ES2204877T3 - HEATING ELEMENT WITH PTC COMPONENTS. - Google Patents

Abstract

The device has several individual PTC elements connected electrically to form a group and selected from a production run of elements so the group maintains a predefined group tolerance with respect to an electrical parameter. A predefinable fixed number of PTC elements is provided for the group with individual tolerances in a range outside that corresponding to the group tolerance so they maintain the group tolerance as nested PTC element groups.

Description

Heating element with PTC components.

The invention relates to an element of heating with several individual PTC components which are electrically switched with each other to form a group of PTC components and are chosen in such a way, from among a PTC component production, which the PTC component group maintains a default group tolerance for a characteristic electrical magnitude.

These types of PTC heating elements are use, for example, for the construction of blocks of heating for electrical heating installations that used in car heating installations for heat the interior space of the vehicle. The element of heating consists of individual PTC components for which are electrically switched p. ex. in parallel. In the Publication of the application DE 44 34 613 A1 a PTC strip heating element for this use, in which the individual PTC components are inserted into distance, next to each other, in openings of a frame of sealing and are held by two plates that are in contact by both sides.

In the construction of this type of PTC heating elements it is desirable to maintain, for a predetermined characteristic electrical magnitude, p. ex. electrical resistance or electrical conductance, a predetermined tolerance, in order to avoid unwanted failures, such as too high current continuity due to too low total resistance of the group of PTC components formed by PTC components electrically switched with each other. In order to maintain tolerance, the measure of, for the construction of a group of PTC components, to choose, from a set of manufactured PTC components, only those with a correspondingly narrow tolerance could be considered. In this case the PTC components that are outside the correspondingly narrow individual tolerance cannot be used. Another possibility would be to allow a variable number of PTC components for the formation of the PTC component group of the heating element, e.g. ex. for a first heating element less PTC components with greater individual electrical resistance and for a second heating element more PTC components with lower resistance, so that in each case the total resistance or total conductance is within the tolerance of desired group However, this would not always be all the places for PTC components in the element of
heating.

The invention poses, as a technical problem, provide a PTC heating element of the type mentioned to principle, in which the group tolerance is maintained predetermined with respect to the electrical characteristic magnitude respectively, all locations for PTC components can be occupied and it should not be rejected if possible functional PTC components of manufacturing for use in the element of heating.

The invention solves this problem by means of a heating element that presents the characteristics of the claim 1. This heating element contains a group of PTC components with a default number of PTC components of fixed way, that is, all the places planned for these are also busy. For use in the heating element not only PTC components whose individual tolerance are allowed is, with respect to the characteristic electrical magnitude corresponding, within a range of individual tolerance corresponding to the default group tolerance but also PTC components, from manufacturing, whose Individual tolerance is outside this range. The majority of the PTC components are chosen for the element of heating in such a way that as a group electrically switched with each other they keep the whole default group tolerance. This can be done, by example, because in cases in which a PTC component chosen is in a direction outside the tolerance range individual corresponding to the group tolerance, one is chosen or several PTC components of the manufacturing found in the another direction, outside this margin of individual tolerance and give place with it that the tolerance of all PTC components formed together is within the group tolerance  default This makes possible, if desired, the use of virtually all PTC components functional for the construction of this type of elements of heating.

In an advantageous improvement of the invention according to claim 2, the electrical resistance or conductance constitutes the determining electrical characteristic magnitude for tolerance consideration and a tolerance of group of ± 15% or less. According to the invention they can be used however PTC components whose individual tolerance is clearly out of this group tolerance, if the components PTCs are used in the PTC component group with tolerances that They diverge in the opposite direction.

An example of advantageous embodiment of the invention explained to continuation. In the drawings, the figures show:

Fig. 1, a top view on an element PTC heating strip with the top plate removed, and

Fig. 2, a diagram of a distribution of typical frequencies of the individual tolerance of PTC components of production to illustrate the selection of PTC components suitable for the heating element of Fig. 1.

Fig. 1 shows a PTC heating element in the form of a strip, of structure known per se, as described in publication DE 44 34 613 A1 cited. A frame of seal 1, for example soft plastic material is provided with several openings 2. In the example shown there are three openings, in which a corresponding number of PTC components 3a, 3b, 3c individual. The PTC 3a components, 3b, 3c are held within them by a lower plate 4 and an upper plate, removed in Fig. 1 in order to allow recognition of PTC components 3a, 3b, 3c. The plates they are also used for heat transport and electrical connection of the PTC components 3a, 3b, 3c.

\hbox{paralelo,}

tres componentes PTC 3a, 3b, 3c para formar un grupo de componentes PTC correspondiente. Al mismo tiempo está predeterminado que la resistencia eléctrica o, equivalente a ello, la conductancia eléctrica del grupo de componentes PTC y con ello del elemento de calefacción debe mantener una cierta tolerancia, designada con anterioridad como tolerancia de grupo. Por ejemplo, puede estar predeterminada como tolerancia de grupo \pm10%. Por otro lado, cada componente PTC 3a, 3b, 3c individual tiene una tolerancia individual respecto de la magnitud eléctrica característica elegida, es decir, aquí respecto de la resistencia o la conductancia eléctricas. Ésta se dispersa en una fabricación en masa de componentes PTC según una distribución de frecuencias como la que se reproduce, para un caso de ejemplo típico, en el diagrama según la Fig. 2.In the strip-shaped heating element PTC they are electrically switched with each other, in

 \ hbox {parallel,} 

three PTC components 3a, 3b, 3c to form a corresponding group of PTC components. At the same time it is predetermined that the electrical resistance or, equivalent thereto, the electrical conductance of the group of PTC components and thereby of the heating element must maintain a certain tolerance, previously designated as group tolerance. For example, it may be predetermined as group tolerance ± 10%. On the other hand, each individual PTC component 3a, 3b, 3c has an individual tolerance with respect to the chosen electrical magnitude, that is, here with respect to the electrical resistance or conductance. This is dispersed in a mass production of PTC components according to a frequency distribution such as the one reproduced, for a typical example case, in the diagram according to Fig. 2.

As can be seen in Fig. 2, the frequency distribution has its maximum for the value of 0% tolerance, that is, the maximum frequency is in these PTC components manufactured whose resistance or conductance electric have the default theoretical value for the manufacturing. However, together with these there are also components PTC with resistance or conductance value that diverges from the value theoretical. While its number increases with increasing distance of the resistance value or effective conductance with respect to the value theoretical, in total there is however a remarkable amount of PTC components that meet their resistance value or conductance in the left striped area B_ {L} of Fig. 2, is that is, they are more than a lower limit value T_ {U} below the theoretical value, or in the right striped B_ {R} area of Fig. 2, is that is, they are more than a higher limit value T_ {O} above theoric value.

If, for the construction of the heating element of Fig. 1, only PTC components of the manufacturing were chosen in each case, whose resistance or conductance is in the central B_ {M} zone of Fig. 2 with tolerances between the lower limit value T_ {U} and the upper limit value T_ {O}, the required group tolerance could be maintained with them. The limitation to the use of only this type of PTC components of this individual tolerance range B_ {M} would, however, have the disadvantage that a large number of PTC components manufactured by mass production would not be used for the construction of the heating element, that is, all the PTC components of the striped areas B_ {L} and B_ {R} of Fig. 2. At the same time the lower and upper limit values T_ {U}, T_ {O} are set in such a way that this individual tolerance margin B_ {M} corresponds to the predetermined group tolerance, that is, when the individual tolerances of the three PTC components 3a, 3b, 3c are at the lower limit of the predetermined group tolerance and, similarly, then, when the individual tolerances of the three PTC components 3a, 3b, 3c are at the upper limit value T_ {O}, a total tolerance value at the upper limit of the group tolerance pr determined. The appearance in each case of this individual tolerance margin
B_ {M} = [T_ {U}, T_ {O}], which must be determined in this way, in terms of its length around the theoretical value with tolerance 0%, obviously depends on the number of PTC components in the group of PTC components and, by what mathematical relationship is the total value of the characteristic electrical magnitude chosen for the group of PTC components from the individual values of the individual PTC components, as is evident to the person skilled in the art.

According to the invention, on the contrary, all PTC components manufactured are advantageous because, during the choice of the three PTC components 3a, 3b, 3c for the heating element, their individual tolerances and a tolerance of a PTC component are taken into account that diverges in one direction is compensated by the choice of one or more PTC components with tolerance that diverges in the other direction. In this way it can be removed, e.g. ex. To fill the three openings 2 of the heating element of Fig. 1, first of all any PTC component such as the first PTC component 3a inserted from a complete set of manufactured PTC components. When this comes from the central individual tolerance margin B_ {M} of Fig. 2, there is also for the second PTC component 3b that practically a total freedom of choice must be inserted. On the contrary, if the first PTC component 3a comes from one of the zones B_ {L} and B_ {R} with a greater deviation from the tolerance, the second component PTC 3b is preferably chosen from the zone B_ {L}, B_ {R} of each of the respective two zones. Depending on the total tolerance resulting from the two PTC components 3a, 3b already chosen, the third PTC component 3c is then chosen suitably either from the central zone B_ {M} of lower tolerance or one of the two zones B_ {L}, B_ {R} of higher tolerance, such that, in total, the tolerance of the three PTC components 3a, 3b, 3c chosen and electrically switched with each other is within the total tolerance
default

Ensuring in this way that each of the various PTC heating elements of a heating block constructed with them maintains the desired tolerance with respect to the electrical resistance or conductance, it is also guaranteed that the electrical resistance or conductance of the heating block is found, in total, within tolerance
default

It is understood that, in this way, you can build heating elements with any number of PTC components If necessary, it can be provided for facilitate the choice of PTC components with in each case the adequate tolerance value, a prior grouping of all PTC components manufactured and functional in predetermined groups with different tolerance intervals. When to a system of manufacturing are made known the number of groups of this type and the corresponding tolerance intervals as well as the number of PTC components that can be inserted into the element of heating, it is in a position to carry out Widely automatic choice and insertion of components PTC

Since, at least for the first PTC component of a heating element to be inserted, there is freedom of full choice regarding the set of manufactured PTC components, obviously you can take advantage of all PTC components manufactured for the manufacture of heating elements corresponding, even those that have a tolerance value high, that is, a high divergence of the electrical magnitude characteristic with respect to the theoretical value. While this kind of PTC components with strong divergence cannot be used mostly in heating elements, however this corresponds smoothly to the fact that in manufacturing only a small number of PTC components of this type, see frequency distribution of Fig. 2.

The use according to the invention of virtually all of the functional PTC components of mass production can be recognized in all elements manufactured heating in which all the rooms are always occupied places for PTC components and at the same time have been used PTC components whose individual tolerances are outside of the individual tolerance zone B_ {M} corresponding to the default group tolerance.

Claims (2)

1. Heating element provided with - a plurality of PTC components (3a, 3b, 3c) individual which are electrically switched with each other to form a group of PTC components and are selected from such way between a production of PTC components, that the group of PTC components maintains a default group tolerance with respect to an electrical characteristic magnitude, characterized because - for the PTC component group it is planned a fixed number, which can be predetermined, of several components PTC (3a, 3b, 3c), which are selected in such a way from a production of PTC components with individual tolerances located in a margin (B_ {L}, B_ {M}, B_ {R}), which is more beyond the individual tolerance range (B_ {M}) of the tolerance default group, which maintain group tolerance as PTC component group switched between each other. 2. Heating element according to claim 1, further characterized in that as the characteristic electrical magnitude the resistance or electrical conductance is chosen and the predetermined group tolerance is ± 15%, at most.