The invention relates to a method and an apparatus for producing a workpiece with internal toothing, especially an internal geared wheel, according to an apparatus for producing a workpiece with internal toothing, especially an internal geared wheel. Such internal toothings are produced by means of flow turning. A cup-like preform is pressed according to DE 198 30 817 A1 by means of tapered rollers during an advancing movement against a clamping chuck which has the external profile of the internal toothing to be produced. Said preform is reduced in its diameter, with the preform rotating relative to the tapered rollers. The material of the cylinder wall region of the preform flows into the profile of the clamping chuck, as a result of which the inner profile of the workpiece is produced. The disadvantageous aspect is the high amount of flexing work which stresses the workpiece material during the flow turning and the thus inadequate quality of the produced internal toothing. A high local introduction of energy is connected with the flexing work which leads to energy losses. The external toothing as pictured therein frequently breaks off as a result of the high stresses on the clamping chuck. Moreover, the productivity of this method is relatively low despite a high need for machinery because only three to four parts per minute can be produced.
It is the object of the present invention to provide a method and an apparatus for an energy-saving production of a workpiece with internal toothing, especially an internal geared wheel, which ensures a substantial increase in the productivity at high quality of the internal toothing with a relatively simple constructional configuration of the apparatus.
This object is achieved by the features of an apparatus for producing a workpiece with internal toothing, especially an internal geared wheel for a gearing, comprises a mandrel with an outside profile according to the internal toothing to be produced as well as a forming tool which reduces during an advancing movement the outside diameter of a cup-like preform, as a result of which material of the cylinder wall region flows into the outside profile of the mandrel. In accordance with the invention, a drawing ring is used as the forming tool which ensures ironing of the cylinder wall region during an advancing movement.
In the direction towards the lower side of the floor of the preform an axially movable counterholder is arranged in such a way that during the ironing it acts with a counterholding force on the lower side of the floor of the preform. The counterholder may comprise a circular pressure surface facing in the direction towards the lower side of the floor, which pressure surface substantially acts upon the entire floor region, or said counterholder may comprise a ring-like pressure surface which is adjusted to the width of the cylinder wall of the preform and is aligned essentially flush with the same and acts upon the edge region of the lower side of the floor of the preform.
An axially movable pressure punch is arranged in the direction towards the face surface of the cylindrical side wall in such a way that during the ironing it acts upon the face surface with a pressure force. The pressure punch can be moved during the ironing by a movement corresponding to the ironing length of the preform in the direction of the advancing movement of the drawing ring.
Advantageously, the axial stroke movement of the pressure punch as occurs during the ironing can be controlled depending on its pressure force. For this purpose the pressure punch is held in an axially movable fashion by means of a hydraulic piston.
The apparatus can advantageously be integrated in a hydraulic press consisting of a bedplate and a press ram. The mandrel is arranged in an axially fixed fashion on the bedplate and the press stamp is held on the mandrel in a manner so as to be axially displaceable by means of a hydraulic piston. The drawing ring is arranged on the press stamp in a preferably fixed manner and the counterholder is arranged thereon preferably in an axially movable fashion by means of a hydraulic piston. The pressure punch is preferably arranged as a cylindrical pressure sleeve. The distance of the pressure surface which is adjusted to the length of the preform to the face side of the mandrel can be adjusted by means of spacer rings for example.
For ejecting the workpiece the mandrel is held in a rotatable manner in the production of a helical gearing.
With respect to the method employed, the production of the workpiece with internal toothing occurs in such a way that a cup-like preform, comprising a floor and substantially cylindrical side walls, is reduced in its outside diameter by means of a mandrel having the external profile according to the internal toothing to be produced, so that the material of the cylinder wall region flows into the external profile of the mandrel. According to the invention, the reduction of the outside diameter occurs by ironing by means of a drawing ring. During the ironing the axial compressive stresses are applied onto the cylindrical side walls of the preform, so that the flow of material into the profile of the mandrel is promoted. The axial compressive stresses are preferably applied by a pressure punch acting upon the face side of the cylinder wall. A counterholder acts simultaneously on the lower side of the floor in order to avoid deformations in the floor region and to apply a counterholding force. The counterholding force of the counterholder and the force of the pressure punch should be controllable with respect to each other in such a way that during the entire ironing process a flow of material is ensured in the radial direction to completely fill the shape of the mandrel.
During the ironing, the pressure punch carries out an axial stroke movement according to the ironing length of the preform in the direction of the advancing movement of the drawing ring which is controlled depending on its pressure force.
The invention allows for the first time producing internally geared workpieces in high quality on a conventional press in an energy-saving manner. The productivity can be increased by four to six times in comparison with flow-turning.
The invention is now explained in closer detail by reference to an embodiment and the pertinent drawings, wherein:
According to
The drawing ring 14 which is arranged in a fixed fashion on the press ram P moves in the pre-stroke with the press ram P in the direction towards the bedplate 1. At the same time, the first hydraulic piston 3 is pressurized and presses the press stamp 9 with the force F1 against the face surface N2 of the preform N (
In order to allow excessive material to flow off and to avoid overloading the tool it is possible according to
According to
It is further advantageous when at the end of the forming process an increased axial pressure for calibration is exerted in order to achieve a better filling and a higher excessive material can flow off as described above. After cylinder 3.1 is situated in its lowermost position. The increased pressure can now be applied in such a way for example that the pressure punch 9 via an intermediate piece Z which comprises a thread G on its outside diameter and is connected above with a ring follower G1 which on its part rest on the cylinder 3.1 and thus on the bedplate 1 via the lower part 2 of the tool.
Number | Date | Country | Kind |
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100 54 399 | Nov 2000 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/DE01/04192 | 11/1/2001 | WO | 00 | 4/30/2003 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO02/36287 | 5/10/2002 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
3694127 | Takahashi et al. | Sep 1972 | A |
3899912 | Orain | Aug 1975 | A |
5823104 | Beisel et al. | Oct 1998 | A |
Number | Date | Country |
---|---|---|
1373547 | Nov 1974 | GB |
1-317653 | Dec 1989 | JP |
6-31374 | Feb 1994 | JP |
Number | Date | Country | |
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20040016281 A1 | Jan 2004 | US |