Planetary gear transmission systems or components – Steering by driving – With infinitely variable drive
Reexamination Certificate
2000-01-24
2001-11-06
Wright, Dirk (Department: 3681)
Planetary gear transmission systems or components
Steering by driving
With infinitely variable drive
C475S027000
Reexamination Certificate
active
06312354
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an integral transaxle apparatus employing a hydrostatic and mechanical axle driving and steering system, including two hydrostatic transmissions (hereinafter, each hydrostatic transmission is called an “HST”) of the same type; one for driving left and right axles, and the other for steering the axles.
2. Related Art
A well-known conventional system for driving and steering left and right axles for wheels or sprockets of tracks, which employs a pair of HSTs provided for the respective axles, is disclosed in U.S. Pat. No. 4,782,650 or Japanese Laid Open Gazette No. Hei 2-261,952, for example. Output rotary speeds of the two HSTs are equalized for straight driving of a vehicle and made different from each other for steering of it.
The conventional system has the problem that the equalization of output rotary speeds between the two HSTs must be precise and if there is difference of capacity between the two, a vehicle is steered differently between leftward and rightward cornering.
The present invention includes an axle driving and steering system including two HSTs and a differential unit. In this regard, one of the HSTs (a driving HST) interlocks with a speed changing operation tool such as a lever or a pedal and transmits power from an engine into the differential unit so as to drive left and right axles forwardly or reversely. The other HST (a steering HST) interlocks with a steering operation tool such as a steering wheel and transmits its output rotational force corresponding to the direction and degree of the steering operation tool into the differential unit so as to differentially drive the axles.
However, even in such a system, the problem still remains that the individual elements serving as the two HSTs and the differential unit, and power transmission mechanisms interlocking the hydraulic motors of the two HSTs with the differential unit are so complicated as to hinder the system from being compacted as an integral apparatus.
Furthermore, the two HSTs should be fed with efficiently cooled fluid while a charge pump therefor is preferably compact.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a compact integral transaxle apparatus employing the above invented axle driving and steering system, so as to save its manufacturing cost and to ease its maintenance.
To attain the object, the integral transaxle apparatus is constructed so that a housing forming a fluid sump therein contains a pair of final output means, a differential unit for differentially connecting the final output means with each other, a first transmission system for steplessly driving the pair of final output means; including a first hydrostatic transmission (a first HST) and a first mechanical transmission, and a second transmission system for accelerating one of the pair of final output means and decelerating the other final output means, including a second hydrostatic transmission (a second HST) and a second mechanical transmission. Power of a prime mover is transmitted into the differential unit through the first HST and the mechanical transmission, and the second mechanical transmission driven by the second HST branches into two parallel drive trains drivingly connected to the pair of final output means, respectively, so that two oppositely directed equal rotational forces are applied onto the pair of final output means by the two drive trains.
The first transmission system is provided for driving a vehicle forward and backward, and the second transmission system is provided for steering the vehicle.
The first HST comprises a variable displacement first hydraulic pump and a first hydraulic motor fluidly connected with each other, and the second HST comprises a variable displacement second hydraulic pump and a second hydraulic motor fluidly connected with each other.
For horizontally compacting the integral transmission apparatus, the pair of final output means are a pair of axles disposed co axially with each other, the first hydraulic pump and the first hydraulic motor are aligned substantially in perpendicular to the axles, and the second hydraulic pump and the second hydraulic motor are aligned substantially in parallel to the axles.
Also, the first hydraulic pump and the first hydraulic motor are aligned along one side of the housing substantially perpendicular to the axles, and the second hydraulic pump and the second hydraulic motor are aligned along another side of the housing substantially parallel to the axles.
Also, the differential unit is opposed to the first HST in the direction of axes of the axles.
Also, the differential unit is disposed on abutting ends of the axles, and one of the axles crosses the first HST between the first hydraulic pump and the first hydraulic motor.
For vertically compacting the apparatus, in the case that the first HST comprises a first center section having fluid passages for fluidly connecting the first hydraulic pump and the first hydraulic motor with each other, cylinder blocks of the first hydraulic pump and the first hydraulic motor are disposed on the opposite side of the first center section as the first mechanical transmission. The motor shaft of the first hydraulic motor may penetrate the first center section.
Also, in the case that the second HST comprises a second center section having fluid passages for fluidly connecting the second hydraulic pump and said second hydraulic motor with each other, cylinder blocks of the second hydraulic pump and the second hydraulic motor are disposed on the opposite side of the second center section as the second mechanical transmission. The motor shaft of the second hydraulic motor may penetrate the center section.
Preferably, cylinder blocks of the first and second hydraulic pumps and the first and second hydraulic motors are disposed on opposite sides of the first and second center sections as the first and second mechanical transmissions.
The center sections of the first and second HSTs may be integral with each other, thereby reducing the number of parts.
The differential unit may comprise a pair of planetary gear units. Each planetary gear unit comprises a sun gear, a ring gear having an internal gear, a plurality of planet gears engaging with the sun gear and the internal gear of the ring gear, and a carrier rotatably supporting the plurality of planet gears and fixed onto each of the final output means. The sun gears of both planetary gear units are integral with each other.
The first mechanical transmission is a gear train engaging with the integral sun gears, and the second mechanical transmission branches into a pair of gear trains respectively engaging with the ring gears of the pair of planetary gear units.
A charge pump for fluidly feeding the two HSTs is disposed in the housing. A conduit for fluid discharged from the charge pump to be supplied into the first and second hydrostatic transmissions in the housing may be partly extended outwardly from the housing, so as to be cooled by the atmosphere. Also, fluid cooling means is preferably provided on the conduit outside the housing, thereby enhancing the effect of oil-cooling.
The charge pump disposed in the housing may be attached onto the center section fluidly connecting the first hydraulic pump and the first hydraulic motor of the first hydrostatic transmission with each other, so as to be driven by the first hydraulic pump of the first hydrostatic transmission and discharge fluid to the first hydrostatic transmission through a fluid passage formed within the center section.
For attaching the charge pump onto the center section, it is preferable that the charge pump integrally forms a seat to be attached onto the center section and a retainer for retaining a strainer. Also, for effective use of the inner space of the housing, cylinder blocks of the first hydraulic pump and the first hydraulic motor of the first hydrostatic transmission are mounted onto one side of the center section, and the charge pump is disposed on the opposite side o
Abend Robert
Andrews Keith J.
Hasegawa Toshiyuki
Irikura Koji
Ishii Norihiro
Kanzaki Kokyukoki Mfg. Co. Ltd.
Sterne Kessler Goldstein & Fox P.L.L.C.
Wright Dirk
LandOfFree
Integral hydrostatic transaxle apparatus for driving and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Integral hydrostatic transaxle apparatus for driving and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Integral hydrostatic transaxle apparatus for driving and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2595446