JPS6088851A - Stirling engine - Google Patents

Abstract

PURPOSE:To form a piston sliding part which offers an effect similar to the effect of a gas bearing, by providing a check valve in an entrance port for a space formed in a piston so that pressurized air is jetted from small holes in the lateral surface of the piston due to the reciprocating motion of the piston. CONSTITUTION:When the pressure of a compression chamber 24 is higher than that of a bounce space 25, a piston 23 moves toward the bounce space 25 so that gas in the bounce space 25 flows into a space 28 in the piston 23 through a check valve 29 to raise the pressure of the space 28. When the pressure of the compression chamber 24 is lowered accompanied with the motion of a displacer 21, the piston initiates to move in the opposite direction to compress the space 28 in the piston due to the similar operation of the check valve 26. Pressurized gas in the space 28 flows into a gap 27 between the piston and the cylinder through small holes in the sliding wall of the piston 23 so that gas bearing if formed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to Stirling engines, in particular to free-piston Stirling engines.

Conventional configuration and its problems In a heat engine that converts thermal energy into mechanical power, a cylinder and a piston that moves within the cylinder are essential components.

The piston must move smoothly in the cylinder, and losses due to friction between the inner wall of the cylinder and the outer wall of the piston during movement must be as small as possible. Otherwise, the efficiency of the engine will decrease, and in extreme cases, the piston will stop moving, making it impractical.

In internal combustion engines that are currently widely used, lubricating oil is used to reduce losses due to friction. If the use of liquid is inappropriate, solid lubricants such as molybdenum disulfide powder are used.

However, in a Stirling engine, which is a closed system in which the working fluid moves back and forth between the expansion space and the compression space, and a regenerator is provided for heat exchange between them, lubricating oil or solid lubricant is used. When using a regenerator, these lubricating materials mix with the working fluid and move through the regenerator, causing a so-called blockage inside the regenerator, which is usually filled with a mesh or wool-like metal. This will significantly reduce the service life.

A gas bearing method is available as a method to eliminate this drawback. That is, this method supplies pressurized gas to the gap between the piston and cylinder to prevent the piston and cylinder from coming into direct contact. Conventionally, as shown in FIG. 1, a displacer and a compressor are movably disposed within a cylinder 14, and a lJ is inserted through a portion of the cylinder 14 located at the piston.
An s-hole 16 was provided through which pressurized gas was supplied from the outside to the piston-cylinder gap. The upper and lower spaces of the displacer 11 are communicated via a regenerator 12.

However, this has the disadvantage of requiring an extra compressor 15 for supplying pressurized gas.

Furthermore, in order to improve output and efficiency in a normal Stirling engine, the pressure of the working fluid is increased to 10 kg/cr! ~1
50A? /Cd in many cases, the compressor must also be constructed to withstand this level of pressure, which has the drawback of making it expensive.

Purpose of the Invention In view of the above-mentioned drawbacks, the present invention provides a Stirling engine having a piston sliding part that has the same effect as a gas bearing without requiring a separate expensive compressor by slightly modifying the piston. The present invention provides a space inside the piston of a Stirling engine, and provides reverse valves on the upper and lower surfaces of the piston, and pressurizes the gas in the piston internal space through the check valve as the piston reciprocates. Pressurized gas flows into the gap between the cylinder and piston through a small hole in the piston wall, allowing the piston to perform smooth reciprocating motion without the need for a separate expensive compressor. That is.

DESCRIPTION OF EMBODIMENTS The present invention will be described below with reference to the drawings. Second
The figure is a diagram schematically showing the main parts of a Stirling engine according to the present invention. In FIG. 2, 21 is a displacer, 122 is a regenerator, 23 is a piston, 24 is a compression space, and 25 (d.

Bounce space, 26H A check valve provided on the compression space side, 27 A check valve provided on the bounce space side, 28 Inner piston space, 29 Inner piston space, 29
3 indicates a piston-cylinder gap, and 30 indicates a small hole provided in the piston wall for blowing out pressurized gas.

Next, the operation will be explained. In a free piston type Stirling engine with this kind of structure, the displacer
21 and the piston 23 reciprocate in the cylinder 31 while having a certain phase difference. If we focus only on the piston, there will be a compression space 24 and a bounce space 25.
The piston can also be considered to perform reciprocating motion due to the pressure difference between the piston and the piston. First, consider a case where the pressure in the compression space 24 is higher than the pressure in the bounce space 25.

The piston 23 moves from the compression space 24 to the balance space 25. At this time, when the pressure in the bounce space 25 is greater than the pressure in the piston internal space 28, the gas in the bounce space 25 passes through the check valve 29. The liquid flows into the piston internal space 28 and increases the pressure within the piston internal space 28. The piston 23 continues to move further toward the bounce space 25 due to the thickness of the compression space 24 and the bounce space 25. During this time, the check valve 26 remains closed, but near the end of this process. When the gas in the piston space is compressed and the pressure of the gas in the piston space 26 becomes greater than the pressure of the gas in the piston interior space 28, the gas flows into the piston interior space 28 through the check valve 29. The flow continues, and the pressure in this space is further increased.When the pressure in the piston internal space 28 becomes greater than the pressure in the compression space 26, the check valve 29 closes and the screw I.
This prevents the pressure in the inner space 28 from decreasing. piston 2
3 sufficiently moves toward the bounce space 25 side, and in combination with the movement of the displacer 21 lowers the pressure in the compressor space 24, the piston begins to move in the opposite direction due to the pressure difference between the bounce space 25 and the compressor space 24, and the piston moves in the opposite direction. A similar operation of the stop valve 26 opens the piston internal space 28.
is pressurized. The gas pressurized in this way passes through the small hole 30 provided in the sliding wall of the piston 23.
It flows into the inter-cylinder gap 27 and forms a gas bearing.

Effects of the Invention As described above, according to the present invention, a space is provided in the piston and a check valve is attached to the inlet and outlet of the piston, so that gas is pressurized as the piston reciprocates, and a separate expensive compressor is not installed. The necessary pressurized gas can be obtained without any trouble, and a gas bearing that operates smoothly can be formed.

Furthermore, in the conventional Stirling engine, a small hole is provided on the cylinder side to allow gas to flow out, so the amplitude of the piston/movement is limited so that one end of the piston does not move out of the position of the small hole. Since the small hole is provided on the piston side, the gas outflow hole always moves with the movement of the piston, and there is no problem that the gas outflow hole will deviate from the piston-cylinder gap regardless of the amplitude of the piston movement. There are practical effects such as dogs.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing a free piston type Stirling engine employing a conventional gas bearing system, and FIG. 2 is a diagram schematically showing a free piston type Stirling engine according to the present invention. 23... Piston, 24... Compression space, 25... Bounce space, 26...
... Check valve, 2γ ... Piston-cylinder gap, 28 ... Piston internal space, 29.
...Bounce space side check valve, 30...Small hole.

Claims (1)

[Claims] A space is provided in the piston, a check valve is installed at the entrance and exit of the space, and the gas in the space is compressed by the reciprocating motion of the piston, and the pressurized gas is spouted into the gap between the piston and the cylinder through a small hole on the side of the piston. Sterling institution.