JPH0437243Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention functions as a fixed ventillary type carburetor with an outer ventilary and an inner ventilary in a low load range, and operates a piston valve in a medium speed range or a high speed range. Regarding the variable ventilure type carburetor, which changes the amount of air introduced and the amount of power fuel by changing the cross section of the intake passage, in particular, it is possible to accurately adjust the amount of power fuel according to the amount of movement of the piston valve. This invention relates to a variable ventilator type carburetor.

[Description of Prior Art] In a constant negative pressure variable ventule type carburetor, a jet needle for main fuel metering is provided at the tip of the piston valve in order to change the fuel flow rate according to changes in the amount of introduced air. Something like this has been used for a long time. However, this jet needle for main fuel metering requires highly accurate machining of its outer shape, which has the drawback of increasing manufacturing costs.

In order to overcome this drawback, the applicant of the present application has proposed a constant negative pressure variable ventile type vaporizer that does not use a jet needle, as shown in, for example, Japanese Utility Model Application No. 60-54760. . This conventional example is shown in a vertical sectional view in FIG. An intake passage 12 is formed within the main body 10 of the carburetor, and an inner ventilate 14 is provided within the intake passage 12. A ventilator valve 15 is provided upstream of the inner ventilee 14, and a throttle valve 16 is provided downstream. Fuel to the inner ventilate 14 is ejected from the float chamber 18 through the main jet 20 and the main fuel passage 22, and from the main nozzle 24. An outer vent turret is formed on the outside of the inner vent lily 14 by the inner wall of the intake passage 12 of the main body 10 and the piston valve 26. A diaphragm 28 is provided at one end of this piston valve 26.
is attached, and the periphery of the diaphragm 28 is fixed to the main body 10. This diaphragm 28
As a result, a negative pressure chamber 30 and an atmospheric chamber 32 communicating with the atmosphere are formed. This negative pressure chamber 30 communicates with the intake passage 12 on the downstream side of the piston valve via a through hole 34 formed in the piston valve 26. This piston valve 26 is always biased toward the inner ventilate 14 by a spring 36 installed in the negative pressure chamber 30 .

A power nozzle 38 for injecting power fuel is provided separately from the main nozzle 24, and the power fuel is injected from the float chamber 18 into the intake passage 12 via the power jet 40 and the power fuel passage 42. be done. The position of the opening at the tip of the power nozzle 38 faces a recessed space 44 formed at a position on the upstream side of the tip of the piston valve 26. This recessed space 4
4 is provided at a position through which incoming air does not pass. The tip opening of the power nozzle 38 is located within the recessed space 44 in a low speed range, and power fuel is not ejected from there. Thereafter, when the piston valve 26 moves in the middle speed range or high speed range, power fuel is injected from the tip opening of the power nozzle 38.

In the variable venture type carburetor configured as described above, fuel is supplied only from the main nozzle 24 in the low speed range, and the amount of introduced air is increased in accordance with the movement of the piston valve 26 in the middle and high speed ranges. At the same time, power fuel is injected from the power nozzle 38. As a result, compared to conventional carburetors, the structure is simpler and the air-fuel ratio can be satisfied in all operating ranges.

[Problems to be solved by the invention] However, in this configuration, since the power nozzle 38 is simply opened, the amount of power fuel changes according to the movement of the piston valve 26, but the amount of introduced air changes. It is not possible to accurately adjust the power fuel amount in response to changes. In addition, when starting at a low temperature, etc.,
5 changes from closed to open, the intake negative pressure on the upstream side of the piston valve 26 fluctuates due to the chiyoke effect,
Even when the piston valve 26 does not move, power fuel is sucked out from the power nozzle 38, resulting in an overrich condition.

In order to solve this problem, power nozzle 3
It is also conceivable to attach a power jet needle to the piston valve 26, such as one inserted into the piston valve 8. However, since the mounting position of the power jet needle to the piston valve 26 is eccentric from the center position of the piston valve 26, and the power nozzle 38 and the piston valve 26 are mounted at different vertical positions, the jet needle It becomes very difficult to align with the power nozzle. Furthermore, if the piston valve 26 rotates even a little during use, the jet needle will come into contact with the power nozzle, causing a malfunction of the jet needle and the like.

[Purpose of the invention] This invention was made in view of the above points, and it is possible to properly adjust the power fuel amount according to changes in the amount of air introduced by attaching a power jet needle to the piston valve. It is an object of the present invention to provide a variable ventilee type carburetor which eliminates the problem of power fuel spouting out when opening/closing a power jet needle and which allows easy alignment of a power jet needle and a power nozzle pipe. It is something.

[Means for Solving the Problems] In order to achieve the above object, the present invention has an inner vent lily and an outer vent lily in the middle of the intake passage, and a main nozzle for injecting main fuel into the inner vent lily. A part of the wall of the outer vent ule is formed by a piston valve that is displaced by negative pressure in the intake passage, and a fuel injection port for power fuel is opened in the outer vent ule, and fuel is injected according to the displacement of the piston valve. In a variable vent ule type carburetor that supplies power fuel from the mouth to the outer vent ule, the power nozzle tube provided with the fuel injection port is arranged such that its axial direction is parallel to the movement direction of the piston valve and from the center position of the piston valve. The piston valve has a jet needle arranged at an eccentric position and inserted into the power nozzle pipe to adjust the amount of power fuel, and a jet needle insertion hole having a diameter larger than that of the jet needle is provided in the piston valve. A projecting member large enough not to be inserted through the hole is attached to the upper part of the jet needle, and a spring is interposed between the projecting member and the piston valve, and the spring prevents the jet needle from coming off from the piston valve. It was designed to be installed on the

[Function] The jet needle is attached to the piston valve by a spring while being inserted through a large diameter hole provided in the piston valve. The mounting position can be moved within the As a result, the jet needle position of the piston valve can be easily aligned with the position of the nozzle tube.

[First example] Next, the present invention will be explained based on the drawings.

FIG. 1 is a longitudinal cross-sectional view showing an embodiment of a variable ventilee type carburetor near a power nozzle according to the present invention. In FIG. 1, the same reference numerals as in FIG. 4 indicate the same parts. The piston valve 26 has a hole 52 at a position facing the power nozzle pipe 50.
is formed. The hole 52 and the power nozzle pipe 50 are provided at a position eccentric from the center position of the piston valve 26 (the piston valve 26 generally has a circular or rectangular cross-sectional shape, so the center position of the cross-sectional shape). This hole 52 has a larger diameter than the maximum diameter of a power fuel metering jet needle 54 attached to the piston valve 26. An E-ring 56 as a projecting member is attached to the jet needle 54 near its upper end, and the jet needle 54 is inserted into the hole 52 with the lower end of the jet needle 54 attached to the spring 58. Thereafter, a presser member 60 that contacts the upper end of the jet needle 54 is attached to the piston valve 26. That is, the jet needle 54 is held in contact with the pressing member 60 by the spring 58 and is attached to the piston valve 26.

The inner wall of the power nozzle tube 50 is formed with a throat portion 62 that projects inward. The jet needle 54 reaches this throat 62,
This throat section 62 adjusts the amount of power fuel. An annular guide 64 for slidingly holding the jet needle 54 is attached to the upper end opening of the power nozzle pipe 50. A fuel injection port 66 for injecting power fuel is located midway in the longitudinal direction of the power nozzle pipe 50 between the guide 64 position and the throat 62 position.
is formed.

With the above structure, at the time of starting or in a low speed range, almost no power fuel passes through the passage cross section at the throat 62 position, and as the speed range changes from a medium speed range to a high speed range, the passage cross section at the throat 62 position becomes smaller. If the shape of the jet needle 54 is properly set so that the amount of power increases and the amount of fuel increases, in response to the change in air amount due to the movement of the piston valve 26,
A desired amount of power fuel can be injected.
This jet needle 54 does not require very high precision, unlike the needle that adjusts the main fuel.

Further, since the jet needle 54 is attached to the piston valve 26 by a spring 58 and is inserted into the large diameter hole 52, the jet needle 54 cannot change its position with respect to the piston valve 26. can. That is, piston valve 2
6 rotates and a positional deviation occurs with respect to the power nozzle pipe 50, the jet needle 54 changes its position with respect to the piston valve 26 and is centered on the power nozzle pipe 50. Therefore, the position of the jet needle 54 can be easily aligned with the position of the power nozzle pipe 50.

Furthermore, since a guide 64 is provided at the tip opening of the power nozzle pipe 50 to prevent the jet needle 54 from shifting, a more accurate amount of power fuel can be supplied and the desired air-fuel ratio can be achieved. can be obtained.

[Second Embodiment] Next, another embodiment of the present invention is shown in FIG. 2, and a sectional view taken along line A--A in FIG. 2 is shown in FIG. This second
In this embodiment, the partial shape of the piston valve and the shape of the jet needle are different from those in the first embodiment. A space 70 is provided on the side surface near the tip of the piston valve 26', and a recess 72 for receiving a spring, which will be described later, is formed above the space 70. Between this space 70 and the distal end surface of the piston valve 26', an introduction groove 74 extending inward from the side surface and an insertion hole 76 having a diameter larger than the width H of the introduction groove 74 are formed in the introduction groove 74. . Jet needle 5 for power fuel metering
The diameter at the normal position near the upper end of 4' is larger than the width H of the introduction groove 74 and smaller than the diameter of the insertion hole 76. An E-ring 56 is attached near the upper end of this jet needle 54', and the E-ring 56
A stepped portion 78 with a smaller diameter on the power nozzle pipe 50 side than the position
is formed, and the diameter of this stepped portion 78 is equal to that of the introduction groove 74.
is smaller than the width H of.

In order to attach this jet needle 54' to the piston valve 26', a spring 80 is inserted between the upper surface of the E-ring 56 of the jet needle 54' and the recess 72 of the space 70 of the piston valve 26'. Small diameter stepped portion 7 of jet needle 54'
8 from the introduction groove 74 toward the insertion hole 76. When the jet needle 54' enters the insertion hole 76, the jet needle 54' is pushed toward the power nozzle pipe 50 by the spring 80, but the E-ring 56 is pressed against the piston valve 26' at the upper position of the insertion hole 76. In this state, the jet needle 54' is held by the piston valve 26' (the state shown in FIG. 2).

In this embodiment, as in the previous embodiment, the amount of power fuel is appropriately adjusted by the jet needle 54'. Also, Jet Needle 5
4' can be freely changed in position within the insertion hole 76 of the piston valve 26', so that the jet needle 54' can be easily aligned with the power nozzle pipe 50.

[Effects of the invention] As described above, according to the variable ventilator carburetor according to the invention, the mounting position of the jet needle relative to the piston valve can be freely changed. Therefore, it is possible to easily align the jet needle to be attached to the piston valve and the power nozzle pipe when attaching them, which has been a problem in the prior art. Further, even if the piston valve rotates during use, no problem will occur even if it becomes misaligned with respect to the power nozzle pipe.

As a result, the power fuel can be adjusted with the jet needle and a more accurate air-fuel ratio can be obtained in all operating ranges than in the prior art. In addition, even if the intake negative pressure may temporarily fluctuate due to the Chi-Yoke effect when opening and closing the Chi-Yoke valve during cold start, etc., the power fuel from the power nozzle is not sucked out by the needle. This eliminates the conventional problem of over-richness.

Furthermore, if a guide for slidably holding the jet needle is attached near the tip opening of the nozzle pipe, there will be no misalignment between the nozzle pipe and the jet needle, and fuel adjustment can be performed more accurately.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing an embodiment of the main part of a variable ventilee type carburetor according to the present invention, FIG. 2 is a cross-sectional view of the main part showing another embodiment of the present invention, and FIG. A cross-sectional view taken along the line A--A in the figure, and FIG. 4 is a vertical cross-sectional view showing a conventional variable ventilate type carburetor. 12...Intake passage, 14...Inner vent lily, 24...Main nozzle, 26'...Piston valve, 50...Power nozzle pipe, 52...
Hole, 54... Jet needle, 56... E-ring, 58... Spring, 62... Throat, 64... Guide, 66... Fuel injection port, 74... Introductory groove, 7
6...insertion hole, 80...spring.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) It has an inner vent turret and an outer vent lily in the middle of the intake passage, the main nozzle for injecting the main fuel is opened in the inner vent lily, and one part of the wall of the outer vent lily is opened. The part is formed by a piston valve that is displaced by negative pressure in the intake passage,
In a variable vent ule type carburetor, a fuel injection port for power fuel is opened in the outer vent turret, and power fuel is supplied from the fuel injection port to the outer vent turret according to the displacement of a piston valve. A jet needle for adjusting the amount of power fuel by arranging a power nozzle pipe so that its axial direction is parallel to the moving direction of the piston valve and eccentrically from the center position of the piston valve, and inserting it into the power nozzle. A jet needle insertion hole having a diameter larger than that of the jet needle is provided in the piston valve, an overhang member of a size that does not allow insertion through the hole is attached to the upper part of the jet needle, and the overhang member and the piston valve are connected to each other. A variable ventilee type carburetor is characterized in that a spring is interposed between the jet needle and the piston valve so that the jet needle is fixed to the piston valve by the spring. (2) A groove having a width narrower than the diameter of the jet needle is formed in the piston valve from its outer surface to the hole, and the jet needle has the groove through which the jet needle reaches the hole. The variable ventilee type carburetor according to claim 1, characterized in that a small diameter portion is formed which is narrower than the width of the variable ventilure type carburetor. (3) Forming a throat in which the cross-section of the passage narrows on the inner wall of the power nozzle tube midway along its length, and installing a guide for slidably holding the jet needle near the tip opening of the nozzle tube, The variable ventilee type carburetor according to claim 1, wherein the power nozzle is provided between a throat position and a guide position.