JPH0148393B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a constant vacuum carburetor equipped with a negative pressure operated valve that moves up and down in the intake tract by the negative pressure generated in the intake tract upstream of the throttle valve. Conventionally,
Such a constant vacuum type vaporizer is, for example, disclosed in Japanese Patent Publication No. 40-12402.
No. 43-23922, etc., which is well known as a negative pressure operated valve placed in the intake duct so that it can be raised and lowered, depending on the magnitude of the negative pressure generated in the intake duct upstream of the throttle valve. By automatically adjusting the opening area of the intake tract, the negative pressure applied to the needle jet (air flow velocity through the needle jet section) is controlled to atomize the air-fuel mixture sucked out from the needle jet into the intake tract. This is to improve the air-fuel ratio and maintain an appropriate air-fuel mixture concentration. The negative pressure operated valve of such a constant vacuum type vaporizer is generally of a cylindrical shape, and its structure will be explained with reference to FIGS. 1 and 2.

Reference numeral 1 denotes a carburetor body through which an intake passage 2 passes through, and a throttle valve 3 is rotatably disposed on the engine side by a throttle valve shaft 4; A float chamber 6 is formed by the float chamber body 5 and the lower recessed portion of the carburetor body 1. A float (not shown), a valve seat disposed in the fuel inflow path, and a float valve are arranged in the float chamber 6, and a constant liquid level is always formed by the cooperation of these elements.

Reference numeral 7 denotes a guide tube with a circular cross section that opens upward and is connected to the intake path 2 on the upstream side (right side in the figure) of the throttle valve 3 of the carburetor body 1. A cylindrical negative pressure operated valve 8 for controlling the opening area of the channel 2 is slidably arranged.

As mentioned above, the negative pressure operated valve 8 is connected to the guide cylinder 7.
The outer diameter φA of the negative pressure operated valve 8 is the same as the inner diameter φB of the guide tube 7 so that the inside can be slid upwardly and downwardly in the figure.
A gap H is provided with a slightly smaller diameter. (For example, this gap is set to about 0.1 mm.) A circular compartment 9 such as a diaphragm, a bellows phragm, or a cylinder is integrally arranged in the upper part of the negative pressure operated valve 8. An atmospheric chamber 10 is formed by the upper opening recess 1A of the main body 1, and a pressure receiving chamber 12 is formed by the partition 9 and a cap 11 covering the upper part thereof, and this atmospheric chamber 10 is not shown. The pressure receiving chamber 12 is communicated with the atmosphere through an atmosphere introduction path, and the negative pressure of the intake passage 2 is introduced into the pressure receiving chamber 12 through a small hole 8A opened at the bottom of the negative pressure operating valve 8, for example.

In addition, a needle jet 13 is opened in the intake passage 2 and is connected to a constant liquid level in the float chamber 6 via a main jet (not shown). The supported jet needle 14 is inserted and arranged, and the gap formed between the jet needle 14 and the needle jet 13 is adjusted by raising and lowering the negative pressure operating valve 8, and the air is sucked into the intake passage 2. The amount of air-fuel mixture is controlled.

Incidentally, reference numeral 15 denotes a coil spring whose one end is locked to the bottom of the negative pressure operated valve 8 and the other end is locked to the cap 11 so as to apply a downward force to the negative pressure operated valve 8. The center of the guide cylinder 7 having a circular cross section, the center of the circular partition 9, and the center of the outer diameter of the coil spring 15 are arranged on the longitudinal axis XX of the negative pressure operated valve 8. .

According to such a conventional constant vacuum type carburetor, when the engine is operating, the intake passage negative pressure generated in the intake passage 2 is introduced into the pressure receiving chamber 12 through the small hole 8A, and the pressure receiving chamber 12 and the atmospheric chamber 10 are separated. Due to the differential pressure of
An upward force is applied to the negative pressure operated valve 8, and an upward operating force is applied to the negative pressure operated valve 8. On the other hand, the negative pressure operated valve 8 receives a downward operating force due to the spring force of the coil spring 15.

Therefore, the negative pressure operated valve 8 is moved by the relative force relationship between the upward force of the partition body 9 and the downward force of the coil spring 15, and the opening of the negative pressure operated valve 8 to the intake passage 2 is caused. degree is determined.

Here, when the force relationship during the upward movement of the negative pressure operated valve 8 is examined in detail with reference to FIG. 3, which is schematically shown, it is as follows. That is, the negative pressure operated valve 8 is: (1) An upward operating force _F1 is applied by the partition 9, and the load center of this operating force _F1 is aligned with the longitudinal axis X- of the negative pressure operated valve 8. It's on X.

(2) A downward operating force F ₂ is applied by the coil spring 15 , and the load center of this operating force F ₂ is on the longitudinal axis XX of the negative pressure operated valve 8 .

(3) When the engine is operating, the engine side end surface 8B (the surface on the throttle valve 3 side) of the negative pressure operated valve 8 receives the intake passage negative pressure generated in the engine. The engine-side end surface 8B of the cylinder 8 is attracted toward the engine (throttle valve 3 side) and pressed against the engine-side guide cylinder surface 7A of the guide cylinder 7, and a frictional force is generated between the contact surfaces.

Here, if the negative pressure operated valve 8 were to move upward, the frictional force between the engine side end surface 8B of the negative pressure operated valve 8 and the engine side guide cylinder surface 7A of the guide tube 7 would cause the negative pressure operated valve 8 to move upward. This acts as a resistance to upward movement, and as a result acts on the negative pressure operated valve 8 as a downward force _F3 .

Then, the engine side end surface 8 of the negative pressure operated valve 8 described above.
B and the engine-side guide cylinder surface 7A of the guide cylinder 7 causes a force _F3 to act at a position L away from the longitudinal axis X-X of the negative pressure operated valve 8. Become.

What should be particularly noted here is that the upward operating force F ₁ by the partition body 9 and the downward operating force F ₂ by the coil spring 15 are based on the longitudinal axis X-X of the negative pressure operated valve 8. As shown above, the force _F3 due to the frictional force between the engine side end surface 8B of the negative pressure operated valve 8 and the engine side guide cylinder surface 7A of the guide cylinder 7 is applied to the longitudinal axis X-X of the negative pressure operated valve 8. It is to act at a distance of L.

According to this, when the negative pressure operated valve 8 is operated upward, the force F ₃ is a bending moment M of (F ₃ ×L) with respect to the longitudinal axis X-X of the negative pressure operated valve 8. is applied to the negative pressure operated valve 8, and when the negative pressure operated valve 8 receives this bending moment M, the gap between the inner diameter φB of the guide cylinder 7 and the outer diameter φA of the negative pressure operated valve 8 is Due to the existence of the gap H, the negative pressure operated valve 8 is tilted within the guide cylinder 7, and the outer surface of the negative pressure operated valve 8 collides with the inner surface of the guide cylinder 7, and the negative pressure operated valve 8 is prevented from rising. give resistance. The frictional resistance force between the outer surface of the negative pressure operated valve 8 and the inner surface of the guide tube 7 due to the inclination of the negative pressure operated valve 8 is due to the bending moment M of (F ₃ ×L). The downward force F ₃ due to the frictional force between the engine-side end surface 8B of the pressure-operated valve 8 and the engine-side guide cylinder surface 7A of the guide cylinder 7 is increased by the moment L.

Therefore, it is not preferable for smooth movement of the negative pressure operated valve 8, and furthermore, it is not preferable for the negative pressure operated valve 8 to move at an angle within the guide cylinder 7 than from the viewpoint of durability.

The constant vacuum type vaporizer according to the present invention has been developed in view of the above points, and an object of the present invention is to provide a constant vacuum type vaporizer having particularly excellent dynamic characteristic performance of a negative pressure operated valve.

Hereinafter, one embodiment of the constant vacuum type vaporizer according to the present invention will be described with reference to FIGS. 4, 5, 6, and 7. Components that are the same as the conventional structure are designated by the same reference numerals, and the description thereof will be omitted.

Reference numeral 20 denotes a negative pressure operated valve that is slidably guided and held in the carburetor main body 1 and moves up and down within the intake passage 2. Bench lily forming part 2
0A, and plate-shaped guide portions 20B protruding laterally from opposing outer surfaces along the longitudinal axis Y-Y of the ventilate forming portion 20A.
The outer diameter φC of the ventilary forming part 20A is smaller than the diameter φD of the intake passage 2, and the outer diameter φC is appropriately set to a diameter and shape that can obtain a stable negative ventilary pressure. It is set to .

Further, the plate-shaped guide portion 2 of the negative pressure operated valve 20
The engine side end face 20C of 0B is the ventilate forming part 2
Center E of the ventilate forming portion 20A in a cross section perpendicular to the longitudinal axis Y-Y of 0A
It is arranged in the vicinity of a line S-S that passes through and is substantially orthogonal to the longitudinal axis direction Z-Z of the intake passage 2. (This is clearly shown in FIG. 5, and the line S-S is on the line Y-Y.) A negative pressure operated valve 20 having such a shape is bored in the carburetor main body 1. It is slidably disposed within a guide tube 21 having a substantially similar shape. More specifically, the ventilate forming portion 20 of the negative pressure operated valve 20
A is disposed in a cylindrical ventilate forming part guide tube 21A that opens upward from the intake passage 2 and is connected to the intake passage 2, and a plate-shaped guide part 20B is arranged in the intake passage 2 from the ventilee forming part guide tube 21A. They are disposed in rectangular grooves 21B that are located on both sides of the longitudinal axis direction Z-Z and are vertically bored.

Note that the ventilary forming portion 20 of the negative pressure operated valve 20
The outer side of A is located outside of the ventilee forming part 20A so that it does not come into contact with the inner circumferential wall of the ventilary forming part guide cylinder 21A even when the negative pressure in the intake passage 2 acts on the negative pressure operating valve 20 during engine operation. The diameter φC is the inner diameter φF of the guide tube 21A of the ventilate forming part.
Must be set smaller.

That is, in the operating state of such an engine, the negative pressure operated valve 20 mainly operates so that the engine side end surface 20C of the plate-shaped guide portion 20B is connected to the engine side surface 21C of the rectangular groove 21B.
It will be guided by coming into contact with.

Reference numeral 22 denotes a partition made of a circular diaphragm, and the center G of the partition 22 is located on the longitudinal axis Y-Y of the ventilate forming portion 20A. The center J of the outer diameter of the coil spring 23, which is contracted and presses the negative pressure operated valve 20 downward, is also arranged on the longitudinal axis YY of the ventilate forming portion 20A.

According to the constant vacuum type vaporizer of the present invention configured as above, the negative pressure operated valve 20 receives the following force.

(1) An upward operating force F ₁ is applied by the partition body 22, and the load center of this operating force F ₁ is on the longitudinal axis Y-Y of the ventilating portion 20A of the negative pressure operated valve 20. be.

(2) A downward operating force F ₂ is applied by the coil spring 23, and the load center of this operating force F ₂ is placed on the longitudinal axis Y- of the ventilate forming portion 20A.
It's on Y.

(3) When the engine is operating, the negative pressure operating valve 20 receives the intake tract negative pressure generated in the engine, which is sucked toward the engine side (left side in the figure). According to this, the plate-shaped guide portion 20B of the negative pressure operated valve 20
The engine side end surface 20C of the rectangular groove 21B is pressed against the engine side surface 21C of the rectangular groove 21B, and a frictional force is generated. Note that the ventilary forming portion 20A of the negative pressure operated valve 20 does not come into contact with the ventilizing forming portion guide cylinder 21A since there is a gap therebetween.

Here, when the negative pressure operated valve 20 attempts to move upward, the engine side end surface 2 of the plate-shaped guide portion 20B
The frictional force between 0C and the engine side surface 21C of the rectangular groove 21B resists the upward movement of the negative pressure operated valve 20, and as a result acts on the negative pressure operated valve 20 as a downward force _F3 .

This force F ₃ is applied to the engine side end surface 20C of the plate-shaped guide portion 20B of the negative pressure operated valve 20 at the ventilium forming portion in a cross section perpendicular to the longitudinal axis Y-Y of the ventilizing forming portion 20A. 2
Passing through the center E of 0A, in the longitudinal axis direction Z of the intake passage 2
- By arranging it near the line S-S perpendicular to Z, the engine-side end surface 20 of the plate-shaped guide portion 20B
C and the engine side surface 21C of the rectangular groove 21B are in contact with the longitudinal axis Y- of the ventilate forming portion 20A.
It will be on a vertical section including Y.

Therefore, when the engine is operated, an upward operating force F ₁ is applied to the negative pressure operated valve 20 via the partition body 22 due to the intake passage negative pressure generated in the intake passage 2.
Downward operating force by coil spring 23
F ₂ and the engine side end surface 20 of the plate-shaped guide portion 20B
A downward force F ₃ due to the frictional force between C and the engine side surface 21C of the rectangular groove 21B acts, and the opening degree of the negative pressure operated valve 20 with respect to the intake passage 2 is determined by the relative force relationship between them. Ru.

In this way, each of the aforementioned operating forces F ₁ , F ₂ , F ₃ is applied to the longitudinal axis Y-
By acting on the cross section including Y and Y-Y, when the negative pressure operated valve 20 is operated, even if the negative pressure operated valve 20 receives intake tract negative pressure, the longitudinal axis of the ventilium forming portion 20A remains unchanged. No bending moment occurs starting from the line Y-Y.

According to this, upward movement of the negative pressure operated valve 20 is simply determined by F ₁ > (F ₂ + F ₃ ), and a bending moment acts on the negative pressure operated valve 20 to cause the negative pressure operated valve 20 to move upward. The valve 20 is tilted to eliminate local contact with the guide cylinder 21 due to the bending moment, and the operability of the negative pressure operated valve 20 can be improved, especially when the negative pressure operated valve with the partition body 22 is used. Even if the upward operating force of the valve 20 is weakened, sufficient opening characteristics of the negative pressure operated valve 20 can be obtained.
This makes it possible to reduce the effective pressure-receiving area of the partition body 22, thereby making it possible to downsize the partition body 22 and, by extension, the carburetor.

Furthermore, since the inclination of the negative pressure operated valve 20 within the guide cylinder 21 is suppressed, local contact of the negative pressure operated valve 20 within the guide cylinder can be prevented, and the portion of the negative pressure operated valve 20 This eliminates mechanical wear and significantly improves durability.Furthermore, since the negative pressure operated valve 20 can move linearly, the dynamic characteristics of the negative pressure operated valve 20 are improved. I was able to do that.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional view showing a conventional constant vacuum vaporizer, Fig. 2 is a cross-sectional view taken along the - line in Fig. 1, and Fig. 3 shows the relationship between the operating force for the negative pressure operating valve in Fig. 1. FIG. 4 is a longitudinal cross-sectional view showing an embodiment of a constant vacuum vaporizer according to the present invention, FIG. 5 is a cross-sectional view taken along line V-V in FIG. 4, and FIG. 4 is a perspective view of the negative pressure operated valve, and FIG. 7 is a schematic diagram showing the relationship of operating force to the negative pressure operated valve in FIG. 4. 20...Negative pressure operation valve, 20A...Ventilary forming part, 20B...Plate-shaped guide part, 20C...
Engine side end surface, 21...Guide cylinder, 21A...Benture forming part guide surface, 21B...Rectangular groove, 21C
...Engine side, 22...Dividing body, 23...Coil spring, Y-Y...Venture forming part 20
The longitudinal axis of A.

Claims (1)

[Claims] 1. A throttle valve is arranged in the intake path that passes through the carburetor body, a guide tube is connected to the intake path upstream of the throttle valve, and a partition made of a diaphragm is placed in the upper part of the guide tube. The negative pressure operated valve is movably arranged, the partition body and the recessed part of the carburetor body form an atmospheric chamber connected to the atmosphere, and the partition body and a cap covering it form a pressure receiving chamber connected to the intake passage, Furthermore, in a constant vacuum carburetor, a coil spring is arranged in the pressure receiving chamber to act in a direction to close the opening of the negative pressure operated valve with respect to the intake passage.
20A, which has a cross-sectional shape smaller than the diameter φD of the intake passage 2 and forms a ventilee V together with the intake passage 2; It is formed by plate-shaped guide parts 20B provided laterally from the opposing outer surfaces of the forming part 20A, and the engine-side end surface 20C of the plate-shaped guide part 20B is aligned with the longitudinal axis Y of the ventilate forming part 20A. - Passing through the center E of the ventilate forming part 20A in the cross section perpendicular to Y,
A line S- perpendicular to the longitudinal axis direction Z-Z of the intake passage 2
S, the ventilary forming part 20A of the negative pressure operated valve is guided in a non-contact manner to the ventilary forming part guide tube 21A bored in the carburetor main body 1, and the plate-shaped guide part 20B is formed into a ventilary forming part. The guide tube 21A is guided in contact with the rectangular grooves 21B formed laterally across the longitudinal axis direction Z-Z of the intake passage 2, and further the partition body 2
2 and the center J of the outer diameter of the coil spring 23 are arranged on the longitudinal axis Y-Y of the ventilate forming part 20A.