WO2017194260A1

WO2017194260A1 - Fuel injection valve for internal combustion engines

Info

Publication number: WO2017194260A1
Application number: PCT/EP2017/058787
Authority: WO
Inventors: Heinrich Werger
Original assignee: Robert Bosch Gmbh
Priority date: 2016-05-11
Filing date: 2017-04-12
Publication date: 2017-11-16
Also published as: DE102016208055A1

Abstract

The invention relates to a fuel injection valve (1) for internal combustion engines for injecting fuel under high pressure into the combustion chamber of an internal combustion engine. The fuel injection valve has a nozzle body (2) having a nozzle chamber (22) formed therein. A nozzle needle (3) is arranged in a longitudinally movable manner in the nozzle chamber (22), wherein a nozzle needle tip (35) of the nozzle needle (3) interacts with a nozzle needle seat (21) formed on the nozzle body (2) by means of the longitudinal movement and thereby opens and closes at least one injection opening (20). A sleeve (10) is arranged in a longitudinally movable manner on the nozzle needle (3). A pressure chamber (14) is formed between the sleeve (10), the nozzle needle tip (35), and the nozzle needle seat (21). A throttle point (15) formed in the sleeve (10) connects the nozzle chamber (22) to the pressure chamber (14) hydraulically. The sleeve (10) is guided in a longitudinally movable manner on the nozzle needle (3), wherein a closing surface (10a) of the sleeve (10) interacts with the nozzle needle seat (21). When the nozzle needle tip (35) lies against the nozzle needle seat (21), the closing surface (10a) is loaded against the nozzle needle seat (21). A driver (11) is arranged on the nozzle needle (3). During the opening stroke motion of the nozzle needle (3), the driver (11) can be brought into engagement with the sleeve (10) such that the closing surface (10a) lifts off from the nozzle needle seat (21) and thereby opens a gap throttle (16) between the closing surface (10a) and the nozzle needle seat (21). The gap throttle (16) connects the nozzle chamber (22) to the pressure chamber (14) hydraulically.

Description

Description title

Fuel injection valve for internal combustion engines

The invention relates to a fuel injection valve for internal combustion engines, as it is used for fuel injection into a combustion chamber of an internal combustion engine.

State of the art

Fuel injection valves, as they are preferably used for fuel injection into a combustion chamber of an internal combustion engine, are known from the prior art. In injection systems that operate according to the so-called common rail principle, compressed fuel is made available in a rail by means of a high-pressure pump and by means of injectors or

Fuel injection valves injected into the respective combustion chambers of an internal combustion engine. The injection is by means of a pressure chamber in the

Fuel injector arranged nozzle needle controlled, the one

Performs longitudinal movement and thereby opens and closes one or more injection openings, which open into the combustion chamber of the internal combustion engine.

It is known from the published patent application DE 10 2004 060 552 A1 that the injection profile of fuel injection valves can be formed depending on the nozzle needle stroke with regard to optimum combustion through the use of two throttle connections, both in one

Nozzle needle seat close sleeve are formed. This will be a first

Throttle connection used, whose effect permanently over the Nozzle needle stroke remains constant. In addition, a second throttle connection is used, whose effect depends on the stroke of the nozzle needle, so that it is switched on during the opening stroke of the nozzle needle only from a certain stroke of the nozzle needle.

The stroke-dependent throttle effect of the known fuel injection valve is relatively susceptible to manufacturing tolerances within the

Tolerance chain of nozzle body, nozzle needle, sleeve and second

Throttle connection.

Advantages of the invention

The fuel injection valve according to the invention for injecting high-pressure fuel into the combustion chamber of an internal combustion engine, in contrast, has the advantages that it has a robust injection behavior compared with manufacturing tolerances.

Furthermore, by reducing the flow velocity in the region of the nozzle needle seat and, consequently, the formation of steam, the most important wear mechanism, namely cavitation damage in the area of the

Nozzle needle seat and the injection openings, reduced or prevented and thus significantly increases the life.

For this purpose, the fuel injection valve has a nozzle body with a nozzle chamber formed therein. In the nozzle chamber, a nozzle needle is arranged longitudinally displaceable, wherein a nozzle needle tip of the nozzle needle by the longitudinal movement cooperates with a formed on the nozzle body nozzle needle seat and thereby opens at least one injection port and closes. A sleeve is arranged longitudinally displaceable on the nozzle needle. Between the sleeve, the nozzle needle tip and the nozzle needle seat is a pressure chamber formed. A throttle point formed in the sleeve connects the nozzle chamber with the pressure chamber hydraulically. The sleeve is guided longitudinally displaceably on the nozzle needle, wherein a closing surface of the sleeve cooperates with the nozzle needle seat. When planting the nozzle needle tip to the nozzle needle seat, the closing surface is braced against the nozzle needle seat. On the nozzle needle, a driver is arranged. During the opening stroke movement of the nozzle needle, the driver can be brought into engagement with the sleeve, so that the closing surface lifts off from the nozzle needle seat and thereby opens a gap throttle between the closing surface and the nozzle needle seat. The gap choke hydraulically connects the nozzle chamber with the pressure chamber.

By this embodiment, the flow cross section can be greatly increased at the gap throttle during the opening stroke of the nozzle needle from the time of engagement of driver to sleeve. The nozzle needle seat and the injection openings are downstream of the throttle point and the

Cleavage choke arranged. The flow rate of the fuel to the injection openings can thus be throttled so that a vapor formation of the fuel is reduced or even prevented. This also reduces or avoids potential cavitation damage. At the same time, however, injection rate shaping can be achieved with large flow rates at the end of the opening process of the nozzle needle.

In advantageous embodiments, the throttle point has a constant

Flow area on. As a result, an advantageous course of injection is achieved, in particular with small strokes of the nozzle needle.

In an advantageous development, the fuel injection valve is designed so that from an opening stroke hi of the nozzle needle, the sleeve is in a positive engagement with the driver. From strokes greater than or equal to

Opening stroke hi thus has the sleeve on the same axial movement as the nozzle needle. Up to the opening stroke hi, however, is an axial

Relative movement between the voltage applied to the nozzle needle seat sleeve and the nozzle needle before. Thus, from the opening stroke hi a second additional throttle is realized, which has a stroke-dependent flow cross-section. The injection characteristic can be made very flexible and advantageous. By the stroke-dependent throttling of the fuel flow in the direction of the nozzle needle seat, the flow velocity of the fuel in the region of the nozzle needle seat is lowered so far that a vapor formation of the fuel is reduced or even prevented.

Advantageously, until the opening stroke hi the sleeve is braced by a retaining spring against the nozzle needle seat. As a result, the bracing of the sleeve takes place in a cost effective and simple manner. Advantageously, the opening stroke hi of the nozzle needle during the opening stroke, to which the driver is to come into engagement with the sleeve, can be adjusted during assembly of the fuel injection valve. For this purpose, the driver is positioned exactly on the nozzle needle. Any manufacturing tolerances can be compensated during assembly.

In advantageous developments, the sleeve is clamped by the retaining spring against the driver from the opening stroke hi. As a result, in hubs greater than the opening stroke hi the sleeve is virtually fixedly connected to the driver and thus also fixed to the nozzle needle. Sleeve and nozzle needle thus perform the same movement in these states. The flow area of the

Gap throttle thus changes proportionally with the stroke of the nozzle needle.

Due to the tension of the sleeve with the nozzle needle seat or with the driver a defined and fixed position of the sleeve is guaranteed at any time of the lifting movement of the nozzle needle. In advantageous embodiments, the retaining spring is arranged in the nozzle chamber. As a result, the design is space-saving and easy to install.

Preferably, the retaining spring is arranged so that it surrounds the nozzle needle. As a result, a particularly space-saving arrangement of the spring is achieved.

In advantageous embodiments, with a maximum opening stroke hi2 of the nozzle needle, the flow cross section of the gap throttle is a multiple of the flow cross section of the throttle point. This can be a very good one

Injection characteristic of the fuel injection valve can be achieved. In particular, both very small and very large injection quantities can be realized without simultaneously causing cavitation damage.

In advantageous embodiments, the nozzle needle seat has a conical shape. Thus, on the one hand, a good sealing effect is achieved when the nozzle needle and the closing surface on the nozzle needle seat abut, on the other hand, when the closing surface is lifted, an advantageous flow geometry results through the gap throttle. The corresponding contact surface on the sleeve, so the

Closing surface, preferably with a slightly different

Opening angle of about ± 0.5 ° designed so that when plant without

Force a circumferential sealing edge between sleeve or closing surface and nozzle needle seat results.

In advantageous embodiments, the driver is arranged in a groove of the nozzle needle. In a simple way, the driver is thus very stable connected to the nozzle needle.

In advantageous developments, the driver has a conical shape. This allows the positive engagement between the driver and the sleeve as a kind of conical compression bandage are performed, whereby relatively high forces can be transmitted.

drawing

Fig. 1 shows a longitudinal section through an inventive

Fuel injection valve, with only the essential areas are shown schematically.

description

Fig. 1 shows schematically a fuel injection valve 1 according to the invention in longitudinal section. The fuel insp ritz valve 1 has a nozzle body 2 formed in a nozzle chamber 22 in which a piston-shaped nozzle needle 3 is arranged longitudinally displaceable. The nozzle needle 3 acts on her the

Combustion chamber facing the end of the nozzle needle tip 35, together with a formed on the nozzle body 2 nozzle needle 21 and can thereby open or close one or more injection openings 20 in the nozzle body 2, can be injected via the fuel into the combustion chamber of an internal combustion engine, not shown. The nozzle chamber 22 is connected via a formed in the nozzle body 2 high-pressure passage 23 with a high-pressure fuel source, not shown, usually a common rail, which provides fuel at high pressure available.

At the combustion chamber opposite end of the nozzle needle 3 is a

Control chamber 6 is formed, on the pressure of the opening and

Closing movement of the nozzle needle 3 is controlled in such a way that at pressure reduction in the control chamber 6, the nozzle needle 3 lifts off from the nozzle needle seat 21 and so the injection ports 20 releases and pressure increase in the control chamber 6, the nozzle needle 3 is pressed against the nozzle needle seat 21 and the injection openings 20 closes. The pressure change of the control chamber 6 is effected by a formed in a valve plate 4 control bore 40, via which, under the control of a control valve, not shown, under high pressure fuel supply or can be removed.

The control chamber 6 is bounded radially by a control chamber sleeve 5, and axially through the valve plate 4 and the nozzle needle 3. The control chamber sleeve 5 continues to perform the longitudinal movement of the nozzle needle 3. The control chamber sleeve 5 is stretched by a nozzle spring 17 against the valve plate 4. The nozzle spring 17 continues to cooperate with a shoulder 30 of the nozzle needle 3; As a result, the nozzle needle 3 is pressed by the nozzle spring 17 against the nozzle needle seat 21.

In the combustion chamber near area of the nozzle chamber 22, a throttle assembly is arranged. The throttle assembly comprises a sleeve 10, a driver 11 and a retaining spring 12. The driver 11 is fixedly arranged on the nozzle needle 3 and the nozzle needle tip 35; the driver 11 can also be designed in one piece with the nozzle needle 3. Depending on the stroke of the nozzle needle 3, the driver comes into positive engagement with the sleeve 10. This intervention takes place in the opening direction of the nozzle needle 3, ie in the illustration of Fig.l upwards, from an opening stroke hi 13. The sleeve 10 is longitudinally displaceable arranged on the nozzle needle 3, forms with this until the opening stroke hi 13 so a kind of axial slide bearing.

The retaining spring 12 is arranged radially surrounding the nozzle needle 3. The

Retaining spring 12 is supported on a shoulder 31 of the nozzle needle 3 and biases the sleeve 10 against the nozzle needle seat 21 so that a closing surface 10a formed on the sleeve 10 cooperates with the nozzle needle seat 21. If the stroke of the nozzle needle 3 is greater than or equal to the opening stroke hi 13, then the retaining spring 12 biases the sleeve 10 against the driver 11, since from this stroke the positive engagement between the driver 11 and the sleeve 10 is formed, for example via conical contact surfaces from driver 11 and sleeve 10. If the stroke of the nozzle needle 3 is greater than the opening stroke hi 13, then the closing surface 10a and thus the sleeve 10 is lifted from the nozzle needle seat 21.

Between the sleeve 10, the nozzle needle tip 35 and the nozzle needle seat 21, a pressure chamber 14 is formed. The pressure chamber 14 is hydraulically connected by a formed in the sleeve 10 throttle body 15 with the nozzle chamber 22. The throttle point 15 is preferably one or more radial bores in the sleeve 10. If the closing surface 10a is lifted from the nozzle needle seat 21, then a stroke-variable gap throttle 16 is formed between the closing surface 10a and the nozzle needle seat 21, which also the nozzle chamber 22 with the pressure chamber 14th connects hydraulically.

When the nozzle needle 3 is open, a further throttle is formed between the nozzle needle tip 35 and the nozzle needle seat 21, the ring throttle 17. However, this plays only a minor role for the injection characteristics of the fuel injection valve 1, since their flow cross-section even at small strokes of the nozzle needle 3 is greater than those of Throttle 15, gap throttle 16 and injection ports 20 is.

The operation of the fuel injection valve 1 is as follows.

If the pressure in the control chamber 6 is lowered by the control valve, the nozzle needle 3 starts its opening stroke movement, lifts off the nozzle needle seat 21 and releases the injection openings 20; the injection process of fuel into the combustion chamber of the internal combustion engine begins. Up to an opening stroke hi 13 of the nozzle needle 3, the sleeve 10 is pressed by the biasing force of the nozzle spring 17 against the nozzle needle seat 21. The pressure in the pressure chamber 14, ie between the throttle point 15 and the nozzle needle seat 12 or the annular throttle 17 is thus lowered immediately after the opening of the nozzle needle 3. Of the Inflow cross section to the annular throttle 17 remains constant, namely defined by the flow cross section of the throttle point 15 until the opening stroke hi 13 of the nozzle needle 3 is exceeded, ie until the driver 11 lifts off the nozzle needle seat 21 and thus additionally releases the variable stroke gap throttle 16. Now, the pressure in the pressure chamber 14 following a function changes, which is defined by the steadily increasing inflow cross section into the pressure chamber 14 through the two throttles throttle 15 and gap throttle 16.

Before the beginning of the closing movement at the end of the injection process, the sleeve 10 is fixed by the driver 11 and the retaining spring 12; between the

Closing surface 10a and the nozzle needle seat 21 is the open gap throttle 16. The gap throttle 16 has a maximum opening stroke hi2 18 compared to the throttle point 15 comparatively large flow rate. Flow cross-section on. In this position, more fuel flows from the nozzle chamber 22 via the gap throttle 16 into the pressure chamber 14 than via the throttle point 15.

The closing movement of the nozzle needle 3 is initiated by the control valve increases the pressure in the control chamber 6. Due to the resulting resulting hydraulic force, the nozzle needle 3 then moves in the direction of the nozzle needle seat 21. This reduces again the flow cross section through the gap throttle 16. Until the opening stroke hi 13 of the driver 11 is in engagement with the sleeve 10. During the opening stroke hi 13, it comes to contact between the closing surface 10a and the nozzle needle seat 21. The gap throttle 16 is thereby closed, so that only the flow cross section through the throttle body 15 remains. At the same time the engagement between the driver 11 and sleeve 10 is released, so that the sleeve 10 is clamped between the nozzle needle seat 21 and the retaining spring 12. At the end of the closing movement, the nozzle needle 3 with her

Nozzle needle tip 35 is pressed against the nozzle needle seat 21 and thus closes the injection openings 20 again. There is no more fuel in the

Combustion chamber. According to the arrangements of the throttle body 15 and the

Gap throttle 16 adjacent to the nozzle needle seat 21, upstream of the

Injection openings 20. There is in the pressure chamber 14 when closed

Nozzle needle 3, the system pressure, so the pressure of the nozzle chamber 22, and is sealed from the nozzle needle tip 35 to the combustion chamber. The full one

System pressure is in opening and closing the nozzle needle 3 in

Speed implemented. This high speed in the area of

Pressure chamber 14 causes a decrease in the local absolute pressure below the vapor pressure in this area. This leads to vapor formation of the

Fuel, which subsequently condenses in areas of higher pressures (or lower local velocities) and causes cavitation damage. These cavitation damages are usually life-time specific for fuel injection valves 1 or nozzle body 2.

Immediately after the start of the nozzle needle opening, the pressure in the pressure chamber 14 drops proportionally to the flow or inflow cross section at the throttle point 15 or to the outflow cross section through the injection openings 20. The

Gap throttle 16 is still closed in this state. Upon further opening of the nozzle needle 3, the gap throttle 16 is now opened. First, however, the summed inflow cross section through throttle point 15 and gap throttle 16 is still lower than the outflow cross section through the injection openings 20. By the stroke-dependent throttling of the inflow to the injection openings 20, the flow velocity in the pressure chamber 14, in particular in the region of the nozzle needle seat 21, so far lowered, that the formation of vapor of the fuel is reduced or prevented. Cavitation damage is avoided and the life of the nozzle body 2, nozzle needle 3, etc. increased.

In summary, the illustrated embodiment describes a variable stroke gap throttle 16 between closing surface 10a and nozzle needle seat 21, which has the following ranges: Area 1: Opening stroke of the nozzle needle 3 from its attachment to the nozzle needle seat 21 to a defined opening stroke hi 13: the sleeve 10 is with its closing surface 10a in contact with the nozzle needle seat 21. The sleeve 10 is clamped by the retaining spring 12 with the nozzle needle seat 21. There is no fuel flow through the gap throttle 16 instead.

Range 2: Opening stroke of the nozzle needle 3 from the opening stroke hi 13 to its maximum opening stroke hi2 18: the gap of the gap throttle 16 is opened and thus defines the flow cross-section through the gap throttle 16, which becomes larger with increasing stroke. The retaining spring 12 clamps the sleeve 10 against the driver 11. Fuel flows through the gap throttle 16th

To both areas a constant second throttle function is connected in parallel, namely that of the throttle body 15, which hi the strokes of the nozzle needle 3, which are smaller than the opening stroke 13, an idling of the pressure chamber 14 is prevented.

Claims

claims

1. Fuel injection valve (1) for internal combustion engines for injection of fuel under high pressure with a nozzle body (2) formed in the nozzle chamber (22) in which a nozzle needle (3) is arranged longitudinally displaceable, wherein a nozzle needle tip (35) of the nozzle needle (3 ) cooperates by the longitudinal movement with a on the nozzle body (2) formed nozzle needle seat (21) and thereby at least one injection port (20) opens and closes, wherein a sleeve (10) on the nozzle needle (3) is longitudinally displaceable, wherein between the sleeve (10), the nozzle needle tip (35) and the nozzle needle seat (21) a pressure chamber (14) is formed, wherein in the sleeve (10) formed throttle body (15) the nozzle chamber (22) with the

Pressure chamber (14) connects hydraulically, characterized in that the sleeve (10) on the nozzle needle (3) is guided longitudinally displaceable, wherein a closing surface (10 a) of the sleeve (10) with the nozzle needle seat (21)

cooperates, wherein at investment of the nozzle needle tip (35) to the

Nozzle needle seat (21) the closing surface (10a) is clamped against the nozzle needle seat (21), wherein on the nozzle needle (3) has a driver (11) is arranged, and the driver (11) in the opening stroke of the nozzle needle (3) with the sleeve (10) is engageable so that the closing surface (10a) lifts from the nozzle needle seat (21) and thereby opens a gap throttle (16) between the closing surface (10a) and the nozzle needle seat (21)

Gap throttle (16) hydraulically connects the nozzle chamber (22) with the pressure chamber (14).

2. Fuel injection valve (1) according to claim 1, characterized in that the throttle point (15) has a constant flow cross-section.

3. Fuel injection valve (1) according to claim 1 or 2, characterized

in that, starting from an opening stroke hi (13) of the nozzle needle (3), the sleeve (10) is in positive engagement with the driver (11).

4. Fuel injection valve (1) according to claim 3, characterized in that up to the opening stroke hi (13), the sleeve (10) by a retaining spring (12) against the nozzle needle seat (21) is clamped.

5. Fuel injection valve (1) according to claim 4, characterized in that from the opening stroke hi (13), the sleeve (10) of the retaining spring (12) is braced against the driver (11).

6. Fuel injection valve (1) according to claim 4 or 5, characterized

characterized in that the retaining spring (12) in the nozzle chamber (22) is arranged.

7. Fuel injection valve (1) according to one of the preceding claims, characterized in that at a maximum opening stroke hi2 (18) of the nozzle needle (3), the flow cross section of the gap throttle (16) is a multiple of the flow cross section of the throttle point (15).

8. Fuel injection valve (1) according to one of the preceding claims, characterized in that the nozzle needle seat (21) has a conical shape.

9. Fuel injection valve (1) according to one of the preceding claims, characterized in that the driver (11) is arranged in a groove of the nozzle needle (3).

10. Fuel injection valve (1) according to one of the preceding claims, characterized in that the driver (11) has a conical shape.