GB2326917A

GB2326917A - Fuel-injection pump for internal combustion engines

Info

Publication number: GB2326917A
Application number: GB9812700A
Authority: GB
Inventors: Joerg-Peter Fischer; Guenter Bofinger; Rolf-Jurgen Giersch; Manfred Naar-Hess; Carlos Alvarez-Avila; Uwe Fitzenreiter; Guenter Veit
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1997-07-02
Filing date: 1998-06-15
Publication date: 1999-01-06
Anticipated expiration: 2018-06-15
Also published as: FR2765626A1; JPH1182068A; DE19728110A1; GB2326917B; GB9812700D0; CN1089850C; CN1204722A

Description

C-1-1 1

DESCRIPTION

2326917 FUEL-INJECTION PUMP FOR INTERNAL COMBUSTION ENGINES The invention relates to a fuel-injection pump for internal combustion engines and is particularly concerned with fuel pumps of the type having a fuelinjection quantity adjusting member, which can be adjusted by virtue of control forces, and an adjustable stop against which the fuel- injection quantity adjusting member comes to rest under the action of a control force, for the purpose of defining the path of the quantity adjusting member, and having a curve which can be adjusted in dependence upon operating parameters and by virtue of which an intermediate lever, which comprises a plurality of arms and can be pivoted about a housing- fixed spindle, is held in position on the curve under the action of a spring, which is supported on the housing of the fuelinjection pump, by means of which intermediate lever it is possible to adjust at least indirectly the stop.

In the case of this type of fuel-injection pump, which is known from DEAl31 46 499, the intermediate lever, which transmits the movement of the adjusted curve to the quantity adjusting member, is designed as a threearmed lever. The compression spring, which adjusts the lever towards the curve, is formed therein as a helical spring and is guided on to a guide spigot, which is connected separately to one lever arm of the intermediate lever. This arrangement is extremely costly to produce and also to assemble. The spring does not have to be used as a separate part on the intermediate lever.

In accordance with the present invention, there is provided an internal combustion engine of the generic type wherein the intermediate lever is 2 designed having two arms and the spring is formed as a substantially hair pinshaped leaf spring whose one spring arm forms a foot part which is coupled to the intermediate lever in an eccentric manner with respect to the spindle and is supported on the intermediate lever in a positionallyfixed manner, and the other spring arm of said leaf spring has a movable arm part which extends in a transverse manner with respect to the foot part and which is supported on the housing of the fuel-injection pump.

In contrast to the known pump described above, fuel-injection pump in accordance with the present invention has the advantage that the intermediate lever is designed having only two arms and thus can be accommodated in a space-saving manner within a fuel-injection pump and the spring is also designed as a space-saving leaf spring. In an advantageous manner the coupling is performed by virtue of a resilient locking action in accordance with claim 2. The embodiment in accordance with claim 3 provides a space-saving design, which is tailored to suit the configuration of the intermediate lever, of the leaf spring which is fixed in position on the intermediate lever in a reliable manner. This is supported by virtue of the embodiment in accordance with claim 4 and claim 5. Furthermore, it is particularly advantageous in the development in accordance with claim 6 that the spring is locked to the intermediate lever by means of a pretensioning force and therefore, in combination with claim 7, the spring is also fixed in position on the intermediate lever in an effective manner without any play.

The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings, in which:- 3 Figure 1 shows a schematically reproduced partial illustration of a fuel- injection pump, wherein the solution in accordance with the invention is applied, with reference to an example from prior art,

Figure 2 shows a partial view of the fuel-injection pump as shown in Figure 1 having the formation, in accordance with the invention, of the intermediate lever and spring, Figure 3 shows a sectional view along the line iii-iii of Figure 2 for a first embodiment of the spring, Figure 4 shows a sectional view along the line iii-iii as shown in Figure 2 for a second embodiment of the spring, Figure 5 shows a plan view of the second embodiment of the spring, and Figure 6 shows a plan view illustration merely of the spring in the direction of the arrow vi of Figure 2.

Figure 1 illustrates a known design of a distributor injection pump which is illustrated in an extremely simplified manner. In a housing 10 a pump piston 12 works in a cylinder 11, which pump piston is set both in a reciprocal movement and simultaneously in a rotating movement by a cam drive 13, 14. The pump piston 12 closes in the cylinder 11 a pump working chamber 15 4 which is filled with fuel from a pump intake chamber during the intake stroke of the pump piston by way of an intake bore 16 and control grooves 17 in the pump piston, which fuel, during the pressure stroke of the pump piston after the intake bore has been closed, is delivered at high pressure by way of a longitudinal bore 18 into a delivery groove 19, which is connected thereto, a pressure valve 21 and a pressure line 22 leading to a fuel-injection valve [not illustrated in detail] on the internal combustion engine. At the end of the delivery a transverse bore 23, which is connected to the longitudinal bore 18, of the pump piston 12, is opened in an annular slide valve 24, so that the fuel, which is further delivered by the pump piston to its upper dead centre, flows back into the intake chamber 25. The said intake chamber is supplied with fuel from a storage container 27 by a pre-delivery pump 26, wherein the delivery pressure present therein is controlled in dependence upon rotational speed and by way of a pressure control valve 28. This pressure serves inter alia to adjust an injection timing piston 55 against a return spring 57, which injection timing piston acts upon the cam drive 13, 14.

In order to control the quantity of fuel, which is delivered at high pressure by the pump piston, a mechanical rotational speed controller 32 is provided which is actuated by centrifugal force and which is disposed within the pump and is set in rotational movement, in a manner which is not illustrated in detail, by a drive shaft 34, which also drives the cam drive 13, 14. Consequently, a controller sleeve 35 of the rotational speed controller 32 is moved in dependence upon rotational speed and as a result a controller lever 36 is adjusted which is to be designated as a delivery quantity adjusting member and is coupled by way of its lever arm to the annular slide valve for the purpose of height adjustment on the pump piston. The lever arm, which is actuated by the controller sleeve, of the control lever which is conventionally designated as a starting lever, is in contact by way of a leaf spring with a clamping lever 37, against which it comes to rest after deformation of the leaf spring and the end of the starting-up procedure under the effect of the displacement of the controller sleeve. Over this adjustment path, the control slide valve 24 moves from a highest position to a full-load position lying further towards the cam drive 13, 14. The further the annular slide valve 24 is adjusted towards the cam drive, the earlier the transverse bore 23 in the pump piston is opened and the earlier the fuel, which is displaced by the pump piston, is controlled in an unpressurized manner into the intake chamber 25, or the smaller is the high pressure injection quantity.

In order to displace further the annular slide valve the clamping lever 37 can be pivoted about the housing-fixed spindle 30 and against the force of a control spring, which in this case is illustrated in a simplified manner merely as a draw spring.

The control spring can be adjusted by virtue of an adjusting lever 31 from outside the housing 10 of the fuel-injection pump. This adjustment serves to determine the desired turning moment of the associated engine or the fuelinjection quantity in different operating ranges.

The highest injection quantity is.determined by virtue of a full-load stop 38 which is provided on an end of an intermediate lever. The intermediate lever is a two-armed lever, which can be pivoted about a housing-fixed spindle 6 40 and which comprises on its one arm 41 a the full-load stop 38 and on its other lever arm 41 b is in operative engagement with a scanning pen 42 which is guided in the housing 10 and protrudes into a cylinder 46 in which it is possible to control an actuator 48 which comprises a cam surface 43 on its peripheral surface. The scanning pen scans this cam surface which is substantially conical in shape and is defined on the one side by a guide piston 45 and is defined on the other side by a guide shaft 58 of the actuator. A return spring 47 and a diaphragm box 49 act upon the guide shaft and both are located within a closed pressure chamber 51, which is supplied with a control pressure 53 by way of a supply bore 52. This pressure can be e.g the pressure from combustion air which has been compressed by a turbo-charger and is supplied to the combustion chambers of the internal combustion engine which is supplied by the fuel-injection pump. Depending upon the air density the full-load injection quantity of the fuel-injection pump is defined and adjusted in this manner.

In the case of this embodiment there is an operating range, wherein the intermediate lever 41 has an adverse affect upon the quantity which is metered by the fuel-injection pump. During the no-load operation of the internal combustion engine, the control spring 39 is completely relaxed, so that the clamping lever together with the control lever 36 are now deflected against the force of a no-load spring 59. The no-load injection quantity is controlled in this manner. In so doing, the clamping lever 37 rises from the intermediate lever 41, so that it is not subjected to any defined force. Consequently, the intermediate lever 41 can vibrate and in order to limit its vibrating movement it 7 passes once again to the clamping lever 37 and, owing to its mass, it triggers at this site a knocking or beating pulse. This influences inturn the position of the annular slide valve 24 and therefore the controlled no-load injection quantity.

In accordance with Figure 2, a leaf spring 60 is coupled to the intermediate lever 41. Figure 2 illustrates the two-armed intermediate lever with the full-load stop 38 at the end of its one lever arm 41 a, and illustrates the scanning pen 42 which lies against the end of the other lever arm 41 b and with its other end follows the cam surface 43. It is evident from the sectional view along the line iii/iii illustrated in Figure 3 that the intermediate lever has a u-shaped cross-section having a base part 62 and two cheeks 63, 64. In the cheeks there are provided bores 65, 66, which are aligned with each other in a flush manner, transverse with respect to the longitudinal extension of the intermediate part, by way of which longitudinal extension the intermediate lever is mounted on the housing-fixed spindle 40. In the region of the bores 65 and 66, the cheeks 63 and 64 comprise a respective neck-like formation 68, 69 which in each case increases the support surface in the region of the bores 65 and 66. At the same time these formations 68, 69 also serve to receive and fix the leaf spring 60 which is formed from a foot part 71 which, outside the surrounding surface of the u-shaped cross-section of the intermediate lever, comes to rest against the base part 62 of said intermediate lever. Two opposite-lying lateral arms 72 and 73 issue from the foot part 71 and encompass the cheeks 63 and 64 of the intermediate lever and engage with openings 74, 75 over the neck-5ke formations 68, 69. In this manner the foot 8 part 71 is initially fixed in position. In the installed state, the lateral arms 72, 73 are essentially prevented from being able to move from the position in which they engage over the neck-shaped formations 68, 69, since adjacent housing parts 10', in which the spindle 40 is inserted, are immediately adjacent to the neck-like formations.

Furthermore, the lateral arms 72 and 73 comprise in the periphery about their openings 74, 75 cam-like projections 76 which can engage into corresponding recesses in the cheeks 63 and 64 andlor furthermore can prevent the leaf spring from being fixed in the rotational direction about the spindle 70 relative to the intermediate lever 41.

A spring arm 78 leads from the foot part 71 on its one end face with respect to the side of one lever arm 41, which supports the fuli-load stop 38, and said spring arm can be divided essentially into three portions. The first portion 80 leads off approximately perpendicular from the foot part 71, the then following second portion extends further, pivoted away from the first portion at an angle of >- 901, below the spindle 40 and the third portion 82 is an end part which subsequently pivots back and which as shown in Figure 2 comes to rest against a housing-fixed wall 83. The three portions of the spring arm 78 thus extend approximately in an s-shaped manner with a relatively rigid region in the first portion 80 stiffened by virtue of the large deflection angle with respect to the first portion and with a third portion 82 which can be deflected in a transverse manner with respect to direction of the foot part 71.

In the installed state as shown in Figure 2, this third spring arm portion 82 lies pretensioned against the housing-fixed wall 83, so that by way of the 9 spring arm and the foot part 71, which is fixedly connected to the intermediate lever, the intermediate lever undergoes a clockwise turning moment, which holds the scanning pen 42 in a fixed position against the cam surface 43 irrespective of the fact whether a force is applied to the intermediate lever 41 by way of the full-load stop 38 and the clamping lever 37. The spring arm 78 consists of two partial arms 85 and 86, as shown in Figure 6. These arms are guided together in the end region 87 of the third portion 82 and form at this site a solid bearing surface. The two-armed spring arm thus serves to provide a high degree of flexibility with good lateral stability.

In order to stabilize further the foot part 71 at the base part 62 of the intermediate lever it is also possible to provide cams 88 as projections 89, which engage behind the base on the end side and thus are also able to counteract a displacement of the leaf spring relative to the intermediate lever.

Figure 3 shows an alternative manner of fixing the lateral arms 72, 73 of the leaf spring to the cheeks 63, 64. For this purpose, the lateral arms comprise in the region of the openings 74, 75 projections which are supported in a resilient manner on the neck-shaped formations 68, 69. This guarantees, therefore, a high degree of fitting accuracy with an optimal fixing arrangement to prevent the leaf spring rotating relative to the intermediate lever.

Therefore, the solution in accordance with the invention always guarantees that the intermediate lever 41 lies constantly against the cam surface 43 by way of the scanning pen 42 and thus is not able to perform any intrinsic movements or oscillating movements. Therefore, stable no- load behaviour is achieved and the full-load stop is guided with high precision. The leaf spring used is arranged in such a manner so as to be extremely spacesaving and owing to its formation is also connected to the intermediate lever 41 in a reliable and positive-locking manner.

Claims

1. A fuel-injection pump for internal combustion engines having a fuelinjection quantity adjusting member, which can be adjusted by virtue of control forces, and an adjustable stop against which the fuelinjection quantity adjusting member comes to rest under the action of a control force, for the purpose of defining the path of the quantity adjusting member, and having a curve which can be adjusted in dependence upon operating parameters and by virtue of which an intermediate lever, which comprises a plurality of arms and can be pivoted about a housingfixed spindle, is held in position on the curve under the action of a spring, which is supported on the housing of the fuelinjection pump, by means of which intermediate lever it is possible to adjust at least indirectly the stop, wherein the intermediate lever is designed having two arms and the spring is formed as a substantially hair pin-shaped leaf spring whose one spring arm forms a foot part which is coupled to the intermediate lever in an eccentric manner with respect to the spindle and is supported on the intermediate lever in a positionally-fixed manner, and the other spring arm of said leaf spring has a movable arm part which extends in a transverse manner with respect to the foot part and which is supported on the housing of the fuel-injection pump.

2. A fuel-injection pump according to claim 1, wherein in order to couple the spring to the intermediate lever, two lateral arms protrude from the foot part in a transverse manner with respect to the foot part and are locked to the intermediate lever in a resilient manner by way of formlocking surfaces.

3. A fuel-injection pump according to claim 2, wherein an opening is 12 provided as the form-locking surfaces in each of the lateral arms and engages in each case over formations, which are provided laterally on the intermediate lever and which receive the bore through which the spindle is guided.

4. A fuel-injection pump according to claim 3, wherein the lateral arms comprise additional locking surfaces, which engage into corresponding locking surfaces on the intermediate lever and prevent any rotation of the lateral arms about the formations.

5. A fuel-injection pump according to claim 3, wherein openings are circular orifices which are surrounded by a pressed-out, elastically deformable, neck-like region and the orifices comprise in the neck-like region an inner diameter which is smaller than the outer diameter of the formations.

6. A fuei-injection pump according to claim 4, wherein the form-locking surfaces of the lateral arms are locked against a restoring force from a resilient deformation of the foot part.

7. A fuel-injection pump according to claim 6, wherein the foot part also comprises locking means, which are held in a resilient manner on locking surfaces of the intermediate lever.

8. A fuel-injection pump according to claim 7, wherein the foot part is held on the surface of a base part of an intermediate lever which has a Ushaped cross-section.

9. A fuel-injection pump according to any of the preceding claims, wherein the other spring arm between the foot part and the arm part comprises a spring arm region, which extends substantially parallel with the foot part.

10. A fuel-injection pump according to claim 9, wherein the spring arm 13 region extends in an inclined manner with respect to the foot part.

11. A fuel-injection pump according to any of the preceding claims, wherein the spring arm is formed from a spring leaf which comprises a central recess extending along the spring arm and which forms at this site two partial arms.

12. A fuel-injection pump substantially as hereinbefore described with reference to and as illustrated in Figs. 2 to 6 of the accompanying drawings.