Power plants – Pressure fluid source and motor – With control means for structure storing work driving energy
Patent
1994-05-18
1995-12-12
Look, Edward K.
Power plants
Pressure fluid source and motor
With control means for structure storing work driving energy
417364, 123 46SC, F16D 3102
Patent
active
054738938
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a free-piston engine having a fluid pressure unit according to the preamble of claim 1.
In a known free-piston engine having a hydraulic unit (see U.S. Pat. No. 3,606,591), a second chamber portion of a second chamber is connected to the compression pressure accumulator through a connecting channel having a two-way valve. A compression stroke starts if a two-way switch is switched from the closed position to an open position. During the first part of the compression stroke hydraulic liquid flows through said two-way valve until, in a second part of the compression stroke, a connecting channel of a first chamber portion of the second chamber takes up the main part of the liquid flow from the compression pressure accumulator. In this prior art piston engine, very high and also conflicting demands are made upon the two-way valve. Then the two-way valve should have a very short switching time, ca. 1 ms, on the one hand requiring a small valve, and the two-way valve should have a relatively large flow capacity on the other hand in order to restrict the loss during the first part of the compression stroke. It is hardly possible to comply with these high and conflicting requirements so that in the present free-piston engines the efficiency is adversely affected by the loss of energy in the two-way valve, while the power of the engine is restricted by the slowness of the two-way valve.
It is an object of the invention to provide a free-piston engine having a fluid pressure unit in which said problem is solved in an effective way.
SUMMARY OF THE INVENTION
According to the invention, only pressure means, for instance a two-way valve connected to the compression pressure accumulator or an independent pulsating small pump, are required to effect a very slight movement of the plunger-shaped piston extension to cause the passage means in the plunger-shaped piston extension to be opened by the closure element whereafter the passage means take over the task of the pressure means. Due to this feature the pressure means is only required to deliver a small amount of hydraulic liquid without involving a great loss of energy. As a result, it is possible to select a very small and quick valve having a small slowness for the two-way valve. Generally speaking, the passage means in the plunger-shaped piston extension can be selected efficiently big to cause a low flow resistance reducing the loss of energy during the flow therethrough. Consequently, the present restrictions to the power of a free-piston engine by the two-way valve is broken down by the invention. The particular valve according to the invention may of course also be used for other functions.
Preferably, there are provided means acting such upon the closure element that when the piston springs back at the end of the expansion stroke the closure element follows the piston and continues to close the passage means, but when the compression stroke starts the closure element opening the passage means.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will hereafter be elucidated with reference to the drawing showing embodiments of a free-piston engine having hydraulic unit by way of example.
FIG. 1 shows a scheme, partly as longitudinal sectional view of the free-piston engine having a hydraulic unit.
FIG. 2 is an enlarged longitudinal sectional view of a part of the hydraulic unit of FIG. 1 illustrating the actual structural proportions of the exemplary embodiment.
FIG. 3-8 show the operation of the hydraulic unit with the help of different working positions of a part of an alternative embodiment of the hydraulic unit according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows an exemplary embodiment of a free-piston engine comprising a cylinder 1 and a movable piston 2 arranged therein. This piston 2 borders one side of the combustion room 3 and is movable between a first position or bottom dead centre in which the volume of the combustion room 3 is at a maximum, and a s
REFERENCES:
patent: 2731793 (1956-01-01), Lewis
patent: 3038298 (1962-06-01), Horgen
patent: 3044452 (1962-07-01), McCrory et al.
patent: 3606591 (1971-09-01), Potma
patent: 3613724 (1971-10-01), Carson
patent: 4599861 (1986-07-01), Beaumont
patent: 4803960 (1989-02-01), Koppen
Achten Peter A. J.
Potma Theodorus G.
Innas Free Piston B.V.
Look Edward K.
Nguyen Hoang
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