US-20260124876-A1 - REFRIGERANT CHARGE DIAGNOSTIC PROCEDURE FOR VEHICLE HEAT PUMP SYSTEMS

US20260124876A1US 20260124876 A1US20260124876 A1US 20260124876A1US-20260124876-A1

Abstract

A diagnostic for heat pumps may include causing heated coolant in a coolant loop to circulate through a heat exchanger that is thermally coupled to a refrigerant loop. The temperature and pressure of the refrigerant may be measured while the heated coolant is circulated through the heat exchanger, and the measured pressure and temperature may be compared to pressures and temperatures for systems that are properly charged with refrigerant to determine if the heat pump system is properly charged.

Inventors

Scott Thomas Vehige

Assignees

FORD GLOBAL TECHNOLOGIES, LLC

Dates

Publication Date: 20260507
Application Date: 20241101

Claims (20)

1 . A method of determining refrigerant charge in vehicle heat pump systems having a heat exchanger that thermally couples a coolant loop to a refrigerant loop; the method comprising: heating and circulating coolant through the coolant loop and through the heat exchanger of the vehicle heat pump system while refrigerant is not circulating through the refrigerant loop of the heat pump system; measuring temperature and pressure of refrigerant in the refrigerant loop while heating and circulating the coolant through the coolant loop and through the heat exchanger; and comparing measured temperature and pressure of the refrigerant to expected temperature and pressure to determine if the refrigerant charge satisfies predefined charge criteria.
2 . The method of claim 1 , wherein: heating the coolant includes actuating an electric heater; and circulating the coolant includes actuating a pump.
3 . The method of claim 1 , wherein: the expected temperature and pressure comprises a table including a plurality of temperatures and corresponding pressures.
4 . The method of claim 3 , wherein: the expected temperature and pressure is determined empirically by measuring temperature and pressure in a vehicle heat pump system that is fully charged.
5 . The method of claim 1 , wherein: the heat exchanger comprises a coolant cooled condenser; the refrigerant loop includes: 1 ) a compressor, 2 ) an expansion valve, 3 ) an outside heat exchanger, and 4 ) a pressure sensor; and wherein the compressor compresses refrigerant whereby, when the compressor is actuated, compressed refrigerant exits an outlet of the compressor and flows through the coolant cooled condenser, through the expansion valve, through the outside heat exchanger, and past the pressure sensor before flowing into an inlet of the compressor; and including: measuring pressure of the refrigerant using the pressure sensor.
6 . The method of claim 1 , including: determining if a refrigerant charge level needs to be measured prior to operation of the heat pump utilizing predefined diagnostic criteria.
7 . The method of claim 6 , wherein: the predefined diagnostic criteria comprises at least one factor selected from the group consisting of: low refrigerant pressure from a previous vehicle drive cycle, a battery reset, and an elapsed time since a prior determination of refrigerant charge in the vehicle.
8 . The method of claim 5 , including: disabling the compressor if the refrigerant charge does not satisfy predefined charge criteria.
9 . The method of claim 8 , including: setting a trouble code if the refrigerant charge does not satisfy predefined charge criteria.
10 . The method of claim 8 , wherein: the trouble code is not set if the refrigerant charge satisfies predefined charge criteria.
11 . The method of claim 1 , wherein: the expected temperature and pressure correspond to temperature and pressure for a fully charged heat pump system.
12 . The method of claim 11 , wherein: the expected temperature and pressure comprise a plurality of temperatures and pressures for a fully charged heat pump system.
13 . The method of claim 12 , wherein: the predefined charge criteria comprises a plurality of temperatures and corresponding pressures measured at a series of times, wherein the plurality of measured temperatures and pressures are within predefined ranges about expected temperatures and pressures for a fully charged heat pump system.
14 . A vehicle comprising: a powered drive system; a body; a heat pump system that is configured to heat a cabin of the vehicle, the heat pump system including a first heat exchanger that thermally couples a coolant loop of the heat pump system to a refrigerant loop of the heat pump system, the coolant loop including a coolant heater and a pump that are fluidly coupled to the first heat exchanger and a thermal load of the vehicle, the refrigerant loop including a compressor that is fluidly coupled to the first heat exchanger, an expansion valve, and an outside heat exchanger; a controller configured to: actuate the coolant heater and the pump to cause coolant to circulate through the coolant loop and through the first heat exchanger of the vehicle heat pump system prior to operation of the refrigerant loop of the heat pump system; and compare temperature and pressure of the refrigerant measured while the coolant is being heated and circulated through the coolant loop and through the first heat exchanger to expected refrigerant temperature and pressure for a fully charged heat pump system to determine if the refrigerant charge satisfies predefined charge criteria.
15 . The vehicle of claim 14 , wherein: the expected temperature and pressure comprises a table including a plurality of temperatures and corresponding pressures.
16 . The vehicle of claim 14 , wherein: the controller is configured to prevent operation of the refrigerant loop if the refrigerant charge does not satisfy the predefined charge criteria.
17 . The vehicle of claim 16 , wherein: the controller is configured to permit operation of the refrigerant loop if the refrigerant charge satisfies the predefined charge criteria.
18 . The vehicle of claim 14 , wherein: the predefined charge criteria comprises at least one temperature and pressure measured at the same time, wherein the at least one measured temperature and pressure are within predefined ranges of expected temperature and pressure.
19 . A method of diagnosing refrigerant charge of a vehicle heat pump system having a heat exchanger that thermally couples a coolant loop to a refrigerant loop; the method comprising: heating and circulating coolant through the coolant loop and through the heat exchanger of the vehicle heat pump system while a compressor of the refrigerant loop is deactivated; measuring changes in temperature and pressure of the refrigerant that result from heating and circulating the coolant through the coolant loop; and comparing the changes in the measured temperature and pressure of the refrigerant to expected changes in temperature and pressure to determine if the heat pump system is properly charged with refrigerant.
20 . The method of claim 19 , including; determining that the heat pump system is properly charged with refrigerant if the changes in the measured temperature and pressure of the refrigerant are within predefined threshold ranges about expected changes in temperature and pressure for a fully charged heat pump system.

Description

FIELD OF THE DISCLOSURE The present disclosure generally relates to heat pumps, and more specifically to a diagnostic procedure to determine if the heat pump system has a proper refrigerant charge. BACKGROUND OF THE DISCLOSURE Heat pump systems have been used in motor vehicles and the like. Proper operation of a heat pump system may require that the system is properly charged with a refrigerant. SUMMARY OF THE DISCLOSURE An aspect of the present disclosure is a method of determining refrigerant charge in vehicle heat pump systems having a heat exchanger that thermally couples a coolant loop to a refrigerant loop. The charge includes heating and circulating coolant through the coolant loop and through the heat exchanger of the vehicle heat pump system without actuating a compressor of the refrigerant loop of the heat pump system. The method further includes measuring temperature and pressure of refrigerant in the refrigerant loop while heating and circulating coolant through the coolant loop and through the heat exchanger of the vehicle heat pump system. The method also includes comparing the measured temperature and pressure of the refrigerant to expected temperature and pressure to determine if the refrigerant charge satisfies predefined charge criteria. Embodiments of the first aspect of the present disclosure can include any one or a combination of the following features: The method may optionally include heating the coolant by actuating an electronic heater.Circulating the coolant optionally includes actuating a pump.The expected temperature and pressure is optionally in the form of a table including a plurality of temperatures and corresponding pressures.The expected temperature and pressure is optionally determined empirically by measuring temperature and pressure in a vehicle heat pump system that is fully charged.The heat exchanger optionally comprises a coolant cooled condenser. The refrigerant loop optionally includes: 1) a compressor, 2) an expansion valve, 3) an outside heat exchanger and 4) a pressure sensor. The compressor may compress refrigerant whereby compressed refrigerants exits an outlet of the compressor and flows through the coolant cooled condenser, through the expansion valve, through the outside heat exchanger, and through (or past) the pressure sensor before flowing into an inlet of the compressor. The method optionally includes measuring pressure of the refrigerant using the pressure sensor.The method may optionally include determining if a refrigerant charge level needs to be measured prior to operation of the vehicle utilizing predefined diagnostic criteria.The predefined diagnostic criteria may include at least one factor selected from the group consisting of low refrigerant pressure from a previous vehicle drive cycle, a battery reset, and an elapsed time since a prior determination of refrigerant charge in the vehicle.The method may optionally include disabling the compressor if the refrigerant charge does not satisfy predefined charge criteria.The method may optionally include setting a trouble code if the refrigerant charge does not satisfy predefined charge criteria.The method may optionally include not setting the trouble code if the refrigerant charge satisfies predefined charge criteria.The expected temperature and pressure optionally correspond to temperature and pressure for a fully charged heat pump system.The expected temperature and pressure optionally comprise a plurality of temperature and pressures for a fully charged heat pump system.The predefined charge criteria optionally comprises a plurality of temperatures and corresponding pressures measured at a series of times, wherein the plurality of measured temperatures and pressures are within predefined ranges about expected temperatures and pressures for a fully charged heat pump system. Another aspect of the present disclosure is a vehicle including a powered drive system, a body, and a heat pump system that is configured to heat a cabin of the vehicle. The heat pump system includes a first heat exchanger that thermally couples a coolant loop of the heat pump system to a refrigerant loop of the heat pump system. The coolant loop includes a coolant heater and a pump that are fluidly coupled to the first heat exchanger and thermal load of the vehicle. The refrigerant loop includes a compressor that is fluidly coupled to the first heat exchanger, and expansion valve, and an outside heat exchanger. The vehicle further includes a controller that is configured to actuate the coolant heater and the pump to cause coolant to circulate through the coolant loop and through the first heat exchanger of the vehicle heat pump system prior to operation of the refrigerant loop of the heat pump system. The controller is also configured to compare temperature and pressure of the refrigerant measured while the coolant is being heated and circulated through the coolant loop and through the first heat exchanger to expected refriger