JPH0742616A - Pilot screw device of carburetor - Google Patents

Abstract

PURPOSE:To maintain good operability, exhaust gas characteristics and fuel economy of an engine by securing a limit member onto the adjusting part of a pilot screw, and disposing the knob part of the limit member at a position corresponding to a locking protrusion. CONSTITUTION:A pilot screw 20 is rotated by giving rotational force to a rotational force applying means G in an adjusting part 24, and the effective opening area of a pilot outlet hole 7 is controlled through a taper needle valve part 21. In this condition, a limit member 30 is secured integratedly onto the adjusting part 24 of the pilot screw 20, thereby disposing the knob part 32 of the limit member 30 at a position corresponding to a locking protrusion part 8B protruding from a pilot screw support boss 8. It is possible for the pilot screw 20 to rotate within a fixed rotational range, that is, while the control part 32 of the limit member 30 is being brought into contact with the locking protrusion part 8B, thus permitting the amount of an air-fuel mixture to be adjusted within the fixed range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carburetor for adjusting and controlling the amount and concentration of air-fuel mixture supplied to an engine, in particular, a carburetor connected to a low-speed fuel system which opens from a throttle valve to an intake passage on the engine side. The effective opening area of the pilot outlet hole is adjusted and controlled by the taper needle valve part of the pilot screw that is screwed to the carburetor body, and the effective opening area of the pilot outlet hole is fixed to the pilot screw after adjusting with the pilot screw. The present invention relates to a pilot screw device of a carburetor that regulates the rotation of the pilot screw within a fixed rotation range by the restricted member.

[0002]

2. Description of the Related Art A carburetor pilot screw device is
After the pilot screw is rotated and the taper needle valve part of the pilot screw accurately adjusts and controls the effective opening area of the pilot outlet hole with respect to the reference carburetor, the rotation of the pilot screw is kept within a certain rotation range. It is required to be regulated and adjustable. This is to adapt the low-speed air-fuel mixture, which is supplied from the pilot outlet hole to the engine, to the individual engine after the carburetor is installed in the engine, and to adjust the running-in condition of the engine in the use process of the engine. It is necessary to adapt optimally according to the operating environment temperature and atmospheric pressure conditions. Emissions of harmful exhaust gas components and appraisal to maintain good fuel economy are performed.

The first conventional vaporizer pilot screw device is constructed as follows. For example, the actual exploitation 55-1
No. 42650. The pilot screw support boss provided on the carburetor body has a pilot outlet hole and a screw hole concentrically connected from its tip, and the pilot outlet hole connected to the low-speed fuel system is in the intake passage on the engine side of the throttle valve. Open. The pilot screw is screwed into the screw hole including the pilot outlet hole, and the taper needle valve part provided at the tip of the pilot screw is arranged in the pilot outlet hole. The adjusting part including the applying means projects toward the outer side of the pilot screw supporting boss. The pilot screw controls the proper effective opening area of the pilot outlet hole by rotating the pilot screw using a rotational force applying means provided in the adjusting portion at the rear end of the pilot screw. In the pilot screw with the rotational position of the pilot screw properly adjusted in this way, a limiting member is press-fitted into the adjusting portion and integrally fixed so that the rotation is regulated within a certain rotational range. The knob portion provided on the member is arranged corresponding to the locking projection provided on the pilot screw support boss. Thus, the pilot screw can rotate normally and reversely within a constant rotation range until the knob portion comes into contact with the locking projection, and the amount of the low speed air-fuel mixture can be variably adjusted within this range.

The second conventional example is the actual Japanese Utility Model Laid-Open No. 54-1364.
No. 25 publication. In order to adjust the air-fuel ratio in the idling of the engine, in the carburetor equipped with an idle adjusting screw, the adjusting screw is covered with an outer wall, the adjusting screw head is provided in two steps, and only the upper head step is cut after adjustment. Or it is a broken one.

[0005]

According to the first conventional carburetor, the restricting member is arranged so as to project from the pilot screw supporting boss. When an unnecessary external force is applied to the restricting member, the restricting member is provided. Although it is press-fitted into the pilot screw, there is a risk that the limiting member will come off the adjusting portion of the pilot screw. To apply an unnecessary external force to the restricting member is to apply an external force mechanically using a tool such as pliers so that the restricting member is intentionally removed from the adjusting portion of the pilot screw. in this way,
When the limiting member comes off from the adjusting part of the pilot screw due to an unnecessary external force applied to the limiting member, the rotational force applying means (specifically, the minus groove) of the adjusting part of the pilot screw is directly exposed to the outside. Will be done. According to the above, the pilot screw is in a rotatable state by inserting a minus driver into the minus groove as the rotational force imparting means. The mixture can be adjusted indefinitely, which is not preferable in terms of engine drivability, exhaust gas characteristics, and fuel economy.

According to the second conventional technique, after adjusting the pilot screw in the manufacturing process of the carburetor,
The rotation of the pilot screw cannot be adjusted at all, and according to this, it is not possible to properly adjust the low-speed air-fuel mixture in the state where the carburetor is attached to the engine, the running-in state of the engine, and the operating environment state.

The present invention has been made in view of the above point, and in a pilot screw equipped with a limiting member, when the pilot screw is in a normal state in which an unnecessary external force is not applied, the rotation of the pilot screw Can be adjusted within a certain rotation range by a limiting member, while
In the state where an unnecessary external force is applied to the restriction member of the pilot screw, the subsequent rotation of the pilot screw is disabled, engine operability, exhaust gas characteristics,
It is an object of the present invention to provide a carburetor pilot screw device capable of maintaining good fuel economy.

[0008]

In order to achieve the above object, a pilot screw device for a carburetor according to the present invention has an effective opening area of a pilot outlet hole connected to a low-speed fuel system that opens to an intake passage on the engine side of a throttle valve. Is adjusted and controlled by the pilot screw screwed to the carburetor body and the effective opening area of the pilot outlet hole is adjusted, and then the rotation of the pilot screw is kept within a certain rotation range by the restricting member fixed to the pilot screw. In the pilot screw device of the carburetor to be regulated, the pilot screw support boss of the carburetor body is
A pilot outlet hole that opens to the intake passage on the engine side of the throttle valve, a screw hole that connects to the pilot outlet hole, and an enlarged hole that connects to the screw hole and that has a larger diameter than the screw hole and that opens to the outer end surface of the pilot screw support boss. When,
And a locking projection projecting from the pilot screw support boss is provided in a part of the pilot screw support boss; and the pilot screw has a taper for adjusting the effective opening area of the pilot outlet hole. A needle valve portion, a threaded portion that is connected to the tapered needle valve portion and that is screwed into a screw hole, and an enlarged collar portion that is connected to the screw portion and that has an outer diameter larger than that of the screw portion and that can be inserted into the enlarged hole; An adjusting part, which is connected to the expanding collar part and has a rotational force applying means for applying a rotational force to the pilot screw, is provided concentrically, and the adjusting part has a reduced diameter having a groove diameter smaller than the outer diameter of the adjusting part. And a knob portion that extends laterally from the fixing portion, and a fixing portion that is fixed to the adjusting portion of the pilot screw. When the pilot screw thread is screwed into the screw hole of the holding boss and the effective opening area of the pilot outlet hole is adjusted by the taper needle valve, the enlarged flange of the pilot screw faces the enlarged hole. At the same time, the expansion collar is supported by applying elastic force to the expansion collar with a spring that can be contracted in the expansion hole, and the fixing part of the restriction member is integrally fixed to the adjustment part of the pilot screw and the knob part of the restriction member is locked. It is arranged corresponding to the protrusion.

[0009]

The pilot screw is rotated by applying the rotational force to the rotational force applying means of the adjusting portion, and the tapered needle valve portion controls the proper effective opening area of the pilot outlet hole. In this state, the restricting member is integrally fixed to the adjusting portion of the pilot screw, whereby the knob portion of the restricting member is arranged corresponding to the locking projection. The pilot screw is rotatable within a fixed rotation range while the knob portion of the limiting member is in contact with the locking projection, and the air-fuel mixture amount can be adjusted within this fixed range.

When an unnecessary external force is applied to the limiting member, the reduced diameter portion of the limiting member cannot withstand this external force, and the reduced diameter portion is broken, and the adjusting portion including the reduced diameter portion and the limiting member are provided by the pilot screw. take off. According to this, the pilot screw including the enlarged flange portion is inserted and arranged in the pilot screw support boss, it is impossible to give a rotational force to the pilot screw, and the pilot screw is held at a fixed position. It Therefore, the drivability, exhaust gas characteristics, and fuel economy due to the unnecessary rotation of the pilot screw are not impaired.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a carburetor pilot screw device according to the present invention will be described with reference to the drawings. The vaporizer main body 1 will be described with reference to FIGS. 1, 2 and 3 and 4. An intake passage 2 penetrates the inside of the carburetor main body 1, and the intake passage 2 is controlled to be opened / closed by a throttle valve 4 attached to a throttle valve shaft 3.
A low-speed fuel system 5 composed of a mixture of low-speed fuel and low-speed air is sucked into the intake passage 2 through a bypass hole 6 and a pilot outlet hole 7.
Corresponding to the end of the throttle valve 4 at the time of low opening of the intake passage 2
And the pilot outlet hole 7 is located in the intake passage 2A on the engine side of the throttle valve 4 (below the throttle valve 4 in the figure).
Open inside. The above is a known structure.

Reference numeral 8 denotes a pilot screw support boss provided on the carburetor main body 1. A locking projection projecting rightward from the right end surface 8A is provided on a part of the right end surface 8A of the pilot screw support boss 8. A section 8B is provided. The pilot screw support boss 8 has the following structure. Particularly, description will be made with reference to FIGS. That is,
The pilot outlet hole 7 described above is provided on the left side in FIG. 3, is opened to the intake passage 2A on the engine side from the throttle valve 4, and the low speed air-fuel mixture is supplied through the low speed fuel system 5. 9
Is a threaded hole, which is connected to the pilot outlet hole 7, and further to the right in the figure from this threaded hole 9, an enlarged hole 10 having a diameter A larger than the diameter of the threaded hole 9 is opened on the right end surface 8A of the pilot screw support boss 8. To do. The pilot outlet hole 7, the screw hole 9, and the enlarged hole 10 are formed concentrically with the pilot screw support boss 8.

Next, the pilot screw 20 will be described with reference to FIGS. In FIG. 5, the pilot screw 20 has a tapered needle valve portion 21 formed on the left side, a threaded portion 22 formed on the tapered needle valve portion 21 toward the right side, and further on the right end of the threaded portion 22. An enlarged flange portion 23 having an outer diameter B larger than the screw diameter of is formed, and an adjustment portion 24 is formed from the right end of the enlarged flange portion 23 toward the right. These, the taper needle valve portion 21, the screw portion 2
2. The enlarged flange portion 23 and the adjusting portion 24 are formed concentrically, and a rotational force imparting means G such as a minus groove is formed at the right end of the adjusting portion 24. Rotational force applying means G is pilot screw 2
It suffices to have a function of imparting a rotational force to 0. It is desirable that the outer diameter C of the adjusting portion 24 is smaller than the outer diameter B of the enlarged flange portion 23, and the pilot screw 20 is rotated by inserting a minus driver into the minus groove as the rotational force imparting means 25 and rotating. Rotational force is applied.

A reduced diameter portion 25 having a diameter D smaller than the outer diameter C of the adjusting portion 24 is formed on the adjusting portion 24. It is desirable that the reduced diameter portion 25 be formed continuously with the right end 23A of the enlarged collar portion 23. The threaded portion 22 of the pilot screw 20 is the pilot screw support boss 8
The taper needle valve portion 21 is inserted and arranged in the pilot outlet hole 7, the enlarged collar portion 23 is arranged so as to face the enlarged hole 10, and the adjusting portion 24
Is arranged outside the right end surface 8A of the pilot screw support boss 8.

Next, the limiting member 30 will be described with reference to FIGS. The limiting member 30 has a tubular shape, and a fitting hole as a fixing portion 31 is formed from the left end surface thereof toward the right side, and a knob portion 32 is formed so as to project laterally from the outer periphery of the fixing portion 31. To be done.

The pilot screw 20 described above is screwed to the carburetor body as follows. That is, the screw portion 22 of the pilot screw 20 is screwed into the screw hole 9 of the pilot screw support boss 8, and a minus driver is inserted into the minus groove as the rotational force imparting means G of the pilot screw 20 to rotate the pilot screw 20. The screw 20 is advanced and retracted along the longitudinal axis direction thereof, and the tapered needle valve portion 21 is provided to appropriately adjust and control the effective opening area of the pilot outlet hole 7.
With the pilot screw adjustment completed,
The enlarged flange portion 23 of the pilot screw 20 is arranged so as to face the enlarged hole 10 of the pilot screw support boss 8 (being within the enlarged hole 10), and the adjustment portion 24 including the reduced diameter portion 25 is arranged on the pilot screw support boss 8. Right end face 8A
It is arranged so as to project further outward. The right end of the enlarged flange portion 23 may slightly project outward from the right end surface 8A of the pilot screw support boss 8, and the reduced diameter portion 25
May be slightly inserted into the enlarged hole 10 and arranged.
Further, a spring S is arranged in a contracted manner in the enlarged hole 10 of the pilot screw support boss 8 when the pilot screw 20 is screwed, and the spring S moves the left end 23B of the enlarged flange portion 23 of the pilot screw 20 to the right. It elastically urges and thus prevents the pilot screw 20 from swaying. By the above, the pilot outlet hole 7 by the taper needle valve portion 21 of the pilot screw 20
The effective opening area of was controlled properly.

In such a state, a fitting hole serving as a fixing portion 31 of the limiting member 30 is applied to the adjusting portion 24 of the pilot screw 20 projecting outward from the right end surface 8A of the pilot screw supporting boss 8 by applying an adhesive. As a result, the limiting member 30 is integrally fixed to the adjusting portion 24 of the pilot screw 20. (The means for fixing the limiting member 30 to the adjusting portion 24 is not limited to the method using the above adhesive) In such a state, the limiting member 30 is outside the right end surface 8A of the pilot screw support boss 8 and The knob portion 32 is arranged with respect to the locking projection 8B of the pilot screw support boss 8 with gaps X and Y in the forward and reverse rotation directions. This state is shown in FIGS. As described above, the adjustment and control of the effective opening area of the pilot outlet hole 7 by the taper needle valve portion 21 of the pilot screw 20 and all the assembly adjustment work of the pilot screw device are completed.

Next, the operation will be described. When the driver or an operator involved in maintenance adjusts the low-speed air-fuel mixture, the driver rotates the knob portion 32 of the restriction member 30. According to this, in FIG. 2, the knob portion 32 of the restricting member 30 can rotate clockwise by X until it comes into contact with the locking protrusion 8B, and the pilot screw 20 fixed to the restricting member 30 is also shown. It rotates in synchronization with the limiting member 30. If the screw portion 22 of the pilot screw 20 is right-handed, the taper needle valve portion 2
1 reduces the effective opening area of the pilot outlet hole 7 in proportion to the clockwise rotation to reduce the low-speed mixture amount.

Next, when the driver or the like rotates the limiting member 30 counterclockwise in FIG. 2, Y is turned counterclockwise until the knob portion 32 of the limiting member 30 comes into contact with the locking projection 8B.
The pilot screw 20 fixed to the limiting member 30 also rotates synchronously with the limiting member 30. Here, the screw portion 22 of the pilot screw 20
When the right-hand screw is turned on, the taper needle valve portion 21 increases the effective opening area of the pilot outlet hole 7 in proportion to the rotation in the counterclockwise direction to increase the low-speed air-fuel mixture amount. As described above, the adjustment of the low-speed air-fuel mixture can be appropriately adjusted only within a certain range, and the improvement of the drivability of the engine is achieved while maintaining the good fuel economy and the emission characteristics of harmful exhaust gas. sell.

Next, the case where the driver or the like intentionally cancels the restriction of the pilot screw 20 within the fixed rotation range by the restriction member 30 will be described. (This is something that should never be done.)
At this time, the driver or the like applies a large external force to the limiting member 30 by using a tool such as pliers or a screwdriver to remove the limiting member 30. According to this, in the adjusting portion 24 of the pilot screw 20, the reduced diameter portion 2 as a portion whose strength is weaker than other portions is provided.
5 is provided in advance, when a large external force is applied to the limiting member 30, the reducing diameter portion 25 is broken, and the limiting member 3
The adjusting portion 24 including 0 breaks from the reduced diameter portion 25 and falls off from the pilot screw 20. This state is shown in Figure 9.
As shown in FIG. 3, the enlarged flange portion 23 of the pilot screw 20 is formed in the enlarged hole 10 of the pilot screw support boss 8.
Pilot screw support boss 8 arranged facing inside
The enlarged flange portion 23 does not protrude from the right end surface 8A of the. According to the above, it is impossible to rotate the pilot screw 20 because there is no part that holds the pilot screw 20 with a tool and applies a rotational force to the pilot screw 20. By rotating the pilot screw 20, an abnormally low speed air-fuel mixture is generated. It cannot be made thicker or thinner, and it is possible to prevent deterioration in fuel economy and emission characteristics of harmful exhaust gas components, which impedes engine drivability.

Further, in particular, since the reduced diameter portion 25 is provided in the adjustment portion 24 outside the enlarged collar portion 23, the reduced diameter portion 2
After the adjusting portion 24 including 5 is dropped, the spring S that applies elastic force to the pilot screw 20 and presses it to one side is still inside the enlarged hole 10 and the enlarged collar portion 2
Since 3 can be pressed to one side, the pilot screw 20 will not loosen or fall out together with the spring S due to vibration. Further, the limiting member 30
When an unnecessary external force is applied to the pilot screw 2, it will break at the reduced diameter portion 25 outside the enlarged collar portion 23.
When the pilot screw 20 is replaced with a genuine product (a new product equipped with the adjusting portion 24), a large force acts on the enlarged flange portion 23 and the screw portion 22 of 0, and the deformation of these portions can be suppressed. The maintenance work can be easily performed.

[0022]

As described above, according to the carburetor pilot screw device of the present invention, during normal operation of the restricting member, the pilot is operated within a constant rotation range until the knob portion of the restricting member abuts on the locking projection. It enables forward and reverse rotation of the screw to adjust the low-speed air-fuel mixture within a certain range.On the other hand, when an unnecessary external force is applied to the restricting member, the reduced diameter part provided in the adjusting part of the pilot screw Since the restricting member including the adjusting part is removed from the pilot screw and the outermost expansion flange part of the pilot screw is arranged so as to face the expansion hole, the rotating force cannot be applied to the pilot screw. Yes, the low-speed air-fuel mixture amount can be maintained constant. Therefore,
The low-speed air-fuel mixture is not significantly changed, so that fuel economy and emission characteristics of harmful exhaust gas components are not deteriorated and engine drivability is not impaired. Further, since the reduced diameter portion is provided in the adjusting portion, the pilot screw can be elastically supported by the spring even after the restricting member comes off, and the bending deformation of the pilot screw can be suppressed. Can be easily performed.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of a pilot screw device of a vaporizer according to the present invention.

FIG. 2 is a right side view of a main part of a pilot screw portion of FIG.

3 is a vertical cross-sectional view of a main part of the carburetor main body in FIG.

FIG. 4 is a right side view of FIG.

5 is a front view of the pilot screw in FIG.

6 is a right side view of FIG.

7 is a vertical cross-sectional view of the limiting member in FIG.

8 is a right side view of FIG. 7.

FIG. 9 is a vertical cross-sectional view showing a state in which a limiting member including an adjusting portion is removed from the pilot screw in FIG.

[Explanation of symbols]

 1 carburetor main body 2A intake passage on engine side 7 pilot outlet hole 8 pilot screw support boss 8A outer end surface of pilot screw support boss 8B locking protrusion 9 screw hole 10 enlarged hole 20 pilot screw 21 taper needle valve portion 22 screw portion 23 Enlarged collar portion 24 Adjustment portion 25 Reduced diameter portion 30 Limiting member 31 Fixed portion 32 Knob portion G Rotational force applying means

Claims (1)

[Claims] 1. An effective opening area of a pilot outlet hole connected to a low-speed fuel system that opens to an intake passage on the engine side of a throttle valve is adjusted and controlled by a pilot screw screwed to a carburetor body, and an effective pilot outlet hole is formed. After adjusting the opening area, in the pilot screw device of the carburetor in which the rotation of the pilot screw is restricted within a certain rotation range by the limiting member fixed to the pilot screw, the pilot screw support boss 8 of the carburetor main body 1 is , A pilot outlet hole 7 opening to the intake passage 2A on the engine side of the throttle valve 4, a screw hole 9 connected to the pilot outlet hole 7, and a screw hole 9
And an enlarged hole 10 that has a larger diameter A than the screw hole 9 and opens to the outer end surface 8A of the pilot screw support boss 8.
, And a locking projection 8B projecting from the pilot screw support boss 8 is provided on a part of the pilot screw support boss 8; A taper needle valve portion 21 for adjusting the effective opening area and a screw portion 22 which is connected to the taper needle valve portion 21 and screwed into the screw hole 9.
And the outer diameter B that is continuous with the screw portion 22 and is larger than the screw portion 22
And an adjusting flange 24 which is connected to the expanding flange 23 and has a rotational force applying means G for applying a rotational force to the pilot screw 20. The reduced diameter portion 2 having the groove diameter D smaller than the outer diameter C of the adjustment portion 24 is provided in the adjustment portion 24.
5 is provided; the limiting member 30 has a pilot screw 2
Fixing part 31 fixed to the adjusting unit 24 of 0, and fixing part 31
And a knob portion 32 that extends more laterally; and a screw portion 22 of the pilot screw 20 is screwed into the screw hole 9 of the pilot screw support boss 8 so that the effective opening area of the pilot outlet hole 7 is tapered. In the state adjusted by 21, the enlarged flange portion 23 of the pilot screw 20 is arranged so as to face the enlarged hole, and the enlarged collar portion 23 is elastically supported by the spring 5 that is contracted in the enlarged hole 10. Then, the fixing portion 31 of the limiting member 30 is integrally fixed to the adjusting portion 24 of the pilot screw 20, and the knob portion 32 of the limiting member 30 is provided with a gap in the forward and reverse rotation directions with respect to the locking projection 8B. A carburetor pilot screw device characterized by being arranged.