Method for the production of an exhaust-gas routing device for a motor vehicle

Abstract

A method for production of an exhaust-gas routing device that has a housing, an elongated substrate, and a compensating element, includes the following steps. At least one parameter of the substrate and/or of the compensating element is determined A target parameter, which describes a variable linked to a target geometry of the housing, is determined based on the measured parameter of the substrate and/or of the compensating element. The substrate and the compensating element are arranged in the housing, and the housing is deformed with an overpressure factor which is determined on the basis of at least one previous deformation of a previously manufactured device. The housing is measured after the deformation, and the thus-established values are compared with the target parameter. An overpressure factor for the deformation of a subsequently manufactured device is adapted if a deviation from the target parameter is detected upon measuring which lies above a defined threshold value.

Claims

1. A method for production of an exhaust-gas routing device for an internal combustion engine, wherein the exhaust-gas routing device includes a housing, an elongated substrate and a compensating element, the method comprising the following steps: a) determining at least one parameter of the elongated substrate and/or of the compensating element, b) determining a target parameter, which describes a variable linked to a target geometry of the housing, based on a measured parameter of the elongated substrate and/or of the compensating element, c) arranging the elongated substrate and the compensating element in the housing, d) deforming the housing with an overpressure factor which is determined on a basis of at least one previous deformation of a previously manufactured exhaust-gas routing device, e) measuring the housing after deformation, and comparing established values with the target parameter, and f) adapting an overpressure factor for a deformation of a subsequently manufactured exhaust-gas routing device if a deviation from the target parameter is detected upon measuring which lies above a defined threshold value.

2. The method of claim 1 wherein the deformation is a pressing-in or a widening.

3. The method of claim 1 wherein the target parameter is a diameter of the housing, a circumference of the housing, and/or a deviation from a pre-set value.

4. The method of claim 1 wherein the threshold value above which the overpressure factor is adapted lies within tolerance limits above which a manufactured exhaust-gas routing device must be rejected.

5. The method of claim 1 wherein a control loop feedback is used in order to adapt the overpressure factor.

6. The method of claim 1 wherein the parameters determined in step a) can comprise a weight of the elongated substrate and/or of the compensating element and/or a geometric measurement of the elongated substrate and/or of the compensating element.

7. The method of claim 1 wherein the housing is tubular.

8. The method of claim 1 wherein the compensating element is placed around the elongated substrate before being introduced into the housing.

9. The method of claim 1 wherein for deformation the housing is positioned in a tool which has several radially movable jaws.

10. The method of claim 9 wherein the radially movable jaws are moved radially by an individual adjustment distance depending on a size of the target parameter and the overpressure factor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages and features of the invention follow from the description below and from the drawings to which reference is made. In the drawings,

(2) FIG. 1 shows a longitudinal section through an emission control device produced according to the invention;

(3) FIG. 2 shows schematic diagrams of measurement devices and tools which are used in the process according to the invention;

(4) FIG. 3 shows a cross section through a device produced according to the invention, wherein the external housing is wound;

(5) FIG. 4 shows a cross section through a device produced according to the invention, wherein the external housing is constructed from shells;

(6) FIG. 5 shows a schematic diagram which shows the stuffing used as an alternative in the process according to the invention; and

(7) FIG. 6 shows a perspective view of a tool used in the process according to the invention, partially in section.

DETAILED DESCRIPTION

(8) FIG. 1 shows an exhaust-gas routing device 10, in particular an emission control device. Such devices are usually installed in motor vehicles, but other applications would also be conceivable. The emission control device can be either a catalytic converter, a particle filter or a combination of both.

(9) The exhaust-gas routing device comprises an elongated, here a substantially cylindrical, substrate 12 which comprises, for example, a ceramic or metallic substrate. For example, the substrate 12 is of a corrugated-board-type support structure which is coated with catalyst material.

(10) The substrate 12 can have a circular cylindrical cross section or any non-circular cross section, e.g. an oval cross section. A circular cylindrical cross section is shown in the figures purely for simplified representation.

(11) The substrate 12 is surrounded by an elastic compensating element 14 which is formed as a support mat. The compensating element 14 is arranged between the substrate 12 and a housing 16.

(12) The housing 16 is designed with very thin walls, in particular made of sheet metal. An inflow funnel 18 and an outflow funnel 19 are connected upstream and downstream respectively to the housing 16.

(13) The substrate 12 together with the compensating element 14 forms a unit which is also called an inlay in the following.

(14) During operation, exhaust gas flows into the substrate 12 via the end face of the inflow funnel 18 and finally leaves the substrate 12 containing fewer pollutants at the opposite end face in order to leave the exhaust-gas routing device 10 via the outflow funnel 19.

(15) The process according to the invention for the production of the exhaust-gas routing device 10 is explained in more detail in the following with reference to FIG. 2.

(16) In FIG. 2 various measuring stations are shown with which various parameters of each individual substrate 12 and each compensating element 14 are established with respect to achieving an optimum clamping force of the inlay in the housing 16. The measuring stations are coupled via a control unit 20 to a tool 35 for mounting and clamping of the inlay in the housing 16. The stations explained in the following are described in the preferred sequence of the production process.

(17) At least one parameter of the substrate 12 is determined individually in a measuring device 22. According to FIG. 2, this parameter is the external geometry (shape and external dimensions, in particular circumference) of the substrate 12, which is preferably established by contact-free measuring sensors.

(18) The measuring can be restricted to a single position on the substrate 12, but it would also be conceivable to measure the substrate 12 at several positions.

(19) Alternatively or additionally, a weight of the substrate 12 can also be determined. It is also conceivable, alternatively or additionally to the absolute values, to record a deviation from a pre-set theoretical value, i.e. to measure the substrate 12 and/or the elastic compensating element 14 relative to the theoretical value.

(20) A CCD camera 22 or a laser measuring device 22 can also be used to determine the external geometry.

(21) Furthermore, different parameters of the compensating element 14 can be determined, for example a weight, a geometry, and/or a compressibility of the compensating element 14.

(22) The measuring device 22 is connected to the control unit 20 in which the obtained measurement values for the substrate 12 and/or the compensating element 14 are stored.

(23) As shown in FIG. 2, in a tension-compression testing machine 24 each individual compensating element 14, i.e. each support mat, is laid flat on a level base 26 and is deformed substantially perpendicular to the base 26 by exertion of a pressure p, wherein the whole compensating element is loaded over its whole surface and the compressibility thus determined.

(24) With the established data on the inlay to be installed, comprising the substrate 12 and the compensating element 14, a target geometry of the external housing 16 matched at least to the compressibility of the compensating element 14 and the geometry of the substrate 12 can be established in the control unit 20, which can be effected by calculation or by comparison with a distribution matrix stored in the control unit 20. The individual target geometry is designed based on the achievement of the required clamping force to be exerted on and matched individually to the inlay.

(25) A variable linked to the target geometry is specified as a target parameter. A variable directly describing the geometry of the housing 16 is chosen as the target parameter but, for example, a statistical value which is established from several measurement points on the housing 16 could also be used. A relative measured variable which is based on a theoretical value could likewise be used as target parameter.

(26) In particular a target diameter or a target circumference of the housing 16 based on the measured parameters of the substrate 12 and/or of the compensating element 14 is determined as target parameter. The target diameter is then the diameter of the housing 16 for which a clamping force which acts on the inlay is optimum.

(27) The inlay is then arranged in a housing 16. For this purpose, the housing 16 can be wound around the inlay, as shown in FIG. 3.

(28) Alternatively, two or more shells 38, 40 can be inserted into one another in order to form the housing 16, as shown in FIG. 4.

(29) In a subsequent process step the housing 16 is deformed, in this case pressed in. During deformation, a so-called overpressure factor K.sub. which is determined on the basis of at least one previous deformation of a previously manufactured device is taken into consideration. This means that the housing 16 is deformed e.g. beyond the target diameter. Thus despite a springing back of the housing 16 at least approximately the target diameter can be reached.

(30) FIG. 6 shows a tool 35 with which the housing 16 is deformed. The tool 35 has several circular segment-shaped jaws 36 which can be moved inwards. The insides of the jaws 36 are adapted to the later shape of the housing 16 in the corresponding range.

(31) The jaws 36 can be moved inwards by an individual adjustment distance, with the result that an adjustment distance can be adapted to the desired target parameter and the overpressure factor K.sub. can simultaneously be taken into consideration.

(32) According to the process according to the invention, the housing 16 is measured after the deformation and a variable corresponding to the target parameter established which is compared with the previously specified value of the target parameter, i.e. for example the external diameter of the housing 16. If the deviation established in suitable manner lies above a threshold value, the overpressure factor K.sub. is adapted, in particular via a control loop feedback. For example the deviations of the most recently manufactured devices, for example, the last five devices, are taken into consideration. This is carried out e.g. by averaging.

(33) The adjusted overpressure factor K.sub. is respectively taken into account for the device manufactured subsequently. This means that no repeated deformation of the same device occurs.

(34) As an alternative to pressing in, a prefabricated housing 16 is widened before the inlay in inserted, as is indicated schematically in FIG. 5. This process is also called stuffing.

(35) As described above, the substrate 12 and the compensating element 14 are measured and the target parameters specified.

(36) According to the current overpressure factor K.sub. the housing 16 is deformed, in this case widened, in a suitable tool. The tool can be constructed similar to the tool 35 shown in FIG. 6, wherein the jaws are arranged to be movable radially outward.

(37) The inlay is then inserted into the housing 16. Here, there can be a further slight deformation of the housing 16, in particular if the inlay has a non-circular cross section.

(38) As described above, the housing 16 is then measured and a deviation of the thus-established values from the target parameter established, following which the overpressure factor K.sub. is adapted, if necessary.

(39) The threshold value above which the overpressure factor K.sub. is adapted lies within tolerance limits above which a manufactured device must be rejected. Moreover, a check is carried out before adaptation of the overpressure factor K.sub. whether the overpressure factor also lies within a pre-set tolerance range. In this way, the manufacture of the exhaust-gas routing device is particularly reliable. In particular, the production of reject parts can be very largely avoided.

(40) Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this disclosure. For that reason, the following claims should be studied to determine the true scope and content of this disclosure.