Abstract: It is an object of the present invention to provide a filter for trapping foreign matter in which a filtration element can trap foreign matter that is admixed to a fluid present inside the filter with good reliability and a comparatively high trapping ratio. Hydraulic oil that has flown from an opening portion into a guide space of a first flow path guide is guided downward by the first flow path guide and directed toward a second flow path guide. As a result, the oil passes through a very narrow gap, that is, a gap with a cross sectional area of the flow path narrowed so as to increase the flow velocity of the hydraulic oil, a rising flow of the hydraulic oil is formed, and this flow is spouted up by the second flow path guide and guided by the first flow path guide toward a filter element. Foreign matter admixed to the hydraulic oil rises with good intensity together with the hydraulic oil and is moved by the hydraulic oil toward the filter element.

Abstract: A plurality of Hall ICs 34A, 34B are disposed around a magnetic rod 32 that is movable along a central axis. The Hall ICs are disposed in different positions in terms of both a straight line distance coordinate in the direction of the central axis and a rotational angle coordinate around the central axis. The amount of displacement of the magnetic rod 32 is calculated based on the average of output signals from the Hall ICs. Errors in the output signals due to a shift and tilt of the magnetic rod are detected and calibration of the measurement method is carried out.

Abstract: A disclosed device eliminates an error in a displacement amount measured value caused by changes over time in a characteristic of a displacement sensor, and can always maintain high accuracy of measurement. When a hydraulic valve, to which the displacement sensor is mounted, is positioned at predetermined positions, output signals from the displacement sensor are acquired as sample values. On the basis of the acquired sample values, a trend of changes over time in the characteristic of the displacement sensor is computed. Settings of a conversion table, which is used for displacement amount computation, are corrected in a direction along the computed trend of changes.

Abstract: In a hydraulic machine, hydraulic pump failure is detected and the pump lifespan is estimated before the pump failure occurs. The discharge pressure 122, oil temperature 126, and drain filter differential pressure 120 are measured, a correlative relationship 128 between the filter differential pressure and the discharge pressure is determined, and a representative filter differential pressure 130 is calculated from this correlative relationship. Using an oil temperature-differential pressure correlation function, the representative differential pressure value 130 is corrected so that the variable component 132 caused by the oil temperature 126 is eliminated therefrom. The long-term trend and the short-term trend of the increase over time of the corrected differential pressure is calculated. A pump failure is predicted or the pump lifespan is estimated based on the degree of deviation between the long-term trend and the short-term trend.

Abstract: In a displacement sensor (10), a shaft (24) of a movable member (14) comprises a tubular part (26) having an opening (26c) at one end. A rod-form permanent is inserted into the tubular part (26) through the opening (26c) . A spacer (32) is fitted over a narrow portion of the rod-form magnet (28). The thickest portion of the magnet (28) and the spacer (32) contact the side wall of the tubular part (26) tightly, so that the magnet (28) is disposed coaxially with the tubular part (26). A stopper (26d) is formed on the opening (26c) of the tubular part (26), so that the magnet (28) does not move axially. Therefore, the magnet (28) is mounted in a prescribed position in a movable member (14) with a high degree of accuracy.

Abstract: A disclosed device eliminates an error in a displacement amount measured value caused by changes over time in a characteristic of a displacement sensor, and can always maintain high accuracy of measurement. When a hydraulic valve, to which the displacement sensor is mounted, is positioned at predetermined positions, output signals from the displacement sensor are acquired as sample values. On the basis of the acquired sample values, a trend of changes over time in the characteristic of the displacement sensor is computed. Settings of a conversion table, which is used for displacement amount computation, are corrected in a direction along the computed trend of changes.

Abstract: In a displacement sensor (10), a shaft (24) of a movable member (14) comprises a tubular part (26) having an opening (26c) at one end. A rod-form permanent is inserted into the tubular part (26) through the opening (26c) . A spacer (32) is fitted over a narrow portion of the rod-form magnet (28). The thickest portion of the magnet (28) and the spacer (32) contact the side wall of the tubular part (26) tightly, so that the magnet (28) is disposed coaxially with the tubular part (26). A stopper (26d) is formed on the opening (26c) of the tubular part (26), so that the magnet (28) does not move axially. Therefore, the magnet (28) is mounted in a prescribed position in a movable member (14) with a high degree of accuracy.

Abstract: In a hydraulic machine, hydraulic pump failure is detected and the pump lifespan is estimated before the pump failure occurs. The discharge pressure 122, oil temperature 126, and drain filter differential pressure 120 are measured, a correlative relationship 128 between the filter differential pressure and the discharge pressure is determined, and a representative filter differential pressure 130 is calculated from this correlative relationship. Using an oil temperature-differential pressure correlation function, the representative differential pressure value 130 is corrected so that the variable component 132 caused by the oil temperature 126 is eliminated therefrom. The long-term trend and the short-term trend of the increase over time of the corrected differential pressure is calculated. A pump failure is predicted or the pump lifespan is estimated based on the degree of deviation between the long-term trend and the short-term trend.

Abstract: A plurality of Hall ICs 34A, 34B are disposed around a magnetic rod 32 that is movable along a central axis. The Hall ICs are disposed in different positions in terms of both a straight line distance coordinate in the direction of the central axis and a rotational angle coordinate around the central axis. The amount of displacement of the magnetic rod 32 is calculated based on the average of output signals from the Hall ICs. Errors in the output signals due to a shift and tilt of the magnetic rod are detected and calibration of the measurement method is carried out.

Abstract: It is an object of the present invention to provide a plural pressure oil energies selective recovery apparatus which can selectively recover pressure oil energies stored in plural pressure oil actuators, based upon recovery conditions. A priority for recovering a return pressure oil from a hydraulic actuator is set in advance for an operation lever of each of the plural hydraulic actuators. If the operation lever is in the non-actuation state at a preceding detection point, the plural pressure oil energies selective recovery apparatus recovers a return pressure oil from a corresponding hydraulic actuator. If the operation lever is in the actuation state, the plural pressure oil energies selective recovery apparatus does not recover a pressure oil.

Abstract: It is an object of the present invention to provide a filter for trapping foreign matter in which a filtration element can trap foreign matter that is admixed to a fluid present inside the filter with good reliability and a comparatively high trapping ratio. Hydraulic oil that has flown from an opening portion into a guide space of a first flow path guide is guided downward by the first flow path guide and directed toward a second flow path guide. As a result, the oil passes through a very narrow gap, that is, a gap with a cross sectional area of the flow path narrowed so as to increase the flow velocity of the hydraulic oil, a rising flow of the hydraulic oil is formed, and this flow is spouted up by the second flow path guide and guided by the first flow path guide toward a filter element. Foreign matter admixed to the hydraulic oil rises with good intensity together with the hydraulic oil and is moved by the hydraulic oil toward the filter element.

Abstract: A balance of force acting on a pool 21 of a control valve 20 is expressed by (P1−P3)·A=F+f When it is assumed that a pressure difference P1−P2 before and after a throttle 42 is &Dgr;P12 to modify the above expression, an expression &Dgr;P12·A+(P2−P3)·A=f+F is obtained. According to the present invention, the force &Dgr;P12·A corresponding to the pressure difference &Dgr;P12 before and after the second throttle 42 of the first term of the left-hand side is applied to the control valve 20 as a force capable of canceling the flow force f at the first term of the right-hand side.

Abstract: It is an object of the present invention to provide a plural pressure oil energies selective recovery apparatus which can selectively recover pressure oil energies stored in plural pressure oil actuators, based upon recovery conditions. A priority for recovering a return pressure oil from a hydraulic actuator is set in advance for an operation lever of each of the plural hydraulic actuators. If the operation lever is in the non-actuation state at a preceding detection point, the plural pressure oil energies selective recovery apparatus recovers a return pressure oil from a corresponding hydraulic actuator. If the operation lever is in the actuation state, the plural pressure oil energies selective recovery apparatus does not recover a pressure oil.

Abstract: Return pressure oil from a pressure oil actuator is supplied to a hydraulic pump/motor as recovering means through a supplying circuit. The hydraulic pump/motor serves as a motor, and a hydraulic pump/motor as regenerating means which is mechanically connected to the first-mentioned hydraulic pump/motor is allowed to serve as a pump. The pressure oil discharged from the second-mentioned hydraulic pump/motor is supplied to a hydraulic pump/motor as driving means and can be stored in the accumulator. The hydraulic pump/motor as the driving means is driven by the pressure oil discharged by the second-mentioned hydraulic pump/motor and the pressure oil stored in the accumulator. With this arrangement, it is possible to recover the energy of the return pressure oil from the pressure oil actuator and to regenerate the recovered energy to be driving energy in the driving means.

Abstract: A balance of force acting on a pool 21 of a control valve 20 is expressed by (P1−P3)·A=F+f When it is assumed that a pressure difference P1−P2 before and after a throttle 42 is &Dgr;P12 to modify the above expression, an expression &Dgr;P12·A+(P2−P3)·A=f+F is obtained. According to the present invention, the force &Dgr;P12·A corresponding to the pressure difference &Dgr;P12 before and after the second throttle 42 of the first term of the left-hand side is applied to the control valve 20 as a force capable of canceling the flow force f at the first term of the right-hand side.

Abstract: A pressure oil energy recovery apparatus or pressure oil energy recovery/regeneration apparatus that does not require much room and can be mounted within a narrow space, capable of broadening the range of applications for recovered energy. A hydraulic pump motor is actuated by the inflow of the return pressure oil flowing out of a hydraulic actuator. The drive force of the hydraulic pump motor is input to allow an electric motor to generate electric energy. The electric energy generated by the electric motor is stored in a battery. When the energy of pressure oil is regenerated, the energy expended during the actuation of the hydraulic actuator by the hydraulic pump is supplemented with the electric energy stored in the battery.

Abstract: Energy of returning pressurized fluid of an actuator is recovered and reused as energy for operating other accumulators. A first pump motor (16) and a second pump motor (17) are mechanically connected to form a pressure converter (18), and a first circuit (22), to which the returning pressurized fluid is supplied, is connected to the first pump motor (16). A pressure accumulator (27) is provided to a second circuit (25) connected to the second pump motor (17). The first circuit (22) is connected to a discharge passage (11) of a primary hydraulic pump (10) by a third circuit (29) and the pressure of a high pressure pressurized fluid is supplied to the discharge passage (11) by the pressure of the high pressure pressurized fluid, and is reused.

Abstract: A pressure compensating valve (7) comprises a main valve (20) that is operated in such a way as to increase the area of the opening between an inlet port (24) and an outlet port (25) by means of pressure acting on a first pressure receiving component (21), that is also operated in such a way as to reduce the area of the opening by means of pressure acting on a second pressure receiving component (22) and pressure acting on a third pressure receiving component (23), and that is designed to allow the pressure (Pa) of the pressured oil flowing to the inlet port (24) to act on the first pressure receiving component (21) and the pressure (Pb) of the load driven by the pressured oil flowing from the outlet port (25) to act on the second pressure receiving component (22); and control pressure producer (7B) for allowing control pressure (Pe) resulting from a reduction in the pressure (Pa) of the inlet port (24) to act on the third pressure receiving component (23).

Abstract: A pressure compensating valve (7) comprises a main valve (20) that is operated in such a way as to increase the area of the opening between an inlet port (24) and an outlet port (25) by means of pressure acting on a first pressure receiving component (21). The pressure compensating valve (7) is also operated in such a way as to reduce the area of the opening by means of pressure acting on a second pressure receiving component (22) and pressure acting on a third pressure receiving component (23). The pressure compensating valve (7) is designed to allow the pressure (Pa) of the pressurized oil flowing to the inlet port (24) to act on the first pressure receiving component (21) and the pressure (Pb) of the load driven by the pressurized oil flowing from the outlet port (25) to act on the second pressure receiving component (22).

Abstract: A target fan rotational speed (R.P.M.) corresponding to a temperature detected by a temperature detector is determined according to a set correlation and the capacity of a variable-capacity hydraulic pump is varied so that the rotational speed of a cooling fan becomes that determined target fan rotational speed. It thereby becomes possible to precisely control the blowing air volume (R.P.M.) of the cooling fan, and, when the cooling fan is driven with a hydraulic source, to construct a hydraulic circuit with fewer parts. Moreover, in cases where the torque absorbed by the fan-drive hydraulic motor fluctuates, control is effected to suppress fluctuations in the cooling fan rotational speed and stabilize the rotation. Furthermore, in cases where the load on the fan-drive hydraulic motor fluctuates, control is effected to suppress fluctuations in the cooling fan rotational speed and stabilize the rotation.