JPH04244560A - Freezer device - Google Patents

Abstract

PURPOSE:To provide an anti-acceleration characteristic when a space rocket is launched by a method wherein each of movable coils in a driving linear motor for a compression piston and an expansion piston of a freezer under an inverse Stirling cycle is short circuited. CONSTITUTION:Means 33 is provided for short circuiting each of a movable coil 9 of a driving linear motor 10 for a compression piston 1 and a movable coil 17 for a driving linear motor 18 for an expansion piston 3. This short circuiting means 33 is operated such that when a space rocket is launched, each of driving motors 10 and 18 is separated from each of difference signal amplifiers 15 and 21, the movable coils 9 and 17 are short circuited and after completion of the launching, the short circuiting means is returned back to its original position, the movable coils 9 and 17 are released from their short circuited states and then a normal operation is started. Accordingly, the movements of the pistons 1 and 3 are restricted with an electromagnetic force caused by the short-circuit of the movable coils 9 and 17 and then influence caused by the high acceleration during a launching can be eliminated.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigeration system using a reverse Stirling cycle used to generate extremely low temperatures, and more particularly to a vibration isolation mechanism thereof.

0002

[Prior Art] Refrigeration equipment that utilizes a reverse Stirling cycle is known as a cryogenic refrigeration system that uses gases that are difficult to liquefy at low temperatures, such as helium, hydrogen, and nitrogen, as refrigerants. Shown in Figure 3. This refrigeration system includes a compression cylinder 2 having a built-in compression piston 1 and an expansion cylinder 4 having a built-in expansion piston 3, and a cooling part 5 is formed at the tip of the expansion cylinder 4. Further, inside the expansion piston 3, a regenerator 6 made of stainless steel wire mesh or the like is provided. The compression cylinder 2 and the expansion cylinder 4 are communicated through a communication pipe 7 via a heat exchanger 13 and a regenerator 6. The compression piston 1 is coupled to a linear motor 10 composed of a permanent magnet 8 having an annular gap and a moving coil 9 capable of linear movement in the axial direction within the gap.The linear motor 10 further includes a compression piston. A position detector 11, for example a differential transformer, is coupled to detect the position of one. The movable parts of the compression piston 1, movable coil 9, and position detector 11 are supported by a support spring 12. The compression piston 1 is driven by the linear motor 10 by a servo system comprising the position detector 11, a comparison circuit 14 serving as signal comparison means, and a deviation signal amplifier 15. The expansion piston 3 is also driven by a permanent magnet 16.
and a moving coil 17.
This is performed by a servo system composed of a position detector 19, a signal comparison circuit 20, and a deviation signal amplifier 21. The drive signal 22 for the expansion piston 3 is a sine wave given by a sine wave generator 23, and the drive signal 24 for the compression piston 1 is the drive signal 22 given a predetermined phase delay by a delay circuit 25. As a result, the compression piston 1 reciprocates while always maintaining a constant phase difference with respect to the reciprocating movement of the expansion piston 3.

When the compression piston 1 and the expansion piston 3 reciprocate while maintaining a constant phase difference, the refrigerant gas compressed in the compression cylinder 2 repeatedly expands at the tip of the expansion cylinder 4 and returns to the cooling unit 5 at a low temperature. occurs. The low temperature generated in the cooling unit 5 each time it expands is stored in the regenerator 6, and the temperature of the cooling unit 5 becomes a constant low temperature.

0004

[Problem to be Solved by the Invention] When the above-mentioned refrigeration system is mounted on a space rocket, for example, the compression piston or the expansion piston may exceed its permissible range, that is, the stroke of the piston due to the large acceleration applied during launch. There is a high possibility that the cylinder head will be hit and damaged. To this end, in order to counteract the acceleration and suppress the vibrations of these pistons,
Methods such as increasing the spring constant of these vibration systems or the pressure of the refrigerant gas acting on the piston can be considered, but the structural specifications of the refrigeration system will change significantly, resulting in an increase in the weight of the system, an increase in input power, etc. As a result, the performance required of the refrigeration system cannot be satisfied.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a refrigeration system that can withstand large accelerations applied during launch when the refrigeration system is mounted on, for example, a space rocket.

[0006]

[Means for Solving the Problems] In order to achieve the above object, a compression cylinder and an expansion cylinder in which a cooling section is formed are connected through a heat exchanger and a regenerator, and each of them is filled with refrigerant gas. By periodically reciprocating the compression piston and expansion piston built into the cylinder with a mutual phase difference, the high-temperature refrigerant gas compressed in the compression cylinder is used for heat radiation and cold storage in the heat exchanger. This is a refrigeration system using a reverse star-linda cycle in which the material is cooled in a container, transferred to a low-temperature expansion cylinder, expanded in the expansion cylinder, lowered to the cooling temperature, and then returned to the compression cylinder through the same path. The compression piston and the expansion piston are each given a phase difference to each other by a linear motor composed of a magnetic field formed in an air gap and a moving coil capable of linear movement in the axial direction within this air gap. In a refrigeration system that reciprocates, means is provided for short-circuiting the moving coil of the linear motor for driving the compression piston and the moving coil of the linear motor for driving the expansion piston.

[0007]

[Operation] In the refrigeration system of the present invention, a means is provided to short-circuit the moving coils of the linear motors for driving the compression piston or the expansion piston. Therefore, when the compression piston or expansion piston starts to move due to the acceleration applied at this time, the moving coil of the linear motor connected to them moves within the magnetic field of the air gap, and as a result, the short-circuited moving coil receives a short-circuit current. flows. The electromagnetic force generated by this short circuit current and the magnetic field of the air gap acts to hinder the movement of the moving coil.
The movement of the compression or expansion piston coupled to the moving coil is constrained and can withstand large accelerations.

[0008]

[Embodiment] FIG. 1 is a system diagram including a partially sectional structure showing the configuration of an embodiment of the refrigeration system of the present invention.The difference from the conventional refrigeration system shown in FIG. A means 33 is provided for short-circuiting the moving coil 9 of the linear motor 10 for driving the expansion piston 3 and the moving coil 17 of the linear motor 18 for driving the expansion piston 3. This short circuit means 33
When launching a space rocket, the linear motor 10 for driving the compression piston 1 and the linear motor 18 for driving the expansion piston 3 are connected to the respective deviation signal amplifiers 15 and 21.
The moving coils 9 and 17 of these linear motors 10 and 18 are short-circuited. When the launch of the space rocket is completed, the shorting means 33 is returned to its original state, the movable coils 9 and 17 are released from the short circuit, and are connected to the respective deviation signal amplifiers 15 to enable normal operation.

FIG. 2 is a block diagram modeling the vibration system of the compression piston 1 or the expansion piston 3 to explain the vibration damping effect of the present invention.The compression cylinder 1 will be described below, but the same applies to the expansion piston 3. It is. In FIG. 2, the movable mass of the compression piston 1, more precisely, the movable mass of the compression piston, the movable coil 9 coupled thereto, the movable parts of the position detector 11, etc. is Mp, and the spring constant of these support springs 12 is Kp. The force exerted by the refrigerant gas on the compression piston 1 is assumed to be proportional to the displacement of the compression piston 1, and its proportionality constant is defined as a gas constant Cy. moreover,
There is a viscous force proportional to the speed of the compression piston 1, and this is defined as the viscosity coefficient Cv. The equation of motion derived from this vibration system model is expressed as the following equation.

0010

[Math 1]

Here, t is time, y(t) is the axial displacement of the compression piston with respect to time, and A(t) indicates the initial displacement. By solving this equation, we can find out the movement of the compression piston. According to calculation results, when the acceleration is more than 10 G, the compression piston is moved more than 30 millimeters, but by using the vibration isolation mechanism of the present invention, this can be suppressed to a few millimeters, making it possible to keep the movement of the compression piston within the normal stroke. becomes possible.

[0012] Although the above explanation has been made regarding an example in which the device is mounted on a space rocket, it can be applied to all applications where similar acceleration is applied.

[0013]

According to the present invention, a means is provided for short-circuiting the moving coils of the linear motors for driving the compression piston or the expansion piston, so that the short-circuit is performed during space rocket launch, and the electromagnetic force generated by this short-circuit is reduced. Since the movement of the compression piston or the expansion piston was suppressed by force, the movement of the compression piston was suppressed to a few millimeters within the normal stroke of the compression piston against the large acceleration of more than 10 G applied during launch. It has no effect on the performance of the refrigeration equipment and is extremely practical.

[Brief explanation of the drawing]

FIG. 1 is a system diagram including a partially cross-sectional structure showing the configuration of an embodiment of the refrigeration system of the present invention.

[Fig. 2] A configuration diagram modeling the vibration system of a compression piston or an expansion piston to explain the vibration isolation effect of the refrigeration system of the present invention shown in Fig. 1.

[Figure 3] System diagram including a partial cross-sectional structure showing an example of the configuration of a conventional refrigeration system

[Explanation of symbols]

1 Compression piston 2 Compression cylinder 3 Expansion piston 4 Expansion cylinder 5 Cooling section 6 Regenerator 7 Communication tube 8 Permanent magnet 9 Moving coil 10 Linear motor (for driving the compression piston) 1
1 Position detector (for compression piston) 13
Heat exchanger 14 Signal comparison circuit (compression piston drive system) 1
5 Deviation signal amplifier (compression piston drive system) 1
6 Permanent magnet 17 Moving coil 18 Linear motor (for driving the expansion piston) 1
9 Position detector (for expansion piston) 20
Signal comparison circuit (of expansion piston drive system) 21
Deviation signal amplifier (of expansion piston drive system) 23
Sine wave generator (expansion piston drive signal) 25
Delay circuit 33 short circuit means

Claims (3)

[Claims] Claim 1: A compression cylinder and an expansion cylinder in which a cooling section is formed are connected through a heat exchanger and a regenerator, and a compression piston and an expansion piston built in each cylinder filled with refrigerant gas are connected to each other through a heat exchanger and a regenerator. By periodically reciprocating with a mutual phase difference, the high-temperature refrigerant gas compressed in the compression cylinder is transferred to the low-temperature expansion cylinder through heat radiation in the heat exchanger and cooling in the regenerator. This is a refrigeration system using a reverse Stirling cycle, in which the air is transferred, expanded in an expansion cylinder, lowered to a cooling temperature, and then returned to the compression cylinder through the same path, with the compression piston and expansion piston each placed in a cavity. In the refrigeration system, the compressor piston is driven by a linear motor that is configured of a magnetic field that is formed and a moving coil that can move linearly in the axial direction within this gap, and that reciprocates periodically with a mutual phase difference. A refrigeration system comprising means for short-circuiting a moving coil of a linear motor for driving the expansion piston and a moving coil of the linear motor for driving the expansion piston. 2. The refrigeration system according to claim 1, wherein the compression piston drive linear motor is coupled to a compression piston position detector, the expansion piston drive linear motor is coupled to an expansion piston position detector, and the expansion piston drive linear motor is coupled to an expansion piston position detector. is driven by a deviation signal between a separately given drive signal and the position signal of the expansion piston position detector, and the compression piston is driven by a drive signal with a predetermined phase delay from the expansion piston drive signal and the compression piston position. A refrigeration system characterized in that the refrigeration is performed using a deviation signal from a position signal of a detector. 3. A refrigeration system according to claim 1 or 2, characterized in that the refrigeration system is used for mounting on a space rocket.