Patent Publication Number: US-6663365-B2

Title: Scroll type compressor

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a scroll type compressor. Particularly, the present invention pertains to structures of a fixed scroll and a movable scroll used in a scroll type compressor. 
     A typical scroll type compressor has a fixed scroll and a movable scroll in a housing. The fixed scroll includes a fixed base plate and a fixed volute portion, which is formed on the fixed base plate. The fixed volute portion has a proximal end and a distal end relative to the fixed base plate. The movable scroll includes a movable base plate and a movable volute portion, which is formed on the movable base plate. The movable volute portion has a proximal end and a distal end relative to the movable base plate. The fixed scroll is engaged with the movable scroll. A number of compression chambers are formed between the fixed scroll and the movable scroll. When the movable scroll orbits the axis of the fixed scroll, each compression chamber moves from the peripheral portion (or outside portion) of the fixed volute portion toward the center of the fixed volute portion. Gas drawn into each compression chamber from the peripheral portion of the fixed volute portion is gradually compressed as the compression chamber moves. 
     When the scroll type compressor is operated, each proximal end portion of the fixed volute portion and the movable volute portion receives a bending moment repeatedly. The bending moment promotes deterioration of the scrolls. This shortens the life of the compressor. Therefore, a compressor that prevents the scrolls from being deteriorated and maintains the compression performance has been proposed in a prior art disclosed in, for example, Japanese Laid-Open Patent Publication No. 10-141255. 
     FIG. 5 is an enlarged partial cross-sectional view illustrating a fixed scroll  1  and a movable scroll  2  of the above publication. The fixed scroll  1  has a fixed volute portion  6  and the movable scroll  2  has a movable volute portion  8 . The fixed volute portion  6  has proximal end corners  6   b  and distal end corners  6   c.  The movable volute portion  8  has proximal end corners  8   b  and distal end corners  8   c.  The proximal end corners  6   b  of the fixed volute portion  6  and the proximal end corners  8   b  of the movable volute portion  8  are arched to prevent the concentration of stress. This shape increases the fatigue strength under the bending moment generated when the compressor operates. Each distal end corner  6   c  of the fixed volute portion  6  is chamfered not to interfere with the corresponding proximal end corner  8   b  of the movable volute portion  8 . The fixed volute portion  6  and the movable volute portion  8  define a compression chamber  15 , which has a predetermined volume. A first chip sealing  17  is located on the distal end of the fixed volute portion  6 . A wear-resistant plate  21 , which is made of metal, is located on a bottom surface  5   a  between adjacent parts of the fixed volute portion  6 . The wear-resistant plate  21  contacts a second chip sealing  18 , which is arranged on the distal end portion of the movable volute portion  8 . The wear-resistant plate  21  is spaced from the distal end portion of the movable volute portion  8 . The distance between the wear-resistant plate  21  and the distal end portion of the movable volute portion  8  is equivalent to the length of the part of the second chip sealing  18  that protrudes from the distal end portion. Therefore, the distal end corners  8   c  of the movable volute portion  8  are not chamfered. This structure permits the compression chamber  15  to be reliably sealed. Thus, the scroll type compressor is smoothly operated. 
     An air conditioning apparatus for vehicles these days is required to have a reduced size and weight and to have a compression mechanism that discharges highly pressurized gas. However, some parts in a compressor are made of aluminum to reduce weight. Thus, a compression mechanism must have improved durability against the high pressure. Furthermore, a prior art sealing method is insufficient and improvement of the sealing is also desired. 
     Specifically, the fixed volute portion  6  and the movable volute portion  8  illustrated in FIG. 5 are plate-like and have a substantially uniform thickness. Thus, if the thickness of the fixed volute portion  6  and the movable volute portion  8  is reduced for reducing weight, the thickness of each proximal end portion of fixed volute portion  6  and movable volute portion  8  is not enough. Thus, the strength of each proximal end portion is insufficient. When the first chip sealing  17  is fitted to the distal end portion of the fixed volute portion  6 , the thickness of the distal end portion needs to be the sum of the width a of the first chip sealing  17  and the thickness b of the outer wall multiplied by two required to support the first chip sealing  17 . For example, when the curvature of the proximal end corners  8   b  of the movable volute portion  8  is increased to increase the strength, the curvature of the distal end corners  6   c  of the fixed volute portion  6  needs to be increased accordingly. As a result, the thickness of the fixed volute portion  6  is increased. 
     The position of the wear-resistant plate  21  is determined by two positioning pieces  20  with respect to the fixed scroll  1 . However, each positioning piece  20  deforms the fixed volute portion  6  or damages the wall of the fixed volute portion  6 . 
     Gas flows between a space between the distal end surface of the movable volute portion  8  and the surface of one of the positioning pieces  20  that faces the distal end surface of the movable volute portion  8 , and a space between the positioning piece  20  and the corresponding proximal end corner  6   b.  Therefore, the gas could leak from the compressor. 
     SUMMARY OF THE INVENTION 
     The objective of the present invention is to provide a scroll type compressor that is reduced in weight and size and has great fatigue strength and a scroll that is sufficiently sealed. 
     To achieve the foregoing objective, the present invention provides a scroll type compressor for compressing gas. The compressor includes a fixed scroll, a movable scroll, a compression chamber, and a plurality of sealing members. The fixed scroll includes a fixed base plate and a fixed volute portion, which is formed on the fixed base plate. The fixed volute portion is tapered and the corners of the proximal end of the fixed volute portion are arched. The movable scroll is arranged to be engaged with the fixed scroll. The movable scroll includes a movable base plate and a movable volute portion, which is formed on the movable base plate. The movable volute potion is tapered and the corners of the proximal end of the movable volute portion are arched. The compression chamber is defined between the fixed scroll and the movable scroll. The compression chamber moves from the peripheral portion of the fixed volute potion toward the center as the movable scroll orbits the axis of the fixed scroll. One of the sealing members is located on the fixed base plate and the other 
     of the sealing members is located on the movable base plate. 
     Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: 
     FIG. 1 is a cross-sectional view illustrating a scroll type compressor according to a first embodiment of the present invention; 
     FIG. 2 is an enlarged partial cross-sectional view illustrating the fixed scroll and the movable scroll of the compressor shown in FIG. 1; 
     FIG. 3 is a partial cross-sectional view of a scroll type compressor according to a second embodiment of the present invention; 
     FIG. 4 is a cross-sectional view taken along line  4 — 4  in FIG. 3; and 
     FIG. 5 is an enlarged partial cross-sectional view illustrating a prior art fixed scroll and movable scroll. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A scroll type compressor according to a first embodiment of the present invention will now be described with reference to FIGS. 1 and 2. 
     As shown in FIG. 1, a scroll type compressor includes a front housing member  30 , a center housing member  31 , and a rear housing member  32 . The front housing member  30 , the center housing member  31 , and the rear housing member  32  form a housing of the compressor. 
     A fixed scroll  35  is integrally formed with the center housing member  31 . The fixed scroll  35  includes a fixed base plate  33  and a fixed volute portion  34 , which is formed on the fixed base plate  33 . The center housing member  31  is communicated with an external refrigerant circuit (not shown) by an inlet  36  for drawing in refrigerant. A movable scroll  39  is accommodated between the center housing member  31  and the front housing member  30 . The movable scroll  39  includes a movable base plate  37  and a movable volute portion  38 , which is formed on the movable base plate  37 . The movable volute portion  38  is engaged with the fixed volute portion  34 . 
     The fixed scroll  35  and the movable scroll  39  define a number of compression chambers  40 . A discharge chamber  41  is defined between the center housing member  31  and the rear housing member  32 . The fixed base plate  33  of the fixed scroll  35  includes a discharge port  42  at its substantial center for discharging refrigerant gas compressed in the compression chambers  40 . The rear housing member  32  includes an outlet  43  for discharging the refrigerant gas in the discharge chamber  41  to the external refrigerant circuit. 
     A drive shaft  45  is located at the center of the front housing member  30 . One end of the drive shaft  45  extends outside the compressor. The drive shaft  45  is rotatably supported by the front housing member  30  through a bearing  44 . The drive shaft  45 , which extends outside the compressor, is connected to the external power source, such as an engine, through a pulley (not shown). The drive shaft  45  has an eccentric shaft  46 . The eccentric shaft  46  is engaged with a boss  48  of the movable scroll  39  through a bush  47 . An anti-rotation mechanism  49  permits the movable scroll  39  to orbit the axis of the fixed scroll  35  and prevents the movable scroll  39  from rotating about its own axis. 
     As shown in FIGS. 1 and 2, the fixed volute portion  34  and the movable volute portion  38  are tapered. As shown in FIG. 2, each side wall of the fixed volute portion  34  is parallel to the opposite side wall of the movable volute portion  38 . The side walls of the fixed volute portion  34  are inclined by the same inclination angle M (first inclination angle) with respect to the fixed base plate  33 . In the same manner, the side walls of the movable volute portion  38  are inclined by the same angle M (second inclination angle) with respect to the movable base plate  37 . Furthermore, the first inclination angle M and the second inclination angle M are equal. The inclination angle M is obtained by a draft angle required for the release from a mold. 
     As shown in FIG. 2, the fixed volute portion  34  and the fixed base plate  33  are connected by arched proximal end corners  50  of the fixed volute portion  34 . The movable volute portion  38  and the movable base plate  37  are connected by arched proximal end corners  51  of the movable volute portion  38 . A first sealing member  52  is arranged on a bottom surface  33   a  of the fixed base plate  33  between adjacent parts of the fixed volute portion  34 . A second sealing member  53  is arranged on a bottom surface  37   a  of the movable base plate  37  between adjacent parts of the movable volute portion  38 . The first sealing member  52  covers the arched portion of the proximal end corners  50  of the fixed volute portion  34  and the second sealing member  53  covers the proximal end corners  51  of the movable volute portion  38 . When the fixed scroll  35  is engaged with the movable scroll  39 , the distal end of the fixed volute portion  34  slides along the second sealing member  53  and the distal end of the movable volute portion  38  slides along the first sealing member  52 . The distal end corners  55  of the fixed volute portion  34  do not contact with the proximal end corners  51  of the movable volute portion  38 . The distal end corners  54  of the movable volute portion  38  do not contact with the proximal end corners  50  of the fixed volute portion  34 . Therefore, the distal end corners  55  of the fixed volute portion  34  and the distal end corners  54  of the movable volute portion  38  need not be chamfered. The same resin used as the material of the first and the second chip sealings  17 ,  18  shown in FIG. 5 is suitable for the material of the first and second sealing members  52 ,  53 . 
     The operation of the compressor constructed as above will now be described below. The external drive source such as an engine drives the drive shaft  45  through the pulley (not shown). When the drive shaft  45  is rotated, the movable scroll  39  orbits the axis of the fixed scroll  35 . The volume of each compression chamber  40  changes as the movable scroll  39  orbits the axis of the fixed scroll  35 . Refrigerant gas is drawn into one of the compression chambers  40  from the external refrigerant circuit through the inlet  36 . The refrigerant gas in the compression chamber  40  is then compressed to a predetermined pressure as the volume of the compression chamber  40  is reduced. The compressed refrigerant gas is discharged to the discharge chamber  41  through the discharge port  42 . The refrigerant gas in the discharge chamber  41  is discharged to the external refrigerant circuit through the outlet  43 . 
     The scroll type compressor according to the first embodiment provides the following advantages. 
     When refrigerant gas is compressed in the compressor, a bending moment is repeatedly applied to each proximal end of the fixed volute portion  34  and the movable volute portion  38 . However, the proximal end corners  50  of the fixed volute portion  34  and the proximal end corners  51  of the movable volute portion  38  are arched. Therefore, the concentration of stress due to the bending moment repeatedly applied to each proximal end portion of the fixed volute portion  34  and the movable volute portion  38  is avoided. Thus, the compressor maintains a certain fatigue strength. Furthermore, the fixed volute portion  34  and the movable volute portion  38  are tapered and each proximal end of the fixed volute portion  34  and the movable volute portion  38  has sufficient thickness. This further increases the fatigue strength. As a result, the life of the compressor is extended. 
     The compression chambers  40  are reliably sealed with the first sealing member  52 , which is located on the bottom surface  33   a  of the fixed base plate  33 , and the second sealing member  53 , which is located on the bottom surface  37   a  of the movable base plate  37 . Therefore, the compression efficiency is sufficient. The first and the second sealing members  52 ,  53  are used instead of the prior art chip seals. Therefore, the thickness of each distal end portion of the fixed volute portion  34  and the movable volute portion  38  is minimized. This reduces the size and weight of the compressor. 
     The fixed volute portion  34  and the movable volute portion  38  are arranged such that each side wall of the fixed volute portion  34  is parallel to the opposite side wall of the movable volute portion  38 . Therefore, the compression chambers  40  are reliably sealed. The fixed scroll  35  and the movable scroll  39  are formed by utilizing the same draft angle. Therefore, the compression chambers  40  are defined by the fixed volute portion  34  and the movable volute portion  38  having the same inclination angle M. Thus, the compression chambers  40 , which are reliably sealed, are easily obtained. Furthermore, the inclination angle M of the side walls of each of the fixed volute portion  34  and the movable volute portion  38  are designed to be equal. This facilitates the manufacturing of molds. Since a draft angle required for the release from a mold is utilized for each side walls of the fixed volute portion  34  and the movable volute portion  38 , machining is not required and the number of manufacturing steps is reduced. The smooth surface formed by molding is utilized as it is. Therefore, the compressor with a great surface hardness and a great durability is obtained. 
     The first sealing member  52  covers the arched portion of the proximal end corners  50  of the fixed volute portion  34  and the second sealing member  53  covers the proximal end corners  51  of the movable volute portion  38 . Therefore, the chamfering processes of the distal end corners  54  of the fixed volute portion  34  and the distal end corners  55  of the movable volute portion  38  are omitted. 
     A scroll type compressor according to a second embodiment of the present invention will now be described with reference to FIGS. 3 and 4. The differences from the embodiment of FIGS. 1 and 2 will mainly be discussed below. In the second embodiment, the structure of the fixed scroll  60  and the movable scroll  70  differs from that of the first embodiment. Other structure of the compressor is the same as the first embodiment and the detailed explanations are omitted. FIG. 3 shows the fixed volute portion  61  of the fixed scroll  60  being engaged with the movable volute portion  63  of the movable scroll  70  (see FIG.  4 ). As shown in FIG. 4, the inclination angle α of the first side wall  63   a  of the movable volute portion  63  with respect to the movable base plate  71  of the movable scroll  70  differs from the inclination angle β of the second side wall  63   b  of the movable volute portion  63  with respect to the movable base plate  71  of the movable scroll  70 . Similarly, the inclination angle γ of the first side wall  61   a  of the fixed volute portion  61  with respect to the fixed base plate  66  of the fixed scroll  60  differs from the inclination angle δ of the second side wall  61   b  of the fixed volute portion  61  with respect to the fixed base plate  66  of the fixed scroll  60 . The fixed scroll  60  and the movable scroll  70  are formed as above when, for example, the draft angle of the side walls are required to be changed between the fixed scrolls  60  and the movable scroll  70  in accordance with the requirements of the molding procedures. The inclination angle γ of the first side wall  61   a  of the fixed volute portion  61 , which faces the first side wall  63   a  of the movable volute portion  63 , is equal to the inclination angle α of the first side wall  63   a  of the movable volute portion  63 . Furthermore, the inclination angle δ of the second side wall  61   b  of the fixed volute portion  61 , which faces the second side wall  63   b  of the movable volute portion  63 , is equal to the inclination angle β of the second side wall  63   b  of the movable volute portion  63 . 
     The second embodiment provides the following advantages in addition to the advantages of the first embodiment illustrated in FIGS. 1 and 2. 
     The inclination angle α of the first side wall  63   a  of the movable volute portion  63  is designed to be different from the inclination angle β of the second side wall  63   b  of the movable volute portion  63 . Similarly, the inclination angle γ of the first side wall  61   a  of the fixed volute portion  61  is designed to be different from the inclination angle δ of the second side wall  61   b  of the fixed volute portion  61 . Therefore, the movable volute portion  63  and the fixed volute portion  61  can be designed in accordance with the requirements of the molding procedures. This facilitates the manufacturing process. 
     The inclination angle δ of the second side wall  61   b  of the fixed volute portion  61  is equal to the inclination angle β of the opposite second side wall  63   b  of the movable volute portion  63 . Therefore, the compression chambers  40  are sealed and the compressor is smoothly operated. 
     It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Particularly, it should be understood that the invention may be embodied in the following forms. 
     Each distal end portion of the fixed volute portion  34 ,  61  and the movable volute portion  38 ,  63  may be coated with a sealing layer. The sealing layer may be made of metal or resin. When the sealing layer is made of resin, the sealing member  52 ,  53  may be made of metal. 
     The present invention may be applied to a compressor with a built-in drive source (canned motor type), that is, a compressor that has an integrated electrical motor for driving the compressor. 
     The inclination of the volute portion of each scroll with respect to the corresponding base plate may be formed by machining the side walls. 
     Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.