JP2009264265A - General-purpose internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a general-purpose internal combustion engine provided with a choke valve on-off mechanism driving a choke valve without newly employing an actuator and improving fuel economy. <P>SOLUTION: In the general-purpose internal combustion engine 10 provided with a throttle valve 60, the choke valve 62, and an actuator (electric motor) 70 connected to a throttle valve via a gear mechanism (throttle valve open close mechanism) 72 and opening and closing the throttle valve, the choke valve on-off mechanism 90 is provided for opening and closing the choke valve 62 in linking with operation of the gear mechanism 72, and the choke valve 62 is driven without newly employing an actuator. Opening of the choke valve 62 is adjusted to an appropriate opening by providing a choke valve opening adjusting mechanism 106 adjusting the opening of the choke valve 62 opened and closed by the choke valve on-off mechanism 90 according to ambient temperature. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a general-purpose internal combustion engine, and more particularly to a general-purpose internal combustion engine provided with an actuator that opens and closes a throttle valve.

  Conventionally, in general-purpose internal combustion engines that are used as a drive source in various applications such as generators and agricultural machinery, an electronically controlled throttle device (electronic governor) that opens and closes a throttle valve with an actuator such as a stepping motor is used. It is widely performed to control the rotational speed with high accuracy.

By the way, in recent years, there has been proposed a technique for improving engine startability by using an auto choke device that opens and closes a choke valve with an actuator and closing the choke valve at a cold start to enrich the air-fuel ratio. ing. When this auto choke device is provided in the above-described general-purpose internal combustion engine, it is common to newly attach an actuator for a choke valve in addition to an actuator for a throttle valve as in the technique described in Patent Document 1, for example.
JP 2007-23838 A (paragraphs 0022, 0036, FIG. 2, etc.)

  When an actuator for a choke valve is added as in the technique described in Patent Document 1, a space for arranging the actuator is required, which causes a problem that the general-purpose internal combustion engine is increased in size. Therefore, it is conceivable to drive the choke valve without using a new actuator by providing a choke valve opening / closing mechanism for driving the choke valve with the actuator for the throttle valve.

  However, if the general-purpose internal combustion engine is simply provided with a choke valve opening / closing mechanism, the choke can be used even when the ambient temperature is relatively high, such as during warm start (hot restart), and the air-fuel ratio need not be enriched. The valve opening / closing mechanism closes the choke valve and enriches the air-fuel ratio, resulting in inconvenience that fuel consumption deteriorates.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a general-purpose internal combustion engine that solves the above-described problems and includes a choke valve opening / closing mechanism that drives a choke valve without newly using an actuator and also improves fuel consumption. .

  In order to solve the above-described object, in claim 1, a throttle valve and a choke valve disposed in an intake passage, and an actuator that is connected to the throttle valve via a gear mechanism to open and close the throttle valve; And a choke valve opening / closing mechanism connected to the gear mechanism and the choke valve for opening and closing the choke valve in conjunction with the operation of the gear mechanism, and the choke valve opened / closed by the choke valve opening / closing mechanism. And a choke valve opening adjusting mechanism that adjusts the opening of the valve according to the ambient temperature.

  The general-purpose internal combustion engine according to claim 2, wherein the choke valve opening adjusting mechanism is connected to the wax portion that is filled with wax that expands and contracts according to the ambient temperature, and is connected to the wax portion. The choke valve opening / closing mechanism is driven according to the expansion / contraction of the motor, and the driving pin is configured to adjust the opening degree of the choke valve.

  In the general-purpose internal combustion engine according to claim 3, the choke valve opening adjusting mechanism is further provided with a heater for heating the wax portion.

  In the general-purpose internal combustion engine according to claim 1, an actuator that opens and closes the throttle valve connected to the throttle valve via a gear mechanism, and a choke valve opening and closing mechanism that opens and closes the choke valve in conjunction with the operation of the gear mechanism. The choke valve can be driven by the actuator that drives the throttle valve. In other words, both the throttle valve and the choke valve can be driven by one actuator. Can be driven without using a new actuator, and a space for arranging the actuator is not required, and it is advantageous in terms of cost. In addition, since the choke valve opening / closing mechanism that adjusts the opening degree of the choke valve that is opened / closed by the choke valve opening / closing mechanism is provided according to the ambient temperature, for example, when the ambient temperature is relatively high such as during warm start. It is also possible to prevent the air-fuel ratio from becoming rich by opening the choke valve, that is, the choke valve can be adjusted to an appropriate opening degree according to the ambient temperature, and fuel consumption can be improved.

  In the general-purpose internal combustion engine according to claim 2, the choke valve opening adjusting mechanism includes a wax portion filled with wax that expands and contracts according to the ambient temperature, and a choke valve opening and closing according to the expansion and contraction of the wax. Since the mechanism is configured to include a drive pin that adjusts the opening of the choke valve, in addition to the effects described above, the opening of the choke valve can be adjusted with a simple configuration, further saving. Space can be achieved.

  In the general-purpose internal combustion engine according to claim 3, since the choke valve opening adjusting mechanism is further provided with a heater for heating the wax portion, in addition to the effect described in claim 2, for example, warm-up After completion, the wax part is heated with a heater, and the choke valve opening / closing mechanism is driven via the drive pin by the thermal expansion of the wax to hold the choke valve in the fully open position. It can also be configured to be held in position. As a result, the choke valve can be reliably prevented from closing during engine operation, and the choke valve is at or near the fully open position even during a warm start that is restarted in a short time after the engine is stopped. Therefore, the air-fuel ratio is not excessively enriched, and thus the fuel consumption can be further improved.

  The best mode for carrying out 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 of 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 and a fuel cut solenoid valve coil (described later) are arranged so as to face the permanent magnet 38 inside the flywheel 36. 4 (hereinafter referred to as “FS coil”), the pulsar coil 42 is installed so as to face the permanent magnet 38 on the outside. The power coil 40, the pulsar coil 42, and the FS coil generate an output (alternating current) synchronized with the rotation of the crankshaft 30. 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 partial cross-sectional plan view showing 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. Each gear is an external gear. 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 throttle return spring 84 (shown in FIG. 2) is disposed on the outer periphery of the throttle shaft 80. The throttle return spring 84 is a torsion coil spring. One end of the throttle return spring 84 is connected to a fourth gear 82 attached to the throttle shaft 80, and the other end is connected to a hook pin 86 (shown in FIG. 2) protruding inside the motor case 52. Connected. The winding direction of the throttle 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. Therefore, the electric motor 70 is connected to the throttle valve 60 via the throttle valve opening / closing mechanism 72 and also connected to the choke valve 62 via the throttle valve opening / closing mechanism 72 and the 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 (one 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.

  In the link 96, a second pin 96d protrudes upward from an end (other end) 96c on the third gear 78 side in FIG. 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.

  As shown in FIG. 2, a choke return spring 102 is disposed on the outer periphery of the choke shaft 92. Similarly to the throttle return spring 84, the choke return spring 102 is also a torsion coil spring. One end of the choke 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 choke return spring 102 is set to a direction in which the choke valve 62 is closed via the choke shaft 92.

  In the choke valve opening / closing mechanism 90, the choke valve 62 is provided with a choke return spring 102 that urges the choke valve 62 in the valve closing direction (fully closed position). Is transmitted to. 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 The two abutting portions 78a and 78b) are abutted while being pressed (pressed).

  In this way, the link 96 has one end 96a connected to the choke shaft 92 via the first pin 96b and the arm 94, and the other end 96c connected to the throttle valve opening / closing mechanism 72 (via the second pin 96d). Precisely, it is connected (contacted) to the first contact portion 78a or the second contact portion 78b) of the third gear 78.

  A choke valve opening adjustment mechanism 106 (shown in FIG. 3) for adjusting the opening of the choke valve 62 is further provided inside the motor case 52. The choke valve opening adjusting mechanism 106 is specifically a thermo wax, and expands and contracts in accordance with the ambient temperature (more precisely, the volume expands as the ambient temperature increases while the ambient temperature decreases). The wax portion 106a is filled with a wax (not shown), the rod 106b connected to the wax portion 106a and linearly displaced by expansion and contraction of the wax, the rod portion 106b and the flange 106c. And a drive pin 106d that is linearly displaced in conjunction with the displacement of the rod 106b, and a case 106e that accommodates them. FIG. 3 shows the choke valve opening adjusting mechanism 106 when the wax is contracted.

  The tip 106d1 of the drive pin 106d is projected outward from a hole 106e1 formed in the case 106e, and is connected to the choke valve opening / closing mechanism 90 (more precisely, the link 96 of the choke valve opening / closing mechanism 90). The side surface 96e) between the moving shaft 100 and the one end 96a can be contacted freely. The drive pin 106d is normally urged by the return spring 106f in the direction in which the drive pin 106d is accommodated in the case 106e, that is, in the direction in which the protrusion amount (protrusion length) L of the tip 106d1 becomes short (downward in the drawing). Therefore, the protrusion amount L of the drive pin 106d is minimized by the biasing force of the return spring 106f when the wax is contracted as shown in FIG.

  The choke valve opening adjustment mechanism 106 further includes a heater 106g that heats the wax portion 106a. Although not shown, the heater 106g is composed of a heating wire such as a nichrome wire, an insulating material and a protective tube covering the heating wire, and generates heat when an operating current is supplied from the power coil 40 and energized. It is an electric heater.

  Returning to the description of FIG. 2, although not shown, the carburetor assembly 54 includes a float chamber connected to a fuel tank, a main nozzle connected to the float chamber via a main jet and a main fuel passage, and a main fuel passage. An idle port and a slow port connected to a slow fuel passage branched off from The main nozzle is disposed at a position facing the venturi 64, while the idle port and the slow port are disposed at a position facing the vicinity of the throttle valve 60.

  When the opening degree of the throttle valve 60 is large, fuel is injected from the main nozzle by the negative pressure of the intake air passing through the venturi 64, and an air-fuel mixture is generated. On the other hand, when the opening degree of the throttle valve 60 is small, the fuel is injected from the idle port or the slow port by the negative pressure of the intake air passing through the throttle valve 60. 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 that the fuel injection amount increases and the air-fuel ratio is enriched. Hereinafter, a state in which the air-fuel ratio in the intake passage 50 is enriched is referred to as a “rich air-fuel ratio state”.

  In FIG. 2, reference numeral 108 denotes a fuel cut solenoid valve (hereinafter referred to as “FS valve”). A valve portion (not shown) of the FS valve 108 is disposed between the float chamber and the main jet, and closes when the coil (shown in FIG. 4 described later) is energized to block the passage of fuel.

  Returning to the description of FIG. 1, 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 (shown in FIG. 4 described later), and the generated combustion gas passes through an exhaust valve 22, an exhaust port 26, a silencer (not shown), and the like. It is discharged outside the engine 10.

  A rotation speed setting volume 110 is arranged at a position that can be operated by the operator, and an output indicating the target engine rotation speed is generated according to the operation of the operator. Outputs of the power coil 40, the pulsar coil 42, and the rotation speed setting volume 110 are input to an ECU (Electronic Control Unit) 112 formed of a microcomputer.

  A combination switch 114 is disposed at a position that can be operated by the operator. The combination switch 114 is connected to the ECU 112. The ECU 112 controls the operation of the engine 10 (for example, the operation of the electric motor 70, the heater 106g, etc.) based on the position of the combination switch 114 and various inputs by the operator.

  FIG. 4 is an explanatory diagram showing the configuration of the ECU 112 and the combination switch 114.

  As shown in FIG. 4, ECU 112 includes rectifier circuit 116, NE (engine speed) detection circuit 120, and control circuit 122. The output of the power coil 40 is input to the rectifier circuit 116, converted into a 12V DC current, and supplied as an operating current to each part of the engine 10 including the ECU 112 and the heater 106g via a circuit (not shown). The output of the power coil 40 is also input to the NE detection circuit 120 and converted into a pulse signal. The pulse signal is input to the control circuit 122, where the engine speed is detected. The ECU 112 further includes a signal shaping circuit 124 and an ignition circuit 126. The output of the pulsar coil 42 is inputted to a signal shaping circuit 124 where it is shaped into an ignition signal synchronized with the rotation of the crankshaft 32 and inputted to the ignition circuit 126 and the control circuit 122.

  The combination switch 114 includes first and second switches 114a and 114b. In FIG. 4, the switches 114a and 114b when the combination switch 114 is operated to the off position are indicated by solid lines, and when the combination switch 114 is operated to the on position, they are indicated by imaginary lines.

  The first switch 114 a is interposed between the FS coil 130 and the FS valve (specifically, the coil) 108. When the second switch 114 b is turned on, a DC current of 12 V generated from the output of the power coil 40 is input to the control circuit 122 and the DC / DC converter 132. The DC / DC converter 132 is connected to the primary coil of the ignition coil 136 via the capacitor 134 and charges the capacitor 134. The secondary coil of the ignition coil 136 is connected to the spark plug 140, and the capacitor 134 is grounded via the thyristor 142.

  The ignition circuit 126 energizes the gate of the thyristor 142 in accordance with the ignition signal from the signal shaping circuit 124 or the control circuit 122, discharges the electric charge charged in the capacitor 134, and energizes the primary coil of the ignition coil 136. Along with this, a high voltage is generated in the secondary coil and a spark is generated between the electrodes of the spark plug 140 to ignite the air-fuel mixture in the combustion chamber 16.

  A rotation speed setting volume 110 is connected to the control circuit 122. The control circuit 122 determines the target opening of the throttle valve 60 and the choke valve 62 based on outputs from the rotation speed setting volume 110 and the NE detection circuit 120, and sends a control signal corresponding to the determined target opening to the motor driver. 144, the electric motor 70 is operated and the valves 60 and 62 are opened and closed to adjust the engine speed and the amount of fuel supplied to the engine 10. Furthermore, the control circuit 122 also controls the operation of the heater 106g based on the output of the NE detection circuit 120 or the like.

  When the combination switch 114 is operated to the on position by the operator, the first switch 114a is turned off, and the supply of the operating current to the FS valve 108 is interrupted. The FS valve 108 is a normally open type, and enables fuel injection from the carburetor 46 when the supply of operating current is interrupted. On the other hand, when the second switch 114b is turned on and the recoil starter 44 is operated in this state, the power coil 40 and the pulsar coil 42 generate outputs along with the rotation of the crankshaft 32, and a 12V DC current and an ignition signal are generated. The ECU 112 is generated and the engine 10 is started, and the engine 10 is started.

  When the combination switch 114 is operated to the off position, the second switch 114b is turned off, whereby the control circuit 122, which has been cut off from the supply of the operating current, performs the ignition cut and stops the engine 10. Further, the first switch 114a is turned on, the FS coil 130 and the FS valve 108 are conducted, and fuel cut is performed. That is, even if the ignition cut is performed, the rotation of the crankshaft 32 does not stop immediately, so the power generation of the FS coil 130 is continued. Therefore, the FS valve 108 is supplied with an operating current from the FS coil 130 for a predetermined period. Close the valve (fuel cut).

  Next, with respect to the opening / closing operation of the throttle valve 60 and the choke valve 62, the operations of the electric motor 70, the throttle valve opening / closing mechanism 72, the choke valve opening / closing mechanism 90, and the choke valve opening adjusting mechanism 106 are mainly shown in FIGS. The description will be given with reference.

  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.

  Also, when the choke valve 62 is closed to enrich the air-fuel ratio, such as when the engine 10 is started, the electric motor 70 operates the throttle valve opening / closing mechanism 72 and displaces the link 96 in conjunction with it to move the choke shaft 92 Is used to open and close the choke valve 62. 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 (hereinafter referred to as “over fully open position”) that exceeds the position by a predetermined opening (indicated by symbol α in FIG. 7).

  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.

  Here, the operation of the choke valve opening adjusting mechanism 106 will be described with reference to FIGS. FIG. 7 shows the choke valve opening adjusting mechanism 106 when the wax is contracted, as in FIG. 3, and FIG. 8 shows it when the wax is expanded.

  As described above, in the choke valve opening adjusting mechanism 106, when the ambient temperature is relatively low, specifically, less than the operating temperature of the choke valve opening adjusting mechanism 106 that is a thermo wax, the wax in the wax portion 106a contracts. Therefore, the protrusion amount L of the drive pin 106d is minimized. As shown in FIGS. 3 and 7, the driving pin 106d at this time does not contact the side surface 96e of the link 96 or slightly contacts it. That is, the tip 106d1 of the drive pin 106d when the wax is contracted is either the link 96 (FIG. 3) that holds the choke valve 62 in the fully open position or the link 96 (FIG. 7) that holds the choke valve 62 in the fully closed position. Even in the state, it is configured not to contact the side surface 96e.

  When the ambient temperature rises due to exhaust heat from the engine 10 or the heat generated by the heater 106g and reaches the operating temperature or more, the wax expands and pushes the rod 106b and the flange 106c upward as shown in FIG. Along with this, the drive pin 106d is displaced upward in the drawing against the urging force of the return spring 106f, and the protrusion amount L increases. The operating temperature is set to about 70 ° C., for example.

  Therefore, when the choke valve 62 is in the fully closed position (FIG. 7), if the displacement of the drive pin 106d due to the expansion of the wax described above occurs, the drive pin 106d presses the side surface 86e of the link 96 as shown in FIG. The link 96 is displaced clockwise around the rotation shaft 100. Accordingly, the second pin 96 is separated from the outer peripheral surface of the third gear 78, while 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 counterclockwise in the figure, and the choke valve 62 is opened to the fully open position. In this way, the drive pin 106d drives the choke valve opening / closing mechanism 90 (link 96, arm 94, etc.) according to the expansion / contraction of the wax to adjust the opening degree of the choke valve 62.

  As described above, in this embodiment, the choke valve 62 is opened and closed by the choke valve opening and closing mechanism 90 that is linked to the operation of the throttle valve opening and closing mechanism 72, and the choke valve 62 opened and closed by the choke valve opening and closing mechanism 90 is opened. The degree can be adjusted according to the ambient temperature using the choke valve opening adjusting mechanism 106.

  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. 9 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 112. 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 biasing force of the throttle return spring 84. At the same time, the choke valve 62 is brought into a fully closed position by the choke return spring 102. In the engine 10, it is assumed that a predetermined time has elapsed since the previous stop, that is, a cold start, the ambient temperature of the choke valve opening adjusting mechanism 106 is relatively low, and the wax is contracted.

  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. After the combination switch 114 is operated to the on position by the operator, the recoil starter 44 is operated, the power coil 40 starts generating power, and the ECU 112 is activated. First, in S10, the throttle valve 60 is in the over fully open position. The operation of the electric motor 70 is controlled so as to be driven (opened / closed) between the fully opened position and the fully opened 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 open position, as shown in FIGS. As a result, the air-fuel ratio in the intake passage 56 is enriched (a rich air-fuel ratio state), and the startability of the engine 10 is improved.

  Next, the routine proceeds to S12, where it is determined whether or not the choke is necessary, in other words, whether or not the warm-up operation is finished and the rich air-fuel ratio state by the choke valve 62 needs to be stopped. The determination in S12 is made based on the output of the NE detection circuit 120, and when the engine speed exceeds a predetermined value (for example, 3000 rpm), it is determined that choke is not necessary.

  If the result in S12 is negative, the process returns to S10, that is, the process in S10 is repeated until it is determined in S12 that choke is not necessary. At this time, the exhaust heat of the engine 10 increases as the engine speed increases. When the ambient temperature of the choke valve opening adjusting mechanism 106 rises to the operating temperature or higher due to exhaust heat of the engine 10, the wax expands and gradually protrudes the drive pin 106d as described above. Accordingly, the drive pin 106d displaces the link 96 to gradually rotate the choke valve 62 in the valve opening direction. In other words, the drive pin 106d decreases the fuel injection amount as the ambient temperature increases due to the increase in the engine speed. , Gradually make the enriched air-fuel ratio lean. In this manner, the opening degree of the choke valve 62 is appropriately adjusted according to the ambient temperature by the choke valve opening degree adjusting mechanism 106 until the ECU 112 is activated and the warm-up operation is completed.

  When the result in S12 is affirmative, the program proceeds to S14, where energization to the heater 106g is started to heat the wax unit 106a. As a result, the wax further expands to further drive (protrude) the drive pin 106d and forcibly open the choke valve 62 to the fully open position, thereby stopping the rich air-fuel ratio state by the choke valve 62.

  Next, in S16, normal control of the throttle valve 60 is executed. Specifically, the throttle valve 60 is driven between the fully closed position and the fully opened position (more precisely, the throttle valve 60 is set to the target in order to maintain the target engine speed input by the speed setting volume 110). The operation of the electric motor 70 is controlled so that the opening degree is reached. 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. Therefore, the choke valve 62 is not closed while the engine is operating.

  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. 10 is a flowchart showing control of the operation of the throttle valve 60 and the like when the engine 10 is stopped, among the operations of the ECU 112. The illustrated program is executed in the ECU 112 at predetermined intervals (for example, 100 msec).

  First, in S100, it is determined whether or not an instruction to stop the engine 10 has been input, specifically, whether or not the combination switch 114 has been operated to the off position. When the result in S100 is negative, the subsequent processing is skipped, while when the result is affirmative, the process proceeds to S102 to stop energization of the heater 106g, and the heating of the wax unit 106a is ended.

  Next, the process proceeds to S104, and the operation of the electric motor 70 is controlled 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 link 96 of the choke valve opening / closing mechanism 90 is driven to close the choke valve 62 to the fully closed position. However, since it is immediately after stopping energization of the heater 106g in S102, the wax is still in an expanded state. Accordingly, the drive pin 106d protruded by the expansion of the wax is in contact with the link 96, and thus the choke valve 62 is held in the fully open position by the drive pin 106d. That is, the choke valve 62 is not closed to the fully closed position immediately after the engine is stopped.

  Since the choke valve 62 is not immediately closed to the fully closed position after the engine 10 is stopped, the choke valve 62 is at the fully open position or in the vicinity thereof even during a warm start in which the engine 10 is restarted in a short time. As a result, the engine 10 can be started without excessively enriching the air-fuel ratio.

  When the ambient temperature of the choke valve opening adjusting mechanism 106 decreases after a predetermined time has elapsed after the engine is stopped, the wax contracts and gradually reduces the protruding amount L of the drive pin 106d. As a result, 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 throttle valve 60 and the choke valve 62 disposed in the intake passage 50 are connected to the throttle valve 60 via the gear mechanism (throttle valve opening / closing mechanism) 72. In a general-purpose internal combustion engine (engine) 10 including an actuator (electric motor) 70 that opens and closes the throttle valve 60, the choke valve 62 is connected to the gear mechanism 72 and the choke valve 62, and the choke is interlocked with the operation of the gear mechanism 72. A choke valve opening / closing mechanism 90 for opening / closing the valve 62 and a choke valve opening adjusting mechanism 106 for adjusting the opening of the choke valve 62 opened / closed by the choke valve opening / closing mechanism 90 according to the ambient temperature are provided. .

  Thus, the choke valve 62 can be driven by the electric motor 70 that drives the throttle valve 60. In other words, both the throttle valve 60 and the choke valve 62 can be driven by one electric motor 70. The choke valve 62 can be driven without using a new electric motor, and a space for arranging the electric motor can be eliminated. Further, the electric motor for the choke valve used in Patent Document 1, the corresponding motor driver (drive circuit) (both shown by imaginary lines in FIG. 4) and harnesses can be reduced, which is advantageous in terms of power consumption and cost. It is.

  Further, since the choke valve opening adjusting mechanism 106 is provided, it is possible to prevent the air-fuel ratio from being enriched by opening the choke valve 62 when the ambient temperature is relatively high, such as during warm start. That is, the choke valve 62 can be adjusted to an appropriate opening degree according to the ambient temperature, and fuel consumption can be improved.

  The choke valve opening adjusting mechanism 106 is connected to the wax part 106a filled with wax that expands and contracts according to the ambient temperature, and is connected to the wax part 106a, and the choke valve opening degree adjusting mechanism 106 corresponds to the expansion / contraction of the wax. The choke valve opening / closing mechanism 90 is driven to include a drive pin 106d for adjusting the opening of the choke valve 62. Thereby, the opening degree of the choke valve 62 can be adjusted with a simple configuration, and further space saving can be achieved.

  Further, the choke valve opening adjusting mechanism 106 is further configured to include a heater 106g for heating the wax portion 106a. As a result, the wax portion 106a is heated by the heater 106g after the warm-up is completed, and the choke valve opening / closing mechanism 90 is driven through the drive pin 106d by the thermal expansion of the wax to hold the choke valve 62 in the fully open position. It is also possible to configure so that the choke valve 62 is forcibly held in the fully open position after the machine is finished. Therefore, the choke valve 62 can be reliably prevented from closing during engine operation, and the choke valve 62 can be in the fully open position or in the vicinity thereof even during a warm start that is restarted in a short time after the engine is stopped. Therefore, the air-fuel ratio is not excessively enriched, and thus the fuel consumption can be further improved.

  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 of a general-purpose internal combustion engine (engine) according to an embodiment of the present invention. It is an expanded sectional view of the carburetor of the general-purpose internal combustion engine shown in FIG. It is a fragmentary sectional top view which shows the state which removed the cover of the motor case of the carburetor shown in FIG. It is explanatory drawing which shows the structure of the electronic control unit and combination switch shown in FIG. 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. 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. 2 is a flow chart showing control of the operation of a throttle valve and the like 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), 50 intake passage, 60 throttle valve, 62 choke valve, 70 electric motor (actuator), 72 throttle valve opening / closing mechanism (gear mechanism), 90 choke valve opening / closing mechanism, 106 choke valve opening adjusting mechanism 106a Wax part, 106d Driving pin, 106g Heater

Claims (3)

  In a general-purpose internal combustion engine including a throttle valve and a choke valve disposed in an intake passage and an actuator connected to the throttle valve via a gear mechanism to open and close the throttle valve, the general purpose internal combustion engine is connected to the gear mechanism and the choke valve. A choke valve opening / closing mechanism for opening / closing the choke valve in conjunction with the operation of the gear mechanism, and a choke valve opening adjusting mechanism for adjusting the opening of the choke valve opened / closed by the choke valve opening / closing mechanism according to the ambient temperature A general-purpose internal combustion engine comprising:   The choke valve opening adjusting mechanism is connected to the wax portion that is filled with wax that expands and contracts according to the ambient temperature, and the choke valve opening / closing mechanism is connected to the wax portion according to the expansion / contraction of the wax. 2. The general-purpose internal combustion engine according to claim 1, further comprising a drive pin that is driven to adjust the opening of the choke valve.   The general-purpose internal combustion engine according to claim 2, wherein the choke valve opening adjusting mechanism further includes a heater for heating the wax portion.

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