A hybrid work machine has an engine, an assist motor, a hydraulic pump which is driven by the total torque of the engine and the assist motor, and an electric storage device which accumulates electric power generated by the assist motor and supplies the electric power when the assist motor performs electric discharge. The continuous electric discharge from the electric storage device due to continuous operation at high load pressure can be suppressed without an operator experiencing an unusual operational characteristic. To this end, a pump flow rate correction control unit judges whether each hydraulic pump is in a high load operation state or not based on the output horsepower and/or the delivery pressure of each hydraulic pump and performs control such that the delivery flow rate gradually decreases when the hydraulic pump is in the high load operation state and this state continues beyond a predetermined time.

A hydraulic control system of an automatic transmission for a vehicle provided with an ISG system is disclosed. The hydraulic control system may include: a mechanical hydraulic pump driven by an engine; a linear solenoid valve to control hydraulic pressure generated by the mechanical hydraulic pump; a first switch valve to selectively supply or not to supply controlled hydraulic pressure to one of friction members; an electric hydraulic pump driven by electric energy; and a second switch valve to selectively supply the hydraulic pressure, generated by the electric hydraulic pump, to the one friction member or to the linear solenoid valve. The hydraulic control system supplies the hydraulic pressure to one of the friction members operated at a gear stage where starting control is performed.

The present disclosure relates to an apparatus for controlling a hydraulic pump for a construction machine. The apparatus for controlling the hydraulic pump for the construction machine according to the present disclosure includes: a hydraulic pump control device configured to generate first and second pump commands for controlling first and second hydraulic pumps so that the first and second hydraulic pumps generate pump torque corresponding to a request value; and a torque controller configured to generate first and second corrected pump commands, which are the corrected first and second pump commands, by a torque inclination map generated by reflecting a dynamic characteristic of an engine, and to provide the first and second corrected pump commands to the first and second hydraulic pumps.

In addition to a main pump 102 having two delivery ports 102a and 102b and performing the load sensing control, two subsidiary pumps 202 and 302 for the load sensing control for respectively performing assist driving on a boom cylinder 3a and an arm cylinder 3b are provided. When driving the boom cylinder 3a or the arm cylinder 3b, a selector valve 141 or 241 is switched and flows of hydraulic fluid are merged together and supplied to the boom cylinder 3a or the arm cylinder 3b. When driving actuators other than the boom cylinder 3a or the arm cylinder 3b, only the hydraulic fluid from the main pump is supplied to the actuators. In short, the hydraulic drive system is configured so that two specific actuators having great demanded flow rates and tending to have a great load pressure difference between each other when driving at the same time can be driven with hydraulic fluid delivered from separate delivery ports. With this configuration, wasteful energy consumption due to pressure loss in a pressure compensating valve can be suppressed, and in cases of driving an actuator of a low demanded flow rate, the hydraulic pump can be used at a point where the volume efficiency is high.

The hydraulic apparatus is set so that the ratio of the pressure-receiving area of the respective bottom oil chambers of the boom cylinder, the arm cylinder and the bucket cylinder to the pressure-receiving area of the respective rod oil chambers matches the ratio of the extruded volume drawn into or discharged from the bottom oil chambers per single rotation by the respective extrusion members of the first hydraulic pump motor, the second hydraulic pump motor and the third hydraulic pump motor to the volume discharged from or drawn into the rod oil chambers.

A work machine includes: a hydraulic actuator; a closed-circuit pump that is connected to the hydraulic actuator in a closed circuit, and supplies and discharges a hydraulic working fluid to and from the hydraulic actuator; an open-circuit pump that is connected to the hydraulic actuator in an open circuit, and supplies the hydraulic working fluid to the hydraulic actuator; a charge pump; a charge flow path that introduces the hydraulic working fluid delivered from the charge pump to the closed circuit; an excess fluid discharging device that discharges an excess hydraulic working fluid of the closed circuit to the charge flow path; and a controller that controls a delivery capacity of the closed-circuit pump and a delivery capacity of the open-circuit pump. The controller increases the delivery capacity of the open-circuit pump, or reduces the delivery capacity of the closed-circuit pump when a state of a pressure of the charge flow path has transited to be lower than a predetermined pressure threshold from equal to or higher than the predetermined pressure threshold, or when a state of the work device has transited to a state of performing the excavation work from a state of not-performing the excavation work.

The present invention provides a controller for hydraulic apparatus (100). The controller is configured to determine (310) that an energy return criteria has been met by movement of a first movement component of a first hydraulic actuator. In response thereto, the controller is further configured to select (320) at least one among a plurality of energy control strategies based on at least one operational characteristic of the hydraulic apparatus, and to control (330) the hydraulic apparatus to implement the energy control strategy during movement of the first movable component in such a way as to meet the energy return criteria. The plurality of energy control strategies comprises a first energy control strategy and a second energy control strategy. The at least one operational characteristic of the hydraulic apparatus comprises an indication of an expected energy recovery of one or more of the energy control strategies. The first energy control strategy comprises transferring energy from the first hydraulic actuator, via a hydraulic machine, to an energy consumer in torque connection with the hydraulic machine. The second energy control strategy comprises transferring energy from the first hydraulic actuator to a low-pressure reservoir of hydraulic fluid in the hydraulic circuit.

A hydraulic control system may include a closed loop hydraulic circuit with at least one hydraulic motor. A plurality of variable displacement pumps may be fluidly connected in parallel in the closed loop hydraulic circuit. A plurality of hydraulic actuators may be configured to adjust the displacement of the variable displacement pumps. A pilot valve assembly may be configured to supply the hydraulic actuators with hydraulic fluid having a pilot pressure corresponding to a desired displacement of the variable displacement pumps. A pressure regulating device may be configured to limit the pilot pressure of the hydraulic fluid supplied to the hydraulic actuators when a working pressure in the closed loop hydraulic circuit reaches a maximum allowable working pressure.

A hydraulic power unit includes a reservoir containing hydraulic fluid, a main output, a pressure sensor, at least one active valve hydraulic pump and at least one passive valve hydraulic pump. A main flow of the hydraulic fluid is discharged through the main output. The pressure sensor includes a pressure signal that is indicative of a pressure of the main flow. Each active valve hydraulic pump is configured to drive a first flow portion of the main flow from the reservoir to the main output when the pressure signal is below a first pressure setpoint. Each passive valve hydraulic pump is configured to drive a second flow portion of the main flow from the reservoir to the main output when the pressure signal is below a second pressure setpoint.

A work machine includes: a hydraulic actuator; a closed-circuit pump that is connected to the hydraulic actuator in a closed circuit, and supplies and discharges a hydraulic working fluid to and from the hydraulic actuator; an open-circuit pump that is connected to the hydraulic actuator in an open circuit, and supplies the hydraulic working fluid to the hydraulic actuator; a charge pump; a charge flow path that introduces the hydraulic working fluid delivered from the charge pump to the closed circuit; an excess fluid discharging device that discharges an excess hydraulic working fluid of the closed circuit to the charge flow path; and a controller that controls a delivery capacity of the closed-circuit pump and a delivery capacity of the open-circuit pump. The controller increases the delivery capacity of the open-circuit pump, or reduces the delivery capacity of the closed-circuit pump when a state of a pressure of the charge flow path has transited to be lower than a predetermined pressure threshold from equal to or higher than the predetermined pressure threshold, or when a state of the work device has transited to a state of performing the excavation work from a state of not-performing the excavation work.