Patent Application
20220325659
This disclosure relates to an air leading type stratified scavenging two-stroke internal combustion engine and an engine-driven working machine using the internal combustion engine as a power source.
As described in Paragraph [0002] of Patent Literature 1, a two-stroke internal combustion engine that performs scavenging with an air-fuel mixture is often used in portable working machines such as brush cutters and chainsaws. This kind of two-stroke internal combustion engine includes a scavenging passage that allows communication between a crank chamber and a combustion chamber. An air-fuel mixture, which has been pre-compressed in the crank chamber, is introduced into the combustion chamber through the scavenging passage, and scavenging is performed with the air-fuel mixture.
Further, as described in Paragraph [0003] of patent literature 1, the two-stroke internal combustion engine has a commonly known problem, “air-fuel mixture (fresh) air blow-by”. To solve this problem, an air leading type stratified scavenging two-stroke internal combustion engine has been proposed and already put into practical use (see Patent Literature 2).
In the air leading type stratified scavenging two-stroke internal combustion engine, the air-fuel mixture is supplied to the crank chamber through an intake port during an intake stroke in which a piston moves from a bottom dead center toward a top dead center. At the same time, air is supplied to the scavenging passage through an air passage. Next, when a scavenging port is opened during a combustion stroke and an exhaust stroke in which the piston moves down from the top dead center, the air in the scavenging passage is introduced into the combustion chamber before the air-fuel mixture in the crank chamber is introduced thereinto. As a result, a combustion exhaust gas is discharged from an exhaust port (scavenging is performed). Subsequently, the air-fuel mixture in the crank chamber is introduced into the combustion chamber. Thus, the air leading type stratified scavenging two-stroke internal combustion engine has an advantage in that the air-fuel mixture blow-by during scavenging is reduced.
Further, an air leading type stratified scavenging two-stroke internal combustion engine having an air duct and a fuel pipe is described in Patent Literature 3 (see, for example, claim 3, and FIG. 2A to FIG. 4C of Patent Literature 3). The air duct allows supply of an atmospheric air for pre-scavenging of the combustion chamber to the scavenging passage. The fuel pipe allows supply of a fuel from a carburetor to the air duct so as to smoothen start of the internal combustion engine. In an embodiment illustrated in FIG. 3 of Patent Literature 3, there is described an air-leading type stratified scavenging two-stroke internal combustion engine in which supply of the fuel from the fuel pipe to the air duct is controlled by a controller including various kinds of sensors.
Further, in Patent Literature 4, there is described an air leading type stratified scavenging two-stroke internal combustion engine including an auxiliary passage (corresponding to the air duct of Patent Literature 3) that is open to the scavenging passage. The fuel passage, which communicates with a fuel accumulating chamber, is open to the auxiliary passage. The amount of fuel supplied to the internal combustion engine via the auxiliary passage is controlled by at least one valve (see, for example, claim 1 and the drawings of Patent Literature 4).
In the air leading type stratified scavenging two-stroke internal combustion engine described in Patent Literature 3, however, the fuel is supplied to the air duct for the purpose of simplifying the engine start to improve startability (see claim 1 and Paragraph [0003] of Patent Literature 3). Thus, the fuel is supplied to the air duct only at the time of engine start.
Further, in the air leading type stratified scavenging two-stroke internal combustion engine described in Patent Literature 4, the fuel is supplied to the auxiliary passage for the purpose of reducing the amount of fuel consumption during idling of the engine to decrease an exhaust gas value (see Paragraph [0005] of Patent Literature 4). Thus, in Patent Literature 4, there is only disclosed control of the amount of fuel supply to the auxiliary passage during idling.
Incidentally, in the air leading type stratified scavenging two-stroke internal combustion engine, air for pre-scavenging may lead to dilution of a fuel concentration or adversely affect responsiveness of the engine at a time of an accelerating or decelerating operation. Thus, the air leading type stratified scavenging two-stroke internal combustion engine has a disadvantage in poor readiness for an operating condition at times other than engine start and idling.
The present invention has been made in view of the circumstances described above, and has an object to provide an air leading type stratified scavenging two-stroke internal combustion engine having improved readiness for an operating condition at times other than engine start and idling and an engine-driven working machine including the internal combustion engine.
In order to solve the problem described above, according the present invention of claim 1, there is provided an air leading type stratified scavenging two-stroke internal combustion engine, including: an air passage configured to allow supply of air to a scavenging passage configured to allow communication between a crank chamber and a combustion chamber; at least one sensor configured to detect an operating condition of the engine; and a fuel valve configured to control fuel supply to the air passage based on detection performed by the at least one sensor, wherein the fuel supply to the air passage is controlled by the fuel valve at times other than start and idling of the engine or at needed times in addition to the start or the idling of the engine.
According to the present invention of claim 2, in the air leading type stratified scavenging two-stroke internal combustion engine of claim 1, the at least one sensor includes any one of a sensor configured to estimate a temperature of the engine, a sensor configured to estimate an accelerating operation of the engine, which is performed by an operator, and a sensor configured to estimate a decelerating operation of the engine, which is performed by the operator.
According to the present invention of claim 3, in the air leading type stratified scavenging two-stroke internal combustion engine according to claim 2, the at least one sensor comprises a rotation speed sensor configured to detect a rotation speed of the engine.
According to the present invention of claim 4, in the air leading type stratified scavenging two-stroke internal combustion engine according to claim 2 or 3, the sensor configured to estimate the temperature of the engine comprises a temperature sensor configured to directly detect a temperature.
According to the present invention of claim 5, in the air leading type stratified scavenging two-stroke internal combustion engine according to claim 4, the temperature sensor is mounted to a cylinder.
According to the present invention of claim 6, the air leading type stratified scavenging two-stroke internal combustion engine according to any one of claims 2 to 5 further includes a control configured to stop the engine immediately after detection of a predetermined high temperature of the engine.
According to the present invention of claim 7, the air-leading type stratified scavenging two-stroke internal combustion engine according to any one of claims 1 to 6 further includes a piston configured to slidably reciprocate inside a cylinder coupled to the crank chamber, the piston having a peripheral surface with piston grooves configured to bring the air passage and the scavenging passage into communication with each other at predetermined timing.
According to the present invention of claim 8, the air leading type stratified scavenging two-stroke internal combustion engine according to any one of claims 1 to 7 further includes an air-fuel mixture passage communicating with the crank chamber. The fuel valve is installed in a component obtained by integrally forming the air passage and the air-fuel mixture passage.
According to the present invention of claim 9, in the air leading type stratified scavenging two-stroke internal combustion engine according to any one of claims 1 to 7, the fuel valve is installed in an intake pipe being separate from a carburetor.
According to the present invention of claim 10, in the air leading type stratified scavenging two-stroke internal combustion engine according to any one of claims 1 to 7, the fuel valve is installed in a carburetor.
According to the present invention of claim 11, there is provided an engine-driven working machine, including the air leading type stratified scavenging two-stroke internal combustion engine of any one of claims 1 to 10 as a power source.
According to the present invention of claim 1, the fuel is supplied to the air passage in accordance with the operating condition of the engine as needed at times other than the start and the idling of the engine or the start or the idling of the engine. When the fuel is supplied to the air passage, the fuel flows from the scavenging passage directly into the combustion chamber. Thus, high responsiveness to combustion is achieved. Meanwhile, the fuel is not supplied to the air passage when the fuel is not needed. Thus, air, which is supplied from the air passage to the scavenging passage, first flows into the combustion chamber to perform scavenging. Thus, air-fuel mixture blow-by, which is a problem specific to a two-stroke internal combustion engine, is prevented.
According to the present invention of claim 2, when the at least one sensor includes the sensor configured to estimate the temperature of the engine, the following actions and effects are obtained. Specifically, when the temperature of the engine, which is detected by the sensor, reaches a predetermined high temperature, the fuel is supplied to the air passage. This fuel directly cools a piston and a cylinder. Thus, the piston and the cylinder are readily and quickly cooled. Preferably, the fuel mixed with lubricating oil is used. In this case, lubrication between the piston and the cylinder is readily and quickly achieved. Further, preferably, when the temperature of the engine reaches the predetermined high temperature, the fuel is supplied to the air passage immediately before the engine is stopped. In this case, the piston and the cylinder are directly cooled. Thus, seizure of the piston and the cylinder is prevented.
Further, according the present invention of claim 2, when the at least one sensor includes the sensor configured to estimate the accelerating operation, the following actions and effects are obtained. Specifically, when the accelerating operation of the engine, which is performed by the operator, is detected by the sensor, the fuel is supplied to the air passage. The fuel directly flows into the combustion chamber, resulting in high reactivity to combustion. Thus, acceleration is achieved in quick response to the accelerating operation of the engine, which is performed by the operator.
Still further, according to the present invention of claim 2, when the at least one sensor includes the sensor configured to estimate the decelerating operation, the following actions and effects are obtained. Specifically, when the decelerating operation of the engine, which is performed by the operator, is detected, the fuel is supplied to the air passage or the fuel supply to the air passage is stopped. In the former case, the fuel is supplied under an air excessive state to instantaneously assist deceleration, achieving the deceleration in quick response to the decelerating operation of the engine, which is performed by the operator. In the latter case, the fuel supply is stopped under a fuel excessive state to instantaneously assist deceleration. Also in this case, the deceleration is achieved in quick response to the decelerating operation of the engine, which is performed by the operator.
According to the present invention of claim 3, it is economical because an existing rotation speed sensor can be used.
According to the present invention of claim 4, the temperature is directly detected by the temperature sensor. Thus, a high-temperature state, in which a failure is liable to occur in the piston or the cylinder, can be more accurately detected. Further, the rotation speed sensor and the temperature sensor are operated in cooperation with each other depending on the case. As a result, the high-temperature state, in which the piston and the cylinder are liable to be damaged, can be more accurately detected.
According to the present invention of claim 5, the temperature is detected in the vicinity of the piston and the cylinder in which a failure may occur. Thus, the high-temperature state can be more quickly and accurately detected.
According to the present invention of claim 6, the engine is stopped immediately after the detection of the predetermined high temperature. Thus, seizure of the piston and the cylinder is prevented.
According to the present invention of claim 7, the fuel supplied to the air passage reaches the scavenging passage via the piston grooves. Specifically, the fuel is brought into direct contact with the peripheral surface of the piston together with air. Thus, cooling performance for the piston is improved.
According to the present invention of claim 8, the air passage, the air-fuel mixture passage, and the fuel valve can be arranged compactly. Thus, such a configuration is particularly suitable when the engine of this disclosure is used as a power source for a small working machine.
According to the present invention of claim 9, it is economical because an existing carburetor can be used without change.
According to the present invention of claim 10, when the carburetor including the fuel valve is prepared in advance, faster and labor-saving assembly work for the engine is achieved. Further, a compact engine can be achieved by installing the fuel valve in a free space in the carburetor.
According to the present invention of claim 11, the actions and effects of the present invention of claims 1 to 10 are obtained.
Now, with reference to the accompanying drawings, a description is given of the embodiments of the present invention.
An air leading type stratified scavenging two-stroke internal combustion engine (hereinafter simply referred to as “engine”) according to the present invention is of air cooled type to be mainly mounted in a portable engine-driven working machine as a power source. Examples of a working machine in which the engine of the present invention is used include portable working machines such as a chainsaw, a brush cutter, a power cutter, a hedge-trimmer, and a power blower.
As illustrated in
An exhaust port 12, an intake port 13, and at least one scavenging port 14 are open on an inner wall of the cylinder 3. These ports 12, 13, and 14 are controlled to be opened and closed at publicly known predetermined timing through the reciprocation of the piston 4. The exhaust port 12 communicates with a muffler (not shown) via an exhaust pipe 15. The intake port 13 communicates with a carburetor 17 via an intake pipe 16. The scavenging port 14 communicates with the crank chamber 8 via a scavenging passage 18. Although not shown, the intake port 13 may be formed in the crankcase 7 in place of the cylinder 3. In this case, a check valve is disposed. The check valve is configured to prevent backflow of an air-fuel mixture in the crank chamber 8 toward the intake pipe 16 when the piston 4 moves down.
Air, which has been purified by an air cleaner 19, is mixed with a fuel in the carburetor 17 to generate an air-fuel mixture. The air-fuel mixture is sucked into the crank chamber 8 through the intake pipe 16 and the intake port 13. The air-fuel mixture is generated in the carburetor 17, and is sucked into the crank chamber 8 during an intake stroke in which a pressure in the crank chamber 8 becomes negative. A type of the carburetor 17 is not limited and as the carburetor 17 suitable for a portable engine-driven working machine including a machine body with a posture frequently changed during work, it is preferred that a diaphragm carburetor having a commonly known configuration be used. The carburetor 17 is coupled to a fuel tank 42 through a main fuel passage 20.
The engine 1 includes an air passage 21 that allows supply of air to the scavenging passage 18 so as to achieve air leading type stratified scavenging. A check valve 21a configured to prevent backflow of air from the scavenging passage 18 is disposed in the air passage 21. The air passage 21 is coupled to an air intake port 22 formed at an end of the scavenging passage 18, which is located on a side closer to the scavenging port 14. The air passage 21 guides the air that has been purified by the air cleaner 19 to the scavenging passage 18. The air is sucked from the air intake port 22 into the scavenging passage 18 through the air passage 21 during the intake stroke in which the pressure of the crank chamber 8 becomes negative. During a scavenging stroke, the air flows from the scavenging port 14 into the cylinder 3 before the air-fuel mixture in the crank chamber 8 flows thereinto, and an exhaust gas in the combustion chamber 6 is discharged from the exhaust port 12.
The engine 1 includes a fuel supply passage 23 configured to allow supply of the fuel to the air passage 21. The fuel supply passage 23 is coupled to the fuel tank 42. A fuel valve 24 is disposed in the fuel supply passage 23. When the fuel valve 24 is opened and the pressure in the crank chamber 8 becomes negative during the intake stroke, the air and the fuel pass through the air passage 21 and are sucked into the scavenging passage 18 through the air intake port 22. The fuel valve 24 is electrically controllable. For example, a solenoid valve (electromagnetic valve) is used as the fuel valve 24. For example, a battery mounted in an engine-driven working machine may be used as a power supply 25 for the fuel valve 24.
The fuel valve 24 is controlled to be opened and closed by a controller 26 including a microcomputer. A result of estimation performed by at least one sensor 27 (27a to 27d) configured to detect an operating condition of the engine 1 is input to the controller 26. The controller 26 controls fuel supply to the air passage 21 with the fuel valve 24 at times other than start and idling of the engine 1 or at needed times in addition to the start or the idling of the engine 1 based on the detection performed by the sensor 27.
At least any one of a sensor 27a, a sensor 27b, a sensor 27b, and a sensor 27d may be used as the at least one sensor 27. The sensor 27a is configured to detect and estimate a temperature of the engine 1. The sensor 27b is configured to detect and estimate a rotation speed (rotation number) of the engine 1. The sensor 27c is configured to detect and estimate an accelerating operation of the engine 1, which is performed by an operator. The sensor 27d is configured to detect and estimate a decelerating operation of the engine 1, which is performed by the operator.
When the rotation speed sensor 27b configured to detect the rotation speed of the engine 1 is used in addition to the temperature sensor 27a configured to detect the temperature of the engine 1 so that the temperature sensor 27a and the rotation speed sensor 27b are operated in cooperation with each other, a high-temperature state, in which the piston 4 and the cylinder 3 are liable to be damaged by seizure, can be more accurately detected.
It is preferred that the sensor 27a configured to estimate the temperature be the temperature sensor 27a configured to directly detect the temperature. It is more preferred that the temperature sensor 27a directly detect a temperature of the cylinder 3 and thus be mounted to the cylinder 3. It is preferred that a specific position on the cylinder 3 at which the temperature sensor 27a is mounted be the cylinder head 5 that is likely to have the highest temperature.
The sensor 27c configured to detect the accelerating operation and the sensor 27d configured to detect the decelerating operation both detect, for example, a position or an angular position of an output operating member (such as a throttle trigger or a throttle lever) 28 of the engine-driven working machine or a throttle valve 29 of the carburetor 17.
Next, an operation of the engine 1 of
As illustrated in
As illustrated in
As illustrated in
In the above-mentioned working strokes of the engine 1, when the fuel valve 24 is actuated to be opened by the controller 26 based on the detection performed by the sensor 27, the fuel is supplied to the air passage 21 as needed in accordance with the operating condition of the engine 1. When the fuel is supplied to the air passage 21, the fuel directly flows into the combustion chamber 6 through the scavenging passage 18. Thus, high responsiveness to combustion is achieved. Meanwhile, the fuel is not supplied to the air passage 21 when the fuel is not needed. Therefore, the air, which has been supplied through the air passage 21 to the scavenging passage 18, first flows into the combustion chamber 6 to perform scavenging. Thus, air-fuel mixture blow-by, which is a problem specific to a two-stroke internal combustion engine, is prevented.
When the temperature sensor 27a detects that the temperature of the engine 1 has reached a predetermined high temperature, the fuel valve 24 is actuated to be opened by the controller 26 to allow the supply of the fuel to the air passage 21. The fuel directly cools the piston 4 and the cylinder 3. Thus, the piston 4 and the cylinder 3 are readily and quickly cooled. This cooling prevents seizure of the engine 1.
Further, a fuel for a two-stroke internal combustion engine is mixed gasoline and lubricating oil. Thus, when the fuel (mixed fuel) is supplied to the air passage 21, lubrication between the piston 4 and the cylinder 3 is readily and quickly achieved with the lubricating oil contained in the fuel. The lubrication also prevents the seizure of the engine 1.
By increasing the amount of fuel supplied to the air passage 21, it is possible to make the air-fuel mixture in the combustion chamber 6 excessive enough to stop the engine. In this way, when the temperature becomes high to bring about a risk of seizure of the engine 1, the engine 1 can be forced to be stopped immediately. The engine 1 is forced to be stopped immediately before occurrence of seizure of the engine 1. Accordingly, the seizure of the engine 1 can be prevented.
When the sensor 27c detects the accelerating operation of the engine 1, which is performed by the operator to increase a speed of the engine 1 to a predetermined value or higher, the fuel is supplied to the air passage 21. The fuel directly flows into the combustion chamber 6, and thus high responsiveness to the combustion is achieved. Accordingly, the acceleration in quick response to the accelerating operation of the engine 1, which is performed by the operator, is achieved.
When the sensor 27d detects the decelerating operation of the engine 1, which is performed by the operator to decrease the speed of the engine 1 to a predetermined value or lower, the fuel is supplied to the air passage 21 or the fuel supply to the air passage 21 is stopped. In the former case, the fuel is supplied under an air excessive state to instantaneously assist the deceleration, achieving the deceleration in quick response to the decelerating operation of the engine 1, which is performed by the operator. In the latter case, the fuel supply is stopped under a fuel excessive state to instantaneously assist the deceleration, also achieving the deceleration in quick response to the decelerating operation of the engine 1, which is performed by the operator.
Next, a modification example of
A piston 101 of
A cylinder wall 100 of a cylinder 105, which is used together with the piston 101 of
As illustrated in
Under a state illustrated in
In the engine including a combination of the piston 101 and the cylinder 105 illustrated in
Next, an engine 30 according to another embodiment of this disclosure is described with reference to
As for the engine 30 of
The carburetor 17 includes a fuel pump 36, a fuel chamber 38, and a main fuel discharge port 40. The fuel pump 36 is connected to a fuel tank 42 of an engine-driven working machine via a check valve 35. The fuel chamber 38 is connected to the fuel pump 36 via a check valve 37. The main fuel discharge port 40 is connected to the fuel chamber 38 via a check valve 39. The main fuel discharge port 40 is open to an intake passage 41 of the carburetor 17.
The fuel pump 36 is preferably a pulse-control diaphragm pump that is driven by a pressure pulse generated in a crank chamber 8 of the engine 30. The fuel pump 36 pumps up a fuel from the fuel tank 42, and supplies the fuel to the fuel chamber 38. A decrease in pressure in the intake passage 41, which is caused by a venturi portion 43, causes the fuel in the fuel chamber 38 to be sucked into the intake passage 41 through the main fuel discharge port 40. When an output operating member (such as a throttle trigger or a throttle lever) of the engine-driven working machine is operated by an operator, an opening degree of a throttle valve 29 disposed in the intake passage 41 is adjusted. As a result, an engine output in accordance with the opening degree of the throttle valve 29 is obtained.
The carburetor 17 also arranges a manual pump 44 disposed therein. The manual pump 44 is configured to pump up the fuel in the fuel tank 42 into the fuel chamber 38 before start of the engine 30. The fuel pump 44 is provided to a return flow passage 45 extending from the fuel chamber 38 to the fuel tank 42. When the operator operates the manual pump 44 before the start of the engine 30, the fuel in the fuel tank 42 is supplied to the fuel chamber 38. As a result, the fuel chamber 38 is filled with the fuel. At the same time, a surplus fuel and a gas such as air bubbles in the fuel chamber 38 are pushed into the fuel tank 42. The manual pump 44 may be provided integrally with the carburetor 17, or may be separate from the carburetor 17.
A fuel supply device 46 for the engine 30 of
In the embodiment illustrated in
An orifice (valve seat or flow passage hole) 55 is open to the valve chamber 49. The orifice 55 communicates with the air passage 34 of the intake pipe 31 through a fuel discharge passage 56 and a fuel discharge port 57. The fuel discharge port 57 is open to the air passage 34 of the intake pipe 31. The fuel valve 48 configured to open and close the orifice 55 is controlled by a controller 26 including a microcomputer similarly to the fuel valve 24 of
The fuel valve 48 is electrically controllable. For example, a solenoid valve (electromagnetic valve) is used as the fuel valve 48. For example, a battery mounted in an engine-driven working machine may be used as the power supply 25 for the fuel valve 48.
As described in Japanese Patent Application Laid-open No. Hei 6-159146, actuation of the fuel valve 48 at the time of engine start can be controlled by an output signal from a primary coil of a flywheel magneto that is rotated through an operation of a recoil starter 58. The recoil starter 58 is configured to start the engine 30. More specifically, when an operator operates the recoil starter 58, an electromagnetic coil 48a of the fuel valve 48 is excited by the controller 26 based on an output signal from the primary coil of the flywheel magneto to thereby actuate the fuel valve 48 to be opened. Then, when the engine 30 reaches idling speed, the electromagnetic coil 48a of the fuel valve 48 is degaussed by the controller 26 based on the output signal from the primary coil of the flywheel magneto to thereby close the fuel valve 48.
When starting the engine 30 having the configuration, the operator first operates the manual pump 44 to supply the fuel in the fuel tank 42 to the fuel chamber 38. As a result, the fuel in the fuel tank 42 moves to the fuel pump 36 and the fuel chamber 38 through the valve chamber 49 so that the fuel chamber 38 is filled with the fuel. At the same time, a surplus fuel and a gas such as air bubbles in the fuel chamber 38 are pushed to the fuel tank 42 through the return flow passage 45. As a result, the engine 30 is smoothly and reliably started.
Subsequently, the operator turns on a start switch for the engine 30, and performs a pulling operation on the recoil starter 58. Then, a piston 4 reciprocates inside a cylinder block 2 through intermediation of a crankshaft 10 and a connecting rod 11. In synchronization with the reciprocation of the piston 4, ignition is performed by a spark plug 9. The reciprocation of the piston 4 inside the cylinder block 2 generates a negative pressure in the intake passage 41 of the carburetor 17 to cause the fuel in the fuel chamber 38 to be sucked into the intake passage 41 through the main fuel discharge port 40. As a result, an air-fuel mixture is generated.
Simultaneously, the pulling operation performed by the operator on the recoil starter 58 actuates the fuel valve 48 to be opened. Thus, the orifice 55 is opened, and the fuel in the valve chamber 49 is sucked into the air passage 34 through the fuel discharge passage 56 by the negative pressure in the air passage 34. As a result, a starting fuel is added to air flowing through the air passage 34, and the air and the starting fuel are supplied to the scavenging passage 18. When the scavenging port 14 is opened, the starting fuel, which has been sucked into the scavenging passage 18, flows into the combustion chamber 6. As a result, the engine 30 is smoothly started. When the engine 30 reaches the idling speed, the fuel valve 48 is automatically closed by the controller 26.
In the embodiment of
In the example of
As a preferred embodiment, the intake pipe 31 is preferably formed of a contractible bellows, without limitation. By using a contractible bellows, when the adapter is disposed between an existing carburetor 17 without the fuel valve 48 or the valve chamber 49 and the intake pipe 31, a thickness dimension of the adapter 59 can be absorbed through contractibility of the intake pipe 31. Thus, an increase in size of a structure that covers the carburetor 17 and the cylinder block 2 can be prevented.
As a suitable example of an arrangement mode of the fuel valve 48, the fuel valve 48 can be installed in the intake pipe 31, which is a component obtained by integrally forming the air passage 34 and the air-fuel mixture passage 33. This configuration enables the air passage 34, the air-fuel mixture passage 33, and the fuel valve 48 to be arranged compactly which is particularly suitable as a power source for a small working machine.
As another suitable example of the arrangement mode of the fuel valve 48, the fuel valve 48 may be installed in the intake pipe 31 being separate from the carburetor 17. In this way, the existing carburetor 17 can be used without modification, which is economical.
As a further suitable example of the arrangement mode of the fuel valve 48, the fuel valve 48 may be installed in the carburetor 17. In this case, when the carburetor 17 including the fuel valve 48 is prepared in advance, there is an advantage in that faster and labor-saving assembly work for the engine 30 is achieved. Further, a compact engine 30 can be achieved by installing the fuel valve 48 in a free space inside the carburetor 17.
The embodiments of the present invention have been described in detail with reference to the drawings, but the present invention is not limited to those of the embodiments described above. For example, changes in design without departing from the scope of the present invention are encompassed in this disclosure. Further, technologies in the above-mentioned embodiments described above may be used in combination as long as there is no particular contradiction or problem in, for example, purpose and configuration.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-183639 | Oct 2019 | JP | national |
The present application is a National Phase of International Application Number PCT/JP2020/035976, filed Sep. 24, 2020, and claims priority to Japanese Application number 2019-183639, filed Oct. 4, 2019.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2020/035976 | 9/24/2020 | WO |
