HEATER PARTICULARLY FOR A MOTOR VEHICLE HVAC SYSTEM

Abstract

A motor vehicle HVAC unit includes a housing, preferably a fan, preferably a coolant evaporator for cooling air to be supplied to the vehicle interior, at least two electric resistance heaters for heating the air to be supplied to the vehicle interior and at least one delay circuit, preferably two delay circuits. The at least two electric resistance heaters are suppliable with electric current, and a device is provided for supplying current to at least one of the at least two electric resistance heaters with a time delay relative to another electric resistance heater, and during the turning on or supplying current to the electric resistance heaters a small maximum current peak requirement is to occur at low technical expenditures.

Description

This nonprovisional application claims priority under 35 U.S.C. §119(a) to European Patent Application No. EP09290807.8, which was filed on Oct. 21, 2009, and which is herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a heater particularly for a motor vehicle HVAC system according to the preamble of claim 1 and to a method for operating a heater of this type according to the preamble of claim 12.

2. Description of the Background Art

Motor vehicle HVAC systems are used for heating and cooling air that is supplied to the interior of a motor vehicle. In this regard, electric heaters or resistance heaters are used for heating the air, particularly in hybrid or electric vehicles. An electric current is passed through the electric resistance heaters and because of the electric resistance of the electric resistance heaters, they become heated, so that the air supplied to the vehicle interior can be heated by passing the air past the electric resistance heaters.

To control different heat outputs of the electric resistance heaters, the electric resistance heaters are supplied with current in pulse width modulation (PWM). When the electric resistance heaters are supplied with pulse-width-modulated current, the electric heat output of the electric resistance heaters is controlled to the effect that the pulse width modulation is changed. This means that for an increase in the electric heat output the turn-on time is lengthened and the turn-off time shortened and conversely during a reduction of the electric heat output the turn-on time is shortened and the turn-off time increased. The electric current for the electric resistance heaters originates from an on-board electrical system as the current source of the motor vehicle. In order not to have a very large maximum current peak requirement for all electric resistance heaters during turning on or supplying current to the electric resistance heaters, i.e., at the beginning of the turn-on time of the pulse-width-modulated current, the pulse-width-modulated current before being supplied to the individual electric resistance heaters is delayed in time by a microcontroller. The electric resistance heaters thereby have turn-on times that are not simultaneous but delayed in time and thereby sequential in time. The maximum current peak requirement for the electric resistance heaters can be reduced thereby, because all electric resistance heaters are not turned on or supplied with current at the same time; i.e., the turn-on times of the electric resistance heaters are not identical.

The microcontroller, which generally has a processor and thereby can run a program or software, is thereby generally arranged in the motor vehicle HVAC system, particularly in the area of the electric resistance heaters. Microcontrollers of this type are time-consuming to produce, however, and thereby expensive and thereby in addition prone to failure during operation.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a heater particularly for motor vehicle HVAC units and a method for operating a heater of this type, in which heater and method during the turning on or supplying of electric resistance heaters with current, a small maximum peak current requirement occurs at low technical cost. The heater should be inexpensive to produce and reliable to operate.

This object is achieved with a heater, particularly for an HVAC unit, comprising a housing, preferably a fan, preferably a coolant evaporator for cooling air to be supplied to the vehicle interior, at least two electric resistance heaters for heating the air to be supplied to the vehicle interior, whereby the at least two electric resistance heaters can be supplied with electric current, and a device for supplying current to at least one electric resistance heater with a time delay relative to another electric resistance heater, whereby the device comprises at least one delay circuit, preferably two delay circuits, and/or the device comprises at least one delay circuit, preferably two delay circuits.

In particular, the at least one delay circuit is at least one, particularly exclusively, analog delay circuit and/or the at least one delay circuit has no processor and/or no program can be run by the at least one delay circuit and/or the at least one delay circuit is an electric and/or electronic circuit, particularly without a processor. Therefore no digital signals or information can be processed in the at least one delay circuit. The delay circuit is therefore an electric and/or electronic circuit with a very simple structure, which in particular has no processor. Therefore, the delay circuit can be produced simply and at reasonable cost, so that the high cost for an expensive and time-consuming microcontroller can be economized.

In another embodiment, the at least one delay circuit comprises at least one capacitor and/or at least one resistor. It is also possible to provide an inductor in addition.

In a supplementary embodiment, the at least one delay circuit comprises exclusively at least one capacitor and/or at least one resistor as an electric and/or electronic component. Because simple electronic components are used, for example, a capacitor and a resistor, the delay circuit can be produced simply and at reasonable cost.

Preferably, the at least one electric resistance heater can be supplied with electric current in pulse width modulation. The supplying of the at least two electric resistance heaters with current therefore corresponds to the passing of current through the at least two electric resistance heaters during the turn-on times of the pulse-width-modulated current.

In a variant, at least one electric resistance heater can be supplied with pulse-width-modulated current delayed in time relative to another electric resistance heater with the at least one delay circuit. The maximum current peak requirement for the at least two electric resistance heaters, particularly for all electric resistance heaters, can be reduced thereby at the beginning of the turn-on times.

Expediently, the at least one electric resistance heater is at least one PTC heater. It is especially advantageous, in this case, if the at least one resistance heater or a majority of electric resistance heaters are combined into a module and advantageously the electric control unit can be or is connected to this module. An electric resistance heater is then, so to speak, a heating section of the module.

In another embodiment, the at least two electric resistance heaters are connected electrically parallel.

In another embodiment, each of the parallel connected electric resistance heaters are each connected to a parallel power line and the parallel power lines are connected to a central power line.

In a further embodiment, in parallel connected electric resistance heaters one delay circuit each is connected in series to the parallel connected electric resistance heaters.

In a supplementary variant, at least two delay circuit devices are connected parallel and/or in series.

The method of the invention for operating a heater, particularly for a vehicle HVAC system, particularly comprises the steps: conduction of electric current through at least two electric resistance heaters, preferably conduction of air through the heater of the vehicle HVAC system, generation of thermal energy by the at least two electric resistance heaters by converting electrical energy into thermal energy, preferably the transfer of the thermal energy generated by the at least two electric resistance heaters to the air to be heated, which preferably is passed through the vehicle HVAC system, so that the air becomes heated, whereby during the supplying of current to the at least two electric resistance heaters, at least one electric resistance heater is supplied with current delayed in time relative to another electric resistance heater, in order to reduce the maximum current peak requirement for the at least two electric resistance heaters during the supplying of current and/or the turning on of the at least two electric resistance heaters, whereby the current is delayed in an analog manner and/or the current is delayed without a program or software being run.

In another embodiment, the current is delayed exclusively in an analog manner, particularly by at least one delay circuit.

In particular, the current passed through the at least two electric resistance heaters is pulse-width-modulated and preferably the pulse width modulation is changed, particularly the turn-on and turn-off times are changed, in order to control and/or to regulate the electric power of the at least two electric resistance heaters.

In another embodiment, the current is delayed by at least one delay circuit in each case for one electric resistance heater.

In another embodiment, the at least two electric resistance heaters are supplied with current in the high voltage range, for example, with a voltage of at least 60 V, 200 V, or 300 V.

Expediently, the vehicle HVAC system comprises at least one air guiding device, particularly a ventilation flap, and/or at least one air passage and/or at least one heat exchanger through which coolant from a combustion engine flows, for heating the air supplied to the vehicle interior, and/or a control unit.

In a supplementary variant, cooling fins are arranged at the at least two electric resistance heaters, in order to increase the surface for heating the air by current passed through the two electric resistance heaters.

PTC heaters (PTC: Positive Temperature Coefficient) are current- conducting materials that have an electric resistance and can conduct current better at lower temperatures than at higher temperatures. Their electric resistance therefore increases with increasing temperature. The PTC heater generally comprises ceramic, which is a PTC thermistor. Independent of the boundary conditions, such as, e.g., applied voltage, nominal resistance, or volume of air at the PTC heater, a very uniform surface temperature arises at the PTC heater.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

FIG. 1 shows a circuit arrangement with three electric resistance heaters and two delay circuits in a first exemplary embodiment;

FIG. 2 shows a circuit arrangement with three electric resistance heaters and two delay circuits in a second exemplary embodiment; and

FIG. 3 shows the time voltage course of a pulse-width-modulated current for the three electric resistance heaters.

DETAILED DESCRIPTION

A circuit arrangement with three resistance heaters 1, formed as PTC heaters 2, is shown in FIG. 1, particularly for a vehicle HVAC unit (not shown) for heating the air passed through the vehicle HVAC unit.

PTC heaters 2 are connected parallel in this case and are supplied with electric current by a current source 4, namely, an on-board electrical system 5 of the motor vehicle outside the vehicle HVAC system. Current source 4 in this case provides current in pulse width modulation. In this regard, the current in pulse width modulation is passed from current source 4 through central power lines 8, as power lines 6, to parallel power lines 7. The electric current in pulse width modulation is passed through PTC heaters 2 by parallel power lines 7. A delay circuit 3 in each case is built into two of the three parallel power lines 7. Delay circuit 3 has no processor, i.e., therefore also cannot run any program or software, and is substantially equipped with simple electric and/or electronic components, for example, at least one capacitor and/or at least one resistor. Delay circuit 3 is therefore especially simple and inexpensive to produce.

The time voltage course of the current passed through the three PTC heaters 2 in pulse width modulation is shown in FIG. 3. Here, the time t is plotted on the abscissa, i.e., the horizontal axis. The electric current is passed through PTC heaters 2 in pulse modulation; i.e., during a turn-on time T_e, current is passed through PTC heaters 2 and during a turn-off time T_a no current is passed through PTC heaters 2. The duration of the turn-on time T_e and the turn-off time T_a in this regard can be changed by current source 4 and thereby the electric heat output of PTC heaters 2 is changed. The longer the turn-on times T_e and the shorter the turn-off times T_a, the higher the electric heat output provided by PTC heaters 2 and conversely. Therefore, during the supplying of current or turning on of PTC heaters 2—i.e., at the beginning of the turn-on time point T_e, the start of the supplying of current or the start of the turn-on times T_e does not occur simultaneously in all PTC heaters 2—the current provided by current source 4 in pulse width modulation is delayed in time by delay circuits 3. The time voltage course of the pulse-width-modulated current for the PTC heater 2, shown at the top in FIG. 1, is shown in the bottom curve in FIG. 3. The middle curve in FIG. 3 shows the time voltage course of the pulse-width-modulated current for the middle PTC heater in FIG. 1 and the top curve in FIG. 3 shows the time voltage curve of the pulse-width-modulated current of PTC heaters 2 shown at the bottom in FIG. 1. The start of the turn-on time T_e here is delayed in each case by a delay time Δt. Delay circuit 3 for the middle PTC heater, shown in FIG. 1, thereby delays the current provided by current source 4 by the delay time Δt and the delay circuit 3, for the bottom PTC heater 2 in FIG. 1, therefore delays the current from current source 4 by two delay times Δt. A phase offset of the pulse-width-modulated current therefore occurs in PTC heaters 2 and parallel power lines 7. The maximum current peak requirement for the three PTC heaters 2 at the beginning of the turn-on times T_e can be reduced thereby.

The circuit arrangement with three PTC heaters 2 and two delay circuits 3 is shown in a second exemplary embodiment in FIG. 2. Substantially only the differences with respect to the first exemplary embodiment according to FIG. 1 will be described below. Delay circuit 3 for PTC heater 2, shown at the bottom in FIG. 2, is not connected directly to central power line 8, but is connected to parallel power line 7 between delay circuit 3 and middle PTC heater 2. Delay circuit 3 therefore receives the already delayed current, which has been delayed by delay circuit 3 for the middle PTC heater 2. The delay times Δt of delay circuits 3 for the middle PTC heater 2 and for the bottom PTC heater 2 are thereby the same. Because of the supplying of delay circuit 3 for the bottom PTC heater 2 with the already delayed current from delay circuit 3 of the middle PTC heater 2, also in the second exemplary embodiment the time voltage course of the pulse-width-modulated current, shown in FIG. 3, occurs again in the three electric resistance heaters 1, although both delay circuits 3 have the same delay times Δt.

Overall, substantial advantages are associated with the vehicle HVAC system of the invention and the method of the invention for operating a vehicle HVAC system. Instead of using a time-consuming and costly microcontroller as a device for supplying the electric resistance heaters 1 with electric current in a delayed manner, as occurs in the state of the art, a simple and inexpensive delay circuit 3 with an analog structure is used, so that considerable manufacturing costs can be saved as a result.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.

Claims

1. A heater comprising: wherein the device comprises at least one delay circuit, preferably two delay circuits.

at least two electric resistance heaters for heating the air to be supplied to the vehicle interior, whereby the at least two electric resistance heaters can be supplied with electric current, and

a device for supplying current to at least one electric resistance heater with a time delay relative to another electric resistance heater,

2. The heater according to claim 1, wherein the at least one delay circuit is at least one, particularly exclusively, analog delay circuit and/or the at least one delay circuit has no processor and/or no program can be run by the at least one delay circuit and/or the at least one delay circuit is an electrical and/or electronic circuit, particularly without a processor.

3. The heater according to claim 1, wherein the at least one delay circuit comprises at least one capacitor and/or at least one resistor.

4. The heater according to claim 3, wherein the at least one delay circuit comprises exclusively at least one capacitor and/or at least one resistor as electric and/or electronic components.

5. The heater according to claim 1, wherein the at least two electric resistance heaters can be supplied with electric current in pulse width modulation.

6. The heater according to claim 5, wherein a first one of the at least two electric resistance heaters can be supplied with pulse-width-modulated current delayed in time relative to another one of the at least two electric resistance heaters with the at least one delay circuit.

7. The heater according to claim 1, wherein at least one of the at least two electric resistance heaters is at least one PTC heater.

8. The heater according to claim 1, wherein the at least two electric resistance heaters are connected electrically parallel.

9. The heater according to claim 8, wherein each of the parallel connected electric resistance heaters are each connected to a parallel power line and the parallel power lines are connected to a central power line.

10. The heater according to claim 8, wherein in parallel connected electric resistance heaters one delay circuit each is connected in series to the parallel connected electric resistance heaters.

11. The heater according to claim 10, characterized in that at least two delay circuit devices are connected parallel and/or in series.

12. A method for operating a heater, particularly for a vehicle HVAC system according to claim 1, comprising the steps: wherein the current is delayed in an analog manner and/or the current is delayed without a program or software being run.

conduction of electric current through at least two electric resistance heaters,

preferably conduction of air through the heater,

generation of thermal energy by the at least two electric resistance heaters by converting electrical energy into thermal energy,

preferably the transfer of the thermal energy generated by the at least two electric resistance heaters to the air to be heated, so that the air becomes heated, whereby

during the supplying of current to the at least two electric resistance heaters, at least one electric resistance heater is supplied with current delayed in time relative to another electric resistance heater, in order to reduce the maximum current peak requirement for the at least two electric resistance heaters during the supplying of current and/or turning on of the at least two electric resistance heaters,

13. The method according to claim 12, wherein the current is delayed exclusively in an analog manner, particularly by at least one delay circuit.

14. The method according to claim 12, wherein the current passed through the at least two electric resistance heaters is pulse-width-modulated and preferably the pulse width modulation is changed, particularly the turn-on and turn-off times are changed, in order to control and/or to regulate the electric power of the at least two electric resistance heaters.

15. The method according to claim 12, wherein the current is delayed by at least one delay circuit in each case for one electric resistance heater.