EP1348865A2 - High pressure fuel pump for a fuel system of an internal combustion engine - Google Patents

Abstract

The pump assembly (10) has a shaft (38) with an eccentric (40) driving pistons (42-46) in cylinders (48-52). Each piston has an inlet valve (54-58) and an outlet valve (60-64). Two cylinders 180 degrees out of phase draw low-pressure fuel (18) from a first pipe junction (80) and deliver high-pressure fuel to a second junction point (74). Fuel passes through a non-return valve (76) to a high-pressure reservoir (24). A third cylinder is 90 degrees out of phase with and directly delivers fuel to the inlet line (66) for the high-pressure reservoir. The system contains a pressure sensor (32) and a control valve (78) which may release high-pressure fuel back from the second junction point to the first.

Description

State of the art

The invention relates to a high-pressure fuel pump for a fuel system of an internal combustion engine, with a A plurality of cylinders with pistons, each one Limit work space with a drive shaft, which at one turn the pistons in a reciprocating motion offset, and with at least one quantity control valve, which at least during a funding cycle Cylinder at least temporarily a delivery room this Can connect cylinders with a pressure relief area.

Such a high pressure fuel pump is from the market known. It is used in such fuel systems used, which in internal combustion engines with gasoline or Diesel direct injection can be used. By a such high pressure fuel pump will run on the fuel compressed to a very high pressure and into a fuel rail ("Rail") promoted and under high pressure there saved. There are several on this fuel rail Injectors connected to the fuel in each Inject combustion chambers.

The drive shaft of the well-known high pressure fuel pump is rigid with a camshaft of the internal combustion engine coupled. Thus, without appropriate measures, the Delivery rate of the fuel pump directly from the speed the internal combustion engine. However, there are operational areas the internal combustion engine, in which despite high speed only little fuel is injected into the combustion chambers, so even little fuel from the high pressure fuel pump must be promoted.

So that the amount of fuel delivered regardless of the speed of the drive shaft can be adjusted therefore, a volume control valve provided by a Control and regulating device is controlled so that it is against Opens briefly at the end of a funding wing. The under high Pressure in the delivery chamber of the fuel pump compressed Fuel is then not in the fuel rail pumped but into an upstream from the high pressure fuel pump drained low pressure area. ever the flow control valve longer during a delivery cycle is open, the lower it is Quantity of fuel reaching the fuel line.

In the upstream of the high pressure fuel pump low-pressure area, however, it occurs when that Flow control valve opens to a sudden Pressure increase. The resulting pressure pulsations can not in itself for such high pressures damage the designed components in this area. Measures are therefore proposed to: To keep pressure pulsations low in the low pressure range. For example, the use of spring-loaded is known Pressure damper.

The object of the present invention is this Pressure pulsations in the low pressure range continue to increase reduce so that this is correspondingly inexpensive can be manufactured and / or long life having.

This is the task of a high pressure fuel pump type mentioned solved in that two cylinders so arranged to each other and the drive shaft so is formed that the piston of these two cylinders approximately 180 ° out of phase with each other Drive shaft are driven, and that at least one Volume control valve is arranged so that the delivery chamber of the currently non-delivering cylinder at least part of the Pressure relief area is.

Advantages of the invention

In the high-pressure fuel pump according to the invention Part of the fuel escapes when that Volume control valve during a delivery cycle Cylinder opens, at least partly no longer in the Low pressure area, but reaches the delivery chamber of the straight non-conveying cylinder. Ultimately, therefore the conveying spaces of two driven by 180 ° out of phase Cylinder "short-circuited"

The fact that the pistons of the two cylinders by 180 ° are driven out of phase with each other the piston of a cylinder in one suction stroke while the piston of the other cylinder is straight in one Funding cycle is located, and vice versa. The one under high pressure in the funding room of the one in a funding cycle Cylinder trapped fuel can do this easily in the increasing displacement of the Flow in the cylinder currently in a suction stroke.

In extreme cases, if the volume control valve during the entire funding cycle is open, none at all More fuel is pumped into the fuel rail and the fuel is instead only between the Delivery spaces of the two cylinders largely depressurized pumped back. The upstream of the high pressure fuel pump low pressure area is thus from relieves harmful pressure pulsations or possibly even completely exempt. This comes in the life of components used in this area.

Particularly advantageous developments of the invention are specified in subclaims.

In a first development, the high-pressure fuel pump at least three cylinders, two At least one flow control valve is assigned to cylinders and the pistons of these cylinders to each other about 180 ° are driven out of phase, and being the third Cylinder arranged and the drive shaft designed so is that the piston of the third cylinder is approximately 90 ° driven out of phase with the other two cylinders becomes. In this way, a three-cylinder fuel pump created which has a high output has, but also in the low pressure range pressure pulsations occurring are comparatively low can be held.

It is particularly preferred that the stroke volume of the third cylinder is smaller than the respective Stroke volumes of the other two cylinders. In the event that also the third cylinder via a volume control valve has its actuation to corresponding Leads to pressure pulsations in the low pressure range the design according to the invention ensures that these pressure pulsations are comparatively low.

It is also possible that the delivery rate is at least one Cylinder via an associated with the cylinder inlet valve can be adjusted. For example, the volume control valve can in any case required inlet valve must be integrated. This Integration is relatively easy. About that in addition, the advantages according to the invention can be achieved without that additional flow channels in the pump housing required are.

If necessary, it can also be provided that at least one of the cylinders via the volume control valve or inlet valve can be switched on and off.

In this case the valve is not very dynamic required so that it can be made cheaper can. Nevertheless, the delivery rate can be Switch off the cylinder at least in the rough frame can be set.

It is particularly preferred if the delivery rooms of the two cylinders with the approximately 180 ° to each other the phase-shifted piston is the same Quantity control valve is assigned. That is why possible, since only one of the two cylinders is always in the Funding cycle is located. Thus, a volume control valve be saved what the manufacturing costs of low pressure fuel pump according to the invention lowers.

It is also suggested that the volume control valve be a is a continuously adjustable valve. Basically, though also a volume control valve with two switch positions conceivable, which has price advantages, since a cheaper power amplifier due to the lower requirements for the switching time can be used. A continuously adjustable valve has the advantage, however, that the amount to be conveyed is very can be set exactly what a reduction in Power consumption of the high pressure fuel pump enables.

In another embodiment of the high-pressure fuel pump according to the invention, the quantity control valve has three connections, one connection leading to the outlet of one delivery chamber, an opposite connection leading to the outlet of the other delivery chamber, and a further opposite connection leading to a high-pressure outlet of the high-pressure pump. Such a hydraulic circuit has the advantage that, in contrast to a valve with only two connections, an additional check valve that is otherwise required can be dispensed with.
Such a high-pressure fuel pump is small and inexpensive.

drawing

Figur 1

eine schematische Darstellung einer Brennkraftmaschine mit einer Hochdruck-Kraftstoffpumpe;

Figur 2

eine vereinfachte hydraulische Prinzipdarstellung der Hochdruck-Kraftstoffpumpe von Figur 1;

Figur 3

eine Darstellung ähnlich Figur 2 einer abgewandelten Hochdruck-Kraftstoffpumpe;

Figur 4

eine Darstellung ähnlich Figur 2 einer nochmals abgewandelten Hochdruck-Kraftstoffpumpe; und

Figur 5

eine Darstellung ähnlich Figur 2 einer nochmals abgewandelten Hochdruck-Kraftstoffpumpe.

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

Figure 1

a schematic representation of an internal combustion engine with a high pressure fuel pump;

Figure 2

a simplified hydraulic schematic diagram of the high pressure fuel pump of Figure 1;

Figure 3

a representation similar to Figure 2 of a modified high pressure fuel pump;

Figure 4

a representation similar to Figure 2 of a further modified high pressure fuel pump; and

Figure 5

a representation similar to Figure 2 of a further modified high pressure fuel pump.

Description of the embodiments

In Figure 1, an internal combustion engine carries this overall Reference number 10. It comprises a fuel system (without Numbered). This promotes an electrical Low pressure pump 14 fuel from a fuel tank 16. From there, the fuel passes through a low pressure fuel line 18 to a high-pressure fuel pump 20, which is only symbolically dash-dotted in FIG. 1 is shown. It is explained in detail below. At the low pressure fuel line 18 is a Pressure damper 22 connected.

The high-pressure fuel pump 20 delivers into a Fuel manifold 24, in the operation of the Fuel is stored under high pressure. To these are several injectors 26 connected, which run the fuel Combustion chambers 28 assigned directly in them inject. A pressure relief valve 30 carries excess Fuel from the fuel rail 24 in the Low pressure fuel line 18 back. A pressure sensor 32 detects the prevailing in the fuel rail 24 Pressure and sends appropriate signals to a control and Control unit 34. This in turn controls the high pressure fuel pump 20 on. Incidentally, this is directly above a clutch, not shown, of one in Figure 1 only symbolically shown camshaft 36 of the Internal combustion engine 10 driven.

The high-pressure fuel pump 20 of the internal combustion engine 10 is shown in more detail in Figure 2: After the high pressure fuel pump 20 includes a drive shaft 38 with an eccentric section 40. On this is an in Figure 2 not shown cam ring attached. Over here intermediate elements of no further interest are shown in a rotation of the drive shaft 38 from the eccentric section 40 three radially arranged pistons 42, 44 and 46 in a back and forth Moved here.

The pistons 42 to 46 are not closer in one shown housing and limit areas Delivery rooms 48, 50 and 52. Via as an inlet valve acting spring-loaded ball check valves 54 to 58 can the delivery rooms 48 to 52 with the low pressure fuel line 18 are connected. Similar spring-loaded ball check valves 60, 62 and 64 form outlet valves with which the delivery spaces 48 to 52 to be connected to a high pressure fuel line 66 can, which leads to the fuel rail 24.

Components 42, 48, 54 and 60 belong to a cylinder 68, the components 44, 50, 56, 62 to form a cylinder 70, and components 46, 52, 58 and 64 to form a cylinder 72.

The cylinders 68 to 72 are hydraulic as follows interconnected:

Guide the exhaust valves 60 and 64 of cylinders 68 and 72 to a node 74. This is over a spring-loaded check valve 76 with the high pressure fuel line 66 connected. The outlet valve 62 of the Cylinder 70 is connected to a node 77 which between the check valve 76 and the high pressure fuel line 66 lies. Node 74 is also via an infinitely adjustable electromagnetic actuated quantity control valve 78 and a node 80 connected to a channel (without reference number), to which in turn all inlet valves 54, 56 and 58 and the Low pressure fuel line 18 are connected.

As can be clearly seen in Figure 2, the Cylinder 68 and cylinder 72 are offset from one another by 180 ° arranged. Because pistons 42 and 46 of cylinders 68 and 72 from the same eccentric section 40 of the drive shaft 38 are driven, they turn when the Drive shaft 38 with a phase shift of 180 ° in a back and forth movement. This means that when the piston 42 of the cylinder 68 moves radially moves outward, the piston 46 of the cylinder 42 after moved radially inward, and vice versa.

To control the delivery rate of the high pressure fuel pump 20 is done as follows:

Is the at a given speed of the drive shaft 38 maximum possible delivery rate of the high pressure fuel pump 20 desired, the volume control valve remains 78 in its normally closed position. At a Suction stroke of a piston 42, 44 or 46 of a cylinder 68, 70 or 72 (one suction stroke corresponds to one radially inward directed movement of a piston 42 to 46) Fuel from the low pressure fuel line 18 over the inlet valves 54, 56 and 58 into the delivery spaces 48, 50 or 52 of the corresponding cylinders 68, 70 or 72 sucked.

With a delivery stroke of one of the pistons 42, 44 or 46 (ie a radially outward movement of one of the Piston 42 to 46) becomes the one in the delivery chamber 48, 50 or 52 enclosed fuel compresses and at Exceeding the opening pressure of the exhaust valves 60, 62, 64 and 76 pressed into the fuel rail 24.

However, at a certain speed Drive shaft 38 is less than the maximum possible Fuel quantity will be promoted, that will Flow control valve 78 during certain periods the delivery cycles of the cylinders 68 and 72 are energized and thus open. When the quantity control valve 78 is open, the between check valve 76 and exhaust valves 60 and 64 area located above node 74, the Flow control valve 78 and the node 80 with the Low pressure fuel line 18 connected. The pressure in this area thus drops significantly, so that the Opening pressure of the check valves 60 or 64 drops.

For example, at the end of a funding cycle of the Piston 42 of the cylinder 68, the quantity control valve 78 energized and open, opens due to pressure drop in the said area, the exhaust valve 60 so that the 48 existing fuel under high pressure in the delivery chamber can flow out. However, since the piston 46 of the Cylinder 72 has a radially inward movement executes, so this cylinder in one suction cycle and the intake valve 58 of this cylinder 72 is open, the escaping from the delivery chamber 48 flows Fuel via the quantity control valve 78 is not complete in the low pressure fuel line 18, but at least partly through the open inlet valve 58 in the Delivery chamber 52 of the cylinder 72.

The volume control valve 78 is described in the above Opened in this way, there is comparatively little Fuel into the low pressure fuel line 18 so that the corresponding pressure surge in the low pressure fuel line 18 is also comparatively low. The components of the low pressure fuel line 18 are therefore spared and the low pressure surge in essentially be absorbed by the pressure damper 22.

When the delivery stroke of cylinder 68 has ended, closes the quantity control valve 78 again. It then opens again for a certain period of time towards the end of the funding cycle of the Cylinder 72, so that the one from the delivery chamber 52 escaping fuel through the exhaust valve 64, the Junction 74, the volume control valve 78, and the Junction 80 to open inlet valve 54 of the then in a suction stroke of the piston 42 of the cylinder 68 arrives.

In extreme cases, when cylinders 68 and 72 have none at all The quantity control valve 78 remains to deliver fuel fully open, so it is constantly energized. In this Fall the fuel between the delivery rooms 48 and 52 of cylinders 68 and 72 pumped back and forth without over check valve 76 into fuel rail 24 to get.

The conveying capacity of the Cylinder 70: Its outlet valve 62 is as shown in FIG. 2 can be seen via the node 77 directly with the High pressure fuel line 66 connected. The corresponding one Channel (without reference number) thus opens downstream from Check valve 76 into the high pressure fuel line 66.

A control of the quantity control valve 78 is therefore open the delivery rate of the cylinder 70 does not affect this promotes with the drive shaft 38 rotating.

It is in the embodiment described above the volume control valve 78 is a switching valve, which goes between two switch positions can be switched down. But it is also possible Use of a continuously adjustable valve. In this The opening pressure of the exhaust valves 60 and 64 may fall continuously adjustable, which is a particularly precise Setting the delivery rate of the high pressure fuel pump 20 allows.

Now, referring to FIG. 3, a Modification of the high pressure fuel pump 20 received. Such elements, components and areas what equivalent functions to the corresponding ones Elements, components and areas of the high pressure fuel pump of Figure 2, the same Reference numerals. They are not explained in detail again.

The difference of the high pressure fuel pump shown in Figure 3 to that shown in Figure 2 the cylinder 70. This is a switchable in the present case Valve 82 assigned, which hydraulically between the Delivery chamber 50 of the cylinder 70 and the low-pressure fuel line 18 is arranged. The valve 82 has two Switch positions: The valve is in switch position 84 82 permeable in both directions. So it's a free one Fluid exchange between the delivery chamber 50 and the Low pressure fuel line 18 possible. In the Switch position 86, the valve 82 works as spring-loaded check valve 56, corresponding to the Inlet valve in Figure 2.

The valve 82 is also from the control and regulating device 34 controllable. In the open state (switch position 84) during a suction stroke of the piston 44 of the cylinder 70 Fuel from the low pressure fuel line 18 in the Delivery chamber 50 sucked in and in the subsequent Delivery stroke straight back into the low pressure fuel line 18 ejected. The valve is located 82, on the other hand, in switch position 56, arrives at one Suction stroke of the piston 44 fuel from the low-pressure fuel line 18 in the delivery room 50, at one Delivery stroke of the piston 44, however, the fuel over exhaust valve 62 and node 77 into FIG High pressure fuel line 66 ejected.

The cylinder 70 can therefore move out and in via the valve 82 be switched on. If the valve 82 is in the Switch position 84, it may be due to the movements piston 44 of cylinder 70 in the low pressure fuel line 18 also come to pressure pulsations. In order to keep this as low as possible, the stroke volume of the Cylinder 70 compared to the stroke volumes of the cylinders 68 and 72 relatively small.

Another variant of a high-pressure fuel pump 20 is shown in Figure 4. Here too wear such Components, elements and areas, which are equivalent Functions for the components described above, Elements and areas have the same Reference numerals and are not explained again in detail.

The high-pressure fuel pump 20 shown in FIG. 4 also has valve 82 with which cylinder 70 can be switched on and off. Beyond that it is Flow control valve 78 designed as a 2/3 way valve, it has two switch positions 86 and 88 and three ports 90, 92 and 94. This has the advantage that between the delivery spaces 48 and 52 of the cylinders 68 and 72 and the high pressure fuel line 66 only two in total Check valves 60 and 64 are required.

This is made possible by the following hydraulic connection: The delivery spaces 48 and 52 of the cylinders 68 and 72 are directly connected to the volume control valve 78. It is the delivery chamber 52 of the cylinder 72 with the connection 90 and the delivery chamber 48 of the cylinder 68 with the opposite connection 94 of the quantity control valve 78 connected. Parallel to the connection of the delivery room 48 with the connection 94 is the delivery chamber 48 via the spring-loaded check valve 60 also with the node 77 or connected to the high pressure fuel line 66.

This node 77 is also spring loaded Check valve 64 with the next to port 94 lying connection 92 of the quantity control valve 78 connected. In switch position 86 of the volume control valve 78 can fuel from the delivery chamber 52 through the Ports 90 and 92 of the volume control valve 78 and that Check valve 64 in the high pressure fuel line 66 stream. Furthermore, fuel from the delivery chamber 48 of the Cylinder 68 through the check valve 60 into the high pressure fuel line 66 stream. The branch parallel to this, which ends in connection 94 is blocked.

In the other switching position 88 of the volume control valve 78 is the delivery chamber 52 via the connections 90 and 94 fluidically directly with the delivery chamber 48 of the cylinder 68 connected. The connection 92, which over the Check valve 64 for high-pressure fuel line 66 leads, however, is blocked. In this The fuel can therefore be in the switching position from the delivery chamber 48 get into the funding space 52, and vice versa.

The embodiment shown in Figure 5 High-pressure fuel pump 20 corresponds to that of Figure 4, with the exception of cylinder 70: this cannot move in and out turned off. Instead it is an inlet valve 56 a normal spring loaded check valve intended.

Claims (8)

High-pressure fuel pump (20) for a fuel system (12) of an internal combustion engine (10), with a plurality of cylinders (68-70) with pistons (42-46), which each delimit a delivery chamber (48-52), with a drive shaft (38), which sets the pistons (42-46) in a to-and-fro motion upon rotation, and with at least one quantity control valve (78, 82), which at least temporarily during a delivery cycle of a cylinder (68-72) a delivery chamber (48-52) of this cylinder (68-72) can connect to a pressure relief area (18, 48, 52), characterized in that two cylinders (68, 72) are arranged in relation to one another and the drive shaft (38) is designed such that the pistons (42, 46) of these two cylinders (68, 72) are driven by the drive shaft (38) approximately 180 ° out of phase with one another, and that at least one quantity control valve (78) is arranged such that the delivery chamber (48, 52) of the currently non-delivering cylinder (68, 72) is at least part of the pressure relief area (52, 48). High-pressure fuel pump (20) according to claim 1, characterized in that it has at least three cylinders (68-72), two cylinders (68, 72) being assigned at least one quantity control valve (78) and the pistons (42, 46) of these Cylinders (68, 72) are driven approximately 180 ° out of phase with one another, and wherein the third cylinder (70) is arranged and the drive shaft (38) is designed such that the piston (50) of the third cylinder (70) is approximately 90 ° out of phase to the other two cylinders (68, 72) is driven. High-pressure fuel pump (20) according to claim 2, characterized in that the stroke volume of the third cylinder (70) is smaller than the respective stroke volumes of the other two cylinders (68, 72). High-pressure fuel pump (20) according to one of the preceding claims, characterized in that the delivery rate of at least one cylinder (70) can be adjusted via an inlet-side valve (82) assigned to the cylinder (70). High-pressure fuel pump (20) according to claim 4, characterized in that at least one of the cylinders (70) can be switched on and off via the inlet-side valve (82). High-pressure fuel pump (20) according to one of the preceding claims, characterized in that the delivery chambers (48, 52) of the two cylinders (68, 72) with the pistons (42, 46) driven in phase displacement with respect to one another by approximately the same quantity control valve ( 78) is assigned. High-pressure fuel pump (20) according to one of the preceding claims, characterized in that the quantity control valve is a continuously adjustable valve (78). High-pressure fuel pump according to one of the preceding claims, characterized in that the quantity control valve (78) has three connections (90-94), one connection (90) for the outlet of the one delivery chamber (52), an opposite connection (94) for the outlet of the another delivery chamber (48), and a further opposite connection (92) leads to a high pressure outlet (66) of the high pressure pump (20).

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