Internal-combustion engines – Two-cycle – Pump and cylinder adjacent
Patent
1990-09-24
1992-10-20
Cross, E. Rollins
Internal-combustion engines
Two-cycle
Pump and cylinder adjacent
123 47A, 123 65E, F24B 1304
Patent
active
051561182
DESCRIPTION:
BRIEF SUMMARY
The present invention relates essentially to a process and a device for supplying air to a cylinder of a self-supercharged two-stroke engine at to at least one group of two cylinders set at 180.degree. by an air transit chamber supplied under pressure and communicating intermittently with an self-supercharging duct, as well as an engine equipped with such a device or putting such a process into operation.
More particularly the invention relates to a process and a device for supplying air to a cylinder of a two-stroke internal combustion engine, to at least one group of two cylinders set at 180.degree., with self-supercharging of under the effect of post-charging where the energy of the exhaust gases from one cylinder in this group serves for the self-supercharging of the other cylinder of this group via an self-supercharging duct connecting the inlet ports of the two cylinders of the same group, the inlet ports being uncovered by the piston longer than the exhaust ports.
In the prior art a large number of proposals are already known for utilising the direct action of the gases leaving a cylinder on a reserve of air in order to compress it and introduce it into a cylinder at an appropriate moment in the cycle in order to supercharge it.
Solutions of this type have already been described in CH-A-593 420 according to which the supply duct 9 constitutes the only route for admitting air into the cylinder via an opening 2, 12 in the piston skirt of the other cylinder in communication with the supply duct 9 when this other piston is in the proximity of the dead top centre (see FIG. 1 and FIG. 4).
The solutions described in CH-A-593 420 are particularly interesting in order to obtain a post-charging effect, particularly for two-stroke engines.
In fact, for a given external compression of the air charge the highest possible filling is obtained due to an increase in the air purity because the mass of residual gases not expelled at the end of the scavenging phase is no longer subjected to later modification during the post-charging phase. This is equivalent to an improvement in the scavenging efficiency and to a better utilisation of the scavenging air.
However, the solutions advocated by CH-A-593 420 lead to a favourable auto-scavenging but show some deficiencies in the supply of air in certain operating conditions of the engine, notably on starting or in the event of a high counter-pressure at the exhaust. In addition, these solutions require a special construction of the bi-cylinder combination which is relatively complex, increasing the total centre to centre distance of the cylinders set at 180.degree. of the same group. It is also possible to envisage an improvement in the air supply by the use of a scavenging pump which is auxiliary to the engine, but this greatly complicates the construction.
The object of the present invention, therefore, is to remedy these major drawbacks which have greatly limited the industrial exploitation of the device and of the process advocated in that document.
To this effect the principal object of the present invention is to solve the new technical problem consisting of providing a process and a device for supplying air to each cylinder of a two-stroke internal combustion engine, to at least one group of two cylinders set at 180.degree., for self-supercharging under the effect of post-charging, which guarantee the supply of air no matter what the operating conditions of the engine may be, notably on starting.
A further principal object of the present invention is to solve the new technical problem consisting of providing a process and a device for supplying air as defined above which make it possible to utilise the natural movement of each piston to transfer the air positively through the self-supercharging duct in spite of the fact that the piston is located at about the dead top centre, that is to say in the inverse position to that which makes it possible to create a pumping effect of the air supply, at the moment when the air supply enters upstream of the self-supercharging du
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patent: 5060602 (1991-10-01), Maissant
Cross E. Rollins
Macy M.
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