Power transmission device

A power transmission device includes: a main case having an inside storing an oil; a drum carrying up the oil; and a partition wall partitioning the inside of the main case into a transmission gear housing containing the drum and a catch tank. An inner wall of the main case includes a down-extending portion extending down toward a feed opening of the catch tank, and extending toward the drum rather than along a vertical plane extending in the vertical direction as the down-extending portion extends downward, and a receding portion bordering on the down-extending portion and extending away from the drum from a bordering point where the receding portion borders on the down-extending portion.

TECHNICAL FIELD

The present invention relates to a power transmission device.

BACKGROUND ART

In order to reduce the oil agitation resistance and suppress generation of a useless power loss, various types of transmissions and the like mounted with a lubricating oil level adjustment device and a lubricating device for example have hitherto been proposed.

For example, a power transmission device for a vehicle disclosed in Japanese Patent Laying-Open No. 2006-307908 is mounted with a lubricating device. This vehicle power transmission device is provided with a casing for storing a gear lubricating oil in its inner bottom portion, a first catch tank for catching to store the oil carried up by a ring gear, and a second catch tank provided separately from the first catch tank for catching to store the oil carried up by a drive gear.

Further, a transfer case disclosed in Japanese Utility Model Laying-Open No. 6-14611 is mounted with a lubricating oil level adjustment device, and the transfer case includes an oil catcher on a casing inner wall on the high-speed gear side. The bottom of the catcher has a leak hole formed therein, so that the input shaft and the output shaft are sufficiently lubricated while low-speed rotations are made and, while high-speed rotations are made, the splashed-up lubricating oil is stored in the oil catcher to lower the oil level and thereby suppress over-agitation of the lubricating oil by the gear.

In a crankcase lubricating structure for a V-type internal combustion engine disclosed in Japanese Patent Laying-Open No. 2007-92742, an oil that have collected in a bottom portion of a crankcase is discharged by means of movements of a connecting rod.

DISCLOSURE OF THE INVENTION

In the vehicle power transmission device disclosed in Japanese Patent Laying-Open No. 2006-307908 and the transfer case, the oil carried up by the gear or the like is caught by the oil tank or oil catcher, and further, even the oil dropping in the housing case containing the gear or the like, or flowing down along the inner surface of the housing case is also caught by the oil tank or oil catcher. As for the oil, the oil has a low temperature and has a high viscosity when the engine is started. Therefore, it takes some time for the oil pumped up by an oil pump to return to the bottom portion of the housing case, and accordingly the oil level in the housing case becomes lower. Thus, when the oil has a low viscosity and even the oil dropping in the housing case or flowing down along the inner surface of the housing case is caught by the oil tank or oil catcher for example, the oil level becomes lower and accordingly the oil level could become lower than an inlet of a strainer provided at the bottom of the housing case.

The present invention has been made in view of the problems as described above. An object of the present invention is to provide a power transmission device that in operation can reduce the oil agitation resistance while a rotating body such as gear is rotationally driven, and can prevent the oil level from becoming too low.

A power transmission device according to the present invention includes: a casing having an inside storing an oil; a rotating body provided rotatably in the casing and rotating while carrying up the oil; and a partition wall partitioning the inside of the casing into a rotating body housing containing the rotating body and an oil storing chamber capable of receiving the oil carried up by the rotating body, being adjacent to the rotating body housing, and located lower than a rotational axis of the rotating body. The partition wall defines a feed opening for feeding the oil into the oil storing chamber, the feed opening being defined lower in position than the rotational axis of the rotating body. An inner wall of the casing includes a down-extending portion and a receding portion. The down extending portion extends down toward the feed opening and, as the down-extending portion runs downward, the down-extending portion extends toward the rotating body rather than along a virtual vertical plane extending in a vertical direction. The receding portion borders on the down-extending portion and extends away from the rotating body from a bordering point where the receding portion and the down-extending portion border on each other. The partition wall includes an opening-defining wall portion located directly below the bordering point where the down-extending portion and the receding portion border on each other, and defining the feed opening together with a part of the inner wall where the bordering point is located. The opening-defining wall portion extends upward and extends away from the rotating body from a part located directly below the bordering point.

Preferably, a distance between the down-extending portion and the rotating body is smaller than a distance between the partition wall and the rotating body. Preferably, the down-extending portion extends along a virtual circle whose center is the rotational axis. Preferably, the down-extending portion protrudes closer to the rotating body, relative to a portion that is a part of the inner wall, located lower than the rotational axis and located opposite to the feed opening with respect to the down-extending portion. The inner wall includes a protruding portion defined by the down-extending portion and the receding portion and protruding toward the rotating body.

Preferably, a distance between the protruding portion and the rotating body is smaller than a distance between the rotating body and a part of the inner wall that is located higher than the protruding portion. Preferably, the power transmission device further includes a strainer disposed in a lower portion of the rotating body housing and capable of removing a foreign material in the oil. The oil storing chamber is located higher than the strainer.

The power transmission device according to the present invention in operation can reduce the agitation resistance of the oil for a rotating body such as gear and can prevent the oil level from becoming too low.

BEST MODES FOR CARRYING OUT THE INVENTION

A power transmission device according to an embodiment of the present invention will be described with reference toFIGS. 1 to 10. It should be noted that, where any number, quantity or the like is referred to in the embodiments described below, the scope of the present invention is not necessarily limited to the number, quantity or the like unless otherwise specified. Further, each element in the following embodiments is not necessarily requisite for the present invention unless otherwise specified. Furthermore, where a plurality of embodiments are illustrated below, it is originally intended that respective features of the embodiments may be combined as appropriate. A power transmission device in the present embodiment refers to an automatic transmission for an automobile. The automobile in the present embodiment refers to an FF layout automobile having its engine placed on the front side of the body and its front wheels operating as drive wheels.

FIG. 1is a schematic cross-sectional view of an automatic transmission in the embodiment of the present invention. The schematic cross-sectional view inFIG. 1corresponds to a cross section of the automatic transmission along line I-I inFIG. 3. The automatic transmission includes an input shaft652to which a rotational force is input. The rotational force that is input to input shaft652is transmitted to each gear as indicated by an arrow695and output from driveshafts666,667.

The automatic transmission includes a rear planetary gear train659, a front planetary gear train658and a counter drive gear654disposed on input shaft652. The planetary gear trains include gears for changing the speed and power.

Front planetary gear train658includes a sun gear710provided rotatably about input shaft652, a plurality of pinion gears730meshing with teeth formed on the outer circumference of sun gear710and rotating along the outer circumference of sun gear710, and a ring gear720provided on the outer circumference side of pinion gears730and meshing with each pinion gear730.

Rear planetary gear train659also includes a sun gear711provided rotatably about input shaft652, a plurality of pinion gears731provided on the outer circumference of sun gear711and meshing with sun gear711, and an annular ring gear721provided on the outer circumference side of pinion gears731and meshing with each pinion gear731.

The automatic transmission includes a clutch400changing connections between the gears that are components of rear planetary gear train659and front planetary gear train658to change the speed and power, and includes a brake401and a brake402for stopping the rotations of the gears.

The automatic transmission includes a drum691connected to clutch400and connected to input shaft652. Drum691rotates about a rotational axis O of input shaft652, and is provided on the outer circumference of clutch400and formed in the shape of a bottomed cylinder.

The automatic transmission includes a counter driven gear656disposed to mesh with counter drive gear654. On the shaft on which counter driven gear656is disposed, a differential drive pinion661is disposed. Differential drive pinion661is disposed adjacently to counter driven gear656.

The automatic transmission includes a differential662. Differential662includes a ring gear663as a second gear. Ring gear663is disposed to mesh with differential drive pinion661. Differential662includes a pinion gear668rotating together with ring gear663. Differential662includes a side gear669disposed to mesh with pinion gear668. Side gear669rotates to transmit the rotational force to driveshafts666,667.

The automatic transmission includes an oil pump665disposed on the axis of input shaft652. Oil pump665is formed to be able to pump up an oil stored in an oil pan673of a main case670described hereinlater.

The automatic transmission includes a torque converter664on the axis of input shaft652. Torque converter664is formed to be able to transmit the rotational force of the engine to input shaft652.

FIG. 2shows a schematic exploded perspective view of a casing of the transmission in the embodiment of the present invention. Referring toFIGS. 1 and 2, the transmission in the present embodiment includes main case670. In main case670, planetary gear trains such as front planetary gear train658and rear planetary gear train659, as well as gears such as counter driven gear656and differential662for example are disposed.

On the engine-side end of main case670, a torque converter housing671is disposed. Torque converter664is disposed in torque converter housing671. On the end opposite to the engine side of main case670, a rear cover672is disposed. On the lower side of main case670, oil pan673for storing the oil is disposed.

The oil in the present embodiment refers to an oil for the automatic transmission that is called ATF (Automatic Transmission Fluid). The oil in the present embodiment has the functions of driving gears for changing the speed and power, transmitting the rotational force of the engine in the torque converter, and providing lubrication for preventing seizure of mechanical elements such as gears, for example.

FIG. 3is a front view seen in the direction of an arrow III inFIG. 2. Referring toFIGS. 2 and 3, a transmission gear housing101, a differential gear housing102and a catch tank350are defined in main case670.

Transmission gear housing101is a housing containing drum691, front planetary gear train658and rear planetary gear train659for example. Drum691has the largest diameter relative to front planetary gear train658and rear planetary gear train659contained in transmission gear housing101.

Transmission gear housing101includes oil pan673in its bottom portion. Oil pan673is formed in the shape of a box whose upper side is opened. Transmission gear housing101is formed to be able to store the oil in its bottom portion.

The automatic transmission includes differential gear housing102as a second gear housing. Differential gear housing102is formed to contain the second gear different from a first gear which is ring gear721. The second gear in the present embodiment refers to ring gear663of differential662for example.

In differential gear housing102of the present embodiment, a plurality of gears of differential662are disposed. The bottom portion of differential gear housing102is formed along the shape of ring gear663that is one of the gears of differential662. Differential gear housing102is formed to be able to store the oil in its bottom portion.

In transmission gear housing101, a main shaft681that is the axis of input shaft652is inserted. In differential gear housing102, a differential shaft682corresponding to the axis of driveshafts666,667connected to differential662is inserted. Above differential shaft682, a counter shaft683that is the shaft of counter driven gear656and differential drive pinion661is inserted.

The automatic transmission includes a strainer674. Strainer674is formed to remove any foreign material from the oil. Strainer674includes an oil inlet674a. Inlet674ais disposed at the bottom of oil pan673. The automatic transmission includes a valve body675disposed on the upper side of strainer674. Valve body675is formed to be able to control switching of meshing relations between gears for changing the speed and power. Valve body675is also formed to be able to control engagement of the clutch in the transmission.

FIG. 4is an enlarged front view showing a part ofFIG. 3in an enlarged state to illustrate catch tank350and its neighborhood. As shown inFIG. 4, a partition wall301is provided to partition the inside of main case670into catch tank350and transmission gear housing101. Catch tank350is located lower than rotational axis O of drum691, and is disposed to be adjacent to differential gear housing102side, with respect to transmission gear housing101.

Partition wall301is disposed away from an inner wall200of main ease670toward drum691, and defines catch tank350in main case670, together with inner wall200of main case670.

Partition wall301includes a sidewall portion307extending in the direction of the height of the automatic transmission and defining a feed opening800for guiding the oil into catch tank350, and a bottom wall portion304having one end connected to the lower end of sidewall portion307and the other end connected to inner wall200of main case670. Feed opening800communicates with catch tank350, and feed opening800is located lower than rotational axis O.

In bottom wall portion304, a communication hole305allowing catch tank350and transmission gear housing101to communicate with each other is formed, such that the oil in catch tank350can be discharged to transmission gear housing101.

FIG. 5is a front view showing in detail a structure of feed opening800and its neighborhood. As shown inFIG. 5, drum691is provided rotatably about rotational axis O. Drum691is formed in the shape of a bottomed cylinder extending in the direction of rotational axis O. On the outer circumferential surface of drum691, projections692extending in the direction of rotational axis O are arranged and spaced from each other in the circumferential direction. A through hole693is provided in a portion located between projections692on the outer circumferential surface of drum691. Via through hole693, the oil for clutch400for example located inside drum691is discharged.

The surface of projections692is a curve extending along a virtual circle C1whose center is rotational axis O.

Inner wall200of main case670defining transmission gear housing101includes a portion202that is at least located higher than catch tank350and located on catch tank350side and differential gear housing102side with respect to rotational axis O, and this portion202is an arc-shaped wall portion202extending along a virtual circle C2whose center is rotational axis O. Arc-shaped wall portion202extends along the surface of projections692of drum691. In the automatic transmission of the present embodiment, arc-shaped wall portion202further extends from a portion located directly above rotational axis O toward the front side in rotational direction B.

Arc-shaped wall portion202is formed on inner wall200, and accordingly main shaft681can be disposed close to ring gear663and differential shaft682, so that the automatic transmission can be downsized.

Inner wall200also includes a down-extending portion203extending downward toward feed opening800. The down-extending portion is adjacent to feed opening800and located on the upper side of the feed opening. In the automatic transmission of the present embodiment, down-extending portion203extends along virtual circle C2whose center is rotational axis O, similarly to arc-shaped wall portion202.

Since down-extending portion203is located lower than rotational axis O, down-extending portion203curves to protrude toward drum691side, as the down-extending portion runs downward.

Down-extending portion203has a lower end bordering on a receding portion204. Receding portion204extends away from drum691as the receding portion runs downward from a bordering point P1where down-extending portion203and receding portion204border on each other. In the present embodiment, receding portion204is also arc-shaped and bordering point P1is a point of inflection of receding portion204and down-extending portion203. The present invention, however, is not limited to this.

An upper end portion (opening-defining wall portion)302of sidewall portion307extends upward from a point P2located directly below bordering point P1and extends away from drum691.

Feed opening800is defined by receding portion204and upper end portion302. Specifically, feed opening800is defined by bordering point P1where receding portion204and down-extending portion203border on each other, a part of partition wall301where point P2is located, and rear cover672shown inFIGS. 1 and 2.

FIG. 6is an exploded front view of the automatic transmission showing a state where several minutes have passed since the time immediately after drive of the engine is stopped.

As shown inFIG. 6, when drive of the engine is stopped and drive of oil pump665is also stopped, the oil pump-up operation by oil pump665is accordingly stopped. Further, the oil having been supplied to oil-supplied portions such as each gear, bearing, and clutch400shown inFIG. 1is returned to oil pan673.FIG. 6shows the state where approximately several minutes have passed since the engine stop, and the oil having been supplied to the oil-supplied portions is not completely returned.

FIG. 7is an exploded front view of the automatic transmission, showing a state where the engine having been stopped is driven.

Referring toFIG. 7, when drive of the engine is stopped for some period of time, the oil temperature decreases and the oil viscosity increases. Therefore, immediately after the engine is driven that has been stopped for some time, the oil having been supplied to each oil-supplied portion does not easily return to oil pan673, and accordingly an oil level R2becomes lower than catch tank350.

The oil supplied to clutch400for example shown inFIG. 1is discharged via through hole693shown inFIG. 5into transmission gear housing101. A part of the oil discharged via through hole693is sprayed onto arc-shaped wall portion202to flow down along arc-shaped wall portion202or drop between drum691and arc-shaped wall portion202.

The oil flowing down along arc-shaped wall portion202falls at bordering point P1from arc-shaped wall portion202to drop downward. Since sidewall portion307is located directly below bordering point P1, the oil dropping from bordering point P1falls on sidewall portion307.

Since upper end portion302extends upward from point P2of sidewall portion307, the oil dropping on sidewall portion307can be prevented from entering catch tank350via feed opening800.

Further, the oil dropping between arc-shaped wall portion202and drum691also drops onto sidewall portion307similarly. The oil dropping on sidewall portion307then flows down on sidewall portion307to be returned to oil pan673.

Down-extending portion203extends along virtual circle C2whose center is rotational axis O and is located lower than rotational axis O. Therefore, as down-extending portion203runs downward, down-extending portion203extends toward drum691rather than along a virtual vertical plane C3extending in the vertical direction. Thus, the oil flowing down along down-extending portion203falls off from bordering point P1in the direction of the tangent of down-extending portion203. Accordingly, the oil flowing down along down-extending portion203falls off from bordering point P1in the direction of the tangent of down-extending portion203, rather than along receding portion204from bordering point P1. In this way, the oil flowing down along down-extending portion203can be prevented from running along receding portion204to enter catch tank350.

Further, most of the oil flowing down along inner wall200of main case670toward feed opening800is the oil sprayed on a portion of arc-shaped wall portion202that is located on differential gear housing102side and catch tank350side with respect to the portion located directly above rotational axis O.

Here, arc-shaped wall portion202extends along on virtual circle C2whose center is rotational axis O and, in a region near feed opening800, arc-shaped wall portion202is located lower than rotational axis O. Accordingly, arc-shaped wall portion202located near feed opening800extends toward drum691rather than along the virtual vertical plane extending in the vertical direction, as the arc-shaped wall portion runs downward. Therefore, the oil flying off from bordering point P1is sufficiently accelerated so that the oil flies toward drum691rather than downward in the vertical direction. Thus, the oil flowing down along on arc-shaped wall portion202runs away from inner wall200at bordering point P1to fly off in the direction away from feed opening800.

In this way, the oil flowing down along arc-shaped wall portion202and down-extending portion203is prevented from entering catch tank350.

Even if the oil enters catch tank350, the oil is returned into oil pan673as described above through communication hole305, since communication hole305shown inFIG. 4is located higher than strainer674and valve body675.

Thus, in the process where the oil supplied to any oil-supplied portion such as clutch400is returned to oil pan673, the oil can be prevented from being caught by catch tank350. Therefore, the oil level in oil pan673can be prevented from becoming low. Accordingly, the oil level can be prevented from becoming lower than inlet674aof strainer674, and strainer674can be prevented from taking in the air.

FIG. 8is an exploded front view of the automatic transmission in a normal travel mode. As shown inFIG. 8, when a vehicle mounted with this automatic transmission travels in a normal mode, the oil temperature is higher than the oil temperature when the engine is started. The oil viscosity accordingly decreases. The oil once supplied by oil pump665to an oil-supplied portion is returned to oil pan673in a shorter period of time as compared with the time when the engine is started. Accordingly, oil level R3inFIG. 8is higher than oil level R2inFIG. 7.

FIG. 9is an exploded front view of the automatic transmission in a high-speed travel mode. InFIG. 9, when a vehicle mounted with this automatic transmission starts traveling at a higher speed than the normal travel mode shown inFIG. 8, the oil temperature becomes higher than the oil temperature in the normal travel mode and accordingly the oil viscosity decreases. Thus, the oil supplied to any oil-supplied portion returns to oil pan673in a shorter period of time than the normal travel mode.

Accordingly, in the high-speed travel mode, the oil level is higher than that in the normal travel mode. The higher oil level allows the oil stored in the bottom portion of transmission gear housing101to become contact with drum691and thus be carried up by drum691.

The oil carried up by drum691runs through feed opening800to enter catch tank350and to be stored in catch tank350. Thus, the oil can be prevented from returning into transmission gear housing101, and the oil level in transmission gear housing101can be lowered. As the oil level in transmission gear housing101lowers, drum691can be prevented from contacting the oil stored in the bottom portion of transmission gear housing101, and the oil agitation resistance in drum691can be reduced. The size of communication hole305is set such that the amount of oil returned per unit time from catch tank350into transmission gear housing101via communication hole305is smaller than the amount of oil supplied per unit time from feed opening800into catch tank350.

Referring again toFIG. 5, a distance L2from arc-shaped wall portion202and down-extending portion203to drum691is smaller than distance L1between sidewall portion307and drum691. Therefore, the oil carried up by drum691properly reaches feed opening800and runs through feed opening800to be stored in catch tank350. In contrast, the portion between down-extending portion203and drum691is narrower. Therefore, the oil adhering to the surface of drum691is brought to touch receding portion204and to be dropped.

In particular, receding portion204and feed opening800are located, in rotational direction B, on the front side of the position of the level of the oil stored in transmission gear housing101, and are further located lower than rotational axis O. Thus, the oil adhering to the surface of drum691can be dropped in an early stage. In this way, the oil adhering to the surface of drum691can be reduced and the rotational resistance of drum691can also be reduced. Accordingly, the drive efficiency of the engine can be improved. Moreover, since sidewall portion307curves away from drum691as the sidewall portion extends upward, the oil carried up by drum691can be properly guided to feed opening800.

FIG. 10is a partial cross-sectional front view showing a modification of down-extending portion203and feed opening800.

As shown inFIG. 10, as down-extending portion203runs downward, down-extending portion203extends toward drum691from the bordering point between down-extending portion203and arc-shaped wall portion202which is adjacent to down-extending portion203on the opposite side to feed opening800. The lower end of down-extending portion203borders on receding portion204, and down-extending portion203and receding portion204define a protruding portion205protruding toward drum691.

Accordingly, the oil flowing down along arc-shaped wall portion202is guided by down-extending portion203toward drum691, and flies off at bordering point P1toward drum691. Thus, the oil flowing down on arc-shaped wall portion202can be prevented from entering catch tank350from feed opening800.

In the example shown inFIG. 10as well, partition wall301includes upper end portion302extending upward from the position directly below bordering point P1and extending away from drum691.

Since protruding portion205protrudes from arc-shaped wall portion202toward drum691, a distance L3between protruding portion205and drum691is smaller than distance L1. Thus, a considerable amount of oil can be caused to drop from the surface of drum691, and accordingly the rotational resistance of drum691can be further reduced.

As indicated by the broken line inFIG. 10, an upper wall portion defining an upper portion of catch tank350may be formed as a bulging portion206bulging upward as the bulging portion runs from the end of receding portion204toward differential gear housing102.

Here, upper end portion302extends further toward differential gear housing102with respect to the position directly below a bordering point P3where bulging portion206and receding portion204border on each other.

Thus, even if a part of the oil flowing down along arc-shaped wall portion202passes through down-extending portion203and flows on the surface of receding portion204, the oil can be caused to drop at bordering point P3between receding portion204and bulging portion206, and the dropping oil can be prevented from entering catch tank350.

Regarding the above description of the embodiments of the present invention, it should be construed that the embodiments described herein are by way of illustration in all respects, not by way of limitation. It is intended that the scope of the present invention is defined by claims, and includes all modifications and variations equivalent in meaning and scope to the claims. Further, the above-referenced numerical values or the like are also by way of illustration, and the present invention is not limited to the above-referenced numerical values and ranges.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a power transmission device, and particularly suitable for a transmission.