Abstract: The hydrokinetic torque converter between the prime mover and the transmission in the power train of a motor vehicle is designed to promote and/or otherwise regulate the flow of hydraulic fluid therethrough. The fluid is circulated between the friction linings on the laminations of the bypass clutch in the housing of the torque converter. In a first embodiment of the method, the flow of fluid in certain parts of the torque converter is opposed or interfered with in such a way that a larger quantity of fluid flows between the laminations of the bypass clutch. In a second embodiment, the resistance to fluid flow through the bypass clutch of the torque converter is reduced. It is also possible to resort to both solutions in one and the same torque converter.

Abstract: A system and method are shown for reducing material in a core which receives a plurality of segments. The invention may further include a plurality of segmented pieces that are arranged to provide a plurality of gaps that lie in a predetermined sweep angle and that may comprise a scoop for facilitating channeling fluid into a gap between adjacent material segments. Various manufacturing approaches are also disclosed for manufacturing and assembling a ring for use in a traditional transmission or clutch plate manufacturing and assembly system.

Abstract: A friction material has a plurality of connected sections and a plurality of oil localization slots. Each connected section is defined by adjacent oil localization slots in the friction material. The oil localization slot has opposing sides that define a reservoir which retains fluid in the oil localization slot when the friction material is formed into a desired shape on an end use product.

Abstract: A bridging clutch for a hydrodynamic torque converter which is designed with at least one friction area on a first converter component, which area can be shifted into working connection with at least one opposing friction area provided on a second converter component by means of an engaging movement or which can be separated from this second component by a disengaging movement in the direction opposite to the engaging movement. At least one of the two converter components acts as a friction lining carrier, which carries a friction lining in the friction area or in the opposing friction area, at least one opening being provided in the friction lining to allow the passage of transport medium, the inflow area of the opening being on the same radial side of the friction lining as its outflow area.

Abstract: A hydrokinetic torque converter with a built-in bypass clutch is provided with an arrangement which regulates the cooling of the clutch at a rate dependent upon the slip between the coaxial driving and driven parts of the clutch, and hence upon the quantity of generated friction heat. The cooling unit for the driving and/or driven part of the clutch can employ, for example, one or more pumps; a supply of a substance which changes its aggregate state from liquid to gaseous or from solid to flowable in response to heating, and vice versa in response to cooling; one or more porous washers in the path for the flow of hydraulic fluid between the customary plenum chambers provided in the housing of the torque converter to move a piston of the driven part of the clutch into and from frictional engagement with the housing; and/or a system of recesses, grooves, channels and/or other passages serving to convey fluid between the chambers at a rate which is higher or highest when the clutch operates with maximum slip.

Abstract: A clutch system for a transmission with one clutch (1) which comprises one disc carrier (3) and one servo mechanism (10) situated within the disc carrier (3) with dynamic pressure balance for actuating the clutch (1) and with a planet carrier of a planetary gear set (26) the spider plate (27) of which abuts in axial direction on a pressure balance space (15) of the dynamic pressure balance of the servo mechanism (10). It is proposed that the spider plate (27) be non-torsionally connected with the disc carrier (3) and be axially fixed via a locking element (31) on the disc carrier (3) in a manner such that the servo mechanism (10) is prestressed against the disc carrier (3) by the axial fixing of the spider plate (27).

Abstract: In the starting clutch, an electrical pump or an engine pump is omitted and a substitutive pump mechanism is obtained with a simple construction thereby to circulate lubricating oil within the starting clutch. There is provided a starting clutch in which lubricating oil supplied form a drive shaft side is circulated within the clutch and input side elements and output side elements are tightened by an axial load to transmit a power and wherein a non-electrically operated pump mechanism is provided within the starting clutch.

Abstract: A start-up element for an automatic transmission, comprising a start-up clutch arranged within a cover, which is flanged to a pump for the operating fluid, whereby a front pump support and gear seal are integrated in the cover.

Abstract: A friction clutch has a plurality of iron inner clutch plates and a plurality of iron outer clutch plates. Both the clutch plates have sliding surfaces which are friction-engaged each other. A thin carbon film in a diamond form, which functions as a solid lubricant, is formed on each of the sliding surfaces of the outer clutch plates by a known method such as the Chemical Vapor Deposition method. A known nitride treatment or quenching and tempering treatment is applied to the sliding surfaces of the inner clutch plates. A coupling device has a pilot clutch mechanism with the friction clutch and an electromagnetic actuator. As a result, the friction clutch is resistant to wear and the coupling device is excellent in durability.

Abstract: A clutch arrangement, especially for a motor vehicle, comprising a housing arrangement (12) which is filled or which can be filled with fluid, at least one first friction element (22) which can be jointly rotated with the housing arrangement (12) and at least one second friction organ (24) which can be jointly rotated with an output element (18) and which can be brought to rest against the at least one first friction element (22) in order to produce at least one interactive friction effect. At least one friction element (22, 24) is embodied in such a way that fluid can circulate around at least certain areas of the friction elements (22, 24).

Abstract: A system and method for supplying cooling fluid for frictional elements, for example multiple disc clutches and multiple disc brakes, in automatic transmissions. The cooling fluid flows through the multiple disc clutch or brake in a predefined manner radially inward or outward, whereby a defined flow through the clutch or brake packet is ensured through a defined pressure difference in the cooling fluid between the cooling fluid supply and the discharge of the cooling fluid. A preferred embodiment of device for supplying the cooling fluid is designed as a ring-shaped channel that partially or fully encloses the clutch or the brake.

Abstract: A hydrokinetic torque converter with a built-in bypass clutch is provided with an arrangement which regulates the cooling of the clutch at a rate dependent upon the slip between the coaxial driving and driven parts of the clutch, and hence upon the quantity of generated friction heat. The cooling unit for the driving and/or driven part of the clutch can employ, for example, one or more pumps; a supply of a substance which changes its aggregate state from liquid to gaseous or from solid to flowable in response to heating, and vice versa in response to cooling; one or more porous washers in the path for the flow of hydraulic fluid between the customary plenum chambers provided in the housing of the torque converter to move a piston of the driven part of the clutch into and from frictional engagement with the housing; and/or a system of recesses, grooves, channels and/or other passages serving to convey fluid between the chambers at a rate which is higher or highest when the clutch operates with maximum slip.

Abstract: A cone clutch is made with a plurality of generally straight grooves machined into the clutch faces of the cone clutch. This allows rapid and efficient evacuation of oil from the clutch faces as the clutch face moves into contact with a mating friction surface. By simplifying the evacuation path for the oil, the operation of the cone clutch is made more predictable and consistent.

Abstract: A hydrodynamic coupling device, especially a hydrodynamic torque converter, includes a housing which is rotatable about an axis of rotation, a turbine wheel mounted for rotation with respect to said housing, and a bridging clutch for transmitting torque between the housing and the turbine. The bridging clutch includes a first friction element which is essentially fixed against rotation with respect to the housing, and at least one second friction element which is essentially fixed against rotation with respect to the turbine, the friction elements having respective friction surfaces which can be brought into contact with each other. A first channel, provided in one of the friction surfaces, has first channel sections with radially closed inner ends and second channel sections with radially closed outer ends.

Abstract: A system and method are shown for reducing material in a core which receives a plurality of segments. The invention may further include a plurality of segmented pieces that are arranged to provide a plurality of gaps that lie in a predetermined sweep angle and that may comprise a scoop for facilitating channeling fluid into a gap between adjacent material segments. Various manufacturing approaches are also disclosed for manufacturing and assembling a ring for use in a traditional transmission or clutch plate manufacturing and assembly system.

Abstract: A clutch element for a unit is driven via a drive shaft, especially for a water pump. The clutch element comprises a temperature- and/or speed-sensitive clutch member which is rigidly connected with the drive shaft and which acts on a part of the unit to be driven depending on the temperature and/or rotational speed, with the clutch member being formed by a clutch disk whose surface forms at least one clutch surface for non-positive connection with a respective counter-surface which is formed by a surface of the part to be driven. At least one clutch surface comprises at least one drainage groove.

Abstract: A reaction plate for a transmission clutch pack includes first and second steel disks each having a contact surface facing the other of the two steel disks and having inner and outer peripheral edges. Each contact surface has grooves formed therein to carry cooling fluid from the inner peripheral edge to the outer peripheral edge to enhance cooling.

Abstract: A slipping friction clutch which has at least on a pair of wet-running friction areas, especially a slipping converter bridging clutch for the hydrodynamic torque of a motor vehicle automatic transmission. In the state under the action of pressure, the two friction areas seal off the radially outward lying high pressure chamber against the radially inward lying lower pressure chamber, whereby at least one of the friction areas has oil-conducting depressions whose ends spaced from one another are directly hydraulically connected with the one of the two pressure chambers and which are configured such that, with a slipping friction coupling, the friction area sliding peripherally exerts a drag action owing to which an oil through flow is induced as a function of the slippage rotational speed which cools the friction area.

Abstract: A wet-type friction clutch plate which keeps lubricant on a frictional slide face, stabilizes frictional torque transmission and suppresses shuddering noise. The wet-type friction clutch plate has the frictional slide face on which a grid of grooves is formed. The frictional slide face frictionally engages with an opposite clutch plate. At least one of the sectional shape and plan shape of each of the grooves is configured to provide the frictional slide face with a &mgr;-v characteristic such that &mgr; increases with an increase in v to prevent self-excited vibration during frictional engagement of the wet-type friction clutch plate with the opposite clutch plate, wherein &mgr; is a coefficient of friction on the frictional slide face and v is a relative rotational speed of the wet-type friction clutch plate relative to the opposite clutch plate.

Abstract: Overheating of various parts of a hydraulic torque converter between the engine and the transmission of the power train in a motor vehicle, wherein the torque converter employs a bypass clutch which generates heat when it is operated with slip, is counteracted by establishing one or more paths for the flow of hydraulic converter fluid from a first plenum chamber at one side of the axially movable piston of the bypass clutch to a second plenum chamber. A first portion of each such path is defined by at least one groove in a friction surface of at least one part of the bypass clutch, and a second portion of each such path is defined by one or more throttling orifices which offers or offer to the fluid flow a resistance several times that of the groove(s).

Abstract: A lock-up clutch for a hydrodynamic torque converter has at least one friction area on a first converter component, which area can be brought into working connection with at least one opposing friction area on a second converter component by an engaging movement of this converter component or which can be separated from this opposing friction area by a disengaging movement in the direction opposite that of the engaging movement. On at least one of the two converter components, a pump device acting in either the friction area or in the opposing friction area is present, which, as a result of its geometric shape, has the effect of building up a pressure gradient, by means of which a forced flow of hydraulic fluid through at least one predetermined section of the friction area and/or of the opposing friction area is produced.

Abstract: A wet-type segmented friction material has a tape-like friction material substrate which is passed through and pressed between a roller having a dent at a center and a flat roller. At the same time, the friction material substrate is heated from an inside and an outside of the rollers so as to carry out a heat press compression processing. Then, a processed friction material substrate has a predetermined cross-section. The processed friction material substrate is cut into segment pieces each having a segment shape by a rotary push cutter having a sharp cutting edge. A cut position of the segment piece is selected such that two straight lines at two lateral sides of the segment shape is located within an area of a compressed portion of the processed friction material substrate. That is, a stepped or sunken compressed portion is provided on both sides of the segment piece.

Abstract: A clutch arrangement, especially for a motor vehicle, comprising a housing arrangement (12) which is filled or which can be filled with fluid, at least one first friction element (22) which can be jointly rotated with the housing arrangement (12) and at least one second friction organ (24) which can be jointly rotated with an output element (18) and which can be brought to rest against the at least one first friction element (22) in order to produce at least one interactive friction effect. At least one friction element (22, 24) is embodied in such a way that fluid can circulate around at least certain areas of the friction elements (22, 24).

Abstract: An assembly of a one-way clutch and a bearing in which a thrust load due to a stator is absorbed and a dynamic pressure is generated is configured to prevent an abrupt temperature rise even when the pressure becomes high so that wear of sliding faces is prevented. The assembly of the one-way clutch and bearing is attached a stator of a torque converter. Dynamic pressure grooves and an escape groove serving as the bearings are formed in at least one of opposing faces of a flange portion formed on the stator and a pump member, or opposing faces of a bearing support which is placed on the side opposite to the flange portion of the stator, and a turbine member.

Abstract: A wet friction plate assembly which is capable of discharging the lubricant existing between the friction plate and the separation plate to restrict the accompanying rotation of the separation plate of a wet multiple-plate clutch etc. while it is disengaged.

Abstract: A wet friction plate of a hydraulic clutch or hydraulic brake for an automatic transmission having a reduced friction resistance in a non-engaged state. A plurality of friction materials disposed in an annular shape with a plurality of radial oil passages each provided between the adjacent friction materials are mounted at two radially inner and outer stages on a surface of a friction plate of a wet hydraulic clutch of an automatic transmission. The friction materials are brought into contact with an annular separator plate to transmit a torque. Inner peripheral edges of each of the friction materials are formed into a V-shape toward a radially outer side.

Abstract: A hydrodynamic coupling device, especially a hydrodynamic torque converter, includes a housing which is rotatable about an axis of rotation, a turbine wheel mounted for rotation with respect to said housing, and a bridging clutch for transmitting torque between the housing and the turbine. The bridging clutch includes a first friction element which is essentially fixed against rotation with respect to the housing, and at least one second friction element which is essentially fixed against rotation with respect to the turbine, the friction elements having respective friction surfaces which can be brought into contact with each other. A first channel, provided in one of the friction surfaces, has first channel sections with radially closed inner ends and second channel sections with radially closed outer ends.

Abstract: In a friction plate formed by fixing a plurality of friction material segments on a core plate, an edge portion opposed to a mating member of an end portion of the friction material segment extends from an inner periphery side to an outer periphery side and has a cross-sectional shape in an axial direction formed of a curved face.

Abstract: A plate (1) for a multiple-plate clutch has at least one friction surface (4) for transmitting a torque, in particular for a wet-running switchable multiple disk clutch. The plate (1) has at least one friction surface (4) which has grooves (7.1, 7.2, 10.1, 10.2) with an inside bordering edge (6) and an outside bordering edge (5), and at least one groove (7.1, 7.2, 10.1, 10.2) that runs from the inside bordering edge (6) to the outside bordering edge (5). The at least one groove (7.1, 7.2, 10.1, 10.2) has at least one bending point (8.1, 8.2, 9.1, 9.2, 11.1, 11.2, 12.1, 12.2) at which the at least one groove (7.1, 7.2, 10.1, 10.2) is bent at an angle (&agr;1, &agr;2, &agr;3, &agr;4).

Abstract: A wet multi-disk clutch comprises an input member (2) and an output member (3), and first disks (22) and second disks (21), which are connected to the input member (2) and the output member (3) respectively and can be pressed together by actuating means (24). In order to create a low-vibration tribosystem with a long life, the first disks (22) are composed of steel and their friction faces are linings (42) composed of carbon fibers embedded in a carbon matrix and having channels (43) leading from the inside outward, and the second disks (21) are composed of steel and their friction faces are provided with a nickel dispersion layer.

Abstract: There is provided a method for producing a friction plate, capable of improving the throughput of friction material and reducing the time and work required for adhering friction material segments to a core plate. The method produces a friction plate having oil grooves communicating between the internal periphery and the external periphery, by fixing friction material segments formed from a friction material to a core plate, and is featured by forming the oil grooves by plastic working of the friction material and fixation of the friction material segments with predetermined gaps therebetween to the core plate.

Abstract: An oil bath disc clutch structure having a series of floater discs having an annular contact face on each of its sides, and friction discs arranged axially alternately with said floater discs around an axis of rotation within a housing having an exteriorly mounted power transmission element, wherein the floater discs are rotated around the axis by a motor shaft, wherein the friction discs are axially slidably keyed to the housing and are provided on each side with a friction material contact face, wherein the contact faces of the floater and friction discs are brought into locking engagement by a centrifugal acting pressure mechanism in order to rotate the housing and element, and wherein large volume oil discharge slots are provided generally radially in the friction material for assisting in the rapid discharge of oil from between the contact faces of adjacent discs during the clutch engagement process brought on by engine acceleration.

Abstract: A friction material has a plurality of connected sections defined by a plurality of notches therebetween. Each notch has an apex which compensates for tear and compression of the friction material when the friction material is circumferentially placed on a flat surface of an annular core plate. In certain embodiments, a multiple linked loading device places the notched friction material adjacent a core plate to form a clutch plate.

Abstract: A multiplate lockup clutch for use in fluid, principally in a torque converter is provided with a multiplicity of friction plates. Each of the friction plates is provided on a friction surface thereof with at least one combined groove, preferably, a plurality of combined grooves. Each combined groove consists of a first groove and a second groove. The first groove extends from an inner circumferential edge to an outer circumferential edge of the friction plate and communicates an inner circumference and an outer circumference of the friction plate with each other. The second groove intersects the first groove and extends in a circumferential direction of the friction plate. As an alternative, a multiplate lockup clutch useful in fluid, primarily in a torque converter is provided with a multiplicity of friction plates, and each of the friction plates is shaped in a waveform as viewed in a circumferential direction thereof.

Abstract: A friction material has a plurality of connected sections defined by a plurality of notches therebetween. Each notch has an apex which compensates for tear and compression of the friction material when the friction material is circumferentially placed on a flat surface of an annular core plate. In certain embodiments, a multiple linked loading device places the notched friction material adjacent a core plate to form a clutch plate.

Abstract: An annular friction liner for a bridging clutch of a torque converter. The liner has a radially extending friction surface engageable with a reaction surface of the torque converter. The friction surface has a plurality of circumferentially spaced grooves extending from a radially inner edge of the friction surface to a radially outer edge thereof. Each groove extends along a serpentine path and has a series of contiguous groove sections which interconnect end-to-end at a substantial angle to one another. This groove path provides a mixing module for promoting turbulence.

Abstract: A slipping friction clutch which has at least on a pair of wet-running friction areas, especially a slipping converter bridging clutch for the hydrodynamic torque of a motor vehicle automatic transmission. In the state under the action of pressure, the two friction areas seal off the radially outward lying high pressure chamber against the radially inward lying lower pressure chamber, whereby at least one of the friction areas has oil-conducting depressions whose ends spaced from one another are directly hydraulically connected with the one of the two pressure chambers and which are configured such that, with a slipping friction coupling, the friction area sliding peripherally exerts a drag action owing to which an oil through flow is induced as a function of the slippage rotational speed which cools the friction area.

Abstract: Overheating of various parts of a hydraulic torque converter between the engine and the transmission of the power train in a motor vehicle, wherein the torque converter employs a bypass clutch which generates heat when it is operated with slip, is counteracted by establishing one or more paths for the flow of hydraulic converter fluid from a first plenum chamber at one side of the axially movable piston of the bypass clutch to a second plenum chamber. A first portion of each such path is defined by at least one groove in a friction surface of at least one part of the bypass clutch, and a second portion of each such path is defined by one or more throttling orifices which offers or offer to the fluid flow a resistance several times that of the groove(s).

Abstract: A wet friction plate of a hydraulic clutch or hydraulic brake for an automatic transmission having a reduced friction resistance in a non-engaged state. A plurality of friction materials disposed in an annular shape with a plurality of radial oil passages each provided between the adjacent friction materials are mounted at two radially inner and outer stages on a surface of a friction plate of a wet hydraulic clutch of an automatic transmission. The friction materials are brought into contact with an annular separator plate to transmit a torque. Inner peripheral edges of each of the friction materials are formed into a V-shape toward a radially outer side.

Abstract: A lock-up clutch for a hydrodynamic torque converter has at least one friction area on a first converter component, which area can be brought into working connection with at least one opposing friction area on a second converter component by an engaging movement of this converter component or which can be separated from this opposing friction area by a disengaging movement in the direction opposite that of the engaging movement. On at least one of the two converter components, a pump device acting in either the friction area or in the opposing friction area is present, which, as a result of its geometric shape, has the effect of building up a pressure gradient, by means of which a forced flow of hydraulic fluid through at least one predetermined section of the friction area and/or of the opposing friction area is produced.

Abstract: A wet type friction member includes a core plate, a plurality of segmental friction units and oil grooves. The segmental friction units are bonded on the core plate at intervals in a ring-shaped manner. The oil grooves are demarcated and formed by facing end surfaces of neighboring two pieces of the segmental friction units, and connect an inner peripheral side of the core plate with an outer peripheral side thereof. At least one of the facing end surfaces of the segmental friction units have a cut-off portion, which is cut off inwardly, at an inner peripheral side end of the facing end surfaces and/or an intermediate portion thereof. The oil grooves are provided with a major-width portion of a wide groove width by the cut-off portion at an inner peripheral side opening of the oil grooves and/or an intermediate portion thereof.

Abstract: A hydrodynamic coupling device is provided including a housing, a lock up clutch, a friction surface mechanism, a fluid duct and three connecting ducts. The lock up clutch has a clutch element arranged in the housing and may be pressed against the housing. The friction surface mechanism is arranged between the clutch element and the housing. The clutch element and the friction surface mechanism separate an interior of the hydrodynamic coupling device into a first fluid space and a second fluid space. The fluid duct means is in the friction surface mechanism and permits the working fluid to flow into and out of the first fluid space while preventing the working fluid from flowing out of the first fluid space into the second fluid space. The connecting ducts are in the fluid duct, with the first connecting duct is capable of permitting flow of the working fluid to the first fluid space, the second connecting duct is capable of permitting flow of the working fluid into and out of the second fluid space.

Abstract: An annular friction-clutch facing (30) for a multi-disk clutch (10) includes an inner edge (32) and an outer edge (34) defining a width (w) of the facing (30). The facing (30) further includes a first group of grooves (136, 236) formed on the facing (30) and having first cross-sectional area. Each groove of the first group (136, 236) has a first opening (38) at the outer edge (34) and a second opening (40) at the inner edge (32) remote from the first opening (38) and is adapted to direct lubricating agents across the width (w) over a substantial area of the facing (30). The facing (30) further includes a second group of grooves (42) formed on the facing (30) and having a second cross-sectional area smaller than the first cross-sectional area. The second group of grooves (42) includes first and second sets of grooves (44, 46, respectively). The grooves of the first set (44) are disposed in intersecting relationship with the grooves of the second set (46).

Abstract: In accordance with one aspect of the present invention, a material for an element of a power transmission-absorption assembly and the method of making such material is disclosed. The material has a pre-selected channel configuration to permit flow of a cooling medium thereacross or therethrough.

Abstract: There is provided a method for producing a friction plate, capable of improving the throughput of friction material and reducing the time and work required for adhering friction material segments to a core plate. The method produces a friction plate having oil grooves communicating between the internal periphery and the external periphery, by fixing friction material segments formed from a friction material to a core plate, and is featured by forming the oil grooves by plastic working of the friction material and fixation of the friction material segments with predetermined gaps therebetween to the core plate.

Abstract: A hydrokinetic torque converter is provided with a lockup clutch wherein the piston and other constituents of the lockup clutch are adequately cooled during each stage of operation of the torque converter and its clutch. The piston of the lockup clutch and/or the component which cooperates with the piston to transmit torque from the housing directly to the turbine of the torque converter is provided with a friction lining which establishes a portion of the path for the flow of fluid coolant between the fluid-filled compartments at opposite sides of the piston. The rate of fluid flow between the compartments is regulated by one or more adjustable valves which are carried by the housing of the torque converter and/or by the piston of the lockup clutch.

Abstract: A friction plate comprising a substantially annular core plate and a frictional material segment disposed on the core plate and including inner and outer peripheries and a concave cut-away portion provided at at least one of corner portions joining sides of the frictional material segment to at least one of the inner and outer peripheries.

Abstract: A segmented friction member for use in a clutch assembly. The friction member is circular and constructed from a paper-like friction layer. An oil groove extends completely through each friction member segment defining inner and outer segments joined by first and second bridges positioned adjacent the fluid inlet and fluid outlet, respectively.

Abstract: A hydrokinetic torque converter is provided with a lockup clutch wherein the piston and other constituents of the lockup clutch are adequately cooled during each stage of operation of the torque converter and its clutch. The piston of the lockup clutch and/or the component which cooperates with the piston to transmit torque from the housing directly to the turbine of the torque converter is provided with a friction lining which establishes a portion of the path for the flow of fluid coolant between the fluid-filled compartments at opposite sides of the piston. The rate of fluid flow between the compartments is regulated by one or more adjustable valves which are carried by the housing of the torque converter and/or by the piston of the lockup clutch.

Abstract: A wet type friction member includes a core plate, a plurality of segmental friction units and oil grooves. The segmental friction units are bonded on the core plate at intervals in a ring-shaped manner. The oil grooves are demarcated and formed by facing end surfaces of neighboring two pieces of the segmental friction units, and connect an inner peripheral side of the core plate with an outer peripheral side thereof. At least one of the facing end surfaces of the segmental friction units have a cut-off portion, which is cut off inwardly, at an inner peripheral side end of the facing end surfaces and/or an intermediate portion thereof. The oil grooves are provided with a major-width portion of a wide groove width by the cut-off portion at an inner peripheral side opening of the oil grooves and/or an intermediate portion thereof.