GB2225056A

GB2225056A - I.C. engine

Info

Publication number: GB2225056A
Application number: GB8827247A
Authority: GB
Inventors: David Franklin Lees
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-11-22
Filing date: 1988-11-22
Publication date: 1990-05-23
Also published as: GB8827247D0

Abstract

Two shafts 1, 2 that are rotatably mounted in the cylinder head have a plurality of recesses 3a, 3b that co-operate with inlet and exhaust openings of respective cylinders. Oil is fed to annular grooves (17, Fig. 5) on either side of each recess 3 through a valve (23, Fig. 6) opened and closed during shaft rotation. <IMAGE>

Description

ROTARY VALVE ASSEMBLIES This invention relates to rotary valve assemblies for internal combustion engines.

Commonly, flow of fuel and exhaust gases into and out of a combustion chamber of an internal combustion engine cylinder is controlled by camoperated, spring or hydraulically loaded ste valves.

Usually, for a t-stroke engine there are twc valves to each cylinder, or combustion chamber, one for inlet and the other for exhaust. however, larger or high performance engines may have four valves per cylinder accommodating the our cycles of the cylinder.

In nown engines the valve assemblies require for their operation a large number of parts machined to high tolerances, with consequent high manufacturing costs, many of the parts being subject to considerable wear and to lubrication and cooling problems. Also, assembly of such engines is both time-consuming and expensive and servicing and replacement of worn parts can be difficult.

Because of the disadvantages of such previously known engines it has been proposed to reduce the number of moving parts, such as with the well-known rotary piston engine. however, for various reasons, such as the need for extremely high tosserances or the need for complicated electronic control systems, such engines have not been a commercial success and have not been generally acceptable.

The present invention aims to overcome the above mentioned disadvantages and provides a rotary valve assembly for an internal combustion engine, sait assembly comprising two substantially parallel shafts that are in use rotatably connecte to the engine drive, each shaft having a plurality of recesses, one@for each cylinder of the engine, each recess being spaced apart longitudinally and circumferentially of its adjacent recess and being co-operable with an inlet or exhaust port of its associated cylinder, whereby rotation of the shaft periodically aligns each recess with its associated port to open that port and permit flow into or out of the associated cylinder.

Preferably, the shafts are mounted In the engine head in which the inlet and exhaust ports are formed and each recess is so shaped as to provide a continuous surface with its port when in 'he fully- open position.

Lubrication of the shafts is preferably achieved via ducts wormed in the head, one duct being associated with each recess and connected to its own valved inlet. Each duct has a fluid flow connection with two annular grooves that are formed in the shaft and are longitudinally spaced apart one each side of the recess.

The location of the ducts and grooves and their sizes can be arranged to suit the requirements of a particular engine.

A rotary valve assembly in accordance with the invention will now be descried, by way of example, with reference to the accompanying drawings in which: figure 1 is a schematic perspective detailed view of the rotary valve assembly llustrating two valve shafts, figure 2 is a serIes of eua-'ed sections showing the sequence of operation of the rotary valve assembly with a piston/cylinder of a four str@ke engine, Figure 3 is a detailed sectional view of the piston/cylinder and valve assembly of Figure 2 in a particular mode of the sequence, Figure 4 is a detailed perspective view of part of the valve assembly, Figure 5 is a detailed sectional side view of an oil feed arrangement associated with one of the valves, Figure 6 is a schematic sectional view taken along lines 6-6 of FIgure 5, and Figure 7 is a schemati@ view from one sie showing part of the ci feed arrangement of Figure 5.

Referring to Figure 1 , the rotary valve assembly comprises two parallel shafts 1,2 each having a plurality of recesses 3a,3b each spaced longitudinally and circumferentially from its adjacent recess. At the end of each shaft is 2 pulley 4 that is connected by a belt 5 to a drive pulley 5 attached to an engine crank shaft .

As best seen in Figures 2 and 3, the shafts 1,2 are rotatably mounted in a cylinder head @ that is secured to an engine block a. The block has a plurality of cylinders 11 with reciprocating pistons 12 and the shafts 1,2 are arranged that 5 recess 3a,3b of each shaft is associated with each cylinder, one recess 3a being arranged to open and close an inlet port 13 and the other recess 3b being arranged to open and close an outlet post @@. For each cylinder there is a spark plug 15.

The operational sequence of the valve assembly in a for stroke engine is @ illustrated in Figure 3, as follows: (1) top dead centre @TDC@ before induction of fuel.

(2) Mid-stroke induction.

(3) Before botttom dead centre (BDC) induction (4) BDC start of compression stroke.

(5) Mid-compression stroke.

(6) Before TDC and ignition.

(7) Ignition at TDC.

(8) Mid-power stroke.

(9) Before BDC and exhaust.

(10) BDC exhaust stroke.

(11) Mid-exhaust stroke.

(12) Before TDC and induction stroke.

It will be appreciated that the location and the shape of each recess 3a,3b and the rotation of the valve shafts 1,2 can be arranged to provide optimum engine performance. In particular, the valve opening can be suited to the velocity of the piston 12. In this way, the approprlate valve 3 is only slightly open as the piston 12 moves slowly (at TDC or BDC) and as the piston accelerates to mid- stroke the valve opens proportionately. This provides a more controllable vacuum source than a conventional stem-valved engine and thus a smootherrunning, more efficient operation.

Also, the surface 16 of each recess 3a,3b can be shaped to provide a continuous surface with the surfaces of the ports 13,14, as best illustrated in Figure 3 which shows the valve in mid-exhaust stroke, thereby facilitating flow through the valve.

Figure 4 illustrates the way in which the position and shape of each recess 3a,3b can be altered to affect the characteristics of the valve assembly. The depth A of the recess in the shaft, the width B of the recess, the shape or radius @ of the bottom surface 16 of the recess an the shaft diameter D can all be altered to suit the cylinder capacity, compression ratio, fue induction ana exhaust expulsion to suit particular engine requirements and applications.

Illustrated in Figures 5 to 7 is an oil feed system of the valve assembly that prevents or reduces to a minimum the ingress of oil Into the combustion chambers of the cylinders 11 whilst permitting proper lubrication of the shaft 1,2.

The oil feed system will be described in relation to one of the valve recesses 7, but it will be appreciated that each recess has a simila Oil feed arrangement.

For each recess 3, the oil feed system comprises two annular grooves 17 formed in the shaft 1,2, the grooves 17 being spaced apart longitudinally of the shaft 1,2 and located one on each side of the recess 3. The grooves 17 are in continuous flow connection with respective outlet ducts 18 connected through a duct 19 to the engine sump (not shown).

Oil feed is through an inlet valve 21 in the head P that can permit flow into a duct 22 formed in the head 8 surrounding the shafts 1,2. The valve 21 is a spring-loaded ball valve, the ball of which is depressed to open the valve when the ball engages the shaft 1,2 but whlch is released to close the valve when the recess 3 is adjacent the valve. In this way the flow of oil through the valve into the Auct 22 and to the annular grooves 17 is not permitted when the recess 3 is adjacent the valve thus reducing the possibility of ingress of oil through the opening 3 to the cylinder combustion chamber.However, sufficient lubrication of the shaft is possible through the duct 22 surrounding the shaft when the recess 7 Is not adjacent the valve 2 Preferably, the duct 22 is generally V-shaped with arms 22a,22b extending from the apex 23 of the V adjacent the-valve 21. The@angle between.

the arms 22a,22b and the extent of the arms around the cIrcumference- of the shaft may be varied, but 1+, has been found that an angle between the ars o about 160 -165 and a circumferential extent of about 60 -130 is suitable for a four cylinder air cooled engine.

The above described rotary valve assembly has many advantages over known stem-valve assemblIes in engines. The number of moving and non-moving parts is drastically reduced: a head incorporating the valve assembly could readily be used to replace an existing head on an ORC engine with only minor modifications to the timing chain or belt: there is no practical revolution speed limit because there is no valve bounce; there is greater power availability because no springs or hydraulic tappets have to be compressed; there is a weight reduction: port sizes can readily be varied to suit high economy or high performance engines; the manufacturing and maintenance costs are lower.

Claims

1 . A rotary valve assemble for an internal combustion engine, said assembly comprising two substantially parallel shafts that are in use rotatably connected to the engine drive, each shaft having a plurality of recesses, one for each cylinder of the engine, each recess beIng spaced apart longitudinally and circumferentlally of its adjacent recess and being co-operable with an inlet or exhaust port, whereby rotation of the shaft periodically aligns each recess with its associated port to open the port and allow flow into or out of its associated cylinder.

2. A rotary valve assembly according to Claim 1, wherein the shafts are mounted in the engine head in which the inlet and exhaust ports are formed, wherein each recess is so shaped as to provide a continuous surface with its port when in the fully open position.

3. A rotary valve assembly according to Claim 2, wherein each recess has opposed sides extending transversely of the shaft and a base that is shaped to provide a continuation of the profile of its associated port when in the fully open position.

4. A A rotary valve assembly according to any one of Clams 4 to 3, wherein each recess is located between two associated longitudinally spaced-apart, annular grooves formed in the shaft, each groove providing a flow path for lubricating ol'.

5. A rotary valve assembly according to Claim 4, wherein the grooves are interconnected through a duct formed in the housing to an oil intermediate the grooves.

6. t rotary valve assembly according to Claim 5, wherein the inlet has a valve that is operated to feed oil through the duct to the grooves during rotation of the shaft but is inoperative when the recess is adjacent the inlet.

7. A rotary valve assembly according to Claim 6, whrein the duct has two arms extending longitudinally and circumferentially of the shaft from the inlet to the respective grooves.

8. A rotary valve assembly according to Claim 7, wherein the circumferential extent of each duct arm is about 160 -165 .

Q. A rotary valve assembly according to Claim 7 or 8 wherein the angle between the duct arms is about 60 -130 .

10. A rotary valve assembly for an internal combustion engine, constructed and arranged substantially as herein described with reference to the accompanying drawings.