DE2403318A1 - FUEL INJECTION PUMP FOR COMBUSTION MACHINES - Google Patents

Description

R. 1931 .

December 20, 1973 Bö / Kb

Attachment to

Patent and

Utility model registration

ROBERT BOSCH GMBH, 7 Stuttgart

Fuel injection pump for internal combustion engines

The invention relates to a fuel injection pump for Internal combustion engines with a pump piston reciprocating in a cylinder bore and rotating at the same time, which, as it rotates, one after the other one extending from an annular groove on its lateral surface with a distributor longitudinal groove of outgoing conveying channels on the circumference of the cylinder bore connects during its conveying stroke and its annular groove constantly is connected to a connecting channel branching off from the pump working space, which is one in the direction of the annular groove contains opening, central non-return valve.

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In a known injection pump of this type, two additional longitudinal grooves branch off from the annular groove, which are symmetrical the distributor longitudinal groove are arranged opposite on the lateral surface of the pump piston. These mutes are during the Delivery stroke of the pump piston, i.e. in the time segments in which the fuel flows into a the conveying channels are fostered, certainly not with any these conveying channels can be connected. The grooves have the task of the delivery stroke of the pump piston, which is otherwise one-sided by one resulting from the base area of the longitudinal distributor groove and the high pressure of the fuel filling it Force was loaded to create a force balance on the pump piston. Due to the location and the area of this additional Muten, a perfect balance of forces can be achieved.

In the case of injection pumps of the above type, however, there are injection quantity spreads, which are caused by the fact that as a result of tolerances of the pump parts, of rotational play and of Torsional vibrations create the connection between the connecting channel and a conveyor channel at different angles of rotation of the pump piston is interrupted, as a result of the pressure wave running back and forth between the nozzle and the check valve the connecting channel and the conveying channels constantly have a different pressure level after each interruption. A However, different pressure levels mean a different fuel volume in each case in the connecting channel and is stored in the conveying channels and must be compensated for each time the conveyance starts. Through this compensation however, the amount of fuel delivered by the pump piston into the cylinder of the internal combustion engine is different great.

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It is therefore the object of the invention to provide a device for an injection pump of the type described at the beginning create with which the injection quantity spreads are avoided or at least greatly reduced.

Solutions have already been put in place to avoid this shortcoming. In a known injection pump is a Partial annular groove is provided on the pump piston, which is opposite a longitudinal distributor groove arranged on the lateral surface of the Parrro piston, which is connected to the pump working space via a longitudinal bore in the pump piston. This pump should one check valve in each of the delivery channels after their branches from the cylinder bore to maintain pressure in the Channels. If the distributor longitudinal groove is in the conveying position, i.e. in overlap with one of the conveying channels, the corresponding the number of cylinders to be supplied are arranged around the cylinder bore, the remaining conveying channels are for Pressure equalization connected to one another via the partial ring groove.

In addition to the necessary large number of check valves, this pump has the disadvantage that the rotation of the pump piston successively with the partial ring groove in connection conveying channels very quickly with the Can compensate for the volume of the other conveying channels, so that pressure oscillations continue to occur here and the individual ' Channels are periodically under different pressure levels. She maintains this pressure level in the moment in which they are cut off again from the partial ring groove. So here, too, there is no certainty that with At the start of delivery in the delivery channels, there is always the same outlet pressure to avoid injection quantity scatter prevails.

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The problem posed is achieved in that in the area of the exit of the conveying channels from the cylinder bore the direction of rotation of the pump piston of the distributor longitudinal groove is adjacent to a throttle channel as one in each stroke position of the pump piston when it rotates ■ connection between one of the delivery channels and the annular groove or the distributor groove is provided, the space requirement of the throttle channel and the distributor longitudinal groove together in Circumferential direction is smaller than the smallest distance between the adjacent outermost boundaries of two successive delivery channels emanating from the cylinder bore.

This has the advantage that after the connection between the connecting channel and the respective one has just been interrupted The conveyor channel that was still open through the longitudinal distributor groove, the connection between these two Channels through the throttle groove as long as the, · distributor longitudinal groove not yet when the pump piston rotates in overlap with the next conveying channel ^ exits came out of the cylinder bore. During this time, a pressure difference between the fuel pressure in Connection channel and the fuel pressure in the delivery channel are gradually equalized via the throttle groove without that it comes to further pressure oscillations as a result of a sudden opening of this connection. This solution represents a measure that is very easy to manufacture, with only a minor one on the original pump parts Change becomes necessary .. The additional dead volume that is added by the throttle groove is only very small and does not have an adverse effect.

A further development according to the invention consists in that the throttle channel has a throttle groove parallel to the longitudinal distributor groove is on the outer surface of the pump piston. This, in turn, is very simple to manufacture and easy to control dominate. So that at the start of delivery of the pump piston not also delivered via the throttle groove

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can be, another embodiment of the invention is that the distance from corresponding boundary edges the throttle groove and the longitudinal distributor groove is smaller than the diameter of the largest in the circumferential direction from the cylinder bore outgoing delivery channels.

A further embodiment according to the invention consists in that the throttle channel extends from the longitudinal distributor groove starting in the circumferential direction extending groove on the outer surface of the pump piston.

Two embodiments of the invention are shown in the drawing and described in more detail below. Show it:

Fig. 1 shows a first embodiment of the invention based on a cross section through a schematically represented distributor injection pump,

Fig. 2, the processing of the invention, the essential part of the pump piston according to the embodiment of FIG. 1 with the existing immediately after closing one of the delivery channels assignment of the pump piston and the conveying duct outlet openings,

3 shows a development of the pump piston corresponding to that of FIG. 2 in the assignment of pump pistons and delivery channel outlet opening immediately before the opening of a delivery channel,

H shows a part of the development of a pump piston according to a second embodiment with * a throttle groove extending in the circumferential direction immediately after closing one of the delivery channels and

5 shows a development corresponding to the exemplary embodiment according to FIG. 4 with the allocation of the longitudinal distributor groove and the feed channel outlet opening immediately before a feed channel opens. -6-

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In a housing 1 of a fuel injection pump, a pump piston 2 works firmly in a cylinder bore 3 of a inserted into the housing of the fuel injection pump Sleeve 4. The pump piston is not shown in detail Means against the force of a return spring not shown in a reciprocating and simultaneous rotating movement offset. A pump working space 6 is created by the pump piston 2 in the cylinder bore 3 including the longitudinal groove 7 arranged in the lateral surface of the pump piston and one in the pump housing 1 running channel 8 is supplied with fuel from a suction chamber 9 as long as the pump piston is on its suction stroke executes or assumes its bottom dead center position. The longitudinal grooves 7 are corresponding to the number of the injection pump To be supplied cylinder of the internal combustion engine arranged distributed on the circumference of the pump piston.

The pump suction chamber 9 is made of a feed pump 11 Fuel tank 12 supplied with fuel. By means of a pressure control valve 13, the pressure in the suction chamber 9 is set in Controlled in a known manner speed-dependent, so that the pressure in the suction chamber increases with increasing speed.

A bore 15 leads from the working space 6 and opens into a space 16. The confluence of the bore 15 into the space 16, together with a valve body 17 and a compression spring 18 arranged in the space 16, forms a check valve 19. This check valve can also be designed as a relief valve in a known design. From the space 16, a connecting channel 21 leads from that runs parallel to the pump axis in the sleeve ¹ I and opens there via a transverse bore 22 in the sleeve into the cylinder bore. 3 The transverse bore 22 is in the working area of an annular groove 25 on the circumference of the

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Pump piston and is with this throughout Delivery stroke of the pump piston connected. From the annular groove 25 a longitudinal distributor groove 26 goes off, which during the delivery stroke of the pump piston after a corresponding rotation

from
the same is connected to a / from the pump cylinder 3 discharging delivery channels 5. The delivery ducts each lead to injection nozzles 28 on the individual cylinders of the internal combustion engine to be supplied with the injection pump and are distributed around the circumference of the cylinder bore 3 according to the number of these cylinders.

In the pump piston 2, an outgoing from the pump working chamber 6 runs Longitudinal channel 30, which is designed as a blind hole and via a transverse hole 31 in the into the pump suction chamber 9 protruding part of the pump piston has a connection to the pump suction chamber. The exit of the cross hole 31 from the pump piston can be controlled by an annular slide 35 which is displaceable tightly on the pump piston. Depending on the position of the ring slide, the transverse bore 31 becomes earlier in the course of the delivery stroke of the pump piston or open later. The ring slide is in its position by an intermediate lever 37 which rotates around an axis 38 is pivotable and with a head 39 in a recess l »0 of the ring slide engages, adjustable. To do this, the Intermediate lever 37 by a speed controller, not shown, as a function of the speed and the load panned.

The injection pump works as follows:

During the downward movement of the pump piston or during its suction stroke, it sucks through one of the longitudinal grooves 7 and the Channel 8 fuel from the pump suction chamber 9 into the pump working chamber 6. By turning the pump piston . · ■ "-8-

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the connection to the channel 8 is interrupted, so that during the upward movement or the delivery stroke of the pump piston, the fuel j as long as the transverse bore 31 and thus the connection from the pump working chamber to the pump suction chamber via the longitudinal channel 30 is closed by the control slide, from the working chamber 6 via the check valve 19 is funded in room 16. From the space 16, the fuel arrives via the connecting channel 21 and the transverse bore 22 into the annular groove 25 , from where it is conveyed via the longitudinal distributor groove 26 into one of the delivery channels 5. The fuel delivery lasts until the transverse bore 31 is released by the ring slide 35 during the stroke movement of the pump piston, so that the fuel now pumped can escape via the longitudinal channel 30 and the transverse bore 31 from the pump working chamber 6 into the suction chamber 9, without In the working space the conveying pressure necessary for conveying into the conveying channels 5 arises. The further the ring slide 35 is displaced downward by the intermediate lever 37, the earlier the transverse bore 34 is opened and the lower the amount of fuel delivered into one of the delivery channels.

In the exemplary embodiment according to FIG. 1, a parallel to the distributor longitudinal groove 26 extends from the annular groove 25 Throttle groove 42 from. This is for technical reasons not to be seen in FIG. 1 and in more detail in FIG. 2, which shows a development of a part of the pump piston with the associated conveying channels 5 shows, clarifies. The throttle groove 42 is opposite to the direction of rotation of the Pump piston adjacent to the longitudinal distributor groove 26 at a distance A which is smaller than the clear width B of the e.g. circular cross-section of the conveyor channels 5. Of course, this cross-section can also have a different shape.

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The distance A between the throttle k2, which has a small cross-section, and the longitudinal distributor groove is designed so that as soon as the longitudinal distributor groove 26 has passed one of the delivery channels as a result of the rotation of the pump piston, the throttle groove has just come into overlap with the cross-section of this delivery channel. This position is shown in FIG. 2. Due to the throttle groove, a connection between the connecting channel 21 and one of the conveying channels 5 in which the conveyance has just been carried out remains. In order to achieve the longest possible overlap of the throttle groove with the conveyor channel cross-section, the distance A is made as large as possible, but smaller than the clear width B of the conveyor channels. Of course, the distance A between the throttle groove and the longitudinal distributor groove can be greater than the width of the conveying channel cross-sections in the circumferential direction, while the space requirement of both grooves together in the circumferential direction, i.e. the distance C, must not be greater than the smallest distance between the delimiting edges of two successive conveying channels, i.e. the distance D. In this case, there is no ^{longer a continuous transition from "fully 1} open conveyor channel" to "throttled open conveyor channel".

The emergence of the pressure differences is due to the fact that as long as the connection between the connecting car: al 21 and the delivery channel 5. There is pressure waves between the check valve 19 and the injection nozzle 28 to and fro and a certain state is blocked at the moment in which by the twisting of the pump piston, the connection between the connecting channel 21 and the delivery channel 5 is interrupted. Respectively dorfe where the pressure wave is at the time of the interruption was located, the higher pressure is set. Will these pressure differences not degraded, this leads to fluctuations in the injection quantity, since at the moment of the start of delivery with a larger one or a smaller amount of fuel compensates for the pressure differences Need to become.

The throttle groove can now be used immediately after the interruption the connection between the conveying channel 5 and the connecting channel 21 a slow :: · pressure equalization take place. With the Throttling effect is avoided in this

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19 :: -ΙΟ pressure compensation can build up vibrations again. Of the Compensation is ended when the throttle groove 42 is no longer in overlap with the conveyor channel cross-section happens at the same time before the start of an overlap of the distributor longitudinal groove 26 with the following conveying channel 5. This assignment can be seen in FIG. The space requirement C of the two grooves in the circumferential direction is therefore smaller than the smallest distance D between the adjacent outermost boundaries of two successive ones Outlet openings of the conveying channels 5

Instead of a throttle 42 lying parallel to the longitudinal distributor groove 26, a throttle groove 42 ^! .Provisioned, which, starting from the longitudinal distributor groove 26, extends in the circumferential direction (see FIG. 4). The cross section of the throttle groove 42 ′ can be essentially the same as that of the throttle groove 42. As can also be seen in FIGS. 4 and 5, the space requirement C of the longitudinal distributor groove 26 and throttle groove 42 'in the circumferential direction is smaller than the smallest distance D between two adjacent delimiting edges of two conveyor channels 5 is equal to the distance between the center of the cross-section of the delivery channels and the same annular groove 25 with the pump piston spaced in the middle.

Of course, there can be a throttle connection between each one of the delivery channels and the longitudinal distributor groove in the direction of rotation of the pump piston in each case adjoining the outlets of the delivery channels in the circumferential surface the cylinder bore are provided. Here, however, the manufacturing effort is considerably greater. For the space requirement

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in the circumferential direction this applies to the preceding examples Said. It must always be ensured that the preceding conveyor channel is completely closed when the distributor longitudinal groove controls the next conveyor channel.

Instead of the grooves, throttle bores can also be used, which begin in the lateral surface between the Take the pump piston and the cylinder bore and move to the annular groove, the longitudinal distributor groove or to each of the delivery channels, to lead.

With the prescribed arrangements, an even residual pressure can be achieved in a simple and economical way can be achieved in the delivery lines 5 and quantity spreads resulting from pressure differences are avoided.

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Claims (5)

-12- Claims (l.y Fuel st off injection pump for internal combustion engines with a pump piston reciprocating in a cylinder bore and rotating at the same time Rotation one after the other an extending from an annular groove on its lateral surface distributor longitudinal groove with one of on the circumference of the cylinder bore connecting delivery channels during its delivery stroke and its annular groove constantly is connected to a connecting channel branching off from the pump working space, which is one in the direction of the annular groove contains opening, central non-return valve, characterized in that in the area of the outlet of the conveying channels (5) from the cylinder bore (3) against the direction of rotation of the pump piston (2) from the longitudinal distributor groove (26) Adjacent a throttle channel (42, 42 ') as one that can be produced in every stroke position of the pump piston during its rotation Connection between one of the conveying channels and the annular groove (25) or the longitudinal distributor groove (26) is provided is, the space requirement (C) of the throttle channel and the longitudinal distributor groove (42, 42 *; 26) together in the circumferential direction is smaller than the smallest distance (D) between the adjacent outermost boundaries of two successive ones from the cylinder bore (3) outgoing delivery channels (5). «-13-509832 / 0018 - 24033Ί8 -13- 2. Fuel injection pump according to claim 1, characterized in that that the throttle channel has a throttle groove (42) parallel to the distributor longitudinal groove (26) on the lateral surface of the pump piston is. 3. Fuel injection pump according to claim 2, characterized characterized in that the distance (A) from corresponding limiting edges of the throttle groove (42) and the distribution groove (26) from one another is smaller than the largest diameter (B) in the circumferential direction of the Cylinder bore outgoing delivery channels (5) 4. Fuel injection pump according to claim 1, characterized in that the D: rosselkanal is a groove (42 ¹ ) extending from the longitudinal distributor groove (26) starting in the circumferential direction on the lateral surface of the pump piston. ■ 5. Fuel injection pump according to claim 1, characterized in that that the throttle channel is a partial annular groove proceeding in each case from the conveying channels. 5 0 9832/0018