Engine control device and engine incorporating the same

Abstract

To shorten the duration time of the run-on phenomenon, while preventing an engine from being activated by firing of an ignition plug, after engine stop based on the operation of a drive stop switch.SOLUTION: An ignition resumption control unit 40 is disposed that resumes control of an ignition plug 14 if a first predetermined time has elapsed or if engine rotation number has fallen below a threshold value, after receiving an engine stop signal. The ignition resumption control unit 40 executes the control of the ignition plug 14, based on resumption ignition timings Tg(R-on) that are timing deviating from an entire ignition timing range set in a normal working area of an engine body 2.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an engine control device for use after an engine is stopped, and an engine incorporating the same. [Background technology]

[0002] When an operator turns on the engine stop switch, which stops the engine operation, that is, when an operator issues an engine stop command, the supply of electricity to the spark plug is cut off and the engine is stopped. Patent Document 1 points out a phenomenon in which residual fuel intermittently burns immediately after high-power operation, even if the engine stop switch is operated. This phenomenon is called the "run-on phenomenon." The combustion of residual fuel that causes the run-on phenomenon is called "run-on combustion."

[0003] To prevent run-on, it is known that when the engine stop switch is turned ON, the power supply to the spark plug is stopped and the fuel supply to the engine is cut off. Patent Document 1 points out the following problem caused by this fuel supply cutoff: When the fuel supply is cut off, the fuel remaining in the engine and intake system undergoes a chemical reaction as it cools, turning into a gummy substance. This gummy substance is highly sticky and can cause the valve system to stick or the fuel injection nozzle to clog.

[0004] To solve this problem, Patent Document 1 proposes continuing to energize the spark plug for a predetermined time (e.g., one second) even after the engine stop switch is turned on. After the engine is stopped, the remaining fuel is drawn into the combustion chamber as the engine moves due to inertia, and then ignited by the spark plug. This allows the remaining fuel to be purged from the intake system and combustion chamber. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP Utility Model Publication No. 57-40662 Summary of the Invention [Problem to be solved by the invention]

[0006] As mentioned above, Patent Document 1 proposes an invention that continues ignition control even after the engine is stopped based on the operation of the engine stop switch. According to this invention, ignition control continues at the ignition timing set in the normal operating range even after the engine is stopped. Therefore, there is a possibility that the engine may be activated by the ignition of residual fuel by the spark plug after the engine is stopped. This possible phenomenon can surprise the operator because the engine continues to operate despite the operation of the stop switch. Furthermore, it increases the time it takes for the engine to completely stop, which simply results in lost time for the operator.

[0007] The object of the present invention is to provide an engine control device and an engine incorporating the same that can shorten the duration of the run-on phenomenon while preventing the engine from being activated by ignition of the spark plug after the engine has been stopped by operating the stop switch. [Means for solving the problem]

[0008] The above technical challenges are The engine itself stops by stopping the ignition control of the spark plugs with the engine stop signal. Rue In the engine control device, After receiving the engine stop signal, The fuel is sucked out of the carburetor by the negative pressure caused by the drop in engine speed due to the cessation of ignition control. A first predetermined time has elapsed or The temperature drops as the ignition control is stopped. The system further includes an ignition restart control unit that restarts control of the spark plug when the engine speed drops below a threshold value, and the ignition restart control unit controls the spark plug based on a restart ignition timing that deviates from the range of all ignition timings set in the normal operating region of the engine body. Rue This can be achieved by providing an engine control device and an engine incorporating the same.

[0009] According to the present invention, spark plug control is resumed when a first predetermined time has elapsed after receiving an engine stop signal or when the engine speed drops below a threshold. This resumed ignition control is performed based on the restart ignition timing. This restart ignition timing is a timing outside the range of all ignition timings set in the normal operating region. This prevents the engine from being activated by spark plug ignition after the engine has stopped, while shortening the duration of the run-on phenomenon.

[0010] The effects and other objects of the present invention will become apparent from the following detailed description of preferred embodiments of the present invention. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram for explaining an overall outline of an engine system according to an embodiment; [Figure 2] FIG. 1 is a diagram for explaining the run-on phenomenon that occurs under fuel supply cutoff and ignition deactivation. [Figure 3] FIG. 4 is a diagram for explaining an example of ignition timing for suppressing run-on. [Figure 4] 10 is a flowchart illustrating a first example of run-on suppression control. [Figure 5] 10 is a flowchart illustrating a second example of run-on suppression control. [Figure 6] FIG. 10 is a diagram for explaining another example of ignition timing for suppressing run-on. [Figure 7] 10 is a flowchart illustrating a third example of run-on suppression control. DETAILED DESCRIPTION OF THE INVENTION [Example]

[0012] A preferred embodiment of the present invention will now be described with reference to the accompanying drawings. Figure 1 is a diagram illustrating an outline of an engine system. The engine system 1 has an engine body 2, an intake system 4 that supplies an air-fuel mixture to the engine body 2, and an exhaust system 6 that exhausts burned gas from the engine body 2 to the outside. In the drawing, reference numeral 8 denotes a muffler.

[0013] The engine body 2 has a combustion chamber 12 defined by a piston 10, and an ignition plug 14 is disposed facing the combustion chamber 12. The piston 10 is connected to a crankshaft 18 by a connecting rod 16, and the crankshaft 18 outputs engine driving force.

[0014] The illustrated engine body 2 is an exemplary four-stroke engine. The engine body 2 has an intake port 20 and an exhaust port 22. The intake port 20 is opened and closed by an intake valve 24. The exhaust port 22 is opened and closed by an exhaust valve 26. An intake system 4 is connected to the intake port 20. An exhaust system 6 is connected to the exhaust port 22. The engine body 2 may be a two-stroke engine. As is well known, two-stroke engines do not have the intake valve 24 or the exhaust valve 26. In a two-stroke engine, the intake port 20 and the exhaust port 22 are opened and closed by a piston 10. Two-stroke engines are currently used in implements such as brush cutters and chainsaws.

[0015] The intake system 4 has an air cleaner 30 at its upstream end, and an intake passage 32 through which air filtered by the air cleaner 30 passes. A throttle valve 34 is disposed in the intake passage 32, and by operating the throttle valve 34, the amount of air introduced into the engine body 2 is adjusted, thereby controlling the engine output. The intake system 4 has a carburetor 36, and a mixture is generated when fuel F in a fuel tank 38 is supplied to the intake passage 32 through the carburetor 36. 。

[0016] The engine system 1 has a control unit 40, to which a temperature signal from an engine temperature sensor 42, which is installed on the mounting seat of the spark plug 14 and detects the temperature of the engine body 2, and a rotation speed signal from a rotation speed sensor 44, which detects the engine rotation speed, are input. In addition, the control unit 40 also receives an engine stop signal from an engine stop switch 46 operated by an operator.

[0017] FIG. 2 is a diagram for explaining the run-on phenomenon. In the figure, the reference symbol "Pt" indicates the point in time when engine stop control is executed based on the input of an engine stop signal. When the engine stop signal is input, the supply of electricity to the spark plug is stopped. As a result, the spark plug is effectively put into a rest state, and the engine body 2 is put into a stopped state, but the engine body 2 continues its rotational motion only due to inertia. As a result, the engine speed drops. As can be seen from FIG. 2, after the engine speed drops to about 1000 rpm, phenomena P1 to P4 occur in which the engine speed increases intermittently several times. This is because Control unit 40 Even though ignition control by the engine has been stopped, the mixture remaining in the combustion chamber 12 self-ignites in combination with the temperature gradient within the combustion chamber 12, and this unintended combustion is called the run-on phenomenon. Because the run-on phenomenon is a combustion that occurs accidentally under such circumstances where ignition control has already been stopped, it is difficult to control with quantitative and fixed control.

[0018] 1, which is a fuel supply device, does not have an electronically controlled fuel supply shutoff valve. In the case of a carburetor 36 that does not have a fuel supply shutoff valve, when negative pressure is created in the combustion chamber 12, fuel is sucked out of the carburetor 36, and the air-fuel mixture may be introduced into the combustion chamber 12 even if ignition is stopped based on an engine stop signal. This makes it easy for a run-on phenomenon to occur after the engine is stopped.

[0019] In this embodiment, the duration of the run-on phenomenon is reduced by engine control executed after the engine is stopped. This engine control includes control to stop energizing the spark plug 14 and ignition restart control executed after a predetermined condition is met after the engine is stopped. First, the ignition restart control is executed when the control unit 40 receives an engine stop signal. However, the current engine speed is continuously monitored by the engine speed sensor 44. Second, when it is detected that the engine speed has dropped below the threshold value Th (FIG. 2), the spark plug 14 is controlled based on the restart ignition timing, which is a timing outside the range of all ignition timings set for the engine 2 in the entire operating range (normal operating range) from idle operation to full throttle operation. This is the ignition restart control. This ignition restart control is called "run-on suppression control." It may be executed after a first predetermined time (e.g., 2 to 4 seconds after the engine is stopped) has elapsed since the engine stop signal was received. Third, the run-on suppression control is terminated when a second predetermined time (for example, 5 to 6 seconds after the engine is stopped) has elapsed.

[0020] The run-on suppression control, described in detail below, is intended to shorten the duration of the run-on phenomenon. As described above, the restart ignition timing, i.e., the run-on suppression ignition timing, is set to a timing that deviates from the range of all ignition timings set for the engine 2 in the normal operating region. For example, if the range of all ignition timings set for the engine 2 in the normal operating region is a crank angle range of 5° to 40° BTDC, a timing that deviates from this range is set as the run-on suppression ignition timing. If the run-on suppression ignition timing were set to the ignition timing during idle operation, which is included in the normal operating region of the engine 2, the ignition of residual fuel by the spark plug 14 could activate the engine and cause it to return to idle operation. For this reason, the run-on suppression control executes ignition control using the run-on suppression ignition timing within an ignition timing range that does not overlap with the ignition timing range set for the normal operating region.

[0021] In particular, it is desirable that the ignition timing range used in the normal operating range and the ignition timing range used in run-on suppression control are not adjacent as rotation speed ranges, but are separated by a predetermined timing range.

[0022] Referring to Figure 3, all ignition timings Tg(nor) set in the normal operating range of the engine body 2 are shown by dashed lines. In this engine body 2, the ignition timings Tg(nor) set in the normal operating range are in the range of 30° to 8° BTDC. Reference symbol Tg(R-on) in Figure 3 indicates ignition timing for run-on suppression. The ignition timing for run-on suppression Tg(R-on) is set in the range of 10° to 20° ATDC. 10° to 20° ATDC is ignition timing that deviates toward the retard side from the range of ignition timing Tg(nor) set in the normal operating range of the engine body 2, i.e., the range of 30° to 8° BTDC.

[0023] More specifically, the example shown in FIG. 3 shows that the run-on suppression ignition timing is set to be retarded from the range of the ignition timing Tg(nor) set in the normal operating range of the engine body 2. As a result, the spark plug 14 is ignited just before the timing at which run-on combustion occurs. This spark can then induce combustion of the residual fuel. In other words, the spark plug 14 does not directly ignite the residual fuel, but rather the combustion of the residual fuel can be induced after the ignition of the spark plug 14. As a modified example, the run-on suppression ignition timing may be set to be advanced from the range of the ignition timing Tg(nor) set in the normal operating range of the engine body 2.

[0024] In engine control, it is preferable to provide a normal operation control mode in which ignition is controlled at each ignition timing set for the entire operating range from idle operation to full throttle operation, and a separate ignition restart control mode in which ignition is restarted at a restart ignition timing. Programs for these control modes are stored in the memory M (FIG. 1) of the control unit 40. When an engine stop signal is received from the engine stop switch 46, the normal operation control mode is switched to the ignition restart control mode before restarting ignition control. When the engine speed falls below the threshold value Th or a first predetermined time has elapsed since the engine was stopped, engine control can be performed based on the ignition restart control mode. Setting the restart ignition timing based on a map of run-on suppression ignition timing Tg(R-on) provides excellent responsiveness.

[0025] 4 is a flowchart showing an example of engine control after the input of the engine stop signal. Referring to FIG. 4, when the engine stop signal is received from engine stop switch 46 in step S1, engine stop control is executed (S2). Here, the engine stop control includes control to stop energizing spark plug 14 and put spark plug 14 into a resting state.

[0026] In the next step S3, the process that has been executed since before the engine was stopped is Rotational speed sensor The current engine speed is monitored by 44 even after the engine is stopped, and this monitoring of the engine speed is continued until the run-on suppression control is completed. Then, in step S4, the run-on suppression ignition timing Tg(R-on) is set. For example, the engine control is switched from the normal operation control mode to the ignition restart control mode.

[0027] In the next step S5, when a first predetermined time has elapsed after the engine stop signal is received, the process proceeds to step S6, where ignition control is resumed. The ignition resume control is executed based on the ignition timing for suppressing run-on described above. This resumed ignition control is executed until a second predetermined time has elapsed (S7). The second predetermined time is set to, for example, 5 to 6 seconds from the input of the engine stop signal. As a variant, the second predetermined time may be set from the time when ignition control is resumed. Once the second predetermined time has elapsed, the process proceeds to step S8, where current to the spark plug 14 is cut off. This ends the ignition resume control.

[0028] Figure 5 is a flowchart relating to another example of run-on suppression control. In the flowchart of Figure 5, steps that are the same as those constituting the flowchart of Figure 4 described above are given the same reference numerals, and their explanations will be omitted. In the engine control example shown in Figure 5, i.e., run-on suppression control, if the current engine speed falls below threshold value Th (Figure 2) in step S10, ignition control is resumed in step S6.

[0029] Figure 6 shows a modification of the run-on suppression ignition timing Tg(R-on) described with reference to Figure 3. In the run-on suppression ignition timing Tg(R-on) shown in Figure 6, 70° BTDC is set as the first timing Tg(R-on-1) in a first range where the engine speed includes 1100 rpm. 8° ATDC is set as the second timing Tg(R-on-2) in a second range where the engine speed includes 1160 rpm. 12° ATDC is set as the third timing Tg(R-on-3) in a third range where the engine speed includes 1250 rpm.

[0030] The first timing Tg(R-on-1) of 70° BTDC is an ignition timing that deviates to the advance side from the range of ignition timing Tg(nor) set in all operating regions, i.e., the normal operating region, of the engine body 2, i.e., the range of 30° to 8° BTDC. The second timing Tg(R-on-2) of 8° ATDC and the third timing Tg(R-on-3) of 12° ATDC are ignition timings that deviate to the retard side from the range of ignition timing Tg(nor) set in the normal operating region of the engine body 2.

[0031] In a preferred embodiment, the set value of the run-on suppression ignition timing Tg(R-on) is changed in response to engine temperature. Taking the run-on suppression ignition timing Tg(R-on) in Figure 6 as an example, when the engine temperature is high (for example, when the temperature of the spark plug seat is 250°C or higher), the reference set values ​​Tg(R-on-1), Tg(R-on-2), and Tg(R-on-3) are shifted toward higher engine speeds. Conversely, when the engine temperature is low, the reference set values ​​Tg(R-on-1), Tg(R-on-2), and Tg(R-on-3) are shifted toward lower engine speeds.

[0032] 7 is a flowchart showing another example of run-on suppression control, and includes a process for changing the setting of the run-on suppression ignition timing Tg(R-on) depending on the temperature. In this setting change process, the run-on suppression ignition timing Tg(R-on) is shifted to the lower rotation speed side from the reference setting value at low temperatures, i.e., the setting values ​​Tg(R-on-1), Tg(R-on-2), and Tg(R-on-3) shown in FIG. 6, and shifted to the higher rotation speed side from the reference setting value at high temperatures.

[0033] In Figure 7, Figure 4 The same steps as those explained in the flowchart above are given the same reference numerals and their explanations will be omitted. When an engine stop signal is received in step S1, the engine temperature is monitored from the engine temperature sensor 42 (S20), and this temperature monitoring continues until the ignition restart control is completed in step S8. S After ignition control is resumed in step S6, the process proceeds to step S21, where it is determined whether or not first run-on combustion has occurred. This run-on combustion can be detected by detecting the acceleration of the engine speed. When this first run-on combustion occurs, ignition is performed based on the first timing Tg(R-on-1), which is a reference setting value. For this first run-on combustion, ignition may be performed at a timing that is shifted in advance from the first timing Tg(R-on-1), which is a reference setting value, depending on the engine temperature.

[0034] In the next step S22, the first to third timings Tg(R-on-1), Tg(R-on-2), and Tg(R-on-3), which are reference set values, are shifted in accordance with the engine temperature in response to the second and subsequent run-on combustions. This shift may be performed gradually, or the timing setting change may be completed in one shift. Ignition control corresponding to each run-on combustion from the second onward is performed based on the reference set values ​​Tg(R-on-1), Tg(R-on-2), and Tg(R-on-3) if the engine temperature is normal (e.g., the spark plug seat temperature is 200 to 250°C). If the engine temperature is lower than this, ignition control is performed at a timing where the reference set values ​​are shifted toward lower revolutions. If the engine temperature is high, ignition control is performed at a timing where the reference set values ​​are shifted toward higher revolutions.

[0035] The run-on suppression control, i.e., ignition restart control, forcibly burns the fuel remaining when the engine is stopped. This allows the remaining fuel to be cleared from the intake system 4, combustion chamber 12, etc., and shortens the duration of the run-on phenomenon. Furthermore, after the engine is stopped based on an engine stop signal, ignition control is resumed after a time interval. This resumed ignition control is executed based on a run-on suppression ignition timing, i.e., restart ignition timing Tg(R-on), which is outside the range of all ignition timings set in the normal operating range of the engine 2. This means that the ignition of the spark plug 14 is not intended to ignite the remaining fuel, but rather to promote the combustion of the remaining fuel in the combustion chamber 12 after the ignition of the spark plug 14. This prevents the engine 2 from being activated by the resumed ignition control and returning to idle operation, for example. [Explanation of symbols]

[0036] 1 Engine System 2 Engine body 14 Spark plug 36 Vaporizer 40 Control Unit 42 Engine temperature sensor 44 RPM sensor 46 Engine stop switch Th threshold Tg(R-on) Restart ignition timing

Claims

1. In an engine control device in which the engine body is stopped by stopping ignition control of a spark plug in response to an engine stop signal, An engine control device having an ignition restart control unit that restarts control of the spark plug after receiving the engine stop signal when a first predetermined time has elapsed during which fuel is sucked out of the carburetor due to negative pressure caused by a drop in engine speed due to the suspension of ignition control, or when the engine speed that drops due to the suspension of ignition control falls below a threshold value, and the ignition restart control unit controls the spark plug based on a restart ignition timing that deviates from the range of all ignition timings set in the normal operating region of the engine body.

2. 2. The engine control device according to claim 1, The engine control device wherein the restart ignition timing is a timing that deviates to the advance side from a range of ignition timings set in the normal operation region.

3. 2. The engine control device according to claim 1, The engine control device wherein the restart ignition timing is a timing that deviates to the retard side from a range of ignition timings set in the normal operation region.

4. 2. The engine control device according to claim 1, The engine control device, wherein the restart ignition timing includes timing that deviates from the range of ignition timing set in the normal operation region to the advance side and timing that deviates from the range of ignition timing set in the normal operation region to the retard side.

5. The engine control device according to any one of claims 1 to 4, The engine control device is configured such that the ignition restart control for restarting the control of the spark plug is terminated by cutting off the power supply to the spark plug after the ignition restart control has been executed for a second predetermined time.

6. An engine incorporating an engine control device that stops the engine body by terminating ignition control of the spark plug in response to an engine stop signal, and in which fuel is supplied by a carburetor, The engine control device an ignition restart control unit that restarts control of the spark plug when, after receiving the engine stop signal, a first predetermined time has elapsed during which fuel is sucked out of the carburetor due to negative pressure caused by a drop in engine speed resulting from the suspension of the ignition control, or when the engine speed that has dropped due to the suspension of the ignition control has fallen below a threshold value; The ignition restart control unit restarts control of the spark plug based on a restart ignition timing that deviates from the range of all ignition timings set in the normal operating region of the engine body.

7. 7. The engine of claim 6, An engine wherein the carburetor does not have a valve that cuts off the fuel supply in response to the engine stop signal.

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