Bearing lubrication system for extension housing of vehicular transmission

A bearing lubrication system for an extension housing of automatic transmission, including an extension housing connected to a transmission case, a valve casing of a hydraulic control system fastened to the transmission case, a transmission output shaft supported in the extension housing, and a sleeve yoke splined to the output shaft and fitted in a bearing portion of the extension housing through a bearing, characterized in that the lubrication system is provided with a forced lubrication means comprising: a bearing lubricant tapping passage branched off from a lubricant oil passage or line pressure conduit in the transmission case or in the valve casing; a bearing lubricant supply passage communicating the bearing lubricant tapping passage with the bearing portion of the extension housing; and a flow control throttle provided in the bearing lubricant tapping passage or in the bearing lubricant supply passage.

BACKGROUND OF THE INVENTION 
i. Field of the Invention 
This invention relates to a bearing lubrication system for extension 
housings of automatic transmissions for motor vehicles. 
ii. Description of the Prior Art 
An extension housing which constitutes part of a vehicular transmission 
case on the side of the transmission output shaft has a bearing portion 
for supporting the output shaft along with necessary lubricative means 
including oil seal. However, since it is located at the rear end of a 
transmission, smooth rotation of the output shaft is often hindered by 
restricted and insufficient supply of lubricant oil to those parts which 
need lubrication, resulting in undesirable output losses. In addition, the 
insufficient supply of lubricant oil gives rise to problems such as 
deterioration of sliding parts due to increased frictional heat generation 
and degradations of other parts induced by deterioration of sliding parts. 
For supplying lubricant oil to a bearing portion of an extension housing 
which supports an output shaft, it has been the conventional practice to 
distribute lubricant oil to inner wall surfaces of the extension housing 
through oil passages formed in the output shaft with the aid of 
centrifugal force, or to distribute the oil to the bearing portions along 
ribs or grooves formed on inner wall surfaces of the extension housing, 
mainly utilizing the drain oil of a governor valve as a lubricant oil. 
These methods of lubrication have the following drawbacks. 
(a) The drain oil which is supplied through the oil passages in the output 
shaft is applied to the inner wall surfaces of the extension housing by 
the centrifugal force, so that it fails to reach the inner wall surfaces 
of the extension housing in low speed operations. 
(b) The oil which is supplied to the bearing portions along grooves or ribs 
formed on the inner wall surfaces of the extension housing hardly 
distributed when the vehicle is in a forwardly inclined state or on a 
downhill. 
(c) The drain oil from the governor valve is not supplied when the shift 
lever is in neutral, reverse and parking positions. 
(d) The drain oil of the governor oil is leaked in a greater amount at high 
temperatures, while the supply of the lubricant along ribs becomes 
difficult at low temperatures due to increased viscosity of the oil. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a bearing lubrication 
system for an extension housing of vehicular automatic transmission, which 
is capable of supplying a lubricant to a bearing portion of an extension 
housing of an automatic transmission stably in a suitable amount without 
influenced by the speed and posture of the vehicle as well as temperature. 
It is another object of the invention to provide a bearing lubrication 
system of the sort mentioned above, employing a forced lubricating means 
capable of supplying a lubricant constantly to the bearing portion of the 
extension housing. 
According to a fundamental aspect of the invention, there is provided a 
bearing lubrication system for an extension housing of vehicular automatic 
transmission, including a transmission case, a speed-change mechanism 
housed in the transmission case, i.e., a gear transmission mechanism, a 
V-belt transmission mechanism or a planetary gear transmission mechanism, 
a hydraulic control system having a valve casing fastened to the 
transmission case, an extension housing connected to the transmission 
case, an output shaft mounted in the extension housing, and a sleeve yoke 
splined to the output shaft and fitted in a bearing portion of the 
extension housing through bushing or bearing, characterized in that the 
bearing lubrication system comprises: a bearing lubricant tapping passage 
communicating with a lubricant oil passage or line pressure passage in the 
transmission case or valve casing; a bearing lubricant supply passage 
communicating the bearing lubricant tapping passage with the bearing 
portion; and a flow control throttle provided in the bearing lubricant 
tapping passage or in the bearing lubricant supply passage. 
In a preferred form of the invention, the bearing lubricant supply passage 
is constituted by a pipe of a simple construction which is easy to 
assemble to communicate the bearing lubricant tapping passage with the 
bearing portion of the extension housing. 
The above-described bearing lubrication means according to the invention 
has the following advantageous effects. 
(1) The lubricant oil can be distributed to the bearing portion of the 
extension housing stably in an appropriate amount without influenced by 
the shift position. 
(2) The lubricant oil can be distributed to the bearing portion of the 
extension housing stably in an appropriate amount irrespective of the 
rotational speed of the output shaft. 
(3) The lubricant oil can be distributed to the bearing portion of the 
extension housing stably in an appropriate amount regardless of the 
posture of the vehicle. 
(4) The lubricant oil can be distributed to the bearing portion of the 
extension housing stably in an appropriate amount free of influences of 
coefficient of viscosity of the lubricant oil. 
The above and other objects, features and advantages of the invention will 
become apparent from the following description and appended claims, taken 
in conjunction with the accompanying drawings which show by way of example 
some preferred embodiments of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS 
Illustrated in FIGS. 1 to 3 is an extension housing bearing lubrication 
system according to the invention, which is incorporated into a typical 
vehicular automatic transmission 2 with four forward and one reverse speed 
ranges including overdrive (OD). 
This vehicular automatic transmission 2 includes: a torque converter 
housing (not shown) accommodating a torque converter, an overdrive 
mechanism and an input shaft of the automatic transmission; a transmission 
case 22 accommodating an intermediate shaft 20 connected to the input 
shaft, a speed-change mechanism 21 including a planetary gear system, 
clutches and brakes for shifts to and from three forward and one reverse 
positions; a hydraulic control system 24 fastened to the lower side of the 
transmission case 22 and including valves of various functions, shift 
valves for switching paths of oil pressure, a throttle valve for producing 
shift signals, an oil pump for generating oil pressure, and a valve casing 
23; an oil pan 25 accommodating the hydraulic control system 24; an 
extension housing 4 fastened to the rear side of the transmission case 22 
by bolts which are not shown, and accommodating an output shaft 3 
connected to the intermediate shaft 20, an electronic vehicle speed sensor 
27a mounted on the output shaft 3 and turned on and off by a lead switch 
which is not shown, or a governor valve 27b mounted on the output shaft 3 
to produce governor pressure commensurate with the rotational speed of the 
output shaft, that is to say, commensurate with the vehicle speed; a 
sleeve yoke 26 splined to the output shaft 3 and supported in a bearing 
portion 5 of the extension housing 4 through a bearing (a radial bearing) 
28; and a forced lubrication means 6 for supplying lubricant oil to the 
bearing portion 5 of the extension housing 4 stably in an appropriate 
amount. 
The bearing portion 5 of the extension housing 4 includes an oil seal 57 
which is mounted on an inner peripheral portion 56 of an extension 55 
projecting rightward in the drawing from the outer end of the bearing 
portion, thereby to prevent intrusion of foreign matter onto the output 
shaft 3 and leakage of the lubricant oil. A dust cover 59 is fitted around 
the outer peripheral portion 58 of the extension 55 to keep foreign matter 
off the oil seal 57. In the lower the bottom of bearing portion 5 is 
provided with a gutter-like extension 51 projecting toward the 
transmission case 22 (leftward in the drawing) and forming an oil pool as 
will be described hereinlater. Further, an oil hole 59A is formed in an 
upper portion of the bearing portion 5, in communication with an oil hole 
28A which is formed in the radial bearing 28. 
The forced bearing lubricating means 6 of the invention further includes an 
oil pool weir 70 which is constituted by the afore-mentioned gutter-like 
extension 51 and an annular plate 70A which is fixed on the inner 
periphery of the gutter-like extension 51 in coaxial relation with the 
output shaft 3. The annular plate 70A has its upper portion 70a supported 
by a holder portion 42 projected from the inner wall 41 of the housing 4, 
and its lower portion 70b supported on the fore end 53 of the gutter-like 
extension 51, forming an oil pool weir 70 to maintain the level of an oil 
pool 79, which is formed on the gutter-like extension 51 between the 
radial bearing 28 and oil pool weir 70, above the lowermost side 28a of 
the radial bearing 28. The lubricant oil is supplied to the bearing 
portion of the extension housing by a lubricant oil supply means which 
includes: a line pressure conduit 62 which supplies line pressure from the 
valve casing 23 to a hydraulic servo (not shown) of a shift mechanism 21 
through an oil chamber 61; a bearing lubricant tapping passage 63 formed 
by drilling or casting in a wall 22a of the transmission case 22 and 
branched off the line pressure conduit 62 at a position between the valve 
casing 23 and oil chamber 61; a flow control throttle (an orifice in the 
particular example shown) 64 mounted in the bearing lubricant tapping 
passage 63 to control the flow rate of lubricant oil by its constricting 
action; a cylinder tube or pipe 18 forming a lubricant supply passage 
connected at its one end 18A to the bearing lubricant tapping passage 63 
preferably through a connecting member 17 having as a seal means a 
cylindrical packing 16 which is fitted in a packing seat 15 formed one of 
joint surfaces 10 of the extension housing 4 and the transmission case 22, 
thereby preventing leakage of the lubricant oil and at the other end 18B 
to the oil holes 59A and 28A in the bearing portion 5 of the extension 
housing 4 and the radial bearing 28, and the pipe 18 being bent in such a 
manner as to evade the output shaft 3, oil pool weir 70, and electronic 
vehicle speed sensor 27a or governor valve 27b. 
With this arrangement, the operating oil (lubricant oil) in the line 
pressure conduit 62 is withdrawn into the cylinder tube 18 through the 
bearing lubricant tapping passage 63 at a suitable rate determined by the 
orifice 64. The lubricant oil which flows out of the terminal end 18B of 
the cylinder tube 18 is supplied to the bearing portion 5, more 
particularly, to the oil hole 59A to lubricate the oil seal 57 and radial 
bearing 28. After lubrication of the oil seal 57 and radial bearing 28, 
the lubricant oil is further distributed to lubricate the sleeve yoke 26 
and output shaft 3 before supply to the oil pool 79. Since the cylinder 
tube 18 is located in a position proximal to the outer periphery of the 
electronic vehicle speed sensor 27a, it is possible to provide an oil 
bleed hole in the cylinder tube 18 for the purpose of lubricating speed 
meter gears (not shown). As a consequence, the output shaft 3 is rotated 
smoothly to reduce losses of output power of the engine which drives the 
output shaft 3, as well as the fuel consumption of the engine. 
Although in the foregoing embodiment, the bearing lubricant tapping passage 
63 is constituted by a hole which is formed by drilling or casting in 
communication with the line pressure conduit 62, it may be formed in the 
valve casing 23 similarly by drilling or casting. 
Further, the cylinder tube 18 which constitutes a bearing lubricant supply 
passage may be replaced by a hole which is formed in the wall of the 
extension housing 4 or in the output shaft 3 by drilling or casting. If 
desired, the orifice 64 which is provided in the bearing lubricant tapping 
passage 63 may be provided in the cylinder tube 18 or in packing 16.