Patent Publication Number: US-2021164198-A1

Title: Work Machine

Description:
TECHNICAL FIELD 
     The present invention relates to a work machine having a blade provided to a track structure, and a swing structure provided swingably on the upper side of the track structure. 
     BACKGROUND ART 
     Patent Document 1 discloses a technology for a bulldozer including a travelable machine body, and a blade provided on the front side of the machine body such that the blade can be raised and lowered, which technology allows for acquisition of the position of the machine body, and the position of the blade. The bulldozer includes: first and second antennas that are attached to an upper section of the machine body, and receive signals from an artificial satellite; a third antenna that is attached to the upper end of a pole coupled to the blade, and receives signals from the artificial satellite; and a control module that measures the position of the machine body by using the signals received at the first and second antennas, and measures the position of the blade by using the signals received at the third antenna. Note that the antennas, and the control module mentioned before form a GNSS (Global Navigation Satellite System). 
     PRIOR ART DOCUMENT 
     Patent Document 
     Patent Document 1: Japanese Patent No. 5356141 
     SUMMARY OF THE INVENTION 
     Problem to be Solved by the Invention 
     A hydraulic excavator, which is one type of work machine, includes: a travelable track structure; a swing structure provided swingably on the upper side of the track structure; a work device that is coupled to the front side of the swing structure, and performs excavation work and the like; and a blade that is provided on the front side of the track structure such that the blade can be raised and lowered, and performs levelling work and the like. 
     There is supposed a case in which the technology described in Patent Document 1 is applied to the hydraulic excavator mentioned above for the purpose of computing and displaying the horizontal coordinates of the blade, and the like in order to assist an operator, for example. That is, in the supposed case, the pole is coupled with the blade, the antenna is attached to the upper end of the pole, and the horizontal coordinates of the blade are computed by using signals received at the antenna. However, in this case, there is a possibility that the work device interferes with the pole or the antenna. 
     Based on the reason mentioned above, there is supposed a case in which the two antennas are attached only to the swing structure, and the horizontal coordinates and the orientation of the swing structure are computed by using signals received at the antennas. However, in this case, the horizontal coordinates of the blade cannot be computed because the orientation of the track structure is unknown. 
     An object of the present invention is to provide a work machine having a blade provided to a track structure, and a swing structure provided swingably on the upper side of the track structure, which work machine allows for computation of the horizontal coordinates of the blade. 
     Means for Solving the Problem 
     In order to achieve the object, the present invention provides a work machine including: a travelable track structure; a swing structure provided swingably on an upper side of the track structure; a work device coupled to a front side of the swing structure; a blade provided on a front side of the track structure such that the blade can be raised and lowered; and a lift cylinder that raises and lowers the blade. The work machine includes: a swing-structure-position acquiring device that acquires a horizontal coordinate and an orientation of the swing structure; a swing sensor that senses a swing of the swing structure; a travel sensor that senses travelling of the track structure; and a controller that computes an orientation of the track structure, and a horizontal coordinate of the blade. The controller computes the orientation of the track structure by using a locus of the horizontal coordinate of the swing structure, the horizontal coordinate being acquired by the swing-structure-position acquiring device, in a case where a swing of the swing structure is not sensed, and travelling of the track structure is sensed; and computes the horizontal coordinate of the blade on a basis of the computed orientation of the track structure, and the horizontal coordinate and the orientation of the swing structure acquired by the swing-structure-position acquiring device. 
     Advantages of the Invention 
     According to the present invention, a work machine having a blade provided to a track structure, and a swing structure provided swingably on the upper side of the track structure allows for computation of the horizontal coordinates of the blade. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view representing the structure of a hydraulic excavator in a first embodiment of the present invention. 
         FIG. 2  is a schematic diagram representing the configuration of a hydraulic drive system in the first embodiment of the present invention. 
         FIG. 3  is a block diagram representing the configuration of an assisting device in the first embodiment of the present invention. 
         FIG. 4  is a flowchart representing a processing procedure of a controller in the first embodiment of the present invention. 
         FIG. 5  is a block diagram representing the configuration of the assisting device in a second embodiment of the present invention. 
         FIG. 6  is a schematic diagram representing the configuration of the hydraulic drive system in a third embodiment of the present invention. 
         FIG. 7  is a block diagram representing the configuration of the assisting device in the third embodiment of the present invention. 
         FIG. 8  is a figure representing the configuration of the assisting device in a fourth embodiment of the present invention. 
         FIG. 9  is a block diagram representing the configuration of the assisting device in a fifth embodiment of the present invention. 
         FIG. 10  is a flowchart representing a processing procedure of a controller in the fifth embodiment of the present invention. 
     
    
    
     MODES FOR CARRYING OUT THE INVENTION 
     A first embodiment of the present invention is explained with reference to the drawings, by using a hydraulic excavator as an example application subject of the present invention. 
       FIG. 1  is a side view representing the structure of a hydraulic excavator in the present embodiment. 
     The hydraulic excavator of the present embodiment includes: a travelable track structure  1 ; a swing structure  2  provided swingably on the upper side of the track structure  1 ; a work device  3  coupled to the front side of the swing structure  2 ; and an earth removing device  4  coupled to the front side of the track structure  1 . 
     The track structure  1  includes a track frame  5 . The track frame  5  includes: a center frame (not illustrated) that extends leftward and rightward relative to the track structure  1 ; a left side frame (see  FIG. 1 ) that is coupled to the left side of the center frame, and extends forward and backward relative to the track structure  1 ; and a right side frame (not illustrated) that is coupled to the right side of the center frame, and extends forward and backward relative to the track structure  1 . 
     A driving wheel  6  is arranged on the rear end of the left side frame, a follower wheel  7  is arranged on the front end of the left side frame, and a crawler (crawler)  8  is wound around and between the driving wheel  6  and the follower wheel  7 . Then, the forward or backward rotation of a left travel motor  9 A rotates the left driving wheel  6  forward or backward, and this in turn rotates the left crawler  8  forward or backward. 
     Similarly, a driving wheel is arranged on the rear end of the right side frame, a follower wheel is arranged on the front end of the right side frame, and a crawler is wound around and between the driving wheel and the follower wheel. Then, the forward or backward rotation of a right travel motor  9 B (see  FIG. 2  mentioned below) rotates the right driving wheel forward or backward, and this in turn rotates the right crawler forward or backward. 
     The swing structure  2  is provided swingably to the center frame via a slewing ring. Then, the rotation of a swing motor  10  in one direction or the opposite direction swings the swing structure  2  leftward or rightward. 
     The earth removing device  4  includes: a lift arm  11  coupled to the front side of the center frame such that the lift arm  11  can pivot upward and downward; and a blade (earth removing plate)  12  that is coupled to a tip section of the lift arm  11 , and extends leftward and rightward relative to the track structure  1 . That is, the blade  12  is provided on the front side of the track structure  1  such that the blade  12  can be raised and lowered. Then, the expansion or contraction of a lift cylinder  13  pivots the lift arm  11  downward or upward, and this in turn lowers or raises the blade  12 . 
     The work device  3  includes: a boom  14  coupled to the front side of the swing structure  2  such that the boom  14  can pivot upward and downward; an arm  15  coupled to a tip section of the boom  14  such that the arm  15  can pivot upward and downward; and a bucket  16  coupled to a tip section of the arm  15  such that the bucket  16  can pivot upward and downward. Then, the expansion or contraction of a boom cylinder  17  pivots the boom  14  upward or downward, the expansion or contraction of an arm cylinder  18  pivots the arm  15  in the crowding direction (withdrawing direction) or the dumping direction (pushing direction), and the expansion or contraction of a bucket cylinder  19  pivots the bucket  16  in the bucket-crowding direction or the dumping direction. 
     The swing structure  2  includes a swing frame  20  forming the base structure, and a cab  21  provided at a front section of the swing frame  20 . On the swing structure  2 , an engine  22  as a prime mover, and equipment such as hydraulic pumps  23 A and  23 B or a control valve device  24  illustrated in  FIG. 2  mentioned below are mounted. 
     An operator&#39;s seat (not illustrated) on which an operator is to be seated is provided in the cab  21 . Travel operation devices  25 A and  25 B (see  FIG. 2  mentioned below) through which instructions for the driving of the travel motor  9 A and the driving of the travel motor  9 B are given, respectively, are provided on the front side of the operator&#39;s seat. A work operation device  26 A (see  FIG. 2  mentioned below) through which instructions for the driving of the arm cylinder  18  and the driving of the swing motor  10  are selectively given is provided on the left side of the operator&#39;s seat. A work operation device  26 B (see  FIG. 2  mentioned below) through which instructions for the driving of the boom cylinder  17  and the driving of the bucket cylinder  19  are selectively given is provided on the right side of the operator&#39;s seat. A blade operation device  27  (see  FIG. 2  mentioned below) through which instructions for the driving of the lift cylinder  13  are given is provided on the right side of the work operation device  26 B. A monitor  30  (see  FIG. 3  mentioned below) is provided on the front right side of the operator&#39;s seat. 
     The hydraulic excavator includes a hydraulic drive system that drives hydraulic actuators in accordance with operation of the operation devices mentioned above. The configuration of the hydraulic drive system is explained by using  FIG. 2 .  FIG. 2  is a schematic diagram representing the configuration of the hydraulic drive system in the present embodiment. 
     The hydraulic drive system of the present embodiment includes: the engine  22 ; the variable displacement hydraulic pumps  23 A and  23 B driven by the engine  22 ; a plurality of hydraulic actuators (specifically, the travel motors  9 A and  9 B, the swing motor  10 , the lift cylinder  13 , the boom cylinder  17 , the arm cylinder  18  and the bucket cylinder  19  mentioned above) driven by a hydraulic fluid from the hydraulic pumps  23 A and  23 B; the control valve device  24  that controls the flow of the hydraulic fluid from the hydraulic pumps  23 A and  23 B to the plurality of hydraulic actuators; and a plurality of operation devices (specifically, the travel operation devices  25 A and  25 B, the work operation devices  26 A and  26 B and the blade operation device  27  mentioned above). 
     Although not illustrated, the travel operation device  25 A has: an operation lever that can be operated forward and backward; a left travel pilot valve that generates and outputs a forward travel pilot pressure (hydraulic pressure) in accordance with a forward operation amount of the operation lever; and a left travel pilot valve that generates and outputs a backward travel pilot pressure (hydraulic pressure) in accordance with a backward operation amount of the operation lever. 
     Similarly, although not illustrated, the travel operation device  25 B has: an operation lever that can be operated forward and backward; a right travel pilot valve that generates and outputs a forward travel pilot pressure (hydraulic pressure) in accordance with a forward operation amount of the operation lever; and a right travel pilot valve that generates and outputs a backward travel pilot pressure (hydraulic pressure) in accordance with a backward operation amount of the operation lever. 
     Although not illustrated, the work operation device  26 A has: an operation lever that can be operated leftward and rightward, and forward and backward; an arm pilot valve that generates and outputs an arm-dumping pilot pressure (hydraulic pressure) in accordance with a leftward operation amount of the operation lever; an arm pilot valve that generates and outputs an arm-crowding pilot pressure (hydraulic pressure) in accordance with a rightward operation amount of the operation lever; a swing pilot valve that generates and outputs a right-swing pilot pressure (hydraulic pressure) in accordance with a forward operation amount of the operation lever; and a swing pilot valve that generates and outputs a left-swing pilot pressure (hydraulic pressure) in accordance with a backward operation amount of the operation lever. 
     Although not illustrated, the work operation device  26 B has: an operation lever that can be operated leftward and rightward, and forward and backward; a bucket pilot valve that generates and outputs a bucket-crowding pilot pressure (hydraulic pressure) in accordance with a leftward operation amount of the operation lever; a bucket pilot valve that generates and outputs a bucket-dumping pilot pressure (hydraulic pressure) in accordance with a rightward operation amount of the operation lever; a boom-pilot valve that generates and outputs a boom-lowering pilot pressure (hydraulic pressure) in accordance with a forward operation amount of the operation lever; and a boom-pilot valve that generates and outputs a boom-raising pilot pressure (hydraulic pressure) in accordance with a backward operation amount of the operation lever. 
     Although not illustrated, the blade operation device  27  has: an operation lever that can be operated forward and backward; a blade pilot valve that generates and outputs a blade-lowering pilot pressure (hydraulic pressure) in accordance with a forward operation amount of the operation lever; and a blade pilot valve that generates and outputs a blade-raising pilot pressure (hydraulic pressure) in accordance with a backward operation amount of the operation lever. 
     Although not illustrated, the control valve device  24  includes a hydraulic pilot type left travel control valve, right travel control valve, arm control valve, swing control valve, bucket control valve, boom control valve and blade control valve. 
     The left travel control valve is switched by the forward travel pilot pressure or the backward travel pilot pressure from the travel operation device  25 A, and controls the flow (direction and flow rate) of the hydraulic fluid from the hydraulic pump to the left travel motor  9 A. Thereby, the left travel motor  9 A is rotated forward or backward. 
     Similarly, the right travel control valve is switched by the forward travel pilot pressure or the backward travel pilot pressure from the travel operation device  25 B, and controls the flow (direction and flow rate) of the hydraulic fluid from the hydraulic pump to the right travel motor  9 B. Thereby, the right travel motor  9 B is rotated forward or backward. 
     The arm control valve is switched by the arm-crowding pilot pressure or the arm-dumping pilot pressure from the work operation device  26 A, and controls the flow (direction and flow rate) of the hydraulic fluid from the hydraulic pump to the arm cylinder  18 . Thereby, the arm cylinder  18  expands or contracts. 
     The swing control valve is switched by the left-swing pilot pressure or the right-swing pilot pressure from the work operation device  26 A, and controls the flow (direction and flow rate) of the hydraulic fluid from the hydraulic pump to the swing motor  10 . Thereby, the swing motor  10  rotates in one direction or in the opposite direction. 
     The bucket control valve is switched by the bucket-crowding pilot pressure or the bucket-dumping pilot pressure from the work operation device  26 B, and controls the flow (direction and flow rate) of the hydraulic fluid from the hydraulic pump to the bucket cylinder  19 . Thereby, the bucket cylinder  19  expands or contracts. 
     The boom control valve is switched by the boom-raising pilot pressure or the boom-lowering pilot pressure from the work operation device  26 B, and controls the flow (direction and flow rate) of the hydraulic fluid from the hydraulic pump to the boom cylinder  17 . Thereby, the boom cylinder  17  expands or contracts. 
     The blade control valve is switched by the blade-lowering pilot pressure or the blade-raising pilot pressure from the blade operation device  27 , and controls the flow (direction and flow rate) of the hydraulic fluid from the hydraulic pump to the lift cylinder  13 . Thereby, the lift cylinder  13  expands or contracts. 
     The hydraulic excavator of the present embodiment includes an assisting device that computes and displays the position of the blade  12  (specifically, the horizontal coordinates and the height of the blade  12 ) in order to assist an operator. The configuration of the assisting device is explained by using  FIG. 3 .  FIG. 3  is a block diagram representing the configuration of the assisting device in the present embodiment. 
     The assisting device of the present embodiment includes antennas  31 A and  31 B, receivers  32 A and  32 B, swing sensors  33 A and  33 B, a lift sensor  34 , a controller  35  and the monitor  30 . 
     The antennas  31 A and  31 B, and the receivers  32 A and  32 B form a satellite positioning system such as a GNSS. As illustrated in  FIG. 1  mentioned above, the antennas  31 A and  31 B are provided on an upper section of the swing structure  2 , and receive signals from an artificial satellite. The receivers  32 A and  32 B are connected to the antennas  31 A and  31 B, respectively. The receiver  32 A measures the position of the antenna  31 A on the Earth (specifically, the horizontal coordinates and the height of the antenna  31 A) by using signals from the artificial satellite received at the antenna  31 A, and outputs the measured position of the antenna  31 A to the controller  35 . Similarly, the receiver  32 B measures the position of the antenna  31 B on the Earth by using signals from the artificial satellite received at the antenna  31 B, and outputs the measured position of the antenna  31 B to the controller  35 . 
     As illustrated in  FIG. 2  mentioned above, the swing sensor  33 A or  33 B is a pressure sensor provided between the swing pilot valve of the work operation device  26 A and the swing control valve of the control valve device  24 . The swing sensor  33 A or  33 B senses a swing pilot pressure, and outputs the swing pilot pressure to the controller  35 . 
     The lift sensor  34  is a displacement sensor that senses the stroke of the lift cylinder  13  as a state quantity related to the raising and lowering of the blade  12 . The lift sensor  34  senses the stroke of the lift cylinder  13 , and outputs the stroke to the controller  35 . 
     Although not illustrated, for example, the monitor  30  has: a control section (e.g. a CPU) that executes calculation processes and control processes on the basis of a program; a storage section (e.g. a ROM and a RAM) that stores the program, and processing results; an operation switch; and a screen display section. The control section of the monitor  30  selects any one of a plurality of modes including a blade-position computation mode in accordance with operation of the operation switch, and controls the display of the screen display section in accordance with the selected mode. 
     Explaining specifically, in a case where the blade-position computation mode is selected, the monitor  30  sends a command for starting blade-position computation to the controller  35 . Then, the monitor  30  receives the position of the blade  12  computed by the controller  35 , and displays the position on the screen display section. Specifically, the position of the blade  12  may be displayed by numerical values or may be represented with shapes. On the other hand, in a case where another mode is selected, the monitor  30  sends a command for ending the blade-position computation to the controller  35 . Then, the position of the blade is not displayed on the screen display section. 
     Although not illustrated, the controller  35  has: a control section (e.g. a CPU) that executes calculation processes and control processes on the basis of a program; and a storage section (e.g. a ROM and a RAM) that stores the program, and processing results. The controller  35  starts blade-position computation control in accordance with a command for starting the blade-position computation from the monitor  30 , and ends the blade-position computation control in accordance with a command for ending the blade-position computation from the monitor  30 . The controller  35  has a swing-structure-position computing section  36 , a track-structure-orientation computing section  37 , a blade-horizontal-coordinate computing section  38  and a blade-height computing section  39 , as functional configurations related to the blade-position computation control. 
     The swing-structure-position computing section  36  of the controller  35  receives the horizontal coordinates of the antennas  31 A and  31 B from the receivers  32 A and  32 B, and computes, as the horizontal coordinates of the swing structure  2 , the horizontal coordinates of the midpoint between the antennas  31 A and  31 B (specifically, the horizontal coordinates of the midpoint of a line segment linking the antenna  31 A and the antenna  31 B, but not the horizontal coordinates of a predetermined swing center point on the center line of the swing of the swing structure  2 ). In addition, the swing-structure-position computing section  36  computes the orientation of the swing structure  2  on the basis of the horizontal coordinates of the antennas  31 A and  31 B. Note that the orientation of the swing structure  2  means a direction that the front side of the swing frame  20  (specifically, the portion to which the work device  3  is coupled) faces. 
     In addition, the swing-structure-position computing section  36  of the controller  35  receives the heights of the antennas  31 A and  31 B from the receivers  32 A and  32 B, and computes, as the height of the swing structure  2 , the average of the heights of the antennas  31 A and  31 B or selects the height of one of the antennas. 
     The track-structure-orientation computing section  37  of the controller  35  computes the orientation of the track structure  1  (details are mentioned below). Note that the orientation of the track structure  1  means a direction that the front side of the track frame  5  (specifically, the portion where the blade  12  is coupled via the lift arm  11 ) faces. 
     On the basis of the orientation of the track structure  1  computed by the track-structure-orientation computing section  37 , and the horizontal coordinates and the orientation of the swing structure  2  computed by the swing-structure-position computing section  36 , the blade-horizontal-coordinate computing section  38  of the controller  35  computes the horizontal coordinates of the blade  12  (specifically, the horizontal coordinates of the center point of the blade  12 ). Explaining specifically, the positional relationship between the midpoint between the antennas  31 A and  31 B and the swing center point of the swing structure  2  is stored in advance, and this positional relationship is used to compute the horizontal coordinates of the swing center point of the swing structure  2  from the horizontal coordinates and the orientation of the swing structure  2 . In addition, the positional relationship between the swing center point of the swing structure  2  and the center point of the blade  12  is stored in advance, and this positional relationship is used to compute the horizontal coordinates of the blade  12  from the horizontal coordinates of the swing center point of the swing structure  2 , and the orientation of the track structure  1 . 
     On the basis of the stroke of the lift cylinder  13  sensed by the lift sensor  34 , and the height of the swing structure  2  computed by the swing-structure-position computing section  36 , the blade-height computing section  39  of the controller  35  computes the height of the blade  12  (specifically, the height of the lower end of the blade  12 ). Explaining specifically, the relationship between the stroke of the lift cylinder  13  and the relative height of the blade  12  relative to the swing center point of the swing structure  2  is stored in advance, and this relationship is used to compute the relative height of the blade  12  from the stroke of the lift cylinder  13 . In addition, the positional relationship between the midpoint between the antennas  31 A and  31 B and the swing center point of the swing structure  2  is stored in advance, and this positional relationship is used to compute the height of the swing center point of the swing structure  2  from the height of the swing structure  2 . Then, the absolute height of the blade  12  is computed on the basis of the height of the swing center point of the swing structure  2 , and the relative height of the blade  12 . 
     Next, contents of processing performed in display control by the controller  35  in the present embodiment are explained by using  FIG. 4 .  FIG. 4  is a flowchart representing a processing procedure of the controller in the present embodiment. 
     At Step S 1 , the track-structure-orientation computing section  37  of the controller  35  decides whether the swing structure  2  is swinging by deciding whether a larger one of the swing pilot pressures sensed by the swing sensors  33 A and  33 B is equal to or higher than a preset threshold, for example. In addition, for example, the time that has elapsed since both the swing pilot pressures sensed by the swing sensors  33 A and  33 B have become smaller than a threshold may be computed, and it may be decided that the swing structure  2  is still swinging if the elapsed time is shorter than a preset threshold. 
     In a case where it is decided at Step S 1  that the swing structure  2  is not swinging (i.e. a swing of the swing structure  2  is not sensed), the result of the decision at Step S 1  is NO, and the process proceeds to Step S 2 . At Step S 2 , the track-structure-orientation computing section  37  of the controller  35  computes the horizontal coordinates of the swing center point of the swing structure  2  on the basis of the horizontal coordinates and the orientation of the swing structure  2  computed by the swing-structure-position computing section  36 , for example, and decides whether the track structure  1  is travelling by deciding whether the horizontal coordinates of the swing center point of the swing structure  2  are changing. 
     In a case where it is decided at Step S 2  that the track structure  1  is travelling (i.e. in a case where travelling of the track structure  1  is sensed), the result of the decision at Step S 2  is YES, and the process proceeds to Step S 3 . At Step S 3 , the track-structure-orientation computing section  37  of the controller  35  computes the current advancing direction of the track structure  1  by using the locus (history) of the horizontal coordinates of the swing structure  2  computed by the swing-structure-position computing section  36 , and treats the current advancing direction as the orientation of the track structure  1 . 
     After Step S 3 , the process proceed to Step S 4 . At Step S 4 , the track-structure-orientation computing section  37  of the controller  35  stores (updates) the relative relationship (relative angle) between the computed orientation of the track structure  1  and the orientation of the swing structure  2  computed by the swing-structure-position computing section  36 . 
     In a case where it is decided at Step S 2  that the track structure  1  is not travelling (i.e. in a case where travelling of the track structure  1  is not sensed), the result of the decision at Step S 2  is NO, and the process proceeds to Step S 5 . At Step S 5 , the track-structure-orientation computing section  37  of the controller  35  decides whether the relative relationship between the orientation of the track structure  1  and the orientation of the swing structure  2  is stored. 
     In a case where the relative relationship between the orientation of the track structure  1  and the orientation of the swing structure  2  is stored at Step S 5 , the result of the decision at Step S 5  is YES, and the process proceeds to Step S 6 . At Step S 6 , by using the stored relative relationship between the orientation of the track structure  1  and the orientation of the swing structure  2 , the track-structure-orientation computing section  37  of the controller  35  computes the current orientation of the track structure  1  from the current orientation of the swing structure  2  computed by the swing-structure-position computing section  36 . Thereby, even if the track structure  1  makes a spin turn, the orientation of the track structure  1  can be computed. 
     After Step S 4  or S 6 , the process proceed to Step S 7 . At Step S 7 , the blade-horizontal-coordinate computing section  38  of the controller  35  computes the horizontal coordinates of the blade  12  on the basis of the orientation of the track structure  1  computed at Step S 3  or S 6  mentioned above, and the horizontal coordinates and the orientation of the swing structure  2  computed by the swing-structure-position computing section  36 . On the basis of the stroke of the lift cylinder  13  sensed by the lift sensor  34 , and the height of the swing structure  2  computed by the swing-structure-position computing section  36 , the blade-height computing section  39  of the controller  35  computes the height of the blade  12 . 
     After Step S 7 , the process proceed to Step S 8 . At Step S 8 , the controller  35  sends a command for displaying a blade position to the monitor  30 , together with the computed horizontal coordinates and the computed height of the blade  12 . Thereby, the monitor  30  displays the position of the blade  12 . 
     In a case where it is decided at Step S 1  that the swing structure  2  is swinging (i.e. a swing of the swing structure  2  is sensed), the result of the decision at Step S 1  is YES, and the process proceeds to Step S 9 . At Step S 9 , the track-structure-orientation computing section  37  of the controller  35  deletes the stored relative relationship between the orientation of the track structure  1  and the orientation of the swing structure  2 . 
     After Step S 9 , the process proceeds to Step S 10 . In addition, in a case where the relative relationship between the orientation of the track structure  1  and the orientation of the swing structure  2  is not stored at Step S 5 , the result of the decision at Step S 5  is NO, and the process proceeds to Step S 10 . At Step S 10 , the track-structure-orientation computing section  37  of the controller  35  sends, to the monitor  30 , a command for displaying an indication that the blade position is unknown. Thereby, the monitor  30  displays an indication that the blade position is unknown. Specifically, numerical value display fields may be left blank, or shapes may be deleted. 
     As mentioned above, in the present embodiment, it is possible to compute the horizontal coordinates and the height of the blade  12  in the hydraulic excavator having the blade  12  provided to the track structure  1  and the swing structure  2  provided swingably on the upper side of the track structure  1 . Then, the horizontal coordinates and the height of the blade  12  can be displayed to assist an operator. 
     Note that, in the explanation above, the antennas  31 A and  31 B, the receivers  32 A and  32 B, and the swing-structure-position computing section  36  of the controller  35  form the swing-structure-position acquiring device described in CLAIMS that acquires the horizontal coordinates and the orientation of the swing structure, and form the swing-structure-position acquiring device that further acquires the height of the swing structure. In addition, the function of the controller  35  to decide whether the swing structure  2  is swinging on the basis of swing pilot pressures forms the swing sensor that senses a swing of the swing structure. In addition, the function of the controller  35  to decide whether the track structure  1  is travelling on the basis of the horizontal coordinates of the swing center point of the swing structure  2  forms the travel sensor that senses travelling of the track structure. 
     In addition, the monitor  30  forms the mode selecting device that selects either the blade-position computation mode in which the position of the blade is computed or the other mode in which the position of the blade is not computed, and forms the display device that displays the horizontal coordinates and the height of the blade computed by the controller. 
     A second embodiment of the present invention is explained by using  FIG. 5 . Note that portions in the present embodiment that are equivalent to their counterparts in the first embodiment are given the same reference characters, and explanation thereof is omitted as appropriate. 
       FIG. 5  is a block diagram representing the configuration of the assisting device in the present embodiment. 
     The assisting device of the present embodiment further includes an inclination angle sensor  40 . The inclination angle sensor  40  senses forward-backward and leftward-rightward inclination angles of the track structure  1 , and outputs the inclination angles to a controller  35 A. 
     On the basis of the orientation of the track structure  1  computed by the track-structure-orientation computing section  37 , the horizontal coordinates and the orientation of the swing structure  2  computed by the swing-structure-position computing section  36 , and the inclination angles of the track structure  1  sensed by the inclination angle sensor  40 , a blade-horizontal-coordinate computing section  38 A of the controller  35 A of the present embodiment computes the horizontal coordinates of the blade  12 . Explaining specifically, inclination angles of the swing structure  2  are computed on the basis of the orientation of the swing structure  2  and the orientation and inclination angles of the track structure  1 . Then, the horizontal coordinates of the swing center point of the swing structure  2  are computed on the basis of the horizontal coordinates, the orientation and the inclination angles of the swing structure  2 . Then, the horizontal coordinates of the blade  12  are computed on the basis of the horizontal coordinates of the swing center point of the swing structure  2  and the orientation and the inclination angles of the track structure  1 . 
     On the basis of the stroke of the lift cylinder  13  sensed by the lift sensor  34 , the height of the swing structure  2  computed by the swing-structure-position computing section  36 , and the inclination angles of the track structure  1  sensed by the inclination angle sensor  40 , a blade-height computing section  39 A of the controller  35 A computes the height of the blade  12 . Explaining specifically, a relative height of the blade  12  is computed from the stroke of the lift cylinder  13 . In addition, the inclination angles of the swing structure  2  are computed on the basis of the orientation of the swing structure  2  and the orientation and the inclination angles of the track structure  1 . Then, the height of the swing center point of the swing structure  2  is computed on the basis of the height, the orientation and the inclination angles of the swing structure  2 . Then, the absolute height of the blade  12  is computed on the basis of the height of the swing center point of the swing structure  2  and the relative height of the blade  12 . 
     In the thus-configured present embodiment also, the horizontal coordinates and the height of the blade  12  can be computed in a similar manner to the first embodiment. Then, the horizontal coordinates and the height of the blade  12  can be displayed to assist an operator. In addition, the precision of the horizontal coordinates and the height of the blade  12  can be enhanced over the first embodiment. 
     A third embodiment of the present invention is explained by using  FIG. 6  and  FIG. 7 . Note that portions in the present embodiment that are equivalent to their counterparts in the first and second embodiments are given the same reference characters, and explanation thereof is omitted as appropriate. 
     It is supposed in the first and second embodiments that levelling work and the like are performed with the blade  12  by causing the track structure  1  to travel forward. In contrast to this, in the present embodiment, it is supposed that levelling work and the like are performed with the blade  12  by causing the track structure  1  to travel forward or backward. Accordingly, the assisting device of the present embodiment includes backward travel sensors  41 A and  41 B that sense backward travel pilot pressures of the travel operation devices  25 A and  25 B. 
     In a case where it is decided at Step S 2  in  FIG. 4  mentioned above that the track structure  1  is travelling, the track-structure-orientation computing section  37  of a controller  35 B of the present embodiment decides whether both the backward travel pilot pressures sensed by the backward travel sensors  41 A and  41 B are equal to or higher than a preset threshold. Then, if both the backward travel pilot pressures are equal to or higher than the threshold, it is decided that the track structure  1  is travelling backward (i.e. backward travelling is sensed), and if both the backward travel pilot pressures are lower than the threshold, it is decided that the track structure  1  is travelling forward (i.e. forward travelling is sensed). 
     At Step S 3  in  FIG. 4  mentioned above, the track-structure-orientation computing section  37  of the controller  35 B computes the orientation of the track structure  1  by using the locus of the horizontal coordinates of the swing structure  2  computed by the swing-structure-position computing section  36  and the result of the sensing whether the track structure  1  is travelling forward or backward. Explaining specifically, in a case where forward travelling of the track structure  1  is sensed, the current advancing direction of the track structure  1  is computed by using the locus of the horizontal coordinates of the swing structure  2  computed by the swing-structure-position computing section  36 , and the advancing direction is treated as the orientation of the track structure  1 . On the other hand, in a case where backward travelling of the track structure  1  is sensed, the current advancing direction of the track structure  1  is computed by using the locus of the horizontal coordinates of the swing structure  2  computed by the swing-structure-position computing section  36 , and the direction opposite to the advancing direction is treated as the orientation of the track structure  1 . 
     In the thus-configured present embodiment also, the horizontal coordinates and the height of the blade  12  can be computed in a similar manner to the first and second embodiments. Then, the horizontal coordinates and the height of the blade  12  can be displayed to assist an operator. In addition, unlike the first and second embodiments, it is possible to cope with levelling work and the like performed with the blade  12  by causing the track structure  1  to travel backward. 
     Note that the function of the controller  35 B described above to decide whether the track structure  1  is travelling on the basis of the horizontal coordinates of the swing center point of the swing structure  2 , and to decide whether the travelling of the track structure  1  is backward travelling on the basis of backward travel pilot pressures forms the travel sensor that senses forward travelling and backward travelling of the track structure. 
     A fourth embodiment of the present invention is explained by using  FIG. 8 . Note that portions in the present embodiment that are equivalent to their counterparts in the first and second embodiments are given the same reference characters, and explanation thereof is omitted as appropriate. 
     In the present embodiment, a swing limiting valve  42  (swing limiting device) is provided between the swing pilot valve of the work operation device  26 A and the swing control valve of the control valve device  24 . The swing limiting valve  42  is a solenoid selector valve that can be switched between a communication position and an interruption position. 
     A controller  35 C of the present embodiment has the swing-structure-position computing section  36 , the track-structure-orientation computing section  37 , the blade-horizontal-coordinate computing section  38 A and the blade-height computing section  39 A, in a similar manner to the controller  35 A of the second embodiment. In addition, the controller  35 C controls the swing limiting valve  42  such that the swing limiting valve  42  is switched from the communication position to the interruption position in accordance with a command for starting the blade-position computation from the monitor  30 . In addition, the controller  35 C controls the swing limiting valve  42  such that the swing limiting valve  42  is switched from the interruption position to the communication position, in accordance with a command for ending the blade-position computation from the monitor  30 . 
     In a case where the swing limiting valve  42  is at the communication position, communication is established through a hydraulic line between the swing pilot valve and the swing control valve. Thereby, it becomes possible to output the swing pilot pressure from the swing pilot valve to the swing control valve. That is, the swing of the swing structure  2  is not limited. On the other hand, in a case where the swing limiting valve  42  is at the interruption position, communication through the hydraulic line between the swing pilot valve and the swing control valve is interrupted. Thereby, it becomes impossible to output the swing pilot pressure from the swing pilot valve to the swing control valve. That is, the swing of the swing structure  2  is limited. 
     In the thus-configured present embodiment also, the horizontal coordinates and the height of the blade  12  can be computed in a similar manner to the first and second embodiments. Then, the horizontal coordinates and the height of the blade  12  can be displayed to assist an operator. In addition, computation and display of the blade position can be enhanced because the swing of the swing structure  2  is limited by the swing limiting valve  42  when the blade-position computation mode is selected by the monitor  30 , unlike the first and second embodiments. 
     Note that although the swing limiting device is the swing limiting valve  42  in the example explained in the fourth embodiment, this is not the sole example, and modifications are possible within a scope not deviating from the gist of the present invention. The swing limiting device may be a swing brake that limits the swing of the swing structure  2  by frictional force, for example. 
     In addition, although not explained in the fourth embodiment particularly, the track-structure-orientation computing section  37  of the controller  35 C may decide whether travelling of the track structure  1  is backward travelling on the basis of backward travel pilot pressures, in a similar manner to the third embodiment. Then, the orientation of the track structure  1  may be computed by using the locus of the horizontal coordinates of the swing structure  2  computed by the swing-structure-position computing section  36  and the result of the sensing whether the track structure  1  is travelling forward or backward. 
     In addition, although, in the example explained in the first to fourth embodiments, the track-structure-orientation computing section  37  of the controllers stores the relative relationship between the computed orientation of the track structure  1  and the orientation of the swing structure  2  computed by the swing-structure-position computing section  36  in a case where a swing of the swing structure  2  is not sensed and travelling of the track structure  1  is sensed, and computes the current orientation of the track structure  1  from the current orientation of the swing structure  2  computed by the swing-structure-position computing section  36  by using the stored relative relationship between the orientation of the track structure  1  and the orientation of the swing structure  2  in a case where a swing of the swing structure  2  is not sensed and travelling of the track structure  1  is not sensed, this is not the sole example, and modifications are possible within a scope not deviating from the gist of the present invention. For example, in a case where a swing of the swing structure  2  is not sensed and travelling of the track structure  1  is sensed, the track-structure-orientation computing section  37  of the controllers may not store the relative relationship between the orientation of the track structure  1  and the orientation of the swing structure  2  (i.e. Step S 4  in  FIG. 4  mentioned above may not be executed). Then, in a case where a swing of the swing structure  2  is not sensed and travelling of the track structure  1  is not sensed, the track-structure-orientation computing section  37  of the controllers may output a command for displaying an indication that the blade position is unknown (i.e. the process may proceed to Step S 10  in a case where the result of the decision at Step S 2  in  FIG. 4  mentioned above becomes NO). 
     In addition, although, in the examples explained in the first to fourth embodiments, the assisting device includes the lift sensor  34 , the controllers compute the height of the swing structure  2 , and the height of the blade  12 , and the monitor  30  displays the height of the blade  12 , this is not the sole example, and modifications are possible within a scope not deviating from the gist of the present invention. For example, the assisting device may not include the lift sensor  34 , the controllers may not compute the height of the swing structure  2 , and the height of the blade  12 , and the monitor  30  may not display the height of the blade  12 . 
     A fifth embodiment of the present invention is explained by using  FIG. 9 . Note that portions in the present embodiment that are equivalent to their counterparts in the first and second embodiments are given the same reference characters, and explanation thereof is omitted as appropriate. 
       FIG. 9  is a block diagram representing the configuration of the assisting device in the present embodiment. 
     The assisting device of the present embodiment performs blade automatic control of computing the horizontal coordinates and the height of the blade  12 , and controlling the operation of the lift cylinder  13  on the basis of the horizontal coordinates and the height of the blade  12 . Accordingly, the hydraulic excavator includes solenoid blade pilot valves  43 A and  43 B. 
     A controller  35 D of the present embodiment has the swing-structure-position computing section  36 , the track-structure-orientation computing section  37 , the blade-horizontal-coordinate computing section  38 A and the blade-height computing section  39 A, in a similar manner to the controller  35 A of the second embodiment. In addition, on the basis of the horizontal coordinates of the blade  12  computed by the blade-horizontal-coordinate computing section  38 A and the height of the blade  12  computed by the blade-height computing section  39 A, the controller  35 D executes the blade automatic control of controlling the blade pilot valves  43 A and  43 B. The controller  35 D starts the blade automatic control in accordance with a command for starting the blade-position computation from the monitor  30  according to operation by an operator, and ends the blade automatic control in accordance with a command for ending the blade-position computation from the monitor  30 . 
     The blade pilot valve  43 A generates and outputs a blade-lowering pilot pressure in accordance with a signal from the controller  35 D, and the blade pilot valve  43 B generates and outputs a blade-raising pilot pressure in accordance with a signal from the controller  35 D. The blade control valve is switched by the blade-lowering pilot pressure or the blade-raising pilot pressure mentioned before, and controls the flow of the hydraulic fluid from the hydraulic pump to the lift cylinder  13 . 
     The controller  35 D stores in advance a target surface of a terrain profile set on the monitor  30 . Alternatively, the controller  35 D receives an input of a target surface of a terrain profile set on an external computer via a communication network or a storage medium, and stores the target surface in advance. Note that the monitor  30  or the external computer forms the target-surface setting device on which a target surface is set. 
     Next, contents of processing performed in the blade automatic control of the controller in the present embodiment are explained by using  FIG. 10 .  FIG. 10  is a flowchart representing a processing procedure of the controller in the present embodiment. 
     Steps S 1  to S 7  and S 9  are the same as the embodiments described above, and so explanation thereof is omitted. 
     In a case where the horizontal coordinates and the height of the blade  12  are computed (i.e. after Step S 7 ), the process proceeds to Step S 11 . At Step S 11 , the controller  35 D controls the blade pilot valves  43 A and  43 B such that the blade  12  (specifically, the lower end of the blade  12 ) approaches the prestored target surface. 
     In a case where at least either the horizontal coordinates or height of the blade  12  are/is not computed (i.e. after Step S 9 , or in a case where the result of the decision at Step S 5  is NO), the process proceed to Step S 12 . At Step S 12 , the controller  35 D controls the blade pilot valves  43 A and  43 B such that the blade  12  moves upward away from the target surface. 
     In the thus-configured present embodiment also, it is possible to compute the horizontal coordinates and the height of the blade  12  in the hydraulic excavator having the blade  12  provided to the track structure  1  and the swing structure  2  provided swingably on the upper side of the track structure  1 . Then, the operation of the lift cylinder  13  can be controlled on the basis of the horizontal coordinates and the height of the blade  12  to assist an operator. 
     Note that although not explained particularly, the monitor  30  may display the position of the blade  12  computed by the controller  35 D in the fifth embodiment, in a similar manner to the first to fourth embodiments. In addition, although not explained particularly, the track-structure-orientation computing section  37  of the controller  35 D may decide whether travelling of the track structure  1  is backward travelling on the basis of the backward travel pilot pressure in the fifth embodiment, in a similar manner to the third embodiment. Then, the orientation of the track structure  1  may be computed by using the locus of the horizontal coordinates of the swing structure  2  computed by the swing-structure-position computing section  36  and the result of the sensing whether the track structure  1  is travelling forward or backward. 
     In addition, although, in the example explained in the fifth embodiment, as illustrated in  FIG. 10  mentioned above, the track-structure-orientation computing section  37  of the controller  35 D stores the relative relationship between the computed orientation of the track structure  1  and the orientation of the swing structure  2  computed by the swing-structure-position computing section  36  in a case where a swing of the swing structure  2  is not sensed, and travelling of the track structure  1  is sensed, and computes the current orientation of the track structure  1  from the current orientation of the swing structure  2  computed by the swing-structure-position computing section  36  by using the stored relative relationship between the orientation of the track structure  1  and the orientation of the swing structure  2  in a case where a swing of the swing structure  2  is not sensed and travelling of the track structure  1  is not sensed, this is not the sole example, and modifications are possible within a scope not deviating from the gist of the present invention. For example, in a case where a swing of the swing structure  2  is not sensed and travelling of the track structure  1  is sensed, the track-structure-orientation computing section  37  of the controller  35 D may not store the relative relationship between the orientation of the track structure  1  and the orientation of the swing structure  2  (i.e. Step S 4  in  FIG. 10  mentioned above may not be executed). Then, in a case where a swing of the swing structure  2  is not sensed and travelling of the track structure  1  is not sensed, the track-structure-orientation computing section  37  of the controller  35 D may control the blade pilot valves  43 A and  43 B such that the blade  12  moves upward away from the target surface (i.e. the process may proceed to Step S 12  in a case where the result of the decision at Step S 2  in  FIG. 10  mentioned above is NO). 
     In addition, in the examples explained in the third to fifth embodiments, in a similar manner to the second embodiment, the assisting device includes the inclination angle sensor  40 , the blade-horizontal-coordinate computing section of the controller  35 B,  35 C or  35 D computes the horizontal coordinates of the blade  12  on the basis of the orientation of the track structure  1  computed by the track-structure-orientation computing section  37 , the horizontal coordinates and the orientation of the swing structure  2  computed by the swing-structure-position computing section  36 , and the inclination angles of the track structure  1  sensed by the inclination angle sensor  40 , this is not the sole example. That is, in a similar manner to the first embodiment, the assisting device may not include the inclination angle sensor  40 , and the blade-horizontal-coordinate computing section of the controller  35 B,  35 C or  35 D may compute the horizontal coordinates of the blade  12  on the basis of the orientation of the track structure  1  computed by the track-structure-orientation computing section  37  and the horizontal coordinates and the orientation of the swing structure  2  computed by the swing-structure-position computing section  36 . 
     In addition, in the examples explained in the first to fifth embodiments, the controllers decide whether the track structure  1  is travelling by deciding whether the swing center point of the swing structure  2  is changing, this is not the sole example, and modifications are possible within a scope not deviating from the gist of the present invention. For example, forward travel sensors that sense the forward travel pilot pressures of the travel operation devices  25 A and  25 B may be provided, and the controllers may decide whether the track structure is travelling (specifically, travelling forward) by deciding whether both the forward travel pilot pressures sensed by the forward travel sensors are equal to or higher than a preset threshold. 
     In addition, although, in the examples explained in the first to fifth embodiments, the swing sensors  33 A and  33 B are pressure sensors that sense swing pilot pressures of the work operation device  26 A, and the controllers decide whether the swing structure  2  is swinging on the basis of the swing pilot pressures sensed by the swing sensors  33 A and  33 B, this is not the sole example, and modifications are possible within a scope not deviating from the gist of the present invention. For example, the swing sensors may be displacement sensors that sense forward and backward displacements of the operation lever of the work operation device  26 A, and the controllers may decide whether the swing structure  2  is swinging on the basis of the forward and backward displacements of the operation lever sensed by the swing sensors. 
     In addition, although, in the examples explained in the first to fifth embodiments, the lift sensor  34  is a displacement sensor that senses the stroke of the lift cylinder  13 , and the controllers compute the relative height of the blade  12  on the basis of the stroke of the lift cylinder  13  sensed by the lift sensor  34 , this is not the sole example, and modifications are possible within a scope not deviating from the gist of the present invention. For example, the lift sensor may be an angle sensor that senses the angle of the lift arm  11 , and the controllers may compute the relative height of the blade  12  on the basis of the angle of the lift arm  11  sensed by the lift sensor. 
     In addition, although in the examples explained in the first to fifth embodiments, the controller having the swing-structure-position computing section, the track-structure-orientation computing section, the blade-horizontal-coordinate computing section, and the blade-height computing section is included, this is not the sole example, and modifications are possible within a scope not deviating from the gist of the present invention. A plurality of controllers each having a different one of the swing-structure-position computing section, the track-structure-orientation computing section, the blade-horizontal-coordinate computing section, and the blade-height computing section may be provided may be included. 
     Note that the hydraulic excavator is explained thus far as an example application subject of the present invention, this is not the sole example. That is, application subjects may be any work machines having a blade provided to a track structure and a swing structure provided swingably on the upper side of the track structure. 
     DESCRIPTION OF REFERENCE CHARACTERS 
     
         
           1 : Track structure 
           2 : Swing structure 
           3 : Work device 
           12 : Blade 
           13 : Lift cylinder 
           30 : Monitor 
           31 A,  31 B: Antenna 
           32 A,  32 B: Receiver 
           33 A,  33 B: Swing sensor 
           34 : Lift sensor 
           35 ,  35 A,  35 B,  35 C,  35 D: Controller 
           36 : Swing-structure-position computing section 
           37 : Track-structure-orientation computing section 
           38 ,  38 A: Blade-horizontal-coordinate computing section 
           39 ,  39 A: blade-height computing section 
           40 : Inclination angle sensor 
           42 : Swing limiting valve 
           43 A,  43 B: Blade pilot valve