JP2024070029A - Speed reducer - Google Patents

Abstract

To realize a structure which can inhibit increase of costs while preventing occurrences of abnormal noise and vibration.SOLUTION: A speed reducer 1 includes: an input member 2; an output member 3; a carrier 4; a first planetary roller mechanism 5; and a second planetary roller mechanism 6. The first planetary roller mechanism 5 includes: a first sun roller 51 which rotates integrally with the input member 2; a first ring roller 52 supported by a portion that does not rotate during use; and a first planetary roller 53 which is supported in a manner that allows the first planetary roller 53 to rotate around its center axis relative to the carrier 4. The second planetary roller mechanism 6 includes: a second sun roller 62 which rotates integrally with the input member 2 and the first sun roller 51; a second ring roller 63 which rotates integrally with the output member 3; and a second planetary roller 64 which is supported in a manner that allows the second planetary roller 64 to rotate around its center axis relative to the carrier 4.SELECTED DRAWING: Figure 1

Description

The present invention relates to an improvement to a reduction gear device that is incorporated, for example, in the drive system of an automobile to reduce the speed of the drive source (increase the torque) before transmitting it to the drive wheels.

A structure equipped with a torque converter and a planetary gear mechanism is widely used as an automatic transmission for automobiles. The planetary gear mechanism includes a sun gear, a ring gear arranged around the sun gear, and multiple planetary gears meshed with the sun gear and the ring gear.

However, unavoidable backlash exists at the meshing points between the sun gear and planetary gear, and between the planetary gear and ring gear. In planetary gear mechanisms, this backlash can cause unpleasant noises and vibrations known as rattle noise.

WO 2020/170297 describes a planetary gear device that can prevent abnormal noise and vibration caused by backlash. The planetary gear device described in WO 2020/170297 includes a first internal gear and a second internal gear, an external gear, three pairs of first and second planetary gears, a sun roller, three pairs of first and second rollers, a carrier, and a first and second ring.

The first and second internal gears are arranged coaxially and capable of relative rotation.

The external gear is arranged radially inward of the first internal gear and the second internal gear and is coaxial with the first internal gear and the second internal gear.

The pair of first and second planetary gears are arranged coaxially with each other. The pair of first and second planetary gears are connected via pair of first and second rollers so that they can rotate together. Each first planetary gear meshes with the first internal gear and the external gear, and each second planetary gear meshes with the second internal gear.

The sun roller is fixedly connected to the external gear so that it can rotate integrally with the external gear. The sun roller has an outer diameter equal to the pitch diameter of the external gear.

The pair of first and second rollers are arranged coaxially with the pair of first and second planetary gears, and are fixedly connected to the pair of first and second planetary gears so as to be able to rotate integrally with the pair of first and second planetary gears. The first roller is in rolling contact with the first ring and the sun roller, and the second roller is in rolling contact with the second ring. The first roller has an outer diameter equal to the pitch diameter of the first planetary gear, and the second roller has an outer diameter equal to the pitch diameter of the second planetary gear.

The carrier supports each of the planetary sections, which are made up of a first planetary gear and a second planetary gear and a first roller and a second roller that are connected to enable unified rotation, so that each planetary section can rotate (spin) around its central axis.

The first ring and the second ring are arranged coaxially with the first internal gear and the second internal gear. The first ring has an inner diameter equal to the pitch diameter of the first internal gear, and the second ring has an inner diameter equal to the pitch diameter of the second internal gear.

The planetary gear device described in WO 2020/170297 combines a planetary gear mechanism, which is a gear drive type power transmission mechanism, with a friction roller mechanism, which is a traction drive type power transmission mechanism, to prevent abnormal noise and vibration caused by backlash.

International Publication No. 2020/170297

In the planetary gear device described in WO 2020/170297, if there is a discrepancy between the reduction ratio in the planetary gear mechanism and the reduction ratio in the friction roller mechanism, harmful slippage occurs at the rolling contact portion of the friction roller mechanism, making wear more likely to progress. If the reduction ratio in the planetary gear mechanism and the reduction ratio in the friction roller mechanism can be closely matched, the occurrence of harmful slippage in the friction roller mechanism can be suppressed.

However, in order to precisely match the reduction ratio in the planetary gear mechanism with that in the friction roller mechanism, the shape accuracy, dimensional accuracy, and assembly accuracy of each component that makes up the planetary gear device must be sufficiently high, which increases costs.

The present invention aims to realize a reduction gear structure that can prevent abnormal noise and vibration while suppressing increases in costs.

One aspect of the reduction gear of the present invention includes an input member, an output member, a carrier, a first planetary roller mechanism, and a second planetary roller mechanism.

The output member is supported coaxially with the input member and capable of relative rotation with respect to the input member.

The carrier is supported coaxially with the input member and the output member and is capable of rotating relative to the input member and the output member.

The first planetary roller mechanism includes a first sun roller, a first ring roller, and at least one first planetary roller.

The first sun roller has a first inner diameter rolling contact surface on its outer circumferential surface and rotates integrally with the input member.

The first ring roller has a first outer diameter rolling contact surface on its inner circumferential surface, is arranged coaxially with the first sun roller, and is supported by a portion that does not rotate even during use.

The first planetary roller has a first rolling surface on its outer circumferential surface that is in rolling contact with the first inner diameter rolling contact surface and the first outer diameter rolling contact surface, and is supported so as to be capable of rotating about its own central axis relative to the carrier.

The second planetary roller mechanism includes a second sun roller, a second ring roller, and at least one second planetary roller.

The second sun roller has a second inner diameter rolling contact surface on its outer circumferential surface, is arranged coaxially with the first sun roller, and rotates integrally with the input member and the first sun roller.

The second ring roller has a second outer diameter rolling contact surface on its inner circumferential surface, is arranged coaxially with the second sun roller, and rotates integrally with the output member.

The second planetary roller has a second rolling surface on its outer circumferential surface that is in rolling contact with the second inner diameter rolling contact surface and the second outer diameter rolling contact surface, and is supported so as to be capable of rotating about its own central axis relative to the carrier.

In one aspect of the reduction gear of the present invention, it is preferable that the first planetary roller and the second planetary roller are out of phase with each other in the circumferential direction.

One aspect of the reduction gear of the present invention may further include a housing that accommodates the first planetary roller mechanism and the second planetary roller mechanism. In this case, the input member is rotatably supported relative to the housing, and the output member is rotatably supported relative to the housing.

The reduction gear of the present invention can prevent abnormal noise and vibration while minimizing increases in costs.

FIG. 1 is a schematic diagram showing a reduction gear transmission according to a first embodiment of the present invention. FIG. 2 is an end view of the reduction gear transmission of the first example as viewed from the axial direction. FIG. 3 is a cross-sectional view taken along line XX of FIG. FIG. 4 is an exploded perspective view showing the reduction gear transmission of the first example.

[First Example of the Embodiment]
A first embodiment of the present invention will be described with reference to Figures 1 to 3. The reduction gear 1 of this example includes an input member 2, an output member 3, a carrier 4, a first planetary roller mechanism 5, and a second planetary roller mechanism 6. The reduction gear 1 reduces the rotation of the input member 2 by a reduction mechanism 7 consisting of the carrier 4, the first planetary roller mechanism 5, and the second planetary roller mechanism 6, and then transmits it to the output member 3. In other words, the reduction gear 1 increases the rotational torque of the input member 2 by the reduction mechanism 7, then transmits it to the output member 3, and outputs it from the output member 3. Furthermore, the reduction gear 1 of this example includes a housing 8 that accommodates the reduction mechanism 7.

In the following description, the axial, radial, and circumferential directions of the reduction gear 1 refer to the axial, radial, and circumferential directions of the input member 2 unless otherwise specified. The axial, radial, and circumferential directions of the input member 2 coincide with the axial, radial, and circumferential directions of the output member 3, and also coincide with the axial, radial, and circumferential directions of the carrier 4. Furthermore, with respect to the reduction gear 1, one axial side refers to the left side in Figs. 1 and 3, which is the input member 2 side, and the other axial side refers to the right side in Figs. 1 and 3, which is the output member 3 side.

In this example, the housing 8 comprises a housing body 9, a bush 14, and a lid body 10.

The housing body 9 comprises a cylindrical portion 11, a hollow circular inward flange portion 12 bent radially inward from one axial end of the cylindrical portion 11, and a hollow circular outward flange portion 13 bent radially outward from the other axial end of the cylindrical portion 11.

The cylindrical portion 11 has engagement grooves 56 extending in the axial direction at multiple locations in the circumferential direction on the inner peripheral surface of one axial side portion. In this example, one axial end of the engagement grooves 56 opens onto one axial side surface of the inward flange portion 12.

The outward flange portion 13 has through holes 15 that penetrate in the axial direction at multiple locations in the circumferential direction. One axial side surface of the outward flange portion 13 is formed as a flat surface that is perpendicular to the central axis of the input member 2.

The bush 14 is configured in an annular shape, has threaded holes 16 at multiple locations in the circumferential direction that open to the other axial side, and has a stepped surface 38 facing the other axial side on one axial side of the inner peripheral surface. The bush 14 is fixed by an interference fit into the other axial side of the cylindrical portion 11 of the housing body 9 with the radially outer end of one axial side abutting against an abutment surface 69 facing the other axial side provided on the inner peripheral surface of the cylindrical portion 11 of the housing body 9.

The lid 10 is configured as a hollow circular plate. The lid 10 has inner diameter side through holes 17 that penetrate in the axial direction at multiple locations in the circumferential direction of the radially inner portion, and has outer diameter side through holes 18 that penetrate in the axial direction at multiple locations in the circumferential direction of the radially outer portion.

The housing body 9, bushing 14, and lid 10 are connected and fixed to each other by threading a bolt 19 inserted through the inner diameter side through hole 17 into the threaded hole 16 to form the housing 8. The housing 8 is supported and fixed to the fixed part by abutting one axial side of the outward flange portion 13 of the housing body 9 against a mounting surface provided on a fixed part that does not rotate even when in use, such as a vehicle body, and threading a bolt (not shown) inserted from the other axial side through the outer diameter side through hole 18 of the lid 10 and the through hole 15 of the housing body 9 into a threaded hole opening on the mounting surface.

The input member 2 is rotatably supported on one axial side of the housing 8 and is driven to rotate by a drive source such as an electric motor or an engine.

In this example, the input member 2 has a stepped cylindrical shape. Specifically, the input member 2 has a small diameter shaft portion 20 on one axial side and a large diameter shaft portion 21 on the other axial side.

In this example, the large diameter shaft portion 21 is rotatably supported on the inward flange portion 12 of the housing body 9 that constitutes the housing 8 via the carrier 4 and three radial bearings 22a, 22b, and 22c. The small diameter shaft portion 20 is connected to the drive source so as to be able to transmit torque.

The output member 3 is supported coaxially with the input member 2 and capable of relative rotation with respect to the input member 2. In this example, the output member 3 is supported rotatably on the other axial side of the housing 8.

In this example, the output member 3 includes a first output member element 23 and a second output member element 24.

The first output member element 23 has a circular plate-shaped substrate portion 25 and a cylindrical shaft portion 26 that protrudes from the center position of the other axial side of the substrate portion 25 toward the other axial side.

The base plate portion 25 has through holes 27 that penetrate in the axial direction at multiple circumferential locations in the radial middle portion.

The second output member element 24 has a stepped cylindrical shape. Specifically, the second output member element 24 is made up of a large-diameter cylindrical portion 28 on one axial side and a small-diameter cylindrical portion 29 on the other axial side, connected by a hollow circular plate-shaped side plate portion 30.

The large diameter cylindrical portion 28 has recesses 31 at multiple locations in the circumferential direction that open to the inner circumferential surface and to one end face in the axial direction.

The small diameter cylindrical portion 29 has multiple screw holes 32 at various locations in the circumferential direction that open onto the other side in the axial direction.

The first output member element 23 and the second output member element 24 are connected and fixed to each other by threading a bolt 33 inserted through the through hole 27 into the screw hole 32 to form the output member 3.

In this example, the small diameter cylindrical portion 29 of the second output member element 24 that constitutes the output member 3 is rotatably supported by a radial rolling bearing 34 inside the bush 14 that constitutes the housing 8.

The radial rolling bearing 34 comprises an inner ring 35, an outer ring 36, and a number of rolling elements 37 arranged to roll freely at multiple locations in the circumferential direction between the inner ring 35 and the outer ring 36.

The inner ring 35 is fitted onto the small diameter cylindrical portion 29 of the second output member element 24, and is axially sandwiched between the radially inner end of the other axial side of the side plate portion 30 of the second output member element 24 and the radially outer portion of one axial side of the base plate portion 25 of the first output member element 23.

The outer ring 36 is fitted inside the bush 14 and is axially sandwiched between the step surface 38 of the bush 14 and the radially inner end of one axial side of the lid 10.

Each rolling element 37 is arranged to be freely rollable at multiple locations in the circumferential direction between the inner ring 35 and the outer ring 36. In this example, each rolling element 37 is composed of a ball. That is, in this example, the radial rolling bearing 34 is composed of a radial ball bearing. However, the radial rolling bearing for rotatably supporting the output member in the housing can also be composed of a cylindrical roller bearing or a bearing unit having multiple rolling bearings.

The carrier 4 is supported coaxially with the input member 2 and the output member 3 and is capable of rotating relative to the input member 2 and the output member 3.

In this example, the carrier 4 comprises a first carrier element 39 and a second carrier element 40.

The first carrier element 39 comprises a substantially cylindrical first base portion 41, a first side plate portion 42, a plurality of first support shaft portions 43, and a plurality of second support shaft portions 44.

The first side plate portion 42 is configured in a generally hollow circular plate shape and protrudes radially outward from one axial end of the first base portion 41.

Each of the first support shaft portions 43 protrudes toward one axial side from multiple equally spaced locations in the circumferential direction on one axial side surface of the first side plate portion 42. Each of the first support shaft portions 43 has a cylindrical shape and a screw hole 45a that opens to one axial side surface.

The first support shaft portions 43 are provided in the same number as the first planetary rollers 53 constituting the first planetary roller mechanism 5 described below. In this example, the first planetary roller mechanism 5 has three first planetary rollers 53. Therefore, the first support shaft portions 43 protrude toward one axial side from three equally spaced locations in the circumferential direction on one axial side surface of the first side plate portion 42.

Each of the second support shafts 44 protrudes toward one axial side from multiple equally spaced locations in the circumferential direction of one axial side surface of the first side plate portion 42, circumferentially deviating from the portion where the first support shafts 43 are provided. Each of the second support shafts 44 has a cylindrical shape and a screw hole 45b that opens to one axial side surface.

The second support shaft portions 44 are provided in the same number as the second planetary rollers 64 constituting the second planetary roller mechanism 6 described later. In this example, the second planetary roller mechanism 6 has three second planetary rollers 64. Therefore, in this example, the second support shaft portions 44 protrude from the circumferential center position between the circumferentially adjacent first support shaft portions 43 on one axial side surface of the first side plate portion 42 toward one axial side. In other words, the second support shaft portions 44 are provided in a portion that is 60 degrees out of phase with the first support shaft portions 43 in the circumferential direction.

The amount of protrusion of the second support shaft portion 44 from one axial side surface of the first side plate portion 42 is smaller than the amount of protrusion of the first support shaft portion 43 from one axial side surface of the first side plate portion 42. In addition, the central axes of the first support shaft portions 43 and the central axes of the second support shaft portions 44 are arranged parallel to each other and exist on the same imaginary circle centered on the central axis of the first base portion 41.

The second carrier element 40 has a substantially cylindrical second base portion 46 and a second side plate portion 47.

The second side plate portion 47 is configured as a substantially hollow circular plate and protrudes radially outward from the other axial end of the second base portion 46.

The second side plate portion 47 has first through holes 48 that penetrate in the axial direction at multiple locations equally spaced in the circumferential direction. In this example, the first through holes 48 are provided at three locations equally spaced in the circumferential direction of the second side plate portion 47.

The second side plate portion 47 also has offset portions 49 that are offset axially to the other side from adjacent portions at equal intervals in the circumferential direction in a portion circumferentially deviated from the portion in which the first through holes 48 are provided. Specifically, in this example, the second side plate portion 47 has three offset portions 49 at the circumferential center positions between the first through holes 48 that are adjacent in the circumferential direction. Each offset portion 49 has a second through hole 50 that penetrates in the axial direction.

Furthermore, the second carrier element 40 has a cylindrical first protrusion 59 that protrudes toward the other axial direction from a portion of the other axial side surface of the second side plate portion 47 that surrounds the opening on the other axial side of the first through hole 48, and has a cylindrical second protrusion 60 that protrudes toward the other axial direction from a portion of the other axial side surface of the second side plate portion 47 that surrounds the opening on the other axial side of the second through hole 50.

The first carrier element 39 and the second carrier element 40 are connected and fixed to each other by butting the end face of one axial side of the first support shaft portion 43 against the end face of the other axial side of the first protrusion 59, and butting the end face of one axial side of the second support shaft portion 44 against the end face of the other axial side of the second protrusion 60, and screwing the bolt 70a inserted through the first through hole 48 into the screw hole 45a provided in the first support shaft portion 43 and screwing the bolt 70b inserted through the second through hole 50 into the screw hole 45b provided in the second support shaft portion 44 to form the carrier 4.

In this example, the carrier 4 is supported by four radial bearings 22a, 22b, 22c, and 22d to enable relative rotation with respect to the input member 2, the output member 3, and the housing 8. Specifically, the radial bearing 22a is arranged between the outer peripheral surface of one axial side portion of the large diameter shaft portion 21 of the input member 2 and the inner peripheral surface of the second side plate portion 47 of the second carrier element 40, and the radial bearing 22b is arranged between the outer peripheral surface of the second base portion 46 and the inner peripheral surface of the inward flange portion 12 of the housing main body 9. In addition, the radial bearing 22c is arranged between the outer peripheral surface of the other axial end portion of the large diameter shaft portion 21 and the inner peripheral surface of the first side plate portion 42 of the first carrier element 39, and the radial bearing 22d is arranged between the outer peripheral surface of the first base portion 41 and the inner peripheral surface of the small diameter cylindrical portion 29 of the second output member element 24 constituting the output member 3.

In this example, all four radial bearings 22a, 22b, 22c, and 22d are sliding bearings. However, some or all of the radial bearings that support the carrier to rotate relative to the input member, output member, and housing can also be radial rolling bearings such as ball bearings or radial needle bearings.

The first planetary roller mechanism 5 comprises a first sun roller 51, a first ring roller 52, and at least one first planetary roller 53.

The first sun roller 51 has a first inner diameter rolling contact surface 54 on its outer circumferential surface and rotates integrally with the input member 2.

In this example, the first inner diameter rolling contact surface 54 is formed directly on the outer peripheral surface of the axially middle portion of the large diameter shaft portion 21 of the input member 2. In other words, the first sun roller 51 is integrally formed with the input member 2.

However, the first sun roller can also be configured separately from the input member. Specifically, the first sun roller can be configured as an annular member having a first inner diameter side rolling contact surface on its outer circumferential surface, and the annular member can be fitted to the input member by spline engagement or the like so as to be capable of transmitting torque.

The first ring roller 52 has a first outer diameter rolling contact surface 55 on its inner circumferential surface, is arranged coaxially with the first sun roller 51, and is supported by a part that does not rotate even when in use.

In this example, the first ring roller 52 is configured in an annular shape, has a first outer diameter side rolling contact surface 55 on its inner circumferential surface, and has first engagement protrusions 57 at multiple locations in the circumferential direction on its outer circumferential surface. The first ring roller 52 is supported so as not to rotate relative to the housing 8 by engaging each of the first engagement protrusions 57 with an engagement groove 56 provided on the inner circumferential surface of the cylindrical portion 11 of the housing main body 9 that constitutes the housing 8.

However, the first outer diameter rolling contact surface can also be formed directly on the inner peripheral surface of the housing. In other words, the first ring roller can be configured integrally with the housing.

The first planetary roller 53 has a first rolling surface 58 on its outer circumferential surface that is in rolling contact with the first inner diameter side rolling contact surface 54 and the first outer diameter side rolling contact surface 55, and is supported so as to be capable of rotating about its own central axis (rotation axis) relative to the carrier 4.

In this example, the first planetary roller mechanism 5 includes three first planetary rollers 53. Each first planetary roller 53 is configured in an annular shape and is rotatably supported by two radial rolling bearings 61a around the first support shaft portion 43 of the first carrier element 39 and the first protruding portion 59 of the second carrier element 40. That is, radial rolling bearings 61a are disposed in the portion between the inner peripheral surface of the end portion on the other axial side of the first planetary roller 53 and the outer peripheral surface of the first support shaft portion 43, and in the portion between the inner peripheral surface of the end portion on one axial side of the first planetary roller 53 and the outer peripheral surface of the first protruding portion 59.

The second planetary roller mechanism 6 includes a second sun roller 62, a second ring roller 63, and at least one second planetary roller 64.

The second sun roller 62 has a second inner diameter rolling contact surface 65 on its outer circumferential surface, and rotates integrally with the input member 2 and the first sun roller 51.

In this example, the second inner diameter rolling contact surface 65 is formed directly on the outer circumferential surface of the large diameter shaft portion 21 of the input member 2, at a portion located on the other axial side of the portion on which the first sun roller 51 is fitted. In other words, the second sun roller 62 is integrally formed with the input member 2 and the first sun roller 51.

However, the second sun roller can also be configured separately from the input member. Specifically, the second sun roller can be configured as an annular member having a second inner diameter rolling contact surface on its outer circumferential surface, and the annular member can be fitted to the input member by spline engagement or the like so as to be capable of transmitting torque.

In this example, the outer diameter of the second sun roller 62 (i.e., the diameter of the second inner diameter rolling contact surface 65) is larger than the outer diameter of the first sun roller 51 (i.e., the diameter of the first inner diameter rolling contact surface 54).

The second ring roller 63 has a second outer diameter rolling contact surface 66 on its inner circumferential surface, is arranged coaxially with the second sun roller 62, and rotates integrally with the output member 3.

In this example, the second ring roller 63 is configured in an annular shape, has a second outer diameter side rolling contact surface 66 on its inner circumferential surface, and has second engagement protrusions 67 at multiple locations in the circumferential direction on its outer circumferential surface. The second ring roller 63 is supported so as to be able to transmit torque to the output member 3 by engaging each of the second engagement protrusions 67 with a recess 31 provided on the inner circumferential surface of the large diameter cylindrical portion 28 of the second output member element 24 that constitutes the output member 3.

However, the second outer diameter rolling contact surface can also be formed directly on the inner peripheral surface of the output member. In other words, the second ring roller can be configured integrally with the output member.

In this example, the inner diameter of the second ring roller 63 (i.e., the diameter of the second outer diameter rolling contact surface 66) is smaller than the inner diameter of the first ring roller 52 (i.e., the diameter of the first outer diameter rolling contact surface 55).

The second planetary roller 64 has a second rolling surface 68 on its outer circumferential surface that is in rolling contact with the second inner diameter side rolling contact surface 65 and the second outer diameter side rolling contact surface 66, and is supported so as to be capable of rotation about its own central axis (rotation axis) relative to the carrier 4. Therefore, the second planetary roller 64 does not rotate (spin) integrally with the first planetary roller 53, but rotates independently of the first planetary roller 53.

In this example, the second planetary roller mechanism 6 includes three second planetary rollers 64. Each second planetary roller 64 is configured in an annular shape and is rotatably supported by two radial rolling bearings 61b around the second support shaft portion 44 of the first carrier element 39 and the second protruding portion 60 of the second carrier element 40. That is, radial rolling bearings 61b are disposed in the portion between the inner peripheral surface of the end portion on the other axial side of the second planetary roller 64 and the outer peripheral surface of the second support shaft portion 44, and in the portion between the inner peripheral surface of the end portion on one axial side of the second planetary roller 64 and the outer peripheral surface of the second protruding portion 60.

That is, in the reduction gear 1 of this example, the carrier 4 is provided with a first support shaft portion 43 and a second support shaft portion 44. The first planetary roller 53 is supported around the first support shaft portion 43 (and the first protruding portion 59) so as to be rotatable about the first support shaft portion 43, and the second planetary roller 64 is supported around the second support shaft portion 44 (and the second protruding portion 60) so as to be rotatable about the second support shaft portion 44.

The second support shafts 44 protrude from multiple equally spaced locations on one axial side of the first side plate 42, circumferentially away from the portion where the first support shaft 43 is provided. Therefore, in this example, the phases of the first planetary roller 53 supported around the first support shaft 43 and the second planetary roller 64 supported around the second support shaft 44 are shifted from each other in the circumferential direction. Specifically, in this example, the phases of the first planetary rollers 53 and the second planetary rollers 64 in the circumferential direction are shifted from each other by 60 degrees.

In this example, in a virtual plane perpendicular to the central axis of the carrier 4, the central axis of each of the first planetary rollers 53 and the central axis of each of the second planetary rollers 64 exist on the same virtual circle centered on the carrier 4. In other words, in a virtual plane perpendicular to the central axis of the carrier 4, the diameter of a first virtual circle centered on the carrier 4 and passing through the central axis of each of the first planetary rollers 53 is the same as the diameter of a second virtual circle centered on the carrier 4 and passing through the central axis of each of the second planetary rollers 64. Therefore, in this example, the outer diameter of the second planetary roller 64 (i.e., the diameter of the second rolling surface 68) is smaller than the outer diameter of the first planetary roller 53 (i.e., the diameter of the first rolling surface 58).

In the reduction gear 1 of this example, traction grease is applied to each surface constituting the rolling contact portion, i.e., the first inner diameter side rolling contact surface 54, the first outer diameter side rolling contact surface 55, and the first rolling surface 58, and the second inner diameter side rolling contact surface 65, the second outer diameter side rolling contact surface 66, and the second rolling surface 68. Traction grease has a higher traction coefficient and a higher coefficient of friction than greases such as soap-based greases that are generally used to lubricate sliding parts, and also has a high pressure-viscosity coefficient, and has the property of hardening into a glass-like state when pressure is applied, but softening when pressure is released.

However, when implementing one embodiment of the reduction gear of the present invention, traction oil can be supplied to each rolling contact portion instead of traction grease. Like traction grease, traction oil has a high pressure-viscosity coefficient and has the property of hardening into a glass-like state when pressure is applied, but softening when pressure is released.

In addition, in the reduction gear 1 of this example, in order to ensure good slipperiness of each rolling contact portion and to prevent wear of each surface constituting the rolling contact portion, the arithmetic mean roughness Ra (JIS B 0601:2013) of each surface constituting the rolling contact portion is set to 0.40 μm or less, preferably 0.30 μm or less, and more preferably 0.20 μm or less. The lower limit of the arithmetic mean roughness Ra of each surface constituting the rolling contact portion is not particularly limited, but may be set to, for example, 0.05 μm from the viewpoint of manufacturing costs.

Furthermore, in the reduction gear 1 of this example, the Vickers hardness Hv (JIS Z 2244:2009) of each surface constituting the rolling contact portion is set to 550 or more, preferably 600 or more, and more preferably 650 or more. This prevents damage such as cracks from occurring in each roller constituting the reduction mechanism 7, i.e., the first sun roller 51, the first ring roller 52, and the first planetary roller 53, as well as the second sun roller 62, the second ring roller 63, and the second planetary roller 64.

In the reduction gear 1 of this example, the rotation of the input member 2 is decelerated by the reduction mechanism 7, which is made up of the carrier 4, the first planetary roller mechanism 5, and the second planetary roller mechanism 6, before being transmitted to the output member 3. In other words, the reduction gear 1 increases the rotational torque of the input member 2 by the reduction mechanism 7, transmits it to the output member 3, and outputs it from the output member 3.

Specifically, the rotation of the input member 2 is transmitted to the output member 3 through the following path. When the first sun roller 51 rotates with the rotation of the input member 2, each of the first planetary rollers 53 rotates (spins) around its own central axis based on the rolling contact between the first inner diameter side rolling contact surface 54 and the first rolling surface 58. When each of the first planetary rollers 53 rotates, each of the first planetary rollers 53 rotates (revolves) around the central axis of the carrier 4 based on the rolling contact between the first rolling surface 58 and the first outer diameter side rolling contact surface 55. With the revolution of each of the first planetary rollers 53, the carrier 4 also rotates around its own central axis, and the second planetary roller 64 supported by the carrier 4 rotates (revolves) around the central axis of the carrier 4. When the second planetary rollers 64 revolve due to the rotation of the carrier 4, and the second sun roller 62 rotates with the rotation of the input member 2, each second planetary roller 64 rotates (spins) around its own central axis based on the rolling contact between the second rolling surface 68 and the second inner diameter side rolling contact surface 65. When each second planetary roller 64 rotates, the second ring roller 63 rotates based on the rolling contact between the second rolling surface 68 and the second outer diameter side rolling contact surface 66, and the output member 3 also rotates.

In the reduction gear 1 of this example, power is transmitted between the rollers that make up the reduction mechanism 7 by rolling contact (traction drive). In other words, the reduction gear 1 of this example does not have any meshing parts between gears in the power transmission path. Therefore, the reduction gear 1 of this example does not generate abnormal noise or vibration caused by backlash that is inevitably present in the meshing parts between gears.

In addition, in the reduction gear device 1 of this example, unlike the planetary gear device described in WO 2020/170297, there is no need to excessively increase the shape accuracy, dimensional accuracy, and assembly accuracy of each component in order to closely match the reduction ratio in the planetary gear mechanism and the reduction ratio in the friction roller mechanism. Therefore, the reduction gear device 1 of this example can suppress increases in costs.

The planetary gear device described in WO 2020/170297 has a planetary gear mechanism, which is a gear drive type power transmission mechanism, and a friction roller mechanism, which is a traction drive type power transmission mechanism, and therefore has a large number of parts, and the costs required for manufacturing, managing, and assembling the parts tend to be high. In contrast, the reduction gear 1 of this example has only a traction drive type reduction gear mechanism 7. In other words, the reduction gear 1 of this example does not have a gear drive type power transmission mechanism, and therefore the number of parts can be reduced compared to the planetary gear device described in WO 2020/170297. Therefore, according to the reduction gear 1 of this example, the costs required for manufacturing, managing, and assembling the parts can be reduced.

The reduction gear 1 of this example can adjust the reduction ratio between the input member 2 and the output member 3 by changing the diameter of each roller that constitutes the reduction mechanism 7. In other words, the reduction gear 1 of this example has a higher degree of freedom in setting the reduction ratio than a structure in which the reduction ratio is adjusted by changing the number of teeth, such as a gear-type reduction gear.

In this example, the outer diameter of the second sun roller 62 is larger than the outer diameter of the first sun roller 51, the inner diameter of the second ring roller 63 is smaller than the inner diameter of the first ring roller 52, and the outer diameter of the second planetary roller 64 is smaller than the outer diameter of the first planetary roller 53. However, as long as harmful slippage at the rolling contact points can be prevented, the diameter of each roller that constitutes the reduction mechanism can be set arbitrarily.

In addition, in this example, in a virtual plane perpendicular to the central axis of the carrier 4, the central axis of each of the first planetary rollers 53 and the central axis of each of the second planetary rollers 64 exist on the same virtual circle centered on the carrier 4. However, as long as harmful slippage at the rolling contact area can be prevented, the diameter of the first virtual circle centered on the carrier and passing through the central axis of the first planetary roller can be made different from the diameter of the second virtual circle centered on the carrier and passing through the central axis of the second planetary roller.

In this example, the phases of the first support shaft portion 43 and the second support shaft portion 44 in the circumferential direction are shifted from each other, so that the phases of the first planetary roller 53 and the second planetary roller 64 in the circumferential direction are shifted from each other. Therefore, the members arranged around the first planetary roller 53 and the members arranged around the second planetary roller 64 can be arranged overlapping in the circumferential direction. Specifically, for example, the radial rolling bearing 61a arranged in the portion between the inner peripheral surface of the end portion on the other axial side of the first planetary roller 53 and the outer peripheral surface of the first support shaft portion 43, and the radial rolling bearing 61b arranged in the portion between the inner peripheral surface of the end portion on one axial side of the second planetary roller 64 and the outer peripheral surface of the second protruding portion 60 can be arranged overlapping in the circumferential direction. Therefore, it is easy to keep the axial dimension of the reduction gear 1 short, and it is easy to configure the reduction gear 1 in a small size.

In the reduction gear 1 of this example, the reduction gear mechanism 7, which is composed of the carrier 4, the first planetary roller mechanism 5, and the second planetary roller mechanism 6, is housed in the housing 8, and the input member 2 and the output member 3 are each rotatably supported relative to the housing 8. Specifically, the reduction gear mechanism 7 is housed in a cylindrical portion 11 provided in the axial middle portion of the housing 8. The input member 2 is rotatably supported via the carrier 4 and radial bearings 22a, 22b with respect to the inward flange portion 12 provided at one end of the housing 8 in the axial direction, and the output member 3 is rotatably supported by a radial rolling bearing 34 with respect to a bush 14 fixed to the other axial side portion of the cylindrical portion 11. Therefore, the reduction gear 1 can be assembled in advance before being incorporated into the drive system of the automobile, etc., and the reduction gear 1 can be easily handled.

The reduction gear 1 of this example can be used not only in the drive system of an automobile, but also as a power transmission device for various mechanical devices.

LIST OF SYMBOLS 1 Reduction gear 2 Input member 3 Output member 4 Carrier 5 First planetary roller mechanism 6 Second planetary roller mechanism 7 Reduction mechanism section 8 Housing 9 Housing body 10 Cover 11 Cylindrical section 12 Inward flange section 13 Outward flange section 14 Bush 15 Through hole 16 Screw hole 17 Inner diameter side through hole 18 Outer diameter side through hole 19 Bolt 20 Small diameter shaft section 21 Large diameter shaft section 22a, 22b, 22c, 22d Radial bearing 23 First output member element 24 Second output member element 25 Base plate section 26 Shaft section 27 Through hole 28 Large diameter cylindrical section 29 Small diameter cylindrical section 30 Side plate section 31 Recess 32 Screw hole 33 Bolt 34 Radial rolling bearing 35 Inner ring 36 Outer ring 37 Rolling element 38 Step surface 39 First carrier element 40 Second carrier element 41 First base portion 42 First side plate portion 43 First support shaft portion 44 Second support shaft portion 45a, 45b Screw hole 46 Second base portion 47 Second side plate portion 48 First through hole 49 Offset portion 50 Second through hole 51 First sun roller 52 First ring roller 53 First planetary roller 54 First inner diameter side rolling contact surface 55 First outer diameter side rolling contact surface 56 Engagement groove 57 First engagement protrusion 58 First rolling surface 59 First protrusion 60 Second protrusion 61a, 61b Radial rolling bearing 62 Second sun roller 63 Second ring roller 64 Second planetary roller 65 Second inner diameter side rolling contact surface 66 Second outer diameter side rolling contact surface 67 Second engagement protrusion 68 Second rolling surface 69 Abutment surface 70a, 70b Bolt

Claims (3)

An input member;
an output member supported coaxially with the input member and capable of relative rotation with respect to the input member;
a carrier supported coaxially with the input member and the output member and capable of rotating relative to the input member and the output member;
a first sun roller having a first inner diameter side rolling contact surface on its outer circumferential surface and rotating integrally with the input member; a first ring roller having a first outer diameter side rolling contact surface on its inner circumferential surface, arranged coaxially with the first sun roller and supported on a portion that does not rotate even during use; and at least one first planetary roller having a first rolling surface on its outer circumferential surface that is in rolling contact with the first inner diameter side rolling contact surface and the first outer diameter side rolling contact surface, and supported so as to be rotatable about its own central axis with respect to the carrier;
a second sun roller having a second inner diameter side rolling contact surface on an outer circumferential surface thereof, disposed coaxially with the first sun roller, and rotating integrally with the input member and the first sun roller; a second ring roller having a second outer diameter side rolling contact surface on an inner circumferential surface thereof, disposed coaxially with the second sun roller, and rotating integrally with the output member; and at least one second planetary roller having a second rolling surface on an outer circumferential surface thereof in rolling contact with the second inner diameter side rolling contact surface and the second outer diameter side rolling contact surface, and supported to be rotatable about its own central axis relative to the carrier;
Equipped with
Reduction gear. The first planetary roller and the second planetary roller are out of phase with each other in the circumferential direction.
The reduction gear according to claim 1 . a housing that houses the carrier, the first planetary roller mechanism, and the second planetary roller mechanism;
the input member is rotatably supported relative to the housing, and the output member is rotatably supported relative to the housing.
The reduction gear according to claim 1 .

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