JPH09152211A - Piston for external combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the thermal efficiency by fully filling and installing a member having low thermal conductivity in the hollow part of a piston for an external combustion engine having the hollow part therein, thereby preventing the transfer of heat and radiation heat due to the convection in the hollow part. SOLUTION: The Vuilleumier cycle as the external combustion engine has a high temperature side cylinder for accommodating a high temperature side piston and a low temperature side cylinder for accommodating a low temperature side piston in such a manner that the high temperature side piston and the low temperature piston are coupled to a piston rod to be reciprocatingly moved. In this case, the pistons 55A of the high and low temperature side pistons are formed by fully filling member 62 having low thermal conductivity in the hollow part 57 of a cylinder 56. As the member 62 having the low conductivity, heat insulator such as ceramic fiber, glass fiber or rock wool is preferably used. Thus, the transfer of gas in the part 57 of the cylinder 56 is prevented by the member 62 having the low conductivity, thereby improving the thermal efficiency by extremely reducing the heat loss.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston for an external combustion engine such as Vilmier cycle or Stirling cycle, which is used for heating / cooling, hot water supply, power, etc.

[0002]

2. Description of the Related Art Some pistons of this type of external combustion engine have a hollow portion in which the inside of the piston is hollow in order to reduce the load on the piston drive portion and the material cost of the piston. However, when the hollow part is formed in the piston,
Convection and radiation of heat may occur, and various proposals have been made to reduce heat loss.

FIG. 2 is a vertical sectional view of a Wilmier cycle as an external combustion engine.

In the figure, the Vilmier cycle is composed of a high temperature side piston (displacer) 1, a low temperature side piston (displacer) 2, and a high temperature side cylinder 3 for accommodating the high temperature side piston (displacer) 1 and a low temperature side piston (display). Sir) 2 low temperature side cylinder 4
And has a high temperature side piston (displacer)
1 is connected to a piston rod 5 disposed at a right angle position to a low temperature side piston (displacer) 2 and reciprocates, and the low temperature side piston (displacer) 2 is connected to a piston rod 6 to reciprocate. ing.

A high temperature chamber 3a is provided in front of the high temperature side cylinder 3, and the high temperature side heat exchanger 7 communicating with the high temperature chamber 3a is heated by an external heat source such as a heater. A high temperature side regenerator 9 and a medium temperature side heat exchanger 10 are provided between the tip of the high temperature side heat exchanger 7 and the middle greenhouse 3b arranged behind the high temperature side cylinder 3. Further, a low temperature chamber 4a is provided in front of the low temperature side cylinder 4, and a low temperature side heat exchanger 11 and a low temperature side are provided between the low temperature chamber 4a and a middle greenhouse 4b arranged behind the low temperature side cylinder 4. The regenerator 12 and the intermediate temperature side heat exchanger 13 are provided. In addition, 14 is a communication passage as a gas flow path which connects the inside greenhouse 3b and the inside greenhouse 4b.

On the other hand, two connecting rods 16 and 17 connected to the piston rod 5 and the piston rod 6 arranged at right angles, the crankshaft 18, and the balance weight 1
9 and 9 constitute a crank mechanism 15 and a crankcase 20.
It is built in. A drive motor (not shown) is directly coupled to the crankshaft 18 on the shaft of the crankshaft 18, and the high temperature side piston (displacer) 1 and the low temperature side piston (displacer) 2 are connected to each other by a crank mechanism 15.
It is configured to reciprocate with a phase difference of °.

With the above construction, first, on the low temperature side, the low temperature side piston (displacer) 2 periodically reciprocates and moves to the left in the figure (from bottom dead center to top dead center). The working gas such as helium in the low temperature chamber 4a flows into the middle greenhouse 4b via the low temperature side heat exchanger 11, the low temperature side regenerator 12, and the middle temperature side heat exchanger 13. At this time, the moved working gas receives the heat stored in the low temperature side regenerator 12 and raises the temperature. When the temperature rises, the volume of the working gas increases due to the expansion of the working gas, and a part of the working gas fills the middle greenhouse 4b. Therefore, the remaining working gas that cannot fully enter the middle greenhouse 4b moves to the middle greenhouse 3b through the communication passage 14. To do.
As a result, the pressure of the working gas in the middle greenhouse 3b rises. Therefore, heat is released from the intermediate temperature side heat exchanger 10 to return the increased temperature to the original level.

Correspondingly, when the high temperature side piston (displacer) 1 descends in the figure (it goes down from the top dead center to the bottom dead center), the working gas inside the middle greenhouse 3b becomes the middle temperature side heat exchanger 10. And flows into the high temperature chamber 3a via the high temperature side regenerator 9. In this process, the working gas that has passed through the high temperature side regenerator 9 receives heat from the high temperature side regenerator 9 and raises the temperature. When the temperature of the working gas in the high greenhouse 3a rises,
The working gas expands, a part of the working gas fills the high temperature chamber 3a, and the remaining working gas is blocked from flowing into the high temperature chamber 3a and moves to the middle greenhouse 4b through the communication passage 14. As a result, the temperature and the pressure of the working gas of the middle greenhouse 4b into which the working gas flows are increased. Therefore, heat is released from the medium temperature side heat exchanger 13 to return the increased temperature to the original level.

On the other hand, when the low temperature side piston (displacer) 2 periodically reciprocates and moves to the right in the figure (from the top dead center to the bottom dead center), the working gas inside the middle greenhouse 4b is discharged. Flows into the low temperature chamber 4a via the medium temperature side heat exchanger 13, the low temperature side regenerator 12 and the low temperature side heat exchanger 11. In this case, the transferred working gas is the low temperature side regenerator 1
Stores heat in 2 and lowers the temperature. For this reason, the working gas contracts, so that a part of the working gas in the high temperature chamber 3a passes through each heat exchanger and the communication passage 14 in order to make up for the insufficient volume, and passes through the low temperature chamber 4a.
Move to. As a result, the working gas in the high temperature chamber 3a, whose temperature and pressure have decreased with the outflow of the working gas, becomes the high temperature side heat exchanger 7.
It absorbs heat from and restores the temperature.

On the other hand, when the high temperature side piston (displacer) 1 rises in the figure (from the bottom dead center to the top dead center), the working gas inside the high temperature chamber 3a rises to the high temperature side regenerator 9 and the high temperature side. Middle greenhouse 3 via the side heat exchanger 10
flow into b. The moved working gas stores heat in the high temperature side regenerator 9 and lowers the temperature. Therefore, the working gas contracts, and a part of the working gas in the low temperature chamber 4a moves to the middle greenhouse 3b through each heat exchanger and the communication passage 14 in order to make up for the insufficient volume. As a result, the working gas in the low temperature chamber 4a, the temperature and pressure of which have decreased with the outflow of the working gas, absorbs heat from the outside through the low temperature side heat exchanger 11 and returns the temperature to the original level.

The piping coming out of the intermediate temperature side heat exchanger 10 is returned to the intermediate temperature side heat exchanger 10 via an outdoor (or indoor) side heat exchanger (not shown), a circulation pump, an intermediate temperature side heat exchanger 13. In addition, the piping coming out of the low temperature side heat exchanger 11 is adapted to return to the low temperature side heat exchanger 11 via an indoor (or outdoor) side heat exchanger (not shown), a circulation pump, and a cooling ( Or heating).

Reference numerals 21 and 22 denote communication holes, 23 is a partition plate disposed in the high temperature side piston (displacer) 1, a hole 23a is formed in the partition plate 23, and 24 is a low temperature side piston (display). Partition plate to be placed on the
The hole 24a is formed.

Next, a Stirling cycle refrigerator as another example of the external combustion engine will be described with reference to FIG.

The Stirling cycle is mainly composed of an expander 26, a compressor 27, and a drive chamber 28.
The expander 26 includes an expansion cylinder 29 and an expansion piston 30 that reciprocates in the cylinder. Similarly, the compressor 27 includes a compression cylinder 31 and a compression piston 32 that reciprocates in the cylinder.

Expansion piston 30 and compression piston 32
Are connected to a crank mechanism 35 arranged inside the drive chamber 28 via piston rods 33 and 34, respectively.
It is driven with a phase difference of 0 °.

A regenerator 36, which is a regenerator, is arranged around the expansion cylinder 29 of the expander 26 and between the containers, and the expansion space 37 generated in front of the expansion piston 30 and the front of the compression piston 32 are connected via the regenerator 36. The gas flow path 39 communicates with the compression space 38 generated in the above, and the gas moves during the refrigeration cycle.

On the other hand, the back pressure side space of the expansion piston 30 and the compression piston 32 is connected by a gas flow passage 40 in order to prevent the loss of the work of the piston. Radiating fins 42, 43 are arranged on the outer peripheral surface of the container of the compressor 27 and the outer peripheral surface of the lower portion of the expander 26.

With this structure, when the crank mechanism 35 of the drive chamber 28 is driven by the rotation of the drive motor (not shown), the compression piston 3 in the compression cylinder 31 of the compressor 27 is driven.
2 moves to the compression space 38 side, and the refrigerant gas as a working gas such as helium that fills the compression space 38 and is difficult to liquefy is compressed.

The compressed refrigerant gas flows into the heat storage device 36 from the gas passage 39. The refrigerant gas that has flowed into the heat storage device 36 is cooled by a material having a large specific heat, for example, a heat storage material made of copper or lead wire mesh or spheres, and flows into the expansion space 37 of the expander 26 to be in a high pressure state. .

Thereafter, the expansion piston 30 in the expansion cylinder 29 of the expander 26 descends with the phase difference of about 90 ° with the compression piston 32. As a result, the expansion space 37 is suddenly expanded and the pressure of the refrigerant gas sharply drops, so that the refrigerant gas becomes a low temperature.

When the expansion piston 30 starts to rise and the compression piston 32 retracts, the low-temperature refrigerant gas passes through the heat accumulator 36, the gas passage 39, and the compression space 3.
Returned to 8. At this time, in the heat storage device 36, the heat storage material is cooled and cold heat is stored.

By the above process, one heat cycle is completed, and this process is repeated by the crank mechanism 35, whereby the temperature of the freezing generation part which is the expansion space 37 and the temperature of the heat accumulator 36 are gradually lowered, The temperature of the refrigerant gas in the freezing generation section becomes low, and the generated cold heat can be taken out and utilized.

By the way, the high temperature side piston (displacer) 1 and the low temperature side piston (displacer) 2 described in FIG. 2 or the expansion piston 30 and the compression piston 32 described in FIG. Can reduce the burden, cost and weight of the crank mechanism 15 and the crank mechanism 35. However, if the inside of the piston is hollow, a new problem arises in that convection and radiation occur in the hollow portion and heat loss increases.

In order to solve this problem, as shown in FIG. 4, the piston 55 has a partition plate 58 and a partition plate 59 arranged in a hollow portion 57 formed in a cylindrical body 56, and the cylindrical body 56 is covered by a cover body 60. After sealing, the rod 61 is connected to the lid 60.

[0025]

However, in the piston 55 as shown in FIG. 4, the partition plates 58 and 59 divide it into three hollow portions 57a, 57b and 57c, and the radiation and convection of the hollow portion 57 are made to some extent. However, since there are still three hollow portions 57a, 57b, 57c, there is a problem that radiation and convection occur in these spaces, heat loss is large, and thermal efficiency is reduced.

Therefore, an object of the present invention is to solve the above problems and provide a piston of an external combustion engine having high thermal efficiency.

[0027]

According to a first aspect of the invention, in a piston of an external combustion engine having a piston having a hollow portion inside, the hollow portion is fully filled with a member having a low thermal conductivity.

According to a second aspect of the present invention, in the piston for an external combustion engine according to the first aspect, the hollow portion is filled with a member having a low thermal conductivity, which is either a bulk shape, a molded article, or a felt shape. That is what I did.

According to a third aspect of the present invention, in the piston of the external combustion engine according to the first or second aspect, as the member having a low thermal conductivity, any one of ceramic fiber, glass fiber, rock wool, and styrofoam heat insulating material is used. Is used.

[0030]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a piston showing an embodiment of the present invention, and a piston 55A is a high temperature side piston (displacer) of the Vilmier cycle shown in FIG.
1 and the low temperature side piston (displacer) 2 as well as the expansion piston 30 and the compression piston 32 of the Stirling cycle shown in FIG. As shown in FIG. 1, the piston 55A includes the cylindrical body 5
6 is characterized in that the hollow portion 57 formed in 6 is filled with a member 62 having a low thermal conductivity.

As the member 62 having a low thermal conductivity,
For example, it is possible to use a bulky (wadding) generally called heat insulating material such as ceramic fiber, glass fiber, rock wool, etc., or foamed polystyrene or felt (belt shaped) obtained by molding and processing these. For example, styrofoam or the like can be used when the piston is used at low temperature, and ceramic fiber or glass fiber can be used when the piston is used at high temperature.

As described above, the cylindrical body 5 of the piston 55A
In the case where the hollow portion 57 formed in 6 is filled with the member 62 having a low thermal conductivity, the movement of gas in the hollow portion 57 of the tubular body 56 is blocked by the member 62 having a low thermal conductivity. Therefore, convection is prevented from occurring in the hollow portion 57 of the cylinder body 56 even if there is a temperature difference between the inside and outside of the cylinder body 56 of the piston 55A. Further, the pressure resistance against the external pressure applied to the cylindrical body 56 can be supplemented by the member 62 having a low thermal conductivity which is fully installed.

For example, in the conventional Vilmier cycle described in FIG. 2, when the low temperature side piston (displacer) 2 moves from the bottom dead center to the top dead center as described above,
While the temperature of the middle greenhouse 4b is raised along with the movement of the working gas, the working gas that cannot enter the middle greenhouse 4b moves to the middle greenhouse 3b to raise the temperature and the pressure. On the other hand, when the high temperature side piston (displacer) 1 falls from the top dead center to the bottom dead center, the temperature and pressure of the high temperature chamber 3a are increased by the movement of the working gas, and the working gas that cannot enter the high temperature chamber 3a is increased. Flow into the middle greenhouse 4b to raise the temperature and pressure.

Further, when the low temperature side piston (displacer) 2 moves from the top dead center to the bottom dead center, the temperature and pressure of the low temperature chamber 4a are lowered with the movement of the working gas, while the high temperature chamber 3a is cooled by the low temperature chamber 4a. Move the working gas to make up for the
The temperature and pressure of the high greenhouse 3a are lowered. On the other hand, when the high temperature side piston (displacer) 1 rises from the bottom dead center to the top dead center, the temperature of the middle greenhouse 3b drops as the working gas moves, and the working gas in the low temperature chamber 4a becomes hot as the pressure decreases. The temperature and the pressure of the low temperature chamber 4a are decreased by being discharged.

As described above, in the high temperature side piston (displacer) 1 and the low temperature side piston (displacer) 2 of the Vilmier cycle, each part of the piston is repeated from high temperature to low temperature and from high pressure to low pressure according to each cycle. In this case, in the present invention, even if the temperature of each portion of the cylinder body 56 of the piston 55A changes, the convection of gas is blocked in the hollow portion 57, and heat transfer due to radiation does not occur.

As a result, the inside temperature of the cylinder body 56 of the piston 55A is substantially maintained at the outside temperature of the piston 55A, the heat loss due to the movement of heat is extremely small, the thermal efficiency is good, and the external combustion that can withstand the external pressure is used. The engine piston is obtained.

Needless to say, the present invention can be applied to other external combustion engines such as the Stirling cycle.

[0039]

As described above, according to the invention of claim 1, since the hollow portion of the piston is filled with a member having a low thermal conductivity, heat transfer due to convection in the hollow portion can be prevented. The transfer of radiant heat can be prevented and the thermal efficiency can be improved.

According to the second aspect of the invention, the thermal efficiency can be improved by using the shape according to the usage conditions.

According to the third aspect of the invention, the thermal efficiency can be improved by using the member having a low thermal conductivity according to the usage conditions.

[0042]

[Brief description of the drawings]

FIG. 1 is a sectional configuration diagram of a piston of an external combustion engine showing an embodiment of the present invention.

FIG. 2 is a cross-sectional configuration diagram showing a Vilmier cycle as an example of a conventional external combustion engine.

FIG. 3 is a cross-sectional configuration diagram showing a refrigerator using a Stirling cycle as an example of a conventional external combustion engine.

FIG. 4 is a cross-sectional configuration diagram showing a piston of a conventional external combustion engine.

[Explanation of symbols]

 1 high temperature side piston (displacer) 2 low temperature side piston (displacer) 3 high temperature side cylinder 3a high greenhouse 3b, 4b medium greenhouse 4 low temperature side cylinder 4a low greenhouse 5,6,33,34,61 piston rod 9 high temperature side regeneration Container 10, 13 Medium temperature side heat exchanger 11 Low temperature side heat exchanger 12 Low temperature side regenerator 26 Expander 27 Compressor 28 Drive chamber 29 Expansion cylinder 30 Expansion piston 31 Compression cylinder 32 Compression piston 55A Piston 56 Cylindrical body 57 Hollow part 60 Lid 62 Member with low thermal conductivity

Claims (3)

[Claims] 1. A piston for an external combustion engine, comprising a piston having a hollow portion inside, wherein the hollow portion is fully filled with a member having a low thermal conductivity. 2. The hollow portion has a bulk shape or
The piston for an external combustion engine according to claim 1, wherein a molded article or a felt-shaped member having a low thermal conductivity is installed in a filled manner. 3. The external combustion engine according to claim 1, wherein a heat insulating material selected from ceramic fiber, glass fiber, rock wool, and styrofoam is used as the member having low thermal conductivity. piston.