US3433172A

US3433172A - Fuel injection pump

Info

Publication number: US3433172A
Application number: US613008A
Authority: US
Inventors: Giuseppe Sola
Original assignee: Fiat SpA
Current assignee: Fiat SpA
Priority date: 1966-02-04
Filing date: 1967-01-31
Publication date: 1969-03-18
Anticipated expiration: 1986-03-18
Also published as: NL6701643A; GB1169302A; AT298882B; DE6608714U; FR1510400A; NL130235C; CH447715A; BE693643A

Description

March 18, 1969 G. SOLA FUEL INJECTION PUMP Sheet Filed Jan. 31, 1967 March 18, 1969 G. SOLA 3,433,172

FUEL INJECTION PUMP Filed Jan. 31, 1967 Sheet 2 012 United States Patent 2,723/ 66 US. Cl. 103-154 Int. Cl. F04b 19/22, 9/04, 15/00 3 Claims ABSTRACT OF THE DISCLOSURE The pumping member of the pump is connected by a link to one arm of a beam which is rotatable about a fulcrum carried by the pump casing. The beam arms are proportioned to uninterruptedly establish contact with the periphery of the driving cam, which cam is formed with a plurality of equal lobes symmetrical in profile. Contact between the beam arms and the cam takes place either over the opposite flanks of one lobe or over the adjacent flanks of .two consecutive lobes, so that when the end of one arm is driven away from the cam axis the other is drawn towards it and vice versa.

The invention relates to fuel-injection pumps for multicylinder internal combustion engines, and more particularly to injection pumps for high-speed diesel engines of the type having a single pumping member which is arranged to distribute fuel to a plurality of cylinders.

Injection pumps having a single pumping member and a distributor are known, for instance through US. Patent No. 2,965,087, wherein the pressure stroke of the pumping member is effected by a multiple-lobe cam, the return or suction stroke of the pumping member being effected by springs. It is also known to use injection pumps of this type for feeding fuel to high-speed diesel engines which have a plurality (6, 8 or even more) of cylinders, and in such a case the cam operating the single pumping member is arranged to rotate at the same speed as the engine shaft.

Experience has shown, however, that in such arrangements the high frequency of the pressure and the suction strokes of the pump member which results from the requirement for a large number of injection pulses during each revolution, gives rise to dynamic stresses which lead to disturbances which adversely aifect the smooth operation of the reciprocating pump member.

It is an object of the present invention to provide an injection pump for a multi-cylinder internal combustion engine, more particularly an injection pump having a single pumping member for a multi-cylinder high-speed engine, which pump at least substantially obviates the abovementioned drawbacks and wherein the pumping member is capable of attaining, in its reciprocations, very high linear velocities, these velocities being achieved without the operational disturbances caused by accelerations and inherent inertia forces, and without alteration of the pattern of motion. It is a further object to ensure that the above requirements are met even with a very high rate of revolution of the operating cam.

According to these and other objects the invention resides in a fuel injection pump for a multi-cylinder internal combustion engine, more particularly a high-speed diesel engine, the pump being of the type including a single pumping member driven by a multiple-lobe cam and means for converting the oscillatory movements derived from the said cam into rectilinear reciprocatory movements and transmitting the said reciprocatory movements to the pumping member, wherein the means are without springs and that the reciprocations of the said pumping "ice member in either direction are constantly positively controlled by rotation of the said cam.

Preferably, the periphery of the cam cooperates with a beam which comprises two arms and is pivoted to the pump casing at the junction of the said arms about an axis which is parallel to the rotational axis of the cam one said arm of the beam being connected to the pumping member by the movement-converting means and each of the two arms being so shaped with respect to the cam periphery that they remain permanently in direct or indirect contact therewith during rotation thereof either with each arm on one of two opposed flanks of the said cam lobe or with each arm on one of the adjacent flanks of two consecutive cam lobes.

Advantageously, each lobe of the cam is so shaped as to be symmetrical with respect to a radial plane which bisects it.

Advantageously also, the beam and the cam are so arranged and dimensioned that, when the radial plane of symmetry of a lobe contains the rotational axis of the beam or when one of the radial planes of the cam, with respect to which the consecutive lobes are symmetrically arranged, contains the said rotational axis of the beam, the said planes constitute also the planes of symmetry of the contact points of the beam and cam.

According to one embodiment of the invention each of the arms of the beam establishes contact with the periphery of the cam via rollers which are equal in diameter and have rotational axes parallel to the rotational axis of the beam.

Preferably, the position of these rollers is such that at the stage half way along their approach stroke to or their return stroke from, the axis of the cam, the imaginary lines connecting their axes with the cam axis and lying in a plane perpendicular to the said cam axis, form an angle which equals half an angle formed by the said planes of symmetry of two consecutive cam lobes.

According to an alternative embodiment each of the two arms of the beam establishes contact with the periphery of the cam by means of a respective shoe portion, the surface of which portion that faces the cam periphery being of rounded profile.

According to a still further alternative one arm of the beam establishes contact with the periphery of the cam by means of a roller having its rotational axis parallel to the rotational axis of the beam, the other arm establishing contact by means of a shoe portion, the surface of which portion that establishes said contact with the periphery of the cam being rounded in profile.

These and other objects and advantages of the invention will be clear from the following description, given with reference to the accompanying drawings which are by way of example and in which:

FIGURE 1 is a diagrammatical side view, partly in cross section, of a portion of a pump according to the invention, which portion comprises an arrangement for operating a single pumping member with a four-lobed cam, the figure illustrating the general principles of operation of the said arrangement;

FIGURE 2 is a cross sectional view through a portion of an injection pump similar so that shown in FIGURE 1, the arrangement for operating the pumping member being shown in greater detail and in an operative position differing from that of FIGURE 1;

FIGURE 3 is a sectional view taken along line IIIIII of FIGURE 2;

FIGURE 4 is a sectional view taken along line IVIV of FIGURE 2; and

FIGURE 5 is a cross sectional view through a modified injection pump also according to the invention, in which the pump arrangement for operating the pumping member comprises a six-lobed cam.

Like parts are provided with like reference numerals throughout the figures.

With reference first to FIGURE 1, in which the bottom portion only of the pump is shown for the sake of clarity, the cam 2, which is rotatable about the axis A, will be seen to be formed with four lobes. In a plane perpendicular to the said axis A, the cam exhibits a periphery which comprises the four lobes, each said lobe being divisible, by one of four radial planes AB, AC, etc., which are separated from each other by right angles, into two lobes halves the

surfaces

3, 3 of which are symmetrical. Such planes are herein referred to for convenience as planes of symmetry and it will be evident that when the number of cam lobes is less or more than four, the angles between the said planes of symmetry of the consecutive lobes will of course differ in value from the angle between the abovementioned planes AB and AC.

Two rollers 4, 5 are provided which bear on the cam periphery, these rollers being rotatably mounted on pivots 6, 7, respectively, the respective axes D, E of which pivots and rollers extend parallel to the axis A. These pivots are supported by a beam 8 which is in turn rotatably mounted on a pivot 9 carried by the pump casing (not shown in FIGURE 1), the axis G of the pivot 9 also extending parallel to the axis A. The aforementioned arrangement is so proportioned that the angle EGD is the supplement of half the angle CAB formed between the planes of symmetry AC and AB of the two consecutive cam lobes.

When the rollers 4 and 5 are located as shown in FIGURE 1, that is to say half way along the stroke between their positions of maximum and minimum spacing from the axis A of the cam 2, the axes D and E of the rollers 4, 5, respectively, are in positions such that the angle formed between the plane extending through either the axis of D or E of a roller 4 or 5, respectively and through the axis G of the beam 8 and the plane extending through the same said axis D or E and the axis A of the cam 2, is a right angle. Similarly, the angle 5 formed between the planes extending through the axes A and D and A and E, respectively, is equal to half the angle a formed between the planes of symmetry AB and AC, that is it equals 360/2n, where n denotes the number of cam lobes.

The pivot 6 has further articulated thereto a link 10, the other end of which link is articulated, by a pivot 10a, to a slide 11 which is slidably mounted in a guide 12 secured to the pump casing. The other end of the slide 11 is connected by a yoke to the pumping member 1 to prevent axial displacements of the member with respect to the slide but to permit rotational movements of the bottom portion of the pumping member 1.

Operation of the above described arrangement is thus as follows:

Starting from the bottom dead center point of the roller 4, rotation of the cam 2 effects the upward movement of the pumping member 1 and a simultaneous and corresponding downward movement of the roller 5 from its top dead center point. Half way through the pumping stroke the various parts are in the position shown in FIGURE 1, and whereafter the upward movement of the pumping member 1 continues until the roller 4 reaches its top dead center point wherefrom it would tend, by its own inertia, to continue its upward movement. It is, however, prevented from this because the roller 5 has simultaneously reached its bottom dead center point and cannot, therefore, further approach the axis of the cam 1.

The lobes and the cooperating rollers 4 and 5 and the beam 8 supporting the latter are so shaped that the roller 4 (or respectively 5) reaches its position of maximum spacing from the axis A of the cam 2 when the roller 5 (or respectively 4) reaches its minimum spacing from the above said axis and contacts the cam periphery along a line L equidistant from the planes of symmetry of two successive lobes.

In the embodiment of the invention shown in FIG- URES 2 to 4 there is likewise provided a pump, the pumping member 1 of which is operated from a four-lobed cam 2, the said cam being rotatably mounted in a pump casing 13. A shown in FIGURE 3, the cam 2 carries on one side a pivot 14 which is rotatably mounted in an inner wall part 15 of the casing 13 and on the other side a sleeve 16, the latter being partly shown broken away in FIGURE 3 to illustrate how it is splined at 17 to the driving shaft 18. If desired, the splined coupling can be in the form of oblique teeth, such an arrangement providing for convenient variation of the timing of the cam 2. The driving shaft 18 is rotated by a transmission of known type (not shown), various transmission ratios such as 1:1, 1:2, 3:4, etc. being adapted to suit particular pumping requirements.

The guide bushing 12 for the slide 11, previously referred to generally in connection with FIGURE 1 and shown in more detail in FIGURES 2, 3 and 4 is formed with a radial flange 12a through which holes are bored for attachment of the bushing by screws 19 to the underside of a frame 20 associated with a housing for the pumping member and overlying the casing 13.

The radial flange 12a on the guide bushing 12 is provided with two

lateral extensions

12b, 12c which extend parallel to one another and which support the pivot 9 for the beam 8 (FIGURE 4) while uiding the opposite ends of the pivots 6, 7, respectively, on which pivots the rollers 4, 5, respectively, are rotatably mounted.

The pivot 6 further acts as the rotational center for elements 10', 10" which together constitute a link which is thus articulated at one of its ends to the pivot 6 and is articulated at the other of its ends to a pivot 10a which extends through an opening in the bottom portion of the slide 11. The upper portion of the said slide 11 is slidable over the opposing

internal surfaces

12, 12" of the guide bushing 12.

The above described mechanism is of course suitable both for operating the pumping member of an injection pump which is capable of effecting only the rectilinear reciprocations as denoted in FIGURE 3 by the arrow 21, and for operating a pumping member which, in addition to such rectilinear reciprocations, is capable also of rotating about its longitudinal axis as denoted in FIGURE 3 by the arrow 22. 3

In the modification shown in FIGURE 5 the rectilinear reciprocations of the pumping member 1 are caused by rotation of a six-lobed cam 23, and the beam 8 with its associated two rollers 4, 5 is replaced by a beam 88 which carries only one roller 4. The beam 88 follows the periphery 23' of the cam 23 by means of the roller 4 and also by means of a shoe portion 24, the operative surface 25 of the shoe which faces the cam periphery 23' being similar in curvature to the roller 4.

With the above described arrangement the motion of the roller 4, the rotational axis of which is connected with the pumping member, is conjugated with the motion of the shoe portion 24, the movement of which away from the cam axis is utilized for effecting the return stroke of the pumping member.

The construction of the embodiment described is such that the two rollers or the roller and shoe are constantly and simultaneously in contact either each one with one of the two opposite sides of a same lobe or each one with one of the adjacent sides of two consecutive lobes. This is of course apart from the existence of a slight safety clearance which is left for effective lubrication.

Consequently, the movement of each of the two camcontacting members, that is to say the two rollers or the shoe and the roller, with respect to the cam center is constantly in push-pull relationship with respect to the movement of the other member. As a result, a pump according to the invention does not require return springs for restoring the pumping member in any direction, and the pattern of motion of the said pumping member on both its upward and its downward strokes is directly governed by the shape of the cam lobes and further controlled by the nature of the beam action.

The cam may have a base diameter which is appreciably larger than that of known pumps, so that even with a relatively short stroke length of the pumping member, a linear velocity of the pumping member can be obtained, which velocity is very high during the injection period. By careful selection of the profile of the two sides of each cam lobe, high speeds can also be obtained over those parts of the stroke of the pumping member wherein the ports thereof are covered and/or uncovered, and the period of opening of the ports in the neighbourhood of the bottom dead center point of the pumping member can be extended. This latter provision particularly facilitates feed in the case of pumps of the distributor type.

Various modifications of the invention are of course possible within the scope of the appended claims.

What I claim is:

1. A fuel injection pump for a multi-cylinder internal combustion engine, said pump having a pump housing and a pumping member driven from a cam disc having a number of cam lobes thereon, said drive being through an oscillating beam having a fixed pivot, and cam lobe engaging rollers at equal distances from the pivot, said oscillating beam being pivotally connected with the pumping member, with the improvements comprising a slide (11) coupling the pumping member with the oscillating beam to move the pumping member axially thereof while allowing rotation of the pumping member, the slide movable in the pump housing in a direction parallel to the axis of the pumping member, the slide being connected to the oscillating beam through a link pivotally connected with the slide and with the beam, the pivotal axis (D) of the connection point of the link with the beam coinciding with the axis (6) of one roller (4) which cooperates with the cam disc, said axis (D) lying in a plane through the axis of the pumping member (1) and parallel to the axis (A) of the cam disc, the oscillation axis (9) of the oscillating beam (8) and the axes of the rollers (4 and 5) supported by said beam being located with respect to each other and with respect to the axis (A) of the cam disc such that in an intermediate position which is symmetrical with respect to the cam lobes, a quadrangle defined by said axes has angles of at the location of the rollers (4 and 5) and at the location of the axis of the cam disc (A) the quadrangle has an angle (5) which is equal to half of an angle (a) between planes of symmetry (AB, AC) of two adjacent cam lobes (3, 3').

2. Fuel injection pump according to claim 1 wherein the said guide is removably mounted in the said pump casing and is provided with lateral projections in which the ends of a pivot constituting the rotational axis of the said beam are rotatably secured.

3. Fuel injection pump according to claim 2 wherein the said lateral projections constitute guides for the ends of pivots for cam-contacting rollers carried by the said beam.

References Cited UNITED STATES PATENTS 2,044,064 6/1936 Dake 103-454 2,777,390 1/1957 Links 103--154 2,606,496 8/1952 Hajek 103--213 FOREIGN PATENTS 1,288,238 2/1962 France.

HENRY F. RADUAZO, Primary Examiner.

US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent NO. 3,433,172 March 18, 1969 Giuseppe Sola It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading to the printed specification, lines 3 and 4, "Flat societa per Azioni should read Fiat Societa per Azioni Signed and sealed this 14th day of April 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr. E.

Attesting Officer Commissioner of Patents