JP2003314307A - Throttle device of general-purpose engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a throttle device of a general-purpose engine which precisely opens and closes a throttle valve when an opening is small, opens and closes the throttle valve at a high opening and closing speed when the opening is large, and prevents sticking of the throttle valve. <P>SOLUTION: The throttle device is so structured that a displacement output of a motor 46 is transmitted through a link lever 80a connected to an output shaft 46s of the motor and a throttle lever 80b connected to a rotational shaft 70s of the throttle valve 70, and a rotation angle (θth) of the throttle lever 80b with respect to a rotation angle (θm) of the link lever 80a becomes minimum when the throttle valve 70 is fully closed or is in a near position. Furthermore, a curvature radius rA of a circular oblong hole 80a1 provided on the link lever 80a and a rotation curvature radius rB obtained by a moving locus of a link pin 80b1 provided on the throttle lever 80b are the same curvature radius. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a throttle device for a general-purpose engine, and more specifically, it is provided with a throttle valve connected to an actuator, and the throttle valve is opened and closed by the actuator, whereby The present invention relates to a throttle device for a general-purpose engine that adjusts intake air.

[0002]

2. Description of the Related Art A general-purpose engine, more specifically, a spark ignition type internal combustion engine in which intake air metered by a throttle valve is mixed with gasoline fuel to be sucked into a cylinder, and the mixture is ignited and burned. In general, a mechanical governor including a weight and a spring drives a throttle device to control the engine speed.

However, recently, even in a general-purpose engine of this type, it is possible to accurately control the engine speed by using an electronic governor in which an actuator such as a step motor or a linear solenoid is connected to a throttle valve. Is being carried out.

As a throttle device driven by an actuator, for example, the techniques described in JP-A-10-47520 and JP-A-2001-263098 can be cited. In these conventional technologies,
A motor is used as an actuator, and the rotation of the motor is transmitted to the throttle valve by connecting the output shaft of the motor and the rotation shaft of the throttle valve via a gear.

[0005]

By the way, as shown in FIG. 11, the relationship between the throttle opening and the intake air amount passing therethrough is such that as the throttle opening (indicated by "θth") decreases, The amount of change in the amount (indicated by “Gair”) increases, and the amount of change in the intake air amount decreases as the throttle opening increases. This is because the pressure difference between the upstream side and the downstream side of the throttle valve decreases as the throttle opening increases, and finally becomes saturated.

Therefore, in order to follow the target engine speed with high accuracy and responsiveness, when the throttle opening is small, the fine opening adjustment is required and the throttle opening is When it is large, it is necessary to adjust the opening at a high opening / closing speed.

In order to precisely open and close the throttle valve, it is necessary to set a large gear reduction ratio because the resolution of the motor (stepping motor) is limited.

On the other hand, in order to increase the opening / closing speed of the throttle valve, it is necessary to set the gear reduction ratio to a small value.

However, in the prior art, since the gear reduction ratio is constant, as shown in FIG.
There was a linear relationship between the rotation angle of the motor (shown by “θm”) and the throttle opening (shown by “θth”).

Therefore, in the prior art, when the gear reduction ratio is set large in order to precisely open and close the throttle valve, the opening and closing speed decreases and the response of the rotational speed control when the throttle opening is large. There was a problem that it deteriorated.

On the contrary, if the gear reduction ratio is set small in order to increase the opening / closing speed of the throttle valve, the opening / closing cannot be performed precisely when the throttle opening is small, so that the engine speed can be controlled accurately. I couldn't. Further, since the driving torque of the throttle valve is reduced, there is a problem that the throttle valve is likely to stick when the throttle opening is small.

Therefore, an object of the present invention is to eliminate the above-mentioned inconvenience, and the throttle valve is precisely opened and closed when the opening thereof is small (that is, when the pressure difference between the upstream and downstream sides of the throttle valve is large). It is possible to open and close at a high opening speed (that is, when the pressure difference between the upstream and downstream of the throttle valve is small), and to prevent sticking of the throttle valve. To provide a throttle device for a general-purpose engine.

[0013]

In order to achieve the above object, in a first aspect of the present invention, a throttle valve connected to an actuator is provided, and the throttle valve is opened and closed by the actuator, In a throttle device for a general-purpose engine for adjusting intake air of a general-purpose engine, one end is connected to an output shaft of the actuator, while the other end is connected to a rotary shaft of the throttle valve, and a displacement output of the actuator is set to the throttle. An output transmission mechanism for transmitting to the valve is provided, and the output transmission mechanism is configured such that displacement of the output transmission mechanism with respect to displacement output of the actuator is minimized when the throttle valve is fully closed or in the vicinity thereof. did.

The displacement of the output transmission mechanism for transmitting the displacement output of the actuator to the throttle valve with respect to the displacement output of the actuator becomes minimum when the throttle valve is fully closed or in the vicinity thereof, in other words, the output transmission. The speed reduction ratio of the mechanism is maximized when the throttle valve is fully closed or close to it, so the throttle valve can be opened and closed precisely when the opening is small and at the same time when the opening is large. Can be opened and closed with a fast opening and closing speed. Moreover, sticking of the throttle valve can be prevented.

According to another aspect of the present invention, the output transmission mechanism has a link lever connected to the output shaft of the actuator, one end connected to the link lever, and the other end connected to the rotary shaft of the throttle valve. A throttle lever connected to the link lever, and the link lever and the throttle lever are arranged such that when the throttle valve is fully closed or in the vicinity thereof, the rotation angle of the throttle lever with respect to the rotation angle of the link lever is minimized. Therefore, the displacement of the output transmission mechanism with respect to the displacement output of the actuator is minimized when the throttle valve is fully closed or in the vicinity thereof.

The output transmission mechanism includes a link lever connected to the output shaft of the actuator, a throttle lever having one end connected to the link lever and the other end connected to the rotary shaft of the throttle valve, and the link lever The angle of rotation of the throttle lever with respect to the angle of rotation is minimized when the throttle valve is located at or near the fully closed position, in other words, the reduction ratio is maximized at or near the fully closed position of the throttle valve. Since the throttle valve is configured, the throttle valve can be opened and closed finely when the opening is small, and can be opened and closed at a high opening and closing speed when the opening is large. Also,
It is possible to prevent the throttle valve from sticking.

According to another aspect of the present invention, the output transmission mechanism includes an elongated hole provided in the link lever and a link pin provided in the throttle lever and movably inserted in the elongated hole. At the same time, the elongated hole is formed in an arc shape having the same radius of curvature as the radius of rotation obtained by the locus of movement of the link pin.

The long hole provided in the link lever and the link pin provided in the throttle lever and movably inserted in the long hole are provided, and the long hole is rotated by the movement locus of the link pin. Since it is formed in the shape of an arc having the same radius of curvature as the radius of curvature, the above-described effects can be further obtained. Further, the link lever and the throttle lever can be designed small, which is advantageous in terms of space. Further, strict alignment between the output shaft of the motor and the rotary shaft of the throttle valve is not required, and the cost can be reduced as compared with the connection by gears.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A general-purpose engine throttle device according to one embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing the throttle device together with a mounted general-purpose engine.

In the figure, reference numeral 10 indicates a general-purpose engine (hereinafter referred to as "engine"), and the engine 10 is
It is a water-cooled 4-cycle OHV type and has a displacement of 196 cc.

The engine 10 has one cylinder 1
2 and a piston 14 is reciprocally housed therein. The piston 14 is connected to a crankshaft 16, and the crankshaft 16 is connected to a camshaft 18 via a gear.

A combustion chamber 20 is formed between the head of the piston 14 and the cylinder wall surface, and an intake valve 24 and an exhaust valve 26 are arranged on the cylinder wall surface, and the combustion chamber 20 and the intake passage 28 or the exhaust passage 30 are provided. Open and close between.

A flywheel 32 is attached to the crankshaft 16, and a recoil starter 34 for an operator to start the engine 10 is attached to a tip end side of the flywheel 32. A generator coil (alternator) 36 is arranged inside the flywheel 32 to generate alternating current. The generated alternating current is converted into direct current through a rectifier circuit (not shown) and supplied to a spark plug (not shown) and the like.

A carburetor 38 is arranged upstream of the intake passage 28. The carburetor 38 is integrally provided with a throttle device 40 that adjusts the intake air amount. Further, the carburetor 38 is connected to a fuel tank (not shown) through a fuel pipe (not shown), is supplied with gasoline fuel stored therein, and injects gasoline fuel from a nozzle into the sucked air. Generate a mixture. The generated air-fuel mixture is in the intake passage 28.
Flow through the intake valve 24, and are sucked into the combustion chamber 20 of the cylinder 12.

The throttle device 40 is connected to a step motor (actuator; hereinafter referred to as "motor") 46, supplied with a command value (step (angle)), and operated, and a throttle valve (see FIG. Open and close (not shown).

A crank angle sensor (rotational speed sensor) 48 composed of an electromagnetic pickup is provided near the flywheel 32, and outputs a pulse for each predetermined crank angle.

An ECU (electronic control unit) 50 housed in a case is arranged at an appropriate position of the engine 10,
The output of the crank angle sensor 48 is sent to the ECU 50.
The ECU 50 comprises a microcomputer, a CPU,
It has a ROM, a RAM and a counter. In the ECU 50, the output pulse of the crank angle sensor 48 is input to a counter, where it is counted and the engine speed is calculated (detected).

The ECU 50 calculates a command value of the motor 46 based on the detected engine speed, etc., so that the detected engine speed matches the target engine speed,
A command value is output to the motor 46 through the motor driver 54 disposed adjacent to the case to operate it. A load (not shown) is connected to the engine 10. Further, in FIG. 1, reference numeral 58 indicates a cooling fan, and reference numeral 60 indicates a head cover.

As described above, the engine speed of the engine 10 is controlled by the electronic governor including the generator coil 36, the throttle device 40, the motor 46, the crank angle sensor 48, the ECU 50 and the motor driver 54.

FIG. 2 is a front view of the throttle device 40. Further, FIG. 3 is a right side view thereof.

Below, referring to both figures, the throttle device 40
The throttle device 40 includes a throttle valve 70 and an output transmission mechanism (hereinafter referred to as “link mechanism”) 80.

The throttle valve 70 is a carburetor 38.
Is provided in the middle of an intake passage (a part of which is shown by a broken line) 90 communicating with the intake pipe 28 of the engine 10.
A link mechanism 80 is connected to the throttle valve 70 to transmit the output of the motor 46.
The motor 46 is internally provided with a reduction gear (not shown) having a constant reduction ratio, and the output shaft 46s outputs the rotational displacement reduced by the reduction gear. Hereinafter, the output of the motor (or the rotation angle θm) is used to mean the decelerated rotational displacement.

The link mechanism 80 comprises a link lever 80a and a throttle lever 80b. Link lever 80
The a has one end connected to the output shaft 46s of the motor 46, and has an arc-shaped elongated hole 80a1 at the other end. Also,
The throttle lever 80b has a link pin 80b1 at one end.
And the other end is connected to the rotary shaft 70s of the throttle valve 70.

Link pin 80 of throttle lever 80b
By movably inserting the b1 into the long hole 80a1, the link lever 80a and the throttle lever 80b are connected so as to be relatively displaceable, as shown in FIG. As a result, the displacement (rotation) output of the motor 46 is transmitted to the throttle valve 70 via the displacement of the link lever 80a and the throttle lever 80b, and the opening degree of the throttle valve 70 is arbitrarily controlled. 2 shows the throttle device 40 when the throttle valve 70 is at the fully closed position (or when the throttle valve 70 is at a fully open position of 90 degrees to prevent sticking, or at a position opened by a few degrees). Shows that when the throttle valve 70 is in the fully open position.

Further, the throttle valve 70 is closed in the closing direction (link mechanism 8) at the tip end side of the throttle lever 80b to which the rotary shaft 70s of the throttle valve is connected.
A return spring 92 for urging 0 from the state shown in FIG. 4 to the state shown in FIG. 2 is attached.
It should be noted that the position of the link mechanism 80 when fully closed is, as shown in FIG. 2, a stopper 94 provided on the side surface of the carburetor 38.
Is defined by the contact of a stopper contact portion 80b2 provided on the throttle lever 80b.

The link mechanism 80 will be described below with reference to FIG.
Will be explained in detail.

FIG. 5 shows the motor 46 and the link mechanism 80.
It is explanatory drawing which shows operation | movement of FIG. In the figure, the solid line indicates the link mechanism 80 when the throttle valve (not shown) is in the fully closed position, and the dashed line when it is in the fully open position.

As shown in the figure, the link mechanism 80 is set so that the motor output shaft 46s, the link pin 80b1 of the throttle lever 80b, and the rotary shaft 70s of the throttle valve are on the same straight line when fully closed. To be done. From this state, the link lever 80a connected to the motor 46 receives the output of the motor 46 and rotates clockwise in the plane of the drawing, so that the throttle lever 80b and the throttle lever 80b are throttled through the link pin 80b1 movably inserted into the slot 80a1. The rotary shaft 70s of the valve is rotated counterclockwise, so that the throttle valve is driven in the opening direction.

Here, as described above, the link mechanism 80
Is set so that the motor output shaft 46s, the link pin 80b1 of the throttle lever 80b, and the rotary shaft 70s of the throttle valve are on the same straight line when fully closed, so the output shaft of the motor 46 when fully closed. The distance between 46s and the link pin 80b1 of the throttle lever 80b becomes the shortest. In other words, when the throttle valve 70 is located at or near the fully closed position, the throttle valve 70 responds to the displacement (rotation) output of the motor 46.
The displacement amount (rotation angle) of is the smallest (finely). In other words, the reduction ratio becomes maximum at or near full closure.

That is, as shown in FIG. 6, the smaller the throttle opening θth is, the smaller the variation dθth of the throttle opening with respect to the variation dθm of the motor rotation angle is, and the larger the throttle opening θth is, the smaller the rotation angle of the motor is. The variation dθth of the throttle opening with respect to the variation dθm becomes large.

Therefore, when the opening of the throttle valve 70 is small (that is, when the pressure difference between the upstream and downstream sides of the throttle valve is large), the throttle valve 70 can be opened and closed precisely. Further, when the opening degree of the throttle valve 70 is fully closed or in the vicinity thereof, the reduction ratio becomes maximum (the driving torque of the throttle valve becomes maximum).
It is possible to prevent the throttle valve 70 from sticking.

Further, when the opening degree of the throttle valve 70 is large (that is, when the pressure difference between the upstream and downstream sides of the throttle valve is small), the throttle valve 70 can be opened and closed at a high opening and closing speed. Improving the responsiveness of engine speed control by reducing the accompanying instantaneous fluctuations in engine speed NE (instantaneous fluctuations (increase) in engine speed when the load turns from the load-on state to the load-off state) Can be made.

Further, the output shaft 46s of the motor and the rotary shaft 70s of the throttle valve are connected via the link lever 80a and the throttle lever 80b, and the link lever 80a and the throttle lever 80b are connected to the long hole 80a1.
And the link pin 80b1 that is movably inserted therein, the strict axis alignment between the output shaft 46s and the rotary shaft 70s is not necessary as compared with the connection by the gear, and the cost can be reduced. .

The long hole 80a1 is used for the link lever 80.
It is formed in an arc shape (indicated by A in FIG. 5) protruding in the rotation direction of a. As shown in FIG. 6, compared with the long hole 80a1 formed in a straight line (broken line), the long hole 8 formed in an arc shape.
0a1 (solid line) is the amount of change in throttle opening dθt
The rate of increase of h becomes large. Therefore, the link lever 80
By forming a in an arc shape, it is possible to set the reduction ratio of the internal gear of the motor 46 to a larger value, and it is possible to obtain the above-described effect more effectively.

Further, the arc-shaped maximum opening (fully open) θth
In order to obtain an opening degree similar to max with a straight line, the link mechanism 80 must be lengthened (the motor output shaft 46s is farther from the movement locus B of the link pin 80b1) as shown by the dashed line in the upper part of the figure. I have to. Therefore, forming the hole 80a1 in an arc shape is advantageous in terms of space.

Here, the radius of curvature rA of the long hole 80a1
The radius of curvature of rotation of the link pin 80b1 (that is, the radius of the arc obtained by the movement locus B of the link pin 80b1) r
B is set to be the same. As a result, the effects described above can be obtained even better. The reason for this will be described below.

FIG. 7 shows the radius of curvature rA of the long hole 80a1
The change amount dθth of the throttle opening when the radius of curvature rB of the link pin 80b1 is set to about 1/2 is shown.
As shown in the figure, if the radius of curvature rA of the long hole 80a1 is set too small, the variation dθth becomes small at a certain throttle opening. On the other hand, if the radius of curvature rA of the long hole 80a1 is set too large, it approaches a straight line, which is disadvantageous in terms of space, and the increase rate of the variation dθth decreases.

Normally, the throttle valve has an opening of about 90 degrees from the fully closed to the fully open (if the fully closed state is opened by a few degrees as described above to prevent sticking, the angle is less than that. ) Has. In the throttle valve having the opening degree of about 90 degrees, the inventors set the curvature radius rA of the long hole 80a1 and the rotation curvature radius rB of the link pin 80b1 to be the same or substantially the same, so that the throttle valve is fully closed to fully open. Therefore, it was found that the variation dθth of the throttle opening can be optimally increased.

FIG. 8 shows the relationship between the throttle opening θth and the motor rotation angle θm when the link mechanism 80 according to this embodiment is used. Throttle opening θth shown in the figure
And the rotation angle θm of the motor, and the relationship between the throttle opening θth and the intake air amount Gair (that is, the pressure difference upstream and downstream of the throttle valve) shown in FIG. The relationship of the intake air amount Gair can be a proportional relationship as shown in FIG.

That is, as shown in FIG. 10, the rotation angle θm of the motor and the change amount dG of the intake air amount with respect to the change amount thereof.
Since the relationship of air / dθm can be made constant,
Regardless of throttle opening, engine speed NE
Can be controlled with high accuracy and responsiveness.

The size of each part of the link mechanism 80 is determined in the same way as the reduction ratio of the gear is determined, and therefore the output torque of the motor 46 is taken into consideration. In the link mechanism 80 according to this embodiment, the shaft distance between the output shaft 46s of the motor and the rotary shaft 70s of the throttle valve is 37 mm, the length of the throttle lever 80b (from the rotary shaft 70s of the throttle valve 70s to the link pin 80b1).
Up to 18.5 mm, the length of the link lever 80a (the length from the motor output shaft 46s to the contact point with the link pin 80b1) is 18.5 mm when fully closed, and 35.9 mm when fully opened. Open / close speed at full opening (throttle opening θ relative to motor rotation angle θm)
The ratio of the change in th) could be about 6.5 times that in the fully closed state.

Thus, in this embodiment,
Since the displacement amount (rotation angle) of the throttle valve 70 with respect to the displacement (rotation) output of the motor 46 is minimized (finely) at or near the fully closed position,
When the throttle opening is small, it can be opened and closed precisely, and when the throttle opening is large, the throttle valve 70 can be opened and closed at a high opening and closing speed.
Therefore, regardless of the throttle opening, the engine speed NE
Can be controlled with high precision and responsiveness. Moreover, sticking of the throttle valve can be prevented. Further, it is possible to reduce the cost as compared with the connection by the gear.

Further, the long hole 80a1 is formed in an arc shape, and the radius of curvature rA of the long hole 80a1 is set to the link pin 80.
Since the rotation radius of curvature rB obtained by the movement locus of b1 is set to be the same, the above-described effects can be further obtained, and the shape of the link mechanism 80 can be designed to be small, which is advantageous in terms of space. Becomes

As described above, in this embodiment,
A throttle device 40 for a general-purpose engine that includes a throttle valve 70 connected to an actuator (motor 46), and the throttle valve 70 is opened and closed by the actuator to adjust the intake air of the general-purpose engine (engine) 10. One end is connected to the output shaft 46s of the actuator, the other end is connected to the rotary shaft 14s of the throttle valve 70, and an output transmission mechanism (link mechanism 80) for transmitting the displacement output of the actuator to the throttle valve 70. And the output transmission mechanism is configured so that the displacement (θth) of the output transmission mechanism with respect to the displacement output (θm) of the actuator is minimized when the throttle valve 70 is located at or near the fully closed position. did.

The output transmission mechanism is a link lever 80a connected to the output shaft 46s of the actuator.
And a throttle lever 80b having one end connected to the link lever 48a and the other end connected to the rotary shaft 70s of the throttle valve 70. The link lever 80a and the throttle lever 80b are connected to the throttle valve 70. When it is located at or near the fully closed position, the rotation angle (θth) of the throttle lever 80b with respect to the rotation angle (θm) of the link lever 80a is minimized, so that the throttle valve 70 is at or near the fully closed position. When positioned, the displacement (θth) of the output transmission mechanism with respect to the displacement output (θm) of the actuator is minimized.

Further, the output transmission mechanism includes an elongated hole 80a1 provided in the link lever 80a and a link pin 80b1 provided in the throttle lever 80b and movably inserted in the elongated hole 80a1. ,
The elongated hole 80a1 is formed in an arc shape having the same radius of curvature rA as the radius of curvature rB of rotation obtained by the movement locus of the link pin 80b1.

In the above description, the step motor is used as an example of the actuator, but the actuator is not limited to this, and any type such as a linear solenoid or a DC motor that can drive the link lever 80a may be used. .

[0059]

According to the present invention, the displacement of the output transmission mechanism for transmitting the displacement output of the actuator to the throttle valve with respect to the displacement output of the actuator is minimum when the throttle valve is fully closed or in the vicinity thereof. With such a configuration, the throttle valve can be opened and closed precisely when the throttle opening is small, and the throttle valve can be opened and closed at a high opening and closing speed when the throttle opening is large. Moreover, sticking of the throttle valve can be prevented.

According to a second aspect of the present invention, similarly to the first aspect, when the throttle opening is small, the throttle valve can be opened and closed precisely, and when the throttle opening is large, the throttle valve can be opened at a high opening / closing speed. It can be opened and closed. Moreover, sticking of the throttle valve can be prevented.

According to the third aspect of the present invention, it is possible to obtain the above-described effect more effectively, and it is possible to design the link lever and the throttle lever to be small, which is advantageous in terms of space. Furthermore, it is not necessary to strictly align the motor output shaft and throttle valve rotation shaft.
The cost can be reduced as compared with the connection by gears.

[Brief description of drawings]

FIG. 1 is a schematic diagram generally showing a throttle device for a general-purpose engine according to an embodiment of the present invention.

FIG. 2 is a front view of the throttle device shown in FIG.

FIG. 3 is a right side view of the throttle device shown in FIG.

4 is a front view similar to FIG. 2, of the throttle device shown in FIG.

5 is an explanatory diagram showing an operation of a link mechanism and the like of the throttle device shown in FIG.

FIG. 6 is an explanatory diagram schematically showing the operation of the link mechanism and the like shown in FIG.

FIG. 7 is an explanatory diagram schematically showing the operation of the link mechanism when the radius of curvature of the elongated hole formed in the link mechanism shown in FIG. 5 is changed.

8 is a rotation angle θ of the motor of the throttle device shown in FIG.
It is a characteristic view which shows the relationship between m and throttle opening (theta) th.

9 is a rotation angle θm and intake air amount G of the motor shown in FIG.
It is a characteristic view which shows the relationship of air.

10 is a rotation angle θm of a motor of the throttle device shown in FIG. 1 and a change amount dGa of an intake air amount with respect to a change amount thereof.
It is a characteristic view which shows the relationship of ir / d (theta) m.

FIG. 11: Throttle opening θth and intake air amount Gair
It is a characteristic view showing the relationship of.

FIG. 12 is a characteristic diagram showing a relationship between a rotation angle θm and a throttle opening θth of a motor of a throttle device according to a conventional technique.

[Explanation of symbols]

10 General-purpose engine (engine) 40 Throttle device 46 Actuator (motor) Output shaft of 46s actuator (motor) 70 Throttle valve 70s Throttle valve rotation axis 80 link mechanism 80a link lever 80a1 long hole 80b Throttle lever 80b1 link pin

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Claims (3)

[Claims] 1. A throttle device for a general-purpose engine, comprising: a throttle valve connected to an actuator; wherein the throttle valve is opened and closed by the actuator to adjust intake air of the general-purpose engine; While being connected to the shaft, the other end is connected to the rotary shaft of the throttle valve,
An output transmission mechanism for transmitting the displacement output of the actuator to the throttle valve is provided, and the output transmission mechanism is configured to output the displacement output of the actuator when the throttle valve is fully closed or in the vicinity thereof. A throttle device for a general-purpose engine, which is configured to have a minimum displacement. 2. The output transmission mechanism includes a link lever connected to an output shaft of the actuator, and a throttle lever having one end connected to the link lever and the other end connected to a rotary shaft of the throttle valve. In addition, the link lever and the throttle lever are provided such that, when the throttle valve is fully closed or in the vicinity thereof, the rotation angle of the throttle lever with respect to the rotation angle of the link lever is minimized. When located at or near full closure,
The throttle device for a general-purpose engine according to claim 1, wherein the displacement of the output transmission mechanism with respect to the displacement output of the actuator is minimized. 3. The output transmission mechanism includes an elongated hole provided in the link lever, a link pin provided in the throttle lever and movably inserted into the elongated hole, and the output hole is provided with the elongated hole. The throttle device for a general-purpose engine according to claim 2, wherein the throttle device is formed in an arc shape having a radius of curvature which is the same as a radius of curvature of rotation obtained by the movement locus of the link pin.