Working machine

Abstract

To provide a technique that can suppress the reduction of torque transmitted from a prime mover to a working part via an output shaft in a working machine.SOLUTION: A working machine comprises: a prime mover including an output shaft; a working part coupled to the output shaft; a slip mechanism; and a fan attached to the output shaft via the slip mechanism. The slip mechanism may be configured to: in a case where a load torque applied to the output shaft when driving the fan is less than a predetermined value, rotate the output shaft and the fan integrally with each other; and in a case where the load torque when driving the fan is greater than or equal to the predetermined value, rotate the output shaft and the fan relative to each other.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a work machine. [Background technology]

[0002] Patent Document 1 discloses a working machine including a prime mover having an output shaft, a working unit connected to the output shaft, and a fan connected to the output shaft. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-210705 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the working machine of Patent Document 1, the working unit and the fan are driven in response to the driving of the prime mover. Depending on the situation in which the working machine is used, the torque required to drive the fan may be greater than that required in the situation in which the working machine is used in the air (hereinafter referred to as "normal usage situation"). In such a case, the torque transmitted from the prime mover to the working unit via the output shaft becomes smaller than that required in the normal usage situation.

[0005] This specification provides a technique capable of suppressing a reduction in torque transmitted from a prime mover to a working section via an output shaft in a working machine. [Means for solving the problem]

[0006] The working machine disclosed in this specification may include a prime mover having an output shaft, a working unit connected to the output shaft, a slip mechanism, and a fan attached to the output shaft via the slip mechanism. The slip mechanism may rotate the output shaft and the fan integrally when a load torque applied to the output shaft when driving the fan is less than a predetermined value, and may rotate the output shaft and the fan relatively when the load torque when driving the fan is equal to or greater than the predetermined value.

[0007] In normal use conditions, the load torque is less than a predetermined value. On the other hand, in conditions different from the normal use conditions, the load torque may be equal to or greater than the predetermined value. According to the above configuration, the slip mechanism rotates the output shaft and the fan together when the load torque when driving the fan is less than a predetermined value. This is because the static friction torque caused by the slip mechanism is greater than the load torque when the load torque is less than the predetermined value. On the other hand, the slip mechanism rotates the output shaft and the fan relatively when the load torque when driving the fan is equal to or greater than a predetermined value. That is, the slip mechanism causes the fan to slip with respect to the output shaft. This is because the static friction torque caused by the slip mechanism is smaller than the load torque when the load torque is equal to or greater than the predetermined value. When the output shaft and the fan rotate relative to each other, the torque of the output shaft required to drive the fan is reduced. Therefore, it is possible to suppress a reduction in the torque transmitted from the prime mover to the working unit via the output shaft. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a perspective view of the chain saw 2 of the embodiment as viewed from above and behind on the left. [Diagram 2] FIG. 2 is a left side view of the chain saw 2 of the embodiment as seen from the left. [Diagram 3] FIG. 2 is a perspective view of the chain saw 2 of the embodiment as viewed from above and to the rear right. [Figure 4]2 is a cross-sectional view of the chain saw 2 of the embodiment as seen from the right. [Diagram 5] 1 is a cross-sectional view of a chain saw 2 of an embodiment as viewed from the front. [Figure 6] 1 is a perspective view of an inner housing 66 according to an embodiment, seen from above and behind the left. [Figure 7] 1 is a perspective view of a fan 70 according to an embodiment, seen from below on the front right side. [Figure 8] FIG. 6 is an enlarged view of the cross-sectional view of FIG. [Figure 9] 1 is a cross-sectional view of a chain saw 2 used in air, viewed from the right. [Figure 10] 1 is a cross-sectional view of a chain saw 2 for use underwater, seen from the right. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] In the following, a representative and non-limiting embodiment of the present invention will be described in detail with reference to the drawings. This detailed description is intended simply to provide those skilled in the art with details for implementing the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. In addition, the additional features and inventions disclosed below can be used separately or together with other features and inventions to provide further improved working machines, manufacturing methods and methods of using the same.

[0010] Furthermore, the combinations of features and steps disclosed in the following detailed description are not essential to the practice of the invention in its broadest sense, but are specifically described only to illustrate representative embodiments of the invention. Furthermore, the various features of the representative embodiments described above and below, and the various features of those described in the independent and dependent claims, do not have to be combined in the exact embodiments described herein, or in the exact order listed, to provide additional and useful embodiments of the invention.

[0011] All features described in the specification and / or claims are intended to be disclosed individually and independently of one another as limitations to the original disclosure and claimed particulars, apart from any configuration of features described in the examples and / or claims. Furthermore, all numerical ranges and group or aggregate descriptions are intended to disclose their intermediate configurations as limitations to the original disclosure and claimed particulars.

[0012] In one or more embodiments, a working machine may include a prime mover having an output shaft, a working unit coupled to the output shaft, a slip mechanism, and a fan attached to the output shaft via the slip mechanism. The slip mechanism may rotate the output shaft and the fan integrally when a load torque applied to the output shaft when driving the fan is less than a predetermined value, and may rotate the output shaft and the fan relatively when the load torque when driving the fan is equal to or greater than the predetermined value.

[0013] In one or more embodiments, when the fan is driven with at least a portion of the fan submerged in water, the load torque may be greater than or equal to the predetermined value, and when the fan is driven with the fan not entirely submerged in water, the load torque may be less than the predetermined value.

[0014] In general, the water resistance applied to the fan when it is driven underwater is greater than the air resistance applied to the fan when it is driven in air. Therefore, the resistance applied to the fan when it is driven in a state where at least a part of the fan is immersed in water is greater than the resistance applied to the fan when it is driven in a state where the entire fan is not immersed in water. As a result, the load torque when at least a part of the fan is immersed in water is greater than the load torque when the entire fan is not immersed in water, and is greater than the predetermined value. According to the above configuration, when at least a part of the fan is immersed in water, the slip mechanism rotates the output shaft and the fan relative to each other. Therefore, when at least a part of the fan is immersed in water, it is possible to suppress a reduction in the torque transmitted from the prime mover to the working unit via the output shaft.

[0015] In one or more embodiments, the slip mechanism may include a biasing member extending axially of the output shaft, one end of the biasing member being coupled to one of the output shaft and the fan and the other end abutting the other of the fan and the shaft.

[0016] According to the above-mentioned configuration, the static friction torque due to the biasing force can be adjusted by adjusting the biasing force of the biasing member. In other words, the predetermined value can be adjusted by adjusting the biasing force of the biasing member. Therefore, the working machine can be adapted to various situations.

[0017] In one or more embodiments, the slip mechanism may further include a washer provided between the other end of the biasing member and the fan in the axial direction. The other end of the biasing member may abut against the other of the fan and the shaft via the washer.

[0018] According to the above configuration, the washer abuts against the fan instead of the biasing member. In a configuration in which the biasing member abuts against the fan, the portion of the fan against which the biasing member abuts may wear out. By having the washer abut against the fan instead of the biasing member, the contact area of ​​the portion abutting against the fan can be increased, and therefore wear on the fan can be suppressed.

[0019] In one or more embodiments, the fan may have a resin fan body having an opening through which the output shaft passes, and a metal bushing provided in the opening. The output shaft may be made of metal. A clearance may be provided between the bushing and the output shaft in a direction perpendicular to the axial direction of the output shaft. At least one of an inner circumferential surface of the bushing and a portion of the output shaft facing the inner circumferential surface may be surface-treated.

[0020] When a work machine is used underwater, the metallic bush and the metallic output shaft may corrode. When the bush and the output shaft corrode, substances caused by corrosion are generated. The substances caused by corrosion may cause the clearance between the bush and the output shaft to disappear. In this case, the output shaft and the fan rotate together regardless of whether the load torque when driving the fan is equal to or greater than a predetermined value. With the above configuration, corrosion of at least one of the bush and the output shaft that faces the inner circumferential surface can be suppressed, and when the load torque when driving the fan is equal to or greater than a predetermined value, the output shaft and the fan can rotate relatively to each other.

[0021] In one or more embodiments, the fan may include a resin fan body having an opening through which the output shaft passes, and a metal bushing provided in the opening. The slip mechanism may include a biasing member extending in the axial direction of the output shaft, one end of the biasing member being connected to the output shaft and the other end being in contact with the bushing of the fan.

[0022] The portion of the fan that the biasing member of the slip mechanism contacts may wear out. Metal bushings are less prone to wear than the plastic fan body. This makes it possible to prevent wear in the portion of the fan that the biasing member of the slip mechanism contacts, thereby improving the durability of the fan.

[0023] In one or more embodiments, the prime mover may be a motor.

[0024] In the case where the prime mover is a motor, if the load torque of the motor becomes excessive, an excessively large current (hereinafter, referred to as "overcurrent") flows through the motor. With the above configuration, it is possible to prevent the overcurrent from flowing through the motor. Therefore, it is possible to protect the motor.

[0025] (Example) As shown in FIG. 1, the chain saw 2 includes a main body 4, a guide bar 6, and a saw chain 8. The guide bar 6 is a long, thin plate-like member attached to the main body 4 so as to protrude forward from the main body 4. The guide bar 6 is made of a metal material such as iron. The saw chain 8 includes a plurality of cutters connected to each other and is attached along the periphery of the guide bar 6. In the following description, as shown in FIG. 2, when the chain saw 2 is placed on a horizontal placement surface S such as the ground, a direction perpendicular to the placement surface S is referred to as the up-down direction of the chain saw 2, a direction in which the longitudinal direction of the guide bar 6 is projected onto the placement surface S is referred to as the front-rear direction of the chain saw 2, and a direction perpendicular to the up-down direction and the front-rear direction of the chain saw 2 is referred to as the left-right direction of the chain saw 2.

[0026] The main body 4 includes a main body housing 10, a front hand guard 12, a front handle 14, a sprocket cover 16 (see FIG. 3), a battery storage section 18, a rear handle 20, and a rear hand guard 22. As shown in FIG. 1, the main body housing 10 is made up of a left housing 24 and a right housing 26. The main body housing 10 has a generally rectangular parallelepiped shape with its longitudinal direction extending in the front-rear direction of the main body 4.

[0027] An intake section 30 having a plurality of intake openings 30a is provided on the left surface of the left housing 24. As shown in Fig. 4, an exhaust opening 24a is provided on the upper front portion of the left housing 24.

[0028] The front handle 14 in FIG. 1 is fixed to the lower surface of the left housing 24 by screwing, and includes a left fixing part 14a extending leftward from the lower surface of the left housing 24, a left grip part 14b extending upward from the left end of the left fixing part 14a, an upper grip part 14c extending rightward from the upper end of the left grip part 14b, and a right fixing part 14d extending rearward and downward from the right end of the upper grip part 14c. As shown in FIG. 3, the right fixing part 14d is fixed to the right housing 26 by screwing behind the sprocket cover 16. The front hand guard 12 is supported rotatably at the front upper part of the main body housing 10. The front hand guard 12 is provided forward of the front handle 14. The front hand guard 12 protects the hand of the user holding the upper grip part 14c of the front handle 14.

[0029] The rear handle 20 extends rearward and downward from the upper rear surface of the main body housing 10 and is bent downward. The rear hand guard 22 extends rearward from the lower rear surface of the main body housing 10 and is connected to the lower end of the rear handle 20. The rear hand guard 22 includes a first guard portion 22a disposed directly below the rear handle 20 and a second guard portion 22b extending rightward from the first guard portion 22a. The rear hand guard 22 protects the hand of a user gripping the rear handle 20.

[0030] A power button 40 is disposed on the upper surface of the rear handle 20 near the front end thereof, allowing the user to switch the power of the chainsaw 2 on and off. A trigger lever 42 is disposed on the lower surface of the rear handle 20 near the front end thereof, allowing the user to operate the rotation drive of the saw chain 8. A lock lever 44 is disposed on the upper surface of the rear handle 20, which switches between a state in which the user is permitted to operate the trigger lever 42 and a state in which the user is prohibited from operating the trigger lever 42. The lock lever 44 is disposed behind the power button 40. When using the chainsaw 2, the user holds the chainsaw 2 by gripping the rear handle 20 with his / her right hand and the front handle 14 with his / her left hand. When the user presses down the lock lever 44 of the rear handle 20 with the palm of his / her right hand from this state, the operation of the trigger lever 42 by the user is permitted. When the user pulls up the trigger lever 42 with the index finger of his / her right hand in this state, the saw chain 8 is rotated.

[0031] The battery storage section 18 is provided between the front handle 14 and the rear handle 20. A battery 50 (see FIG. 4) is stored in the battery storage section 18. The battery storage section 18 includes a battery cover 52 that can be opened and closed.

[0032] As shown in FIG. 4, at the front inside the main housing 10, there are arranged a control unit 60, a motor unit 62, an oil tank 64, an inner housing 66, an inner housing cover 68 (see FIG. 5), a fan 70 (see FIG. 5), a slip mechanism 72 (see FIG. 5), and an oil pump 74 (see FIG. 5). The control unit 60 is arranged above the motor unit 62. The control unit 60 includes a control board 80 and a board support portion 82 that supports the control board 80. The board support portion 82 is provided with a plurality of fins 84 that protrude downward. The oil tank 64 is provided at the front lower portion of the main housing 10. The oil tank 64 stores lubricating oil for lubricating the saw chain 8.

[0033] As shown in FIG. 5, the inner housing 66 includes a control unit housing 90 that houses the control unit 60, a motor unit attachment portion 92, and a fan housing 94 that houses the fan 70. A first boundary wall 96 is provided between the control unit housing 90, the motor unit attachment portion 92, and the fan housing 94 in the up-down direction. As shown in FIG. 4, a first opening 96a that connects the control unit housing 90 and the fan housing 94 is provided at the rear of the first boundary wall 96. A first air flow path 98 through which air flows is formed in the fan housing 94. A second air flow path 100 that connects the first air flow path 98 and the exhaust opening 24a of the left housing 24 is formed in the control unit housing 90. As shown in FIG. 5, a second boundary wall 102 is provided between the motor unit attachment portion 92 and the fan housing 94. A second opening 102a is provided at the center of the second boundary wall 102. 6, an inner housing cover 68 is attached to the left part of the inner housing 66. The outer shape of the inner housing cover 68 corresponds to the outer shape of the left part of the inner housing 66.

[0034] As shown in Fig. 5, the motor unit 62 includes a motor case 110, a waterproof cover 112, and a motor 114. The motor case 110 is fixed to the right surface of the second boundary wall 102 of the inner housing 66 by screwing. The motor case 110 includes a case cylindrical portion 120 and a reduced diameter portion 122 extending leftward from the left end of the case cylindrical portion 120. The axis of the case cylindrical portion 120 coincides with the central axis A of the output shaft 144, which will be described later. The inner diameter of the left end of the reduced diameter portion 122 is smaller than the diameter of the second opening 102a of the second boundary wall 102.

[0035] The waterproof cover 112 includes a cover main body 130 and a lid 132. The cover main body 130 includes a main body side disc 130a, a first cylindrical portion 130b having a cylindrical shape, and a second cylindrical portion 130c having a cylindrical shape. The axes of the main body side disc 130a, the first cylindrical portion 130b, and the second cylindrical portion 130c coincide with the central axis A of the output shaft 144 described later. A main body side opening 130d is provided in the center of the main body side disc 130a. The first cylindrical portion 130b extends rightward from the radially outer end of the main body side disc 130a. The outer diameter of the first cylindrical portion 130b is smaller than the inner diameter of the case cylindrical portion 120 of the motor case 110. Therefore, a gap is provided between the first cylindrical portion 130b and the case cylindrical portion 120 of the motor case 110. The second cylindrical portion 130c extends leftward from the body-side disc portion 130a on the periphery of the body-side opening 130d. The lid portion 132 includes a lid-side disc portion 132a and a third cylindrical portion 132b. A lid-side opening 132c is provided in the center of the lid-side disc portion 132a. The third cylindrical portion 132b extends leftward from the lid-side disc portion 132a on the periphery of the lid-side opening 132c. The lid portion 132 covers the opening at the right end of the cover body portion 130.

[0036] The motor 114 is waterproofed by the waterproof cover 112. The motor 114 is an inner rotor type DC brushless motor. In a modified example, the motor 114 may be an outer rotor type brushless motor or a brushed motor. The motor 114 includes a stator 140, a rotor 142 disposed inside the stator 140, and an output shaft 144 disposed so as to penetrate the center of the stator 140 and the rotor 142 and engaged with the rotor 142. The output shaft 144 extends along a central axis A. The central axis A is parallel to the left-right direction. Hereinafter, the direction along the central axis A will be referred to as the "axial direction." The left end of the output shaft 144 is located to the left of the left end of the waterproof cover 112, and the right end of the output shaft 144 is located to the right of the right end of the waterproof cover 112. That is, the output shaft 144 penetrates the waterproof cover 112 in the left-right direction. A plurality of waterproof members 112a are provided in the waterproof cover 112 at locations where the output shaft 144 passes through.

[0037] A sprocket 150 and a brake base 152 are fixed to the right end of the output shaft 144. A saw chain 8 (see FIG. 1) is hung from the guide bar 6 on the sprocket 150. A brake drum 154 is fitted onto the brake base 152. When the motor 114 is driven, the sprocket 150 rotates together with the output shaft 144, thereby causing the saw chain 8 to rotate around the sprocket 150 and the guide bar 6.

[0038] A fan 70, a slip mechanism 72, and an oil pump 74 are attached to the left end of the output shaft 144. As shown in FIG. 7, the fan 70 includes a resin fan body 160, a metal bush 162, and a rib 169. As an example, the bush 162 is made of stainless steel. The fan body 160 includes a fan disk 164, a plurality of blades 166, and a cover 168. As shown in FIG. 8, a central opening 164a is provided in the center of the fan disk 164. The rib 169 is connected to the fan disk 164 and extends rightward from the fan disk 164 on the periphery of the central opening 164a. The inner diameter of the rib 169 is smaller than the diameter of the central opening 164a. The outer diameter of the rib 169 is smaller than the outer diameter of the fan disk 164.

[0039] The bush 162 is attached to the central opening 164a and the inner peripheral surface of the rib 169. The bush 162 includes a left cylindrical portion 162a and a right cylindrical portion 162b. The left cylindrical portion 162a and the right cylindrical portion 162b are attached to the inner peripheral surface of the central opening 164a and the inner peripheral surface of the rib 169, respectively. An insulating surface treatment (e.g., a coating treatment) is applied to the inner peripheral surface 162c of the bush 162 to prevent corrosion when the bush 162 comes into contact with water. In addition, an insulating surface treatment is also applied to a portion of the output shaft 144 that faces the inner peripheral surface 162c. The inner diameter of the bush 162 is slightly larger than the outer diameter of the portion of the output shaft 144 that faces the bush 162. That is, a clearance C is provided between the bush 162 and the output shaft 144.

[0040] As shown in Fig. 7, the fan disk portion 164 and the multiple blade portions 166 are integrally formed. The multiple blade portions 166 extend rightward from the fan disk portion 164. When the fan 70 is viewed from the right, the multiple blade portions 166 are curved in a counterclockwise direction from the radially inner side toward the radially outer side. The cover portion 168 is welded to the right ends of the multiple blade portions 166. A fan-side intake opening 168a is provided in the center of the cover portion 168. The diameter of the fan-side intake opening 168a is larger than the outer diameter of the rib 169.

[0041] 8, in the output shaft 144, a first groove 144a is formed in the circumferential direction to the right of the bush 162, and a second groove 144b is formed to the left of the bush 162. A right E-ring 170 is fitted into the first groove 144a. A right washer 172 is provided between the right E-ring 170 and the bush 162. The right washer 172 abuts against the right E-ring 170 and the bush 162.

[0042] The slip mechanism 72 is provided on the left side of the fan 70. The slip mechanism 72 includes a central washer 174, a coil spring 176, a left washer 178, and a left E-ring 180. The left E-ring 180 is fitted into the second groove 144b of the output shaft 144. The central washer 174 is disposed at a position where its right surface abuts against the bush 162. The left washer 178 is disposed at a position where its left surface abuts against the left E-ring 180. The coil spring 176 is disposed between the central washer 174 and the left washer 178. The central washer 174 is pressed against the bush 162 by the biasing force of the coil spring 176. The biasing force of the coil spring 176 is adjusted so that when the torque (hereinafter referred to as "load torque") loaded on the output shaft 144 when driving the fan 70 is less than a predetermined value, the fan 70 and the output shaft 144 rotate integrally, and when the load torque when driving the fan 70 is equal to or greater than the predetermined value, the fan 70 and the output shaft 144 rotate relatively to each other.

[0043] Note that a state in which the load torque when driving the fan 70 is less than a predetermined value means a state in which the static friction torque by the slip mechanism 72 is greater than the load torque. In this case, the fan 70 and the output shaft 144 rotate integrally in response to the fan 70 and the output shaft 144 being connected to each other via the slip mechanism 72. Note that a state in which the fan 70 and the output shaft 144 are integral means a state in which the rotation speed of the fan 70 and the rotation speed of the output shaft 144 are approximately the same.

[0044] Furthermore, a state in which the load torque when driving the fan 70 is equal to or greater than a predetermined value means a state in which the load torque exceeds the static friction torque caused by the slip mechanism 72. In this case, the fan 70 and the output shaft 144 rotate relatively to each other as a result of the fan 70 and the output shaft 144 slipping via the slip mechanism 72. Specifically, the fan 70 rotates due to the kinetic friction torque caused by the slip mechanism 72. Note that a state in which the fan 70 and the output shaft 144 are relative to each other means a state in which the rotation speed of the fan 70 is smaller than the rotation speed of the output shaft 144.

[0045] (Chainsaw 2 movement in air) Next, the operation of the chain saw 2 when the chain saw 2 is used in air will be described.

[0046] When the user presses down the lock lever 44 of the rear handle 20 in FIG. 1 and pulls up the trigger lever 42, the motor 114 in FIG. 5 starts to drive and the output shaft 144 rotates. This causes the sprocket 150 connected to the output shaft 144 of the motor 114 to rotate. Also, as shown in FIG. 9, when the chain saw 2 is used in the air, the load torque becomes a torque T1 that is smaller than a predetermined value. This is because the air resistance acting on the fan 70 when the fan 70 is driven is small. In this case, the fan 70 is connected to the output shaft 144 via the slip mechanism 72, and the output shaft 144 and the fan 70 rotate together. That is, the output shaft 144 and the fan 70 rotate together as the motor 114 is driven.

[0047] When the fan 70 is driven, air outside the main housing 10 passes through the intake opening 30a (see FIG. 1) of the left housing 24 and is sucked into the main housing 10. The air that has flowed into the main housing 10 passes around the inner housing 66 (see FIG. 6) and then passes between the waterproof cover 112 and the motor case 110 to the left as shown in FIG. 5. The air passes between the waterproof cover 112 and the motor case 110, thereby cooling the motor 114. The air then passes through the second opening 102a of the second boundary wall 102 and is sucked into the fan 70. As described above, the shape of the multiple blades 166 of the fan 70 is curved in a counterclockwise direction from the radial inside to the radial outside (see FIG. 7). For this reason, the air sucked into the fan 70 is pushed outward in the radial direction and flows into the first air flow path 98 (see FIG. 4). 4, the air that has flowed into the first air flow path 98 passes through the first opening 96a and the second air flow path 100. The air passes through the second air flow path 100, thereby cooling the control board 80. Then, the air in the second air flow path 100 is exhausted to the outside from the exhaust opening 24a of the left housing 24.

[0048] (Chainsaw 2 in water) Next, the operation of the chain saw 2 when the chain saw 2 is used underwater will be described. The user performs the same operation as when the chain saw 2 is used in air, and the motor 114 in FIG. 5 starts to drive, and the output shaft 144 rotates. As shown in FIG. 10, when the chain saw 2 is used underwater, the load torque becomes a torque T2 that is greater than a predetermined value. This is because the resistance of water applied to the fan 70 when the fan 70 is driven underwater is greater than the resistance of air applied to the fan 70 when the fan 70 is driven in air. In this case, the resistance of water applied to the fan 70 exceeds the biasing force of the coil spring 176, and the central washer 174 of the slip mechanism 72 and the bush 162 of the fan 70 slip. As a result, the rotation speed of the fan 70 becomes smaller than the rotation speed of the output shaft 144, and the output shaft 144 and the fan 70 rotate relatively. Specifically, the rotation speed of the fan 70 becomes smaller than the rotation speed of the output shaft 144.

[0049] Thus, in the chainsaw 2 of this embodiment, when the chainsaw 2 is used in air, the output shaft 144 and the fan 70 rotate together, and when the chainsaw 2 is used underwater, the output shaft 144 and the fan 70 rotate relative to each other.

[0050] In one or more embodiments, the chain saw 2 (an example of a "working machine") includes a motor 114 (an example of a "prime mover") having an output shaft 144, a saw chain 8 (an example of a "working unit") connected to the output shaft 144, a slip mechanism 72, and a fan 70 attached to the output shaft 144 via the slip mechanism 72. The slip mechanism 72 rotates the output shaft 144 and the fan 70 together when the load torque when driving the fan 70 is less than a predetermined value, and rotates the output shaft 144 and the fan 70 relatively when the load torque when driving the fan 70 is equal to or greater than the predetermined value.

[0051] When the chain saw 2 is used in air, the load torque is less than a predetermined value. On the other hand, when the chain saw 2 is used underwater, the load torque is equal to or greater than a predetermined value. According to the above configuration, the slip mechanism 72 rotates the output shaft 144 and the fan 70 together when the load torque when driving the fan 70 is less than a predetermined value. This is because the static friction torque caused by the slip mechanism 72 is greater than the load torque when the load torque is less than the predetermined value. On the other hand, the slip mechanism 72 rotates the output shaft 144 and the fan 70 relatively when the load torque when driving the fan 70 is equal to or greater than a predetermined value. That is, the slip mechanism 72 causes the fan 70 to slip relative to the output shaft 144. This is because the static friction torque caused by the slip mechanism 72 is smaller than the load torque when the load torque is equal to or greater than a predetermined value. When the output shaft 144 and the fan 70 rotate relative to each other, the torque of the output shaft 144 required to drive the fan 70 is reduced. Therefore, a reduction in the torque transmitted from the motor 114 to the saw chain 8 via the output shaft 144 can be suppressed.

[0052] In one or more embodiments, when at least a portion of the fan 70 is submerged in water, the load torque is greater than or equal to a predetermined value, and when the fan 70 is not entirely submerged in water, the load torque is less than the predetermined value.

[0053] In general, the water resistance applied to the fan 70 when the fan 70 is driven underwater is greater than the air resistance applied to the fan 70 when the fan 70 is driven by air. Therefore, the resistance applied to the fan 70 when at least a part of the fan 70 is immersed in water is greater than the resistance applied to the fan 70 when the fan 70 is driven when the fan 70 is not entirely immersed in water. As a result, the load torque when at least a part of the fan 70 is immersed in water is greater than the load torque when the fan 70 is not entirely immersed in water, and is greater than a predetermined value. According to the above configuration, when at least a part of the fan 70 is immersed in water, the slip mechanism 72 rotates the output shaft 144 and the fan 70 relative to each other. Therefore, when at least a part of the fan 70 is immersed in water, it is possible to suppress a reduction in the torque transmitted from the motor 114 to the saw chain 8 via the output shaft 144.

[0054] In one or more embodiments, the slip mechanism 72 includes a coil spring 176 (an example of a "biasing member") that extends axially of the output shaft 144, with a left end (an example of a "one end") connected to the output shaft 144 and a right end (an example of a "other end") abutting the fan 70.

[0055] According to the above-described configuration, the static friction torque due to the biasing force can be adjusted by adjusting the biasing force of the coil spring 176. That is, the predetermined value can be adjusted by adjusting the biasing force of the coil spring 176. Therefore, the chain saw 2 can be adapted to various situations.

[0056] In one or more embodiments, the slip mechanism 72 further includes a central washer 174 (an example of a "washer") that is provided axially between the right end of the coil spring 176 and the fan 70. The right end of the coil spring 176 abuts against the fan 70 via the central washer 174.

[0057] According to the above configuration, the central washer 174 contacts the fan 70 instead of the coil spring 176. The portion of the slip mechanism 72 that contacts the fan 70 may wear out. By having the central washer 174 contact the fan 70 instead of the coil spring 176, the contact area of ​​the portion that contacts the fan 70 can be increased, and therefore wear of the fan 70 can be suppressed.

[0058] In one or more embodiments, the fan 70 includes a resin fan body 160 having a central opening 164a through which the output shaft 144 passes and ribs 169 (an example of an "opening"), and a metal bushing 162 provided in the central opening 164a and the ribs 169. The output shaft 144 is made of metal. A clearance C is provided between the bushing 162 and the output shaft 144 in a direction perpendicular to the axial direction. An inner circumferential surface 162c of the bushing 162 and a portion of the output shaft 144 facing the inner circumferential surface 162c are surface-treated.

[0059] When the chain saw 2 is used underwater, the metallic bush 162 and the metallic output shaft 144 may corrode. When the bush 162 and the output shaft 144 corrode, a substance is generated by the corrosion. The substance generated by the corrosion may eliminate the clearance C between the bush 162 and the output shaft 144. In this case, the output shaft 144 and the fan 70 rotate together regardless of whether the load torque when driving the fan 70 is equal to or greater than a predetermined value. With the above-mentioned configuration, it is possible to prevent at least one of the bush 162 and the output shaft 144 from corroding, and when the load torque when driving the fan 70 is equal to or greater than a predetermined value, the output shaft 144 and the fan 70 can rotate relatively to each other.

[0060] In one or more embodiments, fan 70 includes a plastic fan body 160 having a central opening 164a through which output shaft 144 passes, ribs 169, and a metal bushing 162 attached to central opening 164a and ribs 169. Slip mechanism 72 includes an axially extending coil spring 176 having a left end connected to output shaft 144 and a right end abutting bushing 162 of fan 70.

[0061] The portion of the fan 70 against which the coil spring 176 of the slip mechanism 72 abuts may wear out. The metal bushing 162 is less susceptible to wear than the resin fan main body 160. Therefore, it is possible to prevent wear in the portion of the fan 70 against which the coil spring 176 of the slip mechanism 72 abuts, and it is possible to improve the durability of the fan 70.

[0062] In one or more embodiments, the chain saw 2 includes a motor 114 as a prime mover.

[0063] In the case where the prime mover is the motor 114, if the load torque of the output shaft 144 of the motor 114 becomes excessive, an excessively large current (hereinafter, referred to as "overcurrent") flows through the motor 114. With the above configuration, it is possible to prevent the overcurrent from flowing through the motor 114. Therefore, the motor 114 can be protected.

[0064] (First Modification) The "working machine" is not limited to the chain saw 2, but may be a lawn mower, a grass cutter, a hedge trimmer, or the like.

[0065] (Second Modification) The right end of the coil spring 176 of the slip mechanism 72 may be connected to the fan 70, and the left end may abut against the output shaft 144. In this modification, the right end and the left end of the coil spring 176 are examples of "one end" and "the other end" of the "biasing member", respectively.

[0066] (Third Modification) The slip mechanism 72 may include an elastic member such as a disc spring, rubber, etc., instead of the coil spring 176. In another modification, the slip mechanism 72 may not include the central washer 174.

[0067] (Fourth Modification) The fan 70 does not need to include the bush 162. In another modification, the inner circumferential surface 162c of the bush 162 and the portion of the output shaft 144 that faces the inner circumferential surface 162c may not be surface-treated. In a further modification, only one of the inner circumferential surface 162c of the bush 162 and the portion of the output shaft 144 that faces the inner circumferential surface 162c may be surface-treated.

[0068] (Fifth Modification) The slip mechanism 72 may be in contact with the fan main body 160 of the fan 70, which is made of resin.

[0069] (Sixth Modification) The "prime mover" is not limited to the motor 114, but may be an engine or the like.

[0070] (Seventh Modification) In the chain saw 2 described above, the saw chain 8 is provided to the right of the motor 114 in the axial direction, and the slip mechanism 72 and fan 70 are provided in this order to the left of the motor 114. In a modification, the saw chain 8, the fan 70, and the slip mechanism 72 may be provided to the left or right of the motor 114 in the axial direction. [Explanation of symbols]

[0071] 2: chain saw, 4: main body, 6: guide bar, 8: saw chain, 10: main body housing, 12: front hand guard, 14: front handle, 14a: left side fixing part, 14b: left side grip part, 14c: upper grip part, 14d: right side fixing part, 16: sprocket cover, 18: battery storage part, 20: rear handle, 22: rear hand guard, 22a: first guard part, 22b: second guard part, 24: left side housing, 24a: exhaust opening, 26: right side housing, 30: intake part, 30a: intake opening, 4 0: power button, 42: trigger lever, 44: lock lever, 50: battery, 52: battery cover, 60: control unit, 62: motor unit, 64: oil tank, 66: inner housing, 68: inner housing cover, 70: fan, 72: slip mechanism, 74: oil pump, 80: control board, 82: board support, 84: fin, 90: control unit housing, 92: motor unit mounting portion, 94: fan housing, 96: first boundary wall, 96a: first opening, 98: first air flow path, 100 : second air flow path, 102: second boundary wall, 102a: second opening, 110: motor case, 112: waterproof cover, 112a: waterproof member, 114: motor, 120: case cylindrical portion, 122: diameter-reduced portion, 130: cover main body portion, 130a: main body side disc portion, 130b: first cylindrical portion, 130c: second cylindrical portion, 130d: main body side opening, 132: lid portion, 132a: lid side disc portion, 132b: third cylindrical portion, 132c: lid side opening, 140: stator, 142: rotor, 144: output shaft, 144a: first groove, 14 4b: second groove, 150: sprocket, 152: brake base, 154: brake drum, 160: fan main body, 162: bush, 162a: left cylindrical portion, 162b: right cylindrical portion, 162c: inner circumferential surface, 164: fan disc portion, 164a: central opening, 166: blade portion, 168: cover portion, 168a: fan side intake opening, 169: rib, 170: right E-ring, 172: right washer, 174: central washer, 176: coil spring, 178: left washer, 180: left E-ring, A: central axis

Claims

1. A work machine, a prime mover having an output shaft; A working unit connected to the output shaft; A slip mechanism; a fan attached to the output shaft via the slip mechanism; The slip mechanism includes: When a load torque applied to the output shaft when driving the fan is less than a predetermined value, the output shaft and the fan are rotated integrally; a work machine that rotates the output shaft and the fan relatively when the load torque when driving the fan is equal to or greater than the predetermined value.

2. When the fan is driven in a state where at least a portion of the fan is immersed in water, the load torque becomes equal to or greater than the predetermined value, The work machine according to claim 1 , wherein the load torque is less than the predetermined value when the fan is driven in a state where the fan is not entirely submerged in water.

3. The slip mechanism is a biasing member extending in an axial direction of the output shaft, One end is connected to one of the output shaft and the fan, the other end abuts against the other of the fan and the shaft; The work machine according to claim 1 or 2, further comprising the biasing member.

4. the slip mechanism further includes a washer provided between the other end of the biasing member and the fan in the axial direction, The work machine according to claim 3 , wherein the other end of the urging member abuts against the other of the fan and the shaft via the washer.

5. The fan is a resin fan body having an opening through which the output shaft passes; A metal bushing is provided in the opening, The output shaft is made of metal. a clearance is provided between the bush and the output shaft in a direction perpendicular to an axial direction of the output shaft, The work machine according to claim 1 , wherein at least one of an inner circumferential surface of the bush and a portion of the output shaft facing the inner circumferential surface is subjected to a surface treatment.

6. The fan is a resin fan body having an opening through which the output shaft passes; A metal bushing is provided in the opening, 6. The work machine according to claim 1, wherein the slip mechanism is a biasing member extending in the axial direction of the output shaft, one end of the biasing member being connected to the output shaft and the other end of the biasing member being in contact with the bush of the fan.

7. The work machine according to claim 1 , wherein the prime mover is a motor.

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