ELECTRICAL HEATER WITH HEATING REGISTERS MADE OF PTC-ELEMENTS WHICH ARE COUPLED THERMALLY IN SERIES

Abstract

A heating arrangement may include at least one PTC heating device with at least one first PTC heating element. The PTC heating device includes at least one second PTC heating element that is distinct from the first PTC heating element, wherein the first and second PTC heating elements may be arranged in a through-flow direction next to one another. Alternatively, a further PTC heating device with at least one second PTC heating element that is distinct from the first PTC heating element may be provided, wherein the first and second PTC heating devices may be arranged in the through-flow direction next to one another.

Claims

1. A heating arrangement comprising at least one PTC heating device with at least one first PTC heating element, wherein one of: the PTC heating device includes at least one second PTC heating element that is distinct from the first PTC heating element, wherein the first and second PTC heating elements are arranged in a through-flow direction next to one another; or a further PTC heating device with at least one second PTC heating element that is distinct from the first PTC heating element is provided, wherein the first and second PTC heating devices are arranged in the through-flow direction next to one another.

2. The heating arrangement according to claim 1, wherein the first and second PTC heating elements are controllable independently of one another via a controller.

3. The heating arrangement according to claim 1, wherein the at least one first PTC heating element has a first reference temperature T.sub.1Ref and the at least one second PTC heating element a second reference temperature T.sub.2Ref, wherein (T.sub.2Ref−T.sub.1Ref)>5° C.

4. The heating arrangement according to claim 3, wherein one of: (T.sub.2Ref−T.sub.1Ref)>10° C.; or (T.sub.2Ref−T.sub.1Ref)>15° C.

5. The heating arrangement according to claim 2, wherein the controller controls at least the at least one second PTC heating element via pulse width modulation.

6. The heating arrangement according to claim 3, wherein T.sub.1Ref<155° C.

7. The heating arrangement according to claim 3, wherein T.sub.2Ref≥165° C.

8. The heating arrangement according to claim 1, wherein at least two second PTC heating elements and at least two first PTC heating elements are arranged alternatingly in the PTC heating device and next to one another in the through-flow direction.

9. The heating arrangement according to claim 1, wherein at least two PTC heating devices are arranged in the through-flow direction one behind the other.

10. The heating arrangement according to claim 1, wherein at least one second PTC heating element has at least one of a size and a form other than a first PTC heating element.

11. A method for operating a heating arrangement having at least one PTC heating device with at least one first PTC heating element, comprising adjusting a heating output of at least one PTC heating elements via pulse width modulation; wherein one of: the PTC heating device includes at least one second PTC heating element that is distinct from the first PTC heating element, wherein the first and second PTC heating elements are arranged in a through-flow direction next to one another; or a further PTC heating device with at least one second PTC heating element that is distinct from the first PTC heating element is provided, wherein the first and second PTC heating devices are arranged in the through-flow direction next to one another.

12. The method according to claim 11, wherein at least one first PTC heating element is operated without pulse width modulation and at least one second PTC heating element with pulse width modulation.

13. The method according to claim 12, wherein: in a first range exclusively the at least one second PTC heating element is controlled with a pulse width of 0%≤W≤100% such that a heating output within the first range is adjusted; at the end of the first range, the pulse width w is adjusted to 0% and the at least one second PTC heating element is switched off and the at least one first PTC heating element is operated with constant voltage without pulse width modulation; and in a second range the at least one first PTC heating element is continued to be operated with constant voltage and the at least one second PTC heating element is subjected to a pulse width of 0%≤w≤100% such that a heating output of adjusted.

14. An air conditioning system of a motor vehicle comprising a heating arrangement including at least one PTC heating device with at least one first PTC heating element, wherein one of: the PTC heating device includes at least one second PTC heating element that is distinct from the first PTC heating element, wherein the first and second PTC heating elements are arranged in a through-flow direction next to one another; or a further PTC heating device with at least one second PTC heating element that is distinct from the first PTC heating element is provided, wherein the first and second PTC heating devices are arranged in the through-flow direction next to one another.

15. The air conditioning system according to claim 14, wherein the first and second PTC heating elements are controllable independently of one another via a controller.

16. The air conditioning system according to claim 14, wherein the at least one first PTC heating element has a first reference temperature T.sub.1Ref and the at least one second PTC heating element a second reference temperature T.sub.2Ref, wherein (T.sub.2Ref−T.sub.1Ref)>5° C.

17. The air conditioning system according to claim 16, wherein one of: (T.sub.2Ref−T.sub.1Ref)>10° C.; or (T.sub.2Ref−T.sub.1Ref)>15° C.

18. The air conditioning system according to claim 15, wherein the controller controls at least the at least one second PTC heating element via pulse width modulation.

19. The air conditioning system according to claim 16, wherein T.sub.1Ref<155° C.

20. The air conditioning system according to claim 16, wherein T.sub.2Ref>165° C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] It shows, in each case schematically

[0030] FIG. 1 shows a heating arrangement according to the invention in accordance with a first alternative,

[0031] FIG. 2 shows a resistance-temperature profile of a possible PTC heating element,

[0032] FIG. 3 shows a heating output of a pulse width-modulated second PTC heating element,

[0033] FIG. 4 shows a heating output of a first PTC heating element that is not pulse width-modulated,

[0034] FIG. 5 shows a cumulated heating output of the first PTC heating elements and of the second heating elements,

[0035] FIG. 6 shows a heating arrangement according to the invention in accordance with a further embodiment,

[0036] FIG. 7 shows a resistance-temperature profile of two different PTC heating elements,

[0037] FIG. 8 shows a heating arrangement corresponding to a second alternative.

DETAILED DESCRIPTION

[0038] According to FIGS. 1, 6 and 8, a heating arrangement 1 according to the invention, which can be arranged for example in an air conditioning system 2 of a motor vehicle 3, comprises a PTC heating device 4 with at least one, here multiple first PTC heating elements 5 and according to the first alternative embodiment shown in FIGS. 1 and 6, having at least one, here likewise multiple second PTC heating elements 7. According to FIG. 6, a PTC heating device 4 of identical design is additionally provided in the through-flow direction 8 thereafter.

[0039] According to the second alternative embodiment of the heating arrangement 1 according to the invention shown in FIG. 8, a further PTC heating device 13 having at least one second PTC heating element 7 is provided, wherein the two PTC heating devices 4, 13 are arranged in the through-flow direction 8 next to one another. In this case, only first PTC heating elements 5 are arranged in the PTC heating device 4 and only second PTC heating devices 7 in the further PTC heating device 13.

[0040] The two types of PTC heating elements 5, 7 are arranged in the through-flow direction 8 next to one another, in particular alternatingly (see FIG. 1) and are therefore simultaneously circulated about by a fluid flow to be heated, for example air 10.

[0041] The at least one first and the at least one second PTC heating element 5, 7 in the PTC heating device 4 and/or in the further PTC heating device 13 cannot be controlled separately and independently of one another, but jointly, as a result of which, for example through different reference temperatures T.sub.1Ref and T.sub.2Ref of the first and second PTC heating element 5, 7, a large temperature range can be covered. Obviously, the at least two PTC heating elements 5, 7 of the PTC heating devices 4, 13 can be controlled constantly or by means of pulse width modulation in this case. “Constantly” in this case means with the same voltage/current or a pulse width of 100%.

[0042] Likewise provided can be a device 9, for example a control/regulating device, via which the two PTC heating elements 5, 7 or the two groups of first and second PTC heating elements 5, 7, are controllable independently of one another, in particular alternatively but also simultaneously. This offers the major advantage that depending on requested heating output H either the first or the second PTC heating elements 5, 7 or all PTC heating elements 5, 7 can be activated.

[0043] Through the independent controlling of both PTC heating elements 5, 7 or their cumulative controlling each with different outputs it is possible for the first time to completely cover an entire requested output curve with respect to a heating output H and not only, as in the past, individual working points or extracts of the heating output range, as was possible with conventional electric heaters that could only be switched on and off.

[0044] In an advantageous further development of the heating arrangement 1 according to the invention, the first PTC heating elements 5 have a first reference temperature T.sub.1Ref and the second PTC heating elements 7 a second reference temperature T.sub.2Ref, wherein (T.sub.2Ref−T.sub.1Ref)>5° Celsius or >5 Kelvin applies.

[0045] Here, the reference temperature T.sub.Ref is determined as follows: according to FIG. 2, an exemplary resistance-temperature curve of a possible PTC heating element 5, 7 is shown. Up to a starting temperature T.sub.A, such a PTC heating element 5, 7 has an NTC range (negative temperature coefficient), in which the resistance R falls with increasing temperature T, until the resistance R at the starting temperature T.sub.A has reached its low point. T.sub.A is also referred to as the temperature at the turning point. Following this, the PTC heating element 5, 7 upon a further heating changes into the PTC range (positive temperature coefficient), in which the resistance R greatly increases with the temperature T. Now, the reference temperature T.sub.Ref is determined with each PTC heating element 5, 7 in that at the starting temperature T.sub.A twice the resistance according to FIG. 2, i.e. in the example R=20 ohm, is assumed and a point of intersection with the resistance-temperature curve in the PTC range searched at this ohmic value. The associated reference temperature T.sub.Ref is read off the abscissa at this point. By arranging two PTC heating elements 5, 7 that are distinct with respect to their reference temperature T.sub.Ref it is possible to operate the two PTC heating elements 5, 7 nearer to their optimal working point and because of this improve both the output of the heating arrangement 1 and also minimise any voltage or current peaks that may occur.

[0046] Here, for example (T.sub.2Ref−T.sub.1Ref)>10° Celsius or 15° Celsius preferably applies, wherein for example the reference temperature T.sub.1Ref of the first PTC heating elements 5 can be less than or equal to 155° Celsius while the reference temperature T.sub.2Ref of the second PTC heating elements 7 can be greater than or equal to 165° Celsius.

[0047] In a further advantageous embodiment of the solution according to the invention, the at least one device 9 is designed in such a manner that it can control at least or exclusively the second PTC heating elements 7 by means of pulse width modulation. Such a pulse width modulation is shown in the FIG. 3 in different diagrams, wherein on the abscissa the heating output in percent and on the ordinate the pulse width w likewise in percent is plotted.

[0048] In the diagrams of FIGS. 3 to 5, the heating outputs H of two PTC heating elements 5, 7 are recorded, which produce the same heating output. Within each case fully activated PTC heating elements 5, 7, these produce 100% of their output each which corresponds to 50% of the heating output of the heating arrangement 1 each.

[0049] Looking at FIG. 3, pulse width-modulated second PTC heating elements 7 are noticeable in this diagram in the case of which the pulse width-dependent heating output H in the first and second range 11, 12 in the points A and B with 0% modulated pulse width w is 0% while the heating output H in the points C and D with 100% pulse width w there amounts to 100% of the heating output H of the second PTC heating elements 7. This corresponds to 50% of the heating output H.sub.2 of the entire heating arrangement 1.

[0050] In the diagram of FIG. 4, the first PTC heating elements 5 are shown in the case of which no pulse width modulation whatsoever is carried out so that these can be merely switched on and off and then produce either 0 or 100% heating output of the first PTC heating elements 5. Here, the first PTC heating elements 5 in the first range 11 are shown in the switched-off state and in the second range 12 in the switched-on state. Here, in the switched-on state they produce 100% of the heating output H of the first PTC heating elements 5, i.e. H.sub.1, which corresponds to 50% of the heating output H.sub.2 of the entire heating arrangement 1 with simultaneously activated first and second PTC heating elements 5, 7.

[0051] Now combining these two differently controlled PTC heating elements 5, 7, the diagram of FIG. 5 is obtained, in which in a first range 11, via which 0 to 50% of the heating output H of the heating arrangement 1 can be covered, exclusively the second PTC heating elements 7 are subjected to a pulse width between 0%≤W≤100%. By way of this, a heating output H can be achieved of H.sub.0≤H≤H.sub.1, wherein H.sub.1 corresponds to 50% of the heating output H.sub.2 of the heating arrangement 1.

[0052] Here, the second PTC heating elements 7 can be switched off or their pulse width W run down to 0% and subsequently merely the first PTC heating element 5 activated. In this case, the heating output H remain at H.sub.1. Now, if the heating output is to be increased further, the first PTC heating elements 5 in a second range 12 can be continued to be operated with constant voltage while the second PTC heating elements 7 are subjected to a pulse width of 0%≤w≤100% and thereby a heating output H.sub.1≤H≤H.sub.2 adjusted. Because of this, a superimposition of the first PTC heating elements 5 operated with constant voltage and of the second PTC heating elements 7 controlled with pulse width modulation takes place. Because of this, a complete and finally controllable covering of a heating output curve is comparatively easily possible.

[0053] Here it is obviously conceivable that the individual first PTC heating elements 5 or the individual second PTC heating elements 7 can have different sizes or forms or have the same size and the same form. Likewise it is obviously conceivable that besides the PTC heating device 4 at least one such PTC heating device 4 can be additionally arranged in the through-flow direction 8 after the PTC heating device 4, as is shown in FIG. 6, wherein this PTC heating device 4 also comprises at least one further first and second PTC heating element 5, 7 and wherein (T.sub.2Ref−T.sub.1Ref) is at least >5° Celsius applies.

[0054] Likewise it is obviously conceivable that besides the PTC heating device 4 at least one further PTC heating device 13 is additionally arranged in the through-flow direction 8 next to the PTC heating device 4, as is shown in FIG. 8, wherein (T.sub.2Ref−T.sub.1Ref) is at least >5° Celsius applies.

[0055] Here, the further PTC heating device 13 can also comprise at least one second PTC heating element 7 and the PTC heating device 4 at least one first PTC heating element 5, so that in the PTC heating device 4 only first PTC heating elements 5 and in the further PTC heating device 13 only second PTC heating elements 7 are arranged, wherein the PTC heating device 4 and the further PTC heating device 13 or the at least one first PTC heating element 5 and the at least one second PTC heating element 7 can be controlled jointly or independently of one another.

[0056] By way of this, a further finer regulation of the heating output of the heating arrangement 1 is possible. Here, the PTC heating elements 5, 7 can be controlled constantly or by means of pulse width modulation.

[0057] In FIG. 7, resistance-temperature curves of a possible first PTC heating element 5 and of a possible second PTC heating element 7 are shown. The first PTC heating element 5 has a reference temperature T.sub.1Ref of 165° C., while the second PTC heating element 7 has a reference temperature T.sub.2Ref of 205° C. Even with constant controlling of both PTC heating elements 5, 7, this produces different temperature ranges with different optimal working points. In this case (T.sub.2Ref−T.sub.1Ref)=40° C. applies.

[0058] With the heating arrangement 1 according to the invention and the operating method according to the invention it is possible to reduce the dimensions of the current-carrying components, for example conductor tracks and also voltage and current peaks and thereby the vehicle electrical system load, as a result of which the entire vehicle electrical system can be designed for lower loads and thus cost-effectively. Through the individual combinability of the individual PTC heating elements 5, 7 a boost function for brief maximum outputs can also be comparatively easily made available, here through the pulse-width modulated second PTC heating elements 7, without the entire vehicle electrical system having to be designed for comparatively high loads.

[0059] In addition to this, a temperature and volumetric flow monitoring is also possible since the multi-stage PTC heating arrangement 1 besides the functionality of heating, can also use the individual PTC heating elements 5, 7 as measuring elements for determining physical quantities.