Working machine with angle detection device

Provided is a working machine including first and second members, an angle detection device and a connection pin connected to the first and second members to rotate integrally with the second member relative to the first member. The angle detection device has a marker, an angle sensor and a guard member, which has a main guard portion covering the angle sensor and including an inner opposite surface opposed to an end surface of the projecting end portion and a guard-member-side engagement portion. One of the angle sensor and the marker is disposed on the inner opposite surface, the other disposed on the end surface. The first member has a first-member-side engagement portion engaging with the guard-member-side engagement portion to restrain the main guard portion from relative rotation. The guard member can contact with the connection pin to restrain the guard member from relative displacement to the projecting end portion.

TECHNICAL FIELD

The present invention relates to a working machine including a first member and a second member which are rotatably coupled to each other, and an angle detection device which detects an angle that the second member makes with the first member.

BACKGROUND ART

There is conventionally known a working machine equipped with a working device including two members rotatably coupled to each other such as a hydraulic excavator and a crusher, wherein the working device is further provided with an angle sensor for detecting an angle between the two members (e.g. JP H06-049938 U).

FIG. 9andFIG. 10show one example of a working machine of such a type. The working machine includes a first member104, a second member106rotatably attached to the first member104through a joint pin105, a housing body110fixed to the first member104, an angle detection device107including an angle sensor111which is fixed to the housing body110and has a detection shaft, and a lever112which interconnects the detection shaft and an external surface portion of the second member106. The angle sensor111detects a relative angle that the second member106makes with the first member104. The angle detection device107further includes a cover member113, which is arranged, as indicated by hatching inFIG. 9, so as to guard the angle sensor111axially thereof.

The cover member113is, however, not allowed to cover the angle sensor111at the side of the cover member113because of the necessity for avoiding interference between the lever112and the cover member113within a rotational range of the lever112. This causes the angle sensor111to be likely to result in failure due to intrusion of a stone or the like.

In addition, the cover member113may be deformed by physical contact thereof with other member to bring a part of the deformed cover member113into contact with the angle sensor111, which can involve damage of the angle sensor111or disable the angle sensor111from appropriate angle detection. Besides, damage of the lever112itself also disables the angle detection from being performed.

SUMMARY OF INVENTION

An object of the present invention is to provide a working machine including a first member, a second member coupled to the first member so as to be capable of rotational movement in a specific rotational-movement direction with respect to the first member, and an angle detection device including an angle sensor which detects a rotational-movement angle that the second member makes with the first member in the rotational-movement direction, the working machine being capable of reliably guarding the angle sensor without hindering the rotational movement.

To achieve the above object, the present inventors have conceived of providing a guard member which covers an angle sensor and letting a load applied to the guard member be transmitted to a connection pin for coupling a first member and a second member, the connection pin having high rigidity. Specifically, provided is a working machine including: a first member; a second member; a connection pin interposed between the first member and the second member, the connection pin interconnecting the first member and the second member so as to allow the second member to make rotational movement relative to the first member in a rotational-movement direction around the connection pin; and an angle detection device which detects a rotational-movement angle as an angle that the second member makes with the first member in the rotational-movement direction. The connection pin is connected to the second member so as to make rotational movement integrally with the second member while being connected to the first member so as to be able to make rotational movement relative to the first member in the rotational-movement direction, the connection pin having a projecting end portion which projects beyond the first member and the second member in an axial direction of the connection pin. The angle detection device includes a marker, an angle sensor which detects a relative angle position of the marker to the angle sensor in the rotational-movement direction, and a guard member which guards the angle sensor, the marker and the angle sensor being arranged so as to detect an angle that the connection pin makes with the first member in the rotational-movement direction. The guard member has a main guard portion, which covers the angle sensor so as to surround the projecting end portion of the connection pin all around the projecting end portion, and a guard-member-side engagement portion joined with the main guard portion. The main guard portion has an inner opposite surface which is an inner surface opposed to an end surface of the projecting end portion of the connection pin, one of the angle sensor and the marker being a first detection element disposed on the inner opposite surface, the other of the angle sensor and the marker being a second detection element disposed on the end surface of the projecting end portion so as to be opposed to the first detection element with a gap in the axial direction. The first member has a first-member-side engagement portion engageable with the guard-member-side engagement portion, and the first-member-side engagement portion and the guard-member-side engagement portion engage with each other to restrain the main guard portion from relative rotational movement to the first member in the rotational-movement direction. The guard member includes respective parts capable of making contact with an axial end surface and a circumferential surface of the projecting end portion of the connection pin, the contact causing the guard member to be restrained from relative displacement to the projecting end portion.

DESCRIPTION OF EMBODIMENTS

Below will be described an embodiment of the present invention with reference to the drawings.

FIG. 2shows a hydraulic excavator1as a working machine according to the embodiment of the present invention. The hydraulic excavator1includes a lower travelling body2, an upper slewing body3capable of being slewed above the lower travelling body2, and a working device. The upper slewing body3is provided with a driving room3aon a front part thereof. The working device includes: a boom4supported by the upper slewing body3so as to be raised and lowered; a boom cylinder which extends and contracts so as to raise and lower the boom4; an arm6rotatably connected to a distal end of the boom4, the arm6being a first member; an arm cylinder7which extends and contracts so as to rotate the arm6; a crushing device8as an end attachment which is rotatably attached to a distal end of the arm6; an end attachment cylinder9which extends and contracts so as to rotate the crushing device8; a pair of right and left idler links10as a second member rotatably coupled to a distal end portion of the end attachment cylinder9and the arm6, respectively; a bucket link11rotatably coupled to the pair of right and left idler links10and the crushing device8, respectively; and a pair of right and left connection pins12. The end attachment is not limited to the crushing device8, being permitted to be either of various kinds of buckets, a lifting magnet, a grapple and the like. The crushing device8is coupled to a part of the arm6which part is close to the distal end portion of the arm6through an arm side coupling pin13shown inFIG. 3, while being coupled to a distal-end-side end portion of the bucket link11through a link-side coupling pin14shown inFIG. 3.

The pair of right and left idler links10has a proximal end portion and a distal end portion opposite thereto, the distal end portion being coupled to the distal end portion of the end attachment cylinder9. The proximal end portion is connected to the arm6through the connection pin12so as to be able to make rotational movement in a rotational-movement direction around the connection pin12.FIG. 4shows a bidirectional arrow R which indicates a range of the rotational movement of the idler link10with respect to the arm6. Each of the pair of right and left connection pins12according to the present embodiment has an inner end portion rotatably supported by the arm6and an outer end portion connected to the idler link10so as to make rotational movement integrally with the idler link10, the outer end portion including a projecting end portion which projects outwardly beyond the arm6and the idler link10. The projecting end portion has a flange portion12b, which projects radially outwardly beyond other parts over the entire periphery.

The working machine according to the present embodiment further includes an angle detection device20which detects a rotational-movement angle that the idler link10makes with the arm6in the rotational-movement direction. As shown inFIG. 1, the angle detection device20includes a marker21, an angle sensor22, and a sensor mounting bracket23serving as a guard member for guarding the angle sensor22.

The marker21is provided in the outer end portion of one connection pin of the pair of connection pins12, the one connection pin being on the left side of the traveling direction. The marker21is, for example, a disc-shaped or column-shaped position marker, internally having a magnet. As shown inFIG. 7and others, the marker21is fixed to the projecting end portion of the connection pin12, for example, through a pair of screws21a, so as to make rotational movement integrally with the connection pin12.

The angle sensor22detects a relative rotational-movement position of the marker21with respect to the angle sensor22in the rotational-movement direction, namely, a rotational-movement angle. The angle sensor22is, for example, a magnetic non-contact rotary sensor which gets, through an integrated circuit, a direction of a magnetic field formed by the marker21and outputs the calculated angle as an analog signal. Misalignment and a distance between a main body of the angle sensor22and the marker21are required to be below the tolerance. The angle sensor22is disposed so as to be able to detect the rotational-movement angle of the idler link10relative to the arm6as described later, specifically, being attached to the sensor mounting bracket23restrained from relative rotational movement to the arm6as described later.

In the present embodiment, the sensor mounting bracket23is disposed so as to surround the projecting end portion, namely, the outer end portion of the connection pin12, the end portion projecting outwardly beyond a left side surface of the arm6as shown inFIG. 1andFIG. 3. The sensor mounting bracket23, alternatively, may be provided around the end portion of the connection pin12, the end portion projecting from a right side surface of the arm6. The sensor mounting bracket23has respective parts capable of making contact with an axial end surface12aand an outer circumference of the connection pin12, the contact allowing the sensor mounting bracket23to be prevented from coming off from the connection pin12.

The sensor mounting bracket23integrally has a main guard portion24and a guard-member-side engagement portion25.

The main guard portion24is disposed so as to surround the projecting end portion of the connection pin12all around the projecting end portion in the vicinity of the flange portion12bof the connection pin12. The main guard portion24has a cover portion26and a case portion27which are members separated from each other.

The cover portion26has a part allowing the angle sensor22to be fixed thereto and a part allowing the axial end surface12aof the connection pin12to make contact therewith. Specifically, the cover portion26, as also shown inFIG. 6andFIG. 8, has a disc portion26aand a bulbous portion26b. The disc portion26ais, for example, made of metal. The bulbous portion26bbulges radially outwardly beyond the outer circumference edge of the disc portion26a. The bulbous portion26bis formed of, for example, a steel plate bent to having opposite ends, which are welded to the disc portion26a.

The disc portion26ais provided with a plurality of, for example, four, through holes26c. The disc portion26ahas a surface opposed to the axial end surface12aof the connection pin12, namely, an inner side surface, in which a sensor housing recess26dis formed; the angle sensor22is housed in the sensor housing recess26d. The sensor housing recess26dis defined by a circular bottom surface and a cylindrical inner circumferential surface, the bottom surface being an inner opposite surface which is opposed to an end surface of the projecting end portion of the connection pin12.

The disc portion26aincludes a front periphery of the sensor housing recess26d, the front periphery forming a flange-portion housing recess. For example, the flange-portion housing recess has an internal diameter slightly larger than the external diameter of the flange portion12band can be formed to be stepped by cutting the disc portion26a. The flange-portion housing recess is defined by a circular bottom surface having a diameter slightly larger than an external diameter of the flange portion12band by a cylindrical inner circumferential surface continuous with the bottom surface, the bottom surface and the inner circumferential surface constituting a stepped flange contact portion26ecapable of making contact with the axial end surface12aand the cylindrical outer circumferential surface of the flange portion12b.

The angle sensor22, being embedded in the sensor housing recess26d, is fixed to the inner opposite surface of the cover portion26so as to be prevented from rotational movement relative to the cover portion26, for example, through sensor fixing screws22c. The cover portion26is formed with a positioning hole26f. The positioning hole26fis located, for example, between two through holes26cselected from the plurality of through holes26c.

As shown inFIG. 7andFIG. 8, the case portion27has an annular case body27a, a lug portion27bprotruding radially outwardly from the case body27a, and a bush30.

The guard-member-side engagement portion25is continuous with the lug portion27b. The guard-member-side engagement portion25is a portion for restraining the entire main guard portion24including the cover portion26from rotational movement relative to the arm6as the first member. The guard-member-side engagement portion25according to the present embodiment is a projection extending along the axial direction of the connection pin12from the lug portion27btoward the arm6. The projection is shaped to a round bar in the present embodiment. The shape of the projection is, however, not limited thereto but permitted to be also a square-shape or a plate-shape. The bulbous portion26bhas a shape to cover the lug portion27band the guard-member-side engagement portion25to guard them.

As shown inFIG. 7, the case portion27is formed with a plurality of (four inFIG. 7) screw holes27cwhich are opened in the outer surface (in the present embodiment, the left side surface) of the case portion27. Between two of the screw holes27cis formed a positioning pin27dwhich projects toward the cover portion26beyond the outer surface. The positioning pin27dhas a shape capable of being inserted into the positioning hole26fto thereby align the plurality of screw holes27cto the plurality of through holes26cin the cover portion26, respectively. In this state, respective fastening bolts26gare inserted into the through holes26cand screwed into the screw holes27c, thereby fastening the case portion27to the cover portion26through the fastening bolt26g. The thus mutually fastened case portion27(specifically, the bush30of the case portion27) and cover portion26(specifically, the stepped flange contact portion26eof the cover portion26) sandwich the flange portion12bof the connection pin12in the axial direction as shown inFIG. 8.

The angle detection device20further includes grease29as shown inFIG. 8. The grease29fills a space left between the marker21and the angle sensor22, which are disposed between the inner opposite surface of the cover portion26and the axial end surface12aof the connection pin12. The grease29may be additionally fed from the outside as necessary. For example, the connection pin12according to the present embodiment is formed with a grease feeding path12cextending along a center axis of the connection pin12as shown inFIG. 8, allowing the grease29to be fed through the grease feeding path12cto refill the space. The grease29provides, in addition to lubrication between the flange portion12band the case portion27, an effect of preventing dirt or iron filings from entering the space to ensure accurate angle detection and an effect of excluding an influence of water to improve waterproofness of the angle sensor22.

The first member according to the present embodiment includes, in addition to the arm6, a fixing member28as shown inFIG. 1. The fixing member28is fixed to the arm6so as to move integrally with the arm6, being formed with a rotation prevention recess28bas a first-member-side engagement portion. Specifically, in the outer periphery of the connection pin12in the outer surface (the left side surface in the embodiment) of the arm6, there is provided a pair of tapped blocks16in front and behind, to which the fixing member28is fixed through a plurality of bolts28a. The fixing member28has a shape circularly notched to avoid interference with the idler link10. In the edge of thus circularly notched part, the rotation prevention recess28bis formed.

The rotation prevention recess28bhas a shape that receives fitting of the guard-member-side engagement portion25in the rotation prevention recess28balong the axial direction of the connection pin12. The thus mutually engaged rotation prevention recess28band the guard-member-side engagement portion25restrain the main guard portion24including the case portion27and the cover portion26from rotational movement relative to the arm6in the rotational-movement direction.

The fixing member28has a cable insertion recess28cas shown inFIG. 7. The cable insertion recess28c, which is formed in the vicinity of the rotation prevention recess28bin the fixing member28, has a shape allowing a cable22aextending from the angle sensor22to pass through the cable insertion recess28c. The cable22athus passed through the cable insertion recess28ccan be covered with a cable guard bracket22battached to the outer surface (left side surface) of the arm6as shown inFIG. 4to be guarded.

As shown inFIG. 1,FIG. 3andFIG. 8, the bush30has a cylindrical shape making close contact with the inner surface of the case body27a. The bush30has an inner circumferential surface capable of slidable contact with the circumferentially entire outer circumferential surface of the projecting end portion of the connection pin12. This enables a load applied to the case portion27to be reliably transmitted to the connection pin12.

The angle detection device20has a mechanism which suppresses leakage of the grease29. The mechanism includes, for example, a washer31disposed adjacent to the bush30at a position closer to the angle sensor22than the bush30, a sealing member32made of rubber or the like and disposed adjacent to the bush30at a position closer to the arm6than the bush30, and a dust cover member33formed of a steel plate or the like.

Next will be described the action of the angle detection device20.

In the hydraulic excavator1, the end attachment cylinder9extends and contracts to bring the idler link10into rotational movement in the rotational-movement direction around the center axis of the connection pin12, during operation of the crushing device8, involving rotational movement of the connection pin12and the marker fixed thereto integrally with the idler link10in the rotational-movement direction. On the other hand, the angle sensor22attached to the sensor mounting bracket23restrained from rotational movement relative to the arm6senses a rotational-movement angle of the marker21relative to the angle sensor22, namely, an angle in the rotational-movement direction. The thus sensed rotational-movement angle, which corresponds to the rotational-movement angle of the idler link10relative to the arm6, enables the working posture of the crushing device8to be grasped. The grasp of the working posture enables, in combination with control of the angle at which the boom4is raised and lowered, contact prevention control, i.e., control for preventing the crushing device8and the driving room3aor the like from contact with each other, to be performed. This contact prevention control makes it possible to conduct working in a wider area while grasping the actual posture of the crushing device8, than conventional contact prevention control of suppressing movement of the crushing device8under the assumption that the crushing device8would always take a working posture at which the crushing device8is most likely to come into contact with the driving room3aor the like.

In the present embodiment, the marker21is fixed to the connection pin12which makes rotational movement integrally with the idler link10as the second member, while the angle sensor22is fixed to the sensor mounting bracket23restrained from rotational movement relative to the arm6as the first member, at a position where the angle sensor22is opposed to the marker21with a gap in the axial direction of the connection pin12; this eliminates necessity for using a conventional lever which makes rotational movement with a large radius to sense a rotational-movement angle and further eliminates necessity for leaving a space corresponding to the rotational area of the lever. This enables the sensor mounting bracket23to be disposed so as to surround the projecting end portion of the connection pin12all around it to thereby reliably guard the angle sensor22.

In the case where a load is applied to the sensor mounting bracket23in the axial direction of the connection pin12or in a direction vertical to the axial direction, the sensor mounting bracket23can make contact, in the axial direction, with the connection pin12having high strength, or can make radial contact with the outer circumferential surface of the connection pin12, to thereby transmitted the load to the connection pin12. This allows the connection pin12to effectively restrict the sensor mounting bracket23from deformation, thereby making it possible to ensure the guard of the angle sensor22and the marker21and to maintain the relative positional relationship therebetween. Moreover, the prevention of the sensor mounting bracket23as a guard member from coming off from the connection pin12allows a deviation in a positional relationship between the angle sensor22and the marker21to be prevented more reliably.

The sensor mounting bracket23according to the present embodiment, which is divided into the cover portion26and the case portion27to be capable of sandwiching the flange portion12bof the connection pin12therebetween in the axial direction of the connection pin12, can be more reliably restrained from relative displacement to the connection pin12. This makes it possible to effectively restrain the distance between the angle sensor22and the marker21from being changed. This allows a load applied to the cover portion26to be reliably transmitted to the flange portion12band allows a deviation in position of the cover portion26relative to the connection pin12to be reliably prevented, against the load, thus keeping the distance between the angle sensor22and the marker21be constant. Besides, the ability of the sensor mounting bracket23to be divided into the cover portion26and the case portion27facilitates set-up, replacement and the like of the angle sensor22and the marker21.

The guard-member-side engagement portion25projects from the lug portion27bof the case portion27to engage with the rotation prevention recess28bof the fixing member28fixed to the arm6, thereby restraining the entire main guard portion24including the case portion27from rotational movement relative to the arm6. This allows the angle sensor22to detect the rotational-movement angle of the idler link10more reliably.

In the present embodiment, the marker21, to which no wire has to be connected, is fixed to the connection pin12which makes rotational movement together with the idler link10relatively to the arm6, while the angle sensor22, to which a wire has to be connected, is fixed to the arm6through the sensor mounting bracket23as a guard member; this facilitates wiring and protects the wire from damage. Moreover, the cable22acan be covered with the cable guard bracket22bwhile passing through the cable insertion recess28cof the fixing member28, thereby being reliably guarded.

In the present embodiment, the angle sensor22can be guarded even in a distal end portion with which dirt or pieces of metal is likely to come into contact, and, in addition, the rotational-movement angle of the end attachment can be reliably sensed; this makes it possible to reliably prevent the end attachment from contact with, for example, a driving room, to thereby enable the end attachment to be safely used in a range as wide as possible. The working machine according to the present embodiment is, thus, capable of reliably guarding the angle sensor22without hindering rotation of the idler link10relative to the arm6.

The foregoing embodiment is inherently for illustrative purpose only and it is not to be construed as limiting the present invention, an application thereof and a range of the application. The present invention includes the following modes, for example.

Although the marker21, in the embodiment, is fixed to the projecting end portion of the connection pin12while the angle sensor22is fixed to the cover portion26of the sensor mounting bracket23as a guard member, it is also possible to connect the angle sensor22to the connection pin12so as to make rotational movement integrally with the connection pin12and to fix the marker21to a guard member, i.e., a member restrained from rotational movement relative to the first member is regulated.

Although the first-member-side engagement portion according to the embodiment is the rotation prevention recess28bwhich is a recessed part of the block-shaped fixing member28, the first-member-side engagement portion according to the present invention may be configured by, for example, a U-shaped member having an inner surface defining a space which receives insertion of the guard-member-side engagement portion.

Although the angle sensor22according to the embodiment is a sensor which detects an angle position of the marker21by use of a magnetic field, the angle sensor according to the present invention may be other non-contact sensor, for example, an infrared sensor or an optical sensor. Alternatively, it is also possible that the combination of the marker and the angle sensor is constituted by a potentiometer including a wiper and a resistance plate. In either case, the angle sensor and the marker only has to be arranged such that one of the angle sensor and the marker forms a first detection element fixed to a guard member and the other of the angle sensor and the marker forms a second detection element fixed to a connection pin.

Although, in the present embodiment, the first member includes the arm6and the second member includes the idler link10, it is also possible that the first member includes the idler link10and the second member includes the arm6. For example, it is possible that the rotation prevention recess which receives the guard-member-side engagement portion25extending from the cover portion26as in the embodiment is formed in the idler link10and the connection pin12is connected to the arm6so as to make rotational movement integrally with the arm6.

Although the working machine according to the embodiment is the hydraulic excavator1, the working machine provided by the present invention is not limited to a hydraulic excavator. The present invention is widely applicable to working machines such as construction machinery and civil engineering machinery, which include a first member, a second member joined to the first member so as to be capable of rotational movement around a connection pin, and an angle detection device which detects a rotational-movement angle of the second member relative to the first member.

As described above, provided is a working machine including a first member, a second member coupled to the first member so as to be capable of rotational movement in a specific rotational-movement direction with respect to the first member, and an angle detection device including an angle sensor which detects a rotational-movement angle that the second member makes with the first member in the rotational-movement direction, the working machine being capable of reliably guarding the angle sensor without hindering the rotational movement.

The working machine includes: a first member; a second member; a connection pin interposed between the first member and the second member, the connection pin interconnecting the first member and the second member so as to allow the second member to make rotational movement relative to the first member in a rotational-movement direction around the connection pin; and an angle detection device which detects a rotational-movement angle as an angle that the second member makes with the first member in the rotational-movement direction. The connection pin is connected to the second member so as to make rotational movement integrally with the second member while being connected to the first member so as to be able to make rotational movement relative to the first member in the rotational-movement direction, the connection pin having a projecting end portion which projects beyond the first member and the second member in an axial direction of the connection pin. The angle detection device includes a marker, an angle sensor which detects a relative angle position of the marker to the angle sensor in the rotational-movement direction, and a guard member which guards the angle sensor, the marker and the angle sensor being arranged so as to detect an angle that the connection pin makes with the first member in the rotational-movement direction. The guard member has a main guard portion, which covers the angle sensor so as to surround the projecting end portion of the connection pin all around the projecting end portion, and a guard-member-side engagement portion joined with the main guard portion. The main guard portion has an inner opposite surface which is an inner surface opposed to an end surface of the projecting end portion of the connection pin, one of the angle sensor and the marker being a first detection element disposed on the inner opposite surface, the other of the angle sensor and the marker being a second detection element disposed on the end surface of the projecting end portion so as to be opposed to the first detection element with a gap in the axial direction. The first member has a first-member-side engagement portion engageable with the guard-member-side engagement portion, and the first-member-side engagement portion and the guard-member-side engagement portion engage with each other to restrain the main guard portion from relative rotational movement to the first member in the rotational-movement direction. The guard member includes respective parts capable of making contact with an axial end surface and a circumferential surface of the projecting end portion of the connection pin, the contact causing the guard member to be restrained from relative displacement to the projecting end portion.

In the working machine, one of the marker and the angle sensor is disposed, as the second detection element, at the connection pin which rotates integrally with the second member, and the other of the angle sensor and the marker is disposed, as the first detection element, at a position opposed to the second detection element, thereby sensing a relative rotational-movement angle of the second member to the first member in the rotational-movement direction. This eliminates necessity for using a conventional lever to sense the rotational-movement angle and leaving a space corresponding to the rotation range of the lever. This allows the guard member to be disposed so as to surround the projecting end portion of the connection pin all around it to thereby guard the angle sensor reliably. Furthermore, the guard member is able to make contact, in the axial direction and radially, with the connection pin having high strength, when receiving a load in the axial direction of the connection pin or in a direction vertical to the axial direction, to thereby transmit the load to the connection pin. This effectively suppresses deformation of the guard member and thereby ensures the guard of the angle sensor and the marker and suppresses a change in a positional relationship therebetween. Moreover, the guard member, which makes contact with the connection pin to be restrained from relative displacement to the connection pin, can stabilize the positional relationship between the angle sensor and the marker.

It is preferable that the connection pin has a flange portion which projects radially outwardly beyond other parts of the connection pin and the main guard portion has a cover portion which includes a part capable of making contact with the inner opposite surface and the axial end surface of the connection pin and a case portion which sandwiches the flange portion in association with the cover portion in the axial direction of the connection pin. The main guard portion capable of being thus divided into the cover portion and the case portion reliably sandwiches the flange portion of the connection pin in the axial direction of the connection pin to reliably prevent the guard member from coming off from the connection pin and to effectively suppress a change in the distance between the angle sensor and the marker. Besides, the thus divisible main guard portion facilitates set-up, replacement and the like of the angle sensor and the marker.

It is preferable that the flange portion has a cylindrical outer circumferential surface and the cover portion includes a flange-portion housing recess defined by a circular bottom surface capable of making contact with the flange portion in the axial direction and by a cylindrical inner circumferential surface capable of making radial contact with the outer circumferential surface of the flange portion. The cover portion including the flange-portion housing recess can reliably transmit a load applied to the cover portion to the flange portion of the connection pin and reliably prevent the position of the cover portion relative to the connection pin from deviation.

Preferably, the angle detection device further includes grease which fills a space left between the angle sensor and the marker. The grease provides, in addition to lubrication between the flange portion of the connection pin and the case portion, an effect of preventing dirt or iron filings from entering the space to realize accurate angle detection and an effect of improving waterproofness of the angle sensor by excluding an effect of water.

It is preferable that the guard-member-side engagement portion includes a projection which projects from the case portion and the first-member-side engagement portion includes a rotation prevention recess provided in the first member, the rotation prevention recess receiving fitting of the projection in the rotation prevention recess to engage with the projection to thereby restrain the guard member from relative rotational movement to the first member in the rotational-movement direction. Receiving the fitting of the projection, the rotation prevention recess can reliably restrain the case portion from relative rotational movement to the first member to thus make it possible to accurately detect the rotational-movement angle of the second member relative to the first member.

It is preferable that the marker is fixed to the end surface of the projecting end portion so as to make rotational movement in the rotational-movement direction integrally with the connection pin to form the second detection element, while the angle sensor is fixed to the inner opposite surface so as to be prevented from rotational movement relative to the cover portion to form the first detection element. Thus fixing the marker requiring no wire, as the second detection element, to the connection pin which makes rotational movement integrally with the second member and fixing the angle sensor requiring a wire, as the first detection element, to the guard member restrained from relative rotational movement to the first member facilitates wiring of the angle sensor and prevents the wire from be easily damaged.

If including the rotation prevention recess, the first member preferably includes a cable insertion recess located in the vicinity of the rotation prevention recess to allow a cable extending from the angle sensor to pass through the cable insertion recess. The cable insertion recess enables a cable extending from the angle sensor provided in the cover portion to be reliably guarded.

Preferably, the working machine further includes, for example, a lower travelling body, an upper slewing body capable of being slewed above the lower travelling body, and a boom rotatably coupled to the upper slewing body, wherein the first member includes an arm rotatably coupled to a distal end of the boom, and the second member includes an idler link interposed between the arm and an end attachment, the end attachment being attached to the idler link. In the working machine, the angle sensor can be effectively guarded even in the vicinity of the end attachment with which dirt or pieces of metal easily come into contact, and the rotational-movement angle of the end attachment relative to the arm can be reliably sensed. This makes it possible, for example, to safely use the end attachment in a range as wide as possible while reliably preventing the end attachment from contact with a driving room of the upper slewing body or the like.

This application is based on Japanese Patent application No. 2016-085104 filed in Japan Patent Office on Apr. 21, 2016, the contents of which are hereby incorporated by reference.