DE102012222127A1 - Fuel injector for injecting fuel into combustion chamber of internal combustion engine, has hydraulic coupler that is comprised of pair of coupler piston for separating two couplers - Google Patents

Abstract

The injector has a nozzle needle (1) that is guided in a stroke in a high pressure bore (2) of a nozzle housing (3) for opening and closing an injection opening (4). A solenoid actuator (5) with a ring-shaped magnetic coil (6) is provided for directly or indirectly controlling the stroke of the nozzle needle. The magnetic coil cooperates with an armature (7) which is coupled to the nozzle needle through a two-stage hydraulic coupler (8). The hydraulic coupler is comprised of a pair of coupler piston (11,12) for separating the two couplers (9,10).

Description

The invention relates to a fuel injector for injecting fuel into a combustion chamber of an internal combustion engine having the features of the preamble of claim 1.

The fuel injector comprises a nozzle needle, which is guided in a high-pressure bore of a nozzle body for releasing and closing at least one injection opening, and a magnetic actuator with a preferably annular magnetic coil for direct or indirect control of the lifting movement of the nozzle needle. The solenoid cooperates with an armature which can be coupled to the nozzle needle via a multi-stage, preferably two-stage, hydraulic coupler.

State of the art

The use of magnetic actuators to control the lifting movement of the nozzle needle of a fuel injector is well known. The stroke movement of the nozzle needle is indirectly via a servo control chamber or directly controllable. In the case of direct control, it must be ensured that a sufficient force is provided for opening the nozzle needle, since at the currently required system pressures of up to 3000 bar, very high switching forces occur at the nozzle needle. In known directly controlled injectors therefore often the actuator force is increased by means of a force transmission device. With the power transmission, however, a path reduction goes hand in hand, so that it may not be ensured that the nozzle needle opens completely. The required opening force decreases sharply with increasing stroke of the nozzle needle, so that a force transmission is then no longer required.

From the publication DE 10 2010 028 835 A1 a fuel injector for injecting fuel into a combustion chamber of an internal combustion engine is known, which comprises a magnetic actuator for direct control of the lifting movement of a nozzle needle and a two-stage translation device. In a first stage, the translation means effects a force translation to realize the required nozzle needle opening force. After initial opening of the nozzle needle, the translator switches to a second stage where path translation or 1/1 translation is effected. Switching takes place via a mechanical driver as a function of the stroke of the nozzle needle or of an armature cooperating with the magnetic actuator. By this switching principle results in a force jump in the nozzle needle opening force, which has a discontinuous movement behavior of the nozzle needle result. This in turn leads to discontinuities in the quantity characteristic and thus to problems with regard to the metering accuracy.

The present invention has for its object to provide a fuel injector with a magnetic actuator for controlling the lifting movement of a nozzle needle and a multi-stage, preferably two-stage, hydraulic coupler, which does not affect the movement behavior of the nozzle needle in the aforementioned manner.

To solve the problem, a fuel injector with the features of claim 1 is proposed. Advantageous developments of the invention are specified in the subclaims.

Disclosure of the invention

The fuel injector proposed for injecting fuel into a combustion chamber of an internal combustion engine comprises a nozzle needle which is guided in a high-pressure bore of a nozzle body for releasing and closing at least one injection opening, and a magnetic actuator with a preferably annular magnetic coil for direct or indirect control of the lifting movement of the nozzle needle , wherein the magnetic coil cooperates with an armature, which can be coupled via a multi-stage, preferably two-stage, hydraulic coupler with the nozzle needle. The multi-stage hydraulic coupler according to the invention has a first and a second coupler space and a first and a second coupler piston for the separation of the two coupler spaces. Via the first coupler space, the hydraulic coupling of the armature with the nozzle needle is effected, while the second coupler space serves for the hydraulic coupling of the two coupler pistons. The hydraulic coupling via the second coupler space replaces a mechanical entrainment function to switch from a first coupling stage to a second coupling stage. As a result, a continuous transmission of the actuator force is effected on the nozzle needle, wherein the advantages of a multi-stage, in particular two-stage, translator in the adaptation of the actuator characteristic to the required nozzle needle opening force remain or be increased. Because during a first movement phase of the nozzle needle energy is stored in the second coupler space, which can be used in the subsequent movement phase. As a result, an improved adaptation of the force characteristic of the magnetic actuator to the power requirement of the nozzle needle is achieved.

According to a preferred embodiment of the invention, the first coupler piston is connected to the armature and guided in at least one central bore of the second coupler piston high pressure tight. That means the second one Coupler piston at least partially surrounds the first coupler piston. In this way, a compact arrangement can be created, which has a low space requirement. The high-pressure-tight guidance of the first coupler piston in the second coupler piston ensures the separation of the two coupler spaces. Preferably, both pistons are arranged concentrically with each other and concentric with the nozzle needle. It is further provided that the spring force of a spring acts on the first coupler piston in the direction of the nozzle needle. The spring resets the first coupler piston including the armature when the solenoid actuator is deactivated.

Further preferably, the second coupler piston is guided in a central bore of a preferably plate-shaped body high pressure-tight. The spring force of a further spring acts on the second coupler piston in the direction of the nozzle needle directly or indirectly. This means that the further spring can be supported directly or indirectly on the second coupler piston.

As a further development measure, it is proposed that an end face, facing away from the combustion chamber, of the preferably plate-shaped body forms a stroke stop, which cooperates with a preferably annular shoulder formed on the outer peripheral side on the second coupler piston. If the second coupler piston lies with its preferably annular shoulder on the end face of the preferably plate-shaped body, it is in its rest position.

Preferably, at least one end face A _{1 of} the nozzle needle facing away from the combustion chamber and an end face A _{2 of} the first coupler piston facing the combustion chamber and an end face A _{3 of} the second coupler piston facing the combustion chamber define the first coupler space in the axial direction. All faces form hydraulic active surfaces, which are hydraulically coupled via the coupler space. Preferably, for the size of the hydraulic active surfaces A ₁ > A ₃ > A ₂ . In this way, a reinforcement of the actuator force can be effected in a first movement phase of the nozzle needle, so that it is ensured that the force acting on the nozzle needle, initially high closing force is overcome and opens the nozzle needle. Because during the first movement phase, which is initiated upon activation of the magnetic actuator by the stroke of the armature and the armature associated with the coupler piston causes the opposite the end face A _{1 of} the nozzle needle significantly smaller hydraulic effective area A _{2 of} the first coupler piston, the required power transmission, during second coupler piston is still in the rest position, as it acts on the spring force of the other spring and the pressure in the second coupler space. The force transmission during the first movement phase of the nozzle needle depends on the chosen area ratio of the active hydraulic surfaces A ₁ and A ₂ . Preferably, the ratio factor in this phase is 5.

Further preferably, an annular surface A ₄ facing the combustion chamber of a collar section formed on the first coupler piston and an annular surface A _{5 of} the second coupler piston facing away from the combustion chamber delimit the second coupler chamber in the axial direction. This means that the hydraulic active surfaces A ₄ and A ₅ are opposite to the second coupler space. In a second movement phase of the nozzle needle, after the initially high firing force is overcome, the hydraulic coupling of the two coupler pistons via the second coupler space causes the second coupler piston to follow the movement of the armature and of the first coupler piston, respectively. In the first coupler space now act the hydraulic active surfaces A ₂ and A ₃ together. If the sum of the areas A ₂ and A ₃ chosen such that it is at least approximately as large as the area A ₁ , then only a small force transmission is effected according to the Krafterfordernis the nozzle needle. For example, the surfaces may be designed such that during the second movement phase of the nozzle needle only a translation factor 2 or smaller is achieved. In addition, the areas A ₂ and A _{3 may} also be selected such that their sum is greater than A ₁ . Then the actuator force is reduced while the actuator stroke is translated.

The second active coupler space limiting hydraulic active surfaces of the two coupler pistons are preferably the same size. Alternatively, A _{5 can} also be greater than A ₄ .

To limit the first coupler space in the radial direction, a sealing sleeve is proposed, which is preferably supported on the preferably plate-shaped body for guiding the second coupler piston and receives the combustion chamber facing away from the end of the nozzle needle. The sealing sleeve thus seals the first coupler space from the high-pressure bore formed in the nozzle body. In order to hold the sealing sleeve in contact with the preferably plate-shaped body, it is also proposed that the spring force of a spring supported on the nozzle needle urges the sealing sleeve in the direction of the preferably plate-shaped body.

To form the second coupler space, a pressure space can be formed in the second coupler piston through which the first coupler piston is guided in such a way that the collar portion formed on the first coupler piston delimits the second coupler space in the axial direction. In the radial direction of the second coupler piston limits the second coupler space. Alternatively, it can be provided that a sealing sleeve supported on the second coupler piston limits the second coupler space in the radial direction. This has the advantage that an expensive and toleranced double guide of the first coupler piston in the second coupler piston is avoided. Because the collar portion of the first coupler piston is guided high pressure tight in the sealing sleeve. In order to ensure the installation of the sealing sleeve on the second coupler piston, it is further proposed that the sealing sleeve is acted upon in the direction of the second coupler piston by the spring force of the spring, which acts simultaneously on the second coupler piston in the direction of the preferably plate-shaped body.

Preferably, the anchor connected to the first coupler piston is designed as a plunger anchor. This allows a compact, requiring a small space arrangement of the components. Furthermore, the armature is preferably at least partially surrounded by a magnetic body and / or an annular separating body for magnetic separation of the magnetic body from an inner pole body. As a result, the arrangement can be made even more compact. In addition, the magnetic circuit can be extended to the diameter of the injector.

The inner pole body may be a separate body which is inserted into an injector body of the fuel injector. Alternatively, the injector body itself can form the inner pole body. Preferably, a central inlet bore is formed in the injector body and / or in the inner pole body, which is connected to the high-pressure bore of the nozzle body. Due to the central arrangement of the inlet bore increases the high pressure resistance of the fuel injector.

Preferably, the armature is arranged in a high-pressure region of the fuel injector. That is, during operation of the fuel injector, the armature is surrounded by high pressure fuel.

Preferred embodiments of the invention are explained below with reference to the accompanying drawings. These show:

1 a schematic longitudinal section through a first preferred embodiment of a fuel injector according to the invention and

2 a schematic longitudinal section through a second preferred embodiment of a fuel injector according to the invention.

Detailed description of the drawings

The Indian 1 illustrated fuel injector includes a magnetic actuator 5 for direct control of the lifting movement of a nozzle needle 1 working in a high pressure bore 2 a nozzle body 3 for releasing and closing at least one injection opening 4 Hubbeweglich is guided. The magnetic actuator 5 includes a magnetic coil 6 and one with the solenoid 6 interacting anchor 7 , which is designed as a dip anchor. The plunger is at least partially of a magnetic body 21 and an annular separator 22 surrounded, which is the magnetic separation of the magnetic body 21 from a Innenpolkörper 23 serves. The inner pole body 23 is present from an injector body 24 formed of the fuel injector, via a clamping nut 26 with the magnetic body 21 and the nozzle body 3 axially braced. The injector body 24 is from a central inlet bore 25 interspersed, over which the high pressure bore 2 of the nozzle body 3 under high pressure fuel is supplied.

To strengthen the power of the magnetic actuator 5 is also a hydraulic coupler 8th provided, which two coupler spaces 9 . 10 as well as two coupler pistons 11 . 12 includes. The first coupler piston 11 that with the anchor 7 is firmly connected, is formed pin-shaped and has a collar portion 17 on. The second coupler piston 12 is designed as a stepped piston and has in a first section with a smaller outer diameter on a central bore, in which the first coupler piston 11 a first time high pressure tight. A second portion of larger outer diameter has a central bore of the first section expanding cavity, the second coupler space 10 forms and in the axial direction of the collar section 17 of the first coupler piston 11 is limited. About the waistband section 17 is the first coupler piston 11 once again in the second coupler piston 12 high pressure tight. The two coupler spaces 9 . 10 are thus through the two coupler pistons 11 . 12 high pressure-tight.

The second coupler piston 12 is over the first smaller diameter section in a central bore of a plate-shaped body 14 high pressure tight. Due to the design as a stepped piston, the second coupler piston 12 an annular heel 16 on, in the rest position of the second coupler piston 12 on a side facing away from the combustion chamber end face of the plate-shaped body 14 is applied. The plate-shaped body 14 thus serves as a stroke stop at the same time. In the direction of the plate-shaped body 14 is the second coupler piston 12 from the spring force of a spring 15 applied.

The first coupler piston 11 is the spring force of a spring 13 acted upon, on the one hand at the waistband section 16 of the first coupler piston 11 and on the other hand, on the magnetic body 21 is supported and thus the first coupler piston 11 in the direction of the nozzle needle 1 applied.

During the second coupler room 10 from the two coupler pistons 11 . 12 is limited, here is a through the waistband section 17 of the first coupler piston 11 formed annular surface A ₄ and one through the second coupler piston 12 formed annular surface A ₅ as hydraulic active surfaces are opposite, is the first coupler space 9 in the axial direction of a combustion chamber facing away from the end face A _{1 of} the nozzle needle 1 , an end face A _{2 of} the first coupler piston facing the combustion chamber 11 and a combustion chamber facing end face A _{3 of} the second coupler piston 12 and in the radial direction of a sealing sleeve 18 limited. The sealing sleeve 18 is for this purpose on the plate-shaped body 14 supported and in the direction of the plate-shaped body 14 from the spring force of a spring 19 applied. At the first coupler room 9 Accordingly, the end face A _{1 of} the nozzle needle 1 and the faces A ₂ and A _{3 of} the two coupler pistons 11 . 12 as hydraulic active surfaces opposite. The sizes of the hydraulic active surfaces are designed such that in a first coupling stage via the end face A _{2 of} the first coupler piston 11 which is considerably smaller than the end face A _{1 of} the nozzle needle 1 is, a significant increase in force is effected. Only in the second coupling stage occurs the end face A _{3 of} the second coupler piston 12 added as a hydraulic effective area, so that the force increase - according to the requirements is significantly reduced by the new area ratio of the hydraulic active surfaces. Because the sum of A ₂ and A ₃ is only slightly smaller than A ₁ .

The switching from the first to the second coupling stage is via the second coupler space 10 causes. After the first movement phase of the nozzle needle 1 prevails in the first coupler room 9 a greater pressure than in the second coupler space 10 , which has the consequence that the second coupler piston 12 the movement of the first coupler piston 11 follows. The entrainment function is therefore realized hydraulically.

The Indian 2 illustrated fuel injector differs from that of 1 essentially in that instead of the toleranced double guide of the first coupler piston 11 in the second coupler piston 12 the first coupler piston 11 from a sealing sleeve 20 is surrounded, which on the second coupler piston 12 is supported. The second coupler room 10 is therefore in the radial direction of the sealing sleeve 20 limited. The spring force of the spring 15 holds the sealing sleeve in abutment with the second coupler piston 12 , so that the spring force of the spring 15 indirectly the second coupler piston 12 in the direction of the plate-shaped body 14 applied.

The operation of the fuel injector the 2 It does not differ from that of the fuel injector 1 , To open the nozzle needle 1 becomes the magnetic coil 6 of the magnetic actuator 5 energized. The magnetic force of the magnetic actuator 5 draw the anchor 6 including the first coupler piston 11 against the spring force of the spring 13 in the direction of the magnetic coil 6 , By a suitable design of the hydraulic effective surface areas and volume takes the pressure in the first coupler space 9 stronger than in the second coupler space 10 , The nozzle needle 1 opens while the second coupler piston 12 remains in its rest position. By the hydraulic effective area A _{2 of} the first coupler piston 11 significantly smaller than the hydraulic effective area A _{1 of} the nozzle needle 1 is selected, the actuator force is strongly translated. After the nozzle needle 1 has undergone a partial stroke, the opening force is reduced. The pressure in the first coupler room 9 rises above the pressure in the second coupler space 10 , which has the consequence that the second coupler piston 12 is activated and due to the hydraulic coupling via the second coupler space 10 the movement of the first coupler piston 11 follows. The actuator force is significantly less strongly translated in this stage, since the sum of the hydraulic active surfaces A ₂ and A ₃ only slightly smaller than the hydraulic effective area A _{1 of} the nozzle needle 1 is. This ensures that the nozzle needle 1 completely opens.

To close the nozzle needle 1 is the energization of the solenoid 6 finished, leaving the spring force of the springs 13 . 15 the provision of the anchor 7 and the two coupler pistons 11 . 12 causes. The increasing pressure in the first coupler room 9 and the spring force on the one hand on the sealing sleeve 18 and on the other hand at the nozzle needle 1 supported spring 19 , cause the return of the nozzle needle 1 , In the closed position of the nozzle needle 1 prevails in the first coupler room 9 Rail pressure.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 102010028835 A1 [0004]

Claims (11)

Fuel injector for injecting fuel into a combustion chamber of an internal combustion engine comprising a nozzle needle ( 1 ), which in a high-pressure bore ( 2 ) of a nozzle body ( 3 ) for releasing and closing at least one injection opening ( 4 ) is movably guided, and a magnetic actuator ( 5 ) with a preferably annular magnetic coil ( 6 ) for direct or indirect control of the lifting movement of the nozzle needle ( 1 ), wherein the magnetic coil ( 6 ) with an anchor ( 7 ) cooperates via a multi-stage, preferably two-stage, hydraulic coupler ( 8th ) with the nozzle needle ( 1 ), characterized in that the multi-stage hydraulic coupler ( 8th ) a first and a second coupler space ( 9 . 10 ) and a first and a second coupler piston ( 11 . 12 ) for separating the two coupler spaces ( 9 . 10 ) owns. Fuel injector according to claim 1, characterized in that the first coupler piston ( 11 ) with the anchor ( 7 ) and in at least one central bore of the second coupler piston ( 12 ) is guided high pressure-tight, wherein the spring force of a spring ( 13 ) the first coupler piston ( 11 ) in the direction of the nozzle needle ( 1 ). Fuel injector according to claim 1 or 2, characterized in that the second coupler piston ( 12 ) in a central bore of a preferably plate-shaped body ( 14 ) is guided high pressure-tight, wherein the spring force of a spring ( 15 ) the second coupler piston ( 12 ) in the direction of the nozzle needle ( 1 ) directly or indirectly. Fuel injector according to claim 3, characterized in that a combustion chamber facing away from the end face of the body ( 14 ) forms a stroke stop, which with an outer peripheral side on the second coupler piston ( 12 ), preferably annular shoulder ( 16 ) cooperates. Fuel injector according to one of the preceding claims, characterized in that at least one end surface facing away from the combustion chamber (A ₁ ) of the nozzle needle ( 1 ) and a combustion chamber facing end face (A ₂ ) of the first coupler piston ( 11 ) and a combustion chamber facing end face (A ₃ ) of the second coupler piston ( 12 ) the first coupler space ( 9 ) in the axial direction, wherein preferably A ₁ > A ₃ > A ₂ . Fuel injector according to one of the preceding claims, characterized in that an annular surface (A ₄ ) facing the combustion chamber of one of the first coupler pistons ( 11 ) formed Bundabschnitts ( 17 ) and a combustion chamber facing away from the annular surface (A ₅ ) of the second coupler piston ( 12 ) the second coupler space ( 10 ) in the axial direction, wherein preferably A ₅ ≥ A ₄ . Fuel injector according to one of the preceding claims, characterized in that a sealing sleeve ( 18 ) the first coupler space ( 9 ) is limited in the radial direction, wherein preferably the spring force of a at the nozzle needle ( 1 ) supported spring ( 19 ) the sealing sleeve ( 18 ) in the direction of the body ( 14 ). Fuel injector according to one of the preceding claims, characterized in that the second coupler piston ( 12 ) or a sealing sleeve supported thereon ( 20 ) the second coupler space ( 10 ) is limited in the radial direction, wherein preferably the sealing sleeve ( 20 ) of the spring force of the spring ( 15 ) in the direction of the second coupler piston ( 12 ) is acted upon. Fuel injector according to one of the preceding claims, characterized in that the armature ( 7 ) is formed as a dip anchor and at least partially by a magnetic body ( 21 ) and / or an annular separating body ( 22 ) for the magnetic separation of the magnetic body ( 21 ) of an inner pole body ( 23 ) is surrounded. Fuel injector according to claim 9, characterized in that the inner pole body ( 23 ) in an injector body ( 24 ) is inserted or the injector body ( 24 ) the inner pole body ( 23 ), wherein preferably in the injector body ( 24 ) and / or in the inner pole body ( 23 ) a central inlet bore ( 25 ) is formed, which with the high-pressure bore ( 2 ) of the nozzle body ( 3 ) connected is. Fuel injector according to one of the preceding claims, characterized in that the armature ( 7 ) is arranged in a high-pressure region of the fuel injector.

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