DE1275328B - Fuel injection pump for internal combustion engines - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

F02m

German class: 46 c2 -105

Number: 1275 328

File number: P 12 75 328.5-13 (B 93357)

Filing date: July 6, 1967

Opening day: August 14, 1968

The invention relates to a fuel injection pump for internal combustion engines with a change in the fueled Fuel quantity depending on the speed by interrupting the pump delivery at least when the maximum speed is reached due to the opening of a relief channel in the pump working space during the delivery stroke of the pump piston by means of a reciprocating control element, which is driven by the hydraulic fluid of an auxiliary pump in synchronism with the main pump Sense of its slope is driven and during its, caused by a restoring force decline is slowed down by the fact that there is at least some of the liquid that causes its drainage has to press through a throttle element with a variable cross-section, so that with a certain Throttle cross-section and reaching a certain speed the control element as a result of occurrence of the "liquid stop" no longer runs back into its starting position at a fixed stop.

In the known fuel injection pumps of the type described (see, for example, the German patent 1153 941) the end of the fuel injection is determined by the control element by this opens a relief channel. Only the height of the liquid stop has an influence the time of this control. The input of the control element takes place in "forced operation" with the auxiliary pump, for which a liquid volume is included as a transmission medium between the auxiliary pump and the control element is. This volume of liquid has a certain compressibility, which is why it is combined with the mass of the control element forms an oscillatory system, which is caused by the acceleration shock Beginning of each slope of the control element is excited. These vibrations of the control element disturb the Regulation by determining the time of the opening and thus the useful stroke, d. H. that of the injection undesirably change the serving stroke portion of the main pump. The result is an unsteady course of the full-load injection quantity over the speed.

The invention is based on the object of controlling the full-load injection quantity independently of the movement of the control element to determine.

This object is achieved according to the invention in that the pump working space of the main pump has a second relief channel, which, as long as the control element runs back to its starting position, through the pump piston is opened before the control element opens the first relief channel.

An embodiment of the invention is advantageously designed so that the control element is the first Ent-fuel injection pump for
Internal combustion engines

Applicant:

Robert Bosch G. m. B. H.,

7000 Stuttgart 1, Breitscheidstr. 4th

Named as inventor:

Gerald Hofer,

Franz Eheim, 7000 Stuttgart

Claimed priority:

France of 19 July 1966 (69 949)

load channel only opens before opening the second relief channel when the liquid stop has reached a certain height.

Two exemplary embodiments of the invention are shown partially schematically in axial section in the drawing and are described in more detail below. Show it

Fig. 1 and 3 the first embodiment with different devices for generating a Excess amount for starting the internal combustion engine;

F i g. 2 shows diagrams showing the stroke of the control element or the pump piston over the angle of rotation represent;

F i g. 4 shows the second embodiment.

A piston 1 operates in a fuel injection pump and is driven by means not shown in such a way that it executes a reciprocating axial movement and a rotary movement about its axis. While the reciprocating movement serves to deliver the fuel, the piston serves as a distributor when it rotates. This piston is designed as a stepped piston with three stages. The first stage la with the smallest diameter works in a cylinder 2 and serves as the piston of the actual injection pump. The cylinder 2 is pushed over the piston in the shape of a hat and together with the piston 1 α delimits the pump working space 3. The third stage 1b of the piston 1 has the largest diameter and works in a cylinder 4. Piston stage Ib and cylinder 4 together form the auxiliary pump, which actuates a control slide 5 hydraulically. The step lying in the center of the piston 1 lc with a diameter of the piston step la and the piston step 1 is located between the b, serves as a manifold.

809 590/106

3 4

On the surface of the piston stage Ic is a section between two displacement strokes of the KoI ring groove 6 arranged, open into the longitudinal grooves 7. bens 1 the control slide 5 runs in its rest position There are as many longitudinal grooves 7 as cylinder back, which is determined by a fixed stop 28 that the engine is to be supplied with fuel. is. During this decline, the rule-if displaces the engine has four cylinders, the annular groove 6 5 slide 5, driven by the control spring 27, a extended downwards by four longitudinal grooves 7. The part of the fuel in cylinder 18 over Annular groove 6 is with the pump working chamber 3 via a throttle point 61 (control throttle), which is in a Axial bore 8 connected, which is located through several channel 62, thereby reducing the downward movement Inclined bores 9 is braked with the annular groove 6 in connection with the control slide. The free cross stands. During the suction stroke of the piston 1, the regulating throttle 61 is adjustable every time, times one of the longitudinal grooves 7 via a bore 10 with above one of the cross section of the control throttle a suction chamber 11 in connection, so that during 61 dependent speed of the pump occurs the liquid this suction stroke of the pump working chamber 3 from the stop, d. that is, the control slide 5 does not arrive Suction chamber 11 via the bore 10, the longitudinal grooves 7, more in its starting position against the stop 28, and the annular groove 6, the inclined bores 9 and the axial 15 the start and end point of its back and forth bore 8 is supplied with fuel. gangs moves in the direction of the control spring 27. This From the axial bore 8 there is also one which branches off with each displacement stroke through the Radial bore 12, which expands into a longitudinal groove pump to one of the injection nozzles delivered force and reduced during each pressure stroke of the pump material.

kolbensl determines the pump working chamber 3 with one of the 20 in the full load speed range of the engine

Pressure lines 13 connects that to the cylinders so the fixed stop 28 is the starting position of the

of the engine. In the pressure lines 13 there is each control slide 5. Only after the load has decreased

because a check valve 14 is arranged. In which and as a result the speed increases, can

Only one pressure line 13 is shown in the drawing. form a fluid stop.

In reality, there are so many pressure lines in front of 25 An annular groove 29 is provided on the control slide.

deal with how cylinders are to be supplied to the engine, which assigns the one section 30 α of a first

so z. B. four pressure lines, which is evenly connected to the relief channel and in constant connection

the piston axis are distributed. this with a second section 30 b of this design

The auxiliary pump Ib, 4 is connected via a bore 15 load channel when the control slide at

and longitudinal grooves 16, which has covered a certain distance on the surface of the step 30 to its entrance.

Ib are arranged, with fuel from the suction chamber The channel 30 a on the other hand opens into the cylinder,

11 supplied. in which the piston stage 1 c works and protrudes

The longitudinal grooves 16 stand with the bore 15, the annular groove 6 with the pump working space 3 in

in constant connection during the suction stroke of the pump piston. The bore 10 is also here

binding. During the pressure stroke, the fuel 35 and the relief channel 30 a are not in the same

Arranged from the working space of the auxiliary pump over one of the plane passing through the pump axis.

Longitudinal grooves 16 and a channel 17 in a cylinder. The relief channel section 30 δ is above a

18 displaced, in which the control slide 5 works. In channel 31 with the suction chamber 11 in connection. In

A check valve 19 is arranged in the channel 17. the moment in which the annular groove 29 the relief

The bore 15 and the channel 17 are therefore not in 40 channel sections 30 a and 30 δ connects, the

the same plane passing through the pump axis, injection interrupted by the still from the

so that while one of the longitudinal grooves 16 with the pump working chamber displaced fuel into the

Supply bore 15 is in communication, the suction chamber 11 is passed.

Channel 17 is blocked by the piston stage Ib and according to the invention is for the pump working chamber 3

conversely, the supply bore 15 is provided through the 45 yet a second relief channel 32, the

Piston stage 1 b is blocked as long as channel 17 is also controlled by pump piston 1,

a longitudinal groove 16 is in connection. The second relief channel 32 branches off from one

The suction chamber 11 is through a feed pump annular groove 33, which is in the hollow cylinder surface for the

20, e.g. B. a gear pump, is arranged via a pressure channel step section 1 c , and is at normal

21 is fed with fuel, the feed pump 20 50 operating via a channel 32 a with the suction chamber 11 also through the engine connected by the injection. This second relief channel 32 is pump is supplied with fuel, is driven. with the pump work space 3 towards the end of the In order to achieve a speed-dependent pressure in the suction chamber 11, the pressure stroke of the piston 1 is connected when the ring closes received, the pressure channel 21 via a channel groove 6, the annular groove 33 opens. At this moment

22 connected to the suction channel 23 of the feed pump, the injection is interrupted because the fuel den, and there is a throttle point from the pump working space 3 via the axial bore in this channel 22, their cross-section through a piston ring 8, the inclined bores 9, the annular groove 6, the slide 25 is controlled. The piston slide 25 annular groove 33 and the channel 32, 32 a in the suction chamber is on one side of the one in the pressure channel 21 11 flows.

The prevailing fuel pressure is applied and with 60 D _he stroke, which is necessary so that the annular groove 6 can open the increasing speed against the force of an annular groove 33, the restoring spring 26 is shifted so large in any case. This increases selected that at full load, that is, as long as the free cross-section of the throttle point 24 stop occurs, this control takes place, be-The control slide 5 is in the cylinder 18 through the before the first relief channel 30 a, 30 b through the fuel displaced by the auxiliary pump is opened against 6 _S control slide, that is to say that the force of a return spring 27 is displaced at full load. The end of the injection through the displacement stroke of the piston 1 controlled by the pump inlet of the control slide takes place during the second relief channel 32. In the time is correct and not by the control slide 5. The

Vibrations of the control slide mentioned at the beginning, caused by the compressibility of the fuel, the mass of the control slide and the acceleration at the start of the stroke of piston stage 1b , have no influence on the control at full load. In order to eliminate this influence with certainty, the dimensions are chosen so that the control slide 5 at full load, after the piston 1 has opened the second relief channel 32, still covers a safety stroke before it controls the first relief channel 30 α, 30 b. When the load decreases (partial load) and the speed increases, the liquid stop should first have reached a certain level before both relief channels are opened at the same time. Above this speed, the control slide 5 then takes over the control by opening the relief channel 30 a, 30 b before the pump piston opens the second relief channel. The control slide then reduces the amount injected per delivery stroke, the more so the more the drive speed increases and as a result the liquid stop also increases.

FIG. 2 shows two diagrams arranged one above the other, which make it easier to understand what has been described. The upper diagram shows the path C _{n of} the control slide (ordinate) over the angle of rotation α (abscissa) of the drive device (usually in the form of a cam) which sets the piston 1 in a reciprocating motion, while the lower diagram shows the piston stroke C. _{p of} the piston 1 and the amount Q delivered by the pump (ordinate) is also shown over the angle of rotation <x .

In the upper diagram three curves are recorded, one with a continuous line I, one with a dash-dotted line In a straight line and one with a dashed line III.

The solid line I shows the path of the control slide 5 as long as it is falling can run back to the stop 28 in its starting position.

The dash-dotted line shows the path of the control slide after the liquid stop has grown so much that the control slide 5 opens the first relief channel 30 a, 30 b at the same time as the pump piston 1 opens the second relief channel 32.

The dashed line III shows the movement of the control slide and the height of the liquid stop, where the injected quantity is only determined by the control slide.

The control slide 5 opens the first relief channel 30 a, 30 b every time it has reached the position shown in the upper diagram in FIG. 2 is represented by the horizontal line d .

In the lower diagram, the sinusoidal line IV shows the movement of the piston 1. The horizontal line d _x shows the position of the piston 1 at which it opens the second relief channel 32 during its pressure stroke.

From the two diagrams it can be seen that the piston 1 at the moment in which it opens the relief channel 32, has promoted the amount Q ₁ , represented by the intersection f _{t of} the line IV and the horizontal line d _v Movement according to line I, the piston 1 controls the relief channel 32 at the moment - indicated on line IV by point J ₁ - in which the control slide has reached point ^ ₁ . The control slide has not yet reached the line d from which it opens the first relief channel 30 a, 30 b. The piston 1 therefore determines the injection quantity at full load by opening the second relief channel 32, 33.

If the drive speed increases, the control slide 5 no longer reaches its starting position

ίο Stop 28 as a result of the occurrence of the liquid stop. When this liquid stop has reached the level O ₁ , the line II, which now represents the path of the control slide, intersects the horizontal line d at point g ₂ at the same moment that line IV of the pump piston 1 meets line d ₁ at point Z ₁ cuts. Both relief channels are opened at the same time. Until the liquid stop has reached the level O ₁ , the injected quantity remains unchanged and is the same as Q ₁ .

If the speed increases so far that the liquid stop reaches the level 6 ₂ , the control slide covers the path shown by line III. For this height of the liquid stop, the control slide 5 opens the first relief channel 30 a, 30 b at point g ₃ , which corresponds to point / ₂ of line IV and lies before point J ₁ , in which piston 1 the second relief channel 32 opens. As a result of the effect of the liquid stop, the injected amount is reduced to the amount Q ₂ by the control slide.

As shown in FIG. 2, the liquid stop must have reached a certain height (> O ₁ ) so that the control slide can influence the volume control.

An additional embodiment of the invention consists in delivering an excess quantity when starting, which is automatically switched off when the engine to be supplied by the injection pump after starting has reached a certain speed.

As shown in Fig. 1, is for this purpose between the second relief channel 32 and the Channel 32 a is connected to a control slide 34 which works in a cylinder 35. This cylinder is through a channel 36 connected to the suction chamber 11, in which speed-dependent pressure prevails. One Spring 37 tries to hold the slide 34 in its starting position against a stop 38. On the Slide an annular groove 39 is arranged, which is in constant communication with the relief channel 32, while the channel 32 a blocked by the section of the control slide located above the annular groove 39 is as long as the control slide 34 is in the position shown in FIG. 1 is the starting position shown. If the Pressure in the suction chamber 11 after starting the engine and reaching a certain speed a certain Value, the control slide 34 is against the force of the spring 37 against a fixed stop 38 α shifted, whereby the two channels 32 and 32 a connected to one another via the annular groove 39 will. Only now can the second relief channel, as previously described, function step. The point in time at which the control slide 34 connects the channel 32 with the channel 32 a can by changing the force of the spring 37 or by changing the pressure-speed characteristic of the suction chamber 11 can be set.

To control the slide 34 of possible pressure fluctuations in the suction chamber 11 to a large extent

To make it independent, a throttle point 40 is connected in the channel 36.

The cylinder 35 accommodating the slide 34 is on the side of the spring 37 through a channel 41 connected to a space 42 in which there is constant, low pressure and which is the drive means of the Piston 1 receives. A throttle point 43 is advantageously arranged in this channel 41.

The effect of the control slide 34 is also shown in the diagrams in FIG. 2 shown. As long as the control slide 34 keeps the second relief channel 32, 32 a closed, the fuel delivered by the piston 1 is injected until the first relief channel is opened by the control slide 5. This happens according to Fig. 2 at point ^ ₄ , in which the line I intersects the horizontal straight line d. At this moment, piston 1 has reached _{point / 3 according to curve IV.} The amount injected during starting is therefore equal to the amount Q ₃ , the excess amount is O ₃ -O ₁ .

The amount of fuel that is delivered by the pump piston at full load, i.e. before opening the first or second relief duct, can also be adjusted in that the cylinder 2 in which the piston 1 operates at its stage la is axially displaceable. The cylinder 2 is pressed against an adjustable stop 45 by a spring 44, the spring being supported on the other side against the pump housing. The cylinder 2 has several radial bores 46, and radial bores 47 which open into the axial bore 8 are provided in the piston stage 1 a. Advantageously, the radial bores 46 and 47 each merge into an annular groove, which partially overlap in the rest position of the pump piston shown in FIG. 1. The cylinder 2 is located in a space 48 which is connected to the pressure line 21 of the feed pump 20 by a channel 49. Another possibility would be to connect this space 48 to the cam space 42 by a channel 50 (shown in phantom). The delivery of the fuel can therefore only begin when the radial bores 46 and 47 are separated from one another. In the one shown in FIG. 1, the necessary distance to be covered by the piston is equal to h. This stroke portion, which is dependent on the respective axial position of the cylinder 2, results in the amount β ₄ shown in the lower diagram in FIG. 2. This stroke component has the consequence that the delivery rates Q ₁ , Q ₂ and Q ₃ are reduced by the amount ß _4. It was assumed to be equal to zero in the preceding description, which would be possible by adjusting the stop screw 45.

In Fig. 3, an additional embodiment of the injection pump for generating the starting excess quantity is shown. In addition to the in FIG. 1 embodiment shown, the control slide is delayed in its start of work when generating the starting excess quantity. For this purpose, an overflow channel 51 branches off from the pump working space of the auxiliary pump 1 b, 4, which is controlled by the slide 34 and opens into the channel 32 α. In the starting position of the control slide 34 at the stop 38, the overflow channel 51 is opened via a second annular groove 52 arranged on the control slide.

As a result, the control slide 5 remains in its rest position on the stop 28 as long as the Control slide 34 remains at its stop 38, closing the second relief channel 32. at In this embodiment, the control slide remains in its rest position during starting, whereby the excess amount is increased compared to the previous embodiment because the pump piston promotes injection quantity up to its top dead center.

Advantageously, one sees at the point at which the overflow channel 51 opens into the cylinder 35, by means of the control slide 34 before a throttle point 53, the effect of which is as follows: Should any unpredictable cause of the control slide 34 would be blocked in its rest position, then the The effect caused by the throttle 53 above a certain speed is sufficient for the control slide 5 can start its rate control before the engine runs away.

In contrast to the exemplary embodiments shown in FIGS. 1 and 3, in the case of the embodiment shown in FIG. 4, the second relief channel is not controlled by the section lc of the piston 1, but by the section la. For this purpose, the step la has several radial openings 54 which merge into an annular groove and open radial bores 55 in the cylinder 2 to end the delivery stroke. During normal operation, the radial bores 55 open into a space 56 which surrounds the cylinder 2. This space 56 is connected to the suction space 11 via a channel 57.

As with the one shown in FIG. 1 and 3 shown example the delivery rate is determined at full load by opening this second relief channel, in this one Fall by opening the relief bores 55 through the radial bores 54. At full load, here the end of funding is controlled by stage la.

The start of the delivery of the fuel is shown in FIG. 4 through the stage Ic of the piston 1 is determined by the axial bore during the axial or rotating movements of the piston 8 are separated from the supply bore 10.

As in the in F i g. The examples shown in 1 and 2 also include the amount conveyed per stroke at full load can be changed by moving the cylinder 2, but in the example according to FIG. 4 the end of the conveyor is changed by the stage la.

In order to generate a starting excess quantity, a sleeve 58 is arranged in space 56 , which is pushed against a stop 60 by means of a spring 59. This sleeve 58 is arranged around the cylinder 2. In the in F i g. 4, the relief bores 55 are blocked by the sleeve 58. If after starting the pressure in the suction chamber 11 and thus in this chamber 56 by increasing the speed, the sleeve 58 is displaced against the force of the spring 59 and controls the relief bores 55 so that no excess is conveyed.

Apart from the difference mentioned, the pump shown in FIG. 4 operates like the exemplary embodiments according to FIG. 1 and 3.

Claims (9)

Patent claims: 1. Fuel injection pump for internal combustion engines with a change in the amount of fuel delivered depending on the speed by interrupting the pump delivery min- at least when the maximum speed is reached as a result of opening a relief channel of the pump working chamber during the delivery stroke of the pump piston by means of a reciprocating control element, which is driven by the pressure fluid of an auxiliary pump driven synchronously with the main pump in the sense of its downward movement and during its downward movement caused by a restoring force is braked that it has to press at least part of the liquid that caused its discharge through a throttle element with a variable cross-section, so that at a certain throttle cross-section and reaching a certain speed, the control element is no longer in due to the occurrence of the so-called "liquid stop" its starting position runs back to a fixed stop, characterized in that the pump working chamber (3) of the main pump (1 α, 2) has a second relief channel (32, 55) which, as long as the control element (5) runs back to its starting position, through de n pump piston (1 a, 1 c) is opened before the control element (5) opens the first relief channel (30 a). 2. Fuel injection pump according to claim 1, characterized in that the regulating member (5 ) opens the first relief channel (30 a, 30 fc) only before controlling the second relief channel (32, 55) when the liquid stop has reached a certain height . 3. Fuel injection pump according to claim 1 or 2, characterized in that the second relief channel (32, 55) opens into the pump cylinder and is controlled by the pump piston (la, lc). 4. Fuel injection pump according to one of the preceding claims with a multi-stage piston in the main pump, one stage of which serves as a pump piston and the other as a distributor slide, characterized in that the second relief channel (32) is controlled by the stage (Ic) serving as a distributor slide will. 5. Fuel injection pump according to one of the preceding claims, characterized in that that the second relief channel (32, 55) to generate an excess amount during the starting of the injection pump supplying motor is controlled by a closing element (34, 58). 6. Fuel injection pump according to claim 5, characterized in that the closing member (34, 58) controls the second relief channel (32, 55) as a function of the speed. 7. Fuel injection pump according to claim 5 and 6, characterized in that in per se As is known, on the closing member (34, 58) in the closing direction a spring (37, 59) in the opening direction a pressure dependent on the speed Liquid attacks. 8. Fuel injection pump according to one of claims 3, 5, 6 and 7, characterized in that that a control sleeve (58) is used as a closing member, which in relation to the pump cylinder (2) in Can be moved longitudinally and thereby opens the second relief channel (55) in one end position and closes in the other end position. 9. Fuel injection pump according to one of claims 4 to 8, characterized in that the cylinder (2) of the pump piston (la) by an adjustable stop (45) against a The spring (44) is axially adjustable. Considered publications:
German patent specification No. 1153 941. For this purpose 2 sheets of drawings 809 590/106 8.68 © Bundesdruckerei Berlin