Engine

Abstract

An engine comprising a cylinder housing (105) and an engine cylinder (110) at least partially housed within the housing (105). The cylinder (110) has a cylinder wall (118) extending about a cylinder axis (119), and a first cylinder end (120) provided at one axial end of the cylinder wall (118). A piston (115) is mounted for movement within the cylinder (110) in the direction of the cylinder axis (119). The piston (115), the cylinder wall (118) and the first cylinder end (120) define a cylinder chamber (140). The cylinder (110) is moveable in the direction of the cylinder axis (119) relative to the housing (105) to vary the volume of the cylinder chamber (140) for any given position of the piston (115) relative to the housing (105).

Description

FIELD OF THE INVENTION

This invention relates to engines and in particular to variable compression engines.

BACKGROUND OF THE INVENTION

Conventional internal combustion engines generally include at least one piston and engine cylinder combination mounted in an engine block. During operation, fuel and air is introduced into the cylinder and the fuel/air mix is compressed in the cylinder by movement of the piston within the cylinder before being ignited to burn the compressed fuel and produce energy to drive the piston. The piston continually moves (or reciprocates) between an intake position at the bottom of its stroke in the cylinder and a compression position at the top of its stroke in the cylinder. In an engine, the ratio of the volume of the cylinder when the piston is at the bottom of its stroke, to the volume of the cylinder when the piston is at the top of its stroke is known as the compression ratio. Generally, higher compression ratios are more fuel-efficient and produce more power than lower compression ratios. However, higher compression ratios are less suitable under high engine loads than lower ratios. Undesirably, a high quality (and therefore more expensive) fuel is generally required in engines having a high compression ratio to ensure that the fuel in the cylinder is not pre-ignited before the piston reaches the top of its stroke under high engine loads.

The above discussion of background art is included to explain the context of the present invention. It is not to be taken as an admission that any of the documents or other material referred to was published, known or part of the common general knowledge at the priority date of this specification.

SUMMARY OF THE INVENTION

It would be desirable to provide an alternative and/or improved engine when compared to existing engines.

It would also be desirable to provide an engine that potentially provides at least some of the advantages of both high compression ratio engines and low compression ratio engines.

According to a first aspect, the present invention provides an engine comprising:

a cylinder housing;

an engine cylinder at least partially housed within the housing, the cylinder having a cylinder wall extending about a cylinder axis, and a first cylinder end provided at one axial end of the cylinder wall;

a piston mounted for movement within the cylinder in the direction of the cylinder axis;

the piston, the cylinder wall and the first cylinder end defining a cylinder chamber; and

the cylinder being moveable in the direction of the cylinder axis relative to the housing to vary the volume of the cylinder chamber for any given position of the piston relative to the housing.

Preferably, the cylinder is movable between a first position relative to the housing where the cylinder has a first ratio between a maximum and minimum volume of the cylinder chamber during a predetermined movement of the piston within the cylinder and a second position where the cylinder has a second ratio between the maximum and minimum volumes of the cylinder chamber during the same movement of the piston.

The engine may further comprise control means configured to control the position of the cylinder along the cylinder axis relative to the housing.

Preferably, the control means comprises a hydraulic circuit for moving the cylinder relative to the housing.

In one form, the hydraulic circuit further comprises a control valve arranged to selectively prevent hydraulic fluid flow through the circuit to prevent movement of the cylinder along the cylinder axis relative to the housing.

The control valve may be configured to selectively allow flow of the hydraulic fluid through the hydraulic circuit to move the cylinder along the cylinder axis relative to the housing to thereby increase or decrease the effective volume of the cylinder chamber, as desired, for any given position of the piston relative to the housing.

The engine of the present invention has so far been described in the context of having one piston/cylinder combination. However, it is to be appreciated that the engine may comprise a plurality of cylinder/piston combinations mounted in the housing, with the position of each cylinder relative to the housing, being controlled by the hydraulic circuit.

The engine may further comprise: a first cam shaft; a crank shaft; coupling means arranged to couple rotation of the crank shaft to the first cam shaft; and a first actuating means configured to actuate the coupling means to selectively retard and advance the rotation of the first cam shaft relative to rotation of the crank shaft.

Preferably, the control means are configured to move each cylinder relative to the housing on activation of the first actuating means.

Preferably, the coupling means comprises a timing belt.

Preferably, the first actuating means comprises at least one solenoid.

The engine may further comprise: a second cam shaft; and a second actuating means, wherein the coupling means is arranged to couple rotation of the crank shaft to the second cam shaft, and the second actuating means is configured to actuate the coupling means to selectively retard and advance rotation of the second cam shaft relative to the first cam shaft.

In a preferred form, the engine further comprises: a third actuating means, wherein the coupling means is arranged to couple rotation of the crank shaft to the second cam shaft, and the third actuating means is configured to actuate the coupling means to selectively retard and advance rotation of the second cam shaft relative to rotation of the crank shaft.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings. It is to be understood that the particularity of the drawings and embodiments does not supersede the generality of the preceding description of the invention.

DESCRIPTION OF THE DRAWINGS

In the drawings, where the same reference numerals identify the same or like components:

FIG. 1 a is a cross-sectional view of an engine having a high compression ratio according to an embodiment of the invention.

FIG. 1 b is a cross-sectional view of the engine block of FIG. 1a having a low compression ratio.

FIGS. 2 a and 2b are cross-sectional views of an engine according to another embodiment of the invention.

FIG. 3 is a schematic, cross-sectional view of a timing control arrangement according to yet another embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

Referring to FIGS. 1a and 1b of the drawings, there is generally shown an engine block 100 as part of an overall variable compression engine (not illustrated in full). Broadly, the engine block 100 comprises a cylinder housing 105, an engine cylinder 110 partially housed within the cylinder housing 105, and a piston 115 mounted inside the engine cylinder 110. The piston 115 comprises a piston head 125. The engine cylinder 110 comprises a cylinder wall 118 extending about a cylinder axis 119, and a first cylinder end (or cylinder head) 120 provided at one axial end of the cylinder wall 118. The first cylinder end 120 of the engine cylinder 110 comprises a seal 130 extending about the periphery of the cylinder end 120. The seal 130 comprises valves 135 for introducing fuel into the engine cylinder 110 and expelling exhaust emissions from the engine cylinder 110.

A cylinder chamber 140 is defined in the region bounded by the cylinder wall 118, the cylinder end 120 and the piston head 125. The volume of the cylinder chamber 140 changes as the piston 115 moves between the top of its stroke and the bottom of its stroke, as per normal internal combustion engine operation.

The cylinder housing 105 is axially displaceable relative to the cylinder housing 105 by the distance defined approximately between points A and B to vary the operating volume of the cylinder chamber 140 for any given position of the piston 115 relative to the housing 105. This arrangement advantageously provides for the possibility of further varying the volume of the cylinder chamber 140 such that it may be operated as a high compression engine or a low compression engine.

FIG. 1 a illustrates the engine block 100 arranged for a high compression ratio. In this arrangement, the flange portion 150 of the engine cylinder 110 is stopped short of abutting the recess 145 by virtue of a sufficient volume of hydraulic fluid provided in the recess 145. The volume of hydraulic fluid supplied to the recess 145 may be monitored by an engine computer. The arrangement by which fluid is supplied to the recess 145 has been omitted for clarity. When compared to the configuration illustrated in FIG. 1b, the arrangement of FIG. 1a results in a reduction in volume of the cylinder chamber 140 and a higher compression of the fuel in the cylinder chamber 140 when the piston 115 is at the top of its stroke.

FIG. 1 b illustrates the engine block 100 of FIG. 1a when arranged for a low compression ratio. The flange portion 150 of the engine cylinder 110 is distanced from the recess 145 (so that there is a distance between point A and point B). This results in an increase in volume of the cylinder chamber 140 and a lower compression of the fuel in the cylinder chamber 140 when the piston 115 is at the top of its stroke.

The engine cylinder 110 may further comprise control means (not shown) in the form of a hydraulic circuit which introduces an incompressible fluid into the gap formed by the recess 145 and flange 150 to raise or lower the engine cylinder 110 relative to the housing 105 to vary the volume of the cylinder chamber 140 for any given position of the piston 115.

FIGS. 2 a and 2b illustrate an engine block 200 described with reference to the engine block 100 of FIGS. 1a and 1b, but comprising four cylinder housings 205, 215, 225, 235 and four engine cylinders 210, 220, 230, 240, which are linked together in series as part of a four cylinder engine. It will be appreciated that, unlike the arrangement illustrated in FIGS. 1a and 1b, the cylinders 210, 220, 230, 240 comprise inline valves 255 for introducing fuel into the cylinders and expelling exhaust emissions from the cylinders. It will also be appreciated that any number of cylinders could be linked and thus any type of engine could be arranged in this way (such as a 2, 6 or 8 cylinder engine). A hydraulic circuit 250 is shown schematically linking the engine cylinders 210, 220, 230, 240 so that a change in pressure by the hydraulic circuit 250 results in a change of compression ratio in the four engine cylinders 210, 220, 230, 240 due to the cylinders being linked in series. In FIG. 2a, each of the cylinders 210, 220, 230, 240 is operating under high compression; while in FIG. 2b each of the cylinders 210, 220, 230, 240 is operating under low compression. A change in pressure in the hydraulic circuit 250 results in the engine being reconfigured from a low compression engine (as in FIG. 2b) to a high compression engine (as in FIG. 2a) or vice versa. The pressure in the hydraulic circuit 250 can also be increased or reduced so that the engine cylinders 210, 220, 230, 240 can be at any compression between the previously defined high and low compressions.

In operation, and described in the context of the four cylinder engine shown in FIGS. 2a and 2b, the engine operates in the normal manner of a four cylinder engine namely, engine cylinders 210 and 230 having their respective pistons at the top of their stroke and engine cylinders 220 and 240 having their respective pistons at the bottom of their stroke and being driven by a crank shaft (not shown).

FIG. 3 illustrates an engine block 100 described with reference to FIGS. 1a and 1b, but further adapted to change the valve timing of the engine. The engine comprises a first cam shaft 330, a second cam shaft 340, a crank shaft 350 and first and second valves 360, 370 attached to first and second cam shafts 330, 340. The engine block further comprises coupling means 380, which is arranged to couple rotation of the crank shaft 340 to the first and second cam shaft 330, 340 and in turn first and second valves 360, 370. The engine block 100 further comprises first actuating means 300, second actuating means 310 and third actuating means 320 to act on the coupling means 380 to advance or retard the timing of the engine.

The coupling means 380 may be a timing belt or a timing chain. While two separate cam shafts are described, it will be appreciated that a single cam shaft could be used.

The first actuating means 300 is configured to actuate the coupling means 380 between the first cam shaft 330 and the crank shaft 350 to selectively retard and advance the rotation of the first cam shaft 330 relative to rotation of the crank shaft 350. The second actuating means 310 is configured to actuate the coupling means 380 to selectively retard and advance rotation of the second cam shaft 340 relative to the first cam shaft 330. Finally, the third actuating means 320 is configured to actuate the coupling means 380 to selectively retard and advance rotation of the second cam shaft 340 relative to rotation of the crank shaft 350.

Each of the first actuating means 300, second actuating means 310 and third actuating means 320 may be a solenoid which, upon receipt of an input signal from an engine computer (not shown), actuates the coupling means 380 either:

• • (a) directly to shorten (or lengthen) the effective length of the coupling means 380; or
  • (b) indirectly by the solenoid actuating the coupling means 380 via a roller in which the resistance of the roller is used to advance or retard the movement of a portion of the coupling means 380.

The first actuating means 300, second actuating means 310 and third actuating means 320 may be controlled by an engine computer (not shown) so that the actuating means work together to control the timing of the engine. For example, the engine computer sends a signal to the first actuator 300 to actuate coupling means 380 between the first cam shaft 330 and the crank shaft 350 to advance both the first and second valves 360, 370. The engine computer also sends a signal to the second actuator 310 to actuate the coupling means 380 to selectively retard and advance rotation of the second cam shaft 340 relative to the first cam shaft 330 which in turn allows variation of the opening of first and second values 360, 370. At the same time as sending signals to the first actuator 300 and second actuator 310, the engine computer sends a signal to the third actuator 320 to tension the coupling means 380 to maintain the required timing.

Ideally, the engine block 200 of FIGS. 2a and 2b is used in conjunction with the valve timing arrangement of FIG. 3 to control the compression ratio of the engine together with the timing of the engine. In operation, upon receipt of a signal from a suitable sensor in the vehicle (such as a throttle position sensor) the engine computer calculates the most suitable compression ratio for the current conditions and sends a signal to the hydraulic circuit 250 which raises or lowers the engine cylinders 210, 220, 230, 240 by feeding an incompressible fluid (such as oil) into the hydraulic circuit 250. Each of the engine cylinders 210, 220, 230, 240 is, in practical terms, locked to the other cylinders by the hydraulic circuit 250, such that as one engine cylinder is raised or lowered the remaining engine cylinders are likewise raised or lowered. Once the hydraulic circuit has the cylinders in position in accordance with the signal sent by the engine computer, the hydraulic circuit 250 is sealed by a control valve (not shown). The position of the cylinders is then monitored by the engine computer.

Once the compression ratio of the engine has been set by the engine computer to a suitable compression ratio based on an input signal (such as the throttle position sensor) the timing of the engine is then modified by the engine computer based on the new compression ratio of the engine so that the performance of the engine is maximised. The engine computer receives signals from the first, second and third actuators 300, 310 and 320 of FIG. 3, which further include sensors (not shown) to locate the position of the coupling means 380 and thus identify the position of the actuator to the engine computer. Based on this information the engine computer instructs the actuators to advance or retard the timing of the engine to suit the new compression ratio. The engine computer then makes adjustments to the compression ratio and timing of the engine based on information from sensors, or on load variations in the engine. For example, as the engine cylinders 210, 220, 230, 240 of FIG. 2 are raised and lowered the engine computer instructs the first and third actuators 300, 320 shown in FIG. 3 to either actuate or not actuate the coupling means 380 to maintain timing of the engine. The net result of the engine computer controlling both the engine compression ratio and the engine timing is that the timing of the engine is maintained while the compression ratio changes or alternatively, the engine compression ratio can be changed during or after a change in the timing of the engine. In a further alternative, the timing of the engine may be controlled independently of the compression ratio.

The engine computer may also make corrections if the timing or the compression ratio moves out of tolerance.

It will be appreciated that various alterations and/or additions in the particular construction and arrangement of parts previously described may be made without departing from the spirit or ambit of the present invention.

Claims

1. An engine comprising: a cylinder housing; an engine cylinder at least partially housed within the housing; the cylinder having a cylinder wall extending about a cylinder axis, and a first cylinder end provided at one axial end of the cylinder wall; a piston mounted for movement within the cylinder in the direction of the cylinder axis; the piston, the cylinder wall and the first cylinder end defining a cylinder chamber; the cylinder being moveable in the direction of the cylinder axis relative to the housing to vary the volume of the cylinder chamber for any given position of the piston relative to the housing; control means configured to control the position of the cylinder along the cylinder axis; a first cam shaft; a crank shaft; coupling means arranged to couple rotation of the crank shaft to the first cam shaft; and a first actuating means configured to actuate the coupling means to selectively retard and advance the rotation of the first cam shaft relative to rotation of the crank shaft.

2. An engine comprising: a cylinder housing; an engine cylinder at least partially housed within the housing; the cylinder having a cylinder wall extending about a cylinder axis, and a first cylinder end provided at one axial end of the cylinder wall; a piston mounted for movement within the cylinder in the direction of the cylinder axis; the piston, the cylinder wall and the first cylinder end defining a cylinder chamber; and the cylinder being moveable in the direction of the cylinder axis relative to the housing to vary the volume of the cylinder chamber for any given position of the piston relative to the housing.

3. An engine according to claim 2, wherein the cylinder is movable between a first position relative to the housing where the cylinder has a first ratio between a maximum volume and a minimum volume of the cylinder chamber during a predetermined movement of the piston within the cylinder; and a second position where the cylinder has a second ratio between the maximum and minimum volumes of the cylinder chamber during the same movement of the piston.

4. An engine according to claim 2 or 3, wherein the engine comprises control means configured to control the position of the cylinder along the cylinder axis relative to the housing.

5. An engine according to claim 4, wherein the control means comprises a hydraulic circuit for moving the cylinder relative to the housing.

6. An engine according to claim 5, wherein the hydraulic circuit comprises a control valve arranged to selectively prevent hydraulic fluid flow through the circuit to prevent movement of the cylinder along the cylinder axis relative to the housing.

7. An engine according to claim 6, wherein the control valve is configured to selectively allow flow of the hydraulic fluid through the hydraulic circuit to move the cylinder along the cylinder axis relative to the housing to thereby increase or decrease the effective volume of the cylinder chamber, as desired, for any given position of the piston relative to the housing.

8. An engine according to claim 7, comprising a plurality of cylinder/piston combinations mounted in the housing, with the position of each cylinder relative to the housing, being controlled by the hydraulic circuit.

9. An engine according to claim 4 comprising: a first cam shaft; a crank shaft; coupling means arranged to couple rotation of the crank shaft to the first cam shaft; and a first actuating means configured to actuate the coupling means to selectively retard and advance the rotation of the first cam shaft relative to rotation of the crank shaft.

10. An engine according to claim 9, wherein the control means are configured to move each cylinder relative to the housing on activation of the first actuating means.

11. An engine according to claim 9, wherein the coupling means comprises a timing belt.

12. An engine according to claim 9, wherein the first actuating means comprises at least one solenoid.

13. An engine according to claim 9, further comprising: a second cam shaft; and a second actuating means, wherein the coupling means is arranged to couple rotation of the crank shaft to the second cam shaft, and the second actuating means is configured to actuate the coupling means to selectively retard and advance rotation of the second cam shaft relative to the first cam shaft.

14. An engine according to claim 13, further comprising: a third actuating means, wherein the coupling means is arranged to couple rotation of the crank shaft to the second cam shaft, and the third actuating means is configured to actuate the coupling means to selectively retard and advance rotation of the second cam shaft relative to rotation of the crank shaft.

15. An engine, comprising: a first cam shaft; a crank shaft; coupling means arranged to couple rotation of the crank shaft to the first cam shaft; and a first actuating means configured to actuate the coupling means to selectively retard and advance the rotation of the first cam shaft relative to rotation of the crank shaft.

16. An engine according to claim 15, wherein the coupling means comprises a timing belt.

17. An engine according to claim 15, wherein the first actuating means comprises at least one solenoid.

18. An engine according to claim 15, further comprising: a second cam shaft; and a second actuating means, wherein the coupling means is arranged to couple rotation of the crank shaft to the second cam shaft, and the second actuating means is configured to actuate the coupling means to selectively retard and advance rotation of the second cam shaft relative to the first cam shaft.

19. An engine according to claim 18, further comprising: a third actuating means, wherein the coupling means is arranged to couple rotation of the crank shaft to the second cam shaft, and the third actuating means is configured to actuate the coupling means to selectively retard and advance rotation of the second cam shaft relative to rotation of the crank shaft.