A wet-type multi plate clutch having a obtaining hydraulic chamber, which is capable of increasing a fuel consumption efficiency by reducing a load of an oil pump for clutch oil for engaging the clutch and which realizes a simplified structure by eliminating a necessity of a canceller chamber. A disk spring 46 is, at its outer peripheral part, is supported by a clutch drum 10 and contacts, at its inner peripheral part, with a spring presser part 12-1 of the piston 12. The disk spring 46 faces, at the side opposite the piston 12, with clutch pack 20. A forward movement of the piston 12 by operating pressure in a hydraulic chamber is transmitted to the clutch pack 20 via the disk spring 46, resulting in an engaged condition of the clutch pack 20. A driving force of the piston 12 by the hydraulic oil pressure is boosted under a lever ratio a/b of the disk spring 46 and is transmitted to the clutch pack 20. The disk spring 46 to the spring presser part 12-1 without obstructing the slide movement of the piston 12 of obtaining an increased radial length of the spring, resulting in an increased return force of the spring 46 for a positive reverse movement of the piston 12 for obtaining a disengaged condition of the clutch.

Particular embodiments disclosed herein provide a joint of a tray arm assembly, comprising a joint body, a shaft configured to rotate relative to the joint body about a longitudinal axis of the shaft, and a slip clutch assembly, comprising a clutch stack, including a plurality of first clutch plates keyed to the shaft and a plurality of second clutch plates keyed to the joint body. The clutch stack further comprises a spring configured to selectively exert a force on the clutch stack, wherein the force compresses the clutch stack causing a friction between the plurality of first clutch plates and the plurality of second clutch plates with respect to a rotation of the shaft relative to the joint body.

The tooth part includes: a tubular portion having an inner tooth portion formed on an inner peripheral surface and an outer tooth portion formed on an outer peripheral surface; a plurality of inner peripheral wall portions that each extend in an axial direction of the tubular portion and form a tooth tip portion of the inner tooth portion and a tooth bottom portion of the outer tooth portion; a plurality of outer peripheral wall portions that each extend in the axial direction and form a tooth bottom portion of the inner tooth portion and a tooth tip portion of the outer tooth portion; and an annular rib that is joined to the outer peripheral wall portions and that extends in an annular shape on an open end side with respect to the inner peripheral wall portions in the axial direction and radially outward from the inner peripheral wall portions, at an open end of the tubular portion.

The tooth part includes: a tubular portion having an inner tooth portion formed on an inner peripheral surface and an outer tooth portion formed on an outer peripheral surface; a plurality of inner peripheral wall portions that each extend in an axial direction of the tubular portion and form a tooth tip portion of the inner tooth portion and a tooth bottom portion of the outer tooth portion; a plurality of outer peripheral wall portions that each extend in the axial direction and form a tooth bottom portion of the inner tooth portion and a tooth tip portion of the outer tooth portion; and an annular rib that is joined to the outer peripheral wall portions and that extends in an annular shape on an open end side with respect to the inner peripheral wall portions in the axial direction and radially outward from the inner peripheral wall portions, at an open end of the tubular portion.

A method of making a wet friction material includes providing an outer layer on a base layer to form the wet friction material. The base layer includes a first proportion of fiber material and a first proportion of filler material. The outer layer includes a second proportion of fiber material and a second proportion of filler material. The second fiber proportion is less than the first fiber proportion and the second filler proportion is greater than the first filler proportion. The method further includes forming a modified outer layer by burning off the fiber material of the outer layer.

A method of making a wet friction material includes providing an outer layer on a base layer to form the wet friction material. The base layer includes a first proportion of fiber material and a first proportion of filler material. The outer layer includes a second proportion of fiber material and a second proportion of filler material. The second fiber proportion is less than the first fiber proportion and the second filler proportion is greater than the first filler proportion. The method further includes forming a modified outer layer by burning off the fiber material of the outer layer.

A phenol resin for a wet friction material of the invention contains a resol-type phenol resin having, in one molecule, a structural unit A which is derived from a phenol compound having one phenolic hydroxyl group and a structural unit B which is derived from a polyfunctional phenol compound having two phenolic hydroxyl groups.

An object of the present invention is to extend a retention time of clutch oil and enable to efficiently cool clutch plates. A clutch hub (42) which is engaged with the clutch plates in an outer circumference is a press-molding article made from one steel sheet. In its inner circumferential surface, plural oil grooves (74-4) for cooling the clutch plates, which are extended to a shat direction and have a space in a circumferential direction. Each of dams (76) as a press-molding portion extending to radial inward is formed at an end portion of each of the oil groove (74-4). The press-molding of the dams (76) is performed by pressing a front surface side of the clutch hub (42) by punches (82) and disposing inner pressing tools (84) at a back surface side. The dams (76) comprise an upright front surface (76-1) and a back surface (76-2), which are a molding surface molded by using the molding tools. The back surface (76-2) has a steep shape as long as attaching and detaching inner pressing tools (84) is not prevented. Thereby, the retention time of the clutch oil in the oil grooves (74-4) can be extended and cooling efficiency of the clutch plates can be enhanced.

An object of the present invention is to extend a retention time of clutch oil and enable to efficiently cool clutch plates. A clutch hub (42) which is engaged with the clutch plates in an outer circumference is a press-molding article made from one steel sheet. In its inner circumferential surface, plural oil grooves (74-4) for cooling the clutch plates, which are extended to a shat direction and have a space in a circumferential direction. Each of dams (76) as a press-molding portion extending to radial inward is formed at an end portion of each of the oil groove (74-4). The press-molding of the dams (76) is performed by pressing a front surface side of the clutch hub (42) by punches (82) and disposing inner pressing tools (84) at a back surface side. The dams (76) comprise an upright front surface (76-1) and a back surface (76-2), which are a molding surface molded by using the molding tools. The back surface (76-2) has a steep shape as long as attaching and detaching inner pressing tools (84) is not prevented. Thereby, the retention time of the clutch oil in the oil grooves (74-4) can be extended and cooling efficiency of the clutch plates can be enhanced.

Methods and apparatus related to electrolaminate clutches and transmissions are disclosed. A device can include: an input shaft that can be coupled to an electrolaminate sheet; an output shaft that can be coupled rigidly to a spring positioned over the input shaft, where the spring includes a tab that fits a groove of a spring capture ring that can be positioned over the input shaft; and a drum connected to an electrical ground between the electrolaminate sheet and the spring capture ring, where the drum can be coupled rigidly to the spring capture ring. Then, when a voltage is applied to the electrolaminate sheet, the electrolaminate sheet can clamp to the drum and impart rotation of the input shaft to the drum. The imparted rotation can cause the spring capture ring and the spring to rotate and clamp down on the input shaft, imparting rotation to the output shaft.