WO2007071661A1

WO2007071661A1 - High pressure pump with several pistons per cylinder

Info

Publication number: WO2007071661A1
Application number: PCT/EP2006/069877
Authority: WO
Inventors: Martin Keller; Sven Kessler; Dirk Jakob; Johann Egler
Original assignee: Industriehansa Consulting & Engineering Gmbh
Priority date: 2005-12-20
Filing date: 2006-12-19
Publication date: 2007-06-28

Abstract

The invention relates to a pump unit for a high pressure pump, which can have an essentially flat configuration due to a novel piston arrangement. Moreover, the invention relates to a high pressure pump (1) which is equipped with at least one inventive pump unit so that the pump can be embodied as a whole relatively compact. The pump unit comprises a cylinder (3) with a base section (14) which is configured for fitting into a working chamber (5) of the pump (1), as well as a plurality m of pistons (6). The cylinder also comprises a plurality m of piston guides (12) which penetrate the cylinder (3) in order to displaceably accommodate the plurality m of pistons (6) for carrying out the lifting movement.

Description

High pressure pump with several pistons per cylinder

Technical area

The present invention generally relates to the technical field of pump technology. In particular, the invention relates to a pump unit for a high-pressure pump, which can be designed particularly flat due to a novel piston assembly. Furthermore, the invention relates to a

High-pressure pump, which is equipped with at least one pump unit according to the invention, whereby the pump as a whole can be made relatively small construction.

Background of the invention

In the automotive industry, it is now common practice that more and more engines are equipped with an injection system, with which fuel can be injected directly into the cylinders of the engine. In particular, in the recent past, the so-called common rail method has prevailed, in which the injection timing and the injection quantity are controlled by the engine electronics. In this case, electrical signals per cylinder control an electrically actuated valve which is installed in the injector. The short distances between valve and injector result in short pressure rise times, which benefits the combustion process and its control.

In order to be able to transform the fuel to the pressure required for the injection in such injection systems, high-pressure pumps are usually used which compress the fuel to a pressure of up to 2000 bar and more. In addition to such injection pumps, high-pressure pumps are frequently used elsewhere in the automotive industry, but also in other branches of industry, in order to be able to generally transform any fluid to a working pressure. Such high-pressure pumps are well known in various designs and have the common feature that they comprise one or more high-pressure cylinder, in which a high-pressure pump piston runs as a pump element. Depending on the fuel requirement, several of these pump units are arranged in a wide variety of configurations. Thus, for example, series pumps, V-pumps, parallel running or oppositely arranged double row pumps and pumps are known in which the individual pump elements are arranged circular and radially around an eccentric shaft around.

Since such high-pressure pumps are installed, for example, for fuel supply of injection engines in an engine compartment, is often relatively little space for installation of the pump available, which is why it is often desirable to design the high-pressure pump as small as possible. Although attempts have been made to reduce the volume of such high pressure pumps by both the leadership of the piston and the hub itself was dimensioned smaller, but this approach was often not effective, since with the reduction of the stroke of course, a reduction of the pumping volume associated with went so that such modified pumps were no longer able to promote the necessary amount of fuel.

In many cases, high-pressure pumps for common-rail diesel injection systems comprise three pump units, which are arranged in a circle and radially around an eccentric shaft at an angle of 120 ° to one another already attempted to compensate for the lower pumping volume again by the pump was redesigned such that four pump units were provided instead of three pump units, which are now arranged at an angle of 90 ° to each other. However, this arrangement has the disadvantage that due to the phase angle of the individual

Pump elements, the peak drive torque of the eccentric shaft increases by about 40%, which brings a not inconsiderable reinforcement of the eccentric shaft, whereby the space gained is canceled due to the smaller stroke of the piston again.

Presentation of the invention

Based on the problems described above, which have been raised in minimizing the size of a high-pressure pump, an object of the present invention is to provide a realization which makes it possible to form a high-pressure pump less bulky.

According to a first aspect of the present invention, the object underlying the same is achieved with a pump unit comprising a cylinder and a plurality m of pistons. In contrast to known pump units thus runs in a cylinder not only a piston to perform a lifting movement; Rather, a plurality of pistons are movably arranged in a single cylinder to perform a lifting movement in the cylinder. The cylinder is designed so that it also has a plurality m of piston guides, which pass through the cylinder so that the plurality m can be accommodated on piston for performing a lifting movement displaceable in the cylinder. If a plurality m of pistons and a plurality m of piston guides are mentioned here, this naturally means that the plurality m of pistons is always the same size as the plurality m of piston guides. Due to the spatial and constructive circumstances, it has been found that a common pump unit with a correspondingly shaped cylinder can be reshaped so that it can accommodate up to seven pistons movable. On the other hand, the positive effect in terms of reducing the size can already be achieved when the cylinder receives only two pistons displaceable to perform a lifting movement.

The inventive design of a pump unit with more than one piston per cylinder can be achieved that the piston guide length can be reduced in the cylinder, which can be attributed to the fact that the piston guide length calculated approximately 2.75 times the

Piston diameter results. Since more than one piston per cylinder is provided in the inventive design of a pump unit, each individual can be reduced accordingly, so that the piston guide length in the cylinder, which is 2.75 times the piston diameter, lower and thus the cylinder as a whole flatter makes it possible, why a total equipped with such a pump unit high-pressure pump can be designed less bulky.

Although the discernible reader will recognize that the reduction of the piston diameter is accompanied by a reduction of the pumping volume, this reduction can be compensated for by providing a correspondingly larger number of pistons per cylinder. For example, pump volume should be pumped with three smaller diameter pistons can be sufficient, so the pump unit can be easily equipped with a cylinder having four piston guides, so that four pistons in the cylinder can perform a coupled, joint lifting movement, so that in comparison to the variant with three pistons again a higher pumping volume can be promoted.

Should such an increase in the number of pistons per pump unit, for whatever reason, not be feasible, it is also possible due to the inventive design of the pump unit, instead of, for example, three pump units, which are arranged offset by 120 ° to each other, four

To arrange pump units with a phase shift of 90 °, without causing the eccentric shaft would have to be dimensioned much stronger by increasing the peak drive torque. Although, mathematically speaking, the peak drive torque also increases by about 40% as a result of the pump units offset by 90 °, now not only three but four pump units are available to convey a defined pump volume so that each pump unit only has 75 % of the pumping volume originally to be pumped, which in turn means a reduction of peak driving torque to only 6% (75% of 140%) from baseline. Since the moment of resistance of the eccentric shaft whose

However diameter included in the third power (W _T = π D ^3/16), this increase results in a 6% only to a required gain of the Exzenterwellendurchmessers by approximately 2%, however, with respect to the saved space due to the reduction of the piston guides of little consequence falls.

Apart from that, instead of three, five, six or even more, but smaller pump units can be arranged, whereby even a reduction of the eccentric shaft diameter is possible. So that the individual pistons of the plurality of pistons m do not jam or run asynchronously in the execution of a common stroke movement in the cylinder, the individual piston guides of the plurality m can be arranged in the cylinder in the plan view in the cylinder, that adjacent

Piston guides uniformly the same distance from each other. As far as adjacent piston guides are mentioned, these are piston guides arranged in relation to one another, which have the smallest distance to one another. In the event that there are more than two piston guides, this means that the individual piston guides of the plurality m on

Seen in plan view piston guides are arranged so that they form the corners of a regular m-corner.

Of course, however, it is also possible to arrange a plurality of pistons in the cylinder so that they form two nested regular m-corners, with one m-corner is fitted concentrically into another regular polygonal.

So that the plurality m of piston guides can perform a common and synchronous lifting movement in the cylinder, the pump unit according to the invention further comprises a plunger, which forms a plunger bottom foot, wherein the plunger is formed as a whole to in the working space of a pump for performing a lifting movement to be arranged displaceably. The lifting movement of the plunger is transmitted to the individual pistons of the plurality of pistons by being at least indirectly coupled to the plunger bottom of the plunger, so that the pistons execute a common lifting movement together with the plunger bottom. According to a further embodiment of the pump unit according to the invention, the individual piston guides of the plurality m of piston guides pass through the cylinder in such a way that they open at a first end into the working space of the pump and open at a second end into a widened high-pressure area in the cylinder the working space of the pump and the high-pressure area of the cylinder are separated from each other by the piston running in the piston guides.

In order to further reduce the overall height, the pump unit according to the invention further comprises a low-pressure region and a plurality m of valves, wherein the low-pressure region is separated from the high-pressure regions located at the second end of the piston guide by respectively one of the plurality m of valves. The low-pressure region can be delimited, for example, by a cover to the outside, which in turn is attached to an outer portion of the cylinder.

Usually, the plungers are caused by a arranged in the engine room of the pump sliding body to the desired lifting movement. The slider performs in the engine room a combined translational movement in two directions, which is due to the fact that in one

Through hole of the slider rotates the eccentric shaft of the pump. In this way, however, the plungers are caused not only to the desired lifting movement, but also to a translational movement transverse to the lifting movement, which can cause the pistons are applied in an undesirable manner with transverse forces, which ultimately can lead to that the pistons become wedged in the piston guides. To eliminate this undesirable transverse force transmission between the plunger and the individual pistons, it is therefore desirable to decouple the plunger from the individual pistons. For this purpose, the pump unit further comprises a plurality m of power transmission elements with first and second curved, opposing areas, in which case the plunger has a specially designed plunger bottom and each piston of the plurality m of pistons projecting into the working space of the pump specially designed end face , The individual force transmission elements are interposed between the respective end faces of the pistons and the plunger bottom, for which purpose the plunger bottom forms a plurality m of oppositely curved regions in comparison to the curved regions of the force transmission element. Also, the end faces of the pistons also form oppositely curved portions, so that the force transmission elements can be arranged between the end faces of the pistons and the plunger bottom, that the first curved portion of each force transmission element with the opposite curved portion of the respective piston and the second curved portion of each power transmission element is engaged with an oppositely curved portion of the tappet cup.

By arranging the force transmission elements between the end faces of the piston and the plunger bottom a most extensive decoupling of the plunger can be achieved by the piston, so that no or only small lateral forces can be transmitted from the plunger to the individual pistons.

To achieve the best possible decoupling, the

Force transmission element, for example, formed as a ball. However, since the space available in high-pressure pumps is usually limited, the power transmission element can also be a lens-like component with it opposing spherical, concave or convex surfaces are formed, which engage with correspondingly opposite curved surfaces on the plunger bottom or on the end faces of the piston.

As already indicated above, the force transmission elements may be formed as a ball. However, since a spherical design of the power transmission elements is difficult to realize due to the small available space in most cases, the force transmission elements may be formed, for example, as biconvex lenses or as a rotationally symmetrical cutout of such a biconvex lens. Under a rotationally symmetrical section of a

Biconvex lens in this context is understood to mean a biconvex lens in which the opposite convex lens portions do not meet in a common circle, since the lens has a smaller radial extent than that the opposite convex portion could intersect in a common circle. Generally speaking, the first and second curved, opposing areas of the

Force transmission element having a convex curvature and in a corresponding manner, the oppositely curved portions of the plunger element and the piston may have a concave curvature.

A reliable decoupling of the plunger from the piston can be ensured if the first convex portion and the second convex portion of the force transmission elements, the concave portion of the piston and the concave portions of the plunger bottom are double-curved (ie arched in two directions). However, it is of course also possible to provide all curved areas only with a simple curvature, which are curved in one direction only. In order to ensure that the lateral or transverse forces transmitted by the plunger to the pistons are as small as possible and to allow the movement of the plunger element with respect to the pistons as adequate as possible, the curvature of the first convex region and the second convex region of the force transmission elements should be greater than that Curvature of the concave portion of the pistons and the concave portions of the tappet cup. The curvatures of the power transmission elements can be the same size or different sizes. Also, the curvatures of the concave portion of the piston and the concave portions of the tappet cup may be the same size or different sizes.

Although any lens-like curved surfaces on the side of the power transmission elements and on the sides of the piston or the tappet cup are used, however, good results can be achieved if both the concave portion of the piston and the concave portions of the tappet cup designed as spherical, ie spherical recesses are.

In the preceding passages, an exemplary embodiment of the power transmission elements has been described in which they are received by corresponding recesses in the plunger bottom or in the end face of the piston. Alternatively, it is of course also possible that the force transmission element has corresponding recesses or receptacles to accommodate correspondingly bulged areas at the front ends of the piston or the plunger bottom. In this case, the first and second curved, opposing areas of the power transmission elements may for example have a concave curvature, whereas the oppositely curved portions of the tappet cup and the piston rod have a convex curvature. As has already been shown above, the lifting movement of the plunger and the piston is brought about by a sliding body, which in turn is caused by an eccentric shaft to a translational movement in two directions. In this way, however, only a lifting movement of the plunger and the piston can be achieved in one direction to compress a fluid. However, to return the pistons together with the plunger from this compression position to suck new fuel, however, a restoring force must be generated, which can not be brought about with the slider. For this purpose, the pump unit according to the invention further comprises at least one spring which is supported at a first end to the foot portion of the cylinder and a second end at least indirectly on the plunger bottom to produce a restoring force for the common stroke movement of the piston and the plunger.

These springs can for example be arranged concentrically around the individual pistons so that a piston runs inside each individual helical spring. Another embodiment may for example be such that a large spring surrounds all the pistons, so that the pistons perform their lifting movement within the coil spring. Since a preferred arrangement of the pistons and the piston guides is organized such that the individual pistons or piston guides form the corners of a regular m-corner, it may be appropriate to have at least one return spring viewed in plan within the piston guides or pistons to arrange m-squares.

In order to achieve the most uniform possible application of force to the plunger, for example, four springs between the foot portion of the cylinder and a hold-down can be installed, which between the second end of the Feathers and the plunger bottom is fitted. This hold-down device may be a component having a plurality m of arms, so that the hold-down device may extend with its respective arms between the distances of the individual pistons. In this case, the individual arms of the hold-down, for example, cantilevered over the peripheral boundary of the

Extend the tappet cup, so that the above-mentioned four springs in plan view can be arranged outside of the m-corner formed by the piston guides to support on the cantilevered free ends of the blank holder. Such an arrangement may prove to be particularly useful if due to the available space, the springs can not be located inside the m-corner of the piston and also outside the area of the plunger is not enough space available to accommodate the springs.

Although a plunger usually has a continuous circumferential wall, in the present case, however, it can have interruptions, for example, at least in sections, so that the individual arms of the blank holder can extend through the interruptions. In this case, the individual springs can be arranged so that they lie with their centers of gravity outside the plunger. For example, in the case of four springs, this may mean that the hold-down has four arms which extend through the breaks in the peripheral wall of the tappet cup so that the second ends of the springs may bear against the respective arms of the hold-down.

According to a further aspect of the present invention, the object underlying the same is achieved with a high-pressure pump, which comprises a pump housing, in which an engine room for receiving an eccentric shaft and for receiving a driven by the eccentric shaft Slider is formed, which is caused by the eccentric shaft to perform a combined translational movement in two directions. Furthermore, the high-pressure pump according to the invention comprises at least one working space which extends radially outward from the engine room. In this at least one working space, a pump unit with the foot portion of its cylinder is fitted, as already described in detail in the preceding paragraphs.

According to a particular embodiment of the high-pressure pump according to the invention, the latter is designed such that four working spaces extend radially outward from the engine compartment by 90 ° outwards, in each of which a pump unit is fitted, as described above.

Brief description of the drawings

In the following the invention will be explained by way of example with reference to the accompanying drawings. It should be emphasized at this point that the embodiments of the invention shown in the figures only explain these purely by way of example and in particular should not be construed as limiting the scope of protection. It shows:

Fig. 1 shows a cross section through a known high pressure pump with three pump units;

Fig. 2a - 2c illustrates a high-pressure pump according to the invention with four

Pump units in different cross-sectional views represents;

Fig. 3 illustrates a high-pressure pump according to the invention with four

Pump units and three pistons per pump unit in different cross-sectional views;

Fig. 4 illustrates a high-pressure pump according to the invention with four

Pump units and two pistons per pump unit in different cross-sectional views;

Fig. 5 illustrates a high pressure pump according to the invention with four pump units and a piston per pump unit in different cross-sectional views; Fig. 6 illustrates the installation of a power transmission element between

Piston and plunger bottom; and

7 shows an enlarged cross-sectional view in the region of the force transmission element of FIG. 6.

Throughout the figures, like or similar elements are identified by like or corresponding reference numerals. The figures are not to scale, but can reproduce qualitative proportions.

Description of exemplary embodiments of the invention

In the following, for a better understanding of the invention, first under

Referring to Fig. 1 describes a known high-pressure pump. The pump 1 has a housing 2, in which centrally located an engine room 4 is located. From the engine room 4 from three working spaces 5 extend radially outward, in each of which a plunger 10 is arranged. Since the design of the three work spaces 5 is substantially identical, only the upper work space 5 will be discussed in detail below. In the engine room 4 is a slider or "star" 7, which is centrally provided with a through hole in which an eccentric shaft 8 is located. The eccentric shaft 8 rotates with its eccentricity in the through hole of the slider 7, whereby it is caused to perform a combined translational movement in two directions in the engine room 4, as indicated in Fig. 1 by the double arrows. As already mentioned, extending from the engine room 4 three working spaces 5 radially outward, in each of which a plunger 10 is arranged. The work spaces 5 are closed to the outside by a cylinder 3, which is fitted with its cylinder base 14 in the working space 5. In contrast to the cylinder base 14, which thus extends within the housing 2, the cylinder 3 further comprises a cylinder head 15, which lies outside the housing 2 and this closes close to the outside. Through the entire cylinder 3 passes through a through hole, which is formed in the region of the cylinder base 14 as a piston guide 12 for guiding the piston 6. The piston guide 12 thus receives the piston 6 or plunger, which is fastened on its end face on the bottom of the cup-shaped plunger 10 by suitable means. If, in the context of the present invention, plunger bottom 20 is mentioned, this is to be understood as either plunger bottom 20 itself or a transfer plate 18, which is fitted into plunger bottom 20 on the underside.

By the translational movement of the "star" 7 in the engine compartment 4 in two directions, the plunger 10 is caused to move into the working space 5, whereby, since the piston 6 is connected to the plunger 10, the piston 6 also to a lifting movement in the Working cylinder 10 is initiated. By this movement, a medium to be pumped via not shown here

Suction lines are also transported in pressure lines, not shown.

As can be seen from the known high-pressure pump of FIG. 1 shown here, it has very large or very high cylinder heads 15, so that the pump 1 as a whole is relatively bulky. However, since it is not always possible to provide the required installation space for accommodating such large high-pressure pumps, especially in the automotive industry, it would be desirable to size the pump 1 smaller, but without having to accept reductions in the amount of pumping order.

Accordingly, in contrast to the known high-pressure pump in a cylinder 3 shown in FIG. 1, the present invention proposes not only one

Run piston 6, but rather a plurality of m to arrange piston 6 for performing a lifting movement, as shown in FIGS. 2 to 4.

First, an inventive high-pressure pump 1 with four pump units according to the invention will now be explained with reference to FIGS. 2a to 2c. Again, the pump 1, a housing 2, in which centrally located an engine room 4 is located. From the engine room 4 from four working spaces 5 extend to the outside, in each of which a plunger 10 is arranged. Since the design of the four working spaces 5 is essentially identical, only the design of the upper working space 5 will be discussed in detail below. In the engine room 4 is a slider or "star" 7, which is centrally provided with a through hole in which an eccentric shaft 8 is located. The eccentric shaft 8 rotates with its eccentricity in the through hole of the slider 7, whereby it is caused to perform a combined translational movement in two directions in the engine room 4, as indicated in Fig. 2a by the double arrows.

As already mentioned, in the case of the inventive pump 1 shown here, four working spaces 5 extend radially outward from the engine compartment 4, in each of which a plunger 10 is arranged. The working chambers 5 are closed to the outside by viewed in cross-section, very flat T-shaped cylinder 3, in which four piston guides 12 are formed to four pistons in the sixth take. The pistons 6 are attached to the front side by suitable means at the bottom of the cup-shaped plunger 10 and on the transmission or sliding plate 18 by suitable means.

Due to the translational movement of the "star" 7 in the engine room in two directions, the plunger 10 is caused to a lifting movement in the working space 5, whereby, since the pistons 6 are connected to the plunger 10, the piston 6 also to a lifting movement in the working cylinder 12th be initiated. By this lifting movement, a medium to be pumped can be conveyed and pressurized, which will be discussed in more detail later.

As can be seen from Fig. 2a, the cylinder 3 in comparison to the known embodiment of a high-pressure pump according to FIG. 1, a much flatter cylinder head 15, so that the pump 1 according to the invention builds much smaller. In addition, the cylinder base 14 has a lower height, which can be attributed to the lower piston guide length. The small piston guide length and the flatter embodiment of the cylinder head 15 results from the fact that the individual pistons 6 have a smaller diameter, resulting - due to the überschläglichen calculation of the piston guide length to about 2.75 times the piston diameter - a smaller piston guide length and thus a Reduction of the height of the cylinder 3 results.

Although possibly decreases by the reduction of the individual piston diameter, the pumping rate, but this can be compensated again by the fact that a corresponding number of piston 6 is installed in the individual cylinder 3. However, should this not be enough space within the individual cylinder available, it can, as in Fig. 2a 1, a fourth pump unit is provided, so that now the four pump units are arranged at a phase offset of 90 ° to each other. As has already been explained above, however, in the embodiment according to the invention, in which the diameters of the individual pistons 6 have been reduced, there is no or only a slight increase in the diameter

Peak driving torque of the eccentric shaft 8, which is due to the fact that only 75% of the volume must be pumped by each pump unit.

With reference to FIGS. 2a to 2c, the invention

Design of the pump units with multiple pistons 6 per cylinder 3 will be described in more detail. As can be seen from FIG. 2 a, the individual cylinders 3 each have a foot section 15 with which the cylinders 3 are fitted into a respective working chamber 5 of the pump 1. As can be seen in particular in FIG. 2b, the pump unit furthermore has four pistons 6 which run in corresponding piston guides 12 which pass through the cylinder 3, so that the four pistons 6 can perform a lifting movement therein in the desired manner. Although Fig. 2b shows only four pistons 6 running in the cylinder 3, it is of course also possible to run a different number of pistons 6 in the cylinder 3, to which, of course, a correspondingly modified number of piston guides 12 are provided got to. Although the arrangement with four pistons 6 per cylinder 3 may prove advantageous, but less than four, for example two or three, or at higher Pumpfördermenge five, six or even seven pistons 6 per cylinder 3 may be provided, for example, at lower Pumpfördermenge.

As shown in FIG. 2b, the four pistons 6, when viewed in plan, are arranged to form the corner points of a square. Generally speaking the individual pistons 6 in plan view are arranged so that they form the vertices of a regular polygon.

As can further be seen from FIG. 2 a, the individual pistons 6 connect at the end to the bottom 20 of the plunger 10. Although is shown at the here

Execution form the lower side in the plunger a transmission or sliding plate 18 is used, on which the sliding body 7 slides along the underside, but it is of course also possible to form the transmission or sliding plate 18 in one piece with the plunger 10, which is why in the present invention Transmission plate 18 and sliding plate 8 is synonymous with the plunger bottom.

In order to produce the required restoring force, a plurality of springs 13 are fitted between the underside of the cylinder base 14 and the plunger 10. The springs 13 are supported only indirectly on the plunger bottom 20, since between the plunger bottom 20 and the springs 13, a so-called hold-down is inserted, its function and training will be discussed in more detail later. 2b shows the arrangement of the springs 13 in plan view, from which it can be seen that the springs 13 are not completely arranged in the region of the plunger 10. Rather, the plunger 10 has a peripheral wall, which is interrupted in sections, so that in these interruptions or completely outside the plunger 10, the springs 13 can be arranged. Since the springs 13 are thus arranged with its center of gravity substantially outside of the plunger 10, additional means are required to reliably transmit the spring force to the plunger bottom 20.

To ensure this power transmission, the previously mentioned hold-down is fitted between the ends of the springs 13 and the plunger base 20, which has a plurality of arms which extend through the interruptions in the peripheral wall of the tappet cup 10 and kragartig over protrude the plunger bottom 20, so that the springs 13 can be supported on the cantilevered projections of the hold-down. In the arrangement of the piston 6 and the springs 13 shown in Fig. 2b, the hold-down, for example, have an X-shape with four arms, which meet in the center of the four pistons 6, wherein the individual arms by the distances of the individual pistons. 6 protrude outwardly through the interruptions in the peripheral wall of the plunger 10 while standing kragartig on the plunger 10 addition, so that the individual springs 13 can be supported at the free ends of the X-shaped hold-down.

In the following, the fuel delivery and the pressurization by means of the high pressure pump according to the invention will be discussed. First, the fuel is conveyed by means of a feed pump, not shown here in a low pressure chamber 16, which is formed by a cover 9, which is externally attached to the cylinder head 15 tight. The thus formed from the lid 9 low-pressure chamber 16 is separated from the individual high-pressure chambers 16, which are formed in the cylinder head 15 by the continuation of the piston guides 12 by individual valves 21 which tightly separate the high pressure chamber 17 from the low pressure chamber 16 during the compression process of the fuel , For this purpose, the respective high pressure chamber 17 forms a conical

Cylinder seat, on which the valves 21 sealingly abut. In order to convey the fuel conveyed by the prefeed pump into the low-pressure chamber 16 into the high-pressure chamber 17, the plunger 10 together with the individual pistons 6 moves in the direction of the engine compartment 4, whereby a negative pressure is generated in the individual high-pressure chambers 17, which ultimately causes the valves 21 to do so caused to move against a spring force a little way into the individual high-pressure chambers 17, which can flow 21 between the valve seat and the valve fuel in the individual high-pressure chambers 17. As soon as the Tappet 10 moves together with the individual pistons 6 again in the direction of the individual high-pressure chambers 17, the valve 21 sets again to its associated valve seat, whereby the low-pressure chamber 16 is sealed from the high-pressure chamber 17 and the fuel now therein due to the now introduced by the eccentric Lifting can be compressed and compressed in the high-pressure chamber 17, to be finally transported in a pressure line, not shown here.

The restoring force of the individual valves 21 is generated by a spring 22, which is arranged in the low-pressure chamber 16, and is supported on the outside of the cylinder head 15 indirectly via a lower spring plate 23. On the other hand, the spring 22 is supported on an upper valve plate 24, which surrounds the shaft of the valve 21 with a conical inner circumferential surface. The valve stem is circumferentially equipped with an annular groove, in which two opposing valve keys 25 engage positively and which (outside) are also circumferentially equipped with a cone shape, which fits snugly with the inner cone-shaped peripheral surface of the upper spring plate 24. In this way, a spring pressure force can be reliably transmitted via the upper spring plate 24 to the two valve keys 25 and of these on the shaft of the valve 21.

In the following, further piston arrangements will be explained with reference to FIGS. 3 to 5. As the cross-sectional representations of these figures show, initially the fundamental structure of the high-pressure pump according to the invention does not change in contrast to the embodiment of FIG. However, as the right cross-sectional view of FIG. 3 can be seen, which shows a sectional view through one of the cylinder heads of the high-pressure pump shown in the left figure, here Cylinder head 15 only three piston guides 12, in which accordingly three pistons run 6. In a corresponding manner, the cylinder 3 of the pump shown in FIG. 4 only has two piston guides 12 in which, accordingly, only two pistons 6 run. If a piston 6 is still provided, so that finally only one piston 6 is present, one finally reaches the embodiment of a high-pressure pump 1, as shown in FIG. 5, in which only one piston 6 remains in a piston guide 12 in the cylinder 3 of the high-pressure pump 1 is running.

As the transitions between Figs. 2 and 3, 3 and 4 and 4 and 5 can be seen, the basic structure of the high-pressure pump 1 itself does not change, which means that the housing 2 with the disposed in the engine room 4 sliding body 7 together Eccentric shaft 8 remains unchanged. The individual pumps 1 of FIGS. 2 to 5 differ only in the incorporation of different pump units according to the invention, so that very different pump variants with different delivery quantities can be generated starting from one basic pump type by fitting different pump units.

To a secure seal of the high-pressure surfaces but also the

To provide low pressure surfaces available, all of the high-pressure pumps 1 shown in FIGS. 2 to 5 are equipped with a monitoring system, which allows to permanently monitor the tightness of the high and low pressure surfaces. Thus, in the sealing surfaces between the cylinder head 15 and pump housing 2 and between the sealing surfaces between the covers 9 and the cylinder heads 15 suitable detectors 26 are inserted, which are able to detect possibly leaking liquid. All of these detectors 26 are monitored by a central monitoring unit, so that any leakage in a sealing surface can be registered immediately.

Finally, the decoupling between the plungers 10 and the individual pistons 6 will be discussed, which with reference to the

Detailed illustration of Fig. 6 will be explained. Since the "star" 7 in the engine room 4 performs not only in the desired manner a vertical translational, but also a horizontal, translational movement, it slides simultaneously in the horizontal direction on the plunger 10 and at the bottom of the transfer plate 18 along, thereby the piston 6 is transmitted in a favorable manner a lateral force. In addition, such a transverse force application causes a bending moment to be applied to the pistons 6, but the pistons 6 are usually not designed for the removal thereof.

To counteract these negative effects described above, 10 transmission elements 19 are arranged between the end faces of the individual pistons 6 and the plunger bottom 20 of the plunger, as can be seen in the left figure of FIG. 6 in overview. By installing the force transmission elements 19 between the plunger bottom 20 and the end faces of the piston 6, a decoupling between the piston 6 and the plunger 10 is achieved, so that the plunger 10 can move independently of the piston 6, whereby no or only small lateral forces be transmitted.

In the following, a force transmission element 19 will be explained in more detail with reference to the detailed representation of FIG. 6 and FIG. 7. As is apparent from this, between the end face of each piston 6 and the plunger bottom 20 and the transfer plate 18 forming the plunger bottom 20, a force transmission element 19 is fitted. The power transmission element 19 comprises an upper and a lower curved portion, which face each other. In the exemplary embodiment shown, the two curved regions of the force transmission element 19 are formed convexly curved, wherein the bulges extend in two directions, so that the curved region form spherical bulges. However, the spherical ones extend

Bulges not so far radially as to be able to intersect in a common circle. Rather, the force transmission element 19 is bounded radially by a boundary, so that the force transmission element 19 is a rotationally symmetrical section of a biconvex lens. In the plunger bottom 20 and in the end face of the piston 6, curved regions are formed in opposite directions to the regions of curvature of the force transmission element 19 which in the embodiment shown form concave spherical recesses. As can be seen, the curvatures of the spherical recesses in the piston 6 and in the plunger base 20 are smaller than the curvatures of the upper and lower curved portions of the

Force transmission element 19. By this coordination of the curvatures successive can be ensured that the power transmission element 19 can rotate in the recesses of the end face of the piston 6 and in the plunger bottom 20 by a rolling motion. Since the force transmission element 19 can not automatically center in the recesses of the plunger base 20 due to its biconvex lens shape, as would be the case with a spherical shape, a centering element 11 is attached to the end face of the piston 6, which is formed, the force transmission element 19 in the Center recess of the ram bottom. In this case, the centering element 11 may for example be part of a collar shrunk onto the piston 6, which collar is connected to the transfer plate 18 by suitable means. By the interposition of the force transmission elements 19 between the end faces of the individual pistons 6 and the plunger bottom 20 can thus be applied to the plunger 10, a horizontal displacement on the slider 7 without this shift is transmitted in the form of shear forces on the piston 6, as by the interposition of the force transmission element 19 such a horizontal displacement can be at least partially compensated. It should be noted that the transfer plate 18 must be fixed to the plunger 10, which is not shown here.

LIST OF REFERENCE NUMBERS

Claims

Patent claims

A pump unit for a high-pressure pump (1), comprising: - a cylinder (3) having a foot portion (14) adapted to be fitted in a working space (5) of the pump (1); and - a plurality m of pistons (6); the cylinder (3) also having a plurality m of piston guides (12) passing through the cylinder (3) for slidably receiving the plurality m of pistons (6) for the purpose of a lifting movement.

2. Pump unit according to claim 1, wherein the plurality m of piston (6) is the same size as the plurality m of piston guides (12), wherein for m applies: m e {2, 3, 4, 5, 6, 7}.

3. Pump unit according to claim 1 or 2, wherein the individual piston guides (12) of the plurality m of piston guides (12) in plan view are arranged so that adjacent piston guides (12) uniformly the same distance from each other.

4. Pump unit according to claim 3, wherein in the case of m> 2, that the individual piston guides (12) of the plurality of m piston guides in plan view are arranged so that they form the vertices of a regular m-corner.

5. Pump unit according to claim 4, further comprising:

- A plunger (10) with a plunger bottom (18, 20), wherein the plunger (10) is adapted to be slidably disposed in the working space (5) of the pump (1) for performing a lifting movement; wherein the individual pistons (6) of the plurality of pistons (6) with the

Plunger bottom (18, 20) of the plunger (10) for performing a common lifting movement are at least indirectly coupled together.

6. Pump unit according to one of claims 3 to 5, wherein the individual piston guides (12) of the plurality of piston guides (12) pass through the cylinder (3) by at a first end in the working space (5) of the pump (1) and at a second end in a high-pressure region (17) in the cylinder (3) open.

7. Pump unit according to claim 6, further comprising:

a low pressure area (16); and

a plurality m of valves (21); wherein the low pressure region (16) of the at the second end of the piston guides (12) located high-pressure regions (17) is blocked by in each case one of the plurality m of valves (21).

8. Pump unit according to one of claims 1 to 7, further comprising:

a plurality m of force transmitting members (19) having first and second curved opposing portions, said plunger (10) having a plunger bottom (18, 20) and each individual piston

(6) of the plurality m of pistons has an end face projecting into the working space (5) of the pump (1), the plunger bottom (18, 20) forming a plurality m of oppositely curved regions, wherein also the end faces of the pistons (6) form opposite curved regions, and wherein the force transmission elements (19) are arranged between the end faces of the pistons (6) and the plunger base (20) such that the first curved region of each force transmission element (19) with the opposite curved portion of the respective piston (6) and the second curved portion of each force transmitting member (19) with an oppositely curved portion of the tappet cup (10) is engaged.

The pump unit according to claim 8, wherein the first and second curved opposing portions of the power transmission members (19) have a convex curvature and the oppositely curved portions of the tappet cup (10) and the piston (6) have a concave curvature.

10. Pump unit according to claim 9, wherein the first convex portion and the second convex portion of the force transmission elements (19), the concave portion of the piston (6) and the concave portions of the tappet cup (10) are formed double-curved.

A pump unit according to claim 9 or 10, wherein the curvature of the first convex portion and the second convex portion of the power transmission members (19) is greater than the curvature of the concave portions of the pistons (6) and the concave ones

Areas of the tappet cup (10).

12. Pump unit according to one of claims 9 to 11, wherein the concave portions of the piston (6) and the concave portions of the tappet cup (10) are formed as spherical recesses.

13. Pump unit according to one of claims 8 to 12, wherein the force transmission element elements (19) are formed as a ball.

14. Pump unit according to one of claims 8 to 13, wherein the force transmission element elements (19) are formed at least as a rotationally symmetrical section of a biconvex lens.

15. Pump unit according to one of claims 5 to 14, further comprising:

at least one spring (13) which is supported at a first end on the foot portion (14) of the cylinder (3) and at a second end at least indirectly on the plunger base (18, 20) in order for the common stroke movement of the piston ( 6) and the plunger (10) to generate a restoring force.

16. Pump unit according to claim 15, wherein at least one spring (13), viewed in plan view, is arranged within the m-corner formed by the piston guides (12).

17. A pump unit according to claim 15, wherein four springs (13) extend between the foot portion (14) of the cylinder (3) and a hold down, which is fitted between the second end of the springs (13) and the plunger bottom (18, 20) ,

18. Pump unit according to claim 17, wherein the four springs (13) in the plan view outside of the piston guides (12) formed m-corners are arranged.

19. Pump unit according to claim 15, 17 or 18, wherein the plunger (10) has a peripheral wall which at least partially has interruptions, in which the individual springs (13) are arranged so that the centers of gravity of the springs (13) are outside the plunger (10).

20. A pump unit according to claim 17, wherein the hold-down comprises four arms which extend through the breaks in the peripheral wall of the plunger (10), so that the second ends of the springs are supported on the arms of the hold-down.

21. A high pressure pump (10) comprising:

- A pump housing (2) in which an engine compartment (4) for receiving an eccentric shaft (8) is formed,

- At least one working space (5) which extends from the engine room (4) radially outwards, and

- At least one pump unit according to one of claims 1 to 20, which is fitted with the foot portion (14) of its cylinder (3) in the at least one working space (5) of the pump (1).

22. High-pressure pump according to claim 21, wherein from the engine room (4) at least four working spaces (5) radially outwardly 90 ° outwardly extend, in each of which a pump unit is fitted according to one of claims 1 to 20.