FR2596105A3 - FUEL INJECTION PUMP FOR INTERNAL COMBUSTION ENGINES IN WHICH THE PUMP CYLINDER SHAFT IS ACHIEVED IN ONE SINGLE - Google Patents

Abstract

A) FUEL INJECTION PUMP FOR INTERNAL COMBUSTION ENGINES, IN WHICH THE PUMP CYLINDER LINER IS MADE IN A SINGLE PART. B) CHARACTERIZED IN THAT THE PUMP 2 CYLINDER LINER IS MADE IN A SINGLE PART, AND THAT THE RECESS 4 PROVIDED IN THE PUMP CYLINDER 2 FOR HOLDING THE CONTROL DRAWER 5, SHALL RADIALLY ONLY AN ACCESS ON ONE SIDE, IN RELATION TO THE AXIS OF THE CYLINDER, FOR THE INTRODUCTION OF THE CONTROL DRAWER AND THAT THE RECESS 4, VIEW FROM THE ACCESS SIDE, HAS PARALLEL SIDE WALLS 23. C) THE INVENTION CONCERNED A FUEL INJECTION PUMP FOR INTERNAL COMBUSTION ENGINES, IN WHICH THE PUMP CYLINDER LINER IS MADE IN A SINGLE PART.

Description

Fuel injection pump for internal combustion engines, in

  which pump cylinder liner

  is performed in one part ".

  Previous state. The invention relates to a fuel injection pump for internal combustion engines according to the type of the main claim with at least one pump element, whose pump cylinder, in the form of a cylindrical jacket, is in a certain measure movable in rotation and positionable in a corresponding bore of the pump housing, in order to allow the flow control, and the pump piston is driven back and forth in a working stroke and rotatable relative to the fuel control device comprising at least one axially movable control spool inside a recess of the pump cylinder on the pump piston, to allow control of the fuel flow rate. In a known fuel injection pump 20 of this kind, (DE-OS 34 28 174) the recess is formed by an opening passing radially through the pump cylinder liner, so that there is no longer any only two lateral connection connections and the axial and radial forces are supported only by these relatively weak connections. Cylinder liners of this kind are therefore notoriously weakened by the recess which is intended to receive the drawer of

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  command. This weakening may especially adversely affect when the pump cylinder liner is screw-tightened after fitting to a flange of the cylinder liner and axially rests in its lower portion on a shoulder of the pump housing, or also radially on the wall of the crankcase bore

  who receives the pump cylinder liner.

  If the cylinder is not strong enough, deformations of the cylinder liner can occur during tightening in the case of axial or radial tolerances, even if limited, so that the piston of the pump is guided in a leaktight manner. both above and below the recess in the cylinder bore, which is no longer exactly positioned, is subjected to additional friction forces which can lead to premature wear and tear.

insecurities.

  In another known embodiment of a fuel injection pump (EP-A-0181402, FIG. 4), the pump cylinder liner is made in two elements, in which the recess is made by axial drilling ( the pump being seen from above). In this bore is then introduced the upper portion of the liner provided with the flange and is carried out by milling a radial access to the bore. The two pieces will be connected together, either by a method of shearing or by brazing. The recess thus formed is opened by the milling turned towards the adjustment of the drawer on one side, to the control equipment, so that the regulating slide can be introduced on one side

  and that there is the other side a possibility of intervention to achieve its adjustment.

  This recess-shaped arrangement of the recess certainly achieves a relatively high stability against alignment and clamping defects; however, manufacturing is expensive because the two pump cylinder liner pieces should already be aligned exactly at the time of bonding. Additional work passes are thus required, with expensive tools, during which misalignments can not, however, be excluded. The fuel injection pump according to the invention is characterized in that the cylinder liner of the pump is made in one piece, and that the recess provided in the pump cylinder for holding the control spool is radially presents only access on one side, with respect to the axis of the cylinder, for the introduction of the control spool and that the recess - seen from the access side - has parallel side walls, and present on the previous state

  the advantage of largely excluding misalignment despite its extremely simple manufacturing, which primarily results in a long service life of the pump.

  In the technical environment, there was a prejudice in view of this arrangement of the pump cylinder liner, because it was argued that during the heat treatment of parts which are not symmetrically shaped with respect to an axis, defects alignment should occur due to mass accumulation on one side only. For this reason, the cylinder liner of the known fuel injection pump is made in two parts. In particular, with the parallel side walls, the residual wall thickness is achieved in a manner similar to that of the folders having only two connecting pieces - as thick as possible, thus very close to the control spool. . This results in a greater rigidity and a high moment of inertia corresponding to the bending stresses coming from the asymmetric drive forces. 35 According to a development. Advantageous of the invention, the recess will be made by machining with chip removal. Such mechanical machining is possible at low cost, and certainly without risk of deformation or length modification, which could lead to misalignment. According to another advantageous development of the invention, the rear wall of the recess

  seen from the access - is of similar shape to an outer cylindrical shape and has a maximum thickness of wall thickness of the cylinder liner, stepped.

  In this way, the recess can be made as large as possible by using a tail mill as is evident for the control spool, thanks to

  its radial dimension, so that the wall restan15 you can support an optimum effort.

  According to an advantageous development variant of the invention, the rear portion of the recess can be made by cylindrical machining by means of a spherical bur. Also as a result, it is possible to achieve a better approximation between the inner wall of the recess and the outer surface of the control spool and thus an improvement in stability. According to a further advantageous development of the invention, in the rear wall of the recess a channel-shaped passage lumen running in the axis of the pump with parallel walls is provided for the rotational guidance of the pump. control spool, so that at the first adjustment, the rotational position of the control spool is determined with respect to the pump piston and that the passage lumen is made with a tiller at the

  same clamping and together with the recess.

  According to an advantageous development variant 35 of the invention, the recess can be made by casting the pump cylinder, remaining to be machined on this occasion only the bore receiving the piston and the

outer wall of cylinder.

  The following description provides the explanatory drawings for a better understanding of the invention.

drawings:

  Two embodiments of the subject of the invention are shown in the drawings and will be described in more detail in the following.

  FIG. 1 shows a partial section in a fuel injection pump part according to the first embodiment, containing the pump cylinder liner corresponding to the invention; FIG. 2 represents a cross section taken along the line; II-II of FIG. 1; FIG. 3 shows a partial view of the single pump cylinder according to arrow III of FIG. 1; FIG. 4 shows a longitudinal section in a pump cylinder sleeve of the second embodiment of FIG. FIG. 5 shows a cross-section along the line V - of FIG. 4 and

  FIG. 6 is a partial view along arrow VI of FIG. 4.

  Description of the embodiments

  In the first embodiment shown in FIGS. 1 to 3, there is shown a cylinder liner 2 of a fuel injection pump, in a pump casing 1 which is only partially shown. Pump pistons 3 work in cylinder liners 2 installed in line in such a pump casing 1, which are driven, as far as axial displacement is concerned, by the camshaft which is not shown here. In the cylinder liner 2

  is realized-a blind recess 4, which receives the control spool 5 movable axially on the pump piston.

  The control spool 5 can be axially offset by means of an eccentric lever 6, this lever being for this purpose provided with a head 7 which meshes with a transverse groove 8 of the control spool. The pump piston can be rotated at a certain angle by a bushing 9, in that the bush 9 meshes with a flat portion 10 of the pump piston 3, the running movement thereof being free. The bushing 9 has a ring gear in its upper part, in which meshes a rack serving as a control rod. Any other equipment can naturally serve as a means of rotation. The pump piston 3 will be presuled by a pusher on the cam of a camshaft, by means of a spring 12 which is supported on a washer of

spring 13.

  Oblique grooves 15 are disposed on the outer surface of the pump piston 3, which open at their upper end 16 in longitudinal grooves 17. The upper ends of the longitudinal grooves 17 are connected together by a radially running transverse bore 18, in which open a blind bore 19, centrally in the pump piston. which terminates on the front surface 21 of the pump piston 3 delimiting the working chamber of the pump 20. The transverse bore 18 and the blind bore 19 form a connection between the oblique groove 15 and the working chamber of the pump. the pump 20. Two radial cut-off bores 22 are provided in the control spool 5 for the determination of the injection flow rate, which work together with the oblique grooves 15 and the longitudinal grooves 17. The longitudinal grooves 17 have at the bottom and at the top of the sharp edges 24 and 25, which act together with the control edges also forming the front surfaces 26

and 27 of the control spool 5.

  As is particularly clear in Figure 2, the passage 30 between side walls 23 and rear wall 28 of the recess 4 is stepped. These stages appear during the machining with chip removal called milling cutter, being sought to approach as much as necessary from the outer casing 29 of the cylinder liner 10 2, in order to benefit from a sufficiently rigid thickness of the walls, despite the necessary interval for the drawer

of order 5.

  The diameter 31 of the cutters with which this recess 4 has been made has been indicated by dashed lines in FIG. Therefore, the radii 32 remaining in the passage of the recess 4 from the side walls 23 to the upper and lower boundary walls 33 do not interfere, because the control spool 5 is also provided with rays or edges 20 beveled, or the construction dimension of recess 4 will be determined to be of a value corresponding to that required by

the travel of the control spool 5.

  In the second embodiment, shown in Figures 4 to 6, the recess 104 is similar to that of the first embodiment; the

  passages 130, between the side walls 123 and the rear wall 128 are also rounded, also with the spokes 132, so that a better adaptation to the shape of the control spool is achievable.

  The thickness of the wall is at least as strong as that on the rear wall 128 and radii 132 relative to the outer surface 129.

  the stages, it is possible a further approximation between the control spool, which is not repre-

  felt here and the inner wall of the recess 104, so that further optimization of the proportions of the dimensions can be achieved with a corresponding improvement in the stiffness of the jacket

of cylinder 2.

  A passage rounded in this way will be obtained either by machining by means of a spherical cutter 34, as shown in dotted lines in the figures

  4 and 5, or by casting the entire cylinder liner.

  A groove-like passage lumen 35 with parallel walls 36 is provided in the rear wall 125 of the recess 104, in which a control slide guiding apparatus can be engaged so that the control spool can actually perform an axial movement, but be assured

against any rotation.

  This fuel injection pump, according to the invention, operates in the following manner, ex20 plicated with the help of Figure 1: When the pump piston 3 takes the lower position shown in Figure 1, the longitudinal grooves 17 5 of the control spool 5 are released, so that the fuel can circulate substantially without rolling effect, in the working chamber of the pump 20, passing through the channel formed by the transverse bore 16 and the blind bore 19. As soon as the working stroke of the pump piston 3 begins, the longitudinal groove 17 dips more or less early 30 into the control spool, according to the axial position of the control spool 5. As soon as the cutting edge lower control 24 of the longitudinal groove 17 passes in front of the lower front edge 26 of the control spool 5, the pressure required for the injection can be established

  in the working chamber of the pump 20 and the repress-

  fuel to the engine, and therefore the injection, can begin. This injection takes place all the time, until the cut-off bore 22 of the control spool is triggered by the angled groove 15 and the power supply to the motor is interrupted. In the remaining stroke of the pump piston 3, the fuel flows out of the working chamber of the pump 20. From a determined axial position of the control spool 5, the longitudinal groove 17 emerges above the control spool 5, the highest front edge 27

  then partially releasing the longitudinal groove 17.

  All the features mentioned in the previous description, as well as those

  The drawings are only part of the invention, even though they have not been particularly emphasized and in particular not mentioned in the claims.

Claims (4)

R E V E N D I C A T I 0 N S   1) Fuel injection pump for internal combustion engines with at least one pump element, whose pump cylinder, having the shape of a cylindrical jacket, is to a certain extent rotatable and positionable in a corresponding bore of the pump casing, in order to permit flow control, and whose pump piston is reciprocated in a working stroke and rotatable with respect to the fuel control comprising at least one movable control spool axial-ement inside a recess of the pump cylinder on the pump piston, to enable the control of the fuel flow, characterized in that the cylinder liner 15 of the pump (2, 102) is made of a only part, and that the recess (4, 104) provided in the pump cylinder (2, 102) for the holding of the control spool (5), has radially only access on one side, compared to the axis of the cylinder, for the intro and the recess (4, 104) - seen from the access side - has parallel sidewalls (23, 123). 2) Fuel injection pump, according to claim 1, characterized in that 1'éi25 dement (4. 104) is made according to a machining method with chip removal.   3) Fuel injection pump, according to claim 2, characterized in that the rear wall (28) of the recess (4) - view of the access side 30 is made gradually in the vicinity of the outer cylindrical shape and to obtain a maximum thickness   wall of the cylinder liner (2).   4) A fuel injection pump according to claim 2, characterized in that - seen from the access side - the rear wall (126) of the recess 11 (104) is machined by means of a strawberry   spherical (34) in an approximately semi-cylindrical shape.  ) Fuel injection pump,   according to any one of claims 1 to 4, characterized in that a passage lumen (35) is   in the form of a parallel wall groove (36), located on the rear wall (128) of the recess (104), running in   the axis of the pump, and serving to guide the rotation of the control spool.   6) Fuel injection pump, according to claim 1, characterized in that the recess (104) is made by casting the cylinder liner (102).