DE102008027651A1 - Injection pump for an internal combustion engine and internal combustion engine with injection pump - Google Patents

Abstract

An injection pump for an internal combustion engine having a suction chamber (1), a high-pressure chamber (3), a suction bore arrangement with at least one suction) and a piston (4) for shutting off the high-pressure chamber against the suction chamber, with a control edge (5) for connecting suction and high-pressure chamber, wherein the suction holes of the Saugbohrungsanordnung at least two substantially frusto-conical sections (8, 9) with different opening angles (alpha, beta), has a pre-Absteuerbohrung (6), which is formed within a suction bore (2) of the Saugbohrungsanordnung is that during a compression movement of the piston (4), the control edge (5) first connects the pre-Absteuerbohrung (6) with the high-pressure chamber.

Description

The The invention relates to an injection pump for an internal combustion engine according to the preamble of claim 1 and an internal combustion engine with such an injection pump.

From the DE 10 2005 025 601 A1 a generic injection pump for an internal combustion engine according to the preamble of claim 1 with a suction chamber for providing fuel for the internal combustion engine is known, which communicates via two suction holes with a high-pressure chamber. Moves a cam-controlled piston in a compression movement to the high-pressure chamber, so he first blocks the high-pressure chamber against the suction chamber and compressed in the other episode in the high-pressure chamber fuel for injection into a combustion chamber of the internal combustion engine.

Around at constant stroke of the cam-controlled piston different To realize pumping volumes, the piston has at its outer periphery a communicating with the high-pressure chamber recess with a against the Verdichtungsbewegungsrichtung of the piston inclined control edge on. After a high pressure chamber facing the upper edge of the piston Suction and high-pressure chamber has separated, connects with further compression movement the recess suction and high pressure chamber again with each other, as soon as the control edge overflows the suction hole, so that fuel from the high-pressure chamber flows back into the suction hole. By rotating the piston about its axis of motion, the stroke position, in which the inclined control edge passes over the suction hole, given and so the injection of this oblique edge-controlled Piston injection pump with constant stroke movement of the cam-controlled Pistons can be varied.

If the piston in its compression movement against the high-pressure chamber shut off the suction, falls through the abrupt termination the suction process, the pressure in the suction holes, resulting in Bubbles can form in the fuel located there. About track now the control edge of the suction hole, so fuel flows from the high pressure chamber under increased pressure in the suction hole back and can implosion bubbles located there. This cavitation can damage the suction hole, especially for erosion to lead.

The DE 10 2005 025 601 A1 proposes in one embodiment, the suction holes with a cylindrical and two adjoining frustoconical sections form with different opening angles, so that the wall of the suction holes is withdrawn in the cavitation formation and reduces the damaging effect of the imploding bubbles there.

The DE 100 46 564 A1 takes a different approach and suggests already to reduce the formation of bubbles. For this purpose, parallel connections are provided, which are arranged parallel to the suction holes and open in front of the mouth to the piston in a cylinder portion of the suction holes. Through these parallel connections, fuel flows into the cylinder section during the completion of the intake process, thus reducing the pressure drop.

task The present invention is the damage of a Suction bore of an injection pump of an internal combustion engine through To reduce cavitation.

to Solution to this problem is an injection pump after the The preamble of claim 1 by its characterizing features further training. Claim 14 provides an internal combustion engine with such Injection pump under protection.

A injection pump according to the invention for a Internal combustion engine, in particular a high-pressure injection pump for a diesel engine, has a suction space for providing fuel on. Advantageously, fuel can be transported through a pre-feed system promoted this suction, preferably already under increased pressure. The injection pump further has a high-pressure chamber on, in the fuel through a piston to an injection pressure is brought.

suction and high-pressure chamber communicate via a Saugbohrungsanordnung with one, two or more suction holes. This communication can be interrupted by the piston, in the course of one, in particular Cam-controlled, compression movement to the high-pressure chamber initially shuts off the high-pressure chamber against the suction chamber and in the further consequence the pressure of located in the high-pressure chamber Fuel opposite the suction increases to it to inject into a combustion chamber of the internal combustion engine.

The piston has a control edge for connecting the suction and high-pressure chamber, which passes over the suction bore during further compression movement and thus connects the suction and high-pressure chambers again so that fuel can flow back from the high-pressure chamber into the suction bore. Preferably, the piston is designed to be rotatable about its axis of motion and the control edge inclined to the direction of movement of the piston, so that the stroke position in which the control edge passes over the suction hole, and so on Injection can be specified at a constant stroke of the cam-controlled piston. Preferably, the control edge of the piston has no Vorabsteuerkante on.

The Suction bores of the suction bore arrangement have at least two in Essentially frusto-conical sections with different opening angles on. As a result, the wall of the suction holes in the area of Cavitation formation withdrawn. Preferred are the Suction holes that connect the suction and high-pressure chambers, in this respect identical. However, there can be more Suction holes may be provided which have a different geometry and Accordingly, no suction holes represent the Saugbohrungsanordnung.

According to the invention a pre-Absteuerbohrung provided, which is such within a suction hole formed the above-mentioned Saugbohrungsanordnung is that upon a compression movement of the piston, the control edge first connects the pre-Absteuerbohrung with the high-pressure chamber. With others Words has a lower edge in the direction of compression movement the pre-Absteuerbohrung a greater distance from a center line of the suction hole as a direction of compression movement lower edge of the suction hole. Includes the suction bore assembly two or more suction holes, so in each of these suction holes a Such pre-Absteuerbohrung be provided. equally It is also possible within one or more suction holes a pre-diversion well and within one or more others Suction bores do not form a pilot discharge bore.

Thereby, that during a compression movement of the piston, the control edge first the pre-diversion bore overfires and so on Connects to the high pressure chamber, a Absteuerstrahl of the higher Pressure from the high-pressure chamber flowing back fuel through the pre-Absteuerbohrung targeted to portions of the suction hole be directed, whose wall is withdrawn, so that There bubbles with reduced or no harmful effect be brought to implosion. In addition, this is due to the fact that at the beginning of the opening with the first overrun pre-Absteuerbohrung first a smaller cross-sectional area is opened, the volume flow the damaging Absteuerstrahls advantageously reduced. By combining the pilot and pilot truncated sections with different opening angles so the damage a suction bore of an injection pump of an internal combustion engine be reduced by cavitation.

at the same time This Absteuerstrahl in the pre-Absteuerbohrung, according to the invention within formed the suction hole, ie in particular longitudinally thereto its axial extent is open, fuel, in the eventual Bubbles are present, in sections whose wall is withdrawn is, entrain and thus further reduce damage.

Compared to the parallel connections of the DE 100 46 564 A1 , which serve to increase the pressure during the completion of the suction process and are therefore arranged separately from the suction bore and open before the mouth to the piston in the suction hole, such formed within the suction bore pre-Absteuerbohrung can also be made easier.

Prefers is the pilot-Absteuerbohrung in cross-section of the suction hole, in the it is formed circumferentially about a circumferential offset angle in the direction of an orientation of the control edge against a deepest in Verdichtungsbewegungsrichtung Point offset. This circumferential offset angle is preferably larger or equal to 0 ° and less than or equal to 45 °. Especially Preferably, the pre-Absteuerbohrung is so in the circumferential direction offset against a lowest point in the direction of compression movement, that the pilot-Absteuerbohrung substantially symmetrical to the inclined control edge is located. This allows the Absteu erstrahl for different Positions of the control edge, whose orientation depends on their inclination against the direction of movement of the piston results to be optimized.

In a preferred embodiment includes a central axis the pilot-Absteuerbohrung with a central axis of the suction hole, in it is formed, an inclination angle, preferably greater than or equal to 0 ° and smaller or equal to 30 °, in particular less than or equal to 15 ° and more preferably less than or equal to 5 °. Prefers are pre-Absteuerbohrung and / or suction bore rotationally symmetric formed so that its axis of symmetry forms its central axis. For non-rotationally symmetrical cross sections, the central axis can, for example a straight line through two area centers of two axially be spaced cross sections. By this angle of inclination can the Absteuerstrahl particularly favorable to further away from the piston Sections of the suction hole are directed, the wall withdrawn is.

Prefers is a minimum diameter of the suction hole, so for example, the smaller diameter of the smaller truncated cone portion, at most 10 times, more preferably at most 6 times a minimum diameter of the pilot-off pilot hole. As a result, a particularly favorable Absteuerstrahl achieved become.

The opening angle a truncated cone portion closer to the piston is preferred is greater than the opening angle of a from the piston more distant truncated cone section. This will the wall near the mouth of the suction hole to the piston quickly withdrawn, so that there blow through the Absteuerstrahl with reduced or without damaging Effect can be brought to implosion. at the same time improve the flow conditions in the Suction hole.

Especially, when through the Absteuerstrahl bubbles in a nearer to the piston Truncated cone section can be brought to implosion, the opening angle a truncated cone portion adjacent to the suction space substantially equal to 0 °. In the present case, therefore, a purely zylinderischer Generalize the section as a truncated cone section with opening angle 0 ° designates.

suction bores The Saugbohrungsanordnung may generally one or more having cylindrical portion. these can in particular before and / or between two truncated cone sections arranged at 0 ° different opening angles be. Particularly preferred is a cylinder section, with which the suction hole opens towards the piston, steadily Truncated cone section with larger opening angle, for example in the range between 10 ° and 70 °, preferably between 20 ° and 60 ° and more preferably of about 25 ° to which in turn steadily a truncated cone section with smaller opening angle, for example in the area between 0 ° and 40 °, preferably between 0 ° and 20 ° and more preferably from about 0 ° steadily followed.

In the suction holes of the Saugbohrungsanordnung can as wear element each protrude a snout coil screw.

Further Features and advantages emerge from the dependent claims and the embodiments. This shows, partially schematically:

1 a portion of an injection pump according to an embodiment of the present invention in an axial section;

2 a part of the injection pump after 1 in the direction of arrow II in 1 ; and

3 the part of the injection pump 1 in a section along III-III in 2 ,

1 shows a part of an injection pump for an internal combustion engine (not shown) according to an embodiment of the present invention in an axial section with a suction chamber 1 which is supplied with fuel under increased pressure by a feed-forward system (not shown). The injection pump further has a high-pressure chamber 3 on, in the fuel through a piston 4 brought to an injection pressure and through lines 10 to a combustion chamber of the internal combustion engine (not shown) is promoted.

Suction chamber and high pressure chamber communicate via a Saugbohrungsanordnung two suction holes 2 , The suction holes 2 , which are so far identical, have two frustoconical sections 8th . 9 on. The opening angle α of the piston 4 closer truncated cone section 8th is about 25 ° greater than the opening angle β of the flask more distant from the truncated cone section 9 which is about 9 ° in the embodiment. As a result, the wall near the mouth of the suction hole 2 to the piston 4 quickly withdrawn. In another embodiment, not shown, the opening angle β is approximately 0 °.

The suction holes 2 have a cylindrical section 7 on, in front of the two truncated cone sections 8th . 9 is arranged and with which the suction hole opens to the piston.

In the suction holes of the Saugbohrungsanordnung protrudes as a wear element in each case a snout coil screw (not shown).

piston 4 Locks in the course of a cam-controlled compression movement (up in 1 ) first with the suction chamber 2 communicating and from this fuel-filled high-pressure chamber 3 against this and increases in the further consequence of the pressure of the so sucked into the high-pressure chamber fuel to finally inject it into a combustion chamber of the internal combustion engine (not shown).

The piston has a control edge 5 for connecting the suction and high-pressure chamber, the suction bore during further compression movement 2 moves over and so suction and high-pressure chamber again connects with each other, so that fuel flows back from the high pressure chamber into the suction hole and the compression and injection process of the injection pump is stopped. The piston is designed to be rotatable about its movement axis, so that the stroke position, in which the inclined against the direction of movement of the piston control edge 5 the suction hole 2 passes over, varies and so the injection at constant stroke of the cam-controlled piston 4 can be specified.

Within the in 1 left suction hole 2 , ie along its axial extent (from left to right in 1 ) Open to this, is a pre-Absteuerbohrung 6 designed such that at the compression movement of the piston 4 the control edge 5 first the pre-diversion bore 6 with the high pressure room 6 combines. For this purpose, the central axis 6.1 the pre-diversion bore 6 from the central axis 2.1 the suction hole 2 an axial distance a, which is greater than half the diameter D / 2 of the cylinder portion 7 the suction hole 2 ,

Due to the fact that during the compression movement of the piston 4 the control edge 5 first the pre-diversion bore 6 overflows and so with the high-pressure chamber 3 connects, meets a Absteuerstrahl of under higher pressure from the high-pressure chamber back flowing fuel targeted to the truncated cone sections 8th . 9 the suction hole, whose wall is withdrawn, so that there bubbles are brought with reduced or no harmful effect to implosion.

The pre-diversion bore 6 is how out 2 seen in cross section of the suction hole 2 in which it is formed, in the circumferential direction by a circumferential offset angle γ of about 30 ° in the direction of an orientation of the control edge (clockwise in 2 ) against a compression direction in the deepest point of the suction hole 2 offset so that they are symmetrical to the control edge 5 is arranged.

As in 3 shown, closes the center or symmetry axis 6.1 the rotationally symmetrical pre-Absteuerbohrung 6 with the center or symmetry axis 2.1 the rotationally symmetrical suction hole 2 in which it is formed, an inclination angle δ of about 2.5 °. Due to this angle of inclination, the Absteuerstrahl is particularly favorable to the farther from the piston 4 removed truncated cone sections 8th . 9 the suction hole 2 directed, whose wall is withdrawn.

The diameter D of the cylinder section 7 the suction bore is 5 times the diameter d of the pilot-off pilot hole 6 , As a result, a particularly favorable Absteuerstrahl can be achieved.

In the 1 right suction hole 2 is substantially identical to the above-explained left suction hole 2 formed and has insebsondere one - due to the position of the axial section of the 1 in this not visible - pre-Absteuerbohrung on, the above-mentioned pilot-Absteuerbohrung in the left suction hole 2 like.

1

suction

2

suction bore

2.1

center line suction bore

3

High-pressure chamber

4

piston

5

control edge

6

Pre-spill port

6.1

center line Pre-spill port

7

cylinder section

8th

first Truncated cone section

9

second Truncated cone section

10

drilling

a

distance Centerline Pre-diversion bore - Suction bore

d

diameter Pre-spill port

D

diameter suction bore

α

opening angle d. first truncated cone section

β

opening angle d. first truncated cone section

γ

Circumferential offset angle

δ

tilt angle

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 102005025601 A1 [0002, 0005]
• - DE 10046564 A1 [0006, 0016]

Claims (15)

Injection pump for an internal combustion engine, with a suction chamber ( 1 ), a high pressure room ( 3 ), a Saugbohrungsanordnung with at least one, suction and high-pressure chamber connecting, suction bore ( 2 ), and a piston ( 4 ) for shutting off the high-pressure chamber against the suction chamber, with a control edge ( 5 ) for connecting suction and high-pressure chamber, wherein the suction bores of the suction bore arrangement at least two substantially frusto-conical sections ( 8th . 9 ) having different opening angles (α ≠ β), characterized by a pre-Absteuerbohrung ( 6 ), which within such a suction bore ( 2 ) of the suction bore arrangement is formed such that during a compression movement of the piston ( 4 ) the control edge ( 5 ) first the pilot-off pilot hole ( 6 ) connects to the high pressure chamber. Injection pump according to claim 1, characterized in that the pre-Absteuerbohrung ( 6 ) in the cross section of the suction bore ( 2 ), in which it is formed, in the circumferential direction by a circumferential offset angle (γ) in the direction of an orientation of the control edge ( 5 ) is offset against a lowest point in the compression movement direction. Injection pump according to claim 2, characterized the circumferential offset angle (γ) is between 0 ° and 45 °. Injection pump according to one of the preceding claims, characterized in that a central axis ( 6.1 ) of the pilot-off pilot hole ( 6 ) with respect to a central axis ( 2.1 ) of the suction hole ( 2 ), in which it is formed, a distance (a) which is greater than a hydraulic radius (D / 2) of the mouth of the suction bore ( 2 ) to the piston ( 4 ). Injection pump according to one of the preceding claims, characterized in that a central axis ( 6.1 ) of the pilot-off pilot hole ( 6 ) with a central axis ( 2.1 ) of the suction hole ( 2 ) in which it is formed includes an angle of inclination (δ). Injection pump according to claim 5, characterized in that the angle of inclination (δ) is between 0 ° and 30 °, in particular between 0 ° and 15 °. Injection pump according to one of the preceding claims, characterized in that a minimum hydraulic diameter (d) of the pilot discharge bore ( 6 ) at least 0.1 times, in particular at least 0.2 times, a minimum hydraulic diameter (D) of the suction bore ( 2 ) corresponds, in which it is formed. Injection pump according to one of the preceding claims, characterized in that the suction bore arrangement has at least two suction bores ( 2 ) having. An injection pump according to claim 8, characterized in that within at least one suction bore ( 2 ) a pre-Absteuerbohrung ( 6 ) and within at least one other suction bore ( 2 ) no pre-bleed hole is formed or that within each suction bore ( 2 ) of the suction bore arrangement a pre-Absteuerbohrung ( 6 ) is trained. Injection pump according to one of the preceding claims, characterized in that the opening angle (α) of the piston ( 4 ) closer truncated cone section ( 8th ) is greater than the opening angle (β) of a more distant from the piston truncated cone portion ( 9 ). Injection pump according to claim 10, characterized in that the opening angle (β) of a to the suction chamber ( 1 ) adjacent truncated cone section ( 9 ) is substantially equal to 0 °. Injection pump according to one of the preceding claims, characterized in that the suction holes of the Saugbohrungsanordnung one, in particular before or between two truncated cone sections ( 8th . 9 ) arranged cylindrical portion ( 7 ) exhibit. Injection pump according to one of the preceding claims, characterized in that in the suction holes ( 2 ) of the Saugbohrungsanordnung each projecting a snout coil screw. Injection pump according to one of the preceding claims, characterized in that the control edge ( 5 ) is formed without Vorabsteuerkante. Internal combustion engine, in particular diesel internal combustion engine, with at least one cylinder, the one injection pump after a associated with the preceding claims.