EP1431576B1 - Piston pump - Google Patents

Description

State of the art

The invention relates to a piston pump, in particular a high-pressure fuel pump for internal combustion engines with direct injection, with a pump housing and with a quantity control valve with a valve housing.

Such a piston pump is known from DE 199 38 504 A1. In this is a single-cylinder high-pressure pump, which is used in a fuel system of an internal combustion engine and the piston can be offset from a camshaft of an internal combustion engine in a reciprocating motion. In the pump housing of the piston pump, a housing of a quantity control valve is screwed in and sealed by means of O-rings. With the quantity control valve, the flow rate of the piston pump can be adjusted.

DE 198 34 121 A1 discloses a fuel supply system of an internal combustion engine, in which also a fuel pump is used, the quantity control valve to the housing of the fuel pump is flanged.

US 6,135,735 discloses a piston pump having an inlet and an outlet valve received in a common valve cartridge. DE 101 36 705 A1 describes a piston pump with a quantity control valve which is fastened by means of screws to the housing of the piston pump.

Object of the present invention is to develop a piston pump of the type mentioned so that it works with a higher efficiency.

This object is achieved in a piston pump of the type mentioned above in that the valve housing is permanently connected to a head portion of the pump housing rigidly.

Advantages of the invention

The piston pump according to the invention operates with a higher efficiency, since it has less damage volumes. This is made possible by the rigid and non-detachable connection of the valve housing of the quantity control valve with the pump housing of the piston pump. As a result, namely, the O-ring seals can be completely eliminated, or they can at least be made simpler, smaller and more fluid-tight. The quantity control valve and the pump housing thus form an inseparable unit, which also facilitates the production of the piston pump. The advantages of the invention are particularly concise if the pump housing or at least the part to which the quantity control valve is connected, are made of steel, as this allows a particularly good seal.

Advantageous developments of the invention are in Subclaims specified.

In a first development of the piston pump according to the invention, it is proposed that the valve housing is welded to the pump housing. Such Connection between the pump housing and the valve housing is particularly fluid-tight and stabilizes on the one hand the valve housing and on the other hand, the pump housing. In addition, such a welded connection can be placed at a location which is particularly favorable in terms of the reduction of Schadvolumina.

It is also advantageous if the head portion is designed as an overall substantially flat adapter plate, and when the valve housing is connected to the adapter plate. The adapter plate and the valve housing can thus be manufactured as a unit, which simplifies the production. This especially if the adapter plate is made of steel.

In a further development, it is proposed that the quantity control valve comprises a coil part and that the valve housing is inserted from one side and the coil part from the other side into the head portion. When assembling the quantity control valve is automatically fixed to the pump housing or at the head portion.

This fixation is particularly simple and durable when the valve housing is pressed into the head portion and the coil portion is caulked with the head portion.

Another advantageous embodiment of the piston pump according to the invention is characterized in that it has a fixing portion, and that between the head portion and the fixing portion, a line part for discharging leakage fluid is clamped. This line part is easy to manufacture and fixed on the tension in a simple manner.

Analogously, it is also possible for the piston pump to have a fastening section, and for a device for damping pressure pulsations to be clamped between the head section and the fastening section. Since this device is therefore an independent component, the device for damping pressure pulsations can be optimally adapted to the requirements of the specific fuel system.

The preparation of the piston pump is facilitated if the line part and / or the device for damping pressure pulsations can be plugged, as this simple fixation of the respective parts is achieved without special tools are required.

A further advantageous embodiment is characterized in that in each case at least one crescent-shaped flow space is present between a delivery chamber and a high-pressure connection and / or a low-pressure connection in the head section. This facilitates the integration of the quantity control valve, since a complex angular orientation of the valve housing is not required.

The housings are well protected against climatic and environmental influences when the exposed areas of the valve housing and at least partially also the pump housing are molded with a plastic material in one piece. The unit made in this way can therefore be made of materials which, although not resistant to corrosion, are inexpensive and easy to process.

If the quantity control valve comprises an elongate valve element to which a stop sleeve is attached, which cooperates with at least one fixed housing stop, which also serves to guide the valve element, the stroke range of the valve element is exactly limited and achieves a high functional reliability, at the same time small size.

The switching precision of the quantity control valve and thus the precision in adjusting the delivery rate of the piston pump is improved if the quantity control valve comprises a magnetic armature, which is guided by a sleeve made of a non-magnetic material.

In the same direction aims that development in which the quantity control valve comprises an elongated valve element, which is guided by a guide plate which is pressed into a portion of the valve housing. The pressing of the guide plate is also relatively inexpensive.

It is also proposed that the quantity control valve comprises a magnet armature and a counterpole, both of which are at least partially chrome-plated. Through this layer of chromium required for the function of the quantity control valve air gap between the armature and the opposite pole is created in a simple manner. In addition, the smooth running of the armature can be improved by the chrome-plated surface.

When the piston pump comprises an inlet valve with a valve member, which can be acted upon by the valve element of the quantity control valve, form the On the other hand, the intake valve, on the one hand, and the quantity control valve, on the other hand, to a certain extent constitute a functional unit, which leads to a further reduction in the size of the piston pump and to a reduction in the damage volumes. Reference is also made to the disclosure of DE 198 34 121 A1, which is hereby expressly incorporated into the present invention.

It is particularly preferred if, when the valve member is closed, the distance between the valve element and the valve member is determined by at least one adjusting plate, which is arranged upstream of the valve member. In this development can be dispensed with a quantity control valve with a comparatively large stroke, since the gap can be set very accurately and small. As a result, a magnetic circuit design is possible, for example, no longer requires a regulated output stage. The reason for this is that no high initial current is required, with which as quickly as possible a corresponding magnetic field with high initial force is built up to bridge a correspondingly large working gap.

In the same direction aims that development of the piston pump according to the invention, in which when the valve member is closed, the distance between the valve element and valve member is determined by at least one adjusting ring, which is arranged between the valve housing and the pump housing. Such positioning is also relatively easy to implement.

Alternatively, it is possible that when the valve member is closed, the distance between the valve element and valve member by direct fixation of the measured axial Position of the quantity control valve in the pump housing is determined.

drawing

Figur 1:

eine schematische Darstellung eines Kraftstoffsystems mit einer Hochdruck-Kraftstoffpumpe;

Figur 2:

einen teilweisen Schnitt durch einen Bereich eines ersten Ausführungsbeispiels der Hochdruck-Kraftstoffpumpe von Figur 1;

Figur 3:

einen teilweisen Schnitt durch einen anderen Bereich der Hochdruck-Kraftstoffpumpe von Figur 2;

Figur 4:

eine Draufsicht auf einen Bereich der Hochdruck-Kraftstoffpumpe von Figur 2;

Figur 5:

einen teilweisen Schnitt durch einen Bereich eines zweiten Ausführungsbeispiels der Hochdruck-Kraftstoffpumpe von Figur 1;

Figur 6:

einen teilweisen Schnitt durch ein drittes Ausführungsbeispiel der Hochdruck-Kraftstoffpumpe von Figur 1; und

Figur 7:

eine Seitenansicht auf einen Bereich der Hochdruck-Kraftstoffpumpe von Figur 6.

Hereinafter, particularly preferred embodiments of the piston pump according to the invention will be explained in detail with reference to the accompanying drawings. In the drawing show:

FIG. 1:

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

FIG. 2:

a partial section through a portion of a first embodiment of the high-pressure fuel pump of Figure 1;

FIG. 3:

a partial section through another portion of the high-pressure fuel pump of Figure 2;

FIG. 4:

a plan view of a portion of the high-pressure fuel pump of Figure 2;

FIG. 5:

a partial section through a portion of a second embodiment of the high-pressure fuel pump of Figure 1;

FIG. 6:

a partial section through a third embodiment of the high-pressure fuel pump of Figure 1; and

FIG. 7:

a side view of an area of High-pressure fuel pump of Figure 6.

Description of the embodiments

An electric fuel pump ("prefeed pump") with the reference numeral 12 promotes fuel from a reservoir 14. The electric fuel pump 12 delivers the fuel to a high-pressure fuel pump 16. This is not closer to here shown manner of a camshaft of an internal combustion engine 11, to which the fuel system 10 belongs, driven.

The high-pressure fuel pump 16 compresses the fuel to a very high pressure and delivers it to a fuel rail 18 ("rail"). To this several injectors 20 are connected, which inject the fuel directly into each associated combustion chambers 22. The amount of fuel delivered by the high-pressure fuel pump 16 is adjusted by a quantity control valve 24, which is controlled by a control and regulating device 26.

The high-pressure fuel pump 16 is a 1-cylinder piston pump whose piston carries the reference numeral 28 in FIGS. 2 and 3. The piston is guided in a cylinder section 30. This is in turn connected in a manner not shown here manner with a head portion 32 fluid-tight. The cylinder portion 30 and the head portion 32 are part of a pump housing 34.

The quantity control valve 24 comprises a valve housing 36, which in turn consists of a lower part 38 and a top 40. The top 40 is also referred to as a magnetic head. Between the lower part 38 and the upper part 40, a magnetic separator ring 42 is present. It is welded to the two parts 38 and 40 (reference numeral 44). The lower part 38 of the valve housing 36 is welded to the head portion 32 of the pump housing 34 (reference numeral 46). The valve housing 36 of the quantity control valve 24 and the upper part of the head portion 32 of the pump housing 34 in FIG. 2 are encapsulated with a plastic compound 48 in a fluid-tight manner.

The quantity control valve 24 also includes a magnetic housing 50 and a solenoid 52. In the quantity control valve 24, an elongated cylindrical valve element 54 is arranged, on the upper end in Figure 2, a magnet armature 56 is pressed. The valve element 54 is guided in duplicate: on the one hand by an upper needle guide in FIG. 2, which is represented by a guide ring 58 which is firmly connected to the lower part 38 of the valve housing 36. On the other hand by a lower in Figure 2 needle guide, which is designed as a lower angled guide ring 60 which is also fixedly connected to the lower part 38 of the valve housing 36. Both guide rings 58 and 60 may, for example, be pressed into the lower part 38 of the valve housing 36.

On the valve element 54, a sleeve part 62 is pressed between the upper guide ring 58 and the lower guide ring 60, which cooperate with the two guide rings 58 and 60 in the sense of attacks. Between a radially outwardly extending circumferential annular web 64 of the sleeve part 62 and the lower Fuhrungsring 60 also a spring 66 is braced, through which the valve element 54 is pressed in Figure 2 upward when the solenoid 52 inst.

In the head portion 32 of the pump housing 34, an inlet valve 68 is housed. This comprises a valve member 70, which is pressed by a spring 72 against a valve seat 74. In the rest position of the quantity control valve 24 shown in FIG. 2, the valve element 54 is only removed by a small gap s from the valve member 70 bearing against the valve seat 74. A low-pressure inlet, which leads on to the electric fuel pump 12, carries the reference numeral 76 in FIG. 2. An outlet valve bears the reference numeral 78 and leads to a high-pressure port 79. Fluidically between the inlet valve 68, the outlet valve 78 and the piston 28 there is a delivery chamber 80 ,

FIGS. 3 and 4 show a region of the high-pressure fuel pump 16 which lies substantially below the region shown in FIG. It can be seen the pump piston 28, the cylinder portion 30, and the head portion 32 of the pump housing 34. Further, a fastening portion 82 is shown in Figure 3, with the high-pressure fuel pump 16, for example, to an engine block of the engine 11, not shown, to the fuel system 10th heard, can be attached.

In the attachment portion 82 on the one hand and in the head portion 32 on the other hand coaxial blind hole bushings 34 and 86 are present. In the blind holes 84 and 86, respectively, the end of a pipe section 88 is inserted and sealed by O-rings (without reference numeral). The lower blind hole bushing 86 communicates via a leakage channel 30 with a Druckertlastungsnut 92 in the cylinder portion 30. The blind hole bushing 86 also communicates in a manner not shown with the inlet 76. In the pipe section 88, a pressure damper 94 is present.

The structure of the high-pressure fuel pump 16 with the quantity control valve 24 is as follows:

First, the magnet armature 56 is pressed onto the valve element 54. The positioning of the magnet armature 56 relative to the valve element 54 is comparatively coarse, for example with an accuracy of only ± 0.1 mm. Subsequently, the upper guide ring 58 is pressed into the lower part 38 of the valve housing 36. Furthermore, the valve member 54 is inserted and the sleeve member 62 is pressed onto the valve member 54 (when the lower guide ring 60 is pressed to stop, the armature 56 must be previously positioned accordingly fine).

Subsequently, the spring 66 is mounted and the lower guide ring 60 so far pressed into the lower part 38 of the valve housing 36 until a desired working stroke with the valve element 54 is just possible. Now, the magnetic separator ring 42 is mounted and welded on the one hand to the lower part 38 and on the other hand to the upper part 40 of the valve housing 36. Then, the magnet housing 50 is pressed onto the lower part 38 of the valve housing 36.

Furthermore, the lower part 36 of the valve housing 36 is pressed onto the head portion 32 of the pump housing 34 and adjusted so that a desired gap between the valve element 54 and the valve member 70 of the inlet valve 68 is present. A favorable measure of such a gap is about 0.02 to 0.05 mm. Both components are then welded together and encapsulated with the plastic compound 48. For final assembly of the high pressure fuel pump 16, the head portion 32 is attached to the quantity control valve 24 to the cylinder portion 30 of the pump housing 34. For this purpose, the biting edge 116 is stamped and held under a corresponding bias.

FIG. 5 shows a region of a further exemplary embodiment of a high-pressure fuel pump 16. Such elements and regions, which have equivalent functions to elements and regions of the embodiment illustrated in FIGS. 2 to 4, bear the same reference numerals and will not be explained again in detail.

In contrast to the previous embodiment, an adjustment ring 96 is present between the lower part 38 of the valve housing 36 and the head portion 32 of the pump housing 34. By this, the axial position of the quantity control valve 24 is set relative to the high-pressure fuel pump 16. In this way, the gap s between the lower end of the valve element 54 in FIG. 5 and the valve member of the inlet valve which is not visible in FIG. 5 can be set very precisely in the quiescent state of the quantity control valve 24.

The thickness of the adjusting ring 96 is determined by measuring the distance from the bearing surface of the head portion 32 to the valve member 70 and from the bearing surface of the lower part 38 to the lower end of the valve element 54.

Furthermore, in the quantity control valve 24 shown in FIG. 5, the magnet armature 56 is coated with a chromium layer 98. The same applies to a stop plate 100 and a corresponding region of the lower part 38 of the valve housing 36, which cooperate with the magnet armature 56 in the sense of attacks. The armature 56 is guided in a guide sleeve 102 made of a non-magnetic material.

As an alternative to adjusting the gap s between the valve element 54 and the valve member 70 by means of the adjusting ring 96 can also proceed as follows:

First, the valve element 54 is driven in the unthreaded coil 52 into the lower stop in Figure 5, i. until it rests on the valve member 70, which is expediently acted upon by a device with an additional closing force during this process. Via the spring 66, the valve element 54 continues to abut the upper stop plate 100. Subsequently, the valve housing 36 is moved upward by the amount s and then welded to the pump housing 34. Due to the advance, namely by an appropriate positioning of the stop plate 100, set Magnetankerhubs is ensured that the valve element 54 is energized coil 52 assumes the correct position.

Further, the abutment position of the valve member 54 on the valve member 70 may be determined via a pneumatic pressure drop test on the valve as soon as it opens during the adjustment process. Subsequently, the valve housing 36 is again moved upwards by the amount s and then welded to the pump housing 34.

FIG. 6 shows yet another embodiment of a high-pressure fuel pump 16. Again, such elements and regions having equivalent functions to elements and portions of the above-described embodiments bear the same reference numerals and will not be explained again in detail.

The head portion 32 of the pump housing 34 is formed in the embodiment shown in Figure 6 as a substantially flat adapter plate. In these, a stepped bore 104 is present, in which the lower part 38 of the valve housing 36 is pressed in Figure 6 from below. The upper part 40 of the valve housing 36, in which the magnetic coil 52 is present, is then placed in Figure 6 from above on the adapter plate 32 and caulked with this (see Figure 7, reference numeral 105). In the adapter plate 32, the inlet 76 and the outlet 79 with the outlet valve 78 are present. The fluidic connection with the corresponding channels 106 and 108 of the quantity control valve 24 via crescent-shaped flow spaces 110 and 112 in the region of the stepped bore 104 in the adapter plate 32nd

The adjustment of the gap s between the valve element 54 of the quantity control valve 24 and the valve member 70 of the inlet valve 68 in its idle state by an annular disc-shaped adjustment plate 114 which is disposed upstream of the valve member 70 and forms the valve seat 74 in the embodiment shown in Figure 6. The adjusting plate 114 is pressed into the lower part 38 of the valve housing 36. Depending on the requirements, an adjustment plate 114 with a corresponding thickness used. The cylinder portion 30 is sealed against the adapter plate 32 by an annular biting edge 116 formed on the cylinder portion. The thereby forming annular space (without reference numeral) is connected to the inlet 76 and the pressure relief groove 92. About not shown screws, the entire bandage can be braced axially against the cylinder head of the engine.

In the high-pressure fuel pump 16 shown in FIGS. 6 and 7, all relevant connections and functional elements are present in the area of the adapter plate 32. Other installations, such as a low-pressure sensor, a pulsation damper, a pressure relief valve, etc., can be optimally easily complemented.

Claims (18)

1. Piston pump (16), in particular high-pressure fuel pump for internal combustion engines with direct injection, having a pump housing (34) and having a quantity control valve (24) having a valve housing (36), characterized in that the valve housing (36) is connected (46) in a non-releasably rigid manner to a head section (32) of the pump housing (34).
2. Piston pump (16) according to Claim 1, characterized in that the valve housing (36) is welded (46) to the pump housing (34).
3. Piston pump (16) according to either of Claims 1 and 2, characterized in that the head section (32) is configured as an adapter plate which is overall substantially planar, and in that the valve housing (36) is connected to the adapter plate (32).
4. Piston pump (16) according to Claim 3, characterized in that the quantity control valve (24) comprises a coil part (52), and in that the valve housing (36) is introduced into the head section (32) from one side, and the coil part (52) is introduced into the head section (32) from the other side.
5. Piston pump (16) according to Claim 4, characterized in that the valve housing (36) is pressed into the head section (32) and the coil part (52) is caulked with the head section (32).
6. Piston pump (16) according to one of the preceding claims, characterized in that it has a fastening section (82), and in that a line part (88) for leading away leakage fluid is clamped between the head section (32) and the fastening section (82).
7. Piston pump (16) according to one of the preceding claims, characterized in that it has a fastening section (82), and in that a device (94) for damping pressure pulses is clamped between the head section (32) and the fastening section (82).
8. Piston pump (16) according to either of claims 6 and 7, characterized in that the line part (88) and/or the device (94) for damping pressure pulses can be plugged in.
9. Piston pump (16) according to one of the preceding claims, characterized in that in each case at least one crescent-shaped flow space (110, 112) is present between a delivery space (80) and a high-pressure connection (79) and/or a low-pressure connection (76) in the head section (32).
10. Piston pump (16) according to one of the preceding claims, characterized in that the exposed regions of the valve housing (36) and at least partly also of the pump housing (34) are encapsulated in one piece with a plastic material (48) by injection moulding.
11. Piston pump (16) according to one of the preceding claims, characterized in that the quantity control valve (24) comprises an elongate valve element (54), to which a stop sleeve (62) is fastened which interacts with at least one stop (58, 60) which is fixed to the housing and at the same time serves to guide the valve element (54).
12. Piston pump (16) according to one of the preceding claims, characterized in that the quantity control valve (24) comprises a magnet armature (56) which is guided by a sleeve (102) made from a non-magnetic material.
13. Piston pump (16) according to one of the preceding claims, characterized in that the quantity control valve (24) comprises an elongate valve element (54) which is guided by a guide disc (58, 60) which is pressed into a section of the valve housing (36).
14. Piston pump (16) according to one of the preceding claims, characterized in that the quantity control valve (24) comprises a magnet armature (56) and an opposite pole which are both chrome-plated at least in regions.
15. Piston pump (16) according to one of the preceding claims, characterized in that it comprises an inlet valve (68) having a valve member (70) which can be acted on by the valve element (54) of the quantity control valve (24).
16. Piston pump (16) according to Claim 15, characterized in that, when the valve member (70) is closed, the distance between the valve element (54) and the valve member (70) is determined by at least one setting plate (114) which is arranged upstream of the valve member (70).
17. Piston pump (16) according to Claim 15, characterized in that, when the valve member (70) is closed, the distance between the valve element (54) and the valve member (70) is determined by at least one setting ring (96) which is arranged between the valve housing (36) and the pump housing (34).
18. Piston pump according to Claim 15, characterized in that, when the valve member (70) is closed, the distance between the valve element (54) and the valve member (70) is determined by direct fixing of the measured axial position of the quantity control valve (24) in the pump housing (34).

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