The present invention relates to a camshaft with a functional component as an integrated insert as casting and the manufacturing process.
More specifically, the invention relates to a process for the production of camshafts with at least one functional component integrated in the shaft body, taking into account that the material of both the functional component and the body are of different materials; as well as camshafts produced by this process for internal combustion engines.
In the state of the art, a number of processes are known for the manufacture of camshafts, in their most common version camshafts are manufactured from one-piece iron casting; processes for the manufacture thereof are also known by the assembly of the different functional components of the camshaft in a tube, in order to obtain the final part.
Following the chronology for the manufacturing camshafts, the first ones were made of cast iron, because the properties of this material were sufficient for the functional requirements of the internal combustion engines of those times; this technology is still in use. The process of manufacturing these camshafts consists of generating a sand mold that forms the negative design of the shaft to be manufactured, that is, that it forms the silhouette of the shaft and that in turn has a feed channel through which the molten material will enter. Once the sand mold is generated, the molten iron is emptied through the feed channel, the molten iron will take the shape of the mold and once cooled it will generate the desired shaft.
In this same line, some variants of this type of camshaft that appeared later carry a hole in the body, with the purpose of reducing the weight of the same to improve the performance of the internal combustion engine. This process varies from the previous one in the fact that inside the sand mold a glass or sand element is placed, called core, which will avoid the entry of the molten material in such area, thus leaving a hollow in the desired place of the shaft generated.
When the demands of the internal combustion engines began to change, requiring a greater resistance to wear and or compress strength of its components beyond what had been achieved so far through the hardening processes such as flame, induction, TIG (tungsten inert gas), and austempered; combined with the requirement of a lower weight, the industry developed the camshafts assembled, that is, all the components of the camshaft are assembled one by one in a tube (or at the same time—hydraulic hydroforming), all of them usually made of steel.
In the state of the art for the assembled shafts, several assembly processes appeared, changing between them the way to achieve the mechanical grip between the components and the tube, the processes ranging from one involving the knurling of tube and grooving of functional components, to another process where the functional components are heated to dilate them and slide them through the tube and then the part contracts.
Taking the last process as an example, this is achieved by manufacturing separately each of the components of the shaft, such as cams, supports, tail, nose, drags and the tube where all the previous ones are assembled; the manufacturing process of these varies according to their complexity, being able to be machined, sintered, forged or printed. Once having the aforementioned components, all the components are transferred to the assembly cell, where the component that will serve as a reference for the location and assembly of all others is assembled by mechanical pressure (press fit), usually it is the nose, and the adjustment is generated due to the mechanical interference between both parts.
After having the tube with the reference component assembled, the tube is placed vertically and one by one the missing components are placed, which are heated previously and assembled one by one; the heating is done through an induction coil (magnetic field) by the inner bore of each component.
Once heated, the component is taken and placed in the tube body, in the longitudinal and angular position required according to the final design. Once in place, the piece is cooled. The process of heating the components is to expand the inner diameter to avoid the design interference and can slip through the tube, and when cooled the diameter will return to its original size. It should be noted that there is also a designed mechanical interference between the pipe diameter and the component hole to ensure mechanical grip.
Having completed the assembly of all the components that are attached to the shaft, it is usually done to assemble the tail, which comes under mechanical pressure as well as the nose. Upon completion of this, the assembled shaft is finished and ready to continue its machining process as required by the final design.
In series production for assembled camshafts, these processes require a large investment in technology and require specific machinery and equipment. Taking as a reference the process described above, this technology consists of the robotic arms that will assemble the parts, since extreme heating and placement of the components requires extreme precision and a human operator could not achieve such; it also refers to the internal borehole heating machine of the components. All this investment of technology and machinery represents a disadvantage in terms of the final cost of the part and the speed of manufacture.
Another disadvantage of this assembled camshaft process is that in larger shaft diameters as required, for example, for commercial vehicle engines, the forces necessary for assembly increase disproportionately, as well as the time required for assembly the size of robots and heating machines is increasing, and therefore the cost of manufacturing is also increasing due to the machinery required to achieve this.
Taking into account the above-described background, the present invention proposes a solution to the present technical problems by providing a manufacturing process for obtaining a camshaft which combines the benefits of the camshafts manufactured through the foundry and those manufactured by assembly, that is, to have a higher speed of manufacture, not being limited by the size of the camshaft, obtaining a complete piece from the beginning, increasing the resistance of the functional component that requires it through that this same component is of another material and is inserted directly from the molding process prior to the casting and in turn obtaining the required lightness that is so much sought in the internal combustion engine.
The objective of the invention is to provide economical and capable of being used in series on an industrial scale for the manufacture of camshafts with inserted functional components such as cams, supports, drive wheels, control discs, for the production of camshafts. The functional components must be able to be produced with materials of different characteristics and properties related to other materials and the connection between the functional components and the carrier shaft must exhibit a great mechanical resistance in the circumferential direction (torque transmission) and in the longitudinal direction of the shaft carrier.
The present invention relates to a camshaft (30) with a functional component as an assembly insert and the manufacturing process.
More specifically, the present invention relates to a process for the industrial scale production of camshafts manufactured by the casting process with at least one functional component (1) as an assembly insert capable of withstanding the mechanical forces in the circumferential direction (torque transmission) and in the longitudinal direction of the carrier shaft, taking advantage of the rapid fabrication of the cast iron process and the advantage of having the elements subject to higher stresses made, preferably of steel, as in process of assembled shafts.
The functional components such as the cams, the supports, the drive wheels, the control discs, are produced separately, by some manufacturing process such as machining, forging, sintering or printing of a A-type material, preferably steel, they have an internal cavity (10) of suitable geometry through which the B type cast material, preferably iron, passes to be joined to the shaft made by casting during the solidification process, and thus allow the correct fastening for torque transmission and longitudinal gripping.
As shown in
In turn, some preforms called heaters (11a, 11b) are produced separately, of foam material (made by the lost foam process) or similar material useful like plastic or others, which will allow hot metal pass and serve to heat each of the functional components (1). These heaters (11a, 11b) depend on the size and shape of the geometry of each functional component (1), but always keeping in mind that they must cover at least 80% of the upper and lower surface of component (1) and must cover the edges in the change of section that is present in the geometry of the functional component, i.e. the change that occurs between the upper or lower face and its nearest side.
The function of these heaters (11a, 11b) is to heat the functional component (1) from the outside of its geometry, since the inside will be heated by the melted material passing through the bore (3) and will fill up the internal bore (10). Since the edges or section changes are points where it is easier to lose heat by the thermodynamic laws, that is why they must be covered with the heaters (11a, 11b). The advantage of heating the functional component (1) in this way is that the thermal shock of the melted material with the material of the functional component (1) will not be so aggressive and the formation of carbides in the melted material will be avoided.
As shown in
It should be noted that the functional component (1) which comes into contact with the melted material A-type does not reach the required temperature to achieve its melting point, thereby avoiding deformations in both the internal and external geometry and the chemical bonding of both materials.
Important features to consider for the functional component (1):
Important Features to Consider in the Camshaft Manufacturing Process:
In the process of the present invention, cast material preferably cast iron has a use range for pouring between 1390 and 1450° C. For the inoculant the material used is Ferro-silicon, enriched with element strontium.
Number | Date | Country | Kind |
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MX/A/2016/010930 | Aug 2016 | MX | national |
Filing Document | Filing Date | Country | Kind |
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PCT/MX2017/000096 | 8/22/2017 | WO | 00 |