EP1403509B1 - Pressure limiting device and fuel system with such a pressure limiting device - Google Patents

Pressure limiting device and fuel system with such a pressure limiting device Download PDF

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Publication number
EP1403509B1
EP1403509B1 EP20030003826 EP03003826A EP1403509B1 EP 1403509 B1 EP1403509 B1 EP 1403509B1 EP 20030003826 EP20030003826 EP 20030003826 EP 03003826 A EP03003826 A EP 03003826A EP 1403509 B1 EP1403509 B1 EP 1403509B1
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EP
European Patent Office
Prior art keywords
pressure
fuel
limiting device
pressure limiting
collar
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP20030003826
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German (de)
French (fr)
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EP1403509A2 (en
EP1403509A3 (en
Inventor
Helmut Rembold
Wolfgang Bueser
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Robert Bosch GmbH
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Robert Bosch GmbH
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Publication date
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Publication of EP1403509A2 publication Critical patent/EP1403509A2/en
Publication of EP1403509A3 publication Critical patent/EP1403509A3/en
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Publication of EP1403509B1 publication Critical patent/EP1403509B1/en
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M63/00—Other fuel-injection apparatus having pertinent characteristics not provided for in groups F02M39/00 - F02M57/00 or F02M67/00; Details, component parts, or accessories of fuel-injection apparatus, not provided for in, or of interest apart from, the apparatus of groups F02M39/00 - F02M61/00 or F02M67/00; Combination of fuel pump with other devices, e.g. lubricating oil pump
    • F02M63/02—Fuel-injection apparatus having several injectors fed by a common pumping element, or having several pumping elements feeding a common injector; Fuel-injection apparatus having provisions for cutting-out pumps, pumping elements, or injectors; Fuel-injection apparatus having provisions for variably interconnecting pumping elements and injectors alternatively
    • F02M63/0225—Fuel-injection apparatus having a common rail feeding several injectors ; Means for varying pressure in common rails; Pumps feeding common rails
    • F02M63/023—Means for varying pressure in common rails
    • F02M63/0235—Means for varying pressure in common rails by bleeding fuel pressure
    • F02M63/0245—Means for varying pressure in common rails by bleeding fuel pressure between the high pressure pump and the common rail
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M55/00—Fuel-injection apparatus characterised by their fuel conduits or their venting means; Arrangements of conduits between fuel tank and pump F02M37/00
    • F02M55/04—Means for damping vibrations or pressure fluctuations in injection pump inlets or outlets
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M63/00—Other fuel-injection apparatus having pertinent characteristics not provided for in groups F02M39/00 - F02M57/00 or F02M67/00; Details, component parts, or accessories of fuel-injection apparatus, not provided for in, or of interest apart from, the apparatus of groups F02M39/00 - F02M61/00 or F02M67/00; Combination of fuel pump with other devices, e.g. lubricating oil pump
    • F02M63/0012—Valves
    • F02M63/0031—Valves characterized by the type of valves, e.g. special valve member details, valve seat details, valve housing details
    • F02M63/005—Pressure relief valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M63/00—Other fuel-injection apparatus having pertinent characteristics not provided for in groups F02M39/00 - F02M57/00 or F02M67/00; Details, component parts, or accessories of fuel-injection apparatus, not provided for in, or of interest apart from, the apparatus of groups F02M39/00 - F02M61/00 or F02M67/00; Combination of fuel pump with other devices, e.g. lubricating oil pump
    • F02M63/02—Fuel-injection apparatus having several injectors fed by a common pumping element, or having several pumping elements feeding a common injector; Fuel-injection apparatus having provisions for cutting-out pumps, pumping elements, or injectors; Fuel-injection apparatus having provisions for variably interconnecting pumping elements and injectors alternatively
    • F02M63/0225—Fuel-injection apparatus having a common rail feeding several injectors ; Means for varying pressure in common rails; Pumps feeding common rails
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M2200/00—Details of fuel-injection apparatus, not otherwise provided for
    • F02M2200/31—Fuel-injection apparatus having hydraulic pressure fluctuations damping elements
    • F02M2200/315—Fuel-injection apparatus having hydraulic pressure fluctuations damping elements for damping fuel pressure fluctuations
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M2200/00—Details of fuel-injection apparatus, not otherwise provided for
    • F02M2200/40—Fuel-injection apparatus with fuel accumulators, e.g. a fuel injector having an integrated fuel accumulator
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M63/00—Other fuel-injection apparatus having pertinent characteristics not provided for in groups F02M39/00 - F02M57/00 or F02M67/00; Details, component parts, or accessories of fuel-injection apparatus, not provided for in, or of interest apart from, the apparatus of groups F02M39/00 - F02M61/00 or F02M67/00; Combination of fuel pump with other devices, e.g. lubricating oil pump
    • F02M63/0012—Valves
    • F02M63/0031—Valves characterized by the type of valves, e.g. special valve member details, valve seat details, valve housing details
    • F02M63/004—Sliding valves, e.g. spool valves, i.e. whereby the closing member has a sliding movement along a seat for opening and closing
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M63/00—Other fuel-injection apparatus having pertinent characteristics not provided for in groups F02M39/00 - F02M57/00 or F02M67/00; Details, component parts, or accessories of fuel-injection apparatus, not provided for in, or of interest apart from, the apparatus of groups F02M39/00 - F02M61/00 or F02M67/00; Combination of fuel pump with other devices, e.g. lubricating oil pump
    • F02M63/0012—Valves
    • F02M63/0031—Valves characterized by the type of valves, e.g. special valve member details, valve seat details, valve housing details
    • F02M63/0045—Three-way valves

Definitions

  • the present invention relates to a pressure limiting device for a fuel system of an internal combustion engine
  • Pressure limiting devices are known from the market. They are preferably used in such fuel systems, which are used in internal combustion engines with gasoline direct injection. Such fuel systems usually have a low pressure range and a high pressure range. An electric fuel pump delivers the fuel into the low pressure range, from which the fuel via a high pressure pump in a fuel rail ("common rail called) is promoted. The pressure in the fuel rail is usually controlled by a pressure control or a quantity control valve.
  • a pressure limiting device is provided in the high pressure region of the fuel system.
  • This is generally a conventional pressure relief valve with a acted upon by a spring against a valve seat valve element.
  • the valve member lifts off the valve seat so that fuel can flow from the inlet of the pressure relief valve to the outlet and thence back to the low pressure region of the fuel system.
  • the pressure limiting device In general, the pressure limiting device must be arranged in the region of the fuel collecting line, that is to say at a certain distance from the high-pressure pump. The reason for this is that during operation, the high-pressure pump generates pressure pulsations whose peaks can exceed the opening pressure of the pressure-limiting valve. If the pressure limiting valve were to be arranged directly at the high-pressure pump, there would be the danger that the pressure-limiting valve would open due to the pressure pulsations, although the maximum system pressure has not yet been reached. Only at a certain distance from the high pressure pump, it comes to a smoothing of Pressure pulsations due to throttle effects in the fuel line and due to the compressibility of the fuel.
  • the pressure relief valve so that its opening pressure is above the pressure peaks due to the pressure pulsations.
  • This pressure limiting valve can then be arranged in the immediate vicinity of the high pressure pump or even integrated into it. In emergency mode, so if the pressure control of the fuel rail is no longer working properly and then there is a higher pressure in the fuel rail than the normal system pressure, safe operation of the internal combustion engine must still be ensured. This in turn would require the design of the components of the high pressure region of the fuel system to the high opening pressure of the pressure relief valve. However, such components are relatively expensive.
  • a pressure limiting device in which the pressure pulsations are reduced by a compensation chamber, so that the pressure limiting device does not open during normal operation of the fuel pump despite the pressure pulsations caused by the high pressure pump. This allows the arrangement of the pressure relief device also in the vicinity of the high-pressure pump.
  • a pressure limiting device in which a first collar of a piston defines a compensation chamber. As soon as the volume of the compensation chamber increases due to pressure pulsations, the piston lifts off from a valve seat and releases a hydraulic connection between the high pressure region and the low pressure region of the fuel system. As a result, the efficiency of the fuel system deteriorates and the fuel is strongly heated by the dissipated energy.
  • the piston has a second collar, and on the second collar a control edge is formed, that the control edge so cooperates with a recess of the bore, that in the closed state of the pressure limiting device, the hydraulic connection between the high pressure fuel line and Low-pressure fuel line is interrupted, that the pressure limiting device opens only when the compensation chamber has reached a predetermined minimum volume, and that the minimum volume of the overlap of the control edge in the bore in the closed position of the pressure relief device depends.
  • This pressure limiting device according to the invention unlike the pressure limiting device known from the prior art, can be used without adaptation measures in virtually all fuel pumps or fuel systems. As a result, the required variety of variants is greatly reduced, which brings considerable economic advantages in the production, storage and repair of equipped with the pressure limiting device according to the invention fuel systems with it.
  • a spring is clamped between the piston and the housing, which acts on the piston in the direction of the closed position of the pressure limiting device.
  • the piston When the piston has a sealing cone at its end remote from the first collar and the sealing cone rests in the closed position of the pressure limiting device on a sealing seat of the housing, the pressure in the high-pressure region of the fuel system is maintained when the internal combustion engine is shut off, which prevents the formation of vapor bubbles.
  • a shoulder is formed in the housing, and that the piston bears against the shoulder in the closed position of the pressure-limiting device.
  • a further, particularly advantageous embodiment of the invention provides that the piston has a third collar, and that the compensation chamber is additionally limited by the third collar, wherein the diameter of the third collar is smaller than the diameter of the first collar.
  • the resulting hydraulic force is reduced to the first collar, which - with otherwise the same hydraulic boundary conditions - allows a smaller spring between the piston and housing.
  • the spring can be made smaller, which helps reduce the overall volume of the entire pressure limiting device. Due to the fact that a partial compensation of the hydraulic forces takes place between the first collar and the third collar, the forces exerted by the piston on the spring are very small, without the piston diameters becoming very small. In the series production of turned parts with diameters smaller than 4 mm and high precision, the production costs increase compared to slightly larger sized parts. As a result, the cost of the pressure limiting device according to the invention can be minimized.
  • the third collar with the bore defines a space and this space is at least indirectly hydraulically connected to a low-pressure region of the fuel system, so that any accumulating leaks can be dissipated.
  • the present invention also relates to a fuel system for supplying fuel for an internal combustion engine, with a reservoir, with a first fuel pump, which is connected on the input side to the reservoir, with a second fuel pump, which is the input side connected via a fuel connection to the first fuel pump, and with a pressure limiting device, which limits the pressure in a fuel connection on the output side of the second fuel pump.
  • Pressure limiting device is formed in the manner described above.
  • the second fuel pump comprises a 1-cylinder piston pump.
  • the pressure pulsations are particularly pronounced, so that here the pressure limiting device according to the invention works very effectively.
  • the pressure limiting device is attached to the second fuel pump, preferably integrated in this.
  • Such an arrangement of the pressure limiting device within the fuel system has the advantage that it is possible to dispense with a return line from the pressure limiting device, for example, to the low pressure region of the fuel system. As a result, the cost of the fuel system according to the invention are significantly reduced.
  • a fuel system as a whole bears the reference numeral 10. It comprises a low-pressure region 12 and a high-pressure region 14.
  • the low-pressure region 12 comprises a reservoir 16 in which fuel 18 is stored.
  • the fuel 18 is conveyed from the reservoir 16 by a first fuel pump 20.
  • This is an electric fuel pump.
  • the electric fuel pump 20 conveys into a low-pressure fuel line 22.
  • a filter 24 is initially provided after the electric fuel pump 20 as seen in the flow direction. Seen in the flow direction before the filter 24 branches off from the low-pressure fuel line 22 from a branch line 26, which leads back to the reservoir 16.
  • a pressure limiting valve 28 is arranged in the branch line 26 in the branch line 26, which leads back to the reservoir 16.
  • the low-pressure fuel line 22 leads to a second fuel pump 30. This is driven in a manner not shown here by the camshaft of an internal combustion engine (not shown).
  • the second fuel pump 30 is a 1-piston high-pressure pump. Upstream of the high pressure pump 30 are still in the low pressure fuel line 22 a Pressure damper 32 and a check valve 34 is arranged. Between the filter 24 and the pressure damper 32 branches from the low-pressure fuel line 22 from a branch line 36, in which a low-pressure regulator 38 is arranged.
  • the branch line 36 also leads back to the reservoir 16 for the fuel 18. From the high-pressure pump 30, a leakage line 40 leads to the branch line 36.
  • the high-pressure pump 30 conveys into a high-pressure fuel line 42, which leads via a check valve 44 to a fuel manifold 46.
  • Fuel injection valves 48 which in turn inject the fuel into a combustion chamber, not shown, of the internal combustion engine are in turn connected to the fuel manifold 46.
  • the pressure in the fuel rail 46 is detected by a pressure sensor 50.
  • the pressure in the high-pressure fuel line 42 and the fuel manifold 46, ie in the high-pressure region 14 of the fuel system 10, is controlled and / or regulated via a quantity control valve 52.
  • the connection takes place via a branch line 54.
  • the quantity control valve 52 is actuated by a 1, not shown, which in turn receives signals from the pressure sensor 50. In this way, a closed loop for the control of the pressure in the high pressure region 14 of the fuel system 10 is provided.
  • a pressure relief device 56 is combined with the high-pressure pump 30.
  • the exact structure of a first embodiment of a pressure limiting device 56 according to the invention can be seen from FIG. 2:
  • the high-pressure pump 30 and the pressure-limiting device 56 are accommodated in a common housing 58. Only one region of a delivery chamber 60 and the outlet valve 44 arranged on the outlet side of the delivery chamber 60 are visible from the high-pressure pump 30 in FIG.
  • the outlet valve 44 comprises a spherical valve element 64, which is acted upon by a spring 66 against a valve seat 68. Downstream of the exhaust valve 44, the high pressure fuel line 42 is visible.
  • the delivery chamber 60 is sealed off from the high-pressure fuel line 42 by the outlet valve 44.
  • a bore 70 is provided, in which a piston 72 is guided.
  • the piston 72 has a first collar 74 and a second collar 76.
  • the piston 72 is guided over the first collar 74 and the second collar 76 in the bore 70.
  • the fit of bore 70 and first collar 74 is sized so that the annular gap between bore 70 and first collar 74 serves as a throttle.
  • the fit of bore 70 and second collar 76 is sized so that a good sealing effect between the bore 70 and second collar 76 is achieved and the piston 72 is still displaced in the bore 70 still.
  • first collar 74 and second collar 76 has the Piston 72 has an annular groove 78 which communicates hydraulically with the high-pressure fuel line 42.
  • a bottom 80 of the bore 70 and the first collar 74 of the piston 72 define a compensation chamber 82, which is hydraulically connected to the high-pressure fuel line 42 via the annular gap between the bore 70 and the first collar 74.
  • annular recess 84 is concentric with the bore 70 is provided.
  • the annular groove 78 and the second collar 76 of the piston 72 form a control edge 86, which cooperates with the recess 84.
  • the control edge 86 to the recess 84 has an overlap, which is indicated in Figure 2 by the reference numeral 88.
  • the hydraulic connection between the high-pressure fuel line 42 and recess 84 is interrupted in this position of the piston 72.
  • the second collar 76 is wider than the recess 84, so that the piston 72 is always performed regardless of its position in the bore 70 through the first collar 74 and the second collar 76 in the bore 70.
  • a sealing cone 90 is integrally formed on the piston 72.
  • the sealing cone 90 together with a sealing seat 92 formed in the housing 58, separates the recess 84 from a spring chamber 94, which in turn hydraulically communicates with the low pressure line 22.
  • the sealing cone 90 and the sealing seat 92 serve to maintain the pressure in the high-pressure region 14 when the internal combustion engine is switched off.
  • a compression spring 96 is arranged, which is supported at one end against the housing 58 and the other end against the piston 72 and this presses with its sealing cone 90 in the sealing seat 92.
  • the pressure in the delivery chamber 60 increases and the check valve 44 opens, the pressure in the high-pressure fuel line 42 also increases and fuel flows from the high-pressure fuel line 42 into the compensation chamber 82 and the pressure in the compensation chamber 82 increases delayed in time.
  • the delay of the pressure rise in the compensation chamber 82 is caused by the throttling action of the annular gap between the first collar 74 and bore 70.
  • the overlap 88 and the volume of the compensation chamber 88 are designed so that during normal operation of the fuel system 10, the pressure pulsations in the high-pressure region 14 of the fuel system 10 so far be degraded that they have no negative impact on the operation of the fuel system 10 more.
  • the overlap 88 and the volume of the balance chamber 82 are designed so that during normal operation of the fuel system 10, the hydraulic connection between the high-pressure fuel line 42 and low-pressure fuel line 22 is not released. This means that the efficiency of the fuel system 10 remains virtually unchanged during normal operation as a result of the use of the pressure limiting device 56 according to the invention.
  • the fuel pump 30 (see Fig. 1) always delivers the full flow, the pressure in the high pressure region 14 and thus also in the high-pressure fuel line 42 via a - compared with the pressure pulsations during normal operation - long period strongly.
  • the volume of the compensation chamber 82 increases so much that the control edge 86 releases the hydraulic connection between the annular groove 78 and recess 84 and fuel flows from the high-pressure fuel line 42 via the spring chamber 94 in the low-pressure fuel line 22, so that a Degradation of prevailing in the high-pressure fuel line 42 overpressure takes place.
  • the high pressure area 14 of the fuel system 10 is effectively protected against impermissibly high pressures in case of disturbances in flow control.
  • the pressure rise in the high-pressure fuel line 42 and the fuel rail 46 is lower, which is qualitatively represented in the figure 3 by the solid line.
  • the check valve 44 closes and the spring 96 pushes the piston 72 in the direction of the compensation chamber 82 and thereby reduces the volume of the compensation chamber 82 to its original value.
  • the fuel displaced from the compensation chamber 82 flows via the annular groove 78 into the high-pressure fuel line 42 and thus contributes to the pressure maintenance in the high-pressure region 14 of the fuel system 10.
  • the overlap 88 between the control edge 86 and recess 44, the bias and spring rate of the spring 96 and the volume of the compensation chamber 82 and the throttling action between the first collar 74 and bore 70 must, as already mentioned, be matched to one another that at a delivery stroke of the second Fuel pump 30 during proper operation of the fuel system 10, the control edge 86, the recess 84 is not released and thus no fuel from the high-pressure region 14 flows into the low-pressure region 12.
  • FIG. 4 shows a further exemplary embodiment of a pressure limiting device 56 according to the invention.
  • the same components are provided with the same reference numerals and it is the case with respect to Figure 2 said accordingly.
  • the essential difference from the first exemplary embodiment according to FIG. 2 is that the piston 72 has a third collar 100 below the first collar 74.
  • the balance chamber 82 is present in this embodiment between the first collar 74 and the third collar 100 and is an annular space whose volume increases as the piston 72 moves in the direction of the spring 96.
  • the collar 80 of the bore 70 and the third collar 100 define a space 102 which communicates hydraulically via a bore 104 with the spring chamber 94 and thus with the low-pressure fuel line 22.
  • the force acting on the end faces of the piston 72 hydraulic forces are compensated.
  • FIG. 5 shows a third exemplary embodiment of a pressure limiting device 56 according to the invention.
  • the piston 72 has no sealing cone 90.
  • the piston 72 rests with its third collar 100 on a shoulder 106 of the housing 58 and thus defines the maximum overlap 88 of the control edge 86.
  • the third embodiment of an inventive Pressure limiting device 56 is preferably used in fuel systems 10, in which after stopping the engine or in overrun mode, the pressure in the high-pressure region 14 is lowered via a defined leakage.
  • the opening pressure of the pressure limiting device 56 is as independent as possible from the flow through the high pressure fuel line 42.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Fuel-Injection Apparatus (AREA)
  • High-Pressure Fuel Injection Pump Control (AREA)

Description

Stand der TechnikState of the art

Die vorliegende Erfindung betrifft eine Druckbegrenzungseinrichtung für ein Kraftstoffsystem einer Brennkraftmaschine ,The present invention relates to a pressure limiting device for a fuel system of an internal combustion engine,

Druckbegrenzungseinrichtungen sind vom Markt her bekannt. Sie kommen vorzugsweise in solchen Kraftstoffsystemen zum Einsatz, welche bei Brennkraftmaschinen mit Benzin-Direkteinspritzung verwendet werden. Derartige Kraftstoffsysteme verfügen üblicherweise über einen Niederdruckbereich und einen Hochdruckbereich. Eine elektrische Kraftstoffpumpe fördert den Kraftstoff in den Niederdruckbereich, aus dem der Kraftstoff über eine Hochdruckpumpe in eine Kraftstoff-Sammelleitung ("Common-Rail genannt) gefördert wird. Der Druck in der Kraftstoff-Sammelleitung wird üblicherweise durch ein Druckregel- oder ein Mengensteuerventil geregelt.Pressure limiting devices are known from the market. They are preferably used in such fuel systems, which are used in internal combustion engines with gasoline direct injection. Such fuel systems usually have a low pressure range and a high pressure range. An electric fuel pump delivers the fuel into the low pressure range, from which the fuel via a high pressure pump in a fuel rail ("common rail called) is promoted. The pressure in the fuel rail is usually controlled by a pressure control or a quantity control valve.

Um jedoch eine Absicherung gegen einen zu hohen Druck in der Kraftstoff-Sammelleitung insbesondere bei Ausfall der Mengen- bzw. Druckregelung zu schaffen, ist im Hochdruckbereich des Kraftstoffsystems eine Druckbegrenzungseinrichtung vorgesehen. Bei dieser handelt es sich im Allgemeinen um ein übliches Druckbegrenzungsventil mit einem von einer Feder gegen einen Ventilsitz beaufschlagten Ventilelement. Übersteigt der Druck in der Kraftstoff-Sammelleitung.einen bestimmten Grenzwert, hebt das Ventilelement vom Ventilsitz ab, so dass Kraftstoff vom Einlass des Druckbegrenzungsventils zum Auslass und von dort zurück zum Niederdruckbereich des Kraftstoffsystems strömen kann.However, in order to provide protection against excessive pressure in the fuel rail, in particular in the event of failure of the quantity or pressure control, a pressure limiting device is provided in the high pressure region of the fuel system. This is generally a conventional pressure relief valve with a acted upon by a spring against a valve seat valve element. When the pressure in the fuel rail exceeds a certain limit, the valve member lifts off the valve seat so that fuel can flow from the inlet of the pressure relief valve to the outlet and thence back to the low pressure region of the fuel system.

Die bekannte Druckbegrenzungseinrichtung arbeitet bereits sehr gut und vor allem sehr zuverlässig. Allerdings sind den Anordnungsmöglichkeiten des Druckbegrenzungsventils in dem Kraftstoffsystem Grenzen gesetzt.The known pressure limiting device is already working very well and above all very reliable. However, the possible arrangements of the pressure relief valve in the fuel system limits.

Im Allgemeinen muss die Druckbegrenzungseinrichtung im Bereich der Kraftstoff-Sammelleitung, also in einer gewissen Entfernung von der Hochdruckpumpe, angeordnet werden. Der Grund dafür ist, dass die Hochdruckpumpe im Betrieb Druckpulsationen erzeugt, deren Spitzen den Öffnungsdruck des Druckbegrenzungsventils übersteigen können. Würde das Druckbegrenzungsventil unmittelbar bei der Hochdruckpumpe angeordnet werden, bestünde die Gefahr, dass das Druckbegrenzungsventil aufgrund der Druckpulsationen öffnet, obwohl der maximale Systemdruck noch nicht erreicht ist. Erst in einer gewissen Entfernung von der Hochdruckpumpe kommt es zu einer Glättung der Druckpulsationen aufgrund der Drosseleffekte in der Kraftstoffleitung und aufgrund der Kompressibilität des Kraftstoffs.In general, the pressure limiting device must be arranged in the region of the fuel collecting line, that is to say at a certain distance from the high-pressure pump. The reason for this is that during operation, the high-pressure pump generates pressure pulsations whose peaks can exceed the opening pressure of the pressure-limiting valve. If the pressure limiting valve were to be arranged directly at the high-pressure pump, there would be the danger that the pressure-limiting valve would open due to the pressure pulsations, although the maximum system pressure has not yet been reached. Only at a certain distance from the high pressure pump, it comes to a smoothing of Pressure pulsations due to throttle effects in the fuel line and due to the compressibility of the fuel.

Alternativ hierzu wäre es auch möglich, das Druckbegrenzungsventil so auszulegen, dass sein Öffnungsdruck oberhalb der aufgrund der Druckpulsationen vorhandenen Druckspitzen liegt. Dieses Druckbegrenzungsventil kann dann in unmittelbarer Nähe der Hochdruckpumpe angeordnet sein oder sogar in diese integriert werden. Im Notlaufbetrieb, wenn also die Druckregelung der Kraftstoff-Sammelleitung nicht mehr ordnungsgemäß funktioniert und dann ein höherer Druck in der Kraftstoff-Sammelleitung als der normale Systemdruck herrscht, muss dennoch ein sicherer Betrieb der Brennkraftmaschine sichergestellt sein. Dies wiederum würde die Auslegung der Komponenten des Hochdruckbereichs des Kraftstoffsystems auf den hohen Öffnungsdruck des Druckbegrenzungsventil erfordern. Derartige Komponenten sind jedoch relativ teuer.Alternatively, it would also be possible to design the pressure relief valve so that its opening pressure is above the pressure peaks due to the pressure pulsations. This pressure limiting valve can then be arranged in the immediate vicinity of the high pressure pump or even integrated into it. In emergency mode, so if the pressure control of the fuel rail is no longer working properly and then there is a higher pressure in the fuel rail than the normal system pressure, safe operation of the internal combustion engine must still be ensured. This in turn would require the design of the components of the high pressure region of the fuel system to the high opening pressure of the pressure relief valve. However, such components are relatively expensive.

Aus der nachveröffentlichten DE 101 18 936 ist eine Druckbegrenzungseinrichtung bekannt, bei welcher die Druckpulsationen durch eine Ausgleichskammer abgebaut werden, so dass die Druckbegrenzungseinrichtung im Normalbetrieb der Kraftstoffpumpe trotz der von der Hochdruckpumpe verursachten Druckpulsationen nicht öffnet. Dies erlaubt die Anordnung der Druckbegrenzungseinrichtung auch in der Nähe der Hochdruckpumpe.From the subsequently published DE 101 18 936 a pressure limiting device is known in which the pressure pulsations are reduced by a compensation chamber, so that the pressure limiting device does not open during normal operation of the fuel pump despite the pressure pulsations caused by the high pressure pump. This allows the arrangement of the pressure relief device also in the vicinity of the high-pressure pump.

Aus der US 5, 927, 323 ist eine Druckbegrenzungseinrichtung bekannt, bei der ein erster Bund eines Kolbens eine Ausgleichkammer begrenzt. Sobald sich aufgrund von Druckpulsationen das Volumen der Ausgleichskammer vergrößert, hebt der Kolben von einem Ventilsitz ab und gibt eine hydraulische Verbindung zwischen dem Hochdruckbereich und dem Niederdruckbereich des Kraftstoffsystems frei. Dadurch verschlechtert sich der Wirkungsgrad des Kraftstoffsystems und der Kraftstoff wird durch die disspipierte Energie stark aufgeheizt.From US 5, 927, 323 a pressure limiting device is known in which a first collar of a piston defines a compensation chamber. As soon as the volume of the compensation chamber increases due to pressure pulsations, the piston lifts off from a valve seat and releases a hydraulic connection between the high pressure region and the low pressure region of the fuel system. As a result, the efficiency of the fuel system deteriorates and the fuel is strongly heated by the dissipated energy.

Bei der erfindungsgemäßen Druckbegrenzungseinrichtung ist vorgesehen, dass der Kolben einen zweiten Bund aufweist, und an dem zweiten Bund eine Steuerkante ausgebildet ist, dass die Steuerkante so mit einer Ausnehmung der Bohrung zusammenwirkt, dass in geschlossenem Zustand der Druckbegrenzungseinrichtung die hydraulische Verbindung zwischen Hochdruck-Kraftstoffleitung und Niederdruck-Kraftstoffleitung unterbrochen ist, dass die Druckbegrenzungseinrichtung erst öffnet, wenn die Ausgleichskammer ein vorgegebenes Mindestvolumen erreicht hat, und dass das Mindestvolumen von der Überdeckung der Steuerkante in der Bohrung in Schließstellung der Druckbegrenzungseinrichtung abhängt.In the pressure limiting device according to the invention it is provided that the piston has a second collar, and on the second collar a control edge is formed, that the control edge so cooperates with a recess of the bore, that in the closed state of the pressure limiting device, the hydraulic connection between the high pressure fuel line and Low-pressure fuel line is interrupted, that the pressure limiting device opens only when the compensation chamber has reached a predetermined minimum volume, and that the minimum volume of the overlap of the control edge in the bore in the closed position of the pressure relief device depends.

Vorteile der ErfindungAdvantages of the invention

Durch diese Maßnahme ist es möglich, den Abbau von Druckspitzen in der Hochdruck-Kraftstoffleitung durch Drosseln und durch Vergrößern des Volumens der Ausgleichskammer abzubauen. Es hat sich herausgestellt, dass diese Kombination von zwei gleichzeitig wirkenden Maßnahmen zum Abbau der Druckpulsationen besonders wirkungsvoll ist und somit im Normalbetrieb der Kraftstoffpumpe die Druckbegrenzungseinrichtung selbst dann nicht öffnet, wenn die Druckbegrenzungseinrichtung in unmittelbarer Nähe der Hochdruckpumpe angeordnet ist. Erst wenn die Mengensteuerung der Kraftstoffpumpe einen Defekt hat und die Kraftstoffpumpe unabhängig vom Betriebspunkt der Brennkraftmaschine die volle Fördermenge fördert, spricht die Druckbegrenzungseinrichtung an und verhindert unzulässig hohe Drücke in der Hochdruck-Kraftstoffleitung und dem gesamten Hochdruckbereich des Kraftstoffsystems.By this measure, it is possible to reduce the reduction of pressure peaks in the high-pressure fuel line by throttling and by increasing the volume of the compensation chamber. It has been found that this combination of two simultaneously acting measures to reduce the pressure pulsations is particularly effective and thus does not open the pressure limiting device even during normal operation of the fuel pump when the pressure limiting device is arranged in the immediate vicinity of the high pressure pump. Only when the quantity control of the fuel pump has a defect and the fuel pump, regardless of the operating point of the internal combustion engine promotes the full flow, addresses the pressure limiting device and prevents inadmissibly high pressures in the high pressure fuel line and the entire high pressure area of the fuel system.

Diese erfindungsgemäße Druckbegrenzungseinrichtung kann, anders als die aus dem Stand der Technik bekannte Druckbegrenzungseinrichtung, ohne Anpassungsmaßnahmen in nahezu allen Kraftstoffpumpen oder Kraftstoffsystemen eingesetzt werden. Dadurch verringert sich die erforderliche Variantenvielfalt sehr stark, was erhebliche wirtschaftliche Vorteile bei der Herstellung, Lagerhaltung und Reparatur der mit der erfindungsgemäßen Druckbegrenzungseinrichtung ausgerüsteten Kraftstoffsysteme mit sich bringt.This pressure limiting device according to the invention, unlike the pressure limiting device known from the prior art, can be used without adaptation measures in virtually all fuel pumps or fuel systems. As a result, the required variety of variants is greatly reduced, which brings considerable economic advantages in the production, storage and repair of equipped with the pressure limiting device according to the invention fuel systems with it.

Durch die Überdeckung der Steuerkante in der Bohrung kann der mögliche Zuwachs des Volumens der Ausgleichskammer vor dem Öffnen der Druckbegrenzungseinrichtung in weiten Grenzen festgelegt werden.By covering the control edge in the bore of the possible increase in the volume of the compensation chamber can be set within wide limits before opening the pressure relief device.

In weiterer Ausgestaltung der Erfindung ist zwischen dem Kolben und dem Gehäuse eine Feder eingespannt, welche den Kolben in Richtung der Schließstellung der Druckbegrenzungseinrichtung beaufschlagt. Dadurch nimmt die Druckbegrenzungseinrichtung in drucklosem Zustand immer eine definierte Schaltstellung ein.In a further embodiment of the invention, a spring is clamped between the piston and the housing, which acts on the piston in the direction of the closed position of the pressure limiting device. As a result, the pressure limiting device always assumes a defined switching position in a pressureless state.

Wenn der Kolben an seinem dem ersten Bund abgewandten Ende einen Dichtkegel aufweist und der Dichtkegel in Schließstellung der Druckbegrenzungseinrichtung auf einem Dichtsitz des Gehäuses aufliegt, wird bei abgeschalteter Brennkraftmaschine der Druck im Hochdruckbereich des Kraftstoffsystems aufrechterhalten, was die Bildung von Dampfblasen verhindert.When the piston has a sealing cone at its end remote from the first collar and the sealing cone rests in the closed position of the pressure limiting device on a sealing seat of the housing, the pressure in the high-pressure region of the fuel system is maintained when the internal combustion engine is shut off, which prevents the formation of vapor bubbles.

Wenn die Aufrechterhaltung des Drucks im Hochdruckbereich des Kraftstoffsystems bei abgeschalteter Brennkraftmaschine nicht gewünscht wird, kann alternativ vorgesehen werden, dass im Gehäuse ein Absatz ausgebildet ist, und dass der Kolben in Schließstellung der Druckbegrenzungseinrichtung an dem Absatz anliegt.If it is not desired to maintain the pressure in the high-pressure region of the fuel system when the internal combustion engine is switched off, it may alternatively be provided that a shoulder is formed in the housing, and that the piston bears against the shoulder in the closed position of the pressure-limiting device.

Eine weitere, besonders vorteilhafte Ausgestaltung der Erfindung sieht vor, dass der Kolben einen dritten Bund aufweist, und dass die Ausgleichskammer zusätzlich von dem dritten Bund begrenzt wird, wobei der Durchmesser des dritten Bundes kleiner als der Durchmesser des ersten Bundes ist. Dadurch wird die resultierende hydraulische Kraft auf den ersten Bund verringert, was - bei sonst gleichen hydraulischen Randbedingungen - eine kleinere Feder zwischen Kolben und Gehäuse ermöglicht. Dadurch kann die Feder kleiner ausgeführt werden, was das Bauvolumen der gesamten Druckbegrenzungseinrichtung verringern hilft. Dadurch, dass ein teilweiser Ausgleich der hydraulischen Kräfte zwischen erstem Bund und drittem Bund stattfindet, sind die von dem Kolben auf die Feder ausgeübten Kräfte sehr klein, ohne dass die Kolbendurchmesser sehr klein werden. Bei der Serienfertigung von Drehteilen mit Durchmessern kleiner 4 mm und großer Präzision steigen die Herstellungskosten gegenüber etwas größer dimensionierten Teilen stark an. Dadurch können die Kosten der erfindungsgemäßen Druckbegrenzungseinrichtung minimiert werden.A further, particularly advantageous embodiment of the invention provides that the piston has a third collar, and that the compensation chamber is additionally limited by the third collar, wherein the diameter of the third collar is smaller than the diameter of the first collar. As a result, the resulting hydraulic force is reduced to the first collar, which - with otherwise the same hydraulic boundary conditions - allows a smaller spring between the piston and housing. As a result, the spring can be made smaller, which helps reduce the overall volume of the entire pressure limiting device. Due to the fact that a partial compensation of the hydraulic forces takes place between the first collar and the third collar, the forces exerted by the piston on the spring are very small, without the piston diameters becoming very small. In the series production of turned parts with diameters smaller than 4 mm and high precision, the production costs increase compared to slightly larger sized parts. As a result, the cost of the pressure limiting device according to the invention can be minimized.

Es hat sich weiter als vorteilhaft erwiesen, wenn der dritte Bund mit der Bohrung einen Raum begrenzt und dieser Raum mindestens mittelbar mit einem Niederdruckbereich des Kraftstoffsystems hydraulisch in Verbindung steht, so dass eventuell anfallende Leckagen abgeführt werden können.It has also proved to be advantageous if the third collar with the bore defines a space and this space is at least indirectly hydraulically connected to a low-pressure region of the fuel system, so that any accumulating leaks can be dissipated.

Die Wirkung dieser Druckbegrenzungseinrichtung kann sich bestmöglich entfalten, wenn die Ausgleichsbohrung im Gehäuse oder in einem Pumpenkolben der Kraftstoffpumpe angeordnet ist, da die oben beschriebene Glättung der Druckspitzen in unmittelbarer Nähe ihrer Entstehung erfolgt.The effect of this pressure limiting device can unfold in the best possible way if the compensation bore is arranged in the housing or in a pump piston of the fuel pump, since the above-described smoothing of the pressure peaks occurs in the immediate vicinity of their formation.

Die vorliegende Erfindung betrifft auch ein Kraftstoffsystem zum Zuliefern von Kraftstoff für eine Brennkraftmaschine, mit einem Vorratsbehälter, mit einer ersten Kraftstoffpumpe, welche eingangsseitig mit dem Vorratsbehälter verbunden ist, mit einer zweiten Kraftstoffpumpe, welche eingangsseitig über eine Kraftstoffverbindung mit der ersten Kraftstoffpumpe verbunden ist, und mit einer Druckbegrenzungseinrichtung, welche den Druck in einer Kraftstoffverbindung auf der Ausgangsseite der zweiten Kraftstoffpumpe begrenzt.The present invention also relates to a fuel system for supplying fuel for an internal combustion engine, with a reservoir, with a first fuel pump, which is connected on the input side to the reservoir, with a second fuel pump, which is the input side connected via a fuel connection to the first fuel pump, and with a pressure limiting device, which limits the pressure in a fuel connection on the output side of the second fuel pump.

Um ein solches Kraftstoffsystem möglichst variabel bauen zu können, ohne dass zusätzliche Kosten anfallen, wird erfindungsgemäß vorgeschlagen, dass die Druckbegrenzungseinrichtung in der oben beschriebenen Art ausgebildet ist.In order to build such a fuel system as variable as possible, without incurring additional costs, the invention proposes that Pressure limiting device is formed in the manner described above.

Dabei wird vorgeschlagen, dass die zweite Kraftstoffpumpe eine 1-Zylinder-Kolbenpumpe umfasst. Bei einer solchen Kraftstoffpumpe sind die Druckpulsationen besonders ausgeprägt, so dass hier die erfindungsgemäße Druckbegrenzungseinrichtung sehr wirkungsvoll arbeitet.It is proposed that the second fuel pump comprises a 1-cylinder piston pump. In such a fuel pump, the pressure pulsations are particularly pronounced, so that here the pressure limiting device according to the invention works very effectively.

Bei einer besonders bevorzugten Weiterbildung des erfindungsgemäßen Kraftstoffsystems ist die Druckbegrenzungseinrichtung an die zweite Kraftstoffpumpe angebaut, vorzugsweise in diese integriert. Eine derartige Anordnung der Druckbegrenzungseinrichtung innerhalb des Kraftstoffsystems hat den Vorteil, dass auf eine Rückflussleitung von der Druckbegrenzungseinrichtung beispielsweise zum Niederdruckbereich des Kraftstoffsystems verzichtet werden kann. Hierdurch werden die Kosten für das erfindungsgemäße Kraftstoffsystem erheblich gesenkt.In a particularly preferred embodiment of the fuel system according to the invention, the pressure limiting device is attached to the second fuel pump, preferably integrated in this. Such an arrangement of the pressure limiting device within the fuel system has the advantage that it is possible to dispense with a return line from the pressure limiting device, for example, to the low pressure region of the fuel system. As a result, the cost of the fuel system according to the invention are significantly reduced.

Zeichnungdrawing

Nachfolgend werden Ausführungsbeispiele der Erfindung unter Bezugnahme auf die beiliegende Zeichnung im Detail erläutert. In der Zeichnung zeigen:

Figur 1:
eine Prinzipdarstellung eines Kraftstoffsystems mit einer Kraftstoffpumpe, an die eine Druckbegrenzungseinrichtung angebaut ist;
Figur 2:
einen Schnitt durch einen Bereich der Kraftstoffpumpe und ein erstes Ausführungsbeispiels einer Druckbegrenzungseinrichtung von Figur 1;
Figur 3:
ein Diagramm, in dem der Druck im Bereich des Auslasses der Kraftstoffpumpe von Figur 1 über der Zeit dargestellt ist und
Fig. 4, 5:
weitere Ausführungsbeispiele erfindungsgemäßer Druckbegrenzungseinrichtungen.
Hereinafter, embodiments of the invention will be explained in detail with reference to the accompanying drawings. In the drawing show:
FIG. 1:
a schematic diagram of a fuel system with a fuel pump to which a pressure limiting device is attached;
FIG. 2:
a section through a portion of the fuel pump and a first embodiment of a pressure limiting device of Figure 1;
FIG. 3:
a diagram in which the pressure in the region of the outlet of the fuel pump of Figure 1 over time is shown and
4, 5:
Further embodiments of pressure limiting devices according to the invention.

Beschreibung der AusführungsbeispieleDescription of the embodiments

In Figur 1 trägt ein Kraftstoffsystem insgesamt das Bezugszeichen 10. Es umfasst einen Niederdruckbereich 12 und einen Hochdruckbereich 14.In FIG. 1, a fuel system as a whole bears the reference numeral 10. It comprises a low-pressure region 12 and a high-pressure region 14.

Der Niederdruckbereich 12 umfasst einen Vorratsbehälter 16, in dem Kraftstoff 18 bevorratet wird. Der Kraftstoff 18 wird aus dem Vorratsbehälter 16 von einer ersten Kraftstoffpumpe 20 gefördert. Bei dieser handelt es sich um eine elektrische Kraftstoffpumpe. Die elektrische Kraftstoffpumpe 20 fördert in eine Niederdruck-Kraftstoffleitung 22. In dieser ist nach der elektrischen Kraftstoffpumpe 20 in Strömungsrichtung gesehen zunächst ein Filter 24 vorgesehen. In Strömungsrichtung gesehen noch vor dem Filter 24 zweigt von der Niederdruck-Kraftstoffleitung 22 eine Zweigleitung 26 ab, welche zum Vorratsbehälter 16 zurückführt. In der Zweigleitung 26 ist ein Druckbegrenzungsventil 28 angeordnet.The low-pressure region 12 comprises a reservoir 16 in which fuel 18 is stored. The fuel 18 is conveyed from the reservoir 16 by a first fuel pump 20. This is an electric fuel pump. The electric fuel pump 20 conveys into a low-pressure fuel line 22. In this, a filter 24 is initially provided after the electric fuel pump 20 as seen in the flow direction. Seen in the flow direction before the filter 24 branches off from the low-pressure fuel line 22 from a branch line 26, which leads back to the reservoir 16. In the branch line 26, a pressure limiting valve 28 is arranged.

Die Niederdruck-Kraftstoffleitung 22 führt zu einer zweiten Kraftstoffpumpe 30. Diese wird auf hier nicht näher dargestellte Weise von der Nockenwelle einer Brennkraftmaschine (nicht dargestellt) angetrieben. Bei der zweiten Kraftstoffpumpe 30 handelt es sich um eine 1-Kolben-Hochdruckpumpe. Stromaufwärts von der Hochdruckpumpe 30 sind in der Niederdruck-Kraftstoffleitung 22 noch ein Druckdämpfer 32 und ein Rückschlagventil 34 angeordnet. Zwischen dem Filter 24 und dem Druckdämpfer 32 zweigt von der Niederdruck-Kraftstoffleitung 22 eine Zweigleitung 36 ab, in der ein Niederdruckregler 38 angeordnet ist. Die Zweigleitung 36 führt ebenfalls zum Vorratsbehälter 16 für den Kraftstoff 18 zurück. Von der Hochdruckpumpe 30 führt eine Leckageleitung 40 zur Zweigleitung 36.The low-pressure fuel line 22 leads to a second fuel pump 30. This is driven in a manner not shown here by the camshaft of an internal combustion engine (not shown). The second fuel pump 30 is a 1-piston high-pressure pump. Upstream of the high pressure pump 30 are still in the low pressure fuel line 22 a Pressure damper 32 and a check valve 34 is arranged. Between the filter 24 and the pressure damper 32 branches from the low-pressure fuel line 22 from a branch line 36, in which a low-pressure regulator 38 is arranged. The branch line 36 also leads back to the reservoir 16 for the fuel 18. From the high-pressure pump 30, a leakage line 40 leads to the branch line 36.

Ausgangsseitig fördert die Hochdruckpumpe 30 in eine Hochdruck-Kraftstoffleitung 42, welche über ein Rückschlagventil 44 zu einer Kraftstoff-Sammelleitung 46 führt. An die Kraftstoff-Sammelleitung 46 sind wiederum Kraftstoff-Einspritzventile 48 angeschlossen, welche den Kraftstoff in einen nicht näher dargestellten Brennraum der Brennkraftmaschine einspritzen. Der Druck in der Kraftstoff-Sammelleitung 46 wird von einem Drucksensor 50 erfasst.On the output side, the high-pressure pump 30 conveys into a high-pressure fuel line 42, which leads via a check valve 44 to a fuel manifold 46. Fuel injection valves 48 which in turn inject the fuel into a combustion chamber, not shown, of the internal combustion engine are in turn connected to the fuel manifold 46. The pressure in the fuel rail 46 is detected by a pressure sensor 50.

Der Druck in der Hochdruck-Kraftstoffleitung 42 und der Kraftstoff-Sammelleitung 46, also im Hochdruckbereich 14 des Kraftstoffsystems 10, wird über ein Mengensteuerventil 52 gesteuert und/oder geregelt. Dieses verbindet den zwischen dem Rückschlagventil 44 und der Hochdruckpumpe 30 gelegenen Bereich der Hochdruck-Kraftstoffleitung 42 mit dem zwischen dem Rückschlagventil 34 und dem Druckdämpfer 32 gelegenen Bereich der Niederdruck-Kraftstoffleitung 22. Die Verbindung erfolgt über eine Zweigleitung 54. Das Mengensteuerventil 52 wird von einer in Figur 1 nicht dargestellten Steuer- und Regeleinheit angesteuert, welche wiederum Signale vom Drucksensor 50 erhält. Auf diese Weise wird ein geschlossener Regelkreis für die Steuerung des Drucks im Hochdruckbereich 14 des Kraftstoffsystems 10 geschaffen.The pressure in the high-pressure fuel line 42 and the fuel manifold 46, ie in the high-pressure region 14 of the fuel system 10, is controlled and / or regulated via a quantity control valve 52. This connects the region of the high-pressure fuel line 42 between the check valve 44 and the high-pressure pump 30 to the region of the low-pressure fuel line 22 located between the check valve 34 and the pressure damper 32. The connection takes place via a branch line 54. The quantity control valve 52 is actuated by a 1, not shown, which in turn receives signals from the pressure sensor 50. In this way, a closed loop for the control of the pressure in the high pressure region 14 of the fuel system 10 is provided.

Um bei einem Ausfall des Mengensteuerventils 52 einen Überdruck in der Kraftstoff-Sammelleitung 46 zu vermeiden, welcher die Funktionstüchtigkeit der Einspritzventile 48 beeinträchtigen könnte, ist mit der Hochdruckpumpe 30 eine Druckbegrenzungseinrichtung 56 kombiniert. Der genaue Aufbau eines ersten Ausführungsbeispiels einer erfindungsgemäßen Druckbegrenzungseinrichtung 56 ist aus Figur 2 ersichtlich:In case of failure of the quantity control valve 52 a To avoid overpressure in the fuel rail 46, which could affect the functionality of the injectors 48, a pressure relief device 56 is combined with the high-pressure pump 30. The exact structure of a first embodiment of a pressure limiting device 56 according to the invention can be seen from FIG. 2:

Die Hochdruckpumpe 30 und die Druckbegrenzungseinrichtung 56 sind in einem gemeinsamen Gehäuse 58 untergebracht. Von der Hochdruckpumpe 30 ist in Figur 2 nur ein Bereich eines Förderraumes 60 und das auslassseitig vom Förderraum 60 angeordnete Auslassventil 44 sichtbar. Das Auslassventil 44 umfasst ein kugelförmiges Ventilelement 64, welches von einer Feder 66 gegen einen Ventilsitz 68 beaufschlagt wird. Stromabwärts des Auslassventils 44 ist die Hochdruck-Kraftstoffleitung 42 sichtbar. Während eines Saughubs wird der in Fig. 2 nur teilweise dargestellte Förderraum 60 gegenüber der Hochdruck-Kraftstoffleitung 42 durch das Auslassventil 44 abgedichtet.The high-pressure pump 30 and the pressure-limiting device 56 are accommodated in a common housing 58. Only one region of a delivery chamber 60 and the outlet valve 44 arranged on the outlet side of the delivery chamber 60 are visible from the high-pressure pump 30 in FIG. The outlet valve 44 comprises a spherical valve element 64, which is acted upon by a spring 66 against a valve seat 68. Downstream of the exhaust valve 44, the high pressure fuel line 42 is visible. During a suction stroke, the delivery chamber 60, only partially illustrated in FIG. 2, is sealed off from the high-pressure fuel line 42 by the outlet valve 44.

In Strömungsrichtung gesehen unmittelbar hinter dem. Auslassventil ist eine Bohrung 70 vorgesehen, in der ein Kolben 72 geführt ist. Der Kolben 72 weist einen ersten Bund 74 und einen zweiten Bund 76 auf. Der Kolben 72 ist über den ersten Bund 74 und über den zweiten Bund 76 in der Bohrung 70 geführt. Die Passung von Bohrung 70 und erstem Bund 74 ist so bemessen, dass der Ringspalt zwischen Bohrung 70 und erstem Bund 74 als Drossel dient. Die Passung von Bohrung 70 und zweitem Bund 76 ist so bemessen, dass eine gute Dichtwirkung zwischen Bohrung 70 und zweitem Bund 76 erzielt wird und der Kolben 72 trotzdem noch in der Bohrung 70 verschiebbar ist.Seen in the direction of flow immediately behind the. Exhaust valve, a bore 70 is provided, in which a piston 72 is guided. The piston 72 has a first collar 74 and a second collar 76. The piston 72 is guided over the first collar 74 and the second collar 76 in the bore 70. The fit of bore 70 and first collar 74 is sized so that the annular gap between bore 70 and first collar 74 serves as a throttle. The fit of bore 70 and second collar 76 is sized so that a good sealing effect between the bore 70 and second collar 76 is achieved and the piston 72 is still displaced in the bore 70 still.

Zwischen erstem Bund 74 und zweitem Bund 76 weist der Kolben 72 eine Ringnut 78 auf, welche mit der Hochdruck-Kraftstoffleitung 42 hydraulisch in Verbindung steht. Ein Grund 80 der Bohrung 70 sowie der erste Bund 74 des Kolbens 72 begrenzen eine Ausgleichskammer 82, die über den Ringspalt zwischen Bohrung 70 und erstem Bund 74 hydraulisch mit der Hochdruck-Kraftstoffleitung 42 in Verbindung steht.Between first collar 74 and second collar 76 has the Piston 72 has an annular groove 78 which communicates hydraulically with the high-pressure fuel line 42. A bottom 80 of the bore 70 and the first collar 74 of the piston 72 define a compensation chamber 82, which is hydraulically connected to the high-pressure fuel line 42 via the annular gap between the bore 70 and the first collar 74.

Im Gehäuse 58 ist konzentrisch zur Bohrung 70 eine ringförmige Ausnehmung 84 vorgesehen. Die Ringnut 78 und der zweite Bund 76 des Kolbens 72 bilden eine Steuerkante 86, welche mit der Ausnehmung 84 zusammenwirkt. In geschlossenem Zustand der Druckbegrenzungseinrichtung 56, der in Figur 2 dargestellt ist, hat die Steuerkante 86 zu der Ausnehmung 84 eine Überdeckung, die in Figur 2 durch das Bezugszeichen 88 angedeutet ist. In Folge dessen ist die hydraulische Verbindung zwischen Hochdruck-Kraftstoffleitung 42 und Ausnehmung 84 in dieser Stellung des Kolbens 72 unterbrochen.In the housing 58, an annular recess 84 is concentric with the bore 70 is provided. The annular groove 78 and the second collar 76 of the piston 72 form a control edge 86, which cooperates with the recess 84. In the closed state of the pressure limiting device 56, which is shown in Figure 2, the control edge 86 to the recess 84 has an overlap, which is indicated in Figure 2 by the reference numeral 88. As a result, the hydraulic connection between the high-pressure fuel line 42 and recess 84 is interrupted in this position of the piston 72.

Der zweite Bund 76 ist breiter als die Ausnehmung 84, so dass der Kolben 72 unabhängig von seiner Lage in der Bohrung 70 stets durch den ersten Bund 74 und den zweiten Bund 76 in der Bohrung 70 geführt ist.The second collar 76 is wider than the recess 84, so that the piston 72 is always performed regardless of its position in the bore 70 through the first collar 74 and the second collar 76 in the bore 70.

Oberhalb des zweiten Bundes 76 ist ein Dichtkegel 90 am Kolben 72 angeformt. Der Dichtkegel 90 trennt in der in Figur 2 dargestellten Schließstellung der Druckbegrenzungseinrichtung 56 zusammen mit einem im Gehäuse 58 ausgebildeten Dichtsitz 92 die Ausnehmung 84 von einer Federkammer 94, die wiederum mit der Niederdruckleitung 22 hydraulisch in Verbindung steht. Der Dichtkegel 90 und der Dichtsitz 92 dienen der Aufrechterhaltung des Drucks im Hochdruckbereich 14 bei abgestellter Brennkraftmaschine. In der Federkammer 94 ist eine Druckfeder 96 angeordnet, die sich einenends gegen das Gehäuse 58 und anderenends gegen den Kolben 72 abstützt und diesen mit seinem Dichtkegel 90 in den Dichtsitz 92 presst.Above the second collar 76, a sealing cone 90 is integrally formed on the piston 72. In the closed position of the pressure limiting device 56 shown in FIG. 2, the sealing cone 90, together with a sealing seat 92 formed in the housing 58, separates the recess 84 from a spring chamber 94, which in turn hydraulically communicates with the low pressure line 22. The sealing cone 90 and the sealing seat 92 serve to maintain the pressure in the high-pressure region 14 when the internal combustion engine is switched off. In the spring chamber 94 is a compression spring 96 is arranged, which is supported at one end against the housing 58 and the other end against the piston 72 and this presses with its sealing cone 90 in the sealing seat 92.

Damit bei geöffneter Druckbegrenzungseinrichtung 56, wenn nämlich die Steuerkante 86 des zweiten Bunds 76 eine hydraulische Verbindung zwischen der Ringnut 78 und der Ausnehmung 84 freigibt, auch eine hydraulische Verbindung zwischen der Ausnehmung 84 und der Federkammer 94 hergestellt wird, sind in dem zweiten Bund 76 über den Umfang verteilt mehrere Aussparungen 98 eingearbeitet.Thus, when open pressure limiting device 56, namely, when the control edge 86 of the second collar 76 releases a hydraulic connection between the annular groove 78 and the recess 84, and a hydraulic connection between the recess 84 and the spring chamber 94 is made in the second collar 76 via distributed over the circumference several recesses 98 incorporated.

Die Funktionsweise dieser erfindungsgemäßen Druckbegrenzungseinrichtung 56 ist wie folgt:The operation of this pressure limiting device 56 according to the invention is as follows:

Wenn während des Förderhubs der Pumpe 30 der Druck im Förderraum 60 ansteigt und das Rückschlagventil 44 öffnet, steigt auch der Druck in der Hochdruck-Kraftstoffleitung 42 und Kraftstoff fließt von der Hochdruck-Kraftstoffleitung 42 in die Ausgleichskammer 82 und der Druck in der Ausgleichskammer 82 steigt zeitlich etwas verzögert an. Die Verzögerung des Druckanstiegs in der Ausgleichskammer 82 wird durch die Drosselwirkung des Ringspalts zwischen erstem Bund 74 und Bohrung 70 verursacht. Sobald der Druck in der Ausgleichskammer 82 ausreichend hoch ist, um die Anpresskraft der Feder 96 zu überwinden, hebt der Kolben 72 vom Dichtsitz 92 ab; das heißt er bewegt sich in Figur 2 nach oben. Damit nimmt auch das Volumen der Ausgleichskammer 82 zu, so dass der Druckanstieg in der Hochdruck-Kraftstoffleitung 42 und damit im gesamten Hochdruckbereich 14 (siehe Fig. 1) des Kraftstoffsystems 10 verringert wird. Die Überdeckung 88 und das Volumen der Ausgleichskammer 88 sind so ausgelegt, dass im Normalbetrieb des Kraftstoffsystems 10 die Druckpulsationen im Hochdruckbereich 14 des Kraftstoffsystems 10 so weit abgebaut werden, dass sie keine negativen Auswirkungen auf den Betrieb des Kraftstoffsystems 10 mehr haben. Außerdem werden die Überdeckung 88 und das Volumen der Ausgleichskammer 82 so ausgelegt, dass im Normalbetrieb des Kraftstoffsystems 10 die hydraulische Verbindung zwischen Hochdruck-Kraftstoffleitung 42 und Niederdruck-Kraftstoffleitung 22 nicht freigegeben wird. Dies bedeutet, dass durch den Einsatz der erfindungsgemäßen Druckbegrenzungseinrichtung 56 der Wirkungsgrad des Kraftstoffsystems 10 im Normalbetrieb nahezu unverändert bleibt.When, during the delivery stroke of the pump 30, the pressure in the delivery chamber 60 increases and the check valve 44 opens, the pressure in the high-pressure fuel line 42 also increases and fuel flows from the high-pressure fuel line 42 into the compensation chamber 82 and the pressure in the compensation chamber 82 increases delayed in time. The delay of the pressure rise in the compensation chamber 82 is caused by the throttling action of the annular gap between the first collar 74 and bore 70. Once the pressure in the balance chamber 82 is sufficiently high to overcome the contact force of the spring 96, the piston 72 lifts off the seal seat 92; that is, it moves up in Figure 2. Thus, the volume of the compensation chamber 82 increases, so that the pressure rise in the high-pressure fuel line 42 and thus in the entire high-pressure region 14 (see FIG. 1) of the fuel system 10 is reduced. The overlap 88 and the volume of the compensation chamber 88 are designed so that during normal operation of the fuel system 10, the pressure pulsations in the high-pressure region 14 of the fuel system 10 so far be degraded that they have no negative impact on the operation of the fuel system 10 more. In addition, the overlap 88 and the volume of the balance chamber 82 are designed so that during normal operation of the fuel system 10, the hydraulic connection between the high-pressure fuel line 42 and low-pressure fuel line 22 is not released. This means that the efficiency of the fuel system 10 remains virtually unchanged during normal operation as a result of the use of the pressure limiting device 56 according to the invention.

Wenn die Fördermengenregelung des Kraftstoffsystems 10 defekt ist, so dass die Kraftstoffpumpe 30 (siehe Fig. 1) immer die volle Fördermenge fördert, steigt der Druck im Hochdruckbereich 14 und damit auch in der Hochdruck-Kraftstoffleitung 42 über einen - verglichen mit den Druckpulsationen im Normalbetrieb - langen Zeitraum stark an. In Folge dessen vergrößert sich das Volumen der Ausgleichskammer 82 so stark, dass die Steuerkante 86 die hydraulische Verbindung zwischen Ringnut 78 und Ausnehmung 84 freigibt und Kraftstoff aus der Hochdruck-Kraftstoffleitung 42 über die Federkammer 94 in die Niederdruck-Kraftstoffleitung 22 strömt, so dass ein Abbau des in der Hochdruck-Kraftstoffleitung 42 herrschenden Überdrucks stattfindet. Damit wird der Hochdruckbereich 14 des Kraftstoffsystems 10 bei Störungen der Fördermengenregelung wirksam vor unzulässig hohen Drücken geschützt.If the flow control of the fuel system 10 is defective, so that the fuel pump 30 (see Fig. 1) always delivers the full flow, the pressure in the high pressure region 14 and thus also in the high-pressure fuel line 42 via a - compared with the pressure pulsations during normal operation - long period strongly. As a result, the volume of the compensation chamber 82 increases so much that the control edge 86 releases the hydraulic connection between the annular groove 78 and recess 84 and fuel flows from the high-pressure fuel line 42 via the spring chamber 94 in the low-pressure fuel line 22, so that a Degradation of prevailing in the high-pressure fuel line 42 overpressure takes place. Thus, the high pressure area 14 of the fuel system 10 is effectively protected against impermissibly high pressures in case of disturbances in flow control.

In Figur 3 ist der Druckverlauf über der Zeit t qualitativ dargestellt. Wenn auf der Auslassseite der Hochdruckpumpe 30, also beispielsweise in der Hochdruck-Kraftstoffleitung 42 und der Kraftstoff-Sammelleitung 46, ein konstantes Volumen vorhanden wäre, würden im Hochdruckbereich 14 des Kraftstoffsystems 10 aufgrund der Druckpulsationen der Hochdruckpumpe 30 Druckspitzen bis zu einem Spitzenwert von ca. 180 bar auftreten. Eine solche Druckspitze ist in Figur 3 gestrichelt dargestellt. Diese Druckspitze resultiert aus der Beschleunigung der Kraftstoffsäule in der Hochdruck-Kraftstoffleitung 42 durch die Hochdruckpumpe 30. Durch die erfindungsgemäße Druckbegrenzungseinrichtung 56 werden diese im Normalbetrieb des Kraftstoffsystems 10 auftretenden Druckspitzen in der zuvor beschriebenen Weise vermieden. Infolgedessen ist der Druckanstieg in der Hochdruck-Kraftstoffleitung 42 und der Kraftstoff-Sammelleitung 46 geringer, was in der Figur 3 durch die durchgezogene Linie qualitativ dargestellt ist. Sobald der Förderhub der Kraftstoffpumpe 30 beendet ist, schließt das Rückschlagventil 44 und die Feder 96 drückt den Kolben 72 in Richtung der Ausgleichskammer 82 und verringert dadurch das Volumen der Ausgleichskammer 82 auf seinen ursprünglichen Wert. Der aus der Ausgleichskammer 82 verdrängte Kraftstoff strömt über die Ringnut 78 in die Hochdruck-Kraftstoffleitung 42 und trägt somit zur Druckhaltung im Hochdruckbereich 14 des Kraftstoffsystems 10 bei.In Figure 3, the pressure curve over the time t is shown qualitatively. If a constant volume were present on the outlet side of the high-pressure pump 30, that is to say for example in the high-pressure fuel line 42 and the fuel collecting line 46, in the high-pressure region 14 of FIG Fuel system 10 due to the pressure pulsations of the high-pressure pump 30 pressure peaks up to a peak value of about 180 bar occur. Such a pressure peak is shown in dashed lines in FIG. This pressure peak results from the acceleration of the fuel column in the high pressure fuel line 42 through the high pressure pump 30. By the pressure limiting device 56 according to the invention, these occurring in normal operation of the fuel system 10 pressure peaks are avoided in the manner described above. As a result, the pressure rise in the high-pressure fuel line 42 and the fuel rail 46 is lower, which is qualitatively represented in the figure 3 by the solid line. As soon as the delivery stroke of the fuel pump 30 is completed, the check valve 44 closes and the spring 96 pushes the piston 72 in the direction of the compensation chamber 82 and thereby reduces the volume of the compensation chamber 82 to its original value. The fuel displaced from the compensation chamber 82 flows via the annular groove 78 into the high-pressure fuel line 42 and thus contributes to the pressure maintenance in the high-pressure region 14 of the fuel system 10.

Die Überdeckung 88 zwischen Steuerkante 86 und Ausnehmung 44, die Vorspannung und Federrate der Feder 96 sowie das Volumen der Ausgleichskammer 82 und die Drosselwirkung zwischen erstem Bund 74 und Bohrung 70 müssen, wie bereits erwähnt, so aufeinander abgestimmt sein, dass bei einem Förderhub der zweiten Kraftstoffpumpe 30 bei ordnungsgemäßem Betrieb des Kraftstoffsystems 10 die Steuerkante 86 die Ausnehmung 84 nicht freigibt und somit kein Kraftstoff aus dem Hochdruckbereich 14 in den Niederdruckbereich 12 strömt. Erst wenn die Mengenregelung der Kraftstoffpumpe 30 oder ein anderer Defekt mit ähnlichen Auswirkungen auftritt, wird das Volumen der Ausgleichskammer 82 so stark vergrößert, dass die Steuerkante 86 die Ausnehmung 84 freigibt und überschüssiger Kraftstoff über die Ausnehmung 84, die Aussparungen 98, die Federkammer 94 in die Niederdruck-Kraftstoffleitung 22 abströmen kann. Dadurch werden unzulässig hohe Drücke im Hochdruckbereich 14 des Kraftstoffsystems 10 wirkungsvoll unterbunden.The overlap 88 between the control edge 86 and recess 44, the bias and spring rate of the spring 96 and the volume of the compensation chamber 82 and the throttling action between the first collar 74 and bore 70 must, as already mentioned, be matched to one another that at a delivery stroke of the second Fuel pump 30 during proper operation of the fuel system 10, the control edge 86, the recess 84 is not released and thus no fuel from the high-pressure region 14 flows into the low-pressure region 12. Only when the volume control of the fuel pump 30 or another defect with similar effects occurs, the volume of Compensation chamber 82 increased so much that the control edge 86, the recess 84 releases and excess fuel via the recess 84, the recesses 98, the spring chamber 94 can flow into the low-pressure fuel line 22. As a result, impermissibly high pressures in the high-pressure region 14 of the fuel system 10 are effectively prevented.

In Figur 4 ist ein weiteres Ausführungsbeispiel einer erfindungsgemäßen Druckbegrenzungseinrichtung 56 dargestellt. Gleiche Bauteile sind mit gleichen Bezugszeichen versehen und es gilt das bezüglich Figur 2 Gesagte entsprechend.FIG. 4 shows a further exemplary embodiment of a pressure limiting device 56 according to the invention. The same components are provided with the same reference numerals and it is the case with respect to Figure 2 said accordingly.

Der wesentliche Unterschied zu dem ersten Ausführungsbeispiel gemäß Figur 2 besteht darin, dass der Kolben 72 unterhalb des ersten Bunds 74 einen dritten Bund 100 aufweist. Die Ausgleichskammer 82 ist bei diesem Ausführungsbeispiel zwischen dem ersten Bund 74 und dem dritten Bund 100 vorhanden und ist ein ringförmiger Raum, dessen Volumen sich vergrößert, wenn sich der Kolben 72 in Richtung der Feder 96 bewegt.The essential difference from the first exemplary embodiment according to FIG. 2 is that the piston 72 has a third collar 100 below the first collar 74. The balance chamber 82 is present in this embodiment between the first collar 74 and the third collar 100 and is an annular space whose volume increases as the piston 72 moves in the direction of the spring 96.

Der Bund 80 der Bohrung 70 und der dritte Bund 100 begrenzen einen Raum 102, der über eine Bohrung 104 mit der Federkammer 94 und damit mit der Niederdruck-Kraftstoffleitung 22 hydraulisch in Verbindung steht. Damit werden die auf die Stirnflächen des Kolbens 72 wirkenden hydraulischen Kräfte ausgeglichen.The collar 80 of the bore 70 and the third collar 100 define a space 102 which communicates hydraulically via a bore 104 with the spring chamber 94 and thus with the low-pressure fuel line 22. Thus, the force acting on the end faces of the piston 72 hydraulic forces are compensated.

Da die von der Ausgleichskammer 82 auf den Kolben 72 entgegen der Schließkraft der Feder 96 auf den Kolben 72 ausgeübte hydraulische Kraft nur noch auf der ringförmigen Differenzfläche zwischen dem Durchmesser D1 des ersten Bunds 74 und dem Durchmesser D3 des dritten Bunds 100 wirksam ist, ist diese Kraft, bei sonst gleichen Abmessungen der Druckbegrenzungseinrichtung 56, kleiner als die von dem in der Ausgleichskammer 82 befindlichen Kraftstoff auf die Stirnseite des Kolben 72 ausgeübte hydraulische Kraft gemäß dem ersten Ausführungsbeispiel (siehe Figur 2). Dies ist insofern vorteilhaft als man bestrebt ist, die Feder 96 möglichst klein zu bauen und bei Durchmessern unterhalb von 4 mm der fertigungstechnische Aufwand zur Herstellung der erfindungsgemäßen Druckbegrenzungseinrichtungen 56 sehr hoch wird. Deshalb sind der Miniaturisierung des ersten Ausführungsbeispiels gemäß Figur 2 fertigungstechnische und wirtschaftliche Grenzen gesetzt sind.Since the force exerted by the compensation chamber 82 on the piston 72 against the closing force of the spring 96 on the piston 72 hydraulic force only on the annular differential area between the diameter D 1 of the first collar 74 and the diameter D 3 of the third collar 100th is effective, this force, with otherwise the same dimensions of the pressure limiting device 56, smaller than that of the located in the compensation chamber 82 fuel on the end face of the piston 72 exerted hydraulic force according to the first embodiment (see Figure 2). This is advantageous in that one endeavors to build the spring 96 as small as possible and at diameters of less than 4 mm of the production engineering effort to produce the pressure limiting devices 56 according to the invention is very high. Therefore, the miniaturization of the first embodiment shown in FIG 2 manufacturing and economic limits are set.

Mit dem Ausführungsbeispiel gemäß Figur 4 kann auf fertigungstechnisch relativ einfache Weise eine kleine hydraulische Kraft, die entgegen der Schließkraft der Feder 96 wirkt, erzeugt werden, bei Durchmessern des Kolbens 72, die fertigungstechnisch unproblematisch sind.With the embodiment according to FIG. 4, a small hydraulic force, which counteracts the closing force of the spring 96, can be produced relatively easily on the basis of production engineering, with diameters of the piston 72 which are unproblematic in terms of production engineering.

Das hydraulische Verhalten dieses zweiten Ausführungsbeispiels entspricht im Wesentlichen dem des ersten Ausführungsbeispiels.The hydraulic behavior of this second embodiment substantially corresponds to that of the first embodiment.

In Figur 5 ist ein drittes Ausführungsbeispiel einer erfindungsgemäßen Druckbegrenzungseinrichtung 56 dargestellt. Der wesentliche Unterschied zu dem zweiten Ausführungsbeispiel besteht darin, dass der Kolben 72 keinen Dichtkegel 90 aufweist. In Schließstellung der Druckbegrenzungseinrichtung 56 liegt der Kolben 72 mit seinem dritten Bund 100 auf einem Absatz 106 des Gehäuses 58 auf und legt damit die maximale Überdeckung 88 der Steuerkante 86 fest.FIG. 5 shows a third exemplary embodiment of a pressure limiting device 56 according to the invention. The essential difference from the second embodiment is that the piston 72 has no sealing cone 90. In the closed position of the pressure limiting device 56, the piston 72 rests with its third collar 100 on a shoulder 106 of the housing 58 and thus defines the maximum overlap 88 of the control edge 86.

Das dritte Ausführungsbeispiel einer erfindungsgemäßen Druckbegrenzungseinrichtung 56 kommt vorzugsweise in Kraftstoffsystemen 10 zum Einsatz, in denen nach dem Abstellen des Motors oder im Schubbetrieb der Druck im Hochdruckbereich 14 über eine definierte Leckage abgesenkt wird. Durch die Passung zwischen zweitem Bund 76 und Bohrung 70 sowie die Dimensionierung der Überdeckung 88 kann die für diesen Betriebszustand der Brennkraftmaschine erforderliche Leckage eingestellt werden.The third embodiment of an inventive Pressure limiting device 56 is preferably used in fuel systems 10, in which after stopping the engine or in overrun mode, the pressure in the high-pressure region 14 is lowered via a defined leakage. By the fit between the second collar 76 and bore 70 and the dimensioning of the overlap 88 required for this operating condition of the engine leakage can be adjusted.

Allgemein wird bei der Auslegung der erfindungsgemäßen Druckbegrenzungsventile 56 darauf geachtet, dass der Öffnungsdruck der Druckbegrenzungseinrichtung 56 möglichst unabhängig vom Durchfluss durch die Hochdruck-Kraftstoffleitung 42 ist.In general, care is taken in the design of the pressure limiting valves 56 according to the invention that the opening pressure of the pressure limiting device 56 is as independent as possible from the flow through the high pressure fuel line 42.

Claims (9)

  1. Pressure limiting device (56) for a fuel system (10) of an internal combustion engine, the pressure limiting device (56) being arranged between a high pressure fuel line (42) and a low pressure fuel line (22), having a housing (58), having a piston (72) which is guided in a bore (70) of the housing (58) and hydraulically connects the high pressure fuel line (42) and the low pressure fuel line (22) above a certain pressure difference between said fuel lines, the bore (70) and the piston (72) delimiting an equalizing chamber (82), and having a throttle between the high pressure fuel line (42) and the equalizing chamber (82), the piston (72) having a first collar (74), in that the first collar (74) acts as a throttle between the equalizing chamber (82) and the high pressure fuel line (42), characterized in that the piston (72) has a second collar (76) and a control edge (86) is formed on the second collar (76), in that the control edge (86) interacts with a recess (84) of the bore (70) in such a way that the hydraulic connection between the high pressure fuel line (42) and the low pressure fuel line (22) is disconnected in the closed state of the pressure limiting device (56), in that the pressure limiting device (56) only opens once the equalizing chamber (82) has reached a predefined minimum volume, and in that the minimum volume is dependent on the overlap (88) of the control edge (86) in the bore (70) in the closed position of the pressure limiting device (56) .
  2. Pressure limiting device (56) according to Claim 1, characterized in that a spring (96) is compressed between the piston (72) and the housing (58), and in that the spring (96) acts on the piston (72) in the direction of the closed position.
  3. Pressure limiting device (56) according to one of the preceding claims, characterized in that the piston (72) has a sealing cone (90) at its end which faces away from the first collar (74), and in that the sealing cone (90) rests on a sealing seat (92) of the housing (58) in the closed position of the pressure limiting device (56).
  4. Pressure limiting device (56) according to one of the preceding claims, characterized in that a shoulder (106) is formed in the housing (58), and in that the piston rests against the shoulder (106) in the closed position of the pressure limiting device (56).
  5. Pressure limiting device (56) according to one of the preceding claims, characterized in that the piston (72) has a third collar (100), in that the equalizing chamber (82) is additionally delimited by the third collar (100), and in that the diameter (D3) of the third collar (100) is smaller than the diameter (D1) of the first collar (74).
  6. Pressure limiting device (56) according to Claim 5, characterized in that the third collar (100) together with the bore (70) delimits a space (102), and in that the space (102) is at least indirectly hydraulically connected to a low pressure region (12) of the fuel system (10).
  7. Fuel system (10) for supplying fuel (18) for an internal combustion engine, having a storage tank (16), having a first fuel pump (20) which is connected at the input side to the storage tank (16), having a second fuel pump (30) which is connected at the input side to the first fuel pump (20) by means of a fuel connection (22), and having a pressure limiting device (56) which limits the pressure in a fuel connection (42, 46) at the output side of the second fuel pump (30), characterized in that the pressure limiting device (56) is embodied according to one of Claims 1 to 6.
  8. Fuel system (10) according to Claim 7, characterized in that the second fuel pump comprises a single-cylinder piston pump (30).
  9. Fuel system (10) according to one of Claims 7 or 8, characterized in that the pressure limiting device (56) is attached to the second fuel pump (30) and is preferably integrated into the latter.
EP20030003826 2002-09-27 2003-02-20 Pressure limiting device and fuel system with such a pressure limiting device Expired - Lifetime EP1403509B1 (en)

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DE10245084A1 (en) 2004-04-01

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