GB2248657A

GB2248657A - A heavy oil fuel injection pump for fuel-injection internal combustion engines

Info

Publication number: GB2248657A
Application number: GB9120541A
Authority: GB
Inventors: Stanislaw Bodzak; Richard Kinzel; Otto Hagenauer; Gerhard Lehner
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1990-09-29
Filing date: 1991-09-27
Publication date: 1992-04-15
Anticipated expiration: 2011-09-27
Also published as: GB9120541D0; JPH04262060A; JP3367681B2; DE4030951B4; GB2248657B; DE4030951A1

Abstract

A heavy oil fuel injection pump having a lubrication oil groove (6, 11) in the pump piston (2) and/or on the inside wall of the pump piston bushing (1). The lubricating oil is supplied through a bore (7) to one side of the lubrication oil groove (6) and is discharged from the side opposite the supply side, in a manner which is controlled by the pump piston. In the embodiment shown oil leaves the groove (6) when the groove (11) is in alignment, a groove (10) providing a discharge flow path. The lubricating oil thus flows in directed flow through the Iubrication oil groove (6) and leaves it in a pulsed manner. The flow-through cross section of the lubrication oil groove (8) is preferably a maximum of 100% and in particular a maximum of 50%, of the cross section of the supply bore (7). The dwell time of the lubricating oil in the lubrication oil groove is shortened, and deposits are thus reduced or avoided. Several other embodiments are described. <IMAGE>

Description

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DESCRIPTION

A HEAVY OIL FUEL INJECTION DEVICE FOR FUEL-INJECTION INTERNAL COMBUSTION ENGINES This invention relates to a heavy oil fuel injection device for fuel- injection internal combustion engines.

To operate an injection pump with heavy oil, it is necessary to heat the heavy oil to high temperatures. for example up to HO'C, in order to ensure the required viscosity of the heavy oil for injection. As a result, the entire injection pump is heated, and the lubricating oil, which is obtained from the engine lubrication system, is degraded by such heating if it remains too long in the lubrication oil groove in the heated region. The lubricating oil has additives and, under the effect of the heat, lacquer-like deposits are formed which settle on the inside wall of the pump piston bushing and.on the piston skirt. This may even lead to coking. As a result of the narrow piston clearance, which is frequently only 8 to 10 M, such deposits may result in seizure of the piston.

This invention relates, in particular, to an embodiment in which the lubrication oil is.,fsupplied to a lubrication oil groove on one side of the pump element and is removed from the lubrication oil groove, in a manner which is controlled by the pump piston, at the opposite side of the pump element. One such system is known from British Patent Application No. 2 123 492A, in which, the lubricating oil is supplied to a lubrication oil groove located in the pump piston bushing at one side of the piston and is removed again at the other side of the piston in a manner which is controlled by the pump piston, thereby the dwell time in the lubrication oil groove is reduced. However, a second lubrication oil groove is provided in the piston, which slides to a slight extent at the bottom dead centre, over the lubrication oil groove in the pump piston bushing, so that the lubricating oil can pass from the lubrication oil groove located in the pump piston bushing over the entire periphery of this lubrication oil groove into the lubrication oil groove of the piston. However, the lubricant in the lubrication oil groove of the pump piston is not changed, but can only be replenished providing that some of the lubricating oil in the lubrication oil groove of the piston has been used, which is, however, only the case from time to time. The predominant portion of the lubricant remains in the lubrication oil groove of the piston, and thereby dwells for a long time in the heat region and thus forms the above-mentioned lacquer-like -3deposits on the wall of the piston bushing and on the piston skirt. The risk of piston seizure has therefore not been eliminated.

In accordance with the present invention there is provided a heavy oil fuel injection device for fuel injection internal combustion engines, having a pump piston, a pump piston bushing, at least one lubrication oil groove in the pump piston and/or on the inside wall of the pump piston bushing and a leakage oil groove provided above the at least one lubrication oil groove, wherein lubricating oil is supplied to each of the at least one lubrication oil grooves at one side of the pump element and is removed from each of the at least one lubrication oil grooves at the opposite side of the pump element in a manner which is controlled by the pump piston.

This has the advantage that, in all lubrication oil grooves, a specific circuit of the lubricating oil is achieved, such that it is ensured that there is no lubricating oil residue, which can lead to the abovementioned lacquer-like deposits on the running surface of the pump piston bushing and on the piston skirt, in any of the lubrication grooves. In this way, a specific circuit of the lubricating oil through the lubrication oil grooves is achieved, and since the outflow of the lubrication oil grooves is controlled by the piston it is effected in a pulse-like manner, as a result of which complete or substantially complete replacement of the lubricant in the lubrication oil grooves is ensured.

Preferably, a compound oil groove is provided between the lubrication oil groove and the leakage oil groove, from which the compound oil is removed to a location outside the injection pump, the last residue of the heated lubricating oil is also removed from the danger zone. Overall, all quantities of lubricating oil which are in the region of the inside walls of the pump piston bushing and the piston skirt are removed from this region for a short time and replaced by quantities of fresh lubricating oil, in order to prevent the formation of such lacquer-like deposits on the running surface of the pump piston bushing or the piston skirt, and hence to reliably prevent seizure of the piston.

In hitherto known systems, the flow-through cross section is relatively large, there is an insufficient build up of lubricating pressure in the vicinity of the heavy oil groove, and thereby insufficient oil exchange, because the lubricating oil remains too long in the grooves having a large cross section. Apart from this, the large flow-through is also disadvantageous because of a heavy accumulation of oil 1 -5in the pump spring chamber and the necessity of a large lubrication oil pump.

Preferably, the flow-through cross section of the lubrication oil groove is a maximum of 100%, preferably a maximum of 50%, of the cross section of the supply bore in the pump piston,bushing for the lubricating oil, such that a good flow through in the lubrication oil groove is ensured and a flow rate substantially the same as in the supply bore is obtained.

According to a further advantageous embodiment of the invention, the outflow of the lubricating oil from the lubrication oil groove at or near the top dead centre is opened by the pump piston.

This has the advantage that the upper part of the piston shaft is lubricated as well. A sufficient lubrication is obtained in the delivery region, that is from the bottom dead centre of the pump piston by way of the commencement of delivery to the termination of delivery. The pressure in the lubricating oil groove is not reduced and the lubrication oil replaced until the vicinity of the top dead centre. This permits advantageous metering of the lubrication oil flow. If the outflow of the lubricating oil from the lubrication oil groove takes place at the bottom dead centre, as is the case according to British Patent -6Application No. 2 123 492 A, lubrication is restricted to the lower- lying part of the piston shaft.

Preferably, the lubrication oil groove is disposed in the pump piston bushing, wherein the pump piston has a longitudinally extending flattened portion or groove, which, in the rotary positions of the pump piston which occur most frequently during operation, lies approximately diametrically opposite the mouth of the lubricating oil supply bore. In this way, lubricating oil flows through the lubrication oil groove resulting in a substantially complete change in the volume of lubricating oil in the lubrication oil groove. Advantageously, the upper end of the groove or flattened portion opens the lubrication oil groove in the pump piston bushing at or close to the top dead centre, wherein the lubricating oil emerges in a pulsed manner by way of this flattened portion or groove.

According to the invention, the upper end of the groove or flattened portion advantageously opens into a lubrication oil groove, which is provided on the pump piston and which moves to overlap with the lubrication oil groove provided in the pump piston bushing, wherein the cross sections of the two lubrication oil grooves together produce the effective flow-through cross section through the lubrication oil groove.

Preferably, the arrangement is such that a second lubrication oil groove is provided in the pump piston, which groove lies. at top dead centre position, below the lubrication oil groove of the pump piston bushing and into which there opens an upwardly extending groove or flattened portion, which opens the lubrication oil groove of the pump piston bushing at a location which lies opposite the mouth of the lubricating oil supply bore, and that a downwardly extending groove or flattened portion, which is open at the bottom, opens into this lubrication oil groove approximately diametrically opposite the groove or flattened portion. In this way, two lubrication oil grooves are formed through which lubricant simultaneously flows in a directed manner. In this way, a larger region of the pump piston bushing is lubricated.

For a further enlargement of the region of the pump piston bushing which is accessible for lubrication, preferably the pump piston has a further lubrication oil groove formed between the lubrication oil groove and the leakage oil groove or the compound oil groove, which groove is connected by way of a bore in the pump piston to the lubrication oil groove, and from which the lubricating oil can be removed by way of a particularly inclined further bore in the pump piston in the region of the bottom dead centre. It is thereby possible to also supply the region of the piston which is permanently above the lubrication oil groove in the pump piston bushing with lubricating oil in order to achieve lubrication with permanently fresh and uniformly replaced engine oil. Thus deposits can be reliably avoided in this region too.

Preferably, the further lubrication oil groove on the pump piston is disposed in such a way that lubricating oil can be removed by way of the further lubrication oil groove on the pump piston over a maximum of half, in particular a maximum of a quarter, of the stroke of the pump piston. Advantageously, the lubricating oil can be removed from the lubrication oil groove as of half, in particular as of around 75%, of the stroke of the pump piston. In such a mutual arrangement of the lubrication oil groove and of the additional lubricating oil groove on the pump piston, a time-controlled, pulsating lubrication oil flow from the lubrication oil supply bore into the lubricating oil groove on the inside wall of the pump piston bushing and, subsequently, into the lubricating oil groove on the pump piston is maintained. This flow of lubrication oil is thus in the same direction but offset with respect to time in the lubricating oil -9grooves, which are connected to one another through the bore in the piston.

The dimensioning of the cross sections of the further lubricating oil groove are, to effectively prevent deposits and maintain a favourable flow behaviour in the individual lubricating oil grooves, preferably dimensioned such that the cross section of the further lubricating oil groove on the pump piston is smaller than the cross section of the lubricating oil groove on the inside wall of the pump piston bushing.

The invention is further described, by way of example only, with reference to the accompanying drawings, in which:- Fig. 1 is an axial sectional view through a conventional fuel injection device; Fig.2 is an axial sectional view through a fuel injection device constructed in accordance with one embodiment of the present invention; Fig. 3 is a sectional view along the line III-III in Fig. 2; Fig. in Fig. 2; Fig. 5 is a partial longitudinal sectional view through a fuel injection device constructed in accordance with a second embodiment of the present 4 is a sectional view along the line IV-W invention; Figs. 6,7,8 and 9 are views similar to that of Fig. 2 through a third, fourth, fifth and sixth embodiment respectfully of the present invention; Fig. 10 illustrates the region of the two lubrication oil groves of Fig. 9 in detail; Fig. 11 illustrates a section along the line XIXI of Fig. 9; and Fig. 12 illustrates a schematic diagram of the removal of the lubricating oil from the individual lubrication oil grooves of the embodiment illustrated in Figs. 9 to 11.

In Fig. 1 the conventional pump element has a pump piston bushing 1, a pump piston 2 illustrated in the bottom dead centre position and an intake bore 3. A leakage oil groove 4 is provided in the piston 2 from which leakage oil is drained by way of a bore 5 back into the intake bore 3. Lubricating oil is supplied from the lubrication circuit of the engine by way of a bore 7 in the pump piston bushing 1 to a lubrication oil groove 6. In the pump piston bushing 1, between the leakage oil groove 4 and the lubricating oil groove, there is a compound oil groove 8 from which the mixture of heavy oil fuel and lubricating oil is removed by way of a bore 9 into an area lying outside the injection pump. The -11lubricating oil or lubrication oil supplied by way of the bore 7 stands in the lubrication oil groove 6, and thus remains a long time in the heat region of the pump element, which has been heated by the heavy oil fuel, and is precipitated in the form of lacquer-like deposits on the skirt of the pump piston 2 and on the piston running surface of the pump piston bushing 1, wherein coking may occur. Such deposits may lead to seizing of the piston.

According to the embodiment of Fig. 2, the piston has an axial groove or flattened portion 10, as shown in cross section in Figs. 3 or 4. This groove or flattened portion 10 extends in the bottom dead centre position as illustrated up to level a. In this position, the lubrication oil groove 6, which is provided in the pump piston bushing, is not opened. In the top dead centre position, the groove or flattened portion extends up to the level b. It can be seen from this that this groove or flattened portion 10 opens the lubrication oil groove 6 near the top dead centre position. The groove or flattened portion 10 connects the lubrication oil groove 6 on the side of the pump element 19 lying opposite the mouth 15 of the lubricating oil supply bore 7 to the outflow which, as shown in the drawings, is effected into the spring chamber.

In this way, a directed flow of the lubricating oil in the lubrication oil groove 6 is produced, such that the lubricating oil flows out of the lubrication oil groove 6 in a pulsed manner if the groove or flattened portion 10 slides over the lubrication oil groove 6. The cross section of the lubrication oil groove 6 is that same as or smaller than the cross section of the lubricating oil supply bore 7. Thus, as soon as the outflow through the groove or flattened portion 10 is opened, a strong, directed flow is generated in the lubrication oil groove. In the embodiment of Figs. 2 to 4, the groove or flattened portion 10 of the piston 2 extends axially parallel to the piston. Fig. 5 shows that the groove 10 may also be disposed in spiral or helical form in the piston 2.

The embodiment of Fig. 6 differs from the embodiment of Figs. 2 to 4 in that the groove or flattened portion 10 opens into a second lubrication oil groove 11, which is formed in the piston 2. the top dead centre position, the lubrication oil groove 11 of the piston 2 moves to overlap with the lubrication oil groove 6 of the pump piston bushing 1, and the lubricating oil flows out of the groove 6 again by way of the groove or flattened portion 10. In this case, the cross sections of the grooves 6 and 11 should be approximately the same as or smaller than i -13the cross section of the lubricating oil supply bore 7.

The variant of Fig. 7 differs from the embodiment of Figs. 2 to 4 in that, in place of the groove or flattened portion 10, an inclined bore 12 is provided in the piston 2, which opens to the outside approximately in the region of a crosshead 13. This inclined bore 12 opens to form a mouth 14 on the piston skirt, and if this mouth 14 opens the lubrication oil groove 6, a directed flow is once again obtained from the mouth 15 of the lubricating oil bore 7 to the mouth 14 of the inclined bore 12 through the lubrication oil groove 6.

In the embodiment of Fig. 8, a third lubrication oil groove 16 is provided in the pump piston 2 in a region below the lubrication oil groove 6 when the piston is in the top dead centre position. A groove or flattened portion 17 leads in the piston 2 from this lubrication oil groove 16 upwards. This groove or flattened portion 17 opens the lubrication oil groove 6 of the pump piston bushing 1 again at a location which lies opposite the mouth 15 of the lubricating oil supply bore 7. The lubricating oil thus flows in a directed flow from the mouth 15 through the lubrication oil groove 6 to the groove or flattened portion 17 in the piston, and therefrom into the lubrication oil groove 16 of the piston 2. On the -14side of the piston lying diametrically opposite the groove or flattened portion 17, a downwardly directed groove or flattened portion 18 of the piston opens into the lubrication oil groove 16, which leads into the open. Once again, a directed flow from the groove or flattened portion 17 to the groove or flattened portion 18 is obtained in the lubrication oil groove 16.

In the representation of Fig. 9, the reference numerals of the previous figures have been retained for the same components. A fourth lubrication oil groove 20, which cooperates by way of a bore 21 in the piston 2 with the lubrication oil groove 6, is provided between the lubrication oil groove 6 and the compound oil groove 8 or the leakage oil groove 4 on the pump piston 2. The removal of lubricating oil from the lubrication oil groove 20 is effected by way of a further, particularly inclined bore 22 in the piston 2, which opens, similar to that described in the embodiment of Fig. 7, into the spring chamber. Lubricating oil is removed from the lubrication oil groove 6 as in the previous embodiments by way of a flattened portion or groove 10, which extends substantially in the axial direction, in the skirt of the pump piston. As can be seen from Fig. 9, the bores 21 and 22 are disposed in the pump piston 2 in -15such a way that lubricating oil completely flows through the lubrication oil groove 20 in that the lubricating oil is supplied one side and is removed at the end opposite the supply end.

In Fig. 9, the position of the lubrication oil groove 20 on the piston in the region of the top dead centre is schematically indicated by 201.

In the representation according to Fig. 10, the individual mouths of the bores 21 and 22 are shown in greater detail. Lubricating oil passes by way of the supply line 7 into the lubrication oil groove 6, and, as the pump piston 2 moves upwards, the mouth 23 of the bore 21 opens the flow of lubricating oil in the direction towards the bore mouth 24 into the lubrication oil groove 20 on the piston skirt. The lubricating oil passes from there by way of the entire periphery of the lubrication oil groove 20 to the mouth 25 of the bore 22, and from there in the region of the bottom dead centre to a bore outlet 26 of the bore 22 and thus into the spring chamber of the injection pump. In the event of further upwards motion of the pump piston 2, lubricating oil passes, as in the previous embodiments, out of the lubrication oil groove 6 in a region 27 of the lubrication oil groove 6 by way of an outlet opening 28 of the flattened portion or groove 10 into the spring chamber -16of the injection pump as well.

The cross section of the lubrication oil groove 20 on the pump piston 2 is in such case smaller than the cross section of the lubrication oil groove 6 on the inside wall of the pump piston bushing.

In the graph illustrated in Fig. 12, the stroke of the pump piston is plotted against time t or camshaft angle a. It can clearly be seen that, in the region of the bottom dead centre, between a period t, and t2 and a period t5 to t6, a connection is made between the additional lubrication oil groove 20 and the spring chamber of the injection pump by way of the bore 22, whereas, over a time period t3 to tC which extends over the region of the top dead centre, the lubrication oil groove 6 is connected to the spring chamber by way of the groove or flattened portion 10. In such a way, a time-controlled, pulsating flow of lubricating oil is obtained through the grooves 6 and 20, which is in each case offset to one another over time. The lubricating oil is removed from the lubrication oil groove 20 over a time period or a camshaft angle which corresponds to a maximum of half the stroke of the pump piston 2, whereas lubricating oil is removed from the lubrication oil groove 6 from around 75% of the total stroke of the pump piston 2.

Claims

-17CLAIMS

1. A heavy fuel oil injection device for fuel injection internal combustion engines, having a pump piston, a pump piston bushing, at least one lubrication oil groove in the pump piston and/or on the inside wall of the pump piston bushing and a leakage oil groove provided above the at least one lubrication oil groove, wherein lubricating oil is supplied to each of the at least one lubrication oil grooves at one side of the pump element and is removed from each of the at least one lubrication oil grooves at the opposite side of the pump element in a manner which is controlled by the pump piston.

2. A heavy oil fuel injection device as claimed in claim 1, wherein compound oil groove, from which compound oil is removed, is provided between the lubrication oil groove and the leakage oil groove.

3. A heavy oil fuel injection device as claimed in claim 1 or 2, wherein the flow-through cross section of the at least one lubrication oil groove is a maximum of 100% of the cross section of a supply bore provided in the pump piston bushing for the lubricating oil.

4. A heavy oil fuel injection device as claimed in claims 1 or 2, wherein the flow-through crosssection of the at least one lubrication oil groove is -18a maximum of 50% of the cross section of a supply bore provided in the pump piston bushing for the lubricating oil.

5. A heavy oil fuel injection device as claimed in any preceding claim, wherein the outflow of lubricating oil from the at least one lubrication oil groove at or near the top dead centre is opened by the pump piston.

6. A heavy oil fuel injection device as claimed in any of claims 1 to 5, wherein a first lubrication oil groove is disposed in the pump piston bushing, and the pump piston has a longitudinally extending flattened portion or groove, which, in the rotary positions of the pump piston which occur most frequently during operation, lies approximately diametrically opposite the mouth of a or the lubrication oil supply bore.

7. A heavy oil fuel injection device as claimed in claim 6, wherein the upper end of the groove or flattened portion at or near the top dead centre opens the first lubrication oil groove in the pump piston bushing.

8. A heavy oil fuel injection device as claimed in claim 6 or 7, in which the upper end of the longitudinally extending groove or flattened portion opens into a second lubrication oil groove which is -19provided on the pump piston and which moves to overlap with the first lubrication oil groove provided in the pump piston bushing, wherein the cross sections of the first and second lubrication oil grooves together produce the effective flow-through cross section through the first lubrication oil groove.

9. A heavy oil fuel injection device as claimed in any of claims 1 to 7, wherein a third lubrication oil groove is provided in the pump piston, which groove lies, at the top dead centre position, below the first lubrication oil groove of the pump piston bushing and into which there opens an upwardly extending groove or flattened portion, which opens the first lubrication oil groove of the pump piston bushing at a location which lies opposite the mouth or a or the lubrication oil supply bore, and that a downwardly extending groove or flattened portion, which is open at the bottom. opens into this third lubrication oil groove approximately diametrically opposite the upwardly extending groove or flattened portion.

10. A heavy oil fuel injection device as claimed in any of claims 1 to 7, wherein, on the pump piston, a fourth lubrication oil groove is provided between the first lubrication oil groove and the leakage oil groove or a or the compound oil groove, which is 1 -20connected by way of a bore in the pump piston to the first lubrication oil groove and from which lubricating oil can be removed by way of a particularly inclined further bore in the pump piston in the region of the bottom dead centre.

11. A heavy oil fuel injectign device as claimed in claim 9 or 10, wherein the cross section of the fourth lubrication oil groove on the pump piston is smaller than the cross section of the first lubrication oil groove on the inside wall of the pump piston bushing.

12. A heavy oil fuel injection device as claimed in claim 10 or 11, wherein the lubricating oil can be removed by way of the fourth lubrication oil groove on the pump piston over a maximum of a half of the stroke of the pump piston.

13. A heavy oil fuel injection device as claimed in claim 10 or 11, wherein the lubricating oil can be removed via the fourth lubrication oil groove on the pump piston over a maximum of a quarter of the stroke of the pump piston.

14. A heavy oil fuel injection device as claimed in any of claims 1 to 13, wherein the lubricating oil can be removed from the first and/or second lubrication oil grooves as of half of the stroke of the pump piston.

15. A heavy oil fuel injection device as claimed in any one of claims 1 to 14, wherein the lubricating oil is removed from the first and/or second lubrication oil groove as of approximately 75% of the stroke of the pump piston.

16. A heavy oil fuel injection device constructed and adapted to operate substantially as herein described, with reference to and as illustrated in, the accompanying drawings.