Easy engine start system

Abstract

The present invention comprises an engine, a centrifugal clutch for transmitting the drive force of the engine to a driven device, and a control device for adjusting the power of the engine. The engine is accelerated by starting engine power capable of reaching a rotational speed higher than the clutch-in rotational speed at the time of starting. The control device has suppression control for suppressing the starting engine power so that the rotational speed does not exceed the clutch-in rotational speed.

Description

[Technical Field]

[0001] The present invention relates to an engine easy start system that can easily start an engine. [Background technology]

[0002] Conventional manual recoil-type working machines have a lift-up member, and the lift-up member mechanism determines both the amount of air and fuel supplied to the engine. In this manual recoil-type working machine, when starting the engine, the lift-up member is operated to open the throttle to an output opening that does not engage the clutch, and the engine is started.

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-131808

[0004] Conventional manual recoil-type work machines have a lift-up member and control the amount of air and fuel within an output range that does not engage the clutch, so the effectiveness is limited and it can take time to start the engine. DISCLOSURE OF THE INVENTION

[0005] The present invention has been made in consideration of the above points, and its object is to provide a simple engine starting system that can quickly and accurately start the engine even in a manual type such as a manual recoil type work machine.

[0006] The features of the engine easy starting system according to the present invention are as follows: The engine and a centrifugal clutch for transmitting the driving force of the engine to a driven device; a control device that adjusts the output of the engine, When the engine is started, it is accelerated with a starting engine output capable of reaching a rotation speed greater than a clutch-in rotation speed, The control device has a suppression control for suppressing the starting engine output to a rotation speed not exceeding the clutch-in rotation speed. That is the thing.

[0007] According to the present invention, even if the engine is manual, it can be started quickly and accurately. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram of an engine according to an embodiment of the present invention. [Figure 2] 1 is a schematic diagram of an ignition device for an engine according to an embodiment of the present invention. [Figure 3] FIG. 2 is a circuit block diagram of the ignition device 16. [Figure 4] 4 is a flowchart showing a control process when the internal combustion engine 2 is started. [Figure 5] 10 is a diagram showing an example of the relationship between the timing for checking the rotation speed of the internal combustion engine 2 when the internal combustion engine 2 is started and the rotation speed of the internal combustion engine 2. FIG. [Figure 6] FIG. 4 is a diagram showing an example of a condition for canceling the first starting PI control. [Figure 7] FIG. 10 is a diagram showing an example of a condition for canceling the second starting PI control. [Figure 8] 1A is a longitudinal cross-sectional view showing the structure of a vaporizer 7, and FIG. 1B is a transverse cross-sectional view showing the structure of the vaporizer 7. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] <<<<<Outline of this embodiment>>>> <<First Aspect>> According to a first aspect, The engine and a centrifugal clutch for transmitting the driving force of the engine to a driven device; a control device that adjusts the output of the engine, When the engine is started, it is accelerated with a starting engine output capable of reaching a rotation speed greater than a clutch-in rotation speed (the clutch-in rotation speed usually indicates the rotation speed at which the clutch is started), The control device has a suppression control for suppressing the start-up engine output to a rotation speed that does not exceed the clutch-in rotation speed, and the engine easy start system is provided.

[0010] The easy engine starting system according to a first aspect includes an engine, a centrifugal clutch, and a control device.

[0011] When the engine is started, the engine is accelerated with a starting engine output that allows it to reach a rotational speed higher than the clutch-in rotational speed. For example, when the engine is started, the amount of air or fuel supplied to the engine is controlled so that it can reach a rotational speed higher than the clutch-in rotational speed.

[0012] It is sufficient that the clutch-in rotation speed can be reached, but the clutch-in rotation speed is not actually reached. Therefore, the suppression control suppresses the rotation speed to a value that does not exceed the clutch-in rotation speed.

[0013] By controlling the engine at startup using the starting engine output and suppression control, the engine startup operation can be simplified (no need for choke operation, etc.), and even users with low skills can start the engine accurately.In addition, the engine can be started quickly and made ready for use in a short time.

[0014] <<Second Aspect>> The second aspect is the first aspect, a throttle valve for adjusting the amount of intake air into the combustion chamber of the engine; The starting engine output is The throttle opening of the throttle valve is adjusted so that a rotational speed greater than the clutch-in rotational speed can be reached.

[0015] Since the amount of air entering the combustion chamber of the engine is adjusted, it is possible to accurately reach a rotation speed higher than the clutch-in rotation speed.

[0016] <<Third Aspect>> The third aspect is the second aspect, The engine has an output of 0.5 kW to 2 kW, and the throttle opening is targeted to be equal to or greater than the clutch-in rotational speed and equal to or less than twice the clutch-in rotational speed.

[0017] In this way, the engine speed can be increased quickly.

[0018] <<Fourth Aspect>> The fourth aspect is the third aspect, The throttle opening is targeted to be equal to or greater than the clutch-in rotation speed and 1.0 to 1.6 times the clutch-in rotation speed.

[0019] By doing so, it is possible to improve both startability and suppression controllability.

[0020] <<Fifth Aspect>> The fifth aspect is the fourth aspect, The throttle opening is targeted to be equal to or greater than the clutch-in rotational speed and 1.0 to 1.3 times the clutch-in rotational speed.

[0021] By doing so, it is possible to further improve the start-up performance and the suppression control performance.

[0022] <<Sixth Aspect>> The sixth aspect is the first to fifth aspects, A detection unit that detects the number of revolutions of the engine is further provided, The suppression control is This is a feedback control that determines the ignition timing based on the deviation between the target rotation speed and the detected rotation speed.

[0023] Since the engine speed is detected and controlled based on the difference between the detected speed and the target speed, the engine speed can be increased quickly and then stabilized quickly.

[0024] <<Seventh Aspect>> The seventh aspect is the sixth aspect, After the engine has started, the feedback control is started when at least one of the detected number of revolutions, the rotation speed, and the time satisfies a predetermined condition.

[0025] It is possible to transition to feedback control at an appropriate timing.

[0026] <<Eighth Aspect>> The eighth aspect is the sixth or seventh aspect, The feedback control is a first feedback control that performs feedback control so that the rotation speed falls within a first rotation speed range; The second feedback control is performed after the first feedback control, to perform feedback control so that the rotation speed falls within a second rotation speed range that is wider than the first rotation speed range.

[0027] The first feedback control stabilizes the engine speed immediately after the engine is started, and then the second feedback control prepares the engine for rapid acceleration.

[0028] <<Ninth Aspect>> The ninth aspect is any one of the first to eighth aspects, The engine has a recoil that requires a manual pull rope to start.

[0029] By doing so, even a worker with relatively little physical strength can easily start the machine.

[0030] <<Tenth Aspect>> A ninth aspect of the present invention is a ninth aspect of the present invention, It is equipped with a two-stroke engine mounted on a handheld blade work machine.

[0031] This allows for easy starting and safe starting since the clutch is not required.

[0032] <<Eleventh Aspect>> a fuel valve for adjusting the amount of fuel to a combustion chamber of the engine; The opening of the fuel valve is adjusted together with the throttle opening.

[0033] By adjusting not only the amount of air but also the amount of fuel, the engine speed can be increased quickly while being controlled so as not to exceed the clutch-in speed.

[0034] <<Twelfth Aspect>> The engine further includes a linkage mechanism for linking the throttle valve and the fuel valve.

[0035] Since the control is performed by the interlocking mechanism, it is possible to easily control both the amount of air and the amount of fuel.

[0036] <<<<<Details of this embodiment>>>> Hereinafter, an embodiment will be described with reference to the drawings.

[0037] <<<Configuration of Internal Combustion Engine 2>>> FIG. 1 is a schematic diagram of an engine according to this embodiment. As shown in FIG. 1, the internal combustion engine 2 is preferably a two-stroke gasoline engine. The internal combustion engine 2 has a carburetor 7. The carburetor 7 has a throttle valve (a rotating part 72 (see FIG. 8) described later) that adjusts the amount of mixture that flows into the internal combustion engine 2. The throttle valve is operated by a throttle lever, a choke knob (not shown), or the like. A conventionally known throttle valve can be used.

[0038] The internal combustion engine 2 has a cylinder 2a, a crankshaft 2b, a piston 2c, and a spark plug 10. The piston 2c is disposed in the cylinder 2a and connected to the crankshaft 2b. The spark plug 10 is disposed at the top of the cylinder 2a.

[0039] During the compression stroke of the internal combustion engine 2, the piston 2c rises to a top dead center position 2d. Generally, the spark plug 10 is activated to combust the air-fuel mixture in the cylinder 2a before the piston 2c reaches the top dead center position 2d. The combustion of the air-fuel mixture provides the piston 2c with a downward thrust, generating torque on the crankshaft 2b.

[0040] The internal combustion engine 2 can be mounted on a work machine or the like. The work machine can be, for example, an autonomous grass-cutting robot or a handheld work machine.

[0041] The internal combustion engine 2 is preferably equipped with a recoil mechanism that allows a rope to be pulled by hand when starting. This configuration allows even a person with relatively little physical strength to start it easily. Furthermore, it is preferable to have a two-stroke engine mounted on a handheld blade tool working machine. This configuration allows for easy starting and safe starting without the need for a clutch.

[0042] <Output of Internal Combustion Engine 2> The output of the internal combustion engine 2 is the amount of work done by the engine. The output of the internal combustion engine 2 is the torque multiplied by the rotation speed. Specifically, the output of the internal combustion engine 2 is preferably 0.5 kW to 2 kW. When the internal combustion engine 2 is used in a lawn mower equipped with a rotary carburetor, the output of the internal combustion engine 2 is preferably 0.7 kW to 1.4 kW.

[0043] <<<Configuration of ignition device 12>>> Fig. 2 is a schematic diagram of an ignition device for an internal combustion engine 2 according to this embodiment. As shown in Fig. 2, the internal combustion engine 2 has an ignition device 12 that activates an ignition plug 10. A flywheel 14a is attached to a crankshaft (not shown) of the internal combustion engine 2 so as to be movable in conjunction with the crankshaft. The ignition device 12 has a pair of magnets 14b, an iron core 14c, and an input coil 14d.

[0044] The pair of magnets 14b are mounted on the outer periphery of the flywheel 14a. The iron core 14c has a U-shape and is disposed adjacent to the outer periphery of the flywheel 14a. The input coil 14d is wound around the iron core 14c.

[0045] The ignition device 12 has a control device 16, a primary coil 18a, and a secondary coil 18b. The control device 16 is connected to the input coil 14d. The primary coil 18a is connected to the control device 16. The secondary coil 18b is connected to the spark plug 10.

[0046] <<<Configuration of control device 16>>> Fig. 3 is a circuit block diagram showing the circuit configuration of the control device 16. As shown in Fig. 3, the control device 16 has a capacitor 24, a switching element 26, a signal input circuit 32, a microcomputer 20, a power supply circuit 30, a temperature sensor 50, and a temperature detection circuit 52. In Fig. 3, the above-mentioned primary coil 18a and secondary coil 18b are shown as the ignition coil 18.

[0047] When the internal combustion engine 2 is operating, the crankshaft rotates, causing a pair of magnets 14b attached to the flywheel 14a to pass near the U-shaped iron core 14c, which induces a voltage in the input coil 14d and supplies it to the microcomputer 20.

[0048] <<Power supply>> The voltage induced in the input coil 14d is supplied as a power supply voltage to the microcomputer 20 from the IN1 terminal of the microcomputer 20 via the power supply circuit 30. The power supply circuit 30 is composed of a rectifier circuit, a smoothing circuit, etc. (not shown). This allows a stable power supply voltage to be supplied to the microcomputer 20.

[0049] <<Control signals>> The voltage induced in the input coil 14d is supplied as a control signal to the microcomputer 20 from the IN2 terminal of the microcomputer 20 via a signal input circuit 32. The signal input circuit 32 includes a waveform shaping circuit and the like (not shown). This allows the control signal to be supplied to the microcomputer 20. The control signal is a signal that includes one or more pulses for each revolution of the crankshaft. The control signal functions as a reference signal for generating an ignition control signal.

[0050] <<Ignition control>> The microcomputer 20 detects or calculates the number of revolutions (rotational speed) and angular position of the internal combustion engine 2 based on the control signal supplied via the signal input circuit 32. The microcomputer 20 generates an ignition control signal based on the detection result or calculation result, and outputs it to the switching element 26 from the OUT1 terminal.

[0051] The switching element 26 is, for example, a thyristor. The switching element 26 is connected to the OUT1 terminal of the microcomputer 20. When the ignition control signal output from the OUT1 terminal of the microcomputer 20 is LOW, the switching element 26 is in a non-conductive state. When the ignition control signal output from the OUT1 terminal of the microcomputer 20 is HIGH, the switching element 26 is in a conductive state.

[0052] When the ignition control signal output from the microcomputer 20 is set to LOW and the switching element 26 is de-energized, the voltage induced in the input coil 14d charges the capacitor 24. When it is time to ignite the spark plug 10, the ignition control signal output from the microcomputer 20 is set to HIGH, and the switching element 26 is energized, discharging the capacitor 24 and causing current to flow through the primary coil 18a of the ignition coil 18. The current flowing through the primary coil 18a generates a high-voltage pulse in the secondary coil 18b of the ignition coil 18, thereby activating the spark plug 10.

[0053] <<Temperature Sensor 50 and Temperature Detection Circuit 52>> The temperature sensor 50 detects the temperature of the internal combustion engine 2 and outputs a detection signal. The temperature sensor 50 is connected to a temperature detection circuit 52. The temperature detection circuit 52 supplies the detection signal to the microcomputer 20. The detection signal is digitized by the temperature detection circuit 52 or the microcomputer 20. The temperature detection circuit 52 is connected to the IN3 terminal of the microcomputer 20. In this manner, the microcomputer 20 can obtain the temperature of the internal combustion engine 2.

[0054] <<<Engine start control>>> Fig. 4 is a flowchart showing the control process at the start of the internal combustion engine 2. The process shown in Fig. 4 is executed by the microcomputer 20. Fig. 5 is a diagram showing an example of the relationship between the timing for checking the rotation speed of the internal combustion engine 2 in the start mode of the internal combustion engine 2 and the rotation speed of the internal combustion engine 2. Fig. 6 is a diagram showing an example of a condition for canceling the first start-up PI control. Fig. 7 is a diagram showing an example of a condition for canceling the second start-up PI control.

[0055] First, the microcomputer 20 determines whether the condition for transitioning to PI control is met (step S411).

[0056] For example, if the rotation speed of the internal combustion engine 2 becomes greater than the transition judgment rotation speed within a first rotation speed immediately after starting the internal combustion engine 2 and the rotation speed becomes greater than or equal to a second rotation speed, it is determined that the PI control transition condition is met.

[0057] Specifically, as shown in Figure 5, within five revolutions (first revolutions) immediately after starting the internal combustion engine 2 (in start mode), the number of revolutions at which the rotation speed of the internal combustion engine 2 reached 3800 RPM (transition judgment revolutions) or more was three or more times (second revolutions), so the PI control transition condition was deemed to be met and the system transitioned to the first start-up PI control.

[0058] The first rotation speed, second rotation speed, and transition judgment rotation speed described above are merely examples and can be determined as appropriate depending on the structure and characteristics of the internal combustion engine 2. The transition judgment rotation speed is a rotation speed that is lower than the clutch-in rotation speed. In this way, it is possible to transition to the first start-up PI control without engaging the clutch.

[0059] Next, if the PI control transition condition is met (YES), the microcomputer 20 executes the first start-up PI control (step S413). The first start-up PI control is feedback control for stabilizing the rotation speed of the internal combustion engine 2 immediately after engine start. Specifically, the first start-up PI control controls the rotation speed of the internal combustion engine 2 to fall within a first rotation speed range that includes the target rotation speed. By performing this feedback control, the rotation speed of the internal combustion engine 2 can be controlled to quickly reach the target rotation speed and maintain it at that range.

[0060] Although proportional control and integral control, which are feedback controls, are used as the first start-up PI control, PID control (proportional control, integral control, differential control) or other feedback control may also be used. The first start-up PI control may be any control that quickly makes the rotation speed of the internal combustion engine 2 reach the target rotation speed and maintains it thereat.

[0061] Next, the microcomputer 20 determines whether or not the termination condition for the first start-up PI control has been met. The termination condition for the first start-up PI control can be determined based on the temperature of the internal combustion engine 2, the temperature deviation of the internal combustion engine 2, and the time (number of rotations) during which the first start-up PI control is being performed. These conditions make it possible to determine whether or not the internal combustion engine 2 has stabilized immediately after starting. Other conditions may also be used as long as they can determine the stability of the internal combustion engine 2.

[0062] Specifically, first, the microcomputer 20 determines whether or not the temperature of the internal combustion engine 2 is equal to or higher than a predetermined temperature (step S415). The temperature of the internal combustion engine 2 can be detected by the temperature sensor 50 described above.

[0063] If the temperature of the internal combustion engine 2 is below the predetermined temperature (NO), that is, if the temperature of the internal combustion engine 2 has not yet reached a sufficiently high level, the microcomputer 20 determines whether the temperature deviation is equal to or greater than a predetermined value (step S417). The temperature deviation can be calculated from the difference between the temperature when the first start-up PI control was initiated and the temperature currently detected by the temperature sensor 50.

[0064] If the temperature deviation is within the predetermined value (NO), that is, if the temperature change is not large, the microcomputer 20 determines whether a timeout has occurred (whether a predetermined time has elapsed or whether a predetermined number of rotations has been exceeded) (step S419).

[0065] If the timeout has not occurred (NO), the microcomputer 20 returns the process to step S413 and continues the first startup PI control.

[0066] If the temperature of the internal combustion engine 2 is equal to or higher than a predetermined temperature in the judgment process of step S415 (YES), if the temperature deviation is equal to or higher than a predetermined value in the judgment process of step S417 (YES), or if a timeout occurs in the judgment process of step S419 (YES), the microcomputer 20 determines that the termination condition for the first start-up PI control has been met and executes the second start-up PI control (step S421).

[0067] For example, in the example shown in Fig. 6, when the temperature deviation becomes 10°C or more, it is determined that the termination condition of the first start-up PI control is satisfied, and the second start-up PI control is executed. Note that, in addition to the example shown in Fig. 6, as described above, it is also possible to determine that the termination condition of the first start-up PI control is satisfied, and execute the second start-up PI control, when the temperature of the internal combustion engine 2 becomes equal to or higher than a predetermined temperature, or when a predetermined time has elapsed.

[0068] The second start-up PI control is a control for preparing for acceleration after the rotation of the internal combustion engine 2 has been stabilized by the first start-up PI control. Specifically, it is a control for preparing the internal combustion engine 2 so that it can be quickly accelerated in response to the user's work. The second start-up PI control controls the rotation speed of the internal combustion engine 2 so that it falls within a second rotation speed range that is wider than the first rotation speed range of the first start-up PI control. In this way, the allowable range of the rotation speed of the internal combustion engine 2 is widened, making it possible to accommodate quick acceleration.

[0069] Although proportional control and integral control, which are feedback controls, are used as the second start-up PI control, PID control (proportional control, integral control, differential control) or other feedback control may also be used. The second start-up PI control may be any control that controls the rotation speed of the internal combustion engine 2 so that it falls within the second rotation speed range.

[0070] Next, the microcomputer 20 determines whether the termination condition of the second start-up PI control is satisfied. The termination condition of the second start-up PI control can be determined based on the rotation speed of the internal combustion engine 2 and the acceleration state of the internal combustion engine 2. This allows for quick acceleration in response to the user's work. Other conditions may also be used as long as they allow for quick acceleration.

[0071] Specifically, first, the microcomputer 20 determines whether the rotation speed of the internal combustion engine 2 is equal to or greater than a predetermined rotation speed (step S423).

[0072] If the rotation speed of the internal combustion engine 2 is lower than the predetermined rotation speed (NO), the microcomputer 20 determines whether the internal combustion engine 2 is accelerating (step S425).

[0073] If the internal combustion engine 2 is not accelerating (NO), the microcomputer 20 returns the process to step S421 and continues the second starting PI control.

[0074] If the condition for transitioning to PI control is not met in the judgment process of step S411 (NO), if the rotation speed of the internal combustion engine 2 is equal to or higher than a predetermined rotation speed in the judgment process of step S423 (YES), or if the internal combustion engine 2 is accelerating in the judgment process of step S425 (YES), the microcomputer 20 transitions to normal ignition control (step S427) and ends this subroutine.

[0075] For example, in the example shown in Fig. 7, when the rotation speed of the internal combustion engine 2 reaches 8000 RPM or more, it is determined that the termination condition of the second start-up PI control is satisfied, and the control shifts to normal ignition control. Note that, in addition to the example shown in Fig. 7, as described above, it is also possible to transition to normal ignition control when the internal combustion engine 2 enters an accelerating state, which is determined that the termination condition of the second start-up PI control is satisfied.

[0076] <<<Lift-up mechanism>>> 8(a) is a vertical cross-sectional view showing the structure of the carburetor 7 and a horizontal cross-sectional view showing the structure of the carburetor 7. The carburetor 7 according to this embodiment is a rotary throttle valve type carburetor.

[0077] The carburetor 7 has an intake air flow rate control unit 70 and a fuel flow rate control unit 80.

[0078] <<Intake air flow rate control unit 70>> The intake air flow rate control section 70 has a rotatable rotating section 72. The rotating section 72 has a passage 74 through which air can pass. The passage 74 communicates with an air supply hole 76. The passage 74 communicates with a combustion chamber of the internal combustion engine 2. Air from the outside is supplied to the combustion chamber from the air supply hole 76 through the passage 74.

[0079] The rotating part 72 rotates when the user operates the accelerator. The direction of the passage 74 is changed according to the rotation angle θ of the rotating part 72, changing the degree of overlap between the air supply hole 76 and the passage 74. The air flow rate is controlled by the degree of overlap. In this way, the air flow rate supplied to the combustion chamber of the internal combustion engine 2 can be adjusted by the rotation angle θ of the rotating part 72. The rotating part 72 functions as a throttle valve.

[0080] The throttle valve opening is preferably set to a target rotational speed that is equal to or greater than the clutch-in rotational speed and is 1.0 to 1.6 times the clutch-in rotational speed. This allows for good starting performance and suppression controllability. It is even more preferable that the throttle valve opening be set to a target rotational speed that is equal to or greater than the clutch-in rotational speed and is 1.0 to 1.3 times the clutch-in rotational speed. This allows for good starting performance and suppression controllability.

[0081] <<Fuel flow rate control unit 80>> The fuel flow rate control unit 80 has a movable needle 82 and a fuel nozzle 84. The movable needle 82 can move up and down in response to the rotation of the rotating unit 72. The movable needle 82 can be linked to the rotating unit 72 by an interlocking member 86. The interlocking member 86 can be formed by a combination of cams with tapered surfaces, a combination of gears, or the like (not shown). The interlocking member 86 can be any member that converts the rotational movement of the rotating unit 72 into the linear movement of the movable needle 82.

[0082] The tip of the movable needle 82 is movably inserted into a fuel nozzle 84. The fuel nozzle 84 supplies fuel to the combustion chamber of the internal combustion engine 2. Air drawn into the combustion chamber from the passage 74 and fuel discharged from the fuel nozzle 84 are mixed to form an air-fuel mixture, which is supplied to the combustion chamber of the internal combustion engine 2.

[0083] The reciprocating movement of the movable needle 82 changes the depth of insertion into the fuel nozzle 84. The amount of fuel discharged from the fuel nozzle 84 can be adjusted depending on the depth of insertion into the fuel nozzle 84, and the movable needle 82 functions as a fuel valve.

[0084] As described above, the rotating part 72 and the movable needle 82 are linked by the linking member 86. The linking member 86 makes it possible to simultaneously adjust both the amount of air drawn into the combustion chamber from the passage 74 and the amount of fuel discharged from the fuel nozzle 84, thereby enabling the optimum air-fuel ratio to be set according to the opening of the throttle valve.

[0085] Specifically, the interlocking member 86 causes the insertion depth of the movable needle 82 to decrease as the rotation angle θ of the rotating part 72 decreases, and the insertion depth of the movable needle 82 to increase as the rotation angle θ of the rotating part 72 increases. That is, the amount of air can be increased by decreasing the rotation angle θ of the rotating part 72, while the insertion depth of the movable needle 82 can be decreased to increase the amount of fuel (lift-up). Also, the amount of air can be decreased by increasing the rotation angle θ of the rotating part 72, while the insertion depth of the movable needle 82 can be increased to decrease the amount of fuel.

[0086] In this configuration, in which the throttle valve opening and fuel flow control are linked, setting the throttle valve opening to a target engine speed that is less than twice the clutch-in engine speed, based on the clutch-in engine speed, improves engine startability and sustained stability after startup. It is particularly desirable to set the throttle valve opening to a target engine speed that is 1.0 to 1.6 times the clutch-in engine speed. In this configuration, the engine speed at startup is limited to a range higher than the clutch-in engine speed, simplifying the patterns of fuel flow control according to the air volume and suppression control by the ignition device. For example, simply incorporating retardation control for an upper limit engine speed slightly higher than the clutch-in engine speed into the suppression control by the ignition device can achieve stable startability within a predetermined engine speed range and sustained stability after startup.

[0087] Furthermore, it is preferable to configure the throttle valve opening to be set to 1.0 to 1.3 times the clutch-in rotation speed. This configuration not only simplifies the startability and suppression control described above, but also minimizes fuel flow control, i.e., control of the movement of movable needle 82. This allows for quick and reliable startability and sustained stability after start-up, while avoiding the complexity of the carburetor body and peripheral components. This configuration is suitable for portable work machines with engine outputs of 0.5 kW to 2 kW.

[0088] <<<<<Scope of embodiment>>>> As described above, the present embodiment has been described, but the descriptions and drawings that form part of this disclosure should not be understood as limiting, and various embodiments not described herein are included.

Claims

1. The engine and a centrifugal clutch for transmitting the driving force of the engine to a driven device; a control device that adjusts the output of the engine; a detection unit that detects the engine speed, When the engine is started, it is accelerated with a starting engine output capable of reaching a rotation speed greater than a clutch-in rotation speed, the control device has a suppression control that suppresses the starting engine output to a rotation speed that does not exceed the clutch-in rotation speed, The suppression control is This is a feedback control that determines the ignition timing based on the deviation between the target rotation speed and the detected rotation speed. The feedback control is The engine easy start system has a first feedback control that performs feedback control so that the engine speed falls within a first engine speed range that is smaller than the clutch-in engine speed and includes a target engine speed.

2. a throttle valve for adjusting the amount of intake air into the combustion chamber of the engine; The starting engine output is 2. The engine easy starting system according to claim 1, wherein the throttle opening of the throttle valve is adjusted so that an engine speed higher than the clutch-in speed can be reached.

3. 3. The engine easy start system according to claim 2, wherein the engine has an output of 0.5 kW to 2 kW, and the throttle opening is targeted to a rotational speed that is equal to or greater than a clutch-in rotational speed and equal to or less than twice the clutch-in rotational speed.

4. 4. The engine easy start system according to claim 3, wherein the throttle opening is set to a target rotational speed that is equal to or greater than the clutch-in rotational speed and is 1.0 to 1.6 times the clutch-in rotational speed.

5. 5. The engine easy start system according to claim 4, wherein the throttle opening is set to a target rotational speed that is equal to or greater than the clutch-in rotational speed and is 1.0 to 1.3 times the clutch-in rotational speed.

6. 2. The engine easy start system according to claim 1, wherein the feedback control is started when at least one of the detected number of revolutions, the rotation speed, and time satisfies a predetermined condition after the engine has started.

7. The feedback control is 2. The engine easy starting system according to claim 1, further comprising a second feedback control that performs feedback control after the first feedback control so that the engine speed falls within a second engine speed range that is wider than the first engine speed range.

8. 8. The engine easy starting system according to claim 1, wherein the engine is provided with a recoil device that allows a rope to be pulled manually when starting the engine.

9. 9. The engine starting system according to claim 8, comprising a two-stroke engine mounted on a handheld blade tool working machine.

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