TECHNICAL FIELD

The invention relates to improvements in an internal combustion engine. In particular, the present invention relates to an improvement in the connecting rod and crankshaft mechanism of an internal combustion engine which may allow for greater efficiency and increased torque.

BACKGROUND ART

A standard internal combustion engine is manufactured with a constant compression ratio. This means that when an engine is running under varying load conditions the engine cylinder end space volume that the piston compresses the mixture of air and fuel into and this end volume remains unchanged.

By way of contrast in a variable compression ratio engine (VCR engine), cylinder end space is altered in volume while the engine is running to produce a variable compression ratio. Such a variable compression ratio can increase fuel efficiency while under varying engine loads and speeds in response to varying driving demands.

A higher load or a full throttle position in an engine requires a lower compression ratio so that the engine can manage the large amounts of air and fuel being compressed and burnt. As the load on the engine is decreased and there are smaller amounts of air and fuel being compressed and burned and the compression ratio needs to become higher.

A typical VCR engine will vary the compression ratio from 8 -1 to 16 -1. Some attempts have been made to make even a larger cylinder end volume change.

A standard petrol engine has a limit on the maximum pressure encountered during the compression stroke, after which the fuel/air mixture detonates rather than burns. Normally if higher power outputs are required from an engine, more fuel must be burnt and therefore more air is needed. To achieve this, it is a common practice to use turbochargers or superchargers to force more air into an engine. But this would also result in detonation of the fuel/air mixture unless the compression ratio was decreased. The ability of a VCR engine to vary the pressure in the cylinder according to the amount of air and fuel being used by the engine provides the advantage of greater thermal efficiency without the dangers of the engine becoming damaged

However a disadvantage with known VCR engines is that under light load, the engine can lack power and torque and can become more inefficient.

An example of a known VCR engine is that disclosed in US Pat. Ser. No: 7,021 ,254. This VCR engine includes a control actuator and a connecting rod is divided into at least two portions. A control rod is operatively connected to the join of the connecting rod portions.

A piston is configured to selectively move in accordance with displacement of the position of the control rod by altering the angularity of the connecting rod portions.

The disadvantage of the engine arrangement disclosed in this document is that the loading and control of the connecting rods require a constant adjustment to the angles of the connecting rods. As the piston rises and falls in the cylinder the angles alter according to the pushing and pulling of the control rod that is connected directly to the juncture of the connecting rods. There is very little rigidity to this connecting rods arrangement where the cylinder pressure on top of the piston has to be transferred to the crankshaft by means of the three rods joining at the same juncture.

Consequently large amounts of energy are transferred along the control rod back to the hydraulic chamber arrangement and it is difficult to manage this energy transfer.

It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.

All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinence of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.

It is acknowledged that the term 'comprise' may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term 'comprise' shall have an inclusive meaning - i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non- specified components or elements. This rationale will also be used when the term 'comprised' or 'comprising' is used in relation to one or more steps in a method or process.

Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.

DISCLOSURE OF THE INVENTION

In a first preferred embodiment of the present invention there is provided an internal combustion engine comprising:

• a piston configured to move within a piston cylinder throughout a stroke cycle;

• a rotatable crankshaft; and

• a connecting rod assembly comprising:

o a piston connecting rod pivotally connected at one end to the piston at a piston pin; and

o a crankshaft connecting rod pivotally connected at one end to the piston connecting rod at a connecting rod joint and pivotally connected at another end to the crankshaft at a crankshaft offset pivot point wherein the internal combustion engine also comprises a slipper plate positioned between the crankshaft and the piston and configured to direct movement of the connecting rod joint as the connecting rod assembly is moved via rotation of the crankshaft and wherein the position of the slipper plate can be pivoted during use of the internal combustion engine about pivot point to provide for alteration of the movement of the connecting rod assembly to alter the stroke of the piston within the piston cylinder by altering the length of the connecting rod assembly between the piston pin and the crankshaft offset; and wherein the slipper plate pivot point is positioned substantially inline between the connecting rod joint and the crankshaft offset pivot point.

Preferably, the slipper plate is configured to move the connecting rod joint as the connecting rod assembly is moved via rotation of the crankshaft to form a working crank angle between the piston connecting rod and the crankshaft connecting rod when the piston is at its top dead centre (TDC) position and at its position of maximum displacement within the piston cylinder during a piston stroke cycle to slow the travel of the piston through the TDC position and the position of maximum displacement during the piston stroke for a predetermined angle of rotation of the crankshaft.

Preferably, the slipper plate is configured to direct movement of the connecting rod joint via a groove in the slipper plate in which the conrod joint travels. More preferably, the groove is straight.

Preferably, the piston stroke is increased in length by between 1 to 5 %. More preferably, the piston stroke is increased in length by 4 %.

Preferably, the internal combustion engine also comprises at least one backstop configured to limit movement of the connecting rod assembly out of the plane of the slipper plate.

BRIEF DESCRIPTION OF DRAWINGS

Further aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying figures in which:

Figure 1 shows a diagrammatic representation of a preferred embodiment of the present invention in the form of a variable compression ratio internal combustion engine with crankshaft at TDC (0° of rotation);

Figure 2 shows the same preferred embodiment of Figure 1 , but with the crankshaft rotated past its TDC position in a 90° direction of rotation;

Figure 3 shows the same preferred embodiment of Figure 1 , but with the crankshaft rotated past its TDC position in an 180° direction of rotation;

Figure 4 shows the same preferred embodiment of Figure 1 , but with the crankshaft rotated past its TDC position in a 270° direction of rotation;

Figure 5 shows the same preferred embodiment of Figure 1 , but with the crankshaft rotated to its TDC (0° of rotation) position;

Figure 6 shows the same preferred embodiment of Figure 1 , but with the slipper plate rotated to configure the engine to its high output state;

Figure 7 shows the same preferred embodiment of Figure 6, but with the crankshaft rotated past its TDC position in a 90° direction of rotation;

Figure 8 shows the same preferred embodiment of Figure 6, but the crankshaft rotated past its TDC position in a 180° direction of rotation;

Figure 9 shows the same preferred embodiment of Figure 6, but with the crankshaft rotated past its TDC position in a 270° direction of rotation; and

Figure 10 shows the same preferred embodiment of Figure 6, but with the crankshaft rotated to its TDC (0° of rotation) position.

SUMMARY OF THE INVENTION

The present invention has solved the problem of better managing the angle of connecting rod portions whilst they are rising and falling from the motion of the crankshaft rotation by eliminating the need for a direct connection to connecting rod portions such as a control rod actively pushing or pulling the connecting rod portions.

The preferred embodiment of the present invention instead utilizes a component called a slipper plate which better manages the angle of the connecting rods. Manufactured of metal, the slipper plate is positioned between the crankshaft and the piston and manages the angularity of the connecting rod portions.

When the engine is under a light load, the slipper plate is in a vertical position and held tight against a backstop so there is little effort required to hold it in the vertical position.

The slipper plate has a vertical groove where the center of the slipper plate groove is parallel or inline from the crankshaft center to the piston center. At the joint of the two connecting rods a pin and bearing arrangement joins the two connecting rods together and is inserted into the slipper plate vertical groove. The pin is long enough that the end is inserted into a slipper plate groove; the groove keeps the connecting rods join in line with the groove and directs movement of the connecting rods via the join when the slipper plate is moved. It is the slipper plate being held in a motionless state that controls the angularity of the two connecting rods as the crankshaft motion causes the connecting rods to rise and fall. In this way the connecting rods don't need to be pushed or pulled into position via a control rod as previously known.

When the slipper plate is in this vertical alignment the highest piston height is achieved. No work needs to be done by any external arrangement other than to hold the slipper plate in the vertical alignment. The frictional losses are very light when the slipper plate is held in this vertical position. The slipper plate can be held in the vertical position by any mechanical device that can keep the slipper plate motionless while the engine is running in a light load and low speed configuration. When the slipper plate is rotated to the secondary backstop having being moved to that position, no further adjustments need to be made to the slipper plate or the connecting rod portions. The angularities of the two connecting rod portions at their join are controlled by the slipper plate being held against the secondary backstop.

When the slipper plate is rotated to the secondary backstop the connecting rods form a slight angle when the crankshaft reaches its TDC position. This angle causes the piston to drop in height and increase the end volume of the cylinder head arrangement. Also as there is no need for some mechanism to control the angularity and to keep making adjustments to the connecting rods while they are travelling to the TDC or the bottom dead center (BDC) positions.

All that is required is that the slipper plate be held in the angled position against the secondary backstop, and it is the slipper plate design that causes the variable compression ratio in the piston cylinder to occur in the engine.

The present invention can also achieve an advanced connecting rod lever angle past crankshaft top dead center (TDC) position with the piston at its TDC position in relation to the piston cylinder. In addition the connecting rod is longer in length than a conventional connecting rod which is commonly set at half the length of the stroke. These elements improve torque over an equivalent standard engine. In addition a longer dwell time of the piston at its TDC position as a result of this configuration of the connecting rod and crankshaft improves combustion efficiency of the engine over an equivalent standard engine.

In a conventional internal combustion engine using a piston, crankshaft, and connecting rod assembly, the rotation of the crankshaft causes displacement of the piston or an increase in piston cylinder volume from the crankshaft TDC position during its rotation cycle. This increase in cylinder volume causes a loss of pressure in the piston cylinder and the crankshaft is not able to be easily rotated to get work done from the cylinder pressure as there is no leverage on the connecting rod to work with when the piston is at TDC or (i.e. 0°). Furthermore, there is only a very small connecting rod lever available for getting work done for the next 30° of crankshaft rotation. As the crankshaft rotates and the connecting rod lever angle increases to get more work done, there is a continuous drop in the cylinder pressure throughout a further 60° of rotation which results in minimal pressure remaining for the crankshaft to get work done.

Some engine designs produce a dwell period at piston TDC position by offsetting the crankshaft centre from the centerline of the piston cylinder and have used both short and long connecting rods with this arrangement. However, this arrangement also does not produce a true piston dwell period. The moment the crankshaft is rotated 1 degree the piston moves and displaces volume albeit a small amount.

Also, having a longer connecting rod will allow displacement to be slowed down by a very small amount, but the connection of the connecting rod to the crankshaft attachment centre is delayed until the pressure has dropped in the piston cylinder. Therefore, the longer connecting rod will not stop the displacement of the piston from its TDC position in a conventional engine arrangement.

The VCR engine of the present invention prevents any change in cylinder volume occurring while the engine is building peak pressure either during the combustion period when peak cylinder pressure is building or when peak pressure has occurred.

DETAILED DESCRIPTION INCLUDING BEST MODES

In a preferred form of the invention, an internal combustion engine is generally indicated by arrow 1. Fig 1 shows a single piston cylinder 100 and piston 101 arrangement with a crankshaft 110 connected to the piston 101 with a first connecting rod portion 102 and second connecting rod portion 103. The piston 101 is at the top of the cylinder 100 its a top dead center (TDC) position and a slipper plate 104 is in a vertical position resting against the backstop 108.

The first connecting rod portion 102 and the second connecting rod portion 103 are held in vertical alignment by a connecting rod pin 111 and bearing arrangement 107 inserted into a groove 105 of the slipper plate 104.

A secondary backstop 109 is used to limit movement of the slipper plate 104 when not in this vertical alignment. The slipper plate 104 can be rotated from an axis pin or join 106. The position of the slipper plate 104 shown in Fig 1 shows a light load and low rpm engine setting. This arrangement results in a piston stroke of 85.25 mm, which is 3.25mm further in height than a non- VCR engine with the same crank shaft and connecting rod arrangement. This feature combined with a slowing of the piston speed at its TDC position provides for a more efficient combustion of the fuel/air mixture in the piston cylinder 100.

Fig 2 shows the engine crankshaft 110 turned clockwise by 90° and the piston 101 has travelled part way down the cylinder 100. The slipper plate 104 remains in the vertical position resting against the backstop 108. The angularity of the connecting rod portions 102 and 103 are managed by the connecting rod pin 111 and bearing assembly 107 being inserted and retained in the slipper groove 105. The slipper plate 104 can be paired so there is a slipper plate 104 on both sides of the connecting rod portions

102 and 103. This improves the rigidity of the arrangement where the connecting rod pin 111 and bearing arrangement 107 is inserted into both the slipper groove 105 of front and back slipper plates 104.

Fig 3 shows the bottom dead center (BDC) position of the crankshaft 110 when it has rotated 180° from its TDC position. The piston 101 has travelled to the bottom of the cylinder 100. The slipper plate 104 remains unmoved and is resting against the backstop 108.

Fig 4 shows the position of the piston 101 raised towards the top of the cylinder 100 when the crankshaft 110 has turned close to 270° from its TDC position. While the slipper plate 104 remains vertical the first connecting rod portion 102 also remains vertical producing the furthest distance of travel for the piston 101 in the cylinder 100.

Fig 5 shows the crankshaft 110 at its TDC position and the piston 101 at the top of the cylinder 100. The connecting rod portions 102 and 103 are aligned vertically which keeps the piston 101 at the highest point in the cylinder 100. The slipper plate 104 is kept motionless in vertical alignment and resting against the backstop 108 to produce a high compression ratio suitable for an engine running at a light load and low rpm speeds.

Fig 6 shows the engine 1 configuration for a heavy load and higher rpm engine setting. The slipper plate 104 has been rotated clockwise from the slipper plate axis 106 and is now resting against the secondary backstop 109. The backstop 108 is not being used for the heavy load configuration. The crankshaft 110 is at its TDC position, and the piston 101 is at its highest point of travel in the cylinder 100. The stroke of the piston is 82mm which is a drop in stroke length of 3.25mm from the light engine load and lower rpm setting shown in Figs 1 to 5. A stroke of this length with a standard engine arrangement would result in a 41mm connecting rod offset. However, the arrangement of the crankshaft 1 10 and connecting rod portions 102 and 103 of the present invention produces a larger offset of 42.63mm. The connecting rods 102 and 103 are angled with respect to one another to provide a better working angle on the piston 101 and improve torque of the engine 1.

With the slipper plate 104 now motionless and the connecting rod joining pin 111 and bearing arrangement 107 being inserted into the slipper groove 105, the connecting rod portions 102 and

103 form an angularity that causes the piston 101 to drop in height in the cylinder 100. The drop in height of the piston 101 lowers the compression in the cylinder 100 when the piston has finished the compression phase.

Fig 7 shows the crankshaft 110 rotated clockwise 90°. The slipper plate 104 stays motionless in its fixed position rotated to the right in relation to the slipper plate axis point 106 and rest against the secondary backstop 109. The slipper groove 105 manages the angularity of the connecting rod portions 102 and 103 by the connecting rod pin 11 1 and bearing arrangement 107 being held in the slipper groove 105.

The slipper plate 104 being rotated to the right allows the connecting rod portions 102 and 103 to become better aligned to transfer the energy from the piston 101 to the crankshaft 110 during this high load demand stage of the engine 1. With the crankshaft 110 at 90° past its TDC position, the connecting rod portions 102 and 103 are straight.

Fig 8 shows the crankshaft 110 at its BDC position. The crankshaft 110 has turned clockwise 180° from the TDC position. The piston 101 is at the bottom of the stroke in the cylinder 100. The connecting rod portions 102 and 103 are still vertically aligned during this power phase. This vertical alignment is due to the slipper plate 104 being rotated right and held against the secondary backstop 109 and the connecting rods pin 111 and bearing arrangement 107 being held captive in the slipper plate groove 105.

Fig 9 shows the piston 101 has travelled up the cylinder 100 due to the rotation of the crankshaft 1 10. The connecting rod portions 102 and 103 are now angled and this angularity is managed by the connecting rod pin 111 and bearing arrangement 107 being held captive in the slider groove 105. The angularity of the connecting rod portions 102 and 103 is important as this has affected the piston speed and height. The piston 101 will stop rising in the cylinder 100 due to the working angle of the connecting rod portions 102 and 103 and will form a larger end volume which results in a lower compression ratio.

The slider plate 104 will remain in the angled position against the secondary backstop 109 for as long as the engine 1 is under a heavy load. The connecting rod portions 102 and 103 form their working angles by the slider plate 104 being held in the desired position and the connecting rod pin 111 and bearing arrangement 107 being held captive in the slider groove 105.

Fig 10 shows the piston 101 at its position of furthest travel in the cylinder 100 due to the crankshaft being at TDC its position. It is clear that the piston 101 has stopped short of reaching the top of the cylinder 100 due to the angularity of the connecting rod portions 102 and 103. The connecting rod angle has shortened the distance from the top of the piston 101 to the center axis of the crankshaft 110 by a considerable distance.

This angling of the connecting rod portions 102 and 103 provide for a low compression ratio due to the slider 104 being held motionless and the connecting rod joining pin 1 11 and bearing arrangement 107 being held captive in the slider groove 05.

The slipper plate 104 also has the ability to rotate by a number of degrees either to the left or to the right from an axis point that is on a vertical line from the crankshaft center to the piston wristpin center 112 (shown in Fig 10). A person skilled in the art will appreciate that a user can alter the angle or position of the slipper plate 104 to alter the movement of the connecting rod portions 102 and 103.

When a heavy demand is put on the engine 1 a mechanical actuator like an oil ram, stepper motor or the like will push the slipper plate 104 from the primary backstop 108 to the secondary backstop 109. The movement of the mechanical actuator will in turn be managed by the vehicles on board car computer system. The particular arrangement of the mechanical actuator and the car computer system is according to known design.

The preferred embodiment of the present invention shows the slipper plate 104 rotating around 20 degrees from the primary backstop 108 to the secondary backstop 109. Some engine 1 may require more rotation of the slipper plate 104 while other designs will need less movement. A scale 113 (as shown on Fig 10) facilitates alignment of the slipper plate 104 to a required position to change the piston stroke length. Each division mark equates to 0.2 mm of piston height change at the end of each piston stroke. If the slipper plate 104 is rotated towards the left hand end of the scale 113, the piston 101 will increase at the end of its stroke (up to a maximum of 3.25 mm). Rotation of the slipper plate 104 to the right hand end of the scale 113 results in shortening of the piston stroke (up to a maximum of 3.25 mm).

It should be appreciated by those skilled in the art that the description and drawings show crankshaft rotation in a clockwise direction. However, the engine 1 may conceivably be configured to facilitate rotation of the crankshaft 110 in an anti-clockwise direction.

The preferred embodiment of the present invention has a number of advantages over the prior art including:

• Improved efficiency through improved combustion period via a period of piston dwell at the top of the piston cylinder; • Improved torque output via a more efficient connecting rod lever angle compared to a conventional internal combustion engine;

• Improved power output and torque via an increase in piston stroke length depending on engine load;

• Improved reliability over known VCR engines;

• Relatively low cost of production in that the engine of the present invention uses standard piston and cylinder technology with a modified connecting rod and crankshaft. In addition, the piston speed of the engine of the present invention is similar to the piston speed of standard engines resulting in a similar piston wear rate. The modification to the crankshaft is relatively minor consisting of changes to the attachment points of the connecting rod to the crankshaft.

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof as defined in the appended claims.