DE1814682A1 - Self-regulating heating device - Google Patents

Description

OR-INQ. DlPL.-INQ. M.SC. OIPL.-PHYS. OH. 'OIPL.-PHYS.

HÖGER - LEGAL LAW - GRIESSBApH-HAECKER

PATENT LAWYERS IN STUTTGART · ·

A 36 906 h
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12/9/1968 1814682

U.S. Ser.lTo. 692.004

Texas Instruments Incorporated, Dallas, Texas,

UNITED STATES.

Self-regulating heating device

The invention relates to a self-regulating heating device for maintaining a relatively constant ambient temperature in a cavity of a housing, in your at least one PTC heating element with an abnormal emp era door located above which its resistance rises steeply, for which heating element the characteristic curve of the specific resistance as a function of temperature thus has a steeply increasing positive temperature coefficient.

A PTC heating element is a heating element made of one material understood, whose characteristic - specific resistance as puncture of the temperature rises steeply and that a positive one Has temperature coefficient (PTC). Such a material is known and the operation is such that the heating element regulates itself to a certain temperature, which is close to the so-called anomaly temperature.

It is already known to provide ovens for this purpose which use a heating device and a thermostat. The thermostat thus keeps the internal furnace temperature within a certain range. know that the heating current is generated using moving

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switched on and off. That kind of one. Furnace has certain disadvantages lies in this system :, such as a change in temperature due to the _noticeably: also times of the thermostat from a maximum "to a minimum, and from there to a maximum Ms etc. Since a mechanical motion is present , the life of such a device is limited.

Another design uses proportional control, in which relatively complicated electrical circuits serve to prevent heat loss from the power input to the heater of the oven. This can be done, for example, by providing a bridge that has a temperature sensing device which is used to adjust a circuit that contains the heating device. That kind of one. Regulation eliminates the moving contacts when switching on and off and therefore results in more precise temperature control, there is no overflow or thermal oscillation. In addition, the output is relatively constant and also no noise due to mechanical movement. Even so, many ovens of this type make what is known as an electrical noise. In addition, such devices are proportionate complicated and expensive.

It has also been proposed (German patent application P 15 65 872.7), a device with a relatively constant Ambient temperature using self-regulating

to
creating heating elements. With these devices a temperature gain of up to: 30: 1 is achieved. The temperature gain is defined as the change in the ambient temperature divided by the change in the control temperature at constant voltage and heat output, as measured by the temperature according to the characteristic curve of the heating element.

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It has also already been proposed (German patent application P 15 65 889.6) that even higher temperature amplifications thereby to create that a first, steeply rising PTC element with a first cavity to accommodate temperature-sensitive Components is introduced into a second cavity, which is present in a second steep PTG element.

The invention is based on the object of creating a heating device of the type mentioned at the outset, in which the control temperature can be kept within even narrower limits than before. This object is achieved according to the invention in that an outer housing is arranged to create an outer furnace and an inner furnace and in this an inner housing having an inner cavity is arranged to form an outer cavity and that at least one inner housing is arranged in the inner cavity . . PTC heating element and an external heating means is provided in the outer cavity, which keeps the temperature in the outer cavity below the abnormal temperature of the PTC heating element.

In a preferred embodiment, a single toroidal PTG element is used, which is arranged around a cup containing the components. In this case, connecting conductors are connected to this heating element and are guided along the side walls of the electrically insulated housing of the inner furnace. The entire inner furnace is arranged in a heat-conducting envelope in which toroidal PTG heating elements are arranged in additional rooms at two opposite ends. The conductors connected to heating elements in the outer furnace and the other conductors are passed through guide members which are arranged in aligned openings in the outer furnace housing, the conductors still being connected to connections attached to the outer base. The PTC heating elements are held in place by electrically insulating casting material. The PTC heating elements are also connected electrically in parallel to one another.

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The outdoor oven is arranged on seat parts provided on the base, and is resilient against it by means of at least a spring is held, which is arranged between the outer housing and a cover attached to the base ". Further are Means are provided to ensure alignment of the outer oven with respect to the connections on the base.

In order to achieve even tighter temperature control, auxiliary heating elements can be used, which give the heat more evenly to distribute. If necessary, external tension regulating means can also be provided.

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Further features and advantages of the invention emerge from the following description in connection with the drawing, which includes an embodiment of the invention. In the drawing show:

FIg. 1 shows a longitudinal section through an embodiment of the invention,

Fig. 2 is a schematic Schaltscheraa of the device according to Fig. 1.

Dimensions of certain parts as shown in the drawing are partially modified from reality and / or exaggerated in order to facilitate understanding to facilitate.

In the drawing, 10 denotes a heating device according to the invention as a whole, which has a base 12 of electrical insulating material, such as, for example, phenolic resin, which can have any construction. A preferred shape is a circular plate which has an annular shoulder 14 for a lid 16 which is also made of electrically insulating material and fits snugly over the base 12. A recess 18 is provided in the cover 16, into which a projection 20 on the shoulder 1H engages. The base 12 also has a multiplicity of support columns 22 on which an external oven 30 is seated. In a preferred embodiment, there are three such support columns, but only one of them is shown in the drawing; all these pillars are in the same

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lc

Chem spacing arranged on the circumference of the base 12. Furthermore, fasteners are such as screws 24, provided, to secure the lid 16 to the base 12.

The external furnace 30 mounted on the support columns 22 is coaxial arranged in one of the support columns by means of a pin 26, this pin engaging in a corresponding opening 28 on the outer housing of the outer furnace 30.

The outdoor furnace 30 has an upper and a lower housing half 32 or 34, which are made of a thermally highly conductive material, for example Copper, are made and held together by a retaining ring 36 which engages on both housing halves 32 and 34 via flanges 35.

The housing halves 32 and 34 are substantially of approximately equal cup-shaped configuration with a closed end and Zusätzräumen 31 and 33, in which heating elements are arranged as described in more detail below. The jackets of the housing halves together form an outer furnace chamber. The lower housing half has an annular platform 38 which has a multiplicity of openings 40 arranged at a distance. A carrier 42 made of electrically insulating material, such as Ilylon, is arranged on the platform 38 and has tubular guides 46 pointing downwards, which penetrate through corresponding openings 40 of the platform 38. Furthermore, an inner furnace 50 is mounted within a plurality of holding parts 44, for example three, which preferably form part of the carrier 42. (Only one holding part 44 is shown in the drawing).

The inner furnace 50 contains a pack 52 with components contained therein, the temperatures of which are to be controlled. In the in the device shown in the drawing (see in particular Fig.2 ^

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zv / ei diodes are shown as components, but can also only one component or more than two components or any other parts may be present in the package 52. These diodes Dl and D2 have a common connecting conductor L1 and separate connecting conductors L2 and L3. The pack 52 is in a mounting sleeve 54 introduced. Furthermore, a heat transfer material can be used to reduce the heat transfer between the mounting sleeve 54 and the pack 52 to be optimally designed. The assembly ' sleeve 54 is made of a material that conducts heat well, for example aluminum, and has an annular flange 56

An electrically insulating layer is arranged on the surface of the mounting sleeve 54. Although this layer can be applied in various ways, for example by using a thermoplastic resin, it is advantageous to keep the heat conduction at an optimal level. This is especially achieved when anodized aluminum is used. The annular flange 56 of the mounting sleeve 5 ¹ J rests against a shoulder 58 of a tubular housing 60, which consists of a thermally and electrically insulating material, for example thermoplastic resin (preferably nylon). The end 62 of the mapfes 90 has an inner annular flange 64 which has annular slots 66 through which the connecting conductors Ll, L2 and L3 extend. An annular, self-regulating PTC heating element 70 is arranged on the mounting sleeve 54. The layers 72 and 74 made of silver or another conductive material serve as connections on opposite end faces of the heating element 70. Connection conductors L4 and L5 are electrically connected to the layers 72 and 74, for example by soldering. As shown, the lines contact the layers at approximately 360 °, so that there is a uniform flow of electrical current in the heating element 70. A sleeve 80 made of electrically insulating material j for example heat-shrunk Mylar, can be arranged around the circumference of the heating element 70 to

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de possibility of a short circuit of the heating element .

The heating element 70 is also encapsulated by an electrically and thermally insulating cast resin 82 of the usual type. At the end of 62 of the Tubular housing 60, a shoulder 84 is provided on which a disc 86 made of electrically insulating material, for example resin impregnated fiber material, sits. The disk 86 has slots for access to the PTC connection conductors L4 and L5 »Die Shoulder 84 is positioned so that there is a predetermined air gap 88 between the disc 86 on the one hand and the mounting sleeve 54 and the casting resin 82 on the other hand results, so that the Desired thermal insulation is available. Instead of an air gap 88, another insulation can also be used.

A cup 90, which can be made of the same electrically insulating material as the housing, for example nylon, is arranged close to or at a small distance around the tubular housing 60. The cup 90 has a projection 92 which serves as a wedge for the pack and thus holds the pack 52 firmly and tightly in the mounting sleeve. Furthermore, an annular bead 94 on the bottom of the cup 90 presses the connecting conductors Ll, L2 and L3 against the outer bead 63 of the tubular housing 60, so that the heat loss via these conductors is reduced to a minimum. In other words, this reduces the effective size of the heat absorption of the connections. The packing 52 is arranged in close thermal relation to the heating element, so that a very favorable and advantageous control results. As already mentioned, it is expedient to apply a coating of a heat transfer compound, for example a silicone compound, to the outer circumference of the mounting sleeve 54. This facilitates the conduction of heat from the PTC heating element 70 via the mounting sleeve 54 to the pack 52. A good currently available compound is GE 641 Insulgrease. A coating of this heat transfer fluid can also be applied to the outer circumference of the

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Pack 52 are applied, whereby the heat conduction from PTC heating element is further improved.

In the additional spaces 31, 33 of the housing 32, 3 ^ two self-regulating PTC heating elements 100 and 110 are arranged. Are at the opposite end faces of the heating element 100 is electrically conductive terminal layers 102 applied from silver or other good electrically conductive material 10 ¹ I, and similar layers 112, 114 of the heating element 110 are provided at the opposite end faces. Furthermore, a connection conductor L8 is attached to the connection layer 112 and a connection conductor L9 is attached to the connection layer 114 in a similar manner. Furthermore, the connection conductor L8 is surrounded by an insulating jacket 117 and the connection conductor L9 by an insulating jacket 119. In order to prevent a short circuit of the heating current, an insulating sleeve 99 is arranged on the circumference of the heating elements 100 and, which can be of the same type as the sleeve 80. . The heating elements 100 and 110 and the associated connecting conductors are encapsulated by a casting material 120 and 122, respectively.

The base 12 is provided with a multiplicity of openings 13 which are penetrated by pipe sections 15. Connections Tl .- T5 are integrally or permanently connected to these pipe sections. Any number of connections can be made. It results here that Ll are electrically connected to TL, L2 to T2, L3 to T3, L4, L6, L8 to T4 and L5, L7, L9 to T5. The three PTC heating elements are arranged electrically in parallel. The attachment of the conductors can be arbitrary, for example, by soldering. The tube pieces have an annular flange 17 ^e which abut against the base 12th After the conductors have been attached to the connections, the bores in the pipe sections 15 can be sealed, for example by soldering.

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In order to hold the external furnace 30 resiliently, a spring 39 is provided, which absorbs shocks 10 exerted on the device 10. In the example shown, the PTC material for the inner furnace, ie for the heating element 70, has an abnormal temperature of 120.degree. C., while the abnormality for the outer heating elements, ie for the heating elements 100, 110, is 80.degree. The electronic components are placed in the temperature-controlled cavity or in the package 52 of the relatively high abnormal temperature PTC heating element. The inner furnace is in turn placed in the cavity of the PTC heating element, which has a low abnormal temperature of 80 °. The furnace operation or the amplification can now be determined as follows: A furnace that regulates to an accuracy of 5 ° C with an external temperature change to 50 ° C has a amplification of 50: 5 or 10. If combined furnaces are now used, the furnace amplification be multiplied. Therefore, when operating at 120 ° oven with a gain of 30 is brought into an operating with 8O furnace with a gain of 10, this results in an overall gain of 30 times 10 or 300. A 50 ° change in the ambient temperature is therefore a Change of 50: 300 or 0.17 C measured on the component reduced. As shown in the diagram, the protected component is a diode circuit which is introduced into the furnace cavity, as described in detail in German patent application P 15 65 872.7.

It follows that the invention fulfills the stated object namely to achieve an extremely tight temperature control that is better than with electromechanical controls achievable and which can only work with a relatively expensive proportional control system or hybrid system.

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can be matched. Further advantages of the invention are that there is a rapid warm-up as a result of the PTC resistance characteristics results. The oven receives a high power input as it is heated up and stabilizes very quickly, and indeed very quickly in less than 3 minutes compared to the 15-30 minutes required by conventional ovens. the The invention also provides a device which has a long service life and operates very reliably. The standard features are exclusively, from the resistance anomaly of the PTC heating elements dependent, which have an extremely long stability. There are no contacts to wear out, nor any mechanical parts that can shift or also be subject to wear and tear.

Since there are no moving parts, assembly is easy. Basically, the components to be protected are in the packing 52 is inserted, the conductors are then passed through the annular slot 66 in the tubular housing 60 and down through the guides 46 are threaded and then connected to the relevant connections. The upper housing half 32 is then on the lower housing half 34 applied, the ring is around the Splash 35 beaded around, the conductors Ll-L9 penetrating corresponding guides 46. Furthermore, a shrinking, electrically insulating cover 96 may be applied, which the diode conductors and the conductors of the inner heating elements Holds firmly in place and isolated from the outside oven. The establishment is small in size, has a light weight Weight and is secured against shocks and vibrations.

According to the invention, one or more additional heating elements be provided. The two outer heating elements are, in a certain sense, localized heating sources that are

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Housing halves 32, 3 ^ evenly distributed in the outer furnace cavity are. However, normal auxiliary heating elements can also be arranged in series with one or both of these PTC heating elements be.

The PTC heating elements would then be replaced by the auxiliary heating elements regulate heating current flowing through, these auxiliary heating elements strategically at critical points of the external furnace 30 are arranged to ensure an even temperature distribution. An external voltage regulation could, though is minimized in the construction described above, practically completely by adding a simple, cheap regulator regulating the external voltage can be made superfluous. When the heating device 10 external If temperature changes, for example a decrease, are exposed, the response of the furnace is an increase in output. Most of this increase is absorbed by the PTC heating elements in the outside furnace. The performance in the inner oven changes only a little. Therefore, the temperature change due to changes in voltage could be switched off by a simple voltage regulator be, which is designed for relatively small changes in performance and connected so that it is only on acts on the inner furnace. Such a construction would Of course, the oven temperature control has also been improved. If the external voltage regulator were designed to work on the internal oven acts using a reference voltage in the form of a device with a linear, negative temperature coefficient, in this way the internal furnace voltage could be regulated in such a way that it increases linearly with the decrease in the external temperature. If therefore the outside temperature decreases, which also decreases the control temperature of the inside furnace, so the outside voltage regulator would respond

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react so that the inner furnace voltage and therefore also the
Inner oven temperature would be increased. A corresponding adjustment of the negative temperature coefficient of the reference voltage of the
external voltage source to the positive temperature coefficient of the inner furnace control characteristic would result in an almost perfect temperature control.

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Claims (1)

A 36 906 h h-24 1 3 H 6 8? December 9, 1968 Claims 1. Self-regulating heating device for maintaining a relatively constant ambient temperature in a cavity a housing in which at least one PTC heating element with an abnormal temperature is arranged above the be Resistance rises steeply, for which heating element the characteristic of the specific resistance as a puncture of the temperature thus has a steeply increasing positive temperature coefficient, characterized in that to create an outer oven (30) and an inner oven (50) an outer housing (32, 34) and in this with the formation of an outer cavity an inner housing (60) having an inner cavity is arranged and that in the inner cavity at least one inner housing PTC heating element (70) and an external heating means (104, 110) is provided in the outer cavity, which the temperature in Maintains outer cavity below the abnormal temperature of the PTC heating element (70). 2. Apparatus according to claim 1, characterized in that the outer heating means at least one outer PTG heating element (104, 110) whose abnormal temperature is lower than the abnormal temperature of the internal PTC heating element (70) in the Inner cavity is. 3. Apparatus according to claim 1 or 2, characterized in that the heating elements (70, 104, 110) or the heating means are electrical are connected in parallel to each other. 4. Device according to one of the preceding claims, characterized in that the PTC heating elements (70, 104, 110) are at least partially made of Ba ggr. La q _Q , TiO. Device according to one of the preceding claims, characterized in that the PTC heating elements (70, 104, 110) are at least partly made of polymer filled with carbon black. - 15 9Q9830 / 0939 1814632 A 36 906 h h-24
December 9, 1968 6. Device according to one of the preceding claims, characterized in that conductive layers (102, 104; 112, 114; 72, 74) standing on the PTC heating elements (70, 104, 110) and connecting conductors (L3-19) ″ are preferably attached to the conductive layers. 7. Apparatus according to claim 6, characterized in that the conductive layers (102, 104; 112, 114; 72, 74) are arranged on the "two end faces and are separated by an insulating sleeve (99 _S 80) attached to the circumference. 8. Device according to one of the preceding claims, characterized in that the outer housing (32, 34) of good heat . conductive material. 9. Device according to one of the preceding claims, characterized in that the outer housing has ^two housing halves (32, 34) which are tightly connected to one another and designed as cups. 10. Device according to claim 9, characterized in that the housing halves (32, 34) have flanges (35) at the open ends which are firmly connected to one another, preferably by a clamping ring (36). 11. Device according to one of the preceding claims, characterized in that the outer PIC heating element (104, 110) is arranged in an additional space (31, 33) in a good thermally conductive relationship to the outer housing (32, 34). 12. The device according to claim 11, characterized in that the additional space (31, 33) at the bottom of one, preferably both, Housing halves (32, 34) is arranged. 13. Apparatus according to claim 11 or 12, characterized in that that in each additional room (31, 33) an outer PIC heating element (104, 110) is arranged. - 16 - 909830/0939
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December 9, 1968 14. Device according to one of claims 11-13, characterized in that the outer PTC heating element with filling all other parts of the additional space (31, 33) held with electrically insulating material in the additional space (31, 33) is. 15. Device according to one of the preceding claims, characterized in that the at least one outer PTC heating element (104, 110) is annular. 16. Device according to one of the preceding claims, characterized in that part of the outer housing (32, 34) has a Has a plurality of openings (40) and on this part a carrier made of insulating material, in particular a carrier ring (42), whose tubular guides (46) are penetrated by electrical connection conductors (L1-L9). 17. The device according to claim 16, characterized in that a plurality of connections, in particular on the base (12) in the form of connecting pins (T1 - T5) to which the connecting conductors (L1 - L9) are connected. 18. Device according to one of the preceding claims, characterized in that the base (12) has a number of support columns (22) which carry the outer housing (32, 34). 19. Device according to one of the preceding claims, characterized in that a preferably cup-shaped on the base (12) Outer cover (16) is attached, between its closed end and the outer housing (32, 34) a spring (39) is arranged, which presses the outer housing (32, 34) against its support (22). 20. Apparatus according to claim 19, characterized in that Fitting parts (14, 22) are provided such that the base (12), the cover (16) and the outer housing (32, 34) are coaxial. 909830/0939 - 17 - A 36 906 h - 17 - December 9, 1968 21. Device according to one of the preceding claims, characterized in that the inner housing (60) and electrical is thermally insulated or is formed from a corresponding material. 22. Gate direction according to one of the preceding claims, characterized characterized in that the inner housing (60) at one end has a seat, for example in the form of a shoulder (58), on which an electrically insulating and thermally conductive and for> 3ie Acceptance of components suitable assembly member, "for example a mounting sleeve (54)> in particular with its corresponding Splash (56) rests. 23. The device according to claim 22, characterized in that the inner PTC heating element (70) is in good thermal relation is arranged on the circumference of the mounting member (54). 24. Device according to one of the preceding claims, characterized characterized in that one end of the inner housing (60) is covered by an electrically and thermally insulating cover piece, for example a disc (86) is covered. 25 device according to claim 24, characterized in that the other end of the inner housing (60) by an electrical and a thermally insulating cover, for example in the form of an IT cup (90), is covered. 26. The device according to claim 25 »characterized in that Connection lines (L1 - L5) i that in the inner housing (60) are bent so that they run along the outside of the housing between this housing (60) and the cover (90) and openings of the outer housing (32, 34) penetrate. - 18 - 90983 0/0939 18U682 A 36 906 h - 18 - h-24 9 ·. 12.1968 27. The device according to claim 26, characterized in that an insulating cover around the inner housing to isolate the connecting conductors (LI - L5) from the outer housing (32, 34), for example in the form of a sleeve (96) or a cup. 909830/0939 ■ Ί ⁹ · » Blank page