JP2009264268A - Control apparatus for general-purpose internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for a general-purpose internal combustion engine improving fuel economy performances and emission performances and preventing stall by determining appropriate warming up time in the general-purpose internal combustion engine. <P>SOLUTION: Temperature tb of the general-purpose internal combustion engine and outside air temperature ta are detected (S10, S12). The warming up time T2 for warming up the internal combustion engine is determined based on the detected temperature tb of the internal combustion engine and the outside air temperature ta (S16). Quantity of fuel supplied to the internal combustion engine is increased until the warming up time passes from start of the internal combustion engine (S18, S20. S32). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device for a general-purpose internal combustion engine, and more particularly to a control device for a general-purpose internal combustion engine that performs a warm-up operation.

Conventionally, in general-purpose internal combustion engines that are used as drive sources in various applications such as generators and agricultural machines, warm-up operation is performed after startup to stabilize the engine speed, and stall due to sudden opening and closing of the throttle valve It is well practiced to prevent such problems, and examples thereof include the technique described in Patent Document 1 below. In the technique described in Patent Document 1, the choke valve is closed to the choke opening degree corresponding to the outside air temperature, the fuel supply amount (fuel amount) is increased, the warm-up operation is started, and then the choke valve is fully opened. The valve is gradually opened until the warm-up operation ends.
Japanese Patent Laid-Open No. 7-77106 (paragraphs 0036, 0041 to 0044, FIGS. 3 and 4, etc.)

  By the way, in the general-purpose internal combustion engine, if the above-described warm-up operation is performed more than necessary, the fuel consumption performance deteriorates as the fuel increases, and the emission performance also deteriorates. Stalls without stable numbers. Therefore, it is desirable that the warm-up operation is performed for an appropriate time.

  However, since the appropriate (optimum) warm-up time varies depending on the outside air temperature and the state of the internal combustion engine, the warm-up operation is performed by adjusting the choke opening based on only the outside air temperature as in the technique described in Patent Document 1. In other words, if the warm-up time is determined based only on the outside air temperature, the warm-up time may be excessive or insufficient depending on the state of the internal combustion engine, resulting in deterioration of fuel efficiency or stalling. There was a risk.

  Therefore, an object of the present invention is to control a general-purpose internal combustion engine that solves the above-described problems and determines an appropriate warm-up time in the general-purpose internal combustion engine, thereby improving fuel consumption performance and emission performance and preventing stalls. To provide an apparatus.

  In order to solve the above-mentioned object, in claim 1, temperature detecting means for detecting the temperature of a general-purpose internal combustion engine, outside air temperature detecting means for detecting outside air temperature, the detected temperature of the internal combustion engine, and A warm-up time determining means for determining a warm-up time for warming up the internal combustion engine based on an outside air temperature; and supplying the internal combustion engine until the determined warm-up time elapses after the internal combustion engine is started And a fuel amount increasing means for increasing the amount of fuel to be produced.

  In the control apparatus for a general-purpose internal combustion engine according to claim 2, the engine speed detecting means for detecting the engine speed of the internal combustion engine is provided, and the fuel amount increasing means is provided before the warm-up time has elapsed. When the detected engine speed is equal to or higher than a first predetermined value, the increase in the fuel amount is stopped.

  In the control device for a general-purpose internal combustion engine according to claim 3, the operation of the internal combustion engine is stopped when the detected engine speed does not reach the second predetermined value before the warm-up time has elapsed. It comprised so that the operation stop means to be made to be provided.

  In the control device for a general-purpose internal combustion engine according to claim 1, the warm-up time for warming up the internal combustion engine is determined based on the temperature and the external air temperature of the general-purpose internal combustion engine, that is, the warm-up time is not limited to the external air temperature. In addition, it is determined based on the temperature of the internal combustion engine, and the amount of fuel supplied to the internal combustion engine is increased until the warm-up time elapses after the internal combustion engine is started. The warm-up time can be determined. As a result, the warm-up operation performed by increasing the fuel amount can be completed in an appropriate warm-up time, and thus the fuel efficiency and emission performance can be improved accordingly. In addition, since the warm-up time is not insufficient, stall can be prevented.

  In the control device for a general-purpose internal combustion engine according to claim 2, when the engine speed of the internal combustion engine is detected and the engine speed becomes equal to or higher than a first predetermined value before the warm-up time has elapsed, Since the increase in the amount is stopped, in addition to the above-described effect, for example, the first predetermined value is set to a value at which it can be determined that the internal combustion engine is completely warmed up. It is also possible to end the warm-up operation that is performed early, thereby further improving the fuel efficiency and emission performance. Further, even when the warm-up operation is terminated early, the internal combustion engine is in a completely warm-up state, so that no stall occurs.

  In the control device for a general-purpose internal combustion engine according to claim 3, when the engine speed does not reach the second predetermined value before the warm-up time has elapsed, the operation of the internal combustion engine is stopped. In addition to the effect described in claim 2, for example, when it is estimated that some abnormality occurs in the internal combustion engine and the engine speed does not increase, the operation of the internal combustion engine can be stopped reliably.

  The best mode for carrying out the control apparatus for a general-purpose internal combustion engine according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is an overall view showing a control apparatus for a general-purpose internal combustion engine according to an embodiment of the present invention.

  In FIG. 1, reference numeral 10 denotes a general-purpose internal combustion engine (hereinafter referred to as “engine”). The engine 10 is an air-cooled four-cycle single-cylinder OHV type engine (with a displacement of 440 cc, for example), and is used as a drive source in various applications such as a generator and an agricultural machine.

  The engine 10 includes a single cylinder (cylinder) 12, and a piston 14 is accommodated therein so as to be capable of reciprocating. An intake valve 20 and an exhaust valve 22 are disposed at a position facing the combustion chamber 16 of the engine 10, and opens and closes between the combustion chamber 16 and the intake port 24 or the exhaust port 26.

  The piston 14 is connected to a crankshaft 30, and the crankshaft 30 is connected to a camshaft 34 via a cam gear mechanism 32. Further, a load (not shown) such as a generator is connected to one end of the crankshaft 30, while a flywheel 36 is attached to the other end.

  A plurality of permanent magnets 38 are arranged inside the flywheel 36, and a power coil (power generation coil) 40 faces the permanent magnet 38 on the outside so as to face the permanent magnet 38 inside the flywheel 36. Thus, the pulsar coil 42 is installed. The power coil 40 outputs an alternating current having a frequency corresponding to the number of rotations of the crankshaft 30, and the pulsar coil 42 outputs a pulse signal at every predetermined crank angle. In addition, a recoil starter 44 that starts the engine 10 by an operator's manual operation is attached to the crankshaft 30.

  A carburetor 46 is connected to the intake port 24.

  FIG. 2 is an enlarged cross-sectional view of the carburetor 46 shown in FIG.

  As shown in FIG. 2, the carburetor 46 integrally includes an intake passage 50, a motor case 52, and a carburetor assembly 54. The intake passage 50 has a downstream side connected to the intake port 24 via an insulator 56 and an upstream side connected to an air cleaner (not shown) via an air cleaner elbow 58. A throttle valve 60 is disposed in the intake passage 50, and a choke valve 62 is disposed upstream of the throttle valve 60 in the intake passage 50. Further, the intake passage 50 is reduced in diameter between the throttle valve 60 and the choke valve 62 to form a venturi 64.

  A cover 66 is attached to the motor case 52, and an electric motor (actuator) 70 that drives the throttle valve 60 and the choke valve 62 is disposed in an internal space formed by the motor case 52 and the cover 66. The electric motor 70 is specifically a stepping motor and includes a stator and a rotor around which coils are wound. The electric motor 70 is connected to the throttle valve 60 via a throttle valve opening / closing mechanism (gear mechanism) 72.

  FIG. 3 is a plan view of the carburetor 46 shown in FIG. 2 with the cover 66 of the motor case 52 removed. FIG. 3 shows a state in which the throttle valve 60 is in the fully closed position and the choke valve 62 is in the fully open position, as indicated by an imaginary line.

  As shown in FIGS. 2 and 3, the throttle valve opening / closing mechanism 72 includes four gears. Specifically, a first gear 74 is attached to the output shaft 70 </ b> S of the electric motor 70, and the first gear 74 is meshed with a second gear 76 that is rotatably supported inside the motor case 52. The A third gear (eccentric gear) 78 that rotates integrally with the second gear 76 is attached coaxially with the second gear 76. As can be seen from FIG. 3, the teeth of the third gear 78 are formed only on a part of the outer periphery of the third gear 78 (part connected to a fourth gear (described later)).

  The third gear 78 meshes with a fourth gear (eccentric gear) 82 attached to a throttle shaft 80 that supports the throttle valve 60. As a result, the output of the electric motor 70 is transmitted to the throttle shaft 80 while being decelerated in accordance with the gear ratio of the gears 74, 76, 78, 82, thereby opening and closing the throttle valve 60. One of the characteristic features of the throttle valve opening / closing mechanism 72 according to this embodiment is that the throttle valve 60 is opened / closed between a fully closed position and a position where the fully opened position exceeds a predetermined opening according to the operation of the electric motor 70, That is, the throttle valve 60 is opened and closed from the fully opened position to a position exceeding a predetermined opening in the valve opening direction, which will be described later.

  A return spring 84 (shown in FIG. 2) made of a torsion coil spring is disposed on the outer periphery of the throttle shaft 80. One end of the return spring 84 is connected to the fourth gear 82, and the other end is connected to a hook pin 86 (shown in FIG. 2) that projects from the motor case 52. Note that the winding direction of the return spring 84 is set to a direction in which the throttle valve 60 is opened via the throttle shaft 80.

  A choke valve 62 is connected to the throttle valve opening / closing mechanism 72 configured as described above via a choke valve opening / closing mechanism 90. The choke valve opening / closing mechanism 90 is attached to a choke shaft 92 that supports the choke valve 62 and rotates the choke shaft 92. The arm 94 and the throttle valve opening / closing mechanism 72 (more precisely, the throttle valve opening / closing mechanism 72 It consists of a link 96 connecting the third gear 78).

  The link 96 is supported inside the motor case 52 so as to be rotatable about the rotation shaft 100. In the link 96, an end 96a on the arm 94 side is provided with a first pin 96b extending upward in FIG. The first pin 96 b is inserted through a long hole 94 a formed in the arm 94.

  A second pin 96d protrudes upward in FIG. 2 at the end 96c of the link 96 on the third gear 78 side. The second pin 96d is brought into contact with a portion where teeth are not formed on the outer periphery of the third gear 78. The portion where the teeth are not formed on the outer periphery of the third gear 78 (that is, the portion where the second pin 96d abuts) has a substantially disc shape and includes a concave portion. Hereinafter, a concave portion formed on the outer periphery of the third gear 78 is referred to as a “first contact portion” and is denoted by reference numeral 78a. Further, the remaining portion (substantially disk-shaped portion) other than the first contact portion 78a in the portion where the outer peripheral teeth of the third gear 78 are not formed is referred to as a “second contact portion”, which is denoted by reference numeral 78b. Show. The positions where the first and second contact portions 78a and 78b are formed on the outer periphery of the third gear 78 will be described later.

  On the outer periphery of the choke shaft 92, a return spring 102 made of a torsion coil spring is disposed as shown in FIG. One end of the return spring 102 is connected to the arm 94, and the other end is connected to a hook pin 104 protruding inside the motor case 52. The winding direction of the return spring 102 is set to a direction in which the choke valve 62 is closed via the choke shaft 92.

  The choke valve opening / closing mechanism 90 is configured to include the return spring 102 that urges the choke valve 62 in the valve closing direction (fully closed position), so that the urging force is transmitted to the link 96 via the arm 94. Is done. Accordingly, a counterclockwise force acts on the link 96 around the rotation shaft 100, so that the second pin 96 d of the link 96 is connected to the outer peripheral surface of the third gear 78 (specifically, the first or the second 2 abutting portions 78a and 78b), while being always pressed (pressed).

  Returning to the description of FIG. 1, the carburetor assembly 54 is connected to a fuel tank (not shown) and receives fuel supply, and injects an amount of fuel corresponding to the opening of the throttle valve 60 to generate an air-fuel mixture. Further, when the choke valve 62 is closed, the negative pressure in the intake passage 50 caused by the lowering of the piston 14 increases, so the amount of fuel injected from the carburetor assembly 54 increases and the air-fuel ratio is enriched. .

  The air-fuel mixture generated as described above is sucked into the combustion chamber 16 through the intake port 24 and the intake valve 20. The air-fuel mixture sucked into the combustion chamber 16 is ignited and burned by a spark plug (not shown), and the generated combustion gas (exhaust gas) passes through the exhaust valve 22, the exhaust port 26, a silencer (not shown), and the like. Is discharged outside.

  A rotation speed setting volume 110 and an engine stop switch 112 are arranged at positions that can be operated by the operator. The rotation speed setting volume 110 generates an output indicating the target engine rotation speed NED according to the operation of the operator. The engine stop switch 112 outputs an ON signal when an engine stop instruction is input from the operator (when operated).

  An ECU (Electronic Control Unit) 114 is disposed at an appropriate position of the engine 10. The ECU 114 is composed of a microcomputer composed of a CPU, ROM, RAM, an input / output circuit, and the like, and is mounted on an electronic circuit board (not shown in FIG. 1).

  FIG. 4 is a plan view showing the electronic circuit board.

  4, in addition to the ECU 114, the electronic circuit board 116 includes an outside air temperature sensor (outside air temperature detecting means) 120 that detects the outside air temperature ta, and an engine temperature sensor (temperature detecting means) that detects the temperature tb of the engine 10. ) 122 is mounted. The outside air temperature sensor 120 and the engine temperature sensor 122 are specifically a thermistor temperature sensor using electrical resistance.

  The outside air temperature sensor 120 is disposed at an end portion (upper left in FIG. 4) 116a of the electronic circuit board 116. Specifically, the ambient temperature changes on the electronic circuit board 116 according to the outside air temperature, but the engine 10 is in operation. And when it stops, it is placed in a region where the temperature change is relatively small. Therefore, the ambient temperature of the outside air temperature sensor 120 is not affected by the operating state of the engine 10 and has a proportional relationship with the outside air temperature. Therefore, the outside air temperature sensor 120 outputs a signal proportional to the outside air temperature.

  The engine temperature sensor 122 is disposed at a position away from the end portion 116 a of the electronic circuit board 116 (lower right portion in FIG. 4) 116 b, in other words, at a predetermined distance from the outside air temperature sensor 120. In the vicinity of the engine temperature sensor 122, a circuit that generates heat when an operating current is supplied (that is, when the engine 10 is operating) (for example, a power supply circuit (a group of electronic components surrounded by a broken line in FIG. 4)). 124 is installed.

  With this configuration, the ambient temperature of the engine temperature sensor 122 gradually increases to a predetermined temperature when the engine 10 is started, and then gradually decreases when the engine 10 is stopped. The actual temperature of the engine 10 also changes in the same manner as the ambient temperature of the engine temperature sensor 122 according to the operating state of the engine 10. That is, the ambient temperature of the engine temperature sensor 122 and the temperature of the engine 10 are in a proportional relationship, and therefore the engine temperature sensor 122 outputs a signal indicating a temperature proportional to the temperature of the engine 10.

  Returning to the description of FIG. 1, the outputs of the temperature sensor 28, the power coil 40, the pulsar coil 42, the rotation speed setting volume 110, the engine stop switch 112, the outside air temperature sensor 120, and the engine temperature sensor 122 are input to the ECU 114. .

  The output (AC current) of the power coil 40 input to the ECU 114 is input to a bridge circuit (not shown) provided in the ECU 114, where it is converted into DC current by full-wave rectification. This direct current is supplied to each part of the engine 10 as an operating current. The output of the power coil 40 is also input to a pulse generation circuit (NE detection circuit, not shown) provided in the ECU 114 and converted into a pulse signal. Since the frequency of the alternating current generated by the power coil 40 is proportional to the rotational speed of the crankshaft 30, the engine rotational speed NE can be detected based on the pulse signal obtained from the output of the power coil 40.

  Further, the ECU 114 ignites the spark plug at a timing according to the engine speed based on the output (pulse signal) of the pulsar coil 42. Further, the ECU 114 determines the target opening of the throttle valve 60 and the choke valve 62 based on the output of the rotation speed setting volume 110, the detected engine speed NE, the outside air temperature ta, the temperature tb of the engine 10, and the like. A control signal corresponding to the target opening degree is output to a motor driver (not shown) to operate the electric motor 70, and the valves 60 and 62 are opened and closed to open the engine speed NE and the amount of fuel supplied to the engine 10. Adjust.

  Next, the opening / closing operation of the throttle valve 60 and the choke valve 62 will be described with reference to FIG. 3 and FIG. 5 and thereafter, focusing on the operations of the electric motor 70, the throttle valve opening / closing mechanism 72, and the choke valve opening / closing mechanism 90.

  FIG. 5 is an explanatory diagram showing the characteristics of the opening / closing operation of the throttle valve 60 and the choke valve 62.

  When the throttle valve 60 is in the fully closed position, the electric motor 70 rotates the throttle shaft 80 via the first to fourth gears 74, 76, 78, 82 of the throttle valve opening / closing mechanism 72, and the throttle valve 60. Is closed to the fully closed position shown in FIG. 3 and FIG. At this time, as can be seen from FIG. 3, the second pin 96d of the link 96 is in contact with the second contact portion 78b of the third gear 78, and the choke valve 62 is in the fully open position.

  When opening the throttle valve 60 from the fully closed position to the fully opened position, the electric motor 70 rotates the first to fourth gears 74, 76, 78, and 82 in the directions indicated by the arrows in FIG. The throttle shaft 80 is rotated counterclockwise, and the throttle valve 60 is opened to the fully open position. At this time, the second pin 96d slides to the vicinity of the first contact portion 78a, but is still in contact with the second contact portion 78b, and therefore also shown in FIG. Thus, the choke valve 62 is held in the fully open position. Thus, the choke valve opening / closing mechanism 90 holds the choke valve 62 in the fully open position when the throttle valve 60 is between the fully closed position and the fully open position.

  Further, when the choke valve 62 is closed to enrich the air-fuel ratio, such as when the engine 10 is started (during a warm-up operation described later), the electric motor 70 operates the throttle valve opening / closing mechanism 72 and linked to it. The choke valve 62 is opened and closed by rotating the choke shaft 92 by displacing 96. Specifically, the electric motor 70 rotates the gears 74, 76, 78, and 82 in the directions indicated by the arrows in FIG. 7 to further rotate the throttle shaft 80 counterclockwise to fully open the throttle valve 60. The valve is opened to a position exceeding the predetermined opening degree α (hereinafter referred to as “over fully open position”).

  At this time, the second pin 96d slides to the first contact portion 78a by the rotation of the third gear 78. Thereby, the link 96 is displaced counterclockwise around the rotation shaft 100, and the first pin 96b displaces the arm 94 while sliding in the long hole 94a. Due to the displacement of the arm 94, the choke shaft 92 is rotated clockwise in the figure, so that the choke valve 62 is closed to the fully closed position as shown in FIG.

  As described above, the positions at which the first and second contact portions 78a and 78b are formed in the third gear 78 are determined when the second pin 96d contacts the second contact portion 78b, that is, 3 or 6, the choke valve 62 is in the fully open position, the third gear 78 is rotated clockwise in the drawing by the electric motor 70, and the second pin 96 d is in the first contact position. When contacting the contact portion 78a (in the state shown in FIG. 7), the choke valve 62 is set to the fully closed position.

  As described above and as shown in FIGS. 5A to 5C, the choke valve opening / closing mechanism 90 opens and closes the choke valve 62 in conjunction with the operation of the throttle valve opening / closing mechanism 72. More specifically, the throttle valve When 60 is between the fully closed position and the fully open position, the choke valve 62 is held in the fully open position, while the throttle valve 60 is between the fully open position and the over fully open position (the position where the fully open position exceeds the predetermined opening α). In some cases, the choke valve 62 is configured to open and close between a fully open position and a fully closed position.

  In the above description, the operation of the choke valve 62 has been described in two types, the fully open position and the fully closed position. However, since the first contact portion 78a is formed in a concave shape, the second pin 96d and the first contact By appropriately adjusting the contact position with the contact portion 78a, the choke valve 62 can be set to an arbitrary opening degree. That is, the choke valve 62 can be freely opened and closed between the fully open position and the fully closed position by appropriately adjusting the throttle valve 60 between the fully open position and the over fully open position.

  Next, the opening / closing operation of the throttle valve 60 and the choke valve 62 when the engine 10 is started will be described.

  FIG. 8 is a flowchart showing control of the operation of the throttle valve 60 and the like when the engine 10 is started, among the operations of the ECU 114. The illustrated program is executed only once when the engine 10 is started. Before the engine 10 is started, the throttle valve 60 and the choke valve 62 are in the state shown in FIGS. 7 and 5C. Specifically, the throttle valve 60 is set to the fully open position by the urging force of the return spring 84. The choke valve 62 is fully closed by the return spring 102.

  Hereinafter, the opening / closing operation of the throttle valve 60 and the choke valve 62 will be described with reference to the flowchart of FIG. When the recoil starter 44 is operated by the operator and the power coil 40 starts generating power and the ECU 114 is activated, first, the outside air temperature ta is detected based on the output of the outside air temperature sensor 120 in S10, and the process proceeds to S12. Based on the output of the temperature sensor 122, the temperature tb of the engine 10 is detected.

  Proceeding to S14, the stop time T1 of the engine 10 is calculated based on the detected outside air temperature ta and the temperature tb of the engine 10, that is, the elapsed time from the last stop of the engine 10 to the current start is calculated (estimated). ) Specifically, as shown in FIG. 9, the map obtained by subtracting the outside air temperature ta from the temperature tb of the engine 10 is searched in advance for a map stored in the ROM, and the engine 10 is stopped. Time T1 is calculated.

  As can be seen from FIG. 9, when the difference between the temperature tb of the engine 10 and the outside air temperature ta is large, it can be estimated that the engine 10 is restarted in a short time after the engine 10 is stopped (hot restart), and the stop time T1 is short. Is set to be On the other hand, when the difference is small, it can be estimated that the engine has been cold started after a certain period of time has elapsed after the engine 10 is stopped, and thus the stop time T1 is set to be longer.

  Next, the routine proceeds to S16, where a warm-up time T2 for warming up the engine 10 is determined based on the calculated stop time T1. Note that the warm-up time T2 is, for example, the time from when the engine 10 is started to when the operation state (complete warm-up state) occurs in which no stall occurs even when the throttle valve 60 is suddenly opened and closed. Means.

  The determination of the warm-up time T2 will be described in detail. In this embodiment, as shown in FIG. 10, the relationship between the stop time T1 and the warm-up time T2 is previously mapped through experiments, and the calculated stop time T1 is calculated. The warm-up time T2 is determined (calculated) by searching the map.

  As shown in FIG. 10, the warm-up time T2 is set to increase as the stop time T1 becomes longer. This is because when the stop time T1 is relatively short, that is, during warm start, a short warm-up time is sufficient, while when the stop time T1 is relatively long (when cold start), the warm-up is completed. This is because a long time is required. Thus, the stop time T1 is calculated based on the outside air temperature ta and the temperature tb of the engine 10, and the warm-up time T2 for warming up the engine 10 is determined based on the calculated stop time T1.

  Next, in S18, the determined warm-up time T2 is set in a timer (down counter). That is, the elapsed time after the engine 10 is started is measured using a timer. In S20, the amount of fuel supplied to the engine 10 is increased and the warm-up operation is performed. Specifically, the operation of the electric motor 70 is controlled so that the throttle valve 60 is driven (opened / closed) between the over fully open position and the fully open position. By driving the throttle valve 60 as described above, the choke valve 62 is opened and closed between the fully closed position and the fully opened position as shown in FIGS. The choke valve 62 is opened and closed so as to maintain the target engine speed NED input at 110). As a result, the amount of fuel increases, the air-fuel ratio in the intake passage 50 is enriched, the engine 10 is warmed up, and its startability is also improved.

  In S22, the upper limit engine speed (first predetermined value) NE1 and the lower limit engine speed (second predetermined value) NE2 during warm-up operation are determined from the output (target engine speed NED) of the speed setting volume 110. decide. Specifically, the upper limit engine speed NE1 is an engine speed at which it can be determined that the engine 10 has been completely warmed up when the engine speed NE reaches that value, for example, the target engine speed. The value is obtained by adding 300 rpm to NED. Further, the lower limit engine speed NE2 means an engine speed at which it can be estimated that some abnormality has occurred in the engine 10 when the engine speed NE does not reach the value. For example, 300 rpm is subtracted from the target engine speed NED. Value.

  In S24, the engine speed NE is detected, and in S26, it is determined whether or not the detected engine speed NE is equal to or lower than the lower limit engine speed NE2. Affirmative in S26, that is, if the engine speed NE does not reach the lower limit engine speed NE2 before the warm-up time T2 has elapsed since the engine 10 was started, it is estimated that some abnormality has occurred in the engine 10. Therefore, it progresses to S28, performs ignition cut etc., stops the driving | operation of the engine 10, and complete | finishes a program.

  On the other hand, when the result in S26 is negative, the program proceeds to S30, in which it is determined whether the engine speed NE is equal to or greater than the upper limit engine speed NE1. When the result in S30 is negative, the program proceeds to S32, in which it is determined whether or not the timer value has become zero. When the result in S32 is negative, the program returns to S20, and the warm-up operation performed by increasing the amount of fuel described above is continued. Thus, until the timer value becomes 0, in other words, the amount of fuel supplied to the engine 10 is increased until the warm-up time T2 elapses after the engine 10 is started.

  When the result in S32 is affirmative, that is, when the warm-up time T2 has elapsed since the engine 10 was started, the routine proceeds to S34, where the throttle valve 60 is normally controlled. Specifically, the throttle valve 60 is electrically driven so as to be driven between the fully closed position and the fully open position (precisely, in order to maintain the target engine speed NED, the throttle valve 60 is set to the target opening). The operation of the motor 70 is controlled. By driving the throttle valve 60 between the fully closed position and the fully open position, the choke valve 62 is held at the fully open position, as shown in FIGS. (Warm-up operation) is terminated.

  Further, when the result in S30 is affirmative, it can be determined that the engine 10 has been completely warmed up, and it is not necessary to perform any further warming-up operation. ) As described above, when the engine speed NE becomes equal to or higher than the upper limit engine speed NE1 before the warm-up time T2 elapses, the fuel amount increase (warm-up operation) is stopped.

  Next, the opening / closing operation of the throttle valve 60 and the choke valve 62 when the engine 10 is stopped will be described.

  FIG. 11 is a flowchart showing the control of the operation of the throttle valve 60 when the engine 10 is stopped, among the operations of the ECU 114. The illustrated program is executed in the ECU 114 at predetermined intervals (for example, 100 msec).

  First, in S100, it is determined whether or not a stop instruction for the engine 10 has been input, specifically, whether or not the engine stop switch 112 has been operated by the operator to output an ON signal. When the result in S100 is negative, the subsequent processing is skipped, while when the result is positive, the process proceeds to S102 to control the operation of the electric motor 70 so that the throttle valve 60 is driven (opened) to the over fully open position. By driving the throttle valve 60 as described above, the choke valve 62 is closed to the fully closed position as shown in FIG.

  As described above, in the embodiment of the present invention, the temperature detecting means (engine temperature sensor 122. S12) for detecting the temperature tb of the general-purpose internal combustion engine (engine) 10 and the outside air temperature detecting means for detecting the outside air temperature ta. (Outside air temperature sensor 120. S10) and warm-up time determining means (ECU 114. S16) for determining a warm-up time T2 for warming up the internal combustion engine based on the detected temperature tb of the internal combustion engine and the outside air temperature ta. And a fuel amount increasing means (ECU 114. S18, S20, S32) for increasing the amount of fuel supplied to the internal combustion engine until the determined warm-up time elapses after the internal combustion engine is started. It was configured as follows.

  As described above, since the warm-up time T2 is determined not only based on the outside air temperature ta but also based on the temperature tb of the engine 10, it is possible to determine an appropriate warm-up time T2 in the engine 10. As a result, the warm-up operation performed by increasing the fuel amount can be terminated in an appropriate warm-up time T2, and thus the fuel efficiency performance and emission performance can be improved accordingly. In addition, since the warm-up time is not insufficient, stall can be prevented.

  Further, the engine speed detecting means (ECU 114, S24) for detecting the engine speed of the internal combustion engine (engine speed NE) is provided, and the fuel amount increasing means is arranged before the warm-up time T2 elapses. When the detected engine speed NE is equal to or higher than a first predetermined value (upper limit engine speed NE1), the increase in the fuel amount is stopped (S30, S34). As a result, by setting the upper limit engine speed NE1 to a value at which it can be determined that the engine 10 has been completely warmed up, it is possible to quickly end the warm-up operation performed by increasing the fuel amount. The fuel efficiency and emission performance can be further improved. Further, even when the warm-up operation is terminated early, the engine 10 is in a completely warm-up state, so that no stall occurs.

  Further, when the detected engine speed NE does not reach a second predetermined value (lower limit engine speed NE2) before the warm-up time T2 elapses, operation stop means for stopping the operation of the internal combustion engine ( ECU 114. S26, S28). Thereby, for example, when it is estimated that some abnormality occurs in the engine 10 and the engine speed NE does not increase, the operation of the engine 10 can be stopped reliably.

  In the above, the actuator (electric motor 70) for driving the throttle valve 60 and the like is a stepping motor. However, other electric motors or electromagnetic solenoids may be used, and the pump is driven by the electric motor. It may be a hydraulic device.

  Further, the fuel is supplied by the carburetor 46, but the present invention is not limited to this, and an injector (fuel injection valve) may be arranged in the intake port 24 to supply the fuel.

1 is an overall view showing a control device for a general-purpose internal combustion engine (engine) according to an embodiment of the present invention. It is an expanded sectional view of the carburetor shown in FIG. It is a top view which shows the state which removed the cover of the motor case of the carburetor shown in FIG. It is a top view which shows the electronic circuit board by which the electronic control unit shown in FIG. 1 is mounted. It is explanatory drawing which shows the characteristic of the opening / closing operation | movement of the throttle valve and choke valve shown in FIG. It is a top view of the carburetor similar to FIG. It is a top view of the carburetor similar to FIG. 2 is a flow chart showing control of operations of a throttle valve and the like at the time of starting a general-purpose internal combustion engine (engine) among the operations of the electronic control unit shown in FIG. It is a graph which shows the table characteristic of the stop time with respect to the difference of the temperature of external temperature and a general purpose internal combustion engine (engine) used by the process of FIG. Similarly, it is a graph which shows the table characteristic of the warming-up time with respect to stop time used by the process of FIG. 2 is a flowchart showing control of the operation of a throttle valve when the general-purpose internal combustion engine (engine) is stopped, among the operations of the electronic control unit shown in FIG. 1.

Explanation of symbols

  10 engine (general-purpose internal combustion engine), 114 ECU (electronic control unit), 120 outside air temperature sensor (outside air temperature detecting means), 122 engine temperature sensor (temperature detecting means)

Claims (3)

a. Temperature detecting means for detecting the temperature of the general-purpose internal combustion engine;
b. An outside air temperature detecting means for detecting the outside air temperature;
c. A warm-up time determining means for determining a warm-up time for warming up the internal combustion engine based on the detected temperature and outside air temperature of the internal combustion engine;
d. Fuel amount increasing means for increasing the amount of fuel supplied to the internal combustion engine until the determined warm-up time elapses after the internal combustion engine is started;
A control apparatus for a general-purpose internal combustion engine, comprising: e. Engine speed detecting means for detecting the engine speed of the internal combustion engine;
And the fuel amount increasing means stops the increase in the fuel amount when the detected engine speed becomes equal to or higher than a first predetermined value before the warm-up time elapses. The control apparatus for a general-purpose internal combustion engine according to claim 1. f. An operation stop means for stopping the operation of the internal combustion engine when the detected engine speed does not reach a second predetermined value before the warm-up time elapses;
The general-purpose internal combustion engine control device according to claim 2, further comprising:

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