WO2007141058A1

WO2007141058A1 - Fluid pump having a crank mechanism

Info

Publication number: WO2007141058A1
Application number: PCT/EP2007/052491
Authority: WO
Inventors: Wolfgang Bloching; Ümit Dilalan; Mario Köhler; Stephan Notzon
Original assignee: Continental Automotive Gmbh
Priority date: 2006-06-06
Filing date: 2007-03-16
Publication date: 2007-12-13
Also published as: DE102006026220A1; DE102006026220B4

Abstract

The invention relates to a fluid pump, in particular a high-pressure fuel pump for injection systems, having a pump element (12) which is guided in a pump housing for the to and fro movement (14) in the direction of a pump-element axis (16) and can be driven via a crank mechanism (20, 22, 24, 28) by means of a drive element (18), for example a crosstail, which is guided in the direction of the pump-element axis (16). In order to influence the profile of the transverse force which occurs on the drive element (18) during the cyclical operation of the crank mechanism, an 'oblique position' of the crank mechanism (20, 22, 24, 28) is provided according to the invention by an offset of the articulation point (20) of the connecting rod (22) on the drive element (18) with regard to the pump-element axis (16). In contrast with known pumps, this results in asymmetrical transverse-force characteristics with regard to the two pump stroke directions. This asymmetry can be used, in particular, to reduce friction-induced wear.

Description

description

Fluid pump with crank mechanism

The present invention relates to a fluid pump, in particular ^¬ high-pressure fuel pump for injection systems of internal combustion engines, according to the preamble of claim 1.

Such a fluid pump is known, for example, from DE 10 2004 048 714 A1 and comprises a pumping element in the form of a pump piston, which is guided for reciprocating movement in the direction of a pump element axis in a pump housing and is connected in this direction in a form-fitting manner with a so-called crosshead. which is also guided in the direction of the pump element axis in the pump housing and by means of which the pump piston can be driven. To drive the crosshead, a connecting rod is provided, which is articulated on the one hand to an eccentric portion of a rotationally driven about an axis of rotation eccentric shaft and on the other hand on the crosshead. The known pump can be referred to as a radial piston pump with a crank mechanism, the crank mechanism being formed by the rotationally driven eccentric shaft with eccentric section, the connecting rod and the crosshead. By using a separately guided crosshead advantageous lateral forces, d. H. orthogonal forces acting on the pump element axis, from

Pump piston (pumping element) kept away or at least reduced.

However, it has been found to be disadvantageous that derar- term transverse forces are exerted in the pump operating on the crosshead what high beanspruch ^¬ especially for relatively te pumps such. B. a high pressure fuel pump problemati- is table. Tends to increase such transverse forces Rei ^¬ environment and thus reduce the life of the pump.

It is an object of the present invention to influence the course of the on ^¬ operating organ (z. B. Phillips) in cyclic operation of the crank mechanism transverse force occurring in a fluid pump of the type mentioned, Example ^¬ as to reduce a friction-induced wear.

This object is achieved by a fluid pump with the shopping ^¬ paint of claim 1. The dependent claims relate to advantageous further developments of the invention.

The fluid pump according to the invention is characterized in that the articulation point of the connecting rod is offset on the drive element bezüg ^¬ Lich the pumping element axis. This offset results in that an orthogonal to the axis of rotation extending connecting line between the axis of rotation and the Anlenkungs ^{¬ point of} the connecting rod on the drive member with respect to the Pumpele- ment axis is tilted.

In contrast to the known radial piston pump, in which the mentioned connection line is provided parallel or coaxial to Pumpele ^¬ mentachse and thus a "symmetrical transverse force characteristic" for the two stroke directions of

Pumping element results in the lateral force characteristic of the pump according to the invention is asymmetrical with respect to these two pump strokes. This asymmetry is particularly suited to reduced copy ^¬ tion of friction related wear. The transverse force characteristic or the degree of asymmetry of these

Characteristic can be set within certain limits by the concrete choice of the geometric conditions on the crank ^mechanism . The invention can be used very advantageously for fuel pumps, in particular high-pressure fuel pumps for injection systems of internal combustion engines. In particular, comparatively high-pressure high-pressure fuel pumps for accumulator injection systems (eg "common rail") are to be considered here. Delivery pressures of such high-pressure fuel pumps are often in the order of about 2000 bar or more, so that in these applications special demands are placed on the reliability and smoothness of moving in pump operation pump components.

The pumping element can be formed in a manner known per se by a pump piston or pumping plunger which reciprocates with a cylindrical circumferential surface in a cylindrical section of a pump working chamber.

The ends of the connecting rod can be guided to ^¬ means of a bolt on the eccentric portion of the eccentric shaft or the drive member respectively. Each such bolt can enforce in a conventional manner one of two so-called Pleuelaugen the connecting rod. The eccentric shaft side bolt can hereby z. B. be formed by the eccentric section itself.

In a preferred embodiment it is provided that the drive member is formed separately from the pumping element, such as a crosshead as described in the above-mentioned DE 10 2004 048 714 Al. By means of such a construction can be achieved by the leadership of the drive member in the direction of

Pump element axis on the pump element acting shear forces ver ^¬ avoid. A crosshead can z. B. in a coaxial with the pump working space opening in the pump housing and a NEN by means of two plain bearing bushes mounted crosshead bolts, from which a middle bolt section passes through a connecting rod eye. Alternatively or additionally, the connecting rod eye may be provided with a plain bearing bush and / or be provided instead of a sliding bearing a rolling bearing.

The pumping element may, for. B. having a pump element, which is at least in the direction of the pump element axis positively connected to a separate drive member (crosshead) or a drive member hingedly connected to the corresponding connecting rod end bolt (eg., Phillips bolt) is connected.

In a development of the invention, it is provided that the axis of rotation of the eccentric shaft is offset with respect to the pump element axis. Such an offset can also be used to achieve the aforementioned oblique position of an orthogonal connection line between the axis of rotation and the point of articulation of the connecting rod on the drive element with respect to the pump element axis and thus the associated advantages. In a particularly advantageous embodiment of this development, it is provided that the articulation point of the connecting rod on the drive member on the one hand and the axis of rotation of the eccentric shaft on the other hand are offset in different directions with respect to the pump element axis. In this case, the two offsets add up to a certain extent to create a particularly large, yet space-saving inclination.

For many fluid pumps, in particular z. B. common high-pressure fuel pumps for injection systems of internal combustion engines, the pumping element by the fluid in question in the direction of the pumping element axis for the two Pumpelementhub- strained differently. In the case of the radial piston pump according to the abovementioned DE 10 2004 048 714 A1, the load of the pumping element acting in the direction of the pump element axis for the "pumping stroke" is substantially greater than for the "suction stroke".

In a particularly preferred with regard to the reduction of wear embodiment, the inclined position is provided such is that, compared to an embodiment without inclination reduces the force acting on the drive member intermediate and / or ma ^¬ ximum lateral force during that Pumpelementhubs, greater load which the pumping element. In general, the more incriminating pump element stroke will be the "pumping stroke" in which the fluid to be pumped is compressed by the pumping element in the working space or expelled from the working space. In this embodiment, lateral forces can not only on the drive member but also z. B. on the pumping element and / or the guides of these components in the pump housing can be advantageously reduced.

In the pump according to the invention one and the same eccentric shaft, possibly also the same eccentric section, oh ^¬ ne further be provided for actuating a plurality of connecting rods with respective pumping element ("multi-cylinder pump").

The invention will be described below with reference to Ausführungsbei ^¬ games with reference to the accompanying drawings. They show:

1 is a representation for illustrating a crank mechanism of a fluid pump with inclined position ei ^¬ ner connecting line between a Exzenterwel ^¬ lenachse and a Pleuelanlenkungsstelle to an a pumping element or a drive element connected to the pumping element,

FIG. 2 is an illustration for illustrating an offset of a Pleuelanlenkungsstelle on a

Crosshead with respect to a pump element axis, and

Fig. 3 shows the course of a pumping element or drive ^¬ organ for the crank mechanism of FIG. 1 acting lateral force as a function of a Winkelstel ^¬ ment of the crank mechanism during the pumping stroke.

Fig. 1 illustrates some understanding the OF INVENTION ^¬ dung essential components of a fuel pump having a pump piston 12, which for reciprocal movement (see FIG. Arrow 14) 16 is guided pump housing (not shown) in a direction of a pumping member axis.

The length of the arrow 14 in FIG. 1 corresponds approximately to the piston stroke performed in pumping operation by the pump piston 12 between a top dead center and a bottom dead center. The top dead center of the pump piston 12 is shown in dashed lines in Fig. 1.

The top in Fig. 1 end face of the cylindrically shaped pump piston 12 defining a (not shown) working ^¬ space in per se known manner ^¬ valve via an intake valve with a low pressure fuel passage and an outlet with a high pressure fuel passage is in communication , When the piston 12 moves upwards ("pump stroke"), the fuel in the working space is conveyed via the outlet valve into a high-pressure fuel passage, whereas in the case of the opposite piston movement ("intake stroke"). hub ") new fuel from the low-pressure fuel passage is conveyed to the working space.

The pumping element axis 16 drawn in FIG. 1 extends through the center of the (here: circular) pumping element cross section.

In pump operation, the pump piston 12 is driven by a crosshead connected thereto and likewise guided in the direction of the pump element axis 16, of which in FIG. 1 only a crosshead bolt 20 is symbolized.

The cross-head bolt 20 and a therethrough defined crosshead pin axis forms a point of articulation at which an upper end of a connecting rod 22 is pivotally connected with the cross head ^¬.

The lower end of the connecting rod 22 is pivotable about a Anlenkungs- axis 24 around at an eccentric portion of an eccentric rotation axis 28 rotatably driven eccentric shaft ^¬ steered.

The eccentric shaft with the eccentric that these Ab ^¬ cut with the cross-head connecting the connecting rod 22 and the cross head itself thus forming a crank mechanism, of about the rotational axis 28 converts upon rotation of the eccentric shaft, this rotational movement to the reciprocating movement 14 of the piston 12th

During the rotation of the eccentric shaft about the axis of rotation 28 fixed relative to the pump housing, the articulation axis 24 makes a circular movement along a crank circle 30 shown in FIG. 1. In FIG. nal extending transversely to the axis of rotation 28 coordinate axes x (paral lel ^¬ to the pumping member axis 16) and y (orthogonal to the axis Pumpele ^¬ ment 16) located. In this coordinate system, the coordinates of the Anlenkungsachse 24 as x = -r cos (phi) and y = r sin (phi), where r is the distance of the Pleuellenklenkachse 24 of the Exzenterdrehachse 28 ("Kurbelradi ^¬ uss") and phi the likewise indicated in FIG. 1 angle of the hinge line 24 along the crank circle denote 30 ( ^"¬ crank angle").

A special feature of the crank mechanism is that an orthogonal to the axis of rotation 28 extending, so in the drawing ^¬ plane of Fig. 1 extending connecting line 32 between the rotation axis 28 and the upper Pleuelanlenkungsstelle forming the crosshead bolt 20 is inclined with respect to the pumping element axis 16.

In the illustrated embodiment, this oblique position is realized in that the crosshead bolt 20 is arranged offset or "deachsiert" in the y direction relative to the pump element axis 16 and the axis of rotation 28 of the eccentric shaft in the opposite direction (negative y direction) offset relative to the pump element axis 16 is.

In Fig. 1, the offset (Deachsierung) of the crosshead pin 20 with dl and the offset of the eccentric shaft 28 is designated d2.

In the illustrated example, the offset d2 is about as large as the offset dl. In general, it has been found advantageous when the ratio 61/02 is in the range of 0.5 to 1.5 (more preferably in the range of 0.5 to 1.0). Regardless, it is favorable if the "related eccentrics ty", defined as the ratio between the "overall authority ^¬ set" (between the cross-head bolt 20 and the axis of rotation 28) dl + d2 and the connecting rod 1, in the range of 0.01 to 0.1 (more preferably in the range of 0.02 to 0.08). R This particular for crank mechanisms, in which the ratio Zvi ^¬ rule crank radius and connecting rod 1 is in the range of 0.05 to 0.15.

Fig. 2 shows a concrete realization of the offset dl. From this detailed illustration, the mutual position of the crosshead bolt 20, the crosshead 18 and the Pumpkol ^¬ Ben 12 is clearer.

The connected to the pump piston 12 crosshead 18 may, for. Example, have a cylindrical circumferential surface, by means of which the crosshead 18 is slidably guided coaxially to the pump piston 12 in a Gehäuselaufbuchse. Deviating from this, the guidance of the crosshead 18 in the direction of the pumping element axis 16 could, of course, also be provided in another way, for example by guide grooves running in the pump housing in this direction, into which corresponding guide ^{sections of} the crosshead 18 engage.

In the embodiment of FIGS. 1 and 2, the inclination of the connecting line 32 between Exzenterwel ^¬ lendrehachse 28 and upper Pleuelanlenkungsstelle 20 bezüg ^¬ Lich the pumping element axis 16 is used for the purpose of reducing the wear resulting in pump operation. This advantageous effect compared to the conventional arrangement (without inclination) will be explained in more detail with reference to the diagram of FIG. FIG. 3 is a plot of the lateral force Fy acting on the crosshead bolt 20 as a function of the crankangle phi during the "pumping stroke", ie in which the pumping piston 12 is moved from its bottom dead center to its top dead center.

The piston force acting on the piston by the piston 12 to be displaced (in the negative x direction) is assumed to be 8.5 kN by way of example. Which is then in dependence on the crank angle phi depen- resultant lateral force Fy was un ^¬ ter consideration of exemplary values for the crank radius r (mm 3) and the connecting rod 1 (38 mm) determined by a simp ^¬ chen trigonometric calculation.

A transverse force curve Fy (phi), which in the conventional case, d. H. without offset (dl = d2 = 0), is shown in the figure as a transverse force curve 40 (thin line).

At the beginning of the pumping stroke (phi = 0 °), the connecting rod runs in the x direction, so that no transverse force component is generated by the piston force acting on the pump piston 12 in the negative x direction. In the further course of the pumping stroke, the connecting rod is increasingly inclined with respect to the x-direction, so that ei ^¬ ne magnitude increasing lateral force Fy is formed which in non-ferrous gativer y-direction is oriented and at phi = 90 ° Maxi ^¬ mum of about 0 , Reached 7 kN. In the second half of the pumping stroke, the angle between the Pleuelerstre- ckkung and the x-direction decreases again, so that the lateral force Fy decreases in magnitude and at phi = 180 ° again assumes the value 0. In summary, in the conventional case, a maximum lateral force of approximately 0.7 kN and an average transverse force of approximately 0.4 kN result in magnitude. For the inventive case illustrated in Fig. 1 inclined position of the connecting line hiss of the rotation axis 28 and the crosshead bolt 20, for example, dl + d2 = 1, 6 mm assumed results for the lateral force Fy of FIG. 3 for comparison drawn transverse force profile 42nd (thick Li ^¬ never). At the beginning of the pumping stroke (phi about 0 °), the connecting rod is slightly inclined relative to the x-direction so that a transverse force Fy results in the positive y-direction of about 0.4 kN. In the further course of the pumping stroke, the angle between the connecting rod and the x-direction increasingly decreases, is at a crank angle phi of about 30 ° to 0 and then changes the sign. At a crank angle of about 90 °, a local maximum of the (absolute) lateral force Fy of about 0.3 kN results again. In the second half of the pumping stroke of the lateral force Fy decreases again, is at a crank angle ^¬ phi of approximately 150 ° 0 again, and then the pumping stroke increases with the reverse ^¬ inverted sign in the last quarter again to a value of about 0.4 kN. In summary, in the case according to the invention, a maximum transverse force of about 0.4 kN and an average transverse force of about 0.2 kN result in absolute terms.

By provided according to the invention inclined position of the connecting line 32 between Exzenterdrehachse 28 and upper Pleuelanlenkungsstelle 20 thus the transverse force load on the drive member (crosshead) is reduced during the pumping stroke, which in turn brings a reduced wear and an increased life of the pump with it.

In this context it is worth mentioning that at of the inventive design of the angle of the connecting rod relative to the pumping member axis (x-direction) both in the middle and in terms of the maximum takes larger values at ^¬ in the intake stroke. However, with regard to the resulting cross-sectional force Fy not relevant in practice, since the force acting in the x direction during the intake stroke on the pump piston piston ^¬ force mostly much (about a factor of 10 ² to 10 ³ ) is lower than the corresponding piston force in the pump stroke. In other words it is in practice substantially only important to reduce the shear stress during the pumping stroke, which the inventive oblique ^¬ the connecting line 32 between rotational axis 28 and the upper point of articulation 20 positions is achieved very effectively. The associated increase in the transverse force load during the intake stroke can be accepted.

The attached give the above-described embodiment ^¬ NEN numerical values are of course merely by way of example to understand, and can be fied in practice widely ^¬ modes.

What the embodiment illustrated in the exemplary embodiment Querkraftver ^¬ ringerung in the pump stroke is concerned, so it is generally sawn vorzugt when the crank mechanism is designed such that (for a constant piston force in the x direction calculated) lateral force Fy during the pumping stroke twice the sign supporting moderately at least approximately the same change, and in particular for both directions transverse force be ^¬ maximum forces resulted animals. Preferably z. For example, the value of one of the two maximum forces within a +/- 20% interval (more preferably +/- 10% interval) is the value of the other maximum force.

Claims

claims

1. fluid pump, in particular high-pressure fuel pump for injection systems of internal combustion engines, with a pumping element (12) which led to reciprocation (14) in the direction of a pump element axis (16) in a Pumpenge ^¬ housing and by means in the direction of Pumpele ^¬ mentachse (16) guided drive member (18) is driven, and with a connecting rod (22), which hinged on one hand on an eccentric portion (24) about a rotation axis (28) rotatably driven eccentric shaft and on the other hand on the drive member (18) is

That is, the articulation parts (20) of the connecting rod (22) on the drive member (18) are offset relative to the pump element axis (16).

2. Fluid pump according to claim 1, wherein the drive member (18) is formed separately from the pumping element (12).

3. Fluid pump according to one of the preceding claims, wherein the axis of rotation (28) of the eccentric shaft with respect to the pump ^¬ element axis (16) is offset.

4. A fluid pump according to claim 3, wherein the articulation point (20) of the connecting rod (22) on the drive member (18) on the one hand and the axis of rotation (28) of the eccentric shaft on the other hand in different directions with respect to the pumping element axis (16) are offset.

5. Fluid pump according to one of the preceding claims, wherein an inclined position of an orthogonal to the axis of rotation (28) extending connecting line (32) between the axis of rotation (28) and the articulation point (20) of the connecting rod (22) on

Drive member (18) with respect to the pumping element axis (16) is provided such that compared to a version without inclination acting on the drive member (18) acting average and / or maximum lateral force (Fy) during that Pumpelementhubs, which the pumping element (12) stronger loaded.