JPH04209978A - Linear motor compressor - Google Patents

Abstract

PURPOSE:To change a form of extending/contracting a spring and to eliminate its buckling phenomenon so as to prevent the spring from its fatigue failure by using one of two springs as a compression spring and the other as a tension spring, for resiliently supporting a piston of a compressor. CONSTITUTION:In a compressor 1 for use of a Stirling refrigerating machine, a pair of right/left pistons 7, 7 are fitted into a cylinder 6 to generate a gas pressure of predetermined period in a compression chamber 11 by reciprocating each piston 7, by synchronously conducting AC power of predetermined frequency corresponding to a natural frequency, determined by mass of each piston 7 and a spring constant of a spring means 17, in a coil 16 of each linear motor 13. The spring means 17 is formed by providing inner/outer side coil springs 18, 19 concentrically mounted, and the inner/outer side coil springs 18, 19 are constituted respectively as tension and compression springs by setting the inner side coil spring 18 so as to always extend from the natural length and the outer side coil spring 19 so as to always contract from the natural length.

Description

[Detailed description of the invention]

[00011

[Field of Industrial Application] The present invention relates to a near motor compressor for compressing refrigerant supplied to an expander in a Stirling refrigerator, and more particularly to an elastic support structure for a movable part driven by a linear motor. [0002] Conventionally, a free displacer type Stirling refrigerator has been known as a type of small refrigerator that generates cryogenic cold. As an example of this refrigerator, for example, rRefrigerator for
Cryogenic 5 sensors J (NASA
Conference Publication 2
287). This refrigerator is
As shown in FIG. 3, it is configured by a combination of a compressor (a) that compresses refrigerant gas and an expander (k) that expands the refrigerant gas discharged from the compressor (a). The above compressor (a
) includes, for example, a sealed casing (b), a cylinder (C) formed in the casing (b), and a space inside the cylinder (C) that is fitted in the cylinder (C) so as to be reciprocally movable. The piston (e) defines a compression chamber (d), and a linear motor (f) serves as a drive source for reciprocating the piston (e). This linear motor (f) has an annular permanent magnet (g) placed around the cylinder (C).
The magnet (g) generates a magnetic field in a cylindrical gap concentric with the center of the cylinder (C). A substantially inverted cup-shaped bobbin (h) integrally fixed to the piston (e) at the center is arranged in the gap so as to be able to reciprocate, and a drive coil (i) is disposed on the outer periphery of the bobbin (h). is wrapped around it. Further, between the outer bottom surface of the bobbin (h) (the side opposite to the piston (e)) and the inner bottom surface of the casing (b), there is a piston consisting of a coil spring for elastically supporting the piston (e) so as to be able to reciprocate. A spring (j) is installed, and a conductor (il) is connected to the drive coil (i).
By applying an alternating current at a predetermined frequency through (it), the coil (i) and bobbin (h) are driven by the action of the magnetic field passing through the gap, and the piston (e) is reciprocated within the cylinder (C). , gas pressure is generated at a predetermined period in the compression chamber (d). [0003] On the other hand, the expander (k) has a cylindrical cylinder (1), and a cylinder (
1) A free displacer (0) that divides the inner space into an expansion chamber (m) and a working chamber (n) is fitted so as to be able to reciprocate. This displacer (0) is filled with a metal regenerator (OL) (regenerative heat exchanger), and the regenerator (01) is communicated with the expansion chamber (m) and the working chamber (n). Communication holes (o2) and (o3) are opened. Further, a displacer spring (p) made of a coil spring that elastically supports the displacer (0) in a reciprocating manner is disposed within the working chamber (n). is connected to the compression chamber (d) of the compressor (a) via the coupling pipe (q),
The displacer (
By reciprocating the cylinder (0) and expanding the refrigerant gas in the expansion chamber (m), cold is generated in the cold head at the tip of the cylinder (1). [0004]

[Problems to be Solved by the Invention] In the above compressor (a), the mass of the movable parts including the piston (e) and the mass of the piston spring (j) and the air spring caused by the gas in the compression chamber (d), etc. The natural frequency determined by the spring constant is determined by the power frequency (for example, 50Hz) to the linear motor (f) and -
This causes the piston (e) to resonate, and this resonance phenomenon is used to drive the piston (e). Therefore, when mass adjustment of the movable part is restricted, the resonance frequencies are matched by appropriately setting the spring constant of the piston spring (j). In this case, since the natural frequency is high, in order to prevent the piston spring (j) from fatigue failure, it is necessary to increase the spring strength. However, as the length of the spring increases, wasted space increases and the compressor becomes larger, making it impossible to effectively perform its original function. [0005] Therefore, in order to solve these problems, the present inventors constructed a spring that supports the piston with two compression springs arranged concentrically, and when the piston moves forward, one of the springs Also, when double-acting, the other spring is compressed and deformed. [0006] Among the two compression springs arranged concentrically, the inner spring has a smaller diameter, so that a buckling phenomenon occurs when the spring is compressed and deformed. This buckling may cause the spring to come into contact with surrounding parts, leading to fatigue failure, which is not a good solution. [00071] In view of these points, the present invention has been made by further pushing forward the idea of elastically supporting the movable part of a linear motor compressor on one side with two springs as described above. The object is to eliminate the buckling phenomenon by changing the expansion and contraction form of the spring, thereby making the spring more compact and preventing its fatigue failure. [0008]

[Means for Solving the Problems] In order to achieve the above object, in the invention according to claim 1, the piston is elastically supported.
One of the book springs was used as a compression spring, while the other spring was used as a tension spring. [0009] Specifically, as shown in FIG. 1, the present invention includes a cylinder (6) fixed to a fixed body (2), a cylinder fitted into the cylinder (6) so as to be reciprocating, (
6) A piston (which defines a compression chamber (11) in the inner space)
7), a spring means (17) installed between the back surface of the piston (7) and the fixed body (2) and elastically supporting the piston (7) with respect to the fixed body (2); ) has a magnet (15) fixed to the piston (7) and a coil (16) connected to the piston (7). 13) and a near-motor compressor, the spring means (17) is connected to the back surface of the piston (7) and the fixed body (
2) Two coil springs (
18), (19) to none, both coil springs (18)
. (19) One of the springs is a tension spring, and the other is a compression spring. [00101 In linear motor compressors, the piston is not always a movable part, and there are also configurations in which the piston is fixed and the cylinder side moves instead. In order to cope with this, in the invention of claim 2, two coil springs are installed between the movable cylinder and the fixed body, one of which is a tension spring and the other spring is a compression spring. [0011] Specifically, as shown in FIG. 2, the compressor of the present invention includes a piston (7') fixed to a fixed body (2).
and the piston (7') is fitted inside the piston (7').
'), and has a compression chamber (11
) and a movable cylinder (6') with a bottom that forms a partition, and a movable cylinder (6') that is installed between the bottom surface of the movable cylinder (6') and the fixed body (2), and that connects the movable cylinder (6') to the fixed body (2). a coil (16) connected to a magnet (15) fixed to a fixed body (2) and a movable cylinder (6'); and a near motor (13) for reciprocating the movable cylinder (6') by supplying alternating current of a predetermined frequency to the spring means (1).
7) is two coil springs (18) arranged in parallel with each other between the bottom of the movable cylinder (6') and the fixed body (2).
, (19), and both coil springs (18). (19) One of the springs is a tension spring, and the other is a compression spring. [0012] In the invention of claim 3, two springs (18)
, (19) are arranged concentrically, the inner spring (18) having a smaller spring diameter is configured as a tension spring, and the outer spring (19) is configured as a compression spring. [0013]

[Operation] With the above configuration, in the invention according to claim 1,
The piston (7) is elastically supported by a spring means (17) consisting of two coil springs (18) and (19) arranged between its back surface and the fixed body (2).
). One of the springs (19) is a compression spring that is always contracted from its natural length within the range of the reciprocating stroke of the piston (7), and the other is a tension spring that is similarly extended from its natural length. Due to the operation, the piston (7) moves against the fixed body (2
), the compression spring is compressed and deformed, and conversely, when it moves away from the fixed body (2), the tension spring is elongated. At this time, when the two springs (18) and (19) are both compression springs, by using a tension spring as a spring that is likely to buckle, it is possible to avoid buckling the spring, and therefore, the two springs can be prevented from buckling. The springs (18) and (19) can make the refrigerator more compact and prevent fatigue failure of the springs. [0014] In the invention of claim 2, the linear motor (13
) is reciprocated by the operation of the movable cylinder (6'), and when this movable cylinder (6') approaches the fixed body (2), the compression spring is compressed and deformed, and conversely, the fixed body (2)
The tension spring is elongated and deformed when it is separated from the base. In this case as well, buckling of the spring can be avoided in the same way as above. [0015] In the invention of claim 3, two springs (18)
, (19) are arranged concentrically, and the inner spring (18), which has a smaller diameter and is more likely to buckle, is a tension spring. It will be advantageous. [0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. [00171 FIG. 1 shows a compressor (1) for a Stirling refrigerator according to Embodiment 1 of the present invention. This compressor (1) is a conventionally known free displacer type expander (not shown).
(see Fig. 3) to form a refrigerator. The compressor (1) has a cylindrical casing (2) as a fixed body. This casing (2) consists of a pair of left and right cylindrical casing assemblies (3) with substantially the same configuration.
are arranged concentrically, and both casing assemblies (3
), a disc-shaped center base (4) between the openings in (3)
are sandwiched in an airtight manner, and both casing assemblies (
3), (3) and the center base (4) are made of pure iron. A cylinder insertion hole (5) is formed through the center of the center base (4), and a cylindrical cylinder made of stainless steel as a non-magnetic material with both ends open is inserted into the cylinder insertion hole (5). (6) is inserted and supported. Inside this cylinder (6) are a pair of left and right cylindrical pistons (7) having a bottomed center hole (7a) on the back surface.
, (7) are fitted in a slidable manner, and the area surrounded by the cylinder (6) between the pistons (7) and (7) is defined as a compression chamber (11). A gas passage (12) is formed in the center base (4) that penetrates in the radial direction from the cylinder insertion hole (5) to the outer peripheral surface, and the inner end of the gas passage (12) is located at the center of the cylinder (6). It communicates with the compression chamber (11) through a hole (6a) formed through it, and the outer end of the gas passage (12) is connected to an expander (not shown) via a connecting pipe (not shown). (0018) The left and right pistons (7), (7) are drivingly connected to near motors (13), (13) as drive sources for reciprocating the pistons (7), (7), respectively. Each linear motor (1
3) has a cylindrical member (14) made of pure iron fixed to the center base (4), and this cylindrical member (14) has a predetermined connection between the outer periphery of the cylinder (6) and the inner periphery of the casing assembly (3). They are fitted with a gap. An annular permanent magnet (15) is fixed to the outer periphery of the cylindrical member (14) with a predetermined gap from the inner periphery of the casing assembly (3). 14) The center base (4) and the casing assembly (3) are used as yoke to generate a magnetic field of a predetermined strength in the gap between the magnet (15) and the inner peripheral surface of the casing assembly (3). [0019] Each of the pistons (7) has a flange portion (7b) extending radially outward from the end opposite to the center of the cylinder (6) of the piston (7), and the outer periphery of the flange portion (7b) The cylinder (6) extends concentrically with the piston (7) toward the center of the cylinder (6), and its tip portion is capable of reciprocating in the left-right direction in the gap between the magnet (15) and the inner peripheral surface of the casing assembly (3). Cylindrical bobbins (10
) are connected. On the outer periphery of this bobbin (10),
A recessed coil winding portion (10a) is formed at a position facing the magnet (15), and a coil (16) is wound around this coil winding portion. [00201] Then, an alternating current of a predetermined frequency (for example, 50 Hz) corresponding to the natural frequency determined by the mass of each piston (7) and the spring constant of the spring means (17) described later is applied to both linear motors (13), (13). Coil (16), (
16), both pistons (7
). (7) are reciprocated in mutually opposite directions at the above-mentioned natural frequency to generate gas pressure at a predetermined period in the compression chamber (11). (00211 On the back surface of each piston (7), there is a spring means (17) for elastically supporting the piston (7) against the casing assembly (3) of the casing (2) so that the piston (7) can reciprocate within the cylinder (6). That is, a spring holder outer (20) is attached to the center of the inner bottom surface of each casing assembly (3), while a spring holder outer (20) is installed at the center of the bottom surface of the center hole (7a) of each piston (7). A spring holder inner (22) is screwed to the spring holder outer (20), and one end of an inner coil spring (18) constituting one of the spring means (17) is attached to the holder outer (20), for example. The coil spring (18) is immovably attached by screwing into a helical spring attachment groove formed on the outer periphery, and the other end of this coil spring (18) is similarly immovably attached to the outer periphery of the spring holder inner (22). ] Meanwhile, the above casing assembly (3)
An annular groove (24) centered on the cylinder axis is recessed in the center side surface of the cylinder (6). Further, in the bottom wall of the bobbin (10), an annular groove (25) is formed in a surface facing the casing assembly (3) in correspondence with the annular groove (24). A spring means (
An outer coil spring (19) constituting the other of the springs 17) is installed concentrically with the inner coil spring (18). [0023] In the stroke range in which each piston (7) reciprocates, the inner coil spring (18) is always set to extend from its natural length, while the outer coil spring (19) is set to always contract from its natural length. The inner coil spring (18) is configured as a tension spring, and the outer coil spring (19) is configured as a compression spring. Also, both springs (1
The piston (7) is maintained at the neutral position of the reciprocating stroke by the balance of (8) and (19). [0024] In the figure, (26) beam near motor (1
This is a lead wire that supplies power to the coil (16) in 3). (27) is a cover that covers each casing assembly (3), and a heat radiation fin (27a) is provided on the outer peripheral surface of the cover. (27a), . . . are formed. [00253 Next, the operation of the above embodiment will be explained. [0026] With the start of operation of the refrigerator, an AC power source of a predetermined frequency (50 Hz) is synchronously energized to the coils (16), (16) of both linear motors (13), (13) in the compressor (1). be done. Along with this energization, the magnet (
15). (15) due to the action of the magnetic field generated by the coil (1
6), (16) and pistons (7), (7) reciprocate in opposite directions while respectively expanding and contracting spring means (17), (17), and both pistons (7),
(7) advance and retreat in synchronization with each other within the cylinder (6), the volume of the compression chamber (11) increases and decreases, and the compression chamber (
11) A pressure wave of a predetermined period is generated within the range. This compression chamber (1
1) is connected to the expander via the connecting pipe, so in the expander the displacer reciprocates at the same frequency as the pressure wave in the compression chamber (11), and the expansion of the gas in the expansion chamber causes cold. The cold head at the tip of the cylinder is cooled to an extremely low temperature level by repeated reciprocating movements of the displacer. [0027] In this embodiment, each piston (7) has two inner and outer coil springs (1
8) and (19), there is no need to increase the length of the spring to prevent fatigue failure, unlike when the piston (7) is supported by a single spring.
The compressor (1) can be made compact by eliminating wasted space. [0028] Also, the two coil springs (18). Among (19), the inner coil spring (18) is a tension spring,
Since the outer coil springs (19) are each configured as a compression spring, the piston (7) moves backward and away from the opposing piston (7) due to the operation of the linear motor (13) (the inner bottom surface of the casing assembly (3) approach)
In the suction stroke, the outer coil spring (19) is compressed and deformed, and conversely, in the compression stroke, the piston (7) moves forward and approaches another piston (7) (away from the inner bottom surface of the casing assembly (3)). The coil spring (18) is expanded and deformed. At this time, suppose that there are two springs (18) inside and outside,
(19) are both compression springs, the inner coil spring (18), which has a smaller diameter, buckles due to compression deformation.
18) is a tension spring that is always extended from its natural length, so as the piston (7) retreats, its extended length simply becomes smaller, and it does not move further beyond its natural length into a compressed state. Therefore, buckling of the inner coil spring (18) can be avoided. [00293 FIG. 2 shows Embodiment 2. The same parts as in FIG. On the contrary, a movable cylinder is made to reciprocate relative to a fixed piston. [00301 That is, in this embodiment, the center base (4') is disposed between the left and right casing assemblies (3), (3). This center base (4'
) has a substantially disc-shaped flange (4a') sandwiched between the casing assembly (3), (3), and the base end is integrally connected to the center of this flange (4a'). It consists of left and right pistons (7'), (7') extending in the left-right direction on a concentric line from 4a'). In the center of the center base (4') are left and right pistons (7'),
A gas passage (12') penetrating between the tips of (7') is formed, and this gas passage (12N is not shown, but is connected to an expander (not shown) via a connecting pipe. [00311 Each of the above A bottomed movable cylinder (6') is externally fitted onto the piston (7') so as to be able to reciprocate, and a compression chamber (11) is created by the piston (7') in the internal space of each movable cylinder (6'). The compression chamber (11) is always in communication with the gas passage (12').A flange (6b') is formed at the open end of the movable cylinder (6'). 6b') is the beam near motor (1
The bobbin (10) of 3) is attached, and is driven by a linear motor (13) to compress the gas in the compression chamber (11) at regular intervals. [0032] Spring means (17) for elastically supporting the movable cylinder (6') with respect to the casing assembly (3) is provided between the outer bottom surface (back surface) of each movable cylinder (6') and the casing assembly (3). ) has been constructed. This spring means (17) is similar to that of Example 1 above, with inner and outer coils arranged concentrically and parallel to each other between the outer bottom surface of each movable cylinder (6') and the casing assembly (3). It consists of springs (18) and (19), with the inner coil spring (1'8) being a tension spring and the outer coil spring (19) being a compression spring. [0033] Therefore, in this embodiment, both the linear motors (13), the coils (16) of (13),
When AC power is synchronously applied to (16), the coils (16), (16) and the movable cylinder (6')
, (6') reciprocate in opposite directions. Both compression chambers (11), (11
) the volume of the compression chamber (11), (11
) a pressure wave with a predetermined period is generated. [0034] In this case, it is the movable cylinder (6') that is reciprocated by the operation of the linear motor (13), and when the movable cylinder (6') moves backward and approaches the casing assembly (3), it is compressed. The outer coil spring (19) as a spring is compressed and deformed, and the movable cylinder (6')
When the inner coil spring (18) as a tension spring moves forward and moves away from the casing assembly (3), the inner coil spring (18) is elongated and deformed. Therefore, in this example as well, the above Example 1
Similarly, buckling of the spring can be avoided. [0035] In the above embodiment, the inner coil spring (18) of the spring means (17) is a tension spring, and the outer coil spring (19) is a compression spring. Of course, the inner coil spring (18) is a compression spring. Spring and outer coil spring (19)
It is also possible to use it as a tension spring. However, springs that are easily buckled and deformed due to compression are inner coil springs with a small diameter (1
8), the configurations as in each of the above embodiments are preferable. [0036] Furthermore, the two coil springs may not be arranged concentrically, but may be arranged parallel to each other. [0037] Further, in the above embodiment, there are two pistons, cylinders, linear motors (13), etc., but the present invention can also be applied to a compressor equipped with one of these. [0038]

As explained above, according to the invention of claim 1 or 2, in a linear motor compressor for a Stirling refrigerator, a piston or cylinder that reciprocates and compresses gas in a compression chamber by the drive of a linear motor. The movable part is elastically supported on the fixed body by spring means, and this spring means is composed of a compression spring and a tension spring, so that when the movable part is elastically supported by two springs on one side, it will not buckle. By using a tension spring as a flexible spring, buckling of the spring can be avoided, and therefore, by using two springs, it is possible to make the refrigerator more compact and to prevent fatigue failure of the springs. [o o 39] Also, according to the invention of claim 3, when two springs are arranged concentrically, the inner spring becomes a small diameter spring that is easily buckled. It is possible to reliably prevent buckling.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of a compressor according to a first embodiment of the present invention.

FIG. 2 is a diagram corresponding to FIG. 1 showing a second embodiment of the present invention.

FIG. 3 is a sectional view showing a conventional example of a Stirling refrigerator.

[Explanation of symbols]

(1), (1')...Compressor (2)...Casing assembly (fixed body) (6)
, (6')...Cylinder (7), (7')...Piston (11)...Compression chamber (13)...Linear motor (15)...Magnet (16)... Coil (17) Spring means (18) Inner coil spring (tension spring) (19)
・・Outer coil spring (compression spring)

[Figure 2]

Claims (3)

[Claims] Claim 1: A cylinder (6) fixed to a fixed body (2).
, a piston (7) fitted reciprocally into the cylinder (6) and defining a compression chamber (11) in the space inside the cylinder (6), and a back surface of the piston (7) and a fixed body ( 2)
a spring means (17) installed between the spring means (17) and elastically supporting the piston (7) with respect to the fixed body (2); and a spring means (17) connected to the magnet (15) fixed to the fixed body (2) and the piston (7) and a linear motor (13) that reciprocates the piston (7) by supplying alternating current of a predetermined frequency to the coil (16), and the spring means (17) includes:
It consists of two coil springs (18) and (19) arranged in parallel with each other between the back surface of the piston (7) and the fixed body (2), and one of the coil springs (18) and (19) is tensioned. A linear motor compressor, characterized in that one of the compressors is a spring, and the other is a compression spring. Claim 2: A piston (7') fixed to a fixed body (2).
), and by fitting the piston (7') inside, the piston (
7'), and has a compression chamber (1') in the internal space.
1), a bottomed movable cylinder (6') is installed between the bottom of the movable cylinder (6') and the fixed body (2), and the movable cylinder (6') is connected to the fixed body (2). ), and a coil (16) connected to a magnet (15) fixed to a fixed body (2) and a movable cylinder (6'); a linear motor (13) for reciprocating the movable cylinder (6') by supplying alternating current at a predetermined frequency;
7) are two coil springs (18) arranged in parallel with each other between the bottom surface of the movable cylinder (6') and the fixed body (2).
, (19), both coil springs (18), (19)
A linear motor compressor characterized in that one of the two is a tension spring and the other is a compression spring. [Claim 3] Two coil springs (18) and (19) are arranged concentrically, the inner spring (18) being configured as a tension spring, and the outer spring (19) being configured as a compression spring. The linear motor compressor according to claim 1 or 2, characterized in that: