JP2542637B2 - Stirling engine - Google Patents

Description

The present invention relates to a Stirling engine, and more particularly to a Stirling engine, in which a check valve and a solenoid valve are used to increase or decrease the pressure in an operating space to control output. Performing Stirling engine.

(Prior Art) A Stirling engine is drawing attention as an energy-saving ring. Taking a two-piston type Stirling engine as an example, it is configured as follows.

A heater and a cooler are connected to the expansion cylinder and the compression cylinder, respectively, and a regenerator is connected between the heater and the cooler. The expansion piston in the expansion cylinder and the compression piston in the compression cylinder are each connected to the crankshaft via a connecting rod. A working fluid such as helium gas is enclosed in a working space formed in a portion from the expansion cylinder to the compression cylinder.

When the working fluid is heated by the heater and expands, the expansion piston descends and the crankshaft rotates, and when the expansion piston rises, the working fluid is extruded and transferred to the compression cylinder side through the regenerator and the cooler. . Next, the working fluid in the compression cylinder is compressed by the rise of the compression piston, then heated by heat exchange through the cooler and the regenerator, and then reheated by the heater and returned to the expansion cylinder.

In such a Stirling engine, the shaft output of the engine can be changed by changing the filling pressure of the working fluid in the working space. As one method of controlling the output of the Stirling engine, an attempt has been made to control the pressure in the working space by using a check valve, a solenoid valve and a storage tank. An example of using this method is:
Two check valves are installed in anti-parallel connection between the working space (compression cylinder) and the storage tank, and solenoid valves are installed in series in each of these check valves to check the pressure in the working space and the pressure in the storage tank. By using the pressure difference between the operating space and the storage tank, or from the storage tank to the operating space, a working fluid flow in only one direction is generated, and a pressure control mechanism that increases or decreases the pressure in the operating space is provided. It is known. However, in this pressure control mechanism, for example, when the internal volume of the storage tank is about 20 in a 2-piston type 2kW type Stirling engine, the lower limit is about 4MPa if the pressure variable range in the working space is the upper limit of 6MPa.
However, there is a problem that the variable width is small despite the large internal volume of the storage tank.

On the other hand, in the Stirling engine, between the buffer tank and the working space that are normally provided to absorb the pressure fluctuations in the piston back space and to balance the pressures in the piston back space and the crank chamber space, the same idea as described above is used. A pressure control mechanism (Japanese Patent Application No. 60-159348) provided with a check valve and a solenoid valve connected in antiparallel is also proposed,
There is also a problem that the pressure variable width of the working space is narrow.
Further, in the pressure control by the flow of the working fluid between the storage tank and the working space, stepless control is possible,
The flow of the working fluid between the buffer tank and the working space has a drawback that the pressure increases and decreases in steps. This is because if the pumping action of the check valve is stopped, the working space and the buffer tank will balance the pressure through the piston ring and the balancing capillary tube.

(Problems to be Solved by the Invention) As described above, in the conventional pressure control mechanism of the Stirling engine, the pressure variable range of the working space cannot be widened unless the capacity of the storage tank or the buffer tank is increased, and the buffer is not provided. In the system in which the pressure is controlled by using the flow of the working fluid between the tank and the working space, there is a problem that the pressure change in the working space is stepwise and smooth pressure control cannot be performed.

The present invention solves such a problem, and can control the pressure in the working space over a wider range without increasing the capacity of the storage tank or the buffer tank, and the control can be smoothly performed. The purpose is to provide an engine.

[Structure of the Invention] (Means for Solving the Problems) A Stirling engine according to the present invention is a working fluid that flows in a working space in an engine as a pressure control mechanism that controls a filling pressure of the working fluid in the working space. The storage tank for storing and the individual pipes that connect the buffer tank and the working space that are provided in communication with the piston back space in the engine, or the common pipes that join these individual pipes on the working space side, are connected in anti-parallel connection. In addition to providing four or two check valves, individual pipes are also provided with solenoid valves in series with these check valves, respectively. By controlling the opening and closing of these solenoid valves, pressure control in the working space is performed. It was done.

(Operation) According to the configuration of the pressure control mechanism of the present invention, when the pressure in the working space is maximized, the flow of the working fluid from the storage tank to the working space and the operation from the working space to the buffer tank are performed. After opening the solenoid valve provided in series with the check valve that allows the flow of the fluid, the solenoid valve that allows the flow of the working fluid from the buffer tank to the working space may be opened. That is, once the working fluid in the working space is driven to the buffer tank to reduce the pressure in the working space and increase the pressure difference with the storage tank, the working fluid in the storage tank is sent to the working space as much as possible, The working fluid in the buffer tank is drawn into the working space.

On the other hand, in order to reduce the pressure in the working space to a minimum,
Conversely, after opening the solenoid valve provided in series with the check valve that allows the flow of the working fluid from the buffer tank to the working space and the flow of the working fluid from the working space to the storage tank, the buffer is removed from the working space. The solenoid valve that allows the flow of the working fluid to the tank may be opened.

Further, the pressure control only by the flow of the working fluid between the buffer tank and the working space is stepwise, but in the present invention, the stepless pressure control by the flow of the working fluid between the storage tank and the working space is performed. By using the pressure control between the steps, continuous pressure control becomes possible.

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

FIG. 1 is a sectional view showing a schematic configuration of a two-piston Stirling engine according to an embodiment of the present invention.

As shown in FIG. 1, this Stirling engine includes an expansion cylinder 1 for expanding a working fluid, an expansion piston 2 slidably mounted in the expansion cylinder 1, and
A combustion heater 5 and a regenerator 6 and a cooler 7 are arranged between a compression cylinder 3 for compressing a working fluid and a compression piston 4 slidably mounted in the compression cylinder 3, and further expanded. The crank chamber 11 is connected to the piston 2 and the compression piston 4 via connecting rods 8 and 9, respectively.
It has a basic structure in which a crankshaft 10 rotatably provided inside is connected. The crankshaft 10 is connected to an output shaft (not shown). Further, a working space composed of a space surrounded by the expansion cylinder 1 and the expansion piston 2, an inside of the regenerator 6, the cooler 7 and a heat exchanger 16 described later, and a space surrounded by the compression cylinder 3 and the compression piston 4. A working fluid, for example, He gas, is sealed in.

On the other hand, the combustion heater 5 is configured as follows.
A substantially cylindrical combustion chamber 14 is formed above the cylinder head 12 of the expansion cylinder 1 by the heat insulating block 13.
A plurality of bayonet tube type heat exchangers 16 each having a heat transfer fin 15 are arranged around the inside of the inside 14. Each of the heat exchangers 16 has one end of a working fluid passage formed therein communicating with the inside of the expansion cylinder 1 and the other end communicating with the regenerator 6 via a manifold 17 formed within the cylinder head 12. There is. A gas nozzle 18 and a swirler 19 are provided above the combustion chamber 14.
Is arranged. In addition, around the heat insulating block 13,
An air preheater for preheating the combustion air supplied into the combustion chamber 14.
20 are arranged. The air preheater 20 draws in combustion air from the intake cylinder 21, and preheats it by the heat of the combustion exhaust gas discharged from the combustion chamber 14 through the exhaust cylinder 22. Then, this preheated combustion air is fed into the combustion chamber 14 by the swirler 19.
It is swirled in.

A storage tank 24 for storing a working fluid is connected to the constant temperature measurement operation space 23 in the compression cylinder 3, and a piston back space 25 in the compression cylinder 3 and a piston back space in the expansion cylinder 1 are connected to a piston back space. A buffer tank 26 for absorbing pressure fluctuation is connected.
The buffer tank 26 is also connected to the working space 23 via a capillary tube 27 in order to balance the pressure between the piston back space and the crank chamber space.

FIG. 2 is an enlarged view of a pressure control mechanism for controlling the filling pressure of the working fluid in the working space 23 in FIG. As shown in FIG. 2, the pipe connecting the working space 23 and the storage tank 24 is provided with two check valves 31, 32 connected in anti-parallel, and these check valves 31, 32 are also provided. And solenoid valves 33 and 34 are respectively provided in series. The working space 23 is also connected to the buffer tank 26 by a pipe, and this pipe is also connected in anti-parallel 2
The individual check valves 35 and 36 are provided, and the solenoid valves 37 and 38 are provided in series with the check valves 35 and 36, respectively. The solenoid valves 33, 34, 37, 38 are controlled to open and close by a control device (not shown).

Next, the operation of the Stirling engine of this embodiment will be described. Injecting gas fuel from the gas nozzle 18 into the combustion chamber 14 and supplying combustion air from the swirler 19 through the air preheater 20 to form combustion flame, the output shaft connected to the crankshaft 10 is When temporarily rotated by an external power source, the expansion piston 2 and the compression piston 4 reciprocate with a certain phase difference via the crankshaft 10 and the connecting rods 8 and 9. When the expansion piston 2 moves to the compression stroke by this reciprocal movement, the working fluid (He) in the expansion cylinder 1 flows into the compression cylinder 3 via the heat exchanger 16, the manifold 17, the regenerator 6 and the cooler 7. When the expansion piston 2 reaches the top dead center, most of the working fluid flows into the compression cylinder 3. At this time, the heat of the working fluid is taken by the regenerator 6 while passing through the regenerator 6, and then cooled by the cooler 7. When the compression piston 4 starts moving from the bottom dead center to the top dead center with the rotation of the output shaft, the low-temperature working fluid in the compression cylinder 3 is compressed, and the expansion cylinder is routed in the reverse path. It flows into 1. At this time, the working fluid absorbs heat while passing through the regenerator 6 and is heated to a high temperature, and is further heated when passing through the heat exchanger 16 next time. The high-temperature working fluid flowing into the expansion cylinder 1 expands and pushes down the expansion piston 2. After that, the above-described operation is repeated, the output shaft continues to rotate even when the external power source is cut off, and the operation as the Stirling engine is performed.

The high temperature combustion gas generated in the combustion chamber 14 heats the working fluid through the heat exchanger 16 while convection in the combustion chamber 14.
The hot gas after heating becomes combustion exhaust gas, and the air preheating chamber 20
Is used to preheat combustion air.

The operation of increasing the pressure of the working space 23 in the operating state of the Stirling engine will be described with reference to FIG. FIG. 3 shows the working fluid pressure P _W (the working fluid filling pressure in the working space 23) and the pressure in the storage tank 24.
3 shows the relationship between P _S and the pressure Pb in the buffer tank 26. The operating pressure P _W pulsates with the operation of the engine as shown in the figure.

First, from the initial state shown in FIG.
To increase the pressure of the check valve, open the solenoid valve 33 and
Storage tank 24 defined by 31 to working space 23
Flow working fluid only in the direction. When the working space 23 reaches the target pressure due to the flow of the working fluid, the solenoid valve 33 is returned to the closed state to maintain the pressure. Further, if the pressure is saturated with the solenoid valve 33 left open and the target value is not reached, the solenoid valve 37 is opened and the operating space from the buffer tank 26 defined by the check valve 35 is increased. Flow working fluid only in the direction to 23. At this time, the pressure in the working space 23, that is, the shaft output of the engine, increases stepwise, and when the solenoid valve 37 is closed, it returns to the original balanced pressure through the capillary tube 25. In such a case, the solenoid valve 34 is opened and closed to adjust the pressure to the target pressure.

On the other hand, when the pressure in the working space 23 is saturated with the solenoid valves 33, 37 still open and the target value has not been reached, the following special control mode is performed. That is, first, the solenoid valves 33 and 38 are both opened to move the working fluid in the storage tank 24 to the working space 23 and the buffer tank 26 with the maximum source. As a result, the pressure in the buffer tank 26 increases as shown in FIG. 3 (b), and the operating pressure Pb also increases accordingly. Next, the solenoid valve 38 is closed and the solenoid valve 37 is opened conversely to move the working fluid in the buffer tank 26 to the working space 23. By this operation, the filling pressure of the working space 23 is maximized. This is shown in FIG. 3 (c). Here, if the target value is a value lower than this maximum possible filling pressure, it may be adjusted by opening and closing the solenoid valve 34 to reach the target value.

When the pressure in the operating space 23 is reduced contrary to the above, the storage tank is opened from the operating space 23 defined by the check valve 32 by opening the solenoid valve 34 first, completely symmetrically with the pressure increasing operation. The working fluid is caused to flow only in the direction toward 24, and when the working space 23 reaches the target pressure, the solenoid valve 34 is closed back to maintain the pressure. If the target value is not reached even when the solenoid valve 34 remains open, open the solenoid valve 38 to open the check valve.
The working fluid also flows in the direction from the working space 23 defined by 36 to the buffer tank 26.

Then, if the target value is still not reached even when the solenoid valves 34, 38 remain open, the special control mode is executed. That is, by opening both the solenoid valves 34 and 37, the working fluid in the buffer tank 25 is moved to the buffer tank 26 to the maximum extent. Next, the solenoid valve 37 is closed and the solenoid valve 38 is opened conversely so that the working fluid in the working space 23 is moved to the buffer tank 26 and the filling pressure of the working space 23 is minimized.

When controlling the pressure as described above, restrict the piping passage
Optimal control can be performed by optimally adjusting the opening / closing time of the solenoid valve.

FIG. 4 shows a pressure control mechanism according to another embodiment of the present invention, which is the working space 23 shown in FIGS.
The individual pipes that connect between the storage tank 24 and the buffer tank 26 are joined by a common pipe on the working space 23 side, and the four check valves 31, 32, 32 in FIG.
This is an example in which two check valves 41 and 42 corresponding to 35 and 36 are provided. By doing so, the same effect as that of the previous embodiment can be obtained while reducing the number of parts.

EFFECTS OF THE INVENTION According to the present invention, the individual pipes that respectively connect the storage tank and the buffer tank to the working space, or the common pipe that joins these individual pipes on the working space side,
Four or two check valves are installed in reverse parallel connection, and solenoid valves are installed in series with these check valves in individual pipes, and these solenoid valves are opened and closed to control the pressure in the working space. By implementing the special control mode, the variable range of the pressure of the working space is compared with the conventional pressure control by the flow of the working fluid only between the storage tank or the buffer tank and the working space. Therefore, the pressure variable range can be expanded while the tank capacity is kept relatively small. For example, if the storage tank has a capacity of 20, it is 4
Although the pressure variable width is 6 MPa, according to the present invention, the pressure variable width of 3 to 7 MPa can be obtained.

Further, in the present invention, the steps of the pressure control by the flow of the working fluid between the buffer tank and the working space are made continuous by the stepless pressure control by the flow of the working fluid between the storage tank and the working space. It is possible to realize smooth pressure control.

[Brief description of drawings]

FIG. 1 is a block diagram of a Stirling engine according to an embodiment of the present invention, FIG. 2 is a view showing a pressure control mechanism in the same embodiment, FIG. 3 is a view for explaining its operation, and FIG. It is a figure which shows the pressure control mechanism in the other Example of this invention. 1 ... expansion cylinder, 2 ... expansion piston, 3 ... compression cylinder, 4 ... compression piston, 5 ... heater, 6 ... regenerator, 7 ... cooler, 8, 9 ... connecting rod, 1
0 …… Crankshaft, 11 …… Crank chamber, 12 …… Expansion cylinder head, 13 …… Insulation block, 14 …… Combustion chamber, 15…
… Heat transfer fins, 16… Heat exchangers, 17… Manifolds, 18
…… Gas nozzle, 19 …… Swaller, 20 …… Air preheater,
21 …… intake cylinder, 22 …… exhaust cylinder, 23 …… working space, 24 ……
Storage tank, 25 …… Piston back space, 26 …… Buffer tank, 27 …… Capillary tube, 31,32,35,3
6,41,42 …… Check valve, 33,34,37,38 …… Solenoid valve.

Claims (2)

(57) [Claims] 1. A storage tank for storing a working fluid flowing through an operating space in an engine, a buffer tank provided in communication with a piston back space in the engine, the storage tank, the buffer tank and the operating space. Four or two check valves provided in anti-parallel connection to the individual pipes that communicate with each other or the common pipes that join these individual pipes on the side of the working space, and the check valves in series with the individual pipes, respectively. A Stirling engine provided with a solenoid valve and a control means for controlling opening and closing of these solenoid valves. 2. The control means opens a solenoid valve provided in series with a check valve that allows the flow of the working fluid from the storage tank to the working space and the flow of the working fluid from the working space to the buffer tank. After that, the pressure in the working space is maximized by opening the solenoid valve that allows the flow of the working fluid from the buffer tank to the working space, and the flow of the working fluid from the buffer tank to the working space is increased. After closing the solenoid valve provided in series with the check valve that allows the flow of the working fluid from the working space to the storage tank, open the solenoid valve that allows the working fluid to flow from the working space to the buffer tank. The Stirling engine according to claim 1, wherein the pressure in the working space is reduced to a minimum by doing so.