General-purpose engine speed control device

Abstract

To avoid overheat of a general purpose engine.SOLUTION: A rotation speed control device for a general purpose engine is provided in the general purpose engine configured to transmit power to a drive body of a work machine via a centrifugal clutch, and controls the rotation speed of the general purpose engine. The rotation speed control device comprises a rotation speed acquisition unit for acquiring the rotation speed of the general purpose engine, and a combustion control unit for controlling combustion in the general purpose engine on the basis of the rotation speed of the general purpose engine acquired by the rotation speed acquisition unit. Denoting the rotation speed of the general purpose engine, at which the centrifugal clutch is engaged without slip, as a first rotation speed, and the rotation speed, which is higher than the first rotation speed and is lower than the maximum output rotation speed of the general purpose engine and at which the general purpose engine overheats if operated continuously for a predetermined time, as a second rotation speed, the combustion control unit is configured to execute combustion suppression control for suppressing combustion in the general purpose engine if the rotation speed of the general purpose engine acquired by the rotation speed acquisition unit is included between the first rotation speed and the second rotation speed.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a rotation speed control device for a general-purpose engine. [Background technology]

[0002] Some work machines, such as brush cutters, are equipped with a control device that controls the general-purpose engine depending on the operating state. For example, Patent Document 1 discloses that the time that the actual rotation speed of the general-purpose engine remains within the rotation speed band from the rotation speed at which the centrifugal clutch begins to engage to the rotation speed at which the centrifugal clutch enters the engaged state without slipping is monitored, and the combustion process is controlled so that the actual rotation speed of the general-purpose engine falls outside the rotation speed band when this retention time exceeds a predetermined value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-118499 Summary of the Invention [Problem to be solved by the invention]

[0004] However, a work machine (brush cutter) is equipped with a drive body (cutting blade and wheels) that is driven by the power of a general-purpose engine, and the load acting on this drive body can cause the general-purpose engine to heat up, potentially leading to overheating. However, the technology described in Patent Document 1 is intended to suppress the thermal load on the centrifugal clutch due to slippage of the centrifugal clutch, but does not prevent overheating of the general-purpose engine.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a rotation speed control device for a general-purpose engine that can prevent overheating of the general-purpose engine. [Means for solving the problem]

[0006] In order to achieve the above object, a general-purpose engine rotation speed control device according to the present disclosure is provided to a general-purpose engine configured to transmit power to a drive body of a work machine via a centrifugal clutch, and controls the rotation speed of the general-purpose engine. The control device includes: a rotation speed acquisition unit that acquires the rotation speed of the general-purpose engine; and a combustion control unit that controls combustion in the general-purpose engine based on the rotation speed of the general-purpose engine acquired by the rotation speed acquisition unit. When the rotation speed of the general-purpose engine at which the centrifugal clutch is engaged without slipping is defined as a first rotation speed, and a second rotation speed that is greater than the first rotation speed and less than a maximum output rotation speed of the general-purpose engine, and that will cause the general-purpose engine to overheat if operated continuously for a predetermined period of time, the combustion control unit is configured to execute combustion suppression control to suppress combustion in the general-purpose engine when the rotation speed of the general-purpose engine acquired by the rotation speed acquisition unit is between the first rotation speed and the second rotation speed. [Effects of the Invention]

[0007] According to the rotation speed control device for a general-purpose engine of the present disclosure, overheating of the general-purpose engine can be prevented. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a schematic configuration of a work machine including a rotation speed control device according to an embodiment. [Figure 2] 1 is a schematic functional block diagram of a rotation speed control device according to an embodiment; [Figure 3] FIG. 4 is a diagram for explaining a second rotation speed according to one embodiment. [Figure 4] 3 is a flowchart of a method for controlling the rotation speed of a general-purpose engine using a rotation speed control device according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, a rotation speed control device for a general-purpose engine according to an embodiment of the present disclosure will be described with reference to the drawings. The embodiment shows one aspect of the present disclosure, and is not intended to limit the present disclosure. Any modification can be made within the scope of the technical concept of the present disclosure.

[0010] The rotation speed control device for a general-purpose engine according to the present disclosure is provided in a general-purpose engine configured to transmit power to a drive body of a work machine via a centrifugal clutch, and controls the rotation speed of the general-purpose engine. In this disclosure, an example will be described in which the work machine is a brush cutter carried by the user (a so-called walk-behind brush cutter), but the work machine is not limited to a walk-behind brush cutter. Furthermore, the work machine is not limited to a brush cutter, and may be a tea harvester, a brush cutter, or the like, and the general-purpose engine is used as a power source for the tea harvester, brush cutter, or the like.

[0011] <Work machine configuration> 1 is a diagram that shows a schematic configuration of a work machine 100 (brush cutter) that includes a rotation speed control device 1 (hereinafter simply referred to as the rotation speed control device 1) for a general-purpose engine 101 according to one embodiment. As shown in FIG. 1, the work machine 100 includes the general-purpose engine 101, a centrifugal clutch 102, a drive body 104 (cutting blade and wheels), a handle 106, a throttle lever 108, and the rotation speed control device 1.

[0012] The general-purpose engine 101 is not particularly limited as long as it can output power by burning fuel, and may be, for example, a two-stroke reciprocating engine. In the example shown in Figure 1, the general-purpose engine 101 includes an engine body 120, an ignition plug 122, a fan 124, and an alarm device 126.

[0013] The engine body 120 has a cylinder 128 in which a combustion chamber 123 is formed in which a mixture G containing fuel and air is burned, a piston 130 arranged in the combustion chamber 123, and a crankshaft 134 connected to the piston 130 via a connecting rod 132.

[0014] The spark plug 122 is attached to the engine body 120 and ignites the mixture G in the combustion chamber 123. In one embodiment, the spark plug 122 is electrically connected to the rotation speed control device 1 and sparks when a voltage is applied from the rotation speed control device 1.

[0015] The fan 124 is, for example, a centrifugal cooling fan, and is configured to supply cooling air (outside air) to the general-purpose engine 101 as the crankshaft 134 rotates.

[0016] The notification device 126 notifies the user of the work machine 100 of the execution of combustion suppression control, which will be described later, and is, for example, a speaker capable of providing an audible notification, or a display or lighting device (e.g., an LED) capable of providing a visual notification. In one embodiment, the notification device 126 is attached to the handle 106 and is electrically connected to the rotation speed control device 1. The notification device 126 issues a notification in accordance with instructions transmitted from the rotation speed control device 1.

[0017] The centrifugal clutch 102 is connected to both a drive shaft 136 to which the driver 104 is connected and a crankshaft 134, and couples the drive shaft 136 and the crankshaft 134 according to the rotation speed of the crankshaft 134 to transmit the power of the industrial engine 101 to the driver 104. When the crankshaft 134 is not rotating or is rotating at a low speed, the drive shaft 136 and the crankshaft 134 are not coupled to each other, and the power of the industrial engine 101 is not transmitted to the driver 104. As a specific structural example of the centrifugal clutch 102, in the embodiment illustrated in FIG. 1, the centrifugal clutch 102 includes a carrier 102A connected to the crankshaft 134 and a clutch drum 102B connected to the drive shaft 136 and enclosing the carrier 102A. Such a centrifugal clutch 102 transmits the power of the general-purpose engine 101 to the driving body 104 via the drive shaft 136 by applying centrifugal force generated in the support body 102A according to the rotation speed of the crankshaft 134 to the clutch drum 102B.

[0018] In the following description, the rotation speed of the crankshaft 134 is referred to as the rotation speed (rotational speed) of the general-purpose engine 101. In some embodiments, the rotation speed of the general-purpose engine 101 is calculated from the rotation speed of the crankshaft 134 using a predetermined method. Note that the rotation speed of the general-purpose engine 101 may be obtained or calculated from a component of the work machine 100 other than the crankshaft 134.

[0019] The driving body 104 is rotated by the power of the general-purpose engine 101 transmitted via the centrifugal clutch 102 .

[0020] The handle 106 is configured so that it can be gripped by a user of the work machine 100. The throttle lever 108 is connected to a throttle valve 138 that adjusts the amount of mixture G supplied to the combustion chamber 123. The throttle lever 108 is supported by the handle 106 so that it can swing, and the opening of the throttle valve 138 is adjusted by the user operating the throttle lever 108. Hereinafter, it is assumed that the opening of the throttle valve 138 is adjusted to full open when the user is normally operating the work machine 100 (for example, when mowing grass).

[0021] The rotation speed control device 1 controls the rotation speed of a general-purpose engine 101. Such a rotation speed control device 1 is a computer such as an electronic control device, and includes a processor such as a CPU or GPU (not shown), memories such as a ROM and RAM, and an I / O interface. The processor of the rotation speed control device 1 operates (performs calculations, etc.) according to instructions of a program loaded into the memory, thereby realizing each of the functional units of the rotation speed control device 1. Each of the functional units of the rotation speed control device 1 according to one embodiment will be described with reference to FIG. 2.

[0022] (composition) 2 is a schematic functional block diagram of a rotation speed control device 1 according to one embodiment. As illustrated in FIG. 2, the rotation speed control device 1 includes a rotation speed acquisition unit 2, a combustion control unit 4, a timer unit 6, a combustion suppression stop unit 8, and a number counter unit 10.

[0023] The rotation speed acquisition unit 2 acquires the rotation speed of the general-purpose engine 101 (the rotation speed of the crankshaft 134). In one embodiment, as shown in FIG. 1, the work machine 100 is equipped with a rotation sensor 140 that outputs the rotation speed of the crankshaft 134, and this rotation sensor 140 is electrically connected to the rotation speed control device 1. Therefore, as shown in FIG. 2, the rotation speed acquisition unit 2 is able to acquire the output value of the rotation sensor 140 (the rotation speed of the general-purpose engine 101). Hereinafter, the rotation speed of the general-purpose engine 101 acquired by the rotation speed acquisition unit 2 will be referred to as actual rotation speed X.

[0024] The rotation sensor 140 is configured, for example, with a magnet that rotates with the crankshaft and a coil that does not rotate with the crankshaft, and detects changes in magnetic flux accompanying the rotation of the crankshaft 134 as changes in impedance of the coil. In one embodiment, it is assumed that one pulse (a portion where the displacement of the waveform changes significantly) appears during one rotation of the crankshaft 134.

[0025] The combustion control unit 4 controls combustion of the industrial engine 101 based on the actual rotation speed X. The combustion control unit 4 is configured to execute combustion suppression control to suppress combustion of the industrial engine 101 when the actual rotation speed X is between the first rotation speed X1 and the second rotation speed X2.

[0026] The first rotation speed X1 is the lower limit of the range of rotation speeds of the general-purpose engine 101 (rotation speed of the crankshaft 134) at which the centrifugal clutch 102 is engaged without slipping. The state in which the centrifugal clutch 102 is not slipping is a state in which the clutch transmission torque Tc is greater than the engine torque Te, and it is possible to determine whether the centrifugal clutch 102 is slipping by, for example, comparing the rotation speed of the crankshaft 134 with the rotation speed of the driver 104.

[0027] The second rotation speed X2 is greater than the first rotation speed X1, less than the maximum output rotation speed Xo of the general-purpose engine 101, and is the rotation speed of the general-purpose engine 101 at which the general-purpose engine 101 will overheat if it is operated continuously for a predetermined period of time with a load acting on the driving body 104.

[0028] The second rotation speed X2 will be described in detail. Fig. 3 is a diagram for explaining the second rotation speed X2 according to one embodiment. Fig. 3 shows the clutch transmission torque Tc (solid line), engine torque Te (two-dot chain line), and engine output Oe (one-dot chain line) relative to the rotation speed of the general-purpose engine 101. Note that Fig. 3 shows the engine torque Te and engine output Oe when the throttle valve 138 is fully open.

[0029] In one embodiment, as illustrated in Fig. 3, the first rotation speed X1 is the rotation speed at which the clutch transmission torque Tc and the engine torque Te are equal. The clutch transmission torque Tc monotonically increases as the rotation speed of the industrial engine 101 becomes greater than the first rotation speed X1. On the other hand, the engine torque Te decreases as the rotation speed of the industrial engine 101 becomes greater than the first rotation speed X1. In the embodiment illustrated in Fig. 3, the first rotation speed X1 is 4000 rpm.

[0030] Incidentally, the clutch transmission torque Tc monotonically decreases as the rotation speed of the general-purpose engine 101 becomes smaller than the first rotation speed X1. In other words, when the rotation speed of the general-purpose engine 101 becomes smaller than X1, slippage occurs in the centrifugal clutch 102. Then, when the rotation speed of the general-purpose engine 101 decreases to the point where the drive shaft 136 and the crankshaft 134 are no longer connected to each other, the magnitude of the clutch transmission torque Tc becomes constant (zero).

[0031] In one embodiment, as illustrated in FIG. 3, the engine output Oe monotonically increases as the rotational speed of the general-purpose engine 101 becomes greater than the first rotational speed X1, and reaches a maximum at the maximum output rotational speed Xo. The engine output Oe then monotonically decreases as the rotational speed of the general-purpose engine 101 becomes greater than the maximum output rotational speed Xo. When the work machine 100 is operated normally and no load is applied to the driver 104, the rotational speed of the general-purpose engine 101 becomes the rated rotational speed Xmax. In one embodiment, the maximum output rotational speed Xo is smaller than the rated rotational speed Xmax. In the embodiment illustrated in FIG. 3, the maximum output rotational speed Xo is 6500 rpm, and the rated rotational speed Xmax is 7500 rpm.

[0032] As described above, the second rotation speed X2 is greater than the first rotation speed X1 and less than the maximum output rotation speed X0. In the embodiment illustrated in Fig. 3, the second rotation speed X2 is 5000 rpm.

[0033] Even if a load acts on the driver 104 during normal operation of the work machine 100, if the actual rotation speed X is greater than 5000 rpm (second rotation speed X2), a temperature rise in the general-purpose engine 101 is suppressed and the general-purpose engine 101 does not overheat. This is because the load acting on the driver 104 is relatively small, and the rotation speed of the crankshaft 134 is relatively high, so the cooling effect of the fan 124 on the general-purpose engine 101 is sufficiently high. Thus, in one embodiment, the second rotation speed X2 is a rotation speed at which the general-purpose engine 101 may overheat due to the cooling characteristics of the general-purpose engine 101.

[0034] On the other hand, when a load acts on the driver 104 during normal operation of the work machine 100, and the actual rotation speed X is reduced to region A, which is lower than 5000 rpm (second rotation speed X2) and higher than 4000 rpm (first rotation speed X1), the temperature rise of the general-purpose engine 101 is accelerated, which may cause overheating of the general-purpose engine 101. This is because the load acting on the driver 104 is large, and the rotation speed of the crankshaft 134 is small, reducing the cooling effect of the fan 124 on the general-purpose engine 101 (the rotation speed of the fan 124).

[0035] Returning to FIG. 2, the combustion control unit 4 will be described. As illustrated in FIG. 2, the combustion control unit 4 transmits a skip signal Y to the spark plug 122 when the actual rotation speed X falls between the first rotation speed X1 and the second rotation speed X2 for a certain period of time. When the spark plug 122 receives the skip signal Y, it does not execute spark discharge in at least one of the multiple combustion cycles of the general-purpose engine 101. In other words, the combustion control unit 4 skips the combustion of the air-fuel mixture G in the combustion stroke of at least one combustion cycle. In this way, in one embodiment, the combustion control unit 4 executes combustion suppression control (so-called thinned ignition) that suppresses combustion in the general-purpose engine 101 by skipping the combustion stroke at an arbitrary timing.

[0036] The timer unit 6 counts the time during which the actual rotation speed X is between the first rotation speed X1 and the second rotation speed X2. When the value t of the timer unit 6 exceeds a preset time T, the combustion control unit 4 executes combustion suppression control. The set time T may be fixed, for example, 7 seconds, or may vary depending on a variable such as the outside air temperature.

[0037] The rotation speed of the general-purpose engine 101 when the general-purpose engine 101 is idling is set to the combustion suppression stop rotation speed Xa, which is greater than the idle rotation speed Xi and less than the first rotation speed X1. After the combustion control unit 4 has executed the combustion suppression control, the combustion suppression stop unit 8 stops the combustion suppression control when the actual rotation speed X becomes smaller than the combustion suppression stop rotation speed Xa. Specifically, the combustion suppression stop unit 8 instructs the combustion control unit 4 to stop sending the skip signal Y, thereby stopping the combustion suppression control. In one embodiment, after the combustion suppression stop unit 8 has stopped the combustion suppression control, when the actual rotation speed X becomes greater than the combustion suppression stop rotation speed Xa, the combustion control unit 4 executes the combustion suppression control again.

[0038] The rotation speed of the general-purpose engine 101 that is greater than the idle rotation speed Xi and less than the combustion suppression stop rotation speed Xa is defined as the recovery rotation speed Xb. The number of times counter unit 10 counts the number of times p that the general-purpose engine 101 rotates at or below the recovery rotation speed Xb. In one embodiment, the number of times counter unit 10 monitors the waveform acquired by the rotation sensor 140 and counts the number of times pulses appear in the waveform while the general-purpose engine 101 is rotating at or below the recovery rotation speed Xb. In one embodiment, after the combustion suppression stop unit 8 stops the combustion suppression control, if the number of times p is less than a preset number and the actual rotation speed X becomes greater than the combustion suppression stop rotation speed Xa, the combustion control unit 4 executes the combustion suppression control again.

[0039] (operation) The operation of the rotation speed control device 1 according to one embodiment will now be described. FIG. 4 is a flowchart of a method for controlling the rotation speed of a general-purpose engine 101 using the rotation speed control device 1 according to one embodiment. "Start" in FIG. 4 means that the work machine 100 is in normal operation. As illustrated in FIG. 4, the rotation speed control method includes a rotation speed monitoring step S1, a time monitoring step S2, a combustion suppression step S3, a first notification mode monitoring step S4, a combustion suppression stop step S5, a second notification mode monitoring step S6, and a pulse monitoring step S7.

[0040] In the rotation speed monitoring step S1, the actual rotation speed X acquired by the rotation speed acquisition unit 2 is monitored. If the actual rotation speed X is between the first rotation speed X1 and the second rotation speed X2 (rotation speed monitoring step S1: Yes), the timer unit 6 starts counting time, and the process proceeds to the time monitoring step S2. If the actual rotation speed X is not between the first rotation speed X1 and the second rotation speed X2 (rotation speed monitoring step S1: No), the value t of the timer unit 6 is set to zero, and the process returns to the rotation speed monitoring step S1. In other words, the value t of the timer unit 6 is a continuous value.

[0041] To explain this with a specific example, when the load acting on the driver 104 forcibly reduces the actual rotation speed X to less than 5000 rpm (second rotation speed X2), the timer unit 6 starts counting the time. Then, when the actual rotation speed X is between 5000 rpm and 4000 rpm (first rotation speed X1), the timer unit 6 continues counting the time. When the actual rotation speed X is greater than 5000 rpm or less than 4000 rpm, the timer unit 6 counts down to zero.

[0042] In the time monitoring step S2, if the value t of the timer unit 6 exceeds the set time T (time monitoring step S2: Yes), the process proceeds to the combustion suppression step S3. If the value t of the timer unit 6 does not exceed the set time T (time monitoring step S2: No), the process returns to the rotation speed monitoring step S1.

[0043] In the combustion suppression step S3, the combustion control unit 4 executes combustion suppression control. When the combustion suppression control is initiated, changes in the noise and vibration of the general-purpose engine 101 and the stoppage of the driver 104 occur, and therefore the work machine 100 enters a notification mode to notify the user that the general-purpose engine 101 is in an overload state. In some embodiments, when the work machine 100 enters the notification mode, the rotation speed control device 1 instructs the alarm device 126 to issue a notification, thereby smoothly notifying the user that combustion suppression control is being executed.

[0044] In the first notification mode monitoring step S4, if the actual rotation speed X becomes smaller than the combustion suppression stop rotation speed Xa due to the execution of the combustion suppression control in the combustion suppression step S3 (first notification mode monitoring step S4: No), the process proceeds to the combustion suppression stop step S5. If the actual rotation speed X remains larger than the combustion suppression stop rotation speed Xa (first notification mode monitoring step S4: Yes), the combustion suppression control continues, and the process returns to the first notification mode monitoring step S4.

[0045] To explain this with a specific example, when combustion suppression control (thinning-out ignition) is executed by the combustion control unit 4, the actual rotation speed X is reduced to less than 4000 rpm. Then, when the actual rotation speed X is reduced to less than 3700 rpm (combustion suppression stop rotation speed Xa), the process proceeds to combustion suppression stop step S5. On the other hand, if the actual rotation speed X remains greater than 3700 rpm, thinning-out ignition is continued.

[0046] In combustion suppression stop step S5, the combustion suppression stop unit 8 stops the combustion suppression control by the combustion control unit 4. That is, the combustion of the air-fuel mixture G in the combustion stroke is no longer skipped (returning from thinned ignition to normal ignition). When the return to normal ignition is made, the actual rotation speed X begins to increase.

[0047] In second notification mode monitoring step S6, if the actual rotation speed X becomes smaller than the recovery rotation speed Xb after the combustion suppression control is stopped in combustion suppression stop step S5 (second notification mode monitoring step S6: Yes), the number counter unit 10 starts counting the number of times p, and the process proceeds to pulse monitoring step S7. If the actual rotation speed X is larger than the recovery rotation speed Xb (second notification mode monitoring step S6: No), the number of times p is set to zero, and the process returns to first notification mode monitoring step S4.

[0048] In one embodiment, if the actual rotation speed X is greater than the combustion suppression stop rotation speed Xa when returning to the first notification mode monitoring step S4, the combustion suppression control is executed again, and the process returns to the first notification mode monitoring step S4. In other words, thinned ignition and normal ignition are repeated until the opening of the throttle valve 138 is reduced by the user.

[0049] To explain this using a specific example, when a user realizes that the general-purpose engine 101 is in an overload state and releases the throttle lever 108 (closes the throttle valve 138), the actual rotation speed X decreases toward the idle rotation speed Xi (e.g., 2200 rpm). When the actual rotation speed X becomes smaller than 3500 rpm (recovery rotation speed Xb), the process proceeds to pulse monitoring step S7. When the actual rotation speed X is greater than 3500 rpm, the process returns to first notification mode monitoring step S4. In some embodiments, the rotation speed control device 1 stops the notification from the notification device 126 when the throttle lever 108 is released.

[0050] In pulse monitoring step S7, if the number of times p exceeds the set number of times P (pulse monitoring step S7: Yes), control of the rotation speed of the general-purpose engine 101 by the rotation speed control device 1 according to one embodiment ends, and the notification mode of the work machine 100 also ends. If the number of times p is equal to or less than the set number of times P (pulse monitoring step S7: No), 1 is added to the number of times p (p = p + 1), and the process returns to combustion suppression stop step S5. In other words, the number of times p is a continuous value.

[0051] (Actions and Effects) The operation and effect of the rotation speed control device 1 according to one embodiment will now be described. When the general-purpose engine 101 is configured so that power is transmitted to the driving body 104 via the centrifugal clutch 102, the rotation speed of the general-purpose engine 101 is forcibly reduced due to the load acting on the driving body 104 during normal operation of the work machine 100, which may cause the general-purpose engine 101 to heat up and overheat. In particular, when the actual rotation speed X is within the range from the first rotation speed X1 to the second rotation speed X2, the temperature rise of the general-purpose engine 101 may be accelerated.

[0052] According to one embodiment, combustion suppression control is executed when the actual rotation speed X is between 4000 rpm (first rotation speed X1) and 5000 rpm (second rotation speed X2). Therefore, even if the rotation speed of the general-purpose engine 101 is forcibly reduced due to the load acting on the driving body 104 during normal operation of the work machine 100, it is possible to suppress a temperature rise in the general-purpose engine 101 and prevent the general-purpose engine 101 from overheating.

[0053] If the time period (value t of timer unit 6) during which the actual rotation speed X falls between the first rotation speed X1 and the second rotation speed X2 is short, overheating of the general-purpose engine 101 will not occur, and therefore there is no need to execute combustion suppression control. According to one embodiment, when the value t of timer unit 6 exceeds the set time T, combustion suppression control is executed, thereby making it possible to avoid unnecessary combustion suppression control.

[0054] According to one embodiment, by executing the combustion suppression control, the combustion suppression control (thinning-out ignition) can be stopped and the general-purpose engine can be returned to a normal operating state (normal ignition) before the actual rotation speed X drops to the idle rotation speed Xi. Furthermore, according to one embodiment, because thinning-out ignition and normal ignition are repeated, the user can be smoothly notified that the general-purpose engine 101 is in an overload state by changes in sound and vibration, or the drive of the work machine being stopped, and can be prompted to release the throttle lever 108.

[0055] According to one embodiment, the number of pulses appearing in the waveform while the general-purpose engine 101 is rotating at or below the recovery rotation speed Xb is monitored, so that the termination of operation of the rotation speed control device 1 due to the general-purpose engine 101 temporarily rotating at a speed below the recovery rotation speed Xb can be prevented.

[0056] In the embodiment, the second rotation speed X2 is 5000 rpm, but the present disclosure is not limited to this. The second rotation speed X2 may be any rotation speed of the general-purpose engine 101 that is greater than the first rotation speed X1, less than the maximum output rotation speed Xo, and at which the general-purpose engine 101 overheats if operated continuously for a predetermined period of time with a load acting on the driver 104.

[0057] Even if a load is applied to the driver 104 while the work machine 100 is in operation, if the rotation speed of the general-purpose engine 101 is greater than 90% of the maximum output rotation speed Xo, a temperature rise in the general-purpose engine 101 is suppressed and the general-purpose engine 101 does not overheat. On the other hand, if the rotation speed of the general-purpose engine 101 is less than 90% of the maximum output rotation speed Xo, the temperature of the general-purpose engine 101 rises, which may result in overheating of the general-purpose engine 101. In some embodiments, the second rotation speed X2 is less than 90% of the maximum output rotation speed Xo. With this configuration, if the actual rotation speed X is reduced to a rotation speed that may result in overheating, combustion suppression control is executed, thereby making it possible to increase the accuracy of preventing overheating of the general-purpose engine 101.

[0058] In one embodiment, the combustion control unit 4 controls the ignition operation of the spark plug 122 to control the combustion in the general-purpose engine 101, but the present disclosure is not limited to this embodiment. For example, the combustion control unit 4 controls the combustion in the general-purpose engine 101 by adjusting the amount of fuel supplied to the combustion chamber 123. In this case, when the actual rotation speed X is between the first rotation speed X1 and the second rotation speed X2, the combustion control unit 4 reduces the amount of fuel supplied to the combustion chamber 123 to perform combustion suppression control.

[0059] The contents described in each of the above embodiments can be understood, for example, as follows.

[0060] [1] The rotation speed control device (1) of the general-purpose engine (101) according to the present disclosure includes: A revolution speed control device for a general-purpose engine (101) configured to transmit power to a driving body (104) of a working machine (100) via a centrifugal clutch (102), the revolution speed control device being provided to the general-purpose engine (101) and controlling the revolution speed of the general-purpose engine, comprising: a rotation speed acquisition unit (2) that acquires the rotation speed of the general-purpose engine; a combustion control unit (4) that controls combustion of the general-purpose engine based on the rotation speed of the general-purpose engine acquired by the rotation speed acquisition unit, Let the rotation speed of the general-purpose engine at which the centrifugal clutch is engaged without slipping be a first rotation speed (X1), and let a second rotation speed (X2) be a rotation speed that is greater than the first rotation speed and less than the maximum output rotation speed (Xo) of the general-purpose engine, and at which the general-purpose engine will overheat if operated continuously for a predetermined period of time, The combustion control unit is configured to execute combustion suppression control to suppress combustion in the general-purpose engine when the rotation speed of the general-purpose engine acquired by the rotation speed acquisition unit is between the first rotation speed and the second rotation speed.

[0061] When a general-purpose engine is configured to transmit power to a drive mechanism of a work machine via a centrifugal clutch, the load acting on the drive mechanism during operation of the work machine may forcibly reduce the engine's rotation speed, causing the engine to heat up and potentially overheat. In particular, when the engine's rotation speed falls between the first and second rotation speeds, this may accelerate the engine's temperature rise. In contrast, according to the configuration described in [1] above, combustion suppression control is executed when the engine's rotation speed falls between the first and second rotation speeds, thereby suppressing the engine's temperature rise and preventing the engine from overheating.

[0062] [2] In some embodiments, in the configuration described in [1] above, The second rotation speed is less than 90% of the maximum output rotation speed of the general-purpose engine.

[0063] Even if a load is applied to the drive member during operation of the work machine, if the engine speed is greater than 90% of the maximum output speed, the temperature rise of the engine is suppressed and the engine does not overheat. On the other hand, if the engine speed is less than 90% of the maximum output speed, the engine temperature rises, which may lead to overheating. According to the configuration described in [2] above, if the engine speed is reduced to a level that may lead to overheating, combustion suppression control is executed, thereby improving the accuracy of preventing the engine from overheating.

[0064] [3] In some embodiments, in the configuration described in [1] or [2] above, a timer unit (6) that counts a time (t) during which the rotational speed of the general-purpose engine acquired by the rotational speed acquisition unit is included between the first rotational speed and the second rotational speed, The combustion control unit executes the combustion suppression control when the value of the timer unit exceeds a preset time (T).

[0065] If the time (the value of the timer unit) between the first rotation speed and the second rotation speed of the general-purpose engine is short, the general-purpose engine will not overheat, and therefore there is no need to execute combustion suppression control. According to the configuration described in [3] above, combustion suppression control is executed when the value of the timer unit exceeds the set time, so that unnecessary execution of combustion suppression control can be avoided.

[0066] [4] In some embodiments, in the configuration described in any one of [1] to [3] above, a combustion suppression stop rotation speed (Xa) of the general-purpose engine that is greater than an idle rotation speed (Xi) when the general-purpose engine is idling and less than the first rotation speed; The engine further includes a combustion suppression stop unit (8) that stops the combustion suppression control when the rotation speed of the general-purpose engine acquired by the rotation speed acquisition unit becomes smaller than the combustion suppression stop rotation speed after the combustion control unit has executed the combustion suppression control.

[0067] According to the configuration described in [4] above, the combustion suppression control by the combustion control unit can be stopped (the engine is returned to its normal operating state) before the rotation speed of the general-purpose engine drops to the idle rotation speed, thereby notifying the user of the work machine that the general-purpose engine is in an overload state.

[0068] [5] In some embodiments, in the configuration described in [4] above, After the combustion suppression stop unit stops the combustion suppression control, if the rotation speed of the general-purpose engine acquired by the rotation speed acquisition unit becomes greater than the combustion suppression stop rotation speed, the combustion control unit executes the combustion suppression control again.

[0069] According to the configuration described in [5] above, the combustion suppression control by the combustion control unit and the stop of the combustion suppression control by the combustion suppression stop unit are repeated, so that the user of the work machine can be smoothly notified that the general-purpose engine is in an overload state.

[0070] [6] In some embodiments, in the configuration described in [5] above, When the rotation speed of the general-purpose engine that is greater than the idle rotation speed and less than the combustion suppression stop rotation speed is defined as a recovery rotation speed (Xb), The engine further includes a number counter (10) that counts the number of times (p) the general-purpose engine rotates at or below the recovery rotation speed, After the combustion suppression stop unit stops the combustion suppression control, if the number of times counted by the number counter unit is less than a preset number of times (P) and the rotation speed of the general-purpose engine acquired by the rotation speed acquisition unit becomes greater than the combustion suppression stop rotation speed, the combustion control unit executes the combustion suppression control again.

[0071] According to the configuration described in [6] above, even if the general-purpose engine temporarily rotates at a speed lower than the recovery rotation speed, the combustion suppression control by the combustion control unit and the stop of the combustion suppression control by the combustion suppression stop unit can be repeated.

[0072] [7] In some embodiments, in the configuration described in any one of [1] to [6] above, The general-purpose engine further includes an alarm device (126) that notifies the engine that the combustion suppression control is being executed.

[0073] According to the configuration described in [7] above, it is possible to smoothly inform the user of the work machine that combustion suppression control is being executed.

[0074] [8] The general-purpose engine according to the present disclosure includes: The rotation speed control device for a general-purpose engine according to any one of [1] to [7] above, and a fan (124) for cooling the general-purpose engine in accordance with the rotational speed of the general-purpose engine.

[0075] According to the configuration described in [8] above, it is possible to provide a general-purpose engine that can avoid overheating. [Explanation of symbols]

[0076] 1. Rotation speed control device 2. Rotation speed acquisition section 4 Combustion control unit 6 Timer section 8 Combustion suppression stop section 10 Number of times counter 100 Work Equipment 101 General-purpose engine 102 centrifugal clutch 104 Driver 108 Throttle lever 124 Fans 126 Alarm device S1 Rotation speed monitoring step S2 Time monitoring step S3 Combustion suppression step S4 First notification mode monitoring step S5 Combustion suppression stop step S6 Second notification mode monitoring step S7 Pulse monitoring step P Setting number of times T Setting time X Actual rotation speed X1 1st rotation speed X2 Second rotation speed Xa Combustion suppression stop rotation speed Xb Recovery Rotation Speed Xi Idle RPM Xo Maximum output speed p Number of times (count value of the number of times counter) t value (count value of timer section)

Claims

1. 1. A revolution speed control device for a general-purpose engine, the revolution speed control device being provided in a general-purpose engine configured to transmit power to a drive body of a work machine via a centrifugal clutch, and controlling the revolution speed of the general-purpose engine, a rotation speed acquisition unit that acquires the rotation speed of the general-purpose engine; a combustion control unit that controls combustion of the general-purpose engine based on the rotation speed of the general-purpose engine acquired by the rotation speed acquisition unit, Let us assume that the rotational speed of the general-purpose engine at which the centrifugal clutch is engaged without slipping is a first rotational speed, and that a second rotational speed is a rotational speed that is greater than the first rotational speed and less than the maximum output rotational speed of the general-purpose engine, and that the general-purpose engine will overheat if operated continuously for a predetermined period of time. the combustion control unit is configured to execute combustion suppression control to suppress combustion of the general-purpose engine when a time period included in the rotation speed of the general-purpose engine acquired by the rotation speed acquisition unit between the first rotation speed and the second rotation speed exceeds a preset time period. A rotation speed control device for general-purpose engines.

2. the second rotation speed is less than 90% of the maximum output rotation speed of the general-purpose engine; 2. The rotation speed control device for a general-purpose engine according to claim 1.

3. a timer unit that counts a time period during which the rotational speed of the general-purpose engine acquired by the rotational speed acquisition unit is between the first rotational speed and the second rotational speed, The combustion control unit executes the combustion suppression control when the value of the timer unit exceeds the set time.

3. The rotation speed control device for a general-purpose engine according to claim 1 or 2.

4. a combustion suppression stop rotation speed of the general-purpose engine that is greater than an idle rotation speed when the general-purpose engine is idling and smaller than the first rotation speed; a combustion suppression stop unit that stops the combustion suppression control when the rotation speed of the general-purpose engine acquired by the rotation speed acquisition unit becomes smaller than the combustion suppression stop rotation speed after the combustion control unit has executed the combustion suppression control, 3. The rotation speed control device for a general-purpose engine according to claim 1 or 2.

5. when the rotation speed of the general-purpose engine acquired by the rotation speed acquisition unit becomes greater than the combustion suppression stop rotation speed after the combustion suppression stop unit stops the combustion suppression control, the combustion control unit executes the combustion suppression control again.

5. The rotation speed control device for a general-purpose engine according to claim 4.

6. When the rotation speed of the general-purpose engine is higher than the idle rotation speed and lower than the combustion suppression stop rotation speed, the following is defined as a recovery rotation speed: a number counter that counts the number of times the general-purpose engine rotates at or below the recovery rotation speed; after the combustion suppression stop unit stops the combustion suppression control, when the number of times counted by the number counter unit is less than a preset number of times and the rotation speed of the general-purpose engine acquired by the rotation speed acquisition unit becomes greater than the combustion suppression stop rotation speed, the combustion control unit executes the combustion suppression control again.

6. The rotation speed control device for a general-purpose engine according to claim 5.

7. the general-purpose engine further includes a notification device that notifies the engine that the combustion suppression control is being executed.

3. The rotation speed control device for a general-purpose engine according to claim 1 or 2.

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