FLUID-HEATING DEVICE, IN PARTICULAR INTENDED FOR A VEHICLE

The present invention relates to an electrical fluid-heating device, in particular intended for a motor vehicle, comprising at least one electrical heating element (4) intended to heat the fluid, a temperature sensor (83) intended to give information about the temperature of the fluid, a switch (87), called inrush current switch, intended to create an inrush current in a power supply circuit (88) of said one or more electrical heating elements, an opening means (89) for opening said circuit in the event of said inrush current occurring, the temperature sensor (83) and the inrush current switch (87) being positioned independently of one another, the heating device being configured so as to transmit a signal from the temperature sensor (83) to the inrush current switch (87).

The invention relates to a fluid heating device, in particular intended for a vehicle, more particularly for an installation for ventilating, heating and/or air conditioning the vehicle interior and/or the thermal regulation of a battery. It may be in particular an electric or hybrid vehicle that is able to be autonomous.

It is known practice to heat the air intended for the thermal treatment of a vehicle interior through the exchange of heat between an air flow and a heat transfer liquid, using a heat exchanger. In the case of hybrid or electric vehicles, electric heating devices that form a source of heat energy, through which an electric current is circulated to raise the temperature of electric heating elements placed in contact with the heat transfer liquid are known. Heat energy is then exchanged between the electric heating elements and the heat transfer liquid, which in turn heats up before heating the car interior by virtue of the exchanger.

To prevent any overheating, document EP 2 884 519 teaches the use of a means for opening the power supply circuit for the electric heating elements. Said means is actuated through the deformation of a bimetallic strip placed in contact with said electric heating elements. The bimetallic strip deforms when the temperature of the electric heating elements reaches a certain predefined threshold, and ensures the actuation of the means for opening the circuit by means of a leaf.

Such a solution for preventing overheating has a major drawback due to the fact that the bimetallic strip, in order to be positioned correctly with respect to the electric heating elements, must have a specific shape of costly construction. In addition, the bulk resulting from the mechanical coupling between the bimetallic strip and the opening means via the leaf reduces the margin of maneuver for mounting the assembly in the heating device, with the consequence in particular of the risk of the bimetallic strip being positioned outside the region of maximum heating.

It is therefore necessary to find a solution for preventing overheating of the electric heating elements of a heating device which is of simple construction and is easy to mount in said heating device.

The present invention aims to at least partly provide such a solution.

To that end, the subject of the invention is an electric fluid heating device, in particular for a motor vehicle, comprising at least one electric heating element intended to heat the fluid, a temperature sensor intended to give information on the temperature of the fluid, a switch, called the inrush current switch, intended to create an inrush current in a power supply circuit for said one or more electric heating elements, an opening means for opening said circuit in the event of said inrush current occurring, the temperature sensor and the inrush current switch being positioned independently of one another, the heating device being configured to transmit a signal from the temperature sensor to the inrush current switch.

Thus, with a temperature sensor mounted independently of the inrush current switch, the invention simplifies the assembly of the solution for preventing overheating by allowing each of these components to be positioned at the chosen relevant location.

The invention may also comprise any one of the following features, taken individually or in any technically possible combination forming as many embodiments of the invention:the heating device comprises a means for transmitting the signal between the temperature sensor and the inrush current switch;the means for transmitting the signal comprises an electrical conductor;the heating device comprises a microcontroller able to control the inrush current switch;the means for transmitting the signal provides the connection between the temperature sensor and the microcontroller;the heating device further comprises an upstream switch and a downstream switch;the electric heating element is connected in series to the upstream switch and to the downstream switch;one of the upstream or downstream switches is configured to regulate a current flowing through the electric heating element;the upstream switch and the downstream switch are connected to a control circuit board for controlling the current flowing through the electric heating element;the means for opening the circuit comprises at least one fuse;the fuse is connected in series with the electric heating element;the means for opening the circuit is connected upstream of the upstream switch or downstream of the downstream switch;the means for opening the circuit is configured to protect the electric heating element in the event of simultaneous failure of the upstream switch and of the downstream switch;the inrush current switch is connected on a short-circuit line in parallel with the electric heating element;the short-circuit line comprises a first end and a second end;the first end of the short-circuit line is positioned between the electric heating element and the upstream switch and/or the second end of the short-circuit line is positioned between the electric heating element and the downstream switch;the first end of the short-circuit line is positioned upstream of the upstream switch, and/or the second end of the short-circuit line is positioned downstream of the downstream switch;the means for opening the circuit comprises at least one fuse;the fuse is connected upstream of the first end of the short-circuit line or downstream of the second end of the short-circuit line;the fuse is connected upstream of the inrush current switch;the fuse is connected downstream of the inrush current switch;the circuit board comprises a region that is thermally insulated with respect to a main region of said circuit board;the temperature sensor is mounted in the insulated region of the circuit board;the heating device further comprises a heat sink between a chamber for circulation of the fluid and the circuit board.

It should first of all be noted that, in all of the figures, elements that are similar and/or perform the same function are indicated by the same reference.

By convention, unless stated otherwise, the term “longitudinal” applies to the direction in which the largest dimension of the electric heating device extends, the term “transverse” applies to a direction substantially perpendicular to the longitudinal direction, and the term “vertical” refers to the direction perpendicular both to the longitudinal direction and to the transverse direction.

Furthermore, with reference to the orientations and directions defined above, the longitudinal direction will be represented by the axis Ox, the transverse direction will be represented by the axis Oy, and the vertical direction will be represented by the axis Oz. These various axes together define an orthonormal reference system Oxyz shown inFIG.1. Within this reference system, the terms “top” or “upper” will be represented by the positive direction of the axis Oz, the terms “bottom” or “lower” being represented by the negative direction of this same axis Oz.

As is illustrated inFIG.1, the invention relates to a heating device1. Said device is used for heating a fluid, in particular a heat transfer liquid. Said device comprises a housing2for circulation of the fluid, at least one heating element4, two in this instance, a cover6supporting said one or more heating elements, and a control unit8for controlling a power supply current for said one or more heating elements.

In particular, the housing2defines a first chamber21for circulation of the fluid, which first chamber is arranged so as to accommodate said one or more electric heating elements4such that the fluid circulating in said housing is brought into contact with said one or more electric heating elements. The housing2also defines a second chamber22in which is housed the control unit8for controlling the current circulating in said one or more electric heating elements4. Lastly, the housing defines a third chamber23which is separated from the first chamber21by means of the cover6.

The housing2is formed, for example, by die-casting aluminum and/or an aluminum alloy.

To circulate the fluid in the chamber21, the housing2comprises at least a first, inlet pipe (not shown) and at least a second, outlet pipe25in communication with said chamber21. The inlet pipe and the outlet pipe25are arranged on one and the same side of the housing2, in this instance at a bottom26of the housing2.

The outlet pipe25leads directly into the chamber21through a first aperture25a.The inlet pipe leads into the chamber21by way of a second aperture formed at one end of said chamber, opposite the bottom26. The inlet pipe comprises a channel longitudinally bordering the chamber21and leading into said chamber.

Each electric heating element4comprises a shielded resistor41arranged in a spiral and also at least one connection terminal42intended to connect said resistor to a current supply source. Said electric heating elements4extend longitudinally in the housing2through the cover6.

To this end, the cover6comprises openings61in which the electric heating elements4are mounted in such a way that, for each of said electric elements, the resistor41extends in the first chamber21and the terminals42extend through the cover6and lead into the third chamber23. The connection between said cover6and said terminals42is leaktight.

The second chamber22is located above the first chamber21, along the latter, and has an upper edge closed off by means of an upper covering3. Furthermore, the second chamber22comprises vertical projections22aand also a platform22bthat are formed on a separating wall10between said second chamber and the first chamber21.

The heating device further comprises at least one temperature sensor83intended to give information relating to the temperature of the fluid and/or of said one or more electric heating elements4.

As illustrated inFIGS.2and3, the heating device also comprises at least one switch87, called the inrush current switch, intended to create an inrush current in a power supply circuit88for the electric heating elements4, and at least one means89for opening said circuit in the event of said inrush current occurring. The electric heating elements4are connected in parallel in said circuit88. The one or more switches87and the one or more means89for opening the current are integrated, for example, into the control unit8.

According to the invention, the temperature sensor83and the inrush current switch87form two components mounted independently of one another.

Such dissociation makes it possible to mount the sensor83at a distance from the inrush current switch87, said sensor and said switch each being able to be positioned at different locations in the heating device. Moreover, such dissociation makes it possible to provide a plurality of temperature sensors and a plurality of inrush current switches in one and the same heating device.

In particular, the inrush current switch87is connected on a short-circuit line881in parallel with one of the electric heating elements4, said short-circuit line having an upstream end881aand a downstream end881b.The upstream position and the downstream position are defined here with respect to the direction of flow of the current.

According to one feature of the invention, the inrush current switch87reacts in the event of the thermal sensor83receiving information relating to the crossing of a threshold temperature by the heat transfer fluid and/or the electric heating elements4by closing the short-circuit line881, the short-circuit line then shorting said one or more electric heating elements4. The resistance of the power supply circuit then decreases sharply, which creates an inrush current and actuates the opening means89. This opens the circuit88and switches said one or more electric heating elements4off.

The means89for opening the circuit88comprises at least one fuse891which is mounted or connected upstream of the first end881aof the short-circuit line881or downstream of the second end881bof the short-circuit line881.

The power supply circuit88may comprise a set of switches82configured to regulate the current flowing through said one or more electric heating elements4. Each electric heating element4is connected in series to a first current regulating switch, called the upstream switch82A, which communicates with a pulse width modulation (PWM) generator of the control unit8; and a second current regulating switch, called the downstream switch82B, which ensures the safety of said electric heating element4in the event of failure of the upstream switch82A.

The current regulating switches82are chosen from insulated-gate bipolar transistors (IGBTs) and/or metal-oxide-semiconductor field-effect transistors (MOSFETs), known for their ability to handle high supply powers as required in an electric or hybrid vehicle heating application.

In a circuit88comprising an upstream switch82A and a downstream switch82B for regulating the current flowing through an electric heating element4, the means89for opening the circuit88according to the invention intervenes in the event of simultaneous failure of said upstream switch and of said downstream switch. Said means89is positioned upstream of the upstream switch82A or downstream of the downstream switch82B of the electric heating element4.

Additionally, as illustrated inFIG.2, the first end881aof the short-circuit line881is connected to the circuit88upstream of the upstream switch82A and the second end881bof the short-circuit line881is connected to the circuit88downstream of the downstream switch82B.

However, as illustrated inFIG.3, the first end881aof the short-circuit line881may be positioned directly upstream of the electric heating element4, between said electric heating element4and the upstream switch82A. The second end881bof the short-circuit line may be positioned directly downstream of the electric heating element4between said electric heating element and the downstream switch82B.

Such positioning of the ends881a,881bof the short-circuit line881prevents the actuation of the means89for opening the circuit88in the event of untimely triggering of the switch87. Specifically, the short-circuit line881does not short the switches82A,82B which, in normal operation, may regulate the current flowing through the circuit88.

AlthoughFIG.3shows the fuse891positioned upstream of the upstream switch82A, it is quite possible to envisage positioning said fuse between said upstream switch and the electric heating element4. Such positioning of the fuse remains consistent with the spirit of the present invention.

Advantageously, the temperature sensor83may be positioned on an circuit board81, and in particular in a region812that is thermally insulated with respect to a main region813of said circuit board. The means89for opening the circuit88may then be positioned in said main region813or on any other support formed in the second chamber22of the housing2.

With a temperature sensor83positioned on the circuit board81, the recording of an image of the temperature of the fluid contained in the first chamber21may be carried out using a heat sink located between said first chamber and said circuit board.

Advantageously, the connection between the temperature sensor83and the inrush current switch87is provided by a chosen signal transmission means. It is, for example, a means for transmitting a signal of an electrical nature, in particular an electrical conductor.

The signal transmission means is configured also to provide the connection between the temperature sensor83and one of the upstream82A or downstream82B switches via a microcontroller84, said microcontroller allowing the operation of the inrush current switch87to be controlled.

In the case of a plurality of electric heating elements4connected in parallel, one and the same means89for opening the circuit88, in particular one and the same fuse891, and/or one and the same inrush current switch87could be used for multiple, or even all, of the electric heating elements. Specifically, a short-circuit made with respect to one electric heating element is sufficient to short all of the other electric heating elements of the heating device, since the current flows through the electrical line of least resistance.