EP1180593A1

EP1180593A1 - Method of controlling power output of a stirling engine

Info

Publication number: EP1180593A1
Application number: EP00117616A
Authority: EP
Inventors: Gordon Fenn
Original assignee: Cybertech Ventures Inc
Current assignee: Cybertech Ventures Inc
Priority date: 2000-08-16
Filing date: 2000-08-16
Publication date: 2002-02-20

Abstract

A method of controlling power output of a Stirling engine having a casing, a displacer slidably fitted in the casing, and a working piston disposed under the displacer and slidably fitted in the casing, comprising the steps of: providing the casing with a bleeding passage extending radially outwardly between the displacer and the working piston, and providing means for adjusting volume of the bleeding passage, whereby the power output of the Stirling engine can be accurately controlled.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention is related to a method of controlling power of a Stirling engine and in particular to one which can accurately control the power output of an engine.

2. Description of the Prior Art

The conventional Stirling engine is an external combustion reciprocating engine, patented by a Scottish clergyman, Robert Stirling, in 1827. It consists essentially of a cylinder in which a working piston and a displacer operate. When the air or a suitable gas in the cylinder is heated, it expands, driving the working piston. The displacer transfers the air to a cold region for cooling: it is then recompressed by the working piston and transferred by the displacer to the hot region to start the cycle again. Such an engine is very much quieter and cleaner than a petrol or diesel engine. Since that time, various Stirling engine systems have been prototyped and put into limited operation throughout the world. However, the power output of the Stirling engine systems cannot be accurately controlled thereby making them unfit for practical use.
Therefore, it is an object of the present invention to provide a method of accurately controlling power output of a Stirling engine.

SUMMARY OF THE INVENTION

This invention is related to a method of controlling power of a Stirling engine and in particular to one which can accurately control the power output of an engine.
According to a preferred embodiment of the present invention, a method of controlling power output of a Stirling engine having a casing, a displacer slidably fitted in the casing, and a working piston disposed under the displacer and slidably fitted in the casing, comprising the steps of: providing the casing with a bleeding passage extending radially outwardly between the displacer and the working piston, and providing means for adjusting volume of the bleeding passage, whereby the power output of the Stirling engine can be accurately controlled.
It is the primary object of the present invention to provide a method of accurately controlling the power output of a Stirling engine.
The foregoing objects and summary provide only a brief introduction to the present invention. To fully appreciate these and other objects of the present invention as well as the invention itself, all of which will become apparent to those skilled in the art, the following detailed description of the invention and the claims should be read in conjunction with the accompanying drawings. Throughout the specification and drawings identical reference numerals refer to identical or similar parts. Many other advantages and features of the present invention will become manifest to those versed in the art upon making reference to the detailed description and the accompanying sheets of drawings in which a preferred structural embodiment incorporating the principles of the present invention is shown by way of illustrative example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of a first preferred embodiment according to the present invention; and
FIG. 2 is a longitudinal sectional view of a second preferred embodiment according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings. Specific language will be used to describe same. It will, nevertheless, be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated herein being contemplated as would normally occur to one skilled in the art to which the invention relates.
Referring to FIG. 1, the Stirling engine according to the present invention generally comprises a casing 100, a displacer 1, a first connecting rod 11, a second connecting rod 12, a working piston 2, a flywheel 6, and an adjust screw 5. As shown, the casing 100 has an upper end 101 from which heat is transferred to the air inside the casing 100. The upper end 101 may be replaced with a cap made of ceramic or the like so as to enable it to store more energy for heating the air inside the casing 100. The casing 100 is formed with a plurality of fins below the upper end 101 for cooling down the air inside the casing 100. The displacer 1 is fitted into the casing 100 so that it can reciprocate within the casing 100. The first connecting rod 11 is connected with the displacer 1 at one end and the flywheel 6 at the other. The working piston 2 is disposed under the displacer and connected with the flywheel 6 via the second connecting rod 21. The casing 100 is formed with a bleeding passage 4 extending radially outwardly between the displacer 1 and the working piston 2. The adjust screw 5 is threadedly engaged with the outer end of the bleeding passage 4. As the adjust screw 5 is turned slightly into the bleeding passage 4, the volume of the bleeding passage 4 will be changed thereby decreasing the capacity of the casing 100 and therefore increasing the revolution per second of the flywheel wheel 6. Similarly, when the adjust screw 5 is turned slightly out of the bleeding passage 4, the volume of the bleeding passage 4 will be altered thereby increasing the capacity of the casing 100 and therefore decreasing the revolution per second of the flywheel wheel 6. According to our numerous experiments, only a small change in the capacity of the casing 100 will effectively alter the revolution per second of the flywheel 6, so that the power output of the Stirling engine can be controlled easily. In fact, the power output of the Stirling engine can be accurately controlled by using a computer-controlled servomotor to drive the adjust screw 5 and a proportional valve for controlling the fuel to heat the upper end 101 of the casing 100, thereby solving the problem that we long for and making the Stirling engine fit for practical use.
FIG. 2 illustrates a second preferred embodiment of the present invention. As shown, the adjust screw 5 of the first preferred embodiment is replaced with a box 6 in which are mounted a diaphragm 7, a spring 8 and a screw 9. As the screw 9 goes further into the box 6, the spring 8 will exert a pressure to move diaphragm 7 to go inwardly thus decreasing the capacity of the casing 100 and therefore increasing the speed of the flywheel 6, and vice versa.
It will be understood that each of the elements described above, or two or more together may also find a useful application in other types of methods differing from the type described above.
While certain novel features of this invention have been shown and described and are pointed out in the annexed claim, it is not intended to be limited to the details above, since it will be understood that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation can be made by those skilled in the art without departing in any way from the spirit of the present invention.

Claims

A method of controlling power output of a Stirling engine having a casing, a displacer slidably fitted in said casing, and a working piston disposed under said displacer and slidably fitted in said casing, comprising the steps of:

providing said casing with a bleeding passage extending radially outwardly between said displacer and said working piston; and

providing means for adjusting volume of said bleeding passage.
The method of controlling power output of a Stirling engine as claimed in claim 1, wherein said means is an adjust screw threadedly engaged with said bleeding passage.
The method of controlling power output of a Stirling engine as claimed in claim 1, wherein said means includes a box in which are mounted a diaphragm, a spring having an end urging said diaphragm against said bleeding passage, and a screw bearing against another end of said spring.