CN110425256B

CN110425256B - Gear transmission device

Info

Publication number: CN110425256B
Application number: CN201910754253.0A
Authority: CN
Inventors: 熊谷隆秀; 服部泰幸
Original assignee: Nabtesco Corp
Current assignee: Nabtesco Corp
Priority date: 2014-04-30
Filing date: 2015-04-30
Publication date: 2023-02-28
Anticipated expiration: 2035-04-30
Also published as: JP6310764B2; CN105041981A; KR20150125570A; CN105041981B; DE102015207762A1; JP2015209956A; CN110425256A; KR102337724B1

Abstract

The invention provides a gear transmission device with excellent torque transmission efficiency. The gear transmission device (100) comprises an internal gear (10) and an external gear (28). The external gear (28) rotates eccentrically with respect to the internal gear (10). The internal gear (10) has an internal gear member (6) and a cylindrical member (8). The cylindrical member (8) is inserted into a groove (9) provided on the inner peripheral surface of the inner tooth member (6). The external gear (28) meshes with the internal gear (10) by contacting the cylindrical member (8). In the gear transmission device (100), the direction of the grain on the peripheral surface of the cylindrical member (8) is different from the direction of the grain on the surface of the groove (9).

Description

Gear transmission device

The application is characterized in that the application date is 2015, 4 and 30 months, the application number is 201510218547.3, and the inventive name is as follows: a divisional application of the chinese patent application for "gear transmission".

Technical Field

The present specification discloses a technique related to a gear transmission.

Background

There is known a gear transmission device including an internal gear and an external gear that eccentrically rotates with respect to the internal gear while meshing with the internal gear. In such a gear transmission, an internal gear is sometimes formed by inserting a cylindrical member into a groove provided on an inner peripheral surface of an internal gear member. Japanese patent application laid-open No. 2013-185619 discloses the following gear transmission: the surface roughness of the circumferential surface of the cylindrical member (outer pin) in the axial direction is made smaller than the surface roughness thereof in the circumferential direction, thereby reducing friction between the cylindrical member and the groove (outer pin groove). In the following description, japanese patent application laid-open No. 2013-185619 is referred to as patent document 1. Patent document 1 also describes the following: by making the surface roughness of the surface of the groove in the axial direction smaller than the surface roughness thereof in the circumferential direction, friction between the cylindrical member and the groove can be reduced.

Disclosure of Invention

Problems to be solved by the invention

In the gear transmission device of patent document 1, friction between the cylindrical member constituting the internal gear and the groove is reduced, thereby reducing loss due to friction. However, when the friction between the cylindrical member and the groove is reduced, there is a case where the friction between the cylindrical member (the teeth of the internal gear) and the external gear becomes small. As a result, sliding may occur between the internal gear and the external gear. If slip occurs between the internal gear and the external gear, the transmission efficiency of torque is reduced. The present specification discloses a technique for achieving a gear transmission device having excellent torque transmission efficiency while solving the above-described problems.

Means for solving the problems

The technology disclosed in this specification relates to a gear transmission device including: an internal gear; and an external gear that rotates eccentrically with respect to the internal gear. In the gear transmission, the internal gear has an internal gear member and a cylindrical member inserted into a groove provided on an inner peripheral surface of the internal gear member. In addition, the external gear meshes with the internal gear by contacting the cylindrical member. In the gear transmission disclosed in the present specification, the coefficient of friction between the cylindrical member and the external gear is larger than the coefficient of friction between the cylindrical member and the groove.

In the above gear transmission, the columnar member (the teeth of the ring gear) can rotate in the groove. Specifically, when the external gear rotates eccentrically with respect to the internal gear while meshing with the internal gear, the cylindrical member rotates with respect to the groove. The coefficient of friction between the cylindrical member and the external gear is larger than the coefficient of friction between the cylindrical member and the groove. Therefore, the cylindrical member can roll with respect to the external gear by rotating in the groove. That is, the cylindrical member functions as a rolling bearing with respect to the external gear. Since the sliding between the cylindrical member and the external gear can be suppressed, the torque transmission loss of the gear transmission can be reduced. The columnar member functions as a sliding bearing with respect to the groove.

The "external gear that eccentrically rotates with respect to the internal gear" described above includes not only a system in which the external gear eccentrically rotates with respect to the axis of the gear transmission but also a system in which the internal gear eccentrically rotates with respect to the axis of the gear transmission. That is, the "external gear that eccentrically rotates with respect to the internal gear" means that one of the internal gear and the external gear eccentrically rotates with respect to the axis of the gear transmission, and the internal gear and the external gear eccentrically rotate relatively.

Drawings

Fig. 1 is a sectional view of a gear transmission of embodiment 1.

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

Fig. 3 is an enlarged view of a portion surrounded by a broken line III of fig. 2.

Description of the reference numerals

6. An internal tooth member; 8. a cylindrical member; 9. a groove; 10. an inner gear; 28. an outer gear; 100. gear transmission device

Detailed Description

Hereinafter, several technical features of the gear transmission disclosed in the present specification will be described. The matters described below are each technically practical.

The gear assembly may include an internal gear and an external gear. The internal gear and the external gear may eccentrically rotate relative to each other while meshing with each other. That is, the external gear may eccentrically rotate while meshing with the internal gear. Alternatively, the internal gear may eccentrically rotate while meshing with the external gear. The internal gear may include an internal gear member and a cylindrical member inserted into a groove provided on an inner peripheral surface of the internal gear member. In other words, the internal gear may be formed of a groove formed in the inner peripheral surface of the internal gear member and a cylindrical member inserted into the groove. Hereinafter, in this specification, the groove formed in the inner peripheral surface of the inner gear member may be referred to as an insertion groove.

In the case of the type in which the external gear rotates eccentrically, the housing of the gear transmission may also serve as an internal gear member. That is, the internal gear may be formed on the inner periphery of the housing. In this case, the carrier, the crankshaft, and the external gear may be disposed inside the housing. The crankshaft may be rotatably supported by the carrier. The crankshaft may have an eccentric body. The external gear may be engaged with an eccentric body of the crankshaft and eccentrically rotated with the rotation of the crankshaft. The inner gear may have a different number of teeth from that of the outer gear.

The columnar member inserted into the insertion groove may function as a tooth of the inner gear. In this case, an inner peripheral surface of the internal gear member located between the adjacent insertion grooves may function as a tooth groove of the internal gear. The insertion grooves may have an arc shape in a cross section orthogonal to the axis of the gear transmission. The plurality of insertion grooves may extend along an axis of the gear assembly. In this case, the respective insertion grooves may be provided at equal intervals in the circumferential direction of the internal gear member.

When the insertion groove is arc-shaped, the center of an imaginary circle on which the surface of the insertion groove is located may be located on the rotation axis of the cylindrical member, and the diameter of the imaginary circle may be substantially equal to the diameter of the cylindrical member. The cylindrical member may rotate in the insertion groove while contacting the external gear. That is, when the external gear rotates eccentrically relative to the internal gear while meshing with the internal gear, the cylindrical member may rotate in the insertion groove.

When the gear transmission is driven, the coefficient of friction between the cylindrical member and the external gear may be larger than the coefficient of friction between the cylindrical member and the insertion groove. More specifically, the coefficient of friction (rolling coefficient of friction) at the time when the cylindrical member starts sliding against the tooth surface of the external gear may be larger than the coefficient of friction (rolling coefficient of friction) at the time when the cylindrical member starts sliding against the insertion groove. In addition, the surface roughness of the surface of the insertion groove may be smaller than the surface roughness of the tooth surface of the external gear. In this case, the surface roughness may be achieved at different values by machining with different tools. Alternatively, after the insertion groove and the external gear are machined, machining for removing the texture of the surface of the insertion groove may be performed.

The surface roughness of the tooth surface of the external gear may be ra0.2 μm to ra0.5 μm. In the case where the surface roughness is less than ra0.2 μm, sufficient friction cannot be obtained between the cylindrical member and the tooth surface of the external gear, possibly causing the cylindrical member to slide with respect to the tooth surface of the external gear. If the surface roughness is larger than ra0.5 μm, heat generation and the like are likely to occur during driving, and the durability (life) of the external gear may be reduced. Further, in the case where the surface roughness of the tooth surface of the outer gear is Ra0.2 μm to Ra0.5 μm, the surface roughness of the insertion groove may be less than Ra0.2 μm.

The surface roughness of the insertion groove may be less than ra0.3 μm. Further, the surface roughness of the insertion groove may be preferably Ra0.2 μm or less, and particularly preferably Ra0.1 μm or less. In order to avoid the complicated machining process and the increased machining time of the insertion groove, the surface roughness of the insertion groove may be 0.01 μm or more. Further, in the case where the surface roughness of the insertion groove is less than ra0.3 μm, the surface roughness of the tooth surface of the external gear may be ra0.3 μm to ra0.5 μm.

The direction of the texture of the circumferential surface of the cylindrical member may be the same as the direction of the texture of the tooth surface of the external gear. By making the directions of the textures the same, the friction coefficient between the cylindrical member and the external gear can be increased, and sliding of the cylindrical member with respect to the tooth surface of the external gear can be suppressed. Further, the direction of the texture on the circumferential surface of the columnar member may be different from the direction of the texture on the surface of the insertion groove. When the directions of the textures are different, the friction coefficient between the cylindrical member and the insertion groove becomes small, and the cylindrical member is easily slid with respect to the insertion groove. By making the cylindrical member easily slide with respect to the insertion groove, the friction coefficient between the cylindrical member and the external gear can be relatively increased. The direction of the texture on the circumferential surface of the columnar member may be orthogonal to the direction of the texture on the surface of the insertion groove. In addition, the texture refers to a machining mark generated on the surface of the part when the part is machined.

A covering portion may be provided on the surface of the insertion groove. In this case, the friction coefficient between the covering portion and the cylindrical member may be smaller than the friction coefficient between the surface of the insertion groove and the cylindrical member. That is, by providing the covering portion, the cylindrical member can be easily slid with respect to the insertion groove, as compared with the case where no covering portion is provided. The covering portion may be a carbon, fluorine resin, or molybdenum coating film formed on the surface of the insertion groove. It is also possible to reduce the surface roughness of the surface of the insertion groove by providing a covering portion on the surface of the insertion groove.

Examples

Example 1

The basic configuration of the gear transmission 100 is explained with reference to fig. 1 and 2. Fig. 1 shows a longitudinal section through a gear mechanism 100 (a section through the gear mechanism 100 along an axis 12). Fig. 2 shows a cross-sectional view of the gear transmission 100 (a cross-sectional view of the gear transmission 100 along a line orthogonal to the axis 12). The gear transmission 100 includes an internal gear 10, a carrier 4, a crankshaft 14, and an external gear 28.

The internal gear 10 has a housing 6 and an internal gear 8. The internal gear 10 is formed by disposing the plurality of internal gear pins 8 on the inner periphery of the housing 6. The inner pin 8 is cylindrical and inserted into an insertion groove 9 formed in the inner circumferential surface 7 of the housing 6. The insertion grooves 9 are provided at equal intervals in the circumferential direction on the inner periphery of the housing 6. In addition, the insertion groove 9 extends parallel to the axis 12 of the gear transmission 100. That is, the inner pins 8 are provided at equal intervals in the circumferential direction on the inner periphery of the housing 6 and extend parallel to the axis 12. The housing 6 is an example of an internal gear member, and the internal gear pin 8 is an example of a cylindrical member.

The carrier 4 is rotatably supported by the casing 6 via a pair of bearings 22 (hereinafter, may be referred to as main bearings 22). The main bearing 22 restricts movement of the carrier 4 in the axial direction and the radial direction with respect to the casing 6. In the gear transmission 100, angular ball bearings are used as the main bearings 22. The carrier 4 has a first plate 4a and a second plate 4c. The first plate 4a has a columnar portion 4b. The columnar portion 4b extends from the first plate 4a toward the second plate 4c and is fixed to the second plate 4c with bolts 34. The bolt 34 passes through the second plate 4c and is fastened to a bolt groove 34a provided on the columnar portion 4b.

Positioning pins (not shown) for positioning in the circumferential direction are inserted into the columnar portion 4b and the second plate 4c. Fig. 2 shows a pin hole 36 provided in the columnar portion 4b. The second plate 4c is also provided with pin holes (not shown). The positioning pins are inserted into the pin holes 36 through the pin holes of the second plate 4c. Further, an oil seal 18 is disposed between the housing 6 and the first plate 4a.

The crankshaft 14 is rotatably supported by the carrier 4 via a pair of bearings 20. The pair of bearings 20 restricts the movement of the crankshaft 14 in the axial direction and the movement in the radial direction with respect to the carrier 4. In the gear transmission 100, tapered roller bearings are used as the pair of bearings 20. The crankshaft 14 has an input gear 32 and two eccentric bodies 30. The eccentric body 30 is disposed between the pair of bearings 22. The eccentric body 30 is engaged with the external gear 28 via the cylindrical roller bearing 26. The external gear 28 is supported by the carrier 4 via the crankshaft 14. The input gear 32 is disposed outside the pair of bearings 20.

In the gear transmission 100, torque of a motor (not shown) is transmitted to the input gear 32. When the torque of the motor is transmitted to the input gear 32, the crankshaft 14 rotates, and the eccentric body 30 rotates eccentrically accordingly. As the eccentric member 30 eccentrically rotates, the external gear 28 eccentrically rotates while meshing with the internal gear 10. The external gear 28 eccentrically rotates about the axis 12. The two eccentric bodies 30 are eccentric in a symmetrical manner with each other. Therefore, the two external gears 28 eccentrically rotate about the axis 12 in a state of being eccentric in opposite directions with respect to the axis 12. The number of teeth of the external gear 28 and the number of teeth of the internal gear 10 (the number of internal gear pins 8) are different (see fig. 2). Therefore, when the external gears 28 eccentrically rotate, the carrier 4 supporting the external gears 28 rotates relative to the housing 6 in accordance with the difference in the number of teeth between the external gears 28 and the internal gear 10. The axis 12 may also be referred to as the axis of rotation of the carrier 4.

The features of the gear assembly 100 are described with reference to fig. 3. As described above, the external gear 28 eccentrically rotates while meshing with the internal gear 10. More specifically, the external gear 28 eccentrically rotates around the axis 12 while contacting the tooth surface thereof with the circumferential surface of the internal gear pin 8. When the external gear 28 rotates in the arrow R1 direction, the internal gear pin 8 rotates in the arrow R2 direction within the insertion groove 9. The inner pin 8 rotates in the insertion groove 9 while sliding relative to the insertion groove 9.

In the gear transmission 100, the coefficient of friction between the tooth surface of the external gear 28 and the peripheral surface of the internal gear pin 8 is larger than the coefficient of friction between the surface of the insertion groove 9 and the peripheral surface of the internal gear pin 8. Therefore, sliding between the external gear 28 and the internal pins 8 is less likely than between the insertion groove 9 and the internal pins 8. The inner rack pin 8 slides relative to the insertion groove 9 with a force smaller than the force with which it starts sliding on the tooth surface of the outer gear 28. Therefore, when the external gear 28 rotates in the arrow R1 direction, the internal gear pins 8 rotate in the arrow R2 direction while rolling on the tooth surfaces of the external gear 28. The inner pin 8 functions as a rolling bearing with respect to the external gear 28 and functions as a sliding bearing with respect to the insertion groove 9. In the gear transmission 100, at least one of the following processes (1) to (3) is performed on the external gear 28, the internal gear pin 8, and the insertion groove 9.

Treatment (1): the surface roughness Ra of the surface of the insertion groove 9 is made smaller than the surface roughness Ra of the tooth surface of the external gear 28.

Treatment (2): the direction of the texture of the tooth surface of the external gear 28 is adjusted to be the same as the direction of the texture of the peripheral surface of the internal gear pin 8, and the direction of the texture of the surface of the insertion groove 9 is adjusted to be different from the direction of the texture of the peripheral surface of the internal gear pin 8.

Treatment (3): the surface of the insertion groove 9 is covered so that the coefficient of friction between the insertion groove 9 and the internal tooth pins 8 after the covering is lower than the coefficient of friction between the insertion groove 9 and the internal tooth pins 8 before the covering.

By performing the process (1), the coefficient of friction between the external gear 28 and the internal pins 8 can be made larger than the coefficient of friction between the insertion groove 9 and the internal pins 8, without performing a special process on the internal pins 8. The external gear 28 is in contact with the insertion groove 9 (housing 6) via the internal gear pin 8. That is, the inner gear pin 8 is disposed between the outer gear 28 and the insertion groove 9. By performing the process of (1), the external gear 28 and the internal gear pins 8 are less likely to slide relative to each other than between the insertion groove 9 and the internal gear pins 8. More specifically, before the outer gear 28 starts to slide with respect to the inner rack pin 8, the inner rack pin 8 rotates while sliding with respect to the insertion groove 9.

The surface roughness of the tooth surface of the external gear 28 is adjusted to ra0.2 μm to ra0.5 μm. By adjusting the surface roughness to be ra0.2 μm or more, the sliding of the external gear 28 with respect to the internal gear pin 8 can be more reliably suppressed. Further, by adjusting the surface roughness to ra0.5 μm or less, the wear of the tooth surface of the external gear 28 can be suppressed. By adjusting the surface roughness of the tooth surfaces of the external gear 28 to ra0.2 μm to ra0.5 μm, it is possible to suppress deterioration of the external gear 28 and to suppress sliding of the internal gear pins 8 with respect to the external gear 28. Further, by adjusting the surface roughness Ra of the surface of the insertion groove 9 to 0.01 μm to 0.1 μm, the inner pin 8 can be easily slid with respect to the insertion groove 9 while avoiding the complexity of the processing of the insertion groove 9.

By performing the process (2), the friction coefficient between the external gear 28 and the internal pins 8 can be made larger than the friction coefficient between the insertion groove 9 and the internal pins 8 without adjusting the surface roughness Ra of the external gear 28 and the insertion groove 9. For example, in the case where the direction of the grain formed on the surface of the cylindrical part (cylindrical member) is different from the direction of the grain formed on the surface of the flat plate, when the cylindrical member rolls on the surface of the flat plate, the contact area between the cylindrical member and the flat plate is reduced, so that slipping is easily generated therebetween. In contrast, when the direction of the grain formed on the surface of the columnar member is the same as the direction of the grain formed on the surface of the flat plate, the grains are caught by each other, and sliding is less likely to occur between the two. In the process (2), the direction of the grain on the surface of the insertion groove 9 is orthogonal to the direction of the grain on the circumferential surface of the internal tooth pin 8, whereby the internal tooth pin 8 can be more reliably slid with respect to the insertion groove 9.

Specifically, the directions of the textures of the external gear 28, the internal gear pins 8, and the insertion grooves 9 will be described. As described above, the external gear 28 eccentrically rotates about the axis 12. In machining the external gear 28, the machining is usually performed so that the texture of the tooth surface is parallel to the axis 12 or so that the texture of the tooth surface is orthogonal to the axis 12. Similarly, when the peripheral surface of the inner pin 8 and the insertion groove 9 are machined, the machining is also usually performed such that the grain is parallel to the axis 12 or the grain is orthogonal to the axis 12.

Therefore, in the case where the external gear 28 is machined so that the grain is formed parallel to the axis 12, the internal tooth pin 8 is machined so that the grain is formed parallel to the axis 12, and the insertion groove 9 is machined so that the grain is formed in the direction orthogonal to the axis 12. In the case where the external gear 28 is machined so that the grain is formed in the direction orthogonal to the axis 12, the internal gear pin 8 is machined so that the grain is formed parallel to the axis 12, and the insertion groove 9 is machined so that the grain is formed parallel to the axis 12. Further, the direction of the grain can be adjusted by changing the moving direction of the processing tool.

By performing the process (3), the friction coefficient between the external gear 28 and the internal pins 8 can be made larger than the friction coefficient between the insertion groove 9 and the internal pins 8, without performing a special process on the internal pins 8 and the external gear 28. Specifically, in the process (3), decreasing the friction coefficient between the internal gear pins 8 and the insertion grooves 9 corresponds to increasing the friction coefficient between the external gear 28 and the internal gear pins 8. That is, the friction coefficient between the external gear 28 and the internal pins 8 is reduced without changing the friction coefficient between the external gear 28 and the internal pins 8, with the result that the friction coefficient between the external gear 28 and the internal pins 8 is made larger than the friction coefficient between the insertion grooves 9 and the internal pins 8. The surface of the insertion groove 9 can be covered by applying carbon, fluorine resin, molybdenum, or the like to the surface of the insertion groove 9 to form a coating of these materials. The coating (covering portion) is formed so that the coefficient of friction between the insertion groove 9 and the internal pin 8 after the coating is formed is 0.01 to 0.1 μm.

The advantages of the gear assembly 100 are illustrated. As described above, the friction coefficient between the tooth surface of the external gear 28 and the peripheral surface of the internal gear pin 8 is larger than the friction coefficient between the surface of the insertion groove 9 and the peripheral surface of the internal gear pin 8. Therefore, when the gear transmission 100 is driven, sliding is less likely to occur between the external gear 28 and the internal pins 8, and the internal pins 8 function as rolling bearings with respect to the external gear 28. It is possible to suppress transmission loss of torque between the external gear 28 and the internal gear 10.

Specific examples of the present invention have been described in detail above, but these specific examples are merely illustrative and are not intended to limit the scope of the claims. The techniques recited in the claims include modifications and variations of the specific examples described above. The technical features described in the present specification or the drawings are used alone or in various combinations to achieve technical utility, and are not limited to the combinations described in the claims at the time of application. The techniques illustrated in the present specification and drawings are for achieving a plurality of objects at the same time, and techniques for achieving one of the objects have technical utility.

Claims

1. A gear assembly, comprising: an inner gear; and an external gear eccentrically rotating with respect to the internal gear, wherein,

the internal gear has an internal gear member and a cylindrical member inserted into a groove provided on an inner peripheral surface of the internal gear member,

the external gear meshes with the internal gear by contacting the cylindrical member,

the direction of the texture of the circumferential surface of the cylindrical member is orthogonal to the direction of the texture of the surface of the groove.

2. The gear transmission of claim 1,

the coefficient of friction between the cylindrical member and the external gear is larger than the coefficient of friction between the cylindrical member and the groove.

3. The gear transmission of claim 1,

the surface roughness of the surface of the groove is smaller than the surface roughness of the tooth surface of the external gear.

4. The gear transmission of claim 3,

the surface roughness of the tooth surface of the external gear is 0.2-0.5 μm,

the surface roughness of the surface of the groove is less than 0.3 μm.

5. The gear transmission of claim 1,

the direction of the texture of the circumferential surface of the cylindrical member is the same as the direction of the texture of the tooth surface of the external gear.

6. The gear transmission device according to any one of claims 1 to 5,

a covering part is arranged on the surface of the groove,

the coefficient of friction between the cover and the cylindrical member is less than the coefficient of friction between the surface of the slot and the cylindrical member.