DE1079240B - Process for induction hardening of workpieces - Google Patents

Description

GERMAN

It is known that for surface hardening of metal workpieces or workpiece parts inductors are used, which with a current higher frequency are fed. In this case, the workpiece is generally controlled by the induction device includes. Heat the eddy currents that occur in the workpiece when the power is switched on this in the surface layer according to the frequency. When treating cylindrical Workpieces do not experience any difficulties in the formation of the hardness layer. Lie much differently the conditions when instead of such workpieces conical shafts, crankshafts, profiled shafts ti. Like. To be hardened by means of a normal inductor. It can be seen here that the achieved The hardening layer is by no means uniform, as induction hardening, for example of crankshafts, During the heating of the individual cones, a blow of different sizes occurs, which is special is greatest at the middle bearing. As a result, the distance between the pins and the inductor is on the reduced on one side and enlarged on the other. This creates on the scope of the too The hardening surface results in an uneven coupling, whereby the surface at which the coupling is greatest is, has an elevated temperature, which at the same time increases the impact and a mutual agitation generated.

In order to get perfect results in all cases, it is necessary to measure the energy used to be regulated by a controller. Here, too, several arrangements have already been proposed, such. B. for the purpose of regulating the extraction of energy, the metal part also has an adjustable, DC excited Exposure to magnetic field. Another well-known method suggests by the circular Workpiece to influence a control element connected in the control circuit of the power generator, whose active and reactance changes according to the heating program synchronously with the circulation of the Workpiece changes. This type of control with a control element on which the resistance values are determined Corresponding temperature heights or penetration depths in the workpiece can be, for example, at Use medium frequency effectively and only if that occurs during heating Stroke is always the same size and known beforehand. A regulation option according to the changing However, the size of the blow that occurs is not given.

The method according to the invention, however, gives the possibility of uniform heating of a workpiece to be inductively hardened despite the occurrence of non-uniform eccentricity, namely induction hardening methods
of workpieces

Applicant:

VEB machine tool factory

»Hermann Schlimme«,
Berlin-Treptow, Bouchestr. 12th

Arno Woitscheck, Berlin-Hessenwinkel,
has been named as the inventor

ao this according to the invention in that the control voltage is tapped on the resonant circuit itself and acts back on the generator in the sense that the workpiece is heated uniformly.

The method according to the invention works according to the following principle. Due to the heating process occurs during induction hardening, for example of crankshafts, a blow so that the pin does not runs more centrically, but eccentrically. This effect in turn resolves an uneven coupling ratio and fluctuations in the HF current depending on the size of the eccentricity. The result occurring modulation, the frequency of which depends on the revolutions of the crankshaft, is according to the invention demodulated, amplified and fed to the control coil in the grid circle. The regulation of the Lattice circle takes place depending on the size of the demodulated control voltage, caused by the change the effective permeability, through one in one made of a soft magnetic material on the Basis of non-metallic, ferromagnetic ferrites made of iron oxide and one or more oxides divalent metals and mixed crystals or chemical compounds of the general compositions existing RF iron core embedded control coil.

The drawing schematically illustrates an embodiment of the invention.

1 with the crankshaft journals shown in section are designated. If the crankshaft is eccentric, a modulation of the HF current occurs in the inductor 2, which is fed by the glow transformer 3 arranged between it and the primary coil, by changing the induction coupling.

909 769/459

The modulated control voltage is tapped at resistor 4, demodulated at diode 5 and tapped again at the resistor 6 and fed to the amplifier tube 8 via the capacitor 7. The control voltage is transmitted to the control coil 10 through the input transformer 9.

The amplifier tube 8 works in the lower bend of the Ug-Jg characteristic curve by only the positive half-wave the control amplitude becomes effective. This ensures that at maximum coupling one The generator's output is reduced. The power control is carried out by the in the HF circuit of the Generator 11 arranged, embedded in an HF iron core control coil 10 made.

Claims (3)

Patent claims: 1. Method for induction hardening of workpieces, for example crankshafts, in which despite the eccentricity of a shaft or an uneven coupling of the inductor ao uniform heating takes place, characterized in that the control voltage is applied to the resonant circuit tapped itself and acts back on the generator in the sense that the workpiece is heated evenly. 2. Apparatus for the method according to claim 1, characterized in that the generator by the impact that occurs in the workpiece due to the heating process is modulated. 3. Apparatus for the method according to claim 1, characterized by one in one of one soft magnetic material based on non-metallic, ferromagnetic ferrites Iron oxide and one or more oxides of divalent metals and mixed crystals or chemical ones Compounds of the general compositions of the existing HF iron core embedded Control coil that changes the feedback ratio of the generator. Considered publications:
German patent specification No. 970 000. 1 sheet of drawings © 909 769/459 3.60