Abstract:
In a variable displacement swash plate type refrigerant compressor ( 10 ), a stopper ( 28 ) is provided for setting an initial angle of the inclination angle of a swash plate ( 23 ) when a drive shaft ( 19 ) is not driven. When the drive shaft ( 19 ) is driven by a driving power source of the compressor ( 10 ) under a non-operation condition of a refrigerant circuit, the stopper ( 28 ) is moved to permit the inclination angle of the swash plate ( 23 ) to be reduced from the initial angle in response to increase of compression work of the compressor ( 10 ) so as to suppress the increase of the compression work to save the driving power for the compressor ( 10 ).

Description:
BACKGROUND OR THE INVENTION  
         [0001]    This invention relates to a clutchless refrigerant compressor of a variable displacement type and, in particular, to an improvement for reducing a compression work in the clutchless refrigerant compressor during a stop of a refrigerating system including the clutchless refrigerant compressor.  
         PRIOR ART  
         [0002]    A typical clutchless refrigerant compressor of a variable displacement type or a variable capacity type is disclosed in U.S. Pat. No. 5,573,379 (corresponding to JP 07 293429A). The clutchless refrigerant compressor shown therein is typically a swash plate type wherein a swash plate is coupled to a drive shaft with a inclination angle from a plane perpendicular to the drive shaft, the inclination angle being variable between a predetermined maximum angle and a predetermined minimum angle approximately equal to the zero angle. The swash plate is coupled to pistons fitted in cylinder bores and reciprocates the pistons in the cylinder bores by rotation with the inclination angle. The piston stroke is determined by the inclination angle and is the maximum stroke when the inclination angle is the predetermined maximum angle while being minimum when the inclination angle is the predetermined minimum angle. The inclination angle of the swash plate is changed by change of gas pressure within a crank chamber where the swash plate is disposed. A capacity control valve is used for controlling the gas pressure for adjusting the inclination angle of the swash plate to control the compression capacity of the compressor. In order to couple the swash plate to pistons, a conversion mechanism is used for converting nutating motion of the swash plate to reciprocating motion of the pistons. As the conversion mechanism, two types are known in the art, one is a type using a wobble plate connected to pistons and supported non-rotatably but slidable on the swash plate, and the other is a shoe type where two semi-spherical shoes are supported by pistons and are in slidable contact with both surfaces of the swash plate.  
           [0003]    The clutchless refrigerant compressor of the variable displacement type is usually used for a refrigerant compressor in a refrigerating circuit in an automotive air conditioner. The drive shaft is connected to an automotive engine output through a belt and a pulley without electromagnetic clutch. Therefore, the drive shaft is rotated or stopped when the engine is driven or stopped.  
           [0004]    The compressor is designed so that the swash plate is held in the predetermined minimum angle when the drive shaft is stopped. It is desired that the inclination angle is smoothly and rapidly increased from the predetermined minimum angle when the engine starts to drive the drive shaft. In order to meet the desire, U.S. Pat. No. 5,573,379 discloses that the swash plate is designed to generate a moment for moving the swash plate to increase the inclination angle when the swash plate is started to rotate at the minimum inclination angle. Thus, the compression capacity is smoothly and rapidly increased to an appropriate level for providing comfortable air condition.  
           [0005]    However, there is often a case where the air conditioning system is switched off even when the automotive vehicle is driven. In the case, the drive shaft is rotated even when the refrigerating circuit of the air conditioning system is in the off operation. The drive shaft rotation results in increase of the inclination angle of the swash plate by the U.S. Patent indicted above. This means that unnecessary compression work is carried out to waste the engine output.  
         SUMMARY OF THE INVENTION  
         [0006]    Accordingly, it is an object to provide a clutchless refrigerant compressor of a variable displacement type where the compression work is reduced when the drive shaft of the compressor is driven during an off-condition of a refrigerating circuit including the compressor.  
           [0007]    It is another object to provide a clutchless refrigerant compressor of a variable displacement type having the smooth and rapid starting property as well as realizing the above object.  
           [0008]    This invention is applicable to a clutchless refrigerant compressor of a variable displacement type comprising: a compressor housing having therein a crank chamber, at least one cylinder bore, a suction chamber, and a discharge chamber, said suction chamber and a discharge chamber having an inlet port and an outlet port, respectively, for connecting the compressor to a refrigerating circuit; at least one piston fitted into said at least one cylinder bore and being reciprocate within said cylinder bore; a drive shaft extending in the crank chamber in a direction parallel to said cylinder and said piston and rotatably born in the compressor housing, said drive shaft having an axial end portion protruding outward from the compressor housing, said axial end portion being for connecting an external driving source for receiving a driving power to rotate said drive shaft; a rotor fixedly mounted on said drive shaft within said crank chamber to be rotatable together with said drive shaft; a swash plate disposed around said drive shaft and connected to said rotor by a hinge connection at an angular position, as a hinge angular position, around said drive shaft so as to be rotatable together with said rotor and to be able to inclined from a plane perpendicular to a drive axis of said drive shaft, said swash plate making a nutating motion with an inclination angle by rotation together with said rotor, the inclination angle of said swash plate being variable between a predetermined minimum angle approximately equal to a zero angle and a predetermined maximum angle; an urging member providing an urging force to urge said swash plate so that said inclination angle of said swash plate becomes the predetermined minimum angle; a connecting mechanism connecting said swash plate to said piston for converting said nutating motion of said swash plate to reciprocating motion of said piston; and a control mechanism for controlling said inclination angle of said swash plate together or against said urging member by adjusting a pressure within said crank chamber to thereby control the displacement of said compressor.  
           [0009]    According to this invention, the compressor further comprises: determining means for determining the inclination angle of the swash plate to an initial angle when said drive shaft is stopped without being driven by the external driving source, the initial angle being selected larger than the predetermined minimum angle; and releasing means for releasing the inclination angle determining means when compression work of the compressor is increased after said drive shaft is driven by the external driving source. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a sectional view of a compressor according to an embodiment of this invention;  
         [0011]    [0011]FIG. 2 is an enlarged partial sectional view illustrating a main portion in the compressor shown in FIG. 1 for determining initial inclination angle of a swash plate in an non-rotating condition of the swash plate;  
         [0012]    [0012]FIG. 3 is the sectional view illustrating the main portion of FIG. 2 illustrating a condition releasing the initial inclination angle when the swash plate is rotated with an increased rotating speed;  
         [0013]    [0013]FIG. 4 is a sectional view illustrating a main portion of a compressor according to another embodiment, similar to FIG. 2;  
         [0014]    [0014]FIG. 5 is a view illustrating the main portion of FIG. 4, similar to FIG. 3;  
         [0015]    [0015]FIG. 6 is a sectional view illustrating a main portion of a compressor according to still another embodiment, similar to FIG. 2;  
         [0016]    [0016]FIG. 7 is a view illustrating the main portion of FIG. 6, similar to FIG. 3;  
         [0017]    [0017]FIG. 8 is a sectional view illustrating a main portion of a compressor according to another embodiment, similar to FIG. 2; and  
         [0018]    [0018]FIG. 9 is a view illustrating the main portion of FIG. 8, similar to FIG. 3. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0019]    Referring to FIG. 1, a clutchless refrigerant compressor  10  of a variable displacement type according to an embodiment of this invention will be described below. The compressor  10  comprises a compressor housing  11  comprising a front housing  11   a , cylinder block  11   b  and a cylinder head  11   c . The compressor housing  11  defines therein a crank chamber  12 , a plurality of cylinder bores (one is shown)  13 , a suction chamber  14 , and a discharge chamber  15 . The suction chamber  14  and a discharge chamber  15  have an inlet port  16  and an outlet port  17 , respectively, for connecting the compressor  10  to a refrigerating circuit.  
         [0020]    Pistons (one is shown)  18  are fitted into the cylinder bores  13  and reciprocated within the cylinder bores  13 .  
         [0021]    A drive shaft  19  extends in the crank chamber  12  in a direction parallel to the cylinder bores  13  and the pistons  18 , and is rotatably born in the compressor housing  11  by bearings  19   a - 19   c . The drive shaft  19  has an axial end portion  20  protruding outward from the front housing  11   a  of the compressor housing  11 . The axial end portion  20  is for connecting an external driving source (not shown) for receiving a driving power to rotate the drive shaft  19  through a pulley  21  and a belt (not shown).  
         [0022]    A rotor  22  is fixedly mounted on the drive shaft  19  within the crank chamber  12  and rotatable together with the drive shaft  19 .  
         [0023]    A swash plate  23  is disposed around the drive shaft  19  and connected to the rotor  22  by a hinge connection  24  at an angular position, as a hinge angular position, around the drive shaft  19 . Accordingly, the swash plate  23  is rotatable together with the rotor  22  and is able to be inclined from a plane perpendicular to a drive axis of the drive shaft  19 . The swash plate  23  performs a nutating motion with an inclination angle by rotation together with the rotor  22 . The inclination angle of the swash plate  23  is variable between a predetermined minimum angle approximately equal to a zero angle and a predetermined maximum angle.  
         [0024]    An urging member  25  is mounted around the drive shaft  19  between the rotor  22  and the swash plate  23  and provides an urging force A (see FIG. 2) to urge the swash plate  23  so that the inclination angle of the swash plate  23  becomes the predetermined minimum angle.  
         [0025]    A connecting mechanism or a conversion mechanism connects the swash plate  23  to the pistons  18  for converting the nutating motion of the swash plate  23  to reciprocating motion of the pistons  18 . The connecting mechanism comprises a peripheral edge portion  23   a  of the swash plate  23 , a rear end portion  18   a  of each piston  18 , and shoes  26  of semi-spherical shape. The shoes are in a sliding contact with both sides of the peripheral edge portion of the swash plate  23  and are held in the rear end portion  18   a  of the piston  18 .  
         [0026]    A control mechanism  27  including a control valve is contained in the cylinder head  11   c  for controlling the inclination angle of the swash plate  23  together or against the urging member  25  by adjusting a pressure within the crank chamber  12  to thereby control the displacement of the compressor  10 . The control valve  27  is communicated with the crank chamber  12  through a first small path  27   a  and with discharge chamber  15  through a second small path  27   b . The control valve  27  controls communication between the discharge chamber  15  and the crank chamber  12  through the first and second small paths  27   a  and  27   b  to thereby adjust the crank chamber  12 .  
         [0027]    The compressor  10  described above is similar to the compressor known in the prior art.  
         [0028]    According to the present invention, the compressor  10  further comprises means for determining the inclination angle of the swash plate  23  to an initial angle (θ 1 ) when the drive shaft  19  is stopped without being driven by the external driving source. The initial angle is selected larger than the predetermined minimum angle. The compressor  10  also comprises means for releasing the initial inclination angle determining means when compression work of the compressor  10  is increased after said drive shaft is driven by the external driving source.  
         [0029]    As the initial inclination angle determining means, a stopper  28  is mounted on the drive shaft  19  at a predetermined position as an initial position on the drive axis of the drive shaft  19 . The stopper  28  stops the swash plate  23  from changing in inclination due to the urging force A from the urging member  25  when the drive shaft  17  is not driven by the external driving source and maintains the swash plate  23  at a predetermined inclination angle as an initial angle. The stopper  28  is variable in the position on the drive axis. The initial angle is selectable to an angle larger than the predetermined minimum angle of the inclination angle of the swash plate  23 .  
         [0030]    The releasing means comprises a detector for detecting a physical factor corresponding to compression work of the compressor  10  and a driver connected to the detector and the stopper for, when the physical factor detected shows increase of the compression work, driving the stopper from the initial position in a direction of the drive axis to thereby permit the swash plate  23  to move from the initial angle to the predetermined minimum angle due to the urging force from the urging member  25 .  
         [0031]    The detector is a rotating speed sensor for sensing a rotating speed of the drive shaft, which results in the compression work of the compressor.  
         [0032]    Referring to FIGS. 2 and 3, a fixed ring  29  is fixedly mounted on the drive shaft  19  at an axial position on a side opposite to the rotor  22  with respect to the swash plate  23 . The fixed ring  29  has a side surface  29   a  facing the swash plate  23 . The side surface  29   a  is inclined so that a first distance along the drive shaft  19  from the side surface  29   a  to the rotor  22  at the hinge angular position is smaller than a second distance along the drive shaft  19  from the side surface  29   a  to the rotor  22  at an angular position opposite to the hinge angular position. A wedge-like ring  31  having a wedge-shape section is disposed around the drive shaft  19  and is elastically supported by a spring  30  mounted on an outer surface of the fixed ring  29  at an angular position corresponding to the hinge angular position. The wedge-like ring  31  has a inclined side surface  31   a  corresponding to, and being in contact with, the side surface  29   a  of the fixed ring  29  and also has an opposite side surface  31   b . The wedge-like ring  31  has an unbalanced weight around the drive shaft so that a weight is smaller at a half of the wedge-like ring  31  on the side of the hinge angular position than at the other half. As is seen in FIG. 3, the wedge-like ring  31  is diametrically moved along the side surface  29   a  of the fixed ring  29  to a direction toward the opposite side of the hinge angular position against the supporting force of the spring  30  by a centrifugal force (B) caused by rotation together with the drive shaft  19 . The stopper  28  is formed as a protrusion at a position on the opposite side surface  31   b  of the wedge-like ring  31 . The stopper  29  is moved away from the rotor  22  or backward in the direction of the drive axis by the movement of the wedge-shape ring  31  by the centrifugal force B. Thus, the spring  30  and the wedge-like ring  31  serves as the releasing means.  
         [0033]    Referring to FIG. 4 and  5 , the driver comprises an electromagnetic solenoid  42  comprising a fixed magnetic core  43  fixedly mounted on the drive shaft  19 , an electric wire coil  44  wound to the fixed magnetic core  43 , and a movable magnetic core  45  having the stopper  28  and being movable with respect to the fixed magnetic core  43  in a direction of the drive axis. The driver further comprises a solenoid driver  41  connected to the electric wire coil  44  for energizing and disenergizing the electric wire coil  44  in response to the physical factor as detected by the detector  40 . The detector  40  is a pressure sensor for detecting a pressure in the discharge chamber  15 .  
         [0034]    The electromagnetic solenoid  42  further comprises a core urging spring  46  for urging the movable magnetic core  45  so that the stopper  28  is positioned in the initial position. The solenoid driver  41  does not energize the electric wire coil  44  in a normal state, as shown in FIG. 4.  
         [0035]    Referring to FIG. 5, the solenoid driver  41  energizes the electric wire coil  44  when the physical factor detected is determined to increase beyond a predetermined level of the factor, to move the stopper  28  from the initial position against the urging force of the core urging spring  46  in the direction of the drive axis. Therefore, the swash plate  23  is permitted to move from the initial angle to the predetermined minimum angle due to the urging force (A).  
         [0036]    In the embodiment shown in FIGS. 6 and 7, the similar components are shown by same reference numerals in FIGS.  2  and  3 . The similar detector  40  and solenoid driver  41  are omitted for simplification of the drawing. In the embodiment, the core urging spring  46  urges the movable magnetic core  45  so that the stopper  28  is positioned at a remote position than the initial position as viewed from the rotor  22 . The solenoid driver  41  energizes the electric wire coil  44  in a normal state to maintain the stopper  28  at the initial position against the core urging spring  46 , as shown in FIG. 6.  
         [0037]    Referring to FIG. 7, when the factor detected by the detector  40  exceeds a predetermined level, the solenoid driver  41  releases the energization of the electric wire coil  44 . As a result, the stopper  28  is moved from the initial position in the direction of the drive axis by the urging force of the core urging spring  46 . Therefore, the swash plate  23  is permitted to move from the initial angle to the predetermined minimum angle due to the urging force A.  
         [0038]    The embodiment shown in FIGS. 8 and 9 are different in structure from, but same in operation with, that shown in FIGS. 2 and 3. In FIGS. 8 and 9, the similar components are shown by the same reference numerals in FIGS. 2 and 3, but detector  40  and solenoid driver  41  are also omitted for the purpose of simplification of the drawings. Accordingly, further description is omitted for the simplification of the description.  
         [0039]    As the detector  40  in connection with embodiments of FIGS.  4 - 9 , various sensors can be used for detecting physical factor corresponding to the compression work of the compressor  10 .  
         [0040]    The detector  40  can be a pressure sensor for detecting a difference in pressure between the discharge chamber  15  and the suction chamber  14 .  
         [0041]    The detector  40  can be a temperature sensor for detecting a temperature of the compressor  10 .  
         [0042]    The compressor  10  is charged therein with lubricating oil. Therefore, the detector  40  can be a temperature sensor for detecting a temperature of the compressor  10 , or a viscosity sensor for detecting a viscosity of the lubricating oil.  
         [0043]    The detector  40  can also be a temperature sensor for detecting an ambient temperature around the compressor  10 .  
         [0044]    The clutchless refrigerant compressor is used in an automotive air conditioning system. Therefore, the detector  40  can be a temperature sensor for detecting a temperature within a room of the automotive vehicle.  
         [0045]    In the embodiments, there may often be a case where the stopper  28  is moved from the initial position backward to permit the swash plate  23  to move to the predetermined minimum angle during operation of the refrigerating circuit or the air conditioner. However, in the operation, the control valve or control mechanism operates to control the inclination angle of the swash plate  23  for the capacity control. The stopper  28  does not affect the capacity control at all.  
         [0046]    The initial inclination angle can be set as desired, by selecting the initial position of the stopper  28 . Therefore, it is easy to realize the smooth and rapid starting properties of the compressor