Tension mechanism

Abstract

To provide a tension mechanism capable of suppressing increase in size in an axial direction of a rotating shaft.SOLUTION: A tension mechanism includes a rotating body 131 extending along a radial direction from a rotating shaft 105, and a torsion coil spring 140 held by the rotating shaft 105 and energizing the rotating body 131 in a rotation direction. The torsion coil spring 140 includes a coil 141 held by the rotating shaft 105, a first arm 143 extending from one end of the coil 141 and relatively positioned with respect to the rotating shaft 105, and a second arm 145 extending from the other end of the coil 141 and engaged with a plate-like member 133. The second arm 145 is within an arrangement range of the rotating body 131 in an axial direction of the rotating shaft 105.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to tensioning mechanisms. [Background technology]

[0002] Patent Document 1 discloses a tension member that applies tension to an endless rotating chain. The tension member includes a connecting tubular portion rotatably connected to a rotating shaft provided on a frame, and a tension arm provided on the connecting member, and is supported so as to be swingable relative to the rotating shaft. A tension spring is disposed to act on the base end of the tension arm. One end of the tension spring is engaged with the frame, and the other end is bent along the axial direction of the rotating shaft and engaged with the side of the tension arm. A wheel is disposed on the free end of the tension arm so as to be positioned within the loop of the endless rotating chain. The tension member applies tension to the endless rotating chain by the biasing force of the tension spring and the wheel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-312395 Summary of the Invention [Problem to be solved by the invention]

[0004] In a tension mechanism having the above-described tension member, for example, it is required to reduce the size in the axial direction of the rotation shaft.

[0005] The present disclosure aims to provide a tension mechanism that can prevent the size of the rotation shaft from increasing in the axial direction. [Means for solving the problem]

[0006] One example of the tension mechanism is a tension mechanism that applies tension to the endless member (117), and includes a rotating body (131) that is rotatable about a rotating shaft (105) and extends in a radial direction from the rotating shaft (105), and a torsion coil spring (140) that is held by the rotating shaft (105) and biases the rotating body (131) in a rotational direction. The rotating body (131) includes a plate-like member (133) that extends in a radial direction from the rotating shaft (105) as a base end, and a torsion coil spring (140) that is provided at the tip of the plate-like member (133) and biases the rotating body (131) in a rotational direction. and a guide portion (138) that abuts against the end-shaped member (117), and the torsion coil spring (140) includes a winding portion (141) held on the rotating shaft (105), a first arm portion (143) extending from one end of the winding portion (141) and positioned relative to the rotating shaft (105), and a second arm portion (145) extending from the other end of the winding portion (141) and engaged with the plate-shaped member (133), and the second arm portion (145) is within the arrangement range of the rotating body (131) in the axial direction of the rotating shaft (105).

[0007] In the tension mechanism, the first arm (143) of the torsion coil spring (140) held by the rotating shaft (105) is positioned relative to the rotating shaft (105), and the second arm (145) of the torsion coil spring (140) is engaged with the plate-shaped member (133) of the rotating body (131). Therefore, the rotating body (131) is biased by the torsion coil spring (140), thereby applying tension to the endless member (117) abutting against the guide portion (138). Furthermore, the second arm (145) of the torsion coil spring (140) is within the arrangement range of the rotating body (131) in the axial direction of the rotating shaft (105). That is, the second arm (145) does not protrude beyond the arrangement range of the rotating body (131) in the axial direction of the rotating shaft (105). Therefore, the size of the tension mechanism can be prevented from increasing in the axial direction of the rotating shaft.

[0008] In one example, the second arm portion (145) may include an extension portion that extends radially outward from the rotation shaft (105) without being displaced in the axial direction of the rotation shaft (105) and engages with the plate-shaped member (133). In this configuration, there is no need to bend the second arm portion (145) along the axial direction, and therefore the second arm portion (145) does not protrude outward in the axial direction beyond the plate-shaped member (133).

[0009] In one example, the plate-like member 133 includes a bent portion 135 that is bent so that its position in the axial direction of the pivot shaft 105 changes, and the bent portion 135 may include an engaging portion that engages with the second arm portion 145. In this configuration, the engaging portion that engages with the second arm portion 145 can be easily formed.

[0010] An example of the plate-shaped member (133) may include a first plate-shaped portion (134) extending radially from the pivot shaft (105) as a base end, a bent portion (135) bending from the tip of the first plate-shaped portion (134), and a second plate-shaped portion (136) extending radially from the tip of the bent portion (135), wherein the first plate-shaped portion (134) and the second plate-shaped portion (136) are offset from each other in the axial direction of the pivot shaft (105), and the engaging portion may be formed by a through-hole (135a) formed in the bent portion (135). In this configuration, the second arm portion (145) can be engaged with the plate-shaped member (133) by inserting the second arm portion (145) into the through-hole (135a) serving as the engaging portion.

[0011] In one example, the guide portion (138) may be arranged on a surface of the second plate-shaped portion (136) that faces the side on which the first plate-shaped portion (134) is located in the axial direction, and the torsion coil spring (140) may be arranged on a surface of the first plate-shaped portion (134) that faces the side on which the second plate-shaped portion (136) is located in the axial direction. This configuration can prevent the guide portion (138) and the torsion coil spring (140) from protruding from the arrangement range of the plate-shaped member (133) in the axial direction.

[0012] In one example, the plate-shaped member 133 includes a cylindrical shaft portion 132 through which the pivot shaft 105 is inserted, and the guide portion 138 may be located within the arrangement range of the plate-shaped member 133 in the axial direction of the pivot shaft 105. In this configuration, the size of the tension mechanism in the axial direction can be located within the arrangement range of the plate-shaped member 133. [Effects of the Invention]

[0013] According to the present disclosure, it is possible to provide a tension mechanism that can prevent the size of the rotation shaft from increasing in the axial direction. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a perspective view showing a self-propelled mower equipped with an example tension mechanism; [Figure 2] 10A and 10B are diagrams showing a chain case section equipped with an example tension mechanism. [Figure 3] FIG. 1 is a perspective view showing a chain case portion equipped with an example tension mechanism. [Figure 4] FIG. 1 is an exploded perspective view of an example of a chain case with a tension mechanism disassembled therefrom. [Figure 5] FIG. 1 illustrates an example tensioning mechanism. [Figure 6] FIG. 10 is an exploded perspective view of an example tension mechanism with a guide portion disassembled. [Figure 7] FIG. 2 is a cross-sectional view of an example chain case portion. DETAILED DESCRIPTION OF THE INVENTION

[0015] As a specific example of the tension mechanism 130 according to the present disclosure, a tension mechanism 130 provided in a self-propelled brush cutter will be described below with reference to the drawings. Note that in the description of the drawings, the same elements are given the same reference numerals, and duplicated descriptions will be omitted.

[0016] Fig. 1 is a perspective view of a self-propelled mower equipped with an example tension mechanism 130. The self-propelled mower 1 shown in Fig. 1 is a device that can cut grass in a field (for example, the slopes and ridges of a paddy field) while moving together with a walking operator. As shown in Fig. 1, the self-propelled mower 1 comprises a housing 2, traveling wheels 3, a drive unit 5, a transmission unit 6, a chain case unit 100, and a handle 8.

[0017] The housing 2 includes a vehicle frame. The lower surface of the housing 2 is open, and a mower blade that rotates around an axis extending in the up-down direction is provided in this opening. A pair of traveling wheels 3 is provided at each of one end and the other end of the housing 2 in the X direction. The self-propelled brush cutter in this example can travel in either one direction or the other along the X direction. For convenience, the pair of traveling wheels 3 provided at one end in the X direction are referred to as front wheels 3a, and the pair of traveling wheels 3 provided at the other end in the X direction are referred to as rear wheels 3b. Traveling with the front wheels 3a in front is referred to as forward travel, and traveling with the rear wheels 3b in front is referred to as reverse travel. Hereinafter, unless otherwise specified, the front wheels 3a are referred to as the front, and the rear wheels 3b are referred to as the rear.

[0018] The drive unit 5 is provided on the upper part of the housing 2. An example of the drive unit 5 may be an engine that runs on fuel such as gasoline. The drive unit 5 has an output shaft (not shown) that protrudes downward in the vertical direction. The output shaft of the drive unit 5 is input to a transmission unit 6 that is arranged below the drive unit 5. The transmission unit 6 transmits the rotation of the output shaft of the drive unit 5 to the cutting blade provided in the housing 2. The transmission unit 6 also transmits the rotation of the output shaft of the drive unit 5 to the traveling wheels 3 via a chain case portion 100.

[0019] The chain case 100 is provided on one side of the housing 2. In the illustrated example, it is provided on the right side, with the front wheel 3a facing forward. The chain case 100 includes a case body 101, a case cover 103, various sprockets (gears), a chain 117, etc., and transmits the rotation of the output shaft 6a (see FIG. 7) of the transmission device 6 to the running wheels 3.

[0020] The handle 8 is connected to the other side of the housing 2. In the example shown in FIG. 1 , a protruding piece 2a is provided protruding from the left side of the housing 2, with the front wheel 3a side being the front, and the handle 8 is connected to the upper surface of the protruding piece 2a. The handle 8 is gripped by the operator and is a part that transmits the operator's operations to the self-propelled brush cutter 1. For example, the grip portion 8a provided at the upper end of the handle 8 is provided with a clutch lever for switching the clutch of the transmission device 6, a throttle lever for controlling the rotation speed of the drive device 5, and the like. The operator can select forward, neutral, or reverse by switching the clutch lever. In addition, the operator can adjust the traveling speed by operating the throttle lever.

[0021] Fig. 2 is a view of the inside of the chain case unit 100 as seen from the Y direction. Fig. 3 is a perspective view showing the inside of the chain case unit 100. The case cover is not depicted in Figs. 2 and 3. In the storage space formed by the case body 101 and the case cover 103, there are arranged a drive sprocket 111, a driven sprocket 112, a driven sprocket 113, guide rollers 115, 116, a chain 117, a tension mechanism 130, and a guard member 190.

[0022] In one example, the case body 101 is disposed closer to the housing 2 in the Y direction than the case lid 103 and is supported by the housing 2. The case body 101 has a plate-shaped first wall 101a that follows the side surface of the housing 2 and a peripheral wall 101b formed around the periphery of the first wall 101a. The case lid 103 is a member that closes the storage space formed by the first wall 101a and the peripheral wall 101b, and is supported by the case body 101. The case lid 103 has a second wall 103a that faces the first wall 101a and a peripheral wall 103b that is formed around the periphery of the second wall 103a. For example, a flange 101c formed on the peripheral wall 101b of the case body 101 and a flange 103c formed on the peripheral wall 103b of the case lid body 103 are fastened together with fastening members such as bolts and nuts, thereby connecting the case body 101 and the case lid body 103 (see Figure 7).

[0023] The drive sprocket 111 is connected to the output shaft 6a of the transmission 6. For example, the drive sprocket 111 may include a torque limiter. The output shaft 6a of the transmission 6 protrudes in the Y direction from the transmission 6 and is disposed within the accommodation space of the chain case unit 100 through a through-hole (not shown) formed in the case main body 101. In the illustrated example, the drive sprocket 111 is connected to the output shaft 6a that is disposed at the center of the case main body 101 in the X direction. The drive sprocket 111 rotates together with the output shaft 6a of the transmission 6 as the output shaft 6a rotates.

[0024] The driven sprocket 112 is disposed on the front side of the chain case unit 100. The driven sprocket 112 is connected to a pivot shaft 112a that extends along the Y direction. The pivot shaft 112a of the driven sprocket 112 extends to the outside of the chain case unit 100. The front wheel 3a is connected to this pivot shaft 112a. The driven sprocket 113 is disposed on the rear side of the chain case unit 100. The driven sprocket 113 is connected to a pivot shaft 113a that extends along the Y direction. The pivot shaft 113a of the driven sprocket 113 extends to the outside of the chain case unit 100. The rear wheel 3b is connected to this pivot shaft 113a. In one example, the driven sprockets 112 and 113 may have the same shape and may have a diameter larger than the diameter of the drive sprocket 111.

[0025] Guide roller 115 is provided between drive sprocket 111 and driven sprocket 112, close to drive sprocket 111. Guide roller 115 is cylindrical, and is rotatable on a rotation shaft along the Y direction. Guide roller 116 is provided between drive sprocket 111 and driven sprocket 113, close to drive sprocket 111. Guide roller 116 is cylindrical, and is rotatable on a rotation shaft along the Y direction.

[0026] The chain 117 (endless member) is an endless power transmission member that meshes with the drive sprocket 111, the driven sprocket 112, and the driven sprocket 113, transmitting the rotation of the drive sprocket 111 to the driven sprockets 112 and 113. In the illustrated example, the chain 117 is wound around the driven sprockets 112 and 113, which are located on the inside. The drive sprocket 111 meshes with the portion of the chain 117 that rotates on the lower side from below. The guide rollers 115 and 116 are located on the inside of the chain 117 and guide the portion of the chain 117 that rotates on the lower side. The chain 117, guided by the guide rollers 115 and 116, is subjected to a force pressing it toward the drive sprocket 111, preventing the chain 117 from coming off the drive sprocket 111. With this configuration, when the drive sprocket 111 is driven clockwise from the perspective of Figure 2, the driven sprockets 112 and 113 rotate counterclockwise, and when the drive sprocket 111 is driven counterclockwise, the driven sprockets 112 and 113 rotate clockwise.

[0027] The tensioning mechanism 130 is disposed inside the chain 117 and applies tension to the chain 117. In one example, the tensioning mechanism 130 is disposed between the drive sprocket 111 and the driven sprocket 113, at a position closer to the drive sprocket 111 than the center. The tensioning mechanism 130 is located farther from the drive sprocket 111 than the guide roller 116 is. The tensioning mechanism 130 has a rotation center along the Y direction and is biased, for example, in a direction away from the drive sprocket 111. From the perspective of FIG. 2, the tensioning mechanism 130 is biased counterclockwise, and biases the portion of the chain 117 that rotates on the upper side upward.

[0028] The guard member 190 is disposed so as to come into contact with the tensioning mechanism 130 when the tensioning mechanism 130 rotates in the direction opposite to the biasing direction. In other words, the guard member 190 prevents the tensioning mechanism 130 from coming into contact with the drive sprocket 111 and the chain 117 engaged with the drive sprocket 111. An example of the guard member 190 has a rotation shaft 191 that protrudes from the first wall body 101a in the Y direction, and a cylindrical collar 193 that is supported by the rotation shaft 191.

[0029] Next, the tension mechanism 130 will be described in more detail. Fig. 4 is an exploded perspective view of the tension mechanism 130 of an example chain case section 100. Fig. 5 is a view of the example tension mechanism 130 as seen from the X direction. Fig. 6 is an exploded perspective view of the guide section 138 of an example tension mechanism 130. Fig. 7 is a cross-sectional view of the example chain case section 100, corresponding to the cross-sectional view taken along line VII-VII in Fig. 2.

[0030] 4, an example of the tension mechanism 130 includes a rotating body 131 and a torsion coil spring 140. The rotating body 131 is rotatable about a rotation shaft 105 and extends radially from the rotation shaft 105. The rotating body 131 in the illustrated example includes a plate-like member 133 including a shaft portion 132, and a guide portion 138. The shaft portion 132 is a cylindrical portion through which the rotation shaft 105 is inserted. The rotation shaft 105 protrudes from the first wall 101a of the case main body 101 in the Y direction.

[0031] The illustrated pivot shaft 105 has a bolt 105b fixed to the first wall 101a and a cylindrical collar 105a rotatably supported by the bolt 105b. When the case body 101 and the case lid 103 are fastened together, the collar 105a is disposed within the accommodation space, and the tip of the bolt 105b is exposed to the outside from the case lid 103. When the case body 101 and the case lid 103 are fastened together, a nut 105c is fastened to the bolt 105b. The inner diameter of the shaft 132 is larger than the diameter of the pivot shaft 105 (the outer diameter of the collar 105a). Therefore, when the pivot shaft 105 is inserted inside the shaft 132, the shaft 132 is rotatable relative to the pivot shaft 105. The length of the shaft 132 may be slightly shorter than the length from the first wall 101 a of the case body 101 to the second wall 103 a of the case lid 103 .

[0032] As shown in FIG. 5, the plate-shaped member 133 extends radially from the shaft portion 132 on the rotating shaft 105 side as a base end. The plate-shaped member 133 is rotatable around the rotating shaft 105 as a rotation center. The plate-shaped member 133 in the illustrated example includes a first plate-shaped portion 134, a bent portion 135, and a second plate-shaped portion 136. The first plate-shaped portion 134 extends radially from the rotating shaft 105 as a base end along the XZ plane. When viewed from the X direction intersecting the axial direction, the first plate-shaped portion 134 is located closer to the case cover 103 than the center of the shaft portion 132 in the Y direction. The plate-shaped member 133 has a gentle arc shape as viewed from the perspective of FIG. 2. That is, the plate-shaped member 133 curves clockwise as it extends radially outward from the rotating shaft 105 as a center.

[0033] The bent portion 135 is a portion that is bent from the tip of the first plate-shaped portion 134 so that its position in the axial direction of the rotation shaft 105 changes. An example of the bent portion 135 is inclined so as to approach the case main body 101 as it approaches the tip. A through hole 135a (engagement portion) is formed in the bent portion 135. The through hole 135a passes through the bent portion 135 in the plate thickness direction. An example of the through hole 135a may be an elongated hole that extends in the extension direction of the bent portion 135, i.e., in the direction from the first plate-shaped portion 134 toward the second plate-shaped portion 136.

[0034] The second plate-shaped portion 136 is a portion extending radially from the tip of the bent portion 135 and is along the XZ plane. The second plate-shaped portion 136 and the first plate-shaped portion 134 are arranged offset from each other in the axial direction of the rotation shaft 105 and are parallel to each other. In the axial direction of the rotation shaft 105, the first plate-shaped portion 134 is closer to the case lid 103 than the second plate-shaped portion 136, and the second plate-shaped portion 136 is closer to the case main body 101 than the first plate-shaped portion 134. In the radial direction centered on the rotation shaft 105, the length of the second plate-shaped portion 136 may be approximately the same as that of the first plate-shaped portion 134. In other words, the bent portion 135 may be formed in the center of the plate-shaped member 133 in the longitudinal direction.

[0035] Guide portion 138 is a portion that contacts chain 117 and is provided at the tip of plate-shaped member 133. As shown in FIG. 6, one example of guide portion 138 is cylindrical (ring-shaped) and rotatably supported by a rotary shaft 137 provided at the tip of second plate-shaped portion 136. Guide portion 138 has, at the center in the axial direction, a large-diameter portion 138a that has a larger diameter than other portions. In one example, guide portion 138 may be a portion that contacts a roller that constitutes chain 117.

[0036] The pivot shaft 137 is formed at the tip of the second plate-shaped portion 136 along the Y-axis direction toward the case lid 103. A groove 137a is formed in the circumferential direction on the tip side of the pivot shaft 137. With the guide portion 138 supported by the pivot shaft 137, a fastener 139 such as a retaining ring is fixed to the groove 137a exposed on the axial tip side of the guide portion 138, thereby supporting the guide portion 138 rotatably relative to the pivot shaft 137. With this configuration, the guide portion 138 is disposed on a surface 136a of the second plate-shaped portion 136 that faces the side where the first plate-shaped portion 134 is located in the axial direction.

[0037] 5, the guide portion 138 is contained within an arrangement range R1 of the plate-shaped member 133 in the axial direction of the rotation shaft 105. One example of the plate-shaped member 133 is configured to include a shaft portion 132. In the axial direction, the base end of the shaft portion 132 is located closer to the case main body 101 than the second plate-shaped portion 136, and the tip end of the shaft portion 132 is located closer to the case lid 103 than the rotation shaft of the second plate-shaped portion 136.

[0038] Torsion coil spring 140 is held by rotating shaft 105 and biases rotating body 131 in the rotation direction. In the illustrated example, when viewed from the Y direction, a state in which the center of guide portion 138 is located closer to guard member 190 in the X direction than the center of rotating shaft 105 is defined as a reference state. That is, in the reference state, guide portion 138 is shifted clockwise from the 12 o'clock position. If guide portion 138 deviates from this reference position, torsion coil spring 140 biases rotating body 131 so as to return the position of guide portion 138 to the reference position. When chain 117 is engaged with guide portion 138, rotating body 131 moves clockwise (second rotation direction) due to the influence of chain 117, and therefore torsion coil spring 140 biases rotating body 131 counterclockwise (first rotation direction).

[0039] In the illustrated example, torsion coil spring 140 is supported by shaft portion 132 of plate-shaped member 133 that constitutes rotating body 131, and thereby held by rotating shaft 105. Torsion coil spring 140 has a winding portion 141, a first arm portion 143, and a second arm portion 145. Winding portion 141 is a portion around which the wire that constitutes torsion coil spring 140 is wound in a coil shape. In the illustrated example, winding portion 141 has a substantially cylindrical shape as a whole, and a portion of shaft portion 132 of plate-shaped member 133 that protrudes toward case main body 101 is inserted inside winding portion 141. That is, torsion coil spring 140 is disposed on surface 134a of first plate-shaped portion 134 that faces the side where second plate-shaped portion 136 is located in the axial direction.

[0040] The first arm 143 extends from one end of the winding portion 141 and is positioned relative to the rotation shaft 105. The first arm 143 in one example is a portion of the wire constituting the torsion coil spring 140 that extends from an end of the winding portion 141 that is closer to the case body 101. The first arm 143 extends in the Y direction away from the winding portion 141. For example, the position of the first arm 143 relative to the rotation shaft 105 is determined by engaging with the case body 101. In the illustrated example, a through hole 101d is formed in the case body 101 near the rotation shaft 105, and the first arm 143 is engaged with the case body 101 by being inserted through this through hole 101d.

[0041] Second arm portion 145 is a portion of the wire constituting torsion coil spring 140 that extends from the other end of winding portion 141 and engages with plate-shaped member 133. As shown in FIG. 5 , one example of second arm portion 145 includes extending portion 145a that extends radially outward from rotating shaft 105 without substantially displacing in the axial direction of rotating shaft 105. Extended portion 145a engages with plate-shaped member 133 by being inserted into through-hole 135a formed in bent portion 135 of plate-shaped member 133. That is, through-hole 135a formed in bent portion 135 functions as an engaging portion for engaging with second arm portion 145.

[0042] The second arm 145 is contained within the arrangement range R2 of the rotor 131 in the axial direction of the rotation shaft 105. In the illustrated example, the second arm 145 is engaged with a through hole 135a formed in a bent portion 135 located between the first plate-shaped portion 134 and the second plate-shaped portion 136 in the axial direction, and is contained within the formation range of the through hole 135a in the axial direction. Therefore, the second arm 145 is located closer to the case main body 101 than the first plate-shaped portion 134 and closer to the case lid 103 than the second plate-shaped portion 136 in the axial direction of the rotation shaft.

[0043] As explained above, the tension mechanism 130 of one example is provided rotatably about the rotation shaft 105 and includes the rotating body 131 extending in the radial direction from the rotation shaft 105, and the torsion coil spring 140 held by the rotation shaft 105 and biasing the rotating body 131 in the rotation direction. The rotating body 131 includes the plate-like member 133 extending in the radial direction with the rotation shaft 105 as its base end, and the torsion coil spring 140 attached to the tip of the plate-like member 133 and connected to the chain 117. The torsion coil spring 140 includes a winding portion 141 held on the rotating shaft 105, a first arm portion 143 extending from one end of the winding portion 141 and positioned relative to the rotating shaft 105, and a second arm portion 145 extending from the other end of the winding portion 141 and engaging with the plate-shaped member 133, and the second arm portion 145 is within the arrangement range R2 of the rotating body 131 in the axial direction of the rotating shaft 105.

[0044] In the above-described tension mechanism 130, a first arm 143 of a torsion coil spring 140 held by the rotating shaft 105 is positioned relative to the rotating shaft 105, and a second arm 145 of the torsion coil spring 140 is engaged with the plate-like member 133 of the rotating body 131. Therefore, the rotating body 131 is biased by the torsion coil spring 140, so that tension can be applied to the chain 117 abutting against the guide portion 138.

[0045] When engaging the second arm of the torsion coil spring with the plate-shaped member, for example, the second arm may be bent along the axial direction of the pivot shaft 105 and the bent portion may be engaged with the side surface of the plate-shaped member. In this case, the tip of the second arm protrudes toward the case cover from the plate-shaped member, which may increase the thickness of the tension mechanism in the Y direction as a whole. In the above configuration, the second arm 145 of the torsion coil spring 140 is contained within the arrangement range R2 of the rotating body 131 in the axial direction of the pivot shaft 105. In other words, the second arm 145 does not protrude beyond the arrangement range R2 of the rotating body 131 in the axial direction of the pivot shaft 105. Therefore, the size of the tension mechanism 130 in the axial direction of the pivot shaft 105 can be prevented from increasing. In this case, the case body 101 and the case cover 103 can be disposed close to each other, thereby reducing the thickness of the chain case 100 in the Y direction.

[0046] As an example, second arm 145 may include extension 145a that extends radially outward from rotation shaft 105 without being displaced in the axial direction of rotation shaft 105, and that engages with plate-shaped member 133. In this configuration, second arm 145 does not need to be bent along the axial direction, and therefore second arm 145 does not protrude outward in the axial direction beyond plate-shaped member 133.

[0047] One example of plate-like member 133 may include a bent portion 135 that is bent so that its position in the axial direction of rotation shaft 105 changes, and bent portion 135 may include an engaging portion that engages with second arm portion 145. In this configuration, bent portion 135 can be formed so as to bend toward the position where second arm portion 145 extends, so that an engaging portion that engages with second arm portion 145 can be easily formed.

[0048] An example plate-shaped member 133 has a first plate-shaped portion 134 extending radially from the pivot shaft 105 as a base end, a bent portion 135 bent from the tip of first plate-shaped portion 134, and a second plate-shaped portion 136 extending radially from the tip of bent portion 135, where first plate-shaped portion 134 and second plate-shaped portion 136 are offset from each other in the axial direction of the pivot shaft, and the engaging portion may be formed by a through-hole 135a formed in bent portion 135. In this configuration, second arm portion 145 can be engaged with plate-shaped member 133 by inserting second arm portion 145 into through-hole 135a serving as the engaging portion.

[0049] Guide portion 138 may be arranged on a surface of second plate-shaped portion 136 facing the side where first plate-shaped portion 134 is located in the axial direction, and torsion coil spring 140 may be arranged on a surface of first plate-shaped portion 134 facing the side where second plate-shaped portion 136 is located in the axial direction. In other words, guide portion 138 and torsion coil spring 140 may be arranged facing opposing surfaces of plate-shaped member 133. With this configuration, guide portion 138 and torsion coil spring 140 can be prevented from protruding from arrangement range R1 of plate-shaped member 133 in the axial direction.

[0050] The plate-shaped member 133 includes a cylindrical shaft portion 132 through which the rotation shaft is inserted, and the guide portion 138 may be accommodated in the arrangement range R1 of the plate-shaped member 133 in the axial direction of the rotation shaft. In this configuration, the size of the tension mechanism 130 in the axial direction can be accommodated within the arrangement range R1 of the plate-shaped member 133.

[0051] Although the embodiments of the present invention have been described above, the specific embodiments of the present disclosure are not limited to the above examples.

[0052] For example, although an example has been shown in which the first plate-shaped portion 134 and the second plate-shaped portion 136 have approximately the same length, the length of the first plate-shaped portion 134 and the length of the second plate-shaped portion 136 may be different from each other.

[0053] Furthermore, although an example has been shown in which the second arm portion is engaged with the through-hole formed in the bent portion, the second arm portion may be engaged with, for example, the side surface of the bent portion.

[0054] In addition, although an example has been shown in which the plate-shaped member has a bent portion to facilitate engagement with the second arm of the torsion coil spring, for example, a protruding piece that protrudes from the plate-shaped member toward the case body may be provided on the rotor, and the second arm may be engaged with the protruding piece. In this case, a through hole may be provided in the protruding piece, and the second arm may be engaged with this through hole. [Explanation of symbols]

[0055] 1...self-propelled grass trimmer, 105...rotating shaft, 117...chain (endless member), 131...rotating body, 133...plate-shaped member, 138...guide portion, 140...torsion coil spring, 141...winding portion, 143...first arm portion, 145...second arm portion.

Claims

1. A tension mechanism that applies tension to an endless member (117), a rotating body (131) that is rotatable about a rotation axis (105) and extends radially from the rotation axis (105); a torsion coil spring (140) held by the rotation shaft (105) and biasing the rotating body (131) in a rotational direction; The rotating body (131) a plate-like member (133) extending in a radial direction with the rotation shaft (105) as a base end; a guide portion (138) provided at the tip of the plate-like member (133) and abutting against the endless member (117); The torsion coil spring (140) includes a winding portion (141) held by the rotating shaft (105), a first arm portion (143) extending from one end of the winding portion (141) and positioned relative to the rotating shaft (105), and a second arm portion (145) extending from the other end of the winding portion (141) and engaged with the plate-like member (133), The second arm portion (145) is contained within the arrangement range of the rotating body (131) in the axial direction of the rotation shaft (105), The plate-like member (133) includes a bent portion (135) that is bent so that its position in the axial direction of the rotation shaft (105) changes; a first plate-shaped portion (134) extending in a radial direction with the rotation shaft (105) side as a base end; the bent portion (135) bent from the tip of the first plate-shaped portion (134); a second plate-shaped portion (136) extending radially from the tip of the bent portion (135), The bent portion (135) includes an engaging portion that engages with the second arm portion (145), The first plate-shaped portion (134) and the second plate-shaped portion (136) are offset from each other in the axial direction of the rotation shaft (105), The tension mechanism, wherein the engagement portion is formed by a through hole (135a) formed in the bent portion (135).

2. 2. The tension mechanism according to claim 1, wherein the second arm portion (145) includes an extension portion that extends radially outward from the pivot shaft (105) without displacing in the axial direction of the pivot shaft (105) and engages with the plate-shaped member (133).

3. The guide portion (138) is disposed on a surface of the second plate-shaped portion (136) facing a side on which the first plate-shaped portion (134) is located in the axial direction, 3. The tension mechanism according to claim 1, wherein the torsion coil spring (140) is arranged on a surface of the first plate-shaped portion (134) facing the side on which the second plate-shaped portion (136) is located in the axial direction.

4. The plate-like member (133) includes a cylindrical shaft portion (132) through which the rotation shaft (105) is inserted, The tension mechanism according to any one of claims 1 to 3, wherein the guide portion (138) is within an arrangement range of the plate-shaped member (133) in the axial direction of the rotation shaft (105).

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