阅读说明：本技术 气门致动器 (Valve actuator ) 是由 R·斯通 于 2018-05-31 设计创作，主要内容包括：一种用于操作内燃发动机的提升式气门(30)的致动器。所述致动器包括旋转部分(4)和本体部分(2),并且所述旋转部分限定凸轮表面(50,60)。凸轮从动件(10)与所述凸轮表面接合,并且连杆机构在一端处联接到所述凸轮从动件并且在其另一端处联接到气门杆(12)。所述凸轮表面(50,60)被成形为使得,例如在所述致动器失效后所述发动机的活塞将关闭力施加到所述气门杆上引起所述凸轮从动件(10)将旋转力施加到所述旋转部分(4)上。(An actuator for operating a poppet valve (30) of an internal combustion engine. The actuator comprises a rotary portion (4) and a body portion (2), and the rotary portion defines a cam surface (50, 60). A cam follower (10) engages the cam surface and a linkage mechanism is coupled at one end to the cam follower and at its other end to a valve stem (12). The cam surfaces (50, 60) are shaped such that, for example, a piston of the engine applying a closing force to the valve stem after failure of the actuator causes the cam follower (10) to apply a rotational force to the rotating portion (4).)

1. An actuator for operating a valve, the actuator comprising:

a rotating portion and a body portion, wherein the rotating portion is rotatable relative to the body portion about an axis of rotation by actuation of the actuator, and the rotating portion defines a cam surface;

a cam follower engaged with the cam surface as the cam surface rotates; and

a linkage mechanism coupled to the cam follower at one end and coupled to a valve stem at its other end,

wherein rotation of the rotating portion from a first rotational position to a second rotational position causes the cam follower to displace, which in turn causes the other end of the linkage mechanism to move from a first position to a second position, and

wherein the cam surface is shaped such that application of a force on the other end of the linkage urging the other end from its second position towards its first position causes the cam follower to apply a rotational force to the rotary portion to rotate the rotary portion towards its first rotational position.

2. An actuator according to claim 1, wherein the cam surface is shaped such that, when the rotating portion is in its second rotational position, a reference line is spaced from the rotational axis of the rotating portion, the reference line lying on a plane perpendicular to the rotational axis of the rotating portion and orthogonal to the cam surface at the point of contact of the cam follower with the cam surface.

3. An actuator according to claim 1 or claim 2, wherein the cam surface is shaped such that, when the rotary part is in its second rotary position, or in a rotary position in the range from the second rotary position to an intermediate rotary position between the first and second rotary positions, the reference line is spaced from the axis of rotation of the rotary part.

4. An actuator according to any preceding claim, wherein the first position corresponds to a valve closed position and the second position corresponds to a valve open position.

5. The actuator of claim 4, wherein the second position corresponds to a valve fully open position.

6. An actuator according to any preceding claim, wherein the actuator is an electromagnetic actuator, the rotary part comprises a rotor and the body part comprises a stator.

7. An actuator according to any of claims 1 to 5, wherein the actuator is a hydraulic actuator.

8. The actuator of any one of claims 1 to 5, wherein the actuator is a pneumatic actuator.

9. 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 preceding claim, wherein the at least one valve is operable independently of rotation of a crankshaft of the engine, and the other end of the actuator linkage is coupled to the at least one valve to enable the actuator to actuate the at least one valve.

10. The engine of claim 9, wherein the engine is a diesel engine.

11. An engine according to claim 9 or claim 10, wherein the valve comprises a valve stem arranged for reciprocating motion along a valve axis, the piston is arranged for reciprocating motion along a piston axis, and the valve axis is substantially parallel to the piston axis.

Technical Field

The present invention relates to a valve actuator. More particularly, the present invention relates to a rotary actuator having a rotary portion that is rotatable relative to a body portion and that includes a cam-driven linkage mechanism. Such an actuator may be used to operate a poppet valve of, for example, an internal combustion engine.

Background

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

Disclosure of Invention

The present invention provides an actuator for operating a valve, the actuator comprising:

a rotating portion and a body portion, wherein the rotating portion is rotatable relative to the body portion about an axis of rotation by actuation of the actuator, and the rotating portion defines a cam surface;

a cam follower engaged with the cam surface as the cam surface rotates; and

a linkage mechanism coupled to the cam follower at one end and coupled to a valve stem at its other end,

wherein rotation of the rotating portion from a first rotational position to a second rotational position causes the cam follower to displace, which in turn causes the other end of the linkage mechanism to move from a first position to a second position, and

wherein the cam surface is shaped such that application of a force on the other end of the linkage urging the other end from its second position towards its first position causes the cam follower to apply a rotational force to the rotary portion to rotate the rotary portion towards its first rotational position.

In the event of a failure or malfunction of an actuator or part of an associated control system, there is a risk that the head of the valve may come into contact with 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 may be mechanically impeded by the actuator mechanism, thereby increasing the likelihood of substantial damage to one or more components in the event of piston contact with the valve. According to the invention, the linkage mechanism and the cam arrangement may be configured such that, at least in the range of valve strokes where piston-to-valve contact may occur, movement of the valve head towards the valve seat is not impeded by the actuator. Thus, if, for example, a piston exerts a thrust force on the valve head during a crash scenario, the valve head can move, thereby avoiding any damage. In the claimed configuration, the geometry of the cam surface and cam follower and/or linkage may be selected such that, at least over the range of valve travel in which piston to valve contact may occur, the force urging the valve stem towards the valve closed position causes the cam follower via the linkage to apply a torque to the rotating portion of the actuator, causing the cam surface to rotate as it is driven by the actuator during closing of the valve, and thereby allowing the linkage and valve stem to move towards the valve closed position.

The cam follower may be mounted on or coupled to one end of the linkage. The other end of the linkage mechanism may be adapted to be coupled or connected to a valve stem. The linkage mechanism may be operable to translate displacement of the cam follower due to the cam surface of the rotating portion into linear motion of the other end of the linkage mechanism.

Preferably, the cam surface is shaped such that, when the rotating portion is in its second rotational position, a reference line is spaced from the rotational axis of the rotating portion, the reference line lying on a plane perpendicular to the rotational axis of the rotating portion and orthogonal to the cam surface at the point of contact of the cam follower with the cam surface. This spacing between the line of action of the cam follower and the axis of rotation of the rotating portion provides a lever arm such that the undesirable force caused by the piston contacting the valve generates a moment that rotates the rotating portion toward its first rotational position.

In a preferred embodiment, the cam surface is shaped such that, when the rotating portion is in its second rotational position, or in a rotational position in a range extending from the second rotational position to an intermediate rotational position between the first and second rotational positions, the reference line is spaced from the rotational axis of the rotating portion. Thus, over a portion of the rotation section up to and including the rotation of the position corresponding to the valve fully open position, the geometry of the linkage and cam arrangement is such that a force on the other end of the linkage urging the other end of the linkage from its second position towards its first position causes the cam follower to apply a rotational force to the rotation section to rotate the rotation section towards the first rotational position. This may allow a valve coupled to the other end of the linkage mechanism to move towards its closed position when pushed so, for example, due to contact between the piston and the valve head.

The cam lift of the cam surface (i.e., (a) the difference between the distance of the cam surface from the rotational axis of the rotating section at a given point and (b) the distance of the "base circle" (or minimum radius) of the cam surface from the rotational axis of the rotating section) may continuously increase over a portion up to and including the point corresponding to the valve-open position (the portion forming the valve-opening portion of the cam surface). The increased cam lift provides a desired offset between the line of action of the force applied by the cam follower to the cam surface and the axis of rotation of the rotating portion.

Preferably, the first position of the other end of the link mechanism corresponds to a valve closing position and the second position corresponds to a valve opening position. In particular, the second position may correspond to a valve fully open position.

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

The present disclosure further provides 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 the at least one valve is operable independently of rotation of an engine crankshaft, and another end of the actuator linkage 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 engine or a diesel engine. The present disclosure may be particularly advantageous when applied to diesel engines, as this type of engine is intended to operate with a reduced clearance distance between the valve and the piston.

In a preferred embodiment, the valve comprises a valve stem arranged for reciprocating motion along a valve axis, the piston is arranged for reciprocating motion along a piston axis, and the valve axis is substantially parallel to the piston axis. In such a configuration, the piston is likely to apply a force to the valve stem that is substantially parallel to the valve axis with the piston in contact with the valve, thereby reducing the risk of the valve stem bending due to the force applied to it by the piston.

Drawings

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram showing an actuator in combination with a valve, wherein a rotor of the actuator has a symmetrical cam surface;

FIG. 2 is a schematic diagram illustrating an actuator and a valve according to an embodiment of the present invention;

FIG. 3 shows the actuator and valve configuration of FIG. 2 after upward displacement of the valve head; and is

FIG. 4 illustrates a side view of a cam surface profile according to an embodiment of the present invention.

Detailed Description

Fig. 1 shows an electromagnetic actuator and valve configuration outside the scope of the present invention. The actuator comprises a stator 2 in which a rotor 4 is mounted. The rotor is rotatable about an axis of rotation 6. The rotor defines a cam surface 8 which rotates with it. The cam follower 10 remains in contact with the cam surface as the cam surface rotates.

The cam follower may be urged into contact with the cam surface by a biasing means such as a spring. Alternatively, in a deskedolomic (desmodromic) configuration, a second cam and cam follower mechanism may be used to control the closing motion of the valve stem.

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

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

The valve 30 includes a valve stem 12, a valve head 32 rigidly attached to the valve stem, and a valve seat 34 (supported by the engine block). A valve guide (not shown) allows the valve stem to reciprocate linearly along the valve axis in direction D to open and close the valve by engaging or disengaging the valve head 32 from the valve seat 34.

In operating the actuator and valve configuration shown in figure 1, the rotor rotates under the control of the actuator control system such that the cam follower 10 is displaced as it follows the cam surface 8. In the position shown in the figures, the cam follower engages a point on the cam surface which is at its greatest distance from the axis of rotation 6. In this position, the valve is in its fully open position and the valve head 32 is displaced a maximum distance away from the seat 34.

When the rotor is rotated in either direction away from the position shown in fig. 1, the distance of the contact point (of the cam follower on the cam surface) from the axis of rotation decreases. The linkage mechanism causes the valve head to move towards its seat as the cam follower follows the surface. When the cam follower reaches a point on the cam surface at which the distance from its axis of rotation is minimal (on the "base circle" 40 of the cam surface), the valve head comes into engagement with the valve seat.

In the configuration of the form shown in fig. 1, opening and closing the valves may be achieved by oscillating the rotor between two positions or by continuously rotating the rotor in the same rotational direction.

In fig. 1, it can be seen that when the valve is in its fully open position depicted in the figure, a reference line "l" passes through the axis of rotation 6, the reference line lying on a plane perpendicular to the axis of rotation of the rotor and orthogonal to the cam surface at the point of contact of the cam follower with the cam surface. As a result, if the valve head 32 were to be pushed towards its closed position due to a force acting thereon in the direction F, the upward movement of the valve stem would be impeded by the linkage 14 and the rotor 4, since the force along line i would not produce a rotational force on the rotor. If the piston were to come into contact with the valve head in a failure condition, the valve head would be blocked from moving with the piston, resulting in substantial damage.

Fig. 2 and 3 show an actuator and valve combination similar to that of fig. 1. The same reference numerals are used for identical or corresponding features. The configuration of figures 2 and 3 differs from that of figure 1 in that the rotor has a modified cam surface 50. The key difference between the shape of the cam surface 50 of figure 2 and the shape of the cam surface 8 shown in figure 1 occurs at the point on the surface where the cam follower 10 engages when the valve is in its fully open position (as is the case in figures 1 and 2).

When the valve is fully open as shown in figure 2, it can be seen that a reference line "L" is spaced from the axis of rotation of the rotor by a distance "x", the reference line lying on a plane perpendicular to the axis of rotation 6 of the rotor 4 and orthogonal to the cam surface 50 at the point of contact of the cam follower 10 with the cam surface. Thus, if a force F is applied to the valve head to move it towards its valve seat, the linkage 14 causes the cam follower 10 to apply a force to the cam surface along the reference line L. The cam follower applies a moment to the rotor due to the offset x between the line of action of the valve closing force and the axis of rotation of the rotor. This causes the rotor to rotate in a counterclockwise direction in the view shown in fig. 2 and 3, allowing the valve head to move towards its seat. Fig. 3 shows the deployment of the valves and actuators after such movement. Thus, if the piston applies a force F to the valve head, the valve may be displaced by the piston towards its seat, avoiding damage to the valve or the actuator, if in a failure condition.

The geometry and dimensions of the cam surface, cam follower and linkage are selected so that the amount of force on the valve generated during a piston-to-valve contact event (at least for the cam and linkage positions where such contact may occur) will apply sufficient torque to the rotating portion of the actuator to easily overcome the maximum torque that can be generated by the actuator. It will be appreciated that this moment is proportional to the distance "x" (as represented in figure 2) and, thus, over the range of cam follower and cam surface positions over which piston to valve contact may occur, this distance should be large enough to generate the necessary moment.

Fig. 4 is an enlarged view of a cam surface profile 60 embodying the present invention. This cam surface profile has similar features to the cam surface 50 shown in fig. 2 and 3 and will now be described in detail.

In fig. 4, the cam surface profile 60 is divided at the axis of rotation 6 into four successive segments 62, 64, 66 and 68, respectively, at subtended angles a to d. The cam surface is at a minimum distance from the axis 6 along sections 64 and 66, which correspond to the base circle of the cam surface. The cam surface defined by segment 62 gradually and continuously increases its distance from axis 6 from the base circle of segment 64 to near point 70. Starting at point 70, continuing along the cam surface in the same rotational direction, the distance of the cam surface from axis 6 continues to increase further along section 68, and then rapidly decreases to smoothly blend into the base circle at the start of section 66.

Dashed circles 72 and 74 identify possible positions of the cam follower at the beginning of a valve opening event. These dashed circles are located at each end of the base circle segment 66. To open the valve, the rotor rotates clockwise when viewed in the orientation of fig. 4, causing the cam follower to move from section 66 to section 64. Section 64 may correspond to or include a "sound damping ramp" on the cam profile. As the rotor continues to rotate, the cam follower then moves onto a section 62 of the cam profile that moves the cam follower away from the axis of rotation 6. The link mechanism 14 converts this movement of the cam follower into an opening action of the valve. The degree to which the valve is open can be controlled by controlling the amount of rotation of the rotor and thus how far the cam follower travels along the cam surface 62.

In the embodiment of FIG. 4, a point 70 at one end of the cam segment 62 corresponds to a valve fully open position. In the present example it can be seen that, according to the invention, the reference line L (lying on a plane perpendicular to the axis of rotation 6 and at this point orthogonal to the cam surface) is spaced from the axis of rotation.

In the present embodiment, the portion 76 of the cam surface beyond the point 70 along one end of the segment 68 of the cam surface continues to increase its distance from the axis of rotation (i.e., the cam lift increases). In normal use, the cam follower does not travel onto this surface. However, this ensures that if there is piston to valve contact, a rotational force is still applied to the rotor even if the follower does not travel slightly beyond point 70 due to, for example, manufacturing tolerances.

Since the reference line L is offset from the axis of rotation 6, the force has a lever arm with respect to the axis, so that the force exerts a moment on the rotor. This moment overcomes the electromagnetic force acting between the rotor and its stator and the inertia of the rotor, so that the valve closes without causing damage to the valve, to the piston or to any part of the mechanical, electronic or control system.

Such cam surface configurations are intended for use in opening and closing valves in a rocking mode, and not in the full rotation mode described in relation to the configuration of fig. 1. The cam follower is typically unable to move substantially beyond point 70 onto cam surface portion 76 because the valve head is already in its nominal fully open position.

The embodiment of fig. 2 and 3 shows an arrangement comprising an electromagnetic actuator for operating a valve. It should be understood that other types of actuators may be used in accordance with the present disclosure. For example, a rotary hydraulic or pneumatic actuator may be used. In hydraulic or pneumatic embodiments, it may be appropriate to include a pressure limiting valve to allow fluid to be released when the actuator rotates due to the piston contacting the valve.

The actuators for the valve linkage shown in fig. 2 and 3 are merely schematic depictions of examples of suitable linkages for translating movement of the cam follower into linear displacement of a valve stem attached to the other end of the linkage. A range of other suitable linkage configurations will be apparent to the skilled person.