JP6740936B2 - Bearing lubrication structure - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lubrication structure for a rolling bearing in which an inner ring is a clearance fit with respect to a fixed shaft and an outer ring is an interference fit with a rotating body.

A power transmission device arranged between a prime mover such as an engine or a motor mounted on a vehicle and a drive wheel usually incorporates a large number of gears together with rolling bearings. Among them, in a portion having a structure in which a gear is attached to a boss formed on a housing via a rolling bearing, an outer ring of the rolling bearing is press-fitted into the gear by an interference fit. However, regarding the inner ring of the rolling bearing, against the adverse effect caused by the difference in linear expansion coefficient between the material forming the housing, generally an aluminum alloy, and the material forming the inner ring of the rolling bearing, generally steel. Need to be considered. In such a case, the inner ring of the rolling bearing is usually mounted with a clearance fit to the boss of the housing, and it is necessary to deal with the creep phenomenon that occurs between the inner ring of the rolling bearing and the boss of the housing. There is.

Patent Document 1 discloses a technique for dealing with the above-mentioned problem, and an inner side is formed on an outer peripheral surface of a boss portion of a housing or on an inner peripheral surface of a rolling bearing fitted to the boss portion by a clearance fit. Forming a layer and an outer layer overlying the inner layer. The inner layer is made of at least one oxide or hydroxide of Zr, Ti, Si, and the outer layer is made of a solid lubricant such as a fluoropolymer or molybdenum disulfide.

JP, 2008-8434, A

In the conventional method disclosed in Patent Document 1, it is necessary to apply a coating containing a fixed lubricant layer to the outer peripheral surface of the boss portion of the housing and the inner peripheral surface of the rolling bearing, which increases the component cost.

On the other hand, when the rotational drive direction of the gear group that forms part of the power transmission device changes with the acceleration and deceleration of the vehicle, it acts on the gear supported by the boss of the housing via the rolling bearing due to the clearance fit. The direction of the radial load is also changed. Due to the transient creep behavior of the gears generated at this time, the outer peripheral surface of the boss portion of the housing and the inner peripheral surface of the inner ring of the rolling bearing are worn. For this reason, even if the outer peripheral surface of the boss portion of the housing and the inner peripheral surface of the rolling bearing are coated with a fixed lubricant layer, the coating gradually wears due to the occurrence of creep. As a result, the housing needs to be replaced prior to the replacement of the rolling bearing due to its service life, resulting in an increase in running cost.

It is an object of the present invention, even if a creep phenomenon occurs between the boss portion of the housing and the inner ring of the rolling bearing, without coating the outer peripheral surface of the boss portion of the housing or the inner peripheral surface of the inner ring of the rolling bearing, An object of the present invention is to provide a power transmission device capable of suppressing such wear.

According to the present invention, a housing that accommodates a pair of gears that mesh with each other, a circular boss portion that projects from a wall surface of the housing, an outer ring is fitted to one of the gears by a tight fit, and an inner ring is the boss. A power transmission device comprising a rolling bearing fitted to the boss by a clearance fit, wherein the geometrical structure is parallel to the central axis of the boss and extends vertically upward from the central axis of the boss. Formed along the longitudinal direction of the boss portion in the region of the outer peripheral surface of the boss portion surrounded by a plane and a geometrical plane extending horizontally from the central axis of the boss portion toward the meshing point side of the pair of gears. And a lubricating oil guide portion that is formed on a wall surface of the housing with which one end surface of the inner ring abuts and that guides lubricating oil adhering to the wall surface to the recess portion. Is.

In the present invention, part of the lubricating oil scraped up in the housing adheres to the wall surface of the housing and is guided along the wall surface to the recess from the lubricating oil guide portion. Then, the lubricating oil guided to the concave portion by the rotation of the gear is reliably drawn into the fitting gap between the boss portion and the inner ring of the rolling bearing.

According to the power transmission device of the present invention, a part of the lubricating oil scraped up in the housing due to the rotation of the gear is guided along the wall surface of the housing to the recess from the lubricating oil guiding portion, and the lubricating oil is bossed. It is possible to reliably supply the clearance between the portion and the inner ring of the rolling bearing. As a result, even if creep occurs in the rolling bearing, it is possible to suppress wear of the boss portion of the housing and the inner peripheral surface of the inner ring of the rolling bearing.

1 is a conceptual diagram showing a schematic structure of a power transmission device in an embodiment in which a power transmission device according to the present invention is applied to a hybrid vehicle. FIG. 2 is a sectional view developed along a line II-II in FIG. 1. FIG. 3 is a cross-sectional view taken along the line AA in FIG. 2, showing a state in a regenerative mode. FIG. 3 is a cross-sectional view taken along the line AA in FIG. 2, showing a state in a power running mode.

An embodiment in which the power transmission device according to the present invention is applied to a hybrid vehicle will be described in detail with reference to FIGS. 1 to 4. However, the present invention is not limited to such an embodiment, and can be applied to any power transmission device belonging to the spirit of the present invention.

FIG. 1 schematically shows the side surface shape of the housing part of the transaxle case of the hybrid vehicle in the present embodiment, and FIG. 2 shows a part of the internal structure of the housing developed along the line II-II.

The hybrid vehicle in the present embodiment includes, as a prime mover, one internal combustion engine, that is, an engine (not shown) and two rotating electric machines (not shown), but is not limited thereto. The present invention can be applied even to a hybrid vehicle in which the prime mover is composed of one engine and one rotating electric machine. In the present embodiment, the power running mode in which the output of the rotating electric machine and/or the engine is transmitted to drive wheels (not shown) and the regenerative mode in which the rotating electric machine functions as a generator are switched based on the operating state of the vehicle.

A power transmission device T including a planetary gear train 10 and a differential device (not shown) is incorporated between the engine and the two rotary electric machines and the drive wheels.

Both ends of a rotor shaft 31 of the first rotating electric machine, whose stator (not shown) is fixed to the casing 21 of the transaxle case 20, are rotatably supported with respect to the casing 21, and the rotor shaft 31 of the first rotating electric machine. A rotor (not shown) is attached to.

The base end portion of the engine output shaft 32 connected to the engine is rotatably supported by the housing 22 of the transaxle case 20. Further, a bearing 33 is provided between the rotor shaft 31 of the first rotating electric machine and the tip end portion of the engine output shaft 32 that enters inside one end portion (right side in FIG. 2) of the rotor shaft 31 of the first rotating electric machine. It has been incorporated. As a result, the engine output shaft 32 and the rotor shaft 31 of the first rotating electric machine are coaxial and can rotate relative to each other.

A sun gear 11a is formed at one end (right side in FIG. 2) of a hollow sun gear shaft 11 that coaxially surrounds the engine output shaft 32, and the other end of the sun gear shaft 11 is the first rotary electric machine. Is spline-fitted to one end of the rotor shaft 31. A plurality of planetary gear shafts 13 projecting from the carrier 12 parallel to the rotation axis of the engine output shaft 32 are fixed to the disk-shaped carrier 12 fixed to the engine output shaft 32 so as to surround the sun gear portion 11a. ing. A planetary gear 14 that meshes with the sun gear 11 a is rotatably supported on each planetary gear shaft 13 via a bearing 15. An internal gear portion 16a that meshes with the planetary gear 14 is formed on the inner circumference of a gear cylinder 16 that is coaxially arranged with the cylindrical sun gear shaft 11 so as to surround the planetary gears 14. Both ends of the gear cylinder 16 in the longitudinal direction are respectively rotated by a boss portion 21a protruding from the wall surface of the casing 21 of the transaxle case 20 and a boss portion 22a protruding from the wall surface of the housing 22 via a pair of ball bearings 17. It is supported freely. Further, an outer gear portion 16b that meshes with a large gear 41 of a counter shaft (not shown) is formed on the outer peripheral surface of the gear cylinder 16.

The external gear portion 16b of the gear cylinder 16 and the large gear 41 of the auxiliary shaft which meshes with the external gear portion 16b housed in the housing 22 correspond to a pair of gears in the present invention, and these portions, that is, AA in FIG. The cross-sectional shape along the arrow is schematically shown in FIGS. The circular, more specifically, cylindrical boss portion 21a and ball bearing 17 formed on the casing 21 have basically the same configuration. The outer ring 17a of the ball bearing 17 as the rolling bearing in the present invention is fitted to the inner peripheral surface of the gear cylinder 16 in which the outer gear portion 16b is formed by an interference fit, and the inner ring 17b is formed in the housing 22. It is fitted in a circular, more specifically, cylindrical boss portion 22a by a loose fit. Therefore, the inner ring 17b of the ball bearing 17 can be slightly displaced with respect to the boss portion 22a of the housing 22 together with the gear cylinder 16 in which the outer gear portion 16b is formed, in any radial direction corresponding to the fitting gap G between them. .. FIG. 3 shows a state in the regenerative mode, and as shown by an arrow L in the figure, it shows that a radial load in an obliquely upper right direction is applied to the external gear portion 16b of the gear cylinder 16. On the other hand, FIG. 4 shows a state in the power running mode, and as shown by an arrow L in the figure, shows that a radial load in a diagonally lower left direction is applied to the external gear portion 16b of the gear cylinder 16. In this way, the maximum/minimum position of the fitting gap G between the inner ring 17b and the boss portion 22a changes so as to be substantially opposite with the switching between the regeneration mode/powering mode.

A recess 23 is formed on the outer peripheral surface of the boss portion 22a along the longitudinal direction thereof. The concave portion 23 meshes with the geometrical plane P _V parallel to the central axis C of the boss 22 a and extending vertically upward from the central axis C, and the external gear 16 b and the large gear 41 from the central axis C of the boss 22 a. It suffices to be in the region Z of the outer peripheral surface of the boss portion 22a surrounded by the geometrical plane P _H extending horizontally toward the point M side. As a result, the lubricating oil O staying in the recess 23 in the regenerative mode shown in FIG. 3 is drawn from the recess 23 into the fitting gap G (lower left side in FIG. 4) in the power running mode shown in FIG. The lubricating oil O is pushed to the upper right side in FIG. 3 in the regenerative mode. That is, the lubricating oil O in the recess 23 is distributed over the entire area of the fitting gap G between the inner ring 17b and the boss portion 22a by the pump action caused by the radial displacement of the inner ring 17b each time the regeneration mode and the power running mode are switched. Will be guided. Note that if the recess 23 is formed on the outer peripheral surface of the boss portion 22a by removing it from the region Z, it is noted that the lubricating oil O cannot be efficiently supplied to the fitting gap G between the inner ring 17b and the boss portion 22a. I want to. Further, it is preferable that the recess 23 has a shape inclined downward with respect to the horizontal plane so that the lubricating oil O does not remain in itself. In order to guide the lubricating oil O, which flows down the wall surface of the housing 22 to the seat portion 22b having a diameter larger than the boss portion 22a, to the recess portion 23, the seat portion 22b of the housing 22 with which one end surface of the inner ring 17b abuts is guided. The lubricating oil guide portion 24 is formed. Further, it is also effective to form a rib extending from the upper end side of the casing 21 to the lubricating oil guide portion 24 on the wall surface of the casing 21 in a protruding state.

The differential device (not shown) is arranged at the lower end of the transaxle case 20 in which the lubricating oil O is sealed, and the lubricating oil O flows down to the oil sump 20a at the lower end of the transaxle case 20 due to gravity. The auxiliary gear shaft, both ends of which are rotatably supported by the housing 22 and the casing 21 of the transaxle case 20, has an external gear portion 16b of the gear cylinder 16 and a small gear of a rotor shaft (not shown) of the second rotary electric machine. A large gear 41 that meshes with 51 is attached. An output gear 42 that meshes with the final reduction gear 61 of the differential gear is formed on the side of the large gear 41 of the counter shaft.

The rotor shaft of the second rotating electric machine is arranged further above the counter shaft and is located almost directly above the differential device. The aforementioned engine output shaft 32 is arranged further forward than the counter shaft with respect to the differential device and is located further away from the differential device than the counter shaft, but is not limited to this.

As the final reduction gear 61 of the differential gear rotates, the lubricating oil O in the oil sump 20a is scraped up, and the output gear 42 of the auxiliary shaft and the external gear portion 16b of the gear cylinder 16 and the large gear of the auxiliary shaft meshing with the lubricating oil O. Lubricating oil O is supplied to the meshing portion with 41. Normally, the external gear 16b and the large gear 41 are formed as helical gears, and the lubricating oil O flowing into these tooth grooves forms a rotation axis C toward the inner wall of the housing 22 in the vicinity of their meshing point M. It is extruded in a parallel direction, and at the same time, it is extruded above the meshing point M. As a result, as long as the external gear 16b and the large gear 41 are rotating, the lubricating oil O can be retained in the vicinity of the meshing point M between them, and a part of the lubricating oil O can be retained in the seat portion of the housing 22. It can be flipped to the wall surface where 22b is formed. The lubricating oil O attached to the inner walls of the upper ends of the housing 22 and the casing 21 flows down along the inner walls of the housing 22 and the casing 21. Then, the lubricating oil O reaching the upper end portion of the peripheral surface of the seat portion 22b is guided to the portion of the planetary gear train 10 through the periphery of the steel ball 17c between the inner ring 17b and the outer ring 17a of the ball bearing 17, respectively. Finally, while lubricating these, they flow down to the oil sump 20a.

Further, the lubricating oil O that has reached the vicinity of the region Z ahead of the peripheral surface of the seat portion 22b is guided from the lubricating oil guide portion 24 to the recess 23 of the boss portion 22a, and from there, by capillary action, the inner ring 17b and the boss portion. It is supplied to the fitting gap G with 22a. Further, the fitting gap G in the vicinity of the recess 23 changes with switching between the regeneration mode/powering mode, and the outflow of the lubricating oil O from the recess 23 to the fitting gap G is promoted. Further, when creep occurs, the lubricating oil O guided to the recess 23 is further drawn into the fitting gap G between the inner ring 17b and the boss portion 22a, and the inner peripheral surface of the inner ring 17b and the outer peripheral surface of the boss portion 22a are damaged. It can be reduced more reliably.

It should be noted that the present invention should be interpreted only from the matters described in the claims, and in the above-described embodiment, in addition to matters described in any changes and modifications included in the concept of the present invention It is possible. That is, all the matters in the above-described embodiment are not intended to limit the present invention, and may be arbitrarily changed according to the use and purpose thereof, including the configuration not directly related to the present invention. It is a thing.

16b external gear portion 17 ball bearing 17a outer 17b inner race 22 housing 22a boss 23 recess 24 lubricating central axis M engagement point of the oil guiding portion 41 large gear C boss O lubricating oil P _V geometrical plane P _H geometric plane T power transmission device Z area

Claims (1)

A housing that houses a pair of gears that mesh with each other;
A circular boss protruding from the wall surface of this housing,
A power transmission device comprising: a rolling bearing in which one of the gears is fitted with an outer ring by a tight fit and an inner ring is fitted in the boss part by a loose fit,
A geometric plane that is parallel to the central axis of the boss and extends vertically upward from the central axis of the boss, and a geometric plane that horizontally extends from the central axis of the boss to the meshing point side of the pair of gears. A concave portion formed along the longitudinal direction of the boss portion in a region of the outer peripheral surface of the boss portion surrounded by a flat plane,
A power transmission device, comprising: a lubricating oil guide portion formed on a wall surface of the housing with which one end surface of the inner ring abuts and guiding the lubricating oil adhering to the wall surface to the recess.

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