JP6673093B2 - Gear structure and method of manufacturing gear - Google Patents

Description

  The present invention provides a disk-shaped first gear having first gear teeth formed on an outer peripheral surface thereof, and a second gear tooth formed in a cylindrical shape having a diameter smaller than that of the first gear and partially disposed in an axial direction. And a second gear that is coaxial with the first gear and rotates integrally with the first gear, and a method of manufacturing the gear.

  BACKGROUND ART In recent years, battery-type industrial vehicles such as forklifts having a battery device and a drive motor as power sources for traveling have been used in indoor warehouses and the like that dislike exhaust gas from internal combustion engines. For example, in an electric forklift, which is one of battery-type industrial vehicles, the rotational power of a drive motor shaft is reduced and transmitted to a drive shaft via a composite gear in which a large-diameter gear and a small-diameter gear are coaxial. Is transmitting rotational power to the wheels. This composite gear is required to have high rigidity in order to transmit a large torque from the drive motor to the drive shaft.

  Here, Patent Document 1 discloses a speed reducer in which rotational power of an initial reduction gear is reduced by an intermediate gear and transmitted to a latter reduction gear. The intermediate gear is a large-diameter first gear portion to which the rotational power of the initial reduction gear is transmitted, and a second gear portion smaller in diameter than the first gear portion, and rotates integrally with the first gear portion. And a second gear portion for transmitting rotational power to the late reduction gear.

  Patent Document 2 discloses a transmission with a built-in brake for a vehicle housed in a transmission case attached to an electric drive unit of the vehicle, as shown in FIG. The transmission with a built-in brake for a vehicle has a large-diameter drive gear 124 to which the rotational power of the input shaft 128 is transmitted, and a small-diameter sun gear 115 (which is coaxial with the drive gear 124 and rotates integrally with the drive gear). And a drive shaft 123 having a sun gear 115).

  Further, in Patent Document 3, as shown in FIGS. 12 and 13, a cylindrical press-fit portion 213 is first press-fitted into a through hole 211K of a large-diameter gear 211, and thereafter, a circle having a knurl formed on the surface A press-fitting fixing mechanism for press-fitting a columnar knurled portion 214 between a shaft and a disc-shaped body such as a gear is disclosed.

JP-A-2015-64061 Japanese Patent No. 467809 Japanese Utility Model Publication No. 55-1296

  In the structure of the intermediate gear described in Patent Literature 1, the large-diameter first gear portion and the small-diameter second gear portion are coaxially integrated with each other. However, it is considered that the transmission torque is not so large. The first gear portion and the second gear portion are integrated by press fitting. This simple press-fit only structure is not preferable because slippage may occur between the first gear portion and the second gear portion with respect to the torque of the power for traveling of the electric forklift.

  Further, as shown in FIG. 11, the gear structure described in Patent Document 2 has a large-diameter drive gear 124 and a small-diameter sun gear 115 (drive shaft 123) that rotates coaxially and integrally with the drive gear 124. And However, the drive gear 124 and the drive shaft 123 are connected by the spline 125, and there is a possibility that the shaft of the drive gear 124 and the drive shaft 123 oscillates. Further, between the gear teeth of the sun gear 115 and the flange portion of the drive shaft 123, a relief groove 123M for releasing a processing tool (for example, a gear shaper) for forming the gear teeth of the sun gear 115 is essential. This relief groove 123M is not preferable because the diameter of the drive shaft 123 is locally reduced and the rigidity of the drive shaft 123 is reduced. Further, even if an attempt is made to increase the axial length of the gear teeth of the sun gear 115 in order to increase the rigidity with respect to the transmission torque between the sun gear 115 and the planet gear 116, the escape groove 123M is indispensable. The axial length of the teeth cannot be increased.

  In the press-fitting and fixing mechanism of the shaft and the disk-shaped body such as a gear described in Patent Document 3, as shown in FIGS. 12 and 13, the press-fitting portion 213 of the shaft 212 And then the knurl portion 214 is pressed. In this mechanism, since the press-fit portion 213 is provided, the shaft center between the gear 211 and the shaft 212 is prevented from swinging. However, when a large torque such as a running torque of the electric forklift is transmitted to the knurl portion 214, a slip may occur between the gear 211 and the shaft 212. Further, since the flange portion 216 is provided, an escape groove 215A for allowing the knurling tool to escape is essential between the knurl portion 214 and the flange portion 216. In order to avoid slippage between the gear 211 and the shaft 212, even if the axial length of the knurled portion 214 is increased toward the flange portion 216, the escape groove 215A is indispensable. 216 cannot be extended. Further, if the axial length of the knurled portion 214 is increased in the opposite direction, the contact area between the press-fitting portion 213 and the gear 211 decreases, which is not preferable.

  Also, for example, the integrally molded compound gear 320 shown in FIG. 10 has a disk-shaped first gear 321 having first gear teeth 321T formed on the outer peripheral surface thereof, and a cylindrical shape having a smaller diameter than the first gear 321 and having a shaft. A second gear tooth 322T is formed on a part of the outer peripheral surface in the direction, and a second gear 322 coaxial with the first gear 321 is integrally formed. Note that reference numerals 328 and 329 denote bearing devices. For example, when the drive gear 124 and the drive shaft 123 shown in FIG. 11 are constituted by the integrally molded composite gear 320 shown in FIG. 10, the first gear 321 and the second gear 322 are integrally molded, so that the axial center runout is caused. Can be eliminated. However, when the axial length 320L cannot be increased any longer due to mounting reasons or the like, the axial length 322A of the second gear teeth 322T is increased in order to improve the transmission torque of the second gear teeth 322T. Even if it is attempted, a relief groove 322M for releasing a processing tool (for example, a gear shaper) for processing the second gear tooth 322T is indispensable, and the axial length cannot be further increased (the relief groove 322M). Are formed continuously in the circumferential direction). Further, since the diameter of the second gear 322 is locally reduced by the relief groove 322M (diameter 322K> diameter 322G), the rigidity of the integrally molded composite gear 320 is reduced by the relief groove 322M.

  The present invention has been made in view of such a point, and in a gear in which a large-diameter first gear and a small-diameter second gear are coaxial, a second gear is provided with respect to the first gear. A gear structure capable of increasing the axial length of the second gear teeth without slipping, enabling transmission of a larger torque and improving rigidity, and manufacturing of the gear It is an object to provide a method.

  In order to solve the above problems, the gear structure according to the present invention employs the following means. First, a first invention of the present invention provides a disk-shaped first gear having first gear teeth formed on an outer peripheral surface thereof, a columnar shape having a smaller diameter than the first gear, and a part of the first gear in an axial direction. A second gear having a second gear tooth formed on an outer peripheral surface thereof, being coaxial with the first gear, and having a second gear rotating integrally with the first gear. The first gear has a fitting hole that penetrates along a rotation axis, and is provided on an inner peripheral surface of the fitting hole on one end side farther from the second gear teeth along the rotation axis. A first gear-side spline portion having a spline is formed, and a first gear-side non-spline having no spline is provided on the other end side along the rotation axis on the inner peripheral surface of the fitting hole. A spline portion is formed. The second gear has, on the one end side along the rotation axis, a fitting shaft portion that fits into the fitting hole without forming the second gear teeth. A second gear-side spline portion having a spline fitted to a spline of the first gear-side spline portion is formed at a position on the shaft portion corresponding to the first gear-side spline portion. In the position corresponding to the first gear-side non-spline portion, a second gear-side non-spline portion having no spline is formed. The first gear-side spline portion and the second gear-side spline portion are in a fitted state.

  Next, a second invention of the present invention is the gear structure according to the first invention, wherein the first gear has a first gear-side fitting end surface as a surface on the other end side, The second gear teeth are formed so as to protrude radially outward, and when the fitting shaft portion is fitted in the fitting hole of the first gear, the first gear side fitting is performed. A gear structure in which an end surface of the second gear tooth on the side of the first gear is in contact with the mating end surface.

  Next, a third invention of the present invention is the gear structure according to the first invention or the second invention, wherein the inner diameter of the first gear-side non-spline portion is the first gear-side non-spline portion press-fitting. The inside diameter is set to be larger than the largest inside diameter of the first gear side spline portion, which is the largest inside diameter of the first gear side spline portion, and the inside diameter of the second gear side, which is the largest outside diameter of the second gear side spline portion. The spline portion maximum outer diameter is set smaller than the first gear-side spline portion maximum inner diameter. The second gear-side non-spline portion press-fit outer diameter, which is the outer diameter of the second gear-side non-spline portion press-fit outer diameter, is set to be larger than the first gear-side non-spline portion press-fit inner diameter. A second gear spline length, which is a length of the spline formed in the spline portion along the rotation axis, is a length of the spline formed in the first gear-side spline portion along the rotation axis. The gear structure is set to be longer than one gear spline length.

  Next, a fourth invention of the present invention is the gear structure according to the third invention, wherein between the adjacent second gear teeth, an outer peripheral surface of the non-spline portion of the second gear is provided. The gear groove portion is formed to extend to the second gear-side non-spline portion, and the gear groove portion is formed in the second gear-side non-spline portion. Is a cut-out shape formed such that a gear groove depth, which is a depth from the surface of the second gear-side non-spline portion, becomes gradually shallower as the distance from the second gear teeth along the rotation axis increases. It is a gear structure.

  Next, a fifth invention of the present invention is directed to a disk-shaped first gear having first gear teeth formed on an outer peripheral surface thereof, and a columnar member having a smaller diameter than the first gear and having a portion in an axial direction. A second gear tooth formed on the outer peripheral surface of the first gear and being coaxial with the first gear, and a second gear rotating integrally with the first gear. The first gear having a first gear tooth formed on an outer peripheral surface thereof and having a fitting hole penetrating along a rotation axis, wherein the first gear has a fitting hole along an inner peripheral surface of the fitting hole along the rotation axis. A first gear-side spline portion having a spline is formed on one end side remote from the second gear teeth, and a spline is formed on the other end side along the rotation axis on the inner peripheral surface of the fitting hole. Forming a first gear on which a first gear-side non-spline portion having no first gear is formed, and forming the first gear on the outer peripheral surface along the rotation axis by forming the second gear teeth. The second gear having a fitting shaft portion fitted to the fitting hole without forming the second gear teeth on one end side, wherein the first gear in the fitting shaft portion is provided. At the position corresponding to the side spline section, A second gear-side spline portion having no spline is formed at a position on the fitting shaft portion corresponding to the first gear-side non-spline portion. A second gear forming step of forming the formed second gear, inserting the fitting shaft portion into the fitting hole, and fitting the first gear side spline portion and the second gear side spline portion. And a gear assembling step of press-fitting the second gear-side non-spline portion into the first gear-side non-spline portion.

  Next, a sixth invention of the present invention is the method for manufacturing a gear according to the fifth invention, wherein the one end side of the second gear teeth along the rotation axis is the second gear. And the second gear forming step, wherein each of the second gear teeth is formed by hobbing, and the cut-up groove formed by the hobbing is formed by the second gear-side non-spline. This is a method for manufacturing a gear formed in a portion.

  According to the first aspect, the first gear and the second gear are separated from each other without being integrally formed, and the fitting shaft of the second gear is fitted into the fitting hole of the first gear. Thus, the gear teeth of the second gear can be formed by hobbing or the like, and there is no need to provide a relief groove. Therefore, the second gear teeth can be extended in the axial direction, and a larger torque can be transmitted. Further, since there is no need to provide a relief groove, the shaft diameter of the second gear does not locally become thin at the position of the relief groove, and rigidity can be improved. Also, since the first gear and the second gear are fitted with splines, the second gear does not slip with respect to the first gear.

  According to the second invention, since the end face of the second gear tooth on the first gear side is in contact with the fitting end face of the first gear side, the first gear is prevented from swinging with respect to the second gear. be able to. Further, the axial length of the second gear teeth on the side approaching the first gear can be maximized. Therefore, it is possible to transmit a larger torque.

  According to the third aspect, the spline of the second gear side spline portion of the fitting shaft portion of the second gear is appropriately fitted to the spline provided in the first gear side spline portion of the fitting hole of the first gear. It is possible to combine. Thereby, the second gear does not slip with respect to the first gear, and the torque can be appropriately transmitted from the first gear to the second gear (or from the second gear to the first gear). In addition, the second gear-side non-spline portion of the fitting shaft portion of the second gear can be appropriately pressed into the first gear-side non-spline portion of the fitting hole of the first gear. Accordingly, it is possible to prevent the shaft center of the first gear and the second gear from swinging.

  According to the fourth aspect, the radially outward height can be made uniform at any axial position of the second gear teeth.

  According to the fifth aspect, in the first gear forming step, the second gear forming step, and the gear assembling step, a larger torque can be transmitted without the second gear slipping on the first gear. In addition, a gear that can improve rigidity can be appropriately manufactured.

  According to the sixth aspect, the second gear teeth can be formed in a short time by hobbing, and the radially outward height is set at any axial position of the second gear teeth. Can be made uniform.

FIG. 4 is a cross-sectional view illustrating an example of a structure of a drive unit that transmits rotational power of a drive motor for traveling of an electric forklift to a drive shaft. FIG. 2 is an enlarged view of a compound gear in the drive unit shown in FIG. 1. FIG. 3 is an exploded view illustrating the configuration of the compound gear shown in FIG. It is an enlarged view of the circumference of the fitting hole of the 1st gear. It is an enlarged view of the circumference of the fitting shaft part of the 2nd gear. It is VI-VI sectional drawing in FIG. It is an enlarged view of the state where the fitting shaft part of the 2nd gear was fitted in the fitting hole of the 1st gear. 5 is a flowchart illustrating an example of a manufacturing process of the compound gear according to the present embodiment. It is a flowchart explaining the example of the manufacturing process of the conventional integrally molded compound gear shown in FIG. It is sectional drawing explaining the example of the structure of the conventional integrally molded compound gear. FIG. 9 is a cross-sectional view illustrating an example of the structure of a conventional compound gear. It is an exploded view explaining an example of the structure of the conventional gear. FIG. 13 is a cross-sectional view illustrating a state where the conventional gear illustrated in FIG. 12 is assembled.

  An embodiment for carrying out the present invention will be described below with reference to the drawings. In the figure in which the X axis, the Y axis, and the Z axis are described, the X axis, the Y axis, and the Z axis are orthogonal to each other.

● [Example of configuration of drive unit 1 (FIG. 1)]
FIG. 1 shows a cross-sectional view of a drive unit 1 used for traveling of an electric forklift as an example. The drive unit 1 includes a drive motor 10 as a power source, a composite gear 20 to which rotational power of the drive motor 10 is transmitted, a transmission gear 31 to which rotational power is transmitted from the composite gear 20, and a differential 33 from the transmission gear 31. It has drive shafts 34R and 34L to which rotational power is transmitted, housings 2 and 3, and the like.

  The housings 2 and 3 rotatably support the drive motor 10, the compound gear 20, the transmission gear 31, the drive shafts 34R and 34L at appropriate positions.

  The drive motor 10 includes a motor shaft 11 rotatably supported by the housings 2 and 3, a rotor 12 that rotates integrally with the motor shaft 11, a stator 13, and the like. The motor shaft 11 is rotatably supported by the bearing device 18 with respect to the housing 2, and is rotatably supported by the bearing device 19 with respect to the housing 3. The motor shaft 11 has, on one side surface, motor gear teeth 11T that mesh with the first gear teeth 21T of the compound gear 20.

  The compound gear 20 includes a first gear 21, a second gear 22, and bearing devices 28 and 29. The first gear 21 and the second gear 22 excluding the bearing devices 28 and 29 may be used as the composite gear 20. The compound gear 20 is rotatably supported by the bearing device 28 with respect to the housing 2, is rotatably supported by the bearing device 29 with respect to the housing 3, and the first gear 21 and the second gear 22 are integrally formed. Rotate. The first gear teeth 21T formed on the outer peripheral surface of the first gear 21 are engaged with the motor gear teeth 11T, and the second gear teeth 22T formed on the outer peripheral surface of the second gear 22 are connected to the transmission gear of the transmission gear 31. It is in mesh with the teeth 31T. Therefore, the rotational power of the motor shaft 11 is transmitted to the composite gear 20 via the motor gear teeth 11T and the first gear teeth 21T, and the rotational power transmitted to the composite gear 20 is transmitted to the second gear teeth 22T and the transmission gear teeth 31T. Via the transmission gear 31. In the drive unit 1 shown in FIG. 1, the compound gear 20 corresponds to a reduction gear for reducing the rotation from the drive motor 10, and transmits a large running torque from the drive motor 10 to the drive shafts 34R, 34L. Therefore, high rigidity is required.

  Rotational power is transmitted to the drive shafts 34R and 34L from the transmission gear 31 and the housing 32 via the differential 33. The transmission gear 31 and the housing 32 rotate integrally, are rotatably supported by the bearing device 38 with respect to the housing 2, and are rotatably supported by the bearing device 39 with respect to the housing 3. Wheels are connected to the respective distal ends of the drive shafts 34R and 34L via, for example, constant velocity joints or the like.

● [Structure of composite gear 20 (FIGS. 2 to 7)]
FIG. 2 is a cross-sectional view of the composite gear 20 in a state where the first gear 21, the second gear 22, and the bearing devices 28 and 29 are assembled. FIG. FIG. 2 shows a sectional view of a state where the bearing device 22, the bearing device 28, and the bearing device 29 are disassembled. 4 is an enlarged view around the fitting hole 21K (see FIG. 3) in the first gear 21, and FIG. 5 is an enlarged view around the fitting shaft portion 22A (see FIG. 3) in the second gear 22. FIG.

  As shown in FIGS. 2 and 3, the first gear 21 has a disk-like (cylindrical) shape having first gear teeth 21T formed on an outer peripheral surface. The first gear 21 has a fitting hole 21K penetrating along the gear rotation axis 20J. The first gear 21 has a bearing press-fit portion 21A into which the bearing device 28 is press-fitted, and a first gear tooth portion 21B having a first gear tooth 21T and protruding in a flange shape.

  As shown in FIGS. 2 and 3, the second gear 22 has a columnar shape with a smaller diameter than the first gear 21 because second gear teeth 22 </ b> T are formed on a part of the outer peripheral surface. Further, the second gear 22 fits into the fitting hole 21K of the first gear 21 without forming the second gear teeth 22T on one end side (the side of the first gear 21) along the gear rotation axis 20J. It has a fitting shaft portion 22A to be fitted. Further, the second gear 22 has a bearing press-fitting portion 22C on the other end side along the gear rotation axis 20J, into which the bearing device 29 is press-fitted without forming the second gear teeth 22T. The second gear 22 has a second gear tooth portion 22B having a second gear tooth 22T formed on the outer peripheral surface between the fitting shaft portion 22A and the bearing press-fitting portion 22C. As shown in FIG. 2, the second gear tooth length 22 </ b> BL, which is the length of the second gear tooth 22 </ b> T in the direction along the gear rotation axis 20 </ b> J, is between the bearing device 29 and the first gear 21 in the composite gear 20. And the length.

  As shown in FIG. 4, a spline 21S having a spline 21S is provided on one inner side of the inner peripheral surface of the fitting hole 21K of the first gear 21 that is farther from the second gear teeth 22T along the gear rotation axis 20J. One gear side spline portion 21E is formed. A first gear-side non-spline portion 21F having no spline 21S is formed on the other end side along the gear rotation axis 20J on the inner peripheral surface of the fitting hole 21K of the first gear 21. The first gear-side non-spline portion press-fit inner diameter 21FD which is the inner diameter of the first gear-side non-spline portion 21F is the first gear-side spline portion which is the largest inner diameter (the inner diameter of the recess of the spline) in the first gear-side spline portion 21E. It is set slightly larger than the maximum inner diameter 21ED.

  As shown in FIG. 5, a second gear-side spline portion 22E having a spline 22S is formed at a position corresponding to the first gear-side spline portion 21E in the fitting shaft portion 22A of the second gear 22. The spline 22S is a spline for fitting with the spline 21S of the first gear-side spline portion 21E. A second gear-side non-spline portion 22F having no spline 22S is formed at a position corresponding to the first gear-side non-spline portion 21F in the fitting shaft portion 22A of the second gear 22. The maximum outer diameter 22ED of the second gear-side spline portion, which is the largest outer diameter (the outer diameter of the projection of the spline) in the second gear-side spline portion 22E, is larger than the maximum inner diameter 21ED of the first gear-side spline portion shown in FIG. It is set slightly smaller. The second gear-side non-spline portion press-fit outer diameter 22FD, which is the outer diameter of the second gear-side non-spline portion press-fit outer diameter 22FD, is set slightly larger than the first gear-side non-spline portion press-fit inner diameter 21FD shown in FIG. The second gear spline length 22EL (see FIG. 5), which is the length of the spline 22S formed on the second gear-side spline portion 22E along the gear rotation axis 20J, is formed on the first gear-side spline portion 21E. It is set longer (see FIG. 7) than the first gear spline length 21EL (see FIG. 4), which is the length of the selected spline 21S along the gear rotation axis 20J. The length of the fitting shaft portion 22A of the second gear 22 along the gear rotation axis 20J (the second gear spline length 22EL + the second gear press-fitting portion length 22FL (see FIG. 5)) is the same as that of the first gear 21. It is substantially equal to the first gear length 21L (see FIG. 4) along the gear rotation axis 20J.

  FIG. 6 is a sectional view taken along the line VI-VI in FIG. As shown in FIG. 6, between adjacent second gear teeth 22T, a gear groove portion 22M that is a concave portion with respect to the outer peripheral surface of the second gear-side non-spline portion 22F is formed. As shown in FIG. 5, the gear groove 22M is formed to extend to the second gear-side non-spline portion 22F. As shown in FIG. 5, the gear groove portion 22M extended to the second gear-side non-spline portion 22F has a gear groove depth 22P that is the depth from the surface of the second gear-side non-spline portion 22F. The gear teeth 22T are formed so as to gradually become shallower as they move away from the gear teeth 22T along the gear rotation axis 20J. As shown in FIG. 5, the gear groove depth 22P, which is the depth of the gear groove portion 22M, is constant in the second gear tooth portion 22B, but gradually becomes shallow in the second gear-side non-spline portion 22F. It has a cut-up shape having a cut-up portion 22N.

  As shown in FIG. 7, in the structure of the compound gear 20 shown in the present embodiment, the fitting shaft portion 22A of the second gear 22 is inserted into the fitting hole 21K of the first gear 21, and the first gear-side spline The portion 21E and the second gear-side spline portion 22E are in a fitted state. That is, as shown in FIG. 7, the compound gear 20 is in a state where the spline 22S of the second gear-side spline portion 22E is fitted to the spline 21S of the first gear-side spline portion 21E. As shown in FIG. 7, the compound gear 20 is in a state where the second gear-side non-spline portion 22F is press-fitted into the first gear-side non-spline portion 21F. Thus, the first gear 21 is assembled to the second gear 22 to form the composite gear 20.

  In the compound gear 20, the spline 21S and the spline 22S are fitted, so that the first gear 21 does not slip in the rotation direction with respect to the second gear 22. Further, in the compound gear 20, the second gear-side non-spline portion 22F is press-fitted into the first gear-side non-spline portion 21F, so that the axis of the first gear 21 and the second gear 22 does not swing.

  Further, in a state where the fitting shaft portion 22A of the second gear 22 is fitted (and press-fit) into the fitting hole 21K of the first gear 21, as shown in FIG. , The second gear teeth 22 </ b> T on the side of the first gear 21 are in contact with each other. Thereby, the end face of the second gear tooth 22T is in a state of supporting the first gear 21, and it is possible to further prevent the axis of the first gear 21 from swinging with respect to the axis of the second gear 22.

● [Process of manufacturing compound gear 20 (FIG. 2) (FIG. 8) and process of manufacturing conventional gear (FIG. 10) (FIG. 9)]
Next, the manufacturing process (manufacturing method) of the compound gear 20 shown in FIG. 2 will be described with reference to FIG. Steps S110 to S160 show an example of a first gear forming step, steps S210 to S260 show an example of a second gear forming step, and steps S310 and S320 show a gear assembling step of assembling the first gear 21 to the second gear 22. An example is shown.

  First, the first gear forming step shown in FIG. 8 will be described. In the lathe processing in step S110, a schematic shape of the first gear 21 shown in FIG. 3 is formed using a grinding machine or the like. In the spline processing in step S120, a first gear-side spline portion 21E having a spline 21S shown in FIG. 4 is formed using a spline processing tool. In the hobbing process of step S130, each of the first gear teeth 21T shown in FIG. 3 is formed using a hobbing tool. The shape of the first gear 21 has no portion that interferes with the hobbing tool when hobbing the first gear teeth 21T, so that the first gear teeth 21T can be easily formed in a short time. In the shaving processing in step S140, the first gear teeth 21T are finished using a shaving processing tool. In the heat treatment of step S150, the first gear 21 is quenched and annealed. In the polishing in step S160, the outer peripheral surface of the bearing press-fitting portion 21A into which the bearing device 28 is press-fitted and the inner peripheral surface of the first gear-side non-spline portion 21F are polished.

  The process described above is the first gear forming process. In the first gear forming step, the first gear teeth are formed on the outer peripheral surface and have a fitting hole penetrating along the gear rotation axis, and the first gear is formed on one end side of the inner peripheral surface of the fitting hole. A first gear 21 is formed in which a side spline portion is formed, and a first gear-side non-spline portion is formed on the other end side of the inner peripheral surface of the fitting hole.

  Next, the second gear forming step shown in FIG. 8 will be described. In the lathe processing in step S210, a schematic shape of the second gear 22 shown in FIG. 3 is formed using a grinding machine or the like. In the spline processing in step S220, a second gear-side spline portion 22E having a spline 22S shown in FIG. 5 is formed using a spline processing tool.

  In the hobbing process in step S230, each of the second gear teeth 22T shown in FIG. 3 is formed using a hobbing tool. The shape of the second gear 22 has no portion that interferes with the hobbing tool when hobbing the second gear teeth 22T, so that the second gear teeth 22T can be easily formed in a short time. At the time of hobbing, the hobbing tool is moved from the bearing press-fitting portion 22C side to the fitting shaft portion 22A side in parallel with the gear rotation axis 20J to form a gear groove portion 22M having a constant depth. I do. When the hobbing tool reaches the second gear-side non-spline portion 22F, the hobbing tool is gradually moved away from the second gear 22 in addition to the parallel movement with respect to the gear rotation axis. . Thereby, the gear height of the second gear teeth 22T is made uniform (the gear groove depth is made uniform), and a cut-out groove (cut-up portion 22N) is formed in the second gear-side non-spline portion 22F. If the hobbing tool is moved from the bearing press-fitting portion 22C side to the fitting shaft portion 22A side parallel to the gear rotation axis 20J without forming the cut-up portion 22N, the gear groove portion 22M Reaches the second gear-side spline portion 22E, but by forming the cut-up portion 22N, the gear groove portion 22M can be prevented from reaching the second gear-side spline portion 22E.

  In the shaving processing in step S240, the second gear teeth 22T are finished using a shaving processing tool. In the heat treatment in step S250, quenching and annealing of the second gear 22 are performed. In the polishing in step S260, the outer peripheral surface of the bearing press-fitting portion 22C into which the bearing device 29 is press-fitted and the outer peripheral surface of the second gear-side non-spline portion 22F are polished.

  The process described above is the second gear forming process. In the second gear forming step, the second gear teeth are formed on the outer peripheral surface, and the one end has a fitting shaft portion fitted into the fitting hole without forming the second gear teeth. A second gear-side spline is formed at a position corresponding to the first gear-side spline in the fitting shaft, and a second gear-side non-spline is formed at a position corresponding to the first gear-side non-spline in the fitting shaft. The second gear 22 having the portion formed is formed.

  Next, the gear assembling step shown in FIG. 8 will be described. Using the first gear 21 formed in the first gear forming step and the second gear 22 formed in the second gear forming step, the first gear 21 is fitted by fitting and press-fitting the gears in step S310. The fitting shaft of the second gear 22 is fitted into the hole and press-fitted. That is, the fitting shaft portion 22A of the second gear 22 is inserted into the fitting hole 21K of the first gear 21, and the second spline 21S of the first gear-side spline portion 21E of the fitting hole 21K of the first gear 21 is first inserted. The spline 22S of the second gear side spline portion 22E of the fitting shaft portion 22A of the gear 22 is fitted. The fitting shaft portion 22A is further inserted to the back, and the second gear-side non-spline of the fitting shaft portion 22A of the second gear 22 is inserted into the first gear-side non-spline portion 21F of the fitting hole 21K of the first gear 21. The part 22F is press-fitted. Then, in the press-fitting of the bearing in step S320, the bearing device 28 is press-fitted into the bearing press-fitting portion 21A of the first gear 21, and the bearing device 29 is press-fitted into the bearing press-fitting portion 22C of the second gear 22.

  Next, in order to compare the compound gear 20 of the present application shown in FIG. 2 with the conventional integrally formed compound gear 320 shown in FIG. 10, using FIG. An example of the manufacturing process (manufacturing method) will be described. In the lathe processing in step S410, a rough shape in which the first gear 321 and the second gear 322 are integrated is formed using a grinding machine or the like. It should be noted that the step S410 differs from the compound gear 20 of the present invention in that a relief groove 322M is also formed.

  In the hobbing process in step S420, the first gear teeth 321T are formed using a hobbing tool. Since there is no portion that interferes with the hobbing tool around the first gear teeth 321T, the first gear teeth 21T can be easily formed in a short time. The second gear teeth 322T cannot be formed by hobbing because the first gear 321 projecting radially outward in a flange shape interferes with the hobbing tool. In the gear shaper processing in step S430, the second gear teeth 322T are formed using a gear shaper processing tool. Since the relief groove 322M is formed, the second gear teeth 322T can be formed while allowing the gear shaper working tool to escape. Since the first gear and the second gear are integrally formed, the first gear teeth can be formed by hobbing as in the composite gear 20 of the present application, but the second gear teeth can be hobbed. This is different from the composite gear 20 of the present application in that the composite gear 20 cannot be formed by gear shaper processing. Further, since the gear shaper processing is necessary, the relief groove 322M is essential, which is different from the composite gear 20 of the present application.

  In the shaving process in step S440, the first gear teeth 321T and the second gear teeth 322T are finish-processed using a shaving tool, similarly to the composite gear 20 of the present application. When finishing the second gear teeth 322T, the relief groove 322M is formed, so that the second gear teeth 322T can be finished while the shaving tool is released.

  In the heat treatment of step S450, quenching and annealing of the integrally formed gear in which the first gear 321 and the second gear 322 are integrated are performed. In the polishing in step S460, the outer peripheral surface on one end side of the integrally molded gear into which the bearing device 328 is press-fitted and the outer peripheral surface on the other end side of the integrally molded gear into which the bearing device 329 is press-fitted are polished. Then, in the bearing press-fitting in step S470, the bearing device 328 is press-fitted into one end of the integrally formed gear, and the bearing device 29 is press-fitted into the other end of the integrally formed gear.

  As described above, compound gear 20 (see FIG. 3) described in the present embodiment separates first gear 21 and second gear 22 from conventional integrally formed compound gear 320 (see FIG. 10). With the separate structure, the escape groove 322M (see 10) becomes unnecessary. Therefore, the second gear tooth length 22BL (see FIG. 3) of the second gear tooth 22T in the direction of the gear rotation axis 20J is changed to the second gear tooth of the second gear tooth 322T of the integrally formed composite gear 320 in the gear rotation axis direction. It can be longer than the length 322A (see FIG. 10). Therefore, the compound gear 20 can transmit larger torque with the second gear teeth than the conventional integrally formed compound gear 320. Further, since the integrally molded compound gear 320 shown in FIG. 10 has the relief groove 322M, the diameter 322K of the shaft portion of the second gear 322 becomes a locally small diameter 322G at the position of the relief groove 322M, Rigidity is reduced. On the other hand, since the compound gear 20 shown in FIG. 3 has no relief groove, the diameter 22K of the shaft portion of the second gear does not have a portion where the diameter is locally reduced. Therefore, the rigidity of the composite gear 20 is improved as compared with the conventional integrally molded composite gear 320. Further, by using the fitting portion and the press-fitting portion by the spline for fitting the first gear 21 and the second gear 22, the first gear does not slip in the rotation direction with respect to the second gear, and The axis of the first gear does not swing with respect to the axis of the two gears.

  The gear structure of the present invention is not limited to the structure described in the present embodiment, and various changes, additions, and deletions can be made without changing the gist of the present invention. The method for manufacturing a gear of the present invention is not limited to the steps, procedures, and the like described in the present embodiment, and various changes, additions, and deletions can be made without changing the gist of the present invention.

  Further, the gear structure and the gear manufacturing method of the present invention are not limited to the compound gear used for the drive unit of the electric forklift, and can be applied to the compound gear used for various devices transmitting relatively large torque. It is.

DESCRIPTION OF SYMBOLS 1 Drive unit 2, 3 Housing 10 Drive motor 11 Motor shaft 11T Motor gear tooth 20 Composite gear 20J Gear rotation axis 21 1st gear 21A Bearing press-fitting part 21B 1st gear tooth part 21E 1st gear side spline part 21ED 1st gear side spline Part maximum inner diameter 21EL first gear spline length 21F first gear side non-spline part 21FD first gear side non-spline part press-fit inner diameter 21K fitting hole 21M first gear side fitting end face 21S spline 21T first gear tooth 22 second Gear 22A Fitting shaft portion 22B Second gear tooth portion 22C Bearing press-fit portion 22E Second gear side spline portion 22ED Second gear side spline portion maximum outer diameter 22EL Second gear spline length 22F Second gear side non-spline portion 22FD No. 2 gear side non-spline part press fit outer diameter 22M gear groove 22N-vanishing part 22P gear groove depth 22S spline 22T second gear teeth 28 and 29 the bearing device 31 the transmission gear 31T transmission gear teeth 32 tank 33 differential 34R, 34L drive shaft

Claims (6)

A disc-shaped first gear having first gear teeth formed on an outer peripheral surface thereof;
The first gear has a cylindrical shape smaller in diameter than the first gear, and has a second gear tooth formed on a part of the outer peripheral surface in the axial direction, is coaxial with the first gear, and is integrated with the first gear. And a second gear that rotates.
The first gear has a fitting hole penetrating along the rotation axis,
A first gear-side spline portion having a spline is formed on one end side of the inner peripheral surface of the fitting hole that is farther from the second gear teeth along the rotation axis,
On the other end side along the rotation axis on the inner peripheral surface of the fitting hole, a first gear-side non-spline portion having no spline is formed,
The second gear has a fitting shaft portion fitted to the fitting hole without forming the second gear teeth on the one end side along the rotation axis,
At a position corresponding to the first gear-side spline portion in the fitting shaft portion, a second gear-side spline portion having a spline fitted to a spline of the first gear-side spline portion is formed,
At a position corresponding to the first gear-side non-spline portion in the fitting shaft portion, a second gear-side non-spline portion having no spline is formed,
A side of the second gear-side spline portion in the second gear-side non-spline portion is an inner diameter of the first gear-side non-spline portion as the distance from the second gear-side spline portion along the rotation axis increases. The first gear side non-spline portion is formed so that the outer diameter gradually increases to the second gear side non-spline portion press-fit outer diameter set to an outer diameter larger than the inner diameter.
A state in which the first gear-side spline portion and the second gear-side spline portion are fitted, and a state in which the second gear-side non-spline portion is press-fitted into the first gear-side non-spline portion. It is said that
Gear structure. The gear structure according to claim 1, wherein
The first gear has a first gear side fitting end surface as a surface on the other end side,
The second gear teeth are formed so as to protrude radially outward,
In a state where the fitting shaft portion is fitted in the fitting hole of the first gear, the end face of the second gear tooth on the side of the first gear contacts the first gear side fitting end face. Is in a state,
Gear structure. The gear structure according to claim 1 or 2,
Wherein the first gear-side non-splined portion press-fitted inside diameter is the inner diameter of the first gear-side non-splined portion is greater than the first first gear side spline portion maximum inner diameter is the largest inner diameter of the gear-side spline portion And
The second gear side spline portion maximum outer diameter, which is the largest outer diameter of the second gear side spline portion, is set smaller than the first gear side spline portion maximum inner diameter,
The second gear-side non-splined portion press-fitted outer diameter is the outer diameter of the second gear-side non-splined portion is greater than the first gear-side non-splined section press-fitting inner diameter,
A second gear spline length, which is a length of the spline formed in the second gear side spline portion along the rotation axis, is along the rotation axis of a spline formed in the first gear side spline portion. It is set longer than the first gear spline length, which is the length.
Gear structure. The gear structure according to claim 3, wherein
A gear groove is formed between the adjacent second gear teeth so as to be concave with respect to the outer peripheral surface of the second gear-side non-spline portion, and the gear groove is formed on the second gear-side non-spline portion. It is formed by extending to
The gear groove portion formed in the second gear-side non-spline portion has a gear groove depth that is a depth from the surface of the second gear-side non-spline portion, and the gear groove depth is from the second gear tooth to the rotation axis. It is a cut-up shape formed so that it gradually becomes shallower as it goes away along,
Gear structure. A disc-shaped first gear having first gear teeth formed on an outer peripheral surface thereof;
The first gear has a cylindrical shape smaller in diameter than the first gear, and has a second gear tooth formed on a part of the outer peripheral surface in the axial direction, is coaxial with the first gear, and is integrated with the first gear. And a second gear that rotates.
The first gear, wherein the first gear tooth is formed on an outer peripheral surface and has a fitting hole penetrating along a rotation axis, wherein the second gear extends along the rotation axis on an inner peripheral surface of the fitting hole. A first gear-side spline portion having a spline is formed on one end side remote from the gear teeth, and a spline is provided on the other end side along the rotation axis on the inner peripheral surface of the fitting hole. Forming a first gear on which a first gear-side non-spline portion not formed is formed;
The second gear teeth are formed on the outer peripheral surface, and a fitting shaft portion that fits into the fitting hole without forming the second gear teeth is provided on the one end side along the rotation axis. A second gear-side spline portion having a spline fitted to the first gear-side spline portion at a position on the fitting shaft portion corresponding to the first gear-side spline portion. The second gear is further provided with a second gear-side non-spline portion having no spline at a position corresponding to the first gear-side non-spline portion in the fitting shaft portion. The first gear side non-spline portion is an inner diameter of the first gear side non-spline portion as the side of the second gear side spline portion in the gear side non-spline portion moves away from the second gear side spline portion along the rotation axis. S Gently to form the second gear is formed so that the outer diameter increases to the second gear side non spline portion press-fitted outer diameter which is set to a larger outer diameter than the line section press-fitting inner diameter, a second gear forming step When,
The fitting shaft portion is inserted into the fitting hole, the first gear-side spline portion and the second gear-side spline portion are fitted, and the second gear-side non-spline portion is fitted into the first gear-side non-spline portion. Press-fitting the spline portion, and a gear assembling step.
Gear manufacturing method. It is a manufacturing method of the gear of Claim 5, Comprising:
The one end side of the second gear teeth along the rotation axis is adjacent to the second gear-side non-spline portion,
In the second gear forming step, each of the second gear teeth is formed by hobbing, and a cut-up groove by the hobbing is formed in the second gear-side non-spline portion.
Gear manufacturing method.

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