Engine, self-starter unit, and method for altering engine specifications

An engine is equipped with a starter motor which is attached to an engine main body and is configured to perform cranking of a crankshaft. The engine is further equipped with a battery pack (37). The battery pack is equipped with a lithium-based cell which is attached to the engine main body and which is configured to supply electric power which drives the starter motor.

TECHNICAL FIELD

The present invention relates to an engine, a self-starter unit, and a method for altering engine specifications.

The present application claims priority based on Japanese Patent Application No. 2014-219908 filed on Oct. 29, 2014, the contents of which are incorporated herein by reference.

BACKGROUND ART

A so-called general-purpose engine used for agricultural working machines and the like often includes a so-called recoil starter which performs cranking by pulling a rope. Since this recoil starter needs to vigorously and greatly pull the rope, there are cases in which a starting manipulation of an engine becomes a burden on elderly users or the like.

In automobiles and the like, a self-starter is mounted for starting the engine. When the self-starter is used in this way, the engine can be easily started with only a switch manipulation. As a power supply of the self-starter, in many cases, a lead storage battery is used in terms of maintenance and capacity. The lead storage battery used to start the engine is generally large and heavy. Although there is no problem when an installation space is sufficient as in a vehicle such as an automobile, there are cases in which it is difficult to install the lead storage battery in terms of weight increase or securing of the installation space when trying to install the lead storage battery in an agricultural working machine or the like.

Patent Document 1 suggests a technique for reducing a burden on a user caused at the time of starting an engine of a working machine or the like. In Patent Document 1, a self-starter that performs cranking using the power of an electric motor is added to a small engine, and a battery pack made of a lithium secondary battery is housed in a switch box provided at a different position from the small engine.

RELATED ART DOCUMENT

Patent Document

SUMMARY

Problems to be Solved by the Invention

In the technique described in Patent Document 1, a battery pack is housed in a switch box installed on a handlebar of a working machine, which is a location separate from an engine main body of a small engine. Therefore, the size of the switch box increases by an amount corresponding to the housing space of the battery pack, and the weight of the switch box increases. As a result, there is a possibility that adverse influences such as degradation of operability of the handlebar may occur.

An object of the present invention is to provide an engine, a self-starter unit, and a method for altering engine specifications in which the engine can be easily started and degradation of operability accompanied with an increase in the size or an increase in weight of a device driven by an engine output can be suppressed.

Means for Solving the Problem

According to a first aspect of the present invention, an engine is equipped with a starter motor which is attached to an engine main body and is configured to perform cranking of a crankshaft. The engine further includes a battery pack equipped with a lithium-based cell which is attached to the engine main body and which is configured to supply electric power which drives the starter motor.

With such a configuration, the engine can be started by the starter motor, and there is no need to install a power supply driving the starter motor in a device such as a working machine on which the engine is mounted. By using a lithium-based cell, the size of the battery necessary to drive the starter motor can be set to be smaller than when a lead storage battery is used. Therefore, it is possible to miniaturize the battery pack and to easily attach the battery pack to a dead space or the like of the engine main body. As a result, it is possible to easily start the engine, and it is possible to suppress degradation of operability accompanied with an increase in the size and weight of the device driven by the engine output.

According to a second aspect of the present invention, in the engine according to the first aspect, a fan configured to supply cooling air to a cylinder portion of the engine main body may be disposed on a first side of a crankcase of the engine main body in an axial direction of the crankshaft. The starter motor may be disposed on a second side of the crankcase. The starter motor and the lithium-based cell may be disposed on an opposite side of the cylinder portion across an axis of the crankshaft.

With this configuration, it is possible to dispose the battery pack at the farthest position from the cylinder having the highest temperature in the engine main body. Along with the battery pack, the starter motor can also be disposed at the farthest position from the cylinder portion. Therefore, it is possible to suppress a temperature increase of the starter motor or the battery pack. Further, it is possible to shorten the wiring through which a large current flows between the starter motor and the battery pack, thereby reducing the resistance due to the wiring. As a result, it is possible to reduce the burden on the starter motor or the lithium-based cell, and to stably drive the starter motor with high efficiency.

According to a third aspect of the present invention, in the engine, the battery pack according to the second aspect may be attached to a fan cover that covers the fan.

The fan cover which covers the fan that sends the cooling air to the cylinder serves as a passage of outside air to be taken in by the fan. Therefore, the temperature becomes relatively lower than in other places in the engine main body. As a result, the temperature increase of the battery pack can be further suppressed.

According to a fourth aspect of the present invention, in the engine according to any one of the first to third aspects, the engine may further include a switch unit which is attached to the engine main body and is configured to perform a starting manipulation of the engine main body, and the battery pack may be disposed below the switch unit.

With this configuration, it is possible to effectively utilize the space below the switch unit attached to the engine main body.

According to a fifth aspect of the present invention, in the engine, the battery pack according to any one of the first to fourth aspects may be attached to the engine main body via a bracket.

With this configuration, the battery pack can be attached to and detached from the engine main body by simply attaching and detaching the bracket to and from the engine main body. As a result, the battery pack can be easily attached to and detached from the engine main body at the time of assembly or maintenance.

According to a sixth aspect of the present invention, in the engine, the switch unit and the battery pack according to the fifth aspect may be attached to the engine main body via a single bracket.

With such a configuration, the switch unit and the battery pack can be integrally attached to the engine main body. For example, when the switch unit is attached to the engine main body via the bracket, the bracket for the switch unit can be used as a bracket for attaching the battery pack to the engine main body.

According to a seventh aspect of the present invention, the engine may further include a control unit which performs energization from the battery pack to the starter motor, only when the starter motor according to any one of the first to sixth aspects performs cranking.

With such a configuration, it is possible to suppress discharge from the battery pack when the starter motor does not perform cranking. When the battery pack is charged from the generator of the engine main body, the charging efficiency can be improved.

According to an eighth aspect of the present invention, a self-starter unit includes a starter motor which performs cranking of an engine. The self-starter unit further includes a battery pack equipped with a lithium-based cell which is attached to the engine and is configured to supply electric power to the starter motor. The self-starter unit further includes a control unit which controls electric power supply from the battery pack to the starter motor.

By attaching the self-starter unit to the engine main body, it is possible to easily start the engine, and it is possible to suppress degradation of operability accompanied with an increase in the size or weight of the device driven by the engine output.

According to a ninth aspect of the present invention, in the self-starter unit, the control unit in the eighth aspect may perform energization from the battery pack to the starter motor only when the starter motor performs cranking.

With such a configuration, it is possible to suppress discharge from the battery pack when the starter motor does not perform cranking. When the battery pack is charged from the generator mounted on the engine main body, its charging efficiency can be improved.

According to a tenth aspect of the present invention, there is provided a method for altering engine specifications, the method including attaching the self-starter unit of the eighth or ninth aspect to an engine having a recoil starter.

For example, a self-starter unit including a battery pack is attached to an engine having only a recoil starter as a starting device. As a result, the cranking function of the starter motor can be added to the engine, without securing a space for installing the battery pack on the device side operated by the engine output. As a result, it is possible to easily start the engine in a normal state while maintaining the recoil starter as an emergency starting device.

Advantage of the Invention

According to the engine, the self-starter unit, and the method for altering engine specifications, it is possible to easily start the engine and to suppress the degradation of the operability accompanied with an increase in size or an increase in weight of the device driven by the engine output.

DESCRIPTION OF THE EMBODIMENTS

Embodiments

Hereinafter, an engine, a self-starter unit, and a method for altering engine specifications according to an embodiment of the present invention will be described.

FIG. 1is a front view of an engine according to an embodiment of the present invention.FIG. 2is a rear view of the engine according to the embodiment of the present invention.FIG. 3is a left side view of the engine according to the embodiment of the present invention.FIG. 4is a top view of an engine according to an embodiment of the present invention.

An engine1of this embodiment is a so-called general-purpose engine. The engine1is, for example, a single cylinder air-cooled four-stroke engine used as a driving source of an agricultural working machine or the like.

As shown inFIGS. 1 to 4, the engine1mainly includes an engine main body2, a fuel tank3, an air cleaner box4, a muffler5, a recoil starter6, and a self-starter unit7.

A cylinder portion10of the engine main body2extends toward a radial outer side of a crankshaft11. The cylinder portion10is provided to be inclined laterally with respect to a crankcase portion12. The fuel tank3for storing fuel is disposed above the crankcase portion12. An output shaft13is exposed on the rear side of the engine main body2in the embodiment. The output shaft13is linked to the crankshaft11via a reduction mechanism (not shown).

The fuel tank3is formed in a quadrangular shape in which a corner portion is chamfered by a curved surface when viewed from above. A horizontally projected area of the fuel tank3is formed to be slightly smaller than horizontally projected area of the crankcase portion12. The fuel tank3is formed in a flat shape in which its height is smaller than the width and the depth. The fuel tank3feeds fuel by its own weight to a fuel injection device for mixing fuel air or a carburetor. In this embodiment, a carburetor14(seeFIG. 3) is used.

The air cleaner box4and the muffler5are arranged in parallel with the fuel tank3in a horizontal direction. The air cleaner box4is disposed on a first side in a front-rear direction, and the muffler5is arranged on a second side opposite to the air cleaner box4in the front-rear direction. Like the fuel tank3, the air cleaner box4and the muffler5are formed in a quadrangular shape in which corner portions are chamfered by curved surfaces when viewed from above.

The air cleaner box4incorporates an air cleaner (not shown). A carburetor14is arranged below the air cleaner box4. The air cleaner box4removes dust or the like contained in the outside air by an air cleaner. Intake air from which dust or the like is removed by the air cleaner is supplied to the carburetor14. The carburetor14is connected to an intake port (not shown) formed on the front side of the cylinder portion10.

The air cleaner box4has a skirt portion4athat covers the front side of the carburetor14. In the skirt portion4a, a window portion4bfor exposing an on/off switch16(seeFIG. 1) of the engine1toward the front is formed. In the skirt portion4a, a notch portion17is formed at an intermediate position between the fuel tank3and the crankcase portion12in a height direction. A throttle lever18acapable of swinging left and right is disposed in the notch portion17. By swinging the throttle lever18aleft and right, it is possible to adjust the rotational speed of the engine1after starting. Further, in the notch portion17, a choke lever18bis disposed below the throttle lever18ato be swingable left and right.

The muffler5is connected to an exhaust port (not shown) of the cylinder portion10. After reducing the exhaust noise of the engine1, the muffler5discharges the exhaust air to the outside, more specifically, toward the left side.

The recoil starter6is attached to the front side of the crankcase portion12. The recoil starter6includes a spring, a reel, a lever, a rope (none of which is shown), a housing21, and the like.

In the recoil starter6, a rope with a handlebar20attached to its leading end is wound around a reel, and when the handlebar20is pulled, the reel rotates. The reel is connected to the crankshaft11of the engine main body2via a lever and a flywheel. The flywheel fixed to the crankshaft11includes recoil claws (not shown) that permit relative rotation between the reel and the pulley in only one direction. The lever transmits the rotational power of the reel to the crankshaft via the flywheel only when the rope is pulled and the reel rotates. For example, when the user releases her or his hand from the handlebar20, the rope is wound around the reel by the elastic force of the spring. A cooling fan (not shown) is integrally formed on the flywheel, and as the crankshaft11rotates, the air taken in from outside is sent as cooling air for cooling the outer peripheral surface of the cylinder portion10.

The recoil starter6includes a housing21in which a plurality of opening portions21afor taking in the outside air are formed. The housing21is attached to a fan cover22(seeFIG. 3) that houses a cooling fan. The fan cover22is fixed to the crankcase portion12.

As a result, the outside air flowing in from the opening portion21aof the housing21is fed toward the cylinder portion10by the cooling fan inside the fan cover22. The cooling air fed by the cooling fan performs heat exchange on the outer surface of the cylinder portion10, cools the cylinder portion10, and then is discharged to the outside from the rear side. In this embodiment, the housing21is made of a resin and the fan cover22is made of a metal. The recoil starter6is not limited to one having the aforementioned internal structure. As the recoil starter6, those having various internal structures can be applied.

As shown inFIG. 2, the self-starter unit7includes a starter motor30and a key box31.

The starter motor30performs cranking at the time of starting of the engine, in place of the aforementioned recoil starter6. The starter motor30in this embodiment is a DC motor with a brush. The starter motor30is attached to the engine main body2such that its rotor shaft32extends in the direction of the axis O1of the crankshaft11of the engine1. More specifically, in the direction of the axis O1of the crankshaft11, a cooling fan is disposed on the first side of the crankcase portion12, and the starter motor30is disposed on the second side of the crankcase portion12. In other words, the starter motor30is disposed on the side opposite to the cooling fan across the crankcase portion12in the direction of the axis O1of the crankshaft11.

In the crankcase portion12, a portion12alocated on the side opposite to the cylinder portion10across the crankshaft11in the horizontal direction and above the crankshaft11has a thickness in the depth direction thinner than the circumference of the crankshaft11. The above-mentioned starter motor30is attached to a portion in which the thickness of the crankcase portion12is formed to be thin. Here, the starter motor30attached to the crankcase portion12is formed to have a length dimension that does not protrude toward the rear side from the end portion12b(seeFIG. 3) on the rearmost side of the crankcase portion12. A leading end portion (not shown) of the rotor shaft32of the starter motor30meshes with a gear formed on the flywheel only when the starter motor30is driven. That is, by driving the starter motor30, the power of the starter motor30is transmitted to the flywheel, and the engine1can be started.

As shown inFIGS. 1, 2, and 4, the key box31is attached to the fan cover22of the engine main body2. More specifically, the key box31is attached to the engine main body2to be arranged on the upper side of the side surface22aof the fan cover22.

FIG. 5is a perspective view of a state in which the cover of the key box in the embodiment of the present invention is detached.FIG. 6is a plan view of a state in which the cover of the key box in the embodiment of the present invention is detached.

As shown inFIGS. 5 and 6, the key box31includes a bracket34, a cover (seeFIG. 4)35, a key switch36, and a battery pack37.

The bracket34includes a main plate portion40and a side wall portion41. The bracket34in this embodiment is formed of a metal plate.

The main plate portion40is disposed on the side of the aforementioned fan cover22to extend in the up-down direction of the engine1. The main plate portion40has a fixing portion40awhich is fixed to the crankcase portion12by inserting the screw or the like. InFIG. 6, a symbol “40b” is a cover fixing portion which fixes the cover35with screws or the like.

The side wall portion41vertically stands up from the end edge of the main plate portion40. A circular through hole42for fixing the cylindrical key switch36is formed in the upper portion41aof the side wall portion41standing up from the front end edge. A manipulation portion36a(seeFIG. 5) of the key switch36is exposed to the front side of the engine1via the through hole42.

A housing portion43which houses the battery pack37is provided in the bracket34at the lower portion41bof the side wall portion41. The housing portion43is formed by the main plate portion40and lower portions41bof the two front and rear side wall portions41. Here, the lower portion41bof the front side wall portion41forming the housing portion43is formed so that its height dimension in the direction in which it stands up from the main plate portion40is slightly smaller than the upper portion41ato which the key switch36is attached.

The key switch36is manipulated by a user when operating the starter motor30. When operating the starter motor30, the user inserts a key into the key cylinder of the key switch36and rotates the key in a predetermined direction. As a result, a closed circuit is formed between the battery pack37and the starter motor30, and the starter motor30is energized. The key cylinder of the key switch36is urged toward the initial position at which the starter motor30is not operated, and after the engine1is started, when the user releases her or his hand from the key, the operation of the starter motor30is stopped.

The battery pack37is formed in a rectangular parallelepiped shape corresponding to the size of the aforementioned housing portion43. The thickness dimension T of the battery pack37is formed to be slightly smaller than the height dimension H of the lower portion41bof the side wall portion41. A length dimension L1of the battery pack37is formed to be equal to a length dimension L2of the lower portion41bof the side wall portion41. The width dimension D1of the battery pack37is formed to be equal to the width dimension D2of the main plate portion40.

FIG. 7is an electric circuit showing a schematic configuration of a self-starter unit according to an embodiment of the present invention.

As showing inFIG. 7, the key switch36includes a control unit45. The control unit45controls electric power supply from the battery pack37to the starter motor30. More specifically, the control unit45controls on/off of a relay46provided in the middle of the wiring which connects the battery pack37and the starter motor30, thereby controlling the electric power supply to the starter motor30. That is, the control unit45opens and closes a contact48of the relay46by controlling the current flowing through a manipulation coil unit47of the relay46. The relay46in this embodiment uses a normally open contact.

A generator49is further connected to the key switch36. The generator49is provided in the engine main body2to convert the rotational energy of the crankshaft11into electric energy.

The battery pack37includes a plurality of battery cells and protection circuits thereof (none of which is shown) therein. The battery cell of this embodiment includes a lithium ion secondary battery. Here, the battery cell constituting the battery pack37is not limited to the lithium ion secondary battery, and may be a lithium-based cell containing lithium in the negative electrode. The battery pack37in this embodiment uses the lithium ion secondary battery, thereby improving charge and discharge characteristics and reducing the size as compared with batteries such as nickel hydrogen secondary batteries. InFIG. 7, for convenience of illustration, a regulator provided between the battery pack37and the starter motor30is omitted.

Next, the operation of the aforementioned self-starter unit7will be described.

First, when the user performs a manipulation to rotate the key, the manipulation coil unit47of the relay46is energized and the contact48is closed. As a result, electric power is supplied from the battery pack37to the starter motor30. When the user stops the key manipulation, the key cylinder returns to the initial position, the energization to the manipulation coil unit47is stopped, and the contact48is opened. As a result, the starter motor30is stopped. When the engine1is started, electric power is output from the generator49, the electric power is supplied to the battery pack37via the key switch36, and each battery cell is charged.

According to the engine1of the aforementioned embodiment, the engine1can be started by the starter motor30, and there is no need to install a power supply such as a battery pack for driving the starter motor30in a device such as a working machine on which the engine1is mounted. By using a lithium-based cell, the size of the cell required to drive the starter motor30can be set to be smaller than when a lead storage battery is used. Therefore, the battery pack37can be miniaturized and easily attached to a dead space or the like of the engine main body2. As a result, it is possible to easily start the engine, and it is possible to suppress a decrease in operability accompanied with an increase in the size or an increase in the weight of a device such as a working machine driven by the engine output.

Furthermore, by simply attaching and detaching the bracket34to and from the engine main body2, it is possible to attach and detach the battery pack37to and from the engine main body2. As a result, the battery pack37can be easily attached to and detached from the engine main body2at the time of assembly or maintenance.

Furthermore, the battery pack37can be disposed at the farthest position from the cylinder portion10, which has the highest temperature in the engine main body2. Further, together with the battery pack37, the starter motor30can also be disposed at the farthest position from the cylinder portion10. Therefore, it is possible to suppress the temperature rise of the starter motor30and the battery pack37. Furthermore, it is possible to shorten the wiring through which a large current flows between the starter motor30and the battery pack37, thereby reducing the resistance due to the wiring. As a result, it is possible to reduce the burden on the lithium-based cell constituting the starter motor30or the battery pack37, and to stably drive the starter motor30with high efficiency.

Furthermore, since the key box31is attached to the fan cover22which forms a passage of cooling air and has a relatively lower temperature than other locations in the engine main body2, the temperature rise of the battery pack37can be further suppressed.

Further, in the key box31to which the key switch36is attached, since the battery pack37is arranged below the key switch36, it is possible to effectively utilize the space below the key switch36.

Furthermore, the key switch36and the battery pack37can be attached to a single bracket34. Therefore, after the key switch36and the battery pack37are integrated, the key switch36and the battery pack37can be attached to the engine main body. Further, a bracket for attaching the key switch36to the engine main body2can be commonly used as a bracket34for attaching the battery pack37to the engine main body2. As a result, the number of components can be reduced and the mounting work can be simplified.

Further, when the starter motor30does not perform cranking, the wiring between the battery pack37and the starter motor30can be opened by the control unit45. Therefore, it is possible to suppress discharge of the battery pack at times other than cranking. Further, when the battery pack37is charged from the generator49included in the engine main body2, the charging efficiency can be improved.

Modified Example of Embodiment

In the aforementioned embodiment, a case in which the engine1includes the self-starter unit7in advance has been described. However, in the aforementioned self-starter unit7, by causing the user to perform a self-starter unit attaching process (step S01) shown inFIG. 8attached to an engine including only the recoil starter6delivered or stocked as a starting device, it is also possible to alter (modify) the specifications

In this way, it is possible to easily add the cranking function of the starter motor30of the engine1to a device such as a working machine that does not have a dedicated space for installing the battery pack37. As a result, the engine1can be easily started by the starter motor30at a normal time, while the recoil starter is maintained as a starting device for emergencies.

The present invention is not limited to the aforementioned embodiments, but includes various modifications added to the aforementioned embodiments within the scope that does not depart from the gist of the present invention. That is, the specific shapes, configurations, and the like described in the embodiments are merely examples and can be appropriately changed.

For example, in the aforementioned embodiment, a case in which the self-starter unit7is provided in the engine1in which the cylinder portion10is disposed to be inclined with respect to the crankcase portion12has been described. However, the cylinder portion10is not limited to the arrangement of the aforementioned embodiment. For example, the self-starter unit7may be applied to an engine in which the cylinder portion10extends in the vertical direction from the crankcase portion12. Further, the arrangement of the fuel tank3, the air cleaner box4, the muffler5and the like is not limited to the arrangement of the aforementioned embodiment. For example, a fuel pump for sucking up fuel may be provided so that the fuel tank3is disposed below the crankcase portion12.

Further, the arrangement of the self-starter unit7is not limited to the arrangement of the aforementioned embodiment. The arrangement of the self-starter unit7may be appropriately moved, depending on the arrangement of the fuel tank3and the like.

Furthermore, in the aforementioned embodiment, the case in which the key switch36and the battery pack37are fixed to the same bracket34has been described. However, the key switch36and the battery pack37may be fixed to the engine main body2via separate brackets.

Further, the case in which the battery pack37is attached to the engine main body2via the bracket34has been described. However, the invention is not limited to this configuration. For example, the battery pack37may be directly attached to the engine main body2, without using the bracket34.

Furthermore, although the case in which the battery pack37is disposed below the key switch36has been described, the battery pack37may be disposed in a dead space other than the lower side of the key switch36. As long as the battery pack37is attached to the engine main body2, the arrangement of the battery pack37is not limited to the arrangement of the aforementioned embodiment.

Furthermore, in the horizontal direction, the starter motor30and the cooling fan may be arranged on sides opposite to each other across the crankshaft11. However, when there is space for arranging the starter motor30on the cooling fan side, the starter motor30and the cooling fan may be arranged on the same side.

In the aforementioned embodiment, the case in which the shape of the battery pack37is formed in a rectangular parallelepiped shape and the case in which the protection circuit is provided inside the battery pack37has been described. However, the battery pack37is not limited to a battery pack formed in a rectangular parallelepiped shape or a battery pack in which a protection circuit is provided.

INDUSTRIAL APPLICABILITY

The present invention is applicable to an engine, a self-starter unit, and a method for altering engine specifications. According to the engine, the self-starter unit, and the method for altering the engine specifications, it is possible to easily start the engine, and to suppress degradation in operability accompanied with an increase in the size or an increase in the weight of the device driven by the engine output.

BRIEF DESCRIPTION OF THE REFERENCE SYMBOLS