US3834838A

US3834838A - Method of an apparatus for filling a fuel injection pump

Info

Publication number: US3834838A
Application number: US00237141A
Authority: US
Inventors: J Indra
Original assignee: Vysoke Uceni Technicke V Brne
Current assignee: Vysoke Uceni Technicke V Brne
Priority date: 1971-03-24
Filing date: 1972-03-22
Publication date: 1974-09-10
Anticipated expiration: 1991-09-10
Also published as: DE2214184A1; ES430023A1; YU33409B; AT316222B; NL7203728A; GB1368534A; FR2131608A5; ES401054A1; CH538050A; RO56413A; DD97027A5; BR7201713D0; YU74972A; IT950680B

Abstract

Method of and apparatus for filling a piston fuel injection pump of internal combustion engines with fuel. The fuel is fed through a side filling channel into a space over the piston which is under negative gauge pressure during the movement of said piston to its lower dead center, as well as during its movement toward its upper dead center until the filling channel is covered by the edge of the piston at the moment when there is still negative gauge pressure in the area above the piston. During the subsequent displacement of the piston to the upper dead center, the negative pressure in said space disappears and the fuel starts being discharged into the delivery conduit. The volume of fuel flowing through the filling channel is adjustable by varying the entering pressure of the fuel.

Description

O United States Patent 1 1 [1 11 3,834,838

Indra Sept. 10, 1974 [54] METHOD OF AN APPARATUS FDR 2,888,876 6/1959 Nichols 417/490 FILLING A FUEL INJECTION PUMP FOREIGN PATENTS OR APPLICATIONS 1 lnvemorl Jammir Brno, 1,357,519 2/1964 France 417/490 Czechoslovakia [73] Assignee: Vysoke uceni technicke v Brne, Primary ExaminerWilliam L. Freeh Brno, Czechoslovakia Assistant Examiner-Richard E. Gluck [22] Filed: Mar. 22, 1972 21 Appl. No.: 237,141 [57] ABSIRA CT Method of and apparatus for filling a piston fuel injection pump of internal combustion engines with fuel. [30] Forelgn Apphcauon Pm mty Data The fuel is fed through a side filling channel into a Mar. 24, Czechoslovakia pace over the piston is under negative gauge pressure during the movement of said piston to its U-S. lower dead center as we as during its movement to- [51] Int. Cl. F04b 7/04, F04b 39/10 ward its upper dead center until the fining channel is [58] F leld of Search 417/490, 501, 53, 494, covered by the edge f the piston at the moment when 417/499 252; 123/139 AA, 139 there is still negative gauge pressure in the area above 139 AB, 139 139 R the piston. During the subsequent displacement of the piston to the upper dead center, the negative pressure [56] References C'ted in said space disappears and the fuel starts being dis- UNITED STATES PATENTS charged into the delivery conduit. The volume of fuel 2,522,390 9/1950 Peterson 417/252 x flowing through t filling Channel is adjustable y 2,642,804 0/1953 Bowers 417/252 varying the entermg pressure of the fuel. 2,727,493 12/1955 Reiners 123/32 R 10/1957 Aldinger 123/139 R 2 Claims, 2 Drawmg Flgul'es 1 l M Q METHOD OF AN APPARATUS FOR FILLING FUEL INJECTION PUMP The present invention relates to a method of filling a piston fuel injection pump for internal combustion engines, and to an injection pump for performing such method.

The volume of injected fuel charges of known piston injection pump delivered by one piston stroke is changed by means of turning the piston, which is made as a sleeve valve in its upper part, and is provided with a helical change regulating edge. The pump cylinder is provided with at least one radial filling channel. As the pump piston moves from its lower dead center, the fuel which has been sucked into the cylinder through the said filling channel is bypassed back to the fuel source until the upper edge of the piston covers that channel. Subsequently, an effective discharge of the pump into the delivery conduit and to the delivery nozzle begins; the discharge lasts until the regulating edge of the piston has uncovered the said filling channel again. From this moment on, until the upper dead center of the piston is reached, the fuel from the cylinder is again by passed to the fuel source, i.e., filling chamber through the filling channel.

The main feature of this system consists in that a part of the discharged fuel is bypassed before, and a part of the fuel is bypassed after the effective discharge. The bypassing of fuel, especially after the effective discharge has been terminated, is performed at high speeds, particularly in the case of large pumps; this is the case of cavitation erosion on the sealing surface of the piston above the regulating edge. The damage to the sealing surface of the piston due to this type of erosion is so severe that the piston must periodically be exchanged.

Another feature of such system is the fact that only a small sealing surface of the piston is available opposite the filling channel when the piston is adjusted for small injection charges. Particularly in the case of large diameter pistons, the tightness of individual pistons in this area appears to be very irregular, thus causing serious trouble when pumps for multi-cylinder engines must be adjusted.

It is, therefore, an object of the present invention to create a pump without any bypassing of fuel from the cylinder before or after the effective discharge of fuel, thus preventing the above-discussed cavitation erosion from taking place, while insuring excellent piston tightness both for large and for small charges of injected fuel.

In the method according to the present invention the fuel is fed to the negative gauge pressure area above the piston through the side filling channel during the displacement of the piston to the lower dead center and also during movement of the piston toward its upper dead center, until the filling channel is covered by the edge of the piston, while there is still negative gauge pressure, that is, sub-atmospheric pressure, in the area above the piston. Thereupon, during the subsequent displacement of the piston to the upper dead center, the negative gauge pressure in the pump cylinder disappears, and the fuel starts being discharged into the delivery conduit; the volume of fuel flowing through the filling channel is adjustable, so as to vary the volume of the fuel charges.

It is further advantageous when the discharge of fuel into the delivery conduit begins {after the piston has covered the filling channel), when the piston has travelled a distance equalling from one half to one full stroke of the piston during the active fuel delivery.

An object of the apparatus for performing the method according to the present invention consists in that the body is provided with a filling channel preceded by a throttling nozzle or orifice providing means, said channel being connected with the filling chamber.

The foregoing and other features of the invention set out in the appended claims are incorporated in the specifica embodiment hereinafter particularly described with reference to the accompanying drawings in which:

FIG. 1 diagrammatically shows the axial section of the whole injection pump, and

FIG. 2 is a view in section on an enlarged scale of a part of the pump around the filling channel.

A smooth piston lapped into the pump body 2 is pushed to displacement by the cam 3 through the action of the lifting element 4 with a roller, the piston being returned directly by a coil compression spring 5. A relief delivery valve 6 of known construction, represented as a ball valve in order to simplify the drawing, is accommodated in the body 2 above the piston 1. At the side a lateral filling channel 7 debouches into the area above the piston, said filling channel being drilled in the body 2, preceded by a throttle nozzle or orifice providing insert 8. Means is providedto deliver fuel at a controlled constant pressure to a filling chamber 9 in the body 2 in advance of the throttling nozzle8. As a non-limiting example of such means there is shown in FIG. 1 a conventional constant pressure outlet valve 15 interposed in the conduit 14 which supplies fuel to filling chamber 9. As indicated, valve 15 delivers fuel under constant pressure, such constant pressure being adjustable by adjustment of valve 15.

The fuel discharge by piston 1 through the delivery valve 6 is delivered through the channel 10 and the adjacent discharge piping 12 to an injection nozzle (not shown).

As the piston 1 moves from its upper dead center downwards under the action of spring 5,, the delivery valve 6 closes and vacuum is created above the piston the area is now filled with vapors of fuel left over the piston. From the moment when the upper edge of piston 1 starts opening the lateral filling channel 7, the fuel from the filling chamber 9 begins streaming through the throttle valve 8 into the evacuated space above the piston. The fuel is brought to the filling chamber 9 under an overpressure which is adjustable as required. The filling of the space above the piston l continues until piston I has passed through its lower dead center (see position I of piston l as represented in FIG. 2), and until its upper edge 11 has again fully covered the lateral filling channel 7.

The value of the pressure of the fuel fed to the filling chamber 9 is controlled so as always to prevent the evacuated space above the piston 1 from being filled with liquid fuel during the filling period when. theengine. is running. For that reason the piston 1 must perform, in addition, a certain stroke a (FIG. 2) during its movement upwards, in order that the fuel vapors above the piston 1 may disappear and the whole space above the piston 1 shall become filled with liquid fuel only.

See position ll of piston l, as shown in FIG. 2. From this moment on, the effective displacement of fuel takes place, as marked by the stroke from the space above piston 1 over the delivery valve 6 to the upper dead center of the piston 1. See position Ill in FIG. 2. As the piston 1 moves from the upper dead center downwards, the whole described process is repeated.

Under conditions of rated fuel delivery, the stroke a =O.5 to l of stroke b, in order to insure sufficient tightness of piston 1, while preventing pressure shocks from being transmitted from the space above the piston l to the filling chamber 9.

Provided the injection pump is to deliver smaller injection charges of fuel than the rated charge, fuel is brought to the filling chamber 9 under decreased over pressure. During the filling period, then, a smaller volume of fuel streams to the low pressure space above the piston l and, consequently, the fuel vapors during the subsequent pulling stroke of the piston 1 disappear later, thus leaving only a smaller stroke of piston l for effective fuel displacement. If the fuel delivery into the filling chamber 9 is cut, the delivery of fuel to the injection pump is stopped. For the starting speed of the engine, such filling of the space above the piston l with liquid fuel can be obtained by adjusting the pressure in the filling chamber 9 so that effective fuel displacement begins immediately after the channel 7 has been covered by the upper edge 11 of the piston 1. Thus an increase of the starting charge delivery as compared to the rated charge delivery is reached, which contributes to the facilitating of cold engine starts.

Moreover, besides the above-mentioned advantages of better piston tightness and of eliminating the sources of cavitation erosion at the piston, among further advantages of the injection pump of the invention there should be mentioned a simpler design of the piston l, and its longer service life. There is further attained a considerable simplification of the whole injection pump based on the fact that the relatively complicated mechanism for turning the piston l, exacting from the viewpoint of production technology and indispensable for the current injection pumps, can be altogether eliminated.

Although the invention is illustrated and described with reference to one preferred embodiment thereof. it is to be expressly understood that it is in no way limited to the disclosure of such a preferred embodiment, but is capable of numerous modifications within the scope of the appended claims.

What is claimed is:

l. A reciprocating piston fuel injection pump for in ternal combustion engines said pump comprising a pump cylinder, a piston reciprocable in the cylinder between its upper dead center and its lower dead center, means for reciprocating the piston, a side filling channel in the cylinder intermediate the upper and lower dead centers of reciprocation of the piston therein, the cylinder and the fluid displacing end to the piston presenting a space therebetween, the fluid displacing end of the piston having an edge which covers and seals the filling channel during movement of the piston toward its upper dead center, a fuel filling chamber external of the cylinder, a fuel conducting conduit means between the filling chamber and the end of the filling channel removed from the space in the cylinder, a throttling orifice means interposed in said conduit means, and means to subject the fuel in the filling chamber to positive pressure, the parts being so constructed and arranged that negative gauge pressure exists in the space in the cylinder when the filling channel is completely covered by said edge of the piston during the upward movement of the piston, and negative gauge pressure is eliminated from said space by further upward movement of the piston.

2. A fuel injection pump according to claim 1, comprising means to vary the pressure to which the fuel is subjected in the filling chamber.

Claims

1. A reciprocating piston fuel injection pump for internal combustion engines said pump comprising a pump cylinder, a piston reciprocable in the cylinder between its upper dead center and its lower dead center, means for reciprocating the piston, a side filling channel in the cylinder intermediate the upper and lower dead centers of reciprocation of the piston therein, the cylinder and the fluid displacing end to the piston presenting a space therebetween, the fluid displacing end of the piston having an edge which covers and seals the filling channel during movement of the piston toward its upper dead center, a fuel filling chamber external of the cylinder, a fuel conducting conduit means between the filling chamber and the end of the filling channel removed from the space in the cylinder, a throttling orifice means interposed in said conduit means, and means to subject the fuel in the filling chamber to positive pressure, the parts being so constructed and arranged that negative gauge pressure exists in the space in the cylinder when the filling channel is completely covered by said edge of the piston during the upward movement of the piston, and negative gauge pressure is eliminated from said space by further upward movement of the piston.