INJECTOR

Abstract

An injector for injecting fuel including an injector housing, a movable nozzle needle with a nozzle needle tip arranged in the injector housing, and a nozzle needle seat for receiving the nozzle needle tip. A contact pairing of the nozzle needle and the nozzle needle seat here represents a mechanical switch that adopts a closed state upon contact of the nozzle needle tip with the nozzle needle seat and an open state upon interruption of the contact. Provision is additionally made that the injector has an input line and an output line for controlling movement of the nozzle needle, the switch has a first connector connected to the input line and a second connector connected to the injector housing, and a resistor connected between the first connector of the switch and the input line.

Claims

1. An injector for injecting fuel comprising: an injector housing; a movable nozzle needle that is arranged in the injector housing and has a nozzle needle tip; and a nozzle needle seat for receiving the nozzle needle tip, wherein a contact pairing of the nozzle needle and the nozzle needle seat represents a mechanical switch that adopts a closed state on a contact of the nozzle needle tip with the nozzle needle seat and an open state on an interruption of the contact; the injector has an input line and an output line for controlling a movement of the nozzle needle; the switch has a first connector that is connected to the input line and a second connector that is connected to the injector housing; and a resistor is connected between the first connector of the switch and the input line, wherein the resistor is a high temperature resistor chip.

2. The injector in accordance with claim 1, wherein a medium power of the high temperature resistor chip is in a range from 0.10 to 0.12 W.

3. The injector in accordance with claim 1, wherein a working temperature range of the high temperature resistor chip comprises −55° C. to +300° C. so that it also remains operable at very high temperature fluctuations.

4. The injector in accordance with claim 1, wherein the high temperature resistor chip has a non-magnetic design and/or does not have any organic elements.

5. The injector in accordance with claim 1, wherein the input line and the output line are connected to an electromagnet, with the electromagnet.

6. The injector in accordance with claim 1, wherein the input line and the output line each represent a contact of a coil that is part of an electromagnet.

7. The injector in accordance with claim 6, wherein the contacts of the coil consist of a corrosion resistant stainless steel.

8. The injector in accordance with claim 1, wherein the high temperature resistor chip is fastened to the input line and/or output line by means of contact adhesive or soldering in an electrically conductive state.

9. The injector in accordance with claim 1, wherein a line running from the high temperature resistor chip to the switch runs in a plastic overmolding of a magnetic coil, with the magnetic coil being configured to set the nozzle needle into motion.

10. The injector in accordance with claim 1, wherein the injector housing is composed of an electrically. conductive material.

11. A device in accordance with claim 1, wherein the injector housing is connected to a ground potential.

12. An internal combustion engine having an injector for injecting fuel, wherein the injector comprises: an injector housing; a movable nozzle needle that is arranged in the injector housing and has a nozzle needle tip; and a nozzle needle seat for receiving the nozzle needle tip, wherein a contact pairing of the nozzle needle and the nozzle needle seat represents a mechanical switch that adopts a closed state on a contact of the nozzle needle tip with the nozzle needle seat and an open state on an interruption of the contact; the injector has an input line and an output line for controlling a movement of the nozzle needle; the switch has a first connector that is connected to the input line and a second connector that is connected to the injector housing; and a resistor is connected between the first connector of the switch and the input line, wherein the resistor is a high temperature resistor chip.

13. A motor vehicle having an internal combustion engine with an injector for injecting fuel, wherein the injector comprises: an injector housing; a movable nozzle needle that is arranged in the injector housing and has a nozzle needle tip; and a nozzle needle seat for receiving the nozzle needle tip, wherein a contact pairing of the nozzle needle and the nozzle needle seat represents a mechanical switch that adopts a closed state on a contact of the nozzle needle tip with the nozzle needle seat and an open state on an interruption of the contact; the injector has an input line and an output line for controlling a movement of the nozzle needle; the switch has a first connector that is connected to the input line and a second connector that is connected to the injector housing; and a resistor is connected between the first connector of the switch and the input line, wherein the resistor is a high temperature resistor chip.

14. The injector in accordance with claim 1, wherein a medium power of the high temperature resistor chip is between 0.11 to 0.12 W in a time period of 500 μs.

15. The injector in accordance with claim 5, wherein the electromagnet effects a raising of the nozzle needle tip from the nozzle needle seat on application of a current conducted over the input line and the output line.

Description

[0026] Further advantages, details, and features of the present invention will become clear with reference to the following description of the Figures. There are shown:

[0027] FIG. 1: a selected one of an injector in accordance with the invention;

[0028] FIG. 2: an enlarged partial view of FIG. 1 with current flows; and

[0029] FIG. 3: a schematic sketch of the injector in accordance with the invention.

[0030] FIG. 1 shows some parts of an injector 1 in accordance with the invention. The input and output lines 4, 5 can be seen there that correspond to the coil contacts of the coil for the electromagnet on an electromagnetic implementation of the injector 1. The magnetic coil is here surrounded by a fuel overmolding 8 at whose lower end a continuing contact toward the seat plate 9 is arranged. The switch 3 formed of the nozzle needle and the nozzle needle seat that is open or closed in dependence on the state of the injector can be seen from there in a schematic representation. It is not shown in the Figure that the end of the switch remote from the seat plate 9 is connected to ground.

[0031] If the switch 3 is in the closed state and if a current flows through the coil, as is, for example, the case at the start of a raising procedure of the needle, a portion of the current flows from the actual circuit of the input and output lines 4, 5 over the resistor R and the switch in the direction of ground potential.

[0032] In accordance with the invention, a high temperature resistor chip is provided in the line between a coil contact and the first connector of the switch 3 to limit the height of the outflowing current and simultaneously to keep it at a detectable amount.

[0033] FIG. 2 shows an enlarged detail of FIG. 1 and is furthermore provided with current flow arrows. It can be recognized that the current flows from the input line into the electromagnet, more exactly into the winding of the coil of the electromagnet, and then flows back over the output line 5 again. A small amount of current is here taken up by the circuit and flows off over the closed switch. The small amount of current is here marked by smaller arrows.

[0034] FIG. 3 shows an embodiment of the injector 1 in accordance with the invention that has an injector housing 2, an input line 4 leading into the injector housing 2, and an output line 5 leading out of the injector housing 2. An actuator 8 that can be an electromagnet, for example, is furthermore provided to control a nozzle needle. The mechanical switch 3 is furthermore also shown there that results from the interaction of the movement of the nozzle needle and of the nozzle needle seat. If the nozzle needle is raised from its seat and if the nozzle is released for injection, the switch 3 is in its open position. In contrast to this, the contact is closed on the closing of the needle and the switch 3 is in its conductive state. A first connector 6 of the switch 3 is here connected to the input line 4 via a resistor R, a high temperature resistor chip in accordance with the invention. The second connector 7 of the switch 3 is electrically connected to the injector housing 2 that is typically to be considered as equivalent to the ground potential 9 in operation.

[0035] The information whether the needle lift switch 3 is closed or open and thus whether the injection takes place or not is detected by the current difference of the input line from the output line.

[0036] On the activation of the injector, a voltage is applied to the input line and the output line 5 that has the result that the nozzle needle is indirectly set into motion via the actuator 8 that can be designed as an electromagnet. The needle rises from its seat and thus opens the contact. Fuel is injected into the combustion space as a result.

[0037] On the use of such an injector, the differential current method (=fault current recognition) can be used for the detection. The current flowing into the injector is compared with the current flowing out in this process. If the switch 3 is closed, a little more current flows into the injector 1 at one of the connectors than over the second connector. This is due to the fact that some of the current flows directly to ground 9 over the switch 3. It can thus very easily be detected whether the switch is closed or not.

[0038] If, in contrast, the current flowing into the injector is identical to the current flowing out of the injector, the switch 3 is open. If both currents differ, a conclusion on a closed switch 3 can be drawn from this. This kind of detection only works, however, when a voltage is applied to the injector 1 since a current flow is required for the detection.