JP3367507B2 - Free piston type Stirling engine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a free piston Stirling engine having a free piston that reciprocates linearly in a cylinder.

[0002]

2. Description of the Related Art In recent years, with the exhaustion of petroleum resources, a Stirling engine which can be driven by energy resources other than petroleum has attracted attention as an engine replacing a gasoline engine or a diesel engine. This Stirling engine was invented by a Scottish pastor, Robert Stirling, in 1816. It is roughly classified into a displacer type, a two piston type, and a double acting type. Also, as a kind of displacer type Stirling engine, without a crank mechanism,
A free-piston type Stirling engine has also been proposed and put into practical use, in which a difference in inertial mass between the displacer piston and the output piston and a phase difference are provided by a gas spring or the like, and the piston reciprocates linearly in the cylinder.

In this free piston type Stirling engine, a power piston and a displacer are coaxially installed in a cylinder to form an expansion space and a compression space on both axial sides of the displacer, and the power piston and the displacer are opposite to the displacer. The basic structure is a bounce space.

[0004]

This free piston type Stirling engine has a cylinder that can be hermetically sealed, an oilless structure can be easily adopted, and can be composed of a small number of parts, as compared with a Stirling engine having a crank mechanism. Therefore, although the mechanical efficiency and the maintainability are excellent, since the piston is a free piston, the movement of the piston is likely to be disordered, which is a major obstacle to its widespread use. In particular, when using a double-acting type or multiple-type in order to obtain high thermal efficiency and high output, it is necessary to properly adjust the axial phase of the free pistons, but it is necessary to achieve mechanical linkage. It was difficult because I couldn't.

Further, in this type of engine, since a piston ring for preventing gas leakage cannot be used, a leak gas is made to flow between the cylinder and the free piston for lubrication. Therefore, the gas leak loss is large, and a bounce space for obtaining the gas spring is required behind the power piston, and the output loss due to this space is also large.

According to the present invention, the airtightness between the cylinder and the free piston is sufficiently ensured, the movement of the free piston is made smooth, the engine efficiency is improved and the disturbance is suppressed, and moreover, the linkage of the multiple cylinders is accurately performed. It is to provide a free piston type Stirling engine that can be achieved.

[0007]

Means for Solving the Problem and Its Action As a result of diligent study by the applicant of the present invention in order to prevent disturbances in a free piston type Stirling engine, it was found that when the cylinder and the free piston are constantly moving relative to each other. It was found that the free piston is in a floating state due to the gas intervening in it, can move with almost no resistance, and that by giving a rotary motion to the piston, the flywheel effect can be given and the motion of the piston can be controlled, and it is possible to prevent disorder. The present invention has been invented based on the idea.

A free piston type Stirling engine according to a first aspect of the present invention is provided with magnetic rotating means for continuously rotating a free piston that reciprocates linearly in a cylinder in one direction via magnetic force. In this Stirling engine, the free piston continuously rotates in one direction in the cylinder via the magnetic rotation means, and the gas present between the cylinder and the free piston causes the free piston to float, causing almost no resistance. Since it can be moved, it is possible to effectively prevent disorder due to frictional resistance between the two. Further, since the frictional resistance between the two is significantly reduced, mechanical energy loss is reduced and engine efficiency is increased. Moreover, the gas intervening between the two forms a flow in the circumferential direction, and the flow of the gas in the axial direction is blocked, so that the sealing performance is also improved. Furthermore, since the free piston is rotated via magnetic force, it is possible to configure the cylinder in a completely sealed state, and it is possible to use an efficient working gas such as hydrogen or helium that has a small molecular weight and can reduce flow resistance. It will be possible.

The Stirling engine according to claim 2 is
The magnetic rotating means is provided with a magnetic cam for converting the reciprocating linear motion of the free piston into a rotary motion.
In this case, a rotational force in one direction can be applied to the free piston with a simple structure, which is preferable. Also, since the motion pattern of the reciprocating linear motion of the free piston can be changed according to the shape of the magnetic cam, the phase difference between the free pistons can be set appropriately even in the double-acting type or the multiple type. It becomes possible, and by setting the movement pattern of the free piston to an optimum movement pattern, it becomes possible to bring out the engine performance sufficiently. Furthermore, it becomes possible to efficiently generate electricity by converting this rotational movement into electric energy.

A Stirling engine according to claim 3 is
The magnetic rotating means includes a power-generating coil for converting reciprocating linear motion of the free piston into electric energy, and a rotating coil for rotating the free piston by using at least a part of generated electric power. In this case, although the structure is slightly more complicated than that of the Stirling engine according to the second aspect, the rotation speed of the free piston can be arbitrarily adjusted by using the rotation coil.

A Stirling engine according to a fourth aspect is
Piston position detecting means for detecting the axial position of the free piston in the cylinder is provided, and control means for adjusting the axial position of the free piston by exciting the power generating coil or adjusting the power generation load is provided. . In this case, since the axial position of the free piston can be adjusted by using the power generation coil, it becomes possible to move a plurality of free pistons in a linked manner. It is possible to accurately synchronize the engines. Further, since the motion pattern of the reciprocating linear motion of the free piston can be arbitrarily adjusted by the power generating coil, the free piston can be linearly moved in the reciprocating linear motion with the optimum motion pattern, and the engine performance can be sufficiently obtained.

When the Stirling engine according to the fifth aspect is provided, a plurality of cylinders are provided, and a communication passage that connects the plurality of cylinders in series is provided, and the heater, the regenerator, and the cooler are provided in the communication passage. Since the displacer can be omitted, it is possible to realize a high-power engine while significantly reducing the number of constituent parts. However, the present invention can be similarly applied to a Stirling engine in which a plurality of free pistons are provided in the cylinder and a cooler, a regenerator, and a heater are provided in the cylinder between adjacent free pistons.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. As shown in FIGS. 1 and 2, the Stirling engine 1 is a double-acting free piston Stirling engine, and includes four sets of unit engines 4 each having a cylinder 2 and a free piston 3, and these four units.
Adjacent unit engines 4 are provided with four communication passages 5 that annularly communicate the cylinders 2 of the unit engines 4 in a set, a heater 6, a regenerator 7, and a cooler 8 that are provided in the middle of the communication passages 5.
The free piston 3 is configured so that the free piston 3 reciprocates linearly in the cylinder 2 by sequentially performing an isothermal heating process, an isothermal expansion process, an isothermal cooling process, and an isothermal compression process with a phase difference of 90 °. Has been done. Further, in this Stirling engine 1, the magnetic rotation means 10 for continuously rotating the free piston 3 in one direction via magnetism.
And a power generation means 11 for converting the rotational movement of the free piston 3 into electric energy, and the magnetic rotation means 10 is configured to smoothly perform the reciprocating linear movement and the rotational movement of the free piston 3.

The cylinder 2 and the free piston 3 can be constructed in any size according to the generated electric power or the like, and can be constructed of a metal material such as an aluminum alloy like the well-known Stirling engine. However, when used at low temperature, it can be made of synthetic resin material, heat-resistant glass, etc., and made of ceramic material with excellent heat resistance in consideration of use at high temperature in order to improve engine performance. It is also possible. In any case, the Stirling engine 1 is made of a material having mechanical strength, heat resistance, and durability according to usage conditions. The cylinder 2 and the free piston 3 can be made of the same material, or can be made of different materials.
In terms of reciprocating movement in the cylinder 2, it is preferable to use a material that is as light as possible. Further, in the present invention,
It is preferable that the cylinder 2 and the free piston 3 are made of a non-magnetic material because the free piston 3 is rotated by magnetic coupling as described later. Free piston 3
It is preferable that the portion in contact with the high temperature side is made of a heat-resistant heat insulating material to protect the permanent magnet provided in the free piston 3.

Although air can be used as the working gas to be filled in the cylinder 2, in the present invention, since the cylinder 2 can be constructed in a completely sealed state, hydrogen gas or helium gas having a small molecular weight is used. Thus, the flow resistance can be reduced as much as possible. Further, the pressure of the working gas is preferably set to 100 atm or more in order to increase the output.

The opening position of the communication passage 5 with respect to the cylinder 2 may be opened on the upper and lower surfaces of the cylinder 2 as shown in FIG. 1, or may be opened on the peripheral surface of the cylinder 2. Further, in the case where the free piston 3 is opened to the peripheral surface, it can be arranged closer to the center than the lower limit position and the upper limit position of the free piston 3, and the lower end vicinity and the upper end vicinity of the internal space of the cylinder 2 can be utilized as a gas spring. Is.

As shown in FIGS. 2 to 4, the magnetic rotating means 10 converts the reciprocating linear motion of the free piston 3 in the cylinder 2 into a continuous rotary motion in one direction. The wave-shaped magnetic cam 12 integrally provided on the upper portion, and the cylinder 2 facing the magnetic cam 12
When the free piston 3 linearly moves in the cylinder 2, the magnetic attraction force between the magnetic cam 12 and the magnetic spot 13 causes the magnetic spot 13 to move to the magnetic cam 12. The free piston 3 is configured to rotate in one direction by relative movement along the same. However, at least one of the magnetic cam 12 and the magnetic spot 12 can be configured by an induction coil.

The magnetic cam 12 will be described. As shown in a developed view of the peripheral surface of the free piston shown in FIG. 3 and as shown in FIG. A magnetic cam 12 made of a belt-shaped permanent magnet is formed in the groove portion 14 and is mounted along the groove portion 14. The groove portion 14 includes a flat upper groove 14a and a flat lower groove 14b extending substantially in the circumferential direction, and upper and lower grooves 14a,
14b, the magnetic spots 13 are formed by inclined grooves 14c and 14d connected to the magnetic cam 1 in the inclined grooves 14c and 14d.
In a state where the free piston 3 faces the shaft 2, the free piston 3 is configured to move in the axial direction so that a rotational force is applied to the free piston 3. However, in the upper groove 14a and the lower groove 14b, the magnetic cam 12 and the magnetic spot 13 relatively rotate due to the inertial force of the free piston 3.

The amplitude of the magnetic cam 12 depends on the magnetic spot 13
Is set to be approximately the same as the stroke of the free piston 3 so as not to separate from the magnetic cam 12. The number of the magnetic spots 13 may be one or two. However, when two magnetic spots are provided, the magnetic spots 12 are 180 ° out of phase with each other and face the magnetic cam 12. In addition, the groove portion 14 is
In addition to the trapezoidal wave shape shown in FIG. 3, the upper groove 14a or the lower groove 1
It is also possible to adopt a configuration in which at least one of 4b is omitted, or it is possible to form in a triangular wave shape or a sine wave shape. That is, in this Stirling engine 1, since the motion pattern of the reciprocating linear motion of the free piston 3 depends on the shape of the magnetic cam 12 loaded in the groove portion 14, the shape of the magnetic cam 12 should be set appropriately. Thus, the four unit engines 4 can be operated synchronously and the engine efficiency can be sufficiently brought out. Therefore, in consideration of engine efficiency, the shape of the magnetic cam 12 is set to a trapezoidal wave shape, a triangular wave shape, or the like as shown in the figure, other than a sine wave shape which is a general motion pattern.
It is possible to improve engine efficiency.

Since the magnetic cam 12 is formed in a wave shape for two cycles, the free piston 3 makes one rotation by making two reciprocations in the axial direction, but is formed in a wave shape for one cycle. Then, it may be configured to make one rotation for one reciprocation, or may be configured to have a wave shape of three cycles or more and reciprocate for each cycle to make one rotation. Further, the magnetic spots 13 can be provided by the number corresponding to the period of the magnetic cams 12. For example, when the magnetic cams 12 are provided for three periods, a maximum of three magnetic spots 13 can be provided.

It is also possible to provide a plurality of magnetic cams 12 at intervals in the axial direction and provide the magnetic spots 13 so as to face each magnetic cam 12. In this case, the magnetic coupling force between the cylinder 2 and the free piston 3 can be increased, which is suitable for an engine with a large output.

Further, in the above embodiment, the magnetic spot 13 and the magnetic cam 12 are magnetically coupled by the magnetic attraction force, but it is also possible to magnetically couple them by utilizing the repulsive force. Specifically, as shown in FIG.
The free piston 3 is provided with a pair of magnetic cams 12A vertically spaced from each other, the outer surfaces of both magnetic cams 12A are set to different polarities, and the two magnetic cams 12A are faced to each other so that the cylinder 2 has both magnetic cams 12A. A magnetic spot 13A is provided so as to repel, or as shown in FIG. 5B, a pair of magnetic cams 12B is provided on the free piston 3 with an interval vertically, and the polarities on the outer surface side of both magnetic cams 12B are set. The magnetic poles are set to the same pole, and the two magnetic cams 12B are placed on the cylinder 2 so that they face each other.
The magnetic spot 13B is provided so as to repel.

The power generating means 11 includes a power generating magnet 15 which is a permanent magnet provided in the lower portion of the free piston 3 in the circumferential direction,
Power generation coil 1 including a three-phase coil provided in the cylinder 2
6 has a well-known configuration in which the rotational movement of the free piston 3 by the magnetic rotating means 10 is converted into electric energy by the power generation coil 16.
The number of poles of 5 and the number of poles of the power generation coil 16 can be set arbitrarily. Further, the arrangement of the magnetic rotation means 10 and the power generation means 11 can be set arbitrarily, and for example, the vertical positional relationship between the two may be set reversely. However, the power-generating magnet 15 can also be composed of an induction coil.

Although not shown, each unit engine 4
A sensor that detects the rotation angle of the free piston 3 is provided in the, and the power generation load of each unit engine 4 is adjusted.
It is preferable to finely adjust the phase between the unit engines 4.

Next, the operation of the Stirling engine 1 will be described. First, when the Stirling engine 1 is started by energizing the power generation coil 16, the isochoric heating process, the isothermal expansion process, the isovolume cooling process in the cylinder 2,
The isothermal compression process is sequentially performed, and the free piston 3 reciprocates linearly in the axial direction, and the free piston 3 continuously rotates in one direction via the magnetic rotating means 10. Then, this rotational movement is converted into electric energy by the power generation means 11 and output.

When the free piston 3 rotates, the working gas present between the free piston 3 and the cylinder 2 causes the free piston 3 to float, causing the free piston 3 to rotate and reciprocate linearly with almost no resistance. . Moreover, since a flow in the circumferential direction is formed in the working gas interposed between the two, and the flow of the working gas in the axial direction is obstructed, the sealing performance of the working gas from the expansion space to the compression space or the opposite side is improved. Will also improve.

Next, another embodiment in which the configuration of the unit engine 4 is changed will be described. The configuration other than the unit engine 4 is basically the same as that of the above embodiment,
Detailed description thereof will be omitted. As shown in FIG. 6, this unit engine 20 basically uses the power generation means 11 in the unit engine 4 as an electric motor 21, and reciprocates the free piston 3 at the portion where the magnetic rotation means 10 was disposed. A power generation unit 22 for converting linear motion into electric energy is provided, and the electric motor 21 is driven by using a part of electric power generated by the power generation unit 22 to rotate the free piston 3. That is, in the unit engine 20, the power generation means 22 and the electric motor 2
1 and the magnetic rotation means.

The electric motor 21 is the electric power generating means 11 described above.
And a rotating coil 23 formed of a three-phase coil provided on the cylinder 2 side and a rotating magnet 24 formed of a permanent magnet provided on the free piston 3 side. The free piston 3 is configured to rotate by energizing the. However, this electric motor 21 can also be used as a power generation means for converting the rotational movement of the free piston 3 into electric energy.

The power generating means 22 includes a power generating magnet 25, which is an annular permanent magnet provided on the outer peripheral portion of the upper portion of the free piston 3 at regular intervals in the axial direction, and a plurality of sets of solenoids annularly provided on the upper portion of the cylinder 2. The power generation means 22 converts the kinetic energy of the free piston 3 which makes a reciprocating linear motion in the cylinder 2 into electric energy. However, the power generation means 22 combines coil connections so as to generate a predetermined power generation load in accordance with the position of the free piston 3 in the operation cycle, adjusts the speed of the free piston 3, and changes the optimum volume. Is generated and the phase difference of the linkage of the multi-pistons is controlled, but by exciting a desired power-generating coil 26, a suction force or a repulsive force acts between the power-generating coil 26 and the power-generating magnet 25, and It is also possible to use it as a drive means for finely adjusting the axial position of the free piston 3 inside 2.

In addition, the unit engine 20 includes a position regulating coil 27 for regulating the upper limit position and the lower limit position of the free piston 3 and a circumferential position sensor 28 for detecting the circumferential position of the free piston 3. And cylinder 2
A piston position sensor 29 for detecting the axial position of the free piston 3 therein is provided. However, when the space for the gas spring is provided in the cylinder 2, the position regulating coil 27 may be omitted.

Regarding the operation of the Stirling engine provided with the unit engine 20 having such a configuration, the control device 30
The description will be made while explaining the processing contents in step 1. When the engine is started, the power-generating coil 26 of each unit engine 20 is sequentially excited, and the free piston 3 is linearly moved back and forth in a predetermined phase. Once the engine starts,
In the cylinder 2, a constant volume heating process, a constant temperature expansion process, a constant volume cooling process, and a constant temperature compression process are sequentially performed, and the free piston 3 reciprocates linearly in the axial direction. 22 converts into electrical energy.

Further, when the free piston 3 moves to near the top dead center or near the bottom dead center, the position regulating coil 27 on the upper side or the lower side is excited to move the position regulating coil 27.
By the repulsive force between the power generating magnet 25 and the power generating magnet 25.
Are restricted from moving above top dead center or below bottom dead center.

Further, the reciprocating speed of the free piston 3 in each unit engine 20 is obtained based on the signal from the piston position sensor 29, and the heater 6 is controlled so that the reciprocating speed becomes the target speed. The power generation load of each unit engine 20 is adjusted as necessary, and the power generation coil 26 is excited to control the position of the free piston 3 so that the phase of the free piston 3 of each unit engine 20 becomes appropriate. It will be.

On the other hand, a part of the generated electric power excites the rotating coil 23 of the electric motor 21 to continuously rotate the free piston 3 in one direction, and based on the output from the circumferential position sensor 28, The rotation speed of the free piston 3 in each unit engine 20 is obtained, and the power supply to the electric motor 21 is controlled so that this rotation speed becomes the target speed. By rotating the free piston 3 in this manner, the free piston 3 is floated and controlled so as to rotate and reciprocate linearly with almost no resistance as in the case of the above-described embodiment, and is free from the cylinder 2. A circumferential flow is formed in the working gas interposed between the pistons 3 to improve the sealing performance of the working gas from the expansion space to the compression space or the opposite side.

When the free piston 3 is located near the top dead center or the bottom dead center, the electric power supply to the electric motor 21 is temporarily interrupted, and the rotary coil 23 electrically rotates the free piston 3. The linear motion of the free piston 3 may be assisted by converting the energy into energy to generate power and exciting the desired power generation coil 26 with the generated power. That is, the free piston 3 may function as a flywheel, and the reciprocating linear motion of the free piston 3 may be stabilized.

The magnetic rotating means in the above embodiment can be applied to a Stirling engine having only one free piston 3, and two or more free pistons 3 are incorporated in one cylinder. It can also be applied to Stirling engines. However, in the former case, an output piston and a displacer are provided as the free piston 3.

In the above embodiment, the four unit engines 4 and 20 are linked, but the three unit engines 4 and 20 are linked.
Of these three unit engines 4, 20
It may be operated with a phase difference of 0 °. In this case, three-phase AC can be output as generated power by connecting the power-generating coils of the three unit engines 4 and 20 in a delta connection or a star connection, so that commercial power can be economically used without using an inverter or the like. It becomes possible to obtain.

Further, in the case of an engine using a conventional crank mechanism, the phase difference between unit engines is mechanically determined and is fixed unique to the engine, but in the Stirling engine according to the present invention, it is electrically fixed. Since it can be controlled, the speed of the free piston 3 during the expansion output process is increased to increase the ratio of the high temperature side volume in the cylinder 2, whereby the average gas temperature and pressure can be increased and the thermal efficiency can be increased. That is, it suffices to give an optimum movement of the phase difference in each part of the operation and give a phase difference of 120 ° as an average value of the whole. For example, in the unit engine 20, one end of the power generation coil 26 is arranged at a position corresponding to the end of the expansion output process, and the other end is arranged at a position corresponding to the end of the compression process. Since they are placed at different positions, increasing the power generation load at the beginning of the next backward movement, that is, near the dead center of the crank, suppresses the increase in piston speed and increases the phase difference, which causes high temperature. It is possible to help increase the volume ratio and increase the thermal efficiency and output.

[0039]

According to the free piston type Stirling engine according to the first aspect of the present invention, the free piston is kept in a floating state in the cylinder by continuously rotating the free piston in one direction by the magnetic rotating means. Since the frictional resistance between them can be reduced remarkably, the disturbance of the engine can be effectively prevented and the mechanical energy loss can be reduced to improve the engine efficiency. Moreover, since the gas flow formed between the two improves the sealing performance, the loss due to the leak gas can be suppressed. Further, since the free piston is rotated in a non-contact manner via the magnetic force, the cylinder can be configured in a completely sealed state, and an efficient working gas such as hydrogen or helium can be used.

When the magnetic rotating means is provided with a magnetic cam as described in claim 2, it is preferable because a rotational force in one direction can be applied to the free piston with a simple structure.
Also, since the motion pattern of the reciprocating linear motion of the free piston can be changed according to the shape of the magnetic cam, even when using the double-acting type or the multiple type, the phase difference between the free pistons can be set appropriately, It is possible to prevent the engine from being disturbed and to set the movement pattern of the free piston to an optimum movement pattern so that the engine performance can be sufficiently brought out.

As described in claim 3, the magnetic rotating means comprises:
When the power generation coil and the rotation coil are provided, the structure becomes a little complicated, but it is preferable because the rotation speed of the free piston can be arbitrarily adjusted by using the rotation coil.

When the piston position detection means is provided and the control means for adjusting the axial position of the free piston by exciting the power generation coil or adjusting the power generation load is provided as in claim 4, a double-acting type or a multi-action type is provided. Even in the case of the continuous type, the phase difference between the free pistons can be set appropriately to prevent engine turbulence, and the free piston motion pattern can be adjusted to the optimum motion pattern according to the engine operating conditions. As a result, the engine performance can be fully brought out.

If a plurality of cylinders are provided and a communication passage that connects the plurality of cylinders in series is provided as described in claim 5, the displacer can be omitted, so that the number of components is significantly reduced. In addition, it is possible to realize a high-power engine.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram of a Stirling engine.

FIG. 2 is a vertical sectional view of a unit engine.

[Fig. 3] Development view of the peripheral surface of the free piston

FIG. 4 is an explanatory diagram of a magnetic cam

FIG. 5 is an explanatory diagram of a magnetic cam having another configuration.

FIG. 6 is a longitudinal sectional view of a unit engine having another configuration.

[Explanation of symbols]

1 Stirling engine 2 cylinder 3 free piston 4 unit engine 5 communication passage 6 heater 7 regenerator 8 cooler 10 magnetic rotation means 11 power generation means 12 magnetic cam 13 magnetic spot 14 Groove 14a Upper groove 14b lower groove 14c inclined groove 14d inclined groove 15 magnet for power generation 16 power generation coil 12A magnetic cam 13A magnetic spot 12B magnetic cam 13B magnetic spot 20 unit engine 21 electric motor 22 power generation means 23 rotating coil 24 Rotating Magnet 25 Power Generating Magnet 26 Power generation coil 27 Position control coil 28 Circumferential position sensor 29 Piston position sensor 30 Control device

Claims (5)

(57) [Claims] 1. A free piston type Stirling engine, comprising magnetic rotating means for continuously rotating a free piston that reciprocates linearly in a cylinder in one direction via magnetic force. 2. The free piston type Stirling engine according to claim 1, wherein the magnetic rotating means comprises a magnetic cam for converting the reciprocating linear motion of the free piston into a rotary motion. 3. The magnetic rotating means comprises a power generating coil for converting reciprocating linear motion of the free piston into electric energy, and a rotating coil for rotating the free piston by using at least a part of generated electric power. Claim 1
Free piston type Stirling engine described. 4. A piston position detecting means for detecting the axial position of the free piston in the cylinder is provided.
The free piston type Stirling engine according to claim 3, further comprising a control means for adjusting the axial position of the free piston by exciting the power generating coil or adjusting a power generation load. 5. A plurality of the cylinders are provided, and a communication passage that connects the plurality of cylinders in series is provided.
The free piston type Stirling engine according to any one of claims 1 to 4, wherein a heater, a regenerator and a cooler are provided in the communication passage.