Patent Publication Number: US-8118246-B2

Title: Mobile crusher

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a mobile crusher. 
     2. Description of Related Art 
     A mobile crusher including a crusher that crushes raw materials has been typically known. In such a mobile crusher, raw materials conveyed by a feeder are crushed to a predetermined size by the crusher to be discharged by a discharge conveyor. When a detector for detecting the raw materials on the feeder and crusher detects an idling of the feeder or crusher (the idling means that a work implement is operated without raw materials or crushed materials), a controller slows engine speed down to idling rotational speed during the idling, thereby reducing fuel consumption (Document 1: JP-A-2000-136739). Alternatively, a controller may control fuel injection quantity depending on the weight of raw materials mounted on the feeder irrespective of the presence of the raw materials within the crusher (Document 2: JP-A-5-184968). 
     However, in the mobile crusher as disclosed in Document 1, only the engine speed is controlled and the speed of the work implement is not controlled. Thus, a deceleration rate of the work implement speed during the idling is the same as a deceleration rate of the engine speed. Since the engine idling rotational speed is approximately 50% of normal speed, the work implement speed is decelerated by approximately 50%. However, approximately 50% deceleration of the work implement speed is not sufficient for power reduction. 
     In the mobile crusher as disclosed in Document 2, engine output is decreased when the weight of the raw materials mounted on the feeder is reduced even while the raw materials are crushed by the crusher. Thus, an operation quantity of the crusher is reduced and therefore crushing efficiency is reduced. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide a mobile crusher capable of decelerating a work implement after reliably discharging crushed materials, and restarting the work implement smoothly so that reduction in working efficiency can be prevented. 
     A mobile crusher according to an aspect of the invention includes: a crusher that crushes raw materials; a discharge conveyor provided on a lower stream of the crusher to discharge the raw materials crushed by the crusher; a work implement provided on an upper stream of the crusher to produce crushed materials; a crushed material determining unit that determines a presence or absence of the crushed materials to be discharged on the discharge conveyor; a raw material determining unit that determines a presence or absence of the raw materials in the crusher; a work implement speed controller that controls speeds of the crusher, discharge conveyor and work implement based on determination results of the crushed material determining unit and the raw material determining unit. 
     A mobile crusher according to another aspect of the invention includes: a crusher that crushes raw materials; a discharge conveyor provided on a lower stream of the crusher to discharge the raw materials crushed by the crusher; a work implement provided on an upper stream of the crusher to produce crushed materials; a crushed material determining unit that determines a presence or absence of the crushed materials to be discharged on the discharge conveyor; a work implement speed controller that controls speeds of the crusher, discharge conveyor and work implement based on a determination result of the crushed material determining unit. 
     A mobile crusher according to still another aspect of the invention includes: a crusher that crushes raw materials; a discharge conveyor provided on a lower stream of the crusher to discharge the raw materials crushed by the crusher; a work implement provided on an upper stream of the crusher to produce the crushed materials; an engine that activates the crusher, discharge conveyor and work implement; and an engine controller that decelerates an engine speed to a decelerated speed when determining that no load is applied on the crusher, the mobile crusher comprising: hydraulic motors that drive the crusher, discharge conveyor and work implement, respectively; a hydraulic pump driven by the engine to supply hydraulic oil to the hydraulic motors and drive the hydraulic motors; and a work implement speed controller that decelerates speeds of the crusher, discharge conveyor and work implement and reduces a discharge flow rate of the hydraulic pump and rotational speeds of the hydraulic motors so that a deceleration rate of the work implement is larger than a deceleration rate of the crusher when the engine controller decelerates the engine speed to the decelerated speed. 
     In the above-described arrangements, the mobile crusher includes the crusher, discharge conveyor, and work implement controller that controls the drive of the work implement depending on the presence or absence of the crushed materials, that is to say, the presence or absence of the load. When no load is applied, the crusher, discharge conveyor and work implement are decelerated. Thus, fuel consumption can be reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a mobile crusher according to an exemplary embodiment of the invention. 
         FIG. 2  shows a hydraulic circuit according to the exemplary embodiment. 
         FIG. 3  is a block diagram according to the exemplary embodiment. 
         FIG. 4  is a flow chart according to the exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT(S) 
     Exemplary embodiment(s) of the invention will be described below with reference to the attached drawings. 
       FIG. 1  is a side view showing a mobile crusher  1  according to the exemplary embodiment. The mobile crusher  1  crushes raw materials loaded by a loader such as a hydraulic excavator and a wheel loader to produce crushed materials having a predetermined particle size. 
     The mobile crusher  1  includes: a main unit  10  having a pair of undercarriage members  11  (one of which is shown); a feed unit  20  that is provided to the rear side on top of the main unit  10  (on the left side in  FIG. 1 ) for supplying raw materials; a crusher  30  provided to the front side of the feed unit  20  (on the right side in  FIG. 1 ); a power unit  40  provided to the front side of the crusher  30 ; a discharge conveyor  50  extending forward and obliquely upward between a pair of crawlers  15  on a lower portion of the main unit  10 ; and a controller  70  for controlling the discharge conveyor  50  and other work implements. 
     The main unit  10  includes the undercarriage members  11  on the lower portion. The undercarriage members  11  each include the crawler  15  that is wound around a front sprocket wheel  13  driven by a hydraulic motor  12  and a rear idler tumbler  14 . 
     In the feed unit  20 , a grizzly feeder  22  (feeder serving as a work implement) is mounted via a plurality of springs (not shown) on the upper side of right and left side frames  21  protruding rearward. The grizzly feeder  22  is driven by a vibrator  23 . A hopper  24  is provided on the upper side of the grizzly feeder  22 , covering the grizzly feeder  22  from its three sides. Raw materials are thrown into the hopper  24  of which an opening widens upward. A muck shooter  25  is provided on the lower side of the grizzly feeder  22 . The muck shooter  25  delivers to a muck conveyor  26  (work implement) uncrushed materials dropped into the muck shooter  25  after being selected by the grizzly feeder  22 . 
     The crusher  30  is a jaw crusher including a fixed jaw  31  and a swing jaw  32 . When a pulley  34  provided on an end of a main shaft  33  is driven by a hydraulic motor  35  via a V-belt, the swing jaw  32  functions as a swinging link by the rotation of the main shaft  33  to crush the raw materials between the fixed jaw  31  and the swing jaw  32 . The hydraulic motor  35  of the crusher  30  is provided with a crusher pressure sensor  36  serving as a raw material determining unit for measuring a load pressure value P 3 . When the raw materials are crushed by the crusher  30 , the crusher pressure sensor  36  detects the load pressure value P 3  of the hydraulic motor  35  and outputs an electrical signal. The load pressure value P 3  is varied depending on the amount of the raw materials thrown into the crusher  30 . 
     Because whether the raw materials are thrown or not is determined in the crusher  30 , the hydraulic motor  35  of the crusher  30  needs to be constantly operated at low speed even when the raw materials are not present within the crusher  30 . Accordingly, the grizzly feeder  22  for feeding the raw materials to the crusher  30  needs to be also operated at low speed. Thus, the grizzly feeder  22  and crusher  30  cannot be stopped. 
     Referring to a hydraulic circuit of the mobile crusher  1  as shown in  FIG. 2 , the power unit  40  includes an engine  49 , variable displacement hydraulic pumps  52  and  53  driven by the engine  49 , a fuel tank and a hydraulic oil tank  54 . The engine  49  is provided with a fuel injector (not shown) electrically connected to a controller  70 . A fuel injection signal based on a set signal of an engine speed set by a fuel dial  91  is outputted from the controller  70  to the fuel injector (not shown), so that the engine  49  is driven. In an operation mode according to this exemplary embodiment, an engine speed ω, which is the engine speed set by the fuel dial  91  depending on the presence or absence of the raw materials and crushed materials on the grizzly feeder  22 , muck conveyor  26 , crusher  30 , discharge conveyor  50  and magnetic separator  60 , is controlled to be slowed down to a decelerated speed ω 0  (hereinafter referred to as auto deceleration control). Normally, the decelerated speed ω 0  is approximately 50% of the engine speed ω (normal speed) set by the fuel dial  91 . The invention is effectively usable with the auto deceleration control. However, in this exemplary embodiment, it is assumed that the decelerated speed ω 0  is the same as the normal speed ω for facilitating understanding. 
     Hydraulic pressure from the hydraulic pump  52  is supplied to the hydraulic motor  12  of the undercarriage members  11  and the hydraulic motor  35  of the crusher  30  through control valves  111  and  116  while being supplied to the control valve  111  as pilot pressure through a direction switching device  18  provided on a right travel lever  16 . 
     Hydraulic pressure from the hydraulic pump  53  is supplied to the hydraulic motor  12  of the undercarriage members  11 , a hydraulic motor  55  of the discharge conveyor  50 , a hydraulic motor  27  of the vibrator  23  provided on the grizzly feeder  22 , a hydraulic motor  28  of the magnetic separator  60 , and a hydraulic motor  29  of the muck conveyor  26  through the control valves  111  to  115  while being supplied to the control valve  111  as pilot pressure through the direction switching device  18  provided on a left travel lever  17 . The pilot pressures of these control valves  111  to  116  are under electromagnetic proportional control, so that flow rates of hydraulic oil supplied to the hydraulic motors  12 ,  27  to  29 ,  35  and  55  are controlled. 
     The discharge conveyor  50  discharges forward and drops from a height crushed materials, which are dropped from the outlet of the crusher  30 , to accumulate the dropped crushed materials. When raw materials contain foreign substances such as reinforcing steel bars and metal chips, the magnetic separator  60  may be mounted on the front side of the discharge conveyor  50  to remove the foreign substances. The discharge conveyor  50  is provided with a conveyor pressure sensor  51  serving as a crushed material determining unit for detecting a load pressure value P 1  of the hydraulic motor  55 . The load pressure value P 1  is varied depending on the amount of the crushed materials mounted on the discharge conveyor  50 . The grizzly feeder  22  and muck conveyor  26  (work implements) are disposed on an upper stream of the crusher  30  for producing the crushed materials, and the discharge conveyor  50  aid magnetic separator  60  are disposed on a lower stream of the crusher  30 . 
     As shown in  FIG. 2 , the mobile crusher  1  is provided with an operation panel  73  having operation boards or the like. The operation panel  73  includes an engine start-up SW  101 , a mode switching SW  102 , a pressure for traveling SW  103  and a group  100  of ON-OFF switches (SWs) of the work implements. The operation panel  73  is electrically connected to the controller  70 . 
     The work implements SW group  100  includes a feeder start-up SW  104 , a muck conveyor start-up SW  105 , a crusher start-up SW  106 , a discharge conveyor start-up SW  107 , and a magnetic separator start-up SW  108 . Electrical signals from the work implements SW group  100  are inputted to the controller  70 . 
     The crusher pressure sensor  36 , the conveyor pressure sensor  51 , and the fuel dial  91  for setting a speed of the engine  49  are electrically connected to the controller  70 . Signals from the sensors  36  and  51  and the fuel dial  91  are inputted to the controller  70 . 
     Referring to a block diagram of the controller  70  in  FIG. 3 , the controller  70  is equipped with a CPU (Central Processing Unit). The controller  70  includes an engine controller  71  and a work implement controller  72 . The engine controller  71  includes a fuel injection quantity controller  711 , an engine start-up determining unit  712 , and a memory  713 , which are provided by software such as a computer program. The memory  713  stores a decelerated speed ω 0  for driving the engine in a deceleration state (that is to say, a state where the work implements are not operated and the engine speed is slow) while storing the engine speed set by the fuel dial  91 . 
     The work implement controller  72  includes: a mode determining unit  721 ; a pressure-for-traveling determining unit  722 ; a work implement operating state determining unit  723 ; a conveyor pressure comparing unit  724  serving as the raw material determining unit; a crusher pressure comparing unit  725  serving as the crushed material determining unit; a flow rate controller  726  serving as a work implement speed controller for controlling discharge flow rates of the hydraulic pumps  52  and  53  and operations of the control valves  112  to  116 ; and a memory  727 , which are provided by software such as a computer program. The memory  727  stores: a minimum pressure value P 0  of the hydraulic motor  55  when the crushed materials are not fed on the discharge conveyor  50 ; a minimum pressure value P 2  of the hydraulic motor  35  when the raw materials are not thrown into the crusher  30 ; a discharge flow rate Q of the hydraulic pumps  52  and  53  when the crushed materials are not fed on the discharge conveyor  50 ; and pilot pressures of the control valves  112  to  116  in accordance with predetermined rotational speeds N 1L , N 2L , N 3L , N 4L  and N 5L  of the hydraulic motors  27  to  29 ,  35  and  55  when the crushed materials are not fed on the discharge conveyor  50 . 
     Next, functions of the units included in the controllers  71  and  72  will be described below with reference to a flow for controlling the hydraulic motors  27  to  29 ,  35  and  55  of the grizzly feeder  22 , the muck conveyor  26 , the crusher  30 , the discharge conveyor  50  and the magnetic separator  60  of the mobile crusher  1  depending on the presence or absence of the raw materials and crushed materials as shown in  FIG. 4 . 
     An operator initially sets a speed of the engine  49  by the fuel dial  91  and starts up the engine  49  in the operation mode by the engine start-up SW  101  to start up the grizzly feeder  22 , muck conveyor  26 , crusher  30 , discharge conveyor  50  and magnetic separator  60 . 
     The rotational speed set by the fuel dial  91  is stored in the memory  713  and inputted to the fuel injection quantity controller  711  to be set as a desired engine speed ω. At the same time, motor rotational speeds N 1 , N 2 , N 3 , N 4  and N 5  of the hydraulic motors  27  to  29 ,  35  and  55 , which are required for normal crushing operation in the operation mode, are set in the flow rate controller  726  (S 1 ). Subsequently, the flow rate controller  726  determines discharge flow rates of the hydraulic pumps  52  and  53  depending on the motor rotational speeds and engine speed, and controls an angle (inclination angle) of swash plates  52 A and  53 A to drive the hydraulic motors  27  to  29 ,  35  and  55  of the grizzly feeder  22 , muck conveyor  26 , crusher  30 , discharge conveyor  50  and magnetic separator  60  at the motor rotational speeds N 1 , N 2 , N 3 , N 4  and N 5 . 
     Then, the engine start-up determining unit  712  determines whether the engine start-up SW  101  is ON or OFF. When the engine start-up SW  101  is ON, the engine start-up determining unit  712  outputs a start-up signal to the mode determining unit  721  of the work implement controller  72  (S 2 ). 
     Upon receiving the start-up signal from the engine start-up determining unit  712 , the mode determining unit  721  determines which one of a travel mode, operation mode and inspection mode the mode switching SW  102  is positioned at, and then outputs a signal corresponding to the determined mode. More specifically, the mode determining unit  721  outputs a travel-mode signal to the pressure-for-traveling determining unit  722  when determining that the mode switching SW  102  is positioned at the travel mode. Also, the mode determining unit  721  outputs an operation-mode signal or inspection-mode signal to the work implement operating state determining unit  723  when determining that the mode switching SW  102  is positioned at the operation mode or inspection mode (S 3 ). Next, a flow corresponding to each mode will be described. 
     Travel Mode 
     Upon receiving the travel-mode signal from the mode determining unit  721 , the pressure-for-traveling determining unit  722  determines whether a signal indicating at least one of a left forward travel, left rearward travel, right forward travel and right rearward travel is inputted by the pressure for traveling SW  103  or not, and then outputs to the fuel injection quantity controller  711  of the engine controller  71  a travel-determination signal corresponding to a travel pattern (S 4 ). 
     Upon receiving the travel-determination signal indicating any of the above-described travel patterns, the fuel injection quantity controller  711  reads a set value of the engine speed set by the fuel dial  91  and determines a fuel injection quantity to be injected to the engine  49  so as to drive the engine  49  (S 5 ). Then, the above-described steps S 1  to S 5  are repeated. Upon receiving the travel-determination signal indicating that no travel is performed in S 4 , the fuel injection quantity controller  711  reads a decelerated speed ω 0  from the memory  713  to control a fuel injection quantity to be injected to the engine  49  (S 6 ). Then, the above-described steps S 2  to S 4  and S 6  are repeated. 
     Operation Mode 
     Upon receiving the operation-mode signal from the mode determining unit  721 , the work implement operating state determining unit  723  of the work implement controller  72  executes the above-described auto deceleration control. In the exemplary embodiment, the normal speed ω of the engine is the same as the decelerated speed ω 0  for facilitating understanding. Then, the work implement operating state determining unit  723  determines whether the feeder start-up SW  104 , muck conveyor start-up SW  105 , crusher start-up SW  106 , discharge conveyor start-up SW  107  and magnetic separator start-up SW  108  are ON or OFF (S 7 ). When none of the grizzly feeder  22 , muck conveyor  26 , crusher  30 , discharge conveyor  50 , and magnetic separator  60  are operated, the work implement operating state determining unit  723  outputs a non-operation signal to the fuel injection quantity controller  711  of the engine controller  71  (S 7 ). Upon receiving the non-operation signal, the fuel injection quantity controller  711  reads a decelerated speed ω 0  from the memory  713  to control a fuel injection quantity for injecting fuel to the engine  49  depending on the decelerated speed ω 0 . At this time, the fuel injection quantity is usually reduced. However, in this exemplary embodiment, the fuel injection quantity is not varied because of the above-described reason. 
     When at least any one of the grizzly feeder  22 , muck conveyor  26 , crusher  30 , discharge conveyor  50  and magnetic separator  60  is determined to be in operation, the work implement operating state determining unit  723  determines which of the grizzly feeder  22 , muck conveyor  26 , crusher  30 , discharge conveyor  50  and magnetic separator  60  is operated. When determining that all of the grizzly feeder  22 , muck conveyor  26 , crusher  30 , discharge conveyor  50  and magnetic separator  60  are operated, the work implement operating state determining unit  723  outputs an all-operation signal to the conveyor pressure comparing unit  724 . Otherwise, the work implement operating state determining unit  723  outputs a part-operation signal to the fuel injection quantity controller  711  of the engine controller  71  (S 8 ). When all of the grizzly feeder  22 , crusher  30  and discharge conveyor  50  are operated, the mobile crusher is operable for crushing. When one or more of the grizzly feeder  22 , crusher  30  and discharge conveyor  50  is not operated, the mobile crusher is not operable for crushing. 
     Upon receiving the all-operation signal, the conveyor pressure comparing unit  724  repeatedly monitors for a predetermined time a load pressure value P 1  of the hydraulic motor  55  of the discharge conveyor  50  using the conveyor pressure sensor  51  so as to compare the load pressure value P 1  with the minimum pressure value P 0  stored in the memory  727  (S 9 ). The “predetermined time” as described above is longer than a series of operation time for dropping raw materials into the hopper  24 , crushing the raw materials in the crusher  30  and discharging the crushed materials from the discharge conveyor  50 . The same applies in the following description. When the conveyor pressure comparing unit  724  determines that the load pressure value P 1  is larger than the minimum pressure value P 0 , the crushed materials are fed on the discharge conveyor  50 . Therefore, the fuel injection quantity controller  711  of the engine controller  71  drives the engine  49  at the engine speed set by the fuel dial  91  and drives the hydraulic motors  27  to  29 ,  35  and  55  at the motor rotational speeds N 1 , N 2 , N 3 , N 4  and N 5  (S 10 ). Then, the above-described steps S 1  to S 3  and S 7  to S 10  are repeated. 
     Conversely, when the conveyor pressure comparing unit  724  determines that the load pressure value P 1  is smaller than the minimum pressure value P 0  in S 9 , none of the crushed materials are fed on the discharge conveyor  50 . Therefore, the flow rate controller  726  read a discharge flow rate Q of the hydraulic pumps  52  and  53  from the memory  727  and changes an angle of the swash plates  52 A and  53 A to decelerate the motor rotational speeds of the hydraulic motors  27  to  29 ,  35  and  55  of the grizzly feeder  22 , muck conveyor  26 , crusher  30 , discharge conveyor  50  and magnetic separator  60  to N 1M , N 2M , N 3M , N 4M  and N 5M  that are lower than the normal speeds N 1 , N 2 , N 3 , N 4  and N 5  (S 11 ). Thus, a load applied on the hydraulic pumps  52  and  53  is decreased, so that fuel consumption can be reduced. 
     The flow rate controller  726  in a further read pilot pressures of the control valves  112  to  116  from the memory  727  and control the control valves so that the motor rotational speeds of the hydraulic motors  27  to  29 ,  35  and  55  become N 1L , N 2L , N 3L , N 4L  and N 5L . Preferably, N 4L  and N 4M  of the rotational speed of the hydraulic motor  35  of the discharge conveyor  50  are the same, and N 5  and N 5M  of the rotational speed of the hydraulic motor  55  of the magnetic separator  60  are the same. Further, N 3L  is preferably 0.5 times as fast as N 3M  of the rotational speed of the hydraulic motor  28  of the crusher  30 . N 1L  and N 2L  are preferably 0.3 times as fast as N 1  and N 2  of the rotational speeds of the hydraulic motor  27  of the grizzly feeder  22  and the hydraulic motor  28  of the muck conveyor  26 , respectively. In short, a deceleration rate of the grizzly feeder  22  and muck conveyor  26  on the upper stream of the crusher  30  is larger than a deceleration rate of the crusher  30 . When a load applied on the crusher  30  is detected and the speeds of the grizzly feeder  22  and muck conveyor  26  are returned to their normal speeds from a state where no load is applied on the discharge conveyor  50  and the speeds of the grizzly feeder  22  and muck conveyor  26  are decelerated, the feed of the raw materials from the grizzly feeder  22  to the crusher  30  can be slowed down. Thus, even if the return of the speed of the crusher  30  to its normal speed is slower than other devices because of its inertia when the speeds of the grizzly feeder  22  and muck conveyor  26  are returned to their normal speeds, the raw materials can be fed to the crusher  30  after the crusher  30  is completely returned to its normal speed. 
     Next, the crusher pressure comparing unit  725  detects for a predetermined time a load pressure value P 3  of the crusher  30  to compare the load pressure value P 3  with the minimum pressure value P 2  stored in the memory  727  (S 12 ). When the crusher pressure comparing unit  725  determines that the load pressure value P 3  is smaller than the minimum pressure value P 2 , none of the raw materials are thrown into the crusher  30 . Therefore, the flow rate controller  726  maintains the discharge flow rate Q of the hydraulic pumps  52  and  53  while maintaining the decelerated motor rotational speeds of the hydraulic motors  27  to  29 ,  35  and  55  of the grizzly feeder  22 , muck conveyor  26 , crusher  30 , discharge conveyor  50  and magnetic separator  60  (S 13 ). Then, the above-described steps S 2 , S 3 , S 7  to S 9  and S 11  to S 13  are repeated. 
     Conversely, when the crusher pressure comparing unit  725  determines that the load pressure value P 3  is larger than the minimum pressure value P 2  in S 12 , the raw materials are restarted to be thrown into the crusher  30 . Therefore, the fuel injection quantity controller  711  outputs to the fuel injector a fuel injection signal of the engine speed ω set by the fuel dial  91  and drives the engine  49  with fuel injected based on the fuel injection signal. The flow rate controller  726  determines discharge flow rates of the hydraulic pumps  52  and  53  depending on the motor rotational speeds N 1 , N 2 , N 3 , N 4  and N 5  that are set in advance and the set engine speed ω to control an angle (inclination angle) of the swash plates  52 A and  53 A (S 1 ). Then, the above-described steps S 2 , S 3 , S 7  to S 9 , S 11  S 12  and S 1  are repeated. In other words, when the raw materials are thrown into the crusher  30 , the motor rotational speeds of the hydraulic motors  27  to  29 ,  35  and  55  of the grizzly feeder  22 , muck conveyor  26 , crusher  30 , discharge conveyor  50  and magnetic separator  60  are automatically increased. Thus, working efficiency for an operator can be enhanced. 
     When the work implement operating state determining unit  723  outputs the part-operation signal to the fuel injection quantity controller  711 , the fuel injection quantity controller  711  controls a fuel injection quantity so that an amount of fuel corresponding to the engine speed set by the fuel dial  91  is injected to the engine  49 . The flow rate controller  726  determines discharge flow rates of the hydraulic pumps  52  and  53  and controls an angle (inclination angle) of the swash plates  52 A and  53 A. Thus, the hydraulic motors  27  to  29 ,  35  and  55  are driven at the motor rotational speeds N 1 , N 2 , N 3 , N 4  and N 5  for operation (S 10 ). Then, the above-described steps S 1  to S 3 , S 7 , S 8  and S 10  are repeated. Incidentally, when the work implement operating state is the part-operation state, one or two of the grizzly feeder  22 , crusher  30  and discharge conveyor  50  are operated and therefore the mobile crusher is not operable for crushing. The above state in the operation mode may caused by stuck crushed materials. In order for restoration, the motor rotational speeds are controlled at the motor rotational speeds N 1 , N 2 , N 3 , N 4  and N 5  for operation in S 10 . 
     Inspection Mode 
     Upon receiving the inspection-mode signal from the mode determining unit  721  in S 3 , the work implement operating state determining unit  723  determines operating states of the grizzly feeder  22 , muck conveyor  26 , crusher  30 , discharge conveyor  50  and magnetic separator  60 . When none of them are operated, the work implement operating state determining unit  723  outputs a non-operation signal to the fuel injection quantity controller  711 . When at least one of the grizzly feeder  22 , muck conveyor  26 , crusher  30 , discharge conveyor  50  and magnetic separator  60  is operated, the work implement operating state determining unit  723  outputs a part-operation signal to the fuel injection quantity controller  711  (S 14 ). 
     Upon receiving the non-operation signal, the fuel injection quantity controller  711  reads a decelerated speed ω 0  from the memory  713  to control a fuel injection quantity to be injected to the engine  49  depending on the decelerated speed ω 0  (S 6 ). Then, the above-described steps S 2 , S 3  S 14  and S 6  are repeated. Upon receiving the part-operation signal, the fuel injection quantity controller  711  reads an engine speed set by the fuel dial  91  to supply of fuel of fuel injection quantity corresponding to the engine speed so as to drive the engine  49  (S 5 ). Then, the above-described steps S 1  to S 3 , S 14  and S 5  are repeated. 
     Since the load pressure value P 1  of the hydraulic motor  55  of the discharge conveyor  50  is initially detected by the conveyor pressure sensor  51  in the exemplary embodiment, it can be determined that the crushed materials are not fed on the discharge conveyor  50  when the load pressure value P 1  is smaller than the minimum pressure valve P 0 . Accordingly, when the crushed materials are not fed on the discharge conveyor  50 , it is determined that the raw materials or crushed materials are not present on any of the grizzly feeder  22 , muck conveyor  26 , crusher  30 , discharge conveyor  50  and magnetic separator  60 . Thus, the flow rate controller  726  controls the discharge flow of the hydraulic pumps  52  and  53  at Q to decelerate the motor rotational speeds of the hydraulic motors  27  to  29 ,  35  and  55  of the grizzly feeder  22 , muck conveyor  26 , crusher  30 , discharge conveyor  50  and magnetic separator  60 . 
     Then, the load pressure value P 3  of the hydraulic motor  35  of the crusher  30  is detected by the crusher pressure sensor  36  (raw material determining unit). When the load pressure value P 3  is larger than the minimum pressure valve P 2 , it can be determined that the raw materials are present in the crusher  30 . In other words, it can be reliably detected that the raw materials are thrown into the crusher  30 . Accordingly, the engine  49  can be controlled to be driven with fuel having the fuel injection quantity set by the fuel dial  91 . Also, the hydraulic motor rotational speeds of the grizzly feeder  22 , muck conveyor  26 , crusher  30 , discharge conveyor  50  and magnetic separator  60  can be automatically controlled to be returned to the motor rotational speed ω for operation. Though the decelerated speed ω 0  of the engine  49  and the normal speed ω are the same in this exemplary embodiment, fuel efficiency may be further enhanced when the decelerated speed ω 0  is slower than the normal speed ω. When the engine speed is decelerated from the normal speed to the decelerated speed ω 0 , the discharge flow rates of the hydraulic pumps  52  and  53  are correspondingly reduced. Then, the motor rotational speeds of the hydraulic motors  27  to  29 ,  35  and  55  of the grizzly feeder  22 , muck conveyor  26 , crusher  30 , discharge conveyor  50  and magnetic separator  60  are slowed down to N 1E , N 2E , N 3E , N 4E  and N 5E . According to an aspect of the invention, the discharge flow rates of the hydraulic pumps  52  and  53  and the rotational speeds of the hydraulic motors are further reduced from the above-described state. 
     The best arrangements, methods and the like for carrying out the invention are disclosed above, but the invention is not limited thereto. While the invention is particularly explained and illustrated mainly in relation to a specific embodiment, a person skilled in the art could make various modifications in terms of shape, amount or other particulars to the above-described embodiment without departing from the spirit and scope of the invention. 
     Therefore, because the above-disclosed description limiting the shape, amount and the like is merely an exemplified statement for facilitating understanding of the invention and is not a limitation on the invention, a statement using names of the members on which a part of or all of the limitations regarding the shape, amount and the like is eliminated is included in the invention. 
     For example, the crusher pressure sensor  36  detects a load pressure of the hydraulic motor  35  of the crusher  30  to detect whether the raw materials are thrown into the crusher  30  or not in the exemplary embodiment. However, whether the raw materials are thrown into the crusher  30  or not may be detected by detecting a rotational speed of the hydraulic motor  35  of the crusher  30 . Since the rotational speed of the hydraulic motor  35  is varied depending on the presence or absence of the raw materials, whether the raw materials are thrown into the crusher  30  or not can be detected by detecting the variation of the rotational speed. 
     Though the conveyor pressure sensor  51  is used as the crushed material determining unit in the exemplary embodiment, a strain gauge may be alternatively used on a bracket that supports carrier rollers of the discharge conveyor  50 . 
     Though the flow rate controller  726  controls the discharge flow rates of the hydraulic pumps  52  and  53  in the exemplary embodiment, the hydraulic motors  27  to  29 ,  35  and  55  driven by the hydraulic pumps  52  and  53  may be set variable to control the motor rotational speeds. Alternatively, only pilot pressures of the control valves  112  to  116  may be controlled to be electromagnetically proportional to control the flow rates of hydraulic oil supplied to the hydraulic motors  27  to  29 ,  35  and  55 . 
     Though the pressure sensor  36  is used for measuring a load pressure of the hydraulic motor  35  of the crusher  30  as the raw material determining unit in the exemplary embodiment, a rotation sensor may be alternatively used for measuring a motor rotational speed of the hydraulic motor  35  of the crusher  30 . 
     Further, though the motors  27  to  29 ,  35  and  55  for driving the grizzly feeder  22 , muck conveyor  26 , crusher  30 , discharge conveyor  50  and magnetic separator  60  are hydraulically driven in the exemplary embodiment, the motors may be electrically driven. 
     Though the auto deceleration control is executed depending on the presence or absence of the grizzly feeder  22 , muck conveyor  26 , crusher  30 , discharge conveyor  50  and magnetic separator  60  in the exemplary embodiment, the auto deceleration control may be executed by determining a load applied on the crusher  30  by the raw material determining unit. Alternatively, the auto deceleration control may be executed by determining a load applied on the discharge conveyor  50  by the crushed material determining unit. 
     The entire disclosure of Japanese Patent Application No. 2008-139467, filed May 28, 2008, and No. 2009-078912, filed Mar. 27, 2009, are expressly incorporated by reference herein.