JPS6045735A - Fuel injection pump for internal combustion engine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a fuel injection pump for an internal combustion engine, which comprises a reservoir for generating a control pressure for a regulating mechanism of the fuel injection pump.
It has a transfer pump that is driven synchronously with the fuel injection pump and delivers a discharge amount related to the rotational speed, and a pressure control valve that cooperates with the transfer pump, and the pressure control valve has a return spring. It relates to a type having a movable wall which is loaded by a control pressure against a force and is adapted to be adjusted by adjustment of said wall.

PRIOR ART 1 In a fuel injection valve of the type known from Federal Patent Application No. 1,906,885, the pressure control valve has a piston, which is connected to the inner bore of a sleeve closed on one side. It is movable within the piston against the spring force of a thinly wound compression spring as a return spring, which is compressed between the piston and the closed end of the bore. Furthermore, the piston controls the cross-section of the load-relief conduit extending radially from the bore by means of a first end face facing the control pressure opposite the return spring. The load relief conduit communicates with an annular chamber defined by the outer annular groove of the sleeve and the wall of the bore into which the sleeve is tightly fitted. A load relief channel leads from the annular chamber into the fuel storage tank of the injection pump.

Problem to be Solved by the Invention In this case, the piston of the pressure control valve opens a constant outflow cross section up to a predetermined height of the control pressure and then progressively enlarges the outflow cross section of the load relief conduit. It is formed to do so. In this way, a control pressure that gradually increases as required with increasing rotational speed of the fuel injection pump or conveying pump or a control pressure that does not increase almost linearly or abruptly is obtained.

Ru. The disadvantage of such a pressure control valve is that due to manufacturing tolerances in the mass production of such fuel injection pumps, the conveying pumps belonging to this fuel injection pump have different feed rates and, on the other hand, in particular the return of the pressure control valve. The problem lies in that the springs and the return springs of regulating mechanisms actuated by control pressure, such as, for example, injection start regulating devices of fuel injection pumps, have different spring strengths and spring characteristics.

These manufacturing tolerances lead to significant differences in the actual control pressure profile in the result of the adjustment of the adjusting mechanism and with respect to the rotational speed compared to the intended control pressure profile.

To avoid this error, it is necessary to significantly narrow the error bounds at an increased cost.

Means for solving the problem According to an embodiment of the invention, downstream of the variable outlet cross-section an adjustable second limiting cross-section is provided.

A sleeve 4 is screwed into the bore 1 in the casing 2 of the exemplary fuel injection pump (of which only a small portion of the fuel injection pump is shown in cross-section in the drawing). For this purpose, the sleeve has an external thread 5 at one end which partially projects from the casing 2, the external thread being screwed into a corresponding internal thread 5 of the dead weight. The inner bore 7 is tightly closed off by a plug 8 at the end of the sleeve located on the outside of the casing, so that a cylinder 9 is formed inside the sleeve. A piston 10 is fitted into the cylinder with a tight fit, and a return spring 1 is disposed between the plug body 8 and the back portion 11 of the piston 10g.
It is movable against 2. In this embodiment, the return spring is designed as a compressed thin-wound spring. piston 1
0 is prevented from falling off by a fixing ring 14 which is clamped to the end of the bore 7 and prevents an excessively large piston stroke of the piston.

The bore 1 in the housing 2 is designed as a stepped bore in the illustrated embodiment, the first stepped bore having a hole section 1.
a, this first step is somewhat enlarged in diameter to the hole portion 1a, a second step is connected to the hole portion 1b, and this second step further extends to the hole portion. The third step is followed by a hole section IC, in which an internal thread 6 is arranged. A cylindrical portion 1d is further connected outward to the inner thread 6, and the portion 1d
is provided in the outer annular groove 17 of the sleeve.
lz ring 16 is in contact. The sleeve 4 is adapted in diameter to the respective portion 1a, lb of the hole 1 in such a way that the second stepped sleeve provides a tight fit with the hole portion 1b. The first step is at the end protruding into the hole portion la, and the sleeve 4 has an annular groove 19 on its outer circumference: +5-
A tension sealing ring 20 is inserted into the annular groove 19, the sealing ring 20 having a first step co-operating with the hole portion 1a, and a first step forming the sleeve in the hole portion. is used to tightly close off the chamber 22 surrounded by the end face 21 of. The step is therefore arranged so that by forming the hole 1 as a hole, a perfect insertion of the sealing ring 16, 20 as well as a controlled axial movement of the sleeve due to different threading of the sleeve is possible.

Threading of the sleeve is facilitated by a hexagonal section 23 provided at the outermost end protruding from the casing, and the screwing depth of the sleeve is provided in the outer threaded portion of the sleeve 5 protruding from the casing 2. Lock nut 24
Guaranteed by.

The chamber 22 is also connected to the discharge side of a fuel conveying pump 26 that conveys fuel into the menop suction chamber 28. In this case, the fuel conveying pump is driven synchronously with the fuel injection pump and has a feed rate that is dependent on the rotational speed in a known manner.

This repellent fuel pressure acts in the chamber 22 and thus on the end face 29 of the piston 10 at the end of the bore 7 of the sleeve 4. Said piston 10 is displaced against the spring force of the return spring as the fuel pressure in the chamber 22 increases and in this case, as the displacement increases, the end face 29 causes the single or multiple radial bore 3 of the sleeve to be displaced. Controls the opening of each facility one by one. The radial bore 31 communicates with the outer annular groove 32 of the sleeve. The outer annular groove is connected to the longitudinal groove 33,
The longitudinal groove is located at the level of the second stepped load relief conduit 34 leading out of the bore portion 1b. In this case, the longitudinal groove 33 forms a control opening, which is connected to the load relief conduit 34.
The limiting cross section 35 is formed by a difference in size depending on the degree of overlap with the cross section of the opening. This limiting cross section 35 is the narrowest cross section at the connection between the load relief channel 34 and the chamber 22 when the radial bore 31 is completely open. The degree of gravity 7zD between the control cross section of the longitudinal groove 33 and the opening cross section of the load relief channel 34 can be easily adjusted by rotating the sleeve.

In this case, the size of the limiting cross section compensates for errors of the conveying pump 26 or of the return spring 12 or other errors, as already mentioned at the outset.

Connected to the pump suction chamber or directly to the chamber 22VC is a working chamber 36 of a regulating element 37, which operates by means of a control pressure that is dependent on the rotational speed or is regulated by a pressure control valve.

For example, a regulating piston 3 of an injection timing regulating device of known construction.
8 is shown, and the working chamber 36 of the adjusting piston δ9 is connected to the suction chamber 28 via a pressure line 39.

Full load stone adjustable in relation to rotational speed as well
It is also operated in the above format.

For safety reasons, an axial blind bore 41 is also provided in the piston 10 extending from the end face 29, which blind bore 41 connects via a transverse passage 42 to an outer annular groove 4 provided in the piston.
Connected to 3. For example, if the piston 10 is displaced sufficiently large after the maximum opening of the radial bore has occurred, the outer annular groove 43 will coincide with a radial bore 44 extending from the inner bore 7, which radial bore 44 It communicates with a second load reduction conduit 45 which is led out. A chamber 9 between the back 11 of the piston 10 and the plug body 8 is connected to this load relief conduit 45 .

If the limiting cross section is incorrectly closed completely during adjustment of the limiting cross section, the pressure in the plug 22 will not rise arbitrarily. This is because, following the displacement of the piston 10, a load relief takes place via the blind hole 41, the transverse passage 42, the outer annular groove 43 and the second load relief conduit 45. Does such an arrangement limit the maximum control pressure or significantly restrict the subsequent increase in control pressure after the maximum speed has been reached? It can also be used to reduce the amount.

Instead of the conventional type of adjustment of the limiting cross section used in this example, the axial movement of the sleeve can likewise be effected via a threaded screw thread. In this case, instead of a longitudinal groove serving as a control surface, an outer annular groove 32, which is connected to the hole, for example, serves. In exactly the same way, the second step can also be provided with an inner annular groove communicating with the bore portion 1b [the load relief conduit 34, said inner annular groove cooperating directly with the radial bore.

Effects of the Invention The advantage of the fuel injection pump according to the invention is that by means of the second adjustable limiting cross-section in series with the outlet cross-section, the control pressure profile is varied and errors are compensated for in a simple manner. There is a particular thing. In this case there is no need to remove or disassemble the control pressure valve and no need to adapt the components. Significantly larger tolerances are therefore obtained for the components of the injection zone.

With the embodiment of patent claim 2, the limiting cross section can be obtained in a structurally simple manner by changing the position of the housing of the control valve itself without the use of an additional throttling mechanism. A further advantage of the advantageous embodiment according to claim 3 is that the casing of the pressure control valve is a cylindrical part that is easily produced, that the part can be easily sealed in the receiving bore and that The advantage lies in the fact that it can be easily moved or rotated in order to change the limiting cross section. The embodiment according to claim 4 has the advantage of a particularly simple construction, in which case in particular limited cross-sectional changes can be easily obtained with the embodiment according to claim 6. The adjusted position of the longitudinal groove can be fixed particularly easily.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, in which FIG. 1 is a longitudinal sectional view of a pressure control valve provided in a part of the casing of the associated fuel injection pump, and FIG. FIG. 3 is an enlarged view of the pressure control valve in a right-angled section;

Claims (1)

[Scope of Claims] 1. A fuel injection pump for an internal combustion engine, which is driven synchronously with the fuel injection pump and whose rotational speed is controlled to generate a control pressure for the adjustment mechanism (37) of the fuel injection pump. It has a conveying pump (26) for delivering an associated output quantity and a pressure control valve (3) cooperating with this conveying pump, which pressure control valve resists the spring force of the return spring (12). of the type having a movable wall (10) which is loaded by the control pressure and whose outflow cross section from the control pressure side to the unloading chamber (34) can be changed by adjustment of said wall. Fuel injection pump for an internal combustion engine, characterized in that downstream of the variable outlet cross-section (31), an adjustable second limiting cross-section (35) is provided. 2. The pressure control valve has a casing (4) in which a movable wall (10) is arranged, and said casing has a control opening ( 33) having a circumferential surface provided with and further guided by this circumferential surface into the cylinder (1b), from which a load relief conduit (34) is guided;
Fuel injection pump according to claim 1, characterized in that the opening of the load relief conduit forms a restricted cross section (35) by changing the position of the casing. 3. The casing is a cylindrical sleeve (4') closed at one end, which sleeve is movable or pivotable in the bore (la, lb, lc, ld) in which the load relief passage is guided. The piston (10) is movable as a movable wall in the inner bore (7) of the sleeve (4), and the piston (10) extends from the inner bore (7) by means of a control edge. It is adapted to control two outflow openings (31), which on the one hand control openings (32) in the circumferential surface of the sleeve (4);
. Fuel injection pump as described in section. The fuel injection ponzo according to claim 3, wherein the control opening on the circumferential surface of the sleeve (4) is a vertical groove (33), and the sleeve is rotatable. 5. A sleeve (4) is inserted into the bore (1) of the injection pump casing (2) and projects from the injection pump housing by its closed end and has a fixing device (24) in this projecting area. A fuel injection pump according to claim 4. 6. Fuel injection pump according to claim 5, wherein the sleeve is screwed into the bore and has a locking stop nut (24) at the outwardly projecting end. 7 Passage through which the piston (10) extends from the end face (29) (
4L 42.43), this passage is open to the circumferential surface of the piston, and can be connected to the second load reduction passage (44) after the maximum displacement of the piston, and this load reduction passage has an outflow. 4. A fuel injection pump according to claim 3, which is arranged parallel to the cross section (31) and the limiting cross section (35).