WO2000066913A1

WO2000066913A1 - Power transmission apparatus

Info

Publication number: WO2000066913A1
Application number: PCT/AU2000/000369
Authority: WO
Inventors: Peter Bortolin
Original assignee: Peter Bortolin
Priority date: 1999-04-30
Filing date: 2000-04-27
Publication date: 2000-11-09

Abstract

A crank mechanism (10) for an internal combustion engine includes a connecting rod (11) extending to a piston. The mechanism (10) includes a support (12) which rotatably supports a primary shaft (13) for rotation about a longitudinal axis (14). Fixed to but spaced laterally to the primary shaft (13) is a link shaft (16) having a longitudinal axis (15). In operation, the shaft (16) together with its axis (15) rotates about the longitudinal axis (14). Rotatably supported on the shaft (16) is an external gear (17) meshingly engaged with a stationary internal gear (18). The gear (17) when driven rotates about the longitudinal axis (15) while the longitudinal axis (15) rotates about the axis (14) in the opposite rotational direction. This motion therefore causes rotation of the shaft (13) about the axis (14) in the opposite direction to the arrow.

Description

POWER TRANSMISSION APPARATUS

Technical Field

The present invention relates to crank mechanisms and more particularly, but not exclusively, to crank mechanisms for internal combustion engines. The present invention also relates to power transmission apparatus and more particularly, but not exclusively, to crank mechanisms employed in internal combustion engines, both two stroke and four stroke engines.

Background of the Invention

Internal combustion engines are limited in that the torque applied to the crank is limited by the configuration of the crank mechanism. Still further, internal combustion engines have the disadvantage that the connecting rod between the crank shaft and the piston applies a lateral force to the crank shaft. More generally, internal combustion engines are limited as best advantage is not taken of the forces applied to the piston in generating torque. A further disadvantage of known internal combustion engines is that the combustion process is often not efficiently executed. Furthermore, best advantage of the force is applied to the piston when the piston is adjacent top dead centre.

Object of the Invention

It is the object of the present invention to overcome or substantially ameliorate at least one of the above disadvantages and/or more generally to provide an improved power transmission apparatus.

Summary of the Invention

There is disclosed herein a crank assembly having: a primary shaft having a longitudinal axis about which the primary shaft is driven; a link shaft having a longitudinal axis and being attached to the primary shaft to transmit power thereto; coupling means attaching the link shaft to the primary shaft so as to provide for rotation of the link shaft about the longitudinal axis of the link shaft, as well as rotation of the longitudinal axis of the link shaft about the longitudinal axis of the primary shaft; means engaging the link shaft to govern rotation of the longitudinal axis of the link shaft about the longitudinal axis of the primary shaft; an internal gear surrounding the longitudinal axis of the link shaft; an external gear mounted on the link shaft and fixed thereto while being meshingly engaged with the internal gear so that rotation of the longitudinal axis of the link shaft about the longitudinal axis of the primary shaft will cause rotation of the link shaft about the longitudinal axis of the link shaft, the external gear being maintained in meshing engagement with the internal gear by the means engaging the link shaft; a connecting rod being attached to the link shaft at a position spaced radially from the longitudinal axis of the link shaft; and wherein the crank assembly is configured such that the position at which the connecting rod is attached to the link shaft is caused to reciprocate linearly along a path intersecting the longitudinal axis of the primary shaft.

There is further disclosed herein a drive assembly having: a primary shaft having a longitudinal axis about which the primary shaft is driven; an internal gear surrounding the primary shaft; an external gear meshingly engaged with the internal gear so that upon the external gear being driven the external gear has cause to rotate about the longitudinal axis of the external gear as well as the longitudinal axis of the primary shaft; means operatively extending between the external gear and the primary shaft so that rotation of the external gear causes rotation of the primary shaft; a drive member connected to the external gear at a predetermined position spaced from the longitudinal axis of the external gear; and said drive assembly is configured so that said predetermined position reciprocates along a linear path passing through the longitudinal axis of the primary shaft.

There is further disclosed herein a power transmission apparatus including: a base; a driven shaft rotatably supported by the base; an internal gear surrounding the shaft and fixed to the base; an arm fixed to the shaft and extending generally radially therefrom; a planetary gear fixed to the arm and meshingly engaged with the internal gear so that rotation of said planetary gear causes rotation of said shaft; a connecting rod rotatably attached to the planetary gear so that a piston driving said connecting rod causes rotation of said planetary gear, said connecting rod being attached to said planetary gear at a predetermined position on said planetary gear; and wherein said predetermined location reciprocates along a general linear path.

Preferably said connecting rod angularly oscillates across a transverse axis of said shaft, with said predetermined path being inclined with respect thereto by an acute angle.

There is further disclosed herein a power transmission apparatus including: a base; a connecting rod to be driven by a linearly reciprocating piston; a driven shaft having a crank arm rotatably attached to the connecting rod so as to be driven thereby; a bearing assembly supporting the shaft for rotation about the longitudinal axis of the shaft; a bearing support engaging said assembly to enable said assembly to reciprocate along a path generally perpendicular to said axis; a cam surface surrounding said shaft and fixed to said base; and a am arm including a cam follower attached to said shaft and engaged with said cam surface so that movement of said connecting rod to drive said shaft causes movement of said cam follower along said surface.

Preferably the bearing support includes a guide surface or surfaces which cause movement of the assembly in a direction along a line that is at an acute angle with respect to a line along which said piston reciprocates.

Brief Description of the Drawings

Preferred forms of the present invention will now be described by way of example with reference to the accompanying drawings, wherein:

Figure 1 is a schematic end elevation of a crank mechanism;

Figure 2 is a schematic side elevation of the crank mechanism of Figure 1;

Figure 3 is a schematic end elevation of a further crank mechanism;

Figure 4 is a schematic end elevation of a further crank mechanism for an internal combustion engine; Figure 5 is a schematic end elevation of a crank assembly of an internal combustion engine;

Description of the Preferred Embodiments

In Figures 1 and 2 of the accompanying drawings there is schematically depicted a crank mechanism 10 for an internal combustion engine. The crank mechanism 10 includes a connecting rod 11 extending to a piston of the internal combustion engine. Accordingly, the connecting rod 11 is driven.

The crank mechanism 10 includes a support 12 which rotatably supports a primary shaft 13 for rotation about the longitudinal axis 14. The primary shaft 13 is preferably attached to a flywheel (not illustrated).

Fixed to but spaced laterally of the primary shaft 13 is a link shaft 16 having a longitudinal axis 15. In operation, the shaft 16, together with its axis 15 rotates about the longitudinal axis 14.

Rotatably supported on the shaft 16 is an external gear 17, meshingly engaged with a stationary internal gear 18. The connecting rod 11 is rotatably attached to the gear 17 at a position spaced radially from the axis 15.

In this embodiment, the gear 17 when driven rotates in the direction of the arrow 19 about a longitudinal axis 15 while the longitudinal axis 15 rotates about the axis 14 in the opposite rotational direction. This motion therefore causes rotation of the shaft 13 about the axis 14 in the opposite direction to the arrow 19.

The connecting rod 11 is attached to the gear 17 by means of a shaft 20 attached to the gear 17. More particularly, the configuration of the gears 17 and 18 and more particularly the configuration of the crank mechanism 10 is such that the shaft 20 is caused to reciprocate along a linear path 21 passing through the axis 14.

In Figure 2 it should be appreciated that two of the gears 18 are illustrated, with a pair of gears 17 associated therewith. The shaft 20 extends between the gears 17. With the above described preferred embodiment, the connecting rod 11 is subjected to axial loads which apply a force to the piston only in the longitudinal direction of movement of the piston, as opposed to standard internal combustion engines in which the connecting rod also applies a lateral force to the piston.

In Figure 3 there is schematically depicted a crank mechanism 50. In this embodiment the crank mechanism 50 includes an internal gear 51 meshingly engaged with an external gear 52. The external gear 52 is driven by the connecting rod 53 attached to the gear 52 adjacent to the periphery thereof. The gear 52 is provided with a further external gear 54 which is meshingly engaged with a gear 55 attached to the crank shaft 56. When the gear 52 is driven by the connecting rod 53, the gear 52 rotates in the direction of the arrow 57 about the longitudinal axis of the gear 52. Due to the meshing engagement of the gears 51 and 52, the longitudinal axis of the gear 52 will rotate about the longitudinal axis of the crank shaft 56 in the direction of the arrow 58. Meshing engagement of the gears 54 and 55 will cause rotation of the crank shaft 56 in the direction of the arrow 59.

The connecting rod 53 is attached to the gear 52 by means of a bearing 60. It should be further appreciated that the gears 54 and 55 maintain the gear 52 in meshing engagement with the gear 51.

In the embodiment of Figure 3, the gears 51, 52, 54 and 55 are configured so that the longitudinal axis of the gear 52 reciprocates along a linear path 61 passing through the longitudinal axis of the main shaft 56.

With reference to Figure 3, it should be appreciated that the pivot attachment provided by the shaft oscillates along the axis as previously discussed. This has a number of advantages including shorter travel of the shaft relative to conventional reciprocating engines. As the shaft travels along a diameter, its path of travel is shorter relative to the normal angular path followed by the connection onto the crank of previously available internal combustion engines. In Figure 4 of the accompanying drawings there is schematically depicted a crank assembly 150 of an internal combustion engine. The crank assembly 150 includes a driven shaft 151 rotatably supported on a base 152 by means of a bearing 153. Extending from the shaft 151 is a crank arm 154 terminating at its radial extremity with a bearing 155. The bearing 155 supports a planetary gear 156 meshingly engaged with an internal gear 157. The gear 157 is also mounted on the base 152.

Rotatably attached to the gear 156 is a connecting rod 158 by means of a bearing 159 and connecting pin 160, attached to the gear 156.

Upon a driving force being applied to the connecting rod 158 the gear 156 is caused to move in the direction of the arrow 161, while the arm 154 moves in the direction of the arrow 162.

In the embodiment of Figure 4 the gear 156 has a diameter a third of the diameter of the gear 157 so that the gear 156 rotates three times about its supporting shaft 163 for every single rotation of the shaft 151. Still further the internal combustion engine would be configured and the pin 161 located so that the combustion forces would be applied to the connecting rod 158 at a position displaced from "top dead centre" as illustrated in Figure 4.

In the embodiment of Figure 4 a particular advantage is that a power stroke of the connecting rod takes place for every single rotation of the shaft.

In Figure 5 there is schematically depicted the crank assembly 310 of an internal combustion engine. The engine includes a connecting rod 311 attached to the main shaft 313 by a crank arm 314 of the shaft 313. More particularly, a bearing 312 connects the connecting rod 311 and arm 314 so that relative rotation is permitted.

The shaft 313 is supported in a bearing assembly 315 including a bearing 316. The bearing assembly 315 is received within a rectangular aperture 317 so as to permit reciprocation of the bearing 316 along the axis 332 of the aperture 317. The axis 332 is generally perpendicular to the longitudinal axis of the shaft 313, but is offset at an acute angle with respect to the centre line 318 of the arm 314. The longitudinal centre line 318 of the arm 314 is preferably substantially co-linear with the axis along which the above mentioned piston moves.

The aperture 317 has guide surfaces 319 which are part of the engine base 320. These guide surfaces 319 are parallel with the axis 332.

Extending from the shaft 313 is a cam arm 321 including a cam follower

322 which may be a bearing. The cam follower 322 engages a cam surface

323 formed in the base 320. The surface 323 has surface lobes 324 and

325.

For the purpose of description, it should be appreciated that within half a revolution of the mechanism, the crank 314 moves down and up to its original position. That is, the crank spends more time in the up position than the down position. For example, at about the 40° position of the crank arm 318 the crank bearing 316 has already moved to the bottom position of the aperture 317. At approximately the 100-115° position indicated, the crank starts to rise whereas at the 180° position (facing downward), the crank has moved back to the top position and stays at the top position until the crank returns to its 0° position as depicted.

The above described preferred embodiment of the present invention has a number of advantages including eliminating problems associated with a piston being at "top dead centre". Additional torque is generated by interaction between the surfaces 324 and 325 and the cam follower 322. Still further maximum torque is generated when the piston is at "top dead centre".

It should be appreciated that modifications and alterations obvious to those skilled in the art are not to be considered as beyond the scope of the present invention. For example, although the drawings depict a drive mechanism for an internal combustion engine having only one piston, any number of pistons could be provided. For example, in Figure 7, there could be another piston attached to the crankshaft 13, which piston might be attached to a crank arm at a 180° offset from crank arm 14.

Of note in the present invention is that the crankshaft generaly returns to its original position by the time the crank arm has reached the bottom of the stroke (180°) and maintained at that position until the upward stroke is completed.

Claims

1. A crank assembly having: a primary shaft having a longitudinal axis about which the primary shaft is driven; a link shaft having a longitudinal axis and being attached to the primary shaft to transmit power thereto; coupling means attaching the link shaft to the primary shaft so as to provide for rotation of the link shaft about the lingitudinal axis of the link shaft, as well as rotation of the longitudinal axis of the link shaft about the longitudinal axis of the primary shaft; means engaging the link shaft to govern rotation of the longitudinal axis of the link shaft about the longitudinal axis of the primary shaft; an internal gear surrounding the longitudinal axis of the link shaft; an external gear mounted on the link shaft and fixed thereto while being meshingly engaged with the internal gear so that rotation of the longitudinal axis of the link shaft about the longitudinal axis of the link shaft, the external gear being maintained in meshing engagement with the internal gear by the means engaging the link shaft; a connecting rod being attached to the link shaft at a position spaced radially from the longitudinal axis of the link shaft; and wherein the crank assembly is configured such that the position at which the connecting rod is attached to the link shaft is caused to reciprocate linearly along a path intersecting the longitudinal axis of the primary shaft.

2. A drive assembly having: a primary shaft having a longitudinal axis about which the primary shaft is driven; an internal gear surrounding the primary shaft; an external gear meshingly engaged with the internal gear so that upon the external gear being driven the external gear has cause to rotate about the longitudinal axis of the external gear as well as the longitudinal axis of the primary shaft; means operatively extending between the external gear and the primary shaft so that the rotation of the external gear causes rotation of the primary shaft; a drive member connected to the external gear at a predetermined position spaced from the longitudinal axis of the external gear; and said drive assembly is configured so that said predetermined position reciprocates along a linear path passing through the longitudinal axis of the primary shaft.

3. A power transmission apparatus including: a base; a driven shaft rotatably supported by the base; an arm fixed to the shaft and extending generally radially therefrom; a planetary gear fixed to the arm and meschingly engaged with the internal gear so that rotation of said planetary gear causes rotation of said shaft; a connecting rod rotatably attached to the planetary gear so that a piston driving said connecting rod causes rotation of said planetary gear, said connecting rod being attached to said planetary gear at a predetermined location on said planetary gear; and wherein said predetermined location reciprocates along a general linear path.

4. The apparatus of claims 3 wherein said connecting rod angularly oscillates across a transverse axis of said shaft, with said predetermined path being inclined with respect thereto by an acute angle.

5. A power transmission apparatus including: a base; a connecting rod to be driven by a linearly reciprocated piston; a driven shaft having a crank arm rotatably attached to the connecting arm so as to be driven thereby; a bearing assembly supporting the shaft for rotation about the longitudinal axis of the shaft; a bearing support engaging said assembly to enable said assembly to reciprocate along a path generally perpendicular to said axis; a cam surface surrounding said shaft and fixed to said base; and a cam arm including a cam follower attached to said shaft and engaged with said cam surface so that movement of said connecting rod to drive said shaft causes movement of said cam follower along said surface.