DK2429257T3 - Electric heating device - Google Patents

Description

The invention relates to an electric heater according to the precharacterising clause of patent claim 1.

Such electric heaters can be used, for example, in the blow-by system of combustion engines or for heating a tank of an SCR (selective catalytic reduction) system. Examples of such electric heaters are shown on the internet page www.dbk-qroup.de. According to that page, such heaters have a heating portion which is inserted in a correspondingly shaped receiver of the component whose temperature is to be controlled, for example a tank or a flow path of the blow-by gas. This heating portion merges into a plug-in or contacting part, in which the power supply lines for the heater are arranged. In the known heaters, resistor elements, for example PTC heating elements, are used, which are supplied with power via the power supply lines of the contacting part and lie against as large an area as possible of a wall region of the housing portion, so that the heat is transferred directly via the wall of the heating portion and the adjacent wall of the component whose temperature is to be controlled. In order to improve the heat transfer, it is important that a large heat exchange surface is present, on the one hand, and that no insulating air gaps are arranged in the heat transfer path, on the other hand.

It is a problem that, owing to tolerances in production and temperature fluctuations during operation of the heater or of the component to be heated, an insulating air gap can form in the region in which the heating element lies against the wall. This disadvantage can be eliminated if the passages for the regions supporting the heating elements are chosen to be very narrow, but mounting of the heater is then relatively difficult owing to the required narrow fit sizes, so that there is a risk of damage to the heating element, in particular when using PTC modules. A heating device for heating flowing media is known from US 5 262 619 A, which heating device has a heat exchanger which can be heated by means of PTC resistors and has a slit-like pocket. A cuboid substrate body is adapted in terms of its shape to the shape of the pocket and can be inserted therein. The surfaces of the substrate body have recesses for receiving the PTC resistors and a contact spring. The surfaces of the substrate body and of the pocket facing one another are inwardly bevelled from the insertion side. EP 1375997 A discloses a solution in which a heating portion is biased against a face of the component to be heated, so that the transfer of heat takes place in the region in which one side of the heating portion lies against the component to be heated. Such a solution has the disadvantage that the heat exchange surface, and thus the possible heat input into the component, is small owing to the low power density.

In light of the above, the object underlying the invention is to provide an electric heater in which optimal heat transfer is ensured with simple mounting.

The object is achieved by an electric heater having the features of patent claim 1.

Advantageous further developments of the invention are the subject of the dependent claims.

The electric heater according to the invention has a heating portion which can be inserted into a receiver of a component whose temperature is to be controlled. The heater further has heating elements which are supplied with power via power supply lines. According to the invention, the heater is designed with an activation pin which can be moved from a release position into an activation position. In the release position, the heating element is in a mounting position with play, in which the heating element is not or is only negligibly in thermal contact with the wall or in electrical contact with the power supply lines. By displacing the activation pin into the activating position, the heating element or the power supply line is moved into an active position in which thermal and/or electrical contact is made substantially without play and over a large area.

The solution according to the invention thus provides a heater in which the heating elements initially lie against the wall to be heated or the power supply lines with play, not in close contact. For activation of the heater, the activation pin is then moved so that the heating elements are moved or displaced into their active position. In this manner, mounting of the heater is substantially simplified because the heating elements are initially received in the housing with a comparatively large amount of play. In the activation position of the activation pin, that play is then removed, so that the desired thermal and electrical contact with very good heat transfer is produced.

The thermal and/or electrical contacting produced as a result of the displacement of the activation pin is preferably also accompanied by mechanical contacting, which ensures that the heating elements are pressed against the corresponding wall of the receiver of the component. Mechanical contacting can take place in addition to or independently of thermal and electrical contacting. The mechanical contacting of the heating elements can take place indirectly, for example by way of intermediate structural elements, or directly.

In the invention, the heater has at least two heating elements located opposite one another, each having an associated spring element, wherein the activation pin in its activation position dips between the two spring elements in order to urge the heating elements by means of the spring force towards the wall or with the aim of achieving contact. Accordingly, in the first variant, two heating elements can be pressed against opposite walls of the receiver of the component to be heated so that, as a result of the improved heat transfer surface as compared with the prior art cited in the introduction to the description, a considerably improved heat input with a high power density can be achieved.

In a preferred embodiment of the invention, the activation pin has an actuating projection, which protrudes from a housing portion, and an activating portion on the heating element side, which activating portion, for activation of the heater, enters into active connection with the heating element by movement of the actuating projection, wherein the activation pin can lie indirectly or directly against the heating element. It is also advantageous that an electrical mating connector cannot be plugged in when the activation pin is in the release position. Simple protection against misuse is thus provided.

The construction of the heater is particularly simple if at least one of the power supply lines is designed with a spring element which, in the active position of the activation pin, urges the heating element towards the wall.

In a variant of the invention, a spring element is fixed to a power supply line. The spring element can be held, for example, by way of crimp tabs of the power supply line.

In one embodiment of the invention, at least one of the power supply lines is in resilient form so that, by means of the resilient action, tolerance deviations can be compensated for and contact of the heating element over a large area in its active position is ensured.

The power supply line can have an approximately U-shaped construction, wherein a curved region providing the resilient action is formed on a base of the U.

It is preferred according to the invention if both power supply lines are in resilient form and/or have spring elements via which, for example, in each case at least one heating element can be urged towards its active position. A variant of the invention provides that a total of four heating elements are provided, which heating elements are situated opposite one another in pairs and between which there are arranged spring elements and an activation pin.

The activation pin can be made of metal in the form of a stamped bent part having a crimped-over end portion, or can be made of plastics material.

In a further development of the invention, the activation pin is fixed in its activation position by force-based or interlocking engagement with a further structural element of the heater, for example the above-mentioned plug-in part. This fixing in position can be effected, for example, by a catch mechanism in which a tongue snaps into a recess in the activation pin or, in kinematic reversal, a projection of the activation pin snaps into a recess in the plug-in part or in another portion of the heater that is fixed to the housing.

It is preferred according to the invention if the electric heater is designed with PTC resistor elements.

The described design also has the advantage that the heater can be dismantled again. After the activation pin has been deactivated, the heater can be removed again without force and can be replaced, for example, during servicing. However, it must be ensured that the heater is not removed arbitrarily. The use of a special tool is expedient here. A preferred embodiment of the invention will be described in greater detail in the following with reference to schematic drawings, in which:

Figure 1 is a three-dimensional view of an electric heater according to the invention; Figure 2 is a view from above of a heater according to Figure 1;

Figure 3 shows the heater of Figure 1 without insulating film;

Figure 4 shows a plug-in part of the heater of Figure 1;

Figure 5 is a three-dimensional view of the heater according to Figure 1 without the housing;

Figure 6 shows the arrangement according to Figure 5 in a different view;

Figure 7 shows a side view of the heater of Figure 1 without the housing;

Figure 8 shows a detail of a first power supply line of the heater according to Figure 1; Figure 9 shows a detail of a spring element of the heater of Figure 1;

Figure 10 shows a detail of an activation pin of the heater of Figure 1;

Figure 11 shows a detail of a second power supply line of the heater of Figure 1; and Figure 12 shows the heater of Figure 1 inserted into a pocket.

Figure 1 shows a view of a heater 1, which consists in principle of a heating portion 2 and a plug-in part 4. As will be explained in greater detail in the following, the power supply lines for contacting of the heater 1 are arranged in the plug-in part 4. The heating portion 2 is inserted into a receiver or pocket of a component to be heated, for example an SCR tank, the heating portion 2 lying against the wall of the receiver over a large area so that good heat transfer is ensured. In the embodiment shown, an electrically non-conducting insulating film 6 which optimises heat transfer and will be described in greater detail below is provided in the region in which the heating portion 2 lies against the receiver (not shown). In the region of the plug-in part 4 there is attached a plug contour on which a correspondingly profiled connector of the power supply is placed, the plug contour 8 being so designed that mounting in the correct position is ensured.

Figure 2 shows a plan view of the plug-in part 4 from Figure 1. There can be seen a plug flange 10, which in the view according to Figure 2 conceals the heating portion 2 and also acts as an insertion stop therefor. A peripheral wall of the profiled plug-in part 4 delimits a plug cavity 12, into which the above-mentioned plug of the power supply plunges at least in sections. On the base of the plug cavity 12 there can be seen two tongue-like power supply lines 14, 16 of the heating portion 2, which project into the plug cavity, and an actuating projection 18 of an activation pin 20, which actuating projection likewise protrudes into the plug cavity 12. The actuating projection 18 is supported on two spring tongues 22, 24 of the plug-in part 4 and extends through the base of the plug cavity 12 into the heating portion 2. The spring tongues 22, 24 each have a locking projection, which plunges into recesses 26, 78 in the activation pin 20. In the release position of the activation pin 20, the spring tongues 22, 24 engage in the recess 78 in the activation pin 20, which is thus fixed in position against unintentional displacement. If a shear force is applied to the actuating projection 18, away from the observer in the representation according to Figure 2, the resilient engagement of the spring tongues 22, 24 is released so that the activation pin 20 can be displaced towards the heating portion 2. In the active position, the spring tongues 22, 24 then engage in the recess 26 in the activation pin and lock it. This function will be described in greater detail in the following.

Figure 3 shows the heater 1 according to Figure 1 with the insulating film 6 removed. As a result, the actual heating portion 2 is visible, which will be described in greater detail in the following with reference to Figures 5 and 6. Figure 4 shows the plug-in part 4 alone, without the heating portion 2. According to that figure, retaining legs 28, 30, which are arranged on both sides of the heating portion (Fig. 3) and effectively form end walls of the heating portion 2, extend downwards away from the plug flange 10. The retaining legs 28, 30 are in turn designed with a profile 32 which allows them to be fixed in position in the receiver of the component to be heated. The plug-in part 4 of the heater 1 is preferably produced from plastics material by the injection moulding process. A catch lug 33, 35, via which the heating portion 2 can be fixed in position between the retaining legs, is provided on each of the side faces of the retaining limbs 28, 30 facing one another. The catch lugs 33, 35 absorb the force (activation force) on the heating insert which is produced when the activation pin 20 is pushed in according to Figures 5 and 6.

Figure 5 shows a representation of the heater 1 with the plug-in part 4 removed. The U-shaped insulating film 6, the open side regions of which are covered by the above-described retaining legs 28, 30 (not shown in Figure 5), can clearly be seen. In this representation, the two power supply lines 14, 16 and the activation pin 20 with its actuating projection 18 can also be seen. The above-described recess 26, into which the spring tongues 22, 24 (not visible) engage in a resilient manner, this resilient engagement being relatively easy to remove, is formed in the actuating projection.

The heating portion 2 of the heater 1 is in the present case designed with four PTC heating elements 34a, 34b and 36a, 36b, which can clearly be seen in the view according to Figure 6, which shows the heater 1 without the plug-in part 4 in a view rotated through about 90° relative to Figure 5. According to that figure, in each case two PTC heating elements 34a, 34b and 36a, 36b are situated opposite one another in pairs, the large surfaces of the PTC resistor elements running parallel to the large surfaces of the insulating film 6. An approximately U-shaped first contact element 38 of the power supply line 16 plunges into the space between the PTC resistor elements 34a, 34b and 36a, 36b, the structure of which contact element can be seen particularly clearly in Figure 6 and in the detail view according to Figure 8. According to that figure, the first contact element 38 has two electrode plates 40, 42, each of which lies against one of the PTC resistor element pairs 34a, 34b or 36a, 36b and the surface area of which corresponds approximately to that of the associated resistor element pair. The two electrode plates 40, 42 are connected at the end by a base portion 44a, 44b. Each of the base portions 44a, 44b is designed with a curved region 46a, 46b, so that the two electrode plates 40, 42 are movable resiliently and parallel to one another by resilient deformation of the base portions 44a, 44b and the associated curved regions 46a, 46b. According to Figure 5, catch recesses 47, 49 for catching with the catch lugs 33, 35 are formed on the side edges of the electrode plates 40, 42. In addition to catching, the recesses 47, 49 also absorb the activation force.

According to the representations in Figures 5, 6 and 8, the contact tongue 48 is connected to the electrode plate 40 by way of a contact leg 50 which is bent approximately in a U-shape. A spring element 52, 54 (see Figures 6 and 7) is held against each of the two electrode plates 40, 42 of the power supply line 16. In the embodiment shown, two crimp tabs 56a, 56b and 58a, 58b (see Figure 8) are provided on each electrode plate 40, 42 for fixing the spring elements 52, 54 in position, each of which crimp tabs engages laterally around an upper cross-member 60, 62 of the respective spring element 52, 54. According to the detail view in Figure 9 and Figures 6 and 7, the two spring elements 48, 50 further have lower cross-members 64, 66, which run parallel to the upper cross-members 60, 62 and between which two spaced apart spring bridges 68a, 68b and 70a, 70b arch towards one another. In the representations according to Figures 6 and 7, only the spring bridges 68a, 70a that are located at the front in the viewing direction are visible, the associated spring bridges 68b and 70b are concealed by the spring bridges 68a and 70a in the view according to Figure 7 and are not visible in the view according to Figure 6. Two recesses 61a, 61b are formed on the lateral narrow edges of the upper cross-members 60, 62, around which the crimp tabs 56a, 56b; 58a, 58b engage in the mounted state in order to mechanically connect the spring elements 52, 54 to the corresponding power supply lines 14, 16.

Each spring element 52, 54 is thus supported on the associated electrode plate 40, 42 by its upper and lower cross-members 60, 64 and 62, 66, lateral fixing being effected by means of the crimp tabs 56a, 56b and 58a, 58b formed on each electrode plate 40, 42. The two apexes 72, 74 (Figure 7) of the spring bridges 68, 70 are at a comparatively small distance from one another. As can be seen in particular in the representation according to Figure 7, the two electrode plates 40, 42 are slightly spaced apart from the PTC resistor elements 34b, 36b in this mounting state of the heater 1, so that in each case a gap s remains, which allows the PTC heating elements 34, 36 to be inserted virtually without force and thus gently. According to the representation in Figure 7, an activation portion 76 of the activation pin 20 dips into the region between the mutually opposite spring bridges 68, 70 but is not in touching contact with the spring elements 52, 54 in the mounting position or release position (see Figure 7).

When the activation pin 20 is pushed in between the spring elements 52, 54, the cross-members 60, 62 remain fixed in position owing to their connection with the electrode plates 40, 42, produced by means of the crimp tabs 56a, 56b; 58a, 58b. The cross-members 64, 66 on the spring elements 52, 54 are displaced when the activation pin 20 is pushed in, that is to say they do not retain their position.

According to the detail view of the activation pin 20 in Figure 10, the activation pin has an approximately fork-shaped construction, the actuating projection 18 having the recess 26 and a further opening 78 protruding upwards (view according to Figure 10) from a link portion 80 which is angled slightly to the plane of the activation portion 76 and from which there extend two legs 82, 84, which together form the activation portion 76. These legs have a crimped-over end portion 86, 88, which has been bent back by a bending operation to the plane of the portion of the legs 82, 84 at which they are attached, the terminal end regions 90, 92 again being bent slightly out of that plane. Bending the end regions 90, 92 in this manner provides a safeguard in the event of failure of the spring tongue 22, 24. If the spring tongue does not lock the activation pin, the activation pin can be moved only to the level of the spring elements. This prevents an electrical short circuit, which could occur if the activation pin 20 came into contact with the power supply 14. The activation pin 20 is guided displaceably (vertically in Figure 6) in the plug-in part 4 by way of suitable guides.

Figure 11 shows a detail of the second power supply line 14, which has a similar construction to the power supply line 16 described with reference to Figure 8 and is interlaced therewith according to the representations in Figures 5 and 6. The power supply line 14 has two electrode plates 94, 96 which have approximately the same surface area as the electrode plates 40, 42. The two electrode plates 94, 96 are again attached to one another in a resilient manner by way of base portions 98a, 98b which are connected at the ends and each have a curved region 100a, 100b. As can be seen in particular in Figure 6, the electrode plates 94, 96 and the base portions 98a, 98b are located outside the corresponding structural elements of the power supply line 16, the PTC resistor elements 34a, 34b being arranged between the electrode plates 42 and 96 and the PTC resistor elements 36a, 36b being arranged between the electrode plates 40 and 94 (see Figure 7). A contact tongue 102 is attached to the electrode plate 94 by way of a U-shaped portion 104. Both power supply lines 14, 16 are in the form of stamped bent parts. According to Figure 11, a fixing element 110 is formed on the electrode plate 96, as is shown more clearly in the view according to Figure 5. During mounting, the fixing element 110 engages into a corresponding recess in the plug-in part 4, in order to fix the heating portion 2.

Figure 12 shows a heater 1 inserted in a receiver or pocket of a container to be heated, the heating portion 2 being received flush in the pocket 106 and the plug-in part 4 being seated by means of the plug flange 10 on an outer surface 108. The insulating film 6 thereby lies against the peripheral walls of the pocket 106 over a large area, but the end face of the heating portion 2 can be spaced apart from the bottom of the pocket. As has already been explained, for insertion in the pocket 106, the activation pin 20 is left in its position shown in Figure 7, in which the electrode plates 40, 42 and 94, 96 are not in contact with the PTC resistor elements 34, 36 with bias. Furthermore, in the mounting position according to Figure 7, the insulating film 6 is also not pressed against the wall of the pocket 106.

As explained, the gap s between the internal electrode plates 40, 42 and the associated PTC resistor elements 34a, 34b; 36a, 36b is present in the mounting state. After the heater 1 has been inserted into the receiver 106 in a virtually force-free manner, owing to the play s that is present, the activation pin 20, by way of the actuating projection 18 protruding into the plug space 12, is displaced downwards (Fig. 12) from the representation according to Figure 6, either by means of the fitted plug or by means of a suitable tool, so that the two crimped-over end portions 86, 88 each come into contact with the associated spring bridge 52, 54 running parallel thereto and deform it in such a manner that a biasing force is applied to the associated electrode plates 40, 42 and they are biased against the adjacent PTC resistor elements 34a, 34b, 36a, 36b over a large area and with a comparatively high biasing force, so that the gap s closes. By means of that spring force, the external electrode plates 94, 96 with the insulating film 6 surrounding them are also pressed over a large area against the wall of the receiver of the component, so that optimum heat transfer is ensured.

In the representation according to Figure 12, it can clearly be seen that, in the activation position shown, the spring tongues 22, 24 (only the spring tongue 24 is visible in Figure 12) of the plug-in part 4 snap into the recess 26, so that the activation pin 20 is fixed in its vertical position (Figure 12). In the mounting position (Figure 6), the spring tongues 22, 24 plunge with their catch projections into the opening 78 in the activation pin 20, which has a slightly larger area. The activation pin 20 is thereby prefixed in the mounting position. The force F is sufficient to overcome the engagement of the projections of the spring tongues 22, 24 with the recess 78.

If the receiver of the component is made of metallic material, the insulating film 6 serves as electrical insulation. The insulating film can additionally also serve to compensate for slight unevenness in the receiver of the component. A particular advantage of this construction is that any manufacturing tolerances and temperature-related dimension variations can be compensated for by the considerable spring force of the spring bridges 74a, 74b, so that sufficient mechanical, thermal and electrical contact is always ensured. Moreover, mounting of the heater 1 itself and insertion thereof into the receiver is facilitated by the play s.

In principle, this concept can be simplified even further if the actuating projection 18 of the activation pin 20 acts as a power supply line, so that power can then only be supplied when the activation pin 20 is moved into its activation position.

The structural principle underlying the invention can easily be adapted to different sizes and powers.

There is disclosed an electric heater having at least one heating element which can be brought into thermal contact with a wall of a component that is to be heated. The heating portion is provided with an activation pin which can be moved from a release position into an activation position in order to move the heating element, after it has been inserted into the receiver, into an active position in which adequate thermal and/or electrical contact is ensured.

List of reference numerals 1 Heater 2 Heating portion 4 Plug-in part 6 Insulating film 8 Plug contour 10 Plug flange 12 Plug cavity 14 Power supply line 16 Power supply line 18 Actuating projection 20 Activation pin 22 Spring tongue 24 Spring tongue 26 Recess 28 Retaining leg 30 Retaining leg 32 Profile 33 Catch lug 34 PTC resistor element 35 Catch lug 36 PTC resistor element 38 Contact element 40 Electrode plate 42 Electrode plate 44 Base portion 46 Curved region 47 Catch recess 48 Contact tongue 49 Catch recess 50 Contact leg 52 Spring element 54 Spring element 56 Crimp tab 58 Crimp tab 60 Upper cross-member 61 Recess 62 Upper cross-member 64 Lower cross-member 66 Lower cross-member 68 Spring bridge 70 Spring bridge 72 Apex 74 Apex 76 Activation portion 78 Opening 80 Link portion 82 Leg 84 Leg 86 Crimped-over end portion 88 Crimped-over end portion 90 End region 92 End region 94 Electrode plate 96 Electrode plate 98 Base portion 100 Curved region 102 Contact tongue 104 U-shaped portion 106 Pocket 108 Surface 110 Fixing element

Claims (14)

An electric heating device inserted with a heating section (2) into a housing in a component to be thermostated, with heating elements (34, 36), which are supplied with power via power supply (14, 16) and can be brought directly or indirectly in thermal contact with a wall of the receptacle, characterized by an actuating pin (20) which can be adjusted from a release position to an actuating position to position the heating elements (34, 36) from a mounting position where they are not or only to a small extent in thermal contact with the wall or in electrical contact with the associated power supplies (14, 16), to a functional position where the thermal contact and / or electrical contact is guaranteed, the heating device having at least two heating elements (34, 36) positioned opposite to each other and to which in each case is provided a spring element (52, 54), in which the actuating pin (20) in its actuation position dives between the two spring elements (42, 44) to act the heating elements with a spring bias in the direction of the wall or for contact. A heating device according to claim 1, wherein the actuating pin (20) has a projecting operating protrusion (18) and an actuating section (76) on the heating element side, which for actuation comes into contact with one of the heating elements (34, 36). A heating device according to claim 2, wherein the power supplies (14, 16) project into a plug space (12) in a plug part (4), in which the operating protrusion (18) of the actuating pin (20) also protrudes. A heater according to any one of the preceding claims, wherein a spring element (52, 54) is assigned to at least one of the power supplies (14, 16), which spring element in the operating position of the actuating pin (20) pushes one of the heating elements towards the wall or for the purpose of on electrical contact. A heater according to claim 4, wherein the spring element (52, 54) is attached to the power supply (14, 16). A heater according to claim 5, wherein the spring element (52, 54) is held by means of crimping splashes (56, 58). The heater of claim 4 or 5, wherein the power supplies (14, 16) are designed to be resilient. The heater of claim 7, wherein each power supply (14, 16) has an approx. U-shaped configuration, in which case a spring (46, 100) is provided for providing the spring action on a base part (44, 98). The heater of claim 7, wherein both power supplies (14, 16) are of resilient design. A heating device according to one of claims 1 to 9, wherein four heating elements (34a, 34b; 36a, 36b) are provided which are arranged in pairs opposite each other and between which the spring elements (52, 54) are arranged, in common is assigned an activation pin (20). Heating device according to one of the preceding claims, wherein the actuating pin (20) is formed as a punching part with two folded end sections (86, 88) forming the actuating section (76). A heating device according to any one of the preceding claims, wherein the actuating pin (20) is position-fixed force or form-closing in the actuating position. Heating device according to one of the preceding claims, wherein the heating elements are PTC resistance elements (34, 36). Heating device according to one of the preceding claims, wherein the heating section (2) in the area where it abuts against the wall has an insulating foil (6).