EP1777408A1 - Fuel injection valve for internal combustion engines - Google Patents

Abstract

Fuel injection valve has a cavity, which is provided with the housing in which a piezo-actuator (15) is arranged, which exhibits a piezo-element (17). The valve has a piezo-element, which is connected in such a way with the housing by welding or by adhesive bond (40) so that the fuel tank (24) is locked externally.

Description

State of the art

Hub-driven common-rail systems are currently being used increasingly to introduce fuel into direct-injection diesel engines. This means that the injector controlling the valve member is constantly acted upon by the injection pressure and the injection is done by the counterforce is lowered to the valve member. As a result, the valve member, here the valve needle, moves and releases injection openings through which the fuel is injected into a combustion chamber of the internal combustion engine. The advantage here is that the injection pressure can be adapted to the load and the speed of the internal combustion engine.

There are a number of common-rail injectors known, each working on different principles. One concept here is that the fuel injector includes a piezo actuator that directly controls the pressure on a nozzle needle. The piezo actuator is surrounded by fuel, which is provided in a so-called rail and is under injection pressure. Between the nozzle needle and the piezo actuator, a hydraulic coupling space is provided to compensate for length tolerances and thermal drift. Since the entire piezo actuator is surrounded by the fuel, which is under the high fuel pressure of the rail, electrical supply lines must be led out of the piezo actuator to the outside in order to create the control voltage to the piezo actuator can. In the known fuel injection valves, as for example from the DE 10 2004 002299 A1 are known, an actuator base is formed on the piezoelectric actuator, in which the lines are led to the outside. In the actuator base, the lines are led in a Glaseinschmelzung, which are sealed fuel-tight.

The actuator base takes on two tasks. On the one hand, it must absorb the force exerted by the fuel pressure on the piezo actuator and, in addition, the force of a spring, which biases the piezo actuator against the actuator base. This force, which can be some 1000 N in modern fuel injection valves, must be supported on the actuator foot in such a way that it aligns as well as possible with the longitudinal axis of the piezoactuator. Otherwise, it could lead to increased wear, to lateral forces or jamming of the moving parts in the fuel injection valve.

The support of the Aktorfußes on the housing of the fuel injection valve, for example, via a ball-and-cone contact, wherein the actuator foot, a spherical surface and the housing of the fuel injection valve, a conical surface is formed. Between the spherical surface and the conical surface forms a circular sealing line, which also takes over the function of the high-pressure seal in addition to the gimbal of the actuator. The contact pressure and thus the sealing force on the sealing line depends on the rail pressure and on the spring used, which pretensions the piezo actuator. At high Raildrücken usually a sufficiently large force is present to prevent leakage at this point. Disadvantage of this construction, as for example from the DE 103 36 327 A1 is known, however, that at low Raildrücken the sealing force decreases and the required sealing function is no longer ensured.

Advantages of the invention

The fuel injection valve according to the invention with the characterizing features of claim 1 has the opposite over the advantage that at each rail pressure sufficient tightness is given at the contact point between the piezoelectric actuator and the housing of the fuel injection valve. For this purpose, a cavity is formed in the housing of a fuel injection valve, in which a piezoelectric actuator is arranged. The piezo actuator comprises a piezo element, which executes a stroke when a suitable electrical voltage is applied. Between the wall of the cavity and the piezo actuator remains a fuel chamber which can be filled with fuel. On the outside of the housing electrical contacts are formed, to which a suitable electrical voltage can be applied and which are connected via extending in the housing lines with the piezoelectric element. The piezoelectric actuator is connected to the housing by a welded or adhesive connection so that the fuel chamber is closed to the outside fuel-tight and is given at each rail pressure sufficient tightness.

By the dependent claims advantageous developments of the subject invention are possible. In a first advantageous embodiment, the piezo actuator comprises an actuator foot, which is firmly connected to the piezo element. The actuator foot is connected via a weld or adhesive connection to the housing of the fuel injection valve, wherein the lines which connect the contacts with the piezoelectric element pass through the actuator foot. Since the actuator foot is not itself piezo-active, a material can be used which is easily connectable to the material of the housing, that is, for example, welded or can be securely connected by a suitable adhesive connection. However, it can also be provided that the piezoelectric actuator has no Aktorfuß and that the piezoelectric element is bonded directly to the housing. In this case, the electrical lines run exclusively in the housing and are connected at their end to the piezo element.

In a further advantageous embodiment, in each case a planar surface is formed on the actuator base and on the holding body, which forms part of the housing, with which the actuator foot and the holding body abut each other. Such a flat surface can be used to produce a secure adhesive bond between the holding body and the actuator base by adhesive applied between the surfaces. It is also well possible to attach a weld on the outside of the flat surfaces and so safely connect the actuator base with the holding body. In an advantageous manner, the welded connection extends over the entire circumference of the actuator base.

In a further advantageous embodiment, the flat surfaces are formed at the end of a cylindrical portion, wherein in each case a cylindrical portion is formed on the actuator base and on the holding body. Both cylindrical sections surround a sleeve, wherein the sleeve is welded or glued to both cylindrical sections. The sleeve is preferably made of a material that can be either well welded or glued both with the material of the actuator base and with the material of the holding body, so that a secure connection is also given when such a connection directly between the actuator base and holder body difficult to train. In this case, both cylindrical sections advantageously have at least substantially the same diameter.

In a further advantageous embodiment, the actuator base on a cylindrical portion, while on the holding body, a cylindrical receptacle is formed, in which the cylindrical portion of the actuator base in the installed position of the fuel injection valve is arranged. The connection is formed by a welded or glued connection between the cylindrical receptacle and the cylindrical portion of the actuator base, so that a similar good connection is achieved as through the sleeve, but with fewer components.

Further advantages and advantageous embodiments of the subject matter of the invention can be taken from the description and the claims.

drawing

Figur 1

einen Längsschnitt durch ein erfindungsgemäßes Kraftstoffeinspritzventil

Figur 2

eine vergrößerte Darstellung des mit II bezeichneten Ausschnitts von Figur 1

Figur 3

eine alternative Ausgestaltung in einer ähnlichen Darstellung wie Figur 2, wobei hier nur der Haltekörper und der Piezo-Aktor gezeichnet sind,

Figur 4 und Figur 5

in der gleichen Darstellung wie Figur 3 weitere Ausführungsbeispiele der Erfindung.

In the drawing, various embodiments of the fuel injection valve according to the invention are shown. It shows

FIG. 1

a longitudinal section through a fuel injection valve according to the invention

FIG. 2

an enlarged view of the designated II section of Figure 1

FIG. 3

an alternative embodiment in a representation similar to Figure 2, wherein here only the holding body and the piezo actuator are drawn,

FIG. 4 and FIG. 5

in the same representation as Figure 3 further embodiments of the invention.

Description of the embodiments

1 shows a fuel injection valve according to the invention is shown in longitudinal section. The fuel injection valve comprises a housing 1, which comprises a holding body 3, a pressure sleeve 5 and an orifice plate 11, wherein the holding body 3 is screwed to the pressure sleeve 5 via a clamping sleeve 6. To the throttle disk 11, a nozzle 8 connects, which is bolted via a clamping nut 12 with the pressure sleeve 5, so that the nozzle 8 is clamped with the interposition of the throttle disk 11 against the housing 1.

The nozzle 8 comprises a nozzle body 10, in which a bore is formed, in which a piston-shaped nozzle needle 13 is arranged longitudinally displaceable. The nozzle needle 13 controls in the known manner the opening of at least one injection opening 14, via which the fuel is injected directly into a combustion chamber of the internal combustion engine. Between the throttle plate 11 and the combustion chamber facing away from the end face of the nozzle needle 13 on the one hand and between the throttle plate 11 and arranged in the pressure sleeve 5 control pin 25 is a control chamber 28 is formed, wherein the two parts of the control chamber 28 are connected to each other via a throttle 29 which is formed in the throttle plate 11. The control pin 25 is in this case arranged in a formed in the pressure sleeve 5 cavity 7, in which a piezoelectric actuator 15 is present. The piezoelectric actuator 15 comprises a piezoelectric element 17, which consists of a piezoactive material and has a plurality of layers, between which electrodes are formed. The piezoelectric element 17 lies with its end face, which faces the nozzle 8, on the control pin 25, and with the opposite end face on an actuator foot 19, which is part of the piezo-actuator 15. The piezo-element 17 is in this case surrounded by a sleeve which isolates the piezoelectric element 17 to the outside in a liquid-tight manner so that a fuel space 24 remaining between the piezoactuator 15 and the piezoelectric element 17 can be filled with fuel without the functionality of the piezo actuator 15 to affect.

The control pin 25 is surrounded by a tension spring 27, which is supported on the one hand on the control pin 25 and on the other hand via a sleeve 26 on the throttle plate 11. Since the tension spring 27 is arranged under pressure bias, it pushes the control pin 25 against the piezo actuator 15 and thereby characterized with the actuator base 19 against the holding body 3. Thus, the entire piezo element 17 is set under pressure bias, which ensures that the piezo Element 17 never comes under tension during operation. In the holding body 3 electrical contacts 22 are formed, which are connected via electrical lines 21 which extend in the holding body 3, with the piezoelectric element 17. In the holding body 3 is located next to a fuel port 32 through which the fuel injection valve is connected to a high-pressure fuel source, preferably a rail of a common rail system. Via the fuel connection 32, fuel can be conducted under high pressure into the fuel space 24 remaining between the piezoactuator 15 and the wall of the cavity 7. From there, the fuel can continue to flow past the pressure pin 25 through openings, not shown in the drawing, in the throttle disk 11 into the nozzle 8, where it surrounds the nozzle needle 13 and reaches into the region of the injection openings 14.

The operation of the fuel injection valve is as follows: If there is no injection of fuel, the piezo element 17 is energized and has reached its maximum length, so that the control pin 25 minimizes the volume of the control chamber 28. Since a high fuel pressure prevails in the control chamber 28, the valve needle 13 is in their If injection takes place, the energization of the piezoelectric element 17 is reduced, so that the piezoelectric element 14 is shortened. As a result, the valve pin 25 moves away from the nozzle 8 and increases the volume of the control chamber 28, so that the hydraulic force on the end face of the valve needle 13 decreases. By the hydraulic pressure on the valve needle 13, this is moved away from the injection openings 14 after the removal of the closing force and releases them thereby, so that an injection of fuel into the combustion chamber of the internal combustion engine takes place.

FIG. 2 shows an enlargement of the section of FIG. 1 denoted by II. The lines 21, which run in the housing 3, find their continuation in the actuator base 19, where the two lines 21 branch into the two outer electrodes 18, 18 'of the piezo-element 17. Both line 21, 21 'are here in the actuator base 19 in a Glaseinschmelzung 23, 23' out, which ensure a liquid-tight passage of the lines 21, 21 '. On the actuator base 19 is a spherical or spherical shell-shaped contact surface 34 is formed, which abuts a conical contact surface 33 which is formed on the holding body 3. Due to the convex configuration of the contact surface 34, a slight axial offset of the actuator base 19 and thus of the entire piezo actuator 15 is compensated, so that even with slight inclination a sealing line between the two contact surfaces 33, 34 is formed, which surrounds the actuator base 19 on its entire circumference ,

On the actuator base 19, a cylindrical portion 35 is formed, which is arranged in a cylindrical receptacle 37 which is formed on the holding body 3. The receptacle 37 and the cylindrical portion 35 are in this case in their inner diameter or outer diameter matched to one another that the cylindrical portion 35 is guided with little play in the cylindrical receptacle 37. Between the cylindrical receptacle 37 and the cylindrical portion 35, a welded joint 40 is formed, which surrounds the cylindrical portion 35 on its entire circumference. In this way, a tight connection between the holding body 3 and the actuator base 19 is given, which closes the housing 1 liquid-tight to the outside regardless of the pressure in the fuel chamber 24. It is also possible that between the cylindrical receptacle 37 and the cylindrical portion 35 is an adhesive bond, in which case a suitable, fuel-resistant adhesive between the cylindrical portion 35 and the cylindrical receptacle 37 is introduced.

By the Glaseinschmelzung 23, 23 'on the one hand and the welded joint 40 on the other hand, the fuel chamber 24 is sealed liquid-tight to the outside, still being easy mountability is given. Since the holding body 3 is screwed to the pressure sleeve 5 via a clamping sleeve 6, the actuator foot 19 can first connect to the holding body 3 and then connect both parts together through the clamping sleeve 6 with the pressure sleeve 5.

FIG. 3 shows a further exemplary embodiment of the piezoactuator according to the invention with the associated holding body 3. On the holding body 3 here is a cylindrical portion 36 and thereon a planar end face 41 is formed and the actuator base 19 a plane planar end surface 42, wherein the actuator base 19 and holding body 3 at the end faces 41, 42 abut each other. The two end faces 41, 42 are annular disk-shaped and have at least substantially the same outer diameter. To connect the holder body 3 with the actuator base 19, a weld 40 'is formed, which surrounds the actuator base 19 or the holder body 3 over its entire circumference. Instead of the welded joint 40 'may also be provided an adhesive connection, wherein a suitable fuel-resistant adhesive between the two end faces 41, 42 is introduced. The lines 21, 21 'are, as in the embodiment of Figure 2, guided in the holding body 3 and in the actuator base 19 and are completely surrounded by the welded joint 40'. To seal the lines 21, 21 'are here also Glaseinschmelzungen 23, 23'.

The embodiment of Figure 4 differs from the embodiment of Figure 3 in that here a sleeve 44 is provided which surrounds both the holding body 3 and the actuator base 19 in the region of the flat end faces 41, 42. By the same or approximately the same outer diameter in the region of the end faces 41, 42, the sleeve 44 may be formed so that it has only a small clearance, both relative to the holding body 3 and the actuator base 19. The seal is made by two welds 46, 46th ', wherein the sleeve 44 is welded to both the holding body 3 and the actuator foot 19. Both welds 46, 46 'in this case surround the sleeve 44 over its entire circumference. By using a separate sleeve 44, a material can be used which is well weldable both in its mating with the material of the holding body 3 and with the material of the actuator base 19, so that a tight connection over the entire life of the fuel injection valve is achieved.

In addition to a welded connection 46, 46 ', it can also be provided here that the sleeve 44 is connected via an adhesive connection to the holding body 3 or to the actuator foot 19. The fuel-resistant adhesive is in this case applied to the inside of the sleeve 44 and thus seals the passage of the lines 21 to the outside of the housing 1.

Figure 5 shows another embodiment of the piezoelectric actuator 15 according to the invention with associated housing 3 in the same representation as Figure 3 and 4. In contrast to the previous embodiments, here the actuator foot 19 is missing, so that the piezoelectric element 17 glued directly to the housing 3 is. Here, the piezoelectric element 17 abuts with its end face 117 against an at least approximately equally large end face 103 of the housing 3. If the adhesive bond between the end faces 117 and 103 is fuel-resistant in this case too, it is possible to prevent the fuel from penetrating over the service life of the fuel injection valve between the piezo element 17 and the holding body 3. The sealing of the lines 21, 21 'takes place here, as in the previous embodiments, on Glaseinschmelzungen 23, 23'.

For all the exemplary embodiments shown, in the case of a piezo element 17 with internal contacts or contacts mounted on the front side, the electrical lines can be made within the sealing line provided by the welded connection. As a result, the passage of the electrical lines via glass melts may be omitted, since the lines would no longer be subjected to the fuel pressure in the fuel chamber 24.

Claims (10)

Fuel injection valve for internal combustion engines having a housing (1) and a cavity formed therein (7) in which a piezoelectric actuator (15) is arranged, wherein the piezoelectric actuator (15) has a piezo element (17), which when applied a suitable electrical voltage performs a stroke, and with a between the wall of the cavity (7) and the piezo element (15) remaining fuel space (24) which can be filled with fuel, and with electrical contacts (22), the the outside of the housing (1) are arranged and to which an electrical voltage can be applied, wherein the contacts (22) in the housing (1) extending lines (21, 21 ') are connected to the piezoelectric element (15), characterized in that the piezo-element (15) is connected to the housing (1) by a welded or glued connection (40; 40 ';46;46') in such a way that the fuel space (24) is closed to the outside in a fuel-tight manner. Fuel injection valve according to claim 1, characterized in that the piezo-actuator (15) comprises an actuator base (19), wherein the piezo-actuator (15) with the actuator base (19) is firmly connected and the housing (1) with the actuator foot ( 19) is connected via the welded or glued connection (40, 40 ', 46, 46'), wherein the lines (21, 21 ') run through the actuator foot (19). Fuel injection valve according to claim 1, characterized in that the piezo-element (17) is glued directly to the housing (1). Fuel injection valve according to Claim 2, characterized in that the lines (21; 21 ') running in the actuator foot are surrounded by the welded or adhesive connection (40; 40';46; 46 '). Fuel injection valve according to claim 2, characterized in that the housing (1) comprises a holding body (3), in which the lines (21, 21 ') extend, wherein on the actuator base (19) and on the holding body (3) each have a planar end face ( 41, 42) is formed, with which the actuator base (19) and the holding body (3) abut each other. Fuel injection valve according to claim 5, characterized in that between the actuator base (19) and the holding body (3) there is an adhesive connection, which is formed between the flat end faces (41, 42). Fuel injection valve according to claim 5, characterized in that between the actuator base (19) and holding body (3) a welded connection (40; 40 '), wherein the welded connection (40; 40') over the entire circumference of the Aktorfußes (19). Fuel injection valve according to claim 5, characterized in that on the actuator base (19) and on the holding body (3) each have a cylindrical portion (35; 36) is formed, on which the flat end faces (41; 42) are formed, and with a sleeve ( 26) which surrounds both cylindrical portions (35; 36) and which is welded to both cylindrical portions (35; 36) and thereby forms the weld joint (46; 46 '). Fuel injection valve according to Claim 8, characterized in that the two cylindrical sections (35; 36) have at least substantially the same diameter. Fuel injection valve according to claim 2, characterized in that on the actuator foot (19) has a cylindrical portion (35) is formed and on a holding body (3) which is part of the housing (1), a cylindrical receptacle (37) in which the cylindrical Section (35) is arranged in the installed position in the fuel injection valve, wherein the welding or adhesive connection (40) between the cylindrical receptacle (37) and the cylindrical portion (35) is formed.

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