Hydraulic system and emergency operation method

Patent metadata

Field	Value
Publication number	US-10995778-B2
Application number	US-201716089718-A
Country	US
Kind code	B2
Filing date	Mar 31, 2017
Priority date	Mar 31, 2016
Publication date	May 4, 2021
Grant date	May 4, 2021

Abstract

This hydraulic system is provided with: a hydraulic pump; a pilot-type control valve; an electromagnetic proportional valve; a controller; and a pilot pressure switching unit which is capable of switching the electromagnetic proportional valve supply pressure to a first pressure during a normal operation, or to a second pressure lower than the first pressure. The control valve is provided with a bleed-off passage, and is capable of controlling the operating oil pressure supplied to the actuator, according to the opening area thereof. During an emergency operation, the electromagnetic proportional valve supply pressure is switched from the first pressure to the second pressure, the electromagnetic proportional valve is brought into a fully opened state, and the operating oil discharge amount from the hydraulic pump increases and decreases, and the operating oil pressure increases and decreases, and thus the operating speed of the actuator is controlled.

First claim

The invention claimed is:

1. A hydraulic system comprising:
a hydraulic pump;
a pilot-type control valve which supplies an operating oil pressure from the hydraulic pump to an actuator of a working machine;
a pilot pressure source;
an electromagnetic proportional valve which supplies a pilot pressure to the control valve when receiving an electromagnetic proportional valve supply pressure from the pilot pressure source;
an operation lever which receives an operation for operating the actuator;
a controller which controls the electromagnetic proportional valve based on an operation signal from the operation lever; and
a pilot pressure switching unit in which the electromagnetic proportional valve supply pressure is capable of being switched,
wherein the control valve has a bleed-off passage whose opening area increases and decreases according to a stroke of a spool based on the pilot pressure, and is capable of controlling the operating oil pressure to be supplied to the actuator according to the opening area, and
during an emergency operation in which the controller is not capable of controlling the electromagnetic proportional valve,
the electromagnetic proportional valve is brought into a fully opened state,
the pilot pressure switching unit switches the electromagnetic proportional valve supply pressure from a first pressure to a second pressure in order to prevent generation of the operating oil pressure capable of activating the actuator, when an operating oil with a minimum discharge amount passes through the bleed-off passage, the first pressure being a pressure during normal operation, the second pressure being a pressure smaller than the first pressure,
the control valve is operated by the pilot pressure based on the second pressure through the electromagnetic proportional valve, and
as the operating oil discharge amount from the hydraulic pump increases and decreases, the operating oil pressure increases and decreases, and an operation speed of the actuator is controlled.

2. The hydraulic system according to claim 1 , further comprising:
an emergency operation circuit which controls the electromagnetic proportional valve to the fully opened state based on an operation signal from the operation lever during the emergency operation.

3. The hydraulic system according to claim 1 , wherein the electromagnetic proportional valve has a detent type emergency manual operation function and is manually switched to the fully opened state during the emergency operation.

4. The hydraulic system according to claim 1 ,
wherein the hydraulic pump is of a fixed displacement type,
a power source of the hydraulic pump is an engine of the working machine, and
the operating oil discharge amount from the hydraulic pump increases and decreases by an accelerator operation which increases and decreases a rotational speed of the engine.

5. An emergency operation method of a hydraulic system,
wherein the hydraulic system includes:
a hydraulic pump;
a pilot-type control valve which supplies an operating oil pressure from the hydraulic pump to an actuator of a working machine;
a pilot pressure source;
an electromagnetic proportional valve which supplies a pilot pressure to the control valve when receiving an electromagnetic proportional valve supply pressure from the pilot pressure source;
an operation lever which receives an operation for operating the actuator;
a controller which controls the electromagnetic proportional valve based on an operation signal from the operation lever; and
a pilot pressure switching unit in which the electromagnetic proportional valve supply pressure is capable of being switched,

wherein the control valve has a bleed-off passage whose opening area increases and decreases according to a stroke of a spool based on the pilot pressure, and is capable of controlling the operating oil pressure to be supplied to the actuator according to the opening area, and
wherein the emergency operation method comprises:
during an emergency operation in which the controller is not capable of controlling the electromagnetic proportional valve,
a step of bringing the electromagnetic proportional valve into a fully opened state;
a step of switching the electromagnetic proportional valve supply pressure from a first pressure to a second pressure in order to prevent generation of the operating oil pressure capable of activating the actuator, when an operating oil with a minimum discharge amount passes through the bleed-off passage, the first pressure being a pressure during a normal operation, the second pressure being a pressure smaller than the first pressure;
a step of operating the control valve by the pilot pressure based on the second pressure through the electromagnetic proportional valve in the fully opened state; and
a step of, by increasing and decreasing the operating oil discharge amount from the hydraulic pump, increasing and decreasing the operating oil pressure and controlling an operation speed of the actuator.

Assignees

• Tadano Ltd

Inventors

• Kawabuchi Naoto
• Yoshida Naofumi
• Masuda Naotaka
• Fukumori Yasuhiro

Classifications

• F15B2211/8606

  the abnormal condition being a shock · CPC title

• F15B2211/6651

  Control of the prime mover, e.g. control of the output torque or rotational speed · CPC title

• F15B2211/7058

  Rotary output members · CPC title

• B66C13/22

  for electric drives (transmitting control pulses B66C13/40; systems or devices of general application H02P) · CPC title

• F15B20/002 Primary

  Electrical failure · CPC title