JPS631777A - Free piston type compressor - Google Patents

Abstract

PURPOSE:To enable prevention of collision of a piston with a cylinder wall, by a method wherein a pressure in a space, where a piston moving in a cylinder is moved, is regulated. CONSTITUTION:By means of a position signal inputted from a position detector 35 to a control device 36, the average position of a piston 25 is detected. When the average position of the piston 25 is displaced upward based on a set average position, a valve 33 and further a valve 34 are closed to increase a pressure in a space 39. When the piston is lowered to the average position, the opening of the valve 34 is fixed. Reversely, when displaced downward, the valve 34 is closed to lower a pressure in the space 39, and further the valve 33 is opened. As noted above, the pressure in the space 39 is controlled through control of the openings of the valves 33 and 34, and the average position of the piston 25 is always adjusted to a set position. This constitution prevents the piston 25 from collision with a container 20 and a suction valve 29.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a free-piston type compressor in which the piston has an unrestricted range of movement due to a piston-crank mechanism or the like.

Conventional technology The conventional compressor of this type was as follows.

FIG. 2 is a longitudinal cross-sectional view of a conventional compressor. Reference numeral 1 denotes a container, in which the working fluid of the Stirling engine is sealed above the seal 2, and the fluid to be compressed (refrigerant in this embodiment) is sealed below the seal 2.

3 is a heater that heats the working fluid; 4 is a cooler that cools the working fluid; 5 is a displacer that moves up and down slidably on the inner wall of the container 1; and 6 is a displacer that moves slidably on the inner wall of the container 1. While doing so, work is done by the working fluid and the fluid is compressed in the negative space 7.

a piston that compresses and does work on the fluid being compressed;
8 is a spring provided to prevent the piston 6 from descending and colliding with the inner wall of the container 1 when stopped; 9 is a discharge valve; 10 is a suction valve; 11 is an evaporator; 12 is a condenser; is an expansion valve.

The displacer 6 and the piston 6 are slidably movable up and down on the inner wall of the container 1. Therefore, part of the heat that has entered the working fluid from the heater 3 is converted into work done by the working fluid above the piston 6, and the - part is discarded into the cooler 3.

- The volume of the space 7 increases or decreases as the piston 6 moves up and down. Therefore, the low-pressure refrigerant in the suction chamber 14 is sucked into the space 7 when the suction valve 9 opens, and the refrigerant in the space 7 is compressed and discharged into the discharge chamber 16 when the discharge valve 9 opens. The refrigerant discharged into the discharge chamber 16 is cooled and condensed in the condenser 12 to become a high-pressure liquid phase 9, and expanded in the expansion valve 13 to become a low-pressure two-phase gas-liquid phase.It is heated in the evaporator and evaporated to form a low-pressure The gas phase is then sucked into the suction chamber 14 again.

On the other hand, in order to lubricate the sliding surfaces between the piston 6 and the container 1, refrigeration oil is circulated in the refrigerant circuit together with the refrigerant.

Problems to be Solved by the Invention However, such a structure has the following problems.

That is, although the piston 6 moves up and down, the spaces 17 and 1
8, the working fluid reciprocates through a gap 19.

However, the mass of the working fluid that leaks from the space 17 to the space 18 during one reciprocation of the piston 6 is different from the mass of the working fluid that leaks from the space 18 to the space 17. Therefore, the average pressure in the space 17 becomes higher than the average pressure in the space 18, and as a result, the average position of the piston 6 decreases with the passage of operating time, and eventually the bottom surface of the piston 6 collides with the suction valve 10, resulting in destruction. On the other hand, the average pressure in the space 17 becomes lower than the average pressure in the space 18, and as a result, the average position of the piston 6 increases with the passage of operating time, until the piston 6
There was a problem in that the upper surface of the container 1 collided with the container 1 and was destroyed.

Means for Solving the Problems The present invention includes a cylinder, a piston disposed within the cylinder so as to be able to freely slide on the inner wall of the cylinder and reciprocate, and a shaft fixed to the piston and driven by a drive source. and a space A surrounded by the cylinder and the piston, in which a fluid to be compressed is drawn and compressed, and a space B surrounded by the cylinder, the piston, and the shaft. It is a piston type compressor.

Even if the center of movement of the piston moving inside the working cylinder shifts,
By adjusting the pressure in the moving space, the center of movement of the piston can be maintained at a predetermined position, and the piston can be prevented from colliding with the cylinder wall.

Embodiment Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings. Reference numeral 20 denotes a container, in which the working fluid of the Stirling engine is sealed above the seal 21, and the fluid to be compressed (refrigerant in this embodiment) is sealed below the seal 21.

22 is a heater that heats the working fluid; 23 is a cooler that cools the working fluid; 24 is a displacer that moves up and down slidably on the inner wall of the container 2o; and 25 is a displacer that moves slidably on the inner wall of the container 20. 27 is a piston 25 which sucks in and compresses the fluid which is compressed in the force receiving space 26 and performs work on the compressed fluid;
28 is a discharge valve, 29 is a suction valve, 3o is an evaporator, 31 is a condenser, and 32 is an expansion valve. be.

33 and 34 are valves, 35 is a position detector for detecting the position of the piston 25, and 36 is a valve 33. to keep the average position of the piston 25 constant and prevent it from colliding with the container 20 and the suction valve 29. This is a control device that controls the opening degree of 34.

The displacer 24 and the piston 26 are slidably moving up and down on the inner wall of the container 2o. For this reason, heater 2
A part of the heat entering the working fluid from the piston 26 is converted into work done by the working fluid above the piston 26, and a - part is discarded to the cooler 23.

On the other hand, as the piston 25 moves up and down, the volume of the space 26 increases and decreases. Therefore, the low-pressure refrigerant in the suction chamber 37 is sucked into the space 26 when the suction valve 29 opens, and the refrigerant in the space 26 is compressed and discharged into the discharge chamber 38 when the discharge valve 28 opens.

The refrigerant discharged into the discharge chamber 38 is cooled and condensed in the condenser 31 and becomes a high-pressure liquid phase, and expands in the expansion valve 32 to become a low-pressure gas-liquid two phase and is heated and evaporated in the evaporator 3o. The gas becomes a low-pressure gas phase and is sucked into the suction chamber 37 again.

On the other hand, the control device 36 detects the average position of the piston 25 based on the signal of the position of the piston 25 that is input to the control device 36 from the position detector 36. When the average position of the piston 26 deviates upward from the set average position, the valve 33 is closed to increase the pressure in the space 39.
Even if the valve 3 is fully closed, if it still deviates upward, the valve 34 is opened, and when the set average position is reached, the opening degree of the valve 34 is fixed. Conversely, when the average position of the piston 26 deviates downward from the set average position, the space 3
Close the valve 34 to reduce the pressure at 9.

Even if the valve 34 is fully closed, if it still deviates downward, the valve 33 is opened, and when the set average position is reached, the opening of the valve 33 is stopped.

In this way, by controlling the pressure in the space 39 and the opening degrees of the valves 33 and 34, the average position of the piston 26 can always be brought to the set position.

Therefore, there is an effect that the piston 26 does not collide with the container 2o or the suction valve 29.

The amplitude of the piston 25 is controlled by controlling the amount of heat entering the working fluid from the heater 22 using a separate control device not shown in FIG. Further, in the above embodiment, the piston is driven by a Stirling engine, but it may be driven by another drive device.

Effects of the Invention When a compressor is configured using a free piston, the movement of the center of motion of the free piston can be suppressed, so collisions between the free piston and the cylinder wall can be prevented.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a free piston type compressor according to an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view of a conventional free piston type compressor. 2o... Container, 22... Heater, 23
...Cooler, 24...Displacer, 25...Piston, 31...Condenser, 32...Expansion valve, 3o... ····Evaporator,
33, 34... Valve, 36... Position detector, 36... Control device, 1... Container, 3... Heater , 4...Cooler, 5.
... Displacer, 6... Piston,
12...Condenser, 13.River...Expansion valve, 110
109. . Evaporator. Name of agent: Patent attorney Toshio Nakao and one other name
1 figure

Claims (1)

[Claims] a cylinder; a free piston disposed so as to be able to reciprocate and slide freely on the inner wall of the cylinder within the cylinder;
a shaft fixed to the free piston and driven by a drive source; a space surrounded by the cylinder and the free piston and sucking and compressing fluid to be compressed therein; Free piston compressor with means for regulating the pressure in the enclosed space.