Internal-combustion engines – Multiple cylinder – Having rotary output shaft parallel to cylinders
Reexamination Certificate
1999-05-28
2001-06-26
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Multiple cylinder
Having rotary output shaft parallel to cylinders
C123S053500, C123S053600
Reexamination Certificate
active
06250264
ABSTRACT:
A four stroke combustion engine having two separate cam guide devices. Each cam guide device co-operates with its respective set of pistons and with its respective associated set of support rollers according to a “sine”-like concept known per se.
GB 2 019 487 describes a four cylinder two stroke engine in which ignition occurs simultaneously in two of the four cylinders, that is to say in pairs of alternate cylinders. In the patent specification it is indicated that the contour of the cam can be designed so that the pistons can be moved in a most favourable manner in connection with expansion of the combustion product. There is employed a desired level or steady contour for emptying or scavenging of exhaust before new fuel is introduced into the cylinder. In the drawings there is shown, in each of two mutually opposite cam grooves, a more or less rectilinear, local cam contour in mutual turning points lying directly opposite each other forming “sine”-like curve portions. More specifically the rectilinear cam contour is illustrated in only the one of two succeeding, turning points of the “sine”-like curve forming “sine”-like curve portions, namely where the respective pistons occupy one after the other their most remote outer positions with exhaust and scavenging ports open to the maximum.
The present invention, which primarily relates to two cycle engines, but which can also be applied to four stroke engines, takes as its starting point the piston and cylinder arrangement according to the afore-mentioned U.S. Pat. No. 5,031,581.
FR-A-2 732 722 illustrates a two part driving shaft. Each drive shaft part is provided with a disc shaped cam guide device arranged in an inclined plane to the drive shaft axis to generate a mathematical sine-curve movement of the relevant one piston of each pair of opposed pistons. It is proposed to control the compression ratio by axially adjusting the relative distance between the drive shaft parts and accordingly the relative distance between each pair of opposed pistons. This axial adjustment is provided by axially movement of one drive shaft part in relation to the other drive shaft part, i.e. one drive shaft part is axially movable and the other drive shaft is axially immovable.
With the present invention the aim is to be able to regulate the compression ratio in cylinders of the engine in a similar way as suggested in FR-A 2 732 722, but with additional advantages. It is especial interest to provide an engine construction operating in a controlled, precise and reliable manner based on a constructional simple and reliable drive shaft structure.
It is a further aim of the present invention to employ a “sine”-like curve shaped, cam guide device instead of the disc shaped cam guide device suggested in FR-A-2 732 722. By the use of a “sine”-like curve shaped, cam guide device it is made possible to guide the associated pistons in a more advantageous manner to improve the total engine effect. More specifically the “sine”-like curve shaped, cam guide device enables incorporation of different local variations in each engine stroke in order to improve the total engine effect. It is, however, of utmost importance that the cam guide devices and their connection with the drive shaft have a favourable design and are sufficiently reliable in operation.
The arrangement according to the invention is characterised in that at least one of the cam guide devices is axially movable in relation to a one-piece drive shaft and is provided with a hydraulic mechanism, for separately adjusting the position of at least one guide device, including regulation of the relative spacing between the pistons. The hydraulic mechanism includes an annular pressure oil chamber and a simulator piston, which partitions the chamber into two sub-chambers, and each chamber is connected to a respective one of two pressure oil circuits.
By regulating the position solely for the one cam guide device, the regulation arrangement is rendered especially simple and other significant advantages can be obtained in the general function of the engine, as will be described further below.
Alternatively, instead of regulating the position for only the one cam guide device, it is possible to regulate the position for each of the cam guide devices synchronously or individually, all according to the requirements for additional adjustment between the movements of the pistons in each piston pair.
According to the invention one is in a position to regulate the compression ratio in the working chamber between two pistons of each cylinder of the engine in a rather simple and reliable manner by means of the hydraulic mechanism.
By the fact that the cam guide device is common to the one piston of each and all the cylinders there can be achieved effectively and in an accurately controllable manner corresponding regulation of the position for said one piston of each of the cylinders relative to its associated cylinder by means of one and the same pressure oil regulated cam guide device. This means that the position of this one of the guide means and accordingly the position of the related piston of each pair or pistons can be a controlled and reliable manner by means of a rather uncomplicated hydraulic mechanism, i.e. by means of pressurised oil.
According to the invention it is made possible to regulate the working volume between pistons of the cylinders as may be required, that is to say during use, and particularly during a cold start of the engine and back to normal operation after the engine is run sufficiently warm.
A favourable constructional solution of the present invention is that a one-piece drive shaft is being used and that each cam guide device is rotative with the drive shaft and that at least one cam guide device is axially movable along the drive shaft. This means that the cam guide devices and the drive shaft can be realised in rather a compact and dimensionally restricted construction.
A further favourable constructional solution of the present invention is that the pressure oil chamber is defined in an annular spacing between the drive shaft and the cam guide device, and that said piston projects from its cam guide device radially inwardly in the chamber.
It is also advantageous that the piston is passed through parallel to the axis of the drive shaft by a set of driving bolts, which allow a certain axial movement of the piston relative to the drive shaft, while the driving bolts are connected at their respective opposite ends to the drive shaft and connected to a carrying member fastened to the drive shaft.
It is especially interesting according to the invention to change the compression ratio in connection with the starting up of the engine, that is to say on cold start. It is furthermore interesting in addition to be able to change the compression ratio during operation in order thereby to obtain a most favourable compression ratio possible during normal operation. Consequently it can be of interest to change the compression ratio during operation of the engine for various reasons.
It is preferred according to the invention that the one piston of the cylinder, which is designed to regulate the position of in the associated cylinder, constitutes a piston which controls opening and closing of exhaust ports of the cylinder.
In practice, one piston of each cylinder controls the opening and closing of one or more exhaust port(s) of the cylinder and the other piston of each cylinder controls the opening and closing of one or more scavenging port(s).
Accordingly, at the same time as the compression ratio is regulated between the pistons, there is in addition achieved the possibility to of regulating the opening and closing sequence of the associated exhaust ports.
Inter alia the flow-through passages of the exhaust ports can hereby be defined as required. Further the moment of the opening and closing of the exhaust ports can be displaced in relation to normal operation.
Inter alia one can hereby achieve according to the invention a favourable separate control of the exhaust ports via the one group
Carella Byrne Bain Gilfillan Cecchi & Olstein
Hand Francis C.
Huynh Hai
Sinus Holding AS
Wolfe Willis R.
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