GB2076074A - A fuel injection pump to an internal combustion engine - Google Patents

Abstract

A fuel injection pump (10) for internal combustion engines in which the commencement of delivery is determined by a control sleeve (28) which co-operates with a single radial spill port (25b) in the piston (16) and which communicates with the pumping chamber 23 through a blind bore (25a). The control sleeve (28) is axially and non-rotatably slidingly guided on the pump piston by the co- operation between two parallel boundary surfaces thereof with the sides of a rectangular opening (27) in a cylindrical bush (12) in which the piston reciprocates. The control sleeve (28) is axially adjustable by means of a commencement of delivery adjusting device (29) and the pump piston (16) is rotatably by a regulating device (19) to vary the delivery quantity. <IMAGE>

Description

SPECIFICATION A fuel injection pump for an internal combustion engine The invention relates to a fuel injection pump for an internal combustion engine.

British Patent Specification 442,475 describes a fuel injection pump whose control sleeve is axially adjustable for the purpose of varying the commencement of injection and can additionally be rotated for the purpose of varying the delivery quantity by a regulating device which, in a known manner, comprises a pinion and a regulating rod.

The pump piston is guided in the pump housing so as to be non-rotatable and has two radial control ports which are axially offset relative to one another. These control ports communicate with the pump working chamber by way of a central longitudinal bore in the pump piston and, together with the two control edges on the respective end faces of the control sleeve, determine the commencement of delivery and the termination of delivery. An arrangement of this kind requires an entirely novel conception of a pump and, in addition to the device for adjusting the commencement of delivery, the regulating device must also be sealed towards the outside in a fueltight manner, since the adjusting members of the two devices extend into the suction chamber of the injection pump which surrounds the control sleeve and are guided out of the suction chamber for the purpose of actuation.

Furthermore, injection pumps are also known in which the control sleeve serves exclusively to vary the delivery quantity and is rotatable for this purpose, and in which the end of the pump piston at the pump working chamber side is provided with an oblique control edge, the pump piston being rotatable by the regulating device for the purpose of varying the commencement of injection. Thus, in these pumps, the regulating device acting upon the pump piston serves to vary the commencement of injection and not, as is customary, to control the delivery quantity. Thus, conventional speed governors cannot readily be installed, so that stock-keeping is rendered difficult and disadvantages arise when fitting the governors to the injection pumps.

According to the present invention there is provided a fuel injection pump for internal combustion engines, having at least one cylindrical bush in the bore of which is axially movably guided a pump piston having a control passage which establishes communication between a suction chamber and the pump working chamber, a control sleeve which is slidingly guided on the piston and whose axial position is adjustable by a delivery quantity adjusting device and which has at least one first control edge on the drive side for determining the commencement of delivery and a second control edge which slopes relative to the longitudinal axis and which determines the termination of delivery, wherein these control edges cooperate with at least one radial control port of the control passage disposed in the pump piston, and a regulating device which is connected to the pump piston and which varies the relative rotary position between the pump piston and the control sleeve for the purpose of varying the delivery quantity, the control sleeve being guided in a non-rotatable manner in a guide slot in the cylindrical bush by means of two lateral boundary faces which extend parallel to the longitudinal axis of the pump piston.

In the fuel injection pump in accordance with the invention the control sleeve which is guided in the guide slot in the cylindrical bush, and which is secured against turning solely by virtue of its configuration, serves exclusively to adjust the commencement of delivery, and the pump piston can be rotated by means of a regulating device for the purpose of varying the delivery quantity. Thus, the basic construction of fuel injection pumps operating with oblique edge control is retained, and, by virtue of the configuration, in accordance with the invention, of the control sleeve and cylindrical bush, the control sleeve can be used without any substantial increase in the diameter of the pump element.

By providing a rectangular opening in the cylindrical bush it is possible to satisfactorily seal and isolate the suction chamber, formed by the opening and the associated housing bore, from the other pump chambers whilst ensuring the stability of shape and the strength of the cylindrical bush.

Flushing of the suction chamber by the jet of fuel emerging with high energy upon shut-off is prevented by providing a baffle plug. Despite the additional control sleeve, a small overall height of the injection pump can be obtained by virtue of the features of claim 5 in conjunction with those of claim 3 or 4, and fewer structural dimensions with the associated tolerances are responsible for complying with a predetermined injection quantity than in the injection pump known from Figure 4 of British Patent Specification No. 442,475.

The measures set forth in claims 6 to 8 render it possible to equate the commencement of delivery positions of all pump elements in a simple manner in in-line fuel injection pumps and in fuel injection pumps designed in accordance with the invention.

The present invention will now be described further, by way of example only with reference to the accompanying drawings, in which: Figure 1 is a longitudinal section through a single-cylinder fuel injection pump in accordance with the invention, Figure 2 is a side elevation of the pump element used in the injection pump of Figure 1, viewed in the direction of the arrow II of Figure 1, Figure 3 is a cross section taken along the line Ill-Ill of Figure 1, and Figure 4 and Figure 5 are fragmentary sections through a pump element of the second and third embodiments respectively, that is to say, an in-line fuel injection pump having a commencement of delivery adjusting device modified relative to that of the first embodiment.

In the first embodiment, illustrated in Figures 1 to 3, of a fuel injection pump 10 which is provided for external drive by an engine camshaft, and which is fitted in the engine housing, a cylindrical bush 12 is fitted in a pump housing 11 and is secured in the pump housing 11 by means of a fastening flange 13 and bolts 14. A pump piston 1 6 is axially and rotatably guided in a cylindrical bore 15 in the cylindrical bush 12.The pump piston 16 is driven in a known manner by way of a roller tappet 1 8 which is guided in the pump housing 11 and which is movable against the force of a tappet spring 17, and the rotation of the pump piston 1 6 required to control the injection quantity is effected by a regulating device 19 which comprises a regulating rod 21 and a regulating sleeve 22 which is provided with a guide arm 22a and which is coupled to the pump piston 1 6 in the direction of rotation.

That end of the pump piston 1 6 which is remote from the roller tappet 1 8 defines a pump working chamber 23 which is formed by a portion of the cylindrical bore 1 5 which is adjacent to a pressure valve 24, which pump working chamber communicates with a suction chamber 26 of the pump by way of a control passage 25 in the pump piston 1 6 when the pump piston 1 6 is in its illustrated bottom dead centre position. The control passage 25 comprises a blind bore 25a which is incorporated in the pump piston 1 6 from the end face 1 6a thereof, and a single radial control port 25b which commences from the blind bore 25a and opens onto the outer surface of the pump piston 16.

A control sleeve 28 is axially movable and non rotatably guided in a guide slot 27 in the cylindrical bush 12 in the region of the radial control port 25b and is at the same time slidingly fitted on the pump piston 1 6 in a fluid-tight manner. The guide slot 27 is formed by an opening of rectangular cross section (see particularly Figure 2) which passes through the cylindrical bush 12 symmetrically and at right angles to the longitudinal axis thereof. An opening of this kind can be produced in a simple manner with respect to manufacturing technique by reaming. The axial position of the control sleeve 28 is variable arbitrarily or in an automatically controlled manner by means of a commencement of delivery timing device 29.

The commencement of delivery timing device 29 (see Figure 3) chiefly comprises an eccentric bolt 32 which is provided with an adjusting lever 31 and which is rotatably fitted in a stepped transverse bore 33 in the pump housing 11 and is sealed to prevent the egress of fuel. That end of the eccentric bolt which extends into the suction chamber 26 carries an eccentric stud 32a which engages a groove 34 incorporated in the control sleeve 28 and, by virtue of its rotary position determined by the position of the adjusting lever 31, establishes the axial position of the control sleeve 28 which determines the commencement of delivery. The groove 34 is machined in the control sleeve 28 so as to extend at right angles to the longitudinal axis of the pump piston 1 6 and at right angles to two parallel boundary faces 28a of the control sleeve 28.The control sleeve 28 is guided in the guide slot 27 in the cylindrical bush 12, and is at the same time secured against turning, by means of the boundary surfaces 28a.

The end face 28b (see Figure 2) of the control sleeve 28 on the drive side forms a so-called straight, first control edge which extends at right angles to the longitudinal axis of the pump piston 16 and which determines the commencement of injection, and a second oblique control edge 35a which determines the termination of delivery and which slopes relative to the longitudinal axis of the pump piston 1 6, is formed by a shut-off groove 35 which pierces the wall of the control sleeve 28 and which slopes relative to the longitudinal axis of the pump piston 16. This groove can be formed by, for example, erosion of the control sleeve 28.

When the pump piston 1 6 is in its illustrated rotary position, the delivery quantity which has been set is determined by a distance, designated a in Figure 2, between the first control edge 28b and the second control edge 38a. The shut-off groove 35 establishes communication between an interior bore, fitted on the pump piston 1 6, of the control sleeve and the suction chamber 26.

The suction chamber 26 is defined by a stepped portion 36a of a reception bore 36 of the pump housing 11 which accommodates the cylindrical bush 12 and the roller tappet 18, and is otherwise formed by that portion of the guide slot 27 which is not filled by the control sleeve 28.

The first embodiment of the fuel injection pump 10 described with reference to Figures 1 and 3 operates in the following manner: The effective delivery stroke of the pump piston 1 6 commences when the roller tappet 1 8, and thus the pump piston 16, have been lifted by a cam (not illustrated) to an extent that the first control edge 28b on the control sleeve 28 closes the radial control port 25b in the pump piston 16.

Delivery by the pump is terminated when the radial control port 25b enters the shut-off groove 35 and, controlled by the second control edge 35a, the fuel subjected to injection pressure in the pump working chamber 23 is delivered into the suction chamber 26. The effective delivery stroke corresponds approximately to the distance a less the diameter of the control port 25b.

If the injection quantity is to be varied, the regulating rod 21 of the regulating device 1 9 is displaced, and the guide arm 22a rotates the regulating sleeve 22 and thus simultaneously rotates the pump piston 1 6. The radial control port 25b thus assumes a different rotary position and the distance a shown in Figure 2, and thus the direction of the effective delivery stroke, are changed.

If the commencement of delivery is to be varied, the axial position of the control sleeve 28 is changed by way of the commencement of delivery adjusting device 29 in that the control sleeve 28 is displaced axially on the pump piston 1 6 by pivoting of the adjusting lever 31 and by the thus changed position of the stud 32a. The radial control port 25b is then closed at an earlier or later instant by the first control edge 28b on the control sleeve 28 according to the direction of the change of position of the control sleeve 28, and thus the commencement of delivery is advanced or retarded.

If a plurality of the illustrated fuel injection pumps are provided on an engine, the adjusting levers 31 can be actuated by a common control rod, wherein the adjustment of the individual pumps relative to one another can be varied by an eccentric hinge pin 37 on the adjusting lever 31.

The same arrangement of the regulating device 1 9 and of the delivery quantity adjusting device 29 can also be used in so-called in-line injection pumps which are equipped with a plurality of cylindrical bushes 12 and pump pistons 16; An inline injection pump of this kind will be described hereinafter with reference to Figure 4.

Figure 4 shows the features, essential to the invention, of the second embodiment in the form of an in-line injection pump. Each of the pump elements 41 comprising the cylindrical bush 12, the pump piston 1 6 and the control sleeve 28' is fitted and secured in the pump housing 1' ' in a known manner, and the pump piston 16 is rotatable for the purpose of varying the delivery quantity by means of a regulating device 14' provided with an angled regulating rod 21'.

The control sleeve 28' is provided with a shutoff passage 42 which is radially in line with the shut-off groove 35 and which is incorporated in a blind-bore-like manner in the wall of the control sleeve commencing from an outer surface 28d.

The control passage 42 is closed in the region of the outer surface 28d towards the suction chamber 28 by means of a baffle plug 43 located opposite the shut-off groove 35. The shut-off chamber 42 communicates with the suction chamber 26 by way of transverse passages 44 which extend parallel to the longitudinal axis of the pump piston 1 6. The baffle plug 43 which is made from material which is wear-resistant and which, in the present embodiment, is screwed into the wall of the control sleeve 28' and which is secured in its installed position, prevents the suction chamber 26 from being flushed by the shut-off jet emerging with high energy.

A guide arm 45a of an adjusting member 45 engages the adjusting groove 34 located diametrically opposite the shut-off groove 35 and, together with the other adjusting members (not illustrated) of the other pump elements 41, is secured by means of a clamping device 47 to a common adjusting rod 46 of the device 29' for adjusting commencement of delivery. The adjusting rod is in the form of an adjusting shaft 46 rotatablyjournalled in the pump housing 11', and each of the adjusting members 45 clamped to the adjusting shaft 46 is provided with an adjusting opening 49 giving access to a longitudinal groove 48 in the adjusting shaft 46.In order to equate the commencement of delivery positions of all the pump elements 41, and adjusting tool 51 (shown by dash-dot lines) is introduced into the adjusting opening 49 and into the longitudinal groove 48 after loosening the clamping device 47 and, by tilting the tool 51, the position of the adjusting member 45 can be varied relative to the fixed adjusting shaft 46, and thus the vertical position of the control sleeve 28' can be corrected relative to the radial control port 25b in the pump piston 1 6.

The third embodiment illustrated in Figure 5 is also an in-line injection pump which, with the exception of the device 29" for adjusting the commencement of delivery, is identical to the injection pump illustrated in Figure 4. Each of the adjusting members of the delivery quantity adjusting device 29" comprises an eccentric bolt 32" which has an eccentric stud 32a engaging the adjusting nut 34 in the control sleeve 28', a conical fastening stud 32b carrying an adjusting pinion 61, and a screw-threaded stud 32c provided with a clamping nut 62. The conical fastening stud 32b, the screw-theaded stud 32c and the clamping nut 62 form a clamping device 63 for the adjusting pinion 61. An adjusting rod of the commencement of delivery adjusting device 29" in the form of a toothed rack 64 and meshes with all the adjusting pinions 61 of the pump elements 41 arranged in line. After partially loosening the clamping nut 62, and with the toothed rack 64 held in position, the eccentric bolt 32" can be turned relative to the adjusting pinion.

61, and thus the axial position of the control sleeve 28' can be corrected, in order to equate the commencement of delivery positions of all the pump elements 41.

The function of the two embodiments illustrated in Figures 4 and 5 correspond to that described with reference to Figures 1 and 3 and differs therefrom only in that all the control sleeves 28' of an injection pump can be jointly adjusted by a common adjusting rod 46 or 64 for the purpose of varying the commencement of delivery.

Claims (9)

1. A fuel injection pump for internal combusion engines, having at least one cylindrical bush in the bore of which is axially movably guided a pump piston having a control passage which establishes communication between a suction chamber and the pump working chamber, a control sleeve which is slidingly guided on the piston and whose axial position is adjustable by a delivery quantity adjusting device and which has at least one first control edge on the drive side for determining the commencement of delivery and a second control edge which slopes relative to the longitudinal axis and which determines the termination of delivery, wherein these control edges cooperate with at least one radial control port of the control passage disposed in the pump piston, and a regulating device which is connected to the pump piston and which varies the relative rotary position between the pump piston and the control sleeve for the purpose of varying the delivery quantity, the control sleeve being guided in a non-rotatable manner in a guide slot in the cylindrical bush by means of two lateral boundary faces which extend parallel to the longitudinal axis of the pump piston

2. A fuel injection pump as claimed in claim 1, in which the guide slot is formed by an opening of rectangular cross section which passes through the cylindrical bush symmetrically and at right angles to the longitudinal axis thereof.

3. A fuel injection pump as claimed in claim 1 or 2, in which the wall of the control sleeve incorporates a shut-off groove which forms the second control edge and which slopes relative to the longitudinal axis of the pump piston.

4. A fuel injection pump as claimed in claim 3, in which the control sleeve is provided with a shut-off chamber which is incorporated in the wall of the control sleeve in a blind-bore-like manner commencing from an outer surface and radially in line with the shut-off groove, which shut-off chamber is sealed towards the suction chamber in the region of the outer surface by means of a baffle plug located opposite the shut-off groove, and communicates with the suction chamber by means of transverse passages.

5. A fuel injection pump as claimed in claims 3 or 4, having a blind bore of the control passage which is incorporated in the pump piston and commences from the end face thereof at the pump working chamber side, and having the shutoff groove disposed at a distance (a), corresponding to the delivery quantity adjusted at any given time, from the first control edge formed by the end face at the drive end of the control sleeve and connects an interior bore, fitted on the pump piston, of the control sleeve to the suction chamber, and having only a single radial control port commencing from the blind bore and opening at the outer surface of the pump piston.

6. A fuel injection pump as claimed in any of claims 3 to 5, having a plurality of pump elements which are disposed in a row and which comprise a cylindrical bush, a pump piston and a control sleeve and whose control sleeves are axially adjustable by adjusting members of the commencement of delivery adjusting device which are actuatable by a common adjusting rod and which engage an adjusting groove in each control sleeve, the adjusting members engaging the adjusting grooves in thecontrnl sleeves being each provided with a clamping device and, after losening the clamping device, are adjustable relative to the adjusting rod for the purpose of equating the commencement of delivery positions of all the pump elements.

7. A fuel injection pump as claimed in claim 6, in which the adjusting rod is an adjusting shaft which is rotatably-journalled in the pump housing and on which are clamped'the adjusting members for all the pump elements, and each of the adjusting members being provided with a guide arm engaging the adjusting groove in the respective control sleeve and with an adjusting opening giving access to a longitudinal groove in the adjusting shaft.

8. A fuel injection pump as claimed in claim 6, in which each of the adjusting members of the commencement of delivery adjusting device comprises an eccentric bolt having an eccentric stud which engages the adjusting groove in the control sleeve, which eccentric bolt has a fastening stud carrying an adjusting pinion, and a screw-threaded stud provided with a clamping nut of the clamping device, and in which the adjusting rod is a toothed rack which meshes with the adjusting pinions.

9. A fuel injection pump constructed and arranged and adapted to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.