Internal-combustion engines – Transmission mechanism from piston – Crankshaft and connecting rod
Patent
1992-09-10
1994-07-12
Argenbright, Tony M.
Internal-combustion engines
Transmission mechanism from piston
Crankshaft and connecting rod
123 48B, 74 50, F02B 7524
Patent
active
053278631
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to apparatus for converting reciprocating motion to rotary motion and vice-versa comprising a reciprocatory assembly guided for reciprocation in a first direction and comprising first and second reciprocating members each terminating in a planar guide surface transverse to the direction of reciprocation, and spacing tie means interconnecting the two reciprocatory members at opposite ends of the guide surfaces to maintain the guide surfaces parallel, spaced apart and facing each other, a drive block having opposed guide faces each slidably engaged with a respective one of the guide surfaces of the reciprocatory members, and a rotary member taunted for rotation about an axis transverse to the said direction of reciprocation and having an eccentric portion rotatably engaged in the drive block.
Such apparatus is particularly suitable for interconnecting pistons with a crankshaft in positive fluid displacement machines such as pumps and internal combustion engines as proposed for example in EP-A 0,241,243 and U.S. Pat. No. 4,794,887.
A problem in such known apparatus arises from deflections of the guide surfaces due to high loads imposed on them particularly at high speeds, under the tensions generated in the tie means and applied at the ends of the guide surfaces while the drive block bears against an intermediate part of one guide surface.
Apparatus according to one aspect of the invention is characterised in that the spacing tie means comprises, at each end of the guide surfaces, two ties positioned one on each side of the end part of the travel of the outer portion of the drive block. Such an arrangement enables the bending moments applied to the guide-surface-forming portions of the reciprocatory members to be reduced since the two sets of tie means are now less far apart. At the same time, the length of the drive block (in the direction of its motion) may be increased, in relation to the eccentricity or throw of the eccentric portion of the rotary member, to a value such that in all positions of the drive block, the central plane of the apparatus passing through the said axis passes through the drive block.
Apparatus according to ,another aspect of the invention is characterised in that the spacing tie means comprises, for each end of the guide surfaces, two side plates positioned one on each side of the reciprocatory members and secured to the two reciprocatory members at least at intervals along the outer portions of the guide surfaces, each side plate having a reentrant providing clearance for the eccentric portion of the rotary member as it moves relatively to the reciprocatory members parallel to the guide surfaces. Preferably, the reentrant is formed by a parallel-sided and curved-ended slot of width sufficient to clear the said eccentric portion but preferably less than the distance between the opposed guide surfaces. Advantageously, the portions of the side plates, beyond the reentrants, which form the tie means, are made sufficiently stiff to maintain the portions each side of the reentrant parallel, thereby reinforcing the end portion of the reciprocatory members forming the guide surfaces.
Where the eccentric portion is formed by a crankpin connected to the remainder of the rotary member (thus in the form of a crankshaft) by webs, the radially outer portions of the webs may advantageously terminate at a smaller distance from the crankshaft axis than the radially outer part of the crankpin so that the latter projects beyond the webs. This enables the side plates to be brought still closer together.
Advantageously, the side plates and the adjacent portions of the reciprocatory members have load-transmitting interfitting formations therealong.
These measures together result in a very rigid construction which reduces deflection of the guide surfaces, preferably in conjunction with the first aspect of the invention.
In one variant of the apparatus, each side plate is made integral with one of two members forming the two said portions of the reciprocatory assembly. Prefe
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Downton Christopher M.
Feilden Geoffrey B. R.
Argenbright Tony M.
Collins Motor Corporation Ltd
Macy Marguerite
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