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
1999-10-15
2001-09-04
Estremsky, Sherry (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...
C475S080000
Reexamination Certificate
active
06283883
ABSTRACT:
FIELD OF INVENTION
The present invention relates to a power transmission system that includes a rotatable and drivable first shaft which is adapted for co-action with a motor that forms part of a planetary gear arrangement, and a second shaft which is driven by said arrangement, wherein a planet gear belonging to the planet gear arrangement includes a centrally positioned sun wheel that co-acts with said first shaft, a number of planet wheels co-actable with said sun wheel, and a ring wheel co-acting with the planet wheels, and wherein an hydraulic system belonging to the planet wheel arrangement includes a pump unit and a motor unit, among other things.
The inventive power transmission system is adapted to drive a vehicle, preferably a cross-country vehicle, such that the first shaft can be conveniently-driven at a constant or gene. rally constant speed, so as therewith to drive an engine at a speed that corresponds to low contaminant emissions, high fuel economy and/or maximum power, regardless of vehicle driving conditions.
A power transmission system of the aforesaid kind is used to advantage in engine-powered vehicles where there is a need to be able to drive the vehicle in a low speed range, such as cross-country driving, or in a high speed range, such as along roads and highways.
More specifically, the present invention relates to a power transmission system that is based on the use of a planet gear in which the ring wheel belonging to said planet gear is braked and stationary in relation to the chassis when the second shaft, the output shaft, is driven hydraulically within a low speed range and where the ring wheel is free-running and can rotate within a high speed range.
In the following description, the low speed range is illustrated as 0-25 km/hr and the high speed range as 0-50 km/hr, although these speed ranges shall only be seen as examples of speed ranges.
The following description describes the co-action between different wheels, by which is meant preferably nonslipping co-action, such as a gearwheel co-action.
By direct coupling is meant direct co-action between two or more wheels, and by indirect coupling is meant co-action caused through the medium of one or more co-actable wheels.
By “wheel” is primarily meant a “gearwheel” in tooth co-action with one or more adjacent gearwheels.
BACKGROUND OF THE INVENTION
Several different kinds of such-power transmission systems are known in the art.
An example of such systems is described in Patent Publication DE-3 303 886. This publication describes and illustrates a planetary gear arrangement which includes a sun wheel (
13
) connected to a drive shaft (
12
), at least two planet wheels (
18
,
19
), and a ring wheel (
20
) which functions to drive an output shaft (
22
) while using an hydraulic torque converter (
27
,
28
,
29
).
The torque converter comprises two hydraulic pumps (
27
,
28
); each co-acting with its individual planet wheel (
18
,
19
), and connected hydraulically via a hydraulic conduit system (
29
).
Patent Publication U.S. Pat. No. 3,866,490 describes and illustrates a transmission system which uses a planet gear arrangement to regulate the speed of an output shaft in relation to an input shaft.
More specifically, the input shaft (
11
) is connected directly for driving the planet wheel carrier (
16
) via a connection sleeve (
17
), and therewith the planet wheels (
18
,
19
).
The outputs of this planetary gear assembly (
15
) comprise the ring wheel (
20
) on the one hand and the sun wheel (
21
) on the other hand.
A shaft (
29
) co-acts with a gearwheel (
30
) which, in turn, co-acts with a gearwheel (
31
) and drives an hydraulic unit (
33
) with variable displacement.
Patent Publication U.S. Pat. No. 4,750,381 teaches an hydromechanical transmission that can be used as an efficient, continuously variable transmission with the aid of a differential mechanism.
This publication discloses the use of an hydraulic transmission mechanism, a mode selecting mechanism, a locking mechanism and a clutch mechanism.
It will be noted in particular that the input shaft (
11
) acts on the planet wheels, and that the sun wheel is coupled directly to a pump unit (
5
) having a fixed pump/motor displacement, which is coupled hydraulically to a variable displacement unit (
7
).
The publication also describes the use of a locking mechanism (
11
) related to the sun wheel shaft and a clutch (
12
) belonging to the unit (
7
).
Patent Publication GB-A 1 174 778 describes and illustrates a transmission mechanism which is particularly adapted for automotive vehicles, said transmission mechanism being of the kind in which power is divided between a mechanical path and an hydrostatic path.
As with the present invention, this transmission mechanism is adapted particularly for use with cross-country vehicles, such as tractors, and carries out a major part of its work under conditions that require a low speed range and a high torque.
Patent Publication GB-A 1 379 213 illustrates and describes an hydromechanical transmission system that is able to offer a plurality of driving speed ranges.
There is used to this end an input shaft (
10
) and an output shaft (
12
), and a duplicated planetary gear arrangement (
4
) and an hydrostatic transmission (
16
) that can co-act with the two planetary gear arrangements (
14
).
SUMMARY OF THE INVENTION
Technical Problems
When taking into consideration the technical deliberations that a person skilled in this particular art must make in order to provide a solution to one or more technical problems that he/she encounters, it will be seen that on the one hand it is necessary initially to realise the measures and/or the sequence of measures that must be undertaken to this end, and on the other hand to realise which means is/are required in solving one or more of said problems. On this basis, it will be evident that the technical problems listed below are highly relevant to the development of the present invention.
When considering the prior art as described above, it will be seen that a technical problem resides in creating in a power transmission system of the aforedescribed nature conditions which will enable the system to operate within both a low speed range and a high speed range, and to realise the significance of allowing the ring wheel to be braked and made stationary relative to the chassis with regard to the low speed range and to allow the ring wheel to rotate in the high speed range, and therewith realise the significance of allowing the input shaft to drive the sun wheel and allowing the planet wheels to drive an hydraulic pump unit which is coupled hydraulically to an hydraulic motor, said unit functioning to drive the output shaft.
Another technical problem is one of realising the significance of creating while using one single planetary gear assembly including sun wheel, planet wheel and ring wheel such that the low speed range solely utilises an hydraulic system, a variable displacement hydraulic motor, and-an hydraulic clutch arrangement for speed control while using the mechanical planet wheel function in the high speed range, and by causing the hydraulic system to provide a split torque function in this latter application.
In respect of a power transmission system of the aforedescribed nature, a technical problem resides in realising the significance of adapting a first coupling or clutch unit for action between the ring wheel and/or a first gearwheel co-acting with said ring wheel, and a chassis, and adapting a second coupling or clutch unit for action between a second gearwheel co-acting with said hydraulic motor unit and said first gearwheel so as to drive said gearwheels simultaneously.
Another technical problem is one of realising the significance of causing the first coupling element to be in an actively coupled position or state and to lock the ring wheel against rotation in the first speed range, while causing the second coupling unit to be in an inactively-coupled state and therewith permit relative movement between said two gearwheels or the like, where said
Burns Doane , Swecker, Mathis LLP
Estremsky Sherry
Lewis Tisha D.
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