JPS5865933A - Intake device of crank chamber pressurizing type 2-cycle engine - Google Patents

Abstract

PURPOSE:To improve fuel consumption, by forming an intake passage to branch passages of a main intake passage and the first and second intake passages. CONSTITUTION:The first sub-intake passage 20a is closed after closing of a main intake passage 20, further the second sub-intake passage 20b is opened before opening of the main intake passage 20 by a valve plate 18, and reed valves 21a, 21b, permitting only a flow into a crank chamber, are arranged in the downstream side of the sub-intake passages 20a, 20b, in consequence, optimum intake timing can be continuously obtained. Further the reed valves 21a, 21b, provided in the sub-intake passages 20a, 20b, are arranged to the downstream side of the valve plate 18 through a separator plate 17, while an upstream side intake passage 14 of the valve plate 18 is arranged to the downstream side of the valve plate 18, and formed parallelly to the valve plate 18 further tangentially to the circumferential direction, then the intake passage is smoothly formed. In this way, a blow back is prevented to reduce a fuel consumption rate throughout a full range of operation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a crank chamber precompression type two-stroke engine in which the intake passage communicating with the crank chamber is opened and closed by a valve rotating in conjunction with the crankshaft to control the inflow of air-fuel mixture. The purpose is to prevent blowback and reduce fuel consumption, as well as to obtain high output over the entire operating range of the engine.

In a two-stroke engine intake system that uses a valve plate that rotates in conjunction with the crankshaft, the intake timing can be set freely depending on the shape of the valve plate and its mounting position relative to the crankshaft G. It is easy to adjust the timing of air intake into the crank chamber (also, since the valve plate does not intervene in the intake passage when the intake passage is opened, there is less intake resistance;
This has the advantage that the air-fuel mixture can sufficiently flow into the crank chamber. However, in a two-stroke engine using this type of intake system, the intake timing is constant over the entire rotation range G of the engine. However, if you try to obtain high output at low speeds, the air-fuel mixture will not be able to be sucked in sufficiently at high speeds, as shown in Figure 1 (curve A). , high output cannot be expected in the high-speed rotation range.On the other hand, if the timing at which the intake passage is closed by the valve plate is delayed (this will cause more air-fuel mixture to be blown back at low-speed rotation, as shown in curve B in Figure 1). , high output in the low speed rotation range cannot be expected (in other words, in a two-stroke engine using this type of intake system, high output can be obtained in a limited rotation range, but the entire engine operation It is difficult to obtain high output and good fuel consumption in a range of engines, especially for motorcycles, where the operating range is wide from low to high speeds (improvements were still required for engines that require them). .

The present invention has been made in view of the above-mentioned circumstances, and includes an intake passage communicating with the downstream side of the valve plate that rotates in conjunction with the crankshaft, that is, the crank chamber, and a central main intake passage, and a valve sandwiching the main intake passage. The plate is branched into first and second sub-intake passages on the rotation direction side and the reverse rotation direction side, and a reed valve that only allows inflow into the crank chamber is arranged in the sub-intake passage, and the main intake air is controlled by the valve plate. After the passage is closed (this is configured so that the first sub-intake passage can be closed), and before the main intake passage is opened (this is configured so that the second sub-intake passage can be opened), This ensures optimal air intake throughout the engine's rotation range.

Next, embodiments will be described according to the drawings. The second one showing the longitudinal section.
In the figure, a piston 2 is fitted into a cylinder 1 so as to be able to move up and down, and a combustion chamber 4 is formed between a cylinder head 3 on the cylinder 1 and the piston 2. 5 is a spark plug. Piston 2 includes piston pin 6, connecting rod 7, and crank pin 8.
The crankshaft 9 is rotatably supported by a crankcase 12 via a bearing 10. Crank arm 1 installed on crankshaft 9
One end of an intake passage 14 is connected to the crank chamber 13 formed between the intake passage 1 and the crankcase 12, and
The other end of the intake passage 14 is connected to a carburetor 15 .

In the intake passage 14, the part on the cylinder 1 side and the part inside the cover 16 are continuous with a partition plate 17 and a valve plate 18 as boundaries, and the intake passage 14 is opened and closed by the valve plate 18 to control the inflow of the air-fuel mixture. It looks like this. The partition plate 17 is a disk-shaped fixing member held between the cover 16 and the crankcase 12.
A valve plate 18 is rotatably supported within the thin space between the partition plate 17 and the cover 16. The valve plate 18 is a member that is locked to the crankshaft 9 and rotates integrally with the crankshaft 9, and is provided with a fan-shaped notch 19 as shown in FIG. 3, and the direction of rotation is indicated by the arrow R. Front edge 19a and rear edge 19b of notch 19
extend in the radial direction of the valve plate 18.

In addition to the main intake passage 20, the partition plate 17
, that is, the first one on the side of the rotation direction (arrow It) of the valve plate 18.
The sub-intake passage 20a and the reverse rotation direction side (rear side) of the valve plate 18
a second auxiliary intake passage 20b, and a second auxiliary intake passage 20a.
, 20b are attached with G reed valves 21a, 21b and a valve holder 22 as shown in FIG. Since the main intake passage 20 and the first and second auxiliary intake passages 20a and 20b on both sides thereof are arranged in the circumferential direction, the upstream side (the right side in FIG. 4) and the downstream side (the fourth The intake passage 14 continuous to the left side of the figure has a flat cross-sectional shape extending in the circumferential direction, and on the downstream side of the partition plate 17, it faces upstream so that reed valves 21a and 21b can be arranged. It expands in a trumpet shape, extends approximately parallel to the valve plate 18 on the upstream side, and extends tangentially to the circumferential direction, and is connected to the carburetor.

When the engine is running, the piston 2 rises and the crank chamber 13
When the internal pressure decreases, the air-fuel mixture is sucked into the crank chamber 13 from the carburetor 15 via the valve plate 18 and the intake passage 14, and then during the downward stroke of the piston 2, the air-fuel mixture is sucked into the crank chamber 13 through the valve plate 18 and the intake passage 14.
4 is closed by a valve plate 18, and the air-fuel mixture pressurized in the crank chamber 13 by the piston 2 is supplied to the combustion chamber 4 through the scavenging passage 23, and then, during the upward stroke of the piston 2, the air-fuel mixture is supplied to the combustion chamber 4. Explosive combustion occurs due to the compressed air-fuel mixture or a spark from the ignition plug 5, applying explosive pressure to the piston 2,
This force is taken out as rotational force via the connecting rod 7 to the crankshaft 9.

The opening/closing timing of the intake passage 14 by the valve plate 18 is as follows. Approximately 80°$1 from bottom dead center PI in Figure 5
5< Point P8 slightly beyond top dead center P3
The interval Xi up to is the optimum intake interval at low speed rotation of, for example, 2000 to 3000 rpm. Also bottom dead center P
From point P5 approximately 50 to 60' behind l, top dead center P2
For example, the section X to the point pa exceeding 50 to 60 degrees
! is the optimum intake section at high speed rotation, for example 8000 ram. Therefore, in the present invention, the section XII in which the main intake passage 20 is opened by the valve plate 18 is from P8 to P8.
It is appropriate to give up to 4 points. and valve plate front edge 1
The closing timing of the first sub-intake passage 20a by 9a is P.
o. Then, after the main intake passage 20 is blocked at 18 points by the valve plate front edge 19a, the first sub-intake passage 20a is closed.
is closed, and the reed valve 21a attached to the first sub-intake passage 20a can be opened in section X4. As a result, even after top dead center, the inside of the crank chamber becomes negative 1] in a high-speed rotation range (at this point, the first sub-intake passage 20a is kept open by the reed valve 21a, and excess air-fuel mixture is sucked into the crank chamber). I can do something.

The opening timing of the second auxiliary intake passage 201) is determined as Pll. Therefore, the valve plate 18 rotates in the direction of arrow R.
Before the rear edge 19b opens the main intake passage 20 at point 18, the valve plate v6 edge 19b opens the second auxiliary intake passage 20b. When the engine is rotated at high speed, the second auxiliary intake passage 20b can be opened by the load valve 21b to allow the air-fuel mixture to flow into the crank chamber.

The period in which the reed valve 21b can be opened is XII. On the other hand, in the low rotation range, the auxiliary intake passages 20a, 20b are prevented from opening by the action of the reed valves 21a, 211], so only the main intake passage 20 is opened and closed by the valve plate 18&, resulting in optimal intake timing. . Then, as the rotation increases, the auxiliary intake passages 20a, 2Ob & 21a are connected according to the generation timing of intake negative pressure and intake inertia.
, 211) in the forward direction, the intake start timing moves continuously from P8 to P5 and the closing timing moves from P4 to Po in FIG. 5, and the intake timing is kept optimal.

As explained above, in the present invention, when the first sub-intake passage 20a is closed after the main intake passage 20 is closed by the valve plate 18, the second sub-intake passage 20a is closed before the main intake passage 20 is opened. By opening the intake passage 20b and arranging the road valves 21a and 21b on the downstream side of the sub-intake passages 20a and 20b, which allow only inflow into the crank chamber, optimal intake timing can be continuously obtained. It is characterized by the fact that
The reed valves 21a and 21b provided in FIG.
By forming the carburetor 15 approximately tangentially to the
Combined with the smooth configuration of the intake passage from the engine to the crank chamber 13, it is possible to prevent blowback over the entire operating range and reduce fuel consumption. It can provide a two-stroke engine with an excellent crank chamber structure that can obtain high output over a long period of time.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between output and engine speed, Figure 2 is a schematic cross-sectional view of a fir tree, Figure 3 is a schematic cross-sectional view of ■-1ll in Figure 2, and Figure 4 is a cross-sectional view of N-N in Figure 3. , FIG. 5 is a graph showing the opening/closing timing of the intake passage. 9... Crankshaft, 13... Crank chamber, 14... Intake passage, 1
7... Partition plate, 18... Valve plate, 20... Main intake passage, 20a, 20b -= 151, 2nd auxiliary intake passage, 21a. 21b... Reed valve patent applicant Kawasaki Heavy Industries, Ltd. ll- Figure 1

Claims (2)

[Claims] (1) In a crank chamber precompression type two-stroke engine in which the intake passage communicating with the crank chamber is opened and closed by a valve rotating in conjunction with the crankshaft to control the inflow of the air-fuel mixture, the intake passage is connected to the On the downstream side of the valve plate, the main intake passage is branched into a central main intake passage, and first and second auxiliary intake passages sandwiching the main intake passage on the side in the rotational direction of the valve plate and the side in the opposite rotational direction. A reed valve that only allows inflow into the crank chamber is arranged, and the second sub-intake passage is opened before the main intake passage is opened by the temporary valve, and the first sub-intake passage is opened after the main intake passage is closed. An intake system for a crank chamber precompression type two-stroke engine, characterized in that a passage is closed. (2) A partition member is provided on the same root that crosses the intake passage in contact with the valve plate, and the main intake passage and the first and second sub-intake passages are perforated in the partition member. Claim 1, characterized in that the reed valve provided in the second auxiliary intake passage is locked, and one side of the partition member constitutes a sliding seating surface for the valve plate. Intake device (3) of the described crank chamber precompression type two-stroke engine (3) Upstream of the valve plate, the intake passage communicating with the carburetor is approximately parallel to the valve plate,
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