JPH0555030A - Linear actuator - Google Patents

Abstract

PURPOSE: To obtain an inexpensive linear actuator compressor motor for a low-temperature cooling device by providing a specific core having a cylindrical hole formed along a vertical center axis, pistons, circular magnets, and coils. CONSTITUTION: This device is provided with a core 22 having a cylindrical hole 24 formed along a vertical center axis 26, and first and second parallel circular peripheral recessed parts 34 and 36 arranged coaxial to the center axis 26 for providing first and second cavities 38 and 40. Moreover, this device is provided with first and second pistons 28 and 30 arranged in the cylindrical hole 24, first and second circular magnets 46 and 48 arranged in the first and the second circular recessed parts 34 and 36, and first and second coils 51 and 52 arranged in the first and the second circular recessed parts 34 and 36. Then, this device includes a housing 14, constituted of a shell 16 which is integrally formed with the core 22.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to cooling systems.
In particular, the invention relates to compressor motors used in low cost cooling systems.

While the present invention is illustrated herein with reference to an embodiment for a particular application, it should be understood that the invention is not so limited. Those skilled in the art will recognize additional modifications, applications and embodiments within the scope of the present invention and additional areas in which the present invention is particularly useful.

[0003]

Cryogenic coolers are used for a variety of applications including cooling infrared sensors. Cryogenic coolers typically include a compressor driven by a motor that compresses a working fluid that releases energy in the form of heat.
When the working fluid is allowed to expand, it absorbs heat, thereby causing the cooled device or volume to cool. This application generally requires a compressor driven by a powerful motor with low loss.

[0004]

A typical cryocooler uses a rotary motor type compressor, which has been found to be complex and susceptible to wear. Therefore, linear actuators have been developed that are simple in construction and have good wear characteristics. Linear actuators are electromagnetic devices that produce linear mechanical motion in response to the interaction of magnetic and electrical circuits. U.S. Pat. No. 4,808,95 by Godkin et al.
No. 5 (February 28, 1989) discloses a moving coil linear actuator with interleaved magnetic circuits. The interleaved magnetic structure can increase the power in a given volume. However, this structure is complicated and expensive.

Therefore, there is a technical need for an inexpensive linear actuator compressor motor for cryocoolers.

[0006]

Such a technical need is presented by the linear actuator of the present invention which includes a unique core having a cylindrical bore formed through a longitudinal central axis. The core comprises first and second parallel annular peripheral recesses coaxially arranged with respect to a central axis to provide first and second cavities. The linear actuator comprises first and second pistons located within the bore. The first and second annular magnets are arranged in the first and second annular recesses, respectively. The first and second coils are arranged in the first and second annular recesses, respectively. When the coil is energized, a magnetic field is created that interacts with the magnetic field provided by the magnet to cause internal movement of the first and second pistons.

When constructed in a compressor, the present invention includes a cylindrical housing with a core disposed within the housing. The core comprises a cylindrical bore located through the axial center of the core to provide a compression space. The fluid flow path is provided between the compression space and the valve. Also, the first and second parallel annular perimeter recesses are coaxially disposed about the longitudinal axis of the core to provide first and second cavities. The first and second pistons are located in holes on opposite sides of the compression space. The first and second annular magnets and the first and second coils are arranged in the first and second annular recesses, respectively. First and second end caps are attached to the open ends of the housing to close the compressor. First and second springs are located between the first and second end caps and the first and second pistons, respectively. Further, the working fluid is arranged in the housing in the compression space. Also in this device, when the coil is energized, a magnetic field is generated that interacts with the magnetic field provided by the magnets causing the linear movement of the first and second pistons. The movement of the piston acts to compress the working fluid in the compression space.

Accordingly, the present invention provides an inexpensive linear actuator compression motor for a cryocooler.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIG. 1, a compressor 10 includes a linear actuator 12 of the present invention mounted in a housing 14. The housing 14 is constituted by a cylindrical shell 16 which is closed at each end by first and second end caps 18 and 20, respectively. Shell 16
And the first and second end caps 18 and 20 are constructed of steel or other suitable material. The end cap is screwed or welded to the shell 16.

The linear actuator 12 includes a unique solid wall core 22 constructed of cold rolled magnetic steel or other magnetic material, two opposed pistons, two aligned annular magnets and double opposed coils. Contains. The core 22 used to transfer magnetic flux to the air gap in which the coil is located is integral with the shell 16. This is effective in a fixed volume design because the radial space previously taken by the container is available to the motor, which makes the compressor more powerful and more powerful. Furthermore, the design is
Otherwise it incorporates elements that must be manufactured and must be controlled for optimum fit. In particular, problematic interfaces of parts (fasteners, gaskets, etc.) can be mitigated even if not completely removed. In addition, features such as charge valve seats, transmission line seats and hermetic sealing and welding of details are not all separate parts, but machined features on a single bar of magnetic material as discussed in more detail below. Is.

A cylindrical bore 24 is drilled through the axial center of the core 22 along the longitudinal axis 26 to provide a passage for the reciprocating movement of the first and second pistons 28 and 30. It The first and second pistons 28 and 30 are positioned within the bore 24 in opposed relation such that a gas compression space 32 is provided therebetween. The first and second parallel annular circumferential recesses 34 and 36 are circumferentially coaxial about the longitudinal axis 26 of the core 22 to provide first and second cavities 38 and 40. To be cut. In addition, the fluid flow path
42 is provided between the compression space 32 and the gas port 45. First and second annular magnets 46 and 48 are disposed within the first and second annular cavities 38 and 40, respectively. Magnet 46 is constructed of neodymium, iron, boron or other suitable material. The magnets are aligned in the same direction. That is, the first
The permanent magnets 46 of FIG. 2 are polarized in the same radial direction as the second permanent magnets 48 on the other side of the wall between the recesses 36 and 38 of the core 22. Magnets 46 and 48 are preassembled on rings 47 and 49 (shown more clearly in the detailed view of FIG. 2). The rings 47 and 49 are then assembled at each end of the core 22 outside the air gap 50. This is useful in that the magnet is placed in the air gap which is known to minimize stray magnetic fields. Also, the position of the magnet on the outside of the air gap requires a long magnet circumference and tends to include more magnetic material. This is believed to result in a more powerful and effective motor. The air gap 50 is a dimensionally acceptable position in the motor because it contains the running distance of the coil. By placing the magnet ring in this area, the tolerance of this part is not critical. Also, the magnet ring is a simple and open geometric shape. This facilitates placement and assembly of the magnet and molding of the final part. The concentricity of the ring with respect to the piston bore is provided by fixing during final assembly.

First and second coils 51 and 52 are disposed within first and second annular cavities 38 and 40, respectively, inside first and second annular magnets 46 and 48, respectively. Coils 51 and 52 are oppositely aligned. In the preferred embodiment, the coil is in the form of a short solenoid for simplicity of construction. The critical alignment of the compressor is coaxial with each coil and corresponding piston. The coil and piston must be coaxially aligned by gluing while the coil and piston are in alignment during assembly. This relaxes the requirement for exact dimensional limits on individual parts.

The first and second springs 54 and 56 are
And second end caps 18 and 20 and first and second
Between the pistons 28 and 30, respectively.

The first spring 54 is located between a hat-shaped metal washer 58 and a hat-shaped armature plate 60. The armature plate is made of tungsten or other suitable material. Similarly, the second spring
56 is located between the second hat-shaped metal washer 62 and the hat-shaped armature 64. The rubber washer 100, and thus the coil piston device, is fixed in position at each end of the compressor by the end caps 18 and 20 that push the washer against the stops 72 and 74, respectively. Each piston is secured to an associated armature plate by a head screw 66 (one shown in dashed lines, the other not shown) aligned with the longitudinal axis 26 of the compressor 10.

Each coil is energized by wires connected to aluminum terminal blocks 76 and 78 secured to the first and second armature plates 60 and 64, respectively, and extending from the terminal blocks 76 and 78, respectively. Wires 80 and 82 connect to an external power source (not shown). From one side of the compressor to the other,
An opening is provided for the wire to penetrate the external power supply.

The tap hole 84 is provided to charge the air space behind the air gap 50 with a working fluid such as helium. The tap hole communicates with the fill valve 86 and the inlet port 88 (see Figure 3). The working fluid flows along the piston until the equilibrium point is reached.
Flows in. When the coil is energized, a magnetic field is created that interacts with the magnetic field provided by the magnet to cause linear movement of the first and second pistons. The movement of the piston acts to compress the working fluid in the compression space. The vibrations are eliminated by running the same coil piston arrangement with equal amplitude. Stray magnetic fields are suppressed by orienting the coils in opposite directions.

Accordingly, the present invention provides an inexpensive linear actuator compressor motor for cryocoolers.

Thus, the present invention has been described herein with reference to a particular embodiment for a particular application. Those skilled in the art will recognize additional modifications, applications and embodiments without departing from the scope of the present invention.

It is therefore intended to cover any and all such applications, modifications and embodiments by the appended claims without departing from the scope of the present invention.

[Brief description of drawings]

FIG. 1 is a simplified longitudinal cross-sectional view of a preferred embodiment of the linear actuator of the present invention incorporated into a compressor structure.

FIG. 2 is a detailed longitudinal sectional view of a preferred embodiment of the linear actuator of the present invention incorporated into a compressor structure.

FIG. 3 is a detailed cross-sectional view of the preferred embodiment of the linear actuator of the present invention incorporated into a compressor structure.

Claims (6)

[Claims] 1. A cylindrical hole formed along a longitudinal center axis and first and first axes coaxially disposed with respect to the central axis to provide first and second cavities. A core having two parallel annular peripheral recesses, first and second pistons disposed within the cylindrical bore, and first and second pistons disposed within the first and second annular recesses, respectively. An actuator, comprising: a second annular magnet; and first and second coils arranged in the first and second annular recesses, respectively. 2. The linear actuator of claim 1, including a housing in which the core is located. 3. The actuator according to claim 2, wherein the housing is formed of a shell integral with the core. 4. A cylindrical housing, a core disposed in the housing, the core having a cylindrical hole formed along a longitudinal central axis to provide a compression space, the compression space and the valve. A first and second parallel annular peripheral recesses coaxially arranged with respect to a central axis of the core to provide first and second cavities; A first located in the hole on opposite sides of the space
And a second piston, first and second annular magnets respectively arranged in the first and second annular recesses, and first and second respectively arranged in the first and second annular recesses. A second coil and first and second coils mounted on the open end of the housing
And an end cap of the compressor. 5. The compressor of claim 4 including first and second springs disposed between each of the first and second end caps and the first and second pistons. .. 6. The compressor of claim 5 including a working fluid disposed within said housing.