US3029737A

US3029737A - Self-regulating reciprocating pumps

Info

Publication number: US3029737A
Application number: US785738A
Authority: US
Inventors: Bessiere Pierre Etienne
Original assignee: Individual
Current assignee: Individual
Priority date: 1958-01-21
Filing date: 1959-01-08
Publication date: 1962-04-17
Anticipated expiration: 1979-04-17

Description

A ril 17, 1962 P. E. BESSIERE 3,029,737

SELF'TREGULATING RECIPROCATING PUMPS Filed Jan. 8, 1959 I 26 25 V M A :4 5 go 28 INVENTOR Berra ffl'elm B an-avg."

3,029,737 SELF-REGULATING RECIPROCATING PUMPS Pierre Etienne Bessiere, 55 Blvd. du Commandant Charcot, Neuilly-sur-Seine, France Filed Jan. 8, 1959, Ser. No. 785,738 Claims priority, application France Jan. 21, 1958 4 Claims. (Cl. 103-4) The present invention relates to reciprocating pumps which are automatically regulated as a function of the speed by variation of the feed of liquid to the pump. This invention is more especially but not exclusively concerned with fuel injection pumps for internal combustion engines, and in particular diesel engines.

In known pumps of this kind, the beginning of liquid delivery (for instance to fuel injectors) is more and more delayed as the delivery flow rate decreases. In the case of a fuel injection pump for an internal combustion engine, where the factor of regulation is the number of revolutions per unit of time, the advance to injection is therefore reduced when the engine is running on low loads.

The object of the present invention is to provide a self-regulating pump of the above mentioned kind which is better adapted to meet the requirements of practice than those known at the present time and in particular which is such that the beginning of effective delivery is independent of the amount of liquid supplied on every delivery stroke.

The invention consists chiefly in causing every delivery stroke of a first piston driven at a speed proportional to the speed which constitutes the factor'of regulation to produce through hydraulic means a delivery stroke of a second piston (or shuttle) which delivers liquid from a pump chamber from which starts a delivery eonduit and into which opens a feed conduit, means being provided to achieve a hydraulic transmission of the movements of the first piston to the second piston as soon as the first piston starts on its delivery stroke and to produce the return stroke of the second piston, or shuttle, under the effect of the pressure under which liquid to be delivered by the pump is fed to the pump chamber, means being further provided for delaying the beginning of the feed of liquid to said pump chamber until after the beginning of the return stroke of the first piston and/or for braking the flow of the liquid through United States Patent the feed conduit to the pump chamber and/or for braking the return stroke of the second piston or shuttle.

A preferred embodiment of the present invention will be hereinafter described with reference to the accompanying drawing, given merely by way of example and in which the only FIGURE diagrammatically shows in axial section a fuel injection pump made according to the invention.

The pump includes a first piston 1, the delivery strokes of which are hydraulically transmitted to a second piston 2 which constitutes the pump piston proper. Piston 1 is reciprocated in its cylinder 3 by means of a cam 4 at a rate proportional to the speed of the internal com- 'bustion engine which is to be fed with fuel from the pump, said speed constituting the factor of regulation. in the usual manner, the cam positively drives piston 1 during its delivery stroke, whereas a spring 5 drives said piston during its return stroke. A liquid feed conduit 6 opens into cylinder 3 at a point such that the opening of this conduit into this cylinder is cleared only when piston 1 is in its lower dead center position (as shown by the drawing), this opening being closed as soon as piston 1 starts on its delivery stroke (upward stroke). The liquid fed through feed conduit 6 to cylinder 3 is a liquid capable of ensuring the hydraulic transmission from piston 1 to piston 2. This liquid may,

2 at least in some cases, be the fuel that is to be delivered by the pump.

Piston 2 reciprocate-s in a pump cylinder 3 and forms with the upper portion of this cylinder the pump chamber proper. A feed conduit 8 opens into this pump chamber to supply it with the fuel to be delivered by the pump. A delivery conduit 9 advantageously provided with a check-valve 10 leads out from said pump chamber. The lower portion of cylinder 7 and the top portion of cylinder 3 are constantly in communication with each other, for instance through an opening 11 provided in partition extending between these two cylinders. This partition serves to support the lower end of a relatively weak spring 12 which urges piston 2 in the direction of its delivery stroke. Cylinder 7 is further provided with a discharge conduit 13 which is cleared by the bottom edge of piston 2 when said piston, during the delivery stroke of piston 1, reaches the end of its own delivery stroke under the effect of the hydraulic transmission existing between

pistons

1 and 2. As soon as piston 2 clears conduit 13, its delivery stroke is stopped. Of course, means, which will be more explicitely referred to hereinafter, are provided for closing feed conduit 8 during the delivery stroke of piston 2 so that the fuel present in the pump chamber of cylinder 7 can be delivered during said delivery stroke through conduit9 toward the injector or injectors to be fed with fuel.

According to one of the characteristic features of the invention, the return (downward) stroke of piston 2 (which stroke takes place during the return stroke of piston 1 and/or during the period for which said piston 1 is in its lower dead center position and clears the opening of conduit 6) is produced by the pressure of the fuel fed through conduit 8 into the pump chamber of cylinder 7 above piston 2.

This pressure must therefore be higher than that of the liquid fed through conduit 6 and, as a matter of fact, it must be higher than the sum of this pressure and of the force exerted by spring 12 upon piston 2, if such a spring exists. Actually, spring 12 might be replaced by the mere effect of the friction of piston 2 against the inner wall of cylinder 7.

Furthermore, according to another characteristic feature ofthe invention, feed conduit 6 is made to supply a 'sufiicient amount of liquid into cylinder 3 to completely fill up the space existing between

pistons

1 and 2 when piston 1 starts on its upward stroke. Finally, and also according to a characteristic feature of the invention, means are provided for delaying the beginning of the feed or for braking the feed in conduit 8 or for slowing down the return movement of piston 2, thus to produce a reduction of the useful stroke of said piston 2.

In the embodiment of my invention illustrated by the drawing, I make use-of means which are particularly efficient and work with a high accuracy for causing the beginning of the return stroke of piston 2 to take place with a lag with respect to the beginning of the return stroke of piston 1. These means include a slide valve 14 inserted in feed conduit 8 and controlled in such manner that it closes said conduit during the delivery stroke of piston 1, but opens said conduit 8 with a given lag with respect to the beginning of the return stroke of piston 1, this lag being preferably adjustable.

For this purpose, slide evalve 14 is slidably mounted in a cylinder 15 and it is subjected to the action of a spring 16 tending to apply slide valve 14 against a shoulder 17. When slide valve 14 is in contact with this shoulder, its groove 18 opens the flow through conduit 8. Furthermore, the lower end of cylinder 15 is connected through a conduit 19 with a conduit 21, itself connected, with the interposition of a check-valve 20, with a cylinder 22 in which is slidably mounted a piston 23 rigid with piston 1. In the arrangement shown by the drawing, return spring 5 is housed in cylinder 22 and one of its ends bears against piston 23 whereas the other end bears against the pump body. A feed conduit 24 opening mto cylinder 22 has its outlet cleared by piston 23 when said piston is in its lower dead center position (as shown by the drawing) so that cylinder 22 can then be filled w th liquid. This liquid may be the same as that fed to cylinder 3 through conduit 6, so that

conduits

24 and 6 may branch out from a single feed conduit 25. The portion of conduit 21 extending downstream of check-valve and of the point where conduit 19 branches otf therefrom includes a throttled portion 26 preferably adjustable by means of a screw valve 27. This portion of conduit 21 further includes a valve member 28, for instance of the form of a grooved slide valve adapted to close conduit 21 as long as piston 23 is moving on its upward stroke. For this purpose, slide valve 28 is actuated in such manner as to close conduit 21 under the effect of the pressure existing in cylinder 22 during the upward stroke of piston 23, this pressure being transmitted through a conduit 29 to the cylinder 30 in which slide valve 28 is slidable. Slide valve 28 is returned into the position where it opens conduit 21 (as shown by the drawing) by a spring 31.

Consequently, when piston 23 is moving on its upward stroke, it causes the simultaneous closing of

conduits

8 and 21. The upward movement of slide-valve 14 stops when the lower edge thereof clears a notch 32 provided in the portion 8a of conduit '8 located upstream of said slide valve 14. This notch 32 permits the excess of liquid delivered by piston 23 to escape to the outside without causing conduit 8 to be opened. The clearing of notch 32 by slide valve '14 determines the upper limit position of said slide valve. In this position, the lower edge of groove 18 is located at a distance above the top of conduit 8. Slide valve 14 remains inisaid upper position until

pistons

1 and 23 start on their downward strokes. Then, slide valve 28 is pushed upwardly by spring 30 and clears conduit 21 so that slide valve 14 can start moving downwardly. However, in view of the fact that the lower edge of groove 18 is at some distance above conduit 8, the opening of said conduit does not take place immediately as

pistons

1 and 23 start moving down. Some time elapses before conduit 8 is being opened, this delay being due to the braking of the liquid driven out through conduit 21 by slide valve 14 as it flows past the throttled passage 26 (check-valve 20 preventing any return of the liquid toward cylinder 22). I thus obtain a lag of the beginning of the feed of fuel to cylinder 7, with respect to the beginning of the return stroke of piston 1. This lag may be adjusted by varying the cross sectional area of throttled passage 26 and/or varying the compression of spring 16 (through means not shown on the drawing).

The operation of the lows:

Since, at the beginning of the upward stroke of piston 1, the whole space between said piston and piston 2 is pump abovedescribed is as folfilled with liquid, the delivery stroke of piston 2 starts just when piston 1 closes the opening of feed conduit 6. This delivery stroke lasts until the lower edge of piston 2 clears the opening of discharge conduit 13. Spring 12, if such a spring has been provided, is too weak to cause the upward stroke of piston 2 to go on after this time. During this delivery stroke, slide valve 14 keeps feed conduit 8 closed so that the liquid present in the upper chamber (pump chamber) of cylinder 7 delivers fuel into conduit 9, during said upward stroke of piston 2.

When piston 1 starts on its return stroke (downward stroke), slide valve 14 is still keeping feed conduit 8 closed so that piston 2 remains in its upper position where it is kept by spring 12 or merely by the friction against the wall of cylinder 7. It is only when slide valve 14, during its braked downward movement, opens feed conduit 8 75 feed conduit 8 to that the fuel under pressure supplied to cylinder 7 pushes piston 2 downwardly so as to fill up the pump chamber of cylinder 7.

As long as the speed at which piston 1 is driven is below a given value, the fuel fed through conduit 8 is given suflicient time, despite the lag in the opening of this conduit, to push back cylinder 2 to the maximum distance determined either by the compression of spring 12 or by an abutment, before piston 1 starts on its next upward stroke which is immediately transmitted to piston 2. Consequently the amount of fuel supplied on every delivery stroke of piston 2 into conduit 9 is maximum. If, on the contrary, the speed at which piston 1 is driven rises, due to an acceleration of the engine above said given value, piston 1 starts on its delivery stroke before the fuel arriving through feed conduit 8 has been given time to push back piston 2 to the maximum distance. The return strokes of this piston will then be the shorter as the speed of piston 1 .rises more and more above said given value. In other words, the volume of fuel that enters the pump chamber is the smaller as the speed of piston 1 is higher in view of the fact that this volume is proportional to the time elapsing between the opening of conduit 8 by slide valve 14 and the beginning of the next delivery stroke of piston 2, which coincides with the beginning of the delivery stroke of piston 1. I therefore obtain self-regulation without modification of the relative time at which injection begins because whatever be the position of piston 2 in cylinder 7 when piston 1 starts on its upward stroke, piston 2 is immediately driven in the upward direction since, as above stated, the interval between

pistons

1 and 2 is wholly filled with liquid when piston 1 starts 3n its upward stroke and closes the opening of feed conuit 6.

If, for instance, when the speed is equal to the given value for which self-regulation star-ts being obtained, the time for which feed conduit 8 is opened is ,4 of the time elapsing between the beginning of the return stroke of piston 1 and the beginning of its next upward stroke, an increase of the speed of 10% is suificient to stop the. feed of fuel by the pump.

The fineness of regulation of the pump might be fur-- ther improved by having screw 27, which adjusts the cross sectional area of throttled passage 26, controlled by a speed governor so that said cross sectional area is automatically reduced when the speed increases.

An analogous effect might be obtained, according to a first modification, by replacing the lag in the opening of slide valve 14 with respect to the beginning of the return movement of piston 1 by a braking action exerter for instance by a throttled passage provided in feed con duit 8, the cross sectional area of said passage being either fixed or variable as a function of the speed. This throttled passage would brake the inflow of fuel through cylinder 7.

According to another modification, the speed of the return stroke of piston in the lower chamber of cylinder 7 a duit provided with able as a function I might brake 2 by providing discharge cona throttled passage preferably adjustof the speed, by inserting in this discharge conduit a valve member which closes it when piston 1 is moving upwardly and by inserting in the communication hole 11 provided between cylinders 3 and 7 a check-valve permitting the flow of liquid only from cylinder 3 toward cylinder 7.

Of course, in this last mentioned modification, the inside of cylinder 3must be filled with liquid, fiowing through conduit 6, when piston stroke so that this liquid, together with that present in the lower chamber of cylinder 7, serves to transmit immediately the upward movement of piston 1 to piston 2.

In a general manner, while I have, in the above description, disclosed what I deem to be a practical and efficient embodiment of my invention, it should be well 1 starts on its upward understood that I do not wish to be limited thereto as there might be-changes made in the arrangement, disposition and form of the parts without departing from the principle of the present invention as comprehended within the scope of the accompanying claims.

What I claim is:

l. A reciprocatinglaction pump which comprises, in combination, a cylinder, a piston fitting slidably in said cylinder so as to form therewith a pump chamber, a second cylinder fixed with respect to said first mentioned cylinder, constantly open fluid communication means between said two cylinders for connecting one end of said second cylinder with said pump chamber, a piston fitting slidably in said second mentioned cylinder so as to form therewith a pump chamber on the other side of said second mentioned piston from said end of said second mentioned cylinder, means in communication with said first cylinder for filling with liquid, from the beginning of every delivery stroke of said first mentioned piston, the whole volume of said first mentioned pump chamber, said communication means and the portion of said second cylinder on the same side of said second piston as said end of said second cylinder, means for reciprocating said first piston at a rate proportional to a factor of regulation, whereby every delivery stroke of said first piston produces a simultaneous delivery stroke of said second piston, a delivery conduit leading out of said second pump chamber, a feed conduit opening into said second pump chamber for feeding liquid ,under pressure thereto to produce the return strokes of said second piston, means, interposed between said second piston and said second cylinder, for yieldingly opposing the return strokes of said second piston, said second pump chamber being filled with said liquid at the end of each of said return strokes and means operatively connected with said first piston for preventing the flow of liquid through said feed conduit to said second pump chamber until after the beginning of every return stroke of said first piston.

. slidably in said second mentioned cylinder so as to form therewith a pump chamber on the other side of said second mentioned piston from said end of said second mentioned cylinder, means in communication with said first cylinder for filling with liquid, from the beginning of every delivery stroke of said first mentioned piston, the

whole volume of said first mentioned pump chamber, said communication means and the portion of said second cylinder on the same side of said'second piston as said end of said second cylinder,'means for reciprocating said first piston at a rate proportional to a factor of regulation, whereby every delivery stroke of said first piston produces a simultaneous delivery stroke of said second piston, a delivery conduit leading out of said second pump chamber, a feed conduit opening into said second pump chamber for feeding liquid under pressure thereto to produce the return strokes of said second piston, means, interposed between said second pistonand said second cylinder, for yieldingly opposing the return strokes of said second piston, said second pump chamber being filled with said liquid at the end of each of said return strokes, a slide valve inserted in said feed conduit for controlling the flow of said last mentioned liquid toward said second pump chamber, and means operatively connected with said first piston for closing said slide valve during every delivery stroke of said first piston and opening it after the beginning of the return stroke of said second piston.

4. A pump according to claim 3' in which said means for closing said slide valve are hydraulic means and said means for opening said slide valve are resilient means, further including hydraulic means for braking said open ing of said slide,valve.

References Cited in the file of this patent FOREIGN PATENTS 127,951 Great Britain June 5, 191 9 402,603 Great Britain Dec.7, 1933