This is a U.S. National Phase of International Application PCT/AT2007/000286, filed Jun. 13, 2007 and claims the benefit of foreign priority under 35 U.S.C. §119 from Austrian Patent Applications A 1997/2006, filed Jun. 13, 2006, and A 65/2007, filed Jan. 12, 2007, the entire disclosures of which are hereby incorporated by reference herein.
The invention relates to a device for the injection of fuel into the combustion chamber of an internal combustion engine, including at least one high-pressure accumulator, an injector, at least one high-pressure line connecting the high-pressure accumulator with the injector, and a resonator line arranged in parallel with the high-pressure line between the injector and the high-pressure accumulator and including a resonator throttle on the side of the high-pressure accumulator.
In a common rail system, electronically controlled injectors are used for the injection of fuel into the combustion chamber of an engine. The servo valves employed in such injectors cause the injection nozzle to close very rapidly such that strong pressure pulsations will be created on the nozzle seat due to the inertia of the fuel in the consecutive high-pressure bores, which will result in intense wear. The pressure peaks occurring there in the most unfavourable cases will be up to 500 bar higher than the rail pressure.
With rapidly following injection procedures, such pressure vibrations will, moreover, lead to strong deviations of the injection rates. If, for instance, a pressure vibration is induced on the nozzle seat by a preinjection, the injected amount for the second, subsequent injection, at a constant opening time of the nozzle needle, will depend on whether said second injection has been effected at a maximum or at a minimum of said pressure vibration. As low a pressure vibration as possible is therefore desirable at the injector in any operating state of the hydraulic system.
In the patent literature, numerous measures have been described to avoid pressure vibrations in hydraulic systems. In most cases, these comprise attenuation volumes, throttle assemblies, valve assemblies or combinations of such measures. Most frequently employed are throttle assemblies, which ought to contribute to the dissipation of the flow energy into static pressure energy.
Thus, it is, for instance, known from EP 1 217 202 A1 to arrange in parallel, in a high-pressure bore departing from a high-pressure line (common rail) and leading to an injector, a non-return valve as well as a dissipation element so as to enable a more rapid attenuation of pressure vibrations.
In order to minimize pressure pulsations in a fuel injection line that is feed from a high-pressure line, a throttle reducing the cross section of the injection line is provided at the connection site to the high-pressure line according to DE 160 785 A1.
Furthermore, it is also known to use the pressure vibrations occurring in an injection system for the pressure-modulated formation of the injection course. In this context, it is known from DE 102 09 527 A1 to connect the pressure volumes of a first and a second valve via a pressure line. The first and second valves are connected in series, the first valve controlling the pressure supply to the pressure volume of the second valve and the injection pressure level being controlled by the second valve during the injection phases.
DE 102 47 775 A1 addresses a problem which will occur at several injection pulses per cycle, if the time intervals of the former are only a few microseconds. Due to the pressure drop occurring at every injection, the forming pressure waves will not be sufficiently attenuated and, hence, cause uncontrollable irregularities in subsequent injections. The problem is solved by the aid of attenuation means comprised of a porous material, for instance a sintered metal insert, on which the pressure waves are attenuated by multiple reflections and absorptions. The pressure losses occurring thereby are disadvantageous.
The drawbacks of the prior in the following approaches to solve this problem essentially are:
Throttled Flow:
If a throttle for attenuating pressure vibrations is provided between the high-pressure accumulator and the injector, said throttle will, as a side effect, also cause throttling of the main flow. The system pressure prevailing in the rail can thus no longer be utilized to its full extent for an injection. The more effectively the throttle is able to attenuate pressure vibrations, the larger the pressure loss also during injection.
Specific Valve Assemblies:
Valves constitute vibrating systems by themselves and, thus, exhibit pronounced time behaviours which, being additional sources of interference, are undesirable in injection systems. As mechanically moved elements, valves are afflicted with tolerances and suffer from high wear phenomena on account of high actuation frequencies.
Attenuation Volumes:
The common rail as such already provides the largest attenuation volume available in the system. It is true that a substantial reduction of the pressure vibrations could be achieved by an increase in the rail volume. Yet, this would involve the disadvantage of the system becoming very sluggish and no longer readily allowing rapid pressure changes.
A system improved over that prior art is known from DE 103 07 871 A1. In that system, a resonator line comprising a resonator throttle on the side of the high-pressure accumulator is arranged in parallel with the high-pressure line, between the injector and the high-pressure accumulator.
Departing from such a configuration, the present invention aims to improve a device for injecting fuel into the combustion chamber of an internal combustion engine by constructive means as simple as possible, while enabling the avoidance, or as rapid a reduction as possible, of the pressure vibrations harmful to the individual components.
In accordance with the invention, this object is achieved in that the resonator line is comprised of an insert piece pressed into the bore of the high-pressure line and is, in particular, formed within the same. In this case, no separate bore is required for the resonator line such that manufacturing expenses will be considerably reduced. Moreover, such a construction ensures that the respective sections of the high-pressure line and the resonator line are equally long so that, after a reflection of the pressure waves, the extinction of the waves will be caused in the point of juncture.
In a preferred manner, the resonator line is formed as a central bore within the insert piece. The cross sections of the insert piece and the bore of the high-pressure line may have mutually differing contours such that flow cross-sections of the high-pressure line are formed between the insert piece and the wall of the bore of the high-pressure line. In this respect, at least two, in a particularly preferred manner three, circular-segment-shaped flow cross-sections are provided. The flow cross-section of the high-pressure line, in a preferred manner, is to substantially correspond with the flow cross-section of the resonator line.
The invention, therefore, contemplates that the high-pressure line, by the pressing-in of an insert piece, is divided into two independent sections, one of which is equipped with a throttle such that the pressure vibrations created on the nozzle seat will be differently reflected in the two sections, and the reflected vibrations will almost become extinguished because of their phase shift. In doing so, the function of the hydraulic system is reproduced in exactly the same manner as without any throttle, since only the line vibrations are extinguished. The essential advantages of such a configuration are:
According to a preferred further development, a particularly effective extinction will be achieved if the length of the resonator line is tuned to the length of the high-pressure line in such a manner as to cause the mutual attenuation or extinction of the pressure vibrations induced by the injector. The length of the resonator line between the injector and the resonator throttle preferably corresponds substantially to the length of the high-pressure line between the injector and the entry of the high-pressure line into the high-pressure accumulator.
According to a further preferred further development, it is provided that the length of the resonator line between the injector and the resonator throttle as well as the length of the high-pressure line between the injector and the entry of the high-pressure line into the pressure accumulator is each an integer multiple of the wavelength of the pressure vibration induced by the injector.
In the following, the invention will be explained in more detail by way of exemplary embodiments schematically illustrated in the drawing.
Number | Date | Country | Kind |
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A 1008/2006 | Jun 2006 | AT | national |
A 65/2007 | Jan 2007 | AT | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/AT2007/000286 | 6/13/2007 | WO | 00 | 12/15/2008 |
Publishing Document | Publishing Date | Country | Kind |
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WO2007/143768 | 12/21/2007 | WO | A |
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Number | Date | Country | |
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