Power plants – Pressure fluid source and motor – Having distinct cooling or lubricating structure
Reexamination Certificate
1999-12-01
2001-05-22
Nguyen, Hoang (Department: 3748)
Power plants
Pressure fluid source and motor
Having distinct cooling or lubricating structure
C060S487000, C060S488000
Reexamination Certificate
active
06233929
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an axle driving apparatus including a housing and a hydrostatic transmission (HST) contained in the housing. More particularly, it relates to a cooling system for oil in the housing, an arrangement of an oil reservoir for regulating the volume of oil in the housing, and a cooling system for cooling oil in the reservoir in combination with an oil reservoir.
2. Related Art
An axle driving apparatus generally includes an HST having a hydraulic pump and a hydraulic motor fluidly connected with each other, a differential gear unit, and a transmission between a motor shaft of the HST and the differential gear unit. The HST is immersed in an oil sump formed in a housing. Such an axle driving apparatus is generally air-cooled by a cooling fan provided on an input shaft of the hydraulic pump projecting outward from the housing and by fins formed on an outer wall of the housing.
As described in Japanese Laid-Open Gazette Hei. 3-159822, a known axle driving apparatus includes a housing, an interior thereof being divided into first and second chambers. The first chamber contains a hydraulic pump and a hydraulic motor of an HST, and the second chamber contains a differential gear unit and a gear train forming the transmission. An oil reservoir is disposed above the first chamber.
When such a conventional axle driving apparatus utilizes the above mentioned air-cooling system having a cooling fan, the oil located in the housing is not sufficiently cooled by air-cooling the wall of the housing. Thus, the efficiency and life of the HST are reduced.
Known oil reservoirs, as shown by Japanese Laid-Open Gazette Hei. 3-159822, project upwardly from the housing whereby a large vertical space is required for mounting the axle driving apparatus on a vehicle. Also, reservoirs which are disposed so high are generally juxtaposed with an input shaft of the HST which projects vertically upward from the housing. Thus, the reservoir is removed from the air-cooled area exposed to the cooling wind of the cooling fan. Thus, oil in the reservoir cannot be sufficiently cooled by the cooling fan.
When the oil is not cooled sufficiently, the temperature of the oil increases and the HST cannot operate smoothly.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an effective oil cooling system for an improved axle driving apparatus including an HST contained in a housing having a cooling fan disposed at an exterior of the housing for sufficiently cooling the HST and other components contained in the housing.
To achieve the first object, an oil passage is disposed in an air-cooled area in which the wind generated by the cooling fan blows. The cooling fan is provided on an input shaft of the HST which projects outward from the housing. A chamber is formed in the housing. The chamber is filled with oil, thereby defining an oil sump. The HST is housed in the chamber and immersed in the oil sump. The oil passage leads oil from the oil sump through one port and returns it to the oil sump through another port. Oil is cooled more effectively by the cooling fan while flowing through the oil passage as compared to oil in the chamber which is cooled by fanning the housing alone.
At least one of the ports is provided with a pump driven by the input shaft for circulating oil between the oil sump and the oil passage. Accordingly, a substantially continuous flow of oil cooled while flowing through the oil passage flows into the chamber. Simultaneously, a substantially continuous flow of oil flows from the chamber through the other negatively pressurized port for cooling. While the input shaft is rotated, oil circulates substantially continuously between the oil sump and the oil passage whereby the oil sump is always supplied with cool oil. Thus, the HST and other components of such an axle driving apparatus are effectively cooled.
A second object of the invention is to provide an axle driving apparatus including a housing, an HST located in the housing, and a second oil sump (e.g., a reservoir) which regulates the volume of the oil in the housing, wherein the second sump is disposed in a manner that provides a compact design and provides an effective cooling system for the oil in the second oil sump.
To achieve the second object, an input shaft of the HST projects outward from the housing and is oriented substantially vertically. The second oil sump is disposed in an air-cooled area below a cooling fan mounted on a portion of the input shaft which projects out of the housing. The second oil sump effectively receives the wind of the fan, thereby sufficiently cooling the oil in the second oil sump.
The level of the second oil sump is lower than that of a first oil sump in the housing (i.e., a conventional oil sump). The second oil sump may be located on any outer wall area of the housing. Thus, placing the second oil sump on an advantageous area of the housing allows the apparatus to be entirely compacted, whereby the vertical space required for attaching the apparatus to a vehicle is reduced.
A siphon interconnects the second sump and the first sump in the housing, thereby enabling oil to flow between the sumps in both directions. Thus, the volume of oil in the first sump can be simply regulated.
Preferably, a reservoir defining the second sump is mounted on a wall of the housing. Such a reservoir includes a pair of side surfaces which face each other. A pair of first fixtures is located on the pair of sides, respectively. The housing is provided with second fixtures corresponding to the first fixture. The first fixtures are either concave or convex. The second fixtures are shaped to engage with the first fixtures, respectively, and are provided at the both ends of a U-shaped modifiable elastic plate.
Since the reservoir of the present invention is mounted on the wall of the housing, it is easily assembled, simply and firmly mounted upon the wall of the housing. In this regard, the fixtures allow the reservoir to be quickly removed and mounted on the housing. The fixtures are produced easily and at a low cost due to the simple construction.
To achieve both the first and second objects simultaneously, the second oil sump and the oil passage for circulating the oil of the first oil sump are disposed in the air-cooled area of the fan. The siphon is provided for enabling a portion of oil in the oil passage to flow into the second oil sump.
In this construction, the oil passage is made of a conduit having couplings provided at both of ends of the conduit. The housing is provided with a pair of outward openings for communicating the oil passage with the first sump. The couplings cover respective openings. The siphon branches from one of the couplings.
These and other objects, features and advantages of the invention will become more apparent from the detailed description and drawings which follow.
REFERENCES:
patent: 3654761 (1972-04-01), Eickmann
patent: 5394699 (1995-03-01), Matsufuji
patent: 5515747 (1996-05-01), Okada et al.
patent: 5622051 (1997-04-01), Iida et al.
patent: 5802851 (1998-09-01), Krantz
patent: 6073443 (2000-06-01), Okada et al.
patent: 3-159822 (1991-09-01), None
Ishii Norihiro
Okada Hideaki
Kanzaki Kokyukoki Mfg. Co. Ltd.
Nguyen Hoang
Sterne Kessler Goldstein & Fox P.L.L.C.
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