JP2020521913A - Valve actuator - Google Patents

Abstract

An actuator for operating a poppet valve (30) of an internal combustion engine. The actuator comprises a rotating part (4) and a body part (2), the rotating part defining a cam surface (50, 60). The cam follower (10) engages the cam surface and the linkage is connected at one end to the cam follower and at the other end to the valve stem (12). The cam surfaces (50, 60) are shaped such that the cam followers (10) exert a rotational force on the rotating part (4), for example by the action of a closing force on the valve stem by the piston of the engine following a failure of the actuator. It

Description

The present invention relates to valve actuators. More specifically, it relates to a rotary actuator rotatable with respect to a body portion and having a rotary portion including a cam driven linkage. Such actuators may be used, for example, to operate poppet valves in internal combustion engines.

WO 2004/097184 describes a rotary electromagnetic actuator that may be used to open and close the valves of an internal combustion engine. The valve can operate independently of the movement of the engine crankshaft.

The present invention is an actuator for operating a valve,
A rotating portion and a body portion, the rotating portion being rotatable with respect to the body portion about an axis of rotation by actuation of an actuator, the rotating portion defining a cam surface;
A cam follower that engages with the cam surface when the cam surface rotates,
A linkage connected to the cam follower at one end and to the valve stem at the other end,
Rotation of the rotating portion from the first rotational position to the second rotational position causes displacement of the cam follower, which further causes the other end of the linkage to move from the first position to the second position,
The cam surface causes the cam follower to rotate it towards its first rotational position by the action of the force at the other end of the linkage which urges the other end from its second position towards its first position. And an actuator configured to exert a rotating force on a rotating portion.

Should an actuator or part of the associated control system fail or malfunction, there is a risk that the head of the valve may abut the piston of the associated cylinder, causing damage to the valve and/or other parts of the engine. In particular, when the valve is fully open, movement of the valve stem is mechanically hindered by the actuator mechanism, which can result in substantial damage to one or more components when the piston contacts the valve. Can increase. According to the invention, the linkage and cam formation may be arranged such that the movement of the valve head towards the valve seat is not hindered by the actuator, at least over the range of valve movement in which piston-valve contact can occur. Thus, during a collision scenario, for example, if a pressing force is exerted on the valve head by the piston, the valve head can move, thereby avoiding damage. In the alleged configuration, the cam surface and cam follower and/or linkage are dimensioned such that the cam follower is urged by a force that biases the valve stem toward the valve closed position, at least over the range of valve travel in which piston and valve contact can occur. Torque is applied to the rotating portion of the actuator via the linkage, causing the cam surface to rotate as if driven during valve closure by the actuator, thereby causing the linkage and valve stem to move toward the valve closed position. It may be selected to allow.

The cam follower may be attached or coupled to one end of the linkage. The other end of the linkage may be adapted to be connected or connected to the valve stem. The linkage may be operable to translate the displacement of the cam follower by the cam surface of the rotating portion into a linear movement of the other end of the linkage.

The cam surface is in a plane perpendicular to the rotation axis of the rotation portion when the rotation portion is in its second rotation position, and the reference line perpendicular to the cam surface is spaced from the rotation axis of the rotation portion at the contact point of the cam follower. It is preferable that the shape is such that they are arranged at intervals. This spacing between the line of action of the cam follower and the axis of rotation of the rotating part is such that the undesired forces resulting from the contact of the piston and the valve result in a torque that causes the rotating part to rotate towards its first rotational position. A simple lever arm.

In a preferred embodiment, the cam surface is when the rotating portion is in its second rotational position or a rotational position in the range from the second rotational position to an intermediate rotational position between the first and second rotational positions. The reference line is formed so as to be spaced from the rotation axis of the rotating portion. Thus, over the portion of the rotation of the rotating portion that includes and to the position corresponding to the valve fully open position, the geometry of the linkage and cam formation causes the other end of the linkage to move from its second position to its first position. The force at the other end of the biasing linkage causes the cam follower to exert a rotational force on the rotating portion to rotate it toward the first rotational position. This allows the valve connected to the other end of the linkage to move towards its closed position when so biased, for example as a result of contact between the piston and the valve head. May be.

Cam lift of the cam surface (ie (a) distance of the cam surface at a given point from the axis of rotation of the rotating part and (b) distance of the "base circle" (or minimum radius) of the cam surface from the axis of rotation of the rotating part) May be continuously increased up to or including the point corresponding to the valve open position (the portion forming the valve opening of the cam surface). The increased cam lift provides the desired offset between the line of action of the force exerted by the cam follower on the cam surface and the axis of rotation of the rotating part.

Preferably, the first position at the other end of the linkage corresponds to the valve closed position and the second position corresponds to the valve open position. In particular, the second position may correspond to the fully open position of the valve.

The actuator may be an electromagnetic actuator whose rotating part comprises a rotor and whose body part comprises a stator. Alternatively, the actuator may be a hydraulic or pneumatic actuator.

The present invention is further an internal combustion engine including at least one cylinder having at least one intake or exhaust valve, a piston, and an actuator as described herein, wherein at least one valve is of an engine crankshaft. Operable independently of rotation, the other end of the actuator linkage provides an internal combustion engine that is coupled to the at least one valve to enable the actuator to actuate the at least one valve.

The engine may be, for example, a gasoline or diesel engine. The present disclosure may be particularly beneficial when applied to diesel engines because this type of engine tends to operate with a reduced clearance distance between the valve and piston.

In a preferred embodiment, the valve includes a valve stem arranged to reciprocate along a valve axis, the piston arranged to reciprocate along the piston axis, the valve axis being substantially parallel to the piston axis. In such a configuration, should the piston contact the valve, the piston may exert a force on the valve stem that is substantially parallel to the valve axis, thereby bending the valve stem as a result of the force exerted on it by the piston. Has been reduced.

Embodiments of the present invention will now be described by way of example with reference to the accompanying schematic drawings below.

FIG. 1 shows an actuator in combination with a valve, with the rotor of the actuator having a symmetrical cam surface. FIG. 2 is a diagram showing an actuator and a valve according to an embodiment of the present invention. 3 shows the actuator and valve arrangement of FIG. 2 after upward displacement of the valve head. FIG. 4 shows a side view of a cam surface profile according to one embodiment of the present invention.

FIG. 1 illustrates an electromagnetic actuator and valve arrangement outside the scope of the present invention. The actuator comprises a stator 2 having a rotor 4 attached to it. The rotor can rotate around the rotation shaft 6. The rotor defines a cam surface 8 with which it rotates. The cam follower 10 is maintained in contact with the cam surface when the cam surface rotates.

The cam follower may be biased to come into contact with the cam surface by a biasing knitting, such as a spring. Alternatively, in a desmodromic configuration, a second cam and cam follower mechanism may be employed to control the closing movement of the valve stem.

The cam follower 10 is connected to the valve stem 12 by a mechanical linkage 14. The linkage comprises a cam follower arm 16 and a rocker arm 18 which are rigidly connected together and are rotatable about a rocker pivot 20. The cam follower 10 is attached (or integrally formed) to the distal end of a cam follower arm 16.

The rocker arm 18 is pivotally connected to one end 21 of a rigid link arm 22 by a first pivot joint 24. The other end 23 of the link arm 22 is pivotally connected to the valve stem 12 via a second pivot joint 26.

The valve 30 comprises a valve stem 12, a valve head 32 rigidly connected to the valve stem, and a valve seat 34 (supported by the cylinder head of the engine). A valve guide (not shown) allows linear reciprocal movement in direction D by the valve stem along the valve axis to open and close the valve by engaging or disengaging the valve head 32 with the valve seat 34. To

In operation of the actuator and valve arrangement shown in FIG. 1, rotation of the rotor under the control of the actuator control system causes its displacement as the cam follower 10 follows the cam surface 8. In the position shown, the cam follower engages a point on the cam surface which is the maximum distance from the rotary shaft 6. In this position, the valve is in the fully open position and the valve head 32 is displaced a maximum distance from the seat 34.

When the rotor rotates in either direction from the position shown in FIG. 1, the distance of the contact point (on the cam surface by the cam follower) away from the axis of rotation decreases. The linkage moves the valve head toward its seat as the cam follower follows the surface. When the cam follower reaches a point on the cam surface at a minimum distance from its axis of rotation (on the cam surface "base circle" 40), the valve head engages the valve seat.

In the configuration of the configuration shown in FIG. 1, the opening and closing of the valve may be achieved by rocking the rotor between two positions or by continuously rotating the rotor in the same direction of rotation.

In FIG. 1, when the valve is in its fully open position as shown in the drawing, the reference line "l" which is in the plane perpendicular to the axis of rotation of the rotor and which is perpendicular to the cam surface at the point of contact of the cam follower with the cam surface is It can be seen passing through the axis of rotation 6. As a result, if the valve head 32 can be biased towards its closed position as a result of the force acting on it in the direction F, the upward movement of the valve stem causes the force along the line 1 to the rotor. It is hindered by the linkage 14 and the rotor 4 so as not to generate a rotational force. In the event of a failure, if the piston could abut the valve head, the valve head would be prevented from moving with the piston, leading to major damage.

2 and 3 show an actuator and valve combination similar to that of FIG. The same numbers are used for the same or corresponding features. The configuration of FIGS. 2 and 3 differs from that of FIG. 1 in that the rotor has a modified cam surface 50. The important difference between the shape of the cam surface 50 of FIG. 2 and the shape of the cam surface 8 shown in FIG. 1 is that the cam follower 10 is engaged when the valve is in its fully open position (as in FIGS. 1 and 2). It exists at a point on the surface to be merged.

When the valve is fully opened as shown in FIG. 2, the reference line “L”, which is in the plane perpendicular to the rotation axis 6 of the rotor 4 and perpendicular to the cam surface 50 at the contact point of the cam follower 10, is a distance from the rotation axis of the rotor. It can be seen that they are spaced by "x". Thus, linkage 14 causes cam follower 10 to exert a force on the cam surface along reference line L when force F acts on the valve head and moves it towards its valve seat. As a result of the offset x between the line of action of this valve closing force and the axis of rotation of the rotor, the cam follower exerts a torque on the rotor. This causes the rotor to rotate counterclockwise in the views shown in Figures 2 and 3, allowing the valve head to move towards its seat. The arrangement of valves and actuators following such movement is shown in FIG. Thus, under a fault condition, when a force F is exerted on the valve head by the piston, the valve is displaceable by the piston towards its seat, preventing damage to the valve or actuator.

The shape and dimensions of the cam surfaces, cam followers, and linkages are on a valve the size of which is created during the piston-valve contact event (at least relative to the cam and linkage position where this contact may occur). The force is selected to exert sufficient torque on the rotating portion of the actuator to easily overcome the maximum torque that the actuator can produce. It will be appreciated that this torque is proportional to the distance “x” (as shown in FIG. 2), so that this distance is required beyond the range of cam followers and cam face positions where piston-valve contact can occur. Should be large enough to produce sufficient torque.

FIG. 4 is an enlarged view of a cam surface profile 60 embodying the present invention. It has similar features to the cam surface 50 shown in FIGS. 2 and 3, and will be described in more detail here.

In FIG. 4, the cam surface profile 60 is divided into four consecutive sections 62, 64, 66 and 68 on the axis of rotation 6 for the respective angles a to d. The cam surface is at its minimum distance from the axis 6 along the sections 64 and 66 corresponding to the base circle of the cam surface. Section 62 defines a cam surface that gradually and continuously increases its distance from axis 6 from the base circle of section 64 to point 70. Continuing along the cam surface in the same direction of rotation, starting at point 70, the distance of the cam surface from the axis 6 is reduced to 68 at the beginning of the interval 66 before it sharply decreases to smoothly blend into the base circle. Continue to increase further along.

Dashed circles 72 and 74 identify possible positions for the cam followers at the beginning of the valve opening event. They are located at each end of the base circle section 66. To open the valve, the rotor rotates clockwise when viewed in the direction of FIG. 4, which causes the cam follower to move from section 66 to section 64. Section 64 may correspond to or include a "calm ramp" on the cam profile. As the rotor continues to rotate, the cam follower then moves onto the section 62 of the cam profile which causes the cam follower to move away from the axis of rotation 6. The linkage 14 translates this movement of the cam follower into the opening movement of the valve. The degree to which the valve is opened can be controlled by controlling the amount of rotation of the rotor, and thus how much the cam follower moves along the cam surface 62.

In the embodiment of FIG. 4, the point 70 at one end of the cam section 62 corresponds to the valve fully open position. It can be seen that in this embodiment the reference line L (in the plane perpendicular to the axis of rotation 6 and at this point perpendicular to the cam surface) is spaced from the axis of rotation according to the invention.

In this embodiment, the cam surface continues beyond point 70 and increases its distance from the axis of rotation along a portion 76 at one end of section 68 of the cam surface (ie, increased cam lift). In normal use, the cam follower does not move on this surface. However, even if the follower moves slightly beyond point 70, due to manufacturing tolerances, for example, contact between the piston and the valve ensures that a rotational force is exerted on the rotor.

Since the reference line L is offset from the axis of rotation 6, the force has a lever arm with respect to the axis and thereby exerts a torque on the rotor. This torque nullifies the electromagnetic forces acting between the rotor and its stator, as well as the inertia of the rotor, closing the valve without damaging the valve, piston or any part of the mechanical, electrical or control system. Enable that.

Such a cam surface configuration is intended for use in the swing mode of opening and closing the valve, rather than the full rotation mode, as described with respect to the configuration of FIG. The cam follower typically cannot substantially move beyond the point 70 onto the cam face portion 76 because the valve head is already in the nominal fully open position.

The embodiment of FIGS. 2 and 3 shows a formation that includes an electromagnetic actuator that actuates a valve. It will be appreciated that other types of actuators may be used in accordance with the present disclosure. For example, rotary hydraulic or pneumatic actuators may be employed. In hydraulic or pneumatic implementations, it may be appropriate to include a pressure limiting valve so that the actuator can expel fluid as it rotates due to the contact of the piston and valve.

The actuator and valve linkage shown in FIGS. 2 and 3 is merely a schematic representation of an embodiment of a linkage suitable for translating cam follower movement into a linear displacement of a valve stem attached to the other end of the linkage. Ranges of other suitable linkage configurations will be readily apparent to those skilled in the art.

Claims (11)

An actuator for operating a valve,
A rotating portion and a body portion, wherein the rotating portion is rotatable with respect to the body portion about an axis of rotation by actuation of the actuator, the rotating portion defining a cam surface. Part and
A cam follower that engages with the cam surface when the cam surface rotates,
A linkage that is connected to the cam follower at one end and to the valve stem at the other end,
Rotation of the rotating portion from the first rotational position to the second rotational position causes displacement of the cam follower, which further causes the other end of the linkage to move from the first position to the second position. Then
The cam follower causes the rotating portion to rotate the first portion of the rotating portion to the first rotation by the action of the force of the other end of the linkage that urges the other end from the second position toward the first position. Shaped to exert a rotational force on the rotating portion to rotate towards a position,
Actuator. The cam surface is in a plane perpendicular to the axis of rotation of the rotating portion when the rotating portion is in its second rotational position, and a reference line perpendicular to the cam surface at the point of contact by the cam follower is The actuator of claim 1, wherein the actuator is shaped to be spaced from the axis of rotation of the rotating portion. The cam surface, when the rotating portion is in its second rotational position or a rotational position within a range from the second rotational position to an intermediate rotational position between the first and second rotational positions, The actuator according to claim 1 or 2, wherein the reference line is shaped so as to be spaced from the rotation axis of the rotating portion. The actuator according to any one of claims 1 to 3, wherein the first position corresponds to a valve closed position and the second position corresponds to a valve open position. The actuator of claim 4, wherein the second position corresponds to a valve fully open position. The actuator according to claim 1, wherein the actuator is an electromagnetic actuator, the rotating portion comprises a rotor, and the body portion comprises a stator. The actuator according to claim 1, wherein the actuator is a hydraulic actuator. The actuator according to claim 1, wherein the actuator is a pneumatic actuator. An internal combustion engine comprising at least one cylinder having at least one intake or exhaust valve, a piston, and an actuator according to any one of claims 1 to 8, wherein the at least one valve is a crankshaft of the engine. An internal combustion engine that is operable independent of rotation of the at least one valve, the other end of the actuator linkage being coupled to the at least one valve to enable the actuator to actuate the at least one valve. The engine according to claim 9, wherein the engine is a diesel engine. The valve includes a valve stem arranged to reciprocate along a valve axis, the piston arranged to reciprocate along a piston axis, the valve axis being substantially parallel to the piston axis. The engine according to claim 9 or 10.

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