DE102008044043A1 - Fuel injector, particularly common rail injector for injecting fuel in combustion chamber of internal combustion engine, has injection valve element adjusted between closed position and open position releasing fuel in combustion chamber - Google Patents

Abstract

The fuel injector comprises an injection valve element (9) which is adjusted between a closed position and an open position releasing the fuel in a combustion chamber. A control chamber (13) is connected with the injection valve element which is hydraulically connected with an injector return connection (7) by a control valve (20). A pressure regulator (24) comprises a check valve (25) or a hydraulic choke. The control valve is provided with the pressure reducer.

Description

State of the art

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

Known, electromagnetically actuatable fuel injectors have a servo-circuit in order to switch over the occurring high pressures of about 1600 bar can. In the known fuel injectors, for example, in the DE 10 2006 020 724 A1 are described, the coming to use control valves (servo valves) are often designed as ball valves. In fuel injectors, which are intended for use at fuel pressures beyond 1600 bar, so-called, in the closed state in the axial direction pressure-balanced control valves are used. These usually comprise a valve sleeve which can be adjusted by means of an electromagnetic actuator, to which forces act only in the radial direction in the closed state. A problem with known, pressure-balanced control valves in the axial direction is that in these constantly leakage occurs from a high pressure region of the injector in a low pressure region of the injector, from which fuel can flow through a return port.

Disclosure of the invention

Of the Invention has for its object to provide a fuel injector, at which also fuel pressures beyond 1600 bar with a non-pressure compensated in the axial direction control valve switchable are.

These Task is with a fuel injector with the characteristics of Claim 1 solved. Advantageous developments of the invention are given in the subclaims.

Of the Invention is based on the idea of the control valve (servo valve) the fuel injector assign a pressure reducer, with the the maximum on the control valve, more precisely on the adjustable control valve element acting fuel pressure is limited and / or reducible. Different is expressed by the provision of a control valve associated pressure reducer prevents the control valve fuel under rail pressure acts. That way you can in the closed state in the axial direction non-pressure balanced, more cost-effective Control valves, such as ball valves, are used, even when the injection pressure is far higher than 1600 bar. With Advantage can be attributed to the provision of comparatively expensive, in the closed state in the axial direction pressure balanced Control valves that are constantly leaking, be waived.

in the Regarding the constant design of the pressure reducer, there are different possibilities. Particularly preferred an embodiment in which the pressure reducer is a check valve includes, which only when a defined Fuel pressure (release pressure) opens and thus the acting on the control valve element (maximum) fuel pressure reduced. By providing a check valve trained pressure reducer in combination with one in axial Direction non-pressure compensated control valve thus occurs leakage only when exceeding the aforementioned, defined Shutter release on.

additionally or preferably as an alternative to the provision of a check valve For example, the pressure reducer may include at least one hydraulic throttle or be designed as such. With a simultaneous waiver on a check valve occurs, similar to at a pressure balanced in the axial direction in the closed state Control valve, constantly leaking in the direction of the injector return port on - the use of a hydraulic throttle allows However, even at relatively high system pressures of beyond 1600 bar, preferably from beyond 2000 bar use of non-pressure balanced in the axial direction Rich, for example designed as a ball valve control valves.

In Development of the invention is the pressure reducer at least one Assigned bypass line through which flows through the pressure reducer Fuel bypassing the control valve towards the Injector return port can flow. Different is expressed by the flowing through the pressure reducer Fuel deflected by the provision of a bypass channel, preferably directly to the injector return port, bypassing of the control valve.

All particularly preferred is an embodiment of the fuel injector, in which the pressure reducer is designed such that the maximum acting on the control valve element fuel pressure is 2000 bar. The maximum pressure acting on the control valve element is preferred less than 2000 bar, most preferably less than 1800 bar, more preferably greater than or equal to 1600 bar.

As explained above, the use of a pressure reducing valve associated with the control valve element allows the use of a non-pressure balanced in the axial direction in the closed state NEN control valve, which in contrast to a pressure-balanced in the axial direction control valve has the advantage that substantially no leakage occurs in the low pressure region of the fuel injector in the closed state. In addition, a non-pressure balanced in the axial direction control valve is cheaper to produce. With regard to a maximum cost reduction, an embodiment of the fuel injector is preferred in which the control valve is designed as a ball valve, that is, as a valve whose, preferably axially adjustable control valve element is spherically shaped at least in the region of the control valve seat. More preferably, it is the control valve, in particular to form the ball valve as a 2/2-way valve.

in principle it is possible to have a trained as described above Fuel injector with a control valve associated pressure reducer means a piezoelectric actuator (piezo actuator) to operate. For cost and robustness reasons, however, is an embodiment preferred in which for actuating the control valve element the control valve is provided an electromagnetic actuator Ak. The use of non-pressure balanced in the axial direction control valves at pressures beyond 1600 bar failed so far the limited, maximum adjustment force used for coming electromagnetic Actuators.

constructive an embodiment is preferred in which the control valve associated with one of the control valve seat limited valve chamber is, wherein the pressure reducer preferably directly to the valve chamber adjacent or directly connected hydraulically with this. This ensures that the fuel pressure delimited directly in an area acting on the control valve element or diminished.

In Further development of the invention is provided with advantage that between the aforementioned valve chamber and one with the on or multi-part injection valve element operatively connected, preferably from this limited, control chamber arranged an outlet throttle is, by the fuel with open control valve and / or at designed as a hydraulic throttle pressure reducer in the direction the injector return port can flow. The Flow cross sections of the outlet throttle and one of the control chamber assigned inlet throttle should be coordinated with each other be that with the control valve open a net outflow of Fuel from the control chamber results, with the result that the fuel pressure in the control chamber decreases, resulting in an opening direction the injection valve element acting, hydraulic force results.

As already indicated, is an embodiment of the fuel injector particularly preferred, in which the one- or multi-part injection valve element the control chamber, preferably frontally, immediately limited. The injection valve element is one, at least one nozzle hole associated with comprehensive, nozzle hole arrangement, by at opened injection valve element, substantially under rail pressure standing, fuel flow into the combustion chamber of the internal combustion engine can.

Further Advantages, features and details of the invention will become apparent the following description of preferred embodiments as well as from the drawings.

These show in:

1 a highly schematic representation of a designed as a common rail injector fuel injector with a control valve, which is associated with a constructed as a check valve pressure reducer, and

2 an alternative embodiment of a fuel injector, in which the control valve associated pressure reducer is designed as a hydraulic throttle.

In The figures are the same elements and elements with the same Functions marked with the same reference numerals.

1 shows in a highly schematic view of a trained as a common rail injector fuel injector 1 for injecting fuel into a combustion chamber, not shown, of a likewise not shown internal combustion engine of a motor vehicle. 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, of about 2100 bar in this embodiment, stored. To the high-pressure fuel storage 4 is the fuel injector 1 in addition to other, not shown fuel injectors via a supply line 5 connected. The supply line 5 opens into a high-pressure area of the fuel injector 1 belonging, acting as a minirail for pressure oscillation minimization pressure chamber 6 , The fuel flows during an injection process directly from the pressure chamber 6 in the axial direction in the plane of the drawing down into the combustion chamber, not shown, of the internal combustion engine. The fuel injector 1 is via an injector return port 7 to a return line 8th and about this to the reservoir 3 connected. About the return line 8th may be a control amount to be explained later and a leakage amount of fuel from the fuel injector 1 to the reservoir 3 drain and from there from the high pressure circuit are fed back.

Within an injector body not shown is a one-piece injection valve element in this embodiment 9 , which can also be in two parts if necessary, arranged to be adjustable in the axial direction. The injection valve element 9 has at its tip, not shown, a closing surface, with which the injection valve element 9 in a tight contact with a trained within a nozzle body also not shown injection valve seat can be brought. When the injection valve element 9 abuts against its injection valve element seat, that is, is in a closed position, the fuel outlet is blocked from a nozzle body arranged in the nozzle hole arrangement. If, on the other hand, it is lifted from its injection valve element seat, fuel can escape from the pressure chamber 6 between the injection valve element 9 and flow past the nozzle body to the nozzle hole arrangement and there are injected substantially under the high pressure (rail pressure) standing in the combustion chamber.

From an upper front side 10 the injection valve element 9 and a lower, sleeve-shaped section in the plane of the drawing 11 a throttle plate 12 becomes a control chamber 13 bounded over a radially in the sleeve-shaped portion 11 running inlet throttle 14 with high-pressure fuel from the pressure chamber 6 is supplied. The sleeve-shaped section 11 with enclosed control chamber 13 is radially outwardly surrounded by fuel under high pressure, so that an annular guide gap 15 radially between the sleeve-shaped portion 11 and the injection valve element 9 is comparatively fuel-tight.

The control chamber 13 is about one, into the throttle plate 12 introduced, axial flow channel 16 with outlet throttle 18 with a valve chamber 17 connected by means of a control valve element 19 a control valve 20 lockable and with a low pressure area 21 and thus with the injector return port 7 is connectable. From the drainage channel 16 can fuel with open control valve 20 in the low pressure area 21 of the fuel injector 1 and from there to the injector return port 7 flow. For adjusting the non-pressure compensated in the axial direction in the axial direction control valve 20 is a, symbolized only by arrows, preferably designed as an electromagnetic actuator actuator 22 intended. When energizing the actuator 22 raises the control valve element 19 from his control valve seat 23 whereas the control valve element 19 for non-energization of the actuator 22 by means of a closing spring, not shown, back to the control valve seat 23 is adjusted and thereby the valve chamber 17 immediately limited and towards the injector return port 7 seals.

With open control valve 20 So flows fuel from the control chamber 13 between control valve element 19 and control valve seat 23 over in the low pressure area 21 and from there to the injector return port 7 , The flow cross sections of the inlet throttle 14 and the outlet throttle 18 are coordinated so that a net outflow of fuel (tax amount) from the control chamber 13 in the return line 8th and thus in the reservoir 3 results. This reduces the pressure in the control chamber 13 rapidly, causing the injection valve element 9 lifts off from its injection valve element seat, not shown, so that in turn fuel from the pressure chamber 6 can flow through the nozzle hole arrangement in the combustion chamber.

To end the injection process is the energization of the merely indicated actuator 22 interrupted, causing the spherical control valve element 19 by means of the closing spring, not shown, preferably on an armature plate (not shown) of the electromagnetic actuator 22 supported, in the drawing plane down to its control valve seat 23 is adjusted. The through the inlet throttle 14 in the control chamber 13 inflowing fuel ensures a rapid pressure increase in the control chamber 13 and thus for one on the injection valve element 9 acting, hydraulic closing force. The resulting closing movement of the injection valve element 9 is supported by a closing spring, not shown.

As it turned out 1 results is the control valve 20 More specifically, that of the control valve element 19 limited valve chamber 17 a pressure reducer 24 assigned. The pressure reducer 24 is in the illustrated embodiment as a check valve 25 formed, which is a spherical valve element 26 and a compression spring 27 includes. By choosing the compression spring 27 the opening force necessary to adjust the valve element can be adjusted 26 from his valve seat 28 withdraw. The opening force in turn affects the maximum in the valve chamber 17 prevailing fuel pressure. If the opening force is reached, so there is a defined minimum or Auslösekraftdruck in the valve chamber 17 and thus on the control valve element 19 , the pressure reducer opens 24 or the check valve 25 can fuel out of the valve chamber 17 through a bypass channel 29 at the control valve 20 over in the direction of the injector return port 7 stream. The outflowing amount is an unavoidable amount of leakage necessary to over-pressurize the control valve member 19 to avoid that leads to it would ren that the control valve element 19 despite non-energization of the actuator 22 from the control valve seat 23 would take off. Only by means of the pressure reducer 24 achieved pressure reduction will be the use of non-pressure compensated control valves 20 with simultaneous use of the electromagnetic actuator (actuator 22 ) possible. In contrast to a pressure-balanced control valve in the axial direction occurs in the illustrated embodiment, leakage only when a release pressure in the valve chamber 17 and not on permanently.

In 2 is an alternative embodiment of a fuel injector 1 shown in substantially the embodiment according to 1 corresponds so that to avoid repetition in the following only differences to the preceding embodiment will be explained. In terms of the similarities will be on 1 with associated figure description referenced.

Also in the embodiment according to 2 is the valve chamber 17 a pressure reducer 24 assigned. However, this does not include a check valve, but is as a hydraulic throttle 30 formed the pressure in the valve chamber 17 in comparison to the pressure room 6 prevailing fuel pressure (significantly reduced), so that the maximum on the control valve element 19 acting pressure is limited. If necessary, the hydraulic throttle 30 be combined with a check valve. Without check valve occurs at the pressure reducer 24 a permanent leakage, similar to in the axial direction pressure compensated control valves, but it is due to the provision of the hydraulic throttle 30 possible, non-pressure balanced in the axial direction control valves, preferably in combination with an electromagnetic actuator (actuator 22 ), even at pressures beyond 2000 bar use.

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 102006020724 A1 [0002]

Claims (10)

Fuel injector, in particular common-rail injector, for injecting fuel into a combustion chamber of an internal combustion engine, comprising an injection valve element which is adjustable between a closed position and an open position which releases the fuel flow into the combustion chamber (US Pat. 9 ), and one with the injection valve element ( 9 ) Actively connected control chamber ( 13 ), which by means of a control valve ( 20 ) hydraulically with an injector return port ( 7 ), characterized in that the control valve ( 20 ) a pressure reducer ( 24 ) assigned. Fuel injector according to claim 1, characterized in that the pressure reducer ( 24 ) a check valve ( 25 ) and / or a hydraulic throttle ( 30 ). Fuel injector according to claim 2, characterized in that a bypass channel ( 29 ) is provided, through which by the pressure reducer ( 24 ) flowing fuel at the control valve ( 20 ) can flow past. Fuel injector according to one of the preceding claims, characterized in that the pressure reducer ( 24 ) is designed to limit the fuel pressure to a maximum of 2000 bar, preferably to a maximum of 1800 bar, most preferably limited to a maximum of 1600 bar. Fuel injector according to one of the preceding claims, characterized in that the control valve ( 20 ) is designed as a non-pressure-balanced valve in the axial direction in the closed state. Fuel injector according to one of the preceding claims, characterized in that the control valve ( 20 ) is designed as a ball valve, preferably as a 2/2-way valve. Fuel injector according to one of the preceding claims, characterized in that for actuating the control valve ( 20 ) an electromagnetic actuator ( 22 ) or a piezo actuator is provided. Fuel injector according to one of the preceding claims, characterized in that the pressure reducer ( 24 ) hydraulically to a control valve ( 20 ) associated valve chamber ( 17 ) connected directly by means of the control valve ( 20 ) is closable. Fuel injector according to claim 8, characterized in that between the means of the control valve ( 20 ) lockable valve chamber ( 17 ) and the control chamber ( 13 ) an outlet throttle ( 18 ) is arranged. Fuel injector according to one of the preceding claims, characterized in that the control chamber ( 13 ) directly from the one-piece or multi-part injection valve element ( 9 ) is limited.