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...
Reexamination Certificate
2000-05-26
2001-11-13
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...
C192S083000
Reexamination Certificate
active
06315691
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a toothed selector clutch in a hydrostatic/mechanical, split-torque power-shift transmission. The transmission includes both a four-shaft epicyclic-gearwheel transmission and an infinitely variable hydrostatic transmission arranged in parallel. The power shift transmission includes a plurality of gearwheel stages each with an associated toothed selector clutch to thereby provide a plurality of gears. The selector clutch is operated to engage a gear within its associated stage. The hydrostatic transmission allows for an infinite variation of the transmission ratio of the overall hydrostatic/mechanical transmission.
German Patent No. 39 03 877 C1 discloses an infinitely variable, hydrostatic/mechanical power-shift transmission with toothed selector clutches, and is hereby incorporated by reference herein.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved selector clutch for effecting gear changes and, in particular, to provide a clutch that is compact in construction and operates reliably. It is another object of the present invention to provide a selector clutch that can effect gear changes at synchronous speeds in a load-free manner and without interruption to the tractive effort of the transmission.
In accomplishing the foregoing objects, there has been provided according to one embodiment of the present invention a toothed selector clutch in a hydrostatic/mechanical, split-torque power shift transmission having a four-shaft epicyclic-gearwheel transmission and an infinitely variable hydrostatic transmission arranged in parallel. The transmission includes downstream gearwheel stages each with associated toothed selector clutches thereby providing a plurality of gears. The hydrostatic transmission provides an infinitely variable transmission ratio for the hydrostatic/mechanical transmission. The toothed selector clutch includes a coaxial double differential clutch comprising: a clutch carrier mounted on a rotatable shaft; a shift bridge operatively connected to the clutch carrier by radial toothing thereby providing for the transmission of torque between the clutch carrier and the shift bridge and for the axial displacement of the shift bridge. The shift bridge is subjected to a pressure medium on axially opposite ends and includes shift toothing on each of the axially opposite ends. The clutch includes a pair of separately controllable pressure spaces internal to the shift bridge for applying pressure to the opposite ends of the shift bridge, each of the pressure spaces being capable of being subjected to pressure simultaneously to place the shift bridge in a neutral, central position. Each of the pressure spaces are capable of being depressurized individually so that the shift toothing at the end of the shift bridge adjacent the pressurized pressure space engages an adjacent gear at a synchronous speed without transferring load from the shaft to the gear being engaged and without interruption to the transmission of torque from the shaft to an engaged gear designated to be disengaged.
Preferably the clutch carrier includes a guide portion projecting between the two pressure spaces and two annular differential pistons which are situated axially opposite one another. Each of the differential pistons projects into one of the pair of pressure spaces and is configured to be supported axially against the clutch carrier only when shift bridge is in the neutral, central position so that when the shift bridge is displaced axially away from the neutral position into a shift position one of the annular differential pistons is displaced by a drive feature of the shift bridge, preferably toothing, into the adjacent pressure space. The clutch carrier may include a hole for guiding lubricating oil to the region of the drive feature.
The clutch is preferably arranged so that when the shift bridge is in the shift position, the displaced one of the annular differential pistons is configured to rest against an interior axial facing surface of the shift bridge. In addition, a pressurized-oil feed passing through the shaft and a rotating joint may be provided for each of the pressure spaces. The pressure of each of the pressure spaces may be controlled by a solenoid valve located upstream of the associated rotating joint. The shift bridge may include a bleed hole, extending between an internal area between the pair of annular differential pistons and an area external to the shift bridge to relieve pressure in the pressure spaces.
According to another embodiment the clutch may comprise a clutch carrier mounted to a casing; a shift bridge including shift toothing mounted on each of its axially opposite ends. The shift bridge is connected to a rotatable shaft by radial toothing thereby allowing torque transmission from the shaft to the shift bridge. The clutch further includes a double piston mounted in the clutch carrier. The shift bridge is also connected kinematically by a ball bearing to the double piston. The clutch further includes a pair of pressure spaces contained in within the clutch carrier. The double piston is capable of being displaced axially between the pressure spaces and the pressure within each of the pressure spaces is capable of being controlled separately so that when the two pressure spaces are simultaneously pressurized the double piston is positioned in a neutral, central position. Each of the pressure spaces is capable of being depressurized individually so that when one of the pressure spaces is depressurized the double piston and the shift bridge move axially into a shift position so that the shift toothing at the end of the shift bridge adjacent the other pressurized pressure space engages an adjacent gear at a synchronous speed without transferring load from the shaft to the gear being engaged and without interruption to the transmission of torque from the shaft to an engaged gear designated to be disengaged.
Preferably, the toothed selector clutch may further include two annular differential pistons situated axially opposite one another, each piston having an axial face adjacent one of the two pressure spaces, the differential pistons being supported axially against the clutch carrier only when the double piston is in the neutral, central position the differential pistons being configured so that when the double piston is displaced into the shift position of the shift bridge, one of the annular differential pistons is displaced by an associated drive feature of the double piston into the adjacent pressure space. The double piston may also be operatively connected to a displacement sensor.
In its generic aspects, the present invention provides a toothed selector clutch in a hydrostatic/mechanical, split-torque power-shift transmission having a four-shaft epicyclic-gearwheel transmission and an infinitely variable hydrostatic transmission arranged in parallel. The transmission includes downstream gearwheel stages with associated toothed selector clutches thereby providing a plurality of gears. The hydrostatic transmission provides an infinitely variable transmission ratio for the hydrostatic/mechanical transmission. The toothed selector clutch includes a coaxial double differential clutch comprising a shift bridge including shift toothing mounted on each of its axially opposite ends. The shift bridge is operatively connected to a rotatable transmission component by radial toothing thereby allowing torque transmission from the rotating component to the shift bridge and axial movement of the shift bridge relative to the rotating component. The clutch includes a pair of separately controllable pressure spaces, the pressure within each of the pressure spaces capable of being controlled separately so that when the two pressure spaces are simultaneously pressurized the shift bridge is positioned in a neutral, central position. Each of the pressure spaces is capable of being depressurized individually so that when one of the pressure spaces is depressurized the shift bridge moves axiall
Brockschmidt Detlev
Fredriksen Nils
Obermeier-Hartmann Robert
Claas Industrietechnik GmbH
Husch & Eppenberger LLC
Muir Robert E.
Wright Dirk
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