Pipelayer

摘要

A pipelayer includes a pilot pressure control unit. The pilot pressure control unit supplies hydraulic fluid to a pilot port of a warm-up control valve so that the warm-up control valve enters an open state when a winch control valve is in the closed state. The pilot pressure control unit drains hydraulic fluid from the pilot port of the warm-up control valve so that the warm-up control valve enters the closed state when the winch control valve is in the open state. The stroke amount from the stroke end of the closed side of the spool of the warm-up control valve when the meter-out opening of the warm-up control valve is fully closed is larger than the stroke amount from the stroke end of the closed side of the spool of the winch control valve when the meter-in opening of the winch control valve is fully closed.

主权项

1. A pipelayer comprising:
an engine; a hydraulic pump driven by the engine; a hydraulic motor driven by hydraulic fluid discharged from the hydraulic pump; a winch driven by the hydraulic motor; a pump hydraulic circuit through which the hydraulic fluid discharged from the hydraulic pump passes; a drive hydraulic circuit connected to the hydraulic motor and through which hydraulic fluid for driving the hydraulic motor passes; a warm-up hydraulic circuit connected to the hydraulic motor and through which hydraulic fluid for warming up the hydraulic motor passes; a winch control valve provided between the pump hydraulic circuit and the drive hydraulic circuit, the winch control valve allowing communication between the pump hydraulic circuit and the drive hydraulic circuit in an open state, and the winch control valve shutting off communication between the pump hydraulic circuit and the drive hydraulic circuit in a closed state, the winch control valve having a meter-in opening arranged to communicate hydraulic fluid from the pump hydraulic circuit to the drive hydraulic circuit in the open state of the winch control valve, the winch control valve having a spool configured and arranged to be moved between an open-side stroke end and a closed-side stroke end of the winch control valve with a fully-closed stroke position where the meter-in opening becomes fully closed being located between the open-side stroke end and the closed-side stroke end; a warm-up control valve provided between the pump hydraulic circuit and the warm-up hydraulic circuit, the warm-up control valve allowing communication between the pump hydraulic circuit and the warm-up hydraulic circuit in an open state, and the warm-up control valve shutting off communication between the pump hydraulic circuit and the warm-up hydraulic circuit in a closed state, the warm-up control valve having a meter-out opening arranged to communicate hydraulic fluid from the warm-up hydraulic circuit to a drain circuit in the open state of the warm-up control valve, the warm-up control valve having a spool configured and arranged to be moved between an open-side stroke end and a closed-side stroke end of the warm-up control valve with a fully-closed stroke position where the meter-out opening becomes fully closed being located between the open-side stroke end and the closed-side stroke end; and a pilot pressure control unit configured to supply hydraulic fluid to a pilot port of the warm-up control valve so that the warm-up control valve enters the open state when the winch control valve is in the closed state, and the pilot pressure control unit being configured to drain hydraulic fluid from the pilot port of the warm-up control valve so that the warm-up control valve enters the closed state when the winch control valve is in the open state, a maximum stroke amount from the closed-side stroke end to the open-side stroke end of the winch control valve being substantially equal to a maximum stroke amount from the closed-side stroke end to the open-side stroke end of the warm-up control valve, a stroke amount from the closed-side stroke end to the fully-closed stroke position of the warm-up control valve being greater than a stroke amount from the closed-side stroke end to the fully-closed stroke position of the winch control valve.