Output control device, engine system, and output control method

Abstract

To provide an apparatus, system, and method for arbitrarily and precisely adjusting the output of a Stirling engine. [Solution] The output control device 21 is a device for controlling the output of a Stirling engine and includes an internal volume variable member that reciprocates or expands and contracts in a certain direction as gas flows in and out to reciprocate a piston equipped with a Stirling engine, thereby changing the internal volume of the Stirling engine, and an adjustment means for adjusting the range of reciprocation or expansion and contraction of the internal volume variable member. The output control device 21 includes a control cylinder 22 into which gas can flow in from one end, a control piston 23 as an internal volume variable member that closes the other end of the control cylinder 22 and reciprocates inside the control cylinder 22 as gas flows in and out, and an adjuster 24 as an adjustment means for adjusting the range of movement of the control piston 23.

Description

Technical Field

[0001] The present invention relates to an output control device for controlling the output of a Stirling engine, an engine system including the output control device, and an output control method.

Background Art

[0002] A Stirling engine is an engine that reciprocates a piston by utilizing the thermal expansion and contraction of a gas such as air. Since there is no intake or exhaust of gas in a Stirling engine, it is impossible to control the power (output) by controlling the flow rate of the mixed gas inhaled according to the opening degree of a throttle valve, like the throttle mechanism of a gasoline engine, and there is no method for arbitrarily and finely adjusting the output.

[0003] Conventionally, as a technique for controlling the output of a Stirling engine with good responsiveness, a technique of controlling the flow rate of a working fluid flowing through a heater of a Stirling engine with a control valve (see Patent Document 1), and a technique of adjusting the temperature of cooling water supplied to a Stirling engine with a temperature control valve (see Patent Document 2) are known.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the technique described in Patent Document 1 above, the flow rate of the working fluid (gas) flowing through the heater is controlled. However, with a control valve, if there is not a certain degree of pressure difference, the flow rate cannot be appropriately controlled, and it is difficult to arbitrarily and finely adjust the output.

[0006] Furthermore, in the technology described in Patent Document 2 above, the gas inside the cylinder of the Stirling engine has low thermal conductivity, making it difficult to transfer heat. Even if the temperature of the cooling water supplied from the outside is adjusted, it is not possible to quickly change the temperature of the gas. This makes it impossible to quickly change the pressure (compression ratio), and therefore it is not possible to adjust the output arbitrarily and precisely. [Means for solving the problem]

[0007] Therefore, as a result of diligent research, the inventors of the present invention have found that by branching the connection between the heating cylinder and the cooling cylinder and connecting it to a control cylinder having a control piston, and configuring the control piston's range of movement (stroke amount) to be arbitrarily adjusted, the internal volume can be varied during the operation of the Stirling engine, and the output can be arbitrarily and precisely adjusted by varying the internal volume. The above problem is solved by providing the output control device, engine system and output control method of the present invention.

[0008] According to the present invention, an output control device for controlling the output of a Stirling engine, An internal volume variable member that changes the internal volume of a Stirling engine by reciprocating or expanding / contracting in a certain direction as gas flows in and out of the piston that reciprocates the Stirling engine, Adjustment means for adjusting the reciprocating or expanding / contracting range of the internal volume variable member An output control device is provided, which includes the following. [Effects of the Invention]

[0009] According to the present invention, it is possible to arbitrarily and precisely adjust the output of a Stirling engine. [Brief explanation of the drawing]

[0010] [Figure 1] A diagram illustrating an example configuration and operation of a gamma-type Stirling engine. [Figure 2]A diagram for explaining the configuration example and operation of an actual Stirling engine. [Figure 3] A diagram showing a configuration example of an engine system equipped with an output control device. [Figure 4] A diagram showing the first operating state of a Stirling engine and an output control device. [Figure 5] A diagram showing the second operating state of a Stirling engine and an output control device. [Figure 6] A diagram showing the third operating state of a Stirling engine and an output control device. [Figure 7] A diagram showing the fourth operating state of a Stirling engine and an output control device. [Figure 8] A diagram showing the fifth operating state of a Stirling engine and an output control device. [Figure 9] A diagram showing the sixth operating state of a Stirling engine and an output control device. [Figure 10] A diagram showing the seventh operating state of a Stirling engine and an output control device. [Figure 11] A diagram showing the eighth operating state of a Stirling engine and an output control device. [Figure 12] A diagram showing the ninth operating state of a Stirling engine and an output control device. [Figure 13] A diagram showing the tenth operating state of a Stirling engine and an output control device. [Figure 14] A diagram showing the eleventh operating state of a Stirling engine and an output control device. [Figure 15] A diagram showing the twelfth operating state of a Stirling engine and an output control device. [Figure 16] A diagram showing the thirteenth operating state of a Stirling engine and an output control device. [Figure 17] A diagram showing the fourteenth operating state of a Stirling engine and an output control device. [Figure 18] P-V diagrams and T-S diagrams when the control piston is fixed at the same position and when the control piston is allowed to move freely within the control cylinder. [Figure 19] Figure showing test results. [Figure 20] Figure showing another configuration example of an engine system including an output control device. [Figure 21] Flowchart showing the process of controlling the output of a Stirling engine by an output control device. [Figure 22] Figure showing yet another configuration example of an engine system including an output control device. [Figure 23] Figure showing a configuration example of an output control device using a bag-shaped object having a bellows structure. **Embodiments for Carrying Out the Invention**

[0011] Hereinafter, embodiments for carrying out the present invention will be described in detail. However, the present invention is not limited to the embodiments shown below.

[0012] There are three types of Stirling engines called α-type, β-type, and γ-type depending on the difference in the arrangement of components. In any of these types, a component having a certain volume within the engine (a displacer or piston that vibrates within a predetermined range in accordance with the rotation of the power shaft) is reciprocated, and thereby the working fluid (a gas such as air) is caused to flow back and forth between the heating section and the cooling section to perform heating and cooling, raise and lower the temperature, and the power piston connected to the power shaft crank is pushed or pulled by the accompanying pressure change to obtain rotational power.

[0013] In the α-type, each of the two pistons is housed in each of the two cylinders, and each cylinder is heated and cooled by a heating source and a cooling source, respectively. The working fluid is heated and cooled by flowing back and forth between these two cylinders. The β-type and γ-type are composed of a piston as a cylindrical member for extracting output and a displacer piston (hereinafter simply referred to as a displacer), which is a cylindrical member for moving the gas in the cylinder as a cylindrical member to the heating side and the cooling side.

[0014] The output control device of the present invention is a device that controls the output of a Stirling engine by engaging with the fundamental principles of the Stirling engine, and its configuration is applicable to any of the α, β, and γ types.

[0015] This section will explain the fundamental principle of conventional Stirling engines, focusing on the relatively simple γ-type. Figure 1 illustrates an example of the configuration and operation of a γ-type Stirling engine. As shown in Figure 1(a), a Stirling engine has a flywheel 2 attached to a power shaft 1, and a crank 3 attached to the flywheel 2. The crank 3 performs circular motion in accordance with the rotation of the power shaft 1. As shown in Figure 1(b), a power piston 5 is attached to the crank 3 via a connecting rod 4, and the power piston 5 reciprocates within the cylinder 6 in accordance with the rotation of the crank 3 (reciprocating slider-crank mechanism).

[0016] Cylinder 6 is spatially connected to cylinder 8 via a connecting pipe 7, and the sum of the internal volumes of cylinder 6 and cylinder 8 constitutes the total internal volume of the engine. Cylinder 8 can be heated on the heating side (left side in Figure 1(a)) using an alcohol lamp or similar heat source, while the cooling side (right side in Figure 1(a)) is cooled by the atmosphere. A displacer 9 is located inside cylinder 8 and is capable of moving left and right within the cylinder 8. When the displacer 9 moves to either the left or right, it pushes away the working fluid inside, so the working fluid is always moved in the opposite direction to the movement of the displacer 9.

[0017] Figure 1(c) shows the ideal cycle (Stirling cycle) of a Stirling engine in a pressure (P)-volume (V) diagram to illustrate the operation of a γ-type Stirling engine. In the PV diagram, state 1 → state 2 represents the isothermal compression process, in which the power piston 5 compresses the working fluid from the rightmost position with the largest internal volume toward the left, causing the pressure to rise. At this time, the displacer 9 is located on the leftmost side of the cylinder 8, pushing the working fluid away from the heating side and toward the cooling side, resulting in a low working fluid temperature.

[0018] In the PV diagram, the transition from state 2 to state 3 represents the isocclusive heating process. During this process, the power piston 5 reaches the left end of the cylinder 6, and the internal volume is at its smallest. Meanwhile, the displacer 9 moves from left to right within the cylinder 8, moving the working fluid from the cooling side to the heating side through the gap between the inner surface of the cylinder 8 and the outer surface of the displacer 9, thereby heating it. At this time, the temperature of the working fluid rises, and the internal pressure also increases.

[0019] In the PV diagram, the transition from state 3 to state 4 is an isothermal heating and expansion process. During this process, the power piston 5 is pushed to the right by the high-pressure working fluid, causing the crankshaft 3 to rotate and generating work on the surrounding environment.

[0020] In the PV diagram, state 4 → state 1 represents the isococcal cooling process. In the isococcal cooling process, the displacer 9 moves from the right side (cooling side) to the left side (heating side), causing the working fluid to move from the heating side to the cooling side through the gap between the inner surface of the cylinder 8 and the outer surface of the displacer 9, and thus being cooled. When the isococcal cooling process is complete, the cycle returns to state 1 in the PV diagram, and one cycle is completed.

[0021] The cycle shown in the PV diagram in Figure 1(c) represents an ideal Stirling cycle, where the power piston 5 and displacer 9 operate independently, and the isothermal compression, isococcal heating, isothermal expansion, and isococcal cooling processes are carried out completely independently. However, in an actual Stirling engine, the power piston 5 and displacer 9 are connected by linkage mechanisms such as the flywheel 10 and crankshaft 11 shown in Figures 2(a) and (b), and these four processes are carried out with a slight overlap.

[0022] Figure 2 illustrates an example of the configuration and operation of an actual Stirling engine. The difference between the actual Stirling engine shown in Figure 2 and the ideal Stirling engine shown in Figure 1 is that the displacer 9 is connected to the power piston 5 on the power shaft 1 by a reciprocating slider-crank mechanism (flywheel 10 and crank 11, etc.) so as to rotate with a 90-degree phase difference as shown in Figure 2(b), similar to the power piston 5. This allows the engine to operate the displacer 9 using the power it generates itself. As a result, the engine can function as a power source on its own.

[0023] In an actual Stirling engine, the Stirling cycle involves the displacer 9 and power piston 5 operating in overlapping manner rather than completely independently. As shown in the PV diagram in Figure 2(c), the cycle diagram has rounded corners where the processes switch.

[0024] Stirling engines are not good at providing fast power control, unlike the throttle mechanism of an internal combustion engine. This is because Stirling engines use the temperature difference (pressure difference) of a gas as their power source, but even if the amount of heat is changed, there is a large time lag before the temperature difference of the gas is generated, making it difficult to achieve rapid power control.

[0025] Therefore, we branched the connection between the heating cylinder and the cooling cylinder of the γ-type Stirling engine and connected it to a control cylinder having a control piston. By configuring it so that the range of movement (stroke amount) of the control piston could be arbitrarily adjusted, we found that the internal volume could be varied while the Stirling engine was operating.

[0026] When the engine is running, the control piston vibrates in accordance with the changes in the engine's internal pressure. Specifically, when the power piston compresses the engine and attempts to increase the internal pressure, the control piston moves to the opposite side of the control cylinder from the connecting section by the same volume as the power piston's movement in the compression direction, preventing further compression (effectively preventing any change in internal volume). Conversely, when the power piston moves in the expansion direction, the control piston moves towards the connecting section in the control cylinder, effectively canceling out the volume expansion.

[0027] The ratio of the maximum to minimum internal volume of an engine during one cycle can be expressed as the compression ratio. The compression ratio during one cycle can be made smaller by increasing the range (stroke) over which the control piston vibrates within the control cylinder, and larger by decreasing the stroke. Since the output of a Stirling engine changes according to the compression ratio, the output can be freely controlled by changing the compression ratio in this way.

[0028] Figure 3 shows an example of an engine system configuration that includes an output control device for controlling the output of a Stirling engine. Figure 3 is a γ-type Stirling engine and, like the conventional configuration shown in Figure 1, has two cylinders 6 and 8. A power piston 5 is arranged inside cylinder 6 so as to be able to reciprocate in the longitudinal direction of cylinder 6. The power piston 5 is connected to the crank 3 via a connecting rod 4 as a rod-shaped member, and the crank 3 is connected to the flywheel 2.

[0029] A displacer 9 is positioned inside the cylinder 8 so as to be able to reciprocate along the longitudinal direction of the cylinder 8. The displacer 9 is connected to the crank 11 via a rod that can bend midway, and the crank 11 is connected to the flywheel 10. The flywheels 2 and 10 are mounted on the power shaft 1.

[0030] Cranks 3 and 11 are connected at an eccentric position from the center of the flywheels 2 and 10, and as shown in the "upper crank" section of Figure 3, the angle between the straight line passing through power shaft 1 and crank 3 (shown as a dashed line in Figure 3) and the straight line passing through power shaft 1 and crank 11 (shown as a dashed line in Figure 3) is 90°. Therefore, the power piston 5 connected to crank 3 and the displacer 9 connected to crank 11 rotate with a phase difference of 90°. In other words, the power piston 5 and the displacer 9 are adjusted so that when one is moving, the other is nearly stationary.

[0031] Cylinder 6 and cylinder 8 are connected by a connecting pipe 7, which allows the working fluid (gas) in cylinder 6 to move into cylinder 8, or vice versa.

[0032] The gas sealed inside cylinders 6 and 8 and connecting pipe 7 is generally air. In industrial applications, helium may also be used.

[0033] A branch pipe 20 is provided in the connecting pipe 7, and an output control device 21 is connected to the branch pipe 20.

[0034] The output control device 21 mainly consists of a control cylinder 22, a control piston 23, and an adjuster 24. The control piston 23 is housed inside the cylindrical control cylinder 22. Since the control piston 23 is not fixed within the control cylinder 22, its movement depends on the pressure inside the control cylinder 22. An adjuster 24 is installed on the other end of the control cylinder 22, opposite to the end connected to the branch pipe 20, to control the range of motion (control stroke) of the control piston 23. The amount of the control stroke can be arbitrarily adjusted by tightening a screw on the adjuster 24.

[0035] One end of the control cylinder 22 is closed to prevent the control piston 23 from passing through, and a hole smaller than the diameter of the control piston 23 is provided for the inflow and outflow of gas from the engine. The control cylinder 22 has a nozzle portion that protrudes continuously from one end into the hole and can be inserted into the branch pipe 20. Therefore, the control cylinder 22 is installed with the nozzle portion inserted into the branch pipe 20, and gas from the engine flows into the control cylinder 22 through the nozzle portion and the hole.

[0036] The inner surface of the control cylinder 22 and the outer surface of the control piston 23 are adjacent, so ambient air does not flow into the engine, and gases inside the engine do not leak out. Because there is a gap between the adjuster 24 and the control cylinder 22, the space between the control piston 23 and the adjuster 24 is always at atmospheric pressure, regardless of the control stroke.

[0037] On the other side of the control piston 23 (the engine side), the pressure it receives changes in accordance with the change in gas pressure within the engine, which occurs in sync with the operating cycle of the Stirling engine. The pressure received on the engine side of the control piston 23 changes from a pressure lower than atmospheric pressure to a pressure higher than atmospheric pressure, causing gas to flow into or out of the control cylinder 22. As a result, the control piston 23 reciprocates within the range of stroke adjusted by the adjuster 24.

[0038] The power control device and operation of the Stirling engine in the engine system will be described in detail with reference to Figures 4 to 17. The Stirling engine is the γ type shown in Figure 2, and Figures 4 to 17 show the pressure (P)-volume (V) diagram and the positions of the displacer 9, power piston 5, and control piston 23 in each state on the PV diagram.

[0039] Figure 4 shows the positions of the displacer 9, etc., when the PV diagram is in state 1. The range from state 1 to state 2 on the diagram is an isothermal cooling and compression process, the range from state 2 to state 3 is a constant-volume heating process, the range from state 3 to state 4 is an isothermal heating and expansion process, and the range from state 4 to state 1 is a constant-volume cooling process.

[0040] The cycle shown in the diagram, which changes as follows: State 1 → State 2 → State 3 → State 4 → State 1, represents the case where the control piston 23 can move freely within the range of position e to position f of the control cylinder 22, as will be described later. When the control piston 23 is fixed in the same position (when the adjuster 24 is at position f as shown by the dashed line), the cycle changes as follows: State 1 → State 2' → State 3' → State 4 → State 1.

[0041] When the control piston 23 in Figure 4 is fixed in the same position (position f as shown by the dashed line of the adjuster 24), it is the same as when the output control device 21 is not connected. Therefore, in the isothermal cooling and compression process from state 1 to state 2 in the diagram, the power piston 5 moves from position d to position a, and the volume (volume of gas) inside the engine, which connects the two cylinders 6 and 8 with the connecting pipe 7, is always decreasing. Also, in the isothermal heating and expansion process from state 3 to state 4 in the diagram, the power piston 5 moves from position a to position d, and the volume inside the engine is always increasing.

[0042] On the other hand, even when the adjuster 24 moves to position e as shown in Figure 4, and the control piston 23 is able to move freely within the range of position e to position f in the control cylinder 22, in the isothermal cooling and compression process from state 1 to state 2 on the diagram, if the gas pressure is lower than atmospheric pressure when the power piston 5 moves from position d to position c, the control piston 23 is pushed by the atmospheric pressure on the adjuster side and does not move from position f, as shown in Figures 5 and 6, the volume inside the engine decreases, and the gas inside the engine is compressed.

[0043] When the power piston 5 reaches position c, and the pressures on both the adjuster side and the engine side of the control piston 23 balance out at atmospheric pressure, the control piston 23 moves from position f to position e by the amount of volume displaced by the power piston 5, as shown in Figure 7, with the atmospheric pressure line shown as the dashed line in the diagram as the boundary. As a result, there is virtually no change in volume. In other words, the control piston 23 moves towards the adjuster side by the amount of volume displaced by the power piston 5, so the effective internal volume remains constant during this period, as shown in the diagram in Figure 7.

[0044] When the power piston 5 reaches position b and the control piston 23 reaches position e, the control piston 23 can no longer move towards the adjuster. As shown in Figure 8, when the power piston 5 moves from position b to position a, its internal volume decreases and it is compressed, causing the pressure inside the engine to increase.

[0045] As shown in Figure 9, while the power piston 5 is moving from position b to position a, the volume can be considered to have expanded by the amount of free space in the control cylinder 22, so the pressure inside the engine is lower than when the control piston 23 is fixed at position f. That is, when the power piston 5 reaches position a, as shown in the PV diagram of Figure 9, the volume in state 2 is larger than the volume in state 2', and the pressure in state 2 is lower than the pressure in state 2'.

[0046] In other words, while the control piston 23 is moving from position f to position e, no compression occurs on the Stirling cycle. As a result, the area enclosed by states 1, 2, 3, and 4 on the PV diagram (the net work done in the cycle) is smaller than the area enclosed by states 1, 2', 3', and 4, thus keeping the engine output low.

[0047] As shown in Figure 10, as the displacer 9 moves from the heating side to the cooling side, the gas that was on the cooling side moves to the heating side through the gap between the outer surface of the displacer 9 and the inner surface of the cylinder 8. During this time, the power piston 5 remains fixed at position a, and the control piston 23 also remains fixed at position e. Since there is no change in volume, it becomes a constant-volume heating process, and only the pressure increases due to heating.

[0048] As shown in Figure 11, once the displacer 9 reaches the cooling side and the constant-volume heating process is complete, the isothermal heating expansion process begins, and the power piston 5 starts moving from position a to position d.

[0049] As shown in Figure 12, during the isothermal heating and expansion process from state 3 to state 4 on the diagram, the gas pressure is higher than atmospheric pressure from position a to position b' of the power piston 5. Therefore, the control piston 23 is pushed by the internal pressure and does not move at position e, and the volume inside the engine expands. As shown in Figure 13, when the power piston 5 reaches position b' and the pressures on both the adjuster side and the engine side of the control piston 23 balance at atmospheric pressure, the power piston 5 moves beyond the atmospheric pressure line shown by the dashed line on the diagram. As the volume has expanded, the control piston 23 is pushed by the atmospheric pressure from the adjuster side and moves from position e to position f, as shown in Figure 14. Then, as shown on the PV diagram in Figure 14, the internal volume remains virtually constant and there is no pressure change. When the control piston 23 reaches position f, i.e., the engine side, the power piston 5 passes through position c'. At this position, the control piston 23 can no longer move towards the engine. As shown in Figure 15, when the power piston 5 moves from position c' to position d, its internal volume expands again, and the pressure inside the engine decreases.

[0050] Furthermore, during the isothermal expansion process, it can be assumed that the control piston 23 moves from position f to position e, and the volume expands by the amount of free space within the control cylinder 22. Therefore, the pressure inside the engine when the isothermal expansion process begins is lower than when the control piston 23 is fixed in the same position. In other words, the volume in state 3 in the diagram is larger than the volume in state 3', and the pressure in state 3 is lower than the pressure in state 3'.

[0051] As shown in Figure 16, when the power piston 5 reaches position d, the isothermal heating and expansion process ends. Subsequently, as shown in Figure 17, the displacer 9 moves to the heating side, causing the gas that was on the heating side to move to the cooling side through the gap between the outer surface of the displacer 9 and the inner surface of the cylinder 8, thereby cooling it. At this time, the power piston 5 remains at position d, and the control piston 23 also remains at the end, so there is no change in volume, resulting in a constant-volume cooling process where only the pressure decreases due to cooling. This returns to state 1, the next cycle begins, and the process shown in Figures 4 to 17 is repeated.

[0052] Figure 18 shows examples of PV and TS diagrams for cases where the control piston 23 is fixed in the same position and where it is freely movable within the control cylinder 22 in the range of position f to position e. When the control piston 23 is fixed in the same position (position f), the states change in the order of state 1 → state 2' → state 3' → state 4 → state 1. On the other hand, when the state is freely movable within the control cylinder 22 in the range of position f to position e, the states change in the order of state 1 → state 2 → state 3 → state 4 → state 1.

[0053] In an actual Stirling engine, the power piston 5 and the displacer 9 are linked together by a linkage mechanism, so the four processes described above overlap slightly and interfere with each other to form a single cycle. For this reason, in an actual engine cycle, both the PV diagram and the TS diagram have rounded corners, as shown in Figure 18.

[0054] The area on the PV diagram in Figure 18 corresponds to the amount of work done. From this, the area (net work) is larger and the amount of work done is greater in the cycle where the control piston 23 is fixed at position f, changing in the order of state 1 → state 2' → state 3' → state 4 → state 1, compared to the cycle where the control piston 23 moves in the range of position f to position e, changing in the order of state 1 → state 2 → state 3 → state 4 → state 1. Therefore, the engine output is higher in the latter case than in the former case.

[0055] The apparatus according to the present invention allows for continuous and arbitrary adjustment of the range of motion (from position f to position e) of the control piston 23 by an adjuster 24 that adjusts the range of motion of the control piston 23, as shown in Figures 4 to 17. This makes it possible to arbitrarily adjust the volume of states 2 and 3 of the former cycle on the PV diagram to the maximum, state 2', and state 3', thereby enabling control of the output of the Stirling engine.

[0056] On the other hand, the principle of output control in a Stirling engine can also be explained from the perspective of the amount of heat generated. In the temperature (T)-entropy (S) diagram shown in Figure 18, in a cycle in which the position of the control piston 23 moves in the range of position f to position e, and the state changes in the order of state 1 → state 2 → state 3 → state 4 → state 1, the area between state 2-state 3-state 4 and the S axis (the definite integral value from state 2 to state 4) is the amount of heat generated Q. in Therefore, the area between state 4, state 1, state 2, and the S-axis (the definite integral from state 4 to state 2) is the amount of heat cooled (amount of heat released) Q. out This is the result. At this point, Q in -Q outIn other words, the area enclosed by state 1-state 2-state 3-state 4-state 1 represents the amount of heat converted into net work.

[0057] Here, the cycle in which the state changes in the order of state 1 → state 2' → state 3' → state 4 → state 1 when the control piston 23 is fixed at position f has a larger area than the cycle in which the state changes in the order of state 1 → state 2 → state 3 → state 4 → state 1. This means that a larger amount of heat is used for net work, resulting in higher engine output. This means that the volume difference between state 2'-state 2 and state 3'-state 3 during isothermal heating directly corresponds to the difference in the amount of heating. The device according to the present invention can be reinterpreted as varying the engine output by controlling this amount of heating. This can be considered similar to how engine output is controlled in gasoline engines and diesel engines by adjusting the fuel flow rate to change the amount of combustion, i.e., the amount of heating. Conventional Stirling engines could not control the amount of heating in this way because they were external combustion engines, but the present invention makes this possible.

[0058] To demonstrate the effectiveness of the device according to the present invention, a test apparatus shown in Figure 3, following the principle described above, was fabricated and tested. To measure the internal pressure, a pressure sensor was attached to the branch pipe 20, and the data was acquired with an oscilloscope. In addition, to measure the internal volume of the engine from the amount of movement (phase difference) of each piston during engine operation, the rotation angle of the flywheel was acquired using a photoreflector sensor. Furthermore, the engine speed was measured by applying a non-contact type tachometer to the flywheel.

[0059] Figure 19 shows the test results. In the test, the position of the adjuster 24 was adjusted to change the range of motion of the control piston 23 in four stages from position f to position e, and the relationship between volume and internal pressure was measured. As a result, the engine speed reached a maximum of 650 rpm when the range of motion of the adjuster 24 was fixed at position f, and as the range of motion was extended towards position e, the rotational speed decreased to 500 rpm, 300 rpm, and 100 rpm. The area of ​​the cycle at this time (corresponding to the area enclosed by state 1-state 2-state 3-state 4-state 1 in the theoretical cycle) decreased with decreasing rotational speed, and the engine output decreased, confirming that the output could be controlled by adjusting the adjuster 24.

[0060] As described above, according to the present invention, output control can be realized with a simple configuration by connecting the output control device 21 to the connecting pipe 7 of the Stirling engine via a branch pipe 20, and allowing the control piston 23 to reciprocate freely. The output control by the output control device 21 can reduce the engine speed to approximately 150 rpm and can operate stably at this reduced speed.

[0061] Stirling engines generally tend to be unstable when operating at low rotational speeds because the movement of internal gases is not smooth. However, by using an output control device to control the engine, the movement of internal gases can be made smoother, and the operation can be stabilized.

[0062] The output control device has a simple configuration, and control at low rotational speeds is also easy, making it easier to explain the principle during operation and thus suitable for use in educational materials.

[0063] The present invention provides an output control device and an engine system including the output control device and a Stirling engine, and can also provide a method for controlling the output of a Stirling engine using the output control device (output control method). Furthermore, the output control device and engine system may be equipped with magnets 30-33 at both ends of the control cylinder 22 and the control piston 23, as shown in Figure 20. These magnets 30-33 are mounted with their north and south poles repelling each other, so that the impact when the control piston 23 collides with the adjuster 24 and the inner wall of the engine side of the control piston 23 and the control cylinder 22 is reduced by the repulsion of the magnets. As a result, smoother and more stable output control can be achieved compared to the configuration shown in Figure 3.

[0064] Figure 21 is a flowchart showing an example of output control of a Stirling engine by the output control device 21. As explained above, output control includes reciprocating the control piston 23 in step 100 and adjusting the range of movement (stroke amount) of the control piston 23 with the adjuster 24 in step 101. The contents of each step have already been explained in detail above, so the explanation will be omitted here. Note that output control may also be performed by reciprocating the control piston 23 after adjusting the stroke amount with the adjuster 24.

[0065] In the examples shown in Figures 3 and 20, a branch pipe 20 is provided in the connecting pipe 7, and the output control device 21 is connected to the branch pipe 20, but this is not the only option. Therefore, as shown in Figure 22, the output control device 21 may be directly connected to the cylinder 6.

[0066] As described above, on the engine side of the control piston 23 of the output control device 21, the gas pressure inside the engine changes in accordance with the operating cycle of the Stirling engine, and in response to this pressure change, the pressure changes from lower than atmospheric pressure to higher than atmospheric pressure. Even if the output control device 21 is directly connected to the cylinder 6, gas flows into or out of the control cylinder 22, just as if it were connected via the branch pipe 20, and the control piston 23 reciprocates within the range of the stroke amount adjusted by the adjuster 24. For this reason, the same functions as in the examples shown in Figures 3 and 20 can be realized.

[0067] As long as the control piston 23 can reciprocate within the range of the stroke adjusted by the adjuster 24 and its internal volume can be varied, it is not necessarily required to have a structure that distinguishes between the cylinder 6 and the control cylinder 22 as shown in Figure 22. The cylinder 6 can be extended directly toward the adjuster 24, and the control piston 23 can operate within a single cylinder 6. In other words, the cylinder 6 housing the power piston 5 may have an internal space through which gas flows in from one side and out to the other side due to the reciprocating motion of the power piston 5, and the control piston 23 can reciprocate within this internal space. That is, the space between the power piston 5 and the control piston 23, which are simultaneously housed in the cylinder 6, can be used as a substitute for the space of the control cylinder 22.

[0068] Furthermore, in the examples shown in Figures 3, 20, and 22, a control cylinder 22 and a control piston 23 are used, and the control piston 23 is reciprocated within the range of the stroke amount adjusted by the adjuster 24 to vary the internal volume. However, the configuration is not limited to using a control cylinder 22 and a control piston 23.

[0069] Figure 23 shows an output control device 21 that does not use a control cylinder 22 and a control piston 23, and uses a bag-like object (bellows) with a structure that expands and contracts due to the inflow and outflow of gas, for example, a bellows structure which is a repeating mountain fold and valley fold structure. The bellows 40 has an internal closed space into which gas flows in from the cylinder 6 and out of the closed space into which gas flows out. The bellows 40 has a repeating mountain fold and valley fold structure, and when gas flows into the internal closed space, it expands in one direction (away from the cylinder 6), and when gas flows out of the space into the cylinder 6, it contracts in the opposite direction (towards the cylinder 6). In other words, the bellows 40 repeatedly expands and contracts in a certain direction.

[0070] When using a control piston 23, a control cylinder 22 is provided as an outer frame so that the control piston 23 reciprocates in a certain direction. However, since the bellows 40 expands and contracts in a certain direction, there is no need to provide an outer frame like the control cylinder 22, and the bellows 40 alone can expand and contract due to the inflow and outflow of gas.

[0071] Therefore, by determining the range of stroke amount with the adjuster 24, the bellows 40 can only extend up to the adjuster 24 even when fully extended. This allows the bellows 40 to expand or contract within that range, thereby varying the internal volume.

[0072] We have described an example using a control cylinder 22, a control piston 23, and a bellows 40 as a structure for varying the internal volume. However, as long as the internal volume can be varied, it is not limited to the bellows 40; it may be anything that can repeatedly expand and contract like a balloon. Therefore, the output control device 21 can be configured to include an internal volume variable member such as a control piston 23 or bellows 40 that reciprocates or expands and contracts in a certain direction due to the inflow and outflow of gas, thereby varying the internal volume of the Stirling engine, and an adjuster 24 as an adjustment means.

[0073] Although the output control device, output control method, and Stirling engine of the present invention have been described in detail with respect to the embodiments described above, the present invention is not limited to the embodiments described above. It is applicable to power generation devices that use pressure changes of a working fluid, such as gasoline engines and diesel engines, and can be modified to other embodiments, additions, changes, or deletions within the scope that a person skilled in the art can conceive. In any embodiment, as long as the operation and effects of the present invention are achieved, it is included within the scope of the present invention.

[0074] Accordingly, according to the present invention, (1) an output control device for controlling the output of a Stirling engine, comprising: an internal volume variable member that reciprocates or expands and contracts in a certain direction as gas flows in and out to reciprocate a piston of the Stirling engine, thereby changing the internal volume of the Stirling engine; and an adjustment means for adjusting the range of reciprocation or expansion and contraction of the internal volume variable member.

[0075] According to the present invention, (2) an output control device as described in (1) above can be provided, which includes a cylindrical body into which the gas can flow from one end, or an internal space within a cylinder housing the piston, into which the gas flows in from one side and out to the same side due to the reciprocating motion of the piston, wherein the internal volume variable member is a cylindrical member that closes the other end of the cylindrical body or the other side of the internal space and reciprocates within the cylindrical body or the internal space due to the inflow and outflow of the gas.

[0076] According to the present invention, (3) the variable internal volume member is a bag-shaped object having a bellows structure, and an output control device as described in (1) above can be provided.

[0077] According to the present invention, (4) the internal volume variable member is configured such that one end or the inside of the internal volume variable member receives the pressure of the gas, and the other end or the outside of the internal volume variable member receives atmospheric pressure, and when the piston moves to one side due to the compression of the gas during the isothermal compression process of the Stirling cycle, the internal volume variable member is moved or extended to one side when the pressure of the gas becomes equal to the atmospheric pressure, and when the piston moves in the opposite direction to that during the isothermal compression process due to the expansion of the gas during the isothermal expansion process of the Stirling cycle, the internal volume variable member is moved or contracted in the opposite direction to that during the isothermal compression process when the pressure of the gas becomes equal to the atmospheric pressure, thus providing an output control device according to any one of (1) to (3) above.

[0078] According to the present invention, (5) the Stirling engine comprises two cylinders connected by a connecting pipe, and the output control device is connected to one of the two cylinders on which the piston reciprocates, or to a branch pipe branched from the connecting pipe, as described in any of (1) to (4) above.

[0079] According to the present invention, (6) an output control device as described in (1) above can be provided, comprising a cylindrical body into which the gas can flow from one end, the internal volume variable member being a cylindrical member that closes the other end of the cylindrical body and reciprocates within the cylindrical body due to the inflow and outflow of the gas, the Stirling engine comprising two cylinders connected by a connecting pipe, the output control device being connected to a branch pipe branched from the connecting pipe, one end of the cylindrical body being closed so as not to allow the cylindrical member to pass through and having a hole smaller than the diameter of the cylindrical member for the gas to flow in and out, and the cylindrical body having a nozzle portion that protrudes continuously from one end of the cylindrical body into the hole and can be inserted into the branch pipe.

[0080] According to the present invention, (7) first to fourth magnets are attached to the inside of one end of the cylindrical body, both ends of the cylindrical member, and the surface of the adjustment means facing the cylindrical member, the magnetic poles of the opposing surfaces of the first and second magnets attached to the inside of one end of the cylindrical body and one end of the cylindrical member facing the inside of one end of the cylindrical body are the same magnetic pole, and the magnetic poles of the opposing surfaces of the third and fourth magnets attached to the other end of the cylindrical member facing the adjustment means and the surface of the adjustment means facing the cylindrical member are the same magnetic pole, thus providing the output control device described in (6) above.

[0081] Furthermore, according to the present invention, an engine system can also be provided which includes (8) a Stirling engine that uses the temperature difference of a gas to reciprocate a piston, and an output control device according to any one of (1) to (7) above that controls the output of the Stirling engine.

[0082] Furthermore, according to the present invention, (9) a method for controlling the output of a Stirling engine can also be provided, the method including the steps of: varying the internal volume of the Stirling engine by causing a gas that reciprocates a piston of the Stirling engine to flow in and out, thereby causing an internal volume variable member to reciprocate or expand and contract in a certain direction; and adjusting the range of reciprocation or expansion and contraction of the internal volume variable member using an adjustment means. In this case, the internal volume variable member can be configured as described in (2) and (3) above, and can be reciprocated or expanded and contracted at the timing described in (4) above. Also, the Stirling engine can be configured as described in (5) and (6) above, and the output control device can be configured as described in (6) and (7) above. [Explanation of symbols]

[0083] 1...Power shaft 2…Flywheel 3... Crank 4…Connecting rod 5... Power Piston 6…Cylinder 7…Connecting pipes 8...Cylinder 9…Displacer 10…Flywheel 11... Crank 20... Branch pipe 21…Output control device 22... Control cylinder 23... Control piston 24...Adjuster 30-33... Magnets 40... Bellows

Claims

1. An output control device for controlling the output of a Stirling engine, An internal volume variable member that changes the internal volume of the Stirling engine by reciprocating or expanding / contracting in a certain direction as gas flows in and out of the Stirling engine, Adjustment means for adjusting the reciprocating or expanding / contracting range of the internal volume variable member An output control device, including

2. A cylindrical body into which the gas can flow from one end, or a cylinder housing the piston, including an internal space into which the gas flows in from one side and out to the other side due to the reciprocating motion of the piston, The output control device according to claim 1, wherein the variable internal volume member is a cylindrical member that closes the other end of the cylindrical body or the other side of the internal space and reciprocates within the cylindrical body or the internal space due to the inflow and outflow of gas.

3. The output control device according to claim 1, wherein the internal volume variable member is a bag-shaped object having a bellows structure.

4. The output control device according to claim 1, wherein the internal volume variable member is configured such that one end or the inside of the internal volume variable member receives the pressure of the gas, and the other end or the outside of the internal volume variable member receives atmospheric pressure, and when the piston moves to one side due to the compression of the gas during the isothermal compression process of the Stirling cycle, the internal volume variable member is moved or extended to one side when the pressure of the gas becomes equal to the atmospheric pressure, and when the piston moves in the opposite direction to that during the isothermal compression process due to the expansion of the gas during the isothermal expansion process of the Stirling cycle, the internal volume variable member is moved or contracted in the opposite direction to that during the isothermal compression process when the pressure of the gas becomes equal to the atmospheric pressure.

5. The Stirling engine comprises two cylinders connected by a connecting tube, The output control device according to any one of claims 1 to 4, wherein the output control device is connected to one of the two cylinders in which the piston reciprocates, or to a branch pipe branched from the connecting pipe.

6. The aforementioned gas includes a cylindrical body into which the gas can flow in from one end, The variable internal volume member is a cylindrical member that closes the other end of the cylindrical body and reciprocates within the cylindrical body due to the inflow and outflow of the gas. The Stirling engine comprises two cylinders connected by a connecting tube, The output control device is connected to a branch pipe that is branched off from the connecting pipe. One end of the cylindrical body is closed so that the cylindrical member cannot pass through, and has a hole smaller than the diameter of the cylindrical member for the gas to flow in and out. The output control device according to claim 1, wherein the cylindrical body has a nozzle portion that protrudes continuously from one end of the cylindrical body into the hole and can be inserted into the branch pipe.

7. First to fourth magnets are attached to the inside of one end of the cylindrical body, to both ends of the cylindrical member, and to the surface of the adjusting means facing the cylindrical member. The output control device according to claim 6, wherein the magnetic poles of the opposing surfaces of the first and second magnets, which are attached to the inside of one end of the cylindrical body and to one end of the cylindrical member that faces the inside of one end of the cylindrical body, are the same magnetic pole, and the magnetic poles of the opposing surfaces of the third and fourth magnets, which are attached to the other end of the cylindrical member that faces the adjusting means and to the surface of the adjusting means that faces the cylindrical member, are the same magnetic pole.

8. A Stirling engine uses the temperature difference of a gas to move a piston back and forth, An output control device for controlling the output of the Stirling engine and Includes, The output control device, An internal volume variable member that changes the internal volume of the Stirling engine by reciprocating or expanding / contracting in a certain direction as gas flows in and out of the Stirling engine, Adjustment means for adjusting the reciprocating or expanding / contracting range of the internal volume variable member The engine system, including the engine system.

9. A method for controlling the output of a Stirling engine, The steps include: varying the internal volume of the Stirling engine by causing a gas that reciprocates the piston of the Stirling engine to flow in and out, thereby causing an internal volume variable member to reciprocate or expand / contract in a certain direction; The steps include adjusting the range of reciprocating motion or expansion / contraction of the internal volume variable member using an adjustment means, and An output control method, including the following.

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