WO2007060095A1 - Improved displacement unit for a high pressure pump - Google Patents

Abstract

The invention relates to a displacement unit for a high pressure pump (1), which is provided with a specially-designed force transmitting element (19), by means of which it can be ensured that the piston rod (6) of the displacement unit does not experience undesired lateral or transverse forces during operation, as is conventional in known displacement units. For this purpose, it is proposed that the force transmitting element (19) can have a lens-like design and be arranged between the end side of the piston rod (6) and the plunger base (20).

Description

 Improved displacement unit for a high-pressure pump

TECHNICAL AREA

The present invention generally relates to the technical field of pump technology. In particular, the invention relates to a displacement unit for a high-pressure pump, which is equipped according to the invention with a specially designed power transmission element, with which it can be ensured that the piston rod of the displacement unit is different from that usual in known displacement units, no or only small lateral or transverse forces during the Operating experiences.

BACKGROUND OF THE INVENTION

The pump drive of a high-pressure pump usually comprises a pump housing, in which an engine room is formed with at least one working space. In the engine room is a slider, which is referred to in the relevant technical terminology as "star", arranged to perform in the engine room in two directions a combined translational movement in two directions. In the at least one working space at least one cup-shaped plunger is arranged with a plunger bottom to be caused by the slider in the working space to perform a lifting movement. With the plunger while a piston or a piston rod is coupled to be caused in a cylinder to a corresponding stroke movement.

The translational movement of the slider is in such

High pressure pumps usually generated by a simple crank mechanism, an eccentric or a camshaft or the like, which in a Through hole of the slider rotates. Due to the translational movement of the slider, a force is applied to the plunger via a transmission plate, which causes it, including the attached to the plunger bottom piston to said lifting movement. Since the plunger is fitted in the working space with slight running play, and since the slider performs not only a translational movement in the stroke direction of the plunger, but also a translational movement transversely thereto, the plunger tends by the application of force by the slider to tilt in the working space in the worst case even to wedge.

Unless other, very expensive intermediate components are used, the force application point of the slider thus deviates from the central axis, so that in addition to the desired lifting forces undesirable side forces are caused whereby the plunger tilts due to the running clearance in the working space (see Fig. 2). However, since the piston rod can not understand this tilting movement in its working cylinder, undesirably large edge pressures occur at the end face of the piston rod between the plunger base and a transfer plate forming the plunger bottom. In addition, caused by the tilting of the plunger high frictional forces, which cause considerable wear both on the plunger itself and on the piston rod. Ultimately, the piston rod learns by the tilt of the plunger unwanted lateral or transverse forces to the removal of which the piston rod is not designed as a rule and often make the running characteristics of the piston rod improving BeSchichtungen required.

PRESENTATION OF THE INVENTION

The invention has for its object to provide a specially designed displacement unit for a high pressure pump, through its use experiences a lower the piston rod lateral or transverse forces and on the other hand, the edge pressures on the front side of the piston rod can be reduced.

This object of the invention is achieved by a displacement unit for a high-pressure pump, which comprises a cup-shaped plunger with a plunger bottom, a piston rod with an end face and a specially designed power transmission element. In this case, the plunger is designed to be slidably disposed in a working space of the pump. The piston rod is designed to be displaceably arranged in a working cylinder of the pump or the cylinder of the pump. The plunger and the piston rod together form the displacement unit and are coupled together to perform a common lifting movement. For this purpose, the piston rod with its front side immersed in the cup-shaped cavity of the plunger and is attached to the plunger bottom indirectly via the force transmission element using suitable means. The force transmission element is thus interposed between the end face of the piston rod and the plunger bottom to counteract undesirable edge pressures. For this purpose, the force transmission element has a first curved region and a second curved region, the first curved region lying opposite the second curved region. In contrast, the plunger bottom forms an opposite to the curved portions of the force transmission element curved portion which lies in the plunger cup. In a corresponding manner, the end face of the piston rod also forms a region which is curved in the opposite direction to the curved regions of the force transmission element. If it is said here that one area is curved, whereas the other area is curved in opposite directions, this means that one curved area can be concave, for example, whereas the other area can be convex, for example. The power transmission element is arranged between the end face of the piston rod and the plunger bottom or the transfer plate forming the plunger bottom, that the first curved Region of the force transmission element with the opposite curved portion of the piston rod and the second curved portion of the force transmission element with the opposite curved portion of the tappet cup is engaged.

Due to the arrangement of the force transmission element between the end face of the piston rod and the plunger bottom decoupling of the plunger is achieved by the piston rod, so that although the plunger in its working space by a lateral application of force by the slider can tilt slightly, but not the resulting side force on the piston rod is transmitted because a decoupling of the piston rod and the plunger can be ensured by the interposition of the power transmission element. In addition, no unwanted edge pressures occur at the end face of the piston rod, since the power transmission between the plunger and the piston rod over the provided with curved portions

Power transmission element is ensured in a controlled manner.

The invention is based on the finding of Hertz on the contact of two bodies, similar to the case of ball bearings is the case. In the best case, a ball can be used as the force transmission element. However, since the space available in high-pressure pumps is usually limited, the power transmission element can be formed as a lens-like component with opposite spherical, concave or convex surfaces, which with correspondingly opposite curved surface areas on the plunger bottom or on the front side of the piston rod into engagement reaches, as indicated in Fig. 3. The maximum transferable forces can be calculated according to Hertz.

In the event that the force transmission element is formed as biconcave lens component and thus can not center automatically, can be that Center the power transmission element during assembly in the center of the center of the plunger base or the front side of the piston rod by a resilient component. When dimensioning the radii of curvature of the force transmission element, the curved portion of the end face of the piston rod and the curved portion of the plunger bottom should be taken to ensure that the respective convex curved portions have a sufficiently large curvature difference with respect to the concave curved portions of the other components to a sufficient Allow movement and force balance. In this way, as will be explained in more detail later with reference to the figures, to ensure that the plunger is less tilted, so that a better power transmission between the plunger and piston rod can be achieved in the lower side forces remain, the problem of all parts can be sustained and transmitted, which can even make coatings of the piston rod superfluous.

As already indicated above, the force transmission element may be formed as a ball. However, since a spherical formation of the force transmission element is difficult to realize due to the scarce space available, the force transmission element can be formed, for example, as a biconvex lens or as a rotationally symmetrical cutout of such a biconvex lens. A rotationally symmetrical section of a biconvex lens is understood to mean a biconvex lens in which the opposite convex lens sections do not meet in a common circle, since the lens has a smaller radial extent than that of the opposite convex areas in a common circle could cut. Generally speaking, the first and second curved, opposing regions of the force transmission element may have a convex curvature and in a corresponding manner, the oppositely curved regions of the tappet element and the piston rod have a concave curvature. Good force transmission and decoupling of the plunger from the piston can be ensured if the first convex portion and the second convex portion of the force transmission element, the concave portion of the piston rod and the concave portion of the plunger base double-curved (ie in two

Spatial directions arched) are formed. However, it is of course also possible to provide all curved areas only with a simple curvature, which are curved in one direction only.

To ensure that the lateral or transverse forces transmitted by the plunger to the piston rod are as small as possible, and to allow sufficient movement compensation of the plunger member relative to the piston rod, the curvature of the first convex portion and the second convex portion of the force transmission member should be greater than the curvature of the concave portion of the piston rod and the concave portion of the

Plunger cup. The curvatures of the force transmission element may be the same size or different sizes. Also, the curvatures of the concave portion of the piston rod and the concave portion of the tappet cup may be equal to or different in size.

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

In the preceding passages, an exemplary embodiment of the force transmission element has been described in which this is received by corresponding recesses in the tappet socket bottom or in the end face of the piston side. Alternatively, it is of course also possible in that the force transmission element has corresponding recesses or receptacles for receiving correspondingly bulged areas at the front end of the piston rod or on the plunger bottom. In this case, the first and second curved, opposite regions of the force transmission element may, for example, have a concave curvature, whereas the oppositely curved regions of the tappet cup and the piston rod have a convex curvature.

Also in this case, the first concave portion and the second concave portion of the force transmission element, the convex portion of the piston rod and the convex portion of the plunger element double arched, so curved in two spatial directions, be formed, whereas it is of course also possible, of course buckle respective curved areas of the individual components only in one spatial direction.

In order to provide an optimal power transmission as well as sufficient compensation for the movement of the plunger, care must be taken in this case too that the curvatures of the convex regions are matched to the concave regions of the force transmission element. In particular, this means that the curvature of the first concave portion and the second concave portion of the force transmitting member is smaller than the curvature of the convex portion of the piston rod and the convex portion of the tappet cup.

In contrast to the previously described first embodiment of the force transmission element, in which this was designed as a biconvex lens, the force transmission element may thus alternatively be formed as a biconcave lens to accommodate the associated convex portion of the piston rod and the convex portion of the plunger cup, which can be formed as spherical or spherical bulges. As a result of the interposition of the force transmission element according to the invention between the end face of the piston rod and the plunger base, a decoupling of these two components can thus be ensured, so that the plunger can tilt independently of the piston rod. Furthermore, the power transmission element will assume such a position in a lateral displacement of the plunger, in which the lateral or transverse force to be transmitted by the force transmission element is minimal, so that only small lateral or lateral forces are transmitted to the piston rod.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the present invention will be explained purely by way of example with reference to the accompanying drawings. The figures are merely illustrative 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 without a force transmission element;

Fig. 2 shows the pump of Figure 1, wherein the plunger are in a tilted position.

Fig. 3 shows a cross section through a high-pressure pump with a displacement unit according to the invention with a force transmission element;

Fig. 4 shows an enlarged detail of Figure 3 in the transition region between the piston rod and the plunger bottom with a biconvex force transmission element connected between them. Fig. 5 explains the function of the invention

Power transmission element of Fig. 4; and

Fig. 6 shows a transition region between a piston rod and a plunger bottom with a biconcave connected therebetween

Power transmission element.

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 Figs. 1 and 2, a known high-pressure pump is described. The pump 1 has 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 formation of the four work spaces 5 is substantially identical, only the upper work space is shown in detail. 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 passage opening 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. 2 by the double arrows.

As already mentioned, four working spaces extend radially outwards from the engine compartment 4, in each of which a tappet 10 is arranged. The Work spaces 5 are closed to the outside by a cross-sectionally T-shaped cylinder head 3, which is provided centrally with a cylinder or a cylinder bore 12. Of the cylinder 12 extends in the cylinder head 3, a suction line 13 to a suction valve 14 and a pressure line 15 to a pressure valve 16. In the cylinder 12, a piston or plunger 6 is arranged, on whose front side a collar 9 is shrunk, on which in turn a clamping or spring plate 17 engages to secure the piston 6 at the bottom of the cup-shaped plunger 10.

By the translational movement of the "star" 7 in the engine compartment 4 in two directions, the plunger 10 is caused to a lifting movement in 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 12 is initiated. By means of this lifting movement, a medium to be pumped can be conveyed via the suction line 13 into the pressure line 12.

However, since the "star" in the engine room 4 performs not only 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, whereby, as in the Fig. 2 is shown, the plunger 10 is slightly inclined in the working space 5 and tilted in the worst case. Since the piston rod 6 is connected to the plunger 10 via the spring plate 17, such a tilting of the plunger 10 causes a torque is applied to the piston rod 6, for the removal of which the piston rod 6 is usually not designed. Moreover, in the example of FIG. 2 at the right lower edge of the front side of the plunger 6 by the tilting of the plunger 10 in the transition region to the plunger bottom 20 an undesirable high edge pressure, since the piston rod 6 can not tilt as much as the Tappet 10. Ultimately, by the horizontal movement of the slider 7 lateral or transverse forces on the plunger 10th applied, which are undesirably transferred to the piston rod 6.

In order to counteract these negative effects described above, according to the invention a force transmission element 19 is arranged between the end face of the piston rod 6 and the plunger bottom 20 of the plunger 10, as can be seen in overview in FIG. Since in this case the piston 6 is not brought up to the plunger bottom 20 or the plunger bottom 20 forming transfer plate 18, the collar 9 is connected via a modified spring plate 17 with the plunger bottom 20 and the plunger bottom 20 forming transfer plate 18. By installing the force transmission element 19 between the plunger bottom 20 and the end face of the piston 6, a decoupling between the piston 6 and the plunger 10 is achieved, so that the plunger can tilt independently of the piston 6 but can also translate translationally. This can be seen in Fig. 3 by the illustrated translational displacement of the plunger 10 to the left.

In the following, the invention will be explained in more detail with reference to FIGS. 4 and 5. As shown in FIG. 4, between the end face of the piston 6 and the plunger bottom 20 or the transfer plate 18 forming the plunger bottom 20, the force transmission element 19 is fitted. The plunger 10, the piston rod 6 and the force transmission element 20 fitted in between are referred to in the context of the present invention as a displacement unit.

As can be seen from Fig. 4, the power transmission member 19 includes upper and lower curved portions which are opposed to each other. In the embodiment of Fig. 4, the two curved portions of the power transmission element are formed convexly curved, wherein the curvature extends in two directions, so that the curved portions form spherical bulges. However, the spherical extend Bulges not so far radially as to be able to intersect in a common circle. Rather, the force transmission element 19 is limited 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 bottom 20 are smaller than the curvatures of the upper and lower curved portions of the power transmission element 19. By this coordination of the curvatures successive can be ensured that the force transmission element 19 in The recesses of the end face of the piston 6 or in the plunger bottom 20 can rotate by a rolling motion, as shown in FIG. 5. Since she is the

Power transmission element 19 can not automatically center in the recess in the plunger base 20 due to its biconvex lens shape, as would be the case with a spherical shape, a funnel-shaped centering 11 is attached to the end face of the piston 6, which is formed to the force transmission element 19 in the recess to center the plunger floor 20. In this case, the centering element 11 may, for example, be part of the collar 9 shrunk onto the piston 6.

In FIG. 5, the plunger 10 has experienced a lateral force Q via the sliding body 7, as indicated in FIG. 5 by the horizontal arrow. Beside this

Side force Q learns the plunger 10 via the slider 7, a vertical working force P, which is to be transmitted to the piston 6. As long as the plunger 10 only the horizontal force component Q acts, which is the case in one of the two dead centers of the eccentric shaft 8, the plunger 10 is slightly shifted to the left, due to the arrangement of the power transmission element 19 between the Piston 6 and the plunger bottom 20 causes the power transmission element 19 along the recesses in the end face of the piston 6 and in the plunger bottom 20 rolls, so that the originally centric point of contact between the power transmission element 19 and plunger bottom 20 to the right in the points A and Touching point between the power transmission element 19 and the end face of the piston 6 to the left in the point A 'shifted.

Now, if the dead center is exceeded by the eccentric shaft 8, which leads to an increasing workforce P, an ever-increasing working force P is applied to the plunger 10, which causes the contact points A and A 'back in the direction of rotational symmetry axis in the points B and B 'relocate, so that when the worker P has reached its maximum, an approximately centric power transmission from the plunger 10 to the piston 6 can be ensured.

Finally, an alternative embodiment of the displacement unit according to the invention will be briefly described with reference to FIG. 6. In contrast to the exemplary embodiments described with reference to FIGS. 3 to 5, in this case the force-transmitting element 19 has the shape of a biconcave lens, whereas on the end face of the piston 6 and on the front side

Plunger bottom 20 convex protrusions are formed, which engage in the concave recesses in the power transmission element 19. Also in this embodiment of a displacement unit 6, 19, 10 according to the invention, it can be ensured that the plunger 9 can tilt independently of the piston rod 6, so that no or only little unwanted

Moment loads are transmitted to the piston rod 6. In addition, it can be ensured in this embodiment that by a rolling of the power transmission element 19, this aligns with an application by horizontal and vertical forces in a for the power transmission between the plunger 10 and the piston rod 6 always optimal position. This way you can the transmission of undesirable high lateral or transverse forces on the piston rod 6 and the occurrence of unwanted edge pressures excluded or at least reduced.

LIST OF REFERENCE NUMBERS

Claims

PATENT CLAIMS A high-pressure pump displacement unit comprising: a cup-shaped plunger (10) having a plunger bottom (20), the plunger (10) being adapted to be slidably disposed in a working space (5) of the pump (1); a piston rod (6) having an end face, the piston rod (6) being designed to be slidably disposed in a working cylinder (12) of the pump (1); the plunger (10) and the piston rod (6) being coupled to perform a common lifting movement, characterized in that: the displacing unit (6, 10) further comprises a force transmitting member (19) having first and second curved opposing portions, the plunger bottom (20) forms an oppositely curved region lying in the plunger cup (10), and the end face of the piston rod (6) forms an oppositely curved region, the force transmission element (19) thus being between the end face of the piston rod (6) and the plunger bottom (20) is arranged such that the first curved portion of the force transmission element (19) with the opposite curved portion of the piston rod (6) and the second curved portion of the force transmission element (19) with the opposite curved portion of the tappet cup (10) is engaged. 2. Displacement unit according to claim 1, characterized in that the first and second curved, opposite areas of the force transmission element (19) have a convex curvature and the oppositely curved portions of the tappet cup (10) and the piston rod (6) have a concave curvature. 3. displacement unit according to claim 2, characterized in that the first convex portion and the second convex portion of the force transmission element (19), the concave portion of the piston rod (6) and the concave portion of the tappet cup (10) are formed double-curved. 4. Displacement unit according to claim 2 or 3, characterized in that the curvature of the first convex portion and the second convex portion of the force transmission member (19) is greater than the curvature of the concave portion of the piston rod (6) and the concave portion of the tappet cup (10 ). 5. displacement unit according to one of claims 2 to 4, characterized in that the concave portion of the piston rod (6) and the concave portion of the tappet cup (10) are formed as spherical recesses. 6. displacement unit according to one of claims 1 to 5, characterized in that the force transmission element element (19) is designed as a ball. 7. displacement unit according to one of claims 1 to 6, characterized in that the force transmission element element (19) is designed at least as a rotationally symmetrical section of a biconvex lens. 8. Displacement unit according to claim 1, characterized in that the first and second curved, opposite areas of the force transmission element (19) have a concave curvature and the oppositely curved portions of the tappet cup (10) and the piston rod (6) have a convex curvature. 9. displacement unit according to claim 8, characterized in that the first concave portion and the second concave portion of the force transmission element (19), the convex portion of the piston rod (6) and the convex portion of the tappet cup (10) are formed double-curved. 10. Displacement unit according to claim 8 or 9, characterized in that the curvature of the first concave portion and the second concave portion of the force transmission element (19) is smaller than the curvature of the convex portion of the piston rod (6) and the convex portion of the tappet cup (10 ). 11. Displacement unit according to one of claims 8 to 10, characterized in that the convex portion of the piston rod (6) and the convex portion of the tappet cup (10) are formed as spherical bulges. 12. Displacement unit according to one of claims 1 or 8 to 11, characterized in that the force transmission element element (19) is designed as a biconcave lens.