Stepped Opinion

Abstract

This invention provides a stepped pinion that can optimize the meshing of the tooth surfaces regardless of the direction of the transmitted torque, and has a simple structure. [Solution] A stepped pinion 1 is provided on a rotating shaft Sp at a predetermined distance apart in the axial direction, comprising a large-diameter gear portion 1a and a small-diameter gear portion 1b. The large-diameter gear portion 1a has a disc portion D extending radially outward from the rotating shaft Sp and a rim portion R. A reinforcing member 4 is provided to support the portion of the rim portion R that extends axially in one direction from the disc portion D from the inner circumference. The reinforcing member 4 is fixed to the rotating shaft Sp in a state that extends radially outward, and is configured to restrict a first inclination of the rim portion R by bringing its inner circumferential surface into contact with the tip, and to allow a second inclination in the opposite direction to the first inclination that separates the inner circumferential surface of the rim portion R from the tip.

Description

Technical Field

[0001] This invention relates to a stepped pinion provided with gears having different pitch diameters on the same axis.

Background Art

[0002] Patent Document 1 describes an example of a reinforcing structure of a gear member having a large-diameter gear portion and a small-diameter gear portion, each of which is a spur gear. The gear member described in Patent Document 1 is formed by injection molding a resin material such as plastic, and the gear member is made thin in order to mold the gear member with high precision. When this type of gear rotates, the gear is twisted in a direction in which the meshing width of the tooth surface decreases due to the thrust force, which may change the rotation speed of the gear or cause wear of the tooth surface. In order to avoid such inconveniences, a metal reinforcing member is attached to at least one side surface of the gear member described in Patent Document 1. This reinforcing member is a circular metal plate member having an outer diameter equivalent to the inner diameter of the large-diameter gear portion, and is attached to the back surface of the gear member by a plurality of bolts. Also, a reinforcing member having a similar structure can be attached to the front surface of the gear member. In this case, the center of gravity in the axial direction of the gear member with respect to the rotation center of the gear member is made uniform, and the moment of inertia of each reinforcing member is added to the gear member, so that the gear member can rotate stably.

[0003] Also, Patent Document 2 describes a gear that performs reinforcement to regulate the distortion generated in the gear due to the thrust force caused by the spur gear. The gear has spur teeth formed on the outer peripheral surface of a cylindrical rim portion, and a disk portion (or flange) is integrally formed at substantially the center in the width direction on the inner peripheral side of the rim portion. When a load in the thrust direction associated with transmitting torque is applied to the spur teeth, the gear (i.e., the rim portion) tilts with respect to a direction parallel to the rotation center axis. Therefore, in the gear described in Patent Document 2, a reinforcing member is attached along both surfaces of the disk portion (or flange), and the inner peripheral surface of the rim portion is abutted against the tip portion (outer peripheral side end portion) of the reinforcing member to regulate the tilt of the gear. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 8-74971 [Patent Document 2] Japanese Patent Publication No. 2007-040399 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] When a helical gear meshes with a mating gear to transmit torque, it can become distorted or tilted due to the thrust load resulting from the reaction force. In the gears described in Patent Documents 1 and 2, the cylindrical portion with teeth formed on its outer surface is supported from the inner side by reinforcing members placed on its inner side, thereby restricting the distortion or tilt of the actual gear, which is the cylindrical portion. These reinforcing members are attached to both sides of the so-called disc portion connected to the inner side of the cylindrical portion. In particular, the gear described in Patent Document 2 states that tilting to the left and right sides of the disc portion can be restricted or suppressed by reinforcing members similarly provided on both sides.

[0006] The thrust load applied to a helical gear differs depending on the direction of the torque transmitted by the gear (forward rotation and the opposite reverse rotation), and the frequency of torque transmission in the forward rotation direction often differs from the frequency of torque transmission in the opposite reverse rotation direction. In such gear usage scenarios, the configurations described in Patent Documents 1 and 2 may not ensure proper meshing, potentially leading to noise and vibration, and reducing the durability of the gear. In other words, helical gears experience distortion or tilting due to the thrust load associated with torque transmission, and the tooth surface shape and gear assembly are sometimes designed to account for such deformation. The deformation anticipated in this case is the deformation that occurs frequently during normal use, and in terms of tilting, it is a tilt to either the left or the right. Therefore, in the normal operating range, the tooth surface is designed or the gear is assembled to account for this deformation, resulting in proper tooth meshing.

[0007] However, in the configurations described in Patent Documents 1 and 2, the configuration restricts or suppresses tilting or distortion in both left and right directions. Therefore, in the so-called emergency state where the direction of transmitted torque is reversed, the distortion or tilt exceeds the "0" state and tilts or distorts in the opposite direction. As a result, if deformation occurs that was not anticipated for tooth surface setting or assembly, the degree of that distortion or tilt will exceed the amount of distortion or tilt that causes proper meshing (the amount of distortion or tilt from the no-load state where the torque is "0") on the opposite side, compared to the state where proper meshing occurs. In other words, the error from the proper meshing state increases, and noise and vibration may worsen when the transmitted torque is reversed. On the other hand, in the configurations described in Patent Documents 1 and 2, reinforcing members are attached to both sides of the disc. Therefore, the outer circumference of these reinforcing members supports the part of the cylindrical rim, which is essentially a gear, that is closest to the disc, i.e., the part where the tilt originates, from the inside. The base of the rim is the part where the amount of displacement is smallest when tilting occurs. Therefore, if errors occur in processing or assembly between the inner diameter of the rim and the outer diameter of the reinforcing member, it may allow for a large tilt. For this reason, high precision is required in the processing and assembly of the reinforcing member, and manufacturability or ease of assembly is not always good.

[0008] This invention was made in view of the above-mentioned technical problems, and aims to provide a stepped pinion that can optimize the meshing of the tooth surfaces regardless of the direction of the transmitted torque, and moreover, has a simple structure. [Means for solving the problem]

[0009] To achieve the above objective, this invention provides a stepped pinion comprising a large-diameter gear portion having helical teeth on its outer circumference and a small-diameter gear portion having a smaller diameter than the large-diameter gear portion and other helical teeth on its outer circumference, provided on a predetermined rotating shaft at a predetermined distance apart in the axial direction, wherein the large-diameter gear portion comprises a disc portion extending radially outward from the rotating shaft and a cylindrical rim portion extending from the outer circumference end of the disc portion to both sides in the axial direction of the rotating shaft and having the helical teeth formed on its outer circumference, and a reinforcing member is provided to support the portion of the rim portion that extends from the disc portion to one side in the axial direction from the inner circumference side, the reinforcing member is fixed to the rotating shaft in a state extending radially outward, and is configured to restrict a first inclination of the rim portion by bringing the inner surface of the rim portion into contact with the tip, and to allow a second inclination in the opposite direction to the first inclination that separates the inner surface of the rim portion from the tip. [Effects of the Invention]

[0010] According to this invention, when the large-diameter gear portion is tilted to one side in the axial direction of its rotation axis, one end of the reinforcing member contacts the inner circumferential surface of the rim portion of the large-diameter gear portion, thereby restricting further tilting of the large-diameter gear portion. Furthermore, when the direction of the transmitted torque is reversed and a load is applied that causes the large-diameter gear portion to tilt to the other side in the axial direction, the rim portion tilts to the other side and separates from the reinforcing member due to the lack of restriction by the reinforcing member. By setting the shape of the tooth surface and assembly to match the tilt of the large-diameter gear portion to the normal operating state, for example, the meshing of the gears in the normal operating state can be optimized, and vibration, noise, or a decrease in durability can be avoided or suppressed. Conversely, when torque is applied in the opposite direction to the so-called normal operating state and the large-diameter gear portion attempts to tilt to the one side, the outer circumferential end of the reinforcing member contacts the inner circumferential surface of the rim portion, restricting the tilt of the rim portion to the one side. In other words, the tilt of the rim portion from the proper meshing state is limited by the reinforcing member, so the deviation from the proper meshing state, i.e., the meshing error, is reduced. As a result, even if the direction of torque is reversed, the gear meshing state can be optimized, or the deviation or error from the proper meshing state can be reduced, thereby suppressing noise, vibration, and a decrease in durability. [Brief explanation of the drawing]

[0011] [Figure 1] This is a perspective view showing the configuration of a planetary gear mechanism using a stepped pinion in an embodiment of this invention. [Figure 2] This figure shows the configuration of a stepped pinion in an embodiment of the present invention, where (a) is a cross-sectional view along the rotation axis direction of the stepped pinion, and (b) is a side view of the stepped pinion viewed from the front. [Figure 3] (a) is a schematic diagram showing the inclination state of the large-diameter gear section during power application, and (b) is a schematic diagram showing the tooth contact area on the tooth surface. [Figure 4] (a) is a schematic diagram showing the inclination state of the large-diameter gear section during regeneration, and (b) is a schematic diagram showing the tooth contact area on the tooth surface. [Modes for carrying out the invention]

[0012] This invention will be described based on the embodiments shown in the figures. The embodiments described below are merely examples of how this invention can be implemented and do not limit it.

[0013] Figure 1 shows an example of a planetary gear mechanism P to which the stepped pinion 1 in this embodiment of the present invention is applied. The planetary gear mechanism P can be installed in a vehicle such as a hybrid vehicle to distribute the torque of a motor or engine, which is a driving force source, to the drive wheels and a predetermined output member. As shown in Figure 1, the planetary gear mechanism P comprises a sun gear 2, a ring gear 3 arranged concentrically with respect to the sun gear 2, and a plurality of stepped pinions 1 arranged around the sun gear 2. The sun gear 2 is an external gear, and a plurality of helical teeth are formed on its outer circumferential surface. The ring gear 3 is an internal gear, and a plurality of helical teeth are formed on its inner circumferential surface. The stepped pinion 1 comprises a large-diameter gear portion 1a formed at one end and a small-diameter gear portion 1b formed on a pinion shaft Sp, which is a small-diameter rotating shaft extending from the large-diameter gear portion 1a in the direction of the rotation axis. Multiple helical teeth are formed on the outer circumferential surfaces of both the large-diameter gear portion 1a and the small-diameter gear portion 1b. The large-diameter gear portion 1a of each stepped pinion 1 meshes with the sun gear 2, and the small-diameter gear portion 1b meshes with the ring gear 3.

[0014] A motor with a power generation function (i.e., a motor-generator) (not shown) is connected to the sun gear shaft 2a of sun gear 2. When the motor connected to sun gear 2 is functioning as a driving force source, i.e., when the motor is operating, sun gear 2 is rotated by the output torque of the motor. In this state, the stepped pinion 1 inevitably tilts due to the thrust force resulting from the meshing of its helical teeth. In particular, the large-diameter gear portion 1a of the stepped pinion 1, which directly meshes with sun gear 2, tilts with respect to the pinion shaft Sp. Therefore, in the planetary gear mechanism P, at least the large-diameter gear portion 1a of the stepped pinion 1 and sun gear 2 are adjusted so that the meshing of their helical teeth is optimized when the gears are tilted during motor operation.

[0015] As described above, the motor connected to the sun gear 2 has a power generation function. Specifically, when the output shaft of the motor is rotated by an external force, the motor functions as a generator. However, when the motor connected to the sun gear 2 is functioning as a generator, that is, when energy is regenerated by the motor, the thrust force acting between the helical teeth of the sun gear 2 and the helical teeth of the stepped pinion 1 acts in the opposite direction to when the motor is operating. Therefore, when regenerating energy by the motor, the large-diameter gear portion 1a of the stepped pinion 1 is tilted with respect to the pinion shaft Sp in the opposite direction to the inclination direction of the sun gear 2 (the second inclination in this invention). As a result, the helical teeth of the large-diameter gear portion 1a make uneven contact with the helical teeth of the sun gear 2, which may lead to uneven wear of the helical teeth of both and an amplification of noise and vibration.

[0016] To explain the inclination of the large-diameter gear section 1a, as schematically shown in Figure 2, the large-diameter gear section 1a has a disc section (or flange) D extending radially from the pinion shaft Sp, and a cylindrical rim section R integrally provided on the outer circumference of the disc section D, with helical teeth formed on the outer surface of the rim section R. The rim section R extends axially from the disc section D. The rim section R is parallel to the pinion shaft Sp, which is the unloaded state or the design state. When the large-diameter gear section 1a is inclined, it means that the rim section R is no longer parallel to the pinion shaft Sp or its rotational axis, and one end in the tooth trace direction is displaced inward relative to the other end. This deformation occurs at the point where it meshes with the sun gear 2 or ring gear 3.

[0017] To prevent the tilting of the large-diameter gear portion 1a of the stepped pinion 1 (the first tilt in this invention) during regeneration by such a motor, in the embodiment of the present invention, a support plate 4 shown in Figure 2 is provided between the large-diameter gear portion 1a and the small-diameter gear portion 1b of the stepped pinion 1. Figure 2(a) is a schematic cross-sectional view along the rotation axis of the stepped pinion 1 on which the support plate 4 is provided, and Figure 2(b) is a schematic front view of the stepped pinion 1 on which the support plate 4 is provided. As shown in Figure 2, the support plate 4 is a rectangular plate member, positioned opposite the inner circumferential surface of one end of the large-diameter gear portion 1a in the axial direction, and fixed to the pinion shaft Sp. This support plate 4 corresponds to the reinforcing member in this invention.

[0018] To explain the support plate 4 in more detail, the radial length of the support plate 4 relative to the stepped pinion 1 is the length at which the tip contacts the inner circumferential surface of the rim portion R, which is not tilted in the aforementioned design state. Each of the four support plates 4 shown in Figure 2 is fixed by inserting its base end into a groove 1d formed in the pinion shaft Sp. The means for fixing the support plate 4 to the pinion shaft Sp may be any means selected as appropriate; the main point is that the outer peripheral end 4b of the support plate 4 contacts the inner circumferential surface of the rim portion R without generating any particular stress.

[0019] Thus, the inner peripheral end portion 4a of the support plate 4 is fitted into the groove 1d formed on the outer peripheral surface of the small-diameter gear portion 1b, and the outer peripheral end portion 4b of the support plate 4 is not fixed to the inner peripheral surface of the rim portion of the large-diameter gear portion 1a. In the example shown in FIG. 2, the grooves 1d are formed at four locations on the outer peripheral surface of the small-diameter gear portion 1b at equal intervals in the circumferential direction. Therefore, the four support plates 4 are arranged between the large-diameter gear portion 1a and the small-diameter gear portion 1b on the pinion shaft Sp.

[0020] The states of the stepped pinion 1 and the sun gear 2 during the operation of the planetary gear mechanism P are shown in FIGS. 3 and 4. FIG. 3(a) shows the inclination state of the sun gear 2 and the large-diameter gear portion 1a of the stepped pinion 1 during the power running by the motor. As shown by the arrow in FIG. 3(a), during the power running by the motor, a thrust force acts between the spline teeth of the sun gear 2 and the spline teeth of the stepped pinion 1 in the direction in which the large-diameter gear portion 1a of the stepped pinion 1 adheres to the sun gear 2 (in FIG. 3(a), the direction in which the large-diameter gear portion 1a inclines downward to the right at the meshing portion with the sun gear 2 (the second inclination in the present invention)). As described above, the outer peripheral end portion 4b on the outer peripheral side of the support plate 4 only contacts the inner peripheral surface of the rim portion R of the large-diameter gear portion 1a and is not fixed. Therefore, due to the thrust force caused by the meshing of the sun gear 2 and the large-diameter gear portion 1a, the large-diameter gear portion 1a is allowed to incline in the direction in which one end portion in the axial direction of the large-diameter gear portion 1a is separated radially outward from the outer peripheral end portion 4b of the support plate 4.

[0021] The spline teeth of the sun gear 2 and the large-diameter gear portion 1a are formed such that their meshing is optimized in the inclined state of these gears during the power running by the motor. Therefore, during the power running, the meshing of the sun gear 2 and the large-diameter gear portion 1a optimized in this way can be maintained. For example, as schematically shown by enclosing the tooth contact portion A with an ellipse in FIG. 3(b), the tooth contact occurs at substantially the central portion of the tooth surface F of the sun gear 2 and the large-diameter gear portion 1a.

[0022] Figure 4(a) shows the inclination state of the large-diameter gear portion 1a of the sun gear 2 and the stepped pinion 1 during regeneration. As indicated by the arrow in Figure 4(a), during regeneration, a thrust force acts between the helical teeth of the sun gear 2 and the helical teeth of the stepped pinion 1 in a direction that tilts the stepped pinion 1 to the left in Figure 4(a). As a result, the large-diameter gear portion 1a tends to incline (the first inclination in this invention) in a direction in which one end of its axial direction (the left side in Figure 4(a)) is displaced radially inward. Therefore, in this state, the inner circumferential surface of the rim portion R abuts against the outer circumferential end of the support plate 4, thereby restricting further inclination of the large-diameter gear portion 1a of the stepped pinion 1. In other words, during regeneration, the large-diameter gear portion 1a tends to incline in the opposite direction to that during power application, but this inclination is restricted by the support plate 4. Therefore, deviations from the meshing state, which is optimized to match the inclination during power application, are suppressed, and even if meshing errors occur, they are kept to a minimum. For example, as schematically shown in Figure 4(b) with the tooth contact point A enclosed in an ellipse, although it deviates from the center of the tooth surface F, the deviation is small, and the meshing between the helical teeth of the sun gear 2 and the large-diameter gear section 1a does not particularly deteriorate.

[0023] Thus, according to the embodiment of the present invention, when power is applied by the motor connected to the sun gear 2, the large-diameter gear portion 1a is allowed to tilt in a direction such that one end of its axial direction moves radially outward from the outer peripheral end of the support plate 4. Therefore, during power application, the meshing of the helical teeth of these gears, which has been optimized in advance considering the tilt of the sun gear 2 and the large-diameter gear portion 1a, can be maintained.

[0024] On the other hand, during regeneration by the motor, the outer peripheral end of the support plate 4 abuts against the inner peripheral surface of one end of the rim R in the axial direction of the large-diameter gear portion 1a, thereby suppressing the tilting of the stepped pinion 1 or its large-diameter gear portion 1a. Therefore, even during regeneration, the meshing of the helical teeth of the sun gear 2 and the large-diameter gear portion 1a does not particularly deteriorate as described above, thus preventing uneven wear of these gears and suppressing noise and vibration of the planetary gear mechanism P.

[0025] On the other hand, in the embodiment of the present invention, a support plate 4 is provided on the pinion shaft Sp as a reinforcing member that supports the large-diameter gear portion 1a from its inner circumference. Therefore, the point where the large-diameter gear portion 1a is supported by the support plate 4 can be the tip of the rim portion R in the axial direction. Since this tip is the point where the displacement is large when the large-diameter gear portion 1a is tilted, the error in the length of the support plate 4 (the dimension from the pinion shaft Sp to the tip) has little effect on the tilt angle when supporting the large-diameter gear portion 1a. Therefore, the tilt of the large-diameter gear portion 1a or the rim portion R can be controlled with high precision.

[0026] It should be noted that the present invention is not limited to the embodiments described above, and may be modified as appropriate within the scope of the configuration described in the claims. For example, although four support plates 4 are used in the embodiments described above, the number of support plates may be any number as needed, and they may be circular instead of rectangular, in which case only one support plate is required. [Explanation of Symbols]

[0027] 1 Stepped Pinion 1a Large diameter gear section 1b Small diameter gear section 1d groove 2 Sanguia 2a Sun gear shaft 3 Ring gear 4. Support plate (reinforcement member) 4a Inner edge 4b Outer edge A. Tooth contact area D Disk section F tooth surface P Planetary Gear Mechanism R rim section Sp Pinion Shaft (Rotation Axis)

Claims

[Claim 1] A stepped pinion comprising a large-diameter gear portion having helical teeth on its outer surface and a small-diameter gear portion having a smaller diameter than the large-diameter gear portion and other helical teeth on its outer surface, provided on a predetermined rotating shaft at a predetermined distance apart in the axial direction, The large-diameter gear portion has a disc portion extending radially outward from the rotation shaft, and a cylindrical rim portion extending from the outer peripheral end of the disc portion in the axial direction of the rotation shaft on both sides, with the helical teeth formed on its outer peripheral surface. A reinforcing member is provided to support the portion of the rim that extends from the disc portion in one direction in the axial direction from the inner circumference. The stepped pinion is characterized in that the reinforcing member is fixed to the rotation axis in a state extending radially outward, and is configured to restrict a first inclination of the rim portion by bringing the inner circumferential surface of the rim portion into contact with the tip portion, and to allow a second inclination in the opposite direction to the first inclination that separates the inner circumferential surface of the rim portion from the tip portion.

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