DE102011100203A1 - Method for detecting e.g. half-moon seal ring in pipe section using RADAR i.e. frequency modulated continuous-wave-RADAR, involves partially extending object into hollow body that is partially made of plastic material - Google Patents

Abstract

The method involves generating electromagnetic radiation (2) in a terahertz-frequency region with a radiation source (1). The electromagnetic radiation is directed to a hollow body i.e. pipe section, where the electromagnetic radiation reflected from the hollow body and an object (4) i.e. seal, is detected by a radiation detector (5). The object is partially extended into the hollow body that is partially made of plastic material, where the object is extended between the hollow body and a functional element that is connected with the hollow body.

Description

The present invention relates to a method for detecting an object in a hollow body comprising the steps of: providing a hollow body, generating electromagnetic radiation THz frequency range with a radiation source, directing the electromagnetic radiation to the hollow body, detecting the of the hollow body and / or the object reflected electromagnetic radiation with a radiation receiver and / or detecting the transmitted through the hollow body and / or the object electromagnetic radiation with a radiation receiver.

In the production of technical objects, which are flowed through in later operation gas or liquid, there is always the problem that seals between two parts, in particular between a housing and arranged in this functional element must be installed. The presence and proper positioning of such a seal in a housing in most cases depends on the functionality of the finished product decisively. For example, if a sealing ring between the housing of the filter and the filter element itself is not placed correctly in an oil filter for a motor vehicle, the first time the oil filter is pressurized with oil, the filter will leak and the surrounding engine compartment will become considerably dirty or dirty. the engine is damaged due to lack of oil. The same applies to the arrangement of a corresponding seal between two housing sections of such an oil filter.

The same problem arises, for example, when connecting two pipe sections in production.

Since most parts in modern industrial production need to be manufactured with zero fault tolerance, each component must be checked after production to see if the gasket or gaskets are installed at all and, if so, if they are positioned in the right place. to ensure the functionality of the device to be produced.

Since the seal to be tested is usually located in a hollow body, for example a housing or a pipe section, optical inspection from the outside is not possible.

Therefore, in practice, all of the relevant components are X-rayed to obtain an image of whether or not the seal is located at the designated location in the component. The X-ray of parts in production for quality assurance still encounters great reservations with regard to the required job security, ie. H. the radiation protection. Often, therefore, the finished products are moved from production to a quality assurance laboratory, where each piece is individually X-rayed in a suitable protection environment. Such quality assurance outside the actual production line is associated with considerable costs.

It is therefore an object of the present invention to provide a method for quality assurance in the production of hollow bodies which contain seals, which can be integrated inexpensively in production lines. In addition, it is an object of the invention to provide a method for quality assurance of hollow bodies with seals in their interior, which meet the radiation protection requirements for workplaces in production environments.

At least one of the aforementioned objects is achieved according to the invention by a method for detecting an object in a hollow body, comprising the following steps: providing a hollow body, generating electromagnetic radiation in the THz frequency range with a radiation source, directing the electromagnetic radiation onto the hollow body, detecting the electromagnetic radiation reflected by the hollow body and / or the object with a radiation receiver and / or detecting the electromagnetic radiation transmitted through the hollow body and / or the object with a radiation receiver, wherein the object to be detected is a seal which at least partially in the Hollow body extends.

The inspection of such an arrangement comprising a hollow body and a gasket extending at least in sections in the hollow body with the aid of THz radiation has the advantage that it can be inexpensively integrated into a production environment, taking into account all aspects of radiation safety.

For the purposes of the present application, electromagnetic radiation in the THz frequency range is understood as meaning electromagnetic radiation having a frequency in the range from 1 GHz to 30 THz. Commercially available radiation sources and radiation receivers are now available in this frequency range. The THz frequency range has the advantage that many materials, in particular plastics, are transparent to electromagnetic radiation in this frequency range. In this case, electromagnetic radiation is not ionizing in the THz frequency range, in contrast to X-radiation.

A hollow body according to the present invention is a body having a cavity in its interior, in particular a housing portion or a hollow cylindrical pipe section.

A hollow body according to the present invention, however, is not only an example hollow cylindrical body, in the interior of a seal is arranged, but the flange of a tube, wherein the flange for connection to a functional element has a cavity for receiving a seal. If the hollow body is connected, for example, to a wall as a functional element with the aid of its flange, the gasket in the sense of this invention extends in sections in the hollow body.

In one embodiment, the hollow body is connected to a functional element, wherein the seal extends between the hollow body and the functional element. In one embodiment, such a functional element extends at least in sections into the hollow body.

Examples of such an arrangement of a hollow body and a functional element connected to the hollow body, wherein the functional element is sealed relative to the hollow body by means of a seal, are a first housing portion as a hollow body and a second housing portion as a functional element.

Further examples are a first housing section as a hollow body and a filter element as a functional element or a first tubular section as a hollow body and a second tubular section as a functional element. In the latter example, for example, the seal extends between the sleeves of two pipe sections, so that it is no longer visually visible after joining the pipe sections from the outside.

In one embodiment, the hollow body is a portion of a housing of a filter, in particular an oil filter, or a pump.

A prerequisite for the function of the method according to the invention is that the hollow body consists of a material which is at least partially transparent to electromagnetic radiation in the THz frequency range. Therefore, in one embodiment, the hollow body is at least partially made of plastic.

If one measures in a reflection arrangement, wherein it is assumed that the hollow body is made at least in sections from a material transparent to electromagnetic radiation in the THz frequency range, the seal may be made from a material which is intransparent for electromagnetic radiation in the THz frequency range. However, in one embodiment it is expedient if the seal is also produced from a material transparent to electromagnetic radiation in the THz frequency range, preferably from a plastic.

An example of such a seal to be detected by means of the electromagnetic radiation in the THz frequency range is a sealing ring, for example an O-ring or a half-moon ring.

In one embodiment of the invention, the detection of the object takes place by means of RADAR (Radio Detection and Ranging). In this case, the transit time or the path of the radiation from the radiation source via the hollow body to the radiation receiver is determined in particular from the detected radiation.

In principle, there are three methods which can be distinguished from one another for a transit time or travel distance measurement of the electromagnetic radiation between the radiation source, all of which provide the same information about the distance between the object to be tested and the radiation source or the radiation receiver:
In a first embodiment, the step of generating electromagnetic radiation in the THz frequency range with the radiation source comprises frequency modulating the electromagnetic radiation, wherein the change in frequency is preferably constant over time, and in that the step of detecting the electromagnetic radiation with the radiation receiver a determination of a difference frequency between a reference signal and the electromagnetic radiation received by the radiation receiver, and wherein the transit time of the electromagnetic radiation between the radiation source and the radiation receiver is calculated from the difference frequency.

Such a method for calculating the distance between the hollow body and / or the seal works particularly well if the frequency of the generated electromagnetic radiation is continuously varied over time, so that each time point of the radiation is clearly encoded by the radiated frequency. Such a method of distance measurement is also referred to as FMCW radar.

In order to be able to determine the frequency difference between the electromagnetic frequency radiated by the radiation source in the THz frequency range at the defined time and the radiation received by the radiation receiver at the defined time, the radiation receiver is implemented in one embodiment a coherent detection in which a reference signal from the radiation source is mixed with the received signal to produce a signal at the difference frequency.

wobei c die Lichtgeschwindigkeit ist und t die Zeit ist, welche die von der Strahlungsquelle erzeugte und abgestrahlte elektromagnetische Strahlung benötigt, um mit Lichtgeschwindigkeit die Entfernung r zum reflektierten Objekt hin- und zurück zu durchlaufen. Das Verhältnis df/dt bezeichnet die Änderungsrate, mit der die Frequenz f der erzeugten und abgestrahlten elektromagnetischen Strahlung über die Zeit t geändert wird. Diese wird auch als Chirprate bezeichnet.Assuming that the radiation source and the radiation receiver have essentially the same distance from the hollow body and sealing ring to be detected, the distance r (simple distance) between the radiation source or radiation receiver and the hollow body can be determined as follows from the generated difference frequency Δf between the Calculate the frequency of the electromagnetic radiation generated by the radiation source at a defined time and the electromagnetic radiation detected by the radiation receiver at the defined time:

where c is the speed of light and t is the time required for the electromagnetic radiation generated and radiated by the radiation source to travel back and forth at the speed of light with the distance r to the reflected object. The ratio df / dt denotes the rate of change with which the frequency f of the generated and radiated electromagnetic radiation is changed over time t. This is also called Chirprate.

As an alternative to using an FMCW RADAR, in one embodiment of the method according to the invention the step of generating electromagnetic radiation in the THz frequency range with the radiation source comprises generating pulse-shaped electromagnetic radiation in the time domain. The duration of a pulse with a short pulse duration compared to the distance to be detected is easy to determine. For this purpose, the transit time between the radiation source, the hollow body and the radiation receiver can be compared with the transit time of a reference pulse via a known path. Such a method is called impulse RADAR.

Alternatively, the step of generating the electromagnetic radiation in the THz frequency range with the radiation source comprises generating and emitting a plurality of frequencies in succession, and the step of detecting the electromagnetic radiation with the radiation receiver comprises measuring the phase of the electromagnetic radiation for each individual frequency relative to a reference signal. From the measurement of the relative phase angles of the individual radiation components with a plurality of mutually different frequencies, the transit time or the travel path between radiation source, hollow body and radiation receiver can likewise be determined unambiguously.

In the preferred embodiments of the method according to the invention, the seal has a circular symmetry and the sealing surfaces of the hollow body and preferably of a functional element arranged in this are likewise rotationally symmetrical.

In one embodiment, the measurement then suffices at a single point to determine whether a) a sealing ring is present and whether b) it is arranged in the correct position. Therefore, the inventive method can then perform with a single measurement and radiation source and radiation receiver can consist of a single pixel or pixel.

In order to still be able to produce a two-dimensional image with such an arrangement, in another embodiment, the hollow body and / or the seal are rotated about the axis of symmetry of the circular sealing ring and the measurement is repeated at several points in the circumferential direction of the sealing ring, so that a picture of the the entire circumference of the seal receives.

Further advantages, features and applications of the present invention will become apparent from the following description of an embodiment and the associated figures.

1 shows the basic structure of a device used for the inventive method.

2 shows the application of the method according to the invention for detecting the position of an O-ring seal between two pipe sections.

3a shows the measured reflectivity for the device 2 ,

3b shows the measured reflectivity for the device 2 , but without sealing ring.

4 shows the application of the method according to the invention for detecting the position of an O-ring between the flange of a pipe and a wall.

5 shows the application of the method according to the invention for detecting the position of an O-ring in an oil filter.

The measuring equipment off 1 has a radiation source 1 for generating electromagnetic radiation 2 in the THz frequency range, here at 250 GHz, up. In order to make a distance measurement, the frequency of the radiation source 1 generated and radiated electromagnetic radiation 2 varies continuously, as shown by the diagram 3 in the radiation source 1 (Plotted is the radiated frequency over time) is indicated. That is, the frequency is changed continuously with time, with the rate of frequency change being constant.

The of the radiation source 1 generated radiation is emitted and onto the object to be detected 4 directed.

The object to be inspected 4 Back-reflected radiation is detected by means of a radiation receiver 5 detected. This is the radiation receiver 5 to a coherent radiation receiver, ie in the radiation receiver 5 becomes the detected radiation 6 with one from the source 1 originating reference signal 7 mixed and generates a signal with the difference frequency between the generated at a defined time THz signal and the THz signal detected at this defined time. The reference signal 7 reflects the current from the radiation source 1 radiated frequency of electromagnetic radiation.

wobei c die Lichtgeschwindigkeit ist und t die Zeit Ist, welche die von der Strahlungsquelle erzeugte und abgestrahlte elektromagnetische Strahlung benötigt, um mit Lichtgeschwindigkeit die Entfernung r zum reflektierten Objekt hin- und zurück zu durchlaufen.Since the time of generation or radiation of the electromagnetic radiation 2 from the radiation source 1 thus frequency-coded, can be the duration of the electromagnetic radiation 2 between the radiation source 1 , the object 4 and the radiation receiver 5 Immediately determine if the difference frequency between the current from the radiation source 1 radiated signal and the same time defined by the radiation receiver 5 detected signal is known. As the radiation receiver 5 by mixing the reference signal 7 and the detected signal 6 This generates a signal with the difference frequency. The distance r between the radiation receiver 5 and the object to be detected 4 then calculates on the assumption that the radiation source 1 and the radiation receiver 5 the same distance from the object 4 have, as

where c is the speed of light and t is the time it takes for the electromagnetic radiation generated and radiated by the radiation source to traverse the distance r to the reflected object at the speed of light.

In the illustrated embodiment, the radiation source has a bandwidth of the generated and radiated electromagnetic radiation in a range of 230 GHz to 320 GHz, wherein the frequency is changed at a constant rate, so that the range from 230 GHz to 320 GHz is tuned in 100 μs ,

2 shows schematically an arrangement for detecting the presence of a sealing ring 8th in the connection of two pipe sections 9 . 10 , where the pipe sections 9 . 10 together with the sealing ring 8th in this arrangement, the object to be tested 4 ' forms. in the sense of the terminology of the present application forms the first pipe section 9 the hollow body and the second pipe section 10 it is the functional element.

The pipe sections 9 . 10 consist in the illustrated embodiment of polypropylene (PP) and have an outer diameter of about 5.25 cm and an inner diameter of about 3.8 cm. The seal is a rubber O-ring.

Specifically, it is necessary to check according to the inventive method, whether within the first pipe section 9 arranged seal, here an O-ring 8th , at the designated location or not. If the ring 8th is present, it is necessary to check whether it is sitting at the designated place or, for example, when joining the two pipe sections 9 . 10 has slipped. Because the place of the sealing ring 8th between the sealing surfaces 11 . 12 the pipe sections 9 . 10 withdraws an optical inspection, the inventive method offers the possibility of the position of the sealing ring from the outside, ie through the pipe section 9 through without having to use ionizing X-radiation. In the illustrated embodiment of the method according to the invention, the reflected signal is viewed along the schematically indicated direction of incidence 13 at. This creates a significant and unique signature for the in 2 illustrated case of a correct positioning of the sealing ring 8th between the pipe sections 9 . 10 , ie in each case a reflection of the inner or outer walls of the undercut pipe sections can be seen 9 . 10 as well as further characteristic reflections of the sealing ring 8th , The sealing ring slips 8th in comparison to its nominal position or if it is completely missing, the reflections from the surfaces of the sealing ring change 8th or they disappear completely. This is clearly visible in the reflected signal.

While basically for a detection, whether the sealing ring 8th is present or not, the measurement at a point in the circumferential direction of the pipe sections 9 . 10 is sufficient, the measurement at a plurality of measuring points in the circumferential direction around the pipe sections 9 . 10 or the sealing ring 8th repeats around, giving a complete picture of the position of the sealing ring 8th over the entire circumference of the pipe sections 9 . 10 is obtained. This is the object to be tested 4 ' around the axis of symmetry 14 the pipe sections 9 . 10 or the sealing ring 8th turned around. Therefore, one comes even in such an embodiment of the method according to the invention with a single radiation source 1 and a single radiation receiver 5 with only one pixel.

The presentation of the 3A shows the result of a measurement with sealing ring and 3B shows the result of a measurement without a sealing ring. It is in both diagrams of 3A and 3B the reflectivity R in dB (x-axis) against the location z in millimeters (y-axis) in the direction of the arrow 13 out 2 applied. It can be clearly seen that the reflectivity at z = 0, ie on the inside of the pipe section 9 abruptly reduced when there the sealing ring 8th with the interface or sealing surface 12 of the pipe section 9 is in contact.

4 shows the arrangement 1 with an oil filter 4 '' as an object to be tested. The oil filter 4 '' has a housing section 15 (as a hollow body in the sense of the present invention) and a filter element 16 (as a functional element in the context of the present invention). The housing section 15 is with the help of an O-ring 17 opposite the filter element 16 sealed. To detect the presence and the position of the sealing ring 17 ,

5 shows the arrangement 1 with a flange connection as the object to be tested 4 '''' , There is a pipe 18 with a flange 19 connected, which has a cavity for receiving an O-ring seal 20 as a seal. Within the meaning of the present invention, the flange forms 19 a hollow body, inside which the sealing ring 20 sections extends. The flange 19 is against a wall 21 screwed, with the sealing ring 10 the flange 19 against the wall 21 seals.

For purposes of the original disclosure, it is to be understood that all such features as will become apparent to those skilled in the art from the present description, drawings, and claims, even if concretely described only in connection with certain other features, both individually and separately any combinations with other features or feature groups disclosed herein are combinable, as far as this has not been expressly excluded or technical conditions make such combinations impossible or pointless. The brevity and readability of the description is omitted here for the comprehensive, explicit representation of all conceivable combinations of features.

While the invention has been illustrated and described in detail in the drawings and the foregoing description, the description and description is given by way of example only and is not intended to limit the scope, as defined by the claims. The invention is not limited to the disclosed embodiments.

Variations of the disclosed embodiments will be apparent to those skilled in the art from the drawings, the description and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain features are claimed in different claims does not exclude their combination. Reference signs in the claims are not intended to limit the scope of protection.

LIST OF REFERENCE NUMBERS

1

radiation source

2

electromagnetic radiation

3

schematic plot of the radiated frequency versus time

4

object to be tested

4 '

pipe

4 ''

oil filter

4 '' '

flange

5

radiation receiver

6

detected radiation

7

reference signal

8th

seal

9

first pipe section

10

second pipe section

11

Sealing surface of the second pipe section 10

12

Sealing surface of the first pipe section 9

13

incidence direction

14

axis of symmetry

15

housing section

16

filter element

17

O-ring seal

18

pipe

19

flange

20

O-ring seal

21

wall

Claims (13)

Method for detecting an object in a hollow body with the steps of providing a hollow body ( 9 . 15 . 19 ) Generating electromagnetic radiation ( 2 ) in the THz frequency range with a radiation source ( 1 ), Directing the electromagnetic radiation ( 2 ) on the hollow body ( 9 . 15 ), Detecting the electromagnetic radiation reflected from the hollow body and / or the object ( 2 ) with a radiation receiver ( 5 ) and / or detecting the transmitted through the hollow body and / or the object electromagnetic radiation ( 2 ) with a radiation receiver ( 5 ), characterized in that the object to be detected is a seal ( 8th . 17 . 20 ), which extends at least in sections in the hollow body ( 9 . 15 ). Method according to claim 1, characterized in that the seal ( 17 ) between the hollow body ( 9 . 15 . 19 ) and one with the hollow body ( 9 . 15 . 19 ) connected functional element ( 10 . 16 . 21 ). A method according to claim 2 or 3, characterized in that the hollow body is a first housing portion and the functional element is a second housing portion, wherein the housing portions are preferably portions of a housing of a filter or a pump. Method according to one of the claims 1 to 3, characterized in that the hollow body has a first housing section ( 15 ) and the functional element is a filter element ( 16 ). Method according to one of claims 1 to 4, characterized in that the hollow body, a first pipe section ( 9 ) and the functional element a second pipe section ( 10 ). Method according to one of claims 1 to 5, characterized in that the steps of generating electromagnetic radiation ( 2 ) in the THz frequency range with the radiation source ( 1 ) and the detection of the electromagnetic radiation reflected by the hollow body and / or the object ( 2 ) with the radiation receiver ( 5 ) and / or the detection of the transmitted through the hollow body and / or the object electromagnetic radiation ( 2 ) with the radiation receiver ( 5 ) are carried out so that the detection of the object in the hollow body takes place with RADAR. Method according to one of claims 1 to 5, characterized in that the generation of electromagnetic radiation ( 2 ) in the THz frequency range with the radiation source ( 1 ) and detecting the electromagnetic radiation reflected by the hollow body and / or the object ( 2 ) with the radiation receiver ( 5 ) and / or the detection of the transmitted through the hollow body and / or the object electromagnetic radiation ( 2 ) with the radiation receiver ( 5 ) in the form of a transit time measurement of the electromagnetic radiation ( 2 ) between the radiation source ( 1 ) and the radiation receiver ( 5 ) respectively. Method according to claim 7, characterized in that the step of generating electromagnetic radiation ( 2 ) in the THz frequency range with the radiation source ( 1 ) a frequency modulation of the electromagnetic radiation ( 2 ), wherein the change in frequency is preferably constant over time, and in that the step of detecting the electromagnetic radiation ( 2 ) with the radiation receiver ( 5 ) a determination of a difference frequency between a reference signal ( 7 ) and that of the radiation receiver ( 5 ) received electromagnetic radiation ( 2 ) and wherein from the difference frequency the transit time of the electromagnetic radiation between the radiation source ( 1 ) and the radiation receiver ( 5 ) is calculated. Method according to claim 7, characterized in that the step of generating electromagnetic radiation ( 2 ) in the THz frequency range with the radiation source ( 1 ) generating in the time domain pulsed electromagnetic radiation ( 2 ). Method according to claim 7, characterized in that the step of generating the electromagnetic radiation ( 2 ) in the THz frequency range with the radiation source ( 1 ) comprises generating and emitting a plurality of frequencies in chronological succession, and in that the step of detecting the electromagnetic radiation ( 2 ) comprises measuring the phase of the electromagnetic radiation at each frequency relative to a reference signal. Method according to one of claims 1 to 10, characterized in that the radiation receiver ( 5 ) has only a single pixel. Method according to one of claims 1 to 11, characterized in that the hollow body ( 9 . 15 . 19 ) an axis of symmetry ( 14 ), wherein the hollow body ( 9 . 15 . 19 ) during the measurement about the symmetry axis ( 14 ) is rotated. Method according to one of claims 1 to 12, characterized in that the hollow body ( 9 . 15 . 19 ) is at least partially made of plastic.

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