Method for operating a hydraulic pump arrangement, and hydraulic pump arrangement

Abstract

A hydraulic pump arrangement of a portable hydraulic tool operates by an autonomous power supply or is releasably connected to the hydraulic tool by a hose and driven by an electrical power source. A load-dependent control of the hydraulic pump switches between a loaded state and a non-loaded state. A higher electrical power supply is implemented for the loaded state and a lower electrical power supply is implemented for the non-loaded state. To provide energy savings and problem-free operation even in different system pressure conditions, a method fixes a control variable for the load-dependent control that is dependent on work being performed by the hydraulic pump motor. A first threshold value at which switching from the non-loaded state to the loaded state takes place and a second threshold value at which switching from the loaded state to the non-loaded state takes place are assigned to the control variable.

1 . A method for operating a hydraulic pump arrangement of a portable hydraulic tool operated by an autonomous power supply, wherein the hydraulic pump arrangement is releasably connected to the hydraulic tool by a hose connection and is driven by an electrical power source and a load-dependent control of the hydraulic pump takes place by switching from a loaded state to a non-loaded state and vice versa, wherein a first higher electrical power supply is implemented for the loaded state and a second lower electrical power supply is implemented for the non-loaded state, the method comprising:
 establishing at least one control variable for the load-dependent control of the hydraulic pump arrangement and said control variable is dependent as an input value on work that to be performed by a motor of the hydraulic pump arrangement,   assigning to the control variables a first threshold value at which switching from the non-loaded state to the loaded state takes place, and   where necessary assigning to the control variables a second threshold value at which switching from the loaded state to the non-loaded state takes place.   
     
     
         2 . The method as claimed in  claim 1 ,
 wherein   two control variables and are established for the load-dependent control of the hydraulic pump arrangement and said control variables are dependent as input values on the work to be performed by the motor of the hydraulic pump arrangement,   a first threshold value at which switching from the non-loaded state to the loaded state takes place is assigned to the first control variables, and   a second threshold value at which switching from the loaded state to the non-loaded state takes place is assigned to the control variables.   
     
     
         3 . The method as claimed in  claim 1 ,
 wherein   after switching on the hydraulic pump arrangement but before the tool moves, the control process maintains the supply of power to the electric motor from the electrical power source at the second, lower electrical power supply level,   as the tool begins to move under no external load, the control process switches the supply of power to the motor from the electrical power source to the first, higher electrical power supply level.   
     
     
         4 . The method as claimed in  claim 1 ,
 wherein   as movement of the tool under load is stopped, a process of switching from the loaded state to the non-loaded state takes place and if the movement of the tool is continued, in turn a switching process from the non-loaded state to the loaded state takes place.   
     
     
         5 . The method as claimed in  claim 1 ,
 wherein   the second threshold value is a variable value and is updated during the operation.   
     
     
         6 . The method as claimed in  claim 1 ,
 wherein   a third threshold value is assigned to the control variables and a process of switching from the loaded state to the non-loaded state takes place in dependence upon the second threshold value and the third threshold value.   
     
     
         7 . The method as claimed in  claim 1 ,
 wherein   the control variable is the motor current.   
     
     
         8 . The method as claimed in  claim 1 ,
 wherein   the control variable is the pressure and/or the motor torque.   
     
     
         9 . The method as claimed in  claim 1 ,
 wherein   the control variable is a value related to time.   
     
     
         10 . A hydraulic pump device for driving a portable hydraulic tool comprising:
 a housing,   a hydraulic pump,   an electric motor for the purpose of driving the hydraulic pump,   a coupling device for the purpose of connecting the hydraulic pump device to flexible connecting lines for supplying the hydraulic tool with hydraulic fluid,   a control device for the load-dependent control of rotational speed of the motor;   means for detecting at least one of the control variables and said control variable is dependent as an input value upon work to be performed by the motor of the hydraulic pump arrangement,   means for comparing the detected control variables with a first threshold value,   where necessary means for comparing the detected control variables with a second threshold value,   means for switching the power supply of the motor for a loaded state or non-loaded state in dependence upon the detected control variables.   
     
     
         11 . The hydraulic pump device as claimed in  claim 10 ,
 wherein   the control variable is the motor current and/or the pressure and/or the motor torque.   
     
     
         12 . The hydraulic pump device as claimed in  claim 11 ,
 wherein   the process of determining the drop in voltage at a resistor comprises means for detecting the motor current.   
     
     
         13 . The hydraulic pump device as claimed in  claim 11 ,
 wherein   a current measuring device comprises means for detecting the motor current.   
     
     
         14 . The hydraulic pump device as claimed in  claim 10 ,
 further comprising   a storage medium in which the second threshold value is continuously updated.   
     
     
         15 . The hydraulic pump device as claimed in  claim 10 ,
 wherein   the control variable is measured over a time interval.   
     
     
         16 . The hydraulic pump device as claimed in  claim 10 ,
 wherein   the load state switching of the hydraulic pump arrangement comprises a pulse width modulation of the motor voltage.