Planetary gear transmission systems or components – Steering by driving – With infinitely variable drive
Patent
1991-09-26
1992-08-18
Wright, Dirk
Planetary gear transmission systems or components
Steering by driving
With infinitely variable drive
475 28, F16H 344
Patent
active
051394650
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a speed-changing/steering system which is used on a vehicle and which has both linear speed-changing and steering functions, as well as to a method of controlling such a system. More particularly, the present invention is concerned with a 2-path hydromechanical transmission system for use in crawler-type vehicles and also to a method of controlling such a transmission system.
BACKGROUND ART
FIG. 6 shows a conventional power transmission system which is used on crawler-type vehicles such as bulldozers and which is capable of performing both linear speed change and steering. This system, known as 2-path hydrostatic transmission (referred to as 2-path HST, hereinafter) has, for the left and right crawler driving wheels 6, 7, hydraulic pumps 2, 3 driven by an engine 1, hydraulic motors 4, 5 and reduction devices 6a, 6b.
The power transmission system having such a 2-path HST, however, suffers from the following disadvantages due to the fact that all of the torque is transmitted through the HST. superior. large-size vehicles because hydraulic pumps and hydraulic motors capable of transmitting large power are not readily available are or, if available, very expensive. of the hydraulic pumps and motors. vehicle when the control is to be done through the control of operation of the hydraulic pumps and motors.
Accordingly, an object of the present invention is to provide a 2-path hydromechanical transmission (referred to as 2-path HMT, hereinafter) which employs an HST incorporating hydraulic pumps and motors of small capacities and which exhibit high efficiency with simple construction and ease of maneuver, as well as a control method for controlling such a 2-path HMT, thereby overcoming the above-described problems of the prior art.
SUMMARY OF THE INVENTION
To this end, according to the present invention, there is provided a 2-path hydromechanical transmission system, comprising: a power transmission line including independent left and right hydraulic pumps driven by an engine mounted on a vehicle and motors associated with the hydraulic pumps, and reduction planetary gear trains having reduction gear trains and differential planetary gear devices for transmitting the output torques of the hydraulic motors to left and right driving wheels of the vehicle; and an additional power transmission line including a reduction gear device having a bevel gear for distributing the output torque of the engine and forward and reverse 2nd speed clutches to which the output torque of the engine is distributed, and the reduction planetary gear trains for transmitting the output torques of the reduction gear device to the left and right driving wheels.
Left and right drive shafts to which the reduction gear trains and the reduction planetary gear trains are secured are connected to each other through a coupling device having a center clutch.
When the vehicle trams forward at a low speed, an engine mounted on the vehicle drives left and right hydraulic pumps to actuate hydraulic motors, the output torques of the hydraulic motors being transmitted to left and right driving wheels via reduction gear trains and other components, whereas, when the vehicle runs in the reverse direction, the left and right hydraulic motors are reversed.
When the vehicle is steered to the left or right, the connection between left and right drive shafts to which the reduction gear trains and other components are secured is dismissed by disengagement of a center clutch in the coupling device interconnecting the drive shafts, and the operation speeds of the left and right hydraulic motors are made to differ to cause a difference in the rotation speed between the left and right driving wheels, thereby causing the vehicle to be steered.
When the vehicle trams forward at a high speed, a forward 2nd-speed clutch and the center clutch are engaged, whereas, when the vehicle trams in the reverse direction at a high speed, a reverse 2nd-speed clutch and the center clutch are engaged, and the output torque of an
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patent: 3529492 (1970-09-01), Tuck
patent: 3538790 (1970-11-01), Polak
patent: 4183264 (1980-01-01), Reed
patent: 4799401 (1989-01-01), Reed
patent: 4995276 (1991-02-01), Zannberger
patent: 4997412 (1991-03-01), Reed
patent: 5026333 (1991-06-01), Meyerle
patent: 5030177 (1991-07-01), Reed
Kabushiki Kaisha Komatsu Seisakusho
Wright Dirk
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