Chain saw

A chain saw may include a saw chain, a guide bar to which the saw chain is attached, a sprocket configured to move the saw chain along a periphery of the guide bar, a prime mover configured to rotate the sprocket, a housing that houses the prime mover, a bolt protruding from the housing and penetrating a hole provided in the guide bar, and a nut screwed to the bolt to fix the guide bar to the housing. The nut may be exposed to outside. A heat insulating structure may be provided on a heat transfer path between the nut and the guide bar.

This application claims priority to Japanese Patent Application No. 2018-003678, filed on Jan. 12, 2018, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The disclosure herein relates to a chain saw.

BACKGROUND

Japanese Patent Application Publication No. 2014-198367 describes a chain saw. This chain saw includes a saw chain, a guide bar to which the saw chain is attached, a sprocket that moves the saw chain along a periphery of the guide bar, a prime mover that rotates the sprocket, a housing that houses the prime mover, a bolt protruding from the housing and penetrating a hole provided in the guide bar, and a nut screwed to the bolt to fix the guide bar to the housing. The nut is exposed to outside.

SUMMARY

When a cutting target is cut by using a chain saw, a guide bar becomes hot due to frictional heat generated by a saw chain and the guide bar. In a configuration in which a nut is exposed to outside as in the aforementioned one, the nut might become hot due to heat transfer from the guide bar, and a user might inadvertently touch this high-temperature nut. The disclosure herein provides a technique capable of preventing a nut exposed to outside from becoming hot due to heat transfer from a guide bar.

A chain saw disclosed herein may comprise a saw chain, a guide bar to which the saw chain is attached, a sprocket configured to move the saw chain along a periphery of the guide bar, a prime mover configured to rotate the sprocket, a housing that houses the prime mover, a bolt protruding from the housing and penetrating a hole provided in the guide bar, and a nut screwed to the bolt to fix the guide bar to the housing. The nut may be exposed to outside. A heat insulating structure may be provided on a heat transfer path between the nut and the guide bar.

According to the above configuration, the heat insulating structure is provided on the heat transfer path from the guide bar to the nut, so the nut can be prevented from becoming hot due to heat transfer from the guide bar, which became hot, to the nut.

DETAILED DESCRIPTION

In one or more embodiments, a chain saw may comprise a saw chain, a guide bar to which the saw chain is attached, a sprocket configured to move the saw chain along a periphery of the guide bar, a prime mover configured to rotate the sprocket, a housing that houses the prime mover, a bolt protruding from the housing and penetrating a hole provided in the guide bar, and a nut screwed to the bolt to fix the guide bar to the housing. The nut may be exposed to outside. A heat insulating structure may be provided on a heat transfer path between the nut and the guide bar.

According to the above configuration, the heat insulating structure provided on the heat transfer path from the guide bar to the nut can suppress the nut from becoming hot due to heat transfer from the high-temperature guide bar to the nut.

In one or more embodiments, the chain saw may further comprise a sprocket cover constituted of resin and covering the sprocket. The sprocket cover may be interposed between the nut and the guide bar.

According to the above configuration, the heat insulating structure, which is constituted of the resin sprocket cover and provided on the heat transfer path from the guide bar to the nut, can suppress the nut from becoming hot due to the heat transfer from the high-temperature guide bar to the nut.

In one or more embodiments, the sprocket cover may include a sleeve constituted of metal and interposed between the nut and the guide bar, and a heat insulating portion constituted of resin and interposed between the sleeve and the guide bar.

With the configuration in which the resin sprocket cover is interposed between the nut and the guide bar, if a thickness of the sprocket cover interposed between the nut and the guide bar is thick, the sprocket cover might be buckled and damaged when the nut is firmly tightened. In the above configuration, however, the sleeve receives a load upon tightening the nut, so the sprocket cover can be suppressed from being buckled and damaged. In this case, the metal sleeve constitutes a part of the heat transfer path from the guide bar to the nut, however, since the heat insulating portion is provided between the sleeve and the guide bar in the above configuration, the nut can be suppressed from becoming hot due to the heat transfer from the high-temperature guide bar to the nut.

In one or more embodiments, the sprocket cover may include a sleeve constituted of metal and interposed between the nut and the guide bar, and a heat insulating portion constituted of resin and interposed between the nut and the sleeve.

With the configuration in which the resin sprocket cover is interposed between the nut and the guide bar, if the thickness of the sprocket cover interposed between the nut and the guide bar is thick, the sprocket cover might be buckled and damaged when the nut is firmly tightened. In the above configuration, however, the sleeve receives the load upon tightening the nut, so the sprocket cover can be suppressed from being buckled and damaged. In this case, the metal sleeve constitutes a part of the heat transfer path from the guide bar to the nut, however, since the heat insulating portion is provided between the nut and the sleeve in the above configuration, the nut can be suppressed from becoming hot due to the heat transfer from the high-temperature guide bar to the nut.

In one or more embodiments, the chain saw may further comprise a washer constituted of resin. The sprocket cover may include a sleeve constituted of metal and interposed between the nut and the guide bar. The washer may be interposed between the nut and the sleeve.

With the configuration in which the resin sprocket cover is interposed between the nut and the guide bar, if the thickness of the sprocket cover interposed between the nut and the guide bar is thick, the sprocket cover might be buckled and damaged when the nut is firmly tightened. In the above configuration, however, the sleeve receives the load upon tightening the nut, so the sprocket cover can be suppressed from being buckled and damaged. In this case, the metal sleeve constitutes a part of the heat transfer path from the guide bar to the nut, however, since the resin washer between the nut and the sleeve serves as the heat insulating structure in the above configuration, the nut can be suppressed from becoming hot due to the heat transfer from the high-temperature guide bar to the nut.

In one or more embodiments, a heat insulating portion formed by air may be provided between an inner peripheral surface of the hole of the guide bar and the bolt.

As the heat transfer path from the guide bar to the nut, aside from a path that transfers heat from the guide bar to the nut without intervention of the bolt, there also is a path that transfers heat from the guide bar to the bolt and then from the bolt to the nut. In the above configuration, the aerial heat insulating portion is provided on the heat transfer path from the guide bar to the bolt, and thus the nut can be suppressed from becoming hot due to the heat transfer from the high-temperature guide bar to the nut.

In one or more embodiments, a heat insulating portion constituted of resin may be provided between an inner peripheral surface of the hole of the guide bar and the bolt.

As the heat transfer path from the guide bar to the nut, aside from the path that transfers heat from the guide bar to the nut without intervention of the bolt, there also is the path that transfers heat from the guide bar to the bolt and then from the bolt to the nut. In the above configuration, the resin heat insulating portion is provided on the heat transfer path from the guide bar to the bolt, and thus the nut can be suppressed from becoming hot due to the heat transfer from the high-temperature guide bar to the nut.

In one or more embodiments, when the chain saw is in use, the saw chain may be configured to be capable of moving along the periphery of the guide bar at a speed of 18 m/s or more, specifically at 20 m/s or more, and more specifically at 22 m/s or more.

In a case where the saw chain moves at high speed along the periphery of the guide bar, frictional heat between the saw chain and the guide bar becomes high and the guide bar thereby becomes hotter. According to the above configuration, the heat insulating structure is provided on the heat transfer path from the guide bar to the nut, and thus the nut can be suppressed from becoming hot due to the heat transfer from the guide bar having a higher temperature to the nut.

In one or more embodiments, a minimum radius of curvature of the periphery of the guide bar may be 20 mm or less, specifically 15 mm or less, and more specifically 10 mm or less.

In a case where the guide bar includes a portion with a small radius of curvature, the frictional heat between the saw chain and the guide bar becomes high at the portion, as a result of which the guide bar becomes hotter. According to the above configuration, the heat insulating structure is provided on the heat transfer path from the guide bar to the nut, the nut can be suppressed from becoming hot due to the heat transfer from the guide bar having a higher temperature to the nut.

In one or more embodiments, the prime mover may be a motor driven by electric power.

In a case where the prime mover is an electric motor, the housing does not have a portion having very high temperature as compared to a case where the prime mover is an engine, and thus a user is at a greater risk of inadvertently touching the nut exposed to outside without paying much attention. According to the above configuration, the heat insulating structure is provided on the heat transfer path from the guide bar to the nut, and thus the nut can be suppressed from becoming hot due to the heat transfer from the high-temperature guide bar to the nut.

In one or more embodiments, the chain saw may further comprise a battery configured to be detachably attached to the housing. The motor may be configured to be driven by electric power from the battery.

The chain saw configured to drive the motor by the electric power supply from the battery does not require a power cord, which provides improved workability with the chain saw, however, places the user at a greater risk of inadvertently touching the nut exposed to outside. According to the above configuration, the heat insulating structure is provided on the heat transfer path from the guide bar to the nut, the nut can be suppressed from becoming hot due to the heat transfer from the high-temperature guide bar to the nut.

Embodiment

As shown inFIGS. 1 and 2, a chain saw2of the present embodiment includes a main body4, a guide bar6, and a saw chain8. The guide bar6is an elongate and narrow plate-like member attached to the main body4to protrude forward from the main body4. The saw chain8includes a plurality of cutter teeth coupled to each other, and is attached along a periphery of the guide bar6. The main body4has a battery B attached thereto. The chain saw2is configured to cut a cutting target, such as a wood piece, by driving the saw chain8to rotate along the periphery of the guide bar6by using electric power supplied from the battery B. Various types of guide bars may be attached as the guide bar6according to a content of cutting work. In an example shown inFIGS. 1 and 2, a radius of curvature of a distal end of the guide bar6is 10 mm, for example. The chain saw2of the present embodiment is configured to drive the saw chain8to rotate along the periphery of the guide bar6at a speed of 22.5 m/s, for example. In the description below, when the chain saw2is placed on a mounting surface P such as a ground as shown inFIG. 3, a direction perpendicularly intersecting the mounting surface P is termed an up-and-down direction of the chain saw2, a direction that projects a longitudinal direction of the guide bar6on the mounting surface P is termed a front-and-rear direction of the chain saw2, and a direction that perpendicularly intersects both the up-and-down direction and the front-and-rear direction of the chain saw2is termed a left-and-right direction of the chain saw2. In the drawings other thanFIGS. 1 to 3, depiction of the saw chain8is omitted for clearer view therein.

As shown inFIGS. 1 and 2, the main body4includes a left housing10, a right housing12, a side handle14, a hand guard16, a brake cover18, and a sprocket cover20. A main body housing22and a top handle24are configured by the left housing10and the right housing12. The left housing10constitutes outer shapes of left-halves of the main body housing22and the top handle24, and the right housing12constitutes outer shapes of right-halves of the main body housing22and the top handle24.

The main body housing22includes a front main body housing22ahaving a substantially rectangular solid shape with its longitudinal direction in the front-and-rear direction of the main body4, and a rear main body housing22bextending rearward from an upper rear part of the front main body housing22a. A battery receiver22cto which the battery B can be detachably attached by sliding the battery B in the left-and-right direction is provided on a lower surface of the rear main body housing22b. As shown inFIG. 3, in a case where the chain saw2is placed on the mounting surface P in a state where the battery B is attached to the chain saw2, a lower surface of the front main body housing22acontacts the mounting surface P, and a lower surface of the battery B also contacts the mounting surface P.

As shown inFIG. 1, the top handle24includes a support24ahaving a substantially square column shape protruding upward from an upper front surface of the front main body housing22a, and a grip24bwhich has a substantially circular cross section, extends rearward from an upper rear part of the support24a, bends downward, and connects to an upper surface of the rear main body housing22b. A recess24cis provided in an upper surface of the support24a. Inside the recess24c, a power switch26for a user to manipulate to switch power of the chain saw2between on and off, and a power indicator28configured to indicate an on/off state of the chain saw2are provided. A trigger switch30for the user to manipulate to drive and rotate the saw chain8is disposed on a lower front surface of the grip24b. A trigger lock lever32configured to switch between a state that allows the user to manipulate the trigger switch30and a state that prohibits the user from manipulating the trigger switch30is disposed at an upper portion of the grip24b.

The side handle14has a substantially U-shaped outer shape which connects an upper rear left surface of the support24aof the top handle24and a lower rear left surface of the front main body housing22a. A cross-section of the side handle14is substantially circular. Upon using the chain saw2, the user holds the top handle24with his/her right hand and holds the side handle14with his/her left hand to retain the chain saw2. From this state, when the user pushes down the trigger lock lever32of the top handle24with the palm of the right hand, the trigger switch30is allowed to be manipulated by the user. From this state, when the user pushes up the trigger switch30with the index finger of the right hand, the saw chain8is driven to rotate. A hand rest22dwhere the user can place the hand is provided on the upper surface of the rear main body housing22b, that is, at a portion where the grip24bof the top handle24connects to the main body housing22.

As shown inFIG. 4, a motor34, an oil tank36, and an oil pump38are disposed inside the front main body housing22a. Further, a control unit40is disposed inside the rear main body housing22b. The oil tank36is disposed frontward than the motor34and the oil pump38.

As shown inFIG. 5, the motor34is an outer rotor-type DC brushless motor. The motor34includes a stator44onto which a coil42is wound, a rotor46arranged outside the stator44, a cooling fan48engaged to the rotor46, and an output shaft50disposed to penetrate through centers of the stator44and the rotor46and engaged to the cooling fan48. The stator44is fixed to the main body housing22. The coil42of the stator44is connected to the control unit40(seeFIG. 4). Although not shown, the control unit40includes an inverter circuit provided with switching elements and a control circuit configured to control operations of those switching elements, and it is configured to control operation of the motor34by controlling a voltage to be applied to the coil42. The output shaft50is disposed along the left-and-right direction of the chain saw2and is rotatably supported by the main body housing22via bearings52,54. The bearing52is disposed on the right side relative to the stator44, and the bearing54is disposed on the left side relative to the stator44and the cooling fan48. A sprocket56and a brake base58are fixed at a vicinity of a right end of the output shaft50. The sprocket56and the brake base58are disposed on the right side relative to the bearing52. A brake drum60is fitted to the brake base58.

As shown inFIG. 6, the sprocket56is exposed to outside the right housing12. The saw chain8is strapped on the sprocket56from the guide bar6(seeFIGS. 1 to 3). When the motor34is driven, the sprocket56rotates together with the output shaft50, by which the saw chain8rotates around the sprocket56and the guide bar6.

The guide bar6is fixed to the right housing12in a state of being interposed between an inner guide plate61and an outer guide plate62. The inner guide plate61has a shape having its portions near its upper end and lower end curved inwardly (toward the left side of the chain saw2). The outer guide plate62has a shape having its portions near its upper end and lower end curved outwardly (toward the right side of the chain saw2). A long hole6aextending along a longitudinal direction of the guide bar6is provided in the guide bar6. The guide bar6is supported on the main body housing22via a support pin64and a bolt66which penetrate through the long hole6a. As shown inFIGS. 2 and 3, a nut68is attached to the bolt66by being tightened from outside the sprocket cover20and the outer guide plate62. The user can change a distance between the guide bar6and the sprocket56by sliding the guide bar6along the long hole6ain a state where the nut68is loosened, to adjust tension on the saw chain8.

As shown inFIG. 6, the guide bar6is provided with an engagement hole67which engages with an engaging pawl65. As shown inFIG. 7, the engaging pawl65is coupled to an adjustor screw70via a rotation-linear motion converting mechanism69. The rotation-linear motion converting mechanism69is configured to convert rotary motion of the adjustor screw70to linear motion of the engaging pawl65in a direction along the long hole6a. As shown inFIGS. 5 and 6, the adjustor screw70penetrates the long hole6awithout contacting an inner peripheral surface of the long hole6a. When the user rotates the adjustor screw70, the engaging pawl65moves in the direction along the long hole6aof the guide bar6, by which the guide bar6slides in the direction along the long hole6a.

As shown inFIGS. 2 and 3, the sprocket56, the inner guide plate61, the outer guide plate62, and the support pin64are covered by the sprocket cover20. An outer cover23provided with a recess is attached to the sprocket cover20. The outer cover23includes a tightening opening23afor accessing the nut68fastened on the bolt66from outside, and an adjusting opening23bfor accessing the adjustor screw70from outside. The user can tighten or loosen the nut68in a state where the sprocket cover20is attached. Further, the user can adjust the tension of the saw chain8by rotating the adjustor screw70through the adjusting opening23bin the state where the sprocket cover20is attached.

As shown inFIG. 8, the bolt66includes a base portion66afitted to the right housing12, a shaft portion66bhaving a cylinder shape contacting the inner peripheral surface of the long hole6aof the guide bar6, and a threaded portion66chaving an external thread on its outer surface. The nut68includes a head68ahaving an internal thread on its inner surface, and a skirt68bhaving a smaller outer diameter than the head68aand extending from the head68ain an inversed taper shape. The skirt68bof the nut68has a washer71attached thereto. The sprocket cover20includes a washer receiver20a. The washer receiver20ahas a metal sleeve25attached thereto. The internal thread of the head68aof the nut68is screwed onto the external thread of the threaded portion66cof the bolt66. When the nut68is fastened, the inner guide plate61, the guide bar6, the outer guide plate62, the washer receiver20a, the sleeve25, and the washer71are interposed and fixed between the head68aof the nut68and the right housing12. In a state where the nut68is fastened, a heat insulating portion20bconstituted of resin, which is a part of the sprocket cover20, is interposed between the sleeve25and the outer guide plate62, and thus the sleeve25and the outer guide plate62do not make direct contact. In the chain saw2of the present embodiment, the sleeve25receives a load applied to the washer receiver20aof the sprocket cover20when the nut68is tightened, so the washer receiver20aof the sprocket cover20can be suppressed from becoming buckled even in a case where the nut68is firmly tightened.

In the chain saw2of the present embodiment, the outer diameter of the skirt68bis larger than an inner diameter of the washer71. Further, an outer diameter of the washer71is larger than an inner diameter of the tightening opening23aof the outer cover23. Due to this, even in a case where the nut68is detached from the bolt66, the nut68and the washer71are retained by the sprocket cover20and the outer cover23. The nut68and the washer71can be suppressed from falling off.

As shown inFIG. 2, a lower guard21is provided at a lower rear part of the sprocket cover20. The lower guard21is a plate-shaped member extending rearward and downward from a pivot shaft (not shown) along the left-and-right direction, and is configured to rotate about the pivot shaft. The lower guard21has a wider shape than the guide bar6in the left-and-right direction, a left end of the lower guard21is located on the left side relative to a left end of the guide bar6, and a right end of the lower guard21is located on the right side relative to a right end of the guide bar6. The lower guard21is biased by a torsion spring, which is not shown, in an opening direction, and it protrudes rearward and downward from the lower rear part of the sprocket cover20in a state where the user lifts the chain saw2, as shown inFIG. 2. Due to this, cutting chips can be suppressed from flying to the user when a cutting target is cut by using the chain saw2. As shown inFIG. 3, when the chain saw2is placed on the mounting surface P, the lower guard21pivots in a closing direction by contacting with the mounting surface P, and the lower guard21is housed in a space inside the sprocket cover20.

As shown inFIG. 7, the hand guard16is coupled to a brake shoe74via a link mechanism72. The hand guard16is configured to rotate about a pivot shaft along the left-and-right direction of the chain saw2. The brake shoe74is disposed to surround a periphery of the brake drum60. The link mechanism72is configured to shrink a diameter of the brake shoe74when the hand guard16is pressed down forward, and enlarge the diameter of the brake shoe74when the hand guard16is lifted up rearward. When the diameter of the brake shoe74is shrunk, an inner peripheral surface of the brake shoe74and an outer peripheral surface of the brake drum60come into contact, and rotation of the output shaft50is restricted by frictional force therebetween.

The oil tank36shown inFIG. 4stores lubricant oil for lubricating the saw chain8. The oil tank36is provided with a cap76which detachably attaches to a replenishing opening36a(seeFIG. 5) for replenishing the oil tank36with the lubricant oil. As shown inFIG. 1, the cap76of the oil tank36is exposed to outside the left housing10, and is disposed on a front lower left surface of the front main body housing22a. A liquid level checking opening78through which a liquid level in the oil tank36can be visually checked from outside is provided in the left housing10on the front side relative to the cap76.

The oil pump38shown inFIG. 4is configured to cooperate with rotation of the motor34to suction the lubricant oil in the oil tank36through an inlet pipe80and feed out the lubricant oil toward the guide bar6through an outlet pipe82. A worm gear84for driving the oil pump38is fitted at a vicinity of a left end of the output shaft50of the motor34. As shown inFIG. 5, the worm gear84is disposed on the left side relative to the stator44and the cooling fan48and on the right side relative to the bearing54. A discharge amount of the lubricant oil supplied from the oil tank36to the guide bar6by the oil pump38is adjustable by an adjusting pin94(seeFIG. 4).

As shown inFIG. 1, an adjusting opening124through which the adjusting pin94can be accessed from outside is provided in an upper surface of the main body housing22. The user can adjust the discharge amount of the lubricant oil in the oil pump38by inserting a tool from the adjusting opening124and rotating the adjusting pin94. In the left-and-right direction of the chain saw2, the adjusting opening124is disposed on the left side relative to the top handle24. In the front-and-rear direction of the chain saw2, the adjusting opening124is disposed between a portion where the side handle14connects to the top handle24and a portion where the side handle14connects to the main body housing22. By providing the adjusting opening124at such a location, the user can easily insert the tool therein, and the discharge amount of the lubricant oil in the oil pump38can be adjusted easily.

When the cutting target is cut by using the chain saw2, the guide bar6becomes hot due to frictional heat between the saw chain8and the guide bar6. Especially in a case where a radius of curvature at the distal end of the guide bar6is small, a large quantity of frictional heat is generated at the distal end of the guide bar6, and the guide bar6becomes even hotter. In the configuration as with the chain saw2of the present embodiment in which the nut68is exposed to outside by protruding outward than the outer cover23, when the nut68becomes hot due to heat transfer from the guide bar6, there is a risk that the user may inadvertently touch the high-temperature nut68.

As shown inFIG. 8, in the chain saw2of the present embodiment, the outer guide plate62, the heat insulating portion20b, the sleeve25, and the washer71constitute a heat transfer path from the guide bar6to the nut68. This heat transfer path is provided with a heat insulating structure constituted of the resin heat insulating portion20b. With such a configuration, the nut68can be suppressed from becoming hot due to the heat transfer from the high-temperature guide bar6to the nut68.

The heat insulating structure provided on the heat transfer path from the guide bar6to the nut68is not limited to the above example. For example, as shown inFIG. 9, the heat insulating portion20b, which is a part of the sprocket cover20, may be interposed between the sleeve25and the washer71. In this case, the sleeve25does not directly contact the washer71. The sleeve25may directly contact the outer guide plate62. In the configuration shown in FIG.9, the outer guide plate62, the sleeve25, the heat insulating portion20b, and the washer71constitute the heat transfer path from the guide bar6to the nut68. This heat transfer path is provided with the heat insulating structure constituted of the resin heat insulating portion20b. With such a configuration, the nut68can be suppressed from becoming hot due to the heat transfer from the high-temperature guide bar6to the nut68.

Alternatively, as shown inFIG. 10, the heat insulating portion20bmay not be provided in the sprocket cover20, and the washer71constituted of resin may be used instead. In this case, the sleeve25may directly contact the outer guide plate62and the washer71. In the configuration shown inFIG. 10, the outer guide plate62, the sleeve25, and the washer71constitute the heat transfer path from the guide bar6to the nut68. This heat transfer path is provided with the heat insulating structure constituted of the resin washer71. With such a configuration, the nut68can be suppressed from becoming hot due to the heat transfer from the high-temperature guide bar6to the nut68.

Alternatively, as shown inFIG. 11, a diameter of the shaft portion66bof the bolt66may be made smaller than a width of the long hole6aof the guide bar6so that the bolt66does not directly contact the guide bar6. In this case, an air layer between the shaft portion66bof the bolt66and the guide bar6functions as a heat insulating structure on a heat transfer path from the guide bar6to the nut68via the bolt66. With such a configuration, the nut68can be suppressed from becoming hot due to the heat transfer from the high-temperature guide bar6to the nut68. In the example shown inFIG. 11, the bolt66does not receive a load in the up-and-down direction which is applied from the guide bar6to the main body4, and thus another support pin63penetrating the long hole6ais provided. In the configuration shown inFIG. 11, the load in the up-and-down direction which is applied from the guide bar6to the main body4is received by the support pin64and the support pin63, by which the guide bar6can securely be fixed to the main body4.

Alternatively, as shown inFIG. 12, a heat insulating portion66dconstituted of resin may be provided on an outer periphery of the shaft portion66bof the bolt66so that the bolt66contacts the guide bar6via the heat insulating portion66d. In this case, the heat insulating portion66dof the bolt66functions as a heat insulating structure on the heat transfer path from the guide bar6to the nut68via the bolt66. With such a configuration, the nut68can be suppressed from becoming hot due to the heat transfer from the high-temperature guide bar6to the nut68. In the example shown inFIG. 12, another support pin63penetrating the long hole6ais provided so that the heat insulating portion66dof the bolt66does not receive the load in the up-and-down direction applied from the guide bar6to the main body4. In the configuration shown inFIG. 12, the load in the up-and-down direction which is applied from the guide bar6to the main body4is received by the support pin64and the support pin63, by which the guide bar6can securely be fixed to the main body4. Further, the heat insulating portion66dof the bolt66can be suppressed from being damaged.

As above, in one or more embodiments, the chain saw2includes the saw chain8, the guide bar6to which the saw chain8is attached, the sprocket56configured to move the saw chain8along the periphery of the guide bar6, the motor34(an example of the prime mover) configured to rotate the sprocket56, the main body housing22(an example of the housing) that houses the motor34, the bolt66protruding from the main body housing22and penetrating the long hole6a(an example of the hole) provided in the guide bar6, and the nut68screwed to the bolt66to fix the guide bar6to the main body housing22. The nut68is exposed to outside. The heat insulating structure is provided on the heat transfer path between the nut68and the guide bar6. According to the above configuration, since the heat insulating structure is provided on the heat transfer path from the guide bar6to the nut68, the nut68can be suppressed from becoming hot due to the heat transfer from the high-temperature guide bar6to the nut68.

In one or more embodiments, the chain saw2further includes the sprocket cover20constituted of resin and covering the sprocket56. The sprocket cover20is interposed between the nut68and the guide bar6. According to the above configuration, since the heat insulating structure constituted of the resin sprocket cover20is provided on the heat transfer path from the guide bar6to the nut68, the nut68can be suppressed from becoming hot due to the heat transfer from the high-temperature guide bar6to the nut68.

In one or more embodiments, the sprocket cover20includes the sleeve25constituted of metal and interposed between the nut68and the guide bar6, and the heat insulating portion20bconstituted of resin and interposed between the sleeve25and the guide bar6(seeFIG. 8). In the configuration in which the resin sprocket cover20is interposed between the nut68and the guide bar6, if a thickness of the sprocket cover20interposed between the nut68and the guide bar6is thick, the sprocket cover20might be buckled and damaged when the nut68is firmly tightened. In the above configuration, the sleeve25receives a load applied upon tightening the nut68, and thus the sprocket cover20can be suppressed from being buckled and damaged. In this case, the metal sleeve25constitutes a part of the heat transfer path from the guide bar6to the nut68, however, according to the above configuration, since the heat insulating portion20bis provided between the sleeve25and the guide bar6, the nut68can be suppressed from becoming hot due to the heat transfer from the high-temperature guide bar6to the nut68.

In one or more embodiments, the sprocket cover20includes the sleeve25constituted of metal and interposed between the nut68and the guide bar6, and the heat insulating portion20bconstituted of resin and interposed between the nut68and the sleeve25(seeFIG. 9). In the configuration in which the resin sprocket cover20is interposed between the nut68and the guide bar6, if the thickness of the sprocket cover20interposed between the nut68and the guide bar6is thick, the sprocket cover20might be buckled and damaged when the nut68is firmly tightened. In the above configuration, the sleeve25receives the load applied upon tightening the nut68, and thus the sprocket cover20can be suppressed from being buckled and damaged. In this case, the metal sleeve25constitutes a part of the heat transfer path from the guide bar6to the nut68, however, according to the above configuration, since the heat insulating portion20bis provided between the nut68and the sleeve25, the nut68can be suppressed from becoming hot due to the heat transfer from the high-temperature guide bar6to the nut68.

In one or more embodiments, the chain saw2further includes the washer71constituted of resin. The sprocket cover20includes the sleeve25constituted of metal and interposed between the nut68and the guide bar6. The washer71is interposed between the nut68and the sleeve25(seeFIG. 10). In the configuration in which the resin sprocket cover20is interposed between the nut68and the guide bar6, if the thickness of the sprocket cover20interposed between the nut68and the guide bar6is thick, the sprocket cover20might be buckled and damaged when the nut68is firmly tightened. In the above configuration, the sleeve25receives the load applied upon tightening the nut68, and thus the sprocket cover20can be suppressed from being buckled and damaged. In this case, the metal sleeve25constitutes a part of the heat transfer path from the guide bar6to the nut68, however, according to the above configuration, since the resin washer71between the nut68and the sleeve25functions as the heat insulating structure, the nut68can be suppressed from becoming hot due to the heat transfer from the high-temperature guide bar6to the nut68.

In one or more embodiments, the heat insulating portion formed by air is provided between the inner peripheral surface of the long hole6aof the guide bar6and the bolt66(seeFIG. 11). As the heat transfer path from the guide bar6to the nut68, aside from the path that transfers the heat from the guide bar6to the nut68without intervention of the bolt66, there also is the path on which the heat transfers from the guide bar6to the bolt66and then from the bolt66to the nut68. In the above configuration, since the aerial heat insulating portion is provided on the heat transfer path from the guide bar6to the bolt66, the nut68can be suppressed from becoming hot due to the heat transfer from the high-temperature guide bar6to the nut68.

In one or more embodiments, the heat insulating portion66dconstituted of resin is provided between the inner peripheral surface of the long hole6aof the guide bar6and the bolt66(seeFIG. 12). As the heat transfer path from the guide bar6to the nut68, aside from the path that transfers the heat from the guide bar6to the nut68without intervention of the bolt66, there also is the path on which the heat transfers from the guide bar6to the bolt66and then from the bolt66to the nut68. In the above configuration, since the resin heat insulating portion66dis provided on the heat transfer path from the guide bar6to the bolt66, the nut68can be suppressed from becoming hot due to the heat transfer from the high-temperature guide bar6to the nut68.

In one or more embodiments, when the chain saw2is in use, the saw chain8is configured to be capable of moving along the periphery of the guide bar6at a speed of 18 m/s or more, more specifically capable of moving therealong at a speed of 20 m/s or more, and even more specifically capable of moving therealong at a speed of 22 m/s or more.

In a case where the saw chain8moves at a high speed along the periphery of the guide bar6, the frictional heat between the saw chain8and the guide bar6becomes high, and the guide bar6thereby becomes hotter. According to the above configuration, since the heat insulating structure is provided on the heat transfer path from the guide bar6to the nut68, the nut68can be suppressed from becoming hot due to the heat transfer from the higher-temperature guide bar6to the nut68.

In one or more embodiments, a minimum radius of curvature of the periphery of the guide bar6is 20 mm or less, more specifically 15 mm or less, and even more specifically 10 mm or less. In a case where the guide bar6has a portion with a small radius of curvature, the frictional heat between the saw chain8and the guide bar6becomes high at such the portion, as a result of which the guide bar6becomes hotter. According to the above configuration, since the heat insulating structure is provided on the heat transfer path from the guide bar6to the nut68, the nut68can be suppressed from becoming hot due to the heat transfer from the higher-temperature guide bar6to the nut68.

In one or more embodiments, the prime mover configured to rotate the sprocket56is the motor34driven by the electric power. In the case where the prime mover is the motor34, the main body housing22the housing does not have a portion having very high temperature compared to a case where the prime mover is an engine, and thus, the user is at a greater risk of inadvertently touching the nut68exposed to outside without paying much attention. According to the above configuration, since the heat insulating structure is provided on the heat transfer path from the guide bar6to the nut68, the nut68can be suppressed from becoming hot due to the heat transfer from the high-temperature guide bar6to the nut68.

In one or more embodiments, the chin saw2further includes the battery B configured to be detachably attached to the main body housing22. The motor34is configured to be driven by the electric power from the battery B. The chain saw2configured to drive the motor34by the electric power supplied from the battery B does not require a power cord, which provides improved workability with the chain saw2, however, places the user at a greater risk of inadvertently touching the nut68exposed to outside. According to the above configuration, since the heat insulating structure is provided on the heat transfer path from the guide bar6to the nut68, the nut68can be suppressed from becoming hot due to the heat transfer from the high-temperature guide bar6to the nut68.

The chain saw2according to an embodiment may be supplied with electric power through a power cord without attaching the battery B.

The chain saw2according to an embodiment may include an engine instead of the motor34as the prime mover configured to rotate the sprocket56. In this case, the output shaft50connected to the sprocket56may be rotated by being driven by the engine.