FR2489880A1 - VALVE CONTROL MECHANISM FOR INTERNAL COMBUSTION ENGINE - Google Patents

Abstract

IN THIS VALVE CONTROL MECHANISM FOR AN INTERNAL COMBUSTION ENGINE WHICH USES A TOOTHED BELT AND TOOTHED PULLEYS FOR DRIVING THE CAMSHAFT THROUGH THE CRANKSHAFT, THE CLEARANCE X BETWEEN THE BELT TOOTH 4 NOTCH AND THE SPACE 5 BETWEEN TEETH WHICH IS PRESCRIBED FOR THE NORMAL APPLICATION OF A CERTAIN TEETH.

Description

The present invention relates to a mechanism for controlling the

  valves for an internal combustion engine in which a toothed belt essentially formed by an endless traction element, which is part of an inextensible frame and a series of plastic teeth

  flexible molded on this frame, which cooperate with

  plastic metal toothed lees having corresponding teeth and fixed, on the one hand, to the crankshaft and,

  on the other hand, on the camshaft of the internal combustion engine

dull.

  Already known from the published German application NO 29 06 619 a toothed belt for this type of valve control mechanism for an internal combustion engine. In the case of this toothed belt, we have proposed different

  measures to avoid generating vibrations in the drive

camshaft.

  Valve control mechanisms for internal combustion engines which use toothed belts of known construction frequently present difficulties

  which result from the fact that the crankshaft of a

  internal bust, as well as the camshaft of such an engine do not rotate in a uniform way but with torsional vibrations. If this type of valve control mechanism falls within a range of torsional vibration resonance,

  this can cause unwanted relative movements in-

  be the toothed pulleys and the toothed belt and drive

  premature wear of the toothed pulleys.

  The object of the invention is to improve a mechanism

  transmission me known by the German application published NO

  19 57 922, which describes a toothed belt having a pro-

  well-defined toothing and toothed pulleys with

  a corresponding toothing profile, so that this mechanism

  can be used as a control mechanism for

  valves of an internal combustion engine without installing pro-

noise or wear problems.

  According to the invention, this problem is solved by a method

  valve control mechanism for combustion engine.

  internal of the type indicated above and in which the play enters

  the tooth and the spacing of the teeth which is preserit for the app-

  normal bite of a certain toothing is reduced approxi-

matively to half.

  In the aforementioned German application I'T ^ 19 57 922 which forms the basis of the invention, there are formulas for the calculation of a toothing profile for a toothed belt.

  suitable for a particular application and for cal-

  bottom of the corresponding toothing profiles of the toothed wheels

  or the toothed belts, respectively.

  By reducing the play resulting from these formulas between the tip of a tooth of the toothed belt and the entry of the toothed pulley to approximately half of the play calculated according to these formulas, the vibrations of the transmission are avoided.

  toothed belt which produce noise and wear when

  that this transmission is used in a

  controls valves for internal combustion engine which

  carries torsional vibrations. This halving of the normally planned clearance which is carried out in accordance with the invention does not only have the effect of avoiding vibrations

  of the toothed belt transmission but also of

  absorb the torsional vibrations of the shafts of the

  valve control which is driven by the timing belt

  tee. Other characteristics and advantages of the invention

  will appear during the description which follows. the-

  sin appended, given only as an example shows the co-

  peration between the profile of a tooth of a toothed belt and

  the profile of the entry of a toothed pulley.

  the drawing shows a toothed belt 1 in the stretched state.

  This toothed belt 1 is essentially formed of an element

  endless 3 tensile resistant, which constitutes a

  inextensible frame and one, series of molded teeth 4.

  A toothed pulley 2, which is shown as

  developped, that is to say with a rack profile, pre-

  feels a space between the teeth 5 made in accordance with the

  those of the aforementioned application 19 57 922 which is the basis of the invention.

  Interaction between tooth 4 and entry 5 occurs

  duit in this case with a given set X which represents the extent

  the movement of tooth-4 in entry 5.

  In the drawing, a dashed line represents the modified 4 ′ shape of the tooth which leads to a reduction in the

  clearance between tooth 4 'and entry 5 at a value X / 2.

  Of course, instead of widening tooth 4, we can

  also narrow the entry 5 in a corresponding manner.

Claims (3)

Claims   1 - Valve control mechanism for an engine   internal combustion in which a toothed belt   partly formed of an endless traction element, which is part of an inextensible frame and a series of teeth in   flexible plastic material molded onto this frame, which co-   run with metal or plastic toothed pulleys having corresponding teeth and fixed, on the one hand, on   the crankshaft and, on the other hand, on the camshaft of the mo-   internal combustion tor, this mechanism being characterized in that the clearance (x) between the tooth (4) and the space (5) between   teeth which is prescribed for the normal application of a certain   the teeth are reduced to about half (X / 2).   2 - Valve control mechanism according to the re-   vendication 1, characterized in that the reduction of the clearance to half (X / 2) is obtained by corresponding widening   of the tooth (4 ') the space (5) between teeth remaining unchanged.   3 - Valve control mechanism according to the re-   vendication 1, characterized in that the halving of the clearance (X / 2) is obtained by narrowing the space between teeth,   the width of the tooth (4) remaining unchanged.