JP3588722B2 - Low-load operation stabilizer for two-stroke engines - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a two-stroke engine, and more particularly to a low-load operation stabilizing device.
[0002]
[Prior art]
In a two-cycle engine, irregular combustion tends to occur at low speed and low load. This is because a large amount of burned gas remains in the combustion chamber. Such irregular combustion not only results in emission of unburned gas such as HC, but also causes instability of engine rotation. In the case of an outboard motor or the like, the irregular combustion described above is a serious problem because there is a trolling operation range near the idling speed.
[0003]
Conventionally, in order to solve such a problem, the minimum opening degree of a throttle valve provided in an intake passage is set relatively large to increase an intake air amount to increase an intake ratio, thereby suppressing irregular combustion, and an engine associated therewith. The increase in speed was suppressed by greatly retarding the ignition timing.
[0004]
[Problems to be solved by the invention]
However, in such a two-stroke engine, the fuel supply amount also increases with an increase in the intake air amount, resulting in an increase in unburned gas emission, a deterioration in exhaust gas, and a deterioration in fuel consumption (fuel consumption). I was
[0005]
The present invention has been made in view of the above circumstances, and its object is to prevent irregular combustion at low load, particularly at low speed and low load, and to prevent deterioration of exhaust gas due to emission of unburned gas. It is to suppress the deterioration of.
[0006]
[Means for Solving the Problems]
The present invention achieves the above object by providing
An intake passage for supplying fresh air from the atmosphere to the combustion chamber,
An ignition plug facing the combustion chamber,
A fuel injection valve facing the combustion chamber and directly injecting fuel into the combustion chamber;
An exhaust passage for discharging combustion gas in the combustion chamber through an exhaust port on the combustion chamber side;
A two-stroke engine including a pressure release path that communicates with the atmosphere from the combustion chamber via an on-off valve that opens and closes according to the operation stroke of the engine,
An opening on the combustion chamber side of the pressure release path is provided on the opposite side of the ignition plug with respect to the fuel injection valve,
Positioning an axis extending to the combustion chamber side of the fuel injection valve so as to point to a portion inside the combustion chamber excluding the opening,
It is characterized in that the depressurizing passage is connected to the atmosphere from the combustion chamber in the operating region where irregular combustion occurs and at the beginning of the compression stroke.
[0007]
[Action]
When operating at a lower load than planned, the minimum opening of the throttle valve is set to a relatively large value to increase the amount of intake air, increase the intake ratio, and suppress irregular combustion. Combustion gas remaining in the combustion chamber and fresh air sucked in along with the rise of the piston are discharged out of the combustion chamber from the depressurization path together with the rise of the piston. The room is filled with an appropriate amount of fresh air.
Further, an opening on the combustion chamber side of the pressure release passage is provided on the side opposite to the ignition plug with respect to the fuel injection valve, and an axis extending toward the combustion chamber of the fuel injection valve is defined as a portion in the combustion chamber excluding the opening. Since the fuel injection valve is positioned so as to be directed, it becomes difficult for the fuel injected from the fuel injection valve to directly flow out of the opening.
Still further, the pressure release path is connected to the atmosphere from the combustion chamber via an on-off valve that is opened and closed according to the operation stroke of the engine. Is set at the beginning of the compression stroke, which is relatively low, so that the gas in the combustion chamber is removed from the depressurization path almost exclusively by the upward movement of the piston. For this reason, the amount of gas removed from the depressurizing passage is easily made uniform, and variation in the pressure in the combustion chamber can be reduced. As a result, the combustion chamber is always filled with an appropriate amount of fresh air, and combustion during low load operation of the engine is stabilized.
[0008]
【Example】
Hereinafter, the present invention will be described with reference to the illustrated embodiments. In FIG. 1, reference numeral 1 denotes an outboard motor mounted on a rear tail plate of a hull for propelling a boat. The outboard motor 1 includes an engine 2 supported at an upper portion as a main part thereof, and a transmission case 4 for transmitting an output of the engine 2 to a propeller 3. Reference numeral 5 denotes a synthetic resin cowling for covering the outer surface of the engine portion. A top cowling 5a is detachably attached to a bottom cowling 5b fixed to the lower surface of the engine 2.
[0009]
The transmission case 4 is made of an aluminum alloy by casting, and supports a propeller shaft 3a having a propeller 3 at a lower end thereof. 4a is a bevel gear mechanism. The bevel gear mechanism 4a is connected to an output shaft (a crankshaft to be described later) of the engine 2 via a drive shaft 4b via a spline 4c. The bevel gear mechanism 4a turns the rotation of the engine 2 at a right angle and transmits the rotation to the propeller shaft 3a.
[0010]
The engine 2 is a crankcase compression type two-stroke engine, and includes a crankcase and a cylinder 2b that are integrally cast and machined, and a crankcase 2a is formed by the crankcase and the cylinder 2b. 6 is a combustion chamber. The combustion chamber 6 is formed as a space surrounded by a piston 6a slidably fitted into the cylinder 2b and a cylinder head 6b closing an opening of the cylinder 2b. The cylinder head 6b is provided with an ignition plug 6c, a fuel injection valve 6d, and an electromagnetically operated pressure reducing valve 6e as opening / closing means. The pressure reducing valve 6e is provided in a pressure release passage 8e connecting the inside of the combustion chamber 6 and an exhaust passage 8 described later, and is opened and closed by a control device 9 described later, and has a fixed relationship with the rotation of the crankshaft 2d (second embodiment). Alternatively, it is opened and closed without any relationship (first embodiment). As shown in FIG. 1, the opening of the pressure release passage 8e on the combustion chamber 6 side is provided on the opposite side of the ignition plug 6c with respect to the fuel injection valve 6d. The axis of the fuel injection valve 6d extending toward the combustion chamber 6 is positioned so as to point toward the top of the piston 6a, and does not point toward the opening of the pressure release passage 8e. As a result, it becomes difficult for the fuel injected from the fuel injection valve 6d to directly flow out of the opening of the pressure release passage 8e.
[0011]
The piston 6a is connected to a crankshaft 2d supported by the crankcase by a connecting rod 2c. Reference numeral 6f denotes an intake passage connected to the crank chamber 2a, in which an artificially operated throttle valve 6h and a check valve 6j composed of a reed valve are provided, and an air flow from the atmosphere side to the crank chamber side is provided. Although allowed, backflow is prevented.
[0012]
Reference numeral 2e denotes a flywheel supported on the upper end of the crankshaft 2d, on the inner surface of which a magnet of a magnet generator is installed. Reference numeral 2f denotes a power generating coil which cooperates with the magnet, and is supported by a rotating plate 2h so as to be able to rotate around the crankshaft 2d by a slight angle. Therefore, when the flywheel 2e rotates, an electromotive force is generated in the power generation coil 2f attached to the inner surface of the rotating plate 2h. Reference numeral 2j denotes a starting motor that cooperates with a ring gear 2g fixed to the outer periphery of the flywheel 2e.
[0013]
Next, a description will be given of each path in which the intake air is drawn into the engine, burned, and then discharged outside the engine.
[0014]
During the upward stroke of the piston 6a, fresh air is sucked into the crank chamber 2a via the suction passage 6f according to the opening of the throttle valve 6h. Fresh air sucked into the crank chamber 2a is compressed in the crank chamber 2a as the piston 6a descends. The compressed fresh air is introduced into the combustion chamber 6 through a scavenging passage 7 communicating with the crank chamber 2a. The fresh air introduced into the combustion chamber 6 is compressed with the rise of the piston 6a. In the process, the measured fuel is injected from the fuel injection valve 6d facing the combustion chamber 6, and the two are mixed and further mixed. Compressed. In accordance with the ignition timing output from the ignition controller 10, the ignition plug 6c is ignited, and the air-fuel mixture in the combustion chamber 6 ignites and explodes, lowering the piston 6a. With the lowering of the piston 6a, the exhaust port 8a opens, and the combustion gas passes through the exhaust port 8b, passes through the exhaust duct 8c formed in the transmission case 4, and is discharged into the water outside the machine. When the pressure reducing valve 6e is open, the combustion chamber 6 and the exhaust passage 8 are always in communication via the pressure release passage 8e. Therefore, when the pressure reducing valve 6e is open, the exhaust port 8a The combustion chamber 6 is always in slight communication with the outside through the exhaust port 8b even after the valve is closed.
[0015]
Next, the control device 9 will be described. The control device 9 includes a microprocessor, a ROM, a RAM, an oscillation circuit, an input interface, and an output interface. The control device 9 obtains, as input signals, an opening signal of the throttle valve 6h from the throttle valve sensor 9a, and a speed signal and a phase signal of the crankshaft 2d from the crank angle sensor 9b, and performs arithmetic processing. As shown in the figure, an ignition signal, a fuel injection timing signal, a fuel injection amount signal, and a pressure release signal are output. These signals actuate an ignition plug 6c, a fuel injection valve 6d, and a pressure reducing valve 6e provided on the cylinder head 6b, respectively.
[0016]
Next, the operation of the engine control device 9 will be described with reference to a flowchart shown in FIG.
[0017]
First, in step 100, the engine speed is calculated based on the information of the crank angle sensor 9b. In step 102, in order to determine whether or not the engine speed is low, it is determined whether or not the engine speed is, for example, 3000 RPM or less. If not, that is, if the speed is not low, the process proceeds to step 120. In the case of YES, that is, in the case of low speed, it is further determined in step 103 whether or not the engine speed is, for example, 50 RPM or more. In the case of NO, the engine is stopped (step 105) and the control is terminated. On the other hand, in the case of YES, the routine proceeds to step 104, where the ignition controller 10 retards the ignition timing according to the engine speed, and then proceeds to step 106 to determine whether or not the preceding engine speed is, for example, 1800 RPM or less. I do. If NO, proceed to step 112, close the pressure reducing valve 6e, further control the injection amount using the normal fuel injection amount control map based on the throttle valve opening and the engine speed N (step 113), and return to step 100. . In the case of YES, the process proceeds to step 108, the pressure reducing valve 6e is opened, and further, in step 110, the fuel injection valve 6d is controlled to open and close so that the injection amount is increased with respect to the normal fuel injection amount control map, and the process returns to step 100. .
[0018]
On the other hand, when it is determined in step 102 that the engine speed exceeds, for example, 3000 RPM, in step 120, the load state is detected by the throttle valve sensor 9a, and based on the detection result, it is determined whether the load is low in step 122. If NO, the pressure reducing valve 6e is closed in step 126, and the injection amount is controlled by a normal fuel injection amount control map based on the throttle valve opening and the engine speed N (step 127). Thereafter, the process returns to step 100. If it is determined in step 122 that the load is low, the pressure reducing valve 6e is opened, and in step 125, the fuel injection valve 6d is opened and closed so as to increase the injection amount with respect to the normal fuel injection amount control map. Return to
[0019]
Next, as a second embodiment, an example of controlling the apparatus shown in FIGS. 1 and 2 will be described with reference to the flowchart of FIG. Note that the flowchart of FIG. 4 is the same as Steps 108 and 124 of the flowchart of FIG. 3 except for some differences in control, so that 100 is added to the reference numbers of each step in FIG. Steps 208 and 224, which are omitted and different, will be described below.
[0020]
In steps 208 and 224, the pressure reducing valve 6e is opened for a short time at the beginning of the compression stroke or at the end of the explosion stroke. That is, if opened at the beginning of the compression stroke, a part of the gas in the combustion chamber 6 is discharged into the exhaust port 8b through the pressure release passage 8e with the rise of the piston 6a as in the case of the edge member 8d described later. You. If the timing at which the pressure relief passage 8e communicates with the exhaust port 8b is set at the beginning of the compression stroke, the pressure of the gas in the combustion chamber 6 is relatively low at this time. Most of the gas inside is removed from the pressure release passage 8e based only on the upward movement of the piston 6a. For this reason, the amount of gas removed from the pressure release passage 8e is likely to be uniform, and variation in the pressure in the combustion chamber 6 can be reduced. As a result, the combustion chamber 6 is always filled with an appropriate amount of fresh air, and the combustion during the low load operation of the engine is stabilized. Further, if the pressure reducing valve 6e is opened before the opening of the exhaust port 8a at the end of the explosion stroke, a part of the burned gas is discharged therefrom, and the residual gas amount at the end of the exhaust stroke is reduced. It is also possible to reduce the compression ratio at.
[0021]
Next, the configuration of the third embodiment will be described with reference to FIG.
[0022]
The third embodiment has substantially the same configuration as the first and second embodiments, but according to the third embodiment, the exhaust port 8a formed in the cylinder 2b has an upper edge. It is configured to be raised and lowered substantially. That is, in the exhaust passage 8, an edge member 8d, which is a substantially semicircular opening / closing means, is rotatably supported close to the exhaust port 8a, and the edge of the edge member 8d on the cylinder hole side substantially exhausts air. The upper edge of the mouth 8a is constituted. Accordingly, the edge member 8d is rotated counterclockwise (FIG. 5) and moved upward during low load operation according to the operating state of the engine. Therefore, in this embodiment, the range in which the upper edge of the exhaust port 8a moves up and down functions as a pressure release path.
As shown in FIG. 5, the opening at the upper edge of the exhaust port 8a functioning as a pressure release path is provided on the opposite side of the ignition plug 6c with respect to the fuel injection valve 6d. The axis of the fuel injection valve 6d extending toward the combustion chamber 6 is positioned so as to point toward the top of the piston 6a, and is directed toward the upper edge opening of the exhaust port 8a functioning as a pressure release path. Absent. As a result, it becomes difficult for the fuel injected from the fuel injection valve 6d to directly flow out of the opening at the upper edge of the exhaust port 8a.
[0023]
In the case of the third embodiment, the control device 9 calculates the desired opening of the rim member 8d from the speed of the engine, compares the calculation result with the actual opening fed back from the potentiometer, A deviation between them is detected and a signal is output to the motor control means. In the third embodiment, unlike the first embodiment, the opening degree and the ignition timing of the rim member 8d serving as the opening / closing means are controlled based exclusively on the information on the engine speed without including the information on the throttle valve opening degree. ing.
[0024]
By controlling the exhaust port opening timing according to the engine speed, it is no longer necessary to excessively retard the ignition timing at low speed and low load as compared with the prior art. explain.
[0025]
When the engine speed is equal to or higher than a medium speed such as 3000 RPM or more, the exhaust port opening timing is fixed at 98 degrees BTDC, and the engine is controlled in a normal operation state. In the case of 3000 RPM or less, the ignition timing is sequentially retarded until about 1700 RPM. Further, from about 1700 RPM or less to about 900 RPM, the ignition timing is fixed at 2 degrees ATDC, the edge member 8d is rotated, and the exhaust port opening timing is sequentially retarded as shown in the graph of FIG. In the case of 900 RPM or less, the exhaust port opening timing is fixed at, for example, 75 degrees BTDC. The above is the control of the third embodiment shown in FIG.
[0026]
As in the prior art, when the exhaust port opening timing is constant, the engine cannot be controlled to a desired speed unless the ignition timing is further retarded at about 1700 RPM or less, as indicated by the phantom line. This is because the minimum opening of the throttle valve 6h provided in the intake passage 6f is set relatively large to increase the intake air amount and increase the intake ratio to suppress irregular combustion, so that the engine speed increases accordingly. This is because the ignition timing had to be excessively retarded as shown by the imaginary line. On the other hand, in the present invention, it is not necessary to excessively retard the ignition timing as shown by the solid line in FIG.
[0027]
If the in-cylinder fuel injection valve is opened after both the exhaust port 8a and the opening / closing means are closed, fuel blow-through can be reliably prevented, and the unburned fuel component contained in the exhaust gas can be further reduced. it can.
[0028]
【The invention's effect】
As described above, according to the present invention, a part of the mixed gas of fresh air and burned gas once flowing into the combustion chamber is burned through the depressurizing path during low load operation of the engine by using the rise of the piston. Since it is removed from the chamber and reduces the substantial compression ratio, the engine output is reduced without excessively retarding the ignition timing or reducing the minimum opening of the throttle valve. be able to. Therefore, during the low-load operation of the engine, the opening of the throttle valve can be kept relatively large, so that the combustion during the low-load operation is stabilized, and irregular combustion can be prevented, and the fuel is injected into the combustion chamber by the fuel injection valve. In combination with the configuration of directly injecting fuel, unburned fuel components or incompletely combusted gas in the exhaust gas can be reduced, so that deterioration of fuel efficiency can be suppressed.
Further, the opening of the depressurizing passage on the combustion chamber side is provided on the side opposite to the ignition plug with respect to the fuel injection valve, and the axis extending toward the combustion chamber of the fuel injection valve is directed to a part in the combustion chamber excluding the opening. As a result, it is difficult for the fuel injected from the fuel injection valve to directly flow out of the opening, so that deterioration in fuel efficiency can be further suppressed.
Furthermore, the pressure relief passage is made to communicate with the atmosphere from the combustion chamber through an on-off valve that is opened and closed according to the operation stroke of the engine, and the time at which the pressure relief passage communicates with the atmosphere is determined by the gas in the combustion chamber. Is set at the beginning of the compression stroke, which is relatively low, so that the gas in the combustion chamber is removed from the depressurization path almost exclusively by the upward movement of the piston. For this reason, the amount of gas removed from the depressurizing passage is easily made uniform, and variation in the pressure in the combustion chamber can be reduced. As a result, the combustion chamber is always filled with an appropriate amount of fresh air, and combustion during low load operation of the engine is stabilized.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing the configuration of an outboard motor engine according to the present invention.
FIG. 2 is a block diagram of an engine control device.
FIG. 3 is a flowchart showing the operation of the engine.
FIG. 4 is a flowchart showing the operation of the engine according to the second embodiment.
FIG. 5 is a schematic sectional view corresponding to FIG. 1 showing a third embodiment.
FIG. 6 is an operation characteristic diagram showing an operation of an element that determines an engine characteristic.
[Explanation of symbols]
6. Combustion chamber 6b Cylinder head
6c: spark plug
6d: fuel injection valve 6e: pressure reducing valve (open / close valve)
6f intake passage 8 exhaust passage 8a exhaust port 8d rim member (open / close valve)
8e ... Pressure release path

Claims (1)

An intake passage for supplying fresh air from the atmosphere to the combustion chamber,
An ignition plug facing the combustion chamber,
A fuel injection valve facing the combustion chamber and directly injecting fuel into the combustion chamber;
An exhaust passage for discharging combustion gas in the combustion chamber through an exhaust port on the combustion chamber side;
A two-stroke engine including a pressure release path that communicates with the atmosphere from the combustion chamber via an on-off valve that opens and closes according to the operation stroke of the engine,
An opening on the combustion chamber side of the pressure release path is provided on the opposite side of the ignition plug with respect to the fuel injection valve,
Positioning an axis extending to the combustion chamber side of the fuel injection valve so as to point to a portion inside the combustion chamber excluding the opening,
A low-load operation stabilizing device for a two-stroke engine, wherein the pressure relief passage communicates with the atmosphere from the combustion chamber in an operation region where irregular combustion occurs and at the beginning of a compression stroke.

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