EP1072762B1 - Valve command device and internal combustion engine equipped with this device - Google Patents

Abstract

The valve (12) position is controlled by a rocker arm (18), mounted to oscillate on an axis (F1), and driven by rotation of a control cam (22) and is fitted with the means to adjust the lift of the valve. Adjustment is achieved by an adjustment arm (28), which pivots on mobile axis (M1) on the second branch (18B) of the rocker arm. It carries the cam follower roller (30), on mobile axis (R1). A second roller (32), mounted on mobile axis (R2), is carried by the adjustment arm and follows the adjustment cam (34), which is mounted so as to be displaced relative to the fixed base (14).

Description

The present invention relates to a control device of a valve and an internal combustion engine provided with this device.

One of the main criteria for the design and development of an internal combustion engine is most often to increase the performance of the engine for a high rotational speed without degrading the performance, including available torque, low and medium speed.

To achieve this result, it is known to vary the distribution of the engine by modifying the lift of the valves of this engine and / or the setting angle of the cams actuating these valves so as to favor certain performance in a specific range of speed.

Of the existing variable distribution systems, it is known to use three-dimensional cams, that is to say whose profile is variable the along their axis of rotation. Such a design makes it possible, thanks displacement of the camshaft parallel to its axis of rotation, to obtain different distribution configurations. This design is particularly complex and leads to an increase in the longitudinal engine.

FR-A-2,453,979 describes a device for controlling a valve of internal combustion engine, of the type comprising a rocker arm, mounted articulated on a support, around a fixed oscillation axis, provided with a first arm urging the free end of the tail of the valve and a second arm urged by a rotary control cam, and means for adjusting the lifting of the valve.

The means for adjusting the valve lift described in this document, comprising an eccentric associated with an axis of rotation of the rocker, are relatively complex.

Also known from GB-A-12069 is a control device of an internal combustion engine valve according to the preamble of claim 1.

The object of the invention is to propose a control device a simple and inexpensive valve, reduced longitudinal dimensions, this avoiding as much as possible the use of elements that are sensitive to wear, particular elements continuously or frequently urged in rotation.

For this purpose, the subject of the invention is a control device valve, of the aforementioned type, characterized in that the contact surface of the adjusting cam with the second roller is delimited by a rectilinear ramp, and the adjustment cam is slidably mounted in a curvilinear guide secured to the support, so as to describe a curvilinear race centered on a guide axis substantially parallel to the fixed oscillation axis.

• l'axe de guidage coïncide avec le second axe de rotation mobile lorsque la soupape est dans une position de référence,
• il comprend des moyens de réglage du calage angulaire de la came de commande,
• les moyens de réglage du calage comprennent un pivot matérialisant le premier axe de rotation mobile, monté déplaçable dans une lumière curviligne s'incurvant autour d'un axe de rotation fixe de la came de commande,
• la lumière curviligne est centrée sur un axe de calage coïncidant avec l'axe de rotation fixe de la came de commande lorsque la soupape est dans une position de référence,
• les moyens de réglage du calage comprennent des moyens couplés à un arbre à cames portant la came de commande.

According to other features of the invention:

• the guide axis coincides with the second mobile axis of rotation when the valve is in a reference position,
• it comprises means for adjusting the angular setting of the control cam,
• the adjustment means comprise a pivot materializing the first movable axis of rotation, movably mounted in a curvilinear lumen curving around a fixed axis of rotation of the control cam,
• the curvilinear lumen is centered on a wedge axis coinciding with the fixed axis of rotation of the control cam when the valve is in a reference position,
• the setting adjustment means comprise means coupled to a camshaft carrying the control cam.

The invention also relates to a combustion engine internal characterized in that it comprises a valve control device as defined above, the valve being preferably a valve intake.

Figures 1 to 3 are similar elevational views showing a valve control device according to three embodiments of the invention respectively.

FIG. 1 shows a device 10 according to a first embodiment of the invention for controlling a valve 12 of internal combustion engine. This control device 10 is arranged in a cylinder head 14 of the engine.

The valve 12 is movable between a closed position, such shown in FIG. 1, resting on a seat 16 formed in the yoke 14, and an open position (not shown). Valve 12 is resiliently biased back to its closed position using conventional means not shown.

In the example described, the control device 10 is intended to actuate an engine intake valve. However, as a variant, this same device 10 could be used to actuate a valve exhaust.

The control device 10 comprises a rocker 18, mounted articulated on the yoke 14, about a fixed axis of oscillation F1. The rocker 18 is provided with a first arm 18A urging the free end of the tail 20 of the valve 12 and a second arm 18B biased by a cam of rotary control 22. It will be noted that the rocker arm 18 forms a lever of the first kind.

The cam 22 is carried by a conventional camshaft 24 mounted rotating around a fixed axis of rotation F2 forming the axis of rotation of the cam 22.

The control device 10 also comprises means adjusting the lift of the valve 12 having an adjusting member 28 of triangular general shape.

The adjusting member 28 is articulated on the second arm 18B of the rocker arm around a mobile oscillation axis M1. The regulator 28 carries two rotary rollers 30, 32. A first roller 30 is in contact with the control cam 22. This first roller 30 is mounted articulated on the body adjusting 28 around a first mobile axis of rotation R1. The second pebble 32 is in contact with an adjusting cam 34. This second roller 32 is hingedly mounted on the adjusting member 28 around a second axis of rotation mobile R2.

It will be noted that the axes F1, F2, M1, R1 and R2 are substantially parallel to each other. It will also be noted that the three movable axes M1, R1 and R2 form, in a plane perpendicular to them, the three vertices of a triangle. All axes F1, F2, M1, R1 and R2 are distinct two by two.

The adjustment cam 34 is displaceably mounted on the yoke 14 so that for a constant position of the control cam 22 corresponding to a position of the valve 12 where it is open, the displacements of this adjustment cam 34 vary the distance between the fixed oscillation axis F1 and the second mobile rotation axis R2.

Preferably, the contact surface of the adjustment cam 34 with the second roller 32 is delimited by a rectilinear ramp 36.

Also preferably, the adjustment cam 34 is mounted sliding in a curvilinear guide 38 secured to the yoke 14, so as to describe a curvilinear race centered on a substantially guide axis G parallel to the fixed oscillation axis F1.

The guide axis G coincides with the second axis of rotation mobile R2 when the valve 12 is in a reference position, namely the closed position as illustrated in Figure 1.

Thus, when the adjustment cam 34 is rotated in the curvilinear guide 38 while the valve is closed, the ramp 36 remains tangent to the roller 32 without moving the axis R2 since the axes G and R2 are confused and no other room moves. It ensures that, whatever the setting, that is to say regardless of the position of the cam 34, the valve remains closed when the back of the control cam 22 is in contact with the roller 30 (the "back" of a cam being the part of it which corresponds to the closing the valve when it is in contact with the rocker arm or intermediate piece).

The adjustment cam 34 is moved using means conventional devices including, for example, an electric or hydraulic actuator.

During the operation of the control device 10 illustrated in FIG. 1, the rotary cam 22 biases the adjustment member 28 by intermediate of the first roller 30. This adjustment member 28 articulated on the rocker arm 18 and in rolling rest on the ramp 36 via the second roller 32, urges the rocker arm 18 to actuate the valve 12. angular displacement of the cam 22, the second roller 32 rolls on the ramp 36.

To modify the lift of the valve 12, the cam is controlled adjustment device 34 so as to move it in contact with the curvilinear guide 38, which has the effect, for a constant position of the control cam 22 corresponding to a position of the valve where it is open, of change the distance between the fixed oscillation axis F1 and the second axis of R2 mobile rotation. Changing this distance causes a modification of valve lift 12.

It should be noted that the adjustment of the lift of the valve can be realized continuously because the adjustment cam 34 can move continuously in the curvilinear guide 38.

In a conventional manner, the engine comprises an associated crankshaft to the valve control device. The curve of the lifting of the valve depending on the rotation angle of the crankshaft conventionally has a shape general bell (see for example FR-A-2,453,979).

Whatever the position of the adjustment cam 34, the second roller 32 rolls in all cases in contact with the same rectilinear ramp 36 of this adjustment cam 34. As a result, it can be seen that different positions of the adjustment cam 34 lead to different lifts of the valve 12 corresponding to different lift curves of this valve as a function of the angle of rotation of the crankshaft of the engine. These different curves are all substantially symmetrical and present at the opening and closing of the valve of low slope tangents pledges of silence of the device of ordered.

In Figures 2 and 3, there is shown second and third embodiments of the control device 10 according to the invention. On these Figures 2 and 3, elements similar to those of Figure 1 are designated by identical references.

The control device 10 according to the second and third embodiments of the invention comprises means for adjusting the angular setting of the control cam 22.

In the second embodiment of the invention illustrated in FIG. 2, the adjustment means of the setting comprises a pivot 40, materializing the first mobile axis of rotation R1, mounted movable in a curvilinear light 42 curving around the fixed axis of rotation F2 of the cam 22.

Preferably, the curvilinear light 42 is centered on an axis of setting C coinciding with the fixed axis of rotation F2 of the control cam 22 when the valve 12 is in a reference position, namely its closed position as shown in Figure 2.

As previously explained about the G and R2 axes, the that the axes C and F2 coincide when the valve is closed, if moves the pivot 40 in the light 42 in this situation, the roller 30 remains in contact with the back of the cam 22 and no other part moves. So whatever the position of the pivot 40 in the lumen 42, the valve remains closed when it must be, that is to say when the back of the cam 22 is in contact with the roller 30.

The pivot 40 is moved in the curvilinear lumen 42 with the aid of conventional means including, for example, an electric actuator or hydraulic. These means also make it possible to immobilize the pivot 40 in the light 42 in the desired adjustment setting position.

In the third embodiment of the invention illustrated on the FIG. 3, the wedging means comprise conventional means. coupled to the camshaft 24. These conventional means include, for example, for example, a helical type coupling.

In the case of an intake valve, the adjustment means calibration illustrated in Figures 2 and 3 allow to vary the delay or the advance of the opening and closing of the valve 12.

Among the advantages of the invention will be noted the following.

The control device of a valve according to the invention allows the valve lift to be continuously adjusted by means of a adjustment cam 34 whose movements are limited, which reduces the risks of wear.

This risk of wear is all the more limited as the means of valve lift adjustment do not require a rotating element permanently.

Moreover, the opening and closing of the valve are carried out in a progressive and silent way, this using means reduced space, especially in the longitudinal direction of the engine, namely the direction parallel to the fixed axis F1 oscillation of the rocker arm.

In addition, the different curves of lift of the valve in depending on the rotation angle of the crankshaft obtained for different Adjustments of the position of the adjustment cam 34 are symmetrical, the delay to the intake opening (in the case of an intake valve) which can be canceled by the adjustment means of the angular setting of the cam of ordered.

Finally, it will be noted that the device of the invention can be used in an engine comprising one or two camshafts.

Claims (7)

1. A device for controlling a valve (12) of an internal combustion engine, of the type comprising a rocker (18), mounted such that it is articulated on a support (14) about a fixed axis of oscillation (F1) and equipped with a first arm (18A) urging the free end of the stem (20) of the valve (12) and a second arm (18B) urged by a rotating control cam (22), and means (28, 34) for regulating lifting of the valve, comprising a regulating member (28) mounted such that it is articulated on the second arm (98B) of the rocker about a mobile axis of oscillation (M1), a first roller (30) for contact with the control cam (22), this roller (30) being mounted such that it is articulated on the regulating member (28) about a first mobile axis of rotation (R1), and a second roller (32) for contact with a regulating cam (34), this roller (32) being mounted such that it is articulated on the regulating member (28) about a second mobile axis of rotation (R2), the axes of oscillation (F1, M1) and the axes of rotation (R1, R2) all being separate and substantially parallel to one another, the regulating cam (34) being mounted such that it is movable on the support (14) such that, for a constant position of the control cam (22) corresponding to a position of the valve (22) in which the latter is open, movements of this regulating cam (34) alter the distance between the fixed axis of oscillation (F1) and the second mobile axis of rotation (R2), characterised in that the surface by which the regulating cam (34) makes contact with the second roller (32) is delimited by a straight ramp (36), and the regulating cam (34) is mounted such that it slides in a curved guide (38) which is in one piece with the support (14) such that it describes a curved path centred on an axis of guiding (G) which is substantially parallel to the fixed axis of oscillation (F1).
2. A device according to Claim 1, characterised in that the axis of guiding (G) coincides with the second mobile axis of rotation (R2) when the valve (12) is in a reference position.
3. A device according to either of the preceding claims, characterised in that it comprises means (40; 42; 44) for regulating the angular adjustment of the control cam (22).
4. A device according to Claim 3, characterised in that the means for regulating the adjustment comprise a pivot pin (40) which constitutes the first mobile axis of rotation (R1 ) and is mounted such that it is movable in a curved aperture (42) following a curve around a fixed axis of rotation (F2) of the control cam (22).
5. A device according to Claim 4, characterised in that the curved aperture (42) is centred on an adjustment axis (C) coinciding with the fixed axis of rotation (F2) of the control cam when the valve (12) is in a reference position.
6. A device according to Claim 3, characterised in that the means for regulating the adjustment comprise means (44) coupled to a cam shaft (24) bearing the control cam (22).
7. An internal combustion engine, characterised in that it comprises a device for controlling a valve according to any one of the preceding claims, the valve preferably being an intake valve.

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