US3138112A - Injection pump for reciprocating piston internal combustion engines - Google Patents

Description

4 Sheets-Sheet l C. PO RTA ET AL June 23, 1964 INJECTION PUMP'FOR RECIPROCATING PISTON INTERNAL COMBUSTION ENGINES Filed Oct. 5, 1961 2 N w 2 a N mm mm a 8m QM. h I Q Q.

f/il mm N v a Q UQ\ UN III IIJHMN I H l||... 0 NM, MN D g Q I m 4 A S I N I Q w R r mm Q m 3 mm 3 3 L \S N .0 0.0 Q 3 O N t .1:

June 23, 1964 Q PQRTA T 3,138,112

INJEC N PUMP FOR RECIPROCATING PISTON TERNAL COMBUSTION ENGINES 4 Sheets-Sheet 2 Filed Oct. 5, 1961 June 23, 1964 c. PORTA ETAL 3,138,112

INJECTION PUMP FOR RECIPROCATING PISTON INTERNAL COMBUSTION ENGINES Filed Oct. 5, 1961 4 Sheets-Sheet 5 1 a. 17 24 23 I I i 3a June 23, 1964 c. PORTA ETAL 3,133,112

INJECTION PUMF FOR RECIPROCATING PISTON INTERNAL COMBUSTION ENGINES Filed Oct. 5, 1961 4 Sheets-Sheet 4 United States Patent O" 3,138,112 ENJECTIQN P FOR RECIPROCATH IG PISTQN INTERNAL COMBUSTIGN ENGHJES Carlo Porta and Carlo Frascisco, both of Turin, Italy, assignors to Fiat Societa per Azioni, Turin, Italy Filed Oct. 5, 1961, Ser. No. 143,073 Claims priority, application Italy Oct. 7, 1960 2 Qlaims. (Cl. 103-174) This invention relates to fuel injection pumps of multicylinder type for reciprocating piston internal combustion engines. By the expression multicylinder pumps pumps are understood which comprise a pump unit for each cylinder of the engine to be fed with fuel, the units being grouped in a single pump casing.

The pump units of multicylinder pumps, each comprising a cylinder in which a plunger moved endwise by a cam is sealingly slidable can be arranged in line with respect to a pump shaft carrying as many cams as there are pumpunits, or they may be arranged radially around the said shaft and be driven by a single cam on the shaft.

Such multicylinder pumps suffer from several drawbacks which may be summarized as the necessity of providing independent setting means for each pump unit, in order to eliminate differences in delivery of the pump units, and a considerable size and weight of the pump proper and its accessories, more particularly the delivery regulator and injection timer.

Where the timing of injection is effected by phaseshift of either the pump shaft with respect to the shaft of the engine, or of the driving cams for the pump units with respect to the pump shaft, the injection timer should be capable of overcoming the high resisting torque acting on the pump shaft.

This invention provides a multicylinder pump obviating the above mentioned drawbacks, which is moreover reduced in size and weight.

The improved pump is substantially characterized by the fact that it comprises a single control member for the said pump units, in the form of a pivot rotated by the pump shaft, the ends of which sealingly engage a cylindrical recess in a support for the said pivot, the said cylindrical recess connecting with fuel supply means and with said pump units, and means responsive to the rotational speed of the pump shaft adapted to displace the said pivot endwise in the recess in order to vary delivery of the pump members and effect angular phaseshift of the pivot with respect to the pump shaft in order to adjust injection timing.

Further characteristic features and advantages of this invention will be understood from the appended description referring to the accompanying drawings which show a preferred embodiment. n the drawings:

FIG. 1 is a middle axial sectional view of the improved pump;

FIG. 2 is a sectional view on line IIII of FIG. 1;

FIG. 3 is a detail view on an enlarged scale of FIG. 1;

FIG. 4 is a sectional view on line IVIV of FIG. 3;

FIG. 5 is a sectional view on line V--V of FIG. 4;

FIG. 6 is a sectional view on line Vl-VI of FIG. 4;

FIG. 7 is a sectional view on line VII-VII of FIG. 1.

The pump comprises a casing 1 obtained by casting, closed on one end by a cover plate 1a secured to the casing by means of bolts 2.

The casing has rotatable therein a shaft 3 driven by the engine to be supplied with fuel so as to perform one full turn at each engine cycle, the said shaft being supported by a pair of bearings 4, 5 secured in the casing and cover 1a, respectively.

The shaft 3 has keyed thereto or formed thereon in- 3,138,112 Patented June 23, 1964 ternally of the pump casing 1 a shallow bell-member 6 enclosing a disc 7 secured to the casing 1.

The disc 7 is arranged co-axially with the shaft 3 and is provided with a cylindrical hub 7a engaging an aperture bored in a partition 1b in the casing, the hub 701 being provided with a sealing ring 8.

The disc 7 is moreover formed with a plurality of radial cylindrical bores 9 connecting through radial supply ports 10 with an axial cylindrical recess 11 bored in the disc.

The cylindrical bores 9 connect through respective conduits 12 with fittings 13 leading through pipes not shown to the injectors arranged on the cylinders of the engine to be supplied with the fuel.

Plungers 14 are sealingly slidable in the bores 9, their end extending beyond the bores being provided with shoes 15 including rollers 16 adapted to contact the inner surface 6a on the bell-members 6, the said inner surfaces being machined to a cam shape.

The axial cylindrical recess 11 in the disc 7 encloses a pivot 17 providing both a delivery control member for the fuel supply to the bores 9 and a phase-adjusting member for the deliveries from the said bores to the injectors.

To this end the pivot is freely rotatable and axially displaceable in the recess 11 and is formed with fulldiarneter sections 17a, 17b sealingly engaging the respective opposite end sections of the recess to afford the said translational and rotational displacement in a sealing relationship.

The pivot 17 is moreover formed with an intermediate region smaller in diameter than the axial recess 11 and is machined at the region of radial ports 10 to form a sealing shoe 18' of a generally trapezoidal shape, decreasing in Width from one end to the other.

The pivot 17 is rotated by the shaft 3 by means which will be described in detail hereafter, whereby the sealing shoe 18 sequentially covers and uncovers the ports 10 leading to the bores 9.

The axial cylindrical recess 11 is connected by pipes not shown to fuel supply means, so that fuel at the supply pressure is constantly maintained therein.

Fuel flows through the radial ports 10, during the periods the said ports are not intercepted by the sealing shoe 18, to the inside of the bores 9, its pressure being such as to effect radially outward displacement of the plungers 14 causing the rollers 16 to contact with the operative surface of the cam 6a.

As mentioned above the pivot 17 is rotated by the shaft 3. For this purpose the pivot 17 is formed at its end facing the shaft 3 with a spigot 19 (FIG. 3) having an eyelet 20, the spigot 19 being received by a frontal recess 3a in the shaft 3.

The recess 3a receives in addition a sleeve 21 slidable therein against the action of a return spring 22'.

The sleeve 21 is connected to the spigot 19 by a diametrical pin 21a reaching within the eyelet 20 in the spigot. The connection is such that the pin 21a and eyelet 20 permit axial displacement of the pivot 17 but hold it in a the sleeve. The outer cylidrical surface of the sleeve 21 is moreover formed with a groove 23 which is suitably inclined with respect to the generatrices of the said 'cylindrical surface and engages a radial pin 24 fast with the shaft 3. The arrangement is therefore such that the sleeve 21 is carried along in rotation by the shaft 3 and drives in turn the pivot 17, While axial displacements of the sleeve 21 angularly displace the pivot 17 with respect to the shaft 3, the said angular displacements being defined by the configuration of the groove 23.

The free end of the spigot 19 is disc-shaped and is acted upon by a pair of centrifugal Weights 25 knifeedge fulcrumed on spider arms 26 carried by the shaft given angular position with respect to Y 3. The arrangement of the weights is such that their radial expansion by effect of the centrifugal force effects axial displacement of the pivot 17 against the action of a spring 27 acting on the pivot through a leverage which will be described in detail hereafter.

A further pair of centrifugal weights 28 knife-edge fulcrumed on spider arms 29 carried by the shaft 3 acts on the pin 21a fast with the sleeve 21 in such manner that radial expansion of the said weights due to the centrifugal force effects axial displacement of the sleeve against the action of the spring 22. In other words and considering the above description expansion of the centrifugal weights 28 effects an angular phase-shift between the shaft 3 and pivot 17.

As mentioned above the spring 27 opposes the centrifugal action of the weights 25 through a leverage. The chief function of the latter is to permit setting from the outside the characteristics of the resilient force applied by the spring 27 on the weights 25. The leverage includes a first lever 3f pivoted to a pivot 31 secured to the pump casing 1 and having acting thereon the spring 27 through the interposition of a push member or cup 32. The lever is formed at its free end with a fiat 39a urged by the spring 27 into contact with a roller 33 rotatably mounted at the end of a follow-up lever 34 articulated to a crank 35 which can be angularly displaced from an outer lever 36.

The roller 33 is moreover in contact with a lever 38 pivoted to a pivot 39 secured to the pump casing 1, the free end 38a of which acts on the pivot 17 through the interposition of a thrust bearing 39 urged by a cup 40 held in position by a spring 41.

A swing lever 42 acts on the lever 33 to oppose the atcion of the spring 27, the swing lever 42 being urged against the lever 38 by a pre-stressed adjustable spring 43. The spring 43 is provided at one end with a regulating screw 43a, and its expansion towards the lever 42 is limited by an abutment 43b, the latter being fixedly attached to the casing 1 in an intermediate position between the casing and the lever.

Referring to the drawings the operation of the in jection pump is as follows.

The cylinder bores'9 are fed with fuel at the feed pressure through the radial ports 1t} connecting them with the axial cylindrical recess 11. The feed pressure on the fuel, which effects radially outward displacement of the plungers 14 is well below the pressure necessary for opening the injectors.

Through rotation of the shaft 3 hence of the bellrember 6 the rollers 16 sequentially come into contact with the throw-section of the cam 6a. This section effects a radially inward displacement of the plungers 14 and is in phase relationship with the angular position of the pivot 17 so that on inward displacement of each plunger 14 the sealing shoe 18 is in front of its respective radial port 10 to intercept fuel flow therethrough. The fuel pressure in the cylinder bore 9, the plunger of which performs its inward movement, is therefore quickly raised till it reaches the operating pressure of its respective injector which then effects injection.

On continuing rotation of the pivot 17 the sealing shoe 1S uncovers the radial port 1t; relative to the cylinder bore 9 having effected injection, whereby the fuel supply pressure effects outward displacement of the plunger 14 causing the roller 16 to remain in contact with the cam 6a along its slope. The cycle is successively indefinitely repeated on the various pump units.

During inward movement of the plunger the latter is prevented from pursuing its movement by inertia by a hydraulic braking arrangement for the plunger.

For this purpose the port 10 comes during the said inward movement in front of an eyelet-shaped groove 18a formed in the shoe 18 having in its bottom an aperture 1811 which connects the cylinder bore with a longitudinal balancing channel 170 bored in the pivot 17.

The fuel reaches from the channel and lubricates all the control members, whereupon it flows back to the fuel tank. The diameter of the aperture 18b is conveniently reduced to form a throttled passage which opposes flow of fuel therethrough and is thereby capable to brake the inertial movement of the plunger 14.

The fuel quantity delivered on each stroke of the plunger 14 is adjusted by the axial position of the sealing shoe 18 controlled by the centrifugal weights 25 dependently upon the rotational speed of the engine.

As a result of the trapezoidal configuration of the said shoe its axial displacement effects variations in the covering angle of the radial port 10 during delivery to effect adjustment of delivery by reflux.

The timing of injection is automatically effected dependently upon the engine speed through the action of the centrifugal weights 28 which effect phase-shift of the pivot 17 with respect to the shaft 3. This phase shift causes the ports 10 to be closed by the shoe 18 in an angular position selectively shifted with respect to the cam-throw position, whereby injection is timed. The hereinbefore described arrangement of parts for effecting phase-shift is capable with a very near approximation to afford a pre-determined timing law which is materialized by the shape of the groove 23. By adopting a groove comprising two sections of opposite obliquity the arrangement just described affords an advance in timing on starting the engine, which is annulled at low engine speeds and is re-established in accordance with the desired law as the engine speed increases.

The action of the centrifugal weights 25 is opposed by the resilient system including the spring 27, hence the axial position of the sealing shoe 18 can be adjusted at will by angularly setting from the outside the lever 36 and crank 35. Rotation of the lever 36 in anticlockwise direction in FIG. 1 effects vertical upward displacement of the roller 33 and reduction of the effective arm of the lever 30, thereby increasing the resisting arm of the lever 38. Under these conditions the action by the spring 27 effects a smaller displacement and a more powerful thrust on the lever 38, hence on the pivot 17. The contrary occurs on clockwise rotation of the lever 36. When the lever 36 is in the position shown on the drawing (FIG. 1) the spring 27 exerts a reduced return action on the centrifugal weights 25. Consequently, a limited centrifugal force is required for expanding the centrifugal weights and displacing the pivot 17 against the action of the spring 27. Since the displacement of the pivot 17 in the above mentioned direction effects displacement of the sealing shoe 18 so that its narrower region comes opposite the radial ports 10, the latter remain closed over a short angular width or do not close at all, thereby effecting a considerable reflux; consequently, fuel delivery to the injectors is very small or null, and, in the former case, the engine turns at its idling speed. The reduced return force applied by the spring 27 goes hand in hand with the maximum flexibility of the resilient system, since to a given variation in expansion of the centrifugal weights 25 there corresponds a slight variation in the return force for the said weights. Consequently, small variations in speed are sufficient to effect wide strokes of the pivot 17, hence a quick and efficient correction of the fuel deliveries to the injectors. Under these conditions the adjusting arrangement is therei fore of highest sensitiveness.

The contrary takes place on anticlockwise rotation of the outer lever 36, when the return force applied by the spring 27 on the centrifugal weights 25 is highest, so that a high value of the centrifugal force, corresponding to a higher rotational speed of the engine is required to push the pivot 17 against the action of the spring 27 to thereby reduce the delivery. In this case the engine rotates at its high speed setting. Moreover, since a slight axial displacement of the pivot 17 results in a wide stroke of the spring 27, the rigidity of the resilient return system is increased, whereby quick intervention of the adjustment at high rotational speeds of the engine is afforded.

The above described arrangement moreover affords up to a predetermined rotational speed a super-delivery of fuel exceeding the highest delivery at high rotational speed. To this end the super-delivery limiting device comprising the above mentioned swing lever 42 and spring 43 comes into action. Action of the said device for limiting super-delivery is obtained by properly prestressing the spring 43 which opposes the action of the spring 27. At a proper pre-stressing value of the spring 43, the outer lever 36 being rotated anticlockwise to highest setting until the engine rotational speed does not exceed its predetermined value, the centrifugal force of the weights 25 shall be insuflicient to overcome thrust from the two springs 27 and 43. Consequently, the spring 27 causes the pivot 17 to move forward beyond its normal highest delivery position and compress through the swing lever 38 the spring 43.

The function of the spring 41 interposed between the thrust bearing 4% and cup 40 is to push the pivot 17 to its extreme or maximum setting position when the centrifugal force at the low engine speeds preceding stoppage of the engine sinks to minimum values, so that when the engine comes to standstill the system is automatically in the highest enriching position for the fuel delivery in order to facilitate subsequent starting. The reduced rating of the spring causes the spring to be fully compressed already at low speeds by effect of the thrust of the main adjusting members (spring 27 and centrifugal weights 25) and to remain such throughout the normal operating speed range without altering adjustment.

The improved injection pump includes a fuel feed pump of the vane type. The feed pump is driven by the shaft 3 and comprises a pump casing 45 secured to the cover plate In by means of bolts 45b. A rotor 46 carrying radial vanes 47 is rotatably mounted in a seating having a cylindrical surface 45a in the pump casing 45. Ring-shaped resilient members 48 are arranged within the rotor 46 and radially press the vanes 47 causing them to keep in contact with the cylindrical surface 45a of the pump chamber. The resilient members are adapted to absorb slight periodic variations in spacing of the opposite vanes due to eccentricity of the shaft. This ensures the supply pressure even at low speeds of the engine.

In order to afford safe stoppage of the engine, a cock (not shown) is interposed in the piping (not shown) connecting the feed pump 45 with the axial cylindrical recess 11, and is adapted to intercept the piping and returning the fuel to the reservoir through an adjustment valve for the feed pressure, while annulling the feed pressure and delivery to the pump members and annulling flow of fuel and suction by the pump members.

It will be understood from the above description that the improved injection pump is advantageous over conventional pumps in that it requires a minimum mechanical work for effecting adjustment in delivery and timing. More particularly, the work required for timing can be easily performed as described above by a centrifugal weight arrangement in which two devices, namely delivery adjusting and timing devices are grouped together, these devices being of considerable size and weight in prior constructions.

W hat we claim is:

1. An injection pump for reciprocating internal combustion engines comprising; a casing, a plurality of radial pump units within said casing each having an independent plunger and a supply port, a hollow pump shaft coupled for rotation with the engine shaft, a cam on said pump shaft for controlling the stroke of each plunger, a hollow pivot rotated by the pump shaft and arranged concentrically within the pump shaft, a sealing shoe on said pivot controlling in phase relation each supply port, spider arm means carried by the engine shaft, centrifugal weight means pivoted on the spider arm means and positioned and arranged to control the axial and angular position of said pivot relative to said supply ports, adjustable resilient means arranged within a portion of said casing opposing the action of the centrifugal weights on the pivot, a longitudinal conduit within the pivot having its center portion connected in phase relation with the supply port of each pump unit by means of said sealing shoe and its ends open to the portions of the casing housing said adjustable I resilient means and centrifugal weight means, said adjustable resilient means including a pair of one-arm levers each pivoted to the casing, a first spring arranged between the casing and the arm of one lever of said pair of levers,

a second spring arranged between the casing and the arm of the other lever so as to act concurrently with the action of the centrifugal weights on the pivot, the free end of said other lever bearing against the pivot, and a roller simultaneously contacting both arms of said levers, said roller being displaceable from outside the casing with respect to the lever pivots, whereby the displacement of said roller varies the effective arm by which said first spring acts through said levers on the pivot to oppose the action of the centrifugal weights.

2. An injection pump for reciprocating internal combustion engines as defined in claim 1 further comprising an abutment fixedly attached to the casing in an intermediate position between the casing and the arm of the other lever for limiting the expansion of the second spring towards the other lever.

References Cited in the file of this patent UNITED STATES PATENTS Re. 23,326 Fleischel June 9, 1951 1,893,644 Fleischel June 10, 1933 2,087,885 Fleischel July 27, 1937 2,693,708 Baer et al. Nov. 9, 1954 3,032,986 Wright May 8, 1962 3,093,969 Moellmann June 18, 1963 FOREIGN PATENTS 509,474 Great Britain Ian. 14, 1938 (US. Corresponding 2,156,933, filed May 2, 1939) 166,214 Sweden Jan. 23, 1956

Claims (1)

1. AN INJECTION PUMP FOR RECIPROCATING INTERNAL COMBUSTION ENGINES COMPRISING; A CASING, A PLURALITY OF RADIAL PUMP UNITS WITHIN SAID CASING EACH HAVING AN INDEPENDENT PLUNGER AND A SUPPLY PORT, A HOLLOW PUMP SHAFT COUPLED FOR ROTATION WITH THE ENGINE SHAFT, A CAM ON SAID PUMP SHAFT FOR CONTROLLING THE STROKE OF EACH PLUNGER, A HOLLOW PIVOT ROTATED BY THE PUMP SHAFT AND ARRANGED CONCENTRICALLY WITHIN THE PUMP SHAFT, A SEALING SHOE ON SAID PIVOT CONTROLLING IN PHASE RELATION EACH SUPPLY PORT, SPIDER ARM MEANS CARRIED BY THE ENGINE SHAFT, CENTRIFUGAL WEIGHT MEANS PIVOTED ON THE SPIDER ARM MEANS AND POSITIONED AND ARRANGED TO CONTROL THE AXIAL AND ANGULAR POSITION OF SAID PIVOT RELATIVE TO SAID SUPPLY PORTS, ADJUSTABLE RESILIENT MEANS ARRANGED WITHIN A PORTION OF SAID CASING OPPOSING THE ACTION OF THE CENTRIFUGAL WEIGHTS ON THE PIVOT, A LONGITUDINAL CONDUIT WITHIN THE PIVOT HAVING ITS CENTER PORTION CONNECTED IN PHASE RELATION WITH THE SUPPLY PORT OF EACH

Images