DE8716536U1 - Fuel injection pump for internal combustion engines - Google Patents

Description

R. 21527
26.11.1987 Gf/&EEgr;&pgr;)

ROBERT BOSCH GMBH, 7000 STUTTGART 1

Fuel injection pump for internal combustion engines

State of the art

The invention is based on a fuel injection pump according to the type of the main claim. In a fuel injection pump of this type known from DE-P 35 19 029, the drive shaft enters the housing through a shaft seal and is guided here in a plain bearing. A feed pump is coupled to the drive shaft, which pressurizes parts of the housing interior. This pressure also acts on the plain bearing, to which the relief line is attached at about half the length. Due to its cross-section, it drains the amount of leakage oil with almost no line resistance. The remaining length of the plain bearing from the relief line to the shaft seal is insufficiently supplied with the lubricating leakage oil due to the narrow bearing clearance and the associated high flow resistance, which can lead to dry running and blockage of the pump. This effect is further increased by the risk of blockage as a result of the ingress of dirt.

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Advantages of the invention

The fuel injection pump according to the invention with the characterizing features of the main claim has the advantage that the sealing element slides on the shaft in the manner of a plain bearing, but is axially and radially displaceable in relation to the surrounding housing parts and thus does not have to have the machining quality of a plain bearing with guiding functions and has the tolerance relief.

^! nition can be produced cost-effectively. The connection ler

f\ Relief line with the suction side of the feed pump changes the passive drainage of the leakage oil into an active suction by the negative pressure prevailing at the pump inlet. This makes it possible to make the shaft seal less prone to wear by reducing the contact pressure on the drive shaft and to provide a seal between the shaft seal and the drive shaft.

; shaft outlet on the housing due to the prevented leakage oil flow the

The drive shaft can be supported with a roller bearing and in this way the machining effort on the fuel injection pump can be reduced. The measures listed in the subclaims enable further advantageous developments and improvements of the element specified in the main claim and the adjacent parts. It is particularly advantageous to vary the amount of leakage oil by means of graduated seal qualities without thereby impairing the drive shaft bearing and thus the functionality of the fuel injection pump.

drawing

Four embodiments of the invention are shown in the drawing and explained in the following description. Cs

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Figure 1 shows a partial longitudinal section through a fuel injection pump / Figure 2 shows in detail the position of the drive shaft seal / the element with surrounding components and the suction of the feed pump » Figures 3 and 4 show further embodiments of the element for preventing leakage flow.

Description of the embodiments

In the drawing, Figure 1 shows a schematic representation of a partial section through a distributor fuel injection pump in which a drive shaft 2 enters a housing 1, which is guided by a roller bearing 3 and drives a feed pump 4 which feeds into a working chamber 5. Due to leakage along the drive shaft 2 in the direction of the roller bearing 3, the working chamber 5 is connected to an element 6 which is located on the side of the feed pump 4 facing away from the pressure.

This element 6 surrounds the drive shaft 2 as a rotationally symmetrical part and, since it can be moved axially and radially on the drive shaft 2 in the manner of a plain bearing, has a gap between its inner bore and the drive shaft 2. This gap then forms a single passageway for the leakage flow from the working chamber 5 along the drive shaft 2 in the direction of the roller bearing 3 when the other part of the element, a shoulder 9 with an axially directed end face which extends radially to the drive shaft, is axially supported on the side facing away from the working chamber 5 against a housing shoulder 7 directed radially to the drive shaft 2 and in this way blocks the leakage flow from the working chamber 5 this path; but leakage from the working chamber 5 can also occur here. After the element 6, the leakage flow enters a relief chamber 8.

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This relief chamber 8 is delimited by the side of the element 6 facing away from the feed pump 4/ the drive shaft l _t a shaft seal 11/ the housing 1 and a relief line 12. The shaft seal 11 has as an essential feature a pre-stressed sealing lip in the form of a sleeve, which rests on the drive shaft 2 and protects the roller bearing 3 arranged downstream from the leakage flow. The relief line 12 leads from the relief chamber 8 to the suction side 13 of the feed pump 4/ whereby the leakage flow is safely diverted, since the negative pressure on the suction side 13 changes the mere drainage to a suction. This means that the discharge tungsraum 8 And at the same time the sealing lip of the shaft seal 11 is safely and significantly decoupled and relieved from the internal pressure of the working chamber 5, which increases the duration of the functionality of the shaft seal. The second embodiment shown in Figure 2 shows a somewhat more detailed design than the basic representation of the element 6 according to Figure 1 and an alternative solution with regard to the blocking of the leakage flow along the shoulder 9 of the element 6 and the housing shoulder 7.

For this purpose, the housing shoulder 7 has an annular groove 15 on the side facing the shoulder 9, into which a spring-loaded seal 16 is inserted. In conjunction with a seal 16 which is positioned against the feed pump 4 \J supporting and axially pressing against the element 6, here designed as a leaf spring, the shoulder 9 is pressed against the seal 16 and, after the latter has elastically retreated into the annular groove 15, lies firmly against the housing shoulder 7, so that the leakage flow is blocked from passing into the relief chamber 8 in this way.

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the shoulder 9 has one or more grooves 17 on its circumference, into which a corresponding number of pins 18 anchored in the housing 1 engage; this prevents the element 6 from rotating on the drive shaft 2 in order to protect the seal 16. The leakage from the working chamber 5 to the relief chamber 8 therefore only takes place via the gap between the inner bore of the element 6 and the drive shaft 2. Alternatively, the kingnut 15 can also be arranged in the front surface of the shoulder 9. In the embodiment shown in Figure 3, the ring for the seal 16 is larger than in Figure 2. groove 15 and the seal 16 are not present at the locations described/ rather, a corresponding annular groove 19 and a spring-loaded seal 20 inserted therein are introduced into the drive shaft 2 in the area of the inner bore of the element 6 in such a way that the gap between element 6 and drive shaft 2 is closed by the spring-loaded seal 20 and the leakage flow along the drive shaft 2 is prevented. Alternatively, the seal 20 can also be arranged in the outer surface of the inner bore of the element 6. In the area of the surface of the element 6 opposite the drive shaft 2, the element 6 has a longitudinal groove 21 into which a pin 22 anchored in the drive shaft 2 engages, whereby the element 6 is secured against rotation relative to the drive shaft 2 and the seal 20 is thus protected against wear.

The energy storage device 14, which works in the same way as described in Figure 2, is designed here as a helical spring. In addition, as in the embodiment according to Figures 1 and 2, the pressure of the working space δ acts as a sealing force on the element 6. Figure 4 shows an element 15 which, like element 6, is arranged on the drive shaft 2 in the manner of a plain bearing, but differs from element 6 in that it has no shoulder. As a result, the

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Anti-twisting device between element 106 and the drive shaft 2, the \ in the same way as in Figure 3 for element 6 and

the drive shaft 2, the additional function of an anti-displacement device, in that the pin 22 in the groove 21 comes into contact with the lateral boundary surface facing the working space S, whereby the axial displacement force on the element 106 is caused by the internal pressure prevailing in the working space 5.

The sealing function of the element 10Ö is carried out by a ΓΛ annular groove 23, which is located on the casing facing away from the drive shaft 2.

surface and the spring-loaded ring 24 inserted therein, which on the one hand rests against a collar 25 on the housing side that runs concentrically to the drive shaft 2, and on the other hand presses against the lateral boundary of the ring groove 23 facing away from the working chamber 5 due to the internal pressure prevailing in the working chamber 5. Alternatively, the ring 24 can also be arranged in the outer surface of the inner bore of the element 6*«

Claims (9)

R. 21527 26.11.1987 Gf/Hm ROBEET BOSCH GMBH, 7000 STUTTGART 1 Claims 1. Fuel injection pump for internal combustion engines with a housing (1), with a drive shaft (2) mounted in the housing (1), with a feed pump (4) arranged in the housing (1) and driven by the drive shaft (2), which feeds into a working chamber (5) arranged downstream of the feed pump (4), which is connected via a gap delimited by an element (6) surrounding the drive shaft (2) to a relief chamber (8), which is relieved via a relief line (12) and is delimited from the exit of the drive shaft (2) from the housing (1) by a shaft seal (11) which, in the manner of a cuff seal, has a pre-stressed sealing lip which comes into contact with the drive shaft (2), characterized in that the element (6) has an inner bore with which it is mounted on the drive shaft (2) in the manner of a plain bearing and can be displaced axially as well as radially against surrounding housing parts and that the relief line (12) is connected to the suction side (13) of the feed pump (4). 2. Fuel injection pump according to claim (1), characterized in that the gap between the inner bore of the element (6) and «· « t « t « t ii < I Ki <<> « f. With 1*4 * Ji - 2 - 21527 the drive shaft (2) and/or between an end face of the element (6) and a contact surface for this end face of a housing shoulder (7) pointing in the axial direction of the drive shaft (2) (Figure 1). 3. Fuel injection pump according to claim (2), characterized in that the element (6) is prestressed in the axial direction by means of a force accumulator (14) (Figure 2). 4. Fuel injection pump according to claim (2), characterized in that a seal (16) is arranged between the contact surface and the end face (Figure 2). 5. Fuel injection pump according to claim (4), characterized in that the element (6) has one or more grooves (17) which engage in the corresponding pins (18) anchored in the housing (1) to prevent the element (6) from rotating (Figure 2). 6. Fuel injection pump according to claim (2), characterized in that a seal (20) is arranged between the drive shaft (2) in the region of the element (6) and the inner bore of the element (6) (Figure 3). 7. Fuel injection pump according to claim (2) or (6), characterized in that the element (106) has an annular groove (23) in its outer surface, one lateral boundary of which forms the end face and into which an outwardly springing ring (24) is fitted, one axial surface of which forms the contact surface for the end face of the annular groove (23) and the peripheral surface of which is in sealing contact with a collar (25) of the housing (2) (Figure 4). 21527 8. Fuel injection pump according to claim (6) or (7), characterized in that the element (6), (106) is coupled to the drive shaft (2) by a driver (Figure 3). 9. Fuel injection pump according to one of the preceding claims, characterized in that the drive shaft is guided outwardly adjacent to the shaft seal (11) in the housing (1) in a rolling bearing (3). JI4 « 4 &bull; · ItIIIlIl It