Patent Application
20200386301
The present invention relates to a reduction gear.
A vehicle includes a hub bearing that rotatably supports a wheel. In an electric vehicle, for example, as a driving device for rotating the wheel, a motor may be provided near the hub bearing. Such a motor is called “in-wheel motor”. In order to amplify torque generated in the motor, a reduction gear may be provided to the hub bearing. For example, Patent Literature 1 describes a reduction gear including an internal gear and a pinion gear. In Patent Literature 1, a bearing that supports the pinion gear is integrated with an outer ring of a bearing that supports the internal gear.
Further increase of the reduction ratio of the reduction gear may be needed. In this case, if the internal gear is upsized, the reduction ratio of the reduction gear increases. However, if the internal gear in the reduction gear described in Patent Literature 1 is upsized, the size of the outer ring of the bearing that supports the internal gear also increases, and thus the weight of the reduction gear is more likely to increase. Thus, a reduction gear is desired that enables an increase in the reduction ratio and weighs lightly.
The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a reduction gear that enables an increase in the reduction ratio and weighs lightly.
To achieve the above object, A reduction gear according to one embodiment of the present disclosure includes a first bearing that is mounted on a supporting member, an output member that is supported by the first bearing and rotates about a first rotation axis, an internal gear that is coupled to the output member and rotates about the first rotation axis together with the output member, a second bearing that is mounted on the supporting member on an outer side relative to the first bearing in a radial direction, and a pinion gear that is supported by the second bearing, rotates about a second rotation axis different from the first rotation axis, and is engaged with the internal gear. At least a part of the second bearing is located on a side closer to the internal gear with respect to a plane passing through an end portion of the first bearing that is more distant from the internal gear in an axial direction parallel to the second rotation axis and being orthogonal to the second rotation axis.
With this configuration, the pinion gear is supported by the second bearing at a position closer to the internal gear. Thus, backlash in the pinion gear is reduced. Furthermore, the second bearing is a member that is separate from the first bearing, and is located on the outer side relative to the first bearing in the radial direction. Thus, increase in weight according to the distance between the pinion gear and the first bearing is suppressed in comparison to the case where the second bearing is mounted on a member that supports the outer ring of the first bearing. In other words, the weight of the reduction gear is less likely to increase even if the internal gear is upsized in order to increase the reduction ratio. Accordingly, the reduction gear of the present disclosure enables an increase in reduction ratio and weighs lightly.
As a desirable embodiment of the reduction gear, the second bearing is a double-row angular ball bearing.
With this configuration, the second bearing can bear an axial load, a radial load, and a moment load. This eliminates the need to arrange an additional bearing such as a radial needle bearing between a distal end of the pinion gear and the output member. Accordingly, the length of the reduction gear in the axial direction can be reduced.
As a desirable embodiment of the reduction gear, the pinion gear includes a tubular outer shaft and an inner shaft at least a part of which is located on an inner side of the outer shaft and that rotates together with the outer shaft, the outer shaft has a small-diameter portion that is in contact with an inner circumferential surface of an inner ring of the second bearing and a large-diameter portion that is engaged with the internal gear, and the maximum outer diameter of the large-diameter portion is larger than the bore diameter of the inner ring.
In order to increase torque that the pinion gear can transmit, it is preferable that the large-diameter portion that is engaged with the internal gear be larger to a certain extent. Meanwhile, for weight reduction, it is preferable that the second bearing be smaller. However, if the pinion gear is formed of one member, the outer diameter of the large-diameter portion needs to be set smaller than the bore diameter of the second bearing, which makes it difficult to reduce the size of the second bearing while maintaining the outer diameter of the large-diameter portion. By contrast, the pinion gear of the embodiment includes the outer shaft and the inner shaft, and thus the outer diameter of the large-diameter portion can be set larger than the bore diameter of the second bearing. Accordingly, the reduction gear of the embodiment can achieve compatibility between increase in torque that can be transmitted and weight reduction.
As a desirable embodiment of the reduction gear, the inner shaft has a base portion located on an inner side of the small-diameter portion and a torque transmitting portion located on an inner side of the large-diameter portion, the base portion has a first fitting surface that is a cylindrical outer circumferential surface, the small-diameter portion has a second fitting surface that is a cylindrical inner circumferential surface and is in contact with the first fitting surface, one of an outer circumferential surface of the torque transmitting portion and an inner circumferential surface of the large-diameter portion has a groove that extends in the axial direction, and the other of the outer circumferential surface of the torque transmitting portion and the inner circumferential surface of the large-diameter portion has a projection that extends in the axial direction and fits into the groove.
With this configuration, the first fitting surface and the second fitting surface that are located on an inner side of the second bearing are in contact with each other, so that misalignment between the second bearing and the pinion gear is prevented. In other words, misalignment of the rotation axis of the pinion gear with respect to the rotation axis of the second bearing is prevented. With the groove and the projection, torque is transmitted from the inner shaft to the outer shaft at a position overlapping the internal gear. Thus, the length of the reduction gear in the axial direction is shorter than the length thereof in the case when the torque is transmitted at another position (e.g., a position on a side opposite to the large-diameter portion with respect to the second bearing).
As a desirable embodiment of the reduction gear, the second rotation axis is located on an inner side of the internal gear in a radial direction.
As a desirable embodiment of the reduction gear, the first bearing is mounted on the supporting member with an attachment interposed therebetween, the first bearing includes a plurality of first rolling elements that are arranged in a first row and a plurality of second rolling elements that are arranged in a second row, and inner circumferential surfaces of the attachment are in contact with the first rolling elements and the second rolling elements.
With this configuration, the number of parts of the first bearing can be reduced because the first bearing does not include the outer ring. Thus, the reduction gear of the present disclosure can be configured to be light in weight.
According to the present invention, the reduction gear that enables backlash in the pinion gear to be reduced and the weight of which is light can be provided.
Hereinafter, the present invention will be described in detail with reference to the drawings. It should be noted that the present invention is not limited by the following modes for carrying out the invention (hereinafter, referred to as embodiments). Components in the following embodiments include components that those skilled in the art can easily suppose and substantially the same components being components in a what-is-called equivalent range. Furthermore, the components that are disclosed in the following embodiments can be appropriately combined.
The first motor 11 is connected to the transmission device 2 with the first reduction gear 13 interposed therebetween. The first reduction gear 13 increases torque that the first motor 11 outputs and transmits it to the transmission device 2. The first reduction gear 13, for example, doubles the torque that the first motor 11 outputs and transmits it to the transmission device 2. Maximum torque of the first motor 11 is, for example, 25 (Nm). Maximum torque that is transmitted to the transmission device 2 from the first reduction gear 13 is therefore 50 (Nm).
The first reduction gear 13 includes a first gear 131, a second gear 132, and a third gear 133. A first motor gear 111 mounted on a first shaft 110 of the first motor 11 is engaged with the first gear 131. The first gear 131 is engaged with the second gear 132. The third gear 133 is a gear coaxial with the second gear 132 and rotates together with the second gear 132. The third gear 133 is engaged with an input gear 20 of the transmission device 2.
The second motor 12 is connected to the transmission device 2 with the second reduction gear 14 interposed therebetween. The second reduction gear 14 increases torque that the second motor 12 outputs and transmits it to the transmission device 2. The second reduction gear 14, for example, doubles the torque that the second motor 12 outputs and transmits it to the transmission device 2. Maximum torque of the second motor 12 is, for example, 25 (Nm). Maximum torque that is transmitted to the transmission device 2 from the second reduction gear 14 is therefore 50 (Nm).
The second reduction gear 14 includes a first gear 141, a second gear 142, and a third gear 143. A second motor gear 121 mounted on a second shaft 120 of the second motor 12 is engaged with the first gear 141. The first gear 141 is engaged with the second gear 142. The third gear 143 is a gear coaxial with the second gear 142 and rotates together with the second gear 142. The third gear 143 is engaged with a first ring gear 34 of the transmission device 2. The first ring gear 34 has teeth on both of an outer circumferential surface and an inner circumferential surface. That is to say, the first ring gear 34 is an external gear and an internal gear. The third gear 143 is engaged with the teeth on the outer circumferential surface of the first ring gear 34. In other words, the third gear 143 is engaged with the first ring gear 34 as the external gear.
As illustrated in
The input gear 20 receives torque from the third gear 133 of the first reduction gear 13. The sun gear shaft 21 is coupled to the input gear 20. When the first motor 11 is driven, the input gear 20 and the sun gear shaft 21 rotate about a rotation axis A2.
The first planetary gear device 3 is, for example, a single pinion-type planetary gear device. The first planetary gear device 3 includes a first sun gear 31, first pinion gears 32, a first carrier 33, and the first ring gear 34.
The first sun gear 31 is coupled to the sun gear shaft 21. The first sun gear 31 rotates about the rotation axis A2 together with the sun gear shaft 21. The first sun gear 31 is engaged with the first pinion gears 32. The number of teeth of the first sun gear 31 is, for example, 24. The number of teeth of the first pinion gears 32 is, for example, 25.
The first carrier 33 is supported on the case 10 with the clutch 5 interposed therebetween. The first carrier 33 supports the first pinion gears 32 such that the first pinion gears 32 can rotate about rotating axes A32. The rotating axes A32 are arranged in parallel to the rotation axis A2. The first carrier 33 supports the first pinion gears 32 such that the first pinion gears 32 can revolve about the rotation axis A2. The first pinion gears 32 are engaged with the teeth on the inner circumferential surface of the first ring gear 34. In other words, the first pinion gears 32 are engaged with the first ring gear 34 as the internal gear. The first ring gear 34 rotates about the rotation axis A2. The number of teeth of the first ring gear 34 is, for example, 76.
The clutch 5 is, for example, a one-way clutch. The clutch 5 transmits only torque in a first direction and does not transmit torque in a second direction as an opposite direction to the first direction. The clutch 5 is arranged between the case 10 and the first carrier 33. The clutch 5 can restrict rotation of the first carrier 33. To be specific, the clutch 5 can switch between an engaged state restricting revolution of the first carrier 33 and a separated state permitting the revolution of the first carrier 33. That is to say, the clutch 5 enables the first carrier 33 to be rotatable in a specific direction relative to the case 10 and enables the first carrier 33 to be non-rotatable in a direction opposite to the specific direction relative to the case 10.
The second planetary gear device 4 is, for example, a double pinion-type planetary gear device. The second planetary gear device 4 includes a second sun gear 41, second pinion gears 421, third pinion gears 422, a second carrier 43, and a second ring gear 44.
The second sun gear 41 is coupled to the sun gear shaft 21. The second sun gear 41 rotates about the rotation axis A2 together with the sun gear shaft 21. The second pinion gears 421 are engaged with the second sun gear 41. The third pinion gears 422 are engaged with the second pinion gears 421. The number of teeth of the second sun gear 41 is, for example, 47. The number of teeth of the second pinion gears 421 is, for example, 20. The number of teeth of the third pinion gears 422 is, for example, 19.
The second carrier 43 is coupled to the first ring gear 34. The second carrier 43 supports the second pinion gears 421 such that the second pinion gears 421 can rotate about rotating axes A421. The second carrier 43 supports the third pinion gears 422 such that the third pinion gears 422 can rotate about rotating axes A422. The rotating axes A421 and the rotating axes A422 are arranged in parallel to the rotation axis A2. The second carrier 43 supports the second pinion gears 421 and the third pinion gears 422 such that the second pinion gears 421 and the third pinion gears 422 can revolve about the rotation axis A2. The second ring gear 44 is engaged with the third pinion gears 422. The second ring gear 44 rotates about the rotation axis A2. The second ring gear 44 is coupled to the transmission device output shaft 25. The number of teeth of the second ring gear 44 is, for example, 97.
The third reduction gear 6 is arranged between the transmission device 2 and the wheel 100 of the vehicle. The third reduction gear 6 is a final reduction gear. The third reduction gear 6 increases the torque that is input to the transmission device output shaft 25 and outputs it to the output member 15. The third reduction gear 6 includes a fourth pinion gear 61 and a third ring gear 62. The fourth pinion gear 61 is coupled to the transmission device output shaft 25 and rotates about the rotation axis A2 together with the transmission device output shaft 25. The fourth pinion gear 61 is engaged with the third ring gear 62. The third ring gear 62 rotates about a rotation axis A1. The third ring gear 62 is coupled to the output member 15. The output member 15 is coupled to the wheel 100. The output member 15 and the wheel 100 rotate about the rotation axis A1 together with the third ring gear 62. A rotation axis A11 of the first motor 11, a rotation axis A12 of the second motor 12, and the rotation axis A2 of the transmission device 2 are arranged in parallel to the rotation axis A1 of the output member 15.
Power generated in at least one of the first motor 11 and the second motor 12 is transmitted to the wheel 100 through the transmission device 2 and the third reduction gear 6. When the vehicle travels on a downward slope or the like, power generated in the wheel 100 is transmitted to at least one of the first motor 11 and the second motor 12 through the third reduction gear 6 and the transmission device 2. In this case, at least one of the first motor 11 and the second motor 12 is driven as a power generator. Rotation resistance in power generation acts on the vehicle as a regenerative brake.
The control device 9 is a computer and includes, for example, a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), an input interface, and an output interface. The control device 9 is, for example, an electronic control unit (ECU) mounted on the vehicle. The control device 9 controls the angular velocities and rotating directions of the first motor 11 and the second motor 12.
The reduction ratio can be increased in the low gear mode. That is to say, the torque that is transmitted to the transmission device output shaft 25 is increased in the low gear mode. The low gear mode is used mainly when the vehicle needs large torque. The large torque is needed in, for example, climbing or acceleration.
The directions of the torques that are generated in the first motor 11 and the second motor 12 are opposite to each other in the low gear mode. The magnitudes of the torques that are generated in the first motor 11 and the second motor 12 may be the same as or differ from each other. The torque generated in the first motor 11 is input to the first sun gear 31 through the first reduction gear 13, the input gear 20, and the sun gear shaft 21. The torque generated in the second motor 12 is input to the first ring gear 34 through the second reduction gear 14. The clutch 5 is made into the engaged state in the low gear mode. That is to say, the first pinion gears 32 can rotate but cannot revolve in the low gear mode.
The torque that the first motor 11 outputs is assumed to be torque T1 and the torque that the second motor 12 outputs is assumed to be torque T2 in the low gear mode. The direction of the torque T2 is opposite to the direction of the torque T1. The torque T1 output from the first motor 11 becomes torque T3 when passing through the first reduction gear 13. The torque T3 is input to the first sun gear 31 through the sun gear shaft 21. The torque T3 becomes torque T6 when merging with the torque T5 in the first sun gear 31. The torque T5 is transmitted to the first sun gear 31 from the first ring gear 34.
The first sun gear 31 and the second sun gear 41 are coupled to each other with the sun gear shaft 21. The torque T6 output from the first sun gear 31 is transmitted to the second sun gear 41 through the sun gear shaft 21 in the low gear mode. The second planetary gear device 4 amplifies the torque T6. The second planetary gear device 4 distributes the torque T6 into torque T8 and torque T7. The torque T8 is torque of the torque T2 that has been distributed to the second ring gear 44 and is output from the transmission device output shaft 25. The torque T7 is torque of the torque T2 that has been distributed to the second carrier 43.
The torque T8 is output to the third reduction gear 6 from the transmission device output shaft 25. The third reduction gear 6 amplifies the torque T8 to turn it into torque T9. The torque T9 is output to the wheel 100 through the output member 15. As a result, the vehicle travels.
The second carrier 43 and the first ring gear 34 rotate integrally. The torque T7 distributed to the second carrier 43 is combined with the torque T4 output from the second reduction gear 14 in the first ring gear 34. The torque T4 and the torque T7 combined in the first ring gear 34 become the torque T5 through the first pinion gears 32. Thus, the transmission device 2 can increase the reduction ratio because the torque circulates between the first planetary gear device 3 and the second planetary gear device 4. That is to say, the electric vehicle driving device 1 can generate large torque in the low gear mode.
The reduction ratio can be decreased in the high gear mode. The torque that is transmitted to the transmission device output shaft 25 is decreased but friction loss of the transmission device 2 is decreased in the high gear mode. The directions of the torques that are generated in the first motor 11 and the second motor 12 are the same in the high gear mode. The magnitudes of the torques that are generated in the first motor 11 and the second motor 12 are substantially the same. The torque that the first motor 11 outputs is assumed to be torque T11 and the torque that the second motor 12 outputs is assumed to be torque T12 in the high gear mode. Torque T15 illustrated in
The torque T11 of the first motor 11 becomes torque T13 when passing through the first reduction gear 13 in the high gear mode. The torque T12 of the second motor 12 becomes torque T14 when passing through the second reduction gear 14. The clutch 5 is made into the separated state in the high gear mode. That is to say, the first pinion gears 32 can rotate and revolve in the high gear mode. With the separated state of the clutch 5, the circulation of the torque between the first planetary gear device 3 and the second planetary gear device 4 is blocked in the high gear mode. The first carrier 33 can revolve in the high gear mode, so that the first sun gear 31 and the first ring gear 34 can rotate relatively freely. The torque T13 merges with the torque T14 in the second carrier 43. As a result, the torque T15 is transmitted to the second ring gear 44.
The torque T15 is output to the third reduction gear 6 from the transmission device output shaft 25. The third reduction gear 6 amplifies the torque T15 to turn it into torque T16. The torque T16 is output to the wheel 100 through the output member 15. As a result, the vehicle travels. In the high gear mode, the control device 9 appropriately controls the angular velocity of the first motor 11 and the angular velocity of the second motor 12, so that the direction of the torque T16 is reversed. As a result, the vehicle travels backward.
In
In the following description, a direction parallel to the rotation axis A1 is simply referred to as an axial direction. A direction orthogonal to the axial direction is simply referred to as a radial direction. In other words, the radial direction is a direction orthogonal to the rotation axis A1.
As illustrated in
As illustrated in
As illustrated in
As illustrated in
As illustrated in
As illustrated in
In the embodiment, the outer diameter of the second motor 12, the length thereof in the axial direction, and the wound wire structure (winding manner of the second coil 127) thereof are the same as the outer diameter of the first motor 11, the length thereof in the axial direction, and the wound wire structure (winding manner of the first coil 117) thereof. A position of an end portion of the second motor 12 in the axial direction is the same as a position of an end portion of the first motor 11 in the axial direction.
As illustrated in
As illustrated in
As illustrated in
As illustrated in
The clutch 5 is, for example, a what-is-called cam clutch device. As illustrated in
As illustrated in
As illustrated in
In the embodiment, the second bearing 17 is a double-row angular ball bearing. The second bearing 17 bears an axial load, a radial load, and a moment load. As illustrated in
The outer ring 171 is an annular member. As illustrated in
As illustrated in
The rolling elements 172 are arranged between the outer ring 171 and the first inner ring piece 173a and between the outer ring 171 and the second inner ring piece 173b. The rolling elements 172 are positioned by the cages to be aligned at regular intervals. With the rolling elements 172, the first inner ring piece 173a and the second inner ring piece 173b can rotate with respect to the outer ring 171. The first inner ring piece 173a and the second inner ring piece 173b integrally rotate about the rotation axis A2.
The cage 176 is located between the outer ring 171 and the first inner ring piece 173a. The cage 176 holds the rolling elements 172 arranged between the outer ring 171 and the first inner ring piece 173a. The cage 177 is located between the outer ring 171 and the second inner ring piece 173b. The cage 177 holds the rolling elements 172 arranged between the outer ring 171 and the second inner ring piece 173b.
As illustrated in
As illustrated in
The small-diameter portion 651 is press-fitted into the inside of the second bearing 17. The small-diameter portion 651 has a bearing fitting surface 651p that is a cylindrical outer circumferential surface and a second fitting surface 651q that is a cylindrical inner circumferential surface. The bearing fitting surface 651p is in contact with the inner circumferential surfaces of the first inner ring piece 173a and the second inner ring piece 173b.
The large-diameter portion 653 is located on the side closer to the wheel 100 with respect to the small-diameter portion 651. The maximum outer diameter D653 of the large-diameter portion 653 is larger than the bore diameter D173 of the inner ring 173 (i.e., the outer diameter of the small-diameter portion 651). The large-diameter portion 653 has a plurality of teeth 653t and a plurality of grooves 653s. The teeth 653t are formed on the outer circumferential surface of the large-diameter portion 653 as illustrated in
For example, if the maximum outer diameter D653 of the large-diameter portion 653 is reduced, the reduction ratio of the third reduction gear 6 increases. However, the fourth pinion gear 61 needs to withstand large torque, and thus it is desirable that the maximum outer diameter D653 of the large-diameter portion 653 be large to a certain extent. Thus, when the reduction ratio of the third reduction gear 6 is increased, the diameter of the third ring gear 62 needs to be increased.
As illustrated in
The base portion 661 is located on the inner side of the small-diameter portion 651. The base portion 661 is press-fitted into the inside of the small-diameter portion 651. The base portion 661 has a first fitting surface 661q that is a cylindrical outer circumferential surface. The first fitting surface 661q is in contact with the second fitting surface 651q of the small-diameter portion 651.
The torque transmitting portion 663 is located on the inner side of the large-diameter portion 653. The torque transmitting portion 663 has a plurality of projections 663s formed on the outer circumferential surface thereof. The projections 663s extend in the axial direction, and are fitted into the grooves 653s of the large-diameter portion 653. For example, the projections 663s are arranged in the circumferential direction about the rotation axis A2 at regular intervals. In other words, the projections 663s form a spline. The spline formed by the grooves 653s of the large-diameter portion 653 is engaged with the spline formed by the projections 663s of the torque transmitting portion 663. With this configuration, torque is transmitted from the inner shaft 66 to the outer shaft 65.
The coupling portion 665 is located on a side closer to the transmission device 2 with respect to the second bearing 17. The coupling portion 665 extends from the base portion 661 toward the radial direction. The coupling portion 665 is coupled to the second ring gear 44 of the transmission device 2. Thus, the inner shaft 66 rotates integrally with the second ring gear 44. The coupling portion 665 is in contact with the first inner ring piece 173a.
As illustrated in
The third reduction gear 6 does not necessarily has to be arranged between the transmission device 2 and the wheel 100 in the electric vehicle driving device 1. The third reduction gear 6 may be used in another portion of the electric vehicle driving device 1. The third reduction gear 6 does not necessarily have to be used in the electric vehicle driving device 1, and may be used in another portion of the vehicle. The third reduction gear 6 may be also used for a vehicle other than the electric vehicle. For example, the third reduction gear 6 may be used as a member that transmits power of an internal combustion engine as a prime mover. The first motor 11 and the second motor 12 described above are merely examples of a prime mover. The third reduction gear 6 may be also used for a device other than the vehicle. The third reduction gear 6 can be generally used for various devices that transmit power.
The fourth pinion gear 61 does not necessarily have to be coupled to the transmission device 2. For example, the inner shaft 66 of the fourth pinion gear 61 may be coupled to a shaft of a motor, for example. The inner shaft 66 only has to be coupled to at least a rotational member that rotates with power from a prime mover. The above-mentioned second ring gear is merely an example of the rotational member.
The first bearing 16 and the second bearing 17 do not necessarily have to be fixed to the case 10. Such a supporting member on which the first bearing 16 and the second bearing 17 are mounted is not particularly limited if it is a member that can withstand load applied to the first bearing 16 and the second bearing 17.
The whole of the second bearing 17 does not necessarily have to be located in an area between the third plane B3 and the fourth plane B4. For example, a part of the second bearing 17 may be located on the side closer to the transmission device 2 with respect to the third plane B3. At least a part of the second bearing 17 only has to be located on the side closer to the wheel 100 with respect to the third plane B3.
The large-diameter portion 653 does not necessarily have to have a plurality of the grooves 653s. The large-diameter portion 653 only has to have at least one groove 653s. The torque transmitting portion 663 does not necessarily have to have a plurality of the projections 663s. The torque transmitting portion 663 only has to have at least one projection 663s. The large-diameter portion 653 does not necessarily have to have a groove, and the torque transmitting portion 663 does not necessarily have to have a projection. In other words, one of the large-diameter portion 653 and the torque transmitting portion 663 only has to have at least one groove, and the other thereof only has to have a projection that fits into the groove.
Both of the first motor 11 and the second motor 12 may not be necessarily driven in the low gear mode. Only the first motor 11 of the first motor 11 and the second motor 12 may be driven. The numbers of teeth of the above-mentioned gears are merely examples and are not particularly limited.
As described above, the reduction gear (third reduction gear 6) of the embodiment includes the first bearing 16, the output member 15, the internal gear (third ring gear 62), the second bearing 17, and the pinion gear (fourth pinion gear 61). The first bearing 16 is mounted on the supporting member (case 10). The output member 15 is supported by the first bearing 16 and rotates about the first rotation axis (rotation axis A1). The internal gear is coupled to the output member 15 and rotates about the first rotation axis together with the output member 15. The second bearing 17 is mounted on the supporting member on an outer side relative to the first bearing 16 in the radial direction of the internal gear. The pinion gear is supported by the second bearing 17, rotates about the second rotation axis (rotation axis A2) that is different from the first rotation axis, and is engaged with the internal gear. At least a part of the second bearing 17 is located on a side closer to the internal gear with respect to the plane (third plane B3) passing through an end portion of the first bearing 16 that is more distant from the internal gear in an axial direction parallel to the second rotation axis and being orthogonal to the second rotation axis.
With this configuration, the pinion gear (fourth pinion gear 61) is supported by the second bearing 17 at a position closer to the internal gear (third ring gear 62). Thus, backlash in the pinion gear is reduced. Furthermore, the second bearing 17 is a member that is separate from the first bearing 16, and is located on the outer side relative to the first bearing 16 in the radial direction. Thus, increase in weight according to the distance between the pinion gear and the first bearing 16 is suppressed in comparison to the case where the second bearing 17 is mounted on the member (attachment 19) that supports the outer ring of the first bearing 16. In other words, the weight of the reduction gear (third reduction gear 6) is less likely to increase even if the internal gear is upsized in order to increase the reduction ratio. Accordingly, the reduction gear of the embodiment enables an increase in the reduction ratio and weighs lightly.
In the reduction gear (third reduction gear 6), the second bearing 17 is a double-row angular ball bearing.
With this configuration, the second bearing 17 can bear an axial load, a radial load, and a moment load. This eliminates the need to arrange an additional bearing such as a radial needle bearing between a distal end of the pinion gear (fourth pinion gear 61) and the output member 15. Accordingly, the length of the reduction gear (third reduction gear 6) in the axial direction can be reduced.
In the reduction gear (third reduction gear 6), the pinion gear (fourth pinion gear 61) includes the tubular outer shaft 65 and the inner shaft 66 at least a part of which is located on the inner side of the outer shaft 65 and that rotates together with the outer shaft 65. The outer shaft 65 has the small-diameter portion 651 that is in contact with the inner circumferential surface of the inner ring 173 of the second bearing 17 and the large-diameter portion 653 that is engaged with the internal gear. The maximum outer diameter D653t of the large-diameter portion 653 is larger than the bore diameter D173 of the inner ring 173.
In order to increase torque that the pinion gear (fourth pinion gear 61) can transmit, it is preferable that the large-diameter portion 653 that is engaged with the internal gear (third ring gear 62) be larger to a certain extent. Meanwhile, for weight reduction, it is preferable that the size of the second bearing 17 be smaller. However, if the pinion gear is formed of one member, the outer diameter of the large-diameter portion 653 needs to be set smaller than the bore diameter of the second bearing 17, which makes it difficult to reduce the size of the second bearing 17 while maintaining the outer diameter of the large-diameter portion 653. By contrast, the pinion gear of the embodiment includes the outer shaft 65 and the inner shaft 66, and thus the outer diameter of the large-diameter portion 653 can be set larger than the bore diameter of the second bearing 17. Accordingly, the reduction gear of the embodiment can achieve compatibility between increase in torque that can be transmitted and weight reduction.
In the reduction gear (third reduction gear 6), the inner shaft 66 has the base portion 661 located on the inner side of the small-diameter portion 651 and the torque transmitting portion 663 located on the inner side of the large-diameter portion 653. The base portion 661 has the first fitting surface 661q that is a cylindrical outer circumferential surface. The small-diameter portion 651 has the second fitting surface 651q that is a cylindrical inner circumferential surface and is in contact with the first fitting surface 661q. One of the outer circumferential surface of the torque transmitting portion 663 and the inner circumferential surface of the large-diameter portion 653 has the grooves 653s that extend in the axial direction. The other of the outer circumferential surface of the torque transmitting portion 663 and the inner circumferential surface of the large-diameter portion 653 has the projections 663s that extend in the axial direction and fit into the grooves 653s.
With this configuration, the first fitting surface 661q and the second fitting surface 651q that are located on an inner side of the second bearing 17 are in contact with each other, so that misalignment between the second bearing and the pinion gear (fourth pinion gear 61) is prevented. In other words, misalignment of the rotation axis of the second bearing with respect to the rotation axis of the pinion gear is prevented. With the grooves 653s and the projections 663s, torque is transmitted from the inner shaft 66 to the outer shaft 65 at a position overlapping the internal gear (third ring gear 62). Thus, the length of the reduction gear (third reduction gear 6) in the axial direction is shorter than the length thereof in the case when the torque is transmitted at another position (e.g., a position on a side opposite to the large-diameter portion 653 with respect to the second bearing).
As illustrated in
As illustrated in
As illustrated in
As illustrated in
The first inner ring piece 1601 and the second inner ring piece 1602 are annular members. The first inner ring piece 1601 and the second inner ring piece 1602 are in contact with the outer circumferential surface of the output member 15. The second inner ring piece 1602 is arranged on a side closer to the third ring gear 62 than the first inner ring piece 1601 is. The spacer 1603 is arranged between the first inner ring piece 1601 and the second inner ring piece 1602.
The first rolling elements 1604 are arranged in a first row. The first row is arranged between the first inner ring piece 1601 and the attachment 19. The first rolling elements 1604 are positioned by a cage to be aligned at regular intervals. The first rolling elements 1604 are in contact with an inner circumferential surface of the attachment 19 and an outer circumferential surface of the first inner ring piece 1601. In other words, the raceway surfaces of the first rolling elements 1604 are the inner circumferential surface of the attachment 19 and the outer circumferential surface of the first inner ring piece 1601.
The second rolling elements 1605 are arranged in a second row. The second row is arranged between the second inner ring piece 1602 and the attachment 19. The second rolling elements 1605 are positioned by a cage to be aligned at regular intervals. The second rolling elements 1605 are in contact with an inner circumferential surface of the attachment 19 and an outer circumferential surface of the second inner ring piece 1602. In other words, the raceway surfaces of the second rolling elements 1605 are the inner circumferential surface of the attachment 19 and the outer circumferential surface of the second inner ring piece 1602.
As described above, in the reduction gear (third reduction gear 6B) in the second modification, the first bearing 16B is mounted on the supporting member (case 10) with the attachment 19 interposed therebetween. The first bearing 16B includes the first rolling elements 1604 arranged in the first row and the second rolling elements 1605 arranged in the second row. The inner circumferential surfaces of the attachment 19 are in contact with the first rolling elements 1604 and the second rolling elements 1605.
With this configuration, the number of parts of the first bearing 16B can be reduced because the first bearing 16B does not include an outer ring. Thus, the reduction gear (third reduction gear 6B) in the second modification can be configured to be light in weight.
As illustrated in
The outer ring 1607 is an annular member. The outer ring 1607 is in contact with the inner circumferential surface of the attachment 19. The first inner ring piece 1608 and the second inner ring piece 1609 are annular members. The first inner ring piece 1608 and the second inner ring piece 1609 are in contact with an outer circumferential surface of the output member 15. The second inner ring piece 1609 is located on a side closer to the third ring gear 62 than the first inner ring piece 1608 is. An end surface of the second inner ring piece 1609 is in contact with an end surface of the first inner ring piece 1608.
The first rolling elements 1610 are arranged in a first row. The first row is arranged between the outer ring 1607 and the first inner ring piece 1608. The first rolling elements 1610 are positioned by a cage to be aligned at regular intervals. The first rolling elements 1610 are in contact with an inner circumferential surface of the outer ring 1607 and an outer circumferential surface of the first inner ring piece 1608. In other words, the raceway surfaces of the first rolling elements 1604 are the inner circumferential surface of the outer ring 1607 and the outer circumferential surface of the first inner ring piece 1608.
The second rolling elements 1611 are arranged in a second row. The second row is arranged between the outer ring 1607 and the second inner ring piece 1609. The second rolling elements 1611 are positioned by a cage to be aligned at regular intervals. The second rolling elements 1611 are in contact with an inner circumferential surface of the outer ring 1607 and an outer circumferential surface of the second inner ring piece 1609. In other words, the raceway surfaces of the second rolling elements 1611 are the inner circumferential surface of the outer ring 1607 and the outer circumferential surface of the second inner ring piece 1609.
As illustrated in
The first inner ring piece 1613 and the second inner ring piece 1614 are annular members. The first inner ring piece 1613 and the second inner ring piece 1614 are in contact with an outer circumferential surface of the output member 15. The second inner ring piece 1614 is located on a side closer to the third ring gear 62 than the first inner ring piece 1613 is. An end surface of the second inner ring piece 1614 is in contact with an end surface of the first inner ring piece 1613.
The first rolling elements 1615 are arranged in a first row. The first row is arranged between the first inner ring piece 1613 and the attachment 19. The first rolling elements 1615 are positioned by a cage to be aligned at regular intervals. The first rolling elements 1615 are in contact with an inner circumferential surface of the attachment 19 and an outer circumferential surface of the first inner ring piece 1613. In other words, the raceway surfaces of the first rolling elements 1615 are the inner circumferential surface of the attachment 19 and the outer circumferential surface of the first inner ring piece 1613.
The second rolling elements 1616 are arranged in a second row. The second row is arranged between the second inner ring piece 1614 and the attachment 19. The second rolling elements 1616 are positioned by a cage to be aligned at regular intervals. The second rolling elements 1616 are in contact with an inner circumferential surface of the attachment 19 and an outer circumferential surface of the second inner ring piece 1614. In other words, the raceway surfaces of the second rolling elements 1616 are the inner circumferential surface of the attachment 19 and the outer circumferential surface of the second inner ring piece 1614.
In the fourth modification, the first bearing 16D does not include an outer ring as described above, and thus the number of parts of the first bearing 16D can be reduced. Thus, the reduction gear (third reduction gear 6D) in the fourth modification can be configured to be light in weight.
As illustrated in
The first inner ring piece 1618 and the second inner ring piece 1619 are annular members. The first inner ring piece 1618 and the second inner ring piece 1619 are in contact with an outer circumferential surface of the output member 15. The second inner ring piece 1619 is located on a side closer to the third ring gear 62 than the first inner ring piece 1618 is. One end surface of the second inner ring piece 1619 is in contact with an end surface of the first inner ring piece 1618. The other end surface of the second inner ring piece 1619 is in contact with the output member 15. One end surface of the first inner ring piece 1618 is in contact with the output member 15. The first inner ring piece 1618 is positioned by swaging (plastically deforming) the output member 15.
The first rolling elements 1620 are arranged in a first row. The first row is arranged between the first inner ring piece 1618 and the attachment 19. The first rolling elements 1620 are positioned by a cage to be aligned at regular intervals. The first rolling elements 1620 are in contact with an inner circumferential surface of the attachment 19 and an outer circumferential surface of the first inner ring piece 1618. In other words, the raceway surfaces of the first rolling elements 1620 are the inner circumferential surface of the attachment 19 and the outer circumferential surface of the first inner ring piece 1618.
The second rolling elements 1621 are arranged in a second row. The second row is arranged between the second inner ring piece 1619 and the attachment 19. The second rolling elements 1621 are positioned by a cage to be aligned at regular intervals. The second rolling elements 1621 are in contact with an inner circumferential surface of the attachment 19 and an outer circumferential surface of the second inner ring piece 1619. In other words, the raceway surfaces of the second rolling elements 1621 are the inner circumferential surface of the attachment 19 and the outer circumferential surface of the second inner ring piece 1619.
In the fifth modification, the first bearing 16E does not include an outer ring as described above, and thus the number of parts of the first bearing 16E can be reduced. Thus, the reduction gear (third reduction gear 6E) in the fifth modification can be configured to be light in weight.
As illustrated in
The first inner ring piece 1623 is an annular member. The first inner ring piece 1623 is in contact with an outer circumferential surface of the output member 15. One end surface of the first inner ring piece 1623 is in contact with the output member 15.
The first rolling elements 1624 are arranged in a first row. The first row is arranged between the first inner ring piece 1623 and the attachment 19. The first rolling elements 1624 are positioned by a cage to be aligned at regular intervals. The first rolling elements 1624 are in contact with an inner circumferential surface of the attachment 19 and an outer circumferential surface of the first inner ring piece 1623. In other words, the raceway surfaces of the first rolling elements 1624 are the inner circumferential surface of the attachment 19 and the outer circumferential surface of the first inner ring piece 1623.
The second rolling elements 1625 are arranged in a second row. The second row is arranged between the output member 15 and the attachment 19. The second rolling elements 1625 are positioned by a cage to be aligned at regular intervals. The second rolling elements 1625 are in contact with an inner circumferential surface of the attachment 19 and an outer circumferential surface of the output member 15. In other words, the raceway surfaces of the second rolling elements 1625 are the inner circumferential surface of the attachment 19 and the outer circumferential surface of the output member 15.
In the sixth modification, the first bearing 16F does not include an outer ring as described above, and thus the number of parts of the first bearing 16F can be reduced. Thus, the reduction gear (third reduction gear 6F) in the sixth modification can be configured to be light in weight.
As illustrated in
The first inner ring piece 1627 is an annular member. The first inner ring piece 1627 is in contact with an outer circumferential surface of the output member 15. One end surface and the other end surface of the first inner ring piece 1627 are in contact with the output member 15. The first inner ring piece 1627 is positioned by swaging (plastically deforming) the output member 15.
The first rolling elements 1628 are arranged in a first row. The first row is arranged between the first inner ring piece 1627 and the attachment 19. The first rolling elements 1628 are positioned by a cage to be aligned at regular intervals. The first rolling elements 1628 are in contact with an inner circumferential surface of the attachment 19 and an outer circumferential surface of the first inner ring piece 1627. In other words, the raceway surfaces of the first rolling elements 1628 are the inner circumferential surface of the attachment 19 and the outer circumferential surface of the first inner ring piece 1627.
The second rolling elements 1629 are arranged in a second row. The second row is arranged between the output member 15 and the attachment 19. The second rolling elements 1629 are positioned by a cage to be aligned at regular intervals. The second rolling elements 1629 are in contact with an inner circumferential surface of the attachment 19 and an outer circumferential surface of the output member 15. In other words, the raceway surfaces of the second rolling elements 1629 are the inner circumferential surface of the attachment 19 and the outer circumferential surface of the output member 15.
In the seventh modification, the first bearing 16G does not include an outer ring as described above, and thus the number of parts of the first bearing 16G can be reduced. Thus, the reduction gear (third reduction gear 6G) in the seventh modification can be configured to be light in weight.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-183182 | Sep 2017 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2018/028617 | 7/31/2018 | WO | 00 |
