EP-4190979-B1 - WORK MACHINE

EP4190979B1EP 4190979 B1EP4190979 B1EP 4190979B1EP-4190979-B1

Inventors

HOSHINO MASATOSHI
HIJIKATA SEIJI
TSURUGA YASUTAKA
YAGISAWA Ryou
FURUKAWA Shou

Dates

Publication Date: 20260506
Application Date: 20211217

Claims (3)

A work machine (1) comprising: an engine (10); a variable displacement hydraulic pump (12) that discharges a hydraulic oil by using a driving force of the engine (10); a regulator (18) that varies a discharge rate of the hydraulic pump (12); a hydraulic actuator (4d, 4e, 4f) that works by using the hydraulic oil discharged from the hydraulic pump (12); a rotational speed sensor (17) that detects a rotational speed of the engine (10); and a controller (20) that controls the rotational speed of the engine (10) and the discharge rate of the hydraulic pump (12), characterized in that the controller (20) is configured to: in a state where an power of the engine (10) or an output of the hydraulic pump (12) has increased to an increase threshold with the rotational speed detected by the rotational speed sensor (17) being at a first rotational speed, raise the rotational speed of the engine (10) from the first rotational speed to a second rotational speed that is higher than the first rotational speed; in a process of raising the rotational speed of the engine (10) to the second rotational speed, output, to the regulator (18), a signal instructing reduction in the discharge rate of the hydraulic pump (12) so as to keep the power of the engine (10) or the output of the hydraulic pump (12) constant; and after the rotational speed detected by the rotational speed sensor (17) has reached the second rotational speed, output, to the regulator (18), a signal instructing increase in the discharge rate of the hydraulic pump (12) so as to make the power of the engine (10) or the output of the hydraulic pump (12) have a value corresponding to a request load.
The work machine (1) according to claim 1, wherein in a process of raising the rotational speed of the engine (10) to the second rotational speed, the controller (20) outputs, to the regulator (18), a signal instructing reduction in the discharge rate of the hydraulic pump (12) so as to make the power of the engine (10) or the output of the hydraulic pump (12) match the increase threshold.
The work machine (1) according to claim 1, wherein in a state where the power of the engine (10) or the output of the hydraulic pump (12) has decreased to a decrease threshold with the rotational speed detected by the rotational speed sensor (17) being at the second rotational speed, the controller (20) lowers the rotational speed of the engine (10) from the second rotational speed to the first rotational speed; and in a process of lowering the rotational speed of the engine (10) to the first rotational speed, the controller (20) outputs, to the regulator (18), a signal instructing adjustment of the discharge rate of the hydraulic pump (12) so as to make the power of the engine (10) or the output of the hydraulic pump (12) have a value corresponding to a request load.

Description

TECHNICAL FIELD The present invention relates to a work machine equipped with a variable displacement hydraulic pump. BACKGROUND ART Conventionally, a work machine equipped with an engine, a variable displacement hydraulic pump that discharges hydraulic oil by using a driving force of the engine, a regulator that varies the discharge rate of the hydraulic pump, and a hydraulic actuator that works by using the hydraulic oil discharged from the hydraulic pump has been known. In the work machines as described above, there has been known a technique of, for making the hydraulic actuator work at low load, reducing the rotational speed of the engine and driving the engine with high torque while, for making the hydraulic actuator work at high load, increasing the rotational speed of the engine enables both improvement in fuel efficiency and high power to be achieved (for example, see Patent Literature 1). CITATION LIST PATENT LITERATURE Patent Literature 1: JP-A-2007-120426 A work machine in accordance with the preamble of claim 1 is known from EP 3 133 212 A1. SUMMARY OF INVENTION TECHNICAL PROBLEM Here, in order to raise the rotational speed of the engine for the high load, it is necessary to provide not only the torque for an increased load but also the torque transiently necessary for the inertial force of the rotating bodies (engine and hydraulic pump). With this regard, the technique according to Patent Literature 1 has a problem that raising the rotational speed of the engine takes time, and thus results in reduction in workability. The present invention has been made in view of the circumstances above, and an object of the present invention is to provide a technique for achieving both low fuel consumption and ensuring of workability of a work machine that allows the rotational speed of an engine to be switched in accordance with load of a hydraulic actuator. SOLUTION TO PROBLEM In order to achieve the object described above, the present invention provides a work machine comprising: an engine; a variable displacement hydraulic pump that discharges a hydraulic oil by using a driving force of the engine; a regulator that varies a discharge rate of the hydraulic pump; a hydraulic actuator that works by using the hydraulic oil discharged from the hydraulic pump; a rotational speed sensor that detects a rotational speed of the engine; and a controller that controls the rotational speed of the engine and the discharge rate of the hydraulic pump, wherein the controller is configured to: in a state where an power of the engine or an output of the hydraulic pump has increased to an increase threshold with the rotational speed detected by the rotational speed sensor being at a first rotational speed, raise the rotational speed of the engine from the first rotational speed to a second rotational speed that is higher than the first rotational speed; in a process of raising the rotational speed of the engine to the second rotational speed, output, to the regulator, a signal instructing reduction in the discharge rate of the hydraulic pump so as to keep the power of the engine or the output of the hydraulic pump constant; and after the rotational speed detected by the rotational speed sensor has reached the second rotational speed, output, to the regulator, a signal instructing increase in the discharge rate of the hydraulic pump so as to make the power of the engine or the output of the hydraulic pump have a value corresponding to a request load. ADVANTAGEOUS EFFECTS OF INVENTION According to the present invention, it is possible to achieve both low fuel consumption and ensuring of workability of a work machine that allows the rotational speed of an engine to be switched in accordance with load of a hydraulic actuator. The problems, configurations, and advantageous effects other than those described above will be clarified by explanation of an embodiment below. BRIEF DESCRIPTION OF DRAWINGS [FIG. 1] FIG. 1 is a side view of a hydraulic excavator.[FIG. 2] FIG. 2 illustrates a drive circuit of a hydraulic excavator.[FIG. 3] FIG. 3 is a hardware configuration diagram of a hydraulic excavator.[FIG. 4] FIG. 4 illustrates a relation between engine rotational speed and engine torque.[FIG. 5] FIG. 5 illustrates a flowchart of rotational speed control processing.[FIG. 6A] FIG. 6A illustrates a relation between an amount of fuel injection and engine torque.[FIG. 6B] FIG. 6B illustrates a relation between an operation amount of a boom operation lever and a flow rate of a pump.[FIG. 6C] FIG. 6C illustrates a relation between output of a pump and engine torque.[FIG. 7A] FIG. 7A illustrates temporal change in engine rotational speed in the rotational speed control processing.[FIG. 7B] FIG. 7B illustrates temporal change in the engine torque in the rotational speed control processing.[FIG. 7C] FIG. 7C illustrates temporal change in the engine power in the rotational speed control processing.[FIG. 8] FIG. 8 illustrates a relation betwe