JPH0441239Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to an idle adjustment device that adjusts the idle fuel flow rate of a carburetor of an internal combustion engine (hereinafter also referred to as engine).

(Prior Art) Conventionally, fuel during idle operation of an engine is generally supplied from an idle port of a carburetor. The flow rate of this idle fuel is as shown in Figure 5.
Adjustment is made possible by an idle adjustment screw 4 inserted through the adjustment hole 1 and provided with a substantially conical measuring portion 3 located at the entrance 2a of the idle mixture passage 2. 4a is a threaded part, idle adjustment screw 4
By changing the tightening amount of the measuring part 3
The idle fuel flow rate is adjusted by changing the cross-sectional area of the metering passage 5 between the outer circumference of the metering passage 5 and the inner circumference of the idle mixture passage inlet 2a. 6 is a locking spring;
7 is a fuel passage, 8 is a fuel jet, 9 is an air bleed passage, and 10 is an air bleed jet.

As a prior art, there is, for example, Japanese Patent Laid-Open No. 55-98639.

(Problem to be solved by the invention) However, with the above idle adjustment screw 4,
As shown in FIG. 6, the cross-sectional shape of the metering passage 5 is annular, and the length of the wetted edge, which is the contact length of the fuel passing through the metering passage 5, is long compared to the cross-sectional area of the passage 5. Fuel viscosity greatly affects flow rate.

In addition, since the cross-sectional shape of the metering passage 5 is annular,
Depending on the machining accuracy, the axial center of the metering section 3 may be assembled eccentrically, and the amount of eccentricity causes the flow rate to change even in the same metering area. Furthermore, when fuel enters from below and air from above and merges as shown in the figure, even if the amount of eccentricity is the same, the way the air and fuel enter are different when swinging upward and when swinging downward. There were problems such as changes in flow rate.

Therefore, the object of this invention is to provide an idle adjustment device for a carburetor that minimizes the length of the wetted edge of the metering passage and prevents eccentricity of the metering section.

(Means for Solving the Problems) In order to achieve the above object, the carburetor idle adjustment device according to this invention includes an idle adjustment screw that adjusts the idle fuel flow rate flowing through the idle mixture passage of the engine carburetor. An idle adjustment device for a carburetor, wherein the idle adjustment screw is screwed into the adjustment hole and a valve body inserted into an adjustment hole coaxial with the idle mixture passage so as to be slidable in the axial direction thereof. a screw body rotatable with respect to the valve body,
Further, a groove formed in the adjustment hole along the axial direction, a detent attached to the valve body and having a protrusion that slidably engages with the groove, and a detent provided at the tip of the valve body. , a metering section having a cylindrical body inserted into the idle mixture passage, having a diagonally cut sloped surface formed on one side thereof, and the other side slidably contacting a wall surface of the idle mixture passage; It is equipped with

(Function) In the above means, the valve body is moved forward and backward by rotating the screw body in the forward or reverse direction. Since the valve body is prevented from rotating by the engagement between the rotation prevention protrusion and the groove of the adjustment hole, the valve body can be moved forward and backward without being rotated by the screw body.

By forming the measuring portion with a diagonally cut sloped surface formed on one side of the cylindrical body, the cross-sectional shape of the measuring passage becomes approximately semicircular. Therefore, compared to the conventional substantially conical measuring section, a wetted edge having a shorter length can be obtained.

In addition, the valve body, which is rotatable relative to the threaded body, is prevented from rotating by the engagement of the anti-rotation protrusion with the groove of the adjustment hole, and the other side of the metering portion slides against the wall surface of the idle mixture passage. Due to the movable contact, the valve body can be moved forward and backward along the wall surface of the idle mixture passage without rotating around the axis. eccentricity is prevented.

(Example) This invention will be described below based on drawings showing examples. However, components that are the same as those in the prior art are given the same numbers as in FIG. 5, and explanations thereof will be omitted. 1st
The figure is a longitudinal cross-sectional view of the embodiment, and FIG. 4 is a longitudinal cross-sectional view of essential parts of a carburetor including this embodiment. Reference numeral 11 indicates an idle adjustment screw according to this invention, which includes a valve body 12 and a threaded portion (corresponding to a threaded body) 13 that are constructed separately.
and is inserted into the adjustment hole 1. Valve body 1
2 has a rotation stopper 14 at the rear end, and can only move linearly within the adjustment hole 1. The detent 14 is an annular body attached to the rear end of the valve body 12, and has a protrusion 14a formed on the lower side. It prevents rotation. A measuring section 15 is provided at the tip of the valve body 12.
is provided. The side surface of the measuring section 15 has a shape in which the lower side of the cylindrical body in the figure is ground down so as to become thinner toward the tip, so as to form a beveled inclined surface 15a. The upper cylindrical surface of the measuring section 15 slides in contact with the wall surface of the idle mixture passage 2. 1
6 is a return spring.

According to the idle adjustment screw 11 configured as described above, the valve body 12 is moved forward and backward by turning the threaded portion 13. At this time, the measuring passage 17 formed between the outer periphery of the measuring part 15 and the inner periphery of the mixture passage inlet 2a usually has a substantially semicircular cross-sectional shape as shown in the cross-sectional view in FIG. Become. Therefore, the length of the wetted edge is shorter than that of a conventional substantially conical measuring section. Therefore, even if there is a change in the viscosity of the fuel due to a change in temperature, it will not be affected much, and the idle fuel flow rate can be kept almost constant.

Further, since the valve body 12 is prevented from rotating by the engagement between the protrusion 14a of the rotation stopper 14 and the groove 1a of the adjustment hole 1, when the threaded portion 13 is turned, the measuring portion 1
5 does not rotate around the axis, but the upper side always slides in the axial direction in contact with the inner wall of the mixture passage 2.
The axial center of the measuring part 15 does not become eccentric. Therefore, fluctuations in the idle fuel flow rate due to eccentricity as in the prior art are also prevented.

(Effect of the device) As explained above, this device uses a measuring section with a diagonally cut sloped surface formed on one side of the cylindrical body, which reduces the length of the wetted edge compared to the conventional conical measuring section. can be made shorter, reducing the influence of fuel viscosity.

In addition, the valve body, which is rotatable relative to the threaded body, does not rotate around the axis and is moved forward and backward along the wall surface of the idle mixture passage. Eccentricity is prevented, thereby reducing changes in idle fuel flow rate due to the eccentricity.

Therefore, the measurement accuracy of idle fuel can be improved.

[Brief explanation of drawings]

Figures 1 to 4 show an embodiment of this invention, where Figure 1 is a longitudinal sectional view, Figure 2 is a cross sectional view of the measuring section, Figure 3 is a rear end view, and Figure 4 is this embodiment. FIG. FIG. 5 is a longitudinal cross-sectional view of a conventional idle adjustment device, and FIG. 6 is a cross-sectional view of the measuring section. 1...Adjustment hole, 2...Idle mixture passage, 2
a...Inlet, 11...Idle adjustment screw, 12...
... Valve body, 13 ... Threaded part, 15 ... Measuring part, 15
a...Slope surface.

Claims (1)

[Claims for Utility Model Registration] An idle adjustment device for a carburetor, comprising an idle adjustment screw that adjusts the flow rate of idle fuel flowing through an idle mixture passage of a carburetor of an engine, the idle adjustment screw controlling the idle mixture Consisting of a valve body inserted into an adjustment hole coaxial with the air passage so as to be slidable in the axial direction thereof, and a screw body screwed into the adjustment hole and rotatable with respect to the valve body,
Further, a groove formed in the adjustment hole along the axial direction, a detent attached to the valve body and having a protrusion that slidably engages with the groove, and a detent provided at the tip of the valve body. , a metering section having a cylindrical body inserted into the idle mixture passage, having a diagonally cut sloped surface formed on one side thereof, and the other side slidably contacting a wall surface of the idle mixture passage; A carburetor idle adjustment device comprising: