KR20000016325A - Method and device for manufacturing cam shaft - Google Patents

Abstract

PURPOSE: A method and a device for manufacturing a cam shaft are provided to reduce parts and working process, to manufacture a long hollow core body by low cost by improving the operation efficiency and to prevent the reduction of the thickness of the wall of the hollow core body. CONSTITUTION: A device is composed of an upper part(1) and a lower part(2), and a cavity(3) is formed in a certain shape for a cam. A recessed part placed on the end part of a shaft has punches(11a,11b) able to move into a milling recessed part perpendicular to the vertical shaft line of a hollow core shaft(5) via the rams(13a,13b) connected to each hydraulic pressure cylinder(12a,12b). And the punches are placed on the upper part of the outer wall of the hollow core shaft installed inside at a starting position. The two inner milling recessed parts(4) are not punched.

Description

Manufacturing method and apparatus of camshaft

Many methods for manufacturing camshafts are known. These are mainly divided into two different groups.

The first group includes a blank or solid body, and a camshaft forged or cast as a cold casting and manufactured in the prior art. The semifinished products are subjected to other processing, ie first machining and subsequent surface hardening and tempering, followed by polishing of the bearing seat and cam. The disadvantage of the camshaft manufactured in this way is that it has a particularly heavy weight and has a high moment of inertia, which not only adversely affects the bearing, for example, due to torque changes, but also the cost of machining with the blank is significant.

The second group is a composite camshaft in which the cams are manufactured as separate parts and then fixed to the shaft in various ways. As such, the cam can be for example welded to a hollow shaft or slipped on a tube to shrink. For this last manufacturing method, it is known to place the tube or hollow shaft in a suitably concave device after the cam has slipped and expand the tube using a high internal pressure molding method (or hydroforming process). The cam is elastically inflated and the tube is also plastically inflated so that a reliable positioning of the cam on the tube or hollow shaft is formed by interference or forced fit.

In the high internal pressure molding method, the hollow tube body to be molded simultaneously receives an internal pressure and an axial force acting on the end portion. Suitable elastomers are liquids or elastomers. The axial force is generally exerted by a linear device such as a piston, a die or the like which acts directly or indirectly on the end of the workpiece. Examples of shafts joined and configured in this way are known from DE 34 09 541 A1 and DE 35 21 206 A1. A common disadvantage of the methods proposed in the two publications is that the manufacturing of the individual parts to be fixed to the shaft is expensive and expensive, especially in the case of the cam, which incurs a considerable cost in the production of the individual parts. The whole process involved in the process of joining is very complicated.

The present invention relates to a method for producing a long hollow body, in particular a camshaft, and to an apparatus for implementing such a method.

Further details and advantages of the invention are set forth with reference to the accompanying drawings which illustrate preferred embodiments of the invention.

1 is a side view schematically showing the initial and final state of a device according to the invention, showing only the auxiliary device and the workpiece placed therein, without showing the base of the device,

FIG. 2 is a detailed view of FIG. 1 with a punch in the mold capable of individually controlling the force and movement by the hydraulic cylinder, FIG.

3 is a view schematically showing a V-shaped rail for controlling the ram of the punch shown in FIG.

4 is a plan view schematically showing an apparatus having a plurality of locators for stepwise forming a workpiece in an individual molding state,

FIG. 5 is a schematic plan view of an apparatus according to another variant of the invention, having an internally processed workpiece (hollow shaft) and an inner mandrel partially covering the inner wall of the hollow shaft, FIG.

FIG. 6 shows a preformed hollow shaft as a semi-assembled starting material for use, for example, in the apparatus shown in FIG. 1.

The object of the present invention is not only to shorten the apparatus and the work process, but also to increase the operating efficiency (high production rate) to produce a long hollow body at low cost, and at the same time to prevent the reduction of the wall thickness of the hollow body and to carry out the method. It is to provide an apparatus for doing so.

This object can be achieved by the features of the independent claims. That is, in the prior art, the hydroforming process is not only used to expand the hollow shaft to form a forced fit or additional axial fixation as in the case of DE 35 21 206 A1, but also bulging-out. It is not used to form a self-projection, in particular a projection of a cam, integrally from tubular or section material (hereinafter referred to as " hollow body " or " hollow shaft " or " shaft " . Surprisingly, the formation of continuous projections (cams) by bulging provides a number of possible single hollow body manufacturing methods that are extremely economical and can shorten processing times.

In another aspect of the invention, a common feature of many embodiments is that the hollow shaft can be molded in several stages, wherein the cam is continuously molded in relation to the position and / or shape on the shaft. In other words, as will be clearer from the following description, on the one hand the cam is gradually formed into the final shape and on the other hand it can be continuously formed according to the predetermined arrangement on the shaft. Of course, these two methods can be combined with each other.

As such, in a preferred embodiment of the invention, the cam can be continuously molded from the middle of the cam towards the end, which is particularly economical to carry out in one set. Another possibility is to mold the cam from one end of the shaft to the other end. This process is particularly economical because it prevents the individual fabrication of the cam, and the material can now be run axially without blocking the current deformation zone, allowing accurate calibration. According to the invention, the conveying of material from the end of the tube by axial pressing force and traveling motion is not hindered by a pair of cams located forward. In other words, the tube material can be conveyed unimpeded into the current deformation zone. When this is done, shaping of the next pair of cams is performed. This can further increase the deformation of the tube material by the pressure generated in the axial direction, and can increase the elongation at break of the material. In addition, the wall thickness reduction (cam to be molded) in the deformation zone is quite small. In other words, the wall thickness is more uniform and higher structural stability is achieved. In fact, the applicability is even greater.

As such, the cam can be continuously molded in a single or group in a predetermined position against the pressure of a plurality of punches that can be controllably retracted.

For the foregoing description and the following embodiments, the cam can be continuously molded from the intermediate position of the shaft to the end, with particular advantage being achieved by controlling the material to flow into the inner zone, ie the middle zone of the shaft. No further elongation of the material occurs because the flow of material when the material is transported axially during the shaping of the cam is not obstructed by the cam already in place. Thus, for example, it can be made of a material having a low ductility with a bearing seat required for a 12-cylinder engine and a cam with a significant number and a considerable height. In addition, the upsetting of the material at the end of the part is small and the wall thickness is more uniform, further reducing the overall wall thickness if necessary.

According to the invention, cold worked materials such as "tailoredblanks" and "tailored tubes", and monolayer materials, for example steel / steel or sty / aluminum combinations, hollow sandwiches Double materials such as formula bodies and coated hollow bodies can be widely used. For the steel / aluminum combination, steel constitutes the outer support material and aluminum constitutes the inner support material. Therefore, the properties of the material are significantly improved. That is, the steel jacket provides better abrasion, heat treatment and torque characteristics, and also provides an advantage in weight because the inner aluminum layer is also a good support material. Shrink-fitting combinations can be used as a multilayer semifinished product for carrying out the molding process according to the invention, but such semifinished products can also be extruded or by continuous extrusion processes.

In the above-described variant, the punches may be compressed in a predetermined time in a single or pair as needed. In one possible embodiment, the punches can be conveyed and force controlled by a hydraulic cylinder in relation to the other punches. In shaping from the middle to the end of the shaft, no punch is required in the milling recess in the inner cam or associated device. The reason for this is that at that time the cam starts to form, punches in different processes are pressed against the outer wall of the hollow shaft so that deformation of the shaft does not occur at these positions. The cam is only molded late.

As another example of applying hydraulic pressure to a punch or a piston or a die, the movement control can be performed mechanically by a V-shaped rail moving mechanism that moves almost parallel to the longitudinal axis of the hollow shaft and acts directly on the die. If a cam is provided, the punch movement can be adjusted by the proper movement of the V-rail. In other words, in this embodiment, the depression where no pressure is applied and the cam is not formed can be selectively covered or the position where the cam is to be formed is not exposed.

Continuous shaping of the cam from the inside to the outside can be carried out, in particular, by carrying out individual manufacturing steps in different zones of the apparatus in accordance with a preferred embodiment of the present invention. Although it is necessary to move the workpiece from one position in the tool to another between individual processes, the device can be designed more simply and cheaply. Also in this case, no movable element such as a punch or the like is provided. This results in an overall effect without space problems, for example in the case of six cams forming a pair from the inside to the outside, three workpiece locators are required in the apparatus so that corresponding milling recesses are provided respectively.

Alternatively, some selective shaping methods of the cam also operate from the inside of the hollow shaft to operate similarly to the punch described above after inserting the inner mandrel into the hollow shaft, thereby preventing molding at a particular location spaced from the punch. Only the cam that is currently shaped (from inside to outside) is subjected to (partly) internal pressure and deformation occurs. The remaining zones are not pressurized so that the forces causing deformation are not applied. In other words, the hollow shaft, as in the case of a punch, does not support the inner pressure, but instead prevents the inner mandrel from applying pressure to the inner wall of the hollow shaft in the recessed zone where deformation has not yet occurred. As such, only certain moldings are allowed to protrude only by the axial pressure applied mechanically with the inner pressure and finally the mandrel does not protect the inner wall of the hollow shaft from the inner pressure and one or more milling recesses are present.

In practice, it is desirable to use two inner mandrels, which have an outer diameter that is pressed into the hollow shaft at either end and can be pulled into or pulled into the piston that transmits mechanical axial force to the end of the tube. . This allows for local continuous forming of the cam from the center to the end of the shaft. Of course, the inner mandrel is provided with a coaxial passageway so that the pressure medium can reach the inside of the shaft.

This embodiment of the present invention allows a relatively large number of milling recesses to be formed at a relatively low manufacturing cost.

It is to be understood that it is also within the scope of the present invention to use semi-finished products performed according to conventional processes such as, for example, upsetting or cross rolling of hollow shafts. This makes it possible to stack the material at a location on the hollow shaft on which the cam is formed, taking into account the reduction in wall thickness and the suitable ductility of the material.

Before the detailed description of the drawings, there should be some basic description of the drawings. First of all, in Figures 1 and 2 the workpiece at the top of the figure shows the final product shape, while the workpiece at the bottom of the figure shows the initial product shape, and also in Figure 6 the initial state is shown. have. Common to Figs. 1 to 5 is a schematic illustration of a device which is essentially suitable for the inner high pressure forming process (so-called hydroforming process) and is horizontally divided into two parts. The figure shows one or more recesses (engravings or mold necks inside the apparatus), the shaping of the recesses being described in detail below, but inside of which the workpiece to be deformed is laid and mounted on the outer side of the apparatus and known methods The die actuated in an axial direction on the end face, while at the same time a pressure medium is applied to the inside of the hollow shaft so that the workpiece has a high internal pressure and an axial direction acting on the end of the tube. Receive strength. This allows certain protrusions to be formed in the closed device. The side die has a diameter that can be pushed into the device to upset the hollow shaft and has a coaxial passageway through which the pressure medium can enter the inside of the hollow shaft. The free end of the die is provided with a sealing head which serves to seal the semi-finished product (pipe) to the pipe end, to impart an axial force inside the workpiece and to supply pressure into the workpiece. Preferably, the pressure is imparted through a pressure booster (marked as a pressure cylinder) and can be increased (when the liquid inside the pressure booster is compressed) and reduced (when the liquid is removed).

In FIG. 1, shown very briefly to provide a general view, a molding tool is shown comprising an upper half 1 and a lower half 2 of the device. The upper half and the lower half form a cavity 3 as a mold for the final shaping of the camshaft in the closed state. This also applies to the description of other preferred exemplary embodiments. That is, for simplicity of explanation only individual cams are shown in one square and they are sharply radially upset. In the position where the cam should be finally positioned, the cavity 3 exposes the corresponding milling recess 4 (only the case with three numbers in this embodiment to explain the principle only). Inside the recess the corresponding wall zone of the hollow shaft is pressed. The milling recess forms part of the entire mold recess on which the workpiece is placed.

In the lower half of Fig. 1, the initial state of the hollow shaft is shown, while in the upper half it is shown the final state in which the cam 6, i.e. the integral camshaft according to the invention is formed. Reference numeral 7 denotes a lateral compression die having a coaxial passageway through which the pressure medium can pass into the hollow shaft 5, as shown in the left side cross-sectional view, which includes a die head 8; Is provided.

In this embodiment, the hollow tube 5 lies in the forming apparatus 1, 2 having the camshaft shape to be molded and is deformed by an internal high pressure on the conveyed axial material. That is, the hollow shaft 5 exerts an axial pressure by means of a pressure die 7 against the hollow shaft 5 and at the same time feeds the pressure medium through the passage 9 so as to produce the final product from the starting material. Are processed continuously. Under the influence of the two forces, the deformation into the final state shown occurs when the pressure die is advanced into the apparatus.

The same reference numerals are used for parts corresponding to FIG. 1 for the purpose of describing the following embodiments.

In the embodiment shown in FIG. 2, as described above, the device consists of an upper half 1 and a lower half 2 and the cavity 3 is of a predetermined shape for the cam. In the present embodiment, six milling recesses 4 are provided in the apparatus for forming six individual cams. For simplicity, the pressure medium supply passage 9 in the dies 7, 8 is not shown. The outer milling recesses 4a, 4b, i.e. the recesses located towards the end of the shaft, are provided with respective punches 11a, 11b shown only schematically, which punch each hydraulic cylinder as shown by the double arrow. Each ram 13a, 13b connected to 12a, 12b can move into a milling recess perpendicular to the longitudinal axis of the hollow shaft 5. Therefore, the punches 11a and 11b can be controlled in force and movement. In the starting position the punch is located in front of the upper position shown in the figures, ie up against the outer wall of the hollow shaft 5 placed in the apparatus. The two inner milling recesses 4 are not punched.

The process is as follows. Since the four punches 11a and 11b are in the advanced starting position, the inner cam 6 is in the axial direction of the shaft material without the flow of material hindered by the formation of the outer cam, i.e. the material lying near the end of the shaft. By primary supply. When the two inner cam formings are completed, the cylinder 12b and the punch 11b primarily placed on the outside of the machined cam are retracted and the cam 6b is formed next. Here too, the shaping of the end cam 6a has not yet been carried out so that the flow of material in the axial direction is not disturbed. At the end of the hydroforming, the punch 11a is retracted and the corresponding cam 6b is molded.

Instead of the hydraulic action of the punches 11a and 11b, control and movement of the punches may be performed mechanically. A V-shaped rail 14 for this is shown in FIG. 3. The rail has a number of wedge cams 15a and 15b corresponding to the number of punches 11a and 11b and is arranged corresponding to the positions of the punch rams 13a and 13b. In this case, the V-shaped rail 14 is mounted in the region of the hydraulic cylinders 12a, 12b and moves parallel to the longitudinal axis of the hollow shaft 5. In this case, only a single hydraulic cylinder (not shown) is needed to move the V-shaped rail 14 in the direction of the horizontal double arrow in FIG. In the position shown in FIG. 3, the rams 13a and 13b to which the wedge cams 15a and 15b directly act are shown in the forward position, ie the position in which the inner cam 6 is first molded.

As the V-shaped rail 14 moves to the left by simultaneous application of internal pressure, the rams 13a and 13b move downward along the inclined surfaces of the wedge cams 15a and 15b. 11b) is pressed downward.

By using the V-shaped rails, direct control of the process described above with respect to FIG. 2 is possible. This is because the inner V-shaped rail has a shorter surface as in FIG. That is, when the ram 13b moves in the left direction, the ram 13b reaches the inclined surface area of the wedge cam 15b before the ram 13a and, first of all, the cam shaping before the cam forming 6a starts. 6b is executed, which is executed when the ram 13a reaches the inclined surface area of the wedge cam 15a.

In order to further improve the flow of material in the shaping of the inner cam 6, the punch controlled in the manner described above through a ram by a cam (not shown) correspondingly placed between the wedge cams 15a and 15b is milled concave. It is provided in the part 4.

4 shows a particularly preferred embodiment according to the invention, in which no side dies 7 and 8 are shown, in which the three molds of different shapes for the workpiece in the lower half of the device (shown in plan view). The neck is shown and the workpiece 5 is formed in each mold neck individually. The transformation into individual forms of the neck can be carried out simultaneously or sequentially.

4 clearly shows that the manufacture of the camshaft 5 with six cams is carried out in three stages. In the first process step the hollow shaft 5 in the upper mold neck of FIG. 4 is deformed until the two inner cams 6 are molded. The semifinished product thus deformed is moved inside the mold neck which is provided with two further milling recesses 4b which cause the cam 6b to deform in the second step. Finally, the hollow shaft 5 is moved inside the bottom mold neck shown in FIG. 4 with six milling recesses 4, 4a, 4b in which deformation to the final state is carried out.

Similar to the embodiment described above, FIG. 5 shows the lower half 2 of the apparatus for producing a camshaft with six cams 6 in which two inner cams have already been produced. In the case of the device as well, the cam 6 is formed continuously from inside to outside, for which two inner mandrels 16 are used. The mandrel is pressed into the end of the hollow shaft 5 in the state of the intermediate fabrication step so that the area to be later deformed into the outer milling recesses 4a, 4b during the processing from the inside of the hollow shaft from the inner pressure. Protect. For this purpose, the inner mandrel has an outer diameter which can be folded inwardly into the hollow shaft 5 with a suitable clearance from the inner wall. The inner mandrel 16 at the free inner end is provided with a head seal 17 or a V-shaped seal ring, respectively, which seals the pipe or hollow shaft as soon as pressure occurs inside. The higher the pressure, the greater the sealing force of the wedge seal ring. The sealing force is generated by internal pressure.

In this case, the dies 7, 8 have, on the one hand, a diameter which generally corresponds to the outer diameter of the hollow shaft 5, i. As is apparent from one embodiment, the inner mandrel has a large inner diameter with a diameter large enough to be able to be folded in and out. The dies 7, 8 still exert an axial force on the end face of the hollow shaft 5, while the inner mandrel 16 is simultaneously moved into the hollow shaft. The coaxial passage 9 for the pressure medium is located in each inner mandrel 16. This is clearly seen from the part shown in the left half of the figure.

By this concept, the following process sequence can be achieved. First of all, the inner mandrel 16 is moved from the dies 7 and 8 having ends opposite the hollow shaft and into the hollow shaft 5 in the position shown in FIG. 5. This can be done by any suitable means (not shown) provided at the outer ends of the dies 7, 8. For this purpose the inner mandrel can for example protrude through the dies 7, 8 which are outer ends. Under local internal pressure, the two inner cams are shaped in the manner shown.

Next, the inner mandrel 16 is retracted outward enough to expose the zone of the next milling recess 4b so that internal pressure acts on the zone of the hollow shaft, and then forms the cam 6b. Deformed inside the milling recess and preventing friction between the inner wall of the tube and the V-shaped sealing ring 17 on the inner mandrel (160 degrees inner mandrel 16) when the material from the tube end is moved axially simultaneously. Is moved inward by the amount of material supplied.

After the molding of the second cam 6b pair, when the internal pressure is removed, the sealing force on the V-shaped sealing ring 17 is reduced to the minimum (the original elasticity of the sealing ring). The inner mandrel 16 is moved further outward and then the next pair of cams 6a are molded.

Even in this embodiment, in each processing step (shaping of the cam occurs step by step from the middle of the shaft to the end as described many times in connection with the embodiment described above), the material is not disturbed from the end and is not disturbed in pressure. Optimal material transfer is achieved because no deformation has yet occurred in the unstrained zone.

In order to increase the application of the method according to the invention to a number of other possible embodiments, a semi-finished starting product for the hollow shaft 5 is shown in FIG. 6a, which has six cams. It is molded into a camshaft and processed in the state shown in FIG. 6 by conventional methods such as upsetting of hollow shafts, cross rolling and the like. The stack of material 19 is formed at a location that is shaped to counteract the reduction in wall thickness and any inadequate ductility of the material. The semi-finished starting material is suitable for processing in the apparatus shown in FIGS. 1 and 2 and also reduces material flow in view of the lamination of the material.

The present invention is particularly useful for producing elongate hollow bodies with many different applications in the automotive industry.

Claims (13)

In a method for producing a long hollow body having at least one protrusion, in particular a camshaft, using a high internal pressure molding method (hydroforming method), The projection (cam) is a method for producing a long hollow body having a projection, characterized in that the material is preferably molded individually or continuously while feeding the axial direction. 2. A method according to claim 1, wherein said shaping starts at said protrusion located furthest from said feeder and is stepwise processed towards said feeder. The elongated hollow body according to claim 1 or 2, wherein the protrusions are formed continuously, individually or in a group against the pressure and / or the pressure of the movement controllable punch. Manufacturing method. 3. A method according to claim 1 or 2, wherein said manufacturing step is carried out in different zones. The method of claim 1 or 2, wherein the locally selective shaping of the protrusions is controlled by one or more mandrels which are introduced into the hollow body and can be moved longitudinally within the hollow body to conceal the position of the protrusions which are not simultaneously molded. Method for producing a long hollow body having a projection characterized in that. 6. A method according to any one of the preceding claims, wherein a multi-walled semifinished article in the form of a hollow body is processed. Apparatus for performing a method according to any of claims 1 to 6, Milling recesses 4 for forming the protrusions 6 are provided, and the multi-part forming apparatus 1, 2 for receiving the hollow body 5, and Two opposing coaxial dies 7, 8 which act on each end of the hollow body for upsetting the hollow body and are provided with a coaxial passage 9 for feeding the pressure medium into the hollow body. Apparatus comprising a. The device according to claim 7, for carrying out the method according to claim 1, wherein at least a part of the milling recesses 4 move perpendicularly to the longitudinal axis of the hollow body. And an individual punch (11a, 11b) which can be provided. An apparatus according to claim 7, for carrying out the method according to any one of claims 1, 2, 4 and 6. And at least one device provided with a plurality of mold necks each having a different number of milling recesses. 10. Apparatus according to claim 9, characterized in that the shaping device (1,2) of the two parts comprises a plurality of mold necks with a plurality of milling recesses which increase from locator to locator. An apparatus according to claim 7, for carrying out the method according to any one of claims 1, 2, 5 and 6. And at least one hollow inner mandrel (16) which can move longitudinally within the hollow body (5) and can be inserted into each end of the hollow body. Device according to claim 11, characterized in that the inner mandrel (16) is provided at least at an end projecting into the hollow body (5) with a sealant (17) fitted against the inner wall of the hollow body. . 13. Device according to claim 11 or 12, characterized in that the coaxial passageway (9) in the die (7,8) has a diameter through which the inner mandrel (16) can be inserted inside the die (7,8). .