JPH0242124A - Two-cycle engine with scavenging pump - Google Patents

Abstract

PURPOSE:To optimize scavenging at each load by providing the third scavenging port opened/closed according to load in the device in which two scavenging ports are formed to the right and left to the exhaust port of a cylinder, and each port is communicatedly connected to the discharge side of the scavenging pump. CONSTITUTION:The exhaust port 11 opened/closed at a given timing with a piston 3 is formed to the cylinder 2 of a two-cycle engine, and also first and second scavenging ports 16 and 16' similarly opened/closed with the piston 3 are formed to right and left positions slided nearly 90 deg. from the port 11. And a third scavenging port 30 is formed at the position having the same height as these ports 16 and 16' and at the opposite side to the port 11. And the discharge side of a scavenging pump 31 driven with an engine is connected to each port 16, 16', and 30 via scavenging tubes 34, 34', and 35. The space between the suction side of the pump 31 and the third scavenging tube 35 is connected with a bypass passage 37 having a control valve 36 which is controlled according to an accelerator opening.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a two-stroke engine equipped with a scavenging pump for forced air supply, and more particularly to changing the scavenging method under various operating conditions.

[Conventional technology]

In general, a two-stroke engine has one revolution per crankshaft revolution.
Since the cycle ends, self-priming action on the cylinder is not possible. This lick, for example, bis! - Fresh air is introduced into the crankcase by the negative pressure generated in the crank chamber when the piston rises, and the new air is introduced into the cylinder from the scavenging port by the case pressure when the piston falls, and at the same time, the combustion gas is pushed out and exhausted. method is used. Additionally, a throttle valve is provided in the scavenging system for load control, and the amount of scavenging air is adjusted by the valve opening. However, according to such a system, the amount of scavenging air is small when the load is low, resulting in insufficient scavenging air, which causes misfires and makes stable operation impossible. Furthermore, it becomes difficult to obtain smooth torque characteristics that correspond to operating conditions. Since there is a limit to the scavenging ability based on crankcase pressure, there are problems such as difficulty in increasing torque sufficiently under high loads. Therefore, it is desirable to increase the scavenging capacity to always perform good scavenging and to reduce the blow-by of scavenging air.In this respect, the scavenging pressure is increased by the scavenging pump, and the fuel is directly injected into the cylinder by the injector to scavenge the air. It has been proposed to prevent blow-through. Therefore, conventionally, two
Regarding cycle engines, for example, Japanese Patent Application Laid-Open No. 57-20
There is a prior art in Publication No. 3821. Here, the scavenging bonder is rotated at the same speed as the crankshaft, and the scavenging bonder introduces fresh air into the cylinder through the scavenging port. It is also shown that an injection nozzle is installed in the combustion chamber and fuel is directly injected.

[Problem to be solved by the invention]

By the way, in the above-mentioned prior art configuration in which air is scavenged by a scavenging pump, the port area of the scavenging port is generally set based on the output characteristics at low load and high load, and the characteristics at high load are inevitably set. Because it is determined at the expense of
There is a limit to the amount of scavenging air at high loads, and there is a problem in that high output cannot be obtained. Here, increasing the port area of the scavenging port may be considered to increase the amount of scavenging air at high loads, but increasing the port area will reduce the scavenging efficiency at low loads. Therefore, it is desirable to change and control the port area under each operating condition. The present invention has been made in view of the above, and an object of the present invention is to make it possible to appropriately perform scavenging at each load by controlling the number of scavenging ports to be changed according to the engine operating condition. An object of the present invention is to provide a two-stroke engine with a scavenging pump.

[Means to solve the problem]

In order to achieve the above object, the two-stroke engine of the present invention has first ports on the left and right of the exhaust port of the cylinder of the two-stroke engine main body. a second scavenging port; The second scavenging port is connected to the first scavenging port. In the configuration in which the scavenging air pipe is connected to the scavenging pump via the second scavenging pipe, at least a third scavenging port is opened on the side opposite to the exhaust port of the cylinder, and the third scavenging port is connected to a third scavenging air port having a reed valve. The reed valve is connected to the scavenging pump via a scavenging pipe No. 3, and the upstream side of the reed valve is communicated with a bypass passage that bypasses the scavenging pump and is provided with a control valve that opens and closes depending on the load.

[For production]

Based on the above configuration, when the load is high, the control valve is substantially fully closed to generate high scavenging pressure at the third scavenging port as well.
The second and third scavenging ports perform a scavenging operation to ensure a sufficient amount of scavenging air. In addition, when the load is low, the control valve is almost fully opened and a part of the scavenging air from the scavenging pump is returned from the third scavenging pipe to the suction side of the scavenging pump via the bypass passage. The second scavenging air 71 provides efficient scavenging action. Furthermore, the driving force of the scavenging pump during low load is small.

【Example】

Hereinafter, one embodiment of the present invention will be described based on the drawings. In FIG. 1, the overall structure of a two-stroke engine is described. Reference numeral 1 is the main body of the two-stroke engine, and a piston 3 is inserted into a cylinder 2 so as to be able to reciprocate.
A piston 3 is connected to the crankshaft 5 of the crank chamber 4 by a connecting rod 6 which is engraved.
A balancer 7 is provided to offset the reciprocating inertia of the screw I/N 3. An ignition glove 9 is located at the top of the combustion chamber 8.
and an in-cylinder direct injection type injector 10 are attached. An exhaust port 11 is opened in the cylinder 2 and is opened and closed at a predetermined timing by a piston 3.
A catalyst device 13 is connected to an exhaust pipe 12 communicating with the exhaust chamber 1.
4. A muffler 15 is provided. Further, as shown in FIG. 2, on the left and right positions approximately 90 degrees apart from the position of the exhaust port 11 of the cylinder 2, there are Schneeler-type first scavenging ports 16, which are opened and closed at predetermined timing by the piston 3. Second
The first scavenging port 16' is opened, and the first scavenging port 16.
A scavenging system is provided at the second scavenging port 16'. The injector 10 is of a two-fluid type, and after supplying a predetermined amount of fuel, it is pressed with pressurized air and directly injects the mixed fuel and air. Therefore, the fuel passage 20 of the injector 10 is connected to the filter 2.
1. communicates with the fuel tank 23 via the fuel pump 22;
A pressure regulating valve 24 is provided in the middle of the fuel passage 20, and always produces a constant low fuel pressure (slightly higher pressure than the pressurized air). Also, the air passage 25G of the injector 10; has a pressure regulating valve 26. Accumulator 27. A compressor 28 is connected to produce pressurized air. A predetermined amount of fuel is stored in the injector 10 in advance by a fuel pulse from the control unit 45, and the exhaust port 11
After the valve closes, pressurized air is applied to the fuel using an air pulse and the fuel is injected. Next, referring to FIGS. 1 and 2, the scavenging system will be described. In the cylinder 2, the first scavenging port 16. A third scavenging port 30 opens on the opposite side of the exhaust port 11 at the same height position as the second scavenging port 16°. Further, a scavenging pump 31 is installed separately from the engine body 1 with its suction side communicating with the air cleaner 33, and a first scavenging pump 31 is installed immediately after the discharge side of the scavenging pump 31. Second and third scavenging pipes 34, 34°, 3
5 branches and the first. Second and third scavenging ports 16
, 16°, and 30. A bypass passage 37 having a control valve 36 communicates between the suction side of the scavenging pump 31 and the third scavenging pipe 35.
The scavenging pipe 35 has a third
A reed valve 38 is provided to prevent backflow from the cylinder 2 when the scavenging pressure in the scavenging pipe 35 decreases. The scavenging pump 31 is connected to the crankshaft 5 by a transmission means 39, and is constantly driven by engine power. The accelerator pedal 40 is connected to open and close the control valve 36 in inverse proportion to the accelerator opening via a mechanical opening changing means 44 such as a link mechanism. Also, an engine rotation speed sensor 41. which detects the engine rotation speed N, the accelerator opening degree φ, and the cooling water temperature TVT, which determine each operating condition. It has an accelerator opening sensor 42 and a water temperature sensor 43, and each sensor signal is input to a control unit 45 and processed, and the control unit 45 sends a fuel pulse signal and an air pulse signal to the injector 10, and an ignition signal to the spark plug 9. It is designed to be output. Here, the control unit 45 controls the engine rotation speed N. It has a fuel injection amount setting means 46 that inputs the accelerator opening degree φ and the cooling water temperature Tw and calculates the fuel injection amount Ti according to the driving state, and this fuel injection amount Ti is inputted to the pulse generation means 47. First, a fuel pulse corresponding to the fuel injection amount Ti is output to the injector 10 via the drive circuit 48 to store fuel, and then a predetermined air pulse is output to apply pressurized air to the fuel to perform injection. Next, the operation of the two-stroke engine configured as described above will be described. First, during low load with small accelerator opening, the control valve 36
is substantially fully opened and communicates with the bypass passage 37. Therefore, the fresh air discharged from the scavenging pump 31 to the third scavenging pipe 35 only returns to the pump suction side.
The scavenging pressure of the scavenging pipe 35 is reduced, and the pump load does not increase. On the other hand, the scavenging pump 31 is connected to the other first. Second scavenging pipe 34
．． A predetermined scavenging pressure is generated at the exhaust port 34', and the piston 3 is located near the bottom dead center as shown in FIG.
．． Second. When the third scavenging ports 16, 16°, and 30 are opened, air pressurized by the scavenging pressure flows into the cylinder 3 from the first and second scavenging ports 16, 16°. In this case, as shown in FIG. 3 fa), the first. Second scavenging port 16
．． The air flowing in from 16' generates a strong vertical swirl, although the amount of scavenging itself is small, and this scavenging flow sufficiently reversely scavenges up to the upper part of the cylinder 2 to push out residual combustion gas from the exhaust port 11. At this time, since the scavenging pressure of the third scavenging port 30 is low, when the third scavenging port 30 is opened, the gas flows back toward the third scavenging port 30 or is blocked by the reed valve 38. Then, as described above, the scavenging effect is performed efficiently and the exhaust port 11 and the first. Second. Third scavenging port 16, 1f3
', 30 is closed, sufficient constricted swirl scavenging air remains in the cylinder 2. Therefore, the fuel injected by the injector 10 rides on this scavenging air flow, becomes a rich air-fuel mixture near the ignition plug 9, and ignites the ignition plug 9, resulting in good stratified combustion. Further, when the load is high, the control valve 36 is substantially fully closed to cut off the bypass passage 37. Therefore, from the scavenging pump 31, the first.
Second. A high scavenging pressure is generated in the third scavenging air g34. Third
Pressurized air flows in from the scavenging ports 16, 16', 30 as shown in FIG. 3(b). In this case, the flow from the first and second scavenging ports 16, 16' becomes dominant with respect to the overall directionality, producing a vertical swirl in the same way as described above, and efficiently scavenging. Furthermore, compared to when the load is low, the opening degree of the reed valve 38 increases and the area of the scavenging port increases, so the amount of scavenging air increases and high output is obtained. In addition, as shown in FIG. 4, the cylinder 2 is further provided with auxiliary ports 48 and 48' on the third scavenging port 30 side.
The scavenging pipes 49 branched from the scavenging pipe 35 may be connected at 49°. In this case, the number of scavenging ports increases during high loads, so that the scavenging efficiency can be improved. In this embodiment, the control valve 36 is opened and closed by mechanical means in accordance with the accelerator opening degree, but it goes without saying that instead of this, the control valve 36 can be variably controlled in accordance with the signal from the accelerator opening sensor 42.

【Effect of the invention】

As described above, according to the present invention, in a two-stroke engine equipped with a scavenging pump, the number of scavenging ports is changed and controlled according to the load, improving the scavenging efficiency at low loads and reducing the amount of scavenging air at high loads. Therefore, it is possible to improve both low-load combustion 2 operability and the like and high-load output. Furthermore, at low loads, part of the scavenging air flow is bypassed, so the load on the scavenging pump is reduced.

[Brief explanation of the drawing]

FIG. 1(a) is an overall configuration diagram showing an embodiment of a two-stroke engine with a scavenging pump according to the present invention, FIG. 1(b) is a plan view of the main parts, FIG. 2 is a functional block diagram of the control unit, Figure 3(a)
, (b) is a diagram showing the scavenging state of each load, and FIG. 4 is a plan view of the embodiment of the pond. 1... 2-cycle engine body, 2... cylinder. 11... Exhaust port, 16... First scavenging port,
16°...Second scavenging port, 30...Third scavenging port, 31...Scavenging pump, 36...Control valve, 3
7... Bypass passage, 38... Reed valve Fig. 3 (a) (b) Fig. 2

Claims (1)

[Claims] A two-cycle engine main body has first and second scavenging ports on the left and right sides of the exhaust port of the cylinder, and the first and second scavenging ports are connected to each other through first and second scavenging pipes. At least a third scavenging port is opened on the side opposite to the exhaust port of the cylinder, and the third scavenging port is connected to the scavenging pump through a third scavenging pipe having a reed valve. A two-stroke engine with a scavenging pump, characterized in that the reed valve is connected to a scavenging pump, and the upstream side of the reed valve is connected to a bypass passage that bypasses the scavenging pump and includes a control valve that opens and closes depending on the load.