Planetary gear transmission systems or components – With means to vary drive ratio or disconnect drive – Plural elements selectively braked
Reexamination Certificate
1999-09-28
2001-01-23
Lorence, Richard M. (Department: 3681)
Planetary gear transmission systems or components
With means to vary drive ratio or disconnect drive
Plural elements selectively braked
C475S290000, C475S276000
Reexamination Certificate
active
06176803
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to a transmission assembly, and more specifically to a transmission assembly with four planetary gear sets providing nine forward gear ratios and one reverse gear ratio.
BACKGROUND ART
Planetary transmissions are used in applications where strength and durability are required. One such transmission application is in work machines used for earth moving and other heavy duty applications. The strength of the planetary transmission is provided by having multiple planet gears intermeshed with the ring gear and sun gear of each planetary gear set. The multiple planet gears allow higher torque levels to be transmitted than would be possible using single gears as there is greater contact area between the intermeshed gears. Also, since the planet gears are evenly spaced about a planet carrier, the load from the planet gears is more evenly spread around the ring gear of the planetary gear set thereby further increasing the durability of planetary gear sets as compared to other gearing configurations.
For many work machines, it is desirable to have a large number of gear ratios so that the work machine can operate over a wide range of speeds while maintaining the engine in a narrow speed range which delivers maximum torque. The simplest means to provide a large number of gear ratios using planetary gear sets is to have a planetary gear set for each of the desired gear ratios. However, there are a couple of drawbacks to using a large number of planetary gear sets. The first drawback is the high cost associated with a large number of the planetary gear sets. The second drawback is that the greater contact area between the gears of the planetary gear set results in higher frictional losses as power is transmitted through the transmission, thus, reducing the overall efficiency of the transmission.
What is needed therefore is planetary transmission which overcomes the above-mentioned drawbacks.
DISCLOSURE OF THE INVENTION
In accordance with a first embodiment of the present invention, there is provided a transmission assembly having a housing, a first planetary gear set with double planet gears, a second, a third, and a fourth planetary gear each with single planet gears. The transmission assembly further includes an input shaft which drives the sun gear of the first planetary gear set, a first member which connects the planet carrier of the third planetary gear set and the ring gear of the fourth planetary gear set, and a second member which connects the sun gear of the third planetary gear set to the sun gear of the fourth planetary gear set. The transmission assembly yet further includes a third member which connects the ring gear of the first planetary gear set to (i) the planet carrier of the second planetary gear set and (ii) the ring gear of the third planetary gear set. The transmission assembly still further includes a fourth member which connects the planet carrier of the first planetary gear set to the sun gear of the second planetary gear set and an output shaft driven by the planet carrier of the fourth planetary set. The transmission assembly yet further includes (i) a first clutch between the input shaft and the second member, (ii) a second clutch between the input shaft and the first member, (iii) a third clutch between the fourth member and the housing, (iv) a fourth clutch between the ring gear of the second planetary gear set and the housing, (v) a fifth clutch between the third member and the housing, and (vi) a sixth clutch between the first member and the housing.
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Meyer Kevin G.
Paluska, Jr. Roy T.
Caterpillar Inc.
Ho Ha
Lorence Richard M.
Morrison John W.
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