METHOD FOR HEATING A VEHICLE STEERING WHEEL

Abstract

Method for heating a steering wheel of a vehicle comprising at least a first electric heating unit and at least a second electric heating unit supplied by a common supply line defining a maximum supply power, the method comprising: - a first step comprising a phase of supplying an electric current to the at least one first electric heating unit until at least one priority area (10) of the element reaches a temperature setpoint, and a phase of determining a first electric energy supplied to the at least one first electric heating unit to reach the temperature setpoint, - a second step comprising at least one phase of supplying the at least one second electrical heating unit with a second electrical energy calculated on the basis of the first electrical energy, wherein during the second step the at least one first electrical heating unit consumes at most a predetermined part of the maximum supply power and the at least one second electrical heating unit consumes the available supplement of the maximum supply power.

Description

[0001] The present invention relates to a method for heating a vehicle steering wheel.

[0002] US 8 066 324 B2 describes a heating device for a vehicle seat, but the system is complicated because it requires several temperature sensors, which increases the complexity of the control unit (which must therefore be able to receive several measuring lines) and the associated costs.

[0003] JP 2016-185 760 A discloses a heated vehicle seat with a heating element for the seat surface and a heating element for the backrest. It is proposed to heat the seat surface first and then the backrest, with the amount of energy required to heat the seat surface being used to calculate the amount of energy supplied to the heating element in the backrest. This eliminates the need for a temperature sensor in the backrest.

[0004] DE 10 2011 006 713 A1 proposes prioritizing the heating of different areas of a vehicle steering wheel rim so that the areas currently used by the driver are heated most quickly. A similar approach is also described in DE 11 2014 000 795 T5. In each case, no energy measurement is performed.

[0005] An object of the present invention is to overcome the disadvantages of the prior art mentioned in the aforementioned documents and to propose a method for heating a vehicle steering wheel which allows a specific temperature control of a limited area or a limited surface of the element, but remains simple to manufacture, does not consume too much power and optimises the heating overall.

[0006] To this end, the invention relates to a method for heating a steering wheel of a vehicle, comprising at least a first electric heating unit and at least a second electric heating unit supplied by a common supply line defining a maximum supply power, the method comprising: - a first step comprising a phase of supplying an electric current to the at least one first electric heating unit until at least one priority area of ​​the steering wheel reaches a temperature setpoint, and a phase of determining a first electrical energy supplied to the at least one first electric heating unit to reach the temperature setpoint, - a second step comprising at least one phase of supplying the at least one second electrical heating unit with a second electrical energy calculated on the basis of the first electrical energy, wherein during the second step, the at least one first electric heating unit consumes at most a predetermined portion of the maximum supply power, and the at least one second electric heating unit consumes the available supplement of the maximum supply power.

[0007] The method according to the invention therefore proposes supplying the second heating unit during the second step only taking into account the energy supplied to the first heating unit, such that the entire available power is used during the second step, with the energy supply to the first energy unit being limited, which simplifies the overall architecture (no temperature sensor is required on the area heated by the second heating unit). Furthermore, it is possible to supply the first unit with a different electrical power than the second unit during the first step, thus providing a solution for special requirements. In the first step, the method therefore calculates the integral of the electrical power supplied to the first unit as a function of time to determine the first supplied energy.During the second step, the method defines either the heating time (if the heating power is specified) or the heating power (if the heating time is specified) applied to the second heating unit to fully supply the second energy to the second unit. It may also be considered to update the calculation of the heating time or heating power in the second step if, for example, the available power varies in that second step.

[0008] Advantageously, the at least one first electrical heating unit is arranged to heat the at least one priority area and the at least one second electrical heating unit is arranged to heat a different area of ​​the element than the priority area.

[0009] Advantageously, the first step consists in supplying the power primarily to at least one first electrical heating unit.

[0010] Advantageously, the second step comprises at least one phase of supplying an electric current to the at least first electric heating unit to maintain the at least one priority zone of the element at the temperature setpoint. It may be considered to supply power to the first heating unit when the temperature is to be maintained at a minimum value, for example, when this second step lasts a long time. This temperature maintenance requires only a small amount of power, and priority can be given to the second heating unit.

[0011] Such a distribution of the power allocated to the two units allows the rate of temperature rise in the other zone to be optimized without compromising the temperature control of the priority zone. In fact, the power available to the other zone during the second step is variable, with a guaranteed minimum: if, during regulation of the priority zone, the first unit is not consuming electrical power, the electrical power not consumed by the first unit is allocated to the second unit, allowing it to heat more quickly. At the same time, the regulation of the priority zone is not compromised, since a given electrical power is allocated to it with priority when needed.In other words, the priority zone receives a portion of the available power up to a certain limit, and then the other zone benefits from the supplement (the remainder of the available power). However, the priority zone may also consume nothing if the temperature is within the regulation limits, in which case all the available power is allocated to the other zone. For example, if the heating units are equivalent or equal, the first unit cannot be supplied with more than 50% of the maximum power available to maintain the temperature of the priority zone.

[0012] Advantageously, during the first step, the at least one first electric heating unit receives at least 60% of the maximum supply power, and / or the at least one second electric heating unit is supplied with at most 40% of the maximum supply power. Very preferably, during the first step, the at least one first electric heating unit is supplied with at least 70% of the maximum supply power, and the Applicant has found that this value makes it possible to quickly reach the target temperature without unduly impairing the heating of other areas of the element by the at least one second heating unit. During this first step, there is no power allocation from one unit to another, each consuming the power allocated to it.

[0013] Advantageously, during the second step, the at least one second electrical heating unit is supplied by taking into account only the first electrical energy supplied to the at least one first electrical heating unit during the first step, optionally modulated by a heating multiplier coefficient. This means that the method only follows this parameter to supply power to the second heating unit. This makes it possible to dispense with a temperature sensor for the second heating unit. The multiplier coefficient can be fixed or variable, for example depending on the temperature in the vehicle interior. Furthermore, the multiplier coefficient can take into account the power supplied to the first unit, which could affect the heating of the second area if the two areas are close to each other.

[0014] Advantageously, the heating method comprises a third step which begins after the complete supply of the second electrical energy to the at least one second electrical heating unit and consists of the following: - Maintaining the at least one priority area of ​​the element at the desired temperature by supplying the at least one first electrical heating unit with a first electrical holding power, - to supply the at least one second electric heating unit with a second holding electric power calculated based on the first holding electric power supplied to the at least one first electric heating unit during this third step. Even during the third step, the electric current of the second unit is controlled only based on the current supplied to the first heating unit. Temperature detection at other regions of the element is therefore still not required.

[0015] Advantageously, the at least one first electrical heating unit comprises a first electrical resistance, the at least one second electrical heating unit comprises a second electrical resistance, and during the third step, the second holding electrical power supplied to the at least one second electrical heating unit is equal to the first holding electrical power modulated by a ratio of the value of the second electrical resistance divided by the value of the first electrical resistance. It is possible to modulate the second holding power with respect to the first holding electrical power exclusively with the resistance ratio, but it is also possible to modulate the second holding electrical power with a surface area coefficient covered by the heating units, a thermal conductivity coefficient, etc.

[0016] Advantageously, the at least one first electrical heating unit comprises a first electrical resistance, the at least one second electrical heating unit comprises a second electrical resistance, and the second electrical energy is equal to the first electrical energy modulated by a ratio of the value of the second electrical resistance divided by the value of the first electrical resistance. It is possible to modulate the second electrical energy with respect to the first electrical energy only by the resistance ratio, but it is also possible to modulate the second electrical energy with a surface area coefficient covered by the heating units, a thermal conductivity coefficient, etc.

[0017] Advantageously, each temperature measurement step during the first step or during the second step is a temperature measurement step of the at least one priority zone. The heating method therefore only considers the temperature of the priority zone for controlling the heating units.

[0018] Advantageously, the first step is only performed if the target temperature is more than 15 °C higher than the temperature of at least one priority zone. For example, it is possible to provide for an automatic start of the heating process when such a temperature difference is detected.

[0019] Further aspects and advantages of the present invention will become apparent upon reading the following detailed description of an embodiment of the invention, which is given by way of example and illustrated by the accompanying drawings, in which: Fig. Figure 1 is a simplified view of a heated steering wheel incorporating a heating device according to the present invention capable of performing the heating method according to this invention; Fig. 2 a diagram of the steering wheel of Fig. 1 shows temperatures measured when the method according to the present invention is carried out; Fig. 3 shows a heating mat for a heating device according to the invention; and Fig. 4 shows an exemplary current supply during a first step of the method according to the invention.

[0020] Fig. 1 represents a steering wheel comprising: - a hub arranged to attach the steering wheel to a steering column, - a steering wheel rim, - three arms that connect the hub to the steering wheel rim.

[0021] The steering wheel rim comprises two priority zones 10 and two additional zones 20. A first priority zone 10 is located approximately at 10 o'clock, and a second priority zone 10 is located at 2 o'clock. In other words, the two priority zones 10 are located where the driver most frequently places his or her hands while driving the vehicle (10:10 o'clock position).

[0022] When the vehicle is cold, it is advantageous to heat the two priority areas 10 to quickly provide the driver with a pleasant feeling of comfort. The other areas 20 are then heated less quickly.

[0023] For this purpose, the heating device according to the invention comprises: - a first heating unit arranged in the steering wheel rim in the two priority areas 10, - a second heating unit arranged in the steering wheel rim in the other two areas 20.

[0024] For example, it may be considered to provide a resistance layer 30 under the outer layer of the steering wheel rim, as in Fig. 3, with two electrical resistors, each positioned opposite the areas to be heated (a first electrical resistor 11 opposite the priority areas 10 and a second electrical resistor 12 opposite other areas 20). When the first area is bisected by the second area, as in this example, there is electrical continuity (of the electrical conductors) between the two electrical elements associated with each area. Each continuity influences the temperature of the area through which it passes when powered. Depending on the intensity of the influence, the heating and holding coefficients can take into account the effect of these electrical continuities.

[0025] Due to the presence of a rotating electrical connection on the steering wheel hub, the power supply PA is limited to a maximum power supply PMA, and it is essential to calibrate the total value of the heating resistors 11 and 12 as a function of this maximum power supply. Taking this limitation into account, the invention proposes supplying the first resistor of 11 and the second resistor of 12 according to a specific strategy, but in order to heat the priority zones 10 quickly.

[0026] Fig. Figure 2 illustrates an example of heating using the method according to the present invention. The ordinate axis refers to the temperatures measured on the surface of a steering wheel equipped with a heating device according to the present invention, and the abscissa axis represents time.

[0027] The solid curve represents the temperature in the priority areas 10, on the right in the first resistor 11, and the dotted curve represents the temperature in the other areas 20, on the right in the second resistor 12.

[0028] A temperature setpoint C is defined between two horizontal lines, for example between 25 °C and 28 °C. When the vehicle's steering wheel is cold (e.g. 0 °C), the heating process can be activated automatically or by the driver.

[0029] During a first step, between t0 and t1, the first resistor 11 is supplied with a first electrical power P1, which represents the majority of the maximum supply power PMA (e.g., 70% of the maximum supply power PMA), and the remaining available supply power PA is delivered to the second resistor 12 (i.e., 30% of the maximum supply power PMA in this example) as the second electrical power P2. Thus, PMA = P1 + P2.

[0030] It can be observed that the temperature in the priority areas 10 rises faster, between t0 and t1, than the temperature in the other areas 20. During this first step, the heating process also detects a first electrical energy EE1, which is supplied to the first resistor 11 (EE1, the first electrical energy in joules, is the product of the first electrical power P1 in watts by time (t1-t0) in seconds).

[0031] At time t1, the priority zones 10 are at the temperature setpoint C, and then a second step begins to regulate the first resistor 11 to maintain this temperature setpoint. For this purpose, a maximum predefined power is available for the first resistor. The remainder of the available electrical power is then delivered to the second resistor 12, so that PMA = P1+P2 still applies. However, the electrical energy delivered to this second resistor 12 is a second electrical energy EE2, calculated based on the first electrical energy EE1 determined in the first step. Since this first electrical energy made it possible to bring the priority zones 10 to the temperature setpoint C using the temperature measurement, it is therefore reliable to take this first electrical energy EE1 into account to determine the amount of energy to be supplied to the second resistor 12.Of course, the first electrical energy EE1 can be weighted to determine the second electrical energy EE2, depending on a resistance ratio of 12 / 11, a surface area to be heated, another experimental ratio, or the vehicle's interior temperature or, for example, the resistance temperature. Parameters related to the steering wheel structure, such as the presence of decorative elements made of different materials, can also be taken into account.

[0032] As for the first resistor 11, it is only supplied to maintain the temperature setpoint. The supply can be limited to 50% or less of the maximum supply power, and even the second resistor 12 can be supplied with the entire supply power when the first resistor 11 does not need to be supplied, such as between time t1 and time t2. Between time t2 and time t3, the first resistor 11 must be supplied, which reduces the energy supplied to the second electrical resistor 12 and causes its temperature to rise less rapidly. However, at time t3, all of the electrical energy EE2 has been delivered to the second electrical resistor 12, and it is therefore at the setpoint temperature.

[0033] It should be noted that the method according to the invention does not take into account the temperature in the other zones 20. Only the temperature in the priority zones is taken into account to control the first electrical resistance 11, and only the first electrical energy EE1 is taken into account to control the second electrical resistance during the second step between t1 and t3, less the requirements for regulating and maintaining the temperature of the first electrical resistance 11.

[0034] Once the second electrical energy EE2 has been fully delivered to the second electrical resistor 12, a third step begins: maintaining the temperature setpoint of the entire steering wheel. In this third step, the first electrical resistor 11 is controlled depending on its temperature, and the second electrical resistor 12 is controlled in the same way as the first resistor 11, simply multiplying the first electrical power P1 by a holding coefficient to determine the second electrical power P2 supplied to it.

[0035] In other words, the second electrical power P2 is an affine function of the first electrical power P1 supplied to the first electrical resistor 11.

[0036] If 11 and 12 are equivalent or each need to heat an equivalent surface, and the steering wheel is similarly constructed in the two areas to be heated, it may be considered to supply the same electrical power to the two resistors 11 and 12. Thus, it is possible to ensure that both areas are maintained at the same temperature at the same interval using only one temperature sensor.

[0037] Fig. Figure 4 shows an example of the voltage supply to resistors 11 and 12 during the first heating step. During a period T1, which is repeated during the first step, only the first resistor 11 is supplied with the total available electrical power between the beginning of the period and 70% of this period T1. After that, resistor 12 is supplied with the total available electrical power until the end of the period T1.

[0038] Consequently, the first resistor 11 receives approximately 70% of the total available power over the period T1, and the second resistor 12 receives the remainder, i.e., approximately 30% of the total available power. This principle can, of course, be repeated in the second and / or third heating step of the method according to the invention.

[0039] In addition, it may be considered to chop the current during the supply phases of each resistor in order to finely regulate the intensity of the current flowing through each resistor by regulating the chopping frequency.

Claims

[1] Method for heating a steering wheel of a vehicle comprising at least a first electric heating unit and at least a second electric heating unit supplied by a common supply line defining a maximum supply power, the method comprising: - a first step comprising a phase of supplying an electric current to the at least one first electric heating unit until at least one priority area (10) of the element reaches a temperature setpoint, and a phase of determining a first electric energy supplied to the at least one first electric heating unit to reach the temperature setpoint, - a second step comprising at least one phase of supplying the at least one second electrical heating unit with a second electrical energy calculated on the basis of the first electrical energy, wherein during the second step the at least one first electrical heating unit consumes at most a predetermined part of the maximum supply power and the at least one second electrical heating unit consumes the available supplement of the maximum supply power. [2] The method of claim 1, wherein the second step comprises at least one phase of supplying an electric current to the at least first electric heating unit to maintain the at least one priority region (10) of the element at the temperature setpoint. [3] A method according to claim 1 or claim 2, wherein: - during the first step, at least one first electric heating unit receives at least 60% of the maximum supply power. [4] Method according to one of the preceding claims, wherein during the second step the at least one second electrical heating unit is supplied by taking into account only the first electrical energy supplied to the at least one first electrical heating unit during the first step. [5] A method according to any one of the preceding claims, comprising a third step which begins after the complete supply of the second electrical energy to the at least one second electrical heating unit and consists of the following: - maintaining the at least one priority area (10) of the steering wheel at the target temperature by supplying the at least one first electrical heating unit with a first electrical holding power, - supplying a second holding electrical power, which is calculated on the basis of the first holding electrical power, to the at least one second electrical heating unit. [6] The method of claim 5, wherein the at least one first electrical heating unit comprises a first electrical resistance (11), wherein the at least one second electrical heating unit comprises a second electrical resistance (22), and wherein, during the third step, the second holding electrical power supplied to the at least one second electrical heating unit is equal to the first holding electrical power modulated by a ratio of the value of the second electrical resistance (22) divided by the value of the first electrical resistance (11). [7] Method according to one of claims 1 to 5, wherein the at least one first electrical heating unit comprises a first electrical resistance (11), wherein the at least one second electrical heating unit comprises a second electrical resistance (22), and wherein the second electrical energy is equal to the first electrical energy modulated by a ratio of the value of the second electrical resistance (22) divided by the value of the first electrical resistance (11). [8] Method according to one of the preceding claims, wherein each step of measuring a temperature during the first step or during the second step is a step of measuring a temperature of the at least one priority area (10). [9] Method according to one of the preceding claims, wherein the electrical heating of the steering wheel is only carried out if the target temperature is more than 15 °C higher than the temperature of the at least one priority area (10).

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