gear drive

Abstract

Gear drive (100, 300) in which a carrier (10, 310) is mounted by a housing (4) via a bearing (2, 302), wherein the bearing (2, 302) has: an inner ring (46, 346) which has an inclined outer surface (46b) and is attached to the housing (4) or to the support (10, 310); an outer ring (40) having an inclined inner surface (40b) facing the inclined outer surface (46b) of the inner ring (46, 346), and which is then attached accordingly to the carrier (10, 310) or housing (4); cylindrical rolling elements (42) arranged between the inner ring (46, 346) and the outer ring (40); and a ring-shaped cage (44, 144, 244) which is arranged between the inner ring (46, 346) and the outer ring (40) and maintains a distance between adjacent rolling elements (42), wherein one end (44a, 244a) of the cage (44, 144, 244) with a large diameter makes contact with both the housing (4) and the support (10, 310), wherein a contact interface (44d, 244d) between cage (44, 144, 244) and housing (4) or a contact interface (44e, 244e) between cage (44, 144, 244) and support (10, 310) is perpendicular to an axis (30) of the support (10, 310), wherein the other contact surface (44d, 244d) between cage (44, 144, 244) and housing (4) or the contact surface (44e, 244e) between cage (44, 144, 244) and support (10, 310) forms a cylindrical surface that is coaxial to the support (10, 310).

Description

TECHNICAL AREA

[0001] The present application claims priority from Japanese patent application No. 2011-220440, filed on October 4, 2011, the contents of which are hereby incorporated into the present application by reference. The present application relates to a gear transmission. It relates in particular to a gear transmission comprising a cylindrical roller bearing between a carrier and a housing. STATE OF THE ART

[0002] A gear transmission is known in which a gear unit is housed in a casing and a carrier is supported by the casing via a bearing. A gear transmission in which a cylindrical roller bearing is arranged between a casing and a carrier is disclosed in Japanese patent publication no. 2010-159774. In the following description, Japanese patent publication no. 2010-159774 is referred to as patent document 1 (the corresponding German patent is DE 10 2010 004 043 A1). In the cylindrical roller bearing of patent document 1, a cylindrical rolling element is inclined relative to an axis of the carrier. Because the rolling element is inclined to the axis of the carrier, rotation of the carrier exerts a force on the rolling element, which pushes the rolling element outwards.

[0003] In the technology described in patent document 1, the cage is equipped with a function to control the axial movement of the rolling element. That is, the cage prevents the rolling element from moving axially. Specifically, in a bearing disclosed in patent document 1, one end of an annular cage with a larger diameter side makes contact with the housing. The cage holds the rolling elements. The movement of the cage is controlled by its contact with the housing. Consequently, the axial movement of the rolling elements held by the cage is limited.

[0004] JP S55- 10 140 A, JP H05- 58 956 U, and JP 2001- 349 329 A reveal contact of a bearing cage with both the inner bearing ring and the outer bearing ring. SUMMARY OF THE INVENTION

[0005] Gear drives comprise two types: one in which a carrier rotates as the output unit, and another in which a housing rotates as the output unit. The following description refers to the gear drive type in which the housing is stationary and the carrier rotates as the output unit. As the carrier rotates, the rolling elements of a cylindrical roller bearing move around an axis of the carrier. This means that the rolling elements roll against an inner surface of the housing and an outer surface of the carrier. In other words, the rolling elements roll against an inner surface of an outer ring and an outer surface of an inner ring. Along with the movement of the rolling elements, the cage rotates relative to the housing.

[0006] When the cage is brought into contact with the housing as described in patent document 1, friction occurs between the cage and the housing. Consequently, the rotational speed of the cage relative to the housing decreases, and the speed of the rolling elements slows down. The rolling elements can then easily slide relative to the housing and the carrier. This sliding of the rolling elements relative to the housing and the carrier intensifies, and wear on the rolling elements occurs immediately. Thus, the gradual destruction of the cylindrical roller bearing is accelerated, and the service life of the gear drive is shortened. The present description provides a technique to suppress the gradual destruction of a cylindrical roller bearing arranged between a housing and a carrier.

[0007] The technology disclosed in the present description relates to a gear transmission in which a carrier is supported by a housing via a bearing. The bearing comprises an inner ring, an outer ring, several cylindrical rolling elements, and an annular cage. The inner ring is attached to the housing or the carrier. The outer ring is similarly attached to the carrier or housing. The several cylindrical rolling elements are arranged between the inner ring and the outer ring. The cage maintains a distance between adjacent rolling elements. The inner ring has an inclined outer surface. The outer ring has an inclined inner surface. The inner surface of the outer ring faces the outer surface of the inner ring. The cage is arranged between the inner ring and the outer ring. One end of the cage, with a large diameter, makes contact with both the housing and the carrier.One contact surface between the cage and the housing, or one contact surface between the cage and the support, lies perpendicular to an axis of the support. The other contact surface, either between the cage and the housing or between the cage and the support, forms a cylindrical surface that is coaxial with the support.

[0008] According to the gear drive, the cage slides not only relative to the housing but also relative to the support due to contact with both the housing and the support. As described above, in the prior art gear drive, the cage only has contact with the housing. In the gear drive disclosed in the present description, compared to the prior art gear drive, the rotational speed of the cage relative to the housing is increased by the degree of friction between the cage and the support. In other words, the gear drive disclosed in the present description can cause the rotational speed of the cage relative to the housing to be almost half that of the rotational speed of the support relative to the housing. This means that the rotational speed of the cage relative to the housing can be approached to be the same as the rotational speed of the cage when there is no contact with either the housing or the support.Sliding of the rolling elements relative to the housing and carrier is suppressed, and wear of the rolling elements is kept to a minimum. As a result, the gradual destruction of the cylindrical roller bearing is suppressed and the service life of the gear drive is improved.

[0009] Furthermore, the cage rotates smoothly due to the sliding motion relative to both the housing and the carrier. In addition, the cage does not need to maintain constant contact with both the housing and the carrier in the gear drive. When the gear drive is stationary, the cage can be spaced apart from both the housing and the carrier. During operation, the cage can make contact with both the housing and the carrier when the rolling elements are subjected to a force that pushes them outwards. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 shows a cross-sectional view of a gear transmission of a first embodiment. Fig. Figure 2 shows an enlarged cross-sectional view of area II of Fig. 1. Fig. Figure 3 shows a schematic diagram of the external appearance of a cage. Fig. Figure 4 shows a view of the cage, seen from one bearing axis direction (top view). Fig. Figure 5 shows a view of the cage, seen from a direction perpendicular to the bearing axis (front view). Fig. Figure 6 shows a diagram to explain how the rolling elements work. Fig. Figure 7 shows a top view of a cage used in a gear transmission of a second embodiment. Fig. Figure 8 shows a front view of the cage used in the gear transmission of the second embodiment. Fig. Figure 9 shows a top view of a cage used in a gear transmission of a third embodiment. Fig. Figure 10 shows a front view of the cage used in the gear transmission of the third embodiment. Fig. Figure 11 shows a cross-sectional view of a gear transmission of a fourth embodiment. DESCRIPTION OF THE EXECUTION FORMS

[0010] Below are some technical features of the embodiments disclosed in this description. Furthermore, each of the elements described below has its own technical benefit.

[0011] In the gear drive disclosed in the present description, the contact area between the cage and the housing and the contact area between the cage and the carrier can be of equal size. Thus, the sliding motion of the cage relative to the housing and the sliding motion of the cage relative to the carrier can be in equilibrium. Furthermore, the rotational speed of the cage relative to the housing can be approximated to approximately half the rotational speed of the carrier relative to the housing.

[0012] In the gear drive disclosed in the present description, the contact surface between the cage and the housing is perpendicular to the axis of the carrier, and the contact surface between the cage and the carrier is a cylindrical surface coaxial with the carrier. Alternatively, the contact surface between the cage and the carrier is perpendicular to the axis of the carrier, and the contact surface between the cage and the housing is a cylindrical surface coaxial with the carrier. Thus, the cage can be supported in two directions: axially and radially with the carrier. Movement of the cage in the axial direction of the rolling elements can be reliably prevented. Furthermore, the expression "the contact surface is perpendicular to the axis of the carrier" means that the axis of the carrier is perpendicular to the contact surface.

[0013] In the gear transmission disclosed in this description, a groove may be formed on the surface of the cage that makes contact with the carrier (a carrier contact surface). Furthermore, a groove may be formed on the surface of the cage that makes contact with the housing (a housing contact surface). If a groove is formed on the carrier contact surface and / or on the housing contact surface, and the cage is in contact with both the housing and the carrier, lubricant more easily passes from the exterior of the cylindrical roller bearing to its interior. This means that lubricant can pass from the exterior of the cylindrical roller bearing to its interior. Consequently, the lubricant passes through the groove and can migrate to the interior of the cylindrical roller bearing, even if the cage is in contact with both the carrier and the housing.The interruption of an oil film to the rolling elements is prevented, thus minimizing the progression of wear on the rolling elements.

[0014] The technique taught in this description makes it possible to realize a gear transmission in which a cylindrical roller bearing arranged between a housing and a support has a long service life. VERSIONS (First embodiment)

[0015] The embodiment describes a type of gear drive in which an external gear rotates eccentrically while meshing with an internal gear ring. The technique taught in this description can also be applied to another type of gear drive, e.g., a type of gear drive in which an internal gear ring rotates eccentrically while meshing with an external gear.

[0016] Fig. Figure 1 shows a cross-sectional view of a gear unit 100. The gear unit 100 is an eccentric oscillating reduction gear. An external gear 22 rotates eccentrically while meshing with an internal ring gear 24. The number of teeth on the external gear 22 differs from the number of teeth on the internal ring gear 24. The gear unit 100 rotates a carrier 10 by utilizing the difference between the number of teeth on the external gear 22 and the internal ring gear 24. That is, by utilizing the difference in the number of teeth on the external gear 22 and the internal ring gear 24, the gear unit 100 increases a torque, which is transmitted to a crankshaft 16 (i.e., reduces its rotational speed) and delivers the torque to the carrier 10. Furthermore, the carrier 10 is equivalent to an output unit of the gear drive 100. An axis 30 corresponds to a rotation axis of the carrier 10. The axis 30 also corresponds to an axis of the internal gear ring 24.Furthermore, axis 30 also corresponds to an axis of the gear drive 100. In addition, axis 30 is also equivalent to a bearing axis of a (to be described later) cylindrical roller bearing 2.

[0017] The gear unit 100 comprises the inner gear ring 24, the carrier 10, the outer gear 22, and the crankshaft 16. The inner gear ring 24 includes a housing and several inner webs 5. The housing 4 has a small-diameter section 4a and a large-diameter section 4b. The small-diameter section 4a extends along the axis 30 from both ends of the large-diameter section 4b. The inner gear ring 24 is formed on the large-diameter section 4b of the housing 4. The two cylindrical roller bearings 2 are arranged in the small-diameter section 4a.

[0018] The inner gear ring 24 is arranged between the two cylindrical roller bearings 2 in the direction of axis 30. As described above, the outer gear 22 meshes with the inner gear ring 24. Therefore, the outer gear 22 can also be considered to be arranged between the two cylindrical roller bearings 2 in the direction of axis 30. The two cylindrical roller bearings 2 control the movement of the carrier 10 in the axial and radial directions. The two cylindrical roller bearings 2 can be considered the main bearings of the gear drive 100. Details of the cylindrical roller bearings 2 are described below.

[0019] The support 10 is mounted through the housing 4 via the two cylindrical roller bearings 2. The support 10 has a first plate 10a and a second plate 10c. The first plate 10a has a column section 10b. The column section 10b extends from the first plate 10a to the second plate 10c and is attached to the second plate 10c. A first flange 10d is formed at one end of the first plate. The first flange 10d extends radially (in the direction perpendicular to the axis 30). A second flange 10e is formed at one end of the second plate 10c. The second flange 10e extends radially. The cylindrical roller bearings 2 are arranged on the first flange 10d and the second flange 10e. The first flange 10d can also be referred to as the projecting section of the first plate 10a. Furthermore, the second flange 10e can also be referred to as the projecting section of the second plate 10c.Furthermore, the carrier 10 and the housing 4 are made of metal.

[0020] The crankshaft 16 is supported on the carrier 10 by two tapered roller bearings 19. The two tapered roller bearings 19 control the movement of the crankshaft 16 in the axial and radial directions. The crankshaft 16 runs parallel to the axis 30 at a position offset from the axis 30. The crankshaft 16 has an input gear 28 and an eccentric body 18. The input gear 28 is attached to the crankshaft 16 outside the two tapered roller bearings 19. The eccentric body 18 is located between the two tapered roller bearings 19. A through-hole 14 is formed in the outer gear 22. The eccentric body 18 engages in the through-hole 14 via a cylindrical roller bearing 20. The outer gear 22 is supported by the carrier 10 via the crankshaft 16. In the direction of the axis 30, the outer gear 22 is arranged between the two tapered roller bearings 19.

[0021] When the torque of a motor (not shown) is transmitted to the input gear 28, the crankshaft 16 rotates. The eccentric body 18 rotates eccentrically in conjunction with the rotation of the crankshaft 16. The eccentric body 18 rotates eccentrically about an axis (not shown) of the crankshaft 16. The outer gear 22 rotates eccentrically while meshing with the inner ring gear 24, in conjunction with the eccentric rotation of the eccentric body 18. The outer gear 22 rotates eccentrically about the axis 30. The number of teeth on the outer gear 22 and the number of teeth on the inner ring gear 24 (the number of inner webs 5) are different. When the outer gear 22 rotates eccentrically, the support 10 carrying the outer gear 22 rotates relative to the inner gear ring 24 (to the housing 4) according to the difference in the number of teeth of the outer gear 22 and the inner gear ring 24.

[0022] The cylindrical roller bearing 2 is described in detail with reference to Fig. 2 described. The cylindrical roller bearing 2 has an inner ring 46, an outer ring 40, rolling elements 42 (cylindrical rolling elements) and a cage 44. The inner ring 46 is annular. An outer surface 46b of the inner ring 46 is inclined. That is, the outer surface 46b of the inner ring 46 is inclined relative to the axis 30 (see Fig. 1) is inclined. No ribs are provided on the outer surface 46b of the inner ring 46 to limit the movement of the rolling elements 42. The inner ring 46 is pressed onto an outer surface of the second plate 10c of the carrier 10. An inner surface 46a of the inner ring 46 is in contact with an outer surface of the second plate 10c. An end face 46c of the inner ring 46 makes contact with the second flange 10e in the direction of the axis 30. The inner ring 46 is attached to the carrier 10 and is also immovable in the radial direction in the direction of the axis 30 relative to the carrier 10. The inner ring 46 can also be considered to be integral with the carrier 10.

[0023] The outer ring 40 is ring-shaped. An inner surface 40b of the outer ring 40 is inclined. The inner surface 40b of the outer ring 40 is inclined relative to the axis 30. No ribs are provided on the inner surface 40b of the outer ring 40 to limit the movement of the rolling elements 42. The inner surface 40b of the outer ring 40 faces the outer surface 46b of the inner ring 46. The angle of inclination of the inner surface 40b relative to the axis 30 and the angle of inclination of the outer surface 46b relative to the axis 30 are equal. This means that the distance between the inner surface 40b of the outer ring 40 and the outer surface 46b of the inner ring 46 (a space in which the rolling elements 42 are arranged) is constant in the direction of the axis of rotation of the rolling elements 42. The outer ring 40 is pressed into an inner side of the small diameter section 4a of the housing 4.An outer surface 40a of the outer ring 40 makes contact with an inner surface of the housing 4 (with the small-diameter section 4a). An end face 40c of the outer ring 40 makes contact in the direction of the axis 30 with the large-diameter section 4b of the housing 4. The outer ring 40 is fixed to the housing 4 and is also immovable in the radial direction relative to the housing 4 in the direction of the axis 30. The outer ring 40 can also be considered to be integral with the housing 4.

[0024] The rolling elements (cylindrical rolling elements) 42 are arranged between the inner ring 46 and the outer ring 40. One axis of rotation of the rolling elements 42 is relative to the axis 30 (see Fig. 1) inclined. The multiple rolling elements 42 are arranged at equal intervals between the inner ring 46 and the outer ring 40. That is, the multiple rolling elements 42 are arranged at equal intervals around the axis 30. The shape of the rolling elements 42 is cylindrical. The length of the rolling elements 42 in the direction of the axis of rotation is shorter than the length of the outer surface 46b of the inner ring 46 and the inner surface 40b of the outer ring 40. The outer surface of the rolling elements 42 is in contact with the outer surface 46b of the inner ring 46 and the inner surface 40b of the outer ring 40. Furthermore, as described above, no ribs are provided on either the outer surface 46b of the inner ring 46 or the inner surface 40b of the outer ring 40. Therefore, the end faces 42 of the rolling elements 42 are not in contact with the inner ring 46 and outer ring 40 in the direction of the axis of rotation.

[0025] The cage 44 is positioned between the inner ring 46 and the outer ring 40. The cage 44 is made of plastic. As shown in Fig. As shown in Figure 3, the cage 44 is annular and has a first end 44a with a large diameter and a second end 44b with a diameter smaller than that of the first end 44a. The cage 44 has a plurality of receptacles 44c arranged circumferentially. The rolling elements 42 are inserted into the receptacles 44c. The cage 44 maintains a distance between each adjacent rolling element 42. Furthermore, because the rolling elements 42 are inserted into the receptacles 44c, the end faces 42a of the rolling elements 42 are held in the direction of the axis of rotation by the cage 44 (see also Figure 3). Fig. 2) This means that the axial movement of the rolling elements 42 relative to the cage 44 is limited. In other words, the cage 44 limits the movement of the rolling elements 42 in the direction of the axis of rotation. Furthermore, Fig. Figure 3 is a diagram providing a brief explanation of the overall shape of cage 44 and does not depict the exact shape of cage 44. The detailed design of cage 44 will be described below.

[0026] As in Fig. As shown in Figure 2, at the first end 44a of the cage 44, a housing contact surface 44d, which makes contact with the housing 4, and a support contact surface 44e, which makes contact with the support 10, are formed. The housing contact surface 44d is perpendicular to the axis 30 (see Figure 2). Fig. 1) formed. The housing contact surface 44d is an outer surface of the cage 44 and makes contact with an inner surface of the housing 4 (with the section 4a of smaller diameter). The contact surface (a section of the housing contact surface 44d) of the cage 44 and the housing 4 is cylindrical in shape and coaxial with the bearing axis 30. The support contact surface 44e is formed at an end section in the direction of the axis 30. The support contact surface 44e is an end face of the cage 44 in the direction of the bearing axis 30. The support contact surface 44e is in contact with the second flange 10e of the support 10 (the second plate 10c). The contact surface (a section of the support contact surface 44e) of the cage 44 and the support 10 is perpendicular to the axis 30.

[0027] Cage 44 will now be described in detail with reference to Fig. 4, Fig. As described in section 5, the housing contact surface 44d is formed coaxially with the bearing axis 30 on one circumference (on the outer surface of the cage 44). Several outer circumferential grooves 44f are formed in the housing contact surface 44d. The outer circumferential grooves 44f are equivalent to the first grooves. The outer circumferential grooves 44f extend along the bearing axis 30 and are formed at equal intervals around the axis 30. It can also be expressed that the housing contact surface 44d is formed between each adjacent outer circumferential groove 44f. Even if the housing contact surface 44d is in contact with the housing 4, the outer circumferential grooves 44f are not in contact with the housing 4. This means that a gap between the cage 44 and the housing 4 is ensured, even if the housing contact surface 44d is in contact with the housing 4.

[0028] The support contact surface 44e is formed on a plane perpendicular to the bearing axis 30. Several end-face grooves 44g are formed in the support contact surface 44e. The end-face grooves 44g correspond to second grooves. The end-face grooves 44g extend radially around the cage 44 and are spaced equally around the bearing axis 30. The support contact surface 44e is formed between adjacent end-face grooves 44g. The end-face grooves 44g establish a connection between the inner and outer areas of the cage 44. The end-face grooves 44g are not in contact with the support 10, even if the support contact surface 44e is in contact with the support 10. This means that a gap between the cage 44 and the support 10 is ensured, even if the support contact surface 44e is in contact with the support 10.

[0029] The outer circumferential grooves 44f and the end-face grooves 44g are formed alternately in the circumferential direction of the cage 44. In other words, in the circumferential direction of the cage 44, the outer circumferential grooves 44f are formed between the adjacent end-face grooves 44g, and the end-face grooves 44g are formed between the adjacent outer circumferential grooves 44f. The number of outer circumferential grooves 44f corresponds to the number of end-face grooves 44g. Furthermore, a region of the housing contact surface 44d is approximately the same size as a region of the carrier contact surface 44e. That is to say, a Fig. 2 The area W1 shown of the contact interface between the cage 44 and the housing 4 corresponds approximately to an area W2 of the contact interface between cage 44 and support 10.

[0030] Furthermore, in Fig. Figure 2 shows a state in which the housing contact surface 44d is in contact with the housing 4 and the support contact surface 44e is in contact with the support 10. This means that a state is shown in which the first end 44a of the cage 44 makes contact with the housing 4 in a direction perpendicular to the bearing axis 30 (the radial direction of the cage 44) and with the support 10 in the direction of the bearing axis 30. However, when the gear unit 100 is not in operation, the housing contact surface 44d and the support contact surface 44e do not necessarily have to be in contact with the housing 4 and support 10. It is important that the housing contact surface 44d and the support contact surface 44e each have contact with the housing 4 and support 10, respectively, when a force acts that pushes the rolling elements 42 outwards.

[0031] Now, the advantages of the gear drive 100 will be described. Fig. Figure 6 is a diagram illustrating the function of the rolling elements 42 and the cage 44 when the carrier 10 rotates relative to the stationary housing 4. Furthermore, Fig. Figure 6 is a diagram illustrating the functional concept of the rolling elements 42 and the cage 44, but it does not accurately depict the design of the gear drive 100. Furthermore, as described above, the inner ring 46 of the cylindrical roller bearing 2 can be considered integral with the carrier 10. Similarly, the outer ring 40 can be considered integral with the housing 4. Consequently, in Fig. Figure 6 shows the inner ring 46 and the carrier 10 as one part, and the outer ring 40 and the housing 4 are shown as one part. Furthermore, the figures in Fig. The rolling elements 42 shown in Figure 6 represent a cross-section perpendicular to the direction of the axis of rotation.

[0032] When the carrier 10 rotates in the direction of arrow A1, the rolling elements 42 move in the direction of arrow A3 while rotating in the direction of arrow A2. This means that the rolling elements 42 move in the direction of arrow A3 while rolling against the outer surface of the carrier 10 and the inner surface of the housing 4. The cage 44 rotates in the direction of arrow A3 in conjunction with the movement of the rolling elements 42. If the friction between the rolling elements 42 and the carrier 10, and between the rolling elements 42 and the housing 4, is low, the cage 44 will rotate at a speed (0.5 V) that is approximately half the rotational speed V of the carrier 10. As the friction between the rolling elements 42 and the support 10 increases, the speed of the rolling elements 42 approaches the speed of the support 10.Conversely, if the friction between the rolling elements 42 and the housing 4 increases, the speed of the rolling elements 42 approaches the speed of the housing 4 (zero).

[0033] As described above, the first end 44a of the cage 44 is in contact with both the housing 4 and the support 10 (see also Fig. 2) When the cage 44 is in contact with the housing 4 and also with the support 10, a frictional force F1 occurs in the direction of arrow A4 between the cage 44 and the housing 4. Furthermore, a frictional force F2 occurs in the direction of arrow A5 between the cage 44 and the support 10. As described above, the contact area W1 between the cage 44 and the housing 4 is essentially the same as the contact area W2 between the cage 44 and the support 10. Consequently, the frictional force F1 is essentially equal to the frictional force F2. Since the frictional force F1 and the frictional force F2 cancel each other out, the cage 44 rotates in the direction of arrow A3 at a speed close to 0.5 V. The rolling elements 42 also move in the direction of arrow A3 at a speed close to 0.5 V.

[0034] A movement of the rolling elements 42 in the direction of arrow A3 at a speed close to the rotational speed of 0.5 V means that the friction between the rolling elements 42 and the carrier 10, as well as between the rolling elements 42 and the housing 4, is small. In other words, the sliding motion of the rolling elements 42 relative to the carrier 10 and housing 4 is small. Consequently, the wear of the rolling elements 42 (the gradual destruction of the cylindrical roller bearing 2) is kept to a minimum. Furthermore, if the cage is in contact only with the housing, as described in patent document 1 above, only a frictional force equivalent to the frictional force F1 of the bearing 42 is present. Fig. 6, and no frictional force corresponding to the frictional force F2 can be generated. As a result, the rotational speed of the cage decreases, and the friction between the rolling elements and the carrier, as well as between the rolling elements and the housing, increases.

[0035] The wear of the rolling elements is accelerated and the service life of the gear unit is shortened. By ensuring that the cage 44 is in contact with both the carrier 10 and the housing 4, the wear of the rolling elements 42 in the gear unit 100 shown in the present embodiment can be kept low, while at the same time the movement of the rolling elements 42 in the axial direction is restricted.

[0036] Furthermore, the cylindrical roller bearing 2 arranged between the housing 4 and the first plate 10a has the same properties as the cylindrical roller bearing 2 arranged between the housing 4 and the second plate 10c (see Fig. 1) Therefore, a description of the cylindrical roller bearing 2 arranged between the housing 4 and the first plate 10a is omitted.

[0037] Further advantages of the gear unit 100 will now be described. As described above, the contact surface between cage 44 and housing 4 is cylindrical and coaxial with the axis 30. Furthermore, the contact surface of cage 44 and carrier 10 is perpendicular to the axis 30. Based on these properties, the movement of cage 44 is controlled in two orthogonal directions (axial and radial directions of the gear unit 100). This reliably prevents cage 44 (and the rolling elements 42) from detaching from the gear unit 100.

[0038] As described above, the cage 44 is in contact with the housing 4 and the support 10. Consequently, the cage 44 prevents foreign objects from outside the gear unit 100 from entering the housing 4. Furthermore, an oil seal 6 is arranged between the housing 4 and the first plate 10a, and a groove 26 is provided at a location facing the second plate 10c of the housing 4 (see Figure 1). Fig. 1) The groove 26 runs around an outer circumference of the small-diameter section 4a. If another part (e.g., a motor) is attached to the gear unit 100, an O-ring (not shown) is located in the groove 26.

[0039] The oil seal 6 and the O-ring arranged in the groove 26 prevent lubricant trapped in the gear 100 from escaping to the outside. Furthermore, the outer circumferential grooves 44f are formed on the housing contact surface 44d of the cage 44, and the end-face grooves 44g are formed on the support contact surface 44e of the cage 44. Therefore, despite the fact that the cage 44 is in contact with both the housing 4 and the support 10, it is possible for lubricant present on the outside of the cylindrical roller bearing 2 to reach the inside of the cylindrical roller bearing 2. A decrease in the amount of lubricant (oil leakage) in or from the cylindrical roller bearing 2 can be prevented. More precisely, lubricant present in the vicinity of the oil seal 6 can enter the interior of the cylindrical roller bearing 2 through the outer circumferential grooves 44f and the end face grooves 44g.

[0040] When the rolling elements 42 are subjected to a force that pushes them outwards, the cage 44 is pressed against the housing 4 and the support 10. As described above, the cage 44 is made of plastic, and the housing 4 and the support 10 are made of metal. This means that the cage is made of a material with a lower stiffness than the support and the housing. Since the stiffness of the cage 44 is less than the stiffness of the housing 4 and the support 10, the cage 44 can deform when pressed against the housing 4 and the support 10. As a result, the entire cage 44 establishes uniform contact with the housing 4 and the support 10 in the circumferential direction. This means that a gap is unlikely to form between the housing contact surface 44d and the housing 4 or between the support contact surface 44e and the support 10.

[0041] A central through-bore 12 is formed in the direction of the axis 30 in the center of the gear unit 100. Using the central through-bore 12, wiring, piping, or the like can be passed through the gear unit 100. (Second embodiment)

[0042] With reference to Fig. 7, Fig. Section 8 describes a gear transmission of a second embodiment. The gear transmission of the present embodiment differs from the gear transmission 100 only in the shape of the cage. More precisely, a cage 144 of the present embodiment differs from cage 44 with respect to the positional relationship of the outer circumferential grooves formed on the housing contact interface and the end-face grooves formed on the support contact interface. Details common to cage 144 and cage 44 bear the same reference numerals or have two identical appended digits, and no further explanation is provided.

[0043] In the circumferential direction of the cage 144, the outer circumferential grooves 44f and end-face grooves 44g are formed at the same position. Therefore, the outer circumferential grooves 44f and end-face grooves 44g are interconnected. Lubricant present on the outer surface of the cylindrical roller bearing 2 can reach the interior of the cylindrical roller bearing 2 through the outer circumferential grooves 44f and end-face grooves 44g. The cage 144 facilitates the lubricant's entry into the interior of the cylindrical roller bearing 2. (Third embodiment)

[0044] Now, with reference to Fig. 9, Fig. 10 describes a gear transmission of a third embodiment. The gear transmission of the present embodiment differs from the gear transmission 100 only in the shape of the cage. Specifically, a cage 244 of the present embodiment differs from cage 44 in the shape of the outer circumferential grooves formed on the housing contact interface and in the shape of the end-face grooves formed on the support contact interface. Individual features common to cage 244 and cage 44 bear the same reference numerals or have two identical appended digits, and no further explanation is provided.

[0045] As in Fig. As shown in Figure 9, several end-face grooves 244g are formed on a support contact surface 244e. Viewed from the direction of the bearing axis 30, the direction of the end-face grooves 244g is oblique with respect to a line formed by connecting an outer surface (a housing contact surface 244d) of the cage 244 with the bearing axis 30 (see Figure 9). Fig. 4) Each of the multiple end-surface grooves 244g is inclined in the same direction. Furthermore, as shown in Fig. Figure 10 shows several outer circumferential grooves 244f formed on the housing contact surface 244d. Viewed from a direction perpendicular to the bearing axis 30, the direction of the outer circumferential grooves 244f is oblique with respect to the bearing axis 30 (see Figure 10). Fig. 5) Each of the multiple outer circumferential grooves 244f is inclined in the same direction. Furthermore, the end-face grooves 244g and outer circumferential grooves 244f are formed alternately in the circumferential direction of the cage 244. That is, the end-face grooves 244g are formed between adjacent outer circumferential grooves 244f, and the outer circumferential grooves 244f are formed between adjacent end-face grooves 244g.

[0046] When the gear drive is operating, the cage 244 rotates relative to the carrier 10 and housing 4. If the end face grooves 244g are inclined, the lubricant can move easily in the end face grooves 244g along with the rotation of the cage 244. Similarly, if the outer circumferential grooves 244f are inclined, the lubricant can move easily in the outer circumferential grooves 244f along with the rotation of the cage 244. Furthermore, as with the cage 144, the end face grooves 244g and outer circumferential grooves 244f can be interconnected. (Fourth embodiment)

[0047] With reference to Fig. Section 11 describes a gear unit 300. The gear unit 300 is a variant of the gear unit 100, and parts corresponding to those of the gear unit 100 are designated with the same reference numbers or have the same two appended digits, and no further explanation is given.

[0048] In the gear unit 300, an inclined section 346 is provided at a radial end of a first plate 310a and a second plate 310c. The inclined section 346 also serves as the inner ring of a cylindrical roller bearing 302. This means that the inner ring of the cylindrical roller bearing 302 is integral with a carrier 310. In such an embodiment, the inner ring can also be considered to be attached to the carrier 310. A flange 310d is formed on an outer surface in the direction of the axis 30 of the inclined section 346 of the first plate 310a. A flange 310e is formed on an outer surface in the direction of the axis 30 of the inclined section 346 of the second plate 310c. The cage 44 is the same as the cage 44 used in the gear unit 100. Accordingly, the cage 44 is in contact with both the flange 310d and the flange 310e.

[0049] In the preceding embodiments, a gear transmission was described in which a cage is used having a groove on both the carrier contact surface and the housing contact surface. However, the technology disclosed in the present description can also be applied to a gear transmission in which a cage is used having a groove on either the carrier contact surface or the housing contact surface, and to a gear transmission which uses a cage having no groove on either the carrier contact surface or the housing contact surface.

[0050] The preceding embodiments described an example in which the contact area between the cage and housing and the contact area between the cage and the carrier are the same size. However, the contact area between the cage and the housing can be larger than the contact area between the cage and the carrier. Conversely, the contact area between the cage and the carrier can be larger than the contact area between the cage and the housing. Even in this type of embodiment, the friction of the rolling elements can be reduced compared to a conventional gear drive where the cage is in contact only with the housing. If the cage is in contact with both the housing and the carrier, the wear of the rolling elements can be kept low compared to a conventional gear drive.

[0051] The embodiments described above represent an example in which the outer ring is attached to the housing and the inner ring is attached to the carrier. However, the inner ring can also be attached to the housing and the outer ring to the carrier.

[0052] The embodiments described above represent an example in which the housing is stationary and the support rotates relative to the housing. However, the technology disclosed in this description can also be applied to a gear drive in which the support is stationary and the housing rotates relative to the support. Furthermore, the technology disclosed in this description can also be applied to a gear drive in which the crankshaft is arranged coaxially with the axis of the support. Finally, the technology disclosed in this description can also be applied to a gear drive that is not of an eccentric oscillating design.

[0053] In the fourth embodiment, an example was described in which the carrier also serves as the inner ring. The housing can also serve as the outer ring. Furthermore, the carrier can serve as the inner ring and the housing as the outer ring. It is important that the cylindrical roller bearing is positioned between the housing and the carrier, that the axis of rotation of the rolling elements of the cylindrical roller bearing is oblique relative to the axis of the carrier, and that the cage holding the rolling elements has contact with both the housing and the carrier.

[0054] Specific examples of the present invention are described in detail above; however, these examples are merely illustrative and do not limit the scope of the claims. The technology described in the claims also includes various changes and modifications to the specific examples described above. The technical elements explained in this description or the drawings offer technical benefits either independently of one another or through various combinations. At the time of filing the claims, the present invention is not limited to the combinations described. Furthermore, the objective of the examples illustrated by this description or the drawings is to achieve several objectives simultaneously, with the achievement of any one of these objectives conferring technical benefit on the present invention.

Claims

[1] Gear transmission (100, 300) in which a carrier (10, 310) is supported by a housing (4) via a bearing (2, 302), the bearing (2, 302) comprising: an inner ring (46, 346) having an inclined outer surface (46b) and being fixed to the housing (4) or to the carrier (10, 310); an outer ring (40) having an inclined inner surface (40b) facing the inclined outer surface (46b) of the inner ring (46, 346) and which is then fixed to the carrier (10, 310) or housing (4) accordingly; cylindrical rolling elements (42) arranged between the inner ring (46, 346) and the outer ring (40); and an annular cage (44, 144, 244) arranged between the inner ring (46, 346) and the outer ring (40) and maintaining a distance between adjacent rolling elements (42), wherein one end (44a, 244a) of the cage (44, 144, 244) having a large diameter makes contact with both the housing (4) and the carrier (10, 310), wherein a contact interface (44d, 244d) between the cage (44, 144, 244) and the housing (4) or a contact interface (44e, 244e) between the cage (44, 144, 244) and the carrier (10, 310) is perpendicular to an axis (30) of the carrier (10, 310), wherein the respective other contact interface (44d, 244d) between the cage (44, 144, 244) and the housing (4) or the contact interface (44e, 244e) between the cage (44, 144, 244) and the carrier (10, 310) forms a cylindrical surface which is coaxial with the carrier (10, 310). [2] Gear transmission (100, 300) according to claim 1, wherein a contact area (W1) between the cage (44, 144, 244) and the housing (4) is the same size as a contact area (W2) between the cage (44, 144, 244) and the carrier (10, 310). [3] Gear transmission (100, 300) according to one of claims 1 to 2, wherein a groove (44f, 44g, 244f, 244g) is formed at the contact interface (44d, 244d) between the cage (44, 144, 244) and the housing (4) and / or at the contact interface (44e, 244e) between the cage (44, 144, 244) and the carrier (10, 310). [4] Gear transmission (100, 300) according to claim 3, wherein a first groove (44f, 244f) is formed at the contact interface (44d, 244d) between the cage (44, 144, 244) and the housing (4), and a second groove (44g, 244g) is formed at the contact interface (44e, 244e) between the cage (44, 144, 244) and the carrier (10, 310). [5] The gear transmission (100, 300) according to claim 4, wherein the first groove (44f) and the second groove (44g) are formed at the same position in the circumferential direction of the cage (144). [6] A gear transmission (100, 300) according to claim 4, wherein the first groove (44f, 244f) and the second groove (44g, 244g) are formed alternately in the circumferential direction of the cage (44, 244). [7] Gear transmission (100, 300) according to one of claims 4 to 6, wherein the first groove (244f) runs obliquely relative to a bearing axis (30) of the bearing (2, 302), and the second groove (244g) is inclined relative to a line formed by connecting the bearing axis (30) and the outer surface (244d) of the cage (244).

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