Method and device for detecting the commencement of opening of a nozzle needle

Abstract

A method for detecting the commencement of opening of the nozzle needle of an injector of an injection system. In the detection method, the coil of the solenoid injector has a voltage applied to it which is so low that the armature is moved toward the nozzle needle at such a low speed that the abutment causes a stoppage of the armature movement, without the nozzle needle being opened. In this case, the idle travel is overcome, but no injection process is initiated. The abutment of the armature against the nozzle needle is detected, in the current profile, as the commencement of opening of the nozzle needle.

Claims

1. A method for detecting the commencement of the opening of the nozzle needle of an injector of an injection system, with which an armature is displaced by applying a voltage to a coil, the armature overcomes an idle movement and abuts the nozzle needle, comprising the steps of: applying a voltage to the coil such that the armature is displaced with such a speed against the nozzle needle that the armature displacement is stopped by the abutment without opening the nozzle needle; and detecting the abutment of the armature on the nozzle needle in the current profile as the commencement of the opening of the nozzle needle, the applying and detecting being performed without the nozzle needle of the injector being opened.

2. The method as claimed in claim 1, wherein detecting the abutment of the armature on the nozzle needle comprises the steps of forming a first derivative of the current against time, and associating a minimum thereof with the abutment of the armature on the nozzle needle.

3. The method as claimed in claim 2, wherein applying a voltage comprises the step of applying a voltage of 7 V to the coil, the voltage of 7 V being less than a voltage applied to the coil for opening the needle nozzle.

4. The method as claimed in claim 1, wherein applying a voltage and detecting abutment of the armature on the nozzle needle are performed by a control unit of a motor vehicle.

5. A method for detecting the commencement of the opening of the nozzle needle of an injector of an injection system, the injector including an armature, a nozzle needle and a coil, the injector having idle movement between the armature and the nozzle needle, and the armature is movable by applying a voltage to the coil and abuts the nozzle needle in response to the applied voltage, the method comprising: applying a voltage to the coil such that the armature moves, abuts against the nozzle needle, and is stopped by the abutment without opening the nozzle needle, the voltage applied being less than a voltage to open the nozzle needle; and detecting the abutment of the armature on the nozzle needle in the current profile as the commencement of the opening of the nozzle needle, the applying and detecting being performed without the nozzle needle of the injector being opened.

6. The method of claim 5, wherein detecting the abutment of the armature on the nozzle needle comprises forming a first derivative of the current against time, and associating a minimum of the first derivative of the current against time with the abutment of the armature on the nozzle needle.

7. The method as claimed in claim 5, wherein applying a voltage comprises applying a voltage of 7 V to the coil, the voltage of 7 V being less than a voltage applied to the coil for opening the needle nozzle.

8. The method as claimed in claim 5, wherein applying a voltage and detecting abutment of the armature on the nozzle needle are performed by a motor vehicle control unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:

(2) FIG. 1 includes three diagrams in relation to the voltage, current and injection rate profiles for an applied coil voltage of 7 V and 14 V;

(3) FIG. 2 includes three diagrams in relation to the current profile, the first derivative of the current and the injection rate profile for an applied coil voltage of 7 V and 14 V; and

(4) FIG. 3 includes a diagram that shows the simulation results in relation to the profile of the magnetic force, the armature position and the coil current.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(5) The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

(6) With a conventional solenoid injector with idle movement between the armature and the nozzle needle, the solenoid coil has been subjected once to a voltage of 7 V and once to a voltage of 14 V. In both cases, a displacement of the armature took place until abutment on the nozzle needle of the injector occurred. In both cases therefore, the idle movement was overcome. For the voltage of 7 V, however, no further displacement took place after the abutment and consequently no opening process of the nozzle needle occurred, so that no injection process occurred. By contrast, when the voltage of 14 V was applied, the armature moved further together with the nozzle needle after abutment on the nozzle needle, so that the nozzle needle was opened and an injection process took place.

(7) FIG. 1 shows in the upper diagram the respective voltage profile, wherein the upper curve shows the profile for 14 V and the lower curve shows the profile for 7 V. The current profile for said voltages is shown in the middle diagram. The upper curve corresponds to the current profile for 14 V, whereas the lower curve reproduces the current profile for 7 V. Finally, the lower diagram shows the injection rate profile ROI. When the voltage of 14 V is applied, after about 4 ms an injection process takes place, whereas for 7 V no injection process can be detected.

(8) The current profile against time is again shown in FIG. 2 in the upper diagram. Said diagram therefore corresponds to the middle diagram of FIG. 1. The first derivative of the current against time is shown for both voltages of 7 V and 14 V in the middle diagram of FIG. 2. In this case, the upper curve corresponds to the voltage of 14 V, whereas the lower curve corresponds to the voltage of 7 V. In the upper curve a minimum can be seen at about 4 ms, being marked by a dashed line. Said minimum corresponds to the abutment of the armature on the nozzle needle with subsequent opening of the needle and an injection process, as can be seen from the lower diagram of the injection profile. The curve corresponding to 7 V in the middle diagram has a minimum at about 5 ms. As the injection rate profile shows, no injection process occurs in this case, which means that the displacement of the armature is stopped by the abutment on the nozzle needle.

(9) The minimum of the first derivative of the current for a voltage application of 7 V is associated with the armature contact and thereby with the commencement of the opening of the nozzle needle of the injector.

(10) The operability of the method according to the invention has been demonstrated by simulations, the results of which are shown in FIG. 3. The corresponding voltage, to which the coil is subjected so that the armature overcomes the idle movement but the displacement thereof is stopped with abutment on the nozzle needle, can be determined empirically depending on the conditions. Good results have been obtained with the value of 7 V specified here.

(11) FIG. 3 shows the profile of the magnetic force (N), of the armature position (m) and of the coil current (A). With the example shown here, an idle movement of 40 m is overcome. A further displacement of the armature together with the needle does not then take place. The abutment of the armature on the needle (OPP1) can be seen in the current profile.

(12) The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.