EP0906506B1 - Fuel injection pump for an internal combustion engine - Google Patents

Description

State of the art

The invention relates to a fuel injection pump for Internal combustion engines according to the type of patent claim 1. DE-C-24 49 332 is a fuel injection pump known of this type, which has a pump piston, which in a housing bore back and forth and at the same time is driven in rotation. The outlet opening on the pump piston serves as a distributor opening, one after the other various pressure lines supplied with high pressure fuel become. In this known fuel injection pump is about a longitudinal groove opposite the distributor opening arranged in the outer surface of the pump piston, which in constant connection with the high pressure of the distributor opening supplied fuel is. With such a configuration becomes approximately diametrically opposite the distributor opening pressurization between pump pistons and housing bore achieved such that the pump piston is evenly loaded by compressive forces and the inclination reduced to seizure of the piston within the housing bore becomes. The additional groove does not come with regularly the injection lines or injection lines participating in the injection in connection and leads with one at the same time through the distributor opening opened injection line Pressure equalization between these lines in a suction phase of the pump piston.

This configuration has the disadvantage that despite a balance of forces, which is achieved on the pump piston by the large-area grooves in the lateral surface of the moving part there is an interruption in a film of lubricating oil, which Oil film the moving part, the pump piston and Distributor is at the same time, when it rotates in the housing bore should wear.

Advantages of the invention

The fuel injection pump according to the invention with the features of the characterizing part of claim 1 has the opposite the advantage that the pressure compensation surface according to the invention one from the rotational position of the moving part independent compensation force is generated because of the pressure compensation area always remains closed. It can the pressure that is in the area of the pressure equalization area and that of the outlet pressure of the high pressure source at the adjacent outlet opening, by the dimensioning of the first and the second leak distance in the desired Way to be set. This configuration has further the advantage that in the area of the outlet opening high pressure occurring in the wake of the intermittent high-pressure fuel injection due to the deformation of the moving part on the one hand and the housing bore, on the other hand, the size of the leakage distances, in particular their effective flow cross-section so influenced is that a discharge cross-section over the second leak reduced and an inlet cross-section over the first Leakage distance is increased. This increases in the area of Pressure equalization area the pressure with increasing high pressure disproportionately. This tends to increase faster Pressure creates a correspondingly higher compensation force against those in the area of the outlet opening when the high pressure rises force arising there. The sum of the The resulting lateral force is therefore slow to take away increasing pressure level of the high pressure source. By the compensation force, on the other hand, the deformation the moving part and this is the receiving housing bore lower. These deformations are in the moving part Flattening of the circular cross-section in the direction of a elliptical cross-section and in the housing bore Boreholes also with an elliptical cross-section, with the main axes of the respective cross sections are perpendicular to each other. When reducing this Deformation also results in lower cross contractions or transverse extensions transverse to the triggering deformation, see above that a smaller game between the moving part and the Housing bore in the basic dimension of these parts to each other is feasible. Improved with reducing this game the quantity balance of the high pressure injection, in which the leakage losses caused by this game are reduced become. This is done with continued safe operation without the risk of being too tight an excessive surface pressure between the assigned Sharing occurs, with the result of eating the moving Partly in the housing bore.

An advantageous embodiment is according to claim 2 second leak distance essentially twice as long as that first leak distance, which is a favorable volume balance of the Pressure equalization area inflowing high pressure fuel and fuel flowing out again from this pressure compensation surface to a relief room. With the length of the Leakage distances and the resulting cross-sections that arises in the area of the pressure compensation area Set pressure.

In a further advantageous embodiment, the invention Solution in a distributor injection pump according to claim 3 realized.

For more targeted positioning of the pressure compensation surface or the accommodation of several pressure equalization areas in Desired peripheral areas of the moving part are the Pressure compensation areas advantageous according to claim 4 as a longitudinal groove or extending in a longitudinal direction to the axis of the rotating moving part extending flattening or ground surface. By the length of this Longitudinal groove can advantageously the pressure field in the area Pressure equalization area can be determined and it is one Pressure equalization area in a manufacturing and realization relief between otherwise existing ones high pressure grooves or pressure relief grooves in the area to accommodate the outer surface of the moving part.

Advantageously, according to claim 5, a further Groove provided, the main setting the desired gap length in favorable for this setting Areas of the lateral surface is used. The pressure equalization area relatively isolated far from the high pressure Outlet opening must be removed and over the further groove or groove-like flattening up to a desired proximity to this outlet opening is sufficient to to define the first leak distance there. Can also over this continued groove also corresponds to a leakage length be set to a discharge side.

According to claim 6, the partial extent of the pressure compensation surface according to claim 5 substantially parallel to a radial plane to the axis of the moving part made what enables the pressure equalization area if possible to accommodate in the peripheral area of the lateral surface, in which the outlet opening is also provided under Taking into account that during the back and forth Movement of the pump piston not the pressure compensation grooves Range of relief openings from the housing bore come off, get.

In a known manner, the distributor opening according to claim 7 designed as a longitudinal groove, wherein according to claim 8 the further groove, which is from the pressure compensation surface dissipates, is formed as a partial groove, which is in the axial direction ends below or above the distributor longitudinal groove and defines the first leak distance there. The second Leakage path through the pressure equalization area and yourself also formed in the circumferential direction, the one with a relief chamber of the fuel injection pump connected is. Are advantageous according to the claims 11 and 12 several pressure equalization areas are provided, wherein according to claim 13 advantageously the area of the pressure compensation area is larger than the area of the outlet opening, that of the high pressure of the high-pressure fuel source directly is applied is.

Four embodiments of the invention are in the drawing are shown and are described in the following description explained in more detail. FIG. 1 shows a fuel injection pump shown in section and simplified, Figure 2 a distributor piston, in the view as in the pump 1 is used, FIG. 3 is a section along the line III - III through the distributor piston according to FIG. 2, 4 shows a development of the distributor piston according to FIG. 2 together with the assigned inner wall of the housing bore showing the pressure lines leading away from it in a first embodiment, Figure 5 shows a section through the Pump piston along the line V - V of Figure 2 and the this receiving housing part with housing bore, Figure 6 a second embodiment of the invention using a Development of the pump piston, Figure 7 shows a third embodiment of the invention, shown on a settlement of Pump piston and Figure 8 shows a fourth embodiment the invention with an additional annular groove.

Description of the embodiment

Using a piston-type fuel rail injection pump the invention is explained below. In one Housing 1 of such a distributor injection pump is one provided in a pump head 3 pressed cylinder sleeve 4, a distributor pump piston 6 in its axial bore 5 is guided by a cam drive, not shown both in a reciprocating and a rotating Movement. Over the course of his back and forth The movement of the distributor pump piston changes one side pump work space enclosed by him in the cylinder sleeve 4 8 such that this space during the downward stroke of Pump piston, which is also a suction stroke is enlarged and in the upward stroke of the pump piston corresponding to one Conveying stroke is reduced with the promotion of this Pump work chamber 8 fuel brought to high pressure. For this purpose, the distributor pump piston has one of its Front 9 outgoing conveyor channel 10, in the lateral surface 11 of the distributor pump piston in a distributor opening 12 as the outlet opening of the pump work space 8 empties. This distributor opening is preferably a longitudinal groove executed. The distributor opening comes during its rotation each with a delivery stroke of the pump piston of several pressure lines 14 in connection, each as an injection line to a fuel injection valve 15 lead and according to the fuel injectors to be supplied distributed around the circumference of the inner surface the axial bore 5 are arranged. In every pressure line a delivery valve 17 is preferably provided, e.g. as Equal pressure valve or as a valve with a valve member a continuously open throttle connection between the fuel injector and has fuel injection pump. For setting a uniform outlet pressure in the pressure lines after pressure has been applied or after Injection is a filling groove 18 in the lateral surface 11 of the Pump piston 6 is provided, which via a longitudinal channel 19 in Distributor pump piston 6 with an annular groove 20 in the outer surface of the distributor pump piston is connected. This Ring groove is with a relief bore 22 in the cylinder sleeve connected in a pump suction chamber 24 of the Fuel injection pump that flows through one out of one Fuel tank 27 suction feed pump 25 is supplied if necessary with the interposition of a further pre-feed pump. With the help of a pressure control valve 26, which is parallel to the feed pump 25 is arranged, the pressure in the pump suction chamber set. This serves as a low pressure source (24) for fuel to fill the pump work space 8 during of the suction stroke of the pump piston, to provide a Pressure equalization, e.g. via the filling groove 18 and also for relief and inclusion of one not for fuel injection leading part of the displaced from the pump work space Fuel. It is also possible with this speed dependent Pressure to control a spray start adjustment.

The part of the non-fuel injection participating Fuel is controlled by means of a solenoid valve 29, whose valve member 30 has a connecting bore 31 between pump work chamber 8 and one to pump suction chamber 24 leading suction channel 32 when lifting off the valve seat of the Manufactures solenoid valve. This connection serves on the one hand for filling the pump workspace during the suction stroke of the pump piston and on the other hand, as already mentioned, for relief the pump workspace over a certain, defined Pump piston stroke. This can be done before the actual Pump piston stroke with effective delivery are defined the start of fuel injection and also after injection a desired fuel injection quantity to determine of the high pressure injection end. The solenoid valve is thereby electrically controlled by a control device 34.

Figure 1 shows the known design of the distributor injection pump with a solenoid valve for injection quantity control. However, an embodiment according to the invention is only visible in Figure 2. In the pump pistons shown there are the distributor groove 12, the filling groove 18 and one Pressure compensation surface 36 to recognize. The distributor opening 12 and the filling groove are designed as longitudinal grooves. The pressure compensation surface 36 is also longitudinal groove-like, e.g. executed in the form of a bevel. This pressure equalization surface, the diametrically opposite the distributor groove 12 is connected to a partial annular groove 37, which extends to below the distributor groove 12. On average in Figure 3 are the assignments of pressure equalization area 36, distributor groove 12 and filling groove 18 are shown more clearly and the partial ring groove 37 can also be seen in dashed lines. The pressure compensation surface can be used instead of a bevel 36 just as well as flattening produced in some other way be executed. The partial ring groove can also be ground in be carried out. It limits in their rapprochement to the distributor opening 12 at a vertical distance from this a first leakage path 39. Also on the lateral surface 11 the distributor pump piston 6 recognizes the annular groove 20, which was already shown in Figure 1 and the one below Limitation of the sealing outer surface of the pump piston forms, which on the other hand is limited by the partial ring groove 37 is.

These relationships are more clearly shown in FIG the development of the pump piston outer surface shown with the assignment of the mouths 14 of the pressure lines in the Axial bore 5. The upper limit is the result of the End face 9 resulting line shown and as the lower limit the annular groove 20. In between are in a common Radial plane the mouths of the pressure lines 14 in same angular distance from each other. Furthermore, the distributor opening 12 shown with their corresponding position 12 ' after a complete revolution in dashed lines. Approximately halfway between these two positions the pressure compensation surface 36, which is at a safe distance, the is greater than the length of the leak path, below which due to the lowest limit facing away from the pump work area the pressure line 14 certain radial plane. Of this as a bevel or flattened pressure compensation surface 36 leads from its uppermost pump workspace Limitation from the partial ring groove 37 from parallel to a radial plane of the distributor piston 6. As can be clearly seen here sees the partial ring groove ends so that seen in the axial direction partial ring groove and distributor opening 12 overlap, wherein between partial ring groove 37 and the lowest boundary edge 40 the distributor opening over the between the outer surface of the distributor pump piston and lateral surface of the axial bore 5 available Gap the first leakage path 39 is formed. The second leakage path 42 is determined by the vertical distance between the lower, facing away from the pump work chamber 8 Boundary edge 43 and the annular groove 20 are formed. In process the filling groove 18 is also entered, which in Intermediate area between the distributor opening 12 and the Pressure compensation surface 36 is. This overlaps in the circumferential direction seen the distribution opening to a large extent 12 in such a way that when the distributor pump piston rotates 6 also in connection with the individual mouths of the Pressure lines 14 can reach. With the the pressure equalization surface 36 enclosing line 44 is a line of one currently the same high pressure specified in the range between the outer surface of the distributor pump piston 6 and the housing bore during the delivery stroke of the pump piston prevails. It can be seen that in the case of high-pressure production the Surrounding the distributor groove still in the gap between the Shell surface 11 and the housing bore in from the high Pressure is applied. On the other hand, this high pressure will in the area of the filling groove 18 connected to the suction space 24 dismantled and also in the area of not at the high pressure injection involved mouths of the pressure lines 14. In addition to the leakage path 42 described above, the Distance between the closest boundary edge of the Pressure compensation surface 36 to the filling groove 18 or to one of the in the meantime pressure-relieved pressure lines 14 a Leakage path as a second leakage path 42 a or 42 b as an alternative or be formed in addition.

With a fuel injection pump designed in this way the distributor opening becomes intermittent from the high pressure from the pump work space. In the case shown is the distributor opening with one of the mouths 14 of the Pressure lines connected for delivery to the fuel injector 15. The distributor pump piston 6 and the cylinder sleeve 4 from the existing at the distributor groove 12 High pressure applied. This state is in that Section shown in Figure 5 exaggerated, for better Representation of the section through the filling groove 18 avoided has been. 5 shows the distributor groove 12 and the flattening of the pressure compensation surface 36 and the dashed registered course of the ring groove 37, which in the pressure compensation surface 36 opens out and below the distributor groove 12 begins, but is not touched by this. When pressurized, the high pressure results in one Extension of the sleeve in the area of the distributor groove 12 and flattening of the distributor pump piston 6 at the same time, that deviates from the normal play 45 between distributor pump pistons and drilling the cylinder sleeve 4 on this Side is now a much larger distance 47, which favors possible leakage. On the distributor groove 12 diagonally opposite side reduced the normal game quite considerably. In this area the cross section of a possible leakage path is also here in particular the cross section of the second leak path 42, significantly reduced, which has the consequence that about the first leak in the area of the increased distance 47 relatively much fuel under high pressure in the ring groove 37 can drain and reaches the pressure compensation surface 36. Because of the missing or reduced outflow there Via the second leak path 42 there is a substantial pressure increase, which is higher than in one all around same geometric game in the size of the Normal game would exist. This pressure increase causes a high counterforce on the distributor pump piston, which the resulting force from the pressurization in the area counteracts the distributor opening 12. Fit this way the compensation forces caused by the pressure compensation surface generated dynamically to the respective Pressure level. So can the normal game between the distributor pump piston and the axial bore 5 receiving them are kept smaller than without the invention Force balance. This results in less leakage during the entire operation of the distributor injection pump and thus a higher efficiency of the pump and the possibility also generate higher injection pressures. Furthermore is ensured by the distribution of forces that this gap that can be reduced is still too intense a touch the surfaces of the moving parts is avoided and the risk of eating is controlled. It says due to the arrangement of the pressure compensation surface according to the invention with the first leak to the distributor groove 12 and the second leakage path 42 to the annular groove 20 is quite high Available surface area of the distributor pump piston 6 carries within the axial bore 5 and the additionally over this great length between the end face 9 and the annular groove 20 the leakage losses to the low pressure side keeps small. This and the dynamic pressure equalization that is Adapting the pressure curve in the pump work space leads to a safe construction with low leakage loss and high operational safety.

6 shows an alternative embodiment to FIG. 4 of the pump piston, again in the form of a lateral surface development. Deviate from the embodiment Figure 4 are here two pressure compensation areas instead of one 36a and 36b are provided, which are now symmetrical to the filling groove 18 lie, which in turn diametrically opposite the distributor groove 12 lies. These two pressure compensation surfaces 36a and 36b are in turn connected to one another by a partial annular groove 37 ' in such a way that this partial ring groove describes almost 360 ° with the exception of the area in which the filling groove 18 seen in the circumferential direction in overlap with the pressure compensation surfaces 36a and 36b. The first leak route 39 is in turn determined by the vertical distance between Partial ring groove 37 and the lower edge 40 of the distributor groove 12 are formed and the second leak section again between the lower one Limiting edge 43 of the pressure compensation surface 36a or 36b and the annular groove 20. The pressure compensation surfaces are preferred arranged rotated by 120 ° to the distributor groove 12. In addition to this location, the second leak path would also be Another leakage path between the pressure compensation areas 36a or 36b and the filling groove 18 possible.

FIG. 7 shows a third exemplary embodiment, which in turn is based on the exemplary embodiment according to FIG. 4 inspired. However, there is next to a pressure compensation area 136a a pressure field boundary surface 136b is provided, which now continuously connected to one another by an annular channel 137 are. The second leakage path 42 in turn between the lower boundary 43 of the one pressure compensation surface 136a and the annular groove 20 are formed. The first Leakage path 139, on the other hand, is now between the upper boundary edge the pressure field boundary surface 136b and the lower boundary edge 40 of the distributor opening 12. Die For this purpose, the pressure field delimitation surface 136b is aligned with the distributor opening 12 arranged, i.e. the common center line forms a surface line of the outer surface 11 of the distributor pump piston. In this embodiment, the Pressure compensation surface 136a generates a compensation force, while the print field boundary surface 136b mainly the balance pressure supply, but also the limitation of the Distributor groove pressure field and thus serves the shear force.

A fourth exemplary embodiment is shown in FIG. which in turn is based on the exemplary embodiment according to FIG. 6 inspired. However, there are two filling holes instead of the filling groove 18 118a and 118b provided the fill function take. The arrangement of the fill bores 118a and 118b are chosen so that they are during a full work cycle (Suction / delivery) with one of the injection lines 14 overlap. The filling bores are preferably To be arranged at 90 ° to the distributor groove. The second leak gap 142 is between the lower boundary edges 43 of the pressure compensation surfaces 36a, and 36b and one on the outer surface of the distributor pump piston circumferential additional annular groove 48 formed, which lies above the annular groove 20. Another third leakage path 49 between the additional annular groove 48 and the annular groove 20 is formed. That there of the additional Ring groove 48 leakage volumes flowing over the circumference to the ring groove 20, can correspond to the circumference of the gap of the distributor pump piston be different, whereby different pressure conditions develop, one Favor balance of forces. The third leak path 49 is essentially in relation to the second leak path 2.5 times as large.

Claims (16)

1. Fuel injection pump for internal combustion engines with a moving part (6), which is mounted in a housing bore (5) and has on its circumferential surface (11) an outlet opening (12), which is supplied intermittently with fuel under high pressure from a high-pressure source (8) via a passage (10) in the moving part (6) and, in the course of the movement of the moving part (6), enters into connection with a pressure line (14) leading off from the housing bore (5) for the purpose of passing on the fuel supplied by the high-pressure source, and at least one pressure-compensating surface (36; 36a, 36b; 136a, 136b) acted upon by the high pressure is provided on the circumferential surface (11) of the part (6), the said pressure-compensating surface preferably being arranged on the opposite side of this circumferential surface (11) from the outlet opening (12), characterized in that the pressure-compensating surface (36; 36a, 36b; 136a, 136b) is covered continuously by the inner wall of the housing bore (5) and remains self-contained in the course of the movement of the moving part (6) and is connected by a first leakage path (39) between the circumferential surface (11) of the moving part (6) and the inner wall of the housing bore (5) to parts (12) of the fuel injection pump that carry high pressure and is connected by a second leakage path (42) to a region (20) connected to a low-pressure source (24), between the circumferential surface (11) of the moving part (6) and the housing bore (5).
2. Fuel injection pump according to Claim 1, characterized in that the second leakage path (42) is essentially twice as long as the first leakage path (39).
3. Fuel injection pump according to Claim 1 or 2, characterized in that the moving part is a distributor (6), which is driven in rotation and has a distributor opening (12) as an outlet opening, which is supplied periodically with fuel under high pressure and, in the course of the rotation of the distributor (6), comes successively into connection with different pressure lines leading off from the housing bore (5) at the circumference of the distributor (6) so as to pass on the fuel delivered under high pressure to the distributor opening (12) to respective injection valves.
4. Fuel injection pump according to Claims 1 to 3, characterized in that the at least one pressure-compensating surface (36; 36a, 36b; 136a, 136b) is a longitudinal groove or a flattened portion or ground surface extending in the longitudinal direction parallel to the axis of the part moved in rotation.
5. Fuel injection pump according to Claims 1 to 4, characterized in that the pressure-compensating surface (36; 36a, 36b; 136a, 136b) of the moving part (6) has at least one component length preferably in the form of an onward-leading groove or groove-like flat (37, 37', 137) that is machined into the circumferential surface and extends into a region of the circumferential surface (11) in which a minimum distance from the parts carrying high pressure, defined as a first leakage path (39), exists between the moving part (6) and the housing bore (5).
6. Fuel injection pump according to Claim 5, characterized in that the component length (37, 37', 137) of the pressure-compensating surface extends essentially parallel to a radial plane relative to the axis of the moving part (6).
7. Fuel injection pump according to Claim 5 or 6, characterized in that the parts that carry high pressure are a distributor opening, in particular a longitudinal distributor groove (12), machined into the circumferential surface of the moving part.
8. Fuel injection pump according to one of preceding Claims 5 to 7, characterized in that the groove or groove-like flat (36; 36a, 36b; 136a, 136b) and/or the second groove or groove-like flat is/are in the form of a partially annular groove (37, 37'), which is parallel to a radial plane of the moving part and the end of which is in axial overlap with the part (12) carrying high pressure.
9. Fuel injection pump according to one of the preceding claims, characterized in that the second leakage path (42) is formed between the pressure-compensating surface (36; 36a, 36b; 136a) and an adjacent region (18) situated in the circumferential direction of the moving part and connected to the low-pressure source (24).
10. Fuel injection pump according to Claim 9, characterized in that the region connected to the low-pressure source extends into an annular groove (20) in the circumferential surface (11) of the moving part (6).
11. Fuel injection pump according to one of preceding Claims 4 to 11, characterized in that a plurality of pressure-compensating surfaces is provided, which are connected to one another by an encircling groove (137) or groove-like flat extending parallel to a radial plane relative to the axis of the moving part (6) and machined into the circumferential surface.
12. Fuel injection pump according to Claim 9, characterized in that two pressure-compensating surfaces (36a, 36b) are provided in the circumferential surface (11) of the moving part (6) symmetrically to a filling groove (18) and essentially opposite the distributor groove, which filling groove (18) connects the pressure lines (14) successively to a relief space during the rotation of the moving part (6).
13. Fuel injection pump according to one of the preceding claims, characterized in that the size of the compensating surface (36) corresponds to the area of the outlet opening (12).
14. Fuel injection pump according to Claim 11, characterized in that two pressure-compensating surfaces (36a, 36b) are provided in the circumferential surface (11) of the moving part (6), being provided at essentially equal angular intervals to one another and to the distributor groove (12), and two filling holes (118a, 118b) are furthermore provided, which, during the rotation of the moving part (6), successively connect the pressure lines (14) that are not subjected to injection pressure, as the region connected to the low-pressure source, to a relief space and the angular spacing of which relative to one another and to the distributor groove (12) is determined by the mouth of the pressure lines (14) and are situated essentially opposite the two pressure-compensating surfaces.
15. Fuel injection pump according to Claim 14, characterized in that an additional annular groove (48), between which and the annular groove (20) a third leakage path (49) is formed, is provided between the compensating surfaces (36a, 36b) and the annular groove (20) connected to the low-pressure source (24).
16. Fuel injection pump according to Claim 15, characterized in that the length of the third leakage path (49) is essentially 2.5 times the length of the second leakage path (142).

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