JP2546081B2 - Linear motor compressor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear motor compressor for compressing a refrigerant supplied to an expander in a Stirling refrigerator, and more particularly to a measure for improving efficiency of a linear motor as a drive source.

[0002]

2. Description of the Related Art Conventionally, a free-displacer type Stirling refrigerator is known as a kind of small refrigerator for generating cold at an extremely low temperature level. As an example of this refrigerator, for example, "Refrigerator for Cryogenic Sensor
s ”(NASA Conference Publication 2287). This refrigerator, as shown in FIG.
The compressor (a) compresses the refrigerant gas and the expander (k) expands the refrigerant gas discharged from the compressor (a). The compressor (a) is, for example, a hermetic casing (b), a cylinder (c) formed in the casing (b), and reciprocally fitted in the cylinder (c). The cylinder (c) is provided with a piston (e) that defines a compression chamber (d) in the inner space of the cylinder (c), and a linear motor (f) as a drive source that reciprocally drives the piston (e). This linear motor (f) has an annular permanent magnet (g) arranged around the cylinder (c), and this magnet (g) applies a magnetic field to a cylindrical gap concentric with the center of the cylinder (c). generate. A substantially inverted cup-shaped bobbin (h) integrally fixed to the piston (e) at the center of the gap is reciprocally disposed, and a drive coil (i) is provided around the bobbin (h). Is wrapped around. Further, a piston formed of a coil spring for elastically supporting the piston (e) so as to reciprocate between an outer bottom surface of the bobbin (h) (opposite side of the piston (e)) and an inner bottom surface of the casing (b). A spring (j) is erected, and by applying an alternating current of a predetermined frequency to the drive coil (i) through the conductors (i1) and (i1), the drive coil (i) is acted on by the action of the magnetic field passing through the gap. Also, the bobbin (h) is driven to linearly reciprocate the piston (e) in the cylinder (c), and a gas pressure of a predetermined cycle is generated in the compression chamber (d).

On the other hand, the expander (k) has a cylindrical cylinder (l), and the inside space of the cylinder (l) is defined as an expansion chamber (m) and a working chamber (n) in the cylinder (l). A free displacer (o) which is divided into two is fitted so as to be reciprocally movable. This displacer (o) is filled with a metal regenerator material (o1) (regenerative heat exchanger), and the regenerator material (o1) is connected to the expansion chamber (m) and the working chamber (n), respectively. Communication holes (o 2) and (o 3) are opened. A displacer spring (p), which is a coil spring elastically supporting the displacer (o) so as to reciprocate, is disposed in the working chamber (n).
Further, the working chamber (n) is connected to the compression chamber (d) of the compressor (a) via the coupling pipe (q),
Cooling is generated in the cold head at the tip of the cylinder (l) by causing the free displacer (o) to reciprocate by the refrigerant gas pressure from the compressor (a) to expand the refrigerant gas in the expansion chamber (m). It is designed to let you.

[0004]

By the way, a linear motor (f) which is a drive source of such a linear motor compressor is used.
It is conceivable to increase the size of the permanent magnet (g) as one means for achieving higher efficiency. That is, by enlarging the permanent magnet (g), the permanent magnet (g)
The efficiency of the linear motor (f) can be increased by increasing the strength of the surrounding magnetic field and increasing the ratio between the output of the compressor (a) and the electric input to the linear motor (f). However, even if the permanent magnet (g) is enlarged in this way,
When the volume of the yoke portion composed of the cylinder (c) and the like is smaller than the volume of the permanent magnet (g), the magnetic flux is saturated in this yoke portion, and the volume of the permanent magnet (g) is further increased. Even if it is increased, it does not contribute to the high efficiency of the linear motor (f). Therefore, in order to eliminate the saturation of the magnetic flux, it is conceivable to increase the volume of the yoke portion. In this case, not only the space for disposing the permanent magnet (g) but also the disposition of the yoke portion. It is not effective in terms of practicability because it requires a large installation space and leads to an increase in the size of the compressor.

The present invention has been made in view of these points, and provides a linear motor compressor capable of improving the efficiency of the linear motor without increasing the size of the compressor. With the goal.

[0006]

In order to achieve the above object, the present invention provides a plurality of magnetic circuits each formed by a permanent magnet and a yoke member arranged around the permanent magnet to provide a magnetic circuit for each magnet. Made it so that saturation of magnetic flux is less likely to occur in the circuit. Specifically, the invention according to claim 1 is such that a cylinder (4) provided in the fixed body (2) and a reciprocatingly arranged in the cylinder (4), and a compression chamber is provided in a space inside the cylinder (4). A piston (6) partitioning and forming (7), and installed between the piston (6) and the fixed body (2),
Spring means (16) for elastically supporting the piston (6) with respect to the fixed body (2), a magnet (13) attached to the fixed body (2), and a coil (provided on the piston (6) ( 15), a linear motor compression having a linear motor (11) for reciprocating the piston (6) in the cylinder (4) by supplying an alternating current of a predetermined frequency to the coil (15). The machine is assumed. Then, at least the magnet (1) is attached to the linear motor (11).
3) and the fixed body (2), the plurality of magnetic circuits (A) and (B) are formed for one magnet (13).

According to a second aspect of the present invention, in the linear motor compressor according to the first aspect, magnetic circuits (A) and (B) are provided.
When the main magnetic circuit (A) having a small magnetic resistance and the sub magnetic circuit (B) having a large magnetic resistance are provided, an auxiliary magnet (21) is provided in the sub magnetic circuit (B). It was configured.

[0008]

With the above construction, in the invention according to claim 1,
Along with the driving of the compressor, the piston (6) linearly reciprocates in the cylinder (4) while receiving the biasing force of the spring means (16) to change the volume of the compression chamber (7). By this, the fluid in the compression chamber (7) is compressed, and the compressed fluid is discharged toward the expander. The linear motor (11) as a drive source of this compressor has a plurality of magnetic circuits (A) and (B) formed for one magnet (13), and therefore has a permanent magnet (13). ), The magnetic flux saturation in each magnetic circuit (A), (B) is less likely to occur, and the permanent magnet (13) alone is used without increasing the size of the yoke member such as the cylinder (4). The efficiency of the linear motor (11) can be improved by increasing the size.

According to the second aspect of the invention, since the auxiliary magnet (21) is provided in the sub magnetic circuit (B) having a large magnetic resistance, the magnetic flux density in the sub magnetic circuit (B) can be increased. This suppresses the increase in the magnetic flux density of the main magnetic circuit (A), and the saturation of the magnetic flux in the main magnetic circuit (A) can be reliably avoided.

[0010]

(First Embodiment) A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a compressor (1) for a Stirling refrigerator according to the first embodiment. This compressor (1) is combined with a conventionally known free displacer type expander (see FIG. 5), which is not shown, to form a refrigerator. The compressor (1) has a cylindrical casing (2) as a fixed body. The casing (2) comprises casing assemblies (3), (3) and a cylinder member (4). The casing assemblies (3), (3) are a pair of left and right cylindrical members made of pure iron and having substantially the same structure, which are concentric with each other and extend in the direction of the center line thereof. They are arranged so as to face each other at a predetermined interval. And the cylinder member (4)
Are sandwiched between both casing assemblies (3) and (3) via a substantially ring-shaped yoke member (5). The cylinder member (4) is composed of an outer cylinder (4a) and an inner cylinder (4b) connected by a doughnut-shaped connecting portion (4c). The inner cylinder (4b) is a portion that becomes an original cylinder, and the inside thereof is formed in the piston insertion hole (4d). Then, a pair of cylindrical left and right pistons (6) and (6) having a bottomed center hole (6a) are inserted into the piston insertion holes (4d) of the cylinder inner cylinder (4b), respectively. A portion surrounded by the cylinder inner cylinder (4b) between the pistons (6) and (6) is a compression chamber (7). The outer diameter of the piston (6) is slightly smaller than the inner diameter of the cylinder inner cylinder (4b), and a small gap of, for example, about 10 μm is formed between the two. Is sealed by a fluid seal or the like to ensure the airtightness of the compression chamber (7).

A gas passage (8) extending radially from the piston insertion hole (4d) is formed in the cylinder member (4).
Is formed, the inner end of the gas passage (8) opens into the compression chamber (7), while the outer end of the gas passage (8) extends annularly inside the outer cylinder (4a). It is connected to an expander (not shown) through a connecting pipe (10) via 9). A partition wall (7a) that divides the compression chamber (7) into left and right compression chambers (7) and (7) is provided in the center of the compression chamber (7). (7), (7)
Are independently connected to the gas passage (8).

The left and right pistons (6), (6) are drivingly connected to linear motors (11), (11) as a drive source for reciprocally driving the pistons (6), (6). That is, each of the linear motors (11) has a cylindrical member (12) made of pure iron fixed to the inner cylinder (4b) of the cylinder member (4), and the cylindrical member (12) is a cylinder member (12). The outer cylinder (4b) of the cylinder member (4) is externally fitted to the inner cylinder (4b) of 4) so as to leave a predetermined gap. An annular permanent magnet (13) is fixed to the outer periphery of the cylindrical member (12) with a predetermined gap from the inner peripheral surface of the cylinder outer cylinder (4a), and is made of pure iron by the permanent magnet (13). The cylindrical member (12) and the cylinder member (4) are used as yokes to generate a magnetic field of a predetermined strength in the gap between the permanent magnet (13) and the inner peripheral surface of the cylinder outer cylinder (4a).

Each of the pistons (6) has a flange portion (6b) extending radially outward from an end of the piston (6) opposite to the center of the cylinder member (4), and the flange portion (6b). ) Extends to the center of the cylinder member (4) concentrically with the piston (6) and has a tip portion in a gap between the permanent magnet (13) and the inner peripheral surface of the cylinder outer cylinder (4a). A cylindrical bobbin (14) arranged so as to be capable of reciprocating in the left-right direction is connected. A concave coil winding portion (14a) is formed on the outer circumference of the bobbin (14) at a position facing the permanent magnet (13), and the coil (15) is wound around the coil winding portion (14a). Is wrapped around.

Then, an alternating current of a predetermined frequency (for example, 50 Hz) corresponding to the natural frequency determined by the mass of each piston (6) and the spring constant of the spring means (16) described later is applied to both linear motors (11), (). 11) coils (15) and (1)
By supplying electricity in synchronism with 5), both pistons (6) and (6) are reciprocally moved in opposite directions at the above-mentioned natural frequency to generate a gas pressure of a predetermined cycle in the compression chamber (7). Is configured.

On the rear surface of each piston (6), (6), the casing (3) of the casing (2) is arranged so that the piston (6) can reciprocate within the cylinder member (4).
Spring means (16) are provided for elastically supporting the. That is, the spring holder outer (17) is attached to the center of the inner bottom surface of each casing assembly (3), while the spring boulder inner (18) is bolted to the center of the bottom surface of the center hole of each piston (6). It is fastened by a stop. Then, one end of the coil spring (19) which constitutes the spring means (16) is screwed into the spring holder outer (17) by, for example, being screwed into a spiral spring mounting groove formed on the outer periphery of the spring holder outer (17). This coil spring (1
The other end of 9) is also immovably attached to the outer periphery of the spring holder inner (18). The coil spring (19) is set so as to always contract from its natural length within the stroke range in which the piston (6) reciprocates.

As a characteristic configuration of this example,
It is in the magnetic circuit formed by the permanent magnet (13) and the yoke portion around it. Hereinafter, a configuration for forming this magnetic circuit will be described. The configuration for forming the magnetic circuit in this example is shown in the right half of the compressor (1) shown in FIG. That is, as shown in FIG. 2, the inner peripheral surface (12a) and the inner end surface (12b) of the cylindrical member (12) contact the inner cylinder (4b) and the connecting portion (4c) of the cylinder member (4), respectively. Has been done. As a result, as shown by the alternate long and short dash line A in FIG. 2, in the present invention, the permanent magnet (13), the cylindrical member (12), the connecting portion (4c) of the cylinder member (4) and the outer cylinder (4a) are referred to. A first magnetic circuit as a magnetic circuit is formed. Then, as one of the characteristic configurations of the present example, a large diameter portion such that the periphery of the outer end surface (12c) of the cylindrical member (12) has substantially the same diameter as the outer diameter of the permanent magnet (13). (12d) is projected. That is, the outer peripheral end surface of the large diameter portion (12d) is set at a position close to the bobbin (14). On the other hand, as another feature of the present embodiment, the portion of the yoke member (5) facing the large diameter portion (12d) is formed in a convex shape toward the bobbin (14). A protrusion (5a) is formed. With such a configuration, the bobbin (14) is sandwiched between the outer peripheral end surface of the large diameter portion (12d) of the cylindrical member (12) and the inner peripheral end surface of the protruding portion (5a) of the yoke portion (5). They are placed close together. Therefore, apart from the first magnetic circuit (A), as shown by the chain line B in FIG. 2, the permanent magnet (13), the cylindrical member (12), the yoke member (5), and the cylinder member (4) are separated. A second magnetic circuit as a sub magnetic circuit in the present invention is formed across the outer cylinder (4a). As described above, in this example, by providing the two magnetic circuits (A) and (B), even if the permanent magnet (13) is increased in size, the magnetic flux of the magnetic circuits (A) and ( Since it is divided into B), saturation of this magnetic flux is suppressed in each magnetic circuit (A), (B), and the yoke of the cylinder member (4), the cylindrical member (12), etc. is suppressed. It is possible to increase the magnetic field strength by enlarging only the permanent magnet (13) without enlarging the part.

In FIG. 1, (20) is a cover for covering each casing assembly (3).

Next, the operation of the above embodiment will be described. With the start of operation of the refrigerator, the coils (15) of both linear motors (11), (11) in the compressor (1),
AC power of a predetermined frequency (50 Hz) is energized in synchronization with (15). With this energization, the permanent magnet (13),
By the action of the magnetic field generated by (13), the coil (1
5) and (15) and pistons (6) and (6) reciprocate in opposite directions while deforming the coil spring (19), respectively, and these pistons (6) and (6) are reciprocally moved to the cylinder member (4). By moving forward and backward in synchronization with each other, the compression chamber (7)
The volume of the fluid increases or decreases, and a pressure wave having a predetermined cycle is generated in the compression chamber (7). Since the compression chamber (7) communicates with the expander via the connecting pipe (10), the displacer in the expander reciprocates in the same cycle as the pressure wave of the compression chamber (7) to cause the expansion chamber to move. Chilling occurs due to the expansion of the gas, and the cold head at the tip of the cylinder is cooled to a cryogenic level by repeating the reciprocating movement of the displacer.

When the compressor (1) is in operation, as described above, the two magnetic circuits are provided, so that the permanent magnet (13) is increased in size without causing magnetic flux saturation. Compressor due to the increased magnetic field (1)
The ratio between the output of the linear motor and the electric input to the linear motor (11) can be increased, and the efficiency of the linear motor (11) can be improved. That is, according to the configuration of this example, by forming another magnetic circuit (B) in addition to the conventional magnetic circuit (A), the permanent magnet (13) can be generated without causing saturation of the magnetic flux. It is possible to increase the magnetic field by increasing the size of only), and it is possible to improve the efficiency of the linear motor (11) without increasing the size of the compressor.

(Modification) Next, a modification of the first embodiment will be described. This example is shown in the left half of the compressor (1) in FIG. That is, instead of the protruding portion (5a) of the yoke member (5) shown in the first embodiment described above, the auxiliary magnet (21) is arranged on the inner side surface of the yoke member (5). It is a thing. That is, in the second magnetic circuit (B), a small gap is formed between the yoke member (5) and the cylindrical member (12), and this small gap serves as the magnetic resistance in the circuit. According to the configuration of this modification, the auxiliary magnet (21) is provided in this circuit, so that the magnetic flux of the second magnetic circuit (B) can be increased. It becomes possible to form a magnetic flux in the second magnetic circuit (B) at substantially the same level as that of the first magnetic circuit (A), so that the magnetic flux saturation of the first magnetic circuit (A) can be prevented more effectively. This can be done reliably, the permanent magnet can be made even larger, and the magnetic field strength as a whole can be increased.

(Second Embodiment) Next, a second embodiment of the present invention will be described. In this example, the same members as those in the first and the above-described examples are designated by the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, as shown in FIG.
The shing assembly (3) has a disc-shaped bottom plate (3a) and a center hole (6) of the piston (6) extending from the center of the bottom plate (3a).
It is composed of a cylindrical shaft portion (3b) extending toward a). On the other hand, the outer cylinder (4
a) is extended toward the bottom plate portion (3a), and its side end portion is the bottom plate portion (3) of the casing assembly (3).
It is attached to a) by bolting. And
The shaft portion (3b) has a through hole (3c) formed in the center portion, and the outer peripheral portion is in contact with the inner peripheral surface of the center hole (6a) of the piston (6). A first coil spring (22) is provided between the bottom plate portion (3a) of the casing assembly (3) and the flange portion (6b) of the piston (6), and a nut (23) for fixing a permanent magnet. The second coil springs (24) are compressed between the bobbin (14) and the bobbin (14).

With such a configuration, the alternate long and short dash line A in FIG.
As shown in, the first magnetic circuit extending over the permanent magnet (13), the cylindrical member (12), the connecting portion (4c) of the cylinder member (4), and the outer cylinder (4a), as in the first embodiment described above. Are formed. Further, as a feature of this example, apart from the first magnetic circuit (A), as shown by the chain line B'in FIG. 4, the permanent magnet (13), the cylindrical member (12), and the cylinder member (4) are Inner cylinder (4b), piston (6), casing assembly (3), outer cylinder (4) of cylinder member (4)
A second magnetic circuit is formed extending over a). Thus, even in this example, the two magnetic circuits (A) and (B ')
Since the magnetic flux is prevented from being saturated even when the permanent magnet (13) is upsized, the permanent magnet (13) is upsized without increasing the size of the yoke portion. It is possible to increase the magnetic field strength.

(Modification) Next, a modification of the second embodiment will be described. This example is shown in the left half of the compressor (1) in FIG. That is, the auxiliary magnet (25) is arranged in the middle of the outer cylinder (4a) of the cylinder member (4) shown in the second embodiment. According to such a configuration, the auxiliary magnet (25) is provided in the second magnetic circuit (B ′) similarly to the modification of the first embodiment described above, and thus the second magnetic circuit (B ′) is provided. The magnetic flux of the magnetic circuit (B ′) can be increased, the magnetic flux saturation of the first magnetic circuit (A) can be prevented more reliably, and the magnetic field strength as a whole can be further increased.

In each of the above-mentioned embodiments, the compressor in which the piston (6) reciprocates in the cylinder (4) has been described. However, the piston is fixed to the casing and the piston is fixed inside the casing. You may make it employ | adopt to the compressor comprised with the movable cylinder which arrange | positions a piston and can be reciprocated with respect to a piston.

Further, in each of the above-described embodiments, the non-contact type compressor in which the small gap is provided between the cylinder (4) and the piston (6) is described, but the present invention is not limited to this. Not limited to this, the present invention may be applied to a contact type compressor in which a small gap is not formed between the cylinder and the piston.

[0027]

As described above, according to the present invention, the following effects are exhibited. According to the invention described in claim 1, a plurality of magnetic circuits (A) and (B) are formed for one magnet (13) in the linear motor (11), and a magnetic flux is applied to each magnetic circuit (A). , (B), it is difficult to cause saturation of magnetic flux in each magnetic circuit (A), (B) even if the magnet (13) is increased in size, and the yoke member is increased in size. The efficiency of the linear motor (11) can be improved without increasing the size of only the magnet (13).

According to the second aspect of the present invention, the auxiliary magnet (21) is provided in the sub magnetic circuit (B) having a large magnetic resistance,
By increasing the magnetic flux density in the sub magnetic circuit (B), the increase in magnetic flux density in the main magnetic circuit (A) is suppressed, and the main magnetic circuit (A) is suppressed.
The saturation of the magnetic flux in can be reliably avoided, and the size of the magnet (13) in which this saturation occurs can be increased,
The efficiency of the linear motor (11) can be further improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view of a linear motor compressor according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of an essential part showing a magnetic circuit in the first embodiment.

FIG. 3 is a view corresponding to FIG. 1 in a second embodiment of the present invention.

FIG. 4 is a view corresponding to FIG. 2 in the second embodiment.

FIG. 5 is a vertical sectional side view showing a conventional Stirling refrigerator.

[Explanation of symbols]

 (1) Linear motor compressor (2) Casing (fixed body) (4) Cylinder member (cylinder) (6) Piston (7) Compression chamber (11) Linear motor (13) Permanent magnet (15) Coil (16) Spring means (A) First magnetic circuit (main magnetic circuit) (B), (B ') Second magnetic circuit (sub magnetic circuit)

Claims (2)

(57) [Claims] 1. A cylinder (4) provided on a fixed body (2) and a cylinder (4) reciprocally arranged in the cylinder (4) so as to define a compression chamber (7) in a space inside the cylinder (4). A piston (6), a spring means (16) installed between the piston (6) and the fixed body (2), and elastically supporting the piston (6) with respect to the fixed body (2); It has a magnet (13) attached to a fixed body (2) and a coil (15) provided on the piston (6), and the piston (6) is supplied by supplying an alternating current of a predetermined frequency to the coil (15). ), A linear motor (11) for reciprocating in the cylinder (4), wherein the linear motor (11) includes at least the magnet (13) and a fixed body (). 2) One magnetic circuit (A), (B) formed over A plurality of linear motor compressors are formed for each magnet (13). 2. The linear motor compressor according to claim 1, wherein the magnetic circuits (A) and (B) are a main magnetic circuit (A) having a small magnetic resistance and a sub magnetic circuit (B) having a large magnetic resistance. A linear motor compressor comprising an auxiliary magnet (21) provided in the sub magnetic circuit (B).