Drive transmission device and method for manufacturing ring gear

Abstract

This drive transmission device (100) comprises a planetary gear mechanism (5), and a case (6) that accommodates the planetary gear mechanism (5). The planetary gear mechanism (5) is provided with an internal ring gear (53). Formed at an inner surface (61) of the case (6) are a rotation restriction part (65) that restricts the relative rotation of the ring gear (53), and a radial positioning part (66) that positions the ring gear (53) in the radial direction R. Formed at an outer peripheral surface of the ring gear (53) are an engagement part (535) that engages with the rotation restriction part (65), and a fitting part (536) that fits in the radial positioning part (66). The engagement part (535) and the fitting part (536) are disposed at different positions in the axial direction (L).

Description

Drive transmission device and method for manufacturing a ring gear

[0001] The present invention relates to a drive transmission device mounted on a vehicle and including a ring gear, and a method for manufacturing the ring gear.

[0002] Technologies related to drive transmission devices mounted on vehicles are disclosed in, for example, Patent Document 1. Hereinafter, in the description of this background art, the reference numerals and names in Patent Document 1 are cited within parentheses.

[0003] Patent Document 1 discloses a drive transmission device (transmission mechanism 150) including an internal-tooth ring gear (155) and a case (cast part 160) that houses the ring gear (155). The ring gear (155) is connected while being housed in the case (cast part 160). Specifically, an external-tooth-shaped spline (spline-equipped part 152) formed on the outer peripheral surface of the ring gear (155) fits into an internal-tooth-shaped spline (spline-equipped part 162) formed on the inner peripheral surface of the case (cast part 160), thereby connecting the ring gear (155) to the case (cast part 160).

[0004] Here, in order to mesh the ring gear (155) with the first gear part that meshes with it in an appropriate posture, it is necessary to connect the ring gear (155) to the case (cast part 160) with the axis of the spline (spline-equipped part 152) on the ring gear (155) side and the axis of the spline (spline-equipped part 162) on the case (cast part 160) side being aligned. For this reason, in the drive transmission device (transmission mechanism 150) disclosed in Patent Document 1, a plurality of positioning members (biasing connection members 170) for positioning the ring gear (155) with respect to the case (cast part 160) are sandwiched between the inner peripheral surface of the case (cast part 160) and the outer peripheral surface of the ring gear (155). The positioning member (biasing connection member 170) positions the ring gear (155) with respect to the case (cast part 160) by utilizing the reaction force against the compressive force received from the ring gear (155) and the case (cast part 160).

[0005] Japanese Patent Publication No. 2024-536309

[0006] However, in the drive transmission device (transmission mechanism 150) disclosed in Patent Document 1, the positioning member (biasing connecting member 170) positions the ring gear (155) relative to the case (cast portion 160) by the reaction force to the compressive force received from the ring gear (155) and the case (cast portion 160). Therefore, depending on the magnitude of the load acting on the ring gear (155), the radial position of the ring gear (155) relative to the case (cast portion 160) may not be stable. To reduce this possibility, it is also conceivable to configure the ring gear (155) relative to the case (cast portion 160) using only the splines (splined portion 152) on the ring gear (155) side and the splines (splined portion 162) on the case (cast portion 160) side, without using the positioning member (biasing connecting member 170). However, achieving this configuration requires high machining precision for the splines (splined portion 152) on the ring gear (155) side and the splines (splined portion 162) on the case (cast portion 160) side. Furthermore, requiring high machining precision for complex shapes like splines (splined portions 152 and 162) tends to increase machining costs, which in turn tends to increase the manufacturing cost of the drive transmission device (transmission mechanism 150).

[0007] Therefore, there is a need to realize a drive transmission device that can easily reduce manufacturing costs.

[0008] The drive transmission device according to this disclosure comprises a planetary gear mechanism and a case housing the planetary gear mechanism, wherein the planetary gear mechanism includes an internally toothed ring gear, and the direction along the axis of the ring gear is defined as the axial direction and the direction perpendicular to the axis is defined as the radial direction, the inner surface of the case has a rotation restricting portion that restricts the relative rotation of the ring gear and a radial positioning portion that positions the ring gear in the radial direction, the outer circumferential surface of the ring gear has an engaging portion that engages with the rotation restricting portion and a fitting portion that fits into the radial positioning portion, and the engaging portion and the fitting portion are arranged at different positions in the axial direction.

[0009] With this configuration, radial positioning of the ring gear only requires precise machining of the radial positioning portion on the inner surface of the case and the fitting portion on the outer surface of the ring gear, while the rotation restricting portion on the inner surface of the case and the engagement portion on the outer surface of the ring gear only need to perform the function of restricting relative rotation. Therefore, compared to a configuration in which radial positioning is performed using the rotation restricting portion on the inner surface of the case and the engagement portion on the outer surface of the ring gear, the machining costs of the case and ring gear can be easily reduced, and consequently, the manufacturing costs of the drive transmission device can be easily reduced.

[0010] Furthermore, the technical features of the drive transmission device as described above are also applicable to the manufacturing method of the ring gear of the drive transmission device, and therefore, the present invention can also cover such manufacturing methods.

[0011] In this case, the method for manufacturing a ring gear is a method for manufacturing a ring gear comprising a ring-shaped main body, gear teeth formed on the inner circumferential surface of the main body, an engaging portion having multiple protrusions formed at multiple locations in the circumferential direction on the outer circumferential surface of the main body, and a fitting portion formed on the outer circumferential surface at a position in the axial direction different from the engaging portion, wherein the method for manufacturing a ring gear is performed by: a first step of quenching and tempering the entire ring gear; and a second step of machining the portion of the outer circumferential surface including the fitting portion after the first step.

[0012] With this configuration, even if distortion occurs in the shape of the ring gear during the first step, the precision of the mating portion can be easily improved because the mating portion is machined in the second step, which is performed after the first step.

[0013] Skeleton diagram of the drive transmission device of the embodiment Cross-sectional view of the drive transmission device of embodiment 1 Enlarged view of the vicinity of the ring gear shown in Figure 2 Cross-sectional view of IV-IV shown in Figure 3 Cross-sectional view of the drive transmission device of embodiment 2 Enlarged view of the vicinity of the ring gear shown in Figure 5

[0014] An overview of the drive transmission device 100 according to this embodiment will be described with reference to Figures 1 and 2. The drive transmission device 100 is mounted on a vehicle that operates by converting electricity into driving force. Examples of such vehicles include electric vehicles and hybrid vehicles. The drive transmission device 100 comprises a drive element that generates and outputs driving force, and a structural element for supporting the drive element on the vehicle.

[0015] As shown in Figure 1, the drive transmission device 100 includes, as drive elements, a rotating electric machine 1, a power transmission mechanism 2 that transmits power between the rotating electric machine 1 and the drive element, and a planetary gear mechanism 5 that is drive-connected to the power transmission mechanism 2. Here, in this application, "drive connection" refers to a state in which two rotating elements are connected in a manner that can transmit driving force, and includes a state in which the two rotating elements are connected so as to rotate integrally, or a state in which the two rotating elements are connected in a manner that can transmit driving force via one or more transmission members. Such transmission members include various members that transmit rotation at the same speed or at a variable speed, such as shafts, gear mechanisms, belts, chains, etc. The transmission members may also include engagement devices that selectively transmit rotation and driving force, such as friction engagement devices, meshing engagement devices, etc.

[0016] The drive transmission device 100 includes a case 6 as a structural element, as shown in Figure 2. The case 6 houses at least the planetary gear mechanism 5. In this embodiment, the case 6 houses the rotating electric machine 1, the power transmission mechanism 2, the planetary gear mechanism 5, and an auxiliary mechanism (not shown) that assists in the proper operation of these components. The auxiliary mechanism includes, for example, a lubrication circuit for lubricating sliding members (not shown) included in the rotating electric machine 1, the power transmission mechanism 2, and the planetary gear mechanism 5. The rotating electric machine 1, the power transmission mechanism 2, the planetary gear mechanism 5, and the auxiliary mechanism are fixed to the vehicle's structural members via the case 6.

[0017] The rotating electric machine 1 has at least the function of a motor that generates power when power is supplied. The rotating electric machine 1 may also have the function of a generator that generates power when power is supplied. The rotating electric machine 1 is electrically connected to an energy storage device such as a battery or capacitor (not shown). The rotating electric machine 1 then generates driving force by being driven by the electricity stored in the energy storage device.

[0018] In this embodiment, the rotating electric machine 1 comprises a stator 11 and a rotor 12. The example shown in Figure 1 shows an inner rotor type rotating electric machine 1. In the rotating electric machine 1 illustrated in Figure 1, the rotor 12 is housed in a cylindrical stator 11 that extends in the direction of the axis LX. In addition, the rotating electric machine 1 illustrated in Figure 1 is of the rotating field type. Therefore, the rotor 12 is provided with permanent magnets or electromagnets, and the stator 11 is provided with coils.

[0019] The rotor 12 rotates relative to the stator 11. The power transmission mechanism 2 is driven and connected to the rotor 12, and rotational force is transmitted between the rotor 12 and the power transmission mechanism 2. In this embodiment, the rotor 12 is rotatably supported in the case 6, and the stator 11 is fixed to the case 6. The rotor 12 illustrated in Figure 1 comprises a rotor core 121 and a rotor shaft 122 connected to the rotor core 121 so as to rotate integrally with it. The rotor core 121 rotates around a rotation axis that coincides with the axis of the stator 11. The rotor shaft 122 is attached to the rotor core 121 and is rotatably supported in the case 6 via bearings (not shown). The power transmission mechanism 2 is driven and connected to the rotor shaft 122.

[0020] In this embodiment, the stator 11 and rotor 12 have the function of generating rotational force transmitted to the power transmission mechanism 2, and the function of generating electricity using the rotational force transmitted from the power transmission mechanism 2. Specifically, the rotor core 121 constituting the rotor 12 rotates by exciting the coils of the stator 11. As the rotor core 121 rotates, rotational force is transmitted to the power transmission mechanism 2 via the rotor shaft 122. On the other hand, the rotor core 121 may also receive rotational force from the power transmission mechanism 2 via the rotor shaft 122. When the rotor core 121 rotates with the rotational force transmitted from the power transmission mechanism 2, electricity is generated in the stator 11.

[0021] In this embodiment, the power transmission mechanism 2 includes an output member 3 that outputs rotational force to the vehicle's wheels 31, and a differential gear mechanism 4 that transmits power between the output member 3 and the differential gear mechanism 4. The planetary gear mechanism 5 is driven and connected to the differential gear mechanism 4. In the example shown in Figure 1, the power transmission mechanism 2 includes a pair of output members 3. The power generated by the rotating electric machine 1 is transmitted from the planetary gear mechanism 5 to the differential gear mechanism 4, and then transmitted by the differential gear mechanism 4 to each of the pair of output members 3.

[0022] The output member 3 is driven and connected to the vehicle's wheel 31 via the drive shaft DS. Therefore, the wheel 31 rotates as the rotating electric machine 1 generates rotational force. In addition, in this embodiment, the rotational force of the wheel 31 is transmitted to the rotating electric machine 1 via the drive shaft DS, output member 3, differential gear mechanism 4, and planetary gear mechanism 5, causing the rotating electric machine 1 to generate electricity. For example, the braking force when the brakes are applied to a moving vehicle is transmitted to the rotating electric machine 1 as rotational force.

[0023] The differential gear mechanism 4 includes a differential input element 41 that is driven and connected to the rotor 12 via a planetary gear mechanism 5, a first differential output element 42 that is driven and connected to the differential input element 41, and a second differential output element 43 that is driven and connected to the first differential output element 42. The second differential output element 43 distributes the rotational force transmitted from the differential input element 41 to the first differential output element 42 to each of the pair of output members 3. The differential input element 41 illustrated in Figure 2 is a member that includes an external gear and houses the first differential output element 42 and the second differential output element 43 inside. The first differential output element 42 illustrated in Figure 2 is a pair of pinion gears that are rotatably supported by the differential input element 41. The pair of pinion gears are arranged facing each other in the radial direction R. The second differential output element 43 is driven and connected to each of the pair of output members 3. The second differential output element 43 illustrated in Figure 2 is a pair of side gears rotatably supported by the differential input element 41. The pair of side gears are arranged opposite each other in the axial direction L and mesh with each of the pair of pinion gears that constitute the first differential output element 42.

[0024] The planetary gear mechanism 5 is a mechanism that includes a ring gear 53. In this embodiment, as shown in Figures 1 and 2, the planetary gear mechanism 5 includes a sun gear 50, a carrier 51, a pinion 52 rotatably supported relative to the carrier 51, and an internally toothed ring gear 53. The sun gear 50 illustrated in Figures 1 and 2 is formed on the rotor shaft 122. The pinion 52 meshes with the sun gear 50. The carrier 51 rotatably supports the pinion 52 and revolves together with the pinion 52. The driving force generated by the rotating electric machine 1 is output to the differential gear mechanism 4 via the sun gear 50, pinion 52, and carrier 51 in that order.

[0025] The details of the planetary gear mechanism 5 are easier to understand if explained using the ring gear 53 as a reference. For this reason, in the following explanation, the direction along the axis LX of the ring gear 53 will be referred to as the axial direction L. One side of the axial direction L will be the first axial side L1, and the other side of the axial direction L will be the second axial side L2. The direction perpendicular to the axis LX of the ring gear 53 will be the radial direction R. In the radial direction R, the side of the ring gear 53 that approaches the axis LX will be the inner side R1, and the side of the ring gear 53 that moves away from the axis LX will be the outer side R2. The direction around the axis LX of the ring gear 53 will be the circumferential direction C (see Figure 4). Furthermore, the "radial dimension R" described below is a concept that includes the distance in the radial direction R from the axis LX to the object (the so-called "radius"), or the distance in the radial direction R between two objects that are point-symmetric with respect to the axis LX (or an equivalent positional relationship) (the so-called "diameter").

[0026] In this embodiment, the sun gear 50 is provided on the outer circumferential surface of the end of the rotor shaft 122 along its axis. The sun gear 50 illustrated in Figures 1 and 2 is an external-toothed gear whose rotation axis coincides with the axis LX of the ring gear 53, and is formed at the first axial end L1 of the rotor shaft 122.

[0027] In this embodiment, the pinion 52 comprises a first gear portion 521 that meshes with the ring gear 53, a second gear portion 522 positioned on the second axial side L2 relative to the first gear portion 521, and a pinion shaft 523 that rotatably supports the first gear portion 521 and the second gear portion 522. In the example shown in Figures 1 and 2, the second gear portion 522 meshes with the sun gear 50. The first gear portion 521 and the second gear portion 522 are integrally structured and are supported by the carrier 51 via a pinion shaft 523 that extends along the axial direction L and is supported by the carrier 51. Preferably, the planetary gear mechanism 5 comprises a plurality of pinions 52 spaced apart in the circumferential direction C. For example, it is preferable that the planetary gear mechanism 5 comprises three sets of pinions 52.

[0028] Here, as shown in Figures 1 and 2, it is preferable that the outer diameter of the second gear section 522 is larger than that of the first gear section 521. With this configuration, it is easier to secure a large reduction ratio.

[0029] In this embodiment, the carrier 51 is integrally structured with the differential input element 41. The carrier 51 is rotatably supported in the case 6 via a first bearing 511 positioned on the first axial side L1 relative to the pinion 52, and a second bearing 512 positioned on the second axial side L2 relative to the pinion 52.

[0030] In the carrier 51 illustrated in Figure 2, the first shaft end portion 513, the first shaft support portion 514, the support portion 515, the carrier peripheral wall portion 516, the second shaft support portion 517, and the second shaft end portion 518 are arranged in the order described above, from the first axial side L1 to the second axial side L2.

[0031] The first shaft end 513 is a portion that is rotatably supported by the first bearing 511. The first shaft support portion 514 is a portion that supports the end of the pinion shaft 523 on the first axial side L1. The support portion 515 supports the first differential output element 42 and the second differential output element 43 and forms a space in which they are housed. The first shaft support portion 514 illustrated in Figure 2 overlaps with the support portion 515 when viewed from the radial direction R. Here, regarding the arrangement of the two members, "overlapping when viewed from a specific direction" means that when a virtual line parallel to the line of sight is moved in each direction perpendicular to the virtual line, there exists a region in which the virtual line intersects both members. With this configuration, the entire drive transmission device 100 can be easily miniaturized in the axial direction L.

[0032] The carrier peripheral wall portion 516 connects the support portion 515 and the second shaft support portion 517. In the example shown in Figure 2, the carrier peripheral wall portion 516 is positioned to overlap with the sun gear 50 when viewed from the radial direction R, and to overlap with the pinion 52 when viewed from the circumferential direction C. Furthermore, the carrier peripheral wall portion 516 penetrates radially R at a position that overlaps with the second gear portion 522 when viewed from the radial direction R. With this configuration, the second gear portion 522 can be positioned at the portion of the carrier peripheral wall portion 516 that penetrates radially R, so the external dimensions of the second gear portion 522 in the radial direction R are not limited by the dimensions of the carrier peripheral wall portion 516 in the radial direction R. Therefore, it is easier to set a large reduction ratio for the planetary gear mechanism 5.

[0033] The second shaft support portion 517 supports the axial second side L2 end of the pinion shaft 523. The second shaft end portion 518 is rotatably supported by the second bearing 512. In the example shown in Figure 2, the second shaft end portion 518 overlaps with the second shaft support portion 517 when viewed from the radial direction R. Therefore, the entire drive transmission device 100 can be easily miniaturized in the radial direction R.

[0034] As shown in Figures 2 to 4, the ring gear 53 is fixed at a predetermined position on the inner surface 61 surrounding the internal space 60 of the case 6. Here, the inner surface 61 of the case 6 includes an inner circumferential surface that surrounds the internal space 60 from the circumferential direction C, and side surfaces that cover the internal space 60 from the axial direction L. In order to fix the ring gear 53 to the inner surface 61 of the case 6, the inner surface 61 of the case 6 is formed with a rotation restricting portion 65 that restricts the relative rotation of the ring gear 53, and a radial positioning portion 66 that positions the ring gear 53 in the radial direction R. In this embodiment, as shown in Figure 4, in addition to the rotation restricting portion 65 and the radial positioning portion 66, the inner surface 61 of the case 6 is further formed with an axial positioning portion 67 that positions the ring gear 53 in the axial direction L.

[0035] Case 6 comprises a first circumferential wall portion 63 that covers the ring gear 53 from the outer side R2 in the radial direction R, and a side wall portion 62 that covers the ring gear 53 from the axial first side L1, which is one side in the axial direction L. In the example shown in Figure 2, the side wall portion 62 is adjacent to the first circumferential wall portion 63 on the axial second side L2. The first circumferential wall portion 63 and the side wall portion 62 are integrally structured, and the first circumferential wall portion 63 opens on the axial second side L2. With this configuration, when the ring gear 53 is fixed to the inner surface 61 of the first circumferential wall portion 63, the ring gear 53 is positioned at a predetermined position on the inner surface 61 of the first circumferential wall portion 63 through the opening on the axial second side L2 of the first circumferential wall portion 63. Therefore, it is easy to position the ring gear 53 at the fixing position on the inner surface 61 of the first circumferential wall portion 63.

[0036] The rotation restricting portion 65 and the radial positioning portion 66 are positioned at different locations in the axial direction L. In this embodiment, the rotation restricting portion 65 includes one or more protruding convex portions 651 that project from the inner surface 61 of the first circumferential wall portion 63 toward the axis LX. The multiple convex portions 651 illustrated in Figures 3 and 4 are spline-shaped like internal teeth. Each of the multiple convex portions 651 has a base end (protruding base end 65B) that is in contact with the inner surface 61 of the first circumferential wall portion 63, and a tip end (protruding tip end 65A) that is spaced radially R away from the protruding base end 65B. The surface connecting the protruding base end 65B and the protruding tip end 65A (in other words, the surface corresponding to the tooth surface of the spline-shaped convex portion 651) is a smooth surface that extends along the axial direction L.

[0037] In this embodiment, the radial positioning portion 66 engages with the ring gear 53 at least a portion of the inner surface 61 of the first circumferential wall portion 63 when the ring gear 53 is positioned at a predetermined location in the internal space 60 of the case 6. Here, engagement of the ring gear 53 with the inner surface 61 of the first circumferential wall portion 63 means that the ring gear 53 is in contact with the inner surface 61 of the first circumferential wall portion 63, thereby fixing the relative position of the ring gear 53 with respect to the first circumferential wall portion 63. In the example shown in Figures 2 and 3, the radial positioning portion 66 is a circular surface when viewed from the axial direction L. That is, the radial positioning portion 66 has an inner circumferential surface extending in the circumferential direction C. The inner circumferential surface of the radial positioning portion 66 is a smooth surface extending along the axial direction L.

[0038] In this embodiment, the axial positioning portion 67 is formed at an intermediate position of the rotation restricting portion 65 in the axial direction L. This is illustrated in Figures 2 and 3. The axial positioning portion 67 is a groove formed at the protruding tip 65A of the rotation restricting portion 65. By inserting a restricting member 68, which restricts the relative movement of the ring gear 53 in the axial direction L with respect to the first circumferential wall portion 63, into the axial positioning portion 67, the relative movement of the ring gear 53 in the axial direction L with respect to the first circumferential wall portion 63 is restricted.

[0039] To fix the ring gear 53 in a predetermined position in the case 6, the outer circumferential surface of the ring gear 53 is formed with an engaging portion 535 that engages with the rotation restricting portion 65 and a fitting portion 536 that fits into the radial positioning portion 66. In this embodiment, the ring gear 53 comprises gear teeth 534 that mesh with the second gear portion 522 and a ring-shaped body portion 531. The gear teeth 534 are formed on the inner circumferential surface (body inner circumferential surface 532) of the body portion 531. The outer circumferential surface (body outer circumferential surface 533) of the body portion 531 is formed with the engaging portion 535 and the fitting portion 536. With this configuration, the components for fixing the ring gear 53 to the case 6 are concentrated on the outer circumferential surface of the body portion 531, making it easier to manufacture the ring gear 53.

[0040] The engaging portion 535 and the fitting portion 536 are located at different positions in the axial direction L. The engaging portion 535 illustrated in Figures 2 and 3 is located in a position that overlaps with the gear teeth 534 when viewed from the radial direction R. Therefore, it is easy to reduce the axial dimension L of the ring gear 53. Similarly, the rotation restricting portion 65 in the case 6 also overlaps with the gear teeth 534 when viewed from the radial direction R. With this configuration, it is easy to reduce the size of the entire drive transmission device 100 in the axial direction L. On the other hand, the fitting portion 536 illustrated in Figures 2 and 3 is located in a position adjacent in the axial direction L to the position that overlaps with the gear teeth 534 when viewed from the radial direction R. In addition, in the example shown in Figures 2 and 3, the engaging portion 535 and the rotation restricting portion 65 are located inward R1 of the second gear portion 522, beyond the outermost R2 portion (the tip portion of the teeth of the second gear portion 522). With this configuration, the portion of the case 6 that overlaps with the ring gear 53 when viewed from the radial direction R can be miniaturized.

[0041] In this embodiment, the engaging portion 535 protrudes outward R2 from the outer peripheral surface 533 of the main body, as shown in Figures 3 and 4. In the example shown in Figure 4, multiple engaging portions 535 are provided on the outer peripheral surface 533 of the main body at intervals. With this configuration, the force applied to each engaging portion 535 can be reduced by restricting the rotational movement of the ring gear 53.

[0042] The engaging portion 535 illustrated in Figures 3 and 4 is spline-shaped with external teeth. Each of the multiple engaging portions 535 comprises a base end (engaging base end 53A) that contacts the outer peripheral surface 533 of the main body, and a tip end (engaging tip end 53B) spaced radially R away from the engaging base end 53A. The surface connecting the engaging base end 53A and the engaging tip end 53B (in other words, the surface corresponding to the tooth surface in the spline-shaped engaging portion 535 with external teeth) is a smooth surface extending along the axial direction L. In addition, in the example shown in Figures 3 and 4, the radial R dimension of the engaging portion 535 is set such that, when the ring gear 53 is positioned to be fixed to the first circumferential wall portion 63, the engaging tip end 53B is spaced radially R away from the inner surface 61 of the first circumferential wall portion 63. Similarly, the dimension from the protruding base end 65B to the protruding tip 65A of the protrusion 651 of the radial positioning portion 66 in the case 6 is set. In other words, the dimension from the protruding base end 65B to the protruding tip end 65A is set such that, with the ring gear 53 fixed to the inner surface 61 of the case 6, the protruding tip end 65A is positioned with a radial gap R between it and the outer peripheral surface 533 of the main body of the ring gear 53.

[0043] With this configuration, the ring gear 53 can be fixed to the first circumferential wall portion 63 without the need to machine the radial R dimension of the engaging tip 53B of the ring gear 53 and the protruding tip 65A of the case 6 with high precision. Therefore, when forming the complex-shaped engaging portion 535, it is possible to set areas where the machining precision is relatively loose, making it easier to reduce machining costs. In addition, with this configuration, the radial R dimension of the outer circumferential surface 533 of the main body does not require high precision machining to match the radial R dimension of the protruding tip 65A. For this reason, as shown in Figure 4, it is not necessary to perform recess machining on the boundary portion 53C connecting the outer circumferential surface 533 of the main body and the engaging base end 53A to prevent interference with the protruding tip 65A or to create a recess necessary for high-precision machining of the inner circumferential surface 532 of the main body. Therefore, as shown in Figure 4, the boundary portion 53C can be shaped using only the cutting tool for forming the engaging portion 535 (in the example shown in Figure 4, it is arc-shaped when viewed from the axial direction L). Therefore, it is easier to improve the durability of the ring gear 53 against in-plane deformation.

[0044] In this embodiment, the fitting portion 536 fits with at least a part of the inner surface 61 of the first peripheral wall portion 63. Specifically, the fitting portion 536 fits with at least a part of the radial positioning portion 66. In the example shown in FIG. 3, the fitting portion 536 is circular when viewed from the axial direction L. That is, the fitting portion 536 has a cylindrical outer peripheral surface. The outer peripheral surface of the fitting portion 536 is a smooth surface extending along the axial direction L. The outer peripheral surface of the fitting portion 536 fits with the inner peripheral surface of the radial positioning portion 66. In the example shown in FIG. 3, as described above, the radial positioning portion 66 has a circular inner peripheral surface when viewed from the axial direction L. Therefore, in the example shown in FIG. 3, the outer peripheral surface of the fitting portion 536 fits so as to contact the entire circumference of the inner peripheral surface in the radial positioning portion 66. According to this configuration, since the shape of the fitting portion 536 is simple, it is easy to reduce the processing cost of the ring gear 53.

[0045] In this embodiment, as shown in FIG. 3, the ring gear 53 further includes an axial restriction portion 537. The axial restriction portion 537 is formed on the outer peripheral surface 533 of the main body. Specifically, the axial restriction portion 537 is a groove adjacent to the axial positioning portion 67 formed on the outer peripheral surface 533 of the main body in the radial direction R in a state where the ring gear 53 is arranged at the position where it is fixed to the first peripheral wall portion 63. In this state, by inserting a restricting member 68 that can fit over both the axial restriction portion 537 and the axial positioning portion 67 into both, the position of the ring gear 53 in the axial direction L with respect to the first peripheral wall portion 63 is fixed. The restricting member 68 is, for example, a retaining ring having a notch portion where a part of the circumferential direction C is interrupted.

[0046] Hereinafter, a preferable configuration of the case 6 in which the ring gear 53 is fixed to the inner surface 61 will be described.

[0047] As shown in FIG. 2, the case 6 preferably includes a second peripheral wall portion 64 that is disposed on the second axial side L2 with respect to the first peripheral wall portion 63 and covers the second gear portion 522 from the outer side R2 in the radial direction R. Therefore, even if the dimension of the outer shape of the first gear portion 521 in the radial direction R is different from the dimension of the outer shape of the second gear portion 522 in the radial direction R, the dimensions of the first peripheral wall portion 63 and the second peripheral wall portion 64 in the radial direction R can be set according to the first gear portion 521 and the second gear portion 522. According to this configuration, it is easy to optimize the size of the entire case 6 according to the sizes of the first gear portion 521 and the second gear portion 522, and thus it is easy to reduce the size of the entire case 6.

[0048] The inner peripheral surface of the second peripheral wall portion 64 is preferably larger in diameter than the inner peripheral surface of the first peripheral wall portion 63. In the present embodiment, the dimension of the outer shape of the first gear portion 521 in the radial direction R is smaller than the dimension of the outer shape of the second gear portion 522 in the radial direction R. Therefore, the dimensions of the first peripheral wall portion 63 and the second peripheral wall portion 64 in the radial direction R are in a ratio corresponding to the sizes of the outer shapes of the first gear portion 521 and the second gear portion 522.

[0049] Hereinafter, the details of the drive transmission device 100 of Embodiment 1 shown in FIGS. 2 to 4 and the drive transmission device 100 of Embodiment 2 shown in FIGS. 5 and 6 will be described. The drive transmission device 100 of Embodiment 1 and the drive transmission device 100 of Embodiment 2 have different structures for fixing the ring gear 53 to the case 6. Hereinafter, after explaining the details of the fixing structure of the drive transmission device 100 of Embodiment 1, the differences between the fixing structure of the drive transmission device 100 of Embodiment 2 and the fixing structure of the drive transmission device 100 of Embodiment 1 will be described.

[0050] [Embodiment 1] In the present embodiment, as shown in FIGS. 2 and 3, the rotation restricting portion 65 is formed on the inner peripheral surface of the first peripheral wall portion 63, and the radial positioning portion 66 is formed at a position on the inner peripheral surface of the first peripheral wall portion 63 on the first axial side L1 with respect to the rotation restricting portion 65. According to this configuration, when the ring gear 53 is disposed at the fixing position with respect to the first peripheral wall portion 63, the operator can perform the operation while visually recognizing the rotation restricting portion 65 and the engaging portion 535 from the second axial side L2. Therefore, it is easy for the operator to perform the operation.

[0051] Furthermore, in this embodiment, the inner circumferential surface of the radial positioning portion 66 has a smaller diameter than the smallest diameter portion of the rotation restricting portion 65, and the outer circumferential surface of the fitting portion 536 has a smaller diameter than the largest diameter portion of the engagement portion 535. In other words, the radial radius R of the inner circumferential surface of the radial positioning portion 66 is smaller than the radial radius R of the protruding tip 65A of the rotation restricting portion 65. And the radial radius R of the outer circumferential surface of the fitting portion 536 is smaller than the radial radius R of the engagement tip 53B of the engagement portion 535. With this configuration, it is easy to configure the shapes of the case 6 and the ring gear 53 such that the radial radius R decreases as they approach one side in the axial direction L. Therefore, it is easy to simplify the tool path when forming the case 6 and the ring gear 53, and thus it is easy to reduce the overall processing cost of the drive transmission device 100. In the example shown in Figure 3, the fitting portion 536 is located on the first axial side L1 relative to the engaging portion 535, and is positioned radially R1 inward from the engaging portion 535. In the example shown in Figure 3, the fitting portion 536 is the outer circumferential surface of a cylinder positioned radially R1 inward from the engaging base end 53A of the engaging portion 535. With this configuration, the first circumferential wall portion 63 of the case 6 can be shaped such that the radial dimension R decreases as it approaches the side wall portion 62. Similarly, the ring gear 53 can be shaped such that the radial dimension R decreases as it approaches the fitting portion 536 from the engaging portion 535 along the axial direction L. With this configuration, it is easier to secure the path of the cutting tool when forming the outer shape portions of the first circumferential wall portion 63 and the ring gear 53, thus making it easier to reduce the processing costs of both the case 6 and the ring gear 53.

[0052] [Embodiment 2] The drive transmission device 100 of Embodiment 2 will be described with reference to Figures 5 and 6. In the drive transmission device 100 of Embodiment 2, the configuration of the rotation restricting unit 65 and the radial positioning unit 66 differs from that of the drive transmission device 100 of Embodiment 1. Hereafter, the differences between the drive transmission device 100 of Embodiment 2 and the drive transmission device 100 of Embodiment 1 will be described, and the description of the configuration common to the drive transmission device 100 of Embodiment 2 and the drive transmission device 100 of Embodiment 1 will be omitted.

[0053] In this embodiment, the rotation restricting portion 65 is formed on the inner surface of the first circumferential wall portion 63, as shown in Figures 5 and 6, and the radial positioning portion 66 is formed on the inner surface of the first circumferential wall portion 63 at a position L2 in the axial direction second from the rotation restricting portion 65. Furthermore, in this embodiment, the inner surface of the radial positioning portion 66 has a larger diameter than the smallest diameter portion of the rotation restricting portion 65, and the outer surface of the fitting portion 536 has a larger diameter than the largest diameter portion of the engaging portion 535. In other words, the radial R dimension of the inner surface of the radial positioning portion 66 is larger than the radial R dimension of the protruding tip 65A of the rotation restricting portion 65. And the radial R dimension of the outer surface of the fitting portion 536 is larger than the radial R dimension of the engaging tip 53B of the engaging portion 535. In the example shown in Figure 6, the fitting portion 536 is positioned L2 in the axial direction second from the engaging portion 535 and R2 outward from the engaging portion 535. In the example shown in Figure 6, the fitting portion 536 is the outer circumferential surface of a cylinder located outside R2 of the engaging tip 53B of the engaging portion 535. With this configuration, it is easy to secure a large contact area between the fitting portion 536 and the radial positioning portion 66, making it easier to position the ring gear 53 radially R with respect to the first circumferential wall portion 63.

[0054] [Manufacturing Method] The manufacturing method for the ring gear 53 provided in the drive transmission device 100 described above will now be explained. Specifically, the manufacturing method for a ring gear 53 comprising a ring-shaped main body portion 531, gear teeth 534 formed on the inner circumferential surface of the main body portion 531, an engaging portion 535 having multiple protrusions 651 formed at multiple locations in the circumferential direction C on the outer circumferential surface of the main body portion 531, and a fitting portion 536 formed on the outer circumferential surface of the main body portion 531 at a position in the axial direction L different from the engaging portion 535 will be explained. Such a ring gear 53 is often made of chromium-molybdenum steel or other carbon steel.

[0055] Preferably, the ring gear 53 is subjected to a hardening treatment that hardens at least its surface. With this configuration, the ring gear 53 can be miniaturized while maintaining its durability.

[0056] The manufacturing method for the ring gear 53 of this embodiment involves a first step of performing quenching and tempering of the entire ring gear, and a second step of performing machining on the outer circumferential surface including the fitting portion 536 after the first step. In the first step, the surface hardness of the ring gear 53 is increased by quenching and tempering the entire ring gear 53, while allowing for distortion in the shape of the ring gear 53. In the second step, the portion of the fitting portion 536 that fits with the radial positioning portion 66 is machined to a shape that fits accurately with the radial positioning portion 66.

[0057] [Other Embodiments] Next, other embodiments of the drive transmission device 100 will be described.

[0058] (1) In the above embodiment, the drive transmission device 100 was described as being mounted on a vehicle that operates by converting electricity into driving force. However, the drive transmission device 100 may be mounted on a vehicle that operates using driving force generated by an engine. Examples of such a drive transmission device 100 include continuously variable transmissions, stepped transmissions, and other automatic transmissions.

[0059] (2) In the above embodiment, the power transmission mechanism 2 was described as comprising a pair of output members 3 and a differential gear mechanism 4. However, the pair of output members 3 and the differential gear mechanism 4 are not essential components of the power transmission mechanism 2. The power transmission mechanism 2 may be configured to include a power transmission element without speed changes, a stepped transmission, a continuously variable transmission, or other transmission, as long as it can transmit power to the rotating electric machine 1. Also, in the above embodiment, the power transmission mechanism 2 was described as being driven and connected to the rotating electric machine 1 via a planetary gear mechanism 5. However, the power transmission mechanism 2 may be directly driven and connected to the rotating electric machine 1. In this case, the drive transmission device 100 may be configured to drive and connect the rotating electric machine 1 and the planetary gear mechanism 5 via the power transmission mechanism 2.

[0060] (3) In this embodiment, the carrier 51 is described as being integral with the differential input element 41. However, the carrier 51 may be a separate structure from the differential input element 41.

[0061] (4) In the above embodiment, the rotation restricting portion 65, the radial positioning portion 66, and the axial positioning portion 67 were described as being formed on the inner surface of the first circumferential wall portion 63. However, at least a part of the rotation restricting portion 65, the radial positioning portion 66, and the axial positioning portion 67 may be formed on the side wall portion 62 or the second circumferential wall portion 64.

[0062] (5) In the above embodiment, the plurality of protrusions 651 provided on the rotation restricting portion 65 of the case 6 were described as being in the shape of internal teeth splines. Here, "spline-shaped" includes the fact that the plurality of teeth included in the spline are arranged at equal intervals along the circumferential direction C and that they are arranged at intervals according to a specific rule. Arranging the plurality of teeth at intervals according to a specific rule includes, for example, setting a region in which the spacing between the plurality of teeth is set to be relatively narrow and a region in which it is set to be relatively wide. With this setting, for example, with the ring gear 53 fixed to the case 6, the retaining ring, which is a restricting member 68 inserted into the axial positioning portion 67, can be removed by utilizing the region in which the spacing between the plurality of teeth is set to be relatively wide.

[0063] (6) In the above embodiment, the first step was described as quenching and tempering. However, the first step may be a quenching and tempering step, as long as the tooth surface of the internal gear teeth 534 can be hardened to the required degree.

[0064] (7) The method for manufacturing the ring gear 53 in the above embodiment was described as including a first step of hardening and tempering the entire ring gear 53 and a second step of cutting the portion including the fitting portion 536. However, the method for manufacturing the ring gear 53 in this embodiment may also include a heat treatment step as a hardening treatment that is less likely to cause distortion of the shape of the ring gear 53. Examples of such heat treatment steps include gas soft nitriding and other nitriding treatments. With this configuration, the area to be cut in the cutting step that cuts the portion including the fitting portion 536 can be reduced, or the cutting step can be omitted, making it easier to reduce the manufacturing cost of the ring gear 53.

[0065] (8) The configurations disclosed in the embodiments described above can also be applied in combination with configurations disclosed in other embodiments, as long as no inconsistencies arise. With regard to other configurations, the embodiments disclosed herein are merely illustrative in all respects. Therefore, various modifications can be made as appropriate without departing from the spirit of this disclosure.

[0066] [Summary of this embodiment] The embodiment relating to the drive transmission device (100) described above is summarized below.

[0067] The drive transmission device (100) comprises a planetary gear mechanism (5) and a case (6) housing the planetary gear mechanism (5), wherein the planetary gear mechanism (5) includes an internally toothed ring gear (53), and the direction along the axis (LX) of the ring gear (53) is defined as the axial direction (L), and the direction perpendicular to the axis (LX) is defined as the radial direction (R), and the inner surface (61) of the case (6) is defined as the relative rotation of the ring gear (53) A rotation restricting portion (65) that restricts rotation and a radial positioning portion (66) that positions the ring gear (53) in the radial direction (R) are formed, and an engaging portion (535) that engages with the rotation restricting portion (65) and a fitting portion (536) that fits into the radial positioning portion (66) are formed on the outer circumferential surface of the ring gear (53), and the engaging portion (535) and the fitting portion (536) are arranged at different positions in the axial direction (L).

[0068] With this configuration, in order to position the ring gear (53) radially (R), it is only necessary to precisely machine the radial positioning portion (66) on the inner surface (61) of the case (6) and the fitting portion (536) on the outer surface of the ring gear (53), and the rotation restricting portion (65) on the inner surface (61) of the case (6) and the engagement portion (535) on the outer surface of the ring gear (53) only need to perform the function of restricting relative rotation. Therefore, compared to a configuration in which radial positioning (R) is performed using the rotation restricting portion (65) on the inner surface (61) of the case (6) and the engagement portion (535) on the outer surface of the ring gear (53), the machining costs of the case (6) and the ring gear (53) can be easily reduced, and consequently, the manufacturing cost of the drive transmission device (100) can be easily reduced.

[0069] Here, the case (6) preferably comprises a first circumferential wall portion (63) that covers the ring gear (53) from the outside (R2) in the radial direction (R), and a side wall portion (62) that covers the ring gear (53) from the first axial side (L1), which is one side in the axial direction (L). The rotation restricting portion (65) is formed on the inner circumferential surface of the first circumferential wall portion (63), the radial positioning portion (66) is formed on the inner circumferential surface of the first circumferential wall portion (63) at a position on the first axial side (L1) of the rotation restricting portion (65), and the fitting portion (536) is preferably positioned on the first axial side (L1) of the engaging portion (535) and on the inside (R1) in the radial direction (R) of the engaging portion (535).

[0070] With this configuration, it is easy to set the shape of the inner surface of the first circumferential wall portion (63) of the case (6) so that the side closer to the side wall portion (62) has a smaller diameter. This makes it easier to process the inner surface of the first circumferential wall portion (63) of the case (6), and makes it easier to reduce the processing cost of the case (6).

[0071] Furthermore, in a configuration in which the case (6) comprises a first circumferential wall portion (63) that covers the ring gear (53) from the radially (R) outside (R2), and a side wall portion (62) that covers the ring gear (53) from the axial first side (L1), which is one side in the axial direction (L), the planetary gear mechanism (5) comprises a pinion (52) that is rotatably supported with respect to the carrier (51), and the pinion (52) comprises a first gear portion (521) that meshes with the ring gear (53), and the first gear portion (521) The case (6) comprises a second gear portion (522) arranged on the axial second side (L2), which is the other side in the axial direction (L), and the case (6) comprises a second circumferential wall portion (64) arranged on the axial second side (L2) relative to the first circumferential wall portion (63) and covering the second gear portion (522) from the radial outside (R2), wherein the outer shape of the second gear portion (522) is larger in diameter than the outer shape of the first gear portion (521), and the inner circumferential surface of the second circumferential wall portion (64) is larger in diameter than the inner circumferential surface of the first circumferential wall portion (63).

[0072] With this configuration, the inner surface of the second circumferential wall portion (64), which is positioned away from the side wall portion (62) in the axial direction (L), has a larger diameter than the inner surface of the first circumferential wall portion (63). This makes it easier to machine the inner surface of the second circumferential wall portion (64), thus reducing the machining cost of the case (6).

[0073] Furthermore, the fitting portion (536) preferably has a cylindrical outer surface.

[0074] With this configuration, the shape of the mating portion (536) is simple, making it easier to reduce the machining cost of the ring gear (53).

[0075] Furthermore, in a configuration in which the fitting portion (536) has a cylindrical outer surface, the radial positioning portion (66) preferably has an inner surface that fits into the outer surface of the fitting portion (536), the inner surface of the radial positioning portion (66) is smaller in diameter than the smallest diameter portion of the rotation restricting portion (65), and the outer surface of the fitting portion (536) is smaller in diameter than the largest diameter portion of the engagement portion (535).

[0076] With this configuration, it is easy to configure the shapes of the case (6) and the ring gear (53) such that the radial (R) dimension decreases as they approach one side in the axial direction (L). Therefore, it is easy to simplify the tool path when forming the case (6) and the ring gear (53), and thus it is easy to reduce the overall machining cost of the drive transmission device (100).

[0077] A method for manufacturing a ring gear (53) comprises a ring-shaped main body (531), gear teeth (534) formed on the inner circumferential surface of the main body (531), an engaging portion (535) having multiple protrusions (651) formed at a plurality of locations in the circumferential direction (C) on the outer circumferential surface of the main body (531), and a fitting portion (536) formed on the outer circumferential surface at a position in the axial direction (L) different from the engaging portion (535), wherein the method for manufacturing a ring gear (53) is to perform a first step of hardening and tempering the entire ring gear, and a second step of machining the portion of the outer circumferential surface including the fitting portion (536) after the first step.

[0078] With this configuration, even if the shape of the ring gear (53) is distorted in the first step, the fitting portion (536) is machined in the second step which is performed after the first step, making it easier to improve the accuracy of the fitting portion (536).

[0079] The technology described herein can be used in a drive transmission device equipped with a ring gear.

[0080] 5: Planetary gear mechanism, 6: Case, 51: Carrier, 52: Pinion, 53: Ring gear, 61: Inner surface, 62: Side wall, 63: First circumferential wall, 64: Second circumferential wall, 65: Rotation restricting part, 66: Radial positioning part, 100: Drive transmission device, 521: First gear part, 522: Second gear part, 531: Main body, 534: Gear teeth, 535: Engaging part, 536: Fitting part, 651: Protrusion, C: Circumferential direction, L: Axial direction, L1: First axial side, L2: Second axial side, LX: Axial center, R: Radial direction, R1: Inner side, R2: Outer side

Claims

1. A drive transmission device comprising a planetary gear mechanism and a case housing the planetary gear mechanism, wherein the planetary gear mechanism includes an internally toothed ring gear, the direction along the axis of the ring gear is defined as the axial direction, and the direction perpendicular to the axis is defined as the radial direction, the inner surface of the case is formed with a rotation restricting portion for restricting the relative rotation of the ring gear and a radial positioning portion for positioning the ring gear in the radial direction, the outer circumferential surface of the ring gear is formed with an engaging portion for engaging with the rotation restricting portion and a fitting portion for fitting with the radial positioning portion, and the engaging portion and the fitting portion are arranged at different positions in the axial direction.

2. The drive transmission device according to claim 1, wherein the case comprises a first circumferential wall portion that covers the ring gear from the radially outside, and a side wall portion that covers the ring gear from the axial first side which is one side in the axial direction, the rotation restricting portion is formed on the inner circumferential surface of the first circumferential wall portion, the radial positioning portion is formed on the inner circumferential surface of the first circumferential wall portion at a position on the axial first side of the rotation restricting portion, and the fitting portion is positioned on the axial first side of the engaging portion and radially inward of the engaging portion.

3. The drive transmission device according to claim 2, wherein the planetary gear mechanism comprises a pinion rotatably supported with respect to a carrier, the pinion comprises a first gear portion that meshes with the ring gear, and a second gear portion disposed on the axial second side, which is the other side in the axial direction with respect to the first gear portion, the case comprises a second circumferential wall portion disposed on the axial second side with respect to the first circumferential wall portion and covering the second gear portion from the radial outside, the outer diameter of the second gear portion is larger than the outer diameter of the first gear portion, and the inner circumferential surface of the second circumferential wall portion is larger than the inner circumferential surface of the first circumferential wall portion.

4. The drive transmission device according to claim 1, wherein the fitting portion has a cylindrical outer surface.

5. The drive transmission device according to claim 4, wherein the radial positioning portion has an inner surface that fits into the outer surface of the fitting portion, the inner surface of the radial positioning portion has a smaller diameter than the smallest diameter portion of the rotation restricting portion, and the outer surface of the fitting portion has a smaller diameter than the largest diameter portion of the engagement portion.

6. A method for manufacturing a ring gear comprising a ring-shaped main body, gear teeth formed on the inner circumferential surface of the main body, an engaging portion having multiple protrusions formed at multiple locations in the circumferential direction on the outer circumferential surface of the main body, and a fitting portion formed on the outer circumferential surface at a position in the axial direction different from the engaging portion, the method comprising: a first step of performing quenching and tempering of the entire ring gear; and a second step of performing machining of the portion of the outer circumferential surface including the fitting portion after the first step.

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