Core temperature sensor

Abstract

Core temperature sensor (11) comprising a tubular sensor tube (12), at least one temperature sensor (13 - 15) and at least one electrical conductor (17 - 20), wherein the at least one temperature sensor (13 - 15) and the at least one conductor (17 - 20) are mounted on an elastically bendable circuit board (16) which has an end-side first contact surface (21) via which a conductor (17) is connected to at least one external conductor or terminal contact, characterized in that - a width (b) of the circuit board (16) is at least as large as half the inner circumference of the sensor tube (12), - the circuit board (16) is nestled against an inner wall of the sensor tube (12) and - the end-side first contact surface (21) has a double-sided electrically conductive coating, through which direct contact of the first contact surface (21) with an inner wall of the sensor tube (12) is formed.

Description

[0001] The invention relates to a core temperature sensor with a tubular sensor tube, at least one temperature sensor and at least one electrical conductor.

[0002] Core temperature probes are used to determine the core temperature of food during cooking in an oven and to control and, if necessary, regulate the cooking process based on the core temperature. Multi-point core temperature probes are available, which have several temperature sensors, currently up to six. These are designed to compensate for incorrect insertion, where the temperature measurement point is not in the center or core of the food. For example, a core temperature probe inserted too far can be detected if the foremost temperature sensor measures a higher temperature (e.g., the temperature of a heated oven) than a temperature sensor located further back (towards a handle).

[0003] Typical core temperature sensors consist of a sensor tube, usually made of metal, and a handle. The temperature sensors used inside the metal tube are thermocouples or temperature-dependent resistors, particularly thermistors or NTC resistors (NTC: "Negative Temperature Coefficient"). Core temperature sensors also exist that use a plastic tube instead of a metal one.

[0004] When assembling such core temperature sensors, the temperature-dependent resistors are crimped onto electrical leads, with the individual leads being insulated from each other and from the metal tube by insulating sleeves. This type of assembly requires entirely manual labor in manufacturing, involving crimping the resistors and leads, and fitting the insulating sleeves. This type of assembly and manual manufacturing is costly and prone to errors.

[0005] DE 10 2010 063 712 A1 discloses an arrangement for data acquisition in a cooking appliance with a measuring probe comprising at least one sensor, with an evaluation unit connected to the at least one sensor via a two-wire cable, wherein the evaluation unit is configured such that at least one measured value or state of the at least one sensor can be queried. Furthermore, a corresponding method and a cooking appliance with such an arrangement are proposed.

[0006] DE 199 13 195 A1 discloses a measuring insert for resistance thermometers comprising a flexible printed circuit board made of plastic film or the like, at one end of which a temperature-sensitive measuring resistor is provided, which is connected via conductive traces to solder contacts or the like provided at the other end of the printed circuit board for connecting a connecting lead, and a protective tube surrounding the flexible printed circuit board. Reliable heat transfer to the measuring resistor of the printed circuit board is ensured by the fact that the measuring area of ​​the printed circuit board carrying the measuring resistor has a width that is greater than the diameter of the protective tube, so that the fully flexible printed circuit board rests against the inside of the protective tube.

[0007] DE 197 42 236 C2 discloses an electrical sensor, in particular a temperature sensor, with an elongated printed circuit board having at least one conductor track on a substrate made of temperature-resistant materials with an electrically insulating surface, wherein at least two connection contact fields connected to the conductor track(s) are arranged on the surface for electrical connection by means of a melting process with the ends of connecting conductors of a connecting cable, wherein at least one first connection contact field is placed on the front and at least one second connection contact field is placed on the back of the printed circuit board, characterized in that the printed circuit board consists of epoxy, triazines, polyimides or polytetrafluoroethylene and a conductor track has a thickness in the range of 5 µm to 100 µm.which is designed in a meandering shape in plan view and in which the conductor track is designed as a plane at least in the area of ​​the connection contact fields.

[0008] DE 198 03 506 A1 discloses a method for manufacturing an electrical sensor usable as a temperature sensor for ovens or the like, and a sensor comprising at least one electrical sensor arrangement manufactured using thick-film technology, which is applied to an electrically insulating substrate and surrounded by a protective sheath, for example, in the shape of a tube. According to the invention, the substrate supporting the sensor arrangement forms at least part of the sheath, whereby the sensor arrangement is directly attached to the inside of the sheath. The sheath can be manufactured, for example, by bending a stainless steel foil, which is coated with the sensor arrangement via an insulating layer.

[0009] The object of the present invention is to overcome, at least partially, the disadvantages of the prior art and, in particular, to design a core temperature sensor in such a way as to enable simplified installation of the core temperature sensor. In particular, this should be achievable with simple means, reduce manufacturing costs, improve process reliability in production, and / or provide improved, e.g., more accurate, temperature sensing.

[0010] This problem is solved according to the features of the independent claim. Preferred embodiments can be found in particular in the dependent claims.

[0011] To solve the problem, a core temperature sensor is proposed, comprising a tubular sensor tube, at least one temperature sensor, and at least one electrical conductor. The at least one temperature sensor and the at least one conductor are mounted on a flexible circuit board. In other words, a single circuit board is provided for both the at least one temperature sensor and the at least one electrical conductor, the at least one electrical conductor being present, in particular, as conductive traces on the substrate of the circuit board, e.g., printed there. The circuit board has a first contact surface at one end, via which a conductor is connected to at least one external conductor or terminal. The width of the flexible circuit board is at least half the inner circumference of the (tubular) sensor tube.This allows the elastically flexible circuit board to conform to the inner wall of the sensor tube. The first contact surface at the end has a double-sided electrically conductive coating, which establishes direct contact between the first contact surface and the inner wall of the sensor tube.

[0012] Such a core temperature sensor, or rather its components, offer numerous advantages. For example, cost-effective assembly and manufacturing are made possible by machine production of the circuit board with conductive traces and automated component placement. This ensures high quality by eliminating error-prone manual manufacturing steps. Such a circuit board is particularly suitable for arranging a large number of sensors. The position of the sensor elements within the sensor tube or probe can be precisely predetermined by their placement on the circuit board.

[0013] The flexible circuit board can be easily inserted into the sensor tube. The board, especially when combined with components such as the at least one temperature sensor, is flexible enough to bend easily. Due to its elasticity and dimensions, the board securely clamps itself against the inside of the sensor tube.

[0014] The term "close contact" refers specifically to the circuit board lying flat against an inner surface of the tubular sensor tube in its bent state. This can be achieved particularly easily by allowing the elastically bendable circuit board to relax and unroll within the sensor tube after being rolled up and inserted. Close contact has the advantage of creating direct contact between the circuit board and the sensor tube, which reduces thermal resistance between the at least one temperature sensor on the circuit board and the sensor tube. This, in turn, increases the accuracy and response time of the at least one temperature sensor in a very simple way.This applies in particular if the at least one temperature sensor is located on a side of the circuit board facing the sensor tube, since in this case direct contact between the at least one temperature sensor and the sensor tube is possible.

[0015] A circuit board can be understood in particular as a flat carrier on which at least one placement location for a temperature sensor and at least one conductor track for electrical contacting the placement location or the temperature sensor arranged thereon are arranged.

[0016] The probe tube is specifically designed in the form of a tube, with one end closed and tapering to a point so that it can be inserted into the food being cooked. The opposite (handle-side) end is connected to a handle.

[0017] The handle may contain electronic components, particularly evaluation electronics. Such electronics might, for example, be used to determine, process, and / or provide measurement signals and / or measured values ​​from at least one temperature sensor. These signals or measured values ​​can be transmitted wirelessly or via a wired connection to, for example, a cooking appliance (such as an oven) to control an automatic program.

[0018] Alternatively, the circuit board may be directly connected to the cooking appliance wirelessly or via a wired connection, i.e., electronics, especially evaluation electronics, may be located in the cooking appliance, e.g., integrated into a control unit.

[0019] It is a further development that the circuit board has a carrier film as its base material. This offers the advantage that the circuit board is particularly inexpensive and highly flexible. The thickness of the carrier film might, for example, be between 50 and 200 micrometers.

[0020] It is a further development that the circuit board is made of polyimide, or at least contains polyimide. Polyimide offers the advantages of high elastic flexibility, high temperature resistance, good processability during machining and assembly, and low cost. The use of the elastically flexible circuit board allows, in particular, the (assembled) board to be rolled up and subsequently inserted or inserted into the interior of the tubular sensor tube. Advantageously, a lubricant can be omitted during insertion, as the circuit board can be rolled or bent sufficiently so that its rolled outer diameter is adequately smaller than the inner diameter of the sensor tube. Accordingly, a further development consists of the finished circuit board (together with conductor track(s) and temperature sensor(s)) being inserted or pushed into the sensor tube.

[0021] The fact that the elastically bendable circuit board, due to its elasticity and dimensions, securely clamps itself against the inside of the sensor tube is particularly the case when the width of the circuit board is greater than or equal to the (entire) inner circumference of the sensor tube.

[0022] The width can be understood, in particular, as a width perpendicular to the longitudinal extent of the tubular sensor tube. This allows the circuit board to be inserted into the tubular sensor tube after appropriate bending. Upon release, the circuit board's elasticity causes its lateral edges to press against the inner wall of the tubular sensor tube, thus securing itself in place. This enables simple assembly with the following steps: placing the circuit board on the sensor tube, rolling it up perpendicular to its longitudinal direction, and, in particular, fully inserting it into the tubular interior of the sensor tube. Finally, the circuit board is released, allowing it to partially unroll.

[0023] Furthermore, one embodiment includes a circuit board with at least one end-face contact surface via which the at least one conductor is connected to at least one external conductor or terminal. Such a contact or terminal surface on the circuit board enables electrical contacting and simultaneously the fastening of an external conductor or terminal. The external conductor can, for example, lead to electronics located in the handle. Alternatively, the external conductor can be, for example, a cable connected or coupled to a cooking appliance, particularly an oven, for signal transmission.

[0024] A connection contact, for example, might serve as a component of electronics located in the handle. Such electronics can be designed, in particular, as an evaluation and / or control unit to determine measured values ​​from at least one temperature sensor and make them available for further transmission to a higher-level unit such as a cooking appliance.

[0025] A further improvement is that the contact surfaces are located at the end of the circuit board in an area adjacent to an open sensor tube or pipe end in the final assembly state (handle-side end area). This allows access from the outside even when the circuit board is already fully or partially inserted into the pipe or sensor tube, in order to connect the contact surfaces with a cable or electronics.

[0026] One embodiment of this is where at least one external conductor or connection contact is crimped to at least one contact surface. This enables, in particular, automated or machine-assisted contacting (crimping) of the conductor ends leading away from the temperature sensors to the external conductors or connection contacts. Error-prone manual connection steps are eliminated. Further advantages of a crimp connection include its compact size and both electrically reliable contact and mechanically robust connection. In particular, a crimp connection is temperature-resistant and thus allows for use even at higher temperatures, such as 250°C in an oven. However, other connection methods, such as plug connectors or soldered connections, are not excluded.

[0027] Another embodiment involves coating the circuit board with a conductive layer on both sides in the area of ​​at least one contact surface. This facilitates automatic crimping and ensures a particularly reliable electrical contact. It also enables direct contacting of one of the contact surfaces with an electrically conductive sensor tube, thus providing a ground connection. Furthermore, it allows crimping into the sensor tube with simultaneous contacting of the sensor tube, contact surface, and / or shield of an external electrical conductor, such as a core temperature sensor cable.

[0028] Another embodiment involves the circuit board having an opening in the area of ​​at least one such contact surface, in particular by being punched out. Punched-out contact surfaces allow the crimping of further conductors even at positions on the circuit board that are spaced away from the end face. This also enables, in particular, a spatial separation of the contact surfaces in the longitudinal direction, which prevents a short circuit of the electrical conductor levels.

[0029] According to further training, the openings are U-shaped and surround the contact surface. This allows the contact surface to be lifted like a tab and gripped by a connector or a crimp mating element.

[0030] Another design feature is that the circuit board or its base is made of a temperature-resistant material, in particular a material resistant to temperatures up to 250°C. This allows it to withstand typical oven temperatures without damage. Polyimide is one such material.

[0031] Another embodiment involves arranging multiple temperature sensors at intervals along the longitudinal axis of the sensor tube on the carrier. This allows for the evaluation of heat profiles across the food being cooked and, in particular, ensures that a minimum cooking temperature is reached throughout the food, even if the sensor tube is inserted too deeply into or even through the food. According to a further development, the temperature sensors are arranged at equal intervals on the circuit board.

[0032] An alternative or additional configuration involves distributing multiple temperature sensors around the circumference of the sensor tube on the carrier. In other words, the temperature sensors are offset along the circumference of the sensor tube. For example, if a core temperature probe is inserted near an outer edge of the food being cooked, a temperature gradient from the outside of the food to the interior can be detected.

[0033] One further development involves the sensor tube being made of stainless steel or plastic. However, other suitable materials available for use with food during cooking can also be used, e.g., ceramic.

[0034] The invention is described in more detail schematically in the following figures using an exemplary embodiment. For clarity, identical or equivalent elements may be provided with the same reference numerals. Fig. Figure 1 shows a core temperature probe with only a schematically sketched handle; and Fig. Figure 2 shows a circuit board of such a core temperature sensor with electronic components mounted on it.

[0035] Fig. Figure 1 shows a core temperature probe 11 with some components only schematically indicated. The core temperature probe 11 has a tubular sensor tube 12. The sensor tube 12 is essentially a hollow tube and has a closed, tapered section at its front end 35 for piercing the food being measured. At the opposite end, the sensor tube 12 is open, so that access to the interior 33 of the sensor tube 12 is possible through a tube opening 32.

[0036] A circuit board 16 is inserted into the interior 33. The circuit board 16 rests against an inner wall of the sensor tube 12. Towards the open end, the circuit board 16 has a first contact surface 21, which serves to connect a first external conductor (e.g., cable) or contact terminal (not shown). A double-sided, particularly on the outer, electrically conductive coating of the contact surface 21 allows for direct contact between the contact surface 21 and the inner wall of the sensor tube 12. In the case of an electrically conductive inner wall of the sensor tube 12, a ground contact is thus established, for example.

[0037] The sensor tube 12 is closed in the illustration by a handle 34, shown only as a suggestion, which is placed on the tube opening 32 and closes it. The handle 34 can, in particular, include electronics designed to acquire measurement data from internal sensors, to evaluate this data and / or to transmit it to an external control unit, for example, a cooking appliance.

[0038] Fig. Figure 2 shows such a circuit board 16 in a flat, unrolled state. The circuit board 16 consists of a high-temperature resistant, elastic base material, e.g., polyimide, which on the one hand allows processing (printing, assembly with electronic components, etc.) in its flat state and on the other hand is sufficiently flexible or bendable to be bent or rolled up sufficiently for insertion into the tube opening 32 of the sensor tube 12.

[0039] On circuit board 16, a first temperature sensor 13, a second temperature sensor 14, and a third temperature sensor 15 are arranged as examples. These are arranged, in particular, at component placement locations and are electrically connected to two associated contact surfaces 24, 27; 25, 28 and 26, 29, respectively.

[0040] In the exemplary embodiment shown, the three temperature sensors 13, 14, 15 are arranged at equal intervals from each other in a longitudinal direction L. The longitudinal direction L corresponds to a longitudinal direction L of the sensor tube 12. In addition, the third temperature sensor 15 is arranged laterally offset relative to the first and second temperature sensors 13, 14 in the circumferential direction of the sensor tube 12 and in the transverse direction on the circuit board 16.

[0041] The first temperature sensor 13, or rather its contact surface at mounting location 24, is connected to the first contact surface 21 via a first electrical conductor 17. The second temperature sensor 14, or rather its contact surface at mounting location 25, is electrically connected to the second contact surface 22 via a second electrical conductor 18. Similarly, the third temperature sensor 15, or rather its contact surface at mounting location 26, is connected to the contact surface 23 via a third electrical conductor 19. The three contact surfaces 21, 22, 23 serve to connect an external conductor or contact of the electronics located in the handle or a cable leading out of the core temperature sensor 11.

[0042] Furthermore, the three temperature sensors 13, 14, 15 are connected to each other via their respective additional contact surfaces at their mounting locations 27, 28, 29 by a fourth electrical conductor 20.

[0043] While the first contact surface 21 for connecting an external conductor covers the entire end face of the circuit board 16 and is preferably formed on both sides of the circuit board 16, the two further contact surfaces 22, 23 for connecting external conductors are arranged longitudinally along the circuit board 16, spaced apart from the first contact surface 21 and from each other. To facilitate contact, particularly by crimping, a portion of the contact surfaces 22, 23 is surrounded by a U-shaped opening 30 or 31. The two contact surfaces 22, 23 are also preferably coated with an electrically conductive material on both sides. However, if the circuit board 16, in its assembled state, rests directly against a conductive inner tube of the sensor tube 12, it is also possible for these or all of the contact surfaces 21-29 to be coated with a non-conductive material on the side facing the tube in order to prevent short circuits.

[0044] As from Fig.As can be seen in Figure 2, the width b of the circuit board 16, in its transverse direction to the longitudinal direction, is greater than half the inner circumference U, i.e., U > 0.5·π·d, where d represents the inner diameter of the sensor tube 12 shown. Therefore, the circuit board 16 can only be inserted into the interior 33 of the sensor tube 12 in a bent or at least partially curled state. After releasing the curling force, the circuit board 16 uncurls again and thus conforms to the inner wall of the sensor tube 12.

[0045] Of course, the present invention is not limited to the embodiment shown.

[0046] In addition to using an electrically conductive tube for the sensor tube, a plastic tube can also be used.

[0047] In particular, in addition to temperature sensors, other sensor types for recording other physical parameters can also be arranged on the circuit board.

[0048] The temperature sensors can be mounted on the circuit board using standard semiconductor manufacturing methods. In particular, conductor tracks and component placement can be printed on the board; however, other manufacturing processes are also possible, allowing the circuit board to be produced with the conductors or traces and the temperature sensors attached. In addition to the three temperature sensors shown, more or fewer temperature sensors can also be arranged on the circuit board.

[0049] In addition to direct contacting of the contact surfaces with the outer tube or sensor tube and crimp connections, other connection types for electrical contacting of the contact surfaces intended for connection to external components and / or electronic components located in the handle are also possible. Reference symbol list 11 core temperature probes 12 tubular sensor tubes 13 first temperature sensor 14 second temperature sensor 15 third temperature sensor 16 circuit boards 17 first electrical conductor 18 second electrical conductor 19 third electrical conductor 20 fourth electrical conductor 21-23 Contact area for external conductor 24-29 Contact area at placement station 30 Opening 31 Opening 32 Pipe opening 33 Interior 34 handle 35 front end of the sensor tube b Width of the circuit board d Inner diameter of the sensor tube L Longitudinal direction

Claims

[1] Core temperature sensor (11) comprising a tubular sensor tube (12), at least one temperature sensor (13 - 15) and at least one electrical conductor (17 - 20), wherein the at least one temperature sensor (13 - 15) and the at least one conductor (17 - 20) are mounted on an elastically bendable circuit board (16) which has an end-side first contact surface (21) via which a conductor (17) is connected to at least one external conductor or terminal contact, characterized by , that - a width (b) of the circuit board (16) is at least as large as half the inner circumference of the sensor tube (12), - the circuit board (16) is nestled against an inner wall of the sensor tube (12) and - the end-side first contact surface (21) has a double-sided electrically conductive coating, through which direct contact of the first contact surface (21) with an inner wall of the sensor tube (12) is formed. [2] Core temperature sensor (11) according to claim 1, characterized by , that the width (b) of the circuit board (16) is greater than or equal to the inner circumference of the sensor tube (12). [3] Core temperature sensor (11) according to any one of the preceding claims, characterized by , that the first contact surface (21) is crimped into the sensor tube (12). [4] Core temperature sensor (11) according to claim 3, characterized by , that the first contact surface (21) is crimped into the sensor tube (12) together with a shielding conductor of an external electrical conductor. [5] Core temperature sensor (11) according to any one of the preceding claims, characterized by , that the circuit board (16) has at least one further contact surface (22, 23) which is surrounded by a U-shaped, in particular punched, opening (30, 31). [6] Core temperature sensor (11) according to claim 5, characterized by , that the external conductor or connection contact is crimped to at least one further contact surface (22, 23). [7] Core temperature sensor (11) according to any one of the preceding claims, characterized by , that the circuit board (16) is made of a temperature-resistant material, in particular a material that is temperature-resistant up to 250°C. [8] Core temperature sensor (11) according to any one of the preceding claims, characterized by , that several temperature sensors (13 - 15) are arranged at intervals from each other on the circuit board (16) along a longitudinal extension of the sensor tube (12). [9] Core temperature sensor (11) according to any one of the preceding claims, characterized by , that several temperature sensors (13 - 15) are arranged distributed on the circuit board (16) in the circumferential direction of the sensor tube (12).

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