Construction machine

Patent metadata

Field	Value
Publication number	US-11118328-B2
Application number	US-201917056288-A
Country	US
Kind code	B2
Filing date	May 20, 2019
Priority date	Jun 25, 2018
Publication date	Sep 14, 2021
Grant date	Sep 14, 2021

Abstract

An object of the present invention is to provide a construction machine capable of suppressing lugging down of an engine irrespective of contents of operation of an operator and the load state of a hydraulic actuator. A controller 50 includes: a demanded torque estimating section 50 c configured to estimate demanded torque as torque demanded from an engine 9 by the first hydraulic pump on the basis of a demanded velocity of a first hydraulic actuator 1 and a load pressure on the first hydraulic actuator; a demanded velocity limiting section 50 d configured to, in a case in which a demanded torque change rate as a change rate of the demanded torque exceeds a predetermined change rate, limit the demanded velocity such that the demanded torque change rate becomes equal to or lower than the predetermined change rate; and a command calculating section 50 e configured to calculate a delivery flow rate of the first hydraulic pump on the basis of the demanded velocity of the first hydraulic actuator, the demanded velocity being limited by the demanded velocity limiting section.

First claim

The invention claimed is:

1. A construction machine comprising:
an engine;
a variable displacement first hydraulic pump driven by the engine;
a first hydraulic actuator driven by pressure liquid delivered from the first hydraulic pump;
an operation device configured to give instructions for an operation direction and a demanded velocity of the first hydraulic actuator; and
a controller configured to control a delivery flow rate of the first hydraulic pump according to an input from the operation device;
wherein
the construction machine comprises a pressure sensor configured to detect a load pressure on the first hydraulic actuator, and
the controller includes:
a demanded torque estimating section configured to estimate demanded torque as torque demanded from the engine by the first hydraulic pump on a basis of the demanded velocity of the first hydraulic actuator and the load pressure on the first hydraulic actuator;
a demanded velocity limiting section configured to, in a case in which a demanded torque change rate as a change rate of the demanded torque exceeds a predetermined change rate, limit the demanded velocity such that the demanded torque change rate becomes equal to or lower than the predetermined change rate; and
a command calculating section configured to calculate the delivery flow rate of the first hydraulic pump on a basis of the demanded velocity of the first hydraulic actuator, the demanded velocity being limited by the demanded velocity limiting section.

2. The construction machine according to claim 1 , comprising:
a plurality of hydraulic pumps including the first hydraulic pump;
a plurality of hydraulic actuators including the first hydraulic actuator; and
a plurality of control valves capable of changing connection between the plurality of hydraulic actuators and the plurality of hydraulic pumps,
wherein
the pressure sensor is able to detect respective load pressures on the plurality of hydraulic actuators,
the operation device is able to give instructions for respective operation directions and respective demanded velocities of the plurality of hydraulic actuators,
the demanded torque estimating section is configured to estimate the demanded torque as a sum of respective torques demanded from the engine by the plurality of hydraulic pumps on a basis of the respective demanded velocities and the respective load pressures on the plurality of hydraulic actuators,
the demanded velocity limiting section is configured to, in a case in which the demanded torque change rate as the change rate of the demanded torque exceeds the predetermined change rate, limit the respective demanded velocities of the plurality of hydraulic actuators such that the demanded torque change rate becomes equal to or lower than the predetermined change rate, and
the command calculating section is configured to determine assignment of the plurality of hydraulic pumps to the plurality of hydraulic actuators and calculate respective delivery flow rates of the plurality of hydraulic pumps on a basis of the respective demanded velocities of the plurality of hydraulic actuators, the respective demanded velocities being limited by the demanded velocity limiting section.

3. The construction machine according to claim 2 , wherein
the command calculating section is configured to reduce the number of hydraulic pumps assigned to one hydraulic actuator of the plurality of hydraulic actuators according to the demanded velocity of the one hydraulic actuator, the demanded velocity being limited by the demanded velocity limiting section, in a case in which the demanded torque change rate exceeds the predetermined change rate in a state in which two or more hydraulic pumps are assigned to the one hydraulic actuator.

4. The construction machine according to claim 2 , wherein
the plurality of hydraulic actuators include one or more hydraulic cylinders and one or more hydraulic motors, and
the command calculating section is configured to, in a case in which the demanded torque change rate exceeds the predetermined change rate in a state in which the hydraulic cylinder and the hydraulic motor are driven simultaneously, calculate the respective delivery flow rates of the plurality of hydraulic pumps such that the demanded torque of a hydraulic pump assigned to the hydraulic motor is equal to or less than a predetermined ratio of output power torque of the engine.

5. The construction machine according to claim 4 , wherein
the predetermined ratio is set at equal to or less than 50%.

6. The construction machine according to claim 2 , wherein
the plurality of hydraulic pumps are each a double-delivery type hydraulic pump having a pair of input and output ports, and
the plurality of control valves are a plurality of selector valves capable of changing connection between the plurality of hydraulic pumps and the plurality of hydraulic actuators.

7. The construction machine according to claim 2 , wherein
the plurality of hydraulic pumps are each a single-delivery type hydraulic pump having a suction port and a delivery port, and
the plurality of control valves are a plurality of flow control valves capable of adjusting directions and flow rates of the pressure liquid supplied from the plurality of hydraulic pumps to the plurality of hydraulic actuators.

Assignees

• Hitachi Construction Mach Co

Inventors

• Shimizu Juri
• Hiraku Kenji
• Takahashi Hiromasa
• Saitou Teppei
• SUGIKI Shouhei

Classifications

• F15B2211/426

  electrically or electronically · CPC title

• F15B2211/41581

  being connected to an output member and a return line · CPC title

• F15B2211/3059

  having multiple valves for multiple output members · CPC title

• F15B11/165

  for adjusting the pump output or bypass in response to demand · CPC title

• F15B11/0423

  by controlling pump output or bypass, other than to maintain constant speed · CPC title