EP0092447B1 - Distribution device for an axial engine - Google Patents

Description

The present invention relates to an axial motor known as a barrel, with controlled ignition or with compression ignition and relates more particularly to a distribution device for an axial motor comprising for each valve a rocker arm and a pusher actuated by a cam.

Patent FR 2 267 446 (BRILLE) describes an axial motor distribution device in which it was sought to use cams from existing motors and which included a complicated kinematic chain which cannot be generalized in application to any number of cylinders.

The invention aims for this generalization to use a distribution system derived from those of star motors, which motors have from this point of view a certain analogy with axial motors.

It is known, in the field of aviation engines with star cylinders, to control all the intake valves by a cam with several bosses and all the exhaust valves by another cam mounted on the same sleeve.

The adaptation to axial motors of the solutions used in star motors generally poses, due to the proximity of all the cylinder heads of the axial motor, problems of bulk. These problems lead to difficulties in making the proper dispensing movements, in adjusting the clearances and in mass production.

The invention proposes to solve these problems. To this end, the distribution device according to the invention is characterized in that each rocker arm is shown to be pivoting in a rocker arm itself mounted to slide in a direction perpendicular to the stem of the corresponding valve and whose position in translation is obtained by means of a control member with external control urging this rocker arm to bear respectively against a push rod and said valve stem.

This arrangement allows its compactness to greatly reduce the size of the axial motor. The simplicity of the distribution members allows economical construction and smooth operation.

According to another embodiment of the invention, the rocker lever and the rocker holder are received in two cylindrical housings formed in a fixed annular part, mutually parallel and perpendicular to the axis of the engine, and communicating with each other by a space intended for the passage of the rocker arm.

• la figure 1 est une vue d'un moteur axial selon la présente invention en coupe par un plan passant par la came de distribution ;
• la figure 2 est un schéma d'un cylindre et de ses soupapes ;
• la figure 3 est une vue en coupe d'une partie de la distribution suivant les plans de coupe indiqués à la figure 2 ;
• la figure 4 est une vue partielle du moteur axial en coupe par un plan longitudinal passant par l'axe de la pompe à huile, permettant de montrer la commande de la came tournant dans l'exemple choisi dans le même sens que l'arbre moteur ;
• la figure 5 est une vue éclatée en perspective montrant un ensemble poussoir, culbuteur et porte-culbuteur disposé en face de son logement ;
• la figure 6 est une vue en perspective d'un ensemble poussoir, culbuteur et porte-culbuteur en position assemblée ;
• la figure 7 est une vue en coupe partielle d'un mode de réalisation du moteur axial avec les deux cames de commande d'admission et d'échappement ;
• la figure 8 est une vue schématique montrant la conjugaison des surfaces de contact d'un culbuteur et du poussoir correspondant ;
• la figure 9 est un graphique partiel de distribution permettant de calculer le décalage des poussoirs.

Other objects, advantages and characteristics of the invention will appear on reading the description of an embodiment of the invention given without limitation and with reference to the appended drawings in which:

• Figure 1 is a view of an axial motor according to the present invention in section through a plane passing through the timing cam;
• Figure 2 is a diagram of a cylinder and its valves;
• Figure 3 is a sectional view of part of the distribution along the sectional planes shown in Figure 2;
• Figure 4 is a partial view of the axial motor in section through a longitudinal plane passing through the axis of the oil pump, to show the control of the rotating cam in the example chosen in the same direction as the motor shaft ;
• Figure 5 is an exploded perspective view showing a pusher assembly, rocker arm and rocker arm disposed opposite its housing;
• Figure 6 is a perspective view of a pusher, rocker and rocker arm assembly in the assembled position;
• Figure 7 is a partial sectional view of an embodiment of the axial motor with the two intake and exhaust control cams;
• FIG. 8 is a schematic view showing the combination of the contact surfaces of a rocker arm and of the corresponding pusher;
• Figure 9 is a partial distribution graph for calculating the offset of the pushers.

The axial engine shown in Figures 1 and 2 has a cylinder head-cylinder block 2 and a distribution compartment 3. The block 2 essentially comprises five cylinders 4 regularly distributed around the central axis XX 'of the engine and two intake circuits and exhaust described in patent FR 2 267 446 (SHINING) and of which a distinction is made between the inlet chapels 6 opening into a common annular channel 7. The distribution compartment 3 mainly comprises a fixed annular part 8 mounted tightly between two covers 9 and 10, and the following distribution members: a cam 12, rocker arms 17, rockers 21, rocker arms 31, adjustment members 41, exhaust 50 and intake 51 valves, valve guides 54 and valve springs 58.

Distribution is ensured for each cylinder 4 by two valves, one for the intake and one for the exhaust. These homologous valves are arranged concentrically with the axis XX ′ in the cylinder head where the seats 56 of the exhaust 50 and intake valves 51 and of the housings of the guides 54 of the valve stems 52 and 53 are formed. The valves 50 and 51 are controlled by a cam 12 constituted by a drum 13 carrying cam surfaces 14 arranged on its outer periphery.

The cam 12 rotates concentrically with the axis XX 'and is driven, as shown in FIGS. 3 and 4, by a toothed belt 62 from a central pinion 60 mounted on a motor shaft 5, a drive wheel 64 a shaft 65 of the oil pump, a pinion 66 made of material with the shaft 65, a second intermediate pinion 68 and a drive wheel 70 of the cam 12; this wheel 70 is mounted on the drum 13 of the cam 12 and is integral with the latter.

The fixed annular part 8 is removable and held in position between the covers 9 and 10 resting on the block 2. This part 8 is arranged radially between the cam 12 and the valve stems 52 and 53. It comprises pairs of parallel holes 80 and 82 communicating through a space 84. These pairs of identical holes between them are distributed at the periphery of the fixed annular part 8. They are all oriented relative to the central axis XX 'so that the holes 80 are radial and that the axes of the holes 82 are parallel to those of the holes 80. The holes 80 and 82 respectively receive the pusher 17 and the rocker arm 31 which have cylindrical outer surfaces.

The pusher 17 is in the form of a cylindrical part provided with two flats 18 and 19 parallel to the plane of the cam 12, and a groove 23 on the bottom of which the rocker arm 21 is supported by one of its ends 22. This groove 23 has the same orientation relative to the axis XX 'as that of the pairs of holes 80 and 82.

The rocker arm 21 is a flat monobloc lever which consists of a body 24 provided with a pivot formed by two pins 25 and 26. The body 24 is extended by two ends 22 and 28 in the form of a beak; these ends are supported respectively on the pusher 17 and on the end of the valve stem 53.

The rocker arm 31 is a cylindrical piece traversed longitudinally by an axial slot 32 through which the rocker arm 21 bears on the valve stem 53 by one of its ends 28.

This cylindrical part also has an axial groove 34 transverse to the slot 32. The bottom of the groove 34 constitutes the bearings. pivoting of the pins 25 and 26 of the rocker arm. This cylindrical part finally comprises a flat surface 36 perpendicular to the slot 32 and intended to avoid this part contact with the valve spring 58. An adjusting member 41 with external control, mounted on the block 2 acts on the face of end 38 of the rocker arm 30.

The pusher 17, rocker arm 21 and rocker arm holder 31 assembly is mounted in the assembled position in FIG. 6.

The normal embodiment of an axial motor with two cams intended to respectively control the opening of the intake and exhaust valves is illustrated in FIG. 7. The single drum 13 has an end comprising two series of cam surfaces 14 and 15 arranged on its outer periphery; these respectively control the exhaust valve 52 and inlet 53 rods via the pushers 16 and 17, the rocker arms 20 and 21, the rocker arms 30 and 31 with a general offset of the axis of the two cams.

Figure 8 is a view schematically showing the rocker arm in its two extreme positions (Figures 8a and 8c) and an intermediate position (Figure 8b). These three positions show the particular profile which is given to the end 22 of the rocker arm 21 in contact with the corresponding pusher 17 through the bottom of the groove 23. The point of contact of the end 22 with the bottom of the groove 23 is separated from the axis of the pins 25 and 26 by a variable distance because this end rolls on this groove bottom when the pusher is actuated by the cam 12. This variable distance therefore allows a variable multiplication ratio of the rocker arm.

• La courroie crantée 62, illustrée à la figure 4, entraîne la came unique 12 concentriquement à l'arbre moteur et dans le même sens de rotation pour l'exemple choisi. Cette came unique commande, que ce soit pour l'échappement ou pour l'admission, les poussoirs 16 et 17 qui attaquent directement les culbuteurs 20 et 21 ; ces culbuteurs commandent à leur tour directement les soupapes 50 et 51.

The distribution device described above operates as follows:

• The toothed belt 62, illustrated in FIG. 4, drives the single cam 12 concentrically with the motor shaft and in the same direction of rotation for the example chosen. This single cam controls, whether for the exhaust or for the admission, the pushers 16 and 17 which directly attack the rocker arms 20 and 21; these rocker arms in turn directly control the valves 50 and 51.

It is essential that the rocker arms 20 and 21 remain in their pivoting planes without turning or moving laterally in order to ensure correct operation. This problem is solved thanks to the arrangement of the pusher, rocker arm and rocker arm assemblies in the pairs of parallel holes 80 and 82 formed in the fixed annular part 8.

The rocker arm 21 bearing respectively against the pusher 17 and the valve stem 53 can tilt around its pivot constituted by the two pins 25 and 26 because the pusher 17 and the rocker arm 31 are immobilized in rotation due to the nesting of this rocker.

The translational position of the rocker arm 31 is obtained by means of the adjusting member 41 which acts on the end surface 38 of the rocker arm.

With a single cam for intake and exhaust, the exhaust valve is attacked first, which links the valve position and the direction of rotation of the cam.

• δ = 2(γ - α) avec 2γ=π+α+β
• 1) avec α = 20° et β = 40°, 1/68 = 33° environ
• 2) avec α = 15° et β = 45°, 1/68 = 35°

It is also necessary to ensure a suitable offset between two attacks such as, for example, in the five-cylinder axial motor: with an advance at the intake opening equal to α, a delay at the intake closure equal to β and a ratio of the speed of rotation of the camshaft to that of the motor shaft equal to r = + 1/6, the cam has three bumps spaced angularly by 120 ° and the offset of the push rods by the same cylinder is equal to δ / 6, δ being shown in Figure 9.

• δ = 2 (γ - α) with 2γ = π + α + β
• 1) with α = 20 ° and β = 40 °, 1/68 = 33 ° approximately
• 2) with α = 15 ° and β = 45 °, 1/68 = 35 °

As can be seen in FIG. 8, the dispensing device according to the invention allows, thanks to the particular structure of the pusher, rocker arm and rocker arm assembly and to the profile of the end of the rocker arm in contact with the pusher , to vary the ratio of multiplication of the rocker arm. This end 22 of rocker arm has a profile such that on attack, the multiplication ratio is minimal (figure a), which makes it possible to reduce the forces despite the very great inertia, and that at the end (figure C) , this ratio is maximum while the valve spring provides substantially equilibrium.

This property makes it possible to design, for an optimal lifting law with the lowest friction forces, a minimum bump height allowing in certain cases a non-concave cam profile by means of a judicious combination of the values assigned to the radius of the pusher surface in contact with the cam and at the radius of the top of the cam boss.

With the use of a single cam for exhaust and intake, the valve cannot keep its axis parallel to the engine axis as can be envisaged in the case of two separate cams shown in FIG. 7. This is due to the fact that the axes of the two exhaust and intake pushers must be offset by an angle 8/6 located in the vicinity of 33 ° to 35 ° in the example chosen and that the two radial planes containing the valve axes in the case of two cams form a dihedral with an angle less than 8/6.

As the pushers 16 and 17 must work radially with respect to the cam 12, each of the two assemblies comprising a valve, a rocker arm, a rocker arm, a slider for the plunger and two housings for the plunger and the rocker holder, same cylinder 4, is arranged along a plane defined by the intersection of the radius along which the tappet works and the axis of the valve stem, symmetrically to the other together with respect to the plane P passing through the axis of the cylinder and the axis XX 'of the engine. In the chosen example of the five-cylinder engine, the spokes along which the pushers 16 and 17 work are spaced by an angle located in the vicinity of 33 ° to 35 °, symmetrically to the plane P (see Figures 1 and 6).

As appears from the above description, the dispensing device according to the invention comprising modular assemblies each formed by a pusher, a rocker arm and a rocker arm holder, makes it possible to obtain a small footprint of the distribution compartment of a axial motor.

This device makes it possible to adjust and check the play of the rocker arms without any disassembly.

It lends itself well to valve spacing, therefore the use of a single cam for intake and exhaust.

This last property leads to better cooling thanks to the spacing of the intake and exhaust pipes, and an improvement in the shape of the combustion chamber by a possible bringing together of the spark plug from the axis of the cylinder: it also causes better machining of seats and valve guides by allowing a significant increase in the diameter of the tool holder which is thus almost concentric with the axis of the cylinder.

The variation of the multiplication ratio of the rocker arm allows in certain cases to build a cam profile without delicate machining concavity for a given optimal lifting law.

The possibility of lightening the rocker lifter to a large extent and the combination of two pins with a flat lever to form a monoblock rocker contribute to maximum reduction of the total inertia.

The distribution members according to the invention have fairly simple structures which favor their manufacture and their mounting and which thus contribute to reducing the manufacturing costs of the axial motor.

Claims (12)

1. A distribution arrangement for an axial internal combustion engine comprising, for each valve (51), a return spring (58), a rocker arm (21) and a thrust member (17) actuated by a cam (12), characterised in that each rocker arm (21) is journalled in a rocker carrier (31) which is itself mounted slidably in a direction perpendicular to the corresponding valve stem (53) and whose position in respect of translatory movement is obtained by means of an externally actuated adjusting member (41) which urges said rocker arm (21) in a condition of bearing respectively against a thrust member (17) and said stem (53) of the valve (51).

2. An arrangement according to claim 1 characterised in that the rocker arm thrust member (17) and the rocker arm carrier (31) are accommodated in two cylindrical openings (80, 82) provided in a fixed annular member (8), parallel to each other and perpendicular to the axis (XX') of the engine, and communicating with each other by way of a space (84) intended for the rocker arm (21) to pass therethrough.

3. An arrangement according to claim 1 or claim 2 characterised in that the rocker arm (21) is of a one-piece construction and that the pivot axis means thereof comprises two trunnions (25, 26).

4. An arrangement according to any one of claims 1, 2 and 3 characterised in that the rocker arm carrier (31) has a longitudinal axial slot (32) through which the rocker arm (21) bears against the valve stem (53), and an axial groove (34) which is transverse with respect to said slot and the bottom of which forms the bearings for pivotal movement of said rocker arm.

5. An arrangement according to any one of claims 1 to 4 characterised in that the thrust member (17) has two flats (18, 19) which are parallel to the planes of the cams and a groove (23), against the bottom of which the rocker arm (21) bears.

6. An arrangement according to any one of claims 1 to 5 characterised in that the rocker arm (21) has a cylindrical contact directrix surface that is conjugate with the flat face of the bottom of the groove (23) in the thrust member (17), of such a shape that at the beginning of the valve lift ; the multiplication ratio is at a minimum and at the end of said valve lift, said ratio is at a maximum.

7. An arrangement according to any one of claims 1 to 6 characterised in that, for a given valve lift, the cam (12) has a sufficiently low lobe height that the cam profile does not have any concave portions which are difficult to machine.

8. An arrangement according to any one of claims 1 to 7 characterised in that each of the two assemblies comprising a valve, a rocker arm carrier, a rocker arm, a thrust member slot and two housings for the thrust member and the rocker arm carrier, for the same cylinder, are disposed in a plane defined by the intersection of the radius along which the thrust member operates and the axis of the valve stem, symmetrically to the other assembly with respect to the plane passing through the axis of the cylinder and the axis (XX') of the engine.

9. An arrangement according to any one of claims 1 to 8 characterised in that it comprises two rigidly connected cams which are intended respectively to control all the intake and exhaust valves and which are offset longitudinally with respect to each other, the corresponding assemblies, thrust member, rocker arm and rocker arm carrier, all having the same longitudinal offset.

10. An arrangement according to any one of claims 1 to 8 characterised in that it comprises a single cam (12) for controlling all the intake and exhaust valves and successively engaging the exhaust thrust member (16) and the intake thrust member (17) of each cylinder.

11. An arrangement according to claim 10 characterised in that, where the motor comprises five cylinders, the exhaust and intake thrust members (16 and 17 respectively) of the same cylinder (4) are spaced by an angle which is in the vicinity of 33 to 35°.

12. An axial internal combustion engine characterised in that it comprises a distribution arrangement according to any one of claims 1 to 11.

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