Method and diagnostic tester for detecting a fault in a cooling circuit of a motor vehicle

• US 9,403,416 B2
• Filed: 02/15/2012
• Issued: 08/02/2016
• Est. Priority Date: 03/23/2011
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Honig, Benno
• Primary Examiner(s): Do, Truc M
• Application Number:
  US14/006,826
• Publication Number:
  US 20140074349A1
• Time in Patent Office: 1,630 Days
• US Class Current: 1/1
• CPC Class Codes: B60H 1/00585 Means for monitoring, testing or servicing the air-conditioning
• CPC Class Codes: B60H 1/00978 Control systems or circuits characterised by failure of detection or safety means; Diagnostic methods
• CPC Class Codes: F25B 2700/1931 Discharge pressures
• 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: G01M 15/042 by monitoring a single specific parameter not covered by groups G01M15/06 - G01M15/12

Abstract

A method for detecting a fault in a cooling circuit of a motor vehicle, the cooling circuit having, in the flow direction of a refrigerant, a compressor, a condenser, an expansion device and an evaporator, includes the following steps: measuring a first refrigerant pressure when the compressor is turned off; turning on the compressor; and is characterized by the steps: measuring a second refrigerant pressure after a certain time interval; forming a differential value from the second refrigerant pressure measured previously and the first refrigerant pressure; and comparing the differential value with at least one differential value for detecting a fault in the cooling circuit.

Claims

1. A method for detecting a fault in a cooling circuit of a motor vehicle that includes in a flow direction of a refrigerant, a compressor, a condenser, an expansion device, and an evaporator, the method comprising:

(a) measuring a first refrigerant pressure when the compressor is turned off;

(b) turning on the compressor;

(c) measuring a second refrigerant pressure after a predetermined time interval, wherein the predetermined time interval is sufficient to allow the compressor to establish a constant pressure in the cooling circuit;

(d) forming a differential value from the second refrigerant pressure and the first refrigerant pressure; and

(e) comparing the differential value with at least one reference value for detecting a fault in the cooling circuit.

2. The method as recited in claim 1, wherein steps (d) and (e) are carried out by a diagnostic tester.

3. The method as recited in claim 1, wherein the motor vehicle includes an engine which is turned on prior to step (a), the engine being in an idling mode during the measurements.

4. The method as recited in claim 3, wherein the engine is allowed to run for a period of 10 seconds to 30 seconds prior to step (a).

5. The method as recited in claim 3, wherein the engine is allowed to run for a period of about 20 seconds prior to step (a).

6. The method as recited in claim 3, wherein a time interval from turning on the compressor until measuring the second refrigerant pressure is 10 seconds to 50 seconds.

7. The method as recited in claim 3, wherein a time interval from turning on the compressor until measuring the second refrigerant pressure is about 30 seconds.

8. The method as recited in claim 1, wherein the reference value depends on the first refrigerant pressure when the compressor is turned off, a time interval from turning on the compressor until measuring the second refrigerant pressure, and an ambient temperature.

9. The method as recited in claim 1, further comprising:

detecting a fault in the cooling circuit in step (e) when the differential value is smaller than the reference value.

10. The method as recited in claim 1, wherein the measurements of the first and second refrigerant pressures are carried out at a location in the cooling circuit just downstream from the compressor.

11. A diagnostic tester for ascertaining a fault in a cooling circuit of a motor vehicle that includes, in a flow direction of a refrigerant, a compressor, a condenser, an expansion device, and an evaporator, the diagnostic tester comprising:

an arrangement for forming a differential value from a first refrigerant pressure in the cooling circuit ascertained with the compressor turned off, and a second refrigerant pressure ascertained after a predetermined time interval after turning on the compressor, wherein the predetermined time interval is sufficient to allow the compressor to establish a constant pressure in the cooling circuit; and

an arrangement for comparing the differential value with at least one reference value to detect a fault in the cooling circuit.

12. The diagnostic tester as recited in claim 11, wherein the diagnostic tester is designed for connecting to a control unit.

13. The diagnostic tester as recited in claim 12, wherein the control unit includes one of a motor vehicle engine control unit and a motor vehicle air conditioning system control unit.