Hybrid construction machine
First Claim
1. A hybrid construction machine, comprising:
- an engine;
at least one generator motor;
an electric storage device that is charged when the at least one generator motor is caused to perform a power generation operation and that is discharged when the at least one generator motor is caused to perform a powering operation;
an electric storage control system that computes a state of charge of the electric storage device and monitors the electric storage device;
a variable displacement hydraulic pump driven by torques of the engine and the at least one generator motor;
a plurality of hydraulic actuators driven by a hydraulic fluid delivered from the hydraulic pump;
a plurality of operation devices that output operation signals in response to operation amounts for the plurality of hydraulic actuators and instruct the hydraulic actuators to operate;
a controller that controls charge of electric power and discharge of electric power of the at least one generator motor and a delivery flow rate and output power of the hydraulic pump; and
a regulator that controls a displacement of the hydraulic pump to control the delivery flow rate of the hydraulic pump,wherein the controller is configured to;
compute present pump demanded power of the hydraulic pump on the basis of work related information,limit the present pump demanded power in response to a degree of reduction of a state of charge of the electric storage device acquired from the electric storage control system when the state of charge of the electric storage device is lower than a preset first threshold, and compute the limited present pump demanded power as the present pump target output power, andcompute the pump flow rate limiting command value on the basis of the present pump target output power in such a manner that the output power of the hydraulic pump does not exceed the pump target output power,wherein the regulator controls the displacement of the hydraulic pump and controls the delivery flow rate of the hydraulic pump on the basis of the pump flow rate limiting command value, andwherein the controller is further configured to;
set pump minimum power that is lower limit pump output power for limiting pump demanded power in response to the state of charge of the electric storage device, as a pump output power limiting effective threshold that is a second threshold,compute a pump output power limiting maximum value that is pump maximum power corresponding to a normal state in which the state of charge of the electric storage device is equal to or higher than the first threshold, and a pump output power limiting value that is pump output power corresponding to a present state of charge of the electric storage device,compute the present pump demanded power as a value independent of the state of charge of the electric storage device,compute a ratio of a difference between the pump output power limiting value and the second threshold, a difference between the pump output power limiting maximum value, and the second threshold as a limiting ratio that represents the degree of reduction of the state of charge of the electric storage device, andcompute the pump target output power by multiplying a difference between the present pump demanded power and the second threshold by the limiting ratio when the present pump demanded power is equal to or higher than the second threshold, thereby to limit the pump target output power by performing computation in such a manner that an output power part equal to or higher than the second threshold out of the pump target output power is limited in response to the degree of reduction of the state of charge of the electric storage device when the state of charge of the electric storage device is lower than the first threshold.
1 Assignment
0 Petitions
Accused Products
Abstract
It becomes possible to prevent deterioration of an electric storage device due to overdischarge of the electric storage device and engine stalling due to insufficient assist or disabled assist when a charge amount of the electric storage device falls, ensure that work is continuously conducted, suppress an operator from feeling discomfort in operation, and ensure favorable operability. A pump target output power computing section (21) computes present pump demanded power on the basis of work related information, limits the present pump demanded power in response to a degree of reduction of a state of charge of an electric storage device (12a) when the state of charge is lower than a preset threshold, and computes the limited present pump demanded power as present pump target output power. A pump flow rate limiting command value computing section (22) computes a pump flow rate limiting command value on the basis of the present pump target output power in such a manner that output power of a hydraulic pump (9) does not exceed the pump target output power.
7 Citations
6 Claims
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1. A hybrid construction machine, comprising:
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an engine; at least one generator motor; an electric storage device that is charged when the at least one generator motor is caused to perform a power generation operation and that is discharged when the at least one generator motor is caused to perform a powering operation; an electric storage control system that computes a state of charge of the electric storage device and monitors the electric storage device; a variable displacement hydraulic pump driven by torques of the engine and the at least one generator motor; a plurality of hydraulic actuators driven by a hydraulic fluid delivered from the hydraulic pump; a plurality of operation devices that output operation signals in response to operation amounts for the plurality of hydraulic actuators and instruct the hydraulic actuators to operate; a controller that controls charge of electric power and discharge of electric power of the at least one generator motor and a delivery flow rate and output power of the hydraulic pump; and a regulator that controls a displacement of the hydraulic pump to control the delivery flow rate of the hydraulic pump, wherein the controller is configured to; compute present pump demanded power of the hydraulic pump on the basis of work related information, limit the present pump demanded power in response to a degree of reduction of a state of charge of the electric storage device acquired from the electric storage control system when the state of charge of the electric storage device is lower than a preset first threshold, and compute the limited present pump demanded power as the present pump target output power, and compute the pump flow rate limiting command value on the basis of the present pump target output power in such a manner that the output power of the hydraulic pump does not exceed the pump target output power, wherein the regulator controls the displacement of the hydraulic pump and controls the delivery flow rate of the hydraulic pump on the basis of the pump flow rate limiting command value, and wherein the controller is further configured to; set pump minimum power that is lower limit pump output power for limiting pump demanded power in response to the state of charge of the electric storage device, as a pump output power limiting effective threshold that is a second threshold, compute a pump output power limiting maximum value that is pump maximum power corresponding to a normal state in which the state of charge of the electric storage device is equal to or higher than the first threshold, and a pump output power limiting value that is pump output power corresponding to a present state of charge of the electric storage device, compute the present pump demanded power as a value independent of the state of charge of the electric storage device, compute a ratio of a difference between the pump output power limiting value and the second threshold, a difference between the pump output power limiting maximum value, and the second threshold as a limiting ratio that represents the degree of reduction of the state of charge of the electric storage device, and compute the pump target output power by multiplying a difference between the present pump demanded power and the second threshold by the limiting ratio when the present pump demanded power is equal to or higher than the second threshold, thereby to limit the pump target output power by performing computation in such a manner that an output power part equal to or higher than the second threshold out of the pump target output power is limited in response to the degree of reduction of the state of charge of the electric storage device when the state of charge of the electric storage device is lower than the first threshold. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification