A method for determining a target temperature value of a heat transfer liquid entering a cabin heat exchange device

Abstract

Method for determining a target temperature value (TCInt_InCabHtr_Tgt) of a heat transfer liquid entering a cabin heat transfer device (CAB) of an air conditioning system of a motor vehicle, wherein the cabin heat transfer device (CAB) is traversed by a flow rate of heat transfer liquid in a heat exchange relationship with a cabin air flow rate (ṁAir_CabHtr) supplied to the vehicle cabin that flows through, by hitting it, the cabin heat transfer device (CAB), so that it is possible to determine the target temperature value (TCInt_InCabHtr_Tgt) of the heat transfer liquid entering the cabin heat transfer device (CAB) in such a way as to manage the cabin heating phase dynamically and accurately, and without the need of a temperature sensor of the air leaving the cabin heat transfer device (CAB).

Description

[0001] " A method for determining a target temperature value of a heat transfer liquid entering a cabin heat exchange device"

[0002] ★ ★ ★ ★

[0003] TEXT OF THE DESCRIPTION

[0004] Field of the Invention

[0005] The present invention relates to vehicle air conditioning. The invention was developed with particular reference to the heating of the passenger compartment of a vehicle.

[0006] Prior Art

[0007] When it is used for heating, the thermal conditioning system - or air conditioning system - of the passenger compartment of a vehicle performs the function of delivering an air flow rate, at the outlet of a cabin heat exchange device, at a temperature corresponding to the request of a driver or, generally speaking, of a passenger of the vehicle. The vehicle heating system uses a heat transfer liquid for transferring thermal power to the hair impinging upon the cabin heat exchange device, and therefore the temperature value of the air leaving the cabin heat exchange device depends, i. a., on the temperature value of the heat transfer liquid entering the cabin heat exchange device.

[0008] However, the currently known solutions for managing the temperature of the heat transfer liquid entering the cabin heat exchange device do not enable managing the heating phase of the passenger compartment dynamically and accurately, i. e. by means of a management which responds to the (instantaneous and evolving) conditions of the passenger compartment, and which reaches the target temperature with precision. Moreover, the management methods taught in the context of the prior art always envisage the use of a temperature sensor ofthe air leaving the cabin heat exchange device, which, in addition to involving further costs for the vehicle, lacks accuracy.

[0009] Obj ect of the Invention

[0010] The invention aims at solving the technical problems described in the foregoing. Specifically, the invention aims at providing a method for determining a temperature of a heat transfer liquid entering a cabin heat exchange device which enables managing the heating phase of the passenger compartment dynamically and accurately, and which moreover enables eliminating the need for a temperature sensor.

[0011] Summary of the Invention

[0012] The obj ect of the invention is achieved by means of a method having the features set forth in the claims that follow, which form an integral part of the technical teaching provided herein in relation to the invention.

[0013] Brief Description of the Figures

[0014] The invention will now be described with reference to the annexed Figures, which are provided by way of non-limiting example only and wherein:

[0015] - Figure 1 is a flow chart representing a method according to the invention,

[0016] Figure 2 schematically shows a thermal conditioning system for a passenger compartment, specifically for heating the passenger compartment, - Figure 3 is a block diagram representative of an aspect of the invention,

[0017] - Figure 4 is a further block diagram representative of a further aspect of the invention, and

[0018] - Figures 5 to 8 are diagrams showing aspects of the implementation of the method according to the invention.

[0019] Detailed Description

[0020] Reference 1 in Figure 1 and Figure 4 globallydenotes block diagrams representative of a method for determining a target temperature value TClnt_InCabHtr_Tgtof a heat transfer liquid entering a cabin heat exchange device of an air conditioning system of a motor vehicle, according to the invention.

[0021] Referring to Figure 2, wherein the air conditioning system (specifically the portion dedicated to heating the passenger compartment) is denoted with the reference CC, there is schematically shown a cabin heat exchange device CAB, specifically a cabin heater, which is traversed by a flow rate of heat transfer liquid ṁClnt_CabHtrbeing in a heat exchange relationship with a cabin air flow rate mAir CabHtrwhich is supplied to the passenger compartment of the vehicle and which flows through, by hitting it, the cabin heat exchange device CAB. Upstream of the cabin heat exchange device CAB there is preferably provided a cabin heater ECH, which is equally traversed by the flow rate cint cabHtr and is configured to heat the same flow rate before the inlet into the device CAB. The flow rate mclnt CabHtris moreover supplied by a circulation pump CP arranged upstream of the heater ECH, but the arrangement shown is not the only possible arrangement. Moreover, there are present a first temperature sensor TS_A configured to detect a temperature value TAir InCabHtrof the cabin air flow rate ṁAir_CabHtrsupplied to the passenger compartment of the vehicle, which flows through, by hitting it, the cabin heat exchange device CAB, and a second temperature sensor TS_B configured to detect a temperature value Tclnt InCabHtrof the heat transfer liquid entering the cabin heat exchange device CAB. This means, i. a., that the sensor TS_B provides, as a feedback, the instantaneous temperature value Tclnt InCabHtrwhen said temperature converges towards the target value TClnt_InCabHtr_Tgt. Therefore, preferably, there is no sensor measuring thetemperature of the flow rate mAir CabHtrat the outlet of the cabin heat exchange device CAB.

[0022] This being said, in the embodiments of the invention the method includes:

[0023] - determining (block 2 ) a target value of thermal heating power QcabHtr_Tgt for the cabin heat exchange device CAB as a function of a target temperature value TAir_OutCabHtr_Tgtof the cabin air flow rate mAir CabHtrleaving the cabin heat exchange device CAB and as a function of the temperature value TAir InCabHtrof the cabin air flow rate ṁAir_CabHtrentering the cabin heat exchange device CAB,

[0024] - determining (block 4 ) a thermal resistance value RTh_CabHtrof the cabin heat exchange device CAB as a function of the cabin air flow rate mAir CabHtrand of a target value mclnt CabHtr Tgtof the flow rate of the heat transfer liquid through the cabin heat exchange device CAB,

[0025] determining (block 6) the target temperature value TClnt_InCabHtr_Tgtof the heat transfer liquid entering the cabin heat exchange device CAB as a function of said target value of thermal heating power QcabHtr_Tgt r of said thermal resistance value RTh_cabHtr of the cabin heat exchange device CAB, and of said temperature value TAir_InCabHtrof the cabin air flow rate ṁAir_CabHtrentering the cabin heat exchange device CAB. Unless otherwise specified, all the flow rates mentioned in the description that follows are mass flow rates.

[0026] The following description details each determination, providing moreover the illustration of implementation aspects which are preferred according to the present invention.

[0027] Figure 3 shows the functional relation between the implementation of the method according to the invention and a controller 10 of the air conditioning system, orHVAC controller. The controller 10 supplies to the method 1, as input data, the target temperature value TAir_OutCabHtr_Tgtof the cabin air flow rate mAir CabHtrleaving the cabin heat exchange device CAB (which derives from a request of the driver or of a passenger of the vehicle), and the logic state of a variable HtgReqActive, which is representative of the presence of a request for heating the passenger compartment of the vehicle, and which is equal to "0" (FALSE) when there is no such request - i. e. when the air conditioning is not active or when there is a cooling request which leads to bypassing the cabin heat exchange device CAB - and which is equal to "1" (TRUE) when there is said request.

[0028] Referring to the Figures 4 to 6, method diagram 1 and diagrams 20, 30, the value of cabin air flow rate ṁAir_CabHtris determined as a function of a rotational speed SpdBlwrof a blower which supplies a cabin air flow rate ṁAir_Cabincluding the cabin air flow rate ṁAir_CabHtrflowing through the heat exchange device CAB, and as a function of a position PosCabHtrFlapof a device for partializing the traversing of said cabin heat exchange device CAB by the cabin air flow rate. Generally, said partializing device corresponds to a shutter which intercepts a total cabin air flow rate mAir Cabbefore it traverses the cabin heat exchange device CAB. In a manner known per se, the blower draws the total cabin air flow rate ṁAir_Cabfrom the external environment (or from a recirculation branch) and supplies the same to a cabin evaporator, which is part of refrigeration cycle circuit, which in turn is part of the air conditioning system. The total cabin air flow rate ṁAir_Cableaving the cabin evaporator may impinge upon the cabin heat exchange device CAB in a variable amount (between the endpoint values of null / minimum passage and full passage) as a function of the position of the aforementioned shutter.In other words, the cabin air flow rate ṁAir_CabHtrwhich traverses the device CAB is a fraction - which may be equal to one - of the flow rate mAir Cabas determined by the position PosCabHtrFlapof the partializing device.

[0029] Referring to Figure 6, diagram 30, in the preferred embodiment of the invention the rotational speed SpdBlwrand the position PosCabHtrFlapof the partializing device are used as input data for a map M30, which outputs the value ṁAir_CabHtr• The map M30 shows a series of curves ṁAir_CabHtr– SpdBlwrwhich are parameterized with respect to the position PosCabHtrFlap. By way of example, Figure 6 shows four curves ṁAir_CabHtr– SpdBlwrwhich are parameterized with respect to values PosCabHtrFlapl, PosCabHtrFlap2, PosCabHtrFlap3, PosCabHtrFlap4, mentioned in an order of increasing partialization, i. e. in an order of reduction of the flow rate through the cabin heat exchange device CAB (thus, PosCabHtrFlaplis the position which enables the transit of the greatest flow rate f b r cabHtr through the device CAB, and PosCabHtrFlap4is the position which enables the transit of the smallest flow rate riiAircabHtr through the device CAB). Qualitatively, the flow rate ṁAir_CabHtrincreases with the increasing of the rotational speed SpdBlwr, and it decreases with the increasing of partialization; therefore, it is greatest at the position PosCabHtrFlap1, and it decreases as it approaches the position PosCabHtrFlap4.

[0030] Referring to Figure 5, diagram 20, once the flow rate ṁAir_CabHtrwhich traverses the device CAB is known, it is possible to determine the target value QcabHtr_Tgt of the thermal heating power which the device CAB shall output, according to the known enthalpy equation, thus as a product (block 22 ) of the flow rate ṁAir_CabHtrby the specific heat at constant pressure of the air cp Airand by a difference (block 24 ) TAir_OutCabHtr_Tgt-TAir_InCabHtrbetween the target temperature value TAir_OutCabHtr_Tgtof the cabinair flow rate mAir CabHtrleaving the cabin heat exchange device CAB and the temperature value TAir InCabHtrof the cabin air flow rate mAir CabHtrentering the cabin heat exchange device CAB (provided by the sensor TS_A). Moreover, the diagram 20 shows that the output of the block 22, which corresponds to the expression ṁAir_CabHtr· c

[0031]

[0032] p_Air · (TAir_OutCabHtr_Tgt-TAir_InCabHtr) is mediated by a switch SW20, it being one of the input variables thereof. The switch SW20 is controlled as a function of the logic state of the variable CabHtgReqActive, and it assigns to the thermal power QcabHtr Tgt the value mAir CabHtr· cp_Air· (

[0033]

[0034] TAir_OutCabHtr_Tgt-TAir_InCabHtr) output by block 22 — which corresponds to the case shown in Figure 5 - when there is a request for heating the passenger compartment ( CabHtgReqActive = 1 ). On the contrary, if there is no such request, i. e. when CabHtgReqActive = 0, determining the target value QcabHtr_Tgt comprises assigning a null value, block 26 (the case opposite to what is shown in Figure 5).

[0035] Referring to Figure 7, diagram 40, in the preferred embodiment of the invention determining the thermal resistance Rrh_cabHtr of the cabin heat exchange device CAB is implemented as a function of the cabin air flow rate mAir CabHtr which flows through, by hitting it, the device CAB, and as a function of a target value of the flow rate of the heat transfer liquid mclnt CabHtr Tgtwhich traverses the same device CAB while exchanging thermal power with the flow rate ṁAir_CabHtr, This is preferably operated by means of a map M40, which outputs the value Rrh_cabHtr • The map M40 contains a series of curves RTh_CabHtr– ṁClnt_CabHtr_Tgtwhich are parameterized with respect to the flow rate mclnt CabHtr Tgt. By way of example, Figure 6 shows four curves RTh_CabHtr– ṁClnt_CabHtr_Tgtwhich are parameterized with respect to values ṁAir_CabHtr1, ṁAir_CabHtr2, ṁAir_CabHtr3, ṁAir_CabHtr4, mentioned in an order ofdecreasing flow rate, thus mAir CabHtrl> mAir CabHtr2> ṁAir_CabHtr3> ṁAir_CabHtr4. Qualitatively, the thermal resistance Rrh_cabHtr increases with the decreasing of the flow rate ṁClnt_CabHtr_Tgtand increases with the decreasing of the flow rate mAir CabHtr.

[0036] With reference to Figure 8, diagram 50, once the thermal resistance RTh_CabHtrof the device CAB is known, it is possible to determine the target temperature value TClnt_InCabHtr_Tgtof the heat transfer liquid entering the cabin heat exchange device CAB according to Fourier' s law, thus adding (block 52 ), to the temperature TAir InCabHtrof the cabin air entering the device CAB, a temperature change ΔTClnt_InCabHtr_Tgt(in absolute value, since it is a decrease) of the heat transfer liquid across the device CAB, due to the exchange of thermal power with the flow rate ṁAir_CabHtr, which can be calculated as a product (block 54 ) of RTh_CabHtrby QCabHtr_Tgt.The result is a raw target temperature value TClnt_InCabHtrRaw_Tgtof the heat transfer liquid entering the cabin heat exchange device CAB equal to TAir InCabHtr+ RTh_CabHtr· QCabHtr_Tgt, which is mediated by a switch SW50, it being one of two input variables. The switch SW50 is controlled - in the same way as the switch SW20 - as a function of the logic state of the variable CabHtgReqActive and it assigns, to the target temperature value TClnt_InCabHtr_Tgt, the value TClnt_InCabHtrRaw_Tgt= TAir_InCabHtr+ RTh_CabHtr· QCabHtr_Tgtoutput by the block 52 - which corresponds to the case represented in Figure 8 - when there is a request for heating the passenger compartment ( CabHtgReqActive = 1 ). On the contrary, if there is no such request, i. e. when CabHtgReqActive = 0, determining the target temperature value TClnt_InCabHtr_Tgtcomprises assigning a nominal value DefValueCabHtgOff (block 56, for example -40 °C).

[0037] Moreover, as a function of the target value TClnt_InCabHtr_Tgtit is possible to determine a target valueof electric power to be supplied to the electric heater ECH, which is arranged upstream of the heat exchange device CAB, in a manner known per se (again, by means of enthalpy equation and acquisition of the unitary electrothermal conversion yield).

[0038] Thanks to the method according to the invention it is therefore possible to determine the temperature TClnt_InCabHtr_Tgt(which can be checked by means of the sensor TS_B) of the heat transfer liquid entering the cabin heat exchange device CAB by managing the cabin heating phase dynamically and accurately, and moreover eliminating the need of a temperature sensor for the air leaving the cabin heat exchange device. Moreover, the method according to the invention may be applied both to air conditioning systems for vehicles with a thermal powertrain or to hybrid powertrains having various configurations (MHEV, HEV, PHEV, etc. ), and to air conditioning systems for vehicles with an electric powertrain, wherein the air conditioning system is generally part of a larger and more complex thermal conditioning system which also provides for the thermal conditioning, i. a., of a high voltage battery which supplies one or more electric traction motors of the electric powertrain of the vehicle.

[0039] Of course, the implementation details and the embodiments may amply vary with respect to what has been described and illustrated herein, without departing from the extent of the present invention, as defined by the annexed claims.

Claims

CLAIMS1. A method ( 1 ) for determining a target temperature value (TClnt_InCabHtr_Tgt) of a heat transfer liquid entering a cabin heat transfer device (CAB) of a motor vehicle air conditioning system, where the cabin heat transfer device (CAB) is traversed by a flow rate of heat transfer liquid ( Thclnt CabHtr) in a heat exchange relationship with a cabin air flow rate (i'hAir_cabHtr ' supplied to the vehicle cabin that flows through, by hitting it, the cabin heat exchange device (CAB), the method including:- determining (2 ) a target value of heating thermal power ( QcabHtr_Tgt ') for the cabin heat transfer device (CAB) as a function of a target temperature value (TAir_OutCabHtr_Tgt)the cabin air flow rate ( mAir CabHtr) at the outlet of the cabin heat exchange device (CAB) and as a function of a temperature value ( TAir_InCabHtr) of the cabin air flow rate (i'hAir_cabHtr ' at an inlet of the cabin heat exchange device (CAB),determining (4 ) a thermal resistance value R’rh_cabHtr ') of the cabin heat transfer device (CAB) as a function of the cabin air flow rate (i'hAir_cabHtr ' that flows through, by hitting it, the cabin heat exchange device (CAB), and a target value (mcint_cabHtr_Tgt'l of the heat transfer liquid flow rate through the cabin heat transfer device (CAB),determining ( 6) the target temperature value (TClnt_InCabHtr_Tgt) of the heat transfer liquid entering the cabin heat transfer device (CAB) as a function of said target value of heating thermal power ( QcabHtr_Tgt ') r °f said thermal resistance value (RTh_CabHtr) of the cabin heat transfer device (CAB), and of said temperature value (TAir_inCabHtr ) of the cabin air flow rate (mAir CabHtr) an the inlet of the cabin heat exchange device (CAB).

2. The method ( 1 ) according to claim 1, wherein said value of the cabin air flow rate (i'hAir_cabHtr ' flowingthrough, by hitting it, said cabin heat exchange device (CAB), is determined as a function of a rotational speed (SpdBlwr) of a blower supplying a total cabin air flow rate (ṁAir Cab) including said cabin air flow rate flowing through, by hitting it, said cabin heat exchange device (CAB), and a position (PosCabHtrFlap) of a device for partializing the traversing of said cabin heat exchange device (CAB) by the total cabin air flow rate (ṁAir Cab}.

3. The method ( 1 ) according to claim 1 or claim 2, wherein said determining ( 6) the target temperature value (TClnt_InCabHtr_Tgt) of the heat transfer liquid entering the cabin heat exchange device (CAB) includes assigning a nominal value (DefValueCabHtgOff) when there is no heating request (CabHtgReqActive = 0) for the vehicle interior.

4. The method ( 1 ) according to any of the foregoing claims, wherein said determining (2 ) the target value of the heating thermal (Q̇CabHtr_Tgt) includes assigning a null value (26) when there is no request for heating of the vehicle cabin (CabHtgReqActive = 0).

5. The method ( 1 ) according to any of the foregoing claims, further including determining a target value of electrical power to be supplied to an electric heater (ECH) upstream of the cabin heat exchange device as a function of said target temperature value (TClnt InCabHtr Tgt) of the heat transfer liquid entering the cabin heat exchange device (CAB), the electric heater being traversed by said heat transfer liquid.

Images