US20030159667A1 - Adjustment mechanism for valves - Google Patents
Adjustment mechanism for valves Download PDFInfo
- Publication number
- US20030159667A1 US20030159667A1 US10/342,630 US34263003A US2003159667A1 US 20030159667 A1 US20030159667 A1 US 20030159667A1 US 34263003 A US34263003 A US 34263003A US 2003159667 A1 US2003159667 A1 US 2003159667A1
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- United States
- Prior art keywords
- valve
- guide
- path
- rocker arm
- adjustment
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
- F01L1/12—Transmitting gear between valve drive and valve
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
- F01L1/20—Adjusting or compensating clearance
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
- F01L1/30—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of positively opened and closed valves, i.e. desmodromic valves
Definitions
- the present invention relates to improvements in engines, such as internal combustion engines, particularly to the actuation of valves and most particularly, poppet valves for internal combustion engines.
- the present invention also has application to engines or pumps which uses valves.
- valve timing of the reciprocating internal combustion engine has a significant effect on the volumetric efficiency of the engine at particular engines speeds.
- An engine having fixed valve timing ie a fixed crankshaft angle for valve opening before piston at top dead centre and a fixed crankshaft angle for valve closing beyond top dead centre, will have a particular engine speed where it operates most efficiently.
- the fixed synchronisation of the inlet and exhaust valves opening and closing relative to the piston position create the combination giving the most torque.
- valve overlap is desirable at high engine speeds as it increases torque output.
- valve overlap that produces good torque at high engine speeds will cause the engine to run poorly and reduces torque output at low engine speeds. Accordingly, in general, opening the valves earlier and closing them later improves volumetric efficiency at high engine speed at the expense of torque at low engine speed. Conversely decreasing valve overlap increases engine torque at low engine speeds but does not give the best efficiency at high engine speeds.
- valve actuator should accelerate slowly towards the valve, in order to reduce then eliminate the clearance between the valve and the actuator or between any intervening tappet arrangement and the actuator. This is to ensure that the valve and actuator do not impact on each other with large velocities or forces.
- the valve then needs to be opened as quickly as possible in order to facilitate the filling of the cylinder with fresh air and fuel in the case of an intake valve, or empty the cylinder of exhaust gas in the case of an exhaust valve.
- the valve should be held open for as long as possible before closing rapidly.
- the valve should then reseat as gently as possible and then stay closed until the cycle repeats.
- a substantially sinusoidal motion has been found to be acceptable in providing a path for valve movement.
- camshafts have an eccentric cam lobe that actuates a valve, wherein the profile of the cam lobe determines the motion characteristic of the valve.
- a problem with this arrangement is that the camshafts spin rapidly and the valves rely on valve springs to keep them in contact with the outer surface of the cam lobe. As the camshafts spin more rapidly, the valves can leave the surface of the cam lobe due to inertia. This problem has been addressed in part by increasing the strength of the valve spring, however this makes opening the valve harder and increases wear on the cam lobe surface.
- camshafts Another major problem with camshafts is the inability to change the lobe shape, making modification of the motion characteristics of the valve difficult.
- the camshaft needs to be replaced or machined, with the result that torque is only optimised over a narrow speed range for a particular cam lobe profile. This is one of the reasons that engines that perform well at high speed usually lack torque in the lower range of engine speeds.
- the valve springs push against the cam lobes as the camshaft rotates, significant twisting forces are generated along the camshaft, which can result in camshaft breakage.
- One device is a cam shaft having two standard cam lobes for the two inlet valves, and a third cam lobe between the two standard inlet lobes.
- the inlet valves are actuated by the standard cam lobes.
- a pin engages with the valve's actuators, which allows both the valves to be actuated by the third cam lobe, which has a different profile suited to high engine speeds, wherein the inlet valves open earlier and stay open longer.
- a similar mechanism operates in the exhaust valve camshaft.
- This system has the disadvantage that it is not possible to vary the valve opening and closing times between the two predetermined valve motion characteristics, ie there are only two valve opening durations available. This results in a marked “step” in torque output from lower rpm to higher rpm and fails to achieve the maximum torque output across the whole range of engine speeds, as effectively only two specific engine speeds are optimised.
- camshaft speed is not always half the crankshaft speed over parts of a single revolution, but varies according to the engine speed. For example, at low rpm the camshaft may spin at the standard rate of half the crankshaft speed. At higher engine speeds, a mechanism mounted on the camshaft causes the camshaft to spin at lower than half crank speed while opening the valves and keeping them open, thus ensuring that the valves are open over a wider angle than at lower speed.
- valve actuation means comprise a cam shaft which opens the valves.
- Camshafts are difficult to manufacture, and are subject to wear and breakage.
- the present invention provides a means for adjusting the motion characteristics of a valve.
- the motion characteristics of the valve include timing, such as the crankshaft's angular location before the top dead centre reference angle where the valve opens, duration, such as the angle of crankshaft rotation for which the valve will stay open, lift or travel the amount of lift of the valve for a given crankshaft angular location, rate of travel and/or force.
- the adjustment is actuated mechanically.
- the adjustment means is located between a valve actuation means and the valve.
- adjusting the motion characteristics of the valve by way of the present invention, enables selection of engine performance criteria from a range of predetermined characteristics, together with a selection of the degree to which the criteria is to be performed.
- the adjustment of valve motion characteristics may be selected in a manner which accentuates engine torque. Or, selection may be made to accentuate engine fuel economy.
- valve actuation means which produces an approximate sinusoidal motion of valve lift in relation to crankshaft rotation and/or which also allows the motion characteristics of the valve to be varied.
- valve actuation means includes a rotating member.
- the adjustment means varies the valve opening angle, and/or the valve closing angle and/or the valve lift, either individually or collectively. It has been found that it is advantageous to vary the valve lift and duration, and that while these may be done separately, it has been found that it is beneficial to increase valve lift and valve opening duration as engine speed rises.
- the adjustment means varies the valve opening and closing angle and the valve lift collectively.
- the invention provides an apparatus for adjusting the motion characteristics of a valve, including adjustment means to adjust the valve motion in accordance with the adjustment means travel along a non-straight path.
- the invention provides an adjustment means for use in an apparatus for adjusting a motion characteristics of a valve comprising a plate having a guide path.
- the invention provides an apparatus for adjusting the motion characteristics of a valve including a first guide path and a second guide path wherein the motion characteristics of the valve are determined by differences in shape and/or alignment between the first and second guide paths.
- the invention provides an apparatus for adjusting the clearance of a valve actuated by a desmodromic valve actuation means including a valve having a threaded end portion.
- the means for adjusting the motion characteristics of the valve include an adjustment member having a guide path and a pivotally mounted valve actuation member having at least one guide surface, wherein a pin moves along both the guide path and the guide surface, causing the pivotally mounted actuation member to pivot and move the valve.
- the pin is driven in a substantially cyclic motion.
- the guide path of the adjustment member and the guide surface of the valve actuation member are not collateral over their entire length, ie there is a difference in the paths such that they deviate from each other at least over part of their length. This difference in paths produces the movement of the actuation member as the pin travels along both paths. Also, a kinematic inversion of pin and guide is contemplated as an alternative embodiment.
- FIGS. 1 a - 1 d show a schematic representation of an adjustment mechanism in accordance with the present invention in various states of assembly
- FIG. 2 a shows a schematic side view of the adjustment mechanism of the present invention and a prior art valve actuation mechanism
- FIG. 2 b shows a schematic view of a non-desmodromic adjustment mechanism of the present invention and a prior art valve actuation mechanism.
- FIG. 3 shows an isometric view of part of a first embodiment of the adjustment mechanism of the present invention
- FIG. 4 shows an isometric view of all of the first embodiment of the adjustment mechanism of the present invention
- FIGS. 5 a and 5 b show end views of a second embodiment of the adjustment mechanism of the present invention.
- FIGS. 6 a and 6 b show end views of the adjustment mechanism shown in FIGS. 5 a and 5 b;
- FIG. 7 is a graph of typical extremes of variation in lift and duration of the valves compared with the position of the crankshaft, as varied by the adjustment mechanism of the present invention
- FIG. 8 is a first embodiment of a guide plate of the adjustment mechanism of the present invention.
- FIG. 9 is a second embodiment of the guide plate of the adjustment mechanism of the present invention.
- FIGS. 10 a - 10 d are embodiments of rocker arms of adjustment mechanism of the present invention.
- FIG. 11 is a schematic side view of a first embodiment of a slot of a guide plate of the adjustment mechanism in accordance with the present invention.
- FIG. 12 is a schematic side view of a profiled surface of a guide plate of the adjustment mechanism in accordance with the present invention.
- FIG. 13 is a schematic side view of a second embodiment of the slot of the guide plate of the adjustment mechanism of the present invention.
- FIG. 14 is a schematic representation of the slot of the guide plate of the adjustment mechanism of the present invention.
- FIGS. 15 a - 15 d are embodiments of a sliding pin of the adjustment mechanism of the present invention.
- FIGS. 16 a - 16 d are embodiments of the guide plates of the adjustment mechanism of the present invention.
- FIG. 17 a is a first embodiment of a guide plate adjustment means of the adjustment mechanism of the present invention.
- FIG. 17 b is a second embodiment of the guide plate adjustment means of the adjustment mechanism of the present invention.
- FIG. 18 a is a perspective view of a valve clearance adjustment mechanism in accordance with the present invention.
- FIG. 18 b is an exploded perspective view of the valve clearance adjustment mechanism shown in FIG. 18 a.
- a mechanism 10 for adjusting the motion characteristics of a poppet valve 1 .
- the mechanism 10 includes an actuation means, for example a valve crankshaft 12 having a crank pin 13 , which is used to provide the cyclic displacement motion and base timing for actuation of the valve 1 .
- the valve crankshaft 12 is normally driven by the crankshaft (not shown) by known means such as a belt, chain drive, or gears, at half the crankshaft rotation speed.
- the mechanism 10 is typically mounted in the head of a reciprocating four stroke engine (not shown) and further includes a pivot point 14 which is fixed to the head of the engine to pivotally locate a valve actuator, such as rocker arm 16 which actuates the motion of the valve 1 .
- An adjustment member such as guide plate 18 is mounted to the head such that it is able to be moved within a range of positions, for example a first position 20 and a second position 22 as shown in FIGS. 1 b , 5 a , 5 b , 6 a , 6 b and 9 .
- Crank pin 13 is attached to a conrod 24 through aperture 15 at one end and has a member such as a guide member, for example sliding pin 26 , at the other end as shown in FIGS. 1 a - 1 d , 2 and 3 .
- a member such as a guide member, for example sliding pin 26
- the conrod 24 moves the sliding pin 26 along a guide, such as path 25 in the guide plate 18 .
- the guide plate 18 does not move in response to movement of the sliding pin 26 , and the sliding pin 26 is constrained to move along path 25 .
- the sliding pin 26 also travels along a guide path 28 in rocker arm 16 .
- rocker arm 16 there is typically one rocker arm 16 per valve 1 , and accordingly there may be two rocker arms 16 if two inlet (or exhaust) valves are used per cylinder.
- the two rocker arms 16 and guide plates 18 can be served by a single conrod 24 and sliding pin 26 as shown in FIG. 4, thus actuating two valves (inlet or exhaust) simultaneously as in a four valve per cylinder engine head.
- the path 28 may be in the form of a slot having an upper and lower profiled surface, in the case of desmodromic valve actuation, as shown in FIGS.
- the path 25 in the guide plate 18 causes the sliding pin 26 to move in a way constrained by the profile of the path 25 , which causes the rocker arm 16 to pivot about pivot point the pivot point 14 which pushes on the valve 1 via two nuts tightened on the valve stem, as shown in FIGS. 5, 18 a and 18 b and described later, thus causing valve 1 to open and close according to the differences in the profile of path 25 and path 28 .
- It is the difference in path profiles as shown in FIGS. 13 and 14 that causes the rocker arm 16 to pivot, and the profiles of the paths 28 and 25 may be varied according to the motion characteristics desired from the valve, which may vary from engine to engine, or with the purpose of the engine.
- the individual path profiles of the guide plate 18 and rocker arm 16 are not intended to be limited to the various embodiments shown in this specification.
- valve 1 can be replaced by valve system 100 as shown in FIGS. 2 a and 2 b , wherein valve system 100 includes a known shim and bucket arrangement that allows the valve clearance to be adjusted, and a valve spring 101 ensures that the valve stays in contact with the actuator 32 when the valve is closing, which may be used in non-desmodromic or conventional valve actuation.
- the mechanism 10 may simply replace camshaft 102 as a valve actuation means.
- FIGS. 1 a to 1 d The assembled parts of the mechanism 10 can be seen in FIGS. 1 a to 1 d , wherein the assembly of the conrod 24 to the crankshaft 12 by the crank pin 13 , and the attachment of the guide plate 18 and rocker arm 16 to the sliding pin 26 is shown schematically.
- a partially assembled adjustment mechanism is shown in FIG. 3, wherein the assembled valve crankshaft 12 , conrod 24 and sliding pin 26 are seen in relationship to the pivot point 14 which is normally in a fixed position, but can be rotated and includes in this embodiment eccentric section 11 .
- the assembled mechanism 10 is shown in FIG.
- the valve crankshaft 12 rotates at half engine crankshaft speed.
- the conrod 24 is connected at one end to a crank pin 13 on the valve crankshaft 12 and at the other end to the sliding pin 26 .
- the pin 26 is located in a guide path 25 of the guide plate 18 .
- the pin 26 is constrained to move along the path 25 of the guide plate 18 , however the guide plate 18 can move from a first position 20 to a second position 22 , and any number of positions therebetween.
- the profile of the guide path 25 defines the trajectory of pin 26 .
- the pin 26 also slides along path 28 of the rocker arm 16 , and the different profile between the path 28 and path 25 causes the rocker arm 16 to pivot back and forth about pivot point 14 .
- the actuator 32 attached to rocker arm 16 moves with the arm 16 and contacts the end of valve 1 , pushing the valve open and pulling the valve closed.
- a valve spring may close the valve 1 .
- the position of the guide plate 18 can be varied, in the case of FIGS. 2 a , 2 b , 3 and 4 by rotation of the rocker shaft 14 , in a second embodiment adjustment 1 s due to eccentric adjusting shaft 30 as can be seen in FIGS. 5 a , 5 b , 6 a , 6 b 17 a and 17 b.
- the shaft 30 has an eccentric off-centre lobe 31 which can be turned within aperture 34 , thus causing the guide plate 18 to move from a first position 20 wherein the motion characteristics as shown by line 40 a and 40 b of FIG.
- FIG. 7 suit low engine speed, to a second position 22 , wherein the motion characteristics of the valve suit high engine speeds shown by line 42 a and 42 b , also of in FIG. 7.
- the movement of the guide plate 18 can be seen in the comparison of open valve positions shown in FIGS. 5 a and 5 b.
- the adjusting shaft 30 and lobe 31 position the guide plate 18 in the first position 20 .
- the adjusting shaft 30 and lobe 31 position the guide plate 18 in the second position 22 and thus the maximum valve opening, as seen in FIG. 5 b is greater than the maximum valve position seen in FIG. 5 a.
- the operation of the shaft 30 and lobe 31 in the aperture 34 in the guide plate is shown in FIGS. 17 a and 17 b and will be described in more detail below.
- FIG. 7 The motion characteristics of the valves can be seen in FIG. 7, wherein line 40 a represents the valve lift of an inlet valve (vertical axis) versus crankshaft rotation angle (horizontal axis) for the valve 1 actuated by valve crankshaft 12 while the guide plate 18 is in the first position 20 .
- the exhaust valve motion characteristics when the guide plate 18 is in the first position 20 are shown by characteristics when the guide plate 18 is in the first position 20 are shown by line 40 b.
- Line 42 a represents the valve motion characteristics when the guide of an inlet valve when the guide plate 18 is in the second position 22 .
- the exhaust valve motion characteristics when the guide plate 18 is in the second position 22 can be seen in line 42 b.
- FIG. 7 there is a significant difference between valve lift, valve opening duration and valve overlap when the guide plate 18 moves from a first position 20 to a second position 22 .
- the reason for the difference in motion characteristics is that when guide plate 18 is in the first position 20 , the profile of path 28 is positioned such that the differences in the profile between path 25 and path 28 are minimised, as can be seen in FIGS. 5 a , 6 a and 8 and discussed below. This provides a lower valve lift as the pin 26 deflects less, as shown in the position of pin 26 a in FIG. 8.
- the first position 20 of guide plate 18 opens the valve the least amount, and over the shortest angle, and is therefore normally used for low engine speeds where excessive valve overlap is undesirable and increased turbulence is desirable.
- the second position 22 of the guide plate 18 is used to generate larger valve overlap and higher lift in the valves, as seen in the position of the pin 26 b in FIG. 8, and the extension of the valve in FIG. 5 b compared to the extension of the valve in FIG. 5 a. This arrangement is used during high engine speeds where maximum gas flow is required.
- FIGS. 6 a and 6 b show the guide plate 18 in the first position 20 and second position 22 respectively, but the valves in both cases are closed fully, i.e.
- valves regardless of the position of guide plate 18 , the valves still close effectively as shown by the equal positions of the valves in FIGS. 6 a and 6 b.
- the difference in the positions of the plate 18 is clearly seen by the gap between pivot point 14 and guide plate 18 in FIG. 6 b, whereas in FIG. 6 a there is no gap.
- the mechanism 10 allows the guide plate 18 to be positioned at any point between the first position 20 and the second position 22 , thus allowing the amount of valve overlap and/or the angle of valve opening to be adjusted to any point within the predetermined limits of the valve motion characteristics. This also provides the advantage of being able to modify the valve opening angle and/or lift according to any change in the conditions in order to maximise volumetric efficiency.
- the differences between the profiles of path 25 in guide plate 18 and the path 28 in rocker arm 16 are designed to impart the desired valve motion characteristics to the valve.
- the path 25 shown in FIG. 11 is made up of four portions, each with a specific function.
- Portion A is a portion whereby, when the sliding pin 26 is in this portion, the valve will be closed.
- portion B which is a ramp section designed to allow the pin 26 to begin to move at an angle to the direction of motion in portion A.
- FIG. 12 shows the portions A-D of a profiled surface of a guide plate which uses a spring to return the valve to the closed position, and therefore does not require the lower portion of the path.
- the shape of the paths 50 and 51 in FIGS. 11 and 12 respectively are designed to be used with a rocker arm having a substantially straight path 28 .
- the rocker arm would not move relative to the guide plate and accordingly there would be no motion of the valve. Therefore there are numerous shapes that either the path of the guide plate, or the path of the rocker arm can take in order to produce the required motion of the valve providing that the other of the rocker arm or guide plate has a profile that is different.
- the shape of the path 52 of the guide plate shown in FIG. 13 can be used, provided the shape of the rocker arm path 53 differs in the correct areas to provide the motion in the rocker arm.
- This difference in path shapes is shown in FIG. 14 wherein the paths 25 and 28 , have been overlapped in order to highlight the differences in the profiles which then cause the rocker arm to deflect and actuate the valve.
- FIGS. 13 and 14 the differences in the paths in the guide plates and rocker arms can be seen, and the differences relate to valve lift.
- FIG. 13 relates to path 52 in a guide plate that is adjusted rotatably, for example as shown in FIG. 9. It can be seen that this arrangement allows a far greater difference between paths 52 and 53 , and accordingly, a far higher valve lift is achieved than in the linearly adjustable guide plate shown in FIG. 14.
- This increased valve lift shown in FIG. 13 is accomplished without a radical increase in path deviation, which would be necessary in a linearly adjustable guide plate, such as that shown in FIG. 8. It is undesirable to have too large a deviation in any of the paths as this may lead to increased wear on the path surfaces which will cause the valve motion characteristics to change.
- An advantage of the present system is that by altering the differences in the profiles of the paths 25 and 28 , it is possible to produce a valve motion with, for example, a more square top than that shown in FIG. 7.
- the sliding pin can be made with a non-circular cross section, called a wear portion, in the region where it travels along the path 28 .
- a wear portion 160 is shown having a flat upper and lower surface where the pin contacts a straight path 28 .
- the profile of the surfaces varies to match the facing surfaces of the paths.
- the wear surfaces can be flat as in wear surface 160 when used with path 128 in rocker arm 116 as shown in FIG. 10 a.
- the wear surfaces can be curved with a common centre of curvature as shown by wear surfaces 360 in FIG. 15 c to suit a similarly curved path 328 in FIG. 10 c of constant radius. If conventional or non-desmodromic valve actuation mechanisms are used, then the sliding pin only needs one wear surface 260 or 460 as shown in FIGS. 15 b and 15 d , as the valve spring will ensure continuous contact of the wear surface with the opposing path 28 surface.
- FIGS. 10 a - 10 d, 15 a - 15 d , and 16 a - 16 d work together in respective sets.
- a rocker arm 116 having a path 128 as shown in FIG. 10 a is used with a gudgeon pin 126 shown in FIG. 15 a and a guide plate 118 having a path 125 shown in FIG. 16 a.
- This arrangement forms an adjustment mechanism employing desmodromic valve actuation wherein the guide plate 118 is adjusted linearly.
- a rocker arm 216 having a path 228 (FIG. 10 b ) works with a gudgeon pin 226 (FIG. 15 b )and a guide plate 218 having a path 225 (FIG. 16 b ) to form an adjustment mechanism employing a valve to close the valve, wherein the guide plate 218 is adjusted linearly.
- a rocker arm 316 having a curved path 328 (FIG. 10 c ) works with a gudgeon pin 326 (FIG. 15 c ) and a guide plate 318 having a path 325 (FIG. 16 c ) to form an adjustment mechanism employing desmodromic valve actuation, wherein the guide plate 318 is adjusted pivotally.
- a rocker arm 416 having a curved path 428 (FIG. 10 d ) works with a gudgeon pin 426 (FIG. 15 d ) and a guide plate 418 having a path 425 (FIG. 16 d ) to form an adjustment mechanism employing a valve to close the valve, wherein the guide plate 418 is adjusted pivotally.
- FIG. 17 a embodiments of a mechanism for adjusting the position of the guide plate 18 is shown.
- the adjusting shaft 30 is situated in the aperture 34 in the guide plate 18 .
- the eccentric cam lobe 31 on the adjusting shaft 30 causes the guide plate 18 to move linearly, for example, as shown in FIG. 8.
- the amount of linear movement of the guide plate 18 is determined by the amount of rotation of the shaft 30 . This allows the guide plate 18 to be adjusted to any point between and including the two extreme positions, being the first position 20 and the second position 22 .
- the shaft 30 is rotatably received in to an aperture 134 in a guide plate 618 mounted so as to be pivotally adjustable about point 135 .
- eccentric lobes 31 force the guide plate 618 to move.
- the guide plate is constrained to move pivotally and therefore, twisting the shaft 30 causes the guide plate 618 to move.
- the amount of movement of the guide plate 618 can be controlled by the rotation of the shaft 30 .
- a control means (not shown) is used to control the rotation of the shaft 30 for each mechanism 10 which enables the guide plate to be positioned anywhere between the first position 20 and the second position 22 .
- the control means may be a simple device for advancing the valve opening by twisting the shaft, or any other suitable means for moving the guide plate.
- Such mechanisms are commonly used to advance the ignition timing as engine speed rises.
- the valve timing in this case may be adjusted either with or independent of the ignition timing.
- FIG. 9 A further embodiment of a guide plate 518 is shown in FIG. 9 wherein the guide plate 518 is mounted to a rotatable pivot point 535 , so that adjustment of the motion characteristics-of the valve can be made by rotating pivot point 535 to which the guide plate 518 is attached, to any position between the two positions as shown by the arrow and dotted line, rather than linear motion as shown by the arrow in FIG. 8.
- the guide plates in any of the embodiments disclosed may be positioned in discrete locations between the first position 20 and the second position 22 , for example by the use of a stepper motor. This would allow the position of the guide plates to be varied in steps according to data from various parameters such as engine speed, rate of change of engine speed, throttle position and gear position. Accordingly, a fuzzy logic table could be set up to position the guide plates in the optimum position for a set of predefined parameters.
- FIGS. 16 a to 16 d show further alternative arrangements for the guide plates.
- Each guide plate is arranged to be mounted in such a way that its position is able to be controlled in order for the position of the path for the sliding pin to be controlled.
- the path In a non-desmodromic arrangement as shown in FIGS. 16 b and 16 d , there is no requirement for the path to be a slot, and as such profiles 125 and 325 can be used, as a spring acting on the valve can be used in a conventional manner to close the valve and accordingly there will always be pressure on either profile 125 or profile 325 and the underside of the respective rocker arms 118 or 328 .
- This arrangement has the advantage that there is a large body of knowledge regarding the use of valve springs to close a valve. Also, the reciprocating rocker arms may be made lighter.
- FIGS. 17 a and 17 b Embodiments of the means for adjusting the position of the guide plate is shown in FIGS. 17 a and 17 b.
- FIG. 17 a relates to a method of producing linear adjustment in the guide plate using a shaft 30 in an aperture 34 in the guide plate 18 .
- the shaft has a lobe 31 which moves the guide plate to the desired position when the shaft 30 is turned.
- Aperture 34 is designed to move the guide plate 18 linearly, and therefore has substantially straight side walls.
- a single shaft with multiple lobes 31 can be used to move all the guide plates 18 simultaneously.
- FIG. 17 b A further embodiment is shown in FIG. 17 b, wherein the shaft 30 is used to cause a rotational motion in the guide plate 18 .
- the twisting of the shaft 30 with eccentric lobe 31 in aperture 134 causes the guide plate to pivot about fixed point 135 . If the guide plate is mounted about a pivot point, as shown in FIG. 9, then the rotation of the shaft 30 will cause the guide plate to rotate, and thus increase or decrease the difference between the paths in the guide plate and rocker arm, which will effect the motion characteristics of the valve.
- side wall 136 is longer than side wall 137 .
- the rocker arm has pivoted while the guide plate has moved either linearly or pivotally. It can be readily determined that the rocker arm could also move linearly in response to the movement of the pin in the path of the guide plate. Further, the guide plate may be fixed in place, and all the adjustment movements can take place on the rocker arm, eg the rocker arm could have its pivot point moveable with respect to the guide plate. This arrangement has the advantage that the guide plate is then fixed, and all the movement is undertaken by the rocker arm, making the mounting of the guide plate greatly simplified.
- the velocity-of the-air-entering the cylinder is also low, and therefore there is not as much turbulence in the air as it passes the inlet valves into the cylinder. It has been found that decreasing the valve lift and duration increases turbulence and therefore increases fuel atomisation, which increases torque. At higher engine speeds, the turbulence from the faster air flow provides sufficient energy for fuel atomisation, and the limiting factor becomes the amount of air able to be squeezed into the cylinder.
- the present invention allows for the adjustment of not only the valve opening duration, but also valve lift with only one parameter being adjusted.
- the motion characteristics of the valve may also be varied in accordance with factors such as throttle position and also which gear is selected.
- valve lift and duration with engine speed, and that it may be desirable under certain circumstances to decrease valve lift and/or durations of the inlet and/or exhaust valve as engine speed increases which the present invention is also able to accommodate.
- FIG. 18 a there is shown a guide plate 418 used in desmodromic valve actuation, having two branches 420 , each branch having an actuator 32 .
- the actuators 32 sit between an upper flange member 422 and a lower flange member 424 at the upper end of a valve 1 .
- the valve 1 includes a threaded portion 426 , which has a lower nut 425 including the lower flange member 424 threadedly attached thereto, as shown in FIG. 18 b.
- An upper nut 428 which is threadedly attached to the threaded portion 426 of the valve 1 , includes the upper flange member 422 .
- the gap between the upper flange member 422 and the lower flange member 424 may be set by an intermediate shim member (not shown) which would fit between the upper nut 428 and lower nut 425 , whereby the size of the shim determines the gap between the upper flange member 422 and lower flange member 424 .
- the upper flange member 422 includes a spacer 423 which contacts a corresponding spacer 427 on the lower flange member 424 , thus providing the appropriate gap between the flanges.
- the size of the gap is slightly larger than the diameter of the portions of the actuator 32 that contact the upper and lower flanges, thereby allowing a clearance between the flanges and the actuators 32 .
- the upper and/or lower nuts may be held in position by lock nuts (not shown).
- valve clearance may then be adjusted by removing the upper lock nut (if provided), removing the upper nut 428 having upper flange member 422 and spacer 423 , and replacing the upper flange member 422 with spacer with another flange member and spacer of suitable size, then reattaching the lock nut onto the threaded portion of the valve 1 .
- the valve clearance can be adjusted to take into account any wear in the system, without having to replace the guide plate 418 .
- the spacer 423 may be integral with or separate to the upper flange member 422 , and the lower flange member 424 may also be replaced if desired.
- the upper nut 428 and upper flange member 422 may be locked into position by the upper nut 428 , and the gap between the upper and lower flanges can be set by the position in which the upper nut 428 and flange member 422 are set.
Abstract
An apparatus for varying the motion characteristics of a valve typically in an engine includes a rotating member such as a valve crank shaft having a conrod with a sliding pin. The sliding pin is constrained to move along a path in a guide member. The guide member is adjustably attached to the engine, and by adjusting the position of the guide member, the trajectory taken by the pin can be varied. The pin also moves along a path of a pivotally attached rocker arm, the path of the rocker arm being different to the path of the guide member. The difference in the paths causes the rocker arm to pivot, and this in turn causes motion in a valve in contact with the end of the rocker arm. By moving the guide member, the differences in the path of the guide member and rocker arm can be accentuated or minimised, thereby altering the motion characteristics of the rocker arm and in turn the valve. This enables the valve opening duration and/or valve lift to be varied. The valve may be fixed to the end of the valve to allow for desmodromic valve actuation, or the valve may include a spring to keep the valve stem in contact with the rocker arm.
In one embodiment the rocker arm has an actuator having contact surfaces on the valve which are of substantially constant diameter, in order for the valve clearance to be kept constant as the rocker arm pivots to open and close the valve.
An apparatus for adjusting the valve clearance on the above device, including a valve stem having a thread is also disclosed.
Description
- The present invention relates to improvements in engines, such as internal combustion engines, particularly to the actuation of valves and most particularly, poppet valves for internal combustion engines.
- The present invention also has application to engines or pumps which uses valves.
- The available torque from an internal combustion engine is largely dependant on the volumetric efficiency of the engine. For reciprocating piston engines, this efficiency is a measure of the volume of atmospheric air drawn into the cylinder/s during an induction stroke, relative to the swept volume of the cylinder/s.
- The valve timing of the reciprocating internal combustion engine has a significant effect on the volumetric efficiency of the engine at particular engines speeds. An engine having fixed valve timing, ie a fixed crankshaft angle for valve opening before piston at top dead centre and a fixed crankshaft angle for valve closing beyond top dead centre, will have a particular engine speed where it operates most efficiently. At this speed, the fixed synchronisation of the inlet and exhaust valves opening and closing relative to the piston position create the combination giving the most torque.
- Obviously it is desirable to have the most torque possible available over a wide range of engine speeds. To achieve the maximum torque at high engine speeds, it is desirable to have the valves (inlet and exhaust) open for as much piston travel as possible. This gives air more time to enter and exhaust gases more time to exit the cylinder and therefore increases volumetric efficiency. However, there are limiting factors for how much piston travel, or how much of an angle (of crankshaft rotation) the inlet and exhaust valves can be kept open. For example, increasing the angle that the valves are open increases the angle that both the inlet and exhaust valves are open at the same time, which is called valve overlap. Valve overlap is desirable at high engine speeds as it increases torque output. However, the same amount of valve overlap that produces good torque at high engine speeds will cause the engine to run poorly and reduces torque output at low engine speeds. Accordingly, in general, opening the valves earlier and closing them later improves volumetric efficiency at high engine speed at the expense of torque at low engine speed. Conversely decreasing valve overlap increases engine torque at low engine speeds but does not give the best efficiency at high engine speeds.
- It is therefore desirable to have a mechanism whereby the timing of the valve opening and closing can be adjusted according to parameters such as engine speed, in order to optimise the torque across a range of engine speeds. Further, other parameters, such as for example, throttle position and which gear is engaged, may be used to vary the timing of the opening and closing of the valves.
- Apart from valve timing, there are other factors which are important in the operation of reciprocating engine poppet valves. Firstly, just before the valve is opened, the valve actuator should accelerate slowly towards the valve, in order to reduce then eliminate the clearance between the valve and the actuator or between any intervening tappet arrangement and the actuator. This is to ensure that the valve and actuator do not impact on each other with large velocities or forces. The valve then needs to be opened as quickly as possible in order to facilitate the filling of the cylinder with fresh air and fuel in the case of an intake valve, or empty the cylinder of exhaust gas in the case of an exhaust valve. Once opened, the valve should be held open for as long as possible before closing rapidly. The valve should then reseat as gently as possible and then stay closed until the cycle repeats. As there should be no radical changes in motion, (excessive acceleration) of the valve, a substantially sinusoidal motion has been found to be acceptable in providing a path for valve movement.
- The actuation of valves and the control of their motion has been accomplished in the past by the use of camshafts. Camshafts have an eccentric cam lobe that actuates a valve, wherein the profile of the cam lobe determines the motion characteristic of the valve. A problem with this arrangement is that the camshafts spin rapidly and the valves rely on valve springs to keep them in contact with the outer surface of the cam lobe. As the camshafts spin more rapidly, the valves can leave the surface of the cam lobe due to inertia. This problem has been addressed in part by increasing the strength of the valve spring, however this makes opening the valve harder and increases wear on the cam lobe surface.
- Another major problem with camshafts is the inability to change the lobe shape, making modification of the motion characteristics of the valve difficult. To modify the valve timing, the camshaft needs to be replaced or machined, with the result that torque is only optimised over a narrow speed range for a particular cam lobe profile. This is one of the reasons that engines that perform well at high speed usually lack torque in the lower range of engine speeds. Further, as the valve springs push against the cam lobes as the camshaft rotates, significant twisting forces are generated along the camshaft, which can result in camshaft breakage.
- There are existing devices that attempt to solve some of the above problems, however, none are completely satisfactory. One device is a cam shaft having two standard cam lobes for the two inlet valves, and a third cam lobe between the two standard inlet lobes. When the engine is spinning below a certain engine speed, the inlet valves are actuated by the standard cam lobes. When the engine accelerates over a predetermined engine speed, a pin engages with the valve's actuators, which allows both the valves to be actuated by the third cam lobe, which has a different profile suited to high engine speeds, wherein the inlet valves open earlier and stay open longer. A similar mechanism operates in the exhaust valve camshaft. This system has the disadvantage that it is not possible to vary the valve opening and closing times between the two predetermined valve motion characteristics, ie there are only two valve opening durations available. This results in a marked “step” in torque output from lower rpm to higher rpm and fails to achieve the maximum torque output across the whole range of engine speeds, as effectively only two specific engine speeds are optimised.
- Another method of varying the valve opening and closing angle is where the camshaft speed is not always half the crankshaft speed over parts of a single revolution, but varies according to the engine speed. For example, at low rpm the camshaft may spin at the standard rate of half the crankshaft speed. At higher engine speeds, a mechanism mounted on the camshaft causes the camshaft to spin at lower than half crank speed while opening the valves and keeping them open, thus ensuring that the valves are open over a wider angle than at lower speed. In order to make up lost time (as the crankshaft must average one revolution for every two crankshaft revolutions), the camshaft must then spin faster than half crank speed for the remainder of the revolution to ensure that it is in the correct position when it is time for the valves to open again. This system is obviously less than ideal as a complex mechanism is used to vary the speed of the camshaft with respect to the crankshaft over a single revolution. Further, valve lift cannot be modified as the cam lobe profiles cannot be modified.
- Another disadvantage of most valve actuation means is that they comprise a cam shaft which opens the valves. Camshafts are difficult to manufacture, and are subject to wear and breakage.
- It has also been found that the method of adjusting valve clearances between the top of the valve and the valve actuator, for example rocker arm or cam shaft lobe, has disadvantages, such as the need for the clearance adjusting mechanism to be on the rocker arm, thereby adding inertia to the rocker arm, or the use of shims which are difficult to get at under the cam lobes, and require buckets to locate them, which add to the overall length of the valve assembly and therefore add to the dimensions of the engine.
- It is an object of the present invention to alleviate at least one disadvantage associated with the prior art.
- To this end, the present invention provides a means for adjusting the motion characteristics of a valve. The motion characteristics of the valve include timing, such as the crankshaft's angular location before the top dead centre reference angle where the valve opens, duration, such as the angle of crankshaft rotation for which the valve will stay open, lift or travel the amount of lift of the valve for a given crankshaft angular location, rate of travel and/or force. In one form, the adjustment is actuated mechanically. In another form, the adjustment means is located between a valve actuation means and the valve. Advantageously, adjusting the motion characteristics of the valve by way of the present invention, enables selection of engine performance criteria from a range of predetermined characteristics, together with a selection of the degree to which the criteria is to be performed. For example, the adjustment of valve motion characteristics may be selected in a manner which accentuates engine torque. Or, selection may be made to accentuate engine fuel economy.
- It may also be desirable to produce a valve actuation means which produces an approximate sinusoidal motion of valve lift in relation to crankshaft rotation and/or which also allows the motion characteristics of the valve to be varied.
- Usually the valve actuation means includes a rotating member.
- Typically the adjustment means varies the valve opening angle, and/or the valve closing angle and/or the valve lift, either individually or collectively. It has been found that it is advantageous to vary the valve lift and duration, and that while these may be done separately, it has been found that it is beneficial to increase valve lift and valve opening duration as engine speed rises.
- Accordingly, it is desirable that the adjustment means varies the valve opening and closing angle and the valve lift collectively.
- In another form, the invention provides an apparatus for adjusting the motion characteristics of a valve, including adjustment means to adjust the valve motion in accordance with the adjustment means travel along a non-straight path.
- In another form, the invention provides an adjustment means for use in an apparatus for adjusting a motion characteristics of a valve comprising a plate having a guide path.
- In another form, the invention provides an apparatus for adjusting the motion characteristics of a valve including a first guide path and a second guide path wherein the motion characteristics of the valve are determined by differences in shape and/or alignment between the first and second guide paths.
- In another form, the invention provides an apparatus for adjusting the clearance of a valve actuated by a desmodromic valve actuation means including a valve having a threaded end portion.
- In a preferred embodiment, the means for adjusting the motion characteristics of the valve include an adjustment member having a guide path and a pivotally mounted valve actuation member having at least one guide surface, wherein a pin moves along both the guide path and the guide surface, causing the pivotally mounted actuation member to pivot and move the valve.
- Typically, the pin is driven in a substantially cyclic motion.
- Desirably the guide path of the adjustment member and the guide surface of the valve actuation member are not collateral over their entire length, ie there is a difference in the paths such that they deviate from each other at least over part of their length. This difference in paths produces the movement of the actuation member as the pin travels along both paths. Also, a kinematic inversion of pin and guide is contemplated as an alternative embodiment.
- One or more of the preferred embodiments of the present invention will now be described, with reference to the accompanying drawings, wherein:
- FIGS. 1a-1 d show a schematic representation of an adjustment mechanism in accordance with the present invention in various states of assembly;
- FIG. 2a shows a schematic side view of the adjustment mechanism of the present invention and a prior art valve actuation mechanism;
- FIG. 2b shows a schematic view of a non-desmodromic adjustment mechanism of the present invention and a prior art valve actuation mechanism.
- FIG. 3 shows an isometric view of part of a first embodiment of the adjustment mechanism of the present invention;
- FIG. 4 shows an isometric view of all of the first embodiment of the adjustment mechanism of the present invention;
- FIGS. 5a and 5 b show end views of a second embodiment of the adjustment mechanism of the present invention;
- FIGS. 6a and 6 b show end views of the adjustment mechanism shown in FIGS. 5a and 5 b;
- FIG. 7 is a graph of typical extremes of variation in lift and duration of the valves compared with the position of the crankshaft, as varied by the adjustment mechanism of the present invention;
- FIG. 8 is a first embodiment of a guide plate of the adjustment mechanism of the present invention;
- FIG. 9 is a second embodiment of the guide plate of the adjustment mechanism of the present invention;
- FIGS. 10a-10 d are embodiments of rocker arms of adjustment mechanism of the present invention;
- FIG. 11 is a schematic side view of a first embodiment of a slot of a guide plate of the adjustment mechanism in accordance with the present invention;
- FIG. 12 is a schematic side view of a profiled surface of a guide plate of the adjustment mechanism in accordance with the present invention;
- FIG. 13 is a schematic side view of a second embodiment of the slot of the guide plate of the adjustment mechanism of the present invention;
- FIG. 14 is a schematic representation of the slot of the guide plate of the adjustment mechanism of the present invention;
- FIGS. 15a-15 d are embodiments of a sliding pin of the adjustment mechanism of the present invention;
- FIGS. 16a-16 d are embodiments of the guide plates of the adjustment mechanism of the present invention;
- FIG. 17a is a first embodiment of a guide plate adjustment means of the adjustment mechanism of the present invention;
- FIG. 17b is a second embodiment of the guide plate adjustment means of the adjustment mechanism of the present invention;
- FIG. 18a is a perspective view of a valve clearance adjustment mechanism in accordance with the present invention.
- FIG. 18b is an exploded perspective view of the valve clearance adjustment mechanism shown in FIG. 18a.
- Referring to FIGS. 2a, 2 b, 4, 5 aand 5 b, a
mechanism 10 is shown for adjusting the motion characteristics of apoppet valve 1. Themechanism 10 includes an actuation means, for example avalve crankshaft 12 having a crankpin 13, which is used to provide the cyclic displacement motion and base timing for actuation of thevalve 1. Thevalve crankshaft 12 is normally driven by the crankshaft (not shown) by known means such as a belt, chain drive, or gears, at half the crankshaft rotation speed. Themechanism 10 is typically mounted in the head of a reciprocating four stroke engine (not shown) and further includes apivot point 14 which is fixed to the head of the engine to pivotally locate a valve actuator, such asrocker arm 16 which actuates the motion of thevalve 1. An adjustment member such asguide plate 18 is mounted to the head such that it is able to be moved within a range of positions, for example afirst position 20 and asecond position 22 as shown in FIGS. 1b, 5 a, 5 b, 6 a, 6 b and 9. -
Crank pin 13 is attached to aconrod 24 throughaperture 15 at one end and has a member such as a guide member, forexample sliding pin 26, at the other end as shown in FIGS. 1a-1 d, 2 and 3. As thevalve crankshaft 12 turns, theconrod 24 moves the slidingpin 26 along a guide, such aspath 25 in theguide plate 18. Theguide plate 18 does not move in response to movement of the slidingpin 26, and the slidingpin 26 is constrained to move alongpath 25. The slidingpin 26 also travels along aguide path 28 inrocker arm 16. There is typically onerocker arm 16 pervalve 1, and accordingly there may be tworocker arms 16 if two inlet (or exhaust) valves are used per cylinder. The tworocker arms 16 and guideplates 18 can be served by asingle conrod 24 and slidingpin 26 as shown in FIG. 4, thus actuating two valves (inlet or exhaust) simultaneously as in a four valve per cylinder engine head. Obviously the number of valves that can be actuated by a single conrod and/or sliding pin is not limited to two per inlet/exhaust. Thepath 28 may be in the form of a slot having an upper and lower profiled surface, in the case of desmodromic valve actuation, as shown in FIGS. 1a, 1 b, 2 a, 4, 5 a, 5 b, 6 a, 6 b, 10 a, 10 c, 13 and 14 or it may be a single profiled surface in the case of conventional valve actuation with a spring providing the valve closing force as shown in FIGS. 2b 10 b and 10 d. - In either method of valve actuation described above, the
path 25 in theguide plate 18 causes the slidingpin 26 to move in a way constrained by the profile of thepath 25, which causes therocker arm 16 to pivot about pivot point thepivot point 14 which pushes on thevalve 1 via two nuts tightened on the valve stem, as shown in FIGS. 5, 18a and 18 b and described later, thus causingvalve 1 to open and close according to the differences in the profile ofpath 25 andpath 28. It is the difference in path profiles as shown in FIGS. 13 and 14 that causes therocker arm 16 to pivot, and the profiles of thepaths guide plate 18 androcker arm 16 are not intended to be limited to the various embodiments shown in this specification. - Further, the
valve 1 can be replaced byvalve system 100 as shown in FIGS. 2a and 2 b, whereinvalve system 100 includes a known shim and bucket arrangement that allows the valve clearance to be adjusted, and avalve spring 101 ensures that the valve stays in contact with theactuator 32 when the valve is closing, which may be used in non-desmodromic or conventional valve actuation. Themechanism 10 may simply replacecamshaft 102 as a valve actuation means. - The assembled parts of the
mechanism 10 can be seen in FIGS. 1a to 1 d, wherein the assembly of theconrod 24 to thecrankshaft 12 by thecrank pin 13, and the attachment of theguide plate 18 androcker arm 16 to the slidingpin 26 is shown schematically. A partially assembled adjustment mechanism is shown in FIG. 3, wherein the assembledvalve crankshaft 12,conrod 24 and slidingpin 26 are seen in relationship to thepivot point 14 which is normally in a fixed position, but can be rotated and includes in this embodimenteccentric section 11. The assembledmechanism 10 is shown in FIG. 4 wherein twoguide plates 18 are slidingly attached to theeccentric section 11 of therocker shaft 14 and tworocker arms 16 are pivotally attached to thepivot point 14, which would enable themechanism 10 to operate two inlet or exhaust valves. The guide plates, in this case, are constrained to slide linearly by pins (not shown) which fit intoguideways 9. - In operation, the
valve crankshaft 12 rotates at half engine crankshaft speed. Theconrod 24 is connected at one end to a crankpin 13 on thevalve crankshaft 12 and at the other end to the slidingpin 26. Thepin 26 is located in aguide path 25 of theguide plate 18. As thevalve crankshaft 12 rotates, thepin 26 is constrained to move along thepath 25 of theguide plate 18, however theguide plate 18 can move from afirst position 20 to asecond position 22, and any number of positions therebetween. The profile of theguide path 25, as shown in the figures, defines the trajectory ofpin 26. Thepin 26 also slides alongpath 28 of therocker arm 16, and the different profile between thepath 28 andpath 25 causes therocker arm 16 to pivot back and forth aboutpivot point 14. Theactuator 32 attached torocker arm 16 moves with thearm 16 and contacts the end ofvalve 1, pushing the valve open and pulling the valve closed. Where non-desmodromic valve actuation is desired, a valve spring may close thevalve 1. - The position of the
guide plate 18 can be varied, in the case of FIGS. 2a, 2 b, 3 and 4 by rotation of therocker shaft 14, in a second embodiment adjustment 1 s due toeccentric adjusting shaft 30 as can be seen in FIGS. 5a, 5 b, 6 a, 6 b 17 a and 17 b. Theshaft 30 has an eccentric off-centre lobe 31 which can be turned withinaperture 34, thus causing theguide plate 18 to move from afirst position 20 wherein the motion characteristics as shown byline second position 22, wherein the motion characteristics of the valve suit high engine speeds shown byline guide plate 18 can be seen in the comparison of open valve positions shown in FIGS. 5a and 5 b. In FIG. 5a, the adjustingshaft 30 andlobe 31 position theguide plate 18 in thefirst position 20. In FIG. 5b, the adjustingshaft 30 andlobe 31 position theguide plate 18 in thesecond position 22 and thus the maximum valve opening, as seen in FIG. 5b is greater than the maximum valve position seen in FIG. 5a. The operation of theshaft 30 andlobe 31 in theaperture 34 in the guide plate is shown in FIGS. 17a and 17 b and will be described in more detail below. - The motion characteristics of the valves can be seen in FIG. 7, wherein
line 40 a represents the valve lift of an inlet valve (vertical axis) versus crankshaft rotation angle (horizontal axis) for thevalve 1 actuated byvalve crankshaft 12 while theguide plate 18 is in thefirst position 20. The exhaust valve motion characteristics when theguide plate 18 is in thefirst position 20 are shown by characteristics when theguide plate 18 is in thefirst position 20 are shown byline 40 b.Line 42 a represents the valve motion characteristics when the guide of an inlet valve when theguide plate 18 is in thesecond position 22. The exhaust valve motion characteristics when theguide plate 18 is in thesecond position 22, can be seen inline 42 b. As can be seen from FIG. 7, there is a significant difference between valve lift, valve opening duration and valve overlap when theguide plate 18 moves from afirst position 20 to asecond position 22. - The reason for the difference in motion characteristics is that when
guide plate 18 is in thefirst position 20, the profile ofpath 28 is positioned such that the differences in the profile betweenpath 25 andpath 28 are minimised, as can be seen in FIGS. 5a, 6 a and 8 and discussed below. This provides a lower valve lift as thepin 26 deflects less, as shown in the position ofpin 26 a in FIG. 8. - The
first position 20 ofguide plate 18 opens the valve the least amount, and over the shortest angle, and is therefore normally used for low engine speeds where excessive valve overlap is undesirable and increased turbulence is desirable. Thesecond position 22 of theguide plate 18 is used to generate larger valve overlap and higher lift in the valves, as seen in the position of thepin 26 b in FIG. 8, and the extension of the valve in FIG. 5b compared to the extension of the valve in FIG. 5a. This arrangement is used during high engine speeds where maximum gas flow is required. FIGS. 6a and 6 b show theguide plate 18 in thefirst position 20 andsecond position 22 respectively, but the valves in both cases are closed fully, i.e. regardless of the position ofguide plate 18, the valves still close effectively as shown by the equal positions of the valves in FIGS. 6a and 6 b. The difference in the positions of theplate 18 is clearly seen by the gap betweenpivot point 14 and guideplate 18 in FIG. 6b, whereas in FIG. 6a there is no gap. Themechanism 10 allows theguide plate 18 to be positioned at any point between thefirst position 20 and thesecond position 22, thus allowing the amount of valve overlap and/or the angle of valve opening to be adjusted to any point within the predetermined limits of the valve motion characteristics. This also provides the advantage of being able to modify the valve opening angle and/or lift according to any change in the conditions in order to maximise volumetric efficiency. - The differences between the profiles of
path 25 inguide plate 18 and thepath 28 inrocker arm 16 are designed to impart the desired valve motion characteristics to the valve. For example, when used with arocker arm 16 having astraight path 28, thepath 25 shown in FIG. 11, is made up of four portions, each with a specific function. Portion A is a portion whereby, when the slidingpin 26 is in this portion, the valve will be closed. As thepin 26 travels along thepath 25, it moves to portion B, which is a ramp section designed to allow thepin 26 to begin to move at an angle to the direction of motion in portion A. This allows theactuator 32 to be brought into contact with the valve (or valve shim) relatively slowly, as there is usually a small gap between the top of the valve assembly and the valve actuator. Once the valve has contacted the top of the valve, slidingpin 26 enters portion C ofpath 25, where the slope of the path increases greatly and thus causes the actuator to push open the valve quickly. Once the maximum valve opening is approached the slidingpin 26 enters portion D whereby the velocity of the valve while opening is reduced, and the valve starts to decelerate. In portion D, the slidingpin 26 reaches the end of its travel and thevalve crankshaft 12 begins to pull the slidingpin 26 back along the portion D in the reverse direction, thus starting to close the valve again. - FIG. 12 shows the portions A-D of a profiled surface of a guide plate which uses a spring to return the valve to the closed position, and therefore does not require the lower portion of the path. The shape of the
paths straight path 28. - If the path of the rocker arm had a shape the same as the shape of the path of the guide plate, then the rocker arm would not move relative to the guide plate and accordingly there would be no motion of the valve. Therefore there are numerous shapes that either the path of the guide plate, or the path of the rocker arm can take in order to produce the required motion of the valve providing that the other of the rocker arm or guide plate has a profile that is different. As an example, the shape of the
path 52 of the guide plate shown in FIG. 13 can be used, provided the shape of therocker arm path 53 differs in the correct areas to provide the motion in the rocker arm. This difference in path shapes is shown in FIG. 14 wherein thepaths - From FIGS. 13 and 14, the differences in the paths in the guide plates and rocker arms can be seen, and the differences relate to valve lift. FIG. 13 relates to
path 52 in a guide plate that is adjusted rotatably, for example as shown in FIG. 9. It can be seen that this arrangement allows a far greater difference betweenpaths - An advantage of the present system is that by altering the differences in the profiles of the
paths - In order to overcome or reduce wear due to high contact pressure between the
path 28 and the slidingpin 26, it has been found that the sliding pin can be made with a non-circular cross section, called a wear portion, in the region where it travels along thepath 28. - In FIG. 15a, a
wear portion 160 is shown having a flat upper and lower surface where the pin contacts astraight path 28. The profile of the surfaces varies to match the facing surfaces of the paths. For example, the wear surfaces can be flat as inwear surface 160 when used withpath 128 inrocker arm 116 as shown in FIG. 10a. Alternatively the wear surfaces can be curved with a common centre of curvature as shown bywear surfaces 360 in FIG. 15c to suit a similarlycurved path 328 in FIG. 10c of constant radius. If conventional or non-desmodromic valve actuation mechanisms are used, then the sliding pin only needs onewear surface path 28 surface. - It should be noted that the embodiments shown in the FIGS. 10a-10 d, 15 a-15 d, and 16 a-16 d, work together in respective sets. A
rocker arm 116 having apath 128 as shown in FIG. 10a is used with agudgeon pin 126 shown in FIG. 15a and aguide plate 118 having apath 125 shown in FIG. 16a. This arrangement forms an adjustment mechanism employing desmodromic valve actuation wherein theguide plate 118 is adjusted linearly. - Similarly, a
rocker arm 216 having a path 228 (FIG. 10b) works with a gudgeon pin 226 (FIG. 15b)and aguide plate 218 having a path 225 (FIG. 16b) to form an adjustment mechanism employing a valve to close the valve, wherein theguide plate 218 is adjusted linearly. - A
rocker arm 316 having a curved path 328 (FIG. 10c) works with a gudgeon pin 326 (FIG. 15c) and aguide plate 318 having a path 325 (FIG. 16c) to form an adjustment mechanism employing desmodromic valve actuation, wherein theguide plate 318 is adjusted pivotally. - A
rocker arm 416 having a curved path 428 (FIG. 10d) works with a gudgeon pin 426 (FIG. 15d) and aguide plate 418 having a path 425 (FIG. 16d) to form an adjustment mechanism employing a valve to close the valve, wherein theguide plate 418 is adjusted pivotally. - In FIG. 17a embodiments of a mechanism for adjusting the position of the
guide plate 18 is shown. The adjustingshaft 30 is situated in theaperture 34 in theguide plate 18. By rotating the adjustingshaft 30, theeccentric cam lobe 31 on the adjustingshaft 30 causes theguide plate 18 to move linearly, for example, as shown in FIG. 8. The amount of linear movement of theguide plate 18 is determined by the amount of rotation of theshaft 30. This allows theguide plate 18 to be adjusted to any point between and including the two extreme positions, being thefirst position 20 and thesecond position 22. - In FIG. 17b, the
shaft 30 is rotatably received in to anaperture 134 in aguide plate 618 mounted so as to be pivotally adjustable aboutpoint 135. As the shaft is rotated,eccentric lobes 31 force theguide plate 618 to move. The guide plate is constrained to move pivotally and therefore, twisting theshaft 30 causes theguide plate 618 to move. As above, the amount of movement of theguide plate 618 can be controlled by the rotation of theshaft 30. - A control means (not shown) is used to control the rotation of the
shaft 30 for eachmechanism 10 which enables the guide plate to be positioned anywhere between thefirst position 20 and thesecond position 22. The control means may be a simple device for advancing the valve opening by twisting the shaft, or any other suitable means for moving the guide plate. Such mechanisms are commonly used to advance the ignition timing as engine speed rises. The valve timing in this case may be adjusted either with or independent of the ignition timing. - A further embodiment of a
guide plate 518 is shown in FIG. 9 wherein theguide plate 518 is mounted to arotatable pivot point 535, so that adjustment of the motion characteristics-of the valve can be made by rotatingpivot point 535 to which theguide plate 518 is attached, to any position between the two positions as shown by the arrow and dotted line, rather than linear motion as shown by the arrow in FIG. 8. - It should also be understood that the guide plates in any of the embodiments disclosed may be positioned in discrete locations between the
first position 20 and thesecond position 22, for example by the use of a stepper motor. This would allow the position of the guide plates to be varied in steps according to data from various parameters such as engine speed, rate of change of engine speed, throttle position and gear position. Accordingly, a fuzzy logic table could be set up to position the guide plates in the optimum position for a set of predefined parameters. - FIGS. 16a to 16 d show further alternative arrangements for the guide plates. Each guide plate is arranged to be mounted in such a way that its position is able to be controlled in order for the position of the path for the sliding pin to be controlled. In a non-desmodromic arrangement as shown in FIGS. 16b and 16 d, there is no requirement for the path to be a slot, and as
such profiles profile 125 orprofile 325 and the underside of therespective rocker arms - Embodiments of the means for adjusting the position of the guide plate is shown in FIGS. 17a and 17 b. FIG. 17a relates to a method of producing linear adjustment in the guide plate using a
shaft 30 in anaperture 34 in theguide plate 18. The shaft has alobe 31 which moves the guide plate to the desired position when theshaft 30 is turned.Aperture 34 is designed to move theguide plate 18 linearly, and therefore has substantially straight side walls. As many engines of the type that use poppet valves have numerous valves in alignment, a single shaft withmultiple lobes 31 can be used to move all theguide plates 18 simultaneously. - A further embodiment is shown in FIG. 17b, wherein the
shaft 30 is used to cause a rotational motion in theguide plate 18. The twisting of theshaft 30 witheccentric lobe 31 inaperture 134 causes the guide plate to pivot about fixedpoint 135. If the guide plate is mounted about a pivot point, as shown in FIG. 9, then the rotation of theshaft 30 will cause the guide plate to rotate, and thus increase or decrease the difference between the paths in the guide plate and rocker arm, which will effect the motion characteristics of the valve. As theaperture 134 is designed to move theguide plate 18 pivotally,side wall 136 is longer thanside wall 137. - In the above embodiments, the rocker arm has pivoted while the guide plate has moved either linearly or pivotally. It can be readily determined that the rocker arm could also move linearly in response to the movement of the pin in the path of the guide plate. Further, the guide plate may be fixed in place, and all the adjustment movements can take place on the rocker arm, eg the rocker arm could have its pivot point moveable with respect to the guide plate. This arrangement has the advantage that the guide plate is then fixed, and all the movement is undertaken by the rocker arm, making the mounting of the guide plate greatly simplified.
- It can be seen from the embodiments disclosed that the movement of the
guide plate 18 from its first position to the second position causes the slidingpin 26 travelling alongpath 25 to not only increase the crank rotation angle across which the valves open, but also increases valve lift at the same time. These aspects in combination produce a result that is very desirable, as two of the valve characteristics change with only a change in one parameter, that being the movement of the guide plate. It is desirable to have the valves increase their lift at high engine speeds to ensure that the maximum amount of air enters the cylinder or exhaust gas exits from the cylinder in the time provided. However, at low engine speeds, it has been found that increased turbulence in the air entering the cylinder is desirable as it assists in the atomisation of the fuel in the air. When engines operate at low speed, the velocity-of the-air-entering the cylinder is also low, and therefore there is not as much turbulence in the air as it passes the inlet valves into the cylinder. It has been found that decreasing the valve lift and duration increases turbulence and therefore increases fuel atomisation, which increases torque. At higher engine speeds, the turbulence from the faster air flow provides sufficient energy for fuel atomisation, and the limiting factor becomes the amount of air able to be squeezed into the cylinder. The present invention allows for the adjustment of not only the valve opening duration, but also valve lift with only one parameter being adjusted. - The motion characteristics of the valve may also be varied in accordance with factors such as throttle position and also which gear is selected.
- It should be noted that it is not essential to increase valve lift and duration with engine speed, and that it may be desirable under certain circumstances to decrease valve lift and/or durations of the inlet and/or exhaust valve as engine speed increases which the present invention is also able to accommodate.
- In FIG. 18a there is shown a
guide plate 418 used in desmodromic valve actuation, having twobranches 420, each branch having anactuator 32. Theactuators 32 sit between anupper flange member 422 and alower flange member 424 at the upper end of avalve 1. Thevalve 1 includes a threadedportion 426, which has alower nut 425 including thelower flange member 424 threadedly attached thereto, as shown in FIG. 18b. Anupper nut 428, which is threadedly attached to the threadedportion 426 of thevalve 1, includes theupper flange member 422. The gap between theupper flange member 422 and thelower flange member 424 may be set by an intermediate shim member (not shown) which would fit between theupper nut 428 andlower nut 425, whereby the size of the shim determines the gap between theupper flange member 422 andlower flange member 424. - In the embodiment shown, the
upper flange member 422 includes aspacer 423 which contacts acorresponding spacer 427 on thelower flange member 424, thus providing the appropriate gap between the flanges. Typically, the size of the gap is slightly larger than the diameter of the portions of theactuator 32 that contact the upper and lower flanges, thereby allowing a clearance between the flanges and theactuators 32. The upper and/or lower nuts may be held in position by lock nuts (not shown). The valve clearance may then be adjusted by removing the upper lock nut (if provided), removing theupper nut 428 havingupper flange member 422 andspacer 423, and replacing theupper flange member 422 with spacer with another flange member and spacer of suitable size, then reattaching the lock nut onto the threaded portion of thevalve 1. In this way, the valve clearance can be adjusted to take into account any wear in the system, without having to replace theguide plate 418. Thespacer 423 may be integral with or separate to theupper flange member 422, and thelower flange member 424 may also be replaced if desired. - Alternatively, the
upper nut 428 andupper flange member 422 may be locked into position by theupper nut 428, and the gap between the upper and lower flanges can be set by the position in which theupper nut 428 andflange member 422 are set. - It is important that the contact surfaces of
actuator 32 be of constant radius, as in this way the valve clearance will be constant as the valve is opened and closed, and therocker arm 16 moves aboutpivot point 14.
Claims (23)
1. An apparatus for adjusting the motion characteristics of a valve over a range of opening and closing angles including a member in communication with a valve actuator, wherein the member travels along a non-straight path in a guide, and the position of the guide is varied to adjust the direction of motion of the member.
2. The apparatus of claim 1 wherein the valve actuator is a pivotally located arm.
3. The apparatus of claims 1 or 2 wherein the guide includes a plate having a non-straight path.
4. The apparatus of any one of claims 1 to 3 , wherein at least 3 different opening and closing angles are able to be selected over a range of engine speed.
5. An apparatus for adjusting the motion characteristics of a valve, including adjustment means to adjust the valve motion including an adjustment member and a guide member, the guide member moving along a first guide path in the adjustment member and along a second guide path in a valve actuator, wherein the first guide path and the second guide path are not collinear, and the guide member moving along the first and second guide paths causes the valve actuator to move relative to the adjustment member due to the differences in these paths.
6. An apparatus as claimed in claim 5 , wherein the valve actuator includes a rocker arm rotatably mounted around a point, the adjustment member includes a guide plate adjustable in relation to that point, and an actuation means for moving the guide member along the second guide path in the rocker arm and the first guide path in the guide plate wherein differences in the first and second guide paths are reduced when the guide plate is in a first position, compared to the differences in the guide paths when the guide plate is in a second position.
7. Apparatus for adjusting the motion characteristics of a valve including an adjustment means having a plate having a guide path.
8. The apparatus of claim 7 including a valve actuator having a guide path different from the guide path of the adjustment means.
9. The apparatus of claim 8 , wherein the amount of non-alignment of the guide path of the adjustment means and the guide path of the valve actuator determines the motion characteristics of the valve actuator.
10. The apparatus of claim 9 , wherein varying the position of the adjustment means changes the alignment between the guide path of the adjustment means and the guide path of the valve actuator thus adjusting the motion characteristics of the valve.
11. An apparatus for adjusting the motion characteristics of a valve including a first guide path and a second guide path wherein the motion characteristics of the valve are determined by differences in shape and/or alignment between the first and second guide paths.
12. The apparatus of claim 11 , wherein the first guide path is located in an adjustment member, which moves relative to a valve actuator to alter the differences between the shape and/or alignment of the first and second guide paths.
13. An apparatus for adjusting the motion characteristics of a valve including an adjustment means operatively situated between a valve actuation means and the valve, having an adjustment member with a guide path adapted to receive a guide member, the adjustment member being moveable between a first position and a second position, wherein the guide member travelling along the guide path of the adjustment member has a different trajectory when the adjustment member is in the first position than when the adjustment member is in the second position.
14. The apparatus of claim 13 wherein the valve actuation means includes the means for determining the base timing of the valve actuation.
15. The apparatus of claim 13 or 14 where the guide member moves cyclicly.
16. The apparatus of any one of claims 13 to 15 where the position of the adjustment member can be varied over a given range of engine speeds.
17. The apparatus of any one of claims 13 to 16 where the position of the adjustment member can be varied over a given range of engine loads.
18. An apparatus for adjusting the motion characteristics of a valve including an adjustment member having a first guide path, a valve actuator having a second guide path, wherein the adjustment member moves relative to the valve actuator, thus modifying the motion of the guide member moving along the first and second guide paths which also modifies the motion of the guide element.
19. The apparatus of claim 18 wherein the adjustment member and valve actuator include plates.
20. The apparatus of any one of the preceding claims wherein an adjustment mechanism does not have its base timing varied.
21. The apparatus of any of claims 13 to 15 wherein the guide element is pivotally located.
22. The apparatus of any one of the preceding claims wherein the adjustment member is slidably located with respect to the pivot point of the guide element.
23. The apparatus of any one of the preceding claims, wherein the motion characteristics of an inlet valve are variable independently of the motion characteristics of the exhaust valve.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/342,630 US20030159667A1 (en) | 1997-02-13 | 2003-01-15 | Adjustment mechanism for valves |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AUPO5084A AUPO508497A0 (en) | 1997-02-13 | 1997-02-13 | Improvements in poppet valve actuation |
AUP05084 | 1997-02-13 | ||
US36731499A | 1999-08-11 | 1999-08-11 | |
US10/342,630 US20030159667A1 (en) | 1997-02-13 | 2003-01-15 | Adjustment mechanism for valves |
Related Parent Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/AU1998/000090 Continuation WO1998036157A1 (en) | 1997-02-13 | 1998-02-13 | Adjustment mechanism for valves |
US09367314 Continuation | 1999-08-11 |
Publications (1)
Publication Number | Publication Date |
---|---|
US20030159667A1 true US20030159667A1 (en) | 2003-08-28 |
Family
ID=27758290
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US10/342,630 Abandoned US20030159667A1 (en) | 1997-02-13 | 2003-01-15 | Adjustment mechanism for valves |
Country Status (1)
Country | Link |
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US (1) | US20030159667A1 (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1580405A1 (en) * | 2004-03-26 | 2005-09-28 | Stefan Battlogg | Desmodromic valve drive |
US20090151664A1 (en) * | 2007-12-14 | 2009-06-18 | Hyundai Motor Company | Continuous variable valve lift apparatus |
GB2478559A (en) * | 2010-03-10 | 2011-09-14 | Tck Engines Ltd | Timing mechanism to provide variable valve timing in an internal combustion engine |
US20120132159A1 (en) * | 2010-11-30 | 2012-05-31 | Kia Motors Corporation | Continuous variable valve lift apparatus |
US20150198136A1 (en) * | 2014-01-10 | 2015-07-16 | Ford Global Technologies, Llc | Laser ignition system based diagnostics |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
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US4495902A (en) * | 1983-05-05 | 1985-01-29 | Investment Rarities, Incorporated | Mechanism for variably controlling an internal combustion engine valve |
US4572118A (en) * | 1981-12-31 | 1986-02-25 | Michel Baguena | Variable valve timing for four-stroke engines |
US4723515A (en) * | 1983-05-05 | 1988-02-09 | Investment Rarities Incorporated | Mechanism utilizing a single rocker arm for controlling an internal combustion engine valve |
US4898130A (en) * | 1987-10-03 | 1990-02-06 | Jaguar Cars Limited | Valve mechanisms |
-
2003
- 2003-01-15 US US10/342,630 patent/US20030159667A1/en not_active Abandoned
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4572118A (en) * | 1981-12-31 | 1986-02-25 | Michel Baguena | Variable valve timing for four-stroke engines |
US4495902A (en) * | 1983-05-05 | 1985-01-29 | Investment Rarities, Incorporated | Mechanism for variably controlling an internal combustion engine valve |
US4723515A (en) * | 1983-05-05 | 1988-02-09 | Investment Rarities Incorporated | Mechanism utilizing a single rocker arm for controlling an internal combustion engine valve |
US4898130A (en) * | 1987-10-03 | 1990-02-06 | Jaguar Cars Limited | Valve mechanisms |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1580405A1 (en) * | 2004-03-26 | 2005-09-28 | Stefan Battlogg | Desmodromic valve drive |
US20090151664A1 (en) * | 2007-12-14 | 2009-06-18 | Hyundai Motor Company | Continuous variable valve lift apparatus |
US7950360B2 (en) * | 2007-12-14 | 2011-05-31 | Hyundai Motor Company | Continuous variable valve lift apparatus |
GB2478559A (en) * | 2010-03-10 | 2011-09-14 | Tck Engines Ltd | Timing mechanism to provide variable valve timing in an internal combustion engine |
GB2478559B (en) * | 2010-03-10 | 2016-05-25 | Tck Engines Ltd | Internal combustion engine valve control |
US20120132159A1 (en) * | 2010-11-30 | 2012-05-31 | Kia Motors Corporation | Continuous variable valve lift apparatus |
US20150198136A1 (en) * | 2014-01-10 | 2015-07-16 | Ford Global Technologies, Llc | Laser ignition system based diagnostics |
US9243603B2 (en) * | 2014-01-10 | 2016-01-26 | Ford Global Technologies, Llc | Laser ignition system based diagnostics |
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