Method of monitoring refrigerant level

• US 6,708,508 B2
• Filed: 12/11/2001
• Issued: 03/23/2004
• Est. Priority Date: 12/11/2000
• Status: Expired due to Fees

• Current Assignee: BEHR GmbH & Company KG (MAHLE-STIFTUNG GmbH)
• Original Assignee: BEHR GmbH & Company KG (MAHLE-STIFTUNG GmbH)
• Inventors: Kirschner, Volker, Staffa, Karl-Heinz, Mittelstrass, Hagen, Walter, Christoph, Demuth, Walter, Kotsch, Martin, Krauss, Hans-Joachim, Sickelmann, Michael, Raiser, Harald, Heilig, Rainer
• Primary Examiner(s): Tanner, Harry B.
• Application Number:
  US10/012,027
• Publication Number:
  US 20020083723A1
• Time in Patent Office: 833 Days
• Field of Search: 621/25, 621/26, 621/27, 621/29, 622/08, 622/09, 621/30, 621/49
• US Class Current: 62/129
• CPC Class Codes: B60H 1/00978 Control systems or circuits characterised by failure of detection or safety means; Diagnostic methods
• CPC Class Codes: B60H 1/3225 characterised by safety arrangements, e.g. compressor anti-seizure means or by signalling devices
• CPC Class Codes: F25B 2309/061 with cycle highest pressure above the supercritical pressure
• CPC Class Codes: F25B 2500/222 Detecting refrigerant leaks
• CPC Class Codes: F25B 2600/17 by controlling the pressure of the condenser
• CPC Class Codes: F25B 2700/04 Refrigerant level
• CPC Class Codes: F25B 2700/1931 Discharge pressures
• CPC Class Codes: F25B 2700/2106 of fresh outdoor air
• CPC Class Codes: F25B 2700/21161 of the fluid heated by the condenser
• CPC Class Codes: F25B 2700/21173 at the outlet
• CPC Class Codes: F25B 2700/21174 of the refrigerant at the inlet of the evaporator
• CPC Class Codes: F25B 2700/21175 of the refrigerant at the outlet of the evaporator
• CPC Class Codes: F25B 45/00 Arrangements for charging or discharging refrigerant
• CPC Class Codes: F25B 49/005 of safety devices F25B49/02 and F25B49/04 take precedence
• CPC Class Codes: F25B 9/008 the refrigerant being carbon dioxide

Abstract

The invention relates to a method of refrigerant level monitoring in a refrigerant circuit of an air-conditioning or heat-pump system having a compressor and a refrigerant which may, depending on the operating point, be operated in the supercritical range. The method includes standstill level monitoring with the compressor switched off and/or in-operation level monitoring with the compressor switched on. In the case of in-operation level monitoring, the refrigerant overheat (dTü) at the evaporator is registered and, in the event of excessive overheat, it is concluded that there is underfilling. At a standstill, the pressure and temperature of the refrigerant are registered, and it is concluded that there is an improper refrigerant filling level if the pressure (p_KM) lies below a minimum pressure value (p_min) or the temperature (T_KM) lies above a maximum saturation temperature value (T_S) with the pressure being outside a predefinable intended pressure range ([p_u,p_o]).

Claims

1. A method of refrigerant level monitoring in a refrigerant circuit of an air-conditioning or heat-pump system having a compressor and a refrigerant which may, depending on the operating point, be operated in the supercritical range, the method comprising:

at least standstill level monitoring with the compressor switched off, comprising measuring both the pressure (p_KM) and the temperature (T_KM) of the refrigerant, and determining whether the measured refrigerant pressure lies below a temperature-independent predetermined minimum pressure value (p_min) or whether the measured refrigerant temperature lies above a predetermined maximum saturation temperature value (T_S) and the measured refrigerant pressure lies outside a predetermined target pressure range (p_u, p_o), in each case as an indication of improper filling.

2. A method as claimed in claim 1, wherein the target pressure range is limited downward by a temperature-dependent predetermined lower pressure limiting value (p_u) and/or upward by a temperature-dependent predetermined upper pressure limiting value (p_o).

3. A method as claimed in claim 1, further comprising in-operation level monitoring with the compressor switched on, measuring the refrigerant superheat (dTü

) at the evaporator of the system, and determining whether the measured superheat (dTü

) lies above a predetermined limiting value (dTü

_G), as an indication of improper filling.

4. A method as claimed in claim 1, wherein the system comprises an air-conditioning system employing CO₂ as refrigerant.

5. A method as claimed in claim 4, wherein, the refrigerant superheat (dTü

) at the evaporator is measured by using the difference between a refrigerant temperature (T_KVA) measured on the evaporator outlet side and a refrigerant temperature (T_KVE) measured on the evaporator inlet side, or by using the difference between a temperature (T_LVA), measured on the evaporator outlet side, of a medium led over the evaporator for the purpose of cooling the medium, and the refrigerant temperature (T_KVE) measured on the evaporator inlet side.

6. A method as claimed in claim 4, wherein the air-conditioning system comprises an automotive air-conditioning system.

7. An apparatus for refrigerant level monitoring in a refrigerant circuit of an air-conditioning or heat-pump system having a compressor and a refrigerant which may, depending on the operating point, be operated in the supercritical range, the apparatus comprising:

at least a system for standstill level monitoring with the compressor switched off, comprising detectors for measuring both the pressure (p_KM) and the temperature (T_KM) of the refrigerant, and a calculation circuit for determining whether the measured refrigerant pressure lies below a temperature-independent predetermined minimum pressure value (p_min) or whether the measured refrigerant temperature lies above a predetermined maximum saturation temperature value (T_S) and the measured refrigerant pressure lies outside a predetermined target pressure range (p_u, p_o), in each case as an indication of improper filling.

8. An apparatus as claimed in claim 7, further comprising a system for in-operation level monitoring with the compressor switched on, comprising detectors for measuring the refrigerant superheat (dTü

) at the evaporator of the system, and a calculation circuit for determining whether the measured superheat (dTü

) lies above a predetermined limiting value (dTü

_G), as an indication of improper filling.

9. An apparatus as claimed in claim 7, wherein the system comprises an air-conditioning system employing CO₂ as refrigerant.

10. An apparatus as claimed in claim 9, wherein the air-conditioning system comprises an automotive air-conditioning system.

11. An automotive vehicle, comprising an air-conditioner having a refrigerant circuit including a compressor and a refrigerant comprising CO₂ which may, depending on the operating point, be operated in the supercritical range, and a system for refrigerant level monitoring in the refrigerant circuit comprising an apparatus as defined by claim 7.

12. An automotive vehicle as claimed in claim 11, further comprising a system for in-operation level monitoring with the compressor switched on, comprising detectors for measuring the refrigerant superheat (dTü

) at the evaporator of the system, and a calculation circuit for determining whether the measured superheat (dTü

) lies above a predetermined limiting value (dTü

_G), as an indication of improper filling.