US2912935A

US2912935A - Fuel injection pump

Info

Publication number: US2912935A
Application number: US550720A
Authority: US
Inventors: Wick Georg; Wolf Roland
Original assignee: Individual
Current assignee: Individual
Priority date: 1954-12-04
Filing date: 1955-12-02
Publication date: 1959-11-17
Anticipated expiration: 1976-11-17

Description

Nov. 17, 1959 G.w1cK E TAL FUEL INJECTION PUMP 2 Sheets-Sheet 1 Filed Dec. 2, 1955 wm mm INVENTORS N .MM Q. 91m. v,a

eo y GR B Nov. 17, 195.9 G. wlcK Erm. 2,912,935

INJECTION PUMP Filed Dec. 2, 1955 2 Sheets-Sheet 2 /NVENORS Geary Wick Roland T/l' www . and diluting there the lubricating oil.

United,v States Patent FUEL INJECTION PUMP Georg Wick, Wollerau, and Roland Wolf, Richterswil, Switzerland, assignors of one-third to Karl Schroeder, Richterswil, Switzerland v Application December 2, 1955, Serial No. 550,720

Claims priority, application Switzerland December 4, 1954 6 Claims. (Cl. 10S-38) It is known that the operation of Van internal-combustion engine with fuel injection has considerable advantages compared with carbureter operation, for instance, easier starting of the cold engine, an improved volumetric efficiency, a reduction of the specific fuel consumption, the possibility of increasing the compression ratio, a rapid response to changes in the throttle position, and the like.

The injection pump required for fuel injection operationis already developed for a considerable extent for diesel engines, and has been found to be very satisfactory in practical operation, lts function is to feed the quantity of fuel corresponding to the loading state of the engine at any given lmoment to the injection nozzle at a certain time and under a certain pressure. A pump casingaccommodates as many pump elements, each consisting of a piston and a pressure cylinder, as thereare engine cylinders to be supplied with fuel. The pump cylinders are normally driven by means of push rods with rollers from a common camshaft. The pressure stroke is effected by the cams, the suction by spring pressure. Each pump cylinder is closed at its end by means of'a spring-loaded pressure valve connected to a pressure pipe. According to the method of controlling the quanti'ty to beY injected, the fuel injection pumps are divided into pumps with stroke adjustment, throttle control, lift adjustment, and inclined edge control.

ln order rto reduce the leakage as much as possible, it isessential that the pump piston has a very good t in the pump cylinder, and that this is maintained over along period of operation. The latter condition implies a very effective lubrication of the pump piston, which does not involve any difficulties in the case of fuel pumps for diesel engines, because the fuel is gas oil.

But in the case of automobile engines the conditions for -fuel injection pumps are quite different. Since the fuel lto be injected here, preferably petrol, has no lubrieating properties, it must be prevented from moving along the pump system into the camshaft space of the pump,

It became therefore necessary to equip each pump element with a blocking mechanism, while the other piston, between the oil inlet and the f uel chamber, is moved by means of pressure loil introduced between the facing pistons, where the oil under pressure at the -time has a lubricating effect on this second piston during the motions of a pump.

`The drawing shows examples of embodiments of the object of the invention, where: Fig. 1 is a longitudinal section through a first embodiment,

Fig. 2. is a longitudinal section through another embodiment.

Fig. 1 shows for simplicity only a single pump element. A pump casing 1 is lled partly with lubricating oil 3 and is covered by means of a lid 2. A camshaft 4 is arranged normally to the plane of the drawing, and is driven in the anti-clockwise direction. An extension 7 of a swinging lever 9 pivoted on a shaft 8 is supported on the spirally shaped cam 5 with the sharp releasing edge 6. The lever 9 is forked at its lower end and engages with a recess 10 of a piston nut 11. A compression'spring acts against the left-hand end of nut 11, the other end of the spring 12 being accommodated in the sleeve-shaped setting screw 13. A plug 14 seals the aperture to the setting screw. A control piston 15 is screwed into the piston nut 11 and guided closely in a pressure cylinder 16. The left-hand end of the pressure cylinder 16 is provided on its outside with a screw thread on which a stroke-limiting nut 17 is screwed. The said nut is provided along a circumference with teeth 18 engaging with the teeth of a setting rack 19, which is supported so that it can move in the pump casing 1 normally to the plane of the drawing. The stroke-limiting nut 17 carries at its left-hand end a stop ring 20, preferably made of a synthetic material. Instead of arranging the thread fortheV stroke-limiting nut 17 directly against the pressure cylinder 16, it can also be arranged on the outside of a threaded sleeve 21 slidably arranged on the pressure cylinder 16, and whose position can be fixed by means of a Vgrub screw 22. A small hole 23 is arranged laterally in the central part of the pressure cylinder 16, and. the

- inside of the pressure cylinder 16 is connected through the ingfdevice', consistingof two annular grooves arranged f in the pump cylinder, of which the first groove is connectediwith the pump suction space, while lubricating oil is forced into the second groove, where .the pressure is above that of the pump suction space. However, -this method doesv not prevent any fuel leaking along the pump system and reaching the first annular groove. This has been found to be a disadvantage in practice because a part of the pump is not lubricated, and will therefore wear fairlyv rapidly.

. he present invention relates to aifuel injection pump,

inzparticular for. non-lubricating fuels, with at least one pumpv element accommodated in an oil-filled pump casing,l which has the characteristic feature that the pump element lis equipped with a pressure cylinder with two pistons,l which can lmove longitudinally inside the prese'icylinde, the first pistonbeing controlled by VaA drivgitudinal bore 28, whose left-hand end is given the shape of a valve seating, against which a valve ball 29 is pushed by a valve spring 30. The aperture to the suction valve 26is sealed by means of a plug 31. Between the 'latter and the suction valve 26 an orice 32 is provided, which through a fuel admission pipe, not shown in the drawing, is connected to a fuel pump. A duct 33 branches oif between the secondary piston 24 and the suction valve screw 26, and is connected through f a pressure valve consisting of va valve ball 35 under the action of a valve spring 34 through a pressure pipe, which is not shown, to an injection nozzle, which also is not shown.

The method of operation of the device described here is as follows; During each revolution of thevcamshaft 4` thepswinging lever 9 is moved comparatively slowly to the left, and takes the control piston 15 with it, against the action of the compression spring 13. As soon as the `extension 7 drops over the rreleasing edge 6, thevswinging lever 9-and the control pistonlS move suddenly towards the right. This motion is limited by Patented Nov. 17, `1959V the right-hand end ofthe piston nut 11 meeting the stop-ring 20. According to theA setting o f the latter by means of the setting rack 19, the control piston 15 makes a smaller or larger stroke. Since the space between the right-hand end of the control piston 15 andthe lefthand end of the secondary piston is always filled with oil flowing in through the hole 23, this oil is put under pressure, assoon as the control piston has moved far enough to the right to close the hole 23. This pressure increases only until it is capable to overcome the action of the compression spring. 27. As soon as this is the case, the secondary piston 24 is also moved to the right accordingly and in its turn applies a pressure to the fuel admitted through the suction valve 29 30, which is subsequently conveyed through the pressure valve 34, to the injection nozzle.

v By varying the position of the stop ring 20, the q'uantity of fuel admitted to the injection nozzle is determined, while the position of the compression spring 12` detervmines the injection pressure.

It is evident that during each stroke a comparatively small part of the pressure oil acting against the lefthand end of the secondary piston is pushed between the pressure cylinder wall and the curved surface of the. secondary piston 24. This has the result -of lubricating the secondary piston 24 effectively over its entire surface. The loss of lubricating oil is then quite small. The lubricating oil mixing with the fuel cannot exert any noticeable influence on the formation -of the mixture. The sudden motion of the control piston and of the secondary piston has the advantage that also the injection occurs suddenly, so that the fuel is well atomized. lt is a further advantage that the quantity of fuelfed to the engine can always be dosed very accurately, quite independently of the speed of rotation of the camshaft 4 or of the engine.

According to Fig. 2, 1 is again a pump casing closed by means of a lid 2 and partly filled with lubricating oil 3. A camshaft 4 is arranged normally to the p lane of the drawing and driven in the anti-clockwise direction. An extension 7 of a swinging lever 9 pivoted on a shaft S rests against the spirally shaped cam with the sharp releasing edge 6. The latter is forked at its lower end and engages with the annular groove 10 of a sleeve-shaped part 11 of a control pistonlS, against which a compression spring 12 acts, which is supported with its other end on a setting screw 13. A plug 14 seals the aperture to the setting screw 13.. The sleeveshaped partl 11 of the control piston 15 is arranged in the regulating sleeve 21' so that lit can be displaced longitudinally, the sleeve being guided overl a pressure cylinder 16. The regulating sleeve 21 is equipped above with vteeth 1S meshing with the teeth of a setting gear wheel 19. The latter is fixed to a shaft perpendicular to the plane of the drawing. The regulating sleeve 21 is provided above with a control port 23 at its left-hand end. A small port 23 is provided in the intermediate part of the pressure cylinder 16 and across it; the space inside the pressure cylinder `16 is through this port in communication with the oil-filled space inside the pump casing 1 when the control piston 15 assumes its left-hand end position.

A secondary piston 24 is arranged at the right-hand end of the pressure cylinder 16 so as to be capable of sliding longitudinally; it assumes at rest the 'position shown in the drawing andis held in that positionv on one side by a collar 25 of the secondary piston, and von the other side by a compression spring 27 resting against a plug 26. at its yleft-hand end so as to act as a closure valve and is pushed by the spring 27 against its seat when the pump is'not working, so that the penetration of vfuel into the 'pressure cylinder 16 is prevented.

A vertical hole 29 for a suction valve 3() anda vertical lhole 3`1'for pressure valve 32 are provided the pres- The collar, 25 has a conical shape 4 t sure cylinder body 28; both valves being designed as spring-loaded ball valves. The valve springs are retained by two

hollow screws

33 and 34. A pipe connection 35 is provided for connection to the injection nozzle, which is not shown. The fuel is supplied through a lateral hole 36 in the pump casing 1 and one connecting duct 37 for each of the pump elements to the suction valve 30. In order to avoid any damage to the fuel injection pump if the motor should rotate in the reverse direction, the cam 5 isheld lboselyv on the camshaft 4 and is driven in the normal direction of rotation by a spring-loaded pawl 38, which lets `the cani rotate freely if the direction of rotation is reversed.

The fuel injection pump described here operates as follows:

Suction stroke-During each rotation of the camshaft 4 the swinging lever 9 is moved comparatively slowly towards the left and drives the control piston 15, against the action of the compression spring 12. The secondary piston 24 follows also this motion from the right to the left, and since it is shaped as a plunger piston, it iiicreases the fuelpump space and thus enables fuel to pass through the valve 30. i

Working stroke-As soon as the extension 7 drops along the releasing edge 6, the swinging lever 9 andthe control piston 1S move suddenly to the right. This will remove the oil which has entered the space 22 through the control port 23 during the suction stroke. When the control piston 15 reaches the edge of the port 23, no more oil can escape and the lifting strokeis stopped immediately. The stroke is stopped sooner or later, and thus the quantity of fuel is regulated according to the position of the control sleeve. The oil pressure set up in the space 22 when the stroke is completed acts only radially on the contro-l sleeve and has no force components acting against the displacing mechanism 18 and 20. This ensures that the quantity of fuel supplied can be adjusted easily over the entire range of speeds, and also when the engine has stopped. v

The space between the right-hand end of the control piston 15 and the left-hand end of the Secondary piston 24 is always filled with oil, whose volume is compensated by a port 23, which is always uncovered at the end of the suction stroke.

At the commencement of the working stroke the control piston 15 is pushed from the left to the right by the stored energy7 of the spring 12, and the port 23 is closed. The oil, which is now trapped in the pressure cylinder, transfers the energy of the spring 12 to the secondary piston 24, which penetrates into the high-pressure space of the pump, displaces fuel from it and feeds it through the valve 32 to the injection nozzle. The difference between the pressure of the lubricating oil in the pressure cylinder between the two pistons and the back pressure of the fuel is always equal to the pressure exerted by this comparatively weak spring 27. This lubricating oil pressure, tuned to the fuel pressure, ensures that no fuel can penetrate into the Walls of the pressure cylinder, while the lubricating oil consumption is kept to a minimum, .in spite of effective lubrication.

The quantity of lubricating oil passed into the fuel space is so small that it has no effect at all on the formation of the mixture.

The sudden motion of the control piston 15 and ofthe secondary piston 24, which is effected always at the same speed, independently of the speed of rotation, has also the advantage that the injection is effected suddenly, so that the fuel is well atomized. Also, the tolerances of the set quantity of fuel in the individual pump elements of multi-cylinder pumps can be kept within very narrow limits. l While the invention has" been describedv in detail with respect "to now lpreferred example and veinhodirnriit of the invention vit will be understood by those skilled'in the Vart after understanding the invention, that various changes and modifications may be made without departing from the spirit and scope of the invention and it is intended, therefore, to cover all such changes and modifications in the appended claims.

Having thus described our invention, we claim as new and desire to secure by Letters Patent:

1. A fuel injection device of the type described for non-lubricating fuels comprising an oil filled casing, a pressure cylinder, conduit means connecting said cylinder with the interior of said casing, a second conduit means connecting said cylinder with a non-lubricating fuel injection chamber, means for injecting a non-lubricating fuel into said chamber, a pair of pistons disposed in said cylinder in spaced relationship to each other, one of said pistons being spring-biased and extending for substantially its entire length in said cylinder intermediate said first and second mentioned conduit means and the other of said pistons being disposed on the other side of said first mentioned conduit means from said first mentioned piston, and actuating means disposed in said oil filled casing for moving said second mentioned piston toward said first mentioned piston, whereby said first mentioned piston will be displaced and moved into said injection chamber as a result of oil, which is forced under pressure from said first mentioned conduit means against said first mentioned piston in said cylinder with the oil in turn also having a lubricating effect on the first mentioned piston during the entire movement of the first mentioned piston, a camshaft disposed in said oil filled casing, said actuating means including a swinging lever disposed in said oil filled casing and operatively connected to said second mentioned piston and to the camshaft.

2. The device as set forth in claim l including means also disposed within said oil filled casing for adjusting the stroke of said second mentioned piston independently of said actuating means.

3. A fuel injection device of the type described for non-lubricating fuels, comprising an oil filled casing, a

- pressure cylinder, conduit means placing said cylinder in open communication with the interior of said casing, a second conduit means connecting said cylinder with an injection chamber for a non-lubricating fuel, means for injecting a non-lubricating fuel into the said chamber, a pair of pistons disposed in said cylinder in spaced relationship to each other, one of said pistons being springbiased in said cylinder intermediate said first and second mentioned conduit means, and the other of said pistons being disposed on the other side of said first mentioned conduit means from said first mentioned piston, and actuating means disposed in said oil filled casing for moving said second mentioned piston toward said first mentioned piston, whereby said first mentioned piston will be displaced and moved into said injection chamber as a result of oil which is forced under pressure from said first mentioned conduit means against said first mentioned piston in said cylinder with the oil in turn also having a lubricating effect on the full length of the first mentioned piston during the entire movement thereof, a camshaft disposed in said oil filled casing, and said actuating means including a swinging lever operatively connected to said second mentioned piston and to the camshaft, said camshaft being spiral shaped and having releasing edge means for impart-ing sudden movements tov said swinging lever.

4. The device as set forth in claim 3 including means disposed within said oil filled casing for adjusting the stroke of said second mentioned piston independently of said actuating means.

5. The device as set forth in claim 4 wherein said adjusting means comprises a regulating sleeve soy arranged with respect to said cylinder, whereby the sleeve can slide longitudinally thereof.

6. A fuel inject-ion device of the type described for non-lubricating fuels comprising an oil filled casing, a pressure cylinder, a conduit means connecting said cylinder with the interior of said casing, a second conduit means connecting said cylinder with a non-lubricating fuel injection chamber, means for injecting a non-lubricating fuel into said chamber, a pair of pistons disposed in said cylinder in spaced relationship to each other, one of said pistons being spring-biased and extending for substantially its entire length in said cylinder intermediate said first and second mentioned conduit means and the other of said pistons being disposed on the other side of said first mentioned conduit means from said first mentioned piston, actuating means disposed in said oil filled casing for moving vsaid second mentioned piston toward said first mentioned piston, whereby said first mentioned piston will be displaced and moved into said injection chamber as a result of oil, which is forced under pressure from said first mentioned conduit means against 'said first mentioned piston, with the oil in turn also having a lubricating effect on the entire length of the first mentioned piston during the full movement of the same, said actuating means including a swinging lever operatively connected to said second mentioned piston and to a cam, said cam being loosely held on a driving shaft, and a spring-loaded pawl fon driving said cam in the direction of rotation of said driving shaft.

References Cited in the file of this patent UNITED STATES PATENTS Fagerholt Mar. 2, 1954