Valve operating system comprising a two-step roller finger follower

Abstract

 Valve operating system (14) comprising a rocker arm assembly (21) and a locking system (30), wherein the rocker arm assembly (21) comprises a primary arm (22) pivotably mounted around a main pivot axis (Oy) wherein the locking system (30) comprises a movable lock pin (32), characterized in that an outside portion (47) of the lock pin (32) extends at least partly outside the primary arm (22), in that the locking system (30) comprises an electromechanical actuator (44) cooperating with the outside portion (47) of the lock pin (32), and in that the actuator (44) comprises compensating means (42, 43, 55) for lock pin (32) control.

Description

Technical Field

[0001] The present invention generally relates to a valve operating system, especially for use in internal combustion engines where valves are operated with a camshaft.

Background of the Invention

[0002] More particularly the present invention relates to a valve operating system, especially for use in internal combustion engines wherein valves are operated with a camshaft, comprising a rocker arm assembly and a locking system, wherein the rocker arm assembly comprises a primary arm actuation pivotably mounted around a main pivot axis for actuating a valve and a secondary arm pivotably mounted relative to the primary arm around an auxiliary pivot axis located on the primary arm extremity opposite to the main pivot axis, the secondary arm carrying a cam follower element, wherein the locking system comprises a lock pin movable between a lock position, wherein it ties the primary arm motion with the secondary arm motion, and an unlock position, wherein it frees the secondary arm motion relative to the primary arm motion in order to allow the secondary arm to swivel relative to the primary arm.

[0003] According to prior art, a valve operating system with two step roller finger follower typically comprises a locking system hydraulically operated with oil circulating inside the primary rocker arm pivot device through a hole connected with the cylindrical hole of the lock pin. The lock pin is operated in the lock or the unlock position by controlling the oil pressure. Such a system is disclosed for example in US 6,966,291.

[0004] This hydraulic actuation has several drawbacks. It is difficult to switch individual followers on a multiple cylinder combustion engine which causes invalid switch events and which prevents from using the system for all types of combustion strategies.

[0005] Moreover, the operation limits of the valve operating system are determined by the engine oil pressure which is not always the same and which requires oversize of the oil pump, leading to parasitic losses.

Summary of the Invention

[0006] In order to overcome the above mentioned drawbacks, the present invention provides a valve operating system as previously described, characterized in that an outside portion of the lock pin extends at least partly outside the primary arm, in that the locking system comprises an electromechanical actuator cooperating with the outside portion of the lock pin in order to control the axial position of the lock pin, and in that the actuator comprises compensating means allowing lock pin control whatever the angular position of the primary arm is.

[0007] According to other features of the invention:

• the compensating means comprise two curved surfaces, one on the actuating part of the actuator and one on the outside portion of the lock pin, at least one of the curved surfaces being centred generally on the main pivot axis;
• a curved concave surface is arranged on the actuating part of the actuator and is centred generally on the main pivot axis and the outside extremity of the lock pin comprises a curved convex surface in contact with the concave surface;
• at least one curved surface is of semi-spherical shape;
• at least one curved surface is of cylindrical shape;
• the actuator is an electro-mechanical actuator comprising at least a coil and a slidably movable plunger carrying at least one permanent magnet plate cooperating with the coil in order to maintain the plunger in one of its lock and unlock positions;
• the compensating means comprise a coil and a heart plunger made of one piece with the outside portion of the lock pin, the plunger being able to freely swivel inside the coil, and the coil and the plunger constitute the actuator.

[0008] The present invention provides also an internal combustion engine comprising a valve operating system according to the preceding features.

Brief Description of the Drawings

[0009] The present invention is now described by way of example with reference to the accompanying drawings in which:

Figure 1 is a partial perspective view showing an engine equipped with a valve operating system according to the present invention;

Figure 2 is a partial perspective view showing a rocker arm assembly and a locking system included in the valve operating system of figure 1;

Figure 3 is a longitudinal section view showing the valve operating system of figure 1 when the locking system is in its lock position and the rocker arm assembly is not operated;

Figure 4 is a similar view to the one of figure 3 showing the valve operating system when the locking system is in its lock position and the rocker arm assembly is operated;

Figure 5 is a similar view to the one of figure 3 showing the valve operating system when the locking system is in its unlock position and the rocker arm assembly is operated;

Figure 6 is an axial section showing a preferred embodiment of an actuator included in the locking system of figure 1 when the actuator is in its lock position;

Figure 7 is a similar view to the one of figure 6 showing a second preferred embodiment of the actuator comprising two coils;

Figure 8 is a similar view to the one of figure 3 showing a second embodiment of the valve operating system according to the present invention and comprising an electromagnetic contactless actuator.

Description of the Preferred Embodiment

[0010] Figure 1 shows a portion of an internal combustion engine 10 equipped with a valve operating system 14 according to a first embodiment of the invention.

[0011] The combustion engine 10 comprises an engine block 12 on which is rotated a camshaft 16 in order to control a valve train 18. As a simplified representation, only one valve 19 is shown on the figures.

[0012] As can be seen on FIG 1, the camshaft 16 controls the valve train 18 through a valve operating system 14. The valve operating system 14 is represented in details on FIG 2, 3, 4 and 5. It comprises a rocker arm assembly 21, pivotably mounted relative to the engine block 12, and a locking system 30 the function of which will be described later.

[0013] The rocker arm assembly 21 comprises a primary arm 22 which extends mainly along a longitudinal direction Ox and which is pivoted on its right end, regarding figure 3, around a main pivot axis Oy. According to the present embodiment, the main pivot axis Oy is constituted by an articulation 27 of the ball-and-socket joint type. This articulation 27 is constituted of a semi-spherical hollow 29, machined in the pivoted end of the primary arm 22, and of an oil distributor 31 comprising a semi-spherical convex head. Such an articulation type is already disclosed, for example in US 2006/0144356 [§0055].

[0014] In the following description we will use, as a non limiting example, an orthogonal normal direct O-x-y-z coordinate system fixed relative to the engine block 12 wherein Oy is a transversal axis parallel to the camshaft 16, and Oz is a generally vertical axis parallel to the axis of the valve stem 23.

[0015] At its left end (as per FIG 3), the primary arm 22 comprises an actuation surface 25 which is in contact with the end 33 of the valve stem 23.

[0016] Upon operation of the camshaft 16, the primary arm 22 swivels around its main pivot axis Oy between a rest position, which is shown on figure 3, and an actuation position, which is shown on figure 4.

[0017] The primary arm 22 is hollow in its central portion in order to house a secondary arm 24 which extends generally along the longitudinal direction of the primary arm 22.

[0018] The secondary arm 24 is pivotably mounted by its left end, as per FIG 3, relative to the primary arm 22, around an auxiliary pivot axis 28 parallel to the transversal axis Oy and located in the left end of the primary arm 22.

[0019] In the central portion of the secondary arm 24, there is provided a roller cam follower 26 which freely rotates around its transversal axis and which is maintained in permanent contact with an associated cam 37 carried by the camshaft 16.

[0020] According to the present embodiment, a return spring assembly 35 is arranged between the primary arm 22 and the secondary arm 24 in order to maintain the roller cam follower 26 in contact with the cam 37.

[0021] The secondary arm 24 can swivel around its auxiliary pivot axis 28 between an operating position, which is shown on figures 3 and 4, and a non operating position, which is shown on figure 5, upon operation of the camshaft 16, depending on the state of the lock system 30 as it will be seen more clearly later on.

[0022] The lock system 30 comprises a cylindrical lock pin 32, a compression spring 42, and an actuator 44, for example an electro-mechanical actuator. The lock pin 32 is slidably mounted, along a sliding axis a1, in a generally longitudinal guiding-hole 40 machined in the right end, as per FIG 3, of the primary arm 22. The guiding-hole 40 is opened inside the hollow portion of the primary arm 22 so that the inside extremity 41 of the lock pin 32 may be received in a locking slot 39 arranged in the right end of the secondary arm 24, as it is shown on figure 3.

[0023] The outside extremity 43 of the lock pin 32 extends outside the guiding-hole 40, towards the right as shown on figure 3.

[0024] With reference to the primary arm 22, the lock pin 32 has an inside lock position, wherein it is received in the locking slot 39 and an outside unlock position wherein the lock pin end 41 is not engaged in the locking slot 39.

[0025] The lock pin 32 has two portions 45, 47 of distinct diameters connected via a shoulder 46. The guiding-hole 40 has a shoulder surface 49, facing the shoulder 46 so that a spring 42 could be compressed between them biasing the lock pin 32 toward the actuator 44, i.e. toward the right considering figure 3.

[0026] According to an alternative embodiment, the spring 42 could be arranged reversely such that the lock pin 32 would be biased toward the hollow portion of the primary arm 22, i.e. toward the left considering figure 3. Then the default position of the lock pin 32 would be reversed.

[0027] The outside extremity 43 of the lock pin 32 has a semi-spherical convex surface generally centred on a point situated on the lock pin axis a1.

[0028] The actuator 44 comprises a body 51 fixed relative to the engine block 14 and a plunger 53, in the shape of a rod, axially movable along an actuating axis a2. The plunger 53 has on its free end a concave spherical surface 55 of larger radius compared to the convex surface of the outside extremity 43 of the lock pin 32.

[0029] The concave surface 55 is such that, when the primary arm 22 is oscillating during operation of the primary arm 22, the tip point of the lock pin convex surface 43 draws, in the plane O-x-z, an arc of circle centred on the main pivot axis Oy. The concave surface 55 is of a similar radius as this arc of circle.

[0030] According to the present embodiment, the concave surface 55 is arranged on a cap 56 fixed on the free end of the plunger 53. The radius of the concave surface 55 is generally centred on the main pivot axis Oy. The aim of this particular arrangement is to allow the lock pin 32 to remain in contact with the concave surface 55 and to remain constantly operable by the actuator 44.

[0031] According to an alternative embodiment, the concave surface 55 could be of cylindrical shape instead of spherical shape. An advantage of such an embodiment would be to allow controlling of several adjacent lock pins 32 with one single actuator 44 in order to activate/deactivate simultaneously several valves 19.

[0032] The actuator 44 is designed to control the plunger 53 along the actuating axis a2 between an unlock position, which is represented on figure 5, wherein the plunger 53 is stepped back toward the outside, and a lock position, which is represented on figure 4, wherein the plunger 53 is stepped forward toward the inside of the primary arm 22.

[0033] Thanks to the compression spring 42, the lock pin 32 is pushed outside against the concave surface 55 so that, whatever the actuating position of the plunger 53 is, the lock pin 32 remains in contact with the concave surface 55.

[0034] The concave surface 55 together with the compression spring 42 allow compensation of the different angular positions of the lock pin 32 which depends on the swivelling motion of the primary arm 22.

[0035] Advantageously, the actuator 44 is connected to an electronic control unit 57 which controls the actuator 44 depending on engine parameters or any other relevant parameter.

[0036] Now the way the valve operating system 14 according to the invention works will be explained in details.

[0037] Starting from a non operated position of the valve control system 14, which is represented on figure 3, the primary arm 22 is in its rest position and the actuator 44 is controlled in its lock position so that the lock pin 32 is in its lock position wherein its inside extremity 41 is received in the locking slot 39 of the secondary arm 24 to tie the secondary arm motion with the primary arm motion.

[0038] When the cam 37 comes to push down on the cam follower 26, the primary arm 22 swivels with the secondary arm 24 around the main pivot axis Oy and the actuating surface 25 pushes down the valve 19 to open it.

[0039] Swivelling of the primary arm 22 drives the lock pin 32 around the main pivot axis so that the outside portion 43 of the lock pin 32 moves along an arcuate path, considering figure 3 and 4. During the all swivelling motion, the lock pin 32 remains in permanent contact with the concave surface 55 the shape of which following the motion of the lock pin 32. As a consequence, whatever the position of the primary arm 22 is, the lock pin 32 remains in a controllable position.

[0040] When it is required to deactivate the valve 19, the control unit 57 controls the actuator 44 so that the plunger 53 moves from its lock to its unlock position, driving the lock pin 32 to its unlock position. This unlock position makes the secondary arm 24 free relative to the primary arm 22. Thus, when the cam 37 pushes the cam follower 26, the secondary arm 24 swivels around the auxiliary pivot axis 28, without transferring motion to the primary arm 22. The valve 19 stays in its closed state.

[0041] Advantageously, the actuator 44 is an electro-mechanical actuator wherein the axial position of the plunger 53 is controlled by an electromagnetic coil and wherein the plunger 53 comprises two steady positions (lock and unlock positions) in order to prevent the necessity to power on the actuator 44 to maintain the plunger 53, and by the way the lock pin 32, in one of its extreme axial positions.

[0042] A preferred embodiment of the actuator 44 is shown on figure 6. The actuator body 51 contains a coil 58 which is powered through a connector device 60. The coil 58 comprises an armature 62 having two opposite radial surfaces 64, 66 and forming, between the two radial surfaces 64, 66, a guiding pipe 70 through which the plunger 53 is slidably mounted.

[0043] The plunger 53 carries two permanent magnet plates 72, 74 which are mounted on each side of the coil 58 and which will be called locking plate 72 and unlocking plate 74. Each permanent magnet plate 72, 74 is magnetically orientated along the actuating axis a2 in opposite directions so that, depending on the polarity of the supply current for the coil 58, either the locking plate 72 or the unlocking plate 74 is magnetically attracted towards the coil 58 against the corresponding radial surface 64, 66 of the armature 62. The distance D between the two permanent magnet plates 72, 74 is bigger than the longitudinal dimension of the armature 62 so that only one plate 72, 74 could be in contact with the armature 62.

[0044] When the actuator 44 is controlled in its lock position, as can be seen on figure 3 and 6, the current supplied to the coil 58 is such that the south pole of the coil 58 is on the lock plate 72 side. Then the lock plate 72, for which the north pole is orientated towards the coil 58, is attracted towards the coil 58 which provides a motion of the plunger 53 towards its lock position.

[0045] Similarly, a current of reverse polarity is supplied to the coil 58 when the actuator 44 is controlled in its unlock position, as can be seen on figure 5.

[0046] Thanks to the permanent magnet plates 72, 74, the plunger 53 can be maintained magnetically in each one of its lock and unlock positions without requiring electric power. Supply current is required only for transition state between the lock and unlock positions.

[0047] According to a second preferred embodiment, shown on figure 7, the actuator 44 comprises two coils 76, 78 and only one permanent magnet plate 80 arranged between the two coils 76, 78. Depending on supply current polarity, the permanent magnet plate 80 is attracted towards one of the two coils 76, 78 which corresponds either to the lock or the unlock position of the plunger 53.

[0048] Thanks to the use of electronically controlled actuator 44, it is possible to operate individually each locking system 30 which means it is possible to choose exactly which one of the valve 19 should be deactivated.

[0049] A second embodiment of the valve operating system 14 according to the present invention will be described now, referring to figure 8 and focusing on the main differences with the first embodiment.

[0050] In this second embodiment, the actuator 44 is an electromagnetic contactless actuator in which the heart plunger 53 is constituted by the outside portion 47 of the lock pin 32. The coil 82 of the actuator 44 provides an electromagnetic field which controls the displacement of the heart plunger 53 along the actuation axis a1. The diameter of the coil 82 is such that, when the lock pin 32 swivels with the primary arm 22, there is no direct contact between the coil 82 and the lock pin outside portion 47. Thus the coil 82 compensates the swivelling of the lock pin 32 during primary arm motion.

[0051] The coil 82 could be of oval section in the direction of the swivelling motion in order to allow a larger swivelling motion of the locking pin 32 while making the actuator 44 more compact in width along a transversal direction.

[0052] The outside portion 47 of the lock pin 32 is long enough so that the coil 82 provides enough electromagnetic force to control the lock pin 32. Advantageously, the outside portion 47 of the lock pin 32 is tubular in order to minimize the weight in motion without penalizing the actuating power of the actuator 44.

Claims

1. A valve operating system (14), especially for use in internal combustion engines (10) wherein valves (19) are operated with a camshaft (16), comprising a rocker arm assembly (21) and a locking system (30), wherein the rocker arm assembly (21) comprises a primary arm (22) actuation pivotably mounted around a main pivot axis (Oy) for actuating a valve (19) and a secondary arm (24) pivotably mounted relative to the primary arm (22) around an auxiliary pivot axis (28) located on the primary arm (22) extremity opposite to the main pivot axis (Oy), the secondary arm (24) carrying a cam follower element (26), wherein the locking system (30) comprises a lock pin (32) movable between a lock position, wherein it ties the primary arm motion with the secondary arm motion, and an unlock position, wherein it frees the secondary arm motion relative to the primary arm motion in order to allow the secondary arm (24) to swivel relative to the primary arm (22), characterized in that an outside portion (47) of the lock pin (32) extends at least partly outside the primary arm (22), in that the locking system (30) comprises an electromechanical actuator (44) cooperating with the outside portion (47) of the lock pin (32) in order to control the axial position of the lock pin (32), and in that the actuator (44) comprises compensating means (42, 43, 55, 82) allowing lock pin (32) control whatever the angular position of the primary arm (22) is.

2. . The valve operating system (14) according to claim 1, characterized in that the compensating means comprise two curved surfaces (43, 55), one on the actuating part of the actuator (44) and one on the outside portion (47) of the lock pin (32), at least one of the curved surfaces (43, 55) being centred generally on the main pivot axis (Oy).

3. . The valve operating system (14) according to claim 2, characterized in that a curved concave surface (55) is arranged on the actuating part of the actuator (44) and is centred generally on the main pivot axis (Oy) and in that the outside extremity (43) of the lock pin (32) comprises a curved convex surface (43) in contact with the concave surface (55).

4. . The valve operating system (14) according to claim 2 or 3, characterized in that at least one curved surface (43, 55) is of semi-spherical shape.

5. . The valve operating system (14) according to anyone of claims 1 to 4, characterized in that at least one curved surface (43, 55) is of cylindrical shape.

6. . The valve operating system (14) according to anyone of claims 1 to 5, characterized in that the actuator (44) is an electro-mechanical actuator comprising at least a coil (58, 76, 78) and a slidably movable plunger (53) carrying at least one permanent magnet plate (72, 74, 80) cooperating with the coil (58, 76, 78) in order to maintain the plunger (53) in one of its lock and unlock positions.

7. . The valve operating system (14) according to claim 1, characterized in that the compensating means comprise a coil (82) and a heart plunger (53) made of one piece with the outside portion (47) of the lock pin (32), the plunger (53) being able to freely swivel inside the coil (82), and in that the coil (82) and the plunger (53) constitute the actuator (44).

8. . Internal combustion engine (10) comprising a valve operating system (14) according to anyone of the preceding claims.

Drawing