Construction machine

A construction machine comprising:

• a machine body;
• a boom attached to the machine body so as to be rotatable in an upward/downward direction;
• an arm attached to a front end portion of the boom so as to be rotatable in the upward/downward direction or in a forward/backward direction;
• a first hydraulic pump and second hydraulic pump that are of variable displacement type;
• a first regulator and a second regulator that adjust displacement volumes of the first hydraulic pump and the second hydraulic pump;
• a boom cylinder that is supplied with hydraulic fluids delivered from the first hydraulic pump and the second hydraulic pump and drives the boom;
• an arm cylinder that is supplied with hydraulic fluids delivered from the first hydraulic pump and the second hydraulic pump and drives the arm;
• a boom operation device that gives an instruction about operation of the boom;
• an arm operation device that gives an instruction about operation of the arm;
• an operation amount sensor that senses operation amounts of the boom operation device and the arm operation device;
• and
• a controller that controls the first regulator and the second regulator according to the operation amounts of the boom operation device and the arm operation device, wherein
• the construction machine comprises a pressure sensor that senses a delivery pressure of the second hydraulic pump,
• the controller is configured to
• control the second regulator according to a maximum value among a target displacement volume of the second hydraulic pump that is based on a boom raising operation amount of the boom operation device, and a target displacement volume of the second hydraulic pump that is based on an arm crowding operation amount of the arm operation device;
• control the first regulator according to a maximum value among a target displacement volume of the first hydraulic pump that is based on the boom raising operation amount, and a target displacement volume of the first hydraulic pump that is based on the arm crowding operation amount if the boom raising operation amount is smaller than a predetermined operation amount or if the delivery pressure of the second hydraulic pump is equal to or higher than a predetermined pressure;
• and
• control the first regulator according only to the target displacement volume of the first hydraulic pump that is based on the boom raising operation amount if the boom raising operation amount is equal to or larger than the predetermined operation amount, and the delivery pressure of the second hydraulic pump is lower than the predetermined pressure.