EP1361357A2 - Fuel pump, in particular for an internal combustion engine with direct injection - Google Patents

Abstract

Fuel pump comprises a housing containing at least one piston driven backward and forward by drive devices, a working chamber partly delimited by the piston, an inlet channel and outlet channel connected to the working chamber, and a first valve arrangement (64) between the working chamber and the inlet channel and a second valve arrangement (74) between the working chamber and the outlet channel. The valve element (62) of one valve arrangement has a guide section (60) at least partly housed in a guide opening (58) formed in the valve element (72) of the other valve arrangement. The peripheral surface of the guide section and/or the guide opening has at least one recess reducing the contact surface between the guide section and the guide opening. An Independent claim is also included for an alternative fuel pump.

Description

State of the art

The invention first relates to a fuel pump, especially for an internal combustion engine, with Direct injection, with a housing, with at least one Piston, which is received in the housing with Drive means which the piston in a back and forth Moving here with a work space, which is limited in some areas by the piston, with a Inlet duct and with an outlet duct, which with the Work space can be connected to a first one Valve device between the work area and the inlet duct and a second valve device between the work area and Outlet channel, the valve element of one Valve device has a guide section which at least in some areas in a guide opening is included.

Such a fuel pump is known from the market. It serves as a high-pressure fuel pump for diesel engines of motor vehicles. The fuel is pumped in by the high pressure fuel pump under high pressure promoted a fuel rail, in which it is stored under high pressure. From the fuel rail the fuel gets to injectors, which directly into the combustion chambers of the internal combustion engine inject.

In the known fuel pump, the two are Valve devices in a compact unit accommodated. The valve element is supported existing between work space and inlet duct Valve device ("inlet valve") on the valve element between the work area and the outlet duct Valve device ("exhaust valve"). The valve element the inlet valve is also cylindrical Guide pin in a guide opening of the valve element of the exhaust valve.

In the known internal combustion engine, it was found that it is in operation in the intake port of the fuel pump and the upstream components again and again Pressure surges coming. These reduce the efficiency of the Fuel pump. The valves also have to be complex are manufactured. Furthermore, the regulation is based on the Pressure vibrations difficult.

Furthermore, this basically results in internal combustion engines the need to promote fuel in the To completely prevent fuel manifold ( "Zero discharge"). Since one also intended for this Metering unit, which is upstream of the high pressure fuel pump is arranged, even in the closed Always a certain amount of fuel leakage High-pressure fuel pump lets out, so-called Zero feed restrictors between the metering unit and the High pressure fuel pump is used, which is at the exit leakage fuel escaping from the metering unit should lead back. Through these zero-feed throttles however, the starting behavior of the internal combustion engine is disadvantageous affected. Without such zero-feed throttles, however, would even when the metering unit is completely closed continue fuel in from the high pressure fuel pump the fuel manifold are promoted.

The present invention has for its object a Fuel pump of the type mentioned above to further that the internal combustion engine in which they is used, can be manufactured cheaper and has a better starting behavior and at the one safe shutdown of fuel delivery guaranteed is.

This task is the beginning of a fuel pump mentioned type in that the guide opening in Valve element of the other valve device is formed and the peripheral surface of the guide portion and / or the Guide opening has at least one recess which is the contact area between the guide section and Guide opening is reduced.

Advantages of the invention

In the fuel pump according to the invention occur in Inlet channel and upstream of this none of the High pressure fuel pump resulting pressure pulses more on. Thus, valves can be used that are cheaper can be manufactured.

Furthermore, the starting behavior of an internal combustion engine which with the fuel pump according to the invention is significantly improved since the Zero feed throttle can be significantly smaller than so far. In the fuel pump according to the invention namely even if one in front of the fuel pump arranged metering unit to a certain amount of leakage Let fuel through to the fuel pump, no Fueled.

The reason for both measures is that the Functions of the intake valve and the exhaust valve at the fuel pump according to the invention from each other are decoupled. In the known fuel pump namely found that if during a Delivery strokes the outlet valve opens due to Friction effects and a delayed pressure build-up in the Receiving opening of the valve element of the exhaust valve a short opening of the intake valve. this leads to the pressure surge or pressure pulse in the inlet area of the Fuel pump, which in the invention Fuel pump is avoided.

In a multi-cylinder fuel pump, the Inlet channels are interconnected, this leads triggered during a delivery stroke of one cylinder Pressure pulse to open the valve element of the Intake valve on the other cylinder, which is currently in the suction phase. Thus, fuel gets through the suction phase of this cylinder in the work area and will during the subsequent delivery stroke to the fuel manifold transported.

This is the case with the fuel pump according to the invention avoided because of the reduced friction between the valve elements of the intake and exhaust valves cannot achieve the said deadweight effect. The Intake valve of a cylinder that is currently in the Funding phase remains reliably closed.

The decoupling of the valve element of the intake valve from the valve element of the exhaust valve is achieved that the contact area between the two elements is reduced. This will cause friction between the two Elements, which ultimately leads to that Valve element of the exhaust valve during a movement Valve element of the intake valve not moved. According to the invention, a "mechanical" decoupling created.

In an advantageous development of this Fuel pump is suggested to be one Has connecting channel which the guide opening with connects the work space. Such a connection channel prevents it from moving the valve element of the exhaust valve to a pressure drop in the Guide opening comes, which is also a movement of the Valve element of the intake valve could provoke. By this connection channel becomes the harmful pressure impulses prevented even better. According to the invention "hydraulic" decoupling created.

As an alternative to this, it is the case of a fuel pump type mentioned that the guide section on the valve element of the first valve device and the Guide opening is formed in the inlet channel. hereby the two valve elements are completely apart decoupled so that one by the opening movement of the Exhaust valve element provoked Opening movement of the valve element of the intake valve is excluded. In contrast to the two above Refinements of the invention must be made here Circumstances, the valve element of the exhaust valve somewhat can be shortened to an opening movement of the Valve element of the inlet valve the necessary distance between the two valve elements.

Advantageous developments of the inventions are in Subclaims specified.

In a first training it says that the Circumferential surface of the guide section and / or the Guide opening at least one in the longitudinal direction has running recess through which the Contact area between the guide section and Guide opening is reduced and which as Flow channel is used with the valve open. At this Continuing education is the complete decoupling of two valve elements and the particularly low-friction Guiding the valve element of the intake valve with each other coupled. Such a fuel pump thus works very well effectively.

It is possible for a plurality of recesses is available. The more recesses there are, the more the contact area between the Guide section and the guide opening, which ultimately leads to leads to a reduction in the frictional forces. Furthermore is the flow in the by a plurality of recesses Valve range improved.

It is particularly preferred if the recesses are so are formed that between the guide section and Guide opening just a substantially linear There is contact. In this case, the frictional forces minimal between guide section and guide opening. However, it must be ensured that the Contact areas are so large that no excessive Wear occurs.

In a particularly preferred embodiment of the Fuel pump according to the invention it is proposed that the guide section is designed such that it at least three radially extending and preferably wings distributed around the circumference. With such wings is on the one hand safe guidance of the Valve element possible, on the other hand, allow Recesses or the passages between the wings one largely unimpeded flow of fuel. A such fuel pump thus works with high Efficiency.

The same also applies to a fuel pump in which the guide opening is designed so that it at least three radially extending and preferably over the Includes circumferentially distributed wings.

It is advantageous if the wings are ground hollow. This increases the stability of the valve element and creates a larger flow area.

It is also proposed that the valve element of the first valve device on the valve element of the second Valve device is supported via a clamping element so that it is pressed against the associated seat. Such Fuel pump builds very compact.

The attack of the tensioning element on the first valve element is thereby facilitated that the first valve element plate-shaped support section, preferably a disc, includes, on which the clamping element is supported.

drawing

Figur 1

eine schematische Darstellung eines Kraftstoffsystems einer direkteinspritzenden Brennkraftmaschine mit einer Hochdruck-Kraftstoffpumpe;

Figur 2

eine teilweise geschittene Darstellung der Hochdruck-Kraftstoffpumpe des Kraftstoffsystems von Figur 1;

Figur 3

eine Detailansicht der Hochdruck-Kraftstoffpumpe von Figur 2, in der ein Einlass- und ein Auslassventil dargestellt ist;

Figur 4

eine Draufsicht auf ein Ventilelement des Einlassventils von Figur 3;

Figur 5

eine Seitenansicht des Ventilelements von Figur 4;

Figur 6

ein Diagramm, in dem der Druck in einem Einlasskanal der Hochdruck-Kraftstoffpumpe von Figur 2 über der Zeit dargestellt ist;

Figur 7

eine Detailansicht ähnlich Figur 3 eines alternativen Ausführungsbeispiels einer Hochdruck-Kraftstoffpumpe; und

Figur 8

einen Schnitt durch einen Bereich eines dritten Ausführungsbeispiels einer Hochdruck-Kraftstoffpumpe.

Particularly advantageous exemplary embodiments of the invention are explained in detail below with reference to the accompanying drawing. The drawing shows:

Figure 1

is a schematic representation of a fuel system of a direct injection internal combustion engine with a high pressure fuel pump;

Figure 2

a partially sectioned illustration of the high pressure fuel pump of the fuel system of Figure 1;

Figure 3

a detailed view of the high pressure fuel pump of Figure 2, in which an inlet and an outlet valve is shown;

Figure 4

a plan view of a valve element of the inlet valve of Figure 3;

Figure 5

a side view of the valve element of Figure 4;

Figure 6

a diagram in which the pressure in an inlet channel of the high-pressure fuel pump of Figure 2 is shown over time;

Figure 7

a detailed view similar to Figure 3 of an alternative embodiment of a high pressure fuel pump; and

Figure 8

a section through a portion of a third embodiment of a high pressure fuel pump.

Description of the embodiments

In Figure 1, a fuel system as a whole carries this Reference number 10. It serves to supply one Internal combustion engine 12 with fuel. In the Internal combustion engine 12 is a Diesel engine, basically that is shown However, fuel system 10 also for gasoline internal combustion engines used.

The fuel system 10 includes a fuel tank 14, from which a mechanical, designed as a gear pump Fuel pump 16 promotes fuel through a filter 18. The fuel passes from the fuel pump 16 via a Metering unit 20 and a fuel line 21 to one High pressure fuel pump 22. From there it is over a Fuel line 23 further promoted in a fuel rail 24 ("rail") in which the fuel is below high pressure is stored.

Several injectors are on the fuel rail 24 26 connected to the fuel in combustion chambers 28 inject directly. From the fuel line 21 between Metering unit 20 and high-pressure fuel pump 22 branches a zero delivery line 30 in which a zero delivery throttle 32 is arranged. Essential functions of the Internal combustion engine 12 are controlled by a control and Control device 34 controlled or regulated. That's the way it is Metering unit 20 to the control and regulating device 34 connected and controlled by this.

The high-pressure fuel pump 22 is a 4-ram high-pressure pump in a V arrangement (Figure 2). This comes especially with high fuel systems Quantity requirements for use. In Figure 2 are the two Cylinders of a cylinder plane are visible. You wear that Reference numerals 36a and 36b. The cylinders 36a and 36b are Part of a housing 38. Pistons 40a and 40b are in them added. These are from a camshaft 42 in a Moved back and forth. The pistons 40a and 40b limit working spaces 44a and 44b.

The working spaces 44a and 44b of Valve blocks 46a and 46b limited. Their exact structure is explained in detail below. Between Cylinders 36a and 36b sit on the housing 38 Metering unit 20. From this lead inlet channels 48a and 48b in the housing 38 to the valve blocks 46a and 46b. In the Valve blocks 46a and 46b are outlet channels 50a and 50b available. These lead to the fuel line 23 and continue to fuel rail 24.

The valve blocks 46a and 46b are now exemplarily under 3 with reference to a valve block 46 explained. This comprises a cylindrical valve body 52. There is a valve space 54 in it, which via a Connection channel 56 is connected to the work space 44. One leads from the valve chamber 54 to the axis of the valve body 52 Coaxial bore 57 in the installation position towards Working space 44. This forms a guide opening 58 for a guide section 60 of a valve element 62.

A slant (without reference number) in the transition area between the guide opening 58 and the valve space 54 forms a valve seat for the valve element 62. The The valve seat and the valve element 62 form a whole Inlet valve 64 through which fuel from the Metering unit 20 via the inlet channel 48 with its im Valve body 52 formed sections 66 and 57 in the Valve space 54 and further into the work space 44 can.

Extends opposite from the guide opening 58 from the valve chamber 54 a bore 68 in which a Guide section 70 of a valve element 72 is guided. A slant (without reference number) in the transition area between the bore 68 and the outside of the Valve body 52 forms a valve seat for the Valve element 72. The valve seat and the valve element 72 together form an outlet valve 74, via which the Fuel from the work space 44 via the connecting channel 56, the valve chamber 54 and the outlet channel 50 into the Fuel line 23 and on to the fuel rail 24 can reach.

In the valve element 72 of the exhaust valve 74 is for Valve chamber 54 introduced a blind bore 76. On theirs A compression spring 80 is supported on the base side 78. their the other end is due to a paragraph 82 of the Valve element 62 of the inlet valve 64 on. In this way is the valve element 62 of the intake valve 64 against pressed his valve seat. The valve element 72 of the Exhaust valve 74 is countered by a compression spring 84 acted on its valve seat.

The guide section 60 of the valve element 62 of the Intake valve 64 is as shown in FIGS. 4 and 5 can be seen in the form of wings 86a, 86b and 86c executed, which extend radially in a star shape and over the circumference is distributed. At their radial outer ends are wings 86a, 86b and 86c, respectively trained that there is a significantly reduced contact with the wall of the guide opening 58 in the valve body 52 results. Between the wings 86a, 86b and 86c are hollow ground recesses 88a, 88b and 88c available.

The fuel system 10 with the high pressure fuel pump 22 works as follows: The metering unit 20 is from Control and regulating device 34 controlled so that only those Fuel amount to high pressure fuel pump 22 and from this further reaches the fuel collecting line 24, which from the injectors 26 into the combustion chambers 28 is injected. During the suction phase of a cylinder 36a or 36b the piston 40a or 40b moves to the side radially inward so that the pressure in the corresponding Working space 44a or 44b decreases. This also reduces the Pressure in the valve chamber 54, whereby the valve element 62 of the intake valve 64 of the corresponding cylinder 36a or 36b takes off from its seat.

Fuel can thus flow from the metering unit 20 into the Flow work space 44a or 44b. The reaction of the Valve element 62 of the inlet valve 64 is done very much spontaneously because the friction between the guide portion 60 and the guide opening 58 is only very small. At the same time, the valve element 62 is through the Guide section 60 in the guide opening 58 exactly centered so that when closed the Connection between the valve chamber 54 and the inlet duct 48 seals reliably. The recesses 88a, 88b and 88c enable 64 with the inlet valve open largely unimpeded inflow of fuel to the Working space 44a or 44b.

Moved during the delivery phase of a cylinder 36a or 36b the corresponding piston 40a or 40b radially abroad. This increases the pressure in the valve chamber 54, so that the valve element 62 of the intake valve 64 is on again its valve seat comes into contact. If the pressure difference between the valve chamber 54 and the outlet channel 50 large is enough, the valve element 72 of the exhaust valve 74 lifts from the corresponding valve seat so that the fuel from the working space 44 via the valve space 54 into the Fuel manifold 24 can get. Doing so clearly that a movement of the valve element 72 of the Exhaust valve 74 has no direct impact on that Has valve element 62 of the intake valve 64. Only that Compression spring 80 is somewhat relaxed, which, however, due to the in the valve chamber 54 prevailing high pressure for the Position of the valve element 62 is without influence.

If no fuel from the injectors 26 in the Combustion chambers 28 arrives (for example in overrun mode), the metering unit 20 is controlled by the control and regulating device 34 closed. Due to the system, however, it also happens closed metering unit 20 to a certain Leakage amount of fuel, which over the Fuel line 21 into the inlet channels 48a and 48b arrives. However, since the intake valve 64 is from the exhaust valve 74 is decoupled, the inlet valve 64 also remains in in this case reliably closed, so that no Fuel is delivered to the fuel rail 24 becomes. The corresponding pressure curve carries this in FIG Numeral 90.

The decoupling ensures that for example during the delivery stroke of the cylinder 36a Valve element 62 of the intake valve 64 in this cylinder does not stand out from its valve seat and therefore none Trigger pressure pulse in the inlet channels 48a and 48b. There the cylinder 36b is in a suction phase when the Cylinder 36a is in a delivery phase, one could such pressure pulse easily to lift the Valve element 62 of intake valve 64 of cylinder 36b to lead.

This would cause leakage fuel from metering unit 20 into the working space 44b of the corresponding cylinder 36b get, and on to the fuel rail 24th be promoted. These pressure pulses, which at the High pressure fuel pump 22 in intake ports 48a and 48b are avoided, are dashed in Figure 6 shown and designated 92.

In Figure 7 is a valve body 52 of a second Embodiment of a high pressure fuel pump 22nd shown. In Figure 7 such elements and Areas that have equivalent functions to that above have described embodiment, the same Reference numerals. It will not go into detail again received.

In the embodiment shown in Figure 7 is the valve element 62 of the intake valve 64 in the Blind bore 76 of valve element 72 of exhaust valve 74 guided. This therefore forms the guide opening 58. This has the advantage that a conventional valve element 72 can be used for the exhaust valve 74. to Support of the compression spring 80 on the valve element 62 is one Washer 82 is provided which on the axial edges of the Wing 86a, 86b and 86c rests. To equalize the pressure Guide opening 58 is in the wall surrounding this Valve element 72 a pressure equalization bore 94 is present, via a longitudinal groove 96 with the valve chamber 54 communicated.

FIG. 8 shows a region of a modification of that in FIG. 7 Inlet valve 64 shown or that of FIG. 7 Exhaust valve 74 shown. Here are on Guide section 90 of the valve element 62 of the Inlet valve 64 no wings. Instead extend tapered webs 86 from the radial inner peripheral wall of the blind bore 76 of the valve element 72 of the exhaust valve 74.

Claims (11)

Fuel pump (22), in particular for an internal combustion engine (12) with direct injection, with a housing (38), with at least one piston (40) which is accommodated in the housing (38), with drive means (42) which move the piston ( 40) in a to-and-fro movement, with a working space (44) which is delimited in some areas by the piston (40), with an inlet duct (48) and with an outlet duct (50) which can be connected to the working space (44) , With a first valve device (64) between the working chamber (44) and the inlet duct (48) and a second valve device (74) between the working chamber (44) and the outlet duct (50), the valve element (62) of the one valve device (64) having a guide section (60), which is accommodated at least in regions in a guide opening (58), characterized in that the guide opening (58) is formed in the valve element (72) of the other valve device (74) and the peripheral surface of the guide tion section (60) and / or the guide opening has at least one recess (88) through which the contact area between the guide section (60) and the guide opening (58) is reduced. Fuel pump (22) according to Claim 1, characterized in that it has a connecting channel (94, 96) which connects the guide opening (58) to the working space (44). Fuel pump (22), in particular for an internal combustion engine (12) with direct injection, with a housing (38), with at least one piston (40) which is accommodated in the housing (38), with drive means (42) which move the piston ( 40) in a to-and-fro movement, with a working space (44) which is delimited in some areas by the piston (40), with an inlet duct (48) and with an outlet duct (50) which can be connected to the working space (44) , With a first valve device (64) between the working chamber (44) and the inlet duct (48) and a second valve device (74) between the working chamber (44) and the outlet duct (50), the valve element (62) of the one valve device (64) having a guide section (60), which is received in a guide opening (58), characterized in that the guide section (60) on the valve element (62) of the first valve device (64) and the guide opening (58) is formed in the inlet channel (48). Fuel pump (22) according to claim 3, characterized in that the peripheral surface of the guide section (60) and / or the guide opening has at least one longitudinally extending recess (88) through which the contact area between the guide section (60) and the guide opening (58) is reduced and which serves as a flow channel when the valve device (64) is open. Fuel pump (22) according to one of claims 1, 2 or 4, characterized in that a plurality of recesses (88) is present. Fuel pump (22) according to one of Claims 1, 2, 4 or 5, characterized in that the recesses (88) are designed such that there is only a substantially linear contact between the guide section (60) and the guide opening (58). Fuel pump (22) according to one of claims 1, 2 or 5 to 6, characterized in that the guide section (60) is designed such that it comprises at least three radially extending and preferably distributed over the circumference wings (86). Fuel pump (22) according to one of Claims 1, 2 or 4 to 7, characterized in that the guide opening (58) is designed such that it comprises at least three radially extending webs (86) which are preferably distributed over the circumference. Fuel pump (22) according to one of claims 7 or 8, characterized in that the wings (86) are hollow ground. Fuel pump (22) according to one of the preceding claims, characterized in that the valve element (62) of the first valve device (64) is supported on the valve element (72) of the second valve device (74) via a tensioning element (80) such that it is against the associated seat is pressed. Fuel pump (22) according to claim 9, characterized in that the first valve element (62) comprises a plate-shaped support section, preferably a disc (82), on which the tensioning element (80) is supported.

Images