JPH0689960B2 - Chiller - Google Patents

Description

TECHNICAL FIELD The present invention relates to a free displacer type gas cooler used for cooling an infrared device such as a free displacer type Stirling cooler.

[Prior Art] FIG. 7 is a sectional side view showing a schematic configuration of a conventional free displacer type gas cooler disclosed in, for example, Japanese Patent Publication No. 54-28980. In the figure, reference numeral 1 denotes a cylinder, and a piston 2 reciprocates inside the cylinder 1. A cold finger 3 includes a free displacer 4 that reciprocates according to pressure fluctuations of the working gas, and a lower portion thereof communicates with the cylinder 1 by a communication pipe 5. Working surface 4b on top of free displacer 4
Delimits an expansion space 6, which is located above the working surface 2a of the piston 2 and the free displacer 4.
Together with the compression space 7 between the lower working surfaces 4a of the. The heat accumulator 8 provided in the free displacer 4 can communicate with the working gas below through the central hole 9 and can communicate with the upper working gas through the central hole 10 and the radial flow duct 11. The machine also includes a freezer 12 as a heat exchanger for heat exchange between the expanded cold working gas and the object to be cooled.

Seals 13 and 14 are provided between the piston 2 and the wall of the cylinder 1, and seals 15 and 16 are provided between the free displacer 4 and the cold finger 3. The piston 2 is also provided on its underside with a lightweight sleeve 17 made of a non-magnetic and non-magnetizable material such as hard paper or aluminum. A coil 18 is formed by winding a conductor around the sleeve 17, and the coil 18 is connected to lead wires 19 and 20 which pass through the wall of the cylinder 1, and these lead wires 19 and 20 are electrically connected to the outside of the cylinder 1 respectively. It is connected to 21,22. The coil 18 can reciprocate in the annular gap 23 in the axial direction of the piston 2, and this annular gap
Within 23 there is an armature field. The lines of force of this armature magnetic field extend in a radial direction transverse to the moving direction of the coil 18. In this case, the permanent magnetic field is obtained using an annular permanent magnet 24 having upper and lower magnetic poles, a soft iron annular disc 25, a soft iron cylinder 26 and a soft iron circular disc 27. The annular permanent magnet 24, the soft iron annular disk 25, the soft iron cylinder 26, and the soft iron circular disk 27 integrally form a closed magnetic circuit, that is, a closed magnetic force line circuit. Sleeve 17 and coil 1 described above
8, the lead wires 19 and 20, the annular gap 23, the annular permanent magnet 24, the soft iron annular disc 25, the soft iron cylinder 26, and the soft iron circular disc 27 together constitute a linear motor 28 for driving the piston. Further, the piston 2 and the free displacer 4 are reciprocally engaged in the cylinder 1 and the cold finger 3 via the elastic member 29 for piston and the elastic member 30 for displacer, respectively. It defines a fixed position and a neutral position during operation.

Next, the operation of the above-mentioned conventional free displacer type gas cooler will be described. If you connect an AC power supply (not shown) with a resonance frequency of the system to the electric terminals 21 and 22,
The coil under the influence of a radial permanent magnetic field in the annular gap 23.
A Lorentz force acts on 18 in the axial direction, and as a result, the system including the assembly including the piston 2, the sleeve 17, and the coil 18 and the elastic member 29 for the piston is in a resonance state, and the assembly vibrates in the axial direction. To do. The vibration of the piston 2 is generated by the compression space 7, the expansion space 6, the communication pipe 5, the regenerator 8, the central hole 9, the central hole 10,
The working gas enclosed in the working space composed of the radial circulation duct 11 and the freezer 12 is periodically subjected to a pressure change, and a change in the flow rate of the gas passing through the regenerator 8 causes the free displacer 4 to move in a periodic axial direction. Produces alternating vibration force. In this way, the free displacer 4 including the heat accumulator 8 reciprocates axially in the cold finger 3 at the same frequency as the piston 2 but at different phases.

When the piston 2 and the free displacer 4 move while maintaining an appropriate phase difference, the working gas enclosed in the working space constitutes a thermodynamic cycle known as the "reverse Stirling cycle", mainly the expansion space 6 and Generates cold heat in the freezer 12. Regarding the above "reverse Stirling cycle" and the principle of cold heat generation, refer to the document "Cryocool".
ers ”(G. Walker, Plenum Press, New York, 1983, PP ・ 177
~ 123). The principle will be briefly described below.

The heat of compression of the gas compressed in the compression space 7 by the piston 2 is cooled while flowing through the communication pipe 5, and flows into the center hole 9 and the heat accumulator 8. In the heat accumulator 8, it is pre-cooled by the cold heat stored before the half cycle, and the working gas is further cooled by the central hole 10,
It enters the expansion space 6 through the radial flow duct 11 and the freezer 12. Then, when most of the working gas enters the expansion space 6, expansion starts and cold heat is generated in the expansion space 6. The working gas then returns through the flow path and enters the compression space 7 while releasing cold heat to the heat storage device 8 in the reverse order. At this time, heat is taken from the outside in the fliriza 12 to cool the outside. Then, when most of the working gas returns to the inside of the compression space 7, the compression starts again and the next cycle starts. By the above process, the above "reverse Stirling cycle" is completed and cold heat is generated.

[Problems to be Solved by the Invention] Since the above-described conventional free displacer-type gas cooler is configured as described above, when the cooling temperature of the low temperature portion including the expansion space 6 and the freezer 12 changes during operation. The flow rate of the gas passing through the heat storage unit 8 changes, and the driving force of the free displacer 4, and consequently the reciprocating stroke of the free displacer 4, changes accordingly, so that the temperature of the low temperature portion changes greatly at the time of startup. In this case, there is a problem that the free displacer 4 collides with the cold finger 3 to generate vibration and noise. In addition, when a sufficient reciprocating stroke of the free displacer 4 is expected in advance, there is a problem that the dead volume of the working space increases and the efficiency of the cooler and the like decreases.

The present invention has been made to solve such problems, and it is possible to obtain a highly reliable and highly reliable cooler that operates stably without generating vibration or noise with respect to temperature changes in a low temperature part. With the goal.

[Means for Solving the Problems] A cooler according to the present invention is a cooled finger which is in thermal contact with a low temperature portion of a cold finger including an expansion space or a freezer or this low temperature portion and is cooled by the low temperature portion. It is provided with a control system that detects the cooling temperature of the body and adjusts the driving voltage or driving current applied to the motor so as to be within the range of the voltage or current given in advance as a function of the cooling temperature.

[Operation] In the cooler of the present invention, the drive voltage or drive current applied to the motor is based on the cooling temperature of the cold finger detected by the temperature sensor or the cooled object cooled by the low temperature section. Is regulated by the controller to be a voltage or current within a stable operating range given in advance as a function of the cooling temperature, which limits the reciprocating stroke of the free displacer.

[Embodiment] FIG. 1 is a cross-sectional side view showing a schematic configuration of a cooler according to an embodiment of the present invention. The same or corresponding portions as those in FIG. The description is omitted.
In the figure, 31 is a temperature sensor installed in thermal contact with the low temperature part of the cold finger 3, 32 is a cooling temperature signal transmission path for transmitting the cooling temperature signal detected by the temperature sensor 31 to the controller 33, and 34 is The motor drive signal transmission line for transmitting the motor drive signal output from the controller 33 to the power amplifier 35, 36 and 37 are power cables for inputting the output of the power amplifier 35 to the linear motor 28, and each of them is an electric terminal 21. , 22 are connected.

2 is an explanatory diagram showing signal processing of a controller in the cooling machine of FIG. 1, FIG. 3 is a schematic configuration diagram showing a main part for explaining the operation of the cooling machine of FIG. 1, and FIG. FIGS. 3A and 3B are explanatory views comparing the operation of the cooling machine of FIG. 1 and the cooling machine of the conventional example.

Next, the operation of the cooler according to the embodiment of the present invention described above will be described. During the operation of the cooler shown in FIG. 1, the controller 33 supplies the cooling temperature of the low temperature part of the cold finger 3 sent from the temperature sensor 31 via the cooling temperature signal transmission path 32 and the controller 33 beforehand. Cooling temperature −
Calculate the optimum drive voltage from the information on the stable operating voltage range,
It is output to the motor drive signal transmission path 34 as a motor drive signal. The power amplifier 35 proportionally amplifies the power of the motor drive signal and drives the coil 18 connected to the electric terminals 21 and 22 via the power cables 36 and 37, respectively.

Here, the process of signal processing in the controller 33 will be described in more detail with reference to FIG. Cooling temperature T _c transmitted from the temperature sensor 31 is compared with the target temperature T _R at the temperature control unit 38 in the controller 33, the deviation (△ T = T _R -
The control voltage V _o according to T _c ) is output (for example, by a PID control circuit or the like). On the other hand, the cooling temperature _Tc is also input to the drive voltage control unit 39 in the controller 33, and the control output from the temperature control unit 38 is _calculated from the relational expression of the cooling temperature _Tc and the stable operation range voltage V given in advance. It is determined whether or not the voltage V _o is within the stable operation range voltage V (in this embodiment, the case where the upper limit value is set is shown). If it is within the stable operation range voltage V, the control voltage V _{o is determined.} Directly, and in the case other than the stable operation range voltage V, an appropriate value within the stable operation range voltage V (V _{max in} this embodiment) is set as the motor drive signal voltage V ₁ from the drive voltage control unit 39. It is output to the stage power amplifier 35. As described above, the power amplifier 35 proportionally amplifies the motor drive signal voltage V ₁ to drive the drive voltage V _S
Is applied to the linear motor 28 to drive the cooler.

Next, the relationship between the cooling temperature T _c and the stable operation range voltage V will be described with reference to FIGS. 3 and 4 (a) and (b).
In the free displacer type gas cooler as in the present embodiment, as described above, the driving force of the free displacer 4 is mainly given by the pressure loss of the working gas flowing through the regenerator 8. That is, when the temperature of the expansion space 6 decreases and the mass flow rate of the working gas flowing through the heat storage device 8 increases,
Along with this, the driving force of the free displacer 4 increases, and the reciprocating stroke of the free displacer 4 also increases. Thus, the expansion space 6 at the time of starting, etc.
When the temperature of the free displacer 4 is large and drops, the reciprocating stroke of the free displacer 4 sometimes becomes excessive, and this free displacer 4 may cause an obstacle such as a collision with the cold finger 3 (Fig. 4 (a)). reference).

As is clear from the above, in order to keep the reciprocating stroke of the free displacer 4 stable and prevent collisions, the mass flow rate of the gas flowing through the regenerator 8 should be kept within a certain range regardless of the cooling temperature. Just stabilize it. For this reason, in the present embodiment, the maximum value of the drive voltage or drive current input to the linear motor 28 is adjusted according to the cooling temperature of the low temperature portion such as the expansion space 6 by the process shown in FIG. By suppressing the pressure fluctuation range of the working gas, the gas flow rate and eventually the reciprocating stroke of the free displacer 4 are stabilized (see FIG. 4 (b)).

In the cooler which is one embodiment of the present invention shown in FIG. 1 described above, the mechanism in which cold heat is generated in the expansion space 6 when an AC voltage is applied to the electric terminals 21 and 22 is the same as that of the conventional one described above. Since it has already been described in the section of the operation description of the example, detailed description thereof will be omitted here.

In the above-described embodiment, the case where the cold finger 3 and the cylinder 1 are mechanically strongly coupled to each other is described as an integral type cooling machine. However, as in another embodiment of the present invention shown in FIG. It may be a separate type cooling machine in which the finger 3 and the cylinder 1 are separated from each other through the communication pipe 5, and the same effect as that of the above-described embodiment is obtained.

In the above embodiment, a mechanical spring is used as the displacer elastic member 30, but the gas spring chamber 40 may be replaced as in the other embodiment of the present invention shown in FIG. The same effect as that of the above embodiment is obtained.
However, in this case, the driving force of the free displacer 4 is obtained not only by the pressure loss of the gas passing through the heat storage device 8 but also by the pressure difference between the gas spring chamber 40 and the working space, so that the motor driving signal voltage V ₁ The stable operation range is different from that shown in FIGS. 2 and 3 (b).

[Effects of the Invention] As described above, according to the present invention, in the cooling machine, the free displacer is configured to always move within the range of the reciprocating stroke of a certain value or less during operation by the controller of the cooling machine. Therefore, the free displacer does not collide with the cold fingers even when the cooling temperature for cooling the object to be cooled is large, and a highly reliable cooling machine with less vibration and noise is obtained, and the dead volume of the working space is reduced. Since it is possible to reduce the amount of heat, it is possible to achieve an excellent effect such as enabling highly efficient operation of this cooler.

[Brief description of drawings]

FIG. 1 is a sectional side view showing a schematic configuration of a cooling machine according to an embodiment of the present invention, FIG. 2 is an explanatory view showing signal processing of a controller in the cooling machine of FIG. 1, and FIG. FIG. 4 is a schematic configuration diagram showing a main part for explaining the operation of the cooling machine shown in FIG. 4, and FIGS. 4 (a) and 4 (b) are explanations for comparing the operation of the cooling machine of FIG. FIG. 5, FIG. 5 and FIG. 6 are sectional side views showing a schematic configuration of a cooling machine according to another embodiment of the present invention, and FIG. 7 is a sectional side view showing a schematic configuration of a conventional free displacer type gas cooling machine. Is. In the figure, 1 ... Cylinder, 2 ... Piston, 2a, 4a,
4b ... Operating surface, 3 ... Cold finger, 4 ... Free displacer, 5 ... Communication pipe, 6 ... Expansion space, 7
...... Compressed space, 8 …… Heat storage device, 9,10 …… Center hole, 11 ……
Radial flow ducts, 12 …… Freezers, 13,14,15,16…
… Seal, 17 …… Sleeve, 18 …… Coil, 19,20 ……
Lead wire, 21,22 ... electrical terminal, 23 ... annular gap, 24 ...
… Annular permanent magnet, 25 …… Soft iron annular disk, 26 …… Soft iron cylinder, 27 …… Soft iron circular disk, 28 …… Linear motor, 29 …… Elastic member for piston, 30 …… Elastic member for displacer, 31 …… Temperature sensor, 32 ... Cooling temperature signal transmission line, 33 ... Controller, 34 ... Motor drive signal transmission line, 35
...... Power amplifier, 36,37 …… Power cable, 38 …… Temperature control unit, 39 …… Driving voltage control unit, 40 …… Gas spring chamber. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A piston driven by a motor, and a cylinder fitted to the piston and surrounding the piston and the motor, wherein the piston reciprocates in the cylinder to generate a pressure fluctuation in a working gas. And a free displacer driven by the pressure fluctuation,
It is composed of a cold finger fitted to the free displacer and containing the free displacer, and an elastic member for the displacer that fits the free displacer to the cold finger so that the free displacer can reciprocate. On the other hand, by reciprocating in the cold finger with a proper phase difference, the expansion space for generating cold heat in the expansion space and the freezer in the cold finger, the cylinder and the cold finger are communicated with each other, A cooling machine having a communication pipe for guiding pressure fluctuations in a cylinder into the cold finger, wherein the expansion space of the cold finger, the freezer, or the freezer is thermally contacted and cooled by the freezer. A temperature sensor that detects the cooling temperature of the body, A controller for receiving the input of the cooling temperature and adjusting the effective drive voltage or drive current applied to the motor so as to be within the range of the voltage or current given in advance as a function of the cooling temperature. A chiller characterized by having.