JP7528741B2 - Planetary Roller Traction Drive Device - Google Patents

Description

The present invention relates to an improvement to a traction drive device, specifically, a planetary roller traction drive device that transmits power through an oil film formed between a sun roller and a pinion roller, and between a pinion roller and a pair of ring rollers.

Planetary roller traction drive devices are known that are incorporated into the drive systems of EV (Electric Vehicles) and AT (Automatic Transmission) vehicles, or drive systems of machine tools, etc., and transmit the rotational driving force of an electric motor or the like to the driven part by slowing down or accelerating it.

An example of a planetary roller traction drive device is described below with reference to Figures 5 to 8.

In FIG. 5, the reference numeral 1 denotes an input shaft, which includes a sun roller 3 fixed to the outer circumference of the input shaft 1, a pair of ring rollers 9 arranged on the outside of the sun roller 3, a cam side ring 5 with a torque cam mechanism 13 on its back side, and an anti-cam side ring 7 without a torque cam mechanism, and a number of pinion rollers 11 pressed against the ring roller 9 and the sun roller 3. Power is transmitted via oil films formed between the sun roller 3 and the pinion roller 11, and between the pinion roller 11 and the pair of ring rollers 9 (cam side ring 5, anti-cam side ring 7).

The pinion roller 11 has support shafts 11a, 11a protruding forward and backward in the axial direction, and is rotatably supported by a holder 33 via a ball bearing 31. Reference numeral 35 in the drawing denotes a carrier that supports the holder 33 so that it can swing freely.
Each pinion roller 11 is disposed between and in rolling contact with the outer circumferential surface of the sun roller 3 and the inner circumferential surface 5b of the cam side ring 5 and the inner circumferential surface 7b of the anti-cam side ring 7. In the drawing, reference symbol Ax1 indicates the central axis of the sun roller 3.

The inner peripheral surfaces 5b, 7b of the cam side ring 5 and the anti-cam side ring 7 that make up the ring roller 9 are formed in an inclined shape such that the inner diameter decreases from the opposing surface portions 5c, 7c where the rings 5, 7 face each other toward the opposite surface portions 5d, 7d. These inner peripheral surfaces 5b, 7b form the rolling contact surfaces with which the pinion roller 11 comes into contact and rolls.

The ring rollers 9 (cam side ring 5, anti-cam side ring 7) each have multiple claws 5a..., 7a... protruding from their outer periphery that engage with multiple recesses 15a... provided on the inner periphery of the ring drum 15 arranged on the outside, allowing them to move (translate) along the rotation axis Ax2 of the pinion roller 11 and are held so that the rotation phase around the rotation axis does not shift. In the figure, the symbol H1 indicates the vertical direction.

The reference numeral 17 in the figure indicates a preload spring (elastic member) disposed between the end 15c of the ring drum 15 and the anti-cam side ring 7. The preload spring 17 can be appropriately modified in design within the scope of the present invention to be a coil spring, a leaf spring, or the like. When the torque transmitted from the input shaft 1 is small, the preload spring 17 ensures that the contact surface pressure on the rolling contact surface between the ring roller 9 (cam side ring 5, anti-cam side ring 7) and the pinion roller 11 is equal to or greater than a predetermined value.

The torque cam mechanism 13 is composed of the cam side ring 5, a cam disc 19 arranged on the back side of the cam side ring 5, a cam surface (cam groove) 5e provided on the surface facing the cam disc 19, and a ball 27 inserted between the cam surface (cam groove) 19e provided on the surface facing the cam side ring 5. In other words, the cam side ring 5 constitutes the torque cam mechanism 13.

The basic operation of this type of planetary roller traction drive is as follows.
First, the driving force (torque) of an electric motor or the like is input to the input shaft 1, and the torque input to the input shaft 1 is transmitted from the sun roller 3 via an oil film to the pinion roller 11, and further from the pinion roller 11 to the ring roller 9 via an oil film.
The torque transmitted to the ring roller 9 is then transmitted from the ring roller 9 through the cylindrical portion 19a of the cam disc 19 to an output shaft (not shown) that is integral with the cylindrical portion 19a.

As described above, this type of planetary roller traction drive device is equipped with a torque cam mechanism 13 on the back side of one of the ring rollers (the cam side ring 5), and does not have a torque cam mechanism on the back side of the other ring roller (the anti-cam side ring 7). Instead, it employs a configuration in which a pressing force is applied to the power transmission surface by preloading the preload spring (disc spring) 17.

However, in the case of such a conventional configuration, there is a difference in the amount of elastic deformation between the two rings (cam side ring 5, anti-cam side ring 7) due to the difference in their shapes (difference in rigidity). That is, as described above, the cam side ring 5 has a cam surface (cam groove) 5e recessed into the surface facing the cam disc 19. Therefore, the cam side ring 5 has a different shape from the anti-cam side ring 7, which does not have a torque cam mechanism, and is thinner than the anti-cam side ring 7, which means that when the same force is applied, the cam side ring 5 is more likely to deform than the anti-cam side ring 7.

Generally, both rings are designed so that the places where they come into contact with the pinion roller 11 are symmetrical, but if the positional relationship from the center point shifts due to elastic deformation, tilt occurs, and as a result, there is a risk of differences in the position of the contact part relative to the pinion center of gravity and the contact surface pressure between the contact part between the cam side ring 5 and the pinion roller 11 (contact point A in FIG. 6(a)) and the contact part between the anti-cam side ring 7 and the pinion roller 11 (contact point B in FIG. 6(a)). Since the magnitude of the traction force generated on the rolling contact surface changes depending on the contact surface pressure, if the contact surface pressure differs between the contact points A and B, a difference (imbalance) in the magnitude of the traction force will also occur. In FIG. 6(b), symbol Tr1 indicates the traction force at contact point A, and symbol Tr2 indicates the traction force at contact point B.
The existence of a difference in the magnitude and point of action of this traction force is undesirable because it causes skew in the pinion roller 11, which in turn leads to a decrease in power transmission efficiency.

In the conventional configuration, the torque (arrow To1) passing through contact point B is transmitted to the cam side ring 5 via the ring drum 15, merges with the torque (arrow To2) passing through contact point A, and is then transmitted to the output shaft (the flow of torque is shown by the arrows in FIG. 6(a)).
That is, the torque transmission directions at the engagement portions between the ring drum 15 and the claw portions 5a of the cam side ring 5 and the claw portions 7a of the anti-cam side ring 7 are different on the cam side and anti-cam side.
This does not cause a problem during steady torque transmission, but during transient response, it may increase the skew of the pinion roller 11. Furthermore, there is also a risk that the pinion roller 11 may jump outward.

Furthermore, there are prior art techniques that focus on improving the traction surface by hardening the surface of the ring roller, thereby increasing the durability of the entire traction drive device (see Patent Documents 1 and 2). However, these are merely approaches to modifying materials, and do not solve the problem of reduced power transmission efficiency due to skew caused by differences in rigidity of the ring rollers.

Incidentally, a technique disclosed in Japanese Patent Laid-Open No. 2003-233663 is one of the prior art techniques aimed at suppressing the occurrence of the skew phenomenon.
In Patent Document 3, the first rotation shaft side and the second rotation shaft side of the planetary roller are supported by two carrier rollers adjacent in the circumferential direction, and the contact parts of the planetary roller and the internal ring and the carrier pin are not aligned in the radial direction around the main shaft, but are arranged at different positions in the circumferential direction. By adopting such a configuration, it is possible to reduce the gap between the planetary roller and the carrier roller, and it is possible to suppress the occurrence of a skew phenomenon in which the rotation axis of the planetary roller is tilted relative to the main shaft due to the tangential force received from the internal ring.
However, in the prior art disclosed in Patent Document 3, a total of four carrier rollers are required to support one planetary roller, which means that a large number of carrier rollers must be arranged to support each of the multiple planetary rollers arranged throughout the traction drive device. Not only does this complicate the configuration, it also increases the number of parts, which may result in increased production costs, labor costs, and parts management costs.

JP2014-092236A JP 2016-211645 A JP 2017-044232 A

The present invention was made to solve these problems with the conventional technology, and its objective is to provide a traction drive device that can suppress skew of the pinion roller by adopting a simple and low-cost configuration.

In order to achieve the above object, the first aspect of the present invention provides a sun roller fixed to an outer periphery of an input shaft,
a pair of ring rollers arranged on the outside of the sun roller, the pair of ring rollers being composed of a cam side ring having a torque cam mechanism arranged on the rear surface side thereof and an anti-cam side ring having no torque cam mechanism arranged thereon;
a pinion roller that is in pressure contact with the ring roller and the sun roller,
The pair of ring rollers are movable along the rotation axis of the pinion roller between the ring drum disposed on the outside and are held so that the rotation phases around the rotation axis are not shifted,
In a traction drive device that transmits power through oil films formed between the sun roller and the pinion roller and between the pinion roller and the pair of ring rollers,
The planetary roller traction drive device is characterized in that the cam side ring and the anti-cam side ring have the same shape.

The second aspect of the present invention is the torque cam mechanism according to the first aspect of the present invention, further comprising: a cam disc disposed between the cam side ring and a side portion of the ring drum with a gap therebetween;
and a ball interposed between the cam disc and the side of the ring drum,
The planetary roller traction drive device is characterized in that a thrust needle bearing is disposed between the cam disc and the cam side link.

The third aspect of the present invention is the second aspect of the present invention, further comprising an intermediate member disposed between the cam side ring and the thrust needle bearing,
The planetary roller traction drive device is characterized in that an elastic member is disposed between the cam side ring and the intermediate member.

According to the present invention, by adopting a simple and low-cost configuration, it is possible to suppress skew of the pinion roller, and obtain a planetary roller traction drive device with high power transmission efficiency and low cost.

1 is a longitudinal sectional perspective view showing a first embodiment of a traction drive device of the present invention, with a portion cut away and omitted; FIG. 2 is a vertical sectional side view of the traction drive device shown in FIG. 1 with some parts omitted. FIG. 2A is a schematic diagram showing a traction drive device shown in the first embodiment with a portion thereof omitted, and FIG. 2B is a cross-sectional view taken along line X-X of FIG. 2A, showing that the traction forces are balanced. FIG. 4 is a schematic diagram showing a second embodiment of a traction drive device according to the present invention, with some parts omitted. FIG. 1A is a longitudinal perspective view of a conventional traction drive device with a portion cut away and omitted, FIG. 1B is a longitudinal side view of a conventional traction drive device with a portion omitted, and FIG. 1C is a schematic cross-sectional view of the engagement state between a ring roller and a ring drum with a portion omitted. FIG. 1A is a schematic diagram showing a conventional traction drive device with some parts omitted, and FIG. 1B is a cross-sectional view taken along line X-X of FIG. 1A, which is a schematic diagram showing that the traction forces are unbalanced in the conventional traction drive device.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the embodiment is one embodiment of the present invention, and is not to be construed as being limited thereto in any way, and design modifications are possible within the scope of the present invention.
"First embodiment"

Figures 1 to 3 show a first embodiment of the present invention. Figure 1 is a schematic cross-sectional perspective view of the planetary roller traction drive device of this embodiment, with some parts omitted. The planetary roller traction drive device of this embodiment has the following configuration.

The planetary roller traction drive device of this embodiment, like the conventional traction drive device shown in Figure 5, is composed of a sun roller 3 fixed to the outer periphery of the input shaft 1, a pair of ring rollers 9 arranged on the outside of the sun roller 3 and consisting of a cam side ring 5 with a torque cam mechanism 13 arranged in the rear direction and an anti-cam side ring 7 without a torque cam mechanism, and a plurality of pinion rollers 11 (three in this embodiment) that are pressed against the ring roller 9 and the sun roller 3, and is characterized in that the shapes of the cam side ring 5 and the anti-cam side ring 7 are made the same (unified) by differing the arrangement position of the torque cam mechanism 13 from the conventional device.
The following description will focus on the configuration and operation/effects characteristic of the present invention, and detailed description of the configuration and operation/effects similar to those of the conventional traction drive device shown in Figures 5 and 6 will be omitted by assigning the same reference numerals to the same parts as in Figures 5 and 6.

The torque cam mechanism 13 is composed of a cam disc 19 that is disposed at a distance between the side 25 of the ring drum 15 and the cam side ring 5, and balls (rolling elements) 27 that are interposed between the cam disc 19 and the side 25 of the ring drum 15. That is, in this embodiment, the torque cam mechanism 13 is disposed in the direction of the back surface of the cam side ring 5, but is disposed adjacent to the cam side ring 5, which is different from the conventional arrangement in which the cam side ring 5 is a component of the torque cam mechanism.

In this embodiment, the side portion 25 of the ring drum 15 is assumed to be an annular side portion that is assembled via a retaining ring 23 and holds the balls 27 together with the cam disc 19 after the preload spring 17, anti-cam side ring 7, cam side ring 5, thrust needle bearing 29, cam disc 19, and balls 27 are inserted from the open side of the ring drum 15 in this order.

The annular side portion 25 is formed in a flat ring shape having an inner diameter larger than the outer diameter of the cylindrical portion 19a of the cam disc 19, and is disposed outside the cam disc 19 with a predetermined gap therebetween in the axial direction.
A configuration is adopted in which a plurality of claw portions (not shown) are protruded from the outer periphery of the annular side portion 25 to engage with the recesses 15a... of the ring drum 15, thereby enabling the annular side portion 25 to move (translationally move) together with the cam side ring 5 and the anti-cam side ring 7 along the rotation axis Ax2 of the pinion roller 11, and the annular side portion 25 is held so that there is no deviation in rotation phase around the rotation axis with the cam side ring 5 and the anti-cam side ring 7.
A plurality of cam surfaces (cam grooves) 25e are recessed in the circumferential direction on the surface of the annular side portion 25 facing the cam disc 19.

The cam disc 19 is composed of a cylindrical portion 19a that is arranged coaxially with the input shaft 1 and connected to the output shaft side, and a flange portion 19b that is formed by continuously rising from the end of the cylindrical portion 19a in the vertical direction H1 (a direction perpendicular to the central axis of the cylindrical portion 19a).
A plurality of cam surfaces (cam grooves) 19e are recessed in the circumferential direction on the surface of the flange portion 19b facing the annular side portion 25.
This cam surface (cam groove) 19e is formed in the same shape as the cam surface (cam groove) 25e of the above-mentioned annular side portion 25 at a position axially opposite to the cam surface (cam groove) 25e of the above-mentioned annular side portion 25. A ball 27 is fitted between this cam surface (cam groove) 19e and the above-mentioned cam surface (cam groove) 25e of the annular side portion 25.

The retaining ring 23 is formed in a flat ring shape with an inner diameter smaller than the outer diameter of the annular side portion 25, and is arranged so that it abuts against the outer surface of the annular side portion 25 in the axial direction, and its outer periphery is fitted into the fitting portion 15b provided on the inner peripheral surface of the ring drum 15. The retaining ring 23 prevents the annular side portion 25, balls 27, cam disc 19, etc. from coming off in the axial direction.

A thrust needle bearing 29 is arranged between the cam disc 19 and the cam side ring 5.

Therefore, according to this embodiment, the torque cam mechanism 13 is formed between the cam disc 19 and the annular side portion 25 of the ring drum 15, and a thrust needle bearing 29 is disposed between the cam side ring 5 and the cam disc 19, so the cam side ring 5 does not need a cam surface (cam groove). Therefore, it is possible to make the cam side ring 5 have the same shape as the anti-cam side ring 7.

By adopting this embodiment, the shapes of both the cam side ring 5 and the anti-cam side ring 7 can be made identical (standardized), making it less likely that differences (imbalances) in traction force and the resulting skew of the pinion rollers will occur, leading to improved power transmission efficiency.
Furthermore, according to this embodiment, the torque transmission directions at the engagement portions between the claw portion 5a of the cam side ring 5 and the claw portion 7a of the anti-cam side ring 7 and the recess 15a of the ring drum 15 are the same, so there is no effect of promoting skew even during transient response.

The operation and effects of the present embodiment described above will be explained in detail below with reference to FIG. 3, while comparing it with the conventional technology shown in FIG. 6.

In the case of the prior art, when the torque input from the output shaft 1 is transmitted from the sun roller 3 to the pinion roller 11 through the oil film, it twists the cam side ring 5 that is in contact with the pinion roller 11 at point A. The cam side ring 5 constitutes the torque cam mechanism 13 together with the cam disc 19 and the balls 27, so the torque is transmitted from the cylindrical portion 19a of the cam disc 19 to the output shaft (not shown) through the balls 27. Similarly, the power transmitted to the pinion roller 11 twists the anti-cam side ring 7, and the torque from point B is transmitted from the claw portion 7a of the anti-cam side ring 7 to the ring drum 15. Then, the torque flowing from point B to the ring drum 15 is transmitted to the cam side ring 5 through the claw portion 5a of the cam side ring 5, and merges with the torque from point A, and the merged torsion is transmitted to the output shaft (not shown) through the torque cam mechanism 13 (the flow of torque is indicated by an arrow in FIG. 6(a)).
In this way, the torque transmission direction at the engagement portions between the ring drum 15 and the claw portions 5a of the cam side ring 5 and the claw portions 7a of the anti-cam side ring 7 differs on the cam side and anti-cam side. This difference in the torque transmission direction does not cause problems during steady-state torque transmission, but is undesirable because it can promote pinion skew during transient response.
In addition, because the shapes of the cam side ring 5 and the anti-cam side ring 7 are different, there will be a difference in the position and magnitude of the pressing force on the pinion ring 11 (in FIG. 6(a) the pressing force from point A is shown as P1, and the pressing force from point B is shown as P2), which will result in an imbalance in the traction forces (in FIG. 6(b) the traction force at point A is shown as Tr1, and the traction force at point B is shown as Tr2), which may induce skewing of the pinion ring 11.

On the other hand, in this embodiment, when the torque input from the output shaft 1 is transmitted from the sun roller 3 to the pinion roller 11 via the oil film, the torque from point B is transmitted from the claw portion 7a of the anti-cam side ring 7 to the ring drum 15. However, since there is no torque cam mechanism 13 adjacent to the cam side ring 5, the torque from point A is also transmitted from the claw portion 5a of the cam side ring 5 to the ring drum 15, where it merges with the torque that has flowed from the claw portion 7a of the anti-cam side ring 7 to the ring drum 15, twisting the torque cam mechanism 13 composed of the cam disc 19 and the annular side portion 25 located on the outside of the cam side ring 5, twisting the output shaft (not shown) via the balls 27, and the torque goes out from the output shaft (the flow of torque is shown by the arrow in FIG. 3(a)).
According to this embodiment, as described above, the torque transmission direction at each engagement portion between the ring drum 15 and the claw portion 5a of the cam side ring 5 and the claw portion 7a of the anti-cam side ring 7 is the same on the cam side and the anti-cam side, so there is no risk of promoting pinion skew even during transient response.
Furthermore, according to this embodiment, the shapes of the cam side ring 5 and the anti-cam side ring 7 are unified (identical), so there is no difference in the position and magnitude of the pressing force on the pinion ring 11 (in FIG. 3A, the pressing force from point A is indicated by P1, and the pressing force from point B is indicated by P2), and there is no imbalance in the traction forces either (in FIG. 3B, the traction force at point A is indicated by Tr1, and the traction force at point B is indicated by Tr2). As a result, skew induction of the pinion ring 11 is also corrected.

Furthermore, according to this embodiment, it is no longer necessary to machine the cam surface on the back surface of the cam side ring 5 as in the conventional method, which leads to reduced production costs and shorter production time.

Even if the conventional structure shown in FIG. 5 is adopted, if a cam groove of the same shape as the cam groove 5e is formed in the anti-cam ring 7, the ring shape can be unified and the above-mentioned effects can be achieved, and the adoption of such a configuration is also within the scope of the present invention.

The engagement state between the ring roller 9 (the cam side ring 5 and the anti-cam side ring 7) and the ring drum 15 is not particularly limited to this embodiment.
Second Embodiment

4 is a schematic diagram showing a second embodiment of the present invention, which differs from the first embodiment in the position at which the preload spring 17 is disposed. That is, this embodiment is an embodiment in which an intermediate member 37 is disposed between the cam side ring 5 and the thrust needle bearing 29, and the preload spring 17 is disposed between the cam side ring 5 and the intermediate member 37.
The intermediate member 37 is formed in an annular plate shape, and the thrust needle rolling surface thereof is mirror finished.
The other configurations and effects are the same as those of the first embodiment and the prior art shown in FIG. 5, so that the description thereof will be omitted.

In the first embodiment, it is necessary to mirror-finish the thrust needle rolling surface of the cam side ring 5, but according to this embodiment, this is not necessary, which has the further advantage of making work management easier.
In other words, when the configuration of the first embodiment is adopted, two surfaces of the cam side ring 5, the inner surface (pinion roller rolling contact surface) 5b and the surface (thrust needle rolling surface) 5f that contacts the thrust needle bearing 29, need to be mirror-finished.
In this case, when mirror-finishing the inner peripheral surface 5b and then mirror-finishing the thrust needle rolling surface 5f, care must be taken not to damage the already mirror-finished surface on the inner peripheral surface 5b side, but this is not necessary according to the present embodiment, and work management becomes easier.

The ring roller (cam side ring 5 and anti-cam side ring 7) 19 rotates while deforming. If the back surface of the cam side ring 5, which rotates while deforming, is pressed by a bearing as it is, fretting wear may occur. If the cam side ring 5 suffers fretting wear, the pressing force will decrease. According to this embodiment, the elastic deformation itself is absorbed by the preload spring, and the intermediate member 37 does not elastically deform, so fretting wear of the thrust needle bearing 29 on the back surface is reduced.
By adopting the structure of this embodiment, the cam side ring 5 will not be elastically deformed, and fretting wear will also be reduced.

The present invention can also be used in other traction drive devices employing other structures, and can also be used in traction drive devices used in other industrial machines, such as construction machines, agricultural machines, and woodworking machines.

Reference Signs List 1: Input shaft 3: Sun roller 5: Cam side ring 7: Anti-cam side ring 9: Ring roller 11: Pinion ring 13: Torque cam mechanism 15: Ring drum 19: Cam disc 25: Annular side portion (ring drum side portion)
27 ball 29 thrust needle bearing 37 intermediate member

Claims (3)

a sun roller fixed to an outer periphery of the input shaft;
a pair of ring rollers arranged on the outside of the sun roller, the pair including a cam side ring having a torque cam mechanism arranged on its back side, and an anti-cam side ring having no torque cam mechanism arranged thereon;
a pinion roller that is in pressure contact with the ring roller and the sun roller,
The pair of ring rollers are movable along the rotation axis of the pinion roller between the ring drum disposed on the outside and are held so that the rotation phases around the rotation axis are not shifted,
In a planetary roller traction drive device that transmits power through oil films formed between the sun roller and the pinion roller and between the pinion roller and the pair of ring rollers,
A planetary roller traction drive device, characterized in that the cam side ring and the anti-cam side ring have the same shape. The torque cam mechanism includes a cam disc disposed between the cam side ring and the side of the ring drum with a gap therebetween;
and a ball interposed between the cam disc and the side of the ring drum,
2. The planetary roller traction drive device according to claim 1, further comprising a thrust needle bearing disposed between said cam disc and said cam side link. an intermediate member is disposed between the cam side ring and the thrust needle bearing;
3. A planetary roller traction drive device according to claim 2, further comprising an elastic member disposed between said cam side ring and said intermediate member.

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