Abstract:
A piston compressor, particularly a refrigerant compressor includes a compression chamber in a compressor block, the compression chamber being delimited by a cylinder head ( 10 ), the cylinder head ( 10 ) comprising at least one valve plate arrangement with at least one suction valve ( 23, 24 ) and at least one pressure valve ( 21, 22 ), as well as a valve cover ( 12 ). To achieve low manufacturing costs, though maintaining a good efficiency, the valve plate arrangement ( 16 ) is formed by a carrier plate ( 17 ) that comprises the suction valve ( 23, 24, 26, 27 ) and the pressure valve ( 18, 19, 21, 22 ) and is connected by at least one gas-tight connection seam ( 28, 31 ) to the valve cover ( 12 ), the connection seam ( 28, 31 ) separating a suction area ( 32 ) and a pressure area ( 29, 30 ) from one another and sealing at least the pressure area ( 29, 30 ) towards the outside.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     Applicant hereby claims foreign priority benefits under U.S.C. §119 from German Patent Application No. 10 2008 037 672.8 filed on Aug. 14, 2008, the contents of which are incorporated by reference herein. 
     FIELD OF THE INVENTION 
     The invention concerns a piston compressor, particularly a refrigerant compressor with a compression chamber in a compressor block, the compression chamber being delimited by a cylinder head, the cylinder head comprising at least one valve plate arrangement with at least one suction valve and at least one pressure valve, as well as a valve cover. 
     BACKGROUND OF THE INVENTION 
     Such a piston compressor is, for example, known from DE 10 2004 047 159 B4. The valve plate arrangement comprises a pressure valve plate and a suction valve plate. The pressure valve plate and the suction valve plate are connected to each other and the valve cover by welding. The pressure valve plate has several pressure valve elements, which are part of the pressure valve plate. In a similar manner, the suction valve plate has several suction valve elements, which are part of the suction valve plate. 
     DE 103 30 760 B4 shows a further piston compressor, in which, additionally to the pressure valve plate and the suction valve plate, the valve plate arrangement comprises a reinforcement plate. 
     Piston compressors, which are used to compress refrigerants, that is, for example, hermetic or semi-hermetic refrigerant compressors, are manufactured in large numbers. Accordingly, there is an interest in keeping the manufacturing costs low. Usually, however, low manufacturing costs involve the risk that the application properties of the compressor are deteriorated. In particular, there is a risk that the efficiency is reduced. 
     SUMMARY OF THE INVENTION 
     The invention is based on the task of achieving low costs in connection with a good efficiency. 
     With a piston compressor as mentioned in the introduction, this task is solved in that the valve plate arrangement is formed by a carrier plate that comprises the suction valve and the pressure valve and is connected by means of at least one gas-tight connection seam to the valve cover, the connection seam separating a suction area and a pressure area from one another and sealing at least the pressure area towards the outside. 
     With this embodiment, one single plate will be sufficient, namely the carrier plate. Additional plates can be saved, so that the manufacturing costs can be reduced. On the one hand, this occurs through a smaller material consumption and secondly in that only one carrier plate has to be handled during the assembly of the cylinder head. Further, the carrier plate can be made relatively thin, that is, a carrier plate can be used, which does not have natural stability. On the contrary, the stability of the valve plate arrangement does not occur until the carrier plate is connected to the mechanically sufficiently stable valve cover. However, this connection does not only have the task of ensuring a mechanical reinforcement for the carrier plate. It also has the additional task of providing a gas-tight separation between the suction area and the pressure area on the one side and between the pressure area and the environment on the other side. The connection seam can, for example, be made by welding, soldering or gluing. Thus, a sealing between the carrier plate and the valve cover is saved, which contributes to a further cost reduction. As the carrier plate can be made very thin, a relatively small harmful space occurs, which is particularly important in connection with low-temperature compressors. The small thickness of the carrier plate also results in small pressure losses during the flow of the refrigerant gas through the suction and pressure valves. Further, a working of the surface of the carrier plate can be avoided, at least in large areas. 
     Preferably, the suction valve has a suction valve element that is located on one side of the carrier plate, and the pressure valve has a pressure valve element that is located on the other side of the carrier plate. The use of suction and pressure valve elements separated by the carrier plate has the advantage that these valve elements can be worked independently of the carrier plate. In particular, it is much easier to provide the valve elements with an edge rounding, which contributes to a long life. This is possible, as, before the assembly of the valve arrangement, the valve elements are accessible from all sides. The valve elements require no additional plate, through which the gas to be compressed would then have to flow. 
     Preferably, the suction valve element and/or the pressure valve element are connected to the carrier plate by welding or riveting. Accordingly, the carrier plate with valve element or valve elements can be handled and used as one until the manufacturing of the cylinder head. The fixing of the valve elements on the carrier plate can be made automatically. 
     Preferably, the suction valve element and the pressure valve element are made in the form of fins. These fins are fixed unilaterally, that is, with one end, to the carrier plate and can lift off from the carrier plate with the other end to release a suction opening or a pressure opening. As only the suction valve element and the pressure valve element have to be made of relatively expensive valve material, for example laminar valve steel, the material costs are low. 
     Preferably, a sealing is arranged between the cylinder head and the compressor block. The sealing provides tightness between the cylinder head and the compressor block. At least in the area, in which the sealing is located, an expensive working or a grinding of the surface of the carrier plate is not required. Here, the carrier plate can still have a certain roughness, as here the sealing rests. On the side next to the valve cover the carrier plate can also have a certain roughness, as here the tightness is provided by the connection seam or the connection seams. 
     Preferably, the sealing acts upon the suction valve element with a restoring force. Thus, the sealing does not only assume the task of sealing the compression chamber towards the environment, but also the task of quickly restoring the suction valve element after finishing the suction stroke, thus closing the suction valve. An additional spring component can be saved. 
     Preferably, the sealing rests flat on a sealing area of the carrier plate and comprises a recess for the suction valve element. As long as the suction valve is closed, this causes no or only little deformation of the sealing. Only when the suction valve element is lifted from the carrier plate, the restoring force of the sealing acts upon the suction valve element. 
     Preferably, the valve cover has at least one wall, which separates a suction gas channel from a pressure gas channel, the connection seam extending on a side of the wall facing the compression chamber. Thus, the wall can be kept relatively thin, so that large flow cross-sections are available for suction gas and pressure gas in the valve cover. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following, the invention is described on the basis of a preferred embodiment in connection with the drawings, showing: 
         FIG. 1  is a schematic, sectional view of a refrigerant compressor, 
         FIG. 2  shows three main elements of a cylinder head in a perspective, exploded view, 
         FIG. 3  shows the three elements from another angle of vision, 
         FIG. 4  is a unit of valve plate arrangement and valve cover, and 
         FIG. 5  shows the unit of  FIG. 4  with sealing. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  is a schematic view of a refrigerant compressor  1  with a compression chamber  2  formed in a cylinder  3 . The cylinder  3  is located in a compressor block  4 . The volume of the compression chamber  2  can be changed by means of a piston  5 , a drive, not shown in detail, driving the piston  5  to reciprocate via a connecting rod  6 . 
     The cylinder block  4  is located in a suction channel  7 , via which refrigerant gas can be sucked into the compression chamber  2 . A pressure channel  8  is partly guided through the compressor block  4  and supplies compressed refrigerant gas to a pressure gas collector  9 . 
     A cylinder head  10  closes the compression chamber  2  at the front side of the cylinder  3 . Between the cylinder head  10  and the compressor block  4  a sealing  11  is located. In the following, the cylinder head  10  is explained in detail by means of the  FIGS. 2 to 5 . 
     The cylinder head  10  has a valve cover  12 , in which a suction gas channel  13  and two pressure gas channels  14 ,  15  are located. The suction gas channel  13  of the valve cover  12  is connected to the suction channel  7  of the compressor block  4 . The pressure gas channels  14 ,  15  are connected to the pressure channel  8  in the compressor block  4  (also more pressure channels  8  can be formed in the compressor block  4 ). 
     A valve plate arrangement  16  having a relatively simple design is connected to the valve cover  12 . The valve plate arrangement  16  has only one single plate, namely a carrier plate  17 . On the side of the carrier plate  17  facing the valve cover  12 , two pressure valve elements  18 ,  19  are arranged and connected to the carrier plate  17  by means of rivets or welding points  20 . The two pressure valve elements  18 ,  19  cover pressure openings  21 ,  22  in the carrier plate  17 . The pressure openings  21 ,  22  overlap the pressure gas channels  14 ,  15  in the valve cover. 
     On the side facing the sealing  11 , the carrier plate comprises two suction valve elements  23 ,  24 , which are also connected to the carrier plate  17  by means of rivets or welding points  25 . The suction valve elements  23 ,  24  cover suction openings  26 ,  27  in the carrier plate  17 . The suction openings  26 ,  27  overlap the suction gas channel  13  in the valve cover  12 . 
     The pressure valve elements  18 ,  19  and the suction valve elements  23 ,  24  are formed as fins. These fins can, for example, be made of laminar valve steel, meaning that they are elastically deformable. Accordingly, with the corresponding pressure conditions, their free end can lift off from the carrier plate  17 , thus releasing the pressure openings  21 ,  22  or the suction openings  26 ,  27 . As the fins have a longitudinal shape, the lift-off of the free end from the carrier plate  17  will cause a lateral outflow, also with very small opening degrees, which reduces the losses and thus increases the efficiency of the compressor  1 . 
     The carrier plate  17  is made of a relatively thin sheet metal. Thus, it does not have sufficient natural stability to adopt the pressure forces ruling during operation and acting upon the carrier plate  17  from the cylinder  3  or the valve cover  12 . Accordingly, as can be seen from  FIG. 4 , the carrier plate  17  is welded, soldered or glued onto the valve cover  12 . For this purpose, a connection seam  28  is provided, which closes two pressure valve areas  29 ,  30  towards the outside. A further connection seam  31  separates the pressure valve areas  29 ,  30  from a suction valve area  32 . As can be seen from  FIG. 2 , the valve cover  12  has, between the suction gas channel  13  and each pressure gas channel  14 ,  15 , a wall  33  with a side  34  facing the compression chamber  2 . The connection seam  31  extends on this side  34 . This has the advantage that relatively thin walls  33  can be used between the suction gas channel  13  and the pressure gas channels  14 ,  15 , so that an improved flow with small flow losses for the suction and pressure gas can be achieved. The valve cover  12  ensures the mechanical stability of the cylinder head  10  and thus also the carrier plate  17 . 
     The pressure valve elements  18 ,  19  and the suction valve elements  23 ,  24  can be worked before being fixed on the carrier plate  17 . In particular, here an edge rounding can be made, which contributes to achieving a long life. Contrary to an embodiment, in which the valve elements are still made in a plate, here a grinding tool will have easier access. 
     As the carrier plate  17  is relatively thin and, particularly, as only one plate is available, which the refrigerant gas must cross during entry into and discharge from the compression chamber  2 , small pressure losses occur. Further, the harmful space or dead space remains small, so that a favourable efficiency occurs. 
     As can be seen from a comparison of the  FIGS. 4 and 5 , the sealing  11  covers the suction valve elements  23 ,  24  at their fixing area  35 ,  36  and a small area adjacent to that. This causes that, when the suction valve elements  23 ,  24  are lifted off from the carrier plate  17  by supplied gas, the sealing  11  is exposed to a restoring force, which brings the suction valve elements  23 ,  24  back to rest on the carrier plate  17 , when the suction flow ends, and this happens relatively quickly and without the need for further spring elements. 
     As is particularly obvious from  FIG. 3 , the sealing  11  has a recess  37  for each suction valve element  23 ,  24 , the fixing area  35 ,  36  of each suction valve element  23 ,  24  entering said recess  37 . Accordingly, the sealing  11  can rest on the suction valve elements  23 ,  24  in a practically tension-free manner or with little pretension, when the cylinder head  10  is mounted on the compressor block  4 . 
     The cylinder head  10  can be fixed on the compressor block  4  by means of screws, which are guided through openings  38  in the cylinder head  10 . However, it may also be provided that the cylinder head  10  is welded onto the compressor block  4 . In this case, screws or bolts will under certain circumstances not be required. 
     The embodiments shown have a number of advantages. The carrier plate  17  can be made as a thin punched part, which does not only save material, but also an expensive working or grinding of the surfaces on both sides. In the points, in which the carrier plate  17  rests on the sealing  11 , a working is not required. In the points, in which the carrier plate  17  rests on the valve cover  12 , a working is not required either, as long as it is ensured that a connection seam  28 ,  31  can be generated. A sealing between the carrier plate  17  and the valve cover  12  is saved. Due to the small thickness of the carrier plate  17 , a small harmful space occurs, which is particularly important in connection with low-temperature compressors. Due to the connection seam  31 , there is no risk that already compressed pressure gas will leak to the suction side. 
     Due to the small thickness of the carrier plate  17 , only small pressure losses occur when the refrigerant gas passes. The sealing  11  assumes some kind of spring function in pressing the suction valve elements  23 ,  24  against the carrier plate. 
     Merely for the valve elements  18 ,  19 ,  23 ,  24  an expensive valve material is required. The carrier plate  17 , however, can be made of a more cost-effective material. Gaps will not occur around the valve elements  18 ,  19 ,  23 ,  24 , which is the case in connection with traditional cylinder heads, in which the valve elements are arranged in plates and manufactured by means of punching. 
     While the present invention has been illustrated and described with respect to a particular embodiment thereof, it should be appreciated by those of ordinary skill in the art that various modifications to this invention may be made without departing from the spirit and scope of the present invention.