阅读说明：本技术 摆线减速机及其制造方法以及马达单元 (Cycloidal reducer, method for manufacturing same, and motor unit ) 是由 诹访正和 于 2020-03-18 设计创作，主要内容包括：本发明的课题在于通过使构成内齿的销构件低损耗地旋转来实现低噪声化以及高效率化。摆线减速机(1)具备：外齿轮(4),其以能够相对于输入轴(2)的旋转中心(C)偏心旋转的方式安装；内齿轮(5),其具有与外齿轮的各外齿(4t)内接啮合而挠曲并且旋转的多个外销(50)、以及具有圆筒状的内表面并将各个外销保持为旋转自如的保持器(51)；以及载架(6),其仅将外齿轮的自转分量导出。保持器(51)具有沿轴向凹陷设置于其内表面上而保持外销的多个销槽(51a)、以及以横断销槽(51a)的方式在其内表面的整周上凹陷设置的凹槽(51b)。在凹槽(51b)的边缘设置有在外销挠曲且旋转的状态下与外销的外周面面接触的滚动面(51d)。(The invention aims to realize low noise and high efficiency by rotating a pin member constituting internal teeth with low loss. A cycloidal speed reducer (1) is provided with: an external gear (4) that is mounted so as to be capable of eccentric rotation with respect to the rotation center (C) of the input shaft (2); an internal gear (5) having a plurality of outer pins (50) that are bent and rotated while being inscribed and meshed with the outer teeth (4t) of the external gear, and a retainer (51) that has a cylindrical inner surface and rotatably holds the outer pins; and a carrier (6) for deriving only the rotation component of the external gear. The retainer (51) has a plurality of pin grooves (51a) recessed in the axial direction on the inner surface thereof to retain the outer pins, and a groove (51b) recessed across the pin grooves (51a) over the entire circumference of the inner surface thereof. A rolling surface (51d) which is in surface contact with the outer peripheral surface of the outer pin in a state where the outer pin is flexed and rotated is provided at the edge of the recessed groove (51 b).)

1. A cycloidal reducer is characterized by comprising:

an external gear attached to be eccentrically rotatable with respect to a rotation center of the input shaft;

an internal gear having a plurality of outer pins that are flexed and rotated while being in inner-contact engagement with the respective outer teeth of the external gear, and a retainer that has a cylindrical inner surface and rotatably holds the respective outer pins; and

a carrier which derives only a rotation component of the external gear,

the retainer has a plurality of pin grooves recessed in an axial direction on the inner surface to retain the outer pins, and a groove recessed in a manner intersecting the pin grooves over an entire circumference of the inner surface,

a rolling surface that comes into surface contact with an outer circumferential surface of the outer pin in a state where the outer pin is flexed and rotated is provided at an edge of the groove.

2. The cycloidal reducer of claim 1,

in the pin groove, an inner diameter at a position of the rolling surface is larger than an outer diameter of the outer pin, and the inner diameter at a position other than the rolling surface is equal to the outer diameter of the outer pin.

3. The cycloidal reducer of claim 1 or 2,

the retainer is formed of a soft material softer than a material of the outer pin,

the rolling surface is formed by sliding contact when the outer pin rotates.

4. The cycloidal reducer of claim 3,

the outer pin is formed of a ferrous material,

the holder is formed of an aluminum-based material.

5. The cycloidal reducer according to any one of claims 1-4,

the cycloid speed reducer includes a guide portion that keeps a positional relationship in an axial direction of the external gear, the retainer, and the external pin constant.

6. A method of manufacturing a cycloidal reducer, the cycloidal reducer comprising: an external gear attached to be eccentrically rotatable with respect to a rotation center of the input shaft; an internal gear having a plurality of outer pins that are bent and rotated while being in inner-contact engagement with the outer teeth of the external gear, and a retainer that rotatably retains the outer pins; and a carrier for deriving only a rotation component of the external gear,

the method for manufacturing a cycloid speed reducer is characterized by comprising the following steps:

a groove forming step of forming a plurality of pin grooves extending in an axial direction and holding the outer pin, and a groove extending over an entire circumference of the inner surface so as to intersect the pin grooves, in a recessed manner in a cylindrical inner surface of a member to be the holder; and

and a rolling surface forming step of forming a rolling surface by rotating the input shaft to bend and rotate the outer pin toward the inside of the groove, thereby bringing the outer pin into sliding contact with an edge of the groove.

7. The method of manufacturing a cycloidal reducer according to claim 6,

in the groove forming step, an inner surface of the pin groove is formed as a semi-cylindrical surface having an inner diameter equal to an outer diameter of the outer pin and being constant in an axial direction,

in the rolling surface forming step, the rolling surface is cut so that the inner diameter at a position of the rolling surface is larger than the inner diameter at a position other than the rolling surface.

8. A motor unit is characterized by comprising:

the cycloidal reducer of any one of claims 1-5; and

and a motor having a motor rotating shaft connected to the input shaft of the cycloidal reducer.

Technical Field

The present invention relates to a cycloidal reducer, a method of manufacturing the cycloidal reducer, and a motor unit including the cycloidal reducer.

Background

Conventionally, a cycloidal reducer (an internal planetary gear reducer) including an internal planetary gear mechanism and a constant speed internal gear mechanism is known. A typical cycloidal reducer includes an external gear capable of rotating eccentrically with respect to an input shaft, an internal gear meshing with the external gear, a member for deriving only a rotation component of the external gear, and an output shaft connected to the member. For example, patent document 1 discloses a reduction gear in which internal teeth of an internal gear fixed to a housing are formed by external pins loosely fitted into pin holes.

In this reduction gear, the external gear rotates in a swinging manner together with the rotation of the input shaft, and the rotation of the input shaft is output as a reduced rotation (rotation) of the external gear by meshing with an external pin corresponding to the internal teeth of the internal gear and the external gear. As in the reduction gear of patent document 1, since the pin member (outer pin) is used for the internal teeth of the internal gear and the external gear are in rolling contact with each other, mechanical loss (loss) can be reduced and high gear efficiency can be obtained.

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made in view of the above problems, and an object of the present invention is to reduce noise and increase efficiency by rotating a pin member constituting internal teeth with low loss. It is to be noted that the present invention is not limited to these objects, and another object of the present invention is to provide operational effects by the respective configurations described in the embodiments described later, that is, operational effects that cannot be obtained by the conventional technique.

Means for solving the problems

(1) The cycloid speed reducer disclosed herein includes: an external gear attached to be eccentrically rotatable with respect to a rotation center of the input shaft; an internal gear having a plurality of outer pins that are flexed and rotated while being in inner-contact engagement with the respective outer teeth of the external gear, and a retainer that has a cylindrical inner surface and rotatably holds the respective outer pins; and a carrier that derives only a rotation component of the external gear. The retainer has a plurality of pin grooves recessed in the axial direction on the inner surface to hold the outer pins, and a groove recessed across the entire circumference of the inner surface so as to intersect the pin grooves. In addition, a rolling surface that comes into surface contact with an outer circumferential surface of the outer pin in a state in which the outer pin is flexed and rotated is provided at an edge of the concave groove.

(2) Preferably, in the pin groove, an inner diameter at a position of the rolling surface is larger than an outer diameter of the outer pin, and the inner diameter at a position other than the rolling surface is equal to the outer diameter of the outer pin.

(3) Preferably, the retainer is formed of a soft material softer than a material of the outer pin, and the rolling surface is formed by sliding contact when the outer pin rotates.

(4) More preferably, the outer pin is formed of an iron-based material, and the retainer is formed of an aluminum-based material.

(5) Preferably, the cycloid speed reducer includes a guide portion that keeps a positional relationship in an axial direction of the external gear, the retainer, and the external pin constant.

(6) The manufacturing method disclosed herein is a manufacturing method of a cycloid speed reducer, the cycloid speed reducer including: an external gear attached to be eccentrically rotatable with respect to a rotation center of the input shaft; an internal gear having a plurality of outer pins that are bent and rotated while being in inner-contact engagement with the outer teeth of the external gear, and a retainer that rotatably retains the outer pins; and a carrier that derives only a rotation component of the external gear. The manufacturing method includes: a groove forming step of forming a plurality of pin grooves extending in an axial direction and holding the outer pin, and a groove extending over an entire circumference of the inner surface so as to intersect the pin grooves, in a recessed manner in a cylindrical inner surface of a member to be the holder; and a rolling surface forming step of forming a rolling surface by rotating the input shaft to bend and rotate the outer pin toward the inside of the groove, thereby making sliding contact with the edge of the groove.

(7) Preferably, in the groove forming step, an inner surface of the pin groove is formed into a semi-cylindrical surface having an inner diameter equal to an outer diameter of the outer pin and being constant in an axial direction, and in the rolling surface forming step, the rolling surface is cut so that the inner diameter at a position of the rolling surface is larger than the inner diameter at a position other than the rolling surface.

(8) The motor unit disclosed herein includes the cycloidal reducer according to any one of (1) to (5) above; and a motor having a motor rotating shaft connected to the input shaft of the cycloidal reducer.

Effects of the invention

According to the disclosed aspect, the outer pins constituting the internal teeth can be rotated with low loss, and therefore, noise reduction and efficiency improvement can be achieved.

Drawings

Fig. 1 is a diagram illustrating a motor unit according to an embodiment, and schematically illustrates a motor, showing a cycloidal reducer in an axial cross-sectional view.

Fig. 2 is a sectional view taken along line a-a of fig. 1.

Fig. 3 is a perspective view showing an outer pin holder provided to the cycloid speed reducer of fig. 1.

Fig. 4 is a perspective view of the cycloidal reducer of fig. 1.

Fig. 5 is a diagram for explaining the rolling surfaces of the cycloid speed reducer of fig. 1, showing the driving state of the speed reducer.

Fig. 6 is a diagram for explaining the rolling surfaces of the cycloid speed reducer of fig. 1, showing a stopped state of the speed reducer.

Fig. 7 is a flowchart illustrating a method of manufacturing the cycloid speed reducer according to the embodiment.

Description of reference numerals:

1 speed reducer (cycloidal reducer)

2 input shaft

4 outer gear

4t external tooth

5 internal gear

6 carrying frame

7 outer cover (guiding part)

10 Motor

11 motor rotating shaft

22 gasket (guiding part)

50 outer pin

51 outer pin keeper (keeper)

51a pin slot

51b groove

51d rolling surface

Center of rotation of C

Detailed Description

A cycloid speed reducer, a method of manufacturing the same, and a motor unit according to embodiments will be described with reference to the drawings. The embodiments described below are merely examples, and are not intended to exclude the application of various modifications and techniques not explicitly described in the following embodiments. The respective configurations of the present embodiment can be variously modified and implemented without departing from the gist thereof. Further, they can be selected as needed, or can be appropriately combined.

[1. Structure ]

Fig. 1 is a diagram showing a motor unit of the present embodiment, and shows a cycloidal reducer 1 (hereinafter, referred to as "reducer 1") in a cross-sectional view taken along an axial direction, and a motor 10 in a schematic view. In addition, a partially enlarged view is shown in the lower right of the figure. The reducer 1 is an internal planetary gear reducer composed of an internal planetary gear mechanism and a constant-speed internal gear mechanism. The reduction gear 1 of the present embodiment is connected to the motor 10 to form a unit, and reduces the rotational speed of the motor 10 to output the reduced rotational speed. The motor 10 is, for example, a dc motor having a rotor (not shown) that rotates integrally with the motor rotating shaft 11 and a stator (not shown) fixed to the motor housing 12. The motor 10 shown in fig. 1 is an example, and the type, size, and shape thereof are not particularly limited.

The speed reducer 1 of the present embodiment includes an input shaft 2, an output shaft 3, an external gear 4, an internal gear 5, a carrier 6, and a housing 7. Hereinafter, each element will be described with reference to fig. 1 to 6. Fig. 2 is a sectional view taken along line a-a of fig. 1, fig. 3 is a perspective view showing an outer pin holder 51 (holder) described later, and fig. 4 is a perspective view of the reduction gear 1. Fig. 5 and 6 are views for explaining the main part of the reduction gear 1, and fig. 5 shows a driving state of the reduction gear 1 and fig. 6 shows a stopped state of the reduction gear 1.

As shown in fig. 1, the input shaft 2 is a hollow shaft that inputs power of the motor 10 to the reduction gear unit 1, and is coupled to a motor rotation shaft 11 (shown by a broken line in fig. 1) of the motor 10. The input shaft 2 of the present embodiment includes a cylindrical portion 2a having a rotation center C as a central axis, an eccentric portion 2b formed in an axially intermediate portion of the cylindrical portion 2a, and a key groove 2C provided along an axially recessed inner circumferential surface of the cylindrical portion 2 a. The rotation center C of the cylindrical portion 2a coincides with both the center of the motor rotation shaft 11 of the motor 10 and the rotation center of the output shaft 3.

The eccentric portion 2b is a cylindrical portion formed by bulging radially outward from the outer peripheral surface of the cylindrical portion 2 a. The center C' of the eccentric portion 2b is slightly offset from the rotation center C of the cylindrical portion 2 a. The key groove 2c is a groove into which a key (not shown) is fitted for coupling the input shaft 2 and the motor rotating shaft 11 of the motor 10. An inner ring of a ball bearing 9 (second rolling bearing) is fixed to both ends of the cylindrical portion 2 a. Both end portions of the input shaft 2 are rotatably supported by the ball bearings 9.

The output shaft 3 is a hollow shaft for outputting the power amplified by the reduction gear 1, and is disposed coaxially with the cylindrical portion 2a of the input shaft 2. The output shaft 3 of the present embodiment includes a cylindrical portion 3a having a rotation center C as a central axis, and a flange portion 3b formed at one end portion of the cylindrical portion 3 a. The flange portion 3b is a portion for coupling the output shaft 3 and the carrier 6, and is formed with a plurality of through holes (not shown). A fastening connector 31 for connecting to the carrier 6 is fastened to each through hole. In addition, the object may be directly coupled to the carriage 6 when driven to output the output, and in this case, the output shaft 3 may be omitted.

The external gear 4 is a gear that is attached to be eccentrically rotatable with respect to the rotation center C of the input shaft 2. As shown in fig. 1 and 2, the external gear 4 of the present embodiment is externally fitted to the eccentric portion 2b of the input shaft 2 via a needle bearing 21 in a relatively rotatable manner. The external gear 4 is restricted by the washer 22 in such a manner that its axial position does not shift.

As shown in fig. 2, outer teeth 4t having trochoid tooth profiles or circular arc tooth profiles are provided on the outer periphery of the outer gear 4. The external gear 4 has a plurality of cylindrical carrier pin holes 4h axially penetrating around a center hole into which the needle bearings 21 are fitted. In the external gear 4 of the present embodiment, six carrier pin holes 4h are arranged at equal intervals (shifted in phase every 60 degrees) in the circumferential direction on the same circumference. In the reduction gear 1 of the present embodiment, one external gear 4 is attached to the input shaft 2.

The internal gear 5 is a substantially cylindrical gear located on the outer periphery of the external gear 4. As shown in fig. 1 and 2, the internal gear 5 includes a plurality of outer pins 50 that are engaged with the respective external teeth 4t so as to flex and rotate, and an outer pin holder 51 that rotatably holds the respective outer pins 50. The outer pin 50 is a cylindrical pin member that is so thin that it is deflected by a force from the external gear 4 during rotation, and is disposed so that its axial direction is parallel to the rotation center C to function as internal teeth. The number of outer pins 50 (the number of internal teeth) in the present embodiment is a value obtained by adding 1 to the number of external teeth 4t of the outer gear 4. The difference between the number of outer pins 50 (the number of internal teeth) and the number of external gear 4 may be a natural number other than 1 depending on the design of the reduction gear ratio or the like.

As shown in fig. 3, the outer pin holder 51 has a cylindrical outer shape, and the outer pin holder 51 has a cylindrical inner surface. An inner surface of the outer pin holder 51 is formed with a substantially semicircular pin groove 51a recessed in the axial direction and a recessed groove 51b recessed so as to intersect the pin groove 51 a. The pin grooves 51a are grooves for holding the outer pins 50, are provided in the same number as the outer pins 50, and the curvature of the pin grooves 51a substantially coincides with the curvature of the outer pins 50. On the other hand, the groove 51b is a groove for holding a lubricant (e.g., grease or oil), and is formed on the entire circumference of the inner surface of the outer pin holder 51. The outer pin holder 51 of the present embodiment is formed of a soft material softer than the material of the outer pin 50. For example, the outer pin holder 51 is formed of a soft material such as an aluminum-based material (aluminum alloy) or resin, and the outer pin 50 is formed of an iron-based material.

Here, the inner surface shape of the outer pin holder 51 will be described in detail with reference to fig. 5 and 6. The upper right diagrams in fig. 5 and 6 are cross-sectional views obtained by cutting the outer pin holder 51, the outer pin 50, and the external gear 4 along the axial center of the outer pin 50 meshing with the external teeth 4t of the external gear 4. The upper left drawing in fig. 5 and 6 is an enlarged view of the periphery of the edge of the recessed groove 51b, the lower center drawing in fig. 5 is an orthogonal axis cross-sectional view taken at the edge, and the lower center drawing in fig. 6 is an orthogonal axis cross-sectional view taken at the pin groove 51a other than the edge. Here, the "edge" means a corner formed by the bottom surface of the pin groove 51a and the side surface of the recess 51b, and two edges are provided for each pin groove 51 a. As shown in fig. 3, each edge has a semicircular arc shape when viewed in the axial direction.

As shown in fig. 5 and 6, a rolling surface 51d that comes into surface contact with the outer peripheral surface of the outer pin 50 in a state where the outer pin 50 is flexed and rotated is provided on the edge of the concave groove 51b of the outer pin holder 51. In the driving state of the reduction gear 1, the outer pin 50 receives a force (lateral pressure) from the external gear 4 as indicated by an open arrow in fig. 5. Thereby, the outer pin 50 is flexed and rotated toward the radially outer side of the internal gear 5, and rolls and slides in the pin groove 51a as shown in a B-B sectional view. The rolling surface 51d is in surface contact with the outer peripheral surface of the outer pin 50 in this rotated state. In other words, as shown enlarged in fig. 6, the rolling surface 51d is formed in a shape in which the edge of the groove 51b is chamfered.

In the reduction gear 1 of the present embodiment, the rolling surface 51d is cut by sliding contact during rotation of the outer pin 50. Since the outer pin 50 of the present embodiment is a hard material harder than the outer pin holder 51, when the outer pin 50 rotates in a flexed state and continues to slide in contact with the edge, the edge is gradually cut into a substantially arc shape by the outer pin 50 by a predetermined amount, and finally the rolling surface 51d has a cylindrical shape or a shape having a clearance enough to allow the outer pin 50 to smoothly rotate. The edge is blunted at a timing of coming into contact with a predetermined surface of the outer peripheral surface of the outer pin 50. The state in which the wear of the edge is saturated is a state in which the outer pin 50 is most likely to roll, and a portion formed (chamfered) at the edge at this time is the rolling surface 51d described above.

In the outer pin holder 51 of the present embodiment, there are portions having different inner diameters (radii) in one pin groove 51 a. Specifically, the inner diameter at the position of the rolling surface 51d is larger than the inner diameter at the position other than the rolling surface 51 d. The inner diameter of the pin groove 51a is set to be equal to the outer diameter of the outer pin 50 at the position of the rolling surface 51 d. Thus, in the stopped state of the reduction gear 1, as shown in the cross-sectional view orthogonal to the axis in fig. 6, the gap between the outer peripheral surface of the outer pin 50 and the inner surface of the pin groove 51a is substantially zero. On the other hand, as shown in the cross-sectional view orthogonal to the axis in fig. 5, the inner diameter at the position of the rolling surface 51d is larger than the outer diameter of the outer pin 50. Therefore, in the driving state of the reduction gear 1, the gap between the outer peripheral surface of the outer pin 50 and the inner surface of the pin groove 51a is increased, and backlash occurs, so that the outer pin 50 can rotate with low loss.

As shown in fig. 2 and 3, a plurality of through holes 51c through which fastening members 73 for fastening the internal gear 5 and the housing 7 are inserted are provided in parallel in the circumferential direction in the outer pin holder 51. That is, the outer pin holder 51 of the internal gear 5 is fixed to the housing 7 without rotating. Therefore, although the external gear 4 meshing with the internal gear 5 rotates with the eccentric rotation of the input shaft 2, the position of the outer pin 50 meshing with the external teeth 4t does not move, and therefore the external gear 4 oscillates in the direction opposite to the rotation direction of the input shaft 2 by receiving the reaction force from the outer pin 50. Specifically, when the input shaft 2 rotates once, the external gear 4 is shifted in the opposite direction to the internal gear 5 by an amount corresponding to one tooth (rotates). That is, the rotation of the input shaft 2 rotates the external gear 4 in the reverse direction at a speed that is reduced by the inverse number of the number of teeth (1/number of teeth) of the external gear 4.

The housing 7 is a member that houses elements other than the output shaft 3. As shown in fig. 1 and 4, the housing 7 of the present embodiment is configured such that a first housing portion 71 disposed on the motor 10 side (right side in the figure) and a second housing portion 72 disposed on the output shaft 3 side (left side in the figure) are coupled to each other by a plurality of fastening members 73. Each of the first casing 71 and the second casing 72 has a bottomed cylindrical shape and has a circular opening 7a in the bottom. The two housing portions 71 and 72 are attached so as to sandwich the outer pin holder 51 from both axial sides.

The housing 7 of the present embodiment has only a slight gap between both axial end surfaces of the outer pin holder 51 and the end surfaces of the outer pins 50 to such an extent that the outer pins 50 can rotate in the field without lateral displacement, and the axial positions thereof are restricted from being displaced from each other. As described above, the axial position of the external gear 4 is restricted by the washer 22. That is, in the reduction gear 1 of the present embodiment, the housing 7 and the washer 22 function as a guide portion that keeps the axial positional relationship among the external gear 4, the outer pin holder 51, and the outer pin 50 constant. Thereby, the outer peripheral surface of the outer pin 50 and the rolling surface 51d are maintained in a predetermined contact state in the driving state.

The carrier 6 is a member that derives only the rotational component of the external gear 4 described above and transmits the derived component to the output shaft 3. As shown in fig. 1, the carrier 6 includes carrier pins 60 that rotate in inscribed relation with the carrier pin holes 4h of the external gear 4, and support portions 61 that support the carrier pins 60. The carrier pins 60 are cylindrical pin members, are arranged such that the axial direction thereof is parallel to the rotation center C, and have a function of guiding only the rotation component of the external gear 4. As shown in fig. 2, in the carrier 6 of the present embodiment, six carrier pins 60 are provided, and a needle bearing 62 is attached to each carrier pin 60. That is, in the present embodiment, the carrier pins 60 contact the inner peripheral surfaces of the carrier pin holes 4h via the needle bearings 62, whereby the carrier pins 60 rotate the support portions 61 (the carriers 6) while suppressing sliding loss between the carrier pins 60 and the support portions 61.

As shown in fig. 1, the support portion 61 is a portion that supports one end portion of each of the carrier pins 60, and connects all of the carrier pins 60. The carrier pins 60 of the present embodiment are supported so as not to be rotatable relative to the support portions 61 around the axial centers thereof, and the carrier pins 60 and the support portions 61 of the carrier 6 rotate integrally. The flange portion 3b of the output shaft 3 is fixed to the support portion 61. Thereby, the output shaft 3 rotates integrally with the carrier 6. One end of each carrier pin 60 may be supported by the support portion 61 via a bearing, a bush, or the like so as to be relatively rotatable.

Further, the carriage 6 of the present embodiment has two support portions 61 that support both end portions of the carriage pin 60, respectively. The two support portions 61 are disposed to face each other with the external gear 4 interposed therebetween, and support both ends of each carrier pin 60. Each support portion 61 is fixed to an outer ring of the ball bearing 9 that supports the input shaft 2, and is fixed to an inner ring of the ball bearing 8 that rotatably supports the carrier 6 on the outer side. The outer ring of the ball bearing 8 is fixed to the housing 7.

That is, the radially outer ball bearing 8 rotatably supports the support portion 61 with respect to the housing 7, and the radially inner ball bearing 9 rotatably supports the input shaft 2 with respect to the carrier 6. In the reduction gear 1 of the present embodiment, two ball bearings 8 and 9 are provided, and they are disposed at the same axial position. The term "the same axial position" as used herein means not only that the axial positions of the end surfaces of the two ball bearings 8 and 9 are completely matched, but also that the respective balls of the ball bearings 8 and 9 partially overlap in the radial direction. This reduces the axial dimension of the housing 7, and reduces the size of the reduction gear 1.

[2. production method ]

Fig. 7 is a flowchart illustrating an example of the manufacturing method of the speed reducer 1. The following description will focus mainly on a method of forming the inner surface shape of the outer pin holder 51. The components such as the input shaft 2 and the output shaft 3 are prepared in advance.

First, a plurality of pin grooves 51a for holding the outer pins 50 are formed along the axial direction in the cylindrical inner surface of the member (cylindrical member having a constant thickness in the axial direction) serving as the outer pin holder 51 shown in fig. 3 (step S1). In step S1, the inner surface of the pin groove 51a is formed as a semi-cylindrical surface having an inner diameter equal to the outer diameter of the outer pin 50 and being constant in the axial direction. The number of the pin grooves 51a is the same as the number of teeth of the internal gear 5, and the arrangement of the pin grooves 51a is set at equal intervals in the circumferential direction of the inner surface of the outer pin holder 51. A minute gap is provided between two circumferentially adjacent pin grooves 51 a.

Next, the above-described concave groove 51b is formed in the inner surface of the member to be the outer pin holder 51 (step S2). The concave groove 51b extends over the entire circumference of the inner surface so as to intersect the axial intermediate portion of the pin groove 51a, and is recessed into a substantially rectangular shape having a larger depth dimension than the pin groove 51 a. In this stage, a corner (edge) formed by the bottom surface of the pin groove 51a and the side surface of the groove 51b is right-angled. Steps S1 and S2 are referred to as a groove forming step.

After the groove forming process, the input shaft 2, the output shaft 3, the external gear 4, the internal gear 5, the carrier 6, and the housing 7 are assembled (step S3). Then, the input shaft 2 is rotated (the reduction gear 1 is driven), and the outer pin 50 is bent and rotated toward the inside of the groove 51b, thereby being in sliding contact with the edge of the groove 51b to form (cut) the rolling surface 51d (step S4). In other words, when the edge is worn by the outer pin 50, the amount of wear reaches a certain amount without further cutting, and the rolling surface 51d is formed. This step S4 is referred to as a rolling surface forming step.

In the rolling surface forming step, the rolling surface 51d is formed by cutting the edge of the concave groove 51b, and therefore the inner diameter of the pin groove 51a is increased at the position of the rolling surface 51 d. In the rolling surface forming step of the present embodiment, the rolling surface 51d is formed such that the inner diameter at the position of the rolling surface 51d is larger than the inner diameter at the position other than the rolling surface 51 d. In this way, the inner surface shape of the outer pin holder 51 is formed through the groove forming step and the rolling surface forming step.

[3. Effect ]

(1) According to the speed reducer 1 described above, since the rolling surface 51d that comes into surface contact with the outer pin 50 during the bending rotation is provided at the edge of the concave groove 51b, the outer pin 50 can be easily rolled. This enables the outer pin 50 constituting the internal teeth to rotate with low loss, thereby achieving low noise and high efficiency.

(2) In the reduction gear 1 described above, since the pin grooves 51a have portions with different inner diameters, different gap portions can be used separately between when the reduction gear 1 is driven and when it is stopped. That is, during driving, the outer pin 50 is bent and rotated on the rolling surface 51d having a large clearance between the outer peripheral surface of the outer pin 50 and the inner surface of the pin groove 51a, so that a large backlash between the external teeth 4t and the internal teeth (outer pin 50) can be secured, and the rotation loss of the outer pin 50 can be reduced. On the other hand, when the reduction gear 1 is stopped, the outer pin 50 does not flex and the clearance is reduced, so that the backlash between the external teeth 4t and the internal teeth (outer pin 50) can be reduced.

(3) In the speed reducer 1 described above, the outer pin holder 51 is formed of a soft material softer than the outer pin 50, and the rolling surface 51d is formed by the outer pin 50 itself by sliding contact during rotation of the outer pin 50, so the outer pin 50 can be brought into the most easily rolled state. Therefore, the outer pin 50 can be rotated with less loss, and thus noise reduction and efficiency improvement can be achieved. Further, high-precision machining is required to increase the cylindricity of the pin groove 51a to reduce noise, but since this is not necessary, the manufacturing cost can be reduced.

(4) For example, if the outer pin holder 51 is formed of an aluminum-based material and the outer pin 50 is formed of an iron-based material, the rolling surface 51d can be reliably formed on the outer pin holder 51 by the flexural rolling sliding of the outer pin 50.

(5) Further, since the above-described reduction gear 1 is provided with the housing 7 and the washer 22 as the guide portions for maintaining the axial positional relationship among the external gear 4, the external pin holder 51, and the external pin 50 constant, the position of the force applied to the external pin 50 by the external gear 4 can be made constant. This makes it possible to keep the amount of deflection (the manner of deflection) of the outer pin 50 constant, and to constantly rotate the outer pin 50 on the rolling surface 51d, thereby stably achieving low noise and high efficiency.

(6) Since the groove forming step and the rolling surface forming step are included in the above-described manufacturing method, the rolling surface 51d can be formed by the outer pin 50 itself, and the outer pin 50 can be brought into the most easily rolled state. Therefore, the outer pin 50 can be rotated with less loss without requiring high-precision machining, and therefore, noise reduction, high efficiency, and cost reduction can be achieved.

(7) Further, according to the above-described manufacturing method, the pin grooves 51a can be provided with portions having different inner diameters, and different gap portions can be used separately between when the reduction gear 1 is driven and when it is stopped. This ensures a large backlash between the external teeth 4t and the internal teeth (outer pin 50) during driving, reduces the rotation loss of the outer pin 50, and reduces the backlash between the external teeth 4t and the internal teeth (outer pin 50) during stopping.

(8) Further, according to the motor unit configured by the reducer 1 and the motor 10 described above, since the outer pin 50 can be rotated with low loss, it is possible to achieve low noise and high efficiency even in the entire motor unit.

[4. other ]

The reduction gear 1 and the motor unit are examples, and are not limited to the above configuration. In the speed reducer 1 described above, the rolling surface 51d is formed by the outer pin 50 itself as an example, but the rolling surface 51d may be formed by machining. In this case, the material of the outer pin holder 51 and the outer pin 50 is not particularly limited, and for example, the outer pin holder 51 and the outer pin 50 may be formed of the same material. If at least the edge of the recessed groove 51b of the outer pin holder 51 is provided with the rolling surface 51d formed in a shape that comes into surface contact with the outer peripheral surface of the outer pin 50 in a state where the outer pin 50 is bent and rotated (a driving state of the reduction gear 1), the outer pin 50 can be rotated with low loss, and therefore, noise reduction and efficiency improvement can be achieved.

The pin groove 51a is formed to have an inner diameter equal to the outer diameter of the outer pin 50 at a position other than the rolling surface 51d, but may be formed to have an inner diameter slightly larger than the outer diameter of the outer pin 50. The pin groove 51a may have a shape and size such that at least the outer pin 50 can rotate in the pin groove 51 a. The number of the outer pins 50 constituting the internal teeth and the number of the pin grooves 51a supporting the outer pins 50 are not limited to the above numbers. Further, the reduction gear 1 described above is provided with one external gear 4, but the number of external gears 4 may be two or more. In the above-described reduction gear 1, the housing 7 and the washer 22 function as a guide, but a dedicated member having a function as a guide may be separately provided, and the guide may be omitted.

The configurations of the input shaft 2, the output shaft 3, and the housing 7 are not limited to the above configurations. For example, the input shaft 2 may be extended to protrude to the outside of the first housing portion 71, or the cylindrical portion 2a and the eccentric portion 2b may be separately provided and then coupled to each other. The needle bearing 21 is fixed to the eccentric portion 2b of the input shaft 2, but the support structure of the input shaft 2 is not particularly limited. The fixing structure of the output shaft 3 and the carrier 6 is not particularly limited, and the housing 7 may be an integral structure.

Further, the above-described carriage 6 is provided with two support portions 61 that support both end portions of the carriage pin 60, respectively, but only one support portion 61 may be provided to support one end portion of the carriage pin 60. In this case, the other end portion of the carrier pin 60 has a one-side support structure supported only at one end. Further, the needle bearing 62 may not be mounted on the carrier pin 60. The two ball bearings 8 and 9 are disposed at the same axial position, but the axial positions of the bearings 8 and 9 may be different from each other. The bearings 8 and 9 may be rolling bearings, and the type thereof is not limited to ball bearings.