DELIVERY VALVE FOR FUEL INJECTION PUMPS

Abstract: The valve is comprised of a body (128) with an internal chamber (140), and a seat (142) a first valve closure member (150) being axially movable in the body, between an open and a closed position against the said seat; a second seat (160) moving together with the body, a second valve closure member (164), with a stem, collaborating with the second seat; a first spring member pushing the first valve closure member into a closed position, a second spring member pushing the second valve closure member into a closed position.

Description: Delivery valve for fuel injection pumps , This invention refers to internal combustion engines operating in a diesel cycle and more particularly to a delivery valve assembly donwstream of a fuel injection pump, for feeding fuel under pressure to an injector or injection nozzle placed in a head of an engine, 5. which then injects it into a combustion chamber. A delivery valve currently in use comprises, downstream of an injection pump having a pumping component in the shape of a reci¬ procating piston, a valve body held against the pump cylinder by means of a connection or union screwed into a casing which encloses TO. the pump. An obturator or closure member for the valve axially moves inside the valve chamber and has a lower guide part longitudinally grooved to allow a fluid to flow freely, a collar part which extends radially out to make contact with the valve chamber walls and a frustoconical surface which seals against an upper edge of the valve 5. body. The valve closure member is spring biased in a closing position, wherein it has its frustoconical surface against an edge of the valve body. During the injection phase, the fluid, under pressure due to the action of the pump piston, raises the valve closure member against the spring until the collar is freed from the valve body. The 10. -fuel can then flow into the union and through the delivery port. At the beginning of the .return stroke, the vacuum created by the piston together with the action of the spring moves the valve closure member back as far as the collar inside the valve chamber, interrupting the flow, and thus preventing the—fuel contained in the tubing from 15. flowing back to the pump cylinder. Then, as the delivery valve continues its closure stroke under the spring's action until the conical seat of the valve comes to its abutment position, in the tube connecting the injector the volume available for the fuel is increased in a quantity corresponding to 20. this last valve movement. This increase in volume leads to a rapid decrease in pressure inside the tube, thus avoiding dripping from the injector. The inconveniences of this type of valve are as follows: a) the possibility of a partial emptying of the tube connecting -the- _,_-_ 25. injector since this system does not allow for a continual control of this factor; this partial emptying leads to a delay in the next injection; b) the decrease in pressure in the abovementioned tube is not always constant, is difficult to control, and is dependent upon the precision with which the collar has been manufactured. 5. To overcome these inconveniences, a delivery valve has been on the market for some years which has a second seat and a second valve closure member, which is a ball member, in . an upper section thereof, while in the lower part it differs from the delivery valve described above in that it does not have the cylindrical collar seat. With this 10. type of valve it is possible, after the delivery phase, not only to avoid the partial emptying of the tube connected to the injector, but also to mantain the pressure in the abovementioned tube at a level which depends on the specifications of the counter spring for the upper seat ball member. * * 15. This last observation is of fundamental importance since, during the next fuel delivery phase, a delay in the injection, which could happen due to the partial emptying of the tubing, does not occur. This system also has its restrictions, primarily an imperfect and inconstant seal of the ball against the upper seat, and a fixed 20. calibration of the counter spring of the sphere ad thus of the residual pressure in the tubing connecting the injector. This new invention is intended to overcome the li tations mentioned above. The new valve is of a type comprising a valve body which has an inte nal cylindrical valve chamber ccnmrunicating with an injection pump chamber and a rim which forms a first seat; a first obturator or valve closure member axially movable in the valve body and including a guide part for sliding engagenent in the abovementioned chamber of 5. the valve body, longitudinal grooves or passages in communication with the valve chamber, a frustoconical surface of the obturator or member for closing engagement with the aforesaid seat of the valve body and an internal chamber in communication with the valve chamber; a detachable union or connection removably fitted in a casing 10. receiving the valve, which union holds the valve body in position and has an injection hole or nozzle; a first spring member between the union and the first valve closure member to push the latter into a closed position; a second valve seat which is movable with the first valve closure member; a second obturator or valve closure member for 15. engagement with the second seat and held in a closed position by a second spring member; the abovementioned first spring member acting in opposition to the force determined by the pressure in the pump chamber; the second spring member acting in opposition to the force determined by the pressure in the injection duct. According to this 20. invention, said second valve closure member is a stem member with a head designed to engage the abovementioned seat; said second spring member acting against the end of the stem opposite to the head in order to force the aforementioned second valve closure member into a closed position. According to other features, the sealing surface of 25. the second obturator or valve member is a portion of a spherical surface, and the seat has a conical surface. According to one form of this invention, the second seat is machined in the first obturator; in the abovementioned second stem obturator there are guide means to guide the axial movement of the same inside the first obturator. The presence of said guide means facilitates the reciprocal adap¬ tation of the two seats (body-spherical valve closure member) offering excellent and repeatable guarantees of hydraulic seals of the assembly. 5. According to another form of this invention, the second seat is machined in a first washer which has an internal chamber and an outwardly extended flange which is held in place against a surface of the first obturator by means of the first spring member. According to a further feature, the stem of the second obturator has 10. a swelling or enlargβnent at an end opposite the head which is received in an end washer against which the second spring member acts, the abovementioned washer having, when seen from above, a ring-like shape with an opening at least as large as the diameter of the stem. The valve, in one of its forms, incorporates inter- 15. changeable adjustment means placed between the aforementioned second spring member and the abovementioned end washer, which adjustment means are in the form of rings having an opening at least as large as the diameter of the stem of the second obturator. The new valve has notable advantages over the prior art; the seal of 20. the second obturator is better as there is a certain degree of self-centering that takes place; the size of the various parts can be made larger, still retaining the same overall valve size as before, thus enabling the parts to be handled better and with greater ease; it is possible to adjust the settings of the valve within a wide 25. range (about 70 bar, for example), by using the adjustement means, realizing different intervention values for the regulation of the .residual pressure in the tube which connects to the injector, by means of the simple substitution of the adjustment means in the farm of rings. The invention will be described in the following with reference to 5. the attached drawings, wherein: Fig. 1 is a longitudinal sectional view through an aiibodiment of the new delivery valve, which is shown in a closed position; Fig. 2 is an enlarged sectional view along 2-2 in Fig. 1 ; Fig. 3 is an enlarged perspective view of a washer component; 10. Fig. 4 is an enlarged perspective view of an adjustment ring; Fig. 5 is a view similar to Fig. 1 ; the valve is shown in the delivery phase, with the conical obturator raised aijd ^ the stem obturator closed; Fig. 6 is a view similar to Figs. 1 and 5; the " valve is shown in the 15. return phase, with the conical obturator closed and the stem obturator open; Fig. 7 is a diagram which has as x-coordinates the number of revolutions of the injection pump and as y-coordinates the flow rate; the lines of the graph show the readings for 20. various types of injection valves; Fig. 8 is a longitudinal sectional view through a further, actually preferred embodiment of the new injection valve, shown in its closed condition; Fig. 9 is an enlarged sectional view taken along 9-9 in Fig. 8. 25. A new type of delivery valve for fuel injection, for.diesel internal combustion engines is indicated throughout the drawings with the number 10 and is placed between an injection pump 12 and a tube (not shown) which connects up to the injector, which injects fuel into the engine's combustion chamber. The pump 12, inside a casing 14, comprises a cylinder 16 in the 5. chamber 18 of which a piston 20 moves up and down. One or more ports 22 in the cylinder wall connect the cylinder chamber 18 with a chamber 24 in which fuel always at low pressure is collected. A lower surface 26 (the terms "upper", "lower", etc. refer to Figure 1 and are not restrictive) of a valve body 28 is .received on an upper 10. surface 25 of cylinder 16. This valve body 28 is held in position by means of a connector or union 30, which, with an external screw thread 32, screws into an internal screw thread 34 of casing 14, this being a type of mounting which is already well-known.. Between connector or connection 30 and casing 14 there is a sealing 15. gasket 36; between connector 30 and body 28 there is a sealing ring 38. The ^ valve body ' ' 28 has an internal chamber 40 and a circular upper seal seat 42. The connector 30 has an internal chamber 44 connected to a delivery port 45 which is in turn connected to the injector by 20. means of a tube (not shown). A first obturator or valve closure member 50 is able to move along the central longitudinal axis of the chamber and the connector. The obturator is comprised of a lower guide section 51 , provided with axial grooves on the external surface thereof, or rather with 25. vertical tabs or tongues 51 ' substantially running the length of the chamber 40, which tongues define between them spaces 52 or channels to allow the fuel or fluid to pass. The obturator also has an external frustoconical surface 53, which makes a seal with the abovementioned seat 42. At least one through hole 54 in the obturator 5. wall connects an internal opening 55 of the same with the grooves and the chamber 18. On one upper surface of the first obturator 50 rests a first washer or lower washer 58 which has a cylindrical internal opening 59 and on the lower side a conical seat 60. The washer 58 is biased agai_nst the- obtcpator by- a s rang- 62 which ae st __m__.t -a_ϊ 10. abutment surface 63 in the chamber 44 of connector 30. A second valve closure member 64 has a head 65' and a stem 66. The head 65 has a tapered surface for engagement against conical seat 60. The stem 66, with its larger end 66' opposite the head is engaged into, a second washer or end washer 68. The second valve closure 1 . member 64 is biased in a closed position by a spring 70, which acts against the lower washer 58 and the end washer 68, with the interposition of one or more adjustment rings 72. Both the end washer 68 and the adjustment rings 72 have an interrupted form, as can be . .seen in Figs. 3 and.4, " sα that they can be easily mounted onto th p 20. shank or stem 66. It will be noted that the valve, by unscrewing the connector 30, is easily dismantled into two interchangeable parts, one of which comprises casing 28 and the closure member 50 and the other connector 30, washer 58, spring 62, washer 68, spring 70, and closure member 25. 64. It will also be noted that the adjustment rings 72 can be easily changed to vary the force with which the spring 70 acts on closure member 66. The following explains how the delivery valve 10 functions. During the delivery phase, the piston 20 pressurizes the fuel (taken 5. in through 22) in the chamber 18. The pressure overcomes the force of spring 62 and lifts up the conical valve closure member 50 from seat 43- .valve closure member 64 is- έspt closed against seat ' The ' Fuel under pressure enters chamber 44 and leaves through hole 45. When piston 20 begins to descend, the conical valve closure member 50 10. ccmes to rest against its seat 42 under the action of vacuum and of spring 62. The valve closure member 64 assumes an open or closed position on seat 60 depending on whether the pressure in the injection port exerts a force greater or lesser than that of the spring 70; this, as was said above, can be easily adjusted by 15. interposing one or more rings 72; it follows that the pressure in hole 45 and the delivery duct can be easily controlled. In Fig. 7 are clearly shown the results obtained with a valve £ this type, in comparison with the results obtained with the valves of the preceding technology. The x-ccordinates indicate the revolutions per 20. minute of the fuel injection pump, while the y-coordinates refer to the rate of flow in cubic centimeters obtained for 600 delivery strokes. Three groups of values are shown, each relating to different metering of fuel. The dotted lines refer to a prior art valve having a single valve closure member, the solid lines refer to a prior art 25. valve having a double closure member, the second closure member being spherical, and the broken line refers to the valve of this invention. It can be clearly seen that the last type gives increased rates of flow. Referring now to Figs. 8 and 9, a second presently preferred embodiment of this valve, indicated with 100, will be described. To 5. label the different elements thereof, the same numbers have been used as those in the first embodiment increased by 100, and those elements which are identical to those of the first embodiment will not be described 1 in- detail. Thus number 128 indicates the valve body, held in position by means 10. of connector 130; 140 is the valve chamber, with the seal seat 142. The connector 130 has an internal chamber 144, in cσimunication with the delivery hole 145. A first valve closure member 1 0 is movable axially, that is along the central longitudinal axis of the chamber and the connector. The 15. valve closure member is comprised of a lower guide part 151 , which has flat axial portions on the external surface, and extended parts 151 ' which guide along the walls of chamber 140; these define spaces or passages 152 for the passage of the fuel or fluid. The valve closure member also has an external frustoconical surface 153, which 20. seals against the forementioned seat 142. An internal chamber 155, or through hole, of the valve closure member is in ccmmunication with the valve chamber 140 and with the connector chamber 144. At the base of the valve closure member 151 is a conical seat 160. 25. A second valve closure member 164 is received in the chamber 155 and slidable therein and comprises a movable head 165 and a stem 166. The head 165 has a tapered preferably spherical surface, for engagement against the conical seat 160. One part of the stem has flat axial portions or channels and guiding surfaces for the movement inside 5. chamber 155. Stem 166 is engaged with its larger end 166' opposite the head, into an end washer 168. The second valve closure member 164 is held in a closed position by a spring 170, which acts against the first valve closure member 150 and the end washer 168, with the interposition of one or more adjustment rings. Both the end washer 10. 168 and the adjustment rings 172 have an interrupted form, so that they can be easily mounted on to the shank or ste 166. The valve 100 works in a similar way to valve 10.

Claims: C L A I M S 1. A delivery valve for fuel ' injection -systems in diesel internal combustion engines, of a type comprising: - a valve body (28, 128) having an internal chamber (40, 140) in communication with a chamber (18) of an injection pump (12) and a - rim-constituting a first seat (42, 142)r~" - a first valve closure member (50, 150) axially movable in the valve body and comprised of a guide part ( 1 , 151 ) for sliding engagement in the said chamber of the body and having axial passages (52, 152) in communication with the valve body chamber (40, 140) and a O- frustoconical surface (53, 153) for closing engagement with the said seat in .the body, an internal chamber (55, 155) in communication with said valve body chamber (40, 140); - a connector (30, 130) mounted in a detachable way in a casing which contains the valve, said connector holding in position the valve 1 - body and having a delivery hole (45, 145); - a first spring member (62, 162) acting between the connector and the first valve closure member to bias this latter in a closed position; - a second seat (60, 160) movable with the first valve closure 20. member; - a second valve closure member (64, 164) for engagement with the said second seat and biased in a closed position by a second spring member (70, 170); - said first spring member (62, 1 2) acting in opposition to the 5. force determined by the pressure in the pump chamber; - said second spring member (70, 170) acting in opposition to the force determined by the pressure in the delivery duct characterized in that •- said second valve closure member? (-64..1-64.5. is a. star, valve. c_2___≤ure. 10. member which has a head (65, 165) for engagement into the said second seat - said second spring member (70, 170) acting to force the said second valve closure member into a closed position. 2. A valve according to claim 1 , characterized in that 15. the said second seat is machined in the first valve closure member and the said second valve closure member is contained at least in part in the internal chamber of the first valve closure member and is movable within it. 3. A valve according to claim 1 , characterized in that 20. the said second seat is machined into a first washer having a through hole and the said first washer has a flange extended outwards and kept in position against a surface of the first valve closure member by means of the said first spring member. 4. A valve according to claim 1 , characterized in that 25. the said stem has an enlargement at the end opposite the head, and said enlargement is held in an end washer against which the second spring member acts, the said second washer having when seen from above, the form of a ring with an opening at least as large as the diameter of the stem. 5. A valve according to claim 1 , characterized in that it 5. comprises ajustment means acting on the said second spring member, said adjustment means being in the form of rings having an opening at least equal to the diameter of the stem of the second valve closure member.. 6. A valve according to claim 2, characterized in that 10. the second valve closure member has, along at least part of its stem inside the chamber of the first valve closure member, guide parts for ■ engagement against the wall of the said chamber, and axial passages, spaced from the said wall, the guide parts being to guide the axial movement of the second valve closure member inside the first.

Inventors: CODINI NICOLO, PASTORI GIUSEPPE, CODINI, NICOLO, PASTORI, GIUSEPPE
Applicants: DISA DIESEL INIEZIONE SPA
Application year: 1986
Main classification: F02M59
IPC codes: F02M59