US2396602A

US2396602A - Liquid pump

Info

Publication number: US2396602A
Application number: US288942A
Authority: US
Inventors: Posch Oskar
Original assignee: Individual
Current assignee: Individual
Priority date: 1938-08-13
Filing date: 1939-08-08
Publication date: 1946-03-12
Anticipated expiration: 1963-03-12

Description

o. Poser-1 March 12, 1926.

LIQUID PUMP 4 Sheets-Sheet 1 Filed Aug. 8, 1959 a; .v ia

Y W a v 47 /////A U INY'VENTOR OJ/fA/PPOJCW Y d- ATTQRNgYS/ March 12, 1946. O, Pose 2,396,602:

LIQUID PUMP Filed Au fa, 1959 4 Sheets-Sheet 2 mvmo'a 2.3704 Pox/l BY a M z a :96 ATTORNEYS March 12, 194 0. P5SCH 2,396,602

LIQUID PUMP Filed Aug. 8, 1939 4 Sheets-Sheet 3 INVENTOR Y Qf/MPPOIC/l ATTORNEYS I March 12, 1946. o. POSCH 2,396,602

' LIQUID PUMP Filed Aug. 8, 1939 4 Sheets-Sheet 4 INVENTOR. V Y OJ/(A/P P010? Patented Mar. 12, 1946 LIQUID PUMP Oskar Posch, Stuttgart-Bad-Cannstatt, Germany; vested in the Alien Property Custodian Application August 8, 1939, Serial No. 288,942

In Germany August 13, 1938 a Y 12 Claims.

These improvements in liquid pumps, particularly concern fuel-injection pumps for internal combustion engines.

One object is to attain greater reliability of operation and more accurate amount of the liquid to be delivered, particularly when fuel has to be injected in very small quantities. In this connection it is important to prevent the occurrence or collection in the pump of vapour or air bubbles which would otherwise form an elastic cushion. Such cushions when compressed and re-ex panded in the cycle of piston movement, are liable to impair or even completely interrupt the pump delivery.

The invention provides a pump, wherein the delivery of fuel is performed by two co-axial pump pistons displaceable relatively to each other, one of the two pistons preferably being mechanically driven whilst the other piston is loaded by spring pressure which tends to bring the opposed ends of the two pistons into positive contact. Suction is effected by the movement apart of the pistons, one of the two pistons being preferably held by an abutment, and delivery is effected by the movement towards each other of the two pump pistons, and particularly under the pressure of th spring loading after the opening of the outlet passage. The opposed end surfaces of the two pump pistons enclosing the pump chamber between them are so constructed and machined that when they encounter each other at the end of the pressure stroke they bear on each other completely closely so that no harmful space remains between them.

A further object of the invention is to provide a graduated and progressive spring loading whereby the two pistons ends aforesaid are brought into positive contact, particularly so that the full maximum loading determining the delivery pressure commences only shortly before the opening of the pressure outlet passage whilst otherwise only a comparatively slight spring loading exists. This results in increased reliability and accuracy of operation by reason of the spar= ing of the pump parts and reduction of the leakage losses. Also adjustments to be performed under some circumstances upon the pump parts are facilitated.

Another object is the provision of a special relief passage giving an abrupt termination of the delivery so that dripping of the fuel at the injection nozzle, is avoided particularly when long delivery ducts are present. The relief passage is preferably controlled by one of the two pistons, for example by means of a controlling groove a further modifications, and

which is separate from the pump chamberand establishes communication between the pump outlet to the relief passage. The relief may occur before or after the termination of the pressure stroke of the positively driven pump piston. In the former case, the controlling groove is preferably arranged in the positively driven piston and in the latter case preferably in'the non-positively moved piston.

In order to achieve at high speeds, a reduction of the quantity injectedper stroke, as is desir-- able for the sake of torque constancy, provision is made for throttling the fuel flowing from the pump tothe injection nozzle at higher speeds. The throttling means may be adjustable, and

' may take the form of a changeable or adjustable throttling plate.

Yet another object is the provision of appropriate means for regulating the quantity delivered or the timingof the delivery and in particular, the termination .of delivery, that is the termination of the injection period in the case of injection pumps. However the commencement of delivery and the termination of delivery may also be controllable simultaneously The regulation of the termination of delivery is preferably performed by means of an inclined edge of a controlling groove provided in one of the two pump pistons for controlling the relief passage,

the piston being rotatably adjustable for varying the control exercised by the inclined edge.

Further'features and objects of the invention will appear from the following description with reference to the annexed drawings wherein:

Figure 1 is a vertical section of one form of pump in accordance with the invention,

Figures 2 and 3 illustrate modifications of Figure 1,

Figure 4 is a fragmentary view illustrating a modification of Figure 3, l

Figures 5 and 6 are vertical sections of still Figures '7 and 8 are diagrams illustrating pump deliveries under different controls. 7

In Figure 1, two pump rams or

pistons

2 and 3 acting against each other are arranged co-axial ly in a cylinder body I. The pump piston 2. which is shown in its lowerdead-centre position, is driven by a cam 4, designed in accordance with the desired injection law, and a return spring 5. The pump piston 3 is loaded, in the position illustrated, by a comparatively weak spring 6 which presses it by means of its collar '1 against an axially adjustable abutment 8. For example, the abutment may be adjustable by screwing it up or down in the recess in which it is inserted. A stronger spring I only comes in to action upon the pump piston 3 when the latter has risen by the amount :I:, at which moment the abutment formed between the end surface I2 of the lower piston 2 and the end surface II of the upper piston 3 has an axial length 11 in the lower deadcollar 1 provided on the pump piston I bears upon the annular abutment I which is adjustable as to its level but is normally fixed. During the further downward movement of the pump piston 2, the pump piston 3 can no longer follow the said movement, the end surfaces Iland I2 separate from each other again and first of all an absolute vacuum is formed between them which is not disturbed by the presence of vapours, as every trace of fuel residues has been previously removed. When, in the course.of the further downward movement, the suction passa e II is centre position of the driven piston I. 'The suction or inlet port II is then uncovered and the pressure or outlet port II is closed. There may be several of each of these ports. For the axial adjustment of the annular abutment I. a displaceable rack Ia may engage teeth on the annulafabutment. 1

j' The manner of operation is as follows:

'jIfthe pump piston 2 is moved upwardly by the then after passing over the suction passage or passages II, it forces the quantity of fuel located in the pump chamber l4 against the end surface II of the pump piston 3. Up to this moment, only the opposing pressure of the spring I acts against the upward movement of. the pump piston I. Shortly before the pump piston I, during its upward movement, opens the pressure passage or passages II, the collar 1 on the pump piston I, after a movement .1: thereof, comesinto contact with the abutment II subject to the loading of the spring 9. Upon the further upward movement of the pump piston 2, the pressure of liquid in chamber'll must rise to such an extent as to overcome the opposing pressure. of the two springs I and I. Thereafter, the .pump piston I also rises further and finally opens the outlet II, the liquid fuel then passing into the v outlet II under the maximum pressure lust reached. Such maximum pressure is determined fb'y the force of the two springs I and I and can be varied within very wide limits by changing the springs or varying their force. Preferably, the upper dead-centre position of the pump piston I is so determined that its end surface I2 in this dead-centre position reaches preciselyto the level of the outlet II.

The delivery terminates when the pump piston I has forced into the outlet II the last residue of the quantity of fuel located between the end surfaces I2 and II. Inorder to ensure that even the last trace of a quantity of fuel still present is actually delivered and that the pump is actually free from any harmful space, the end surfaces I2 and II are ground one on the other. Upon their contact at the end of the pressure stroke, therefore, vapour or air bubbles, irrespective of what proportion they may have, are forced through the outlet II so that the subsequent pumping action is not interfered with by the presence of such vapour or air bubbles. Consequently the use of an additional feed pump,

for example, is unnecessary, as also is the provision of a de-aerating screw without which the removal of vapour or air bubbles isnot possible in pump systems already known.

Upon the downward movement of the pump piston 2 after the delivery, the pump piston I follows the same in its downward movement under the influence ofthe springs I and 9 until I!- nally the abutment I ll bears upon the cylinder housing I and, after a further movement 2:, the

opened by the pump piston 2, then fresh fuel flows into the pump chamber II under the influence of the full atmospheric pressure. As already explained, the dimension u of the pump chamber II and the quantity of fuel sucked in, are determined by the abutment I. Thus the quantity of fuel delivered can be regulated in simple and reliable fashion by variation of the level of the abutment I. Owing to the fact that the mem ber controlling the pressure passage II, namely the pump piston 1, acts after the fashion of a slide valve, it is not possible for it to partake, of harmful resonance oscillations in the pressure passage such as poppet valves, for example, are liable to suffer. This is of decisive importance particularly at very high revolution speeds (5,000 to 10,000 injections per minute). Furthermore the subject of the present invention, by reason of this arrangement. is particularly suitable for the operation of open injection nozzles.

'I'he stepwise increase of the spring loading of the pump piston I by the additional cutting in of the further spring I shortly before the openins of the pressure passage II has the followin advantages: Firstly the full spring pressure which is necessary for" the attainment'of the maximum delivery pressure never bears upon the abutment I and creates no difllculty in the ad- :Iustment of such abutment. Furthermore, the leakage loss between the pump pistons and the cylinder is reduced to a minimum by the stepwise increase of the pressure, because a low liquid pressure corresponding to the weak spring I obtains in the fuel in the pump chamber II over the largest part of the pump stroke. Only at the last instant does the liquid pressure rise to its maximum value so that the harmful effect of the leakage loss cannot develop to the-extent known in other pump systems in the short period only which thereafter remains.

In Figures 2-6, similar or corresponding parts are indicated by the same reference numerals as in Figure 1.

In Fig. 2, the pump is illustrated in the first part of the downward stroke of the two pistons and is essentially the same as that in Fig. 1. It differs in respect of the upper pump piston I which is provided with a constriction passage or relief groove H which, after the piston I has executed a short portion of the downward stroke, establishes communication between the outlet II and a relief passage II. The latter preferably leads back tothe fuel tank. so that the fuel present in excess in the delivery (such excess being due to the elasticity of the injection ducts and the compressibility of the fuel) can pass back into the tank for example by the shortest path. This arrangement gives instant relief in the outlet II.

In Fig. 3, wherein the pump pistons are shown in the upper dead-centre, another mode of relief is illustrated. There is provided on the lower Q asaaeoa point which does not come into conpiston 2, at a tact with the suction passage in theupward stroke (that is a point distant from the end surface l2 of the lower piston 2 by more than the depth of stroke), a constriction I9 which opens the relief-connection passage shortly before the upper dead-centre position of the lower piston 2. The constriction l9 then .connects'the pressure passage ii to the relief passage l8 leading back to the fuel tank 2 I, whereby there is instantaneous relief of pressure in the outlet l6. This mode of relief, in comparison withthat illustrated in Fig. 2, has the advantage that the relief and, consequently, the termination of in jection take place shortly before the upper deadcentre position of the lower piston 2. Thus that part of the injection is cut out which, owing, to the already decelerated piston movement, would otherwise result in a lingering injection which might cause dripping at the injection nozzle.

Furthermore, as illustrated in Fig. 3, a throttling plate 22, preferably changeable, is provided in the pressure passage [6 beyond the branching point of the passage 20. Its manner of operation is as follows:

During delivery, the fuel is forced to pass through the narrow bore in the small nozzle plate 22, since the relief-connection passage 20 is still closed by the pump piston 2. At low revolution speeds, there is sufficient time available for the whole of the fuel charge to penetrate through the narrow bore in the nozzle late 22. Shortly before the upper dead-centre position of'the pump piston 2, the throat-like constriction l9 opens the relief-connection passage 20, whereby an instantaneous relief of pressure in the outlet 16 takes place. At high revolution speeds, on the other hand, the time does not suffice for the flow through the nozzle plate 22 and residual fuel remains between the end surfaces l2 and iii of the two pistons. By the subsequent relief action, however, the fuel situated between the end surfaces l2 and i3 is completely discharged under the pressure of the

springs

5 and 9 through the relief-connection passage 20, the constriction I9 the pump chamber under pressure. The inlet valve is thus constructed as a non-return valve" to permit flow into the pump chamber but not in the reverse direction. In order to give light fuels no opportunity to vaporise, the mouth 28 of the suction passage is made suiliciently wideand is so arranged that the end surfaces i2 and I3 of the pump pistons 2 and-3' separate opposite this mouth at the commencement of the. suction stroke, that is whenthe collar 1 rests upon the abutment 8. By this means, any formation of vacuum is avoided andthe fuel flowing in under,

pressure passes into the pump chamber, unseat-.

ing the valve (for example a ball or disc valve) against the loading of the spring 24. During the subsequent upward movement of the pump-piston 2, the inlet valve 25 closes and preventsa return flow of the fuel into the suction passage,

. whereby any pulsatory liquid movementwhich and the relief passage l8 until the end surfaces l2, l3 bear on each other closely and without any intervening space.

The throttling plate '22 may alsov be advantageously employed in a form of construction in accordance with Fig. 2 wherein the relief passage is controlled by-the upper spring-loaded piston 3 and the delivery continues beyond the upper dead centre of the driven lower piston 2.

Fig.4 illustrates a'loading spring 23 which may be substituted for the

springs

6 and 9 in any one of the preceding examples. The spring 22 has a spring characteristic which is obtained by reason of the fact that it has different coil diameters. By this means, fluttering phenomena, such as occur with cylindrical springs for example, are suppressed since the parts of the volute spring 23 vibrating with different natural frequencies interfere with each other in the development of oscillations. The employment of progressive springs, such as 23, enables the abutment l0 il lustrated in Figs. 1 to 3- tobe dispensed with.

production of noise owing to its hammering mode of operation.

In Fig. 5,.there is an inlet valve 25 loaded by a spring 24 in the suction passage 15. The inflowing fuel is placedunder pressure by a pump 21 in front of the inlet and constructed in any desired manner, so that the fuel is supplied into might give rise to local bubble formation is avoided. a

The employment of afeed pump 21 is primarily useful for very light fuels. Owing to the. fact that the suction or inlet passage is subjected to pressure; the boiling or vaporising point of the liquid therein also arises. It is then possible to set the pump for a maximum delivery pressure which is made so high that the temperatures occurring in operation lie below the boiling temperature of the fuel subjected to the pressure in question so that formation of vapour inthe suction passage is prevented. The operation of the pump is thereby further improved. Preferably, when a feed pump is employed, the inlet valve 25 is also provided in order to-prevent a pulsatory liquid movement in the passage l5. However, in some cases, the inlet valve may also be dispense with for reason of simplicity.

In Fig. 6, the controlling groove I8. is provided with an inclined controlling edge 28. Furthermore, t e pump piston 2 can be turned about its axis thr ugh a, certainangle, for example by a displaceable rod which engages by means of a pin in a fork- Soon th piston. Upon upward movement of the piston 2, the fuel situated in the pump chamberi4 is delivered under pressure, after opening of the outlet I8, until the-inclined controlling edge 28, cut in the pressure piston 2 passes over the relief passage 20. Thereupon an abrupt relief of the pressure in the pump chamher and in the outlet l6 takes'place. The man-v such as 28 is known. By turning the pressure piston 2, the time of the commencement of the relief may be influenced at'will and consequently the delivery can be interrupted /earlier or. later. The commencement of delivery may then remain unaltered. By this means, a gradual and stepless variation of the quantities delivered and injected is inade possible.

However, if desired, the commencement of injection may be regulated as well as the termination of injection. For this purpose, for. example, use is made of the axially adjustable abutment 8 which serves, in the previously described manner, for the limitation of the movement of the piston 3 and by adjustment of which the time at which This is desirable because it gives rise to the l the outlet I6 is connected to/thepump chamber ll is' determined.

: Since the 'quantity of fuel entering at is dependent upon the limitation of the stroke of the controlling piston 8 in its downward movement; it is possible to regulate the quantity of fuel delivered to the injection nozzles of an internal combustion engin both by rotatably adlusting the piston 2 and also by adjusting the level of the abutment 8, the termination of injection being varied in the former case and the commencement of injection in the latter case.

These two regulating possibilities are illustrated in the diagrams according to Figs. 7 and 8 in which the quantity Q delivered is plotted against the crank angleor the time a. In Figure '7, A indicates the commencement of injection and E, E, E, E the termination of injection for different adjustments.

y In Figure 8, A. A A A indicate different.

commencements of the injection for several adjustments and E indicates the abrupt termination thereof.

In injection-type internal combustion engines with widely varying revolution speed, it is desirable to be ableto vary the injection timing as desired. By the simultaneous use of the two modes of regulation described above, it is possible to shift the injection period as desired, without thereby varying the quantity injected, this is accomplished by adjusting both the commencement of injection and also the termination of injection .to an earlier or later time. However, the commencement of injection and the termination of injection may be varied differently, or only the one or the other may be varied at one time, it being possible also to suit the time of injection to the loading for the time being.

For common adjustment of the abutment 8 and piston 2 by means of the regulating rods 8A and 28 thereof, these latter may be coupled together. In some cases, the adjustability of the abutment 8 may be dispensed with. Furthermore, a spring 6 in every case maybe replaced by a spring 23, or by two

springs

8 and 9, or by other suitable resilient means. Finally, a throttling plate 22 or similar throttling, device may be arranged in the pressure passage, for example, of any of the constructions.

I claim; v

1. A liquid pump comprising a pump housing enclosing a. pump cylinder, two coaxial pump pistons therein displaceable relatively to each other, the end surfaces of said pistons enclosing a pump chamber between them, said cylinder having a pump-inlet passage, a pump-outlet passage and a relief passage, said inlet and outlet passages being the only passages in direct communication with the pump chamber, resilient means operativ'e for forcing one pump piston in the direction towards the other, and controlling means operative' for controlling communication between the relief passage and the pump-outlet passage.

2.'A pump according to claim 1, wherein a recess in the second of the two pump pistons is provided as means for controlling communication between the relief passage and the pumpoutlet passage, said recess having no direct connection with said pump chamber.

.3. A pump according to claim 1, in combination with driving mechanism for driving the second of the two pump pistons, the driven pump piston controlling the pump inlet and the resiliently forced pump piston controlling the pump outlet, adjusting means operative for turning the driven pump piston formed with an inclined controlling groove, separate from and not directly connected with the pump chamber, for variably controlling the communication between the pump outlet and the relief passage.

4. A pump according to claim 1, in combination with means for adjusting the said controlling means in such fashion that the time at which the relief passage is brought into com munication with the pump-outlet passageis varied.

5. A pump according to claim 1, wherein provision is made, as the controlling means for the communication between the relief passage and the pump-outlet passage of a controlling groove, with an inclined controlling edge in the second of the two pistons and having no direct connection with said pump chamber, in combination with means for turning the piston about its axis.

6. A pump according to claim 1, in combination with a normally open throttling device in the pump-outlet passage beyond the point of communication of the relief passage with the outlet passage.

7. In a fuel-injection pump with a pump housing and a pump cylinder located therein, a pump piston, a driving mechanism for driving the pump piston, a further pump piston located coaxialiy therewith in the same pump cylinder, the end surfaces of the two pump pistons enclosing the pump chamber between them and being formed in such a manner that they may lie closely against one another without any intervening space, resilient means operative for moving the last-named pump piston towards the first-named pump piston, said cylinder having a fuel inlet passage whose connection to the pump chamber is controlled by the first-named piston, a fuel outlet passage whose connection to the pump chamber'is controlled by the secondnamed pump piston in' such fashion that the fuel, after opening of the outlet passage by the second-mentioned piston, is forced into the outlet passage under the pressure of the resilient means, and a fuel-relief passage, means for conmeeting the relief passage to the outlet passage and means for regulating the time at which this connectionis established.

8. In a fuel-injection pump with a pump housing and a pump cylinder located therein, a pump piston, a driving mechanism for driving the pump piston, a further pump piston located coaxially therewith in the same pump cylinder, the end surfaces of the two pump pistons enclosing the pump chamber between them, resilient means operative for moving the last-named pump piston towards the first-named pump piston, said cylinder having a fuel inlet passage whose connection to the pump chamber is controlled by the first-named piston, a fuel outlet passage whose connection to the pump .chamber is controlled by the second-named named piston, and a fuel-relief passage having no direct connection with said pump chamber, means for connecting the relief passage to the outlet passage, and a throttling device in the outlet passage beyond the point of connection of the relief passage to the outlet passage.

9. A liquid pump comprising a pump housing with a pump cylinder, two co-axial pump pistons therein displaceable relatively to each other. whose end surfaces enclose a pump chamber between them, said cylinder having a pump-inlet passage and a pump-outlet passage, said passages being controlled by the pistons, a driving mechanism for driving the one pump piston. resilient means by which the other pump piston is forced toward the first-named pump piston and which forces the liquid into the pump outlet under pressure upon the establishment of communication between the pump chamber and the pump outlet, said pistons having closed parallel end faces, the edges of which are surrounded by and closely guided in said cylinder, means independent; of said piston end faces for interrupting the pressure obtained in the pump outlet, and means for regulating the time of this interruption in that part of the stroke in which the pump outlet is in communication with the pump space, in such a manner that after interruption of the pressure the entire amount of liquid present in the chamber is discharged by the resilient means into the pump outlet, and the two pump pistons lie with their end faces tightly against one another.

10. In a fuel-injection pump with a pump housing and a pump cylinder located therein, a pump piston, a driving mechanism for driving the pump piston, a second pump piston located co-axially therewith in the same pump cylinder, the end faces of the two pump pistons enclosing the pump chamber between them and being formed in such a manner that they lie closely against one another without any intervening space, resilient means for moving the last mentioned pump piston toward the first mentioned pump piston, said cylinder having a fuel inlet passage whose connection to the pump chamber is controlled by the first-named piston and a fuel outlet passage connected to the pump .time of the termination of injection.

11. In a fuel injection pump, the combination in accordance with claim 10, in combination with means for regulating the time of the commencement of the connection of the fueloutlet passage to the pump chamber and thereby the commencement of injection.

12. In a fuel injection pump, the combination in accordance with claim 10, in combination with an adjustable abutment for limiting the movement of the second mentioned pump piston produced by spring pressure, so that it can follow the first mentioned pump piston only as far as this controllable end position determined by the adjustable abutment, the time of the commencement of injection being, accordingdy varied byadjustment of said abutment.

OSKAR POSCH.