EP1733139A1

EP1733139A1 - Common rail injector

Info

Publication number: EP1733139A1
Application number: EP05707805A
Authority: EP
Inventors: Hans-Christoph Magel
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2004-03-31
Filing date: 2005-01-19
Publication date: 2006-12-20
Anticipated expiration: 2025-01-19
Also published as: ATE390557T1; WO2005095788A1; US7387110B2; EP1733139B1; US20070221177A1; DE502005003465D1; DE102004015744A1

Abstract

A common rail injector having an injector housing having a fuel supply line which communicates with a central high-pressure fuel source outside the injector housing and with a pressure chamber inside the injector housing, from which pressure chamber, as a function of the position of a 3/2-way control valve, fuel subjected to high pressure is injected. The 3/2 way control valve, includes a valve piston, movable back and forth in the injector housing between a position of repose and an injection position, which piston is coupled hydraulically with a piezoelectric actuator that is subjected to the pressure from the high-pressure fuel source.

Description

Common rail injector

description

The invention relates to a common rail injector for injecting fuel into a combustion chamber of an internal combustion engine, comprising an injector housing which has a fuel inlet which is connected to a central high-pressure fuel store outside the injector housing and to a pressure chamber within the injector housing which is injected with high pressure fuel depending on the position of a 3/2-way valve.

State of the art

A pressure-translated fuel injector is known from German published patent application DE 102 29 415 A1, which is supplied with fuel under high pressure via a high-pressure storage space. A supply line extends from the interior of the high-pressure storage space to a pressure booster, which is integrated in the fuel injector. The pressure intensifier is enclosed by an injector body of the fuel injector. The fuel injector further comprises a metering valve which is designed as a 3/2-level valve. The metering valve can be designed as a solenoid valve as well as operated via a piezo actuator. In addition, the metering valve can also be designed as a servo valve or as a direct switching valve. Known common rail injectors are usually controlled using servo valves or solenoid valves, which are expensive and sensitive to tolerances.

The object of the invention is to provide a common rail injector for injecting fuel into a combustion chamber of an internal combustion engine, with an injector housing which has a fuel inlet which has a central high-pressure fuel reservoir outside the inector housing and with a pressure space inside the injector housing This creates a connection from which, depending on the position of a 3/2-way valve, high-pressure fuel is injected, which can be produced cost-effectively and works reliably even at high pressures.

Presentation of the invention

The task is for a common rail injector for injecting fuel into a combustion chamber of an internal combustion engine, with an injector housing that has a fuel inlet that has a central high-pressure fuel source or a high-pressure fuel reservoir outside the injector housing and with a pressure chamber inside the injector housing in Connection is established, from which, depending on the position of a control valve, in particular a 3/2-way valve, high-pressure fuel is injected. solved in that the control valve, in particular the 3/2-way valve, comprises a valve piston which can be moved back and forth in the injector housing between a rest position and an injection position and which is hydraulically coupled to a piezo actuator which acts on the pressure from the high-pressure fuel source is. The piezo actuator is pressurized axially, radially or transversely. The piezo actuator is used to actuate the valve piston. The efficiency of the injector is improved by the elimination of the control quantity that occurs with servo valves. The necessary axial preload for the piezo actuator is generated at least partially hydraulically. As a result, no large spring forces have to be realized in the injector, which results in space advantages and cost advantages. Due to the very fast switching speed of the valve with piezo actuator, the tolerance behavior of the injector can be improved. In addition, the smallest quantity capability (pre-injection quantities) is ensured.

A preferred exemplary embodiment of the common rail injector is characterized in that the injector housing comprises a hydraulic coupling chamber which is pressurized with the pressure from the high-pressure fuel reservoir and via which the piezo actuator is hydraulically coupled to the valve piston. For example, an essentially circular-cylindrical head made of metal can be attached to the piezo actuator, the end face of which limits the hydraulic coupling space. On the opposite side, the hydraulic coupling space is preferably delimited by an end face of the valve piston. The hydraulic coupling space is used to compensate volume expansions of the piezo actuator due to temperature fluctuations in operation. In addition, a force / displacement ratio between the piezo actuator and the valve piston can be realized.

Another preferred exemplary embodiment of the Co mon-rail injector is characterized in that a first end of the valve piston delimits the hydraulic coupling space and a second end of the valve piston protrudes into a valve control chamber which is connected to a fuel return in the injection position of the valve piston , and which is in the rest position of the valve piston with the pressure from the high-pressure fuel accumulator. The fuel return can, for example, be connected to a fuel tank and enables a rapid pressure reduction in the valve control room. In the rest position of the valve piston, the injector is filled, at least partially, with fuel via the valve control chamber.

Another preferred exemplary embodiment of the common rail injector is characterized in that a first sealing edge, which interrupts a connection between the valve control chamber and the fuel return line in the rest position of the valve piston, and a second sealing edge is formed on the valve piston, which is in the injection position of the Valve piston interrupts a connection between the high-pressure fuel accumulator and the valve control chamber. When the valve piston is at rest, the injector is not activated, which means that there is no injection. In the Injection position of the valve piston is injected with high-pressure fuel from the injector into the combustion chamber of an internal combustion engine.

Another preferred exemplary embodiment of the common rail injector is characterized in that a valve piston guide section is formed at the first end of the valve piston, the diameter of which is somewhat smaller than the diameter of the first sealing edge. As a result, a small hydraulic contact pressure is generated in the rest position of the valve piston, which ensures tight contact of the first sealing edge with its associated valve seat, which can be provided on the injector housing.

Another preferred exemplary embodiment of the common rail injector is characterized in that the diameter of the second sealing edge is somewhat smaller than the diameter of the valve piston guide section. As a result, a small hydraulic contact pressure is generated in the injection position of the valve piston, which ensures tight contact of the second sealing edge with its associated valve seat, which can be provided on the injector housing.

Another preferred exemplary embodiment of the common rail injector is characterized in that the valve piston is formed in one piece. The one-piece design has the advantage that both sealing edges are guided through the valve piston guide section. Another preferred exemplary embodiment of the common rail injector is characterized in that the valve piston is constructed in several parts, in particular in two parts. The multi-part design provides manufacturing advantages, especially in connection with a multi-part valve body.

Another preferred exemplary embodiment of the common rail injector is characterized in that the valve control chamber is connected to a valve member control chamber. Nozzle needles are preferably used as the valve member, the tip of which is pressed against an appropriately designed nozzle needle seat by means of a prestressed nozzle spring. When the pressure in the valve control chamber is reduced via the 3/2-way valve, the tip of the nozzle needle lifts off its seat and fuel is injected into the combustion chamber of the internal combustion engine through injection holes.

Another preferred exemplary embodiment of the common rail injector is characterized in that the valve control chamber is connected to a pressure booster control chamber. The pressure booster control chamber is used to control a pressure booster piston which can be accommodated so that it can move back and forth in the injector housing.

Further advantages, features and details of the invention emerge from the following description, in which various exemplary embodiments of the invention are described in detail with reference to the drawing. drawing

Show it:

Figure 1 shows a first embodiment in longitudinal section through the injector with a pressure booster and

2 shows a second exemplary embodiment in a longitudinal section through the injector without a pressure booster.

Description of the embodiments

1 shows a longitudinal section through a common rail injector 1, which is supplied with fuel under high pressure via a high-pressure storage chamber 2 (common rail), which is only indicated schematically. A fuel feed line 3, 4 extends from the interior of the high-pressure storage chamber 2 to a pressure booster 5, which is integrated into the fuel injector 1. The pressure intensifier 5 is enclosed by an injector housing 6.

The injector housing 6 comprises an injector body 7 and a nozzle body 8, which has a central guide bore 9. A nozzle needle 10 is guided to move back and forth in the guide bore 9. The nozzle needle 10 has a tip 11 on which a sealing surface is formed which interacts with a sealing seat which is formed on the nozzle body 8. When the tip 11 of the nozzle needle 10 comes into contact with its sealing surface located in the sealing seat, a plurality of spray holes 12, 13 are closed in the nozzle body 8. When the nozzle needle tip 11 lifts off its seat, high-pressure fuel is injected through the spray holes 12, 13 into the combustion chamber of the internal combustion engine.

A pressure shoulder 14 is formed on the nozzle needle 10 and is arranged in a pressure chamber 15 in the nozzle body 8. The nozzle needle 10 is biased by a nozzle spring 16 with its tip 11 against the associated nozzle needle seat. The nozzle spring 16 is received in a nozzle spring chamber 17, which is recessed in the injector body 7. The nozzle spring chamber 17 is connected to a pressure booster control chamber 23 via a connecting channel 18, in which a throttle 19 is arranged. In addition, the nozzle spring chamber 17 is connected to a pressure booster chamber 22 via a connecting channel 20, in which a throttle 21 is provided.

The pressure booster chamber 22 is formed by a section of a central bore in the injector body 7, in which an end 24 of a pressure booster piston 25 is accommodated so that it can move back and forth. The end 24 of the pressure booster piston 25 has the shape of a circular cylinder which has a smaller diameter than the adjoining part of the pressure booster piston 25. The other end of the pressure booster piston 25 projects into a pressure booster working space 26 which communicates with the high-pressure fuel reservoir via the fuel feed line 3, 4. room 2 communicates. In the pressure booster Working space 26, a pressure booster spring 27 is arranged, by means of which the pressure booster piston 25 is biased in the direction away from the nozzle needle 10.

The pressure booster chamber 22 is connected to the pressure chamber 15 in the nozzle body 8 via a connecting channel 28. The pressure booster control chamber 23 is connected via a connecting channel 29 to a valve control chamber 30, which is recessed in a valve body 31. An intermediate piece 32 is arranged between the valve body 31 and the injector body 7, in which a central connecting channel 33 is recessed. The connection channel 33 creates a connection between the pressure booster work chamber 26 and the valve control chamber 30.

The valve control chamber 30 is formed by a section of a central bore which is recessed in the valve body 31. The valve control chamber 30 has a larger diameter than the section of the bore facing away from the intermediate piece 32. In the central bore of the valve body 31, a valve piston 34 is movably received back and forth. The valve piston 34 has a valve piston guide section 35 which is guided in the central bore of the valve body 31. At the end of the valve piston 34 facing away from the valve piston guide section 35, a first sealing edge 36 is formed which bears against a sealing seat which is formed on the valve body 31. A second sealing edge 37 is formed on the end face of the valve piston 34 facing away from the valve piston guide section 35 can come into investment. Between the valve piston guide section 35 and the first sealing edge 36, a return channel 38 is provided in the valve body 31, which is connected to a fuel tank (not shown).

To the valve body 31, a Piezoaktorkör- per 39 connects, which is closed by a lid ^'40th The cover 40, the piezo actuator body 39, the valve body 31, the intermediate piece 32, the injector body 7 and the nozzle body 8 together form the injector housing 6. In the piezo actuator body 39, a central piezo actuator space 41 is recessed, which is connected to the fuel supply line via a connecting channel 42 3 and thus communicates with the high-pressure storage space 2. A piezo actuator 43 is arranged in the high-pressure piezo actuator chamber 41, which has a piezo actuator head 44 made of metal with a free end face 45. A collar 46 is formed on the piezo actuator head 44. A piezo actuator spring 47 is clamped between the collar 46 and a piezo actuator sleeve 48. The piezo actuator head 44 is displaceable in the axial direction relative to the piezo actuator sleeve 48. A sealing edge is formed on the piezo actuator sleeve 48 and bears against the valve body 31. In the interior of the piezo actuator sleeve 48, a hydraulic coupling chamber 41 is formed between the end face 45 of the piezo actuator head 44 and the free end face of the valve piston guide section 35 of the valve piston 34, which is acted upon by high pressure from the high pressure storage chamber 2. In Figure 1, the common rail injector 1 is shown in its deactivated state. The valve piston 34 is in its rest position. The first sealing edge 36 is in contact with the associated sealing seat, which is formed on the valve body 31. Rail pressure is present in the hydraulic coupling space 49. This is ensured by a suitable design of the sealing gaps. The components in the guide area of both coupler pistons are designed in such a way that they are also subjected to high pressure from the outside. This avoids a widening of the sealing gaps due to the coupler room pressure which impairs the function. Alternatively, the coupler space could also be filled using a correspondingly small throttle. The valve control chamber 30 is also supplied with the rail pressure from the high-pressure storage chamber 2 via the fuel supply lines 3, 4, the pressure booster working chamber 26 and the connecting channel 33. The pressure booster control chamber 23 is also subjected to the rail pressure via the connecting channel 29. Rail pressure also prevails in the pressure booster chamber 22, the nozzle filter chamber 17 and the pressure chamber 15.

To activate the common rail injector 1, the piezo actuator 43 is energized via electrical lines 51, 52 and expands. The expansion of the piezo actuator 43 leads via the piezo actuator head 44 to an increase in pressure in the hydraulic coupling space 49. This increase in pressure leads to an axial movement of the valve piston 34 downwards, that is to say toward the nozzle needle 10. The valve piston 34 moves down until the second Sealing edge 37 comes to rest on the intermediate piece 32 and interrupts the connection between the connecting channel 33 and the valve control chamber 30. At the same time, the first sealing edge 36 lifts from its sealing seat on the valve body 31 and opens a connection to the valve control chamber 30 and the return channel 38. The valve piston 34 is then in its injection position (not shown). The valve control chamber 30 is relieved of pressure due to the connection to the return channel 38. The latter is also relieved of pressure via the connecting channel 29 between the valve control chamber 30 and the pressure booster control chamber 23. Since the pressure booster working chamber 26 is still subjected to the rail pressure from the high-pressure storage chamber 2 via the fuel supply lines 3, 4, the pressure booster piston 25 moves downward, that is to the nozzle needle 10, as a result of which the fuel in the pressure booster chamber 22 is compressed. This pressure increase also has an effect in the pressure chamber 15 via the connecting channel 28. This in turn leads to the nozzle needle 10 lifting off its seat and fuel being injected.

The optimized design with the piezo actuator 43 in the rail pressure, the rail pressure in the hydraulic coupling chamber 49 and suitable pressure surfaces on the valve piston 34 result in a very simple and inexpensive overall construction. The necessary axial preload for the piezo actuator 43 is mainly generated hydraulically. The 3/2-valve piston 34 is controlled directly by the piezo actuator 43. The hydraulic coupling lungsraum 49 is provided to compensate for temperature expansions and for force / displacement translation. The valve piston 34 is almost completely pressure-balanced. This is achieved in that a pressure surface X is formed on the valve piston, which is constantly subjected to high pressure from the injector inlet. As a result, only a small actuator force is required to move the valve and a small and inexpensive piezo actuator can be used. The valve structure with the valve body 31 and the intermediate piece 32 in connection with the one-piece valve piston 34 with a flat seat allows easy manufacture.

The valve piston 34 can also be completely pressure-balanced. In this case, the necessary closing forces to ensure the tightness of the valve seats must be provided by preloaded springs or the actuator.

The valve piston 34 can also be designed as a multi-part piston assembly, the two control edges being arranged in one component and the piston section, which delimits the coupler space, in another component. As a result, the valve body can also be formed in several parts. This offers advantages when manufacturing very small valve geometries.

FIG. 2 shows a common rail injector 1 without a pressure booster. The common rail injector 1 shown in FIG. 2 comprises the same piezo actuator body, the same injector body and the same intermediate piece as the common rail injector shown in Figure 1. The same parts are provided with the same reference numerals. To avoid repetition, reference is made to the previous description of FIG. 1. Only the differences between the two embodiments are discussed below.

In the common rail injector 1 shown in FIG. 2, the valve control chamber 30 is connected to a nozzle needle control chamber 57 via a connecting channel 55 in which a throttle 56 is arranged. The nozzle needle control chamber 57 is arranged within a sealing sleeve 58 which is equipped with a bite edge. In addition, the nozzle needle control chamber 57 is delimited by an end face of a nozzle needle 59. A collar 60 is formed on the nozzle needle 59. A spring 61 is pretensioned between the collar 60 and the sealing sleeve 58 such that the biting edge of the sealing sleeve 58 is pressed against the injector housing. On the other hand, the tip of the nozzle needle 59 is held in contact with the associated nozzle needle seat due to the biasing force of the spring 61. A pressure chamber 63 is connected to the nozzle needle tip via flats 65, 66. In addition, the pressure chamber 63 is connected to the high-pressure storage chamber 2 via a connecting channel 68 and the fuel feed lines 3, 4. The connection anal 68 is connected to the nozzle needle control chamber 57 via a connection channel 69 and a connection channel 70, in which a throttle 71 is arranged. The common rail injector 1 shown in FIG. 2 is in the deactivated state. The first sealing edge 36 is closed and the second sealing edge 37 is open. Rail pressure is present in the coupling space 49. The valve control chamber 30, the nozzle needle control chamber 57 and the pressure chamber 63 are also under rail pressure. The valve piston 34 is in its rest position.

To activate the common rail injector 1 shown in FIG. 2, the piezo actuator 43 is energized and expands. This causes an increase in pressure in the hydraulic coupling space 49 and thereby a movement of the valve piston 34 downwards. The first sealing edge 36 opens and the second sealing edge 37 closes, so that a connection between the valve control chamber 30 and the return 38 is released. As a result, the valve control chamber 30 is relieved of pressure. This pressure relief also has an effect in the nozzle needle control chamber 51 via the connecting channel 55, so that the tip of the nozzle needle 59 lifts off the associated seat, as a result of which fuel is injected into the combustion chamber of the internal combustion engine.

Claims

claims

1. Common rail injector for injecting fuel into a combustion chamber of an internal combustion engine, with an injector housing (7, 8, 31, 32, 39, 40) that has a fuel inlet (3, 4) that is connected to a central one High-pressure fuel source (2) outside the injector housing and with a pressure chamber (15; 63) within the injector housing, from which, depending on the position of a control valve, in particular a 3/2-way valve, high-pressure fuel is injected, characterized that the control valve, in particular the 3/2-way valve, comprises a valve piston (34) which can be moved back and forth in the injector housing between a rest position and an injection position and is hydraulically coupled to a piezo actuator (43) which is connected to the pressure from the High-pressure fuel source (2) is acted upon.

2. Common rail injector according to claim 1, characterized in that the injector housing (7, 8, 31, 32, 39, 40) comprises a hydraulic coupling chamber (49) acted upon by the pressure from the high-pressure fuel reservoir, via which the piezo actuator ( 43) is hydraulically coupled to the valve piston (34).

3. Common rail injector according to claim 1 or 2, characterized in that a pressure surface is formed on the valve piston (34), which is constantly acted upon by high pressure from the fuel supply (3).

4. Common rail injector according to claim 2 or 3, characterized in that a first end of the valve piston (34) delimits the hydraulic coupling chamber (49) and a second end of the valve piston (34) projects into a valve control chamber (30) which is connected to a fuel return (38) in the injection position of the valve piston (34) and which is acted upon by the pressure from the high-pressure fuel accumulator (2) when the valve piston (34) is at rest.

5. Common rail injector according to claim 4, characterized in that on the valve piston 34 a first sealing edge (36) which in the rest position of the valve piston (34) interrupts a connection between the valve control chamber (30) and the fuel return (38) , and a second sealing edge (37) is formed, which in the injection position of the valve piston (34) interrupts a connection between the high-pressure fuel accumulator (2) and the valve control chamber (30).

6. Common rail injector according to claim 5, characterized in that at the first end of the valve piston (34) a valve piston guide portion (35) is formed, the diameter of which is slightly smaller than the diameter of the first sealing edge (36).

7. Common rail injector according to claim 6, characterized in that the diameter of the second sealing edge (37) is slightly smaller than the diameter of the valve piston guide section (35).

8. Common rail injector according to claim 6 or 7, characterized in that the valve piston (34) is formed in one piece.

9. Common rail injector according to claim 7 or 8, characterized in that the valve piston (34) is constructed in several parts, in particular in two parts.

10. Common rail injector according to one of the preceding claims, characterized in that the valve control chamber (30) with a valve member control chamber (57) is connected.

11. Common rail injector according to one of claims 1 to 9, characterized in that the valve control chamber (30) is in communication with a pressure booster control chamber (23).