Dynamic seal "type cassette " with angular detection device; it's producing method

CASSETTE TYPE DYNAMIC JOINT WITH ANGULAR MARKING DEVICE; PROCEDURE FOR ITS IMPLEMENTATION

The present invention relates to an angular encoding device intended, for example, to mark the top dead center (TDC) of an internal combustion engine crankshaft, which is useful for optimizing its operation.

Known tracking devices comprise a toothed wheel driven with the reaction plate of the clutch and having a singularity, for example in the form of a longer tooth. A sensor, for example inductive, identifies this singularity and, after a certain number of rising edges, emits a control signal corresponding to TDC; this makes it possible to capture the average speed of rotation of the motor, on which the level of the currents of the signals detected depends.

The drawback of this known technique lies essentially in the need to perform mechanical indexing during assembly in order to create a reference: the singularity of the toothed wheel must be positioned very precisely with respect to the top dead center of the crankshaft.

In addition, the vibratory phenomena of the user member, in particular in the case of heat engines, can distort the marking.

Phonic wheel and inductive sensor devices have the same type of drawback.

The object of the present invention is to remedy these drawbacks, and to take advantage of the presence of a dynamic seal of the cassette type on the crankshaft shaft to constitute an angular locating device for this crankshaft.

For this purpose, a dynamic seal of the cassette type in accordance with the present invention, of the type comprising a sleeve with an annular flange suitable for being wedged in rotation on a rotating shaft, and an annular seal support surrounding said sleeve, this seal comprising a lip circular seal resting tightly on the outer surface of said sleeve, this support being able to be adjusted in a sealed manner in a suitable housing of a fixed part, so that said dynamic seal ensures the seal between said fixed part and said rotating shaft, is characterized in that said annular flange is covered with a layer of a coating of magnetizable material carrying at least one track on which is inscribed a series of markers polarized alternately in the peripheral direction, this track comprising at least one singular mark, and in that said seal support bears opposite said track at least one magnetic field detector.

Thanks to such a seal, it will no longer be necessary to proceed, during assembly, to mechanical indexing to create a reference. The seal can be mounted on the shaft in any angular position, and it will suffice, by rotating the engine (the starter) a few turns to locate the angular gap (a) between the singular mark and the TDC of the crankshaft. , and memorize it once and for all, in order to then know, by comparison, the position of this TDC during normal engine operation.

In addition, the vibratory phenomena of the motor are completely overcome, because the variations in the air gap (space between the magnetic field detector and the coating of the collar) will have no influence on the counting of the pulses generated by the marks. polarized of this coating.

Finally, we can keep the performance of a dynamic seal in the same size as a standard seal, with the same flexibility of assembly by the choice of active magnetic technology and by the electronic auto-indexing by memorization which come. to be described.

Advantageously, said series of alternately polarized marks comprises equiangular sectors polarized alternately north and south over the entire periphery of said track, with the exception of a neutral sector constituting said singular mark.

It will also be advantageous to provide that said coating of magnetizable material is elastoferrite and that said magnetic field detector is formed by a Hall effect probe or a magnetoresistance.

The invention also relates to a method of implementing a seal in accordance with the above, characterized in that said seal is mounted in any angular position on said shaft, the shaft is brought into the angular position of desired reference, the magnetic field detector is connected to its power supply, which provides an angular reference signal, the shaft is rotated, and finally, the angular phase shift between said singular coordinate system and said desired reference position of the shaft is identified and stored in memory.

An embodiment of the invention will now be described by way of non-limiting example with reference to the figures of the appended drawing in which:

- Figure 1 is a half-view in axial section of a dynamic seal of the cassette type according to the invention;

- Figure 2 is a schematic front view showing the magnetized track of the coating of the collar; and

FIG. 3 shows the diagram of the pulse signals coming from the magnetic field detector (Hall voltage V = f (t)) with the memorized signal for identifying the TDC of an internal combustion engine.

In FIG. 1, the dynamic seal of the cassette type comprises a sleeve 1 with an annular flange 2, suitable for being fixed in rotation on a rotating shaft 3, for example of the crankshaft of an internal combustion engine, and a support 4 of an annular seal 5 made of elastomer with a circular sealing lip 6 (reference 7 designates backpressure ridges ensuring better sealing). The elastomeric material 13 of the seal covers the entire surface of the support 4, so as to ensure a tight fixing in the corresponding housing of the fixed part 7.

These arrangements being known, the invention relates more precisely to the fact that the annular collar 2 is covered with a layer of a coating 8 of magnetic material (elastoferrite) carrying a circular track 9 (FIG. 2) on which is inscribed a series of equiangular sectors polarized alternately north and south, referenced 10, with an interruption at the level of a sector 11 constituting a singular reference point among the reference marks 10. This constitutes a coding adapted to the concept of absolute angular positioning.

At least one magnetic field detector, advantageously a Hall effect probe (or a magnetoresistance) 12, is overmolded in the elastomeric material 13 of the support 4, opposite track 9, and transmits a train of pulses 14 (figure 3) on an external connector 15 which can be connected to the motor power supply unit and which is connected to the Hall sensor 12 by a cable 16, the reference 17 designating an electronic module integrated into the connector 15. The role of this module is to ensure the processing of the signal 14, the management of the notion of absolute and the auto-indexing.

The innovative feature of the cassette-type dynamic seal thus described is that it incorporates active magnetic technology, allowing self-indexing by memorization, regardless of the mounting position of the cassette seal on the shaft 3, of particular angular positions, or to know at any time the angular position of the rotating part of the user member (crankshaft) in addition to sensing a rotational speed (simply incremental).

Thus, the seal being mounted on the shaft 3 in any angular position of the singular sector 11 (corresponding to the free space 18 in the pulse train 14), it will suffice to make the motor perform a few revolutions to locate the pulse 19 corresponding to the top dead center (TDC) of the engine, and to memorize in the module 17 its angular offset a with the singular reference mark 11, in order then to obtain a precise identification of this TDC during normal operation, this whatever the speed of rotation ω of the motor.

The invention has the advantage that the measurement (counting of pulses) is practically insensitive to interference and vibrations, the thickness E of the air gap having very little influence on the amplitude of the pulses 14, and the variations being in any case insufficient to pass the detection threshold of the Hall probe.

It will also be noted that the number of parts to be assembled can be reduced compared with the assembly of a dynamic seal of the conventional cassette type providing the same functions.