Abstract: A method of controlling a four-wheel drive vehicle permits reverse travel on a low-? road without engaging shock. In a four-wheel drive vehicle in which two-wheel drive and four-wheel drive can be changed over by means of a rotation transmission device having a two-way clutch and an electromagnetic coil for controlling engagement of the two-way clutch, the traveling direction of the vehicle is detected with rotation sensors for detecting the rotational direction of the front and rear wheels. If the traveling direction of the vehicle is different from the traveling direction of the range, the two-way clutch is engaged.

Abstract: The magnetic attraction force of an electromagnetic coil in an electromagnetic clutch is increased in a limited installation space, thereby improving reliability of operation. The dimensions of a field core housing the electromagnetic coil and a rotor are optimized to increase the magnetic attraction force. The thicknesses of cylindrical portions on the inner-diameter side of the field core and the rotor have larger thicknesses than those of cylindrical portions on its outer-diameter side so that the sectional areas of both cylindrical portions will be equal to each other. Also, a rotation transmission device provided with an electromagnetic clutch is proposed which can avoid deterioration of its sealing property and damage to its bearing and avoid cost increase.

Abstract: A rotation transmission device is provided in which the two-way clutch is prevented from engaging while the inner member is rotating not engaged with the outer member. The two-way roller clutch includes an outer member, a cam ring mounted in the outer member, a plurality of rollers each mounted between the cylindrical surface of the outer member and one of the cam surfaces on the cam ring, and a retainer for retaining the rollers. The device further comprises a rotor mounted between the solenoid and the retainer so as to be nonrotatable relative to the outer ring, an armature mounted so as to be nonrotatable relative to the retainer and axially movable, and a spring for axially biasing the armature away from the rotor, and an engaging plate mounted so as to be nonrotatable relative to the inner member and axially immovable.

Abstract: The magnetic attraction force of an electromagnetic coil in an electromagnetic clutch is increased in a limited installation space, thereby improving reliability of operation. The dimensions of a field core housing the electromagnetic coil and a rotor are optimized to increase the magnetic attraction force. The thicknesses of cylindrical portions on the inner-diameter side of the field core and the rotor have larger thicknesses than those of cylindrical portions on its outer-diameter side so that the sectional areas of both cylindrical portions will be equal to each other. Also, a rotation transmission device provided with an electromagnetic clutch is proposed which can avoid deterioration of its sealing property and damage to its bearing and avoid cost increase.

Abstract: In the friction agitation joining method according to the present invention, two plate-shaped joining members different in thickness, or a first joining member (1) and a second joining member (2), are butted against each other with a level difference formed at upper surface sides thereof. A rotating probe (42) of the joining tool (40) is inserted into the butted portion (3) of said first and second joining members (1,2) from the upper surface sides thereof. Joining-direction front sides of the first joining member (1) and the second joining member (2) with respect to the probe inserted position is pressed by a first front pressing roller (11) and a second front pressing roller (11), respectively, from the upper surface sides thereof.

Abstract: A friction agitation joining tool (10A, 10B) includes a rotor (11) having an end portion to be pressed onto at least one of surfaces of joining members (11a, 1b) and a probe (13) to be inserted into a joining portion (3) of the joining-members (1a, 1b), wherein the probe (13) has a diameter smaller than a diameter of the rotor (11). An end face (12) of the end portion of the rotor (11) is formed into a concave surface dented from a periphery of the end face (12) toward a rotational center of the end face (12). The probe (13) is protruded from the rotational center of the end face (12). The end face (12) is provided with a spiral groove (15) or an annular groove (16) surrounding the probe (13). By performing the joining operation with the joining tool (10A, 10B), a joined member with a good joint can be obtained.

Abstract: A method of controlling a four-wheel drive vehicle is provided which permits reverse travel on a low-&mgr; road without engaging shock. In a four-wheel drive vehicle in which two wheel drive and four-wheel drive can be changed over by means of a rotation transmission device having a two-way clutch and an electromagnetic coil for controlling engagement of the two-way clutch, the traveling direction of the vehicle is detected with rotation sensors for detecting the rotational direction of the front and rear wheels, and if the traveling direction of the vehicle is different from the traveling direction of the range, the two-way clutch is engaged.

Abstract: A bearing provided with a rotation sensor comprises an outer ring, an inner ring and rolling elements, and a magnetic ring is engaged with the inner diametral surface of the outer ring. Thus, a highly reliable bearing provided with a rotation sensor exerting no bad influence on a magnetic sensor can be provided.

Abstract: A friction stir welding method conducts contact welding on two welding target members having different high temperature deformation resistances by using a welding tool having a rotatable welding head, contacting the two welding target members having different high temperature deformation resistances against each other so as to generate a difference in height between the two welding target members on a surface side in a thickness direction, arranging the rotating head in a state in which the head is embedded into a contact section of the two welding target members or a neighborhood of the contact section from the surface side, and relatively moving the welding head to the two welding target members along the contact section in this state, is provided.

Abstract: To provide a compact bearing assembly equipped with a rotation sensor capable of detecting not only pulse signals for detecting the number of revolution, but also a home position signal, the bearing assembly equipped with the rotation sensor includes a rotatable member (2) and a non-rotatable member (3) with rolling elements (4) interposed between the rotatable and non-rotatable members (2) and (3) to permit the rotatable member (2) to be rotatable relative to the non-rotatable member (3). The rotatable member (2) is provided with a magnetic encoder (7) and the non-rotatable member (3) is provided with magnetic sensors (8A) to (8C). The magnetic encoder (7) includes first and second to-be-detected elements (7A) and (7B) each having a plurality of equally spaced, opposite magnetic poles defined therein so as to alternate with each other in a direction circumferentially thereof.

Abstract: The magnetic attraction force of an electromagnetic coil in an electromagnetic clutch is increased in a limited installation space, thereby improving reliability of operation. The dimensions of a field core housing the electromagnetic coil is coil and a rotor are optimized to increase the magnetic attraction force. The thicknesses of cylindrical portions on the inner-diameter side of the field core and the rotor have larger thicknesses than that of cylindrical portions on its outer-diameter side so that the sectional areas of both cylindrical portions will be equal to each other. Also, a rotation transmission device provided with an electromagnetic clutch is proposed which can prevent deterioration of sealing property and damage to the bearing and avoid cost increase.

Abstract: A bearing provided with a rotation sensor comprises an outer ring, an inner ring and rolling elements, and a magnetic ring is engaged with the inner diametral surface of the outer ring. Thus, a highly reliable bearing provided with a rotation sensor exerting no bad influence on a magnetic sensor can be provided.