Internal-combustion engines – Transmission mechanism from piston – Crankshaft and connecting rod
Patent
1997-08-14
1998-07-28
Okonsky, David A.
Internal-combustion engines
Transmission mechanism from piston
Crankshaft and connecting rod
F02B 7522
Patent
active
057850291
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
The invention relates to a reciprocating piston engine, especially an internal combustion engine as is known, for example from U.S. Pat. No. 2,271,766.
This document teaches a reciprocating engine with hypocycloid crank drive which comprises an eccentric rod connected at both ends with pistons in cylinders located diametrically opposed to one another. This eccentric rod consists of a master con-rod, mounted on a stroke eccentric of the hypocycloid, for one of the pistons and a shorter slave con-rod for the other piston, articulated to the bearing cover of the master con-rod. Both pistons are also connected with articulation with the respective connecting rods so that this known eccentric rod is bendable and therefore serves especially to reduce the stresses that result from the components of the crank drive that move because of variations in tolerance.
The particular disadvantage of this known arrangement is the difference in piston wear caused by the con-rods being of different lengths.
The goal of the invention is to design an eccentric rod with a kinematically more favorable bendability.
This goal is achieved according to the present invention by forming the eccentric rod of rod segments angularly movable around the axis of the bearing opening (for the stroke eccentric), with the angular movements of the rod sections being elastically limited as a function of the admissible tilting movements of the pistons permanently attached to the respective rod sections.
As a result of the central bending according to the invention of the eccentric rod in conjunction with a degree of bending that can be set as a function of the piston geometry, uniform and considerably reduced piston wear is achieved in an advantageous manner. In addition, the eccentric rod according to the invention provides a kinematically safe support for the hypocycloid crank drive as it passes through the central position with the piston in a TDC/BDC position by virtue of the fact that the angular movements of the rod sections of the centrally bendable eccentric rod are preferably limited as a function of elasticities that grow progressively more rigid.
Another advantage is the use of the bending eccentric rod according to the invention in a hypocycloid crank drive with Watt straight guidance. As is known, the center of the Watt linkage, which is coaxial to the axis of the bearing opening of the eccentric rod, instead of a long and ideal straight guideline, moves along a slightly loop-shaped guideline whose deviations from the ideal straight guideline are advantageously reduced by means of the bending eccentric rod as it operates.
The design of the invention comprises an eccentric rod composed of three parts with two eccentric rod segments each connected with a piston, whose end areas facing one another are disposed with guidance and a movable rotational angle in an annular central part that contains the bearing opening for the stroke eccentric. The eccentric rod sections can be fastened in advantageous fashion on the middle part, with the respective piston in each cylinder being mounted in simple fashion to the cylinder head by the eccentric rod section. Since this means that one double piston mounted on a one-piece piston rod can be prevented from pushing from one cylinder into the opposite cylinder, the engine block can be designed with structurally integrated bearing eyes for a crankshaft bearing, said eyes projecting in the direction of the eccentric rod according to the invention. In this way, the rigidity of the engine block is increased.
In addition, the eccentric rod sections according to the invention can comprise ribs that are spaced as far apart as possible to achieve high bending stiffness in view of the piston diameter, said ribs being connected integrally at one end with a relatively short piston and on the other end, on the bearing side, with a guide surface for the connecting arc that performs the bending movement. This design considerably simplifies the manufacture of the eccentric rod
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patent: 4498372 (1985-02-01), Pareja
patent: 4727794 (1988-03-01), Kmicikiewicz
patent: 4905540 (1990-03-01), Hughes et al.
patent: 5560327 (1996-10-01), Brackett
patent: 5673666 (1997-10-01), Beardmore et al.
Bayerische Motoren Werke Aktiengesellschaft
Okonsky David A.
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