Clutch mechanism and power tool

A clutch mechanism configured to be disposed between an input shaft and an output shaft to limit a rotational torque transmitted from the input shaft to the output shaft, the clutch mechanism comprising:

• a first clutch plate configured to be drivably connected to one of the input shaft and the output shaft, the first clutch plate being disposed to be rotatable about a rotation axis and having an engaging projection projecting in a direction of the rotation axis;
• a second clutch plate configured to be drivably connected to an other of the input shaft and the output shaft, the second clutch plate being disposed to face the first clutch plate in the direction of the rotation axis and to be rotatable about the rotation axis, the second clutch plate having a small-diameter retaining hole extending therethrough in the direction of the rotation axis and a large-diameter retaining hole extending therethrough in the direction of the rotation axis, the large-diameter retaining hole having a diameter larger than that of the small-diameter retaining hole;
• an engagement member selected from a small-diameter engagement member corresponding to the small-diameter retaining hole and a large-diameter engagement member corresponding to the large-diameter retaining hole, the large-diameter engagement member having a diameter larger than that of the small-diameter engagement member, the engagement member being disposed in a corresponding one of the small-diameter retaining hole and the large-diameter retaining hole and retained in the corresponding retaining hole so as to be displaceable in the direction of the rotation axis;
• and
• a slide member abutting against the engagement member in the direction of the rotation axis to press the engagement member toward the first clutch plate;
• wherein the clutch mechanism is configured to transmit a rotational torque between the first clutch plate and the second clutch plate through engagement of the engagement member with the engagement projection in a rotational direction, and wherein when a load equal to or greater than a predetermined maximum rotational torque acts, the engagement projection causes the engagement member to be displaced in the direction of the rotation axis, together with the slide member, so as to cancel the engagement between the engagement projection and the engagement member in the rotational direction, thereby canceling transmission of the rotational torque;
• and
• wherein the maximum rotational torque is greater when the large-diameter engagement member is selectively disposed in the large-diameter retaining hole than when the small-diameter engagement member is selectively disposed in the small-diameter retaining hole.