Planetary gear transmission systems or components – Fluid drive or control of planetary gearing – Fluid pump and motor in one of plural paths to or from...
Reissue Patent
2000-01-31
2001-11-27
Wright, Dirk (Department: 3681)
Planetary gear transmission systems or components
Fluid drive or control of planetary gearing
Fluid pump and motor in one of plural paths to or from...
C475S078000, C475S082000
Reissue Patent
active
RE037458
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an improved transmission of the type including a combination of hydrostatic (fluid) and mechanical drives. More specifically, the present invention relates to a transmission which may transmit power solely through the hydrostatic portion of the transmission, solely through the geared portion of the transmission, or in combination through both the hydrostatic and geared portions of the transmission.
BACKGROUND OF THE INVENTION
Both hydrostatic transmissions and geared transmissions are used in agricultural and construction equipment to transmit power from engines to equipment for accomplishing a desired task. For example, transmissions are used to properly transmit power to the wheels of a vehicle, or to a vehicle implement such as a rotor on an agricultural combine. However, depending upon the application, it is seldom that either a geared transmission or a hydrostatic transmission will provide the best performance for all of the transmission requirements. Two important considerations in selecting transmissions are their efficiency and range of input and output speed variability. In general, hydrostatic transmissions provide extremely high speed variability between the input and output, but are less efficient than geared transmissions.
Turning to the rotor of a combine, such rotors usually are relatively high in mass, and as the size of combines increases, become increasingly larger. Typical combines now use variable pulley belt drives to transmit power to the rotors. However, the power required to rotate the larger rotors of larger combines cannot be effectively transmitted through conventional belt drives. Also, the current machines have a provision to manually rotate the rotors in reverse, after they become clogged with excess material. This is not only cumbersome but also less effective with larger machines. Accordingly, in the larger combines there is a move toward using geared transmissions to drive the rotor and provide an engine-powered reversing feature. However, one of the problems with geared transmissions is the limited variability in speed. This limitation restricts the operator's ability to optimize rotor speed to obtain peak harvesting efficiency. Another problem with geared transmissions is the amount of energy which must be dissipated by the input clutch when engaging the power source to initiate rotation of the rotor. Due to the high inertia of large combine rotors, initiating rotation of the rotor when the combine engine is rotating at operating speed results in substantial wear of the input clutch to the transmission.
In view of the need for an improved transmission having improved variability between transmission input and output speed while maintaining efficiency, it would be desirable to combine the features of a hydrostatic transmission with a geared transmission.
SUMMARY OF THE INVENTION
The present invention provides a hydro-mechanical transmission. The transmission includes a clutch rotatably supported by a housing. The clutch includes a first input shaft, a second input shaft and a first output shaft, and is configured to selectively couple the output shaft to the first and second input shafts. The transmission also includes a motor coupled to the second input shaft, and a differential assembly coupled to the first output shaft. The differential assembly is rotatably supported by the housing, and includes a third input shaft coupled to the first output shaft, a fourth input shaft coupled to the motor, and second output shaft. The speed of the second output shaft is a combination of the speeds of the third and fourth input shafts.
The present invention also provides a method for increasing the speed of the output of the hydro-mechanical transmission. The method includes the steps of operating the first input shaft at a first rotational speed, operating the clutch to couple only the second input shaft with the first output shaft, and increasing the rotational speed of the motor to a speed which rotates the second output shaft at a second rotational speed such that the ratio of the first and second rotational speeds is within a predetermined range of a predetermined ratio. After the ratio of the first and second rotational speeds is within the predetermined range, the clutch is operated to couple the first input shaft with the first output shaft.
The present invention further provides a threshing system for a combine including a clutch having a first input shaft, a second input shaft and a first output shaft. The clutch is configured to selectively couple the output shaft to the first and second input shafts. The system also includes a hydraulic motor coupled to the second input shaft and a differential assembly. The differential assembly includes a third input shaft coupled to the first output shaft, a fourth input shaft coupled to the motor, and a second output shaft. The speed of the second output shaft is a combination of the speeds of the third and fourth input shafts. The system also includes an internal combustion engine coupled to the first input shaft, a hydraulic pump coupled to the engine and in fluid communication with the hydraulic motor, and a threshing rotor coupled to the second output shaft.
The present invention still further provides a method for increasing the speed of the rotor of the threshing system. The method includes the steps of operating the first input shaft at a first rotational speed defined by the speed of the engine, operating the clutch to couple only the second input shaft with the first output shaft, and increasing the rotational speed of the motor to a speed which rotates the rotor at a second rotational speed such that the ratio of the first and second rotational speeds is within a predetermined range of a predetermined ratio. After the ratio of the first and second rotational speeds is within the predetermined range, the clutch is operated to couple the first input shaft with the first output shaft.
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Case Corporation
Foley & Lardner
Wright Dirk
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