Abstract:
An external control variable displacement compressor varies its displacement based on the pressure in a control chamber. The compressor has a valve chamber defined in a housing. The valve chamber has an opening to accommodate an electrically operative control valve. The control valve controls pressure in the control chamber due to an external electrical signal. An electrical power supply line is connected to the control valve, the power supply line being in contact with an opening of the valve chamber. The valve chamber opening is surrounded by a circumferential wall. An agonic surface formed on the circumferential wall is constituted of a rounded surface formed by rounding a corner of the opening and/or a chamfered surface formed by chamfering a top of the opening, and is formed on a part of or the entire circumferential wall. The power supply line is to be in contact with the agonic surface. Therefore, it is capable of preventing the power supply line from wearing out.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to variable displacement compressors that are used in vehicle air conditioners. More particularly, the present invention relates to an improvement of a housing for a control valve in the external control variable displacement.  
           [0002]    U.S. Pat. No. 5,865,604, which corresponds to Japanese Unexamined Patent Publication No. 8-338364, describes a variable displacement compressor that the displacement is controlled by the pressure difference between the pressure in the control chamber and the pressure in the suction chamber. The displacement of the compressor is controlled by supplying refrigerant gas to the control chamber from the discharge chamber via a supply passage and releasing the gas into the suction chamber via a bleed passage. A displacement controlling structure of the compressor includes an electrically operative control valve in the passageway of the supply passage, which alters the size of an area of the supply passage. An energized solenoid of the control valve urges a valve body of the control valve toward the direction in which a valve hole closes. The value of the supplied current to the control valve is decided based on the comparison between predetermined temperature and detected temperature of a passenger compartment. A large difference between the detected temperature detected by a temperature sensor and the predetermined temperature set by a temperature controller indicates that cooling load is greatly needed. This causes the opening amount of the valve hole to become smaller. Thus, the inclination of a swash plate increases, and the discharge capacity of the compressor increases.  
           [0003]    As shown in FIG. 5, an electrically operative control valve  80  is accommodated in a valve chamber  85  defined in a rear housing  90 . The valve chamber  85  has an opening surrounded by a circumferential wall or a base portion  86  protruding from an outer circumferential wall surface of the rear housing  90 . The base portion  86  forms annularly and an inner circumferential surface  87  of the base portion  86  has an annular recess  88 . A circular clip  89  is fitted to the recess  88 , by which prevents the control valve  80  from falling out of the valve chamber  85 . A connector  81 , a center of which protrudes outwardly, is arranged on the base portion and is provided with a connection assembly  82  to which an electrical power supply line  83  to energize the solenoid (not shown) is electrically connected. The power supply line  83  is covered with a cover  91  which protects the power supply line  83 .  
           [0004]    The control valve  80  is generally installed to the rear housing  90  and protrudes its end outwardly from the outer circumferential wall of the rear housing  90 . This projection causes to hinder from installing a compressor to an object. Particularly, mounting a compressor on a vehicle as a part of air conditioner, a mounting space is restricted and the control valve  80  is required to reduce the projection from the outer circumferential wall of the rear housing  90 .  
           [0005]    According to the prior compressor, the connection assembly  82  of the connector  81  is set back from the base portion  86  toward the valve chamber  85 . This arrangement of the connection assembly  82  frequently causes the power supply line  83 , which connects an external drive circuit to the connection assembly  82 , to contact with a periphery of the base portion  86 . However, the prior compressor is only designed to define the valve chamber  85  to accommodate the control valve  80  and is not assumed the power supply line  83  to be in contact with the periphery of the base portion  86 . Therefore, the periphery of the base portion remains edged.  
           [0006]    Meanwhile, the power supply line  83  is protected by the cover  91 , but the cover  91  does not protect until the connection assembly of the power supply line  83 . A certain length of the uncovered power supply line  83  is necessary for electrical connecting to the connector  81 . In other words, the power supply line  83  is not protected by the cover  91  in order to secure the efficiency of the connecting work.  
           [0007]    When the uncovered power supply line  83  contacts with a periphery of the base portion, long-term vibration of the compressor and an engine to which the compressor is installed cause the contact surface of the power supply line  83  to wear out.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention contemplates to alleviate the above-mentioned inconveniences. Accordingly, it is an object of the present invention to provide an external control variable displacement compressor which is capable of preventing an electrical power supply line of an electrically operative control valve from wearing out.  
           [0009]    To achieve this object, an external control variable displacement compressor has a housing, a control chamber defined in the housing and an electrically operative control valve accommodated in the housing to control pressure in the control chamber. The displacement of the compressor is varied based on the pressure in the control chamber. The control valve controls the pressure in the control chamber due to an external electrical signal. A valve chamber which is defined in the housing has an opening to accommodate the control valve and an agonic surface formed at the opening. An electrical power supply line connected to the control valve is in contact with the agonic surface. According to the present invention, when the power supply line is in contact with the opening of the valve chamber, the agonic surface supports the power supply line, which prevents the power supply line from wearing out.  
           [0010]    Furthermore, the present invention has such a feature that the agonic surface is formed on a part of a circumferential wall surrounding the opening.  
           [0011]    Furthermore, the present invention has a following feature that the circumferential wall formed along the valve chamber opening protrudes from an outer circumferential wall surface of the housing and the projection of the agonic surface from the outer circumferential wall surface of the housing is less than the rest of the circumferential wall. According to the present invention, even if the circumferential wall protrudes from the outer circumferential wall surface, contact stress of the power supply line against the circumferential wall becomes smaller than that of the prior compressor. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. 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:  
         [0013]    [0013]FIG. 1 is a cross-sectional side view of a compressor according to an embodiment of the present invention;  
         [0014]    [0014]FIG. 2 is an enlarged partial side view, with a part cut away, illustrating a base portion of a valve chamber of FIG. 1;  
         [0015]    [0015]FIG. 3 is an enlarged cross-sectional partial side view illustrating an embodiment of the present invention;  
         [0016]    [0016]FIG. 4 a  is an enlarged cross-sectional partial side view illustrating another embodiment of the present invention;  
         [0017]    [0017]FIG. 4 b  is an enlarged cross-sectional partial side view illustrating another embodiment of the present invention; and  
         [0018]    [0018]FIG. 5 is an enlarged partial side view, with a part cut away, illustrating a base portion of a prior art valve chamber. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]    An embodiment of the present invention will now be described with reference to FIGS. 1 through 3.  
         [0020]    As shown in FIG. 1, a compressor housing is constituted of a front housing  12 , a cylinder block  11  and a rear housing  13 . The front housing  12  is coupled to the front end of the cylinder block  11 . The rear housing  13  is coupled to the rear end of the cylinder block  11  with a valve plate  18 , a suction valve plate  19 , a discharge valve plate  20  and a retainer plate  21  fixed therebetween. A suction chamber  22  and a discharge chamber  23  are defined in the rear housing  13 . A control chamber  121  is defined in the front housing  12 . A drive shaft  16  extends through the front housing  12  and the cylinder block  11  and is rotatably supported by the housing. A swash plate  14  is supported by the drive shaft  16  in a manner allowing the swash plate  14  to rotate integrally and tilt with respect to the drive shaft  16 . A plurality of cylinder bores  111  are formed in the cylinder block  11  around the drive shaft  16  at same interval. Each bore  111  accommodates a piston  15  so as to reciprocate. Each piston  15  is operatively coupled to the swash plate  14  by a pair of shoes  17 . The rotation of the drive shaft  16  is transmitted to each piston  15  by way of the swash plate  14  and the shoes  17  and is converted to reciprocation of each piston  15  in the associated cylinder bore  111 .  
         [0021]    Suction ports  181  are defined in the valve plate  18 , which communicate to the suction chamber  22  and each cylinder bore  111 , respectively. Discharge ports  182  are also defined in the valve plate  18  and in the suction valve plate  19 , which communicate to the discharge chamber  23  and each cylinder bore  111 , respectively. Suction valves  191  are formed on the suction valve plate  19 . Discharge valves  201  are formed on the discharge valve plate  20 . The suction valve  191  opens and closes the suction port  181 . The discharge valve  201  opens and closes the discharge port  182 .  
         [0022]    As the drive shaft  16  is rotated by an external drive source (not shown) and the piston  15  is moved from a top dead center to a bottom dead center, refrigerant gas in the suction chamber  22  forces out the suction valve  191  and flows into the cylinder bore  111  via the suction port  181 . As the piston  15  is moved from the bottom dead center to the top dead center, the refrigerant gas sucked into the cylinder bore  111  is compressed to a predetermined pressure. The compressed refrigerant gas in the cylinder bore  111  forces out the discharge valve  201  and flows into the discharge chamber  23  via the discharge port  182 . An opening degree of the discharge valve  201  is regulated by abutting with a retainer  211  which is formed on the retainer plate  21 . The refrigerant gas in the discharge chamber  23  is discharged into an external refrigerant circuit (not shown) via a discharge passage  51 . The refrigerant gas flown into the external refrigerant circuit flows back to the suction chamber  22  via a condenser, an expansion valve and an evaporator arranged on the external refrigerant circuit.  
         [0023]    The suction chamber  22  communicates with the control chamber  121  via a bleed passage  29 . The discharge chamber  23  communicates with the control chamber  121  via a supply passage  26  in which an electrically operative control valve  27  is arranged. The valve chamber  28  which is bored to define in the rear housing  13  accommodates the control valve  27 . The supply passage  26  supplies the refrigerant gas in the discharge chamber  23  to the control chamber  121 .  
         [0024]    A solenoid  39  of the control valve  27  is energized in accordance with the value of supplied current or signal which is to flow from a drive circuit  44 . A controller (not shown) controls the drive circuit  44  to flow the electric current in response to the difference between compartment temperature detected by a temperature sensor (not shown) and predetermined temperature set by a temperature controller (not shown).  
         [0025]    The pressure in the suction chamber  22  (suction pressure) acts on a bellows  361  via a pressure sensing chamber  363 . The suction pressure in the suction chamber  22  reflects a cooling load. A valve body  37  is connected to the bellows  361 , and opens and closes a valve hole  38 . An atmospheric pressure in the bellows  361  and an urging force of a pressure sensing spring  362  urge the valve body  37  to open the valve hole  38 . The bellows  361 , the pressure sensing chamber  363  and the spring  362  constitute sensing means  36 . The energized solenoid  39  by supplied current to a coil  392  draws a movable core  393  toward a fixed core  391 , the cores  391 ,  393  and the coil  392  constituting the solenoid  39  of the control valve  27 . In other words, an electromagnetic force of the solenoid  39  urges the valve body  37  to close the valve hole  38  against an urging force of an open-urging spring  40 . A follow-up spring  41  urges the movable core  393  toward the fixed core  391 . An opening amount of the valve hole  38  is determined by a resultant force of the electromagnetic force of the solenoid  39 , the urging force of the follow-up spring  41 , the urging force of the open-urging spring  40  and the urging force of the sensing means  36 . The control valve  27  acts in correspondence to the value of supplied current.  
         [0026]    When the value of supplied current increases, the opening amount of the valve hole  38  decreases and the amount of refrigerant gas from the discharge chamber  23  to the control chamber  121  decreases. The refrigerant gas in the control chamber  121  flows out via the bleed passage  29 , which causes the pressure in the control chamber  121  to decrease. Accordingly, an inclination angle of the swash plate  14  increases and the discharge capacity of the compressor increases. As the value of supplied current decreases, the opening amount of the valve hole  38  increases and the amount of supplied refrigerant gas from the discharge chamber  23  to the control chamber  121  increases. Consequently, as the pressure in the control chamber  121  increases, the inclination angle of the swash plate  14  decreases and the discharge capacity of the compressor decreases.  
         [0027]    As the value of supplied current to the solenoid  39  is zero, the opening amount of the valve hole  38  becomes maximum. As shown in FIG. 1, two-dot chain line indicates that the inclination angle of the swash plate  14  becomes minimum. As the electric current resumes flowing, the opening amount of the valve hole  38  becomes smaller and the pressure in the control chamber  121  decreases. Accordingly, the inclination of the swash plate  14  increases from the minimum.  
         [0028]    The above-mentioned compressor has the same structure as those in the prior external control variable displacement compressor. Now an embodiment of the present invention will be described as the following.  
         [0029]    As shown in FIG. 1, the valve chamber  28  defined in the rear housing  13  is constituted of a small diameter portion  281  which accommodates the sensing means  36  of the control valve  27  and a large diameter portion  282  is surrounded at its opening by a circumferential wall or a base portion  283  protruding from an outer circumferential wall surface  131  of the rear housing  13 . As shown in FIGS. 2 and 3, an annular recess  285  is formed on an inner circumferential surface  284  of the base portion  283 . As shown in FIG. 3, an annular tapered surface  286  is formed along the inner peripheral surface and is inclined toward outwardly therefrom. This annular tapered surface  286  is formed around the opening of the base portion  283 , on which a partial periphery of the base portion  283  is formed as a groove  290 . The groove  290  is formed by the steps of (1) chamfering in a direction perpendicular to the inner surface of the valve chamber  28  a top of the base portion where the groove is formed, so as to make a chamfered surface  287  and reduce the height there relative to the rest of the base portion, and (2) rounding a corner between the chamfered surface  287  and the tapered surface  286  to make an agonic surface thereon. Therefore, the agonic groove  290  is constructed by three surfaces, chamfered, rounded and tapered surfaces. The projection of the groove  290  from the outer circumferential wall surface  131  of the housing is less than the rest of the base portion  283 . As shown in FIG. 3, a chain line indicates a plane of the chamfered surface elongatedly.  
         [0030]    The above-mentioned valve chamber  28  accommodates the control valve  27 . As shown in FIGS. 1 and 2, a connector  42  is formed on the solenoid  39  side of the control valve  27 . The connector  42  has a projection on its central surface, and the power supply line  43  extends toward a direction perpendicular to the inner circumferential surface  284  from a connection assembly  47  of the projection. The above-mentioned groove  290  is formed on a direction to which the power supply line  43  extends over. A cover  46  which protects the power supply line  43  covers the power supply line  43  just before the base portion  283 . The power supply line  43  plunges its end into the valve chamber  28 , extends over the base portion  283  so as to be in contact with the groove  290  formed on the base portion  283  and is connected to the drive circuit  44 . The control valve  27  is fixed into the valve chamber  28  by means of a circular clip  45  fitted in an annular recess  285  being in contact with the connector  42  end. Besides, as shown in FIG. 2, the power supply line  43  is not in contact with the groove  290  because of avoiding the figure being complicated. The power supply line  43  is in contact with the groove  290  in the actual embodiment.  
         [0031]    The above-mentioned embodiment allows the following advantageous effects to be obtained.  
         [0032]    The tapered surface  288  with which the power supply line  43  is in contact is chamfered and is rounded. Accordingly, not covered with the cover  46 , the power supply line  43  is received by an agonic plane or a curved surface. This protects the power supply line  43  from wearing out with the vibration of a compressor and an engine.  
         [0033]    Furthermore, the groove  290  is constituted of the tapered surface  288 , chamfered surface  287  and rounded surface, and the projection of the groove  290  is less than the rest of the base portion  283 . Accordingly, a deformation for the power supply line  43  extending over the base portion  283  can be reduced, and the power supply line  43  lasts better than that of the prior art.  
         [0034]    Without departing from the spirit or scope of the invention, for example, the following modes allow the same advantageous effects of the embodiment to be obtained.  
         [0035]    The agonic surface groove can be formed by only rounding a predetermined portion of the base portion  283 , as shown in FIG. 4 a . The same advantageous effects can be obtained.  
         [0036]    As shown in FIG. 4 b , not forming the groove  290  but chamfering and rounding the far-ranging or the entire base portion periphery allow the power supply line  43  to be connected more freely.  
         [0037]    The compressor of the embodiment protrudes its base portion  283  of the valve chamber  28  from the outer circumferential wall  131  of the rear housing. However, a compressor which its base portion does not protrude can be embodied.  
         [0038]    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 of the appended claims.