EP0463900B1 - Lubrication system for the contacting surfaces of a camshaft and a hydraulic tappet for an internal combustion engine - Google Patents

Description

The present invention relates to a system for lubricating the surfaces in contact with a camshaft and a hydraulic tappet for an internal combustion engine according to FR-A-2 006 542.

These pushers generally comprise a jacket comprising a first hydraulic compression chamber for adjusting the clearance of a corresponding valve, this chamber being supplied from a source of fluid through a first orifice formed in the side wall of the jacket, when the pusher is in the high position.

In internal combustion engines, in which the valves are actuated by hydraulic tappets, it is necessary to lubricate the surfaces in contact with the camshaft and the tappet. For this, an oil bath is created in the bottom of the cylinder head of the engine, this oil bath also making it possible to evacuate the calories released by the friction of the moving parts.

To supply this oil bath, we currently use either a lubrication ramp provided in the cylinder head cover or attached to it, or a supply channel for the hydraulic lifters with pressurized fluid, provided in the cylinder head, practicing in this cylinder head of the holes opening on the one hand into this channel and on the other hand, at the level of the cams.

However, these different solutions have a certain number of drawbacks. Indeed they require additional parts or machining. Furthermore, the fluid flow is permanent so that there can be an overabundance of fluid in the bottom of the cylinder head, which means that the overflow must be discharged to the oil tank located at the bottom of the engine.

The object of the invention is therefore to solve these problems by proposing a lubrication system for surfaces in contact with the camshaft and the hydraulic valve which is simple, reliable and which avoids any machining or addition of additional parts in the cylinder head.

To this end, the subject of the invention is a system for lubricating the surfaces in contact with a camshaft and a hydraulic tappet for an internal combustion engine, in which the tappet comprises a jacket comprising a first hydraulic compression chamber for adjusting the clearance of a corresponding valve, supplied from a source of fluid through at least one first orifice formed in the side wall of the jacket, when the pusher is in the high position, characterized in that the jacket comprises a second hydraulic chamber, above the first, at least one second orifice opening into the second chamber, formed in its side wall above the first, at a distance corresponding to the stroke of the pusher, so that the second chamber is supplied from the source when the pusher is in the low position, and at least a third orifice formed in its upper wall, opening on the one hand in the second chamber and on the other hand near the surfaces in contact with the camshaft and the tappet to lubricate them.

• La figure 1 est une vue en coupe d'une partie d'un moteur à combustion interne illustrant différents systèmes de lubrification d'un arbre à cames et d'un poussoir, de l'état de la technique ;
• la figure 2 est une vue en coupe partielle d'un poussoir hydraulique de l'état de la technique ;
• la figure 3 est une vue en coupe partielle d'un poussoir hydraulique entrant dans la constitution d'un système de lubrification selon l'invention ; et
• les figures 4 et 5 illustrent le fonctionnement d'un système de lubrification selon l'invention.

The invention will be better understood with the aid of the description which follows, given solely by way of example and made with reference to the appended drawings in which:

• Figure 1 is a sectional view of a portion of an internal combustion engine illustrating different lubrication systems of a camshaft and a tappet, of the prior art;
• Figure 2 is a partial sectional view of a hydraulic plunger of the prior art;
• Figure 3 is a partial sectional view of a hydraulic tappet forming part of a lubrication system according to the invention; and
• Figures 4 and 5 illustrate the operation of a lubrication system according to the invention.

As can be seen in Figure 1, and as already mentioned, to supply the oil bath created in the bottom of the cylinder head to lubricate the contact surfaces of a camshaft 1 and a hydraulic tappet 2, in the state of the art, either a lubrication ramp 3 made in the cylinder head cover 4 or attached to it, or the channel 5 for supplying the hydraulic tappets with pressurized fluid, making holes in the cylinder head 6. One end of these holes opens into this channel and the other, at the level of the cams. As previously mentioned, these different solutions have a certain number of drawbacks which will not be recalled.

The hydraulic tappets 2 of the prior art, one of which is shown in Figure 2, have a jacket 8 and a piston assembly 9 used to adjust the clearance of a corresponding valve. An annular spacer 10 disposed between the piston assembly 9 and the side wall of the jacket 8, delimits an annular chamber 11 intended to contain the hydraulic fluid necessary for the operation of the pusher. This fluid is introduced into this chamber by means of an annular groove 12 formed in the external surface of the side wall of the jacket, and of an orifice 13 opening on the one hand into the chamber 11 and on the other hand into the groove 12, from the feed channel 5 described with reference to FIG. 1.

An orifice 14 (Figure 1), one end of which opens into this channel 5, is also provided in the cylinder head, to supply this chamber with fluid when the pusher is in the high position.

If we now refer to Figure 3 which is a sectional view of a pusher used in the constitution of a lubrication system according to the invention, we see that it has the same elements as those described in look of Figure 2 namely a jacket 15, a piston assembly 16, a first annular spacer 17 between the side wall of the jacket and the piston assembly, a first orifice 18 opening into a first annular groove 19 for the supply of a first chamber 20 of fluid necessary for the operation of the piston assembly. According to the invention, the jacket 15 comprises a second hydraulic chamber 21 formed above the first. The first and second hydraulic chambers of this jacket are separated by an annular spacer 22 one end of which is fixed to the interior surface of the side wall of the jacket 15 and the other to the interior surface of the top wall of this jacket.

This jacket also includes at least a second orifice 23 opening into this second chamber 21, this orifice being formed in the side wall of the shirt, above the first orifice 18 at a distance corresponding to the stroke of the pusher so that the second chamber 21 is supplied from the source 5 when the pusher is in the low position, as will be described in more detail below. This orifice also opens into an annular groove 24 parallel to the groove 19 described above.

The jacket also comprises at least a third calibrated orifice 25 formed in its upper wall, this orifice opening on the one hand into the second chamber 21 and on the other hand near the surfaces in contact with the camshaft and the tappet to lubricate them. It should be noted that the annular spacers 17 and 22 can be fixed in any suitable manner in the jacket, for example by crimping or welding by electronic bombardment.

As can be seen in FIG. 4, when the pusher 2 is in the high position, the supply conduit 5 and the orifice 14 opening into it are opposite the orifice 18 formed in the side wall of the jacket 15, this orifice opening into the chamber 20 of pressurized fluid necessary for adjusting the clearance of a corresponding valve. On the other hand, if the pusher is in the low position (FIG. 5) the channel 5 for supplying fluid and the orifice 14 opening into it, are opposite the conduit 23 supplying the second chamber 21. Thus in this position of the plunger the source of fluid feeds this second chamber 21, the pressurized fluid escaping from this chamber through the orifice 25 formed in the upper wall of the jacket near the surfaces in contact with the camshaft and the pusher, to lubricate them.

The orientation and size of this orifice 25 can be determined to precisely direct a certain amount of fluid on the facing surfaces to obtain optimal lubrication.

It is thus possible to control the flow of lubrication fluid towards these surfaces insofar as this flow takes place in each chamber only during part of the working time. This structure makes it possible to avoid any machining or the addition of additional parts in the cylinder head or the cylinder head cover and requires only a minor modification of the pusher.

It goes without saying of course that other modes of realization can be considered. Thus, for example, the annular groove 24 (FIG. 3) may have several orifices spaced around its periphery to improve the filling of the second chamber. Likewise, several orifices oriented differently may be provided in the upper wall of the pusher to ensure the simultaneous lubrication of several elements, for example in the case of engines having twin camshafts or valve controls by combined cam / latch devices.

Claims (4)

1. A system for lubrication of the contact surfaces of a camshaft and a hydraulic tappet in an internal combustion engine, wherein the appet (2) has a casing (15) including a first hydraulic compression chamber (20), for adjustment of the clearance of a corresponding valve, and fed by a fluid supply (5) via at least a first aperture (18) provided in the lateral wall of the casing (15), when the tappet is in its raised position, characterised in that the casing (15) comprises a second hydraulic chamber (21), above the first, and with at least a second aperture (23) which opens into the second chamber (21) and is arranged in the lateral wall thereof, above the first aperture, at a distancc corresponding to the displacement of the tappet, in order that the second chamber (21) can be fed from the supply (5) when the tappet is in its lowered position, at least a third aperture (25), provided in the upper wall of the chamber, opening, on the one hand, into the second chamber (21) and, on the other hand, in the vicinity of the contact surfaces of the camshaft and the tappet for lubrication thereof.
2. A lubrication system in accordance with claim 1, characterised in that the second aperture (23) opcns into an annular recess (24) provided in the exterior surface of the lateral wall of the casing (15).
3. A lubrication system in accordance with claim 1 or 2, characterised in that the first and second chambers (20, 21) in the casing (15) are separated by an annular distance tube (22), one end thereof being secured on the interior surface of the lateral wall of the casing (15), and the other on the interior surface of the upper wall of the casing.
4. A lubrication system in accordance with any one of the preceding claims, characterised in that a plurality of differently oriented apertures are provided in the upper wall of the casing.

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