JOINT MECHANISM FOR CONSTRUCTION MACHINE

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims the benefit of priority from Japanese Patent Application Serial No. 2024-007407 (filed on Jan. 22, 2024), the contents of which are hereby incorporated by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates to a joint mechanism for a construction machine.

BACKGROUND

The excavator disclosed in Japanese Patent Application Publication No. S63-300130 (“the '130 Publication”) includes a self-propelled main body, an arm extending from the main body, a bucket for excavation, and a power transmission mechanism. The bucket is connected to a distal end of the arm. The power transmission mechanism is located at the connection point between the bucket and the arm. The bucket receives power from the power transmission mechanism and rotates relative to the arm.

In an excavator such as disclosed in the '130 Publication, foreign matter such as dirt may adhere to the connection point between the bucket and the arm. If a large amount of such foreign matter enters the power transmission mechanism, it may cause malfunction of the power transmission mechanism. The same issue can arise not only at the connection point between the arm and the bucket, and not only in excavators, but also in any construction machine with a power transmission mechanism located at the connection point between two parts.

SUMMARY

According to one aspect, a joint mechanism for a construction machine comprises: a first member having a first facing surface; a second member rotatable around a rotation axis relative to the first member and having a second facing surface facing the first facing surface; a power transmission mechanism for transmitting power for rotation to the second member; a first wall protruding from the first facing surface and having an annular shape around the rotation axis; and a second wall protruding from the second facing surface and having an arc-like shape around the rotation axis; wherein the power transmission mechanism is located on an inner side of the first wall in a radial direction around the rotation axis, and wherein the second wall is located on an outer side of the first wall in the radial direction and overlaps at least partly with the first wall in a direction along the rotation axis.

In the above configuration, the first and second walls are arranged alternately on the radially outer side of the power transmission mechanism. Thus, the power transmission mechanism is guarded doubly on the radially outer side, thereby inhibiting foreign matter from reaching the power transmission mechanism.

The joint mechanism for a construction machine may further comprise a third wall protruding from the second facing surface and having an annular shape around the rotation axis, wherein the third wall may be located between the power transmission mechanism and the first wall in the radial direction and may overlap at least partly with the first wall in the direction along the rotation axis.

The second wall may extend around the rotation axis for 180 degrees or more. The second member may include a bucket with an opening, an opening direction refers to a direction perpendicular to an opening surface of the bucket and extending from an interior to an exterior of the bucket through the opening surface, as viewed in a direction along the rotation axis, a first straight line refers to a virtual straight line connecting the rotation axis and the opening surface by a shortest distance, and a second straight line refers to a virtual straight line extending from the rotation axis in the opening direction, and in a circumferential direction around the rotation axis, the second wall may extend over an entire angular region formed by the first straight line and the second straight line on a side toward which the opening surface is open.

The joint mechanism for a construction machine may further comprise: a first stopper protruding from the first member; and a second stopper protruding from the second member and configured to contact the first stopper when the second member has rotated by a first angle in a first rotational direction from a predetermined reference position.

The joint mechanism for a construction machine may further comprise a third stopper protruding from the second member and configured to contact the first stopper when the second member has rotated by the first angle from the reference position in a direction opposite to the first rotational direction.

The joint mechanism for a construction machine may further comprise: a power source configured to provide power to the power transmission mechanism; and a controller configured to control the power source, wherein the controller may be capable of: receiving a switching signal from an outside of the controller; and switching, based on the switching signal, between a first mode, in which power output by the power source is limited to less than a specified value, and a second mode, in which power output by the power source is permitted to be equal to or larger than the specified value.

A joint mechanism for a construction machine according to another aspect comprises: a first member; a second member rotatable relative to the first member; a first stopper protruding from the first member; and a second stopper protruding from the second member and configured to contact the first stopper when the second member has rotated by a first angle from a predetermined reference position.

In the above configuration, the first and second members can be impacted by rotating the second member to collide the second stopper with the first stopper. The impact provided on the first and second members makes it possible to remove foreign matter from the first and second members. Thus, foreign matter can be removed promptly from the first and second members. Since foreign matter can be removed from the first and second members, it can be inhibited that foreign matter reaches a power transmission mechanism located around the first and second members and configured to rotate the second member, for example.

The joint mechanism for a construction machine may further comprise a power transmission mechanism connecting the first member and the second member so as to be capable of relative rotation and configured to transmit power for rotation to the second member, wherein the second member may include a bucket with an opening.

The second member may include a bucket with an opening, an opening direction refers to a direction perpendicular to an opening surface of the bucket and extending from an interior to an exterior of the bucket through the opening surface, and as viewed in a direction along a rotation axis of the second member, when the second stopper is at a position at which the second stopper contacts the first stopper, a virtual half line extending from the rotation axis in a direction opposite to the first stopper may intersect a virtual half line extending from the opening surface in the opening direction.

Advantageous Effects

The above technical idea can inhibit foreign matter from reaching the power transmission mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an excavator.

FIG. 2 is a perspective view of a first bracket.

FIG. 3 is a sectional view of a bucket joint mechanism.

FIG. 4 is an enlarged view of the region Z in FIG. 3.

FIG. 5 is a perspective view of a second bracket.

FIG. 6 is a side view of the bucket joint mechanism showing that an excavation member is located at a reference position.

FIG. 7 is a side view of the bucket joint mechanism showing that a first stopper and a second stopper are in contact with each other.

FIG. 8 is a schematic view showing dirt accumulated in a recess.

FIG. 9 is a schematic view showing dirt being discharged from the recess.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
<Overall Configuration>

As shown in FIG. 1, an excavator 500 includes a main body 502, a boom 504, and a bucket joint mechanism 510. The main body 502 has a crawler 502A for traveling and a vehicle body 502B including a driver seat. The boom 504 extends from the vehicle body 502B. The boom 504 connects between the vehicle body 502B and the bucket joint mechanism 510. The boom 504 can rotate relative to the vehicle body 502B around the end of the boom 504 on the vehicle body 502B side.

As shown in FIG. 1, the bucket joint mechanism 510 includes an arm 520. The arm 520 is a first member. The arm 520 includes an arm body 521 and a first bracket 10.

The arm body 521 has an elongated shape. One end of the arm body 521 in its longitudinal direction is connected to the boom 504. The arm body 521 can rotate relative to the boom 504 around one end of the arm body 521.

The first bracket 10 is located at the end of the arm body 521 opposite to the end thereof connected to the boom 504. As shown in FIG. 2, the first bracket 10 includes a base 12 and a retainer 14.

As shown in FIG. 1, the base 12 extends, from the end of the arm body 521 in its longitudinal direction, toward the opposite side to the arm body 521. As shown in FIG. 2, the base 12 is shaped like a plate. The width of the main surfaces of the base 12 increases with the distance from the arm body 521. The main surfaces of the base 12 are the two surfaces of the base 12 having the largest area.

As shown in FIG. 2, the retainer 14 has an annular shape. The outer circumferential surface of the retainer 14 is connected to the end of the base 12 opposite to the arm body 521. As shown in FIG. 3, one of the two directions along the central axis of the retainer 14 is referred to as the first direction X1, and the other is referred to as the second direction X2. The first and second directions X1 and X2 are collectively referred to as the axial direction XA. The axial direction XA coincides with the direction along the thickness of the base 12. The central axis of the retainer 14 is hereafter referred to as the base rotation axis P. The radial direction from the base rotation axis P is referred to simply as the radial direction. The circumferential direction around the base rotation axis P is referred to simply as the circumferential direction.

As shown in FIGS. 2 and 4, the bucket joint mechanism 510 includes a first wall 16. The first wall 16 protrudes in the first direction X1 from a first facing surface 14A, or the end surface of the retainer 14 in the first direction X1. In this embodiment, the first wall 16 is formed integrally with the retainer 14. The first wall 16 has an annular shape around the base rotation axis P. The width of the first wall 16 in the radial direction is uniform for the entire circumference. The inner diameter of the first wall 16 is the same as the inner diameter of the retainer 14. The inner circumferential surface of the first wall 16 is flush with the inner circumferential surface of the retainer 14.

As shown in FIG. 3, the bucket joint mechanism 510 includes a drive unit 100. The drive unit 100 is retained by the retainer 14 of the first bracket 10. The drive unit 100 includes a housing 102, a motor 104, and a power transmission mechanism 106. FIG. 3 is a schematic view showing the arrangement of the parts of the bucket joint mechanism 510, in which the relationship between the sizes of, for example, the motor 14 and other parts does not necessarily correspond to the actual one.

The housing 102 houses the motor 104. The motor 104 is electrically powered. The motor 104 includes a motor body 104A and an output shaft 104B. The motor body 104A is fixed to the housing 102. The output shaft 104B protrudes from the motor body 104A in the first direction X1. The output shaft 104B is rotatable relative to the motor body 104A. The output shaft 104B is rotatable in both forward and reverse directions. Although not shown in the drawings, the output shaft 104B has a plurality of teeth formed on the outer circumferential surface thereof. The motor 104 is the power source that provides power to the power transmission mechanism 106.

The power transmission mechanism 106 is located on the first direction X1 side of the motor 104. The power transmission mechanism 106 is a speed reducer that reduces the rotation of the output shaft 104B of the motor 104 at a predetermined gear ratio and outputs the reduced rotation.

The power transmission mechanism 106 includes a case 60. The case 60 includes a case body 62, a plurality of teeth 64, and a flange 66. The case body 62 is located on the first direction X1 side of the housing 102. The case body 62 has a cylindrical shape. The case body 62 is located radially inside the retainer 14 of the first bracket 10. The outer diameter of the case body 62 is substantially the same as the inner diameter of the retainer 14. The central axis of the case body 62 substantially coincides with the base rotation axis P. In other words, the base rotation axis P is also the central axis of the power transmission mechanism 106. The end of the case body 62 on the first direction X1 side is located at substantially the same position as the end of the retainer 14 on the first direction X1 side. The case body 62 is covered by the housing 102 on the second direction X2 side.

The plurality of teeth 64 protrude from the inner circumferential surface of the case body 62. The plurality of teeth 64 are arranged at equal intervals in the circumferential direction. In the axial direction XA, the teeth 64 are located near the center of the case body 62.

The flange 66 protrudes from the outer circumferential surface of the case body 62. The flange 66 has an annular shape. The outer diameter of the flange 66 is substantially the same as the outer diameter of the retainer 14 of the first bracket 10. The end of the flange 66 on the first direction X1 side faces the end of the retainer 14 on the second direction X2 side. The flange 66 and the retainer 14 are fixed together with bolts B1 at a plurality of locations.

The power transmission mechanism 106 includes a carrier 70. The carrier 70 includes a first plate 71, a second plate 72, and a plurality of columns 73. The first plate 71 is located inside the case body 62. The first plate 71 is located close to the end of the case body 62 on the first direction X1 side. The first plate 71 has a disc-like shape. The diameter of the first plate 71 is smaller than the inner diameter of the case body 62. The central axis of the first plate 71 substantially coincides with the base rotation axis P. The end of the first plate 71 on the first direction X1 side protrudes slightly in the first direction X1 beyond the end of the case body 62 on the first direction X1 side. The end of the first plate 71 on the second direction X2 side is located on the first direction X1 side of the teeth 64 of the case 60. A bearing Y1 is interposed between the outer circumferential surface of the first plate 71 and the inner circumferential surface of the case body 62. The first plate 71 has a plurality of through holes 71H. There are, for example, three through holes 71H. The through holes 71H are located radially off the base rotation axis P. The through holes 71H extend through the first plate 71 in the axial direction XA. The plurality of through holes 71H are arranged at equal intervals in the circumferential direction.

The second plate 72 is located inside the case body 62. The second plate 72 is located close to the end of the case body 62 on the second direction X2 side. The second plate 72 has a disc-like shape. The diameter of the second plate 72 is the same as the diameter of the first plate 71. The central axis of the second plate 72 substantially coincides with the base rotation axis P. The end of the second plate 72 on the second direction X2 side is located at substantially the same position as the end of the case body 62 on the second direction X2 side. The end of the second plate 72 on the first direction X1 side is located on the second direction X2 side of the teeth 64 of the case 60. A bearing Y1 is interposed between the outer circumferential surface of the second plate 72 and the inner circumferential surface of the case body 62. The second plate 72 has a plurality of through holes 72H. The plurality of through holes 72H are provided in pairs with the plurality of through holes 71H in the first plate 71. In other words, the number of through holes 72H is the same as the number of through holes 71H in the first plate 71. The through holes 72H extend through the second plate 72 in the axial direction XA. Each of the through holes 72H has a central axis that substantially coincides with the central axis of the paired one of the through holes 71H in the first plate 71.

The plurality of columns 73 protrude from the second plate 72 in the first direction X1. The columns 73 are located radially off the base rotation axis P. The columns 73 have a cylindrical shape. The plurality of columns 73 are arranged at equal intervals in the circumferential direction. The columns 73 are formed integrally with the second plate 72. The end surfaces of the columns 73 on the first direction X1 side are in contact with the first plate 71. In other words, the columns 73 connect between the first plate 71 and the second plate 72. The columns 73 and the first plate 71 are fixed together with bolts B2.

The power transmission mechanism 106 includes a first external gear 91. The first external gear 91 is located inside the case body 62. In the axial direction XA, the first external gear 91 is located between the first plate 71 and the second plate 72 of the carrier 70. Specifically, in the axial direction XA, the first external gear 91 is located at the same position as the teeth 64 of the case 60. The first external gear 91 has a generally disc-like shape. The diameter of the first external gear 91 is smaller than the inner diameter of the case body 62. The central axis of the first external gear 91 is parallel with the base rotation axis P. A plurality of teeth are formed on the outer circumferential surface of the first external gear 91. The plurality of teeth are arranged at equal intervals in the circumferential direction. FIG. 3 does not show the teeth of the first external gear 91. Some of the plurality of teeth located in a part of the circumference are in mesh with the teeth 64 of the case 60. On the other hand, there is a gap between the other of the plurality of teeth located in the other part of the circumference and the teeth 64 of the case 60.

The first external gear 91 has a plurality of first through holes 91A. The first through holes 93A are located radially off the central axis of the first external gear 91. The first through holes 91A extend through the first external gear 91 in the axial direction XA. The first through holes 91A are located so as to correspond to the columns 73. The first through holes 91A are penetrated by the columns 73. The diameter of the first through holes 91A is larger than the diameter of the columns 73.

The first external gear 91 has a plurality of second through holes 91B. The plurality of second through holes 91B are provided in pairs with the plurality of through holes 71H in the first plate 71. In other words, the number of second through holes 91B is the same as the number of through holes 71H in the first plate 71. The second through holes 91B are located radially off the central axis of the first external gear 91. The second through holes 91B extend through the first external gear 91 in the axial direction XA. Each of the second through holes 91B is in communication with the paired one of the through holes 71H in the first plate 71.

The power transmission mechanism 106 includes a second external gear 92. The second external gear 92 is located inside the case body 62. The second external gear 92 is adjacent to the first external gear 91 in the axial direction XA. Thus, in the axial direction XA, the second external gear 92 is located between the first plate 71 and the second plate 72 of the carrier 70, as is the first external gear 91. Additionally, in the axial direction XA, the second external gear 92 is located at the same position as the teeth 64 of the case 60. The second external gear 92 is configured in the same manner as the first external gear 91. Specifically, the second external gear 92 has first through holes 92A that correspond to the columns 73. The second external gear 92 also has a plurality of second through holes 92B that pair with the plurality of through holes 72H in the second plate 72. Each of the second through holes 92B is in communication with the paired one of the through holes 72H in the second plate 72. The second through holes 92B are also in communication with the second through holes 91B in the first external gear 91. As a result, continuous shaft holes are formed of the through holes 71H in the first plate 71, the second through holes 91B in the first external gear 91, the second through holes 92B in the second external gear 92, and the through holes 72H in the second plate 72. There are a plurality of such shaft holes provided so as to correspond to the number of through holes 71H in the first plate 71. The shaft holes are also arranged at equal intervals in the circumferential direction.

The power transmission mechanism 106 includes a plurality of transmission shafts 80. Each of the transmission shafts 80 is provided for one of the shaft holes. The transmission shaft 80 includes a main shaft 81, a first eccentric portion 83, and a second eccentric portion 85.

The main shaft 81 has a cylindrical shape. The main shaft 81 extends in the axial direction XA. The most part of the main shaft 81 is located in the shaft hole. Specifically, the end of the main shaft 81 on the first direction X1 side is located in the through hole 71H of the first plate 71. The most part of the main shaft 81 on the second direction X2 side is located in the through hole 72H of the second plate 72. A part of the main shaft 81 protrudes from the through hole 72H of the second plate 72 in the second direction X2.

The first eccentric portion 83 is located on the middle part of the main shaft 81 in the axial direction XA. Specifically, the first eccentric portion 83 is located in the second through hole 91B of the first external gear 91. The first eccentric portion 83 protrudes from the outer circumferential surface of the main shaft 81. In plan view in the axial direction XA, the first eccentric portion 83 has a circular outer shape. In plan view in the axial direction XA, the center of the first eccentric portion 83 is off the center of the main shaft 81. A bearing Y2 is interposed between the outer circumferential surface of the first eccentric portion 83 and the second through hole 91B of the first external gear 91.

The second eccentric portion 85 is located on the middle part of the main shaft 81 in the axial direction XA. Specifically, the second eccentric portion 85 is located in the second through hole 92B of the second external gear 92. As with the first eccentric portion 83, the second eccentric portion 85 protrudes from the outer circumferential surface of the main shaft 81. In plan view in the axial direction XA, the second eccentric portion 85 has a circular outer shape. In plan view in the axial direction XA, the center of the second eccentric portion 85 is off the center of the first eccentric portion 83 and the center of the main shaft 81. A bearing Y2 is interposed between the outer circumferential surface of the second eccentric portion 85 and the second through hole 92B of the second external gear 92.

The power transmission mechanism 106 includes a plurality of transmission gears 87. Each of the transmission gears 87 is provided for one of the transmission shafts 80. The transmission gear 87 is mounted on the part of the main shaft 81 protruding from the through 72H of the second plate 72 in the second direction X2. The transmission gear 87 has a generally annular shape. The main shaft 81 is fixed to the central hole of the transmission gear 87. Although not shown in the drawings, the transmission gear 87 has a plurality of teeth formed on the outer circumferential surface thereof.

The transmission gear 87 is in mesh with the teeth on the output shaft 104B of the motor 104. The transmission gear 87 transmits the rotation of the output shaft 104B of the motor 104 to the transmission shaft 80. The transmission shaft 80 transmits its own rotation caused by the rotation of the transmission gear 87 to the first external gear 91 and the second external gear 92 via the first eccentric portion 83 and the second eccentric portion 85. The first external gear 91 and the second external gear 92 rotate oscillatorily under the power from the first eccentric portion 83 and the second eccentric portion 85, respectively. In other words, the first external gear 91 rotates relative to the case body 62 while oscillating so as to vary the circumferential region meshing with the teeth 64 of the case 60. The second external gear 92 operates in the same manner. The rotation of the first and second external gears 91 and 92 is transmitted to the carrier 70 via the columns 73. The carrier 70 then rotates around the base rotation axis P. Specifically, the carrier 70 rotates relative to the case 60 fixed by the first bracket 10.

As shown in FIG. 1, the bucket joint mechanism 510 includes an excavation member 530. The excavation member 530 is a second member. The excavation member 530 includes a bucket 531 and a second bracket 20. The bucket 531 has a box-like shape with an opening 535.

As shown in FIG. 3, the second bracket 20 is located on the first direction X1 side of the first bracket 10. The second bracket 20 has a plate-like shape. The direction along the thickness of the second bracket 20 coincides with the axial direction XA. The second facing surface 20A, which is one of the main surfaces of the second bracket 20, faces the second direction X2. The main surfaces of the second bracket 20 are the two surfaces of the second bracket 20 having the largest area.

As shown in FIG. 5, the second bracket 20 includes a first portion 21 and a second portion 22. The plan view of the bucket joint mechanism 510 in the axial direction XA will be hereinafter referred to as the specific plan view. As shown in FIGS. 5 and 6, in the specific plan view, the second bracket 20 is formed of the first portion 21 having a semicircular shape and the second portion 22 located on the opposite side to the arc in the first portion 21, and the first portion 21 and the second portion 22 are joined together. The center of the arc in the first portion 21 is located on the base rotation axis P. The diameter of the arc in the first portion 21 is smaller than the outer diameter of the retainer 14 of the first bracket 10, and is larger than the outer diameter of the first wall 16 protruding from the first bracket 10. As shown in FIG. 6, in the specific plan view, the outer edge of the second portion 22 is formed of a first outer edge portion 22A extending in a straight line from one end of the arc of the first portion 21, a second outer edge portion 22B extending in a straight line from the other end of the arc of the first portion 21, and a third outer edge portion 22C connecting the first outer edge portion 22A and the second outer edge portion 22B in a straight line. The first outer edge portion 22A and the second outer edge portion 22B are closer to each other toward the direction away from the first portion 21. In the specific plan view, the first outer edge portion 22A has a smaller length than the second outer edge portion 22B. The third outer edge portion 22C connects with the bucket 531.

As shown in FIGS. 4 and 5, a second wall 27, which is an element of the bucket joint mechanism 510, protrudes in the second direction X2 from the second facing surface 20A of the second bracket 20. In this embodiment, the second wall 27 is formed integrally with the second bracket 20. The second wall 27 has an arc-like shape located around the base rotation axis P. The most part of the second wall 27 is located on the first portion 21 of the second bracket 20. A part of the second wall 27 reaches the second portion 22 of the second bracket 20. For example, the width of the second wall 27 in the radial direction is slightly larger than the width of the first wall 16 in the radial direction. The outer diameter of the second wall 27 is the same as the outer diameter of the first portion 21 of the second bracket 20. The outer circumferential surface of a part of the second wall 27 located on the first portion 21 is flush with the outer circumferential surface of the first portion 21. The inner diameter of the second wall 27 is slightly larger than the outer diameter of the first wall 16 protruding from the first bracket 10. The dimension of the second wall 27 in the axial direction XA is substantially the same as the dimension of the first wall 16 in the axial direction XA.

As shown in FIGS. 4 and 5, a third wall 28, which is an element of the bucket joint mechanism 510, protrudes in the second direction X2 from the second facing surface 20A of the second bracket 20. In this embodiment, the third wall 28 is formed integrally with the second bracket 20. The third wall 28 has an annular shape around the base rotation axis P. The third wall 28 spans both the first portion 21 and the second portion 22 of the second bracket 20. For example, the width of the third wall 28 in the radial direction is slightly larger than the width of the second wall 27 in the radial direction. The outer diameter of the third wall 28 is slightly smaller than the inner diameter of the first wall 16. The inner diameter of the third wall 28 is slightly larger than the diameter of the first plate 71 of the carrier 70. The dimension of the third wall 28 in the axial direction XA is substantially the same as the dimension of the second wall 27 in the axial direction XA.

As shown in FIG. 3, the second bracket 20 is fixed to the first plate 71 of the carrier 70. Specifically, the second facing surface 20A of the second bracket 20 faces the surface of the first plate 71 facing the first direction X1. The second bracket 20 and the first plate 71 are fixed together with the columns 73 of the carrier 70 by the bolts B2 fixing the columns 73 and the first plate 71. As a result of the second bracket 20 being fixed to the first plate 71, the second bracket 20 can rotate together with the carrier 70 around the base rotation axis P. Thus, the second bracket 20 receives the power for rotation transmitted from the power transmission mechanism 106 via the carrier 70. Since the second bracket 20 can rotate together with the carrier 70, the second bracket 20 can rotate relative to the first bracket 10 around the base rotation axis P. Thus, the first bracket 10 and the second bracket 20 are connected together by the power transmission mechanism 106 so as to be capable of relative rotation. The base rotation axis P is the rotational center of the second bracket 20 and thus of the excavation member 530.

As shown in FIG. 4, the second bracket 20 is fixed to the carrier 70, and thus the second facing surface 20A of the second bracket 20 faces the first facing surface 14A of the retainer 14 of the first bracket 10. The first wall 16 protruding from the first facing surface 14A of the first bracket 10 and the second and third walls 27 and 28 protruding from the second facing surface 20A of the second bracket 20 are arranged alternately in the radial direction. This point will now be described in detail. As described above, the end of the first plate 71 on the first direction X1 side protrudes slightly in the first direction X1 beyond the end of the case body 62 on the first direction X1 side. A part of the first plate 71 forms a protruding end 71A protruding from the case body 62 in the first direction X1. The third wall 28 protruding from the second bracket 20 is located on the radially outer side of the protruding end 71A. In the axial direction XA, the third wall 28 is located so as to overlap the entire region of the protruding end 71A. Furthermore, the first wall 16 protruding from the first bracket 10 is located on the radially outer side of the third wall 28. In other words, the third wall 28 is located between the first wall 16 and the protruding end 71A of the first plate 71 in the radial direction. In the axial direction XA, the first wall 16 is located so as to overlap the entire region of the third wall 28. Furthermore, the second wall 27 protruding from the second bracket 20 is located on the radially outer side of the first wall 16. In the axial direction XA, the second wall 27 is located so as to overlap the entire region of the first wall 16. Thus, in the circumferential range where the second wall 27 is present, the third wall 28, the first wall 16, and the second wall 27 are arranged in this order radially outward from the protruding end 71A of the first plate 71. The third wall 28, the first wall 16, and the second wall 27 form a triple labyrinth structure. As shown in the lower part of FIG. 3, in the circumferential range where the second wall 27 is not present, the third wall 28 and the first wall 16 are arranged in this order radially outward from the protruding end 71A. The third wall 28 and the first wall 16 form a double labyrinth structure. The space defined by the inner circumferential surface of the retainer 14 of the first bracket 10 and the second facing surface 20A of the second bracket 20 is referred to as the housing chamber 30 for the power transmission mechanism 106. In this embodiment, the triple or double labyrinth structure is formed in the gap that communicates the housing chamber 30 with the outside. With respect to the axial direction XA, there is a slight gap between each of the protruding ends of the first, second, and third walls 16, 27, and 28, which form the labyrinth structure, and the wall surface facing the protruding end. For example, there is a slight gap between the protruding end of the first wall 16 and the second facing surface 20A of the second bracket 20. There is also a slight gap between the protruding end of the second wall 27 and the first facing surface 14A of the first bracket 10.

The position of the second wall 27 in the circumferential direction will now be described. As a premise, the attitude of the bucket 531, which is integrated with the second bracket 20, is described. As shown in FIG. 6, the bucket 531 has a box-like shape with the opening 535. The direction perpendicular to the opening surface 535A of the bucket 531 and extending from the interior to the exterior of the bucket 531 through the opening surface 535A is referred to as the opening direction V. The direction perpendicular to the opening surface 535A is also the direction of the view in which the apparent area of the region enclosed by the opening edge of the opening 535 is largest. A virtual circle around the base rotation axis P is referred to as the first virtual circle. The opening direction V is along the tangent line at the position where the first virtual circle passes through the opening surface 535A of the bucket 531. The bucket 531 is connected to the third outer edge portion 22C of the second portion 22 of the second bracket 20 in such an attitude. The first outer edge portion 22A of the second portion 22 is connected to a part of the outer wall of the bucket 531 that is close to the opening 535. The second outer edge portion 22B of the second portion 22 is connected to a part of the outer wall of the bucket 531 that is close to the bottom of the bucket 531.

The position of the second wall 27 in the circumferential direction will now be described in detail. The excavation member 530 is hereinafter assumed to be in the specific plan view. As shown in FIG. 6, the virtual straight line connecting the base rotation axis P and the opening surface 535A by the shortest distance is referred to as the first straight line U1. The virtual straight line extending from the base rotation axis P in the opening direction V is referred to as the second straight line U2. In other words, the second straight line U2 is a half line starting at the base rotation axis P and extending in the opening direction V. In the circumferential direction, the second wall 27 extends over the entire specific angular region UN, which is the angular region formed by the first straight line U1 and the second straight line U2 on the side toward which the opening surface 535A is open. Furthermore, the second wall 27 extends not only in the specific angular region UN, but also to the side opposite to the specific angular region UN across the second straight line U2. The second wall 27 extends from near the first straight line U1 for about 200 degrees around the base rotation axis P. With respect to the specific angular region UN, the side toward which the opening surface 535A is open can also refer to the side oriented in the opening direction V. The specific angular region UN in this embodiment spans about 100 degrees.

As shown in FIG. 2, the bucket joint mechanism 510 includes a first stopper 51. The first stopper 51 is located on the base 12 of the first bracket 10. Of the two main surfaces of the base 12, the one facing the first direction X1 is referred to as the first main surface 12A. The first stopper 51 protrudes from the first main surface 12A in the first direction X1. The first stopper 51 is located near the middle of the two diverging sides of the base 12. The first stopper 51 has a rectangular parallelepiped shape. With respect to the first direction X1, the protruding end of the first stopper 51 reaches the same position as the main surface of the second bracket 20 facing the first direction X1.

As shown in FIG. 5, the bucket joint mechanism 510 includes a second stopper 52. The second stopper 52 protrudes outward from the outer edge of the second bracket 20. The second stopper 52 is located near the boundary between the end of the arc of the first portion 21 and the second outer edge 22B of the second portion 22. When the second bracket 20 is viewed in the specific plan view, the second stopper 52 has a generally triangular shape. Specifically, the second stopper 52 has a contact surface 52A corresponding to one side of the triangle and a sloping surface 52B corresponding to another side. The contact surface 52A protrudes generally radially from the outer edge of the second bracket 20. The sloping surface 52B is located closer to the second portion 22 of the second bracket 20 than is the contact surface 52A. The sloping surface 52B connects the protruding end of the contact surface 52A and the second outer edge 22B of the second portion 22.

As shown in FIG. 5, the bucket joint mechanism 510 includes a third stopper 53. The third stopper 53 is provided symmetrically to the second stopper 52 across the base rotation axis P. Specifically, the third stopper 53 has a contact surface 53A protruding radially outward from the outer edge of the second bracket 20 and a sloping surface 53B extending from the protruding end of the contact surface 52A to the first outer edge portion 22A of the second portion 22.

As described above, the second and third stoppers 52 and 53 are symmetrically arranged across the base rotation axis P. Thus, as shown in FIG. 6, the contact surface 52A of the second stopper 52 and the contact surface 53A of the third stopper 53 are substantially separated by 180 degrees in the circumferential direction. Here, a description is given of a predetermined reference position. The reference position of the excavation member 530 refers to the position of the excavation member 530 in which the distance from the second stopper 52 to the first stopper 51 and the distance from the third stopper 53 to the first stopper 51 are equal in the circumferential direction. As shown in FIG. 7, the contact surface 52A of the second stopper 52 contacts the first stopper 51 when the excavation member 530 rotates by a predetermined angle (first angle) from the reference position in the first rotational direction. Similarly, the contact surface 53A of the third stopper 53 contacts the first stopper 51 when the excavation member 530 rotates by the predetermined angle from the reference position in the second rotational direction opposite to the first rotational direction. In this embodiment, the above predetermined angle is about 90 degrees.

As shown in FIG. 7, when the excavation member 530 is viewed in the specific plan view together with the first bracket 10, the half line extending from the base rotation axis P in the direction opposite to the first stopper 51 is referred to as the virtual half line U3. In the specific plan view of the excavation member 530 together with the first bracket 10, when the second stopper 52 is in contact with the first stopper 51, the virtual half line U3 is located on the opening direction V side of the opening surface 535A. In other words, when the second stopper 52 is in contact with the first stopper 51, the virtual half line U3 intersects the virtual half line extending from the opening surface 535A in the opening direction V.

As shown in FIG. 1, the bucket joint mechanism 510 includes a battery 202 and an inverter 204. The battery 202 and the inverter 204 are located in the vehicle body 502B, for example. The battery 202 is electrically connected to the inverter 204 via a power line. In addition, the inverter 204 is electrically connected to the motor 104 shown in FIG. 3 via a power line (not shown). The inverter 204 performs DC-AC power conversion between the battery 202 and the motor 104.

As shown in FIG. 1, the bucket joint mechanism 510 includes a first operating device 231 and a second operating device 232. The first and second operating devices 231 and 232 are located near the driver seat in the vehicle body 502B. The first and second operating devices 231 and 232 can receive operations from the driver of the excavator 500. The first operating device 231 is, for example, a joystick. The first operating device 231 outputs, in accordance with the driver's operation, a rotation signal containing information for instruction of the rotational drive and the rotational direction of the excavation member 530. The second operating device 232 is, for example, a push switch. The second operating device 232 outputs, in accordance with the driver's operation, a switching signal containing information for instruction to control the motor 104 in a second mode (described later). The second operating device 232 is operated by the driver to switch between On and Off. When the second operating device 232 is turned On by the driver, it starts outputting the switching signal. When the second operating device 232 is turned Off by the driver, it stops outputting the switching signal.

The bucket joint mechanism 510 includes a controller 200. The controller 200 may be formed as one or more processors that perform various processing in accordance with a computer program (software), or one or more dedicated hardware circuits such as application-specific integrated circuits (ASICs) that perform at least a part of the various processing, or a circuitry including a combination thereof. The processors include a CPU and a memory such as a RAM or ROM. The memory stores program codes or instructions configured to cause the CPU to perform processes. The memory, or a computer-readable medium, encompasses any kind of available medium accessible to a general-purpose or dedicated computer.

The controller 200 is connected to the inverter 204 in a wired or wireless manner. The controller 200 controls the inverter 204 to control the motor 104. Thus, the controller 200 controls the motor 104.

The controller 200 is connected to the first operating device 231 and the second operating device 232 in a wired or wireless manner. The controller 200 can receive signals output by the first and second operating devices 231 and 232. The controller 200 controls the motor 104 in accordance with the signals from the first and second operating devices 231 and 232. Specifically, the controller 200 causes, in accordance with the rotation signal, the output shaft 104B of the motor 104 to rotate in either the forward or reverse direction. The controller 200 can switch between the first mode and the second mode as a control mode for controlling the magnitude of the torque associated with this rotation. The controller 200 switches the control mode of the motor 104 depending on whether or not the switching signal has been received. When the controller 200 has not received the switching signal, it controls the motor 104 in the first mode. In the first mode, the controller 200 controls the motor 104 so that the motor 104 outputs a predetermined set torque in rotating the output shaft 104B of the motor 104 in accordance with the rotation signal. For example, the set torque has multiple levels of predetermined values. The driver of the excavator 500 can switch the set torque through the operation of an operating device, which is not shown in the drawings. The highest set torque applicable in the first mode is below a specified value. In other words, the first mode is a control mode that limits the torque output by the motor 104 to less than the specified value. The specified value is predetermined as a torque that can provide a large impact not required in normal excavation work when the components of the excavation member 530 strike other objects. Along with such a torque limit, in the first mode, the rotational speed of the output shaft 104B of the motor 104 and the acceleration of the rotation of the output shaft 104B are each limited to less than a certain value. In addition to these torque limits, the first mode also imposes a limit on the rotational range of the output shaft 104B of the motor 104. The rotational position of the excavation member 530 taken when the second stopper 52 is positioned in the second rotational direction by an avoidance angle relative to the first stopper 51 is referred to as the first rotational position. The avoidance angle is, for example, ten degrees. The rotational position of the excavation member 530 taken when the third stopper 53 is positioned in the first rotational direction by the above avoidance angle relative to the first stopper 51 is referred to as the second rotational position. In the first mode, the controller 200 restricts the rotational range of the output shaft 104B so that the excavation member 530 rotates within the range from the first rotation position to the second rotation position centered on the reference position.

On the other hand, when the controller 200 has received the switching signal, it controls the motor 104 in the second mode. In the second mode, the controller 200 controls the motor 104 so that the motor 104 outputs a predetermined permitted torque in rotating the output shaft 104B of the motor 104 in accordance with the rotation signal. The permitted torque is larger than the specified value. In other words, the second mode is a control mode that permits the torque output by the motor 104 to be equal to or larger than the specified value. In addition, in the second mode, the restrictions on the rotational speed of the output shaft 104B of the motor 104 and the acceleration of the rotation of the output shaft 104B that were imposed in the first mode are lifted. In the second mode, the controller 200 also does not restrict the rotational range of the output shaft 104B.

Suppose that the bucket 531 is now performing the excavation work. As the bucket 531 excavates dirt, the dirt can adhere to the first and second brackets 10 and 20 located around the bucket 531. Some of the dirt adhering to the first and second brackets 10 and 20 will attempt to enter the housing chamber 30 through the gap between the first facing surface 14A of the first bracket 10 and the second facing surface 20A of the second bracket 20. As shown in FIG. 3, in the configuration of this embodiment, a triple or double labyrinth structure is formed between the first facing surface 14A of the first bracket 10 and the second facing surface 20A of the second bracket 20. The labyrinth structure prevents dirt from entering the housing chamber 30.

Specifically, as shown in FIG. 4, in the circumferential region where the triple labyrinth structure is formed, the second wall 27, the first wall 16, and the third wall 28 are arranged alternately in the radial direction. If dirt attempts to enter such a structure from the outside, the outer circumferential surface of the second wall 27, which constitutes the outermost part of the labyrinth structure, will first prevent the entry of the dirt. Suppose that the second wall 27 fails to prevent the entry of the dirt and a small amount of dirt enters the gap between the second wall 27 and the first facing surface 14A of the first bracket 10. The first wall 16 protruding from the first bracket 10 is located on the radially inner side of and directly in front of the gap between the second wall 27 and the first facing surface 14A of the first bracket 10. Therefore, even if the dirt enters radially inward through the gap, the outer circumferential surface of the first wall 16 prevents further entry of the dirt. Further, suppose that the first wall 16 fails to prevent the entry of the dirt and a small amount of dirt enters the gap between the first wall 16 and the second facing surface 20A of the second bracket 20. The third wall 28 protruding from the second bracket 20 is located on the radially inner side of and directly in front of the gap between the first wall 16 and the second facing surface 20A of the second bracket 20. Therefore, even if the dirt enters radially inward through the gap, the outer circumferential surface of the third wall 28 prevents further entry of the dirt.

On the other hand, as shown in the lower part of FIG. 3, in the circumferential region where the double labyrinth structure is formed, the first wall 16 and the third wall 28 are arranged alternately in the radial direction. If dirt attempts to enter such a structure from the outside, the outer circumferential surface of the first wall 16, which constitutes the outermost part of the labyrinth structure, will first prevent the entry of the dirt. Suppose that the first wall 16 fails to prevent the entry of the dirt and a small amount of dirt enters the gap between the first wall 16 and the second facing surface 20A of the second bracket 20. The third wall 28 protruding from the second bracket 20 is located on the radially inner side of and directly in front of the gap between the first wall 16 and the second facing surface 20A of the second bracket 20. Therefore, even if the dirt enters radially inward through the gap, the outer circumferential surface of the third wall 28 prevents further entry of the dirt.

In the circumferential region where the triple labyrinth structure is formed, the most part of the outer circumferential surface of the second wall 27 located outermost in this labyrinth structure is flush with the outer circumferential surface of the first portion 21 of the second bracket 20, as shown in FIG. 5. Therefore, as shown in FIG. 4, the outer circumferential surface of the second wall 27 is exposed to the outer space. Therefore, even if dirt once adheres to the outer circumferential surface of the second wall 27, the dirt will quickly scatter from the outer circumferential surface of the second wall 27 due to the momentum of rotation of the excavation member 530. In contrast, in the circumferential region where the double labyrinth structure is formed, as shown in the lower part of FIG. 3, the outer circumferential surface of the first wall 16 located outermost in this labyrinth structure is not exposed to the outside but forms the bottom of a recess 29, which is described as follows. The recess 29 is defined by the outer circumferential surface of the first wall 16, together with the portion of the first facing surface 14A of the first bracket 10 on the radially outer side of the first wall 16 and the portion of the second facing surface 20A of the second bracket 20 on the radially outer side of the first wall 16. As shown in FIG. 8, the recess 29 extends over the entire circumferential region where the second wall 27 is not present. In FIGS. 8 and 9, the region where the recess 29 is present is hatched. Dirt tends to accumulate in the recess 29. For example, suppose that a part of the recess 29 is located below the base rotation axis P, as shown in FIG. 8. And suppose that dirt has accumulated in the recess 29. In FIGS. 8 and 9, the region W where dirt is present is enclosed by a single dotted line. With dirt in the recess 29, the excavation member 530 rotates, and the second wall 27 rotates accordingly. At this time, the end 27A of the arc of the second wall 27 pushes the dirt accumulated in the recess 29 in the circumferential direction. The end 27A of the second wall 27 pushes the dirt along the recess 29 while aggregating the dirt located sparsely to some degree. As shown by the arrow W1 in FIG. 9, when the amount of aggregated dirt pushed forward by the end 27A of the second wall 27 is large, the dirt cannot be held in the recess 29 and is pushed out of the recess 29. The dirt is then discharged from the recess 29. Particularly in a part of the recess 29 where the dirt moves upward, the dirt tends to be pushed out of the recess 29 with the aid of its own weight. In other words, as the excavation member 530 rotates, the dirt accumulated in the recess 29 is discharged by being scraped away by the end 27A of the second wall 27.

In forming the labyrinth structure between the first facing surface 14A of the first bracket 10 and the second facing surface 20A of the second bracket 20, it is also possible to form the second wall 27 in an annular shape. In this case, the triple labyrinth structure extends over the entire circumference. However, the triple labyrinth structure extending over the entire circumference proposes the following concerns. If the triple labyrinth structure extends over the entire circumference, dirt is less likely to enter the interior, while it is difficult to discharge the dirt accumulated between the walls of the labyrinth structure to the outside. Therefore, when discharging the dirt accumulated between the walls of the labyrinth structure during maintenance for example, it is necessary to disconnect the first bracket 10 from the second bracket 20 and then perform cleaning work, which is a time-consuming process.

In this regard, according to the embodiment having the triple labyrinth structure extending only in a part of the circumference, it is easier to discharge the dirt accumulated between the walls of the labyrinth structure. Therefore, the dirt accumulated between the walls of the labyrinth structure can be discharged, for example, by pouring water down the walls, without disconnecting the first bracket 10 from the second bracket 20. Thus, the maintenance work is facilitated.

In performing the excavation work, the driver of the excavator 500 basically uses the first mode to operate the excavation member 530. In the first mode, the controller 200 rotates the excavation member 530 in the first or second rotational direction while restricting the rotational range of the output shaft 104B of the motor 104. In accordance with the above restriction of the rotational range, the controller 200 rotates the excavation member 530 within the range in which the second and third stoppers 52 and 53 protruding from the second bracket 20 do not contact the first stopper 51 protruding from the first bracket 10.

When dirt adheres to the first bracket 10, the second bracket 20, and the bucket 531 during the excavation work, the driver of the excavator 500 uses the second mode to operate the excavation member 530. In the second mode, the controller 200 lifts the restriction on the rotational range of the output shaft 104B of the motor 104. In addition, in the second mode, the controller 200 increases the output torque of the motor 104 to a level higher than in the first mode. As shown in FIG. 7, when the controller 200 rotates the excavation member 530 in the first rotational direction in the second mode, the second stopper 52 strikes the first stopper 51 hard. The impact at this instant causes the dirt to fall from the first bracket 10, the second bracket 20, and the bucket 531. When the controller 200 rotates the excavation member 530 in the second rotational direction in the second mode, the third stopper 53 strikes the first stopper 51 hard. The impact at this instant causes the dirt to fall from the first bracket 10, the second bracket 20, and the bucket 531.

(1) In the configuration of the embodiment, the second wall 27 having an arc-like shape is located on the radially outer side of the first wall 16 having an annular shape. As described above in Function 1 of Embodiment, in the circumferential region where the second wall 27 is present, the first wall 16 and the second wall 27 prevent dirt from entering the housing chamber 30 through the gap between the first facing surface 14A of the first bracket 10 and the second facing surface 20A of the second bracket 20. On the other hand, as described above in Function 1 of Embodiment, in the circumferential region where the second wall 27 is not present, the end 27A of the second wall 27 pushes away the dirt on the outer circumferential surface of the first wall 16 as the excavation member 530 rotates. Thus, even in the circumferential region where the second wall 27 is not present, the dirt is prevented from entering the housing chamber 30. Such configuration of the embodiment can considerably inhibit the dirt from reaching the power transmission mechanism 106.

(2) In the configuration of the embodiment, in addition to the first wall 16 and the second wall 27, the third wall 28 having an annular shape is located on the radially inner side of the first wall 16. This forms the triple labyrinth structure and the double labyrinth structure in the gap connecting the housing chamber 30 to the outside. In this way, the triple labyrinth structure and the double labyrinth structure can be combined to provide both of the following two advantages. First, the labyrinth structure is present at the entire circumference to prevent the dirt from entering the housing chamber 30 at the entire circumference. Second, since a part of the circumference is the double labyrinth structure instead of the triple, the maintenance work is easier, as described above in Function 1 of Embodiment.

(3) In this embodiment, the second wall 27 extends for 180 degrees or more. In this way, the circumferential dimension of the second wall 27 is long enough to maximize the circumferential region where the triple labyrinth structure is present. This makes it more difficult for dirt to enter the housing chamber 30.

(4) The region around the opening 535 of bucket 531 is particularly prone to adhesion of dirt. To address this issue, in the embodiment, the second wall 27 extends over the entire specific angular region UN formed by the first straight line U1 and the second straight line U2, as shown in FIG. 6. The specific angular region UN corresponds to the part of the first bracket 10 and the second bracket 20 close to the opening 535 of the bucket 531, where dirt is particularly likely to adhere. In this way, the part where dirt is particularly likely to adhere is guarded by the second wall 27, so as to more effectively inhibit the dirt from entering the housing chamber 30.

(5) The configuration of the embodiment includes the first stopper 51 protruding from the first bracket 10 and the second stopper 52 protruding from the second bracket 20. The presence of the first and second stoppers 51 and 52 allows the following. As described above in Function 2 of Embodiment, the excavation member 530 is rotated to collide the second stopper 52 against the first stopper 51, causing falling of the dirt adhering to the first bracket 10 and the second bracket 20. Thus, the dirt can be dropped off the first and second brackets 10 and 20 themselves. As a result, the dirt adhering to the first and second brackets 10 and 20 is almost completely removed. With less dirt adhering to the first and second brackets 10 and 20, the risk of the dirt entering the housing chamber 30 is also minimized.

(6) In this embodiment, the second bracket 20 has two stoppers: the second stopper 52 and the third stopper 53. Either of these two stoppers can collide against the first stopper 51 when the second bracket 20 is rotated in either forward or reverse direction. Therefore, in impacting the first bracket 10 and the second bracket 20, one of the second stopper 52 and the third stopper 53 closer to the first stopper 51 at the current rotational position of the second bracket 20 should collide against the first stopper 51. Therefore, in colliding the stoppers against each other, a large amount of rotation is not required for the second bracket 20 and thus the excavation member 530. Thus, the power consumption of the battery 202 can be minimized.

(7) The controller 200 of the embodiment can control the motor 104 in the second mode in which the torque output by the motor 104 is larger than in the first mode. The second mode allows the second stopper 52 or the third stopper 53 to strike the first stopper 51 hard. Thus, a large impact can be provided on the first and second brackets 10 and 20. Therefore, dirt can be effectively removed off the first and second brackets 10 and 20.

(8) The excavator disclosed in the '130 Publication includes a self-propelled main body, an arm extending from the main body, and a bucket for excavation. The bucket is connected to a distal end of the arm. The bucket is rotatable relative to the arm.

In an excavator such as disclosed in the '130 Publication, foreign matter such as dirt may adhere to the connection point between the bucket and the arm. If such foreign matter is left in place, the presence of the foreign matter can cause friction at the connection point during operation and lead to deterioration of the connection point. Therefore, it is desirable to remove the foreign matter promptly. However, it is not practical for the excavator driver to get out of the driver's seat to remove the foreign matter each time it adheres. Therefore, a structure is required that enables removal of foreign matter without the driver having to leave the driver's seat. The same issue can arise not only at the connection point between the arm and the bucket, and not only in excavators, but also in any construction machine with two connected parts one of which is rotatable relative to the other.

The configuration of the embodiment includes the first stopper 51 protruding from the first bracket 10 and the second stopper 52 protruding from the second bracket 20. The presence of the first and second stoppers 51 and 52 allows the following. As described above in Function 2 of Embodiment, the excavation member 530 is rotated to collide the second stopper 52 against the first stopper 51, causing falling of the dirt adhering to the first bracket 10, the second bracket 20, and in addition, the bucket 531. Thus, the dirt can be dropped off these members quickly.

In this embodiment, dirt is dropped off various parts of the bucket joint mechanism 510 by collision of the first stopper 51 and the second stopper 52. With this configuration, the bucket joint mechanism 510 alone can drop the dirt off various parts without using anything other than the excavator 500. Therefore, when removal of dirt is necessary, the dirt can be removed immediately on the spot. Also, at this time, the driver does not need to leave the driver's seat. When the excavation member 530 is operated with dirt adhering to it, the weight of the excavation member 530 is increased, resulting in higher power consumption of the battery 202. As described above, the configuration of the embodiment allows the driver to drop the dirt off on the spot when necessary, so that the driver can drop the dirt off as soon as he or she notices that the amount of the adhered dirt is increasing. Therefore, the configuration of the embodiment makes it possible to avoid a situation in which excavation work is performed with a large amount of dirt adhered. Such configuration of the embodiment can reduce the power consumption of the battery 202.

In addition, in the configuration of the embodiment, the second bracket 20 only needs to be rotated as in the excavation work to collide the first stopper 51 and the second stopper 52 in order to drop the dirt off. Therefore, the driver does not need to perform complicated operations related to the excavator 500 to drop the dirt off, and only needs to perform the same operations as in the excavation work. Therefore, in the configuration of the embodiment, there is no burden on the driver in dropping the dirt off.

Furthermore, the configuration of the embodiment employs a very simple structure with only protrusions on the first and second brackets 10 and 20, respectively, to drop the dirt off various parts of the bucket joint mechanism 510. Therefore, the overall configuration of the bucket joint mechanism 510 is not complicated, thus avoiding the increase in size and number of parts.

(9) For a construction machine with the bucket 531, it is inevitable that a large amount of dirt adhere around the bucket 531 in the operation of excavating dirt with the bucket 531. In such a construction machine, it is particularly effective to employ the above configuration related to the stoppers.

(10) As shown in FIG. 7, in this embodiment, when the second stopper 52 contacts the first stopper 51, the virtual half line U3 is located in the opening direction V as viewed from the opening 535 of the bucket 531. The excavation work is often performed with the virtual half line U3 extending generally vertically, in combination with the direction of the arm 520. Therefore, due to the position of the virtual half line U3 relative to the opening direction V described above, the opening 535 of the bucket 531 faces downward at the position where the second stopper 52 contacts the first stopper 51. Therefore, it is easy to drop off the dirt inside the bucket 531 when the second stopper 52 collides against the first stopper 51.

Modification Examples

The foregoing embodiment can be modified as described below. The above embodiment and the following modifications can be implemented in combination to the extent where they are technically consistent to each other.

In the above embodiment, dirt was taken as an example of foreign matter. However, it is also possible that the foreign matter is other than dirt. For foreign matter other than dirt, the parts of the bucket joint mechanism 510 still function in the same manner as in the above embodiment.

The configuration of the power transmission mechanism 106 is not limited to the example in the above embodiment. The power transmission mechanism 106 may be configured in any manner so as to be able to transmit power to the second bracket 20 to rotate the second bracket 20. The power source is not limited to the example in the above embodiment. Any power source can be used that is able to provide power to the power transmission mechanism 106. For example, the power source may be a hydraulic motor. The power source is not limited to those that provide rotary motion power to the power transmission mechanism 106, but may be, for example, those that provide linear motion power to the power transmission mechanism 106. In this case, the power transmission mechanism 106 converts the linear motion into rotary motion and transmit it to the second bracket 20.

With respect to the way to control the power source, the way to set the torque in the first mode is not limited to the example in the above embodiment. The first mode may be configured in any manner such that the torque output by the motor 104 can be limited to less than a specified value. For example, the magnitude of torque available in the first mode may be switched continuously rather than stepwise. It is also possible that only one torque magnitude is available in the first mode.

The way to set the torque in the second mode is not limited to the example in the above embodiment. The second mode may be configured in any manner such that the torque output by the motor 104 is permitted to be equal to or larger than the specified value. It is also possible that the magnitude of torque output by the motor 104 can be switched stepwise or continuously within the second mode.

The way to set the specified value is not limited to the example in the above embodiment. The specified value may be set appropriately as a boundary value to switch between the torque required for the excavation work and the torque required for removing foreign matter.

The specified value may vary depending on the type of component employed as the power source. The variable indicating the power of the power source can also vary depending on the type of component employed as the power source. Furthermore, the way of control by the controller 200 may vary depending on the type of component employed as the power source. No matter what power source is used, any configuration is possible as long as the power output by the power source is limited to less than the specified value in the first mode, while the power output by the power source is permitted to be equal to or larger than the specified value in the second mode.

It is not required that the controller 200 be configured to switch between the first and second modes. For example, in the case where the motor 104 is employed as the power source as in the above embodiment, it is also possible to eliminate the second mode and eliminate the restriction of the rotational range of the output shaft 104B of the motor 104 in the first mode for the excavation work. Even though the torque available in the first mode is relatively small, colliding the second stopper 52 or the third stopper 53 against the first stopper 51 will cause a significant impact on the first bracket 10 and the second bracket 20, and thus foreign matter can be removed off these brackets. For example, the controller 200 may constantly use the control mode that does not restrict the rotational range of the output shaft 104B of the motor 104 and does not restrict the torque output by the motor 104. Even in this case, if the driver of the excavator 500 can control the rotational range of the output shaft 104B of the motor 104 and the torque output by the motor 104 through his or her own operation, the driver is capable of the following. The driver can rotate as necessary the excavation member 530 to the position where the second stopper 52 or the third stopper 53 collides against the first stopper 51, or stop the rotation of the excavation member 530 before the second stopper 52 or the third stopper 53 collides against the first stopper 51.

The aspect of the switching signal is not limited to the example in the above embodiment. For example, the switching signal may be a signal indicating that the motor 104 should be controlled in the first mode, instead of a signal indicating that the motor 104 should be controlled in the second mode as in the above embodiment. There may be multiple switching signals, such as a first signal indicating that the motor 104 should be controlled in the first mode and a second signal indicating that the motor 104 should be controlled in the second mode. Also, the switching signal need not be continuously output for the entire period of time during which the designated control mode is in use, as in the above embodiment, but may be output only at the timing of switching between the first and second modes. The switching signal may be output in any manner as long as it allows the controller 200 to determine the switching between the first and second modes. The processing of the controller 200 should be set according to the aspect of the switching signal.

The aspect of the operating device that outputs the switching signal is not limited to the examples in the above embodiment. For example, when multiple switching signals are used as in the above modification example, one operating device may output two such signals, or alternatively, a separate operating device may be provided for each signal. The aspect of the operating device is not limited as long as it can output the switching signals.

The shape of the first stopper 51 is not limited to the example in the above embodiment. The first stopper 51 may have a cylindrical shape, for example. The first stopper 51 may have any shape capable of contact with the second stopper 52.

The location of the first stopper 51 is not limited to the example in the above embodiment. The first stopper 51 may be located at any position as along as it can contact the second stopper 52. The shape of the second stopper 52 is not limited to the example in the above embodiment. The second stopper 52 may have a rectangular parallelepiped shape, for example. The second stopper 52 may have any shape capable of contact with the first stopper 51.

The location of the second stopper 52 is not limited to the example in the above embodiment. The second stopper 52 may be located at any position as along as it can contact the first stopper 51 when the second bracket 20 has rotated by the predetermined angle from the reference position. The predetermined angle is not limited to the example in the above embodiment. Furthermore, it is not essential that the second stopper 52 is positioned to meet the requirements of the position in relation to the opening direction V and the virtual half line U3 in the above embodiment. As long as the second stopper 52 is located at such a position that it can contact the first stopper 51, the foreign matter can be removed by the impact of the second stopper 52 colliding against the first stopper 51.

As with the second stopper 52, the shape and the location of the third stopper 53 are not limited to the examples in the above embodiment. The third stopper 53 may be located asymmetrically from the second stopper 52. The shape of the third stopper 53 may be different from that of the second stopper 52.

The third stopper 53 may be eliminated. The way to set the reference position is not limited to the example in the above embodiment. The reference position may be set as appropriate, taking into account the rotational range of the excavation member 530 and the direction of the opening 535 of the bucket 531 that will be required during the excavation work.

The first and second stoppers 51 and 52 are not essential in terms of inhibiting foreign matter from reaching the power transmission mechanism 106. Even without the first and second stoppers 51 and 52, the first and second walls 16 and 27 will inhibit foreign matter from reaching the power transmission mechanism 106.

The dimension of the second wall 27 in the circumferential direction is not limited to the example in the above embodiment. This dimension may be larger or smaller than the example in the above embodiment. This dimension may be smaller than 180 degrees. Regardless of the length of the dimension, the second wall 27 will serve to inhibit the entry of foreign matter from the outside.

The location of the second wall 27 in the circumferential direction is not limited to the example in the above embodiment. The second wall 27 may be present only in a part, not the entirety, of the specific angular region UN, or it may be absent throughout the specific angular region UN. The second wall 27 may be present anywhere in the circumferential direction.

There may be more than one second wall 27. Specifically, the second wall 27 having an arc-like shape may be provided at each of separate positions in the circumferential direction. The dimension of the second wall 27 in the axial direction is not limited to the example in the above embodiment. The second wall 27 may have any dimension in the axial direction as long as the second wall 27 and the first wall 16 overlap at least partly in the axial direction. The dimension of the second wall 27 in the axial direction may differ depending on its location in the circumferential direction. As with the second wall 27, the dimension of the first wall 16 in the axial direction is not limited to the example in the above embodiment. As described above, any dimension is possible as long as the second wall 27 and the first wall 16 overlap at least partly in the axial direction.

It is not essential that the third wall 28 has an annular shape. Specifically, the third wall 28 may have an arc-like shape. As with the second wall 27, the dimension of the third wall 28 in the axial direction is not limited to the example in the above embodiment. The third wall 28 may have any dimension in the axial direction as long as the third wall 28 and the first wall 16 overlap at least partly in the axial direction.

The third wall 28 may be eliminated. The shapes of the first bracket 10 and the second bracket 20 are not limited to the examples in the above embodiment. Each bracket may be configured in any manner as long as it achieves its intrinsic function of holding the power transmission mechanism 106 and transmitting the power from the power transmission mechanism 106 to the bucket 531, while having provided thereon a respective wall necessary to form the labyrinth structure and a respective stopper necessary to remove foreign matter.

The first wall 16 and the second wall 27 may be exchanged between the brackets. Specifically, the first wall 16 may protrude from the second bracket 20, and the second wall 27 may protrude from the first bracket 10. In this case, the excavation member 530 constitutes the first member, and the arm 520 constitutes the second member. Even in the case where the first wall 16 and the second wall 27 are exchanged between the brackets, the first wall 16 should have an annular shape, and the second wall 27 having an arc-like shape should be located on the radially outer side of the first wall 16. When the excavation member 530 and thus the second bracket 20 are rotating, the first bracket 10 is rotating as viewed from the second bracket 20. In other words, if one is configured to rotate relative to the other, the power transmission mechanism 106 can be regarded as providing the power for rotation to both of them. Thus, such configuration satisfies the relationship that the power transmission mechanism 106 transmits the power for rotation to the second member, even if the first and second members are exchanged.

The first wall 16 and the second wall 27 are not necessarily applied to the connection point between the excavation member 530 and the arm 520. For example, they may be applied to the connection point between the arm 520 and the boom 504. Any point where two members facing each other are mutually rotatably connected is susceptible of the same configuration as in the above embodiment, in which the first wall and the second wall protrude from these two members. In the case where the first wall 16 and the second wall 27 are provided at a point other than the connection point between the excavation member 530 and the arm 520, it is also possible to add the third wall 28 and/or the first stopper 51 and the second stopper 52.

The construction machine to which the first wall 16 and the second wall 27 are applied is not limited to the excavator 500. Even for construction machines other than the excavator 500, if they have points where two members facing each other are mutually rotatably connected, the first wall 16 and the second wall 27 can be applied to such points, as described above.

The first and second walls 16 and 27 are not essential in terms of removing foreign matter from the first and second brackets 10 and 20. Even without the first and second walls 16 and 27, the first and second stoppers 51 and 52 can be used to remove foreign matter from the first and second brackets 10 and 20.

The first stopper 51 and the second stopper 52 are not necessarily applied to the connection point between the excavation member 530 and the arm 520, including the case where the first wall 16 and the second wall 27 are eliminated. For example, they may be applied to the connection point between the arm 520 and the boom 504. Any point having two members, one of which rotates relative to the other, can be configured in the same manner as in the above embodiment, in which the first stopper 51 protrudes from one of these two members and the second stopper 52 protrudes from the other. Depending on where the first and second stoppers 51 and 52 are applied, it is also possible that the two members are not connected by the power transmission mechanism 106, or even the power transmission mechanism 106 is not present around the two members. Even in such a case, the two stoppers can be collided with each other to achieve the effect of the impact for removing the foreign matter. In other words, it is not required that the power transmission mechanism 106 be present at the point to which the first and second stoppers 51 and 52 are applied.

The construction machine to which the first stopper 51 and the second stopper 52 are applied is not limited to the excavator 500. Even for construction machines other than the excavator 500, if they have points with two members one of which rotates relative to the other, the first stopper 51 and the second stopper 52 can be applied to such points, as described above.

The foregoing embodiments describe a plurality of physically separate constituent parts. They may be combined into a single part, and any one of them may be divided into a plurality of physically separate constituent parts. Irrespective of whether or not the constituent parts are integrated, they are acceptable as long as they are configured to solve the problems.

According to the foregoing embodiments, a plurality of functions are distributively provided. Some or all of the functions may be integrated. Any one of the functions may be partly or entirely segmented into a plurality of functions, which are distributively provided. Regardless of whether or not the functions are integrated or distributively provided, they are acceptable as long as they are configured to attain the object of the disclosure.

JOINT MECHANISM FOR CONSTRUCTION MACHINE

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