Patent Publication Number: US-6705843-B1

Title: NVH and gas pulsation reduction in AC compressor

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to compressors, and more particularly relates to mufflers for reducing noise in compressors. 
     BACKGROUND OF THE INVENTION 
     Existing compressors, such as air conditioning compressors found in vehicles, are relatively noisy. Accordingly, many compressors include a built-in flow noise control device or muffler. Unfortunately, these devices are usually a bulky addition to the compressor casting or housing, increasing the overall size and mass of the compressor significantly. Furthermore, these mufflers typically communicate with the discharge flow or the suction flow through a long and narrow passage. This passage is strictly a communication channel, and does not direct flow in a manner that effectively utilizes the interior of the muffler. One drawback includes a large flow loss due to the structure of the communication channel. Flow loss refers to a pressure loss in the flow due to the restricted flow passage. The more flow loss, the more power is required to compress same amount of refrigerant through a passage. Therefore, there exists a need to provide a muffler for a compressor that not only reduces the flow loss through the muffler, but which also reduces the overall size, weight and cost of the compressor. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides a muffler for a compressor that is incorporated into the existing rear housing portion of the compressor housing. In this way, the present invention provides a compressor which has reduced size and weight compared to existing compressors with external mufflers, mufflers as well as reducing the amount of flow loss. In turn, the efficiency of the compressor is increased (i.e. lower power consumption) due to streamlined flow with less turbulence. Additionally, the integral muffler adds stiffness to the rear housing that attributes to lower vibration. Preferably, a muffler chamber is defined within a discharge chamber, and the discharge chamber is further sub-divided into first and second portions. Discharge flow entering the first portion of the discharge chamber must flow through the muffler chamber before reaching the second portion of the discharge chamber for exit through a discharge port. Generally, the muffler chamber is defined by a muffler wall which includes restrictions to regulate the flow from the first portion to the second portion of the discharge chamber. Additional features include further subdividing the discharge chamber into several smaller cavities, as well as providing high pressure fluid directly to the second portion and discharge port. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention, and together with the description serve to explain the principles of the invention. In the drawings: 
     FIG. 1 is a perspective view of a rear housing and muffler constructed in accordance with the teachings of the present invention; [insert a brief description of each drawing, being sure that each drawing is separately labeled (e.g.,  1 ,  2 A,  2 B,  3 ,  4 , etc.) and individually described]. 
     FIG. 2 is a top view of the rear housing and muffler depicted in FIG. 1; 
     FIG. 3 is a cross-sectional view taken about the line  3 — 3  of FIG. 2; and 
     FIG. 4 is a perspective view similar to FIG. 1, but depicting a portion of a cylinder block partially cut away. 
    
    
     While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Turning now to the figures, FIGS. 1-3 illustrate a rear housing  20  having a muffler  40  for reducing the noise, vibration and harshness in a compressor (not shown). Generally, the muffler  40  provides a damping effect to reduce the turbulence of fluid flow, as well as any pulsations in the flow. As a result of reduced flow turbulence and pulsations, the noise and vibration are reduced. Further, the efficiency of the compressor is increased due to the streamlined flow having less turbulence. 
     The rear housing  20  forms one element of a housing for the compressor. The rear housing  20  includes an end wall  26  and is positioned at one end of the compressor for communicating flow into and out of the compressor. The rear housing  20  includes an outer wall  22  extending axially from the end wall  26  around its outer periphery. The outer wall  22  is annular in shape. As used herein, “annular” refers to a ring-shape structure (i.e. having no particular beginning or end), although not necessarily circular. 
     The outer wall  22  defines a plurality of female connectors shown as threaded openings  24 . Typically, a threaded fastener is utilized to connect the rear housing  20  to the main housing by way of the threaded openings  24 . As shown in FIG. 4, the rear housing is positioned immediately downstream of a cylinder block  15  containing a plurality of pistons (not shown) reciprocating within their respective bores  17 . The cylinder block  15  has been shown partially cut-away in FIG.  4 . As will be described in more detail herein, the rear housing  20  supplies low pressure fluid to the compressor, and more particularly the piston bores  17 , as well as directs high pressure fluid produced by the compressor and discharged via the bores  17 . 
     To accomplish the above, an inner wall  32  is formed within the rear housing  20 . As with the outer wall  22 , the inner wall  32  extends axially from the end wall  26  of the rear housing  20 . The inner wall  32  is completely circumscribed by the outer wall  22 . The inner wall  32  is annular in shape, and more specifically the inner wall  32  is flower-shaped, having a plurality of peaks and troughs to facilitate cooperation with the input and output of the cylinder bores  17 , as shown in FIG.  4 . The volume between the outer wall  22  and the inner wall  32  defines a suction chamber  25  which is utilized to supply low pressure fluid to the compressor. The supply of low pressure fluid is provided via a suction port  26  which is in fluid communication with the suction chamber  25 , as best seen in FIG.  2 . Within the inner wall  32 , and as will be described in more detail herein, a discharge chamber  35  is formed for receiving high pressure fluid from the compressor. The discharge chamber  35  is in fluid communication with a discharge port  28  as shown by the dotted lines of FIG.  2 . 
     In accordance with the present invention, a muffler  40  is integrally formed within the rear housing  20  to reduce the noise, vibration and harshness of the fluid flow. As shown in the figures, the muffler  40  includes a muffler wall  42  that extends axially from the end wall  26 . The muffler wall  40  is annular in shape, and as shown in the figures, is preferably circular in shape. The muffler wall  42  is located within the inner wall  32  and is completely circumscribed thereby. Thus, the muffler chamber  45  is completely circumscribed by the discharge chamber  35 . Accordingly, the discharge chamber  35  is best defined as the volume between the inner wall  32  and the muffler wall  42 , although it will be recognized that discharge fluid does flow through both the discharge chamber  35  and muffler chamber  45 . Thus, the discharge chamber  35  is ring-shaped and is completely circumscribed by the suction chamber  25 . The muffler wall  42  defines an interior volume defined as the muffler chamber  45 . 
     As the muffler  40  is incorporated into the rear housing  20  and the discharge chamber  35 , it can be seen that the total outside dimensions of the rear housing  20  remain unchanged. The aforementioned walls (as well as the chambers, ports and channels that they define to direct the fluid flow) are cast directly into the rear housing  20 , which eliminates any additional machining operations. Further, the refrigerant flow is directed to flow through the discharge chamber  35  in muffler  40  in such a way as to fully utilize the internal volume effectively, reducing flow turbulence and pulsations which in turn reduces the noise and vibration. The integral formation of the muffler adds stiffness to the rear housing that attributes to lower vibration. 
     For directing the flow, at least two divider walls  52 ,  54  extend between the muffler wall  42  and the inner wall  32 . As shown in the figures, the illustrated embodiment of the rear housing  20  and muffler  40  includes a third divider wall  56  that extends between the muffler wall  42  and the inner wall  32 . The divider walls  52 ,  54 ,  56  are spaced apart to sub-divide the discharge chamber  35  into first, second and third portions denoted as  35   a ,  35   b  and  35   c , respectively. The second portion  35   b  of the discharge chamber  35  is fluidically connected with the discharge port  28  for the transfer of high pressure fluid. The first and third portions  35   a ,  35   c  of the discharge chamber  35  are not in direct fluid communication with each other or the second portion  35   b , but rather are in fluid communication with the muffler chamber  45 . As best seen in FIG. 1, the muffler wall  42  includes a first opening  44   a  connecting the first portion  35   a  to the muffler chamber  45 . The muffler wall  42  also defines a second opening  44   b  fluidically connecting the second portion  35   b  to the muffler chamber  45 . As the muffler wall  42  is completely annular, it has a wall portion positioned between the second portion  35   b  of the discharge chamber  35  and the muffler chamber  45 . Finally, the muffler wall  42  defines a third opening  44   c  fluidically connecting the third portion  35   c  to the muffler chamber  45 . 
     In the illustrated embodiment, the second portion  35   b  of the discharge chamber  35  further includes a shield wall  58  within the second portion  35  to define a shield chamber  35   d . The shield wall  58  includes an opening  59  fluidically connecting the second portion  35   b  of the discharge chamber  35  to the shield chamber  35   d . The shield chamber  35   d  is directly connected for fluidic communication with the discharge port  28 . 
     In operation, the cylinder bores  17  suck fluid from the suction chamber  25  at a relatively low pressure (supplied by suction port  26 ). The compressor and its cylinder pistons pressurize the fluid and discharge relatively high pressure fluid into the discharge chamber  35 . As shown in FIG. 4, the cylinder block  15  includes a plurality of cylinder bores  17 . At one end of each bore  17  the cylinder block  15  defines a suction opening  18  and a discharge opening  19 . Typically, the flow through the suction openings  18  and the discharge openings  19  are regulated by one-way valves to ensure the proper direction of flow. As illustrated, the rear housing  20  is designed for use with a cylinder block  15  having seven cylinder bores  17  and seven sets of suction and discharge openings  18 ,  19 . 
     Accordingly, it can be seen that the compressor discharges high pressure fluid through the discharge openings  19  into the discharge chamber  35 , and more particularly into the first portion  35   a , second portion  35   b , third portion  35   c , and the shield chamber  35   d . The high pressure fluid in the first and third portions  35   a ,  35   c  of the discharge chamber  35  are required to flow through the first and third openings  44   a ,  44   c  and into the muffler chamber  45 . This fluid flow then follows a path through the second opening  44   b  in the muffler wall  42  and into the second portion  35   b  of the discharge chamber  35 . Flow then follows a path through the opening  59  in the shield wall  58  into the shield chamber  35   d  and exits via the discharge port  28  which is directly in communication with the shield chamber  35   d.    
     This flow path defined by the muffler wall  42 , divider walls  52 ,  54 ,  56 , shield wall  58 , and their respective openings, acts to reduce the turbulence and pulsations in the discharge flow, thereby reducing the noise and vibration of the compressor. The openings  44   a ,  44   b ,  44   c  in muffler wall  42 , as well as opening  59  in shield wall  58 , act as restrictions which regulate the flow from one chamber to the next. While these restrictions do not substantially change the pressure of the fluid or its flow rate, these restrictions do have a dampening effect of reducing the turbulence and pulsations in the fluid flow. It will be recognized that the efficiency of the compressor is increased (i.e. lower power consumption) due to streamlined flow with less turbulence. Preferably, openings  44   a  and  44   c  are notches in an upper end of the muffler wall  42 , and are generally smaller than the larger opening  44   b , which is also a notch in the muffler wall  42 . Preferably, opening  59  is also a large notch formed in the shield wall  58 . 
     The first and second portions  35   a ,  35   b  of the discharge chamber  35  are in fluid communication only through the muffler chamber  45 . The restrictions are sized to reduce the turbulence of the fluid flow. Similarly, the third portion  35   c  and second portion  35   b  of the discharge chamber  35  are not in direct fluid communication. The restrictions attenuate the turbulence of the fluid flow from the first and third portions  35   a ,  35   c  of the discharge chamber to the second portion  35   b  of the discharge chamber  35 . 
     It will also be recognized that the compressor and one or two piston cylinders  17  directly provide high pressure fluid to the second portion  35   b  of the discharge chamber, which is proximate the discharge port  28 . When the shield wall  58  is employed as shown, one discharge opening  19  provides high pressure fluid directly to the shield chamber  35   d  which is in direct fluid communication with the discharge port  28 . Thus, the supply of high pressure fluid is not delayed or compromised by the muffler  40  of the present invention. 
     Accordingly, it will be recognized by those skilled in the art that the present invention provides a muffler which is integrally incorporated into the rear housing of a compressor. In this way, the muffler reduces the overall size, weight and cost of the compressor. Additionally, the integral muffler adds stiffness to the rear housing that attributes to lower vibration. Furthermore, additional machining operations are not required as the muffler can be cast directly into the rear housing. Finally, the refrigerant flow is directed through the discharge chamber and muffler in such a way as to fully utilize the volume effectively to reduce flow turbulence, while not causing any significant flow loss or delay in fluid supply. In turn, the efficiency of the compressor is increased (i.e. lower power consumption) due to streamlined flow with less turbulence. 
     The foregoing description of various embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Numerous modifications or variations are possible in light of the above teachings. The embodiments discussed were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.