EP1320433A1

EP1320433A1 - Method for producing a hollow shaft, in particular a camshaft and a camshaft produced according to said method

Info

Publication number: EP1320433A1
Application number: EP01986277A
Authority: EP
Inventors: Bodo Furchheim; Franz-Josef Schleifstein
Original assignee: Salzgitter Antriebstechnik GmbH and Co KG
Current assignee: Salzgitter Antriebstechnik GmbH and Co KG
Priority date: 2000-09-29
Filing date: 2001-09-24
Publication date: 2003-06-25
Also published as: WO2002028564A8; AU2002223431A1; WO2002028564A1; DE10194184D2; JP2004510585A; US20040034975A1; US6961998B2

Abstract

The invention relates to a method for producing a hollow shaft, in particular a camshaft according to an internal high-pressure forming (IHF) process. According to said method, cams and/or machine elements are mounted at intervals onto the outer surface of the hollow shaft, depending on the use of the latter, by a non-positive and/or positive fit, in a position appropriate to their function. The invention also relates to a hollow shaft produced according to said method. The invention aims to improve the efficiency of the method. To achieve this: the cams and/or machine elements required for the function of the hollow shaft (1) are pushed onto and positioned on the shaft in a location and position related to their function, when the hollow shaft is placed in the forming tool; an element (5) with approximately the same external diameter as the internal diameter of the hollow shaft is placed in at least one end of said shaft; the hollow shaft together with the cams and/or machine elements that have been pushed onto the same and the inserted element are placed in an IHF tool; once the IHF tool has been closed, a medium is caused to act under the required high-pressure in the hollow shaft.

Description

Process for producing a hollow shaft, in particular camshaft ^ and hollow shaft produced thereafter

The invention relates to a method for producing a hollow shaft, in particular camshaft, according to the hydroforming process (IHU), whereby on the outer lateral surface of the hollow shaft, adapted to its use, cams and / or machine elements in a non-positive and / or positive position and position are distributed in a functionally appropriate manner. The machine elements can be, for example, gear wheels, drives, cams or the like. A preferred area of application is camshafts for motor vehicle engines.

It is known to produce camshafts for motor vehicle engines by means of the hydroforming process (IHU), in that a hollow shaft is expanded by the action of pressure after the cams have been pushed on. Liquids are preferably used as the pressure medium. The pushed-on cams are non-positively and positively connected to the shaft (DE 34 09 541 A1). Even if this method is very well suited for the application of machine elements and cams to the shaft and is used in practice, shafts produced in this way still have the defect that function elements, which are manufactured separately in another method, are connected to the shaft at their ends have to. Bolts with an appropriate fit are inserted into the shaft and non-positively connected to the shaft by means of pins. It is also common to weld or press these bolts into the shaft. These bolts either protrude from the shaft and are threaded in this area, or they have an internal thread.

The general trend in mechanical engineering, especially in the construction of motor vehicle engines, is to reduce the weight with at least the same output wrestlers. For this purpose, the camshafts have been used as hollow shafts for some time. The experts have endeavored to manufacture them in such a way that the necessary machine elements are connected to the hollow shaft with a high degree of safety and low manufacturing costs.

Hollow shaft applications exist in which a connection to drives is required at one or both ends. For this purpose, it is known to design these machine elements in such a way that they are designed as a sleeve which are pushed onto the shaft and fastened. The machine element is designed as a flange at the outer end to which the coupling takes place (DE 38 00 912 A1). There are shortcomings with regard to the high mechanical manufacturing effort for the element, the exact fit on the shaft and the non-positive connection to the shaft. The connection can also be established by IHU, but does not remedy all defects.

It is known to deform the ends of the hollow shaft by kneading or upsetting so that thickening takes place, the inside diameter is reduced and the outside diameter is brought to a level by material accumulation in such a way that a machine element applied in a known manner is fastened. The end of the shaft is to be compressed using the IHU method so that a collar or flange is created. These process steps can also be carried out by kneading or round kneading (DE 197 10 84.8).

Together, all known methods for producing elements connected to the hollow shaft for the purpose of coupling or storage have the disadvantage that the method of producing and non-positively and positively connecting to the shaft requires at least one additional process step. In addition, there is mechanical processing. For example, joining processes are required and subsequent hardening and / or To edit. A fit is also required, which in turn increases the effort.

The object of the invention is to make the method described in the introduction more rational.

According to the invention, this object is achieved according to claim 1. Claims 2 to 1 1 show advantageous refinements of the method. A hollow shaft produced according to the invention is defined in claim 12; Claims 13 to 18 relate to expedient configurations of this hollow shaft.

According to the invention, two methods which are known per se independently of one another are combined. The IHU process with upsetting is used almost simultaneously.

Depending on their function, machine elements, for example gearwheels and / or cams, are arranged on the hollow shaft and pushed onto the hollow shaft in their function-related position. This hollow shaft, pre-equipped in this way, is inserted into an hydroforming tool. In a known manner, a plunger is moved in the axial direction at least against one end of the hollow shaft while the pressure medium of the hydroforming tool works simultaneously. As a result, the hollow shaft is expanded relatively strongly at those locations where no machine element is positioned on the outside, while in the area where a machine element is positioned, it is non-positively and positively connected by the internal pressure. At the same time, with the action of pressure and the movement of the plunger in the axial direction, the hollow shaft with the inserted element is compressed, thereby thickening the material and positioning the element in the hollow shaft in a force-fitting and form-fitting manner and thus serving as a conclusion due to its design adapted to the use of the hollow shaft the hollow shaft and connection to other units. Depending on the geometric design of the element used, this compression causes material of the hollow shaft to be brought in front of and / or behind it. So that the element is locked in the axial direction. If an axially continuous bore is made in the element, then the pressure becomes effective on both sides of this element.

According to the use of the hollow shaft, preferably as a camshaft, i.e. When it is mounted, connected to the corresponding units of a motor or other drive elements, the element is mechanically separated with the hollow shaft and a flat surface is created. For example, a hole or a thread is made in this.

It is also possible, adapted to the function of the hollow shaft, to mechanically process the element after the connection to the hollow shaft in such a way that a bolt or a threaded bolt remains. In this embodiment, the shape of the element can also be prefabricated before it is introduced and connected to the hollow shaft.

Another embodiment of the solution is that the element forms a unit with the stamp of the hydroforming tool, which acts axially at the same time as the pressure medium, and protrudes into the hollow shaft. After completing the IHU procedure, the stamp with the element is pulled out. Depending on the design of the hydroforming tool and the diameter of the element, the end of the hollow shaft is given the shape required for its function. The final dimension is produced by known mechanical processing.

If the element remains in the hollow shaft, the element is locked in the axial direction, that is to say connected non-positively and positively to the hollow shaft. It may also be advantageous to reduce the diameter of the element between its two ends, which improves the connection to the hollow shaft.

Depending on the intended use of the hollow shaft, it may be advantageous to separate the hollow shaft on the end face in the region of the element after the element has been pressed in, so that a flat surface is produced. The cutting is expediently carried out by cutting. An axially extending thread can subsequently be introduced into this surface in order to fasten any part or machine element.

The advantage of the method according to the invention is that two highly productive methods, hydroforming and upsetting, are combined at the same time in one method using machine elements that are easy to manufacture and can be connected to the hollow shaft. This results in very short manufacturing times.

A further advantage is that the method and the special design of the machine elements, in particular the elements to be inserted into the hollow shaft, mean that very little reworking is required. The hollow shafts produced by the process, in particular cam shafts for motor vehicle engines, are extremely light and are inexpensive.

The prior art and the invention are described using exemplary embodiments. The associated drawings show:

1a and b embodiments of the ends of a hollow shaft according to the prior art,

Figure 2 partial section through an IHU tool with inserted

Hollow shaft 3a to 3c execution of a hollow shaft with a fixed element,

FIG. 4 partial section through a hollow shaft with an inserted element and attached cams, and

Figure 5 Execution of one end of the hollow shaft without an element remaining in it.

FIGS. 1 a and 1 b show how one end of a hollow shaft is manufactured according to the prior art. The hollow shaft 1 is treated in the region of its one end by a kneading method known per se or also by upsetting such that if the outer diameter D _{A of} the hollow shaft 1 remains, the inner diameter Dj of the hollow shaft 1 is reduced to the diameter D _{B of} a bore 2. This means that material accumulation occurs in the end area. This upsetting takes place by heating, hammering or in another forming process. Either the bore 2 is made during this process and then has to be reworked mechanically, or the end of the hollow shaft 1 is completely closed and the bore 2 or a thread 3 is then made after the end face has been machined.

The method according to the invention is described with reference to FIG.

A hollow shaft 1 is inserted into a known hydroforming tool 4, the outer diameter D _{A of} which corresponds to the inner diameter of the tool 4. At the same time, an element 5 whose outer diameter D _{E is} slightly smaller than the inner diameter D | the hollow shaft 1, inserted into the hollow shaft 1 at a predetermined location. The tool 4, which is usually in two parts, is closed. A plunger 6 of the tool 4 is moved axially under high pressure, with simultaneous action of a pressure medium in the hollow shaft 1, against its end face. there The material of the hollow shaft 1 compresses in such a way that the element 5 is enclosed by the material of the hollow shaft 1 to such an extent that the previous inner diameter D _{f of} the hollow shaft 1 is reduced to D ,,. The element 5 is thus connected to the hollow shaft 1 in a positive and / or non-positive manner under high pressure. An end section is cut off in a known manner on a line 7, preferably by means of cut-off grinding, and a flat surface is formed, into which, for example, a thread is introduced.

Different embodiments of the element 5 are shown in FIGS. 3a to 3c. Depending on the action of the stamp 6 and the pressure medium and the geometry of the element 5, the material of the hollow shaft 1 is compressed in front of and behind the element 5 and the inner diameter D, of the hollow shaft 1 is reduced to D _π . The stamp 6 of the IHU tool presses in the direction of the arrow. In the embodiment according to FIG. 3b, the pressure medium acts through the bore 8 on both sides of the element 5, although it only penetrates from one side. This design of the element 5 is particularly advantageous if the element 5 is arranged further away from the end of the hollow shaft 1. In FIG. 3a, the stamp 6 acts on one side and the printing medium on the other side in order to achieve the material accumulation.

In Figure 3c, the element 5 is conical.

FIG. 4 shows how a machine element 9 or cam is simultaneously applied to the hollow shaft 1 in the area of the element 5. According to Figure 3b, the material is piled up on both sides. Surprisingly, it has been found that at this point of the hollow shaft 1 its outer diameter D _A increases and the machine element 9 applied there is simultaneously connected to the hollow shaft 1 in a force-fitting and / or positive manner. This example shows how previously separate procedures can be carried out in a single IHU procedure. This is an advantage of the method according to the invention.

Figure 5 shows another embodiment of the method. The punch 6, which at the same time pushes acting axially with the pressure medium, is firmly connected in its front part with the otherwise separate element 5, the punch means 6 is formed as a front side member 5. ¹ The material flow resulting from the method is limited by the element 5 ', the outside diameter of which is <the inside diameter of the hollow shaft 1, when thickening or compressing inwards, and thus material is locally outwards but also inwards in front of the element 5' brought. In contrast to the examples in FIGS. 2 to 4, the complete pressure stamp 6, 5 ^{1 is} removed from the hollow shaft 1 after the IHU process has ended. The stamp 6 can, however, also be connected to the hollow shaft 1 in a non-positive and positive manner by a corresponding design of the element 5 'and the hydroforming tool and is mechanically separated from the element 5' after the end of the process.

The elements 5 and machine elements 9 or cams are produced in a known manner in a preceding process.

Claims

claims:

1. A method for producing a hollow shaft, in particular a camshaft, according to the hydroforming process (IHU), with the function and distribution of the cams and / or machine elements in a positionally and positively position and position on the outer lateral surface of the hollow shaft, adapted to their use be applied, characterized in that

the cams and / or machine elements required for the function of the hollow shaft are pushed and positioned on the hollow shaft when inserting the hollow shaft at the function-related location and position;

an element with approximately the same outer diameter as the inner diameter of the hollow shaft is positioned in at least one end of the hollow shaft;

- The hollow shaft with the cams and / or machine elements pushed onto it and the inserted element is inserted into an IHU tool;

after the IHU tool has been closed, a medium is brought into effect in the hollow shaft under the required high pressure;

at the same time as the medium acting from the inside, at least one plunger is pressed axially against at least one end face of the hollow shaft, so that the See pressure of the stamp caused material flow to fill the IHU shape, whereby the element is enclosed by the material of the hollow shaft and the cams and / or machine elements by the expansion of the hollow shaft with a positive and / or positive fit

Hollow shaft are connected; and that

the end of the hollow shaft which is closed by the element is mechanically machined in accordance with the function of the hollow shaft.

2. The method according to claim 1, characterized in that the axially acting against the end face of the hollow shaft stamp is formed at its end directed in the direction of the hollow shaft so that after completion of the hydroforming process by pulling out the

Stamp a defined recess is made as the end of the hollow shaft.

3. The method according to claim 1, characterized in that at the closed end of the hollow shaft by mechanical processing creates a flat surface and an internal thread or a hole is introduced into this.

4. The method according to claim 1, characterized in that a bolt or threaded bolt is worked on the element.

5. The method according to claim 3 or 4, characterized in that the element introduced into the hollow shaft has already obtained the approximate function-related shape in a previous mechanical process and is machined according to the IHU process and functionally.

6. The method according to any one of the preceding claims, characterized in that the machine elements, cams and elements are manufactured in a separate process.

7. The method according to any one of the preceding claims, characterized in that the end of the hollow shaft produced by the hydroforming process is mechanically reworked inside and / or outside.

8. The method according to claim 1 or 3 to 6, characterized in that the hollow shaft is separated according to the IHU method in the area of the introduced element by a machining process, preferably cut-off, that a flat surface is formed.

9. The method according to claim 8, characterized in that holes and threads are made in the flat surface.

10. The method according to any one of the preceding claims, characterized in that the machine elements and / or cams and / or elements are made of a different material than that of the hollow shaft.

1 1. The method according to claim 2, characterized in that the hydroforming tool is enlarged in its inner diameter in a defined area of the end of the hollow shaft to be produced, so that the

The outer diameter of the hollow shaft is increased in this area by the material flow.

12. Hollow shaft, in particular camshaft, manufactured according to one of the preceding claims, with cams and / or machine elements attached to the hollow shaft (1) depending on the use of the hollow shaft (1). elements (9) which are functionally connected to the hollow shaft (1) on the hollow shaft (1) expanded by internal high-pressure forming, characterized in that the hollow shaft (1) is at least one force and is positively closed, and that the element (5) is machined geometrically and mechanically adapted to the function of the hollow shaft.

13. Hollow shaft according to claim 12, characterized in that the element (5) has a bore (8) or an internal thread.

14. Hollow shaft according to claim 12, characterized in that the element (5) on its part extending over the hollow shaft (1) is designed as a bolt, pin or threaded bolt.

15. Hollow shaft according to claim 12, characterized in that the element (5) is a solid bolt and is provided with a phase on at least one side.

16. Hollow shaft according to claim 12, characterized in that the element (5) has an axially continuous bore (8).

17. Hollow shaft according to one of claims 12 to 15, characterized in that the element (5) has a reduced diameter in a region between its two ends.

18. Hollow shaft according to one of claims 12 to 17, characterized in that the element (5) is conical in its outer diameter towards one end.