JP2007177758A - Carburetor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carburetor capable of supplying appropriate quantity of fuel for start at a time of cold engine. <P>SOLUTION: The carburetor 1 is provided with an intake air flow path 21 distributing intake air to an engine, a fuel storage part 22 storing fuel from the fuel tank, a fuel supply flow path 30 for start supplying fuel for start from the fuel storage part 22 to the intake air flow path 21, and a solenoid valve 3 provided in a middle of the fuel supply flow path 30 for start. The fuel supply flow path 30 for start between a fuel intake part 31 and the intake air flow path 21 is formed in a straight line shape. Consequently, pressure loss of fuel between the fuel intake part 31 and the intake air flow path 21 is suppressed, and the carburetor 1 can easily draws out fuel to the intake air flow path 21 by negative pressure generated in the intake air flow path 21 without retention of fuel. Since appropriate quantity of fuel for start can be supplied at a time of cold engine, startability of the engine can be secured. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a carburetor, and more particularly, to a carburetor with an auto choke applied to a portable work machine engine such as a brush cutter.

  Conventionally, a mower for mowing is known as a portable work machine. In such a brush cutter, a cutting blade and a nylon cutter provided at the tip of the outer pipe are driven by a two-cycle engine or the like, but the engine is usually provided at the rear end side of the outer pipe or a backpack type. Then, it will be carried on the operator by an appropriate shoulder device (for example, refer to Patent Document 1 and Patent Document 2).

By the way, in recent years, in order to improve the startability of the engine, a brush cutter adopting an auto choke has appeared. There are various types of auto chokes, but the present inventors have provided a solenoid valve (solenoid valve) integrally with the carburetor and opened this solenoid valve to overconcentrate the intake flow path in the carburetor. The structure which supplies the fuel for operation, ie, the fuel for starting, is proposed.
In such a carburetor, an auto choke is often effective only when the temperature is lower than a predetermined temperature, that is, when the engine is cold (see, for example, Patent Document 3).

Japanese Patent Laid-Open No. 10-150825 JP 09-294441 A JP 2002-339805 A

  However, in such a conventional carburetor, the supply flow path for supplying the starting fuel from the fuel intake portion that is opened and closed by the solenoid valve to the intake flow path in the carburetor is complicated due to restrictions on the shape of the carburetor body. It was said. For this reason, the pressure loss in the supply flow path becomes large, the fuel stays in the supply flow path, and the fuel may not easily reach the intake flow path. Therefore, there has been a problem that the startability is still not improved, for example, the operation of rotating the output shaft of the engine at the time of starting, that is, the number of cranking increases.

  An object of the present invention is to provide a carburetor capable of supplying an optimal amount of starting fuel when the engine is cold.

  The carburetor according to claim 1 of the present invention includes an intake passage for circulating intake air to the engine, a fuel storage portion for storing fuel from a fuel tank, and a starting fuel from the fuel storage portion to the intake passage. A starting fuel supply passage to be supplied and a passage opening / closing means provided in the middle of the starting fuel supply passage, and at least one of the starting fuel supply passages is opened and closed by the passage opening / closing means. And the intake passage is formed in a straight line.

  A carburetor according to a second aspect of the present invention is the carburetor according to the first aspect, wherein a portion that is opened and closed by the flow path opening and closing means has a seat surface that contacts the flow path opening and closing means in a closed state. A sheet member is provided, and the sheet diameter of the sheet member is set to a maximum of 1.0 mm.

  In the above, according to the first aspect of the present invention, the carburetor is formed by communicating in a straight line between at least a portion of the starting fuel supply passage that is opened and closed by the passage opening and closing means and the intake passage. As a result, the pressure loss of the fuel between the portion opened and closed by the passage opening and closing means and the intake passage is suppressed, and the fuel is easily retained in the intake passage by the negative pressure generated in the intake passage without staying in the fuel. Can be pulled out. Therefore, this carburetor can supply an optimal amount of starting fuel when the engine is cold, and can supply an air-fuel mixture having an optimal concentration to the engine, so that the engine can be started.

  According to the invention of claim 2, the carburetor is supplied through the sheet member when the sheet diameter of the sheet member provided at the portion opened and closed by the flow path opening and closing means is set larger than 1.0 mm. Although the fuel becomes excessive and the engine becomes foggy and the startability is deteriorated, the startability of the engine can be prevented from being deteriorated by setting the seat diameter to 1.0 mm at the maximum. Therefore, this carburetor can fully exhibit the choke function with respect to the cold engine and can make the engine startability the best.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of the carburetor 1 of the present embodiment. FIG. 2 is an enlarged cross-sectional view showing a main part of the carburetor 1.
As shown in FIG. 1, the carburetor 1 includes a carburetor main body 2 and a solenoid valve 3 as a channel opening / closing means for an auto choke attached to the carburetor main body 2.

  The carburetor main body 2 is a device that mixes air and fuel, and has a generally known configuration. Therefore, here, in describing the operation (flow of fuel) as the carburetor body 2, such a general configuration will be described in a simplified manner.

  Although not shown, the fuel from the fuel tank is supplied to the fuel reservoir 22 through the inlet pipe 25 and the internal flow path in the carburetor body 2. At this time, in the middle of the internal flow path, a pump part that operates due to pressure fluctuations in the crankcase accompanying the reciprocation of the piston is provided, and fuel is sent to the fuel storage part 22 by this pump part. The fuel in the fuel reservoir 22 is also sent into the nozzle 23 that communicates therewith. The nozzle 23 is arranged coaxially with the rotational center of the rotary valve 24 that rotates in conjunction with the throttle operation, and the tip projects into a through hole 24 </ b> A provided in the rotary valve 24.

  Subsequently, when the rotary valve 24 is rotated by a throttle operation, the intake flow rate through the through hole 24A increases, and the fuel in the nozzle 23 is formed in the opening 23A formed at the tip of the nozzle 23 due to the negative pressure generated in the through hole 24A. To the through hole 24A. That is, since the needle 23B that has blocked the opening 23A moves in a direction to further open the opening 23A in conjunction with the rotation of the rotary valve 24, the fuel from the nozzle 23 is drawn out by the negative pressure.

On the other hand, since the fuel reservoir 22 is isolated by the diaphragm chamber 29A and the diaphragm 29 communicating with the outside air, when the fuel is drawn out from the nozzle 23, the diaphragm 29 moves toward the inside of the fuel reservoir 22. Then, the hammer 29B at the center of the diaphragm 29 pushes the arm 27A connected to the reservoir needle 27 that has blocked the communication hole 28 between the fuel reservoir 22 and the end portion 26 of the internal flow path. Then, the storage portion needle 27 moves and opens the communication hole 28, so that fuel is supplied into the fuel storage portion 22, and a constant amount of fuel is always stored in the fuel storage portion 22.
The fuel drawn out to the through hole 24A as described above is mixed with air, and the mixture is supplied to the engine through the intake passage 21 communicating with the through hole 24A.
In addition, the dimension of the venturi diameter D1 which is an internal diameter of the intake flow path in this embodiment is set in the range of 10.5 to 12.5 mm. The carburetor 1 having a venturi diameter D1 set to a size in this range is applied to a two-cycle engine having a displacement of 20 to 40 CC.

  Further, since the carburetor body 2 is provided with the solenoid valve 3 for auto choke, the following starting fuel supply flow path 30 is formed. That is, the starting fuel supply flow path 30 includes a fuel intake portion 31 that houses a distal end of a movable iron core 60 (described later) of the solenoid valve 3 and a first supply that supplies the fuel in the fuel storage portion 22 to the fuel intake portion 31. A flow path 32 and a second supply flow path 33 that supplies the fuel that has passed through the fuel intake portion 31 to the intake flow path 21 are configured.

  A cylindrical sheet member 38 is press-fitted into the fuel intake portion 31. The seat member 38 divides the fuel intake portion 31 into two spaces 31A and 31B on the upstream side and the downstream side, and includes a communication passage 31C that allows the fuel intake portion 31 to communicate with each other.

  Of the first and second supply channels 32, 33, the second supply channel 33 is formed so that the fuel intake portion 31B and the intake channel 21 communicate with each other in a straight line. Here, by forming the second supply flow path 33 in a straight line, the carburetor 1 suppresses the pressure loss of the fuel in the second supply flow path 33, and the fuel stays in the second supply flow path 33. Therefore, the fuel can be easily supplied to the intake passage 21. Moreover, such a 2nd supply flow path 33 can be drilled by the drilling etc. from the intake flow path 21 side.

  The solenoid valve 3 includes a movable iron core 60, a coil spring 61 that urges the movable iron core 60 downward in the figure, and a cylindrical coil 62 provided on the outer periphery of the movable iron core 60. As shown in FIG. 2, a conical contact portion 60A is formed at the tip of the movable iron core 60, and a synthetic rubber conical cap 60B is provided to cover the conical contact portion 60A. In the state where the cylindrical coil 62 is not excited, the conical cap 60B is in contact with the seat surface 38A, which is the contact portion of the seat member 38, so that fuel does not flow through the communication path 31C. The conical cap 60B is attached to improve the sealing performance. When the cylindrical coil 62 is excited, the movable iron core 60 moves against the coil spring 61 and the conical cap 60B moves away from the seat member 38, so that the fuel intake portion 31A communicates with the fuel intake portion 31B. The fuel flows through the communication passage 31C.

  Here, in addition to the solenoid valve 3, the auto choke includes a temperature sensor that detects the temperature of the engine and a control unit that controls the solenoid valve 3 based on the detection result of the temperature sensor. The engine startability is improved by controlling the auto choke to operate when the temperature of the engine is equal to or lower than a predetermined temperature set in advance.

  At the time of starting the engine, when the auto choke is effective, the solenoid coil 3 is open because the cylindrical coil 62 is in an excited state, and the fuel intake portion 31 and the first and first intake valves 21 enter the intake passage 21 in the carburetor body 2. 2 Fuel is supplied from the fuel tank through the supply passages 32 and 33. Therefore, the air-fuel mixture made rich in the fuel in the intake passage 21 is supplied to the engine.

  Here, as shown in FIG. 2, the seat diameter D <b> 2 of the seat member 38 disposed in the fuel intake portion 31 is set to a maximum of 1.0 mm in order to prevent excessive supply of fuel. . If the seat diameter D2 is set to be larger than 1.0 mm, the engine becomes foggy and the startability deteriorates. In the present embodiment, the seat diameter D2 is optimized in order to sufficiently exhibit the choke function with respect to the cold engine to make the engine startability the best. As a result, the sheet diameter D2 is set to 0.6 mm.

It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
For example, in the above embodiment, the solenoid valve 3 is employed as the flow path opening / closing means. However, an actuator using a piezoelectric motor or the like may be used as the flow path opening / closing means. Can be of any structure.
In the embodiment, the first supply channel 32 that supplies the fuel in the fuel storage unit 22 to the fuel intake unit 31 is not formed in a straight line, but the first supply channel 32 is used as the second supply channel. Similarly to the path 33, it may be formed in a straight line.

In addition, 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 material, quantity, and other detailed configurations.
Therefore, the description limited to the shape, material, etc. 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 is included in this invention.

  The present invention can be effectively used for an engine in which a carburetor including an auto choke is employed.

Sectional drawing of the carburetor of one Embodiment of this invention. Sectional drawing which expands and shows the principal part of the carburetor of embodiment same as the above.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Carburetor, 3 ... Solenoid valve (flow-path opening means), 21 ... Intake flow path, 22 ... Fuel storage part, 30 ... Fuel supply flow path for starting, 31 ... Fuel intake part (It is opened and closed by flow-path opening / closing means) 38 ... sheet member, 38A ... sheet surface, D2 ... sheet diameter

Claims (2)

In the carburetor
An intake passage for circulating intake air to the engine;
A fuel reservoir for storing fuel from the fuel tank;
A starting fuel supply flow path for supplying a starting fuel from the fuel reservoir to the intake flow path;
Channel opening and closing means provided in the middle of the starting fuel supply channel,
A carburetor characterized in that at least a portion of the starting fuel supply flow path that is opened and closed by the flow path opening / closing means and the intake flow path are formed in a straight line. The carburetor according to claim 1.
The portion that is opened and closed by the flow path opening and closing means is provided with a sheet member having a sheet surface that comes into contact with the flow path opening and closing means in the closed state,
A carburetor characterized in that the sheet diameter of the sheet member is set to a maximum of 1.0 mm.

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