JP2008111363A - Carburetor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carburetor capable of sufficiently suppressing the leading air amount supplied at the acceleration staring of an engine, in simple structure. <P>SOLUTION: The carburetor used for a stratified scavenging two-stroke engine is equipped with an air fuel mixture passage supplying an air fuel mixture to the engine; a leading air passage 5 supplying leading air to the engine; a flow rate control valve controlling an air fuel mixture flow rate in the air fuel mixture passage; and a rotary valve 8 controlling the leading air flow rate in the leading air passage by synchronizing with the flow rate control valve, and a plate-shaped member 11 parallel to the rotating shaft of the rotary valve 8 and having a plane-shaped part 11A along the communication direction of a passage part 8A is installed in the passage 8A of the rotary valve 8. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a carburetor, and more particularly to a carburetor for a stratified scavenging two-cycle engine.

  Conventionally, some carburetors used in a stratified scavenging two-cycle engine have used a butterfly valve as a flow rate adjustment valve on the mixture passage side and a rotary valve as a flow rate adjustment valve on the leading air passage side (Patent Document) 1). The carburetor with this structure uses the characteristic of the rotary valve, that is, the characteristic that the change in the opening area is small in the low engine speed range (valve opening) and suppresses the amount of leading air in the low speed range. The acceleration performance can be improved.

Japanese Patent Laid-Open No. 2006-161776

However, in the technique of Patent Document 1, since the change in the opening area on the rotary valve side is only small, the amount of leading air is not sufficiently suppressed, and sufficient acceleration performance cannot always be obtained. There is.
It is also possible to use a lost motion mechanism as an interlocking mechanism between the butterfly valve and the rotary valve so that the rotary valve starts to open with a certain delay with respect to the butterfly valve. There is a problem that the structure becomes complicated by providing the lost motion mechanism.

  An object of the present invention is to provide a carburetor having a simple structure and capable of sufficiently suppressing the amount of leading air supplied at the start of engine acceleration.

  A carburetor according to claim 1 of the present invention is a carburetor used in a stratified scavenging two-cycle engine, an air-fuel mixture passage for supplying air-fuel mixture to the engine side, a lead air passage for supplying lead air to the engine side, A flow rate adjusting valve that adjusts the flow rate of the air-fuel mixture in the air-fuel mixture passage, and a rotary valve that operates in synchronization with the flow rate adjusting valve to adjust the flow rate of the leading air in the leading air passage. The passage portion of the valve is provided with a plate-like member having a planar portion that is parallel to the rotation axis of the rotary valve and extends in the communication direction of the passage portion.

  The carburetor according to a second aspect of the present invention is the carburetor according to the first aspect, wherein the planar portion of the plate-like member is provided on the rotating shaft and is parallel to the communication direction of the passage portion. It is characterized by being.

  The carburetor according to claim 3 of the present invention is the carburetor according to claim 1 or 2, wherein the length of the plate-like member in the communication direction of the passage portion is equal to or greater than the outer diameter of the rotary valve. It is characterized by being.

  A carburetor according to a fourth aspect of the present invention is the carburetor according to any one of the first to third aspects, wherein the rotary shaft passes through a passage portion of the rotary valve on the rotating shaft. A needle reaching the flow rate adjusting valve is provided, and a thickness dimension of the plate-like member is equal to or less than an outer diameter dimension of the needle.

  According to the first aspect of the present invention, since the plate-like member is provided in the passage portion of the rotary valve on the leading air side, the passage portion communicates with the leading air passage by the rotation of the rotary valve at the start of engine acceleration. Even if it starts, the plate-like member becomes the flow path resistance, and the flow rate of the leading air can be sufficiently suppressed, and the acceleration performance can be reliably improved by preventing the mixed air from being diluted in the combustion chamber during acceleration. In addition, it is a simple structure in which a plate-like member is simply provided in the passage portion, and unlike the case where a lost motion mechanism is provided, there is no concern that the structure becomes complicated.

According to the invention of claim 2, since the plate-like member is provided in parallel to the communication direction of the passage portion, the flow resistance when the rotary valve is fully opened can be further reduced, and when the engine is in a high rotation range, etc. The leading air can be efficiently supplied to the engine.
According to the invention of claim 3, by setting the length dimension of the plate-like member to be equal to or larger than the outer diameter dimension of the rotary valve, even in the partial opening state immediately after the passage portion of the rotary valve starts to communicate with the leading air passage. By maintaining the leading air passage in a blocked state, the leading air flow rate can be made substantially zero, and the acceleration performance can be further improved.
According to the invention of claim 4, if the needle is originally provided, even if a plate-like member is added, the flow resistance in the fully opened state hardly increases and the supply of the leading air is good. Can be done.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is an exploded perspective view showing a carburetor 1 of the present embodiment. FIG. 2 is a side view of the fully closed carburetor 1 as seen from the engine side (not shown). FIG. 3 is a cross-sectional view of the carburetor 1 in the fully closed state. 1 to 3, the carburetor 1 is for a stratified scavenging two-cycle engine, and includes a storage portion 2 that stores gasoline fuel from a fuel tank, and a passage formation portion 3 that is provided above the storage portion 2 in the figure. I have.

  The storage unit 2 incorporates a pump function that operates by pressure pulsation in the crankcase of the engine, and has a structure in which fuel is drawn from the tank by this pump function. The drawn fuel is again drawn into the passage forming portion 3 by a negative pressure due to pressure pulsation, and the fuel and the intake air mix to generate an air-fuel mixture. Since such a structure is a structure generally used for a carburetor, further detailed description thereof is omitted here.

  The passage forming portion 3 is provided with an air-fuel mixture passage 4 that generates the air-fuel mixture and supplies it to the engine side, and a leading air passage 5 that supplies the stratified scavenging leading air to the engine side. In addition, a valve unit 6 that passes through each of the passages 4 and 5 is inserted into the passage forming portion 3. The valve unit 6 has a structure in which a rotary valve (flow rate adjusting valve) 7 that adjusts the mixture flow rate in the mixture passage 4 and a rotary valve 8 that adjusts the leading air flow rate in the leading air passage 5 are integrally provided. Thus, the rotary valves 7 and 8 rotate in synchronization with each other in response to the accelerator operation.

  As shown in FIG. 3, the valve unit 6 is provided with a needle 9 that passes through the passage portion 8A of the rotary valve 8 and reaches the passage portion 7A of the rotary valve 7, and the storage portion 2 has the rotary valve 7. A cylindrical portion 10 protruding from the passage portion 7A is provided. The tip of the needle 9 is inserted into the cylindrical portion 10, and the amount of insertion changes according to the amount of rotation in the valve unit 6. That is, a needle valve is constituted by the needle 9 and the cylindrical portion 10, and fuel corresponding to the flow path resistance depending on the insertion amount of the needle 9 passes through the cylindrical portion 10 from the storage portion 2 to the passage portion 7A by the negative pressure described above. Withdrawn, an air-fuel mixture is generated.

  In each rotary valve 7, the outer diameter dimension of the rotary valve 8 on the leading air side is larger than the outer diameter dimension of the rotary valve 7 on the air-fuel mixture side, and each rotary valve 7 is at the start of acceleration from the idling state. , 8 at the beginning of opening, first, as shown in FIG. 4, the mixture-side rotary valve 7 having a small outer diameter is opened, and the passage portion 8A of the leading-air-side rotary valve 8 is slightly delayed. It communicates with the leading air passage 5 (the timing when it is fully opened is the same). However, in this embodiment, as soon as the passage portion 8A begins to appear in the leading air passage 5, the front and rear of the leading air passage 5 are not completely communicated with each other, but a structure in which communication is performed later is adopted.

  As shown in FIG. 5 and FIG. 6 in a fully opened state, the center in the passage portion 8A of the rotary valve 8 is parallel to the rotational axis of the rotary valve 8 and along the direction of communication of the passage portion 8A. A plate-like member 11 having a planar portion 11A is provided. The planar portion 11A of the plate-like member 11 in the present embodiment is provided on the rotating shaft and is also parallel to the communication direction of the passage portion 8A.

  The plate thickness of the plate-like member 11 is equal to or less than the outer diameter of the needle 9 (substantially the same in this embodiment), and the cross-sectional area of the passage portion 8A is substantially the same as when the plate-like member 11 is not provided. Yes (the cross-sectional area at the center of the passage portion 8A is equal). The length of the plate member 11 in the communication direction is the same as the outer diameter of the rotary valve 8. Naturally, such a plate-like member 11 rotates integrally with the rotary valve 8.

  As a result, as shown in FIG. 7A, when the rotary valve 8 is in the fully closed state, the leading air passage 5 is blocked and, as shown in FIG. Even in the partial opening state, although a part of the passage portion 8A appears in the leading air passage 5, the front and rear of the leading air passage 5 are blocked by the plate-like member 11. As a result, as shown in (C), at the start of acceleration, the leading air side rotary valve 8 can be opened with a certain delay behind the mixture side rotary valve 7, and the leading air flow rate at the start of acceleration can be reduced. The acceleration performance can be greatly improved with sufficient suppression.

  And, as shown in (D), when the rotary valve 8 is fully opened, a large amount of leading air can be supplied with the original large opening area of the passage portion 8A, thereby preventing the air-fuel mixture from being blown through and a layered scavenging two-cycle engine. The function as can be surely exhibited. Moreover, since the plate-like member 11 has a simple structure that is simply provided in the passage portion 8A, it is possible to prevent the structure from becoming complicated, and there is no inconvenience such as hindering assembly.

  Here, when the plate-like member 11 is not provided (Normal), when the plate-like member 11 having a length dimension (4 mm) approximately half of the outer diameter dimension of the rotary valve 8 is used at the center of the passage portion 8A. (Short) When the plate-like member 11 of the present embodiment having the same length (8 mm) as the outer diameter of the rotary valve 8 is used at the center of the passage 8A (Long), the engine acceleration test Went. As a test method, acceleration was started 5 seconds after the engine was started, and the time (seconds: s) required to reach a certain engine speed was measured. The number of times of measurement is 3 times.

  FIG. 8 shows the test results. According to the results shown in FIG. 8, it can be seen that the acceleration characteristics can be improved by providing the plate-like member 11. This confirmed the effect of the present invention. Moreover, it can be said that the longer dimension of the plate-like member 11 is equal to the outer diameter dimension of the rotary valve 8, the acceleration characteristics can be improved, and the longer one is more effective.

The best configuration, method, and the like for carrying out the present invention have been disclosed above, but the present invention is not limited to this. That is, the invention has been illustrated and described with particular reference to certain specific embodiments, but without departing from the spirit and scope of the invention, Various modifications can be made by those skilled in the art in terms of quantity and other detailed configurations.
Therefore, the description limited to the shape, quantity and the like disclosed above is an example for easy understanding of the present invention, and does not limit the present invention. The description by the name of the member which remove | excluded the limitation of one part or all of such restrictions is included in this invention.

  For example, in the above embodiment, the length of the plate-like member 11 is the same as the outer diameter of the rotary valve 8, but as shown in FIG. 9, even when the length is larger than the outer diameter. In such a case, the opening timing of the rotary valve 8 can be further delayed with respect to the mixture-side rotary valve 7.

  Moreover, in the said embodiment, although the rotary valve 7 was provided in the mixed air side, such a flow regulating valve may be a butterfly valve, and the leading air side should just be a rotary valve.

  The present invention can be suitably used as a carburetor for a stratified scavenging two-cycle engine mounted on a portable working machine such as a brush cutter, an engine blower, or a chain saw.

The disassembled perspective view which shows the carburetor which concerns on one Embodiment of this invention. The side view which looked at the fully closed carburetor from the air cleaner side. Sectional drawing of the carburetor of a fully closed state. The side view which shows the carburetor of the partial opening state. The side view which shows the carburetor of a full open state. Sectional drawing which shows the carburetor of a full open state. The figure for demonstrating operation | movement of the rotary valve of the leading air side. The figure which shows the acceleration test result of an engine. The figure which shows the modification of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Carburetor, 4 ... Mixture passage, 5 ... Leading air passage, 7 ... Rotary valve which is flow control valve, 8 ... Rotary valve, 8A ... Passage part, 9 ... Needle, 11 ... Plate-shaped member, 11A ... Planar shape Department.

Claims (4)

A carburetor used in a stratified scavenging two-cycle engine,
An air-fuel mixture passage for supplying air-fuel mixture to the engine side;
A leading air passage for supplying leading air to the engine side;
A flow rate adjusting valve for adjusting the flow rate of the air-fuel mixture in the air-fuel mixture passage;
A rotary valve that operates in synchronization with the flow rate adjusting valve and adjusts the leading air flow rate in the leading air passage;
The passage portion of the rotary valve is provided with a plate-like member having a planar portion parallel to the rotation axis of the rotary valve and along the communication direction of the passage portion. Carburetor. The carburetor according to claim 1.
The planar portion of the plate-like member is provided on the rotating shaft, and is parallel to the communication direction of the passage portion. The carburetor according to claim 1 or 2,
The length of the plate-like member in the communication direction of the passage portion is equal to or greater than the outer diameter of the rotary valve. The carburetor according to any one of claims 1 to 3,
On the rotating shaft, a needle that penetrates the passage portion of the rotary valve and reaches the flow rate adjustment valve on the mixture side is provided,
A thickness of the plate member is equal to or less than an outer diameter of the needle.

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