SK285010B6 - Method of production camshafts with more numbers of cams especially the camshaft and device for the same - Google Patents

Abstract

Described is the method and device for producing longitudinal hollow body components, not only with a saving in tooling and working steps but also with increased efficiency, projections or cams (6) from a hollow shaft (5) are made by high internal pressure forming in such a way that the form and/or position of the projections (6) can be shaped in several steps.

Description

Technical field

The invention relates to a method for manufacturing an elongated hollow shaft with a plurality of cams, in particular a camshaft, and to an apparatus for carrying out the method.

BACKGROUND OF THE INVENTION

A number of methods for producing camshafts are known. In principle, they can be divided into two groups.

The first group comprises a conventional camshaft, which is either forged or cast as a blank, either as a solid body or as a shell cast from hardened cast iron, after which the two blanks must be further machined, first mechanically by chipping, and then it is necessary to refine their surface by subsequent heat treatment, and finally to grind the bearing parts and cams. The drawbacks of the camshafts thus produced are, in particular, their high weight and, consequently, the high moment of inertia, which have an adverse effect on the bearings, for example in torque variations, and on the high costs associated with machining the workpiece.

The second group consists of coupled cam shafts, in which the cams are manufactured separately and then individually connected to the shaft in different ways. Thus, for example, the cams may be welded, in particular onto the hollow shaft, or may be hot-placed on the tube. In the latter process, it is known to place the tube or hollow shaft with the cams slid in the tool of the corresponding shape and then open the tube by the internal high-pressure forming method, whereby the cams are elastically and the tube plastically expanded to achieve a firm press fit. hollow shaft.

When the tube is expanded by the internal high-pressure forming method, the molded hollow tubular body is simultaneously loaded with internal pressure and axial force acting on its ends. Liquids or elastomers are suitable as pressure means. The axial force is usually performed by means of rigid tools, such as pistons, punches and the like, which directly or indirectly apply pressure to the ends of the workpiece.

Exemplary embodiments of shafts to be coupled or executed in this way are known from DE 34 09 541 A1 and DE 35 21 206 A1. Common to both known designs is that fixed functional parts need to be manufactured separately, the production of which, especially in the case of cams, is associated with high costs, notwithstanding that the entire process associated with their mounting is expensive.

A method is further known from U.S. Pat. No. 2,222,762 according to which the tubular blanks are first heated and then inserted into a mold. After heating, the easy-forming blank is stabilized from the inside by means of a support medium, gas or liquid. The axial forces exerted either by the movably formed mold or by means of independent punches simultaneously press the blank into the mold, with the support medium ensuring that the heated blank does not collapse. The disadvantage of this method is that it is first necessary to heat the blank to obtain the necessary plasticity and to be pressed into the mold. This heating, in addition to changing the structure, also constitutes another work operation, which increases production costs. This patent specifies a method of manufacturing hollow bodies using internal pressure and the body is under high axial pressure. The swelling procedure may be simultaneous or separate for two or more parts of the hollow shaft. In addition, the working pressure is exerted only by xial forces, resulting in an uneven flow of material and thus an uneven stress distribution in the blank. This patent does not solve the characteristic method of shaping the cams, which would start in the central part and the hollow shaft and proceed to its ends. Although there is general guidance on how to subject the hollow body to axial pressure, there is nothing about feeding the material to all extended locations. One of the problems that arise when expanding the hollow shaft in the manner described is the thinning of its wall.

JP 57 206530 A discloses a method for producing a camshaft according to which a pre-heated hollow body is pressed into a mold in a single operation by means of a pressurized liquid. It must first be heated; furthermore, in this method no further axial displacement follows, which also leads to uneven flow of material; furthermore, there is no sequence of forming operations in this method, the method comprising only a single forming operation and not a process by which the material is fed using axial forces important to eliminate material congestion.

SUMMARY OF THE INVENTION

The problem solved by the present invention is to provide a method and apparatus for carrying out the method by which at reduced production costs, reduced tool costs and reduced work operations, it will be possible to produce elongated hollow bodies with an increased degree of efficiency, i. j. at higher productivity and without reducing wall thickness.

This problem is solved by a method apparent from the features of the main claim, when a method of manufacturing an elongated hollow shaft with a plurality of cams, in particular a camshaft, by high pressure internal forming, wherein the hollow shaft to be shaped is inserted into at least two piece tool and coaxially and internally The pressure punches with sealing heads are subjected to axial forces, the inner part of the hollow shaft being coaxial channels in the pressure punch and the sealing head being supplied with a pressure environment, the pressure punches and their sealing heads having a diameter allowing them to be inserted into at least two-piece tool and cam. are individually or in pairs successively formed into a central portion of the hollow shaft towards its ends, progressively axially advancing the hollow shaft material into the formed cams.

It is preferred that the shaping process of the elongated hollow shaft starts from at least one shaft end of the arranged punch on the most distal cams in the central portion of the hollow shaft and is progressively carried out towards the punch.

Advantageously, the method for producing the elongated hollow shaft is realized in such a way that the outer cams are formed against the pressure of a plurality of pressure and / or reciprocating slide slides either individually or in pairs in succession.

Advantageously, the method for manufacturing the elongated hollow shaft is realized in such a way that the individual manufacturing operations are carried out in different parts of the at least two-piece tool.

Advantageously, the method for producing the elongated hollow shaft is implemented such that the locally directed shaping of the cams is controlled by means of at least one inner mandrel, which is introduced into the hollow shaft, is longitudinally displaceable therein and overlaps positions in which no cams are currently being formed.

Advantageously, the method for producing the elongated hollow shaft is realized by forming a multi-walled hollow blank.

A method for producing an elongated hollow shaft having a plurality of cams, in particular a camshaft, by high pressure internal forming, comprising at least a two-piece hollow shaft insertion and shaping tool, the at least two-piece hollow shaft insertion and shaping tool being provided with recesses for inserting two coaxial but oppositely arranged and individually acting hollow shaft press punches with sealing heads equipped with coaxial channels for introducing a pressurized environment into the interior of the hollow shaft, is realized by a device characterized in that it comprises at least one hollow shaft and pressure dies and the sealing heads of a longitudinally movable hollow inner mandrel which is retractable into the individual end of the hollow shaft and which at least at its end extending into the hollow shaft is provided with a face-to-face seal on the inner wall of the hollow shaft.

Advantageously, the device for carrying out a method for producing an elongated hollow shaft with a plurality of cams, in particular a camshaft, by high pressure internal forming comprises a movable slide movable perpendicular to the axis of the hollow shaft at least into one of the recesses. Advantageously, the apparatus for carrying out a method for producing an elongated hollow shaft with a plurality of cams, in particular a camshaft, by high pressure internal forming comprises at least one at least two-piece tool with a set of forming cavities with different recesses.

Advantageously, the apparatus for carrying out a method for producing an elongated hollow shaft with a plurality of cams, in particular a camshaft, by high pressure internal forming comprises at least a two-piece tool provided with a set of forming cavities with a gradually increasing number of recesses.

It is preferred that the coaxial channels in the pressure dies and the sealing heads have a diameter allowing the insertion of the inner mandrels into the hollow shaft.

It should also be noted that it is also within the scope of the invention to start from a blank which has been preformed by, for example, printing and / or cross-rolling the hollow shaft. This procedure allows to build up material at the points of the hollow shaft where the cams are to be formed in order to counteract wall reduction and possible under-expansion of the material.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention are shown in the drawings. 1 shows schematically the basic construction of the tool without additional tools, with the intermediate product inserted in its initial and final state, in side and sectional view, FIG. 2 shows the tool with respect to FIG. 1, with details and with the aid of individual hydraulic cylinders, double-sided slide slides in several mold cavities; FIG. 3 shows schematically a wedge strip for operating the slide punches according to FIG. 2, FIG. 4 is a diagrammatic top and cross-sectional view of a tool half with a plurality of receiving locations for progressively forming a blank, which is shown in a respective processing state at each receiving location; FIG. 5 a half of a tool for another variation of use, with the semi-finished, semi-finished, stored. j. hollow shaft, and with inner mandrels partially overlapping the inner wall of the hollow shaft, schematically in cross-section and in a top view, FIG. 6 shows a preformed hollow shaft which can serve as a preform for further shaping, for example, in the tool of FIG. First

DETAILED DESCRIPTION OF THE INVENTION

Before describing the drawings in detail, some basic remarks should be made. Thus, first of all, it should be noted that at the top of FIG. 1 and 2, the semi-finished product is shown in its final shape, while in its lower parts its starting state is shown, optionally in FIG. 6 shows its initial interoperative condition. For FIG. 1 to 5 it is moreover common that they schematically illustrate tools which are fundamentally suitable for the high pressure internal forming method and are preferably divided in a horizontal plane. They are provided with successive recesses, described in more detail below, i.e. j. the internal cavities of the tool in which the workpiece to be shaped, in this case a hollow shaft, is deposited, which is then subjected to frontally acting forces in the axial direction by means of punches arranged in a manner known from the tool, it presses the pressure environment so that the workpiece is loaded by high internal pressure and axial force acting on the ends of the tube. This results in a desirable bulge in the closed tool. The diameter of the side punches is such that the punches can be inserted into the tool and can press the hollow shaft, provided with coaxial channels through which the pressurized environment can pass into the hollow shaft cavity. The punches are provided at their free end with sealing heads serving to seal the workpiece, i. j. tubes at both ends and to introduce axial forces into the blank as well as to apply pressure to the inner part thereof. The pressure is preferably applied by means of a multiplier with a structure similar to that of a hydraulic cylinder, and can be increased because the liquid is compressed in the interior of the multiplier, or reduced as the fluid pressure decreases.

For a general idea, FIG. 1 shows a simplified two-part tool with an upper half 1 and a lower half 2, which in the closed state form a hollow space 3 as a mold for the final shape of the cam hollow shaft 5. This is to be noted - and this also applies to further illustrating other preferred embodiments of the invention - that the individual cams are shown in a single plane for ease of understanding; it is obvious that they are generally radially angularly offset. In the places where the cams are to be formed, the hollow space 3 is provided with corresponding recesses 4, in the illustrated embodiment only three recesses 4, because this is a representation of the principle of solution, and the corresponding parts of the hollow shaft walls are pushed into these recesses 4. The recesses form part of the total number of internal tool cavities (form-nest) in which the precursor stock is stored.

In the lower half of FIG. 1 shows the initial state with the hollow shaft 5 mounted, while in the upper half of FIG. 1 shows a finished state with finished cams 6, i.e. a camshaft made according to the invention in one piece of material. The pressure punches 7 are provided with sealing heads 8 and a transverse coaxial channel 9, in cross-section shown on the left side, through which the pressurized medium enters the interior of the hollow shaft 5.

In this exemplary embodiment, the tube, as a hollow shaft 5, is inserted into the upper half of the two-part tool 1, and the lower half of the two-part tool 2 having the camshaft geometry and internal high pressure and shaped by axial material feed. That is, the hollow shaft 5 gradually moves from its starting state to its final state, so that the pressure punches 7 engage and exert pressure on the front surfaces of the hollow shaft 5, while supplying the pressure fluid through the coaxial channels 9 due to the action of both overlapping of force during the insertion of the dies 7 into the inner part of the tool, the hollow tube is transformed into the final state shown.

In the following embodiments of the invention, the same reference numerals as in FIG. First

As already mentioned, in the exemplary embodiment of FIG. 2, the two-part tool consists of the upper tool half laz of the lower tool half 2, and its hollow space 3 is formed in the geometry required for the camshaft to be produced. In this embodiment, six recesses 4 for the six cams to be produced are arranged in the tool. For the sake of simplicity, the coaxial ducts 9 for supplying the pressurized medium are not shown in the dies 7 for the sake of simplicity. Each of the outer recesses 4, 4a facing the ends of the hollow shaft, only the outer slides 11a or the inner slides 11b, which are displaceable practically in the vertical direction with respect to the recessed double arrows, are schematically shown here. a push rod 13a or an inner drawbar 13b connected to the hydraulic outer and inner hydraulic cylinders 12a, 12b. Thereby the slides 11a, 11b are displaceably operable in both directions; in the starting position, they are located with their front face in the position shown in the drawing as the upper position, i.e. in the position in which they engage the outer wall of the hollow shaft 5. The two inner recesses 4 are not provided with a slide.

An exemplary manufacturing method is as follows:

Since the two inner cams and the two outer slides 11b are in the extended starting position, they are formed initially inside the cam 6 without axial displacement of the shaft material without the flow of the material being limited by the formation of the outer cams, t. j. cams lying closer to the ends of the shaft. After the two inner cams 6 have been molded with the outer hydraulic cylinders 12b outwardly from the two finished cams 6, the inner slides 11b are displaced, and the outer cams 6b are shaped therefrom, yet the axial flow of the material is not reduced, yet there is no shaping of the outer cams 6a at the end sides of the shaft. In the last phase of the high pressure internal molding, the outer slides 11a are displaced and the corresponding outer cams 6a are formed.

Instead of the hydraulic actuation of the outer slides 11a and inner slides 11b, these slides 11a, 11b can also be mechanically operated. For this purpose, the wedge strip 14 shown in FIG. 3, in which the wedge cams, the outer wedge cam 15a, or the inner wedge cam 15b, respectively, are arranged in the order corresponding to the position of the outer push rod 13a and the inner pull rod 13b. The wedge 14 in this case is arranged in the region of the hydraulic cylinders, the inner hydraulic cylinder and the outer hydraulic cylinder, 12b and is movable in a direction parallel to the elongated person of the hollow shaft 5, the outer wedge cams 15a and the inner wedge cams 15b directly acting on the corresponding the outer push rods 13a, or the inner pull rods 13b. In this case, only a single hydraulic cylinder (not shown) that moves the wedge bar 14 in the direction shown in FIG. 3 two-way horizontal arrow. In the position shown in FIG. 3, the outer thrust rods 13a and inner thrust rods 13b on which the outer and inner wedge cams 15a, 15b are directly applied are in the retracted state, i.e. in the position in which the cams 6 are first formed.

When the wedge bar 14 is moved to the left (FIG. 3), the external and internal slides 11a, 11b are compressed under the internal pressure in the hollow shaft 5, since their outer thrust rod 13a or the inner drawbar rod 13b can along the bevel of the outer wedge the cams 15a, or the inner wedge cams 15b, bend downwards.

The wedge strip 14 described above allows direct actuation in the sense of the procedure explained with reference to FIG. 2 because, as is also apparent from FIG. 3, the inner wedge cams have shorter faces, i.e., when moving to the left, the inner traction rods 13b positioned in front of the outer thrust rods 13a reach the skew area of the wedge cams 15b rather than the outer thrust rods 13a, so that before forming the outer cams 6a first to form additional outer cams 6b. The shaping of the outer cams 6a occurs only when the outer push rods 13a reach the bevel region of the outer wedge cams 15a.

To further improve the creep of the material in the shaping of the cams 6, recesses 4 may also be provided with slides, correspondingly defined by punches operated by the wedge cams (not shown here) arranged between the wedge cams 15a, 15b.

Fig. 4, in which the side punches 7 are not shown, represents a particularly preferred embodiment of the invention. In plan view there is shown the lower half 2 of a two-piece tool with three mold cavities of different geometry, i. j. a different number of recesses, wherein a camshaft 5 is formed in each cavity in a corresponding operation. The shaping in the individual mold cavities can take place simultaneously or sequentially.

FIG. 4, it is clear that the illustrated production of the six-cam camshaft is performed in three operations, the hollow shaft 5 being subjected to a first shaping operation in the forming cavity shown in the upper part of FIG. 4, in which the two cams 6 are formed. The blank thus formed is then transferred to the molding cavity shown, which is provided with two further external recesses 4b. In this second operation, additional outer cams 6b are formed on the hollow shaft 5 by injecting material into the other outer recesses 4b. Finally, the hollow shaft 5 is transferred to a forming cavity equipped with the six recesses 4, 4a, 4b shown in the lower part of FIG. 4 in which the final shaping is carried out.

Fig. 5 also represents a preferred embodiment of the invention. It shows the lower half 2 of a two-part camshaft tool with six cams 6 on which two cams 6 have already been formed. Also by means of this tool, the cams 6 are produced progressively from the inside outwards. To this end, two internal mandrels 16 are used which, in the position shown in the in-process procedure, are inserted into the hollow shaft 5 as far as possible so as to close and protect against high internal pressure those areas in which the walls have walls only in the next operation. press the hollow shaft 5 into the outer recesses 4a and the inner recesses 4b. To this end, the inner mandrels 16 have an outer diameter which permits them

SK 285010 Β6 telescopic insertion into the hollow shaft 5 with a corresponding clearance against its inner wall. At their free end lying inwardly, the inner mandrels 16 are provided with a face seal 17 or wedge-sealing rings which seal the tube or hollow shaft 5 as soon as pressure increases in the inner part thereof. The higher the pressure, the greater the sealing force of the wedge seal rings; the sealing force is thus derived from the internal pressure.

The punches 7 in this case are designed such that, on the one hand, they have an outer diameter which, as in the exemplary embodiments described so far, permits introduction into the tool recess, i.e. a diameter which approximately corresponds to the outer diameter of the hollow shaft 5, The previously described exemplary embodiments have an expanded embodiment, and its diameter is so large that the inner mandrels 16 can be bi-directionally moved therein. Thus, the punches 7 can bi-directionally exert their axial force on the end faces of the hollow shaft 5 while moving the inner mandrels. 16. The coaxial conduit 9 for the pressurized medium is now in each of the inner mandrels 16. The details of this procedure are apparent from the embodiment shown in section on the left of FIG. 5th

According to this concept, the following process can be carried out: First, the inner mandrels 16 from the end portion of the pressure punches 7 abutting the hollow shaft are moved to the position shown in FIG. 5 and are inserted into the hollow shaft 5, which can be carried out by means of suitable elements (not shown here) at the outer end of the pressure punches 7, the inner mandrels 16 for example being able to pass through the pressure punches 7 to their outer end. Upon subsequent application of local internal pressure, both internal cams are formed as shown.

In the next phase, the inner mandrels 16 are moved outwardly until the area of the other recesses 4b is released, so that the internal pressure can now act on these areas of the hollow shaft 5 into which the other outer cams 6b can be formed while simultaneously axially moving The inner mandrels 16 are displaced inwardly in order to replenish the necessary amount of material to avoid friction between the wedge face seal 17 on the inner mandrels 16 and the inner wall of the tube.

The formation of this second pair of additional outer cams 6b is always followed by a relief of the internal pressure, whereby the sealing force of the wedge-sealing rings of the face seal 17 is minimized while maintaining the elastic intrinsic proportion of the wedge-sealing rings. Thereafter, the inner mandrels 16 are pushed further outwardly to form a further pair of outer cams 6a.

In this version, too, an optimum supply of material can be achieved, because, as already mentioned in connection with the exemplary embodiments described above, in each operation where the cams are formed progressively from the central portion of the hollow shaft towards its end portions, The material must be pushed away from the ends of the pipe without restraint, since it has not yet been deformed in these areas not yet under pressure.

Only to supplement these various applications of the method according to the invention, FIG. 6 shows an initial blank for a hollow shaft 5 to be formed into a six-cam camshaft and which is in the state shown in FIG. 6, produced by conventional techniques, such as compression, cross-rolling, and the like, where there are accumulations of material 19 at the points where the cams are to be formed to counteract the reduction in wall thickness and possible insufficient material expansion. Such a preform is suitable, for example, for processing in the tool shown in FIG. 1 and 2, wherein the axial flow of the material is also reduced due to the accumulation of material.

Industrial usability

In particular, the invention is for the manufacture of elongated hollow shafts with a plurality of cams by high pressure internal forming, which are widely used in the automotive industry in particular.

Claims (11)

PATENT CLAIMS Method for manufacturing an elongated hollow shaft (5) with a plurality of cams (6, 6a, 6b), in particular a camshaft, by high pressure internal forming, in which the hollow shaft (5) to be shaped is inserted into at least a two-part tool (1). 2) and axial forces are applied to the inner part of the hollow shaft (5) by means of coaxial and internally arranged pressure punches (7) with sealing heads (8), with coaxial channels (9) in the pressure punch (7) and sealing head into the inner part introduces a pressure environment, characterized in that the pressure punches (7) and their sealing heads (8) have a diameter allowing them to be inserted into at least a two-piece tool (1,2) and the cams (6, 6a, 6b) respectively or individually in pairs they successively shape from the central part of the hollow shaft (5) towards its ends, with the gradual axial displacement of the hollow shaft material (5) into the formed cams (6, 6a, 6b). Production method according to claim 1, characterized in that the shaping process starts from at least one end of the shaft (5) of the arranged punch (7) on the most distal cams (6) in the central part of the hollow shaft (5) and gradually it further extends towards the pressure punch (7). Production method according to claim 1 or 2, characterized in that the outer cams (6a, 6b) are shaped against the pressure of several pressure and / or reciprocating slide slides (11a, 11b) either individually or in pairs in succession. Production method according to claim 1 or 2, characterized in that the individual production operations are carried out in different parts of the at least two-part tool (1, 2). Production method according to claim 1 or 2, characterized in that the locally directed shaping of the cams (6, 6a, 6b) is controlled by means of at least one inner mandrel (16) which is introduced into the hollow shaft (5) therein. longitudinally displaceable and overlapping positions in which no cams (6, 6a, 6b) are currently being formed. Method according to one of Claims 1 to 5, characterized in that a multi-walled hollow blank is formed. Apparatus for carrying out a method for producing an elongated hollow shaft (5) with a plurality of cams (6, 6a, 6b), in particular a camshaft, by high pressure internal forming, comprising at least a two-piece tool (1, 2) for inserting and shaping the hollow shaft (5) ), wherein the at least two-part tool (1, 2) for inserting and shaping the hollow shaft (5) is provided with recesses (4, 4a, 4b) for inserting the emerging cams (6, 6a, 6b), and two coaxial but There are pressure punches (7) opposing and individually acting on the ends of the hollow shaft (5) with sealing heads (8) provided with coaxial channels (9) for bringing the pressure environment into the interior of the hollow shaft (5), according to claim 1, characterized in that it comprises at least one hollow inner mandrel (16), which can be inserted into the end of the hollow shaft (5), and which can be inserted at least on its hollow shaft (5) and in the pressure dies (7) and the sealing heads (8) the end extending into the hollow shaft (5), each provided with a face seal (17) abutting the inner wall of the hollow shaft (5). Apparatus according to claim 7, characterized in that it comprises a movable slide (11a, 11b) movable perpendicular to the axis of the hollow shaft (5) in at least one of the recesses (4, 4a, 4b). Apparatus according to claim 7, characterized in that it comprises at least one at least two-piece tool (1, 2) with a set of forming cavities with different numbers of recesses (4,4a, 4b). Apparatus according to claim 9, characterized in that the at least two-piece tool (1, 2) is provided with a set of forming cavities with a progressively increasing number of recesses (4,4a, 4b). Apparatus according to claim 7, characterized in that the coaxial channels (9) in the pressure dies (7) and the sealing heads (8) have a diameter enabling the inner mandrels (16) to be inserted into the hollow shaft (5).