EP2344749B1 - High-pressure fuel pump for an internal combustion engine - Google Patents

Description

State of the art

The invention relates to a high-pressure fuel pump for an internal combustion engine according to the preamble of claim 1.

Direct-injection high-pressure fuel pumps usually have a low-pressure range and a high-pressure range. An electric prefeed pump delivers the fuel from a tank into the low-pressure region, from which the fuel is conveyed via the high-pressure fuel pump into a fuel rail ("common rail") connected to the high-pressure region. The pressure in the fuel rail is usually controlled by a pressure control and / or a quantity control valve, the valves u.a. be controlled by an evaluation of signals from a pressure sensor of a control and / or regulating device. The pressure control valve can also work mechanically.

From the EP 0 299 337 A2 . EP 0 837 986 B1 . EP 0 974 008 B1 and DE 196 12 413 A1 Devices are already known to control the fuel pressure.

From the DE 103 27 411 A1 a pressure relief valve for a high-pressure fuel pump is known.

From the DE 10 2007 010 502 A1 is a high-pressure fuel pump with an electrically actuated metering unit known.

From the post-published DE 10 2007 030 224 A1 is a high-pressure fuel pump with a hydraulically actuated metering unit known.

From the WO 2005/031161 A2 is a high-pressure fuel pump with a pressure damper known. Through the pressure damper, the fuel flows into the pump element of the high-pressure fuel pump.

Disclosure of the invention

The object of the invention is to provide or further develop a fuel high-pressure pump for an internal combustion engine of the type mentioned, which works reliably and is compact. In addition, the fuel high-pressure pump should be inexpensive.

The object is achieved by a high-pressure fuel pump for an internal combustion engine with the features of claim 1. Advantageous developments can be found in the subclaims.

On account of the configuration of the high-pressure fuel pump, on the one hand installation space in the engine compartment of a motor vehicle is saved; on the other hand, the well-known external dimensions of the high-pressure fuel pump can be maintained by clever integration of the pressure control device in the high-pressure fuel pump. Additional hydraulic lines are not required. This advantageously leads to a very compact construction of the high-pressure fuel pump. Due to the omission of the quantity control of the fuel, the high-pressure fuel pump also requires no quantity control valve with an associated output stage and an electrical control line. Furthermore, the pressure sensor necessary for an electronic control can be dispensed with. This makes the invention particularly cost effective and also saves engine power. Since the unnecessary amount of fuel is diverted to the low pressure range, a pressure limiting function is guaranteed.

The present invention is based on the idea that when using a less pressure-sensitive fuel system in an internal combustion engine, for example, a constant pressure system, can be dispensed with a complex electronic quantity control of fuel. The pressure control in the high pressure area is carried out in this condition then via a mechanical pressure control device which is integrated into the high-pressure pump. The pressure control device is arranged hydraulically between the low-pressure region and the high-pressure region. Upon reaching a pre-adjustable opening pressure of the pressure control device, the unused amount of fuel from the high pressure area is returned to the low pressure area. As a result, an at least substantially constant pressure on the high-pressure side arises during operation of the internal combustion engine.

In a first development, it is proposed that the mechanical pressure control device comprises a mechanical pressure control valve, in particular a mechanical, for example, spring-loaded check valve. Mechanical pressure control valves are relatively simple, reliable and therefore inexpensive. This especially applies to check valves. Such also builds extremely small and is therefore easily integrated into the high-pressure fuel pump.

It is particularly advantageous if upstream of a valve element of the pressure-regulating device, a mechanical throttle is arranged upstream, so that negative effects on the control behavior in the fuel rail, especially when using single-cylinder fuel pumps, due to unwanted pressure pulsations of the high-pressure pump can be reduced. This reduces wear of the pressure regulating valve. The throttle may be formed as a separate throttle element or other cross-sectional constriction in a high pressure side inlet channel, a valve seat body or a receiving opening in the pump housing.

It is further provided that the pressure control valve is arranged eccentrically in the pump housing of the high-pressure fuel pump in a bore, and that optionally also a connection bore is arranged eccentrically from the pressure regulating valve to the high-pressure region. The central central region in the pump housing is known to be reserved for the actual pump functions of the high-pressure fuel pump. In the off-center area, however, there is enough room to integrate the pressure control function. This makes the high-pressure fuel pump to a very effective and compact structure. In addition, this makes the machining of the pump housing easier.

Furthermore, it is proposed that a limit pressure in the high-pressure region is established by a valve spring and / or a sealing diameter between valve element and valve seat of the pressure regulating device. This means that in the design of the pressure control device, and possibly during assembly of the high-pressure fuel pump, the limit pressure can be precisely adjusted. So it requires no adjustment to the manufactured or already installed in a motor vehicle fuel high-pressure pump. In addition, it is proposed that the pressure control device has a cartridge-like valve housing. Thus, the pressure control device can be manufactured and adjusted as a separate module and then added to the pump housing and, for example, held by a pressure between the sleeve and the pump housing. The adjustment of the function of the pressure control valve is easier because among other things, with a hydraulic adjustment of the opening pressure, the pump housing does not have to be cleaned for further assembly steps. In addition, the pump housing is not a reject part in a misadjustment.

It is also advantageous if the inlet valve is arranged coaxially with the pump piston of the high-pressure fuel pump. This makes it possible to achieve a high degree of delivery of fuel from the low-pressure region, which is further enhanced if, between a pressure damper of the high-pressure fuel pump and the inlet valve, the diameter of the corresponding connection bore is relatively large with respect to the opening of the inlet valve.

Brief description of the figures

Figur 1

eine schematische Darstellung eines Kraftstoff-Systems mit einer Kraftstoff-Hochdruckpumpe;

Figur 2

eine perspektivische Ansicht der Kraftstoff-Hochdruckpumpe von Figur 1;

Figur 3

einen teilweisen Längsschnitt durch die Kraftstoff-Hochdruckpumpe aus Figur 1 mit einem geschnittenen Einlassbereich;

Figur 4

einen Längsschnitt der Kraftstoff-Hochdruckpumpe aus Figur 1 mit einem geschnittenen Auslassbereich;

Figur 5

einen Längsschnitt der Kraftstoff-Hochdruckpumpe aus Figur 1 mit einem geschnittenen Druckregelventil (Schnittebene V-V in Figur 6);

Figur 6

einen Querschnitt durch die Kraftstoff-Hochdruckpumpe aus Figur 1; und

Figur 7

eine Darstellung ähnlich Figur 5 einer Variante der Kraftstoff-Hochdruckpumpe aus Figur 2.

Hereinafter, exemplary embodiments of the invention will be explained by way of example with reference to FIGS. Show it:

FIG. 1

a schematic representation of a fuel system with a high-pressure fuel pump;

FIG. 2

a perspective view of the high-pressure fuel pump of FIG. 1 ;

FIG. 3

a partial longitudinal section through the fuel high-pressure pump FIG. 1 with a cut inlet area;

FIG. 4

a longitudinal section of the high-pressure fuel pump FIG. 1 with a cut outlet area;

FIG. 5

a longitudinal section of the high-pressure fuel pump FIG. 1 with a cut pressure control valve (sectional plane VV in FIG. 6 );

FIG. 6

a cross section through the high-pressure fuel pump FIG. 1 ; and

FIG. 7

a representation similar FIG. 5 a variant of the high-pressure fuel pump FIG. 2 ,

Detailed description

Based on FIG. 1 The structure and general function of the high-pressure fuel pump according to the invention are explained in principle. FIG. 1 shows a schematic representation of a fuel system 8 for an internal combustion engine (not shown) with a high-pressure fuel pump 10. The fuel system is, as will be explained, in an in FIG. 1 subdivided low-pressure region 12 shown on the left hand side and a high pressure region 14 shown on the right hand side. A pre-feed pump 16 arranged in the low-pressure region 12 pumps fuel from a fuel reservoir 18 via a low-pressure line 20 with a prefeed pressure to an inlet connection 22 of the high-pressure fuel pump 10. In the high-pressure fuel pump 10, a filter 24 and a pressure damper 26 are arranged in the low-pressure region 12. The pressure damper 26 dampens pulsations arising in the high-pressure fuel pump 10 on the low-pressure side and ensures a high delivery rate even with high numbers of rotations and cams.

Via an inlet valve 28, the fuel is sucked into a working chamber 30 of the high-pressure fuel pump 10. The volume of the working space 30 depends on the position of a pump piston 32 in a pump cylinder 34. During a downward movement of the pump piston 32, the working space 30 is increased, whereby fuel is sucked. During the upward movement of the pump piston 32, the fuel is highly compressed and conveyed via an outlet valve 36 and an outlet connection 38 belonging to the high-pressure region 14 via a high-pressure line 40 into a rail 42. To the rail 42 injectors 44 are connected, which inject the fuel directly into combustion chambers 46 of the internal combustion engine.

The pump piston 32 is driven by a cam 48, which is driven by the internal combustion engine - for example via a cam or crankshaft (not shown). The cam 48 may also be part of the cam or crankshaft. A sealing of the pump piston 32 to the cam 48 via a sealing element 50. A piston leakage, which arises in the gap between the pump piston 32 and the pump cylinder 34 is returned via a return line 52 in the low pressure region 12.

Since in normal operation the delivery rate of the pump piston 32 is greater than the injected fuel quantity, an unused fuel quantity on the high-pressure side 14 is returned to the low-pressure region 12 via a purely mechanically operating pressure regulating valve 54. The pressure in the fuel manifold 42 thus substantially corresponds to the opening pressure of the pressure regulating valve 54.

Even in the high-pressure region 14, in particular when using single-cylinder pumps, pulsations occur. These pulsations could adversely affect the pressure control function in the rail 42. For decoupling, a throttle 56 is arranged hydraulically in front of the pressure regulating valve 54, whereby the pulsations before the pressure regulating valve 54 and its wear are reduced.

The following figures show the structure of the high-pressure fuel pump 10 in perspective or sectional views more in detail. It should be noted that for simplicity and clarity, not all components are provided with reference numerals in all figures.

FIG. 2 shows the high-pressure fuel pump 10 in a perspective view. The inlet connection 22 (low-pressure region 12) and the outlet connection 38 (high-pressure region 14) are arranged on a pump housing 58. In the inlet pipe 22, a filter 64 is integrated. Furthermore, the high-pressure fuel pump 10 comprises an inwardly dented cover 66 and a flange plate 68 for fastening the high-pressure fuel pump 10, for example, to a cylinder head of the internal combustion engine. Both parts 66 and 68 are fixedly connected to the pump housing 58. The pump piston 32 projects out of the pump housing 58 down. A piston spring 70 is supported on the one hand on a spring plate 72 which is fixedly connected to the pump piston 32, and on the other hand (not visible) on the pump housing 58 from. The force of the piston spring 70 is thus introduced via the spring plate 72 in the pump piston 32. This ensures during operation that the pump piston 32 always follows the cam contour.

How out FIG. 3 shows the inlet port 22 is connected to the filter 64 via a to a longitudinal axis 73 of the pump housing 58 eccentric bore 74 with a lying below the cover 66 receiving space (no reference numeral) for the pressure damper 26. The receiving space is in turn connectable to the pump working chamber 30 via two bore sections 78 and 80 coaxial with the pump housing 58 and the inlet valve 28. The pump piston 32 is displaceably mounted in a cylinder liner 82. During a suction phase of the pump piston 32, the fuel passes through the holes 78 and 80 and the inlet valve 28 into the pump working space 30. As out FIG. 4 As can be seen, the pump working chamber 30 and the outlet valve 36 are hydraulically connected via a bore 88 in the pump housing 58 with each other. From the Figures 5 and 6 It can be seen that the pressure control valve 54 is arranged eccentrically in the pump housing 58 in a bore 90 in parallel to the longitudinal axis 73. The cutting plane of FIG. 5 So it is not centered, but is spaced from the longitudinal axis 73. High pressure side, the pressure regulating valve 54 is connected via a spaced from the longitudinal axis 73 bore 92 with the outlet valve 36. On the outlet side, the pressure regulating valve 54 is connected via the bore 90 with the receiving space for the pressure damper 26. The pressure regulating valve 54 includes a valve seat (not numbered) on a valve seat body 94 with an inlet bore 95, a ball valve body 96, a spring guide 98, a valve spring 100 and a spring holder 102nd

The valve seat body 94 is firmly anchored, for example via a pressure in the bore 90. Via the spring guide 98, the valve spring 100 pushes the valve body 96 into the valve seat. In FIG. 5 the valve body is spherical. Depending on the spring force and sealing diameter between valve body 96 and valve seat 94 results in a defined opening pressure. At the top in FIG. 5 the valve spring 100 is supported on the spring holder 102. The spring holder 102 is in turn firmly anchored in the bore 90 (for example via a pressure). During assembly of the pressure regulating valve 54, the opening pressure is set via the press-in path of the spring holder 102.

The high-pressure fuel pump 10 operates as follows: During a downward movement of the pump piston 32 ("suction stroke"), fuel is injected via the inlet valve 28 into the working space 30. During an upward movement ("delivery stroke"), the fuel in the working space 30 is compressed and conveyed via the outlet valve 36 into the high-pressure line 40. Exceeds the pressure in the high pressure region 14, the limit pressure of the pressure control valve 54, this opens by the valve body 96 lifts off the valve seat, so that fuel can flow into the receiving space of the pressure damper 26 and thus in the low pressure region 12. If the pressure in the high-pressure region 14 drops below the limiting pressure of the pressure regulating valve 54, this closes again. In this way, the pressure in the high-pressure region 14 is kept substantially constant, namely at the limit pressure or opening pressure of the pressure regulating valve 54.

FIG. 7 shows a variant of the high-pressure fuel pump 10. It is true that such elements and areas that have equivalent functions to previously described elements and Beereichen, carry the same reference numerals and are not explained again.

In the alternative variant shown, the pressure regulating valve 54 is realized as a cartridge solution. The assembly of the pressure control valve 54 and the setting of the opening pressure can be done outside of the pump housing 58 here. The valve seat body 94 is inserted into a sleeve 104 and held, for example via a pressure. After assembly of the valve body 96, the spring guide 98 and the valve spring 100 and the spring holder 102 is inserted into the sleeve 104. Again, the spring force and thus the opening pressure is adjusted by the position of the spring holder 102. The spring holder 102 may, as in FIG. 7 shown, are screwed into the sleeve 104. As an alternative to the screw solution, pressing is also possible. After the pressure regulating valve 54 is mounted and is set, it is assembled as an assembly in the pump housing 58 and held for example via a pressure between the sleeve 104 and the pump housing 58.

At the in FIG. 7 shown variant of the high-pressure fuel pump 10, a throttle 56 is further positioned in the bore 92. It is also conceivable to arrange the throttle 56 in the bore 90. As an alternative to the throttle 56, the inlet bore 95 can also have a reduced cross-section in some areas in the valve seat body 94, as a result of which a throttling function is likewise achieved.

Claims (11)

1. High pressure fuel pump (10) for an internal combustion engine with direct injection, having a pump housing (58), an inlet valve (28), an outlet valve (36), a pressure damper (26), an inlet-side low pressure region (12) and an outlet-side high pressure region (14), characterized in that the high pressure fuel pump (10) has a purely mechanical pressure control device (54) for controlling a constant pressure in the high pressure region (14), in that the pressure control device (54) has a valve seat, a valve seat body (94) with an inflow bore (95), a spherical ball valve body (96), a spring guide (98), a valve spring (100) and a spring holder (102), in that an inlet of the pressure control device (54) is connected to the high pressure region (14) of the high pressure fuel pump (10), and in that an outlet of the pressure control device (54) is connected to a receiving space of the pressure damper (26), and in that the high pressure fuel pump has a pump housing (58), in that a cover (66) is connected fixedly to the pump housing (58), in that a receiving space of the pressure damper (26) lies below the cover (66), in that an inlet stub (22) is connected via a bore (74) which is parallel and eccentric with respect to a longitudinal axis (73) of the pump housing (58) to the receiving space for the pressure damper (26), which receiving space lies below the cover (66), and in that the receiving space is connected via the inlet valve (28) to the pump working space (30) and the pressure control device (54) is arranged in the pump housing (58) eccentrically in a bore (90) which serves as receiving opening, parallel to the longitudinal axis (73) of the pump housing (58).
2. High pressure fuel pump (10) according to Claim 1, characterized in that the mechanical pressure control device comprises a mechanical pressure control valve, in particular a mechanical non-return valve (54).
3. High pressure fuel pump (10) according to Claim 1 or 2, characterized in that a throttle (56) is arranged upstream of a valve element (54) of the pressure control device (54).
4. High pressure fuel pump (10) according to Claim 3, characterized in that the throttle (56) is configured in a valve seat housing of the pressure control valve (54) and/or a connecting bore (92) in the pump housing (58) for the pressure control device (54) and/or an inflow channel to the pressure control device (54).
5. High pressure fuel pump (10) according to one of the preceding claims, characterized in that the pressure control device (54) is arranged in the cylindrical pump housing (58) in the receiving opening (90) which is arranged offset with respect to the longitudinal axis (73) of the pump housing (58).
6. High pressure fuel pump (10) according to one of the preceding claims, characterized in that a connecting bore (92) which runs transversely with respect to the longitudinal axis (73) of the pump housing (58) from the pressure control device (54) to the high pressure region (14) is spaced apart from the longitudinal axis (73).
7. High pressure fuel pump (10) according to one of the preceding claims, characterized in that in the case of the pressure control device (54), by way of the valve spring (100) and/or a sealing diameter between the valve element (96) and the valve seat (94), a limit pressure is fixed in the high pressure region (14).
8. High pressure fuel pump (10) according to one of the preceding claims, characterized in that the pressure control device (54) has a cartridge-like valve housing (104) which is inserted into the receptacle opening (90) of the pump housing (58), preferably is pressed into said receiving opening (90).
9. High pressure fuel pump (10) according to one of the preceding claims, characterized in that the inlet valve (28) is arranged coaxially with respect to a pump piston (32) of the high pressure fuel pump (10).
10. High pressure fuel pump (10) according to one of the preceding claims, characterized in that the pressure control device (54) is arranged parallel with respect to a pump piston (32) of the high pressure fuel pump (10) in the receiving opening (90) of the pump housing (58).
11. High pressure fuel pump (10) according to Claim 10, characterized in that the receiving opening (90) is connected to the high pressure region (14) of the high pressure fuel pump (10) via a connecting bore (92).

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