EP1970556B1 - Injector - Google Patents

Description

The invention relates to an injector, according to the preamble of claim 1, wherein the injector has a arranged in a running with a head side and a foot chamber chamber piezo element, the foot side is associated with a piston, the chamber in a foot-side chamber and in a head-side chamber divided, wherein a high pressure medium line opens via a connecting line in an injection element.

The DE 103 26 046 A1 discloses an injection nozzle for an internal combustion engine, in particular in a motor vehicle. The injection nozzle has a nozzle body, which has at least one injection hole on. In a needle guide of the nozzle body, a nozzle needle is guided, with which the injection of fuel through the at least one spray hole is controllable. It is provided with an actuator drive-coupled control piston having a first control surface. The nozzle needle has a first compensator surface, or is drive-coupled with a compensator piston having a first compensator surface. The first compensator surface is hydraulically coupled to the first control surface via a first hydraulic path. The first control surface is hydraulically coupled via a second hydraulic path with a supply line which supplies the at least one injection hole under high pressure fuel.

The DE 102 54 466 A1 relates to a fuel injection valve. A piezo actuation field of a fuel injection valve drives an actuation piston via a large diameter piston and a pump chamber to push down a valve body of a control valve and to open a low pressure drain port. This is intended to open a nozzle needle and inject fuel. A chamfered part is formed at an upper end of the drainage hole. The chamfered portion is formed so that a channel area increases significantly in an upward direction. Therefore, the energy of a fuel spray jetting out into an overflow chamber is drastically reduced, and a force acting in a direction to inhibit the movement of the agitation piston is reduced.

The DE 102 60 289 A1 discloses an injector for fuel injection into an internal combustion engine, comprising a housing having an actuator unit which urges a crankpin on axial actuation of the actuator at its lower end, and means for sealing the actuator unit against a fuel-filled leakage space extending located below the device. The device comprises a flexible plastic ring, which is designed to center the crank pin in the axial direction and tightly enclose. Further, a metal ring is provided which sealingly surrounds the plastic ring and sealingly arranged to the housing and secures against axial displacement in the interior of the housing.

The DE 103 33 688 B3 discloses a fuel injector having an injector, a high pressure fuel delivery line to the injector, a control valve controlling pressure in a control chamber of the injector associated with said conduit, the movable valve member of which is actuatable by an actuator via a hydraulic coupler, the two having a coupler volume of the coupler cooperating, linearly arranged one behind the other piston. A cross-sectional area of the movable valve member is pressurized with the control valve closed by the control chamber at high pressure. The fuel injector further includes means for filling the volume of the coupler via guide gaps of the pistons with pressurized fuel. A filling space arranged between the pistons is connected to said conduit. The actuator-facing piston, which has a cross-sectional area f4, is mechanically coupled to the actuator via a rod having a smaller cross-sectional area f5 than f4, the other piston having a cross-sectional area f2 via another rod having a smaller cross-sectional area than f2 f1 actuates the control valve. The two opposite ends of the pistons engage in associated translation spaces, which are connected via a channel. The cross-sectional areas are chosen so that f3 + f2 - f1 <f2, such that the control valve is at least partially balanced with force. The direction of the opening movement of the movable valve member coincides with the direction of fuel flowing out of the control chamber.

The DE 198 23 937 B4 describes a servo valve for an injection valve for the injection of fuel into an internal combustion engine with a control chamber, which can be supplied with fuel under system pressure from a high-pressure accumulator and can be brought via an outlet throttle with a non-pressurized return to a fuel tank. The pressure prevailing in the control chamber pressure acts on a movable nozzle body, which is provided with a nozzle needle, which releases or closes injection holes in the movement of the nozzle body. The flow of fuel to and from the control chamber is controlled by the servo-valve, which has a movable valve body and which selectively connects the control chamber to the high-pressure accumulator or connects the control chamber to the non-pressurized return. The outlet throttle is designed as a movable, plate-shaped piston, which is arranged in a space between the control chamber and the servo valve and servo valve side has a sealing surface. The plate-shaped piston is provided with a drain opening and is hydraulically actuated by the fuel flow to and from the control chamber so that when a fuel flow into the control chamber opens an inlet opening and the fuel inlet is closed from the control chamber, the inlet opening. The plate-shaped piston is arranged freely movable in the space between the control chamber and the servo valve, wherein the inlet opening is arranged in the plate-shaped piston in the region of the sealing surface.

The DE 198 37 890 B4 discloses a fuel injector having a control chamber, wherein the pressure in the control chamber is in operative communication with a nozzle needle and the pressure in the control chamber controls the nozzle needle. The fuel injection valve also has a servo valve, which has a closing body and an associated valve seat, wherein the servo valve between the control chamber and a return channel is arranged. The closing body closes in a closed position a drain, wherein an actuator is provided which actuates the closing body. The closing body has a part-spherical closing head, which is associated with the valve seat. The closing body merges into a closing handle. Further, a valve spring is provided which comprises the closing stem and biases the closing head against the valve seat. It is an inlet channel provided with an inlet throttle to the control chamber, one between the control chamber and the servo valve arranged drain channel is provided, which has an outlet throttle, which limits the fuel drain from the control chamber.

The EP 1167 746 B1 discloses a fuel injection valve device for an internal combustion engine, comprising a housing with an injection opening formed therein, a needle valve for opening and closing the injection port, a control chamber formed in the housing for applying a fuel pressure to the needle valve in an opening direction of the needle valve, a spring for applying a Biasing force on the needle valve in a closing direction of the needle valve, a piezoelectric actuator for increasing and decreasing a fuel pressure in the control chamber, a piston which slides with the needle valve and is applied with the fuel pressure of the control chamber, and a pressure accumulating chamber formed in the housing for storing a fuel to be supplied to the injection port. In the housing, a further control chamber is formed, which is in communication with a fuel supply line to apply a fuel pressure to an upper end surface of the piston in the closing direction of the needle valve. The piston is acted upon at its lower end surface in the control chamber with a fuel pressure in the opening direction of the needle valve, wherein the further control chamber communicates via a connecting device with the pressure storage chamber.

The EP 1 240 240 B1 revealed like that DE 198 37 890 B4 a fuel injection valve having a control chamber connected to an inlet channel, the pressure in the control chamber being in operative connection with a nozzle needle, and the pressure in the control chamber controlling the nozzle needle, with a servo valve having a closing body and an associated first valve seat, wherein the servo-valve is disposed between the control chamber and a return passage and the closing body closes a drain in a closed position, with an actuator that actuates the closing body, wherein the closing body has a part-spherical closing head, which is associated with the first valve seat. The closing head merges into a closing handle. A valve spring is provided which includes the closing stem and biases the closing head against the first valve seat. The closure body has a central Kopfabflachung that the first valve seat assigned. The actuator is in operative connection with a plunger, which is guided through the first valve seat and rests on the Kopfabflachung.

• eine Steuerkammer, um einen Druck in einer Ventilschließrichtung auf eine Ventilnadel auszuüben;
• ein Steuerventil in einer Dreiregelventilstruktur, um zwischen einer Kommunikation und einer Unterbrechung der Steuerkammer mit dem genannten Hochdruckkanal und einem Niederdruckkanal zu wechseln, um den Druck in der Steuerkammer anzuheben oder zu senken; und
• eine Antriebseinheit, um ein Ventilelement des Steuerelementes anzutreiben, um das Ventilelement selektiv auf einem niederdruckseitigen Sitz in Kommunikation mit dem Niederdruckkanal oder einem hochdruckseitigen Sitz in Kommunikation mit dem Hochdruckkanal zu setzen, indem
• die Antriebseinheit einen Aktuator für eine Längenänderung aufweist, wenn dieser elektrisch betrieben ist und einem Gleitpin, der in einem Gleitloch gleitet, um eine Antriebskraft in Übereinstimmung mit der Längenänderung des Aktuators zu übertragen, wobei der Gleitpin einen pinähnlichen Fortsatz aufweist, der in Kontakt mit dem Ventilelement des Steuerventils steht, welches in einer Ventilkammer aufgenommen ist,
• ein Raum um den pinähnlichen Fortsatz zwischen einem Gleitabschnitt des Gleitpins und dem niederdruckseitigen Sitz angeordnet ist, der mit dem Hochdruckkanal durch einen Verengungsabschnitt verbunden ist, wobei ein Durchmesser des niederdruckseitigen Sitzes geringer oder gleich einem Durchmesser des hochdruckseitigen Sitzes ist, und
• der Druck in der Steuerkammer in Kommunikation mit der Ventilkammer als eine Hilfskraft wirkt, so daß eine hochdruckseitige Sitzschließkraft geringer oder gleich einer niederdruckseitigen Öffnungskraft wird.

The EP 614 893 A1 relates to a fuel injector for injecting fuel from a common rail through a high pressure passage comprising:

• a control chamber for applying a pressure in a valve closing direction to a valve needle;
• a control valve in a three-control valve structure for switching between communication and interruption of the control chamber with said high-pressure passage and a low-pressure passage to raise or lower the pressure in the control chamber; and
• a drive unit to drive a valve member of the control member to selectively set the valve member in communication with the low pressure passage or a high pressure side seat in communication with the high pressure passage on a low pressure side seat by:
• the drive unit has an actuator for a length change when electrically operated and a sliding pin sliding in a sliding hole to transmit a drive force in accordance with the change in the length of the actuator, the slide pin having a pin-like projection in contact with the actuator Valve element of the control valve, which is accommodated in a valve chamber,
• a space is arranged around the pin-like projection between a sliding portion of the sliding pin and the low-pressure side seat connected to the high pressure passage through a throat portion, wherein a diameter of the low pressure side seat is less than or equal to a diameter of the high pressure side seat, and
• the pressure in the control chamber in communication with the valve chamber acts as an assist force, so that a high-pressure-side seat-closing force becomes less than or equal to a low-pressure-side opening force.

The WO 02/061265 discloses a valve for controlling fluids, comprising a valve member axially movable valve member which cooperates with a valve closure member for opening and closing the valve, and having a working as a hydraulic ratio hydraulic chamber which is filled to compensate for leakage losses with liquid, said Hydraulic chamber is connected directly to at least one leading to a high-pressure region filling channel, which has at least one throttle element for adjusting a filling amount of the hydraulic chamber.

The JP 2002322957 A discloses a fuel injector for performing a post-injection in the vicinity of a main injection.

• einen Steuerventilraum, der mit einer Kraftstoffzuführleitung verbunden ist, um Hochdruckkraftstoff einzuführen;
• eine Kraftstoffleckagekammer, die mit einer Kraftstoffrückführung verbunden ist;
• eine Verbindungsleitung zur Verbindung der Steuerventilkammer und der Kraftstoffleckagekammer;
• und einem Steuerventil, das in der Steuerventilkammer montiert ist, wobei das Steuerventil die Verbindungsleitung konstant schließt. Das Kraftstoffeinspritzventil weist weiter ein Anhebeelement und einen piezoelektrisch gesteuerten Aktuator auf, der das Steuerventil öffnet, wobei die Kraftstoffeinspritzung durch Öffnen des Steuerventils mittels des Anhebeelementes durchgeführt wird.

The JP 2003293893 A relates to a fuel injection valve comprising:

• a control valve space connected to a fuel supply line for introducing high-pressure fuel;
• a fuel leakage chamber connected to a fuel return;
• a connection line for connecting the control valve chamber and the fuel leakage chamber;
• and a control valve mounted in the control valve chamber, wherein the control valve closes the connection line constantly. The fuel injection valve further includes a lifting member and a piezoelectrically controlled actuator that opens the control valve, wherein the fuel injection is performed by opening the control valve by means of the lifting member.

Internal combustion engines, in particular novel diesel engines use injectors for injecting fuel or diesel into a combustion chamber of the Combustion engine. Each combustion chamber is preferably assigned at least one injector.

In FIG. 1 is a first generation of injectors shown. In a closed state, the valve 106 or 107 is closed. In the chambers 110 and 109 system pressure prevails. Both chambers 110 and 109 are supplied by the supply line 108. The chamber 111 is connected to at least one throttle 112 to the combustion chamber and thereby acted upon by the pressure of the combustion chamber. The balance of forces on the needle 101 is directed downwards and pushes the needle into the seat 114. Thus, no fluid flows from the chamber 109 via the seat 114 into the chamber 111. As shown in FIG FIG. 1 as well as the following figures of the prior art, the needle is not drawn throughout. It is possible that a one-piece needle or a multi-part needle is used. Is known, combinations of needle and piston rod with possibly additional adapters, such as the EP 1 167 746 is removable, provide. Therefore, the needle is referred to below as a needle unit due to the possible one-piece or multi-part design.

To open the injector, the valve or the throttle 106 or 107 is opened. As a result, liquid or fuel flows out of the chamber 110 via the throttle 106 or 107 into the return system. As a result, the pressure in the chamber 110 drops. The pressure which occurs here is dependent on the flow characteristic of the throttle 105, through which liquid flows into the chamber 110 and the outflow volume flow from the throttle 106 or 107 and the leakage flow along the needle unit and the piston 101st

When the pressure in the chamber 110 has fallen far enough, the opening forces on the needle unit (lower area [chambers 109 and 111]) predominate and the needle unit moves upward. As a result, the seat 114 opens and liquid flows from the supply line 108 via chamber 109 into the chamber 111. From there, the liquid flows via at least one throttle 112 into the combustion chamber. To close the valve, the throttle 106 or 107 is closed, so that the pressure in the chamber 110 increases and the balance of forces on the needle unit 101 is changed so that it moves in the closing direction. After closing system pressure is restored in all chambers.

As a disadvantage of this known injector FIG. 1 is to be considered that an external leakage for the control of the valve is absolutely necessary, with only an indirect control of the valve by a leakage current to the throttles is possible. The lifting speed of the needle unit is disadvantageously determined by the predetermined throttles. In addition, in many executed injectors, a further external leakage is additionally observed on the guide of the needle unit (from chamber 109 or 110 via bearing gaps to the return system). By the indirect control of the needle unit, a very slow system is provided, the needle speed is only possible by a variation of the throttles (drain throttles 106, 107 or 105 and leakage flow along needle or piston 101).

Since a faster (direct) control of the needle unit is advantageous for novel internal combustion engines, in particular for new diesel engines, various piezo-directly-actuated injectors have been proposed to increase the performance. In FIG. 2 is shown in a simplified form such a piezo-actuated version, as this example from the EP 1 167 746 is known. In this directly actuated version is a piezoelectric element 207 in a chamber with liquid (fuel), which is supplied from a line 206. Via an internal leakage on a cylinder piston 214, the liquid also flows into the chamber 208. This chamber is further connected via a connection with the chamber 211. In the closed state of the injector, the piezoelectric element 207 is driven or charged. The balance of forces on the needle unit 201 holds this as to the embodiment of the known injector FIG. 1 described in the closed state.

To open the injector, the piezoelectric element 207 is discharged. As a result, it shortens and the pressure in the chamber 208 decreases. Via the line 209, the pressure in the chamber 211 also falls. As a result, the balance of forces at the needle unit 201 moved so far that the injector opens. Low internal leakage on the piston 214 causes fluid to flow from the chamber 215 into chamber 208 and via the connection 209 into the chamber 211. Fluid also flows through the gap between the needle unit 201 and the housing 210 from the chamber 203 into the chamber 211 the pressure in the chambers 208 and 211 rises again and the needle unit closes slowly. This behavior is necessary for the system start (filling of the system) and in case of malfunction, for example, when the piezo element is clamped (emergency closing).

To close the piezoelectric element 207 is charged. As a result, the piston 214 moves downward and increases the pressure in the chamber 208 and 211, so that the needle unit 201 is moved to the closed position.

During operation of an internal combustion engine, in particular a diesel engine, the previously described injector is normally closed for approximately 90 to 95% of the operating time of the internal combustion engine. Disadvantageously, the piezoelectric element must be kept in this state in the charged state. This means a high electrical and mechanical load on the piezoelectric element.

To prevent this disadvantage or to achieve a robust and energy-saving injector with a long service life, is therefore provided in a possible variant, which opens the injector in the actuated state and keeps the injector closed in the non-actuated state, with a direct proportionality between Actuator movement and needle unit exists. Any contemplated mechanical reversal of motion is associated with increased manufacturing effort, increased part diversity and increased probability of failure.

Another variant of a fuel injector or injector, for example, according to the WO2005 / 075811 is in simplified form in FIG. 4 shown. Here, the piezoelectric element 410 is also discharged in the closed state. An opening of the needle unit 401 is achieved by the loading and thus the connected lengths of the piezoelectric element 410. This increases the pressure in the chambers 408 and 405. In some variations of this design, the chamber 408 is integrated directly into the chamber 405. The pressure rise in the chamber 405 creates a additional force on the needle unit 401, causing it to move to the opening position.

To close the valve, the piezo element 410 must be discharged again. As a result, the pressure in the chamber 408 and 405 drops, so that a closing resultant force acts on the needle unit 401.

In this known variant, it is disadvantageously imperative to generate a pressure increase above the existing system pressure from the supply line 413. This creates an increased load on the material, so that the life is reduced and the size of the injector must be increased.

The invention is therefore based on the object with simple means to improve an injector of the type mentioned in that the above-mentioned disadvantages are repealed.

According to the invention the object is achieved by an injector with the features of claim 1, wherein a high-pressure connection channel communicates with the high-pressure medium line and opens in the foot-side chamber, so that in the head-side chamber, a negative pressure is created when the piezoelectric element is actuated.

The invention is based on the finding that so far with direct actuated injectors always the end face of the piezoelectric element used and the volume connected thereto for controlling the Injektornadel or the needle unit have been used. As a result, it is always necessary to accept at least one of the disadvantages listed above. With the invention, however, not the end face, but the inner surface of the piston is used. As a result, an extremely simple construction of an injector is advantageously provided, which has none of the disadvantages mentioned. In particular, the advantageous injector has embodiments which have no control leakage and no constant, external leakage in the closed / open state. In the sense of the invention, external, undesired leakage means a leakage in which the liquid leaves the injector, that is to say into a low-pressure reflux system, For example, gets into a fuel tank. As internal, desired leakage within the meaning of the invention, a leakage is meant in which liquid passes through connections, gaps or channels within the injector from one chamber to another chamber. In addition, advantageously no further mechanical components for reversing the movement are necessary, wherein an increase in pressure for opening the injector can be dispensed with. It is particularly advantageous that the piezoelectric element is discharged during the closed state. The advantageous injector has a small number of components and a low load on the piezoelectric element, wherein an additional pressure increase during the injection of, for example, fuel, in particular diesel in a combustion chamber is possible, wherein the pressure increase may be temporary or limited in time.

Appropriately, it is provided that viewed in longitudinal section between end faces of the piston and a chamber inner wall, a gap is arranged so that the head-side chamber via internal leakage flows from the foot-side chamber can be filled or that the two chambers communicate with each other. Conveniently, it is provided that the head-side chamber is connected via a connecting line with an injection element which has a housing arranged in a needle or needle unit, which is spaced from the head side to a housing head, so that a free space is formed, in which the connecting line opens, and wherein the needle or the needle unit is assigned to a seat at the foot so as to alternately open or close the fuel supply from a gap via the high-pressure medium line to a combustion chamber via an injection chamber and at least one throttle, and wherein the gap between the needle body and the Housing inner wall is arranged. The gap dimension can, seen in the axial direction, have a changing amount in a preferred embodiment, which means that the gap or its gap dimension in front of the seat can be greater than in front of the free space.

It is expedient for the purposes of the invention, when in the free space, a spring is arranged, which bears against both the housing head and on the needle head. Possible in the sense of the invention is that in the high-pressure medium line, a check valve may be arranged.

In the non-actuated state, all chambers are subjected to system pressure. Only in the injection chamber, the combustion chamber pressure prevails, which is usually smaller than the pressure from the high-pressure medium line. By this pressure difference and the additional spring force of the spring, the needle or the needle unit is pressed into the seat. As a result, the injector is closed, there is no external leakage and the piezo element is not charged.

In the injector according to the invention it is provided that the piston is assigned to a foot side arranged on the piezoelectric element piston rod which engages through a crosspiece arranged in the chamber, wherein the transverse web divides the chamber into a piezo chamber and into a piston chamber, wherein the piston chamber by means of the piston in the head-side chamber and is divided into the foot-side chamber, wherein the high-pressure connection channel opens into the foot-side chamber, so that in the head-side chamber, a negative pressure is created when the piezoelectric element is actuated.

In order to achieve that the piezo chamber is also kept under system pressure, a connection from the high-pressure medium line opens directly into the piezochamber according to the invention.

In order to establish a communication between the head-side chamber and the piezochamber, it can be provided that the piston rod is seen in longitudinal section spaced from the end faces of the transverse web, but it can also be expediently provided that passage openings are arranged in the piston and / or in the transverse web , In addition, the overflow behavior between the chambers can be influenced by additional throttles and / or check valves.

As a variant not according to the invention it is provided that the piezochamber is connected via a connecting line to a fuel tank, so that the piezoelectric element is not under high pressure. Here, the piezochammer is no longer connected to the high-pressure medium line, so that the piezochamber is acted upon only with the tank pressure. This ensures that a sealing of the piezoelectric element is easier, but a small (external) leakage must be accepted, since liquid can flow between the arranged between the piston rod and the end faces of the crosspiece gap and get into the tank. Advantageously, it is therefore provided that the gap height should be as low as possible.

In an embodiment according to the invention it is provided that the piezo chamber is associated with a sealing element so that between the transverse web and the sealing element an intermediate chamber is arranged, which may be connected to a return Niederducksystem or the fuel tank. By means of this advantageous embodiment, the piezoelectric element can be kept completely dry, wherein in the resulting intermediate chamber only a lower pressure, namely the tank pressure is present, so that here advantageously a simple seal can be used.

But if no external leakage is accepted, it is expediently provided in a further embodiment not according to the invention to remove the connection of the intermediate space to the tank, whereby the pressure in the intermediate chamber rises to system pressure. However, the sealing element must then seal against high pressure. Although this makes a somewhat more complicated high-pressure seal necessary, this allows an externally leak-free injector. In addition, the resulting intermediate chamber can then be connected to the high-pressure medium line in order to achieve a rapid pressure equalization in the intermediate chamber.

Fig. 3

prinzipielle Darstellungen von möglichen Trennebenen einer Nadeleinheit, und

Fig. 5

einen Injektor mit einem in einer Kammer angeordneten Piezoelement in einer ersten Ausgestaltung,

Fig.6

den Injektor aus Figur 5 mit im Vergleich zu Figur 5 umgekehrt angeordneten Kammer, in der das Piezoelement angeordnet ist,

Fig. 7

einen Injektor in einer zweiten Ausgestaltung mit der Kammer, in der das Piezoelement angeordnet ist,

Fig. 8

eine Vergrößerung aus Figur 7,

Fig. 9

den Injektor aus Figur 7 mit im Vergleich zur Figur 7 umgekehrt angeordneter Kammer, in der das Piezoelement angeordnet ist,

Fig. 10

einen Injektor mit einem in einer Kammer angeordneten Piezoelement in erfindungsgemäßer Ausgestaltung, und

Fig. 11

den Injektor aus Figur 10 mit einer im Vergleich zu Figur 10 umgekehrt angeordneten Kammer, in der das Piezoelement angeordnet ist.

Further advantageous embodiments of the invention are disclosed in the subclaims and the following description of the figures. Show it:

Fig. 3

basic representations of possible parting planes of a needle unit, and

Fig. 5

an injector having a piezoelectric element arranged in a chamber in a first embodiment,

Figure 6

out the injector FIG. 5 with compared to FIG. 5 reversely arranged chamber in which the piezoelectric element is arranged,

Fig. 7

an injector in a second embodiment with the chamber in which the piezoelectric element is arranged,

Fig. 8

an enlargement FIG. 7 .

Fig. 9

out the injector FIG. 7 with compared to FIG. 7 reversely arranged chamber in which the piezoelectric element is arranged,

Fig. 10

an injector with a piezoelectric element arranged in a chamber in the inventive design, and

Fig. 11

out the injector FIG. 10 with one compared to FIG. 10 reversely arranged chamber in which the piezoelectric element is arranged.

In the different figures, the same parts are always provided with the same reference numerals, so that these are usually described only once.

FIG. 5 shows an injector 1, which has a arranged in a running with a head side 2 and a foot 3 chamber 4 piezoelectric element. The piezoelectric element 6 is associated with the foot side a piston 7. The piston 7 separates the chamber 4 in a foot-side chamber 8 and a head-side chamber 9. The foot-side chamber 8 is connected via a high-pressure connection channel 11 directly to a high-pressure medium line 12 in conjunction, so that in the head-side chamber 9, a negative pressure is formed when the piezoelectric element 6 is actuated and lengthens, wherein the high-pressure medium line 12 opens via a connecting line 13 in an injection element 1.4.

The injection element 14 has a housing 16 arranged in a needle 17, the head side (needle head) is spaced from a housing head 18 so that a free space 19 is formed. The needle 17 is associated with a seat 21 on the foot side, so as to open or close the fuel supply to a combustion chamber, not shown, alternately. In the presentation according to FIG. 5 as well as the following figures, the needle is not drawn throughout. It is possible that a one-piece needle or a multi-part needle is used. Examples of a possible separation level are in FIG. 3 shown. Therefore, the needle is referred to below as a needle unit due to the possible one-piece or multi-part design. The needle 17 protrudes on the foot side into an injection chamber 22. In the region of the injection chamber 22, at least one throttle 23 is arranged in the housing 16 in the area of the injection chamber 22 so that liquid can flow or be injected from the injection chamber 22 into the combustion chamber. In the illustrated embodiment, two throttles 23 are provided as seen in longitudinal section. Between the needle body and a housing inner wall 24, a gap 26 is arranged. The gap of the gap 26 may have seen in the axial direction a changing amount in a preferred embodiment, which means that the gap or its gap in front of the seat 21 may be greater than before the free space 19. The injection chamber 22 is connected to the combustion chamber the throttle (s) 23 connected. The gap 26 or the high-pressure medium line 12 is separated from the injection chamber 22 and thus the combustion chamber.

At the in FIG. 5 longitudinal section shown is formed between end faces 27 of the piston 7 and a chamber inner wall 28 of the chamber 4, a gap 29 or arranged.

The head-side chamber 9 is connected via a connecting line 31 with the injection element 14, wherein the connecting line 31 opens into the free space 19.

In the free space 19, a spring 32 is arranged in the illustrated embodiment, which bears against both the housing head 18 and the needle head 33.

In the high pressure medium line 12, a check valve 34 may be arranged, this option is shown by dash-dot.

The piezoelectric element 6 is connected on the head side to the head side 2 of the chamber 4. In the in FIG. 5 illustrated embodiment, the foot side 3 of the chamber 4 is oriented in the direction of the housing head 18 of the injection element 14. In contrast, in the embodiment according to Fig. 6 the foot side 3 of the chamber 4 is oriented away from the housing head 18 of the injection element 14, wherein the head side 2 of the chamber 4 is oriented in the direction of the housing head 18 of the injection element 14. Except for the inversion of the chamber 4 (the chamber 4 is virtually on the head) corresponds to the embodiment according to Fig. 6 according to the embodiment Fig. 5 ,

On the operation of the injector 1 according to the embodiments of the Figures 5 and 6 will be discussed further below.

At the in FIG. 7 illustrated embodiment of the injector 1, the piston 7 is assigned to a foot side arranged on the piezoelectric element 6 piston rod 36. The piston rod 36 passes through a transverse web 37 arranged in the chamber 4, wherein the transverse web 37 divides the chamber 4 into a piezochamber 38 and into a piston chamber 39. The piston chamber 39 is divided by the piston 7 in the head-side chamber 9 and the foot-side chamber 8, wherein the high-pressure connection channel 11 opens directly into the foot-side chamber 8, so that in the head-side chamber 9, a negative pressure is formed when the piezoelectric element 6 is actuated and lengthens. In FIG. 7 is further shown that a connection 41 from the high pressure medium line 12 can open directly into the piezo chamber 38.

Between the transverse web 37 and its longitudinal faces recognizable end faces 40 and the piston rod 36, a gap 42 is formed or arranged. Preferably, between the high-pressure connection channel 11 and the connection 41, in turn optionally a check valve 34 may be provided, which is arranged in the high-pressure medium line 12.

In FIG. 7 the chamber 4 is oriented with its base 3 in the direction of the housing head 18 of the injection element 14, in contrast to in FIG. 9 again a reverse arrangement similar to that in FIG. 6 is shown.

FIG. 7 shows a basic structure of the injector 1. The piezoelectric element 6 is integrated in the chamber 4. The chamber 4 or the piezo chamber 38 is preferably connected via the connection 41 directly to the high pressure medium line 12 and thus can always allow a direct pressure equalization between the piezo chamber 38 and the high pressure medium line 12. Of course, the connection 41 can also be dispensed with. Since the foot-side chamber 8 is connected directly to the high-pressure medium line 12, a direct pressure equalization can also be made possible here.

The head-side chamber 9 is filled with liquid by internal leakage flows from the foot-side chamber 8 (along the piston 7) and the piezo chamber 38 (along the piston rod 36). An additional filling can be achieved by attaching further connections between these chambers, which is exemplified in FIG. 8 is shown. Furthermore, a preferably throttled connection line between the chambers 9 and 19 and the high-pressure medium line 12 is conceivable. The Überströmverhalten between the chambers can be influenced by zusätliche throttles and / or check valves. In FIG. 8 is the high-pressure connection channel 11 and the connecting line 31 is not shown.

The head-side chamber 9 is connected via the connecting line 31 with the free space 19 in the injection element 14, as already described. The connecting line 31 can be changed by flow restrictors and / or check valves in the flow behavior.

The free space 19 can additionally be filled by the liquid present in the gap 26 via an internal leakage at the guide of the needle unit.

In the non-actuated state of the piezoelectric element 6 all chambers 8, 9, 19 and 38 and the gap 26 are subjected to system pressure. In the injection chamber 22 By this pressure difference and the additional spring force of the spring 32, the needle 17 and the needle unit is pressed in the drawing plane down into the seat 21. Thus, the injector 1 is closed, there is no external leakage, and the piezoelectric element 6 is not charged.

To open the injector 1, the piezoelectric element 6 is energized and thereby elongated. As a result, the piston 7 is displaced downwards, that is to say in the direction of the foot 3, and reduces the foot-side chamber 8. Since the foot-side chamber 8 is connected directly to the high-pressure medium line 12, no or only a minimal increase in pressure results. Parallel to the reduction of the foot-side chamber 8, the head-side chamber 9 is increased. Since the pressure in the head-side chamber 9 can be compensated only by small, internal leakage currents, the pressure drops. The head-side chamber 9 is in communication with the free space 19, whereby here also the pressure drops. Due to the reduced pressure in the free space 19, the resulting force acts on the needle 17 or on the needle unit in the opening direction and the needle 17 or the needle unit lifts off the seat 21. Now the needle 17 or the needle unit moves upwards until the equilibrium of forces on the needle 17 or on the needle unit has been compensated. This is achieved by the reduction of the free space 19 and the resulting increase in the chamber pressure in the free space 19. The pressure in the foot-side chamber 8 changes only slightly, since it is directly connected to the high-pressure medium line 12. Since the piezo chamber 38 is also connected directly to the high-pressure medium line 12 in a preferred embodiment, the pressure changes only slightly here as well.

As soon as the needle 17 or the needle unit lifts or lifts, liquid flows through the high-pressure medium line 12 and through the gap 26 via the seat 21 into the injection chamber 22. From there, the liquid continues to flow via the at least one throttle 23 into the combustion chamber or into the combustion chamber.

The stroke of the needle 17 or the needle unit in this case depends on the area ratio of the piston surface to the head-side chamber 9 in relation to the needle surface in the Clearance 19 off (A9 / A19). As a result of this area ratio, the needle stroke can thus be changed (amplified or reduced) in comparison to the piezohub.

The following applies: Stroke (needle) = stroke (piezo) · A9 / A19.

This ensures that a sufficient stroke of the needle 17 and the needle unit is reached.

As long as in the head-side chamber 9 and the free space 19 is a lower pressure than in the connected chambers 8 (foot-side chamber 8) and 26 (gap between the needle body and the housing inner wall 24) liquid flows through internal leakage in the head-side chamber 9 and in the free space 19th This is done via the leakage points on the piston 7, the piston rod 36 and the needle 17 and the needle unit and possibly additionally attached connections between the various chambers. An additional filling can be achieved by means of preferably throttled connecting lines between the chambers and the high-pressure medium line 12. As a result of the internal leakage, the free space 19 and the head-side chamber 9 slowly fill up with additional fluid, as a result of which the needle 17 or the needle unit slowly moves into the seat 21. This movement is additionally promoted by the spring 32.

This internal leakage is preferred so that the chambers 9 and 19, ie the head-side chamber 9 and the free space 19, can be filled with liquid during start-up or in the event of a malfunction (for example a defective piezoelement), thereby injecting the injector 1 or the injection element 14 close. A permanent injection is thereby prevented, which represents a quasi-safety function.

To close the injector 1, the piezoelectric element 6 is discharged, whereby it is shortened. As a result, the pressure in the head-side chamber 9 and in the free space 19 increases, whereby the balance of forces on the needle 17 and the needle unit is shifted so far that accelerates the needle 17 and the needle unit in its closing direction. As a result, the injector 1 is closed and the injection is ended.

In this embodiment according to the FIGS. 7 and 9 has the additional volume around the piezoelectric element 6, which is usually large in relation to the remaining chambers a positive effect on the injector behavior. It serves as a storage reservoir, whereby just the pressure drop occurring at the beginning of the injection is reduced and pressure fluctuations are reduced.

A transient increase in fluid pressure during injection may be beneficial to combustion. This is possible by the arrangement of the optional check valve 34 in the high-pressure medium line 12. As a result, the pressure in the chamber 8 or in the foot-side chamber 8 during the working movement of the piston 7 is not compensated for more via the high-pressure medium line 12. Therefore, the pressure in the foot-side chamber 8 and the gap 26 increases, whereby a higher injection pressure is present. In addition, the buoyant force acting on the needle 17 or on the needle unit in the seating area 21 is increased by the higher pressure, so that the opening of the needle 17 and the needle unit is accelerated.

In the embodiment of the exemplary injector 1 according to FIG. 9 only changes the position of the piezoelectric element 6 and the piston 7, which does not change the already described principle, so that the in FIG. 9 illustrated embodiment is conceivable.

In the in the Figures 5 and 6 illustrated embodiment, the separation of the piezo chamber 38 of the head-side chamber 9 is basically repealed by dispensing with the crossbar. Nevertheless, by means of the piston 7, the head-side chamber 9 and the foot-side chamber 8 are formed. Here, the chamber 4 is no longer connected to the piezoelectric element 6, so in this case the head-side chamber 9 directly to the high-pressure medium line 12.

The piston 7 is in the embodiment of the Figures 5 and 6 attached directly to the piezoelectric element 6. The foot-side chamber 8 is connected directly to the high-pressure medium line 12, wherein the free space 19 is connected behind the needle or above the needle 17 or above the needle unit with the head-side chamber 9.

The head-side chamber 9 is filled in this embodiment in the non-actuated state of the piezoelectric element 6 by internal leakage to the piston 7 and its recognizable in longitudinal section end faces 27 (gap 29) and the connecting line 31. The clearance 19 is filled by the connecting pipe 13 and internal leakage at the guide of the needle unit (gap 26). In the non-actuated state that is in Figures 5 and 6 shown system pressure balanced (corresponding to the embodiment of the FIGS. 7 and 9 ).

The energization of the piezoelectric element 6 causes an elongation of the piezoelectric element 6 and an enlargement of the head-side chamber 9. As a result, the pressure in the head-side chamber 9 and via the connecting line 31 also drops into the free space 19. According to the embodiment of the FIGS. 7 and 9 opens the injection element 14 by the changed force conditions on the needle 17 and on the needle unit. The chambers 19 and 9 or the free space 19 and the head-side chamber 9 are slowly refilled by the internal leaks on the piston 7 and on the needle 17 or on the needle unit, which is also preferred here as a safety function. This can be influenced by additional connections and / or throttle points between the chambers and / or the high-pressure medium line 12. The pressure in the foot-side chamber 8 is compensated by the high-pressure medium line 12 during the entire process.

To close the piezoelectric element 6 must be discharged, which makes it shorter. As a result, the head-side chamber 9 is downsized, and the pressure rises in the head-side chamber 9 and the clearance 19. The higher pressure causes a resultant closing force on the needle 17 or on the needle unit, whereby the needle 17 or the needle unit closes. Otherwise, the same remarks apply to the embodiment according to the FIGS. 7 and 9 described.

Also in the embodiment of the Figures 5 and 6 can be achieved by means of the optional check valve 34, a temporary or temporary pressure increase.

In contrast to FIG. 5 has FIG. 6 also only a change in the position of the piezoelectric element 6 and the piston 7 arranged thereon, whereby the basic operation as to FIG. 5 described is not changed.

All aforementioned embodiments have in common that additional throttles, nozzles, check valves and / or volumes may be provided to change the characteristic behavior of the injector 1 between all chambers and / or in all lines, connections or channels. By means of the injectors described by way of example according to the embodiments of the FIGS. 5 to 9 Advantageously, a very uncomplicated construction of the injector 1 is achieved, which also has (in the absence of actuation of the piezoelectric element 6) no external leakage. The needle control is achieved directly via a hydraulic coupling, wherein the speed is adaptable by speed variation of the piezoelectric element 6. The injector according to the respective embodiments has few components, in particular, no additional components for a reversal of direction are necessary. In addition, no pressure increase is necessary for opening, but a temporary or temporary increase in the injection pressure can be achieved. A further advantage is that the piezoelectric element is not charged in the closed state.

The same advantages as in the embodiments of the FIGS. 5 to 9 are also in an injector according to the embodiments of the Figures 10 and 11 reachable. The Figures 10 and 11 , especially FIG. 10 shows an inventive embodiment or advantageous development of the injector 1 according to the embodiment of FIGS. 7 and 9 , In this embodiment, it is considered that the piezoelectric element 6 should not be under high pressure. In contrast to FIG. 7 is in the embodiment after FIG. 10 provided that the piezochamber 38 is no longer connected directly to the high-pressure medium line 12. Instead, the piezo chamber 38 is connected via a connecting line 43 to a fuel tank 44 or liquid tank. As a result, the piezo chamber 38 is acted upon only with the tank pressure or the pressure prevailing in the medium tank. As a result, the sealing of the piezoelectric element 6 is generally easier, but with a small, external leakage through the gap 42, which is arranged between the piston rod 36 and the recognizable in longitudinal section end faces 40 of the transverse web 37, and the line 43 must be accepted. Advantageously, however, the gap height of the gap 42 is kept very low.

In order to keep the piezoelectric element 6 completely dry, so that it is not washed around by the liquid, a sealing element 46 is additionally provided, such as FIG. 10 shows. The sealing element 46 is associated with the piezochamber 38 such that an intermediate chamber 47 is arranged or formed between the transverse web 37 and the sealing element 46. The intermediate chamber 47 is like FIG. 10 can be seen, connected via the connecting line 43 to the fuel tank 44. As a result, there is only a slight pressure in the intermediate chamber 47, namely the pressure prevailing in the fuel tank, so that a simple seal can be used here. In the piezochamber 38 occurs due to the seal no more liquid. The piezo element is dry.

Otherwise, the injector according to the embodiment of FIG. 10 the same operation as the injector according to the embodiment according to Fig. 7 ,

Not shown is a development that is based on the fact that no external leakage is accepted. This is dispensed with a connection to the fuel tank. As a result, however, the pressure in the intermediate chamber 47 increases to system pressure, whereby the sealing element 46 must seal against high pressure. Although this makes a more complicated high-pressure seal necessary, it enables an externally leak-free injector. In addition, then the intermediate chamber 47 can be connected to the high-pressure medium line 12 in order to achieve a rapid pressure equalization in the intermediate chamber 47. This embodiment is in the Figures 10 and 11 not shown, wherein the embodiment according to FIG. 11 only in turn by a reverse arrangement of the chamber 4 in comparison to FIG. 10 distinguished.

In the embodiments described above, the piston 7 or its piston rod 36 is connected directly to the piezoelectric element 6. It is also conceivable embodiment, not shown, in which the piston 7 and its Piston rod 36 and the piezoelectric element 6 are not necessarily firmly connected. For this purpose, a force accumulator or a spring could be provided, which can be arranged in the foot-side chamber 8. The spring would be supported in the foot-side chamber 8 on the one hand on the piston 7 and the other on the foot side 3, so that the piston 7 is pressed in the direction of the piezoelectric element 6. In this embodiment, tensile stresses on the piezoelectric element 6 would be avoided since no restraining forces can be built up during the shortening of the piezoelectric element.

The injector 1 shown in the respective embodiments can be particularly preferably used for injection of diesel fuel into the combustion chamber of diesel engines, without limiting the use thereof. For example, in this case an injection of media, preferably liquids thought, as for example in gasoline engines or in the exhaust aftertreatment to name just a few examples different for use in diesel engines. The diesel engines can be installed, for example, in cars, trucks, ships, buses or trains. When used in diesel engines, the high-pressure medium line 12 is then preferably designed as a common rail.

The terms line, connection, channels mean in the context of the invention, a connection from one place to another, which can be designed as separate lines but of course as an internal channel.

Claims (5)

1. Injector which has a piezo element (6) arranged in a chamber (4) which is formed with a head side (2) and a foot side (3), to the foot side of which piezo element (6) is fastened a piston (7) which divides the chamber (4) into a foot-side chamber (8) and a head-side chamber (9) and is arranged in the chamber (4), with a high-pressure medium line (12) opening out in an injection element (14) via a connecting line (13), which injection element (14) has a needle (17) which is arranged in a housing (16) and which is spaced apart at the head side from a housing head (18) such that a clearance (19) is formed, and with the needle (17) being assigned, at the foot side, to a seat (21) in order to thereby alternately open or close the fuel supply to a combustion chamber via an injection chamber (22) and at least one throttle (23), and with a gap (26) being arranged between the needle body and the housing inner wall (24), with the piston (7) being assigned to a piston rod (36) which is arranged at the foot side on the piezo element (6) and which extends through a transverse web (37) arranged in the chamber (4), with the transverse web (37) dividing the chamber (4) into a piezo chamber (28) and a piston chamber (39), with the piston chamber (39) being divided by means of the piston (7) into the head-side chamber (9) and the foot-side chamber (8), with a high-pressure connecting duct (11) opening out in the foot-side chamber (8) such that a vacuum is generated in the head-side chamber (9) when the piezo element (6) is actuated, with the head-side chamber (9) being connected to the injection element (14) via a connecting line (31), and with the connecting line (31) opening out into the clearance (19),
   characterized by
   a seal element (46) which keeps the piezo element (6) completely dry and which is assigned to the piezo chamber (38) such that an intermediate chamber (47) is arranged between the transverse web (37), which is arranged in the chamber (4), and the seal element (46), from which intermediate chamber (47) a connecting line (43) leads to a fuel tank (44) such that only a low pressure prevails in the intermediate chamber (47).
2. Injector according to Claim 1,
   characterized in that,
   as viewed in longitudinal section, a gap (29) is arranged between end sides (27) of the piston (7) and a chamber inner wall (28).
3. Injector according to Claim 1,
   characterized in that
   a spring (32) is arranged in the clearance (19), which spring (32) bears both against the housing head (18) and also against the needle head (33).
4. Injector according to one of the preceding claims,
   characterized in that
   a non-return valve (34) is arranged in the high-pressure medium line (12).
5. Injector according to Claim 1,
   characterized in that
   passage openings are arranged in the piston (7) and/or in the transverse web (37).

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