Patent Publication Number: US-11396839-B2

Title: Hydraulic drive fan control device

Description:
TECHNICAL FIELD 
     The present invention relates to a control device for a hydraulic drive fan that supplies cooling air to a heat exchange device. 
     BACKGROUND ART 
     A construction machine of a dump truck or the like is provided with a heat exchange device of a radiator that cools engine cooling water, an oil cooler that cools hydraulic oil and the like, and a cooling fan that supplies cooling air to the heat exchange device, which are mounted thereon. There is known a hydraulic drive fan, which is driven by a hydraulic motor, as this cooling fan. The hydraulic motor is rotated by pressurized oil that is delivered from a hydraulic pump driven by a prime mover of an engine or the like, and the hydraulic drive fan is driven and rotated by the hydraulic motor. 
     A dump truck that works in an excavating site of a mine or the like loads cargos of earth and sand or the like excavated using a hydraulic excavator or the like, on a loading platform, and carries the cargoes to a destination. The dump truck travels for a large part of working hours and stops when the cargo is loaded on the loading platform and when the cargo loaded on the loading platform is unloaded. In addition, the dump truck performs an unloading work of the cargo by inclining the loading platform by a hoist cylinder in the stopped state. 
     An engine rotational speed of the dump truck is relatively stable at the traveling time but, when the dump truck stops at a place for performing a loading work or unloading work, the engine rotational speed varies minutely caused by adjusting a stopping position or a traveling speed. Meanwhile, at the unloading work time, the engine rotational speed varies minutely due to changing a delivery flow amount of the hydraulic pump in accordance with a speed, an operation and the like of expanding and contracting the hoist cylinder. In this way, since the flow amount of the hydraulic pump fluctuates when the engine rotational speed varies, a rotational speed of the hydraulic drive fan also varies. 
     In general, in a case of controlling the rotational speed of the hydraulic drive fan, feedback control and PI control (proportional and integral control) are executed such that a deviation between a target fan rotational speed and an actual fan rotational speed becomes equal to 0. However, in a case of using the feedback control or the PI control for controlling the rotational speed of the hydraulic drive fan, a peak pressure (a surge pressure) or pressure hunching tends to be easily generated in a hydraulic circuit for driving the hydraulic drive fan. As a result, not only the rotational speed of the hydraulic drive fan tends to easily vary, but also there is a problem that hydraulic equipment devices such as a hydraulic motor, a hydraulic hose and the like configuring the hydraulic circuit are damaged. Meanwhile, the rotational speed of the hydraulic drive fan abruptly varies largely, which introduces damages of blades of the fan, and the like. In addition, when the pressure hunching is generated, fluctuations (pressure variation) or repeated stresses are generated in the inside of the hydraulic equipment devices configuring the hydraulic circuit, which introduces abrasion and a reduction in strength of the hydraulic equipment devices. 
     On the contrary, there is proposed a control device for a hydraulic drive fan that is provided with a hydraulic drive fan that is driven by a hydraulic motor, a variable displacement hydraulic pump that is driven by an engine and delivers pressurized oil to the hydraulic motor, a control valve that controls a capacity of the variable displacement hydraulic pump, and a controller that sends an instruction signal to the control valve. In the control device for the hydraulic drive fan, the controller calculates a target fan rotational speed based upon an engine water temperature, a hydraulic oil temperature and an engine rotational speed. The controller outputs a current instruction required for causing a fan rotational speed to match the target fan rotational speed to the control valve to feedback control the fan rotational speed (Patent Document 1). 
     In the control device for the hydraulic drive fan according to Patent Document 1, the rotational speed control of the fan is executed by the PI control for suppressing an abrupt variation of the fan rotational speed, and the integral action is cancelled when it is required to largely move the control valve, limiting a control amount of the control valve to a predetermined change amount. As a result, generation of the peak pressure in the oil path for connection of the hydraulic pump and the hydraulic motor and generation of the pressure hunching in the delivery pressure from the hydraulic motor can be prevented. 
     PRIOR ART DOCUMENT 
     Patent Document 
     
         
         Patent Document 1: Japanese Patent Laid-Open No. 2009-243389 A 
       
    
     SUMMARY OF THE INVENTION 
     However, in the control device for the hydraulic drive fan according to Patent Document 1, the control amount of the control valve is suppressed to the predetermined change amount when it is required to largely move the control valve, the responsiveness of the feedback control deteriorates. Since the delivery flow amount of the hydraulic pump is largely affected by not only the capacity of the hydraulic pump but also the engine rotational speed, in a case where the engine rotational speed varies minutely at the loading work or unloading work time as in the case of the dump truck, the fan rotational speed cannot be matched to the target fan rotational speed to be incapable of suppressing the variation of the fan rotational speed. As a result, there is posed a problem that the peak pressure or the pressure hunching is generated in the hydraulic circuit for driving the hydraulic drive fan. 
     The present invention is made in view of the aforementioned problems in the conventional technology, and an object of the present invention is to provide a hydraulic drive fan control device that can suppress variation in a fan rotational speed to suppress generation of a peak pressure or pressure hunching in a hydraulic circuit. 
     The present invention is applied to a hydraulic drive fan control device comprising: a variable displacement hydraulic pump that is driven by a prime mover and varies a delivery capacity in response to a control signal to be inputted to a capacity variable part; a hydraulic motor that is driven by pressurized oil to be delivered from the variable displacement hydraulic pump; a hydraulic drive fan that is driven by the hydraulic motor; a flow amount control valve that is disposed in an oil path establishing connection between the variable displacement hydraulic pump and the hydraulic motor and varies a flow amount of the pressurized oil to be delivered to the hydraulic motor in response to a control signal to be inputted to a pilot part; a rotational speed detector that detects a rotational speed of the prime mover; and a controller that outputs a control signal to the variable displacement hydraulic pump and the flow amount control valve based upon a detection value of the rotational speed detector. 
     The present invention is characterized in that the controller includes a calculation control section configured to: when an output time of a timer continues for a constant time or more in a state where the detection value of the rotational speed detector is kept as a value equal to or more than a predetermined threshold value, output a first valve control signal to the flow amount control valve for rotating the hydraulic drive fan at a first rotational speed; when the output time of the timer does not continue for the constant time or more in a state where the detection value of the rotational speed detector is kept as the value equal to or more than the threshold value, output a second valve control signal by which the flow amount is minimized, to the flow amount control valve for stopping rotation of the hydraulic drive fan; when the output time of the timer continues for the constant time or more in a state where the detection value of the rotational speed detector is kept as the value equal to or more than the threshold value, output a first pump control signal to the variable displacement hydraulic pump for rotating the hydraulic drive fan at the first rotational speed; and when the output time of the timer does not continue for the constant time or more in a state where the detection value of the rotational speed detector is kept as the value equal to or more than the threshold value, output a second pump control signal by which the delivery capacity is minimized, to the variable displacement hydraulic pump for stopping the rotation of the hydraulic drive fan. 
     According to the present invention, the first valve control signal is outputted to the flow amount control valve from the calculation control section and the first pump control signal is outputted to the variable displacement hydraulic pump, whereby the hydraulic drive fan can be rotated at the first rotational speed. Meanwhile, the second valve control signal is outputted to the flow amount control valve from the calculation control section and the second pump control signal is outputted to the variable displacement hydraulic pump, whereby the rotation of the hydraulic drive fan can be stopped. As a result, the rotational speed of the hydraulic drive fan can be suppressed from varying minutely following the variation in the rotational speed of the prime mover, and the peak pressure or the pressure hunching in the hydraulic circuit connected to the hydraulic drive fan can be suppressed from being generated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a configuration diagram of a hydraulic drive fan control device according to a first embodiment of the present invention. 
         FIG. 2  is a characteristic line diagram showing a relation between a pump control amount to be inputted to a regulator in a hydraulic pump and a pump capacity of the hydraulic pump. 
         FIG. 3  is a characteristic line diagram showing a relation between a valve control amount to be inputted to a pilot part in a flow amount control valve and an opening area of the flow amount control valve. 
         FIG. 4  is a flow chart showing determination processing of fan predetermined rotational speed control, fan idling rotational speed control and fan rotation stopping control by controller. 
         FIG. 5  is a flow chart showing a processing content of the fan predetermined rotational speed control. 
         FIG. 6  is a flow chart showing a processing content of the fan idling rotational speed control. 
         FIG. 7  is a flow chart showing a processing content of the fan rotation stopping control. 
         FIG. 8  is a characteristic line diagram showing a temporal relation between an engine rotational speed, a pump capacity of the hydraulic pump and a rotational speed of a hydraulic motor. 
         FIG. 9  is a configuration diagram of a hydraulic drive fan control device according to a second embodiment. 
         FIG. 10  is a characteristic line diagram showing a relation between a relief pressure control amount to be inputted to a pressure control part in a variable relief valve and a relief pressure of the variable relief valve. 
         FIG. 11  is a flow chart showing a processing content of the fan predetermined rotational speed control. 
         FIG. 12  is a flow chart showing a processing content of the fan idling rotational speed control. 
         FIG. 13  is a flow chart showing a processing content of the fan rotation stopping control. 
         FIG. 14  is a flow chart showing determination processing of fan predetermined rotational speed control and fan rotation stopping control according to a third embodiment. 
         FIG. 15  is a flow chart showing a processing content of the fan predetermined rotational speed control. 
         FIG. 16  is a flow chart showing a processing content of the fan rotation stopping control. 
         FIG. 17  is a characteristic line diagram showing a temporal relation between an engine rotational speed, a pump capacity of a hydraulic pump and a rotational speed of a hydraulic motor. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, an explanation will be in detail made of a hydraulic drive fan control device according to the present invention with reference to the accompanying drawings. 
       FIG. 1  to  FIG. 8  show a first embodiment of the present invention. A hydraulic drive fan control device  1  as shown in  FIG. 1  is mounted on a construction machine such as a dump truck. The hydraulic drive fan control device  1  is configured of a hydraulic pump  2 , a hydraulic motor  6 , a hydraulic drive fan  7 , a flow amount control valve  8 , a rotational speed detector  14 , a pressure detector  15 , a controller  16  and the like. 
     The variable displacement hydraulic pump  2  (hereinafter, referred to as “hydraulic pump  2 ”) configures a hydraulic source together with a tank  3 . The hydraulic pump  2  is connected to an output shaft  4 A of an engine  4  and is driven by the engine  4 . A suction port of the hydraulic pump  2  is connected to the tank  3 , and a delivery port of the hydraulic pump  2  is connected via a fan pipe line  5  to an inflow port of a hydraulic motor  6 . The hydraulic pump  2  suctions hydraulic oil in the tank  3  and delivers pressurized oil to the fan pipe line  5 . A delivery flow amount Q 1  (L/min) of the hydraulic pump  2  is a value found by multiplying a pump capacity q 1  (cc/rev) of the hydraulic pump  2  by an engine rotational speed N 1  (min −1 ) of the engine  4 . 
     The hydraulic pump  2  is configured such that a pump capacity changes by changing a tilting angle of a swash plate  2 A, for example, and has an electromagnetic drive regulator  2 B as a capacity variable part. The regulator  2 B changes the tilting angle of the swash plate  2 A in accordance with a pump control amount Cp (A) to be supplied from the controller  16  to change the pump capacity of the hydraulic pump  2 . The pump control amount Cp is supplied to the regulator  2 B as an instruction current (a pump control signal) from the controller  16 . It should be noted that a hybrid prime mover composed of an electric motor or by a combination of an engine and an electric motor may be used as a prime mover that drives the hydraulic pump  2 . 
     The hydraulic motor  6  is configured of a fixed capacity hydraulic motor. A hydraulic drive fan  7  is attached to an output shaft  6 A of the hydraulic motor  6 . The hydraulic motor  6  is driven by pressurized oil supplied to an inflow port from the hydraulic pump  2  to rotate the hydraulic drive fan  7 . The inflow port of the hydraulic motor  6  is connected via the fan pipe line  5  to a delivery port of the hydraulic pump  2  and an outflow port of the hydraulic motor  6  is connected to the tank  3 . Here, a rotational speed N 2  (min −1 ) of the hydraulic motor  6  is a value found by dividing a flow amount Q 2  (L/min) of the pressurized oil to be supplied to the hydraulic motor  6  through a flow amount control valve  8  by a capacity q 2  (cc/rev) of the hydraulic motor  6 . 
     The hydraulic drive fan  7  is attached to the output shaft  6 A of the hydraulic motor  6  and is driven by the hydraulic motor  6 . In the present embodiment, a rotational speed of the hydraulic drive fan  7  is equal to a rotational speed of the hydraulic motor  6 . The hydraulic drive fan  7  is composed of an axial-flow fan, and supplies cooling air to, for example, heat exchangers of a radiator, an oil cooler and the like (none of them is shown), which are mounted on a dump truck. Power L 2  (kW) at some rotational speed of the hydraulic drive fan  7 , pressure P 2  (MPa) of the pressurized oil to be supplied to the hydraulic motor  6  and a flow amount Q 2  (L/min) of the pressurized oil through the flow amount control valve  8  to be supplied to the hydraulic motor  6  have a relation of the following Formula 1. 
     
       
         
           
             
               
                 
                   
                     P 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     2 
                   
                   = 
                   
                     
                       
                         L 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         2 
                       
                       
                         Q 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         2 
                       
                     
                     × 
                     60 
                   
                 
               
               
                 
                   [ 
                   
                     Formula 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                   ] 
                 
               
             
           
         
       
     
     The flow amount control valve  8  is disposed in the halfway of the fan pipe line  5  to be positioned between the hydraulic pump  2  and the hydraulic motor  6 . The flow amount control valve  8  is configured of an electromagnetic valve having a solenoid part  8 A as a pilot part. The flow amount control valve  8  opens against a spring  8 B by a control signal to be inputted to the solenoid part  8 A from the controller  16 . The flow amount control valve  8  changes an opening area (a valve opening) in accordance with a valve control amount Cv (A) to be inputted to the solenoid part  8 A from the controller  16 . The valve control amount Cv is supplied to the solenoid part  8 A as an instruction current (a valve control signal) from the controller  16 . 
     Here, the flow amount Q 2  (L/min) of the pressurized oil to be supplied to the hydraulic motor  6  through the flow amount control valve  8  can be found according to the following Formula 2. It should be noted that in Formula 2, C is a contraction coefficient. The contraction coefficient C is defined by shapes of the fan pipe line  5  and a flow path of the flow amount control valve  8 , a flow speed of the pressurized oil and viscosity of the pressurized oil. A 1  (mm 2 ) is an opening area of the flow amount control valve  8 . P 1  (MPa) is a delivery pressure (a pressure of the pressurized oil in the fan pipe line  5 ) of the hydraulic pump  2 . P 2  (MPa) is a pressure of the pressurized oil to be supplied to the hydraulic motor  6 . ρ (kg/m 3 ) is density of the pressurized oil. 
     
       
         
           
             
               
                 
                   
                     Q 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     2 
                   
                   = 
                   
                     
                       C 
                       · 
                       A 
                     
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                     × 
                     
                       
                         
                           2 
                           ⁢ 
                           
                             ( 
                             
                               
                                 P 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                               
                               - 
                               
                                 P 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 2 
                               
                             
                             ) 
                           
                         
                         ρ 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Formula 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     2 
                   
                   ] 
                 
               
             
           
         
       
     
     A check valve  9  is connected to the halfway of the fan pipe line  5  to be positioned between the hydraulic motor  6  and the flow amount control valve  8 . The check valve  9  allows flow of the hydraulic oil toward the fan pipe line  5  from the tank  3  and blocks the reverse flow. For example, in a state where the hydraulic drive fan  7  is rotating, in a case where the opening area of the flow amount control valve  8  becomes equal to 0 to stop the supply of the pressurized oil to the hydraulic motor  6 , a negative pressure is generated in the inflow port side of the hydraulic motor  6 . When the negative pressure is generated in the inflow port side of the hydraulic motor  6 , the check valve  9  is operable to supply the hydraulic oil in the tank  3  to the inflow port of the hydraulic motor  6 . Thereby, the rotational speed of the hydraulic motor  6  can be suppressed from varying (stopping) abruptly. 
     A relief valve  10  is disposed in the halfway of the fan pipe line  5 . The inflow port of the relief valve  10  is connected to the fan pipe line  5  and the outflow port of the relief valve  10  is connected to the tank  3 . The relief valve  10  sets a delivery pressure of the pressurized oil to be delivered to the fan pipe line  5  from the hydraulic pump  2  and discharges an extra pressure exceeding the set delivery pressure to the tank  3 . The relief valve  10  defines the maximum pressure in the hydraulic circuit for driving the hydraulic drive fan  7 . 
     A working machine pipe line  11  is connected to a branch point  5 A disposed in the halfway of the fan pipe line  5 . The branch point  5 A is disposed between the hydraulic pump  2  and the flow amount control valve  8 . A working machine  12  composed of a hydraulic actuator is connected to the working machine pipe line  11 . For example, a hydraulic actuator (not shown) such as a hoist cylinder lifting/lowering a loading platform of a dump truck is used as the working machine  12  and lifts/lowers the loading platform of the dump truck in response to delivery of the pressurized oil from the hydraulic pump  2 . 
     A working machine operation device  13  is disposed in an operator&#39;s room (not shown) of a dump truck, for example. The working machine operation device  13  is operated for driving the working machine  12  of the hoist cylinder or the like, and the working machine  12  is driven in accordance with an operation amount of the working machine operation device  13 . The working machine operation device  13  is connected to an input port  16 A of the controller  16 , and a detection signal in accordance with the operation amount to the working machine operation device  13  is supplied to the input port  16 A. 
     The rotational speed detector  14  is disposed in the vicinity of the engine  4  and is connected to the input port  16 A of the controller  16 . The rotational speed detector  14  detects the engine rotational speed N 1  (min −1 ) as the rotational speed of the output shaft  4 A of the engine  4  and supplies a detection signal in accordance with this rotational speed to the input port  16 A of the controller  16 . 
     The pressure detector  15  is disposed in the halfway of the fan pipe line  5  to be positioned between the hydraulic pump  2  and the flow amount control valve  8 . The pressure detector  15  is connected to the input port  16 A of the controller  16 . The pressure detector  15  detects the delivery pressure P 1  (MPa) of the hydraulic pump  2  that has performed the delivery to the fan pipe line  5  and supplies a detection signal in accordance with this pressure to the input port  16 A in the controller  16 . 
     The controller  16  includes the input port  16 A, an output port  16 B, a memory  16 C, a calculation control section  16 D, a timer  16 E and the like. The input port  16 A is connected to the working machine operation device  13 , the rotational speed detector  14  and the pressure detector  15 . The output port  16 B is connected to the regulator  2 B of the hydraulic pump  2  and the solenoid part  8 A of the flow amount control valve  8 . The calculation control section  16 D supplies a control signal to the regulator  2 B of the hydraulic pump  2  and the solenoid part  8 A of the flow amount control valve  8  based upon detection signals to be supplied to the input port  16 A from the working machine operation device  13 , the rotational speed detector  14  and the pressure detector  15  and an output time from the timer  16 E. That is, the calculation control section  16 D configures a valve control part and a pump control part. The timer  16 E is connected to the calculation control section  16 D. 
     Here, a relation between the pump control amount Cp (A) as the pump control signal to be inputted to the regulator  2 B of the hydraulic pump  2  and the pump capacity q 1  (cc/rev) of the hydraulic pump  2  is shown as a characteristic line diagram in  FIG. 2 . That is, in a case where the pump control amount Cp becomes equal to a first pump control amount Cp 1  as a first pump control signal, the pump capacity q 1  becomes a pump capacity q 1   p  at the fan predetermined rotational speed time to be described later. In a case where the pump control amount Cp becomes equal to or more than a second pump control amount Cp 2  as a second pump control signal, the pump capacity q 1  becomes a minimum pump capacity q 1   m . In a case where the pump control amount Cp becomes equal to a third pump control amount Cp 3  as a third pump control signal, the pump capacity q 1  becomes a pump capacity q 1   i  at the fan idling rotational speed time to be described later. 
     Meanwhile, a relation between the valve control amount Cv (A) as the valve control signal to be inputted to the solenoid part  8 A of the flow amount control valve  8  and the opening area A 1  (mm 2 ) of the flow amount control valve  8  is shown as a characteristic line diagram in  FIG. 3 . That is, in a case where the valve control amount Cv becomes equal to or less than a first valve control amount Cv 1  as a first valve control signal, the opening area A 1  becomes a maximum opening area. In a case where the valve control amount Cv becomes equal to or more than a second valve control amount Cv 2  as a second valve control signal, the opening area A 1  becomes equal to 0. In a case where the valve control amount Cv becomes equal to a third valve control amount Cv 3  as a third valve control signal, the opening area A 1  becomes an opening area A 1   i  at the fan idling rotational speed time. 
     The hydraulic drive fan control device  1  according to the first embodiment has the configuration as described above. Next, an explanation will be made of an operation of the hydraulic drive fan control device  1  with reference to  FIG. 4  to  FIG. 7 . 
     In a case where the dump truck on which the hydraulic drive fan control device  1  is mounted starts from the stopped state, the controller  16  executes the determination processing as shown in  FIG. 4 . Thereby, the controller  16  determines which one of fan predetermined rotational speed control, fan idling rotational speed control and fan rotation stopping control should be applied to the hydraulic drive fan  7 . At this time, the calculation control section  16 D in the controller  16  sets an initial value of a fan predetermined rotational speed flag to OFF, an initial value of a fan idling rotational speed flag to OFF, and an initial value of a fan rotation stopping flag to ON. In addition, the hydraulic pump  2  is set to the minimum pump capacity q 1   m  by the regulator  2 B. 
     First, the controller  16  obtains the engine rotational speed N 1  detected by the rotational speed detector  14  and the operation amount of the working machine operation device  13  in step  1 , which are stored in the memory  16 C. A plurality of pieces of the engine rotational speeds N 1  in the past are stored in the memory  16 C. In a case where the piece number of the stored engine rotational speeds N 1  reaches the maximum value, the engine rotational speed is in order updated to the latest engine rotational speed N 1 . 
     Next, in step  2 , the calculation control section  16 D determines whether or not the working machine  12  is operated by the working machine operation device  13 . In a case where “YES” is determined in step  2 , that is, in a case where the working machine  12  is operated, the process goes to step  3 , wherein the fan rotation stopping control as shown in  FIG. 7  is executed. 
     In a case where “NO” is determined in step  2 , that is, in a case where the working machine  12  is not operated, the process goes to step  4 . The calculation control section  16 D measures a continuation time during which the engine rotational speed N 1  is equal to or more than a predetermined threshold value (hereinafter, referred to as “predetermined engine rotational speed N 1   s ”) in step  4 . In this case, the calculation control section  16 D measures the continuation time during which the engine rotational speed N 1  is equal to or more than the predetermined engine rotational speed N 1   s  based upon the plurality of pieces of engine rotational speeds N 1  stored in the memory  16 C and an interval time (a memory cycle of the memory  16 C based upon the output time of the timer  16 E) for executing the memory processing of the engine rotational speed N 1 . 
     Next, in step  5 , the calculation control section  16 D determines whether or not the output time of the timer  16 E continues for a constant time or more in a state where the engine rotational speed N 1  is kept as a value equal to or more than the predetermined engine rotational speed Nis. In a case where “NO” is determined in step  5 , the process goes to step  6 , wherein the fan idling rotational speed control as shown in  FIG. 6  is executed. Meanwhile, in a case where “YES” is determined in step  5 , the process goes to step  7 , wherein the fan predetermined rotational speed control as shown in  FIG. 5  is executed. 
     In this way, the controller  16  executes the fan predetermined rotational speed control in a case where the output time of the timer  16 E continues for the constant time or more in a state where the engine rotational speed N 1  is kept as the value equal to or more than the predetermined engine rotational speed N 1   s  in a state where the working machine  12  is not operated. This fan predetermined rotational speed control rotates the hydraulic drive fan  7  at a fan predetermined rotational speed as a first rotational speed. In addition, the controller  16  executes the fan idling rotational speed control in a case where the output time of the timer  16 E does not continue for the constant time or more in a state where the engine rotational speed N 1  is kept as the value equal to or more than the predetermined engine rotational speed N 1   s  in a state where the working machine  12  is not operated. The fan idling rotational speed control rotates the hydraulic drive fan  7  at a fan idling rotational speed as a second rotational speed lower than the fan predetermined rotational speed. Further, the controller  16  executes the fan rotation stopping control that stops the hydraulic drive fan  7  in a case where the working machine  12  is operated. 
     Next, an explanation will be made of the fan predetermined rotational speed control by the controller  16  with reference to  FIG. 5 . In this case, the fan predetermined rotational speed of the hydraulic drive fan  7  corresponds to the first rotational speed to be set when the output time of the timer  16 E continues for the constant time or more in a state where the engine rotational speed N 1  is kept as the value equal to or more than the predetermined engine rotational speed N 1   s  as a threshold value. 
     In the fan predetermined rotational speed control as shown in  FIG. 5 , the calculation control section  16 D sets a fan idling rotational speed flag to OFF in step  11 , and thereafter, reads in the pump capacity q 1   p  of the hydraulic pump  2  at the fan predetermined rotational speed time from the memory  16 C in step  12 . The pump capacity q 1   p  of the hydraulic pump  2  at the fan predetermined rotational speed time is in advance defined and is stored in the memory  16 C. 
     Next, in step  13 , the calculation control section  16 D determines whether or not the fan rotation stopping flag is ON. In a case where “NO” is determined in step  13 , the process goes to step  17 , and in a case where “YES” is determined in step  13 , the process goes to step  14 . In step  14 , the calculation control section  16 D determines whether or not the pump control amount Cp to be outputted to the regulator  2 B of the hydraulic pump  2  is equal to the second pump control amount (the second pump control signal) Cp 2  for setting the hydraulic pump  2  to the minimum pump capacity q 1   m.    
     In a case where “NO” is determined in step  14 , the process goes to step  15 . In step  15 , the calculation control section  16 D outputs the second pump control signal Cp 2  to the regulator  2 B of the hydraulic pump  2  and sets the hydraulic pump  2  to the minimum pump capacity q 1   m , and thereafter, the process goes to step  16 . In this way, in an initial stage where the hydraulic drive fan  7  transfers to the fan predetermined rotational speed, the step  13  to step  15  are executed, whereby the pump capacity q 1  of the hydraulic pump  2  at the starting time of the hydraulic drive fan  7  once becomes equal to the minimum pump capacity q 1   m . As a result, the rotation of the hydraulic drive fan  7  can be suppressed from varying abruptly. 
     In a case where “YES” is determined in step  14 , in step  16 , the calculation control section  16 D sets the fan rotation stopping flag to OFF, and then, the process goes to step  17 . In step  17 , the calculation control section  16 D determines whether or not the valve control amount Cv to be outputted to the solenoid part  8 A of the flow amount control valve  8  is equal to the first valve control amount (the first valve control signal) Cv 1  for maximizing the opening area A 1  of flow amount control valve  8 . In a case where “NO” is determined in step  17 , in step  18 , the calculation control section  16 D outputs the first valve control amount Cv 1  to the solenoid part  8 A to maximize the opening area A 1  of the flow amount control valve  8 . In this case, the calculation control section  16 D outputs the first valve control amount Cv 1  to the solenoid part  8 A with a predetermined change amount per a predetermined unit time. In this way, in an initial stage where the hydraulic drive fan  7  transfers to the fan predetermined rotational speed, the step  17  and step  18  are executed, whereby it is possible to gradually increase the flow amount of the pressurized oil to be supplied to the hydraulic motor  6  at the starting time of the hydraulic drive fan  7 . As a result, the rotation of the hydraulic drive fan  7  can be suppressed from varying abruptly. 
     In a case where “YES” is determined in step  17 , in step  19 , the calculation control section  16 D determines whether or not the pump control amount Cp to be outputted to the regulator  2 B of the hydraulic pump  2  is equal to the first pump control amount (the first pump control signal) Cp 1  for setting the hydraulic pump  2  to the pump capacity q 1   p  at the fan predetermined rotational speed time. In a case where “NO” is determined in step  19 , in step  20 , the calculation control section  16 D outputs the first pump control amount Cp 1  to the regulator  2 B and sets the hydraulic pump  2  to the pump capacity q 1   p  at the fan predetermined rotational speed time. In this case, the calculation control section  16 D outputs the first pump control amount Cp 1  with a predetermined change amount per a predetermined unit time. In this way, in an initial stage where the hydraulic drive fan  7  transfers to the fan predetermined rotational speed, the step  19  and step  20  are executed, whereby at the starting time of the hydraulic drive fan  7 , it is possible to gradually increase the pump capacity q 1  of the hydraulic pump  2  to the pump capacity q 1   p  at the fan predetermined rotational speed time. As a result, the rotation of the hydraulic drive fan  7  can be suppressed from varying abruptly. 
     In a case where “YES” is determined in step  19 , since the pump capacity q 1  of the hydraulic pump  2  becomes equal to the pump capacity q 1   p  at the fan predetermined rotational speed time, the hydraulic motor  6  can rotate the hydraulic drive fan  7  at the fan predetermined rotational speed. In addition, the calculation control section  16 D sets the fan predetermined rotational speed flag to ON in step  21 , and thereafter, ends the control processing. 
     Next, an explanation will be made of the fan idling rotational speed control by the controller  16  with reference to  FIG. 6 . In this case, the fan idling rotational speed of the hydraulic drive fan  7  corresponds to the second rotational speed to be set when the output time of the timer  16 E does not continue for the constant time or more in a state where the engine rotational speed N 1  is kept as the value equal to or more than the predetermined engine rotational speed N 1   s  as a threshold value. The fan idling rotational speed is set to a value lower than the fan predetermined rotational speed as the first rotational speed and greater than 0 (a state of the rotation stop). 
     In the fan idling rotational speed control as shown in  FIG. 6 , the calculation control section  16 D sets the fan predetermined rotational speed flag to OFF in step  31 , and thereafter, the process goes to step  32 . In step  32 , the calculation control section  16 D reads in a pressure P 2   i  (MPa) of the pressurized oil to be supplied to the hydraulic motor  6 , a flow amount Q 2   i  (L/min) of the pressurized oil passing through the flow amount control valve  8  and a pump capacity q 1   i  (cc/rev) of the hydraulic pump  2  at the fan idling rotational speed time from the memory  16 C. The pressure P 2   i , the flow amount Q 2   i  and the pump capacity q 1   i  at the fan idling rotational speed time are in advance defined and are stored in the memory  16 C. 
     Next, in step  33 , the calculation control section  16 D obtains the delivery pressure P 1  of the hydraulic pump  2  based upon the detection signal from the pressure detector  15 . In subsequent step  34 , the calculation control section  16 D determines whether or not the fan rotation stopping flag is ON. In a case where “NO” is determined in step  34 , the process goes to step  38 , and in a case where “YES” is determined in step  34 , the process goes to step  35 . 
     In step  35 , the calculation control section  16 D determines whether or not the pump control amount Cp to be outputted to the regulator  2 B in the hydraulic pump  2  is equal to the second pump control amount (a second pump control signal) Cp 2  to make the pump capacity of the hydraulic pump  2  the minimum pump capacity q 1   m . in a case where “NO” is determined in step  35 , the calculation control section  16 D outputs the second pump control amount Cp 2  to the regulator  2 B in step  36  to make the pump capacity of the hydraulic pump  2  the minimum pump capacity q 1   m . In the initial stage where the hydraulic drive fan  7  transfers to the fan idling rotational speed, the step  34  to step  36  are executed, whereby the pump capacity q 1  of the hydraulic pump  2  at the starting time of the hydraulic drive fan  7  becomes equal to the minimum capacity once. As a result, the rotation of the hydraulic drive fan  7  can be suppressed from varying abruptly. 
     In a case where “YES” is determined in step  35 , the calculation control section  16 D sets the fan rotation stopping flag to OFF in step  37 , and thereafter, the process goes to step  38 . 
     In step  38 , the calculation control section  16 D determines whether or not the pump control amount Cp to be outputted to the regulator  2 B in the hydraulic pump  2  is equal to the third pump control amount (a third pump control signal) Cp 3  to make the pump capacity of the hydraulic pump  2  the pump capacity q 1   i  at the fan idling rotational speed time. In a case where “NO” is determined in step  38 , the calculation control section  16 D outputs the third pump control amount Cp 3  to the regulator  2 B in step  39  to make the pump capacity of the hydraulic pump  2  the pump capacity q 1   i  at the fan idling rotational speed time. In this case, the calculation control section  16 D outputs the third pump control amount Cp 3  with a predetermined change amount per a predetermined unit time. In this way, in the initial stage where the hydraulic drive fan  7  transfers to the fan idling rotational speed, the step  38  and step  39  are executed, whereby the pump capacity q 1  of the hydraulic pump  2  at the starting time of the hydraulic drive fan  7  can be gradually increased to the pump capacity q 1   i  at the fan idling rotational speed time. As a result, the rotation of the hydraulic drive fan  7  can be suppressed from varying abruptly. 
     In a case where “YES” is determined in step  38 , in step  40 , the calculation control section  16 D sets the fan idling rotation speed flag to ON, and then, the process goes to step  41 . In step  41 , the calculation control section  16 D calculates the third valve control amount (a third valve control signal) Cv 3  to be outputted to the solenoid part  8 A of the flow amount control valve  8  for controlling the hydraulic drive fan  7  to the fan idling rotation speed. In this case, the calculation control section  16 D calculates an opening area A 1   i  of the flow amount control valve  8  for the flow amount Q 2  of the pressurized oil to be supplied to the hydraulic motor  6  to be equal to the flow amount Q 2   i  at the fan idling rotational speed time. The opening area A 1   i  of the flow amount control valve  8  is calculated according to the Formula 2 and according to the following Formula 3 on a condition that the pressure P 2  of the pressurized oil to be supplied to the hydraulic motor  6  is made to the pressure P 2   i  of the pressurized oil supplied to the hydraulic motor  6  at the fan idling rotational speed time. In addition, the calculation control section  16 D calculates the third valve control amount Cv 3  to be outputted to the solenoid part  8 A of the flow amount control valve  8  for controlling the flow amount control valve  8  to have the opening area A 1   i . 
     
       
         
           
             
               
                 
                   
                     A 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     i 
                   
                   = 
                   
                     
                       
                         Q 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         2 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         i 
                       
                       C 
                     
                     × 
                     
                       
                         ρ 
                         
                           2 
                           ⁢ 
                           
                             ( 
                             
                               
                                 P 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                               
                               - 
                               
                                 P 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 2 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 i 
                               
                             
                             ) 
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Formula 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     3 
                   
                   ] 
                 
               
             
           
         
       
     
     Next, the calculation control section  16 D outputs the calculated third valve control amount Cv 3  to the solenoid part  8 A of the flow amount control valve  8  in step  42 . Thereby, the opening area A 1  of the flow amount control valve  8  becomes equal to the opening area A 1   i  at the fan idling rotational speed time, and the hydraulic motor  6  can rotate the hydraulic drive fan  7  at the fan idling rotational speed. In addition, the calculation control section  16 D ends the control processing. 
     Next, an explanation will be made of the fan rotation stopping control by the controller  16  with reference to  FIG. 7 . 
     In the fan rotation stopping control as shown in  FIG. 7 , in step  51 , the calculation control section  16 D sets the fan predetermined rotational speed flag and the fan idling rotational speed flag to OFF and the fan rotation stopping flag to ON, and the thereafter, the process goes to step  52 . 
     In step  52 , the calculation control section  16 D obtains the engine rotational speed N 1  detected by the rotational speed detector  14 , the delivery pressure P 1  of the hydraulic pump  2  detected by the pressure detector  15  and the operation amount of the working machine operation device  13 . 
     Next, in step  53 , the calculation control section  16 D determines whether or not the valve control amount Cv to be outputted to the solenoid part  8 A of the flow amount control valve  8  is equal to the second valve control amount (the second valve control signal) Cv 2  for making the opening area A 1  of flow amount control valve  8  equal to 0. In a case where “NO” is determined in step  53 , in step  54 , the calculation control section  16 D outputs the second valve control amount Cv 2  to the solenoid part  8 A of the flow amount control valve  8 . Thereby, the opening area A 1  of the flow amount control valve  8  becomes equal to 0 to transfer the rotational speed N 2  of the hydraulic motor  6  to 0. 
     In step  53 , in a case where “YES” is determined, in step  55 , the calculation control section  16 D calculates the pump control amount Cp required for the operation of the working machine  12  based upon the engine rotational speed N 1 , the delivery pressure P 1  of the hydraulic pump  2  and the operation amount of the working machine operation device  13 , which are obtained in step  52 . 
     Next, in step  56 , the calculation control section  16 D outputs the calculated pump control amount Cp to the regulator  2 B of the hydraulic pump  2  to set the pump capacity of the hydraulic pump  2  to the pump capacity q 1  required for the operation of the working machine  12 . As a result, the working machine  12  can operate by the pressurized oil delivered from the hydraulic pump  2 . In addition, the calculation control section  16 D ends the control processing. 
     Next, an explanation will be made of an operational effect of the hydraulic drive fan control device  1  according to the first embodiment with reference to  FIG. 8 .  FIG. 8  shows a change with time in the engine rotational speed N 1 , the pump capacity q 1  of the hydraulic pump  2  and the rotational speed N 2  of the hydraulic motor  6  at the working time of the dump truck. 
     First, a period from time t 0  to time t 1  shows a state where the dump truck is traveling toward an unloading area, for example. During the period from time t 0  to time t 1 , the engine rotational speed N 1  as shown in a characteristic line  17  is kept as the value of the predetermined engine rotational speed N 1   s  or more as the threshold value for the constant time or more. Accordingly, the hydraulic drive fan  7  is controlled by the fan predetermined rotational speed control as shown in  FIG. 5  during the period from time t 0  to time t 1 . Thereby, the pump capacity q 1  of the hydraulic pump  2  as shown in a characteristic line  18  becomes equal to the pump capacity q 1   p  at the fan predetermined rotational speed time during the period from time t 0  to time t 1 . In addition, the opening area A 1  of the flow amount control valve  8  is maximized. As a result, the rotational speed N 2  of the hydraulic motor  6  for driving the hydraulic drive fan  7  becomes, as shown in a characteristic line  19 , equal to the fan predetermined rotational speed during the period from time t 0  to time t 1 . 
     Next, a period from time t 1  to time t 2  shows a state where the dump truck starts to decelerate near the unloading area and stops in the unloading area. The engine rotational speed N 1  varies minutely as shown in the characteristic line  17  for speed adjustment, and when the engine rotational speed N 1  becomes less than the predetermined engine rotational speed Nis, the hydraulic drive fan  7  is controlled by the fan idling rotational speed control as shown in  FIG. 6 . Thereby, the pump capacity q 1  of the hydraulic pump  2 , as shown in the characteristic line  18 , transfers to the pump capacity q 1   i  at the fan idling rotational speed time. In addition, the opening area A 1  of the flow amount control valve  8  is controlled to the opening area A 1   i  at the fan idling rotational speed time and the flow amount of the pressurized oil to be supplied to the hydraulic motor  6  through the flow amount control valve  8  is controlled to the flow amount Q 2   i  at the fan idling rotational speed time. Thereby, the rotational speed N 2  of the hydraulic motor  6  for driving the hydraulic drive fan  7  transfers, as shown in the characteristic line  19 , to the fan idling rotational speed. As a result, the flow amount Q 2  of the pressurized oil to be supplied to the hydraulic motor  6  can be suppressed from minutely varying following the variation in the engine rotational speed N 1  and the rotational speed of the hydraulic drive fan  7  can be suppressed from abruptly varying. 
     Here, the pump capacity q 1  of the hydraulic pump  2  keeps the pump capacity q 1   i  at the fan idling rotational speed time, but since the engine rotational speed N 1  varies, the delivery flow amount Q 1  of the hydraulic pump  2  varies. However, the opening area A 1  of the flow amount control valve  8  is controlled to the opening area A 1   i  at the fan idling rotational speed time. Therefore, the flow amount Q 2  of the pressurized oil to be supplied to the hydraulic motor  6  through the flow amount control valve can be kept as the flow amount Q 2   i  at the fan idling rotational speed time to suppress the variation in the rotational speed of the hydraulic drive fan  7 . 
     Next, at time t 2 , the dump truck stops at the unloading area, and for performing the unloading work, the working machine  12  operates in response to an operation of the working machine operation device  13 . Thereby, the pressurized oil is delivered to the working machine  12  from the hydraulic pump  2 , and the engine rotational speed N 1  minutely varies as shown in the characteristic line  17  in accordance with the operation state of the working machine  12 . At this time, a signal in accordance with the operation amount of the working machine operation device  13  is inputted to the controller  16  to control the hydraulic drive fan  7  by the fan rotation stopping control as shown in  FIG. 7 . Thereby, the opening area A 1  of the flow amount control valve  8  transfers to 0, and the hydraulic oil in the tank  3  is supplied through a check valve  9  to the inflow port of the hydraulic motor  6 . Accordingly, the hydraulic motor  6  rotates by inertia, and the rotational speed N 2  of the hydraulic motor  6  is gradually reduced. 
     In addition, the dump truck performs the unloading work and the delivery flow amount Q 1  of the hydraulic pump  2  increases or decreases in accordance with the operation state of the working machine  12  during the period from time t 2  to time t 3 . Therefore, the engine rotational speed N 1  minutely varies as shown in the characteristic line  17 . At this time, since the opening area A 1  of the flow amount control valve  8  is kept as 0, after the rotation of the hydraulic motor  6  by inertia is stopped, the rotational speed N 2  of the hydraulic motor  6  becomes equal to 0 as shown in the characteristic line  19 . As a result, it is possible to suppress the variation in the rotational speed of the hydraulic drive fan  7  during a period when the working machine  12  is operating. 
     Next, at time t 3 , the dump truck terminates the unloading work and starts the travel toward the loading area from the unloading area, for example. At this time, when the speed of dump truck increases, the engine rotational speed N 1  varies as shown in the characteristic line  17  and the hydraulic drive fan  7  is controlled by the fan idling rotational speed control as shown in  FIG. 6 . At this time, the pump capacity q 1  of the hydraulic pump  2  is set to the minimum value as shown in the characteristic line  18 , which thereafter, transfers to the pump capacity q 1   i  at the fan idling rotational speed time with a predetermined change amount per a predetermined unit time. In addition, the opening area A 1  of the flow amount control valve  8  is controlled to the opening area A 1   i  at the fan idling rotational speed time, and the flow amount Q 2  of the pressurized oil to be supplied to the hydraulic motor  6  becomes equal to the flow amount Q 2   i  at the fan idling rotational speed time. 
     In addition, during the period from time t 3  to time t 4 , since the dump truck adjusts the traveling speed, the engine rotational speed N 1  varies as shown in the characteristic line  17 . At this time, the pump capacity q 1  of the hydraulic pump  2  keeps the pump capacity q 1   i  at the fan idling rotational speed time, but since the engine rotational speed N 1  varies, the delivery flow amount Q 1  of the hydraulic pump  2  varies. However, the opening area A 1  of the flow amount control valve  8  is controlled to the opening area A 1   i  at the fan idling rotational speed time. Therefore, the flow amount Q 2  of the pressurized oil to be supplied to the hydraulic motor  6  through the flow amount control valve  8  can keep the flow amount Q 2   i  at the fan idling rotational speed time to suppress the variation in the rotational speed of the hydraulic drive fan  7 . 
     Next, the traveling speed of the dump truck increases, and in time t 4 , the engine rotational speed N 1  reaches the predetermined engine rotational speed Nis. At this time, it is required to distinguish a case where the dump truck is performing the speed adjustment near the unloading area over a case where the dump truck is performing the unloading work using the working machine  12 . Therefore, the fan idling rotational speed control is executed during a period where the engine rotational speed N 1  keeps the value of the predetermined engine rotational speed N 1   s  or more to time t 5  when a constant time ts or more elapses from time t 4 . 
     In addition, when the engine rotational speed N 1  keeps the value of the predetermined engine rotational speed N 1   s  or more for the constant time ts or more in time t 5 , the hydraulic drive fan  7  is controlled by the fan predetermined rotational speed control as shown in  FIG. 5 . Thereby, the opening area A 1  of the flow amount control valve  8  is maximized with a predetermined change amount per a predetermined unit time. The pump capacity q 1  of the hydraulic pump  2  becomes, as shown in the characteristic line  18 , equal to the pump capacity q 1   p  at the fan predetermined rotational speed time with the predetermined change amount per the predetermined unit time. Thereby, the rotational speed N 2  of the hydraulic motor  6  gradually transfers to the fan predetermined rotational speed from time t 5  as shown in the characteristic line  19 . As a result, the rotational speed of the hydraulic drive fan  7  can be suppressed from abruptly varying following the variation in the engine rotational speed N 1  to suppress variation in the rotation of the hydraulic drive fan  7 . 
     Next, during a period from time t 5  to time t 6 , for example, the dump truck is traveling toward the loading area, and the engine rotational speed N 1  keeps the value of the predetermined engine rotational speed N 1   s  or more over the constant time is or more. The fan predetermined rotational speed control continues to be executed during the period from time t 5  to time t 6 . In addition, in time t 6 , the dump truck transfers to the deceleration travel, and when the engine rotational speed N 1  becomes less than the predetermined engine rotational speed Nis, the hydraulic drive fan  7  is, as similar to time t 1  as described before, controlled by the fan idling rotational speed control. 
     In this way, the hydraulic drive fan control device  1  according to the first embodiment, even when the engine rotational speed N 1  varies at the working time of the dump truck, can set the rotational speed N 2  of the hydraulic motor  6  to three kinds of the fan predetermined rotational speed, the fan idling rotational speed and 0. Thereby, the pump capacity q 1  of the hydraulic pump  2  is controlled, making it possible to suppress the variation in the delivery flow amount Q 1  of the hydraulic pump  2 . In addition, the opening area A 1  of the flow amount control valve  8  is controlled, making it possible to control the flow amount Q 2  and the pressure P 2  of the pressurized oil to be supplied to the hydraulic motor  6 . Accordingly, the rotational speed N 2  of the hydraulic motor  6  can be suppressed from minutely varying following the variation in the engine rotational speed N 1 . As a result, it is possible to suppress the generation of the peak pressure or the hunching in the hydraulic circuit to extend lifetime of the hydraulic equipment devices such as the hydraulic motor  6 , the fan pipe line  5  and the like configuring the hydraulic circuit. 
     In addition, the hydraulic drive fan control device  1  makes the pump capacity q 1  of the hydraulic pump  2  equal to the minimum pump capacity q 1   m  once at the time of rotating the hydraulic drive fan  7  from the stopped state, and thereafter, the minimum pump capacity q 1   m  is increased to the pump capacity q 1   p  at the fan predetermined rotational speed time or the pump capacity q 1   i  at the fan idling rotational speed time. As a result, the rotation of the hydraulic drive fan  7  can be suppressed from abruptly varying to suppress the generation of the peak pressure or the hunching in the hydraulic circuit. 
     Further, when the hydraulic drive fan control device  1  changes the rotational speed of the hydraulic drive fan  7 , the hydraulic drive fan control device  1  outputs the valve control signal to the flow amount control valve  8  with a predetermined change amount per a predetermined unit time and outputs the pump control signal to the hydraulic pump  2  with a predetermined change amount per a predetermined unit time. Thereby, the flow amount of the pressurized oil to be supplied to the hydraulic motor  6  can be gradually increased. As a result, the rotation of the hydraulic drive fan  7  can be suppressed from abruptly varying to suppress the generation of the peak pressure or the hunching in the hydraulic circuit. 
     Next,  FIG. 9  to  FIG. 13  show a second embodiment of the present invention, and the second embodiment is characterized in that the relief valve  10  according to the first embodiment is formed of a variable relief valve. It should be noted that in the second embodiment, components identical to those in the first embodiment are referred to as identical reference numerals, and the explanation is omitted. 
     A hydraulic drive fan control device  21  as shown in  FIG. 9  is, as similar to the first embodiment, configured of the hydraulic pump  2 , the hydraulic motor  6 , the hydraulic drive fan  7 , the flow amount control valve  8 , the rotational speed detector  14 , the pressure detector  15 , the controller  16  and the like. However, the hydraulic drive fan control device  21  differs in a point where a variable relief valve  22  is disposed in the halfway of the fan pipe line  5 , from the hydraulic drive fan control device  1  according to the first embodiment. 
     The variable relief valve  22  is disposed in the halfway of the fan pipe line  5  and sets a delivery pressure of the pressurized oil to be delivered to the fan pipe line  5  from the hydraulic pump  2  and discharges an extra pressure to the tank  3 . The variable relief valve  22  has a pressure control part  22 A, and a relief pressure Pr 1  (MPa) of the variable relief valve  22  changes in accordance with a relief pressure control amount Cr (A) to be outputted to the pressure control part  22 A from the controller  16 . The relief pressure control amount Cr (A) is supplied to the pressure control part  22 A as an instruction current (a control signal) from the controller  16 . 
     Here, a relation of the relief pressure control amount Cr (A) to be inputted to the pressure control part  22 A from the controller  16  and the relief pressure Pr 1  (MPa) of the variable relief valve  22  is made as shown in a characteristic line diagram in  FIG. 10 . That is, in a case where the relief pressure control amount Cr becomes equal to a first relief pressure control amount Cr 1 , the relief pressure Pr 1  becomes equal to the relief pressure Pr 1   p  at the fan predetermined rotational speed time. In a case where the relief pressure control amount Cr becomes equal to a second relief pressure control amount Cr 2 , the relief pressure Pr 1  becomes equal to the minimum relief pressure Pr 1   m . In a case where the relief pressure control amount Cr becomes equal to a third relief pressure control amount Cr 3 , the relief pressure Pr 1  becomes equal to the relief pressure Pr 1   i  at the fan idling rotational speed time. 
     The hydraulic drive fan control device  21  according to the second embodiment has the configuration as described above, and next, an explanation will be made of the fan predetermined rotational speed control by the controller  16  with reference to  FIG. 11 . 
     In the fan predetermined rotational speed control as shown in  FIG. 11 , the calculation control section  16 D sets the fan idling rotational speed flag to OFF in step  61 . Next, in step  62 , the calculation control section  16 D reads in the pressure P 2  of the pressurized oil to be supplied to the hydraulic motor  6 , the flow amount Q 2  of the pressurized oil passing through the flow amount control valve  8 , the pump capacity q 1   p  of the hydraulic pump  2  and the relief pressure Pr 1   p  of the variable relief valve  22  at the fan predetermined rotational speed time from the memory  16 C. 
     Next, in step  63 , the calculation control section  16 D determines whether or not the fan rotation stopping flag is ON. In a case where “NO” is determined, the process goes to step  67 , and in a case where “YES” is determined in step  63 , the process goes to step  64 . In step  64 , the calculation control section  16 D determines whether or not the pump control amount Cp to be outputted to the regulator  2 B of the hydraulic pump  2  is equal to the second pump control amount Cp 2 . In a case where “NO” is determined in step  64 , in step  65 , the calculation control section  16 D outputs the second pump control amount Cp 2  to the regulator  2 B of the hydraulic pump  2 . 
     In a case where “YES” is determined in step  64 , in step  66 , the calculation control section  16 D sets the fan rotation stopping flag to OFF, and thereafter, the process goes to step  67 . In step  67 , the calculation control section  16 D outputs the first relief pressure control amount Cr 1  to the pressure control part  22 A of the variable relief valve  22  and defines the relief pressure Pr 1  of the variable relief valve  22  as the relief pressure Pr 1   p  at the fan predetermined rotational speed time. 
     Next, in step  68 , the calculation control section  16 D determines whether or not the valve control amount Cv to be outputted to the solenoid part  8 A of the flow amount control valve  8  is equal to the first valve control amount Cv 1 . In a case where “NO” is determined in step  68 , in step  69 , the calculation control section  16 D outputs the first valve control amount Cv 1  to the solenoid part  8 A of the flow amount control valve  8  with a predetermined change amount per a predetermined unit time. Meanwhile, in a case where “YES” is determined in step  68 , in step  70 , the calculation control section  16 D determines whether or not the pump control amount Cp to be outputted to the regulator  2 B of the hydraulic pump  2  is equal to the first pump control amount Cp 1 . 
     In a case where “NO” is determined in step  70 , in step  71 , the calculation control section  16 D outputs the first pump control amount Cp 1  to the regulator  2 B of the hydraulic pump  2  with a predetermined change amount per a predetermined unit time. In a case where “YES” is determined in step  70 , since the pump capacity q 1  of the hydraulic pump  2  becomes equal to the pump capacity q 1   p  at the fan predetermined rotational speed time, the hydraulic motor  6  can rotate the hydraulic drive fan  7  at the fan predetermined rotational speed. In addition, the calculation control section  16 D sets the fan predetermined rotational speed flag to ON in step  72 , and thereafter, ends the control processing. 
     Next, an explanation will be made of the fan idling rotational speed control by the controller  16  with reference to  FIG. 12 . 
     In the fan idling rotational speed control as shown in  FIG. 12 , the calculation control section  16 D sets the fan predetermined rotational speed flag to OFF in step  81 . Next, in step  82 , the calculation control section  16 D reads in the pressure P 2  of the pressurized oil to be supplied to the hydraulic motor  6 , the flow amount Q 2  of the pressurized oil passing through the flow amount control valve  8 , the pump capacity q 1   i  of the hydraulic pump  2  and the relief pressure Pr 1   i  of the variable relief valve  22  at the fan idling rotational speed time from the memory  16 C. 
     Next, in step  83 , the calculation control section  16 D obtains the delivery pressure P 1  of the hydraulic pump  2  based upon the detection signal from the pressure detector  15 . In subsequent step  84 , the calculation control section  16 D determines whether or not the fan rotation stopping flag is ON. In a case where “NO” is determined, the process goes to step  88 , and in a case where “YES” is determined in step  84 , the process goes to step  85 . In step  85 , the calculation control section  16 D determines whether or not the pump control amount Cp to be outputted to the regulator  2 B of the hydraulic pump  2  is equal to the second pump control amount Cp 2 . In a case where “NO” is determined in step  85 , in step  86 , the calculation control section  16 D outputs the second pump control amount Cp 2  to the regulator  2 B of the hydraulic pump  2 . 
     In a case where “YES” is determined in step  85 , in step  87 , the calculation control section  16 D sets the fan rotation stopping flag to OFF, and thereafter, the process goes to step  88 . In step  88 , the calculation control section  16 D outputs the third relief pressure control amount Cr 3  to the pressure control part  22 A of the variable relief valve  22  and defines the relief pressure Pr 1  of the variable relief valve  22  as the relief pressure Pr 1   i  at the fan idling rotational speed time. As a result, the delivery pressure of the pressurized oil to be delivered to the fan pipe line  5  from the hydraulic pump  2  is limited to the delivery pressure at the fan idling rotational speed time. 
     Next, in step  89 , the calculation control section  16 D determines whether or not the pump control amount Cp to be outputted to the regulator  2 B of the hydraulic pump  2  is equal to the third pump control amount Cp 3  for making the pump capacity of the hydraulic pump  2  the pump capacity q 1   i  at the fan idling rotational speed time. In a case where “NO” is determined in step  89 , in step  90 , the calculation control section  16 D outputs the third pump control amount Cp 3  to the regulator  2 B of the hydraulic pump  2  with a predetermined change amount per a predetermined unit time. 
     In a case where “YES” is determined in step  89 , in step  91 , the calculation control section  16 D sets the fan idling rotational speed flag to ON, and then, the process goes to step  92 . In step  92 , the calculation control section  16 D outputs the first valve control amount Cv 1  to the solenoid part  8 A of the flow amount control valve  8  with a predetermined change amount per a predetermined unit time to maximize the opening area A 1  of the flow amount control valve  8 . At this time, the pressure in the fan pipe line  5  is reduced to the relief pressure Pr 1   i  at the fan idling rotational speed time by the variable relief valve  22 . Therefore, the pressure P 2  of the pressurized oil to be supplied to the hydraulic motor  6  through the flow amount control valve  8  the opening area A 1  of which is maximized, is made to the pressure P 2   i  at the fan idling rotational speed time, and the hydraulic motor  6  can rotate the hydraulic drive fan  7  at the fan idling rotational speed. 
     Next, an explanation will be made of the fan rotation stopping control by the controller  16  with reference to  FIG. 13 . 
     In the fan rotation stopping control as shown in  FIG. 13 , in step  101 , the calculation control section  16 D sets the fan predetermined rotational speed flag and the fan idling rotational speed flag to OFF and sets the fan rotation stopping flag to ON, and then, the process goes to step  102 . In step  102 , the calculation control section  16 D obtains the engine rotational speed N 1  detected by the rotational speed detector  14 , the delivery pressure P 1  of the hydraulic pump  2  detected by the pressure detector  15  and the operation amount of the working machine operation device  13 . 
     In subsequent step  103 , the calculation control section  16 D determines whether or not the valve control amount Cv to be outputted to the solenoid part  8 A of the flow amount control valve  8  is equal to the second valve control amount Cv 2 . Ina case where “NO” is determined in step  103 , in step  104 , the calculation control section  16 D outputs the second valve control amount Cv 2  to the solenoid part  8 A of the flow amount control valve  8 . Thereby, the opening area A 1  of the flow amount control valve  8  becomes equal to 0, and the rotational speed N 2  of the hydraulic motor  6  transfers to 0. 
     In a case where “YES” is determined in step  103 , in step  105 , the calculation control section  16 D outputs the predetermined relief pressure control amount Cr to the pressure control part  22 A of the variable relief valve  22 . As a result, the relief pressure Pr 1  of the variable relief valve  22  is set to a pressure required for the operation of the working machine  12 . 
     In subsequent step  106 , the calculation control section  16 D calculates the pump control amount Cp required for the operation of the working machine  12  based upon the engine rotational speed N 1 , the delivery pressure P 1  of the hydraulic pump  2  and the operation amount of the working machine operation device  13 , which are obtained in step  102 . In step  107 , the calculation control section  16 D outputs the calculated pump control amount Cp to the regulator  2 B of the hydraulic pump  2  to make the pump capacity of the hydraulic pump  2  the pump capacity q 1  required for the operation of the working machine  12 . Thereby, the working machine  12  can operate by the pressurized oil to be delivered from the hydraulic pump  2 . 
     In this way, the hydraulic drive fan control device  21  according to the second embodiment, even when the engine rotational speed N 1  varies depending upon the working condition of the dump truck, can set, as similar to the first embodiment, the rotational speed N 2  of the hydraulic motor  6  to three kinds of the fan predetermined rotational speed, the fan idling rotational speed and 0. Thereby, the rotational speed N 2  of the hydraulic motor  6  can be suppressed from minutely varying following the variation in the engine rotational speed N 1 . 
     Further, the hydraulic drive fan control device  21  can optionally adjust the maximum pressure in the fan pipe line  5  by the variable relief valve  22 . Accordingly, when the rotational speed N 2  of the hydraulic motor  6  is controlled to three kinds of the fan predetermined rotational speed, the fan idling rotational speed and 0, it is possible to set the maximum pressure in the fan pipe line  5  suitable for each of the rotational speeds. 
     Next,  FIG. 14  to  FIG. 17  show a third embodiment of the present invention, and the third embodiment is characterized in that the fan idling rotational speed control is not executed to the hydraulic drive fan and two kinds of the controls composed of the fan predetermined rotational speed control and the fan rotation stopping control are executed thereto. It should be noted that the configuration of the hydraulic drive fan control device according to the third embodiment is the same as that of the hydraulic drive fan control device  1  as shown in  FIG. 1 . 
     The controller  16  determines which of the fan predetermined rotational speed control and the fan rotation stopping control should be applied to the hydraulic drive fan  7  by the determination processing as shown in  FIG. 14 . 
     In step  111 , the controller  16  obtains the engine rotational speed N 1  detected by the rotational speed detector  14  and the operation amount of the working machine operation device  13 , which are stored in the memory  16 C. Next, in step  112 , the calculation control section  16 D determines whether or not the working machine  12  is operated by the working machine operation device  13 . In a case where “YES” is determined in step  112 , the process goes to step  113 , wherein the fan rotation stopping control as shown in  FIG. 16  is executed. In a case where “NO” is determined in step  112 , the calculation control section  16 D measures a continuation time during which the engine rotational speed N 1  becomes equal to or more than the predetermined engine rotational speed N 1   s  in step  114 . 
     Next, in step  115 , the calculation control section  16 D determines whether or not the engine rotational speed N 1  is kept as the value equal to or more than the predetermined engine rotational speed N 1   s  for a constant time or more. In a case where “NO” is determined in step  115 , the process goes to step  113 , wherein the fan rotation stopping control as shown in  FIG. 16  is executed. Meanwhile, in a case where “YES” is determined in step  115 , the process goes to step  116 , wherein the calculation control section  16 D executes the fan predetermined rotational speed control as shown in  FIG. 15 . 
     In this way, according to the third embodiment, the controller  16  executes the fan rotation stopping control in a case where the working machine  12  is operated and in a case where the engine rotational speed N 1  is not kept as the value equal to or more than the predetermined engine rotational speed N 1   s  for a constant time or more. In addition, the controller  16  executes the fan predetermined rotational speed control in a case where the engine rotational speed N 1  is kept as the value equal to or more than the predetermined engine rotational speed N 1   s  for the constant time or more. 
     Next, an explanation will be made of the fan predetermined rotational speed control by the controller  16  with reference to  FIG. 15 . 
     In the fan predetermined rotational speed control as shown in  FIG. 15 , in step  121 , the calculation control section  16 D reads in the pump capacity q 1  of the hydraulic pump  2  at the fan predetermined rotational speed time from the memory  16 C, and the process goes to step  122 . In step  122 , the calculation control section  16 D determines whether or not the pump control amount Cp to be outputted to the regulator  2 B of the hydraulic pump  2  is equal to the second pump control amount Cp 2 . In a case where “NO” is determined in step  122 , in step  123 , the calculation control section  16 D outputs the second pump control amount Cp 2  to the regulator  2 B of the hydraulic pump  2 . In a case where “YES” is determined in step  122 , in step  124 , the calculation control section  16 D determines whether or not the valve control amount Cv to be outputted to the solenoid part  8 A in the flow amount control valve  8  is equal to the first valve control amount Cv 1 . 
     In a case where “NO” is determined in step  124 , in step  125 , the calculation control section  16 D outputs the first valve control amount Cv 1  to the solenoid part  8 A with a predetermined change amount per a predetermined unit time. In a case where “YES” is determined in step  124 , in step  126 , the calculation control section  16 D determines whether or not the pump control amount Cp to be outputted to the regulator  2 B of the hydraulic pump  2  is equal to the first pump control amount Cp 1 . 
     In a case where “NO” is determined in step  126 , in step  127 , the calculation control section  16 D outputs the first pump control amount Cp 1  (A) to the regulator  2 B of the hydraulic pump  2  with a predetermined change amount per a predetermined unit time. Meanwhile, in a case where “YES” is determined in step  126 , since the pump capacity q 1  of the hydraulic pump  2  becomes equal to the pump capacity q 1   p  at the fan predetermined rotational speed time, the hydraulic motor  6  can rotate the hydraulic drive fan  7  at the fan predetermined rotational speed. In addition, the calculation control section  16 D sets the fan predetermined rotational speed flag to ON in step  128 , and thereafter, ends the control processing. 
     Next, an explanation will be made of the fan rotation stopping control by the controller  16  with reference to  FIG. 16 . 
     In the fan rotation stopping control as shown in  FIG. 16 , the calculation control section  16 D sets the fan predetermined rotational speed flag to OFF in step  131 , and thereafter, the process goes to step  132 . In step  132 , the calculation control section  16 D obtains the engine rotational speed N 1  detected by the rotational speed detector  14 , the delivery pressure P 1  of the hydraulic pump  2  detected by the pressure detector  15  and the operation amount of the working machine operation device  13 . 
     In subsequent step  133 , the calculation control section  16 D determines whether or not the valve control amount Cv to be outputted to the solenoid part  8 A of the flow amount control valve  8  is equal to the second valve control amount Cv 2 . Ina case where “NO” is determined in step  133 , in step  134 , the calculation control section  16 D outputs the second valve control amount Cv 2  to the solenoid part  8 A. Thereby, the opening area A 1  of the flow amount control valve  8  becomes equal to 0, and the rotational speed N 2  of the hydraulic motor  6  transfers to 0. 
     Meanwhile, in a case where “YES” is determined in step  133 , in step  135 , the calculation control section  16 D calculates the pump control amount Cp required for the operation of the working machine  12 . In addition, in step  136 , the calculation control section  16 D outputs the calculated pump control amount Cp to the regulator  2 B of the hydraulic pump  2 . Thereby, the pump capacity of the hydraulic pump  2  is made to the pump capacity q 1  required for the operation of the working machine  12 , and the working machine  12  can operate by the pressurized oil to be delivered from the hydraulic pump  2 . 
     An explanation will be made of the operational effect of the hydraulic drive fan control device according to the third embodiment with reference to  FIG. 17 . 
     In  FIG. 17 , a period from time t 0  to time t 1  shows a state where the dump truck is traveling toward an unloading area, for example and a period from time t 5  to time t 6  shows a state where the dump truck is traveling toward a loading area. During the period from time t 0  to time t 1  and during the period from time  5  to time  6 , the engine rotational speed N 1  of the engine  4  is kept, as shown in the characteristic line  17 , as the value of the predetermined engine rotational speed N 1   s  or more for a constant time is or more. Accordingly, during the period from time t 0  to time t 1  and during the period from time  5  to time  6 , the hydraulic drive fan  7  is controlled by the fan predetermined rotational speed control as shown in  FIG. 15 . Thereby, during the period from time t 0  to time t 1  and during the period from time  5  to time  6 , the rotational speed N 2  of the hydraulic motor  6  for driving the hydraulic drive fan  7  becomes, as shown in a characteristic line  23 , equal to the fan predetermined rotational speed. 
     Next, the period from time t 1  to time t 2  shows a state where the dump truck decelerates to approach and stop in the unloading area, and the period from time t 2  to time t 3  shows a state where the dump truck is performing the unloading work. The period from time t 3  to time t 4  shows a state where the dump truck adjusts the traveling speed to travel from the unloading area to the loading area. During the period from time t 1  to time t 4 , the engine rotational speed N 1  minutely varies as shown in the characteristic line  17 . 
     In the third embodiment, the hydraulic drive fan  7  is controlled by the fan rotation stopping control as shown in  FIG. 16  during the period from time t 1  to time t 5 . During the period from time t 1  to time t 5 , the opening area A 1  of the flow amount control valve  8  becomes equal to 0, and after the rotation of the hydraulic drive fan  7  by inertia is finished, the rotational speed N 2  of the hydraulic motor  6  becomes, as shown in the characteristic line  23 , equal to 0. As a result, since the hydraulic drive fan  7  is kept in the stopped state, it is possible to suppress the variation in the rotational speed of the hydraulic drive fan  7  following the variation in the engine rotational speed N 1 . 
     In this way, according to the third embodiment, even when the engine rotational speed N 1  varies as shown in the characteristic line  17  in  FIG. 17  at the working time of the dump truck, the rotational speed N 2  of the hydraulic motor  6  for rotating the hydraulic drive fan  7  can be, as shown in the characteristic line  23 , controlled to two kinds of the fan predetermined rotational speed and 0. Accordingly, the rotational speed N 2  of the hydraulic motor  6  can be suppressed from minutely varying as shown in the characteristic line  24  shown in a two-dot chain line in  FIG. 17 . As a result, it is possible to suppress the generation of the peak pressure or the hunching in the hydraulic circuit to extend a lifetime of the hydraulic equipment devices configuring the hydraulic circuit. 
     It should be noted that the embodiment takes as an example a case where the pump capacity q 1  of the hydraulic pump  2  increases the more as the value of the pump control amount Cp to be inputted to the regulator  2 B is smaller. However, the present invention is not limited thereto, but the pump capacity q 1  decreases the more as the value of the pump control amount Cp is smaller. 
     In addition, the embodiment takes as an example a case of using the normally-closed type flow amount control valve  8  that closes when the control signal is not inputted to the solenoid part  8 A and opens when the control signal is inputted to the solenoid part  8 A. However, the present invention is not limited thereto, but the normally-opened type flow amount control valve  8  may be used. 
     The embodiment takes as an example a case where at the time of rotating the hydraulic drive fan  7  from the stopped state, the pump capacity q 1  of the hydraulic pump  2  is once reduced to the minimum pump capacity q 1   m , and thereafter, is increased to the pump capacity q 1   p  at the fan predetermined rotational speed time or the pump capacity q 1   i  at the fan idling rotational speed time. However, the present invention is not limited thereto, but may be configured such that the opening area A 1  of the flow amount control valve  8  is once minimized, and thereafter, is increased to the maximum opening area at the fan predetermined rotational speed time or the opening area A 1   i  at the fan idling rotational speed time. 
     Further, the embodiment takes as an example a case where the rotation of the hydraulic drive fan  7  is stopped during the period in which the working machine  12  is operating. However, the present invention is not limited thereto, but may be configured such that, for example, in a case where a flow amount and a pressure of the pressurized oil to be supplied to the working machine  12  are secured, the pressurized oil is simultaneously supplied to the hydraulic motor  6 , whereby the hydraulic drive fan  7  is rotated at the working time of the working machine  12 . 
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
         
           
               1 ,  21 : Hydraulic drive fan control device 
               2 : Hydraulic pump 
               2 B: Regulator (Capacity variable part) 
               4 : Engine (Prime mover) 
               5 : Fan pipe line (Pipe line) 
               6 : Hydraulic motor 
               7 : Hydraulic drive fan 
               8 : Flow amount control valve 
               8 A: Solenoid part (Pilot part) 
               12 : Working machine 
               13 : Working machine operation device 
               14 : Rotational speed detector 
               15 : Pressure detector 
               16 : Controller 
               16 D: Calculation control section