Motor vehicles – Having four wheels driven – Including pump and fluid motor – or generator and electric...
Patent
1997-10-22
2000-09-19
Dickson, Paul N.
Motor vehicles
Having four wheels driven
Including pump and fluid motor, or generator and electric...
180308, 60427, 60459, B60L 17356
Patent
active
061198021
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to the art of vehicles and, more particularly, to a hydraulic drive system for a vehicle.
2. Discussion of the Prior Art
Hydraulic drive systems for vehicles are known in the art. Most notably is the use of hydraulic drive systems on earthworking vehicles and other heavy machinery which operate in high torque/low speed environments. However, it has also been heretofore proposed to incorporate such drive systems on passenger vehicles.
In designing a new drive system for a vehicle, one must carefully weigh the efficiency advantages of the drive system against its associated cost. Because of these considerations, initial attempts at hydraulic drive systems have generally concentrated on combining a conventional drivetrain with a hydraulic power system. More specifically, the internal combustion engine and transmission assembly is retained and the output thereof drives a pump which supplies the necessary fluid to the hydraulic power system. A major advantage of such an arrangement is that the vehicle can be readily assimilated into the marketplace since the driving characteristics, as seen from a driver of the vehicle, is essentially unchanged. Unfortunately, the cost associated with such vehicles is much higher than conventional internal combustion engine driven vehicles and therefore these hydraulically driven vehicles have not been commercially successful.
Other known system designs obviate the need for a conventional transmission and simply permit the internal combustion engine to directly drive a pump used to supply hydraulic fluid to the system. In these known systems, a conventional accelerator or throttle member is controlled by the operator in order to adjust the operating speed of the engine and, generally, the engine is systematically started and stopped depending on sensed system pressure. The problem with these known systems is that they cannot be readily assimilated into the marketplace, they are rather costly given the fact the internal combustion engines (or correspondingly sized electric motors) are large (generally commensurate in horsepower ratings to conventional vehicle engines) and they are not efficient as compared to alternative drivetrains.
SUMMARY OF THE INVENTION
The basic objects of the present invention are to provide a hydraulic drive system for a vehicle wherein the system will be user-friendly so as to not require any additional training for use and will represent a drive system that exceeds potential alternatives with respect to operation efficiency. In addition, when applied to a passenger vehicle, the system will meet or exceed current standards with respect to acceleration, speed, handling, operating noise, dependability and cost; exhibit an increase in current mileage standards; and significantly reduce undesirable emissions.
These objects have been achieved by developing a hydraulic drive system that has a design generally based on volume instead of pressure. According to the invention, multiple drive units are drivingly connected to the vehicle wheels and torque requirements are met by the addition and subtraction of the number of drive units receiving fluid from a pump. With this arrangement, system pressure need only be maintained in an acceptable range. System pressure is developed by driving the pump by means of a power source or prime mover which can be constituted by an internal combustion engine that utilizes gasoline, propane, natural gas etc. or an electric motor. System pressure is built-up and maintained in an accumulator for use as needed.
In a preferred embodiment incorporating an internal combustion engine used to develop system pressure to four driven wheels, when additional system pressure is required, a pressure sensor triggers a speed regulator for the engine to increase the RPMs of the engine to an optimal running speed. When system pressure is again established within an acceptable range, the engine is automatically idled. As indicated above, shifting of the vehicl
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Anser, Inc.
Dickson Paul N.
Diederiks, Jr. Everett G.
Jasmin Lynda
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