WO1990002247A1

WO1990002247A1 - Wobble ball/plate engine mechanism

Info

Publication number: WO1990002247A1
Application number: PCT/AU1989/000339
Authority: WO
Inventors: Joseph Scalzo
Original assignee: Scalzo Patents Pty. Ltd.
Priority date: 1988-08-16
Filing date: 1989-08-08
Publication date: 1990-03-08

Abstract

An engine mechanism (10) has an output member (16) rotatable on a main axis (A) in a cylinder block (12). A wobble member (30) defines a part spherical surface (34) having a centre of curvature on axis (A), and arms (28) in a plane (X) inclined to axis (A). Each arm (28) has a piston (26) reciprocable on an axis (P) in a respective cylinder (24) parallel to axis (A). A bearing member (36) defines a part spherical surface (38) complementary to, and in sliding contact with, surface (34). A coupling (66) pivotally inter-connects member (30) and member (16) at respective first and second locations spaced laterally from axis (A). The first location at member (30) is able to orbit around axis (A) and is on a line (B) which is perpendicular to plane (X) and passes through the centres of curvature of surfaces (34 and 38). Member (30) is constrained by coupling (66) against rotation on axis (A), while allowing its arms (28) to traverse a lemniscate path dictated by the inclination of plane (X) to axis (A), with orbital movement of the first location about axis (A) and rotation of member (16).

Description

OBBLE BALL/PLATE ENGINE MECHANISM

This invention relates to improved forms of wobble plate mechanisms of the fixed and variable displacement types which are applicable to internal and external combustion engines and pumps.

Conventional wobble plate engine mechanisms include a cylinder block having a mainshaft rotatable therein; a drive hub obliquely mounted on the mainshaft for rotation therewith; a wobble plate rotatably mounted on the drive hub; and a plurality of cylinders arranged in the cylinder block around the mainshaft, each with a piston reciprocally movable therein along a respective axis substantially parallel to the rotational axis of the mainshaft. Each piston is coupled to a respective arm of the wobble plate; the coupling between each piston and respective arm typically being via a gudgeon pin and crosshead reciprocable in a bore of an extension of the piston. As the output shaft rotates, each piston is forced to reciprocate in its cylinder, and reciprocation of the pistons correspondingly causes the output shaft to rotate. Also, as the mainshaft and drive hub rotate, each arm of the wobble plate traverses a lemniscate path (a figure of eight on the surface of a sphere). This movement is accomodated in the wobble plate/piston couplings by the radial freedom afforded by the crosshead in the piston extension bore and tangential freedom afforded by endwise movement of the gudgeon pin, with its arm, in the crosshead bore.

Almost all previous designs of such wobble plate engine mechanisms have relied in mounting the wobble plate on the drive hub via radial and thrust bearings. This arrangement has contributed to very high frictional losses and has made the incorporation of an effective stabilising mechanism very difficult to achieve, to the extent that these type of engines generally could not be regarded as viable alternatives to the conventional cranked engines. In addition, the wobble plate/gudgeon pin/crosshead/piston extension/C-shape bore interfaces, commonly found in this type of engine, contribute to high frictional losses, particularly at high speeds, tending to make the overall engine uncompetitive and uneconomical.

Stabilisation of the wobble plate, to achieve the correct lemniscate path of each arm throughout a cycle, is important to assist in the balancing and internal motion of the .engine. Previous attempts to provide stabilisation of the wobble plate generally have proved to be unworkable, complicated, large power absorbers, unstable and/or bulky, but more importantly, they usually have been, unable to operate at high speeds consistent with modern high speed engines.

The present invention is directed at addressing the problems associated with the wobble plate bearings and high speed stabilisation. The invention is directed to providing improved mechanisms comprising wobble plate arrangements. The invention also provides arrangements of constant velocity couplings providing stabilisation, and methods of altering the angle and position of the wobble plate or ball fo.r altering the displacement of the engine.

In each form, the improved engine mechanisms of the invention includes a cylinder block with a plurality of cylinders arranged around its circumference parallel to the rotational axis of the camshaft drive and output member. However, before proceeding with description of the invention, it is appropriate to draw attention to the need for a departure from usual terminology. Generally, that referred to as the wobble plate has a body of relatively simple, annular form, with thrust and radial bearings being provided between its inner circumference and the drive hub. The present invention departs from such arrangement by one or other of two variants in which components normally identified as a wobble plates are herein collectively identified as wobble members. In a first of those variants, the wobble member has a body of annular section, but has a part spherical external surface beyond which extend the radial arms for connection to the pistons. For ease of identification, the wobble member according to that first variant is referred to individually as a wobble ball. In a second variant, the wobble member is of annular section, but has a part spherical internal surface and, as it otherwise is analogous to the conventional wobble plate, it is identified individually by that designation. In each case, an engine mechanism according to the invention will be designated as being of the wobble plate type.

According to the invention, there is provided an engine mechanism of the wobble plate type, the mechanism including a cylinder block having an output member rotatable therein about an axis of rotation (herein referred to as the main axis); a wobble member defining a part spherical surface which has a centre of curvature substantially co-incident with the main axis, the wobble member having a plurality of arms (typically five) spaced therearound and each extending in a plane which is oblique with respect to the main axis; a plurality of cylinders arranged around the main axis, each with a piston reciprocally movable therein along a respective piston axis substantially parallel to the main axis, each piston being coupled to a respective arm of the wobble member; a bearing member defining a part spherical surface which has a centre of curvature substantially co-incident with the main axis and provides a bearing surface complementary to, and in sliding contact with, the part spherical surface of the wobble member; and a coupling member pivotally connected to the wobble member and the output member, the coupling member being pivotally connected to the wobble member at a location spaced laterally from said main axis and from its connection to the output member, said location being located on a line which passes through the centre of curvature of the respective part spherical surface of the wobble member and the bearing and which is substantially perpendicular to the plane in which said arms extend. The arrangement is such that the wobble member is constrained by the coupling member so as to be non-rotatable with respect to the main axis, while allowing its arms to traverse lemniscate paths dictated by the inclination, with respect to the main axis, of the plane in which the arms extend and such that, during such movement of the arms, the output member rotates as a consequence of orbital movement around the main axis of the connection between the wobble member and the coupling member.

In a first variant, the wobble member is a wobble ball having a body defining an external surface providing the part spherical surface. In such case, the arms of the wobble ball extend radially outwardly with respect to, preferably from, that part spherical surface. Also in that variant, the bearing member partially encloses the body of the wobble ball, with its part spherical surface being an internal surface thereof. The bearing member defines a plurality of openings through which the arms of the wobble ball extend. The bearing member preferably is formed of at least two parts for ease of its assembly in relation to the wobble ball, with the parts being releasably secured together such as by bolts. In a second variant, the wobble member is a wobble plate having an annular body of which a radially inner circumference defines an internal said part spherical surface, with the arms extending, such as in a conventional arrangement from an outer circumferential surface. In that second variant, the bearing member is located within the body of the wobble plate, with its part spherical bearing surface being an external surface.

The engine mechanism according to the invention may be of a fixed or variable displacement type. In the case of a fixed displacement mechanism, the wobble member is secured so that the centre of curvature of its part spherical surface remains at a fixed location on the main axis. The plane in which its arms extend thus remains at a constant inclination to the main axis. Such fixed displacement arrangement preferably is retained by the bearing member being secured against movement along the main axis and/or by the coupling member between the wobble member and output member restraining the wobble member such that the centre of curvature of its part spherical surface is fixed in relation to the main axis.

In the case of a variable displacement mechanism, the wobble member and the bearing member are movable together to adjust the location of the centres of curvature of their respective part spherical surfaces along the main axis. As a consequence of such movement, the inclination and position of the plane in which the arms wobble member extends is varied relative to the main axis, thereby adjusting the stroke of the pistons. The engine mechanism preferably has a drawing mechanism which is operable to draw the bearing member and, with it, the wobble member, along the main axis. The drawing member preferably is continuously, and reversably, operable to move the wobble and bearing members between two extreme conditions setting maximum and minimum inclinations of the wobble .member arms and corresponding variation in engine displacement.

In the first variant utilising the wobble ball, the latter may have a short radial shaft, which is perpendicular to the plane of its arms, and by which the wobble ball is connected to the output member by the coupling member. The shaft preferably is connected via a bearing and trunnion to the coupling member, with the latter preferably being a link system which allows the inclination of the wobble ball shaft to be altered relative to the main axis of the output, member. A non-rotating but mutating constant velocity (CV) coupling preferably is placed between the wobble ball and the bearing member, along the main axis. The centre of the CV coupling (or CV coupling system) most preferably is substantially at the centre of the wobble ball and in the plane in which the arms extend, to allow the wobble ball arms to traverse a lemniscate path dictated by the inclination of the arms and that plane relative to the main axis, as the output member rotates. For an engine to be kinematically stable at all variable displacement positions, the respective lemniscate path corresponding to each angular position of the wobble ball, must be allowed to occur. In the second variant utilising a wobble plate arrangement, the wobble plate may be connected to a radial shaft within the bearing member by radial pins which extend through slots in the bearing member. The coupling member may connect the wobble plate to the output member via such shaft, such as via a trunnion. The radial shaft moves in unison with the wobble plate and rotates the output member via a bearing and the trunnion. The coupling member may comprises a link system similar to that detailed in relation to the wobble ball arrangement. A mutating constant velocity coupling system preferably joins the bearing member and the radial shaft thus allowing the wobble plate, via the radial shaft, to move through its lemniscate path. The part spherical surface of the wobble member most preferably is hardened to enhance wear resistance. The complementary surface of the bearing member may be lined with a suitable bearing material, or the bearing member may be formed from a suitable bearing material. The wobble plate arrangement allows a greater bearing surface area between its part spherical surface and the part spherical surface of the bearing member, and is likely to be better suited to larger engines.

An important aspect of the invention is the adoption of a constant velocity joint within a non-rotating but mutating wobble member for effective stabilisation, thus eliminating large rotating thrust and radial bearings a_.nd other power absorbing elements normally found in most other previous designs. The constant velocity coupling between the wobble ball and bearing member can take many forms. A single CV joint can be used provided that it can withstand high angularity, in the order of 20 degrees, high orbiting speeds in excess of 6000 rpm, high peak torque reaction generated within an engine, and long operating life. Known designs of single CV joints are normally not capable of meeting this specification and the preferred form of the CV stabilising arrangement is for the adoption of a double constant velocity joint or a double Cardan joint. This arrangement allows for the maximum angularity to be halved through each CV joint and thus enables the requirements of an engine to be satisfied.

In each variable displacement form of the invention means most preferably are provided for the balancing of the engine at every stroke position by variable weights on diagonally opposite sides of the plane in which the arms of the wobble member extend.

The invention will now be described, by way of example only with reference to the accompanying drawings in which:

Figure 1 is a longitudinal cross section of a wobble plate type of engine mechanism, according to one embodiment of the invention, showing one piston in the bottom dead centre position and the engine in the maximum displacement position.

Figure 2 is a longitudinal cross section of an engine mechanism according to another embodiment, illustrating aspects of the invention with one piston in the bottom dead centre position and the engine in the maximum displacement position;

Figure 3 shows an alternative variable stroke adjusting mechanism using a sliding member within the output member; Figure 4 is a cross sectional view of an alternative CV joint using two Cardan type of couplings adaptable to the respective embodiments Figures 1 and 2;

Figure 5 is a cross sectional view of the connection of Figure 1 (but able to be used in Figure 2), between the piston and wobble member; and

Figure 6 is a part section showing the connection, common to Figures 1 and 2, between the wobble member orbiting radial shaft and the output member via a trunnion and link system. In Figure 1, the engine mechanism 10 is shown in sufficient detail to enable a full appreciation of its construction and operation. Mechanism 10 has a cylinder block 12 with an associated rear case 14, and an output member 16 rotatable on main axis of rotation A in bearings 18 in rear case 14 and bearings 20 in a support plate 22 mounted on case 14. Block 12 defines a plurality of cylinders 24 spaced uniformly around main axis A, with each cylinder 24 having a piston 26 coupled to a respective arm 28 of wobble member 30. Typically there are five arms 28 uniformly spaced around member 30, with a corresponding number of pistons 26. Each piston

26 is reciprocable in its cylinder 24 along a respective axis P, parallel to main axis A, by or to cause rotation of output member 16.

Wobble member 30 is of a form identified herein as a wobble ball. It has a body 32 which defines a part spherical outer surface 34 from which its arms 28 extend radially. Each arm 28 has its centre line in a common plane X which is inclined with respect to, and extends transversely of, main axis A. The centre of curvature of part spherical surface 34 is substantially co-incident with the intersection of axis A and plane X.

Within rear case 14 and extending around axis A, there is a bearing member or socket 36 in which body 32 of wobble ball 30 is held. Socket 36 defines a part spherical inner surface 38 which has a centre of curvature substantially co-incident with that of surface

34 of body 32. Surface 38 preferably is lined with a bearing surface 40 in smooth, sliding contact with surface 34. Alternatively, socket 36 is made of a suitable bearing material, or provision is made for the supply of lubricant between surfaces 34 and 38, or surface 34 is coated with a suitable bearing material. Surface 34 preferably is hardened if surface 38 is lined or socket 36 is made of, a suitable bearing material, while surface 38 preferably is hardened if surface 34 is coated with such material. One or both of surfaces 34 and 38 may be hardened if provision is made for supply of lubricant therebetween.

Socket 36 defines around axis A a number of openings

41 through each of which a respective arm 28 extends.

Each opening 41 is of a width, circumferentially around axis A, sufficient to provide clearance to each side of its arm 28 during its lemniscate movement. Also, parallel to axis A, each opening 41 is of a length sufficient to provide clearance for such movement of its arm 28 as the corresponding piston 26 reciprocates between from its top dead centre to its bottom dead centre position. In each case, the clearances are to allow for movement of the arm 28 in a lemniscate path, while the clearances parallel to axis A are to be sufficient to accommodate variation in such lemniscate movement with variation in the stroke of pistons 26, as hereinafter explained.

Socket 36 is mounted in bore 42 which is defined by rear case 14 and extends parallel to main axis A. Bore 42 allows socket 36 to slide axially therein, but constrains socket 36 against rotation with respect to axis . A. Such constraint may be provided by any convenient arrangement, such as by at least one key-way inter-fitting between bore 42 and socket 36 along a line parallel to axis A. . At its side remote from output member 16, socket 36 has an annular extension 44 substantially concentric with axis A. An annular piston member 46 is coupled to extension 44, by bolts 48, so as to be axially in line therewith. Piston member 46 is located in bore 48 of cylinder member 50 secured in cylinder block 12, with piston and cylinder members 46,50 having opposed flanges 52,54 carrying respective seals 56,58. Oil under pressure is able to be supplied via passage 60, by an external pump (not shown) , and is applied between flanges 52,54 to draw piston member 46, and also socket 36 and wobble ball 30, to the left as mechanism 10 is viewed in Figure 1. Such movement to the left, as hereinafter will be apparent, increases the angle of inclination of plane X with respect to axis A, decreasing the stroke of pistons 26 and, hence, the displacement of mechanism 10. Movement to the right has the opposite consequences.

In the arrangement illustrated, the assembly of piston and cylinder members 46,50 in effect is a piston/cylinder of a single acting configuration. However, it may be required to be of a double acting configuration, enabling positive oil pressure movement of socket 36 in either direction. Under normal engine operating condition, positive oil pressure movement to increase engine displacement is not required as the engine can be designed to have at all times an axial force in the direction to increase engine displacement.

At its side remote from extension 44, wobble ball 30 has a radial shaft 62 located within annular body 64 of output member 16. Shaft 62 has an axis B which is substantially perpendicular to plane X and which substantially passes through the intersection of plane X and main axis A. As shown in Figures 1 and 6, a coupling member comprising split link 66 connects wobble ball 30, via its shaft 62, to output member 16. Link 66 is pivotally connected to shaft 62 by thrust and radial bearings 68 and 70, respectively, and a trunnion 72 connected to link 66. The pivotal connection between link 66 and shaft 62 enables pivoting of link 66 relative to shaft 62 on axis C of trunnion 72. Axis C is located to one side of axis A and is both substantially parallel to plane X and substantially normal to and intersects axis B. Link 66 is pivotally connected, at its end remote from shaft 62, to output member 16 by anchor pin 74. The pivotal connection provided by pin 74 enables pivoting of link 66 relative to member 16 on axis D of pin 74, with axis D being substantially parallel to axis C, but offset to the other side of axis A from axis C. Thrust pads 76 between trunnion 72 and parallel surfaces 78 defined by body 64 of output member 16 locate trunnion 72 centrally with respect to -a plane common to axes A and B. Thrust and radial bearings 68, 70 respectively may be replaced by a self-aligning bearing combination to allow for deflection of shaft 62 and/or misalignment between shaft 62 and trunnion 72.

In the arrangement of mechanism 10 thus far described, reciprocation of pistons 26 causes lemniscate movement of arms 28 and corresponding movement of body 32 of wobble ball 30 in socket 36. In such movement of body 32, bearing surface 40 enables surface 34 of body 32 to slide over surface 38 of socket 36. The movement of body

32 causes shaft 62 to orbit around main axis A, at a constant inclination of its axis B with respect to axis A while the inclination of plane X is constant with respect to axis A. Due to link 66 coupling shaft 62 and output member 16, the latter is caused to rotate on axis A by the orbiting movement of shaft 62. The overall relationship, of course, is reversed if output member 16 is caused to rotate on axis A, causing reciprocation of pistons 26.

If piston 46 is moved along axis A, socket 36 and wobble ball 30 are moved in the same direction, causing a change in the inclination of arms 28 and plane X with respect to axis A. Resultant change in the inclination of shaft 62 and axis B with respect to axis A is enabled by corresponding pivoting of link 66 on axes C and D; with thrust pads 76 sliding along surfaces 78, parallel to axis A, due to consequential movement of trunnion 72. Each arm 28 of wobble ball 30, as shown in Figure 5, is connected to a respective piston 26 via a tangential gudgeon pin 80 rotatable, but not slidable, in a cross-head 81 of supporting connecting rod 82, by a bearing 83 secured by bearing retainer 84. The other end of connecting rod 82 contains a ball joint 85 coupled to a gudgeon pin 86 of piston 26. The overall connection allows for the motion of the centre point of the arm 28 at the centre point of gudgeon pin 80 to perform the required lemniscate motion corresponding to each stroke position.

For correct engine operation the wobble ball 30 must be prevented from rotating, but the locus of any point on a plane radiating from the centre, as in the case of the centre of gudgeon pin 80, must be allowed to move through a lemniscate motion which is dictated by the radius of the point and the angle of plane X relative to main axis A. This correct motion is achieved by a constant velocity (CV) coupling assembly 87 between the wobble ball 30 and non-rotatable socket 36. Any type of CV coupling can be used, provided that it can withstand the high speeds and loads inherent in an engine, and at large angles usually in the order of 20 degrees from main axis A. Normally CV couplings are not able to handle large angularities at high speeds, together with high peak torque loads. However, .in the embodiment shown in Figure 1, a double CV coupling is employed. This has the effect of halving the angle of each CV coupling and thus substantially improving its speed capabilities. The CV coupling assembly 87 shown in Figure 1 comprises two ball-in-groove CV couplings, one of the plunging type 87a. and the other of the fixed type 87b. to allow small linear adjustment during engine stroke changes. The location of the centre of each CV coupling 87a.,87b must be substantially equi-distant from the centre of curvature of wobble ball 30 along axes A and B, respectively. Plunging CV coupling 87a. has an inner race 88 fixed by extension 89 thereof to extension 44 of socket 36 by bolts 48 along axis A. A combined outer race 90 joins the two CV couplings via their respective balls 91 and 92 and cages 93 and 94. In this arrangement, a central plane Y of the combined CV coupling, radial to the centre line of outer race 90, substantially bisects the angle between plane X and a plane Z perpendicular to axis A at its intersection with plane X. Plane Y is the bisecting plane and determines the lemniscate motion of each arm 28.

A drive at the side of wobble ball 30 remote from output member 16 is provided for the camshaft and balance weight arrangements. This is achieved by a tongue and groove connection 95 at the centre of wobble ball 30 by shaft 96 rotating in sleeve 97 of splined connector 98 and shaft 99 rotating in inner race 88; with shafts 96 and 99 each supported on bearings 96a., 99a.. The orbiting motion of radial shaft 62 causes shaft 96 to rotate and in turn rotates shaft 99 via the tonge and groove connection 95.

Variation in the engine stroke is achieved by the axial movement of socket 36 along main axis A of engine mechanism 10 by hydraulic piston 46. This axial movement causes wobble ball 30 within the socket 36 to change its angle of inclination determined by the geometric position of anchor pin 74 and the centre of trunnion 72 relative to the centre of. wobble ball 36. The geometry of these three points also determines the compression ratio variation between the maximum and minimum stroke positions.

The engine mechanism 10 requires to be in static and couple balance at all stroke positions. Dynamic balance is achieved by placing balance weights diagonally opposite from the centre of wobble ball 30 to balance the couple created by the reciprocating and wobbling components. The output member 16 can be constructed in such a manner that there is a weight bias towards the anchor pin 74 side of main axis A plus part of a variable balance ring 101 radially slidable on two rods 102 within the output member 16. Gear segments 103 fixed to either side of the anchor pin 74 mate with gear racks 104 machined into the rods 102, and allow the balance ring 101 to be moved radially in the opposite direction to the movement of radial shaft 62 as radial shaft 62 is moved nearer to main axis A, as would be the case when the engine 10 moves from maximum to minimum stroke. By suitable design of the movement of balance ring 101, both the static and couple balance can be varied by a single movement to either perfectly balance the engine at every stroke position or to reach acceptable balance conditions. Alternatively lever, cam and gear mechanisms driven by the movement of anchor pin 74 and split link 66, can be designed to achieve the desired movement of balance ring 101.

The balance weights 105 and 106 driven by shaft 99 are axially located by bearing 107 and plate 108. Oppositely inclined keys 109 (or splines) on shaft 99 mate with corresponding slots 109a. in weights 105 and 106. Axial movement of shaft 99 causes weights 102 and 106 to rotate in opposite directions by less than 90 degrees, causing the centre of mass to be altered relative to main axis A. The inclination of keys 109 to axis A is dependent on the rate of effective change of mass required to balance the engine through its stroke variation range. In the engine mechanism 110 shown in Figure 2, components corresponding or equivalent to components of mechanism 10 of Figure 1 are identified by the same reference numeral, plus 100. In essence, mechanism 110 differs from mechanism 10 principally in that wobble member or plate 130 and its socket 136 of Figure 2 are of a converse or inverted construction, compared with wobble ball 30 and socket 36 of Figure 1. Thus, wobble plate 130 surrounds socket 136, with plate 130 having a part spherical internal surface 134 which is slidable on a part spherical external surface 138 of socket 136. Also, openings for arms 128 or wobble plate 130 are not required in socket 136. Rather, socket 136 is provided with openings 141 by which wobble plate 130 is connected to part spherical body 143 of hub member 145 by respective pins 147 in line with each arm 128. Hub member 145 thus is made integral with", and forms part of, wobble plate 130 and is provided with shaft 162.

Hub member 145 most conveniently is of integral construction. Socket 136 preferably is formed of at least two parts for ease of assembly around body 143 of member 145, with the parts of socket 136 being releaseably secured together by bolts (not shown) . Fitted between each pair of arms 128, the body 132 of wobble plate 130 has a respective separable bearing insert 149 secured thereto by bolts (not shown); inserts 149 being fitted after assembly of body 132 on socket 136. Also, arms 128 are separable from body 132, and are secured thereto by bolts 151 after insertion of pins 147. As shown, bolts 151 pass through a flange 153 by which each pin 147 is connected to its arm 128.

Surface 134 of wobble plate 130 is slidable on surface 138 of socket 136 by bearing material 140 therebetween. However, the internal, part spherical surface 139 of socket 136 preferably is spaced from, rather than in sliding contact with, the external surface of hub member 145.

Adjacent output member 116, socket 136 is provided with a radially outwardly extending flange 153. Supports 155 fixed to flange 153 secure socket 136, via segmented sliding surfaces 157 in case 114 and segmented bearings

159 while extension 144 of socket 136 is slidable, but non-rotatable in bearing 161 in cylinder block 112.

The orbiting motion of shaft 162, about main axis A, produces rotational motion of output member 116. Rotation of member 116 is via thrust and journal bearings 168, 170, trunnion 172, split link 166 and anchor pin 174, in a similar manner to that described with reference to Figure 1. Each arm 128, provided by a continuation of a respective pin 147, is coupled to the connecting rod 182 of its piston 126 via respective radial and thrust bearings 163 and 165 and trunnion 167. However, the coupling between connecting rods 184 and arms 128 can, if required, being according to the arrangement of Figure 1.

• In the form of mechanism 110 as illustrated, it is of a variable displacement type, although a drawing system such as shown in Figure 1 with reference to the hydraulic actuator comprising piston 46 and cylinder 50 has been omitted for ease of illustration. Alternatively, another known form of drawing system can be used, as is possible in mechanism 10. Also, as will be appreciated, each of mechanisms 10 and 110 readily is able to be adapted to a fixed displacement type, obviating the need for a drawing mechanism and enabling a simplified coupling between the wobble member and the output member.

Mechanism 110, as with that of Figure 1, requires to be in static and couple balance at all stroke positions. This can be achieved in the manner described in Figure 1, or by alternative known arrangements for fixed or variable displacement engines.

Mechanism 110 of Figure 2 is provided with a CV coupling system similar to that of mechanism 10 of Figure 1. Detailed description of this therefore is not necessary, beyond pointing out that the connection of the system to wobble plate 130 is provided within, and to, body 143 of hub member 145. Mechanism 110 enables greater bearing surface area between surface 134 of wobble plate 130 and surface 138 of socket 136 than is practical for surfaces 34,38 of mechanism 10. Thus, mechanism can be more suitable for larger engines than mechanism 10. Figure 3 shows an alternative connection 210 between the wobble member of an engine mechanism of the invention and the output member. Figure 3 illustrates this alternative in relation to the mechanism 10 of Figure 1 for shaft 62 and output member 16 thereof (shown in Figure 3 as shaft 262 and output member 216). However, it is to be appreciated that the alternative connection is equally applicable to mechanism 110 of Figure 2 for connecting shaft 162 to its output member 116.

As in Figure 1, the alternative utilizes a split link 266 connected to shaft 262 via thrust and radial bearings 268, 270 and trunnion 272. Thus, at - shaft 262, the arrangement is essentially as described in relation to Figure 1. However, at the end of link 266 remote from shaft 262, output member 216 is provided with a sliding pin 271 movable along its axis E in bearings 273,275.

Link 266 has a boss 277 through which pin 271 extends and is secured such that link 266 is movable with pin 271 in cut-out 279 of output member 216. Axes B and E are in a common plane which also contains axis A, although the inclination of axis E to axis A is selected to provide the combined stroke changing variations for pistons 26 and the desired compression ratio adjustments. In Figure

3, the connection 210 is shown in the maximum stroke condition, as is the case for engine mechanism 10 as shown in Figure 1. As piston 46 in Figure 1 is drawn to the left, to decrease the stroke of pistons 26, the angle of inclination of axis B with respect to axis A is reduced, with relative rotation between shaft 262 and link 266 on axis C of trunnion 272. However, as link 266 is constrained against rotation by location of pin 271 in boss 277 and by bearings 273,275, pin 271 is caused to slide in bearings 273,275 and to draw link 266 with it along and transversely with respect to axis A. As indicated, connection 210 can be used in mechanism 110 of Figure 2, to couple shaft 162 to output member 116. This applies whether mechanism 110 is of a variable displacement type as illustrated, or is adapted to be of a fixed displacement type. However, of course, where of the fixed displacement type, provision would not be needed for pin 271 to slide, as link 266 and shaft 262 will remain in with their respective axes B and E in a constant angular, relationship to axis A, although a less complex coupling normally would be used for a fixed displacement mechanism rather than that of Figure 3.

Figure 4 shows an alternative embodiment of CV joint assembly 300, for a wobble ball 302 (of which the arms are not shown) held in a socket (not shown but similar to socket 36 of Figure 1) for providing the centering function. Assembly 300 splits the total angle between the two individual Cardan joints 303,304 of assembly 300. In addition, assembly 300 allows two shafts 306 and 308, coupled by a tongue and groove connection 310, to pass through the centre of assembly 300 at varying angles, to provide drive for a cam-shaft and balance weight (not shown) similar to the arrangement of Figure 1. Shaft 308 is supported by bearings 312 and 314 in yoke 316 fixed to the interior of the wobble ball 302. Shaft 306 is supported by bearing 318 in splined connector 320 fixed to a interior of a socket (not shown but similar to socket 36 in Figure 1) . A second yoke 322 connects with the connector 320 at spline 323 to allow small axial movement required during stroke changing operation. Two crosses 324 and 326 and central double yoke 328, via several bearings 330, complete the double Cardan CV joint assembly 300.

Finally, it is to be understood that various alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the spirit or ambit of the invention.

Claims

CLAIMS :

1. An engine mechanism of the wobble plate type, the mechanism including a cylinder block having an output member rotatable therein about an axis of rotation (herein referred to as the main axis); a wobble member defining a part spherical surface which has a centre of curvature substantially co-incident with the main axis, the wobble member having a plurality of arms spaced therearound and each extending in a plane which is oblique with respect to the main axis; a plurality of cylinders arranged around the main axis, each with a piston reciprocally movable therein along a respective piston axis substantially parallel to the main axis, each piston being coupled to a respective arm of the wobble member; a bearing member defining a part spherical surface which has a centre of curvature substantially co-incident with the main axis and provides a bearing surface complementary to, and in sliding contact with, the part spherical surface of the wobble member; and a coupling member pivotally connected to the wobble member and the output member, the coupling member being pivotally connected to the wobble member at a location spaced laterally from said main axis and from its connection to the output member, said location being located on a line which passes through the centre of curvature of the respective part spherical surface of the wobble member and the bearing and which is substantially perpendicular to the plane in which said arms extend; the arrangement being such that the wobble member is constrained by the coupling member so as to be non-rotatable with respect to the main axis, while allowing its arms to traverse lemniscate paths dictated by the inclination, with respect to the main axis, of the plane in which the arms extend and such that, during such movement of the arms, the output member rotates as a consequence of orbital movement around the main axis of the connection between the wobble member and the coupling member.

2. An engine mechanism according to claim 1, said mechanism being of a variable displacement type, wherein the wobble member and the bearing member are movable together to adjust the location of the centres of curvature of their respective part spherical surfaces along the main axis such that the inclination and position of the plane in which the arms of the wobble member extend is selectively variable relative to the main axis, thereby enabling adjustment of the stroke of the pistons, the mechanism further including a drawing mechanism which is operable to draw the bearing member and, with it, the wobble member, along the main axis.

3. An engine mechanism according to claim 2, wherein the drawing member is continuously, and reversably, operable to move the wobble and bearing members between two extreme conditions setting maximum and minimum inclinations of the wobble member arms and corresponding variation in engine displacement.

4. An engine mechanism according to any one of claims 1 to 3, wherein the wobble member is a wobble ball having a body defining an external surface providing the part spherical surface the arms extending radially outwardly with respect to the external surface, and wherein the bearing member partially encloses the body of the wobble ball, with its part spherical surface being an internal surface thereof, the bearing member defining a plurality of openings through each of which a respective one of the arms extend.

5. An engine mechanism according to claim 4, where the bearing member is formed of at least two parts for ease of its assembly in relation to the wobble ball, with the parts being releasably secured together.

6. An engine mechanism according to any one of claims 1 to 3, wherein the wobble member is a wobble plate having an annular body of which a radially inner circumference defines an internal said part spherical surface, with the arms extending from an outer circumferential surface; the bearing member being located within the body of the wobble plate, with its part spherical bearing surface being an external surface.

7. An engine mechanism according to claim 4 or claim

5, wherein the wobble ball has a short radial shaft which is perpendicular to the plane of said arms, and by which the wobble ball is connected to the output member by the coupling member.

8. An engine mechanism according to claim 7, wherein the shaft is connected via a bearing and trunnion to the coupling member, with the coupling member comprising a link system which allows the inclination of the shaft to be altered relative to the main axis of the output member.

9. An engine mechanism according to claim 8, wherein a non-rotating but mutating constant velocity coupling extends along the main axis and operatively inter-connects the wobble ball and the bearing member.

10. An engine mechanism according to claim 9, wherein the constant velocity coupling has a centre substantially at the centre of the wobble ball and in the plane in which the arms extend, to allow the arms to traverse a lemniscate path dictated by the inclination of the arms and that plane relative to the main axis, as the output member rotates.

11. An engine mechanism according to claim 6, wherein the wobble plate is connected to a radial shaft by radial pins which extend through slots in the bearing member, with the shaft extending perpendicular to the plane of said arms and the coupling member connecting the wobble plate to the output member via said shaft, the shaft being movable in unison with the wobble plate and thereby rotating the output member.

12. An engine mechanism according to claim 11, wherein the shaft is connected via a bearing and trunnion to the coupling member, with the coupling member comprising a link system which allows the inclination of the shaft to be altered relative to the main axis of the output member.

13. An engine mechanism according to claim 12, wherein a non-rotating but mutating constant velocity coupling extends along said main axis and operatively inter-connects said bearing member, via said shaft, to said wobble plate.

14. An engine mechanism according to claim 13, wherein the constant velocity coupling has a centre substantially at the centre of the wobble plate and in the plane in which the arms extend, to allow the arms to traverse a lemniscate path dictated by the inclination of the arms and that plane relative, to the main axis, as the output member rotates.

15. An engine mechanism according to any one of claims 11 to 14, wherein said shaft projects from an enlarged body portion thereof located within said bearing member, with said radial pins engaging with said body portion.