Work machine and control method for work machine

1. A work machine comprising:

a hydraulic cylinder that drives a working unit in a movable range;

a detection device that detects a posture of the working unit;

a control valve configured to adjusting an amount of a working oil supplied to the hydraulic cylinder;

a control device includes a computer system, configured

to detect an operation signal when the working unit is operated;

to determine whether the working unit at a stop position in the movable range has started moving based on the operation signal;

to set a deceleration section including an end position of the movable range and a deceleration ratio of the working unit in the deceleration section, based on the posture of the working unit in a stopped state at the stop position, and a threshold determined in accordance with the posture of the working unit in the stopped state at the stop position; and

to output a command signal to the control valve such that the working unit moves from the stop position to the end position based on the deceleration section and the deceleration ratio.

2. The work machine according to claim 1 , comprising an operation device that operates the hydraulic cylinder,

wherein the movable range between the stop position and the end position includes:

a section that includes the stop position, and where the working unit moves based on the operation of the operation device; and

the deceleration section that includes the end position, and where the working unit moves based on the command signal output by the control device.

3. The work machine according to claim 1 ,

wherein the posture of the working unit includes an angle of the working unit,

the threshold includes a first threshold and a second threshold smaller than the first threshold, and

the control device enlarges the deceleration section when the angle of the working unit in the stopped state is equal to or less than the first threshold.

4. The work machine according to claim 3 ,

wherein the deceleration section includes a first deceleration section where the working unit is decelerated with a predetermined deceleration, and a second deceleration section where the working unit is moved to the end position at a constant minimum deceleration ratio, and

the control device enlarges the deceleration section by enlarging the second deceleration section without changing the first deceleration section.

5. The work machine according to claim 3 ,

wherein

the control device increases a minimum deceleration ratio when the angle of the working unit in the stopped state is equal to or less than the second threshold.

6. The work machine according to claim 1 ,

wherein the end position is an upper end position when the working unit is raised.

7. The work machine according to claim 1 , which is a rearward small-swinging type excavator that includes a lower traveling body and an upper swing body,

wherein a counterweight arranged at a rear portion of the upper swing body is defined in a predetermined dimension related to a swinging radius of the upper swing body.

8. A control method for a work machine, comprising:

detecting a posture of a working unit driven by a hydraulic cylinder in a movable range;

determining whether the working unit at a stop position of the movable range has started moving based on an operation of the working unit;

setting a deceleration section including an end position of the movable range and a deceleration ratio of the working unit in the deceleration section, based on the posture of the working unit in a stopped state at the stop position, and a threshold determined in accordance with the posture of the working unit in the stopped state at the stop position; and

outputting a command signal to a control valve, which is configured to adjusting an amount of a working oil supplied to the hydraulic cylinder, such that the working unit moves from the stop position to the end position based on the deceleration section and the deceleration ratio.