192 clutches and power-stop control – Transmission control and clutch control – Interrelated
Reexamination Certificate
1999-07-30
2001-06-05
Bonck, Rodney H. (Department: 3681)
192 clutches and power-stop control
Transmission control and clutch control
Interrelated
C074S325000, C074S335000, C192S003510
Reexamination Certificate
active
06241066
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a working vehicle having a propelling clutch, a main change speed device and an auxiliary change speed device. More particularly, the invention relates to a shift control apparatus of this type of working vehicle.
2. Description of the Related Art
In a conventional working vehicle, when the auxiliary change speed device is shifted, the propelling clutch is operated automatically in an interlocked relationship thereto. Thus, an auxiliary change speed operation may be effected without requiring an additional operation to break power transmission from the engine to the auxiliary change speed device. However, in the conventional working vehicle, when the shift gear of the auxiliary change speed device is switched from a non-transmitting position to a transmitting position, the traveling device such as wheels is connected to the main change speed device through the auxiliary change speed device. After a shifting operation of the auxiliary change speed device is completed and before the propelling clutch is engaged, the main change speed device is in a state of transmitting power at a certain speed and has a relatively strong inertia to remain in that state. As a result, when the traveling device is connected to the main change speed device after the auxiliary change speed operation, the main change speed device imparts a resistance to the traveling device in inertial motion, which tends to produce a shock of change speed.
SUMMARY OF THE INVENTION
The object of this invention is to provide a structure for shifting a propelling transmission which allows a change speed operation to be carried out while minimizing a shock of change speed, and without requiring additional operations to break and restore transmission of engine output.
The above object is fulfilled, according to this invention, by a working vehicle comprising an engine, a propelling clutch driven by said engine, a first change speed unit driven by said propelling clutch and shiftable to a plurality of speed stages and to neutral by switching of a plurality of change speed clutches, a second change speed unit driven by said first change speed unit and shiftable between a transmitting position and a neutral position, traveling means driven by drive transmitted from said second change speed unit. The working vehicle further has associating means for automatically switching said propelling clutch and said change speed clutches in response to a shifting operation of one of said first and second change speed units such that, when said one of said first and second change speed units is shifted, said propelling clutch is disengaged and the other of said first and second change speed units is switched to neutral, and when said one of said first and second change speed units is switched to a transmitting state, said propelling clutch is engaged and the other of said first and second change speed unit is returned to a transmitting state. The associating means is operable to return said other of said first and second change speed units to the transmitting state, and then to engage said propelling clutch.
We now take an example where the main change speed device is a first change speed unit and auxiliary change speed device is a second change speed unit for the sake of simplicity.
With the above construction, when shifting the auxiliary change speed device (the second change speed unit), for example, the associating means operates automatically to disengage the propelling clutch and place the main change speed device (the first change speed unit) in neutral, thereby stopping power transmission from the engine to the auxiliary change speed device. Subsequently, the propelling clutch is automatically engaged, and the main change speed device is automatically returned to the transmitting state, to transmit engine output to the auxiliary change speed device.
In the returning operation, the main change speed device is first returned to the transmitting state, and then the propelling clutch is engaged. That is, the main change speed device is in neutral when the traveling device is connected to the main change speed device with the auxiliary change speed device switched to a transmitting state. Thus, the connection is made in such a way that the main change speed device imparts a less resistance to inertial movement of the traveling device than in the prior art. When the propelling clutch returns to an engaged state, the main change speed device has already returned to the transmitting state. Thus, the traveling device and main change speed device have dynamic inertia. A component of the propelling clutch interlocked to the main change speed device is connected to a component thereof interlocked to the engine in a way to produce little or no shock.
Thus, in time of an auxiliary change speed operation, the associating means automatically disengages the propelling clutch and main change speed device. The change speed operation may be performed in a simple way without requiring additional operations to break and restore transmission of the engine output to the auxiliary change speed device. Moreover, the traveling device returns to the driving state after the change speed operation, with the main change speed device hardly imparting resistance to the movement of the traveling device, and with the propelling clutch subjected to little or no shock. Consequently, the working vehicle may run smoothly and easily with little shock resulting from change speed operations.
The present invention is not limited to the above situation but can also be applied to the situation where, for example, the main change speed device (the first change speed unit) is shifted to a different speed position in which case, the propelling clutch and the auxiliary change speed device (the second change speed unit) is automatically switched to neutral by the associating means.
REFERENCES:
patent: 5429005 (1995-07-01), Fukui et al.
patent: 5651289 (1997-07-01), Asada et al.
Asada Akihiro
Kubota Hironobu
Bonck Rodney H.
Kubota Corporation
Lewis Tisha D.
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
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