Hydraulic Machinery

Abstract

The invention addresses the problem of avoiding insufficient flow being supplied to the hydraulic actuator and speed becoming insufficient during light loads in hydraulic machinery such as hydraulic shovels when the engine rotation speed is set low during normal work. The solution is to increase the discharge flow of the hydraulic pump ( 2 ) by increasing the rotation speed of the engine ( 1 ) above the target rotation speed set by the engine rotation speed-setting means ( 14 ) when the hydraulic pump ( 2 ) discharge pressure is at the light load pump discharge pressure, the hydraulic pump ( 2 ) inclination angle is at the maximum inclination angle, and the negative control signal pressure is at the signal pressure when the hydraulic actuator-operating means ( 7 ) is at full operation.

1 . A hydraulic machine comprising:
 an engine;   a variable capacity hydraulic pump driven by the engine, and having a capacity and operable as a hydraulic pressure supply source;   an adjustable control coupled to the hydraulic pump, the adjustable control disposed to vary the capacity of the hydraulic pump;   a hydraulic actuator fluidly coupled to and operable by the hydraulic pump;   a control valve fluidly disposed between the hydraulic pump and the hydraulic actuator that is adapted to be displaced a displacement amount in accordance with an operation amount of an operator actuator control so as to control a pressure oil supply flow rate from the hydraulic pump to the hydraulic actuator;   a negative control circuit that outputs a negative control signal pressure to the adjustable control to increase or decrease a discharge flow rate of the hydraulic pump in accordance with the displacement amount of the control valve;   an engine rotation speed control operable to set a target rotation speed of the engine; and   an engine control device that controls a rotation speed of the engine based on the target rotation speed set with the engine rotation speed control;   a pump pressure detection sensor disposed and adapted to detect a discharge pressure of the hydraulic pump;   a pump capacity detection sensor disposed and adapted to detect the capacity of the hydraulic pump; and   a negative control signal pressure detection sensor disposed and adapted to detect the negative control signal pressure,   wherein the engine control device is adapted to increase the engine rotation speed to be higher than the target rotation speed set with the engine rotation speed control, when the discharge pressure of the hydraulic pump detected by the pump pressure detection sensor means is not larger than a preset pump discharge pressure in a light load state, the pump capacity detected by the pump capacity detection sensor means is at a maximum capacity of the hydraulic pump, and the negative control signal pressure detected by the negative control signal pressure detection sensor is not larger than a preset negative control signal pressure in a fully operated state of the operator actuator control.   
     
     
         2 . The machine as claimed in  claim 1  wherein the hydraulic actuator includes at least one of a drive motor, a swing motor, and a cylinder. 
     
     
         3 . A method of controlling a hydraulic circuit including
 providing to an engine control device a signal indicative of pump discharge pressure,   providing to the engine control device a signal indicative of an inclination angle of an adjustable swashplate associated with a variable capacity hydraulic pump,   providing to the engine control device a signal indicative of a negative control pressure,   providing to the engine control device a signal indicative of a setting of a rotation speed of an engine disposed to drive the hydraulic pump,   determining whether the negative control signal pressure is not larger than a preset signal pressure,   determining whether the pump discharge pressure is not larger than a preset pump pressure,   determining whether the inclination angle of the adjustable swashplate is at a maximum inclination angle at which the capacity of the hydraulic pump is at a maximum,   if the negative control signal pressure is not larger than the preset signal pressure, if the pump discharge pressure is not larger than the preset pump pressure, and if the inclination angle is at the maximum inclination angle, then performing an engine rotation speed increasing control to increase the engine rotation speed up to a light-load state rotation speed higher than a target rotation speed set by an engine rotation speed control.   
     
     
         4 . The method of  claim 3  further including controlling the engine rotation speed to achieve the target rotation speed set with the engine rotation speed control if any of the following is determined:
 the negative control signal pressure is larger than the preset signal pressure, 
 the pump discharge pressure is larger than the preset pump pressure, and 
 the inclination angle is not at the maximum inclination angle. 
 
     
     
         5 . The method of  claim 3  wherein providing a signal indicative of pump discharge pressure includes sensing pressure within the variable capacity hydraulic pump. 
     
     
         6 . The method of  claim 3  wherein providing a signal indicative of the inclination angle includes sensing the inclination angle of the adjustable swashplate associated with the pump, 
     
     
         7 . The method of  claim 3  wherein providing a signal indicative of a setting of a rotation speed of an engine disposed to drive the hydraulic pump includes determining the position of an engine rotation speed control. 
     
     
         8 . The method of  claim 3  wherein providing a signal indicative of a negative control pressure includes sensing the negative control signal pressure. 
     
     
         9 . The method of  claim 3  further including setting the preset signal pressure based upon a negative control signal pressure when at least one operator actuator control is in a fully operated state. 
     
     
         10 . The method of  claim 9  wherein the fully operated state is when at least one control valve is displaced by a maximum displacement amount. 
     
     
         11 . The method of  claim 3  further including setting the preset pump pressure as a pump discharge pressure in a light load state. 
     
     
         12 . The method of  claim 3  wherein the light-load state rotation speed is higher than the target rotation speed set with the engine rotation speed control by a predetermined rotation speed. 
     
     
         13 . The method of  claim 12  wherein the predetermined rotation speed is set for each target rotation speed. 
     
     
         14 . The method of  claim 4  wherein providing a signal indicative of pump discharge pressure includes sensing pressure within the variable capacity hydraulic pump. 
     
     
         15 . The method of  claim 4  wherein providing a signal indicative of the inclination angle includes sensing the inclination angle of the adjustable swashplate associated with the pump. 
     
     
         16 . The method of  claim 4  wherein providing a signal indicative of a setting of a rotation speed of an engine disposed to drive the hydraulic pump includes determining the position of an engine rotation speed control. 
     
     
         17 . The method of  claim 4  wherein providing a signal indicative of a negative control pressure includes sensing the negative control signal pressure. 
     
     
         18 . The method of  claim 4  further including setting the preset signal pressure based upon a negative control signal pressure when at least one operator actuator control is in a fully operated state. 
     
     
         19 . The method of  claim 4  further including setting the preset pump pressure as a pump discharge pressure in a light load state. 
     
     
         20 . The method of  claim 4  further including setting the preset signal pressure based upon a negative control signal pressure when at least one operator actuator control is in a fully operated state, and setting the preset pump pressure as a pump discharge pressure in a light load state, and wherein providing a signal indicative of pump discharge pressure includes sensing pressure within the variable capacity hydraulic pump, providing a signal indicative of the inclination angle includes sensing the inclination angle of the adjustable swashplate associated with the pump, providing a signal indicative of a setting of a rotation speed of an engine disposed to drive the hydraulic pump includes determining the position of an engine rotation speed control, and providing a signal indicative of a negative control pressure includes sensing the negative control signal pressure.