Abstract: A compound magnetic material having high heat resistance is provided. A fabrication method of a compound magnetic material includes the step of preparing mixed powder including an organic resin and compound magnetic particles. The long-period heat resistance temperature of the organic resin is at least 200° C. The containing ratio of the organic resin to the compound magnetic particles exceeds 0 mass % and not more than 0.2 mass %. The compound magnetic particle includes a metal magnetic particles, and a coat layer containing metal oxide, directly bound to the surface of the metal magnetic particle. The fabrication method of a compound magnetic material includes the steps of forming a compact by introducing mixed powder into a die having a lubricant applied to its surface and conducting warm-compacting, and applying heat treatment to the compact.

Abstract: A hydraulic control circuit of a boom cylinder for a work machine, which, when controlling the supply and discharge of pressurized oil with respect to a boom cylinder, improves fuel efficiency, work efficiency in combined operations, and work efficiency and operationality in work of difficult boom operations, such as debris raking-up work and bumping work, etc. The hydraulic control circuit of a boom cylinder is provided with a first change valve for holding the boom control valve in the neutral position, a communication line for causing the head side oil chamber and the rod side oil chamber to communicate with each other, an opening and closing valve for opening and closing the communication line, and a pilot operation check valve that is changed to an unidirectional state where, although an oil flow from the head side oil chamber to the rod side oil chamber is permitted, a reverse flow is hindered, and a bi-directional state is permitted where the oil flows in both directions.

Abstract: An oil hydraulic circuit having a pilot operated control valve, for performing control of pressure oil supply to a hydraulic actuator and a pilot valve gear for outputting a pilot pressure to the control valve, that improves operationality when a fine operation is performed. The pilot valve gear has a first pressure controller that outputs a pilot pressure corresponding to the degree of operation of an operating lever and a second pressure controller that reduces the pilot pressure outputted from the first pressure controller based on a signal from an operating speed changeover switch and outputs the reduced pilot pressure to the control valve.

Abstract: A hydraulic control circuit of a boom cylinder for a work machine, which, when controlling the supply and discharge of pressurized oil with respect to a boom cylinder, improves fuel efficiency, work efficiency in combined operations, and work efficiency and operationality in work of difficult boom operations, such as debris raking-up work and bumping work, etc. The hydraulic control circuit of a boom cylinder is provided with a first change valve for holding the boom control valve in the neutral position, a communication line for causing the head side oil chamber and the rod side oil chamber to communicate with each other, an opening and closing valve for opening and closing the communication line, and a pilot operation check valve that is changed to an unidirectional state where, although an oil flow from the head side oil chamber to the rod side oil chamber is permitted, a reverse flow is hindered, and a bi-directional state is permitted where the oil flows in both directions.

Abstract: To perform boom-down operation by operating a boom cylinder (6) by an external load (W) while simultaneously operating an arm cylinder (26) or a bucket cylinder (27) in the state the bucket is off the ground, a first boom directional control valve (2) and a regeneration boom valve (13) are controlled to the neutral position and the open position respectively so that the hydraulic oil is regenerated from a line (9) located at the oil-returning side of the boom cylinder (6) through the regeneration boom valve (13) to a line (5) located at the oil-feeding side. Therefore, the volume of the hydraulic oil that can be supplied from the pressurized oil source (4) to the arm cylinder (26) or the bucket cylinder (27) via the second arm directional control valve (24) or the bucket directional control valve (25) is increased by the amount equivalent to the amount of the oil that is not supplied from the pressurized oil source (4) to the boom cylinder (6).

Abstract: The invention relates to a hydraulic control circuit for a boom cylinder in a work machine, which, when controlling supply and discharge of pressurized oil with respect to a boom cylinder, improves fuel efficiency, work efficiency in combined operations, and improves work efficiency and operationality in work of difficult boom operations such as debris raking-up work and bumping work, etc.

Abstract: A center bypass line (13) and a parallel line (14) are connected to a hydraulic pump (10). The center bypass line (13) is adapted to sequentially feed working fluid to a plurality of throttling selector valves (28),(15),(16),(29). The parallel line (14) is adapted to independently feed working fluid to the throttling selector valves (28),(15),(16),(29). Between the swing selector valve (15) and the arm-dedicated selector valve (16), a supply port of the arm-dedicated selector valve (16) is connected to a supply line (18) and another supply line (19), which branch off respectively from the center bypass line (13) and the parallel line (14), and a swing priority valve (21) is disposed in the supply line (19). Degree of opening-area of the swing priority valve (21) is pilot-controlled by a pressure reducing valve (31), which is designed such that its delivery pressure (P1) is reduced according to increase in remote control pressure that is used to operate the swing selector valve (15).

Abstract: In an oil hydraulic circuit comprising a pilot operated type control valve for performing control of pressure oil supply to a hydraulic actuator and a pilot valve gear for outputting a pilot pressure to this control valve, in order to improve operationality in a case where a fine operation is performed, the pilot valve gear (8) comprises a first pressure controller (9) for outputting a pilot pressure corresponding to the degree of operation with an operating lever (12) and a second pressure controller (10) for reducing the pilot pressure outputted from this first pressure control means based on a signal from an operating speed changeover switch 16 and outputting the reduced pilot pressure to the control valve 5.

Abstract: There is provided a flow dividing valve capable of instantaneously and continuously setting the ratio of flow rates for dividing the fluid in an inlet port into a plurality of outlet ports. The flow dividing valve comprises a flow rate control spool for dividing a flow rate of the fluid in said inlet port into a predetermined ratio of flow rates, and a flow rate ratio-setting spool for setting said ratio of flow rates to control said flow rate control spool, said flow rate ratio-setting spool being operated by a control signal from an external unit.

Abstract: A pilot-operated proportional control electromagnetic relief valve has a needle guide portion snugly fitted around the outer surface of a needle. The needle guide portion guides vertical movement of the needle, and is located at the center of a stopper so as to be coaxial with the stopper. A cylindrical inner wall portion of the stopper is so bored in the lower part of the adapter as to be coaxial with the needle guide portion. A cylindrical outer wall portion to be snugly fitted in the cylindrical inner positioning wall portion is so formed around the outer surface of a seat as to be coaxial with the seat portion. The outer circumferential surface of the needle is snugly fitted in the needle guide portion of the adapter so that the needle guide portion guides the axial travel of the needle, and the cylindrical inner wall portion of the adapter and the cylindrical outer wall portion of the seat are snugly fitted together.

Abstract: Cylinder drift resulting from internal leakage of a recycling circuit, which recycles oil returned from the arm cylinder of a hydraulic shovel to the hydraulic supplying end, is reduced by an hydraulic circuit which includes a recycle valve attached directly to a control valve. When working fluid is returned from a rod chamber of arm cylinder into the control valve, the recycle valve recycles a part of the working fluid through a recycle selector valve to the hydraulic supplying end. A pilot operated check valve is disposed in the oil channel that connects the rod chamber and recycle selector valve together. When extending arm cylinder of the hydraulic shovel, pilot pressure from control valve shifts a pilot selector valve in such a direction as to open pilot operated check valve. When control valve is at the neutral position, pilot selector valve is shifted back to the return position and closes pilot operated check valve so that return oil of arm cylinder is prevented from working on recycle selector valve.

Abstract: A fluid-operated valve includes a control spool, actuated by a source of pilot pressure to control a pilot flow of fluid from a loading pressure inlet port to a drain line. The pilot flow passes a throttle which reduces the fluid pressure acting in one direction, thereby performing stroke compensation of the actuation of a valve poppet. A differential pressure compensation valve is moved to partially block fluid flow to a rate control orifice group in response to a difference in pressure on the two sides of the rate control orifice group to control further the actuation of the valve poppet, whereby differential pressure is compensated.