JP7291602B2 - power tools - Google Patents

Description

The present invention relates to a power tool with a clutch mechanism.

In a power tool such as an electric driver using an electric motor or an air drill using an air motor as a drive unit, a clutch mechanism is provided between the rotary drive shaft of the drive unit and the output shaft to which a machining tool such as a driver bit or a drill bit is attached. is provided to limit the maximum rotational torque applied from the drive unit to the output shaft (Patent Documents 1 and 2). For example, by providing an electric screwdriver with a clutch mechanism, it is possible to limit the rotational torque applied to the screw through the driver bit and prevent the screw from being damaged. In addition, when the screw is seated and the rotational torque suddenly increases, the clutch mechanism releases the driving connection, it is judged that the screw tightening is completed, and the motor is stopped or the number of screws tightened is counted. You can also make it

For example, in the clutch mechanism provided in the above-described electric driver, the clutch ball arranged on the output shaft side is arranged so as to engage with the clutch member on the rotary drive shaft side in the rotational direction, and the clutch ball is moved to the side of the clutch member by a spring. to keep the clutch ball engaged with the clutch member. While the clutch ball is engaged with the clutch member in the rotational direction, rotational torque is transmitted from the rotary drive shaft to the output shaft. direction to release the engagement between the clutch ball and the clutch member in the rotational direction, thereby releasing the transmission of rotational torque. Disengagement of the clutch mechanism is detected by detecting displacement of the clutch ball in the direction of the rotation axis by a sensor, and control such as stopping the driving of the motor is performed.

International Publication No. 2017/038846 JP 2017-42878 A

The clutch mechanism operates while the parts are in mechanical contact as described above, and when the clutch mechanism is released, the engaging members rub against each other with a strong force. Therefore, each part of the clutch mechanism wears out as it continues to operate. However, as the wear of the parts that make up the clutch mechanism progresses, the amount of displacement in the direction of the rotation axis when one engaging member rides over the other engaging member decreases, resulting in the maximum transmitted torque. may become smaller, or it may become impossible to detect that the clutch mechanism has been released. In order to check the state of wear of the clutch mechanism of the above-mentioned power tool, it is necessary to disassemble the power tool and directly check the parts constituting the clutch mechanism, but such work is very complicated. .

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a power tool in which the state of wear of a clutch mechanism can be monitored without disassembling the power tool.

That is, the present invention
a drive having a rotary drive shaft;
an output shaft having a tool mounting portion to which a machining tool is mounted and driven to rotate about a rotation axis as the driving portion is driven;
a first clutch engaging member drivingly connected to one of the rotary drive shaft and the output shaft and rotated about the rotational axis; a second clutch engaging member that rotates around the rotational axis, and a displacement member in contact with the second clutch engaging member, the first clutch engaging member and the second clutch engaging member are engaged in the rotational direction to transmit rotational torque from the rotary drive shaft to the output shaft, and when a load equal to or greater than a predetermined maximum rotational torque acts, the first clutch engagement member is operated by the second clutch engagement member. is displaced along with the displacement member in the direction of the rotational axis, disengaging the first clutch engaging member and the second clutch engaging member in the rotational direction, thereby canceling the transmission of the rotational torque. a clutch mechanism configured to
a position sensor for detecting the position of the displacement member in the direction of the rotation axis;
a computing unit configured to determine the wear state of the clutch mechanism based on the output value of the position sensor when the clutch mechanism stops transmitting the rotational torque;
to provide a power tool comprising:

In this power tool, the wear state of the clutch mechanism is determined based on the output value of the position sensor when the clutch mechanism stops transmitting rotational torque. Therefore, it is possible to monitor the state of wear of the clutch mechanism without disassembling the power tool. It is also possible to determine the necessity of maintenance and maintenance.

Further, the computing unit compares the output value of the position sensor when the clutch mechanism stops transmitting the rotational torque with a predetermined wear determination reference value, and the output value reaches the wear determination reference value. It is also possible to issue an error signal if this is not the case.

With such a configuration, it is possible to take measures such as stopping the driving of the driving section based on the error signal and displaying the error on the error display section.

Specifically, when the output value of the position sensor exceeds a predetermined release determination reference value and then returns to within the range of the release determination reference value, the clutch mechanism releases transmission of the rotational torque. and stopping the driving of the drive unit, and the output value of the position sensor during the period from when the output value of the position sensor exceeds the release determination reference value to when it returns to within the release determination reference value. Among them, the output value having the largest difference from the release determination reference value is stored, and the stored output is received when a signal instructing start of driving of the driving unit is received after the driving of the driving unit is stopped. value is compared with the wear determination reference value, and if the stored output value does not reach the wear determination reference value, the driving of the driving unit is not started, and the stored output When the value has reached the wear determination reference value, the driving of the drive unit can be started.

Further, the clutch mechanism may further include a clutch spring that biases the second clutch engaging member toward the first clutch engaging member in the direction of the rotation axis via the displacement member. can.

Further, the position sensor is a photoelectric sensor having a light projecting portion and a light receiving portion facing each other, and when the second clutch engaging member is displaced, a part of the displacement member is moved to the light projecting portion and the light receiving portion of the photoelectric sensor. and the light receiving section to partially block the light projected from the light projecting section toward the light receiving section, and the photoelectric sensor outputs according to the amount of light received by the light receiving section. Values can change.

Also, the clutch mechanism is arranged to face a first clutch plate that is drivingly connected to the rotary drive shaft and rotated about the rotation axis in the direction of the rotation axis with respect to the first clutch plate. and a second clutch plate drivingly connected to and rotating with the output shaft about the axis of rotation, the first clutch plate having a retaining recess in a surface facing the second clutch plate. and the second clutch plate has a holding hole penetrating in the direction of the rotation axis, the first clutch engaging member is held in the holding recess so as to rotate together with the first clutch plate, A second clutch engaging member may be held in the holding hole so as to be displaceable in the direction of the rotation axis and rotated together with the second clutch plate.

In this case, the first clutch engaging member may be a cylindrical engaging member extending in the radial direction of the rotation axis, and the second clutch engaging member may be a spherical engaging member.

An embodiment of a power tool according to the present invention will be described below with reference to the accompanying drawings.

1 is a cross-sectional view of an electric driver according to one embodiment of the present invention; FIG. FIG. 2 is a functional block diagram of the electric driver of FIG. 1; 2 is an enlarged view around the clutch mechanism of the electric driver of FIG. 1; FIG. FIG. 4 is an enlarged view of the periphery of the clutch mechanism, showing a state in which the tubular shaft portion of the output shaft is pushed; FIG. 4 is an exploded perspective view of parts constituting the clutch mechanism as viewed from above; FIG. 4 is an exploded perspective view of the parts that make up the clutch mechanism as seen from below; 4 is an enlarged view of the surroundings of the clutch mechanism, showing the clutch mechanism disengaging rotational torque; FIG. 4 is a flow chart showing the operation when determining the state of wear; 4 is an enlarged view of the periphery of the clutch mechanism when a small-diameter spherical engagement member is arranged in the inner holding hole; FIG. FIG. 10 is an enlarged view of the periphery of the clutch mechanism of FIG. 9, showing a state in which the clutch has released rotational torque transmission;

An electric driver (power tool) 1 according to one embodiment of the present invention includes, as shown in FIG. an output shaft 16 having a tool mounting portion 14 to which a tool (tool) is detachably mounted; a planetary gear mechanism 20 that decelerates and transmits rotation of a rotary drive shaft 18 of the electric motor 12; and a clutch mechanism 22 disposed between. Rotational torque of the electric motor 12 is transmitted to the output shaft 16 via the planetary gear mechanism 20 and the clutch mechanism 22 . Further provided in the tool housing 10 are a starting photoelectric sensor 24 for starting the driving of the electric motor 12 and a braking photoelectric sensor (position sensor) 26 for stopping the driving of the electric motor 12 . , the driving and stopping of the electric motor 12 are controlled based on the output values of these photoelectric sensors 24 and 26, as will be described later.

As shown in FIG. 2, the control circuit 28 arranged in the tool housing 10 stores a calculation unit 30, a motor control unit 32 for controlling the drive of the electric motor 12, control programs, control parameters, and the like. A memory 34 is provided for doing so. The starting photoelectric sensor 24 and the braking photoelectric sensor 26 are connected to a computing unit 30, and the computing unit 30 starts and stops driving the electric motor 12 based on the output values of the starting photoelectric sensor 24 and the braking photoelectric sensor 26. to control. The electric screwdriver 1 also includes an error display section 36 arranged at a position easily visible to the operator so as to display that an error has occurred due to the light emission of the LED. The start photoelectric sensor 24 has a light projecting portion (not shown) and a light receiving portion 24a facing each other. It is designed to output the output value according to Similarly, the photoelectric sensor 26 for braking has a light projecting portion (not shown) and a light receiving portion 26a facing each other. It is designed to output the output value according to In this embodiment, the starting photoelectric sensor 24 and the braking photoelectric sensor 26 are configured so that their output values increase as the amount of light received by the light receiving portions 24a and 26a decreases.

As shown in FIG. 3, the output shaft 16 includes a solid shaft portion 38 connected to the clutch mechanism 22 and a tubular shaft portion 40 arranged so as to slide on the outer peripheral surface 38a of the solid shaft portion 38. Consists of The solid shaft portion 38 and the cylindrical shaft portion 40 are fixed in the rotational direction. A spherical lock piece 44 is arranged in a lock piece holding hole 42 formed in the tubular shaft portion 40 , and a sleeve 46 is arranged on the outer peripheral surface 40 a of the tubular shaft portion 40 . When the sleeve 46 is displaced from the illustrated position to the tip side (lower side in the drawing), the locking element 44 can be displaced radially outward. When the driver bit is inserted into the insertion hole 48 of the cylindrical shaft portion 40 in this state and the sleeve 46 is returned to its original position, the driver bit is fixed to the output shaft 16 . Thus, the tool mounting portion 14 of the output shaft 16 is composed of the tubular shaft portion 40 , the locking piece 44 and the sleeve 46 . When the tool housing 10 is gripped with the driver bit attached to the tool attachment portion 14 and the driver bit is pressed against the screw, as shown in FIG. Pushed into 10. When the cylindrical shaft portion 40 is pushed in, the switch plate 52 arranged at the rear end portion 50 of the cylindrical shaft portion 40 also displaces the cylindrical shaft portion 40 together. Then, the switch plate 52 enters between the light projecting portion of the start photoelectric sensor 24 and the light receiving portion 24a to partially block the light projected from the light projecting portion toward the light receiving portion 24a. . As the amount of entry of the switch plate 52 increases, the amount of light received by the light receiving portion 24a decreases, and as a result, the output value of the start photoelectric sensor increases. The computing unit 30 starts driving the electric motor 12 when it receives an output value (a signal instructing start of driving) from the start photoelectric sensor 24 that is greater than a predetermined start threshold.

The clutch mechanism 22 includes a first clutch plate 54 drivingly connected to the rotary drive shaft 18 of the electric motor 12 via the planetary gear mechanism 20 and a first clutch plate 54 fixedly drivingly connected to the solid shaft portion 38 of the output shaft 16 . 2 clutch plate 56. The first clutch plate 54 and the second clutch plate 56 are rotatably arranged around the rotation axis R, respectively. Also, the second clutch plate 56 is arranged to face the first clutch plate 54 . As shown in FIGS. 5 and 6, the facing surface 55 of the first clutch plate 54 facing the second clutch plate 56 is formed with a radially extending holding groove (holding concave portion) 58 . A cylindrical engaging member (first clutch engaging member) 60 extending in the radial direction of the rotation axis R is rotatably held therein. The second clutch plate 56 has two inner holding holes 62 penetrating in the direction of the rotation axis R and two outer holding holes 64 penetrating in the direction of the rotation axis R at positions radially outside the inner holding holes 62 . is formed. The outer holding hole 64 has a larger diameter than the inner holding hole 62 . A small-diameter spherical engaging member (second clutch engaging member) 66 is held in the inner holding hole 62 , and a diameter larger than the small-diameter spherical engaging member 66 is held in the outer holding hole 64 . A large-diameter spherical engaging member (second clutch engaging member) 68 is held. However, only one engaging member is used, and when assembling the electric screwdriver 1, a small-diameter spherical engaging member 66 corresponding to the inner holding hole 62 and a large-diameter spherical engaging member 66 corresponding to the outer holding hole 64 are used. One of the spherical engagement members 68 is selected and only the selected engagement member is positioned within the corresponding retention hole. 1 and 3, a large-diameter spherical engaging member 68 is selectively arranged in the outer holding hole 64. As shown in FIG. As shown in FIG. 6 , the facing surface 55 of the first clutch plate 54 has an inner side that engages with the small-diameter spherical engaging member 66 when the small-diameter spherical engaging member 66 is arranged in the inner holding hole 62 . An engagement surface 55a and an outer engagement surface 55b that engages with the large-diameter spherical engagement member 68 when the large-diameter spherical engagement member 68 is disposed in the outer holding hole 64 are formed. The inner engagement surface 55a projects further toward the second clutch plate 56 than the outer engagement surface 55b by the difference in diameter between the small-diameter spherical engagement member 66 and the large-diameter spherical engagement member 68. . As a result, when the small-diameter spherical engaging member 66 is arranged in the inner holding hole 62 , the small-diameter spherical engaging member 66 protrudes from the second clutch plate 56 , and the large-diameter spherical engaging member 66 protrudes inside the outer holding hole 64 . The height at which the large-diameter spherical engaging member 68 protrudes from the second clutch plate 56 when the engaging member 68 is arranged is the same.

As shown in FIG. 3, the clutch mechanism 22 further includes a displacement member 70 that is displaceable in the direction of the rotation axis R with respect to the second clutch plate 56 and the solid shaft portion 38 of the output shaft 16 . The displacement member 70 includes a slide member 72 that slides on the outer peripheral surface 38a of the solid shaft portion 38 in the direction of the rotation axis R, a thrust receiving member 76 that is rotatable with respect to the slide member 72 by a bearing 74, and a sensor pin 80 arranged to be displaced in the direction of the rotation axis R together with the slide member 72 and the thrust receiving member 76 by being pressed against the thrust receiving member 76 by the spring 78 . A thrust receiving member 76 of the displacement member 70 is pressed toward the second clutch plate 56 via a transmission pin 84 by a clutch spring 82 . Since the large-diameter spherical engaging member 68 is in contact with the engaging surface 72 a of the sliding member 72 , the thrust receiving member 76 and the sliding member 72 are interposed between the first clutch plate 54 and the cylindrical engaging member 60 . is energized by

As shown in FIG. 4, when the cylindrical shaft portion 40 of the output shaft 16 is pushed in and the driving of the electric motor 12 is started, the rotary drive shaft 18 of the electric motor 12 is drivingly connected through the planetary gear mechanism 20 . The first clutch plate 54 and the cylindrical engagement member 60 are rotated around the rotation axis R. Then, the cylindrical engaging member 60 is engaged with the spherical engaging member 68 in the rotational direction, and rotational torque is transmitted to the second clutch plate 56 via the spherical engaging member 68 . Since the second clutch plate 56 is fixed to the solid shaft portion 38 of the output shaft 16 , rotational torque is transmitted to the output shaft 16 . The cylindrical engaging member 60 and the spherical engaging member 68 are engaged on a curved surface, and the spherical engaging member 68 moves from the cylindrical engaging member 60 in the direction of the rotation axis R in a state where rotational torque is transmitted. A force is received in a direction away from the cylindrical engaging member 60 . On the other hand, the spherical engagement member 68 is biased toward the first clutch plate 54 by the clutch spring 82 . Therefore, while the force received from the cylindrical engaging member 60 is within the range of the biasing force of the clutch spring 82, the spherical engaging member 68 is not displaced in the direction of the rotation axis R, and the cylindrical engaging member 60 and the spherical engaging member 68 are not displaced. The state in which the coupling member 68 is engaged in the rotational direction and the rotational torque is transmitted is maintained.

When a load equal to or greater than a predetermined maximum rotational torque acts on the clutch mechanism 22, the spherical engagement member 68 is pushed in the direction of the rotation axis R by the cylindrical engagement member 60, compressing the clutch spring 82 and moving together with the displacement member 70. It is displaced away from the first clutch plate 54 (downward in the figure). As shown in FIG. 7, when the spherical engaging member 68 is displaced to a state where it completely rides on the cylindrical engaging member 60, the cylindrical engaging member 60 and the spherical engaging member 68 are engaged in the rotational direction. is released, and transmission of rotational torque from the first clutch plate 54 to the second clutch plate 56 is also temporarily released. At this time, the sensor pin 80 of the displacement member 70 enters between the light projecting portion and the light receiving portion 26a of the photoelectric sensor 26 for braking. As a result, the sensor pin 80 partially blocks the light projected from the light projecting portion toward the light receiving portion 26a. In this embodiment, when the amount of light received by the light receiving section 26a decreases, the output value of the photoelectric sensor 26 for braking increases according to the decreased amount of light. Therefore, the calculation unit 30 can detect the position of the sensor pin 80 between the light projecting unit and the light receiving unit 26a based on the output value of the photoelectric sensor 26 for braking. The calculation unit 30 determines that the clutch mechanism 22 has released the transmission of the rotational torque and stops driving the electric motor 12 when the output value of the brake photoelectric sensor 26 exceeds a predetermined release determination reference value.

In the clutch mechanism 22, the cylindrical engaging member 60 and the spherical engaging member 68 rub against each other while receiving a relatively large force. Therefore, as the electric screwdriver 1 is repeatedly used, the cylindrical engaging member 60 and the spherical engaging member 68 are gradually worn out. In addition, rubbing movement may occur between the spherical engagement member 68 and the slide member 72 and between the slide member 72 and the thrust receiving member 76, and these members may also wear out. As the members constituting the clutch mechanism 22 wear in this manner, the spherical engagement member 68 rides on the cylindrical engagement member 60, and when the transmission of the rotational torque by the clutch mechanism 22 is released, the sensor pin 80 is pulled. The amount of light entering between the light projecting portion of the brake photoelectric sensor 26 and the light receiving portion 26a becomes smaller. In the electric driver 1, the calculation unit 30 monitors the output value of the photoelectric sensor 26 for braking, and based on the output value of the photoelectric sensor 26 for braking, the sensor pin 80 is detected between the light projecting unit and the light receiving unit 26a. The position is detected to determine the state of wear of the clutch mechanism 22 .

Determination of the state of wear in the electric driver 1 is specifically performed by the operation shown in the flowchart of FIG. When the electric screwdriver 1 is connected to the power supply, the calculation unit 30 is activated (S10). The calculation unit 30 monitors the output value of the start photoelectric sensor 24, and when the output value of the start photoelectric sensor 24 becomes greater than a predetermined start threshold value (S12), the driver bit attached to the tool attachment unit 14 is It is determined that it has been pushed in, and rotation of the electric motor 12 is started (S14). Next, the calculation unit 30 monitors the output value of the photoelectric sensor for brake 26, and when the output value of the photoelectric sensor for brake 26 becomes larger than a predetermined release determination reference value (S16), it becomes equal to or less than the release determination reference value. value (S17), the maximum output value with the largest difference from the release determination reference value among the output values during that period is stored in the memory 34 (S18), and the driving of the electric motor 12 is stopped ( S20). The computing unit 30 monitors the output value of the start photoelectric sensor 24 again, and when the output value of the start photoelectric sensor 24 changes to a value larger than the start threshold value (S22), the brake threshold value stored in the memory 34 is detected. The maximum output value of the photoelectric sensor 26 is compared with a predetermined wear determination reference value (S24). When the maximum output value rises to the wear determination reference value and is equal to or greater than the wear determination reference value, it is determined that the sensor pin 80 is sufficiently displaced and the clutch mechanism 22 is not so worn. The driving of the electric motor 12 is restarted (S14). On the other hand, if the maximum output value does not reach the wear determination reference value and is therefore smaller than the wear determination reference value, it is determined that the sensor pin 80 is not sufficiently displaced and the clutch mechanism 22 is worn. and an error signal is issued (S26). When the error signal is issued, the error display section 36 emits light to indicate that the wear of the clutch mechanism 22 has progressed beyond a certain level. Further, in this case, the driving of the electric motor 12 is not started. The starting photoelectric sensor 24 and the braking photoelectric sensor 26 may be designed so that their output values decrease when the amount of light received by the light receiving section 26a decreases. In this case, the driving of the electric motor 12 is started when the output value of the start photoelectric sensor 24 changes to a value smaller than the start threshold. Further, when the output value of the photoelectric sensor 26 for brake changes to a value smaller than the release determination reference value and then returns to a value equal to or higher than the release determination reference value, it is determined that the clutch mechanism 22 has been released. If the minimum output value, which has the largest difference from the release judgment reference value, does not fall below the wear judgment reference value and is greater than the wear judgment reference value, an error signal is issued.

As shown in FIGS. 9 and 10, instead of the large-diameter spherical engaging member 68, a small-diameter spherical engaging member 66 can be selectively placed in the inner holding hole 62 for assembly. As described above, the small-diameter spherical engaging member 66 arranged in the inner holding hole 62 engages with the inner engaging surface 55a on the facing surface 55 of the first clutch plate 54, which protrudes from the outer engaging surface 55b. match. 9 in which the clutch mechanism 22 is not released, the displacement member 70 of the clutch mechanism 22 is at the same position as in FIG. Therefore, the position of the sensor pin 80 with respect to the photoelectric sensor 26 for braking is also the same. On the other hand, in the state of FIG. 10 in which the clutch mechanism 22 is released, the displacement amount of the displacement member 70 is smaller than in the state of FIG. Therefore, the amount by which the sensor pin 80 enters between the light projecting portion and the light receiving portion 26a of the photoelectric sensor 26 for braking is smaller than in the case of FIG. Therefore, when the small-diameter spherical engagement member 66 is selectively arranged, the release determination reference value and the wear judgment reference value are larger than when the large-diameter spherical engagement member 68 is selectively arranged. is set to

When the displacement amount of the displacement member 70 when the clutch mechanism 22 is released is smaller, the clutch mechanism 22 is released with smaller rotational torque. Further, when the positions where the spherical engaging members 66 and 68 are engaged with the cylindrical engaging member 60 are located radially inward with respect to the rotational axis R, the clutch mechanism 22 is disengaged with a smaller rotational torque. It will be. Therefore, when the small-diameter spherical engaging member 66 is selectively arranged in the inner retaining hole 62 , a smaller diameter is obtained than when the large-diameter spherical engaging member 68 is selectively arranged in the outer retaining hole 64 . The rotational torque releases the clutch mechanism 22 . That is, depending on whether the large-diameter spherical engaging member 68 is arranged in the outer holding hole 64 or the small-diameter spherical engaging member 66 is arranged in the inner holding hole 62, the maximum rotational torque that can be transmitted by the clutch mechanism 22 can be increased. It is possible to change the

In the electric driver 1, the wear state of the clutch mechanism 22 is determined based on the output value of the photoelectric sensor 26 for braking when the clutch mechanism 22 stops transmitting the rotational torque. Based on this determination result, the amount of compression of the clutch spring 82 is increased to adjust the magnitude of the rotational torque when the clutch mechanism 22 is released, and the need for replacement or maintenance of the clutch mechanism 22 is determined. It becomes possible to It should be noted that the determination of the state of wear does not indicate only the two states of whether or not the wear has exceeded a certain amount, but indicates the degree of progress of wear based on the output value of the photoelectric sensor 26 for brakes in three or more stages or in an analog manner. may be shown steplessly.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments. For example, the cylindrical engaging member as the first clutch engaging member may be a member having a different shape such as a spherical shape instead of a cylindrical shape. It is good also as a protrusion which protruded from. Similarly, the spherical engagement member as the second clutch engagement member may also have another shape or be formed integrally with the displacement member. Further, the first clutch member is drivingly connected to the output shaft, the second clutch engaging member is drivingly connected to the rotary drive shaft of the electric motor, and the displacement member is displaced toward the rotary drive shaft when the clutch mechanism is released. It can also be configured to Furthermore, other types of sensors such as magnetic sensors and mechanical switches can be used as position sensors for detecting the position of the displacement member. Furthermore, in the above-described embodiments, the power tool according to the present invention is described as an example of an electric driver having an electric motor as a drive unit. Alternatively, other power tools such as an air tool having an air motor as a driving part can be used.

1 Electric screwdriver (power tool)
10 tool housing 12 electric motor (driving unit)
14 Tool mounting portion 16 Output shaft 18 Rotation drive shaft 20 Planetary gear mechanism 22 Clutch mechanism 24 Start photoelectric sensor 24a Light receiving portion 26 Brake photoelectric sensor (position sensor)
26a Light receiving portion 28 Control circuit 30 Calculation portion 32 Motor control portion 34 Memory 36 Error display portion 38 Solid shaft portion 38a Outer peripheral surface 40 Cylindrical shaft portion 40a Outer peripheral surface 42 Locker holding hole 44 Locker 46 Sleeve 48 Insertion hole 50 Rear End 52 Switch plate 54 First clutch plate 55 Opposing surface 55a Inner engagement surface 55b Outer engagement surface 56 Second clutch plate 58 Holding groove (holding recess)
60 Cylindrical engaging member (first clutch engaging member)
62 inner holding hole 64 outer holding hole 66 small diameter spherical engaging member (second clutch engaging member)
68 large-diameter spherical engagement member (second clutch engagement member)
70 displacement member 72 slide member 72a engagement surface 74 bearing 76 thrust receiving member 78 spring 80 sensor pin 82 clutch spring 84 transmission pin R rotation axis

Claims (7)

a drive having a rotary drive shaft;
an output shaft having a tool mounting portion to which a machining tool is mounted and driven to rotate about a rotation axis as the driving portion is driven;
a first clutch engaging member drivingly connected to one of the rotary drive shaft and the output shaft and rotated about the rotational axis; a second clutch engaging member that rotates around the rotational axis, and a displacement member in contact with the second clutch engaging member, the first clutch engaging member and the second clutch engaging member are engaged in the rotational direction to transmit rotational torque from the rotary drive shaft to the output shaft, and when a load equal to or greater than a predetermined maximum rotational torque acts, the first clutch engagement member is operated by the second clutch engagement member. is displaced along with the displacement member in the direction of the rotational axis, disengaging the first clutch engaging member and the second clutch engaging member in the rotational direction, thereby canceling the transmission of the rotational torque. a clutch mechanism configured to
a position sensor for detecting the position of the displacement member in the direction of the rotation axis;
a computing unit configured to determine the wear state of the clutch mechanism based on the output value of the position sensor when the clutch mechanism stops transmitting the rotational torque;
A power tool with The computing unit compares the output value of the position sensor when the clutch mechanism stops transmitting the rotational torque with a predetermined wear determination reference value, and the output value does not reach the wear determination reference value. 2. A power tool as claimed in claim 1, adapted to issue an error signal if a failure occurs. When the computing unit returns to within the range of the release determination reference value after the output value of the position sensor exceeds a predetermined release determination reference value, the clutch mechanism releases transmission of the rotational torque. and stopping the driving of the drive unit, and the output value of the position sensor during the period from when the output value of the position sensor exceeds the release determination reference value to when it returns to within the release determination reference value. Among them, the output value having the largest difference from the release determination reference value is stored, and the stored output is received when a signal instructing start of driving of the driving unit is received after the driving of the driving unit is stopped. value is compared with the wear determination reference value, and if the stored output value does not reach the wear determination reference value, the driving of the driving unit is not started, and the stored output 3. The power tool according to claim 2, wherein driving of the drive unit is started when the value reaches the wear criterion value. 4. The clutch mechanism of claim 1, further comprising a clutch spring that biases the second clutch engaging member toward the first clutch engaging member in the direction of the rotation axis through the displacement member. A power tool according to any one of the preceding claims. The position sensor is a photoelectric sensor having a light projecting portion and a light receiving portion facing each other, and when the second clutch engaging member is displaced, a part of the displacement member is the light projecting portion and the light receiving portion of the photoelectric sensor. and partially block the light projected from the light projecting portion toward the light receiving portion, and the photoelectric sensor outputs an output value according to the amount of light received by the light receiving portion. 5. A power tool according to any one of the preceding claims, adapted to change. The clutch mechanism is arranged to face the first clutch plate in the direction of the rotation axis, and a first clutch plate that is drivingly connected to the rotary drive shaft and rotated about the rotation axis. a second clutch plate drivingly connected to and rotating with the output shaft about the axis of rotation, the first clutch plate having a retaining recess in a surface facing the second clutch plate; The second clutch plate has a holding hole penetrating in the direction of the rotational axis, the first clutch engaging member is held in the holding recess so as to rotate together with the first clutch plate, and the second 6. A power tool according to any one of claims 1 to 5, wherein a clutch engagement member is held in said holding hole so as to be displaceable in the direction of said rotation axis and rotated together with said second clutch plate. . 7. The power tool of claim 6, wherein said first clutch engaging member is a cylindrical engaging member extending radially of said axis of rotation and said second clutch engaging member is a spherical engaging member.

Images