Patent Application
20130307661
The invention relates to a protective device with a thermal protection element that is tripped when there is a rise in temperature above a threshold temperature value. The preferred intended use of the protective device is the control electronics of a motor vehicle component, in which the thermal protection element is disposed in the region between the control electronics and a connecting lead frame. A motor vehicle component, in the context of this description, is understood to mean, in a particular example, a radiator fan drive with an electronically controlled DC motor for cooling the cooling water of a motor vehicle.
German published patent application DE 10 2007 011 548 A1 describes an adjustment system of a motor vehicle, such as for example a window lifter, a seat adjustment mechanism or a door or sliding roof drive, which is operated by an electric motor and has drive electronics for controlling the electric motor. In addition to software-based thermal protection, a thermal fuse element in the form of a spring element as overload protection is held in a segment of a strip conductor between two solder points that leads to the electric motor. If there is an overload current flowing for a certain time, the solder at one of the solder points is melted, so that, as a result of the biasing of the spring element, the strip conductor is spontaneously interrupted. This thermal fuse may be configured as a biased spring element similar to a spiral spring, as a leaf spring or as a cross-sectional constriction in the manner of an expanding-wire fuse.
German patent DE 10 2007 025 345 B4 describes using in a DC fan motor of a motor vehicle a thermal protection element in the form of a TCO element (thermal cut-off element), a fusible link or a bimetal switch in connection with a plastic-encapsulated lead frame, which is disposed between a DC voltage supply connection and control electronics and is thermally coupled to the latter. If the temperature of the control electronics exceeds a predetermined threshold value, the thermal protection element trips and interrupts the electrical connection between the DC voltage supply connection and the control electronics.
A TCO element (thermal cut-off element) is understood here as meaning a spring-biased pair of contacts connected by way of solder, the contacts of which open and interrupt the circuit when the solder melts as a result of the spring restoring force. A fusible link is usually realized by a fusible element connecting two electrical contacts. The fusible element heats up as a result of the current flowing through it and melts if the rated current is significantly exceeded.
The prior art thermal protection elements are configured, on the one hand, for electronically controlled electric motors and, on the other hand, for a rather low current carrying capacity and a relatively small operating temperature range of up to about 80° C.
It is accordingly an object of the invention to provide a protective device which overcome the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which provides for a particularly reliable protective device that is configured, in particular, for control electronics of a motor vehicle component and is particularly suitable for performing a protective function in that context.
With the foregoing and other objects in view there is provided, in accordance with the invention, a protective device, comprising:
a thermal protection element configured to trip upon a temperature rise above a threshold temperature value;
said thermal protection element having two conductor segments with conductor ends, facing one another at an interruption point, and each of said conductor segments having a connecting end;
a fluxing agent disposed to bridge said interruption point and having a melting temperature adapted to the threshold temperature value.
The protective device is particularly configured for the thermal protection of a control electronics of a motor vehicle component, in particular for a drive of a radiator fan.
With the above and other objects in view there is also provided, in accordance with the invention, a thermal protection element, comprising:
a first conductor segment formed with a conductor end, facing an interruption point, and a connecting end;
a second conductor segment formed with a conductor end, facing the interruption point, and a connecting end; and
a fluxing agent, bridging the interruption point and connecting said conductor end of said first conductor segment and said conductor end of said second conductor segment.
In other words, the thermal protection element has two conductor segments, bridged in the region of an interruption point by a fluxing agent. The conductor segments have conductor ends facing one another to form the interruption point and in each case have a connecting end, these connecting ends forming the two contact ends of the thermal protection element.
The fluxing agent enclosing the two conductor ends of the conductor segments reaches around at least one of the conductor ends in the longitudinal direction of the conductor over a conductor segment that is set in a specific relation to the width of the interruption point and is shorter than the width of the interruption point. Particularly suitable is an overlapping region or enclosing portion of the respective conductor segment that is 10% of the overall length of the thermal protection element extending over the two conductor segments, including the interruption point. Proven to be particularly expedient is an overall length of the thermal protection element of 30 mm with a width of the interruption point of 5 mm, and so the respective enclosing portion preferably on both sides of the interruption point at the conductor ends is 3 mm. With approximately circular cross sections of the conductor segments and of the fusing point, these dimensions are suitably combined with a diameter of the fluxing agent that is 2 to 2.5 times, preferably 2.2 times, the diameter of the conductor segment.
In accordance with a particularly preferred feature of the invention, one of the connecting or contact ends of the thermal protection element is connected to a contact of a connecting lead frame of a wiring or cabling harness, for example leading from the on-board battery of the motor vehicle to the electronics and there to a circuit board (PCB) assigned thereto, while the other connecting end is then connected to a contact of the control electronics or of the circuit board. In the case of this embodiment or this intended use, the connecting lead frame is expediently encapsulated in a suitable material to produce an insulating wiring or cabling connection housing.
The melting temperature of the fluxing agent is adapted to a threshold temperature value, which is dependent on the choice of material and the dimensions, and possibly also the geometry, of the fluxing agent. The melting temperature is preferably between 170° C. and 260° C. The threshold temperature value is for its part determined by an inadmissibly high rise in temperature in the respective electronics. If the temperature of the or in the electronics rises to values above the threshold temperature value, and consequently above the melting temperature of the fluxing agent, the latter melts and interrupts the current/voltage supply to the electronics.
The fluxing agent is suitably a solder of a metal alloy adapted to the threshold temperature value, in particular with constituents of lead, tin, silver and/or copper. The structural or cross-sectional form of the thermal protection element may be round or polygonal. If the fluxing agent bridge of the thermal protection element is incorporated in a housing, the molten material—that is to say the melted fluxing agent or solder—can be absorbed by a filling material. As an additional function, this may also serve for quenching a possible arc.
In principle, crimp-like pinched connections of the connecting ends of the thermal protection element to the contacts of the conductor and the electronics are indeed conceivable. However, the contact of the connecting lead frame is preferably an insulation displacement contact for clamping-contacting of the assigned connecting end of the thermal protection element. The contact of the control electronics is also an insulation displacement contact mounted on the circuit board, for example by the SMD technique, for the clamping-contacting of the assigned connecting end of the thermal protection element.
In order to realize a current carrying capacity that is as high as possible, as also required for example in the preferred application for a radiator fan drive, the insulation displacement contacts are formed as pairs of contacts. For this purpose, two insulation displacement contacts are respectively disposed at a distance from one another and are connected in an electrically conducting manner to one another, the insulation displacement slits of which being in line with one another.
The advantages achieved with the invention are, in particular, that virtually any desired external geometry (round, angular, straight or curved) can be realized by means of the thermal protection element, preferably bridged with solder, with at the same time a simple construction. Furthermore, the thermal protection element according to the invention does not contain any movable parts, so that in particular there is also no mechanical stress, for example as a result of a biasing force. The interruption of the current flow consequently specifically does not take place by movable mechanical components, and the galvanic growing together of the opened fluxing agent bridge leads to renewed melting of the fluxing agent. Consequently, there is sustained safety even after the initial tripping.
Furthermore, the tripping temperature of the thermal protection element can be predetermined by the choice of fluxing agent. Furthermore, the force effect on the circuit board (PCB) of the electronics is reduced during assembly of the wiring or cabling harness. In the case of variants of the embodiment without thermal protection, the pressing in of an enameled copper wire instead of the thermal protection element into the insulation displacement contacts is also possible.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in protective device, in particular for the control electronics of a motor vehicle component, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
Reference will now be had to the figures of the drawing in which components that correspond to one another are provided with the same reference signs throughout the figures.
A further pair of insulation displacement contacts 5 with likewise two insulation displacement contacts 5a and 5b spaced apart from one another are mounted on the circuit board 2, for example by the SMD technique (surface mounted device), and if need be electrically contacted there with a strip conductor.
As can be seen from the pair of insulation displacement contacts 5 in
As can be seen from
The thermal protection element 1 consists of a first conductor segment 9 and a second conductor segment 10, which are spaced apart from one another to form an interruption point 11. The interruption point 11 is bridged by a fluxing agent 12 in the form of a solder, for example a lead solder. For this purpose, the conductor ends 9a and 10a of the conductor segments 9 and 10, respectively, are spaced apart opposite one another and are connected to one another in an electrically conducting manner by way of the solder 12.
The connecting ends 9b and 10b lying opposite the conductor ends 9a, 10a of the conductor segments 9, 10 are fixed in the insulation displacement contacts 5 and 4, respectively, and are consequently connected in an electrically conducting manner on the one hand to the connecting lead frame 3 and on the other hand to a strip conductor of the circuit board 2 contacted with the pair of insulation displacement contacts 5. As can be seen comparatively clearly from
The thermal protection element 1 is consequently exposed to a development of heat occurring in the electronics, and consequently in the region of the circuit board 2. Since the circuit board 2, and consequently the electronics, is/are usually in a drive housing, for example of a radiator fan drive, the development of heat of the electronics under some circumstances leads to a rise in temperature, for example as a result of ingressing moisture and resultant undesired current flows. If the temperature rises above a certain threshold temperature value, the solder 12 melts, whereby the electrically conducting connection between the conductor segments 9 and 10 is interrupted in the region of the interruption point 11. The melting temperature of the solder 12 is in this case set to the threshold temperature value. This takes place substantially by the geometry and the dimensions, i.e. the size, of the solder 12 and the material thereof, which for its part is composed on the basis of an appropriately chosen metal alloy of components such as lead, tin, silver and/or copper. The melting temperature is typically 170° to 260° C., for example approximately 180° C.
The thermal protection element 1 also has a housing 14, which in the exemplary embodiment is cylindrical. The housing 14 encloses the interruption point 11 with the solder 12 and at least partially the conductor segments 9 and 10 in the region of their conductor ends 9a and 10a, respectively. Inside the housing 14 there is a filling material 15, which in the case of the solder 12 melting absorbs it. The filling material 15 may also be intended and designed for quenching an arc. The housing 14 also ensures that the melting solder remains encapsulated within the thermal protection element 1.
The conductor segments 9, 10 are formed for example from copper wires, the wire cross sections of which are adapted to the required current carrying capacity of the thermal protection element 1. The cross-sectional area of the conductor segments 9, 10 is of almost any form desired, and may be round or polygonal. The conductor segments 9, 10 may also be straight—as shown in the exemplary embodiment—or else curved.
a and 6b show the thermal protection element 1 in cross section and in longitudinal section, respectively. As can be seen, the fluxing agent 12 encloses the conductor end 9a and the conductor end 10a in the longitudinal direction L of the conductor over a conductor segment a, which is shorter than the width b of the interruption point 11. The conductor segment a is ten percent (10%) of the total length c extending over the two conductor segments 9, 10, including the interruption point 11, where preferably c=30 mm, b=5 mm and consequently a=3 mm. The diameter dS of the fluxing agent 12, preferably consisting of tin (Sn) or containing tin, is preferably 4 mm with a diameter dL of the, or each, conductor segment 9, 10, preferably consisting of copper (Cu), of 1.8 mm.
The stator 17 consists of a stack of sheets, which is encapsulated in a plastic casing 23. The motor support 18 is formed in particular by a one-piece die casting of aluminum. The electronics compartment cover 22 is preferably an injection molding of plastic. The fastening of the motor 16, and consequently of the entire fan, to the vehicle takes place by way of the motor support 18, which for this purpose is provided with three screw lugs 24, protruding from its outer periphery. The motor 16 is a brushless self-cooled internal-rotor motor.
In particular from
Although the thermal protection element 1 preferably serves as a protective device for the control electronics of a motor vehicle component, the invention is not restricted to the exemplary embodiments described above. Rather, other variants of the invention may also be derived from it by a person skilled in the art without departing from the subject matter of the invention. For example, the thermal protection element 1 is suitable for fitting between in turn a lead frame and a brush card or between an inductor and a brush list of the electric motor or for fitting into a PCB or circuit board by means of selective soldering. In particular, furthermore, all of the individual features described in connection with the various exemplary embodiments can also be combined with one another in some other way without departing from the subject matter of the invention.
The following is a list of reference numerals and symbols used in the above description of the drawing figures:
| Number | Date | Country | Kind |
|---|---|---|---|
| 202011011820.2 | Jan 2011 | DE | national |
This application is a continuation, under 35 U.S.C. §120, of copending international patent application No. PCT/EP2012/000258, filed Jan. 20, 2012, which designated the United States; this application also claims the priority, under 35 U.S.C. §119, of German application No. 20 2011 011 820.2, filed Jan. 21, 2011; the prior applications are herewith incorporated by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2012/000258 | Jan 2012 | US |
| Child | 13947343 | US |
