Abstract: Provide a hydraulic circuit that can prevent damage to the oil cooler while suppressing excessive rise in the temperature of the operating oil.

Abstract: Problem to be solved: To provide a hydraulic circuit for the construction machine which enables to use the relief valve of low capacity in the work tool circuit. Solution: The hydraulic circuit 2 for a construction machine has: a hydraulic pump 4 of variable capacity, a work tool 6 operated by hydraulic oil delivered by the hydraulic pump 4, a work tool operating device 10 to output a signal for operating the work tool 6, a control valve 14 allowing the hydraulic pump 4 to supply the hydraulic oil to the work tool 6 based on the signal output from the work tool operating device 10, a tool's relief valve 44 to release the hydraulic oil flowing between the control valve 14 and the work tool 6, a pressure sensor 46 to detect a pressure of hydraulic oil flowing into the work tool 6, and a controller 48 to reduce a delivery rate from the hydraulic pump 4 when the pressure detected by the pressure sensor 46 exceeds a predetermined value.

Abstract: Problem to be solved: To provide a hydraulic circuit for the construction machine which enables to use the relief valve of low capacity in the work tool circuit. Solution: The hydraulic circuit 2 for a construction machine has: a hydraulic pump 4 of variable capacity, a work tool 6 operated by hydraulic oil delivered by the hydraulic pump 4, a work tool operating device 10 to output a signal for operating the work tool 6, a control valve 14 allowing the hydraulic pump 4 to supply the hydraulic oil to the work tool 6 based on the signal output from the work tool operating device 10, a tool's relief valve 44 to release the hydraulic oil flowing between the control valve 14 and the work tool 6, a pressure sensor 46 to detect a pressure of hydraulic oil flowing into the work tool 6, and a controller 48 to reduce a delivery rate from the hydraulic pump 4 when the pressure detected by the pressure sensor 46 exceeds a predetermined value.

Abstract: The present invention makes it possible, in an HST drive circuit wherein an HST pump and an HST motor have been separately stored in a pump case and a motor case, to efficiently cool the HST drive circuit. A cooling line for, while discharging a relief oil from a charge circuit 9 for replenishing an HST closed circuit 5 with a pressure oil into a pump case 3, making the discharged oil flow into a reservoir 7 through the pump case 3, a communicating pipe 14, a motor case 4, and an oil cooler 16 is formed, so that hydraulic oil circulating through an HST pump 1, an HST motor 2, and the HST closed circuit 5 is cooled by an oil flowing through the cooling line.

Abstract: The present invention relates to a display apparatus that is switched to an image signal via a wireless communication unit automatically when an image signal cable is disconnected from a connector. The image signal is transmitted by a cable 6 connected to the connector C1 of the apparatus D1 or a wireless LAN. When a switch S1 detects that the cable 6 is connected to the connector C1, a switching circuit 2 is switched to the cable-side to display the image signal via the cable. When the switch S1 detects disconnection of the cable 6, the switch circuit is switched to the side of a CPU 5 to display the image signal via the wireless LAN.

Abstract: The present invention makes it possible, in an HST drive circuit wherein an HST pump and an HST motor have been separately stored in a pump case and a motor case, to efficiently cool the HST drive circuit. A cooling line for, while discharging a relief oil from a charge circuit 9 for replenishing an HST closed circuit 5 with a pressure oil into a pump case 3, making the discharged oil flow into a reservoir 7 through the pump case 3, a communicating pipe 14, a motor case 4, and an oil cooler 16 is formed, so that hydraulic oil circulating through an HST pump 1, an HST motor 2, and the HST closed circuit 5 is cooled by an oil flowing through the cooling line.

Abstract: The present invention relates to a display apparatus that is switched to an image signal via a wireless communication unit automatically when an image signal cable is disconnected from a connector. The image signal is transmitted by a cable 6 connected to the connector C1 of the apparatus D1 or a wireless LAN. When a switch S1 detects that the cable 6 is connected to the connector C1, a switching circuit 2 is switched to the cable-side to display the image signal via the cable. When the switch S1 detects disconnection of the cable 6, the switch circuit is switched to the side of a CPU 5 to display the image signal via the wireless LAN.