Abstract: Provided is a wet friction plate which can realize a further reduction of drag torque while suppressing a decrease in the total area of frictional sheets. A clutch friction plate 200 is formed by providing frictional sheets 210 and oil grooves 220 on a flat annular metal core 201. On a side surface of the metal core 201 facing a clutch plate 103, a plurality of small frictional sheets 210 and oil grooves 220 are alternatingly arranged along the circumferential direction of the metal core 201. The frictional sheets 210 are disposed to form frictional-sheet groups 211 each including five frictional sheets 210 disposed successively. Outer and inner peripheral edges 213 and 214 of the frictional sheets 210 of each frictional-sheet group 211 form continuously changing arcuate contours 213a and 214a such that the distances L213 and L214 between the outer and inner peripheral edges 213 and 214 and the center of rotation O of the metal core 201 continuously change.

Abstract: A friction clutch device includes clutch plates which are retained through meshing engagement on the inner peripheral surface of an outer case, which is rotatably driven by an engine. Each clutch plate includes a flat, annular pressing element which is pressed against a clutch friction plate for frictional contact therewith. Engagement protrusions are formed on the outer peripheral surface of the pressing element. The engagement protrusions fit into recessed engagement grooves provided on the outer case and mesh with the outer case. Proiectinq portions which project toward the inner peripheral surface of the outer case are formed on the outer peripheral surface of the pressing element.

Abstract: Provided is a wet friction plate which can realize a further reduction of drag torque while suppressing a decrease in the total area of frictional sheets. A clutch friction plate 200 is formed by providing frictional sheets 210 and oil grooves 220 on a flat annular metal core 201. On a side surface of the metal core 201 facing a clutch plate 103, a plurality of small frictional sheets 210 and oil grooves 220 are alternatingly arranged along the circumferential direction of the metal core 201. The frictional sheets 210 are disposed to form frictional-sheet groups 211 each including five frictional sheets 210 disposed successively. Outer and inner peripheral edges 213 and 214 of the frictional sheets 210 of each frictional-sheet group 211 form continuously changing arcuate contours 213a and 214a such that the distances L213 and L214 between the outer and inner peripheral edges 213 and 214 and the center of rotation O of the metal core 201 continuously change.

Abstract: A plate element which can reduce drag torque, a friction clutch device including such a plate element, and a brake device including such a plate element are provided. A friction clutch device 100 includes clutch plates 103 which are retained, through meshing engagement, on the inner peripheral surface 101a of an outer case 101, which is rotatably driven by an engine. Each clutch plate 103 includes a flat, annular pressing element 103a which is pressed against a clutch friction plate 107 for frictional contact therewith. Engagement protrusions 103b are radially formed on the outer peripheral surface of the pressing element 103a. The engagement protrusions 103b are fit into recessed engagement grooves 101b provided on the outer case 101 and are meshed with the outer case 101. Projecting portions 103c which project toward the inner peripheral surface 101a of the outer case 101 are formed between adjacent engagement protrusions 103b on the outer peripheral surface of the pressing element 103a.

Abstract: A clutch which can realize further reduction of drag torque, a method for reducing the drag torque of the clutch, and a clutch friction plate used in the clutch are provided. In a clutch 100, clutch plates 103 and clutch friction plates 110, both of which are flat and annular, are alternatingly arranged, and clutch oil is supplied to spaces between the clutch plates 103 and the clutch friction plate 110. Each clutch friction plate 100 has small-groove groups 113 and fan-shaped grooves 114 formed on a surface of a metal core 111, which is flat and annular. Each small-groove group 113 includes a plurality of small grooves 113a which are parallel to one another and extend from the inner peripheral side to the outer peripheral side of the metal core 111. Each fan-shaped groove 114 is formed adjacent to the corresponding small-groove group 113 such that its width increases from the inner peripheral side toward the outer peripheral side of the metal core 111.

Abstract: A compression coil spring is used as a return spring which is stored in the housing of a clutch to urge the clutch piston in its returning direction. The effective number of turns of the compression coil spring is two or less, and the number of turns at an end-turn portion thereof is more than 0.45 and not more than 0.7. The compression coil spring is used in the compressed state throughout the operating stroke of the clutch piston. The number of turns at the end-turn portion is desirably within the range of 0.5 to 0.65, more desirably within the range of 0.55 to 0.62.