JPS63143370A - Free piston type stirling engine - Google Patents

Abstract

PURPOSE:To facilitate the control of the faculty of an engine by forming a flow passage which communicates to the space divided in each pressure by a displacer and/or power piston and installing a flow rate adjusting valve controlled according to the position of the displacer, etc. into the flow passage. CONSTITUTION:The inside of a cylinder is divided into a high temperature space 5 and a low temperature space 6 by fitting a displacer 1 in free reciprocating movement into a cylinder, and the part between the both spaces 5 and 6 is connected by a side passage in which a heater 2, regenerator 3, and a cooler 4 are arranged. Further, in the low temperature space 6, a power piston 7 with which a compressor piston 9 is integrally connected through a rod 8 is fitted, and a gas spring space 17 is formed under the piston 7. The low temperature space 6 and the gas spring space 17 are allowed to communicate through a flow passage 18 into which a pump 15, tank 16, and a flow rate adjusting valve 14 are installed. The flow rate adjusting valve 14 controls the flow rate through a control circuit 13 according to the output of a sensor 12 for detecting the position of the power piston 7.

Description

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

Conventional technology The Stirling engine, which is an external combustion engine, is highly efficient.

It has many features such as quietness and fuel versatility.

Stirling engines can be roughly divided into two types: free-piston Stirling engines in which the displacer and/or power piston are not restrained by a crank mechanism, and Stirling engines in which the displacer and power piston are connected to a crank mechanism (hereinafter referred to as mechanical Stirling engines). ).

In free-piston Stirling engines, the power piston is generally not restrained by the crankshaft or connecting rod, so
It has the advantage of low mechanical loss. However, since the displacer and piston move freely, position control is extremely important, such as preventing them from colliding with the cylinder wall.

Conventionally, there has been a method of using a center hole as a method for this type of position control (Japanese Patent Application Laid-Open No. 58-47144).

FIG. 4 shows a typical example of a conventional free piston Stirling engine using a center hole.

Generally, when the piston 21 reciprocates, the amount of gas movement from the gap between the piston 21 and the cylinder wall 22 often has directionality. The difference in movement amount between the amount of gas moving from above to below the pick and piston 21 and the amount of gas moving from below to above causes a difference in the average pressure of each space. This pressure difference causes the piston 21 to be pushed toward the lower pressure side and collide with the cylinder wall 22. In this example, in order to prevent this, even if there is a difference in the average pressure of the gas in the spaces 23 and 24, when the reciprocating piston 21 passes a certain position (for example, the center position of the piston's reciprocating movement), By communicating the flow paths 26 and 26 and moving the gas, the average pressure in the spaces 23 and 24 is maintained in balance,
The purpose is to cause the piston 21 to reciprocate around a certain position.

Problems to be Solved by the Invention In the above-mentioned conventional system, power loss occurs due to the gas passing through the center hole, so the center hole and passage cannot be made large enough to accommodate all kinds of changes, and changes in the pressure waveform in the working space and Since it is difficult to deal with fluctuations in the amount of leakage from the gap between the piston and the cylinder wall, the center position of the piston's reciprocating motion is also not constant. Furthermore, when a free piston Stirling engine is used together with a compressor as a drive source for a heat pump, the stroke of the piston may change in response to load fluctuations. In this case, in order to increase the volumetric efficiency of the compressor, the top clearance of the compressor must be made as small as possible, but with the conventional system described above, it is difficult to set the piston at an arbitrary position.

Therefore, the present invention attempts to solve the above problems while taking advantage of the feature that the free piston can respond to load fluctuations by changing the stroke without increasing the operating frequency.

Means to Solve the Problem The present invention is a rain space that is pressure-divided by a piston or a displacer that reciprocates within a cylinder (here, the pressure waveform, including the phase, is different from the pressure-divided space). The free piston type is characterized by connecting a flow channel (referring to a space) to a flow path equipped with a flow control valve, pump, and tank, and is equipped with a device (sensor) and control circuit to detect the position of the piston or displacer. It is a sterling institution.

Function The present invention detects the position of the piston or displacer and adjusts it to the optimum position in accordance with the detected position to cope with changes in load, so it is possible to easily control engine performance by changing the stroke.

In this way, it is possible to take advantage of the features of the free piston type and at the same time prevent the piston from colliding with the cylinder wall. Further, at the time of starting, the piston can be adjusted to any position, and starting can be easily performed.

EXAMPLE Hereinafter, an example of the present invention will be described based on the accompanying drawings. FIG. 1 shows an example in which a compressor used for a heat pump is incorporated into an engine. In this figure, when the displacer 1 reciprocates up and down, the working gas such as helium sealed inside the Stirling engine is transferred to the heater 2. Regenerator 3. It passes through the cooler 4 and reciprocates between the high temperature space 6 and the low temperature space 6. For example, when the displacer 1 moves upward, the working gas in the high-temperature space 5 passes through the heater 2, stores the heat of the gas itself in the regenerator 3, and is transferred to the cooler 4.
It is cooled down and moved to the low temperature space 6 side. At this time, a proportion of the working gas in the space above the power piston 7 is on the low-temperature space 6 side, and the pressure of the working gas decreases to pull up the power piston 7. At this time, the compressor piston 9 connected by the rod 8 also moves upward, and the suction valve 1o opens to suck in refrigerant gas. Conversely, when the displacer 1 moves downward, the working gas flowing into the low temperature space 6 passes through the cooler 4, absorbs the heat stored in the regenerator 3, is heated by the heater 2, and moves to the high temperature space 5 side. .

At this time, the proportion of the working gas in the space above the power piston 7 is on the high temperature space 6 side, and the working gas pressure increases, pushing the power piston 7 downward. At this time, the compression piston 9 also moves downward, and the discharge valve 11 opens to discharge refrigerant gas. By the way, let's assume that there is more leakage from the gap between the power piston 7 and the cylinder wall from the top to the bottom (
(naturally or forced with a pumping effect). At this time, when the position of the power piston 7 is detected by the sensor 12 and the flow rate control valve 14 is opened through the control circuit 13, the working gas in the tank 16, which is pressurized by drawing in the working gas in the low temperature space θ by the pump 15, is , when the pressure is higher than the gas pressure in the gas spring space 17, the flow path 18. The gas flows into the spring space 17 through the flow control valve 14 . At this time, the position of the power piston 7 is controlled by adjusting the opening degree of the flow rate control valve 14 and changing the amount of gas movement (in the case of this embodiment, the compressor piston is connected to the compressor piston by a rod 8). Since the position of 9 can be set to any desired position and the top clearance can be made small, control such as increasing the volumetric efficiency of the compressor can be easily performed.

Next, another embodiment of the present invention will be described.

FIG. 2 is a longitudinal cross-sectional view of a main part of a Stirling engine according to another embodiment. In order to simplify the explanation, elements common to those in FIG. 1 are given the same numbers as in FIG. 1. A check valve 19 is provided in parallel with the pump 16, and when the pressure in the low temperature space 6 becomes higher than the pressure in the tank 16, the working gas in the low temperature space 6 flows into the tank 16 and the pressure is accumulated. .

(Gas inflow occurs in the shaded area in Figure 3.)
The accumulated gas is sent to the sensor 12. Gas flows into the spring space 17 and controls the positions of the pistons 7 and 9 according to the opening degree of the flow control valve 14 controlled by the control circuit 13. The pump 16 is used to increase the pressure in the tank 16 when the pressure in the tank 16 is insufficient to operate only by the check valve 19, at startup, or when there is no pressure fluctuation in the low temperature space 6.

Also, the check valve 20 is connected to gas, and the gas in the spring space 17 is connected to the tank 1.
6. Prevent backflow into the tank.

This example shows an example in which a flow path is provided on the power piston side, but it is also possible to provide a flow path between the low temperature space and the gas and spring spaces on the displacer side, and the direction of the check valve. Of course, the position of the sensor may also be changed depending on the direction of leakage of the working gas, and the sensor may be installed at a position desired to be controlled.

Effects of the Invention As described above, the present invention provides a free piston type Stirling engine in which a space separated by pressure by a reciprocating member such as a displacer or a piston is communicated with a flow path equipped with a pump or a flow rate control valve. In addition, a sensor detects the position of a reciprocating member, and a control circuit changes the opening of the flow rate control valve to change the average pressure in the rain space, thereby providing a Stirling engine that can arbitrarily set the position of the member. It is possible.

[Brief explanation of the drawing]

Fig. 1 is a schematic longitudinal cross-sectional view of a free piston type Stirling engine according to an embodiment of the present invention, Fig. 2 is a longitudinal cross-sectional view of main parts of a different embodiment of the present invention, and Fig. 3 is a schematic longitudinal cross-sectional view of a free piston type Stirling engine according to an embodiment of the present invention. Pressure Wave Station FIG. 4 is a vertical sectional view of the main part of a typical conventional free piston Stirling engine. 1...Displacer, 7...Power piston, 12...Sensor, 13...
Control circuit, 14...Flow rate control valve, 16...
...Pump, 17...Flow path. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3

Claims (2)

[Claims] (1) The space inside the cylinder is divided into a high-temperature space and a low-temperature space by a reciprocating displacer, and a side passage with a heater, a regenerator, and a cooler is provided between the high-temperature space and the low-temperature space. A pump, a gas reservoir space, and a flow rate control valve are provided between a flow path that communicates a space that is divided by pressure by the displacer and/or the power piston, and a pump, a gas reservoir space, and a flow rate control valve. and a position detection device for the displacer or power piston, and according to the output of the position detection device,
A free piston Stirling engine, comprising a control device for controlling the flow rate regulating valve, wherein the direction of the pump and check valve is opposite to the leakage direction of the working gas. (2) A free piston Stirling engine according to claim 1, wherein a check valve is provided in parallel with the pump.