JPH0377378B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a carburetor that adjusts and controls the amount and concentration of air-fuel mixture supplied to an engine, and in particular relates to a carburetor that adjusts and controls the amount and concentration of air-fuel mixture supplied to an engine, and particularly relates to a carburetor that has a throttle valve connected to an intake passage. This invention relates to a method of manufacturing a sliding throttle valve type carburetor movably disposed within a guide cylinder, and is often used as a carburetor for motorcycle engines.

[Conventional technology]

Conventionally, as mentioned above, sliding throttle valve type carburetors are often used in motorcycles, and since they tend to be smaller in size and have higher output, it is desirable to improve the suction efficiency of the carburetor. . A vaporizer aimed at improving this inhalation efficiency was achieved by Japanese Patent Application No. 152940/1983 filed by the present applicant.

This is achieved by making the sliding throttle valve have a side surface facing the engine side and a side surface facing the air cleaner side, the side surface facing the engine side being arc-shaped, and the side surface facing the air cleaner side being connected to the end of the side surface facing the engine side. This uses a sliding throttle valve formed by a straight part that is perpendicular to the longitudinal axis of the intake passage and a connecting part that connects the straight part. According to this, the groove in the guide section of the sliding throttle valve to the carburetor body can be made extremely small, and this allows the engine to maintain good suction efficiency, making it possible to improve the output. It was made.

In manufacturing such a carburetor, in particular, the engine-side surface of the throttle valve guide cylinder is processed by milling because it has an arcuate shape.

[Problem that the invention seeks to solve]

This conventional method of manufacturing a sliding throttle valve type carburetor has the following problems.

Machining of the throttle valve guide cylinder is performed by milling, which requires many man-hours and increases manufacturing costs.

According to milling, since the process is always performed using a rotating cutting tool, it is difficult to expect an improvement in accuracy, especially near the relatively narrow straight section (guide side) where the engine-side guide cylinder surface and the air cleaner-side guide cylinder surface meet. . This is because the diameter of the bearing portion that holds the cutting tool is small and cannot maintain high rigidity.

If the surface roughness obtained through machining changes, the sliding resistance and wear resistance of the sliding throttle valve will change significantly. Therefore, it is necessary to obtain a uniform surface roughness, and cutting tool management etc. It is difficult to control cutting conditions.

[Means for solving problems]

The method of manufacturing a sliding throttle valve type carburetor according to the present invention was devised in view of the above-mentioned drawbacks, and the main purpose is to reduce manufacturing costs. and a side surface facing the air cleaner side, the side surface facing the engine side is arc-shaped, and the arc-shaped end of the side surface facing the engine side and the end of the side surface facing the air cleaner side are respectively connected to the longitudinal axis of the intake passage. In addition to being connected at the guide side surface approximately along the core line, a cutaway is provided at the bottom of the sliding throttle valve from the side facing the air cleaner side to the side facing the engine side, and the center of the jet needle to be placed on the sliding throttle valve is connected. Connect the ends of the side faces opposite to the air cleaner side and place the sliding throttle valve on the engine side from a line perpendicular to the longitudinal axis of the intake passage, and pass the sliding throttle valve from the top of the carburetor body to the lower recess of the carburetor body. In a sliding throttle valve type carburetor which is movably arranged in a throttle valve guide cylinder provided with The intake passage is formed by casting perpendicular to the longitudinal axis of the intake passage, and the engine side side of the throttle valve guide cylinder is shaped similar to the engine side opposite side of the sliding throttle valve to make it small in size. The throttle valve guide cylinder is formed by casting perpendicular to the direction axis, and then the throttle valve guide cylinder is broached.The engine side side is broached using the air cleaner side side as a guide for the broaching tool, and then The lower part of the throttle valve guide cylinder that opens into the lower recess is closed off with a jet block.

[Effect]

In machining the throttle valve guide cylinder, the side surface on the air cleaner side is used as a guide in broaching, and only the side surface on the engine side is broached.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a sliding throttle valve type carburetor according to the present invention will be described below with reference to FIGS.

Reference numeral 1 denotes a carburetor body through which an intake passage 2 passes, and a throttle valve guide cylinder 3 is opened in connection with the intake passage 2, while a lower concave portion 1A of the carburetor body 1 and a float chamber body 4 are connected to each other. A float chamber 5 is formed by this. A float F is disposed within the float chamber 5, and the float F operates a valve seat disposed at the end of a fuel inflow path (not shown) and a float valve that opens and closes the valve seat. Form and maintain a constant liquid level. 6 is a sliding throttle valve, which will be explained in more detail with reference to FIG.

The sliding throttle valve 6 is formed by an engine side facing side surface 6A (left side in the figure) facing the engine side and an air cleaner side facing side surface 6B facing the air cleaner side. The side surface 6A is formed in an arc shape (semicircular shape with a single radius R). Then, guide side surfaces 6C and 6C are provided from the arcuate ends A and B of the engine side facing side surface 6A, respectively, along the longitudinal axis XX of the intake passage 2, and other guide surfaces 6C and 6C are provided. Ends C, D
An air cleaner side facing side surface 6B is formed from the side opposite to the engine side facing side surface 6A. (The width H of the guide side surfaces 6C, 6C is preferably a small width of about 3 millimeters.) Furthermore, the air cleaner side opposing side surface 6B will be described in detail. From the other ends C and D of the guide side surfaces 6C and 6C, the longitudinal axis X-
A connecting portion that straddles the straight line portions 6D, 6D substantially orthogonal to X and the longitudinal axis XX of the intake passage 2, and projects from the straight line portions 6D, 6D toward the air cleaner side (right side in FIG. 3). 6E.

Furthermore, a cutaway 6F is provided at the bottom of the sliding throttle valve 6 that opens into the intake passage 2 to control the intake passage negative pressure that acts on the needle jet, which will be described later. An inclined surface is formed from the opposing side surface 6B toward the engine side opposing side surface 6A.

It is located on the longitudinal axis X-X of the intake passage 2 of the sliding throttle valve 6, and is closer to the engine than the line C-D connecting the ends C and D of the side surface 6B facing the air cleaner side (see Fig. 3). The center K of the jet needle 7 is located on the left side). More specifically, a jet needle insertion hole 6 into which the jet needle 7 is inserted and held.
The center of the hole G may be placed on the line CD or on the engine side from the line CD.

Reference numeral 8 designates a needle jet opening into the intake passage 2, and the needle jet 8 is immersed below a constant liquid level in the float chamber 5 via a main fuel jet 9.

In particular, the carburetor main body 1 has a structure as shown in FIGS. 4 and 5. That is, the throttle valve guide tube 3 is formed by casting from above the intake passage 2 to the lower recess 1A of the carburetor body 1, and the cross-sectional shape of the throttle valve guide tube 3 is shaped like a sliding type. The cross-sectional shape of the throttle valve guide tube 3 is made to substantially match the cross-sectional shape of the throttle valve 6, and the engine side surface 3A and the air cleaner side side surface 3B of the throttle valve guide tube 3 are designed as follows. That is, the air cleaner side side surface 3B is the sliding throttle valve 6.
The shape is the same as that of the air cleaner side opposite side surface 6B, and the longitudinal axis X-
It is formed by casting perpendicular to X.

The engine-side side surface 3A is made similar in shape to the engine-side opposing side surface 6A of the sliding throttle valve 6, and has a slight machining allowance of, for example, 0.15 mm, to have a machining allowance for later broaching.
It has a small shape of about a millimeter, and is formed by casting perpendicular to the longitudinal axis X--X of the intake passage 2.

Then, the air cleaner side side surface 3 mentioned above.
B. An example of casting out of the engine-side side surface 3A in a direction perpendicular to the longitudinal axis XX of the intake passage 2 will be described with reference to the dashed dotted line in FIG. That is, the upper end core 20A extends from the upper opening U of the throttle valve guide cylinder 3 to the lower recess 1A of the carburetor main body 1, and the lower core 20A is opposed to the upper core 20A from the lower recess 1A of the carburetor main body 1. 20B, the upper core 20A is formed with a surface corresponding to the engine-side side surface 3A that is orthogonal to the intake passage 2, while the lower core 20B is formed with a surface that corresponds to the air cleaner-side side surface that is orthogonal to the intake passage 2. 3B
is formed.

These upper core 20A and lower core 20
B and B are matched at mutually inclined surfaces M and N within the throttle valve guide cylinder 3. In a mold structure having such a mold structure, the cores 20A and 20B are set at an angle greater than θ and less than 90 degrees with respect to the longitudinal axis X-X of the intake passage 2 between the inclined surfaces M and N. By pulling it out, the intake passage 2 is located on the engine side side 3A and the air cleaner side side 3B inside the throttle valve guide cylinder 3.
Each side surface 3A orthogonal to the longitudinal axis XX,
3B can be formed.

Next, broaching of the throttle valve guide tube 3 will be explained. The broaching tool (not shown) does not have a blade on the side corresponding to the air cleaner side side 3B, but has a blade only on the side corresponding to the engine side side 3A. A broach tool is then inserted into the throttle valve guide tube 3. At this time, the broach is guided by the air cleaner side side surface 3B of the throttle valve guide tube 3, and only the engine side side surface 3A is inserted. It is used for broaching.

Therefore, broaching does not require machining the entire circumferential surface of the throttle valve guide cylinder 3, and the cutting allowance can be made almost evenly, so it is possible to improve machinability. Since the cutting allowance can be made almost uniform regardless of the depth of the throttle valve guide cylinder 3, the shape of the throttle valve guide cylinder 3 can be manufactured with extremely high accuracy.

Furthermore, in manufacturing the broach cutting tool, it was possible to use a single-edged blade instead of a double-edged blade, which enabled a significant cost reduction of the cutting tool.

Also, the one shown in Fig. 6 is the throttle valve guide cylinder 3.
The engine side side surface 3A is not broached entirely, but only the parts necessary for performance are cut.

That is, 3A' is an intake passage outer peripheral protrusion that surrounds the intake passage 2 as a whole, and 3A'' passes through the approximately longitudinal axis X-X of the intake passage 2, and extends in the longitudinal direction of the throttle valve guide cylinder 3. Central guide protrusion along axis Y-Y, 3
A is a side guide protrusion that passes through the longitudinal axis XX of the throttle valve guide tube 3 and is located on both sides of the longitudinal axis YY of the throttle valve guide tube 3. The outer peripheral protrusion 3A', the central guide protrusion 3A'', and the side guide protrusion 3A are molded to be smaller than the dimensions of the sliding throttle valve 6, and the machining allowance for these protrusions is 1 mm. The following are preferable in terms of tool life and machined surface roughness.

Then, the throttle valve guide cylinder 3 is broached in the same manner as described above, but in this example, only a limited part of the engine side side surface 3A is processed, so the cutting takt time is further reduced. This makes it possible to further reduce processing costs.

〔Effect of the invention〕

As described above, the method for manufacturing a sliding throttle valve type carburetor according to the present invention has the following effects.

The throttle valve guide cylinder has its upper and lower parts open, and the engine-side and air cleaner-side sides of the throttle valve guide cylinder are formed by casting at right angles to the longitudinal axis of the intake path. During broaching, the side surface on the engine side was broached using the side surface on the air cleaner side as a guide for the broaching tool, so the side surface on the engine side could be machined with a nearly constant cutting allowance, and the side surface on the air cleaner side could also be used as a guide. It is possible to form the throttle valve guide tube extremely accurately and at right angles to the intake passage,
Furthermore, in broaching, one of the blades is used as a guide, and the other blade is used to process the sliding surface on one side, making it possible to improve workability and reduce the cost of cutting tools.The main body of the carburetor It can be manufactured accurately and at low cost.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the sliding throttle valve type carburetor according to the present invention, FIG. 2 is a top plan view of the state shown in FIG. 1 with the top cover removed, and FIG. 3 is the same as in FIG. 1. 4 is a longitudinal sectional view of only the carburetor body after completion of molding, 5 is a plan view of the top of 4, and 6 is a detailed explanatory view from the top plane of a sliding throttle valve used in 5 is a vertical sectional view taken along the - line in FIG. 4. FIG. 1... Carburetor main body, 2... Intake path, 3... Throttle valve guide tube, 3A... Engine side side, 3A'... Intake path outer periphery protrusion, 3A''... Center guide protrusion, 3A
...Side guide protrusion, 3B... Air cleaner side side surface.

Claims (1)

[Scope of Claims] 1. The sliding throttle valve 6 is constituted by a side surface 6A facing the engine side and a side surface 6B facing the air cleaner side, the side surface facing the engine side is arcuate, and the arcuate end of the side surface facing the engine side is arcuate. The portions A and B and the ends C and D of the opposite side surface 6B on the air cleaner side are respectively formed into guide side surfaces 6C and 6 that are substantially along the longitudinal centerline X-X of the intake passage 2.
A cutaway 6F is provided at the bottom of the sliding throttle valve 6 from the air cleaner side facing side 6B to the engine side facing side 6A. End C of air cleaner side opposing side surface 6B,
D, and the sliding throttle valve 6 is connected from the upper part of the carburetor body 1 to the lower concave part of the carburetor body 1. In a sliding throttle valve type carburetor movably arranged in the throttle valve guide tube 3 which is provided through the throttle valve guide tube 1A, the air cleaner side side surface 3B of the throttle valve guide tube 3
The air cleaner side opposite side 6 of the sliding throttle valve 6
The same shape as B, and the longitudinal axis X-X of the intake passage 2
On the other hand, the engine-side side surface 3A of the throttle valve guide tube 6 is shaped similar to the engine-side opposite side surface 6A of the sliding throttle valve 6 to make it small in shape, and the longitudinal direction of the intake passage 2 is The throttle valve guide cylinder 3 is formed by casting perpendicular to the axis X-X, and then the engine side side surface 3A is broached using the air cleaner side side surface 3B as a guide for a broaching tool. Lower recess 1 of carburetor body 1 afterward
A method for manufacturing a sliding throttle valve type carburetor in which the lower part of a throttle valve guide cylinder 3 opening at A is closed with a jet block 10. 2. The sliding throttle valve 6 is composed of a side surface 6A facing the engine side and a side surface 6B facing the air cleaner side. The ends C and D of the opposite side surface 6B on the cleaner side are connected to a guide side surface 6C, which extends approximately along the longitudinal axis X-X of the intake passage 2, respectively.
6C, and a cutaway 6F is provided at the bottom of the sliding throttle valve 6 from the air cleaner side opposing side surface 6B to the engine side opposing side surface 6A, and the center K of the jet needle 7 disposed on the sliding throttle valve 6 is provided. The ends C and D of the opposite side surface 6B on the air cleaner side are connected and arranged on the engine side from a line C-D perpendicular to the longitudinal axis X-X of the intake passage 2, and the sliding throttle valve 6 is connected to the carburetor main body. In a sliding throttle valve type carburetor movably arranged in a throttle valve guide tube 3 which is provided to penetrate from the upper part of the carburetor body 1 to the lower recess 1A of the carburetor body 1;
The air cleaner side opposite side 6 of the sliding throttle valve 6
The same shape as B, and the longitudinal axis X-X of the intake passage 2
On the other hand, the engine-side side surface 3A of the throttle valve guide cylinder 6 is made similar in shape to the engine-side opposite side surface 6A of the sliding throttle valve 6 to make it small and surround the intake passage 2. The outer peripheral protrusion 3A of the intake passage, the central guide protrusion 3A'' passing through the approximate longitudinal axis XX of the intake passage 2 and along the longitudinal axis YY of the throttle valve guide cylinder 6, and the central guide protrusion 3A'' of the intake passage 2. Approximately longitudinal axis X-
The longitudinal axis of the throttle valve guide cylinder 3 passes through X Y-Y
Side guide protrusions 3A, 3A located on both sides of
, and the longitudinal axis X-X of the intake passage 2
When forming the throttle valve guide tube 3 by casting, the air cleaner side surface 6B is used as a guide for the broaching tool, and the air intake passage outer peripheral protrusion 3A' and the center guide protrusion on the engine side surface 6B are cast. 3A'' and the side guide protrusion 3A are broached, and then the lower part of the throttle valve guide tube 3, which opens into the lower recess 1A of the carburetor body 1, is closed with a jet block 10. How to make the utensils.