EP0291383A1 - Method and apparatus for heat-treating camshafts - Google Patents

Abstract

This machine comprises essentially torches (14) capable of producing an electric arc and carried by a trolley (13) capable of being moved by virtue of a digitally controlled motor (18) in a horizontal direction (Y) parallel to the axis (A) of the cam (41) shaft (40) to be treated, this trolley (13) being carried by an intermediate trolley (21) capable of being moved by virtue of another digitally controlled motor (24) in a horizontal direction (Z) perpendicular to the axis (A) of the camshaft, which intermediate trolley is mounted vertically movable on the framework (33) of the machine in a vertical direction (X) perpendicular to the axis (A) of the camshaft by virtue of yet another digitally controlled motor (30) carried by the framework (33). <??>This machine permits the heat treatment by remelting of a number of identical camshafts arranged horizontally and intended for motor vehicles. <IMAGE>

Description

The present invention relates to a machine for heat treatment by reflow of the surface or carried by the cams carried by a camshaft.

It is known that reflow is a heat treatment process consisting in carrying out a point fusion on a surface, such as a cam span, using an electric arc surrounded by a jet of inert gas and produced by a torch. This produces a "hardening" or hardening of the surface or cam surface which is generally swept by the electric arc so that the treatment is carried out over the entire surface to be treated.

More precisely, we know from document US-A-4 312 685 for example, camshaft remelting machines in which a vertical movement of the torch is carried out using a mother cam so that the torch is at constant distance from the surface to be treated, the camshaft itself being driven in a rotational movement combined with an axial translational movement so as to effect the scanning.

Such a machine has drawbacks resulting in particular from the fact that the point of impact of the torch is generally located on an inclined surface of the cam, especially when the latter has a pointed apex, and it follows that the electric arc torch causes a dip or concavity on the surface or cam surface, since the molten metal flows due to the inclination of said surface. In other words, after the reflow treatment, we obtain a surface or cam bearing unfit for use and requiring significant rework.

The object of the present invention is in particular to remedy these drawbacks by proposing an improved machine for the heat treatment by reflow of the cams carried by the camshafts, which machine in no case risks damaging the surface or cam bearing and advantageously allows automatically process sets of identical and different camshafts.

To this end, the invention relates to a machine for the heat treatment by reflow of the cams carried by a camshaft and of the type comprising means for rotating the shaft along its axis disposed horizontally, at least one torch capable of perform a fusion by electric arc at a point on the surface of the cam to be treated, and means of displacement of this torch relative to the camshaft, characterized by independent means with numerical control allowing the displacement of said torch according to three orthogonal directions, and namely a first vertical direction perpendicular to the axis of the camshaft, a second horizontal direction parallel to the axis of the camshaft, and a third horizontal direction perpendicular to the axis of the camshaft.

According to another characteristic of the invention, the displacement of the torch in the above-mentioned third direction is controlled by means of independent numerical control allowing the torch to be located on the generator of contact with the horizontal tangent plane.

Thus, as can be understood, the heat treatment by reflow is always carried out on a part of the surface or cam surface lying in a horizontal plane, so that there is practically no longer any risk of causing concavities in this surface or cam span, as explained above.

According to another characteristic of the invention, the aforementioned torch is carried by a carriage which can be displaced by a motor with numerical control in the aforementioned second direction, this carriage being itself carried by an intermediate carriage which can be displaced by another motor with control digital in the aforementioned third direction, which intermediate carriage is mounted vertically movable on the frame of the machine in said first direction by means of yet another numerically controlled motor.

It will also be specified here that the machine according to this invention comprises as many torches as the shaft to be treated comprises cams or pairs of cams and that the number of identical camshafts which can be processed simultaneously by the machine, said shafts being each initially oriented by an indexing system so that the treatment begins identically on all the cams of the trees.

This indexing system, which is associated with the means for rotating each shaft, comprises a finger cooperating with a groove made on the shaft.

According to another characteristic of the invention, the above-mentioned intermediate carriage consists of a square-shaped element, one side of which carries the aforementioned carriage and the other side of which is mounted. horizontally movable on a plate or the like itself vertically sliding mounted on the machine frame.

The displacement of the aforementioned carriages carrying the torches is ensured by roller screws controlled by belts driven by a numerically controlled motor carried by the aforementioned intermediate carriage or bracket.

As for the horizontal displacement and perpendicular to the axis of the shaft, of the aforementioned intermediate carriage, this displacement is ensured by a ball screw driven by a numerically controlled motor carried by the aforementioned plate which is provided with bars on which can slide said intermediate carriage.

The vertical displacement of the aforementioned plate on the frame of the machine is ensured by a numerically controlled motor carried by said frame which comprises vertical bars on which slide sleeves or the like integral with said plate.

According to yet another characteristic of the invention, the movements of the torches in the three above-mentioned orthogonal directions, as well as the rotational movement of the camshaft are controlled by a computer having in memory all the positions relative to each instant.

According to yet another characteristic of the machine according to this invention, each torch can perform in the vertical plane perpendicular to the camshaft an angular displacement defined by a numerically controlled motor carried by the carriage carrying the torch.

According to another embodiment, the machine according to the invention comprises a plurality of torches, each torch being carried by a carriage suitable for performing a vertical movement, this carriage being carried by an intermediate carriage suitable for effecting a horizontal movement perpendicular to the 'shaft and all intermediate carriages being carried by a single carriage suitable for performing a horizontal movement parallel to the tree.

• La figure 1 est une vue très schématique en élévation et de côté d'une machine conforme aux principes de l'invention ;
• La figure 2 est une vue schématique de cette machine suivant la flèche II de la figure 1 ;
• La figure 3 est une vue schématique et de dessus de cette machine ;
• La figure 4 est une vue schématique montrant comment s'effectue l'impact de l'arc électrique produit par la torche suivant un plan horizontal tangent aux génératrices de ladite came ; et
• La figure 5 est une vue très schématique, correspondant sensiblement à la figure 3 et montrant comment s'effectue le traitement de quatre arbres à cames identiques traités par la machine.

However, other characteristics and advantages of the invention will appear better in the detailed description which follows and refers to the appended drawings, given solely by way of example, and in which:

• Figure 1 is a very schematic elevational and side view of a machine according to the principles of the invention;
• Figure 2 is a schematic view of this machine along arrow II of Figure 1;
• Figure 3 is a schematic top view of this machine;
• Figure 4 is a schematic view showing how the impact of the electric arc produced by the torch takes place in a horizontal plane tangent to the generatrices of said cam; and
• Figure 5 is a very schematic view, substantially corresponding to Figure 3 and showing how the treatment of four camshafts is carried out identical processed by the machine.

Referring to Figures 1 to 3, we see that a machine according to the principles of the invention essentially comprises a frame 33 supporting torches 14 movable above shafts 40 each carrying a plurality of cams 41, these shafts being supported horizontally and able to rotate along their axis A.

The shafts 40 are supported by a lower frame 3 on which is articulated a jack 1 which actuates by its rod 1a and by means of a connecting rod, a control bar 2. This control bar 2 which is fixed to the frame 3 by bearings is equipped with four connecting rods 4 acting respectively on four tailstock 5 holding one end of the shafts 40, as can be seen on the lower left part of FIG. 1.

The other end of the shafts 40 is held by means which will now be described and which allow the shafts 40 to rotate during the heat treatment by reflow.

As it clearly appears in FIG. 1, a motor 6 allows, by means of a connecting rod-crank system 7, the reciprocating movement (forward and backward) of a carriage 8 supporting a system 9 with drive point 10. With this system 9 is associated an indexing finger 11 which cooperates with a groove made in the shaft 40 and not shown.

The system 9 does not need to be described in detail and it will only be said that it pivots the shaft 40 in search of its indexing position and the rotation of the assembly indexed according to the program of treatment. In other words, the shaft 40 rotates until the finger 11 engages in the groove of the shaft, and at this time, it is certain that the shaft is correctly oriented in the initial position for allow the reflow cycle to start.

12 has shown a motor which, by means of an appropriate transmission, enables the spikes 10 and therefore the shafts 40 to rotate around their axis A.

Returning to the torches 14, these can move relative to the frame 33 in three orthogonal directions, and namely, as seen in the figures, a first vertical direction X and perpendicular to the axis A of the trees, a second direction Y horizontal and parallel to the axis A, and a third direction Z horizontal and perpendicular to the axis A, this displacement in the three directions mentioned above can be effected while the shafts are driven in rotation by the motor 12. All the movements are controlled by separate numerically controlled motors, under the control of a computer having in memory all the laws of movement, and this in such a way that the point of impact of the electric arc of the torches is located on the generator of contact with the horizontal tangent plane, as will be explained later.

The torches 14, as can be seen in FIGS. 1 to 3, are supported by two carriages 13 each supporting two torches 14 and which are guided on bars 16 clearly visible in FIG. 1, in the direction Y, that is i.e. parallel to the axis A of the camshafts 40.

The movement of the carriages 13 is ensured by a numerically controlled motor 18 which acts on roller screws 17 of each carriage 13, by means of pulleys 19 and toothed belts 20 (FIG. 2).

The assembly described above consists essentially of the carriages 13 and the motor 18 is supported by an intermediate carriage taking the form of a bracket 21 clearly visible in FIG. 1.

The displacement of this square in the direction Z, that is to say horizontally and perpendicular to the axis A of the shaft 40, is ensured by a motor 24 with digital control which acts on a ball screw 25 (figure 2) by means of pulleys 25a and a toothed belt 26. The bracket 21 is guided by bars 22 and sockets 23 (see more particularly Figure 3), so that said bracket can move in the direction Z.

The above assembly, namely the motor 24 and the bars 22 slidingly supporting the bracket 21, is supported by a plate 27 which can be seen clearly in FIGS. 1 to 3.

This plate 27 is mounted vertically sliding in the direction X on the upper frame 33 of the machine.

More specifically, the frame 33 includes vertical bars 28 on which ball bushings 29 which are integral with the plate 27 can move.

Thus, a numerically controlled motor 30, supported by the frame 33, can act on a ball screw 31 (FIG. 2) by means of heaps and a toothed belt 32 to control the vertical movement of the plate 27 and therefore the vertical movement of the bracket 21 and the carriages 13.

As can be clearly seen in FIG. 1, the bracket 21 comprises a side 21a supporting the carriages 13, and another side 21b which is itself mounted horizontally movable on the plate 27 itself mounted vertically sliding on the upper frame 33 of the machine.

This machine can perfectly include, without departing from the scope of the invention, another motor (not shown) installed between the carriage 13 and the torches associated therewith, to allow each torch to perform an angular displacement in the vertical plane perpendicular to the camshaft 40, this in order to be able to orient the torch in an appropriate manner, towards the center of the part to be treated.

It is important to note here that the displacement of the torches 14 along the Z axis is provided to allow the point of impact of the torch to be located, as can be seen in FIG. 4, on the generator G in contact with the horizontal tangent plane H. In other words, the torch 14, by virtue of the programming, will permanently seek the generator G of the cam 41 with a tangent and horizontal plane to produce the electric arc there. Thus, advantageously avoid the concavity phenomena occurring on the surface or surface of the cam 41, since the impact will always take place on a horizontal part of the cam, and this while the shaft 40 is rotated.

Furthermore, it will be noted that the torches 14 will be subjected to an alternating movement in the direction Y parallel to the axis A of the shaft 40 so as to be able to sweep approximately the entire width of the bearing surface of the cams 41 during the rotation of said shaft.

This rotational movement of the camshaft 40 around its axis A will be slow enough with respect to the aforementioned reciprocating movement for the scanning to be done with overlap.

However, the operation of the machine which has just been described will be explained briefly in what follows, with particular reference to FIG. 5 which represents four shafts 40 comprising four cams or four identical pairs of cams (A, B, C and D ), all the cams having the same profile but different orientations. The torches 14 naturally perform the same movement and, as can be seen in FIG. 5, are arranged so as to treat simultaneously on the four shafts a cam.

In other words, after orientation of the four shafts thanks to the indexing system described above, the first torch T₁ treats the cam A of the first shaft, the torch T₂ treats the cam B of the second shaft and so on, it being understood that after treatment cams A, B, C and D belonging respectively to the four shafts 40, the four shafts are moved using an appropriate system, in the direction of the arrow F, so that the cam B of the first shaft located at right of Figure 5, is processed by the torch T₂, that the cam C of the second shaft is processed by the torch T₃, and so on.

The machine which has just been described makes it possible to treat a single category of shafts 40, as has been said previously.

If you want to process a second category of camshafts after the first category of trees, it is necessary to complete the treatment on the first category of trees before switching the machine to another program .

Also, according to another embodiment according to this invention, each torch 14 can be carried by a carriage suitable for performing a vertical movement, this carriage being carried by an intermediate carriage suitable for effecting a horizontal movement perpendicular to the shaft and all intermediate carriages being carried by a single carriage capable of performing a horizontal movement parallel to the shaft, locating means constituting for example an optical marker, being provided for, before the initiation of the heat treatment, switch the torch to the appropriate program. In other words, it is possible to have different programs carried out simultaneously by the different torches, provided of course that all the cams have the same span width.

A machine has therefore been produced according to the invention comprising torches whose displacement can be programmed and in which the laws of displacement in the different directions can be modified, and which makes it possible to carry out a heat treatment by reflow on each cam homogeneously, efficiently and with less risk of damaging the range of the cams.

Of course, the invention is in no way limited to the embodiments described and illustrated which have been given only by way of example.

On the contrary, the invention includes all the technical equivalents of the means described and their combinations if these are carried out according to the spirit.

Claims (11)

1. Machine for the heat treatment by reflow of the cams carried by a camshaft and of the type comprising means for rotating the shaft along its axis arranged horizontally, at least one torch capable of achieving fusion by electric arc at a point of the surface of the cam to be treated, and of means for moving this torch relative to the camshaft in three orthogonal directions, and namely a first direction (X) vertical and perpendicular to the axis of the shaft cam, a second direction (Y) horizontal and parallel to the axis of the camshaft, and a third direction (Z) horizontal and perpendicular to the axis of the camshaft, characterized in that it comprises independent numerically controlled means (12, 18, 24, 30) ensuring respectively the rotation of the shaft (40) and the displacements of said torch (14) along the three aforementioned axes, and this so that the means independent digital control (24) operating the torch in the third direction (Z) allows the point of impact of this torch to be located on the generator (G) in contact with the horizontal tangent plane (H). 2. Machine according to claim 1, characterized in that the movements of the torches (14) in the three orthogonal directions (X, Y, Z) as well as the rotational movement of the camshaft (40) are controlled by a computer having in memory all the positions relative to each instant. 3. Machine according to claim 1 or 2, characterized in that the aforementioned torch (14) is carried by a carriage (13) movable by a numerically controlled motor (18) in said second direction (Y), this carriage being carried by an intermediate carriage (21) movable by another numerically controlled motor (24) in said third direction (Z), which intermediate carriage is mounted vertically mobile on the frame (33) of the machine in said first direction (X) thanks to yet another numerically controlled motor (30). 4. Machine according to one of claims 1 to 3, characterized in that it comprises as many torches (14) that the shaft (40) comprises cams (41) or pairs of cams and that the number of identical camshafts which can be treated simultaneously by the machine, said shafts each being initially oriented by an indexing system so that the treatment begins identically on all the cams (41). 5. Machine according to claim 4, characterized in that the aforementioned indexing system, associated with the aforementioned means for rotating each shaft, comprises a finger (11) cooperating with a groove formed on the shaft (40). 6. Machine according to claim 3, characterized in that the above-mentioned intermediate carriage (21) consists of a square-shaped element, one side (21a) of which carries the above-mentioned carriage (13) and the other side (21b) ) is mounted horizontally movable on a plate or the like (27) itself vertically sliding mounted on the frame (33) of the machine. 7. Machine according to one of claims 1 to 4, characterized in that the movements of the above-mentioned carriage (s) (13) carrying the torches (14) are ensured by roller screws (17) controlled by belts (20) driven by a numerically controlled motor (18) carried by the aforementioned intermediate carriage or square (21). 8. Machine according to claim 1, 2, 3, 6 or 7, characterized in that the horizontal displacement and perpendicular to the axis (A) of the shaft (40) of the aforementioned intermediate carriage (21) is ensured by a ball screw (25) driven by a numerically controlled motor (24) carried by the aforementioned plate (27) which is provided with bars (22) on which said intermediate carriage can slide. 9. Machine according to one of claims 1, 2, 3, 6, 7 or 8, characterized in that the vertical displacement of the aforementioned plate (27) on the frame (33) of the machine is provided by a motor ( 30) numerically controlled carried by said frame which comprises vertical bars (28) on which slide sleeves (29) integral with said plate. 10. Machine according to any one of the preceding claims, characterized in that each torch (14) can perform in the vertical plane perpendicular to the camshaft (40) an angular displacement defined by a numerically controlled engine carried by the carriage (13) carrying the torch. 11. Machine according to claim 1, characterized in that it comprises a plurality of torches (14), each torch being carried by a carriage suitable for performing a vertical movement, this carriage being carried by an intermediate carriage suitable for carrying out a horizontal movement perpendicular to the shaft and all the intermediate carriages being carried by a single carriage suitable for carrying out a horizontal movement parallel to the shaft.

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