"Lubricant guide pin for a distribution apparatus of an endothermic motor"

[0001] The present invention relates to a guide pin for a distribution apparatus of an endothermic motor.

[0002] Endothermic distribution apparatuses, both Diesel and Otto cycle, comprise mechanisms placed between the cylinder valves and cam shafts. The purpose of said mechanisms is to regulate and control the valve lift or opening and closing depending on the rotation of the engine shaft with which the cam shafts are connected and synchronised.

[0003] In the prior art valve drive mechanisms exist which comprise a rocker arm, finger or lifter mechanically connected to the valve to control the lift movement and, in some cases, the closing movement thereof. In fact, in some types of distribution , the valves are closed by the thrust of specific closing springs while, in desmodromic distributions, the drive mechanisms of the valves guide both the opening and closing of said valves.

[0004] The aforementioned valve mechanisms are usually hinged in a fixed point, by means of one or more guide pins, so as to rotate under the thrust of the cam shaft.

[0005] The guide pins are highly stressed mechanical elements because of the friction with the respective drive mechanism and, in addition, because of the shear stresses and cyclic fatigue they are subjected to.

[0006] In the pins typical of the prior art such problems have not yet been resolved or at most only partially resolved. Said pins, in fact, incur in breakages due mainly to the problems spoken of.

[0007] The patent application BS2010A000202 in the Applicant's name, seeks to protect embodiments of the pin, and specifically, embodiments in specific materials, suitable to withstand such shear and fatigue stresses and above all, wear.

[0008] However, the problem remains in the prior art of the lubrication between the pin and mechanism which remains extremely difficult, especially in adverse operating conditions such as the presence of high temperatures.

[0009] The purpose of the present invention is to make a guide pin which overcomes such drawback effectively, i.e. lubricating the pin as well as possible and in particular its contact surface with the mechanism, minimising the problem of friction.

[0010] Such purpose is achieved by a guide pin according to claim 1.

[0011] Other embodiments of the guide pin according to the invention are described in the subsequent claims.

[0012] Further characteristics and advantages of the present invention will be more clearly comprehensible from the description given below of its preferred and non-limiting embodiments, wherein:

[0013] - figure 1 shows a cross-section view of a first distribution apparatus comprising a guide pin according to the present invention;

[0014] - figure 2 shows a cross-section view of a second distribution apparatus comprising a guide pin according to the present invention;

[0015] - figures 3 and 3a are respectively a side view and a plan view of the guide pin in one embodiment;

[0016] - figures 4 and 4a are respectively a side, partly cross-sectioned view and a plan view of the guide pin in a further embodiment.

[0017] With reference to the aforementioned drawings, reference numeral 4 globally denotes a guide pin for a drive mechanism 8 of valves 12 of a distribution apparatus 16 of an endothermic motor.

[0018] The guide pin 4 is an overall cylindrical shape and defines a rotation axis X-X for the associable drive mechanism 8.

[0019] The drive mechanism 8 of the valves 12 may be of various types and, for example comprises a rocker arm, finger or lifter operatively connected to the valve 12 to control the opening and/or closing movement thereof. [0020] The valve 12 is typically a mushroom valve and comprises stem 18, by means of which it is operatively connected to the drive mechanism 8 and a head 20, connected to the stem 18 on the opposite side to the drive mechanism 8. The head 20 is used to occlude the opening of the relative suction or exhaust duct 24 which the valve 12 is mounted on.

[0021] The drive mechanism 8 is hinged to said guide pin 4 so as to rotate around the rotation axis X-X identified by said guide pin .

[0022] The drive mechanism 8 is fixed, preferably hinged, in an intermediate point thereof, in relation to which there are two opposite ends; a first control end 28, mechanically interfaced to the valve 12, and in particular to the stem 18, and second drive end 32 which receives the motion from a relative cam shaft 36 of the distribution apparatus 16.

[0023] The connection between the second drive end 32 may be directly to the cam shaft, for example by sliding

(figure 1) or a connection rod 15 may be interposed

(figure 2 ) .

[0024] The guide pin 4 is thus fixed in relation to the drive mechanism 8 and is suitable to support said drive mechanism in rotation.

[0025] In a preferred embodiment, the pin 4 has a lateral surface 40 suitable to come into contact with said drive mechanism 8.

[0026] Preferably, the pin 4 also has a cross-section axis S-S perpendicular to the rotation axis X-X; in other words, cross-sectioning the cylindrical guide pin 4 along the cross-section axis S-S, perpendicular to a plane lying on the rotation axis X-X, a circle is obtained.

[0027] In a preferred embodiment, the. pin 4 comprises on said lateral surface 40 a flattening 50 which extends in length parallel to the rotation axis X-X in a central portion of the pin 4. The purpose of said flattening 50 is that of containing the lubricant liquid in such a way as to bathe the inner surface of the mechanism 8 facing it.

[0028] Preferably, in relation to the rounded lateral surface 40, the flattening 50 is internally hollowed towards the pin 4, for example by means of a tool for the purpose, and parallel to the rotation axis X-X.

[0029] Preferably the flattening is inside the pin 4 by several tenths of millimetre.

[0030] Preferably the flattening 50 is made in a symmetrical manner centrally. to the pin 4.

[0031] Preferably, along the extension of the flattening 50, two opposite ends 51 may be identified; preferably said ends 51 also join together the difference in level of the flattening 5 and the lateral surface 40.

[0032] In a preferred embodiment, on the lateral surface 40 the pin 4 further comprises a lubrication groove 60; said lubrication groove 60 extends circumferentially around the pin 4, in other words turning around the pin 4 in its entirety, inclined in relation to the direction of the cross-section axis S-S. The purpose of said groove 60, similarly to the flattening 50, is to contain the lubricant liquid in such a way as to bathe the inner surface of the mechanism 8 facing it. In addition the lubrication groove 60 is also intended to permit the feeding of lubricant liquid in the flattening 50 itself.

[0033] Preferably, the lubrication groove 60 is a channel made in the lateral surface 40 with a radius of several tenths of millimetre.

[0034] In a preferred embodiment, the lubrication groove 60 extends starting from one end 51 of the flattening 50.

[0035] Preferably, the lubrication groove is inclined in relation to the cross-section axis S-S substantially by 10°-20°, preferably by 15°. a indicating the angle between the cross-section axis S-S and the direction of inclination of the lubrication groove 61, the angle a is thus comprised between 10 and 20°.

[0036] In a preferred embodiment, the lubrication groove 60 extends in a helical pattern along the pin 4. [0037] In a further embodiment variation the pin 4 comprises two lubrication grooves 60 extending in opposite directions, for example in a helical pattern.

[0038] Preferably, the two lubrication grooves 60 intersect on the side opposite the flattening 50.

[0039] In a preferred embodiment, as well as the lubrication grooves 60, the pin 4 also comprises a circumferential lubrication groove 61, i.e. which extends parallel to the cross-section axis S-S.

[0040] Preferably, the circumferential lubrication groove 61 is perfectly positioned on the centreline of the guide pin 4.

[0041] Preferably, the characteristics and purposes of the circumferential lubrication groove 61 are the same as those of the lubrication groove 60.

[0042] In said embodiment, preferably, the lubrication groove 60 and the circumferential lubrication groove 61 intersect on the opposite side of the pin 4 to the flattening 50.

[0043] Preferably, in addition, the guide pin 4 also comprises a lubrication duct 70 suitable for crossing it internally, to convey the lubricant liquid from one side of the pin to the other.

[0044] In a preferred embodiment, the lubrication duct 70 also passes through or intersects the rotation axis X-X. [0045] The lubrication duct 70 thus has two ends or mouths positioned on the lateral surface 40.

[0046] Preferably, one of the ends or mouths of the lubrication duct 70 comes out in a lubrication groove 60.

[0047] In one embodiment variation, said end or mouth of the lubrication duct comes out in the point where the lubrication grooves 60 >, intersect, and even where the circumferential lubrication groove 61 intersects.

[0048] In a preferred embodiment, the guide pin 4 is made of metal, preferably bronze or brass; in further variants the guide pin 4 is made of aluminium or an aluminium alloy for example comprising 7A1, Si, Cu, n, Mg .

[0049] Preferably, the lateral surface 40 is coated by means of special heat treatments.

[0050] The method of making a guide pin 4 according to the invention is described below.

[0051] In particular, the pin is cut to size, for example starting from a solid circular cross-section bar made of the aluminium alloy described above.

[0052] The lubrication grooves 60 and if provided for, the circumferential lubrication groove 61 are then made on ^" the lateral surface 40.

[0053] Heat treatments are then performed on the guide pin 4.

[0054] Innovatively, the guide pin according to the invention permits a much more efficient lubrication than the guide pins of the prior art.

[0055] Advantageously, the guide pin according to the invention bathes a much wider area with the lubricant liquid than the guide pins of the prior art.

[0056] In addition, advantageously, thanks to the guide pin according to the invention the friction created between the lateral surface of the pin and the mechanism is minimised.

[0057] According to a further advantageous aspect, the guide pins do not need to be in low friction coefficient materials given that the problem is resolved by the structure and positioning of the components comprised in the pin.

[0058] According to a further advantageous aspect, the pin can be made in a material suitable to withstand the shear and cyclic fatigue forces.

[0059] Advantageously, the manufacturing of the guide pin according to the. -invention is not entirely revolutionised. In addition, advantageously, by means of numerical control machines the lubrication groove inclined in relation to the cross-section axis S-S can be reproduced in a single operation.

[0060] According to a further advantageous aspect, by means of numerical control machines the lubrication grooves can be produced with a helical pattern according to different angles of inclination and in a variable number, from one upwards.

[0061] According to a further advantageous aspect, the pin according to the invention by having improved lubrication, i.e. better distributed, may be minimised and made in smaller dimensions than those of the prior art .

[0062] Advantageously, a pin of minimised dimensions and thus occupying less space also entails a series of advantages in the design, placement and construction of the motor itself.

[0063] A person skilled in the art may make numerous modifications and variations to the guide pins described above so as to satisfy contingent and specific requirements, while remaining within the sphere of protection of the invention as defined by the following claims.