Vehicle transmission

A vehicle transmission including a rotatable input shaft connected to a driving source; a countershaft parallel to the input shaft; a differential unit below the countershaft, to which rotation is input from the countershaft, and coupled to right and left wheels; a case member containing the input shaft, countershaft, and the differential unit; a differential chamber disposed in the case member, contains the differential unit, and is separated from an oil storage chamber; and a differential separation member separating the differential chamber from the storage chamber, and formed along the differential unit ring gear, which meshes with an output gear of the countershaft. The differential separation member has an opening so the output gear can mesh with the ring gear, a communication portion, formed in an upper part of the differential separation member, and located on an upstream side of the opening in a rotation direction of the ring gear during forward traveling, discharges oil from the differential chamber, and a wall member on a side of an output gear meshing portion and the ring gear with respect to the communication portion, and contacts the differential separation member outer surface.

INCORPORATION BY REFERENCE

The disclosures of Japanese Patent Application No. 2010-083440 filed on Mar. 31, 2010 and International Application No. WO2010JP072484 filed on Dec. 14, 2010 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to vehicle transmissions that contain a differential unit in a case, and more particularly to case structures.

DESCRIPTION OF THE RELATED ART

In general, vehicle transmissions such as an automatic transmission and a hybrid drive device transmit power to wheels via a differential unit in order to allow a rotation difference between the left and right wheels. For example, conventionally known front engine front drive (FF) type transmissions, which are mounted in a transverse direction, integrally contain the differential unit in a case of the transmission.

In such vehicle transmissions containing the differential unit in the case, it has been proposed to provide a weir member 4 to separate a differential chamber 5 containing a differential mechanism (a differential unit) 10 from an oil pan chamber 3 storing hydraulic oil, so that the oil pan chamber 3 and the differential chamber 5 have different oil levels, and that the hydraulic oil in the differential chamber 5 is discharged into the oil pan chamber 3 by rotation of a ring gear 14 of the differential mechanism 10 (see Japanese Patent Application Publication No. JP-A-2008-19886). In this manner, the transmission 1 described in Japanese Patent Application Publication No. JP-A-2008-19886 reduces the amount of hydraulic oil in the differential chamber as much as possible to reduce the resistance when stirring the hydraulic oil during rotation of the ring gear 14.

SUMMARY OF THE INVENTION

However, in the transmission described in Japanese Patent Application Publication No. JP-A-2008-19886, a secondary shaft 8 is provided on the upper side of the ring gear 14, and the ring gear 14 meshes with a final gear 9 of the secondary shaft 8 before the hydraulic oil caught by the ring gear 14 is discharged into the oil pan chamber 3. Thus, the hydraulic oil caught by the ring gear 14 may be caused to stay in the grooves of the teeth of the ring gear 14 in the meshing portion where the ring gear 14 meshes with the final gear 9, and may flow back to the differential chamber 5 as it is. Moreover, the hydraulic oil scattered from a counter driven gear 13 of the secondary shaft 8 may flow into the differential chamber 5 from above.

It is an object of the present invention to provide a vehicle transmission that is capable of efficiently discharging, into a storage chamber, oil in a differential chamber that contains a differential unit, and is structured so that the oil is less likely to flow into the differential chamber.

A vehicle transmission according to the present invention (see, e.g.,FIGS. 5 to 9C) includes: an input shaft that is connected to a driving source and rotates; a countershaft provided parallel to the input shaft; a differential unit, which is positioned below the countershaft, to which rotation is input from the countershaft, and which is coupled to right and left wheels; a case member that contains the input shaft, the countershaft, and the differential unit; a differential chamber that is located in the case member, contains the differential unit, and is separated from a storage chamber that stores oil; and a differential separation member that separates the differential chamber from the storage chamber, and is formed along a ring gear of the differential unit, which meshes with an output gear of the countershaft. In the vehicle transmission, the differential separation member has an opening that opens so that the output gear can mesh with the ring gear, a communication portion, which is formed in an upper part of the differential separation member, and is located on an upstream side of the opening in a rotation direction of the ring gear during forward traveling, and which discharges the oil from the differential chamber, and a wall member that is provided on a side of a meshing portion of the output gear and the ring gear with respect to the communication portion, and stands so as to contact an outer surface of the differential separation member.

Thus, the communication portion for discharging the oil contained in the differential chamber is provided on the upstream side of the meshing portion of the ring gear of the differential unit and the output gear of the countershaft in the rotation direction of the ring gear during forward traveling. Accordingly, the oil caught by the ring gear can be efficiently discharged out of the differential chamber via the communication portion. Moreover, since the wall member is provided above the communication portion, the oil scattered from above the communication portion can be prevented from flowing into the differential chamber through the communication portion. Thus, since the oil contained in the differential chamber can be efficiently discharged through the communication portion, and the wall member can prevent the oil from flowing into the differential chamber through the communication portion, the oil level in the differential chamber can be maintained at a low level, and the stirring resistance of the ring gear can be reduced.

The present invention (see, e.g.,FIGS. 5-9C) is characterized in that the wall member has a main body portion that stands upward with a lower side of the wall member being in contact with the outer surface of the differential separation member, and a guide portion that guides the oil, which flows from above the communication portion along the outer surface of the differential separation member, to a side below the communication portion.

Thus, by using the guide portion, the oil scattered from above the differential chamber can be guided to the side below the communication portion after flowing onto the outer surface of the main body portion. This can reduce the amount of oil that flows into the differential chamber.

Moreover, specifically (see, e.g.,FIGS. 4A-4D), it is preferable that the guide portion be formed by bending the main body portion, and be formed so that a width of the guide portion decreases from the main body portion toward a tip end.

That is, since the guide portion is formed by bending the main body portion of the wall member, and is formed so that the width of the guide portion decreases from the main body portion toward the tip end, the oil discharged from the communication portion can be efficiently discharged. This can prevent the oil discharged from the communication portion from flowing back into the differential chamber.

It is preferable that the differential separation member (see, e.g.,FIGS. 4A-4D,6, and7) have the case member, a rib member that extends from the case member along an outer peripheral surface of the ring gear, and a semispherical reservoir plate that covers the differential unit from a side opposite to an inner surface of the case member with the ring gear interposed therebetween, and that the communication portion be formed in the rib member.

Thus, the oil can be efficiently discharged from the communication portion formed in the rib member.

It is also preferable that the wall member (see, e.g.,FIGS. 4A-4D) be formed integrally with the reservoir plate.

That is, since the wall member is formed integrally with the reservoir plate, the wall member can be provided without processing the case member. This facilitates processing, and can also contribute to reduction in cost.

It is also preferable that the wall member (see FIGS.8and9A-9C) be formed separately from the reservoir plate, and that the wall member be attached to the rib member so as not to protrude beyond a mating end face of the rib member with the reservoir plate.

That is, since the wall member is formed separately from the reservoir plate, and the wall member is attached to the rib member so as not to protrude beyond the mating end face of the rib member with the reservoir plate, assembly capability is increased, and the wall member can be prevented from being damaged by contact with other members during assembly.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention will be described below with reference to the accompanying drawings. The automatic transmissions of the present embodiments are six-forward speed automatic transmissions that are preferably mounted on a front engine front drive (FF) vehicle, and the “lateral direction” as used herein corresponds to the lateral direction in the state in which the automatic transmission is actually mounted on a vehicle. Note that the “vertical direction” as used herein is defined based on the state in which the automatic transmission is mounted on the vehicle. In the state in which the automatic transmission is mounted on the vehicle, the right side inFIG. 2corresponds to the front side of the vehicle, and the left side inFIG. 2corresponds to the rear side of the vehicle.

First Embodiment

[General Structure of Automatic Transmission]

First, the general structure of an automatic transmission1to which the present invention can be applied will be described below. As shown inFIG. 1, the FF type automatic transmission1includes a case member6that contains a speed change mechanism3, a countershaft portion4, and a differential unit5. An input member (a front cover and a center piece)10as the automatic transmission1which can be connected to an engine (a driving source)19, and a torque converter2having a lockup STOP clutch2aare disposed forward of the case member6.

The torque converter2is positioned on an axis centered on an input shaft7of the speed change mechanism3, which is located coaxially with an output shaft of the engine19, so that a driving force from the engine19is output to the input shaft7while allowing a rotational speed difference from the engine19, or is directly output to the input shaft7by engaging the lockup clutch2a. In other words, the input shaft7is structured to rotate by connecting to the engine19via the torque converter2.

The countershaft portion4is positioned on a countershaft12located on an axis that is parallel to the input shaft7. The differential unit5is positioned so as to have differential shafts15,15connected to right and left wheels18,18, on an axis parallel to the countershaft12.

The speed change mechanism3is provided with a planetary gear (a speed reduction planetary gear) DP on the input shaft7, and is also provided with a planetary gear unit (a planetary gear set) PU rearward of the planetary gear DP. The planetary gear DP is a so-called double pinion planetary gear including a first sun gear S1, a first carrier CR1, and a first ring gear R1, and having, on the first carrier CR1, a pinion P2meshing with the first sun gear S1, and a pinion P1meshing with the first ring gear R1so that the pinions P2, P1mesh with each other.

The planetary gear unit PU is a so-called Ravigneaux type planetary gear including, as four rotating elements, a second sun gear S2, a third sun gear S3, a second carrier CR2, and a second ring gear R2, and having, on the second carrier CR2, a long pinion P3meshing with the third sun gear S3and the second ring gear R2, and a short pinion P4meshing with the second sun gear S2so that the long and short pinions P3, P4mesh with each other.

The first sun gear S1of the planetary gear DP is held stationary with respect to the case member6. The first carrier CR1is connected to the input shaft7to rotate in the same manner as that of the input shaft7(hereinafter referred to as the “input rotation”). Moreover, the first ring gear R1rotates at a speed reduced from that of the input rotation, namely rotates as “reduced rotation,” by the first sun gear S1that is held stationary, and the first carrier CR1that rotates as the input rotation. The first ring gear R1is connected to a first clutch C1and a third clutch C3.

The third sun gear S3of the planetary gear unit PU is connected to a first brake B1so as to be capable of being held stationary with respect to the case member6, and is connected to the third clutch C3so that the reduced rotation of the first ring gear R1can be input to the third sun gear S3. The second sun gear S2is connected to the first clutch C1so that the reduced rotation of the first ring gear R1can be input to the second sun gear S2.

Moreover, the second carrier CR2is connected to a second clutch C2to which the rotation of the input shaft7is input, so that the input rotation can be input to the second carrier CR2via the second clutch C2. The second carrier CR2is also connected to a one-way clutch F1and a second brake B2, so that rotation of the second carrier CR2in one direction with respect to the case member6is restricted via the one-way clutch F1, and so that the second carrier CR2can be held stationary via the second brake B2. The second ring gear R2is connected to a counter gear8that is supported so as to be rotatable relative to a center support member fixed to the case member6.

A large-diameter input gear (a counter driven gear)11, which is fixed to the countershaft12of the countershaft portion4, meshes with the counter gear8, and a differential ring gear (a ring gear)14of the differential unit5meshes with the countershaft12via a small-diameter output gear12athat is formed on the outer peripheral surface of the countershaft12. The differential ring gear14is fixed to a differential gear13, and is connected to the right and left differential shafts15,15via the differential gear13.

The case member6will be described below. As shown inFIGS. 2-3, the case member6has a transmission case6(seeFIG. 2) that contains the input shaft7, the countershaft12, and the differential unit5, and a housing case6b(seeFIG. 3) that is attached to the transmission case6afrom the engine side. The case member6is integrally formed by attaching the housing case6bto the transmission case6aby a plurality of bolts.

The case member6contains, in a lower front part of the automatic transmission1(that is, on the driving source side (the right side) in the state in which the automatic transmission1is mounted on the vehicle), the differential unit5that is formed by the differential ring gear14, the differential gear13, and the differential shafts15. The countershaft12is provided above the differential unit5. The countershaft12is provided at a horizontal position different from that of the differential shafts15, and the countershaft12, the differential shafts15, and the input shaft7are arranged in a triangular pattern in the case member6.

A storage chamber B for storing oil that is sucked by a strainer, not shown, is formed in the lower side of the case member6. The differential unit5is contained in a differential chamber A, which is located in the case member and is separated from the storage chamber B by a differential separation member20. The differential separation member20is formed along the differential ring gear14, and includes the transmission case6a, a rib member21that extends from the transmission case6aalong the outer peripheral surface of the differential ring gear14, and a reservoir plate30(seeFIGS. 4A-4D) that will be described in detail later.

As shown inFIG. 2, the rib member (hereinafter referred to as the “transmission rib”)21of the transmission case6ais formed by an upper rib22that extends from the transmission case6aon the upper side of the differential chamber A, and a lower rib23that extends upward from the bottom of the transmission case6aalong the outer peripheral surface of the differential ring gear14. Between the upper rib22and the lower rib23is an opening24athat opens so that the differential ring gear14can mesh with the output gear12aof the countershaft12.

The upper rib22extends from the transmission case6atoward a meshing portion E where the differential gear14meshes with the output gear12a, and to the outer diameter side of the input gear11of the countershaft12, and the tip end of the upper rib22is bent upward along the outer peripheral surface of the input gear11. This reduces the possibility that oil scattered from the countershaft12, the input gear11, and the output gear12aonto an upper part of the inner surface of the transmission case6amay enter the differential chamber A. That is, the oil scattered from the countershaft12, the input gear11, and the output gear12ais actively introduced into a space portion S between the transmission case6aand the outer surface of the upper rib22, and is guided and discharged to the housing case side, whereby the amount of oil that flows into the differential chamber A is reduced.

A cutout22ahaving a constant width is provided in an intermediate portion of the upper rib22so as to extend toward an inner surface6a1of the transmission case6a(in the axial direction of the differential shafts15). The cutout22ais formed on the upstream side of the opening24ain a rotation direction (a rotation direction R2inFIG. 5) of the differential ring gear14during forward traveling, so that oil caught by the differential ring gear14can be discharged from the differential chamber A to the storage chamber B before the oil reaches the meshing portion E.

As shown inFIG. 3, a housing rib25having substantially the same shape as that of the upper rib22of the transmission case6ais formed in the housing case6b. The upper rib22and the housing rib25are structured so that when the housing case6bis attached to the transmission case6a, the outer peripheral surface of the upper rib22is substantially flush with the outer peripheral surface of the housing rib25, and the oil entering the space portion S can be guided to the housing case side.

Unlike the upper rib22, the housing rib25protrudes like eaves on the outer diameter side of the reservoir plate30, and does not directly form the outer wall of the differential chamber A. Thus, no cutout22afor discharging the oil from the differential chamber A is provided in an intermediate portion of the housing rib25. However, the base end of the housing rib25, which is located on the side opposite to the tip end thereof that is bent upward along the outer peripheral surface of the input gear11, opens without connecting to the housing case6b. This opening of the housing rib25serves as a discharge port25afor discharging the oil, which flows into the space portion S between the case member6and the rib members21,25formed by the transmission rib21and the housing rib25, toward the storage chamber B.

As shown inFIGS. 4A-4D, the reservoir plate30is a substantially semispherical (bowl-shaped) case member that protrudes in a central portion34thereof. On the outer peripheral edge of the reservoir plate30are formed wide, fin-like flange portions31a,31blocated on the upper and lower sides of the reservoir plate30.

The outer peripheral edge of the reservoir plate30is formed so as to open partially, and this opening34bcommunicates with an insertion hole34a, which is formed in the middle of the reservoir plate30to insert the differential shafts15therethrough. A wall member33that stands upward is formed integrally with the reservoir plate30, between the opening34band the upper flange31b.

The wall member33is formed by a main body portion33athat extends to the side opposite to the central portion34that protrudes toward the housing case in the axial direction of the differential shafts15, and a guide portion33bthat is formed by bending the end of the main body portion33alocated on the housing case side, at an obtuse angle toward the flange portion31b. The guide portion33bhas a triangular shape so that the width of the guide portion33bdecreases from the main body portion33atoward the tip end of the guide portion33b, and the tip end of the guide portion33bextends to the flange portion31b. More specifically, as shown inFIG. 4A, the main body portion33ahas a rectangular shape as viewed from the front, and the guide portion33bis formed by bending a corner of the main body portion33alocated on the upper side in the reservoir plate30. The guide portion33bis structured so that a base end33b1does not start at the same position as that of base ends33a1,33a2of the main body portion33a.

That is, the main body portion33ais structured to necessarily stand perpendicularly at the attachment portion33a1to the reservoir plate30, and the lower edge33a2that contacts the upper rib22. The guide portion33bis formed by bending the main body portion33ain an intermediate part of the standing of the base ends33a1,33a2of the main body portion33a.

Especially as shown inFIG. 4D, the guide portion33bhas a triangular shape as its upper edge33b3is always located at the same height as the main body portion33a, and its lower edge33b2is tilted upward, so that the distance1between the guide portion33band the reservoir plate30increases toward the tip end of the guide portion33b.

The structure of the differential chamber A in the state in which the reservoir plate30is attached will be described below with reference toFIGS. 5 and 6. As shown inFIGS. 5 and 6, the differential chamber A is formed by attaching the semispherical reservoir plate30to a boss6b1, which protrudes from the inner surface of the housing case6btoward the transmission case6a, via an attachment portion35. The differential chamber A is substantially spherical along the differential unit5.

In the state in which the reservoir plate30is attached, the flange portions31a,31bof the reservoir plate30extend along the lower rib23and the discharge port25aof the housing rib25, respectively, from which the oil tends to leak, and these flange portions31a,31bare in close contact with the rib members21,25so as not to allow the oil to flow into the differential chamber A. These flange portions31a,31bare pressed from the housing case side to the transmission case side by the housing rib25, whereby the flange portions31a,31bare more firmly in close contact with the rib members21,25.

The opening34bof the reservoir plate30and the opening24aof the transmission rib21together form an opening24in the differential chamber A, so that the differential ring gear14can mesh with the output gear12aof the countershaft12via the opening24.

In an upper part of the differential separation member20, the cutout22aof the upper rib22and a hole32of the reservoir plate30together form a communication portion26for discharging the oil caught by the differential ring gear14, at a position on the upstream side of the opening24in the rotation direction of the differential ring gear14during forward traveling. The differential chamber A communicates with the space portion S (the storage chamber B) formed outside the differential chamber A, by the communication portion26.

The wall member33of the reservoir plate30is provided on the meshing portion E side of the communication portion26. The wall member33stands upward so that the main body portion33aextends along the upper edge of the cutout22a(the edge located on the downstream side in the rotation direction R2of the differential ring gear14during forward traveling), and the lower side of the wall member33contacts the outer surface of the upper rib22(the surface of the upper rib22located on the side opposite to the surface faced by the differential shaft15. This prevents oil F2scattered into the space portion S from flowing into the differential chamber A through the communication portion26. That is, the wall member33stands perpendicularly from the outer surface of the upper rib22to prevent the oil from flowing into the differential chamber A through the cutout22a.

The oil F2, which flows from the side above the communication portion26along the outer surface of the upper rib22and the main body portion33a, is guided to the side below the communication portion26by the guide portion33bof the wall member33, which is bent at a predetermined angle toward the housing case6b.

Oil flow around the differential chamber will be described below with reference toFIGS. 5 to 7. When the driver gets into the vehicle, starts the engine19, and shifts the shift range to D range, power of the engine19is transmitted from the input shaft7to the countershaft12via the counter gear8and the input gear11.

When the power is transmitted from the input shaft7to the countershaft12, the countershaft12starts rotating from above toward the meshing portion E via the inlet of the space portion S (in a rotation direction R1ofFIGS. 5 and 7), and the power transmitted to the countershaft12is transmitted to the differential ring gear14of the differential unit5via the output gear12a. Thus, the differential ring gear14rotates from below toward the meshing portion E via the communication portion26(in the rotation direction R2ofFIGS. 5 and 7), and the power transmitted to the differential unit5is transmitted to the right and left wheels18by the differential shafts15.

When the countershaft12starts rotating in the direction R1, the oil is scattered from the input gear11and the output gear12ainto the space portion S. The oil F2entering the space portion S flows along the outer surface of the upper rib22to the lower side of the case member6, and is blocked by the main body portion33aof the wall member33when the oil F2is about to reach the communication portion26.

The oil F2blocked by the main body portion33aflows along the main body portion33a, and is guided toward the housing case by the guide portion33bthat is bent from the main body portion33atoward the housing case. The oil F2guided toward the housing case flows into the discharge port25aof the housing rib25, and flows along the outer surface of the semispherical reservoir plate30back into the storage chamber B.

On the other hand, when the differential ring gear14starts rotating in the direction R2, oil F1caught by the differential ring gear14is discharged out of the differential chamber through the communication portion26that is formed by the cutout22aextending through the upper rib22in the direction perpendicular to the axial direction of the differential shafts15.

After being discharged from the differential chamber A, this oil F1flows onto the back surface of the main body portion33aof the wall member33by inertia and flows along the main body portion33a, and also flows while being collected toward the housing case by the triangular guide portion33b. The oil F1that flows toward the housing case flows into the discharge port25aof the housing rib25, and flows along the outer surface of the semispherical reservoir plate30back into the storage chamber B.

As described above, the wall member33is formed to stand on the side above the communication portion26. This can prevent the oil entering the space portion S from flowing into the differential chamber through the communication portion26. In addition to the hole32of the reservoir plate30, the cutout22ais formed in the upper rib22as the communication portion26. This enables the oil F1to be discharged also from the upper rib side, whereby the oil can be efficiently discharged from the differential chamber A. Thus, since the possibility that the oil may flow into the differential chamber is reduced, and also the oil can be efficiently discharged from the differential chamber A, the oil level in the differential chamber can be maintained at a low level, and the stirring resistance of the differential gear14can be reduced.

Moreover, the guide portion33bis provided so as to be bent from the main body portion33aof the wall member toward the housing case, and this guide portion33bis formed in a triangular shape. Thus, the oil F2that flows from the side above the communication portion26can be guided to the discharge port25abeyond the communication portion26so as to flow back into the storage chamber B. Moreover, the oil F1discharged from the communication portion26can be guided toward the housing case, and the possibility that the oil F1may flow back into the differential chamber can be reduced.

Note that in the first embodiment, the communication portion26extending through the differential separation member20is formed by the cutout22aformed in the upper rib22and the hole32of the reservoir plate30. However, a through portion need only be formed in at least the upper rib22, and the cutout22amay be a through hole that extends from the differential chamber A into the space portion S.

The wall member33need not necessarily be formed integrally with the reservoir plate30. For example, the wall member33may be formed integrally with the upper rib22, and the guide portion33bof the wall member33need only be shaped so that the width of the guide portion33bdecreases from the main body portion toward the tip end, such as a trapezoidal shape, and need not necessarily have a triangular shape.

Moreover, in the first embodiment, the tip end of the guide portion33bis located at substantially the same position as that of the lower end of the cutout22a. However, as shown inFIG. 8, the guide portion33bmay extend significantly downward beyond the cutout22a, and may be formed so as to protrude toward the housing case.

Second Embodiment

A second embodiment of the present invention will be described below. Note that in the second embodiment, the wall member of the first embodiment is formed separately from the reservoir plate, and the guide portion is shaped so as not to protrude toward the housing case. Description of the same structure as that of the first embodiment will be omitted. In the first embodiment, the cutout22aof the upper rib22and the hole32of the reservoir plate30together form the communication portion26for discharging oil caught by the differential ring gear14. In the second embodiment, however, the hole32of the reservoir plate30is not provided, and only the cutout22aof the upper rib22forms the communication portion26.

As shown inFIGS. 9A-9CandFIGS. 10A-10F, a wall member40is formed as an independent part that is separate from the reservoir plate30and the upper rib22. The wall member40is formed by attachment portions41a,41b,41cfor attaching the wall member40to the upper rib22, inflow preventing portions42,43for preventing oil from flowing into the cutout22aof the upper rib22from the side of the opening24a, and a discharge portion43for guiding oil discharged from the cutout22atoward the housing case6band discharging the oil into the storage chamber B.

Specifically, the wall member40is structured by connecting a bag-shaped cover portion43that covers the cutout22a, to a main body portion42formed by a rectangular plate member standing along an upper edge22a1of the cutout22a, in the state in which the wall member40is attached to the upper rib22. The main body portion42and an outer surface43aof the cover portion43form the inflow preventing portions42,43.

That is, as shown inFIGS. 10A-10F, a surface (hereinafter referred to as the “front surface”)42aof the main body portion42facing the opening24ais a tapered surface tilted from the side of the transmission case6ato the side of the housing case6b, so that oil flowing from the side of the opening24ais guided toward the housing case6b(in the direction shown by arrow H inFIG. 9C) along the slope of the front surface42aof the main body portion42, and flows back into the storage chamber B.

As shown inFIGS. 10A and 10F, the height of the main body portion42increases toward the housing case6b, so that even if oil flows toward the housing case6b, the oil does not flow beyond the main body portion42. Even if the oil flows downward beyond the main body portion42, no oil flows into the differential chamber A through the cutout22aas the cutout22ais covered by the cover portion43.

The oil that has flown beyond the main body portion42is guided along the outer surface43aof the cover portion43to the side below the cutout22aor toward the housing case6bso as to flow back into the storage chamber B. That is, the outer surface43aof the cover portion43serves as a guide portion for guiding the oil flowing from above along the upper rib22to the side below the cutout22a.

The cover member43(the wall member40) is formed so as to open on the housing case side, and is structured so that its end face43clocated on the housing case side is substantially flush with a mating end face22bof the upper rib22with the reservoir plate30. In other words, the guide portion43is structured so as not to protrude toward the housing case6bbeyond the mating end face22bof the upper rib22with the reservoir plate30, namely a mating face X of the transmission case6aand the housing case6b(see alsoFIGS. 9A and 9B).

On the other hand, the cover portion43that forms the guide portion also forms the discharge portion by its inner surface43b, and the inner surface43bof the cover portion43has an upper standing surface43b1that stands on the back side of the main body portion42, and a lower standing surface43b2that stands so as to face the upper standing surface43b1.

An end of the cover member43, which is located on the downstream side in the rotation direction of the differential ring gear14during forward traveling and forms the lower standing surface43b2, is curved inward, so that the cover member43has a substantially J shape when viewed from the side. A guide passage45through which oil discharged from the cutout22aflows is formed by an end43d(hereinafter referred to as the “eaves portion”) located inside the cover portion43and extending in the shape of eaves toward the main body portion42, and the lower standing surface43b2.

Moreover, like the front surface42aof the main body portion42, the lower standing surface43b2is a tapered surface tilted from the side of the transmission case6ato the side of the housing case6b. Thus, the oil discharged from the cutout22aflows onto the upper standing surface43b1of the inner surface of the cover member, and flows into the guide passage45via a side surface43elocated on the transmission case side, due to a momentum generated when the oil flows onto the upper standing surface43b1. The oil is then discharged toward the housing case along the slope of the lower standing surface43b2to flow back into the storage chamber B.

The attachment portions41a,41b,41cfor attaching the main body portion42and the cover portion43to the upper rib22are provided at two positions on the housing case side of the wall member40(in the direction shown by arrow H inFIG. 10E), namely below the main body portion42and at an attachment base of the eaves portion43d, and at one position on the transmission case side of the wall member40(in the direction shown by arrow M inFIG. 10E), namely below the main body portion42.

Each of the attachment portions41a,41b,41cserves as a substantially U-shaped insertion portion for inserting therethrough an edge of the cutout22aprovided in the upper rib22. The first attachment portion41aprovided below the main body portion42on the housing case side is structured so as to be inserted on the upper edge22a1of the cutout22. The second attachment portion41bprovided at the attachment base of the eaves portion43don the housing case side is structured so as to be inserted on a lower edge (an edge located on the upstream side in the rotation direction R2of the differential ring gear14during forward traveling)22a2of the cutout22a. The third attachment portion41cprovided below the main body portion42on the transmission case side is structured so as to be inserted on a side edge (a side edge located on the transmission case side of the cutout, seeFIG. 2)22a3of the cutout22a.

Thus, since the wall member40is structured as a separate member from the reservoir plate30, the wall member40need not be extended from the reservoir plate that protrudes toward the housing case, and the guide portion of the wall member40can be formed by the cover portion43connected to the lower side of the main body portion42. Accordingly, the wall member40can be contained in the transmission case, and the guide portion can be prevented from being damaged by contact with a member provided on the housing case side, when assembling the transmission case6aand the housing case6btogether. This can increase assembly capability of the automatic transmission, and also can increase the yield.

More specifically, the transmission case6aand the housing case6bare assembled together after attaching the wall member40to the cutout22aof the upper rib22and attaching the reservoir plate30to the transmission case6a. At this time, since the guide portion43of the wall member40does not protrude beyond the mating face X of the transmission case6aand the housing case6b(seeFIGS. 9A-9C), the possibility of contact between the guide portion43and a member on the housing case side can be reduced.

Since the wall member40is attached separately from the reservoir plate30, the wall member40is not damaged by contact with the upper rib22when attaching the reservoir plate30to the transmission case6a.

Moreover, since the guide portion43is formed by the bag-shaped cover portion43that covers the cutout22afrom above, the oil that has flown beyond the main body portion42can be prevented from flowing into the differential chamber A through the cutout22a.

Since the main body portion42is formed integrally with the cover portion43, and the wall member40is fixed to the upper rib22by the plurality of attachment portions41a,41b,41c, the strength of the wall member40can be increased, and the wall member40can be held more firmly in close contact with the outer surface of the upper rib22.

Moreover, since the wall member40is structured as an independent part, three-dimensional taper shapes, such as the front surface42aof the main body portion42and the slope of the lower standing surface43b2, can be formed by injection molding, casting, etc. In particular, since the wall member40can be formed by injection molding, the wall member40can be easily formed by plastic such as resins.

Note that although the upper standing surface43b1, onto which the oil discharged from the cutout22afirst flows, is structured as a flat surface in the second embodiment, the upper standing surface43b1may be a tapered surface tilted from the transmission case side to the housing case side like the lower standing surface43b2. Alternatively, the discharge portion43bmay be structured, in which the upper standing surface43b1is a tapered surface tilted from the housing case side to the transmission case side so that the oil discharged from the cutout22ais efficiently collected to the guide passage45and is discharged from the guide passage45toward the housing case.

Alternatively, a discharge port that connects the inner surface43bwith the outer surface43aof the cover member43may be provided on the transmission case side of the lower standing surface43b2that forms the guide passage45, so that the oil accumulated on the transmission case side of the guide passage45due to a lack of a momentum can be discharged out of the cover portion43.

The first and second embodiments are described with respect to a six-forward speed automatic transmission. However, it is to be understood that the present invention may be applied to any type of stepped automatic transmission such as an eight-forward speed automatic transmission, and may be applied to any type of vehicle transmission such as a continuously variable transmission having a three-axis structure, a hybrid drive device, or a manual transmission. It is also to be understood that the inventions disclosed in the first and second embodiments may be combined in any manner.

The vehicle transmission of the present invention can be mounted on passenger cars, trucks, buses, and the like, and is especially preferable when used as a vehicle transmission such as a multi-stage automatic transmission or a continuously variable automatic transmission, or a hybrid drive device.