CN100441864C - linear compressor - Google Patents

Abstract

A linear compressor has a cylinder section that includes a cylinder bore and a stator with an air gap through which a connecting rod passes. Pistons (3, 4) are disposed in cylinder bores and are slidable therein. The main spring (15) connects the cylinder part (10) directly or indirectly to the piston. The connecting rod is connected between the main spring (15) and the pistons (3, 4). At least one armature rotor pole is disposed along the link. The armature rotor poles are in the form of one or more flat blocks (2) of permanent magnetic material supported on connecting rods (47) which are enlarged to define the armature rotor poles. The connecting rod (47) is only supported at one end by the pistons (3, 4) and at the other end by the main spring (15). A connecting rod (47) comprises a compliant connection between the pistons (3, 4) and the armature rotor.

Description

linear compressor

This application is a divisional application of No. 00820050.5 Chinese invention patent application "Linear Compressor" submitted on October 17, 2000.

technical field

This invention relates to linear compressors, especially but not exclusively to compressors for refrigerators.

Background technique

Compressors, especially refrigerator compressors, are usually driven by rotary electric motors. However, even in their most efficient form, there are huge losses associated with crank systems that convert rotary motion into linear reciprocating motion. Alternatively a rotary compressor can be used which does not require a crank, but has high centripetal loads, resulting in huge frictional losses. Linear compressors driven by linear motors do not have these losses and can be designed so that the bearing loads are low enough that an aerostatic gas bearing as disclosed in U.S. Pat. Low bearing loads.

A discussion of aerostatic gas bearings includes "Aerostatic Bearing Design" by J.W. Powell, published in 1970 by the London Mechanical Publishing Limited. Producing effective gas bearings is difficult with normal manufacturing tolerances and equipment.

Existing compressors are installed in hermetic casings which, in use, serve as a reservoir for refrigerant gas. Refrigerant gas is fed into the compressor from the accumulator and discharged from the compressor through the casing through the discharge pipe.

The operation of the compressor involves the reciprocation of moving parts, causing the compressor unit to vibrate along all three axes. To reduce external noise effects of vibrations, the compressor is mounted on isolation springs inside a hermetically sealed housing.

With linear compressors, the piston vibrates relative to the cylinder along only one axis, resulting in reaction forces on any fixed components. One proposed solution to this problem is to run simultaneously a pair of compressors arranged in a balanced and opposite manner. However, this configuration is too complex and expensive for commercial products such as domestic refrigerators. Another solution proposed is to add a resonant weight to reduce vibration. However, this approach limits the operation of the compressor because the counterweight is a negative feedback device and is limited to fundamental unbalanced forces. Another proposal was presented in "Small Rotary and Linear Low-Temperature Generating Coolers for IR Systems" by Gully and Hanes, Proceedings of the 6th International Conference on Cryogenic Coolers, Plymouth, MA, 1990. This solution involves independently supporting the piston and cylinder parts of the compressor in the housing so that the stator acts as a counterweight. However, there were problems implementing such a design in a domestic refrigerator when the mass of the piston was low. In this type of compressor, when the discharge pressure increases, the force of the compressed gas acts as a spring (gas spring), which increases the operating speed as the discharge pressure increases. This is also problematic because the "third" mode of vibration (where the piston and cylinder vibrate synchronously with each other but not synchronously with the compressor casing) is only slightly within the ideal "second" mode of vibration (where the casing does not vibrate, and Piston and cylinder are out of sync). Thus, the housing begins to vibrate excessively when the "gas spring" kicks in and effectively raises the "second" mode frequency to and eventually above the "third" mode.

For many applications, it is desirable that the compressor should be small in size. This reduces the size of all components including the spring and resonance system. Reducing the size of the compressor requires the compressor to run at a higher frequency. The combination of size reduction at higher frequencies will increase the stress in the spring element. In some linear compressors, the main spring is made from pressed spring steel. It has been found that the edges cut during the pressing operation require careful polishing to regain the spring steel original strength and frequently fail due to unintentional stress concentrations.

Another problem with compressors is that they generally have heat buildup, especially near the compressor block and cylinder head. Heat buildup is caused by friction between moving elements and heat transfer from compressed refrigerant. Heat buildup creates major problems in terms of increased wear, operating conditions, and tolerances between components that vary with the period of time the compressor has been operating. These effects are especially pronounced for linear compressors that may run for long periods of time and for which narrow clearances are important, especially when using aerostatic gas bearing systems.

Another heating effect is from the irreversible heat loss prior to re-expansion from the refrigerant remaining in the compression space after compression. In a linear compressor, about 15% of the compressed refrigerant may not be vented, compared to about 5% in a crank driven compressor. These heat sources, which are negligible in existing compressors, are important heat sources in linear compressors.

One method of cooling the block and cylinder head of a compressor involves the use of liquid refrigerant supplied from a condenser in a subsequent refrigeration system. For example in US patent US2510887 liquid refrigerant from the condenser is fed to a first cooling jacket surrounding the cylinder block and thus to a second cooling jacket surrounding the compressor head and subsequently injected from the venturi tube arrangement Connected in the discharge line between the cylinder head and the condenser. This is within the range of standard crank driven compressors. Also within the scope of standard crank driven compressors, US5694780 shows a line in which the liquid refrigerant from the condenser is raised to a higher pressure by a pump. Liquid refrigerant is pumped into a cooling jacket that surrounds the compressor cylinder. Liquid refrigerant is forced from the cooling jacket into a discharge header in the compressor cylinder head where it mixes with the compressed refrigerant as it exits the compressor. The disadvantage of this arrangement is that an additional pump is required for the liquid refrigerant to pass through the cooling jacket surrounding the cylinder and subsequently overcome the pressure of the compressed gas into the discharge header.

A number of linear compressors have been developed to replace existing rotary reciprocating compressors that are already commercial products. In order to have a compact size, a compressor in which a stator, an armature rotor, a cylinder, and a piston are all centrally arranged has been manufactured. However, the size of the existing compressor limits the size of the machine room of the refrigerator and results in wasted space around the compressor in the machine room.

Contents of the invention

The object of the present invention is to provide a compact linear compressor capable of overcoming the above-mentioned disadvantages of the prior art.

In a first aspect, the present invention provides a linear compressor comprising:

a cylinder part including a cylinder bore and a stator with an air gap;

a piston disposed in and slidable in said cylinder bore;

a main spring connecting said cylinder portion directly or indirectly to said piston;

a connecting rod between the main spring and the piston, passing through the air gap of the stator and connecting the main spring to the piston; and

one or more substantially flat blocks of permanent magnetic material supported on said link with the large face of said blocks facing the stator, said permanent magnetic material being magnetized to define at least one armature rotor pole (armature pole).

In another aspect, the present invention provides a linear compressor comprising:

a cylinder part including a cylinder bore and a stator with an air gap;

a piston disposed in and slidable in said cylinder bore;

a main spring connecting said cylinder portion directly or indirectly to said piston;

a connecting rod between the main spring and the piston, passing through the air gap of the stator and connecting the main spring to the piston; and

at least one armature rotor pole disposed along said link;

Wherein the connecting rod is supported at one end by the piston and away from the one end by the main spring.

In another aspect, the present invention provides a linear compressor comprising:

the cylinder portion including the cylinder bore;

a piston disposed in and slidable in said cylinder bore;

a main spring connecting the cylinder portion directly or indirectly to the piston; and

A connecting rod between said main spring and said piston and connecting said main spring to said piston, having at least one of the following connections as a compliant connection:

(a) the connection between said piston and piston rod; and

(b) the connection between said piston rod and said main spring;

A compliant connection transmits side and axial loads, but allows rotation within the cylinder bore about an axis transverse to the axis of reciprocation of the piston.

In yet another aspect, the present invention provides a linear compressor comprising: a piston and a cylinder cooperating with each other, and an electromagnetic linear motor, the relative movement of the piston and cylinder is controlled by a spring system, and the electromagnetic linear motor is fabricated as driving the relative motion of the piston and cylinder at the resonant frequency of the spring system;

a compression space above said piston;

a chamber surrounding the cylinder;

a cooled high-pressure refrigerant inlet to the chamber, allowing refrigerant from the refrigeration circuit after the condenser to enter the chamber;

a compressed refrigerant outlet from the compression space; and

A compressed refrigerant discharge path leads from the compression space to the chamber.

In yet another aspect, the present invention provides a linear compressor comprising:

a cylinder section comprising a cylinder housing, a cylinder bore in the cylinder housing, a cylinder head at one end of the cylinder housing, and a stator having a pair of stator sections with windings , each stator portion is connected to said cylinder housing at an end opposite said cylinder head such that an air gap is located between said stator portions;

a piston disposed in and slidable in said cylinder bore;

a main spring located at the end of the stator remote from the cylinder head, directly or indirectly connected between the piston and the cylinder portion;

a connecting rod passing through the stator air gap between the main spring and the piston and connecting the main spring to the piston; and

An armature rotor disposed along and connected to the connecting rod operating in the air gap of the stator.

In yet another aspect, the present invention provides a spring for connecting between a cylinder and a piston portion of a linear compressor in a linear compressor, the spring comprising:

A closed loop of high fatigue strength metallic steel wire having a first straight portion in a first plane and a second straight portion in a second plane parallel to the first, and a substantially constant curvature first and second helical portions, each helical portion connected between one end of the first straight portion and one end of the second straight portion, the helical portions having the ability to move from the first portion to the The same bending direction of the second part.

In yet another aspect, the present invention provides a linear compressor comprising:

cylinder part;

Piston part;

a main spring connected between the cylinder portion and the piston portion and running in a direction of reciprocating movement of the piston portion relative to the cylinder portion;

sealed shell;

a linear motor arranged to operate between said cylinder portion and said piston portion;

A cylinder portion spring device connected between said cylinder portion and said housing portion and running along said reciprocating direction; characterized by:

(a) said cylinder portion spring means constituted by the combined effect of the necessary connection between the cylinder portion and the sealed housing, including a discharge tube extending from said cylinder portion at least to said housing; and

(b) said cylinder part spring means has low stiffness, said piston part has a mass less than 1/5 of the mass of said cylinder part, and is not directly connected between said piston part and said housing The piston part of the spring device.

In yet another aspect, the present invention provides a linear compressor comprising:

the cylinder portion including the cylinder bore;

a piston disposed in and slidable in said cylinder bore;

a main spring connecting the cylinder portion to the piston, the connection of the main spring to the cylinder portion comprising at least one pair of mounting tabs on the main spring;

With respect to an abutment surface on the cylinder portion of each of the protrusions of the main spring, each of the protrusions of the main spring abuts against a corresponding abutment surface, the abutment the surface is shaped to prevent the respective said projections from moving away from each other in one direction; and

a spring stop abutting said protrusion from said one direction, said spring stop having a total preload abutting said protrusion at least in excess of the expected power applied to said main spring in said one direction pressure.

In yet another aspect, the present invention provides a method of manufacturing a linear compressor for coupling a piston of the linear compressor to a spring of the linear compressor, said method comprising the following steps which may be performed in any order:

(a) disposing the piston at a predetermined axial position in the compressor cylinder bore;

(b) setting the piston connection position of the spring that has been connected to the cylinder portion at a position based on a predetermined displacement amount of the spring or a position at which the spring exerts a predetermined reaction force; and

(c) integrating said piston with said piston connection location of said spring at a strict axial spacing determined from the spacing obtained in steps (a) and (b).

For those skilled in the field to which the present invention pertains, many changes in the structure of the present invention as well as many different embodiments and applications can be proposed without departing from the scope of the claims of the present invention. The contents and descriptions disclosed herein are for the purpose of illustration only and do not constitute limitations on the present invention.

Description of drawings

1 is a partial exploded view of a linear compressor according to a preferred embodiment of the present invention viewed from above;

Figure 2 is an exploded view of the motor and compressor assembly viewed from another direction;

Figure 3 is an exploded view of the head end of the compressor assembly viewed from one direction; and

Figure 4 is an exploded view of the head end of the compressor assembly viewed from another direction.

Detailed ways

The overall structure

The embodiment of the invention shown in the figures involves permanent magnet linear motors driving a resonant reciprocating compressor, operating together in a hermetic housing. The compressor comprises pistons 3, 4 reciprocating in a cylinder bore 71 and operating on a working fluid which is alternately sucked into and discharged from a compression space at the head end of the cylinder. A cylinder head 27 connected to the cylinder blocks closes the open ends of the cylinder bore 71 to form a compression space and includes inlet and outlet valves 118, 119 and associated manifolds. The compressed working gas is discharged from the compression space through the outlet valve 119 into the discharge manifold. The discharge header directs the compressed working fluid into the cooling jacket 29 surrounding the cylinder block 71 . The discharge pipe 18 passes from the cooling jacket 29 and leads to the outside of the sealed housing.

The cylinder block 71 and the cooling jacket 29 are integrally formed as a single body 33 (for example, one casting). The cooling jacket 29 includes one or more open end chambers 32 positioned generally relative to the reciprocating axis of the cylinder 71 and surrounding the cylinder 71 . The open end chamber 32 is substantially closed (by the cylinder head assembly 27 ) to form a cooling jacket space.

The linear motor comprises a pair of opposing stator sections 5,6 which are rigidly connected to the cylinder casting 33.

Pistons 3, 4 reciprocating in cylinder 71 are connected to cylinder assembly 27 by a spring system. It operates at or close to its natural resonant frequency. The main spring element of the spring system is the main spring 15 . The pistons 3 , 4 are connected to the main spring 15 via a piston rod 47 . The mainspring 15 is connected to a pair of brackets 41 extending from the cylinder casting 33 . The pair of brackets 41, the stator parts 5, 6, the cylinder casting 33 and the cylinder head assembly 27 together form the cylinder part 1 referred to in the discussion of the spring system.

A piston rod 47 connects the pistons 3 , 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 along it and constitutes the armature rotor of the linear motor.

In order to keep the frictional loads between the pistons 3 , 4 and the cylinder 71 low, and in particular to reduce any side loads, the piston rod 47 is elastically and flexibly connected to the main spring 15 and the pistons 3 , 4 . In particular, an elastic connection is formed between the main spring end 48 of the piston rod 47 and the main spring in the form of a melt-plastic connection between the molded button 49 on the main spring 15 and the piston rod 47 . At its other end, the piston rod 47 includes a pair of spaced apart annular flanges 3, 36 which fit within the piston sleeve 4 to form the piston. Flanges 3 , 36 are spaced in series with a pair of articulation areas 35 , 37 of piston rod 47 . The pair of hinged areas 35, 37 are formed with major axes bent at right angles to each other.

At the main spring end 48 the piston rod 47 is effectively radially supported by its connection to the main spring 15 . The main spring 15 is made so that it can reciprocate but substantially resists any sideways movement in the cylinder or movement perpendicular to the direction of piston reciprocation. In a preferred embodiment of the invention, the lateral stiffness is approximately three times the axial stiffness.

The assembly including the cylinder portion is not rigidly mounted in the sealed housing. It is free to move in the reciprocating direction of the piston except for the support connection to the housing: discharge pipe 18, liquid refrigerant injection line 34 and rear support spring 39. The discharge pipe 18, the liquid refrigerant injection line 34, and the rear support spring 39 are respectively formed as springs of known characteristics in the cylinder in the piston reciprocating direction. For example, the discharge pipe 18 and the liquid refrigerant injection line 34 may be formed as coil springs proximate their ends, which pass through the sealed case 30 .

The total reciprocating motion is the sum of the motions of the pistons 3, 4 and the cylinder parts.

gas bearing

Pistons 3, 4 are radially supported in the cylinder by aerostatic gas bearings. The cylinder portion of the compressor includes a cylinder casting 33 having a bore 71 therethrough and a cylinder liner 10 located in the bore 71 . The cylinder liner 10 may be made of any material suitable to reduce piston wear. For example, it can be made of a fiber reinforced plastic component such as carbon fiber reinforced nylon with 15% PTFE (preferably also for piston rods and piston sleeves), or it can be made of graphite flake cast iron with self-lubricating effect. The cylinder liner 10 has a through opening 31 extending from its outer cylindrical surface 70 to its inner bore 71 . The pistons 3, 4 travel in bores 71 and these openings 31 form gas bearings. A source of compressed gas is supplied to opening 31 through a series of gas bearing passages. The gas bearing channel leads at one end to a gas bearing supply manifold formed as an annular chamber around the cylinder liner 10 at its head between the cylinder liner 10 and the cylinder bore 71 . The gas bearing supply manifold is in turn supplied by the compressed gas manifold of the compressor through a small supply duct 73 . The undersized supply duct 73 controls the pressure in the gas bearing supply duct, thereby limiting the gas consumption of the gas bearing.

The gas bearing channels are formed as grooves 80 on the outer wall 70 of the cylinder liner 10 . The groove 80 combines with the walls of the other cylinder bore 71 to form a sealed passage to the opening 31 . It should be appreciated that although the grooves could alternatively be formed on the inner wall of the cylinder bore 71, they are easier to form on the cylinder liner 10 than on the cylinder casting 33, as an outer surface rather than an inner surface. surface. Being able to machine grooves in the surface of one or the other of the components rather than having to drill channels is a huge manufacturing improvement.

It has been found that the pressure drop in the gas bearing passage must be similar to the pressure drop in the exhaust gas flow between the pistons 3 , 4 and the bore 71 of the cylinder liner 10 . Since (for an efficient compact compressor) the clearance between the pistons 3, 4 and the cylinder liner bore 71 is only 10 to 15 microns, the cross-sectional dimensions of the channels must also be very small (about 40 microns deep x 150 microns wide). These small dimensions make fabrication difficult.

However, in a preferred embodiment of the invention, mating can be facilitated by increasing the channel length so that the cross-sectional area can also be increased to eg 70 microns x 200 microns. This takes advantage of the ability to form grooves 80 of any suitable shape in the surface of the cylinder liner 10 . The groove 80 can be formed with any path, and if a tortuous path is chosen, the length of the groove 80 can be significantly greater than the straight path from the gas bearing supply manifold to the corresponding opening 31 forming the gas bearing. The preferred embodiment has gas bearing grooves 80 following a helical path. The length of the respective paths is chosen according to the preferred cross-sectional area of the channel, which can be chosen for ease of manufacture (eg machining or possibly by some other form such as precision moulding).

cylinder part

Each part 5, 6 of the stator carries a winding. Each section 5, 6 of the stator is formed with an "E" shaped stack of laminations such that the windings are wound around a central rod. The windings are insulated from the lamination stack by plastic bobbins. The specific form of each stator section forms no part of the invention and there are many possible configurations which will be apparent to those skilled in the art.

As already mentioned the cylinder part 1 comprises the cylinder block 71 with the associated cooling jacket 29, the cylinder head 27 and the linear motor stator parts 5, 6, all of which are rigidly connected to each other. Also, the cylinder portion 1 includes mounting locations for the main spring 15 , the discharge pipe 18 and the liquid refrigerant injection pipe 34 . It also has mounting means for connecting the cylinder section to the mainspring 15.

The block and sleeve casting 33 has upper and lower mounting brackets 41 extending from its ends away from the cylinder head. The spring 15 , the preferred form of which will be described below, includes a rigid mounting plate 43 at one end thereof for attachment to the cylinder casting 33 . A pair of laterally extending protrusions 42 project from the mounting plate 43 and are spaced from the mounting plate 43 in a direction toward the cylinder casting 33 . The protrusion 43 is arranged in axial alignment with the spring portions 67 , 68 entering the mounting plate 43 proximate the spring ends. The upper and lower mounting brackets 41 of the cylinder casting 33 each include a mounting slot for one protrusion 42 . The mounting slot takes the form of a tenon joint 75 on the inner face 76 of the mounting bracket 41 extending from the free end of the bracket 41 towards the cylinder casing 29 . At least one conical protrusion 78 is formed on an inwardly facing face 82 of each dovetail 75 . Each such protrusion 78 has a vertical face 79 facing the cylinder casting 33 such that the protrusion 78 forms a barb for a snap fit connection during assembly. In particular, the lateral spacing of protrusions 42 , which substantially matches the spacing between the dovetailed opposing faces 82 , enables protrusions 42 to pass barbs 78 solely by deformation of protrusions 42 , mounting bracket 41 , or both. Once past the protrusion or barb 78 , the projection 42 is confined between the vertical face 79 of the barb 78 and the vertical face 83 forming the end face of the tenon joint 75 . An auxiliary dovetail or recess 84 is formed on the outer face 85 of each mounting bracket 41 . The mortise 84 extends axially along the outside and is spaced from the free end 77 of the respective mounting bracket 41 such that each auxiliary mortise 84 at least meets the corresponding mortise 75 on the inner face of the mounting bracket 41 . Mortise joints 75 and 84 are sufficiently deep that when they meet or overlap at least one axial opening 86 is formed between them.

Clamping spring 87 , preferably formed from a stamped and folded sheet of non-magnetic metal, has a central opening 88 therethrough so that it may fit over the pair of mounting brackets 41 . Clamping spring 87 has a rearwardly extending bracket 89 associated with each mounting bracket 41 . The free ends 90 of these brackets 89 slide in the outer dovetails 84 of the mounting bracket 41 and are small enough to pass through the axial opening 86 between the outer and inner dowels 84 and 75 . As the protrusions 42 of the main spring mounting plate 43 are held in place in the internal dovetail 75 of the mounting bracket 41 , the free ends 90 press against the protrusions 42 and hold them against the vertical face 79 of the corresponding barb 78 . Keeping the clamp spring 87 under load provides a predetermined preload against the protrusion 42 .

Preferably, the clamping spring performs the parallel task of mounting the stator parts 5 , 6 . The central hole 88 through the clamping spring 87 is precisely dimensioned relative to the mounting bracket 41 , at least in a lateral direction relative to the mounting bracket 41 . Clamping spring 87 includes a stator portion clamping surface 91 at each of its side regions 92 that span between mounting brackets 41 of cylinder casting 33 .

The cylinder casting 33 includes a pair of protruding stator support blocks 55 projecting from the spring facing face 58 of the cooling jacket 29 at locations between the locations of the mounting brackets 41 .

Each "E"-shaped lamination stack of stator sections 5, 6 has a vertically oriented step 69 on its outer face 56. In each case, this is an outward step in a direction away from the motor air gap. The portion of each outer face 56 closer to the air gap may suitably rest on the support block 55 of the cylinder casting 33 or the stator mating surface 91 of the clamp spring 87 . When held in place, the natural attraction between the motor parts will cause the stator parts 5, 6 to attract each other. The width of the air gap is maintained by abutting the vertical step 57 against the mounting block 55 and the outer edges 40, 72 of the clamp spring 87, respectively. To assist in vertically orienting the stator sections 5, 6, each mounting block 55 (stator mating surface) includes a notch 57 in its outer edge which is vertically aligned with the dimensions of the "E" shaped lamination stack. match.

This part of the motor is assembled in a series of operations. The piston assembly is introduced into the cylinder casting 33 . First, the piston assembly comprising the piston rod 47 with integral flanges 3, 36, piston sleeve 4 and armature rotor magnet 2 is assembled. The piston, formed by the piston sleeve 4 and the front flange 3 forming the piston face, is pushed into the bore 71 of the cylinder while being guided through the cylinder opening 7 between the cylinder castings 33 . The piston rod 47 is thus located between the brackets 41 . The inwardly facing face 76 of the bracket 41 includes an axial slot 28 extending from the dovetail 75 along the centerline. Outwardly extending protrusions 130 on the piston rod 47 reciprocate in these slots 28 during operation. The precision of the assembly is such that normally (in the absence of impact or external movement) the protrusion 130 does not contact the slot surface. However, at their ends closest to the cylinder casting 33 , the slots 28 include a narrow and shallow portion 131 which provides a tight fit with the protrusion 130 of the connecting rod 47 . The piston assembly is pushed into the cylinder bore 71 until the protrusions 130 engage in these narrow portions 131 and until the piston face is in a predetermined position relative to the machined cylinder head receiving face 133 of the cylinder casting 33 .

Clamping spring 87 is mounted on mounting bracket 41 and mainspring 15 is fitted to bracket 41 by engaging protrusion 42 in inwardly facing dovetail 75 and by barb or protrusion 78 . The clamping spring 87 is urged in a direction away from the cylinder casting 33 and pressed against the mounting protrusion 42 until sufficient space is obtained between the stator portion mating surface 91 of the clamping spring 87 and the mounting block 55 of the cylinder casting 33 Insert the stator parts 5,6. The stator parts 5 , 6 are thus inserted in their place and the clamping spring 87 is released. The width of the stator parts 5 , 6 is maintained at a predetermined compression on the clamping spring 87 .

A connection is then made between the main spring 15 and the piston rod 47 . It should be noted that the piston remains in a predetermined position further towards the cylinder head than during operation of the compressor. The connection is made by melting the plastic of the molded button 25 on the main spring 15 and the plastic of the rear end 48 of the piston rod 47 . Welding is performed by hot plate welding. At the time of hot plate welding, the main spring 15 preferably extends to a predetermined position or until the main spring 15 applies a predetermined force. Hot plate welding and welding between the two plastic elements allows the piston face to be in a predetermined position and the main spring 15 to be in its predetermined displacement, which will give the piston a precise alignment with respect to the cylinder casting 33 once the spring 15 has been released to its neutral position position. This is the case irrespective of any eccentricity or accumulated inaccuracies in the form of spring 15 due to tolerances of the elements in the assembled chain.

cylinder head

The open end of the cylinder casting 33 is closed by the compressor head 27 . The compressor head thus closes the open end of the cylinder block 71 and the open end of the cooling jacket chamber 32 surrounding the cylinder block 71 . Overall, the cylinder head 27 includes four plates 100 to 103 stacked together, with an intake muffler/suction manifold 104 .

The open end of the cylinder casting 33 includes a head retaining flange 135 . The head securing flange 135 has a plurality of threaded holes 136 spaced around its periphery into which securing bolts are threaded to draw the stacked plates 100 to 103 together and secure them to the face of the cylinder casting 33 .

An annular tenon joint 133 is provided on the face of the flange 135 . On the opposite side of the flange 135, the mortise 133 includes outwardly extending protrusions 137, 138 serving as orifices for the discharge tube 18 and the return tube 34, respectively.

Openings are provided between the three chambers of the cylinder casting 33 .

The first head plate 100 is mounted on the cylinder casting 33 in an annular dovetail joint 133 . It is relatively flexible and acts as a gasket. It closes the cylinder casing opening, but has a main central opening so that it does not cover the open end of the cylinder 71 . The compressed gas return port 110 passes through the plate 100 adjacent to the protrusion 138 associated with the liquid refrigerant return tube 34 . The edge of the opening 110 closest to the outer wall of the cooling jacket 29 is slightly spaced from that wall at least in the vicinity of the protrusion 138 . The effect of this is to create a small area of reduced pressure immediately behind the plate 100 and near the protrusion 138 of the dovetail 135 as the gas moves through the opening 110 into the cooling jacket chamber.

Another opening 115 is formed through the plate 100 at a location closer to the discharge duct 18 .

The second header plate 101 is assembled on the first plate 100 . The second plate 101 is larger in diameter than the plate 100 and is rigid. It can be made of steel, cast iron, or sintered steel. The plate 101 is wider than the mortise in which the plate 100 is located. The plate 101 abuts against the flange face and presses the first plate 100 onto the dovetail. The plate 101 has openings 139 spaced around its periphery, the dimensions of which are selected so that the threaded portions of the bolts can pass freely therethrough.

The second header plate 101 includes a compressed gas discharge opening 111 aligned with the opening 110 . It also includes a further opening 117 aligned with the opening 115 on the first plate 100 .

A portion of the plate 101 closes the cylinder opening 116 of the plate 100 . The suction port 113 and the discharge port 114 pass through this part of the plate 101 . A spring steel inlet valve 118 is fixed to the face of the plate 101 facing the cylinder such that one head thereof covers the suction port 113 . The base of inlet valve 118 is clamped between plate 100 and plate 101 , its position being fixed by pin 140 . A spring steel discharge valve 119 is mounted to the face of the plate 101 facing away from the cylinder. One head thereof covers the discharge port 114 . The base of the valve 119 is clamped between the second plate 101 and the third plate 102 and is positioned by a pin 141 . The discharge valve 119 fits and operates in the discharge manifold opening 112 of the third plate 102 and the discharge manifold 142 formed on the fourth plate 103 . The inlet valve 118 (except for its base) is located and operates in the compression space of the cylinder.

The spring steel inlet and outlet valves 118, 119 operate integrally under the prevailing pressure. When the piston is retracted in the cylinder 71, the pressure on the cylinder side of the inlet valve 118 is lower than the pressure on the inlet manifold side of the inlet valve. Accordingly, the inlet valve 118 opens to allow refrigerant to enter the compression chamber. As the piston advances in the cylinder 71, the pressure in the compression space is higher than the pressure in the inlet manifold, and the inlet valve 118 is held in the closed position by this pressure difference. The inlet valve 118 is biased towards this closed position by its own resiliency.

Similarly, the discharge valve is normally biased in a closed position which is held in that position by the pressure prevailing during retraction of the piston in cylinder 71 . During the advance of the piston in the cylinder 71, it is pushed into the open position by a higher pressure in the compression space than in the discharge manifold.

The third plate 102 is mounted in a circular joint 143 on the face 144 of the fourth plate 103 facing the cylinder. Plate 102 is relatively flexible and acts as a gasket, which is compressed between fourth plate 103 and second plate 101 . The third plate 102 includes a large opening 112 aligned with a wide tenon joint 142 on a face 144 of the fourth plate 103 . The opening 112 together with the dovetail 142 forms a discharge manifold into which compressed refrigerant flows from the discharge port 114 .

A further opening 121 through the third plate 102 is aligned with a dovetail 145 on a face 144 of the fourth plate 103 . The opening 121 is also aligned with the openings 117 and 115 of the second plate 101 and the first plate 100 . Gas filter 120 receives compressed refrigerant from dovetail 145 and feeds gas bearing supply passage 73 through holes 146, 147 in the first and second plates.

The suction opening 95 through the third plate 102 is aligned with the suction opening 113 on the second plate 101 . The opening 95 is also aligned with the suction opening 96 through the fourth plate 103 . A conical or frusto-conical suction opening 97 on the face 98 of the fourth plate 103 leads to the suction opening 96 . The suction port 96 is closed by the intake muffler 104 . The intake muffler 104 comprises, for example, a one-piece molding having a generally open space on its side facing the cylinder casting. This space is closed by the fourth plate 103 when it is connected to the fourth plate. The intake muffler 104 can be connected to the stacked plates 100 to 103 by any possible means, for example by fitting the surrounding lip of the intake muffler into a channel on the face of the fourth plate 104, or by passing through the muffler. Bolts from the flanges attach these head plates to the block casting, which secures the intake muffler to the fourth plate as part of the stack. The intake muffler 104 includes a passage 93 extending from the closed suction manifold space to an open end in a direction away from the cylinder casting 33 . This passage is a refrigerant suction passage. When the compressor is in its hermetic housing, the inner protrusion 109 of the suction pipe 12 extending through the hermetic housing protrudes into the suction passage 93 with a relatively large clearance.

cooling jacket

As mentioned above, the interconnected cooling jacket chambers 32 are arranged around the compression cylinder 71 . When compressing the refrigerant gas, the gases reach a state of temperature much higher than when they entered the compression space. This heats the cylinder head 27 and the block liner 10 .

In the present invention, a supply of liquid refrigerant is used to cool the block wall/liner, cylinder head and compressed refrigerant.

Liquid refrigerant is supplied from the condenser outlet of the refrigeration system. It is supplied directly into the cooling jacket chamber 32 surrounding the cylinder block. The freshly discharged compressed refrigerant flows into the cooling jacket chamber before exiting the compressor through discharge pipe 18 . In the cooling jacket chamber 32 , the liquid refrigerant evaporates, absorbing a large amount of heat from the compressed gas, the surrounding walls of the block casting 33 and the cylinder head 27 .

The liquid refrigerant exiting the condenser is at a slightly lower pressure than the refrigerant immediately after compression, which is an obstacle to liquid flow to the discharge side of the pump. However, preferably a passive structure is used to allow liquid refrigerant to flow into the cooling jacket. In the present invention, this is achieved through several aspects of the construction of the compressor. First, a small area of reduced pressure is created immediately adjacent the exit from the liquid return line 34 into the cooling jacket space. The origin of the lower pressure region has been discussed above. It is generated by the flow of compressed gas into the cooling jacket through the compressed gas openings 110 in the header plate 100 . The second aspect is the slight inertial pumping effect created by the reciprocating motion of the liquid refrigerant return tube 34 along its length. The reciprocating motion is a result of the operation of the compressor and the associated reciprocating motion of the entire cylinder section. The vibration of the cylinder produces variable accelerations in the axially aligned portion 148 of the return conduit 34, which creates a fluctuating pressure at the end of the liquid return conduit 34 as it overlaps the inlet 33. Since liquid evaporates immediately upon entering the cooling jacket during high pressure surges, any reverse flow during low pressure surges is gas flow. Since gas has a very low density compared to liquid, very little mass flow is returned through the small recess connecting the liquid return pipe 34 to the cooling jacket. As a result, there is a net flow of refrigerant into the cooling jacket.

A third aspect is that, for domestic refrigerator and freezer purposes, the compressor can be located under the condenser. It has been found that if the liquid refrigerant from the condenser does not enter the cooling jacket at a sufficient rate, a liquid refrigerant head is formed in the line extending to the compressor, which tends to cause the pressure of the liquid refrigerant to be closer to that of compression refrigeration agent pressure. This effect has been found to provide a self-compensating measure as the relative pressure in the system dictates against the entry of liquid refrigerant into the cooling jacket space.

refrigerant

Another approach for reducing the heat build-up by the compressor involves refrigerant. It has been found that the use of isobutane (R600a) as a refrigerant in linear compressors yields synergistic advantages over the use of other refrigerants.

A fundamental difference between linear compressors and existing compressors is the amount of volume above the piston at "top dead center". In existing compressors, this volume is fixed by the compressor geometry at the smaller displacement portion. In a free-piston linear compressor, the "dead" volume varies with power input and discharge pressure. At moderate power, the dead volume can be a large fraction of the operating displacement, even as high as 25%.

The dead volume acts as a gas spring, absorbing and releasing energy during compression and re-expansion. However, it is an imperfect spring due to irreversible heat exchange with the cylinder walls. The heat exchange is proportional to the increase in temperature of the refrigerant during compression (or decrease in temperature during expansion). The temperature rise depends on the gas specific heat rate. For the commonly used refrigerant R134a, the specific heat ratio is 1.127. It is similar for other commonly used refrigerants such as CFC12. However, for isobutane (R600a), the specific heat ratio is 1.108. The table below gives the adiabatic temperature at which the gas is compressed to saturation pressure matching the condensation temperature of refrigerators (OC evaporator temperature) and freezers (-18C evaporator temperature). Both had 32C superheated gas entering the compressor and a condenser temperature of 42C (these are typical values).

Accordingly, the properties of isobutane and other refrigerants with low specific heat rates were found to match the physical properties of linear compressors especially. This improvement has been verified by experiments.

A series of tests were carried out on a 450 liter refrigerator. It has a mass flow meter on the suction line before the compressor. Refrigerators are tested in an environmental chamber according to AS/NZS 4474.1-1997. The first tests were performed with the refrigerant R134a. Two tests were then carried out using the refrigerant R600a (isobutane). The test results are as follows:

R134a R600a (Test 1) R600a (Test 2) T_condenser 34.3 33.3 33.5 T_Evaporator -3.5 -6.1 -4.5 input power 22.3 18.1 17.8 Cooling power 75.25 75.01 75.07 Displacement 7.96 8.7 8.48 Coefficient of performance 3.38 4.14 4.23

The test results show that the coefficient of performance of the linear compressor running on isobutane is significantly improved compared to running on R134a.

spring system

The cylinder 9 is supported by the discharge pipe 18 and the liquid refrigerant injection pipe 34, which have a combined stiffness K _cylinder in the axial direction. The support spring 39 has a very low stiffness in the axial direction and has negligible influence. The piston sleeve 4 is radially supported by gas bearings formed by cavities and channels in the boundary of the cylinder bore and the cylinder liner 10 . In order for the piston and cylinder to resonate, the main spring has a stiffness K _such that the resonance frequency _fn can be obtained from the following relationship:

Among them, m _{piston and} m _cylinder are buffer masses on the piston and cylinder springs. Due to the increase in stiffness caused by compressed gas, the natural frequency f _n is usually 10 to 20 Hz, which is smaller than the ideal operating frequency to increase the frequency.

As mentioned above, the compressor motor consists of two parts, the stators 5 , 6 and the magnets on the armature rotor 22 . The magnetic interaction of the stators 5, 6 and the armature rotor 22 produces a reciprocating force on the piston.

The alternating current in the stator coils need not be sinusoidal, as long as the alternating frequency is close to the natural resonant frequency of the mechanical system, the alternating current will cause the piston to move substantially relative to the cylinder casting 33 . The resonant force creates a reaction force on the stator part. The stator parts 5 , 6 are rigidly mounted to the cylinder assembly by means of clamping springs 87 .

It is proposed in the invention that the main spring 15 has a much higher stiffness than the active cylinder spring. The main spring is raised to the "second" mode frequency above the "third" mode frequency, so that the "gas spring" then only further separates the mode frequency.

The actual operating frequency (the "second" mode frequency) is determined by the complex relationship of the masses of the piston and cylinder and by the stiffness of the cylinder spring and main spring 15 . When the discharge pressure is high, the stiffness of the compressed gas must be increased to the stiffness of the main spring. However, since the cylinder spring is quite soft (e.g. 1/10 the stiffness of the main spring), the operating frequency can be given with reasonable accuracy by:

By reducing the vibrating mass and ensuring that the cylinder springs are relatively soft, external vibrations due to sources other than the fundamental vibration caused by piston/cylinder movement are virtually eliminated. By not having specific cylinder springs at all, and using the (typically 1000N/m) intrinsic stiffness of the discharge pipe 18 (or in the case of cooling pipes, the combined stiffness of the discharge pipe and cooling pipe, ie 2000N/m) , the stiffness of the cylinder spring can be reduced to a minimum.

For a compressor resonating at about 75 Hz, with a piston mass of about 100 g, and a cylinder to piston mass ratio of ten to one, the main spring (K _main ) must be 40000 N/m. Usually this value is lower for gas springs than for main springs, but not much lower. In the above case, if the gas spring (K _gas ) is designed to be around 15000 N/m, the operating frequency might be expected to be 99 Hz.

main spring

Higher operating frequencies reduce motor size but require greater spring rates and thus create higher stresses in the springs. It is important for the life of the compressor to use the highest quality spring material. In the past, main springs made of pressed spring steel plates were often used. However, the edges cut during the pressing operation require careful polishing to regain the original fatigue strength of the spring steel.

In a preferred embodiment of the invention, the mainspring is formed from music wire of circular cross-section, which has very high fatigue strength and does not require subsequent polishing.

A preferred embodiment of the main spring is shown in FIGS. 1 and 2 . The spring takes the form of a continuous ring twisted into a double helix. The free ends of the wire lengths forming the spring 15 are fixed in a mounting plate 43 having a protrusion 42 for mounting to a compressor component. As shown in FIG. 3 and described above, these protrusions 42 are fitted to the cylinder part 1 , in particular in slots of the bracket 41 . The spring 15 has a further mounting location 62 for mounting to another compressor component, as shown in FIG. 3 and described above. In the preferred form it is connected to the piston rod 47 by a molded plastic button. The spring 15 includes a pair of curved portions 63, 64 which respectively surround the cylinder mounting plate with a constant radius of curvature. Each curved portion extends over approximately 360°. Each section is smoothly curved at its two ends. At the mounting plate transitions 65, 66, they are bent such that their portions 67, 68 at the block mounting plate are radially aligned. The sharp bends 65, 66 are selected to maintain a substantially uniform stress along the transition. The alignment of the cylinder mounting ends 67, 68 is then aligned with the cylinder mounting plate. The constant bending portions 63, 64 of the spring 15 can be of any range. In the illustrated embodiment, they each have an extent of approximately 360°.

As shown in Figures 1 and 2, the mounting plate 43 of the spring 15 is located on the other side thereof. The central mounting location 62 is located on the closer side thereof. The constant bend portions 63 , 64 are each smoothly curved at their lower ends so as to be mutually aligned and continuous in diameter across the general circle of the spring at the mounting location 62 . The diameter is positioned substantially perpendicular to the aligned ends 67 , 68 of the cylinder section mounting plate 43 .

The constant radius bends 63 , 64 are flexed by displacement of the piston mounting location 62 relative to the mounting plate 43 . Since the radius is constant, the flexural stress along each portion 63, 64 is also substantially constant. If the spring ends are mounted in the mounting plate 43 and at the piston mounting location 62, the radial or substantially radial orientation at the cylinder mounting portions 67, 68 and the piston mounting location 62 reduces any flexural stresses, thereby improving The installation of spring 15 and cylinder body part and piston part has been improved.

Applications of Linear Compressors

The linear compressor according to the preferred embodiment of the present invention is mainly used in domestic refrigeration systems, such as freezers, refrigerators or refrigerator/freezer combinations. This compressor can be a direct replacement for other types of compressors, such as rotary crank compressors. The linear compressor receives low-pressure evaporated refrigerant through a suction pipe 12 and discharges high-pressure compressed refrigerant through a discharge pipe 13 . In refrigeration systems, the discharge pipe 13 is usually connected to the condenser. Suction line 12 is connected for receiving evaporated refrigerant from one or more evaporators. Liquid refrigerant delivery line 14 receives condensed refrigerant from the condenser (or from an accumulator or refrigerant line after the condenser) for cooling the compressor as described above. A process tube 16 is also included through the sealed housing for evacuating the refrigeration system and filling it with the refrigerant of choice.

The composition of a refrigeration system including the compressor of the present invention does not form part of the present invention. Many useful refrigeration system configurations are known and many more are possible. The compressor of the present invention may be used in any such system.

The use of the compressor according to the preferred embodiment of the present invention is not limited to refrigeration systems of household refrigerators and freezers, and can also be used in refrigeration systems of air conditioners. It can also be used in gas compressors for non-refrigerant purposes, in which case the delivery of liquid refrigerant for cooling can be omitted.

Operation and control of the linear compressor can be done by suitably energizing the stator sections 5,6. Disposed through the sealed housing 30 is a power connector 17 which fits into the opening 19 . A suitable control system for powering the windings does not form part of the present invention, many alternative drive systems for brushless DC motors are known and suitable. A suitable drive system is further described in International Patent Application PCT/NZ00/00105.

advantage

Many advantages of the linear compressor according to the preferred embodiment of the present invention have been described in the above detailed description. Some other advantages not mentioned include:

(a) The resiliently flexible connection of the piston connecting rod to the piston, and main spring to the mounting bracket 41 of the cylinder casting 33, together with the light weight of the piston and proper choice of materials for the piston sleeve and cylinder liner, can eliminate the need for The need to add lubricant to the compressor. Thus, the unwanted presence of oil lubricant in the refrigerant of the entire refrigeration system, or the need for an accumulator or separator for oil lubricant can be eliminated.

(b) Lightweight piston and connecting rod assemblies reduce the magnitude of the vibrational momentum of the two main compressor structures, thereby reducing the vibration transmitted to the hermetic housing.

(c) The main spring is made of a material having a high fatigue life that does not require additional polishing operations after forming the main spring, and the shape and construction of the main spring is such that, for the required spring strength, the amount of material used, Spring weight and spring size are minimized.

(d) Placing the armature rotor magnets on the piston rods such that the piston rods run directly in the stator air gap provides a laterally compact linear motor, enabling the armature rotor to operate between the two parts of the stator. Adjust precisely and efficiently.

(e) Compliant connections between the piston and the piston rod and from the rod to the cylinder section ensure that the piston sleeve does not exert localized stresses in the cylinder bore due to incorrect non-axial positioning.

(f) The use of isobutane refrigerants in linear compressors may provide synergistic advantages over the use of other refrigerants with higher specific heat rates.

(g) Delivery of liquid to the cooling jacket surrounding the cylinder provides evaporative cooling to the cylinder and cylinder head assembly, and the combined compressed air flow leaving the compressor. Evacuation of high-pressure gas in the cooling jacket can be achieved without the need for active pumping devices.

(h) The overall compressor structure is very suitable for use in household appliances. Due to the low overall height of the hermetic casing, the size of the refrigerator or refrigerant machine space can be reduced. Due to interior space considerations, machine rooms usually extend across the entire width of the appliance, regardless of the components it needs to house. However, its height and depth are usually determined by the maximum height and depth requirements of the assembled compressor. The low profile of the linear compressor according to the invention is due to the fact that the compressor elements are arranged end to end rather than concentrically.

(i) Compressor main spring and motor components are subject to a degree of elastic preload determined by component geometry, size and shape. Due to imperfect assembly, due to normal manufacturing tolerances, or due to the effects of motor operation, the likelihood of parts coming loose and subsequently bumping, rattling or malfunctioning during compressor operation is reduced or eliminated.

(j) The piston rod is welded to the main spring in the manner described in the hot plate welding process so that the piston face is precisely positioned relative to the neutral position of the main spring. As a result, the compressor can be run with lower cylinder head clearance, ensuring that the piston does not hit the cylinder head at the front end of its travel.

Claims (8)

1, a kind of Linearkompressor comprises:

Comprise cylinder bore and cylinder part with stator of air gap;

Be arranged in the described cylinder bore and the piston that can slide therein (3,4);

Described cylinder part is connected to main spring (15) on the described piston directly or indirectly;

Between described main spring (15) and described piston (3,4) and the described air gap by described stator and described main spring is connected to connecting rod (47) on the described piston; And

Be supported on the permanent-magnet material on the described connecting rod (47), described permanent-magnet material is magnetized to limit at least one armature rotor utmost point;

It is characterized in that described permanent-magnet material comprises one or more flat substantially pieces (2), the big face that makes described is towards stator.

2, Linearkompressor as claimed in claim 1, it is characterized in that, described cylinder part comprises the housing (33) around described cylinder bore, described stator has two stationary parts (5 that have winding that are positioned at described air gap opposite side, 6), described stationary part (5,6) is respectively against described cylinder shell setting.

3, Linearkompressor as claimed in claim 2 is characterized in that, cross structure (91) is connected between the end of described stationary part (5,6) away from described cylinder shell (33), and described main spring is connected with described cross structure (91).

4, Linearkompressor as claimed in claim 2, it is characterized in that, cross structure (91) is connected described stationary part (5,6) between the end away from described cylinder shell (33), and a pair of fixed component (41) from described cylinder part extend be connected described cross structure and be positioned on the described air gap and under described cylinder shell (33) between, described cross structure (91) is pressed against described stationary part (5,6) on the described cylinder shell (33).

5, Linearkompressor as claimed in claim 4, it is characterized in that, each described stationary part (5,6) lean against a side of each described fixed component, make on the described air gap and under described stationary part (5,6) be to keep at interval by the width of described fixed component (41).

6, as the arbitrary described Linearkompressor of claim 1 to 5, it is characterized in that, be suspended in the seal casinghousing (30), have closes vent passage from the compression volume that limits by described cylinder bore and described piston (3,4) to the outlet of passing described seal casinghousing (30).

7, Linearkompressor as claimed in claim 6 is characterized in that, described exhaust passage is included in the discharge tube (18) that extends between described cylinder part and the described seal casinghousing (30).

8, as claim 6 or 7 described Linearkompressors, it is characterized in that, air-breathingly enter described seal casinghousing (30), and air-breathingly be inhaled into described Linearkompressor compression volume from the gas that is arranged in described seal casinghousing (30) from suction pipe (12).

Images