WO1999018349A1

WO1999018349A1 - Directly controlled injection valve, especially a fuel injection valve

Info

Publication number: WO1999018349A1
Application number: PCT/EP1998/005940
Authority: WO
Inventors: Martin DÜSTERHÖFT; Gunter GÜRICH; Hermann Josef Laumen; Karl Joachim SCHMÜCKER
Original assignee: Fev Motorentechnik Gmbh & Co. Kommanditgesellschaft
Priority date: 1997-10-02
Filing date: 1998-09-18
Publication date: 1999-04-15
Also published as: DE19881449D2; JP2001520720A; DE29717649U1

Abstract

The invention relates to an injection valve, especially a fuel injection valve, comprising a housing (2) wherein a pressure chamber (3) is located. A supply line (9) for the liquid to be injected under pressure opens into this pressure chamber, said supply line (9) being connected to a liquid supply (10). The pressure chamber (3) also has at least one outlet (7) which is configured as an injection nozzle. A valve needle (5) which is connected to a piston (4) and which is guided in such a way that it can move against the force of a return spring (6) is also arranged in the pressure chamber (3). Said valve needle closes the outlet (7) when the pressure chamber is pressureless. The inventive injection valve also has control valve (13) which is located in the line (9) for the liquid, said control valve being relieved of pressure and being connected to the actuating drive (14).

Description

Name: Directly controlled injection valve, especially fuel injection valve

description

In piston internal combustion engines with fuel injection in the so-called common rail technology, the fuel to be injected is kept constant under a predetermined pressure by means of a pump in an upstream pressure system. The injection valves of the individual cylinders are directly connected to this pressure system, so that when an injection valve is opened, the fuel under pressure can be injected into the cylinder practically without delay from the pressure system. Up to now, the injection valves have been controlled via a servo valve. Since a servo valve only switches a partial flow, it can be dimensioned very small, which results in very short switching times. The fuel flow to be injected is then switched by the valve needle, which is controlled by the servo circuit. The disadvantage of this system is that the dynamic behavior of the injection valve is determined less by the fast servo valve than by the dynamic behavior of the servo circuit as a whole, which is generally slower than the servo valve.

The dynamics of the injection valve can be significantly improved if the fuel flow to be injected is switched with a valve connected to an actuator. For direct control of the injection, it has been proposed to actuate the valve needle directly, for example with a piezoelectric actuator (DE-A-36 21 541; Rumphorst, "A New Electronic High-Pressure Injection System for Diesel Engines", MTZ 56, Haft 3, 1995) . The disadvantage of this proposed solution is that the large pressure-loaded areas on the valve needle at the high injection pressure mean that a very large actuator with corresponding power reserves is required, which is not only expensive but in turn sluggish and which requires high electrical energy to switch in the case of the usually electrically actuated actuators.

The invention has for its object to provide an injection valve which enables a direct switching of the fuel flow to be injected, but which, on the other hand, enables the use of actuators, in particular electric actuators, which allow operation with a representable amount of energy.

This object is achieved by an injection valve, in particular a fuel injection valve, with a housing in which a pressure chamber is arranged, into which a supply line for the liquid to be injected under pressure opens and which has at least one outlet opening designed as an injection nozzle a valve needle connected to a piston and displaceably guided against the force of a return spring is also arranged, which closes the outlet opening when the pressure chamber is depressurized, and with a pressure-relieved control valve arranged in the supply line for the liquid and connected to an actuator. This arrangement has the advantage that the fuel flow to be injected can be switched directly, ie as a full flow, via the control valve. If the control valve is opened, the pressure chamber is directly connected to the pressurized liquid supply, in motor vehicles with the common rail, the high fuel pressure against the force of the return spring lifting the valve needle via the piston, so that the fuel flows through the as an injection nozzle trained outlet opening can emerge again from the pressure chamber. If the control valve is closed, the pressure chamber is depressurized so that the return spring can push the valve needle back into the closed position. It is important here that the control valve is designed as a pressure-relieved valve, so that despite the fact that the full current, which is under high pressure, is switched directly via the control valve, only small actuating forces are released via the pressure relief of the valve itself are to be applied. The control valve can either be designed as a slide valve or as a seat valve. In the simplest embodiment, the control valve can be designed as a 2/2-way valve. However, it is particularly advantageous if the control valve is designed as a 3/2-way valve which, depending on the control position, connects the feed line to the high-pressure side or to the low-pressure side of the liquid supply. As a result, the pressure chamber is connected to the low pressure in the closed position of the valve needle, so that the pressure chamber is quickly relieved of pressure and thus a quick closing of the valve needle is possible and post-injection is avoided.

In a particularly advantageous embodiment of the invention, it is provided that the control valve has an overflow chamber which is connected to the pressure chamber via a nozzle feed line and in which a slide body which is connected to the actuator is movably guided to and fro, which in one end position has the feed line blocks against the overflow space and releases in the other end position and that the feed line opens into an annular space which is delimited at a distance from the slide body by a piston body connected to it and that the pressure-effective area of the slide body and piston body is the same, at least almost the same. This configuration avoids pressure-loaded surfaces which, when pressurized by the liquid flow to be switched, could cause an externally effective force. By assigning an additional piston body to the slide body, a force equilibrium of the pressurized surfaces is brought about, so that only the actuating forces have to be applied for the movement of the slide body, both for the movement into the open position and for the return movement and the locked position are practically determined only by the flow, mass and friction forces to be overcome. The arrangement of an additional piston body for the slide body can be used both for the design of the control valve as a slide valve and for the design of the control valve as a seat valve. valve are provided. In the case of a slide valve, the slide body itself is designed as a piston, so that the requirement can be met here via the same piston diameter. When designed as a seat valve, these requirements can be met in that the sealing edge of the valve seat has the same diameter as the piston, so that the effective pressure-loaded areas are very small.

In the design of the control valve as a 3/2-way valve, it is provided according to the invention that a discharge line is assigned to the overflow space on the side facing away from the mouth of the supply line, which is connected to the nozzle supply line in the blocking position of the slide body. This ensures that when the control valve is closed, the amount of liquid in the pressure chamber no longer has to be displaced through the outlet opening by the piston connected to the valve needle, but can flow out via the drain line immediately after the control valve is closed. This ensures that the restoring force of the return spring allows the valve needle to be moved into the closed position very quickly and without injection.

In an expedient embodiment of the invention it is provided that a flow restrictor is arranged in the drain line. During the switching process, i.e. H. during the time in which the slide body is moved from its blocking position into the open position, the supply line connected to the high pressure is connected via the overflow space to the discharge line, which in turn is connected to the low pressure, so that here direct discharge of high pressure liquid is possible. The arrangement of a flow restrictor in the drain line results in a delay in the liquid outflow and a largely avoidance of a disturbing pressure drop.

In an advantageous embodiment of the invention, it is provided that the control valve with its actuator in an axial direction device behind the pressure chamber is assigned to the housing. This arrangement ensures that the line lengths between the outlet opening on the one hand and the control valve on the other hand are reduced to a minimum, so that dead times are practically avoided here.

An electromagnetic, magnetostrictive or even a piezoelectric actuator can be used as the actuator, since these actuators have a small space requirement and can accordingly also be integrated into the housing of the control valve. It is expedient here if the actuator is hydraulically operatively connected to the slide body. This offers the possibility of producing relatively large travel ranges on the slide body side with small travel ranges on the actuator side.

The invention is explained in more detail with reference to schematic drawings of exemplary embodiments. Show it:

Fig. 1 in the form of a flow diagram with an arrangement

2/2 way valve,

2 in the form of a flow diagram an arrangement with a 3/2-way valve,

3 shows an injection valve in longitudinal section,

4 is an enlarged view of the valve area X in Fig. 3,

Fig. 5 is an enlarged view of the valve area X in Fig. 3 for another. Embodiment.

The schematic illustration in FIG. 1 shows an injection valve 1 with a housing 2, which has a pressure chamber 3, in which a valve needle 5 connected to a piston 4 counteracts the force of a return spring 6 moved back and forth i-st.

The pressure chamber 3 has at least one nozzle opening 7 forming the injection nozzle, which can be closed by the tip 8 of the valve needle 5 via the return spring 6.

A nozzle feed line 9.1 for the liquid to be injected opens into the pressure chamber 3 and is connected to a pressure-relieved control valve 13 which is connected to a liquid supply 10 via a feed line 9. The liquid supply 10 is essentially formed by a pressure accumulator 11 and a high-pressure pump 12, the high-pressure pump 12 in the pressure accumulator 11 keeping the liquid constant at a predetermined admission pressure.

The control valve 13 can be actuated via an actuator 14. In the exemplary embodiment shown here, the control valve 13 is designed as a 2/2-way valve.

The space 15 of the housing 2 facing away from the nozzle needle 5 is connected via a return line 16 to the low-pressure side 17 of the liquid supply, so that leakage liquid quantities escaping from the pressure space 3 can flow into the space 15.

In the position of the control valve 13 shown in FIG. 1, the pressure chamber 3 is depressurized, so that the force of the return spring 6 presses the valve needle 5 with its tip 8 onto its seat and closes the nozzle opening 7.

If the control valve 13 is switched, the pressure chamber 3 is connected directly to the pressure accumulator 11, so that the piston 4 is raised against the force of the return spring 6 by the liquid pressure and the nozzle opening 7 is released, so that a for the duration of the opening appropriate amount of liquid injected into the space to be supplied, for example in the cylinder of a piston internal combustion engine becomes. As soon as the control valve 13 is moved back into the closed position, the liquid pressure in the pressure chamber 3 drops and the tip of the valve needle 5 closes the opening 7 again.

The circuit diagram acc. FIG. 2 shows the system described with reference to FIG. 1 with a control valve 13 designed as a 3/2-way valve. The structure otherwise corresponds to the structure according to FIG. Fig. 1, so that the same reference numerals are given for the same components. The only difference is that the pressure chamber 3 is connected to the low-pressure side 17 of the liquid supply 10 via a return line 16.1. If the control valve 13 is switched, then the return line 16.1 is closed and, as previously described, the supply line 9 is connected to the pressure accumulator 11 so that the injection process can take place. If the control valve 13 is then switched back, the connection shown in FIG. 2 between the pressure chamber 3 via the inlet line 9 and the outlet line 16.1 with the low-pressure side 17 is established, so that in this way the pressure chamber 3 is virtually depressurized with the switching process and so the valve needle 5 can close faster and post-spraying or dripping is avoided.

In order to be able to take full advantage of the advantages offered by direct switching of the liquid stream, it is expedient if the length of the feed line 9.1 between the control valve 13 and the pressure chamber 3 is as short as possible. 3 shows an exemplary embodiment of a fuel injection valve with an integrated control valve. The control valve is designed as a 2/2-way valve, so that in terms of structure and function according to the circuit diagram. Fig. 1 can be referenced. Reference numerals used in Fig. 1 are adopted for identical components.

The structure of the injection valve itself corresponds to the schematic representation according to FIG. Fig. 1, so that for the same Components here are given the same reference numerals.

The valve needle 5 provided with the piston 4, which passes through the pressure chamber 3, is guided axially displaceably in the housing 2. The valve needle 5 is held in the closed position by the force of the return spring 6. The supply line 9.1 opens into the pressure chamber 3.

In the exemplary embodiment shown here, the control valve 13 is integrated into the injection valve and is assigned to the housing 2 in the axial direction, in the flow direction in front of the pressure chamber 3. Details of the structure are explained in more detail below with the aid of an enlarged illustration in FIG. 4.

The control valve 13 essentially consists of an overflow chamber 18 which is connected to the pressure chamber 3 via the nozzle feed line 9.1 and in which a slide body 19 is movably guided to and fro, which is connected to the actuator 14.

The supply line 11, which is connected to the pressure accumulator 11 (not shown here), opens into the overflow space 18 at one end. The slide body is now designed such that, in one end position, as shown here, it blocks the supply line 9 with respect to the overflow space 18 and releases in the other end position as soon as the slide body is moved into the other end position via the actuator 14 and thus the direct connection between the feed line 9 and the nozzle feed line 9.1 is established and the injection process can thus take place. If the actuator 14 is deactivated, then the slide body 19 is pushed back into its locked position by means of a return spring 21.

Since the slide body 19 is exposed to the full liquid pressure via the feed line 9, an annular space 22 is provided for pressure relief, which is at a distance from the slide body. is limited by a piston body 23 connected to it. The arrangement here is such that the pressure-effective surfaces of the slide body 19 on the one hand and the piston body 23 on the other hand are the same, or at least almost the same. By this measure, a pressure relief of the slide body is effected, so that the liquid pressure applied via the pressure accumulator 11 has no or practically no force effect on the slide body in the opening direction or in the closing direction, so that the force of the actuator 14 on the one hand and for moving the slide body into the open position the force of the return spring 21 is sufficient for the return movement. The injection valve can be designed as a slide valve or as a seat valve.

In the exemplary embodiment shown here, a piezo-electric actuator is provided as the actuator 14, the end face 24 of which is closed off by a membrane 25 which delimits a pressure chamber 26. The pressure chamber 26 is connected via a liquid line 27 to the piston 23 on the slide body 19, so that when the actuator is activated and the length change associated therewith, liquid is pressed out of the pressure chamber 23 via the line 27, which then pushes the slide body 19 moves to its open position. Leakage lines 28 ensure that the amount of liquid required for displacement of the slide body 19 is always balanced in the pressure chamber 26.

In the enlarged representation acc. Fig. 4 shows details for the control valve 13 as a 2/2-way seat valve. As the illustration shows, the overflow chamber 18 has a seat 18.1 at its end positions that define the closed position. The slide body 19 has a correspondingly assigned seat 19.1. The arrangement is now such that the inner surface of the seat surface 18.1 also delimits the guides 29 for the slide body, so that the piston 23 delimiting the annular space 22 also has the same diameter as the inner edge of the seat surfaces. This ensures that in the The closed position shown here, via the high pressure which is present in the annular space via the feed line 9, acts on both the slide body 19 in the opening direction and the piston 23 in the closing direction and thus brings about the desired pressure relief and thus the force of the return spring 21 is sufficient to to keep the slide body 19 in the closed position or to return it to the closed position. The piezoelectric actuator enables a variable valve lift and thus a variable opening cross section, as a result of which the flow and thus the injection rate can be influenced.

In Fig. 5, the design of the control valve as a 3/2-way seat valve is also shown on a larger scale. Since the basic structure corresponds to the structure described with reference to FIG. 4, reference can again be made to the previous description. The only difference is that a further annular space 30 is assigned to the slide body 19 on the side facing away from the annular space 22, into which the return line 16.1 opens. This ensures that, in the illustrated blocking position, the pressure chamber 3 is connected via the nozzle feed line 9.1 and the overflow chamber 18 to the return line 16.1 and thus to the low pressure side 17 of the liquid supply 10. If the actuator moves the slide body 19 into its other end position, then the return line 16.1 is closed off from the overflow chamber 18, so that the liquid can only flow into the pressure chamber 3 via the direct connection between the feed line 9 and the nozzle feed line 9.1.

Since a direct flow connection between the high-pressure supply line 9 and the return line 16.1 connected to the low-pressure side 17 is now established for a short time during the switching process, and because of the pressure drop, a liquid drain with pressure drop would also take place here briefly, is expedient in the drain line 16.1 a throttle 31 provided hen so that a "short circuit" between the high pressure side and the low pressure side of the system is avoided.

3, 4 and 5 can be seen, the control valve 13 can also be structurally integrated in a simple manner into the injection valve, so that there is a narrow injection valve with short flow paths between the pressure chamber 3 and the valve itself.

Claims

Expectations

1. Injection valve, in particular fuel injection valve, with a housing (2) in which a pressure chamber (3) is arranged, into which a supply line (9) connected to a liquid supply (10) for the liquid to be injected under pressure opens and the at least one as Injection nozzle formed outlet opening (7), in which a valve needle connected to a piston (4) and displaceably guided against the force of a return spring (6)

(5) is arranged, which closes the outlet opening (7) when the pressure chamber (3) is depressurized and with a pressure-relieved control valve (13) arranged in the feed line (9) for the liquid, which is connected to an actuator (14).

2. Injection valve according to claim 1, characterized in that the control valve (13) is designed as a slide valve.

3. Injection valve according to claim 1, characterized in that the control valve is designed as a seat valve.

4. Injection valve according to one of claims 1 to 3, characterized in that the control valve (13) is designed as a 2/2-way valve.

5. Injector according to one of claims 1 to 3, characterized in that the control valve (13) is designed as a 3/2-way valve that the feed line (9) depending on the control position with the high pressure side (11) or with the low pressure side

(17) the liquid supply (10) is connected.

6. Injection valve according to one of claims 1 to 5, characterized in that the control valve (13) has an overflow chamber (18) which via a nozzle feed line (9.1) with the

Pressure chamber (3) is connected and in which a slide body (19) connected to the actuator (14) is movably guided back and forth, which is in one end position the feed line (9) blocks from the overflow space (18) and in the other end position the feed line (9) releases the feed line (9) into an annular space (22) which is at a distance from the slide body (19) by one with it connected piston body (23) is limited and that the pressure-effective area of slide body (19) and piston body (23) is the same, at least almost the same.

7. Injection valve according to one of claims 1 to 6, characterized in that the overflow space (18) on the side facing away from the confluence of the feed line (9) is assigned a discharge line (16, 1) which, in the locked position of the slide body (19) the nozzle feed line (9.1) is connected.

8. Injection valve according to one of claims 1 to 7, characterized in that a flow restrictor (31) is arranged in the return line (16).

9. Injection valve according to one of claims 1 to 8, characterized in that the control valve (13) with its actuator (14) in the axial direction, in the flow direction before the pressure chamber (3), the housing (2) is assigned.

10. Injection valve according to one of claims 1 to 9, characterized in that the actuator (14) is formed by an electromagnetic actuator.

11. Injection valve according to one of claims 1 to 9, characterized in that the actuator (14) is formed by a magnetostrictive actuator.

12. Injection valve according to one of claims 1 to 9, characterized in that the actuator (14) is formed by a piezoelectric actuator.

13. Injection valve according to one of claims 1 to 12, characterized in that the actuator (14) is hydraulically operatively connected to the slide body (19).