Oil feeding method and device for oiling a 2-cycle engine

Abstract: The present invention relates to an oil feeding method and device for oiling a 2-cycle engine wherein the oil feeding interval is rendered adjustable while the oil feeding quantity per one stroke of the oil pump is kept at its minimum within the ordinary operating range of the engine but the oil feeding quantity per one stroke of the oil pump is rendered adjustable while the oil feeding interval is kept at its minimum within the high load-high speed operating range.

Description: The present invention relates to an oil feeding method and device for intermittently supplying oil to a 2 stroke engine in response to the engine operating conditions employing a separate feeding system. In the separate oil feeding system, recently employed frequently for lubricating 2 stroke gasoline engines in which fuel-air mixture produced by the carburetor is supplied to the crank chamber through an intake passage, the oil supply quantity is determined by the oil feeding quantity per one stroke and the oil feeding interval of the oil pump. To be concrete, the oil feeding quantity is determined to become more in proportion to the engine load and the oil feeding interval (period between two feed strokes) is determined to become shorter with the increase of the engine speed. Thus, it is well known to supply engine oil intermittently with an oil pump in a 2 stroke engine. Accordingly the quantity of oil to be supplied is controlled in terms of the quantity of oil being supplied per one stroke of the oil pump and the oil supplying interval. Normally the quantity of oil being supplied per one stroke of the oil pump is increased in proportion to the engine load and the oil supplying interval is shortened as engine speed increases. Such a lubricated metering system detecting engine load and engine speed is disclosed in US-A-4,369,743. In said document showing an electronic lubricant metering system the engine operating conditions are detected in terms of engine load and engine speed to feed a transistor circuit which finally actuates a solenoid of the oil pump. Thus the duty ratio of the solenoid is varied in response to the engine operating conditions detected and it is the changing of the frequency of control output pulses of a controlling transmitor which varies the oil/fuel ratio of the oil and gas mixture delivered to the engine. However, if the oil feeding quantity per one stroke of the oil pump is increased with the increase of the engine load, the amount of oil particles discharged together with the exhaust gas without lubricating sliding surfaces of the engine is increased causing a disorder of generating quantity of oil which normally exceeds the capabilities of the oil pump which experience difficulties to follow. Accordingly, it is an object of the present invention to provide an oil feeding method and device for intermittently supplying oil to a 2 stroke engine which is able to supply each sliding surface with a required quantity of oil and to suppress wasteful discharge of oil particles to a minimum, i.e. to supply sufficient oil to the engine parts under all engine running conditions but to reduce the oil which is discharged from the exhaust ports of the engine in order to reduce blue smoke in the exhaust gas. In order to perform the afore-indicated objectives the oil feeding method according to the present invention for intermittently supplying oil to a two stroke engine comprises varying of the amount of oil supplied to the engine in response to engine speed and engine load such that a high load/high speed operating range of the engine is distinguished from the remainder ranges of engine operation and that under high load/high speed conditions the amount of oil fed per one stroke of the oil pump is variable while keeping fixed at its minimum value an oil feeding interval between two successive feeding strokes of the oil pump, but rendering the oil feeding interval between two successive feeding strokes of the oil pump variable while keeping fixed at its minimum value the amount of oil fed per one stroke of the oil pump outside the high load/high speed operating conditions of the engine. Under apparatus aspects of the present invention it is suggested than an oil feeding device for intermittently supplying oil to a two stroke engine is designed to include a detecting means for sensing the speed and load conditions of the engine and a controller which receives the engine load and speed responsive signals from the detecting means to control an oil pump in response to said engine operating condictions detected. According to the present invention the controller controls independently of each other an oil feeding quantity per one stroke of the oil pump and an oil feeding interval between two successive feeding strokes of the oil pump. Accordingly, the present invention improves a 2-stroke engine which is supplied with engine oil intermittently by an oil pump in such a manner that in the high engine load-high engine speed operating condition of the engine the oil supplyng interval is held fixed to a minimum duration whereas the quantity of oil supplied during one stroke of the oil pump is made variable resulting in an increased quantity of oil being supplied during one stroke of the oil pump for increasing the quantity of oil per unit time. On the other hand, during the other engine running conditions the quantity of oil which is supplied during one stroke of the oil pump is fixed to a minimum amount whereas simultaneously the oil supplying interval is varied in order to shorten the oil supplying interval for increasing the quantity of oil per unit time. The present invention both in its method and apparatus aspects is advantageous in that during normal engine running condition, i.e. engine operating condition except for the high engine load-high engine speed operating range the oil which is discharged from the exhaust port of the engine is reduced as the oil feeding quantity per one stroke of the oil pump is fixed to be minimal. Accordingly less blue smoke will be created. Moreover, under high engine load-high engine speed running conditions a sufficient amount of oil can be supplied to the necessary parts of the engine by controlling said oil feeding quantity per one stroke of the oil pump during the oil supplying interval of minimal duration. Of course it could be considered to fix the oil feeding quantity per one stroke of the oil pump to a minimum as the normal engine running condition, for example during high engine load-low engine speed operating conditions, however then under high engine load-high engine speed conditions the oil pump could not follow the engine speed as it would be required to shorten the interval extremely in order to obtain a satisfying quantity of oil being supplied per unit of time. According to experiments, oil particle generation becomes conspicuously abundant just after an oil feeding which is effected intermittently, and this tendency becomes significant as the oil feeding quantity per one stroke of the oil pump is increased. Accordingly, it becomes clear that, to reduce oil particle generation, it is necessary to keep the oil feeding quantity per one stroke of the oil pump at its minimum and to shorten the oil feeding interval within a range where seizure resistances, wear resistances, etc., of the sliding surfaces are kept satisfactory by lubrication. According to this invention, since the oil feeding quantity per one stroke of the oil pump is fixed at its minimum and the oil feeding quantity required per unit of time is secured by adjusting the oil feeding interval within the ordinary operating range out of the high-load high-speed operating range, oil can be supplied in near-stationary flow, and the discharge of oil particles can be suppressed to its minimum while a required quantity of oil can be fed to every sliding surface. Ideally, the oil feeding quantity per one stroke of the oil pump is to be fixed at its minimum as mentioned above even within the high-load high-speed range, but the oil feeding interval for fulfilling oil feeding quantity requirement per unit time becomes extremely short, which is difficult for the oil pump to follow. Therefore, the oil feeding quantity per one stroke of the oil pump is adjusted with the oil feeding interval fixed at its practically minimum value within the high-load high-speed operating range. Accordingly even within the high-load high-speed operating range, the oil feeding quantity per one stroke of the oil pump can be kept minimum within a range where problems about seizure resistanes, etc., of sliding surfaces will not be caused. Further, the above oil feeding method can be practically effected by the device according to this invention. Preferred embodiments of the present invention are laid down in the subclaims. In the following an embodiment of the present invention is explained in conjunction with the appended drawings, wherein Fig. 1 is a construction illustration of an oil feeding device according to the present invention, Fig. 2 is a construction illustration showing the oil pump and its driving-controlling system of the oil feeding device according to Fig. 1, Fig. 3 is a map for determining the oil feeding quantity per one stroke of the oil pump and the oil feeding interval of the oil pump in response to the engine operating conditions, and Fig. 4 is a graph showing the control domains. First is described the fundamental construction of the oil feeding device referring to Fig. 1, in which the reference number 1 denotes a 3-cylinder 2 stroke diesel engine, the cylinder body 2 of which has three cylinders formed in parallel, within each of which is fitted a piston 4 vertically slidably. Each piston 4 is connected to the crankshaft 6 rotatably disposed within the crankcase 5 through a connecting rod 7. The cylinder head 8 covering the top of the cylinder body 2 has sub combustion chambers S formed for each of the cylinders 3 into each of which is faced the tip of the fuel injection valve 9. One end of the crankshaft 6 is connected/disconnected to the input shaft 12 of the transmission 11 through a clutch 10, and the rotation transmitted to the input shaft 12 is in turn transmitted to the output shaft 13 with a speed changed through speed change gear trains (not shown) operable by the shift lever 14. In this 2 stroke diesel engine 1, during the intake/compression stroke when the piston 4 goes up causing a vacuum in the crank chamber 15 of the crankcase 5, air drawn by this vacuum is supplied into the crank chamber 15 through the intake passage (not shown), and then is primarily compressed by the piston 4 coming down during the explosion/exhaust stroke. When the piston 4 opens the exhaust port and the scavenging ports formed through the cylinder 3 during the explosion/exhaust stroke, this primarily compressed air flows into the cylinder 3 through the scavenging ports to push out the exhaust gas produced during the previous cycle into the exhaust port. Then, after the exhaust port and the scavenging ports are closed by the going-up piston 4 during the intake/compression stroke, the air in the cylinder 3 is compressed by the piston 4 to make a high pressure and a high temperature. When the piston 4 nearly reaches its top dead center, an appropriate quantity of fuel is injected by the fuel injection valve 9 into the sub combustion chamber S, and is ignited and combusted by the high-temperature high-pressure air in the cylinder 3. Hereupon, the piston 4 is pushed down by the high combustion prssure working on the piston top primarily compressing the air in the crank chamber 15. Similar actions are repeated thereafter, and the engine 1 is continuously rotated. In this engine 1, a required minimum quantity of oil is supplied directly and intermittently to every sliding surface by the oil pump 20 driven by the engine 1. That is, the oil from the pump 20 is intermittently supplied to the journals of the crankshaft 6 through an oil passage 21 and its branch passages 22, and further to the big end of each connecting rod 7 from there, to lubricate these portions. On the otherhand, the oil from the pump 20 is supplied to the piston sliding surface of each cylinder 3 through an oil passage 23 and its branch passages 24 to lubricate it. This oil pump 20 has an oil reservoir 30 connected through an oil passage 25. The oil feeding quantity Q per one stroke of the oil pump 20 and the oil feeding interval I of this oil pump 20 can be adjusted independently in response to the engine speed by pulse motors 26 and 27 shown in Fig. 2, respectively, both electrically connected to the controller 40. The controller 40 has a potentiometer 51 for detecting the opening of the accelerator 50 and a rotation sensor 60 for detecting the rotating speed of the crank shaft 6 both connected electrically, and determines the oil feeding quantity per one stroke Q and the oil feeding interval I of this oil pump 20 on the basis of accelerator opening data detected by the potentiometer 51 and the engine speed data detected by the rotation sensor independently of the engine operating conditions, and controls the drive of pulse motors 26 and 27 according to the values of the determined quantity Q and interval I. In this embodiment, the oil pump 20, pulse motors 26 and 27, controller 40, potentiometer 51, rotation sensor 60, etc., constitute the oil feeding device according to this invention. Next is desribed the oil feeding method according to this invention referring to the above-mentioned oil feeding device. The accelerator opening and the engine speed are detected by the potentiometer 51 and the rotation sensor 60, respectively, while the engine 1 is running, and these detection signals are sent to the controller 40 as mentioned above. The controller 40 determines the oil feeding quantity per one stroke Q and the oil feeding interval I of the oil pump 20 on the basis of these detection signals (that is, on the basis of the engine operating conditions), and controls the drive of the oil pump 20 (that is, the drives of the pulse motors 26 and 27) so that the values of the oil feeding quantity Q and the oil feeding interval I may be fulfilled. The controller 40 has a map shown in Fig. 3 memorized within it, which map is divided into plural addresses according to engine speeds and accelerator openings, at each of which addresses have been determined the optimum oil feeding quantity Q and interval I. To be concrete, within the ordinary operating range (domain A in Fig. 4) out of the high-load high-speed operating range where the accelerator opening and the engine speed are greater, the required oil feeding quantity per unit time (that is, oil feeding quantity required not to cause problems relating to seizure resistance and wear resistance of sliding surfaces such as journals of the crankshaft 6) is secured by adjusting the oil feeding interval I while fixing the oil feeding quantity per one stroke Q at its minimum. By adjusting the oil feeding interval I while keeping the oil feeding quantity per stroke Q at its minimum as mentioned above, oil particle discharge can be suppressed to its minimum as is clear from the above-mentioned experimental results. On the other hand, within the high-load high-speed operating range (domain B in Fig. 4), the required oil feeding quantity per unit time is secured by adjusting the oil feeding quantity per one stroke Q while fixing the oil feeding interval I at its realizable minimum, because, although the oil feeding quantity per one stroke Q is ideally to be fixed at its minimum as mentioned above even within the high-load high-speed operation g range, such a small oil feeding quantity per one stroke Q requires an extremely short oil feeding interval I for fulfilling the oil feeding quantity requirement per unit time, which is difficult for the oil pump (especially mechanical oil pump) to follow. Accordingly, even within this high-load high-speed operating range, the oil feeding quantity per one stroke Q can be kept minimum within a range where problems about seizure resistances and wear resistances of sliding surfaces will not be caused, and thus oil particle generation can be suppressed to its minimum. Since this embodiment employs a mechanical oil pump, the oil feeding quantity per one stroke Q can be adjusted more precisely as compared with the case of the electromagnetic oil pump. Although the above embodiment employs the accelerator opening and the engine speed as the parameters for detecting the engine operating conditions, more exact oil feeding control becomes possible by employing also the cooling water temperature, intake air temperature, etc., in addition. This invention is of course applicable also to the 2 stroke engine not having a fuel injection valve and the 2 stroke engine employing the separate oiling system which supplies oil into the intake passage. As is clarified by the above desription, since the oil feeding interval is rendered adjustable while the oil feeding quantity per one stroke of the oil pump is kept at its minimum within the ordinary operating range, but the oil feeding quantity per one stroke of the oil pump is rendered adjustable while the oil feeding interval is kept at its minimum within the high-load high-speed operating range according to this invention, discharge amount of the oil particles can be suppressed to its minimum while feeding required quantity of oil to ever sliding surface. Further, the above oil feeding method can be practically effected by the oil feeding device according to claim 3.

Claims: An oil feeding method for intermittently supplying oil to a two stroke engine wherein the amount of oil being supplied to the engine is variable in response to the engine speed and the engine load detected, such that a high load/high speed operating range of the engine is distinguished from the remainder ranges of engine operation and that under high load/high speed conditions the amount of oil fed per one stroke (Q) of the oil pump (20) is variable while keeping fixed at its minimum value an oil feeding interval (I) between two succesive feeding strokes of the oil pump (20) but rendering the oil feeding interval (I) between to successive feeding strokes of the oil pump (20) variable while keeping fixed at its minimum value the amount of oil fed per one stroke (Q) of the oil pump (20) outside the high load/high speed operating condition of the engine. An oil feeding method as claimed in claim 1, characterized in that the operating range of the engine is detected and corresponding signals are fed to a controller (40) which determines the desired oil feeding quantity per one stroke (Q) of the oil pump (20) and the corresponding feeding interval (I) of the oil pump (20) to control the drive of pulse motors (26,27) in response to the sensed operating condition represented by the values of the signals in order to actuate the oil pump (20) in compliance with the determined oil feeding quantity (Q) and oil feeding interval (I). An oil feeding device for supplying intermittently oil to a two stroke engine, comprising a detecting means (51,60) detecting the speed and load conditions of the engine, and a controller (40) receiving said engine load and speed responsive signals from the detecting means (51,60) representing the operating conditions, and an oil pump controlled in response to said engine operating conditions through said controller (40), characterised in that , the controller (40) controls independently of each other an oil feeding quantity per one stroke (Q) of the oil pump (20) and an oil feeding interval (I) between two successive feeding strokes of the oil pump (20). An oil feeding device as claimed in claim 3 characterized in that the oil pump (20) driven by the engine is adapted to supply a required minimum quantity of oil directly and intermittently to each lubricated sliding surface of the engine. An oil feeding device as claimed in claim 3 or 4 characterized in that the oil pump (20) connected via an oil passage (25) within an oil reservoir (30) intermittently supplies oil to the journals of a crankshaft (6) through an oil passage (21) and its branch passage (22) and from that portion to the big end of each connecting rod (7) as well as to the piston sliding surface of each cylinder (3) through an oil passage (23) and its branch passage (24), respectively. An oil feeding device as claimed in claim 5, characterized by a sensor arrangement (51,60) including a potentiometer (51) for detecting the degree of throttle opening in conjunction with the angular position of an accelerator pedal (50) and an engine revolution speed sensor (60) detecting the speed of the crankshaft (6), the outputs of the sensor arrangement (51,60) being fed to the controller (40) which, in turn is electrically connected with independent pulse motors (26,27) adapted to activate the oil pump (20) according to the control signals of the controller (40).

Inventors: ITO HIDEAKI, MATSUO NORITAKA, ITO, HIDEAKI, MATSUO, NORITAKA
Applicants: YAMAHA MOTOR CO LTD, YAMAHA HATSUDOKI KABUSHIKI KAISHA
Application year: 1990
Main classification: F01M3
IPC codes: F01M3, F02B1, F01M1, F02B75