WO2000036277A1

WO2000036277A1 - Engines

Info

Publication number: WO2000036277A1
Application number: PCT/GB1999/004120
Authority: WO
Inventors: Cyril Andrew Norton
Original assignee: Cyril Andrew Norton
Priority date: 1998-12-11
Filing date: 1999-12-10
Publication date: 2000-06-22
Also published as: AU1787900A; GB9827394D0

Abstract

An internal combustion engine is described in which a piston (12) is reciprocally movable in a piston cylinder (10). The engine comprises a body (8) defining the cylinder (10) for receiving the piston (12), a fluid passage (34, 36) in the body (8) to permit passage of fluid into or from the cylinder (10), and a substantially cylindrical valve member (42, 43) positioned in the body passage (34, 36), the valve member (42, 43) defining a passage (44) having first and second radially directed openings (46, 48) at opposite ends thereof, said first and second openings (46, 48) being axially offset and the valve member (42, 43) being rotatable in the body (8) to selectively open and close the body passage (34, 36).

Description

ENGINES

This invention relates to internal combustion engines, including spark ignition, compression ignition, two stroke and four stroke cycle engines, and in particular to such engines provided with rotary valves. The invention also related to other devices and machines which may be provided with rotary valves, such as pumps and compressors.

Existing four stroke internal combustion engines utilise poppet valves to control the intake and exhaust of air and exhaust gases into and from the engine cylinders. In recent years significant advances in valve design have taken place, leading to improved engine "breathing". However, a number of significant disadvantages remain, as discussed below.

The configuration of a poppet valve is such that intake air and exhaust gases must pass around the valve head, which places limitations on the improvements in engine breathing that are possible without reverting to complex multi-valve designs; many engines are now provided with four and even five valves per cylinder. Further, in order to withstand the loads which are experienced in use, poppet valves must be constructed from sophisticated and relatively expensive materials .

Poppet valves commonly rely on coil springs to close the valves, although hairpin springs and other valve closing means have been used. Particularly in high speed engines, the springs must provide a significant valve- closing force. Accordingly, opening the valves, against the springs, consumes a significant proportion of the engine output. There is a move towards smaller high speed multivalve engines, and in such engines up to 10% of engine output may be required for valve operation. Typically, however, parasitic losses of engine output due to valve operations are around 3%.

Maintenance and repair of poppet valves is difficult and cannot be achieved without substantive disassembly of the engine. In many applications, such as engines in military vehicles, the complexity of valve repairs may preclude repairs being carried out in the field, and may result in the abandonment and loss of otherwise serviceable vehicles. Further, in the event of a failure of a poppet valve, or the poppet valve operating mechanisms, for example breakage of a cam belt, the effect on an engine may be catastrophic, requiring extensive and expensive repairs.

It is among the objectives of the embodiments of the present invention to obviate or mitigate these difficulties .

According to one aspect of the present invention there is provided an internal combustion engine in which a piston is reciprocally movable in a piston cylinder, the engine comprising: a body defining a cylinder for receiving a piston; a fluid passage in the body to permit passage of fluid into or from the cylinder; and a substantially cylindrical valve member positioned in the body passage, the valve member defining a passage having first and second radially directed openings at opposite ends thereof, said first and second openings being axially offset and the valve member being rotatable in the body to selectively open and close the body passage.

The term cylinder is used herein when referring to the piston chamber of the engine, and is intended to encompass all chamber configurations which are not circular in cross- section, such as oval section chambers or other chambers such as those found in rotary engines and in the ankel configuration .

In comparison with an engine provided with poppet valves, an engine including one or more of such rotary valve members may be configured to provide better breathing, and driving these rotating valves is likely to consume significantly less power. It is also likely that such an engine will be easier to maintain and that the valve member may be constructed from less expensive materials than those utilised in the manufacture of poppet valves. By modifying one or more of the body passage and valve passage configuration, the interaction between the body passage and the valve passage openings, and the rotation of the valve member, it is also possible to modify the engine characteristics, for example the body passage may be opened or closed gradually or abruptly, and a triangular valve passage opening will open the body passage relatively gradually and close the passage relatively abruptly. In addition, the timing and shape of the passage or outlet opening in the rotating valve in combination with the shape of the port at the head of the combustion chamber, may be profiled in such a way as to influence the direction of the incoming flow to a specific region of the combustion chamber if so desired, thereby producing specific turbulence patterns to influence the combustion process .

Preferably, the valve passage openings are offset sufficiently to allow provision of a circumferential seal on the valve member between the openings . In one embodiment, the seal may be L-shaped, a leg of the seal being located in one of the valve member and the engine body, and a foot of the seal in sliding contact with the other of the valve member and body. Of course other seal arrangements may be used, incorporating different cross- sections and materials depending on the requirements dictated by the fuels and operating parameters of the engines . In the preferred embodiment of the invention, in which a complete engine cycle equates to a 360° rotation of an output member or shaft, this arrangement permits the valve member to be rotated at the same speed as the output member . Preferably also, the valve passage openings are oppositely directed, and the valve passage may be in the form of an S-bend.

Preferably also, at least two valve members are provided, one serving as an intake valve and the other serving as an exhaust valve, avoiding the high temperature gradients that would be experienced by use of a single valve member serving both purposes . The valve member may be incorporated, with advantage, in a conventional engine having a piston coupled via a piston rod to a rotating crankshaft, or may with greater advantage be incorporated in an engine as described in 098/59155, the disclosure of which is incorporated herein by reference, in which the piston movement may vary from the harmonic motion of a conventional piston engine. In particular, the lengths and duration of the piston strokes may be varied from simple harmonic motion, as may the rate of piston travel, as described below. In one embodiment, the piston may move further upwardly in the cylinder between the exhaust and induction strokes than between the compression and working strokes; the final volume at the end of the exhaust stroke may be relatively small, providing enhanced scavenging of the exhaust gases. Further, this volume may be significantly smaller than that achievable in engines using conventional poppet valves, as the volume need not accommodate a valve member extending into the cylinder.

In addition, the piston may move further downwardly between the intake and compression strokes than between the working and exhausting strokes, doing without the conventional latter portion of the working stroke, which contributes little to the engine output. To improve the volumetric efficiency of the engine, the induction stroke may be longer, in one or both of length and duration, than one or more of the other strokes. The induction stroke may also correspond to a greater degree of rotation of the rotating power output shaft than one or more of the compression, power and exhaust strokes. The compression stroke may be shorter in one or both of duration and length than one or more of the other strokes, and may also correspond to a lesser degree of rotation of the power shaft than one or more of the other strokes. Preferably, the piston moves at substantially constant or increasing velocity over a portion of the compression stroke, most preferably at least prior to ignition of a fuel\air charge in the cylinder. Where the duration of the compression stroke is relatively short, this may be translated to a relatively high rate of compression of the charge prior to ignition. This more rapid compression of the intake air or intake charge results in less heat being transmitted through the cylinder head and cylinder walls and, hence, the charge has more energy at the point of ignition. One advantage of this is that embodiments of the engine are, under specific conditions, capable of successfully burning kerosene and diesel fuels without having to employ substantial preheating arrangements, such as hot bulb components, and relatively high compression ratios used in conventional engines. Heavier fuels may, of course, require pre-heating in order to achieve the required dispersion into the fuel- air mixture .

With a view to simplifying construction and reducing costs, the engine may comprise a monoblock casting containing the working cylinder and combustion space with one or more valve ports machined or otherwise formed in the end or head of the casting. The rotary valve apparatus may simply be bolted or otherwise secured on the head of the casting .

Although reference is made above to an engine, those of skill in the art will also recognise that the disclosed valve configuration may also be utilised in compressors and other machines .

The invention also relates to an engine as described in W098\59155 provided with one or more rotary valves, which valves need not necessarily be of the form set out above .

These and other aspects of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figures la, lb, lc and Id are sectional schematic illustrations of an engine arrangement in accordance with an embodiment of the present invention;

Figure 2 is a sectional view of a valve of the engine of Figure la; Figure 3 is a sectional view corresponding to a view on line 3 - 3 of Figure 2 ;

Figure 4 is an enlarged view of a typical seal arrangement of the valve of Figure 2 ; and Figure 5 is a graph illustrating the cycle pattern of piston movement and rotary valve timing of the engine of Figure la .

Reference is first made to Figures la to Id of the drawings, which are sectional schematic illustrations of an engine arrangement in accordance with an embodiment of the present invention. The figures illustrate an engine block 8 defining a cylinder 10 and containing a piston 12 utilised to drive a rotating power shaft 14 in direction A. Drive is transferred from the piston 12 to the shaft 14 via a piston rod 16, a bell crank 18 and a power cam 20. The bell crank 18 is pivotally mounted to the engine block 8, at 22, and includes a roller 24 for engaging the surface of the power cam 20. In addition, the crank 18 carries a further roller 26 for engaging a follower cam 28 mounted on the power shaft 14 adjacent the power cam 20. The configuration of the crank 18 and the cams 20, 28 translate the reciprocal movement of the piston 12 in the cylinder 10 to rotational movement of the power shaft 14. However, the movement of the piston 12 is not harmonic, as is the case in conventional reciprocating piston engines, as will be described.

The lower part of the engine as described above is substantially similar to the arrangement described in my earlier International Patent Application W098\59155. However, the engine in accordance with the present invention includes different valving; whereas the engine illustrated in my earlier application included conventional poppet valves, the engine in accordance with the present invention includes rotary valves 30, 32, one of the valves 30 being shown in greater detail in Figures 2, 3 and 4 of the drawings. As may be seen from Figures la to Id, the valves 30, 32 are located in the cylinder head and are located in an intake passage 34 and an exhaust passage 36, respectively. In this particular example the intake passage 34 is provided with a fuel injector 38 and a spark plug 40 is located in the cylinder head between the passages 34, 36 (if running the engine as a diesel the illustrated spark plug position may be used as the primary fuel injection point) .

In the illustrated embodiment each valve 30, 32 includes a cylindrical valve member 42, 43, each member rotating on an axis parallel to the axis of the power shaft

14, and also, in the case of the four stroke engine, rotating at the same speed as the power shaft 14.

Reference will now be made in particular to Figures 2, 3 and 4 of the drawings, which illustrate the rotary valve 30, and which valve 30 will be described as exemplary of both valves 30, 32. The valve member 42 defines an S- shaped valve passage 44, with the valve passage inlet opening 46 being laterally offset from the valve passage outlet opening 48, and the openings 46, 48 being oppositely radially directed. This arrangement permits provision of a circumferential seal 50 between the openings 46, 48, the seal being shown in greater detail in Figure 4. The seal 50 comprises a raised circumferential rib 52 extending from the valve member 42 into a corresponding annular groove 54 in the engine body 8. Further, in this particular example, the rib 52 defines a stepped slot 56 which accommodates an L-shaped stainless steel sealing ring 58 of the Dykes type. A leg of the sealing ring 58 extends into the slot 56, with a foot of the ring 58 extending around the face of the groove 54. Externally of the sealing ring 58 the clearance between the rib 52 and groove 54 provides a gas\air passage 60. The valve member 42 is mounted to the engine body 8 via bearings 62, one of which is illustrated in Figure 2. Each bearing 62 includes a pair of silicone rubber bearing seals 64 and a pair of O-rings 66 provided on either side of a bearing sleeve 68. The bearing 62 is in communication with oil passages, such that lubricating oil may pass radially inwardly through the bearing 62.

The drawings only illustrate a single piston and cylinder, though of course the present invention may be utilised in a multi-cylinder engine of any appropriate configuration. Where two or more pistons are provided in line a plurality of valve members 42 may be coupled together, utilising a tongue and groove arrangement 70 as illustrated in Figure 2.

It will be noted by those of skill in the art that the provision of the rotary valves 30, 32 permits, if desired, provision of a monoblock casting to form the engine block

8, the casting defining the working cylinder and the combustion space, with the valve ports being machined in the end or head of the casting and the rotary valve arrangement simply secured onto the head of the monoblock casting, by bolts or other suitable fasteners.

Reference is now also made to Figure 5 of the drawings which is a graph illustrating the pattern of piston movement and rotary valve timing over one revolution of the engine power shaft 14. It will be noted that the stroke duration varies from stroke-to-stoke, as does the length of the stroke . Of course the stroke arrangement may be selected to suit the application of the engine, and we show by way of illustration a typical intake stroke arrangement corresponding to 29% of the duration of one revolution of the power shaft 14 and which, due to the shaping of the cams 20, 28, causes the piston to move over an extended stroke. From Figure la, which illustrates the piston 12 at the beginning of the intake stroke, it will be noted that there is only a very small unswept volume remaining within the cylinder 10; unlike a conventional engine, there is no need to accommodate the extended poppet of the exhaust valve . In this particular example the relatively long duration of the intake stroke and the relatively long travel of the piston 12 during the stroke improves the breathing capacity of the engine. Figure 5 also illustrates the intake valve opening, and it will be noted that in this example the valve 30 opens fairly abruptly, the opening initiating before the piston has reached the top of exhaust stroke, and the valve opening is maintained at a maximum for a period through the "middle" of the stroke, and then closes more gradually towards the end or bottom of the stroke .

In this example, the compression stroke equates to 21% of one revolution of the power shaft 14 and the profiles of the cams 20, 28 are selected such that the piston 16 moves upwardly through the stroke at a constant high velocity, producing a high rate of compression. The volume remaining in the cylinder 10 at the top of the compression stroke is greater than the volume remaining at the top of the exhaust stroke, and is selected to provide the appropriate compression ratio. As noted above, the relatively rapid compression of the intake air or intake charge results in less heat being transmitted through the cylinder head and cylinder walls and, hence, the charge has more energy at the point of ignition.

In this example, the working or power stroke equates to 22% of one revolution of the power shaft 14, and it will be noted that the piston movement is abbreviated, with the effect that the "power" volume of the cylinder is significantly lower than the volume swept by the piston during the intake stroke .

The exhaust stroke corresponds to 28% of one rotation of the power shaft 14, and over the exhaust stroke the piston moves upwardly within the cylinder 10 to leave only a very small volume, thus providing more effective scavenging than is possible with a conventional engine or an engine provided with poppet valves . From Figure 5 it will be noted that the opening of the exhaust valve 32 follows a similar pattern to the opening of the intake valve 30 during the intake stroke, that is a relatively abrupt opening, a period during which the valve flow area is a maximum, and a gradual closing of the valve.

It will be apparent to those of skill in the art that the engine configuration described above allows far greater control over the combustion process and the performance and characteristics of an internal combustion engine, by allowing variation in the stroke length and duration, rate of piston movement, and valve flow characteristics, so that all the variables may be tailored to achieve maximum efficiency of each stroke while designing the engine for a specific application, while operating to either the four or two stroke cycle.

It will also be apparent to those of skill in the art that the above-described embodiment is merely exemplary of the present invention, and that various modifications and improvements may be made thereto, without departing from the scope of the invention. For example, the rotary valves as described herein may be utilised in a conventional SI or CI internal combustion engine, operating on either two or four stroke cycles, or indeed in a compressor or pump. As noted above, on both Otto and Diesel cycle engines, the fuel injection points may be via the cylinder head, or may be via the charge inlet parts, and will of course be specified to suit the specific engine specification. Further, in other embodiments, the valve members may be rotatable around an axis perpendicular or otherwise inclined to the power shaft. Also, the seal arrangement illustrated above is only one of many that may be desired or required when operating with different fuels and power requirements; for example, different seal materials or cross sections may be preferred or required. In the above described embodiment the exhaust stroke is such that only a very small volume of exhaust gas remains in the cylinder. In other embodiments, different main cam profiles may be utilised to provide a predetermined volume of exhaust gas remaining in the cylinder, to mix with the incoming charge, and thus control exhaust gas recirculation (EGR) , as is currently used for controlling combustion to improve emission levels .

Claims

1. An internal combustion engine in which a piston is reciprocally movable in a piston cylinder, the engine comprising : a body defining a cylinder for receiving a piston; a fluid passage in the body to permit passage of fluid into or from the cylinder; and a substantially cylindrical valve member positioned in the body passage, the valve member defining a passage having first and second radially directed openings at opposite ends thereof, said first and second openings being axially offset and the valve member being rotatable in the body to selectively open and close the body passage.

2. The engine of claim 1, wherein the valve passage openings are offset sufficiently to allow provision of a circumferential seal on the valve member between the openings .

3. The engine of any of the preceding claims, in which a complete engine cycle equates to a 360° rotation of an engine output member and the valve member to be rotated at the same speed as the output member.

4. The engine of any of the preceding claims, wherein the valve passage openings are oppositely directed.

5. The engine of any of the preceding claims, wherein the valve passage is in the form of an S-bend.

6. The engine of any of the preceding claims, wherein at least two valve members are provided, at least one serving as an intake valve and at least one other serving as an exhaust valve . _*

7. The engine of any of the preceding claims, wherein the engine is a four stroke engine and the piston moves through induction, compression, power and exhaust strokes and dives a rotating output shaft.

8. The engine of claim 7, wherein the piston movement in the cylinder between the exhaust and induction strokes is selected to provide a predetermined volume of the end of the exhaust stroke such that a known volume of exhaust gas is left in the cylinder to mix with the incoming charge.

9. The engine of claim 7, wherein the piston moves further upwardly in the cylinder between the exhaust and induction strokes than between the compression and working strokes, the final volume at the end of the exhaust stroke being relatively small for enhanced scavenging of exhaust gases .

10. The engine of claim 7, 8 or 9, wherein the piston moves further downwardly between the intake and compression strokes than between the working and exhausting strokes.

11. The engine of any of claims 7, 8, 9 or 10, wherein the induction stroke is longer, in at least one of length and duration, than one or more of the other strokes.

12. The engine of any of claims 8 to 11, wherein the induction stroke corresponds to a greater degree of rotation of the rotating output shaft than one or more of the compression, power and exhaust strokes.

13. The engine of any of claims 8 to 12 , wherein the compression stroke is shorter in one at least one of duration and length than one or more of the other strokes.

14. The engine of any of claims 8 to 13, wherein the compression stroke corresponds to a lesser degree of rotation of the output shaft than one or more of the other strokes .

15. The engine of any of claims 8 to 14, wherein the piston moves at substantially constant or increasing velocity over a portion of the compression stroke.

16. The engine of claim 15, wherein the piston moves at substantially constant or increasing velocity over a portion of the compression stroke prior to ignition of a fuel\air charge in the cylinder.

17. The engine of any of claims 1 to 8 , wherein the engine comprises a piston coupled via a piston rod to a rotating crankshaft.

18. The engine of any of the preceding claims, wherein the engine comprises a monoblock casting containing the working cylinder and combustion space with one or more valve ports formed in the end or head of the casting and the rotary valve apparatus is secured on the head of the casting.

19. A fluid handling machine in which a piston is reciprocally movable in a piston cylinder, the machine comprising : a body defining a cylinder for receiving a piston; a fluid passage in the body to permit passage of fluid into or from the cylinder ; a substantially cylindrical valve member positioned in the body passage, the valve member defining a passage having first and second radially directed openings at opposite ends thereof, said first and second openings being axially offset and the valve member being rotatable in the body to selectively open and close the fluid passage.