Motor vehicles – Power – Including traction motor of kind driven by noncompressible...
Reexamination Certificate
1998-07-28
2001-06-26
Vanaman, Frank (Department: 3611)
Motor vehicles
Power
Including traction motor of kind driven by noncompressible...
C180S053620
Reexamination Certificate
active
06250414
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a working vehicle having an engine disposed in a forward position of a vehicle body, and a propelling transmission disposed in a rearward position of the vehicle body for receiving engine output transmitted through a hydraulic stepless transmission.
2. Description of the Related Art
As an example of conventional working vehicles as noted above, an agricultural tractor is disclosed in Japanese Patent Laying-Open Publication H7-329587. This tractor has a body frame formed of an engine, a front transmission integrated with the rear of the engine, a transmission frame coupled at a forward end thereof to the front transmission, and a rear transmission coupled to the rear end of the transmission frame. A hydraulic stepless transmission is mounted in the transmission frame for changing speed of engine output and transmitting it to the rear transmission.
The above prior art vehicle has a complicated construction since the body frame and transmissions must be formed separately. This vehicle has a further disadvantage that an upper portion of the vehicle body is at a high level above the ground while the bottom of the vehicle body is at a low level above the ground.
Other conventional examples of working vehicles are disclosed in U.S. patent Ser. No. 4,997,760 and Japanese Patent Laying-Open Publication S64-16436. In these working vehicles, a stepless transmission is operable by a change speed pedal. The driver may operate the stepless transmission easily with a foot to control the running speed of the vehicle. In these working vehicles, the change speed pedal and a control part of the transmission are relatively remote from each other longitudinally of the vehicle body. Thus, where the change speed pedal and transmission are connected to each other through an interlocking mechanism (pivotal links and rods, etc.), friction and flexibility of connecting parts in the interlocking mechanism result in increased operational resistance and play, which impair response and tend to worsen operability of the vehicle. Besides, the change speed pedal is located at a low level for the level at which the transmission is disposed, and is low relative to the driver's seat. Consequently, when the driver depresses the change speed pedal, an excessive force acts on the driver's foot at a relatively early stage of operation. This results in inconveniences of a reduced shifting range and the like which tend to worsen operability.
As a further example of conventional working vehicles, a tractor is disclosed in Japanese Patent Laying-Open Publication H7-32897. In this tractor, a change speed pedal is supported by a support bracket fixed to a body frame. The change speed pedal is coupled to a trunnion (control part) of a stepless transmission through a link and so on. Running speed may be changed by controlling the stepless transmission with the change speed pedal. In many tractors, the driving deck is supported by the body frame through rubber cushions. In the tractors having a change speed pedal supported by the body frame as in this conventional tractor, the driver's foot attempting to operate the change speed pedal may inadvertently deviate therefrom when a relative displacement due to running vibration or the like occurs between the driving deck above the rubber cushions and the body frame below the rubber cushions.
SUMMARY OF THE INVENTION
An object of this invention is to provide a working vehicle having a simple construction regarding a body frame and transmissions while enabling easy shifting operations.
Another object of this invention is to provide a working vehicle having a change speed pedal of excellent operability for effecting change speed operations.
A further object of this invention is to provide a relatively simple speed control structure for allowing a stepless transmission to be controllable by a change speed pedal with excellent operability even for a working vehicle having a driving deck supported by a body frame through rubber cushions or the like.
The above objects are fulfilled, according to this invention, by a working vehicle comprising:
an engine disposed adjacent one end in a fore and aft direction of a vehicle body;
a propelling transmission case disposed adjacent the other end in the fore and aft direction of the vehicle body; and
an HST case disposed between the engine and the propelling transmission case;
the HST case housing a hydraulic stepless transmission having a hydraulic pump and a hydraulic motor for changing speed of engine output and transmitting the engine output to the propelling transmission in the propelling transmission case;
the HST case defining an oil chamber accommodating the hydraulic pump and the hydraulic motor;
wherein the engine, the propelling transmission case and the HST case constitute a body frame.
According to the above construction, the stepless transmission case is disposed between the engine and the propelling transmission case to form the body frame in combination with the engine and the propelling transmission case. The body frame has a simplified construction with the stepless transmission case used for forming the body frame. Moreover, a driving deck is located at a relatively low level so that the driver may board and alight from the deck with ease. Despite the low level of the deck, the bottom of the vehicle body is at a relatively high level to be free from contact with projections on unleveled terrain. Thus, the vehicle has an improved running performance.
The above working vehicle may further comprise a main clutch housing connected to the rear of the engine, wherein the HST case is connected between the main clutch housing and the propelling transmission case to increase frame strength.
To position the upper surface of the HST case in a reduced level and the bottom thereof in an elevated level, the hydraulic pump and the hydraulic motor may be arranged in the HST case transversely instead of vertically of the vehicle body, or a control device (a servo cylinder and a servo valve) for varying a swash plate angle of the hydraulic pump may be disposed on a side surface of the HST case.
Further, the hydraulic pump may advantageously have an intake port and a drain port arranged in a direction relative to the vehicle body different from a direction of arrangement of an intake port and a drain port of the hydraulic motor. For example, the ports of one may be arranged vertically while the ports of the other are arranged transversely of the vehicle body. Then, an oil line between the intake port of the hydraulic pump and the drain port of the hydraulic motor, and an oil line between the drain port of the hydraulic pump and the intake port of the hydraulic motor, may include minimum bends or bypasses to avoid a complicated layout. The two oil lines have a short and simple configuration.
In a preferred embodiment of the invention, the hydraulic stepless transmission is disposed adjacent and rearwardly of the main clutch, the hydraulic stepless transmission being operable by a change speed pedal disposed in a position above the hydraulic stepless transmission and where the hydraulic stepless transmission and the change speed pedal overlap each other in plan view.
Generally, the change speed pedal, if disposed adjacent the main clutch, is in an appropriate positional relationship with a driver's seat, to be easily operable without applying an excessive force to the driver's foot and through an increased depressing stroke. Where the hydraulic stepless transmission is disposed adjacent and rearwardly of the main clutch, the change speed pedal may also be disposed adjacent the main clutch. Besides, where the change speed pedal is operatively connected to the hydraulic stepless transmission through an interlocking mechanism, the interlocking mechanism may be small and light and free from excessive operational resistance and play at connections. This facilitates a control operation using the change speed pedal, and assures an improved response to
Hanamoto Kiyoshi
Miyake Hiroshi
Nagasawa Shota
Nakatani Yasunobu
Nishi Keishiro
Kubota Corporation
Vanaman Frank
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
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