Internal-combustion engines – Two-cycle – Rear compression
Patent
1998-12-14
2000-12-19
Dolinar, Andrew M.
Internal-combustion engines
Two-cycle
Rear compression
123 65A, F02B 3328
Patent
active
061615099
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The subject invention refers to a cylinder for a two-stroke combustion engine intended for a handheld working tool, preferably a chain saw, and the exhaust duct and transfer ducts of the cylinder are symmetrically arranged around a mutual symmetry plane which follows the centre line of the cylinder, and at the mouth of the exhaust duct outside the cylinder a mounting plane with mounting holes for a directly mounted muffler is arranged.
BACKGROUND OF THE INVENTION
Due to requirements of low weight and compact design portable working tools are usually run by a crankcase scavenged two-stroke engine. However, a crankcase scavenged four-stroke engine is also conceivable. As a result of the crankcase scavenging the engine is lubricated by oil in the fuel. This means that the tool can be used and managed in different directions during running, i.e. sideways or upside-down. The tools usually have a carburetor connected to an inlet duct, but also a low pressure injection system can be of interest. Since the tool can be used in a lot of positions there is a risk for fuel drops to accumulate inside the inlet duct and then be tipped into the cylinder when the tool's inclination is changed. This can bring about that the engine stops. The greatest risk for this is at lower engine speed. This has also brought about that the carburettor usually is placed near the inlet port, i.e. that the inlet duct is short. Considering engine power at operating speed it would however be preferable to use a longer inlet duct. This could however be associated with said difficulties as well as pure space problems. Therefore the carburetor usually is placed adjacent the cylinder's top section, and provided with some kind of heat protecting baffle. This baffle implies a complication at the same time as temperature problems can still arise for the carburettor. Furthermore, the inlet duct is usually turned obliquely down towards the crankcase. Owing to this the inlet gases can not assist in cooling the critical area around the exhaust port.
PURPOSE OF THE INVENTION
The purpose of the subject invention is to substantially reduce the above outlined problems.
SUMMARY OF THE INVENTION
The above mentioned purpose is achieved in a cylinder, in accordance with the invention, having the characteristics appearing from the appended claims.
The cylinder according to the invention is thus essentially characterized in that at least one inlet port is located in the cylinder wall and/or in an adjacent crankcase half, and that the cylinder's inlet duct towards the inlet port is so arranged that it forms a fixed and heat-conducting part of the cylinder, and has a length longer than 0.8 times the diameter of the cylinder, preferably longer than 1.0 times the diameter. Conditions are hereby created for having an extremely long inlet duct of the engine in the handheld working tool. The inlet duct of the cylinder is preheated and due to its large length conditions are created to connect a relatively long duct section upstreams towards the carburetor. For, this long preheated section vaporizes fuel drops very efficiently. Furthermore the location of the inlet port is creating conditions for an advantageous drawing of the engine's inlet duct and for cooling the area at the exhaust port. The working tool can thus have an engine with an extremely long inlet duct. This creates opportunities for increasing the engine's traction power at normal running speed, and can give higher power and/or cleaner exhaust gases at operating speed. For, owing to increased throttling on the exhaust side less exhaust emissions can be achieved with retained power, i.e. an advantage of power and/or emission. The reason for this improvement is that a higher engine charging efficiency can be obtained at the present engine speed. This is achieved due to a more favourable Helmholz resonance frequency. The resonance frequency is determined essentially by the relation between the length of the inlet duct and the crankcase volume, which is relatively well reflected by the
REFERENCES:
patent: 4121552 (1978-10-01), Mithuo et al.
patent: 4287860 (1981-09-01), Fujikawa et al.
patent: 4337734 (1982-07-01), Iio
patent: 4353333 (1982-10-01), Iio
patent: 4607598 (1986-08-01), Kamata
patent: 4736716 (1988-04-01), Ohyama
patent: 5025760 (1991-06-01), Webb et al.
patent: 5251580 (1993-10-01), Torigai
patent: 5471960 (1995-12-01), Nagao et al.
patent: 5490483 (1996-02-01), Tanikake et al.
patent: 5870981 (1999-02-01), Knaus et al.
patent: 5881687 (1999-03-01), Sakaguchi et al.
patent: 6016776 (2000-01-01), Jonsson
Dahlberg Goran
Frojd Magnus
Hartz Niels
Naslund Ulf
Aktiebolaget Electrolux
Dolinar Andrew M.
Huynh Hai
LandOfFree
Cylinder does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cylinder, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cylinder will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-263286