GB2287092A

GB2287092A - Monitoring nozzle holes

Info

Publication number: GB2287092A
Application number: GB9404193A
Authority: GB
Inventors: David William Lloyd
Original assignee: VERNON GAUGING SYSTEMS Ltd
Current assignee: VERNON GAUGING SYSTEMS Ltd
Priority date: 1994-03-04
Filing date: 1994-03-04
Publication date: 1995-09-06
Also published as: GB9404193D0

Abstract

To monitor holes in manufactured nozzle components 10, electromagnetic radiation is projected through the nozzle holes from a predetermined position relative to one end of the nozzle hole eg from a light finger 21, and projected onto a suitable medium 23 at one or more predetermined distances from the other end of the nozzle hole, the position and/or shape of detected beams of radiation on the medium allowing calculation of the size and disposition of the holes. Fuel injection nozzles which emit fuel from nozzle holes each at the same angle from the nozzle axis may be monitored using a conical screen 23 which is perpendicular to all the emergent beams 16 and 17. A video camera may record images of the light falling on a screen 23 when the nozzle is at each of two distances from the screen for determining the parameters of the holes. <IMAGE>

Description

Monitoring of Manufactured Components The present invention relates to apparatus and a method of monitoring manufactured components for conformity with desired measurements.

A problem exists in the manufacture of components which have a hole or bore whose length is larger than its diameter. Typical components are nozzles either fuel injection nozzles or paint spray nozzles. To date, no practical dry solution has been found for measurement of these holes and manufactures rely on spraying liquid under pressure through a nozzle under test and monitoring the spray pattern on a target or using a camera system. Both methods are very primitive and scientific control of production and performance relies very much on experience.

The present invention provides apparatus and method for monitoring the dimensions of small holes by transmitting light from the interior of the component through the small holes by transmitting light from the interior of the component through the small holes and capturing the image. The capture image is then analysed and a accurate representation of the hole or holes can be readily created.

In use, the accuracy of this technique is better than 0.002 mm which provides valuable data for production components and also for analysing prototypes.

In order that the present invention be more readily understood, embodiment thereof will now be described by way of example with reference to the accompanying drawings in which: Figs. 1A and 1B show a sectional side view and a plan view of a typical component which requires monitoring; Fig. 2 shows a diagrammatic layout of apparatus according to the present invention; Fig. 3 shows a plan view of the screen component shown in fig. 2; Fig. 4 shows an overall front view of apparatus according to the present invention; Fig. 5 shows a diagrammatic side view of a conical screen to assist understanding the present invention; and Fig. 6 is a diagram showing the geometry of a nozzle.

Before describing the preferred embodiment of the present invention it is useful to understand that in the following description the term nozzle hole is intended to be read in a broad, general sense to refer to any hole in some static medium whose length is usually than its diameter. Further, when the term "geometric location" is used this is intended to be defined as the mathematical prescriptions specifying the centre of the hole forming the nozzle. This prescription has two components. The first is a suitable frame of reference (usually attached to the object containing the nozzle). The second is the set of parameters identifying a straight line representing the centre line of the nozzle. In any three dimensional space, four parameters are needed to specify a line.

Referring now to the drawings, figs. 1A and 1B show respectively a sectional side view and plan of a typical component which requires careful monitoring.

The component shown is a fuel injection nozzle but could be any other similarly shaped component. The nozzle 10 has an elongate bore 11 which is closed at one end 12 of the nozzle 10 with the exception of a plurality of small holes 13 which extend through the end wall of the nozzle into the bore 11. These holes are disposed equally spaced around a circle whose centre is on the access of the bore 11 and the hole extends through the end wall at a angle a to a plane projecting normal to the access of the bore 11. Turning now to figure 2, this shows a general arrangement for monitoring the size and disposition of the holes 13 in the nozzle 10. The apparatus comprises a table 20 which provides a datum surface on which the nozzle 10 is mounted.Means for illuminating the interior of the nozzle are provided in the form of a light finger 21 which produces an intense source of light which is then projected through the holes 13 in the nozzle 10. A screen 23 is located above the nozzle 10 and receives light projected the holes 13.

The light received on the screen 23 is monitored using any suitable arrangement but in this case we prefer to use a video camera.

In use, two sets of measurements are taken.

The first set is taken with the table 20 and nozzle 10 in the position in full lines in fig. 2 which produces beams of light 16 which impinge on a conical surface 24 of the screen 23 at a first position. Relative movement between the screen and the nozzle then takes place either by moving the screen towards the nozzle or the nozzle towards the screen and a further set of light beams 17 impinge on the screen at a second position on the conical surface 24. These positions are shown in fig. 3.

The nozzle, the conical surface 24 of the screen 23 and the optical axis of the video camera are all aligned to be on the same optical access. Further the conical surface 24 is a special defuse reflecting surface. Instead of a screen with a special defuse reflecting surface it would be possible to detect the position of the beams of light using a sensor for example a CCD array in which case the video camera would not be necessary. If a beam of light is detected directly by a sensor then for multiple nozzle applications, many distributed sensors are needed (or the part moved to align each nozzle with the sensor).

By using a reflecting surface with known geometry we can measure multiple nozzles with a single sensor and minimum part movement.

Instead of moving the nozzle or screen 23 between 2 measurement locations in order to provide 2 points of measurement, it would also be possible to use a pair of fixed by displaced surfaces interposed in the path of the beams. The surface nearest the nozzle exist holes is made semi-reflecting so that part of the beam is reflected by the second surface and both reflected beams are detected by the sensor.

There are a variety of available surfaces and any surface with known geometry can be used. For practical applications planar or conical surfaces are the most appropriate.

Figure 5 shows in more detail a cross section showing the pattern of dots produced by the light beams on the conical surface.

Figure 6 shows a diagram to explain in geometrical terms the nozzle arrangement which will enable a person skilled in the art to understand the type of processing which will be required in order to check the various dimensions of the nozzle holes.

X and Y is the field of view over which the optical system can measure. Angle '1A is the vertical angle referenced to the perpendicular centre line of the component and angle "B" is the radial angle from a defined point radilly on the component (in most cases there is a feature on the component that allows a radial reference). "M-N" is the hole being measured for vertical angle, radial angle and height of the hole at "N". The results of the image is repeated at two planes, thus providing a necessary accurate vertical displacement which provides the distance into the solution. With this displacement and the results obtained from the two planes the computations of results possible are numerous and not restricted to those defined herein.

Finally, Figure 4 shows the arrangement of apparatus according to the present invention in which the left hand side of the drawing shows the actual measurement apparatus incorporating the video camera, the nozzle locating table and the screen, while the right hand side of the figure shows the computation apparatus and displays.

Claims

CLAIMS:

1. A method for testing at least one parameter of a nozzle hole, wherein electromagnetic radiation is projected through the nozzle hole from a predetermined position relative to one end of the nozzle hole, and recorded on a suitable medium at one or more predetermined distances from the other end of the nozzle hole, the position and/or shape of a detected beam of radiation on the recording medium allowing calculation of the parameter.

2. The method of claim 1 wherein the recording medium is substantially perpendicular to the beam of radiation.

3. The method of claim 1 or 2 wherein the electromagnetic radiation is projected through a plurality of nozzle holes, the projected beams being recorded on the medium.

4. The method of claim 3 wherein the recording medium is conical in shape, the beams intersecting the cone substantially perpendicularly.

5. The method of claim 4 wherein the distance of the recording medium from the nozzle hole is controlled by moving the cone in the direction of its axis of symmetry.

6. The method of claims 1-5 specifically adapted to the testing of fuel injection nozzles.

7. Apparatus for testing at least one parameter of a nozzle hole, comprising means for generating electromagnetic radiation at a predetermined position relative to one end of the nozzle hole and whereby to project through the nozzle hole to form a beam of radiation; means for recording a section through the beam of radiation at one or more predetermined distances from the other end of the nozzle hole; and means for calculating the parameter of the nozzle hole from the position and or shape of the beam section.

8. Apparatus as claimed in claim 6 wherein the recording medium is substantially perpendicular to the beam of radiation.

9. Apparatus as claimed in claims 6 or 7 comprising a plurality of nozzle holes, the projected beams being recorded on the medium.

10. Apparatus as claimed in claim 8 wherein the recording medium is conical in shape, the beams intersecting the cone substantially perpendicularly.

11. Apparatus as claimed in claim 9 further comprising means for moving the conical recording medium relative to the nozzle holes in the direction of the axis of the conical recording medium.

12. Apparatus as claimed in any of claims 6-10 specifically adapted to the testing of fuel injection nozzles.

13. A method for testing at least one parameter of a nozzle hole substantially as hereinbefore described and with reference to the accompanying drawings.

14. Apparatus for testing at least one parameter of a nozzle hole substantially as hereinbefore described and with reference to the accompanying drawings.