EP1598551B1 - Fuel injection device - Google Patents

Description

The invention relates to a device for injecting fuel into a combustion chamber of an internal combustion engine, with a fuel injector which can be acted upon by a high-pressure source with high-pressure fuel and actuated via a metering valve, through which the pressure in an injection valve member control chamber is controlled so that a Injector member for injecting fuel opens and closes.

State of the art

From the German patent application DE 102 94 15 A1 a device for injecting fuel into a combustion chamber of an internal combustion engine having a fuel injector is known, which can be acted upon by a high-pressure shaft with high-pressure fuel and actuated via a metering valve. An injection valve member, which is acted upon in the closing direction by a closing force, is enclosed by a pressure chamber. To dampen the opening speed of the injection valve member, such as a nozzle needle, without interfering with rapid closing of the injection valve member the injection valve member associated with a independently movable damping element which defines a damping space and at least one overflow channel for connecting the damping chamber with a further hydraulic space. The damping element may be formed as a damping piston, which is surrounded by the other hydraulic space.

Out WO 2004/007974 A2 Furthermore, a device for injecting fuel into a combustion chamber of an internal combustion engine with a fuel injector is known, in which the injection pressure of the fuel injector is increased by means of a pressure booster by a pressure booster control chamber via a control line is depressurized and the pressure in a nozzle needle control chamber via an outlet throttle and emptied over an inlet throttle device can be filled. The pressure booster control chamber and the nozzle needle control chamber are connected via a hydraulic connection. In this embodiment, the pressure booster control chamber is controlled by a first metering valve and the nozzle needle control chamber by a second metering valve.

The object of the invention is to provide a device for injecting fuel into a combustion chamber of an internal combustion engine having a fuel injector which can be acted upon by a high-pressure source with high-pressure fuel, in which the injection pressure is amplified by a hydraulic pressure booster in the fuel injector. The device should work reliably, be simple and inexpensive to produce.

Presentation of the invention

The object of the invention is achieved in that the nozzle needle control chamber can be emptied via an outlet throttle device and an inlet throttle device, wherein the pressure booster control chamber and the nozzle needle control chamber are connected via a hydraulic connection, wherein the hydraulic connection between the pressure booster control chamber and nozzle needle control chamber contains a second control line, wherein the nozzle needle control chamber via the outlet throttle in the second control line can be emptied and filled via the inlet throttle from the second control line, and wherein the throttle cross section of the outlet throttle is smaller than the throttle cross section of the inlet throttle.

The outlet throttle device allows a slow opening of the injection valve member. The inlet throttle allows a fast closing of the injection valve member. The slow opening of the injection valve member improves the minimum quantity capability of the fuel injection device. The rapid closing of the injection valve member improves the emission values of the internal combustion engine. The two separate throttle devices provide the advantage that opening and closing speed of the injection valve member are independently adjustable.

A preferred embodiment of the fuel injection device is characterized in that a valve element is provided, which is closed when the injection valve member control chamber is emptied, and which is open when the injection valve member control chamber is filled.

A further preferred exemplary embodiment of the fuel injection device is characterized in that one of the throttle devices, in particular the outlet throttle device, develops its throttling action only when the injection valve member control chamber is emptied and no throttling action develops during filling of the injection valve member control chamber, but an unimpeded passage guaranteed by fuel. As a result, the closing of the injection valve member is accelerated.

A further preferred embodiment of the fuel injection device is characterized in that the two throttle devices are connected in series. As a result, a simple construction is made possible, which is economically feasible in terms of manufacturing technology.

A further preferred exemplary embodiment of the fuel injection device is characterized in that the two throttle devices are arranged centrally with respect to the longitudinal axis of the fuel injector. This arrangement provides manufacturing advantages, since both throttle bodies can be edited in the middle.

A further preferred embodiment of the fuel injection device is characterized in that the outlet throttle device comprises a throttle element with a sealing edge which is biased by a spring element so that the sealing edge is pressed against an associated sealing seat when the throttle element is flowed through in the discharge direction, and so in that the sealing edge lifts off from its sealing seat when the throttle element is flowed through in the filling direction. The combination of a throttle with a check valve enables a compact design with a shortened fuel injector length.

A further preferred embodiment of the fuel injection device is characterized in that the throttle element comprises a biased by the spring element and equipped with a throttle point having a throttle hole throttle piston whose free end forms a stroke stop for the injection valve member. This prevents the pressure in the injection valve member control chamber from falling too much after the injection valve member has been opened.

A further preferred embodiment of the fuel injection device is characterized in that the stroke stop of the nozzle needle is designed so that a first sealing seat and a second sealing seat are closed when the combustion chamber remote end of the nozzle needle comes to rest on the throttle piston. This prevents that when the nozzle needle is open, the pressure on the inside of a sealing sleeve in an annular space between the throttle piston and the sealing sleeve drops too much. As a result, an undesirably large deformation of the sealing sleeve can be prevented.

A further preferred embodiment of the fuel injection device is characterized in that the nozzle needle comes into abutment in its upper stroke stop with its end remote from the combustion chamber at a sealing edge, which is formed on an injector housing portion. This prevents that after needle opening, the pressure on the inside of a sealing sleeve drops too much, so that an undesirably large deformation of the sealing sleeve is prevented.

A further preferred embodiment of the fuel injection device is characterized in that the two throttle devices are connected in parallel. This arrangement provides advantages in the operation of the fuel injector.

A further preferred embodiment of the fuel injection device is characterized in that the outlet throttle device comprises a throttle element, which is connected in series with a check valve, that the throttle element is flowed through in one direction, in particular the filling direction, and is closed in the discharge direction. This structure is manufacturing technology particularly easy to implement.

A further preferred embodiment of the fuel injection device is characterized in that the inlet throttle device is arranged off-center relative to the longitudinal axis of the fuel injector. As a result, the inlet throttle device can be assigned a larger pressure-loaded surface, which allows a faster closing of the injection valve member.

A further preferred exemplary embodiment of the fuel injection device is characterized in that the outlet throttle device is arranged centrally with respect to the longitudinal axis of the fuel injector is. The central arrangement simplifies the processing of the throttle point during production.

The present invention relates to an injector with pressure booster or pressure booster and the control of the pressure booster via the rear space.

Further advantages, features and details of the invention will become apparent from the following description in which, with reference to the drawings, various embodiments are described in detail. The features mentioned in the claims and in the description may each be essential to the invention individually or in any desired combination.

drawing

Figur 1

ein erstes Ausführungsbeispiel der erfin- dungsgemäßen Kraftstoffeinspritzeinrich- tung im Längsschnitt durch den Kraftstof- finjektor;

Figur 2

einen vergrößerten Ausschnitt aus Figur 1;

Figur 3

eine ähnliche Ansicht wie in Figur 2 ge- mäß einem weiteren Ausführungsbeispiel;

Figur 4

eine ähnliche Darstellung wie in Figur 1 gemäß einem weiteren Ausführungsbeispiel;

Figur 5

eine ähnliche Darstellung wie in Figur 1 gemäß einem weiteren Ausführungsbeispiel;

Show it:

FIG. 1

a first embodiment of the fuel injection device according to the invention in longitudinal section through the fuel injector;

FIG. 2

an enlarged section FIG. 1 ;

FIG. 3

a similar view as in FIG. 2 according to a further embodiment;

FIG. 4

a similar representation as in FIG. 1 according to a further embodiment;

FIG. 5

a similar representation as in FIG. 1 according to a further embodiment;

Description of the embodiments

The description of the device according to the invention for damping the lifting movement of an injection valve member is based on a fuel injector with pressure booster. The proposed device for damping the lifting movement, in particular with regard to a reduction of its opening speed, can also be used on other fuel injection systems, such as pump-nozzle systems and pump-line-nozzle systems, distribution injection systems and also high-pressure accumulator injection systems, the fuel injector none Take pressure translation.

In FIG. 1 is a longitudinal section through a common rail injector 1 shown, which is supplied via an only schematically indicated pressure accumulator space 2 (common rail) with fuel under high pressure. From the interior of the high pressure accumulator 2, a fuel supply line 3, 4 extends to a pressure booster 5, which is integrated into the fuel injector 1. The pressure booster 5 is enclosed by an injector housing (not shown). The injector housing includes an injector body and a nozzle body having a central guide bore. In the guide bore, a nozzle needle 10 is guided back and forth movable. The nozzle needle 10 has a tip 11, on which a sealing surface is formed, which cooperates with a sealing seat, which is formed on the nozzle body. When the tip 11 of the nozzle needle 10 with its sealing surface is in contact with the sealing seat, two spray holes 12, 13 are closed in the nozzle body. When the nozzle needle tip 11 lifts off its seat, high pressure fuel is injected through the injection holes 12, 13 into the combustion chamber of the engine.

In the nozzle body, a pressure chamber 15 is formed, which communicates via a connecting channel 18 with a pressure booster chamber 22 in connection. In the pressure booster chamber 22 is supplied with high-pressure fuel, which is further compressed in response to the pressure in a pressure booster control chamber 23. For this purpose, one end 24 of a pressure booster piston 25 protrudes into the pressure booster chamber 22. The end 24 of the pressure booster piston 25 has substantially the shape of a circular cylinder whose outer diameter is smaller than the outer diameter of the section 25 of the pressure booster piston. In a pressure booster working chamber 26, a pressure booster spring 27 is arranged, by means of which the pressure booster piston 25 is biased in the direction of the nozzle needle 10 away.

The pressure booster control chamber 23 communicates via a connecting channel 29 with a 3/2-way valve 32 in connection, which in turn communicates via a connecting channel 34 and the fuel supply lines 3,4 with the high-pressure accumulator chamber 2. In addition, the 3/2-way valve 32 has a port 35 to a fuel tank (not shown).

In the in FIG. 1 shown position of the 3/2-way valve is the pressure booster control chamber 23 via the connection channels or connecting lines 29, 34, 3 and 4 with the high-pressure fuel storage chamber 2 in connection. Via a check valve 40 and a connecting line 41, the pressure booster chamber 22 communicates with the pressure booster control chamber 23. The check valve 40 has a check ball, which is biased for example by means of a check valve spring against a check valve seat that the pressure booster chamber 22 is filled via the connecting lines 41, 29, 34, 3 and 4 from the high-pressure fuel reservoir 2 with fuel when the Pressure in the booster chamber 22 is smaller than in the high-pressure fuel chamber 2.

The pressure booster chamber 22 communicates via a connecting line 42 with a nozzle needle control chamber 44, which is also referred to as a damping chamber. The nozzle needle control chamber 44 is bounded at the top by a portion 45 of the injector. The Injektorgehäuseabschnitt 45 has a central bore in which in a throttle piston 50, a first throttle 47, which is also referred to as a drain throttle, and a second throttle 48 are formed, which is also referred to as inlet throttle. Since both throttles, in particular the outlet throttle 47 with the smaller throttle cross-section, are flowed through or, when the pressure in the control chamber 41 decreases, the opening of the nozzle needle 10 takes place relatively slowly. The closing of the nozzle needle 10 is effected by a pressure increase in the nozzle needle control chamber 44. The pressure increase is caused by fuel flowing from the high-pressure fuel storage 2 via the supply lines 3, 4, the connecting channel 34, the pressure booster control chamber 23, the connecting channel 41, the connecting channel 42 and the inlet throttle 48 past the throttle body 61 in the nozzle needle control chamber 44.

The nozzle needle control chamber 44 is bounded laterally by a sealing sleeve 56, which has a biting edge 57. The biting edge 57 opposite side of the sealing sleeve 56 is acted upon by a compression spring 58 which is biased between the sealing sleeve 56 and a collar 54 which is formed on the nozzle needle 10. On the one hand, the biasing force of the spring 58 causes the biting edge 57 of the sealing sleeve 56 to abut against the injector section 45. On the other hand, the biasing force of the spring 58 causes the tip 11 of the nozzle needle 10 to be pressed against its associated sealing seat.

The combustion chamber facing away from the outer edge of the collar 51 on the throttle piston 50 forms a sealing edge 61 which is pressed by the prestressed compression spring 53 against an associated sealing seat, which is provided on the Injektorgehäuseabschnitt 45. The Preload force of the compression spring 53 and the throttle cross section of the outlet throttle 47 are selected so that the throttle piston 50 lifts off with its sealing edge 61 of the associated seat on the Injektorgehäuseabschnitt 45 when flows through the connecting line 42 and the inlet throttle 48 with high pressure fuel. The high-pressure fuel raises the throttle piston 50 from the sealing edge 61 and can then flow past the outlet throttle 47 into the nozzle needle control chamber 44. As a result, a fast closing of the nozzle needle 10 is ensured. When filling the nozzle needle control chamber 44 via the connecting channel 42, only the inlet throttle 48 unfolds its throttling effect, but not the outlet throttle 47.

The nozzle needle 10 is guided in the shaft, wherein flow channels 59, 60 are provided in the guide region, passes through the fuel from the pressure chamber 15 to the tip 11 of the nozzle needle 10. The pressure chamber 15, in which the nozzle closing spring 58 is arranged, is formed in the upper nozzle region.

In deactivated hibernation, which is in FIG. 1 is shown, the pressure booster control chamber 23 is acted upon by the 3/2-way valve 32 with the same pressure as the pressure booster working chamber 26. The connection to the return line 35 is closed. The pressure booster piston 25 is pressure balanced and there is no pressure gain. The nozzle needle 10 is closed. The throttle piston 50 is in contact with the injector housing section 45 with the sealing edge 61.

To activate the injector, the pressure booster control chamber 23 is depressurized. For this purpose, the pressure booster control chamber 23 is decoupled from the high-pressure accumulator 2 with the aid of the 3/2-way valve 32 and is depressurized via the connecting line 29 into the return line 35. The pressure in the compression chamber 22 is thereby increased according to the transmission ratio of the pressure booster 5 and forwarded to the injection nozzle. The injector starts to open. Since the collar 51 of the throttle piston 50 rests against the injector housing section 45, ie the sealing seat is closed at 61, fuel must be displaced via the outlet throttle 47 and then via the inlet throttle 48 from the nozzle needle control chamber 44, which is also referred to as a damping chamber. This reduces the needle opening speed. By way of the flow rate of the outlet throttle 47, the needle opening speed can thus be set.

In the enlarged view of the FIG. 2 it can be seen that the first throttle 47 is formed in a central bore of a throttle piston 50, which has a collar 51. The collar 51 of the throttle piston 50 is biased by a compression spring 53 against the tip 11 opposite end of the nozzle needle 10. The pressure in the nozzle needle control chamber 44 serves to control the injection of fuel through the injection holes 12, 13. The outlet throttle 47 has a smaller throttle cross-section than the inlet throttle 48. If the 3/2-way valve from the in FIG. 1 shown position is switched to its second (not shown) position, then the nozzle needle control chamber 44 via the connecting lines 42, 41, 29 and 35 in the (not shown) fuel tank emptied or relieved. When emptying or relieving the nozzle needle control chamber 44, both the first throttle 47 and the second throttle 48 are flowed through. Due to the pressure drop in the nozzle needle control chamber 44, the nozzle needle 10 lifts with its tip 11 from the associated sealing seat.

As long as the pressure booster control chamber 23 is relieved of pressure, the pressure booster 5 remains activated and compresses the fuel in the booster chamber 22, which can also be referred to as a compression chamber. The compressed fuel is forwarded to the nozzle needle 10 and injected. The throttle piston 50 is also designed as a stroke stop for the nozzle needle 10. As a result, the stroke stop of the nozzle needle 10 is adjustable over the height or length of the throttle piston 50, whereby a high accuracy of the Nadelhubs is achieved in the production of the injector. The stroke stop of the nozzle needle 10 may be formed so that the sealing seat at 61 and another sealing seat at 62 are closed when the combustion chamber distal end of the nozzle needle 10 comes to rest on the throttle piston 50. This prevents that with open nozzle needle 10, the pressure on the inside of the sealing sleeve 56 in the annular space between the throttle piston 50 and the sealing sleeve 56 drops too much. As a result, an undesirably large deformation of the sealing sleeve 56 can be prevented.

At the in FIG. 3 illustrated embodiment, the throttle piston 50 is formed shorter than that in the FIGS. 1 and 2 illustrated embodiment. In FIG. 3 forms the throttle piston 50 no stroke stop for the nozzle needle 10. The nozzle needle 10 comes in the in FIG. 3 illustrated embodiment in its upper stroke stop with its combustion chamber remote end 62 to a sealing edge 63 for conditioning, which is formed on the Injektorgehäuseabschnitt 45. This prevents that after needle opening, the pressure on the inside of the sealing sleeve 56 drops too much, so that an undesirably large deformation of the sealing sleeve 56 is prevented.

To terminate the injection of the printer amplifier control chamber 23 is separated by the 3/2-way valve 32 from the return line 35 and acted upon by the rail pressure, that is connected to the high-pressure fuel storage 2. As a result, rail pressure builds up in the pressure booster control chamber 23 and the connecting line 41, which can also be referred to as a control line. At the same time, the pressure in the pressure booster chamber 22 and the pressure chamber 15 drops to rail pressure. The throttle piston 50 lifts off from the Injektorgehäuseabschnitt 45 and thus releases the sealing seat at 61. Thus, the fuel can only flow throttled through the inlet throttle 48 in the nozzle needle control chamber 44, whereby in the nozzle needle control chamber 44 also rail pressure is built up. This closes the nozzle needle 10. For needle closing the nozzle needle control chamber 44 does not have to be filled via the small throttle 47, allowing a fast needle closing becomes. The needle closing speed can be adjusted via the inlet throttle 48, regardless of the opening speed.

By means of a suitable system design, an overshoot of the pressure in the chambers 23 and 44 via system pressure and undershooting in the chamber 15 under system pressure can be achieved for a short time in the needle closing phase. This achieves a quick needle closure. In the closing phase occurs in the damping chamber 44, a higher pressure than in the pressure chamber 15, which is also referred to as an intermediate space. In this case, the sealing sleeve 56 can be released from the contact point on the throttle piston 50 and the closing pressure in the nozzle needle control chamber 44 breaks. Due to the closing spring force on the nozzle needle 10, however, this continues its closing movement. This opening of the sealing sleeve 56 can be used to achieve a flushing of the nozzle needle control chamber 44. This prevents heating of the fuel in the nozzle needle control chamber 44. If opening of the sealing sleeve 56 is not desired, this can be avoided by a correspondingly large spring force of the compression spring 58 or by an additional spring force on the sealing sleeve 56.

After pressure equalization of the system, the pressure booster piston 25 is returned to its initial position by the booster spring 27, which may also be referred to as a return spring. In this case, the pressure booster chamber 22 is filled via the check valve 40. The throttle piston 50 is by the compression spring 53 in its closed rest position reset. The connecting line 41, which may be designed, for example, as a control bore, may alternatively also be connected to the region of the pressure booster working space 26 / high-pressure reservoir 2.

In FIG. 4 is a similar fuel injector as in FIG. 1 shown. The same reference numerals are used to designate like parts. To avoid repetition, the preceding description of the FIG. 1 directed. In the following, only the differences between the two embodiments will be discussed.

FIG. 4 shows an embodiment with two separately formed throttle paths 71 and 73 in the nozzle needle control chamber 44. In the throttle path 71, a discharge throttle 72 is provided. In the throttle path 73, a check valve 74 and an inlet throttle 75 are provided. Due to the separately formed throttle paths 71 and 73, the volume of the nozzle needle control chamber 44 can be kept very small, whereby a vibration-reduced needle opening can be achieved. The nozzle needle control chamber 44 is connected via the throttle 72 to the control line 41. In addition, the nozzle needle control chamber 44 is connected to the control line 41 via the throttle 75 and the check valve 74. The needle opening speed is determined by the drain throttle 72. The needle closing speed can be adjusted via the inlet throttle 75.

In FIG. 5 is a similar fuel injector as in FIG. 4 shown. The same reference numerals are used to designate like parts. To avoid repetition, the preceding description of the FIG. 4 directed. In the following, only the differences between the two embodiments will be discussed.

At the in FIG. 5 illustrated embodiment, another design of the nozzle needle 10 is used. The two inlet paths 71 and 73, which can also be referred to as throttle paths, open into a nozzle needle control chamber 80, in which a nozzle needle spring 81 is arranged. By the biasing force of the nozzle needle spring 81, the nozzle needle 10 is held with its tip 11 against the associated sealing seat in abutment. On the nozzle needle 10, a pressure shoulder 83 is formed, which is arranged in a substantially annular pressure chamber 84. The pressure chamber 84 is connected via a connecting line 86 to the pressure booster chamber 22 in connection. When the pressure in the nozzle needle control chamber 80 decreases, the nozzle needle 10 lifts with its tip 11 from the associated seat and the high-pressure fuel in the pressure chamber 84 is injected through the injection holes 12, 13 in the combustion chamber of the internal combustion engine.

Claims (13)

1. Device for the injection of fuel into a combustion chamber of an internal combustion engine, having a metering valve (32) and having a fuel injector (1) which can be loaded with highly pressurized fuel via a high-pressure source (2) and can be actuated via the metering valve (32), the pressure in a first control line (29) being built up by the activation of the metering valve (32), with the result that a pressure intensifier (5) is activated by a pressure-intensifier control space (23) being relieved of pressure via the first control line (29) via a return line (35), it being possible for the pressure in a nozzle-needle control space (44) to be controlled via the metering valve (32) in such a way that a nozzle needle (10) opens and closes for the injection of fuel, it being possible for the nozzle-needle control space (44) to be emptied via an outflow throttle device (47, 72) and to be filled via an inflow throttle device (48, 75), and the pressure-intensifier control space (23) and the nozzle-needle control space (44) being connected via a hydraulic connection, characterized in that the hydraulic connection between the pressure-intensifier control space (23) and the nozzle-needle control space (44) contains a second control line (41), in that the nozzle-needle control space (44) can be emptied via the outflow throttle device into the second control line (41) and can be filled via the inflow throttle device from the second control line (41), and in that the throttle cross section of the outflow throttle device (47, 72) is smaller than the throttle cross section of the inflow throttle device (48, 75).
2. Fuel injection device according to Claim 1, characterized in that a valve element (74) is provided which is closed when the injection valve-element control space (44) is emptied and which is open when the injection valve-element control space (44) is filled.
3. Fuel injection device according to one of the preceding claims, characterized in that the outflow throttle device displays its throttling action only during emptying of the injection valve-element control space (44) and does not display any throttling action during filling of the injection valve-element control space (44), but rather ensures an unimpeded passage of fuel.
4. Fuel injection device according to Claim 3, characterized in that the two throttle devices are connected in series.
5. Fuel injection device according to Claim 3 or 4, characterized in that the two throttle devices are arranged centrally in relation to the longitudinal axis of the fuel injector (1).
6. Fuel injection device according to one of Claims 3 to 5, characterized in that the outflow throttle device comprises a throttle element (50) with a sealing edge (61), which throttle element (50) is prestressed by a spring element (53) in such a way that the sealing edge (61) is pressed against an associated sealing seat when the throttle element (50) is flowed through in the emptying direction, and in such a way that the sealing edge (61) raises up from its sealing seat when the throttle element (50) is flowed through in the filling direction.
7. Fuel injection device according to Claim 6, characterized in that the throttle element (50) comprises a throttling piston which is prestressed by the spring element (53), is equipped with a through hole which has a throttle point, and the free end of which forms a stroke stop for the nozzle needle (10).
8. Fuel injection device according to Claim 7, characterized in that the stroke stop (62) of the nozzle needle (10) is configured in such a way that a sealing seat (61) and a further sealing seat (62) are closed when that end of the nozzle needle (10) which is remote from the combustion chamber comes into contact with the throttling piston (50).
9. Fuel injection device according to one of Claims 1 to 6, characterized in that, at its upper stroke stop, the nozzle needle (10) comes into contact with its end (62) which is remote from the combustion chamber with a sealing edge (63) which is formed on an injector-housing section (45).
10. Fuel injection device according to one of Claims 1 to 3, characterized in that the two throttle devices are connected in parallel.
11. Fuel injection device according to Claim 10, characterized in that the inflow throttle device comprises a throttle element (75) which is connected in series to a non-return valve in such a way that the throttle element (75) is flowed through only in the filling direction and is closed in the emptying direction.
12. Fuel injection device according to Claim 10 or 11, characterized in that the inflow throttle device is arranged eccentrically in relation to the longitudinal axis of the fuel injector (1).
13. Fuel injection device according to one of Claims 10 to 12, characterized in that the outflow throttle device is arranged centrally in relation to the longitudinal axis of the fuel injector (1).

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