Fuel Adjustment Mechanism

Abstract

To provide a fuel adjustment mechanism capable of forming a main body portion in compact and reducing assembling man-hour by reducing the number of components.SOLUTION: A fuel adjustment mechanism 2 includes a limit cap 60 mounted on a needle valve inserted into an adjustment hole 12. An inner peripheral surface of a second hole portion 14 of the adjustment hole 12 has formed therein a restriction groove 15, and a guide groove 17 extending in an axial direction of the second hole portion 14 from the restriction groove 15 to an outer surface of a main body portion 10. An outer peripheral surface of the limit cap 60 has formed therein a projecting portion 61 inserted into the restriction groove 15, and the projecting portion 61 can pass the guide groove 17. The main body portion 10 has formed therein a cast hole 16 extending in a direction crossing the axial direction of the second hole portion 14 from the restriction groove 15 to the outer surface of the main body portion 10.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a fuel adjustment mechanism used for adjusting the air-fuel ratio of an air-fuel mixture.

Background Art

[0002] In a fuel adjustment device which is a carburetor of an internal combustion engine, a fuel adjustment mechanism for adjusting the air-fuel ratio of an air-fuel mixture is provided. The fuel adjustment mechanism includes a main body portion in which an adjustment hole communicating with a flow path of the carburetor is formed, a needle valve screwed into a screw groove in the adjustment hole, and a limit cap externally fitted to the needle valve. Then, by engaging the needle valve and the limit cap in the circumferential direction, the needle valve and the limit cap rotate in conjunction with each other.

[0003] In the above-described fuel adjustment mechanism, by rotating the needle valve around its axis and adjusting the protruding amount of the needle valve into the flow path, the flow rate of the fuel flowing through the flow path can be increased or decreased. Moreover, a protrusion is formed on the outer peripheral surface of the limit cap, and this protrusion is inserted into a limiting groove formed on the inner peripheral surface of the adjustment hole. Then, by restricting the movement of the protrusion by the limiting groove, the rotation of the needle valve is restricted.

[0004] When casting the main body portion of the above-described fuel adjustment mechanism, a mold for forming the adjustment hole is pulled out in the axial direction of the adjustment hole. At this time, a groove portion having the same width as the limiting groove is formed from the limiting groove to the outer edge of the adjustment hole. That is, the outer end portion of the adjustment hole is enlarged in diameter.

[0005] In addition, in the fuel adjustment mechanism, in order to prevent the limit cap from being pulled out of the adjustment hole without using a special tool, it is necessary to reduce the gap between the inner peripheral surface of the outer end portion of the adjustment hole and the outer peripheral surface of the limit cap. Therefore, as a conventional fuel adjustment mechanism, there is one in which after casting the adjustment hole, an annular guide member is fitted into the outer end portion of the adjustment hole to reduce the gap around the limit cap (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2021-085373 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] In the conventional fuel adjustment mechanism described above, where a guide member is fitted to the outer end of the adjustment hole, the inner diameter of the adjustment hole becomes larger, which leads to the problem of the main body becoming larger. Furthermore, the conventional fuel adjustment mechanism described above has the problem of increasing the number of parts and increasing the assembly man-hours.

[0008] The present invention aims to solve the aforementioned problems and provide a fuel adjustment mechanism that can be made compact, reduces the number of parts, and lowers the assembly time. [Means for solving the problem]

[0009] To solve the aforementioned problems, the present invention provides a fuel adjustment device Used A fuel adjustment mechanism, the flow path and the flow path The device comprises a main body having an adjustment hole leading to a flow path, a needle valve inserted into the adjustment hole, and a limit cap attached to the needle valve. The adjustment hole has a first hole leading to the flow path of the main body and a second hole opening to the outer surface of the main body. The needle valve has a first shaft portion screwed into the first hole and a second shaft portion housed in the second hole. The second shaft portion and the limit cap fitted onto the second shaft portion are configured to engage in the circumferential direction of the limit cap. In the axial intermediate portion of the second hole, Inner circumferential surface of the second hole He made a depression in it. Restriction groove for limiting rotation A is formed on the inner circumferential surface of the second hole. The restricting groove part from the outer surface of the main body The opening of the second hole The guide extends axially across the second hole. grooveA projection is formed on the outer circumferential surface of the limit cap, which is inserted into the limit groove, and the projection is capable of passing through the guide groove. A cast hole is formed in the main body portion, extending from the limit groove to the outer surface of the main body portion in a direction intersecting the axial direction of the second hole portion. [Effects of the Invention]

[0010] In the fuel adjustment mechanism of the present invention, the cast hole formed in the main body is formed when the mold for forming a limiting groove on the inner circumferential surface of the second hole is removed from the main body in a direction intersecting the axial direction of the second hole during casting of the main body. In the fuel adjustment mechanism of the present invention, it is not necessary to make the inner diameter of the outer end of the adjustment hole larger in order to form a limiting groove on the inner circumferential surface of the adjustment hole. Therefore, even without attaching a part to the outer end of the adjustment hole, the gap between the inner circumferential surface of the outer end of the adjustment hole and the outer circumferential surface of the limit cap can be reduced. As a result, the fuel adjustment mechanism of the present invention can be made compact, the number of parts can be reduced, and the assembly man-hours can be reduced. [Brief explanation of the drawing]

[0011] [Figure 1] This is a perspective view showing a fuel adjustment device according to an embodiment of the present invention. [Figure 2] This is a side cross-sectional view showing a protruding portion of a fuel adjustment device according to an embodiment of the present invention. [Figure 3] This is an exploded perspective view showing a fuel adjustment device according to an embodiment of the present invention. [Figure 4] This is a cross-sectional perspective view showing the limit cap of a flow rate adjustment limiting member according to an embodiment of the present invention. [Figure 5] Figure 1 is a cross-sectional view (VV) showing a fuel adjustment device according to an embodiment of the present invention. [Figure 6] This is a front view showing the adjustment holes of a fuel adjustment device according to an embodiment of the present invention. [Figure 7] This is a bottom view showing a protruding portion of a fuel adjustment device according to an embodiment of the present invention.

Best Mode for Carrying Out the Invention

[0012] An example of an embodiment of the present invention will be described in detail with reference to the drawings as appropriate. As shown in FIG. 1, the fuel adjustment mechanism 2 of the present embodiment is used in the fuel adjustment device 1. The fuel adjustment device 1 of the present embodiment is, for example, a carburetor (intake device) of an internal combustion engine of a small working machine such as a chainsaw or a blower.

[0013] The fuel adjustment mechanism 2 includes a main body portion 10 and a flow rate adjustment restricting member 3 assembled to an adjustment hole 12 formed in the main body portion 10. The main body portion 10 is a single metal part formed by casting. Inside the main body portion 10, a flow path (not shown) for generating a mixture of fuel and air is formed. Two adjustment holes 12, 12 are opened on the tip surface of the protruding portion 11 formed on the front surface of the main body portion 10. Both adjustment holes 12, 12 are arranged side by side in the horizontal direction. The adjustment hole 12 is a through hole communicating with the flow path through which fuel flows.

[0014] In the main body portion 10 of the present embodiment, the adjustment hole 12 arranged on the left side of FIG. 6 is a hole portion for adjusting the air-fuel ratio of the mixture when the output shaft of the internal combustion engine rotates at a low speed. Further, the adjustment hole 12 arranged on the right side of FIG. 6 is a hole portion for adjusting the air-fuel ratio of the mixture when the output shaft of the internal combustion engine rotates at a high speed. Note that FIG. 6 shows a state in which the flow rate adjustment restricting member 3 (see FIG. 3) described later is removed from the adjustment hole 12.

[0015] In the present embodiment, the configurations of both adjustment holes 12, 12 and the two flow rate adjustment restricting members 3, 3 respectively assembled to both adjustment holes 12, 12 are the same. Therefore, in the following description, the adjustment hole 12 arranged on the left side of FIG. 6 and the flow rate adjustment restricting member 3 assembled to the adjustment hole 12 will be described, and the description of the adjustment hole 12 arranged on the right side of FIG. 6 and the flow rate adjustment restricting member 3 assembled to the adjustment hole 12 will be omitted.

[0016] As shown in Fig. 2, a first hole portion 13 is formed at a portion on the inner end side (the flow path side of the main body portion 10) of the adjustment hole 12, and a second hole portion 14 is formed at a portion on the outer end side (the tip side of the protruding portion 11) of the adjustment hole 12. The first hole portion 13 is a hole portion having a circular cross-section that communicates with the flow path in the main body portion 10 (see Fig. 5). A screw groove is formed on the inner peripheral surface of the first hole portion 13.

[0017] The second hole portion 14 is a hole portion having a larger diameter than the first hole portion 13, and opens to the tip surface of the protruding portion 11. The first hole portion 13 opens to the bottom surface of the second hole portion 14. In addition, in the present embodiment, as shown in Fig. 6, the side portions of both second hole portions 14, 14 of the two adjustment holes 12, 12 are connected, and both second hole portions 14, 14 constitute one hole portion.

[0018] On the inner peripheral surface of the second hole portion 14, a restriction groove 15 is formed at an intermediate portion in the axial direction. The restriction groove 15 is a portion that depresses the inner peripheral surface of the second hole portion 14 as shown in Fig. 5, and extends in the circumferential direction of the second hole portion 14. The restriction groove 15 of the present embodiment is formed in a range of an angle of approximately 90 degrees in the circumferential direction of the adjustment hole 12 with the central axis of the adjustment hole 12 as the center point.

[0019] In the present embodiment, a punching hole 16 communicates from the restriction groove 15 to the bottom surface of the main body portion 10 (see Fig. 7). The punching hole 16 extends linearly in a direction intersecting the axial direction of the second hole portion 14 (adjustment hole 12). The punching hole 16 is a hole portion that is inevitably formed when the main body portion 10 is cast. When the main body portion 10 is cast, a mold extending in a direction intersecting the axial direction of the second hole portion 14 is arranged from the second hole portion 14. By pulling out this mold in a direction intersecting the axial direction of the second hole portion 14, the restriction groove 15 is formed on the inner peripheral surface of the second hole portion 14. At this time, the punching hole 16 is formed from the restriction groove 15 to the bottom surface of the main body portion 10.

[0020] Furthermore, if the mold for forming the limiting groove 15 is removed in the axial direction of the second hole 14, a groove with the same width as the limiting groove 15 will be formed extending from the limiting groove 15 to the outer edge of the second hole 14. In other words, the outer end of the second hole 14 will be enlarged in diameter. In contrast, in this embodiment, by removing the mold for forming the limiting groove 15 in a direction intersecting the axial direction of the second hole 14, as shown in Figure 6, the limiting groove 15 can be formed in the axial middle portion of the inner circumferential surface of the second hole 14 without the outer end of the second hole 14 expanding in diameter.

[0021] On the inner circumferential surface of the second hole 14, a guide groove 17 extending in the axial direction is formed on the outer end side (the tip side of the protruding portion 11) of the limiting groove 15, as shown in Figure 2. The inner end of the guide groove 17 communicates with the limiting groove 15, and the outer end of the guide groove 17 opens to the tip surface of the protruding portion 11. The guide groove 17 is the part through which the projection 61 of the limit cap 60 passes when the limit cap 60, described later, is inserted into the adjustment hole 12 from the outside.

[0022] As shown in Figure 1, the flow rate adjustment limiting member 3 of this embodiment includes a needle valve 30 inserted into the adjustment hole 12 and a limit cap 60 attached to the needle valve 30. The needle valve 30 is a member for adjusting the air-fuel ratio of the fuel mixture.

[0023] As shown in Figure 3, the needle valve 30 is a linear member with a circular cross-section overall. As shown in Figure 2, a first shaft portion 31 is formed on the inner end side (left side in Figure 2), and a second shaft portion 32 is formed on the outer end side (right side in Figure 2) of the needle valve 30 (see Figure 3). The first shaft portion 31 and the second shaft portion 32 of the needle valve 30 are made of metal.

[0024] The first shaft portion 31 is positioned on the inner end side (left side in Figure 2) of the needle valve 30 when assembled to the adjustment hole 12, and is the part that is inserted into the first hole portion 13 of the adjustment hole 12. A screw groove is formed on the outer circumferential surface of the first shaft portion 31, and the first shaft portion 31 is screwed into the screw groove formed on the inner circumferential surface of the first hole portion 13. By rotating the needle valve 30 around its axis, the amount of insertion of the needle valve 30 into the first hole 13 is increased or decreased, and the amount of protrusion of the needle valve 30 into the flow path is adjusted, thereby controlling the flow rate of fuel circulating in the flow path. In this way, the air-fuel ratio of the mixture can be adjusted by rotating the needle valve 30 around its axis.

[0025] The second shaft portion 32 is connected to the first shaft portion 31 and, when assembled to the adjustment hole 12, is positioned on the outer end side (right side in Figure 2) of the first shaft portion 31 and is housed within the second hole portion 14 of the adjustment hole 12. As shown in Figure 3, a tip groove 33 is formed on the tip surface of the second shaft portion 32 to allow the needle valve 30 to be rotated around its axis using a tool such as a screwdriver. In this embodiment, the tip groove 33 is formed in a straight line so that the tip of a flathead screwdriver can engage with it, but the tool used to rotate the needle valve 30 is not limited. For example, a cross-shaped groove may be formed on the tip surface of the second shaft portion 32 to accommodate a Phillips screwdriver, or a hexagonal hole may be formed on the tip surface of the second shaft portion 32 to accommodate a hex wrench.

[0026] As shown in Figure 3, a first uneven surface 34 formed by knurling (flat processing) is created on the outer circumferential surface of the second shaft portion 32, extending around its entire circumference. The first uneven portion 34 is a part in which multiple linear grooves extending in the axial direction of the needle valve 30 are arranged at equal intervals in the circumferential direction of the second shaft portion 32. In this embodiment, the first uneven portion 34 is formed on the outer circumferential surface of the second shaft portion 32 by knurling, but the method is not limited. For example, the first uneven portion 34 may be formed on the second shaft portion 32 by cutting, assembling other parts, molding, etc.

[0027] As shown in Figure 2, on the outer circumferential surface of the second shaft portion 32, a pressure contact portion 35 is provided on the side of the first shaft portion 31 that is closer to the first uneven portion 34, which is then press-fitted into the limit cap 60 described later. The pressure contact portion 35 is an annular resin part that is fitted onto the second shaft portion 32 (see Figure 3). The pressure contact portion 35 is integrally molded with the second shaft portion 32 by insert molding. Thus, the needle valve 30 consists of a metal first shaft portion 31 and second shaft portion 32 and a resin pressure contact portion 35, which together constitute a single component.

[0028] The limit cap 60 is a cylindrical metal component that is fitted onto the second shaft portion 32 of the needle valve 30 (see Figure 3). When assembled to the adjustment hole 12, the limit cap 60 is fitted onto the needle valve 30 and housed within the second hole portion 14. As shown in Figure 3, a projection 61 protrudes from the outer circumferential surface of the limit cap 60. In this embodiment, the projection 61 is formed on the outer circumferential surface of the limit cap 60 slightly towards the base end (inner end) than the axial center.

[0029] A second set of protrusions 62 is formed on the inner circumferential surface of the limit cap 60, extending around its entire circumference. As shown in Figure 4, the second set of protrusions 62 consists of multiple linear projections 62a extending in the axial direction of the limit cap 60, arranged in the circumferential direction of the limit cap 60. In this embodiment, pairs of protrusions 62a, 62a are arranged at intervals around the circumferential direction of the limit cap 60. In this configuration, the number of protrusions 62a is reduced compared to the case where single protrusions 62a are arranged at equal intervals around the circumferential direction of the limit cap 60.

[0030] As shown in Figure 2, when the limit cap 60 is fitted onto the second shaft portion 32 of the needle valve 30, the second recessed portion 62 of the limit cap 60 and the first recessed portion 34 of the needle valve 30 are engaged in the circumferential direction of the limit cap 60 and the needle valve 30. As a result, the limit cap 60 rotates around the axis in conjunction with the rotation of the needle valve 30 around its axis.

[0031] When the limit cap 60 is housed in the second hole 14, the entire projection 61 of the limit cap 60 is positioned within the limit groove 15. When the limit cap 60 rotates circumferentially, the projection 61 shown in Figure 5 contacts the circumferential end face of the limit groove 15, allowing the projection 61 to move within a range of 90 degrees of rotation around the axis of the adjustment hole 12. As a result, the limit cap 60 can rotate 1 / 4 turn around its axis. The needle valve 30, onto which the limit cap 60 is fitted, can also rotate 1 / 4 turn around its axis.

[0032] As shown in Figure 2, when inserting the limit cap 60 into the second hole 14, the orientation of the limit cap 60 around its axis is adjusted so that the projection 61 passes through the guide groove 17. Then, when the limit cap 60 is inserted into the second hole 14 and the inner edge of the limit cap 60 is in contact with the bottom surface of the second hole 14, the entire projection 61 is positioned inside the limit groove 15, but inside the guide groove 17. At this time, as shown in Figure 5, the projection 61 is positioned at one end in the circumferential direction in the axial cross-section of the limit groove 15. When the limit cap 60 is housed in the second hole 14, the projection 61 does not engage with the guide groove 17, allowing the limit cap 60 to rotate around its axis within the second hole 14.

[0033] In the flow rate adjustment limiting member 3, as shown in Figure 2, when the limit cap 60 is fitted onto the second shaft portion 32 of the needle valve 30, the pressure contact portion 35 of the needle valve 30 is pressed against the inner circumferential surface of the second recessed portion 62 of the limit cap 60. The minimum inner diameter of the second recessed portion 62 (the inner diameter at the top of each projection 62a) is smaller than the maximum outer diameter of the pressure contact portion 35 of the needle valve 30. When the limit cap 60 is fitted onto the needle valve 30 from the tip side toward the base side, the pressure contact portion 35 of the needle valve 30 is press-fitted into the second recessed portion 62 of the limit cap 60. At this time, each projection 62a of the metal second recessed portion 62 bites into the outer circumferential surface of the resin pressure contact portion 35. In other words, the outer circumferential surface of the pressure contact portion 35 is scraped by the tops of each projection 62a of the second recessed portion 62, while the pressure contact portion 35 is press-fitted into the second recessed portion 62 and fixed in place. In this way, the needle valve 30 is press-fitted into the limit cap 60, thereby fixing the needle valve 30 and the limit cap 60 in the axial direction.

[0034] Next, the procedure for assembling the flow rate adjustment limiting member 3 to the adjustment hole 12 of the fuel adjustment mechanism 2 shown in Figure 1 will be described. First, as shown in Figure 2, the first shaft portion 31 of the needle valve 30 is inserted into the first hole portion 13 of the adjustment hole 12, and the screw groove of the first shaft portion 31 is screwed into the screw groove of the first hole portion 13. Then, by rotating the needle valve 30 around its axis, the amount of insertion of the needle valve 30 into the adjustment hole 12 is increased or decreased, and the amount of protrusion of the inner end of the needle valve 30 into the flow path is adjusted to control the air-fuel ratio of the mixture.

[0035] Next, the limit cap 60 is inserted into the adjustment hole 12 from the outside. At this time, the projection 61 of the limit cap 60 is passed through the guide groove 17 of the second hole portion 14 of the adjustment hole 12.

[0036] As the limit cap 60 is moved towards the inner end of the adjustment hole 12, the second protrusion 62 of the limit cap 60 moves axially and engages with the first protrusion 34 of the needle valve 30. As a result, the second protrusion 62 of the limit cap 60 and the first protrusion 34 of the needle valve 30 are engaged in the circumferential direction. Furthermore, the pressure contact portion 35 of the needle valve 30 is press-fitted into the second recessed portion 62 of the limit cap 60, thereby fixing the needle valve 30 and the limit cap 60 in the axial direction. In this embodiment, as shown in Figure 4, because the spacing between the projections 62a of the second recessed portion 62 of the limit cap 60 is large, the set opening (circumferential position of the needle valve 30) does not shift, and the second recessed portion 62 and the first recessed portion 34 interlock and are fixed in place. In this way, even if the pressure contact portion 35 of the needle valve 30 shown in Figure 2 is press-fitted into the second recessed portion 62 of the limit cap 60, the opening can be fixed without shifting.

[0037] When the limit cap 60 is attached to the second shaft portion 32 of the needle valve 30 in this manner, as shown in Figure 5, the projection 61 of the limit cap 60 is positioned at one end in the circumferential direction in the axial cross-section of the limit groove 15. Furthermore, the projection 61 is positioned at one end of the circumferential direction of the axial cross-section of the limiting groove 15 as its reference position, and can rotate 1 / 4 turn clockwise (right-hand) within the limiting groove 15 as shown in Figure 5. As a result, the limit cap 60 and the needle valve 30 can rotate 1 / 4 turn clockwise (right-hand) as shown in Figure 5 from the reference position where the needle valve 30 is assembled into the adjustment hole 12 to properly adjust the air-fuel ratio of the mixture.

[0038] In this embodiment, when the needle valve 30 is rotated clockwise from the reference position as shown in Figure 5, the fuel flow rate passing through the passage decreases, thereby diluting the fuel concentration in the fuel mixture. Because the projection 61 cannot rotate counterclockwise (leftward) from its reference position due to the limiting groove 15, the needle valve 30 cannot be rotated counterclockwise from its reference position in Figure 5. In this way, in this embodiment, the air-fuel ratio within the movable range of the limit cap 60 is configured so that the fuel concentration does not become richer than the air-fuel ratio of the mixture at the position of the needle valve 30, which is set as the reference position.

[0039] As shown in Figure 2, the flow rate adjustment limiting member 3 comprises a needle valve 30 inserted into an adjustment hole 12 formed in the main body 10 of the fuel adjustment device 1, which is a vaporizer, and a metal limit cap 60 attached to the needle valve 30. The needle valve 30 has a first metal shaft portion 31 that is screwed into a first hole portion 13 formed on the inside of the adjustment hole 12, and a second metal shaft portion 32 that is housed in a second hole portion 14 formed on the outside of the adjustment hole 12. A first uneven portion 34 is formed on the outer circumferential surface of the second shaft portion 32, and a resin-made pressure-contact portion 35 is provided on the outer circumferential surface of the second shaft portion 32 on the side of the first shaft portion 31 that is closer to the first uneven portion 34. This pressure-contact portion 35 is integrally molded with the second shaft portion 32. The outer circumferential surface of the limit cap 60 has a projection 61 which is inserted into a rotation-limiting groove 15 formed on the outer circumferential surface of the second hole 14. The inner circumferential surface of the limit cap 60 has a second projection 62 which engages with the first projection 34 of the needle valve 30 in the circumferential direction of the limit cap 60. Furthermore, the pressure contact portion 35 of the needle valve 30 is configured to be pressed against the second uneven portion 62 on the inner circumferential surface of the limit cap 60.

[0040] In the flow rate adjustment limiting member 3 of this embodiment, as shown in Figure 5, the projection 61 of the limit cap 60 is positioned within the limiting groove 15 of the adjustment hole 12 of the main body 10, and the movement of the projection 61 is restricted by the limiting groove 15, thereby restricting the rotation of the needle valve 30. This makes it possible to keep the fuel concentration of the mixture within an appropriate range.

[0041] In the flow rate adjustment limiting member 3 of this embodiment, as shown in Figure 1, the entire tip of the limit cap 60 is open. With this configuration, the tip of a general-purpose tool such as a screwdriver can be inserted into the limit cap 60 from the tip and engaged with the needle valve 30, making it easier to adjust the air-fuel ratio of the mixture. In other words, because the opening of the tip surface of the limit cap 60 is wide, special tools (for example, those with a tapered tip) are not required. Also, because the tip of the tool can be easily and accurately inserted into the tip groove 33 of the needle valve 30, the tip groove 33 is less likely to deform.

[0042] In the flow rate adjustment limiting member 3 of this embodiment, as shown in Figure 2, the first recessed portion 34 of the needle valve 30 and the second recessed portion 62 of the limit cap 60 are made of metal and are resistant to deformation, so the needle valve 30 and the limit cap 60 can be reliably engaged at a desired position in the circumferential direction. This prevents the needle valve 30 from rotating around its axis relative to the limit cap 60, and thus prevents the reference value of the air-fuel ratio of the mixture from shifting.

[0043] In the flow rate adjustment limiting member 3 of this embodiment, since the contact portion 35 of the needle valve 30 is made of resin, which is more flexible than metal, when the contact portion 35 is pressed against the second recessed portion 62 of the limit cap 60, each projection 62a of the second recessed portion 62 bites into the outer circumferential surface of the contact portion 35. In this embodiment, the tops of each projection 62a provided on the inner surface of the metal limit cap 60 bite into the outer circumferential surface of the resin contact portion 35, fixing the contact portion 35 by grinding it down. As a result, the limit cap 60 is securely fixed to the needle valve 30 in the axial direction, preventing unintentional rotation.

[0044] In the needle valve 30 of the flow rate adjustment limiting member 3 of this embodiment, the metal first shaft portion 31 and second shaft portion 32 and the resin pressure contact portion 35 are integrally molded by insert molding, thus reducing the number of parts in the flow rate adjustment limiting member 3. As a result, the assembly man-hours for the fuel adjustment device 1 are reduced, and production efficiency can be improved.

[0045] In the fuel adjustment mechanism 2 of this embodiment, a guide groove 17 is formed on the inner circumferential surface of the second hole 14, extending from the limit groove 15 to the outer surface of the main body 10 in the axial direction of the second hole 14. The projection 61 formed on the outer circumferential surface of the limit cap 60 can pass through the guide groove 17. Furthermore, as shown in Figure 5, the main body 10 of the fuel adjustment mechanism 2 in this embodiment has a cast hole 16 that extends from the limiting groove 15 to the outer surface of the main body 10 in a direction intersecting the axial direction of the second hole 14.

[0046] In this fuel adjustment mechanism 2, the limiting groove 15 is formed on the inner circumferential surface of the adjustment hole 12 by removing the mold for forming the limiting groove 15 in a direction intersecting the axial direction of the second hole 14. Therefore, there is no need to enlarge the outer end of the adjustment hole 12. Therefore, in the fuel adjustment mechanism 2 of this embodiment, the gap between the inner surface of the outer end of the adjustment hole 12 and the outer surface of the limit cap 60 can be reduced without attaching any parts to the outer end of the adjustment hole 12. As a result, in the fuel adjustment mechanism 2 of this embodiment, the main body 10 can be made compact, and the number of parts can be reduced, thereby reducing the assembly time.

[0047] Furthermore, in the fuel adjustment mechanism 2 of this embodiment, since the casting hole 16 extends from the limiting groove 15 to the bottom surface of the main body 10, the casting hole 16 is less conspicuous and dust is less likely to enter the casting hole 16.

[0048] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and can be modified as appropriate without departing from its spirit. In this embodiment, as shown in Figure 1, a fuel adjustment mechanism 2 and a flow rate adjustment limiting member 3 used in a fuel adjustment device 1, which is a vaporizer for the internal combustion engine of a small work machine such as a chainsaw or blower, are described, but the devices to which the present invention can be applied are not limited.

[0049] In this embodiment, as shown in Figure 5, the projection 61 of the limit cap 60 can rotate 1 / 4 turn within the limit groove 15. However, the shape of the projection 61 and the limit groove 15, as well as the range in which the projection 61 can rotate, are not limited and are set appropriately according to the required adjustment amount.

[0050] In this embodiment, as shown in Figure 2, the needle valve 30 is provided with a resin pressure contact portion 35, but the configuration of the needle valve 30 and the limit cap 60 is not limited. For example, a resin pressure contact cylinder portion may be provided in part of the limit cap 60, and the metal needle valve 30 may be press-fitted into this pressure contact cylinder portion.

[0051] In the fuel adjustment mechanism 2 and flow rate adjustment limiting member 3 of this embodiment shown in Figure 1, the flow rate of fuel is adjusted, but the flow rate of air may also be adjusted using the present invention. [Explanation of symbols]

[0052] 1 Fuel regulator 2 Fuel adjustment mechanism 3. Flow rate adjustment limiting member 10 Main body 11 Protrusion 12 Adjustment hole 13 First hole 14 Second hole 15 limiting grooves 16 casting holes 17 Guide groove 30 Needle valve 31 First shaft part 32 Second shaft part 33 Tip groove 34 First uneven part 35 Pressure-welded section 60 Limit Cap 61 Protrusion 62 Second uneven part 62a protrusion

Claims

1. A fuel adjustment mechanism used in a fuel adjustment device, A main body having a flow path and an adjustment hole leading to the flow path, A needle valve inserted into the adjustment hole, The needle valve is fitted with a limit cap, The adjustment hole has, The first hole in the main body is connected to the flow path, A second hole is formed on the outer surface of the main body, The aforementioned needle valve includes, A first shaft portion that is screwed into the first hole, A second shaft portion is formed which is housed in the second hole portion, The second shaft portion and the limit cap fitted onto the second shaft portion are configured to engage with the limit cap in the circumferential direction. In the axial intermediate portion of the second hole, a rotation-restricting groove is formed by recessing the inner circumferential surface of the second hole, A guide groove is formed on the inner circumferential surface of the second hole, extending in the axial direction of the second hole from a part of the restricting groove to the opening of the second hole that opens to the outer surface of the main body. The outer circumferential surface of the limit cap has a projection that is inserted into the limiting groove, and the projection is capable of passing through the guide groove. The fuel adjustment mechanism is characterized in that the main body portion has a cast-out hole formed therein that extends from the limiting groove to the outer surface of the main body portion in a direction intersecting the axial direction of the second hole portion.

2. A fuel adjustment mechanism according to claim 1, The fuel adjustment mechanism is characterized in that the casting hole extends from a part of the limiting groove to the outer surface on the bottom side of the main body.

3. A fuel adjustment mechanism according to claim 1, The fuel adjustment device is a fuel adjustment mechanism characterized by being a vaporizer.

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