Construction machine

Patent metadata

Field	Value
Publication number	US-9080311-B2
Application number	US-201214351335-A
Country	US
Kind code	B2
Filing date	Nov 19, 2012
Priority date	Nov 29, 2011
Publication date	Jul 14, 2015
Grant date	Jul 14, 2015

Abstract

A control pressure switching valve is disposed between a displacement regulator and a pressure control valve. The control pressure switching valve is switched between a control position (j), in which a load sensing control pressure (PLS) is permitted to be outputted from the pressure control valve to the displacement regulator, and a control release position (k), in which the load sensing control pressure (PLS) to be outputted to the displacement regulator is reduced to a prescribed low pressure value. When the regeneration of a filter is determined to be necessary, the controller switches the control pressure switching valve to the control release position (k). When the load sensing control pressure (PLS) is reduced to the low pressure value with the control pressure switching valve switched to the control release position (k), the displacement regulator increases a delivery displacement of a hydraulic pump, thereby increasing rotational load of an engine.

First claim

The invention claimed is:

1. A construction machine, comprising:
an engine being a prime mover;
an exhaust gas purifying device disposed at an exhaust side of said engine and having a filter for purifying exhaust gas;
a pressure detector disposed in said exhaust gas purifying device to detect a differential pressure between front and rear sides of said filter;
a variable displacement type hydraulic pump driven by said engine and having a displacement variable portion;
a displacement regulator configured to variably control a delivery displacement of a pressurized oil by said hydraulic pump;
a hydraulic actuator driven by said pressurized oil delivered from said hydraulic pump;
a directional control valve configured to control a flow rate of said pressurized oil supplied from said hydraulic pump to said hydraulic actuator;
a pressure control valve configured to output a load sensing control pressure (PLS) to said displacement regulator such that a delivery pressure of said hydraulic pump becomes higher than a maximum load pressure of said hydraulic actuator by a target differential pressure;
a controller configured not only to control rotation of said engine but also to perform a filter regeneration process in said exhaust gas purifying device; and
a control pressure switching valve configured to be switched by a control signal from said controller to either a control position, in which said load sensing control pressure is permitted to be outputted without any change from said pressure control valve to said displacement regulator, or a control release position, in which said load sensing control pressure to be outputted to said displacement regulator is reduced to a prescribed low pressure value, is disposed between said displacement regulator and said pressure control valve,
wherein, when the regeneration of said filter is determined to be necessary based on said differential pressure between the front and rear sides of said filter detected by said pressure detector, said controller outputs said control signal, thereby switching said control pressure switching valve from said control position to said control release position, and
wherein, when said load sensing control pressure is reduced to said low pressure value with said control pressure switching valve switched from said control position to said control release position, said displacement regulator increases said delivery displacement of said hydraulic pump so as to raise a temperature of said exhaust gas of said engine to a temperature required for the regeneration of said filter, thereby increasing rotational load of said engine.

2. The construction machine according to claim 1 , further comprising:
an operation detector for detecting whether or not said directional control valve is in a neutral position,
wherein, when said operation detector detects that said directional control valve is in said neutral position and the regeneration of said filter is determined to be necessary, said controller outputs said control signal to switch said control pressure switching valve from said control position to said control release position.

3. The construction machine according to claim 1 , further comprising:
an operation lock detector for detecting whether or not said directional control valve is locked in a neutral position,
wherein, when said operation lock detector detects that said directional control valve is locked in said neutral position and the regeneration of said filter is determined to be necessary, said controller outputs said control signal to switch said control pressure switching valve from said control position to said control release position.

4. The construction machine according to claim 1 , wherein said displacement variable portion of said hydraulic pump is configured to be tilted by said displacement regulator to vary said delivery displacement of said pressurized oil, and
wherein said hydraulic pump is provided with a tilting position limiting device configured to permit said displacement variable portion to be tilted by said displacement regulator between a maximum tilting position and a minimum tilting position as long as said control pressure switching valve is being held in said control position and limit a tilting position of said displacement variable portion within a prescribed range in a case where said control pressure switching valve is switched from said control position to said control release position by said control signal from said controller.

5. The construction machine according to claim 1 , further comprising:
a plurality of said hydraulic actuators and a plurality of said directional control valves, as well as a plurality of pressure compensating valves for controlling each differential pressure between front and rear sides of said plurality of directional control valves,
wherein said pressure control valve controls said load sensing control pressure to be higher than said maximum load pressure of said plurality of hydraulic actuators by a target differential pressure.

Assignees

• Hitachi Construction Machinery

Inventors

• Yoshida Hajime
• Ishii Hajime
• Takebayashi Yoshifumi
• Noguchi Shuuhei
• Kurikuma Hajime

Classifications

• E02F9/2217

  with energy recovery arrangements, e.g. using accumulators, flywheels · CPC title

• E02F9/2285

  Pilot-operated systems · CPC title

• F02D29/04

  peculiar to engines driving pumps · CPC title

• E02F9/2225

  using pressure-compensating valves · CPC title

• F01N3/023

  using means for regenerating the filters, e.g. by burning trapped particles · CPC title