Patent Application
20060043209
Both pressure-controlled and stroke-controlled injection systems can be used to deliver fuel into combustion chambers of autoignition internal combustion engines. Injection systems with high-pressure reservoirs have the advantage that the injection pressure can be adapted to the load and speed of the engine. A high injection pressure is required in order to reduce emissions produced and achieve a high specific output of the engine. Since the pressure level that high-pressure fuel pumps can achieve in the high-pressure reservoir is limited for strength reasons, a pressure booster at the fuel injector can be used boost pressure further in fuel injection devices with a high-pressure reservoir.
DE 199 10 907 A1 has disclosed a fuel injection device that has a pressure booster unit disposed between a pressure reservoir and a nozzle chamber. Its pressure chamber communicates with the nozzle chamber via a pressure line. A bypass line is also provided, which is connected to the pressure reservoir. The bypass line is connected directly to the pressure line. The bypass line can be used for a pressure injection and is disposed parallel to the pressure chamber so that it is continuously open independent of the movement and position of a movable lever of the pressure boosting unit.
DE 102 18 904.8 relates to a fuel injection device. This proposed version of a fuel injection device for internal combustion engines has a fuel injector, which can be supplied from a high-pressure fuel source, and has a pressure-boosting unit. The closing piston of the fuel injector protrudes into a closing pressure chamber so that the closing piston can be subjected to fuel pressure in order to produce a force that acts on the closing piston in the closing direction; the closing pressure chamber and the return chamber of the pressure boosting unit are constituted by a shared closing pressure/return chamber. All of the partial regions of the closing pressure/return chamber are permanently connected to one another to permit the exchange of fuel. The pressure boosters known from DE 199 10 970 A1 and DE 102 18 904.8 are actuated by means of an exertion of pressure on or relief of pressure in a return chamber of the pressure booster. Controlling a pressure booster via the return chamber is advantageous in terms of discharge losses and permits a simple triggering of the pressure booster by means a 2/2-way valve.
The disadvantage of the pressure boosters known from DE 199 10 970 A1 and DE 102 18 904.8 is the routing of the control bore for relieving the pressure in the return chamber of the pressure booster. Due to the fact that the control valve for the pressure booster is disposed above the pressure booster in most internal combustion engines for space reasons, it is necessary for the control line that is subjected to the fuel pressure prevailing in the high-pressure reservoir to be routed out of the return chamber of the pressure booster and past the pressure booster. This requires a larger outer diameter of the fuel injector into which the pressure booster is incorporated, as a rule in the head region, or requires an eccentric placement of the pressure boosting element that is disposed in the pressure booster and is, as a rule, embodied in the form of a piston. This previously required line routing resulted in bore intersections in the control line for exerting pressure on or relieving pressure in the return chamber of the pressure booster. As a rule, bore intersections involve high material stresses, which require costly machining steps and are detrimental to a durable design of a fuel injector.
The design proposed according to the invention makes it possible to achieve an improvement in the high-pressure tightness of a fuel injector with a pressure booster. The elimination of a control line running along the outside of the fuel injector with pressure booster reduces the external dimensions of the fuel injector or avoids a placement of a pressure booster eccentric to the fuel injector.
A control line disposed in the booster piston and extending coaxial to the symmetry axis of the fuel injector advantageously avoids bore intersections of the kind that necessarily occur in external lines because of the connection location of the high-pressure connections and reduces material stresses, which in turn extends the service life of the fuel injector with pressure booster. The central control line, which is for relieving pressure in or exerting pressure on a differential pressure chamber used to actuate the pressure booster, extends through a pressure booster working chamber that is subjected to high pressure. A seal between this working chamber and the central control line can be achieved by means of a sealing sleeve that is prestressed by a spring element and advantageously cooperates with a flat seat in the working chamber. This makes it possible to compensate for manufacture related tolerances in a fuel injector with pressure booster that is comprised of a number of housing parts to be joined to one another. The central control line extends through an extension, which is embodied on the piston of the pressure booster and has a guide section for the movable sealing sleeve disposed on the piston extension.
In another embodiment variant of the concept underlying the invention, a piston extension on the booster piston of the pressure booster can be contained in a high-pressure-tight guide provided in one of the housing parts of the fuel injector with pressure booster. The high-pressure-tight guide of the piston extension is designed so that it is effective along the entire stroke path of the pressure booster piston and separates the central control line from the working chamber of the pressure booster.
Instead of a piston extension embodied on the piston of the pressure booster and housing the central control line, the pressure booster piston can contain a piston that has a conduit extending all the way through it. According to this embodiment variant, a sealing point can be embodied as a flat seat in order to seal the central control line off from the working chamber of the pressure booster. On the one hand, this makes it possible to compensate for tolerances between the housing parts and on the other hand, permits a simple manufacture from a production engineering standpoint. In another embodiment variant of a fuel injector with pressure booster, the pressure booster has a piston element extending all the way through it, which in turn has a conduit extending all the way through it. Depending on the stroke path of the pressure booster, the conduit is connected to the differential pressure chamber of the pressure booster via a first outlet cross section or via the first outlet cross section and a second outlet cross section. This makes it possible to control the pressure buildup of the pressure booster in accordance with a desired injection pressure.
The central control line can be used in all pressure boosters that are controlled via a differential pressure chamber.
The invention will be explained in detail below in conjunction with the drawings.
According to the first exemplary embodiment of the concept underlying the invention shown in
The injector body 4 of the fuel injection device 1 has a first housing part 8, an additional, second housing part 9, and an injector housing 10 that encompasses an injection valve element 24. The first housing part 8 and the second housing part 9 rest against each other along a butt joint 32.
The injector body 4 of the fuel injection device 1 contains a pressure booster 11. The pressure booster 11 includes a working chamber labeled with the reference numeral 12, which can be acted on with highly pressurized fuel via an inlet 13 branching from the high-pressure line 3. The pressure booster 11 has a pressure booster piston 14 that has a first end 15 oriented toward the working chamber 12 and a second end 16 oriented toward a differential pressure chamber 17. At the second end 16, the pressure booster piston 14 rests against a return spring 18, which in turn rests against an annular surface inside the second housing part 9 of the injector body 4. The pressure booster piston 14 of the pressure booster 11 acts on a high-pressure chamber 19 contained in the lower region of the second housing part 9. When the end of the pressure booster piston 14 oriented toward the high-pressure chamber 19 travels inward, the fuel contained in this chamber is compressed even more as a function of the boosting ratio of the pressure booster 11, and flows into a control chamber 20 and into a nozzle chamber 23 contained in the injector housing 10 via a nozzle chamber inlet 22. The nozzle chamber 23 encloses the injection valve element 24 of the fuel injection device in a region in which a pressure shoulder is provided on the injection valve element 24. An annular gap extends from the nozzle chamber 23 to the end of the fuel injection device 1 oriented toward the combustion chamber. Via the annular gap, injection openings 25 at the combustion chamber end of the fuel injection device 1 are acted on with fuel. These injection openings are unblocked with a vertical movement of the injection valve element 24 so that highly pressurized fuel can be injected via the injection openings 25 into a combustion chamber 26 of an autoignition internal combustion engine.
The exertion of pressure on the control chamber 20 in order to actuate the injection valve element 24, which is embodied for example in the form of a nozzle needle, occurs via a line that contains an inlet throttle 21 and connects the nozzle chamber 20 to the high-pressure chamber 19 of the pressure booster 11. The control chamber 20 contains a nozzle spring 27, which encompasses a pin 28 of the injection valve element and rests against an annular surface of the injection valve element 24. A discharge line 29 that contains an outlet throttle 30 extends between the differential pressure chamber 17 of the pressure booster 11 and the control chamber 20.
The pressure booster piston 14 of the pressure booster 11 contains a central control line 31. The central control line 31 is connected to the differential pressure chamber 17 of the pressure booster 11 via a lateral opening 41 embodied in the pressure booster piston 14. The lateral opening 41 is in turn connected to a conduit 40 representing the central control line 31, which conduit passes through the section of the pressure booster piston 14 sealing the working chamber 12 off from the differential pressure chamber 17 and extends through a piston extension 34 disposed at the first end 15 of the pressure booster piston 14. The piston extension 34 that contains the conduit 40 and is disposed at the first end 15 of the pressure booster piston 14 extends into the recess 35 in the first housing part 8 of the injector body 4. A first sealing sleeve 36 can move within a guide section 42 on the piston extension 34 of the pressure booster piston 14. The first sealing sleeve 36 has an annular shoulder 39 against which an adjusting spring 38 rests. With its end opposite from the first sealing sleeve 36, the adjusting spring 38 rests against the first end 15, encompassing the piston extension 34. The adjusting spring 38 acts on the first sealing sleeve 36 mounted on the piston extension 34 so that its sealing surface 37 rests against the underside of the first housing part 8 of the injector body 4. This allows a high-pressure-tight connection 33 to be produced, which seals the central control line 31 off from the working chamber 12 of the pressure booster 11. According to the exemplary embodiment shown in
The exemplary embodiment shown in
At the beginning of an injection, the on-off valve 5 is switched from its position shown in
The injection openings 25 that feed into the combustion chamber 26 of an autoignition internal combustion engine are acted on with highly pressurized fuel as a result of the vertical stroke motion of the injection valve element 24 and inject this fuel into the combustion chamber 26 of the engine.
With a subsequent switching of the on-off valve 5, the high-pressure reservoir 2 exerts pressure on the differential pressure chamber 17 via the high-pressure line 3, the inlet 6, the overflow line 43, and the recess 35 in the first housing part 8. From there, the fuel flows through the conduit 40 constituting the central control line 31 and travels into the differential pressure chamber 17 via the lateral opening 41, once again acting on the differential pressure chamber 17 with the pressure level prevailing in the high-pressure reservoir 2. This relieves the pressure in the high-pressure chamber 19 as well as in the nozzle chamber 23 encompassing the injection valve element 24 in the injector housing 10. The nozzle spring 27 pushes the injection valve element 24 into its seat oriented toward the combustion chamber, thus terminating the injection. The control chamber 20 is refilled via the discharge line 29, which in this case allows fuel to flow through in the opposite direction, refilling the control chamber 20. The high-pressure chamber 19 of the pressure booster 11 is refilled with an overflow of fuel from the control chamber 20 that flows into the high-pressure chamber 19 via the line containing the inlet throttle 21.
In the embodiment variant of the concept underlying the invention shown in
According to the embodiment variant shown in
Highly pressurized fuel flows through the high-pressure line 3 to the first housing part 8 of the injector body 4 of the fuel injection device 1. It is conveyed via the inlet to the on-off valve 5. The on-off valve 5 has a connection to the low-pressure side return 7 and to an overflow line 43 leading to the recess 35 contained in the first housing part 8. The branch 13 of the high-pressure line 3 inside the first housing part 8 acts on the working chamber 12 of the pressure booster 11 with highly pressurized fuel. The pressure booster 11 has a pressure booster piston 14 that seals the working chamber 12 of the pressure booster 11 off from the differential pressure chamber 17 of the pressure booster 11. The pressure booster piston 14 includes the piston extension 34 attached to the first end 15. A first washer 51 is disposed on the piston extension 34 extending through the working chamber 12 in the second housing part 9. An additional, second washer 52 is provided above the pressure booster piston 14, inside the working chamber 12 of the pressure booster 11. A return spring 18 is disposed between the first and second washers 51, 52 and returns the pressure booster piston 14 to its initial position inside the second housing part 9.
The lower end of the pressure booster piston 14 acts on the high-pressure chamber 19 contained in the second housing part 9 of the injector body 4. The high-pressure level that can be achieved in the high-pressure chamber 19 depends on the boosting ratio of the pressure booster 11 and is higher than the pressure level prevailing in the high-pressure reservoir 2. Fuel flows from the high-pressure chamber 19 of the pressure booster 11 at a further increased pressure level, traveling via the nozzle chamber inlet 22 into the nozzle chamber 23 in the injector housing 10. In the region of the nozzle chamber 23, the injection valve element 24, which can be embodied for example as a nozzle needle, has a pressure shoulder that encompasses the injection valve element 24. The nozzle chamber 23 inside the injector housing 10 has an annular gap extending from it via which the highly pressurized fuel can flow from the nozzle chamber 23 to the injection openings 25. When the injection valve element 24 is open, very highly pressurized fuel is injected through the injection openings 25 into the combustion chamber 26 of the autoignition internal combustion engine.
In addition, a line section extends from the high-pressure chamber 19 to the nozzle chamber 20. This line section contains an inlet throttle 21. The control chamber 20 for the injection valve element 24 contains a nozzle spring 27, which rests against an annular surface of the injection valve element 24 at one end, encompassing a pin 28. At the other end, the nozzle spring 27 rests against a wall of the second housing part 9 delimiting the nozzle chamber 20. An overflow of control volume from the nozzle chamber 20 into the differential pressure chamber 17 of the pressure booster 11 occurs via the discharge line 29 that contains an outlet throttle 30 and connects the nozzle chamber 20 to the differential pressure chamber 17.
The pressure booster piston 14 of the pressure booster 11 contains a central control line 31. The central control line 31 is embodied as a conduit 40 that passes through both the piston extension 34 and the pressure booster piston 14 and has a lateral opening 41 at its lower end that feeds into the differential pressure chamber 17. This lateral opening can be embodied as a bore, a conduit, or the like contained in the pressure booster piston 14. From the lateral opening 41 in the pressure booster piston 14, the conduit 40 extends into the recess 35 in the first housing part 8 of the injector body 4. The first housing part 8 encompasses the head region of the piston extension 34 in a high-pressure-tight guide 50. The high-pressure-tight guide 50 inside the first housing part 8 transitions into the recess 35 and is embodied with an axial length that corresponds to the stroke path of the pressure booster piston 14. This assures that a high-pressure seal between the recess 35 inside the first housing part 8 and the working chamber 12 of the pressure booster 11 is maintained along the entire stroke path of the pressure booster piston 14 of the pressure booster 11.
In the position shown in
When the on-off valve 5 is actuated, i.e. when it is moved from the switched position shown in
However, if the on-off valve 5 is switched into its initial position shown in
The embodiment variant shown in
The embodiment variant of a fuel injector with pressure booster shown in
Otherwise, the exemplary embodiment shown in
The exemplary embodiment of a fuel injection device shown in
A relief of the pressure in the differential pressure chamber 17 of the pressure booster 11 is produced through actuation of the on-off valve 5. When the on-off valve 5 is actuated, the overflow line 43 is brought into connection with the low-pressure side return 7 as a result of which the pressure in the differential pressure chamber 17 is relieved into the low-pressure side return via the lateral opening 41, the chamber 63, and the central control line 31 (conduit 40) contained in the piston part 60. The fuel in the working chamber 12 acts on the first end 15 of the pressure booster piston 14, causing the end of the pressure booster piston 14 oriented toward the high-pressure chamber 19 to travel into this high-pressure chamber.
When the on-off valve 5 is actuated, low pressure prevails in the overflow line 43 and therefore against the upper piston surface of the piston part 60. The area of the piston part 60 in the working chamber 12 generates a hydraulic sealing force. This presses the piston part 60 against the housing part 8. In addition, it is also possible for the piston part to be prestressed by means of a spring in order to press it against the lower end surface of the housing part 8 delimiting the working chamber 12.
When the lower end of the pressure booster piston 14 travels into the high-pressure chamber 19, this increases the pressure of the fuel contained therein in accordance with the pressure boosting ratio of the pressure booster 11. The fuel flows from the high-pressure chamber 19 to the nozzle chamber 23 via the nozzle chamber inlet 22. In the region of the nozzle chamber 23, the injection valve element 24, which can be embodied for example as a nozzle needle, has a pressure shoulder that causes the injection valve element 24 to move vertically in the opening direction, i.e. into the control chamber 20, in response to the highly pressurized fuel flowing into the nozzle chamber 23. The fuel contained in the nozzle chamber 23 flows through the annular gap encompassing the injection valve element 24, to injection openings 25 and from there, is injected into the combustion chamber 26 of the autoignition internal combustion engine. The fuel volume displaced when the nozzle of the injection valve element 24 travels upward in the nozzle chamber 20 flows through the discharge line 29 and the throttle restriction 30 contained therein, and to the pressure-relieved differential pressure chamber 17. From there, the displaced control volume flows through the lateral opening 41, the chamber 63, the central control line 31 inside the piston part 60, and the overflow line 43 to the on-off valve 5 and from there, into the low-pressure side return 7.
Both during filling and during pressure relief of the differential pressure chamber 17 of the pressure booster 11, the working chamber 12, which is continuously acted on by the fuel pressure level contained in the high-pressure reservoir 2, is effectively sealed off from the central control line 31, which extends in the form of a conduit 40 through the piston part 60. Manufacture-related component tolerances between the first housing part 8 and the second housing part 9 can be advantageously compensated for by providing a flat seat 61 in the head region, i.e. at the enlarged end of the piston part 60 oriented toward the first housing part 8.
In the fuel injection device shown in
Highly pressurized fuel flows from the high-pressure reservoir 2 via the high-pressure line 3 into the working chamber 12 of the pressure booster 11. In this exemplary embodiment, the working chamber 12 is disposed in the upper region of the injector body 4 of the fuel injection device 1. The servo-hydraulic on-off valve 70 has a servo piston (valve body 71) and a control valve disposed in the return 73. The on-off valve 70 is connected to the working chamber 12 of the pressure booster via a line. The letters ND indicate a low-pressure side return that likewise branches off from the valve housing of the on-off valve 70. When the on-off valve 70 is in the idle state, a control edge labeled VQ1 is open and a control edge labeled VQ2 is closed. The control line 31 is consequently connected to the working chamber 12 of the pressure booster. When the valve 70 is switched, the control edge VQ1 is closed and the control edge VQ2 is opened so that the central control line 31 is connected to the low-pressure side return ND.
The servo-hydraulic 3/2-way valve has a low-pressure side return 73 leading from it to a fuel reservoir not shown in
The pressure booster piston 14 seals the working chamber 12 of the pressure booster 11 off from the differential pressure chamber 17 integrated into the injector body 4. The return spring 18 is contained in the working chamber 12 of the pressure booster 11. This return spring 18, encompassing a sleeve-shaped region of the pressure booster piston 14, rests against the first washer 51 and the second washer 52. The first washer 51 is attached to the upper end of the pressure booster piston 14, while the second washer 50 can be inserted into the wall of the injector body 4. The second washer 52 is disposed above the first end 15 of the pressure booster piston while the second end 16 of the pressure booster piston 14 constitutes a delimiting surface of the differential pressure chamber 17 of the pressure booster 11.
In the exemplary embodiment of the fuel injection device 1 shown in
According to the exemplary embodiment in
In the switched position of the servo-hydraulic 3/2-way valve 70 shown in
The second sealing sleeve 81 seals the control chamber 20 and therefore the differential pressure chamber 17 of the pressure booster 11 off from the high-pressure chamber 19, which functions as a nozzle chamber in the pressure booster 11. The prestressing spring 82 contained in the high-pressure chamber 19 acts on the second sealing sleeve 81 and assists it in its sealing action.
With the exemplary embodiment shown in
The pressure relief of the differential pressure chamber 17 occurring via the outlet cross sections 77 and 78 causes a pressure increase to occur in the high-pressure chamber 19 in accordance with the boosting ratio of the pressure booster 11, which high-pressure chamber 19 functions as a nozzle chamber in the exemplary embodiment according to
| Number | Date | Country | Kind |
|---|---|---|---|
| 10247903.8 | Oct 2002 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/DE03/03314 | 10/7/2003 | WO | 4/11/2005 |
