DE1184153B - Pump for fuel injection working with a reciprocating motion - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Class: F02f

German class: 46 c2-115 /02

Number: 1184 153

File number: B 70159 I a / 46 c2

Filing date: December 29, 1962

Opening day: December 23, 1964

The invention relates to a reciprocating motion pump for fuel injection, whose drive mechanism has rollers, which with an annular end cam cooperate, the interaction of the rollers with the elevations of the cam together the axial reciprocation of the piston of the pump is generated with a counter spring.

In known injection pumps of this type, the surface of the cam on which the rollers roll has the shape of a surface which is generated by the rotation of a straight line which rotates about the axis OO ' (see FIG. 1) of the end cam and always remains perpendicular to this axis. If the rollers rolling on such a surface are cylindrical, friction between the surface of the cam and the rollers is inevitable. In this case the circular path B on which the inner edge b of each roller runs is shorter than the circular path A on which the outer edge α of each roller runs (see FIG. 2). Therefore, if each roller rolls without friction at an intermediate point c , the trajectory of which is indicated by the dash-dotted circular line C in FIG. 2, it rolls with friction on all other circular paths on which it is in contact with the running surface of the cam, the signs of the sliding movement incidentally being opposite to those on the other side on one side of the circular line.

It has therefore already been proposed to make the end cam and the rollers conical. Through this however, the rollers are also loaded in the axial direction. At high pump pressures therefore axial thrust bearings are required on the rollers. In addition, the tapered rollers are more expensive than cylindrical rollers.

In a special case of a known spur cam gear, some of them are very small Radius having sections of the individual elevations of the face lobe ground to a Avoid breaking out of these spots.

It has also been proposed to replace the cylindrical rollers with barrel-shaped (or with a convex surface). In these devices, however, this roll form has a quick one Wear of the rollers results in all the pressure with which the rollers attach to the cam support, constantly acting on the same very narrow strip of rollers.

The aim of the invention is to provide the pressures with which the rollers are supported on the running surface of the cam to a larger area of the rollers with a reciprocating movement
working pump for fuel injection

Applicant:

Societ6 Anonyme pour! 'Exploitation of the

Procedes Chimiques et Physiques, Zug (Switzerland)

Representative:

Dr.-Ing. W. Lampert, patent attorney,

Stuttgart W, Breitscheidstrasse, 4

Named as inventor:

Pierre Etienne Bessiere, Neuilly-sur-Seine,

Seine (France)

Claimed priority:

France of January 16, 1962 (884 993)

divide and so reduce their wear and tear, and consists cjajin that the running surface of the cam and / or the device carrying the rollers are designed so that for the successive Instantaneous positions, which the rollers on the running surface of the cam during the rotation of the rollers or of the cam about the axis of the cam occupy the angle between the axis of a each roller and the generatrix of the cam with which the roller is in contact one after the other comes, change at least within a certain angular range of this rotation, the cam and / or the rollers have a convex surface.

According to a first embodiment of this characteristic, the "running surface of the cam is not." formed by a surface which is generated by a straight line which extends around the axis of the The cam rotates and always remains parallel to itself, in particular always perpendicular to the axis of rotation, but rather by a surface that is generated by rotating a straight line around the axis of the cam whose inclination with respect to this axis of rotation is variable during its rotation about this axis is, furthermore, the rollers rolling on this surface have a barrel shape (or spherical shape).

In this design, the contact area changes small extent between the cam

409759/123

and the rollers their position on the rollers, so that successively all points of the rollers the contact pressure are exposed, which considerably reduces the wear and tear on the rollers.

This first embodiment is applicable both when the rollers rotate around the axis of the Rotate the cam, which is then stationary, as well as when the axes of rotation of the rollers are stationary and the cam rotates around its axis.

According to a second embodiment of the identifier according to the invention, which in particular Applicable when the rollers rotate about the axis of the cam, the rotatable holder receives the cam a certain flexibility, so that the inclination of the axes of the rollers with respect to the Generating the cam, with which the rollers come into contact one after the other, with the Pressing changes how much the holder is exposed to during each cycle of the pump, where the surface of the rollers or the surface of the cam or both surfaces have a spherical shape to have. As a result, the position of the raceways on the cam changes with the injection pressure changes, thereby reducing the wear of the cam as each point of the same passes the role has to endure only at a certain pressure in the working chamber of the pump. The raceways therefore change according to the combinations of speed and flow rate, their Number is infinite, which significantly reduces the wear on the cam and rollers.

The invention is explained below by way of example with reference to the drawings.

Fig. 1 shows schematically in a partially axially sectioned side view of the invention Fuel injection pump;

F i g. 2 is a section along line II-II of FIG

F i g. 3 shows the cam in a section along the line III-III in FIG. 2 as well as the position of Roll at the moment in which they are in the cutting plane;

F i g. Fig. 4 is a corresponding section along the line IV-IV of Fig. 2;

F i g. 5 and 6 show another embodiment of the invention in a schematic section of the cam two different positions, which determined the rollers on this cam to two take at different times;

F i g. 7 and 8 show two variant embodiments of the embodiment shown in FIG. 5 and 6 shown embodiment;

F i g. 9 and 10 show two different embodiments in a schematic side view a crosshead used in the second embodiment of the invention.

The invention is hereinafter as applied to the injection pump of an internal combustion engine explained, e.g. B. a diesel engine or a gasoline engine.

The drive shaft 1 of the injection pump is marked with So one proportional to the speed of the shaft of the motor on which the injection pump is attached Speed driven. The shaft is mounted in the base 2 of the pump so that they are around their Axis is rotatable, but not axially displaceable. The fork-shaped head la of the shaft 1 takes as Holder of two rollers 4 formed crosshead 3 on. The rollers 4 are arranged on both sides of the head and lie against an annular stationary face cam 5, which has as many elevations as the pump piston reciprocates during a complete rotation of the Wave 1 should run.

The crosshead 3 is connected to the shaft 1 only to rotate, but can move under the action freely adjust the elevations of the cam 5 in the direction of the axis of the shaft 1. The surface of the Cam 5 forms the raceway of the rollers, which are kept constantly in contact with the cams by a spring 6. For the transmission of the and axial movements of the crosshead on the piston 7 of the pump, the latter rests with it its outer end in the form of a spherical cap 8 on a plate 9 corresponding to the shape of the crosshead 3. The spherical end 8 is pressed against the plate 9 by the spring 6, one of which End is supported on a ball bearing 10 on the body 11 of the pump, while the other end puts against a ring 12, which is pushed onto the piston and rests on a widening of the same, whereby at the same time the pressure of the Spring is transferred to the crosshead 3 and the rollers 4.

When the piston 7 is to perform not only axial reciprocations, but also a rotation around its axis, in order to fulfill the task of a distributor, the ring 12 is also useful for non-rotatable connection of the piston 7 with the crosshead. The ring 12 is then on the one hand with pins 13 which enter into holes formed in the crosshead, and on the other hand with a wedge which goes into one formed in the surface of the piston 7 Groove 14 engages.

If the piston fulfills the task of a distributor, it has z. B., as in FIG. 1 shown its upper end has a longitudinal groove 15, which one after the other during the successive Delivery strokes the various delivery lines 16 of the pump with the pressure chamber of the cylinder 17 the pump in which the piston 7 works, connects, each delivery line 16 having a specific injection nozzle feeds.

In the case of the in FIG. 1 and 2, it is assumed that four delivery lines 16 are present. As a result, the cam 5 must also have four elevations so that the rollers produce four reciprocations of the piston 7 during one complete revolution about the axis OO '.

The pressure chamber is filled with fuel to be pumped when the piston 7 is at its lower (outer) dead center is via an access channel formed in the body of the pump 11 18, a groove 19 and an axial channel 20, the groove and the axial channel in the piston 7 are trained.

The devices for changing the delivery rate of the pump are shown in FIG. 1 not shown, since they do not form the subject of the invention.

About the pressures with which the roles are attached support the running surface of the cam, distribute it over a larger area of the rollers and thus their wear to reduce, is used in the in F i g. 4 embodiment shown the tread of the Cam designed so that the generatrix of the cam, with which each roller is successively in

Contact comes while it rotates about the axis OO ' , have a variable inclination with respect to the axis of the barrel-shaped roller, this axis practically always remains perpendicular to the axis of rotation OO' of the holder 3 (Fig. 3).

3 and 4 show two sections of the cam 5, offset from one another by an angle α, along the lines III-III and IV-IV of FIG. The angle by which the generating line of the cam is inclined at the point of section III-III is an obtuse angle β, while at the point of section IV-IV the generating line of the cam is at an acute angle with respect to the axis OO ' γ is inclined. Between the two sections III-III and IV-IV, the inclination of the generatrix changes continuously so that it changes from the angle β to the angle; ■. In other words, during its rotation around OO ' around the central angle α, each roller encounters generators, the inclinations of which are constantly changing, whereby the point of contact ao differs from that with C ₁ in FIG. 3 to the point C ₂ in FIG. 4 shifts designated point. The inclinations of the generators at two diametrically opposite points of the annular cam 5 are of course opposite, and the extensions of the generators form the same angle with the axis OO ' , as can be clearly seen from FIG. 3 and 4.

The ratio between the variable inclinations of the generatrix and the radius with which the surface of the rollers is designed to be convex is expediently chosen so that the generators in the boundary inclinations form tangents to the two ends of the convex rollers. This has the consequence that the point of contact between each roller and the cam constantly moves over the entire length of each roller from α to b.

If the cam has four elevations, as assumed in the case of the pump shown in FIGS is, the angle α between the generatrix with opposite limit inclinations is preferably 90 °.

From the above it can be seen that in the embodiment of FIG. 1 to 4 the instantaneous point of contact between each roller and the surface of the cam is almost point-like so that there is no substantial friction between the cam and the roller. Furthermore, the almost punctiform contact surface shifts so that practically the entire surface of the roller takes part in the contact under pressure, which must be constantly maintained between each roller and the cam. Since the wear of the roller and the cam depends on the number of elevations on which each roller runs per second, this number in turn being a function of the speed of rotation of the crosshead 3 about the axis OO ' , it is achieved that each point of the roller at The same speed of the crosshead runs over a considerably smaller number of elevations than in the case of the known cams with a conoid surface.

According to a second embodiment of the invention, the inclination of the generatrix of the cam with respect to the axis of the rollers is not changed, as in the first embodiment, the inclination of which remains practically invariable with respect to the axis of rotation OO ' , but the inclination of the axis of the rollers changed with respect to the generating line of the cam, which can then have a constant inclination with respect to the axis of rotation OO ' .

To change the inclination of the axis of the rollers, the crosshead 3 is given a certain elasticity, so that it bends more or less according to the variable pressures which are exerted on it by the piston of the pump when the pump is working. Thus, in FIG. 5 shows the center line ZZ 'of a crosshead at the moment in which the pressure exerted by the piston on the crosshead is greatest during its delivery stroke, while FIG. 6 shows the center line ZZ 'of the same crosshead when the pressure on the pump piston is lowest during the suction stroke of the same, the deflection of ZZ' at low pressures (Fig. 6) that for high pressures (Fig. 5 ) can be opposite.

In the case of the one shown in FIG. 5 and 6, the rollers 4 have a barrel shape, while the cam 5 has a rectangular cross-section. Thanks to the elastic deformation of the crosshead, the point of contact with the cam shifts from the point c ₃ to the point C ₄ between the limit fences shown in FIGS. 5 and 6. A similar effect can be obtained by means of the elastic deformability of the crosshead if cylindrical rollers are used and the running surface of the cam 5 is given a somewhat spherical shape (see FIG. 8). The effect of this second embodiment is that the trajectories on the cam change position with the injection pressure, which reduces the wear of the cam at which each point only has to withstand the passage of the roller at a certain pressure in the working chamber of the pump. The tracks change according to the combinations of speed and flow rate, the number of which is infinite, so that the wear on the cam and the rollers is considerably reduced.

In the case of pumps working with very high pressures, the pressures between the rollers and the cam at the moment of the largest stroke (maximum load) of the piston to a proportionate large surface to distribute, expediently the surface of the cam when approaching the highest points of its elevations give a shape which corresponds to that of the surface of the rollers, d. In other words, in the case of barrel-shaped rollers, the cam is given a somewhat hollowed-out shape at this point (see Fig. 7), while in the case of rollers with straight generators (Fig. 8) the generators of the cam also get a straight shape when approaching the highest points. You get then the friction mentioned at the outset occurs between the rollers and the cam, but these occur only on a small fraction of the length of the career path (around 20%).

The (g F i. 5 and 6), the curvature of the rollers 4 (g F i. 8) or the running surface of the cam determining radius R depends on the flexibility of the crosshead, and must be chosen so that when the large deflections of the straight Generating the cam or the rollers are always tangential to the curved surface of the rollers or the cam. In any case, the radius R is always relatively large. For rolls with a large diameter

With a diameter of 12 to 25 mm, which is preferably between 16 and 18 mm, this radius is between 0.20 and 2 m, preferably between 0.5 and 1.50 m. The curvature is therefore considerably less than that shown in the drawings in which this is exaggerated for the sake of clarity. The radius of curvature R of the cam (FIG. 8) is of the same order of magnitude.

It should be noted that the radius of curvature of the spherical surface is that in the first Embodiment (Figs. 1 to 4) of the invention were used Roles expediently receives a value of the same order of magnitude as mentioned above, i.e. H. between 0.20 and 2 m, preferably between 0.5 and 1.50 m.

The elastically deformable crosshead can be designed in very different ways. Two Embodiments are shown in FIGS. 9 and 10 by way of example.

According to FIG. 9 the crosshead is formed by a certain number of elastic lamellae 21, the ends of which are fastened in holders 22 for the ends of the axles to which the rollers 4 are attached are.

As shown in Fig. 10, the crosshead is integral with the ends of the axles of the rollers it contains however, a slot 23 extending over a substantial part of its length.

The invention can be modified. In particular, the cam can only have two diametrically opposed cams Have elevations and run over as many fixed-axis rollers as there are motor cylinders, e.g. B. four roles with fixed axis for a four-cylinder engine. Furthermore, the characteristics of the above embodiments be present at the same time.

Claims (6)

Patent claims: 1. With a reciprocating motion pump for fuel injection, the drive mechanism of which has rollers which cooperate with an annular end cam, the interaction of the rollers with the lobes of the cam together with a counter spring the axial reciprocations of the piston of the pump generated, characterized in that the running surface of the cam (5) and / or the device (crosshead 3) carrying the rollers (4) are designed so that for the successive instantaneous positions which the rollers on the running surface of the cam during the rotation of the Rolls or of the cam assume around the axis of the cam (O-O '), the angles (β, γ) between the axis of each roller and the generatrix of the cam with which the roller comes into contact successively, at least within a certain one Change the angular range (α) of this rotation, the cam and / or the rollers having a spherical surface. 2. Pump according to claim 1, characterized in that the track of the cam (5) is generated by the rotation of a straight line around the axis of the cam (O-O ') , the inclination of which with respect to this axis of rotation during its rotation about this axis is variable, and that the rollers (4) rolling on this surface have a barrel shape (or a spherical shape) (Fig. 3, 4). 3. Pump according to claim 1, characterized in that the rotatable crosshead (3) of the Roles has a certain flexibility, such that the inclination of the axes of the rollers (4) with respect to the generatrix of the cam (5) with which the rollers successively contact come, with the pressures that the crosshead (3) changes during each work cycle exposed to the pump, with the surface of the rollers or the surface of the Cam or these two surfaces have a spherical shape. 4. Pump according to claim 1, characterized in that the surface of the cam (5) in near the highest points of their elevations has a shape which is similar to the surface of the Rolls adjusts so that at this point a linear contact between the rollers and the Cam arises (Fig. 7). 5. Pump according to claim 1, characterized in that the radius of curvature of the spherical surface of the rollers or the cam is between 0.20 and 2 m and preferably between 0.5 and 1.50 m. 6. Pump according to claim 1, characterized in that the crosshead (3) has one or more Has slots which extend over the entire thickness of the crosshead and transverse to lie in the direction of the axis of the pump (Fig. 9, 10). Considered publications:
German Patent Nos. 918 842, 1074 350; U.S. Patent No. 2,455,571. 1 sheet of drawings 409 759/123 12.64 © Bundesdruckerei Berlin