WO2006069884A1

WO2006069884A1 - Linear compressor and corresponding drive unit

Info

Publication number: WO2006069884A1
Application number: PCT/EP2005/056356
Authority: WO
Inventors: Alexander Schade; Jan-Grigor Schubert
Original assignee: BSH Bosch und Siemens Hausgeräte GmbH
Priority date: 2004-12-23
Filing date: 2005-11-30
Publication date: 2006-07-06
Also published as: EP1831559B1; RU2007121771A; DE102004062302A1; CN101087954A; CN101087954B; RU2376497C2; EP1831559A1; US20080089796A1

Abstract

A drive unit for a linear compressor comprises a frame (21, 29, 30) and an oscillating body (24, 10). Said oscillating body is mounted in the frame (21, 29, 30) via at least one diaphragm spring (8) and can be moved back and forth in one direction. The diaphragm spring (8) comprises a plurality of limbs (14), fastened with one end to the frame (21, 29, 30) and with the other end to the oscillating body (24). Two limbs (14) each have inversely curved sections (18, 19) between the two ends.

Description

Linear compressor and drive unit for it

The present invention relates to a linear compressor, in particular for use for compressing refrigerants in a refrigerator, and in particular a drive unit for driving an oscillating linear piston movement for such a linear compressor.

From US Pat. No. 6,596,032 B2 a linear compressor is known, the drive unit of which comprises a frame and a vibrating body mounted in the frame via a diaphragm spring. The oscillating body comprises a permanent magnet, a piston rod rigidly connected to the permanent magnet, and a piston articulated to the piston rod and reciprocable in a cylinder. The movement of the piston is driven by an electromagnet arranged around the cylinder, which interacts with the permanent magnet. A disc-shaped diaphragm spring is bolted to the center of the piston rod, and the outer edge of the diaphragm spring is connected to a yoke surrounding the cylinder, the electromagnet and the permanent magnet.

The oscillating body and the diaphragm spring form a vibratory system whose natural frequency is determined by the mass of the oscillating body and the diaphragm spring and the stiffness of the diaphragm spring. The diaphragm spring allows only small vibration amplitudes, since each deflection of the vibrating body is associated with an expansion of the diaphragm spring. Due to the low vibration amplitude, it is difficult to reliably make the dead volume of the cylinder small. However, the larger the dead volume, the worse the efficiency of the compressor. The small stroke also forces the cylinder to be proportionate to the large diameter length to achieve a given throughput. It is complicated to adequately seal the correspondingly large circumference of the piston.

Since the vibrating body is held in the radial direction only by its connection with the spring, there is the possibility that the head of the piston rod carrying the piston reciprocates and grinds on the cylinder wall. To prevent this, a gas pressure bearing for the piston is provided, that is, the swept by the piston cylinder wall has openings that communicate with the high pressure outlet of the Linear compressor are connected to form a gas cushion between the inner wall of the cylinder and the piston. However, such a pressurized gas bearing only works if the required overpressure is present at the outlet of the linear compressor, that is not when the compressor starts or runs out. At these times, there is a risk that the piston grinds on the cylinder wall, so that the compressor wears prematurely.

A linear compressor according to the preamble of claim 1 is known from US 6 641 377 B2. In this double-piston linear compressor each piston is held by two respective two-armed diaphragm springs.

Due to the curvature of the arms, a larger piston stroke is possible, but each diaphragm spring exerts a torque on the piston in the deflected state. If this torque is not compensated for exactly, the piston in addition to its linear oscillatory motion of a torsional vibration, and it can be wobbled movements of the piston are excited, which can lead to contact between the piston and cylinder and consequently to increased wear.

Object of the present invention is to provide a low-wear drive unit for a linear compressor with a frame and mounted in the frame via a diaphragm spring vibrating body in which the diaphragm spring allows a large stroke of the vibrating body, or reach a high throughput at low piston diameter can.

The object is achieved in that the plurality of arms of the diaphragm spring each engage with one end on the frame and with another end on the vibrating body, and that the arms between the two ends in pairs have sections with opposite curvature. Thus, the arms do not extend in the shortest path between the two ends, so that when the vibrating body is deflected they can stretch and approach the rectilinear shape without having to stretch the material of the arms. Within a same workpiece, it is quite easy to make the arms so that their torques compensate each other exactly; if, as described in US6 641 377 B2, two diaphragm springs are provided with curved in each different direction arms can Deviations in material thickness from one spring to the other thwart compensation or at least make it considerably more difficult.

Preferably, the diaphragm spring has pairs of arms with portions curved in respective opposite directions.

In the simplest case, each arm has a single unidirectional curved section. Each such arm also exerts a torque on the oscillating body supported by it, which, however, is compensated by the pair of oppositely curved arms paired with it.

Preferably, each arm has two portions curved in different directions. Again, since the different curved portions cause torques in opposite directions, so that the torque of each arm can be made very small or made to disappear.

It is also advantageous to provide at least a second diaphragm spring, the arms of which act on a region of the oscillating body which is spaced from the engagement region of the first diaphragm spring in the direction of the oscillating movement. By means of the two diaphragm springs, the oscillating body is reliably guided linearly in the direction of the desired oscillatory movement, and a lateral evasive movement, which could lead to contact between a piston carried by the oscillating body and a cylinder surrounding the piston, can be avoided.

The arms of a same diaphragm spring preferably hang together in one piece at their attacking on the frame ends and / or at their attacking on the oscillating body ends. The frame engaging ends may be connected by a frame integral with the leaf springs.

In order to enable a large stroke without the risk of material fatigue, the arms of the at least one diaphragm spring should be made of a very thin material. Its strength can be so tight that it is sufficient only to prevent lateral deflection of the vibrating body. However, such a weak diaphragm spring would result in a low natural frequency of the drive unit - A -

and thus lead at a given stroke to a low throughput of a driven by the drive unit compressor. In order to achieve sufficient for a required throughput natural frequency of the drive unit, each arm is preferably associated with a return spring, which counteracts deformation of the arm, so that the diaphragm spring together with the return springs each form an elastic system whose rigidity is significantly greater than that Diaphragm spring alone.

The effective spring constant of the correlation of diaphragm spring and return spring can be made adjustable in order to tune the natural frequency of the drive unit as needed.

As a return spring, a coil spring is preferably used.

The invention also relates to a linear compressor having a working chamber, a reciprocating in the working chamber for compressing a working fluid piston and a coupled to drive the reciprocating motion to the piston drive unit of the type described above.

Further features and advantages of the invention will become apparent from the following description of embodiments with reference to the accompanying figures. Show it:

1 shows a schematic section through a linear compressor.

Fig. 2 is a plan view of a diaphragm spring for use in the linear compressor of Fig. 1 according to the invention;

Fig. 3 is a plan view of a second embodiment of a diaphragm spring;

Fig. 4 is a partially sectioned side view of a linear compressor with the diaphragm spring shown in Fig. 3; and Fig. 5 shows a further embodiment of a diaphragm spring.

The linear compressor for a refrigerator shown in Fig. 1 comprises a compressor chamber 1, which is bounded on the one hand by a movable piston 2 and on the other hand by a cylinder 3, which is composed of a pipe section 4 and a cover 5. In the lid 5 are, not shown, in a conventional manner, a suction nozzle, a discharge nozzle and valves that allow an influx of refrigerant in the compressor chamber only via the suction nozzle and a drain only via the discharge nozzle.

The pipe section 4 is concentrically surrounded by a second pipe section 6 and connected to it via a radial flange 7. At the end facing away from the flange 7 of the pipe section 6, the circumference of a diaphragm spring 8 is fixed. At the center of the diaphragm spring 8, a vibrating body 9 is mounted, which is composed of a piston rod 10, to which the piston 2 is articulated, a flange 11 fixed to the piston rod 10 and a permanent magnet 12 which is secured to the flange 11 and into the space between the pipe sections 6, 4 dips. Also housed in the gap electromagnets for exerting a force in the direction of the piston rod 10 on the permanent magnet 12 are omitted in the figure.

It comprises a circumferential outer ring 13 and of the ring 13 from each spirally inwardly extending pairwise mirror-inverted arms 14, which are connected at their ends facing away from the ring 13 with each other. A central opening 15 is provided for screwing the piston rod 10.

The diaphragm spring 8 is made of spring steel or other elastically deformable but substantially non-stretchable material. The central region of the diaphragm spring 8 is elastically deflectable with little force in a direction perpendicular to the plane of FIG. 2, the deflection resulting in the arms 14 slightly reducing their curvature in plan view and the central region being rotated slightly counterclockwise. The resistance of the diaphragm spring 8 against a displacement of the central region in the plane of Fig. 2 is substantially greater than the resistance to a deflection perpendicular to this plane, so that at the Opening 15 of the diaphragm spring 8 fixed end of the piston rod 10 is reliably guided linearly movable.

A second embodiment of the diaphragm spring 8 is shown in Fig. 3 in a plan view. This embodiment has a closed outer ring 13. This ring is here of rectangular shape, but this is of little importance for the function of the diaphragm spring. From the corners of the frame 13, four arms 14 extend toward the central region 16, each of which is composed of three straight sections 17 and two curved sections 18, 19 connecting the sections 17. The two sections 18, 19 of each arm 14 each have opposite direction of curvature. Four holes 20 for attachment of the diaphragm spring are located at the corners of the frame thirteenth

By deflecting the central portion 16, this results in a slight bowing of the curved portions 18, 19. Due to the opposite curvature directions of the two portions 18, 19 of each arm, the buckling results in opposing torques, respectively, so that from each individual arm 14 the central region 16 applied torque is low. In addition, the torques of adjacent arms 14 each compensate each other because each one of them is the mirror image of the other and the torques exerted by them therefore equal opposite. The central region 16 and consequently also a piston rod 10 fastened thereto are thus guided exactly linearly and without torsion.

Fig. 4 shows a partially sectioned side view of a linear compressor in which diaphragm springs 8 of the type shown in Fig. 3 are used. The compressor has a frame with a central chamber 21, wherein in two opposite walls, here with reference to the illustration in FIG. For the sake of clarity, referred to as ceiling 22 and bottom 23, openings are formed, through which play a rod-shaped oscillating mass 24 extends. The chamber is provided to receive unillustrated electromagnets for driving a reciprocating motion of a permanent magnet inserted into the oscillating mass.

The ends of the oscillating mass 24 are at the central portions 16 of two diaphragm springs 8 of the form shown in Fig. 3 by means of screws or rivets 25th attached. The frame 13 of each diaphragm spring 8 in turn rests on projecting from the ceiling 22 and the bottom 23 of the central chamber 21 webs 26. The height of the webs 26 defines the maximum stroke of movement of the oscillating mass 24; If this maximum stroke is exceeded, the central regions 16 of the diaphragm spring 8 abut against the ceiling 22 or floor 23.

The diaphragm springs 8 are held on the webs 26 each by screws or rivets 27, each crossing a foot piece 28 of an upper or lower yoke 29, 30 and one of the holes 19 in the corners of the frame 13 and engage in the central chamber 21.

The lower yoke 30 supports two coil springs 31, each of which is placed so that free headers 32 of them, as indicated by a dash-dotted outline in Fig. 3, respectively contact the curved portions 18 of two arms 14 when deflected downwardly , and so resist a deflection of the oscillating mass 24 down. Corresponding coil springs 31, which contact the curved portions 18 of arms of the upper diaphragm spring 8 and counteract upward deflection of the oscillating mass, are provided on the upper yoke 29.

The upper yoke 29 also carries a cylinder 33 into which a piston connected to the oscillating mass 24 via a piston rod 10, which is not visible in the figure, can be moved back and forth. Since the oscillating mass 24 is guided exactly linearly by the two diaphragm springs 8, the piston rod 12 and with it the piston carried by it can not move transversely to the direction of movement, and grinding of the piston on the inner wall of the cylinder 33 can be avoided.

When the oscillating mass 24 is at one of the reversal points of its trajectory, all of its kinetic energy is stored in the form of strain energy in the diaphragm springs 8 and the coil springs 31, the distribution of energy being directed to the types of springs according to their respective spring constants. The diaphragm springs can therefore be made very thin and easily deformable, so that no material fatigue occurs even with long-lasting operation, because the energy that the diaphragm springs for lack of sufficient rigidity are unable to store, can be absorbed by appropriately sized coil springs 31. In addition, with a same model of diaphragm spring compressors with different throughput can be realized by the diaphragm springs are each combined with coil springs with different spring constants, each resulting in different natural frequencies of the oscillatory system.

It is also conceivable to make the natural frequency of a drive assembly tunable by the coil springs 31 are each slidably mounted on the yokes 29, 30. The closer the area of the arms 14 touched by the head pieces 32 of the coil springs 31 to the central area 16 of the diaphragm springs 8, the stiffer the overall system of diaphragm spring and coil springs, and the higher the natural frequency of the resulting drive unit.

In the extreme case, it is possible to replace the two coil springs 31 of each yoke 29, 30 each with a single helical spring which directly contacts the central region 16.

Fig. 5 shows a modification of the diaphragm spring 8 of Fig. 3, which is used in their place in the compressor of FIG. In the diaphragm spring of Figure 5, the outer frame 13 has been omitted. Instead, only the two right and the two left arms 14 are connected at their ends remote from the central region 16 by a strip of material 34. The operation does not differ from that of the diaphragm spring of FIG. 3.

Claims

claims

1. Drive unit for a linear compressor with a frame (21, 29, 30) and in the frame (21, 29, 30) via at least one diaphragm spring (8) mounted, in a direction reciprocally movable oscillating body (24, 10) in that the diaphragm spring (8) has a plurality of arms 14, which engage with one end on the frame (21, 29, 30) and with another end on the oscillating body (24), and between the two ends have a curved course, characterized in that in each case two of the arms (14) have oppositely curved sections (18, 19).

2. Drive unit according to claim 1, characterized in that each arm (14) has two curved in different directions sections (18, 19).

3. Drive unit according to claim 1, characterized in that it comprises at least a second diaphragm spring (8), and that the first and the second diaphragm spring (8) in the direction of the oscillatory movement spaced areas of the oscillating body (24, 10) attack.

4. Drive unit according to one of the preceding claims, characterized in that the arms (14) of a same diaphragm spring (8) at their on the oscillating body (24, 10) engaging ends (16) are integrally connected.

5. Drive unit according to one of the preceding claims, characterized in that the arms (14) of a same diaphragm spring (8) at their on the frame (21, 29, 30) engaging ends integrally related.

6. Drive unit according to claim 5, characterized in that the frame (21, 29, 30) engaging ends by a with the arms (14) integral frame (13) are connected.

7. Drive unit according to one of the preceding claims, characterized in that each arm (14) is associated with a return spring (31), which counteracts a deformation of the arm (14).

8. Drive unit according to claim 7, characterized in that the rigidity of the diaphragm spring (8) in the deformation direction is smaller than that of

Return spring (31) is

9. Drive unit according to claim 7 or 8, characterized in that an effective spring constant of the combination of diaphragm spring (8) and return spring (31) is adjustable.

10. Drive unit according to claim 7, 8, or 9, characterized in that the return spring (31) is a helical spring.

11. Drive unit according to one of the preceding claims, characterized in that the mass of the oscillating body (24, 10) is greater than the mass of all springs (8, 31).

12. A linear compressor with a working chamber, a in the working chamber for compressing a working fluid reciprocally movable piston and a for

Driving the reciprocating motion to the piston coupled drive unit according to one of the preceding claims.