JP6380372B2 - Power transmission gear and manufacturing method thereof - Google Patents

Description

  The present invention relates to a power transmission gear and a manufacturing method thereof.

  Vehicles such as automobiles are required to improve NVH (noise, vibration, and harshness) performance such as noise and vibration, and drive in addition to reducing noise for body components such as various panels and frames. It is also required to reduce the noise caused by meshing between power transmission gears provided in a transmission and a differential device that constitute a power transmission path from the power source to the drive wheels.

  In addition, in order to improve the fuel efficiency of the engine in a vehicle using an engine as a drive source, and to reduce the power consumption of the motor in a vehicle using a motor as a drive source, Further, it is required to reduce the weight of a power transmission gear provided in a transmission or a differential device that constitutes a power transmission path from a drive source to a drive wheel.

  For example, Patent Document 1 discloses a hub portion that is fitted to a rotating shaft, a disk portion that extends radially outward from the hub portion, and a disk portion that is designed to reduce noise and weight of a power transmission gear. In a power transmission gear having a rim portion provided at an outer peripheral end and having a tooth portion formed on an outer peripheral surface, the disk portion extends in the circumferential direction of the rotating shaft and has a plurality of through holes extending in the axial direction, What has the connection part located between several through-holes is disclosed.

  The power transmission gear is provided with a plurality of through holes extending in the circumferential direction in the disk part, thereby reducing the rigidity around the axis of the disk part and providing a connecting part positioned between the plurality of through holes when the gears mesh. It is said that noise due to meshing can be reduced and weight reduction can be achieved by elastic deformation.

JP 2005-69401 A

  However, in the power transmission gear housed in the housing together with the lubricating oil, such as a differential gear of a differential device that lifts the lubricating oil stored in the housing and supplies the lubricating oil to a required lubricating portion such as a gear meshing portion. When a through-hole penetrating in the axial direction is provided as in the power transmission gear described in FIG. 1, there is a risk that the rotational resistance of the power transmission gear may increase when the power transmission gear rotates. It may cause deterioration of fuel consumption performance.

  Therefore, an object of the present invention is to provide a power transmission gear and a method for manufacturing the same that can reduce noise and reduce the weight without increasing the rotational resistance of the power transmission gear.

  In order to solve the above problems, the present invention is configured as follows.

First, the invention according to claim 1 of the present application is a power transmission gear that is housed together with lubricating oil in a housing and provided with a tooth portion that protrudes from the root circle to the outer peripheral side on the outer peripheral portion. A plurality of cavities having the same length in the circumferential direction are arranged at equal intervals in the circumferential direction on the inner circumferential side of the root circle, and the power transmission gear includes a differential case that houses the outer circumferential part and a differential mechanism. An inner peripheral portion in communication with the shell portion, and the plurality of hollow portions are provided on an inner peripheral side of the root circle inside the outer peripheral portion, and the power transmission gear is coupled to the differential case. A differential ring gear, and an outer peripheral portion, an inner peripheral portion that communicates with a shell portion of the differential case that houses the differential mechanism, and both sides that connect the outer peripheral portion and the inner peripheral portion on both sides in the axial direction. And having the side part A plurality of connecting portions for connecting the outer peripheral portion and the inner peripheral portion with a predetermined width in the circumferential direction and connecting the side portions on both sides are provided in the circumferential direction inside the fling gear. A plurality of first cavities having the same length in the circumferential direction and arranged at equal intervals in the circumferential direction are provided on the inner circumferential side of the root circle of the dent ring, and the differential ring gear is formed integrally with the differential case The first hollow portion is provided at a position overlapping the tooth portion and the differential ring gear in the axial direction .

The invention of claim 2 is the invention according to claim 1, in the interior of the radially inner side of the front Kigaishu portion the differential ring gear, the outer peripheral portion, the inner peripheral portion, said side portions and A second cavity portion defined by the connecting portion is provided.

The invention according to claim 3 is the invention according to claim 2 , wherein a plurality of reinforcing ribs provided on the differential case are coupled to the side surface portion of the differential ring gear, The differential ring gear is connected to the side surface portion corresponding to a portion where the reinforcing rib is coupled to the side surface portion.

According to a fourth aspect of the present invention, in the second or third aspect of the present invention, the second cavity is used as a lubricating oil reservoir that stores lubricating oil. Lubricating oil discharge holes for discharging the lubricating oil stored in the second cavities from the outer peripheral surface of the diffring gear are provided in communication with the second cavities.

Furthermore, the invention according to claim 5 is a method of manufacturing a power transmission gear that is housed together with lubricating oil in a housing and has a tooth portion that protrudes from the root circle to the outer peripheral side on the outer peripheral portion. A plurality of hollow portions having the same length in the circumferential direction are arranged at equal intervals in the circumferential direction on the inner circumferential side of the root circle, and the power transmission gear houses the outer circumferential portion and the differential mechanism. An inner peripheral portion communicated with a shell portion of the differential case, the plurality of hollow portions are provided on the inner peripheral side of the root circle inside the outer peripheral portion, and the power transmission gear includes: a differential case; It is a coupled differential ring gear, and connects the outer peripheral part, the inner peripheral part connected to the shell part of the differential case that houses the differential mechanism, and the outer peripheral part and the inner peripheral part on both sides in the axial direction. With side parts on both sides A plurality of connecting portions for connecting the outer peripheral portion and the inner peripheral portion with a predetermined width in the circumferential direction and connecting the side portions on both sides are provided in the circumferential direction inside the differential ring gear, and the outer peripheral portion A plurality of first cavities having the same length in the circumferential direction and arranged at equal intervals in the circumferential direction are provided on the inner circumferential side of the root circle in the interior, and the differential ring gear is integrated with the differential case The power transmission gear is formed by a three-dimensional additive manufacturing method so that the first cavity is provided at a position overlapping the tooth portion and the differential ring gear in the axial direction. To do.

  According to the first aspect of the present invention, the power transmission gear housed together with the lubricating oil in the housing has a plurality of hollow portions having the same length in the circumferential direction on the inner circumferential side of the root circle. Are arranged at equal intervals in the circumferential direction. As a result, the compliance of the power transmission gear in which the cavity portion is not formed by forming the low rigidity portion in which the cavity portion is provided in the circumferential direction of the power transmission gear and the high rigidity portion in which the cavity portion is not provided. The peak at a predetermined frequency is distributed to the low frequency side peak due to the low rigidity part and the high frequency side peak due to the high rigidity part to widen the base and reduce the noise caused by meshing in relation to the compliance of the counter gear. it can. Note that compliance refers to the amount of displacement in the tooth contact direction of each gear meshing with each other.

  By appropriately setting the size of the cavity portion arranged in the circumferential direction of the power transmission gear, the compliance peak of the power transmission gear is appropriately adjusted to the peak on the low frequency side and the peak on the high frequency side for dispersion. Thus, the base can be widened, and noise due to meshing can be effectively reduced.

  Further, by providing a plurality of cavities inside the power transmission gear, the weight can be reduced by the cavities, and the power transmission gear can be used when the power transmission gear is housed in the housing together with the lubricating oil. The rotation resistance of the gear is not increased. Therefore, noise can be reduced and weight can be reduced without increasing the rotational resistance of the power transmission gear.

Also, the dynamic force transmitting gear, and the outer peripheral portion of teeth is provided, and a inner peripheral portion which is contacted with the shell portion of the differential case that houses the differential mechanism, a plurality of cavities, the internal peripheral portion Is provided on the inner peripheral side of the root circle in the case, the noise due to the meshing of the power transmission gear can be effectively reduced, and the above-described effect can be effectively achieved.

Also, the dynamic force transmitting gear is a differential ring gear, the outer peripheral portion and the inner peripheral portion which is contacted with the shell portion of the differential case, both side surfaces of which respectively connect the outer peripheral portion and the inner peripheral portion in the axial direction on both sides A plurality of connecting portions for connecting the outer peripheral portion and the inner peripheral portion and connecting the side portions on both sides are provided in the circumferential direction in the differential ring gear.

A plurality of first cavities having the same length in the circumferential direction and arranged at equal intervals in the circumferential direction are provided on the inner circumferential side of the root circle inside the outer circumferential portion , and the diff ring gear includes: The first cavity is integrally formed, and is provided at a position where the tooth and the diff ring gear overlap in the axial direction.

  By providing a plurality of first cavities inside the outer periphery of the diff ring gear, when the diff ring gear is housed in the housing together with lubricating oil, the noise is reduced and the weight is reduced without increasing the rotational resistance of the diff ring gear. Can be achieved.

In addition, the second hollow portion defined by the outer peripheral portion, the inner peripheral portion, the side surface portion, and the connecting portion is provided inside the differential ring gear on the radially inner side of the outer peripheral portion, so that the connection provided inside the differential ring gear. While securing the strength and rigidity of the diff ring gear by the portion, the weight can be reduced by the second cavity portion defined by the outer peripheral portion, the inner peripheral portion, the side surface portion, and the connecting portion provided inside the diff ring gear. By providing the second cavity inside the diff ring gear, when the diff ring gear is housed in the housing together with the lubricating oil, the def ring gear is secured while maintaining the strength and rigidity without increasing the rotational resistance of the def ring gear. Can be further improved.

According to the invention of claim 3 , a plurality of reinforcing ribs provided on the differential case are coupled to the side surface portion of the diff ring gear, and the connecting portion is a portion where the reinforcing ribs on the side surface portion of the diff ring gear are coupled. The strength and rigidity of the diff ring gear can be increased by being connected to the side surface corresponding to the above, and the above-described effects can be effectively achieved.

According to the invention described in claim 4 , the second cavity is used as a lubricating oil reservoir for storing lubricating oil, and is stored in the second cavity by communicating with the second cavity in the diff ring gear. By providing a lubricating oil discharge hole for discharging the lubricated oil from the outer peripheral surface of the diff ring gear, the second hollow portion provided in the def ring gear is engaged with the def ring gear and a gear meshed with the def ring gear. It can be effectively used as a lubricating oil reservoir for supplying lubricating oil to the lubrication required parts.

Furthermore, according to the invention described in claim 5 , a plurality of cavities having the same length in the circumferential direction are arranged at equal intervals in the inner circumferential side of the root circle, and the power transmission gear is The outer peripheral portion and the inner peripheral portion communicated with the shell portion of the differential case that houses the differential mechanism, and a plurality of hollow portions are provided on the inner peripheral side of the root circle inside the outer peripheral portion to transmit power The differential gear is a differential ring gear coupled to the differential case, the outer peripheral portion, the inner peripheral portion connected to the shell portion of the differential case, and the side surfaces on both sides connecting the outer peripheral portion and the inner peripheral portion on both sides in the axial direction. And a plurality of connecting portions for connecting the outer peripheral portion and the inner peripheral portion and connecting the side portions on both sides are provided in the circumferential direction inside the differential ring gear. It has the same length in the circumferential direction on the circumferential side and is arranged at equal intervals in the circumferential direction The first cavity of the plurality is provided that, the differential ring gear is formed integrally with the differential case, the first hollow portion, as can be provided in a position overlapping in the axial direction of the teeth and the ring gear, power transmission By forming the gears by the three-dimensional additive manufacturing method, it is possible to manufacture a power transmission gear that can reduce noise and reduce weight without increasing rotational resistance by using the three-dimensional additive manufacturing method.
The power transmission gear includes an outer peripheral portion provided with a tooth portion and an inner peripheral portion communicated with a shell portion of a differential case that houses the differential mechanism, and the plurality of hollow portions are provided inside the outer peripheral portion. By being provided on the inner peripheral side of the root circle, noise due to meshing of the power transmission gear can be effectively reduced, and the above-described effect can be effectively achieved.
The power transmission gear is a differential ring gear, and includes an outer peripheral portion, an inner peripheral portion connected to the shell portion of the differential case, and side portions on both sides connecting the outer peripheral portion and the inner peripheral portion on both sides in the axial direction. And a plurality of connecting portions for connecting the outer peripheral portion and the inner peripheral portion and connecting the side surface portions on both sides are provided in the circumferential direction in the differential ring gear.
A plurality of first cavities having the same length in the circumferential direction and arranged at equal intervals in the circumferential direction are provided on the inner circumferential side of the root circle inside the outer circumferential portion, and the diff ring gear includes: The first cavity is integrally formed, and is provided at a position where the tooth and the diff ring gear overlap in the axial direction.
By providing a plurality of first cavities inside the outer periphery of the diff ring gear, when the diff ring gear is housed in the housing together with lubricating oil, the noise is reduced and the weight is reduced without increasing the rotational resistance of the diff ring gear. Can be achieved.

It is sectional drawing which shows the differential apparatus provided with the gearwheel for power transmission which concerns on embodiment of this invention. It is a perspective view of the differential ring gear and differential case of a differential apparatus. It is a side view of a differential ring gear and a differential case. It is a figure which shows the diff ring gear and differential case seen from the Y4 direction in FIG. FIG. 5 is a cross-sectional view of a diff ring gear and a diff case along line Y5-Y5 in FIG. FIG. 4 is a cross-sectional view of a differential ring gear and a differential case along a line Y6-Y6 in FIG. 3. FIG. 4 is a cross-sectional view of a diff ring gear and a differential case along line Y7-Y7 in FIG. It is sectional drawing of the diff ring gear and differential case which expand and show the A section in FIG. It is a cross-sectional perspective view of the outer peripheral part of a diff ring gear which expands and shows a part of A section in FIG. FIG. 9 is a developed cross-sectional view of the outer peripheral portion of the diff ring gear along the line Y10a-Y10a in FIG. It is a graph which shows the compliance with respect to the frequency of a diff ring gear and an output gear.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view showing a differential apparatus provided with a power transmission gear according to an embodiment of the present invention. A differential device including a power transmission gear according to an embodiment of the present invention is mounted on a front engine / front drive vehicle, and is disposed as a drive source disposed on a front portion of a vehicle body and horizontally disposed on a front portion of the vehicle body. Power is transmitted from the engine through a transmission.

  As shown in FIG. 1, the differential device 10 is rotatably supported by a housing 1 of a transmission via a bearing 2 and is housed in the housing 1. The differential device 10 includes a diff ring gear 20 as a power transmission gear that meshes with an output gear 3 that is an output portion of a transmission, and a differential case 30 coupled to the diff ring gear 20. The diff ring gear 20 and the differential case 30 are integrated. Is formed.

  The differential device 10 also includes a differential mechanism 40 housed in the differential case 30, and the differential mechanism 40 is fixed to the differential case 30 and extends in a direction perpendicular to the vehicle width direction, and is freely rotatable on the pinion shaft 41. And a pair of left and right side gears 43 meshing with the pair of pinion gears 42.

  The side gear 43 is spline-fitted with the left and right axles 4 respectively fitted to the differential ring gear 20 and the differential case 30, and the axle 4 is attached to the differential ring gear 20 and the differential case 30 together with the side gear 43. Relative rotation is possible.

  The differential device 10 is provided in a power transmission path from the engine to the front wheels, and transmits the power transmitted from the engine via the transmission to the left and right axles 4 so as to have a rotational difference according to the traveling situation. It is transmitted to the left and right front wheels.

  In the housing 1, lubricating oil is stored at the bottom of the housing 1, and the lubricating oil storage level OL is set so that the tooth portion 21 located below the diff ring gear 20 is immersed in the lubricating oil. . As a result, when the diff ring gear 20 rotates, the lubricating oil is lifted up by the teeth 21 of the diff ring gear 20, and the lubricating oil is supplied to the required lubrication portions such as the meshing portion 5 between the def ring gear 20 and the output gear 3. It is like that.

  2 is a perspective view of a differential ring gear and a differential case of the differential device, FIG. 3 is a side view of the differential ring gear and the differential case, and FIG. 4 is a diagram showing the differential ring gear and the differential case as viewed from the Y4 direction in FIG. 5 is a cross-sectional view of the differential ring gear and the differential case along line Y5-Y5 in FIG.

  As shown in FIGS. 2 to 5, the differential case 30 includes a shell portion 31 that is formed in a substantially spherical shape and accommodates the differential mechanism 40 therein. The shell portion 31 is provided with a window hole 32 for accommodating the pinion gear 42 and the side gear 43 constituting the differential mechanism 40 at a 180 ° symmetrical position, and is formed in a substantially cylindrical shape on both the left and right sides corresponding to the side gear 43. An axle insertion portion 33 is provided. The axle 4 is inserted through the axle insertion portion 33.

  The differential case 30 is also provided with reinforcing ribs 34 that connect the differential case 30 and the differential ring gear 20. In the present embodiment, four reinforcing ribs 34 extending in the axial direction along the shell portion 31 are provided on both sides of the two window holes 32 provided in the shell portion 31 of the differential case 30.

  As shown in FIG. 4, the differential ring gear 20 coupled to the differential case 30 includes a tooth portion 21 that protrudes from the root circle L1 toward the outer peripheral side, and the tooth portion 21 is provided so as to extend in the axial direction of the differential ring gear 20. It has been. The differential ring gear 20 is a helical gear in which the tooth trace of the tooth portion 21 has a predetermined twist angle with respect to the axial direction of the differential ring gear 20, and the output gear 3 that meshes with the differential ring gear 20 also has a tooth trace in the axial direction of the output gear. In contrast, a helical gear having a tooth portion having a predetermined twist angle is used.

  As shown in FIG. 5, the differential ring gear 20 includes an outer peripheral portion 22 provided with a tooth portion 21, and an inner peripheral portion 24 provided on the radially inner side of the outer peripheral portion 22 and communicated with the shell portion 31 of the differential case 30. And side portions 26 on both sides for connecting the outer peripheral portion 22 and the inner peripheral portion 24 on both sides in the axial direction of the diff ring gear 20 so as to close the space between the outer peripheral portion 22 and the inner peripheral portion 24. Yes.

  In the present embodiment, a part of the shell portion 31 of the differential case 30 also serves as the inner peripheral portion 24 of the differential ring gear 20, and the inner peripheral portion 24 of the differential ring gear 20 and the shell portion 31 of the differential case 30 are communicated. Further, on one side surface portion 26 of the differential ring gear 20, a coupling portion 35 that is a portion to which a reinforcing rib 34 provided on the differential case 30 is coupled is provided.

  6 is a cross-sectional view of the diff ring gear and the differential case along line Y6-Y6 in FIG. 3, FIG. 7 is a cross-sectional view of the diff ring gear and the differential case along line Y7-Y7 in FIG. 3, and FIG. FIG. 9 is a cross-sectional view of the differential ring gear and the differential case showing the portion A in FIG. 7 in an enlarged manner, and FIG.

  As shown in FIG. 6, in the outer peripheral portion 22 of the diff ring gear 20, a plurality of, in the present embodiment, three circumferentially extending cavity portions 51 extending in the circumferential direction on the inner peripheral side of the root circle L <b> 1. Is provided. The three circumferentially extending cavities 51 have the same length in the circumferential direction of the diffring gear 20, and are arranged at equal intervals in the circumferential direction of the diffring gear 20. The three circumferentially extending cavities 51 have the same length in the radial direction and the axial direction of the diffring gear 20 and are formed in the same shape.

  In the diff ring gear 20, the three circumferentially extending hollow portions 51 have the same length in the circumferential direction and are arranged at equal intervals in the circumferential direction, so that the circumferential portion of the diff ring gear 20 is circumferentially disposed on the outer circumferential portion 22. A low-rigidity portion 23a, which is a portion where the direction extending cavity portion 51 is provided, and a high-rigidity portion 23b, which is a portion where the circumferential direction extending cavity portion 51 is not provided, are formed.

  As shown in FIG. 6, the diff ring gear 20 also includes a plurality of members that connect the outer peripheral portion 22 and the inner peripheral portion 24 to the inside of the diff ring gear 20 radially inward of the outer peripheral portion 22 and connect the side surface portions 26 on both sides. In this embodiment, four connecting portions 28 are provided.

  The four connecting portions 28 are provided so as to extend in the radial direction between the outer peripheral portion 24 and the inner peripheral portion 24 and to extend in the axial direction between the side surface portions 26 on both sides, and have a predetermined width in the circumferential direction. They are spaced apart in the circumferential direction. The four connecting portions 28 correspond to the connecting portions 35 of the reinforcing ribs 34 on the side surface portion 26 of the diff ring gear 20, and are connected to the portion 35 where the reinforcing ribs 34 are connected to the side surface portion 26 of the diff ring gear 20 from the anti-reinforcing rib side. It is connected.

  The connecting portion 28 divides a space closed by the outer peripheral portion 22, the inner peripheral portion 24 and the side surface portions 26 on both sides of the diff ring gear 20 in the circumferential direction, and the diff ring gear 20 has a radially inner side from the outer peripheral portion 22. Inside the diff ring gear 20, an inter-connection cavity 52 is defined by the outer peripheral part 22, the inner peripheral part 24, the side part 26 and the connection part 28.

  Inside the outer peripheral portion 22 of the diff ring gear 20, as shown in FIGS. 6 to 9, a root circular outer cavity 53 extending in the axial direction of the def ring gear 20 on the outer peripheral side from the root circle L 1, and a root circle A root circle inner cavity portion 54 extending in the axial direction of the diff ring gear 20 on the inner peripheral side from L1 is provided. The root circular outer cavity portion 53 and the tooth root circular inner cavity portion 54 are provided on the outer peripheral side of the outer peripheral portion 20 relative to the circumferentially extending cavity portion 51.

  As shown in FIG. 9, the root circular outer cavity portion 53 is a tooth that is provided inside the tooth portion 21 and is a dangerous cross section of the diff ring gear 20 where stress is concentrated when power is transmitted via the def ring gear 20. It is formed so as to ensure the thickness of the bottom fillet portion 21a.

  The root circle outer cavity portion 53 is provided on the outer peripheral side with a predetermined thickness or more from the tooth bottom circle L1, and is provided on the inner side with a predetermined thickness or more from the tooth surface, the tooth tip, and both end surfaces of the tooth portion 21. In the cross section orthogonal to the axial direction, the triangular shape is formed so as to taper off toward the tooth tip side of the tooth portion 21 along the tooth surface of the tooth portion 21. In addition, you may make it form the root bottom outer side cavity part 53 in a trapezoid shape in a taper shape toward the tooth tip side of the tooth part 21 along the tooth surface of the tooth part 21. As shown in FIG.

  As shown in FIG. 9, the thickness of the bottom fillet portion 21a which is a dangerous cross section of the diff ring gear 20 where stress is concentrated when power is transmitted via the def ring gear 20 also for the root bottom inner cavity portion 54. It is formed to ensure.

  The root circle inner cavity portion 54 is provided inside the outer peripheral portion 22 and is provided on the inner peripheral side with a predetermined thickness or more from the root circle L1, and is provided on the outer peripheral side with a predetermined thickness or more from the circumferentially extending cavity portion 51. In addition, the outer peripheral portion 22 is provided on the inner side by a predetermined thickness or more from both end faces.

  Specifically, the root-bottom-side inner cavity portion 54 is formed in a triangular shape that tapers toward the inner peripheral side of the diffring gear 20 in a cross section orthogonal to the axial direction of the diffring gear 20. The cavity part 54a and the 2nd bottom-bottom circle inner side cavity part 54b which is formed in a triangular shape in a taper shape as it goes to the outer peripheral side of the differential ring gear 20 are provided. The first tooth bottom circle inner cavity portion 54a and the second tooth bottom circle inner cavity portion 54b are alternately arranged at a predetermined interval in the circumferential direction of the diff ring gear 20 on the inner peripheral side of the tooth root circle L1. .

  In addition, the first root bottom inner cavity portion 54 a is formed in a trapezoidal shape so as to taper toward the inner peripheral side of the diffring gear 20, and the second root bottom circle inner cavity portion 54 b is formed on the outer peripheral side of the diffring gear 20. You may make it form in a trapezoid shape in a taper shape as it goes.

  FIG. 10 is a developed cross-sectional view of the outer peripheral portion of the diff ring gear along the line Y10a-Y10a in FIG. In FIG. 10, the root-bottom circle inner cavity portion 54 provided inside the outer peripheral portion 22 of the diffring gear 20 along the line Y10b-Y10b in FIG. 8 is also indicated by a broken line.

  As shown in FIG. 10, the outer root circular cavity portion 53 is provided so as to extend in the direction of the tooth trace of the tooth portion 21, and the inner root root cavity portion 54, specifically, the first root circular inner cavity portion. 54a and the root bottom inner cavity portion 54b are provided so as to extend in a direction crossing the tooth trace direction of the tooth portion 21.

  In the present embodiment, the root bottom outer cavity portion 53 has a predetermined twist angle with respect to the axial direction of the diff ring gear 20, similarly to the tooth trace of the tooth portion 21, and the root bottom circle inner cavity portion 54 is A predetermined torsion angle is provided on the opposite side to the bottom circular outer cavity portion 53 with respect to the axial direction of the diff ring gear 20.

  Thus, in the inside of the differential ring gear 20, in the order from the radially inner side to the radially outer side, the inter-connection portion cavity portion 52, the circumferentially extending cavity portion 51, the root circular inner cavity portion 54, and The root bottom outer cavity 53 is disposed.

  In the differential ring gear 20, the inter-connection portion cavity portion 52, the circumferentially extending cavity portion 51, the root bottom inner cavity portion 54, specifically, the first bottom bottom circle inner cavity portion 54 a and the second bottom bottom circle inner cavity The portion 54b and the root bottom outer cavity portion 53 communicate with the outside of the diff ring gear 20, respectively.

  As shown in FIG. 5, a first communication hole 61 is formed in one side surface portion 26 of the diff ring gear 20 to communicate the inter-connection portion cavity portion 52 with the outside of the diff ring gear 20. The first communication hole portion 61 is provided corresponding to the inter-connection portion cavity portion 52, and as shown in FIG. 4, a plurality of first communication hole portions 61 are arranged on a circumference having substantially the same radius.

  Further, as shown in FIG. 8, the outer peripheral portion 22 of the diff ring gear 20 has a second communication hole portion that extends in the radial direction and communicates the inter-connecting portion cavity portion 52 and the circumferentially extending cavity portion 51. 62, a third communicating hole 63 extending in the radial direction and communicating with the circumferentially extending cavity 51 and the second root bottom inner cavity 54b of the root inner cavity 54, and extending in the circumferential direction A fourth communication hole 64 communicating the first root bottom inner cavity portion 54a and the second root bottom inner cavity portion 54b of the adjacent root bottom inner cavity portion 54; A fifth communication hole 65 is formed which communicates the first root bottom inner cavity 54 a and the bottom root outer cavity 53 of the cavity 54.

  The outer peripheral portion 22 of the diffring gear 20 also has a sixth communication hole that extends in the radial direction to the tooth portion 21 and communicates the root bottom outer cavity portion 53 and the tooth tip that is a part of the outer peripheral surface of the diffring gear 20. A portion 66 is formed.

  Accordingly, the inter-connection portion cavity portion 52, the circumferentially extending cavity portion 51, the tooth root circle inner cavity portion 54, and the tooth bottom circle outer cavity portion 53 that are provided inside the differential ring gear 20 are the first communication hole portion 61, The second communication hole 62, the third communication hole 63, the fourth communication hole 64, the fifth communication hole 65, and the sixth communication hole 66 communicate with the outside of the differential ring gear 20. .

  As shown in FIG. 9, the sixth communication hole 66 formed in the tooth portion 21 of the diff ring gear 20 is not limited to this, but the sixth communication hole 66 disposed on one side in the axial direction of the diff ring gear 20. A communication hole 66, a sixth communication hole 66 disposed on the axially central side of the diff ring gear 20, and a sixth communication hole 66 disposed on the other axial side of the diff ring gear 60 are provided.

  As shown in FIG. 10, the fifth communication hole portion 65 that communicates the root bottom outer cavity portion 53 and the first root bottom inner cavity portion 54a is not limited to this, but the diff ring gear 20 is not limited thereto. A fifth communication hole 65 disposed on one side in the axial direction, a fifth communication hole 65 disposed on the center side in the axial direction of the diff ring gear 20, and a fifth communication hole disposed on the other side in the axial direction of the diff ring gear 60. 5 communication holes 65 are provided.

  The 4th communicating hole part 64 which connects the 1st tooth bottom circle inside cavity part 54a and the 2nd tooth bottom circle inside cavity part 54b, and the circumferential direction extension cavity part 51 and the tooth root circle inside cavity part 54 are connected. The third communication hole 63 is also provided with communication holes 64 and 63 disposed on one side in the axial direction, the central side in the axial direction, and the other side in the axial direction of the diff ring gear 20.

  In the present embodiment, the inter-connection portion cavity portion 52 is used as a lubricating oil storage portion that stores lubricating oil, and the sixth communication hole portion 66 communicates with the inter-connection portion cavity portion 52 to connect the inter-connection portion cavity portion 52. Is used as a lubricating oil discharge hole for discharging the lubricating oil stored in the differential ring gear 20 from the outer peripheral surface, and the first communication hole 61 is a cavity between the connecting parts on the radially inner side from the outer peripheral part 22 of the differential ring gear 20. 52 is used as a lubricating oil introduction hole that communicates with 52 and introduces lubricating oil into the inter-connection portion cavity 52.

  The sixth communication hole 66 includes a root bottom outer cavity 53, a fifth communication hole 65, a first bottom circle inner cavity 54a, a fourth communication hole 64, a second root bottom inner cavity 54b, The third communicating hole 63, the circumferentially extending cavity 51, and the second communicating hole 62 are communicated with the inter-connection cavity 52.

  As shown in FIG. 1, in the vehicle equipped with the differential device 10, the lubricating oil storage level OL is such that the tooth portion 21 located at the lower portion provided on the outer peripheral portion 22 of the diffring gear 20 is located below the liquid level. At the same time, the first communication hole 61 provided in the side surface portion 26 of the diff ring gear 20 is set to be positioned below the liquid level.

  Thus, when the lubricating oil is introduced into the inter-connection portion cavity portion 52 of the diff ring gear 20 through the first communication hole portion 61 and the lubricating oil is stored in the inter-connection portion cavity portion 52 and the diff ring gear 20 is rotated, Lubricating oil stored in the inter-connection portion cavity portion 52 is discharged from the outer peripheral surface of the diff ring gear 20 through the sixth communication hole portion 66, and lubricates a lubrication required portion such as the meshing portion 5 between the def ring gear 20 and the output gear 3. Oil is supplied.

Here, the noise reduction effect by the differential ring gear 20 of the differential apparatus 10 is demonstrated.
FIG. 11 is a graph showing the compliance with respect to the frequency of the diff ring gear and the output gear. In FIG. 11, the frequency is plotted on the horizontal axis, and the compliance, which is the amount of displacement in the tooth contact direction of the diff ring gear 20 and the output gear 3 meshing with each other, is plotted on the vertical axis, and the compliance characteristics of the diff ring gear 20 and the output gear 3 are shown. The tooth contact direction refers to the normal direction of each tooth surface at a contact point between the tooth surface of the tooth portion of the differential ring gear and the tooth surface of the tooth portion of the output gear.

  In FIG. 11, the compliance with respect to the frequency of the diff ring gear 20 is indicated by a broken line D1, and the compliance with respect to the frequency of the output gear 3 is indicated by an alternate long and short dash line D2. Further, in FIG. 11, the inter-connecting portion cavity 51 and the second root bottom circle inside instead of the second communicating hole 62 and the third communicating hole 63 without providing the circumferentially extending cavity 51 in the differential ring gear 20. For a diff ring gear provided with a communication hole that communicates with the cavity 54b, the compliance with respect to frequency is indicated by a solid line D3.

  As shown in FIG. 11, the compliance D2 with respect to the frequency of the output gear 3 has a peak at the predetermined frequency f1, a peak at the predetermined frequency f2 higher than the frequency f1, and as it goes away from the frequency f1 toward the lower frequency side. The compliance becomes smaller and the compliance becomes larger as the frequency f2 moves away from the higher frequency side, and the frequency f1 and the frequency f2 tend to increase from a decreasing tendency to a predetermined frequency as a boundary.

  On the other hand, the compliance D3 with respect to the frequency of the diff ring gear provided with the communication hole portion that connects the inter-connection portion cavity portion 51 and the second root bottom inner cavity portion 54b without providing the circumferentially extending cavity portion 51 has a frequency f1. And the frequency f2 has a peak at a predetermined frequency f3, and the compliance decreases as the distance from the frequency f3 increases on the low frequency side and the high frequency side.

  On the other hand, the compliance D1 with respect to the frequency of the differential ring gear 20 provided with the circumferentially extending cavity 51 has a peak at the frequency f4 on the lower frequency side than the frequency f3, and the frequency f5 on the higher frequency side than the frequency f3. And has a peak between the frequency f4 and the frequency f5.

  Thus, in the differential ring gear 20, by providing the circumferentially extending cavity portion 51, the low rigidity portion 23a in which the circumferentially extending cavity portion 51 is provided in the circumferential direction and the circumferentially extending cavity portion 51 are provided. The peak at the predetermined frequency f3 of the compliance of the diff ring gear that is not formed with the high-rigidity portion 23b and is not formed with the circumferentially extending cavity 51 and the peak at the low-frequency side frequency f4 due to the low-rigidity portion 23a The base is widened by being distributed to the peak at the frequency f5 on the high frequency side by the portion 23b.

  Accordingly, the compliance with respect to the frequency of the diff ring gear and the compliance with respect to the frequency of the output gear are higher than the intersection X1 on the lower frequency side than the frequency f3 and the frequency f3 in the diff ring gear in which the circumferentially extending cavity 51 is not provided. In contrast to the frequency-side intersection X2, in the diff ring gear 20 provided with the circumferentially extending cavity 51, the intersection X1 ′ on the lower frequency side than the frequency f4 and the intersection X2 ′ on the higher frequency side than the frequency f5. In the diff ring gear 20, the intersection between the compliance of the diff ring gear 20 and the compliance of the output gear 3 is changed to an intersection with high compliance.

  The noise due to the meshing of the gears has a correlation with the compliance of the gears meshing with each other, and the smaller the sum of the compliances of the gears meshing with each other, the smaller the noise. Therefore, the compliance between the differential gear 20 and the compliance of the output gear 3 By changing the intersection to an intersection with high compliance, the sum of compliance can be increased, and noise due to meshing can be reduced.

  In the present embodiment, the three circumferentially extending cavities 51 are formed inside the outer peripheral portion 22 of the diff ring gear 20, but are not limited to the three circumferentially extending cavities 51, It is possible to form a circumferentially extending cavity. It is preferable that the circumferentially extending cavity portion 51 formed inside the outer peripheral portion 22 of the diff ring gear 20 is an odd number of circumferentially extending cavity portions 51.

  When the odd-numbered frequency extending cavities 51 are formed, the circumferential extending cavities 51 are provided at 180 degrees symmetrical positions of the portions located between the circumferential extending cavities 51, and the circumferential extending cavities are provided. Compared to the case where the even number of circumferentially extending cavities 51, which are parts positioned between the circumferentially extending cavities 51, are also formed in the 180-degree symmetrical position of the part located between 51, the diffring gear 20. Compliance characteristics can be accurately adjusted.

  In the differential device 10 configured as described above, the differential ring gear and the differential case 20 are integrally formed by a three-dimensional additive manufacturing method using a 3D printer, and the differential ring gear 20 includes a root circle L1 inside. A plurality of circumferentially extending cavities 51 having the same length in the circumferential direction are integrally formed on the inner circumferential side by a three-dimensional additive manufacturing method so as to be arranged at equal intervals in the circumferential direction.

  Further, the differential ring gear 20 includes an outer peripheral portion 22 provided with a tooth portion 21, an inner peripheral portion 24 connected to the shell portion 31 of the differential case 30, and the outer peripheral portion 22 and the inner peripheral portion 24 on both sides in the axial direction. The diff ring gear 20 has a plurality of connecting portions 28 in the circumferential direction that connect the outer peripheral portion 22 and the inner peripheral portion 24 and connect the side surface portions 26 on both sides. In addition, it is integrally formed by a three-dimensional additive manufacturing method so that a cavity 52 between the connecting parts defined by the outer peripheral part 22, the inner peripheral part 24, the side face part 26 and the connecting part 28 is provided.

  Further, the diff ring gear 20 is provided with a tooth bottom circle outer cavity 53 extending in the axial direction of the def ring gear 20 on the outer peripheral side of the root circle L1 inside the tooth portion 21, and at the inside of the outer peripheral portion 22. It is integrally formed by a three-dimensional additive manufacturing method so that a root circle inner cavity portion 54 extending in the axial direction of the diff ring gear 20 is provided on the inner peripheral side from L1.

  Further, the diff ring gear 20 includes a connecting portion cavity 52, a circumferentially extending cavity 51, a root circular inner cavity 54, and a root circular outer cavity 53 formed in the differential ring gear 20 in the first portion. It communicates with the outside of the diff ring gear 20 through the communication hole 61, the second communication hole 62, the third communication hole 63, the fourth communication hole 64, the fifth communication hole 65, and the sixth communication hole 66. Thus, it is integrally formed by the three-dimensional additive manufacturing method.

  The specific printing method in the three-dimensional additive manufacturing method is not particularly limited. However, when a metal such as iron is used as the material of the diff ring gear 20 and the differential case 30, for example, an electron can be placed at an arbitrary position on the spread metal powder layer. By irradiating a beam or a laser, the irradiated portion is sintered and shaped, and then a powder sintering layered shaping method that repeats an operation of spreading the next layer may be employed. After the differential ring gear 20 and the differential case 30 are formed by the three-dimensional additive manufacturing method, the tooth surface can be finished.

  When the differential ring gear 20 and the differential case 30 are formed by a three-dimensional additive manufacturing method, the inter-connection portion cavity portion 52, the circumferentially extending cavity portion 51, the root bottom inner cavity portion 54, and the teeth that are formed inside the differential ring gear 20 are formed. The bottom circular outer cavity portion 53 is formed with a communication hole portion communicating with the outside of the diff ring gear 20 in order to remove the metal powder provided in the portions corresponding to the cavity portions 52, 51, 54, 53. In the present embodiment, the metal powder provided in the portions corresponding to the cavities 52, 51, 54, 53 is the first communication hole 61, the second communication hole 62, the third communication hole 63, and the fourth communication. It is removed to the outside of the diff ring gear 20 through the hole 64, the fifth communication hole 65, and the sixth communication hole 66.

  In the present embodiment, the first communication hole portion 61 for introducing the lubricating oil into the inter-connection portion cavity portion 52 is provided on the side surface portion 26 of the differential ring gear 20, but instead of the first communication hole portion 61, or In addition to the first communication hole portion 61, as a lubricating oil introduction hole portion that communicates with the inter-connection portion cavity portion 52 radially inside the outer peripheral portion 22 of the diff ring gear 20 and introduces the lubricating oil into the inter-connection portion cavity portion 52. The portion of the shell portion 31 of the differential case 30 that also serves as the inner peripheral portion 24 of the differential ring gear 20 (indicated by reference numeral 61 ′ in FIG. 5) has a communication hole portion that communicates the inside of the shell portion 31 with the inter-connection portion cavity portion 52. It is also possible to provide it.

  In such a case, when the diff ring gear 20 is rotated, a part of the lubricating oil swept up by the tooth portion 21 of the diff ring gear 20 is introduced into the shell portion 31 of the diff case 30 and introduced into the shell portion 31. The lubricating oil thus introduced is introduced into the inter-connection portion cavity 52 through a communication hole that communicates the inside of the shell portion 31 with the inter-connection portion cavity 52.

  In the present embodiment, the root circular outer cavity 53 and the root circular inner cavity 54 are provided inside the outer peripheral portion 22 of the diff ring gear 20. It is also possible to provide only one of 53 and the inner root part cavity part 54, or not to provide both the outer root part cavity part 53 and the inner root part cavity part 54.

  Even when only one of the root root outer cavity portion 53 and the tooth root inner cavity portion 54 is provided, or when neither the tooth root outer cavity portion 53 nor the tooth root inner cavity portion 54 is provided, the diff ring gear 20 is provided. In particular, there are a lubricating oil discharge hole portion that communicates with the inter-connection portion cavity portion 52 and discharges the lubricating oil stored in the inter-connection portion cavity portion 52 from the outer peripheral surface of the diff ring gear 20, and an outer peripheral portion 22 of the diff ring gear 20. Lubricating oil introduction holes that communicate with the inter-connecting portion cavity 52 and introduce the lubricating oil into the inter-connecting portion cavity 52 are provided on the radially inner side.

  Further, in the present embodiment, the sixth communication hole portion 66 as a lubricating oil discharge hole portion provided in the diff ring gear 20 is formed so as to communicate with a tooth tip that is a part of the outer peripheral surface of the diff ring gear 20. However, it may be provided so as to communicate with the tooth bottom that is a part of the outer peripheral surface of the diff ring gear 20.

  Further, in the present embodiment, the inter-connection portion cavity portion 52 is used as a lubricating oil reservoir, and the first communication hole 61 is set to be lower than the lubricating oil storage level OL. It is also possible to set the portion 61 further radially inward so as to be above the lubricating oil storage level OL so that the inter-connection portion cavity portion 52 is not used as the lubricating oil storage portion.

  As described above, in the power transmission gear 20 according to the present embodiment, a plurality of hollow portions 51 having the same length in the circumferential direction are arranged at equal intervals in the circumferential direction on the inner circumferential side of the root circle L1. Yes. As a result, a low-rigidity portion 23a provided with a cavity 51 in the circumferential direction of the power transmission gear 20 and a high-rigidity portion 23b provided with no cavity 51 are formed, and the power without the cavity 51 formed. The peak at the predetermined frequency of the compliance of the transmission gear 20 is distributed to the low frequency side peak P1a by the low rigidity portion 23a and the high frequency side peak P1b by the high rigidity portion 23b to widen the skirt, and the compliance of the counterpart gear 3 Therefore, noise due to meshing can be reduced.

  By appropriately setting the size of the cavity 51 arranged in the circumferential direction of the power transmission gear 20, the compliance peak of the power transmission gear 20 is appropriately adjusted to the peak on the low frequency side and the peak on the high frequency side. Accordingly, the base can be widened and the noise caused by the meshing can be effectively reduced.

  Further, by providing a plurality of hollow portions 51 in the power transmission gear 20, the weight can be reduced by the hollow portions 51, and the power transmission teeth 20 are stored in the housing 1 together with the lubricating oil. In this case, the rotational resistance of the power transmission gear 20 is not increased. Therefore, noise can be reduced and weight can be reduced without increasing the rotational resistance of the power transmission gear 20.

  The power transmission gear 20 includes an outer peripheral portion 22 provided with a tooth portion 21 and an inner peripheral portion 24 communicated with a shell portion 31 of a differential case 30 that houses a differential mechanism 40, and includes a plurality of hollow portions. 51 is provided on the inner peripheral side of the root circle L <b> 1 inside the outer peripheral portion 20, so that noise due to the meshing of the power transmission gear 20 can be effectively reduced.

  The power transmission gear 20 is a diff ring gear, and includes an outer peripheral portion 22, an inner peripheral portion 24 connected to a shell portion 31 of the differential case 30, and side portions 26 on both sides. In addition, a plurality of connecting portions 28 that connect the outer peripheral portion 22 and the inner peripheral portion 24 and connect the side surface portions 26 on both sides are provided in the circumferential direction.

  A plurality of first cavities 51 having the same length in the circumferential direction and arranged at equal intervals in the circumferential direction are provided on the inner circumferential side of the root circle L1 inside the outer circumferential portion 22, and the outer circumferential portion 22 is provided. A second cavity portion 52 defined by the outer peripheral portion 22, the inner peripheral portion 24, the side surface portion 26, and the connecting portion 28 is provided inside the differential ring gear 20 on the radially inner side.

  By providing the plurality of first cavities 51 inside the outer peripheral portion 22 of the diff ring gear 20, when the def ring gear 20 is housed together with the lubricating oil in the housing 1, without increasing the rotational resistance of the def ring gear 20. Noise reduction and weight reduction can be achieved.

  In addition, while the strength and rigidity of the diffring gear 20 are secured by the connecting portion 28 provided inside the diffring gear 20, the weight can be reduced by the second cavity 52 provided inside the diffring gear 20. By providing the second cavity 52 inside the diff ring gear 20, when the def ring gear 20 is housed in the housing 1 together with the lubricating oil, the strength of the diff ring gear 20 and the rotation resistance of the def ring gear 20 are not increased. It is possible to further reduce the weight while ensuring the rigidity.

  A plurality of reinforcing ribs 34 provided in the differential case 30 are coupled to the side surface portion 26 of the differential ring gear 20, and the connecting portion 28 corresponds to a portion 35 in which the reinforcing ribs 34 are coupled to the side surface portion 26 of the differential ring gear 20. By connecting to the side surface portion 26, the strength and rigidity of the diff ring gear 20 can be increased.

  The second cavity 52 is used as a lubricating oil reservoir that stores lubricating oil. The lubricating oil stored in the second cavity 52 in communication with the second cavity 52 is communicated with the diffring gear 20 from the diffring gear. Lubricating oil discharge holes 66 that are discharged from the outer peripheral surface 20 are provided. As a result, the second cavity 52 provided inside the diff ring gear 20 is used to store lubricating oil to supply lubricating oil to the lubrication required parts such as the meshing portion 5 between the diff ring gear 20 and the gear 3 meshing with the diff ring gear 20. It can be used effectively as a part.

  Further, the three-dimensional additive manufacturing method is used for the power transmission gear 20 so that a plurality of hollow portions 51 having the same length in the circumferential direction are arranged at equal intervals in the circumferential direction on the inner circumferential side of the root circle L1. By using the three-dimensional additive manufacturing method, it is possible to manufacture the power transmission gear 20 that can reduce noise and reduce weight without increasing rotational resistance.

  The present invention is not limited to the illustrated embodiments, and various improvements and design changes can be made without departing from the scope of the present invention.

  As described above, according to the present invention, it is possible to reduce noise and reduce the weight without increasing the rotational resistance of the power transmission gear. Therefore, the differential gear of the differential device mounted on the vehicle, etc. In the case of manufacturing a power transmission gear, there is a possibility of being suitably used in the vehicle manufacturing industry.

DESCRIPTION OF SYMBOLS 1 Housing 3 Output gear 5 Engagement part 10 Differential apparatus 20 Differential ring 21 Tooth part 22 Outer peripheral part 24 Inner peripheral part 26 Side part 28 Connection part 30 Differential case 31 Shell part 34 Reinforcement rib 40 Differential mechanism 51 Circumferentially extending cavity part (first 1 cavity)
52 Cavity between connecting parts (second cavity)
53 Tooth root outer cavity portion 54 Tooth root inner cavity portion 61, 62, 63, 64, 65, 66 Communication hole L1 Tooth root circle

Claims (5)

A power transmission gear housed together with lubricating oil in a housing and provided with a tooth portion protruding from the root circle to the outer peripheral side on the outer peripheral portion,
A plurality of cavities having the same length in the circumferential direction on the inner circumferential side of the root circle are arranged at equal intervals in the circumferential direction ,
The power transmission gear includes the outer peripheral portion and an inner peripheral portion that is in communication with a shell portion of a differential case that houses the differential mechanism.
The plurality of hollow portions are provided on the inner peripheral side of the root circle inside the outer peripheral portion,
The power transmission gear is a differential ring gear coupled to a differential case, the outer peripheral portion, an inner peripheral portion connected to a shell portion of the differential case that houses a differential mechanism, the outer peripheral portion, and the inner peripheral portion, And side portions on both sides for connecting the two sides on both sides in the axial direction,
A plurality of connecting portions for connecting the outer peripheral portion and the inner peripheral portion with a predetermined width in the circumferential direction and connecting the side portions on both sides are provided in the circumferential direction inside the differential ring gear,
A plurality of first cavities having the same length in the circumferential direction and arranged at equal intervals in the circumferential direction are provided on the inner circumferential side of the root circle inside the outer circumferential portion,
The differential ring gear is formed integrally with the differential case,
The first hollow portion is provided at a position overlapping the tooth portion and the axial direction of the diff ring gear,
A power transmission gear characterized by that. Inside diameter said at inward differential ring gear than the previous Kigaishu portion, the outer peripheral portion, the inner peripheral portion, the second cavity being defined by the side portion and the connecting portion is provided,
The power transmission gear according to claim 1 . A plurality of reinforcing ribs provided on the differential case are coupled to the side surface portion of the differential ring gear,
The connecting portion is connected to the side surface portion corresponding to a portion where the reinforcing rib is coupled to the side surface portion of the differential ring gear.
The power transmission gear according to claim 2 . The second cavity is used as a lubricating oil reservoir that stores lubricating oil,
The differential ring gear is provided with a lubricant discharge hole that communicates with the second cavity and releases the lubricant stored in the second cavity from the outer peripheral surface of the differential ring gear.
The power transmission gear according to claim 2 or claim 3 , wherein A method of manufacturing a power transmission gear that is housed together with lubricating oil in a housing and provided with a tooth portion that protrudes from the root circle to the outer peripheral side on the outer peripheral portion,
A plurality of hollow portions having the same length in the circumferential direction are arranged at equal intervals in the circumferential direction on the inner circumferential side of the root circle, and the power transmission gear accommodates the outer circumferential portion and the differential mechanism. An inner peripheral portion communicated with a shell portion of the differential case, wherein the plurality of hollow portions are provided on an inner peripheral side of the root circle inside the outer peripheral portion, and the power transmission gear is provided in the differential case. A differential ring gear coupled to the outer peripheral portion, the inner peripheral portion connected to the shell portion of the differential case housing the differential mechanism, and the outer peripheral portion and the inner peripheral portion connected to each other on both sides in the axial direction. A connecting portion for connecting the outer peripheral portion and the inner peripheral portion with a predetermined width in the circumferential direction and connecting the side portions on the both sides. Provided in a plurality in the circumferential direction, A plurality of first cavities having the same length in the circumferential direction and arranged at equal intervals in the circumferential direction are provided on the inner circumferential side of the root circle inside the circumferential portion, and the differential ring gear includes the differential case The power transmission gear is formed by a three-dimensional additive manufacturing method so that the first cavity is provided at a position overlapping the tooth portion and the axial direction of the diff ring gear .
A method for manufacturing a power transmission gear.

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