Machine element or mechanism – Elements – Gear casings
Reexamination Certificate
1999-07-23
2001-02-20
Green, Mary Ann (Department: 3682)
Machine element or mechanism
Elements
Gear casings
C474S043000
Reexamination Certificate
active
06189412
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a transmission which is used on a vehicle, and particularly to the configuration of a housing (i.e., a transmission case) used for a belt-type continuously variable transmission which comprises a pair of pulleys and a belt disposed around these pulleys.
BACKGROUND OF THE INVENTION
Power transmissions which transmit power by a belt disposed around a pair of pulleys have been well-known and are widely used. As such a transmission, a belt-type continuously variable transmission comprises a pair of pulleys, each pulley having a variable groove width, and a belt disposed therearound. The V-belt pitch radii of the pulleys are variably changed by adjusting the groove widths of the pulleys, so that the speed ratio of the transmission is continuously varied. It has been known that this type of transmission can be used on a vehicle as disclosed in Japanese Laid-Open Patent Publication No. H4(1992)-258528, which was filed by the same applicant as for this application.
This vehicular continuously variable transmission comprises a drive and driven pulleys, a belt, a forward-reverse selector mechanism, a starting mechanism, a reduction train, a differential mechanism, etc. in a hosing, and for lubricating these mechanisms, forced-feed lubrication or sprinkled lubrication by gear rotation is carried out. The oil used for this lubrication is also used as a hydraulic pressure controlling fluid (hydraulic oil) for controlling the adjustment of the groove widths of the drive and driven pulleys and for controlling a clutch.
The hydraulic pressure which is used for the forced-feed lubrication and for the hydraulic control is generated by a hydraulic pump which is driven by an engine through a gear or a chain mounted on a shaft that is coupled to the engine, and the hydraulic pressure is delivered to the components which require lubrication and to the components which require hydraulic pressure control. After the hydraulic pressure is used for the respective purposes, the hydraulic oil flows downward from the respective components. Therefore, the transmission includes an oil well or an oil pan to collect the hydraulic oil, which is then recirculated by the hydraulic pump.
In this vehicular transmission, the hydraulic oil, which has been used for forced-feed lubrication and hydraulic pressure control, flows on and along the inner surface of the housing, which accommodates the continuous speed change mechanism, the starting mechanism, the reduction train, the differential mechanism, etc. of the transmission, and the oil flows through an opening which is provided in the lower portion of the housing, to the oil pan. In the housing, the space for accommodating each mechanism is partitioned with a cover, or the wall of the housing is configured to partition the accommodation space for each mechanism. In this case, an independent oil outlet is provided in the accommodation space partitioned for each mechanism.
However, in this construction of the continuously variable transmission, the position of each mechanism, i.e., the above mentioned continuous speed change mechanism, the starting mechanism, the reduction train, the differential mechanism, etc. in the housing is not arranged evenly equidistant with respect to the oil pan, and the lubrication oil, after being used, comes out of the rooms which are partitioned for the respective mechanisms in different amounts. Therefore, the hydraulic oil returning from each mechanism to the oil pan joins in the way back and forms a complicated flow in the housing, which may tend to produce bubbles and vortices in the hydraulic oil in the oil pan. As a result, the lubrication oil which is sucked from the oil pan into the oil pump may include mingled air, which may cause a shortage in the real amount of lubrication oil that is supplied to each mechanism and a decline of the pressure that is needed for proper lubrication. Also, the oil may acquire a high temperature, which renders the oil to lose viscosity and less effective as a lubricant.
SUMMARY OF THE INVENTION
It is an object of the present invention to equalize the flow of lubrication oil in a continuously variable transmission in the direction which is perpendicular to the input and output shafts of a continuous speed change mechanism.
It is another object of the present invention to stabilize the flow of lubrication oil returning to an oil pan in a continuously variable transmission.
It is yet another object of the present invention to eliminate bubbling of lubrication oil in an oil pan in a continuously variable transmission.
In order to achieve these objectives, the present invention provides a vehicular transmission which comprises a continuous speed change mechanism, a driving force transmission mechanism, a housing and an oil pan. The continuous speed change mechanism includes a drive pulley which is disposed on an input shaft, a driven pulley which is disposed on an output shaft, and a belt which is disposed around these pulleys for torque transmission. The housing accommodates the continuous speed change mechanism and the driving force transmission mechanism which includes a starting mechanism (also, a reduction train, a differential mechanism, a power transmission mechanism for an oil pump, etc.), and the oil pan is disposed at the lower part of the housing. The housing comprises a first room which accommodates the continuous speed change mechanism and a second room which accommodates the driving force transmission mechanism including the starting mechanism, and the first and second rooms are positioned above the oil pan. In the housing, at least one oil discharge passage is provided for each side of the oil pan in the horizontal direction perpendicular to the input and output shafts, and each oil discharge passage is positioned near and above the oil pan and used for returning the hydraulic oil (or lubrication oil) from each of the mechanisms in the first and second rooms to the oil pan. Furthermore, at least one inlet opening is provided for each of the oil discharge passages, and these inlet openings are positioned in the horizontal direction in the inner walls of the first and second rooms near and above both the sides of the oil pan.
This type of belt-type continuously variable transmission, which comprises a belt-type continuous speed change mechanism including a drive pulley, a driven pulley and a belt is very likely to lose transmission efficiency if the lubrication oil becomes short. Therefore, necessary lubrication must be maintained while preventing the flow of the lubrication oil from becoming a rotational resistance (or friction). By making the first room accommodating the continuous speed change mechanism as an independent room as described above, the necessary lubrication of the continuous speed change mechanism is carried out sufficiently while reducing the rotational resistance to a minimum.
The driving force transmission mechanism, which includes the starting mechanism, the reduction train, the differential mechanism, etc., is a mechanism which requires the output of the continuous speed change mechanism, and it includes gears and clutches. In the present invention, the driving force transmission mechanism is placed in the second room as a unit, so the system for the lubrication of the gears, the clutches, etc. is efficient. Furthermore, in the housing, at least one oil discharge passage is provided for each side of the oil pan in the horizontal direction perpendicular to the input and output shafts of the continuous speed change mechanism to return the hydraulic oil which is used for the control and lubrication of the mechanisms in the first and second rooms. These oil discharge passages are positioned near and above both the sides of the oil pan, which is partitioned by the walls of the housing with respect to the first and second rooms. In this construction, the lubrication oil returning from each room to the oil pan becomes an independent flow, so the flow of the lubrication oil is smooth without any deviation. As a
Ishikawa Tomoaki
Kita Hiroyuki
Kuroda Shuji
Ohyama Eiji
Suzuki Eiji
Armstrong, Westerman Hattori, McLeland & Naughton
Green Mary Ann
Honda Giken Kogyo Kabushiki Kaisha
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