JPH03263558A - Free piston type expansion engine - Google Patents

Abstract

PURPOSE:To improve heat insulating efficiency by providing a solenoid control device to open and close a delivery valve through movement in an axial direction of the valve plate and the small piston of the delivery valve secured to a valve rod and a reciprocating expansion piston having an engaging part engaged with the outer periphery of the small piston. CONSTITUTION:A bottom dead center (a) of a piston 62 is detected by position sensors 48, 49, and 50. In this case, an solenoid-operated type armature 22 for opening and closing a delivery valve, extending through the piston 62 and connected to a valve rod 23 coupled to a small piston type delivery valve 21 is pulled through the flow of a current through a stator 26 and a linear motor, a simultaneously, is reversed to move the piston 62 toward a top dead center. When the delivery valve is closed at a point c' and the piston 62 is reversed at a top dead center, similar operation described above is carried out by means of information from the position sensor systems. An expansion chamber 20 further reduces a working fluid temperature, a compression chamber 34 compresses fluid through utilization of a force generated when the expansion chamber 20 is expanded, and cools a part as cooling fluid simultaneously with recovery of a heat insulation expansion work.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to the liquefaction of gases such as argon, nitrogen, hydrogen, helium, etc., as well as the cooling of superconducting magnets to be loaded onto magnetic levitation trains, medical applications, etc. It is highly efficient and generates temperatures as low as about 200 or less in absolute temperature, which are used in small coolers and liquefaction machines such as the Claude and inverted Playton cycles used in nuclear magnetic resonance devices. This invention relates to the structure of a reciprocating piston expansion engine that has high durability.

[Conventional technology] Existing large refrigerators and liquefaction machines use high-speed rotation expansion turbines, and their energy efficiency and reliability are
Higher than other refrigeration cycles. However, in small machines with a refrigeration temperature of about 4 and a refrigeration output of 5 to 50 watts, the working fluid used in the cycle (single gas or mixed gas of helium, hydrogen, neon, nitrogen, hereinafter referred to as fluid) is To tell)
The use of an expansion turbine is not possible due to the low flow rate.

Therefore, a reciprocating piston type expansion engine (hereinafter referred to as engine) must be used as an alternative for generating low temperatures. However, conventionally, this engine's adiabatic expansion efficiency (isentropic expansion efficiency, hereinafter referred to as efficiency)
compared to 60 to 80% for expansion turbines.
Furthermore, the reliability was low due to many failures, and the durability was low at about 1,000 to 2,000 hours.

Conventionally, the reason for the low reliability of this engine is that when the valve opens and closes during a short period of time during the cycle, high and low pressure fluid flows in and out of the valve, which places a large mechanical load on the valve plate and valve opening/closing mechanism. The impact caused damage to the valve plates and failure of the cam mechanism, reducing the reliability of the engine.

Regarding durability, the piston vibrates within the cylinder during reciprocating motion, or reciprocates off-axis, causing uneven wear of the piston rings and hastening the deterioration of engine performance. In particular, when the engine was used horizontally, the piston rings deteriorated in a short period of time.

In addition, regarding the improvement of valve operation, the so-called valve stemless expansion engine, which does not have valve stems to drive the opening and closing of the intake and discharge valves at low temperatures, was developed by the applicants (Cryogenic Engineering Vol. 6, p. 188). , published by the Cryogenics Society). One of the features of this valve stemless expansion engine is that there is no heat intrusion from room temperature through the valve stem, and there is no need for an opening/closing drive mechanism, which allows for a simple structure, but on the other hand, there is a problem with the timing of opening and closing the intake valve. However, there was a drawback that the opening and closing timings of the discharge valve were fixed. As a result, the adiabatic expansion process from the high-pressure fluid becomes insufficient, and losses due to the recompression process increase, making it difficult to obtain high adiabatic efficiency. Its typical structure is shown in Figure 5, and P represents the effect of fat expansion work by the fluid in the engine.
A v-diagram is shown in FIG. 6(a), and the process of low temperature generation will be explained using both figures.

The structure consists of a cylinder 6 made of thin stainless steel, a piston 5 that moves back and forth to adiabatically expand the fluid and generate work, an expansion chamber 9 that adiabatically expands the fluid and lowers the temperature, and fluids with the same shape on the left and right. Press the intake valve 8 and its valve plate at all times.
Spring 10 to close, discharge valve 7 and spring to adjust its opening/closing force! 1.12. Cone rod 13, crankshaft 14, handwheel 2, power transmission system 15.17, which is a mechanism that transmits the work generated by the piston, rotates it smoothly, and recovers power. 15.17. Smooth power recovery and piston The structure includes a driving induction motor 1, a gas seal 4, and a crosshead 3.

The mechanism of low temperature generation is described below. FIG. 5 shows an example of a conventional engine in which the piston 5 is at the bottom dead center and the discharge valve 7 is open. (Position a' in Figure 6) If this engine operates ideally to obtain maximum efficiency, the suction process of high-pressure fluid d-
e, adiabatic expanded overexpanded fat-a, lower temperature than the inhaled temperature;
Discharge process a-bSb-c when the pressure becomes low and the discharge valve opens and the fluid exits the engine.

At point 0, there is a process c-d in which the discharge valve closes and the fluid remaining in the expansion chamber is recompressed, and the area surrounded by this line represents the ideal work done by the engine.

[Problems to be Solved by the Invention] Problems in the conventional engine as described above will be described below.

That is, when the piston 5 approaches the top dead center from the bottom dead center during the discharge process, the low-pressure fluid in the expansion chamber 9 is pushed out, but the lower piston 1G pushes the suction valve 8 open, and the spring 10.11 .12 hysteresis and other safety considerations, the discharge valve 7 must be closed at the 02 point earlier than the 02 point at which the high-pressure fluid begins to enter the expansion chamber 9. Therefore, the discharge process becomes a'-b'-c'. Next, the discharge valve 7 closes at a', and when the piston 5 approaches the top dead center, the fluid remaining in the expansion chamber 9 is recompressed and the piston lower part 16 pushes the suction valve 8, so a little fluid begins to leak. (C/point)
, the pressure increases to C''-d (recompression process). At point d, the suction valve 8 opens, and high-pressure fluid (for example, 16 atmospheres of helium) enters the expansion chamber until it closes at point e (suction process). e The process from point A to point a is an ideal adiabatic fat swelling process, but the elastic modulus of each spring 11 and 12 may be changed or the discharge valve 7 may be changed.
Even if the weight of the material is changed, the discharge valve 7 opens at a point a' where the length is not much shorter than the length F-c' excluding the clearance O-F between the piston and the cylinder. That is, the pressure of the fluid is lowered without any work (a'-b') from a state where the pressure is still high and the adiabatic swelling process is insufficient. When the piston 5 moves further towards the bottom dead center, the fluid that once left the engine is drawn into the expansion chamber 9 again and becomes b'-b, and then as the piston moves to the bottom dead center, it moves towards the top dead center b'-c'. It is discharged between.

As a result, the fat expansion work done by the engine is a'b'-c'
-de is the area surrounded by e. In other words, the work a' a, b, b'
The area surrounded by d, C/, and C# decreases.

The main cause of this loss is a problem with the opening/closing mechanism of the discharge valve, which uses contact between a spring and a piston to determine the timing of opening and closing of the discharge valve. In other words, the optimal opening phase (between a-b-a') and closing phase (c') of the discharge valve required in one cycle.
-d-e-a) is different, it is difficult to open and close the discharge valve at the optimal timing even if the force of the spring 11.12 and the weight of the valve 7 are adjusted only by the position of the piston 5 in the cylinder 6. Met. Therefore, it has been experimentally impossible to obtain high efficiency.

In addition, when the engine is operated at 300 revolutions per minute or more, the fluid pressure becomes over-expanded between bb' and bb' in Figure 6(b) and drops below 1 atm which is the cycle standard, causing the piston to At point b, the force acts in the reverse direction, and between b and c' toward the top dead center, the loss increases further because the temperature is slightly increased due to compression.

Note that the suction valve 8 is pushed by the piston lower part 16 and begins to open.
The distances from point 0 to point 2 and point e, where the piston acts in the reverse direction and faces the bottom dead center and closes the intake valve, are approximately the same.

The second drawback of general fat-swelling engines is that the power generation process in which high-pressure fluid pushes the piston occurs within a narrow phase range of e-a during one cycle, as shown in Figure 6(a). As a result, impact force and eccentric force are applied to the bearings 1g and 1 of the crank mechanism including the gas seal 4 and connecting rod 13.
9 had accelerated the deterioration of these.

This can be prevented to some extent by adding a handwheel 2, but
There is a drawback that the size of the device increases and the weight increases.

That is, there are problems in mechanically converting the linear motion of the piston into rotational motion by intervening a crankshaft or the like, and in recovering the power using an independent system such as an induction motor.

Third, even if the piston 5, which is connected to the crankshaft 14 and moves reciprocatingly as shown in Fig. 5, is mechanically machined and assembled with high precision, the cylinder is relatively long (for example, the inner diameter is approximately 40 mm and the length is approximately 40 mm). It is difficult and almost impossible to reciprocate the piston so that the blood pressure in the circumferential direction of the gas seal 4 is constant across the entire length (within 400 mm) of the shaft center.

That is, the mounting of the bearing 18 and the crankshaft mechanically forces the movement of the piston within the cylinder with precision. Furthermore, eccentric force is applied when the piston is reciprocated by the crankshaft. As a result, the gas seal 4 wears unevenly, reducing the durability of the engine.

[Means for Solving the Problems] The present invention attempts to eliminate the drawbacks of the conventional engines by providing a piston reciprocating engine structure that is highly efficient and highly durable.

That is, the present invention provides a reciprocating engine used in a Claude cycle or a reverse Preyton cycle in which a working fluid is expanded adiabatically to generate a low temperature, in which both ends of the engine are movable in the axial direction with respect to a casing by respective bearings. An electromagnetic control device for opening and closing the discharge valve by controllingly moving a supported valve stem, a valve plate and a small piston of a discharge valve fixed to the valve stem in the axial direction; The expansion piston is reciprocated by a linear motor, and has a fitting part at its lower end that fits with the outer periphery of the small piston of the discharge valve, and the electromagnetic The discharge valve is always closed by the actuation force of the control device and the biasing forces of the springs disposed in the electromagnetic control device and the small piston, and A position marker provided and a fixed position sensor detecting the position marker detect a position and/or speed signal of the expansion piston in the cylinder, and based on the detected signal, the speed and/or speed of the expansion piston is determined. Or, to control the traveling direction and opening/closing of the discharge valve, and furthermore, what about the side of the expansion piston opposite to the expansion chamber side? A free piston type expansion engine characterized in that a compression chamber is provided in a normal temperature part, and a part of the adiabatic expansion work performed by the expansion piston in the expansion chamber is recovered by the compression work of a compressor constituted by the compression chamber. This is what we are trying to solve.

[Operations] The present invention solves the drawbacks of the conventional expansion engine by using the above solution, but basically, the valve stemless engine shown in Fig. 5 is relatively easy to use as an intake valve in the main working chamber. An automatic suction valve (hereinafter referred to as suction valve), which has shown good functionality, is used.

By these means, the action of the present invention is that the piston 6
The position and speed of the piston within the cylinder 81 are accurately detected by the position marker 48 attached to the cylinder 21 and the fixed position sensor 49.50, and the movement of the discharge valve 21 is thereby electromagnetically controlled. 21 can be opened and closed at optimal timing and at high speed, opening at point a and closing at point C'.

As a result, the hatched areas a', a, and b in FIG.

b', d, c, and c' can be removed, improving insulation efficiency.

[Example] The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, and FIG. 2 shows a case where the expansion piston in the embodiment of FIG. 1 is located at the top dead center (lower side in the drawing). In FIG. 1, a small piston shape is attached to a valve stem 23 that passes through a substantially central axis position of the piston 62, and a fluid expansion space 20 formed by a cylinder 61 and an expansion piston (hereinafter referred to as piston) 62. discharge valve 21 (hereinafter referred to as the discharge valve), guide bearings 24 and 25 for the valve stem at both ends of the valve stem, an armature 22 for electromagnetically driving the discharge valve attached to the valve stem, and its stator (solenoid, etc.) 26. Double-inserted main spring 28゜29 which plays the role of constantly pushing the piston 62 back to the bottom dead center to open the suction valve 27 and recovers a portion of the work generated during fat expansion.
, a plurality of permanent magnets 30, a yoke (movable element) 31, and a yoke (mover) 31 for a linear motor that confirms the position of the piston by power recovery and a position sensor system described below, and reciprocates the piston B2 between optimal positions. 132, yoke (stator) 33,
A compression chamber 34, a suction valve 35, which constitute a compressor that directly recovers the work generated by the piston 62 as fluid compression work;
Discharge valve 36 is shown.

Low-temperature springs 37, 38 and normal-temperature springs 39 that apply force in the direction to keep the discharge valve 21 and suction valve 27 closed at all times, and a ring-shaped plate with a groove cut to open the discharge valve 27. , a push rod 40 and its spring 41 that constitute the damper. Piston ring 42, low temperature seal ring 4
3, the fixed seal ring 44, 45, the guide bearing 46 of the suction valve 27, the piston lower part 47, attached to the piston 62, depending on its position in the cylinder 61, the discharge valve 2
1 and the reciprocating movement and speed control of the piston 62 (for example, a cylinder-shaped reflector with black and white stripes at regular intervals on the inner surface; hereinafter referred to as a position marker) 48 and a position sensor consisting of a position sensor (such as a light emitting diode) 49 which is a light emitting part and a position sensor (hot diode or other transistor) 50 which is a light receiving part and is fixed in response to the detection thereof.
system, the generated power is recovered by fluid compression in the compression chamber 34,
Fin pipe 5 connected from discharge valve 36 to a radiator (not shown)
1. A fluid port 52 that is cooled and returns from the suction valve 35 to the compression chamber 34, a low-temperature high-pressure fluid suction port 53 and a low-pressure fluid discharge port 54, a cover 57, a fluid space 58, a yoke holder 59 for the linear motor; This structure is composed of a piston holder 60.

Note that a piston 62 that moves the reflector of the position marker 48
The position sensor 49, which is a light emitting part, and the position sensor 50, which is a light receiving part, may be fixed in the vicinity of the permanent magnet 30 that works in conjunction with the permanent magnet 30, and at a position where it can be detected.

Light is applied to the reflective plate of the position marker 48, which has a black and white striped pattern at regular intervals, and the speed is detected from the interval of the reflected light, or the position is detected by integrating the pulses. Furthermore, if the measured value of the relationship between speed and position is recorded in ROM in advance, and the magnitude of the current in the linear motor winding 32 is controlled in proportion to the difference by comparing it with the measured value, the piston 62
It is possible to control the speed of In addition, it is also possible to provide an optical limit switch or an eddy current type proximity switch in the compression space of the normal temperature portion of the piston, and to control the direction of the reciprocating movement of the piston using a linear motor.

Furthermore, a third electrical control circuit is used to detect the movement direction of the piston and the opening/closing timing of the discharge valve, and to switch between them.
As shown in figure (a), a light emitting part a is attached to the cylinder (not shown).
, b and the light receiving section are fixed in a facing manner, and the stator 26 (solenoid) for controlling the linear motor and opening/closing of the discharge valve 21 can be turned on and off by blocking and transmitting light due to the vertical movement of the normal temperature part of the piston 62. (b) is its basic electric circuit and f is the power supply. When the piston 62 is at the top dead center in (1) of (a), the output is turned on so that the piston blocks light so that it does not receive light, and the transmission (light reception) in (2)
to turn off the output and turn the current on and off, solenoid c
, d and relay e to open and close the discharge valve 21,
It is also possible to drive and control the moving direction of the piston 62 with a linear motor. It goes without saying that by increasing the number of light emitting parts, light receiving parts, relay solenoids, etc., it is possible to more precisely control the speed and position of the piston, as well as the opening and closing of the discharge valve 21.

FIG. 4 also shows a valve stem 23 and a small piston-shaped discharge valve 21 which is a connecting part thereof. The holder 83, stopper 6
4. An armature 22 for driving the discharge valve 21 is shown. The valve stem 23 is connected to the 23-g portion bearing 25 by the bearing 24.
Part 23-h is retained by . The piston 62 is moved freely between the armature 22 and the holder 63 by a linear motor, with the valve stem 23 as its center and guided by the piston 62. .

Therefore, the piston 62 is attached to the bearing 25 of the normal temperature part of the valve stem 23.
If the bearings 24 and low-temperature section are assembled so that they are aligned with the axial center of the cylinder 62 at each position, the cylinder 62 will self-align at any position with uniform clearance (between cylinder and piston) during reciprocating motion. ) is guaranteed. As a result, the piston ring 42
The surface pressure in the circumferential direction relative to 1 has become uniform, eliminating uneven wear and making it possible to withstand long-term operation. In addition, the outer circumference of the small piston-shaped discharge valve 21 made of solid lubricant also serves as a cylindrical bearing with respect to the piston 62, and prevents the occurrence of vibration of the piston, thereby preventing deterioration of the piston ring 42. Make sure not to. In addition, valve stem 23
Further the bearing of armature 22 and position sensor 49.5
It may be provided in the 23-1 section between 0 and 0.

Next, the working strokes of the engine of the present invention will be described in order. First, it is the first stroke, and Fig. 1 shows the piston 6.
2 is at the bottom dead center, the high-pressure fluid undergoes adiabatic expansion and becomes lower in temperature, resulting in lower pressure and the volume of the expansion chamber 20 is maximized.

At this time, the discharge valve 21 in the expansion chamber 20 opens at point a in FIG. 6(a), indicating that the pressure is at the lowest level b.

At this time, the fluid in the compression chamber 34 is compressed by the fat expansion work, the discharge valve 3B is opened at about 2 atmospheres, and the fluid is guided to the circulation cooling device. That is, the compressed fluid exits from the outlet 51, enters a radiator (not shown), is cooled, returns to the fluid space 58 in the cover 57 from the inlet 52, cools the bearing 25 and the stator 26, and is returned to the compression chamber again.

Next, in the second stroke, the working fluid in the expansion chamber 20 flows through the valve hole 5B and the discharge port 5 for the piston 62 to move toward the top dead center.
4, it is discharged outside the engine until the discharge valve 21 closes at point C'. This discharge process is essentially different from the structure of the discharge valve shown in FIG. For example, at point C') the discharge valve 2
1. It is now possible to close the solenoid at high speed by turning the solenoid's current on or off. The same applies to point a.

In the compression chamber 34, which recovers power by compressing one fluid, the volume increases, so that the cooled fluid begins to enter the compression chamber 34 from the fluid space 57 as the valve plate of the suction valve 35 opens.

Next, in the third stroke, the discharge valve 21 closes at point C' and the fluid remaining in the expansion chamber 20 is compressed (recompressed). At the same time, the force of the spring 41 in the piston lower part 47 begins to increase, and the push rod 40 forming a damper with a grooved ring-shaped plate enters the expansion chamber 20 from the suction port 53 to push the protrusion 55 of the suction valve 27. start. (In addition, the suction valve 27
has one or more pistons 62 at top dead center d
When the suction valve 27 is fully opened (FIG. 2 shows this state) and the piston 62 is reversed and heads toward the bottom dead center, the lower piston 4
The force of pushing the protrusion 55 of the suction valve 27 of the push rod 40, which is pushed by the spring 41 contained in the damper 7, weakens and the suction valve 27 closes (during the suction process, as shown in FIG. 6(a) d-e). On the other hand, the compression chamber 34 is just before starting compression from the maximum volume. In FIG. 2, the piston 62 is at the top dead center position, the volume of the expansion chamber 20 is almost zero, the suction valve 27 is open, and the compression chamber 34, which performs power recovery by fluid compression, is at its maximum, just before the discharge valve 36 closes. It is in a state.

Then, in the fourth stroke, the high pressure fluid pushes the piston 62 to provide thrust to the linear motor, simultaneously compressing the main spring 28, 29 and further reducing the volume of the compression chamber 34, which is at about room temperature. That is, the high-pressure fluid confined in the expansion chamber 20 does work while pushing the piston B2, expands to point a, and has a low temperature (adiabatic fat expansion process, e
-a).

As mentioned above, one cycle of the engine is completed through four strokes: suction, adiabatic expansion, discharge, and recompression. During this time, the helium that entered the engine at 16 atmospheres and 20 degrees will expand adiabatically and become approximately 1 atmosphere, approximately 11.2 degrees.

The insulation efficiency at this time is 60%.

Note that part of the expansion work generated in the adiabatic fat expansion process of e-a is the power generated by the linear motor by applying thrust to the piston, the compression work of the main spring, and the compression work of compressing the same fluid as the working fluid. It is recovered by three methods of load work.

During this time, the pressure of the fluid in the compression chamber 34 is initially about 1 atm, but increases as the volume of the compression chamber 34 decreases, and at a pressure of 2 atm, the discharge valve 36 opens and enters the radiator and is cooled. and return to space 58. However, this pressure is
4 has a large dead volume, and if the power is recovered at too high a temperature, the temperature in this area will rise and have a negative effect on the sensor, linear motor, etc., and the piston will not be able to reciprocate smoothly, which is undesirable. Therefore, one of the features of the present invention
The first is that three power recovery methods are used in combination to cool and circulate the fluid without increasing the pressure in the compression chamber 34 so much that it functions as a blower for cooling the functional parts.

The bottom dead center point a of the piston is the position sensor system 48°49,
50, at this time passing through the piston 62 (preferably at approximately the central axis position), an electromagnetically operated type for opening and closing the discharge valve is connected to the valve rod 23 connected to the small piston type discharge valve 21. At the same time as the armature 22 is pulled by applying current to the stator 26, the linear motor is reversed to move the piston B2 toward the top dead center.

Similar operations are performed using information from the position sensor system when closing the discharge valve at point C' and reversing the piston 62 at top dead center.

The purposes of the expansion chamber 20 and the compression chamber 34 are opposite; the former lowers the temperature of the working fluid by performing expansion work, and the latter compresses the fluid by utilizing the force generated when the former expands, thereby reducing the adiabatic expansion work. Along with recovery, parts are cooled as a cooling fluid.

In addition, one or more light emitting parts and light receiving parts of the position marker and fixed position sensor of the piston 62 may be attached, or multiple small holes may be inserted into the side surface of the piston 62 so that when the light emitting part and the light receiving part coincide with each other, It is also possible to turn on and off the current of an electromagnetically driven stator (in the sense of including an asture) for opening and closing the discharge valve, or to switch the driving direction of the linear motor. Although not shown, a differential transformer may be used to detect the position of a reciprocating iron piece connected to the piston 62 by moving it within a high-frequency coil to open/close a discharge valve or switch the driving direction of a near motor. good.

Also, a position marker 48 (a small hole for light transmission, a reflector, a magnet, an iron piece, a striped cylinder, etc.) attached to the reciprocating piston 62 and a fixed position sensor 49.50
(A combination of light emitting parts and light receiving parts using hot transistors, light emitting diodes, LEDs, etc.) detects changes in light, magnetism, induced current, etc., converts this into electricity, and discharges the discharge valve by armature 22 and stator 2B. At the same time as the electromagnetic opening/closing drive of 21, the reciprocating movement of the piston 62 may be controlled by a linear motor 30, 31, 32, and 33.

In addition, compared to the conventional engine shown in Figure 5, an electromagnetically driven discharge valve and a position sensor system have been added, so the position and speed of the piston inside the cylinder can be accurately detected, and the discharge valve can be opened at point a. Closing at point C' can now be performed at high speed in an optimal position. As a result, the areas a', a,
By removing b, b' and d, c'C', the insulation efficiency was greatly improved.

Incidentally, although the above is explained by one embodiment of the present invention,
The present invention is not limited to the above embodiments as long as the features of the present invention can be implemented.

For example, the discharge valve opening/closing mechanism in the present application can also be applied to a crank type expansion engine.

[Effects of the Invention] As described above, the free piston expansion engine of the present invention has the following effects.

1) In order to open and close the discharge valve at the optimum timing, the discharge valve 21 has a position marker 48 attached to the piston 62.
The position and speed of the piston inside the cylinder 61 are accurately detected by the fixed position sensors 49 and 50, and a
It is now possible to open and close at optimal timing and at high speed, opening at point C' and closing at point C'.

As a result, the hatched areas a', a, and b in FIG.

The insulation efficiency was improved by removing b', d, CL, and CJ.

2) The piston/cylinder is shown in 1.2.13. in Fig. 5.
Since the reciprocating mechanism using the crankshaft of 14, 15, and 17 is eliminated and a free piston is used, and the valve stem serves as a guide at the center of the axis of the piston, assembly is possible without high mechanical precision. As a result, it has become possible to always reciprocate the piston at the center of the cylinder using a linear motor.

3) Power recovery is based on the information from the position sensor system mentioned above, and uses three linear drive/movement mechanism methods: linear motor, fluid compression, and spring elasticity, to create redundancy in the power recovery mechanism. In addition to improving reliability, the engine weight was reduced by simplifying the drive mechanism.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention, and FIG.
FIG. 3(a) is a conceptual diagram of an embodiment of the detection device of the present invention; (1) is a cross-sectional view when the expansion piston 62 of the embodiment shown in the figure is at the top dead center position; (2) is a case where the expansion piston 62 conducts signals a and b; FIG. 3(b) is a circuit diagram of a detection device; FIG. 4 is a diagram of the embodiment of FIG. 1; FIG. 5 is a sectional view of a conventional engine, and FIGS. 6(a) and 6(b) are p-v diagrams for explaining the performance of the engine. 20... Fat expansion space, 21... Discharge valve, 23... Valve stem, 24... Valve stem guide bearing, 25... Valve stem guide bearing, 26... Stator, 27...・・Suction valve,
28... Main spring, 29... Main spring, 3
0... Permanent magnet for linear motor, 31... Yoke for linear motor, 32... Winding wire, 33... Stator,
34... Compression chamber, 35... Suction valve, 36... Discharge valve, 37... Spring, 48... Position marker,
49... Position sensor, 5... Position sensor, 57... Cover, 58... Fluid space, 61... Cylinder, 62... Fat expansion piston.

Claims (1)

[Scope of Claims] 1) In a reciprocating free piston type expansion engine used in a Claude cycle or a reverse Brayton cycle, which generates a low temperature by adiabatically expanding a working fluid, each end of the engine is connected to the casing. an electromagnetic control device for opening and closing the discharge valve by controllingly moving in the axial direction a valve stem movably supported in the axial direction by a bearing, and a valve plate and a small piston of the discharge valve fixed to the valve stem; A free piston, characterized in that the central axis is penetrated by the valve stem, and the lower end has a fitting part that fits with the outer periphery of the small piston of the discharge valve, and has an expansion piston that reciprocates. type expansion engine. 2) The discharge valve is always closed by the actuation force of the electromagnetic control device and the urging forces of springs disposed in the electromagnetic control device and the small piston. The free piston expansion engine according to claim 1, characterized in that: 3) Detecting a signal of the position and/or speed of the expansion piston in the cylinder by a position marker disposed on the expansion piston and a fixed position sensor that detects the position marker, and based on the detected signal, 2. The free piston type expansion engine according to claim 1, wherein the speed and/or traveling direction of the expansion piston and the opening/closing of the discharge valve are controlled. 4) A compression chamber is provided in a room temperature section on the side opposite to the expansion chamber side of the expansion piston, and a part of the adiabatic expansion work in the expansion chamber by the expansion piston is performed by the compressor constituted by the compression chamber. The free piston type expansion engine according to claim 1, wherein the free piston type expansion engine is adapted to be recovered by work.