WO2015091598A1

WO2015091598A1 - Heating device

Info

Publication number: WO2015091598A1
Application number: PCT/EP2014/078137
Authority: WO
Inventors: Andreas Petereit; Christoph Wendt
Original assignee: Iee International Electronics & Engineering S.A.
Priority date: 2013-12-20
Filing date: 2014-12-17
Publication date: 2015-06-25
Also published as: LU92342B1

Abstract

In electric vehicles, the cabin air cannot be heated with the waste heat of an internal combustion engine. The present invention relates to a heating device, which is preferably arranged in electrically powered vehicles for heating a limb or a body in proximity thereof. A capacitive measurement is used for detecting a limb or body in proximity of at least one planar heating element (4). If the measured capacitance is indicative of a body or limb in proximity thereof, the at least one planar heating element is heated.

Description

HEATING DEVICE

Technical field

[0001 ] The present invention generally relates to a heating device. The invention more particularly relates to a heating device to be arranged inside an electrically powered vehicle.

Background Art

[0002] In traditional automotive vehicles, the waste heat of the combustion engine is used to provide the cabin heating of the vehicle. In electrically powered vehicles no combustion heat is available for heating the vehicle cabin. As an increasing number of cars are powered exclusively by electric engines alternative heating methods and devices have to be provided for heating the vehicle cabin of electrically powered vehicles.

[0003] Vehicle cabins can be heated e.g. by arranging surface heaters therein. Surface heaters are known from the prior art and are frequently used inside vehicle seats as seat heaters.

[0004] The surface heaters require electric energy to operate. In electrically powered cars, electric energy is primarily used to power the electric propulsion engine. As electric energy is provided by batteries arranged inside a car, the maximal range of the car depends on the maximum capacity of the batteries, the energy consumption of the electric propulsion engine and the energy consumption of secondary consumers, e.g. surface heaters, radio, climate control, light. To guarantee a maximum range, the electrical power consumption of the heaters has to be kept at a minimum.

[0005] To optimize the energy consumption, the surface heaters are only activated, if the passenger is in proximity thereof. Proximity measurements can be carried out by a seat occupancy sensor incorporated in a substrate as described in the European patent application EP 1 256 483 A2.

[0006] EP 1 256 483 A2 describes a seat occupancy sensor with a plurality of pairs of electrical wires. Each pair of electrical wires defines a capacitive element and each capacitive element is connected to a detector circuitry via a connecting wiring. The occupancy sensor can thus be used to trigger certain electrical appliances such as for example seat heaters. The occupancy sensors can be further used for activating/deactivating seat belt reminders or provide input for security features such as e.g. airbags.

[0007] However, there is a problem of integrating a surface heater and an occupancy sensor into a surface cover. The problem is particularly significant if the surface heaters and occupancy sensors have to be applied on curved or thin surfaces, e.g. an armrest, a steering wheel or a middle console.

Technical problem

[0008] It is an object of the present invention to provide an improved heater. This object is achieved by an approximation-controlled heater as claimed in claim 1 .

General Description of the Invention

[0009] The present invention relates to a heating device, which may e.g. be arranged in electrically powered vehicles. The heating device comprises at least one planar heating element comprising at least one layer of resistive material arranged between first and second busses made of electrically conductive material. The first and second busses are connectable to a power source in such a way that, in operation, an electrical current flows from one of said first and second busses across the layer of resistive material to a respective other one of said first and second busses. The at least one heating element is operatively connected to a control unit for controlling the at least one planar heating element in operation, such that the at least one planar heater element is preferably either turned "on" or "off. If the planar heating element is turned "on" the planar heating element is connected to the power source. If the planar heating element is turned "off', the planar heating element is not connected to the power source.

[0010] According to the invention, the control unit further comprises an evaluation module capable of supplying an alternative signal to the at least one layer of resistive material and/or to said first and second busses of the planar heating element for detecting a quantity indicative of a capacitance or a variation in capacitance relating to the planar heating element. The planar heating element is the preferably controllable by the control unit based on said capacitance or said a variation of capacitance.

[001 1 ] With the heating device as described, the planar heater element may be controlled to be operable only if its operation "makes sense". The planar heating element is e.g. preferably only turned "on" if a variation in capacitance relating to the at least one layer of resistive material and/or to said first and second busses of the planar heater element is detected that indicates that a part of a passenger is in proximity of the planar heating element. If no part of the passenger's body is in proximity of the planar heater element, the heater element may be turned "off' because its operation would not contribute substantially to the well-being of the passenger. The electrical energy consumption of the heater device is thus optimized, since the heater device only consumes electrical power if the variation in capacitance relating to the planar heating element is indicative of a body part, e.g. a limb, of a person in proximity of the planar heating element.

[0012] The heating device according to the present invention thereby advantageously combines the heating and detecting function in a single operative element, i.e. only one device is required for measuring and heating alternatively. Thus the planar heating element can be integrated easily on a surface or on a cover in a vehicle cabin. As the detecting and heating is carried out be the same device the planar heating element operates more accurately. If two separate detecting and heating elements were arranged one above the other in or on a surface the detecting element would perturb the heating element and vice-versa. If the detecting element and the heating element were arranged displaced one from the other in a surface the object or limb would be either detected or heated optimally, but the object or limb would not detected and heated optimally.

[0013] Preferably, the at least one planar heater element comprises a carrier layer made of a thin flexible material with said first and second busses and/or said at least one layer of resistive material being applied onto said carrier layer. The thin flexible material is preferably a textile material of a polymer film with printed conductors (busses and resistive layer) arranged thereon. Due to the flexibleness, the at least one planar heater element can be arranged on curved surfaces. The at least one planar heater element does not loose any of its capabilities for heating or measuring even when applied on a curved surface.

[0014] Preferably, the control unit is configured for receiving a user input. The control unit then advantageously controls the at least one planar heater element based amongst others on the user input. The user input can be an instruction to start the operation of the vehicle heating system or the user input can be an instruction to regulate the heating power supplied from the power source to the heating element. Alternatively the user input may be the turning of the ignition key or the pushing of the start button.

[0015] The heating device preferably also comprises an environmental input to the control unit. The control unit then controls the at least one planar heater element amongst others by the environmental input. The environmental input preferably comprises an outside temperature and/or a vehicle cabin interior temperature. If the outside temperature or cabin temperature is above a predetermined threshold temperature, the at least one planar heater element is preferably not turned on.

[0016] According to a preferred embodiment of the invention, the planar heating element is arranged in at least a roof and/or an armrest and/or a dashboard. By implementing the planar heating element into surfaces close to the passenger's limbs or close to the passenger's body, the comfort of the passenger inside the vehicle cabin is increased.

[0017] Advantageously, the planar heating element is heatable even if no variation in capacitance is detected, i.e. the control unit can also control the planar heating element without relying on the capacitance measurement. If e.g. a user input is supplied for heating without the capacitive measurement then the control unit can control the planar heating element such, that heat is provided by the planar heating element irrespective of the presence or absence of a body part in the vicinity of the heater element.

[0018] The at least one planar heater element can be shaped/designed according to the surface it has to be arranged on or in. The at least one planar heater element preferably has the shape of a square or rectangular, but any other geometric shape is also possible. [0019] Preferably, the at least one layer of resistive material of the at least one planar heater element comprises a resistive PTC material. In a resistive PTC material, the electrical resistance of the material increases with the temperature of the heating element. Due to the increasing electrical resistance, the current flowing through the heating element decreases with increasing temperature and thus the resistive PTC material limits the maximum heating temperature T_heat-

[0020] During operation of the heating device, i.e. if the power source is connected to the planar heating element, the planar heating element is preferably periodically disconnected from the power source to measure a variation in capacitance. If no body part is detected near the planar heating element, the at least one planar heater element may remain turned "off. If a body part is detected near the planar heating element, the at least one planar heater element is turned "on" again. The heating device is thus able to turn the planar heating element to "off' if no body part is near the planar heating element.

[0021 ] It will be noted that the heating device can comprise additional heating elements operatively connected to the control unit. The control unit may then be capable of measuring a change in capacitance of each heating element connected thereto. Additionally or alternatively, the additional heating elements are not controlled by a change in capacitance. In result "traditional" heating elements can be installed in parallel to planar heating elements to further optimize the heating of the vehicle cabin.

Brief Description of the Drawings

[0022] Further details and advantages of the present invention will be apparent from the following detailed description of several not limiting embodiments with reference to the attached drawings, wherein:

Fig. 1 is a schematic view of a first embodiment of a heating device;

Fig. 2 is a schematic view of a second embodiment of a heating device;

Fig. 3 is a schematic view of a preferred heating device with more than one heater element. Description of Preferred Embodiments

[0023] The heating device 2 comprises a planar heating element 4, which can be integrated easily in or on the surfaces in a vehicle cabin. The planar heating element 4 of the heating device 2 in fig .1 is preferably arranged in surfaces in proximity of the passenger's body or the passenger's limbs inside an electrically powered vehicle. The planar heating element 4 can be arranged e.g. in an armrest, a vehicle seat, a steering wheel, a backrest of a vehicle seat or/and a middle console.

[0024] The planar heating element 4 preferably comprises a layer of resistive material 7, e.g. a resistive PTC material, which is arranged between two busses 6, 8. In operation, the busses 6, 8 of the planar heating element 4 are connected via an electrical circuit 10 to a power source, e.g. the vehicle battery, so that an electrical current flows via the busses 6, 8 across the layer of resistive material 7. A control unit 14 is operatively connected to a controllable switch 16 of the circuit for controlling the power supply from the power source 12 to the one planar heating element 4.

[0025] The planar heating element 4 is preferably approximation controlled, meaning that the heater element 4 is only powered if the user's body or a limb is in proximity of the planar heating element 4. For detecting an object in proximity of the planar heater element 4, the control unit 14 preferably comprises an evaluation module 15 configured for detecting a variation in capacity with respect to the planar heating element 4. Furthermore a second controllable switch 24 is preferably provided in the electrical circuit 10 for disconnecting the second bus 6 of the planar heating element 4 from the power source 12, so that the planar heating element is entirely decoupled from the power source of both the switches 16 and 24 are in an open position.

[0026] Various detection modes can be used for detecting the proximity of a passenger's body part. The evaluation module may for instance be configured to detect a capacitive coupling between the heating element and vehicle ground, which capacitive coupling is influenced by the presence of a conductive body part in the vicinity of the heating element. An alternating voltage signal may e.g. be supplied from the evaluation module 15 of the control unit 14 via at least one of the busses 6, 8 to the planar heating element. The planar heating element 4 emits an alternating electromagnetic field which is influenced by a body part of a passenger.

[0027] One convenient mode to detect an object in proximity of the planar heating element 4 is the so called "loading mode". In "loading mode", the control module 15 measures the current "pulled" from the planar heating element 4 by the body or limb of a passenger in proximity thereof. If the "pulled" current exceeds a predefined threshold value stored in the evaluation module 15, the planar heating element 4 is turned "on". Alternatively, the planar heating element 4 can also be operated in "transmit mode" or "shunt mode", in which the capacitive coupling of the electromagnetic field into a second electrode, which is preferably connected to ground, is detected. In yet another embodiment, the planar heating element 4 can be operated as a switched capacitor in order to determine the relevant capacitance.

[0028] In case the heating device 2 is operated and the switches 16 and 24 are in open position, the planar heating element 4 performs as proximity sensor. If a body or limb is in proximity to the heating device 2, the planar heating element 4 is electrically connected to the power source 12 by closing switches 16 and 24, which are arranged in the electrical circuit 10. When the switches 16 and 24 are in closed position, a current flows through the planar heating element 4 until the planar heating element 4 is heated to a desired temperature.

[0029] It will be noted that the heating device 2 as described does not require an additional dedicated occupancy sensor. In result, the planar heating element 4 is easier to install into or on surfaces inside the vehicle cabin. This is particularly relevant if the planar heating element 4 is integrated into a surface. Since the planar heating element 4 serves alternatively as a proximity detector and a surface heater less cabling is required in comparison to a separate proximity detector and surface heater. Furthermore, less material is required for producing the planar heating element 4.

[0030] It should be noted, that the planar heating element 4 should not be operated simultaneously as a capacitive occupant detection sensor and as a resistive heater element. A detection of proximity of a body part is preferably carried out when the heating device is first activated by the user. Once an object or limb has been detected, the switches 16 and 24 are closed and the planar heating element 4 is powered in order to generate heat. In this heating mode the heating element can no longer be used as an electrode for detecting a body or limb in proximity thereof.

[0031 ] In order to avoid continuous heating operation even if a body or limb that is no longer in proximity of the planar heating element 4, switches 16 and 24 are opened periodically for a short presence detection operation to check whether a body or limb still is in proximity thereof. If there is no body or limb close to the planar heating element 4, at least one of the switches 16 and 24 remains open and the heating element is no longer supplied with the heating current. If there still is a body or limb close to the planar heating element 4, switches 16 and 24 are closed again, and the planar heating element 4 is operated as a heater once again.

[0032] The control unit 14 controls the switch 16 and/or not only based on the measurements inputs but also based on other inputs, such as e.g. user inputs 18 or environmental inputs 20.

[0033] The user inputs 18 may include parameters that the user is able to set, modify or choose, e.g. the heater temperature setting or the heater on/off setting. The user can deactivate the heating of the planar heating element 4, if he does not want the heating device 2 to be turned on.

[0034] In addition to the user inputs 18, other inputs to the control unit may comprise environmental inputs 20 such as e.g. the outside temperature and/or the cabin temperature. Alternatively or additionally an input from a batter control 22 may be provided, to prevent the planar heating element 4 from draining the battery e.g. if the remaining power of the battery falls below a predetermined threshold.

[0035] In operation, when starting the vehicle or when the heating device is triggered or activated by user input, the switches 16 and 24 are in the open position and a condition relating to the capacitance of the capacitive system formed by planar heating element 4 and its environment is detected, e.g. the disturbance of an electrical field generated around the planar heating element 4 by objects or body parts in its vicinity. A passenger's limb or a body part in proximity of the planar heating element 4 influences the measured capacitance. This capacitance of said heating element 4 or a change of capacitance due to the proximity of a body part is evaluated by the evaluation module 15. If the change in capacitance is above (loading mode) a predetermined threshold value, the user settings and the environmental settings correspond to the required values, the switch 16 is closed and the planar heating element 4 is activated.

[0036] The control unit 14 closes the switches 16 and 24 of the heating device, if all of the other parameters correspond to the predetermined values. The control unit 14 checks, if the cabin temperature is below the predetermined temperature. If for example the cabin temperature exceeds the predetermined temperature, the switch 16 is not closed. Furthermore, if the desired temperature set by the user is lower than the temperature of the planar heating element 4, the switch 16 is not closed.

[0037] If the battery runs low on energy, at least one of the switches 16 and 24 is not closed and the planar heating element 4 is not turned on.

[0038] In closed position, a current, preferably a pulsed current is applied to the busses of the planar heating element 4 and the heating element is generating heat. The heating temperature T_heat is preferably limited by the resistive material of the planar heating element 4. According to a particularly advantageous embodiment of the invention, a material with a PTC (positive temperature coefficient) is used for limiting the maximum heating temperature T_heat, max = 60- 70°C.

[0039] Fig. 2 shows an embodiment of a heating device, in which during the detection mode, the capacitive coupling between the planar heater element 4 and a second electrode 26 is detected. This coupling is indicated in Fig. 2 by the capacitance 28. The second electrode 26 is operatively coupled to the evaluation module 15 of the control unit 14. It will however be noted that the second electrode 26 may be connected to ground. The skilled person will further appreciate, that in a possible embodiment, the second electrode 26 may also be a second planar heater element.

[0040] For providing additional heating power, the surface of the planar heating element 4 can be increased. However, the greater the surface of the planar heating element 4 the more energy is required for powering the planar heating element 4. Another arrangement for increasing the heating power is illustrated in Fig. 3. In Fig. 3 an additional planar heating element 104 is connected to the control unit 14 by an electrical circuit 1 10. Additional planar heating element 104 also preferably comprises a layer of resistive material 107, e.g. a resistive PTC material, which is arranged between two busses 106, 108. The two busses 106, 108 connect the planar heating element 104 to the power source 1 12 (which may be power source 12). As the environmental input 20 and the user input 18 are already provided to the control unit 14, there is no need of an additional control unit 14. The switches 1 16 and 124 are operated amongst others by the measurement inputs of the planar heating element 104 provided to the control unit 14. The heater element 4 and the heater element 104 are both approximation controlled. Both heater elements 4, 104 can be turned "of or "off independently from each other.

Legend:

2 heating device

4, 104 planar heating element

6,8, 106, 108 bus

7, 107 layer of resistive material

10, 110 electrical circuit

12, 112 power source

14 control unit

15 evaluation module 16,24, 116, 124 switch

18 user input

20 environmental input

22 current meter

26 second electrode

Claims

1 . A heating device comprising:

- at least one planar heating element, said planar heating element comprising at least one layer of resistive material arranged between first and second busses made of electrically conductive material,

- a power source connectable to said first and second busses in such a way that, in operation, an electrical current flows from one of said first and second busses across the layer of resistive material to a respective other one of said first and second busses; and

- a control unit operatively connected to said at least one planar heating element for controlling said at least one planar heating element in operation,

characterized in that:

said control unit comprises at least one evaluation module capable of detecting a quantity indicative of a capacitance or a variation of capacitance relating to said at least one layer of resistive material and/or to said first and second busses of at least one planar heating element, wherein said planar heating element is controllable by said control unit based on said capacitance or said a variation of capacitance.

2. A heating device according to claim 1 , wherein said at least one planar heating element comprises a carrier layer made of a thin flexible material, and wherein said first and second busses and/or said at least one layer of resistive material are applied onto said carrier layer.

3. A heating device according to any one of the preceding claims, wherein said control unit is configured for receiving a user input and wherein said control unit controls said at least one heater element based amongst others on said user input.

4. A heating device according to any one of the preceding claims, wherein said control unit is configured for receiving an environmental input and wherein said control unit controls said at least one heater element based amongst others on said environmental input.

5. A heating device according to any one of the preceding claims, wherein said at least one planar heating element is arranged in at least a roof and/or an armrest and/or a dashboard of a vehicle.

6. A heating device according to any one of the preceding claims, wherein said at least one heating element is heatable even if no variation in capacitance is detected.

7. A heating device according to any one of the preceding claims, wherein said at least one layer of resistive material of said at least one heating element comprises a resistive PTC material.

8. A heating device according to any one of the preceding claims, wherein more than one planar heating element is operatively connectable to said control unit.