Abstract:
An apparatus for controlling compressor discharge capacity includes a variable capacity compressor, a capacity adjustment device, a signal processing device, a capacity setting device, and a signal comparing device. The capacity adjustment device regulates a discharge capacity of the variable capacity compressor. The signal processing device receives a signal corresponding to a discharge capacity of the variable capacity compressor. The capacity setting device sets a first discharge capacity target value for the variable capacity compressor. The signal comparing device compares the discharge capacity signal to the fist discharge capacity target value and sends an activation signal to the capacity adjustment device, such that the discharge capacity signal approaches the first discharge capacity value.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a capacity control apparatus for variable capacity-type compressors for use in automotive air conditioning systems. In particulars the present invention relates to a capacity control apparatus that may directly control an actual discharge capacity of variable capacity-type compressors, and which may be used to control refrigeration circuits in automotive air conditioning systems 
     2. Description of Related Art 
     A capacity control apparatus for a variable capacity-type compressor is described in, for example, Japanese (Unexamined) Patent Publication No. 64-073178. In this known variable capacity-type compressor, a discharge capacity of the compressor is regulated by a control means, e.g., an electromagnetic valve or the like. The control means regulates the discharge capacity of the compressor based on a measured physical characteristic related to cooling efficiency of a refrigeration circuit, e.g., a pressure or a temperature of a refrigerant. 
     In this known variable capacity-type compressor, the actual discharge capacity of the compressor may be adjusted, as needed. For example, the discharge capacity of the compressor may be adjusted in response to a condition of the refrigeration circuit, e.g., to an increased air conditioning load on the refrigeration circuit. Moreover, actual discharge capacity of the compressor may be adjusted toward a predetermined discharge capacity target of the compressor. For example, a target discharge capacity value of the compressor may be established, and the actual discharge capacity may be adjusted toward the target discharge capacity value. Therefore, in such known variable capacity type compressors, in which an engine of a vehicle may drive the compressor, a load fluctuation of the compressor may not correspond to a load of the engine. As a result, efficient operation of the compressor may not be achieved. 
     In order to improve the efficiency of such compressors, such compressors may include a discharge capacity control apparatus for a variable capacity-type compressor, as described in Japanese Patent No. 3060676. In this known variable capacity-type compressor, a torque detection device is positioned on the compressor to measure a torque of a drive of the compressor, e.g., a torque of a drive shaft of a compressor or the like. An output of a vehicle engine then may be adjusted based on the measured value of torque driving the compressor. 
     Nevertheless, in known variable capacity-type compressors having such a torque detection device, the compressor load is measured, and this measurement is used to control the air conditioning system of the vehicle. Nevertheless, the discharge capacity of the compressor is not adjusted toward a predetermined target discharge value of the compressor. 
     SUMMARY OF THE INVENTION 
     Therefore, a need has arisen for a discharge capacity, control apparatus for variable capacity-type compressors that regulates operation of the compressor, so that the compressor discharge capacity approaches or reaches a discharge capacity target value. 
     According to an embodiment of the present invention, an apparatus for controlling compressor discharge capacity comprises a variable capacity compressor, a capacity adjustment device, a signal processing device, a capacity setting device, and a signal comparing device. The capacity adjustment device regulates a discharge capacity of the variable capacity compressor. The signal processing device receives a signal corresponding to a discharge capacity of the variable capacity compressor. The capacity setting device sets a first discharge capacity target value for the variable capacity compressor. The signal comparing device compares the discharge capacity signal to the first discharge capacity target value and second an activation signal to the capacity adjustment device, such that the discharge capacity signal approaches the first discharge capacity target value. 
     In another embodiment of the invention, an apparatus for controlling compressor discharge capacity comprises a variable capacity compressor, a capacity adjustment device, a signal processing device, a capacity setting device, a first signal comparing device, a detection device a pressure setting device, and a second signal comparing device. The capacity adjustment device regulates a discharge capacity of the variable capacity compressor. The signal processing device receives a signal corresponding to a discharge capacity of said variable capacity compressor. The capacity setting device sets a first discharge capacity target value of the variable capacity compressor. The first signal comparing device compares the discharge capacity signal to the first discharge capacity target value and sends a first activation signal to the capacity adjustment device, such that the discharge capacity signal reaches the first discharge capacity value. The detection device detects a first pressure value in a refrigeration circuit including the variable capacity compressor. A pressure setting device sets a second pressure target value. A second signal comparing device compares the first pressure value with the second pressure target value and sends an activation signal to the capacity adjustment device, such that the first pressure value approaches the second pressure target value. The compressor discharge capacity controlling apparatus may comprise a switching device that selectively connects the first signal comparing device and the second signal comparing device to the capacity adjustment device. 
     In another embodiment of the invention, an apparatus for controlling compressor discharge capacity comprises a variable capacity compressor, a capacity adjustment device, a signal processing device, a capacity setting device, a first signal comparing device, a detection device, a temperature setting device, and a second signal comparing device. The capacity adjustment device regulates a discharge capacity of the variable capacity compressor. The signal processing device receives a signal corresponding to a discharge capacity of said variable capacity compressor. The capacity setting device sets a first discharge capacity target value of the variable capacity compressor. The first signal comparing device compares the discharge capacity signal to the first discharge capacity target value and sends an activation signal to the capacity adjustment device, such that the discharge capacity signal reaches the first discharge capacity value. The detection device detects a first temperature value in a refrigeration circuit including the variable capacity compressor. A temperature setting device sets a second temperature target value. A second signal comparing device compares the first temperature value with the second temperature target value and sends an activation signal to the capacity adjustment device, such that the first temperature value approaches the second temperature target value. The compressor discharge capacity controlling apparatus may comprise a switching device that selectively connects the first signal comparing device and the second signal comparing device to the capacity adjustment device. 
     According to a further embodiment of the invention, a method of controlling a discharge capacity of a variable capacity compressor connected to a refrigeration circuit comprises the following steps. A first discharge capacity value of the variable capacity compressor is set. A discharge capacity of the variable capacity compressor is detected. The discharge capacity value is compared with the first discharge capacity target value. The discharge capacity of the variable capacity compressor is adjusted, such that the discharge capacity value approaches the first discharge capacity value. 
     Other objects, features, and advantages of embodiments of this invention will be apparent to persons of ordinary skill in the art from the following detailed description of the invention and the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention may be understood more readily with reference to the following drawings. 
     FIG. 1 shows a schematic of a capacity control apparatus of a compressor, according to an embodiment of the present invention. 
     FIG. 2 shows a schematic of a capacity control apparatus of a compressor, according to another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Where features of the following embodiments of the present invention are substantially similar to those of other embodiments, similar parts have been given similar numbers, and explanations for these similar parts may be omitted from the descriptions of subsequent embodiments. 
     FIG. 1 shows a discharge capacity control mechanism  1  of a variable capacity-type compressor  2  for a vehicle air conditioning system according to an embodiment of the present invention. Variable capacity-type compressor  2  may be a swash plate-type compressor. Variable capacity-type compressor  2  may comprise a cylinder block  12 , a front housing  7 , and a cylinder head  14 . Cylinder block  12  may be substantially cylindrical. Front housing  7  may be positioned at one end of cylinder block  12 . Cylinder head  14  may be positioned at another end of cylinder block  12 . A crank chamber  8  may be formed between cylinder block  12  and front housing  7 . Moreover, a suction chamber  15  and a discharge chamber  16  may be formed within cylinder head  14 . Cylinder block  12 , front housing  7 , and cylinder head  14  may be connected by a plurality of fasteners, e.g., bolts (not shown). Compressor  2  also may comprise a plurality of cylinder bores  13  formed in cylinder block  12 . Cylinder bores  13  may be positioned around a central axis of cylinder block  12 , e.g., in an annular configuration, and may be offset radially from the central axis of cylinder block  12 . 
     Compressor  2  may comprise a drive shaft  4 , a cam rotor  5 , a swash plate  6 , a plurality of pairs of shoes  10 , and a plurality of pistons  11 . Drive shaft  4  may extend through crank chamber  8 , alone a central axis of compressor  2 . Drive shaft  4  may be supported rotatably by front housing  7  and cylinder block  12 , via bearings  30   a  and  30   b , which may be mounted in front housing  7  and cylinder block  12 , respectively. Compressor  2  may comprise an electromagnetic clutch  3 . A drive belt (not shown) may engage a pulley of electromagnetic clutch  3  and transmit a driving force from a driving source (not shown), e.g., an engine of a vehicle, to electromagnetic clutch  3 . When electromagnetic clutch  3  engages drive shaft  4 , the driving force off the driving source may be transmitted by electromagnetic clutch  3  to drive shaft  4 . Moreover, cam rotor  5  may be fixed to drive shaft  4  to rotate with drive shaft  4  and may be positioned within crank chamber  8 . Swash plate  6  also may be positioned within crank chamber  8  and may be slidably mounted on drive shaft  4 . Swash plate  6  may be connected to cam rotor  5  via hinge mechanism  9 , so that an inclination angle of swash plate  6  may vary, and so that swash plate  6  may rotate with drive shaft  4 . Although electromagnetic clutch  3  may transmit the driving force of the driving source to drive shaft  4 , the driving source may be coupled directly to drive shaft  4  in another embodiment of the present invention. 
     A piston  11  may be positioned within each cylinder bore  13 , so that each piston  11  may reciprocate independently within its respective cylinder bore  13 . Each piston  11  may include a pair of substantially semispherical cavities, which may be formed at an end of each piston  11 . Each piston  11  may be connected to swash plate  6 , via a pair of shoes  10 . Each shoe  10  comprises a semispherical portion and a flat portion. A semispherical portion of each shoe may be positioned in a respective semispherical cavity of each piston  11 , while a flat portion of each shoe may contact a surface of swash plate  6 . In this way, each shoe of a pair of shoes  10  may slidably contact a surface of swash plate  6 . 
     Compressor  2  may comprise a discharge capacity adjustment device  17   a  which may adjust a discharge capacity of compressor  2 . Capacity adjustment device  17   a  may comprise an electromagnetic control valve  17 , a first communication path  18 , and a second communication path  19 . First communication path  18  and second communication path  19  may establish communication between discharge chamber  16  and crank chamber  8 . Electromagnetic control valve  17  may be positioned between first communication path  18  and second communication path  19 . Electromagnetic control valve  17  may be opened to enable fluid communication between first communication path  18  and second communication path  19  or closed to prevent fluid communication between first communication path  18  and second communication path  19 . In this way, electromagnetic control valve  16  may control the amount of refrigerant that flows between crank chamber  8  and discharge chamber  16 . 
     Capacity adjustment device  17   a  may control the discharge capacity of compressor  2  in the following manner. The discharge capacity of compressor  2  may vary with a length of a stroke of each piston  11 . The length of a stroke of each piston.  11  may vary with the inclination angle of swash plate  6 . The inclination angle of swash plate  6  may be controlled by controlling a pressure in crank chamber  8 . The pressure in crank chamber  8  may be controlled by controlling the amount of a refrigerant, e.g., a refrigerant gas, that passes between crank chamber  8  and discharge chamber  16 , via first communication path  18  and second communication path  19 . By controlling the amount of refrigerant that flows between crank chamber  8  and discharge chamber  16  via first communication path  18  and second communication path  19 , capacity adjustment device  17   a  may control the inclination angle of swash plate  6  and the stroke length of each piston  11 , thereby enabling capacity adjustment device  17   a  to control the discharge capacity of compressor  2 . 
     A rod  21  may be positioned within drive shaft  4  and may slide in an axial direction within drive shaft  4 , i.e., in a direction substantially parallel to a longitudinal axis of drive shaft  4 . Swash plate  6  may be connected to rod  21 , via a pin  20 . Rod  21  may slide within drive shaft  4  in an axial direction in response to changes in the inclination angle of swash plate  6 . Thus, a position of rod  21  in an axial direction within drive shaft  4  corresponds to an inclination angle of swash plate  6 . A detection member  22  may be positioned at an end of rod  21  that projects from drive shaft  4 . A position sensor  23   a  may detect a position of detection member  22 . Thus, a position of rod  21  and an inclination angle of swash plate  6  may be detected by position sensor  23   a , via detection of a position of detection member  22 . Because the discharge capacity of compressor  2  and stroke length of each piston correspond to the inclination angle of swash plate  6 , the discharge, capacity of compressor  2  may be measured by detecting a position of detection member  22 . Moreover, the discharge capacity of compressor  2  and the stroke length of each piston  11  may be converted to a position of rod  21 , via swash plate  6  and pin  20 , such that a discharge capacity of compressor  2  may be derived from a detected position of rod  21 . This mechanism constitutes a capacity detection device  23  according to an embodiment of the invention. 
     A capacity control device  24  may be connected to position sensor  23   a  of capacity detection device  23  and electromagnetic control valve  17  of capacity adjustment device  17   a . Capacity control device  24  may comprise a signal processing device  25 , e.g., an electric circuit, a capacity setting device  26 , e.g., an electric circuit, a signal comparing device  27 , e.g., an electric circuit, and an amplifier  28  for energizing a solenoid of electromagnetic valve  17 . Signal processing device  25  may receive signals from position sensor.  23   a  of capacity detection device  23 . Each signal may correspond to a position of detection member  22  and rod  21  detected by position sensor  23   a  of capacity detection device  23  and thus to a position of swash plate  6  and to a discharge capacity of compressor  2 . 
     Capacity setting device  26  may establish a compressor discharge capacity target value. Signal comparing device  27  may compare the detected signal received from signal processing device  25  to the compressor discharge capacity target value. Based on the comparison, signal comparing device  21  may transmit a feedback value signal to amplifier  28 . Feedback value signal may be based on a difference, if any, between the detected signal and the compressor discharge capacity target value. In response to the received feedback value signal, amplifier  28  transmits an activation signal to electromagnetic valve  17  to energize the solenoid of electromagnetic control valve  17 . Thus, by establishing compressor discharge capacity target values, capacity setting device  26  may control a pressure in crank chamber  8 , thereby controlling the discharge capacity of compressor  2  based on the compressor discharge capacity target value. Each compressor discharge capacity target value may be selected from values in a range of about 0% of a discharge capacity target value to about 100% of a discharge capacity target 
     According to this embodiment of the invention, the discharge capacity of compressor  2  may be detected directly, i.e., by detecting a position of rod detection member  22  and rod  21 , and by converting that detected position to a corresponding discharge capacity of compressor  2 . This detected discharge capacity may be compared to a predetermined discharge capacity target value, so that the discharge capacity of compressor  2  may be regulated without regard to other factors that may affect the discharge capacity of compressor  2 . For example, a feedforward control may be used to adjust the discharge capacity of compressor  2 , so that the detected value of a position of rod  21  and, thus, the discharge capacity of compressor  2  may approach and eventually reach a discharge capacity target value. 
     FIG. 2 shows a discharge capacity control mechanism  1 ′ of a variable capacity-type compressor  2 ′ for a vehicle air conditioning system according to a further embodiment of the present invention. In this embodiment of the invention, the configuration of discharge capacity control mechanism  1 ′ may be substantially similar to the configuration of discharge capacity control mechanism  1  of the previous embodiment, except that discharge capacity control mechanism  1 ′ may comprise a second capacity control device  31 . Second capacity control device  31  may control the discharge capacity of compressor  2 ′ through a feedback control based on a signal that corresponds to a detected pressure or a detected tempera of a refrigeration circuit. Moreover, discharge capacity control mechanism  1 ′ may comprise first capacity control device  24 ′ in addition to second capacity control device  31 , so that a discharge capacity of compressor  2  may be regulated by first capacity control device  24 ′ via a feedback control based on a signal that corresponds to a detected position, of rod  21 , as discussed in the previous embodiment, or through a, feedback control based on a signal that corresponds to a detected pressure or a detected temperature of a refrigeration circuit. According to this embodiment, a switching device  37  may connect second capacity control device  31  or first capacity control device  24 ′ to amplifier  28 . 
     Second capacity control device  31  may comprise a sensor, e.g., a pressure sensor  33   a , a temperature sensor  33   b , or the like, a signal processing device  34 , e.g., an electric circuit, a pressure setting device  35 , e.g., an electric circuit, a signal comparing device  36 , e.g., an electric circuit, and an amplifier  28  for energizing a solenoid of electromagnetic valve  17 . Pressure sensor  33   a  may be positioned in a refrigeration circuit. For example, pressure sensor  33   a  may be positioned between a suction chamber  15  of compressor  2 ′ and an evaporator  32  to detect a pressure of refrigerant in the refrigeration circuit, e.g., a pressure of refrigerant in suction chamber  15  of compressor  2 ′. Pressure setting device  35  may set a pressure control target value. Signal comparing device  36  may compare the pressure detected by pressure sensor  33   a  with the predetermined pressure control target value set by pressure setting device  35 . Based on this comparison, signal comparing device  36  may transmit a feedback value signal to amplifier  28 . The feedback value signal may correspond to a difference, if any, between the pressure detected by pressure sensor,  33   a  and the predetermined pressure control target value set by pressure setting device  35 . Amplifier  28  may transmit a signal to electromagnetic valve  17  to energize the solenoid of electromagnetic control valve  17 . 
     Thus, the discharge capacity of compressor  2 ′ may be controlled by detection a pressure of a refrigerant in a refrigeration circuit and by comparing the detected pressure to a predetermined pressure control target value set by pressure setting device  35 . A feedforward control or the like, may be used to control second capacity control device  31 , so that the detected pressure value approaches and reaches the predetermined target pressure control value. 
     In another embodiment of the invention, a temperature sensor  33   b  may detect a temperature of refrigeration circuit, e.g., a temperature of fins of evaporator  32 , a temperature of air passing through evaporator  32 , or the like. Pressure setting device  35  may set a temperature control target value. Signal comparing device  36  may compare the temperature detected by temperature sensor  33   b  with the temperature control target value set by pressure setting device  35 . Based on this comparison, signal comparing device  36  may transmit a feedback value signal to amplifier  28 . The feedback value signal may correspond to a difference, if any, between the temperature detected by temperature sensor  33   a  and the temperature control target value set by pressure setting device  35 . Amplifier  28  may transmit a signal to electromagnetic valve  17  to energize the solenoid of electromagnetic control valve  17 . Thus, capacity control device  31  enables regulation of the discharge capacity of compressor  2 ′, via the detected temperature of evaporator  32  or the detected pressure of refrigerant in the refrigeration circuit. 
     A switching device  37  may selectively connect first capacity control device  24 ′ and second capacity control device  31  to amplifier  28 . For example, switching device  37  may connect first capacity control device  24 ′ to amplifier  28 , so that signal comparing device  27  may send a feedback signal to capacity adjustment device  17   a . Switching device  37  may connect second capacity control device  31  to amplifier  28 , so that signal comparing device  36  may send a feedback signal to capacity adjustment device  17   a  Switching device  37  may be activated by an external controller (not shown). External controller may activate switching device  37  to connect first capacity control device  24 ′ or second capacity control device  31  to amplifier  28  depending upon a desired outcome, e.g., reducing energy consumption, matching a load of compressor  2 ′ to a load of the vehicle engine, controlling the flow of refrigerant in the refrigeration circuit, or the like. 
     Thus, according to one embodiment of the invention, a discharge capacity control device may regulate the discharge capacity of a compressor directly, e.g., by detecting the discharge capacity of a compressor and regulating the detected discharge capacity toward a predetermined discharge capacity control value, without regard to other factors that may affect the discharge capacity of the compressor. Moreover, according to another embodiment of the invention, a discharge capacity control device may regulate the discharge capacity of a compressor indirectly, e.g., by detecting a pressure or a temperature of a refrigeration circuit, so that the detected discharge capacity may be adjusted based on a variety of considerations, e.g., reducing energy consumption, matching a load of compressor  2 ′, to a load of the vehicle engine, controlling the flow of refrigerant in the refrigeration circuit, or the like. In addition, the discharge capacity control device of the present invention may regulate discharge capacity by a feedforward control, so that discharge capacity of the compressor may be regulated in an efficient manner. 
     While the invention has been described in connection with preferred embodiments, the invention is not limited thereto. It will be understood by those skilled in the art that other embodiments, variations and modifications of the invention will be apparent to those of ordinary skill in the art from a consideration of the specification or a practice of the invention disclosed herein and may be made within the scope of the invention.