Joints and connections – Rod end to transverse side of member – Rod and side deformingly interlocked
Reexamination Certificate
1996-03-12
2001-08-28
Dayoan, B. (Department: 3628)
Joints and connections
Rod end to transverse side of member
Rod and side deformingly interlocked
C403S282000, C074S445000, C029S509000
Reexamination Certificate
active
06280115
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to control shafts to which control elements are affixed and to a method for manufacturing such control shafts.
German Offenlegungsschrift No. 37 17 190 discloses a camshaft for controlling valves in internal combustion engines in which the camshaft consists of a cylindrical shaft member onto which control elements in the form of cams are pushed so as to be connected rigidly to the shaft. In that case the cams are designed as one-piece sintered parts having an aperture which is provided with radial projections to receive the shaft. The shaft is formed with regions having a slightly larger diameter in certain areas, the axial extent of those regions corresponding to the width of the control cams. As the cams are pushed onto the regions of enlarged diameter, the radial projections in the aperture cut grooves along the enlarged region and the material displaced from the grooves is evidently lost. An extremely torsionally rigid connection is formed in this way between the cams and the shaft member.
That document also discloses a method for the manufacture of the above-mentioned camshaft in which a first enlarged shaft region is formed and, after a first cam has been mounted on that region, further regions of enlarged diameter are formed in succession and, after each enlarged diameter region is formed, another cam is pushed onto that region.
German Offenlegungsschrift No. 44 23 107 discloses the manufacture of cams, such as those for controlling the intake and exhaust valves of an internal combustion engine, from a multiplicity of layers of flat stock. For this purpose, a number of layers of stock are punched out of a steel sheet, for example a cold-rolled steel sheet, and then mounted together to form a cam assembly. In the punching operation, an aperture is formed in each layer to receive a shaft member when assembled and, at a distance from the resulting shaft aperture and parallel with the shaft axis, the cam assembly has an opening with a diameter which is significantly smaller than that of the shaft aperture. A pin formed with a collar and having a length which is greater than the width of the cam assembly is then inserted through smaller opening in the assembly. A washer is mounted on the projecting end of the pin and is welded to the pin on the side facing away from the cam. This arrangement of a pin and a washer-prevents the sheet assembly from falling apart but it does not prevent relative displacement between the adjacent layers of flat sheet stock about the longitudinal center line of the pin. This requires separate laser welds along two opposed grooves in the shaft aperture.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a control shaft carrying a control element and a method for its manufacture which overcome disadvantages of the prior art.
Another object of the invention is to provide a control shaft arranged so that the control elements, in addition to being fixed in a torsionally rigid manner on the shaft member, are also fixed in both axial directions on the shaft member.
A further object of the invention is to provide a method for the manufacture of such a control shaft which is as efficient and economical as possible.
These and other objects of the invention are attained by displacing shaft material to raise a burr on the shaft member so as to secure the control element axially on the shaft member. The burr can be raised from shaft member by upsetting, for example.
In a particularly advantageous and simple embodiment, the burr which secures the control element axially in one direction is formed by pushing the control element onto a region of enlarged diameter of the shaft member. An additional burr, which secures the control element in the other axial direction, is separately produced on the other side of the control element.
The first burr can be raised in a particularly successful manner if the control element for the aperture which receives the shaft member has an edge with a sufficiently sharp contour. This can be accomplished successfully using control elements which are sintered in one piece, for example, but those are expensive to produce.
In an advantageous embodiment of the invention, the control elements are formed from a multiplicity of layers of flat stock mounted axially adjacent to each other. These layers are punched out of correspondingly thin steel sheets, thereby producing sufficiently sharp edges at the shaft opening for the displacement of shaft material when pushed onto the shaft member. To hold the individual layers of stock together reliably and to avoid the necessity for separate welds, the control element has an opening which is spaced from the shaft member aperture and which has its axis parallel to that of the shaft aperture to receive a clamping element which passes through the entire control element and presses the individual layers of flat stock axially together.
The burr raised on the enlarged diameter shaft region by the pushing on of the control element can be made to form an encircling bead by providing a circular aperture in the control element. However, a particularly torsionally rigid connection can be achieved if the aperture has projections which extend radially inwardly so that, as the control element is pushed on the shaft member, grooves are cut into the enlarged diameter region and a number of burr accumulations corresponding to the number of grooves is formed in the process.
The additional burr on the other side of the control element is raised by displacement of shaft material in a comparable manner. For this purpose a punch having a circular burr-forming opening with a sufficient clearance, for example, is slipped over the shaft member and forced onto the enlarged diameter region, displacing shaft material against the control element in the process.
The control shaft according to the invention can be produced in a particularly advantageous manner by a method in which a first region with an enlarged diameter is made on the shaft member, this region having a greater axial length than the width of the first control element, and the first control element is forced onto this enlarged diameter region to displace shaft material and raise the first burr in order to secure the control element axially. The additional burr is then raised by pushing the punch onto the enlarged diameter region so that the control element is clamped axially between the two burrs. To raise this burr, the burr-forming opening in the punch has a diameter which is slightly smaller than that of the corresponding enlarged diameter region of the shaft member.
The above-mentioned method can advantageously be carried out in a manner which reduces the cost by forming the control elements using a multiplicity of identical layers of flat stock which are punched out with corresponding apertures to form the aperture which receives the shaft member. During this process, additional identical openings also are formed in each layer of the flat stock with their axis parallel to and spaced from the axis of the shaft apertures. The individual layers of flat stock are then mounted together in the same orientation automatically to form an assembly of the layers, the aligned individual layer openings providing a continuous opening in the assembly. A pin which has a stop at one end, such as for example, a rivet-type fastener, and which has an axial length greater than that of the opening, is inserted through the opening. By then upsetting the pin axially to form another stop at the other end and provide a clamping element, the assembly of layers is permanently held tightly together. The second stop can also be formed in some other way, for example by pressing a ring onto the pin.
This arrangement prevents twisting of the individual layers relative to each other about the longitudinal center line of the clamping element.
The invention is not restricted to the exemplary embodiment described below. The control shaft can, for example, be a camshaft for controlling intake and exhaust
Beier Alfred
Distler Dietrich
Baker & Botts LLP
Dayoan B.
Miller William L.
Volkswagen AG
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