GB2360579A

GB2360579A - Air conditioning system for a motor vehicle

Info

Publication number: GB2360579A
Application number: GB0006035A
Authority: GB
Inventors: Laurent Pittion; Jean-Luc Menager
Original assignee: Renault SAS; Delphi Technologies Inc
Current assignee: Renault SAS; Delphi Technologies Inc
Priority date: 2000-03-14
Filing date: 2000-03-14
Publication date: 2001-09-26
Also published as: GB0006035D0

Abstract

An air conditioning system (10) for a passenger compartment of a motor vehicle comprises a first heat exchanger (14) positionable outside the passenger compartment; a second heat exchanger (18) positionable inside the passenger compartment; an expansion device (16) positioned in a first fluid passage (22) between the heat exchangers; a compressor (12) for pumping fluid into a second fluid passage (24) either in a first direction (X) or in a second direction (Y); control means (30) electrically connected to the compressor for controlling the operation of the compressor; an air duct (56) for opening into the passenger compartment, the second heat exchanger being positioned in the duct; an air blower (60) positioned in the duct for blowing air through the second heat exchanger; an opening (62) in the duct leading to ambient air located downstream of the second heat exchanger; a first gate (66) pivotally mounted in the duct at a position downstream of the opening, the first gate normally substantially closing the opening; controlling means (30) and actuator (70) for moving the first gate to a second position to open the opening and to substantially close the duct during a period of pumping of the fluid in the second direction (Y). Means (30) actuates the air blower when the first gate is in the second position, thereby reducing the risk of internal fogging of the windscreen.

Description

2360579 AIR CONDITIONING SYSTEM FOR A MOTOR VEHICLE

Technical Field

The present invention relates to an air conditioning system for the passenger compartment of a motor vehicle, and more particularly to an air conditioning system which can provide both heating and cooling for the passenger compartment; and to a method of operating such an air conditioning system.

Background of the Invention

Air conditioning systems for the passenger compartments of motor vehicles are well known. Such systems include arrangements for the flow of air across the internal surface of the windscreen of the motor vehicle.

In general, these systems comprise an inside heat exchanger (located within the passenger compartment) and an outside heat exchanger (located outside the passenger compartment). A pair of fluid passages connect the heat exchangers to allow the circulation of fluid through the heat exchangers. An expansion device is positioned in one of the fluid passages. A compressor and accumulatorldryer is positioned in the other fluid passage. When fluid is pumped by the compressor through the outside heat exchanger, the expansion device, the inside heat exchanger and the accumulator/dryer in succession, air passing through the inside heat exchanger is cooled as the air flows into the passenger compartment across the windscreen. When fluid is pumped in the reverse direction through the inside heat exchanger, the expansion device, the outside heat exchanger and the accumulatorldryer in succession, air passing through the inside heat exchanger is heated as the air flows into the passenger compartment across the windscreen. A reversing valve can be positioned in the other fluid passage to provide the required flow direction for the fluid.

During the cooling cycle, the air passing through the inside heat exchanger may be de-humidified, leading to a build-up of condensation on the 2 inside heat exchanger. During a subsequent heating cycle, the condensation may be evaporated, increasing the risk of internal fogging of the windscreen. This potential problem may be avoided either by limiting the time of the heating cycle, or by using a second inside heat exchanger during the heating cycle (with the first inside heat exchanger only being used during a cooling cycle). Both of these potential solutions have limitations.

Summary of the Invention

It is an object of the present invention to overcome the above mentioned problem.

An air conditioning system in accordance with the present invention for a passenger compartment of a motor vehicle comprising a first heat exchanger positionable outside the passenger compartment; a second heat exchanger positionable inside the passenger compartment; a first fluid passage between the first and second heat exchangers; a second fluid passage between the first and second heat exchangers; an expansion device positioned in the first fluid passage; a compressor for pumping fluid into the second fluid passage either in a first direction sequentially through the first heat exchanger, the expansion device, and the second heat exchanger, or in a second direction sequentially through the second heat exchanger, the expansion device, and the first heat exchanger; control means electrically connected to the compressor for controlling the operation of the compressor; an air duct for opening into the passenger compartment, the second heat exchanger being positioned in the duct; an air blower positioned in the duct for blowing air through the second heat exchanger; an opening in the duct leading to ambient air located downstream of the second heat exchanger; a first gate pivotally mounted in the duct at a position downstream of the opening, the first gate normally substantially closing the opening; means for moving the first gate to a second position to open the opening and to substantially close the duct during a period of pumping of the fluid in the second direction; and means for actuating the air blower when the first gate is in the second position.

3 The present invention provides an air conditioning system which operates dependent on sensed conditions to reduce the risk of internal fogging of the windscreen without the need for limiting the time of operation of the heating cycle and without the need for another heat exchanger inside the 5 passenger compartment.

The present invention also includes a method of operating an air conditioning system in accordance with the present invention.

Brief Description of the Drawings

The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:- Figure 1 is a schematic view of an air conditioning system in accordance with the present invention; and Figure 2 is a cross-sectional view of a compressor and control valve for use in the air conditioning system of Figure 1.

Description of the Preferred Embodiment

Referring to Figure 1 of the drawings, the air conditioning system 10 in accordance with the present invention is for use in a motor vehicle for heating or cooling the passenger compartment (not shown) of the motor vehicle, including the flow of air across the internal surface of the windscreen (not shown) of the motor vehicle. The air conditioning system 10 comprises the usual components of a compressor 12, an outside heat exchanger 14, an orifice tube or other expansion device 16 (such as a thermal expansion valve), an inside heat exchanger 18, and an accumulator/dryer 20. A first fluid passage 22 fluidly connects the outside heat exchanger 14 with the inside heat exchanger 18 by way of the expansion device 16. A second fluid passage 24 fluidly connects the outside heat exchanger 14 with the inside heat exchanger 18 by way of a reversing valve 32. The compressor 12 and the accumulator/dryer 20 fluidly connect with the second fluid passage 24 by way of the reversing valve 32.

4 The inside heat exchanger 18 is positioned in a first portion 54 of an air duct 56. A second portion 58 of the duct 56 is positioned radially adjacent the first portion 54, with the first and second portions extending substantially parallel to one another and relative to the longitudinal axis of the duct. An air blower 60 (such as an electrically driven motor and scroll fan) is located at one end of the duct 56 and is actuated to blow air through the inside heat exchanger 18 and through the second portion 58, in the direction of arrow A, into the_passenger compartment. An opening 62 to ambient (outside) air is formed in the first portion 54 of the duct 56 downstream of the inside heat exchanger 18. A heater core 64 is preferably positioned in the duct 56 downstream of the inside heat exchanger 18 and the second portion 58. The heater core 64 receives coolant fluid from the coolant system for the engine of the motor vehicle. In this case, a temperature door 74 may be positioned in the duct 56 upstream of the heater core 64 and downstream of the first and second portions 54,58 for adjusting the mix of heated and unheated air reaching the passenger compartment. As an alternative to the door 74, a flow control valve may be fluidly connected to the heater core 64. A first gate 66 is pivotally mounted in the duct 56 at a position downstream of the opening 62. The first gate 66 is normally positioned to substantially close the opening 62, but is movable by a suitable actuator 70 to a second position to open the opening and to substantially close the first portion 54 of the duct 56 downstream of the opening and the inside heat exchanger 18. A pivotally mounted second gate 68 is positioned in the duct 56. The second gate 68 is normally positioned to substantially close the second portion 58 of the duct 56, but is movable by a suitable actuator 72 to a second position to open the second portion.

During normal (cooling) operation of the air conditioning system 10, the reversing valve 32 is set to allow fluid flow in the direction X such that air passing through the inside heat exchanger 18 is cooled so that the air conditioning system operates to cool the passenger compartment.

When initial, supplemental, or prolonged heating of the passenger compartment is required, the reversing valve 32 is actuated to reverse the flow of refrigerant fluid (in the direction Y) through the inside heat exchanger 18, the orifice tube 16 and the outside heat exchanger 14. In this mode, the air conditioning system 10 acts like a heat pump such that air passing through the inside heat exchanger 18 is heated so that the air conditioning system operates to heat the passenger compartment.

The compressor 12 is preferably an electronically variable compressor the operation of which is controlled by an electronic displacement control valve 26. An example of a suitable compressor 12 and control valve 26 is shown in Figure 2. The compressor 12 shown in Figure 2 is a wobble plate compressor. As an alternative, a swash plate compressor may be used, or any other electronically controlled compressor. As a further alternative, the compressor may be a fixed displacement compressor.

The compressor 12 includes a pulley 80 which is connected to a rotatable shaft 82, and which is driven by a belt 84. A wobble plate 86 is mounted on the shaft 82. The wobble plate 86 is connected to one or more pistons 88. A crankcase chamber 90 is positioned on one side of the pistons 88, with the wobble plate 86 positioned in the crankcase chamber. An outlet chamber 92 and an inlet chamber 94 are positioned on the opposite side of the pistons. The inlet chamber 94 is fluidly connected to the accumulator 20. The outlet chamber 92 is fluidly connected to the reversing valve 32. The other components of the air conditioning system 10 are fluidly connected as shown in Figure 1. Fluid flow through the chambers 90, 92, 94, and hence the fluid pressure in the chambers, is controlled by the control valve 26.

The control valve 26 has a first port 96 fluidly connected to the outlet chamber 92; a second port 98 fluidly connected to, and acting as an inlet to, the crankcase chamber 90; a third port 100 fluidly connected to, and acting as an outlet from, the crankcase chamber 90; and a fourth port 102 fluidly connected to the inlet chamber 94. The control valve 26 is electrically 6 connected by a line 28 to a control unit 30 which is preferably a microprocessor or other computer control unit.

The control unit 30 is electrically connected to one or more sensors which provide signals used by the control unit to control the operation of the compressor 12. For example, the control unit 30 may be connected by a line 34 (Figure 1) to a temperature sensor and/or dewpoint sensor 36 which monitors the temperature of the air leaving the inside heat exchanger 18; by a line 51 to a sensor 53 monitoring windscreen temperature; by a line 42 connecting the control unit 30 to a temperature sensor 44 monitoring ambient temperature; by a line 45 to a temperature sensor 46 monitoring the temperature inside the passenger compartment; and/or by a line 47 to a sensor 48 monitoring vehicle speed. The control unit 30 may also be electrically connected by a line 50 to a manually operated control device 52 located inside the passenger compartment and operable by a passenger in the motor vehicle to select a required temperature inside the passenger compartment and/or to select the speed of the blower 60. The control unit 30 is also connected to the air blower 60, and to the actuators 70,72 for the first and second gates 66,68 by suitable lines (not shown).

The stroke of the compressor 12 (or, more precisely, the displacement or stroke of the pistons 88) is controlled by the operation of the control valve 26. The duty cycle of the control valve 26 is actuated to adjust crankcase fluid pressure Pc in the crankcase chamber 90; the inlet suction fluid pressure Ps in the inlet chamber 94; and the discharge fluid pressure Po in the outlet chamber 92. When the crankcase fluid pressure Pc is substantially the same as the inlet suction fluid pressure Ps, the stroke of the compressor 12 is at a maximum. When the crankcase fluid pressure Pc is greater than the inlet suction fluid pressure Ps, the stroke of the compressor 12 is reduced from the maximum stroke. By suitable control of the control valve 26, the stroke of the compressor 12 can be controlled.

In an alternative arrangement, the stroke of the compressor 12 may be controlled by an electronic control valve that meters fluid flow from 7 the outlet chamber 92 to the crankcase chamber 90 and uses a fixed bleed from the crankcase chamber to the inlet chamber 94. In a further alternative, the reverse arrangement may be used - that is metering fluid flow from the crankcase chamber 90 to the inlet chamber 94 and using a fixed bleed from the outlet chamber 92 to the crankcase chamber. As with the duty cycle arrangement described above, these alternative arrangements also control the stroke of the compressor 12 by effecting the pressure in the crankcase chamber 90 and the pressure balance across the piston 88.

The control unit 30 monitors the signals from the sensors 36, 53, 44, 46, 48 and the control device 52 and controls the operation of the controlvalve 26, and hence the operation of the compressor 12 dependent on the sensed signals. Such an arrangement provides more precise control of the pumping capacity of the compressor 12 during the heating cycle of the air conditioning system 10 when the passenger compartment is being heated or cooled.

In accordance with the present invention, when the control unit determines the presence of, or the risk of the presence of, condensation on the inside heat exchanger 18 during heat pump mode, the control unit moves the first gate 66 to its second position to open the opening 62 and to substantially close the first portion 54 of the duct 56, and actuates the blower to blow air through the inside heat exchanger 18. Also, the second gate 68 is moved by the control unit 30 to its second position to allow air to be blown through the second portion 58 of the duct 56 (and through the heater core 64, if present). Any condensation which is present on the inside heat exchanger 18 is blown out of the first portion 54 of the duct 56 through the opening 62 to ambient or outside air to substantially prevent the condensation reaching the passenger compartment. When the control unit 30 determines the presence of, or the risk of the presence of, condensation on the inside heat exchanger 18 during heat pump mode is negligible, the control unit moves the first gate 66 to substantially close the opening 62, the second gate 68 is moved to 8 substantially close the second portion 58 of the duct 56, and the blower 60 is turned off (if not required).

The control unit 30 may use logic steps to determine the control of the first gate 66 and the blower 60. For example, the control unit 30 may monitor the change in operation of the air conditioning system 10 from the cooling mode to the heat pump mode, and move the first gate 66 to its second position and actuate the blower 60 at the start of the heat pump mode. In this case, the first gate 66 may be moved back to its first position either after a predetermined time, or when such action is determined as acceptable based on signals from one or more of the sensors when compared to figures in a lookup table stored in the control unit. In an alternative arrangement, the control unit 30 may control the first gate 66 and the blower 60 based on signals from a humidity sensor mounted on or adjacent the inside heat exchanger 18.

The control unit 30 may also move the first gate 66 to its second position and actuate the blower 60 for a predetermined time either when the vehicle engine is switched off, and/or at predetermined time intervals, to reduce the risk of build-up of condensation on the inside heat exchanger 18. In a further alternative, where the air conditioning system 10 has a de-ice mode (that is, the air conditioning system 10 is run in cooling mode to remove ice formed on the outside heat exchanger 14), the control unit may move the first gate 66 to its second position during the de-ice mode in order to prevent cold air being blown into the passenger compartment by way of the inside heat exchanger 18.

The present invention therefore provides an air conditioning system 10 which has a heat pump mode in which the risk of internal fogging of the windscreen of the passenger compartment is significantly reduced.

Alternative reverse flow means, rather than the reversing valve 32, may be provided in the air conditioning system in accordance with the present invention. The control unit 30 may also be connected to the reversing valve 32 for controlling operation of the reversing valve. In certain 9 circumstances, the second portion 58 of the duct 56 and the second gate 68 may be omitted.

Claims

Claims

1. An air conditioning system for a passenger compartment of a motor vehicle comprising a first heat exchanger positionable outside the passenger compartment; a second heat exchanger positionable inside the passenger compartment; a first fluid passage between the first and second heat exchangers; a second fluid passage between the first and second heat exchangers; an expansion device positioned in the first fluid passage; a compressor for pumping fluid into the second fluid passage either in a first direction sequentially through the first heat exchanger, the expansion device, and the second heat exchanger, or in a second direction sequentially through the second heat exchanger, the expansion device, and the first heat exchanger; control means electrically connected to the compressor for controlling the operation of the compressor; an air duct for opening into the passenger compartment, the second heat exchanger being positioned in the duct; an air blower positioned in the duct for blowing air through the second heat exchanger; an opening in the duct leading to ambient air located downstream of the second heat exchanger; a first gate pivotally mounted in the duct at a position downstream of the opening, the first gate normally substantially closing the opening; means for moving the first gate to a second position to open the opening and to substantially close the duct during a period of the pumping of the fluid in the second direction; and means for actuating the air blower when the first gate is in the second position.

2. An air conditioning system as claimed in Claim 1, wherein the means for moving the first gate comprises an actuator which is controlled by the control means.

3. An air conditioning system as claimed in Claim 1 or Claim 2, wherein the means for actuating the blower comprises the control unit.

11 4. An air conditioning system as claimed in any one of Claims 1 to 3, wherein the air duct includes a first portion and a second portion positioned radially adjacent one another, the second heat exchanger being positioned in the first duct, and the first gate substantially closing the first portion when in the second position.

5. An air conditioning system as claimed in Claim 4, further comprising-a second gate pivotally mounted in the duct, the second gate normally substantially closing the second portion; and means for moving the second gate to a second position to open the second portion when the first gate is in its second position.

6. An air conditioning system as claimed in Claim 5, wherein the means for moving the second gate comprises an actuator controlled by the control means.

7. An air conditioning system as claimed in any one of Claims 1 to 6, wherein the control means comprises a microprocessor.

8. An air conditioning system as claimed in any one of Claims 1 to 7, wherein a heater core is positioned in the duct downstream of the second heat exchanger.

9. An air conditioning system as claimed in any one of Claims 1 to 8, further comprising reverse flow means in the second fluid passage for controlling the direction of the flow of fluid.

10. An air conditioning system as claimed in Claim 9, wherein the reverse flow means comprises a reversing valve.

12 11. A method of operating an air conditioning system as claimed in any one of Claims 1 to 10, comprising the steps of determining the start of fluid flow in the second direction and/or the presence of condensation on the second heat exchanger during fluid flow in the second direction and/or the risk of the presence of condensation on the second heat exchanger during fluid flow in the second direction; moving the first gate to its second position on such determination; actuating the air blower on such determination; and moving the- first gate to its normal position either a predetermined thne, after such determination andlor on determination of the lack of presence of condensation on the second heat exchanger and/or on determination of the negligible risk of the presence of condensation on the second heat exchanger.

12. A method as claimed in Claim 11, wherein the air conditioning system has a second gate as claimed in Claim 5, further comprising the steps of moving the second gate to its second position when the first gate is moved to its second position; and moving the second gate to its normal position when the first gate is moved to its normal position.

13. A method as claimed in Claim 11 or Claim 12, wherein the determination steps comprise logic steps.

14. A method as claimed in Claim 11 or Claim 12, wherein the determination steps comprise measuring the humidity of the air leaving the second heat exchanger.

15. A method as claimed in any one of Claims 11 to 14, wherein the first gate is moved to its second position and the air blower is actuated at predetermined time intervals for a predetermined period of time when fluid is flowing in the second direction.

13 16. A method as claimed in any one of Claims 11 to 15, wherein the first gate is moved to its second position and the air blower is actuated for a predetermined period of time when the vehicle engine is switched off.

17. A method as claimed in any one of Claims 11 to 16 in which the air conditioning system has a de-ice mode, wherein the first gate is moved to its second position when the air conditioning system is running in de-ice mode.

18. An air conditioning system substantially as herein described with reference to, and as shown in, the accompanying drawings.

19. A method substantially as herein described with reference to the accompanying drawings.