Desmodromic valve closing and opening device

Abstract

Desmodromic device for closing and opening a valve. The invention relates to a desmodromic device for closing and opening a valve allowing the valve to be opened via a single alternately pivoting latch. It consists of a valve which has two surfaces (1) and (2) which face each other and a latch which has two parts (5) whose ends partially surround the valve on either side of the valve collar between the surfaces (1) and (2) and each of the ends of the two parts (5) of the latch has two rounded surfaces (3) and (4) for respective contacts with each of the surfaces (1) and (2) of the valve. The device according to the invention is particularly intended for variable volume chambers. Figure to be published for the abstract: Figure 12

Description

Title of the invention: Desmodromic device for closing and opening a valve

[0001] The present invention relates to a desmodromically controlled valve closing and opening device intended in a generally non-exhaustive manner for variable volume chambers.

[0002] The device according to the invention relates to a valve closing and opening device in which a rotating pawl pivoting alternately relative to a cylinder head is connected to two cams of one or two camshafts on the one hand, and on the other hand connected to a valve.

[0003] In the current state of the art, desmodromic valve closing and opening control systems comprise two latches for each valve, one intended to close it and one intended to open it. In order to reduce the manufacturing cost, friction and energy consumption of the desmodromic valve closing and opening control system, the device according to the invention aims, starting from a valve and a latch adapted to allow the closing and opening of the valve with a single latch.

[0004] The device according to the invention does not concern the link between the two cams and the pawl.

[0005] In the device according to the invention, a single rotating pawl pivoting alternately relative to the cylinder head controls the closing and opening of one or possibly several valves.

[0006] In the device according to the invention, the link between the pawl and the valve is provided so that there is play when the valve is in the closed position and there is no or almost no play when the valve is in the approximately three-quarter open position, a position which, in the closing or opening phase of the valve, corresponds to the situation where the acceleration of the valve along its translation axis changes direction, and or to avoid shocks and vibrations harmful to the longevity and operation of the system, it is necessary that there is no or almost no play between the valve and the pawl in this situation of approximately three-quarter open position of the valve.

[0007] In the device according to the invention, the clearance at closing between the latch and the valve allows the valve to be closed without harmful stresses and this independently of the phenomena of thermal expansion due to temperature variations in the valve, the latch and the other surrounding elements.

[0008] In the device according to the invention, a valve has two flat surfaces which face each other while two parts of a pawl have ends which surround by entially the valve collar between the two facing valve surfaces, the two parts of the pawl whose respective ends partially surround the valve on either side of the valve collar between the two facing valve surfaces having at their ends two rounded surfaces for respective contacts with each of the two facing valve surfaces, called rounded pawl surfaces which, in order to reduce friction, may be wheels carried by the ends of the parts of the pawl which partially surround the valve on either side of the valve collar between the two facing valve surfaces.

[0009] [Fig.l] represents a valve of the device according to the invention. [Fig.2] represents a valve of the device according to the invention. [Fig.3] represents a latch without wheels of the device according to the invention. [Fig.4] represents a latch without wheels of the device according to the invention. [Fig.5] represents a latch without wheels of the device according to the invention. [Fig.6] represents a latch with four wheels of the device according to the invention. [Fig.7] represents a latch with four wheels of the device according to the invention. [Fig.8] represents a latch with four wheels of the device according to the invention. [Fig.9] shows the valve seat as well as the valve in the closed position and the latch with wheels of the device according to the invention. [Fig. 10] shows the valve seat as well as the valve in the closed position and the latch with wheels of the device according to the invention. [Fig. 11] shows the valve seat as well as the valve in the closed position and the latch with wheels of the device according to the invention. [Fig. 12] shows the valve seat as well as the valve in the three-quarter open position and the pawl with wheels of the device according to the invention. [Fig. 13] shows the valve seat as well as the valve in the three-quarter open position and the pawl with wheels of the device according to the invention. [Fig. 14] shows the valve seat as well as the valve in the three-quarter open position and the latch with wheels of the device according to the invention.

[0010] With reference to these drawings in which the valve guide, the cams and the parts of the pawl linked to the cams as well as the bearings of the pawl are not shown, the valve comprises two flat surfaces (1) and (2) which face each other, which are both normal to the axis of the neck of the valve and are such that by rotating the valve around its axis the occupied volume remains unchanged, the pawl comprises two parts (5) whose ends partially surround the valve on either side of the neck of the valve between the surfaces (1) and (2) of the valve which face each other, each of the two parts (5) of the pawl comprising at the end two rounded surfaces (3) and (4) for respective linear contacts with the surfaces (1) and (2), are for the link between the pawl and the valve four rounded surfaces of which two (3) for linear contact with the face (1) intended to open the valve and two others (4) for linear contact with the face (2) intended to close the valve, with an alternative rotational movement of the pawl which allows that there is no play between the pawl and the valve in the three-quarter open position of the valve by a contact or quasi-contact between the surfaces (1) and (3) as well as a contact or quasi-contact between the surfaces (2) and (4), and that there is play between the pawl and the valve in the closed position of the valve by a play between the surfaces (1) and (3) and by a play between the surfaces (2) and (4).

[0011] In the device according to the invention, in the three-quarter open position of the valve and in a section plane normal to the pivot axis of the pawl, the curves corresponding to the rounded surfaces (3) and (4) have radii of curvature at the level of contact with (1) and (2) of which the sum of these two radii of curvature is strictly less than the distance between the surfaces (1) and (2) and this so that the play appears when the pawl pivots while closing the valve.

[0012] In the context of an industrial application, the valve may include a magnet or an electromagnet near its stem to ensure the valve is properly closed during its closing phases.

[0013] In order to increase the structural strength and reduce the rotational inertia of the pawl, the two parts (5) of the pawl which surround the valve on either side of the collar between the two surfaces (1) and (2) can be joined together near the axis of the pawl, and together they have a shape which is similar to that of a tuning fork.

Claims

Claims

1. Desmodromic valve closing and opening device comprising a valve positioned by contacts with a rotary pawl pivoting alternately relative to a cylinder head, the valve comprising two flat surfaces (1) and (2) which face each other and are both normal to the axis of the valve neck, the pawl comprising two parts (5) whose ends partially surround the valve on either side of the valve neck between the two surfaces (1) and (2) of the valve which face each other, each of the two parts (5) of the pawl comprising at its end two rounded surfaces (3) and (4), one (3) for linear contact with the surface (1) of the valve and the other (4) for linear contact with the surface (2) of the valve, characterized in that in the closed position of the valve there is a clearance between the surfaces (1) and (3) as well as a clearance between the surfaces (2) and (4),in that in the three-quarter open position of the valve the surfaces (3) and (4) of the pawl are respectively in contact or quasi-contact with the surfaces (1) and (2) of the valve, in that in the three-quarter open position of the valve and in a section plane normal to the pivot axis of the pawl the curves corresponding to the rounded surfaces (3) and (4) have radii of curvature at the level of contact with (1) and (2) of which the sum of these two radii of curvature is strictly less than the distance between the surfaces (1) and (2).,

2. Device according to claim 1 characterized in that four wheels carried by the pawl act as surfaces (3) and (4) of the pawl for contact with the surfaces (1) and (2) of the valve.

3. Device according to claim 1 or claim 2 characterized in that said valve comprises near its tail a magnet or an electromagnet allowing it to be closed properly in its closing phases.

4. Device according to any one of the preceding claims, characterized in that said pawl in reciprocating rotational movement has a position determined by a double contact between the pawl and two cams of a camshaft.

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