Patent Publication Number: US-2020277955-A1

Title: Scroll compressor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a United States nation phase patent application based on PCT/KR2018/012289 filed on Oct. 17, 2018, which claims the benefit of German Patent Application No. 10 2018 124301.4 filed on Oct. 2, 2018 and German Patent Application No. 10 2017 125542.7 filed on Nov. 1, 2017, the entire disclosures of which are hereby incorporated herein by reference. 
    
    
     FIELD 
     The invention relates to a scroll compressor which operates efficiently in air conditioning mode and in heat pump mode. 
     BACKGROUND 
     Scroll compressors for refrigeration circuits of air conditioning systems are usually designed so that they operate efficiently mainly in air conditioning mode, that is, in cooling mode. The aim is low power consumption at maximum flow rate. This leads to low outlet temperatures at a certain pressure ratio and speed. However, in a heat pump circuit it is necessary to reach high discharge temperatures in order to heat up the internal cabin space. An efficient scroll compressor is therefore required to achieve high pressure ratios in order to achieve a high discharge temperature. However, the volumetric efficiency drops at higher pressure ratios and the compressors become less efficient. The bearing loads are also increasing. 
     Conventional scroll compressors with a wrap angle in the range between 440° and 900° require two pre-outlets and one main outlet to be able to operate efficiently. Every outlet is closed through a valve after the pressure in a compression chamber drops below the high pressure. This avoids hot gas from streaming back into the compression chamber and thus making the compressor inefficient. Prior art air conditioning compressors are for this reason provided with triple discharge valves, the so-called 3-port finger valve. For a scroll compressor that operates in a heat pump circuit, which requires high exhaust gas temperatures, it would be advantageous for hot gas to be able to stream back into the compression chamber. 
     SUMMARY 
     It is now the object of the invention to propose a refrigerant scroll compressor, which operates efficiently not only in air conditioning mode but also in heat pump mode. 
     Said object is met by a scroll compressor with the features shown and described herein. 
     The solution is to design the scroll geometry in such a way that the high pressure is achieved under all air conditioning requirements before the refrigerant is able to exit via the main discharge opening. There is therefore no valve required at the main outlet. It has been observed that omitting the valve at the main outlet, which creates an additional dead volume, has no negative influence on performance. In heat pump mode the pre-discharge valves remain closed and the entire refrigerant is discharged from the main outlet. The return flow from the high-pressure side leads to poor compression and high outlet temperatures at low pressure conditions. 
     The scroll compressor according to the invention is comprised of a housing with a suction inlet and a system outlet. A first scroll element with a spiral that is formed on a first plate is arranged fixed in the housing. The housing comprises, furthermore, a rotatably arranged, second scroll element with a second spiral that is formed on a second plate, wherein said second spiral is rotated at an angle with the first spiral, being arranged radially offset and put together in such a way that the second spiral can roll off in the instance of a rotation of the second scroll element on the first spiral whilst forming a suction chamber, a central chamber and a discharge chamber, wherein, in the first plate, two eccentrically arranged pre-outlets, each of which may be shut off by way of a valve, and a centrally arranged main outlet for a refrigerant that is supplied via the suction inlet, are formed. The main outlet leads into a discharge cavity with a dead volume, wherein said discharge cavity is formed between the main outlet and the system outlet and is provided with a discharge valve in the direction of the system outlet. In this instance no valve is provided at the opening of the main outlet into the discharge cavity for shutting off the main outlet. The discharge valve and the discharge cavity may be attached by way of a bracket in the housing. 
     The advantage of the invention lies in the fact that the scroll compressor, which may simply be called a compressor, is able to operate in heat pump mode at lower pressures and lower speeds. This leads to an improved NVH behavior, lower power consumption and a lower bearing load. This makes it possible, advantageously, to achieve a greater service life in bearings, or the bearing size may be reduced. A significant advantage is also that the scroll compressor according to the invention has an improved NVH behavior when shutting down. 
     According to one implementation variation of the scroll compressor according to the invention provision may be made that the discharge cavity is formed by the entire hollow space of the housing part called rear head on the outlet side of the scroll compressor, wherein the volume of the discharge cavity corresponds to the dead volume. In this instance provision may be made for the main outlet and the two pre-outlets to lead into the discharge cavity. Furthermore, the discharge cavity may be formed by a dome, which is arranged at the outlet side on the first plate and thereby covers the main outlet and the two pre-outlets. 
     According to a further implementation variation of the scroll compressor according to the invention, in which only the main outlet leads into the discharge cavity, the discharge cavity is formed by a dome, which is arranged at the outlet side on the first plate and thereby covers the main outlet, wherein the two pre-outlets lead into an intermediate space, which is formed between the discharge cavity and the system outlet. Expediently, provision may be made so that an intermediate space is present between the discharge cavity and the system outlet. In this instance the intermediate space may be formed such that the two pre-outlets and the outlet of the discharge cavity lead into the intermediate space. 
     The scroll compressor according to the invention may advantageously be provided with an overall wrap angle of 660°. This makes it possible that, between each of the spirals of the scroll elements, a suction chamber, a central chamber and a discharge chamber are formed. In this instance, the required high pressure is always achieved in the central chamber under all checkpoints without shutting off the main outlet with a valve. Only the pre-outlets open and close. 
     The invention includes, moreover, an application of the above-described scroll compressor in air conditioning mode or in heat pump mode, wherein the valves of the pre-outlets are opened and closed in air conditioning mode for producing cold temperatures, and wherein the valves of the pre-outlets remain closed in heat pump mode for producing heat. 
    
    
     
       DRAWINGS 
       Further details, features, and advantages of embodiments of the invention become apparent from the following description of exemplary embodiments with reference to the respective drawings. Shown are in: 
         FIG. 1 : a schematic representation of a scroll element of a scroll compressor, 
         FIG. 2 : a 3-port finger valve according to prior art, 
         FIG. 3 : a schematic, cross-sectional representation of a first implementation variation of the scroll compressor according to the invention, 
         FIG. 4 : a schematic, cross-sectional representation of a second implementation variation of the scroll compressor according to the invention, 
         FIG. 5 : a schematic, cross-sectional representation of a third implementation variation of the scroll compressor according to the invention, 
         FIGS. 6A and 6B : a first schematic representation for the detailed description of the air conditioning mode, 
         FIGS. 7A and 7B : a second schematic representation for the detailed description of the air conditioning mode, 
         FIG. 8 : a diagram depicting the isotropic compression of the scroll compressor for the detailed description of the air conditioning mode, and 
         FIG. 9 : a diagram depicting the isotropic compression of the scroll compressor for the detailed description of the heat pump mode. 
     
    
    
     DETAILED DESCRIPTION OF AN EMBODIMENT 
     Repeated features are marked in the figures with the same reference numerals. 
       FIG. 1  depicts a scroll element  1  in representation A with spiral  2 , two pre-outlets  3  and one main outlet  4 . Representation B shows the design at the outlet side of the scroll element  1  with the two pre-outlets  3  and the main outlet  4 . 
       FIG. 2  depicts a so-called 3-port finger valve  5  as it is commonly used in prior art for shutting off the two pre-outlets  3  with the fingers or blades  6  and for shutting off the main outlet  4  with the main blade or the center blade  7 , respectively. The 3-port finger valve enables the simultaneous opening and closing of the pre-outlets  3  and the main outlet  4 . 
     According to the design of the scroll compressor according to the invention no valve is provided at the main outlet  4  so that the main outlet  4  is always open, wherein the main outlet  4  leads into a discharge cavity. 
       FIG. 3  depicts a schematic, cross-sectional view of a first implementation variation of the scroll compressor according to the invention. The scroll compressor according to the invention comprises a housing  9  with a suction inlet  10  and a system outlet  11 . A first scroll element  1  with a spiral  2  that is formed on a first plate  12  is arranged fixed in the housing  9 . The housing  9  comprises, furthermore, a rotatably arranged, second scroll element  13  with a second spiral  15  that is formed on a second plate  14 , wherein said second spiral  15  is rotated at an angle with the first spiral  2 , being arranged radially offset and put together in such a way that the second spiral  15  can roll off in the instance of a rotation of the second scroll element  13  on the first spiral  2  whilst forming a suction chamber SC, a central chamber MC and a discharge chamber DC (see  FIGS. 6 and 7 ), wherein, in the first plate  12 , two eccentrically arranged pre-outlets  3 , each of which may be shut off by way of a valve  16 , and a centrally arranged main outlet  4  for a refrigerant that is supplied via the suction inlet  10 , are formed. 
     The main outlet  4  leads into a discharge cavity  17  with a dead volume, wherein said discharge cavity  17  is formed between the main outlet  4  and the system outlet  11  and is provided with a discharge valve  18  in the direction of the system outlet  11 . In this instance no valve is provided at the outlet of the main outlet  4  into the discharge cavity  17  for shutting off the main outlet  4 . The discharge valve  18  and the discharge cavity  17  may be attached by way of a bracket  19  in the housing  9 . In this implementation variation, the pre-outlets  3  and the main outlet  4  lead into the discharge cavity  17 . 
       FIG. 4  depicts a schematic, cross-sectional representation of a second implementation variation of the scroll compressor according to the invention as per  FIG. 3  but with the difference that the discharge cavity  17  is formed by means of a dome  8 , which only covers the main outlet  4  so that the pre-outlets  3  lead into an intermediate space  20 , which is formed between dome  8  and the system outlet  11 . 
       FIG. 5  depicts a schematic, cross-sectional representation of a third implementation variation of the scroll compressor according to the invention as per  FIG. 4  but with the difference that the dome  8  is designed such that it covers the pre-outlets  3  and the main outlet  4  so that the pre-outlets  3  and the main outlet  4  lead into the discharge cavity  17 . 
       FIGS. 6 and 7  depict a schematic representation for the detailed description of the air conditioning mode. Each shows different rotational angles of the first spiral  2  and the second spiral  15 , wherein between each of the spirals  15  and  2  a suction chamber SC, a central chamber MC and a discharge chamber DC are formed.  FIG. 6A  depicts a rotational angle of 0° and 360° respectively, wherein the suction chamber SC has a pressure of 35 bar, the central chamber MC a pressure of 130 bar and the discharge chamber DC a pressure of 130 bar. In contrast to  FIG. 6A  the rotational angle in  FIG. 6B  is 90°, whereas the central chamber MC has a pressure of 45 bar. 
       FIG. 7A  depicts a rotational angle of 180°, wherein the central chamber MC has a pressure of 57 bar. At a rotational angle of 270°, as depicted in  FIG. 7B , the central chamber MC has a pressure of 79 bar. 
       FIG. 8  shows a diagram of the isotropic compression of the scroll compressor for the detailed description of the air conditioning mode in section  21  and in section  22  in which the valves of the pre-outlets  3  in section  21  are opened and closed. There is no high-pressure flow in the combined, inner compression chamber, which is formed by the discharge chamber DC and the discharge cavity  17 , although there is no main discharge valve present at the main outlet  4 . The discharge chamber DC and the discharge cavity  17  are at the same level. The compressor has low discharge temperatures. The total wrap angle is 660° so that the three compression chambers (suction chamber SC, central chamber MC and discharge chamber DC) may always be formed. Due to the characteristics of the specific refrigerant CO2 the required high pressure is achieved inside the central chamber MC under all checkpoints (360° rotational angle). Thus, no main discharge valve is required. Only the pre-outlets  3  close and open. 
       FIG. 9  shows a diagram depicting the isotropic compression of the scroll compressor for the detailed description of the heat pump mode in section  21  and section  22 . The valves  16  of the pre-outlets  3  remain closed in heat pump mode. A discharge of high pressure is possible since the main outlet  4  is always open. The pressure in the compression chamber is at a lower pressure level than the pressure in the discharge cavity  17 . The scroll compressor generates high discharge temperatures, which are required for an efficient function of the heat pump.