EP1458976B1

EP1458976B1 - Reciprocating compressor

Info

Publication number: EP1458976B1
Application number: EP02787459A
Authority: EP
Inventors: Jürgen Süss
Original assignee: Danfoss AS
Current assignee: Danfoss AS
Priority date: 2001-12-27
Filing date: 2002-12-18
Publication date: 2006-08-16
Anticipated expiration: 2022-12-18
Also published as: DE60214037D1; ATE336656T1; JP2005513352A; DE10163893A1; EP1458976A1; WO2003056177A1; DE10163893B4; US20050152799A1; AU2002351744A1

Abstract

The invention concerns a reciprocating compressor, particularly for refrigerants, with a cylinder housing, in which at least one cylinder chamber is arranged, and a cylinder head, which delimits the cylinder chamber and has a valve plate with a suction valve arrangement that is connected with a suction chamber, and with a pressure valve arrangement, which is connected with a pressure chamber that is separated from the suction chamber. It is endeavoured to improve the sealing between the suction chamber and the pressure chamber. For this purpose, the valve plate has, on the side facing away from the cylinder chamber, a projection, which separates the suction chamber from the pressure chamber.

Description

The invention concerns a reciprocating compressor, particularly for refrigerants, with a cylinder housing, in which at least one cylinder chamber is arranged, and a cylinder head, which delimits the cylinder chamber and has a valve plate with a suction valve arrangement that is connected with a suction chamber, and with a pressure valve arrangement, which is connected with a pressure chamber that is separated from the suction chamber eg. Pub. No.: US-A-2001/0022942.
A reciprocating compressor of this kind is known from US 6,206,655 B1. Here, the cylinder head has a valve plate, which bears on the cylinder housing and limits the cylinder chamber front side. Two suction valves and two pressure valves are arranged in the valve plate. On the valve plate is resting a sealing on which again a cylinder head cover is resting. Firstly, by means of a circumferential wall the sealing seals the chamber between the valve plate and the cylinder head cover towards the outside. Between oppositely arranged circumferential wall sections a partition is provided, which separates the suction chamber from the pressure chamber. The cylinder head cover, the sealing, the valve plate and additional valve elements are fitted on the cylinder housing by means of screws.
A further refrigerant compressor is known from DE 33 32 259 A1. Here, the cylinder head has a valve plate and a cylinder head cover, the cylinder head cover having cavities, which form a suction chamber and a pressure chamber.
Such embodiments have proved their value in practice. The manufacturing is simple and up to certain requirements they are reliable in operation. The refrigerant gas is sucked in through the suction chamber. During the suction stroke of the piston it flows from the suction chamber through the suction valve arrangement into the cylinder chamber. After compression the gas is pressed into the pressure gas chamber through the pressure valve arrangement. The two valve arrangements ensure that the gas takes the right path.
In compressors working with high working pressures or high pressure differences between the suction chamber and the pressure chamber, problems occur in connection with the sealing between the suction side and the pressure side. An overflow of refrigerant gas from the pressure chamber into the suction chamber reduces the efficiency of the compressor. This is particularly critical in refrigeration systems, which are operated with refrigerants, which have a high volumetric cooling capacity. When, for example, CO₂ (carbon dioxide) is used as refrigerant, the same cooling capacity will require the compression of a smaller gas volume than with other refrigerants. For this reason, the volume of the cylinder chamber can be reduced, for example by reducing the cylinder diameter. However, a reduction of the cylinder diameter also reduces the amount of space available for the suction opening and the pressure opening and primarily for the suction valves and the pressure valves. The corresponding openings must therefore be arranged closer to each other, which further complicates a reliable sealing. Of course, also the diameter of the openings could be reduced. This would, however, cause an increase of the flow resistance and thus also of the pressure losses, which again would have a negative effect on the compressor efficiency.
The invention is based on the task of improving the sealing between the suction chamber and the pressure chamber.
With a reciprocating compressor as mentioned in the introduction, this task is solved in that on the side facing away from the cylinder chamber, the valve plate has a projection, which separates the suction chamber from the pressure chamber.
Thus, the sealing between the suction chamber and the pressure chamber is integrated in the valve plate. The projection is made in one piece with the valve plate, that is, it is reliably fixed on the valve plate.
Between the valve plate and the projection, a penetration of gas is not possible. Therefore, the foot of the projection, that is, the transition into the valve plate, can be made relatively thin, so that the suction opening and the pressure opening can be placed relatively close to each other, without getting problems with the sealing because of a too small sealing width. The required minimum width of the projection and thus the minimum distance between the suction opening and the pressure opening therefore to a high degree depends on the relation between working pressures and the strength of the valve plate material. Further, the integration of the sealing in the valve plate involves an additional advantage. The valve plate is mechanically stabilised. As this stabilisation is placed between the suction opening and the pressure opening, it is practically automatically arranged in the area of the largest cylinder diameter, that is, in an area, which is particularly exposed to deformation. The stabilisation clearly reduces the risk of deformation. This additionally improves the sealing. The suction valve and the pressure valve do not necessarily have to be integrated in the valve plate. It is sufficient for the valve plate to act as carrier for the suction valve and the pressure valve, as known from the state of the art.
Preferably, the thickness of the valve plate is smaller in the area of the pressure valve arrangement than in the area of the suction valve arrangement. Thus, the volume of the dead space can be reduced, so that the efficiency of the compressor can be further improved. The reduction of the thickness of the valve plate is possible, because the mechanical stress caused by the pressures ruling in the cylinder chamber can now substantially be absorbed by the valve plate projection.
Preferably, the pressure valve arrangement has a pressure opening into the pressure chamber, which lies next to the projection. The pressure opening is a "hole" in the valve plate, which weakens the valve plate. When now combining this weakening with the stabilisation caused by the projection, the weakening is substantially compensated. Additionally, the projection can, under certain circumstances, be used to guide the gas entering through the pressure opening. Thus, favourable flow conditions can be obtained.
Preferably, the suction chamber and/or the pressure chamber are delimited in the circumferential direction by walls, which are formed by projections on the valve plate. Thus, not only the separating wall between the suction chamber and the pressure chamber is integrated in the valve plate, but also the circumferential walls of these two chambers. Also these circumferential walls can then be made with a relatively high degree of strength, which corresponds to the strength of the valve plate in general, so that particularly in the area of the pressure chamber relatively high pressures can be achieved.
Preferably, the cylinder head has a cover, which has, at least on the bottom side facing the valve plate, a plane surface. This simplifies the manufacturing. Such a cover is particularly useful, when both the suction chamber and the pressure chamber are surrounded by walls, which are integrated in the valve plate.
Preferably, at least the projection separating the suction chamber from the pressure chamber has, on the end turning away from the valve plate, a larger thickness than near the valve plate. In other words, the head of the projection is thicker than its foot. Thus, the width of the sealing line between the suction chamber and the pressure chamber can be further extended. At the head of the projection, where the cover is supported, there are relatively few limitations with regard to the space available. This space is not limited by the positioning of the suction opening and the pressure opening. Accordingly, here the sealing between the suction chamber and the pressure chamber can be further improved.
Preferably, between the suction chamber and the pressure chamber, the projection forms, at least in sections, a double wall with two wall sections, between which a gas volume is arranged. This gas volume provides a good thermal isolation between the suction chamber and the pressure chamber. The gas sucked into the suction chamber will not be so heavily heated by the hot limiting wall of the pressure chamber, which has a positive effect on the volumetric compressor efficiency. The double wall also gives an even better mechanical strengthening of the valve plate.
Preferably, the suction valve arrangement has a suction opening to the suction chamber, which is, at least partly, arranged within the projection between the suction chamber and the pressure chamber. Thus, on a whole, the projection can be wider than suggested by the distance between the suction opening and the pressure opening. Further, this measure enables a wider contact zone between the projection and the cover, that is, an improved sealing.
Preferably, the suction valve arrangement is connected with a gas reservoir via a suction path lined with a plastic material. The plastic material forms a thermal isolator, so that an undesirable heating of the gas sucked in can be avoided. The suction path is made so that the gas sucked in gets the least possible contact with the metallic and hot parts of the valve plate. This also improves the compressor efficiency.
It is particularly preferred that the suction path is in the form of a suction muffler. Thus, the suction opening is connected directly with the outlet of the suction muffler.
In the following, the invention is described in detail on the basis of preferred embodiments in connection with the drawings, showing:

Fig. 1: a schematic cross-sectional view of a compressor
Fig. 2: a sectional view II-II according to Fig. 1
Fig. 3: a modified embodiment
Fig. 4: a third embodiment in a view corresponding to that in Fig. 2

Fig. 1 shows a schematic sectional view of a reciprocating refrigerant compressor 1 with a cylinder housing 2, in which a cylinder chamber 3 is arranged. In the cylinder chamber 3 a piston 4 can move up and down. The required drive is known per se and therefore not shown in detail. The movement direction of the piston 4 is shown by means of a double arrow 5. The movement of the piston 4 increases or reduces the cylinder chamber 3.
Further, the compressor 1 has a cylinder head 6 comprising a valve plate 7 and a cover 8.
In the valve plate is arranged a suction opening 9, which can be closed by a suction valve 10. Via the suction opening 9 the cylinder chamber 3 is connected with a suction chamber 11, which is formed in the cylinder head 6.
Further, the valve plate 7 has a pressure opening 12, which can be closed by a pressure valve 13. Via the pressure opening 12 the cylinder chamber 3 is connected with a pressure chamber 14, which is also formed in the cylinder head 6.
Between the suction chamber 11 and the pressure chamber 14 the valve plate has a projection 15, which is made in one piece with the valve plate 7. Further, the valve plate 7 has, in the area of its edge, a circumferential projection 16, which is connected with the projection 15 between the suction chamber 11 and the pressure chamber 14. The two projections 15, 16 thus surround the suction chamber 11 and the pressure chamber 14. The cover 8 bears on the projections 15, 16, so that the suction chamber 11 and the pressure chamber 14 are additionally delimited by the valve plate 7 and the cover 8.
The contact face between the projection 15 and the cover 8 forms a sealing zone 17 between the suction chamber 11 and the pressure chamber 14. The width of the sealing zone 17 can be further increased in that the upper end of the projection 15, that is, the end turning away from the valve plate 7, has a widening 18, as shown by dotted lines.
In the area of the suction chamber 11, the valve plate has a thickness s and in the area of the pressure chamber a thickness d, the thickness d being smaller than the thickness s. This makes it possible to keep the length of the pressure opening 12 small. The pressure opening 12 is part of the so-called dead space of the compressor 1, that is, even though the gas available in this space will be brought to a higher pressure in the upper dead centre position of the piston, however, it will not be supplied to the pressure chamber 14. The smaller the dead space is, the higher is the compressor efficiency. The reduction of the thickness d in the area of the pressure chamber enables a reduction of the volume of the dead space.
The reduction of the thickness of the valve plate 7 in the area of the pressure chamber is possible, because the projection 15 contributes to a stiffening of the valve plate 7 and thus an improved resistance towards deformation. The fact that the valve plate 7 deforms less also enables an improved bearing on the cover 8, that is, the risk that leakages occur here is extremely small.
The suction opening 9 is at least partly arranged within the projection 15 between the suction chamber 11 and the pressure chamber 14. For this purpose, it has a bend extension. As can be seen particularly from Fig. 2, this embodiment involves the advantage that the projection 15 can have a width b, which is larger than a distance a between the suction opening 9 and the pressure opening 12. However, the wider the projection 15, or rather the sealing zone 17 with the cover 8, is, the better is the sealing between the suction chamber 11 and the pressure chamber 14.
The pressure opening 12 is arranged close to the projection 15. The weakening of the valve plate 7 caused by the suction opening 12 is compensated by the strengthening provided by the projection 15.
Fig. 2 shows that the suction chamber 11 has a suction connection 19 and the pressure chamber 14 has a pressure connection 20, the gas being compressed in the cylinder chamber 3 entering the suction chamber 11 via the suction connection 19 and leaving the pressure chamber 14 through the pressure connection 20. Lines, which can be connected to both connections 19, 20 are known per se and therefore not shown in detail.
Fig. 3 shows a modified embodiment in a view that corresponds to that in Fig, 2. The same parts here have the same reference numbers.
As opposed to the embodiment shown in Figs. 1 and 2, here the projection has the form of a double wall with two sections 15a and 15b, the section 15b being substantially wider than the section 15a. This is caused by the fact that the pressure in the pressure chamber 14 is higher than the pressure in the suction chamber 11, which means that the pressure chamber 14 requires a better sealing towards the environment, which can be achieved by a wider sealing zone at the section 15b. Between the two sections 15a, 15b is arranged a gas volume 21, which causes a thermal isolation between the two wall sections 15a, 15b. This thermal isolation causes that the section 15a has a lower temperature than the section 15b. Due to the increased temperature of the gas in the pressure chamber, which has been brought to a higher pressure, the section 15b will be warmer than the gas sucked into the suction chamber 11 through the suction connection 19. When the gas sucked in is heated, it expands and can thus only fill the cylinder chamber 3 with a reduced mass of the gas.
Shown is that the gas volume 21 is open towards the environment. In this case a permanent replacement of the gas available in the gas volume 21 can take place. However, the gas volume 21 can also be closed or evacuated, if required, to increase the thermal isolation.
Fig. 4 shows a further embodiment example, which substantially corresponds to that in Fig. 2. The difference is that a suction muffler 22 has been arranged in the suction chamber 11. The suction muffler 22 has an adapter 23, which is led through the suction connection 19. The suction muffler 22 is made of a plastic material, which has very poor heat conductivity. The suction muffler 22 has an adapter 24, which is led immediately into the suction opening 9. With this embodiment it is achieved that the gas sucked in has no contact with the hot metallic surfaces of the valve plate or the cover. Thus, it is not so heavily heated, meaning that the efficiency of the compressor 1 can be further improved.
However, it is not necessary in all cases to arrange a complete suction muffler 22 in the suction chamber 11. Another alternative is to simply line the suction chamber 11 with a plastic material or another thermal isolation and to arrange the suction muffler outside the cylinder head 6.

Claims

Reciprocating compressor (1), particularly for refrigerants, with a cylinder housing (2), in which at least one cylinder chamber (3) is arranged, and a cylinder head (6), which delimits the cylinder chamber and has a valve plate (7) with a suction valve arrangement (10) that is connected with a suction chamber (11), and with a pressure valve arrangement, which is connected with a pressure chamber (14) that is separated from the suction chamber (11), characterised in that on the side facing away from the cylinder chamber (3), the valve plate (7) has a projection (15), which separates the suction chamber (11) from the pressure chamber (14).
Compressor according to claim 1, characterised in that the thickness (d) of the valve plate (7) is smaller in the area of the pressure valve arrangement (13) than in the area of the suction valve arrangement (10).
Compressor according to claim 1 or 2, characterised in that the pressure valve arrangement (13) has a pressure opening (12) into the pressure chamber (14), which lies next to the projection (15).
Compressor according to one of the claims 1 to 3, characterised in that the suction chamber (11) and/or the pressure chamber (14) are delimited in the circumferential direction by walls, which are formed by projections (16) on the valve plate (7).
Compressor according to claim 4, characterised in that the cylinder head (6) has a cover (8), which has, at least on the bottom side facing the valve plate (7), a plane surface.
Compressor according to claim 4 or 5, characterised in that at least the projection (15) separating the suction chamber (11) from the pressure chamber (14) has, on the end turning away from the valve plate (7), a larger thickness than near the valve plate (7).
Compressor according to one of the claims 1 to 6, characterised in that between the suction chamber (11) and the pressure chamber (14), the projection (15) forms, at least in sections, a double wall with two wall sections (15a, 15b), between which a gas volume (21) is arranged.
Compressor according to one of the claims 1 to 7, characterised in that the suction valve arrangement (10) has a suction opening (9) to the suction chamber (11), which is, at least partly, arranged within the projection (15) between the suction chamber (11) and the pressure chamber (14).
Compressor according to one of the claims 1 to 8, characterised in that the suction valve arrangement (10) is connected with a gas reservoir via a suction path lined with a plastic material.
Compressor according to claim 9, characterised in that the suction path is in the form of a suction muffler (22).