DE102009027494A1 - Fuel injector with pressure compensated control valve - Google Patents

Abstract

The injector (1) has a control valve element (26) adjustable between two switching positions. The valve element is formed and arranged such that no or reduced resulting hydraulic force is exerted in an axial direction on the valve element by pressure in a control chamber (17) when a hydraulic connection between the chamber and a low pressure region (10) is disconnected in one of the switching positions. The valve element sealingly lies at a guiding sleeve (32) in the other switching position for sealing a hydraulic connection between a control valve chamber (24) and a high pressure region (8).

Description

State of the art

The The invention relates to a fuel injector for injecting Fuel in a combustion chamber of an internal combustion engine, in particular a common rail injector, according to the preamble of claim 1.

From the DE 10 2004 030 445 A1 a fuel injector is known which has a control valve (servo valve). The control valve is designed as a so-called 3/2-way valve and controls the connection between a directly from an injection valve element control space and a low pressure area (leakage oil space) of the fuel injector. The control valve has a control valve element, which can be adjusted axially by means of an actuator, for example an electromagnetic or piezoelectric actuator, within a control valve chamber and thus cooperates with a first control valve seat and with a second control valve seat. If the control valve element is in contact with the first (upper) control valve seat, the connection between the control space bounded by the injection valve element and the low-pressure region of the fuel injector is blocked. At the same time, a bypass throttle is opened, via which the control chamber is refilled. When the control valve element is in contact with the second (lower) control valve seat, the bypass throttle is closed and the hydraulic connection between the control chamber and the low pressure region of the fuel injector is established, as a result of which the pressure in the control valve chamber drops, which in turn causes the injection valve element to move from its position Injector valve seat lifts and thus releases the flow of fuel through a nozzle hole arrangement in the combustion chamber of the internal combustion engine. A disadvantage of the non-pressure balanced control valve is that the load of the actuator with increasing rail pressure continues to increase. As a result, given a known actuator with the known principle, there is no potential for a further system pressure increase.

From the present application at the time of filing not yet disclosed DE 10 2008 001 330 The applicant is aware of an alternative injector concept with a pressure compensated control valve (servo valve). As a matter of principle, this new servo principle does not switch against rail pressure, but it is structurally guided by a low-pressure connection under the control valve element. This means that the opening force of the control valve, depending on the degree of pressure compensation, less and less dependent on the rail pressure. Thus, the new injector concept offers the potential of a further system pressure increase without unduly increasing the actuator load. The control valve member of the control valve is disposed in a control valve space which is bounded radially outwardly by a single plate member, to the axially below a throttle plate and axially above an actuator space limited component abuts. The new injector seems to be optimized in terms of shortened Rückbefüllbarkeit the control room.

Disclosure of the invention

Of the Invention has for its object to provide a fuel injector, on the one hand, sufficient potential for system pressure increases on the other hand, a minimized Rückfüüllzeit realized for refilling the control room.

These Task is using a fuel injector with the characteristics of Claim 1 solved. Advantageous developments of the invention are given in the subclaims. In the context of Invention fall all combinations of at least two of in the description, the claims and / or the Figures revealed features.

The invention is based on the idea of a second, in particular lower control valve seat on which the control valve element of the control valve (servo valve) sealingly abuts in the second switching position to interrupt the immediate hydraulic connection between the high pressure region of the fuel injector and the control valve chamber on a guide sleeve form for the control valve, which leads, preferably not sleeve-shaped, in particular bolt-shaped, control valve element on its outer periphery. In other words, in the second switching position of the control valve, which is preferably formed of a 3/2-way valve, the control valve element bears directly against the guide sleeve in a sealing manner. In this way, a large cross-sectional area is released in the first switching position in which the control valve element is not sealingly against the guide sleeve, through which the control valve space and thus preferably via an outlet throttle, the control chamber can be refilled. This in turn results in a much faster closing of the one- or multi-part injection valve element with a turn resulting greater robustness of the fuel injector. Due to the closeability of the hydraulic connection between the high-pressure region of the fuel injector, preferably between a pressure chamber of the fuel injector and the control valve element, also during the injection, a significantly lower control amount than in conventional pressure-balanced fuel injectors can be realized with permanently acting Fülldrossel at one after the concept of the inventor trained trained fuel injector which is preferably designed as a throttle connection hydraulic connection between the high pressure region of the fuel injector and the control valve chamber by the second, preferably lower, control valve seat can be separated. This advantage is so important because with pressure-balanced fuel injectors due to the existing permanent leakage anyway very large and therefore expensive high-pressure pumps are required and due to the invention, the possibility is created to use smaller and thus cheaper high-pressure pumps, whereby the system costs are reduced overall. The minimized control valve volume also results in a significantly lower map slope, which makes it possible to use fast Entschrosselnde nozzles, whereby the engine power can be increased without deteriorating the smallest quantity capability of the fuel injector. The fuel injector according to the invention has particularly good hydraulic properties by the simultaneous presence of a bypass (hydraulic connection between the high pressure region and the control valve chamber) and a minimum control valve chamber volume, which in combination to extremely fast refilling the control valve chamber and thus the control chamber and thus in turn a very quick reversal of the injection valve element with said flat map leads.

The Refill time needed to To refill the control room, can in further training of This invention can be reduced to a minimum, instead of in the a helical compression spring a diaphragm spring as a valve spring for the control valve is used. Preferably, the plate spring arranged such that the control valve element in the direction first switching position, d. H. towards the first control valve seat Federkraftbeaufschlagt, so that the control valve element against the spring force of the spring plate from the first switching position in the second switching position must be moved. Through the education of Spring as a plate spring can keep the control valve volume to a minimum be reduced, resulting in the first switching position of the control valve an accelerated pressure increase in the control valve chamber and thus also results in the control room. The combination of the formation of the second control valve seat on the guide sleeve for the control valve element brings with the training of the control valve spring as a diaphragm spring minimal refilling times with it, resulting in one extremely fast turnaround, d. H. Closing the injection valve element results.

Especially appropriate is a variant of the fuel injector, in which the hydraulic connection between the high-pressure area, for example, the control chamber radially outside surrounding pressure chamber and the control valve chamber as throttle connection is trained. This can be realized in a simple manner be that in the hydraulic connection a throttle bore integrated, which is particularly preferred, as later will be explained, arranged in a throttle plate is, to the axially the guide sleeve for the control valve element is applied.

Especially expedient with a view to minimizing the Control valve volume is the spring, in particular the diaphragm spring, contrary to their spring force, the control valve element on its way adjusted from the first switching position to the second switching position must be at one end axially on the control valve element, in particular on a peripheral collar of the control valve element and on the other end the guide sleeve for the control valve element supported. Preferably, the spring is arranged such that they are not complete even in the second switching position of the control valve flattened.

in the With regard to the concrete design of the hydraulic connection between the high pressure area of the fuel injector and the control valve space There are different possibilities. Most notably preferred is a variant in which the hydraulic Compound includes a gap, the radially outside directly from the guide sleeve and radially inside is limited directly from the control valve element. It is the intermediate space formed as an annular space preferably contoured in this way and arranged that from the high-pressure fuel in the space no resulting axial forces on the Control valve element result.

In Development of the invention is provided with advantage that the the aforementioned gap over at least one in the guide sleeve Inserted sleeve bore hydraulically permanently with one Annular space is connected, which radially inward of the guide sleeve is limited and preferably radially outward from the inner circumference a frontal recess is limited in a throttle plate. By the arrangement of one filled with high pressure fuel Annular space radially outside the guide sleeve can be comparatively fuel-tight guide gaps between the control valve member and the guide sleeve be ensured, causing leakage losses from the previously explained Interspace in a radially outward of the guide sleeve and limited in the axial direction of the control valve member, be minimized on low pressure space.

It is particularly preferred if the annular space arranged radially outside the guide sleeve is conveyed via a channel in a throttle plate, on which the guide sleeve rests in the axial direction with the high-pressure region, preferably a the control chamber radially outwardly surrounding pressure chamber is connected. Particularly preferably, this channel is designed as a throttle bore.

Especially expedient is an embodiment of the Fuel injector, in which the control valve element on the outer circumference leading guide sleeve, in particular on a side facing the piezoelectric actuator in particular a biting edge for sealing engagement with the control valve member having in the second switching position. By providing a biting edge good fuel-tightness can be ensured, thereby a fuel outlet via the hydraulic connection in the control valve chamber in the second switching position of the control valve is prevented.

in principle the fuel can be actuated with an electromagnetic actuator become. However, a variant is particularly preferred with piezoelectric actuator, preferably between the piezoelectric Actuator and the control valve element, a coupler is provided with on the one hand a Kraftwegübersetzung is feasible and with the other, thermally induced expansion effects can be compensated.

In Development of the invention is provided with advantage that the hydraulic connection between the control room and the control valve room, so the hydraulic connection through which in the second switching position the control valve fuel from that of the injection valve element limited control room can flow into the low pressure area, at least two, running in different Injektorbauteilen Has sections. Very particularly preferably runs a section in a previously explained throttle plate and another portion in a control valve space radially outside bounding plate.

Further Advantages, features and details of the invention will become apparent the following description of a preferred embodiment as well as the drawing.

These shows in the only one

1 a schematic representation of a fuel injector with pressure compensated in the axial direction control valve and with a piezoelectric actuator for actuating the control valve.

In 1 is a designed as a common-rail injector fuel injector 1 for injecting fuel in a combustion chamber, not shown, of a likewise not shown internal combustion engine of a motor vehicle in a schematic representation. A high pressure pump 2 Promotes fuel from a reservoir 3 in a high-pressure fuel storage 4 (Rail). In this fuel, especially diesel or gasoline, under high pressure, stored in this embodiment about 2000 bar. To the high-pressure fuel storage 4 is the fuel injector along with other, not shown injectors via a supply line 5 connected. The supply line 5 flows into a supply channel 6 inside the fuel injector 1 , which in turn into a pressure room 7 that like the supply channel 6 to the high pressure area 8th of the fuel injector 1 heard, flows. The one in from a nozzle body 9 radially outside limited pressure chamber 7 inflowing fuel flows during an injection process directly into the combustion chamber of the internal combustion engine. The fuel injector 1 , more precisely a low pressure area 10 of the fuel injector 1 , Is connected via an injector return connection, not shown, to a return line 11 connected. About the return line 11 may be a later to be explained control amount of fuel in the fuel injector 1 to the reservoir 3 drain and be fed from there from the high pressure circuit again.

Inside the nozzle body 9 is a one-piece here as a nozzle needle trained injection valve element 12 arranged axially adjustable. This can also be made in several parts instead of the one-piece training and, for example, consist of a control rod and a coupled with this nozzle needle. In any case, the preferably one-piece injection valve element protrudes 12 in the drawing plane down to an injection valve element seat 13 with which it cooperates sealingly in a conventional manner. When the injection valve element 12 at its injection valve element seat 13 is present, ie, is in a closed position, the fuel outlet from a plurality of injection openings comprehensive nozzle hole arrangement 14 blocked. On the other hand, is it from its injection valve element seat 13 lifted off, can fuel from the pressure chamber 7 in an area below the injection valve element 12 and from there through the nozzle hole arrangement 14 , are essentially injected under high pressure (rail pressure) standing in the combustion chamber.

From an upper front side 15 the injection valve element 12 and a spring-loaded in the plane of the drawing sleeve 16 is a tax room 17 limited, the one in a throttle plate 18 on which the sleeve 16 supported in the axial direction, introduced inlet throttle 19 with high pressure fuel from the high pressure area 8th , here the supply channel 6 , is supplied. Alternatively, the inlet throttle 19 also as a radial bore in the sleeve 16 be provided. The sleeve 16 with enclosed control room 17 is radially outwardly surrounded by fuel under high pressure, so that an annular guide gap between the sleeve 16 and injection valve element 12 is comparatively fuel-tight.

The sleeve 16 is supported in the axial direction from below on the aforementioned throttle plate 18 from, in addition to the inlet throttle 19 an outlet throttle 20 having drainage channel 21 is introduced. The drainage channel 21 belongs as well as with this aligned in the flow direction channel 22 , which in an axial to the throttle plate 18 adjacent plates 23 is introduced to a hydraulic connection between the control room 17 and one radially outward of the plate 23 limited control valve room 24 , The control valve room 24 is in a lower section of a stepped bore 25 in the plate 23 brought in. Axially adjustable within the control valve chamber 24 is a bolt-shaped control valve element 26 a control valve 27 arranged, which by means of a piezoelectric actuator 29 via a hydraulic coupler 29 between an upper first switching position, ie between an upper first control valve seat 30 and a lower, ie second switching position, that is, a second control valve seat 31 is adjustable. At the control valve 27 it is a 3/2-way valve.

When the control valve element 26 is in the second (lower) switching position, so the control valve element 26 at the later to be explained later guide sleeve 32 for the control valve element 26 trained second control valve seat 31 Fuel may be present from the minimum volumetric control valve space 24 at the first control valve seat 30 over in the low pressure area 10 and from there to the return line 11 stream. By in this switching position on the out of the channel 22 and the drainage channel 21 existing hydraulic connection from the control room 17 Subsequent fuel decreases the fuel pressure in the control room 17 rapidly. This is due to the fact that the flow area of the outlet throttle 20 greater than that of the inlet throttle 19 , so that when located in the second switching position control valve 27 a net outflow of fuel (fuel tax amount) from the control room 17 results. Due to the pressure drop in the control room 17 raises the injection valve element 12 from the injection valve element seat 13 off, allowing fuel through the nozzle hole arrangement 14 can flow into the combustion chamber of the internal combustion engine.

Will the control valve element 26 moved in the plane of the drawing upwards into the first switching position, so that the control valve element 26 at first, at the plate 23 trained control valve seat 30 is applied, is the hydraulic connection between the control room 17 and the low pressure area 10 locked. At the same time, a hydraulic connection to be explained later 33 between the high pressure area 8th , more precisely the pressure chamber 7 and the control valve room 24 open, leaving fuel through this hydraulic connection 33 and the channel 22 as well as the drainage channel 21 in the control room 17 flow and there can cause an increase in pressure. In addition, fuel continues to flow via the inlet throttle 19 to, which in total to a rapid pressure increase in the control room 17 leads, causing the injection valve element 12 in the drawing plane down on the injection valve element seat 13 is adjusted and thus the injection process is terminated.

The hydraulic connection between the high pressure area 8th and the control valve room 24 includes a throttle bore 35 in the throttle plate 18 , wherein the throttle bore 35 the pressure room 7 with an annulus 36 hydraulically connects, with the annulus 36 radially outward from the inner periphery of a frontal bore in the throttle plate 18 and radially inward from the outer periphery of the guide sleeve 32 for the control valve element 26 is limited. The annulus 36 stands over a sleeve bore 37 in permanent hydraulic connection with a gap 38 radially outward of the inner circumference of a central bore in the guide sleeve 32 and radially inward from the outer periphery of the control valve member 26 is limited. In the second (lower) switching position of the control valve 27 is the gap 38 from the control valve room 24 via one on the guide sleeve 32 trained biting edge 39 separated, sealing with the underside of a circumferential covenant 40 the control valve element 26 interacts. The biting edge 39 is located on the front side of an axial, annular extension 41 the guide sleeve 32 , The extension 41 creates axial space to accommodate a plate spring 42 (Control valve spring), against whose spring force the control valve element 26 during energization of the piezoelectric actuator 28 must be moved in the drawing plane down to the second switching position. By providing a plate spring 42 as a control valve spring, the volume of the control valve chamber 24 minimized as shown. The plate spring 42 is supported in the axial direction on an upper end side of the guide sleeve 32 and in the other axial direction from below at the circumferential collar 40 the control valve element 26 from.

In the control valve element 26 it is a control valve element that is at least approximately pressure-balanced in the axial direction 26 ; This means that when the control valve element 26 is in the upper (first) switching position, act in the axial direction no (or possibly only small) resulting hydraulic forces. This is achieved by the control valve element 26 on a lower front side 43 is subjected to low pressure. The lower front side 43 limited in the axial direction up a compensation chamber 44 that the low pressure area 10 of the fuel injector 1 heard or via a low pressure channel 45 is hydraulically connected to the injector return port. The compensation room 44 is radially outward of the guide sleeve 32 limited, the control valve room 24 limited in the axial direction down. The guide sleeve 32 is over a majority of its axial extent in a frontal bore in the throttle plate 18 and lies with an upper portion of its outer periphery sealingly at a lower portion of the inner periphery of the stepped bore 25 on, leaving the annulus 36 opposite the control valve room 24 is sealed.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 102004030445 A1 [0002]
• - DE 102008001330 [0003]

Claims (10)

Fuel injector for injecting fuel into a combustion chamber of an internal combustion engine, in particular a common rail injector, comprising a one-part or multi-part injection valve element ( 12 ) for opening and closing at least one injection opening, wherein the injection valve element ( 12 ) a control valve ( 27 ) is assigned, which one adjustable between a first and a second switching position, in a control valve chamber ( 24 ) arranged control valve element ( 26 ), wherein in the first switching position, a hydraulic connection between a with the injection valve element ( 12 ) Actively connected control room ( 17 ) and a low pressure area ( 10 ) of the fuel injector ( 1 ) and a hydraulic connection ( 33 ) between a high pressure area of the fuel injector ( 1 ) and the control valve room ( 24 ) is open and wherein in the second switching position, the hydraulic connection between the control room ( 17 ) and the low pressure area ( 10 ) and the hydraulic connection between the high pressure area ( 8th ) and the control valve room ( 24 ) is interrupted, characterized in that the control valve element ( 26 ) is designed and arranged such that by the pressure in the control room ( 17 ) no or only a small resulting hydraulic force in the axial direction of the control valve element ( 26 ) is applied when the hydraulic connection ( 33 ) between the control room ( 17 ) and the low pressure area ( 10 ) in the first switching position of the control valve element ( 26 ) is interrupted and that the control valve element ( 26 ) in the second switching position for sealing the hydraulic connection ( 33 ) between the high pressure area ( 8th ) and the control valve room ( 24 ) sealingly on a control valve element ( 26 ) on its outer circumference leading guide sleeve ( 32 ) is present. Fuel injector according to claim 1, characterized in that that the spring is designed as a plate spring. Fuel injector according to one of claims 1 or 2, characterized in that the hydraulic connection ( 33 ) between the high pressure area ( 8th ) and the control valve room ( 24 ) as throttle connection, preferably by the provision of a throttle bore ( 35 ), is trained. Fuel injector according to one of the preceding claims, characterized in that the spring on the one hand axially on a peripheral collar ( 40 ) of the control valve element ( 26 ) and on the other hand axially on the guide sleeve ( 32 ) for the control valve element ( 26 ) is arranged abstützend. Fuel injector according to one of the preceding claims, characterized in that the hydraulic connection ( 33 ) a radially outward of the guide sleeve ( 32 ) and radially inward of the control valve element ( 26 ) includes limited space. Fuel injector according to claim 5, characterized in that the intermediate space via at least one sleeve bore ( 37 ) in the guide sleeve ( 32 ) with a radially inward of the guide sleeve ( 32 ) limited annulus ( 36 ) connected is. Fuel injector according to one of the preceding claims, characterized in that the guide sleeve ( 32 ) axially to a throttle plate ( 18 ), in which one, preferably as a throttle bore ( 35 ) bore, as a section of the hydraulic connection ( 33 ) between the high pressure area ( 8th ) and the control valve room ( 24 ) is introduced. Fuel injector according to claim 7, characterized in that the guide sleeve ( 32 ) a biting edge for sealing cooperation with the control valve element ( 26 ) in the second switching position. Fuel injector according to one of the preceding claims, characterized in that for actuating the control valve ( 27 ) a piezoelectric actuator ( 28 ) is provided. Fuel injector according to one of the preceding claims, characterized in that the hydraulic connection ( 33 ) between the control room ( 17 ) and the control valve room ( 24 ) passes through two axially adjacent components.

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