated with a laser beam having a wavelength of 1.0 or less so that the reflectance becomes 0.6 or less.
A laser other than a semiconductor laser can also be used as long as it can be set to be not more than μm and the light collection width should be not less than 1.0 mm.

As described above, when the inner ring gear 11 moves in the axial direction against the bias of the leaf spring 13 to form a single hypoid ring gear that is appropriately meshed with the pinion gear 10 together with the outer ring gear 12. In particular, in the case of the structure shown in FIG. 5, the lower surfaces of the radially outer ends of the arms 13b of the leaf spring 13 which are interfaces that abut each other and the inner flange 15 of the inner ring base 15
An external force is generated that separates the upper surface of c from the upper surface. However, according to the joining method of the present invention, the inner ring base 1
5 or a gear mechanism in which the inner ring gear 11 and the leaf spring 13 are joined to each other.
Since the pin spring is pinched and joined by 0 to restrict the bending deformation due to the bending of the leaf spring 13, it is possible to sufficiently oppose such external force. When the arm 13b of the leaf spring 13 bends and the inner ring gear 11 moves in the axial direction, the position of the arm 13b in the radial direction at which the inner ring base 15 is joined changes, so that the two 13b, Relative displacement occurs at the interface of the rivet 20 and the rivet hole 1.
An external force is generated such that 3d or 15d tries to collide. However, in the gear mechanism in which the inner ring base 15 or the inner ring gear 11 and the leaf spring 13 are joined by the joining method of the present invention, the semiconductor laser is welded and joined, and the relative movement in the radial direction due to the deflection of the leaf spring 13 ( Since the displacement is restrained, it is possible to sufficiently oppose such external force. Therefore, the inner ring base 15 or the inner ring gear 11 and the leaf spring 1
3 or the rivet holes 13d, 15
There is no backlash due to the abutment of d with the shaft portion of the rivet 20 as the mechanical fastening means, and the connection between the inner ring base 15 or the inner ring gear 11 and the leaf spring 13 is ensured, so that the hypoid gear mechanism can be accurately formed. It will work.

[0063]

According to the first aspect of the present invention, the joint between the sintering member and another member is irradiated with a laser beam by a semiconductor laser, and the joints are melt-joined to each other. It is possible to provide a method for joining sintered members, which can appropriately melt-join the joined portions without causing the molten layer of the portions to erupt or melt down.

According to the second aspect of the present invention, the wavelength is 1.0 μm or less at the joint between the sintering member and another member so that the reflectance is 0.6 or less, and the converging width is 1. By irradiating a laser beam of 0 mm or more and fusion-bonding the joints to each other, a laser beam having an appropriate energy output is efficiently radiated, so that a molten layer at the joint of the sintering member is ejected or melts down. Thus, it is possible to provide a method of joining sintered members that can appropriately melt-join the joined portions without joining.

According to the third aspect of the present invention, in the first or second aspect of the invention, prior to irradiating the joint portion with the laser beam, the sintered member and another member are fastened by mechanical fastening means. Thereby, since the sintering member and the other member are positioned, it is possible to easily and accurately fusion-bond the joints to each other, and further, the sintering member and the other member are joined by the mechanical fastening means. After being fastened, the joining portion is further fused and joined, so that external forces such as separating the joining surfaces can be opposed by mechanical fastening means, and the joining surfaces can slide on each other. It is possible to provide a method of joining sintered members that can be countered by an external force that is caused by a fusion-bonded joint.

According to the fourth aspect of the present invention, the sintering member and another member are fastened by mechanical fastening means.
Due to the fusion bonding by the semiconductor laser, external forces such as separating the bonding surfaces can be opposed by mechanical fastening means, and against external forces such as sliding the bonding surfaces. Since it is possible to oppose each other by the fusion-bonded joint, it is possible to provide a joint structure of the sintered member that can surely join the sintered member and another member.

According to the fifth aspect of the present invention, the ring gear and the leaf spring can be easily and accurately joined by sandwiching and joining the ring gear and the leaf spring by mechanical fastening means and then by welding. In addition, it is possible to provide a joining method capable of suppressing generation of play and the like due to wear when the leaf spring is bent.

According to a sixth aspect of the present invention, in the fifth aspect of the present invention, each arm of the ring gear and the leaf spring is
Since the welded portion is welded outside in the radial direction, the welded portion is located outside the radially intermediate position sandwiched and joined by the mechanical fastening means of the ring gear, so that the crack due to the bending of the arm portion of the leaf spring. It is possible to provide a joining method capable of preventing occurrence of cracks and the like.

According to the seventh aspect of the present invention, in the sixth aspect of the present invention, not only is the case where each arm of the leaf spring is directly joined to a single ring gear but also the case where it is joined to the base of the ring gear. Can be provided.

According to an eighth aspect of the present invention, in the invention according to any one of the fifth to seventh aspects, the wavelength of the welded joint is 1.0 μm or less so that the reflectance is 0.6 or less;
A laser beam having a condensing width of 1.0 mm or more is irradiated to form a ring gear formed from a sintered member whose density is low and pores may remain, or a weld joint portion between a base portion thereof and a leaf spring. In order to efficiently irradiate a laser beam with an appropriate energy output on the ring gear formed from the sintered member or the melted layer at the joint of the base of the ring gear or the melted layer at the joint of the base, the joints of the ring gear and the base of the ring gear are welded to each other. Since it is possible to perform appropriate welding connection, it is possible to provide a method capable of reliably performing welding connection with a leaf spring even when the ring gear or its base portion is formed of a sintered member.

According to the ninth aspect of the present invention, the ring gear and the leaf spring are sandwiched and joined by mechanical fastening means and are welded together, so that the ring gear and the ring gear can be axially connected to each other. A leaf spring for movably elastically supporting the leaf spring is easily and reliably joined, and an external force generated when the ring gear moves in the axial direction and the leaf spring bends away from the interface between the ring gear and the leaf spring. Can be counteracted by restraint by pinching and joining using mechanical fastening means, and external force that slides at the interface between the ring gear and the leaf spring can be countered by restraint by welding. Therefore, it is possible to provide a gear mechanism capable of suppressing generation of play and the like due to wear when the leaf spring is bent.

According to a tenth aspect of the present invention, in the ninth aspect of the present invention, the leaf spring has a ring-shaped portion whose radially inner side is supported by the base material, and a radially outer portion extending from the ring-shaped portion. An arm portion joined to a plurality of ring gears formed so as to extend radially, and each of the arm portions of the ring gear and the leaf spring is welded and joined on a radially outer side thereof, so that such a welded portion is formed. However, since it is located outside the radially intermediate position where the ring gear is mechanically fastened and joined by the mechanical fastening means, a gear mechanism that can prevent the occurrence of cracks and cracks due to bending of the arm portion of the leaf spring. Can be provided.

According to an eleventh aspect of the present invention, in the invention of the tenth aspect, the ring gear comprises a ring gear portion having a tooth surface and a base portion supporting the ring gear portion. The gear that can be joined to each arm of the leaf spring by being joined to each arm can be applied not only to a single ring gear but also to a ring gear consisting of a ring gear and a base. A mechanism can be provided.

According to the twelfth aspect of the present invention, in the invention of the tenth or eleventh aspect, the local deformation portion is provided in each arm portion, so that when the arm portion of the leaf spring bends, its elastic deformation is reduced. Since the local deformation portion allows the arm portion of the leaf spring unreasonably, the axial movement of the ring gear is not hindered and the length of the radial joint position of the arm portion to the ring gear is not hindered. In order to reliably function so as to absorb the change in load, it is possible to reduce the load on the mechanical fastening means and the welded joint that are being clamped and joined, and to prevent the occurrence of cracks and cracks in the welded joint. In addition, a gear mechanism having a longer life can be provided.

According to the thirteenth aspect, the ninth to the ninth aspects
2. In the invention according to any one of (2) and (3), the ring gear or its base portion is formed from a sintered member, and the ring gear or its base portion and the leaf spring are welded to each other by a semiconductor laser, so that the density is low. For a ring gear formed from a sintered member that may remain, or a welded joint between its base and a leaf spring,
Since the semiconductor laser can irradiate the laser beam with an appropriate output, the joint layer of the ring gear formed from the sintered member or the melted layer of the joint portion of the base portion does not squirt or melt off, and the joint portion of each other is formed. An appropriately welded gear mechanism can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a hypoid gear function of an electric power steering apparatus to which the present invention is applied.

FIG. 2 is a partially enlarged sectional view of FIG.

FIG. 3 is a partially enlarged sectional view of FIG. 2 for explaining a joint state of an inner ring base and a leaf spring.

FIG. 4 is a bottom view of a state where the inner ring base and the leaf spring are joined.

FIG. 5 is a cross-sectional view for explaining another embodiment of a joint state between an inner ring base and a leaf spring.

FIG. 6 is a cross-sectional view for explaining still another embodiment of a joint state between an inner ring base and a leaf spring.

FIG. 7 is a graph showing the reflectance with respect to the wavelength of laser light.

FIG. 8 is a perspective view showing that the arm portion of the leaf spring and the inner ring base are fastened to each other by rivets and welded according to the present invention. FIG. 7 is an explanatory view showing that there is no relative displacement between the joints.

FIG. 9 is an explanatory view showing that a load on a joint portion due to bending of an arm portion is reduced by providing a locally deformable portion capable of elastic deformation in an arm portion of a leaf spring according to the present invention.

FIG. 10 shows a case where it is assumed that the arm portion of the plate-shaped leaf spring and the inner ring base are joined only by welding.
It is an expanded sectional view for explaining a state where a crack or a crack occurs inside a welding part when an inner ring base is raised by the bias of a leaf spring.

FIG. 11 shows a case where it is assumed that an arm portion of a plate-shaped leaf spring and an inner ring base are joined only by welding.
It is an expanded sectional view for explaining the state where a leaf spring acts like this when an inner ring base descends, and a crack or a crack occurs outside a welding part.

[Description of sign]

 Reference Signs List 2 hypoid gear mechanism 9 hypoid ring gear 10 hypoid pinion gear 11 inner ring gear 12 outer ring gear 13 leaf spring 13a ring-shaped part 13b arm 15 inner ring base (sintered member) 20 rivet 21 welded part 22 locally deformed part

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3D033 CA04 3J030 BB03 BB17 BC02 BC10 CA10 4E068 BA00 CA04 CA07 CA11 CD01 DA03 DB00

Claims (13)

[Claims] 1. A method for joining a sintered member formed by sintering and another member, wherein the joint between the sintered member and the other member is irradiated with a laser beam by a semiconductor laser to join each other. A method for joining sintered members, wherein the portions are melt-joined. 2. A method for joining a sintered member formed by sintering and another member, wherein a wavelength of the joint between the sintered member and the other member is set so that the reflectance is 0.6 or less. A laser beam having a converging width of not more than 1.0 μm and a condensing width of not less than 1.0 mm to melt-join the joined portions. 3. The method according to claim 1, wherein the sintering member and another member are fastened to each other by a mechanical fastening means before the laser beam is applied to the joining portion. . 4. A joint structure between a sintered member formed by sintering and another member, wherein the sintered member and the other member are fastened by mechanical fastening means and fused by a semiconductor laser. Characteristic joint structure of sintered members. 5. A joining method of a ring gear and a leaf spring for elastically supporting the ring gear movably in an axial direction, wherein the ring gear and the leaf spring are welded and joined after being clamped and joined by mechanical fastening means. A method for joining a ring gear and a leaf spring, characterized in that: 6. A leaf spring has a ring-shaped portion whose radial inner side is supported by a base material and an arm portion joined to a plurality of ring gears extending radially outward from the ring-shaped portion. 6. The method according to claim 5, wherein each of the arm portions of the ring gear and the leaf spring is welded and joined on a radially outer side thereof. 7. The ring gear according to claim 6, wherein the ring gear includes a ring gear portion having a tooth surface and a base portion supporting the ring gear portion, and the base portion and each arm portion of the leaf spring are joined. The joining method of the ring gear and the leaf spring described in the above. 8. The ring gear or its base is formed from a sintered member, and the welded joint has a reflectance of 0.6.
The ring gear and plate according to any one of claims 5 to 7, wherein the irradiation is performed by irradiating a laser beam having a wavelength of 1.0 µm or less and a condensing width of 1.0 mm or more so that: Spring joining method. 9. A gear mechanism comprising a gear, a ring gear meshing with the gear, and a leaf spring for elastically supporting the ring gear movably in an axial direction, wherein the ring gear and the leaf spring are mechanically fastened. A gear mechanism characterized in that the gear mechanism is sandwiched and joined by means and welded. 10. A leaf spring having a ring-shaped portion whose radial inner side is supported by a base material and an arm portion joined to a plurality of ring gears extending radially outward from the ring-shaped portion. The gear mechanism according to claim 9, wherein the ring gear and each arm portion of the leaf spring are welded to each other on a radially outer side thereof. 11. A ring gear comprising: a ring gear portion having a tooth surface; and a base portion supporting the ring gear portion, wherein the base portion and each arm portion of the leaf spring are joined. The gear mechanism according to claim 10. 12. The gear mechanism according to claim 10, wherein a locally deformed portion is provided on each arm. 13. The ring gear or its base portion is formed of a sintered member, and the ring gear or its base portion and a leaf spring are welded and joined by a semiconductor laser. 2. The gear mechanism according to 1.