Patent Publication Number: US-6210132-B1

Title: Partition means for directing air flow over a cooler in an oilless scroll compressor

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a compressor of the type used for air compressor, refrigeration, air-conditioning, etc., and more particularly to an oil-free scroll compressor. 
     An oil-free scroll compressor, which does not use oil, such as a lubricating oil, for the flow passage of the operation gas, is a well known compressor for use in air compressor, refrigeration, and air condition. In this oil-free scroll compressor, two sealed spaces are defined by wraps and end plates on the outer wall surface of an orbiting scroll wrap and a stationary scroll wrap by combining the orbiting scroll and the stationary scroll, each of which is equipped with spiral wraps perpendicular to an end plate, while the inside of the wraps face one another. The sealed spaces move towards the center portion due to the relative motion of both scrolls. As their volumes thus decrease, a gas sucked from the outer peripheral sides of these scrolls is compressed and is discharged from a discharge port disposed at the center portion of the stationary scroll. When the operation gas is compressed in this way by the relative motion of the orbiting scroll and the stationary scroll, the scroll compressor generates heat. This also holds true for other types of compressors handling gas. Japanese Patent Laid-Open No. 217580/1995 describes a two-stage oil-free screw compressor having a small capacity of 22 kW to 37 kW, for example, wherein the first stage discharge air temperature reaches about 190 to about 240° C. Therefore, in the scroll compressor which is of the same displacement type, heat generation of a similar level can be expected if the compressor ratio, etc., is the same. 
     When the compressor generates heat, the clearance of each portion of the compressor changes from the design value due to thermal deformation, and the compressor becomes less reliable. At the same time, performance of the compressor drops due to a leakage from clearances caused by the thermal deformation, etc. Therefore, a cooling system for effectively guiding the heat generated inside the compressor to the outside has been necessary, and an example of such a system is described in Japanese Patent Laid-Open No. 217580/1995 and Japanese Utility Model Laid-Open No. 104384/1983. 
     According to Japanese Laid-Open No. 217580/1995, a pre-cooler for primarily cooling a gas discharged from a low pressure stage compressor element is interposed between the low pressure stage compressor main body and an intercooler in a two-stage oilless scroll compressor, and this pre-cooler is accommodated inside an exhaust duct and is cooled by exhaust air flowing through each cooler. This technique retains the effect of dissipating heat generated by the scroll compressor from the compressor to a certain extent, but is not yet sufficient for improving the reliability by cooling the compressor as a whole. In other words, though this approach considers how to cool the cooler on the discharge side of the cooling fan, it does not take cooling of the compressor element disposed on the suction side into consideration. In this regard, if the compressor element which generates a high compression heat is cooled by air, the mass of cooling air increases and a problem develops in that the noise increases due to the increase of a flow velocity inside the exhaust duct. Additionally, the compressor element, the cooling fan, the cooler, etc., are disposed plane-wise, and require a large installing space. Therefore, a reduction of the size of the compressor can not be achieved. 
     According to Japanese Utility Model Laid-Open No. 104384/1983, on the other hand, a compressor driven by a vertical motor is disposed below the motor, a blower is disposed above the motor, and they are accommodated in a casing so as to cool the compressor as a whole using the blower. According to this technique, however, the air steam around each portion of the compressor changes depending on the flow passage resistance, and all the heat generating portions cannot always be cooled. 
     SUMMARY OF THE INVENTION 
     It is therefore a main object of the present invention to achieve a low noise oil-free scroll compressor which can eliminate the problems described above. 
     It is another object of the present invention to achieve an oil-free scroll compressor which does not need a large installing space. 
     An oil-free scroll compressor, of the type to which the invention applies, comprises scroll compressor element having an orbiting scroll and a stationary scroll; a motor for driving the scroll compressor element; a cooler for cooling an operation gas compressed by the scroll compressor element; a cooling fan for blasting cooling air subjected to heat-exchange with the operation gas by the cooler; and a casing for accommodating these members. A first embodiment of the present invention for accomplishing the objects described above employs a construction wherein partition means for partitioning a suction flow passage and a discharge flow passage of the cooling fan is provided in the casing. Preferably, this partition means divides the inside of the casing into two chambers with the suction side of the cooling fan as a part thereof. 
     Preferably, a dryer for dehumidifying the operation gas cooled by the cooler is accommodated in the casing, a discharge port for cooling air is formed on the ceiling plate portion of the casing, a suction port for cooling air is formed on the side portion of the casing, and a first flow passage, through which cooling air introduced via the suction port flows from above to below, a second flow passage, through which cooling air flows from below to above to flows out via the discharge port, and a third flow passage, connecting the first and second flow passage, are exclusively disposed in the casing. Preferably, the second and third flow passages are constituted by a duct respectively. 
     A second embodiment of the present invention for accomplishing the objects described above employs a construction wherein the motor and the scroll compressor elements are disposed in a stratified form, and the cooling fan and the cooler are disposed in a stratified form. These two stratified arrangements are preferably juxtaposed on the floor surface of the casing. 
     Preferably, the casing is shaped into a rectangular parallelepiped, the motor is accommodated at the lowermost portion of this rectangular parallelepiped through insulating means for vibration-insulation from the casing, the duct is disposed above the motor, the scroll compressor element is disposed above the duct, a dryer for dehumidifying the operating as compressed by the scroll compressor element, the cooler is interconnected to the scroll compressor element, partition means is a duct defining the cooler and the cooling fan from other members, an exhaust port is formed on the ceiling plate side of the casing, and a suction port is formed on the side surface of the casing on the opposite side to the cooling fan. 
     Further, a first flow passage through which cooling air flows from above to below, a second flow passage through which cooling air flows from below to above and a third flow passage which connects these first and second flow passages are exclusively disposed inside the casing. Further, the second and third flow passages are preferably constituted by a duct. 
     In an oil-free scroll compressor of the type wherein a scroll compressor element, a motor and a cooler accommodated inside a casing are cooled by a cooling fan fitted to a double-end motor, the third embodiment of the present invention for accomplishing the afore-mentioned objects comprises a duct for communicating the suction side of the cooling fan and the scroll compressor elements; and an exhaust duct with a built-in cooler disposed on the discharge side of the cooling fan. Preferably, the duct and the exhaust duct are disposed in such a manner as to cross each other substantially orthogonally. 
     Preferably, a duct for communicating the suction side of the cooling fan and the scroll compressor element and an exhaust duct with a built-in cooler on the discharge side of the cooling fan are disposed, and the distance from the shaft end portion of the scroll compressor element to the end portion of the cooler in the motor axial direction is smaller than the distance from the end of the motor opposite to the cooling fan fitting end to the end face of the cooling fan. 
     In each of the embodiments described above, cooling means comprising a plurality of fins are preferably disposed on both side surfaces of the scroll compressor element in a direction orthogonal to the axis of rotation inside the scroll compressor element. It is particularly preferable for the orbiting scroll of the scroll compressor element to be a double scroll equipped with spiral wraps on both sides of an end plate. 
     Each of the embodiments of the present invention provides the following functions and effects. The cooler is disposed on the discharge side of the cooling fan and the duct is interconnected to the suction side of the cooling fan. Since the compressor element is disposed on the upstream side of the duct, air after cooling the compressor element is sucked by the fan and flows into the cooler. Therefore, the cooler is cooled by outside air, the quantity of cooling air can be reduced, the discharge flow velocity drops, and a lower noise can be expected. 
     Because the compressor element and the cooler are disposed above the double-end motor, the area of installation can be reduced. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 to  3  shown an oil-free scroll compressor according to an embodiment of the present invention, wherein: 
     FIG. 1 is a longitudinal sectional view of the scroll compressor; 
     FIG. 2 is its front view; and 
     FIG. 3 is its side view. 
     FIGS. 4 to  6  show an example of an oil-free scroll compressor element used for the embodiment shown in FIGS. 1 to  3 , wherein: 
     FIG. 4 is a transverse sectional view of the oil-free scroll compressor element; 
     FIG. 5 is its front view; and 
     FIG. 6 is its bottom view. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Hereinafter, a preferred embodiment of the present invention will be explained with reference to FIGS. 1 to  6 . 
     FIG. 1 is a longitudinal sectional view of an oil-free scroll compressor according to a preferred embodiment of the present invention, and FIGS. 2 and 3 are a front view and a side view of the oil-free scroll compressor, respectively. Referring to FIG. 1, reference numeral  1  denotes a compressor element, reference numeral  1   a  denotes a cooling air outlet of the compressor element  1 , and reference numeral  2  denotes a double-end motor equipped with a cooling fan  4  on its shaft on one of the sides and with an M sheave  7  for driving the compressor element on its shaft on the other side. The motor  2  and the compressor element  1  are disposed on respective stages of a motor base  13 , which is constituted into two states. The motor base  13  is installed on a common base through a vibration-isolation rubber mounting  14  so as to insulate with respect to the vibration of the common base  15 . 
     A V-pulley  8  is fitted to the comparison element  1 , and the driving force of the double-end motor  2  is transmitted to the rotary shaft of the compressor element  1  through the V belt  9 . An exhaust duct  12  is formed substantially vertically on the discharge side of the cooling fan  4 , and a fin tube type cooler  3  is disposed inside this exhaust duct  12  and above the cooling fan  4 . A main duct  11  is formed on the suction side of the cooling fan  4  and between the compressor element  1  and the double-end motor  2  substantially in parallel with the double-end motor shaft. A duct equipped with partition walls  11   a  and  12   a  is interposed between one of the sides of the main duct  11  and the exhaust duct  12  so as to prevent air flowing into the suction side of the cooling fan  4  from mixing with air flowing out from the discharge side. On the other hand, the other end of the main duct  11  is connected to a fin cover disposed on both sides of the fin  23  so that cooling air flowing through the compressor element  1  is guided to the cooling fan  4 . The compressor element  1  is connected to the cooler  3  by a conduit  5 , and the cooler  3  and a dryer  16  disposed above the compressor element  1  are connected by a conduit  6 . In other words, high pressure and high temperature air compressed by the oil-free scroll compressor is subjected to heat-exchange by the cooler  3  with external air and is cooled to air at not higher than 55° C. The dryer  16  constitutes a refrigeration cycle, and the inflow air temperature is limited to not higher than 55° C. Therefore, since the discharge gas of the compressor is pre-cooled by the cooler  3 , the dryer  16  can be operated at a suitable temperature. 
     Reference numeral  32  denotes a casing for accommodating the compressor unit as a whole, and suction ports  17  and  18  and a dryer suction port  19  are disposed on the right side surface of the casing  22 , respectively. A dryer exhaust port  20  and an exhaust port  21  are disposed at the upper part of the casing  22 . 
     The air flow for cooling the compressor element  1  and the cooler  3  in the oil-free scroll compressor according to the present invention having the construction described above will be explained. When the double-end motor  2  is turned on, the cooling fan  4  rotates simultaneously with the double-end motor  2 , and cooling air is sucked into the casing from the suction ports  17  and  18  formed on the right side surface of the casing  22 . Outside air sucked into the casing cools the double-end motor  2  and the compressor element  1  disposed in the proximity of the suction ports  17  and  18 . 
     Fins  23  are formed on both side surfaces of the compressor element  1 . Therefore, cooling air flowing in from the suction port  18  flows through the side portions of the compressor element  1  while the fins  23  function as a guide. Then, cooling air flows into the main duct  11  through the cooling air outlet  1   a  formed at the lower portion of the compressor element  1 , and is subsequently sucked by the cooling fan  4  from the main duct  11  through the flow passage between the partition walls  11   a  and  12   a.  Outside air sucked from the suction port  17  flows in the axial direction through the peripheral portion of the double-end motor  2  and flows into the cooling fan  4  from the outflow port defined in the partition wall  11   a  disposed on the cooling fan fitting end side of this double-end motor  2 . Therefore, a part the cooling air sucked into the casing  22  cools the compressor element  1  and then passes through the main duct  11  and flows into the cooling fan  4 , while the remaining cooling air cools the double-end motor and then flows into the cooling fan. After passing through the cooling fan  4 , this cooling air is directed toward the cooler  3  for cooling it. 
     In consequence, the cooler  3  can be cooled by using air after use for cooling the compressor element  1 , and excessive cooling air, which is necessary when the cooler and the compressor element are separately cooled, is not required, so that the mass of cooling air can be reduced, the discharge flow velocity becomes lower and the operation noise can be reduced. 
     Next, details of the compressor element will be explained with reference to FIGS. 4 to  6 . 
     FIG. 4 is a transverse sectional view of the compressor element of the oil-free scroll compressor shown in FIG.  1 . FIGS. 5 and 6 are a front view and a bottom view of the oil-free scroll compressor element shown in FIG. 4, respectively. Spiral wraps  31  are formed on both surfaces of an end plate  30  to form an orbiting scroll. This orbiting scroll is sandwiched by two stationary scrolls having spiral wraps formed thereon. Power is transmitted from the double-end motor  2  to a main crank shaft  34  through the pulley  8 , and power of the double-end motor  2  is transmitted to an auxiliary crank shaft  35  by timing pulleys  32  and  36  and a timing belt  33  for transmitting power to these timing pulleys. 
     These two crank shafts are rotatably supported by bearings in the peripheral portion of the end plate not equipped with the wraps, and are also supported rotatably at predetermined positions of the stationary scroll. A fluid section port is provided to the stationary scroll while a discharge port is disposed at the center of the stationary scroll in such a manner as to correspond to the wraps at the peripheral portions of the stationary scroll and the orbiting scroll. When power is transmitted from the double-end motor to the pulley, the crank shaft  34  rotates, and the auxiliary shaft  35 , too, rotates in synchronism with the main crank shaft  34  through a timing pulley  32  and a timing belt  33  for synchronization. Due to this rotation, the orbiting scroll rotates with a predetermined radius without turning on its own axis. In consequence, the fluid is sucked from the suction portion into the compressor chamber defined by the orbiting scroll and the wraps of the two stationary scrolls. As the rotation of the orbiting scroll proceeds and the compressor chamber moves from the peripheral portion of the end plate to the center portion, the fluid reaches a predetermined pressure and is then discharged from the discharge port. 
     During this compression process, the temperature of the operation gas rises and the temperature rise is remarkable particularly at its center portion, which should be cooled. As shown in FIGS. 5 and 6, because the timing pulleys are fitted to the crank shaft in the proximity of both end portions of the compressor element, there is hardly any space, but a sufficient space can be secured at the center exclusive of the discharge port portion of the compressor. Therefore, the cooling fins  23  are formed at this portion. Because the rotary shaft of the double-end motor and the crank shaft are in parallel with each other for the sake of convenience of power transmission, the longitudinal direction of the fins is set to a direction which is perpendicular to both the axis of rotation of the double-end motor and a straight line connecting the axes of the crank shafts. The height of the fins  23  from the casing outer wall of the compressor element  1  is set to a predetermined height in consideration of both of the fluid resistance and the heat radiation capacity. The pitches between the fins  23  are also determined similarly. 
     Incidentally, it is the double-end motor  2  among the components of the oil-free scroll compressor accommodated in the package casing that has the greatest installation area. Therefore, the compressor can be made compact by defining the outer profile of the casing based on the occupied area of the double-end motor. In other words, because the pulleys and the blower are fitted to both shaft end portions of the double-end motor, the disposition of the other components is determined in such a manner as not to deviate as much as possible from the occupied area of the double-end motor inclusive of these components. Because the motor is heavy and is likely to generate a vibration, etc., it is installed at the lower portion of the compressor. 
     The lengths of the compressor element  1  and the cooler  3  are not greater than the length of the double-end motor  2 , inclusive of the cooling fan  4 , in the axial direction. Because the scroll compressor has low vibration and low noise, its influences on the casing are not great even when it is disposed above the double-end motor  2 . In order to secure the installation area of the cooler and the cooling flow passages, duct passages are defined between the compressor element and the fan and between the cooling fan and the cooler. In this way, the length in the longitudinal direction of the installation area can be reduced to a minimum and the saving of space can be accomplished. 
     Incidentally, although the motor base and the duct have separate structures in the embodiment described above, either one of them may double as the other. Further, the embodiment described herein is merely exemplary, but is in no way restrictive, and all modifications utilizing the genuine spirit of the present invention are naturally embraced in the scope of the present invention. 
     According to the present invention, cooling air flows in the sequence of the compressor element -cooling fan -cooler. Therefore, the mass of cooling air can be reduced, and a lower noise operation can be achieved by reducing the discharge flow velocity. 
     According to the present invention, further, the principal components of the cooling system, such as the compressor element; and the cooler, are accommodated within the size of the double-end motor inclusive of the cooling fan in the axial direction, and they are disposed above the double-end motor. In consequence, the installation space can be reduced.