DE2825579C3 - Method and device for remelt hardening of the cams of a camshaft of a brake engine - Google Patents

Description

each power level being assigned to an interval of radii of curvature and

L (R) = power at radius R, L ^ = power at radius Λ Φ «,

a = hardness depth

2. Method for remelt hardening the cams of a camshaft of an internal combustion engine, at which the surface to be hardened of the cams of the camshaft rotating at constant speed in constant distance past an energy source which causes remelting and oscillates across the width of the cams, characterized in that it is cylindrical in shape the power of the energy source is controlled according to the surface to be hardened

L (R)

whereby

L (R) = power at radius R, La, = power at radius /? = »,

a - hardness depth is.

3. The method according to claim 1 or 2, in which an arc is used for remelting, characterized in that the current of the arc is controlled.

4. Device for performing the method according to one or more of the preceding claims, with a camshaft receiving, rotatable clamping device and at least one at the same distance from the cam contour of the hardening cam-guided burner which is supplied with power by a generator, characterized in that a changeover switch (20, 23) is provided which controls the output power of the generator (21) depending on the position of the camshaft or the cam to be hardened.

5. Vorrichlung according to claim 4. mil one the Rotation of the camshaft relieving Schaller, characterized in that one with the switch (19) cooperating control circuit (20) is provided, which the burner current accordingly controls the angle of rotation of the camshaft.

6. The device according to claim 4, at least one radially shifting to the camshaft or to the cam The invention relates to a method for remelt hardening the cams of a camshaft Internal combustion engine according to the preamble of patent claim 1 or 2.

The invention also relates to a device for carrying out the method. In a known device (DE-GM 77 02 409)

for hardening the cam running surfaces of camshafts for internal combustion engines according to the TIG remelting hardening process, the cam running surface, which has different radii of curvature, is always the same Distance past a burner as an energy source-

leads, which is supplied by a generator with power of constant strength, with the between Cams and torches skipping arc melted the surface like webs and through the immediate cooling is hardened. How yourself turned out to be during remelt hardening of workpieces with different radii of curvature distributed over the circumference, different shape qualities and hardness depths result, which reduce the wear resistance of the surface to be hardened before and hardship errors can cause.

DE-PS 6 44 844 describes a method for flame hardening camshafts. To do this, the distance between the flame and the axis of rotation of the camshaft is used not changed to size workpiece surfaces rem distance from the axis of rotation durd; the cooler ones To apply flame zones.

With this method, the power consumption is shown in which the power of the energy source remains constant, thus depending on the distance between the ones to be processed

Surface from the axis of rotation.

To avoid errors in hardness induction hardening of different radii of curvature having workpieces has already been proposed (DE-AS 12 59 918), this ^f au smooth surface temperature with true-to-contour isotherms. This is achieved in that the frequency of the heating current used is reduced when the workpiece surface with the smaller radius of curvature has reached about the Curie temperature. With the Verrin Increasing the frequency can also increase the specific performance in the workpiece. Accordingly, the surface with small radii of curvature is first heated quickly up to the Curie temperature. By reducing the fre-

bO quenz their power consumption is then reduced, while now growing in the areas of mil Radii of curvature a sharp Tcmpcraiiiranheliuri); he follows. As a result, the desired temperature should be at the the entire surface of the workpiece

b "> tig can be achieved, whereby a uniform hardness quality and hardness layer can be achieved.

The frequency and the specific power are switched depending on the temperature

the surface area with the smaller radii of curvature and is therefore not applicable to remelt hardening, which always only has local areas be melted.

The object of the invention is to further develop the remelting process in such a way that also surfaces can be hardened with different radii of curvature with a uniform hardening depth. Next should an apparatus for performing the method according to claims 1 or 2 are shown.

The object according to the method is achieved with the features of claim 1 or 2. In contrast the teaching of DE-PS 6 44 884 or DE-AS 12 59 918 is the hardness depth and the burner output solely on the radius of curvature and not on the temperature of different areas of the workpiece controlled As the inventor recognized, there is between the depth of hardness and the radius of curvature the surface to be hardened with the same power supplied to the surface unit. Due to the uniform supply of energy for each volume unit of the workpiece to be remelted there is the advantage of a uniform hardness quality and depth of hardness with minimal energy consumption.

Claim 1 describes a method in which the burner output is gradually controlled, claim 2 specifies a method with continuous control of the burner output.

Claim 3 characterizes one that has been tried and tested in practice How the procedure will be carried out.

The claims 4 to 6 characterize advantageous features of a device for performing the method according to the invention.

The invention is explained in more detail below using an exemplary embodiment. The drawing shows in

F i g. 1 is a diagram showing the ratio of the power output as a function of the radii of curvature a cam of a camshaft for an internal combustion engine can be seen,

F i g. 2 shows a schematic representation of an inventive Device for hardening the cam running surfaces of a camshaft using the TIG remelting hardening process, in the view S of FIG. 3, with a derived from the angle of rotation of the camshaft Control of the remelting energy and

F i g. 3 shows the same device in section along the line IH-111 of FIG. 2. with one derived from the burner stroke, gradual control of the remelting energy.

On the diagram in FIG. 1, the power of the energy source to be controlled for uniform hardening of a cam of a camshaft is plotted in a curve at an example hardening depth a = 2 mm. The abscissa shows the radii of curvature R in millimeters and the ordinate shows the power required for uniform remelting, the value I corresponding to a power required according to the hardening process used with a radius of curvature oo. As errcchcnbar from the diagram be seen and according to the above equation, the power output L (R) at cincni radius of curvature to the cam 10 mm = 0.9L "and a radius of curvature of 3 mm = 0.66 L ^ be uniform to a Hardness; i = 2 mm and to achieve a constant hardness quality. It goes without saying that the curve shifts accordingly with increasing hardness depth α in the abscissa of the diagram.

In Figures 2 and 3 is a device for remelt hardening Shown according to the TIG remelting hardening process. It has a machine base 1 on, on which a plate 2 is slidably mounted. On the plate 2 there is a clamping device for a to hardening camshaft 3 arranged. The clamping device consists on the one hand of a tailstock 4 with a tip holder 5 and on the other hand from one

ίο Bearing block 6 in which a conical sleeve 7 is rotatably mounted The conical sleeve 7 sits on a common shaft with a drive wheel 8, which is via a toothed belt 9 is driven by an electric motor 10. The toothed belt 9 also spans another drive wheel 11, which is connected to a master camshaft 12 rotatably arranged parallel to the camshaft 3 In the conical sleeve 7 a driver (not shown) is provided, which is in a corresponding groove the camshaft 3 engages and thus ensures a constantly defined position of the camshaft 3 in relation to the drive wheel 8 The drive wheels 8 and 11 * iron the same Number of teeth and are set to each other in such a way that the cams of the camshaft 3 and the master camshaft 12 rotate synchronously with each other. With the machine base 1 are corresponding to the number of to hardening - η cams angled 30 ° in the upper area Guides 13 connected on which slides 14 are mounted. On the carriage 14 are burner 15 and the Master camshaft 12 scanning and thereby the radia-ϊεπ Stroke of the carriage 14 or burner 15 causing plunger 16 attached. For the sake of simplicity, the F i g. 2 only two burners 15 or carriage 14 are shown while the rest are indicated by center lines are.

On one end face of the machine base 1, an eccentric 17 is mounted, which is driven by an electric motor (not shown) is driven and starts at the end face of the plate 2 in such a way that this with one of the Width of the cam corresponding amplitude oscillates According to the invention, a control disk 18 (FIG. 2) is arranged coaxially with the drive wheel 8 for the camshaft 3, the markings on their outer circumference indicating the angle of rotation of the camshaft is and runs past a switch 19, the corresponding pulses to a not shown sewing Control circuit 20 emits In control circuit 20, the respective radii of curvature of the individual Cams broken down to their angular position on the camshaft 3 stored so that the control circuit 20 controls the generators 21 present for each burner 15 in such a way that for each defined rotational angle position of the camshaft 3, the output of the generators 21 output to the respective burner 15 is the current at the burners 15 passing radii of curvature of the cams according to the diagram of FIG. 1 corresponds. It goes without saying that the control disk 18 is also provided with corresponding markings for the on or off. Turning off the burner 15 is provided so that the control circuit 20 <; ine central control of the entire

W) th remelting or hardening sequence of the camshaft 3 forms.

In Fig.3 is a simplified control of the eitves Generators 21 are shown in which the radial stroke of the corresponding burner 15 or carriage 14 is emitted is asked. This control is particularly suitable for simple cam shapes with only one approach and one Deceleration ramp. If you divide the entire stroke of the carriage 14 into two or more partial strokes, so can

for certain intervals of radii of curvature which lie in a partial stroke, a step-by-step control approximating the curve in the diagram in FIG. 1 the output power of the generator 21 can be achieved. For this purpose, there is an inductive transmitter 22 in the area of the slide 14 arranged, which monitors the stroke of the carriage 14 and in the partial stroke in which the burner 15 the upper Melts around the area of the cam tips of the cam, controls a changeover switch 13, which controls the output power of the generator 21 by switching the con- bars 14 reduced. It is understood that in this control each burner 15 or carriage 14, an inductive transmitter 22 and a switch 23 are required, which the control respective generator 21.

For this purpose 3 sheets of drawings

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25th

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Claims (1)

Patent claims: 1. Method of remelt hardening the cams a camshaft of an internal combustion engine, in which the surface to be hardened of the cam with constant speed rotating camshaft at a constant distance past an energy source causing remelting and oscillating across the width of the cams, characterized in that with a cylindrical shape of the surface to be hardened, the power of the energy source is gradually controlled in approximation to the formula baren, the slide following the cam contour, the carries the burner, characterized in that a transmitter (22) is arranged in the area of the slide (14) which, depending on the stroke of the burner (15) or the carriage (14) controls a switch (23) which controls the output power of the generator (21) between at least two current levels switches