Vehicle HVAC system

A HVAC system and method for a vehicle is disclosed. The air conditioning portion of the HVAC system may be able to store and release refrigerant in charge bottle while operating in an air conditioning mode. The air conditioning portion of the HVAC system may be able to employ the refrigerant flowing through the evaporator to provide supplemental heat.

BACKGROUND OF THE INVENTION

The present application relates generally to a heating ventilating and air conditioning (HVAC) system for a vehicle.

Conventional vehicle HVAC systems have a refrigeration circuit and a heating circuit. The conventional refrigeration circuit includes a compressor, which compresses the refrigerant and sends it through to a condenser, where heat is removed from the refrigerant. The refrigerant then flows through an expansion device, dropping the temperature further, before it enters an evaporator in an HVAC module of a passenger compartment. The evaporator absorbs heat from air flowing through it before the air flows into the passenger compartment. The refrigerant then flows from the evaporator back into the compressor to start the process over again. The conventional heating circuit employs a heater core in the HVAC module in the passenger compartment, where hot coolant from the engine cooling system flows through it to heat the air before it flows into the passenger compartment.

The refrigeration circuit has drawbacks in that, for refrigerant systems employing expansion valves and receiver dryers, storing the refrigerant above a critical charge by sub-cooling is required. The refrigerant storage occurs in the condenser, which increases the pressure drop in the system and thus reduces the condenser capacity. This results in reduced system efficiency.

The heating circuit has drawbacks in that the heater core cannot provide heat to the air flowing through it until the engine has time to warm up the coolant. This becomes even more of a concern as modern engines become more efficient, thus producing less excess heat to warm up the engine coolant. Electric powered heaters can be provided for supplemental heating while the coolant warms up. However, this electric heat may not be very energy-efficient and may further burden the vehicle electrical system that may be operating near its capacity in the first place.

Thus, it is desirable to provide an HVAC system for a vehicle that may provide heating or air conditioning in a more efficient or timely manner.

SUMMARY OF THE INVENTION

An embodiment contemplates a vehicle HVAC system having an air conditioning portion that may include a compressor, a condenser operatively engaging a refrigerant output from the compressor, an evaporator, and an expansion device operatively engaging a refrigerant output from the condenser and a refrigerant input to the evaporator. The embodiment may also include a charge bottle selectively connectable to the refrigerant output from the condenser.

An embodiment contemplates a method of operating a vehicle HVAC system having an air conditioning portion with a main refrigerant loop, the method comprising the steps of: determining if air conditioning is desired; determining if a refrigerant charge is too high; determining if a refrigerant charge is too low; opening a refrigerant outflow valve, located between a refrigerant output of a condenser and a charge bottle, to remove some of the refrigerant charge from the main refrigerant loop and store it in the charge bottle, if determined that air conditioning is desired and the refrigerant charge is too high; and opening a refrigerant inflow valve, located between a refrigerant input of an evaporator and the charge bottle, to add some of the refrigerant charge from the charge bottle into the main refrigerant loop, if determined that air conditioning is desired and the refrigerant charge is too low.

A method of operating a vehicle HVAC system having an air conditioning portion with a main refrigerant loop, the method comprising the steps of: determining if supplemental heat is desired; directing a refrigerant from a refrigerant output of a compressor into a refrigerant input to an evaporator, bypassing a condenser and an expansion device, if determined that supplemental heat is desired; determining if air conditioning is desired; and directing a refrigerant from the refrigerant output of the compressor into a refrigerant input of the condenser, and from a refrigerant output of the condenser through an expansion device into the refrigerant input of the evaporator, if determined that air conditioning is desired.

An advantage of an embodiment may be overall improved operating efficiency of the refrigerant system, which may allow for less power consumption. The effective condenser capacity may be maximized, minimizing the pressure drop across the condenser.

An advantage of an embodiment may be improved stability in charge sensitive systems since the appropriate valve can be opened for short durations when there is excess or insufficient compressor mass flow capacity.

An advantage of an embodiment may be to provide the capability to store reserve cooling charge for short durations.

An advantage of an embodiment may be the ability of the air conditioning portion of the HVAC system to provide supplemental heating.

DETAILED DESCRIPTION

FIG. 1illustrates a schematic diagram of an air conditioning portion20of an HVAC system22for a vehicle24, with a refrigerant flow path shown for a standard air conditioning operating mode. The refrigerant lines with arrows in FIGS.1and3-5indicate the direction of refrigerant flow for the particular operating mode illustrated in that figure, while refrigerant lines without arrows indicate no refrigerant flow through those lines for that particular operating mode.

The air conditioning portion20may be partially in an engine compartment26and partially in a passenger compartment28of the vehicle24. A compressor30—typically driven by a vehicle engine (not shown)—compresses the refrigerant, which then travels from a refrigerant output of the compressor30through a refrigerant line32to a three-way valve34. The three-way valve34connects to a refrigerant line36leading to a refrigerant input to a condenser38and to a refrigerant line40leading to a charge bottle42. The three-way valve34is electrically operable to switch the flow between refrigerant line36and refrigerant line40. A refrigerant line44extends from a refrigerant output of the condenser38to a thermostatic expansion valve46. A refrigerant line48extends from the expansion valve46to a refrigerant input to an evaporator50, located in an HVAC module51in the passenger compartment28, and another refrigerant line52extends from a refrigerant output of the evaporator50to the expansion valve46. Refrigerant line54extends from the expansion valve46to a refrigerant input to the compressor30.

The expansion valve46has a variable orifice that controls the amount of refrigerant flowing into the evaporator50, with the orifice controlled by the pressure and temperature of the refrigerant leaving the evaporator50. This is why the expansion valve46is in communication with the refrigerant at both the inlet and outlet to the evaporator50.

The air conditioning portion20of the HVAC system22also includes a pair of valves that can be automatically opened and closed to selectively allow flow to and from the charge bottle42. A refrigerant line56extends from the charge bottle42to a refrigerant inflow valve58, and another refrigerant line60extends from the refrigerant inflow valve58to the inlet to the evaporator50. Refrigerant line62extends from the charge bottle42to a refrigerant outflow valve64, and another refrigerant line66extends from the refrigerant outflow valve64to refrigerant line44. The term inflow is used relative to valve58to indicate that refrigerant flows from the charge bottle42back into the main refrigerant loop67when the inflow valve58is open. The term outflow is used relative to valve64to indicate that refrigerant flows out from the main refrigerant loop67into the charge bottle42when the outflow valve64is open.

The refrigerant flow path, as indicated by the arrows inFIG. 1, results from the three-way valve34being positioned to direct flow to the condenser38, and both the inflow and outflow valves58,64being closed. This is the refrigerant flow path for a standard air conditioning operating mode. One will note that, in this operating mode, there is no flow into or out of the charge bottle42—all of the flow is through the main refrigerant loop67.

FIG. 2illustrates a possible packaging arrangement for a portion of the HVAC system22illustrated inFIG. 1. While other packaging arrangements for the components shown inFIG. 1can be used, this packaging arrangement may provide for a relatively compact and easy to install assembly. The arrangement described inFIG. 2has many items in common with that ofFIG. 1and to avoid unnecessary repetition of the description, the same reference numerals have been used to refer to the same items, even if not specifically discussed relative toFIG. 2. The condenser38may include a heat exchanger core68and a condenser header70. The charge bottle42may be mounted to the condenser header70, with the three-way valve34and the refrigerant inflow valve58in close proximity thereto. The three-way valve34may be mounted close to the condenser refrigerant inlet72, while the refrigerant outflow valve64may be mounted close to the condenser refrigerant outlet74. While improving packaging, this arrangement also allows for the outlet of the charge bottle42leading to the refrigerant inflow valve58to be at the bottom of the charge bottle42. This may avoid concerns with oil trapping.

FIG. 3is a schematic diagram similar toFIG. 1, but illustrating a refrigerant flow path when the HVAC system22is in the air conditioning operating mode and refrigerant is flowing from the main refrigerant loop67into the charge bottle42. The arrangement described inFIG. 3has the same elements shown asFIG. 1and to avoid unnecessary repetition of the description, the same reference numerals have been used to refer to the same elements, even if not specifically discussed relative toFIG. 3. Removing some of the refrigerant charge from the main refrigerant loop67is accomplished by positioning the three-way valve34to direct flow through the condenser, leaving the refrigerant inflow valve58closed, and opening the refrigerant outflow valve64until the charge is corrected by removing the desired amount of refrigerant from the main refrigerant loop67and storing it in the charge bottle42.

FIG. 4illustrates a schematic diagram similar toFIG. 1, but illustrating a refrigerant flow path when the HVAC system22is in the air conditioning operating mode and refrigerant is flowing from the charge bottle42into the main refrigerant loop67. The arrangement described inFIG. 4has the same elements shown asFIG. 1and to avoid unnecessary repetition of the description, the same reference numerals have been used to refer to the same elements, even if not specifically discussed relative toFIG. 4. Adding some refrigerant charge to the main refrigerant loop67is accomplished by positioning the three-way valve34to direct flow through the condenser, leaving the refrigerant outflow valve64closed, and opening the refrigerant inflow valve58until the charge is corrected by adding the desired amount of refrigerant stored in the charge bottle42to the main refrigerant loop67.

FIG. 5illustrates a schematic diagram similar toFIG. 1, but illustrating a refrigerant flow path when the HVAC system22is in a supplemental heat operating mode. The arrangement described inFIG. 5has the same elements shown asFIG. 1and to avoid unnecessary repetition of the description, the same reference numerals have been used to refer to the same elements, even if not specifically discussed relative toFIG. 5. Providing supplemental heat is accomplished by positioning the three-way valve34to direct the refrigerant into the charge bottle42rather than through the condenser38, opening the refrigerant inflow valve58to receive refrigerant from the charge bottle42and direct it to the evaporator50(bypassing the expansion valve46), and leaving the outflow valve64closed.

FIG. 6illustrates a possible method for operating the air conditioning system shown inFIGS. 1-5. A determination is made whether supplemental heat is desired, block100. If it is, then the three-way valve34is positioned to bypass the condenser38and the refrigerant inflow valve58is opened, block102, and the compressor30is operated, block104. If supplemental heat is not desired, then a determination is made whether air conditioning is desired, block106. If not, then compressor operation is ceased, block108.

If air conditioning is desired, a determination is made whether the refrigerant charge is too high, block110. If the refrigerant charge is too high, the three-way valve34is positioned for flow through the condenser38, the refrigerant outflow valve64is opened, and the compressor30is operated while the refrigerant charge is reduced to the desired level, block112. Once the refrigerant charge is reduced to the desired level, the three-way valve34is maintained for flow through the condenser38, the outflow valve64is closed, block114, and the compressor30continues to operate, block104.

If the refrigerant charge is not too high, then a determination is made whether the refrigerant charge is too low, block116. If the refrigerant charge is too low, the three-way valve34is positioned for flow through the condenser38, the refrigerant inflow valve58is opened, and the compressor30is operated while the refrigerant charge is increased to the desired level, block118. Once the refrigerant charge is increased to the desired level, the three-way valve34is maintained for flow through the condenser38, the inflow valve58is closed, block114, and the compressor continues to operate, block104.

If the refrigerant charge is not too low, then the three-way valve34is maintained for flow through the condenser38, both the inflow and outflow valves58,64are left closed, block114, and the compressor30is operated, block104.

This method allows for maintaining a more desirable amount of refrigerant charge in the main refrigerant loop67during air conditioning operating mode, which may improve system efficiency at different ambient and evaporator load conditions. The improved system efficiency may reduce the work the compressor30does, which may improve vehicle fuel economy. In addition, the valves34,58can be used to bypass the condenser38, allowing the evaporator50to be used to provide supplemental heat.

An alternative to the system and method embodiments disclosed above may include, eliminating the charge bottle42and refrigerant outflow valve64from the HVAC system22, and eliminating the method steps relating to increasing or decreasing the refrigerant charge in the main refrigerant loop67. This will allow for operation in a standard air conditioning mode as well as a supplemental heat mode, but will eliminate the modes that add or remove refrigerant from the main refrigerant loop67. Another alternative to the system and method embodiments disclosed above may include eliminating the three-way valve34from the HVAC system22, and eliminating the method steps relating to providing supplemental heat. This will allow for a standard air conditioning operating mode, as well as the air conditioning operating modes that allow refrigerant charge to be removed from or added to the main refrigerant loop67. An additional alternative embodiment to the HVAC system22disclosed above may include replacing the three-way valve34with two open/close only valves (not shown).