JP6310764B2 - Gear transmission - Google Patents

Description

  This specification discloses the technique regarding a gear transmission.

  2. Description of the Related Art A gear transmission including an internal gear and an external gear that rotates eccentrically relative to the internal gear while meshing with the internal gear is known. In such a gear transmission, the internal gear may be formed by inserting a columnar member into a groove provided on the inner peripheral surface of the internal gear member. In Patent Document 1, the surface roughness in the axial direction on the circumferential surface of the columnar member (outer pin) is made smaller than the surface roughness in the circumferential direction, and the friction between the columnar member and the groove (outer pin groove) is reduced. A gear transmission is disclosed. Patent Document 1 also describes that the surface roughness in the axial direction on the surface of the groove can be made smaller than the surface roughness in the circumferential direction to reduce the friction between the cylindrical member and the groove.

JP 2013-185619 A

  In the gear transmission of patent document 1, the friction between the cylindrical member which comprises the internal gear, and a groove | channel is made small, and the loss by friction is reduced. However, if the friction between the cylindrical member and the groove is reduced, the friction between the cylindrical member (the teeth of the internal gear) and the external gear may be reduced. As a result, slippage may occur between the internal gear and the external gear. When slippage occurs between the internal gear and the external gear, the torque transmission efficiency decreases. The present specification, which solves the above problems, discloses a technique for realizing a gear transmission having excellent torque transmission efficiency.

  The technology disclosed in this specification relates to a gear transmission provided with an internal gear and an external gear that rotates eccentrically relative to the internal gear. In the gear transmission, the internal gear includes an internal gear member and a cylindrical member that is inserted into a groove provided on the internal peripheral surface of the internal gear member. Further, the external gear meshes with the internal gear by contacting the cylindrical member. In the gear transmission disclosed in this specification, the friction coefficient between the cylindrical member and the external gear is larger than the friction coefficient between the cylindrical member and the groove.

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

  The above-mentioned “external gear that rotates eccentrically relative to the internal gear” is not only a form in which the external gear rotates eccentrically with respect to the axis of the gear transmission, but also the axis of the gear transmission. The form which rotates eccentrically is also included. That is, “an external gear that rotates eccentrically relative to the internal gear” means that one of the internal gear and the external gear rotates eccentrically with respect to the axis of the gear transmission, and the internal gear and the external gear. It means that the gear rotates relatively eccentrically.

Sectional drawing of the gear transmission of 1st Example is shown. FIG. 2 shows a cross-sectional view along the line II-II in FIG. 1. The enlarged view of the part enclosed with the broken line III of FIG. 2 is shown.

  Hereinafter, some technical features of the gear transmission disclosed in this specification will be described. The items described below have technical usefulness independently.

  The gear transmission may include an internal gear and an external gear. The internal gear and the external gear may rotate relatively eccentrically while meshing with each other. That is, the external gear may rotate eccentrically while meshing with the internal gear. Alternatively, the internal gear may rotate eccentrically while meshing with the external gear. The internal gear may include an internal gear member and a columnar member that is inserted into a groove provided on the internal peripheral surface of the internal gear member. In other words, the internal gear may be formed by a groove formed on the inner peripheral surface of the internal tooth member and a cylindrical member inserted into the groove. Hereinafter, in this specification, the groove | channel formed in the internal peripheral surface of an internal-tooth member may be called an insertion groove | channel.

  When the external gear is a type that rotates eccentrically, the case of the gear transmission may also serve as the internal gear member. That is, the internal gear may be formed on the inner periphery of the case. In this case, a carrier, a crankshaft, and an external gear may be arranged inside the case. The crankshaft may be rotatably supported by the carrier. The crankshaft may include an eccentric body. The external gear may engage with the eccentric body of the crankshaft and rotate eccentrically as the crankshaft rotates. The internal gear may have a number of teeth different from the number of teeth of the external gear.

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

  When the insertion groove has an arc shape, the center of the virtual circle including the surface of the insertion groove is located on the rotation axis of the cylindrical member, and the diameter of the virtual circle and the diameter of the cylindrical member may be substantially equal. The cylindrical member may rotate in the insertion groove while being in contact with the external gear. That is, when the external gear rotates relatively eccentrically while meshing with the internal gear, the columnar member may rotate within the insertion groove.

  When the gear transmission is driven, the friction coefficient between the cylindrical member and the external gear may be larger than the friction coefficient between the cylindrical member and the insertion groove. More specifically, the friction coefficient (rolling friction coefficient) when the cylindrical member starts to slide against the tooth surface of the external gear is the friction coefficient (rolling friction) when the cylindrical member starts to slide against the insertion groove. (Coefficient). Further, 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, different values of surface roughness may be achieved by machining with different tools. Or after processing an insertion groove and an external gear, processing which removes a line of a surface of an insertion groove may be performed.

  The surface roughness of the tooth surface of the external gear may be Ra 0.2 μm or more and Ra 0.5 μm or less. When the surface roughness is less than Ra 0.2 μm, sufficient friction cannot be obtained between the cylindrical member and the tooth surface of the external gear, and the cylindrical member slips with respect to the tooth surface of the external gear. Can happen. Further, when the surface roughness exceeds Ra 0.5 μm, heat generation or the like is likely to occur during driving, and the durability (life) of the external gear may be reduced. In addition, when the surface roughness of the tooth surface of the external gear is Ra 0.2 μm or more and Ra 0.5 μm or less, the surface roughness of the insertion groove may be less than Ra 0.2 μm.

  The surface roughness of the insertion groove may be less than Ra 0.3 μm. The surface roughness of the insertion groove is preferably Ra 0.2 μm or less, and particularly preferably Ra 0.1 μm or less. In addition, in order to avoid a complicated processing step of the insertion groove and an increase in processing time, the surface roughness of the insertion groove may be 0.01 μm or more. When the surface roughness of the insertion groove is less than Ra 0.3 μm, the surface roughness of the tooth surface of the external gear may be Ra 0.3 μm or more and Ra 0.5 μm or less.

  The direction of the lines on the peripheral surface of the cylindrical member may be the same as the direction of the lines on the tooth surface of the external gear. By making the line direction the same, the friction coefficient between the columnar member and the external gear increases, and it is possible to suppress the columnar member from sliding against the tooth surface of the external gear. Further, the direction of the lines on the peripheral surface of the columnar member may be different from the direction of the lines on the surface of the insertion groove. If the direction of the streak is different, the coefficient of friction between the columnar member and the insertion groove becomes small, and the columnar member becomes slippery with respect to the insertion groove. By making the columnar member slip easily with respect to the insertion groove, the friction coefficient between the columnar member and the external gear can be relatively increased. The direction of the lines on the peripheral surface of the columnar member may be orthogonal to the direction of the lines on the surface of the insertion groove. The streak is a processing mark generated on the surface of the part when the part is processed.

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 columnar member may be more slidable with respect to the insertion groove than when the covering portion is not provided. The covering portion may be a carbon, fluororesin, or molybdenum film formed on the surface of the insertion groove. By providing a covering portion on the surface of the insertion groove, the surface roughness of the surface of the insertion groove may be reduced.

(First embodiment)
With reference to FIG.1 and FIG.2, the basic structure of the gear transmission 100 is demonstrated. FIG. 1 shows a longitudinal sectional view of the gear transmission 100 (a sectional view along the axis 12 of the gear transmission 100). FIG. 2 shows a cross-sectional view of the gear transmission 100 (cross-sectional view along a line perpendicular to the axis 12 of the gear transmission 100). The gear transmission 100 includes an internal gear 10, a carrier 4, a crankshaft 14, and an external gear 28.

  The internal gear 10 includes a case 6 and an internal tooth pin 8. An internal gear 10 is formed by arranging a plurality of internal teeth pins 8 on the inner periphery of the case 6. The internal tooth pin 8 has a cylindrical shape and is inserted into an insertion groove 9 formed on the inner peripheral surface 7 of the case 6. The insertion grooves 9 are provided at equal intervals in the circumferential direction of the inner periphery of the case 6. Further, the insertion groove 9 extends in parallel to the axis 12 of the gear transmission 100. That is, the internal teeth pins 8 are provided at equal intervals in the circumferential direction of the inner periphery of the case 6 and extend parallel to the axis 12. The case 6 is an example of an internal tooth member, and the internal tooth pin 8 is an example of a columnar member.

  The carrier 4 is rotatably supported by the case 6 by a pair of bearings 22 (hereinafter sometimes referred to as main bearings 22). The main bearing 22 restricts the carrier 4 from moving in the axial direction and the radial direction with respect to the case 6. In the gear transmission 100, an angular ball bearing is used as the main bearing 22. The carrier 4 includes a first plate 4a and a second plate 4c. The first plate 4a includes 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 by bolts. The bolt 34 passes through the second plate 4c and is fastened to a bolt groove 34a provided in the columnar portion 4b.

  A positioning pin (not shown) for positioning in the circumferential direction is inserted into the columnar part 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 pin passes through the pin hole of the second plate 4 c and is inserted into the pin hole 36. An oil seal 18 is disposed between the case 6 and the first plate 4a.

  The crankshaft 14 is rotatably supported by the carrier 4 by a pair of bearings 20. The pair of bearings 20 restricts the crankshaft 14 from moving in the axial direction and 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 includes 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 eccentric body 30 rotates eccentrically as the crankshaft 14 rotates. As the eccentric body 30 rotates eccentrically, the external gear 28 rotates eccentrically while meshing with the internal gear 10. The external gear 28 rotates eccentrically around the axis 12. The two eccentric bodies 30 are eccentrically symmetrical to each other. Therefore, the two external gears 28 eccentrically rotate around the axis 12 while being eccentric with respect to the axis 12 in opposite directions. The number of teeth of the external gear 28 and the number of teeth of the internal gear 10 (number of internal pins 8) are different (see FIG. 2). Therefore, when the external gear 28 rotates eccentrically, the carrier 4 supporting the external gear 28 rotates relative to the case 6 according to the difference in the number of teeth between the external gear 28 and the internal gear 10. The axis 12 can also be referred to as the rotation axis of the carrier 4.

  The characteristics of the gear transmission 100 will be described with reference to FIG. As described above, the external gear 28 rotates eccentrically while meshing with the internal gear 10. More specifically, the external gear 28 rotates eccentrically around the axis 12 while the tooth surface contacts the peripheral surface of the internal tooth pin 8. When the external gear 28 rotates in the direction of the arrow R1, the internal tooth pin 8 rotates in the direction of the arrow R2 in the insertion groove 9. The internal pin 8 rotates within the insertion groove 9 while sliding with respect to the insertion groove 9.

  In the gear transmission 100, the friction coefficient between the tooth surface of the external gear 28 and the peripheral surface of the internal tooth pin 8 is larger than the friction coefficient between the surface of the insertion groove 9 and the peripheral surface of the internal tooth pin 8. . Therefore, the external gear 28 and the internal tooth pin 8 are less slippery than the insertion groove 9 and the internal tooth pin 8. The internal tooth pin 8 slides with respect to the insertion groove 9 with a force that is weaker than the force when the tooth surface of the external gear 28 starts to slide. Therefore, when the external gear 28 rotates in the direction of arrow R1, the internal pin 8 rotates in the direction of arrow R2 while rolling the tooth surface of the external gear 28. The internal pin 8 functions as a rolling bearing for the external gear 28 and functions as a sliding bearing for 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 tooth pin 8, and the insertion groove 9.

Process (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.
Process (2): The direction of the line of the tooth surface of the external gear 28 is adjusted to be the same as the direction of the line of the peripheral surface of the internal tooth pin 8, and the direction of the surface of the insertion groove 9 is set to the internal tooth pin 8 Adjust so that it is different from the direction of the streaks on the circumference.
Process (3): The surface of the insertion groove 9 is coated, and the friction coefficient between the insertion groove 9 and the internal tooth pin 8 after coating is determined from the friction coefficient between the insertion groove 9 and the internal tooth pin 8 before coating. make low.

  By performing the process (1), the coefficient of friction between the external gear 28 and the internal tooth pin 8 is reduced between the insertion groove 9 and the internal tooth pin 8 without performing any special process on the internal tooth pin 8. The coefficient of friction can be larger. The external gear 28 is in contact with the insertion groove 9 (case 6) via the internal tooth pin 8. That is, the internal tooth pin 8 is disposed between the external gear 28 and the insertion groove 9. By performing the process (1), the external gear 28 is less likely to slip relative to the internal pin 8 as compared with the insertion groove 9. More specifically, the internal tooth pin 8 rotates while sliding with respect to the insertion groove 9 before the external gear 28 starts to slide with respect to the internal tooth pin 8.

  In addition, the surface roughness of the tooth surface of the external gear 28 is adjusted to Ra 0.2 μm or more and 0.5 μm or less. By adjusting the surface roughness to Ra 0.2 μm or more, the external gear 28 can be more reliably suppressed from sliding with respect to the internal tooth pin 8. Further, by adjusting the surface roughness to Ra 0.5 μm or less, it is possible to suppress wear of the tooth surface of the external gear 28. By adjusting the surface roughness of the tooth surface of the external gear 28 to Ra 0.2 μm or more and 0.5 μm or less, the internal tooth pin 8 slides with respect to the external gear 28 while suppressing the deterioration of the external gear 28. This can be suppressed. Further, by adjusting the surface roughness Ra of the surface of the insertion groove 9 to 0.01 μm or more and 0.1 μm or less, the internal tooth pin 8 is inserted into the insertion groove 9 while avoiding complicated processing of the insertion groove 9. On the other hand, it can be made slippery.

  By performing the processing (2), the coefficient of friction between the external gear 28 and the internal tooth pin 8 can be reduced without adjusting the surface roughness Ra of the external gear 28 and the insertion groove 9. The coefficient of friction between the pins 8 can be larger. For example, when the direction of the lines formed on the surface of the cylindrical part (columnar member) is different from the direction of the lines formed on the surface of the flat plate, when the cylindrical member rolls on the surface of the flat plate, the cylindrical member The contact area between the flat plate and the flat plate is reduced, and slippage easily occurs between the two. On the other hand, when the direction of the streak formed on the surface of the columnar member is the same as the direction of the streak formed on the surface of the flat plate, the streaks are caught and slippage between them is less likely to occur. In the process (2), by making the direction of the streak on the surface of the insertion groove 9 orthogonal to the direction of the streak on the peripheral surface of the internal tooth pin 8, the internal tooth pin 8 is more reliably slipped with respect to the insertion groove 9. Can be made easier.

  The direction of the streaks of the external gear 28, the internal tooth pin 8, and the insertion groove 9 will be specifically described. As described above, the external gear 28 rotates eccentrically around the axis 12. When processing the external gear 28, the external gear 28 is typically processed so that the tooth surface line is parallel to the axis 12, or the tooth surface line is orthogonal to the axis 12. To be processed. Similarly, when processing the peripheral surface of the internal tooth pin 8 and the insertion groove 9, typically, the streak is processed so as to be parallel to the axis 12 or the streak is orthogonal to the axis 12. It is processed as follows.

  Therefore, when processing the external gear 28 so that the line is formed in parallel to the axis 12, the internal tooth pin 8 is processed so that the line is formed in parallel to the axis 12, and the insertion groove 9 is in the axis line. 12 so as to be formed in a direction orthogonal to 12. When processing the external gear 28 so that the lines are formed in a direction perpendicular to the axis 12, the internal teeth pin 8 is processed so that the lines are formed parallel to the axis 12, and the insertion groove 9 Is processed so that the streaks are formed parallel to the axis 12. It should be noted that the direction of the lines can be adjusted by changing the direction in which the tool to be processed is moved.

  By performing the process (3), the coefficient of friction between the external gear 28 and the internal gear pin 8 is reduced between the insertion groove 9 and the internal gear 8 without performing a special process on the internal gear pin 8 and the external gear 28. The friction coefficient between the tooth pins 8 can be made larger. Specifically, in the process (3), the friction coefficient between the external gear 28 and the internal pin 8 is relatively increased by reducing the friction coefficient between the internal tooth pin 8 and the insertion groove 9. To do. That is, by reducing the friction coefficient between the internal tooth pin 8 and the insertion groove 9 without changing the friction coefficient between the external gear 28 and the internal tooth pin 8, the external gear 28 and the internal tooth are consequently obtained. The friction coefficient between the pins 8 is made larger than the friction coefficient between the insertion groove 9 and the internal tooth pin 8. The surface of the insertion groove 9 can be covered by coating the surface of the insertion groove 9 with carbon, fluorine resin, molybdenum or the like and forming a film of these materials. The coating (covering portion) is formed so that the coefficient of friction between the insertion groove 9 and the internal tooth pin 8 after forming the coating is 0.01 μm or more and 0.1 μm or less.

  The advantages of the gear transmission 100 will be described. As described above, the friction coefficient between the tooth surface of the external gear 28 and the peripheral surface of the internal tooth pin 8 is larger than the friction coefficient between the surface of the insertion groove 9 and the peripheral surface of the internal tooth pin 8. For this reason, when the gear transmission 100 is driven, slippage hardly occurs between the internal gear pins 8 of the external gear 28, and the internal gear pin 8 functions as a rolling bearing with respect to the external gear 28. Torque transmission loss can be suppressed between the external gear 28 and the internal gear 10.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

6: Internal gear member 8: Cylindrical member 9: Groove 10: Internal gear 28: External gear 100: Gear transmission

Claims (4)

A gear transmission comprising an internal gear and an external gear that rotates eccentrically relative to the internal gear;
The internal gear includes an internal gear member, and a columnar member inserted in a groove provided on the internal peripheral surface of the internal gear member,
The external gear meshes with the internal gear by contacting the cylindrical member,
Friction coefficient between the cylindrical member and the external gear, rather larger than the frictional coefficient between the cylindrical member and the groove,
Surface roughness of the surface of the groove, the gear transmission has less than the surface roughness of the tooth surfaces of the external gear. The surface roughness of the tooth surface of the external gear is 0.2 μm or more and 0.5 μm or less,
The gear transmission according to claim 1 , wherein a surface roughness of the groove is less than 0.3 μm.   The gear transmission according to claim 1 or 2, wherein the direction of the lines on the peripheral surface of the cylindrical member is the same as the direction of the lines on the tooth surface of the external gear, and is different from the direction of the lines on the surface of the groove. A gear transmission comprising an internal gear and an external gear that rotates eccentrically relative to the internal gear;
The internal gear includes an internal gear member, and a columnar member inserted in a groove provided on the internal peripheral surface of the internal gear member,
The external gear meshes with the internal gear by contacting the cylindrical member,
Friction coefficient between the cylindrical member and the external gear, rather larger than the frictional coefficient between the cylindrical member and the groove,
A gear transmission in which the direction of the lines on the peripheral surface of the cylindrical member is the same as the direction of the lines on the tooth surface of the external gear, and is different from the direction of the lines on the surface of the groove .

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