gear

Abstract

To provide a gear capable of suppressing deterioration of tooth root stress while ensuring an oil passage. [Solution] A gear (1) includes a cylindrical body (3) fitted to a rotatable shaft (2) and rotating relative to the shaft (2), and a plurality of meshing teeth (4) formed on the outer peripheral surface of the cylindrical body (3). At least one groove (5) for introducing or discharging lubricating oil is formed on the inner peripheral surface of the cylindrical body (3). The groove (5) is located circumferentially on a straight line (7) along the radial direction passing through the center of the arc-shaped tooth thickness (6) of the meshing teeth (4). In the axial direction of the cylindrical body (3), the groove (5) extends along the tooth trace of the meshing teeth (4) and is open at both axial end faces of the cylindrical body (3). As a result, the tooth root thickness is thick where the groove (5) is located, which prevents a decrease or insufficiency in rigidity or strength at the tooth base. Furthermore, because the groove (5) is open at both end faces, stagnation of lubricating oil is prevented, minimizing shear resistance.

Description

[Technical Field]

[0001] The present invention relates to a gear having an oil passage. [Background technology]

[0002] It is well known that in power transmission mechanisms and power split mechanisms, when the gear and shaft rotate relative to each other, lubricating oil must be circulated through the gap between the gear and shaft. By ensuring that the lubricating oil does not flow excessively through the gap, the shear resistance force generated between the gear and shaft can be minimized.

[0003] Patent Documents 1 and 2 describe differentials in which lubricating oil is distributed through gaps between side gears and axles inserted into the side gear bosses and rotating relative to each other. The differential described in Patent Document 1 is said to ensure smooth oil flow by providing grooves extending from the inner periphery of the side gear bosses to the outer periphery. Furthermore, the differential described in Patent Document 2 includes, in addition to the grooves described in Patent Document 1, a spiral groove formed on the inner periphery of the bosses of the casing body as an oil passage, and a spiral groove simultaneously machined as a tooth bottom when the side gears are cut. As a result, sufficient lubricating oil is supplied to the grooves and spiral grooves during differential rotation, preventing seizure and noise.

[0004] Patent Document 3 describes a compressor that focuses on improving the lubricating oil supply capacity. In Patent Document 3, a spiral groove is formed on the inner peripheral surface of the bearing, and the cross-sectional area of ​​the spiral groove is larger at the base than at the tip portion facing upward. With this configuration, it is said that the amount of oil supplied to the tip side is reduced, thereby suppressing the amount of lubricating oil ejected, while the cross-sectional area of ​​the spiral groove at the base portion can be increased. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 09-004698 [Patent Document 2] Japanese Patent Application Publication No. 09-112656 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-008558 Summary of the Invention [Problem to be solved by the invention]

[0006] In the configurations described in Patent Documents 1 and 2, a groove is formed to spread lubricating oil in the gap between the gear and the shaft inserted into the gear boss and rotating relative to it. If the spiral groove described in Patent Document 3 is formed on the inner peripheral surface of the boss of Patent Documents 1 and 2, it is expected that the fluidity of the lubricating oil will be improved.

[0007] However, when the gear described above is a gear with dimensional restrictions, such as when used in a planetary gear, it is difficult to ensure the thickness of the tooth root. In particular, forming a spiral groove can result in a thin tooth root, which can reduce or insufficient the rigidity or strength of the tooth base.

[0008] The present invention has been made in light of the above technical problems, and has an object to provide a gear that can prevent a decrease or insufficiency in the rigidity or strength of the tooth base while ensuring an oil passage. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, the present invention provides a gear comprising a cylindrical body that is fitted onto a rotatable shaft and rotates relative to the shaft, and a plurality of meshing teeth formed on the outer peripheral surface of the cylindrical body, wherein at least one groove portion for introducing or discharging lubricating oil is formed on the inner peripheral surface of the cylindrical body, and the position of the groove portion in the circumferential direction of the cylindrical body is on a straight line along the radial direction that passes through the center of the circular arc tooth thickness of the meshing teeth, and in the axial direction of the cylindrical body, it extends along the tooth trace of the meshing teeth and is open to both end faces in the axial direction of the cylindrical body. [Effects of the Invention]

[0010] The gear of the present invention has at least one groove formed on the inner peripheral surface of the cylindrical body for introducing or discharging lubricating oil. The groove is located circumferentially on a straight line along the radial direction that passes through the center of the arc-shaped tooth thickness of the meshing teeth, and extends axially along the tooth trace of the teeth. Therefore, the location of the groove is a portion where the tooth root thickness is thick, which prevents a decrease or insufficiency in the rigidity or strength of the tooth base.

[0011] Furthermore, since the grooves are open to both end faces of the cylinder in the axial direction, stagnation of the lubricating oil is prevented, resulting in improved fluidity and minimizing shear resistance. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a simplified perspective view for explaining a gear according to an embodiment of the present invention. [Figure 2] FIG. 2 is a simplified front view for explaining a gear according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] 1 and 2, a gear 1 according to an embodiment of the present invention is a gear that is rotatably fitted onto a shaft 2 and includes a cylindrical body 3 that rotates around a center line L (hereinafter referred to as the central axis L) of the shaft 2 and relative to the shaft 2. The shaft 2 and the cylindrical body 3 may rotate relative to each other or as a unit by an engagement mechanism (not shown).

[0014] A plurality of meshing teeth 4 are formed on the outer peripheral surface of the cylindrical body 3. The tooth traces of the meshing teeth 4 of the gear 1 shown in Figures 1 and 2 are helical gears that are inclined with respect to the central axis L.

[0015] At least one groove 5 for spreading lubricating oil is formed on the inner peripheral surface of the cylindrical body 3, and the groove 5 shown in Figures 1 and 2 is formed for each meshing tooth 4. This groove 5 increases the fluidity of the lubricating oil by introducing or discharging it, in order to minimize the shear resistance force generated between the cylindrical body 3 and the shaft 2 of the gear 1.

[0016] Next, the grooves 5 will be described in detail. The grooves 5 are located circumferentially on a radial line 7 passing through the center of the arc-shaped tooth thickness 6 of the meshing teeth 4, and extend axially along the tooth trajectories of the meshing teeth 4. In the grooves 5 shown in FIG. 1 , one end of a certain portion is located on a radial line 7 passing through the center of the arc-shaped tooth thickness 6 of the meshing teeth 4, and the other end is located on a radial line 7' passing through the center of the arc-shaped tooth thickness 6' of the meshing teeth 4, and the grooves are cut to a predetermined depth from the inner circumferential surface of the cylinder 3 toward the radially outward direction. Both ends of the grooves 5 open to both axial end faces of the cylinder 3. In other words, the grooves 5 are formed along the tooth trajectories of the meshing teeth 4 of the gear 1, and are open and communicated because there is nothing blocking them at both ends.

[0017] In the gear 1 of the present invention, at least one groove for introducing or discharging lubricating oil is formed on the inner peripheral surface of the cylindrical body 3. The position of the groove 5 in the circumferential direction of the cylindrical body 3 is on a straight line 7 along the radial direction that passes through the center of the circular arc tooth thickness 6 of the meshing tooth 4, and in the axial direction of the cylindrical body 3, it extends along the tooth trace of the meshing tooth 4. Therefore, the location of the groove 5 is a part where the tooth bottom thickness is thick, which makes it possible to suppress a decrease or insufficiency in rigidity or strength of the tooth base.

[0018] Furthermore, since the groove portion 5 is open to both end faces of the cylindrical body 3 in the axial direction, it prevents the lubricating oil from stagnating, thereby improving fluidity and minimizing shear resistance.

[0019] The above-described embodiment is merely an example of how the present invention can be implemented, and is not intended to limit the scope of the present invention. For example, the gear 1 described in the embodiment is a helical gear, but the present invention is not limited to this. Similar functions and effects can be achieved with a spur gear whose tooth trace is a straight line parallel to the central axis L.

[0020] Furthermore, although the groove 5 of the gear 1 described in the examples is formed for each meshing tooth 4, this is not limited thereto, and the gear 1 may have one groove 5 or may have multiple grooves 5 spaced at equal intervals between each other. In short, it is sufficient that at least one groove 5 for introducing or discharging lubricating oil is formed on the inner circumferential surface of the cylindrical body 3 of the gear 1. [Explanation of symbols]

[0021] 1. Gears 2-axis 3 Cylinder 4. Interlocking teeth 5 Groove 6 Circular tooth thickness 7 Straight line along the radial direction at the center of the tooth thickness L Center line (center axis line)

Claims

[Claim 1] A gear including a cylindrical body that is fitted onto a rotatable shaft and rotates relative to the shaft, and a plurality of meshing teeth formed on an outer peripheral surface of the cylindrical body, At least one groove for introducing or discharging lubricating oil is formed on the inner circumferential surface of the cylindrical body, The grooves are positioned in the circumferential direction of the cylinder on a straight line along the radial direction that passes through the center of the arc tooth thickness of the meshing teeth, and extend along the tooth trace of the meshing teeth in the axial direction of the cylinder, and are open to both end surfaces of the cylinder in the axial direction. A gear characterized by:

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