JP2000146339A - Gas compressor expander - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas compressor expander capable of obtaining a stable apparatus efficiency by preventing an increase in a starting torque of a driving means and an increase in an input power when restarted. SOLUTION: The gas compressor expander comprises a position detecting means 22 for detecting a position in a cylinder 3 of a piston, and a control means 24 for stopping reciprocating of the piston under the control of a drive means 25 so that a piston position to be detected by the means 22 becomes a predetermined position when the drive of the means 5 is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas compression / expansion machine such as a Stirling engine for generating power and a Stirling refrigerator for generating low temperature.

[0002]

2. Description of the Related Art In recent years, there has been an urgent need to develop techniques for preserving various samples and various materials at extremely low temperatures in advanced technology fields such as the field of biotechnology and the field of electronic devices. In particular, gas compression / expansion machines such as Stirling refrigerators are attracting attention as means for achieving the extremely low temperature, and are going to be widely used for cooling, biomedical freezers, freezers, etc. for various infrared sensors, superconducting devices, and the like.

Here, the structure of a conventional displacer type Stirling refrigerator will be described with reference to FIG.

An expansion cylinder 2 and a compression cylinder 3 are attached to the refrigerator body 1 at an angle difference of 90 degrees, and a displacer 6 built in the expansion cylinder 2 and a piston built in the compression cylinder 3 7 are connected to a common crank mechanism 5 and are reciprocally driven in a state where the phases are shifted from each other.

In the displacer 6, a cold storage material 14 made of, for example, a sintered metal is filled in a cylindrical body 17 having both ends opened, and a working gas flowing from one opening of the cylindrical body 17 is supplied to the cold storage material 14. In the process of passing through the inside and flowing out of the other opening, heat exchange with the cold storage material 14 is performed.

The displacer 6 also has a function as a regenerative heat exchanger, and its heat exchange performance greatly affects the coefficient of performance of a Stirling refrigerator.

The expansion-side cylinder 2 and the compression-side cylinder 3 are separated from the crank chamber 12 by oil seals 8 and 9, respectively. The base end of the expansion-side cylinder 2 and the tip end of the compression-side cylinder 3 are The communication portions 4 communicate with each other. Oil 10 is injected into the crank chamber 12.

FIG. 4 shows the operation of the Stirling refrigerator with time T on the horizontal axis and stroke S on the vertical axis.

In the Stirling refrigerator, the displacer 6 reciprocates as shown by curves B and C in FIG. 4 and the piston 7 reciprocates as shown by curve D in FIG. The space 11 changes in volume in a width region between the straight line A and the curve B in FIG. 4, and the compression space 13 of the compression side cylinder 3 changes in volume in a width region between the curves C and D in FIG. I do.

As a result, in the stroke of FIG. 4, the gas in the compression space 13 is compressed with the rise of the piston 7, and flows into the expansion side cylinder 2 through the communication pipe 4 (ideally, the isothermal compression). ). In the process of FIG. 4, this gas passes through the cold storage material 14 in the displacer 6 and exchanges heat with the cold storage material 14 to lower the temperature (constant volume cooling). The gas that has passed through the cold storage material 14 flows into the expansion space 11 of the expansion-side cylinder 2 in the process shown in FIG. 4, and then expands as the piston 7 descends (ideally, isothermal expansion). Next, in the process of FIG. 4, as the displacer 6 rises, the gas in the expansion space 11 passes through the cold storage material 14 and exchanges heat with the cold storage material 14 to increase the temperature. Again flows into the compression space 13 (fixed volume heating).

As a result, the cold head 15 provided on the head of the expansion-side cylinder 2 is cooled.

[0012]

In the Stirling refrigerating machine having the above structure, a driving motor (not shown) as a power source for rotating the crankshaft 16 of the crank mechanism 5 when the operation is stopped. However, the stop position of the piston 7 was not controlled at all.

For this reason, when the piston 7 stops at the position on the crank mechanism 5 side from the stroke center position, the gas gradually moves from the back space side of the piston 7 to the working space side, and the operation in the working space is started. There is a risk that the volume of the gas will increase. As a result, when restarting the refrigerator,
Since the compression work corresponding to the increased working gas volume is added, it is necessary to increase the starting torque of the drive motor and to increase the input power to the drive motor at the start.

In general, when assembling the refrigerator, gas is often filled with the piston 7 positioned at the center of the stroke, but the position of the piston 7 when the operation of the refrigerator is stopped is different from the stroke center. In such a case, there is a possibility that gas movement may occur between the working space side and the back space side of the piston 7 as described above, and the volume of the working gas may be reduced during initial operation of the refrigerator and during restart operation. As a result, the efficiency of the apparatus may be reduced.

[0015] The present invention has been made in view of the above points, and eliminates the fluctuation of the working gas volume due to the stoppage of the operation of the apparatus, increases the starting torque of the driving means at the time of restart, and increases the input power. It is an object of the present invention to provide a gas compression / expansion machine capable of preventing the occurrence of a gas pressure and achieving a stable apparatus efficiency.

[0016]

According to the present invention, there is provided a gas compression / expansion machine, comprising: a position detecting means for detecting a position of a piston in a cylinder; and a position detecting means for stopping driving by the driving means. Control means for controlling the driving means so as to stop the reciprocating movement of the piston so that the piston position to be moved becomes a predetermined position.

Specifically, a compression side cylinder, a piston slidable in the compression side cylinder, an expansion side cylinder, a displacer slidable in the expansion side cylinder, and the piston and the displacer are mutually connected. A driving means for transmitting a driving force so as to reciprocate with a predetermined phase difference between the piston and the piston. And stopping the reciprocating motion of the piston by controlling the driving means so that when the driving by the driving means is stopped, the piston position detected by the position detecting means becomes a predetermined position. Control means for performing the operation. And
The control means controls the driving means so that the piston position detected by the position detection means becomes the stroke center position.

By using this configuration, when the operation of the refrigerator is stopped, gas movement between the working space side and the back space side of the piston can be prevented, and the working gas volume can be prevented from fluctuating.

Further, a non-contact type displacement sensor may be used as the position detecting means.

Further, the driving means is a driving motor for transmitting a driving force to a driving mechanism for reciprocating the piston, and the position detecting means detects the piston position based on the rotational position of the driving motor. May be.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A case where the present invention is applied to the above-described Stirling refrigerator shown in FIG. 3 will be described in detail with reference to the drawings. Since the operation of the Stirling refrigerator is the same as that of the conventional one, the description is omitted.

FIG. 1 is a schematic sectional view of a Stirling refrigerator to which the present invention is applied. In addition, in this Stirling refrigerator, the expansion side cylinder 2 and the compression side cylinder 3 are provided in parallel. Further, in the present embodiment, the gas is charged at the time of assembling the refrigerator with the piston 7 positioned at the stroke center. As shown in FIG. 1, a laser displacement gauge 22 as a position detecting means for detecting the position of the piston 7 in the compression side cylinder 3 is disposed above the upper wall portion 21 of the compression side cylinder 3.

An opening having a diameter of about 30 mm is formed in the upper wall portion 21 so that the laser light emitted from the laser displacement meter 22 is reflected by the piston 7 and the reflected light returns.
A transparent pressure-resistant glass 2 having a thickness of about 5 mm in the opening.
3 is fixed. In this embodiment, a case is described in which a laser displacement meter is used as the position detecting means 22. However, other detecting means, such as an MR sensor using a magnetoresistive element (MR element), a magnetic sensor, and the like, are used. May be used.

The detection output of the laser displacement meter 22 is input to control means 24 for controlling the driving of a driving motor 25.

Next, the configuration of the control means 24 will be described with reference to FIG. FIG. 2 is a block diagram of a control circuit using a microcomputer as the control means 24.
The control means 24 includes an MPU 241 (micr
and a ROM 242 (read-o) as a read-only memory in which a control unit is stored.
nly memory), a RAM 243 (random access memory) as a working area of the MPU 241, and an I / O port 244 for inputting and outputting signals to and from the outside.

When the user operates the start / stop switch 26 provided on the refrigerator main body 1 during the operation, the stop signal of the start / stop switch 26 is transmitted to the MPU 241 via the I / O port 244. Is input to And M
In response to the input of the stop signal, the PU 241 reduces the rotation speed of the drive motor 25 via the I / O port 244 to change the operation to a low-speed operation in which the operation can be stopped immediately, and the piston 7 detected by the laser displacement meter 22. Is acquired via the I / O port 244.

When the MPU 241 detects that the piston 7 is located at the center of a predetermined stroke based on the position information from the laser displacement meter 22, a control signal for stopping the drive of the drive motor 25 is provided. Is output to the drive motor 25 via the I / O port 244.

On the other hand, when the apparatus is restarted, a start signal is inputted to the MPU 241 via the I / O port 244 by operating the start / stop switch 26 by the user. The MPU 241 controls the rotation speed of the drive motor 25 via the I / O port 244 in accordance with the input of the start signal so that the piston 7 reciprocates at a predetermined steady frequency in the compression side cylinder 3. I do.

Thus, when the operation of the apparatus is stopped, the piston 7 can be stopped at the stroke center position, and every time the operation of the apparatus is stopped, the gas moves between the working space side and the back space side of the piston 7. Does not occur and the working gas volume does not fluctuate. Therefore, at the time of restarting the apparatus, the starting torque and input power of the drive motor 25 do not increase, and the working gas volume differs between the state at the time of the initial filling of the refrigerator and the state at the time of the restart operation. Also, the efficiency of the apparatus is not reduced.

The description of the above embodiment is for the purpose of illustrating the present invention, and should not be construed as limiting the invention described in the claims or reducing the scope thereof.
Further, the configuration of each part of the present invention is not limited to the above embodiment, and various modifications can be made within the technical scope described in the claims.

For example, a case has been described in which a non-contact type sensor such as a laser displacement meter is used as the position detecting means for detecting the position of the piston 7. However, the present invention is not limited to this. The position of the piston 7 may be detected from the rotational position of the drive motor 25 based on the relationship.

In the above embodiment, the case where the piston 7 is positioned at the center of the stroke when the operation is stopped has been described. However, if the piston position when the working gas is initially sealed in the refrigerator is other than the center of the stroke, It is preferable to stop at the piston position at the time of the initial filling.

[0033]

As described above, according to the present invention, the fluctuation of the working gas volume due to the stoppage of the operation of the apparatus can be eliminated, and the increase of the starting torque of the drive means and the increase of the input power at the time of restart can be prevented. And stable device efficiency can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a Stirling refrigerator according to one embodiment of the present invention.

FIG. 2 is a control block diagram of a microcomputer serving as control means 24 provided in the refrigerator of FIG.

FIG. 3 is a schematic sectional view of a conventional Stirling refrigerator.

FIG. 4 is a diagram illustrating a process of a Stirling refrigeration cycle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Refrigerator main body 2 Expansion side cylinder 3 Compression side cylinder 4 Communication pipe 5 Crank mechanism (drive mechanism) 6 Displacer 7 Piston 8, 9 Oil seal 10 Oil 11 Expansion space 12 Crank chamber 13 Compression space 14 Cold storage material 15 Cold head 16 Crank Axis 22 Laser displacement meter (Position detecting means) 24 Control means 25 Drive motor (Drive means) 26 Start / stop switch

Claims (5)

[Claims] 1. A gas compression / expansion machine which reciprocates a piston inside a cylinder by a driving means to compress or expand a working gas, wherein: a position detecting means for detecting a position of the piston in the cylinder; Control means for controlling the driving means so as to stop the reciprocating movement of the piston so that the piston position detected by the position detection means becomes a predetermined position when stopping. Compression and expansion machine. 2. A compression side cylinder, a piston slidable in the compression side cylinder, an expansion side cylinder, a displacer slidable in the expansion side cylinder, and the piston and the displacer are fixed to each other. A driving means for transmitting a driving force so as to reciprocate with a phase difference, and for detecting a position of a piston in a compression-side cylinder in a gas compression / expansion machine for compressing and expanding a working gas by reciprocation of a piston Position detecting means, and control means for controlling the driving means to stop the reciprocating movement of the piston so that when the driving by the driving means is stopped, the piston position detected by the position detecting means becomes a predetermined position. And a gas compression / expansion machine comprising: 3. A gas compression / expansion system according to claim 1, wherein said control means controls said driving means so that a piston position detected by said position detection means becomes a stroke center position. Machine. 4. The gas compression / expansion machine according to claim 1, wherein said position detection means is a non-contact type displacement sensor. 5. The driving means is a driving motor for transmitting a driving force to a driving mechanism for reciprocating a piston, and the position detecting means detects a piston position based on a rotation position of the driving motor. The gas compression / expansion machine according to any one of claims 1 to 3, wherein: