JP3374940B2 - Starting operation mechanism of rotary throttle valve carburetor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carburetor for an internal combustion engine mounted on a portable working machine such as a chemical spraying machine and a brush cutter, and more particularly to a starting fuel increasing mechanism for enhancing cold startability.
The present invention relates to a starting operation mechanism of a rotary throttle valve carburetor.

[0002]

2. Description of the Related Art Generally, in starting an internal combustion engine in a low temperature atmosphere, it is necessary to supply a rich air-fuel mixture to the engine because the vaporization of fuel is poor. For this reason, the conventional throttle valve type carburetor adopts a so-called bystarter mechanism having a starter rich mixture supply passage hole for limiting the air supplied to the carburetor, and a so-called bystarter mechanism. However, there is a drawback in that the configuration of is complicated and the adjustment of each mechanism is troublesome.

In the rotary throttle valve type carburetor disclosed in Japanese Patent Laid-Open No. 1-294947, the throttle valve is axially moved to supply a rich air-fuel mixture, but the structure becomes a little complicated, and a backpack type work is performed. In the case of the aircraft, it was difficult for the driver to carry out the starting operation while carrying the backpack.

The rotary throttle valve type carburetor disclosed in Japanese Utility Model Publication No. 63-6438 is one in which the throttle valve is axially moved by a starting operation lever, and the structure is simple, but vibrations at the time of initial explosion of the engine and The impact may cause the throttle valve to return to the idle position, making it difficult to accurately control the opening degree of the throttle valve at the time of starting.

In the rotary throttle valve type carburetor according to Japanese Patent Application No. 5-31080 filed by the present applicant, when the engine is cold started,
In order to supply a rich air-fuel mixture to the engine, there are only two cam surfaces that axially move the throttle valve (only one works effectively), and the amount of starting fuel supplied to the engine depends on the ambient temperature and engine temperature. It is not possible to obtain the starting fuel amount corresponding to. By design, when the cam lift is set to a low temperature (for example, −5 ° C.), the starting fuel is too rich when the temperature is higher than the set value, and the engine is difficult to start after one or two manual recoil operations.

The lower the atmospheric temperature and the engine temperature, the larger the amount of starting fuel, and conversely, the smaller the amount of starting fuel, the smaller the amount of starting fuel, so that the engine can be started with the minimum number of recoil operations and the appropriate warm-up is performed. Because you have the time, handling the engine and work equipment is easy.

[0007]

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a stepwise cam lift of a cam surface that gives axial movement to a throttle valve in order to obtain a starting fuel amount suitable for atmospheric temperature in winter. Another object of the present invention is to provide a starting operation mechanism for a rotary throttle valve carburetor that can be continuously changed.

[0008]

In order to achieve the above object, the structure of the present invention controls the air amount by the rotation of the throttle valve lever and the fuel amount by the axial movement of the throttle valve lever. In a rotary throttle valve carburetor start-up operation mechanism that axially moves a throttle valve lever by rotating a start-up operation lever coupled to a cylindrical cam member, at least three flat cams having different heights from the axial center are provided. The surface is provided so as to be engageable with the throttle valve lever and gives a cam lift in the axial direction to the throttle valve according to the atmospheric temperature.

[0009]

A cylindrical cam member that pushes up the throttle valve lever in the opening direction of the combustion injection hole of the fuel supply pipe is provided between the cover plate of the carburetor body and the throttle valve lever. At the time of cold starting of the engine, when the cylindrical cam member is rotated against the force of the spring in accordance with the atmospheric temperature, the throttle valve lever is pushed up to a predetermined fuel increase position even if the throttle valve lever remains in the idle position.

When the throttle valve lever is rotated in the fully open direction after the engine is started, the throttle valve lever is disengaged from the cylindrical cam member, and the cylindrical cam member is returned to its original position by the force of the spring. Even if the throttle valve lever is returned to the idle position, the cylindrical cam member does not contact the throttle valve lever.

The cam lift in the middle of the cylindrical cam member provides a starting fuel amount suitable for the atmospheric temperature in spring and autumn, for example.

[0012]

1 is a front sectional view of a rotary throttle valve type carburetor equipped with a starting operation mechanism according to the present invention, and FIG. 2 is a plan view showing a throttle valve lever omitted. The rotary throttle valve type carburetor is configured such that the end flange 38a of the carburetor main body 38 is brought into contact with the intake port of the engine via a heat insulating pipe (not shown) and is fitted to the engine by a bolt passing through a pair of left and right bolt insertion holes 38b. Fixed to the wall of. The main body 38 is provided with a starting fuel amount increasing mechanism A and a throttle valve lever 21 in the upper part, and a constant pressure fuel supply mechanism B and a suction type primer pump C in the lower part. The main body 38 has a cylindrical intake passage 17 extending perpendicularly to the plane of the drawing,
It has a vertical cylindrical portion 3 orthogonal to the intake passage 17. The cylindrical portion 3 is fitted with the throttle valve 5 such that the throttle valve 5 can rotate and can move up and down (axial movement). The cylindrical throttle valve 5 is provided with a slot hole 5b penetrating in the lateral direction, the small diameter shaft portion 5a protruding upward penetrates the cover plate 34 closing the cylindrical portion 3, and the throttle valve lever 21 is coupled to the upper end portion. To do.

The coil spring 2 surrounding the shaft portion 5a is interposed between the cover plate 34 and the throttle valve 5, and has one end locked to the cover plate 34 and the other end locked to the throttle valve 5, respectively. The hollow shaft portion 5a is screwed into the boss portion of the needle 16 to form the cap 1
Closed by 8. The bottom wall of the cylindrical portion 3 fits and fixes the jet 6 and the fuel supply pipe 4. Fuel supply pipe 4 is needle 1
6 is inserted, and the opening degree of the fuel injection hole 4a is adjusted as the throttle valve 5 moves up and down.

In the constant pressure fuel supply mechanism B, the intermediate body 23 is joined to the lower end wall of the main body 38 with the membrane 25 interposed therebetween, and the intermediate body 23 is connected to the upper side of the membrane 25 by 2 mm.
A pulsating pressure chamber 24 for introducing the pulsating pressure of the crank chamber of the cycle engine and a pump chamber 26 are defined below the membrane 25. The intermediate body 23 is formed by sandwiching the membrane 12 on the lower end wall of the intermediate body 30.
And a constant pressure fuel chamber 13 on the upper side of the membrane 12
Atmospheric chambers 11 are defined on the lower sides of the respective parts. The lever 8 pivotally supported on the wall portion of the constant pressure fuel chamber 13 is rotatably supported by a spring 9 interposed between the lever 8 and the top wall of the constant pressure fuel chamber 13 so that the left end of the lever 8 is located at the center of the membrane 12. It is brought into contact with the projecting piece, and the right end is engaged with the inflow valve 7.

When the membrane 25 vibrates up and down by the pulsating pressure of the pulsating chamber 24, the fuel in the fuel tank (not shown) is sucked into the pump chamber 26 through the pipe 39, the filter 37 and the suction valve (not shown). The fuel in the pump chamber 26 is a discharge valve (not shown),
It is discharged to the constant pressure fuel chamber 13 through the chamber 36 of the main body 38 and the inflow valve 7. When the constant pressure fuel chamber 13 is filled with fuel, the membrane 12 is pushed down, and the inflow valve 7 is closed as the lever 8 rotates counterclockwise. On the contrary, when the fuel in the constant pressure fuel chamber 13 becomes low, the membrane 12 is pushed up by the atmospheric pressure, and the inflow valve 7 opens as the lever 8 rotates clockwise against the force of the spring 9.

The fuel in the constant pressure fuel chamber 13 is composed of a thin elastic plate, a check valve 27, a jet 6, a fuel supply pipe 4, and a fuel injection hole 4.
It is sucked into the slot hole 5b via a and is supplied to the engine while being mixed with the air flowing in the intake passage 17.

The suction type primer pump C for replenishing the constant pressure fuel chamber 13 with fuel before starting the engine divides the pump chamber 15 by connecting a void 42 to the lower surface of the intermediate body 30 with a holding plate 41. The center wall of the chamber 15 is combined with a composite valve 14 integrally provided with a mushroom type suction valve and a discharge valve.
When the void 42 is crushed, the fuel vapor or air in the pump chamber 15 pushes open the flatly crushed pipe portion of the axial center of the composite valve 14 and flows out into the chamber 10, where it passes through a passage (not shown). Return to the tank. When the spoid 42 is released, the pump chamber 15 becomes a negative pressure, and the fuel vapor and air in the constant pressure fuel chamber 13 pass through the passage 28,
After passing through 29 and 40, the peripheral portion of the composite valve 14 is pushed open and sucked into the pump chamber 15.

As shown in FIG. 2, the peripheral edge of the cover plate 34 is reinforced by ribs 34b and is joined to the main body 38 by a pair of bolts 50. The cover plate 34 has an adjustment bolt 51 screwed into the boss portion 32 formed at the right end portion thereof, and regulates the return position, that is, the idle position, by the force of the coil spring 2 (FIG. 1) of the throttle valve lever 21. The throttle valve lever 21 shown in phantom in FIG. 2 has a throttle valve 5 whose center portion is indicated by a cap 18.
The right end portion, which is fixed to the shaft portion 5a of the rotary shaft 5a and rotatably supports the swivel 31, is adjusted by the force of the coil spring 2.
It is urged against the end of. The swivel 31 is connected to one end of a remote control cable (not shown).

The fan-shaped left end of the throttle valve lever 21 has a lower cam surface, and a cover plate 34 is provided by the force of the coil spring 2.
Is abutted on the ball 52 supported by. Therefore, when the throttle valve lever 21 is rotated counterclockwise from the idle position shown in FIG. 2, the throttle mechanism lever 21, the throttle valve 5, and the needle 16 are pushed up together by the cam mechanism, and the intake passage of the slot hole 5b. The opening degree with respect to 17 increases, and the opening degree of the fuel injection hole 4a also increases. The structure described above is almost the same as that of the conventional rotary throttle valve type carburetor.

In FIG. 1, the slot hole 5b and the intake passage 17 are shown to be orthogonal to each other, but in reality, the throttle valve lever 21 is regulated at the idle position by the adjusting bolt 51, and the slot hole 5b is intake. It crosses the passage 17 diagonally.

In the starting operation mechanism of the rotary throttle valve type carburetor according to the present invention, a cylindrical bearing portion 34a formed at the left end portion of the cover plate 34 is provided with a hollow cylindrical cam member 45 for weight reduction. Be movably supported. Cylindrical cam member 45
To the circumferential notch 55 formed on the outer peripheral surface of the bearing portion 34a.
The retaining pin 46 protruding from is engaged.

As shown in FIG. 3, according to the present invention, the notch 55 of the cylindrical cam member 45 has an end wall 55a spaced apart in the circumferential direction,
55b, the rotation range is regulated by the retaining pin 46, and normally it is rotationally biased to the position shown in FIG. 3 by the force of the spring 49. The spring 49 (FIG. 2) is the bearing portion 34a.
Is wound around the outer peripheral surface of the bearing, one end of which is locked to the cylindrical cam member 45 and the other end of which is locked to the bearing portion 34a.

As shown in FIG. 1, the right end of the cylindrical cam member 45 projects downward of the throttle valve lever 21, and has a flat cam surface 60a that does not contact the lower surface of the throttle valve lever 21 and the throttle valve lever 21. Flat cam surfaces 60b, 60 that abut the lower surface
c and (FIG. 4). That is, the cylindrical cam member 45
The cam surfaces 60a, 60b, 60c of the above are different in height from the center of the shaft (cam lifts L1, L2, L3). Cylindrical cam member 45
The left end portion of is connected to the starting operation lever 45a (FIG. 2).

The intermediate cam lift L2 is designed to obtain a starting fuel amount suitable for the atmospheric temperature in spring and autumn, for example. Even if the number of cam surfaces is increased, it is cumbersome for the operator to operate the start operation lever by judging the atmospheric temperature each time, and it becomes difficult to operate. Therefore, there are three cam surfaces as in the present invention. Is enough.

Next, the operation of the starting operation mechanism of the rotary throttle valve type carburetor according to the present invention will be described. As shown in FIG. 4, normally, the cam surface 60 a of the cylindrical cam member 45 is
The throttle valve lever 21 projects below but does not come into contact. At the time of cold starting, when the cylindrical cam member 45 is rotated about 60 ° in the direction of the arrow in FIG. 4 against the force of the spring 49 by the starting operation lever 45a corresponding to the outside air temperature, the cam surface 60b causes the throttle valve lever 21 to move. When the cylindrical cam member 45 is further rotated about 60 ° (rotating until the end wall 55b contacts the retaining pin 46), the cam surface 60c abuts the lower surface of the throttle valve lever 21. The throttle valve lever 21 is pushed up, the amount of starting fuel is increased, and cold starting of the engine is facilitated.

Even if the starting operation lever 45a is stopped at the intermediate position, one of the cam surfaces 60b and 60c has a throttle valve lever 2 on either side.
The surface of the cylindrical cam member 45 and the cam lift L are in contact with each other to maintain a stable posture, and the relationship between the cylindrical cam member 45 and the cam lift L is obtained as shown in FIG. When the rotation amount of the cylindrical cam member 45 is 60 ° or less, the cam surface 60a of the cylindrical cam member 45 projects to the lower side of the throttle valve lever 21 but does not come into contact with the cam surface 60a of the cylindrical cam member 45. There is a gap t between the lower surface of the throttle valve lever 21 and the lower surface.

After the engine is started, when the throttle valve lever 21 is rotated counterclockwise in FIG. 2, that is, in the fully open direction, the side edge 21a of the throttle valve lever 21 is moved to the cam surface 60b or the cam surface 60.
Remove from c. At this time, the cylindrical cam member 45 is returned to the position shown in FIGS.

In the embodiment shown in FIG. 1, the axial movement amount (cam lift) L2-t, L3- of the throttle valve lever 21 when the engine is started.
t is the cam surfaces 60a, 60b, 60 of the cylindrical cam member 45.
c, and is left to the selection of the cam surfaces 60a, 60b, 60c corresponding to the ambient temperature of the driver.

In the embodiment shown in FIGS. 6 and 7, the throttle valve lever 21 is provided by the spiral bimetal 67 as a heat sensitive member.
The cam lift that gives axial movement to is continuously changed according to the ambient temperature so that the optimum starting fuel amount and warm-up time can always be obtained. A bearing portion 34a that projects radially outward is integrally formed with a cover plate 34 that closes the upper end portion of the main body 38, and an eccentric sleeve 66 is fitted between the bearing portion 34a and the cylindrical cam member 45. The retaining pin 46 passes through the slit of the eccentric sleeve 66, and then the notch 5 of the cylindrical cam member 45.
5 is engaged.

The bimetal 67 is arranged on the outer peripheral side of the bearing portion 34a. The bimetal 67 has one end 67b locked to the cylindrical portion 34a and the other end 67a joined to the eccentric sleeve 66. Specifically, the end 6 of the bimetal 67
7a is locked to a pin 68 extending from a lever 69 connected to an eccentric sleeve 66. As shown in FIG. 7, the eccentric sleeve 66 is formed with the outer peripheral surface 66a and the inner peripheral surface 66b eccentric. The cylindrical cam member 45 is provided with a flat cam surface 60a and a flat cam surface 60c. 1 and 2 for other configurations.
The same as the embodiment shown in FIG.

When the bimetal 67 expands and contracts in the circumferential direction in response to high and low atmospheric temperatures, the eccentric sleeve 66 rotates forward and backward within half a rotation, the cylindrical cam member 45 is displaced downward and upward, and the throttle valve lever 21 moves. Lower surface and cam surface 60a of the cylindrical cam member 45
The gap t between and increases and decreases. As indicated by the line 71 in FIG. 8, as the atmospheric temperature becomes lower, the cam surface 60a of the cylindrical cam member 45 rises as the eccentric sleeve 66 rotates, and the line 7
As indicated by 1, the gap t is reduced. Therefore, when the engine is started, the cam lift L3-t when the cylindrical cam member 45 is rotated counterclockwise in FIG.
Will increase.

If the bimetal 67 is connected to the wall of the engine through a heat transfer member such as a heat pipe, the cam surface 6 can be operated even when the cylindrical cam member 45 is operated when the engine is restarted.
It is possible to prevent 0c from pushing up the throttle valve lever 21.

[0033]

As described above, according to the present invention, since at least three cam surfaces having different heights from the axial center of the cylindrical cam member are provided, the cylindrical cam member is manually rotated to respond to the atmospheric temperature. If the cam surface is selected, the throttle valve lever is pushed up step by step by the cylindrical cam member according to the atmospheric temperature, the throttle valve is held in the starting operation position, and the engine can be smoothly started with the minimum number of recoil operations. can get.

After the warm-up is completed (after about 10 seconds), when the throttle valve lever is rotated in the opening direction, the cylindrical cam member is disengaged from the throttle valve lever and automatically returns to the normal position. Is very easy.

The flat cam surface of the cylindrical cam member is stably engaged with the lower surface of the throttle valve lever at the starting operation position, and the engagement of the cam surface may be released due to vibration or impact at the initial explosion of the engine. Absent.

Since the cylindrical cam member is provided with a flat cam surface, the structure of the starting operation mechanism is simple, the variation due to mass production is small, and the operation is reliable and stable.

Since the eccentric sleeve fitted between the shaft hole of the bearing portion of the starting operation lever and the cylindrical cam member is rotationally displaced by the temperature sensitive member in accordance with the ambient temperature or the engine temperature,
The axial cam lift given to the throttle valve changes continuously,
The optimum amount of starting fuel and the appropriate warm-up time for the ambient temperature can be obtained.

Since the bimetal is disposed substantially concentrically with the starting operation lever, the overall size is small and the connection between the bimetal and the eccentric sleeve is easy.

[Brief description of drawings]

FIG. 1 is a front sectional view showing a rotary throttle valve type carburetor equipped with a starting operation mechanism according to the present invention.

FIG. 2 is a plan view showing the same carburetor with a throttle valve lever removed.

FIG. 3 is a side sectional view of a cylindrical cam member in the starting operation mechanism.

4 is a side cross-sectional view of the cylindrical cam member taken along the line 4A-4A in FIG.

FIG. 5 is a diagram showing a relationship between a rotation amount of a cylindrical cam member and a cam lift.

FIG. 6 is a front sectional view showing a rotary throttle valve type carburetor provided with a start operation mechanism according to a modified embodiment of the present invention.

7 is a side cross-sectional view of the cylindrical cam member taken along the line 7A-7A in FIG.

8 is a diagram showing the relationship between the amount of rotation of the eccentric sleeve of FIG. 7 and the cam lift.

[Explanation of symbols]

5: Throttle valve 21: Throttle valve lever 34: Cover plate 3
4a: Bearing part 38: Vaporizer main body 45: Cylindrical cam member 45a: Start operation lever 49: Spring 60a, 60
b, 60c: Cam surface 62: Eccentric sleeve 67: Bimetal

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-63-38674 (JP, A) JP-A-63-29048 (JP, A) JP-A 1-294947 (JP, A) JP-A 62- 159753 (JP, A) JP 56-148650 (JP, A) Actual opening 59-133759 (JP, U) Actual opening Flat 6-83943 (JP, U) Actual opening Flat 6-67841 (JP, U) S. 63-6438 (JP, Y1) (58) Fields investigated (Int.Cl. ⁷ , DB name) F02M 1/16 F02M 9/08

Claims (5)

(57) [Claims] 1. An air amount is controlled by rotation of a throttle valve lever, and a fuel amount is controlled by axial movement of a throttle valve lever.
In a starting operation mechanism of a rotary throttle valve type carburetor that gives axial movement to a throttle valve lever by rotating a start operation lever connected to a cylindrical cam member, the cylindrical cam member has at least three different heights from an axis. A starting operation mechanism for a rotary throttle valve type carburetor, characterized in that a flat cam surface is provided so as to be engageable with a throttle valve lever, and an axial cam lift is given to the throttle valve in accordance with atmospheric temperature. 2. The starting operation of the rotary throttle valve type carburetor according to claim 1, wherein the lowest cam surface of the cam surfaces does not come into contact with the lower surface of the throttle valve lever and does not interfere with idle operation of the engine. mechanism. 3. An air amount is controlled by rotating the throttle valve lever, and a fuel amount is controlled by axial movement of the throttle valve lever.
In a starting operation mechanism of a rotary throttle valve carburetor, which gives axial movement to a throttle valve lever by rotating a starting operation lever coupled to a cylindrical cam member, between a shaft hole of a bearing portion of the starting operation lever and the cylindrical cam member. The eccentric sleeve inserted in
A starting operation mechanism for a rotary throttle valve type carburetor, which is rotationally displaced by a temperature sensitive member in accordance with an ambient temperature or an engine temperature to continuously change an axial cam lift given to the throttle valve. 4. The starting operation mechanism for a rotary throttle valve carburetor according to claim 3, wherein the temperature sensitive member is a spiral bimetal. 5. The rotary throttle valve carburetor starter according to claim 3, wherein the spiral bimetal has the same axis as the starter operation lever and is arranged on the outer peripheral side of the bearing portion of the starter operation lever. Operating mechanism.