JP2007170404A - Spring for linear compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact linear compressor constructed to solve a defect of former technology. <P>SOLUTION: This linear compressor is provided with a cylinder part 33 and a piston part 4. A spring 15 connects the cylinder part and the piston part. The spring is a closed loop of high fatigue strength metal wire. The loop is provided with a first straight section in a first plane and a second straight section in a second plane. The second flat plane is in parallel with the first flat plane. A first and a second spiral sections connect the first straight section and the second straight section. The spiral sections have roughly constant curvature and are arranged to have same bending direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates in detail, but not exclusively, to a linear compressor for a refrigerator.

  A compressor, particularly a compressor for a refrigerator, is conventionally driven by a rotary electric motor. However, even in the most efficient forms of these compressors, there is a significant loss associated with a crank system that converts rotational motion into linear reciprocating motion. As a variant, a rotary compressor which does not require a crank can be used, but again there is a high centripetal force which results in a considerable friction loss. A linear compressor driven by a linear motor (linear motor) does not cause such loss, and such a linear compressor uses an aerodynamic gas bearing as disclosed in US Pat. No. 5,525,845. The bearing load can be designed to be low enough to be used. In this case, a low bearing load is realized by using a connecting rod that is compliant on the side.

  The discussion on aerodynamic gas bearings W. By Powell, “Design of Aerostatic Bearings” (London, UK), The Machinery Publishing Company Limited, 1970 Has been. However, efficient gas bearing manufacturing is difficult with normal manufacturing tolerances and equipment.

  Conventional compressors are installed in a hermetic (hermetic seal) housing, which acts as a refrigerant gas reservoir during use. Refrigerant gas is drawn from the reservoir into the compressor and exhausted through an exhaust conduit extending from the compressor to the housing.

  In the operation of the compressor, the movable part reciprocates, and this causes vibration of the compressor unit in all three axes. In order to reduce the external noise effect of this vibration, the compressor is attached to an anti-vibration spring provided in the hermetic housing.

  In the case of a linear compressor, the piston vibrates only in one axial direction with respect to the cylinder, and as a result, the reaction force applied to any of these components is constant. One proposed solution to this problem is to balance a pair of compressors and operate the compressors synchronously in opposed configurations. However, this configuration is too complex and costly to be used as a commodity, for example, a home electric refrigerator. Another proposed solution is to add a resonant counterweight (balance weight) to reduce vibrations. However, this method limits the operation of the compressor. This is because the counterweight is a negative feedback device and is limited to basic unbalance forces. Another solution is the Gully and Hanes paper, “Vibration Characteristics of Small Rotary and Linear Cryogenic Coolers for IAR Systems”. "Small rotary and linear cryogenic coolers for IR systems", proposed in the minutes of the 6th International Cryocooler Meeting held in Plymouth, Massachusetts, USA, 1990. In this solution, it is required that the piston portion and the cylinder portion of the compressor in the housing are separately supported so that the “stator acts as a counterweight”. However, in implementing this design, a problem arises in home electric refrigerators when the mass of the piston is small. In such a compressor, when the discharge pressure increases, the force of the compressed gas acts as a spring (“gas spring”), and this spring action increases the operating speed as the discharge pressure increases. This is because the “third” vibration mode (in this case, the piston and cylinder vibrate in phase with each other, but out of phase with the compressor shell) is the desired “second” mode (in this case, the shell vibrates). The problem is that the piston and cylinder are only slightly higher than As a result, when the “gas spring” is activated and the “second” mode frequency is effectively increased to the “third” mode, and finally higher than this, the shell begins to vibrate at an unacceptable level.

  For many applications, it is desirable for the compressor to be of a small size. This reduces the size of the spring and all components including these resonant systems. To reduce the size of the compressor, it is necessary for the compressor to operate at a higher frequency. The combination of miniaturization and high frequency increases the stress on the spring component. In some linear compressors, the main spring is made of a spring steel stamped sheet. It has been found that the edges cut in the press work need to be carefully ground to restore the original strength of the spring steel sheet, and in many cases breakage due to accidental stress concentration.

  Another problem with compressors is generally that heat is generated, particularly near the compressor cylinder and cylinder head. Heat generation is caused by friction between moving parts and heat transferred from the compressed refrigerant. The generation of heat raises important issues regarding operating conditions and tolerances between parts that change with increasing wear and compressor operating time. These effects can be particularly noticeable for linear compressors that operate over a long period of time and where strict clearance is particularly important, especially when aerodynamic gas bearing systems are used.

  Another effect of heating is due to irreversible heat loss prior to re-expansion from the refrigerant remaining in the compression space after compression. In linear compressors, up to 15% of compressed refrigerant may not be expelled, compared to up to 5% in the case of crank-driven compressors. This heat source, which is negligible for conventional compressors, is an important source for linear compressors.

  One way to cool the compressor cylinder and cylinder head is to use liquid refrigerant supplied from a condenser in a subsequent refrigeration system. For example, in US Pat. No. 2,510,887, liquid refrigerant from a condenser is directed to a first cooling jacket that surrounds a cylinder and from there to a second cooling head that surrounds a compressor head. And then discharged from the venturi device into a discharge line connecting the cylinder head and the condenser to each other. This is the case for a standard crank drive compressor. Further, in the case of a standard crank drive compressor, US Pat. No. 5,694,780 shows a circuit for boosting liquid refrigerant from a condenser to a high pressure by a pump. This liquid refrigerant is pumped into a cooling jacket surrounding the compressor cylinder. The liquid refrigerant is expelled from the cooling jacket to the discharge manifold and into the cylinder head of the compressor, where it mixes with the compressed refrigerant exiting the compressor. This arrangement has the disadvantage that an additional pump is needed to push liquid refrigerant through the cooling jacket surrounding the cylinder and then into the exhaust manifold against the pressure of the compressed gas.

  Many linear compressors were designed as drops upon replacement of existing commercial rotary and reciprocating compressors, so they are formed inside conventional compressor seats. To achieve this, a compact size compressor was manufactured in which the stator, armature, cylinder and piston were all concentrically housed. However, the size and shape of the conventional compressor limits the size of the refrigerator's mechanical compartment, thereby creating wasted space in the compartment surrounding the compressor.

  An object of the present invention is to provide a compact linear compressor configured to solve the above-mentioned drawbacks.

In a first aspect, the present invention provides:
A spring connected between a cylinder and a piston of a linear compressor,
A first straight portion in a first plane, a second straight portion in a second plane parallel to the first plane, and first and second spiral portions having a substantially constant curvature. With a closed loop of high fatigue strength metal wire with
Each helical portion connects the end of the first straight portion and the end of the second straight portion;
A spring having the same curving direction in which the helical portion moves from the first portion to the second portion.

In another aspect, the present invention provides
A cylinder part;
A piston part;
A spring that extends between the cylinder portion and the piston portion and connects the cylinder portion to the first linear portion and connects the piston portion to the second linear portion. It is a linear compressor.

In yet another aspect, the invention provides:
A method of manufacturing a linear compressor so that a piston of the linear compressor can be connected to a spring of the linear compressor,
(A) disposing the piston at a predetermined axial position within the bore of the compressor;
(B) disposing the piston at a piston coupling position of a spring that is already coupled to the cylinder portion at a position based on a predetermined displacement of the spring or a position that generates a predetermined reaction force;
(C) joining the piston and the piston coupling position of the spring at an axial separation position fixed according to the separation position obtained in steps (a) and (b),
Steps (a) and (b) are methods in which either may be first.

  Those skilled in the art will envision many variations on the various embodiments and applications of the invention without departing from the scope of the invention as set forth in the claims. The disclosure herein is merely exemplary and is not intended to limit the invention.

The practical embodiment of the present invention shown in the overall configuration includes a permanent magnet linear motor that drives a reciprocating compressor that operates in a closed casing. The compressor has pistons 3 and 4 that reciprocate in the cylinder bore 71, are drawn into a compression space provided at the end of the cylinder on the head side, and operate with a working fluid that is expelled therefrom. . A cylinder header 27 coupled to the cylinder seals the open end of the cylinder bore 71 to form a compression space, and the cylinder head has an inlet valve 118, an outlet valve 119 and an associated manifold. The compressed working gas exits the compression space through outlet valve 119 and flows into the exhaust manifold. The exhaust manifold directs the compressed working fluid into the cooling jacket 29 that surrounds the cylinder 71. A discharge pipe 18 extends out of the cooling jacket 29 through the sealed casing.

The cylinder 71 and the jacket 29 are integrally formed as a single part 33 (for example, a casting). The jacket 29 has one or more open chambers 32 that are substantially aligned with the reciprocating axis of the cylinder 71 and surround the cylinder 71. The open chamber 32 is substantially sealed to form an inner jacket space (by the cylinder head assembly 27).
The linear motor has a pair of oppositely located stator portions 5, 6 that are firmly connected to the cylinder casting 33.

  The pistons 3 and 4 that reciprocate in the cylinder 71 are connected to the cylinder assembly 27 via a spring system. The spring system operates at or near its own resonant frequency. The main spring element of the spring system is the main spring 15. The pistons 3 and 4 are connected to the main spring 15 via a piston rod 47. The main spring 15 is connected to a pair of leg portions 41 extending from the cylinder casting 33. The pair of leg portions 41, the stator portions 5 and 6, the cylinder molded product 33, and the cylinder head assembly 27 together constitute what is referred to as the cylinder portion 1 when the spring system is described.

  The piston rod 47 connects the pistons 3 and 4 to the main spring 15. The piston rod 47 is preferably a rigid piston rod. The piston rod has a plurality of permanent magnets 2 spaced from each other along the piston rod, and forms an armature of a linear motor.

  In order to reduce the frictional force acting between the pistons 3 and 4 and the cylinder 71, and in particular to reduce the lateral load, the piston rod 47 is elastic and movable on both the main spring 15 and the pistons 3 and 4. It is connected to. In particular, the flexible connecting portion is formed between the main spring and the end 48 on the main spring side of the piston rod 47 in the form of a fusion plastic connecting portion between the integrally formed button 49 provided on the main spring 15 and the piston rod 47. It is formed between. The piston rod 47 has a pair of spaced apart circular flanges 3, 36 at the other end, which are fitted into the piston sleeve 4 to form a piston. . The flanges 3 and 36 are alternately arranged with the pair of hinged regions 35 and 37 of the piston rod 47 in a continuous state. The pair of hinged regions 35 and 37 are formed to have main bending axes that are perpendicular to each other.

  The main spring side end 48 of the piston rod 47 is effectively supported in the radial direction by its connecting part to the main spring 15. The main spring 15 is configured to allow reciprocal motion but substantially resist lateral motion or transverse motion relative to the reciprocating direction of the piston within the cylinder. In a preferred embodiment of the present invention, the lateral stiffness is about 3 times the axial stiffness.

The assembly constituting the cylinder part is not securely mounted in the sealed casing. The assembly is free to move in the reciprocating direction of the piston away from the support connection to the casing, i.e. the discharge pipe 18, the liquid refrigerant injection line 34 and the rear support spring 39. The discharge pipe 18, the liquid refrigerant injection line 34, and the rear support spring 39 are each formed to have a known characteristic in the reciprocating direction of the piston in the cylinder. For example, the tubes 18, 34 may be formed in a spiral or helical spring adjacent to their ends extending through the sealed casing 30.
The entire reciprocation is the sum of the movements of the pistons 3 and 4 and the cylinder part.

The gas bearing pistons 3 and 4 are supported radially in the cylinder by aerodynamic gas bearings. The cylinder portion of the compressor includes a cylinder casting 33 provided with a bore 71 passing therethrough and a cylinder liner 10 provided within the bore 31. The cylinder liner 10 may be made of a suitable wear material that reduces piston wear. For example, the cylinder liner may be made from a fiber reinforced plastic composite, such as carbon fiber reinforced nylon with 15% PTFE (which is also preferred for piston rods and sleeves), or graphite flakes. It may be cast iron having a self-lubricating effect. An opening 31 is provided through the cylinder liner 10, and this opening 31 extends from the outer cylindrical surface 70 of the cylinder liner to its inner bore 71. The pistons 3 and 4 move within the internal bore 71, and these openings 31 form gas bearings. Compressed gas is supplied to the opening 31 by a series of gas bearing passages. The other ends of the gas bearing passages open into the gas bearing supply manifold, which is a circular chamber between the liner 10 and the cylinder bore 71 around the cylinder liner 10 at its head end. Is formed. The gas bearing supply manifold is supplied with gas by the compressed gas manifold of the compressor head through a narrow supply passage 73. Since the size of the supply passage 73 is small, the pressure in the bearing supply manifold is controlled, and as a result, the gas consumption of the gas bearing is limited.

  The gas bearing passage is formed as a groove 80 provided in the outer wall 70 of the cylinder liner 10. These grooves 80 are combined with the walls of other cylinder bores 71 to form a sealed passage that leads to the opening 31. As a modification, grooves may be provided in the inner wall of the cylinder bore 71, but it will be understood that these grooves are formed more easily on the liner 10 side than the cylinder casting 33 and on the outer surface rather than the inner surface. . The ability to machine grooves in the surface of one or the other part without the need to drill or bore the passage is a significant manufacturing improvement.

  It has been found that the pressure drop in the gas bearing passage must be similar to the pressure drop in the outlet flow between the pistons 3, 4 and the bore 71 of the cylinder liner 10. Since the clearance between the pistons 3 and 4 and the cylinder liner bore 71 (to obtain an effective compact compressor) is only 10-15 microns, the cross-sectional dimension of the passage must also be very small. Certain (depth about 40 microns, width 150 microns), the dimensions are so small that manufacturing is difficult.

  However, in a preferred embodiment of the present invention, this matching is facilitated by increasing the length of the passages and also increasing the cross-sectional area to, for example, 70 microns x 200 microns. This utilizes the fact that a groove 80 having any appropriate shape can be formed on the surface of the liner portion 10. A groove 80 with an arbitrary path can be formed, and if a tortuous path is selected, the length of the groove 80 is greater than the direct path from the gas bearing supply manifold and the respective gas bearing formation opening 31. May be significantly longer. The preferred embodiment has a gas bearing groove 80 that follows a helical path. The length of each path is formed according to the preferred cross-sectional area of the passage, such a preferred cross-sectional area to facilitate manufacturing (machining or in some other form, eg, manufacturing by precision molding). You can choose.

Each part 5 and 6 of a cylinder part stator is equipped with winding. Each part 5, 6 of the stator comprises an “E” shaped stack with windings around the central pole. The winding is insulated from the stack by a plastic bobbin. The particular form of each stator portion does not form part of the present invention, and many forms will occur to those skilled in the art.
As mentioned above, the cylinder part 1 has a cylinder 71 with an associated cooling jacket 29, cylinder head 27 and linear motor stator parts 5 and 6, all of which are firmly connected to one another. Further, the cylinder part 1 has attachment points for the main spring 15, the discharge pipe 18 and the liquid injection pipe 34. The cylinder part 1 further includes an attachment part for connecting the cylinder part to the main spring 15.

  The cylinder and jacket casting 33 has upper and lower mounting legs 41 extending from its ends away from the cylinder head. The spring 15 (its preferable form will be described later) has a rigid mounting bar 43 provided at one end and connectable to the cylinder casting 33. A pair of laterally extending lugs or protrusions 42 extend from the mounting bar 43 with a spacing from the mounting bar 43 in a direction toward the cylinder casting 33. The lug 42 is arranged to be axially aligned with the spring portions 67, 68 immediately adjacent to the spring end entrance to the mounting bar 43. The upper and lower mounting legs 41 of the cylinder casting 33 each have mounting slots for receiving lugs 42 respectively. The mounting slot is in the form of a cut or tongue groove 75 provided in the inner surface 76 of the mounting leg 41 extending from the free end 77 of the leg 41 towards the cylinder jacket 29. At least one tapered protrusion 78 is formed on the inwardly facing surface 82 of each tongue and groove 75. Each such projection 78 has a vertical surface 79 facing the cylinder casting 33 such that, during assembly, the projection 78 forms a piercing or barbed portion for connection by a snap fit. In particular, the lateral spacing of the lugs 42, which substantially matches the spacing between the opposing surfaces 82 of the tongue and groove groove, passes only the barbs 78 due to deformation of the lugs 42 and / or the mounting legs 41. It ’s like that. Once passed through the protrusion or barb 78, the lug 42 is captured between the vertical surface 79 of the barb 78 and the vertical surface 83 forming the end face of the tongue groove 75. Additional tongue and groove or recesses 84 are formed in the outer surface 85 of each of the mounting legs 41. The tongue groove 84 extends in the axial direction along the outer surface 85, and each tongue groove 84 is provided at least on the inner surface 76 of the attachment leg 41 from the free end 77 of each attachment leg 41. They are located at a distance such that they meet the corresponding ridge grooves 75. The tongue and groove grooves 75, 84 are deep enough that at least the axial opening 86 is configured between them when they meet or overlap.

  A center opening 88 is provided in the clamp spring 87 which is preferably made of a non-magnetic sheet metal which is punched and bent so that the clamp spring 87 can be fitted to the pair of mounting legs 41. The clamp spring 87 has a leg 89 extending rearward in association with each mounting leg 41. The free ends 90 of these legs 89 slide within the tongue groove 84 on the outer surface of the mounting leg 41, and an axial opening between the outer tongue groove 84 and the inner tongue groove 75. Small enough to pass 86. With the legs 42 of the main spring mounting bar 43 positioned at a fixed position in the inner tongue groove 75 of the mounting legs 41, the free end portions 90 are pressed against the lugs 42, and they are respectively connected to the barbs. A vertical surface 79 of 78 is held in contact. A predetermined preliminary load is supplied to the lug 42 by holding the craft spring 87 in a weighted state.

As for a clamp spring, it is desirable to perform the operation | work which attaches the stator parts 5 and 6 in parallel. The central hole 88 provided in the clamp spring 87 is strictly dimensioned with respect to the mounting leg 41 at least laterally with respect to the mounting leg 41. The clamp spring 87 has a stator partial clamp surface 91 in each of its side regions 92 that straddle the mounting legs 41 of the cylinder casting 33.
The cylinder casting 33 has a pair of protruding stator support blocks 55 extending from a face 58 facing the spring of the jacket 29 at a position between the mounting leg 41 parts.

  Each of the “E” shaped stacks of stator portions 5, 6 has a vertical step 69 provided on their outer surfaces 56 oriented in the vertical direction. In each case, this is an outward step directed in a direction away from the motor gap. A part of each of the surfaces 56 positioned close to the air gap abuts on the support block of the cylinder casting 33 or the stator engagement surface 91 of the clamp spring 87 as appropriate. When in position, the inherent attraction between the motor parts pulls the stator portions 5 and 6 together. The width of the gap is maintained by providing the vertical step portion 57 in contact with the outer edge portion 40 of the mounting block 55 and the outer edge portion 72 of the clamp spring 87. In order to further position the stator portions 5 and 6 in the vertical direction, a notch 57 is provided at the outer edge of the stator engaging surface of each mounting block 55, and this notch 57 is “E” in the vertical direction. Matches the dimensions of the letter stack.

  This part of the motor is assembled in a series of operations. The piston assembly is attached to the cylinder casting 33. First, a piston assembly including a piston rod 47 with integral flanges 3 and 36, piston sleeve 4 and armature magnet 2 is assembled. The piston formed by the piston sleeve 4 and the leading flange 3 forming the piston face is pushed into the cylinder bore 71 introduced through the cylinder opening 7 located between the legs 41 of the cylinder casting 33. Therefore, the piston connecting rod 47 is located between the leg portions 41. The inwardly facing surface 76 of the leg 41 has an axial slot 28 extending from the tongue and groove 75 along the centerline. An outwardly extending lug 130 provided on the piston connecting rod 47 reciprocates within these slots 28 during operation. The assembly accuracy is generally such that the lug 130 does not contact the surface of the slot (in the absence of knocking or external movement). However, the slot 28 has a narrow and shallow portion 131 at these ends closest to the cylinder casting 33, which is in an interference fit with the lug 130 of the connecting rod 47. The piston assembly is pushed into the cylinder bore 71 until the lug 130 fits into these narrowed portions 131 and the face of the piston takes a predetermined position relative to the machined cylinder head receiving face 133 of the cylinder casting 33.

  The main spring 15 is attached to the leg portion 41 by fitting the clamp spring 87 to the attachment leg portion 41 and fitting the lug 42 into the notch 75 facing inward and passing the barbs or protrusions 78. Space sufficient to push the clamp spring 87 away from the cylinder casting 33 to introduce the stator portions 5 and 6 between the stator portion engaging surface 91 of the clamp spring 87 and the mounting block 55 of the cylinder casting 33. Until the mounting lug 42 is pressed. Next, the stator portions 5 and 6 are introduced into these fixed positions, and the clamp spring 87 is released. The widths of the stator portions 5 and 6 maintain the clamp spring 87 in a predetermined compressed state.

  Next, a connecting portion is formed between the main spring 15 and the piston rod 47. It should be noted that the piston is in a predetermined position closer to the cylinder head than when the compressor is in operation. The connecting portion is formed by fusing the plastic of the integrally molded button 25 of the main spring 15 and the plastic of the rear end portion 48 of the piston connecting rod 47. Fusion is performed by hot plate welding.

  During hot plate welding, the spring 15 is preferably extended to a predetermined position or until the spring 15 exerts a predetermined force. Once the piston face is in its predetermined position and the spring 15 is released into its neutral position by hot plate welding and fusing of the two plastic parts with the predetermined displacement, the cylinder face 33 is fixed. The exact location of the piston is obtained. This is the case regardless of the accumulated error due to the eccentricity in the form of the spring 15 or the tolerances of the parts in a series of assemblies.

The opening end of the cylinder head cylinder casting 33 is sealed by the compressor 27. The compressor head thereby seals the cylinder 71 and the open end of the cooling jacket chamber 32 surrounding the cylinder 71. As a general form, the cylinder head 27 is composed of four plates 100 to 103 in a stacked state together with a suction muffler / intake manifold 104.
The opening end of the cylinder casting 33 has a head fixing flange 135. The head fixing flange 135 has a large number of screw holes 136 provided around the periphery thereof, and fixing bolts are tightened in the screw holes to draw the stacked plates 100 and 103 together. These are fixed to the face of the cylinder molded product 33.

An annular ridge groove 133 is provided on the face of the flange 135. The tongue and groove groove 133 has lobes 137 and 138 extending outwardly on opposite sides of the flange 135, and these lobes 137 and 138 serve as ports for the discharge pipe 18 and the return pipe 34, respectively.
An opening is provided between the three chambers of the cylinder casting 33.

The first head plate 100 is fitted to the open end of the cylinder molded product 33 in the annular ridge groove 133. This is relatively flexible and acts as a gasket. The first head plate seals the opening of the cylinder jacket, but has a main central opening and does not cover the opening end of the cylinder 71. A compressed gas return port 110 passes through the plate 100 adjacent to the lobe 138 associated with the liquid refrigerant return tube 34. The edge of this opening 110 closest to the outer wall of the cooling jacket 29 is located at a distance from the wall at least in the vicinity of the lobe 138. This effect is that a narrow vacuum region is created just behind the plate 100 and adjacent to the lobe 138 of the ridge groove 135 with gas flowing through the opening 110 into the cooling jacket chamber. It is in.
Another opening 115 is provided through the plate 100 at a location near the discharge tube 18.

The second head plate 101 is positioned in a state of covering the first plate 100. The second plate 101 has a diameter larger than that of the plate 100 and is rigid. This second plate may be made of steel, cast iron or sintered steel. The plate 101 is wider than the tongue and groove groove in which the plate 100 is fitted. The plate 101 is positioned in contact with the face of the flange and presses the first plate 100 against the tongue and groove. Plate 101 has openings 139 spaced around its periphery, which are dimensioned to allow the threaded portion of the bolt to pass freely.
The second head plate 101 has a compressed gas discharge opening 111 that is aligned with the opening 110. The second head plate further has another opening 117 aligned with the opening 115 of the first plate 100.

  A part of the plate 101 seals the cylinder opening 116 of the plate 100. However, that portion of the plate 101 passes through the intake port 113 and the discharge port 114. A spring steel inlet valve 118 is fixed to the face of the plate 101 facing the cylinder, and its head portion covers the intake port 113. The base of the inlet valve 118 is clamped between the plate 100 and the plate 101, and its position is fixed by the alignment pin 140. A spring steel discharge valve 119 is attached to the face of the plate 101 away from the cylinder. The head portion covers the discharge opening 114. The base of the valve 119 is clamped between the second plate 101 and the third plate 102 and is positioned by a mating pin 141. The discharge valve 119 operates in these while being fitted in the discharge manifold opening 112 of the third plate 102 and the discharge manifold 142 formed in the fourth plate 103. Inlet valve 118 fits within the cylinder compression space (away from its base) and operates therein.

The spring steel inlet and outlet valves 118, 119 operate without problems under the influence of the pressure being generated. In a state where the piston is retracted in the cylinder 71, a low pressure exists in a state where the low pressure is applied to the cylinder side rather than the inlet manifold side of the inlet valve 118. Thus, the inlet valve 118 opens so that refrigerant can enter the compression chamber. With the piston moving forward in the cylinder 71, a higher pressure exists in the compression space than in the inlet manifold, and the inlet valve 118 is maintained in its closed position by this pressure difference. The inlet valve 118 is biased toward this closed position by its own elasticity.
Similarly, the discharge valve is normally biased to a closed position that is maintained by the pressure generated during the retraction of the piston in the cylinder 71. The discharge valve is pressed to the open position in a space higher in the compression space than in the discharge manifold during advancement of the piston in the cylinder 71.

  The third head plate 102 is fitted in a circular tongue groove 143 provided on a face 144 facing the cylinder of the fourth plate 103. The plate 102 is relatively flexible, acts as a gasket, and is positioned in a compressed state between the fourth plate 103 and the second plate 101. The third plate 102 has a large opening 112 that is aligned with a large tongue and groove groove 142 provided on the face 144 of the fourth plate 103. The opening 112 and the tongue and groove 142 together form a discharge manifold, and the compressed refrigerant flows from the discharge port 114 into the discharge manifold.

  Another opening 121 provided through the third plate 102 is in alignment with the tongue and groove 145 provided in the face 144 of the fourth plate 103. The opening 121 is also in alignment with the opening 117 of the second plate 101 and the opening 115 of the first plate 100. The gas filter 120 receives the compressed refrigerant from the tongue and groove 145 and sends it to the gas bearing supply passage 73 through the holes 146 and 147 of the first and second plates.

  The intake opening 95 provided through the third plate 102 is in alignment with the intake port 113 provided in the second plate 101. The opening 95 is also in alignment with the intake port 96 that passes through the fourth plate 103. A tapered or frustoconical intake 97 provided in the face 98 of the fourth plate 103 leads to the intake port 96. The intake port 96 is sealed with a suction muffler 104. The suction muffler 104 is formed of an integrally molded product having a considerably wide open space provided on a side portion facing the cylinder casting, for example. This space is sealed by the fourth plate 103 when the fourth plate 103 is connected to the suction muffler. The suction muffler 104 can be bolted to the cylinder casting by many possible means, for example by fitting the peripheral lip of the muffler into a channel provided in the fourth plate 103 or by the head plate via the muffler flange. , Thereby fixing the muffler to the fourth plate 103 as part of the stack of plates 100-103, thereby connecting to the stack of plates 100-103. The suction muffler 104 has a passage 93 extending from the sealed intake manifold space so as to open in a direction away from the cylinder molded product 33. This passage is a refrigerant intake passage. With the compressor disposed within the hermetic housing, an internal projection 109 of the intake tube 12 extending through the hermetic housing extends into the intake passage 93 with a wide clearance.

Cooling Jacket As described above, the cooling jacket chamber 32 connected to each other is provided around the compression cylinder 71. When the refrigerant gas is compressed, the gas reaches a temperature that is significantly higher than the temperature at which it entered the compression space. Thereby, the cylinder head 27 and the cylinder wall liner 10 are heated.

  In the present invention, liquid refrigerant is used to cool the cylinder wall / liner, cylinder head and compressed refrigerant. Liquid refrigerant is supplied from the outlet of the condenser of the refrigeration system. Liquid refrigerant is supplied directly into the cooling jacket chamber 32 surrounding the cylinder. The refrigerant discharged in the newly compressed state flows into the cooling jacket chamber 32 before exiting the compressor via the discharge pipe 18. In the chamber 32, the liquid refrigerant absorbs a large amount of heat from the compressed gas, the wall around the cylinder casting 33 and the cylinder head 27 and evaporates.

  The liquid refrigerant exiting the condenser is in a slightly lower pressure state than the refrigerant just after compression, which becomes a barrier against the flow of liquid to the discharge side of the pump. However, it is preferred to use a passive structure to allow liquid refrigerant to flow into the cooling jacket. In the present invention, this is achieved by several features of the compressor structure. First, a narrow area under pressure is provided immediately adjacent to the outlet from the liquid return line 34 into the jacket space. How to form this low pressure region has been described above. This is caused by the compressed gas flowing into the jacket through the compressed gas opening 110 of the head plate 100. The second feature is a slight inertial pumping effect obtained by the reciprocating motion of the liquid refrigerant return pipe 34 in its longitudinal direction. This reciprocation is the result of the operation of the compressor and the associated reciprocation of the entire cylinder, and the vibration of the cylinder causes a variable acceleration condition of the axially aligned length portion 148 of the return pipe 34, This acceleration state variation results in a varying pressure state at the end where the liquid return tube 34 intersects the inlet 33. Since the liquid evaporates as soon as it enters the cooling jacket during high pressure fluctuations, the reverse flow during low pressure fluctuations is a gas flow. Since the gas is much less dense than the liquid, very little mass flow returns through a small notch joining the liquid return line 34 to the cooling jacket. As a result, there is a net flow of refrigerant into the cooling jacket. The third feature is that in a domestic electric refrigerator or fridge / freezer, the compressor can be installed under the condenser for its intended purpose. If the liquid refrigerant from the condenser does not flow into the cooling jacket at a sufficient flow rate, the liquid refrigerant head increases in the line extending to the compressor, thereby bringing the liquid refrigerant pressure close to the pressure of the compressed refrigerant. It has been found. This effect has been found to provide a measure of self-compensation at a point in time when the relative pressure in the system establishes for liquid refrigerant flowing into the cooling jacket space if not so configured.

Another method of reducing the heat generated by the refrigerant compressor is associated with the refrigerant. It has been found that the use of isobutane (R600a) as a refrigerant in a linear compressor provides a synergistic advantage over the use of other refrigerants.
One fundamental difference between a linear compressor and a conventional compressor is the amount of volume or space above the piston at “top dead center”. In conventional compressors, this volume is fixed to a fraction of the displacement by the compressor geometry. In a free piston linear compressor, this “dead” space varies with power or power input and discharge pressure. With moderate power, the dead space can be as high as 25% of the displacement during operation.

The dead space absorbs and releases energy during compression and re-expansion and acts as a gas spring. However, this is an insufficient spring action due to irreversible heat exchange with the cylinder wall. This heat exchange is approximately proportional to the temperature rise of the refrigerant during compression (or the temperature drop during expansion). This temperature rise depends on the specific heat ratio of the gas. In the case of R134a, which is a commonly used refrigerant, this ratio is 1.127. This is almost the same as other commonly used refrigerants such as CFC12. However, in the case of isobutane (R600a), the specific heat ratio is 1.108. The table below lists the adiabatic temperatures of gases compressed to a saturation pressure matched to the condensation temperature for the refrigerator (0 ° C. evaporation temperature) and the freezer or fridge / freezer (−18 ° C. evaporation temperature). Both have a 32 ° C. superheated gas entering the compressor and a condensation temperature of 42 ° C. (these are typical values).

Cooling medium evaporation temperature
-18 0
Isobutane 87 ℃ 69 ℃
HFC134a 99 ° C 77 ° C
CFC12 104 ° C 79 ° C
Thus, it can be seen that the characteristics of isobutane and other refrigerants having a low specific heat ratio are particularly matched with the physical characteristics of the linear compressor. This improvement was verified by experiment.

A series of tests were conducted on a 450 liter refrigerator. This refrigerator had a mass flow meter provided in the suction line before the compressor. The refrigerator was tested in an environmental chamber according to standard AS / NZS4474.1-1997. First, the test was conducted using refrigerant R134a. Next, this test was conducted for two cases using refrigerant R600a (isobutane). The test results were as follows.
R134a R600a (Test 1) R600a (Test 2)
TCONDENSOR 34.3 33.3 33.5
TEVAPOTOROR -3.5 -6.1 -4.5
Input power 22.3 18.1 17.8
Refrigeration power 75.25 75.01 75.07
Displacement amount 7.96 8.7 8.48
Coefficient of performance 3.38 4.14 4.23
The test results show that the performance case of a linear compressor operating with isobutane is significantly improved compared to operating with R134a.

ｍ_piston'及びｍ_cylinder'がピストン及びシリンダスプリングに加わるばね質量である場合、固有振動数ｆ_nは通常、所望の動作周波数よりも１０〜２０Ｈｚ低く、それにより、圧縮ガスに起因する剛性の増大による周波数の増加に対応するようになっている。 The spring system cylinder 9 is supported by the discharge pipe 18 and the liquid refrigerant injection pipe 34, and these pipes have an overall rigidity K _{cylinder ′} in the axial direction. The support spring 39 has a very small axial rigidity, and its effect is negligible. The piston sleeve 4 is supported in a radial direction by a gas bearing formed by a cavity and a passage provided at a boundary portion between the cylinder bore and the cylinder liner 10. The main spring has rigidity K _{main ′} so that the resonance of the piston and cylinder can be obtained, and the resonance frequency f _{n ′} can be estimated from the following relational expression.

When m _{piston ′} and m _{cylinder ′} are spring masses applied to the piston and cylinder spring, the natural frequency f _n is typically 10-20 Hz below the desired operating frequency, thereby increasing the stiffness due to the compressed gas. It corresponds to the increase of the frequency by.

As described above, the compressor motor has a stator formed of two parts 5 and 6 and a magnet provided on the armature 22. The magnetic interaction between the stator (5, 6) and the armature 22 generates a reciprocating force applied to the piston.
The alternating current in the stator coil (which need not necessarily be a sine wave) will cause a significant movement of the piston relative to the cylinder assembly casting 33. However, the condition is that the alternating frequency is close to the natural resonance frequency of the mechanical system. This vibration force generates a reaction force applied to the stator portion. In this manner, the stator portions 5 and 6 are firmly attached to the cylinder assembly by the clamp spring 87.

  In the present invention, it is proposed that the main spring 15 has a rigidity much greater than that of an effective cylinder spring. The main spring has a “second” mode frequency higher than the “third” mode frequency, so that the “gas spring” merely pulls the mode frequency apart from each other.

The actual operating frequency (“second” mode frequency) is determined by the complicated relationship between the piston and cylinder mass and the rigidity of the cylinder spring and main spring 15. Further, if the discharge pressure is high, the rigidity of the compressed gas must be added to the rigidity of the main spring. However, when the cylinder spring is extremely soft (for example, 1/10 of the rigidity of the main spring), the operating frequency can be determined fairly accurately by the following equation.

External vibrations due to sources other than the fundamental frequency due to piston / cylinder motion can be substantially eliminated by reducing the vibration mass and making the cylinder springs relatively soft. Without using a specific cylinder spring at all, the rigidity of the cylinder spring can be reduced to the minimum value by using the inherent rigidity (usually about 1,000 N / m) of the discharge pipe 18 (or when using a cooling pipe) , The rigidity of both the discharge pipe and the cooling pipe are combined, ie 2,000 N / m).
In order for the compressor to resonate with a piston mass of about 100 g at about 75 Hz and a cylinder to piston mass ratio of 10: 1, the main spring (K _main ) needs to be about 40,000 N / m. There is. Typically, the value of the gas spring is lower than that of the main spring, but not so low. In the above case, the operating frequency is estimated to be 99 Hz when the gas spring (K _gas ) operates at about 15,000 N / m.

If the main spring operating frequency is increased, the size of the motor is reduced, but high spring rigidity is required. As a result, the stress generated in the spring is increased. Therefore, it is important for the life of the compressor to use the highest quality spring material. Conventionally, a main spring made from a pressed spring steel sheet is often used. However, the edges cut during the pressing process require careful polishing to restore the original fatigue strength of the spring steel sheet.
In a preferred embodiment of the invention, the main spring is made from a piano wire with a circular cross section, which has a very high fatigue strength without the need for subsequent polishing.

  A preferred embodiment of the main spring is shown in FIGS. This spring is in the form of a continuous loop twisted into a double helix. One wire forming the spring 15 has a free end fixed in a mounting bar 43 with a lug 42 attachable to one of the compressor parts. As can be understood from the description of FIG. 3 and the above description, these lugs 42 are attached to the cylinder portion 1, and are particularly fitted in the slots of the leg portions 41. As is apparent from the description of FIG. 3 and the above description, the spring 15 has another attachment point 62 that can be attached to another compressor component. In the preferred form, this connection is made to the piston rod 47 via a molded plastic button 25. The spring 15 has a pair of curved portions 63, 64 with a substantially constant radius of curvature, each of which extends around the cylinder mounting bar. Each of these curved portions extends over a length of about 360 °. Each part is smoothly curved at both ends. At the mounting bar transitions 65, 66, these portions are curved so that their lengths 67, 68 at the cylinder mounting bar are aligned radially. The sharp bends 65, 66 are selected to maintain a substantially uniform stress distribution along the transition. When the cylinder mounting ends 67, 68 are aligned, they align with the cylinder mounting bar. The portions 63 and 64 having a constant curvature of the spring 15 may have any length. In the example shown, the length of each of these portions is about 360 °.

  As shown in FIGS. 1 and 2, the mounting bar 43 of the spring 15 is located on another side thereof. The central mounting location 62 is on the near side. The constant curvature portions 63, 64 each have their lower ends smoothly curved so as to continue in radial alignment with each other across the overall circle diameter of the spring at the attachment point 62. . This alignment of diameters is substantially perpendicular to the alignment of the ends 67, 68 at the cylinder mounting bar 43.

  The curved portions 63 and 64 having a constant curvature radius are placed in a twisted state due to the displacement of the piston mounting portion 62 with respect to the mounting bar 43. Since the radius is constant, the torsional stress along each of the portions 63, 64 is also substantially constant. The radial direction or substantially radial direction at the cylinder mounting portions 67, 68 and the piston mounting location 62 reduces torsional stress, where the end of the spring fits into the mounting bar 43 at the piston mounting location 62. In addition, as described above, the attachment of the spring 15 to both the cylinder portion and the piston portion is improved by being in the radial direction or substantially in the radial direction.

INDUSTRIAL APPLICATION FIELD OF THE LINEAR COMPRESSOR The linear compressor of the preferred embodiment of the present invention is primarily intended to be employed in a domestic refrigeration system, such as a freezer, electric refrigerator or refrigerator / freezer combination. Such linear compressors can directly replace other types of compressors, for example rotary crank compressors. The linear compressor receives the low-pressure evaporated refrigerant through the suction pipe 12 and sends out the compressed refrigerant through the discharge stub 13 at a high pressure. In a refrigeration system, the discharge stub 13 is generally connected to a condenser. The suction pipe 12 is connected to receive evaporated refrigerant from one or more evaporators. The liquid refrigerant delivery stub 14 receives condensed refrigerant from the condenser (or from an accumulator or refrigerant line located downstream of the condenser) for use in cooling the compressor as previously described. A process tube 16 extending through the sealed casing is also provided for use in evacuating the refrigeration system and filling with a selected refrigerant.
The entire configuration of the refrigeration system incorporating the compressor of the present invention does not form the main part of the present invention. Many useful refrigeration systems are known and many more configurations are possible. The compressor of the present invention is useful in any such system.

  The usefulness of the compressor according to a preferred embodiment of the present invention is not limited to a refrigeration system for home electric refrigerators and freezers, but can also be used for a refrigeration system for an air conditioner. In addition, such a compressor can be used as a gas compressor for applications that do not use a refrigerant that can dispense with delivery of a liquid refrigerant for cooling.

  The operation and control of the linear compressor is performed by appropriately energizing the stator portions 5 and 6. A power or power supply connector 17 is provided through the sealed casing 30 in a state attached to the opening 19. A suitable control system for energizing the windings does not form part of the present invention, and many other drive systems for brushless DC motors are well known and can be used. A suitable drive system is described in detail in the applicant's co-pending international application PCT / NZ00 / 00105.

Advantages A summary of the many advantages of the linear compressor of the preferred embodiment of the present invention is set forth in the foregoing description. Some of the other advantages that have not been outlined are:
(A) The elastic connection between the piston connecting rod and the piston, and the mounting leg 41 of the cylinder casting 33 via the main spring, and the light weight of the piston and the proper construction material of the piston sleeve and cylinder liner Coupled with the choice, no additional lubricant in the compressor is required. Thus, an undesirable presence of oil lubricant in the refrigerant or an accumulator or separator of oil lubricant is not required throughout the refrigeration system.
(B) The lightweight piston and connecting rod assembly reduces the magnitude of the vibration momentum of the two main compressor structural members and, as a result, reduces the vibration transmitted to the sealed casing.
(C) Since the main spring is made of a material having a long fatigue life, the main spring does not require an additional polishing operation after molding, and the size and shape of the main spring is determined by the desired spring strength. Minimize material usage, spring weight and spring size.
(D) the side with the correct and effective alignment of the armature operation between the two parts of the stator by attaching the armature magnet to the piston connecting rod with the piston connecting rod operating directly in the stator gap; A compact linear motor can be obtained.
(E) The compliant joint between the piston and the piston connecting rod and between the connecting rod and the cylinder part does not exert a local pressure in the cylinder bore due to the inaccuracy of the piston sleeve and the specific axial direction. Like that.
(F) It has been found that the use of isobutylene refrigerant in a linear compressor provides a synergistic advantage compared to the use of a refrigerant with a high specific heat ratio.
(G) Liquid feed into the cooling jacket surrounding the cylinder provides a cooling action by evaporation into the combined compressed gas stream leaving the cylinder and cylinder header assembly and compressor. Feeding into the high pressure gas in the jacket is accomplished without the need for an active pumping device.
(H) The overall configuration of the compressor is suitable for use in household electrical equipment. The size and shape of the machine space for the refrigerator or freezer can be reduced because the overall height of the sealed casing is low. Due to the consideration of the interior space, the machine compartment as a whole extends the entire width of the electrical equipment, regardless of the components that need to be accommodated. However, its height and depth are generally determined by the maximum height and depth requirements suitable for the compressor. The reason why the linear compressor of the present invention has a low profile (thin) is that the compressor is not concentric but is arranged end to end.
(I) The main spring and the motor part of the compressor receive an elastic preload determined by the geometrical arrangement and dimensions of these components. Parts are loose during operation of the compressor due to incomplete assembly, normal manufacturing tolerances or effects of motor operation, resulting in a bang, rattle, or Reduce or eliminate the risk of failure.
(J) The piston face is accurately positioned with respect to the neutral position of the main spring by fusing the piston rod to the main spring by the hot plate welding method as described above. As a result, the compressor can be operated in a state where the cylinder head clearance is reduced with confidence that the piston does not hit the cylinder head at the front end of the movement.

It is the partial exploded view seen from the top of the linear compressor of preferred embodiment of the present invention. FIG. 2 is an exploded view of a motor side end portion of the compressor assembly viewed from a direction different from FIG. 1. It is an exploded view of the head side end portion of the compressor assembly viewed from one direction. It is an exploded view of the head side end part of the compressor assembly seen from another direction.

Claims (9)

A spring connected between a cylinder and a piston of a linear compressor,
A first straight portion in a first plane, a second straight portion in a second plane parallel to the first plane, and first and second spiral portions having a substantially constant curvature. With a closed loop of high fatigue strength metal wire with
Each helical portion connects the end of the first straight portion and the end of the second straight portion;
The spiral portion has the same direction of curvature moving from the first portion to the second portion;
A spring characterized by that. A plurality of transition portions between the first and second straight portions and the first and second spiral portions;
Each transition portion is aligned with the linear portion at one end and the spiral portion at the other end and is curved with decreasing curvature toward the spiral portion between the ends,
The spring according to claim 1. An orientation of the second portion in the second plane is orthogonal to an orientation of the first portion in the first plane;
The spring according to claim 1 or 2. A mounting block connected to the first portion and having a third plane parallel to the first plane;
A pair of protrusions extending outward in the orientation direction of the first linear portion,
The spring according to any one of claims 1 to 3. A plastic composite mounting button molded in a central region of the second straight portion;
The spring according to any one of claims 1 to 4. A cylinder part;
A piston part;
The spring according to any one of claims 1 to 5, wherein the spring extends between the cylinder part and the piston part, the cylinder part is connected to the first straight part, and the piston part is used as a second straight part. And a linear compressor including a connecting spring. A method of manufacturing a linear compressor so that a piston of the linear compressor can be connected to a spring of the linear compressor,
(A) disposing the piston at a predetermined axial position within the bore of the compressor;
(B) disposing the piston at a piston coupling position of a spring that is already coupled to the cylinder portion at a position based on a predetermined displacement of the spring or a position that generates a predetermined reaction force;
(C) joining the piston and the piston coupling position of the spring at an axial separation position fixed according to the separation position obtained in steps (a) and (b),
Either of the steps (a) and (b) may be performed first,
A method characterized by that. The step (c) further comprises the step of fusing an extension from the piston to the mounting button of the spring;
In the melting step, an axial dimension of the button or the extension is changed from a pre-assembly dimension.
The method of claim 7. The step (b) is disposed at a position displaced beyond the normal operating position of the piston, and an element connected to the piston part engages with an element of the cylinder part, thereby causing the element of the piston part to engage with the cylinder. A step of disposing at a predetermined position in a plane orthogonal to a reciprocating axis of the piston in
The method according to claim 7 or 8.

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