Abstract:
A compressor that reduces pressure pulsation includes a mounting member for attaching the compressor to a vehicle support. The mounting member is integrally formed with an end wall of a rear housing member. A suction chamber and a discharge chamber are defined in the rear housing member. The discharge chamber is located outside the suction chamber and surrounds the suction chamber. An auxiliary chamber is formed in the mounting member. The auxiliary chamber is centrally located. The auxiliary chamber increases the volume of the suction chamber, which reduces pulsation. Since the auxiliary chamber is formed in the mounting member, neither the weight or the volume of parts that might interfere with other devices is increased.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a compressor having a structure for suppressing pulsation. 
     A typical compressor includes a rotatable shaft, piston s housed in cylinder bores, a suction chamber and discharge chamber. As each piston is reciprocated in the corresponding cylinder bore by rotation of the rotatable shaft, gas is drawn into the cylinder bore from the suction chamber, which is defined in a rear housing member. The gas is then compressed by the piston and discharged to the discharge chamber, which is defined in the rear housing member. 
     The discharge chamber suppresses pulsation of discharged gas, and the suction chamber suppresses pulsation of drawn gas. The greater the volume of the discharge chamber is , the more effectively the discharge pulsation suppression is. Also, the greater the volume of the suction chamber is, the more effective the suction pulsation suppression is. 
     Japanese Unexamined Patent Publication No. 11-125178discloses a compressor that suppresses discharge pulsation. The compressor of the publication has a bracket protruding from a rear housing member. The outer wall of the rear housing member bulges by the same amount as the bracket. The bulge is hollow, and the interior of tho bulge forms part of a discharge chamber. This structure e increases the volume of the discharge chamber, which improves the pulsation suppression without increasing the axial dimension of the compressor. 
     However, such expansion of the discharge chamber expands the total area of the walls defining the discharge chamber, which increases the weight of the compressor. Although the axial dimension of the compressor is not increased, the volume of the compressor increased. As a result, the compressor is more likely to interfere with other devices. The increased weight and size are disadvantageous when installing the compressor in a vehicle. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an objective of the present invention to provide a compressor that effectively suppresses pressure pulsation without increasing the weight of the compressor or the volume of any part that might cause interference during installation. 
     In accordance with the present invention, there is provided a compressor comprising a housing having a suction chamber and a discharge chamber defined therein. Gas is drawn from the suction chamber into cylinder bores and discharged from the cylinder bores into the discharge chamber by the reciprocating movement of a plurality of pistons driven by the rotation of a rotatable shaft. The housing is provided with a mounting member for attaching the compressor to a mounting object outside the compressor. The mounting member is fixed to the wall of the housing adjacent to at least one of the suction chamber and the discharge chamber. An auxiliary chamber that augments at least one of the suction chamber and the discharge chamber is formed by a recess in the wall at the location of the mounting member. 
     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 compressor according to a first embodiment of the present invention; 
     FIG. 2 is a rear view of the compressor shown in FIG. 1; 
     FIG. 3 is a cross-sectional view taken along line  3 — 3  of FIG. 1; 
     FIG. 4 is a cross-sectional view taken along line  4 — 4  of FIG. 1; 
     FIG. 5 is a rear view illustrating a compressor according to a second embodiment; 
     FIG. 6 is a cross-sectional view taken along line  6 — 6  of FIG. 5; 
     FIG. 7 is a cross-sectional view illustrating a compressor according to a third embodiment of the present invention; 
     FIG. 8 is a rear view similar to FIG. 2 illustrating a compressor according to a fourth embodiment of the present invention; and 
     FIG. 9 is a cross-sectional view similar to FIG. 3 illustrating the compressor of FIG.  8 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the drawings, like numerals are used for like elements throughout. 
     A variable displacement compressor according to a first embodiment of the present invention will now be described with reference to FIGS. 1 to  4 . The compressor is used in a vehicle. 
     As shown in FIG. 1, the housing of the compressor includes a front housing member  12 , a cylinder block  11  and a rear housing member  17 . A control pressure chamber  121  is defined by the front housing member  12  and the cylinder block  11 . A rotatable shaft  13  is supported by the front housing member  12  and the cylinder block  11  and is rotated by a vehicle engine (not shown). A swash plate  14  is supported by the rotatable shaft  13  in the control pressure chamber  121 . The swash plate  14  rotates integrally with and inclines relative to the rotatable shaft  13 . Cylinder bores  111 , the number of which is six in this embodiment, are formed in the cylinder block  11  about the rotatable shaft  13 . A piston  15  is housed in each cylinder bore  111 . Rotation of the swash plate  14  is converted into reciprocation of each piston  15  by shoes  16 . 
     A rear housing member  17  is coupled to the cylinder block  11 . A rear housing member  17  is secured to the cylinder block  11  with a valve plate  18 , two valve flap plates  19 ,  20  and a retainer plate  21 . A suction chamber  22 , which is a suction pressure zone, and a discharge chamber  23 , which is a discharge pressure zone, are defined in the rear housing member  17 . As shown in FIGS. 3 and 4, the suction chamber  22  and the discharge chamber  23  are divided by a substantially annular wall  25 . The wall  25  extends from an end wall  24  of the rear housing member  17  in the axial direction of the compressor. The discharge chamber  23  is located radially outside of the suction chamber  22 . 
     Suction ports  181  are formed in the valve plate  18 . As shown in FIG. 4, the suction ports  181  are located radially inside of the wall  25 . Each suction port  181  corresponds to one of the cylinder bores  111 . The suction ports  181  are arranged on a circle C centered on a point  131 , which is on the axis of the rotatable shaft  13 . Discharge ports  182  are formed in the valve plate  18 . The discharge ports  182  are located radially outside of the wall  25 . Each discharge port  182  corresponds to one of the cylinder bores  111 . Suction valve flaps  191  are formed on the suction valve flap plate  19 . Discharge valve flaps  201  are formed on the discharge valve flap plate  20 . Each suction valve flap  191  opens and closes the corresponding suction port  181 . Each discharge valve flap  201  opens and closes the corresponding discharge port  182 . 
     A gas introduction passage  30  is formed adjacent to the end wall  24  of the rear housing member  17 . The passage  30  extends from a circumferential wall  31  of the rear housing member  17  through the discharge chamber  23  and opens to the suction chamber  22 . An outlet  301  of the passage  30  is located in the vicinity of the center point  131  of the circle C. 
     When each piston  15  is moved from the top dead center position to the bottom dead center position, refrigerant gas is drawn into the corresponding cylinder bore  111  from the suction chamber  22  through the corresponding suction port  181  and past the corresponding suction valve flap  191 . When each piston  15  is moved from the bottom dead center position to the top dead center position, the refrigerant gas is compressed in the cylinder bore  111  and is then discharged to the discharge chamber  23  through the corresponding discharge port  182  and past the corresponding discharge valve flap  201 . Retainers  211  are formed on the retainer plate  21  to limit the opening degree of the discharge valve flaps  201 . Refrigerant in the discharge chamber  23  then flows to the suction chamber  22  through the external refrigerant circuit  32 , which includes the condenser  33 , the expansion valve  34 , the evaporator  35  and the gas introduction passage  30 . 
     The discharge chamber  23  is connected to the control pressure chamber  121  by a supply passage  26 . The supply passage  26  supplies refrigerant from the discharge chamber  23  to the control pressure chamber  121 . An electromagnetic displacement control valve  27  is located in the supply passage  26 . The control valve  27  is controlled by a controller (not shown). The controller determines the value of current supplied to the control valve  27  based on the vehicle compartment temperature, which is detected by a compartment temperature sensor (not shown), and a target temperature, which is set by a temperature adjuster (not shown). The control valve  27  then operates based on the suction pressure in the suction chamber  22  and sets the actual suction pressure to a value that corresponds to the value of the supplied current. When the value of the supplied current is increased, the control valve  27  decreases the flow rate of refrigerant from the discharge chamber  23  to the control pressure chamber  121 . Since refrigerant flows to the suction chamber  22  from the control pressure chamber  121  through a pressure release passage  29 , the pressure in the control pressure chamber  121  decreases. Accordingly, the inclination angle of the swash plate  14  is increased, which increases the displacement of the compressor. The increase in the compressor displacement lowers the suction pressure. When the value of the supplied current is decreased, the control valve  27  increases the flow rate of refrigerant from the discharge chamber  23  to the control pressure chamber  121 , which raises the pressure in the control pressure chamber  121 . Accordingly, the inclination angle of the swash plate  14  decreases and the displacement is decreased. The decrease in the displacement raises the suction pressure. When the value of the current is zero, the opening degree of the control valve  27  is maximized, and the inclination angle of the swash plate  14  is minimized as illustrated by a broken line in FIG.  1 . 
     As shown in FIG. 1, mounting members  36 ,  37  are integrally formed with the front housing member  12  at the upper and lower surfaces. Bolt holes  361 ,  371  are formed in the mounting members  36 ,  37 , respectively. The holes  361 ,  371  extend parallel to each other and perpendicular to the rotatable shaft  13 . As shown in FIGS. 1 and 2, a mounting member  28  is formed integrally with the rear housing member  17  at the rear surface of the end wall  24 . The mounting member  28  corresponds to the suction chamber  22  with the wall  24  in between. A bolt hole  281  is formed in the mounting member  28 . The hole  281  extends parallel to the holes  361 ,  371  and perpendicular to the shaft  13 . 
     As shown in FIG. 2, bolts  38 ,  39 ,  40  are inserted into the holes  361 ,  371 ,  281  to fix the compressor to supporting parts  41 ,  42 ,  43  within a vehicle&#39;s engine compartment. 
     As shown in FIGS. 1 and 3, the suction chamber  22  is surrounded by the wall  25  and the end wall  24  of the rear housing member  17 . An auxiliary chamber  44  is formed in the mounting member  28 . Specifically, the auxiliary chamber  44  is formed by an axially extending recess in the end wall  24  at the location of the mounting member  28 . The auxiliary chamber  44  communicates with the suction chamber  22 , which increases the volume of the suction chamber  22 . An axial projection of the auxiliary chamber  44  includes the radial center of the suction chamber  22 . 
     The first embodiment has the following advantages. 
     (1-1) The mounting members  28 ,  36 ,  37  are necessary for installing the compressor in the vehicle. The auxiliary chamber  44  is formed in the mounting member  28 . Therefore, the volume of the suction chamber  22  is increased without increasing the weight and the volume of the compressor. The increase of the volume of the suction chamber  22  reduces the suction pulsation. Accordingly, noise and vibration created in the evaporator  35  due to the pulsation are reduced. 
     (1-2) The gas introduction passage  30  extends from the periphery of the compressor to the suction chamber  22 . Therefore, the gas passage  30  is longer than the radial dimension of the discharge chamber  23 . The passage  30  functions as a restrictor that reduces the suction pulsation. 
     (1-3) The outlet  301  of the passage  30  is near the center point  131  of the circle on which the suction ports  181  are located. The radial center of the suction chamber  22  lies within an axial projection of the auxiliary chamber  44 . The suction chamber  22 , which includes the auxiliary chamber  44 , is generally cylindrical. The location of the outlet  301  is therefore spaced substantially equally from each suction port  181 , which minimizes the pressure fluctuation at the outlet  301 . Pressure fluctuations at the outlet  301  create suction pulsation, which is transmitted to the external refrigerant circuit  32  through the passage  30 . The evaporator  35 , which is located in the passenger compartment, is vibrated by an element of the pulsation that has a resonance frequency. However, since the pressure fluctuation is minimized, the suction pulsation is minimized. The noise caused by the vibration of the evaporator  35  is reduced, accordingly. 
     A second embodiment will now be described with reference to FIGS. 5 and 6. Like or the same reference numerals are given to those components that are like or the same as the corresponding components of the embodiment of FIGS. 1 to  4 . 
     In this embodiment, a bulge  45  is formed in the mounting member  28 . The bulge  45  however does not hinder the installation of the compressor due to its location. A second auxiliary chamber  451  is formed in the bulge  45 . The second auxiliary chamber  451  is a recess formed in the surface  241  of the end wall  24  that faces the suction chamber  22 . The auxiliary chambers  44 ,  451  form part of the suction chamber  22 . 
     A third embodiment will now be described with reference to FIG.  7 . Like or the same reference numerals are given to those components that are like or the same as the corresponding components of the embodiment of FIGS. 1 to  4 . 
     In this embodiment, a discharge chamber  23 A is located radially inside in the rear housing member  17  and a suction chamber  22 A is located radially outside of the discharge chamber  23 A. A displacement control valve  27 A controls the flow rate of refrigerant supplied from the discharge chamber  23 A to the control pressure chamber  121  through a refrigerant supply passage  26 A. Also, refrigerant flows from the control pressure chamber  121  to the suction chamber  22 A through a pressure release passage  112 , which has a throttle. The pressure in the control pressure chamber  121  is determined by the flow rate of refrigerant through the pressure release passage  112  and the flow rate of refrigerant from the control valve  27 A to the control pressure chamber  121  through the refrigerant supply passage  26 A. 
     An auxiliary chamber  44 A is formed in a mounting member  28 A and extends from the surface  242  of the end wall  24  of the discharge chamber  23 A. The auxiliary chamber  44 A forms part of the discharge chamber  23 A. The volume of the discharge chamber  23 A is increased by the volume of the auxiliary chamber  44 A. The radial center of the discharge chamber  23 A lies within an axial projection of the auxiliary chamber  44 A. 
     The auxiliary chamber  44 A, which is formed in the mounting member  28 A, increases the volume of the discharge chamber  23 A without increasing the weight and volume of the compressor. The augmentation of the discharge chamber  23 A reduces the discharge pulsation. 
     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. 
     (1) In the illustrated embodiments, the auxiliary chambers  44 ,  44 A extend from the surfaces  241 ,  242  of the end wall  24  into the interior of the mounting members  28 ,  28 A, respectively. However, as long as the chambers  44 ,  44 A are formed by axially extending recesses in the end wall  24  at the location of the mounting members  28 ,  28 A, the chambers  44 ,  44 A need not extend into the interior of the mounting members  28 ,  28 A. In this case, if the auxiliary chambers are formed by recesses in the end wall at locations not corresponding to the mounting members, the strength of the wall at those locations is lowered. However, in the present invention, such a problem does not occur, because the recesses are formed in the end wall at the locations of the mounting members. 
     (2) In each illustrated embodiment, the chamber  22  or  23 A that is located inside is connected to the auxiliary chamber  44 ,  44 A. However, if the rear housing member  17  has a mounting member that extends near both the suction chamber  22 ,  22 A and the discharge chamber  23 ,  23 A, two auxiliary chambers  45 A,  45 B may be formed to augment the suction chamber  22 ,  22 A and the discharge chamber  23 ,  23 A, respectively, as shown in FIGS. 8 and 9. 
     (3) The mounting members  28 ,  28 A are integrally formed with the end wall  24  of the rear housing member  17 . However, the mounting member  28 ,  28 A may be formed on the circumferential wall  31 . In this case, an auxiliary chamber may be formed in the mounting member to increase the volume of a peripheral chamber. That is, in the first and second embodiments, such an auxiliary chamber would increase the volume of the discharge chamber  23 . In the third embodiment, such an auxiliary chamber would increase the volume of the suction chamber  22 A. 
     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.