APPARATUS FOR DETECTING LEAKAGE OF FLUID IN AUTOMOBILE FUEL INJECTORS

TECHNICAL FIELD • The present invention relates to an apparatus for detecting leakage of fluid in automobile fuel injectors. In particular, the present invention relates to an apparatus for detecting leakage of fluid in an injector supplied with a test fluid under pressure ^' and provided with an outlet hole, which is obtained in correspondence with an end face of the injector, and cooperates with a shutter that is movable between an open position and a closed position of said outlet hole.

The apparatus comprises a light source to irradiate the end face of the injector using light radiation in a given wavelength and a sensing device to measure the intensity of the light radiation reflected by said end face.

Since the intensity of the light radiation reflected by the end face of the injector varies according to the amount of test fluid that is present on said end face, the output signal of the sensing device is related to the leakage of test fluid from the injector. BACKGROUND ART

The known apparatus of the kind described above have several drawbacks mainly deriving from the fact that said apparatus are relatively imprecise since the

intensity of the light radiation measured by the sensing device varies with changes in certain uncontrollable parameters during the test such as, for instance, the surface finish of the end face of the injector or interference with the ambient light.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide an apparatus for detecting leakage of fluid in automobile fuel injectors that overcomes the drawbacks described above and is simple and inexpensive to produce .

According to the present invention there is provided an apparatus for detecting- leakage of fluid in automobile fuel injectors as set forth in the claims. BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described with reference to the attached drawings, illustrating a non- limiting embodiment thereof, in which: figure 1 is a schematic exploded perspective view of a preferred embodiment of the apparatus according to the present invention; figure 2 is a perspective view of a detail of the apparatus of figure 1; and figure 3 is a cross-section of the detail of figure 2.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to figure 1, number 1 indicates, as a whole, an apparatus for sensing leakages of fluid in

an automobile fuel injector 2 of a known type (figure

2), which, is connected to a device (not illustrated) for supplying a test fluid under pressure capable of absorbing, in the same way as the fuel used in

5 automobiles, light radiation in the ultraviolet light wavelength range, and is provided with an outlet hole

(not illustrated) which cooperates with a shutter (not illustrated) movable between an open position and a closed position of said outlet hole (not illustrated) .

10 According to that illustrated in figures 2 and 3, the apparatus 1 comprises a detector cell 3 comprising, in turn, a plate 4 that is substantially parallelepiped in shape having an upper wall 5 and a lower wall 6 substantially parallel to one another, two side walls 7

^' 15 substantially parallel to one another and orthogonal to the walls 5 and 6, and two side walls 8 substantially parallel to one another and orthogonal to the walls 5, 6 and 7.

The plate 4 is also provided with a hole 9, which

20 has a longitudinal axis 10 substantially orthogonal to the walls 7, extends through the plate 4, and comprises a narrowed central portion 11, two widened end portions 12, arranged on opposite sides of the portion 11, and which open outwardly in correspondence with the walls 7,

25 and two intermediate portions 13 connecting the portion 11 to the portions 12.

The portion 11 is axially closed by means of two closing elements 14, which are transparent to light

radiation in the ultraviolet light wavelength range, are mounted inside the portions 13 transversely.- ^; to the axis 10, are made, preferably, of quartz and define, with said portion 11, a chamber 15 for containing a contrast fluid, preferably a hydrocarbon, which is different to the test fluid contained in the injector 2.

In particular, the contrast fluid and the test fluid have different capacities for absorbing the light radiation in the ultraviolet light wavelength range. In the specific case, the contrast fluid is substantially transparent, and in any case more transparent than the test fluid, to light radiation in the ultraviolet- light wavelength range.

The chamber 15 is provided with a feed valve 16, which is mounted in a seat 17 obtained in one of the walls 8 transversely to the axis 10, and communicates with the chamber 15 to feed the contrast fluid into the chamber 15, and an outlet valve 18, which is mounted in a seat 19 obtained in the other wall 8 transversely to the axis 10, and communicates with the chamber 15 to discharge the contrast fluid to the outside of said chamber 15.

Each portion 12 internally houses a sleeve 20, which is mounted inside the portion 12 coaxially to the axis 10, and supports a collimating lens (figure 1) mounted inside said sleeve 20.

The plate 4 is also provided with a further hole 22, which has a longitudinal axis 23 substantially

transversal to the axis 10 and orthogonal to the walls 5 and 6, is limited internally by a stepped face 24 tapered towards the axis 10, opens outwardly in correspondence with the ^" upper wall 5, and is connected to an intermediate point of the chamber 15.

The hole 22 internally houses a cylindrical sleeve 25, which is mounted coaxially to the axis 23, and supports a lower end of the injector 2 to enable said outlet hole (not illustrated) of said injector 2 to communicate hydraulically with the chamber 15.

With reference to figure 1, the apparatus 1 also comprises a ^' light source 26, which is connected to one of the lenses 21 (hereinafter indicated by 21a) by means of an optical fiber 27, and is suitable to deliver light radiation, preferably pulsed, in the ultraviolet light wavelength range, to the lens 21a, and, thus, to the chamber 15.

The source 26 is connected to the optical fiber 27 by means of the interposition of a filtering device 28 suitable to block the light radiation in the infrared light wavelength range and thus only allow the light radiation in the ultraviolet light wavelength range and visible light to travel along the optical fiber 27.

The apparatus 1 also comprises a sensing device 29, which is connected to the other lens 21 (hereinafter indicated by 21b) by means of an optical fiber 30, is suitable to measure the intensity of the light radiation leaving the chamber 15, and, in the specific case,

comprises an optical sensor normally referred to as a photodetector .

The device 29 is connected to the optical fiber 30 by means of the interposition of a reducing device 31 arranged between the optical fiber 30 and the device 29 to reduce the intensity of the light radiation supplied to the device 29 and a filtering device 32 arranged between the devices 29 and 31 to block the light radiation in the visible light wavelength range and thus only allow the light radiation in the ultraviolet light range to reach the device 29.

In use, the light radiation emitted by the source 26 is supplied in the first instance through the filtering device 28, then along the optical fiber 27 and finally through the collimating lens 21a in order to pass through the containment chamber 15 with a substantially cylindrical shape.

The light radiation leaving the containment chamber 15 is then supplied in the first instance through the collimating lens 21b in order to alter its cylindrical shape, then along the optical fiber 30, through the reducing device 31 and the filtering device 32, and finally to the sensing device 29, which sends an output signal proportional to the intensity of said light radiation.

The intensity of the light radiation measured by the device 29, and, thus, the output signal of said device 29 vary according to the contents of the chamber

15. Thus, in case of leakages from the injector 2, the presence of test fluid in the chamber 15 determines a partial absorption of the light radiation supplied through said chamber 15 and, thus, a different output signal of the device 29.

The output signals of the device 29 can be used to plot a characteristic curve in which each output signal of the device 29 corresponds to a given quantity of test fluid in • the chamber 15 and, thus, a given leakage from the injector 2, and to calculate the leakages from the injector 2 over a given period of time and, thus, the mean leakage from said inj ector 2.

According to an alternative embodiment that is not illustrated, the apparatus 1 comprises a sensing device completely identical to the sensing device 29 and a light dividing device arranged between the light source 26 and the filtering device 28 to selectively supply the light radiation emitted by the light source 26 partly to the filtering device 28 and partly to said sensing device in order to measure the intensity of the light radiation emitted by said light source 26.