EP1606507A1

EP1606507A1 - Contact device for an injector of a fuel-injection system, in addition to an injector comprising a contact device

Info

Publication number: EP1606507A1
Application number: EP04721158A
Authority: EP
Inventors: Jürgen Dick; Hellmut Freudenberg; Willibald SCHÜRZ
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2003-03-26
Filing date: 2004-03-17
Publication date: 2005-12-21
Also published as: DE10313623A1; WO2004085826A1

Abstract

A common problem in modern common rail injection systems, in particular those with a rapid injection rate, is that undesirable dispersions occur for the quantity of fuel that is to be injected. A fundamental cause is that it is never known at exactly what point the valve needle (3) rests on its valve seat (37) or when the upper section of the valve needle (3) strikes the second stop. The invention thus provides a contact device for an injector (13) of an injection system, said device being used to monitor the position of the valve needle (3) on its valve seat (37) or its second stop on a first housing part (1). The electric contact (31;45) and the current supply (electric line 34) are located outside the fuel-filled high-pressure zone of the injector (13), thus preventing any sealing problems of the injector (13).

Description

description

Contacting device for an injector of an injection system for fuel injection and injector with a contacting device

The invention relates to a contacting device for an injector of an injection system, which can be used for fuel injection into the cylinder of an internal combustion engine, or the injector according to the independent claims 1 and 12. that after the valve needle is lifted from its seat, the nozzle needle opens very quickly, resulting in very steep quantity characteristics. As a result, the amount of fuel to be injected is difficult to calculate, so that statistically undesirable scatter can result for the amounts of fuel actually injected.

The problem described is already known and has been attempted to be solved, for example, by monitoring the seating or lifting of the valve needle from its valve seat with the aid of a seat contact measurement.

In a known contacting device with a seat contact measurement, for example the electrical measuring contact is arranged in the high-pressure area of the injector filled with fuel. The electrical measuring contact detects the pressure drop in the high-pressure system that occurs when the valve needle is lifted from its valve seat. Since the electrical connection cable is also partly led through the high-pressure area of the injector, there are considerable sealing problems with respect to the unpressurized surrounding areas. There is a risk at the lead-through points that an undesired leak can occur in the course of the operating time. In particular high temperatures in the engine area as well as large temperature fluctuations, aggressive force Substances and material problems can lead to not inconsiderable functional risks for the entire injection system within the long service life of the vehicle and thus endanger trouble-free operation in practice. Furthermore, it appears disadvantageous that the known constructions are complex and relatively expensive to manufacture.

The invention has for its object to provide a contacting device for an injector, which is simple and inexpensive to manufacture and ensures reliable functioning of the injector. This object is achieved with the features of the independent claims 1 and 12.

The contacting device according to the invention for an injector or the injector with the contacting device has the advantage over the known solution that no electrical lines or contacts have to be laid in the high-pressure area of the injector. It is considered particularly advantageous that when measuring the movement of the valve needle from its lower valve seat to its upper, second stop, only a simple electrical measurement is carried out, which is carried out, for example, as a current, voltage, resistance, capacitance measurement or the like becomes. The valve needle acts together with its valve seat or the second stop as

Switch contact, so that its electrical function can be easily checked. This simple solution is achieved in particular in that the second housing part is designed to be electrically insulated from its neighboring further housing parts.

The measures listed in the dependent claims provide advantageous further developments and improvements to the contacting device or the injector specified in the independent claims 1 and 12. It is considered to be particularly advantageous that the insulating layer of the second housing part in the region of the separation level Has an interruption. At this point, an electrical contact can be arranged via which the second housing part can advantageously be electrically contacted. This makes it easy to connect the second housing part to a measuring device.

A preferred inexpensive solution is also seen in the fact that the interruption of the insulating layer is arranged outside the lines carrying fuel. As a result, special contact or cable bushings to the high-pressure part of the injector are not required, so that no leaks can occur. Furthermore, this results in a simple and risk-free installation option for the electrical contact.

In order to be able to easily install the electrical contact for contacting the second housing part, a recess is provided in the region of the interruption of the insulating layer in the first housing part. The electrical contact is inserted into this recess. It then advantageously forms a permanent and secure electrically conductive connection with the second housing part.

Furthermore, it is provided to make a further bore on the first housing part, which is preferably guided from above to the electrical contact in the recess. A corresponding electrical line can easily be laid through the bore to the contact, so that the potential on the second housing part can be queried from the outside.

A particularly simple and inexpensive solution also consists in forming the electrical contact, for example with an insulating plate, and then inserting it into the recess in such a way that its contact lug has an insulating effect on the first housing part and produces a permanently conductive connection to the second housing part. Furthermore, it appears to be advantageous to connect the electrical contact to an external measuring device with the aid of an electrical line. The measuring device is designed, for example, to measure a test current or a test voltage, so that it can be determined in a simple manner whether the valve needle of the injector rests on its valve seat, has lifted off it, or is in contact with its second stop when the injection nozzle is fully open.

Before the two housing parts of the injector are assembled, the electrical contact with the preassembled electrical line is simply inserted into the recess or the electrical line is inserted into the further bore. By assembling the two housing parts, the contact lug of the electrical contact is automatically pressed onto the non-insulated location of the second housing part and thus establishes a permanent conductive connection.

In this way, the electrical connection to the measuring device creates an electrical circuit via the electrical line, the electrical contact, the second housing part, the valve needle with its valve seat and back via the ground connection, which is only connected to and / or lifted off Nozzle needle can be influenced by its valve seat.

Another essential aspect of the invention is that by connecting the measuring device to the circuit, the measuring device can easily recognize the fitting or lifting of the valve needle from its valve seat and / or the striking of its second stop. The measuring device is thus able to deliver a seat signal for the valve needle to a control computer, with which the opening duration of the valve needle and thus the amount of fuel to be injected can then be determined more precisely. An embodiment of the invention is shown in the drawing and is explained in more detail in the following description.

FIG. 1 shows a schematic illustration of a cross section through an injector for fuel injection, in which the contacting device according to the invention is arranged,

FIG. 2 shows sections of the injector with a first contacting device according to the invention and

FIG. 3 shows a second exemplary embodiment for an electrical contact.

1 shows a schematic illustration of an injector 13 of a common rail injection system which can be used for fuel injection into an internal combustion engine of a motor vehicle. The injector housing has a first housing part 1, a second housing part 2 located underneath and a third housing part 21 in the lower part of FIG. The first and second housing parts 1, 2 lie flat against one another at a separation plane 7. The first housing part 1 is plate-shaped, with a depression 11 being provided on an upper longitudinal side. The depression 11 has a bottom which is approximately parallel to the

Separation plane 7 runs and extends approximately to the middle of the first housing part 1. The side walls of the depression 11 are conical, so that the diameter of the depression 11 widens toward its opening and merges into a side surface of the first housing part 1.

A valve body 10, which rests in a valve seat 12, is arranged approximately in the middle of the bottom of the depression 11. The valve body 10 is spherical and its diameter extends to just below the upper one

Side surface. In Figure 1, the valve seat 12 is semicircular and receives the valve body 10 in a form-fitting manner. Furthermore, an outlet throttle 4 is arranged in the first housing part 1 and connects the valve seat 12 to a connecting chamber 6. The outlet throttle 4 opens into the valve seat 12 and is sealed off by the valve body 10. On the side of the valve body 10 facing away from the depression 11, the outlet throttle 4 opens approximately at right angles into the connecting chamber 6.

The connecting chamber 6 is designed as an elongated groove, the outlet throttle 4 opening into the middle of the groove.

The groove of the connecting chambers 6 is introduced into a lower side surface of the first housing part 1. At the left end of the Verbindungska mer 6 opens an inlet throttle 5. The connecting chamber 6 is designed such that its right half opens into a control chamber 8 approximately from the start of the outlet throttle 4.

In Figure 1, the second housing part 2 is approximately T-shaped. The control chamber 8 is formed in the middle of the region of the second housing part 2 which runs perpendicular to the first housing part 1. The control chamber 8 receives a movable valve needle 3. The area of the second housing part 2 extending transversely to the control chamber 8 corresponds in length and width approximately to the dimensions of the first housing part 1. Axially parallel to the valve needle 3, the inlet throttle 5 is arranged in one of the two areas of the housing part 2 arranged transversely to the guide area of the control chamber 8, the one end with the

Connection arm 6 and is connected at its second end to an inlet 42 of a fuel line, not shown. The fuel line is connected to a high-pressure accumulator, which holds the fuel under high pressure. The cylindrical inlet throttle 5 runs parallel to the axis of the valve needle 3 and, at its end facing the first housing part 1, merges into a funnel, the widened opening of which points downwards.

The injector 13 has a control device which preferably controls the valve body 10 by means of a piezoelectric actuator 16 and a pressure body 15. These units are arranged in a valve housing 14 of the injector 13. The pressure body 15 is located on the side of the first housing part 1 facing away from the second housing part 2 and has at its lower end an opening which is adapted in shape and scope to the outer periphery of the valve body 10 and which receives the valve body 10.

On the side facing away from the valve body 10, the pressure body 15 is operatively connected to the actuator 16. The actuator 16 causes the valve body 10 to be pressed into the valve seat 12 in a vertical direction of movement with the interposition of the pressure body 15 and to be lifted out of this position. In this way, the outlet throttle 4 located in the middle of the bottom of the depression 11 is sealed.

On the side of the sink 11 there is a drain device (not shown in FIG. 1) for discharging fuel from the sink 11 and for further feeding into a high-pressure system from which the inlet throttle 5 and an injection chamber 17 are fed. The inlet throttle 5 is connected via the inlet 42 to a high-pressure accumulator, not shown in FIG. 1, which provides fuel under high pressure.

The valve needle 3, which is guided in a first bore 43 of the second housing part 2, is shown in a position in which a valve head 18, which is arranged at the lower end of the valve needle 3, is correspondingly shaped Valve seat 37 presses and closes two injection holes 19 which open into a combustion chamber 9 in a sealing manner. A fuel inlet 20 is connected to the inlet throttle 5 and the injection chamber 17 in accordance with FIG.

The injection chamber 17 is designed in the region of the valve head 18 as a valve seat 37. Depending on the position of the valve head 18, the injection chamber 17 is hydraulically connected to the injection holes 19. Depending on the position of the valve head 18, fuel may or may not be injected into the combustion chamber 9. In the control chamber 8 above the valve needle 3, the fuel is under pressure, whereby the valve needle 3 is biased towards the valve seat 37, its first stop.

Depending on the pressure in the control chamber 8, the valve needle 3 moves in the direction of the injection holes 19 to seal them, or alternatively in the direction of the control chamber 8 to inject fuel via the injection holes 19 into the combustion chamber 9 of the internal combustion engine. In the fully opened state, the valve needle 3 rests with its upper end in the region of the connecting chamber 6 on the lower wall surface of the first housing part 1, which forms the second stop.

On the injector 13 shown in FIG. 1, the second housing part 2 was covered with an insulating layer 30, which is preferably applied to its outer wall surfaces and electrically insulates the second housing part 2 from its neighboring housing parts 1, 21. For the

Insulating layer 30 can be any resistance materials that are either applied to the wall surfaces of the second housing part 2 or develop an insulating effect between the adjacent housing parts 1, 21. The third housing part 21 has an axial, third bore 39, so that there is between the valve needle 3 and the inner wall of the third bore 39 cannot form an electrically conductive connection.

No insulating layer 30 is arranged between the valve needle 3 and the second housing part 2, so that there is always an electrical connection between these two components 2, 3. Furthermore, the insulating layer 30 is interrupted at a predetermined point 38. At this point 38, an electrical contact 31 is inserted, which brings about a permanent electrical connection with the second housing part 2. As a predetermined location 38, a location in the area of the separation plane 7 is preferably provided which lies outside the fuel-carrying high-pressure area of the injector 13, so that no sealing problems can arise. The valve needle (also called an actuator) 3 thus forms a closed circuit via the electrical contact 31 with the further housing parts 1, 21 when the valve needle 3 is seated on its valve seat 37. Another closed circuit alternatively also arises when the valve needle 3 has lifted off its valve seat 37 and bears on its second stop on the lower surface of the first housing part 1, since in this case the circuit is closed via the first housing part 1.

To test the two alternative circuits, a further bore 40 is arranged in the first housing part 1 parallel to the central axis of the injector 13 and is led to a recess 32. The recess 32 is wider than the bore 40 and is arranged on the lower side of the first housing part 1 in the region of the separation plane 7. The recess 32 receives the electrical contact 31. The electrical contact 31 has an insulating part 33 which is inserted into the recess 32 in such a way that the contact lug of the electrical contact 31 is electrically insulated from the first housing part 1. On the other hand, when assembling the two housing parts 1, 2, the contact lug becomes against the non-insulated surface of the second housing part 2. pressed so that a permanent electrical connection is created between the contact lug and the second housing part 2. The electrical contact 31 can be connected to an external measuring device 35 via the valve housing 14 by means of an electrical line 34 which is drawn through the further bore 40 up to the electrical contact 31. The measuring device 35 is used to check whether the two circuits described above are alternately open or closed. The measuring device 35 can be designed as a voltage, current, capacitance or resistance meter, which emits corresponding signals to a control computer (not shown in FIG. 1) when the two circuits are opened or closed. The control computer then calculates the injection duration or the amount of fuel to be injected as a function of the received signals.

As can also be seen in FIG. 1, the first circuit is formed by the measuring device 35 via the electrical line 34, the electrical contact 31, the second housing part 2, the valve needle 3, the valve seat 37 and back via the ground connections 36 , closed when the valve needle 3 rests on its (lower) valve seat 37. Alternatively, the first circuit is open and the second circuit is closed, which is formed by the measuring device 35, the electrical line 34, the electrical contact 31, the second housing part 2, the valve needle 3, the first housing part 1 and back via the measurement connections 36, when the valve needle 3 strikes with its upper end in the control chamber 8 against the underside of the first housing part 1 designed as a second stop. In this way, the movement of the valve needle 3 from one stop to the other stop can be monitored precisely and thus the amount of fuel to be injected can be calculated more precisely. FIG. 2 shows a detail and in an enlarged representation of an exemplary embodiment for the arrangement of the electrical contact 31. As described above for FIG. 1, the electrical contact 31 is arranged in the cutout 32, which is on the lower surface of the first housing part 1 in the region the separation level 7 is introduced. The electrical contact 31 is designed to be resilient and, after assembly of the two housing parts 1, 2, in the region of the non-insulated point of the second housing part 2, presses with its resilient contact lug against the upper surface of the second housing part 2 Insulating part 33 in the recess 32. As already explained, the current is supplied via the electrical line 34, which is led through the further bore 40 of the first housing part 1. The insulating layer 30 causes an electrical insulation of the second housing part 2 against the two adjacent housing parts 1, 21 and also against a nozzle clamping nut 41, with which the housing parts 1, 2, 21 are pressed together during assembly. The valve needle 3 slides along the first bore 43, which is preferably drilled centrally through the second housing part 2. The third bore 39 of the third housing part 21 is broader, so that there is an insulating space between the valve needle 3 and the bore 39, which can be filled with fuel.

In an alternative embodiment of the invention it is provided that instead of the resilient electrical contact 31, the electrical line 34 is screwed directly onto the non-insulated point of the second housing part 2, welded on or implemented as a plug connection (FIG. 3). In the latter case, a correspondingly narrower bore 44 can be introduced into the second housing part 2 as an extension to the further bore 40 as a contact socket, into which a commercially available, insulated contact plug 42 can be inserted or screwed in from above. In this case, the recess 32 and the electrical contact 31 with its insulating part 33 would be omitted, thereby reducing the manufacturing costs could be even less. The further structure corresponds to that of FIG. 2. To measure the movement of the valve needle 3, the measuring device 35 is designed using a measuring method known per se. This can be a current, a voltage, a resistance, a capacitance measurement or the like in the circuit. The measured resistance value or the measured capacitance value of the circuit is then preferably used in order to compare the valve needle (3) with the valve seat (37) and / or the valve needle (3) to strike the at least one valve by comparing it with a predetermined, stored value Detect housing part (1).

Claims

claims

1. Contacting device for an injector (13) of an injection system, the injector (13) having at least a first and a second housing part (1, 2) that the two housing parts (1, 2) are connected to one another at a separation level (7) and that the second housing part (2) has a third bore (39), in which a valve needle (3) is arranged so as to be axially displaceable, the second housing part (2) and its at least one adjacent housing part (1, 21) An electrical insulating layer (30) is arranged in the injector (13), which is interrupted at a predetermined location (38) and that an electrical contact (31; 42) is positioned at the predetermined location (38) via which an electrical connection (34 ) between the first and second housing parts (1, 2) can be produced.

2. Contacting device according to claim 1, characterized in that the interruption of the insulating layer (30) is arranged in the region of the separation plane (7).

3. Contacting device according to one of claims 1 or 2, characterized in that the interruption of the insulating layer (30) is arranged outside of lines carrying fuel.

4. Contacting device according to one of claims 1 to 3, characterized in that the first housing part (1) in the region of the interruption of the insulating layer (30) has a recess (32).

5. Contacting device according to one of the preceding claims, characterized in that the first housing part (1) has a further bore (40) which forms an access from the outside to the electrical contact (31; 42).

6. Contacting device according to one of the preceding claims, characterized in that the electrical contact (31) can be inserted into the recess (32) such that its

Contact tab is insulating to the first housing part (1) and conductive to the second housing part (2).

7. Contacting device according to one of the preceding claims, characterized in that in the further bore (40) an electrically insulated line (34) can be inserted, which on the one hand with the electrical contact (31; 42) and on the other hand with an external measuring device (35) is connectable.

8. Contacting device according to one of the preceding claims, characterized in that the electrical contact

(42) is designed as a plug and can be inserted into the further bore (40) together with the electrical line (34).

9. Contacting device according to one of the preceding claims, characterized in that starting from the measuring device (35) via the electrical line (34), the electrical contact (31; 42), the second housing part (2), the valve needle (3rd ) with its valve seat (37) or alternatively via the first housing part (1) and back via a ground connection (36) a closed circuit can be formed.

10. Contacting device according to one of the preceding claims, characterized in that the measuring device (35) is designed to lift the valve needle (3) from its valve seat (37) and / or to strike the valve needle (3) against the at least one housing part ( 1) to be detected by means of a resistance measurement or a capacitance measurement of the circuit, preferably by comparing the measured resistance value or the measured capacitance value with a predetermined value.

11. Contacting device according to one of the preceding claims, characterized in that the electrical line (34) at the non-insulated point of the second housing part (2) is attached by direct screwing, welding or by a plug connection.

12. Injector with a contacting device according to one of claims 1 to 11.