Method for controlling an assembly comprising a passenger compartment air conditioning system and a heated windshield.

Abstract

[Method for controlling an assembly comprising a vehicle cabin ventilation device (2) (1) and a heated windshield (3), including a step of calculating a dew point temperature from a humidity measurement, a step of measuring the temperature of the windshield (3), a step of calculating the temperature difference between the windshield temperature and the dew point temperature, a step of activating the heated windshield when the temperature difference is below an upper limit, and a step of controlling the ventilation device (2) so as to maintain an air recirculation rate by the ventilation device above a limit. Figure for the abstract: Fig. 1]

Description

Title of the invention: Method for controlling an assembly comprising a passenger compartment air conditioning device and a heated windshield.

[0001] The invention relates to a method of controlling an assembly comprising a vehicle cabin air conditioning device and a heated windshield, as well as a vehicle implementing such a method.

[0002] It is known to defrost a vehicle windshield, that is, to remove condensation from the inner or outer surface of the windshield, by heating the windshield. Windshield heating is generally achieved by blowing hot air onto the inner surface of the windshield using the vehicle's air conditioning and ventilation system. It is also known to install a transparent electric heating element within the windshield, particularly between the two layers of glass forming a laminated windshield. Activating this element heats the windshield, creating a heated windshield. Heating the windshield allows the fine water droplets that form condensation to evaporate, thus creating a defrosting function.

[0003] For example, US patent 11458818 describes a vehicle with a heated windshield and a means for controlling the power supply to the heated windshield that implements a method for reducing the energy consumption of said heated windshield. The control means uses data on the air temperature inside the vehicle and the temperature outside the vehicle, and optionally a measurement of the air humidity inside the vehicle, to determine whether condensation is forming on the windshield, and activates the heated windshield when the conditions for condensation formation correspond to those defining the occurrence of condensation. The control means activates the heated windshield for a predetermined time and then turns it off. A further check of the conditions is then performed to determine whether the heated windshield needs to be reactivated.

[0004] The disadvantage of such a solution is that it is not optimal for reducing the energy consumption of the defrosting system, the activation of the heated windshield is only activated for a predetermined operating time and only when the conditions corresponding to the presence of fog are met.

[0005] The objective of the invention is to overcome these drawbacks. In particular, one of the aims of the invention is to provide a method for controlling an assembly comprising a vehicle cabin air conditioning and windshield defrosting system using a heated windshield, thereby minimizing energy consumption in situations where there is a risk of fogging without compromising passenger thermal comfort.

[0006] This objective is achieved according to the invention, by means of a method for controlling an assembly comprising a vehicle cabin air conditioning system and a heated windshield capable of defrosting said windshield, the air conditioning system comprising a ventilation device capable of recycling at least a portion of the air from the vehicle cabin at a variable recycling rate, the heated windshield having an inner surface oriented towards the vehicle cabin, the method comprising - a step involving measuring the humidity of the air near the inner surface of the windshield, - a step to calculate the dew point temperature from the previously measured humidity reading, - a step involving measuring the windshield temperature at the level of the inner surface of said windshield, - a step to calculate the temperature difference between the windshield temperature and the dew point temperature, - a step to activate the heated windshield when the temperature difference is below an upper limit, so as to increase the temperature difference above said upper limit, - a step of controlling the ventilation system so as to maintain an air recirculation rate by the ventilation system higher than a limit recirculation rate of at least 30%, preferably at least 50% or at least 70%.

[0007] Advantageously, the air conditioning system's energy consumption remains low thanks to maintaining a high rate of cabin air recirculation, particularly when this rate is high, i.e., by limiting the amount of outside air introduced into the cabin. Indeed, since a large portion of the air introduced into the cabin comes from the vehicle's interior through recirculation, it is already at a temperature close to the user's desired setpoint temperature, and the energy requirement is limited to adding or removing heat from the small amount of outside air introduced and to the reduced heat addition or removal from the recirculated air. At the same time, the amount of energy needed to prevent fogging is reduced to heating only the heated windshield.This process also allows the vehicle's air conditioning system to maintain its setting for passenger comfort, meaning that air is not directed onto the inside of the windshield. Passenger thermal comfort is maintained while preventing fogging and minimizing energy consumption for both the air conditioning system and the heated windshield.

[0008] In a particular embodiment of the invention, the upper limit is equal to 5°c.

[0009] In another embodiment of the invention, when the difference in temperature where the temperature is below a lower bound, said lower bound being below the upper bound, and above a critical bound, the ventilation device control step modifies the introduction of air into the passenger compartment so that at least a portion of the air introduced into the passenger compartment is directed towards the inner surface of the windscreen in order to increase the speed and / or flow rate of the air circulating over the inner surface of the windscreen while maintaining a recirculation rate above the limit recirculation rate, preferably at least 30%, preferably at least 50% or at least 70%.

[0010] Thus, when the risk of fogging becomes significant due to a small difference between the dew point and the windshield temperature, air circulation over the inner surface of the windshield prevents fogging by removing moisture. It is understood that the critical limit is lower than the lower limit. Maintaining a high air recirculation rate, i.e., below the maximum recirculation rate, allows for low energy consumption by the air conditioning system for the air supplied to the passenger compartment. For example, the recirculation rate can be the same as in situations where there is no risk of fogging, i.e., with the temperature difference above the upper limit.

[0011] In a particular embodiment of the invention, the lower limit is equal to 2°c.

[0012] In another embodiment of the invention, when the temperature difference is below the critical limit, the air recirculation rate is reduced, during the piloting stage of the ventilation device, so as to be below the limiting recirculation rate and to increase the amount of outside air introduced into the passenger compartment, preferably a part or all of the air introduced into the passenger compartment being directed towards the inner surface of the windshield.

[0013] Thus, advantageously, a greater quantity of air from outside the vehicle is introduced into the vehicle's passenger compartment compared to the quantity of outside air introduced when the temperature difference exceeds the critical limit, eliminating the risk of fogging or rapidly removing fog if it has already begun to form on the inside surface of the windshield. Indeed, outside air, being drier than inside air, has a greater capacity to absorb moisture from the windshield surface, and therefore to remove any fog that has already formed. Consequently, energy consumption is only increased when the risk of fogging is very high, or even certain.

[0014] For example, the critical limit corresponds to the temperature difference between the windshield and the dew point temperature at which fogging is certain. For example, the critical limit is equal to 0°C.

[0015] In another embodiment of the invention, the heated windshield is powered following a supply power dependent on the temperature difference, preferably the power increasing with the decrease in the temperature difference.

[0016] In another embodiment of the invention, the power supply to the heated windshield is a function of the air recirculation rate.

[0017] For example, the power supply is modified according to the temperature difference and / or the recirculation rate by following charts obtained through simulation or testing. This arrangement optimizes the energy consumption of the heated windshield to the bare minimum, while maintaining good thermal comfort for the passenger, by reducing the use of air from outside the vehicle and prioritizing airflow within the vehicle cabin for passenger comfort.

[0018] In another embodiment of the invention, the power supply to the heated windshield is a function of the speed and / or flow rate of air circulating over the inner surface of the windshield.

[0019] Thus, advantageously, the risk of fogging is reduced with optimized energy consumption. The power supply is modified according to the difference in speed and / or airflow over the inner surface of the windshield, following charts obtained, for example, by simulation or testing.

[0020] The invention also relates to a vehicle comprising a passenger compartment air conditioning system and a heated windscreen, the air conditioning system comprising a ventilation device capable of recycling at least a portion of the air from the passenger compartment of the vehicle according to a variable recycling rate and of introducing air into the passenger compartment, the windscreen having an inner surface oriented towards the passenger compartment, the vehicle further comprising a temperature sensor of the inner surface of the windscreen and a humidity sensor inside the passenger compartment of the vehicle, preferably near the inner surface of the windscreen, and a control unit for the heated windscreen and the ventilation device implementing the method as described above.

[0021] The invention will be better understood upon reading the following description, given solely by way of example and made with reference to the accompanying drawings, in which:

[0022] [Fig-1] schematically represents a vehicle according to the invention.

[0023] [Fig.2] schematically represents the process according to the invention.

[0024] [Fig.3] represents a curve of the evolution of a temperature difference dT by relation to the dTs and dTi terminals during the implementation of the process according to the invention.

[0025] [Fig.4] represents a nomogram showing the power supply to a windshield heating based on a temperature difference and an air recirculation rate.

[0026] The drawings are schematic representations to facilitate understanding of the invention. The components are not necessarily shown to scale. The same reference numerals correspond to the same components from one figure to another.

[0027] Figure 1 represents a vehicle 1 according to the invention comprising a passenger compartment air conditioning system and a heated windshield 3. The air conditioning system includes a ventilation device 2 capable of recycling at least a portion of the air from the vehicle's passenger compartment at a variable recycling rate R. The air conditioning system includes one or more heat exchangers, not shown, capable of modifying the temperature of the air introduced into the vehicle's passenger compartment by the ventilation device 2, i.e., capable of adding or removing heat from the air intended to be introduced into the vehicle 1. The windshield 3 has an inner surface facing the passenger compartment.The vehicle 1 further comprises a temperature sensor for the inner surface of the windscreen 3 and a humidity sensor inside the passenger compartment of the vehicle 1, preferably near the inner surface of the windscreen 3, and a control unit (not shown) for the heated windscreen 3 and the ventilation device 2. The temperature sensor for the inner surface of the windscreen 3 and the humidity sensor are, for example, integrated into a fog sensor 4 located on the inner surface of the windscreen 3.

[0028] The dew sensor is a sensor known to those skilled in the art. Such a sensor classically comprises a device for detecting the humidity level of the air, for example in the form of a printed circuit board forming a capacitive sensor bonded to the inner surface of the windshield 3, an air temperature sensor near the inner surface of the windshield 3, a temperature sensor of the inner surface of the windshield 3, and an electronic board arranged to determine the dew point temperature Tr from the humidity level and the air temperature measured near the inner surface of the windshield. Other types of means for determining the dew point temperature can be used, such as, for example, a device comprising a humidity sensor, an air pressure sensor, and an electronic board, and calculating the dew point temperature as a function of the humidity level and atmospheric pressure.The calculation of the dew point temperature is carried out using formulas known to those skilled in the art, or simplified approximation formulas also known to those skilled in the art.

[0029] The heated windshield 3 is, for example, a windshield comprising two layers of glass separated by a layer having an interlayer incorporating a transparent electrical resistor capable of heating the glass layers when an electric current passes through it. Such a heated windshield 3 is known to those skilled in the art.

[0030] The ventilation device 2 conventionally includes an external air inlet 21, An air intake 22 draws air from outside the vehicle, and ventilation ducts 20a, 20b, and 20c supply air to the passenger compartment. A blower sets the air in motion and blows it at specific speeds and flow rates into the vehicle's passenger compartment through the ventilation ducts 20a, 20b, and 20c.

[0031] The control unit is connected to the heated windshield 3 and the air conditioning system, and in particular to the ventilation system 2. In the illustration in [Fig. 1], the ventilation system 2 includes at least one defrosting duct 20a directing the air blown by the blower to the inner surface of the windshield 3 via a defrosting nozzle, at least one central duct 20b directing the air to nozzles that direct the air towards the passengers' torsos, and at least one lower duct 20c directing the air towards the passengers' feet. The central duct 20b, for example, includes adjustable nozzles at its end through which air is introduced into the passenger compartment of the vehicle 1. To direct the air towards one of these ducts, the ventilation system includes, for example, one or more movable direction flaps. Other ducts may be provided, for example, to air condition rear passengers.

[0032] The air conditioning device includes an air recycling system, also called air recirculation, such as an adjustable recycling flap, allowing the air recycling rate R to be modified, i.e. modifying the quantity of outside air introduced into the passenger compartment of the vehicle 1 via the outside air inlet 21, relative to the quantity of air drawn from the passenger compartment by the interior air inlet 22.The air recirculation rate R is a value corresponding to the percentage of interior air in the total air introduced into the passenger compartment: thus, a recirculation rate of 100% corresponds to the absence of outside air in the air introduced into the passenger compartment, i.e. to total recirculation of the air in the passenger compartment, while a recirculation rate of 0% corresponds to the absence of interior air in the air introduced into the passenger compartment via the ventilation device 2, i.e. that all the air introduced into the passenger compartment by the ventilation device 2 comes from outside the vehicle.

[0033] Figure 2 illustrates a method for an assembly comprising a vehicle cabin air conditioning unit 1 and a heated windshield 3, implemented by the control unit. The control method includes a step 100 of measuring the air humidity near the inner surface of the windshield 3, a step 200 of calculating the dew point temperature from the humidity measurement taken in step 100, a step 300 of measuring the temperature of the windshield 3, for example, the temperature at the inner surface of the windshield 3, a step 400 of calculating the temperature difference dT between the windshield temperature and the dew point temperature, and a step 500 of activating the heated windshield 3 when the temperature difference dT is less than an upper bound dTs, so as to increase the temperature difference dT above said upper bound dTs by heating the windscreen 3, and a step 600 of controlling the ventilation device 2 so as to have an air recirculation rate R by the ventilation device greater than a limit recirculation rate RO, for example of at least 30%, at least 50% or at least 70%.

[0034] Activating the heated windshield 3 increases the temperature of the inner surface of the windshield 3, and thus increases the temperature difference between the dew point temperature and the temperature of the inner surface of the windshield 3. When this difference, i.e. the difference dT between the temperature of the inner surface of the windshield 3 and the dew point temperature, is greater than the upper limit dTs, the risk of fogging is eliminated, and the heated windshield is switched off to reduce energy consumption. The evolution of the temperature of the inner surface of the windshield 3 as a function of time is illustrated in [Fig.2], by a curve which illustrates the increase in the temperature difference dT when the heated windscreen 3 is activated, and conversely its decrease when the heated windscreen 3 is not activated under conditions in which the outside temperature is lower than that of the windscreen so as to cool the heated windscreen 3 when it is not activated.

[0035] The value of the temperature difference dT is a value from the group of rational numbers, and can therefore be positive or negative. In this sense, a negative value of the temperature difference dT is considered smaller than a positive value.

[0036] Activating the heated windshield 3 increases the windshield temperature to a level where the risk of fogging is eliminated, while maintaining a recirculation rate R higher than the limit recirculation rate R0, meaning without having to draw in more air from outside the vehicle. Maintaining this recirculation rate avoids the need to expend energy heating additional outside air and also allows for the maintenance of air distribution via the ventilation system through ducts 20a, 20b, and 20c for passenger comfort, specifically without directing a large quantity of air onto the inner surface of the windshield 3.

[0037] When the temperature difference dT is less than a lower bound dTi and greater than a critical bound dTc, the ventilation device 2 directs some of the air introduced into the passenger compartment towards the inner surface of the windshield 3 so as to increase the air velocities circulating over the inner surface of the windshield 3 in the piloting step 600 of the ventilation device 2. In other words, when the temperature difference dT approaches the critical bound dTc, the ventilation device 2 modifies the distribution of the airflow introduced into the passenger compartment so as to send more air into the defrosting duct 20a and thus increase the speed and / or flow rate of the air circulating over the inner surface of the windshield 3, compared to a In this situation, the temperature difference dT exceeds the lower bound dTi. However, the recycling rate remains at a level R higher than the limiting recycling rate RO. For example, the recycling rate R remains within similar values ​​to a situation where the temperature difference dT exceeds the upper bound dTs or the lower bound dTi. The lower bound dTi is smaller than the upper bound dTs, and the critical bound dTc is smaller than the lower bound dTi.

[0038] For example, the lower bound dTi is equal to 2°C and the critical bound is equal to 0°C, and the upper bound is equal to 5°C.

[0039] When the temperature difference dT is less than the critical limit dTc, the air recirculation rate R is reduced so as to be less than or equal to the limiting recirculation rate RO, and thus to increase the amount of outside air introduced into the passenger compartment. In other words, when the temperature difference dT is less than the critical limit dTc, the ventilation system is controlled in such a way as to increase the amount of outside air introduced into the vehicle's passenger compartment. The critical limit dTc corresponds, for example, to a temperature difference dT between the temperature of the windshield surface 3 and the dew point temperature at which condensation is certain to form on the inner surface of the windshield 3.

[0040] In one embodiment, when the temperature difference dT is less than the critical limit dTc, the ventilation device is controlled to also increase the quantity of air sent to the inner surface of the windshield 3 so as to increase the speed and / or flow rate of the air circulating over the inner surface of the windshield 3, with a large quantity of outside air, so as to prevent the formation of fog and / or remove any fog that may have formed on the inner surface of the windshield. By increasing the quantity of outside air in the air sent to the windshield 3, and thus reducing the quantity of reused interior air, the defrosting capacity of the air blown onto the windshield surface is increased, in particular because the air outside the vehicle is less humid than the air inside the vehicle.

[0041] In one embodiment, the heated windshield 3 is powered by a supply power P that is a function of the temperature difference dT, for example, the power P increasing as the temperature difference dT decreases, and / or a function of the air recirculation rate R, and / or a function of the speed and / or flow rate of the air circulating over the inner surface of the windshield. That is to say, the supply power of the heated windshield 3 is controlled according to the evolution of one or more of these parameters.

[0042] To adapt the power supply to the heated windshield 3, the control unit uses, for example, nomograms, such as the one illustrated in [Fig. 4]. These nomograms are obtained, for example, by simulation or by laboratory tests, at the within the scope of a person skilled in the art. For example, as illustrated in [Fig. 4], for a recycling rate of 70% and a temperature difference dT of 5°C, the power P used to supply the heated windshield 3 is 120 Watts, while for a recycling rate of 30% it will be 50 Watts. The curves illustrated in [Fig. 4] are given as examples: they depend, among other things, on the characteristics of the vehicle, the technology used to manufacture the heated windshield 3, and the air circulation speeds on the inner surface of the windshield when air is blown into the defrosting duct 20a.

[0043] The air recirculation rate R is determined for example according to the position of the recirculation flap of the ventilation device 2 which manages the amount of outside air introduced into the passenger compartment.

[0044] The speed and / or flow rate of air circulating on the surface can be determined as a function of the speed of a blower used to blow air towards the passenger compartment of the vehicle and the position of a flap directing the air towards the defrosting duct 20a.

Claims

Demands

1. A method for controlling an assembly comprising a vehicle cabin air conditioning system (1) and a heated windshield (3) capable of defrosting said windshield (3), the air conditioning system comprising a ventilation device (2) capable of recycling at least a portion of the air from the vehicle cabin (1) according to a variable recycling rate (R), the heated windshield (3) having an inner surface oriented towards the vehicle cabin (1), the method comprising a step (100) of measuring the humidity of the air near the inner surface of the windshield (3), a step (200) of calculating a dew point temperature from the humidity measurement taken in step (100), a step (300) of measuring the temperature of the windshield (3) at the level of the inner surface of said windshield (3), a step (400) of calculating a temperature difference (dT) between the temperature of the windshield (3) and the temperature of dew,an activation step (500) of the heated windscreen (3) when the temperature difference (dT) is less than an upper limit (dTs), so as to increase the temperature difference (dT) above said upper limit (dTs), a control step (600) of the ventilation device (2) so as to maintain an air recirculation rate (R) by the ventilation device greater than a limit recirculation rate (R0) of at least 30%, preferably at least 50% or at least 70%.

2. Method according to claim 1, wherein the upper bound (dTs) is equal to 5°c.

3. A method according to any one of the preceding claims, wherein when the temperature difference (dT) is less than a lower bound (dTi), said lower bound (dTi) being less than the upper bound (dTs), and greater than a critical bound (dTc), the step (600) of controlling the ventilation device modifies the introduction of air into the passenger compartment so that at least a portion of the air introduced into the passenger compartment is directed towards the inner surface of the windscreen (3) in order to increase the speed and / or flow rate of the air circulating over the inner surface of the windscreen (3) while maintaining a recirculation rate greater than the limit recirculation rate (R0), preferably of at least 30%, preferably of at least 50% or of at least 70%.

4. A method according to the preceding claim, wherein the lower bound (dTi) is equal to 2°C

5. A method according to the preceding claim, wherein when the temperature difference (dT) is less than the critical limit (dTc), the air recirculation rate (R) is reduced, during the piloting step (600) of the ventilation device, so as to be less than the limit recirculation rate (RO) and to increase the amount of outside air introduced into the passenger compartment, preferably a part or all of the air introduced into the passenger compartment being directed towards the inner surface of the windscreen (3).

6. A method according to any one of the preceding claims, wherein the heated windshield (3) is supplied with a supply power (P) dependent on the temperature difference (dT), preferably the power increasing with the decrease in the temperature difference (dT).

7. Method according to any one of the preceding claims, the supply power (P) of the heated windshield (3) is a function of the air recirculation rate (R).

8. A method according to any one of the preceding claims, wherein the supply power (P) of the heated windshield (3) is a function of the speed and / or flow rate of air circulating over the inner surface of the windshield.

9. Vehicle (1) comprising a passenger compartment air conditioning system and a heated windscreen (3), the air conditioning system comprising a ventilation system (2) capable of recycling at least a portion of the air from the passenger compartment of the vehicle according to a variable recycling rate (R) and of introducing air into the passenger compartment, the windscreen (3) having an inner surface oriented towards the passenger compartment, the vehicle further comprising a temperature sensor for the inner surface of the windscreen and a humidity sensor inside the passenger compartment of the vehicle, preferably near the inner surface of the windscreen, characterized in that said vehicle (1) comprises a control unit for the heated windscreen (3) and the ventilation system (2) implementing the method according to one of the preceding claims.

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