JPH02213655A - Controller device for ultra-low temperature expansion machine - Google Patents

Abstract

PURPOSE:To reduce an abnormal vibration or noise of an expansion machine by a method wherein a displacement of a displacer in respect to a cylinder is detected and a valve means for changing-over a feeding or a discharging of gas in respect to an interior of cylinder is studied and controlled in such a way as the displacement of the displacer may show a predetermined ideal characteristic. CONSTITUTION:When an expansion machine is operated, refrigerant gas is supplied or discharged to or from expansion chambers 9 and 10 under a changing-over operation of a valve means 20, a displacer 4 is reciprocated within a cylinder 2 and its displacement is detected by a displacer displacement detecting means 25. At the second memory means (m2), the present time control instruction of the displacer 4 is stored. The control instruction of the present time moving cycle of the displacer 4 is corrected in response to a displacement detected by a displacer displacement detecting means 25 and a rational displacement characteristic in the moving cycle of the displacer 4 stored by the first memory means (m1), and this is applied as the next time moving cycle control instruction and stored in sequence. The valve means 20 is controlled for its operation in response to the present time moving cycle control instruction of the displacer 4 stored in the memory means (m2).

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is a highly insulated refrigerant that expands high-pressure refrigerant gas supplied from a compressor in an expansion chamber within a cylinder by reciprocating movement of a displacer. The present invention relates to a control device for controlling the movement of a displacer in a cryogenic expansion machine that generates cold at a low temperature level.

(Prior Art) Conventionally, as disclosed in, for example, Japanese Unexamined Patent Publication No. 58-214758, a compressor that compresses helium gas as a refrigerant gas and an expander that expands the compressed gas have been used. are connected to a closed circuit by high-pressure piping and low-pressure piping, and a switching valve in the expander connects the high-pressure and low-pressure piping alternately to the engraving chamber in the cylinder of the expander, and the switching operation of the switching valve The so-called improved Solvay cycle and G-M cycle (Gifford/Gifford/ Helium refrigerators such as the McMahon cycle are well known and widely used for various purposes.

However, this gas pressure-driven cryogenic refrigerator has a problem in that when the expander is in operation, the displacer reciprocating within the cylinder collides with the end of the cylinder, and the impact causes abnormal vibrations.

Therefore, in the conventional technique disclosed in Japanese Patent Application Laid-Open No. 61-262558, a power absorption chamber having the same diameter as the expansion chamber is formed in the cylinder, and the power absorption chamber is connected to the high pressure circuit of the refrigeration gas cycle. The valves are connected to each other through a gas inflow circuit with a control valve interposed therebetween, and to the low pressure circuit through a gas inflow circuit with a low pressure control valve interposed therebetween, and the opening degree of each of the above valves is determined based on the movement position of the disbo racer. It has been proposed that the movement of the displacer is controlled by the pressure in the power absorption chamber, thereby suppressing the collision with the end of the cylinder.

(Problems to be Solved by the Invention) In this type of expansion machine, at the start of operation, the mass flow rate of the refrigerant gas is small during the so-called cool-down stage in which the cooling section is cooled from room temperature to the lowest temperature.
While the displacer becomes easier to move, in the steady state of operation after cool-down (when the minimum temperature is reached), the mass flow rate of gas increases, making it difficult for the displacer to move, resulting in a stroke of the displacer before and after cool-down. changes as shown in FIG. That is,
Because the switching valve opens and closes in a fixed pattern regardless of the movement of the displacer, the
As shown by the line (the displacement speed of the displacer increases,
The displacer collides with the upper and lower ends of the cylinder while maintaining high speed, creating a large impact. Thereafter, as shown by line B, the displacer gradually becomes difficult to move, collides with the upper and lower ends of the cylinder at a small speed (or zero speed), and the impact becomes small. However, when the minimum temperature is reached, the displacement speed of the displacer becomes very small as shown in line C, but the switching valve opens before the displacer reaches the upper and lower ends of the cylinder, and the displacer is accelerated by the pressure drop drive, causing a large collides with the cylinder at speed.

However, the above-mentioned proposal does not take into account such changes in the stroke of the displacer before and after cool-down, and has the disadvantage that abnormal vibrations and noise during expansion machine operation cannot always be stably reduced.

The present invention has been made in view of the above points, and its purpose is to provide a gas pressure-driven cryogenic expander that drives a displacer using gas pressure as described above.
Even if the movement characteristics of the displacer change due to changes in the mass flow rate of refrigerant gas before and after cool-down, the tapping of the displacer colliding with the cylinder end is suppressed, thereby reducing abnormal vibration and noise of the expander. The goal is to be able to constantly and stably reduce the

Means for Solving the Problem To achieve this object, the solution of the invention is based on the displacement of the displacer relative to the cylinder or the surge volume communicating with the drive chamber in the cylinder delimited by the displacer. Valve means for detecting the pressure change corresponding to the displacement of the displacer and switching the supply and discharge of gas into the cylinder or the pressure in the drive chamber in the cylinder so that the displacer displacement or pressure change has ideal characteristics set in advance. This is to learn and control the pressure adjustment means for adjustment.

That is, as shown in FIG. 1, the invention according to claim (1) includes a sealed cylinder (2);
a displacer (displacer) that is reciprocably fitted into the cylinder (2) and defines expansion chambers (9) and (10) in the inner space of the cylinder (2);
4) and the expansion chamber (9) for refrigerant gas such as helium discharged from the compressor.

Valve means (20) for switching supply and discharge to (10)
The displacer (4) is reciprocated as the valve means (20) is switched, and the refrigerant gas is transferred to the expansion chamber (9).
The premise is a cryogenic expander that expands in (10) to generate cryogenic level cold.

A displacer displacement detection means (23) for detecting the displacement of the displacer (4), a control command for the current movement cycle of the displacer (4), and a control command for the next movement cycle are sequentially stored; The displacement characteristics of the displacer (4) detected by the detection means (23) are compared with the ideal displacement characteristics of the first storage means (m2), and a control command for the current movement cycle is issued based on the change in the error. a second storage means (m2) that corrects the control command for the next movement cycle; and a second storage means (m2) that corrects the control command for the next movement cycle;
20) is provided.

In addition, in the invention set forth in claim (2), the cryogenic expander is such that the displacer (4) connects the space inside the sealed cylinder (2) to the expansion chambers (9), (10) and the drive chamber ( 8), and is also equipped with pressure adjustment means (16), (28) such as an orifice valve for adjusting the pressure of the drive chamber (8).

In this cryogenic expander, the above-described displacer displacement detection means (23) and first and second memory means (m+), (mz) are provided, and the above-mentioned pressure adjustment means (16), (28) are provided. ) based on a control command for the current movement cycle of the displacer (4).

Furthermore, in the invention set forth in claim (3), the cryogenic expander includes a surge volume (18) communicating with the drive chamber (8) in the cylinder (2), and a refrigerant for the expansion chambers (9) and (10). This cryogenic expander is equipped with a valve means (20) for switching gas supply and discharge, and a pressure detection means (37) for detecting the actual pressure in the surge volume (18), and a displacer ( 4) a first storage means (m2) for storing ideal pressure change characteristics set in advance in the surge volume (18) in the movement cycle; and a control command for the current movement cycle and control for the next movement cycle. The commands are stored sequentially, and the surge volume (1) detected by the pressure detection means (37) is
8) Compare the pressure change characteristics in the above first storage means (m2) with the ideal pressure change characteristics, modify the control command for the current movement cycle based on the change in error, and adjust the control command for the next movement. Second storage means 1, (m2
) and a control means (57) for controlling the operation of the valve means (20) based on the control command for the current movement cycle.

Furthermore, in the invention as set forth in claim (4), the cryogenic expander is based on the assumption that the displacer (4) uses the space inside the sealed cylinder (2) as the expansion chamber (9).

(10) and the drive chamber (8),
Also, a pressure adjustment means (16) such as an orifice valve for adjusting the pressure in the drive chamber (8).

(28) is provided.

In this cryogenic expander, pressure detection means (37) for detecting the actual pressure in the surge volume (18) described above, first and second storage means (m+),
(mz), and the pressure adjustment means (
A control means (57) is provided for controlling the operation of 16) and (28) based on a control command for the current movement cycle of the displacer (4).

(Function) With this configuration, in the invention described in claim (1), when the expander is operated, refrigerant gas is supplied to the expansion chambers (9) and (10) in the cylinder (2) by switching operation of the valve means (20). Gas is supplied and discharged, and the displacer (4) is reciprocated within the cylinder (2) as the gas is supplied and discharged. The displacement of this reciprocating displacer (4) is detected by the displacer displacement detection means (23). The second storage means (m2) stores the current control command for the displacer (4), and also stores the displacement detected by the displacer displacement detection means (23) and the first storage means (m2). Displacer (4) remembered by
Based on the change in the error from the ideal displacement characteristic in the movement cycle, the control command for the current movement cycle of the displacer (4) is modified and sequentially stored as the control command for the next movement cycle. Further, the control means (57) controls the operation of the valve means (20) based on the control command for the current movement cycle of the displacer (4) stored in the second storage means (m2). Through such learning control, each time the displacer (4) repeats its movement cycle, its displacement characteristics are successively corrected to become the ideal displacement characteristics stored in the first storage means (m2), and finally It is converged so that the error becomes zero. Therefore, the ideal displacement characteristic of the displacer (4) is that the displacer (4) moves at a constant speed in the middle of the cylinder (2), and when it reaches the upper and lower ends of the cylinder (2), the speed becomes approximately zero, and the displacer (4) moves at a constant speed in the middle of the cylinder (2). Assuming the characteristic (4) that no violent collision occurs, even if the movement resistance of the displacer (4) changes due to a change in the gas mass flow rate before and after cooling down the expander, the displacement characteristic is stored in the first storage means. It is possible to converge to the ideal characteristic of (m2), and therefore it is possible to always stably suppress the tapping of the displacer (4) and reduce abnormal vibrations and noise of the expander, regardless of whether before or after cool-down.

Further, in the invention as set forth in claim (a), similarly to the above, as the displacer (4) reciprocates within the cylinder (2), the pressure adjustment means (16) and (28) control the drive chamber (8).
The internal pressure is adjusted so that it stays within a substantially constant range. Then, the second storage means (m2) records the change in the error between the displacement of the displacer (4) detected by the displacer displacement detection means (23) and the ideal displacement characteristic of the first storage means (m2). Based on this, the control commands for the current movement cycle are modified to become the control commands for the next movement cycle, and these control commands for the current and next movement cycles are sequentially stored. The control means (57) also controls the pressure adjustment means (16) based on the control command for the current movement cycle stored in the second storage means (m2).
(28) is operationally controlled. Through such learning control, each time the displacer (4) repeats its operation cycle, its displacement characteristics are sequentially corrected to become the ideal displacement characteristics stored in the first storage means (m2). Therefore, similarly to the above, it is possible to always stably reduce abnormal vibrations and noise of the expander caused by tapping of the displacer (4), regardless of whether the expander is cooled down or not.

Furthermore, in the invention described in claim (3), the cylinder (2)
As the displacer (4) reciprocates within the drive chamber (8), the pressure within the surge volume (18) that communicates with the drive chamber (8) changes in accordance with the displacement of the displacer (4), and this pressure is detected by pressure detection. Detected by means (37). Based on the change in error between this pressure and the ideal characteristic of surge volume pressure change stored in the first storage means (m2), the control command for the current movement cycle is corrected and used as the control command for the next movement cycle. and these are stored in the second storage means (m2) depending on luck. Furthermore, the control means (57
), the operation of the valve means (20) is controlled based on the current control command stored in the second storage means (m2).

Through this learning control, each time the displacer (4) repeats its operation cycle, the surge volume (18
) is successively corrected to become the ideal pressure change characteristic stored in the first storage means (m2), so that the movement resistance of the displacer (4) before and after cool-down of the expander Even if the pressure changes in the surge volume (18), which corresponds to the displacement characteristics, can be converged to the ideal characteristics, it is possible to always stably reduce abnormal vibrations and noise of the expander.

Further, in the invention as set forth in claim (4), similarly to the above, the displacement changes in response to the displacement of the displacer (4) within the cylinder (2). Based on the change in error between the pressure in the surge volume (18) and the ideal characteristic of surge volume pressure change stored in the first storage means (m2), the control command for the current movement cycle is corrected and the control command for the next movement is adjusted. These are used as control commands for the movement cycle, and depending on luck, these are stored in the second storage means (m).Then, the control means (57)
The pressure adjusting means (16) based on the current control command stored in the storage means (m2) of.

(28) is operationally controlled. With this learning control, each time the displacer (4) repeats its operating cycle,
The pressure change characteristic within the surge volume (18) is the first
The pressure change characteristics are sequentially corrected to the ideal pressure change characteristics stored in the storage means (m2) of Surge volume corresponding to (1
8) Internal pressure change characteristics can be converged to ideal characteristics, and abnormal vibrations and noise of the expander can be constantly and stably reduced.

(First Embodiment) Hereinafter, an embodiment of the present invention will be described based on the drawings from FIG. 2 onwards.

FIG. 2 shows the overall configuration of a first embodiment in which the present invention is applied to a helium refrigerator with an improved Solvay cycle, and (1)
is an expansion machine that adiabatically expands helium gas as a refrigerant gas, and this expansion machine (1) has an upper large diameter part (2a
) and a lower small-diameter portion (2b), the cylinder has a closed cylindrical cylinder (2) with a two-stage structure, and a casing (3) is integrally attached to the upper end of this cylinder (2). .

A displacer (4) (displacer) is fitted into the cylinder (2) so as to be able to reciprocate. The displacer (4) is integrally connected to a closed cylindrical large diameter part (4a) that slides within the large diameter part (2a) of the cylinder (2), and to the lower end of the large diameter part (4a), and is integrally connected to the lower end of the large diameter part (4a). 2) and a closed cylindrical small diameter part (4b) that slides inside the small diameter part (2b). A bottomed cylindrical four part (4c) is formed at the upper end of the large diameter part (4a) of the displacer (4), and a cylinder (2) is formed in the bottom wall of the casing (3) in the recess (4c). A cylindrical sliding contact part (2C) attached to hang down inside is inserted, and the outer peripheral surface of the sliding contact part (2C) and the displacer (4
) is hermetically sealed with the inner peripheral surface of the recess (4C) by an inner peripheral seal (5) fitted on the inner peripheral surface of the recess (4C). In addition, a first stage seal (6) is attached to the outer periphery of the large diameter part (4a) of the displacer (4), and a second stage seal (7) is attached to the outer periphery of the small diameter part (4b). With the seals (5) to (7), the inner space of the cylinder (2) is divided into an annular drive chamber (8) and a first stage expansion chamber (9) in order from the top.
) and a second stage expansion chamber (10), and the inner circumferential seal (5
) and a sliding contact portion (2C) define a gas inflow/outflow chamber (11).

Further, the large diameter portion (4a) of the displacer (4) has a communication hole (
12) and the first stage expansion chamber (9) through a communication hole (13), and this large diameter portion (4
A first stage regenerator (not shown) consisting of a regenerator type heat exchanger is fitted inside a). Also, displacer (4)
The inside of the small diameter portion (4b) is connected to the first stage expansion chamber (9) through a communication hole (14) and to the second stage expansion chamber (10) through a communication hole (14).
5), and are in constant communication with each other through the small diameter portion (4b).
A second stage regenerator (not shown) similar to the first stage regenerator is fitted inside.

The casing (3) also has a surge volume (
18) is formed, and this surge volume (18
) and the gas flow resistance of the orifice valve (16) to maintain the pressure in the intermediate chamber (8) approximately constant.

(19) is the expansion chamber (9) (10) in the cylinder (2).
) is a gas pipe for supplying and discharging helium gas to and from the cylinder (2), one end of which connects to the displacer recess (4C) through the space in the through hole (2d) of the earthen wall of the cylinder (2) and the sliding contact part (2c).
It communicates with the gas inflow/outflow chamber (11) inside. Gas piping (
The other end of 19) is connected to a high/low pressure control valve unit (20) as a valve means for switching the supply and discharge of helium gas to and from the expansion chambers (9) and (10).

This valve unit (20) is connected to the discharge side of a compressor (not shown) for compressing helium gas via a high pressure pipe (21), and to the suction side of the same via a low pressure pipe (22). In the valve unit (20), the gas pipe (19) is connected to the high pressure pipe (21) or the low pressure pipe (22).
), and when the gas pipe (19) is connected to the high pressure pipe (21), high pressure helium gas from the compressor is passed through the gas pipe (19) to the expansion chamber (9) in the cylinder (2). ) and (10) to raise the displacer (4), and when the gas pipe (19) is connected to the low pressure pipe (22), the expansion chambers (9) and (10) are filled with gas. The displacer (4) is lowered by expanding and discharging the helium gas into the low-pressure pipe (22), and the expansion of the helium gas accompanying the up-and-down movement cycle of the displacer (4) cools the helium to a cryogenic level. is configured to occur.

Furthermore, a displacement meter (23) is attached to the casing (3) as a displacer displacement detection means for detecting the displacement (movement position) of the displacer (4). As shown in enlarged detail in Fig. 5, this displacement meter (23) consists of a bottomed cylindrical pressure-resistant container that is integrally attached to the earthen wall of the cylinder (2) and whose interior communicates with the drive chamber (8). A case (24), a coil (25) disposed around the outer periphery of the case (24), and a coil (25) that is reciprocatably fitted into the case (24) and whose lower end is connected to the large diameter portion of the displacer (4). (4a) A core (26) is screwed onto the upper end. The coil (25) includes, for example, a primary coil (25a) magnetically coupled by a core (26) and two secondary coils (25b) connected in series with opposite polarities, as shown in FIG. 25b) for the primary coil (25a), which changes depending on the amount of movement of the core (26).
The strength and weakness of the magnetic coupling of the two secondary coils (25b) and (25b) are determined by the secondary coil (25b).

(25b) The displacement of the displacer (4) is detected by detecting each induced electromotive force.

The output signal of this displacement meter (23) is input to a control unit (50) that controls the operation of the control valve unit (20). This control unit (50) performs the control shown in FIG. 3. That is, the control unit (50) has two memories, a memory (m2) and a memory (m2), and a memory (m2).
As shown in FIG. 4, an ideal output waveform yd corresponding to an ideal displacement characteristic in one cycle of movement of the displacer (4) is stored in advance.

This ideal output waveform yd is set to a waveform such that the speed becomes approximately zero when the displacer (4) reaches the upper and lower ends of the cylinder (2) during reciprocating movement of the displacer (4).

In addition, the input signal from the displacement meter (23) in the controlled system)'(k>(k-1, 2, . . . indicates the number of movement cycles of the displacer (4)) is the A/D converter ( After being converted into a digital signal in step 51), it is compared with the output signal of the memory (m2) and its error e (
k) is calculated. This error e (k) is the differential part (53
) is numerically differentiated to obtain a differential error coefficient (k), the differential error (k) is multiplied by a coefficient in the two-law section (54), and then the control output u (k) from the control section (57) is added. After that, it is stored in the memory (m2) again as the control output u (k+1) for the next cycle. Before the above error is added, the control output u (k) output from the memory (m2) by the control unit (57) is converted into an analog by the D/A converter (56) and is converted into an analog signal by the control valve unit of the controlled system. (20) is input.

That is, in this embodiment, the memory (m2) allows
A first storage means is configured to store a preset ideal displacement characteristic of the displacer (4).

The memory (m2) sequentially stores control commands for the current movement cycle of the displacer (4) and control commands for the next movement cycle, and also stores the displacement of the displacer (4) detected by the displacement meter (23). Compare the characteristics with the ideal displacement characteristics in the memory (m+) (first storage means), and based on the change in the error, modify the control command for the current movement cycle and use it as the control command for the next movement cycle. A second storage means is configured.

Further, the control unit (57) controls the opening/closing timing or opening degree of the valve unit (20) based on the control command for the current movement cycle of the displacer (4) stored in the memory (m2). is configured.

Therefore, in the above embodiment, when the expander (1) is operated, the control unit (50) switches the high/low pressure control valve unit (20) to the cylinder (2).
) in the expansion chamber (9).

The supply and discharge of helium gas to and from the cylinder (10) are switched, and the displacer (4) reciprocates within the cylinder (2) as the gas is supplied and discharged. That is, gas piping (19
) is switched to communicate with the high pressure pipe (21), room temperature high pressure helium gas from the compressor flows through the gas pipe (19) to the recess (4C) of the displacer (4). gas inflow and outflow chamber (11
) and then from this chamber (11) through each regenerator in the displacer (4) and then sequentially into the expansion chamber (9).

(10), and is cooled to an extremely low temperature by heat exchange while passing through the regenerator. Furthermore, the expansion chamber (9) is created by introducing this high-pressure helium gas.

The pressure in the drive chamber (10) becomes higher than that in the drive chamber (8), and the displacer (4) rises due to this differential pressure.

As the displacer (4) moves upward, the expansion chambers (9) and (10) below it are further filled with high pressure gas. Thereafter, the valve unit (20) closes, but even after the valve closes, the displacer (4) rises due to inertia, and as a result, the helium gas in the gas inflow/outflow chamber (11) flows into both expansion chambers (9). ), move to (10).

After the displacer (4) reaches the rising end position, the valve unit (20) is switched so that the gas pipe (19) communicates with the high pressure pipe (21), and with this valve opening switching, the expansion chamber The helium gas in (9) and (10) undergoes Simon expansion, and this gas expansion causes cooling. This extremely low temperature helium gas
Contrary to when the gas is introduced, the gas passes through the regenerator in the displacer (4) and returns to the gas inlet/outlet chamber (11), during which time the regenerator is cooled and warmed to room temperature. Then, this normal temperature helium gas is discharged to the outside of the expander (1), flows through the gas pipe (19) and the low pressure pipe (22) to the compressor, and is sucked into the compressor. With this gas discharge, the expansion chamber (9).

The gas pressure in (10) decreases, and the displacer (4) descends due to the pressure difference with the drive chamber (8), and the downward movement of this displacer (4) causes the expansion chambers (9), (10
) is further discharged to the outside of the expander (1). Next, the valve unit (20) closes again, but even after this, the displacer (4) descends to the lower end position and expands into the expansion chamber (9).

(10) The gas inside is exhausted and the state returns to the initial state.

With the above, one cycle of operation of the expander (1) is completed,
Thereafter, the same operation as above is repeated.

In this case, the displacement of the reciprocating displacer (4) is detected by the displacement meter (23). In addition, the memory (m2) of the control unit (50) stores the control command for the current movement cycle for each cycle of the displacer (4), and also stores the control command for the current movement cycle of the displacer (4).
), and the ideal displacement characteristic of the displacer (4) stored in the memory (rr++). Based on the change in error, the control command for the current movement cycle is corrected and the control command for the next movement cycle is adjusted. This control command is stored in the memory (m2) together with the control command for the current movement cycle. The control unit (57) then controls the high and low pressure control valve unit (20) based on the control command for the current movement cycle of the displacer (4) stored in the memory (m2).
The opening/closing timing or degree of opening is controlled. For this reason,
Through such learning control, each time the displacer (4) repeats its operation cycle, its displacement characteristics are successively corrected to become the ideal displacement characteristics stored in the memory (m2), and eventually the error becomes zero. It is converged so that The ideal displacement characteristic of the displacer (4) stored in the memory (m2) is such that the displacer (4) does not collide with the upper and lower ends of the cylinder (2) as shown in FIG. Even if the movement resistance of the displacer (4) changes due to changes in the gas mass flow rate before and after the cool-down of the expander ( Regardless of before or after cool-down in step 1), the tapping of the displacer (4) colliding with the upper and lower walls of the cylinder (2) can be suppressed, and abnormal vibrations and noise of the expander (1) can be reduced. .

(Second Embodiment) FIG. 7 shows a second embodiment in which the present invention is applied to a helium refrigerator having a gas pressure-driven GM cycle. Furthermore, the second
The same parts as those in the figures are given the same reference numerals, and detailed explanation thereof will be omitted.

That is, in this embodiment, the piston portion (4d) is integrally formed at the upper end portion of the displacer (4). On the other hand, the piston portion (4d) is located at the upper end of the cylinder (2).
) is fitted in a reciprocating manner, and a drive chamber (8) defined by a piston part (4d) is formed in the upper part of the space inside the cylinder part (2e). There is. Further, a gas inflow/outflow chamber (11) is formed at the upper end of the cylinder (2).
) is opened at one end of the gas pipe (19).

In the drive chamber (8), an instantaneous switching valve (28) whose operation is controlled by a control unit (50) is connected to a pipe (
27), and this switching valve (28) is connected to the discharge side (high pressure side) and suction side (low pressure side) of the compressor. The switching valve (28) has two switching positions (1), CU), a first and a second switching position, and a position (1).
When switched to position (n), the drive chamber (8) is communicated with the discharge side of the compressor, and when switched to position (n), the drive chamber (8) is communicated with the suction side of the compressor. This switching valve (28) is then controlled by the control unit (50) to control the displacer (
By controlling the switching in a fixed pattern according to the displacement of the drive chamber (8), the pressure in the drive chamber (8) is adjusted to be substantially constant. The rest of the structure is the same as that of the above embodiment.

In addition to the above-mentioned two switching positions (I) and (n), in place of the above-mentioned instantaneous switching valve (28), as shown in FIG. A switching valve (2g
') may be adopted.

Therefore, in this embodiment as well, the opening/closing timing and opening degree of the valve unit (20) are controlled in a learning manner so as to have ideal displacement characteristics according to the displacement of the displacer (4), and therefore the same effects as in the above embodiment are achieved. be able to.

(Third Embodiment) FIG. 9 shows a third embodiment. In each of the above embodiments, the opening/closing timing and opening degree of the high/low pressure control valve unit (20) are controlled, whereas the cylinder (2) By adjusting the pressure of the intermediate pressure within the displacer (4)
It is designed to control the movement of.

That is, in this embodiment, in the same configuration as the first embodiment, a gas flow path (17) that communicates with the drive chamber (8) in the cylinder (2) and the surge volume (18) is provided. The orifice valve (16') constitutes pressure regulating means, and the orifice valve (16') is a variable needle valve whose opening degree can be variably adjusted.

Specific examples of this needle valve include one that utilizes the piezoelectric force of a piezoelectric element (34) as shown in FIG. 10, one that utilizes the displacement of a piezoelectric element (34) as shown in FIG. As shown in FIG. 12, a device utilizing deformation of a piezoelectric element (34) is employed. In the valve shown in FIG. 10, a fixed sleeve (30) is formed through the case (29). The inner space of the case (29) is divided into a gas chamber (32) and an element chamber (33) by a flexible partition wall (31).
), and the partition wall (31) has a fixed orifice (
a flow rate adjustment unit (30) that adjusts the gas flow rate at the orifice (30) by changing the degree of opening of the opening end into the gas chamber (32);
1a) is provided protrudingly. On the other hand, in the element room (33),
A laminated piezoelectric element (34
) is placed between the back surface of the partition wall (31) and the bottom surface of the element chamber (33), with a hook being passed between the back surface of the partition wall (31) and the bottom surface of the element chamber (33).
4), the opening degree of the orifice (30) is controlled by adjusting the voltage applied to the control unit (50). In addition, (35) is the gas chamber (32
), and (36) is a communication hole that opens the element chamber (33) to the outside in order to reduce the displacement resistance of the partition wall (31).

Furthermore, in the case shown in FIG. 11, only the gas chamber (32') is formed within the case (29), and the gas chamber (32')
The piezoelectric element (34) connects its base end to the gas chamber (32').
The element (34) is disposed in a fixed state on the inner bottom surface, and the tip of the element (34) is disposed opposite to the opening end of the fixed orifice (30) into the gas chamber (32'), so that no voltage is applied to the piezoelectric element (34). By adjusting the voltage, the piezoelectric element (34
) is deformed so that its tip controls the opening degree of the orifice (30).

Furthermore, in the one shown in FIG. 12, a deformation orifice (30') is formed through the center of the piezoelectric element (34), and as the piezoelectric element (34) deforms, the orifice (30')
Adjust its opening by deforming itself. These valves (16') use piezoelectric elements (34), so
It is characterized by its fast response speed.

In this embodiment, the orifice valve (16'
) is configured so that the opening degree of the opening is controlled by a control unit (50). This orifice valve (16
') is the same as in the first embodiment (see Fig. 3), and the memory (m2) stores the preset ideal displacement characteristic of the displacer (4), and the memory (m2) Then, the current and next movement cycles of the displacer (4) are sequentially memorized, and the displacement meter (2) is
The displacement characteristics of the displacer (4) detected by step 3) are compared with the ideal displacement characteristics in the memory (m2), and based on the change in the error, the control command for the current movement cycle is corrected and the next movement is performed. Use as cycle control command. Then, the control unit (57) controls the opening degree of the orifice valve (16) based on the current control command stored in the memory (m2), and controls the opening of the drive chamber (8) and surge volume (18). The movement of the displacer (4) is controlled by adjusting the gas flow.

Note that normal control is performed on the high and low pressure control valve unit (20).

Therefore, in this embodiment, the displacement of the displacer (4) during operation of the expander (1) is detected by the displacement meter (23), and this displacement signal is transmitted to the control unit (
50) and its control unit (50)
Based on the output, the opening degree of the orifice valve (16) is controlled by learning so that the displacement characteristic of the displacer (4) converges to the ideal characteristic stored in the memory (m2).

Therefore, as in each of the above embodiments, the displacement characteristics of the displacer (4) are constantly corrected to the ideal characteristics even before and after cooling down the expander (1), so that tapping of the displacer (4) is suppressed by the ideal characteristics. and an expansion machine (1
) to stably reduce vibration and noise.

(Fourth Embodiment) In the same configuration as the second embodiment, normal control is performed on the high and low pressure control valve unit (20),
Alternatively, a switching valve (28) that adjusts the pressure in the drive chamber (8) within the cylinder (2) may be controlled to open or close.

That is, the fourth embodiment of the present invention has the same basic configuration as the second embodiment (described with reference to FIG. 7), and the displacement of the displacer (4) is detected by the displacement meter (23). , whose displacement characteristics are determined by the control unit (5
The opening degree of the switching valve (28) is adjusted so that the ideal characteristic stored in the memory (m2) of 0) is obtained. In other words, during the downward movement stroke of the displacer (4), the switching valve (28) is switched to the switching position (n) immediately before it collides with the lower end of the cylinder (2), and the drive chamber (8) is moved to the suction side of the compressor. in order to prevent the displacer (4) from colliding due to the pressure drop in the drive chamber (8), and during the upward stroke of the displacer (4), its cylinder (2
) Just before the collision with the upper end, move the switching valve (28) to the switching position (
1) to communicate the drive chamber (8) with the compressor discharge side, and to increase the pressure in the drive chamber (8) and prevent the displacer (4) from colliding.
28) to perform learning control. Therefore, in this embodiment, the switching valve (28) constitutes a pressure regulating means.

Therefore, this embodiment can provide the same effects as those of the above embodiments.

(Fifth Example) Further, FIG. 13 shows a fifth example. In this example,
Instead of the displacement of the displacer (4), the pressure within the surge volume (18) corresponding to the displacement of the displacer (4) is detected.

That is, in this embodiment, as shown in FIG. 14, the pressure within the surge volume (18) is
Based on the fact that it corresponds to the displacement of
4) Instead of directly detecting the displacement of
A pressure gauge (37) is provided for detecting the pressure within 18).

The output signal of this pressure gauge (37) is input to a control unit (50), and this control unit (50) controls the high and low pressure control valve unit so that the pressure in the surge volume (18) has ideal pressure change characteristics. The opening/closing timing and opening degree of (20) are controlled by learning.

That is, the memory (m2) of the control unit (50)
) stores an ideal pressure change characteristic within the surge volume (18) that is preset in correspondence to the ideal displacement characteristic in one cycle of the displacer (4). The memory (m2) also stores the control command for the current movement cycle of the displacer (4), and also stores the surge volume (
18) Based on the change in error between the pressure change characteristics in the memory (m2) and the ideal pressure change characteristics in the memory (m2), the control command for the current movement cycle is corrected and stored as the control command for the next movement cycle.

Further, the control section (57) controls the opening/closing timing or opening degree of the valve unit (20) based on the control command for the current movement cycle stored in the memory (m2).

Therefore, in this embodiment, the displacer (4)
With the reciprocating movement of the surge volume (18), the pressure within the surge volume (18) fluctuates as shown in FIG. 14 in response to the displacement. The pressure inside this surge poly neem (18) is measured by the pressure gauge (37).
), and the output signal of this pressure gauge (37) is input to the control unit (50). In the control unit (50), the surge volume (18)
The control command for the movement cycle of the displacer (4) is sequentially modified in accordance with the change in the error between the pressure change characteristics in the internal space and the ideal characteristics stored in the memory (m2).
57) controls the opening/closing timing or opening degree of the valve unit (20). Therefore, the displacer (4
)'s movement before and after cooldown, and its tapping can be suppressed in a stable manner at all times.

Particularly in this case, since the pressure gauge (37) is used as a sensor that indirectly detects the displacement of the displacer (4), there is an advantage that the reliability of the sensor can be improved.

(Sixth Example) FIG. 15 shows a sixth example. In this embodiment, basically, the surge volume (18
), and based on the pressure of this surge volume (18), the orifice valve (16) located in the flow path between the drive chamber (8) and the surge volume (18) is opened. The degree is controlled by learning. Therefore, this embodiment can also provide the same effects as the fifth embodiment.

In each of the above embodiments, the displacer (4) is driven directly by gas pressure, but the present invention is of a type in which a slack piston is inserted into a cylinder so as to be able to reciprocate, and the displacer is driven by the piston. It can also be applied to the expansion machine.

Furthermore, it goes without saying that the present invention can be applied to systems that use refrigerant gases other than helium gas, such as in each of the above-mentioned embodiments.

(Effects of the Invention) As described above, according to the inventions described in claims (1), (21, (3), and (4)), in a gas pressure-driven cryogenic expander, the displacement of the displacer with respect to the cylinder,
Or a valve means or cylinder that detects a pressure change in a surge volume communicating with a drive chamber in the cylinder and switches the supply and discharge of gas to and from the cylinder so that the displacer displacement or pressure change has ideal characteristics set in advance. By learning and controlling the orifice means for adjusting the pressure in the internal drive chamber, even if the movement resistance of the displacer changes due to changes in the gas mass flow rate before and after cool-down of the expander, its displacement characteristics can be maintained. Alternatively, the pressure characteristics within the surge volume can be converged to ideal characteristics that prevent the displacer from colliding with the upper and lower ends of the cylinder each time the displacer repeats its movement cycle, so it is always stable and suppresses tapping of the displacer even before and after cool-down. This makes it possible to reduce abnormal vibrations and noise of the expander.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of the present invention. 2 to 6 show the first embodiment of the present invention, FIG. 2 (another overall configuration diagram), FIG. 3 is a block diagram showing the control system, and FIG. 4 shows the displacement characteristics of the displacer. 5 is a sectional view showing the mounting structure of the displacement meter, and FIG. 6 is an electric circuit diagram showing the operating principle of the displacement meter. FIG. 7 is a diagram corresponding to FIG. Figure 8 is a diagram showing a modified example of the switching valve. Figures 9 to 12 show the third embodiment, tIS9 is a diagram corresponding to Figure 2, and Figures 10 to 12 are diagrams of the orifice valve. 13 and 1 are cross-sectional views showing specific examples.
FIG. 4 shows the fifth embodiment, FIG. 13 is a diagram corresponding to FIG. 2, and FIG. 14 is a characteristic diagram showing the characteristics of the pressure change in the surge volume and the displacement of the displacer. FIG. 15 is a diagram corresponding to FIG. 2 showing the sixth embodiment. FIG. 16 is a characteristic diagram showing the displacement characteristics of a conventional displacer. (1)...Expansion machine, (2)...Cylinder, (4)...
... Displacer, (8) ... Drive chamber, (9),
(10)...expansion chamber, (16), (16')...
Orifice valve (pressure adjustment means), (18)...Surge volume, (20)...High and low pressure control valve Uni-Soto (valve means), (23)...Displacement meter (displacer displacement detection means), ( 28), (28')...
Switching valve (pressure adjustment means), (37)...pressure gauge (
pressure detection means), (50)...control unit, (rr++)...memory (first storage means), (
m2)...Memory (second storage means), (57)...
-Control unit (control means). Figure 10 Figure 10 Clearance Figure 14 Time

Claims (4)

[Claims] (1) A sealed cylinder (2), and a displacer (4) fitted in the cylinder (2) so as to be able to reciprocate and define expansion chambers (9) and (10) in the inner space of the cylinder (2).
) and a valve means (20) for switching the supply and discharge of refrigerant gas such as helium discharged from the compressor to and from the expansion chambers (9) and (10). Displacer displacement detecting the displacement of the displacer (4) in a cryogenic expander that reciprocates and generates cryogenic level cold by expansion of refrigerant gas in the expansion chambers (9) and (10). a detection means (23), a first storage means (m_1) that stores ideal displacement characteristics set in advance in the movement cycle of the displacer (4), and a control command for the current movement cycle and control for the next movement cycle. The commands are sequentially stored, and the displacement characteristics of the displacer (4) detected by the displacer displacement detection means (23) are compared with the ideal displacement characteristics of the first storage means (m_1), and the change in the error is detected. A second storage means (m_2) corrects the control command for the current movement cycle based on the control command for the next movement cycle, and operates the valve means (20) based on the control command for the current movement cycle. A control device for a cryogenic expander, characterized in that it is provided with a control means (57) for controlling. (2) A sealed cylinder (2), which is fitted in the cylinder (2) so as to be able to reciprocate, and which expands the space inside the cylinder (2) into expansion chambers (9), (10) and an intermediate pressure chamber (8). a displacer (4) that is partitioned into a displacer (4), pressure adjusting means (16), (28) for adjusting the pressure of the drive chamber (8), and an expansion chamber (9) for the refrigerant gas such as helium discharged from the compressor. ),
Valve means (20) for switching supply and discharge to (10)
The displacer (4) is reciprocated in response to switching of the valve means (20), and the refrigerant gas is expanded into the expansion chamber (9).
, (10) in which the displacer (4) generates cryogenic level cold by expansion.
Displacer displacement detection means (23) for detecting displacement of
and a first storage means (m_1) for storing preset ideal displacement characteristics in the movement cycle of the displacer (4), and for sequentially storing control commands for the current movement cycle and control commands for the next movement cycle. , and the displacement characteristics of the displacer (4) detected by the displacer displacement detection means (23) are stored in the first storage means (m).
The second storage means (m_2) corrects the control command for the current movement cycle based on the change in the error by comparing it with the ideal displacement characteristic of m_1), and uses the control command for the next movement cycle as the control command for the next movement cycle.
), and a control means (57) for controlling the operation of the pressure adjustment means (16) and (28) based on a control command for the current movement cycle. (3) A sealed cylinder (2), fitted in the cylinder (2) so as to be able to reciprocate, and converting the inner space of the cylinder (2) into the expansion chambers (9), (10) and the drive chamber (8). A displacer (4) forming a partition, a surge volume (18) communicating with the drive chamber (8), and supply and discharge of refrigerant gas such as helium discharged from the compressor to and from the expansion chambers (9) and (10). The displacer (4) is reciprocated as the valve means (20) is switched, and the refrigerant gas expands in the expansion chambers (9) and (10) to reach a cryogenic level. In a cryogenic expander that generates cold, pressure detection means (37) detects the actual pressure in the surge volume (18), and pressure detection means (37) detects the actual pressure in the surge volume (18) during the movement cycle of the displacer (4). A first storage means (m_1) that stores the set ideal pressure change characteristics, a control command for the current movement cycle and a control command for the next movement cycle, and the pressure detection means (37) The detected pressure change characteristics in the surge volume (18) are compared with the ideal pressure change characteristics in the first storage means (m_1), and the control command for the current movement cycle is corrected based on the change in error. and a second storage means (m_2) for storing a control command for the next movement cycle, and a control means (57) for controlling the operation of the valve means (20) based on the control command for the current movement cycle. A control device for a cryogenic expansion machine characterized by: (4) A sealed cylinder (2), fitted in the cylinder (2) so as to be able to reciprocate, and converting the inner space of the cylinder (2) into the expansion chambers (9), (10) and the drive chamber (8). A displacer (4) forming a partition, a surge volume (18) communicating with the drive chamber (8), pressure adjustment means (16), (28) for adjusting the pressure of the drive chamber (8), and a compressor. The expansion chamber (9) for refrigerant gas such as helium discharged from the
, (10) valve means (20
), and the displacer (4) is reciprocated in response to switching of the valve means (20) to expand the refrigerant gas expansion chamber (9).
), (10) In a cryogenic expander that generates cryogenic level cold by expansion, the surge volume (
18) Pressure detection means (37) for detecting the actual pressure within
and a first storage means (m_1) that stores ideal pressure change characteristics set in advance in the surge volume (18) during the movement cycle of the displacer (4), and a control command for the current movement cycle and the next time. sequentially stores the control commands for the movement cycles of the pressure detecting means (3).
7) The pressure change characteristics in the surge volume (18) detected by the above are compared with the ideal pressure change characteristics in the first storage means (m_1), and the current movement cycle is controlled based on the change in error. A second storage means (m_2) that corrects the command and uses it as a control command for the next movement cycle, and control that operates and controls the pressure adjustment means (16) and (28) based on the control command for the current movement cycle. 1. A control device for a cryogenic expander, comprising means (57).