GEARBOX HOUSING

Abstract

Gearbox housing, comprising: a wall section (2); a bearing section (3) with a through-hole (31) penetrating the wall section (2) for receiving a power transmission shaft, wherein the bearing section (3) projects cylindrically from the wall section (2); and a rib (41) which projects from the wall section (2) in the same direction as the bearing section (3) and has an arc section (43), characterized in that, viewed in the direction of the central axis (O1) of the bearing section (3), the wall section (2) comprises: i) a planar first wall section (21) whose contour is defined by the bearing section (3), the arc section (43) of the rib (41) and the two common tangents (L1, L2) to the bearing section (3) and the arc section (43) of the rib (41), and ii) a second wall section (22) in a region outside the planar first wall section (21);and the flat first wall section (21) is offset in the projection direction of the bearing section (3) relative to the second wall section (22).

Description

BACKGROUND OF THE INVENTION1. Field of the InventionThe present invention relates to a transmission case provided in an automatic transmission or the like.2. Prior ArtAs described in Japanese Patent Laid-Open No. 2002-349667 (JP 2002-349667 A), in an automatic transmission to be mounted on a vehicle, a transmission is housed in a transmission case. Further, the transmission case has a through hole in which a power transmission shaft is inserted, and the peripheral portion around the through hole is formed as a bearing portion in which the power transmission shaft is rotatably supported. The bearing portion has a cylindrically protruding shape from a surface of the gear case (also referred to as a main surface).Further, as described in Japanese Patent Laid-Open No. 2015-218900 (JP 2015-218900 A), a rib is provided on a surface of the transmission case around the outer periphery of a gear provided in a power transmission mechanism for operating an oil pump or the like.WO 2015 / 151609 A1 and DE 10 2011 054 956 A1 disclose transmission housings according to the preamble of claim 1.SUMMARY OF THE INVENTIONOn the power transmission shaft of JP 2015-218900 A, a gear for power transmission is provided. For this reason, a radial or axial force generated during the transmission of the gear wheel is transmitted from the power transmission shaft to the bearing portion. As described above, since the bearing portion has a shape cylindrically protruding from the surface of the transmission case, vibrations may occur in the bearing portion due to insufficient strength (support strength with respect to the power transmission shaft) of the transmission case, with the result of noise generation.Conceivable measures for preventing the vibrations of the bearing section are an increase in the wall thickness of the transmission housing and the addition of a reinforcing rib. However, they are disadvantageous because they cause a large weight increase of the transmission case.Proceeding from WO 2015 / 151609 A1, the present invention has the object of providing a transmission housing in which vibrations of a bearing section can be prevented without a great increase in weight.A transmission case according to the present invention includes: a wall portion; a bearing portion having a through hole penetrating the wall portion for receiving a power transmission shaft, the bearing portion projecting cylindrically from the wall portion; and a rib projecting in the same direction as the bearing portion from the wall portion and having an arc portion. The wall portion has, as viewed in the direction of the central axis of the bearing portion: i) a planar first wall portion whose contour is defined by the bearing portion, the arc portion of the rib and the two common tangents to the bearing portion and the arc portion of the rib, and ii) a second wall portion in a region outside the planar first wall portion; the planar first wall portion is offset relative to the second wall portion in the protruding direction of the bearing portion.According to the above aspect, the strength of the transmission case increases. That is, by the case shape, even when a radial or axial force generated in the power transmission is transmitted from the power transmission shaft to the bearing portion, vibrations of the bearing portion are prevented. It is also possible to increase the strength of the transmission case without increasing the wall thickness of the transmission case, whereby vibrations of the bearing portion and noise generation can be prevented without a great increase in the weight of the transmission case.According to the above aspect, the bearing portion is further connected to the rib by the wall portion offset in the protruding direction of the bearing portion. This increases the strength of the transmission housing. For this reason, even when a radial or axial force generated in the power transmission is transmitted from the power transmission shaft to the bearing portion, vibrations of the bearing portion are prevented by the offset wall portion. Because the wall portion is offset, the strength of the gear case can be increased without increasing the wall thickness of the gear case, whereby vibrations of the bearing portion and noise generation can be prevented without a great weight increase of the gear case. Furthermore, the region in which the wall section is offset is the region between the two common tangents to the bearing section and the arc section of the rib and is as small as possible in order to still achieve the desired effect. Accordingly, it is possible to achieve the desired effect and to minimize structural changes.The arc portion of the rib may have a central axis parallel to the central axis of the bearing portion.Further, the size of the protrusion of the bearing portion relative to the second wall portion may be larger than the size of the protrusion of the rib relative to the second wall portion, and the size of the offset of the planar first wall portion relative to the second wall portion may be smaller than the size of the protrusion of the bearing portion and the size of the protrusion of the rib.According to the invention, the gear case having a cylindrical bearing portion and a rib having an arc portion has a case shape defined by connecting two common tangents to the bearing portion and the arc portion of the rib. It is accordingly possible to increase the strength of the transmission case without increasing the wall thickness of the transmission case, and to prevent vibrations of the bearing portion and noise generation without a great increase in the weight of the transmission case.BRIEF DESCRIPTION OF THE DRAWINGSWith reference to the accompanying drawings, wherein the same reference numerals designate the same elements, features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below, wherein: FIG. 1 is a side view showing a part of a transmission case; FIG. 2 is a view viewed in the direction of arrow II in FIG. 1 ; and FIG. 3 is a sectional view taken along the line III-III in FIG. 1.DETAILED DESCRIPTION OF EMBODIMENTSReferring now to the drawings, an embodiment of the invention will be described. The embodiment describes a case where the invention is applied to a transmission case of an automatic transmission to be mounted or installed in a vehicle.FIG. 1 is a side view showing a part of a transmission case 1 according to the present embodiment. Further, FIG. 2 is a view as seen from the arrow II in FIG. 1, and FIG. 3 is a sectional view taken along the line III-III in FIG. 1, and as shown in these views, the transmission case 1 includes a wall portion 2, a bearing portion 3, a first rib 41, and a second rib 42.The wall section 2 is formed by a vertical wall which extends in the vertical direction in the transmission housing 1 and has a wall thickness which gives the transmission housing 1 a predefined strength.The bearing portion 3 is integrally formed with the wall portion 2 and has a substantially cylindrical protruding shape from the surface of the wall portion 2. At the center of the bearing portion 3, a through hole 31 is formed which receives a power transmission shaft (not shown). The bearing portion 3 is formed with the through hole 31 penetrating the wall portion 2 so that the power transmission shaft is received in the through hole 31, and protrudes from the wall portion 2 in a cylindrical shape. Further, on the inside of the through hole 31, a metal bearing (not shown) rotatably supporting the power transmission shaft is disposed.The ribs 41, 42 surround the outer periphery of a sprocket provided for driving an oil pump (not shown) in a power transmission mechanism. The ribs 41, 42 protrude from the wall portion 2 in the same direction as the bearing portion 3.The first rib 41 has an arc portion 43 having a central axis O 2 parallel to the central axis O 1 of the bearing portion 3. The arc portion 43 surrounds an upper part of the sprocket. Further, from both ends of the arc portion 43, chain protecting portions 44, 45 are formed extending in the longitudinal direction of a chain (not shown) of the power transmission mechanism.The second rib 42 is formed in a circular arc shape having a central axis O 3 parallel to the central axis O 1 of the bearing portion 3. The second rib 42 surrounds a lower portion of the sprocket.Note that the wall portion 2 includes a first wall portion 21 between the bearing portion 3 and the first rib 41, and a second wall portion 22 including the other region. A feature of the present embodiment is the configuration of the first wall portion 21 between the bearing portion 3 and the first rib 41.Specifically, as shown in FIG. 1, the gear housing is configured to have a shape defined by the connection of the bearing portion 3 and the arc portion 43 of the first rib 41 by two common tangents L 1, L 2 (see the virtual lines in FIG. 1 ) to the bearing portion 3 and the arc portion 43 of the first rib 41 as viewed in the direction of the central axis O 1 of the bearing portion 3. Specifically, in the region between the bearing portion 3, the arc portion 43 of the rib 41, and the two common tangents L 1, L 2 to the bearing portion 3 and the arc portion 43 of the rib 41 are offset in the protruding direction (rightward in FIG. 3 ) of the bearing portion 3 relative to the second wall portion 22 in the other region.Specifically, as shown in FIG. 2, the amount of protrusion of the bearing portion 3 relative to the second non-offset wall portion 22 is T 1 and the amount of protrusion of the first rib 41 is T 2, whereas the amount of offset of the first wall portion 21 is T 3. The size of the protrusion T 1 of the bearing portion 3 is slightly larger than the size of the protrusion T 2 of the first rib 41, while the amount of the offset T 3 of the first wall portion 21 is smaller than the size of the protrusion T 1 of the bearing portion 3 and the size of the protrusion T 2 of the first rib 41.To the transmission case 1 thus configured, a transmission cover (not shown) is fixed after a shift device is accommodated. When the gear cover is fastened, a joining portion formed on the outer edge of the gear housing 1 and a joining portion formed on the outer edge of the gear cover are placed on top of each other and fastened to each other with screws.The technical effect of the present embodiment will be described below. As described above, the first wall portion 21 in the region between the bearing portion 3, the arc portion 43 of the rib 41, and the two common tangents L 1, L 2 to the bearing portion 3 and the arc portion 43 of the rib 41 is offset in the protruding direction of the bearing portion 3 relative to the second wall portion 22 in the other region. For this reason, the bearing portion 3 is connected to the first rib 41 by the first wall portion 21 offset in the protruding direction of the bearing portion 3. This increases the strength of the transmission case 1, that is, the strength of the transmission case 1 is increased by effectively using a rib (the first rib 41) for the gear. For this reason, even when a radial or axial force generated in the power transmission is transmitted from the power transmission shaft to the bearing portion 3, vibrations of the bearing portion 3 are prevented by the first offset wall portion 21. By the offset of the first wall portion 21, the strength of the transmission case 1 can be increased without increasing the wall thickness of the transmission case 1, whereby vibrations of the bearing portion 3 and noise generation can be prevented without a great increase in the weight of the transmission case 1.Furthermore, the region in which the wall portion 2 is offset is the region between the bearing portion 3, the arc portion 43 of the rib 41 and the two common tangents L 1, L 2 to the bearing portion 3 and the arc portion 43 of the rib 41, which is kept as small as possible in order to still achieve the desired effect. As a result, it is possible to achieve the desired effect and to minimize structural changes. Thus, according to the arrangement of the present embodiment, it is possible to achieve the desired effect with good mass efficiency.Other embodiments -The above-shown embodiment relates to a case where the present invention is applied to the transmission case 1 of an automatic transmission to be mounted on a vehicle. However, the present invention is not limited thereto, but may be applied to a transmission case of a transmission installed in something other than a vehicle.Further, the above embodiment relates to a configuration in which the first wall portion 21 is offset between the rib (the first rib 41) for the gear and the bearing portion 3. However, the present invention is not limited thereto; the rib is not necessarily the rib for the gear, and does not need to protrude in the same direction as the bearing portion 3 from the wall portion 2, and does not need to have an arc portion. For example, it is also possible to use a rib disposed so as to surround the outer periphery of a gear provided on a power transmission shaft other than the power transmission shaft to be inserted into the through hole 31. That is, a wall portion in a region between two common tangents to the arc portion of the rib and the bearing portion 3 may be offset in the protruding direction of the bearing portion 3 relative to a wall portion in the other region.The present invention is applicable to a transmission case having a rib surrounding a sprocket and a bearing portion.

Claims

A transmission case, comprising: a wall portion (2); a bearing portion (3) having a through hole (31) penetrating the wall portion (2) for receiving a power transmission shaft, wherein the bearing portion (3) cylindrically protrudes from the wall portion (2); and a rib (41) protruding from the wall portion (2) in the same direction as the bearing portion (3) and having an arc portion (43), characterized in that, as viewed in the direction of the central axis (O1) of the bearing portion (3), the wall portion (2) includes: i) a planar first wall portion (21) whose contour is defined by the bearing portion (3), the arc portion (43) of the rib (41), and the two common tangents (L1, L2) to the bearing portion (3) and the arc portion (43) of the rib (41), and ii) a second wall portion (22) in a region outside the planar first wall portion (21); and the planar first wall portion (21) is offset relative to the second wall portion (22) in the protruding direction of the bearing portion (3).The transmission case according to claim 1, wherein the arc portion (43) of the rib has a central axis (O2) parallel to the central axis (O1) of the bearing portion (3).The transmission case according to claim 1, wherein: the size of the protrusion (T1) of the bearing portion (3) relative to the second wall portion (22) is larger than the size of the protrusion (T2) of the rib (41) relative to the second wall portion (22); and the size of the offset (T3) of the planar first wall portion (21) relative to the second wall portion (22) is smaller than the size of the protrusion (T1) of the bearing portion (3) and the size of the protrusion (T2) of the rib (41).

Images