Method for manufacturing a heating element for a vehicle catalytic converter of a motor vehicle, and manufacturing apparatus

Abstract

A method for manufacturing an electric heating element (2) for a vehicle catalytic converter of a motor vehicle, wherein a starting material (3) of the heating element (2) is processed with a processing parameter to manufacture the heating element (2), characterized in that during the manufacturing of the heating element (2) from the starting material (3) an electrical resistance of the heating element (2) is measured and a value of the processing parameter is adjusted for a further course of manufacturing as a function of the electrical resistance, wherein a heating wire is used as the starting material and a stretching of a heating conductor (4) of the heating element (2) formed from the heating wire is used as the processing parameter.where the heating conductor has a first cross-sectional area for a first value of the processing parameter and a second cross-sectional area that differs from the first for a second value of the processing parameter.

Description

[0001] The invention relates to a method for manufacturing an electric heating element for a vehicle catalytic converter, wherein a starting material for the heating element is processed with a processing parameter. The invention further relates to a manufacturing device for manufacturing the heating element.

[0002] For example, German patent application DE 10 2018 104 602 A1 is known from the prior art. This document describes a heating system for a drive train or a component thereof, as well as a method for its manufacture. To create a device of the aforementioned type that can be integrated cost-effectively into an existing system, it is proposed that at least one heating element for electrically heating a drive train or a component thereof be combined with an existing component for thermal and / or acoustic shielding, wherein the heating element is arranged electrically and thermally insulated between two layers forming the insulating layer of the shielding. Furthermore, patent application WO 2010 131094 A2 discloses a method for manufacturing surface structures with integrated temperature control and / or heat flow measurement.

[0003] The publication EP 0 768 107 A1 relates to a honeycomb heating element with a honeycomb structure made of an electrically conductive material, featuring slots for resistance adjustment and electrodes (3) attached thereto for electrifying the same. The slots are designed in the honeycomb structure such that parallel circuits are formed within the honeycomb structure when it is electrified.

[0004] Furthermore, the following documents are known from the prior art: DE 691 08 998 T2, DE 39 01 157 A1, DD 2 51 228 A1, DE 38 18 735 A1, DD 1 28 556 A1, DE 34 25 718 A1 and DE 22 30 663 A.

[0005] The object of the invention is to propose a method for manufacturing a heating element for a vehicle catalyst of a motor vehicle which has advantages over known methods, in particular ensuring high reproducibility of the heating element despite tolerances of the starting material, wherein in particular a property of the heating element is set to a predetermined value with high accuracy.

[0006] This is achieved according to the invention by a method for manufacturing a heating element for a vehicle catalytic converter of a motor vehicle with the features of claim 1. It is provided that during the manufacturing of the heating element from the starting material, an electrical resistance of the heating element is measured and a value of the processing parameter for a further manufacturing process is adjusted depending on the electrical resistance, wherein a heating wire is used as the starting material and a stretching of a heating conductor of the heating element formed from the heating wire is used as the processing parameter, wherein the heating conductor has a first cross-sectional area at the first value of the processing parameter and a second cross-sectional area different from the first cross-sectional area at a second value of the processing parameter.

[0007] The heating element preferably forms part of the vehicle catalytic converter, but can of course also exist separately. The vehicle catalytic converter serves to perform exhaust aftertreatment of exhaust gas, which is generated, for example, by the vehicle's engine. The engine is preferably an internal combustion engine designed and configured to propel the vehicle. With the aid of the vehicle catalytic converter, pollutants contained in the exhaust gas are converted into less harmful products.

[0008] The conversion rate of the vehicle catalyst depends significantly on its current temperature. Therefore, it is necessary to heat the vehicle catalyst to its operating temperature as quickly as possible. The operating temperature is preferably understood to be the temperature of the vehicle catalyst at which it exhibits the desired conversion rate(s). For example, the operating temperature of the vehicle catalyst is between 400 °C and 900 °C. The vehicle catalyst is preferably in the form of a three-way catalyst, in particular a regulated three-way catalyst, an oxidation catalyst, or a storage catalyst, in particular an NO catalyst. x -storage catalyst, or an SCR catalyst.

[0009] During operation of the engine, the vehicle's catalytic converter is exposed to the exhaust gas produced by the engine. This heats the catalytic converter towards its operating temperature or maintains it at that temperature. However, it is possible that the catalytic converter may not be heated quickly enough by the exhaust gas. In modern vehicles, the engine is also deactivated, at least temporarily, during operation. This can occur, for example, in hybrid vehicles. In such a configuration, the vehicle is driven electrically, at least temporarily, by an electric traction motor.

[0010] Consequently, the engine does not produce any exhaust gas to heat the catalytic converter or maintain it at operating temperature. As a result, the catalytic converter cools down, so that when the engine is restarted, it is at a temperature below its operating temperature. This means that the pollutants contained in the exhaust gas are only partially converted, or not converted at all, and are thus released into the vehicle's environment.

[0011] To prevent this, the vehicle catalytic converter is equipped with a heating element. This heating element allows the catalytic converter to be heated independently of the engine's operation. The heating element is electrically powered, meaning that electrical energy is supplied to it to heat the catalytic converter. The heating element is in the form of a heating resistor or at least incorporates one. For example, the heating element may be arranged so that the exhaust gas first flows through it before entering the filter element of the catalytic converter, thus heating the filter element indirectly via the exhaust gas. However, it is also possible for the heating element to be directly connected to the filter element, allowing the filter element to heat up even without an exhaust gas flow.

[0012] The heating element is manufactured from the raw material, which is processed accordingly. The processing parameter is used during this process. The processing parameter describes, for example, the cross-sectional area of ​​the heating element or a heating conductor within the heating element. It may be intended, for instance, to process the raw material with a constant processing parameter during the manufacturing of the heating element. In this case, the electrical resistance of the heating element may only be measured after the raw material has been processed, i.e., after the heating element has been formed. If the electrical resistance deviates from a predetermined target resistance, the heating element can be adjusted, for example, through post-processing.For example, it is possible to locally modify the heating element to change its resistance towards the target resistance or to adjust the resistance to the target resistance. However, this approach results in locally varying heating power of the element.

[0013] For this reason, it is now planned to adjust the resistance of the heating element during the processing of the raw material. Once the raw material has been processed, the heating element will have a resistance that corresponds to the target resistance, at least within a certain tolerance. In other words, the heating element is manufactured from a certain quantity of the raw material, which is processed accordingly, namely with the processing parameter. During the processing of this quantity of raw material, the processing parameter is continuously, or at least at discrete intervals, adjusted so that after the raw material has been processed, the resistance of the heating element corresponds to the target resistance. Thus, once the quantity of raw material has been completely processed or consumed, the heating element is manufactured.No downstream steps are necessary to adjust the resistance to the target resistance. The resulting heating element therefore exhibits extremely uniform heating performance, and the effort required to manufacture it is comparatively low.

[0014] These advantages are achieved by continuously, or at least at discrete intervals, measuring the resistance of the heating element during its production from the raw material. Depending on the resistance, the value of the processing parameter is adjusted for the subsequent stages of production. For example, the processing of the raw material begins with an initial value of the processing parameter. After a certain period, the resistance of the heating element is measured, and if the measured resistance deviates from the expected resistance, the value of the processing parameter is adjusted so that the processing of the raw material continues with a second value of the processing parameter, which differs from the first.

[0015] The value of the processing parameter can be adjusted as frequently as desired during the processing of the input material.

[0016] This process is particularly preferably carried out continuously or at discrete intervals, preferably periodically. The processing parameter is, for example, a cross-sectional area of ​​the heating element, which is adjusted along the longitudinal extent of the heating element or the heating conductor. Cross-sectional areas with different cross-sectional areas can thus be formed during the processing of the starting material by varying the length of the heating element or the heating conductor.

[0017] The described method for manufacturing the electric heating element has the advantage that the resistance of the element can be set to the specified value with high accuracy and minimal effort. When manufacturing multiple heating elements in this way, high reproducibility and process reliability are ensured, so that the manufactured heating elements are consistent in their electrical resistance, at least within a certain tolerance. In particular, no post-processing of the heating elements is necessary.

[0018] The invention provides that a heating wire is used as the starting material and a stretching of a heating conductor formed from the heating wire of the heating element is used as the processing parameter, wherein the heating conductor has a first cross-sectional area at the first value of the processing parameter and a second cross-sectional area different from the first at the second value of the processing parameter. The heating wire used as the starting material initially has a constant cross-sectional area along its longitudinal extent, i.e., along its longitudinal central axis. During processing of the heating wire, it is stretched so that the cross-sectional area changes, namely decreases.

[0019] The stretching of the heating wire refers to the elongation of the heating wire along its longitudinal axis, which occurs during the processing of the raw material. The stretching, or rather its value, is adjusted during processing depending on the resistance of the raw material. Different values ​​of the processing parameter result in correspondingly different cross-sectional areas of the heating conductor, or the processed heating wire. With the first value of the processing parameter, the heating conductor has the first cross-sectional area, and with the second value, the second cross-sectional area. This approach allows for a particularly simple and cost-effective manufacturing process for the heating element.

[0020] It is not provided for in the invention that a sheet material is used as the starting material and a cross-sectional area of ​​a heating conductor of the heating element formed from the sheet material is used as the processing parameter, wherein the heating conductor has a first cross-sectional area for a first value of the processing parameter and a second cross-sectional area different from the first for a second value of the processing parameter. The sheet material is understood to be a material which, before processing, has a significantly larger cross-sectional area than the finished heating conductor. For example, the cross-sectional area of ​​the sheet material is larger by a factor of at least 5, at least 10, at least 25, or at least 50 than the cross-sectional area of ​​the heating conductor of the heating element.

[0021] For example, the surface material is essentially cuboid in shape, meaning that in a first direction and in a second direction perpendicular to the first direction, it has significantly larger dimensions than in a third direction perpendicular to both the first and second directions. For example, the dimensions in each of the first and second directions are larger by a factor of at least 5, at least 10, at least 25, or at least 50 than the dimensions in the third direction.

[0022] The sheet material is processed to manufacture the heating element in such a way that the heating conductor has the same dimensions in the third direction as the sheet material. To form the heating conductor, the sheet material is therefore subdivided in the first direction and / or the second direction, so that, viewed in cross-section along the longitudinal extent of the formed heating conductor, the cross-sectional area is varied to achieve the resistance of the heating element corresponding to the desired resistance.

[0023] As explained above, the cross-sectional area of ​​the heating conductor corresponds to the first cross-sectional area for the first value of the processing parameter and to the second cross-sectional area for the second value of the processing parameter. Reference is made to the corresponding explanations, which can be consulted for further information. The use of the sheet material allows for a very high degree of flexibility regarding the shape of the heating element.

[0024] It is not provided for in the invention that a multilayered surface material or a metal foam is used as the surface material. The multilayered surface material consists of several material layers, each of which is made of an electrically conductive material. The material layers are electrically connected to one another. For example, the material layers are corrugated. Preferably, in this case, they are arranged such that flow channels are formed between them, each of which is bounded on opposite sides by one of the material layers. The metal foam is particularly preferably an open-cell metal foam, so that the exhaust gas can flow through it. The use of the metal foam has the advantage that the vehicle catalyst is heated particularly effectively.

[0025] A further development of the invention provides that, to form the heating conductor from the sheet material with a specific cross-sectional area, the sheet material is processed by separating and / or removing material. To achieve the specific cross-sectional area, the sheet material is processed. Separating processing here refers in particular to cutting, machining, or ablation. Ablation, on the other hand, includes laser cutting or waterjet cutting. Ablation ultimately also results in separation, for example, cutting out or trimming. The aforementioned manufacturing processes enable the rapid and cost-effective production of the heating element.

[0026] It is not according to the invention that the sheet material is processed by laser cutting or waterjet cutting to form the heating conductor. This has already been mentioned above. The respective cutting method serves to cut the heating conductor out of the sheet material so that, after cutting, the heating conductor has a smaller cross-sectional area than the sheet material. The cutting is carried out in such a way that the dimensions of the heating conductor after its formation correspond to the dimensions of the sheet material in the third direction defined above. No cutting takes place in this third direction. Laser cutting or waterjet cutting enables the production of the heating conductor with particularly high flexibility.

[0027] It is not according to the invention that the surface material is processed in such a way that the heating conductor runs in a meandering shape. Thus, after its formation, the heating conductor does not have a straight longitudinal center axis; rather, its longitudinal center axis is curved, at least in some areas or even throughout. The curvature can vary along the longitudinal extent of the heating conductor, in particular changing its sign, so that the meandering shape of the heating conductor is achieved. For example, the heating conductor consists of a series of semi-oval heating conductor sections. These semi-oval sections can be directly adjacent to one another. However, it can also be provided that a straight section of the heating conductor is arranged between each pair of semi-oval sections. The meandering design of the heating conductor results in a particularly high specific heating power of the heating element.

[0028] A further development of the invention provides that a curve for the electrical resistance is defined over a processing stage, and the value of the processing parameter is selected such that the measured resistance is adjusted towards a target resistance determined from the curve based on the processing stage. As already mentioned, a specific quantity of the starting material is provided before processing, which is then completely processed to manufacture the heating element.

[0029] Processing progress refers, for example, to the proportion of the raw material already processed relative to the total quantity of raw material provided. For instance, the provided quantity of raw material has a specific length, particularly in the case of heating wire. In this case, the processing progress corresponds, for example, to the already processed length of the raw material relative to its total length. In the case of sheet material, the processing progress corresponds, for example, to the length of the heating conductor already formed relative to the total length of the heating conductor to be formed.

[0030] The electrical resistance curve as a function of the processing progress describes the electrical resistance that the heating element or the starting material should exhibit at the current processing stage. This curve is fixed and therefore the same for all electrical heating elements produced. During the heating element's formation, the electrical resistance is read from the curve based on the current processing progress, determining the desired resistance at that moment. This read-out electrical resistance corresponds to the target resistance.

[0031] If the resistance measured at the current processing stage deviates from the target resistance, the processing parameter is adjusted so that, during the subsequent formation of the heating conductor, the measured resistance changes in the direction of the target resistance. The adjustment of the processing parameter is carried out in such a way that there is no sudden jump in the value or the resulting cross-sectional area, but rather a continuous progression. This ensures a particularly uniform heating output of the electrical heating element.

[0032] A further method for manufacturing a vehicle catalyst for a motor vehicle is disclosed, which has an electrical heating element, in particular a heating element manufactured according to the method described in this document, wherein a starting material for the heating element is processed with a processing parameter. It is provided that during the manufacturing of the heating element from the starting material, the electrical resistance of the heating element is measured and a value of the processing parameter is adjusted for further manufacturing depending on the electrical resistance.

[0033] The advantages of such a design for the heating element and the vehicle catalyst, respectively, have already been mentioned. Both the method for manufacturing the heating element and the method for manufacturing the vehicle catalyst can be further developed as described in this document, and reference is made to these details.

[0034] Furthermore, the invention relates to a manufacturing device for producing an electric heating element for a vehicle catalyst of a motor vehicle, in particular for carrying out the method according to the description in this document, wherein the manufacturing device is provided and designed to process a starting material of the heating element for producing the heating element with a processing parameter.The manufacturing device is designed and configured to measure the electrical resistance of the heating element during its production from the starting material and to adjust a value of the processing parameter for further production depending on the electrical resistance, wherein a heating wire is used as the starting material and a stretching of a heating conductor of the heating element formed from the heating wire is used as the processing parameter, wherein the heating conductor has a first cross-sectional area at the first value of the processing parameter and a second cross-sectional area different from the first cross-sectional area at a second value of the processing parameter.

[0035] Reference is again made to the explanations within this description regarding the advantages and possible beneficial further developments of the manufacturing device.

[0036] The invention is explained in more detail below with reference to the exemplary embodiments shown in the drawing, without limiting the invention. The drawing shows: Fig. 1 a schematic representation of a manufacturing device for the production of an electric heating element for a vehicle catalytic converter of a motor vehicle and of the electric heating element itself, and Fig. 2 a diagram showing the course of an electrical resistance of the heating element over a processing stage.

[0037] The Fig. Figure 1 shows a schematic representation of a manufacturing device 1 for producing an electric heating element 2, such as that used, for example, in a vehicle catalytic converter. The heating element 2 is formed from a starting material 3 by cutting a heating conductor 4 from the starting material 3 using a cutting device 5. In the embodiment shown here, the cutting device 5 is a laser cutting device, so that the starting material 3 is processed by laser cutting to form the heating conductor 4.

[0038] The cutting device 5 can be repositioned according to arrows 6 to form the heating conductor 4. The cutting device 5 is controlled by a control unit 7, which also controls its repositioning. The control unit 7 is connected to a measuring device 8, which serves to measure the electrical resistance of the heating element 2. For this purpose, the measuring device 8 is electrically connected to the heating conductor 4, specifically at opposite ends of the heating conductor 4.

[0039] During the manufacturing of the heating element 2, i.e., during the formation of the heating conductor 4, the electrical resistance of the heating element 2 is measured continuously or at discrete intervals. Based on the measured resistance, the value of a processing parameter is adjusted. This parameter is used to process the starting material 3 (present here as a sheet material) to form the heating conductor 4. This adjustment is made so that, after processing the starting material 3, the heating element 2 has an electrical resistance that corresponds exactly to a target resistance or at least within a certain tolerance.

[0040] The Fig.Figure 2 shows a diagram in which a curve 9 of the electrical resistance is recorded over a processing step. In the embodiment shown here, curve 9 corresponds to a range and is bounded below by a lower limit 10 and above by an upper limit 11. A curve 12, on the other hand, shows, purely by way of example, the measured resistance that occurs or is measured during the manufacture of the heating element 2 or the formation of the heating conductor 4.

[0041] At certain processing stages, a target resistance is determined based on curve 9 or limits 10 and 11 and compared with the actually measured resistance. If the measured resistance deviates from the target resistance, the processing parameter used to process the starting material 3 to manufacture the heating element 2 is adjusted so that the resistance changes in the direction of the target resistance. For example, the measured resistance is adjusted to the target resistance by adapting the processing parameter or by appropriately controlling and / or repositioning the cutting device 5.

[0042] The described design of the manufacturing device 1, or the described procedure for manufacturing the heating element 2, has the advantage that the manufactured heating element 2, immediately after its manufacture or immediately after the formation of the heating conductor 4 through processing of the starting material 3, has a resistance that corresponds to the target resistance or at least corresponds within a certain tolerance. This results in high reproducibility and process reliability when manufacturing several identical heating elements 2. In particular, no reworking of the heating element 2 is necessary because, immediately after the formation of the heating conductor 4 from the starting material 3, the heating element 2 exhibits the desired resistance. REFERENCE MARK LIST: 1 Manufacturing device 2 heating elements 3 Starting material 4 heating conductors 5 Cutting device 6 Arrow 7 Control unit 8 measuring device 9 Course 10 border 11 border 12 Course

Claims

[1] Method for manufacturing an electric heating element (2) for a vehicle catalyst of a motor vehicle, wherein a starting material (3) of the heating element (2) is processed with a processing parameter to manufacture the heating element (2), characterized by, that during the manufacture of the heating element (2) from the starting material (3) an electrical resistance of the heating element (2) is measured and a value of the processing parameter for a further course of manufacture is adjusted depending on the electrical resistance, wherein a heating wire is used as the starting material and a stretching of a heating conductor (4) of the heating element (2) formed from the heating wire is used as the processing parameter, wherein the heating conductor has a first cross-sectional area for a first value of the processing parameter and a second cross-sectional area different from the first cross-sectional area for a second value of the processing parameter. [2] Method according to claim 1, characterized by, that a curve (9) is defined for the electrical resistance over a processing step and the value of the processing parameter is chosen such that the measured resistance is adjusted in the direction of a target resistance determined from the curve (9) on the basis of the processing step. [3] Manufacturing device (1) for manufacturing an electric heating element (2) for a vehicle catalyst of a motor vehicle, for carrying out the method according to one or more of claims 1 to 2, wherein the manufacturing device (1) is provided and configured to process a starting material (3) of the heating element (2) for manufacturing the heating element (2) with a processing parameter, characterized by, that the manufacturing device (1) is further provided and designed to measure an electrical resistance of the heating element (2) during the manufacture of the heating element (2) from the starting material (3) and to adjust a value of the processing parameter for a further course of manufacture depending on the measured electrical resistance, wherein a heating wire is used as the starting material and a stretching of a heating conductor (4) of the heating element (2) formed from the heating wire is used as the processing parameter, wherein the heating conductor has a first cross-sectional area for a first value of the processing parameter and a second cross-sectional area different from the first cross-sectional area for a second value of the processing parameter.

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