Classifications

• • 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
• • 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

• THIS INVENTION relates to the operation of reciprocating valves of the type commonly used in internal combustion engines.
• This type of valve is generally known as a “Poppet Valve”, and is used in combination with a cam device.
• the resultant arrangement is employed in order to allow the internal combustion engine to "breath” i.e. in most four-stroke egnines, it is normal to employ one intake valve and one outlet or exhaust valve per cylinder.
• each valve should be made capable of reaching its designed lift elevation instantaneously, remain open for the whole of its designed period, and close instantaneously.
• it is very difficult to achieve anything like this requirement as a steeply profiled cam is both noisy and prone to excessive wear.
• the weight of the valve/spring combination prohibits truly rapid acceleration as this would place undue strain upon various components involved.
• the present invention aims to provide an improved valve arrangement and, to this end, there is provided a valve arrangement in which a reciprocable valve member is biased into a closed position by resilient means extending between two abutment members whose separation in the directlon of movement of the volvc member is variable, and actuating means are provided for moving one of the abutment members to which the valve member is operatively coupled to displace the valve from its closed position towards an open position and for moving the other abutment member to maintain the separation of the abutment members during at least an initial portion of the movement of the valve member.
• An advantage of the present invention is that the opening of the valve and the tensioning of the return spring or fluid etc, is no longer confined to a single action, i.e., in opening the valve and compressing the return spring, large loads are created and a very narrow time factor is involved, with the onus of compromise too heavily upon the successful operation of the necessary components which result in restraints being included in the basic initial design of almost every internal combustion engine.
• the present invention retains the use of basic well-known valve gear components together with a small amount of desmodromic thinking.
• the result is a semi-desmodromic device which retains the simplicity of the normal gear-train but imbues it with the meticulous and exacting performance capabilities of the best desmodromic types.
• the present invention enables the use of steeply graduated, flat-peak cams without the hitherto inherent mechanical problems normally associated with this approach.
• Figure 1 shows the basic principles of the invention applied to a single poppet valve
• Figure 2 is a plan view of a cam disc as shown in Figure 1;
• Figure 3 shows an embodiment of the invention incorporating electromagnetic actuation
• Figure 4 shows a variation on the actuating means of Figure 1 ;
• Figure 5 shows a diagrammatic section of the cam disc of Figure 1 ;
• Figure 6 shows an end elevation view of an embodiment of the invention incorporating an overhead cam system.
• Figure 7 is a side elevation view of Figure 6;
• Figure 8 shows the change in cam/follower contact angle in Figure 6
• Figure 9 is a variation of Figure 8.
• Figure 10 shows a composite layout of a disc/overhead embodiment of the invention.
• Figure 1 1 is a view of the cam profile of Figure 10;
• Figure 12 shows an overhead/cam disc layout
• Figure 13 is a variation on Figure 12;
• Figure 14 shows an end inside/outside cam arrangement
• Figure 15 shows a shaft device for accelerating the opening of a poppet valve.
• Figure 1 is a hypothetical layout depicting a single poppet valve 4 of the overhead type, in that it is situated directly above the cylinder 28.
• the inlet, or outlet duct 27 is situated between the valve 4 and the manifold 29.
• the cylinder-head 26 is shown to be water-cooled.
• this valve can be used in any type of internal combustion engine type.
• the valves may be placed at any angle relative to the piston crown and may be side valves, or any other layout design.
• Figure 1 features a double rockcr assembly with two rocker arms 8, 10 and 9, 1 1 being pivoted, at approximately mid point in either case, on fulcrum axles 14 and 15 with shoulders 16, 17.
• each arm either side of the fulcrum axles 14 and 15 is hypothetical and any desirable length can be included according to requirements.
• Displacement of the rocker arms is achieved by a cam disc arrangement 25 of which Figure 2 is a diagrammatic plan view and of which Figure 5 is a peripheral contour drawing.
• the crosssection of the cam-disc 25 depicted in Figure 1 is that shown as being crosssection X-X in Figure 5.
• the cam-disc 25 is free-running upon a fixed vertical axle 20 and a means of causing its rotation is schematically indicated by a gear-tooth or sprocket member 23.
• the disc may be rotated by any suitable means, i.e. belt, chain, electric motor, hydraulic system, air pressure system etc.
• the upper rocker 8, 10 is positioned with one end thereof against the upper surface of the cam disc 25, while the opposite end is fashioned so as to form a valve-cap 6 and valve-spring seat or abutment 1.
• This is shown as a rigid unitary construction, however, a flexible or pivoting design could be substituted and a composite structure could be included.
• the valve is attached to the seat/cap 1 , 6 in the accepted manner as used in present valve arrangements.
• valve 4 is mounted in a valve-guide 5. If it is assumed that valve 4 is an intake-valve, then it will be seen that Figure 5 has been broken-up into the four-stroke cycle pattern in the following way: "a"/"b" is the "firing" stroke; “b"/"c” is the “exhaust” stroke, “c"/d” is the intake-stroke and “d"/a” is the compression-stroke.
• the upper surface of the disc rises sharply between sections “ b"/"c” and "c"/”d” which corresponds with the opening flank of a normal lobe-type cam. However, it rises very steeply and terminates in a plateau, sustained for almost the enitre length of the intakestroke "c"/"d".
• the plateau, of sustained peak ends with an abrupt downward slope, or ramp between sections "c"/"d” and "d”/”a". This second ramp corresponds with the closing section of a normal lobe-type cam.
• the rocker arm 8, 10 is placed against the upper surface of the cam disc 25 and provided with a cam follower 12.
• the rotation of cam-disc 25 will cause the rocker 8, 10 to be actuated by the follower 12 coming into contact with the ramp between "b"/"c" and "c"/”d". This will cause lever 10 to rise, and lever 8 to fall.
• lever 8 Is attached to valve-cap 6 and vahc 4, together with spring-seat 1 then it is clear that the action of the camdisc 25 will cause the valve to open (i.e. accelerate downwards), the spring to compress against spring-seat or abutment 2 and the action to reverse upon the plateau terminating contact ai the point of the closing-ramp reaching the follower 12.
• Figure 5 indicates that at or around point "bc"/"cd” there is a parallel rise in the surface profile to that of the ramp featured on the upper surface. This will mean that followers 12 and 13 will describe the same trajectory, or trace, thereby moving rockers 8, 10 and 9, 1 1 in the same direction and at the same rate.
• cam-disc 25 has been replaced by a double disc construction. This provides the possibility of further control and variation, in that the cam-disc 25a may be driven with, or independently of, cam-disc 25b.
• Figures 3 and 4 offer an alternative method of effecting the initial opening function of the volvc by making use of electro-magnetic and even electro-static octuation.
• the energy required to open the valve in an electromagnetic system would drop considerably, thereby allowing a realistic system to be contemplated.
• a solenoid is capable of holding a given position, once achieved, with a modest energy requirement, it would be reasonable to consider using such a device to open the valve/spring combination to its desired elevation. Once this is achieved, the solenoid would then hold its position, meanwhile allowing a mechanical cam to apply the delayed tension to the return spring.
• the energy being supplied to the solenoid could be either completely cut-off or reduced, thus allowing the return spring to exert its energy upon the unrestricted valve assembly, and close the valve in the normal way.
• a pulse of energy were again applied to the solenoid, just before the valve reached its seat 4a, then the result would be to decelerate the assembly. (Any hold, or intermittent pause, or brake situations and/or positions could be contemplated).
• Figure 3 shows a solenoid 30 being used in conjunction with a single sided cam-disc 25, the cam-track being featured on the underside of the disc.
• the centre axle 20 of Figure 1 is replaced by a hollow post 19 in which the solenoid drive pin 31 is received in a free-running condition.
• the post 19 could be a separate item or as shown, part of the basic cylinder-head structure 26.
• Rocker arm 8, 10 has a follower 12 which engages pivotally the tip of the pin 31, thereby ensuring that any travel created in pin 31 by the solenoid 30 will be transferred directly to rocker-arm 8, 10.
• any electrical input to the solenoid 30 will pause pin 31 to travel upwards and away from the solenoid 30. This will cause the rocker arms to respond in exactly the same way as previously described in respect of Figure 1 but without the need to provide an upper cam face.
• the lower contour of Figure 5 will then provide a means of placing the spring 3 under tension pressure for as long as the solenoid 30 is provided with electricity. Therefore, the sustained peak situation is no longer the result of a mechanical cam profile coming into contact with a follower.
• the duration of the open condition of the valve and the degree of opening arc now, in this example, a function of the electrical input to the solenoid and the duration of said input.
• valve timing is possible, in that, it Is possible to use a micro-processor, for example in conjunction with the ignition distribution network, in order to determine the actuation of a particular valve, together with the duration of the dwell (sustained peak), elevation (extent of the valve's travel), and any deceleration or semi-closed situation.
• a micro-processor for example in conjunction with the ignition distribution network, in order to determine the actuation of a particular valve, together with the duration of the dwell (sustained peak), elevation (extent of the valve's travel), and any deceleration or semi-closed situation.
• FIGS 6 and 7 show two views of an overhead camshaft arrangement, embodying the delayed tension principle of the present invention.
• This embodiment is similar in operating function to the layout described in Figure 1 , however, the calliper-type rockers have been replaced by a direct valve tappet 12 and a tension cage 32, both receiving their actuation from a muiti-lobed camshaft 34.
• the overhead camshaft is a well established format and the provision of two basic cam profiles, in replacement for the single such device, is a straight-forward development.
• the layout depicted by Figures 6 and 7 emphasises the overall simplicity of the realisation.
• cams 25d and 25c indicate a similar arrangement to that depicted in respect of the cam-disc 25 of Figures 1 and 2, in that the lift ramp of the opening/sustaining cam 25d corresponds to a negative profile on cam 25c, i.e. the falling section on cam 25c is shown as being a mirror profile of the rising section of cam 25d.
• the lift ramp on 25d causes the follower 12 to open the valve 4 and follower 13a, attached to the cage device 32, also moves in the same direction and at the same raie of acceleration. This results in the cage 32, the top spring-seat 1, the valve 4, the spring 3, and the lower spring-scat 2 moving together without applying any compressive pressure to spring 3.
• Figures 8 and 9 indicate the change in cam/follower contact angle as the cam ramp or lobe is followed.
• the increase in elevation causes the follower to assume a quite different radial pitch.
• the indicated rocker arm pivot assembly 14, 16 provides an at rest datum position of 1 D. As the ramp takes effect, the datum position moves up through datum points (2D/3D/4D/5D) etc., the follower 12 face to cam face angle increasing as the graduation takes place.
• Figure 10 is a composite design, or layout, of a disc/overhead type of arrangement.
• a gear driver 23 is connected to a feed-shaft 20 which is coupled to a cam-disc 25.
• There are two sets of cam profiles included see Figure 1 1) this means that the disc, in four-stroke operation, would revolve at one quarter engine speed, rather than one half as is usu ⁇ i.Therefore, when the corn-disc 25 is caused to rotate, the reaction of the cam-disc followers will cause da. 6 to activate scat I and 32 to activate seat 2.
• the same compressive cycle can, therefore, be presumed as in previous embodiment and variations as already described can be assumed for this layout also.
• Figure 12 is also an overhead/cam-disc layout.
• the spring 3 and the two seats 1 and 2 are part of the split disc construction, i.e. the seat/cap 1, 6 is in point of fact, the upper of a disc arrangement as depicted in Figure 4 and seat/cap 2, 23 is the lower of the pair.
• this component also provides the drive gear 23 in composite form.
• valve 4 is attached, in free-running but constant communication, with seat 1 by way of a bearing located collar 37.
• valve will be prevented (by means not shown) from rotating and is confined to reciprocation only.
• Figure 13 is a direct variation of Figure 4, in that, it is twin disc arrangement. However, top disc 25a has been omitted and the black arrow
• T indicates that any desirable means, as previously described for example, solenoid etc, may be considered for providing the top half of the device.
• the base section is included as for Figure 4. Further combinations of spring elements can be included and it is intended that the whole device rotates with the exception of the valve 4. However, if the spring 3 and seats 1 and
• section 25b/2a/2b/2/7 reciprocates as a result of rotational involvement with fixed followers 13a, 13b.
• Figure 14 is an inside/outside cam arrangement, suitable for use in a similar device as depicted by Figures 6 and 7.
• the outer section 39 contains the opening ramp and plateau section
• the inner section 38 includes the usual negative opening fall, together with the spring compression ramp.
• the followers 12 and 13 are as previously described.
• Rotation is as indicated by the skeletal arrow R, and the operating direction (the movement derived from the followers 12 and 13) is indicated by the solid black arrow.
• Figure 15 is a shaft device for accelerating the opening of the valve without direct action of a rotating com, I.e., the leading edge, or ramp, is replaced by a captive bolt arrangement which drives the valve into its open position by way of linear force.
• the shaft 45 is provided with a cross-bored cylinder 47, in which a drive spring 48 is situated and abuts a valve spring adjustment cap 44 secured into the bore.
• a shield or retaining annulus 46 is provided in order to ensure that the spring 48 is kept compressed, after being so rendered by compression ramp 42.
• the spring 48 is held in compression until it reached the break in the retention wail directly above valve 4. This allows the spring 48 to expand and drive captive piston 41 downwards and outwards, thus pushing valve 4 clear of the plateau section 39. Therefore, the valve .4 is accelerated to an elevation equal to the sustaining peak 39 and once there, retained in the open position.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Valve-Gear Or Valve Arrangements (AREA)

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• 1985
  • 1985-12-14 GB GB858530846A patent/GB8530846D0/en active Pending
• 1986
  • 1986-12-12 EP EP19870900202 patent/EP0248069A1/de active Pending
  • 1986-12-12 GB GB08629785A patent/GB2184783A/en not_active Withdrawn
  • 1986-12-12 AU AU67712/87A patent/AU6771287A/en not_active Abandoned
  • 1986-12-12 WO PCT/GB1986/000761 patent/WO1987003645A1/en not_active Ceased
  • 1986-12-13 CN CN86108730A patent/CN86108730A/zh active Pending

Non-Patent Citations (1)

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