Abstract: Provided is a hydraulic drive apparatus for a construction machine capable of achieving both of cavitation prevention and improvement of regeneration efficiency. The apparatus includes a regenerative motor configured to regenerate energy of hydraulic fluid discharged from a slewing motor, a first regeneration tank line for returning regeneration discharge fluid from the regenerative motor to a tank through a back pressure valve which is provided in a makeup line, a second regeneration tank line for returning the regeneration discharge fluid directly to the tank so as to bypass the back pressure valve, a regeneration-tank-line selector valve, and a regeneration-tank-line-selection control section configured to shift the regeneration-tank-line selector valve to pass the regeneration discharge fluid through the first regeneration tank line during slewing deceleration and otherwise through the second regeneration tank line.

Abstract: Provided is a hydraulic drive apparatus for a construction machine capable of achieving both of cavitation prevention and improvement of regeneration efficiency. The apparatus includes a regenerative motor configured to regenerate energy of hydraulic fluid discharged from a slewing motor, a first regeneration tank line for returning regeneration discharge fluid from the regenerative motor to a tank through a back pressure valve which is provided in a makeup line, a second regeneration tank line for returning the regeneration discharge fluid directly to the tank so as to bypass the back pressure valve, a regeneration-tank-line selector valve, and a regeneration-tank-line-selection control section configured to shift the regeneration-tank-line selector valve to pass the regeneration discharge fluid through the first regeneration tank line during slewing deceleration and otherwise through the second regeneration tank line.

Abstract: A construction machine, including: a hydraulic pump; a working attachment including a boom, a boom cylinder, and another fluid-supplied cylinder closer to a leading end than the boom cylinder; first and second operation devices for the boom cylinder and the fluid-supplied cylinder; first and second control valves; a flow-rate-limiting section; and an anti-cavitation circuit. The fluid-supplied cylinder receives fluid-supply from the hydraulic pump, together with the boom cylinder. A reaction force upon work accompanying extension of the fluid-supplied cylinder increases the rod-side pressure of the boom cylinder and reduces a head-side pressure. The flow-rate-limiting section limits a supply flow rate to a head-side fluid chamber of the boom cylinder only during a boom-raising-operation with the rod-side pressure higher than the head-side pressure in the boom cylinder. The anti-cavitation circuit replenishes hydraulic fluid from a tank to the head-side fluid chamber.

Abstract: A lighting device 10 according to this invention includes a light guide plate 16, a reflection sheet 21, and a light source unit LU. The light guide plate 16 is a plate-like member and includes a light entrance surface 16c through which light enters and a light exit surface 16a through which the light in the light guide plate 16 from the light entrance surface 16c exits. The reflection sheet 21 is arranged such that a front surface 21a thereof is on a rear plate surface 16b of the light guide plate 16 and such that an end portion 211 of the reflection sheet 21 is located more to an outer side than the light entrance surface 16c. The light source unit LU includes a light source board 18, a plurality of light sources 17, and a connector 19A configured to relay an electric power supply to the light sources 17.

Abstract: A construction machine, including: a hydraulic pump; a working attachment including a boom, a boom cylinder, and another fluid-supplied cylinder closer to a leading end than the boom cylinder; first and second operation devices for the boom cylinder and the fluid-supplied cylinder; first and second control valves; a flow-rate-limiting section; and an anti-cavitation circuit. The fluid-supplied cylinder receives fluid-supply from the hydraulic pump, together with the boom cylinder. A reaction force upon work accompanying extension of the fluid-supplied cylinder increases the rod-side pressure of the boom cylinder and reduces a head-side pressure. The flow-rate-limiting section limits a supply flow rate to a head-side fluid chamber of the boom cylinder only during a boom-raising-operation with the rod-side pressure higher than the head-side pressure in the boom cylinder. The anti-cavitation circuit replenishes hydraulic fluid from a tank to the head-side fluid chamber.

Abstract: A light source device with an improved contrast ratio between a bright portion and a dark portion of a displayed image and a display divide including the light source device. In order to change a reflectance of a portion of a reflection sheet 110, 111 with gradation in response to light and dark of portions of an image displayed on a display panel 201, a control mechanism 202 arranged to control the display panel 201 is provided. A first storing mechanism 104 and a second storing mechanism 105 arranged to store signals generated by the control mechanism 202, a calculation mechanism 103 arranged to calculate reflectances of portions of the reflection sheet 110, 111, a third storing mechanism 106 arranged to store the reflectances calculated by the calculation mechanism 103, and a reflectance control mechanism 107 arranged to control the reflection sheet 110, 111 based on the reflectances are provided.

Abstract: A hydraulic drive device capable of utilizing return oil effectively while maintaining a driven speed of a hydraulic actuator, as well as a working machine having the hydraulic drive device, are provided. The hydraulic drive device includes a controller. During an external force applying period in which a return oil pressure exceeds a discharge pressure from a hydraulic pump, the controller specifies a regenerating flow rate capable of being conducted to a regeneration oil passage and a surplus flow rate other than the regenerating flow rate on the basis of power required of the hydraulic pump out of return oil other than return oil which is conduced to a tank through a control valve, then conducts the return oil of the regenerating flow rate to the regeneration oil passage and controls an MO valve and a regulator so that the return oil of the surplus flow rate is conducted to an outlet oil passage.

Abstract: A hydraulic circuit for actuating an electromagnetic proportional pressure reducing valve by a command current outputted from a controller based on an operation amount of a remote control valve, and by a secondary pressure of the pressure reducing valve, actuating a common bleed-off valve which is a hydraulic pilot type spool valve is provided. In the controller, as a correction processing for correcting characteristics of a proportional valve command value which is a current value given to the pressure reducing valve and the opening area of the spool valve, at an inflection point at which the degree of change of a pump pressure increases, an actual proportional valve command value at a time of obtaining the pump pressure is compared to a theoretical proportional valve command value of a case of no tolerance, and a correction to compensate for a difference between the both command values is performed.

Abstract: A light source device with an improved contrast ratio between a bright portion and a dark portion of a displayed image and a display divide including the light source device. In order to change a reflectance of a portion of a reflection sheet 110, 111 with gradation in response to light and dark of portions of an image displayed on a display panel 201, a control mechanism 202 arranged to control the display panel 201 is provided. A first storing mechanism 104 and a second storing mechanism 105 arranged to store signals generated by the control mechanism 202, a calculation mechanism 103 arranged to calculate reflectances of portions of the reflection sheet 110, 111, a third storing mechanism 106 arranged to store the reflectances calculated by the calculation mechanism 103, and a reflectance control mechanism 107 arranged to control the reflection sheet 110, 111 based on the reflectances are provided.

Abstract: A display device for performing image display by irradiating light from a light source to a display panel includes a transparent EL sheet which is disposed at aback surface side of the display panel and kept transparent in a non-luminous state, a reflection sheet which reflects the light from the light source to the display panel, a display control unit which controls the image display on the display panel, and a light emission control unit which controls light emission on the transparent EL sheet, wherein when the light emission control unit brings at least a part of a surface of the transparent EL sheet into a luminous state corresponding to the image display on the display panel controlled by the display control unit, an emitted light is irradiated to the display panel together with the light from the light source and the light reflecting from the reflection sheet.

Abstract: A hydraulic drive device capable of utilizing return oil effectively while maintaining a driven speed of a hydraulic actuator, as well as a working machine having the hydraulic drive device, are provided. The hydraulic drive device includes a controller. During an external force applying period in which a return oil pressure exceeds a discharge pressure from a hydraulic pump, the controller specifies a regenerating flow rate capable of being conducted to a regeneration oil passage and a surplus flow rate other than the regenerating flow rate on the basis of power required of the hydraulic pump out of return oil other than return oil which is conduced to a tank through a control valve, then conducts the return oil of the regenerating flow rate to the regeneration oil passage and controls an MO valve and a regulator so that the return oil of the surplus flow rate is conducted to an outlet oil passage.

Abstract: With respect to a method of controlling a pump flow rate of a hydraulic pump, a method having a small flow rate command value is selected between a pressure feedback control for controlling the pump flow rate based on a set pressure (a cutoff pressure) and a pump pressure, and, an ordinary control for controlling the pump flow rate based on operation information, and in a case that the pressure feedback control is selected, a flow rate increasing control for increasing the flow rate command value after the case with the passage of time is performed.

Abstract: A hydraulic control device for a working machine includes control valves; hydraulic actuators controlled by corresponding control valves and divided into groups; unified bleed-off valves disposed on discharge lines of first and second hydraulic pumps; central bypass paths provided in the control valves, the central bypass paths of each group being connected in tandem so as to form a central bypass line; and bypass-cutting valves disposed on the central bypass lines, the bypass-cutting valves being automatically switched so as to open the central bypass lines when the unified bleed-off valves are not operated.

Abstract: There is provided a hydraulic controller for a working machine in which a pilot hydraulic pressure source is connected in common to a plurality of pilot-operated hydraulic devices each having a pilot pressure input unit, and a common pilot pressure input switching valve is adapted to control the switching between a pilot pressure input from the pilot hydraulic pressure source to each pilot pressure input unit and a relief of the input. The switching control of a pilot pressure input by the pilot pressure input switching valve is performed based on the operating state of the working machine and pilot pressure input conditions of the respective pilot-operated hydraulic devices.

Abstract: A first group is supplied with hydraulic power from a first hydraulic pump. In the first group, an arm control valve is disposed at the most downstream position. A throttle is provided at the entrance of the arm control valve. Thus, a circuit is configured to give priority to boom raising or bucket excavation. During a combined operation, according to the operation amount of boom pulling or bucket excavation, a controller decreases the upper limit of the discharge amount of the first hydraulic pump determined by the operation amount of arm pulling and increases the recycling rate of oil to the expansion side of an arm cylinder.

Abstract: A hydraulic control system for a working machine according to the present invention includes a regulator control valve for controlling an operation of a pump regulator and a controller for sending a control signal for changing a discharge quantity of the pump to the regulator control valve in accordance with an operation amount of an operating means. On the basis of the control signal, a secondary pressure in the regulator control valve is fed to the pump regulator. This system further includes a fail-safe valve disposed in a control line joining the pump regulator and the regulator control valve. The fail-safe valve has an ordinary position for sending the secondary pressure to the pump regulator and a fail-safe position for sending an oil pressure from a path other than the regulator control valve to the pump regulator in such a manner that a predetermined discharge amount is ensured.

Abstract: A hydraulic control system for a working machine according to the present invention includes a regulator control valve for controlling an operation of a pump regulator and a controller for sending a control signal for changing a discharge quantity of the pump to the regulator control valve in accordance with an operation amount of an operating device. This system further includes a fail-safe valve disposed in a control line joining the pump regulator and the regulator control valve. The fail-safe valve is configured so as to switch from an ordinary position to a fail-safe position in accordance with a failure signal indicative of failure in the regulator control valve.

Abstract: With respect to a method of controlling a pump flow rate of a hydraulic pump, a method having a small flow rate command value is selected between a pressure feedback control for controlling the pump flow rate based on a set pressure (a cutoff pressure) and a pump pressure, and, an ordinary control for controlling the pump flow rate based on operation information, and in a case that the pressure feedback control is selected, a flow rate increasing control for increasing the flow rate command value after the case with the passage of time is performed.

Abstract: A hydraulic circuit for actuating an electromagnetic proportional pressure reducing valve by a command current outputted from a controller based on an operation amount of a remote control valve, and by a secondary pressure of the pressure reducing valve, actuating a common bleed-off valve which is a hydraulic pilot type spool valve is provided. In the controller, as a correction processing for correcting characteristics of a proportional valve command value which is a current value given to the pressure reducing valve and the opening area of the spool valve, at an inflection point at which the degree of change of a pump pressure increases, an actual proportional valve command value at a time of obtaining the pump pressure is compared to a theoretical proportional valve command value of a case of no tolerance, and a correction to compensate for a difference between the both command values is performed.

Abstract: A hydraulic control device for a working machine includes control valves; hydraulic actuators controlled by corresponding control valves and divided into groups; unified bleed-off valves disposed on discharge lines of first and second hydraulic pumps; central bypass paths provided in the control valves, the central bypass paths of each group being connected in tandem so as to form a central bypass line; and bypass-cutting valves disposed on the central bypass lines, the bypass-cutting valves being automatically switched so as to open the central bypass lines when the unified bleed-off valves are not operated.