Unload circuit

Patent metadata

Field	Value
Publication number	US-10801531-B2
Application number	US-201716085767-A
Country	US
Kind code	B2
Filing date	Mar 24, 2017
Priority date	Mar 24, 2016
Publication date	Oct 13, 2020
Grant date	Oct 13, 2020

Abstract

The unload circuit includes a pump oil passage that connects between a hydraulic pump and a direction control valve, a tank oil passage that connects between the direction control valve and a hydraulic tank, a pressure compensating flow control valve interposed between the pump oil passage and the tank oil passage, a pilot operated relief valve interposed between the pump oil passage and the tank oil passage, and an unloading solenoid valve interposed in a vent oil passage of the pilot operated relief valve. The failure diagnosis device includes a pressure sensor that measures a pressure of the pump oil passage, and a controller that receives a pressure signal from the pressure sensor. The controller performs failure diagnosis of the unload circuit based on a differential pressure between a first pump oil passage pressure during unloading and a second pump oil passage pressure during on-loading.

First claim

The invention claimed is:

1. An unload circuit for returning hydraulic oil from a hydraulic pump to a hydraulic tank with no load, the unload circuit comprising:
a pump oil passage that connects between the hydraulic pump and a direction control valve,
a tank oil passage that connects between the direction control valve and the hydraulic tank,
a pressure compensating flow control valve interposed between the pump oil passage and the tank oil passage,
a pilot operated relief valve interposed between the pump oil passage and the tank oil passage,
an unloading solenoid valve interposed in a vent oil passage of the pilot operated relief valve,
a pressure sensor that measures a pressure of the pump oil passage; and
a controller that controls an energizing state of the unloading solenoid valve and that receives a pressure signal from the pressure sensor, wherein
the controller performs failure diagnosis of the unload circuit based on a differential pressure between a first pump oil passage pressure measured by the pressure sensor during an unloaded state when the controller controls the unloading solenoid valve to a first energizing state and a second pump oil passage pressure measured by the pressure sensor during an on-load state when the controller controls the unloading solenoid valve to a second energizing state.

2. The unload circuit according to claim 1 , wherein the controller diagnoses that the unload circuit is failed when the differential pressure is equal to or less than a predetermined value.

3. The unload circuit according to claim 1 , wherein the controller performs failure diagnosis of the unload circuit on condition that the hydraulic pump starts to be driven.

4. The unload circuit according to claim 3 , wherein
the hydraulic pump is driven via a power take-off (PTO), and
the controller performs failure diagnosis of the unload circuit based on a differential pressure between the first pump oil passage pressure after the unloaded state is maintained for a predetermined time and the second pump oil passage pressure after switching to the on-load state after the hydraulic pump starts to be driven.

Assignees

• Tadano Ltd

Inventors

• Kawabuchi Naoto
• Yoshida Naofumi
• Fukumori Yasuhiro

Classifications

• B66C23/90 Primary

  Devices for indicating or limiting lifting moment · CPC title

• E02F9/24

  Safety devices {, e.g. for preventing overload (E02F9/226 takes precedence)} · CPC title

• F15B11/028

  for controlling the actuating force (F15B11/024 takes precedence) · CPC title

• F15B20/00

  Safety arrangements for fluid actuator systems; Applications of safety devices in fluid actuator systems; Emergency measures for fluid actuator systems · CPC title

• F15B20/004

  Fluid pressure supply failure · CPC title