POWER CONTROL UNIT AND ARRANGEMENT OF SUCH A POWER CONTROL UNIT WITH AN ELECTRIC HEATING DEVICE

Description

Application area and state of the art

[0001] The invention relates to an arrangement of a power control unit for controlling or adjusting the power output of an electric heating element. In particular, the power control unit is arranged together with the electric heating element in a cooktop. Advantageously, the cooktop has several heating elements, each of which has its own associated power control unit.

[0002] Such power control devices are known from DE 198 33 983 A1. They control the power of an electric heating device by intermittent operation, i.e., by operating the heating device at full power during an on-time or switching it off during an off-time. The ratio between these two times determines the average continuous power supplied to the electric heating device and converted into heat by the heating device.

[0003] A power control device known from the prior art includes a mechanical adjustment mechanism with which the aforementioned on-time and off-time can be changed. Often, there is a desire for a very precise setting of the continuous power output of the electrical heating device controlled by it. This is not significant for high or very high continuous power outputs of the electrical heating device, but it is for very low continuous power outputs. Such low power outputs are required, for example, for certain sauces or for melting chocolate or similar temperature-sensitive foods.

[0004] From DE 197 38 677 A1, another power control device for an electric heating element in a cooktop is known, which has a power switch designed as a snap-action switch. It has a release device with a bimetallic release. A heating device is provided for the bimetallic release, which has two separately controllable heating elements. This allows the release device to be heated to different intensities.

[0005] From US 4 829 279 A, ​​a further power control unit is known with a power switch as a snap switch and a release device for it.

[0006] From EP 3 177 107 A1, an induction cooktop and a method for its operation are known, wherein a specific, predetermined cooking vessel temperature is to be achieved. The induction cooktop has a control unit and several induction heating coils for inductively heating a cooking vessel. A control unit monitors the power supply to the induction heating coils. A low, continuous average surface power output can also be used. Task and solution

[0007] The invention is based on the objective of creating an arrangement of a power control device with an electric heating device controlled by it, with which problems of the prior art can be solved and it is particularly possible to increase the accuracy of the control of the power, preferably in the low power range.

[0008] This problem is solved by an arrangement with the features of claim 1. Advantageous and preferred embodiments of the invention are the subject of the further claims and are explained in more detail below. The wording of the claims is incorporated by express reference into the description.

[0009] The power control unit is designed as a modular unit, specifically within a housing. It includes a power switch, which is designed as a snap-action switch or a spring-loaded switch. The power switch is a mechanical switch. It has an elongated switching arm with a power switching contact at one end. This power switching contact can be pressed by the switching arm against a mating contact of the power control unit, thereby closing the power switch. After opening, the power switching contact is a certain distance from the mating contact. Closing and opening occur very quickly or abruptly, which is achieved by the snap-action design in a known manner. A release device, which includes a release mechanism, is provided to actuate or trigger the power switch.This trigger is located at the other end of the switching arm and can initiate a switching operation, i.e., open or close the circuit breaker.

[0010] The release device thus includes the release mechanism, which comprises a bimetallic strip or is formed by or consists of a bimetallic strip, advantageously in the form of an elongated strip or as an elongated arm. The release device further includes a heating element for the release mechanism, as is known in the prior art. The release mechanism has a free end that rests against the aforementioned switching arm end of the circuit breaker's switching arm to trigger or actuate it. Another end of the release mechanism is preferably fixed to the release device. The heating element runs at a small distance from the release mechanism, advantageously less than 2 mm when the release mechanism is at room temperature. Furthermore, the heating element can be elongated and extend at least partially along the release mechanism or in essentially the same direction, preferably at least in overlapping positions.

[0011] The heating device comprises a flat support with an electrically insulating surface on which a heating conductor is arranged. Advantageously, the heating conductor is designed as a thick-film heating conductor, or alternatively as a thin-film heating conductor. Preferably, the heating conductor is arranged on the surface of the support facing away from the trigger. Alternatively, it can also be arranged on the side facing the trigger, which allows for even faster heating of the trigger due to thermal radiation. In this case, an electrically insulating cover or coating is advantageously provided.

[0012] One possible aspect of the invention is that the support is made of ceramic and has a thickness of less than 1.5 mm. Advantageously, the thickness is even less than 1 mm, and particularly advantageously it is between 0.1 mm or 0.4 mm and 0.75 mm.

[0013] One aspect of the invention is that the power control unit has an elongated compensating bimetal strip. This compensating bimetal strip has a freely movable compensating end and an opposing mounting end. While the compensating end is pressed directly or indirectly against the tripping device, the other mounting end is attached to the power control unit. For example, it can be attached to a stable metallic bridge to which other aforementioned functional units are also attached, advantageously the tripping device and the circuit breaker. The bridge can be a switching bridge to which the tripping device and / or the circuit breaker are preferably also attached, advantageously being spring-loaded and / or movable. The switching bridge is advantageously fixed and immovably arranged on the housing, particularly on a housing base, and is most advantageously injection-molded or plugged in.The compensation bimetal is preferably made of material SBCL / DS / 751-108, as supplied by Shivalik. Preferably, the compensation bimetal can be attached to the power control unit at its mounting end, in particular to a aforementioned bridge or switching bridge that is fixedly attached to a housing of the power control unit, advantageously in a non-movable manner. The switching bridge can form the stop for the compensation bimetal, such that the distance between the two, or the maximum travel distance for the compensation bimetal to the stop, is 1.0 mm, preferably a maximum of 0.8 mm. It can be at least 0.1 mm or at least 0.2 mm.

[0014] The compensating bimetal strip and the release mechanism are spring-loaded relative to each other and are in contact with each other or are pressed against each other with spring force. This spring-loaded contact is advantageously achieved by a correspondingly resilient and pre-tensioned design of the release mechanism or its attachment to the power control unit, for example, by means of a spring-loaded metal strip. Furthermore, the compensating bimetal strip is designed such that the direction of movement of its free compensating end is at an angle between 0° and 45° to the direction of movement of that area of ​​the release mechanism against which the compensating end is in contact or pressed.

[0015] The thin ceramic substrate results in low heat capacity. This, in turn, means that the heating element heats up very quickly and can thus rapidly heat the bimetallic release mechanism, causing it to deform and trigger the circuit breaker, particularly opening it quickly. This allows for a very short time, advantageously 2 to 5 seconds, from the moment the heating element starts heating until the circuit breaker opens. Rapid opening of the circuit breaker primarily increases the accuracy of controlling the heating element's power, especially at low continuous power levels.

[0016] The inclusion of a compensating bimetallic strip not only allows for adjustments to varying room or ambient temperatures, which in Central Europe are typically within a relatively narrow range of 5°C to a maximum of 35°C. Furthermore, when installed in a cooktop, the power control unit, which may have been in operation for an extended period, can be exposed to significantly higher temperatures exceeding 50°C, especially if an oven located below it is also being heated for a prolonged time. On average, oven operation generates temperatures of approximately 80°C in the cooktop and at the power control unit, potentially reaching up to 125°C. This unpredictable influence affects the behavior of the bimetallic trigger, so the compensating bimetallic strip can at least partially, and advantageously largely or even completely, eliminate the influence of the ambient temperature on the bimetallic trigger.The precise dimensioning and material selection for the compensation bimetal and its arrangement relative to the triggering device with the bimetallic trigger is a design that is easily achievable for a person skilled in the art. SBCL / DS / 751-108 from Shivalik is preferred as the material. The compensation bimetal allows for high accuracy, especially at low power levels to be set or achieved by the power control unit, and is particularly advantageous in the lowest power range when the duty cycle is much shorter than the duty cycle.

[0017] In an advantageous embodiment, the compensation bimetal exhibits a specific thermal curvature between 0.00003 / K and 0.00006 / K, particularly 0.000043 / K. This is relatively small, but sufficient for the compensation effect when the differences in ambient temperature are as described above. Providing only one of these two aspects is already considered sufficient to improve the switching accuracy of the power control unit of the inventive arrangement, especially in the low continuous power range.

[0018] If both aspects are planned together, this improvement is obviously even greater.

[0019] In one embodiment of the invention, the compensation bimetal is designed such that its freely movable compensation end moves away from the triggering device as the temperature rises. Thus, the freely movable compensation end moves in approximately the opposite direction to the trigger or the free trigger end. This reduces or eliminates the influence of a changing, particularly rising, ambient temperature on the trigger or the triggering device by compensating for it.

[0020] In a preferred embodiment of the invention, the entire release mechanism is designed as a bimetallic strip. It can have a constant width and be bent into a rounded hook shape at the release end to allow for easy movement against the switching arm end of the circuit breaker's switching arm. This is, however, known from the prior art mentioned above. In a possible embodiment of the invention, the release mechanism is resiliently attached to or mounted on the power control unit. Advantageously, a resilient metal component is provided here, which can also supply current to the heating element. Furthermore, a receptacle for the heating element can be provided on this resilient component, so that it only needs to be inserted, for example, and is then mechanically held and electrically connected. The release mechanism is advantageously permanently connected to the resilient metal component, preferably by spot welding.

[0021] The compensation bimetal is preferably rigidly attached to the power control unit at its mounting end, for example, welded to a contact bridge or a contact connector. Thus, the spring-loaded mounting of the trigger mechanism is sufficient to ensure that the trigger mechanism is spring-loaded against the compensation bimetal.

[0022] In a possible further development of the invention, an adjustable stop can be provided at the free end of the compensating bimetal, which serves to directly contact or press against the trigger. The adjustable stop can be a screw extending longitudinally from the compensating bimetal towards the contact point on the trigger, for example, a setscrew adjustable from the outside. Advantageously, this adjustable stop or the screw is aligned perpendicular to a surface or section of the compensating bimetal.

[0023] In a further possible embodiment of the invention, the power control unit can be configured to close and open the circuit breaker more frequently than once per minute when the average continuous controlled power is less than 20% of the maximum or continuous power. This is advantageously provided when the average continuous controlled power is less than 10% or even less than 6% of the maximum continuous power. Because the power control unit can now switch or trigger more quickly, more frequent switching is possible, and thus even a relatively low continuous power can be set more precisely by pulse-width modulation. A further advantage of such more frequent switching is that not only is the average continuous power, but the overall power consumption can also be adjusted more precisely.The fact that the continuous power output can be set more precisely is not only due to thermal inertia, but also that temperature fluctuations in a cooking vessel heated by the heating element are smaller. This is better and gentler on the food being heated or warmed in it, because the heating process is more even.

[0024] Alternatively, at the aforementioned low average continuous controlled power, the switching frequency can also be such that the circuit breaker is opened and closed less than once per minute. In this case, the cycle time can be longer than one minute; advantageously, it can be between one and one and a half or even two minutes.

[0025] Advantageously, the tolerance of the power setting at the lowest setting position of the power control unit can be within a tolerance range of + / - 2.5% of the nominal power value, preferably + / - 1.5% of the nominal value.

[0026] The heating power of the heating device can range from 4 W to 40 W at room temperature, preferably between 5 W and 25 W. Additionally or alternatively, the heating element of the heating device can exhibit a positive temperature coefficient of its electrical resistance. Thus, in one embodiment, the heating power of the heating element can decrease during operation from approximately 20 W at room temperature to just under 10 W at an operating temperature between 400°C and 500°C.

[0027] By assigning a power control unit to a heating element, additional wiring effort can be saved. Furthermore, in such an arrangement in a cooktop with multiple heating elements, it is possible to provide that only some of the heating elements are equipped with a power control unit of the inventive arrangement, while the other heating elements are equipped with a conventional power control unit. This allows some of the heating elements to be specifically designed to operate very precisely in the low power range.

[0028] A heating element is advantageously a radiant heating element, and it is particularly advantageous for all heating elements of the cooktop to be radiant heating elements. Each radiant heating element is assigned its own power control unit. According to the invention, the continuous surface power of a heating element at a low or maximally low setting of the power control unit is less than 0.5 W / cm², in particular less than 0.25 W / cm², and preferably less than 0.2 W / cm². As explained above, a high degree of accuracy and consistency of the power setting can be achieved with the power control unit of the inventive arrangement, especially at such lower or very low continuous average surface powers.

[0029] The reduced mass of the trigger mechanism's support allows for a 20% to 30% faster rise in the heating curve of the heating device. This significantly increases the heat flow and overall heat transfer towards the trigger, resulting in a faster trigger response.

[0030] The duty cycle (ED) – the ratio of on-time to the sum of on-time and off-time – can be less than 5%, thus enabling very precise adjustment at low power levels. Due to the reduced mass of the carrier, the switching speed can also be increased without significantly raising the maximum temperature of the heating element or the heating device for the bimetallic release. Advantageously, it is only a maximum of 10K above a typical maximum temperature.

[0031] In a further development of the invention, the power control unit can have a housing for the circuit breaker and the tripping device, wherein the housing is made of plastic, preferably of thermoplastic polymer such as polyphenylene sulfide. This is available as material Lusep GP 4650 NA from LG Chemical. The housing can have a base, preferably formed in one piece, on which the circuit breaker and the tripping device are mounted. The base is preferably made of the same material as the housing.

[0032] In an arrangement according to the invention, comprising an electric heating element and a power control unit as described above, the power control unit is permanently assigned to the heating element and electrically connected to it. Advantageously, such an arrangement is a cooktop with several electric heating elements, each with its own power control unit. Advantageously, the heating elements are radiant heating elements, and according to the invention, at least those that are controlled by a power control unit of the inventive arrangement.

[0033] According to the invention, the continuous average surface power of a heating device controlled by a power control unit according to the invention is less than 0.5 W / cm² when the power control unit is set to a low or maximum low setting, and in particular less than 0.25 W / cm². Preferably, it can even be less than 0.2 W / cm².

[0034] These and other features are evident not only from the claims but also from the description and the drawings, whereby the individual features, either alone or in combination, may be implemented in one embodiment of the invention and in other fields, and may represent advantageous and individually protectable embodiments for which protection is claimed here. The division of the application into individual sections and subheadings does not limit the general validity of the statements made therein. Brief description of the drawings

[0035] Exemplary embodiments of the invention are shown schematically in the drawings and are explained in more detail below. The drawings show: Fig. 1 an interior view of a power control unit of the inventive arrangement with closed contacts, Fig. 2 the power control unit made of Fig. 1with heated bimetals and open contacts, Fig. 3 a simplified schematic representation of the arrangement of a compensation bimetal on the one hand and a trigger on the other hand with mirror-image bimetals, Fig. 4 a top view and a side view of a heating device, Fig. 5 a side view of a power control unit of the inventive arrangement as a unit, Fig. 6 a top view of a cooktop according to the invention with four radiant heating devices and a power control unit for each, Fig. 7 a diagram showing the average temperature of a heating conductor of the heating device as a function of the supply voltage and the thickness of a ceramic carrier, and Fig. 8 a similar diagram Fig. 7 with higher resolution and when considering a significantly shorter time at the beginning of the heating process. Detailed description of the exemplary implementations

[0036] In the Fig. 1A power control unit 11 of the inventive arrangement is shown in the open state, so that the internal components are visible from the front. The power control unit 11 forms a unit with a housing 12 and a base 13, on which most of the functional units or components shown here are arranged or attached. These are made of plastic, advantageously polyphenylene sulfide such as Lusep GP4650 NA. This ensures good resistance to high temperatures. The power control unit 11 has a power switch 14 as its central component, as is known per se from the prior art. The power switch 14 has a switching arm 15, which has a switching arm end 17 on the right and a contact end 22 on the left.Slightly to the right of a switching contact 23 at the contact end 22, a portion of the switching arm 15 projects upwards in a bridge-like or arc-like manner as a snap element 19 and is supported at its right free end against a support 20 by means of a blade bearing. The portions of the switching arm 15 extend past the snap element 19 and the support 20 on both sides. If the point where the snap element 19 abuts the support 20 is below the surface of the switching arm 15 in this area, then the contact end 22 with the power switching contact 23 is pressed upwards by the force of the resiliently curved snap element 19. The power switching contact 23 then rests against a mating contact 25, which is fixedly arranged on a stationary mating contact bridge 26. The mating contact bridge 26 is cast or injection-molded into the device base 13 and can be configured according to... Fig. 5 At the rear, a plug connector S protrudes for electrical connection.

[0037] Is the point at which the snap element 19 rests against the support 20 above the surface of the switching arm 15 extending to the left and right of it, as shown by the Fig. 2 As shown, the spring force of the snap element 19 pushes the contact end 22 downwards. The contact between the power switching contact 23 and the mating contact 25 is thus released, and there is a sufficient contact gap between them; the switch or circuit breaker 14 is therefore open.

[0038] In a known manner, the circuit breaker 14 is located on a switching arm carrier 28, which is attached to a switching bridge 30 by means of a spring bearing 29. The spring bearing 29 is made of thin, resilient metal. The switching bridge 30, similar to the mating contact bridge 26, is attached or molded into the base 13 of the device and may protrude from the rear of the power control unit 11 as a plug connector S.

[0039] The switching arm carrier 28 has a downwardly projecting bulge 28' which rests against an outer circumference of a switching drum 32, resiliently held in place by the spring force of the spring bearing 29. The switching drum 32 has a variable diameter, as is known from the prior art. It is mounted on a switching shaft 33, which can be rotated by an operator using the knob K (see also...). Figs. 5 and 6Depending on the change in diameter of the switching drum 32, the switching arm carrier 28 and the entire power switch 14 are moved upwards or downwards, which adjusts the aforementioned duty cycle (ED) value and thus sets a different continuous power output at a heating device controlled by the power control unit 11. The state shown here corresponds to a rotation angle of approximately 50° and a relatively low continuous power output, for example, 10% to 20% of the maximum continuous power output of the heating device. The smaller the thickness of the switching drum 32, the further downwards the switching arm carrier 28, together with the switching arm 15, moves, and the longer it takes until the end of the switching arm 17 is pressed downwards to such an extent that contacts 23 and 25 separate. This is known from the prior art.

[0040] The switching arm end 17 is pressed downwards by the release device 35, specifically by a release 37 or its lower right hook end 38, which presses down onto the switching arm end 17. The release 37 is an elongated bimetallic strip of constant width in the form shown here. Its left end is connected, advantageously welded, to a spring bearing 40, which in turn is attached to the switching bridge 30. The spring bearing attempts to push the release device 35 upwards. The release 37 is designed as described below with reference to the Fig. 3 It is explained that with a fixed left end, it bends downwards with the right area, especially with the hook end 38, as the temperature increases.

[0041] In addition to the trigger 37, the release device 35 also has a receptacle 41, which is formed at the end of the spring bearing 40. A heating device 43 is inserted into this receptacle 41 in a manner known per se for fastening, which in Fig. 4The heating device 43 is shown in more detail below. The heating device 43 essentially rests against the upper surface of the trigger 37 in its left area, but is not attached to it. At its right end, a spring end 53 of a contact spring 52 rests against the upper surface of the heating device 43. The contact spring 52 is attached at its lower right to a contact bridge 55, which is advantageously cast or injection-molded into the base of the device 13 and protrudes from its rear side as a plug connector S. At its upper right, the contact spring 52 is supported by a bearing pin 54, around which it is wound several times. The spring force of the spring end 53 presses downwards. The contact spring 52 forms one electrical contact with the heating device 43. The other electrical contact is formed by the receptacle 41 together with its spring bearing 40.

[0042] A compensating bimetallic strip 58, which is approximately perpendicular to the switching bridge 30, is attached to the top. An adjusting screw 59, designed here as a setscrew or socket head cap screw, is screwed into the compensating bimetallic strip 58 at its right end. The adjusting screw 59 rests against the receptacle 41. By turning the adjusting screw 59 in or out, the release device 35 can be moved downwards, towards or away from the switching arm 15 and the switching drum 32, while the compensating bimetallic strip 58 remains stationary. This allows the power control unit 11 to be adjusted to the release temperature or release point, thus adjusting the accuracy of the power control unit 11.

[0043] The bimetallic structure of the compensation bimetal 58 can be derived from the Fig. 3This can be seen more clearly. The compensation bimetal 58 can have a specific thermal curvature between 0.00003 / K and 0.00006 / K. Advantageously, it can be the aforementioned SBCL / DS / 751-108 from Shivalik. The layer sequence, as the respective hatching illustrates, is exactly mirrored to that of the trigger 37 located below it. Thus, while the trigger 37 bends downwards at its left free end when heated, starting from its attachment to the spring bearing 40, the compensation bimetal 58 bends upwards from its left fixed end. In this way, a compensation distance KA, i.e., a distance between the compensation bimetal 58 and its stop, can be provided in a range between 0 and 1.0 mm, preferably between 0 and 0.8 mm, up to the stop. This stop is formed here by the switching bridge 30, in particular by its rightmost outermost end, which results from the Fig. 2As can be seen, the switching bridge 30, and thus the stop, does not yield. The compensation bimetal 58 cannot deform or bend beyond this stop and can only travel a maximum of the specified compensation distance KA. The compensation distance KA is defined by the clear width between the end of the switching bridge 30 and the top surface of the compensation bimetal 58; see also Fig. 1 , where the compensation bimetal 58 is at its limit, i.e. deflected to its maximum extent, which also deflects the release device 35 to its maximum extent upwards.

[0044] This bending movement is illustrated by the arrows to the right. If the temperature at the power control unit 11 rises sharply, for example, because it has been in operation for a longer period and because an oven located under a cooktop has been heated up for a while, the bimetallic release 37 bends slightly downwards solely due to the higher ambient temperature. The compensating bimetallic strip 58 bends slightly upwards, up to the maximum extent of the stop formed by the switching bridge 30. It is designed and arranged such that the effect on the release 37 is neutralized by the compensating bimetallic strip 58, i.e., the two movements resulting from the higher ambient temperature cancel each other out or compensate for each other.

[0045] While in Fig. 1 A state of the power control unit 11 is shown when it is switched on and when the temperature at the compensation bimetal 58 is approximately 25°C, then in Fig. 2 A state is depicted in which the temperature of the compensation bimetal 58 is 125°C. This can be reached, for example, at 170°C at the heating device 43 itself. Furthermore, when the power switch 14 is closed, i.e., when the power switching contact 23 and the counter contact 25 are in contact, the heating device 43 is in operation and heats the trigger 37 considerably. This occurs particularly quickly due to the design according to the invention with the thin support of the heating device 43.

[0046] Due to the rapid heating, the release mechanism 37 quickly bent downwards, so far that it opened the circuit breaker 14 in the manner described above. The power switching contact 23 detached from the mating contact 25. With the circuit breaker 14 open, the heating device 43 is no longer heated, causing the release mechanism 37 to cool down and bend upwards again. At a specific point in time, namely when the contact point of the snap element 19 on the support 20 moves below the surface of the switching arm 15 next to it, the circuit breaker 14 closes again. Then the heating device 43 is operated again, and the release mechanism 37 is heated once more.

[0047] As can be seen, the relatively high temperature of 125°C has caused the compensating bimetal 58 to bend significantly upwards. This allows the spring force of the spring bearing 40 to push the entire release mechanism 35 further upwards. Without this compensating effect, the hook end 38 of the release 37 would have pushed the switching arm end 17 down even further, or the circuit breaker 14 would have opened earlier, but only due to the significant heating. The switching behavior would therefore be significantly different than in the cool state, which is particularly noticeable at low continuous power levels. At the very low or minimal power levels mentioned earlier, such as 5% of the maximum continuous power, deviations become even more pronounced and disruptive.

[0048] The second aspect mentioned at the beginning, concerning the compensation bimetal 58, has thus been explained. The first aspect mentioned at the beginning will be discussed in relation to... Fig. 4 The heating device 43, which has a ceramic substrate 44, is explained. This substrate can, for example, be made of silicon nitride and be electrically insulating. The ceramic substrate 44 is elongated and rectangular with a width B, a length L, and a thickness D. Here, the thickness D is 0.63 mm, which is significantly thinner than typical substrates, which are more than 1 mm or even more than 1.5 mm thick. On a top surface 45 of the substrate, a first contact field 48 is applied to the left and a second contact field 49 to the right, each near the end. A heating conductor 50, designed as a thick-film heating element, runs between them. It has PCT properties. Its power output can be just a few watts, for example, 5 W or 10 W.

[0049] The left first contact field 48 is electrically contacted by means of the receptacle 41. The contact spring 52 rests against the right second contact field 49 with its spring end 53 for electrical contact. The arrangement of the heating device 43 in the power control unit 11 according to Fig. 1 The arrangement is such that the upper surface 45 with the heating conductor 50 points away from the trigger 37 below, meaning the trigger is located close to the underside 46 of the ceramic carrier 44. Even faster heating of the trigger 37 could be achieved by arranging the heating conductor 50 on the underside 46 of the ceramic carrier 44 facing it. In particular, electrical contact via the contact spring 52 would then be more difficult, although not impossible. The surface of the heating conductor 50 would then, of course, have to be electrically insulated from the bimetallic trigger 37, which may have at least a partially electrically conductive surface.

[0050] In the Fig. 5 A complete power control unit 11 is shown in a highly simplified side view. Several plug connectors S protrude from the rear of the housing 12, which connect to the base of the unit 13 according to Fig. 1 They are cast or injected. The electrical connection of the power control unit 11 is made to them.

[0051] A knob K is mounted on the front of the switching shaft 33, serving as a manual handle. By turning it, the switching shaft 33 and thus also the switching drum 32 are rotated, and the position of the circuit breaker 14 is changed, in particular its distance from the release 37.

[0052] In Fig. 6A cooktop 60 according to the invention is shown as the arrangement mentioned above. The cooktop 60 has a cooktop plate 61 with four radiant heating devices 62a, 62b, 62c and 62d on or under the cooktop plate 61. Such radiant heating devices have been known for a long time and were the standard for such heating systems for a long time. Reference is made, for example, to EP 590315 A2.

[0053] At the front of the cooktop 60 are four power control units 11a, 11b, 11c and 11d, each with a knob Ka, Kb, Kc and Kd. Power control unit 11a with knob Ka is assigned to the radiant heating element 62a for its operation, etc.

[0054] In the Fig. 7The diagram shows the average temperature of the heating conductor 50 of the heating device 43 over time. The solid curves represent a state-of-the-art heating device with a ceramic substrate 1.5 mm thick. The lower, thin solid curve represents operation at 230 V. This curve reaches a temperature of slightly over 330°C after approximately 150 seconds. To simulate a theoretically possible increase in power, a higher voltage of 280 V is used, resulting in a temperature profile corresponding to the upper, thick solid curve. This curve reaches a temperature of 370°C.

[0055] The curves for the heating device of the inventive arrangement with the thin ceramic support are shown with dashed lines. The thin dashed curve is for operation with a mains voltage of 230V. The temperature reached continuously is approximately 330°C, after three to four minutes. If the supply voltage is increased from 230V to 280V, the temperature rises, with the maximum continuous temperature then reaching almost 400°C. This is the thick dashed curve. It is reached after a similar time.

[0056] The curves, particularly at the start of the heating process, show that reducing the thickness of the heating element has a significantly greater impact on the rapid temperature rise than simply increasing the heating power. In this regard, further reference is also made to the... Fig. 8Reference is made to the figure, which also shows the temperature over time, albeit on a different scale and with a supply voltage of 230V. This is therefore the temperature of the heating device itself. On the left, the temperature profile for the thin ceramic support 44 of the heating device 43 of the inventive arrangement is shown as a dashed line. With this, a temperature of 120°C is reached after only 4 seconds, and a temperature of 170°C after 8 seconds. To reach a temperature of 120°C, a heating device with a conventional, thicker ceramic support according to the prior art takes about 7.5 seconds, i.e., 3.5 seconds longer. The higher temperature of 170°C is reached after 13 seconds, which is already a time difference of 5 seconds.

[0057] It can be seen from this that reducing the thickness of the heating element's support 43 produces a greater and better effect than simply using a more powerful heater or heating conductor. Admittedly, increasing the power of the heating element or heating conductor also results in faster heating and thus faster switching of the power control unit. However, the associated effects of a higher final temperature and thus greater heating of the interior of the power control unit, which typically and advantageously has a plastic housing, are significantly more disadvantageous in comparison.

[0058] It is advantageous that the heating element has PTC 50 characteristics in its electrical resistance. This ensures that the heating device does not overheat and potentially become unresponsive during operation.

Claims

1. Arrangement of a power control device (11) with an electric heating device (62), wherein the power control device (11): - is designed to control the power of the electric heating device (62) and is permanently assigned to the electric heating device (62) and electrically connected to it, - is designed as a structural unit, - has a power switch (14) that is designed as a snap switch with a switching arm (15), wherein a power switch contact (23) is arranged at one contact end (22) of the switching arm (15) and a trigger (37) is located at the other switching arm end (17) for triggering a switching operation, - has a release device (35) for the power switch (14), wherein the release device (35) has a trigger (37) with a bimetal and a heating device (43) for the trigger (37), wherein the trigger (37) abuts against the switching arm end (17) of the switching arm (15) of the power switch (14) with a free trigger end (38), wherein the heating device (43) runs at least partially along the trigger (37) and at a small distance therefrom, in particular less than 2 mm in the state of the trigger (37) at room temperature, wherein the heating device (43) has a flat carrier (44) with an electrically insulating upper side on which a heating conductor (50) is arranged, wherein - the power control device (11) has an elongated compensation bimetal (58) with a freely movable compensation end that is pressed against the release device (35), wherein ∘ the compensation bimetal (58) and the release device (35) are in spring-loaded contact with each other, o the compensation bimetal (58) is designed such that the direction of movement of the free compensation end is at an angle between 0° and 45° to the direction of movement of that region (41) of the release device (35) against which the compensation end is pressed, o the compensation bimetal (58) is attached to the power control device (11) with another fastening end, characterized in that: - the electric heating device is a radiant heating device (62) and the arrangement is a hob (60) with a hob plate (61) and the radiant heating device (62), - a continuous average power output of the radiant heating device (62) at a low or maximum low setting of the power control device (11) is less than 0.5 W / cm2.

2. Arrangement according to claim 1, characterized in that the compensation bimetal (58) is designed in such a way that the compensation end moves away from the release device (35) as the temperature rises.

3. Arrangement according to claim 1 or 2, characterized in that the compensation bimetal (58) has a specific thermal curvature between 0.00003 / K and 0.00006 / K, in particular of 0.000043 / K.

4. Arrangement according to one of the preceding claims, characterized in that a compensation distance is provided as a distance between the compensation bimetal (58) and a stop (30) of the compensation bimetal (58) in a range between 0 mm and 1.0 mm, preferably between 0 mm and 0.8 mm.

5. Arrangement according to claim 4, characterized in that the compensation bimetal (58) is fastened with the fastening end to the power control device (11), in particular to a switching bridge (30) which is firmly attached to a housing of the power control device (11), wherein the switching bridge (30) forms the stop for the compensation bimetal (58).

6. Arrangement according to one of the preceding claims, characterized in that the trigger (37) consists of a bimetal or is a bimetal and is attached to the release device (35) with one end opposite the trigger end (38) at the release device (35).

7. Arrangement according to one of the preceding claims, characterized in that the release device (35) is spring-mounted, whereas the compensation bimetal (58) is rigidly attached to the power control device (11) with the fastening end in such a way that the release device (35) rests against the compensation bimetal (58) under spring pressure.

8. Arrangement according to one of the preceding claims, characterized in that an adjustable stop is provided at the free compensation end of the compensation bimetal (58) for bearing against the trigger (37), in particular a screw (59) extending in the longitudinal direction from the compensation bimetal (58) to the bearing surface on the trigger (37).

9. Arrangement according to one of the preceding claims, characterized in that the power control device (11) is designed to close and open the power switch (14) more than once per minute at a controlled continuous average power of less than 20% of the maximum continuous power, in particular less than 10% of the maximum continuous power, preferably less than 5% of the maximum continuous power.

10. Arrangement according to one of the preceding claims, characterized in that a tolerance on the lowest setting position of the power control device (11) is within a tolerance range of + / -1.5% of the nominal value.

11. Arrangement according to one of the preceding claims, characterized in that a heating power of the heating device (43) is between 4 W and 40 W at room temperature, preferably between 10 W and 25 W.

12. Arrangement according to one of the preceding claims, characterized in that the carrier (44) has a thickness of less than 1 mm, preferably a thickness between 0.1 mm and 0.75 mm.

13. Arrangement according to one of the preceding claims, characterized in that the power control device (11) has a housing (12) for the power switch (14) and the release device (35), wherein the housing is made of plastic, preferably thermoplastic such as polyphenylene sulfide, wherein, in particular, the housing has a device base (13) on which the power switch (14) and the release device (35) are mounted, wherein, preferably, the device base (13) is made of the same material as the housing (12).

14. Arrangement according to one of the preceding claims, characterized in that the continuous average power output of the radiant heating device (62) is less than 0.25 W / cm2 when the power control device (11) is set to a low or maximum low setting, preferably less than 0.2 W / cm2.