Patent Publication Number: US-7904224-B2

Title: Excavator control mode switching device and excavator

Description:
This application is a U.S. National Phase Application under 35 USC 371 of International Application PCT/JP2006/300246 filed Jan. 12, 2006. 
     TECHNICAL FIELD 
     The present invention relates to a control-mode switching device of a construction machine and a construction machine. More specifically, it relates to a control-mode switching device and a construction machine that are capable of easily switching the operation modes of a construction machine such as an excavator. 
     BACKGROUND ART 
     A hydraulic excavator as shown in  FIGS. 13A and 13B  is known as a construction machine for excavating and loading earth and sand, which includes: a traveling hydraulic motor  1  for traveling a lower traveling body a; a swing hydraulic motor  2  for swinging an upper swing body b; work equipments c (a boom  3 , an arm  4  and a bucket  5 ) mounted on the front side of the upper swing body b; and a boom cylinder  6 , arm cylinder  7  and bucket cylinder  8  for driving the work equipments c. 
     The hydraulic excavator performs a sequence of operations during an excavating process such as excavation, lift-up swing, earth removal and lift-down swing. Especially during the lift-up swing, while the boom is lifted up and the arm is dumped (as shown in  FIG. 13A ), swing operation is conducted toward a loading platform of a dumper truck d that is stopped around forty-five, ninety or one-hundred-eighty degrees from the excavated point (as shown in  FIG. 13B ). 
     When the swing and boom movements or the swing and arm movements are concurrently conducted, pressure in swing circuit is influenced by boom circuit or arm circuit, where, if the boom circuit or the arm circuit is in low pressure, the swing circuit is also in low pressure, so that smooth swing movement may not be conducted. 
     Further, since the swing angle differs according to the stop position of the dumper truck d, an operator controls spool-opening degree of flow control valve of hydraulic actuators for each operation to control supply flow rate toward respective circuits to match both of the movements. For instance, the supply flow rate to the respective circuits is controlled so that: when the dumper truck d is stopped at forty-five degrees position from the excavated point, the boom-lift movement is accelerated and swing speed is decelerated; and, when the dumper truck d is stopped at one-hundred eighty degrees position from the excavated point, the swing speed is accelerated and boom-lift speed is decelerated, thereby matching both of the movements. However, such operation is very difficult and exhausting. 
     Accordingly, the Applicant of the present application has proposed a hydraulic control circuit of a hydraulic excavator for resolving the above problems (Patent Document 1). 
     Specifically, the hydraulic control circuit of a hydraulic excavator includes: hydraulic actuators respectively for boom-lifting, arm-lifting and swinging movement; boom control lever; arm control lever; swing control lever; hydraulic circuit for driving the hydraulic actuators based on the operation on the control levers; and an operation-mode selecting switch. When one of boom-priority mode, swing-priority mode and standard mode is selected by the operation mode selecting switch, pressure oil is preferentially flowed to the hydraulic circuit corresponding to the selected mode. 
     [Patent Document] Japanese Patent Publication No. 2583148 
     DISCLOSURE OF THE INVENTION 
     Problem to be Solved by the Invention 
     However, in the hydraulic control circuit of hydraulic excavator as described in the above patent document 1, when the boom-priority mode or the swing-priority mode is to be selected while operating the boom control lever, arm control lever and swing control lever, one hand has to be released from the control lever in order to switch the operation mode selecting switch, resulting in troublesome switching operation. 
     An object of the present invention is to provide a control-mode switching device and a construction machine capable of easily switching operation modes. 
     Means for Solving the Problems 
     A control-mode switching device of a construction machine according to an aspect of the present invention includes: a plurality of actuators that conduct different movement; a driving means that respectively drives the plurality of actuators; a plurality of control levers that command movements of the driving means; a plurality of detecting means that respectively detect arrival of the control levers to the proximity of ends of the control ranges of the control levers; a mode judging means that judges whether a priority operation mode in which output of selected one or more of the driving means becomes larger than that in a normal mode or power ratio of the selected one or more of the driving means as compared to other driving means becomes larger is taken or not based on a combination of detected conditions of the detecting means; and a drive controlling means that, when it is judged by the mode judging means that the priority operation mode is taken, controls the driving means so that the output of the selected one or more of the driving means becomes larger than that in the normal mode or the power ratio of the selected one or more of the driving means as compared to other driving means becomes larger. 
     The output of the driving means is speed, power and the like. Further, that “output of selected one or more of the driving means becomes larger than that in a normal mode” means that the output during the priority operation mode becomes larger than the output during the standard operation mode. That “the power ratio of the selected one or more of the driving means as compared to the other driving means becomes larger” means all of the situations where the power ratio is relatively increased in relation to the output of the other driving means as in a case where the output of the other driving means is lowered without changing the output of the selected one or more of the driving means. 
     According to the above arrangement, when the control lever is manipulated, the actuator is driven via the driving means. Accordingly, desired operation can be executed by manipulating a plurality of control levers to simultaneously or sequentially drive the plurality of actuators. 
     During the operation, when it is desired to, for instance, accelerate a certain actuator, the control lever for driving the actuator is manipulated to the proximity of the end of the control range of the lever. Then, the arrival of the control lever to the proximity of the control range is detected by the detecting means. Subsequently, in accordance with the combination of detected conditions of the detecting means, whether the priority operation mode is taken or not is judged. When it is judged that the priority operation mode is taken, the driving means is controlled so that the output of the selected one or more driving means corresponding to the priority operation mode becomes larger than that in the normal mode or the power ratio as compared to the other driving means becomes larger. Accordingly, the movement of the selected actuator(s) can be, for instance, accelerated. 
     Accordingly, since the operation mode can be switched to the priority operation mode only by manipulating the control lever to the proximity of the end of the control range while manipulating the control lever without releasing the control lever, the switching operation to the priority operation mode can be facilitated. 
     In the above control-mode switching device of a construction machine, the mode judging means preferably includes: a storing means that stores a plurality of priority operation modes corresponding to the combination of the detected conditions of the detecting means; and a selecting means that selects the priority operation mode corresponding to the combination of the detected conditions of the detecting means from the storing means. 
     According to the above arrangement, since the plurality of priority modes are stored in the storing means corresponding to the combination of the detected conditions of the detecting means, the priority operation mode set in accordance with the combination of the detected conditions of the detecting means can be easily changed. 
     In the above control-mode switching device, the actuator is preferably a hydraulic actuator, the driving means preferably includes a hydraulic circuit and a flow-rate controlling means that controls a flow rate of the hydraulic circuit, and, when it is judged by the mode judging means that the priority operation mode is taken, the drive controlling means preferably controls the flow-rate controlling means preferably so that pressure oil supply that is supplied to selected one or more of the hydraulic circuits becomes larger than pressure oil supply that is supplied to the other hydraulic circuit. 
     According to the above arrangement, since the actuator includes a hydraulic actuator and the respective driving means includes hydraulic circuit, great force can be exerted when applied on a machine that requires considerable power (e.g. excavator) and satisfactory excavating operation can be achieved. Further, since the drive controlling means is configured to control the flow-controlling means so that the pressure oil supply supplied to the hydraulic circuit becomes larger than the pressure oil supply supplied to the other hydraulic circuit, the drive controlling means can be achieved with a relatively simple arrangement. 
     In the control-mode switching means of construction machine of the present invention, an engine for driving the plurality of driving means is preferably provided and the drive controlling means preferably increases and decreases the power of the engine. 
     Alternatively, in the control-mode switching device of construction machine of the present invention, a battery for driving the plurality of driving means is preferably provided and the drive controlling means preferably increases and decreases the power of the battery. 
     According to the above arrangement, since the priority operation mode is conducted by increasing and decreasing the power of the engine for executing the priority operation mode, the entire power can be augmented. 
     In the above control-mode switching device, the actuator preferably includes a hydraulic actuator, the driving means preferably include a hydraulic circuit and a variable pressure-control valve that controls the pressure in the hydraulic circuit, and, when it is judged by the mode judging means that the priority operation mode is taken, the variable pressure-control valve preferably is controlled so that pressure in the selected one or more of the hydraulic circuits becomes larger. 
     According to the above arrangement, since the actuator is provided by the hydraulic actuator and the respective driving means is provided by the hydraulic circuit, where the priority operation mode is executed by controlling the variable pressure-control valve provided in the hydraulic circuit, simple arrangement can be achieved. 
     In the control-mode switching device of a construction machine of the present invention, a notifying means that allows an operator to recognize an arrival of the control lever to the proximity of the control range is preferably provided. 
     According to the above arrangement, since the notifying means that allows an operator to recognize the arrival of the control lever to the proximity of the control range is provided, an operator can recognize the arrival of the control lever to the proximity of the end of the control range. 
     A construction machine according to another aspect of the invention includes the above-described control-mode switching device of the present invention. 
     According to the above arrangement, a construction machine having the function of the above-described control-mode switching device can be provided. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic illustration of a control lever according to a first embodiment of the invention; 
         FIG. 2  is an illustration showing a relationship between control force of a control lever and PPC pressure according to the first embodiment; 
         FIG. 3  is a diagram showing a hydraulic control circuit according to the first embodiment; 
         FIG. 4  is a diagram showing an internal arrangement of a controller according to the first embodiment; 
         FIG. 5  is an illustration showing details of priority operation modes according to the first embodiment; 
         FIG. 6  is an illustration showing details of priority operation modes according to a modification of the first embodiment; 
         FIG. 7  is a flowchart of the above modification; 
         FIG. 8  is a diagram showing a hydraulic control circuit according to a second embodiment of the invention; 
         FIG. 9  is a schematic illustration of a control lever according to the second embodiment; 
         FIG. 10  is an illustration showing a relationship between control force of a control lever and an output signal according to the second embodiment; 
         FIG. 11  is a diagram showing a control system circuit according to a third embodiment of the invention; 
         FIG. 12  is an illustration showing a modification of a control lever of the invention; 
         FIG. 13A  is an illustration for showing swing movement of an excavator; and 
         FIG. 13B  is another illustration for showing the swing movement of the excavator. 
     
    
    
     EXPLANATION OF CODES 
       2  . . . swing hydraulic motor (hydraulic actuator),  6  . . . boom cylinder (hydraulic actuator),  7  . . . arm cylinder (hydraulic actuator),  10  . . . variable displacement hydraulic pump (a component of driving means and hydraulic circuit),  11  . . . delivery line (a component of driving means and hydraulic circuit),  12  . . . pressure compensated flow-control valve (a component of driving means and hydraulic circuit, flow-rate controlling means),  13  . . . variable displacement hydraulic pump (a component of driving means and hydraulic circuit),  14  . . . delivery line (a component of driving means and hydraulic circuit),  15  . . . pressure compensated flow-control valve (a component of driving means and hydraulic circuit, flow-rate controlling means),  16  . . . pressure compensated flow-control valve (a component of driving means and hydraulic circuit, flow-rate controlling means),  22   a  . . . arm control lever,  22   b  . . . swing control lever,  22   c  . . . boom control lever,  22   d - 22   f  . . . electric control levers,  23  . . . controller,  23 A . . . mode judging unit,  23 A 1  . . . storing means,  23 A 2  . . . selecting means,  23 B . . . drive controlling means,  66 , 67  . . . variable pressure-control valves,  72   a , 72   c , 72   d , 72   e  . . . limit switch (detecting means),  80  . . . notifying unit,  91  . . . engine,  110  . . . battery 
     BEST MODE FOR CARRYING OUT THE INVENTION 
     An embodiment of the invention will be described below with reference to attached drawings. 
     First Embodiment 
       FIG. 1  is a schematic illustration of a control lever used in the present embodiment.  FIG. 2  is an illustration showing output characteristics of control force of the control lever and PPC (Pilot Pressure Control) pressure. 
     A control lever  22  opens valves V 1  and V 2  in accordance with operating direction and angle, so that pressure oil from a pilot pump P is fed into pilot lines PT 1  and PT 2  through the valves V 1  and V 2 . 
     When the stroke range of a normal control lever is 100%, the control lever  22  can be operated to around 110%. When the operation stroke of the control lever  22  exceeds 100%, an operation feeling is given where the lever does not move without applying further greater control force. For instance, when the operation stroke of the control lever  22  exceeds 100%, movable part of the control lever  22  touches a biasing unit such as a spring, so that a control force greater than the previous control force is required for moving the lever on account of the reaction force of the biasing unit. 
     A range in which the operation stroke of the control lever  22  exceeds 100% to be around 110% is called as a kickdown range (KDE). When the control lever  22  reaches to the kickdown range, i.e. when the control lever  22  reaches to the proximity of the end of manipulable range, limit switches (detecting means) LS 1  and LS 2  are turned on, thereby detecting that the control lever  22  has reached to the kickdown range. The PPC pressure output within the kickdown range stays the same. 
     Among the hydraulic control circuits, a hydraulic control circuit of three hydraulic actuators, i.e. boom-driving hydraulic cylinder (referred to as a boom cylinder hereinafter)  6 , arm-driving hydraulic cylinder (referred to as an arm cylinder hereinafter)  7  and swing hydraulic motor  2  according to the present invention, are shown in  FIG. 3 . 
     The hydraulic control circuit is a two-pump type including two variable displacement hydraulic pumps  10  and  13 . The boom cylinder  6  is connected to a delivery line  11  of the variable displacement hydraulic pump  10  via a pressure compensated flow-control valve  12  for controlling the flow rate and flow direction. A delivery line  14  of the variable displacement hydraulic pump  13  includes two branch lines  14   a  and  14   b . The swing hydraulic motor  2  is connected to the branch line  14   a  via a pressure compensated flow-control valve  15 . The arm cylinder  7  is connected to the branch line  14   b  via a pressure compensated flow-control valve  16 . 
     Incidentally, the variable displacement hydraulic pumps  10  and  13  are driven by an engine  91  (in  FIG. 3 , though it is illustrated that the engine  91  is connected respectively to the pumps  10  and  13 , the pumps  10  and  13  are actually driven by the single engine  91 ), where the maximum engine speed and maximum power of the engine  91  is controlled by a command signal of a controller  23  through a governor (not shown). 
     The boom cylinder  6 , the arm cylinder  7  and the swing hydraulic motor  2  are connected to the two variable displacement hydraulic pump  10  and  13  in parallel, and are also connected to a reservoir  18  through a return circuit  17 . 
     The pressure compensated flow-control valves  12 ,  15  and  16  are pilot-operated type. A main line  20  of a pilot pump  19  are connected to both ends of the respective pressure compensated flow-control valves  12 ,  15  and  16  via pilot lines  73   a  to  73   f  of the respective control levers  22   a ,  22   b  and  22   c.    
     A limit switch (second detecting means)  72   a  for detecting that the boom control lever  22   c  reaches to the kickdown range when the boom control lever  22   c  is operated in a boom-lift-up direction is provided on the boom control lever  22   c ; limit switches  72   c  and  72   d  (first detecting means) for detecting that the swing control lever  22   b  reaches to the kickdown range when the swing control lever  22   b  is operated in both right and left rotary directions are provided on the swing control lever  22   b ; and a limit switch  72   e  (third detecting means) for detecting that the arm control lever  22   a  reaches to the kickdown range when the arm control lever  22   a  is operated in an arm excavating direction is provided on the arm control lever  22   a.    
     The limit switches  72   a ,  72   c ,  72   d  and  72   e  are connected to the controller  23  via signal circuits  71   a ,  71   c ,  71   d  and  71   e.    
     Variable displacement pressure-control valves  67  and  66  are connected to the delivery lines  11  and  14  of the variable displacement hydraulic pumps  10  and  13 . When the pilot valves  61  and  63  are switched by a command signal output from the controller  23  through the signal circuits  60  and  62 , pilot pressure from the pilot pump  19  is applied to an operating section of the variable pressure-control valves  67  and  66  through pilot lines  64  and  65 . Accordingly, maximum pressure (relief pressure) of the delivery lines  11  and  14  of the variable displacement hydraulic pumps  10  and  13  are controlled. Incidentally,  26  denotes a return line of the pilot hydraulic pressure. 
     The pressure compensated flow-control valves  12 ,  15  and  16  are provided with a mechanism for restricting a spool stroke within the control valves to control maximum flow rate. When the pilot valves  75   b ,  75   c  and  75   d  are switched by a command signal output from the controller  23  through the signal circuits  74   b ,  74   c  and  74   d , the pilot pressure from the pilot pump  19  is applied to the operating section of the respective pressure compensated flow-control valves  12  and  15  to restrict the flow rate of the pressure compensated flow-control valves  12  and  15 . 
     The hydraulic pumps  10  and  13 , the delivery lines  11  and  14  and the pressure compensated flow-control valves  12 ,  15  and  16  constitutes a hydraulic circuit (driving means) for driving the hydraulic actuators (the swing hydraulic motor  2 , the boom cylinder  6  and the arm cylinder  7 ). 
     Pressure compensating valves  27   a ,  27   b  and  27   c  for detecting and compensating discharge pressure of the hydraulic pumps  10  and  13  relative to the required flow rate of the respective actuators (the boom cylinder  6 , the arm cylinder  7  and the swing hydraulic motor  2 ) are provided on the pressure compensated flow-control valves  12 ,  15  and  16 . The pressure compensating valves  27   a ,  27   b  and  27   c  are connected to load sensing regulators  28   a  and  28   b  of the hydraulic pumps  10  and  13  through pilot lines  29   a  and  29   b.    
     The load sensing circuit is configured as follows. The pressure on the maximum load pressure side of a pilot line  33  for detecting the maximum load pressure of the swing hydraulic motor  2  from an outlet port  32  of the pressure compensated flow-control valve  15  and a pilot line  31  for detecting the maximum load pressure of the arm cylinder  7  from an output port  30  of the pressure compensated flow-control valve  16  is detected by a shuttle valve  34 . The pressure on the maximum load pressure side of a pilot line  35  connected to the shuttle valve  34  and a pilot line  37  for detecting the maximum load pressure of the boom cylinder  6  from the outlet port  36  of the pressure compensated flow-control valve  12  is detected by a shuttle valve  38 , which on one hand is input to the load sensing regulator  28   a  of the hydraulic pump  10  through the pilot line  29   a  and on the other hand is input to the load sensing regulator  28   b  of the other hydraulic pump  13  through the pilot line  29   b.    
     A swing load sensing switching valve  40  is provided on the load sensing circuit. The switching valve  40  is controllably switched by an electromagnetic pilot valve  52  controlled by a signal circuit  51  of the controller  23  through a pilot line  41 . 
     The load sensing regulators  28   a  and  28   b  respectively include pilot-operated load sensing valves  44   a  and  44   b  provided between the delivery lines  11  and  14  and servo pistons  42   a  and  42   b  for controlling swash-plate inclination of the hydraulic pumps  10  and  13 . Pilot lines  29   a  and  43   a  are connected to both ends of one of the load sensing valves  44   a , and pilot lines  29   b  and  43   b  are connected to both ends of the other load sensing valve  44   b.    
     When the sum of the maximum load pressure introduced by the pilot lines  29   a  and  29   b  and spring force of springs  45   a  and  45   b  becomes greater than the discharge pressure of the hydraulic pumps  10  and  13  introduced by the pilot lines  43   a  and  43   b , the load sensing valves  44   a  and  44   b  switches from (A) position to (B) position to return the pressure oil of the servo pistons  42   a  and  42   b  to the reservoir  18  to increase swash-plate angle of the hydraulic pumps  10  and  13  to augment the discharge flow rate. On the contrary, when the sum of the maximum load pressure and the spring force becomes smaller than the discharge pressure of the hydraulic pumps  10  and  13 , the load sensing valves  44   a  and  44   b  switches from the (B) position to the (A) position, so that the pressure oil from the pilot lines  43   a  and  43   b  enters into the servo pistons  42   a  and  42   b  to decrease the swash-plate angle of the hydraulic pumps  10  and  13  to reduce the discharge flow rate. 
     In other words, the discharge pressure P 1  of the hydraulic pump  10  is applied from the line  43   a  to one of the operating sections of the load sensing valve  44   a , and the load pressure LP 1  introduced by the pilot line  29   a  and the spring force are applied on the other operating section of the load sensing valve  44   a . Accordingly, when P 1 &gt;LP 1 , the swash-plate angle of the hydraulic pump  10  is controlled to be decreased, and, when P 1 &lt;LP 1 , the swash-plate angle of the hydraulic pump  10  is controlled to be increased. 
     Further, the discharge pressure P 2  of the hydraulic pump  13  is applied from the line  43   a  to one of the operating sections of the load sensing valve  44   b , and the load pressure LP 2  introduced by the pilot line  29   b  and the spring force are applied on the other operating section of the load sensing valve  44   b . Accordingly, when P 2 &gt;LP 2 , the swash-plate angle of the hydraulic pump  13  is controlled to be decreased, and, when P 2 &lt;LP 2 , the swash-plate angle of the hydraulic pump  13  is controlled to be increased. 
     With the use of the above load sensing system and the pressure compensated flow-control valves  12 ,  15  and  16 , while restraining the discharged pressure oil of the hydraulic pumps  10  and  13  to a required flow rate to serve for energy saving, the respective pressure compensating valves  27   a ,  27   b  and  27   c  are controlled by the maximum load pressure of the respective hydraulic actuators (the boom cylinder  6 , the arm cylinder  7  and the swing hydraulic motor  2 ). 
     The delivery lines  11  and  14  of the two variable displacement hydraulic pumps  10  and  13  are interconnected by a communication line  46 . The communication line  46  is provided with a merge/branch switching valve  47  of the discharged pressure oil of both of the hydraulic pumps  10  and  13 . The switching valve  47  is controllably switched by pilot pressure of a pilot line  48  in accordance with actuation of an electromagnetic pilot valve  50  commanded by the controller  23  via a signal circuit  49 . 
     Incidentally, a load sensing pressure on/off switching valve  53  controllably interlocked with the merge/branch switching valve  47  is provided in the load sensing circuit. 
     The hydraulic control circuit having thus arranged load-sensing system is operated under various priority modes set in advance in the controller  23  so that operation matching can be changed by flow-rate distribution for simultaneous operation of the swing mechanism and the boom or arm while excavating earth and sand with lift-up swing and loading into a dumper truck, and instantaneous operation under a predetermined rated power of an engine can be conducted when hard soil is to be excavated. 
     Specifically, as shown in  FIG. 4 , the controller  23  includes: a mode judging unit  23 A that judges whether a priority operation mode in which an output of selected one or more of the driving means can be set higher than a normal mode or output ratio can be set higher as compared to the other driving means is taken or not in accordance with the signals from the limit switches  72   a ,  72   c ,  72   d  and  72   e  provided on the respective control levers  22   a ,  22   b  and  22   c ; and a drive controlling means  23 B that controls the driving means so that, when the mode judging unit  23 A judges that the priority operation mode is taken, an output of selected one or more of the driving means corresponding to the priority operation mode is set higher than that in the normal mode or the output ratio is set higher as compared to the other driving means. 
     The mode judging unit  23 A includes a storing means  23 A 1  that stores a plurality of priority operation modes in accordance with the combination of on/off conditions of the limit switches  72   a ,  72   c ,  72   d  and  72   e , and a selecting means  23 A 2  that selects a priority operation mode corresponding to the combination of on/off conditions of the limit switches  72   a ,  72   c ,  72   d  and  72   e  from the storing means  23 A 1 . 
     The drive controlling means  23 B transmit a command signal to the pilot valve  50 , the pilot valves  75   b  to  75   d , the pilot valve  52  and the pilot valves  61  and  63  in accordance with the priority operation mode selected by the mode judging unit  23 A to perform the priority operation mode. 
     In accordance with the combination of on/off conditions of the limit switches  72   a ,  72   c ,  72   d  and  72   e , (I) standard operation mode and seven priority operation modes, i.e. (II) excavating power-up mode, (III) swing priority mode, (IV) boom lift-up priority mode, (V) arm excavation priority mode, (VI) power-up mode (swing+boom), (VII) power-up mode (boom+arm) and (VIII) power-up mode (swing+arm) are stored in the storing means  23 A 1  as shown in  FIG. 5 . Further, in accordance with the respective modes, the condition of the merge/branch switching valve  47 , the swing load sensing switching valve  40 , variable pressure-control valves  67  and  66  and the pilot valves  75   b ,  75   c  and  75   d  that restrict maximum flow rate of the respective flow-control valves  12 ,  15  and  16 , and the speed/power condition of the engine are stored corresponding to the respective modes. 
     Incidentally,  55  denotes a monitor, on which respective operation modes are displayed. 
     (1) Standard Mode 
     When (1) ninety-degree swing operation and boom-lift-up operation are simultaneously conducted and (2) approximately the same flow rate is desired without giving priority to one of the swinging movement and the boom movement and instantaneous increase in excavating force and engine power is not necessary, the respective control levers  22   a ,  22   b  and  22   c  are operated within a normal stroke range. In other words, the control levers are used without reaching to the kickdown range. 
     Under the above condition, the command signal from the controller  23  is not transmitted to the pilot valve  50 . Accordingly, since the pilot valve  50  is located at the position shown in  FIG. 3 , the pilot pressure applied on the operating section of the merge/branch switching valve  47  is drained from the pilot line  48  to the reservoir  18  and the merge/branch switching valve  47  is off-driven to be positioned at a merge position shown in  FIG. 3 . In other words, the pressure oil from the hydraulic pump  10  and the pressure oil from the hydraulic pump  13  are merged through the merge/branch switching valve  47 . 
     When the boom control lever  22   c  is operated under this condition, the pressure oil from the pilot pump  19  is applied to the operating section of the pressure compensated flow-control valve  12  through the pilot lines  73   a  and  73   b  to advance and retract the boom cylinder  6 . In other words, the boom is lifted up and down. 
     When the swing lever  22   b  is operated, the pressure oil from the pilot pump  19  is applied to the operating section of the pressure compensated flow-control valve  15  through the pilot lines  73   c  and  73   d . Consequently, the swing hydraulic motor  2  is turned clockwise and counterclockwise. In other words, swinging movement is conducted. 
     When the arm control lever  22   a  is operated, the pressure oil from the pilot pump  19  is applied to the operating section of the pressure compensated flow-control valve  16  through the pilot lines  73   e  and  73   f  to advance and retract the arm cylinder  7 . 
     On the other hand, the command signal from the controller  23  is transmitted to the pilot valve  52  in the standard mode. Then, since the pilot valve  52  is switched, the pilot pressure from the pilot pump  19  is applied to the operating section of the swing load sensing switching valve  40  from the pilot line  41  through the pilot valve  52 , so that the swing load sensing switching valve  40  is on-driven to be at “cutoff” position. 
     Accordingly, the load pressure for driving the swing hydraulic motor  2  is blocked by the swing load sensing switching valve  40 , the load pressure of the boom cylinder  6  is detected by the shuttle valve  38 . The load pressure is applied to the load sensing valve  44   a  through the pilot line  29   a  and is also applied to the operating section of the load sensing valve  44   b  through the pilot line  29   b.    
     Accordingly, the discharge pressure P 1  of the hydraulic pump  10  is applied from the line  43   a  to one of the operating sections of the load sensing valve  44   a , and the load pressure LP 1  introduced by the pilot line  29   a  and the spring force are applied on the other operating section of the load sensing valve  44   a . As a result, when P 1 &gt;LP 1 , the swash-plate angle of the hydraulic pump  10  is controlled to be decreased, and, when P 1 &lt;LP 1 , the swash-plate angle of the hydraulic pump  10  is controlled to be increased. 
     Further, the discharge pressure P 2  of the hydraulic pump  13  is applied from the line  43   a  to one of the operating sections of the load sensing valve  44   b , and the load pressure LP 2  of the boom cylinder  6  introduced by the pilot line  29   b  and the spring force are applied on the other operating section of the load sensing valve  44   b . As a result, when P 2 &gt;LP 2 , the swash-plate angle of the hydraulic pump  13  is controlled to be decreased, and, when P 2 &lt;LP 2 , the swash-plate angle of the hydraulic pump  13  is controlled to be increased. 
     In other words, when the boom and swing mechanism are simultaneously operated in the standard mode, the swash-plate angle of the hydraulic pumps  10  and  13  are controlled to correspond to the load pressure of the boom actuator (the boom cylinder  6 ) to supply required flow to the respective actuators of the boom and the swing mechanisms (the boom cylinder  6  and the swing hydraulic motor  2 ). 
     (II) Excavating Power-Up Mode (Single Operation) 
     For instance, when the arm is solely operated for excavation, the arm control lever  22   a  is operated to the kickdown range beyond the normal range. 
     Accordingly, a command signal from the controller  23  is transmitted to the pilot valve  61 . Then, the pilot valve  61  is switched and the pilot pressure from the pilot pump  19  is applied to the operating section of the variable pressure-control valve  66  from the pilot line  64  through the pilot valve  61 . As a result, the variable pressure-control valve  66  is on-driven to be located at boost position. In other words, the drive hydraulic circuit of the arm cylinder  7  is boosted (110% boosted relative to rated pressure), so that excavating force can be temporarily increased during the operation. 
     Similarly, when the swing mechanism is solely operated, the swing control lever  22   b  is manipulated to the kickdown range beyond the normal range for temporarily increasing the swing power during the operation. 
     Further, when the boom is solely lifted up, the boom control lever  22   c  is manipulated to the kickdown range beyond the normal range. 
     Accordingly, a command signal from the controller  23  is transmitted to the pilot valve  63 . Then, the pilot valve  63  is switched and the pilot pressure from the pilot pump  19  is applied to the operating section of the variable pressure-control valve  67  from the pilot line  65  through the pilot valve  63 . As a result, the variable pressure-control valve  67  is on-driven to be located at boost position. In other words, the drive hydraulic circuit of the boom cylinder  6  is boosted (110% boosted relative to rated pressure), so that boom-lifting force can be temporarily increased during the operation. 
     (III) Swing Priority Mode (Swinging Force and Speed Up) 
     For instance, when (1) one-hundred-eighty degree swing and boom lift-up are simultaneously conducted and (2) load pressure on the swing hydraulic motor  2  is great and large amount of flow is necessary or temporary increase in swinging force is required for operation, only the swing control lever  22   b  is solely manipulated to the kickdown range beyond the normal range. 
     Accordingly, a command signal from the controller  23  is transmitted to the pilot valve  50 . Then, the pilot valve  50  is switched and the pilot pressure from the pilot pump  19  is applied to the operating section of the merge/branch switching valve  47  from the pilot line  48  through the pilot valve  50 . As a result, the merge/branch switching valve  47  is on-driven to be located at branch position. 
     At this time, the pilot pressure from the pilot pump  19  is applied to the operating section of the load sensing pressure on/off switching valve  53  to switch the load sensing pressure on/off switching valve  53  to “a” position. 
     Simultaneously, a command signal from the controller  23  is transmitted to the pilot valve  75   b . Then, the pilot valve  75   b  is switched and the pilot pressure from the pilot pump  19  is applied to lowering side operating section of the pressure compensated flow-control valve  12  from the pilot valve  75   b . As a result, raising-side spool stroke in the pressure compensated flow-control valve  12  is restricted, thereby regulating boom-raising side flow rate. 
     Further, a command signal from the controller  23  is transmitted to the pilot valve  61 . Then, the pilot valve  61  is switched and the pilot pressure from the pilot pump  19  is applied to the operating section of the variable pressure-control valve  66  from the pilot line  64  through the pilot valve  61 . As a result, the variable pressure-control valve  66  is on-driven to be located at boost position. In other words, the drive hydraulic circuit of the swing hydraulic motor  2  is boosted (110% boost relative to rated pressure), so that only the swing force can be temporarily increased for simultaneously conducting the swing operation and boom-lift-up operation. 
     On the other hand, the command signal from the controller  23  is not transmitted to the pilot valve  52 . Accordingly, the pilot pressure applied to the pilot valve  52  is drained from the line  41  to the reservoir  18 , so that the pilot valve  52  is off-driven to be switched to “link” position shown in  FIG. 3 . 
     Accordingly, the load pressure for driving the swing hydraulic motor  2  is applied to the operating section of the load sensing valve  44   b  through the swing load sensing switching valve  40 , the shuttle valve  34 , the pilot line  35 , “a” position of the load sensing pressure on/off switching valve  53  and the pilot line  29   b.    
     Accordingly, the discharge pressure P 2  of the hydraulic pump  13  is applied from the line  43   a  to one of the operating sections of the load sensing valve  44   b , and the load pressure LP 2  of the swing hydraulic motor  2  introduced by the pilot line  29   b  and the spring force are applied on the other operating section of the load sensing valve  44   b . As a result, when P 2 &gt;LP 2 , the swash-plate angle of the hydraulic pump  13  is controlled to be decreased, and, when P 2 &lt;LP 2 , the swash-plate angle of the hydraulic pump  13  is controlled to be increased. 
     Accordingly, when the swing priority mode is selected, the hydraulic pump  13  independently supplies required flow rate to the swing hydraulic motor  2  and the drive circuit pressure can be boosted. In this case, the boom cylinder  6  is controlled based on differential pressure between the discharge pressure P 1  and the load pressure LP 1  as in the above standard mode. However, since the spool stroke of the pressure compensated flow-control valve  12  is restricted, the flow rate from the hydraulic pump  10  is also restricted. 
     In other words, when the boom movement and swing movement are simultaneously conducted in the swing priority mode, the flow rate from the hydraulic pump  10  to the boom actuator (boom cylinder  6 ) is regulated, and since the swash-plate angle of the hydraulic pump  13  is regulated corresponding to the load pressure simultaneously with the boosting of the drive hydraulic circuit of the swing actuator (swing hydraulic motor  2 ), the drive force and required flow rate of the swing hydraulic motor  2  are augmented. 
     (IV) Boom-Up Priority Mode (Boom-Up Excavating Force and Speed Up) 
     For instance, when the swing operation and the boom-up operation are simultaneously conducted and (1) swing angle is relatively small (forty-five degrees for instance) and (2) large amount of flow rate is required for boom-up operation or temporary increase in boom-up force is required for operation, only the boom control lever  22   c  is manipulated to the kickdown range beyond the normal range. 
     Accordingly, a command signal from the controller  23  is transmitted to the pilot valve  50 . Then, the pilot valve  50  is switched and the pilot pressure from the pilot pump  19  is applied to the operating section of the merge/branch switching valve  47  from the pilot line  48  through the pilot valve  50 . As a result, the branch switching valve  47  is on-driven to be located at branch position. 
     At this time, the pilot pressure from the pilot pump  19  is applied to the operating section of the load sensing pressure on/off switching valve  53  to switch the load sensing pressure on/off switching valve  53  to “a” position. 
     Simultaneously, a command signal from the controller  23  is transmitted to the pilot valve  52 . Then, the pilot valve  52  is switched and the pilot pressure from the pilot pump  19  is applied to the operating section of the swing load sensing switching valve  40  from the pilot line  41  through the pilot valve  52 . As a result, the load pressure for driving the swing hydraulic motor  2  is blocked by the swing load sensing switching valve  40 . 
     Further, the command signal from the controller  23  is transmitted to the pilot valve  75   c  or the pilot valve  75   d . Then, the pilot valve  75   c  or the pilot valve  75   d  is switched, so that the pilot pressure from the pilot pump  19  is applied from the pilot valve  75   c  or the pilot valve  75   d  to the side opposite to the driving side operating section of the pressure compensated flow-control valve  15 . As a result, driving-side spool stroke inside the pressure compensated flow-control valve  15  is restricted to regulate the swing flow rate. 
     Further, a command signal from the controller  23  is transmitted to the pilot valve  63 . Then, the pilot valve  63  is switched and the pilot pressure from the pilot pump  19  is applied to the operating section of the variable pressure-control valve  67  from the pilot line  65  through the pilot valve  63 . As a result, the variable pressure-control valve  67  is on-driven to be located at boost position. 
     In other words, the drive hydraulic circuit of the boom cylinder  6  is boosted (110% boost relative to rated pressure), so that only the boom-up force can be temporarily increased for simultaneously conducting the swing operation and boom-lift-up operation. 
     On the other hand, the load pressure of the boom cylinder  6  is applied to the operating section of the load sensing valve  44   a  through the pilot line  29   a , and the load pressure of the swing hydraulic motor  2  is not applied to the operating section of the load sensing valve  44   b.    
     Accordingly, the discharge pressure P 1  of the hydraulic pump  10  is applied from the line  43   a  to one of the operating sections of the load sensing valve  44   a , and the load pressure P 1  introduced by the pilot line  29   a  and the spring force are applied on the other operating section of the load sensing valve  44   a . As a result, when P 1  (discharge pressure of hydraulic pump  10 )&gt;LP 1  (load pressure of the boom cylinder), the swash-plate angle of the hydraulic pump  10  is controlled to be decreased, and, when P 1 &lt;LP 1 , the swash-plate angle of the hydraulic pump  10  is controlled to be increased. 
     Further, when the load pressure from the swing hydraulic motor  2  is not applied to the load sensing valve  44   b , the load sensing valve  44   b  is controlled by the discharge pressure P 2  of the hydraulic pump  13 . When the discharge pressure P 2  becomes greater than the spring force, the swash-angle plate is controlled to be decreased. 
     Accordingly, when the boom-up operation and the swing operation are simultaneously conducted in the boom-up priority mode, the flow rate from the hydraulic pump  13  to the swing actuator (swing hydraulic motor  2 ) is regulated, and, simultaneously with the boosting of the drive hydraulic circuit of the boom actuator (boom cylinder  6 ), the swash-plate angle of the hydraulic pump  10  is controlled corresponding to the load pressure, so that drive force and required flow rate of the boom cylinder  6  are augmented. 
     Incidentally, when the arm cylinder  7  is driven, the load pressure of the arm is applied to the operating section of the load sensing valve  44   b  through the shuttle valve  34 , the pilot line  35 , the “a” position of the switching valve  53  and the pilot line  29   b . Accordingly, when P 2 &gt;LP 2 , the swash-plate angle of the hydraulic pump  13  is controlled to be decreased, and, when P 2 &lt;LP 2 , the swash-plate angle of the hydraulic pump  13  is controlled to be increased, so that required flow rate can be supplied to the arm cylinder  7 . 
     (V) Arm Excavation Priority Mode (Arm Excavating Power and Speed Up) 
     For instance, when arm-excavation operation and boom-up operation are simultaneously conducted for rough finish and (1) arm-excavation speed has to be accelerated or (2) only arm excavating power is temporarily increased, only the arm control lever  22   a  is manipulated to the kickdown range beyond the normal range. 
     Accordingly, a command signal from the controller  23  is transmitted to the pilot valve  50 . Then, the pilot valve  50  is switched and the pilot pressure from the pilot pump  19  is applied to the operating section of the merge/branch switching valve  47  from the pilot line  48  through the pilot valve  50 . As a result, the branch switching valve  47  is on-driven to be located at branch position. 
     At this time, the pilot pressure from the pilot pump  19  is applied to the operating section of the load sensing pressure on/off switching valve  53  to switch the load sensing pressure on/off switching valve  53  to “a” position. 
     Simultaneously, a command signal from the controller  23  is transmitted to the pilot valve  52 . Then, the pilot valve  52  is switched and the pilot pressure from the pilot pump  19  is applied to the operating section of the swing load sensing switching valve  40  from the pilot line  41  through the pilot valve  52 . As a result, the load pressure for driving the swing hydraulic motor  2  is blocked by the swing load sensing switching valve  40 . 
     Further, a command signal from the controller  23  is transmitted to the pilot valve  75 . Then, the pilot valve  75   b  is switched and the pilot pressure from the pilot pump  19  is applied to the lowering side operating section of the pressure compensated flow-control valve  12  from the pilot valve  75   b . As a result, the raising-side spool stroke in the pressure compensated flow-control valve  12  is restricted, thereby regulating the boom-raising side flow rate. 
     Further, a command signal from the controller  23  is transmitted to the pilot valve  61 . Then, the pilot valve  61  is switched and the pilot pressure from the pilot pump  19  is applied to the operating section of the variable pressure-control valve  66  from the pilot line  64  through the pilot valve  61 . As a result, the variable pressure-control valve  66  is on-driven to be located at boost position. 
     In other words, the drive hydraulic circuit of the arm cylinder  7  is boosted (110% boost relative to rated pressure), so that only the arm-excavating force can be temporarily increased for simultaneously conducting the arm excavating operation and boom-lift-up operation. 
     On the other hand, the load pressure of the arm cylinder  7  is applied to the operating section of the load sensing valve  44   b  through the pilot line  29   b , and the load pressure of the swing hydraulic motor  2  is not applied to the operating section of the load sensing valve  44   b.    
     Accordingly, the discharge pressure P 2  of the hydraulic pump  13  is applied from the line  43   a  to one of the operating sections of the load sensing valve  44   b , and the load pressure LP 2  of the arm cylinder  7  introduced by the pilot line  29   b  and the spring force are applied on the other operating section of the load sensing valve  44   b.    
     As a result, when P 2  (discharge pressure of hydraulic pump  13 )&gt;LP 2  (load pressure of the arm cylinder  7 ), the swash-plate angle of the hydraulic pump  13  is controlled to be decreased, and, when P 2 &lt;LP 2 , the swash-plate angle of the hydraulic pump  13  is controlled to be increased. 
     In other words, when the boom-up movement and arm-excavation are simultaneously conducted in the arm-excavation priority mode, the flow rate from the hydraulic pump  10  to the boom actuator (boom cylinder  6 ) is regulated, and since the swash-plate angle of the hydraulic pump  13  is regulated corresponding to the load pressure simultaneously with the boosting of the drive hydraulic circuit of the arm actuator (arm cylinder  7 ), the drive force and required flow rate of the arm cylinder  7  are augmented. 
     (VI) Power-Up Mode (Swing+Boom-Up) 
     In some cases, it is desirable to increase power for rapid loading operation and the like. For instance, when large amount of flow is required to both actuators in order to simultaneously accelerate the boom-up speed and the swing speed, the swing control lever  22   b  and the boom control lever  22   c  are manipulated to the kickdown range beyond the normal range. 
     Under the above condition, the command signal from the controller  23  is not transmitted to the pilot valve  50 . Accordingly, since the pilot valve  50  is located at the position shown in  FIG. 3 , the pilot pressure applied on the operating section of the merge/branch switching valve  47  is drained from the pilot line  48  to the reservoir  18  and the merge/branch switching valve  47  is off-driven to be positioned at a merge position shown in  FIG. 3 . In other words, the pressure oil from the hydraulic pump  10  and the pressure oil from the hydraulic pump  13  are merged through the merge/branch switching valve  47 . 
     On the other hand, a command signal from the controller  23  is transmitted to the pilot valve  52 . Then, the pilot valve  52  is switched and the pilot pressure from the pilot pump  19  is applied to the operating section of the swing load sensing switching valve  40  from the pilot line  41  through the pilot valve  52 . As a result, the load pressure for driving the swing hydraulic motor  2  is blocked by the swing load sensing switching valve  40 . 
     Simultaneously, a command signal from the controller  23  is transmitted to the pilot valves  61  and  63 . Then, the pilot valves  61  and  63  are switched and the pilot pressure from the pilot pump  19  is applied to the operating section of the variable pressure-control valves  66  and  67  from the pilot lines  64  and  65  through the pilot valves  61  and  63 . As a result, the variable pressure-control valves  66  and  67  are on-driven to be located at boost position. 
     Further, the command signal from the controller  23  is transmitted to a governor (not shown) for controlling the speed and power of the engine for driving the hydraulic pumps  10  and  13 . Then, the speed and power of the engine is controlled to be raised (about 100% relative to rated speed and power). 
     In other words, the speed and power of the engine for driving the hydraulic pumps  10  and  13  are increased, the boom-up speed and swing speed can be simultaneously raised in the loading operation and the like, so that loading operation can be speedily conducted. 
     On the other hand, the load pressure of the arm cylinder  7  is applied to the operating section of the load sensing valve  44   b  through the pilot line  29   b , and the load pressure of the swing hydraulic motor  2  is not applied to the operating section of the load sensing valve  44   b.    
     Accordingly, the discharge pressure P 2  of the hydraulic pump  13  is applied from the line  43   a  to one of the operating sections of the load sensing valve  44   b , and the load pressure LP 2  of the arm cylinder  7  introduced by the pilot line  29   b  and the spring force are applied on the other operating section of the load sensing valve  44   b . As a result, when differential pressure of the discharge pressure P 2  of hydraulic pump  13  and the load pressure LP 2  of the arm cylinder  7  is P 2 &gt;LP 2 , the swash-plate angle of the hydraulic pump  13  is controlled to be decreased, and, when P 2 &lt;LP 2 , the swash-plate angle of the hydraulic pump  13  is controlled to be increased. 
     (VII) Power-Up Mode (Boom-Up+Arm-Excavation) 
     Similarly, large amount of flow is required to both actuators in order to simultaneously accelerate the boom-up speed and the arm-excavation speed, the boom control lever  22   c  and the arm control lever  22   a  are manipulated to the kickdown range beyond the normal range. 
     Under the above condition, the command signal from the controller  23  is not transmitted to the pilot valve  50 . Accordingly, since the pilot valve  50  is located at the position shown in  FIG. 3 , the pilot pressure applied on the operating section of the merge/branch switching valve  47  is drained from the pilot line  48  to the reservoir  18  and the merge/branch switching valve  47  is off-driven to be positioned at a merge position shown in  FIG. 3 . In other words, the pressure oil from the hydraulic pump  10  and the pressure oil from the hydraulic pump  13  are merged through the merge/branch switching valve  47 . 
     On the other hand, a command signal from the controller  23  is transmitted to the pilot valve  52 . Then, the pilot valve  52  is switched and the pilot pressure from the pilot pump  19  is applied to the operating section of the swing load sensing switching valve  40  from the pilot line  41  through the pilot valve  52 . As a result, the load pressure for driving the swing hydraulic motor  2  is blocked by the swing load sensing switching valve  40 . 
     Simultaneously, a command signal from the controller  23  is transmitted to the pilot valves  61  and  63 . Then, the pilot valves  61  and  63  are switched and the pilot pressure from the pilot pump  19  is applied to the operating section of the variable pressure-control valves  66  and  67  from the pilot lines  64  and  65  through the pilot valves  61  and  63 . As a result, the variable pressure-control valves  66  and  67  are on-driven to be located at boost position. 
     Further, the command signal from the controller  23  is transmitted to a governor (not shown) for controlling the speed and power of the engine  91  for driving the hydraulic pumps  10  and  13 . Then, the speed and power of the engine  91  is controlled to be raised (about 100% relative to rated speed and power). 
     In other words, since the speed and power of the engine  91  for driving the hydraulic pump  10  and  13  increase, the boom-up speed and the arm-excavation speed can be simultaneously accelerated, so that excavation operation and the like can be speedily conducted. 
     Incidentally, since the swash-plate angle control of the hydraulic pumps  10  and  13  is the same as the effect of the above-described (VI), explanation thereof is omitted. 
     (VIII) Power-Up Mode (Swing+Arm Excavation) 
     When large amount of flow is required on both of the actuators for simultaneously increasing arm-excavation speed and swing speed in order to temporarily increase the power for speedy swing ground-smoothing and the like, the arm control lever  22   a  and the swing control lever  22   b  are manipulated to the kickdown range beyond the normal range. 
     The effect of the above arrangement is the same as the effect of the above-described (VI) and the explanation thereof is not described. 
     Modification of First Embodiment 
     Though one limit switch  72   a  is provided on the boom control lever  22   c , two limit switches  72   c  and  72   d  are provided on the swing control lever  22   b  and one limit switch  72   e  is provided on the arm control lever  22   a , a bucket control lever may be provided in addition to the boom control lever  22   c , the swing control lever  22   b  and the arm control lever  22   a  and two limit switches for detecting the kickdown range may be provided to the control levers to set the priority operation modes in accordance with the combination of on/off conditions of the limit switches. 
     For instance, as shown in  FIG. 6 , excavating power up mode, boom priority mode, arm priority mode, bucket priority mode, swing priority mode and power-up mode may be set in accordance with the combination of on/off conditions of boom switch BSW 1  (up, down), arm switch ASW (excavation, dump), bucket switch BSW 2  (excavation, dump) and swing switch TSW (right, left), and corresponding mode may be selected and executed based on the combination of on/off conditions of the switch. 
     During execution process, as shown in  FIG. 7 , after on/off conditions of the switches are determined (ST 1 ), the mode is judged based on the combination of the on/off conditions of the switches (ST 2 ). Specifically, whether the combination of the on/off conditions of the switches is included in the designated modes shown in  FIG. 6  or not is judged. When the combination is not included in the designated operation modes, normal operation is conducted as the standard mode (normal mode) (ST 3 ). 
     When the combination can be found in the designated operation modes, the process goes to either one of excavating power-up mode (ST 4 ), boom priority mode (ST 5 ), arm priority mode (ST 6 ), bucket priority mode (ST 7 ), swing priority mode (ST 8 ) and power-up mode (ST 9 ). 
     Subsequently to the excavating power-up mode (ST 4 ), the variable pressure-control valve is boosted (ST 10 ). Specifically, the variable pressure-control valves  66  and  67  are switched to the boost position. 
     In the boom priority mode (ST 5 ), after control flow rate other than the boom is slightly reduced in the respective driving hydraulic circuits, the process of ST 10  is conducted. In the arm priority mode (ST 6 ), after control flow rate other than the arm is slightly reduced in the respective driving hydraulic circuits, the process of ST 10  is conducted. In the bucket priority mode (ST 7 ), after control flow rate other than the bucket is slightly reduced in the respective driving hydraulic circuits, the process of ST 10  is conducted. In the swing priority mode (ST 8 ), after control flow rate other than the swing mechanism is slightly reduced in the respective driving hydraulic circuits, the process of ST 10  is conducted. In the power-up mode (ST 9 ), after raising the power of the engine  91 , the process of ST 10  is conducted. 
     In the above examples, since the control flow rate of the drive hydraulic circuit other than the selected priority operation mode is restrained to increase the control flow rate of the hydraulic circuit corresponding to the selected priority operation mode relative to the control flow rate of the other hydraulic circuits. Consequently, priority is given to the hydraulic circuit corresponding to the selected priority operation mode. In this arrangement, existing hydraulic circuit can be used for implementing the present invention. 
     Second Embodiment 
       FIG. 8  shows a hydraulic control circuit of a hydraulic excavator according to second embodiment of the invention. The hydraulic control circuit of the present embodiment differs from the hydraulic control circuit of the first embodiment in the following. 
     The PPC type control levers  22   a ,  22   b  and  22   c , the limit switches  72   a ,  72   c  and  72   d , the main line  20  and the pilot lines  73   a ,  73   b ,  73   c ,  73   d ,  73   e  and  73   f  are omitted from the first embodiment and electric control levers  22   d ,  22   e  and  22   f  are provided in place thereof. In this connection, pilot valves (electromagnetic proportional control valve)  25   a ,  25   b ,  25   c ,  25   d ,  25   e  and  25   f  are provided to the controller  23  via signal circuits  24   a ,  24   b ,  24   c ,  24   d ,  24   e  and  24   f , the pilot valves  25   a ,  25   b ,  25   c ,  25   d ,  25   e  and  25   f  being connected to both ends of the pressure compensated flow-control valves  12 ,  15  and  16 . 
     As shown in  FIGS. 9 and 10 , the electric control levers  22   d ,  22   e  and  22   f  are manipulable to a range approximately 110% (kickdown range) relative to stroke range of normal control lever (100%) in the same manner as the control levers  22   a ,  22   b  and  22   c  used in the first embodiment. When the operation stroke of the control lever  22  exceeds 100%, an operation feeling is given where the lever does not move without applying further greater control force. 
     Further, when the control levers  22   d ,  22   e  and  22   f  are manipulated, the output signal proportionally changes from stroke 0% to stroke 110% of the kickdown range. The controller  23  (as part of the first, second and third detecting means) recognizes that the control levers  22   d ,  22   e  and  22   f  have reached to the kickdown range when the output signal received from the control levers  22   d ,  22   e  and  22   f  exceeds a predetermined value (SL). 
     The same effects and advantages as the first embodiment can be expected in the second embodiment. 
     Third Embodiment 
       FIG. 11  shows a control system circuit of an electric excavator according to third embodiment of the invention. The control system circuit of the present embodiment differs from the hydraulic control circuit of the first embodiment in the following. 
     In the second embodiment, instead of the swing actuator (swing hydraulic motor  2 ), the pressure compensated flow-control valve  15  of the swing hydraulic motor  2 , the boom actuator (boom cylinder  6 ), the pressure compensated flow-control valve  12  of the boom cylinder  6 , the arm actuator (arm cylinder  7 ) and the pressure compensated flow-control valve  16  of the arm cylinder  7 , a swing actuator (swing electric motor  102 ), an inverter  115  of the swing electric motor  102 , a boom actuator (boom cylinder device  106 ), an inverter  112  of the boom cylinder device  106 , an arm actuator (arm cylinder device  107 ) and an inverter  116  of the arm cylinder device  107  are provided. A battery  110  and a capacitor (electrical condenser)  113  that is charged by the battery  110  are connected to the inverters  115 ,  112  and  116  via a power controller  120 . 
     In this connection, a control signal from the controller  23  is transmitted to the respective inverters  115 ,  112  and  116 , the power controller  120 , the battery  110  and the capacitor  113  via the signal circuits  24   a ,  24   c ,  24   e ,  24   g ,  24   h  and  24   i.    
     When the electric control levers  22   d ,  22   e  and  22   f  are constructed by the same levers as those used in the second embodiment, the same effects and advantages as the first embodiment are expected in the third embodiment. 
     Further, since the total output is controlled by the command from the controller  23  to the inverters  12 ,  15  and  16  and the power controller  120 , the output (110%) when the power-up mode is set on is also increased by the command from the controller  23  to the inverters  12 ,  15  and  16  and the power controller  120 . 
     It should be readily understood that the present embodiment is applicable to a combination of hydraulic actuator and electric actuator (so-called hybrid excavator). 
     Incidentally, the scope of the present invention is not limited to the above-described embodiment, but includes modifications and improvements as long as an object of the present invention can be achieved. 
     For instance, though the operation feeling (notifying unit) provided to the control lever is designed so that, when the control lever reaches to the kickdown range, control force greater than previous control force is required for moving the control lever, other arrangement is possible. On the contrary, the control lever may be designed so that, when the control lever reaches to the kickdown range, the control lever can be moved with a force smaller than the previous force. Alternatively, a notifying unit  80  as shown in  FIG. 12  may be used. 
     The notifying unit  80  shown in  FIG. 12  includes: a sector-shaped rotary plate  81  provided at a rotation support point of the control lever  22 ; two slide bars  83 A and  83 B that are in contact with oblique sides of the rotary plate  81  and are advanced and retracted in accordance with the rotation of the rotary plate  81 , the slide bars including notched grooves  82 A and  82 B arranged in the axial direction sandwiching intermediary projections  87 A and  87 B; springs  84 A and  84 B that biases the slide bars  83 A and  83 B so that the respective ends of the slide bars  83 A and  83 B touch the oblique sides of the rotary plate  81 ; balls  85 A and  85 B slidably provided on the sides of the slide bars  83 A and  83 B; and springs  86 A and  86 B that press and bias the balls  85 A and  85 B in a direction to touch the sides of the slide bars  83 A and  83 B. 
     According to the above arrangement, the rotary plate  81  is rotated in accordance with the rotation of the control lever  22 . Then, either one of the slide bars  83 A and  83 B are slid downward (in the figure) in accordance with the rotary direction. When one of the projections  87 A and  87 B of either one of the slide bars  83 A and  83 B reaches to the position of the balls  85 A and  85 B, the projection  87 A or  87 B pushes the balls  85 A or  85 B against the springs  86 A or  86 B, so that the force for downwardly (in the figure) sliding the slide bars  83 A and  83 B is momentarily changed. Accordingly, an operator who manipulates the control lever  22  feels the change in the control force of the control lever  22  and can recognize that the control lever has reached to the kickdown range. 
     Further, the movement of the control lever may not be felt by the control force but by visual sense, auditory sense, touch and the like. Specifically, arrival of the control lever to the kickdown range may be notified on a display device using a character or a picture, by sound from a speaker, or vibration of the control lever. 
     Further, the detecting means for detecting the arrival of the control lever to the proximity of the control range may not be a limit switch as in the above embodiments, but other arrangement is possible. For instance, an electric contact point that is electrically in contact with the control lever may be provided adjacent to the control range of the control lever and the arrival is detected when the electric contact point touches the control lever. Alternatively, an optical sensor is provided adjacent to the control range of the control lever and the arrival may be detected when the control lever blocks the optical sensor.