WO2018104339A1

WO2018104339A1 - Method for producing cams, camshafts and camshaft modules and cams produced in such a way

Info

Publication number: WO2018104339A1
Application number: PCT/EP2017/081578
Authority: WO
Inventors: Marko CURLIC; Aaron PFITSCHER
Original assignee: Thyssenkrupp Presta Teccenter Ag; Thyssenkrupp Ag
Priority date: 2016-12-06
Filing date: 2017-12-05
Publication date: 2018-06-14
Also published as: DE102016123557A1

Abstract

The present invention relates to a method for producing cams (10) for camshafts, in which the following steps are carried out: a) providing at least one cam (10) made of electrically conductive material, in particular of metal, and then b) machining the cam (10) by electrochemical machining, wherein the cam (10) forms the anode and a tool forms the cathode, an electrolyte is introduced between the cam and the tool, and an electric voltage is applied to the cam and the tool for removing cam material.

Description

Method for producing cams, camshafts and

Camshaft modules and cams produced in this way

description

The invention relates to a method for producing cams for camshafts and a cam produced in such a way for use in a built

Camshaft. Furthermore, the invention relates to a method for producing camshafts and a method for producing camshaft modules.

Methods of manufacturing cams and assembled camshafts, such as hydroforming or hydroforming techniques, are known. In built camshafts, the cams and the shaft are made separately and by a shaft-hub connection force and

positively connected. In hydroforming processes for producing a press connection between the shaft and the hub, hollow shafts are used to introduce forces into the shaft.

A method for producing non-rotationally symmetrical rings and cam rings is known, for example, from DE 10 2006 006 029 B3. The

Cam rings are separated from a rotationally symmetrical steel tube and formed by stamping forming in a non-rotationally symmetrical shape. Subsequently, the formed ring is tempered and the end faces hard worked. The formed rings are connected to a camshaft tube, which is expanded by a hydroforming process.

WO 00/51759 A1 discloses a method for producing a camshaft from a tube, wherein support rings or hardened cams are produced in a separate method and these are connected to the camshaft. In this case, the cams and the thin-walled tube are inserted into a hydroforming forming tool and connected by axial forces introduced into the tube by means of the internal high-pressure forming tool. The axial forces are generated by a pressure medium and expand the tube, so that a positive and positive connection between the cam and tube is made.

However, the known methods of manufacturing cams and assembled camshafts are disadvantageous in several respects. The cams are time-consuming individually produced in various process steps, such as cutting, forming and tempering. For internal high-pressure joining for producing the shaft-hub Connection can tensions, in particular by the plastic deformation of the shaft, occur in the shaft and it must be kept certain distances between the cams, since when chamfering forms in the shaft. A compact design of the camshaft is therefore not given. It is also not possible to produce camshaft modules with the known methods.

The invention has for its object to provide a method for producing cams for camshafts, which is improved in view of a process optimization for the production of cams. The invention is further based on the object of specifying a method for producing camshafts and a method for producing camshaft modules. Furthermore, the invention has the object, a cam for use in a built

Specify camshaft.

This object is achieved by a method for producing cams for camshafts with the features of claim 1.

Furthermore, the object with regard to the method for producing camshafts by the subject of claim 10 is achieved. With regard to the method for producing camshafts, the object is achieved by the subject matter of claim 11. With regard to the cam, the invention is solved by the subject matter of claim 12.

The invention is based on the idea to provide a method for producing cams for camshafts, in which the following steps are carried out: a) providing at least one cam of an electric

conductive material, in particular of metal, and then

b) machining the cam by electrochemical removal, wherein the cam is the anode and a tool is the cathode, an electrolyte is introduced between the cam and the tool, and an electrical voltage is applied to the cam and the tool for removing cam material.

An advantage of the invention is that the cams according to the invention can be machined in a single step, without any intervention between tools and cam a mechanical contact is formed. Therefore, mechanical loads, microcracks and structural changes in the cams are largely avoided. Also, such a cam has a lower residual stress than the known cams. Another advantage is that the tools for machining the cams do not wear out and the cams do not have to be additionally deburred. Furthermore, almost all metals, in particular high-alloyed and hardened materials, can be processed electrochemically. The cams are therefore one of the requirements of the valve train

corresponding conductive material produced. The cam is connected as an anode and the processing tool as a cathode to a voltage source, in particular a DC voltage source, wherein cam and tool are preferably arranged in an aqueous electrolyte solution. In the

Electrolytic solution takes place a charge exchange between the cam and tool, whereby the cam is machined without contact targeted with the highest precision.

Overall, the invention provides a method of manufacturing a cam that saves cost, time and is easy with high precision.

Preferred embodiments of the invention are specified in the subclaims.

In a preferred embodiment, step a) of the method includes forming a semi-finished product to form the cam. During forming, for example, a cast starting material is formed into a cam, wherein the material maintains its mass and its cohesion. Advantageous on

Forming is the high material utilization, low production time and high workpiece quality, z. B. by an improved fiber flow.

Preferably, the cam is forged. In other words, as

Material used for the cams a steel or sintered material. Steel cams are forged as a blank and then machined. With sintered cams, the cam geometry can be made more accurately, so less

Machining after production is required. Forging is characterized by a greater freedom of design and a wide range of options for heat and surface treatment. In contrast to machining, tougher workpieces with an improved fiber profile can be produced. In a further preferred embodiment, step a) of

Procedure the surface grinding of the cam. Surface grinding has the advantage that it can be used well for machining hard surfaces, such as the outer contour of the cams. Furthermore, while a high dimensional and

Shape accuracy can be generated.

It is further preferred that step a) of the method comprises heat-treating the cam, in particular hardening the cam. By the

Heat treatment or hardening increases the mechanical resistance of the cam by deliberately changing and transforming its structure.

Heat treated, especially hardened cams have an optimal

Increase in strength and high wear resistance.

In a particularly preferred embodiment, step b) of

Method of producing an inner contour of the cam. Specifically, the inner contour of the cam is processed electrochemically. The advantage of this is that no additional clearing of the inner contour is necessary, and thus costs can be saved.

It is further preferred that step b) of the method comprises producing an outer contour of the cam. In other words, for example, chamfers and other arbitrary outer contours are produced electrochemically. It is particularly advantageous that by the inherent stress-free

Material removal soft transitions and high quality surfaces can be produced without burr formation.

Preferably, step b) of the method comprises producing a

End contour of the cam. The production of the end face contour by the electrochemical metal working has the advantage that not

tread-bound surface qualities, in particular average roughness depths <Rzl, can be produced. Furthermore, a profile grinding of the cams is no longer necessary because the surface quality corresponding to the requirements is already generated by the electrochemical machining. Furthermore, the

Reduced production costs, since there is no use of grinding mandrels and thus the handling is simplified. Further preferably, a plurality of cams are processed simultaneously in step b) of the method. Thus, several cams, in particular up to about 48 pieces, can be processed simultaneously electrochemically in one step. Compared to other manufacturing processes, process steps and process time can be reduced by eliminating the need to process the cams individually, such as: B. clamping between grinding arbors during grinding.

In the context of the invention, a method for the production of

Camshaft specified, in which the following steps are carried out in order:

a) rolling a shaft;

b) cooling the shaft and heating at least one cam made by the method of claim 1; c) prefixing the shaft and the cam;

d) Adjusting the end position of the cam on the shaft and

Balancing the temperatures of the shaft and the cam.

The camshafts so formed can be easily and inexpensively produced in a few process steps. In the first step of the method, the shaft is rolled in order to produce on the shaft a geometry on which the cam can be positioned accurately. Rolling is understood to mean a non-cutting cold forming process in which the existing surface profile of the toothed shaft is plastically deformed. It is pressed a roller burnishing tool with several cutting perpendicular to the outer surface of the toothed shaft to the rotating toothed shaft. The force is chosen so that the roller burnishing tool works non-cutting, but merely deforms the material. A flow of material from the teeth between the cutting edges and between the tooth flanks takes place.

In the second step, cooling the shaft and heating at least one cam, the shaft is cooled and the cam is heated so that the volume of the shaft is reduced under the influence of cold and the cam expands under the action of heat, so shaft and cam powerless can be joined. In other words, the circumference of the shaft is reduced

(Shrinking), and the circumference of the inner contour of the cam stretched so that the cams can be pushed onto the shaft. This has the advantage that the cams do not have to be pressed under high force on the shaft, which can lead to seizure or damage to the mating surfaces. Furthermore, costs can be saved, since the use of special oils for producing the press connection is not required.

In the third process step, the prefixing of the shaft and the cam, the cams are positioned axially on the rolled shaft exactly. The stretched cam is placed on the rolling geometry of the shaft to press-fit after balancing the shaft and cam temperatures.

In the last process step, the cams are aligned radially and axially on the shaft and the temperatures of the shaft and the cam are adjusted. Specifically, the components are set by means of force-displacement monitoring axial and angle-oriented to final position. This creates a non-positive and positive compression connection between the cam and shaft, wherein the cams are aligned according to the requirements of the valve train.

The pre-fitting may include pre-positioning, which may be performed powerless to the shaft so that the cam is arbitrarily aligned on the shaft. When pre-positioning is required because of the low coverage only a very small joining force. It is therefore advantageous for the subsequent joining to the end position if there is a defined position or angular orientation.

In the context of the invention, a further method for producing camshaft modules is specified, in which the following steps in this

Order to be performed:

a) providing a cylinder head cover, in particular with

integrated bearing shells;

b) rolling at least one shaft;

c) cooling at least one shaft and heating at least one cam made by the method of claim 1; d) Arrange, especially in the cups, and Vorfügen

at least one wave and the cam in the

Cylinder head cover; and e) Adjusting the end position of the cam on the shaft and

Balancing the temperatures of the shaft and the cam.

The camshaft modules produced in this way are characterized by a particularly compact design and weight reduction. Thus, the

Fuel consumption and emissions of vehicles lowered. Furthermore, the camshaft module according to the invention has low system costs

Processing and assembly advantages. It is particularly advantageous that the cams and camshafts can be joined in the cylinder head cover. Specifically, the shaft is cooled so that it can be joined powerless in the cylinder head cover or bearing shells and at the same time with the heated cam. This is with camshafts, for example, through

Innenhochdruckfügeverfahren be prepared, not possible because the cams are already joined before mounting the cylinder head. In addition, the method may alternatively or additionally comprise a single or a combination of a number of features mentioned above with reference to the method for producing camshafts.

In the context of the invention, a cam for use in a built-up camshaft, which is produced by the method according to the invention, is furthermore specified. Preferably, the cam is forged, hardened and

ground flat. Subsequently, the cam with the ECM procedure

(electrochemical metal working) edited. The cam may alternatively or additionally comprise one or a combination of a number of features previously mentioned in relation to the method for producing cams for camshafts.

In summary, the invention enables the production of cams for camshafts, wherein in one step, the inner contour, Einführfasen and the outer contour of the cam can be produced. That's why

Machining process easy to perform and requires no high time and / or cost. Otherwise, the procedure can be used individually

Saved work steps such as spindles, broaching and grinding can be saved. Furthermore, the number of teeth of the cam can be changed as desired and it is not surface-bound surface qualities produced. In the following, the invention will be described in greater detail with reference to the accompanying diagrammatic drawings with reference to FIG

Embodiments explained.

Show it

Fig. 1 is a perspective view of a cam after a

inventive embodiment;

Fig. 2a is a perspective view of a cam after another

inventive embodiment;

2b shows a section through the cam of FIG. 2a,

Fig. 3 shows a sliding cam in section after another

inventive embodiment;

In Fig. 1, a cam 10 according to an embodiment of the present invention is shown. The cam has a non-rotationally symmetrical or oval outer contour 12 with a wall thickness corresponding to the requirements. The cam 10 further includes an opening 15 for engagement with a camshaft

to be connected. The outer circumference of the opening 15 forms the inner contour 11 of the cam 10. Between the outer surface 16 and the inner contour 12, an insertion chamfer 13 is arranged.

The cam 10, in particular the Einführfase 13, the inner contour 11 and the outer contour 12 are, with the ECM method (electrochemical

Metalworking). In this case, the cam 10 in an electrolyte solution, for. As an aqueous solution of sodium chloride or sodium nitrate, introduced and applied as an anode with a voltage. In the solution, it is processed with a tool cathode contactless by a charge exchange, wherein an electron current detaches metal ions from the cam 10 and thereby the

produces desired shape or surface quality.

In Fig. 2a is a cam 10 according to another invention

Embodiment shown. The cam 10 has an oval outer surface 10 with an opening 15. The opening 15 serves to receive a camshaft and is formed with an inner contour 11 corresponding to the shaft. To simply connect the cam with the shaft, axially set back end faces 14 with Einführfasen on the outer surface 16 of the cam 10 are arranged. As shown in Fig. 2b, the axially set back end surfaces 14 and

Einführfasen be designed differently. Furthermore, the opening 15 and the outer contour 12 can vary according to the requirements of the valve train or the camshaft.

The protruding profile and the outer contour 12 are produced by the ECM method.

Fig. 3 shows a cam 10, in particular a sliding cam, according to another embodiment of the invention. The sliding cam 10 is formed of a shift gate 18 and left and right thereof arranged cam tracks 17, with each of the cam tracks 17, a different valve lift can be adjusted. The sliding cam may include a plurality of shift gates 18 and any number of cam tracks 17. The shift gate 18 serves for the axial displacement of the cam 10. The inner contour 11 has

Recesses 19 on to connect the cam 10 with a shaft, in particular a rolled shaft. Particularly preferably, the sliding cam 10 is rotatably but axially slidably connected to the shaft. The inner contour 11 may further comprise torque transmitting depressions, not shown. The inner contour 11 with the recess and outer surfaces are manufactured or processed by the ECM method.

Sliding cam 10 have the advantage that a shift of the switching points to higher or lower speeds is possible by splitting a map into several valve lift. Furthermore, valve / cylinder shutdown can be realized. This allows a fuel consumption reduction and thus the reduction of C0 ₂ emissions. Reference character list cam

inner contour

outer contour

chamfer

axially set back face

opening

outer surface

cam track

shift gate

recess

Claims

claims

Method for producing cams (10) for camshafts, in which the following steps are carried out:

a) providing at least one cam (10) made of an electrically conductive material, in particular of metal, and then b) machining the cam (10) by electrochemical removal, the cam (10) forming the anode and a tool forming the cathode, an electrolyte is introduced between the cams and the tool and an electrical voltage is applied to the cam and the tool for removing cam material.

Method according to claim 1

dad u rch nets that net

Step a) comprises the forming of a semifinished product to form the cam (10).

Method according to claim 2

dad u rch nets that net

the cam (10) is forged.

4. The method according to any one of the preceding claims

dad u rch nets that net

Step a) comprises the surface grinding of the cam (10).

5. The method according to any one of the preceding claims

dad u rch nets that net

Step a) comprises heat treating the cam (10), in particular hardening the cam (10).

6. The method according to any one of the preceding claims

dad u rch nets that net

Step b) comprises the production of an inner contour (11) of the cam (10).

7. The method according to any one of the preceding claims

dad u rch nets that net Step b) comprises producing an outer contour (12) of the cam (10).

8. The method according to any one of the preceding claims

dad u rch nets that net

Step b) comprises producing an end contour of the cam (10).

9. The method according to any one of the preceding claims

dad u rch nets that net

several cams (10) are processed simultaneously in step b).

10. Method for producing camshafts, in which the following steps are performed in this order:

a) rolling a shaft;

b) cooling the shaft and heating at least one cam (10) made by the method of claim 1; c) inserting the shaft and the cam (10);

d) adjusting the end position of the cam (10) on the shaft and

Balancing the temperatures of the shaft and the cam (10).

11. A method of manufacturing camshaft modules in which the following steps are performed in this order:

a) providing a cylinder head cover, in particular with

integrated bearing shells;

b) rolling at least one shaft;

c) cooling at least one shaft and heating at least one cam (10) made by the method of claim 1;

d) Arrange, especially in the cups, and Vorfügen

at least one shaft and the cam (10) in the

Cylinder head cover; and

e) Adjusting the end position of the cam (10) on the shaft and

Balancing the temperatures of the shaft and the cam (10).

12. cam (10) made according to one of claims 1 to 10 for use in a built camshaft.