GB2412408A - Valve gear for an internal combustion engine - Google Patents

Abstract

Valve gear for an internal combustion engine comprises a pair of fingers 30, 32 interposed between a cam 10 and an associated valve stem 20. The lower finger 30 is supported by a support element 52 which can move, under, for example, hydraulic control, to adjust the valve gear geometry. Such movement may, for example, serve to adjust valve clearances or to equalise valve movement between engine cylinders at tickover or at other engine speeds.

Description

24 1 2408

VALVE GEAR

This invention relates to valve gear for operating a valve in an internal combustion engine.

In my British Patent Application No 0315246.9,1 disclose valve gear for operating a valve in an internal combustion engine, the valve gear comprising a camshaft carrying a cam which acts on a first pivotable finger, the first finger having an actuating surface which contacts a second pivotable finger, the second pivotable finger being in driving engagement with the valve.

Valve gear in accordance with British Patent Application No 0315246.9 is particularly useful in engines as disclosed In my earlier British Patent GB 2190140, in which the valve lift, duration and timing can be adjusted while the engine is running. The adjustment of valve operation is achieved by varying the profile of each cam along its axis, so that part of the cam surface, as viewed from the side, is Inclined to the axis about which the cam rotates. The camshaft is axially displaceable to move the cam across the bucket so as to vary the effect of the cam on valve operation.

My British Patent Application No 0315246.9 discloses an engine having two Inlet valves operated by a single second pivotable finger. Although application of the valve gear to a pair of Inlet valves In each cylindems disclosed, the same principle could be applied to a pair of exhaust valves.

In some circumstances, valve gear as disclosed in British Patent Application No 0315246.9 can lead to variations in operation between the two valves operated by the same second pivotable finger, and between the valves of different cylinders. For example, manufacturing tolerances may result in different valve clearances between the two inlet valves operated by the same second pivotable finger. Furthermore, manufacturing tolerances, and possibly differential thermal expansion effects, can cause the relationship between the different cam lobes on the camshaft and the associated valves to vary from cylinder to cylinder.

Such effects are particularly evident when the engine is idling, since small variations In air flow between valves and between cylinders can have a significant effect on the fuel consumption, emissions and operating stability of the engine.

According to the present invention, there is provided valve gear for operating a valve in an internal combustion engine, the valve gear comprising a camshaft carrying a cam which acts on a first pivotable finger, the first finger having an actuating surface which contacts a second pivotable finger, the second pivotable finger being in driving engagement with the valve and being pivotably supported by a support element which is movable relatively to a cylinder head of the internal combustion engine.

With valve gear in accordance with the present Invention, adjustment of the support element changes the geometric relationship between the valve and the cam which drives it. Consequently, this relationship can be adjusted for each valve (or pair of valves operated by the same cam), enabling the operation of the valves to be optimised for any operating condition of the engine, for example at idling.

The support element is preferably movable in a direction which lies in a plane perpendicular to the axis of the camshaft, which direction may be parallel to the direction of valve movement. However, In some embodiments, it may be desirable for the support element to be movable in a direction inclined to the direction of valve movement.

In a preferred embodiment, the movement of the support element is achieved under hydraulic control. For example, each support element may be associated with a valve, such as a solenoid valve, which admits oil under pressure to an operating chamber to displace the valve in one direction, or to allow the oil to drain to enable the support element to move in the opposite direction.

Movement of the support element may be controlled in response to air flow through the valve (or pair of valves) actuated by the respective second pivotable finger. In a multi cylinder engine, the support elements for the second pivotable fingers of the respective valves may be adjusted independently in order to achieve uniform air flows through each of the valves. Thus, even if manufacturing tolerances result in dimensional differences, or effects such as differential thermal expansion occur, the operation of all of the valves can be equalsed. It Is also possible to disable each cylinder individually under map control. For example some cylinders could be disabled to achieve a balanced (in terms of firing order) effective temporary reduction In engine capacity, and therefore in fuel consumption and emissions during idling in traffic. Alternatively, or in addition, cylinder disablement may be achieved using a special cam profile as disclosed in my earlier International patent application published as WO 01/88345 To achieve this control, an air flow sensor may be provided in the air flow path through the valve (or pair of valves) of each cylinder.

The support element may cooperate with the respective second pivotable finger in any suitable manner, but in a preferred embodiment, the support element has a hemispherical surface which engages a complementary surface in the respective second pivotable finger. Such a connection between the support element and the second pivotable finger enables the second pivotable finger to move relatively to the support element about axes extending in any direction. An advantage of this arrangement is that, in an engine having two Inlet valves per cylinder, the second pvotable finger may tilt relatively to the support element about an axis extending perpendicular to a plane containing the directions of movement of the valves. This enables the second pivotable finger to adopt a position in which it acts on both valves equally, avoiding different operation of the two valves as a result of, for example, different valve clearances.

Another aspect of the present invention provides an internal combustion engine including a camshaft carrying a plurality of cams, the camshaft being axially displaceable relatively to a cylinder head of the engine by means of a motor having a rotary output shaft, the camshaft being connected to the motor by a coupling element which is rotatable but axially fixed with respect to the camshaft, the coupling element being axially displaceable but rotationally fixed to a housing of the motor, and being connected to the output shaft of the motor by a connection by which rotation of the output shaft of the motor causes axial displacement of the connection element.

Preferably, the motor is disposed coaxially with respect to the camshaft and is accommodated, at least partially, within a drive element for driving the camshaft in rotation. Hydraulic means, for example, in the form of an annular piston surrounding the motor, may be provided for rotating the camshaft relative to the drive means.

Another aspect of the present invention provides a second pivotable finger for use in valve gear as described above, the second pivotable finger having features, separately or in combination, as described more specifically below.

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 shows a forward part of valve gear of an internal combustion engine; Figure 2 is an enlarged partial view of the valve gear of figure 1 in a different position; Figure 3 is a sectional view generally on the line lil-lil in Figure 1; Figures 4 and 5 are views of a component of the valve gear; figures 6 and 7 are views of another component of the valve gear; Figure 8 is a diagrammatic view showing sensor positions in the engine of Figure 1; Figure 9 is a diagrammatic view showing control circuitry in the engine of Figure 1; and Figure 10 is a valve lift diagram for the engine of figure 1.

Figures 1 to 3 show a cylinder head 5 which, in the embodiment illustrated, has a separate cam carrier 6. A camshaft 8 is supported by the cam Gamer 6, and has a series of cams 10 distributed along it, only one of which is shown in Figures 1 to 3.

The camshaft is rotatable about a camshaft axis 12.

The admission of fuel-ar mixture into the cylinder 4 is controlled by two inlet valves, of which only the valve stems 20 are shown, and the exhaust of combustion products is controlled by two exhaust valves (not shown). The valve stems move in valve guides 22 and are biased to the closed position (upwardly as shown in Figure 1) by valve springs 24 in a conventional manner.

As shown in Figure 1, the cam 10 varies in profile along the axis 12. Although the base circle 26 is parallel to the axis 12, parts of the cam which extend beyond the base circle vary in distance from the axis 12 in the axial direction. The cam 10, or the entire camshaft 8, is movable axially so that the part of the cam 10 that is effective to operate the valves 14 changes to alter the valve lift, duration and timing. The mechanism for displacing the camshaft 8 will be described below with reference to Figures 1 and 2, but alternatively it may be as described in GB 2190140, GB 2341659 or GB 2359608.

The action of the cam 10 Is transferred to the valves through a first pivotable finger 30 and a second pivotable finger 32. The first finger 30 is pivotable about an axis 34 which is fixed to the cam carrier 6. The axis 34 is defined by cylindrical bosses 36 which project to each side from the finger 30. These bosses 36 serve to support the first finger 30 against forces applied to it by the cam 10 in the direction of the camshaft axis 12, and so avoid the transmission of these forces to the second finger 32 and the valve stems 20. Bosses of alternative shapes to those shown in Figures 4 and 5 may be used, or the first finger 30 may have a generally triangular shape, widening towards the pivot axis 34. The first finger 30 is cranked, having a first portion 38 which, in the valve-closed condition shown in Figure 1, extends obliquely from the axis 34 towards the valve stem 20, and a second portion 40 which extends substantially transversely of the lengthwise direction of the valve stem 20.

The first finger 30 is shown in greater detail in Figures 4 and 5. The portion 40 includes a part cylindrical recess 44 which extends in the lengthwise direction of the portion 40 and receives a cam engaging element 46 (Figures 1 and 3) which is in the form of a half roller having a part cylindrical surface cooperating with the recess 44 and a flat surface which engages the cam 10. The cam engaging element 46 is thus able to rock in the recess 44 so that the flat surface can align with the engaging surface of the cam which, as will be appreciated from Figure 1, vanes In Inclination relatively to the axis 12 as the cam rotates.

The surface of the portion 40 of the first finger 30 Includes, on the side opposite the recess 44, a recess 48 which acts as a guide track as described in my earlier British patent application no. 0315246.9.

The second finger 32 is mounted for pivotal movement about axes passing through a point 50 defined by a support element 52 mounted in the cam carrier 6. The support element has a hemispherical end 54 centred on the point 50, and the finger 32 has a complementary hemispherical recess 57 which receives the end 54 of the support element 52. The second finger is shown in more detail in Figures 6 and 7. The second finger 32 extends generally radially of an axis passing through the point 50 and parallel to the camshaft axis 12. At the end away from the support element 52, the second finger 32 terminates at a downwardly directed foot 56. At the transition between the radially extending part of the second finger 32 and the foot 56, there is a bore 58, approximately parallel to the camshaft axis 12. Half way along this bore 58 there is a notch 60 which is sufficiently wide to receive the portion 40 of the first finger 30. The first finger 30 thus supports the second finger 32 against lateral forces, i.e. forces parallel to the camshaft axis 12. As shown in Figure 7, the foot 56 has a continuous straight surface for engagement with the tips of the valve stems 20. However, in an alternative embodiment, the foot 56 includes recesses 59 (Figure 3) for receiving the valve stems to assist stable location of the finger 32.

The shape of the second finger 32 as shown In Figures 6 and 7 results in a higher stiffness/mass ratio at the valve compared with that of the second finger disclosed in my British Patent Application No 0315246.9, and contributes to an overall system having high stiffness compared with known variable valve lift systems. A system as described herein may therefore be suitable for high-speed engines (i.e. engines operating at speeds in excess of 7000 RPM for road use).

In the assembled condition, the bore 58 receives a track engaging contact element in the form of a roller 62. As shown In Figures 1 and 3, the roller 62 engages the track 48 in the first finger 30. Also, the foot 56 engages the ends of the valve stems 20.

In the position shown In Figure 3, the base circle 26 of the cam 10 contacts the half roller 46. The first finger 30 is consequently in its uppermost position about the pivot axis 34. Since the position of the second finger 32 is determined by abutment of the pin 36 with the track 48, the second finger 32 is also in its uppermost position about the axis 50 under the influence of the valve spring 24. The valve is thus closed.

Rotation of the camshaft causes the nose of the cam 10 to come into contact with the half roller 46, so pivoting the first finger 30 in a clockwise direction about the axis 34.

This in turn causes the second finger 32 to rotate about the point 50, also in a clockwise direction about an axis parallel to the camshaft axis 12, to cause the valves to begin to open. Eventually, the valves reaches their fully open positions, "hereafter further rotation of the camshaft 8 will cause the valves to close again under the action of the springs 24.

It will be appreciated that, because the second finger 32 is supported by the support element 52 at the hemispherical end 54, the finger 32 is able to pivot not only about an axis parallel to the camshaft axis 12, but also about other axes passing through the point 50. In particular, the finger 32 can pivot about an axis passing through the point and perpendicular to a plane containing the lengthwise axes of the valve stems 20.

Consequently, the finger 32 can pivot about the point 50 to equalise itself on the two valve stems 20, so taking up any difference in valve clearance between the valves. To assist in this lateral rocking motion of the second finger 32, the pin 62 engaging the track 48 in the first finger 30 may be slightly barrelled, ye it may have a convex surface as viewed perpendicular to its axis. Furthermore, the side faces of the notch 60 in the second rocker 32 may diverge from each other in the upwards direction (as seen in Figure 6) with a convex surface to accommodate the rocking motion of the finger 32 relative to the first finger 30.

The recesses 59, as shown in Figure 3, could be replaced by elongated holes (elongated in the direction towards and away from the point 50), into which convex radiussed plugs are inserted for engagement with the valve stems 20. Alternatively, as shown in Figures 1 and 3, the recesses could be defined by vertical tags that project downwardly on each side of each valve stem. In either form of the recesses 59, the bottom surface of each recess is preferably convex as viewed in two perpendicular planes, again to ensure satisfactory seating of the second finger 32 on the tips of the valve stems 20.

In the valve gear disclosed in my earlier British Patent Application No 0315246.9, the axis about which the second finger 32 pivots during opening and closing of the valves is substantially fixed (although it may undergo minor adjustment in the manner of a hydraulic tappet to take up valve clearances during operation). A consequence of this is that any variations in valve clearances between the cylinders of the engine cannot be adjusted for. Furthermore, other variations in operation between the cylinders of the engine may occur, for example as a result of differential thermal expansion between the cylinder head and the camshaft. Such thermal effects can result in the active part of each cam 10 varying between the cylinders of the engine. Such effects may be particularly marked at idle or tick over of the engine. In accordance with the present invention, these effects can be eliminated by adjustment of the support element 52 in the direction shown by an arrow 62. For example, as indicated in dashed outline in Figure 3, raising the support element 52, assuming a constant position for the valve stem 20, causes the pin 62 to move upwards and to the right away from the track 48.

In practice, of course, the second finger 32 will be biased upwardly by the valve spring 24, acting through the valve stem 20, to bring the pin 62 into contact with the track 48.

However, it will be appreciated that, by adjustment of the support element 52, it is possible to vary the degree of valve opening for any particular rotational position of the cam 10.

By suitable control of the support elements 52 for the valves of each cylinder of an engine, it is thus possible to ensure that, for each rotational camshaft position, the degree of valve opening (or more precisely, the air flow velocity through the valve) can be equalised across all of the cylinders of the engine.

The camshaft 8 is driven in rotation from the crankshaft of the engine by means of a belt 66 which drives a drive element which, in this embodiment, is a pulley 68. The drive element may alternatively be a sprocket or gear wheel. The pulley is supported by two plain bearings, on opposite sides of the belt 66, to avoid structure borne noise as compared with roller bearings. This arrangement provides a stiff and light independent support structure for the pulley 36 (or other drive element). The camshaft is movable axially to vary the maximum lift and opening duration of the valves of the engine, and the rotational position of the camshaft 8 relative to the pulley 68 can also be varied in order to change the valve timings. These adjustments are achieved by a camshaft control mechanism 70 situated towards the front of the engine. This mechanism is shown in Figure 1 and, on an enlarged scale, in Figure 2.

The camshaft 8 is rotationally supported on the cam carrier 6 by bearing caps 72. The forward end of the camshaft 8 (ie the nght-hand end as seen in Figure 1) Is hollow and accommodates a sleeve 74 on which the camshaft is rotatable Thrust bearings 76 are provided to support axial thrust between the camshaft 8 and the sleeve 74. A retaining ring 78 is screwed into the crankshaft 8 to retain the sleeve 74. A split support housing 80, 82 is secured to the cam carrier 6 and supports the pulley 68 for rotation. An annular cylinder 84, screwed onto the pulley 68, is accommodated in the housing part 82, and receives an annular piston 86. The piston 86 Is biased Into the cylinder 84 (ie to the right as seen in Figure 1) by a spring 88 which is retained in the pulley 68 by a lip 69. The housing part 82 is secured to the engine (cylinder head or block) by any suitable means (not shown) and may form part of an all-enveloping cover for the front of the engine.

A brush or stepper motor 90 comprises a casing 92, a casing nose 94 and an output shaft 96. The casing 92 is secured to the housing part 82, and extends within the annular cylinder 84. The casing nose 94 is provided with axial splints 98 which cooperate with axial splines 100 formed within the sleeve 74. The sleeve 74 also has an internal screwthread 102 which cooperates with an external screwthread 104 on the output shaft 96 of the motor 90 to provide a non-overhauling slow thread enabling accurate and backlash-free positioning of the camshaft on the output shaft 96.

The annular piston 86 has on its inner surface an axial spline 108 which cooperates with an external axial spline 110 on the crankshaft 8. On its external surface, the piston 86 has a helical spline 112, which cooperates with an Internal helical spline 114 on the pulley 68.

It will be appreciated that the casing 92 of the motor 90 is fixed with respect to the cam carrier 6, and consequently to the cylinder head 5. The sleeve 74 is thus rotationally fixed with respect to the cylinder head 5 by virtue of the splines 98, 100. However, the sleeve 74, taking with it the camshaft 8, can be displaced axially with respect to the cylinder head 5 upon rotation of the output shaft 96, by virtue of the screwthreads 104, 106. Consequently, by controlled rotation of the motor 90, valve lift and duration can be adjusted by axial displacement of the camshaft 8.

Oil can be admitted or discharged from the Interior of the annular cylinder 84 by means of passageways 116, controlled by suitable valves. If oil is admitted to the cylinder 84, the piston 86 is displaced to the left, as seen in figures 1 and 2, against the action of the spring 88. By virtue of the helical splines 112, 114, this displacement of the piston 86 causes it to rotate with respect to the pulley 68, this rotation being transmitted to the camshaft 8 by virtue of the axial splines 108, 110. If the supply of oil to the cylinder 84 is terminated and a drain path opened, the piston 86 is returned to the right, as seen in Figures 1 and 2, by the spring 88. Consequently, by controlling the supply and return of oil to and from the cylinder 84, the relative rotational positions of the pulley 68 and the camshaft 8 can be adjusted continuously, so as to vary the valve timing of the engine. It will be appreciated that adjustment of the valve timing by the cylinder and piston unit 84, 86 and adjustment of valve lift and duration by the motor 90, can be effected Independently of each other.

By situating the motor 90 and the cylinder and piston unit 84, 86 axially of the camshaft 8 and extending within the pulley 68, and by using the interior of the annular cylinder 84 to accommodate the motor 90, the packaging of the control mechanism can be made very compact, taking up little more space, If any, than the drive arrangement of a camshaft having no facility for adjustment. It will be appreciated that the forward end of the camshaft is enlarged so that the portion carrying the splices 110 can move over the motor casing 92 when the camshaft is fully advance by the action of the screw threads 104, 106. The use of the motor 90, acting on the camshaft through the sleeve 74, enables highly accurate positioning of the camshaft 8.

Figures 8 and 9 show, in schematic form, control circuitry for use in the engine of Figures 1 to 3. Figure 8 shows an electronic control unit (ECU) 118 which receives inputs from the various sensors, as follows: a pulley sensor 120, responsive to rotation of the pulley 68 a relative camshaft rotation sensor 122 responsive to rotation of the camshaft 8 relative to the pulley 68 as caused by displacement of the piston 86.

a camshaft displacement sensor 124 responsive to axial displacement of the camshaft 8 by operation of the motor 90 a crankshaft sensor 126 responsive to crankshaft rotation other sensors 128.

On the basis of outputs from the sensors 120 to 128, the ECU 118 is able to determine the current operating status of the various components of the valve gear and to provide output signals for controlling the motor 90 and valves controlling the supply or discharge of oil from and to the cylinder 84 in order to adjust valve lift, duration and valve timing. 1 1

Figure 9 shows, schematically, an engine 2 having four cylinders, each provided with an air intake duct 130. Within the cylinder head 5, each Intake duct 130 is branched into two passages controlled by the respective valves represented by the valve stems in Figure 1. An air flow sensor 132 is disposed in each intake duct 30. The output signal from each sensor 132 is fed to an ECU 134. Figure 9 shows the second pivotable finger 32 for each cylinder as well as the support element 52 for each second finger 32. An oil gallery 136 extends through the cylinder head 5 for selective connection, via a solenoid valve (not shown) to a bore 138 (Figure 3) within which each support element 52 is accommodated.

The ECU 134 also receives control inputs from other sensors 140 as well as engine map data 142 governing operation of the engine under various conditions.

In operation, for example at tick over of the engine, the map data 142 specifies an idling speed for the engine, as sensed by the crankshaft sensor 126. In achieving the idling speed, the ECU 118 adjusts the valve lift, duration and timing by appropriate control of the piston 86 and the motor 90. However, at the idling speed, the air flow rate through the intake ducts 130 as sensed by the sensors 132 may vary between cylinders. This variation may have undesirable consequences on fuel efficiency, emissions and engine operating stability. To avoid these effects, the sensors 132 provide signals to the ECU 134, and the solenoids controlling the flow of oil from the gallery 136 to the individual chambers 138 containing the support elements 152 are controlled in order to raise or lower the respective support elements 52 so as to equalise the air flows through the Intake ducts 130. As a result, all of the cylinders operate under the same conditions, regardless of differences in manufacturing tolerances and/or thermal or other differences.

Furthermore, valve gear as described above enables continuous adjustment of valve operation to compensate for changes occurring during engine warmup. For example, when the engine is cold, valve clearances will be intentionally increased, and consequently there is little danger of any individual clearances closing completely and causing valves to remain permanently open. However, it is preferable for the camshaft 8 to be dimensioned so that it positions the cams 10 accurately when the engine is at its normal operating temperature. This means that the cams 10 will be displaced relatively from the valve stems 20 when the engine is cold. Consequently, when the engine Is cold, the critical adjustment to be achieved by displacing the support elements 52 is to compensate for the incorrect positions of the cams l O. However, as the engine warms up, this adjustment becomes less critical, and instead it becomes important to compensate for variations in valve clearance. The ability of the support elements 52 to vary continuously in position means that active valve clearance is possible by active correction to the fixed map valve clearance at the particular measured airflow, ensuring optimum operation of the engine at all temperatures. The above features will allow benefits to be achieved by lowering emissions and fuel consumption and improving engine smoothness Figure 10 is a lift diagram for a valve controlled by valve gear in accordance with the present invention. At full power, represented by a line A, the maximum valve lift is approximately 10.5 mm. Line B is a minimum lift line, and represents valve movement at tick over, assuming a fixed support element 52 (ie the support element 52 is In the same position when the engine is at tick over (line B) as when the engine is at maximum power (line A).

By adjusting the position of the support element 52, the cylinder in question can be caused to operate within the shaded area in Figure 10, and consequently both the maximum lift and the duration of valve opening can be reduced within a continuous range Thus, by controlling valve lift within the shaded region by suitable control of the support element 52, the operating conditions of all of the cylinders of the engine can be equalised. Furthermore, because the second finger 32 can tilt about an axis perpendicular to the plane containing the longitudinal axes of the valve stems 20, the operation of the valves of each pair can also be equalised.

Valve gear as described above has significant cost benefits over knownvariable valve lift systems. Since adjustment of the support elements can compensate for manufacturing vacations, component tolerances can be relatively relaxed, leading to savings in component manufacturing costs. Furthermore, several features of the valve gear, for example the use of the motor 90 to displace the camshaft 10, lead to a reduction in part count, resulting in reduced assembly and component stocking and management costs.

Claims (14)

1. Claims: 1. Valve gear for operating a valve in an internal combustion

   engine, the valve gear comprising a camshaft carrying a cam which acts on a first pivotable finger, the first finger having an actuating surface which contacts a second pivotable finger, the second pivotable finger being in driving engagement with the valve and being pivotably supported by a support element which is movable relatively to a cylinder head of the internal combustion engine.
2. 2. Valve gear as claimed in claim 1, in which the support element is movable in a direction which lies in a plane perpendicular to the axis of the camshaft.
3. 3. Valve gear as claimed in claim 1 or 2, in which the support element is movable in a direction parallel to the direction of valve movement.
4. 4. Valve gear as claimed in claim 1 or 2, In which the support element is movable In a direction inclined to the direction of valve movement.
5. 5. Valve gear as claimed in any one of the preceding claims, in which the support element is movable under hydraulic control.
6. 6. Valve gear as claimed in claim 5, in which the supply of hydraulic fluid to move the support element is controlled by means of a valve.
7. 7. Valve gear as claimed in claim 5 or 6, in which the movement of the support element is controlled in response to air flow through the valve.
8. 8. Valve gear as claimed in claim 7, in a multicylinder engine, in which the movement of the support element for a valve of each cylinder is controlled in response to variations in airflow between the valves of the respective cylinders.
9. 9. Valve gear as claimed in claim 8, in which an airflow sensor is provided in the air flow path through the valve of each cylinder.
10. 10. Valve gear as claimed in any one of the preceding claims, in which the support element is provided with a hemispherical contact surface engaging the second

    pivotable finger.
11. 11. Valve gear as claimed In any one of the preceding claims, In an engine having two inlet valves per cylinder, in which the second finger has two valve engaging portions for engaging the two valves.
12. 12. Valve gear as claimed in claim 1 1 when appendant to claim 10, in which the support element permits tilting of the second finger about an axis extending perpendicular to a plane containing the directions of movement of the valves.
13. 13. Valve gear substantially as described herein with reference to, and as shown in, the accompanying drawings.
14. 14. An Internal combustion engine provided with valve gear in accordance with any one of the preceding claims.