Abstract: A method of suppressing a pulsation of axial type hydraulic pump/motor includes performing a pressure accumulation operation in which each of ports of each of two pressure accumulation oil passages exclusively communicates with a corresponding one of communication holes and pressure inside one of the cylinder bores is accumulated in a corresponding one of the pressure accumulation oil passages through the communication hole in two levels, the communication holes being provided for each of the cylinder bores to communicate with inside of each of the cylinder bores and having opening portions sliding on the respective ports with rotation of the cylinder block to communicate with the respective ports; and performing an accumulated pressure collection operation in which the pressure accumulated in the pressure accumulation oil passage is collected in one of the cylinder bores in two levels.

Abstract: The system includes: a variable displacement hydraulic pump supplying pressure oil to a hydraulic actuator; a pressure detector detecting a pump discharge pressure from the hydraulic pump; a control valve controlling a supply of the pressure oil to the hydraulic actuator; a controller controlling a pump displacement of the hydraulic pump; a hydraulic motor rotating an upper structure of the construction machine; a swing relief valve defining a relief pressure of the hydraulic motor; and a control lever switching a control valve for the hydraulic motor. The controller includes: an adjuster that, when a pump discharge pressure detected by the pressure detector exceeds a first set value, conducts an adjustment to reduce the pump displacement; and a canceller that cancels the adjustment when the pump discharge pressure falls below a second set value. The second set value is equal to or larger than the first set value.

Abstract: A hydraulic motor 10 of the invention includes a detected unit 52 formed on an outer circumferential surface of a cylinder block 14 and a rotation sensor 50arranged opposed to the detected unit 52 for detecting the detected unit 52. The rotation sensor 50 is provided on a position corresponding to a position between a deepest portion 41 of a cylinder hole 29 and a rear end face 28 of the cylinder block in an axial direction of the cylinder block. A fan driving device 60 is provided with the hydraulic motor 10, a bracket 61 to which the hydraulic motor is attached in a state in which a tip end of the rotational shaft 13 is arranged on a surface side thereof through a through-hole 64 and a fan 62 attached to the rotational shaft 13 and is driven by the hydraulic motor.

Abstract: A method of suppressing a pulsation of axial type hydraulic pump/motor includes performing a pressure accumulation operation in which each of ports of each of two pressure accumulation oil passages exclusively communicates with a corresponding one of communication holes and pressure inside one of the cylinder bores is accumulated in a corresponding one of the pressure accumulation oil passages through the communication hole in two levels, the communication holes being provided for each of the cylinder bores to communicate with inside of each of the cylinder bores and having opening portions sliding on the respective ports with rotation of the cylinder block to communicate with the respective ports; and performing an accumulated pressure collection operation in which the pressure accumulated in the pressure accumulation oil passage is collected in one of the cylinder bores in two levels.

Abstract: The system includes: a variable displacement hydraulic pump supplying pressure oil to a hydraulic actuator; a pressure detector detecting a pump discharge pressure from the hydraulic pump; a control valve controlling a supply of the pressure oil to the hydraulic actuator; a controller controlling a pump displacement of the hydraulic pump; a hydraulic motor rotating an upper structure of the construction machine; a swing relief valve defining a relief pressure of the hydraulic motor; and a control lever switching a control valve for the hydraulic motor. The controller includes: an adjuster that, when a pump discharge pressure detected by the pressure detector exceeds a first set value, conducts an adjustment to reduce the pump displacement; and a canceller that cancels the adjustment when the pump discharge pressure falls below a second set value. The second set value is equal to or larger than the first set value.

Abstract: A fan drive system for driving an engine cooling fan mounted in a working machine is described. The fan drive system includes a variable displacement pump that supplies oil to an actuator and is also used as a hydraulic pump for the hydraulic motor that drives the cooling fan. A pump displacement of a variable displacement pump can be controlled in accordance with the load of the working machine, and when a load is not generated in the working machine, the pump displacement of the variable displacement pump can be controlled in accordance with a load pressure of a hydraulic motor which drives a cooling fan. Examples of such working machines include a forklift, a skid steer loader (SSL) and a crawler dump.

Abstract: A hydraulic motor 10 of the invention includes a detected unit 52 formed on an outer circumferential surface of a cylinder block 14 and a rotation sensor 50 arranged opposed to the detected unit 52 for detecting the detected unit 52. The rotation sensor 50 is provided on a position corresponding to a position between a deepest portion 41 of a cylinder hole 29 and a rear end face 28 of the cylinder block in an axial direction of the cylinder block. A fan driving device 60 is provided with the hydraulic motor 10, a bracket 61 to which the hydraulic motor is attached in a state in which a tip end of the rotational shaft 13 is arranged on a surface side thereof through a through-hole 64 and a fan 62 attached to the rotational shaft 13 and is driven by the hydraulic motor.

Abstract: An arrangement structure of a swash plate hydraulic pump which can be used in a wide range of construction equipment and industrial vehicles and is small in size, simple in structure, and inexpensive is provided. For this purpose, an arrangement structure of a swash plate hydraulic pump (1) comprises a driving source (3) and a plurality of swash plate hydraulic pumps (4, 8) which are connected to the driving source and discharge pressurized oil, and the plurality of swash plate hydraulic pumps include at least one swash plate hydraulic pump (8) of the second and subsequent swash plate hydraulic pumps which has a driving shaft (9) provided on a plane almost perpendicular to a driving shaft (6) of the first swash plate hydraulic pump (4) coupled to the driving source.

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: 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: An arrangement structure of a swash plate hydraulic pump which can be used in a wide range of construction equipment and industrial vehicles and is small in size, simple in structure, and inexpensive is provided. For this purpose, an arrangement structure of a swash plate hydraulic pump (1) comprises a driving source (3) and a plurality of swash plate hydraulic pumps (4, 8) which are connected to the driving source and discharge pressurized oil, and the plurality of swash plate hydraulic pumps include at least one swash plate hydraulic pump (8) of the second and subsequent swash plate hydraulic pumps which has a driving shaft (9) provided on a plane almost perpendicular to a driving shaft (6) of the first swash plate hydraulic pump (4) coupled to the driving source.

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: 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.

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: Air blower apparatus (20) in which a fan boss (41) at the rotational center portion of a fan (29) has a recessed form. Meanwhile, the central part of the body portion (21) of the air blower apparatus (20), i.e., a boss portion (38), has a projecting form to be housed within the recessed fan boss (41). The central part of the body potion (21), i.e., the boss portion (38), is housed within the recessed fan boss (41) at the rotational center portion of the fan (29), and the rotary shaft (39) of the body portion (21) of the air blower apparatus (20) is mounted on the fan (29).

Abstract: The present invention has an object to enable to supply a discharged pressurized fluid of a hydraulic pump without any energy loss with an arbitrary flow rate distribution ratio to a plurality of actuators. A discharged pressurized fluid of the hydraulic pump 11 is supplied to the first and second actuators 15 and 16 via the first and second variable displacement type hydraulic pump/motors 13 and 14. The first variable displacement type hydraulic pump/motor 13 and the second variable displacement type hydraulic pump/motor 14 are mechanically connected to rotate at the same revolution speed. By this, the pressurized fluid is supplied to the first and second actuators 15 and 16 depending upon displacements of the first and second variable displacement type hydraulic pump/motors.

Abstract: A system that can recover flows of a hydraulic pressure fluid returned from a plurality of hydraulic actuators is disclosed which includes a plurality of fluid recovery circuits (15, 19, 25 and 27) into which flows of a hydraulic pressure fluid returned from such a plurality of actuators are admitted, and a main fluid recovery circuit (36). There is provided a selector means (30, 31, 32, 33, 34, 35, 37) for permitting at least one of the plural fluid recovery circuits (15, 19, 25 and 27) selectively to communicate with the main fluid recovery circuit (36). The system, by permitting at least one of a plurality of fluid recovery circuits to communicate with a main fluid recovery circuit, enables a hydraulic return pressure fluid from at least one of a plurality of actuators to be recovered and hence is applicable to a working machine involving a plurality of hydraulic actuators.