JPH042727A - Hardening treatment of camshaft surface - Google Patents

Abstract

PURPOSE:To improve the accuracy in hardening a cam surface by detecting the position and width of the cam to be treated utilizing a remelting torch used as a sensor to correct the cam position data and oscillation amt. CONSTITUTION:A TIG torch 5 is moved in the X and Y directions by control parts 9 and 10, the gap between the cam surface and the torch 5 is kept constant in synchronization with the rotation of a camshaft S, and the cam is oscillated within the cam width and remelted. At this time, the camshaft S is stopped prior to remelting, an extremely weak current is applied to the torch 5 from a control part 11, and the cam is oscillated by about one stroke at an oscillating velocity V corresponding to the set oscillation amt. W plus a specified volume alpha. Consequently, an electric discharge is generated between the torch 5 tip and cam surface, the cam width, oscillation amt. and center position of the cam width are obtained by the change in the applied voltage, and the position data and oscillation amt. data are corrected based on the measured cam position and width.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for hardening the cam surface of a cast iron camshaft by remelting it with high-density energy.

Conventional technology and its challenges The cam surface of a cast iron camshaft used in internal combustion engines is
A remelting surface hardening treatment method in which remelting (remelting treatment) is performed using high-density energy such as IG arc, electron beam, laser, etc. and surface hardening by allowing it to cool is disclosed in, for example, JP-A-62-151552 and JP-A-62-151552. It is known from Publication No. 59-47369 and the like.

In this processing method, while rotating the camshaft, a remelt torch, such as a TIG torch, placed opposite the cam surface is oscillated within the width of the cam in synchronization with this rotational movement, thereby applying melting energy to the cam surface and remelting it. For example, by sequentially performing such treatment from the cam at one end of the camshaft to the cam at the other end, a chilled structure with high hardness and excellent wear resistance is formed in the remelted portion of each cam surface. This is the basic idea.

In such a processing method, the position to which the remelt torch should be moved according to the position of the cam to be processed and the amount of oscillation at which the remelt torch should be oscillated at that position are stored and set in advance in the NC control system of the remelt torch. However, the actual cam position and cam width dimensions may vary due to manufacturing errors or thermal expansion during preheating treatment. If the above process is performed with such dimensional variations, the cam width of the cam to be processed and the oscillation amount of the remelt torch will be offset from each other in the axial direction. This is undesirable because a defect called "melting sag" occurs in some parts.

Therefore, in order to prevent such processing defects, for example, in Japanese Patent Application Laid-Open No. 60-230938, the edge portion of the cam to be processed is detected by an optical sensor, and the processing of the torch is started according to the detected position. I'm trying to reset the position.

However, with this method, the structure becomes complicated because the sensor must be placed close to the cam to be processed, and the sensor becomes contaminated due to spatter generated by the processing, making it difficult to maintain the desired detection accuracy over a long period of time. The problem is that it is difficult to maintain.

The present invention has been made in view of the above problems.
The remelt torch itself is used as a sensor to detect the position and cam width of the cam to be processed, thereby eliminating the need for a conventional optical sensor. The object of the present invention is to provide a processing method that prevents such defects.

Means for Solving the Problems The present invention oscillates a remelt torch, which is opposed to the cam surface of a cam to be processed, in the cam width direction based on preset cam position data and oscillation amount data. In the method of hardening by applying melting energy and remelting, prior to the hardening process, a weak current is passed through the remelt torch and the oscillation amount is slightly larger than the preset oscillation amount. The actual position and cam width of the cam to be processed are detected from the voltage change of the remelt torch when the remelt torch is oscillated, and the cam width is set in advance based on the actual measurement data of the cam position and cam width mentioned above. It is characterized by correcting cam position data and oscillation amount data.

Embodiment FIGS. 2 and 3 are explanatory diagrams of the configuration of a processing apparatus to which the present invention is applied.

In the figure, S is a cast iron camshaft having a plurality of cams CI, C2, . Jl, J2... are journal parts.

Reference numeral 5 denotes a TIG torch (hereinafter simply referred to as a torch) as a remelt torch, and this torch 5 moves in the radial direction of the camshaft S (
The camshaft S has a function of moving in the axial direction (X direction) of the camshaft S by the action of the motor 7 and the pole screw 8. The position of the torch 5 is controlled based on commands from each torch position control section 9, 10. That is, the torch 5 is connected to the cam c1. to be processed. After moving to a position facing either of the camshafts S, move it in the X direction in synchronization with the rotation of the camshaft S so that the gears and fs between the cam surface and the tip of the torch 5 are always constant. The position is controlled and at the same time the camshaft S
By oscillating within the cam width of the cam to be processed in synchronization with the rotation of the cam, remelt processing is performed on the cam surface.

11 is a current/voltage control unit that controls energization to the torch 5;
Reference numeral 12 denotes a main control device that collectively controls not only the current/voltage control section 11 but also a torch position control section 10.11 and a cam rotation control section 13.

The main controller 12 includes an arithmetic control section 14 and a storage section 15, and the storage section 15 stores each cam CI.

The oscillation amount W and oscillation speed V1 for oscillating the torch 5 according to the position data P of C2..., each cam CI, the cam width m of C2..., and the processing necessary for the curing process as described later. A current value It, a weak current value I3 necessary for cam width detection as pre-processing, etc. are set and stored in advance.

Each cam c1. The position data P of c2... is the camshaft S supported at both ends by centers 2 and 3 as shown in FIG.
Each cam c1.
The distance p1.c2... to the center position of the cam width m. p2
It is set as... Further, the oscillation amount W is set to be approximately the same value as the cam width dimension m. Furthermore, the above weak current value 1. The final value is set, for example, to a value of 1/4 to 115 of the processing current value (2).

Therefore, in the above processing device, the cam c1. c.
The torch 5 is sequentially moved and positioned to the corresponding positions in the order of 2, .

For example, during the remelting process of the cam CI shown in FIGS. 3 and 4, preprocessing conditions are selected and set in response to a process start command as shown in FIG. The conditions set here are the position data P1 of the cam C1 to be processed, the oscillation amount W, the oscillation speed V, and the weak current value 11.

When the pretreatment conditions are set, the camshaft S rotates,
After the nosed knob part is extended so that the nose top part of the cam C1 is opposed to the torch 5, the camshaft S is temporarily stopped.

At the same time, the torch 5 moves from the origin position to the position of the cam C1, and is positioned so that the gap G between the tip of the torch 5 and the cam C1 becomes a predetermined value. At this time, the position where the torch 5 is positioned is the center position of the cam width m.

Then, while the camshaft S remains stopped, the torch 5 is oscillated about one round trip at the oscillation speed ■ under an oscillation amount (W + α) obtained by adding a predetermined value α to the set oscillation amount W.

The current applied during the oscillation operation as a pretreatment is a weak current value (■), so although it does not lead to melting of the cam surface, a discharge phenomenon occurs between the tip of the torch 5 and the cam surface, and this discharge Due to this phenomenon, the energizing voltage of the torch 5 changes.

That is, when the torch 5 is oscillated at an oscillation amount (W+α) slightly larger than the cam width dimension m, the cam width dimension m corresponds to the cam width dimension m as shown in FIGS. 4(A) and (B). Due to the above-mentioned discharge phenomenon, the voltage (2) becomes high (and when the torch 5 comes off on both sides of the cam width m, the voltage V
becomes significantly lower.

Therefore, the load voltage V of the torch 5 is monitored during the oscillation operation as the pre-processing described above, and the position data of the torch 5 at the position a where the voltage V suddenly increases as shown in FIG. Read the position data at the position where the voltage V suddenly became low.

These position data are detected by a position detector attached to the Y-direction feeding system of the torch 5, which detects one end surface e of the camshaft S.
The distance from the point to the positions a and b is detected as LI1+L12.

When the data at positions a and b are read, the torch 5 temporarily returns to the original position, while the calculation processing unit 14 calculates the actual cam width m1 of the cam C1 by calculating the formula (1). ) A predetermined correction formula C is added to the value of the actual cam width m1 determined by the formula (2) to determine the oscillation amount W1 corresponding to the actual cam width as in formula (2).

mI=Lll-L12 (1) W
, -m, +C... (2) Furthermore, Fig. 4 (
Equation (3) is calculated based on the position data L II at position a in B) and the oscillation amount Wl described above to obtain position data P II at the center position Q of the cam width m in the cam C1.

P++=L-z+ (m+/2)-・-・-(3) Next, as processing conditions, the weak current value 1. Processing current value I is set instead of , and at the same time position data P of cam C1 is set.
1 and the oscillation rate fiW, the actually measured position data Po1 and the oscillation amount W obtained by the above calculation are respectively set.

In other words, the preset position data P1 of the cam C1
and the oscillation amount W is corrected based on the actual measurement value.

When the processing conditions are set, the camshaft S rotates and stops once the remelt processing start position is determined, while at the same time the torch 5 moves from the origin position to the position of the cam C1, and the tip of the torch 5 and It is positioned so that the gap with the cam C1 is a predetermined value G. At this time, torch 5
The position at which cam position is determined is based on the above cam position data P1. This is the location specified by.

Then, the camshaft S rotates again, and in synchronization with the rotation of the camshaft S, the torch 5 performs an oscillating operation based on the oscillation amount W, thereby performing remelt processing on the cam C1. Since the oscillation rate fiW at this time has been corrected based on the actual measurement value of the cam width m of the cam C1 as described above, the oscillation rate is The amount W1 is not offset in the axial direction.

Effects of the Invention As described above, according to the present invention, the remelt torch is used as a sensor for detecting the cam width, and the preset value is determined based on the actual cam position and cam width of the cam to be processed. By correcting the cam position data and oscillation amount data, the cam width and oscillation amount do not offset in the axial direction as in the past, and processing defects such as "melt dripping" can be prevented. Of course, since a sensor separate from the remelt torch is not required, the structure can be simplified, and the influence of sensor detection errors and installation errors on detection accuracy is significantly smaller than before, which improves detection accuracy and processing accuracy. Improvements can be made.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, and is a flowchart during processing operation, FIG. 2 is a configuration explanatory diagram showing an outline of a processing device to which the method of the present invention is applied, and FIG. The enlarged views of FIGS. 4A and 4B are explanatory diagrams showing the relationship between the cam width of the cam to be processed and the torch voltage. 5...TIG torch (remelt torch), 11...
Current/voltage control unit, 12... Main control device, 14...
Arithmetic control unit, cl, c2... cam, S... camshaft. Figure 3S Figure 4 (A) Figure 4 (B)

Claims (1)

[Claims] (1) Oscillating a remelt torch facing the cam surface of the cam to be processed in the cam width direction based on preset cam position data and oscillation amount data,
In the method of hardening by applying melting energy to the cam surface and remelting it, prior to the hardening process, a weak current is passed through the remelt torch and an oscillation amount slightly larger than the preset oscillation amount is applied. The remelt torch is oscillated under the conditions of
A method for surface hardening a camshaft, the method comprising modifying preset cam position data and oscillation amount data.