Patent Application
20070079698
The present application is related, in terms of its subject matter, to copending applications Ser. No. 10/381,953, having a 35 US 371(c) date of Aug. 22, 2003; and Ser. No. 10/476,126, having a 35 US 371(c) date of Jun. 10, 2004, both of which applications are presently pending, and the inventors of which are the same as in the present application.
1. Technical Field
This invention relates to a variation of reciprocating fluid machines colloquially called “scotch yoke” devices.
2. Background Art
Known scotch yoke devices include one or more pairs of horizontally opposed pistons reciprocating in respective cylinders. Each piston of a pair is rigidly attached to the other so the pair of pistons move as a single unit. The pistons reciprocate along parallel axes which may be coaxial or which may be offset. A crank is provided centrally of the pair of pistons with an offset mounted in a slider. The slider in turn is mounted in the piston assembly between opposing sliding surfaces, which extend perpendicularly to the axes of the pistons. The slider is thus constrained to move perpendicularly to the piston axes and so, as the crank rotates, the pistons are caused to reciprocate along the piston axis, with a true sinusoidal motion. In certain circumstances the provision of a true sinusoidal motion is preferable to the quasi-sinusoidal motion provided by a crank and connecting rod arrangement found in most internal combustion engines or pumps. However such devices have certain drawbacks. Neither the slider, which reciprocates in a vertical plane, nor the pistons, can be dynamically balanced by a rotating mass. Whilst this can be partially compensated for in a multi-pair device, this still leaves rocking couples.
Further in the conventional arrangement the slider slides between a single pair of opposed surfaces which lie on either side of the big end bearing. The pistons must be arranged along parallel axes and the distance between the sliding surfaces of the slider and the guide surfaces of the pistons must be larger than the diameter of the big end on the crank.
The present invention aims to at least ameliorate some of the disadvantages of the prior art and, in preferred forms, provides devices in which paired pistons are not rigidly connected together, are not necessarily coaxial and in which better dynamic balancing is achieved. The invention also allows use of uneven numbers of pistons mounted on a single big end bearing pin.
In one form the invention in effect decouples the pistons from each other and provides each piston with its own pair or group of sliding surfaces and its own slider. The sliding surfaces for each piston do not lie on either side of the big end but are positioned remote from the big end. The sliding surfaces may be compound surfaces. This decoupling means that each piston is not relying on the coupling with the other piston or pistons to move in both directions and allows each piston to move along a separate axis and at a different phase to all other pistons. Whilst pistons may be interconnected via a common linkage which carries the various sliding surfaces, the pistons are not rigidly connected together. Thus a V-configuration may be achieved with a pair of pistons or a 120° layout with three pistons, for instance.
An important part of the invention is the use of restricting means which guide the piston or other parts of the piston arrangement. The restricting means are located in a position which may be broadly described as to the side of the sliding surfaces but not in line with their direction of slide.
In one broad form the invention provides a scotch yoke fluid device which includes:
a crank including a big end having an axis which orbits about a main axis for the crank;
connecting means mounted on the big end axis;
at least one piston mounted for reciprocal motion in a cylinder along a piston axis, the piston having a cross-sectional area perpendicular to the piston axis, the piston having guide means including a linear surface transverse to the piston axis, the guide means engaging engagement means on the connecting means; and
at least one restricting means for constraining the piston to move along the piston axis;
wherein the piston guide means bisects the piston cross-sectional area and at least part of each restricting means is located within a volume defined by the piston cross-sectional area projected along the piston axis, but is not located along the centre line of the bisection formed by the piston guide means.
Preferably, the guide means includes surfaces which extend substantially perpendicularly to the respective piston axis. However, the guide surfaces may extend at other than 90° to the respective piston axis. Even when the guide surfaces are “perpendicular” to the piston axis, the guide surfaces may deviate from the perpendicular by up to 5° either way. The engagement means may be two or more parallel linear surfaces which correspond and slide relative to the guide surfaces. Alternatively, the engagement means may include two or more roller bearings or the like.
In this embodiment, the linear parallel opposed guide surfaces may be located on the connecting means and the engagement means may be mounted on the piston. In preferred forms there are two or three pistons mounted on slider means on each big end bearing. The pistons may be arranged at equal angles about the main axis if desired.
The guide means may be integral with the piston or may be located on a separate structure attached to the piston. Where a separate structure is provided, it may be pivotably mounted to the piston, preferably using a gudgeon pin arrangement. This allows one to use conventional pistons with connecting rods incorporating the guide means.
The crankshaft may be fixed relative to the cylinders or may be movable so as to alter the compression ratio and/or the timing of the pistons in the cylinders. In a V configuration, movement of the crankshaft along the bisector of the included angle between the cylinders results in a change in compression ratio without any change in phase. An alternate arrangement provides for the crankshaft axis to rotate about a distant axis, so raising or lowering the crankshaft. These arrangements may be used with a single piston engine. Movement of the crank may be in any direction.
When two pistons per big end are utilised, the pistons may be arranged in a V-configuration. The V-configuration may be at any angle, such as 90°, 60°, 72° or any other desired angle. The number of pistons per big end is only constrained by physical size limitations. Each big end may have a single connecting means upon which multiple pistons are mounted or there may be a multiple connecting means mounted on each big end bearing with each connecting means having an associated piston mounted upon it.
When multiple pistons are mounted to one big end, they may be located the same distance from the main axis or different pistons may be at different distances from the main axis.
Whilst the guide means and complementary engagement means include preferably simple planar surfaces in cross section, other configurations are possible, to provide additional locating surfaces perpendicular to the line of the guide means.
This invention, in some embodiments, proposes scotch yoke type fluid devices in which each piston may be decoupled from any other piston mounted on the same big end of a crank, so allowing each piston to move along a cylinder axis which may be at an angle to any other cylinder axis. In producing such devices, it has been discovered that the pistons may be rotated in the cylinders about an axis generally perpendicular to the cylinder axis, causing damage to the device. To prevent this occurring it has been proposed to use restricting means mounted on, connected to or integral with the piston to maintain the pistons in a correct orientation and to prevent unwanted rotation or deflection of the piston. In some embodiments, the invention also proposes second restricting means located outward of the piston and cylinder bores. This requires extra space within the crank case and so increases the size of the fluid device.
Preferably all the restricting means are contained within a volume defined by a projection of the cylinder's cross sectional area along the cylinder axis. However, the guide means or the restricting means, or both, may extend out of this volume. Further, the restricting means may lie within the volume but may be positioned not along the centre line of the bisection.
The restricting means may be formed integrally with the piston body or may be one or more separate items attached to the piston body. Where the restricting means are separate units, a single unit may be provided which is rigidly or pivotably mounted to the piston body. The restricting means may include one or more guide members, including tubes or rods, which extend substantially parallel to the piston axis. Where the restricting means includes two or more guide members, these guide members may be located symmetrically or asymmetrically relative to the piston's cross sectional centre.
Preferably the guide means extends through the centre of the piston's cross sectional area.
Where two or more pistons are mounted on one big end, the pistons may lie in a single plane or may lie in two or more planes.
Preferably, the device of the invention includes stabilising means engaging the connecting means to limit the connecting means to a single orientation as it orbits the main axis.
The stabilising means may include the engagement of the connecting means with the at least one piston. The stabilising means may include a separate linkage pivotably mounted to both the connecting means and the crankcase.
The crank mechanism may be a simple crank with an offset big end bearing or it may be a compound mechanism which provides for other than simple circular motion of the big end bearing at a constant angular velocity. Examples of compound crank mechanisms are disclosed in PCT International Patent Application Nos. PCT/AU97/00030 and PCT/AU98/00287, the disclosures of which are incorporated herein.
The invention, in another embodiment, includes a feature whereby the main axis of the crank mechanism is movable along at least one path relative to the cylinder or cylinders and the engagement means is configured such that the at least one piston is neither substantially retarded or advanced.
Where the device includes pistons arranged in a V configuration the main axis of the crank mechanism preferably moves along a linear path which bisects the included angle of the V. Alternatively, the main axis of the crank mechanism may move along an arc.
In another embodiment, the connecting means has a centre of mass located on or adjacent to the big end axis.
Preferably, the crank includes a counter weight which substantially and/or dynamically balances the mass of the connecting means relative to the crank axis.
Preferably, the crank has an effective centre of mass, which, together with the connecting means and the at least one piston, remains stationary or substantially stationary relative to the crank axis as the crank rotates.
In another embodiment, the device has two pistons arranged in a non-opposed pair, the configuration of the connecting means and the engagement means being such that the motion of each piston is simple harmonic motion.
In another embodiment, the device has at least one pair of pistons, each pair of pistons having a mass the motion of which is equivalent to a single mass orbiting in an orbit.
Preferably the orbit is a circle, but it may be elliptical.
Preferably the motion of each of the pistons is simple harmonic motion.
The invention, in another broad form, also provides a fluid device, which includes:
a crank including a big end having an axis which orbits about a main axis for the cranks;
connecting means mounted on the big end axis;
at least one pair of pistons, each piston being mounted for reciprocal motion in a respective cylinder along a respective piston axis, the piston axes of each pair being at 90° to each other, each piston engaging engagement means on the connecting means;
wherein each pair of pistons has a mass the motion of which is equivalent to a single mass orbiting in an orbit;
the centre of mass of the connecting means is located on or adjacent the big end axis; and
the crank includes a counter weight located generally diametrically opposite the big end and having a centre of mass remote from the crank axis, the counter weight including the equivalent of:
a first mass to statically and/or dynamically balance all or part of the mass of the big end bearing relative to the crank axis;
a second mass to statically and/or dynamically balance all or part of the mass of the connecting means relative to the crank axis; and,
a respective third mass to statically and/or dynamically balance all or part of the mass of each pair of pistons relative to the crank axis.
Preferably the angle is 90°.
Preferably the orbit is a circle and the third mass preferably statically and/or dynamically balances the mass of the pistons.
Where the orbit is not a circle, the third mass may balance the mass of the pistons in a first direction. The first direction is preferably parallel or perpendicular to a bisector of the axes of each pair of pistons.
In all forms of the invention the connecting means (when present) may have non-rotary motion relative to the piston. Preferably there is no rotary motion whatsoever, except as allowed by clearances.
The invention, in another broad form, provides a piston-type fluid device which includes:
a crank having a main axis and including a lag end member having an axis which rotates about the main axis;
at least one piston arrangement having at least one piston mounted for reciprocal motion in a cylinder along a piston axis, the piston having a cross-sectional area perpendicular to the piston axis;
at least one follower located between the member and the piston for transferring motion of the member to the piston, the follower reciprocating along a linear path, having a centre line, between two end points; and
at least one restricting means for constraining the piston to move along the piston axis;
wherein at least part of each restricting means is located within a volume defined by the piston cross-sectional area projected along the piston axis, but is not located on the centre line between the two end points.
The device may have each piston assembly having two surfaces with the offset member bearing on one surface and the follower bearing on the other surface.
The device may have a single follower which bears on both surfaces or it may have two followers, each of which bears on one of the respective surfaces.
Each piston arrangement may have one piston or it may have two pistons. Where two pistons per arrangement are provided, preferably the at least one follower is located below the pistons.
The member is preferably a circular cam having its centre offset from the crank axis.
The device may have two or more piston arrangements for each member.
Where two or more pistons arrangements for each member are provided, they may reciprocate along piston axes extending at any angle to each other. Preferably there are two piston arrangements per offset member extending at 90° to each other.
Where two piston arrangements extending at 90° to each other are provided, preferably there are provided two followers, each of which engages both piston arrangements.
The invention, in another broad form, also provides a scotch yoke fluid device which includes:
In preferred embodiments, the scotch yoke element includes surfaces which extend substantially perpendicularly to the respective piston axis, as already discussed.
The restricting means, which is also discussed in relation to a previous aspect of the invention, above, is intended to alleviate “jamming” of the piston in the cylinder, which can provide a problem at high temperature. It is desirable to maintain the piston so that it is aligned with the piston axis. Several preferred embodiments of the restricting means are described in connection with the drawings. It will be appreciated that when the restricting means is located within the “footprint” of the piston, metallic mass of the fluid device is minimised.
As will be seen from the drawings, in some embodiments, the restricting means is formed in pairs and a line drawn from one member to the other of the pair would be perpendicular to the longitudinal path. In other embodiments, the restricting means includes members which are located on either side of the longitudinal path, but transversely, not perpendicularly.
The restricting means may be mounted to the block within the footprint of the piston, thus minimising the size of the device of the invention.
In another broad form, the invention also provides a fluid device, which includes:
The means for adjusting may include a slot, groove or surface which engages the intermediate connecting means.
The intermediate connecting means preferably engage in or with guide means to stabilise the at least one piston in the cylinder. Preferably the means for adjusting includes the guide means, but the guide means may be separate.
The means for adjusting may be movable transversely or longitudinally relative to the cylinder axis or both. The guide means may be rotatable about an axis.
The means for adjusting may include a linear, single radius curved or multi-radius curved slot/s, groove/s, surface/s or the like. The intermediate means may include sliding or rolling contact members to engage the means for adjusting.
The means for adjusting may be movable to change the effective stroke of the pistons, the effective compression ratio of the device or the position/time path followed by the pistons or a combination of any of the foregoing.
In another embodiment, the device of the invention includes means for adjusting the distance between the piston and the engagement means.
The means for adjusting in this aspect of the invention may include a compressible connecting rod.
Above is described how a fluid device may be fully or substantially statically or dynamically balanced or both about the crank axis. It will be appreciated that the additional mass of the restricting means may be balanced as described above. It will also be appreciated that whilst balancing of pistons mounted on a single crank is the norm, balancing of a device with pistons mounted on separate big ends is possible if the big ends are coaxial.
Above are disclosed devices in which piston motion is achieved by sliders mounted on big ends and in which two or more pistons may be mounted on a single slider but each of which moves along a separate path to each other.
Because each piston is not directly connected to any other piston, there is a tendency for the pistons to rotate in the cylinders about an axis generally parallel the crank axis. This can lead to destructive failure of the device. Providing restricting means, extending parallel to the cylinder axis, prevents such rotation, and this has been disclosed above. In some embodiments, the restricting means lies above the swept volume of the crank shaft and big end. The restricting means can be placed so that at various parts of the cycle they extend into the projection of the area swept by the crank and slider. This results in a more compact device.
In conventional scotch yoke type piston fluid machines a slider is rotatably mounted on the big end of a crank, which orbits about a main axis. The slider is constrained to move along a linear slot in the piston assembly which is generally perpendicular to the cylinder axis. Thus, as the crank rotates, the piston is caused to reciprocate along the cylinder.
In conventional single piston devices, the linear slot is positioned on the cylinder axis and so that at top dead centre the big end lies between the piston and the main axis.
The present invention creates various novel and inventive configurations which depart from this standard.
In a further embodiment of the invention, at top dead centre, the main axis lies between the piston and the big end axis.
This, in effect, is the reverse of the norm.
In another embodiment the main axis is not located on the or any of the at least one cylinder axes.
Preferably, when the or one of the pistons is at top or bottom dead centre a line joining the main and big end axes is parallel to and spaced from the respective cylinder axis of the one piston.
Usually in scotch yoke engines or pumps two opposed pistons are rigidly connected together about a yoke. A slider, which is rotatably mounted on a big end of a crank, slides within the yoke and causes the pistons to reciprocate.
The present invention aims to provide improved yoke constructions, which allows, in preferred forms, for two identical parts to be utilised to build up the yoke assembly. The assembly may be a split generally axially or transversely relative to the cylinder axis. In preferred forms the number of fixing components required is reduced whilst allowing for simple manufacture of the components.
In one broad form the invention provides a yoke assembly for a scotch yoke type fluid device having opposed pistons reciprocating in opposed cylinders having parallel cylinder axes, the yoke assembly mounted on the two pistons and including an engagement portion for receiving an engagement member rotatably mounted on a big end of a crank shaft and in which the engagement means reciprocates as the crank rotates, said engagement portion being split into two parts.
The engagement portion may be split along a plane generally parallel to the cylinder axes or a plane generally perpendicular to the cylinder axes.
The two parts may be identical or may be dissimilar.
Preferably only two fixings are required to securely hold the two parts together.
The engagement portion preferably includes two opposed channels in which the engagement means reciprocates. Each of the channels may be defined by only one of the parts or both parts may define part of each channel.
Preferably, where identical parts only define all or part of one channel each, each part includes legs which extend and engage the other part. These legs may be located at opposite ends of the channel but on the same lateral side; the same end but opposite lateral sides of the channel or opposite ends and opposite lateral sides of the channel. Preferably, a single fixing may hold two legs, one for each part, simultaneously.
Where non-identical parts are utilised, one part may have two or more spaced apart legs located adjacent the channel and the other part may have no legs or one leg adjacent the channel.
Preferably, the legs are located at the ends of the channel but a single leg may be positioned adjacent the channel at a mid-point. In this construction the crank cannot pass through the engagement portion.
It is found that the decoupled, paired piston/s, scotch yoke devices of this invention may be balanced perfectly in that the centre of mass of the moving parts of the engine (the crank, the pistons and their members, and any interconnecting members between the cranks big end and the pistons) remains exactly stationary and centred on the main axis as the device members rotate, orbit and reciprocate through its cycle. A pair of pistons arranged at 90 degrees to each other and sharing the same big end axis may be perfectly balanced. A pair of pistons arranged at 90 degrees to each other and having coaxial big ends, similarly may be perfectly balanced (although in this embodiment a rocking couple may be set up).
An engine that is of a V configuration that is other than 90 degrees may be balanced perfectly as well. This may be achieved by splitting the big end so that there are two big end axes per pair of reciprocating masses, i.e., pistons. The two big ends axes are angularly displaced from one another about the main axis.
The invention shall be better understood from the following, non-limiting description of preferred forms of the invention, in which:
FIGS. 14 to 28 show various configurations of the guide surfaces of the invention (
FIGS. 31 to 39 are axial cross-sections through a big end and embodiments of a connecting means according to the invention.
FIGS. 41 to 47 show further variations of the connection between the connecting means and the engagement means of the piston.
a is a top view of the embodiment of
FIGS. 63 to 68 show end views of further embodiments of the invention.
FIGS. 69 to 78, 78a and 79 to 80 show end views of a slider arrangements used in embodiments of the invention.
FIGS. 85 to 126 show underside plan views of various pistons made according to the invention.
FIGS. 127 to 129 show isometric views of a further piston made according to the invention.
FIGS. 130 to 132 show isometric views of a further piston made according to the invention.
FIGS. 133 to 135 show isometric views of a further piston made according to the invention.
FIGS. 136 to 138 show isometric views of a further piston made according to the invention.
FIGS. 139 to 141 show isometric views of a further piston made according to the invention.
FIGS. 142 to 144 show isometric views of a further piston made according to the invention.
FIGS. 145 to 147 show isometric views of a further piston made according to the invention.
FIGS. 148 to 150 show isometric views of a further piston made according to the invention.
FIGS. 151 to 153 show isometric views of a further piston made according to the invention.
FIGS. 154 to 156 show isometric views of a further piston made according to the invention.
FIGS. 157 to 159 show isometric views of a further piston made according to the invention.
FIGS. 160 to 162 show isometric views of a further piston made according to the invention.
FIGS. 163 to 165 show isometric views of a further piston made according to the invention.
FIGS. 166 to 168 show isometric views of a further piston made according to the invention.
FIGS. 169 to 171 show isometric views of a further piston made according to the invention.
FIGS. 172 to 174 show isometric views of a further piston made according to the invention.
FIGS. 175 to 177 show isometric views of a further piston made according to the invention.
FIGS. 178 to 180 show isometric views of a further piston made according to the invention.
FIGS. 181 to 183 show isometric views of a further piston made according to the invention.
FIGS. 184 to 186 show isometric views of a further piston made according to the invention.
FIGS. 187 to 189 show isometric views of a further piston made according to the invention.
FIGS. 190 to 192 show isometric views of a further piston made according to the invention.
FIGS. 193 to 195 show isometric views of a further piston made according to the invention.
FIGS. 211 to 213 are end views of the embodiment of
FIGS. 230 to 233 show perspective conceptual views of various yoke constructions.
Referring to
Rotatably mounted on bearing pin 16 is a slider 18. The slider has two tongues 20, 22.
The slider 18 extends generally perpendicular to the axis 14 whilst the tongues extend generally parallel to the axis 14. As best seen in
Each of the tongues 20, 22 engages in a T-shaped slot 30 of a respective piston 32. Each piston is mounted in a cylinder 34 and constrained for linear movement along a respective cylinder axis 36. Each slot 30 preferably extends substantially perpendicular to the cylinder axis 36 and extends diametrically across the centre of the piston. Both ends of the slot 30 are open. The slider 18 can thus move sideways relative to the piston but must move axially with the piston along axis 36. Where the slot 30 does not extend at 90° to the piston axis 36, sideways movement of the tongue 20 or 22 relative to the piston 32 will cause axial motion of the piston 32. This enables one to control the motion of the piston 32 beyond a pure sinusoidal motion.
The piston 32 is constrained to move along its piston axis 36 and as the crank 12 rotates the slider 18 rotates about the crank axis 14. The motion of each tongue 20, 22 has a component parallel to the respective piston axis 36 and a component perpendicular to the respective piston axis 36. Thus, the pistons 32 reciprocate in their respective cylinders 34 with the tongues 20, 22 sliding sideways in their respective slots 30. The combination of the linear movement of the piston 32 and the tongue 20, 22 in the slot 30 maintains the slider 18 in a constant orientation as the crank rotates, irrespective of other pistons. In the embodiment of
Because each of the pistons is decoupled from any other piston, the orientation and position of the pistons may be chosen as desired. There is no need for the piston axes to extend radially from the crank axis. The piston axes may extend radially from an axis, but this axis may be remote from the crank axis. The piston axes may be parallel and spaced from each other on either side of the crank axis.
Rotation of the crank 52 causes the pistons 66, 68 to reciprocate vertically within the cylinders 70, 72 with the arms 58, 60 moving sideways relative to the pistons 66, 68.
Referring to FIGS. 5 to 7 there is shown a reciprocating piston device 210 having two pistons 232 reciprocating in respective cylinders 234 at 90° to each other. A connecting device 218 connects the two pistons to big end pin 216 of crankshaft 212 via tongues 220 and slots 230 in the pistons 232. The connecting device 218 has two webs 240, one for each piston, which are offset axially relative to each other. This allows the pistons 232 to overlap each other and so be brought closer to the crank axis 214. Lubrication ducts 242 are provided to supply pressurised oil from the big end pin 216 to the sliding surfaces of the tongues 220 and slots 230.
The connecting device 218 includes a counter weight 244 extends downwardly on the opposite side of the big end pin 216 to tongues 220, bisecting the angle between the two webs 240. This counter weight 244 is sized so that the centre of inertia and preferably also the centre of mass of the connecting device 218 lies on the big end axis 246. It will be appreciated that, when the pistons are spaced equally about the crank axis 214, the webs 240 will balance each other and a separate counter weight may not be needed.
As the connecting device 218 orbits the crank axis 214, no rotational forces are generated relative to the big end axis 246, which would cause the connecting device 218 to attempt to rotate about the big end and which would need counter turning forces to be generated at the slot 230/tongue 220 interface. In addition, since the centre of inertia of the connecting device 218 remains on the big end axis 246, it is a relatively simple matter of adding an appropriate amount of mass to the counter weight 244 on the crank shaft 212 diametrically opposite the big end axis 246 to provide a dynamically balanced crankshaft/connecting device combination. It will be appreciated that for other piston arrangements, so long as the centre of inertia of the connecting device 218 lies on the big end axis 246, then it may be dynamically balanced.
This leaves the reciprocating mass of the pistons 232. The velocity of the pistons 233 follows a pure sinusoidal path and in combination the two pistons 232 are the equivalent of a single rotating mass. This may be balanced by adding an appropriate mass to the crankshaft 212, thereby resulting in a dynamically balanced device. For a V twin configuration, a single piston mass is added to the back of the crankshaft 212. For a four piston star configuration, two piston masses are added to the crank counter weight.
Referring to
Referring to
Referring to
Vertical movement of the crankshaft 12 may be achieved utilising conventional means, such as hydraulic rams or the like. The line represented by arrow A bisects the angle between pistons 82.
It will be appreciated that a movable crank may be utilised with a single piston and that the movable crank may be moved along paths other than the bisector in a V-twin engine, for example. The crank may be moved at a, say, 15° to the vertical. This has no effect other than to need more crank movement to achieve the same change in compression ratio.
FIGS. 14 to 29 show a number of variations of the guide surfaces of the piston and the corresponding surfaces on the engagement means.
The device of
The connecting rods each have a sideways extending arm 316 which engages a slider 318 which slides in guides 320 parallel to the respective cylinder axis. The connecting rod 312 may be integral with the slider 318 or it may be connected by way of a pivotable joint 322, as shown. The joint 322 may be a single axis joint or a ball type joint. In the embodiment shown, the arms 316 extend parallel to the slots 314. However they may extend at any angle.
The guides 320 aid in stabilising the respective piston 302 because the tolerances required can result in the piston 302 rotating very slightly in the bore and cause seizing or the like. If very tight tolerances are used, the guides 320 may not be needed. The guides 320 may be integral with the crank case or may be separate items attached to the crank by way of bolts and the like
The gudgeon pins 310 of the pistons 302 may be at 90° to the crank axis as no rotational movement of the connecting rod 312 relative to the piston 302 will occur. Use of the pistons 302 with gudgeon pins 310 allows one to use “off the shelf” pistons.
A slave crank, 338 is provided which rotates about an axis 340 parallel to the axis 331 of the primary crank. A link 342 is pivotably mounted on both the connecting means 334 at 344 and the slave crank 338 at 346. The distance of pivot point 346 from the slave axis 340 is the same as that of the big end 332 from the primary axis 331. The slave crank 338 and link 342 thus aid in maintaining the connecting means 334 in a fixed orientation as the primary crank 330 rotates. It will be appreciated that this stabilisation technique may be used with any of the embodiments described herein.
FIGS. 41 to 47 show further variations possible of the connection between the connection means and the engagement means of the piston or pistons mounted thereon. Roller bearings are shown in
The two cranks 508 and 510 are preferably linked, such as by gears, so that they rotate together. As they rotate the connecting means 512 describes a sinusoidal vertical motion and so causes the pistons 502, 504 to describe similar motion.
Whilst the connecting means 512 is free to slide sideways relative to the linkage 507, there will be some sideways loading on the linkage 507. Accordingly guide surfaces 520 and 522 are provided either side of the linkage 507 to prevent sideways motion.
Each linkage 838 has a slot 839 extending in a vertical plane through the linkage 838. Each slot 839 has parallel vertical end walls 841 and located in each slot is a slider 844, having parallel vertical end walls 846. Each slider 844 is free to move vertically in the respective slot 839.
A crank 840 extends horizontally through the linkages 838 and the sliders 844. The sliders 844 each have a circular opening 848 through which the crank passes. The crank has a circular cam 842 which has a size corresponding to the opening 848. The cam centre is offset from the crank axis and so as the crank 840 rotates, the cam centre orbits the crank axis. This causes the slider 844 to move vertically and horizontally relative to the crank axis.
Vertical motion of the sliders 844 is “lost” due to the vertical freedom of the sliders 844 relative to the piston assemblies, whilst horizontal motion causes the piston assemblies to oscillate horizontally in a true sinusoidal motion.
This construction has a number of advantages over existing similar systems. The main advantage is that interposing of a slider between the cam 842 and the slot walls 841 removes application of point loads, which would otherwise occur. Instead the load is transferred over large surfaces from the cam 842 to the slider 844 and from the slider 844 to the slot 839.
a show a twin piston engine 850 similar to that of
FIGS. 58 to 60 show a four piston device 860 having pairs of pistons 862a, b arranged at 90° to each other. Each piston has an extension 864 having end walls 868 and 870 extending perpendicular to the respective piston axis. The extensions 864 extend to one side of the piston axis, as best seen in
The crank includes an offset circular cam 872 which engages the four walls 868a, b, 870a, b. As the crank rotates, the cam 872 causes both pistons 862a, b to reciprocate in their respective cylinders, not shown.
Whilst the
Two sliders 880 are interposed between the cam 872 and the end walls 868a, b and 870a, b. Each slider bears on the inner face 868 of one piston and the outer face 870 of the other piston. As the crank 866 rotates this causes the sliders 880 to move both pistons. It will be appreciated that as a piston 862 moves toward the crank 866, the slider bearing on the respective end wall 870 will push the piston 862 toward the crank whilst as the piston 862 moves away from the crank 866, the other slider 880 bearing on the inner wall 868 will push the piston away from the crank. As with the
a shows a crank 1060 having a main, circular cam 1062 which is engaged by slider components 1064. Each slider component has a cam follower 1066. This cam follower is intermittently engaged by a second cam 1068 as the crank rotates.
It is to be understood that the various forms of the slider and the engagement means on the sliders may be used with any of the other forms of the invention in any practical combination possible and the various forms are not limited to use with the components shown in the specific figures.
Referring to FIGS. 81 to 84 there is shown a V-twin fluid device 2010 (
Each of the pistons 2012 has a T-shaped slot 2018 which extends diametrically across each piston. The connecting means 2016 has corresponding T-shaped tongues 2020 which engage in the slots 2018. Each of the tongues 2020 has a two part construction—the cross arms are formed of a planar web 2024 which is attached to the vertical web 2026 by bolts 2028.
Located on either side of the slot 2018 are two axially extending planar webs 2030. These webs 2030 are diametrically opposite each other and extend perpendicularly to the slot 2018 but do not extend out of the footprint of the piston. The webs 2030 are integral with the piston body.
The fluid device has a series of U-shaped guides 2032 which engage the webs 2030, as seen in
The guides are preferably located on the crank case by way of a locating pin 2034 and then bolted via bolt holes 2036.
The guides 2032 serve to limit movement of the pistons both parallel and transverse to the slot 2018 and so enable the skirt length of the piston to be reduced, if desired.
Because the webs 2030 are located to the sides of the slot, rather than at one or both of its ends, the size of the crank case need not be any greater than a conventional crank case. Further, because the webs 2030 do not extend outside the footprint of the piston, an existing crank case can be relatively easily modified to take the crank and piston assembly.
The webs and the slot 2018 may be formed integrally with the piston 2012 and so be formed of the piston material. Alternatively, separate components may be provided and the piston assembly built up from those components. Preferably, the bearing surfaces of the slot 2018 and the webs 2030 are suitably treated to provide a hard wearing surface or are provided with separate inserts to provide a suitable surface. It is to be understood that oil lubrication will be provided to the bearing surfaces via oil galleries or by oil splashing.
FIGS. 85 to 126 show bottom plan views of different configurations of piston webs or vertical guide means which may be used with the connecting means 2016 shown in
FIGS. 85 shows a piston 2040 having a single axial web 2042. The web 2042 extends perpendicularly to the slot 2018 along a radial line. The web 2042 also extends beyond the piston's circumference. The web 2042 may be integral with the piston or a separate component.
FIGS. 127 to 129 show a piston 20242 with a vertically extending guide bar 20244 and a horizontal slide bar 20246. The bar 20244 extends from the lower surface of the main body 20248 of the piston 20242. The horizontal bar 20246 is mounted on an inner side of the vertical bar 20244. The bar 20246 is engaged by a suitable engagement means on the connecting means whilst the vertical bar 20244 is engaged by a suitable guide surface mounted on the crank case.
FIGS. 130 to 132 show a piston 20250 with a vertical guide bar 20252 and a horizontal bar 20254. The horizontal bar 20254 has a re-entrant slot 20256 for slideably engaging a corresponding tongue on a connecting means.
FIGS. 133 to 135 show a piston 20258 having a main body 20260. Rotatably mounted to the main body by a gudgeon pin 20262 is a engagement/guide means 20264. This engagement means includes a horizontally extending portion 20266 and a vertical extending portion 20268. The horizontal portion includes a slot 20270 which slideably receives a complimentary tongue on the connecting means whilst the vertical portion 20268 is engaged by a guide mounted on the crank case. It will be noted that the vertically extending portion extends above and below the horizontally extending portion.
FIGS. 136 to 138 show a piston assembly 20272 with a Z-shaped horizontally extending member 20274 which slideably engages a complimentary surface on the connecting means. Guide webs 20275 engage guides mounted on the crankcase.
FIGS. 139 to 141 show a piston assembly 20276 in which a vertical guide bar 20278 extends from the base of the main body 20280 of the piston. A horizontal bar 20282 is mounted on the main body 20280 independently of the vertical guide bar 20278.
FIGS. 142 to 144 show a piston assembly 20283 having a main body 20284 and an engagement/guide assembly 20286 mounted to the main body by pins or bolts 20288. The engagement/guide assembly 20286 has two vertical legs 20290 and a cross bar 20292. Mounted on the cross bar 20292 is a horizontally extending T-shaped engagement member 20294 which extends perpendicular to the plane of the two vertical guide bars 20290. This member 20294 is engaged by the connecting means.
FIGS. 145 to 147 show an assembly 20296 similar to that of FIGS. 142 to 144 and a similar engagement/guide assembly 20300 is mounted to the main body 20298 of the piston 20296. The assembly 20300 is mounted to the main body 20298 by a gudgeon pin 20302 which extends in the plane of the two legs 20290. The assembly 20300 may pivot about the pins 20302.
FIGS. 148 to 150 show a piston assembly 20304 having a main body 20306 on which is mounted an H-shaped guide assembly 20308. The assembly is mounted to the main body 20306 via pins 20310. Mounted on the cross bar 20309 of the assembly 20308 is a horizontally extending engagement bar 20312. The bar 20312 is pivotably mounted to bar 20309 via pin 20314. The bar 20312 has a T-shaped slot 20316 for engaging a T-shaped tongue on the engagement means.
FIGS. 151 to 153 show a piston assembly 20318 having a guide/engagement means 20320 mounted to the main body 20322 via pin 20324. A cross bar 20326 extends between vertical members 20328 and includes a T-shaped slot 20330.
FIGS. 154 to 156 show a guide engagement assembly 20332 having a cross bar 20334, four vertical guide bars 20336 and a central connecting bar 20338. There are two vertical guide bars 20336 on either side of the cross bar 20334. The cross bar has a T-shaped slot 20339.
FIGS. 157 to 159 show an assembly similar to that of FIGS. 154 to 156 except that the cross bar 20340 is T-shaped, rather than having a T-shaped slot.
FIGS. 160 to 162 show an assembly 20342 similar to that of FIGS. 157 to 159 attached to a piston body 20344 by two pins 20346 so that pivoting is not possible.
FIGS. 163 to 165 show a piston assembly 20350 having a guide/engagement means 20352 mounted on a pin or cross bar 20354 of the piston body 20356. The pin or cross bar 20354 may be separate from or integral with the body 20356. The assembly is retained on the cross bar 20354 by bolt 20358.
FIGS. 166 to 168 show a guide/engagement assembly 20360 similar to that of FIGS. 154 to 156 but retained on the piston body 20362 by two pins 20364.
FIGS. 169 to 171 show a piston assembly 20366 functionally identical to that of FIGS. 166 to 168 but in which there is a single unitary structure and only one vertical guide bar 20368 on each side of the horizontal engagement bar as opposed to two.
FIGS. 172 to 174 show a piston assembly 20370 similar to that of FIGS. 127 to 129 but in which a horizontal slot 20372 is provided for engagement with the connecting means.
FIGS. 175 to 177 show a piston assembly 20374 having a single vertical guide bar 20376 and a T-shaped engagement bar 20378 depending from the guide bar 20376.
FIGS. 178 to 180 show a piston assembly functionally identical to the FIGS. 130 to 132 embodiment except that the re-entrant slot 20380 is much nearer to the piston body 20382.
FIGS. 181 to 183 show a piston assembly 20450 having two vertical guide bars 20452 extending from the piston body 20454. A crossbar 20456 is mounted inwardly of the bars 20452 and extends horizontally. The crossbar has a diamond shaped slot 20458 which receives a corresponding tongue mounted on the connecting means.
FIGS. 184 to 186 show a piston assembly 20460 having a piston body 20462 from which descends a guide bar/engagement assembly 20464. This assembly 20464 includes a T-shaped engagement portion 20466 having a cross bar 20468 which in turn defines an L-shaped slot 20470 to receive an L-shaped tongue mounted on a connecting means. A vertical guide bar 20472 descends from the piston body 20462. Preferably the guide bar 20472 is integral with the engagement portion 20466 but it may be separate. The guide bar 20472 preferably extends below the horizontal cross bar 20468.
FIGS. 187 to 189 show a piston assembly 20474 having a piston body 20476 and a guide/engagement assembly 20478 pivotably mounted to the body 20476 by gudgeon pin 20480. The assembly 20478 has a T-shaped portion comprising vertical leg 20482 and horizontal cross bar 20484. The cross bar has a T-shaped slot 20486 in a side wall 20488 for receiving a corresponding tongue on the connecting means.
FIGS. 190 to 192 show a piston assembly 20490 having a piston body 20492 with four vertical and parallel guide bars 20494 extending downwards. The four bars 20494 are located at the corners of a square centred on the centre of the piston's circumference.
An engagement means 20496 is pivotably mounted on the piston via gudgeon pin 20498 and is located between the vertical guide bars 20494. The engagement means includes a flat cross bar 20500 which may engage in a T-shaped slot on the connecting means.
FIGS. 193 to 195 show a piston assembly 20502 having a piston body 20504 with a guide/engagement assembly 20506 attached to the body 20504 by two pins 20508. The assembly 20506 has a vertical post 20510 and a first cross bar 20512 having four vertical guide posts 20514, each arranged at one of its corners. Mounted to the underside of the first cross bar 20512 is a second T-shaped cross bar 20516 which is engaged by a corresponding T-shaped slot on the connecting means.
Referring to
The intermediate members 3022 have a sliding arm 3026 mounted in a slider 3028. The slider 3028 defines a linear slot parallel to the respective cylinder axis 3030. The intermediate member 3022 is thus constrained to move parallel to the cylinder axis 3030. The connector 3018 is limited to motion relative to the members 3022 which is perpendicular to the cylinder axis 3030 and so as the crank 3012 rotates the pistons 3014 are caused to follow a true sinusoidal path.
When the axes of the primary and secondary slide are parallel the inner piston 3074 does not move relative to the outer piston. When the axes are not parallel the inner piston moves relative to the outer piston as the crank rotates and the sliding members travel along the respective slides.
It will also be noted that the intermediate member 3022 is pivotably mounted on the piston 3072, dispensing with the connecting rod. To provide the necessary degree of freedom, there is provided a separate sliding member 3084 which is pivotably attached to the intermediate member 3022.
The two sliders can also be moved sideways along axis 3086 so as to change the displacement or the compression ratio of the device. The sideways movement of the two sliders may be independent of each other. Pivot points are shown at A, B, C and D.
(The description for
Referring to FIGS. 210 to 217 there is shown a fluid device 4010 having a crank 4012 rotating about a crank axis 4013 and two pistons 4014 reciprocating in cylinders 4016 in a V configuration. The two pistons 4014 are connected to the crank 4012 via a single slider mechanism 4018, which is rotatably mounted on the big end 4020 of the crank 4012. The big end 4020 extends between webs 4022 (one of which is shown). The slider 4018 has two T-shaped tongues 4024 which slidably engage in corresponding slots 4026 (
Extending downwards from the base area of each piston are two guide bars 4028. These bars 4028 extend on either side of the slider 4018 and slot 4026. In addition, each bar extends below the slot 4026 toward the crank axis 4013. Whilst two bars 4028 per piston are shown, it will be appreciated that only one or more than two bars per piston may be used. Where two or more bars are used it is not essential that they be located symmetrically relative to the cylinder/piston axis; the bars may be positioned to one side of the slot 4026 or asymmetrically on both sides.
A corresponding number of guides 4030 (
As best seen in
As the crank 4012 rotates, the pistons 4014 reciprocate in their cylinders 4016 and, as seen in FIGS. 210 to 213, the guide bars 4028 move up and down with the pistons 4014 into and out of the volume swept by the big end 4020.
At bottom dead centre (
Referring to
Mounted on the engagement means 5024, or integral therewith, is a piston 5026, which is mounted in a cylinder 5028 for reciprocal motion along cylinder axis 5030.
The engagement means 5024 is in the form of a triangular loop and the connecting means 5020 is positioned so that the linear slot 5022 always lies with the big end axis 5018 between the slot 5022 and the piston 5026. The piston 5026 is constrained to move along the cylinder axis 5030 and so, as the crank 5012 rotates, the slot 5022 remains horizontal with the connecting means 5020 moving both vertically (and moving the piston) and side ways, relative to the engagement means 5024.
The effect of this arrangement is that the crank axis may be moved nearer the cylinder head 5032 than otherwise.
In the
The
Two co-axial cylinders 5062 are provided with respective pistons 5064 mounted for motion along the common axis 5066. The crank axis 5054 is remote from axis 5066.
The two pistons 5064 are mounted on or integral with a common engagement means 5068, which is generally T-shaped with an arm 5070 extending away from axis 5066. Preferably, the arm 5070 extends at 90° to the axis 5066 but this is not essential. Also, preferably, the arm 5070 extends from approximately mid-way between the pistons 5064, but again this is not essential.
The arm 5070 engages the connecting means 5060, preferably via a sliding tongue and groove or slot arrangement to allow motion of the connecting means along the arm 5070. The arm 5070 is preferably linear but need not be.
The arm 5070 extends past the connecting means 5060 and at its free end has a guide member 5072 which is mounted on or in guide means 5074. The guide means 5074 defines a slot 5076 which extends parallel to axis 5066 and so aids in ensuring that motion of the pistons 5064 and engagement means 5068 is parallel to axis 5066. Guide member or members 5078 mounted along the axis 5066 also aid in stabilising the motion of the pistons 5064. In this embodiment, the pistons 5062 are mounted for reciprocation on the opposite side of big end 5056 from guide means 5074.
In this embodiment, there is provided a common engagement means 5082 which engages the connecting means. The engagement means is effectively the same as two of the engagement means of the
Referring to
The yoke assembly includes two identical pieces 6026a and 6026b. Each piece has a centrally located mounting 6028 on which a piston 6016 mounts, a transverse section 6030 and a longitudinal section 6032.
The transverse section 6030 extends generally perpendicular to the cylinder axes whilst the longitudinal 6032 section extends generally parallel to the cylinder axes.
A channel 6034 extends in the transverse and longitudinal sections 6030, 6032 in which the slider 6022 is located. At the free end 6036 of the transverse section 6030 are bolt holes 6038 whilst at the free end 6040 the longitudinal section there are bolt holes 6042. The two identical parts are joined with the free ends 6036 of the transverse sections 6030 engaging the free ends 6040 of the longitudinal sections 6032 of the other part. The bolt holes 6038 and 6042 align and the two parts are secured together with the bolts 6044 and nuts 6046.
A tubular spacer 6048 is positioned within the channel through which the bolts 6044 pass to prevent over tightening and crushing of the slot.
As best seen in
The opposing faces of the two pairs of arms 6066 are each provided with two stud holes 6068 and studs 6070 are provided to locate the two halves together. The two halves are secured together by bolts 6074 which pass through bolt holes 6076 at each end of the arms 6066 and screw into the opposing arm 6066. The ends of the arms 6066, when joined, form a receptacle 6078 into which the piston is mounted. This receptacle allows the piston to rotate about the cylinder axis.
The assembly also includes joining members 6080. These joining members are located within the channel and have threaded studs 6082 which extend through holes 6084. The members 6080 are secured to the two halves by nuts 6086 and serve to resist bending of the two halves of the assembly out of a plane.
FIGS. 230 to 233 show conceptually components for building up yoke assemblies.
The other portion 6094 has a transverse arm 6106, piston mounting portion 6108 and two arms 6110 extending from adjacent the ends of the transverse arm 6106. The arms 6110 extend from the same side of the transverse arm 6106 and at their free ends have holes 6112. The transverse arm 6106 has a central bolt hole 6114.
When assembled the central arm 6100 is attached to transverse arm 6106 by a bolt passing through hole 6104 into hole 6114. Similarly arms 6110 are attached to transverse arm 6096 by bolts passing through holes 6112 into holes 6102. The bolt holes 6102 and 6114 may be threaded or unthreaded. Three bolts are required for assembly.
It will be appreciated that this configuration may only be used where the big end does not pass through the yoke.
Turning now to
In this embodiment, engagement means 7012 are centred on big end axis 7010. For each piston 7008a and 7008b, the engagement means 7012 are located to one side of the big end axis 7010.
It will be appreciated that it is best if the pistons reciprocate in a manner that they are one half of a sinewave out of phase from each other. Provided that the pistons are of the same mass, the engine will be perfectly balanced. It is also obvious that the crank disk and scotch yoke embodiments of the invention that are of V configuration may be balanced in the same way and that X, horizontally opposed or 180 degree configuration devices of the invention may also be balanced similarly.
It is also clear that an engine designer may wish to construct a fluid scotch yoke type device of a type depicted and described herein wherein a degree of imbalance is in some way preferred. Accordingly, the invention includes devices with their pistons displaced at not quite one quarter of a sine wave out from each other, say up to 10%-20% or even up to 50% of the sine wave out of true balance. This still fits broadly within the scope of the invention.
For the purpose of this discussion, the engine is a 90 degree vee twin, with the cylinders 45 degrees to the left and right of a vertical centre line. The engine is assumed to be rotating clockwise so that when the crankshaft is vertical, the left piston is going up and the right piston is at the same relative position in its cylinder but doing down.
The engine is assumed to be made up of the following components:
Crankshaft whose mass is concentrated in two positions namely the counterweight and the big-end.
Conrod whose mass is concentrated in 3 positions, the left slider, the right slider and the counterweight directly below the big-end.
The left and right pistons whose mass is assumed to be concentrated at the centre of their respective bores and some distance above the respective sliders.
The stationary parts of the engine (crank case, block, etc.) are assumed to be rigidly mounted so they can be disregarded in considering engine balance issue.
Imagine the engine is assembled, starting as follows: Install a crankshaft which is balanced on its own. That is, its centre of mass is at its centre of rotation, the main bearing. Clearly this is perfectly balanced.
Now add the component referred to as the “con-rod”. Because the left and right slider mechanisms will be above the big-end, the conrod will require its own counterweight located directly below the big-end if we want its centre of gravity to be at the big-end. If to the crankshaft counterweight is added an amount calculated from the total mass of the conrod, the centre of gravity can be kept at the main bearing and the assembly so far will still be perfectly balanced.
Note that the conrod maintains the same orientation all the time so that it is in fact “orbiting”. Because its centre of mass is at the big end, it will have no tendency to rotate as the crankshaft rotates. If the mass of the conrod counterweight is reduced, so that the conrod centre of mass was above the big-end, then the conrod would tend to rock as the crankshaft rotated. Provided it is prevented from actually rocking, its centre of mass will still describe a circle of the same radius and can still be perfectly balanced by the crankshaft counterweight.
There is thus a design choice here whether to reduce the load on the slider mechanisms by balancing the conrod or whether to reduce the mass of the conrod and the mass of the crankshaft counterweight thereby reducing inertial forces generally. An alternative would be to prevent the conrod from rotating by other means such as a second crank mechanism.
If are now added pistons, the engine is put out of balance. However, because the piston motion is perfectly simple harmonic and the pistons are 90 degrees out of phase, the two together are exactly equivalent to one piston mass travelling in a circle. It is necessary, therefore, merely to add to the crankshaft counterweight a mass calculated from the mass of one piston (and adjusted to allow for the ratio of crankshaft throw to crankshaft counterweight distance) and the whole engine remains perfectly balanced.
This is easiest to visualise if one tilts one's head to the left so that the left piston appears to be moving vertically and the right piston moving horizontally. When the left piston is at its highest point, the crankshaft counterweight is at its lowest point. At the same instant, the “right-hand” piston is at mid-stroke and travelling to the right. As far as the horizontal motion of the crankshaft counterweight is concerned, it is at midstroke and travelling to the left. The crankshaft counterweight can therefore be adjusted to exactly balance both pistons.
The centre of mass of all moving parts of the engine remains exactly stationary. There are no higher order effects as in a conventional engine. These arise because the piston motion is not simple harmonic and the motion of a conventionally driven piston is not simple harmonic and the motion of a conventionally driven piston is not symmetrical near top and bottom dead centre.
It is also interesting to note that the internal kinetic energy of the slider engine of this invention is also constant throughout its cycle. Provided the angle of the cylinders is 90 degrees, then the combined kinetic energy of the pistons is constant. This means that there is no tendency for the mechanism to resist rotating at constant angular velocity.
The following is the theory behind the balancing of the engine with offset big ends.
A is the angle between the bores of 2 cylinders in a vee engine.
D is the angle between lines extending from the main axis to the big ends.
If D is set equal to 2*(A-90), the centre of gravity of the two pistons will be found to move in a circle so that it can easily be balanced by a counterweight on the crankshaft.
If the connecting rods are allowed to pivot relative to the pistons, it is assumed that the connecting rods are sufficiently long that the motion of the pistons is simple harmonic. Where pivoting is not allowed or limited to very small amounts the motion will inherently be simple harmonic motion to practical effect.
The mass of the connecting rods is ignored.
Angles are measured positive anticlockwise from the positive X axis.
Assume the first bore is a 0 degrees.
The second bore is at an angle A degrees.
When the big end for the first piston is at 0 degrees (so that the first piston is at TDC) the big end of the second piston is at D degrees.
Consider the general case when the big end for the first piston is at R degrees and the big end of the second piston is at D+R degrees.
The X co-ordinate of the first piston is Cos(R) measured with respect to its mean position.
The Y co-ordination of the first piston is always zero.
The radius of the crankshaft for the second piston is also unit length, but in the general case under consideration, the value of the radius projected onto the axis of the second bore is Cos(A-D-R).
Since it is of interest only to look at variations in the position of the centre of gravity of the pistons, the second piston can be taken to be at:
X=Cos(A−D−R)*Cos(A)
Y=Cos(A−D−R)*Sin(A)
The centre of gravity of the two pistons together can be taken as:
X=Cos(A−D−R)*Cos(A)+Cos(R)
Y=Cos(A−D−R)*Sin(A)+0
Note that these should both be divided by 2, but this is omitted to simplify the appearance of the algebraic expressions.
It turns out that for any value of A, if D is set at D=2*(A−90), then the centre of gravity of both pistons together moves in a circle and can be easily balanced by a counterweight attached to the crankshaft.
That this is the case can be proved by substituting 2*A−180 for D in the above expressions which become
X=Cos(A−2*A+180−R)*Cos(A)+Cos(R)
Y=Cos(A−2*A+180−R)*Sin(A)+0
This is the equation of a point moving in a circle of radius Sin(A).
Thus the motion of the two pistons together can be counterbalanced by a single mass, equal in mass to one piston mass rotating on a radius of Sin(A) times the crankshaft radius. (The fact that there are actually two pistons compensates for the factor of 2 which was omitted in the expressions for X and Y above).
It will be appreciated that when A=90°, i.e. a 90° V configuration, that D=0°, i.e., the axes of the two big ends are not offset but are coaxial. Thus a 90° V configuration with a single big end is merely a special case where D=0°.
It will be apparent to those skilled in the art that many modifications and variations may be made to the embodiments described herein without departing from the spirit or scope of the invention.
The invention has industrial applicability in relation to fluid machines in general and more specifically to internal combustion engines and pumps.
| Number | Date | Country | Kind |
|---|---|---|---|
| PP9573 | Apr 1999 | AU | national |
| PQ0287 | May 1999 | AU | national |
| PQ0795 | Jun 1999 | AU | national |
| PQ0895 | Jun 1999 | AU | national |
| PQ1653 | Jul 1999 | AU | national |
| PQ1654 | Jul 1999 | AU | national |
| PQ1956 | Jul 1999 | AU | national |
| PQ2150 | Aug 1999 | AU | national |
| PQ2205 | Aug 1999 | AU | national |
| PQ2206 | Aug 1999 | AU | national |
| PQ2341 | Aug 1999 | AU | national |
| PQ2388 | Aug 1999 | AU | national |
| PQ2408 | Aug 1999 | AU | national |
| PQ2808 | Sep 1999 | AU | national |
| PQ2809 | Sep 1999 | AU | national |
This application is a continuation of, and claims the priority of the filing date and foreign priority of U.S. Ser. No. 09/937,740, presently pending, which was an application under 35 USC 371 of PCT/AU00/00281, filed Apr. 3, 2000.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 09937740 | Mar 2002 | US |
| Child | 11400027 | Apr 2006 | US |
