US3834184A

US3834184A - Centrifugal injection timing control device for fuel injection pumps in diesel engines

Info

Publication number: US3834184A
Application number: US00376186A
Authority: US
Inventors: E Hofmann; H Lehmann
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1972-07-27
Filing date: 1973-07-03
Publication date: 1974-09-10
Anticipated expiration: 1991-09-10
Also published as: JPS4945224A; AT326419B; FR2194882A1; ATA654773A; GB1441415A; DE2236832B2; DE2236832C3; FR2194882B1; DE2236832A1

Abstract

A centrifugal injection timing control device for use with a fuel injection pump having a camshaft, in a diesel engine, is described which device comprises at least one flyweight which swivels against the force of at least one compressible return spring and which changes, by its swivelling movements and in dependence on the rpm of the engine, the mutual rotary position of two coaxially arranged shafts, one of which is the camshaft and serves as the driven shaft, the other shaft being the driving shaft, and which flyweight is supported on a bolt being connected to the driving shaft paraxially with the latter; first abutment means for said return spring, associated with the driven shaft, and second abutment means for the return spring, being supported articulatedly on a stub of the bolt, which stub protrudes in the axial direction from the flyweight on the bolt; and wherein the rpm-dependent characteristic of the relative rotary positions of the two shafts expressed by an adjustment angle phi is controllable from a cam track provided on a lever-shaped motiontransmitting member being rigidly connected to the camshaft for movement with the latter, and which device is improved by the provision, as the second abutment means, of a bracket having on its side facing away from the return spring a recess having a bearing face of U-shaped cross section, and means for securing the bracket on the stub against displacement in the axial direction.

Description

PAIENIEU str1 01914 SHEET 10F 2 1 CENTRIFUGAL INJECTION TiMiNG CONTROL DEVICE FOR FUEL INJECTION PUMPS IN DIESEL ,ENGINES BACKGROUND OF THE INVENTION sel engi-nes which device comprises (a) at least one flyweight which swivels against the force of at leastone compressible return spring and which changes, by its vswivelling movements and in dependence on the rpm of the engine, the mutual rotary position of two coaxially arranged shafts, one of which is a camshaft of the fuel injection pump'and serves as the driven shaft and the other of which serves as -the drivingshaft, and which lyweight is supported on a bolt being connected to the driving shaft and having an' axis which is parallel thereto; (b) first abutment means for the return spring, associated with' the driven shaft, and (c) second abutment means for the return spring being supported articulatedly on a stub of the said bolt which stub protrudes in the axial direction from theflyweight on the bolt, and wherein the rpm-dependent characteristic of the relative rotary positions of the two aforesaid shafts, ex-

pressed by an angle of adjustment QS, is controllable from a cam track which is built into a'lever-shap'ed motion transmitting member being rigidly connected to the camshaft for movement with the latter.

In centrifugal injection timing control devices of this type, the rpm range in which the device operates, and the angle of adjustment by which the rotary positions of the two shafts are adjusted to each other, can be adapted to the fuel injection system in which the timing device is used, and to the engine to which the system pertains, by a corresponding adjustment ofthe force of the return spring. This is achieved in a known manner by replacing the return spring with another having a different resilience and/or by the insertion of washers at the abutments ofthe spring. In the latter case, the initial tension of the spring is altered, thereby determining the rpm at which the timing device begins to operate.

In order tobe able to exchange the return spring or washers in known timing devices of the aforedescribed type, it is necessary to either disassemble entirely or at least partly the camshaft of the injection pump which forms a unit together with the timing device. This procedure is costly and time-consuming; also, it should be noted that the undetachable connection of the driven element of the timing device with the camshaft has been used in these known systems to eliminate a drawback of timing devices of other known types being detachably connected to the camshaft of the injection pump, which drawback consisted in the camshaft being misalignedduring the assembly ofthe timing device, so that it is not possible to attain the necessary rotation of the timing device due to an excessive deviation from a true rotary motion. l

It has also been known or suggested to equip centrifugal timing devices of the initially described type with a device for limiting the changes in the mutual rotary position of the driving and the driven shafts to several predetermined angles of adjustment. This device is, for example, needed when using a timing device in a series of engines which can be adjusted to different full-load performance values by limiting the full-load rpm without requiring any other essential changes. Such rpms also require corresponding angles of adjustment d. However, the most important reason for this limitation of the angles of adjustment da resides in the need for ceasing or stopping the adjusting motion when the fullload rpm has been attained. If no such limitation is provided the timing device tends to vibrate when fluctuations occur in the moment of rotation or the rpm. A loud operational noise is caused by the vibrations of the elements of the timing device, the engine runs unevenly, and the timing device is likely to wear rapidly` or to be destroyed. In order to eliminate this drawback, the initially described known centrifugal timing device is provided with a bolt projecting from the flyweight thereon which bolt is inserted in a slot of -a limiting disc, the length of which slot limits the motion of the flyweight, thereby limiting also the arbitrarily determin able change in the mutual rotary position of the two shafts; this previously suggested timing device is furthermore provided with a ring mounted on the bolt portion projecting from under the flyweight which ring abuts an inner edge remote from the rotational axis of the timing device of a recess provided in the driving shaft, and the external diameter of which ring is dimensioned in correspondence with the determinable change in the mutual rotary position of the two shafts. In order to be able to exchange the aforesaid ring or the limiting disc, the driving shaft must be detached from the camshaft of the pump, which is only possible by removing the return springs. For this purpose, it is therefore necessary to disassemble the camshaft at least partly or entirely.

OBJECTS AND SUMMARY OF THE INVENTION It is, therefore, an object of the invention to improve the centrifugal injection timing control device of the initially described type in such a manner that the camshaft ofthe injection pump can be left in its assembled condition, when changes in the range of adjustment, in the angle of adjustment tb or the limitation of changes in the mutual rotary positions of the driving and the driven shafts are to be made.

This object is attained according to the invention, by providing as the second abutment for each return spring, a bracket which is mounted on, and is axially secured to, a bearing pin or bolt and which has a bearing face of U-shaped cross section which is open on the side away from the return spring supported by the bracket. The U-shaped bearing face makes it possible,

by means of a suitable tool, to hold the bracket together with the return spring in a position relative to the first spring abutment in which the driving shaft with the bolt and the flyweight thereon can be detached from the driven shaft, i.e., from the camshaft of the injection pump. Thereby, the device for limiting changes in the mutual rotary positions of the shafts and/or the return springs become freely accessible.

By providing the stub, supporting the second spring abutment, of the tlyweight-bearing pin with an annular groove which is engaged by a bridge protruding into the U-shaped bearing face of the bracket, it is made possible to detach the spring-bearing bracket in a simple manner and, at the same time, to secure the bracket against axial displacement on the pin stub bearing the same. In an advantageous embodiment of the invention, the bridge is provided with a semi-circular interior boundary face, having a radius equal to the radius of vexemplary embodiments takenin conjunction with the drawings.

BRIEF DEscRIrTIoN oF THE DRAWINGS FIG. l shows a preferred embodiment of the timing device according tothe invention in a sectional view, taken in the'planesd'efined Iby line I'-l in FIG. 2;

FIG. 2 shows a sectional view of the same embodiment, taken in a plane along line lII.-II, in FIG. 1; and

FIG. 3 shows an enlarged view in perspective of a y designated by 46 in FIGS. 1

spring-supporting-bracket and 2.

DESCRIPTION oF THE EMBODIMENT The camshaft l'of an injection pump l1'(only indicated schematically by phantom lines) bears a centrifugal timing device 12 which comprises a driving flange 13 serving as driving shaft, which is supported on a vshaft member 14 of .camshaft 10, and which bears a number of pins 15 whose axes are parallel to the axis of the camshaft 10, on which pins flyweights 18 are mounted for swivelling movement. Camshaft 10 serves as the driven shaft of the timing device.

A clutch disc 22 provided with claws 21 is mounted on a protruding stub 20 of driving -flange 13, and is connected with the driving flange 13 by means of screws entered into bores from the frontal face of flange 13. The timing device l2 is coupled to the driving members (not shown) of an internal combustion engine by means of a second clutch member (also not shown) which engages the claws 21 of clutch disc 22. Instead of clutch disc 22 a pinion may be used when a gear drive is employed.

Each of the flyweights 18 is provided with a bolt 25, spaced from its swiveling point about pin l5; the bolt bears a roller 26 engaging a cam track 27 which is provided on a lever-shaped motiontransmitting member 28; member 28 is rigidly mounted on camshaft 10 as an undetachable part of the latter. Roller 26 is secured against axial shifting by means of a retaining ring 29 fastened on bolt at its terminal portion 25a, and by a collar 30 mounted on the other terminal portion 25b of bolt 25 projecting beyond flyweight 18 which terminal portion 25h extends into a recess 31 of the discshaped part 32 of the driving flange 13v and is guidedl therein during swivelling displacements of the fly weights 18. For reasons of manufacture, 4the crosssectional configuration of recess 31 in the illustrated embodiment is of round shape (see FIG. 2), but it may also have any other shape', as long as the full swivelling rotation of bolt 25 or of bolt-portion 25b and collar 30 thereon is not impeded. The radial distance A between the central axis .of driving flange 13 and that point on the inner edge 33 (FIG. 2) of recess 3l, against which the end collar 30 abuts when flyweight 18 is in its outermost position, limits the path of the flyweights 18 and,

'the collars 30 limit the swivelling path of the flyweights 18 to a size which determines a given, arbitrarilyadjustable change in the pivoting position (angle of adjustment rbf) of driving flangel 13 relative to the camshaft 10; consequently, the angle of adjustment of the timing device-can be alteredby replacing the collars 30 by others' havinga different diameter.

The timing device is provided with

lubricating bores

41, 41a and 41b, for lubricating the bearings4 of flange 13 and the othervparts of thetiming device, and is surrounded, as a protection against loss of lubricant, by a casing 42` which is rigidly mounted on the injection pump 11'. Casing42 is provided with agasket 43 which seals the timing device 12, also when the latter rotates during operation, against the outside. The centrifugal forces of the flyweights 18 which occur during operation of the timing device 12, are counteracted by pairs of compression springs 45 which are supported on two

abutments

46 and 48, thefirst of which, 4 6', is provided on the lever-shaped member 28, in the form of trunnions for centering the springs 45. The second abut- 4ment is constituted by a bracket 48 and is mounted articulatedly on stub 15a of flyweight-bearing pin l5 which protrudes in axial direction from the flyweight 18 thereon.

The spring-bearing bracket 48 is provided with a Bridge 51 and groove 52 together position bracket 48 in the axial direction. Bridge 5l has an inner face 53 of circular cross-section theradius of which is equal to the radius of the bearing face 50, and the circular arc described by the bridge face 53 is displaced relative to the circular arc of face 50 by almost the depth t of the annular groove 52 in the direction towards the aperture of U-shaped bearing face 50, i.e., toward the end faces 49 of bracket 48. The displacement is slightly smaller than the depth t of the annular groove 52 in order to ensure that the bridge 51 does not rest on the bottom of annular groove 52.

OPERATION OF THE EMBODIMENT The operation of the described centrifugal timing device is known per se, and will be explained only briefly hereinafter.

The compression springs 45 serve to press the free end portions 18a of flyweights 18 inwardly, which is, in particular, attained by a corresponding shape of cam track 27 on the lever-'shaped member 28'. However, with an increasing rpm, the flyweights 18 swivel outwardly against the force of the compression springs 45 in the direction indicated by arrow 60, and turn the driven

elements

28 and 10 from their positions with regard to the driving elements 13 and 22 of the timing device until the collars 30 contact the inner edges 33 of the recesses 31. i

For example, depending on the diameter D of the collars 31, an adjustment of the angle d, to 3, 4, 5, 6 or 7 between the driving flange 13 and the camshaft 5 l of the injection pump l 1 may be effected. The maximalangle of adjustment ibmax, e.g. 8, is attained, when the flyweights 18 follow their largest possible path of swivelling motion. This is, for instance, achieved when removing the collars 30, so that the bolt 25, or its stub 25b, contacts itself the inner edge 33 of the recess 3l, thereby, at the same time preventing the rotating weights 18 from abutting against the stationary housing 42. In order to limit the effective range of the timing device to the angles of adjustment described above, the collars 30 must be exchanged. For this purpose, the

-driving flange 13 must be removed which is made possible by the special design of the bracket 48. By means of a special tool, such as for example pliers, which on the one hand grips the bracket 48, and on the other hand engages a recess 28a (see FIG. 2) of the levershaped member 28, springs 45 are compressed and the 'bracket 48 is moved so close to the abutment 46 that the bridge 51 is disengaged from the annular groove 52 at the stub 15a of pin 15, and the driving flange 13 can be drawn off, whereby the collars 30 become accessible. Due to the above-described shape of driving ange 13, the pressure springs 45 also become accessible, so that they can be exchanged, if necessary, against others having a different compressibility, whenever this should be desired in order to change the timing characteristics. In the same manner, the'washers 54 underlying the ends of the pressure springs 45 (FIG. 2) can be exchanged in this same operation, in order to change the initial tension of the pressure springs, and consequently the rpm, at which the timing device begins its adjusting operation.

Thanks to the provision of the bracket 48, the abovedescribed exchanges of elements in the timing device according to the invention are greatly facilitated as they can be carried out without disassembling entirely or partly the camshaft 10 of the injection pump 1 1, thus affording a significant saving in time and expenses.

A surface 18b of the one flyweight 18 serves as a stop for the free end position 18a of the other flyweight 18.

What we Claim is:

1. ln a centrifugal injection timing control device for use with a fuel injection pump in a diesel engine, which device comprises a. at least one flyweight which swivels against the force of at least one compressible return spring and which changes by its swivelling movements and in dependence on the rpm of the engine, the mutual rotary position of two coaxially arranged shafts, one of which is a camshaft and serves as the driven shaft, and the other of which serves as the driving shaft, the flyweight being supported on a bolt which is connected tothe driving shaft and which defines an axis parallel to the axis of the driving shaft; b. first abutment means for said return spring, associated with said driven shaft, and c. second abutment means for said return spring, being supported articulatedly on a stub of said bolt, which stub protrudes in axial direction from said flyweight on said bolt; and wherein the rpm-dependent characteristic of the relative rotary positions of said two shafts expressed by an adjustment angle is controllable from a cam track provided on a lever-shapecl motion-transmitting member being rigidly connected to said camshaft for movement with the latter,

the improvement comprising, as said second abutment means, a bracket having on its side facing away from said return spring a recess having a bearing face of U-shaped cross section, and means for securing said bracket on said stub against displacement in the axial direction.

2. The improvement as described in claim 1, wherein said bracket comprises a bridge extending in said recess across the bottom part of said bearing face of U-shaped cross section, andsaid stub has an annular groove engaged by said bridge.

3. The improvement as described in claim 2, wherein said bridge has a curved recessed face of circular crosssection the radius of which is equal to the radius of the rounded portion of said bearing face of U-shaped cross section, the maximum distance by which said bridge projects from said bearing face of U-shaped crosssection being slightly smaller than the depth of said annular groove in said stub.

Claims

1. In a centrifugal injection timing control device for use with a fuel injection pump in a diesel engine, which device comprises a. at least one flyweight which swivels against the force of at least one compressible return spring and which changes by its swivelling movements and in dependence on the rpm of the engine, the mutual rotary position of two coaxially arranged shafts, one of which is a camshaft and serves as the driven shaft, and the other of which serves as the driving shaft, the flyweight being supported on a bolt which is connected to the driving shaft and which defines an axis parallel to the axis of the driving shaft; b. first abutment means for said return spring, associated with said driven shaft, and c. second abutment means for said return spring, being supported articulatedly on a stub of said bolt, which stub protrudes in axial direction from said flyweight on said bolt; and wherein the rpm-dependent characteristic of the relative rotary positions of said two shafts expressed by an adjustment angle is controllable from a cam track provided on a levershaped motion-transmitting member being rigidly connected to said camshaft for movement with the latter, the improvement comprising, as said second abutment means, a bracket having on its side facing away from said return spring a recess having a bearing face of U-shaped cross section, and means for securing said bracket on said stub against displacement in the axial direction.

2. The improvement as described in claim 1, wherein said bracket comprises a bridge extending in said recess across the bottom part of said bearing face of U-shaped cross section, and said stub has an annular groove engaged by said bridge.

3. The improvement as described in claim 2, wherein said bridge has a curved recessed face of circular cross-section the radius of which is equal to the radius of the rounded portion of said bearing face of U-shaped cross section, the maximum distance by which said bridge projects from said bearing face of U-shaped cross-section being slightly smaller than the depth of said annular groove in said stub.