GB1601533A

GB1601533A - Method of testing injection nozzles

Info

Publication number: GB1601533A
Application number: GB21642/78A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1977-12-24
Filing date: 1978-05-23
Publication date: 1981-10-28
Also published as: FR2412716A1; FR2412716B1; SE7813184L; DE2757996A1; IT7831115A0; IT1101325B

Description

(54) A METHOD OF TESTING INJECTION NOZZLES (71) We, ROBERT BOSCH GMBH., a German company of Postfach 50, 7000 Stuttgart 1, Germany, do hereby declare the invention, for which we pray that a patent may be granted to. us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a method of testing an injection nozzle.

Injection nozzles, especially fuel injection nozzles, need to be tested for their behaviour under operating condltions. More specifi cally, they need to be tested for fluid-tightness and chattering. For the former test, the nozzle is subjected to a pressure slightly below its rated opening pressure for a control period during which no drops should emerge from the nozzle. For the latter test, the nozzle is supplied with a quantity of fluid at a pre determined pressure whereupon the valve member oscillates or may be caused to oscillate. With good nozzles, fluid emerges in a substantially uniformly chopped manner whereas with bad nozzles, the fluid emerges in a non-uniformly chopped manner or even in a continuous flow.

In the past, testing for fluid-tightness and chattering was undertaken by means of visual observation. That method is laborious, inaccurate and leads to excessive demands on the testing personnel.

In accordance with the invention a method of testing an injection nozzle is provided, which includes the steps of projecting a laser beam past the outlet from the nozzle under test onto a light sensitive sensor which generates electrical signals proportional to the intensity of the laser beam and passing the electrical signals to an electronic evaluating device providing information concerning the behaviour of the nozzle.

Preferably, the light-sensitive sensor is a photodiode.

The electrical signals may be processed in the electronic evaluating device in either an analog manner or a digital manner. Whatever the manner of processing may be, the signals may be represented as analog signals on a viewing screen which may form part of an oscillograph.

During a fluid-tightness test, the nozzle is supplied with fluid at a pressure lower, by a predetermined amount, than the rated opening pressure of the nozzle, for example 10 bars lower, and preferably over a control period which may last, for example, 10 seconds.

In order that the invention may be clearly understood and readily carried into effect a method of testing a nozzle for its fluid-tightness and chattering behaviour will now be described with reference to the accompanying drawing which shows a fuel injection nozzle arranged for testing in accordance with the invention.

As can be seen from the drawing, a laser 12 projects a laser beam 13 past the outlet 10 from an injection nozzle 11 and onto a light-sensitive sensor in the form of a photodiode 14. Electrical signals generated in the photodiode 14 are passed through an elec trical conductor 15 to an electronic evaluating device 16.

Two kinds of test procedure relating to the behaviour of the nozzle 11 can be carried out with the apparatus shown in the drawing.

During one procedure, in which the nozzle is tested for fluid-tightness, fluid is supplied to the nozzle (indicated by the arrow in the drawing) at a pressure which is lower than the rated opening pressure of the nozzle by a predetermined amount, for example 10 bars.

The fluid is supplied under pressure for a control period, for example 10 seconds, which can be varied according to requirements. No drops of fluid should emerge from the nozzle during the control period.

With good nozzles, that is to say fluidtight nozzles, the laser beam is of uniform brightness, that is, it is not darkened or obscured by drops of fluid. On the other hand, with bad nozzles, it is not of uniform brightness since it is darkened or obscured as often as drops of fluid emerge from the nozzle opening 10. This darkening of the laser beam causes the photodiode to generate signals which are passed to, and automatically evaluated in, the electronic apparatus 16 and are also visually observed on the viewing screen of an oscillograph, for example, of a monitor 18. Thus, the device 16 provides information concerning the behaviour of the injection nozzle.

During another procedure, in which the nozzle is tested for chattering, the nozzle 11 is supplied with fluid at a predetermined delivery rate and at a predetermined pressure.

Its valve member then oscillates or is caused to oscillate. With a good nozzle, the fluid, engine fuel for example, leaving the nozzle 11 emerges in a uniformly chopped manner but, with a bad nozzle, the fluid emerges either in a non-uniformly chopped manner or even in a continuous stream. Thus, with a good nozzle, the photodiode 14 receives a beam of substantially uniform intensity and with a bad nozzle the photodiode 14 receives a beam of fluctuating intensity. Once again, the signals from the photodiode 14 are evaluated automatically in the electronic device 16 which again provides information concerning the behaviour of the nozzle.

Thus, the same apparatus can be used in accordance with the method of the invention for testing injection nozzles for fluid-tightness and chattering. In both cases, amplitude and frequency, or pulse duration, of the signals generated by the photodiode 14 are evaluated electronically in the electronic evaluating device 16.

A monitor 17, which may also be in the form of an oscillograph viewing screen, provides a visual observation of the signals generated by the photodiode 14, for adjustment and control purposes.

WHAT WE CLAIM IS:- 1. A method of testing an injection nozzle which includes the steps of projecting a laser beam past the outlet from the nozzle under test onto a light sensitive sensor which generates electrical signals proportional to the intensity of the laser beam and passing the electrical signals to an electronic evaluating device providing information concerning the behaviour of the nozzle.

2. A method according to claim 1, in which the light sensitive sensor is a photodiode.

3. A method according to claim 1 or claim 2, in which the electrical signals are processed in the electronic evaluating device in an analog manner.

4. A method according to claim 1 or claim 2, in which the electrical signals are processed in the electronic evaluating device in a digital manner.

5. A method according to claim 3 or claim 4, in which the electrical signals processed in the electronic evaluating device are represented as analog signals on a viewing screen.

6. A method according to claim 5, in which the viewing screen forms part of an oscillograph.

7. A method according to any preceding claim, in which the injection nozzle under test is supplied with a quantity of fluid at a predetermined pressure.

8. A method according to any one of claims 1 to 6, in which the injection nozzle under test is supplied with fluid at a pressure slightly lower than the rated opening pressure of the nozzle.

9. A method according to claim 8, in which the injection nozzle under test is supplied with fluid at a pressure which is 10 bars lower than the rated opening pressure of the nozzle.

10. A method according to claim 9, in which the nozzle is supplied with fluid under pressure over a specified control period.

11. A method according to claim 10, in which the specified control period is -10 seconds.

12. A method of testing an injection nozzle for determining its fluid tightness and/or its chattering behaviour, substantially as herein described.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. causes the photodiode to generate signals which are passed to, and automatically evaluated in, the electronic apparatus 16 and are also visually observed on the viewing screen of an oscillograph, for example, of a monitor 18. Thus, the device 16 provides information concerning the behaviour of the injection nozzle. During another procedure, in which the nozzle is tested for chattering, the nozzle 11 is supplied with fluid at a predetermined delivery rate and at a predetermined pressure. Its valve member then oscillates or is caused to oscillate. With a good nozzle, the fluid, engine fuel for example, leaving the nozzle 11 emerges in a uniformly chopped manner but, with a bad nozzle, the fluid emerges either in a non-uniformly chopped manner or even in a continuous stream. Thus, with a good nozzle, the photodiode 14 receives a beam of substantially uniform intensity and with a bad nozzle the photodiode 14 receives a beam of fluctuating intensity. Once again, the signals from the photodiode 14 are evaluated automatically in the electronic device 16 which again provides information concerning the behaviour of the nozzle. Thus, the same apparatus can be used in accordance with the method of the invention for testing injection nozzles for fluid-tightness and chattering. In both cases, amplitude and frequency, or pulse duration, of the signals generated by the photodiode 14 are evaluated electronically in the electronic evaluating device 16. A monitor 17, which may also be in the form of an oscillograph viewing screen, provides a visual observation of the signals generated by the photodiode 14, for adjustment and control purposes. WHAT WE CLAIM IS:-

1. A method of testing an injection nozzle which includes the steps of projecting a laser beam past the outlet from the nozzle under test onto a light sensitive sensor which generates electrical signals proportional to the intensity of the laser beam and passing the electrical signals to an electronic evaluating device providing information concerning the behaviour of the nozzle.