WO1988005130A1

WO1988005130A1 - Manufacture of the movable element of a pressure valve

Info

Publication number: WO1988005130A1
Application number: PCT/DE1987/000569
Authority: WO
Inventors: Karl Konrath; Klaus Krieger; Hermann Schmidt; Rolf Lutz; Johann Oberl
Original assignee: Robert Bosch Gmbh
Priority date: 1986-12-29
Filing date: 1987-12-04
Publication date: 1988-07-14
Also published as: DE3644597A1

Abstract

A process for manufacturing the movable element (117) of a pressure valve for fuel injection pumps by material removal. The movable element has a closing cone (123), a balance piston (128) an several fuel guiding recesses (125) extending in the axial direction of a guiding shaft (118). Several such elements (117) are simultaneously produced from a previously hardened bar, the rotation-symmetric notches (131) and openings being effected in a known manner by turning tools, whereas the recesses (125) are for example produced by rotating tools, in particular grinding tools, transversely moved with respect to the axis of the bar.

Description

Production of the movable valve member of a pressure valve

State of the art

The invention is based on a method for the manufacture of the movable valve member of a pressure valve for fuel injection pumps according to the preamble of the main claim. The manufacturing process of such a valve member is therefore of particular importance, since these valve members are manufactured in extraordinarily high numbers, namely numbers that are a multiple of the number of pumps, in addition to the number of spare parts corresponding to the engine cylinder to be supplied, since it is a wearing part acts, so that any simplification in the manufacturing process results in immediate cost savings. Added to this is the importance of the pressure relief valve of a fuel injection pump and in particular of the valve member on the quality of the fuel injection and thus the combustion in the internal combustion engine. The pressure relief valve is arranged between the pump working valve of the fuel injection pump and the injection nozzle on the internal combustion engine in the pressure line and thus acts on the already metered fuel injection quantity. The pressure relief valve serves on the one hand as a non-return valve in order to avoid that the fuel in the pressure line is sucked back to the pump work space during the suction stroke of the pump piston and on the other hand as a relief valve in order to relieve the pressure piston in the one between the pressure relief valve and the injection nozzle union line section from the push-to release part ^-th by the discharge piston is withdrawn by dipping into the guide bore of the valve carrier a corresponding volume from the pressure line. This relief is primarily necessary in order to avoid that a high fuel pressure remaining in the pressure line, in particular in connection with pressure waves, leads to the fuel injection nozzle opening again and fuel being able to be injected into the combustion chamber. Such post-injection leads to a substantial deterioration of the exhaust gas, as well as to other disadvantages, such as, for example, coking of the injection openings of the injection nozzle.

The position of the relief piston and in particular its

the control edge first immersed in the guide bore and the relief volume caused by it are individual to the respective internal combustion engine, i.e. the pressure lines, the injection nozzle, etc. are matched, so that the manufacturing quality is of particular importance here. The problem here is that it is a wearing part, which consists of steel and must be finally hardened, which greatly limits the possibilities of simplifying the manufacturing process.

How such a known valve member of a pressure relief valve is constructed can be found in US Pat. No. 2,163,313, and in the Bosch publication "Technical Instruction Diesel Injection Pumps PE and PS", July 1981 edition (order number VDT -U 2/1). As can be seen from the representations of these documents, the valve members are always a carrier part which has the closing cone and relief piston and the guide shaft essentially formed by webs, but also running in the longitudinal direction in this guide shaft, serving as recesses for the fuel guide Grooves, which are obtained by machining, a turning tool, whose axis of rotation extends transversely to the valve axis, so that a turning tool radius on the end face of the longitudinal

end of the recesses remains. In order to obtain a precise immersion edge of the relief piston, it is necessary to provide a recess between this part of the shaft formed by webs and recesses and the relief piston, in the course of which the recesses open with their face radius.

This represents a significant disadvantage in terms of production technology but also functionally. If, for example, a large relief volume is required, the grooves must be made correspondingly short so that these end radii do not run into the relief piston, as a result of which its plunge edge would be destroyed and the desired spray quality would not be achieved would be more achievable.

A functional disadvantage is also that widening of the relief piston is at the expense of the remaining guide shaft and thus the

Lead quality deteriorates, unless different lengths of valve members are manufactured for different width relief pistons, which also affects the dimensions of the entire pressure relief valve, with the consequences of an expensive variety of types with correspondingly expensive storage, etc.

The manufacturing process of these known valves takes place in such a way that the blank is machined in the unhardened state due to the changing manufacturing axes and clamping problems and is then only reworked after hardening.

Advantages of the invention

The inventive method for producing the movable valve member of a pressure relief valve with the characterizing features of the main claim has the advantage that several valve members can be made simultaneously from a rod that is already hardened and that in particular. The disadvantageous radius at the front end of the recess is eliminated by means of a computer control due to the cutting process running transversely to the rod axis, as a result of which an exact plunge karite extending parallel to the valve seat can be generated on this end wall. In addition to the fact that this type of production is much faster than the known one, it is also less expensive and much more precise in terms of production, so that the above-mentioned disadvantages of the known methods are avoided.

According to an advantageous embodiment of the invention, three grinding mechanisms work to produce the recesses.

test simultaneously on a valve member, which compensates for the forces acting on the tool during machining, not to mention the more rational production method. The design of the valve member with only three recesses is particularly advantageous here, since sufficient cross-sections for the fuel line can thus be achieved even with a flat cut, without the ones remaining on the radial end faces of the webs and being guided in the guide bore of the valve carrier Guide areas become too small. Although it is known to get on a movable valve member of a pressure valve three -gewon¬ by straight grindings nene recesses (German Patent 1,264,149), ^'only with the main difference being that this is • neither a pressure relief valve, nor is a valve manufactured in large series, but rather a valve member with a central bore, which if then can only be manufactured individually.

According to a further advantageous embodiment of the invention, three rotating machining disks are used as the cutting tool, the axis of rotation of which runs parallel to the axis of the rod or the valve member, without overlapping the disk diameter in the end position of the machining. While maintaining the above advantages, it is also achieved that the cross section of the

Recesses is increased in that they are tunnel-like arched through the radius of the tool towards the valve axis.

According to a further embodiment of the invention, the front wall delimiting the recesses in the longitudinal direction also serves as the outer end face of the relief piston, so that the relief piston acts as an extension of the guide shaft without interrupting the guide. The particular advantage is that, on the one hand, the width of the relief piston no longer has any influence on the length of the actual guide, that is to say also of the guide shaft, and on the other hand, the puncture which previously required limiting the relief piston can be saved. As a result, the number of types can be reduced, so that for different motors and thus different .relief volumes, some parts of the pressure relief valve, such as, for example, the valve carrier, can be configured identically and only the movable valve member has recesses of different lengths and thus correspondingly differently sized relief pistons. In the case of a relief valve for a larger return suction quantity, such as, for example, 50 mπ.3, the guide length in this embodiment according to the invention is extended by 60% without the valve member itself being therefore extended. Further advantages and advantageous embodiments of the invention can be found in the following description, the drawing and the claims.

drawing

An embodiment of the object of the invention is shown in two variants in the drawing and described in more detail below. FIG.

1 greatly simplifies the arrangement of a pressure relief valve in a distributor injection pump shown partially and in longitudinal section, FIG. 2 shows the pressure relief valve from FIG. 1 on an enlarged scale in a first variant, FIG. 3 shows a section along line III / III in FIG.

2 by the pressure valve, FIG. 4 the second variant of a valve member on an enlarged scale, and FIG.

5 shows a section along line V / V in Fig. 4 including the machining circles.

Description of the embodiment

In the case of the distributor injection pump shown in the drawing, of which only the distributor head is shown as a cutout, a pump piston 1 is turned into a reciprocating and, at the same time, rotating at the arrows indicated by means not shown

Movement driven. With its end face 2 facing away from the drive, it delimits one side of a pump work chamber 4 present in a cylinder liner 3. A suction channel 5 opens into the pump work chamber 4 and can be controlled via longitudinal grooves 6 provided in the pump piston. The pump piston 1 has a central axial bore 7, from which a radial bore 8 branches off, which merges into a distributor groove 9, which is also arranged in the pump piston 1 and opens into the lateral surface thereof. Through this distributor groove 9, which is designed as a longitudinal groove, pressure lines 11 beginning in the cylinder liner 3 are successively connected to the pump working chamber 4 during the rotary movement of the pump piston 1, the inputs of these pressure lines 11 being evenly distributed in the cylinder liner 3 around the pump piston 1 and the number of the number correspond to the stroke movements of the pump piston 1 during one revolution and thus the number of motor cylinders to be supplied. A regulating slide 12 is arranged on the pump piston 1 in an axially displaceable manner and can be axially displaced on the pump piston 1 by a speed controller, not shown, which can work with mechanical or electrical means. A transverse bore 13 of the axial bore 7 is controlled with the regulating slide 12, which opens into the lateral surface of the pump piston 1 and after a certain distance of

the position of the control slide-dependent stroke of the pump piston 1 is exposed by the control slide 12, so that the pump work chamber 4 is connected to a suction chamber 14 under feed pump pressure, from which the suction channel 5 also branches off.

A pressure relief valve 16 is arranged in each of the pressure lines 11, which each lead to an injection nozzle 15 on the engine.

As can be seen above all from FIG. 2 and partially from FIG. 4 (the corresponding reference numbers are increased by 100), the pressure valve 16 has a movable valve member 17, 117, the stem 18, 118 of which in a guide bore 19 of a valve carrier 21 is guided and is loaded in the closing direction by a closing spring 22 with its closing cone 23, 123 towards a valve seat 24. Recesses 25, 125 are provided in the shaft 18, 118, the shaft 18, 118 having radial guide surfaces 26, 126 for guiding in the guide bore 19 on the remaining webs 27, 127.

A relief piston 28, 128 is provided upstream of the closing cone 23, 123 and slides radially in the guide bore 19 to fit a lower end edge 29. points, which initiates the pressure relief when immersed in the guide bore 19. An annular groove-like recess 31, 131 is present between the closing cone 23, 123 and this relief piston 28, 128 ^' .

The fuel injection pump works as follows: During the downward suction stroke of the pump piston 1, it sucks fuel from the suction chamber 14 via the suction channel 5 and one of the longitudinal grooves 6 into the pump working area 4. The axial bore 7 and transverse bore 13, as well as the radial bore 8 and the distributor groove 9 are blocked on the one hand by the control slide 12 and on the other hand by the cylinder liner 3. During the pressure stroke which then turns upwards and in which the pump piston is rotated by a corresponding angle, for example in the case of a 6-cylinder pump by 30 °, the suction channel 5 is then blocked by the pump piston 1 and the radial bore 8 or Distributor groove 9 is opened by one of the pressure lines 11, so that the fuel from the pump working chamber 4 is conveyed under pressure via the axial bore 7, the radial bore 8, the distributor groove 9 and the pressure line 11 to the injection nozzle 15. The fuel flows in this pressure line 11 via the pressure relief valve 16. At the beginning of the pressure delivery, the movable valve member 17 of this pressure relief valve 16 is counteracted

the closing spring 22 is displaced, the closing cone 23, 123 lifting off from the valve seat 24, so that after a certain "relief stroke" has been covered, the relief piston 28, 128 emerges from the guide bore 19 and the fuel delivered via the recesses

27, 127 can flow to the injector 15. After a certain delivery stroke of the pump piston has been covered

1, the transverse bore 13 is exposed by the control slide 12, so that the remaining fuel can flow directly from the pump work chamber 4 back into the suction chamber 14. The longer this stroke is, that is, the higher the control slide 12 is pushed upwards, the greater the amount that is injected and vice versa. After completion of the pressure conveying Pührungsflachen 26, 126 of the webs 27, ^"the injector 15 closes, and almost simultaneously the Druckent¬ lastungsventil 16. In the closing movement of the Druckent¬ lastungsventils 16 which slide" 127 in the guide hole 19, wherein after covering a pre-stroke of the relief piston

28, 128 with its lower end edge 29, 129 dips into the guide bore 19, so that the discharge piston from this passage of the end edge 29, 129 past the valve seat 24, from the pressure line section between the pressure relief valve 16 and the injector 15 a certain amount of fuel from this Sucks line section back, whereby a pressure relief takes place.

This relief is ended when the closing cone 23, 123 rests on the valve seat 24. The relief volume corresponds to the cross section of the relief piston 28, 128 times its height, the height when the valve is closed from the distance between the end edge 29, 129 of the relief piston 28, 128 to the sealing point of the closing cone 23, 123 on the Valve seat 24 results.

According to the invention, these recesses 25, 125 are obtained by machining, the tools for this machining, for example milling or grinding, being actuated transversely to the axis of the valve member 17, 117, in contrast to the known production methods in which the direction of movement in the axial direction he follows. Manufacturing methods were selected as an example of the two variants, in each of which three recesses 25, 125 are provided.

In the first variant shown in FIGS. 2 and 3, these recesses 25 are obtained by machining which causes a flat base area of the recess. This can be achieved, for example, by a planing, filing or surface grinding process. The recesses 25 terminate in a recess 33 which runs parallel to the recess 31. The puncture 33 can, however -14-

be considerably narrower than in the case of recesses which have been obtained by milling tools and whose axis runs transversely to the valve axis, because no large tool outlet is required. This provides a longer guide length for the shaft.

In the second variant shown in FIGS. 4 and 5, the recesses 125 extend in length to the relief piston 128, so that its lower end edge 129 also represents the boundary edge of an end wall 32 of these recesses which runs transversely to the valve axis. This end edge 129 is interrupted in its circulation around the relief piston 128 only by the width of the guide surfaces 126 of the webs 127.

Apart from the fact that the guide surface 126 of the webs 127 is thereby widened by the width of the relief piston 128, machining can be used in a simple manner in production terms to produce the end wall 32 where the relief piston 128 should have its lower end edge 129 . This can be produced very easily using modern manufacturing methods, the closing cone surface 123 or the upper boundary edge 36 of the relief piston 128 being able to serve as the measuring output.

Another essential feature can be seen in FIG. 5.

According to which the recesses 125 are produced by rotating tools 37, the axes of rotation 38 of which are arranged parallel to one another and also to the axis of the valve member 117. The tools 37 are shown in a position which they assume towards the end of the processing, it being evident that the circular disks of the tools 37 do not touch. By simultaneously pressing radially inward during machining, the forces acting radially on workpiece 117 are compensated for. In addition, the passage cross section of the recesses 125 is increased by the circular surface segment that results from the radius of the machining disk.

Of course, a larger number may be used by rotating tools, for example, four or five, resulting in a correspondingly different Gestal¬ the recesses tung 125. ^{'simultaneous} Arbei¬ the tools th and to obtain the guide surfaces 126, however, has ensured be that the tool diameters do not overlap, even if, for example, three are obtained in two steps with six recesses.

With three valve members machined simultaneously by one rod, even tools with a large diameter can be -16-

knives are used by machining one valve member in succession, so that the tools engage simultaneously, but offset in the longitudinal direction.

All the features shown in the description of the following claims and the drawing can be essential to the invention both individually and in any combination with one another.

Claims

Expectations

1. ^" Method for producing the movable valve member (17, 117) of a pressure valve. ^' . (16) for a fuel injection pump, the valve member having a closing cone (23, 123) and a relief piston (28, 128) Guide shaft (18, 118) in the axial direction recesses (25, 125) of the same cross-section, characterized in that several such valve members (17, 117) are obtained simultaneously from an already hardened rod which, in a manner known per se, has the rotational symmetry ¬ punctures and tapping are effected by means of turning tools and that the recesses (25, 125) are produced by cutting tools (37) moved transversely to the rod axis.

2. Manufacturing method according to claim 1, characterized gekenn¬ characterized in that for producing the recesses (25, 125) at least three simultaneously and thus the machining pressure compensating tools (37) are engaged.

3. Manufacturing method according to claim 1 or 2, characterized in that as a cutting tool

(37) serve three rotating processing disks, the axis of rotation (38) of which runs parallel to the axis of the rod or of the valve member (117), without overlapping the disk diameter in the end position of the processing.

4. Manufacturing method according to one of the preceding claims, characterized by the use of grinding tools as a tool.

5. Manufacturing method according to one of the preceding claims, characterized in that the recesses (125} in the longitudinal direction delimiting end wall (32) simultaneously serves as the outer end face of the relief piston (128), so that the relief piston (128) as an extension of the guide ¬ shaft (118) acts without interrupting the guide.