case

Abstract

To reduce an inclination of an output shaft to reduce a load applied to an annular part.SOLUTION: A case including a driving force transmission device has: an end surface provided with an annular part and a plurality of ribs extending radially around the annular part, and a bottom surface provided with an opening part and connected to the end surface. The plurality of ribs has a pair of ribs facing each other with respect to the center of the annular part. The end surface has a first region on the bottom side with respect to the pair of ribs, and a second region on the opposite side of the first region with respect to the pair of ribs. The rigidity of the pair of ribs is higher than the rigidity of the other ribs, and the rigidity of the second region of the end surface is lower than the rigidity of the first region.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a case. [Background technology]

[0002] Patent Document 1 discloses a case that houses a driving force transmission device. An annular portion is provided on an end face of the case. An output shaft connected to the driving force transmission device inside the case is inserted into the annular portion.

[0003] An opening is provided in the bottom surface, which is the area below the peripheral wall of the case. For example, a member for connecting a component inside the case to a component outside the case is inserted through the opening. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-047230 Summary of the Invention [Problem to be solved by the invention]

[0005] When the output shaft rotates, a load acts on the annular portion that supports the output shaft in the direction of the rotation axis of the output shaft. The load is also transmitted to the end face of the case that supports the annular portion and to the peripheral wall surface that is connected to the end face. An opening is provided in the bottom surface of the peripheral wall. Therefore, the bottom surface has lower rigidity than the top surface of the peripheral wall. In other words, when a load is applied in the direction of the rotation axis, the lower region of the end surface connected to the bottom surface is more likely to deform than the upper region of the end surface connected to the top surface. If the lower area of ​​the end face deforms more than the upper area, the output shaft supported by the annular portion may tilt. If the output shaft rotates while tilted, the load on the annular portion increases in that area.

[0006] In the case, it is required to reduce the inclination of the output shaft and reduce the load on the annular portion. [Means for solving the problem]

[0007] In one aspect of the present invention, The driving force transmission device is installed inside the vehicle. an end surface provided with a circular ring portion and a plurality of ribs extending radially from the circular ring portion; a bottom surface having an opening and connected to the end surface; the plurality of ribs include a pair of ribs facing each other with respect to the center of the annular portion, the end surface has a first region on the bottom surface side with respect to the pair of ribs and a second region on the opposite side of the pair of ribs from the first region, The rigidity of the pair of ribs is higher than the rigidity of the other ribs, The second region of the end face has a lower rigidity than the first region. [Effects of the Invention]

[0008] According to one aspect of the present invention, the tilt of the output shaft can be reduced, thereby reducing the load applied to the annular portion. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating a driving force transmission device. [Figure 2] FIG. 2 is a view of the transmission case as seen from the rear side of the vehicle. [Figure 3] FIG. 3 is a cross-sectional view taken along line AA in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line BB in FIG. [Figure 5] FIG. 5 is a view of the transmission case as seen from below. [Figure 6] FIG. 6 is a diagram illustrating the width of the rib. [Figure 7]FIG. 7 is a diagram illustrating the operation of the transmission case. [Figure 8] FIG. 8 is a diagram showing a comparative example. [Figure 9] FIG. 9 is a cross-sectional view of a transmission case according to the first modification. [Figure 10] FIG. 10 is a diagram showing the configuration of a horizontal rib according to the second modification. DETAILED DESCRIPTION OF THE INVENTION

[0010] In the following description, an example will be described in which a case according to an embodiment of the present invention is applied to a transmission case provided in a vehicle. In the following description, when a second element (component, part, etc.) is connected to a first element (component, part, etc.), a second element (component, part, etc.) is connected downstream of a first element (component, part, etc.), or a second element (component, part, etc.) is connected upstream of a first element (component, part, etc.), it means that the first element and the second element are connected so that power can be transmitted. The power input side is upstream, and the power output side is downstream. The first element and the second element may also be connected via another element (clutch, other gear mechanism, etc.).

[0011] "Overlapping when viewed from a predetermined direction" means that multiple elements are lined up in a predetermined direction, and is synonymous with "overlapping in a predetermined direction." Examples of the "predetermined direction" include the axial direction, radial direction, gravity direction, and vehicle travel direction (forward and backward directions). When a drawing shows multiple elements (components, parts, etc.) arranged in a specific direction, it may be assumed that the description in the specification contains a sentence explaining that they overlap when viewed from the specific direction.

[0012] "Not overlapping when viewed from a predetermined direction" and "offset when viewed from a predetermined direction" mean that multiple elements are not lined up in a predetermined direction, and are synonymous with "not overlapping in a predetermined direction" and "offset in a predetermined direction." Examples of the "predetermined direction" include the axial direction, radial direction, gravity direction, and vehicle travel direction (vehicle forward direction, vehicle backward direction). If a drawing shows that multiple elements (components, parts, etc.) are not aligned in a specified direction, it may be assumed that the description in the specification contains a sentence explaining that they do not overlap when viewed from a specified direction.

[0013] "When viewed from a predetermined direction, a first element (component, part, etc.) is located between a second element (component, part, etc.) and a third element (component, part, etc.)" means that when observed from a predetermined direction, it can be observed that the first element is located between the second element and the third element. "Predetermined direction" refers to an axial direction, a radial direction, the direction of gravity, the vehicle traveling direction (the vehicle forward direction, the vehicle backward direction), etc. For example, if the second element, the first element, and the third element are arranged in that order along the axial direction, the first element can be said to be located between the second element and the third element when viewed from the radial direction. If the drawings show that the first element is located between the second element and the third element when viewed from a predetermined direction, it can be considered that the description in the specification contains a sentence explaining that the first element is located between the second element and the third element when viewed from the predetermined direction.

[0014] When two elements (parts, sections, etc.) overlap when viewed in the axial direction, the two elements are coaxial.

[0015] "Axial direction" means the axial direction of the rotation axis of a component that constitutes the device. "Radial direction" means the direction perpendicular to the rotation axis of a component that constitutes the device. The component is, for example, a motor, a transmission, etc.

[0016] The present embodiment will be described below. FIG. 1 is a diagram illustrating a driving force transmission device. FIG. 2 is a view of the transmission case as seen from the rear side of the vehicle. FIG. 3 is a cross-sectional view taken along line AA in FIG. FIG. 4 is a cross-sectional view taken along line BB in FIG. FIG. 5 is a view of the transmission case as seen from below. 2 to 4, the ribs 47 are cross-hatched. In Fig. 5, the area of ​​the bottom surface 22 is hatched. Figs. 3 to 5 show only the rear side of the transmission case 1.

[0017] As shown in FIG. 1, the driving force transmission device 100 includes a torque converter TC, an input shaft IS, a transmission TM, and an output shaft OS.

[0018] In the driving force transmission device 100, a torque converter TC, an input shaft IS, a transmission TM, and an output shaft OS are provided along a transmission path of output rotation about a rotation axis X of an engine (not shown).

[0019] In the driving force transmission device 100, the output rotation of the engine is transmitted from the torque converter TC via the input shaft IS to the transmission TM. The speed of the output rotation transmitted to the transmission TM is changed by changing the combination of engagement / disengagement of multiple friction engagement elements (not shown) that make up the transmission TM. The output rotation, which has been changed in speed by the transmission TM, is transmitted to drive wheels of a vehicle (not shown) via an output shaft OS.

[0020] As shown in Figure 1, the torque converter TC is housed in a converter housing CH, and the transmission TM is housed in a transmission case 1 (case). The drawings show directions based on the state in which the transmission case 1 is installed on the vehicle. The rotation axis X direction is disposed along the vehicle longitudinal direction, which is perpendicular to the vertical line VL direction. One side of the rotation axis X direction (the left side in the drawings) is the front side of the vehicle, and the other side (the right side in the drawings) is the rear side of the vehicle. The direction perpendicular to the rotation axis X direction and the vertical line VL direction is called the vehicle width direction (see FIG. 2). In the following description, "upper" and "lower" refer to "upper" and "lower" in the direction of the vertical line VL. "Front" and "rear" refer to "front side of the vehicle" and "rear side of the vehicle" in the vehicle fore-and-aft direction (direction of the rotation axis X). "Inner peripheral side" and "outer peripheral side" refer to "radially inside of the rotation axis X" and "radially outside of the rotation axis X."

[0021] As shown in Figure 1, a converter housing CH is joined to one end (vehicle front side) of a transmission case 1. A bracket BK is joined to the other end (vehicle rear side) of the transmission case 1. The bracket BK is attached to the vehicle body with bolts or the like. The transmission case 1 and the converter housing CH are supported on the vehicle body via the bracket BK.

[0022] An oil pan OP for storing lubricating oil (not shown) is fixed to the bottom of the transmission case 1. A control valve CV is housed in the space surrounded by the oil pan 5 and the transmission case 1.

[0023] As shown in Fig. 1, the transmission case 1 has a cylindrical peripheral wall surface 20 that surrounds the rotation axis X. A converter housing CH is joined to the vehicle front side of the peripheral wall surface 20. As shown in Fig. 3, the transmission case 1 has an end surface 40 provided on the vehicle rear side of the peripheral wall surface 20. As shown in Fig. 2, the end surface 40 extends in a region where the vertical line VL direction and the vehicle width direction intersect.

[0024] The peripheral wall surface 20 has a top surface 21 as the region above the horizontal line HL. The peripheral wall surface 20 also has a bottom surface 22 as the region below the horizontal line HL. The horizontal line HL is a line segment that intersects with the rotation axis X and the vertical line VL. In FIG. 2, the outline of the bottom surface 22 is shown by hidden lines. When viewed from the direction of the rotation axis X, the bottom surface 22 has an arc shape. As shown in FIG. 5, the bottom surface 22 is the region of the peripheral wall surface 20 that is visible when the transmission case 1 is viewed from below.

[0025] As shown in FIG. 3, an opening 23 is provided in the bottom surface 22. The opening 23 extends in the width direction of the vehicle on the bottom surface 22. The opening 23 is provided to penetrate the bottom surface 22 in the direction of the vertical line VL. As shown in FIG. 3, the opening 23 is formed in an area of ​​the bottom surface 22 on the rear side of the vehicle, i.e., an area near the end surface 40. Members for connecting components inside the transmission case 1 to components outside the transmission case 1 are inserted through the opening 23. For example, members for connecting the control valve CV shown in FIG. 1 to the transmission TM are inserted through the opening 23.

[0026] As shown in Fig. 3, an annular portion 41 is provided on the end face 40. The annular portion 41 has an opening 42 that penetrates the end face 40 in the direction of the rotation axis X, and support portions 43 and 44 that surround the opening 42. The support portions 43 and 44 are cylindrical. The support portion 43 protrudes from the end face 40 toward the front of the vehicle inside the transmission case 1. The support portion 44 protrudes from the end face 40 toward the rear of the vehicle outside the transmission case 1.

[0027] The output shaft OS is inserted through an opening 42 in the annular portion 41. A needle bearing NB is provided on the inner peripheral surface of the support portion 43. A bearing B is provided on the inner peripheral surface of the support portion 44. The output shaft OS is rotatably supported by the annular portion 41 via the needle bearing NB and the bearing B. When the output shaft OS is not tilted, the rotation axis X passes through the center of the annular portion 41.

[0028] A joint portion 45 is provided on the outer periphery of the end face 40. The joint portion 45 protrudes from the outer periphery of the end face 40 toward the rear of the vehicle. As shown in Fig. 2, the joint 45 is provided with a plurality of bosses 46. In the illustrated example, four bosses 46 are provided on the horizontal line HL of the joint 45 and below the horizontal line HL. Bolt holes for fastening bolts are formed in the bosses 46. The bracket BK (see Fig. 1) is joined to the joint 45 by fastening the bosses 46 with bolts. The boss portion 46 is provided so as to bulge outward in the radial direction from the joint portion 45. That is, the portion of the joint portion 45 where the boss portion 46 is provided has a large radial width.

[0029] The end face 40 is provided with a plurality of ribs 47 extending radially around the annular portion 41. Each rib 47 extends from the support portion 44 of the annular portion 41 toward the outer periphery. An inner peripheral end 471 of the rib 47 is joined to the outer periphery of the support portion 44 of the annular portion 41. An outer peripheral end 472 of the rib 47 is joined to a joining portion 45 provided on the outer periphery of the end face 40. The ribs 47 increase the strength of the end face 40 that supports the annular portion 41.

[0030] As shown in FIG. 3 , the rib 47 is provided on the vehicle rear side of the end face 40. The rib 47 protrudes from the end face 40 toward the vehicle rear side. The rib 47 has an inclined surface 473 as a surface located on the vehicle rear side. The inclined surface 473 is inclined in a direction approaching the end face 40 from the inner peripheral end 471 toward the outer peripheral end 472. That is, the rib 47 is provided such that the height H decreases from the inner peripheral end 471 connected to the annular portion 41 toward the outer peripheral end 472 connected to the joint 45. In other words, by providing the inclined surface 473 on the rib 47, the area of ​​the connection portion between the rib 47 and the joint 45 becomes smaller than the area of ​​the connection portion between the rib 47 and the annular portion 41. The height H of the rib 47 means the length from the end face 40 to the inclined surface 473 in the direction of the rotation axis X.

[0031] As shown in FIG. 2, the plurality of ribs 47 include a pair of horizontal ribs 47c, 47c (a pair of ribs) arranged along a horizontal line HL. The horizontal ribs 47c, 47c are arranged opposite to each other with respect to the center of the annular portion 41 through which the rotation axis X passes. Note that the ribs 47 other than the horizontal ribs 47c, 47c may be arranged opposite to the center of the annular portion 41, as shown in Fig. 2, or may be arranged at offset positions. The number of ribs is not limited to the example shown in the figure, and can be changed as appropriate.

[0032] The region of the end face 40 below the horizontal ribs 47c, 47c is referred to as the first region 40A, and the region above is referred to as the second region 40B. The first region 40A is the region that connects to the bottom surface 22 of the peripheral wall surface 20. The second region 40B is the region that connects to the top surface 21 of the peripheral wall surface 20. In the following description, when it is necessary to distinguish between the ribs in the first region 40A and the ribs in the second region 40B, they will be denoted by reference numerals 47a and 47b, respectively.

[0033] The rigidity of the second region 40B of the end surface 40 is set to be lower than the rigidity of the first region 40A. In the embodiment, the rigidity of the first region 40A and the second region 40B is adjusted by making the heights H (see FIG. 3) of the ribs 47a and 47b different. 3, the rib 47a in the first region 40A and the rib 47b in the second region 40B each have an inclined surface 473. The inclination angle of the inclined surface 473 of the rib 47a is different from that of the inclined surface 473 of the rib 47b. Here, the inclination angle refers to the angle of the inclined surface 473 with respect to the vertical line VL, which is the direction in which the end face 40 extends. The inclination angle β of the inclined surface 473 of the rib 47b is larger than the inclination angle α of the inclined surface 473 of the rib 47a (α<β). That is, the inclination of the rib 47b is steeper than the inclination of the rib 47a. The other ribs 47a, 47b (see FIG. 2) in the first region 40A and the second region 40B are also set to the same inclination angles α, β.

[0034] In this way, by making the inclination of the rib 47b steeper than the inclination of the rib 47a, the height H of the rib 47b can be made lower than the height H of the rib 47a. Here, the height H of the rib 47 means the length in the direction of the rotation axis X from the end face 40 of the rib 47 to the inclined face 473, as described above. At the inner peripheral end 471 connecting to the annular portion 41, the rib 47b has the same height H as the rib 47a. However, because the inclination of the rib 47b is steep, the rib 47b becomes lower than the rib 47a as it approaches the outer peripheral end 472. Therefore, the average height H of the ribs 47b is lower than the average height H of the ribs 47a. That is, the ribs 47b are lower than the ribs 47a when viewed as a whole.

[0035] The greater the height H (length in the direction of rotation axis X) of the rib 47, the greater the rigidity against a load in the direction of rotation axis X. In other words, the rigidity of the second region 40B provided with the low rib 47b is lower than the rigidity of the first region 40A provided with the tall rib 47a.

[0036] Horizontal ribs 47c, 47c (see FIG. 2) located at the boundary between the first region 40A and the second region 40B are set to have higher rigidity than the other ribs 47a, 47b. As shown in FIG. 2, the horizontal ribs 47c, 47c have a symmetrical shape with respect to the center of the annular portion 41 (rotation axis X). As shown in Fig. 4, each of the horizontal ribs 47c has an inclined surface 473. The inclination angle γ of the inclined surface 473 of the horizontal rib 47c is smaller than the inclination angles α and β (see Fig. 3) of the inclined surfaces 473 of the other ribs 47a and 47b (γ<α<β). That is, the inclined surface 473 of the horizontal rib 47c is gentler than the inclined surfaces 473 of the ribs 47a and 47b in the first region 40A and the second region 40B.

[0037] In this way, by making the inclination of the rib 47c gentler than the inclination of the ribs 47a and 47b, the horizontal rib 47c becomes higher than the ribs 47a and 47b. At the inner peripheral end 471 where the horizontal rib 47c connects to the annular portion 41, the horizontal rib 47c has the same height H as the ribs 47a and 47b. However, toward the outer peripheral end 472, the horizontal rib 47c has a gentler slope and is therefore taller than the ribs 47a and 47b. Therefore, the average height H of the horizontal rib 47c is higher than the average height H of the ribs 47a and 47b. In other words, the horizontal rib 47c is higher overall than the other ribs 47a and 47b.

[0038] As described above, the greater the height H (length in the direction of the rotation axis X) of the rib 47, the greater the rigidity against the load in the direction of the rotation axis X. In other words, the rigidity of the horizontal rib 47c is higher than the rigidity of the other ribs 47a and 47b.

[0039] 2, the horizontal ribs 47c, 47c are each joined to a boss 46 for bolt fastening provided on the joint 45. On the other hand, the other ribs 47a, 47b are joined to a portion of the joint 45 where the boss 46 is not provided. The boss portion 46 is fastened to the bracket BK (see FIG. 1) by a bolt or the like (not shown). That is, the boss portion 46 is supported on the vehicle body via the bracket BK. Therefore, the portion of the joint 45 where the boss portion 46 is provided is less susceptible to deformation due to input of load than other portions. That is, the rigidity of the portion of the joint 45 where the boss portion 46 is provided is higher than the rigidity of other portions. Furthermore, the boss portion 46 has a larger radial width and is thicker than the joint 45. By joining the horizontal rib 47c to the boss portion 46, the rigidity of the connection between the horizontal rib 47c and the joint 45 is higher than that of the other ribs 47a, 47b.

[0040] FIG. 6 is a diagram illustrating the widths of the ribs 47a, 47b, and 47c. As shown in FIG. 6, the other ribs 47a, 47b have a constant circumferential width Wa from the annular portion 41 toward the outer periphery. The horizontal rib 47c has a shape in which the width Wb gradually increases from the annular portion 41 toward the outer periphery. Here, the widths Wa and Wb refer to the widths in the circumferential direction around the rotation axis X. At the outer peripheral end 472 of the horizontal rib 47c that is joined to the boss portion 46, the width Wb of the horizontal rib 47c is at its maximum (Wb max At the inner peripheral end 471 that joins to the annular portion 41, the width Wb of the horizontal rib 47c is minimum (Wb min ) Maximum width Wb of horizontal rib 47c max is larger than the width Wa of the other ribs 47a and 47b (Wb max >Wa). Minimum width Wb of horizontal rib 47c min is smaller than the width Wa of the other ribs 47a and 47b (Wb min <Wa)。 Furthermore, it is preferable that the intermediate width Wd of the horizontal rib 47c is larger than the width Wa of the other ribs 47a and 47b (Wb mid >Wa). Intermediate width Wb mid The width Wb of the horizontal rib 47c refers to the width at the intermediate position of the horizontal rib 47c in the radial direction of the rotation axis X. In this way, the horizontal rib 47c has a wide shape overall, which makes it more rigid than the other ribs 47a and 47b. At the same time, the width Wb of the horizontal rib 47c is set small at the inner peripheral end 471 that is joined to the annular portion 41. This increases the rigidity of the horizontal rib 47c while preventing the connection between the horizontal rib 47c and the annular portion 41 from becoming too strong.

[0041] The operation of the transmission case 1 will now be described. FIG. 7 is a diagram for explaining the operation of the transmission case 1. The output shaft OS rotates around the rotation axis X due to the input from the driving force transmission device 100. As shown in Figure 7, when the output shaft OS rotates, a load L acts in the direction of the rotation axis X on the bearing B, the needle bearing NB, and the annular portion 41 that support the output shaft OS. The load L acts as a force toward the rear of the vehicle in the direction of the rotation axis X. The annular portion 41 is supported by the end face 40. Therefore, the load L is also transmitted to the end face 40 that supports the annular portion 41 and the peripheral wall surface 20 that is connected to the end face 40.

[0042] FIG. 8 is a diagram showing a comparative example. In the comparative example, the first region 40A and the second region 40B are set to have the same rigidity, i.e., the ribs 470 in the first region 40A and the second region 40B are set to have the same inclination angle. As described above, the first region 40A of the end surface 40 is connected to the bottom surface 22, which is the region below the peripheral wall surface 20. The bottom surface 22 is provided with the opening 23. That is, the upper surface 21 of the peripheral wall surface 20 has a continuous wall surface from the vehicle rear side connected to the end surface 40 to the vehicle front side, whereas the bottom surface 22 has a discontinuous wall surface at the opening 23 provided near the end surface 40. Therefore, the portion of the bottom surface 22 where the opening 23 is provided has lower rigidity than other portions. That is, the first region 40A is connected to the bottom surface 22, which has lower rigidity than the upper surface 21. Therefore, even if the first region 40A and the second region 40B have the same rigidity, the first region 40A is more likely to deform than the second region 40B because it is connected to the lower rigid bottom surface 22. As shown in Fig. 8, when a load L in the direction of the rotation axis X is applied, the end surface 40 does not deform uniformly as a whole, and the first region 40A may deform more than the second region 40B.

[0043] When the annular portion 41 is not deformed, the rotation axis X of the output shaft OS passes through the center of the annular portion 41 (see FIGS. 2 and 3). However, as shown in FIG. 9, when the first region 40A side of the annular portion 41 is deformed toward the rear of the vehicle due to the load L, the output shaft OS tilts. The output shaft OS tilts downward as it moves from the rear of the vehicle toward the front of the vehicle. This causes the rotation axis X of the output shaft OS to deviate from the center of the annular portion 41. If the output shaft OS rotates while remaining in a tilted state, there is a possibility that the load acting on the needle bearing NB, bearing B, and the annular portion 41 that support the output shaft OS will increase in some areas. In particular, a large load will act on the needle bearing NB provided on the support portion 43 on the front side of the annular portion 41.

[0044] On the other hand, in the configuration of the embodiment shown in FIG. 7, the rigidity of the second region 40B is set to be lower than the rigidity of the first region 40A. Specifically, the rib 74b of the second region 40B is lower in the direction of the rotation axis X than the rib 74a of the first region 40A, so that the rigidity of the second region 40B against the load L in the direction of the rotation axis X is lower than the rigidity of the first region 40A. As a result, in the embodiment, the second region 40B is more easily deformed than in the comparative example shown in Fig. 8. Furthermore, in the embodiment, the rigidity of the horizontal ribs 47c, 47c is higher than that of the other ribs 47a, 47b. That is, in the embodiment, the first region 40A connected to the bottom surface 22 where the opening 23 is provided and the second region 40B where the low rib 47b is provided are similarly easily deformed, but the horizontal ribs 47c, 47c at the boundary between the first region 40A and the second region 40B are less likely to deform. 7, when a load L is applied to the end face 40, the end face 40 rotates around the highly rigid horizontal ribs 47c, 47c in a direction that offsets the deformation of the first region 40A toward the rear of the vehicle (as indicated by the dotted arrow in the figure). Specifically, the second region 40B, which has low rigidity, rotates around the horizontal ribs 47c, 47c as an axis of rotation, deforming toward the rear of the vehicle, and a force acts to push the first region 40A, which is attempting to deform toward the rear of the vehicle, back toward the front of the vehicle.

[0045] In this way, the deformation of the first region 40A is offset by the deformation of the second region 40B, which reduces the tilt of the output shaft OS caused by the large deformation of the first region 40A of the annular portion 41, as seen in the comparative example. By reducing the tilt of the output shaft OS, it is possible to reduce the local increase in the load on the annular portion 41, the bearing B, and the needle bearing NB.

[0046] As described above, the horizontal ribs 47c, 47c are made wider than the other ribs 47a, 47b to increase their rigidity, but the inner peripheral end 471 that connects to the annular portion 41 is narrower (see FIG. 6). If the inner peripheral end 471 were also made wider, the connection between the horizontal rib 47c and the annular portion 41 would be too strong, which could hinder rotation around the horizontal ribs 47c, 47c (see FIG. 7). Therefore, by making the inner peripheral end 471 of the horizontal ribs 47c, 47c narrower, the rigidity of the horizontal ribs 47c, 47c is ensured while rotation around the horizontal ribs 47c, 47c is less likely to be hindered.

[0047] Furthermore, in this embodiment, the inclination angles α, β, and γ of the rib 47a in the first region 40A, the rib 47b in the second region 40B, and the horizontal rib 47c are made different from each other to change the rigidity. The end surface 40 and the rib 47 connect the annular portion 41 and the joint portion 45. Therefore, deformation of the annular portion 41 is absorbed by the joint portion 45 via the end surface 40 and the rib 47. In other words, deformation of the end surface 40 reduces excessive deformation of the annular portion 41. Here, if the inclined surface 473 is not provided on the rib 47, the height H of the rib 47 will be the same throughout, and the annular portion 41 will be firmly connected to the joint portion 45. However, if the connection between the annular portion 41 and the joint portion 45 becomes strong, the end surface 40 will be less likely to deform, and therefore the end surface 40 will not be able to absorb deformation of the annular portion 41. As in the embodiment, by providing an inclined surface 473 on the rib 47 and making the area of ​​the connection portion between the rib 47 and the joint 45 smaller than the area of ​​the connection portion between the rib 47 and the annular portion 41, the end face 40 becomes more easily deformed, and deformation of the annular portion 41 can be absorbed and reduced. In the embodiment, by varying the inclination angles α, β, and γ of the inclined surfaces 473 of the ribs 47a, 47b and the horizontal rib 47c, it is possible to control the rigidity of the end face 40. Furthermore, since the inclination angles of the multiple ribs 47 can be adjusted individually, it is possible to finely control the rigidity.

[0048] Examples of the transmission case 1 (case) according to an embodiment of the present invention are listed below. (1) The transmission case 1 houses the driving force transmission device 100 therein. The transmission case 1 has an end surface 40 and a bottom surface 22. The bottom surface 22 is a region of the peripheral wall surface 20 below a horizontal line HL. The end surface 40 is provided with a circular ring portion 41 and a plurality of ribs 47 extending radially from the circular ring portion 41 around the periphery. The bottom surface 22 has an opening 23 formed therein, and the bottom surface 22 is connected to the end surface 40 . The plurality of ribs 47 include horizontal ribs 47c, 47c (a pair of ribs) that face each other with respect to the center of the annular portion 41. The end surface 40 has a first region 40A and a second region 40B. The first region 40A is a region below the horizontal ribs 47c, 47c (toward the bottom surface 22). The second region 40B is a region above the horizontal ribs 47c, 47c (opposite the first region 40A). The rigidity of the horizontal ribs 47c, 47c is higher than the rigidity of the other ribs 47a, 47b. The rigidity of the second region 40B of the end surface 40 is lower than the rigidity of the first region 40A.

[0049] By configuring the transmission case 1 in this manner, the inclination of the output shaft OS can be reduced, and the load applied to the annular portion 41 can be reduced. Specifically, an annular portion 41 is formed on an end surface 40 of the transmission case 1, which houses the driving force transmission device 100. An output shaft OS, to which driving force is input from the driving force transmission device 100, is inserted into the annular portion 41. The end surface 40 is connected to the peripheral wall surface 20. An opening 23 is formed in a bottom surface 22, which is the area below the peripheral wall surface 20.

[0050] The output shaft OS rotates when a driving force is input from the driving force transmission device 100. Due to the rotation, a load L acts in the direction of the rotation axis X on the annular portion 41 that supports the output shaft OS. The load L also acts on the end surface 40 that supports the annular portion 41 and the peripheral wall surface 20 that is connected to the end surface 40.

[0051] Because the bottom surface 22 of the peripheral wall surface 20 has openings 23 formed therein, it has lower rigidity and is more susceptible to deformation than the top surface 21. If the first region 40A connected to the bottom surface 22 deforms more due to the load L than the second region 40B connected to the top surface 21, the output shaft OS supported by the annular portion 41 will tilt. If the output shaft OS rotates while remaining tilted, the load on the annular portion 41, the bearing B, and the needle bearing NB may increase in some areas.

[0052] In the embodiment, the rigidity of the second region 40B of the end face 40 is lower than that of the first region 40A. Furthermore, the rigidity of the horizontal ribs 47c, 47c at the boundary between the first region 40A and the second region 40B of the end face 40 is higher than the rigidity of the other ribs 47a, 47b. As a result, when a load L acts in the direction of the rotation axis X, the end face 40 rotates about the highly rigid horizontal ribs 47c, 47c in a direction that offsets the deformation of the first region 40A. Specifically, the second region 40B, which has lower rigidity, rotates about the horizontal ribs 47c, 47c as the rotation axis in a direction that deforms toward the rear of the vehicle. This rotation acts as a force that pushes the first region 40A, which is attempting to deform toward the rear of the vehicle, back toward the front of the vehicle.

[0053] In this manner, in the embodiment, the deformation of the first region 40A is offset by the deformation of the second region 40B, thereby reducing the tilt of the output shaft OS caused by the large deformation of the first region 40A of the annular portion 41. By reducing the tilt of the output shaft OS, it is possible to reduce a partial increase in the load applied to the annular portion 41.

[0054] (2) The horizontal ribs 47c, 47c are higher than the other ribs 47a, 47b. This allows the rigidity of the horizontal ribs 47c, 47c to be higher than the rigidity of the other ribs 47a, 47b, making it easier for rotation to occur around the horizontal ribs 47c, 47c. Specifically, by making the height H of the horizontal ribs 47c, 47c in the direction of the rotation axis X greater than the height H of the other ribs 47a, 47b, it is possible to increase rigidity against the load L in the direction of the rotation axis X generated by the rotation of the output shaft OS.

[0055] (3) The ribs 47 have inclined surfaces 473 that are inclined toward the end face 40 as they move from the annular portion 41 toward the radially outer side (outer periphery) of the rotation axis X. The inclination angle γ of the inclined surfaces 473 of the horizontal ribs 47c, 47c is smaller than the inclination angles α, β of the inclined surfaces 473 of the other ribs 47a, 47b. By making the inclination of the horizontal rib 47c gentler, the average height H of the horizontal rib 47c can be made higher than the average height H of the other ribs 47a, 47b. This makes it possible to make the horizontal rib 47c higher than the other ribs 47a, 47b and increase rigidity. The inclined surface 473 of the rib 47 is provided so that the joint portion 45 can easily absorb and deform the deformation of the annular portion 41. By adjusting the inclination angle of this inclined surface 473, the rigidity of the horizontal rib 47c relative to the other ribs 47a and 47b can also be easily adjusted.

[0056] (4) In the transmission case 1, the horizontal ribs 47c, 47c have portions that are wider than the other ribs 47a, 47b. The width means the width in the circumferential direction around the rotation axis X.

[0057] The horizontal rib 47c has a wide portion, so that the rigidity of the horizontal rib 47c can be made higher than the rigidity of the other ribs 47a and 47b.

[0058] (5) In the transmission case 1, the horizontal ribs 47c, 47c have a shape in which the width increases from the annular portion 41 toward the outer periphery. max The minimum width Wb of the horizontal ribs 47c is greater than the width Wa of the other horizontal ribs 47a and 47b. min is smaller than the width Wa of the other ribs 47a and 47b.

[0059] When the horizontal rib 47c is shaped so that its width increases from the annular portion 41 toward the outer peripheral joining portion 45, the width Wb of the horizontal rib 47c is at its maximum (Wb max ) The width Wb of the horizontal rib 47c is minimum (Wb min ) This allows the horizontal rib 47c to have a wider portion, thereby increasing the rigidity of the horizontal rib 47c. At the same time, by reducing the width of the inner peripheral end 471 that is joined to the annular portion 41, the connection between the horizontal rib 47c and the annular portion 41 is not too strong. This makes it less likely that rotation occurring around the horizontal ribs 47c, 47c will be hindered when the load L is applied.

[0060] (6) The horizontal ribs 47c, 47c are connected to the boss portion 46 provided on the outer periphery of the end face 40. The boss portion 46 is fastened to the bracket BK by a bolt or the like (not shown). That is, the boss portion 46 is supported on the vehicle body via the bracket BK. Therefore, the portion of the joint 45 where the boss portion 46 is provided is less susceptible to deformation due to input of load than other portions. That is, the rigidity of the portion of the joint 45 where the boss portion 46 is provided is higher than the rigidity of other portions. Furthermore, in the joint 45 provided on the outer periphery of the end face 40, the boss portion 46 for bolt fastening is formed thick. By joining the horizontal rib 47c to the boss portion 46, the rigidity related to the connection of the horizontal rib 47c can be increased.

[0061] (7) In the transmission case 1, the ribs 47b provided in the second region 40B of the end face 40 are lower than the ribs 47a provided in the first region 40A.

[0062] By making the ribs 47a of the first region 40A higher than the ribs 47b of the second region 40B, the rigidity of the second region 40B against the load L in the direction of the rotation axis X can be made lower than that of the first region 40A.

[0063] (8) The ribs 47 have inclined surfaces 473 that are inclined toward the end face 40 as they move from the annular portion 41 toward the radially outer side (outer periphery) of the rotation axis X. The inclination angle β of the inclined surface 473 of the rib 47b provided in the second region 40B is larger than the inclination angle α of the inclined surface 473 of the rib 47a provided in the first region 40A.

[0064] By making the inclination of the rib 47b steeper, the average height H of the rib 47b can be made lower than the average height H of the rib 47a. This makes it possible to make the rigidity of the second region 40B, in which the rib 47b is provided, lower than the rigidity of the first region 40A, in which the rib 47a is provided. The inclined surface 473 of the rib 47 is provided so that the joint portion 45 can easily absorb and deform the deformation of the annular portion 41. By adjusting the inclination angle of this inclined surface 473, the rigidity of the first region 40A where the rib 47a is provided and the second region 40B where the rib 47b is provided can also be easily adjusted.

[0065] <Variation 1> Fig. 9 is a cross-sectional view of the transmission case 1 according to Modification 1. Fig. 9 shows only the rear side of the transmission case 1. In the first modification, the same components as those in the above-described embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. 9, in Modification 1, the rigidity of each region is adjusted by making the thicknesses of the first region 40A and the second region 40B of the end face 40 different. Here, "thickness" means the length of the end face 40 in the direction of the rotation axis X. Specifically, the thickness T2 of the second region 40B of the end face 40 is smaller than the thickness T1 of the first region 40A (T1>T2). The inclination angles of the ribs 47a and 47b may be different from each other as in the embodiment, or may be the same. With this configuration, the rigidity of the second region 40B against the load L in the direction of the rotation axis X is lower than that of the first region 40A. As a result, similar to the embodiment described above, when the load L acts on the annular portion 41, the end face 40 rotates around the horizontal ribs 47c, 47c, causing the second region 40B, which has lower rigidity, to deform toward the rear of the vehicle. This rotation acts as a force that pushes the first region 40A, which is attempting to deform toward the rear of the vehicle, back toward the front of the vehicle. This reduces the inclination of the output shaft OS, thereby reducing the load on the annular portion 41.

[0066] (9) In the transmission case 1, the thickness T1 of the first region 40A of the end face 40 in the direction of the rotation axis X can be made thicker than the thickness T2 of the second region 40B in the direction of the rotation axis X.

[0067] By making the first region 40A thicker than the second region 40B, the rigidity of the second region 40B against a load in the direction of the rotation axis X can be made lower than that of the first region 40A. As a result, when a load L in the direction of the rotation axis X acts on the annular portion 41, a force acts on the annular portion 41 to rotate the second region 40B, which has lower rigidity, toward the rear of the vehicle around the horizontal ribs 47c, 47c, which have higher rigidity, and deformation of the first region 40A toward the rear of the vehicle is reduced.

[0068] <Variation 2> FIG. 10 is a diagram showing the configuration of a horizontal rib 47d according to the second modification. In the above-described embodiment, the horizontal rib 47c has a shape in which the circumferential width gradually narrows from the outer peripheral end 472 to the inner peripheral end 471 (see FIG. 6), but is not limited to this form. 10, for example, the horizontal rib 47d may have the same width We up to the vicinity of the center in the radial direction of the rotation axis X. The width We may be wider than the width Wa of the ribs 47a and 47b. The width of the horizontal rib 47d may also be gradually narrowed from the center in the radial direction toward the inner diameter side. As in the embodiment, the width of the inner peripheral end 471 of the horizontal rib 47d may be narrower than the width Wa of the ribs 47a and 47b. With this configuration, the rigidity of the horizontal rib 47d is increased while the connection with the annular portion 41 is not too strong, and rotation of the end face 40 around the horizontal ribs 47d, 47d is less likely to be hindered.

[0069] In this embodiment, an example in which the transmission case 1 according to an aspect of the present invention is mounted on a vehicle has been described, but the present invention is not limited to this aspect. The case according to an aspect of the present invention can also be applied to things other than vehicles. Furthermore, when multiple examples and modified examples are described in this embodiment, these may be combined in any desired manner.

[0070] Although the embodiment of the present invention has been described above, the above embodiment merely shows one application example of the present invention, and the technical scope of the present invention is not intended to be limited to the specific configuration of the above embodiment. Appropriate modifications are possible within the scope of the technical concept of the invention. [Explanation of symbols]

[0071] 1: Transmission case (case) 22: Bottom 21: Opening 40: End face 40A: 1st area 40B:Second area 41: Circular part 46: Boss Club 47, 47a, 47b: Ribs 47c, 47d: horizontal ribs 100: Driving force transmission device

Claims

1. A case in which a driving force transmission device is installed, an end surface provided with a circular ring portion and a plurality of ribs extending radially from the circular ring portion; a bottom surface having an opening and connected to the end surface; the plurality of ribs include a pair of ribs facing each other with respect to the center of the annular portion, the end surface has a first region on the bottom surface side with respect to the pair of ribs and a second region on the opposite side of the pair of ribs from the first region, The rigidity of the pair of ribs is higher than the rigidity of the other ribs, The second region of the end face has a lower rigidity than the first region.

2. The case according to claim 1 , wherein the pair of ribs have a height greater than the other ribs.

3. The plurality of ribs have inclined surfaces that are inclined in a direction approaching the end surface as they move from the annular portion toward the outer periphery, 3. The case according to claim 2, wherein the inclination angles of the inclined surfaces of the pair of ribs are smaller than the inclination angles of the inclined surfaces of the other ribs.

4. The case according to any one of claims 1 to 3, wherein the pair of ribs have portions that are wider than the other ribs.

5. The pair of ribs have a shape in which the width increases from the annular portion toward the outer periphery, The maximum width of the pair of ribs is wider than the width of the other ribs, The case according to claim 4 , wherein the minimum width of the pair of ribs is smaller than the width of the other ribs.

6. The case according to any one of claims 1 to 5, wherein the pair of ribs are connected to bosses provided on the outer periphery of the end face.

7. 7. The case according to claim 1, wherein the height of the ribs provided in the second region is lower than the height of the ribs provided in the first region.

8. The case described in claim 7, wherein the plurality of ribs have inclined surfaces that incline in a direction approaching the end face as they move from the annular portion toward the outer periphery, and the inclination angle of the inclined surfaces of the ribs provided in the second region is greater than the inclination angle of the inclined surfaces of the ribs provided in the first region.

9. The case according to any one of claims 1 to 8, wherein the thickness of the first region of the end face is greater than the thickness of the second region.

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