Abstract:
An intake-gas throttle device in the intake pressure region of an air-conditioning compressor, in particular for air-conditioning systems of motor vehicles, the device controlling the delivery rate of the air-conditioning compressor.

Description:
[0001]    The present invention relates to a suction-gas throttle device in the suction zone of an air-conditioning compressor, in particular for air-conditioning systems of motor vehicles, the device controlling the delivery rate of the air-conditioning compressor. 
       BACKGROUND 
       [0002]    Suction-gas throttle devices of this kind are generally known. In these devices, automatic throttling of the suction gas can be effectively accomplished only by means of an on-off controller, and volume flow control is possible only by internal control, such as in the case of internally controlled variable displacement compressors. This type of control still requires the use of an additional clutch for the compressor. 
       SUMMARY OF THE INVENTION 
       [0003]    In view of the above, it is an object of the present invention to provide an external volume flow control device for a suction throttling system which operates completely independently of the volume flows and pressures prevailing in the system. In particular, the adjustment should be simple from a mechanical point of view. 
         [0004]    The present invention provides a suction-gas throttle device in the suction pressure zone of an air-conditioning compressor, in particular for air-conditioning systems of motor vehicles, the device controlling the delivery rate of the air-conditioning compressor and being provided with a pilot device. 
         [0005]    A suction-gas throttle device is preferred in which the pilot device controls a variable cross-sectional area of the throttle, for example, by means of a slide valve provided in the suction flow zone of the air-conditioning compressor. Also preferred is a suction-gas throttle device in which one side of the slide valve is connected to a pilot pressure chamber, and the other side of the slide valve is connected to the pressure zone in the suction flow zone of the air-conditioning compressor that is located downstream of the suction-gas throttle device. 
         [0006]    In accordance with a preferred embodiment of the present invention, the pilot pressure chamber may be connected via an inflow resistance to the suction flow zone upstream of the suction-gas throttle device, and via an outflow resistance to the suction flow zone downstream of the suction-gas throttle device, or vice versa. 
         [0007]    In a preferred embodiment of the present invention of a suction-gas throttle device, the inflow resistance is in the form of a valve. Also preferred is a suction-gas throttle device in which the valve is actuated by solenoid in a pulse-width modulated manner. 
         [0008]    Moreover, a suction-gas throttle device is preferred in which the outflow resistance of the pilot pressure chamber is a constant flow resistance provided, for example, by a restrictor. 
         [0009]    In another preferred embodiment of a suction-gas throttle device according to the present invention, the slide valve is movable against a spring force and the pressure from the pilot pressure chamber that prevails downstream of the suction-gas throttle device, so that the main cross-sectional area of the throttle can be continuously reduced by moving the slide valve. 
         [0010]    Also preferred is a suction-gas throttle device in which the pulse-width modulation pulsation of the pilot valve may be attenuated by the volume in the pilot pressure chamber, so that an approximately constant pilot pressure which may be proportional to the pulse-width modulation signal may be built up in the pilot pressure chamber, and the slide valve may not pulsate, but may assumes a proportional valve position. This has the advantages that, because of the attenuating properties of the gas-filled pilot pressure chamber and its dimensioning for piloting purposes, it is possible to use a pulse-width modulated valve, while nevertheless the main stage, for example, the slide valve, may assumes a non-pulsating position which may be proportional to the pulse width. 
         [0011]    Furthermore, a suction-gas throttle device is preferred in which the slide valve may be disposed between the suction pressure zone of the air-conditioning system and the suction pressure zone of the compressor. Also preferred is a suction-gas throttle device in which the inflow valve of the pilot device may be disposed between the suction pressure zone of the air-conditioning system and the pilot pressure chamber. Moreover, a suction-gas throttle device is preferred in which the outflow resistance of the pilot device may be disposed between the pilot pressure chamber and the suction pressure zone of the air-conditioning compressor. 
         [0012]    In one embodiment of the suction-gas throttle device according to the present invention, the slide valve may be in the form of a diaphragm slide valve. In another embodiment of the suction-gas throttle device according to the present invention, the slide valve may be in the form of a piston slide valve. Also preferred is a suction-gas throttle device in which a sliding sleeve may have openings which, together with openings provided in a guide sleeve, form a throttling point for the suction flow of the air-conditioning compressor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0013]    The present invention will now be described with reference to the FIGURE. 
           [0014]    The single FIGURE shows a piloted suction-gas throttle device. 
       
    
    
     DETAILED DESCRIPTION  
       [0015]    A housing  1  has an inlet in communication with the suction zone  3  of an air-conditioning system, and an outlet in communication with the suction zone  5  of an air-conditioning compressor. An opening  7  in housing  1  has permanently disposed therein a guide sleeve  9  on which is slidably mounted a sliding sleeve  11  having a diaphragm  13 . Sliding sleeve  11  has approximately semicircular openings  14 , and guide sleeve  9  has corresponding larger openings  15 , so that when the sliding sleeve is advanced, the total cross-sectional area of the throttle, which is defined by the overlap of openings  14  and  15 , throttles the suction flow passing through the suction-gas throttle device to the compressor. Sliding sleeve  11 , which is integrally connected to diaphragm  13 , is pressed against its rear stop by a coil spring  17 . 
         [0016]    Housing  1  further has a pilot device for this slide valve device, said pilot device substantially including a pulse-width modulated valve  19 , an outflow resistance  21 , here in the form of a constriction, for example, a restrictor, and a pilot pressure chamber  23  formed by the conduit volume between valve  19  and resistance  21  and by the volume of the pressure chamber behind diaphragm  13 . Suction pressure zone  3 , which is in communication with the air-conditioning system, is connected by an inflow conduit  25  to pilot valve  19 , and an outflow conduit  27  leads from outflow restrictor  21  to the suction pressure zone downstream of the suction-gas throttle device, for example, to the suction pressure zone  5  of the air-conditioning compressor. 
         [0017]    The operation of the pilot device is described as follows. When pulse-width modulated valve  19  is closed, for example, by an external electronic control circuit  29 , the connection to suction pressure zone  3  of the air-conditioning system is interrupted. Pilot pressure zone  23  is in communication with the suction pressure of the air-conditioning compressor in zone  5  via pilot outflow conduit  27  and restrictor  21 , so that the pressures in front of and behind diaphragm  13  are the same. Consequently, coil spring  17  holds sliding sleeve  11  and its openings  14  in the position shown; providing maximum open area for flow through the suction-gas throttle device. When valve  19  is now opened for increasingly greater time periods by an increasing pulse-width modulated signal, the gas flowing from suction pressure zone  3  through pilot line  25  into pilot pressure chamber  23  causes a pressure to build up therein at an increasingly higher rate than in zone  5  downstream of the suction-gas throttle device. This is because the outflow of gas from pilot pressure chamber  23  is retarded by restrictor  21 , and because said outflow may occur at a rate which may be slower than the rate at which gas flows from the slightly higher suction pressure in zone  3  through conduit  25  into pilot pressure chamber  23 . Thus, the pilot pressure behind diaphragm  13  increases and moves diaphragm  13 , and thus sliding sleeve  11 , against the force of spring  17  and against the suction pressure in zone  5 , thereby reducing the cross-sectional opening area provided by the overlapping openings  15  of guide sleeve  9  and  13  of sliding sleeve  11 . Since the medium in pilot pressure chamber  23  is a gas, the pulsations of valve  19  are attenuated in this gas volume and are not imparted to the movement of sliding sleeve  11 , so that, in spite of the pulse-width modulated signal of pilot valve  19 , the cross-sectional area of the throttle can be adjusted to a constant non-pulsating position which is proportional to the signal. This has not been possible in the known prior art. Thus, the pilot control system provided in accordance with the present invention allows adjustment of a smooth, for example, constant, main throttle setting using a pulse-width modulated, for example, oscillating, input signal, the throttle setting being proportional to the pulse width and used for controlling the suction volume flow of an air-conditioning compressor. 
       LIST OF REFERENCE NUMERALS 
       [0000]    
       
           1  housing 
           3  inlet 
           5  outlet 
           7  opening 
           9  guide sleeve 
           11  sliding sleeve 
           13  diaphragm 
           14  semicircular openings 
           15  openings 
           17  coil spring 
           21  outflow resistance 
           23  pilot pressure chamber 
           25  inflow conduit 
           27  outflow conduit 
           29  electronic control circuit