Hydraulic switching valve, and a free piston engine provided the

Details Hydraulic switching valve, and a free piston engine provided the Hydraulic switching valve, and a free piston engine provided the

1997-04-28

1999-11-16

Nguyen, Hoang

Power plants

Internal combustion type free piston device supplies motive...

251 3002, F02B 7104

Patent

active

059836385

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a hydraulic switching valve according to the preamble of claim 1. Such switching valves are known as non-return valves and are used in hydraulic systems to ensure a proper operation thereof.
The flow in the conduit in which the valve is incorporated moves the valve body and the valve body blocks the flow in the conduit when it is pressed sealingly against the housing by this flow and the pressure generated by it, as a result of which this valve closes very quickly and also opens very quickly again after reversal of the direction of flow.
Because of its conventional structure, this non-return valve is only adapted for blocking a liquid flow through a conduit in one single direction and for unblocking the conduit very quickly when the pressures on the conduit connections are reversed. The opening of the valve is achieved within a very short time as a result of the fact that the valve body clears the entire flow opening at once under the influence of the pressure on the conduit connections.
It has been found that there is a need for a valve which remains closed for some time after the reversal of the pressures on the conduit connections, and which opens after the flow in the conduit has been unblocked by a control system, whereupon the liquid starts to flow.
The present invention aims to provide a hydraulic valve which opens very quickly after receiving a signal to that end, thereby unblocking a large oil flow.
To achieve this, the valve is executed in accordance with the characterizing part of claim 1.
By using a non-return valve, which can be locked in the direction of flow, a quick-switching valve is obtained. The short switching time chiefly results from the fact that the pressure difference across the valve is also responsible for the movement of the valve body, so that the latter can move very quickly and thus unblock the conduit completely within a very short time.
In a specific application, the hydraulic switching valve is employed as a starting valve in the hydraulic control system of a free-piston engine as described hereinafter with reference to FIG. 1. In such an engine, the power of the engine is determined by, among other factors, the stroke frequency, which is determined to a large extent by the rate at which the starting valve can open and take the oil supply from the pressure accumulator to the chamber to the maximum value thereof, without inadmissible flow losses. In conventional embodiments of this type of starting valve, the valve consists of an electrically actuated valve which unblocks the oil flow. Since the oil flow to be unblocked here is large, this usually implies that the electric part must be designed accordingly large, as a result of which the valve switches slowly, so that the maximum attainable frequency of the engine, and hence the maximum power that can be generated by the engine, will be limited. On the other hand, when the starting valve given a small size, allowing it to switch quickly, the pressure drop in the oil flow owing to flow losses in the starting valve becomes too big, resulting in a poor hydraulic efficiency of the engine. The oil flow rate is also lower in that case, as a result of which the free piston starts more slowly and the stroke frequency again is limited.
The aim of the invention is to provide a free-piston engine in which a large oil flow can be unblocked within a very short time, so that an engine with a high stroke frequency can be obtained.
To this end, the engine is provided with a starting valve according to one of claims 1-5.
By incorporating the quick-switching valve in the conduit between the pressure accumulator and the chamber, it is possible to have the engine make a new stroke shortly after the piston assembly has come to a standstill on the outer dead centre. Thus, the frequency of the engine can be controlled between a low value and a high value.
The invention is further explained with reference to the drawing with figures showing the application of a hydraulic switching valve in a free-piston engine as well as v

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patent: 4326380 (1982-04-01), Rittmaster et al.
patent: 4599861 (1986-07-01), Beaumont
patent: 5156080 (1992-10-01), Pelto-Huikko
patent: 5328147 (1994-07-01), Stobbs
patent: 5645263 (1997-07-01), Aardema

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