Patent Publication Number: US-8529219-B2

Title: Variable displacement compressor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the National Stage of International Patent Application No. PCT/JP2008/067788, filed Oct. 1, 2008, which claims the benefit of Japanese Patent Application No. 2007-272719, filed Oct. 19, 2007, the disclosures of which are incorporated herein by reference in their entirety. 
     TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to a variable displacement compressor having an opening-degree adjustment valve which variably controls an opening area of a flow passage, which is also called a suction passage, in the flow passage between a suction port and a suction hole communicating with a cylinder bore, and specifically, relates to a variable displacement compressor which is suitable as a compressor provided in a refrigeration circuit of an air conditioning system for vehicles. 
     BACKGROUND ART OF THE INVENTION 
     An opening-degree adjustment valve which variably controls an opening area of a flow passage and which is provided in a flow passage between a suction port and a suction hole communicating with a cylinder bore, of a compressor of an air conditioning system for vehicles, etc., such as shown in  FIG. 6 , is known. In  FIG. 6 , symbol  100  implies an opening-degree adjustment valve, and opening-degree adjustment valve  100  having casing  101  and valve body  102  is provided in a flow passage, which is also called a suction passage, between a suction port of a compressor and a suction hole of a cylinder bore, where casing  101  is disposed in the suction passage and valve body  102  is contained in casing  101  movably. Casing  101  is formed in a shape of a cylinder having the bottom, and small opening section  103  and large opening section  104  are formed on a side surface of casing  101 . Further, by spring  105  which is provided in casing  101 , valve body  102  is urged in a direction of shutting opening  104 , which means a direction of decreasing an opening area of the flow passage. Furthermore, even in a condition where valve body  102  is urged by spring  105  in the direction of decreasing the opening area of the flow passage, small opening section  103  is always opened without closing. 
     In such opening-degree adjustment valve  100 , because gas in a suction chamber is sucked into the cylinder bore at the time of the compressor startup, etc., the pressure in the suction chamber decreases, and valve body  102  is pushed downward in  FIG. 6 , or in a direction of increasing the opening area of large opening section  104 , and the opening area of the flow passage increases. On the other hand, when a fluid sucked from a suction port side is decreased at the time of the compressor shutdown, etc., valve body  102  is pushed upward in  FIG. 6 , or in a direction of decreasing the opening area of large opening section  104 , by the bias force of spring  105 . In addition, space  106  of which volume is varied by casing  101  and valve body  102  as valve body  102  moves is provided in opening-degree adjustment valve  100 , and space  106  communicates with flow passages other than the space through communication path  107 . When valve body  102  moves, because a gap is formed between valve body  102  and inner peripheral surface  101   a  of casing  101  so that refrigerant is flowed from communication path  107  into space  106  and flowed out therefrom, the resonance movement of valve body  102  comes to be restrained. 
     However, opening-degree adjustment valve  100  keeps an opening-degree which makes a differential pressure through opening-degree adjustment valve  100  be nearly constant. Therefore, when there exists liquid refrigerant in an evaporator of the air conditioning system for vehicle at the compressor startup, etc., it may be caused that opening-degree adjustment valve  100  operates as the compressor starts up so as to rapidly increase the opening area of the flow passage and the liquid refrigerant in the evaporator flows into the compressor at once, causing the liquid compression, so as to adversely affect the compressor. Further, a torque limiter might operate when a compressor is a clutchless compressor. 
     Furthermore, when the rotation speed of an engine as a drive source of the compressor increases as a vehicle runs, the discharge displacement of the variable displacement compressor increases temporarily. Until the discharge displacement has been controlled to decrease, especially in a case where the movement to control the displacement delays, the refrigerant flow rate is increased by the amount multiplied by the engine rotation speed increase and the discharge displacement, so that the power consumption increases. Therefore, there might be a bad influence on an engine control and an acceleration performance of the vehicle. As a reason why the movement to control the displacement of the compressor delays, it can be given that even if the refrigerant flow rate of the compressor increases when the engine rotation speed increases, because of the great volume of the refrigerant in the evaporator, the inner pressure fluctuation in the evaporator can be restrained and the suction pressure decrease also becomes slow. Furthermore, it can be also given as a reason why the movement to control the displacement of the compressor delays, that during a middle-low load operation, the discharge pressure decreases and the refrigerant flow rate from a discharge chamber for controlling the displacement decreases, so that the inner pressure increase in a crank chamber slows.
     Patent document 1: JP-2001-289177-A   

     DISCLOSURE OF THE INVENTION 
     Problems to be Solved by the Invention 
     Accordingly, an object of the present invention is to provide a variable displacement compressor of which durability and reliability has been improved by preventing from a liquid compression at the time of the compressor startup, etc., and which can perform a superior response in controlling the displacement. 
     Means for Solving the Problems 
     To achieve the above-described object, a variable displacement compressor according to the present invention is a variable displacement compressor comprising an opening-degree adjustment valve, which is provided in a flow passage between a suction port and a suction hole communicating with a cylinder bore, to variably control an opening area of the flow passage, characterized in that a resistance against a movement of a valve body of the opening-degree adjustment valve in a direction of increasing the opening area of the flow passage is made to be greater than a resistance against a movement in a direction of decreasing the opening area. 
     In the present invention, because the resistance against the movement of the valve body in the direction of increasing the opening area of the flow passage is made to be greater than the resistance against the movement in the direction of decreasing the opening area, even if there exists liquid refrigerant at the compressor startup, etc., an inconvenience that the liquid refrigerant is sucked into the compressor at once is prevented, so that the liquid compression can be surely prevented. In addition, because the resistance through the opening-degree adjustment valve is greater in the direction of increasing the opening area of the flow passage, the pressure loss in a downstream site increases when the engine rotation speed increases. Therefore, because the differential pressure between the internal pressure of the crank chamber and the internal pressure of the suction chamber increases, the discharge displacement can decrease quickly to decrease an excessive power generation, so that the response of the displacement control can be improved. 
     It is possible that the above-described opening-degree adjustment valve comprises a casing placed in the flow passage and a valve body which is provided movably relative to the casing and which is urged by a spring in the direction of decreasing the opening area. In such a composition, when the opening area of the flow passage increases, the valve body is moved in the direction of increasing the opening area of the flow passage against the spring which urges in the direction of decreasing the opening area of the flow passage. And when the valve body is moved in the direction of decreasing the opening area of the flow passage, the valve body is quickly moved by the spring. Therefore, the resistance against the movement of the valve body in the direction of increasing the opening area of the flow passage can be easily made greater than the resistance against the movement in the direction of decreasing the opening area. 
     It is preferable that a space of which volume is varied by the casing and the valve body in accordance with an increase/decrease of the opening area of the flow passage is formed in the opening-degree adjustment valve. And, it is preferable that a communication path capable of communicating between the space and the flow passage positioned outside the space and a valve mechanism which closes the communication path when the opening area is increased and which opens the communication path when the opening area is decreased are provided. In such a structure, when the opening area of the flow passage is decreased, because the communication path is opened by the valve mechanism and refrigerant is flowed into the space, the valve body can be moved quickly in a direction of decreasing the opening area of the flow passage. 
     The valve body can be provided slidably relative to the casing. In this case, it is sufficient that a sliding resistance of the valve body for a direction of increasing the opening area of the flow passage is made to be greater than a sliding resistance of the valve body for a direction of decreasing the opening area. 
     The sliding resistance can be adjusted, for example, by interposing a sliding member between the valve body and the casing. As the sliding member, a ring-shaped resin member extending in a circumferential direction of the valve body or a lip-shaped rubber member extending in a circumferential direction of the valve body can be employed, for example. 
     If the opening-degree adjustment valve is formed to be a valve having a function for throttling to narrow down the flow passage, which means a suction passage, a suction pulse generated from a vibration of the suction valve transmitted to an evaporator, etc. can be reduced by the function for throttling of the suction passage. 
     Such a structure of the opening-degree adjustment valve in the variable displacement compressor according to the present invention is applicable to every variable displacement compressor provided with this kind of opening-degree adjustment valve. Specifically, it is suitable as a variable displacement compressor which is provided in a refrigeration circuit of an air conditioning system for vehicles, and which requires to prevent from a delay of the movement for controlling the displacement of a compressor which might adversely affect on the control of an engine as a drive source of the compressor and on a acceleration performance of a vehicle. 
     Effect According to the Invention 
     In the variable displacement compressor according to the present invention, because the resistance against the movement of the valve body of the opening-degree adjustment valve in the direction of increasing the opening area of the flow passage is greater than the resistance against the movement in the direction of decreasing the opening area at the compressor startup, etc., an inconvenience that the liquid refrigerant in the evaporator in the refrigeration circuit is sucked into the compressor at once is prevented, so that the liquid compression can be surely prevented. In addition, because the resistance through the opening-degree adjustment valve is greater in the direction of increasing the opening area of the flow passage, when the rotation speed of the engine as a drive source of the compressor increases, the pressure loss in a downstream site of the opening-degree adjustment valve increases and the displacement decreases quickly. Therefore, the excess power generation can be reduced and the response of the displacement control can be improved. 
    
    
     
       BRIEF EXPLANATION OF THE DRAWINGS 
         FIG. 1  is a vertical sectional view of a variable displacement compressor according to the first embodiment of the present invention. 
         FIG. 2  is an enlarged sectional view of an opening-degree adjustment valve of the variable displacement compressor in  FIG. 1 . 
         FIG. 3  is an enlarged sectional view of an opening-degree adjustment valve according to the second embodiment of the present invention. 
         FIG. 4  is an enlarged sectional view of an opening-degree adjustment valve according to the third embodiment of the present invention. 
         FIG. 5  is a characteristic diagram, showing compressor power, shaft torque, pressure in the crank chamber and the suction pressure change when the engine rotational speed increased for the variable displacement compressor shown in  FIG. 1 . 
         FIG. 6  is an enlarged sectional view of a opening-degree adjustment valve of a conventional variable displacement compressor. 
         FIG. 7  is a characteristic diagram, showing compressor power, shaft torque, pressure in the crank chamber and the suction pressure change when the engine rotational speed increases for the variable displacement compressor shown in  FIG. 6 . 
     
    
    
     EXPLANATION OF SYMBOLS 
     
         
           1 : variable displacement compressor 
           2 : front housing 
           3 : cylinder block 
           4 : cylinder head 
           5 : crank chamber 
           6 : cylinder bore 
           7 : piston 
           8 : shoe 
           9 : swash plate 
           10 : hinge mechanism 
           11 : rotor 
           12 : drive shaft 
           13 : radial bearing 
           14 : displacement control valve 
           15 : clutch mechanism 
           16 : inner wall 
           17 : suction chamber 
           18 : discharge chamber 
           19 : valve plate 
           20 : suction hole 
           21 : discharge hole 
           22 : suction port 
           23 : discharge port 
           24 : flow passage from suction port to suction hole 
           25 ,  35 ,  38  opening-degree adjustment valve 
           26 : casing 
           26   a : brim section of casing 
           26   b : inner peripheral surface of casing 
           27 : spring 
           28 : valve body 
           29 : groove 
           30 : small opening section 
           31 : large opening section 
           32 : space 
           33 : communication path 
           34 : valve mechanism 
           36 : groove 
           37 : ring-shaped resin member 
           39 : lip-shaped rubber member 
       
    
     THE BEST MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, desirable embodiments of a variable displacement compressor according to the present invention will be explained referring to figures. 
       FIG. 1  shows a variable displacement compressor according to the first embodiment of the present invention. Besides, variable displacement compressors in the embodiments to be described are composed as variable displacement compressors used for a refrigeration circuit of air conditioning system for vehicles. In  FIG. 1 , variable displacement compressor  1  has front housing  2 , cylinder block  3  and cylinder head  4 . Crank chamber  5  is formed between front housing  2  and cylinder block  3 . Plural cylinder bores  6  are provided along a circumferential direction. Piston  7  is inserted reciprocably in each cylinder bore  6 . Swash plate  9  contacts slidably with one end of piston  7  through a pair of shoes  8 . Swash plate  9  of which inclination angle is provided to be variable is coupled with rotor  11  which rotates integrally with drive shaft  12  through hinge mechanism  10 . A stroke of piston  7  is altered by changing the inclination angle of swash plate  9 , so that the discharge displacement of the compressor is changed. 
     One end of drive shaft  12  is supported rotatably by radial bearing  13  fixed to cylinder block  3 . In addition, displacement control valve  14  which controls the discharge displacement is provided in cylinder block  3 . Clutch mechanism  15  is provided at the other end of drive shaft  12 , and the driving force from an engine, which is not shown, is transmitted to drive shaft  12  or interrupted therefrom, in accordance with ON/OFF of clutch mechanism  15 , respectively. 
     Inside of cylinder head  4  is sectioned into suction chamber  17  and discharge chamber  18  by inner wall  16 . Valve plate  19  is provided between cylinder block  3  and cylinder head  4 , and suction hole  20  corresponding to each cylinder bore  6  and discharge hole  21  are bored on valve plate  19 . 
     Refrigerant sucked from suction port  22  connected to the low pressure side of the refrigeration circuit into suction chamber  17  is sucked into cylinder bore  6  through suction hole  20 , and the refrigerant which has been compressed in cylinder bore  6  by reciprocation movement of piston  7  is discharged into discharge chamber  18  through discharge hole  21 . Discharge port  23  is communicated with discharge chamber  18 , and discharge port  23  is connected to the high pressure side of the refrigeration circuit. 
     In flow passage  24  which extends from suction port  22  via suction chamber  17  to suction hole  20 , opening-degree adjustment valve  25  which controls the opening area of flow passage  24  is provided. As shown in  FIG. 2 , opening-degree adjustment valve  25  has casing  26  and valve body  28 , where casing  26  is disposed in flow passage  24  at the bottom end of suction port  20  in this embodiment and valve body  28  is provided movably with respect to casing  26  and urged in a direction of decreasing the opening area of flow passage  24  by spring  27 . In this embodiment, brim section  26   a  of casing  26  is fitted into groove  29  provided at the bottom end of suction port  22 . 
     Small opening section  30  and large opening section  31  are provided in casing  26  of opening-degree adjustment valve  25 . And valve body  28  is urged by spring  27  in a direction of closing large opening section  31 , which means a direction of decreasing the opening area of flow passage  24 . Further, even in a condition where valve body  28  is urged in a direction of decreasing an opening area of flow passage  24  by spring  27 , small opening section  30  is always opened without closing. 
     Furthermore, in opening-degree adjustment valve  25 , space  32  whose volume is altered in accordance with the increase and decrease of the opening area of flow passage  24  is formed with casing  26  and valve body  28 . Space  32  is communicated with a flow passage outside the space through communication path  33  provided at the bottom of casing  26 . Valve mechanism  34  is provided in communication path  33 . In opening-degree adjustment valve  25 , when refrigerant is sucked through suction valve  20  into cylinder bore  6  and the pressure at the downstream site of opening-degree adjustment valve  25  decreases, valve body  28  is moved downward in  FIG. 2  against the biasing force of spring  27 , so that the opening area of large opening section  31  increases and the opening area of flow passage  24  increases. In this state, though communication path  33  is closed by valve mechanism  34 , refrigerant in space is permitted to discharge from a gap, between valve body  28  and inner surface  26   b  of casing  26 . However, because communication path  33  is closed by valve mechanism  34 , the discharge speed of refrigerant in space  32  becomes slow, and the resistance against the increase of the opening area of flow passage  24  increases. On the other hand, when the suction pressure of refrigerant falls, valve body  28  is moved upward in  FIG. 2  by the spring force of spring  27 , so that the opening area of large opening section  31  decreases and the opening area of flow passage  24  decreases. And when valve body  28  is moved in a direction of decreasing the opening area of flow passage  24 , communication path  33  is opened by valve mechanism  34  and space  32  is communicated with other flow passages, so that the refrigerant is flowed into space  32 . Therefore, by the force of spring  27  and refrigerant which is flowed into space  32 , valve body  28  is moved in a direction of decreasing the opening area of flow passage  24  immediately. In other words, the resistance against the movement of valve body  28  in the direction of increasing the opening area of flow passage  24  is greater than the resistance against the movement in the direction of decreasing the opening area of flow passage  24 . 
     In this embodiment, because the resistance against the movement of valve body  28  in the direction of increasing the opening area of flow passage  24  is greater than the resistance against the movement in the direction of decreasing the opening area, even if there exists liquid refrigerant in the evaporator at the compressor startup, etc., such an inconvenience that the liquid refrigerant is sucked at once into the compressor is prevented and the liquid compression can be surely prevented. In addition, the resistance through opening-degree adjustment valve  25  in the direction of increasing the opening area of flow passage  24  is greater. Therefore as shown in  FIG. 5 , because the pressure loss at the downstream site of opening-degree adjustment valve  25  increases when the engine rotation speed increases, in a variable displacement compressor of which the differential pressure between the inner pressure of the crank chamber and suction pressure is controlled so as to keep nearly constant, the differential pressure increases and the discharge displacement is reduced immediately. Therefore, the generation of excessive power can be reduced and the response to control the displacement can be improved. 
       FIG. 3  shows opening-degree adjustment valve  35  of a variable displacement compressor according to the second embodiment of the present invention. Besides, because opening-degree adjustment valve  25  in the first embodiment is the same as opening-degree adjustment valve  35  as to an essential structure, the explanation will be omitted by giving the same number to the same member. In this embodiment, valve body  28  is provided slidably with respect to casing  26 , and the sliding resistance of valve body  28  is greater in the direction of increasing the opening area of flow passage  24  than that in the direction of decreasing the opening area thereof. In this embodiment, groove  36  extending along the circumferential direction on the external surface of valve body  28  is formed, and ring-shaped resin member  37  is fitted into groove  36 . The sliding resistance of valve body  28  can be controlled by ring-shaped resin member  37 . 
     Ring-shaped resin member  37  is fitted into groove  36  as protruding its bottom end toward the side of inner peripheral surface  26   b  of casing  26  as shown in  FIG. 3 . In such a structure, because valve body  28  slides as the bottom end of ring-shaped resin member  37  scratches the inner peripheral surface  26   b  of casing  26  when valve body  28  moves downward in  FIG. 3 , which means a direction of increasing the opening area of the flow passage, the sliding resistance of valve body  28  is greater in the direction of increasing the opening area of flow passage  24  than that in the direction of decreasing the opening area. 
     Even in this embodiment, because the resistance against the movement of valve body  28  in the direction of increasing the opening area of flow passage  24  is greater than the resistance against the movement in the direction of decreasing the opening area, the liquid compression is prevented according to the function of the first embodiment and the displacement control responsiveness at the time of increase of the engine rotational speed can be improved. 
     As well, this embodiment can be combined with the first embodiment. Such a combination makes it possible to prevent the liquid compression more efficiently and to improve the displacement control responsiveness further in a case of the increase of the engine rotational speed. 
       FIG. 4  shows opening-degree adjustment valve  38  of a variable displacement compressor according to the third embodiment of the present invention. Besides, because opening-degree adjustment valve  25  in the first embodiment is the same as opening-degree adjustment valve  38  about an essential structure, the explanation will be omitted by giving the same number to the same member. In this embodiment, valve body  28  is provided slidably with respect to casing  26 , and the sliding resistance of valve body  28  is greater in the direction of increasing the opening area of flow passage  24  than that in the direction of decreasing the opening area thereof. In this embodiment, groove  36  extending along the circumferential direction on the external surface of valve body  28  is formed, and lip-shaped rubber member  39  is fitted into groove  36 . The sliding resistance of valve body  28  can be controlled by lip-shaped rubber member  39 . 
     Lip-shaped rubber member  39  is fitted into groove  36  as protruding its tip side toward the side of inner peripheral surface  26   b  of casing  26  as shown in  FIG. 4 . In such a structure, when valve body  28  moves downward in  FIG. 4 , which means a direction of increasing the opening area, a seal structure is formed between the tip of lip-shaped rubber member  39  and inner peripheral surface  26   b  of the casing, so that the gas in space  32  can be discharged only from communication path  33 . On the other hand, when valve body moves upward in  FIG. 4 , which means a direction of decreasing the opening area, the sealing performance of a gap between the tip of lip-shaped rubber member  39  and inner peripheral surface  26   b  of the casing reduces, so that gas enters space  32  even through the gap. Therefore, the sliding resistance of valve body  28  is greater in the direction of increasing the opening area of flow passage  24  than that in the direction of decreasing the opening area thereof. Even in this embodiment, because the resistance against the movement of valve body  28  in the direction of increasing the opening area of flow passage  24  is greater than the resistance against the movement in the direction of decreasing the opening area, the liquid compression is prevented according to the function of the first embodiment and the displacement control responsiveness at the time of increase of the engine rotational speed can be improved. 
     As well, this embodiment can be combined with the first embodiment. Such a combination makes it possible to prevent the liquid compression more efficiently and to improve the displacement control responsiveness further at the increase of the engine rotational speed. 
     INDUSTRIAL APPLICATIONS OF THE INVENTION 
     A variable displacement compressor according to the present invention is applicable to a variable displacement compressor having an opening-degree adjustment valve, and is specifically suitable as a variable displacement compressor provided in an refrigeration circuit of an air conditioning system for vehicles.