Patent Publication Number: US-6334763-B2

Title: Capacity-controlled scroll-type compressor having internally-bypassing system

Description:
This application is a division of application Ser. No. 09/212,861 filed Dec. 17, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a capacity-controlled scroll-type compressor having an internally-bypassing system. 
     This application is based on patent applications Ser. Nos. Hei 9-363832, Hei 9-363833, and Hei 9-363834 filed in Japan, the contents of which are incorporated herein by reference. 
     2. Description of the Related Art 
     In conventional capacity-controlled scroll-type compressors having an internally-bypassing system, when the capacity of the compressor is controlled, a temperature difference occurs between an area through which higher-temperature bypassing gas passes and another area through which lower-temperature suction gas passes. Therefore, a gap at a tip provided on the head of each tooth near a gas-suction inlet tends to decrease and thus scuffing occurs. 
     On the other hand, when the capacity of the compressor is controlled, the temperature of a portion of scrolls, which is close to the main stream of higher-temperature bypassing gas, is higher than the temperature of other portions. Therefore, the teeth of the higher-temperature portion is extended, thereby decreasing a gap at a tip of the teeth and also generating scuffing in this case. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to solve the above problem related to scuffing due to decrease of such a tip gap. 
     Therefore, the present invention provides a capacity-controlled scroll-type compressor having an internally-bypassing system, the compressor comprising a housing, scrolls, and a gas-suction inlet, wherein the gas-suction inlet is positioned at the low-pressure side inside the housing; and the length of teeth of a portion of the scrolls, which is closer to the gas-suction inlet, is shorter than teeth of other portions of the scrolls. 
     According to this structure, when the capacity is controlled, it is possible to prevent the tip gaps near the gas-suction inlet from becoming smaller than those of other portions; thus, scuffing can be prevented between the heads of the target spiral lap and the inner surface of an end plate in the compressor. 
     The present invention also provides a capacity-controlled scroll-type compressor having an internally-bypassing system, the compressor comprising scrolls, wherein the length of teeth of a portion of the scrolls, which is close to the main stream of a bypassing gas, is shorter than teeth of other portions. 
     According to this structure, when the capacity is controlled, it is possible to prevent the tip gaps near the main stream of a bypassing gas from becoming smaller than those of other portions; thus, scuffing can be prevented between the heads of the target spiral lap and the inner surface of an end plate in the compressor. 
     In the above structures, the target portion for shortening the teeth may be of a hardening-processed scroll of the above scrolls 
     The present invention also provides a capacity-controlled scroll-type compressor having an internally-bypassing system, the compressor comprising a gas-suction inlet positioned near the main stream of a bypassing gas so as to suppress increase in the temperature of an area neighboring the main stream of the bypassing gas. 
     Also in this arrangement, when the capacity is controlled, it is possible to prevent the tip gaps near the main stream of a bypassing gas from becoming smaller than those of other portions; thus, scuffing can be prevented between the heads of the target spiral lap and the inner surface of an end plate in the compressor. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view in the longitudinal direction, showing a scroll-type compressor as the first embodiment according to the present invention. 
     FIG. 2 is a sectional view along line “B—B” in FIG.  1 . 
     FIG. 3 is a sectional view along line “C—C” in FIG.  1 . 
     FIG. 4 is a sectional view in the longitudinal direction, showing a scroll-type compressor as the second embodiment according to the present invention. 
     FIG. 5 is a sectional view along line “B—B” in FIG.  4 . 
     FIG. 6 is a sectional view along line “C—C” in FIG.  4 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The first embodiment of the present invention is shown in FIGS. 1-3. FIG. 1 is a sectional view in the longitudinal direction, FIG. 2 is a sectional view along line “B—B” in FIG. 1, and FIG. 3 is a sectional view along line “C—C” in FIG.  1 . 
     In FIG. 1, reference numeral  1  indicates a housing which comprises cup-like main body  2 , and front housing  6  fastened to the body  2  using a bolt (not shown). Rotational shaft  7  is supported by the front housing  6  via bearings  8  and  9 , in a freely rotatable relationship. 
     Fixed scroll  10 , revolving scroll  14 , and capacity-control block  50  are provided inside the housing  1 . This fixed scroll  10  comprises end plate  11  and spiral lap  12  disposed on inner surface  11   a  of the plate  11 , and the surface faces end plate  15 . The revolving scroll  14  comprises the end plate  15  and spiral lap  16  which is disposed on inner surface  15   a  of the plate  15 , and the surface faces the end plate  11 . 
     Inside projecting disk-shaped boss  20 , provided at a center area in the outer surface (opposite to inner surface  15   a ) of end plate  15  of revolving scroll  14 , drive bush  21  is inserted in a freely rotatable state via revolving bearing  23 . Slide hole  24  is provided in the drive bush  21 , and eccentric drive pin  25  is inserted into the slide hole  24  so as to perform a freely-sliding motion of the pin. The projecting drive pin  25  is eccentrically provided on an end face of larger-diameter portion  7   a  of rotational shaft  7 , the portion  7   a  being provided on an end of the main body  2  side of the rotational shaft  7 . 
     The axes of the revolving and fixed scrolls  14  and  10  are separated from each other by a predetermined distance, that is, they are in an eccentric relationship, as shown in FIG.  2 . In addition, the phases of these scrolls differ by 180°, and they are engaged with each other. 
     Accordingly, as shown in FIG. 1, tip seals  17 , provided and buried at each head surface of spiral lap  12 , are in close contact with surface  15   a  of end plate  15 , while tip seals  18 , provided and buried at each head surface of spiral lap  16 , are in close contact with surface  11   a  of end plate  11 . The side faces of spiral laps  12  and  16  make linear contact at plural positions and thus plural compression chambers  19   a  and  19   b  are formed essentially at positions of point symmetry with respect to the center of the spiral, as shown in FIG.  2 . 
     Also as shown in FIG. 2, a central part of end plate  11  is bored to provide discharge port  29 , and a pair of bypassing ports  33   a  and  33   b,  joined with compression chambers  19   a  and  19   b  during compression, are provided. 
     In addition, the capacity-control block  50  is arranged in a manner such that this block is in close contact with the outer surface of end plate  11 , thereby limiting concave areas  87  and  88 . The head of screwing bolt  13  which passes through the capacity-control block  50  and the cup-like main body  2  is inserted into end plate  11  of the fixed scroll  10 , thereby fastening the fixed scroll  10  and the capacity-control block  50  to the cup-like main body  2 . 
     The outer-peripheral surface of flange  51  arranged at the outer end of the capacity-control block  50  is in close contact with the inner surface of the cup-like main body  2 , thereby dividing the inside of housing  1  into plural chambers. That is, discharge cavity  31  is limited at the outside of flange  51 , while low-pressure chamber  28  is limited at the inside of the flange  51 . 
     As shown in FIG. 3, at a central area of capacity-control block  50 , discharge hole  53  joined with discharge port  29  is provided, and opening/closing operations of this hole  53  is performed using discharge valve  30  which is attached to the outer surface of capacity-control block  50  via bolt  36 . 
     Cylinder  54  like a blind opening is provided at one side of discharge hole  53 , and blind opening  55  is provided at the other side, in parallel with the cylinder  54 . 
     By inserting cup-like piston  56  into cylinder  54  in a closed and freely-sliding state, control pressure chamber  80  is limited at the side of the inner end of piston  56  while chamber  81  is limited at the other side. This chamber  81  is joined with suction chamber  28 . 
     In cylinder  54 , connection hole  92  joined with discharge hole  53  and connection hole  89  joined with concave area  88  are provided. 
     The piston  56  is forced toward control pressure chamber  80  by coil spring  83  which is inserted between the piston and spring bearing  82 . 
     A circular groove  93 , arranged along the outer-peripheral surface of piston  56 , is linked with chamber  81  via plural holes  94  in any operational state. 
     On the other hand, control valve  58  is inserted into the opening  55 . This control valve  58  senses a high pressure inside the discharge cavity  31  and a low pressure inside the low-pressure chamber  28 , and generates a control pressure in accordance with the sensed pressure. 
     As shown in FIG. 1, between the peripheral edge of the outer surface of end plate  15  of revolving scroll  14  and an inner end face of front housing  6 , thrust bearing  36  and Oldham link  26  are inserted. 
     In order to balance a dynamically unbalanced situation due to a revolving motion of the revolving scroll  14 , balance weight  27  is attached to drive bush  21 , and balance weight  37  is attached to the rotational shaft  7 . 
     In addition, piping fitting  40  is fastened to an upper portion of cup-like main body  2  via bolt  41 , and gas-suction path  42  and gas-discharge path  43  are limited between the piping fitting  40  and the outer-peripheral surface at the upper side of the cup-like main body  2 . 
     This gas-suction path  42  is joined with low-pressure chamber  28  via gas-suction inlet  44 , and the gas-discharge path  43  is joined with the discharge cavity  31  via hole  45 . 
     Accordingly, at the time of a full-loading operation of the compressor, when the rotational shaft  7  is rotated, revolving scroll  14  is driven via eccentric drive pin  25 , slide hole  24 , drive bush  21 , revolving bearing  23 , and boss  20 . The revolving scroll  14  revolves along a circular orbit, while rotation of the scroll  14  is prohibited by the Oldham link  26 . 
     In this way, the line-contact portions in the side faces of spiral laps  12  and  16  gradually move toward the center of the “swirl”, and thereby compression chambers  19   a  and  19   b  also move toward the center of the swirl while the volume of each chamber is gradually reduced. 
     Accordingly, gas, which has flowed into low-pressure chamber  28  through gas-suction path  42  and gas-suction inlet  44 , enters from an opening which is limited by the outer peripheral edges of spiral laps  12  and  16  to compression chambers  19   a  and  19   b.  This gas is gradually compressed and reaches central chamber  22 . From the central chamber, the gas passes through discharge port  29  and discharge hole  53 , and presses and opens discharge valve  30 , and thereby the gas is discharged into discharge cavity  31 . The gas is then discharged outside via hole  45  and gas-discharge path  43 . 
     At the time of a non-loading operation of the compressor, a low pressure for control is generated via the control valve  58 . When this control pressure is introduced into control pressure chamber  80 , piston  56  receives the restoring force of coil spring  83  and is forced and positioned as shown in FIG.  1 . 
     In this way, gas during compression in compression chambers  19   a  and  19   b  is introduced via bypassing ports  33   a  and  33   b,  concave areas  87  and  88 , and connection hole  89 , into chamber  81 . On the other hand, the gas after compression is introduced from central chamber  22  via discharge port  29 , discharge hole  53 , connection hole  92 , groove  93 , and holes  94 , into the chamber  81 . Both flows of gas meet in chamber  81 , and merged gas flows through groove  84 , formed by cutting a portion of the outer peripheral surface of end plate  11  of the fixed scroll  10 , into low-pressure chamber  28 . 
     At the time of a full loading operation of the compressor, a high pressure for control is generated using control valve  58 . When this control pressure is introduced into the control chamber  80 , piston  56  moves back against the impact-resilience force of coil spring  83  and the outer end of the piston comes into contact with spring bearing  82 . Accordingly, both connection holes  89  and  92  are closed by piston  56 . 
     On the other hand, when in an operation mode for controlling (or reducing) capacity, a control pressure corresponding to a desired reducing ratio is generated using control valve  58 . When this control pressure acts on the inner end face of piston  56  via control chamber  80 , piston  56  is positioned where the pressing force due to the control pressure and the impact-resilience force by the coil spring  83  are balanced. 
     Therefore, under conditions of lower control pressure, only connection hole  89  is open, and a portion of the gas during compression in compression chambers  19   a  and  19   b  is discharged into low-pressure chamber  28  according to the degree of opening of the connection hole  89 . 
     In addition, the connection hole  92  is gradually opened in accordance with increase of the control pressure. The degree of opening of the hole  92  is thus increased, and when the hole  92  is fully opened, the capacity of the compressor becomes zero. 
     At the time of a non-loading operation of the compressor, that is, When the capacity is controlled, a high-temperature bypassing gas flows through chamber  81  of cylinder  56  into low-pressure chamber  28 . Therefore, the temperature of an area neighboring the main stream of the bypassing gas, that is, the temperature of a lower portion of the cup-like main body  2 , is increased, while the low temperature of an area neighboring the gas-suction inlet  44 , into which low-temperature suction gas flows, that is, the temperature of an upper portion of the cup-like main body  2 , is maintained. Therefore, a temperature difference occurs in the cup-like main body  2 , and accordingly, a difference of thermal expansion occurs. 
     Here, the fixed scroll  10  is fixed to the cup-like main body  2 . Therefore, if a thermal-expansion difference occurs there, the gap between the head of a portion of spiral lap  12  near the gas-suction inlet  44  and the inner surface  15   a  of end plate  15 , and also the gap between the head of a portion of spiral lap  16  near the gas-suction inlet  44  and the inner surface  11   a  of end plate  11 , that is, “tip gaps” of such portions become smaller than those of other portions. 
     Therefore, in the present invention, the length (of the teeth) of such a portion of spiral lap  12  of fixed scroll  10  and/or the length (of the teeth) of such a portion of spiral lap  16  of revolving scroll  14  positioned near the gas-suction inlet  44  are shorter than those of other portions by approximately 20 μm. This setting is suitably performed within approximately 90°. 
     Accordingly, when the capacity is controlled, it is possible to prevent the tip gaps near the gas-suction inlet  44  from becoming smaller than those of other portions; thus, scuffing can be prevented between the head of spiral lap  12  and the inner surface  15   a  of end plate  15 , and also between the head spiral lap  16  and the inner surface  11   a  of end plate  11 . 
     Also when the capacity is controlled and a high-temperature bypassing gas flows through chamber  81  of cylinder  56  into low-pressure chamber  28 , the temperature of portions of spiral laps near the flow of bypassing gas is increased and the portions thermally expand. Accordingly, the gap between the head of a portion of spiral lap  12  near the gas-suction inlet  44  and the inner surface  15   a  of end plate  15 , and also the gap between the head of a portion of spiral lap  16  near the gas-suction inlet  44  and the inner surface  11   a  of end plate  11 , that is, “tip gaps” of such portions become smaller than those of other portions. 
     Therefore, also regarding these portions, the length (of the teeth) of such a portion of spiral lap  12  of fixed scroll  10  and/or the length (of the teeth) of such a portion of spiral lap  16  of revolving scroll  14  positioned near the main stream of the bypassing gas are shorter than those of other portions by approximately 20 μm. This setting is suitably performed within approximately 90°. 
     Accordingly, when the capacity is controlled, it is possible to prevent the tip gaps near the main stream of the bypassing gas from becoming smaller than those of other portions; thus, scuffing can be prevented between the head of spiral lap  12  and the inner surface  15   a  of end plate  15 , and also between the head spiral lap  16  and the inner surface  11   a  of end plate  11 . 
     Preferably, regarding the above two cases, in order to realize necessary dimensional tolerance, if the inner surface of the end plate of one of the fixed and revolving scrolls  10  and  14 , and the outer surface of the relevant spiral lap are subjected to a surface-hardening process, the target teeth of the surface-hardened spiral lap are made shorter. 
     The second embodiment of the present invention is shown in FIGS. 4-6. FIG. 4 is a sectional view in the longitudinal direction, FIG. 5 is a sectional view along line “B—B” in FIG. 4, and FIG. 6 is a sectional view along line “C—C” in FIG.  4 . 
     The second embodiment has an arrangement similar to that of the first embodiment except for positions of gas-suction inlet  44  and relevant elements joined or connected therewith. In FIGS. 4-6, parts which are identical or have identical functions to those shown in FIG. 1-3 are given identical reference numbers. 
     In the present embodiment, piping fitting  40  is fastened to a lower portion of cup-like main body  2  via bolt  41 , and gas-suction path  42  and gas-discharge path  43  are limited between the piping fitting  40  and the outer-peripheral surface at the lower side of the cup-like main body  2 . 
     Therefore, at the time of a non-loading operation of the compressor, a low pressure for control is generated via the control valve  58 . When this control pressure is introduced into control pressure chamber  80 , piston  56  receives the restoring force of coil spring  83  and is forced and positioned as shown in FIG.  4 . 
     Full-loading and non-loading operations of the compressor in the present embodiment are similar to those of the first embodiment. 
     Here, when the capacity is controlled, a high-temperature bypassing gas flows through chamber  81  of cylinder  56  into low-pressure chamber  28 . Therefore, if the main stream of the bypassing gas and the gas-suction inlet  44  are distant from each other in the housing, the temperature of portions of fixed and revolving scrolls  10  and  14  neighboring the main stream of the bypassing gas is increased and the portions thermally expand; thus, the gap between the head of the relevant portion of spiral lap  12  and the inner surface  15   a  of end plate  15 , and also the gap between the head of the relevant portion of spiral lap  16  and the inner surface  11   a  of end plate  11 , that is, tip gaps become smaller than those of other portions, as explained in the first embodiment. 
     However, in the present embodiment, the gas-suction inlet  44  is provided near the main stream of the bypassing gas; thus, increase in the temperature of an area neighboring the main stream of the bypassing gas can be suppressed by using low-temperature suction gas which is suctioned from the gas-suction inlet  44 . 
     Accordingly, when the capacity is controlled, it is possible to prevent the tip gap near the main stream of the bypassing gas from decreasing in comparison with the tip gaps of other areas; thus, scuffing can be prevented between the head of spiral lap  12  and the inner surface  15   a  of end plate  15 , and also between the head spiral lap  16  and the inner surface  11   a  of end plate  11 .