Abstract: A ring gear that, together with a sun gear and a pinion gear that is disposed radially outward of the sun gear and meshes with the sun gear, forms a planetary gear unit, the ring gear includes: a body, internal teeth that are configured to mesh with the pinion gear and that are formed in at least a part of an inner peripheral surface of the body, and external teeth that have a lower hardness than the internal teeth and that are formed in at least a part of an outer peripheral surface of the body, wherein a surface nitrogen concentration in the internal teeth is higher than that in at least tooth surfaces of the external teeth.

Abstract: A ring gear that, together with a sun gear and a pinion gear that is disposed radially outward of the sun gear and meshes with the sun gear, forms a planetary gear unit, the ring gear includes: a body, internal teeth that are configured to mesh with the pinion gear and that are formed in at least a part of an inner peripheral surface of the body, and external teeth that have a lower hardness than the internal teeth and that are formed in at least a part of an outer peripheral surface of the body, wherein a surface nitrogen concentration in the internal teeth is higher than that in at least tooth surfaces of the external teeth.

Abstract: A hydraulic control device for an automatic transmission, the hydraulic control device including: a first layer having a first parting surface and a plurality of first grooves formed in the first parting surface; and a second layer that has a second parting surface and a plurality of second grooves formed in the second parting surface and facing the plurality of first grooves, and that is stacked on the first layer in a stacking direction with the second parting surface facing the first parting surface of the first layer, so that the plurality of first grooves and the plurality of second grooves form a plurality of first oil passages.

Abstract: A shaft has a hole that extends radially outward from an inner portion and opens in an outer peripheral surface. An opening of the hole has an outer shape which has a first curvature and a second curvature that is smaller than the first curvature when viewed in a radial direction of the shaft. The hole has, in the radial direction of the shaft, an outer hole portion that extends radially inward from an open end while maintaining the outer shape, a tubular inner hole portion that has a smaller hole diameter than the outer hole portion, and a diameter reduction portion in which the diameter is reduced from the outer hole portion towards the inner hole portion. The outer hole portion, the diameter reduction portion, and the inner hole portion are formed so as to be arranged in this order from the radially outer side.

Abstract: A valve part that includes a body and a spool housing, wherein the spool housing has: a main body that has a hole that slidably houses a spool, a port formed in a wall surface of the hole of the main body and configured to vary a state of communication between an inside and an outside of the main body in accordance with a position of the spool, a communication hole that extends from the port toward a radially outer side, a first projection in which the communication hole is formed and which is formed so as to project from an outside surface of the main body toward the radially outer side, and a first opening at which the communication hole opens at a distal end of the first projection.

Abstract: An oil film is formed between side faces of a pump gear and side faces of a pump casing to thereby reduce wear and reduce sliding resistance. To form the oil film predetermined numbers of recesses are provided in both side faces of a drive gear and in both side faces of a driven gear of the gear pump. The recesses serve to hold oil. The oil held in the recesses oozes out to between the opposing and contacting side faces to thereby form the oil films therebetween.

Abstract: An oil film is formed between side faces of a pump gear and side faces of a pump casing to thereby reduce wear and reduce sliding resistance. To form the oil film predetermined numbers of recesses are provided in both side faces of a drive gear and in both side faces of a driven gear of the gear pump. The recesses serve to hold oil. The oil held in the recesses oozes out to between the opposing and contacting side faces to thereby form the oil films therebetween.