FR2790425A1 - AIR CONDITIONING SYSTEM FOR VEHICLES - Google Patents

Abstract

The invention relates to an air conditioning system for vehicles, comprising at least one fan (7), a heating device (9), a mechanism (13, 14) for adjusting the degree of heating of the device. heater (9), a WIND mode air discharge port (16), a FOOT mode air discharge port (17), means for selecting an air discharge mode (21, 22) among a WIND mode, a WIND mode. FOOT and a FOOT mode by opening / closing each air discharge port, and means for controlling the heater by calculating a magnitude to be adjusted from the heating degree adjustment mechanism (13, 14) and the sending a signal of the calculated quantity to the heating degree adjustment mechanism (13, 14) so that the indoor air temperature approaches a target temperature. The system includes means for estimating the temperature of the air discharged from the WIND mode air discharge port (16) and the temperature of the air discharged from the FOOT mode air discharge port (17). .

Description

AIR CONDITIONING SYSTEM FOR VEHICLES

  The present invention relates to an air conditioning system for vehicles, and more specifically to an automatic control technology of an air conditioning system using an automatic air conditioner which automatically controls

air discharge ports.

  In an automatic air conditioner, generally without estimating the temperatures of the air exhausted from the respective air discharge ports (eg, WIND mode air discharge port and FOOT mode air discharge port ), a target temperature of the air discharged by each air discharge port is calculated, and a heating degree of a heater is calculated and decided with reference to the target temperature. The selection of each air discharge mode (for example, VENT mode, VENT.PIED mode and FOOT mode) is determined and performed with reference to the target temperature. In addition, the determination of an air discharge mode to be selected is not changed depending on the presence of sunshine. Therefore, the control to switch the air discharge mode is performed, for example, as depicted in Fig. 5, in the relationship between the heating degree of a heater and each mode.

  air discharge to be selected.

  In such a known automatic air conditioner, however, although the switching of the air discharge mode is determined by a target temperature of discharged air, an actual temperature of the discharged air may not always correspond to the temperature. target, and therefore, an unpleasant discharge air temperature may occur, such as a high vented air temperature in

  low air temperature discharged in FOOT mode.

  Generally, a driver may feel embarrassed when he receives an air stream at a high temperature (for example, greater than or equal to 30 C) on the upper half of the body. Conversely, he may feel embarrassed when he receives a stream of air at a low temperature (for example, less than 30 C) on his feet. In the known method described above for selecting an air discharge port as a function of a target discharge air temperature, the air discharge port can be selected only according to a schematic value (in accordance with FIG. in other words, an average value of all discharge ports) of a discharge air temperature to be controlled, and the air temperature at each discharge port may not be exactly determined. Therefore, in such a known system, a troublesome discharge air temperature can occur when the control is not appropriate for the current situation. In addition, since the determination of an air discharge mode to be selected is not changed depending on the presence of sunshine in the known system, the following problem may occur. Namely, generally, a driver feels a slight heat on the upper half of the body when sunshine is present. For example, if we consider a situation in which the outside air temperature is 2 to 3 C with sunshine present and a situation in which the outside air temperature is 12 to 13 C and without sunshine and that the target air unloaded temperatures of these two situations are the same (e.g., about 35 C), in the first situation, the desirable air discharge mode is the VENT.PIED mode, which can eliminate the feeling of heat to the upper half of the body due to sunlight, causing the driver to feel a slight flow of air at or below room temperature (around 25 C) on the upper half of the body, and in the second In this situation, the desirable air discharge mode is the FOOT mode which can produce a heating sensation by causing the driver to feel a flow of air at a temperature above ambient are feet. In the known system described above, however, since only one mode, which is the WIND.PIED or FOOT mode, can be selected in each of the situations described above, the comfortable feeling of heating can be

impaired in both cases.

  It is an object of the present invention to provide a vehicle air conditioning system which can control the system on the basis of a determination to switch the air discharge mode appropriately, and which can prevent an uncomfortable discharged air temperature occurs, thus permanently

nice air conditioning.

  To achieve the above object and others, a vehicle air conditioning system according to the present invention comprises at least one fan sending air into the passenger compartment of a vehicle along an air path , a heater disposed in the air path for heating air supplied by the fan, a mechanism for adjusting a heating degree of the heater, a VENT mode air discharge port directing the discharged air in the direction of a position between a vertical medial portion and an upper portion of the passenger compartment of a vehicle, a FOOT mode air discharge port directing the discharged air in the direction of a position corresponding to the feet of the driver, means for selecting an air discharge mode from a WIND mode, a WIND SIDE mode and a FOOT mode by opening / closing each air discharge port, and a means for controlling the heating degree of the heating device in calculan t a magnitude to be adjusted of the heating degree adjusting mechanism and sending a signal of the calculated magnitude to the heating degree adjusting mechanism so that the indoor air temperature approaches a target temperature. In the air conditioning system, there is provided means for estimating the temperature of air discharged through the VENT air discharge port and means for estimating the temperature of air discharged through the discharge port of FOOT mode air, respectively. The air discharge mode selection means selects an air discharge mode with reference to each of the temperature of the air discharged from the vent air discharge port and the temperature of the discharged air. by the FOOT mode air discharge port which are estimated by the estimation means of

unloaded air temperature.

  In the vehicle air conditioning system, provision may also be made for a means for estimating or detecting the temperature of the air entering the heating device, and each of the temperature of the air discharged through the discharge port of the vehicle. VENT air mode and the temperature of the air discharged through the FOOT mode air discharge port can be estimated by reference to the heating degree of the heater and the air temperature entering the heater. heating. In addition, in the air conditioning system, a means for estimating or sensing the temperature of the air entering the heater may also be provided, the heating degree adjusting mechanism may comprise a heating mechanism. opening / closing to adjust an air flow through the heater and an air flow bypassing the heater, the heater may include a hot water heater whose heat source is a high liquid. temperature, the temperature of the air having passed through the heating device can be estimated with reference to the information concerning the amount of air sent by the fan and the degree of opening of the opening / closing mechanism, and each of the temperature air discharged from the WIND mode air discharge port and the temperature of the air discharged through the FOOT mode air discharge port can be estimated with reference to the estimated temperature of the air passed through the heater, the degree of opening of the opening / closing mechanism, and the temperature of the incoming air

in the heating device.

  In addition, it is preferable that the air discharge mode selection means switches the air discharge mode in all control situations so that the temperature of the air discharged through the air discharge port VENT mode shall not be greater than any of the first set of predefined threshold temperatures and the temperature of the air discharged from the VENT air discharge port shall not be less than any of a second group of predefined threshold temperatures. If a means is also provided for detecting a magnitude of sunshine reaching the vehicle, the air discharge mode selecting means may modify each of the first and second predetermined threshold temperature groups in response to the magnitude of sunshine. detected. In the control, the air discharge mode selection means can change the first set of lower temperature levels and / or can change the second set of preset temperatures upwards if the amount of sunshine

detected is important.

  In the vehicle air conditioning system according to the present invention, the temperature of the air discharged through the WIND mode air discharge port and the temperature of the air discharged through the air discharge port of FOOT mode are estimated by the discharged air temperature estimation means, respectively. The selection of the air discharge ports, ie the selection of an optimal air discharge mode for the current situation can be determined by reference to the estimated temperatures of the air discharged by the air ports. respective air discharge. Therefore, the occurrence of an unpleasant discharge air temperature, for example, a high temperature of the air discharged in the WIND mode or a low temperature of the air discharged in FOOT mode, can be avoided, a situation optimal can be automatically controlled, and a

  Pleasant air conditioning can still be achieved.

  The estimate of the temperature of the air discharged at each air discharge port may be more accurate with reference to the temperature of the air entering the heater, the estimated temperature of the air having passed through the device the degree of opening of the opening / closing mechanism, the degree of heating of the heating device, etc. In addition, if a means is provided for detecting a magnitude of sunshine and if the predefined temperatures of the first and second groups are changed in response to the amount of sunshine detected, the situation can be controlled in a more optimal temperature range. depending on the sunshine condition at the moment, and more air conditioning

  nice to give a more comfortable feeling can be realized.

  For example, in the presence of sunshine, the operating speed of the BI-LEVEL mode can be increased, and an airflow from the VENT mode air discharge port to the upper half of the body can be increased.

  to be generated, further reinforcing the pleasant sensation.

  Other objects, features and benefits of this

  invention will become more clearly apparent in the detailed description of the

  preferred embodiments of the invention, given hereinafter with reference to the accompanying drawings in which: Figure 1 is a schematic diagram of an air conditioning system according to an embodiment of the present invention; Fig. 2 is a block diagram illustrating the manner in which control is performed in a main controller of the air conditioning system of Fig. 1; Figure 3 is a graph showing an embodiment of the control shown in Figure 2, in the absence of sunshine; Figure 4 is a graph showing another embodiment of the control shown in Figure 2, in the presence of sunshine; and Fig. 5 is an explanatory diagram showing a control situation of a known air conditioning system. Figure 1 mainly describes the mechanical part of an air conditioner 1 for a vehicle. An air path 2a is formed in an air duct 2, and an interior air introduction port 3 and an external air introduction port 4 are open at an inlet position 1 0 of the duct 2. A switching damper 5 controls the ratio of the amount of air sucked from port 3 to that of port 4. The sucked air is sent into the air duct 2 by a fan 7 driven by an engine. 6. The amount of air sent by the fan 7 is

  adjusted by the controller motor 6.

  An evaporator 8 is arranged as a cooler at a position downstream of the fan 7, and a hot water heater 9 is disposed as a heater at a position downstream of the latter. The engine cooling water, which is a high temperature liquid, is circulated in the hot water heater 9 as the heat source of the heater 9, and the sucked air is heated by the device

hot water heating 9.

  A refrigerant circulated in a cooling cycle 11 is transmitted to the evaporator 8. The refrigerant is compressed, for example, by a variable displacement compressor (not shown), condensed by a condenser (not shown), sent to the compressor. 8 by means of a tank tank (not shown) and an expansion valve 12, and sucked into the compressor since

the evaporator 8.

  An air mixing damper 13 is disposed at a position immediately downstream of the hot water heater 9 as an opening / closing mechanism. The ratio of the amount of air passing through the heater 9 to that bypassing it is controlled by adjusting the degree of opening of the air mixing damper 13 actuated by a damper control device

of air mixture 14.

  The conditioned temperature air is supplied to the passenger compartment of a vehicle by respective air discharge ports 15, 16 and 17 (eg, a DEF mode air discharge port, a discharge port of VENT mode air to direct the discharged air in the direction of a position between a vertically central portion and an upper portion in the passenger compartment of the vehicle, and a FOOT mode air discharge port 17 to direct the air air discharged in the direction of a position corresponding to the driver's feet). Respective dampers 18, 19 and 20 are arranged as open / close devices for the respective air discharge ports 15, 16, 17. The respective dampers 18, 19 and 20 are actuated by a control device of the respective damper 21, and thus, the air discharge ports 15, 16 and 17 to be opened or closed are selected. In BI-LEVEL mode, the WIND 16 mode air discharge port and port

  FOOT mode air discharge 17 are both used.

  The opening degrees of these air discharge ports 15, 16 and 17 are automatically changed by an automatic control. The conditions of the respective control modes are checked, by

example, as follows.

  () WIND mode: 100% of the air in quantity is discharged through the port

VENT mode air discharge 16.

  O) BI-LEVEL mode: 50% of the air in quantity is discharged by the

  FOOT mode air discharge port 17.

  (3) FOOT mode: 70% of the air in quantity is discharged through the FOOT mode air discharge port 17, and 30% of the air in quantity is

  discharged through DEF 15 mode air discharge port.

  The voltage (rotational speed) applied to the motor 6 of the fan 7, and the damper control devices 14 and 21 are controlled based on the signals sent from a main controller 22. In the main controller 22, a signal of a target ambient temperature defined by an ambient temperature control device 23, an outdoor air temperature signal detected by an outdoor air temperature sensor 24, an indoor air temperature signal detected by a temperature detector, 25, a sunshine amount signal detected by a sunshine detector 26, a water temperature signal of the engine cooling water detected by a water temperature detector 27, a signal of air temperature having passed through the evaporator 8 detected by an air temperature sensor on the outlet side of the evaporator 28, and an air temperature signal entering the disp Heating element 9 detected by an air temperature sensor on the input side of the heater, are entered, respectively. In the air conditioner 1, the air conditioning according to the present invention is controlled, for example, as described in

figure 2.

  As described in the block diagram shown in FIG. 2, the target ambient temperature signal Ts defined by the ambient temperature control device 23, the radiation amount signal RAD detected by the sun detector 26, the external air temperature signal AMB detected by the outdoor air temperature detector 24 and the indoor air temperature signal Tr detected by the indoor air temperature detector 25 are input to the main controller , respectively. On the basis of these input signals, a target discharged air temperature Toc is calculated in a target unloaded air temperature calculation step 35 according to the following equation: Toc = Kp (Ts - Tr) + f (AMB , RAD, Ts)

  o Kpi is a predefined proportional constant.

  The voltage BLV applied to the motor 6 of the fan 7 is calculated from the target unloaded air temperature Toc in the voltage calculation step of the fan motor 36 according to the following equation: BLV = f (Toc) o la function f (Toc) represents a generally V-shaped curve depending on the variable Toc. The engine voltage controller

  fan 37 (see Figure 1) is controlled on the basis of this BLV.

  The amount of air passing through the heater 9 in each air discharge mode is estimated from BLV in step

  estimating the amount of air passing through the heater 38.

  The estimated amount of air VOL is calculated for each outdoor air supply condition and indoor air circulation condition based on the outside air and indoor air switching condition information. determined by the switching damper 5 at the present time. If outside air is introduced and the mode is controlled in WIND or BI-LEVEL mode, VOL is calculated according to the following equation: VOL = al. BLV. OP If the mode is controlled in FOOT mode, in FOOT / DEF mode or in DEF mode, VOL is calculated according to the following equation: VOL = a2. BLV. OP If the indoor air is circulated and the mode is controlled in VENT mode or BI-LEVEL mode, VOL is calculated according to the following equation: VOL = bi. BLV. OP If the mode is controlled in FOOT mode, in FOOT / DEF mode or in DEF mode, VOL is calculated according to the following equation VOL = b2. BLV. OP o ai, a2, bl, b2 are predefined constants, and OP is a degree of opening of the opening / closing mechanism (damping of

  air mixture 13) determined by the calculation described below.

  On the basis of the amount of air passing through the heating device VOL estimated by the calculation described above, of the water temperature signal 40 on the input side of the heating device TW detected by the water temperature detector 27, and of the air-inlet temperature signal 41 on the inlet side of the heater Tins detected by the inlet-side air temperature sensor of the heater 29, the outlet-side air temperature of the heater TH is estimated in FIG. step of estimating the outlet air temperature of the heating device 42 by calculation according to the following equation: TH = (c - d.VOL). (TW - Tins) + Tins

  o c and d are predefined constants.

  On the basis of the calculated TH value, the target unloaded air temperature described above Toc and air temperature on the inlet side of the heater Tins, the opening degree OP of the mixing damper air 13 is calculated in the step of calculating the degree of opening according to the following equation OP = (Toc - Tins) / (TH - Tins) On the basis of the calculation result described above, a target signal PT , which is sent to a potentiometer in the air mixing damper control device 14 which controls the degree of opening of the air mixing damper 13, is calculated in the step of calculating the signal of target potentiometer 44 according to the following equation: PT = f (OP) The operation of the air mixture damper control device 14 is controlled by the target potentiometer signal PT, o

  "f 'designates a function decided appropriately.

  Based on the air mixing damper opening degree OP described above, the estimated air temperature on the outlet side of the heater TH and the detected air temperature on the inlet side of the heater. At the same time, each air temperature discharged by each air discharge port in each conditioning mode is estimated in the unloaded air temperature estimation step 45

as following.

  In VENT mode, the exhaust air temperature Tv-v is estimated by calculation according to the following equation Tvv = f1 (OP, TH, Tins) Similarly, in BI-LEVEL mode, the exhaust air temperature Tb- v is estimated by calculation according to the following equation Tb-v = f2 (OP, TH, Tins) The exhaust air temperature Tb-r PIED, in BI-LEVEL mode is estimated by calculation according to the following equation Tb-f = f3 (OP, TH, Tins), In FOOT mode, the unloaded air temperature FOOT Tf-f is estimated

  by calculation according to the following equation.

  Tf-f = f4 (OP, TH, Tins) The behavior of function fi is indicated as shown in FIGS. 3 and 4 by the third curve from the uppermost line which is represented by a solid line on each Fig. In the same figures, the behavior of the f2 function is indicated by the dotted line curve at the bottom. The behavior of the f3 function is indicated by the dotted line curve at the top. The behavior of the f4 function is indicated by the second curve from the topmost line represented by a long dashed line. Therefore, in any mode, the reason that the unloaded air temperature curves are positioned higher than the unloaded air temperature curves

WIND is this.

  With reference to FIG. 1, the heater 9 is disposed on the lower surface of the conduit 2 which is positioned on the side of the FOOT mode air discharge port 17. In addition, in the air mixing zone surrounded by the DEF 15 mode air discharge port, the VENT mode air discharge port 16, and the FOOT mode air discharge port 17, even if the cold air has bypassed the heater 9 and the hot air passed through the heater 9 are mixed, the air mixing damper 13 has an effect of directing hot air passed through the heater 9 in the direction of the discharge port FOOT mode air 17. Therefore, the mixture of cold air and hot air is not complete, a relatively low temperature air can be discharged through the VENT mode air discharge port 16 , and a relatively temperature air

  High can be discharged through the FOOT mode air discharge port 17.

  The difference between the temperatures of the air discharged by the two ports is intentionally formed, and the value of the difference depends on the degree of heating of the heating device, more precisely, the degree of the air mixing damper 13 ( OP), as shown on

Figures 3 and 4.

  An optimum air discharge mode to be controlled at the present time is determined in the step of determining the air discharge mode 46 on the basis of the respective estimated discharged air temperatures in the respective modes. The optimal air discharge mode is selected as a mode that does not provide any unpleasant feeling to a driver, such as a mode capable of avoiding a HIGH or HIGH temperature, as previously indicated. On the basis of this determination, the respective air discharge port dampers 18, 19 and 20 are

  controlled by the damper control device 21.

  The conditions for switching an air discharge mode are defined, for example, as follows. In the present case, the predefined temperatures of the first and second groups are modified according to the presence or absence of sunshine. The presence or absence of sunshine is determined by comparing the signal of amount of sunshine RAD to a predefined threshold value. If the sun is not present, Tla and Tlb are defined as a first group of threshold temperatures, each of them being used as the first preset temperature in a mode switching condition with a hysteresis, and T2a and T2b are defined as a second group of threshold temperatures, each of which is used as the second preset temperature in a mode switching condition with a hysteresis. If sunshine is present, Tla 'and Tlb' are defined as a first threshold temperature group, each of which is used as the first preset temperature in a mode switching condition with a hysteresis, and T2a 'and T2b' are defined as a second group of threshold temperatures, each of which is used as the second preset temperature in a mode switching condition with a hysteresis. The programming for switching the air discharge mode is defined as follows: <In the absence of sunshine> (Switching from the VENT mode to BI-LEVEL mode: The mode is switched when the discharge temperature of air

  WIND estimated Tv-v in WIND mode reaches T la.

  0 Switching from BI-LEVEL mode to WIND mode: The mode is switched when the estimated VENT airflow temperature Tv-v in WIND mode reaches T lb. (3 Switching from BI-LEVEL mode to FOOT mode: The mode is switched when the air discharge temperature

  FOOT estimated Tf-r in FOOT mode reaches T2b.

   ) Switching the FOOT mode to BI-LEVEL mode: The mode is switched when the air discharge temperature

  FOOT estimated Tf-r in FOOT mode reaches T2a.

  <When there is sunshine> (D Switching from the WIND mode to the BI-LEVEL mode: The mode is switched when the air discharge temperature

  WIND estimated Tvv in WIND mode reaches Tl a '.

    Switching from BI-LEVEL mode to WIND mode: The mode is switched when the air discharge temperature

  WIND estimated Tvv- in WIND mode reached T l b '.

  C Switching from BI-LEVEL mode to FOOT mode: Mode is switched when the air discharge temperature

  FOOT estimated Tf-f in FOOT mode reaches T2b '.

   ) Switching the FOOT mode to BI-LEVEL mode: The mode is switched when the estimated FOOT discharge temperature Tf-f in FOOT mode reaches T2a '. In the present invention, it is also preferred to modify the first and second predefined temperatures described above Tla ', Tlb', T2a 'and T2b' in response to the amount of sunshine. For example, if the amount of sunshine is high, it is preferred that the first preset temperatures be lowered as a function of the amount of sunshine, and that the second preset temperatures be increased depending on the amount of sunshine. As a result of such an automatic control based on the estimated unloaded air temperature, a control characteristic can be obtained, for example, as shown in FIGS. 3 and 4. In FIGS. represent the operating characteristics under automatic control. As shown in FIGS. 3 and 4, the mode is switched to an optimal mode as a function of

  The air temperature discharged at the present moment.

  In FIGS. 3 and 4, a predefined temperature T1a of the first group is set at an upper limit of a pleasant venting air temperature, and a predefined temperature T2a of the second group is set at a lower limit of a temperature pleasant foot air discharge. In FIG. 3, if the relations between Tla and Tlb and between T2a and T2b are defined such that Tla> Tlb and T2a <T2b, in the absence of sunshine, it is avoided that an unpleasant air discharge temperature occurs, such as an exhaust air temperature

  WIND too high or exhaust air temperature too low.

  In addition, FIG. 4 represents a control characteristic in the presence of sunshine, and since the first predefined temperatures are set at values of Tla 'and Tlb' lower than the values of Tla and Tlb applied in the presence of sunshine, a lower vented air temperature may be produced. In addition, since the second predefined temperatures are set at values of T2a 'and T2b' lower than the values of T2a and T2b applied in the absence of sunshine, the operational domain for applying the BI-LEVEL mode can be expanded. , and the sensation of heat can be eliminated by the VENT air discharge. Although several aspects of the present invention have been

  described in detail here, the scope of the invention is not limited thereto.

  It will be apparent to those skilled in the art that various modifications can be made without departing from the scope of the invention.

Claims (6)

  1. Air conditioning system for vehicles comprising at least one fan (7) delivering air into the passenger compartment of a vehicle along an air path (2a), a heater (9) disposed in said air path for heating said air supplied by said fan (7), a mechanism for adjusting the degree of heating (13, 14) of said heater (9), a vent air discharge port (16) directing the discharged air in the direction of a position between a vertically medial portion and an upper portion of said passenger compartment of said vehicle, a foot-mode air discharge port (17) directing the discharged air in the direction of a a position corresponding to the driver's feet, a means for selecting an air discharge mode (21, 22) from a WIND mode, a WIND SIDE mode and a FOOT mode by opening / closing each air discharge port, and means for controlling said degree of heating of said heating device (9) in calculation a magnitude to be adjusted from said heating degree adjusting mechanism (13, 14) and outputting a signal of said calculated magnitude to said heating degree adjusting mechanism (13, 14) such that the air temperature interior approaching a target temperature, characterized in that means for estimating the air temperature discharged by said VENT air discharge port (16) and means for estimating the air temperature discharged by said air port; FOOT mode air discharge (17) are provided, respectively, and in that said air discharge mode selection means (21, 22) selects an air discharge mode with reference to each of said temperature air discharged from said VENT mode air discharge port (16) and said air temperature discharged from said FOOT mode air discharge port (17) which are   estimated by said discharged air temperature estimation means.   An air conditioning system according to claim 1, characterized in that means for estimating or sensing the temperature of the air entering said heater (9) is also provided, and each of said temperature of the air discharged by said VENT mode air discharge port (16) and said air temperature discharged by said FOOT mode air discharge port (17) can be estimated with reference to said degree of heating of said device of heating (9) and at said temperature of the air entering said device heating (9).   3. Air conditioning system according to claim 1, characterized in that a means for estimating or detecting the temperature of the air entering said heating device (9) is also provided, said adjustment mechanism of the degree heater (13, 14) includes an opening / closing mechanism for adjusting a flow rate of air passing through said heater (9) and a flow of air bypassing said heater, said heater comprises a heater hot water heater whose heat source is a high temperature liquid, the temperature of the air having passed through said heater (9) is estimated with reference to the information concerning the amount of air supplied by said fan (7) and the degree of opening of said opening / closing mechanism, and each of said air temperature discharged by said VENT mode air discharge port (16) and said vented air temperature. adjusted by said FOOT mode air discharge port (17) can be estimated with reference to said estimated temperature of the air having passed through said heater (9), at said degree of opening of said opening / closing mechanism , and to said   temperature of the air entering said heating device (9).   4. Air conditioning system according to any one of   preceding claims, characterized in that said means for   air discharge mode selection (21, 22) switches said air discharge mode under all control conditions so that the temperature of the air discharged from said WIND mode air discharge port (16) is not greater than any one of a first set of predefined threshold temperatures and the temperature of the air discharged by said FOOT mode air discharge port (17) is not less than any of among a second group of preset threshold temperatures.   An air conditioning system according to claim 4, characterized in that means for detecting the amount of sunshine reaching said vehicle is also provided, and said air discharge mode selecting means (21, 22) ) modifies both said first and second predetermined threshold temperature groups   in response to said detected amount of sunshine.   Air conditioning system according to claim 5, characterized in that the air discharge mode selection means (21, 22) modifies said first group of predefined temperatures downwards and / or modifies said second group. temperature thresholds predefined upward when said amount of sunshine detected is high.