Patent Publication Number: US-2002011013-A1

Title: Hydraulic excavating mobile machine

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention mainly relates to a hydraulic excavating mobile machine which can reasonably control an operation of a working implement in a construction equipment provided with an excavating working implement such as a hydraulic power shovel.  
       [0003] 2. Description of the Related Art  
       [0004] Of various operations carried out using hydraulic power shovels, there is an operation for leveling the ground (generally called as a raking operation) in which a bucket is used in a working implement. The raking operation has been carried out as shown in FIG. 1, for example. In the raking operation, operations of lifting a boom  102  and excavating with a bucket  101  at a top end of an arm  103  are carried out simultaneously with operations of respective operating cylinders  104  and  105  being combined. In this case, the arm  103  moves in the direction of the movement by gravity to draw a locus of the bucket  101  from the start point of the operation going under a target line on the ground as shown by a broken line b in FIG. 1. Prevention of the bucket  101  from going under the target line in such a way depends largely on an ability of an operator. Therefore, a skill is required in carrying out the operation.  
       [0005] Moreover, there is an operation of using a heavy weight attachment in the working implement, as in an operation such as shown in FIG. 2A (the same parts as those in FIG. 1 are denoted by the same reference numerals) carried out by using a crusher  106  for demolition. Such an operation is often carried out with the weight of the crusher  106  attached to the top end of the arm  103  being heavier than that of a generally used bucket, and with the top end of the arm  103  directed toward an elevated target. Furthermore, in carrying out deep excavation, as shown in FIG. 2B, for securing a necessary lifting speed of the working implement, an operation for increasing the operating speed of the operating cylinder  104  of the boom  102  side becomes necessary. This is carried out by relieving a throttle of an unillustrated pressure compensating valve for lifting the boom  102  relative to that of the arm  103 . In either of the above case, the lifting operation of the boom  102  and the operation of the arm  103  are carried out in being simultaneously combined. Such a combined operation can not be smoothly carried out as being desired without skilled control in operating both of the operating cylinders  104  and  105 . In the present status, even for carrying out such an operation, the difficulty has to be overcome only by an ability of an operator. In other word, the operation is still depends on the skill of the operator.  
       [0006] As a disclosed related art about the present invention, there is JP-A-11-316611 in which the same inventor has proposed a pressure compensating valve suited for being applied to a hydraulic pressure control of simultaneous operation of a plurality of actuators. It is disclosed that the pressure compensating characteristic of the pressure compensating valve varies in compliance with a controlling pressure to make it possible to obtain the desired pressure compensating characteristic by changing the controlling pressure.  
       [0007] The disclosed pressure compensating valve, however, yet provides no solution for carrying out effective operation with a plurality of the actuator made operated in combination as described above. Therefore, the combined operation is still carried out depending on the skill for such a operation of an operator, which leaves the problem in that no such kind of operation can be effectively carried out without highly skilled operator.  
       [0008] The present invention has been made in view of such a situation, and it is an object of the present invention to provide a hydraulic excavating mobile machine which has a function that can carry out a desired operation with a combined operation of a plurality of actuators controlled by an operator selecting an operation mode at hand without being required to have any skill.  
       SUMMARY OF THE INVENTION  
       [0009] For achieving the above object, a hydraulic excavating mobile machine according a first aspect of the present invention comprises a machine at least two parts of which is operated by respective hydraulic actuators, a directional control valve provided in each pressurized fluid supply line to each of the actuators, a pressure compensating valve provided in each pressurized fluid supply line to each of the actuators, an operation mode selecting unit provided in a cab of the mobile machine, a controller providing a control signal, and a variable pressure compensating value function storing unit provided in the controller. The pressure compensating valves are operated by the control signal from the controller having the variable pressure compensating value function storing unit according to an operation mode selected by the operation mode selecting unit to thereby control a rate of amount of a pressurized fluid supplied to each of the actuators.  
       [0010] In the present invention, a value of a supplying ratio of pressurized fluid to each of a plurality of the actuators are set beforehand in the variable pressure compensating value function storing unit in the controller. With the supplying ratio set in this way, an operator selects the operation mode by the operation mode selecting unit provided in the cab to change a condition for throttling the pressure compensating valve in the pressurized fluid supply line to each of a plurality of the actuators. Thus, each degree of the pressure compensation can be controlled in a condition commensurate with the operation. Hence, when the operator operates an operation lever, a pressure control valve connected thereto is operated to perform an operation control with the degree of compensation of the amount of the operating pressurized fluid supplied to the actuator kept as being specified. Therefore, according to the present invention, by selecting an operation mode by the operation mode selecting unit, two operated parts, for example, are set in operating conditions different from each other such that one is controlled to be fast operated while the other slowly operated. This made it possible to provide a combined operation of a plurality of actuators that is carried out according to a procedure set beforehand without depending on skills of operators.  
       [0011] In the present invention, a strong compensating function storing unit is better provided as the variable pressure compensating value function storing unit in the controller. Moreover, a weak compensating function storing unit is better provided as the variable pressure compensating value function storing unit. This allows a fixed pressure compensation to be carried out such that the arm operation is controlled by using the former strong compensating function storing unit, while, the boom operation is carried out by using the weak compensating function storing unit, for example. Hence, there is offered an advantage that an operation in a machine accompanied with a combined operations of an arm and a boom provided in the machine can be reasonably carried out with an operating condition of each being specified.  
       [0012] In the present invention, the operation mode selecting unit is better provided with an operation mode selecting switch and a variable level adjusting switch to allow a degree of pressure compensation in the pressure compensating valve by the variable pressure compensating value storing unit to be variable. This offers an advantage that a setting of an operating condition of each of a plurality of the actuator can be adjusted according to the operating condition in addition to the setting of the initial condition.  
       [0013] Furthermore, a hydraulic excavating mobile machine according to a second aspect of the present invention comprises a machine at least two parts of which is operated by respective hydraulic actuators, a directional control valve provided in each pressurized fluid supply line to each of the actuators, a pressure compensating valve provided in each pressurized fluid supply line to each of the actuators, a monitor installed in a cab of the mobile machine, an operation mode selecting unit provided in the monitor, a resistor, and a solenoid valve. Thus, an electric signal from the operation mode selecting unit is inputted to each of the pressure compensating valves through the resistor and the solenoid valve to operate the pressure compensating valve to thereby control an amount of a pressurized fluid supplied to each of the actuators.  
       [0014] According to the second aspect of the present invention, by selecting an operation mode by the monitor, installed in a cab and provided with the operation mode selecting unit, an electric signal corresponding to the selected operation mode produces a voltage across an electric resistor (resistor). The produced voltage operates a solenoid valve connected to the resistor, by which the voltage is converted to a corresponding hydraulic signal. The converted hydraulic signal controls a degree of pressure compensation by the pressure compensating valve in a condition commensurate with the operation. For example, a pressure compensation by a pressure compensating valve on a selected side is made to be carried out under a set condition different from that for the other pressure compensation valve. Thus, the operating condition of the actuator on the selected side is changed from that of the other actuator. Hence, a combined operation of a plurality of actuators, which operation was previously carried out by a skill of an operator, can be carried out in accordance with the set condition for improving operation efficiency. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0015]FIG. 1 is an explanatory view of a problem in raking operation carried out by a hydraulic power shovel;  
     [0016]FIG. 2A is a view showing a mode of previous operation in the hydraulic power shovel with a working implement provided with a heavyweight attachment;  
     [0017]FIG. 2B is a view showing a mode of previous operation in the hydraulic power shovel in deep excavation;  
     [0018]FIG. 3 is a hydraulic control circuit diagram showing a mode of a first example according to the present invention;  
     [0019]FIG. 4 is a flow chart showing an operation process in a hydraulic excavating mobile machine in the first example;  
     [0020]FIG. 5 is a hydraulic control circuit diagram showing only a principal part of a second example according to the present invention;  
     [0021]FIG. 6 is a hydraulic control circuit diagram showing a mode of a third example according to the present invention; and  
     [0022]FIG. 7 is a flow chart showing an operation process in a hydraulic excavating mobile machine in the third example. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0023] In the following, specific embodiments of the hydraulic excavating mobile machine according to the present invention will be explained with reference to the drawings.  
     [0024] First Example  
     [0025] An example of the embodiments is presented as a hydraulic power shovel. In FIG. 3, there is shown a hydraulic control circuit diagram showing a mode of a first example of the present invention.  
     [0026] In the example, there are provided a hydraulic pump  1  driven by an engine mounted on a mobile machine, a hydraulic cylinder  2  for operating a boom (equivalent to an actuator in the present invention), and a hydraulic cylinder  3  for operating an arm (equivalent to an actuator in the present invention). For supplying operating pressurized fluid from the hydraulic pump  1  to the bottom sides of the hydraulic cylinders  2  and  3 , operating fluid supplying circuits  4  and  5  are provided, in which pressure control valves  6  and  7  are provided, respectively. Between the pressure control valve  6  and the hydraulic cylinder  2 , there is provided a pressure compensating valve  10 , and between the pressure control valve  7  and the hydraulic cylinder  3 , there is provided a pressure compensating valve  10   a.    
     [0027] Operating levers  11  and  12  on the left and right are connected to the pressure control valves  6  and  7  and are also electrically connected to the controller through pressure switches  13  and  13   a , respectively. From outlet side fluid lines  4 ′ and  5 ′ of the pressure compensating valves  10  and  10   a  in the operating pressurized fluid supplying circuits  4  and  5  to both of the hydraulic cylinders  2  and  3 , pilot circuits  15  and  15   a  are branched for taking out operating load pressures, respectively. The pilot circuits  15  and  15   a  are connected to a shuttle valve  16 .  
     [0028] To the pressure compensating valves  10  and  10   a , there are connected operating solenoid valves  17  and  17   a  receiving pilot pressurized fluid from the pilot hydraulic pump  8 , respectively. To the operating solenoid valves  17  and  17   a , electric signal circuits  30  and  31  are connected so that the operating solenoid valves  17  and  17   a  receive control signals from the controller  14  for individually operating the pressure compensating valves  10  and  10   a , respectively.  
     [0029] The controller  14  is equipped with a known control device and a variable pressure compensating value function storing unit. To the variable pressure compensating value function storing unit, there is inputted beforehand an instruction value for setting a supplying ratio of operating pressurized fluid supplied to the hydraulic cylinder  2  for boom operation to the fluid supplied to the hydraulic cylinder  3  for arm operation in the combined operation. In addition to this, there is also inputted various values that allow the above supplying ratio of operating pressurized fluid to be further finely set in variable. In a normal operation, the supplying ratio of operating pressurized fluid to the hydraulic cylinder  2  to that to the hydraulic cylinder  3  is taken as 1:1. While, in the raking operation, for example, the supplying ratio of operating pressurized fluid to the hydraulic cylinder  2  for boom operation to that to the hydraulic cylinder  3  for arm operation is set as:  
     [0030] boom operation 1: arm operation 0.8.  
     [0031] In the operation using the heavyweight attachment, or in the deep excavation, the ratio is set as:  
     [0032] boom operation 0.9: arm operation 1.  
     [0033] It is, however, to be understood that the ratio values are not limited to the above.  
     [0034] To such controller  14 , there is provided in an unillustrated cab a monitor  18  that is provided with, for example, two operation mode selecting switches (operating buttons)  18   a  and  18   b  as an operation mode selecting unit for carrying out selection in compliance with an operation mode. The monitor  18  is connected to the controller with a signal circuit so that operation conditions of the boom and the arm can be selected in compliance with the operating mode by the operation mode selecting switch  18   a  and  18   b  when an operator in the cab carries out an operation accompanied with the combined operation. In addition, the monitor  18  is also provided with a variable level adjusting switch  19  (with a structure like a variable resistor switch) so that an operation can be carried out with a fixed controlled variable, discontinuously provided by the operation mode selecting switches  18   a  and  18   b , made further finely varied.  
     [0035] In such an example, in carrying out the raking operation, for example, of the operation mode selecting switches  18   a  and  18   b  on the monitor installed in the cab, an operator presses one of operating buttons for the selecting switches suited for a target operation. Then, from the selected operation mode selecting switch, an instruction signal is sent to the controller  14 , from which in this case instruction values suitable for the raking operation are transmitted to the operating solenoid valves  17  and  17   a . Namely, one of specified signals is transmitted to the operating solenoid valve  17  for operating the pressure compensating valve  10  in the operating pressurized fluid supplying circuit  4  that supplies the operating pressurized fluid to the hydraulic cylinder  2  for boom operation. While, the other one of the specified signals is transmitted to the operating solenoid valve  17   a  for operating the pressure compensating valve  10   a  in the operating pressurized fluid supplying circuit  5  that supplies the operating pressurized fluid to the hydraulic cylinder  3  for arm operation. The operating solenoid valves  17  and  17   a  operates the pressure compensating valves  10  and  10   a , respectively, so that operating pressurized fluid supplied to the hydraulic cylinder  3  for arm operation is throttled at a specified ratio to that supplied to the hydraulic cylinder  2  for boom operation. Specifically, the pressure compensating valve  10   a  on the arm operation side is more throttled.  
     [0036] As a result, an operating speed of the arm becomes slower than that of the boom. In other word, in the raking operation, when leveling the ground surface by a bucket attached to the top end of the arm, an operation of pulling the bucket toward the cab is carried out with the speed of lifting the boom being a little larger than that of pulling the arm (see FIG. 1). Therefore, this allows the ground leveling to be carried out accurately only by an operation of the operating levers for simple movements of the boom and the arm for making the bucket excavate from the ground surface to finish the ground leveled without requiring an operator to have a special skill after a scraping angle by the bucket has been once determined. On the contrary, previous ground leveling was carried out by a skill of an operator based on his experience for controlling the movements of the arm and boom.  
     [0037] Moreover, in carrying out such an operation that the arm side is heavily loaded (a deep excavation or an operation with a heavy weight attachment, see FIGS. 2A and 2B), on pressing the other operating button at the monitor  18 , a signal from the selecting switch corresponding to the pressed button makes the controller  14  to select an instruction value suited for the operation with the heavyweight attachment. Then, instruction signals corresponding thereto are sent to the operating solenoid valves  17  and  17   a  to operate the pressure compensating valves  10  and  10   a , respectively. This, in contrast with the above, more throttles the operating pressurized fluid supplied to the hydraulic cylinder  2  for boom operation than that supplied to the hydraulic cylinder  3  for arm operation at a specified ratio thereto. Specifically, the throttle of the pressure compensating valve  10   a  on the arm lifting side is more released. After operating conditions for the arm and the boom are thus set in compliance with the operation, the operator operates the operation levers  11  and  12  to provide the operating speed of the hydraulic cylinder  3  for arm operation as being a little faster than that of the hydraulic cylinder  2  for boom operation. Hence, in the case of deep excavation, for example, in carrying out an operation of lifting up excavated earth by the bucket, the boom can be smoothly lifted up with a state of pulling the arm toward the cab being maintained. Thus, scooping up of the earth and sand by the bucket can be efficiently carried out.  
     [0038] Also in the case of carrying out demolition with a heavyweight attachment attached to the top end of the arm as in a demolition crusher, reduction in the speed of the arm relative to the lifting speed of the boom can be prevented. When lifting the boom with an object grasped by the crusher, a previous operation, being carried out with the object grasped and held by a crusher relief, caused a pump pressure to increase with a resulting decrease in a pump discharge pressure. In addition, a flow rate adjustment was carried out by the pressure compensating valve for lifting the boom to result in reduction in a boom lifting speed. In the present invention, a ratio of a throttled area for a pressure compensation for lifting the boom to that for lifting the arm is increased. This reduces the pump pressure to make a flow rate ratio of the operating pressurized fluid provide priority to lifting the boom, by which the boom lifting speed can be increased.  
     [0039] In actively operating either the boom or the arm, when adjustment of an operating speed ratio of them is necessary depending on conditions of operations, a variable level adjusting switch  19  provided on the monitor  18  is operated for carrying out level adjustment. With this, an instruction value of control is compensated for the initially set value in the controller  14  depending on the adjusted setting value. Consequently, a ratio of the supplied operating pressurized fluid to the hydraulic cylinder for the boom to that for the arm is changed to allow a desired operation. The above ratio can be set with a supplying condition for one hydraulic cylinder fixed and that for the other hydraulic cylinder only controlled.  
     [0040] When finishing such a combined operation of the boom and the arm, the selected operation mode is canceled by operating the operation mode selecting switch on the monitor  18 . This further cancels the instruction by the controller  14  to the pressure compensating valves  10  and  10   a  to return the operation condition to the normal one. Thus, in subsequent operation, loaded pressures at the hydraulic cylinders  2  and  3  in the operating pressurized fluid supplying circuit  4  and  5  are detected, respectively, for the pressure adjustment carried out by the shuttle valve  16 .  
     [0041] Next, an operation process in the hydraulic excavating mobile machine in the first example will be explained according to a flow chart shown in FIG. 4.  
     [0042] S 1 : On starting the operation, when carrying out a special operation (raking operation, for example), a button for the operation mode selecting switch  18   a  or  18   b  is pressed on the monitor  18  in the cab. This makes the process go to step S 2 . When no button is pressed (No), the operation is decided to be a normal operation and the process is shifted to step S 8 .  
     [0043] S 2 : A decision is made as to whether or not a combined operation with the boom and the arm is carried out as the special operation. When the combined is to be carried out, the process is made to go to step S 3 . When the result of the decision is “No”, the process is shifted to step S 6  as being an individual operation.  
     [0044] S 3 : When the combined operation is selected, a specified pressure compensation level is selected in compliance with the operation. Namely, for example, when the operation is the above raking operation, the pressure compensation level corresponding to the raking operation is selected in the controller  14 .  
     [0045] S 4 : An instruction signal, corresponding to the selected pressure compensation level, is transmitted from the controller  14  to the operating solenoid valve  17   a  on the arm side to operate the operating solenoid valve  17   a.    
     [0046] S 5 : The pressure compensating valves  10  and  10   a  are operated through the operating solenoid valves  17  and  17   a  in compliance with signals of amounts of operations by the operating levers  11  and  12  in combined operation, respectively. By the pressure compensation performed by the pressure compensating valves  10  and  10   a , the supply of the operating pressurized fluid to the respective hydraulic cylinders  2  and  3  is controlled to carry out combined operation of the operating machine for performing a target operation. When the combined operation is finished and the operating condition is returned to normal one, the process returns to step S 1  again.  
     [0047] While, in step S 2 , when it is selected that each of the boom and the arm is operated as an individual operation, the operation is carried out as follows.  
     [0048] S 6 : Hydraulic signals corresponding to signals of amounts of operation by the operating lever  11  and  12  are outputted (from the pressure control valves  6  and  7 ), respectively.  
     [0049] S 7 : The operating machine is operated in compliance with signals of amounts of operation by the operating lever  11  and  12  in the individual operation.  
     [0050] In addition, when a normal operation is selected in step S 1 , the operation is carried out as in a general operation as follows.  
     [0051] S 8 : Hydraulic signals corresponding to signals of amounts of operation by the respective operating lever  11  and  12  are outputted (from the pressure control valves  6  and  7 ).  
     [0052] S 9 : The operating machine is operated in compliance with signals of amounts of operation in the combined operation by the operating lever  11  and  12 .  
     [0053] When the individual operation or the operation of the operating machine in the normal operation is finished, the process returns to step S 1  and is shifted to the next operation with the above operation procedure.  
     [0054] In this way, in the first example, once an operation mode corresponding to the target operation is selected by the operation mode selecting unit (the operation mode selecting switch  18   a  and  18   b  in the monitor  18 ), the pressure compensating valves carry out subsequent control about a ratio of the amount of the operating pressurized fluid supplied to the hydraulic cylinder for the boom operation to that supplied to the hydraulic cylinder for the arm operation (degree of compensation), which ratio has been set by the controller  14  beforehand. This makes it possible to perform the subsequent operation as aimed at only by simply operating the operating levers. Therefore, even an unskilled operator can operate the operating machine smoothly without effort to achieve the intended object.  
     [0055] Second Example  
     [0056] Next, a second example will be explained with reference to FIG. 5. Instead of the configuration of the first example in which instruction signals from the monitor  18  are transmitted to the operating solenoid valves  17  and  17   a  for operating the throttles of the pressure compensating valves  10  and  10   a  through the controller  14 , the configuration of the second example is provided so that instruction signals from the monitor  18  are transmitted to the operating solenoid valves  17  and  17   a  through simple paths as shown in FIG. 5. The second example is the same as the first example in the basic configuration. Hence, the same or similar parts are denoted by the same reference numerals or characters as those in the first example.  
     [0057] In the second example, instruction signals are transmitted from the operation mode selecting switches  18   a  and  18   b  provided on the monitor  18  to the operating solenoid valves  17  and  17   a  through resistors  21  and  22 , and the operating solenoid valves  17  and  17   a  provides hydraulic signals for throttling the pressure compensating valves  10  and  10   a , respectively. The resistors  21  and  22  can be either fixed or variable.  
     [0058] In the second example thus configured, a control system for the combined operation of the operating machine is operated in the same way as in the above first example. Thus, the hydraulic cylinder  2  for the boom operation and the hydraulic cylinder  3  for the arm operation are controlled in compliance with the selected operation mode, so that the operation can be easily carried out without depending on high skills.  
     [0059]FIG. 6 is a hydraulic control circuit diagram showing a mode of a third example according to the present invention. The third example is configured as using electric operating levers. Since the basic configuration thereof is the same as those of the above examples. Thus, the same or similar parts are denoted by the same reference numerals or characters as those in the above examples with detailed explanation to be omitted.  
     [0060] For the case of using the electric operating levers, there is provided a constitution in which a potentiometer (not shown) is provided for each of electric operating levers  25  and  26  for transmitting an amount of a lever operation. The potentiometer normally provides a voltage ranging from an upper limit of 5V to a lower limit of 0V as an electric signal. A neutral zone having a slight range of dead band is provided at around 2.5V corresponding to a neutral position of the lever so that the electric signal generation is unresponsive to a slight initial movement of the lever from the neutral position. A voltage produced at each of the potentiometers by operating each of the operating levers is outputted as an electric signal to the controller  14 . From the controller  14 , control signals corresponding to the outputted electric signals are transmitted to solenoid proportional control valves  27  and  27   a . From the solenoid proportional control valves  27  and  27   a , hydraulic signals corresponding to the control signals are transmitted to the operating parts of the pressure control valves  6  and  7  provided in the operating pressurized fluid supplying circuit  4  and  5  to the hydraulic cylinders  2  and  3 , respectively. In addition, like in the first example, to the pressure compensating valves  10  and  10   a  provided between the outlet of the pressure control valve  6  and the inlet of the hydraulic cylinder  2 , and between the outlet of the pressure control valve  7  and the inlet of the hydraulic cylinder  3 , there are inputted hydraulic signals from the operating solenoid valves  17  and  17   a , respectively. To the operating solenoid valves  17  and  17   a , the electric signal circuits  30  and  31  are connected so that instruction signals are transmitted thereto from the controller  14 .  
     [0061] In such an example, like in the above first and second examples, selection of an operation mode, made by the operation mode selecting switches  18   a  and  18   b  (operation buttons) on the monitor  18  provided in the cab when a combined operation is necessary, allows a selected operation signal to be inputted to the controller  14 . The controller  14  then transmits operation instruction signals, corresponding to the selected operation mode, to the operating solenoid valves  17  and  17   a . The operating solenoid valves  17  and  17   a  then throttle or release the corresponding pressure compensating valves  10  and  10   a  to control amounts of operating pressurized fluids supplied to the corresponding hydraulic cylinders  2  and  3 , respectively. Thus, an amount of the operating pressurized fluid supplied to one of the hydraulic cylinders is throttled or less throttled compared with that to the other hydraulic cylinder so that the operating pressurized fluids are supplied to the hydraulic cylinders with supplying ratios different from each other. As a result, a difference is caused between the operation speed of the arm and that of the boom to make it possible to provide a movement complying with the selected operation, so that the intended object can be easily achieved.  
     [0062] Third Example  
     [0063] Following this, an operation process in the hydraulic excavating mobile machine in the third example will be explained according to a flow chart shown in FIG. 7.  
     [0064] T 1 : On starting the operation, when carrying out a special operation (raking operation, for example), a button for either the operation mode selecting switch  18   a  or that  18   b  is pressed on the monitor  18  in the cab. This makes the process go to step T 2 . When no button is pressed (No), the operation is decided to be a normal operation and the process is shifted to step T 8 .  
     [0065] T 2 : A decision is made as to whether or not a combined operation with the boom and the arm is carried out as the special operation. When the combined operation is to be carried out, the process is made to go to step T 3 . When the result of the decision is “No”, the process is shifted to step T 6  as being an individual operation.  
     [0066] T 3 : When the combined operation is selected, a specified pressure compensation level is selected in compliance with the operation. Namely, for example, when the operation is the above raking operation, the pressure compensation level corresponding to the raking operation is selected in the controller  14 .  
     [0067] T 4 : An instruction signal, corresponding to the selected pressure compensation level, is transmitted from the controller  14  to the operating solenoid valve  17   a  on the arm side (the operating solenoid valve  17  on the boom side) to operate the operating solenoid valve  17   a  (the operating solenoid valve  17 ).  
     [0068] T 5 : The pressure compensating valve  10   a  (the pressure compensating valve  10 ) is operated by a hydraulic signal from the operating solenoid valve  17   a  (the operating solenoid valve  17 ). By the pressure compensation, the supply of the operating pressurized fluid to the hydraulic cylinder  3  (the hydraulic cylinder  2 ) is controlled to carry out combined operation of the working implement for performing a target operation. In compliance with signals of amounts of operations by the operating levers  25  and  26  in combined operation, output signals are provided from the controller  14  to the solenoid proportional control valves  27  and  27   a , respectively. By the solenoid proportional control valves  27  and  27   a , the pressure control valves  6  and  7  carry out control operations of the hydraulic cylinders  2  and  3  with the levels of the above selected pressure compensation being maintained. When the combined operation is finished and the operating condition is returned to normal one, the process returns to step T 1  again.  
     [0069] While, in step T 2 , when it is selected that each of the boom and the arm is operated as an individual operation, the operation is carried out as follows.  
     [0070] T 6 : Electric signals corresponding to signals of amounts of operation by the operating lever  25  and  26  are outputted to the controller  14  from the operating lever  25  and  26 , respectively.  
     [0071] T 7 : The signals of amounts of operation by the operating lever  25  and  26  in the individual operation are outputted from the controller  14  to the solenoid proportional control valves  27  and  27   a , respectively. The hydraulic signals from the solenoid proportional control valves  27  and  27   a  operate the working implement in compliance with the above signals of the amounts of lever operation.  
     [0072] In addition, when a normal operation is selected in step T 1 , the operation is carried out as in a general operation as follows.  
     [0073] T 8 : Electric signals corresponding to signals of amounts of operation by the respective operating lever  25  and  26  are outputted from the controller  14 .  
     [0074] T 9 : The operating machine is operated in compliance with signals of amounts of operation in the combined operation by the operating lever  25  and  26 .  
     [0075] When the individual operation or the operation of the working implement in the normal operation is finished, the process returns to step T 1  and is shifted to the next operation with the above operation procedure.  
     [0076] In this way, also in the third example, once an operation mode corresponding to the target operation is selected by the operation mode selecting unit (the operation mode selecting switches  18   a  and  18   b  in the monitor  18 ), the pressure compensating valves  10  and  10   a  carry out subsequent control about a ratio of the amount of the operating pressurized fluid supplied to the hydraulic cylinder for the boom operation to that supplied to the hydraulic cylinder for the arm operation (degree of compensation), which ratio has been set by the controller  14  beforehand. This makes it possible to perform the subsequent operation as aimed at only by simply operating the electric operating levers. Therefore, even an unskilled operator can operate the operating machine smoothly without effort to achieve the intended object.  
     [0077] In the foregoing explanations, the actuators for carrying out control are given as hydraulic actuators. The present invention, however, can be also flexibly applied to the cases in which other types of hydraulically operated equipment are used as the actuator.