Abstract:
The invention relates to a filling device for motor vehicle air-conditioning systems which can be operated with harmless and natural refrigerants, in particular CO 2 . The filling device is to have a high safety standard, while at the same time being simple to operate and having a cost-effective makeup. For this purpose, the filling device comprises a connection ( 12 ) for connecting the device ( 10 ) to the air-conditioning system, a drainage line ( 18 ), containing a drainage valve ( 24 ), for draining off the refrigerant of the air-conditioning system in a defined manner, a pumping-off line ( 20 ) which has a pump ( 36 ) and is connected to the connection ( 12 ), for completely pumping off refrigerant residues and any other impurities, and a refrigerant feed line ( 22 ), connected to the connection ( 12 ), for filling the air-conditioning system with refrigerant from a refrigerant reservoir ( 44 ).

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a filling device for motor vehicle air-conditioning systems, which is required for the maintenance of air-conditioning systems in order to exchange old spent refrigerant for new refrigerant. 
     EP 0 315 296 B1 discloses a refrigerant recovery system, by means of which refrigerant can be extracted from an air-conditioning system, purified and fed to the air-conditioning system again. This known refrigerant recovery system is suitable for air-conditioning systems which are operated with the refrigerants R 12  or R 134   a.  These refrigerants, because of their hydrocarbon content, are extremely harmful to the environment and should not be discharged into the environment, and it is therefore necessary to have a refrigerant recovery system of this type with a multiplicity of components, such as an evaporator, condenser, compressor and various valves, and with a complicated makeup. 
     A refrigerant recovery system of this type is not necessary or expedient for air-conditioning systems which contain harmless and natural refrigerants, for example, CO 2 . 
     One object of the present invention, therefore, is to provide a filling device for a motor vehicle air-conditioning system that uses harmless refrigerants, in particular CO 2 , which has a simple makeup and is correspondingly cost-effective and which meets a high safety standard. 
     Another object of the invention is to provide a method for draining and filling an air-conditioning system. 
     SUMMARY OF THE INVENTION 
     In accomplishing the objects of the invention, there has been provided according to one aspect of the invention, a filling device for a motor vehicle air-conditioning system comprising: 
     (a) a connection for connecting the device to the air-conditioning system; 
     (b) a drainage line, comprising a drainage valve, for draining off the refrigerant of the air-conditioning system at a predetermined rate; 
     (c) a pumping-off line which comprises a pump and is connected to the connection, for pumping off refrigerant residues substantially completely; and 
     (d) a refrigerant feed line, connected to the connection, for filling the air-conditioning system with refrigerant from a refrigerant source. 
     According to another aspect of the present invention, there is provided a draining and filling device for motor vehicle air-conditioning system comprising: 
     (a) a connector for connecting the filling device to a motor vehicle air conditioning system; 
     (b) a connecting line connected to said connector, said line comprising: 
     (i) a drainage line for draining off refrigerant from said motor vehicle air conditioning system; 
     (ii) a pumping-off line for pumping off refrigerant residues from said motor vehicle air conditioning system, and 
     (iii) a refrigerant feed line for filling said motor vehicle air conditioning system with refrigerant; 
     (c) a refrigerant outlet arranged at the end of said drainage line for discharging drained off refrigerant into the surroundings; 
     (d) a refrigerant reservoir connected to said line via said refrigerant feed line; 
     (e) a heater for heating said refrigerant reservoir and refrigerant contained therein; and 
     (f) a weighing device on which said refrigerant reservoir is mounted. 
     According to still another aspect of the present invention, there is provided a method of draining and filling a motor vehicle air-conditioning system comprising: 
     (a) connecting a connector of a filling device to a filling valve of said motor vehicle air conditioning system; closing a third shutoff valve; opening the filling valve as well as a first shutoff valve, a second shutoff valve and a fourth shutoff valve; 
     b) establishing refrigerant throughflow via said connector through a device for reducing pressure; discharging old refrigerant exiting from said device via an oil separator into the atmosphere; 
     c) pumping off substantially all refrigerant, moisture or dirt remaining in the motor vehicle air-conditioning system via said connector; 
     d) setting a filling pressure as a function of temperature and content of a refrigerant filling reservoir; 
     e) heating said refrigerant filling reservoir; 
     f) filling said motor vehicle air-conditioning system with refrigerant via said connector; and 
     g) separating said draining and filling device from said motor vehicle air-conditioning system. 
     Further objects, features and advantages of the invention will become apparent from the detailed description of preferred embodiments that follows, when considered together with the accompanying drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The FIGURE shows a schematic block diagram of the filling device according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     According to the invention, the filling device has only one connection for connecting the device to the air-conditioning system, with essentially three lines branching off from the connection. The first line is designed as a drainage line and contains a drainage valve, by means of which the refrigerant, in particular CO 2 , can be drained off in a defined manner. A defined slow drainage of the refrigerant is particularly important in CO 2  air-conditioning systems, since, if the CO 2  were drained off in an uncontrolled way, the polymers, for example seals, used in the air-conditioning system could be damaged. A second line is designed as a pumping-off line having a pump, by means of which moisture, dirt and residual filling quantities of the CO 2  can be pumped off from the air-conditioning system completely, so that the air-conditioning system can then be filled with fresh CO 2  via a feed line. The CO 2  is provided in a commercially available refrigerant reservoir. 
     The filling device according to the invention offers a high safety standard, has a simple and correspondingly cost-effective makeup and can therefore be operated in a simple way even by unskilled personnel. 
     In a refinement of the invention, an oil separator is provided in the drainage line, so that, when the refrigerator oil co-transported by the CO 2  is being drained off, this oil is not discharged into the environment, but can be collected and disposed of. 
     In order to ensure a defined rate of drainage of the CO 2 , a pressure reducer is provided in the drainage line, so that the CO 2  can be drained off at a predetermined mass or volume flow rate. 
     So that the fresh CO 2  filling pressure can be set reliably, a pressure gage is provided in the feed line. 
     To enable reaching the necessary filling pressures, the refrigerant reservoir has heating means by which the CO 2  present in the reservoir can be heated, so that the air-conditioning system can be filled at the appropriate pressure, for example 70 bar. In order to assure that the heating power does not become too high, thus resulting in an excessively high pressure which could cause damage to the air-conditioning system, a safety circuit for limiting the heating power is provided. 
     In a motor vehicle air-conditioning system with CO 2  as refrigerant, a defined quantity of CO 2  must be introduced, while the tolerance of ±10 grams should not be exceeded. In order that these tolerance limits can be adhered to, a balance is provided, by means of which the refrigerant quantity extracted from the reservoir can be determined exactly. 
     In a further refinement of the invention, the pump, for emptying the air-conditioning system completely, is designed as a vacuum pump, by means of which the gaseous CO 2  can be pumped off and a defined vacuum can be generated in the lines and components of the refrigerating circuit, so that a leakage test can also be carried out on the refrigerating circuit. When a vacuum is being generated, the CO 2  dissolved in the refrigerator oil is also expelled from the oil and pumped off. The vacuum generated serves additionally for dehumidifying the refrigerating circuit. 
     To simplify the operating capability, a control apparatus for controlling all the components of the filling device, such as the valves, the heating means, the balance, etc., is provided, by means of which the individual components can be activated centrally. All the essential operations, such as the defined drainage of the refrigerant, the generation of the vacuum in the refrigerating circuit, the checking and setting of the filling pressure and the defined filling of the air-conditioning system with a defined quantity of refrigerant with a defined mass flow, can thereby be automated. 
     To ensure that the individual lines can withstand the high pressures which may arise, they should consist preferably of steel or aluminum. 
     Maximum flexibility of use is advantageous, and to this end, the entire filling device is accommodated in a housing and is designed to be transportable. This may be implemented in a known way, for example, by means of rollers on the housing. 
     The invention is explained in detail below by means of an exemplary embodiment with reference to the drawing. The single figure of the drawing shows a schematic block diagram of the filling device according to the invention and is merely exemplary of the invention. 
     A filling device  10  according to the invention has a connection  12  for connecting the filling device  10  to a motor vehicle air-conditioning system. The connection  12  has connected to it a line  14  which can be shut off via a first shutoff valve  16  and which is divided into a drainage line  18 , a pumping-off line  20  and a refrigerant feed line  22 . 
     The drainage line  18  has a second shutoff valve  24 , a device for reducing the pressure  26  and an oil separator  30  in a series connection. Arranged at the end of the drainage line  18  is a refrigerant outlet  32 , via which drained-off refrigerant can be discharged into the surroundings. 
     The pumping-off line  20  has a third shutoff valve  34  and a following vacuum pump  36 . Between the shutoff valve  34  and the vacuum pump  36 , a safety line  38  branches off, in which a nonreturn valve is arranged, so that, when large quantities of refrigerant appear at the inlet  40  of the vacuum pump  36 , they do not have to be removed completely via the vacuum pump  36 , but can be discharged into the surroundings via the safety line  38  and the nonreturn valve  40 . 
     The refrigerant feed line  22  connects the line  14  to a refrigerant reservoir  44 , in which the refrigerant, in particular CO 2 , to be introduced into the air-conditioning system is provided. For safety reasons, commercially available liquid-gas bottles with a riser are used as reservoir  44 . The reservoir  44  can be cut off via a gas-bottle valve  46 . The feed line  22  can likewise be shut off via a fourth shutoff valve  48 . When the valves  46 ,  48  and  16  are opened in order to fill the air-conditioning system, a throttle device  50  prevents refrigerant from flowing too quickly out of the reservoir  44  into the line system of the filling device  10 . The filling pressure of the air-conditioning system is set as a function of the temperature and of the refrigerant quantity present in the reservoir  44  and can be read off on pressure gages  52  and  54  provided in the line  14  and the feed line  22 . In order to cause refrigerant to flow out of the reservoir  44 , the operating pressure in the reservoir  44  must always be higher than the pressure currently prevailing in the refrigerating circuit. In order, as required, to generate the operating pressures necessary for this purpose in the reservoir, the refrigerant reservoir  44  has heating means  60 , by which the refrigerant reservoir and therefore the refrigerant located in it can be heated. 
     The heating power can be regulated via an electronic regulating circuit, so that the corresponding operating pressure is reached in the reservoir and the heating means  60  is regulated to a lower setting when the pressures are too high. Furthermore, a mechanical safety cutout  62  is provided, having a temperature sensor  63  which is arranged on the reservoir  44  and which is connected to the safety cutout via a capillary tube. When the safety limit temperature is reached, the supply of electricity to the heating means  60  is interrupted. 
     A second safety line  56 , which can be opened via a safety valve  58 , branches off from the feed line  22 . In an emergency, the safety valve  58  can also be opened by hand, when the pressure in the feed line  22  is too high for unknown reasons. 
     The refrigerant reservoir  44  is mounted on a weighing device, such as balance  64 , so that an exactly determinable refrigerant quantity can be extracted from the refrigerant reservoir  44  via an indicator and control apparatus  66  of the balance  64 . Other conventional devices for measuring quantity of refrigerant supplied to the air-conditioning system can be employed instead, including flow measuring devices. 
     The motor vehicle air-conditioning system is filled according to the following method steps: 
     In the first place, the filling device  10  is connected with its connection  12  to a filling valve  68  of the motor vehicle air-conditioning system which is arranged on the vehicle. The third shutoff valve  34  is closed, the filling valve  68  and also the first, second and fourth shutoff valves  16 ,  24  and  48  are opened, and refrigerant is fed to the device for reducing the pressure  26  in such a way that a desired throughflow is established. Old refrigerant can then be discharged slowly via the oil separator  30  into the atmosphere in a defined manner via the outlet  32 . When the pressure in the air-conditioning system and in the lines of the filling device  10  has fallen to ambient pressure and therefore the throughflow through the drainage line  18  has fallen to zero, the second shutoff valve  24  is closed, the vacuum pump  36  is started, and the third shutoff valve  34  is opened, so that the remaining refrigerant and any other moisture and dirt are then pumped off from the air-conditioning system via the pumping-off line  20 . 
     After the remaining refrigerant has been pumped off from the air-conditioning system, the third shutoff valve  34  and the filling valve  68  are closed and the gas-bottle valve  46  is opened. A specific filling pressure is then set as a function of the temperature and content of the reservoir  44 . In order to reach the filling pressure, the refrigerant reservoir  44  may, if appropriate, be heated via the heating means  60 . The indicator  66  of the balance  64  has previously been read off, so that it is possible to determine the refrigerant extracted from the refrigerant reservoir  44 . Refrigerant then flows from the refrigerant reservoir  44  into the line system of the filling device  10 . The refrigerating circuit of the air-conditioning system is filled by opening the filling valve  68  on the vehicle in a controlled way. 
     After the prescribed refrigerant quantity is reached, the filling valve  68  is closed. The refrigerant quantity introduced corresponds to the decrease in weight of the reservoir  44 . The refrigerant in the line system of the filling device  10  is discharged into the surroundings by the gas-bottle valve  46  being closed and by the second shutoff valve  24  being opened. The filling device  10  can subsequently be separated from the refrigerating circuit. 
     The entire emptying and filling operation may take place automatically by means of a conventional control apparatus, not illustrated in any more detail, as already described initially. For this purpose, advantageously, the refrigerant quantity to be introduced can be entered in the control apparatus, e.g. a microprocessor control system. 
     The disclosure of German Patent Application No. 100 15 976.1, filed Mar. 30, 2000, is hereby incorporated by reference in its entirety.