Patent Publication Number: US-11649612-B2

Title: Work machine

Description:
TECHNICAL FIELD 
     The present invention relates to a work machine. 
     BACKGROUND ART 
     With a work machine including a work implement (front work implement), typified by a hydraulic excavator, an operator directs operation of the work implement by an operation lever (operation device) and thereby the work implement is driven. Thereby, the work machine shapes a terrain profile that is a working target into a desired shape. Machine guidance (MG) exists as a technique that aims at assisting such work. The MG is a technique that implements operation assistance of the operator by informing the operator of the positional relationship between data of a design surface (referred to also as target surface) showing a desired shape of a working target desired to be finally realized and work equipment that excavates the working target. 
     As a technique obtained by adding an improvement to the conventional MG, there is a technique described in Patent Document 1. In this document, a display system of a construction machine showing the positional relationship between work equipment and a target surface is disclosed. The display system of the construction machine includes a movement direction calculating section that calculates a predicted movement direction of the work equipment based on at least one of a calculated value of a position-posture calculating section that calculates the position and posture of a work implement based on a state amount relating to the position and posture of the work implement and the operation amount of an operation device of a work device. The display system includes also a work equipment display control section. (1) When movement of the work equipment is predicted by the movement direction calculating section, the work equipment display control section changes, on a display screen of a display device, the display position of an image of the work equipment according to the predicted movement direction in such a manner that the area of a region located on the side of the predicted movement direction from the image of the work equipment becomes larger than that in the case of displaying the image of the work equipment at a reference position. (2) In the case other than (1), the work equipment display control section displays the image of the work equipment at the reference position on the display screen. The display system includes also a target surface display control section that displays, on the display screen, an image of the target surface included in the display screen when the image of the work equipment is displayed at a display position decided by the work equipment display control section. That is, the shape of the target surface existing in the predicted travelling direction of the work equipment (predicted movement direction) is displayed relatively widely compared with a shape relating to the other directions. 
     PRIOR ART DOCUMENT 
     Patent Document 
     Patent Document 1: JP-2016-204840-A 
     SUMMARY OF THE INVENTION 
     Problem to be Solved by the Invention 
     In Patent Document 1, the predicted movement direction of the work equipment, which is not used in the conventional MG, i.e. the direction of the velocity vector of the work equipment, is used. Thereby, the shape of the target surface existing in the direction of the velocity vector of the work equipment is allowed to be displayed relatively widely and the operator is allowed to easily understand the shape of the target surface existing in the direction of the velocity vector. 
     When data on the work machine that is not actively used as a trigger for change in the contents of the MG conventionally (direction of the velocity vector of the work equipment in the above-described example) is used as in this technique, new functions can be added to the MG and functions of the MG can be improved. There is a possibility that, due to the addition and improvement of functions of the MG, the MG in conformity with the intention of the operator becomes possible and the operator is enabled to intuitively recognize the situation of the work machine, for example. 
     For example, when an operator inputs arm crowding operation in the technique of Patent Document 1, a region existing in the predicted movement direction of the work equipment calculated from the operation is widely displayed on the screen. However, whether the work equipment has actually moved is not considered in this technique. Therefore, the same displaying is carried out also when the claw tip gets contact with very hard soil in the arm crowding operation and the arm operation stops with an arm cylinder being in an overload state, for example. When the operator intends arm dumping operation in order to eliminate the stop state of the arm in such a scene, there is a possibility of the occurrence of an inconvenience that the shape of the target surface existing in the arm dumping direction can not be understood in advance because displaying change of the screen is not carried out unless actually the arm crowding operation is stopped or the arm dumping operation is input. That is, there is room for improvement in the technique of this document. 
     An object of the present invention is to intend addition and improvement of functions of the MG in a work machine. 
     Means for Solving the Problem 
     The present application includes plural means for solving the above-described problem. To cite one example thereof, there is provided a work machine including an articulated work implement including work equipment, an actuator that drives the work implement, an operation device that makes an instruction of operation of the actuator, a controller configured to calculate a position of the work implement and calculate a distance between the work equipment and a predetermined target surface and calculate a positional relationship between the work equipment and the target surface, and an informing device that informs the positional relationship between the work equipment and the target surface, the work machine including an actuator state sensor that detects a state of the actuator, wherein the controller calculates a velocity of the work equipment based on the position of the work implement and an operation amount of the operation device, and changes contents of informing by the informing device according to the velocity of the work equipment, the distance between the work equipment and the target surface, and the state of the actuator detected by the actuator state sensor. 
     Advantages of the Invention 
     According to the present invention, the situation under which a work machine is put can be grasped more objectively by considering the state of the actuator in addition to conventional data, and functions of the MG can be added and improved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a configuration diagram of a hydraulic excavator. 
         FIG.  2    is a schematic diagram of a hydraulic circuit relating to the hydraulic excavator. 
         FIG.  3    is a functional block diagram of a controller. 
         FIG.  4    is a diagram showing the hydraulic excavator that carries out alignment work by boom operation. 
         FIG.  5    is a diagram showing the hydraulic excavator that carries out alignment work by bucket operation. 
         FIG.  6    is a diagram showing one example of a display screen of a display device. 
         FIG.  7    is a diagram showing one example of the display screen of the display device. 
         FIG.  8    is a control flow by the controller according to a first embodiment. 
         FIG.  9    is a diagram showing one example of a graph that defines a threshold. 
         FIG.  10    is a diagram showing one example of the graph that defines the threshold. 
         FIG.  11    is a diagram showing the hydraulic excavator that carries out linear excavating by arm operation. 
         FIG.  12    is a diagram showing one example of the display screen of the display device. 
         FIG.  13    is a diagram showing one example of the display screen of the display device. 
         FIG.  14    is a control flow by the controller according to a second embodiment. 
         FIG.  15    is a control flow by the controller according to the second embodiment. 
         FIG.  16    is a diagram showing the locus of the bucket tip (circular arc D) and a target surface. 
         FIG.  17    is a diagram showing one example of a graph that defines a threshold. 
         FIG.  18    is a functional block diagram of a guidance contents change section according to a fourth embodiment. 
         FIG.  19    is a control flow by the controller according to the fourth embodiment. 
         FIG.  20    is a diagram showing one example of the display screen (enlargement mode) of the display device. 
         FIG.  21    is a diagram showing one example of the display screen (enlargement mode) of the display device. 
         FIG.  22    is a diagram showing one example of the display screen (overall mode) of the display device. 
         FIG.  23    is a control flow by the controller according to modification example 1 of the fourth embodiment. 
         FIG.  24    is a control flow by the controller according to modification example 2 of the fourth embodiment. 
         FIG.  25    is a diagram showing one example of a graph that defines a coefficient. 
         FIG.  26    is a control flow by the controller according to modification example 3 of the fourth embodiment. 
     
    
    
     MODES FOR CARRYING OUT THE INVENTION 
     Embodiments of the present invention will be described below by using the drawings. In the following, the description will be made by taking as an example a hydraulic excavator as a work machine. As the front work implement of the hydraulic excavator, what is composed of a boom, an arm, and work equipment and includes a bucket as the work equipment is exemplified. However, what includes an attachment other than the bucket may be employed. Furthermore, a work machine other than the hydraulic excavator may be employed. In addition, when plural same constituent elements exist, alphabets are often given to the tail ends of characters (numbers). However, these alphabets are omitted and these plural constituent elements are represented collectively in some cases. For example, when three pumps  300   a ,  300   b , and  300   c  exist, they are represented as pumps  300  collectively in some cases. 
     First Embodiment 
       FIG.  1    is a configuration diagram of a hydraulic excavator according to a first embodiment of the present invention. In  FIG.  1   , a hydraulic excavator  1  is composed of a front work implement  1 A and a machine body  1 B. The machine body  1 B is composed of a lower track structure  11  and an upper swing structure  12  swingably attached on the lower track structure  11 . The front work implement  1 A is configured by joining plural driven members (boom  8 , arm  9 , and bucket  10 ) that each pivot in the perpendicular direction. The base end of the boom  8  of the front work implement  1 A is pivotally supported by the front part of the upper swing structure  12  with the intermediary of a boom pin. The arm  9  is pivotally joined to the tip of the boom  8  with the intermediary of an arm pin. The bucket  10  is pivotally supported by the tip of the arm  9  with the intermediary of a bucket pin. 
     The boom  8 , the arm  9 , the bucket  10 , the upper swing structure  12 , and the lower track structure  11  configure driven members driven by a boom cylinder  5 , an arm cylinder  6 , a bucket cylinder  7 , a swing hydraulic motor  4 , and right and left travelling motors  3   a  and  3   b  that are not shown in the diagram, respectively. Operation instructions to these driven members  8 ,  9 ,  10 ,  12 , and  11  are output according to operation, by an operator, of a travelling right lever  13   a , a travelling left lever  13   b , an operation right lever  14   a , and an operation left lever  14   b  mounted in a cab on the upper swing structure  12 . These travelling levers  13  and operation levers  14  are referred to also as an operation device  15  collectively. Furthermore, the operation right lever  14   a  functions as an operation lever  15   a  for the boom and an operation lever  15   c  for the bucket in  FIG.  2   , and the operation left lever  14   b  functions as an operation lever  15   b  for the arm and an operation lever  15   d  for swing in  FIG.  2   . 
     The operation device  15  of the present embodiment is a device of a hydraulic pilot system. A pilot pressure (often referred to as operation pressure or operation signal) according to the operation amount (for example, lever stroke) of each lever is supplied to flow control valves  16   a  to  16   d  (see  FIG.  2   ) according to the operation direction of the respective levers to drive these flow control valves  16   a  to  16   d . In  FIG.  2   , diagrammatic representation of the operation levers for travelling and flow control valves corresponding thereto is omitted. 
     Hydraulic fluid delivered by a hydraulic pump  2  driven by a prime mover (engine)  49  is supplied to hydraulic actuators such as the swing hydraulic motor  4 , the boom cylinder  5 , the arm cylinder  6 , and the bucket cylinder  7  through the flow control valves  16   a ,  16   b ,  16   c , and  16   d  (see  FIG.  2   ). The boom cylinder  5 , the arm cylinder  6 , and the bucket cylinder  7  expand and contract by the supplied hydraulic fluid. Thereby, the boom  8 , the arm  9 , and the bucket  10  each pivot and the position and posture of the bucket  10  located at the tip of the front work implement  1 A change. Furthermore, the swing hydraulic motor  4  rotates by the supplied hydraulic fluid and thereby the upper swing structure  12  swings around a swing axis relative to the lower track structure  11 . Moreover, the travelling right hydraulic motor  3   a  and the travelling left hydraulic motor  3   b  rotate by the supplied hydraulic fluid and thereby the lower track structure  11  travels. 
     Meanwhile, in order to enable measurement of the pivot angle of the boom  8 , the arm  9 , and the bucket  10 , a boom angle sensor  21  is attached to the boom pin that joins the upper swing structure  12  and the boom  8 , an arm angle sensor  22  is attached to the arm pin that joins the boom  8  and the arm  9 , and a bucket angle sensor  23  is attached to the bucket pin that joins the arm  9  and the bucket  10 . Furthermore, a machine body inclination angle sensor  24  that detects the inclination angles of the upper swing structure  12  (machine body  1 B) in the front-rear direction and the right-left direction with respect to a reference surface (for example, gravitational direction) is attached to the upper swing structure  12 . The angle sensors  21 ,  22 , and  23  can be each replaced by an angle sensor that outputs the angle with respect to the reference surface (for example, gravitational direction). 
     Furthermore, to the boom cylinder  5 , the arm cylinder  6 , and the bucket cylinder  7 , a boom cylinder pressure sensor  25 , an arm cylinder pressure sensor  26 , and a bucket cylinder pressure sensor  27  that can measure the pressure generated in the respective cylinders and are shown in  FIG.  3    are attached. The respective pressure sensors  25 ,  26 , and  27  are composed of at least two pressure sensors so that the pressure of the bottom side and the rod side of the hydraulic cylinders  5 ,  6 , and  7  for which they are set can be detected. However, the pressure sensors  25 ,  26 , and  27  are each expressed by one symbol as simplification in the present specification. 
       FIG.  2    is a hydraulic circuit diagram of the hydraulic excavator  1 . The hydraulic pump  2  and a pilot pump  48  are driven by the prime mover  49 . Hydraulic fluid supplied from the hydraulic pump  2  drives hydraulic actuators such as the boom cylinder  5  and the swing motor  4 . Hydraulic fluid supplied from the pilot pump  48  drives the flow control valves  16 . 
     The hydraulic fluid delivered from the hydraulic pump  2  goes through the flow control valves  16   a  to  16   d  and is supplied to the hydraulic actuators such as the boom cylinder  5 , the arm cylinder  6 , and the bucket cylinder  7 . The hydraulic fluid supplied to the hydraulic actuators goes through the flow control valves  16   a  to  16   d  again and is discharged to a tank  50 . 
     The pilot pump  48  is connected to a lock valve  51 . Lock of the lock valve  51  is released through operation of a gate lock lever (not shown) mounted in the cab by the operator and thereby the hydraulic fluid from the pilot pump  48  comes to flow to the downstream of the lock valve  51 . The downstream of the lock valve  51  is connected to a pilot pressure control valve  52  for boom raising, a pilot pressure control valve  53  for boom lowering, a pilot pressure control valve  54  for arm crowding, a pilot pressure control valve  55  for arm dumping, a pilot pressure control valve  56  for bucket crowding, a pilot pressure control valve  57  for bucket dumping, a pilot pressure control valve  58  for right swing, a pilot pressure control valve  59  for left swing, and so forth. 
     The pilot pressure control valve  52  for boom raising and the pilot pressure control valve  53  for boom lowering can be operated by the operation lever  15   a  for the boom. The pilot pressure control valve  54  for arm crowding and the pilot pressure control valve  55  for arm dumping can be operated by the operation lever  15   b  for the arm. The pilot pressure control valve  56  for bucket crowding and the pilot pressure control valve  57  for bucket dumping can be operated by the operation lever  15   c  for the bucket. The pilot pressure control valve  58  for right swing and the pilot pressure control valve  59  for left swing can be operated by the operation lever  15   d  for swing. 
     At the downstream of the pilot pressure control valve  52  for boom raising, the pilot pressure control valve  53  for boom lowering, the pilot pressure control valve  54  for arm crowding, the pilot pressure control valve  55  for arm dumping, the pilot pressure control valve  56  for bucket crowding, the pilot pressure control valve  57  for bucket dumping, the pilot pressure control valve  58  for right swing, and the pilot pressure control valve  59  for left swing, pressure sensors (not shown) that detect the pilot pressure are each disposed as an operator operation sensor  36 . The operation amount of the respective operation levers  15   a ,  15   b ,  15   c , and  15   d  by the operator can be detected by this pressure sensor. As the specific operator operation sensor  36  of the present embodiment, the following pilot pressure sensors are disposed: a pilot pressure sensor for boom raising disposed on a pilot line  529  for boom raising; a pilot pressure sensor for boom lowering disposed on a pilot line  539  for boom lowering; a pilot pressure sensor for arm crowding disposed on a pilot line  549  for arm crowding; a pilot pressure sensor for arm dumping disposed on a pilot line  559  for arm dumping; a pilot pressure sensor for bucket crowding disposed on a pilot line  569  for bucket crowding, a pilot pressure sensor for bucket dumping disposed on a pilot line  579  for bucket dumping, a pilot pressure sensor for right swing disposed on a pilot line  589  for right swing; and a pilot pressure sensor for left swing disposed on a pilot line  599  for left swing. 
     A shuttle block  46  is set on the downstream side of the above-described eight pilot pressure sensors and the configuration is made in such a manner that a control signal (pilot pressure) can be output from the shuttle block  46  to a regulator  47  attached to the hydraulic pump  2 . The shuttle block  46  controls the pressure of the control signal used for control of the hydraulic pump  2 . The regulator  47  changes the delivery flow rate of the hydraulic pump  2  by adjusting the tilting angle of the hydraulic pump  2  according to the operation amount of the operation device  15 . The flow control valve  16   a  for the boom is connected to the downstream of the pilot line  529  for boom raising and the pilot line  539  for boom lowering with the intermediary of the shuttle block  46 . The flow control valve  16   b  for the arm is connected to the downstream of the pilot line  549  for arm crowding and the pilot line  559  for arm dumping with the intermediary of the shuttle block  46 . The flow control valve  16   c  for the bucket is connected to the downstream of the pilot line  569  for bucket crowding and the pilot line  579  for bucket dumping with the intermediary of the shuttle block  46 . The flow control valve  16   d  for swing is connected to the downstream of the pilot line  589  for right swing and the pilot line  599  for left swing with the intermediary of the shuttle block  46 . The flow control valves  16   a  to  16   d  are configured to operate according to the pilot pressure output from the operation device  15  and be capable of controlling the flow rate of the hydraulic operating fluid supplied to the respective hydraulic actuators  4 ,  5 ,  6 , and  7  according to the operation amount of the operation device  15 . 
     A controller  20  responsible for the MG is mounted in the hydraulic excavator  1 . The controller  20  has an input interface, a central processing unit (CPU) that is a processor, a read only memory (ROM) and a random access memory (RAM) that are storing devices, and an output interface (none is shown). The input interface converts signals from the respective devices connected to the controller  20  in such a manner that the CPU can carry out calculation. The ROM is a recording medium in which a control program for executing the MG including processing relating to flowcharts to be described later and various kinds of data and so forth necessary for execution of these flowcharts are stored. The CPU executes predetermined calculation processing for signals taken in from the input interface, the ROM, and the RAM  94  in accordance with the control program stored in the ROM. The output interface creates a signal for output according to the calculation result in the CPU and outputs the signal to an informing device and thereby can actuate the informing device. Although the controller  20  of the present embodiment includes semiconductor memories of the ROM and RAM as the storing device, they can be replaced particularly as long as the replacement is a storing device and the controller  20  may include a magnetic storing device such as a hard disk drive, for example. 
     In  FIG.  3   , a functional block diagram of the controller (controller)  20  mounted in the hydraulic excavator  1  is shown. As shown in this diagram, the controller  20  of the present embodiment functions as a work implement posture sensing section  28 , a work equipment velocity estimating section  29 , a target surface distance and work equipment angle calculating section  30 , and a guidance contents change section  31 . Furthermore, to the controller, a work implement posture sensor  34 , a target surface setting device  35 , the operator operation sensor  36 , an actuator state sensor  37 , an informing device  38 , and a GNSS (Global Navigation Satellite System) antenna  17  are connected. 
     The work implement posture sensor  34  is composed of the boom angle sensor  21 , the arm angle sensor  22 , the bucket angle sensor  23 , and the machine body inclination angle sensor  24 . 
     The target surface setting device  35  is an interface to which data relating to a predetermined target surface  62  that should be formed by excavating of the hydraulic excavator  1  (including position data and inclination angle data of each target surface) can be input, and can also store the input data relating to the target surface  62 . The target surface  62  is what is obtained by extracting and modifying a design surface in a form suitable for working. The target surface setting device  35  can connect to an external terminal (not shown) that stores three-dimensional data of the target surface defined on a global coordinate system (absolute coordinate system). The position data of the target surface  62  is created based on the position data of the design surface that is the final target shape that should be formed by excavating of the hydraulic excavator  1 . Normally, the target surface  62  is set on the design surface or above that in the case of excavating, and is set on the design surface or below that in the case of embankment. The input of the data relating to the target surface  62  through the target surface setting device  35  may be manually carried out by an operator. Furthermore, the target surface  62  does not need to be defined on the global coordinate system and may be defined on a local coordinate system of the hydraulic excavator  1  set on the upper swing structure  12 , for example. In this case, the need to mount the GNSS antenna  17  is eliminated in terms of calculation of the position of the upper swing structure  12  (position of the machine body  1 B) in the global coordinate system. 
     The GNSS antenna  17  is attached onto the upper swing structure  12  and receives a navigation signal from plural (normally four or more) navigation satellites to output the signal to the controller  20 . Data on the navigation signal received by the GNSS antenna  17  is used when position data in the global coordinates regarding the upper swing structure  12  (machine body  1 B) is computed. The number of GNSS antennas  17  may be one. However, the posture of the upper swing structure  12  can be calculated when two GNSS antennas  17  are mounted. 
     The operator operation sensor  36  is composed of the already-described eight pressure sensors that acquire the pilot pressure generated due to operation of the operation device  15  by the operator (i.e. pilot pressure sensor for boom raising, pilot pressure sensor for boom lowering, pilot pressure sensor for arm crowding, pilot pressure sensor for arm dumping, pilot pressure sensor for bucket crowding, pilot pressure sensor for bucket dumping, pilot pressure sensor for right swing, pilot pressure sensor for left swing). To the work equipment velocity estimating section  29  in the controller  20 , detection values of the pilot pressure sensor for boom raising and the pilot pressure sensor for boom lowering are output as a boom operation signal and detection values of the pilot pressure sensor for arm crowding and the pilot pressure sensor for arm dumping are output as an arm operation signal and detection values of the pilot pressure sensor for bucket crowding and the pilot pressure sensor for bucket dumping are output as a bucket operation signal. 
     The actuator state sensor  37  is a device for detecting the physical amount showing the state of the hydraulic actuators  5 ,  6 , and  7 . In the present embodiment, the actuator state sensor  37  is composed of the boom cylinder pressure sensor  25 , the arm cylinder pressure sensor  26 , and the bucket cylinder pressure sensor  27  and the controller  20  is capable of calculating the load acting on the respective hydraulic actuators  5 ,  6 , and  7  based on the output of the respective pressure sensors  25 ,  26 , and  27 . 
     The informing device  38  is a device for informing the operator of at least the positional relationship between the bucket  10  and the target surface  62  and, in the present embodiment, is composed of at least a display device  39  such as a monitor and a sound output device  40  such as a speaker. 
     The work implement posture sensing section  28  is a section that calculates posture data of the front work implement  1 A (posture data of the boom  8 , the arm  9 , and the bucket  10 ) and position data of the tip (claw tip) of the bucket  10  in the local coordinate system set on the upper swing structure  12 . The work implement posture sensing section  28  calculates the posture data of the front work implement  1 A and the coordinates of the tip (claw tip) of the bucket  10  in the local coordinate system based on a boom angle signal, an arm angle signal, and a bucket angle signal input from the work implement posture sensor  34  and dimension data of the boom  8 , the arm  9 , and the bucket  10  recorded in the storing device in the controller  20 , and outputs the calculation result thereof to the target surface distance and work equipment angle calculating section  30 . 
     The target surface distance and work equipment calculating section  30  is a section that calculates the target surface distance that is the distance between the target surface  62  and the bucket tip and the work equipment angle that is the angle formed by the target surface  62  and the back surface of the bucket  10 . The target surface distance and work equipment angle calculating section  30  calculates the position data in the global coordinates regarding the upper swing structure  12  based on the navigation signal input from the GNSS antenna  17  and calculates posture data in the global coordinates regarding the upper swing structure  12  based on roll angle data and pitch angle data of the machine body  1 B input from the work implement posture sensor  34 . Then, the target surface distance and work equipment angle calculating section  30  uses the position data and the posture data in the global coordinates regarding the upper swing structure  12  to convert the posture data of the front work implement  1 A and the position data of the bucket tip in the local coordinate system input from the work implement posture sensing section  28  to values in the global coordinate system. The target surface distance and work equipment angle calculating section  30  calculates the target surface distance based on the position data of the bucket tip calculated in this manner and the position data of the target surface  62  input from the target surface setting device  35 . Furthermore, the target surface distance and work equipment angle calculating section  30  calculates the work equipment angle based on the position data and the posture data of the bucket tip and the position data of the target surface  62 . 
     Examples of alignment work of the bucket  10  based on operation of the operation device  15  by an operator are shown in  FIG.  4    and  FIG.  5   . Here, the alignment work (alignment operation) of the bucket  10  is work (operation) of moving the bucket  10  to a start position (referred to as “work start position”) of work carried out through causing the arm  9  to carry out crowding operation or dumping operation (typically excavating). Various kinds of work by arm operation are carried out after the alignment work is completed. In  FIG.  4   , alignment work of lowering the boom  8  to move the bucket  10  to the work start position on the target surface  62  is shown. In  FIG.  5   , alignment work of causing the bucket  10  to pivot to move the bucket  10  to the work start position on the target surface  62  is shown. 
     In  FIG.  4   , a situation is shown in which an operator aligns the tip of the bucket  10  onto the target surface  62  by operating the operation device  15  and causing the boom  8  to carry out lowering operation. Specifically,  FIG.  4    shows a series of work by which a transition is made from a state S 1  in which the bucket  10  exists above the target surface  62  and is separate from the target surface  62  to a state S 2  in which the bucket  10  is still at the work start position on the target surface  62 . 
     In the state S 1 , a velocity vector generated at the tip of the bucket  10  due to the lowering operation of the boom  8  by the operator is defined as V, and the component parallel to the target surface  62  in V is defined as Vxsrf and the perpendicular component is defined as Vzsrf. Furthermore, regarding the sign of Vzsrf, the vertical upward direction with respect to the target surface  62  is deemed as positive and the vertical downward direction with respect to the target surface  62  is deemed as negative. 
     The calculation of the velocity vector V is carried out by the work equipment velocity estimating section  29  based on detection values of the work implement posture sensor  34  and the operator operation sensor  36 . Specifically, the velocities of the respective hydraulic cylinders  5 ,  6 , and  7  are calculated from the pilot pressures (operation signals) to the respective hydraulic cylinders  5 ,  6 , and  7  generated due to operation of the operation device  15  by the operator and the respective hydraulic cylinder velocities are converted to the angular velocity of each of the boom  8 , the arm  9 , and the bucket  10  by using the posture data of the work implement  1 A. Moreover, the angular velocity is converted to the velocity vector of the tip of the bucket  10  and thereby the velocity vector V is figured out. As already described, the posture data of the work implement  1 A can be calculated from the angle signals of the boom  8 , the arm  9 , and the bucket  10  input from the work implement posture sensor  34 . 
     In  FIG.  4   , a current-state terrain profile  61  that is an excavation target exists only near the target surface  62 . In this case, when the front work implement  1 A makes the transition from the state S 1  to the state S 2 , it is hard for the excavation load on the front work implement  1 A due to the current-state terrain profile  61  to increase even when the bucket  10  comes close to the vicinity of the target surface  62 . For this reason, the possibility of entry of the bucket  10  into the lower side of the target surface  62  becomes high when the component Vzsrf perpendicular to the target surface  62  in the velocity vector V of the bucket tip generated due to operator operation is large in the negative direction. In the present embodiment, whether or not an excavation load is acting on the front work implement  1 A is determined by the guidance contents change section  31  based on whether or not the pressure that is the pressure generated in the hydraulic cylinder  5 ,  6 , or  7  and is detected by the pressure sensor  25 ,  26 , or  27  is equal to or higher than a predetermined threshold. Then, if the detected pressure of the pressure sensor  25 ,  26 , or  27  is equal to or higher than this predetermined threshold, it is determined that an excavation load is acting on the relevant hydraulic cylinder. 
     Also in  FIG.  5   , similarly to the above description, the velocity vector V generated at the tip of the bucket  10  can be computed and the possibility of entry of the bucket  10  into the lower side of the target surface  62  becomes higher when the component Vzsrf perpendicular to the target surface  62  in the velocity vector is larger in the negative direction. 
     The guidance contents change section  31  determines whether or not the possibility of entry of the bucket  10  into the lower side of the target surface  62  due to operator operation is high based on the perpendicular component Vzsrf of the velocity vector V, the target surface distance, the pressure of the hydraulic actuators (hydraulic cylinders)  5 ,  6 , and  7 , and the angle of the bucket  10  with respect to the target surface  62 . When determining that the possibility of entry is high in this determination, the guidance contents change section  31  outputs a warning informing flag to the informing device  38 . 
     When the warning informing flag is input from the guidance contents change section  31 , the informing device  38  carries out informing different from the normal MG (see  FIG.  7   ) in which the distance between the bucket claw tip and the target surface is shown by a light bar  391  while the positional relationship between the bucket  10  and the target surface  62  is shown by an image. Specifically, as shown in  FIG.  6   , the display device  39  informs the operator of that the operation amount to the operation device  15  is excessive by displaying a popup message  392  showing that the operation amount is excessive and flickering the light bar  391  showing the distance between the target surface  62  and the bucket claw tip. Furthermore, from the sound output device  40 , also as sound, sound different from the normal MG such as sound different in the frequency, is output. Thereby, the informing device  38  informs the operator of that the operation amount is excessive. The informing in this manner allows the operator to recognize that the operation amount of oneself is excessive before the bucket  10  reaches the target surface  62 . Thus, the entry of the bucket  10  into the target surface  62  can be prevented. For comparison, one example of the display screen of the display device  39  when the warning informing flag is not output, i.e. at the time of the normal MG, is shown in  FIG.  7   . In the screen of the display device  39  in  FIG.  7   , a positional relationship display part  395  in which an image of the bucket  10  and the target surface  62  is displayed, a target surface distance display part  393  that shows the distance between the bucket claw tip and the target surface  62  by a numerical value, and a target surface direction display part  394  that shows, by an arrow, the direction of the target surface  62  when the claw tip of the bucket  10  is deemed as the basis are set. 
     The light bar  391  turns on according to the distance between the target surface  62  and the bucket  10 . The light bar  391  in  FIG.  7    is composed five segments that are disposed serially in the vertical direction and can turn on, and dots are given to the upper-side three segments that are on in the diagram. In the present embodiment, only the central segment turns on when the claw tip of the bucket  10  exists at a distance of ±0.05 m from the target surface  62 . Two segments, the central segment and the segment on the upper-side thereof, turn on when the claw tip exists at a distance of 0.05 to 0.10 m from the target surface  62 . Three segments, the central segment and the two segments on the upper-side thereof, turn on when the claw tip exists at a distance beyond 0.10 m from the target surface  62 . Similarly, two segments at the center and on the lower-side thereof turn on when the distance is −0.05 to −0.10 m, and three segments, the central segment and the two segments on the lower-side thereof, turn on when the distance is beyond −0.10 m. In the example of  FIG.  7   , the upper-side three segments are on because the distance to the target surface  62  is +1.00 m. 
       FIG.  8    shows a control flow by the controller  20  of the present embodiment. The controller  20  repeatedly carries out the flow of  FIG.  8    at a predetermined control cycle. When the processing is started, first, in a step S 101 , the work equipment velocity estimating section  29  computes the velocity of the respective hydraulic cylinders  5 ,  6 , and  7  from the boom operation signal, the arm operation signal, and the bucket operation signal input from the operator operation sensor  36 . 
     Next, in a step S 102 , the work equipment velocity estimating section  29  converts the cylinder velocity of the step S 101  to the angular velocity based on dimension data of the boom  8 , the arm  9 , and the bucket  10  (driven members) and posture data thereof (boom angle signal, arm angle signal, and bucket angle signal), and converts it to the velocity vector V of the tip of the bucket  10 . 
     Next, in a step S 103 , the work equipment velocity estimating section  29  computes the horizontal component Vxsrf and the perpendicular component Vzsrf of the velocity vector V with respect to the target surface  62  from the velocity vector V of the tip of the bucket  10 . 
     In a step S 104 , the guidance contents change section  31  determines whether or not the perpendicular component Vzsrf of the velocity vector V with respect to the target surface  62  is smaller than a predetermined threshold. When the perpendicular component Vzsrf is in the direction toward the lower side of the target surface  62 , that is, when the bucket  10  exists on the upper side relative to the target surface  62 , the direction in which the bucket  10  moves toward the target surface  62  (downward direction) is negative. Here, the threshold of the step S 104  is set to zero. When the threshold is set to zero, if the perpendicular component Vzsrf is smaller than the threshold, the guidance contents change section  31  determines that the velocity of the bucket  10  is a velocity in such a direction as to come closer to the target surface  62  from the upper side of the target surface  62 , and the processing proceeds to a step S 105 . 
     In the step S 105 , the distance between the target surface  62  and the tip of the bucket  10  (target surface distance) is input from the target surface distance and work equipment angle calculating section  30  to the guidance contents change section  31  and the guidance contents change section  31  determines whether or not the target surface distance is equal to or shorter than a predetermined threshold. If the target surface distance is equal to or shorter than the threshold, the guidance contents change section  31  determines that the bucket tip has come close to the target surface  62 , and the processing proceeds to a step S 106 . The threshold in the step S 105  is a value for determining whether or not the bucket claw tip has come close to the target surface  62 . For example, the maximum value of the target surface distance that involves a possibility of entry of the tip of the bucket  10  into the lower side of the target surface  62  due to operation of the operation device  15  can be selected as the threshold. 
     In the step S 106 , the guidance contents change section  31  determines whether or not the pressure relating to the actuator of the operation target by the operation device  15  in the pressures of the actuators  5 ,  6 , and  7  input from the actuator state sensor  37  is equal to or lower than a predetermined threshold. In the present embodiment, the threshold is set to a value comparable to a pressure when the front work implement  1 A is not in contact with the working target (current-state terrain profile  61 ) and operates in the air (that is, when a load does not act on the respective hydraulic cylinders  5 ,  6 , and  7 ). That is, the pressure exceeds the threshold when the front work implement  1 A gets contact with the working target having a certain level of hardness. If it is determined that the actuator pressure is equal to or lower than the threshold, the guidance contents change section  31  determines that the work implement  1 A is not in contact with the current-state terrain profile  61  in operation of the operation device  15 , and the processing proceeds to a step S 107 . 
     In the step S 107 , the angle formed by the bottom surface of the bucket  10  and the target surface  62  (work equipment angle) is input from the target surface distance and work equipment angle calculating section  30  to the guidance contents change section  31  and the guidance contents change section  31  determines whether or not the work equipment angle is equal to or larger than a predetermined threshold. As already described, the work equipment angle can be computed from the posture of the front work implement  1 A and the inclination (roll angle and pitch angle) of the machine body  1 B acquired from the work implement posture sensor  34 , the data on the target surface acquired from the target surface setting device  35 , and the dimension data of the bucket  10  recorded in the controller  20 . If the work equipment angle is smaller than the threshold, it is conceivable that the operator is intending work of pressing the bottom surface of the bucket  10  against the current-state terrain profile  61  (bumping work). Conversely, if the work equipment angle is equal to or larger than the threshold, it is deemed that the operator is intending excavating, and the processing proceeds to a step S 108 . As above, the threshold of the step S 107  is a value for determining whether the work intended by the operator is bumping or excavation, and it is preferable to set the threshold in a range of zero to 45 degrees. As the threshold is brought closer to zero, the possibility that the intended work is determined as excavating and the processing proceeds to the step S 108  becomes higher. 
     In the step S 108 , it is determined that the possibility of entry of the bucket  10  into the lower side of the target surface  62  is high, and the warning informing flag is issued. Then, the controller  20  ends the processing and waits until the next control cycle. 
     On the other hand, the processing proceeds to a step S 109  if the condition is not satisfied in any of the step S 104 , the step S 105 , the step S 106 , and the step S 107 . In the step S 109 , the controller  20  ends the processing without issuing the warning informing flag and waits until the next control cycle. 
     Operation and Advantages 
     If boom lowering operation through the operation device  15   a  has been carried out as shown in  FIG.  4    in the hydraulic excavator  1  configured in the above-described manner, when the target surface distance is equal to or shorter than the threshold (step S 105  in  FIG.  8   ) and the pressure of the boom cylinder  5  is equal to or lower than the threshold (step S 106 ), the controller  20  deems that the bucket  10  has not yet gotten contact with the current-state terrain profile  61 , and carries out determination of the contents of work based on the work equipment angle (step S 107 ). Then, if the work equipment angle is equal to or larger than the threshold, the controller  20  determines that boom lowering operation is being carried out in alignment work (that is, excavating), and displays the message  392  indicating that the boom lowering operation amount is excessive on the display device (step S 108 ). Due to this, the operator can recognize that the lever operation by oneself is excessive and is prompted to reduce the operation amount. Therefore, the entry of the bucket  10  into the lower side of the target surface  62  can be prevented. On the other hand, if the work equipment angle is smaller than the threshold, the controller  20  deems that the angle formed by the back surface of the bucket  10  and the target surface  62  is substantially parallel, and determines that boom lowering operation is being carried out in bumping work, and does not display the message  392  indicating that the boom lowering operation amount is excessive (step S 109 ). That is, in bumping work, the message  392  is not displayed even when the bucket  10  comes close to the target surface  62  in boom lowering operation. Therefore, the operator can concentrate on the bumping work without feeling annoyance at the message. 
     Furthermore, if the bucket claw tip has come close to the target surface by bucket crowding operation through the operation device  15   b  as shown in  FIG.  5   , when the target surface distance is equal to or shorter than the threshold (step S 105  in  FIG.  8   ) and the pressure of the boom cylinder  5  is equal to or lower than the threshold (step S 106 ), the controller  20  deems that the bucket  10  has not yet gotten contact with the current-state terrain profile  61 , and carries out determination of the contents of work based on the work equipment angle (step S 107 ). Normally, when bucket crowding operation is being input, the angle formed by the back surface of the bucket  10  and the target surface  62  (work equipment angle) becomes equal to or larger than the threshold. Therefore, the controller  20  determines that bucket crowding operation is being carried out in alignment work (that is, excavating), and displays the message  392  indicating that the bucket crowding operation amount is excessive on the display device  39  (step S 108 ). This allows the operator to recognize that the lever operation by oneself is excessive. Thus, the operator can prevent the entry of the bucket  10  into the lower side of the target surface  62  by reducing the operation amount. 
     As described above, when the contents of notification to the operator through the display device  39  (informing device  38 ) are changed based on the state of the actuator  5  or  7 , provision of the unnecessary warning message  392  to the operator in bumping work can be avoided. Therefore, the operator can carry out the bumping work without feeling annoyance at the message  392 . 
     Furthermore, the contents of informing by the informing device  38  are changed according to the perpendicular component Vzsrf of the velocity vector V with respect to the target surface  62 , the actuator pressure, the target surface distance, and the work equipment angle. Due to this, the informing device  38  does not issue an unnecessary warning and makes a warning when the possibility of entry of the bucket into the lower side of the target surface  62  is high. This can prevent the entry of the bucket into the target surface  62  more surely. 
     The determination processing of the perpendicular component Vzsrf of the step S 104  and the determination processing of the target surface distance of the step S 105  may be integrated into one kind of processing and be executed as follows. What is shown in  FIG.  9    is a graph in which the perpendicular component Vzsrf of the velocity vector V with respect to the target surface  62  is plotted on the ordinate axis and the target surface distance is plotted on the abscissa axis. Here, the processing may be caused to proceed to the step S 106  when the perpendicular component Vzsrf and the target surface distance enter a hatching part shown in the fourth quadrant of the graph, and the processing may be caused to proceed to the step S 109  if this is not the case. Even when the perpendicular component Vzsrf of the velocity vector V is the same, the possibility of entry into the target surface  62  varies depending on the target surface distance. For this reason, the informing device  38  is enabled to issue a warning more appropriately by setting a hatching region that associates the perpendicular component Vzsrf with the target surface distance like that shown in  FIG.  9   , in other words, by carrying out setting in such a manner that the threshold of the perpendicular component Vzsrf monotonically decreases in response to reduction in the target surface distance. 
     Furthermore, the threshold of the perpendicular component Vzsrf of the velocity vector V in the step S 104  and the threshold of the target surface distance in the step S 105  may be changed according to the angle of the arm  9  with respect to the boom  8 . In the state in which the arm cylinder  6  is operated in the contraction direction and the arm  9  stretches (that is, state in which the radius of swing is large), the moment of inertia is larger and it becomes more difficult to stop boom lowering operation. For this reason, it is preferable to change the threshold according to the angle of the arm  9 . Specifically, it is preferable to set the magnitude of the threshold larger to cause warning issuance more readily in the state in which dumping operation of the arm  9  is being carried out through contraction of the arm cylinder  6  than in the state in which crowding operation of the arm  9  is being carried out through expanding the arm cylinder  6 . For example, as shown in  FIG.  10   , when a threshold Vzth relating to the perpendicular component Vzsrf of the velocity vector is changed to Vzth′ and a threshold Dth relating to the target surface distance is changed to Dth′, the region of progression to the step  106  enlarges and warning issuance can be caused more readily. In addition, the boundary line between the hatching region and the non-hatching region in the fourth quadrant may be moved in such a direction as to increase the area of the hatching region (for example, right direction or upper right direction). 
     Moreover, the processing of the step S 104  and the processing of the step S 105  may be integrated to be executed as follows. A predicted time until the bucket  10  reaches the target surface  62  may be computed from the perpendicular component Vzsrf of the velocity vector V and the target surface distance and the processing may be caused to proceed to the step S 106  when the predicted time has become equal to or shorter than a threshold. The predicted time in this case can be computed when the target surface distance is divided by the perpendicular component, for example. 
     The processing of the step S 107  may be omitted from the flowchart of  FIG.  8   . 
     Second Embodiment 
     Next, an embodiment when excavation operation by the arm  9  is included will be described. Description of the part overlapping with the first embodiment is omitted. 
     As shown in  FIG.  11   , operation combined with the boom  8  is necessary in the case of causing the arm  9  to pivot in an excavation direction shown by an arrow in the diagram by arm crowding operation by an operator through the operation device  15  and forming the target surface  62  with a straight line shape. Specifically, raising operation or lowering operation of the boom  8  to cancel out the perpendicular component of the velocity vector of the tip of the bucket  10  with respect to the target surface  62 , generated by crowding operation of the arm  9 , is necessary. Specifically, when the perpendicular component of a velocity vector in the negative direction (vertical downward direction with respect to the target surface  62 ) arises due to the arm  9 , it needs to be canceled out by raising operation of the boom  8 . Conversely, when the perpendicular component of a velocity vector in the positive direction (vertical upward direction with respect to the target surface  62 ) arises, it needs to be canceled out by lowering operation of the boom  8 . 
     In excavation operation of the arm  9 , a display example when it is determined that the possibility of entry into the target surface  62  is high due to insufficiency of raising operation of the boom  8  is shown in  FIG.  12   . A display example when it is determined that the possibility of entry into the target surface  62  is high due to an excess of lowering operation of the boom  8  is shown in  FIG.  13   . This can notify the operator that the operation is excessive or insufficient, and can alleviate the entry of the bucket  10  into the target surface  62 . 
       FIG.  14    shows a control flow by the controller  20  of the second embodiment. The controller  20  repeatedly executes the flow of  FIG.  14    at a predetermined control cycle. When the processing is started, the work equipment velocity estimating section  29  executes computation processing of the velocity of the respective hydraulic cylinders  5 ,  6 , and  7  (step S 101 ), computation processing of the velocity vector V of the bucket tip (step S 102 ), and computation processing of the perpendicular component Vzsrf of the velocity vector V (step S 103 ) similarly to the flow of  FIG.  8   . 
     Next, in a step S 211 , the work equipment velocity estimating section  29  computes a velocity vector Va generated due to operation of the arm  9  based on dimension data of the boom  8  and the arm  9  and posture data thereof (boom angle signal and arm angle signal) and the velocity of the arm cylinder  6  in the step S 101 , and computes a perpendicular component Vazsrf of the velocity vector Va with respect to the target surface  62 . 
     In a step S 201 , the guidance contents change section  31  determines whether excavation operation of the arm  9  is being carried out by the operator (that is, crowding operation thereof is being carried out) based on the arm operation signal. If it is determined that excavation operation of the arm  9  is being carried out here, the processing proceeds to a step S 202 . 
     In the step S 202 , the guidance contents change section  31  determines whether or not the perpendicular component Vzsrf of the velocity vector V of the bucket tip (bucket claw tip) is equal to or smaller than a threshold. The processing proceeds to a step S 203  if it is determined that the perpendicular component Vzsrf is equal to or smaller than the threshold here, and the processing proceeds to a step S 209  if this is not the case. The threshold relating to the perpendicular component Vzsrf in the step S 202  may be made identical to the threshold relating to the step S 104  in  FIG.  8    or may be made different. 
     In the step S 203 , the guidance contents change section  31  determines whether or not the target surface distance is equal to or shorter than a threshold. The processing proceeds to a step S 204  if it is determined that the target surface distance is equal to or shorter than the threshold here, and the processing proceeds to the step S 209  if this is not the case. The threshold relating to the target surface distance in the step S 203  may be made identical to the threshold relating to the step S 105  in  FIG.  8    or may be made different. 
     In the step S 204 , the guidance contents change section  31  determines whether or not the actuator pressure is equal to or lower than a threshold. The processing proceeds to a step S 205  if the actuator pressure is equal to or lower than the threshold, and the processing proceeds to the step S 209  if this is not the case. The threshold relating to the actuator pressure in the step S 204  may be made identical to the threshold relating to the step S 106  in  FIG.  8    or may be made different. 
     In the step S 205 , the guidance contents change section  31  determines whether or not the angle formed by the bottom surface of the bucket  10  and the target surface (work equipment angle) is equal to or larger than a threshold. If the angle is smaller than the threshold, it is conceivable that pressing work is being carried out with the bottom surface of the bucket  10  by operation of the arm  9 . The processing proceeds to a step S 206  if the angle is equal to or larger than the threshold, and the processing proceeds to the step S 209  if this is not the case. The threshold relating to the work equipment angle in the step S 205  may be made identical to the threshold relating to the step S 107  in  FIG.  8    or may be made different. 
     In the step S 206 , the guidance contents change section  31  determines whether or not the perpendicular component Vazsrf of the velocity vector Va of the bucket  10  with respect to the target surface  62  generated due to the operation of the arm  9 , calculated in the step S 211 , is negative. The processing proceeds to a step S 207  if the perpendicular component Vazsrf is negative, and the processing proceeds to a step S 208  if this is not the case (if the perpendicular component Vazsrf is zero or positive). 
     In the step S 207 , the guidance contents change section  31  determines that the possibility of entry into the target surface  62  is high due to insufficiency of raising operation of the boom  8  or excess of excavation operation of the arm  9 , and issues a warning informing flag that informs that effect (boom-raising-insufficiency warning informing flag). A screen display example of the display device  39  when the boom-raising-insufficiency warning informing flag is input is shown in  FIG.  12   . In  FIG.  12   , a message  392 A indicating that boom raising is insufficient or arm crowding is excessive is displayed due to the boom-raising-insufficiency warning informing flag. The operator can be notified that boom raising operation is insufficient or arm crowding operation is excessive by this message  392 A, and the entry of the bucket  10  into the target surface  62  can be prevented by operation change by the operator who has recognized it. Although the operator is informed of both insufficiency of boom raising and excess of arm crowding by the message  392 A in the example of  FIG.  12   , the operator may be informed of either one. 
     If it is determined that the velocity in the perpendicular direction generated due to the operation of the arm  9  is not negative in the step S 206 , the processing proceeds to the step S 208 . 
     In the step S 208 , the guidance contents change section  31  determines that lowering operation of the boom  8  is excessive and the possibility of entry into the target surface  62  is high, and issues a warning informing flag that informs that effect (boom-lowering-excess warning informing flag). A screen display example of the display device  39  when the boom-lowering-excess warning informing flag is input is shown in  FIG.  13   . In  FIG.  13   , a message  392 B indicating that boom lowering is excessive is displayed due to the boom-lowering-excess warning informing flag. The operator can be notified that lowering operation of the boom  8  is excessive by the message  392 B, and the entry of the bucket  10  into the target surface  62  can be prevented by operation change (reduction in boom lowering operation) by the operator who has recognized it. 
     The processing proceeds to the step S 209  if the condition is not satisfied in any of the step S 202 , the step S 203 , the step S 204 , and the step S 205 . In the step S 209 , issuance of the warning informing flag due to excavation operation of the arm  9  is not carried out. 
     The processing proceeds to a step S 210  if the condition is not satisfied in the step S 201  (that is, excavation operation of the arm  9  is not being carried out). Processing in the case of the proceeding to the step S 210  is shown in  FIG.  15   . 
     In  FIG.  15   , the guidance contents change section  31  executes processing of a step S 300 , a step S 301 , a step S 302 , a step S 303 , a step S 304 , and a step S 305 . These kinds of processing are each the same processing as the processing of the step S 104 , the step S 105 , the step S 106 , the step S 107 , the step S 108 , and the step S 109  shown in  FIG.  8    and therefore description thereof is omitted. 
     As described above, in the present embodiment, the contents of informing (contents of MG) by the informing device (display device  39 ) are changed according to whether or not arm operation through the operation device  15  exists. Specifically, the contents of informing to the operator are changed depending on the direction of the perpendicular velocity component Vazsrf generated due to arm operation. This allows the operator to carry out more appropriate operation in the situation in which combined operation of the boom  8  and the arm  9  is necessary. For example, in the situation of the step S 207 , the operator can recognize that boom raising operation is insufficient, and excavation along the target surface  62  is enabled by increasing the operation amount of the boom raising operation. 
     By the way, there are steps in which similar determination processing using the predetermined threshold is executed in the flow shown in  FIG.  14    and the flow shown in  FIG.  15   . The thresholds of these steps may be made different. Furthermore, it is preferable to set the thresholds in such a manner that the determination result in each step becomes YES more readily (that is, warning informing flag is issued more readily) in the flow of  FIG.  15    than in the flow of  FIG.  14   . For example, the target surface distance and the threshold are compared in the steps S 203  and S 301 . The thresholds may be set to 100 mm in the step S 203  and be set to 1000 mm in the step S 301 . Due to this, the excavation force is ensured in accordance with  FIG.  14    at the time of excavating by the arm  9  and entry into the target surface  62  is surely prevented in accordance with  FIG.  15    at the time of alignment work without arm operation. Thus, it becomes possible to carry out informing suitable for each work. 
     Third Embodiment 
     The present embodiment is a modification example of the first embodiment. The guidance contents change section  31  of the present embodiment is characterized by carrying out the following operation. When operation of the boom  8  through the operation device  15  exists, the guidance contents change section  31  computes the intersection of the movement locus of the claw tip of the bucket  10  (“locus D” to be described later) and the target surface  62  (“reaching point” to be described later) and carries out predictive calculation of a velocity vector Vtgt of the bucket claw tip at the intersection. Then, the guidance contents change section  31  changes the threshold of at least one of the step S 104  and the step S 105  in the first embodiment according to a component Vztgt perpendicular to the target surface  62  in the velocity vector Vtgt at the intersection and thereby changes the contents of informing by the informing device  38 . 
     In alignment work by lowering operation of the boom  8 , when the angles of the arm  9  and the bucket  10  do not change (that is, when operation to the arm  9  and the bucket  10  does not exist and only lowering operation of the boom  8  is carried out), the intersection of the locus D (see  FIG.  16   ) drawn by the tip of the bucket  10  and the target surface  62 , i.e. the reaching point on the target surface  62  of alignment work (hereinafter, often referred to as “reaching point”), can be computed before the bucket  10  reaches the target surface  62  or the current-state terrain profile  61 . Specifically, computation can be carried out as follows, for example. When the angles of the arm  9  and the bucket  10  do not change, the tip of the bucket  10  at the time of lowering operation of the boom  8  moves to draw a circular arc that has the base end part of the boom  8  (pivot center) as the center and has the distance between the boom base end part and the bucket tip as the radius. Thus, the intersection of this circular arc and the target surface  62  becomes the reaching point. 
     Furthermore, the perpendicular component Vztgt (see  FIG.  16   ) with respect to the target surface  62  in the velocity vector Vtgt (see  FIG.  16   ) of the bucket claw tip at the reaching point can also be computed similarly to the perpendicular component Vzsrf in the step S 103 . Moreover, the threshold relating to the target surface distance in the step S 105  and the threshold relating to the perpendicular component Vzsrf in the step S 104  are changed according to the direction and magnitude of the perpendicular component Vztgt. This can prevent displaying of the unnecessary message  392  to the operator and improve usability of the MG. 
     The movable range of the bucket  10  and the target surface  62  are shown in  FIG.  16   . A hatching part E shown by the region in which hatching is carried out is the movable range of the bucket  10 . Furthermore, the circular arc D shows the locus of the tip of the bucket  10  with the posture of the arm  9  and the bucket  10  shown in  FIG.  16   . When the target surface  62  exists at a position like that shown in  FIG.  16   , the angle formed by the velocity vector Vtgt and the target surface  62  is comparatively small and the magnitude of the perpendicular component Vztgt thereof becomes comparatively small. For this reason, even when lowering operation of the boom  8  is fast, the amount of bucket entry into the target surface  62  becomes comparatively small. In this case, it will be reasonable to change the threshold of the step S 104  or the step S 105  in such a direction that informing of a warning is carried out less readily. For example, the threshold relating to the target surface distance in the step S 105  in  FIG.  8    in the first embodiment can be changed as in a graph shown in  FIG.  17    according to the direction and magnitude of the perpendicular component Vztgt. 
     The graph of  FIG.  17    is what is obtained by plotting the perpendicular component Vztgt of the velocity vector Vtgt at the reaching point on the abscissa axis and plotting the threshold of the target surface distance (distance threshold) on the ordinate axis. The distance threshold is set in such a manner that, when the perpendicular component Vztgt of the velocity vector at the reaching point is negative, the distance threshold also increases according to increase in the magnitude thereof. If the distance threshold is set in this manner, the distance threshold becomes larger when the magnitude of the negative perpendicular component Vztgt is larger. Therefore, the warning informing flag is issued earlier than in the first embodiment as a result. On the other hand, the distance threshold becomes smaller when the magnitude of the negative perpendicular component Vztgt is smaller. Therefore, the warning informing flag is issued in the situation in which the bucket  10  has come closer to the target surface  62  than in the first embodiment as a result. Furthermore, when the perpendicular component Vztgt of the velocity vector Vtgt at the reaching point becomes zero or when the perpendicular component Vztgt is positive and the bucket  10  exists on the upper side relative to the target surface  62 , the distance threshold may also be set to zero as shown in  FIG.  17    and the warning informing flag may be always kept from being issued. Moreover, the warning informing flag may be always kept from being issued when the intersection of the locus (circular arc) D drawn by the tip of the bucket  10  and the target surface  62  does not exist. 
     Fourth Embodiment 
     The present embodiment is different from the above respective embodiments in that the present embodiment includes the guidance contents change section  31  shown in  FIG.  18   . Description is omitted as appropriate regarding the same part as the above embodiment. The guidance contents change section  31  of the present embodiment includes a display mode deciding section  31   a , a bucket display position deciding section  31   b , and a target surface display position deciding section  31   c.    
     The display mode deciding section  31   a  is a section that decides which of an enlargement mode (see  FIGS.  20  and  21   ) and an overall mode (see  FIG.  22   ) is selected as a display mode of a screen that displays the positional relationship between the bucket  10  and the target surface  62 , according to a velocity vector Vb generated due to operation of the boom  8 , the velocity vector Va generated due to operation of the arm  9 , the target surface distance, and the pressure of the actuators  5 ,  6 , and  7 , and outputs the result thereof to the display device  39  as a display mode command. The bucket  10  and the target surface  62  are displayed in the screen in the enlargement mode (first screen) on the display device  39  as shown in  FIGS.  20  and  21   . Furthermore, in the screen in the overall mode (second screen), a wider range than the screen in the enlargement mode (first screen) is included and at least the whole of the hydraulic excavator  1  and the target surface  62  are displayed as shown in  FIG.  22   . To the display mode deciding section  31   a , a signal showing the display mode in which displaying is currently carried out on the display device  39  (display mode signal) is input from the display device  39 . Furthermore, the target surface distance is input from the target surface distance and work equipment angle calculating section  30 , the pressures of the respective cylinders  5 ,  6 , and  7  are input from the actuator state sensor  37 , and the velocity vectors Vb and Va are input from the work equipment velocity estimating section. 
     The bucket display position deciding section  31   b  is a section that changes and decides the position at which an image of the bucket  10  is displayed on the screen of the display device  39  according to the velocity vector V, the target surface distance, and the pressures of the actuators  5 ,  6 , and  7 , and outputs the result thereof to the display device  39  as a bucket display command. To the bucket display position deciding section  31   b , the position of the bucket claw tip and the posture of the bucket  10  are input from the work implement posture sensing section  28  and the operation signals to the boom  8 , the arm  9 , and the bucket  10  are input from the operator operation sensor  36 . In addition, the pressures of the respective cylinders  5 ,  6 , and  7  are input from the actuator state sensor  37  and the velocity vector V of the claw tip of the bucket  10  (estimated work equipment velocity) is input from the work equipment velocity estimating section. 
     The target surface display position deciding section  31   c  is a section that decides the position at which an image of the target surface  62  (line segment) is displayed on the screen of the display device  39  based on the bucket display command input from the bucket display position deciding section  31   b  and target surface data input from the target surface setting device  35 , and outputs the result thereof to the display device  39  as a target surface display command. 
     The display device  39  controls the display mode of the screen showing the positional relationship between the bucket  10  and the target surface  62  based on the display mode command input from the display mode deciding section  31   a . Furthermore, the display device  39  controls the display position of the bucket  10  in the screen based on the bucket display command input from the bucket display position deciding section  31   b  and controls the display position of the target surface  62  in the screen based on the target surface display command input from the target surface display position deciding section  31   c.    
     In a site of excavating, not only the shape of the target surface  62  around the bucket but also the shape of the target surface  62  existing in the direction in which the bucket  10  is to be moved is desired to be grasped in advance in some cases. Meanwhile, in the case of shaping the current terrain profile into the target shape by the bucket  10 , the target surface  62  is desired to be grasped in detail in some cases. In such a case, it is effective to change the positional relationship between the target surface  62  and the bucket  10  in the display screen of the display device  39  and vary the display magnification of the bucket  10  and the target surface  62  in the screen. 
       FIG.  19    is a flowchart of processing executed by the guidance contents change section  31  of the present embodiment. First, in a step S 400 , the display mode deciding section  31   a  determines whether the target surface distance is equal to or shorter than a threshold. If it is determined that the target surface distance is equal to or shorter than the threshold, the processing proceeds to a step S 401 . 
     In the step S 401 , the display mode deciding section  31   a  determines whether the current displaying is in the enlargement mode based on the display mode signal. The processing proceeds to a step S 403  if it is determined that the current display mode is the enlargement mode. On the other hand, the processing proceeds to a step S 402  if it is determined that the current display mode is not the enlargement mode. 
     In the step S 402 , the display mode deciding section  31   a  outputs the display mode command to change the display mode to the enlargement mode to the display device  39 . 
     In the step S 403 , the bucket display position deciding section  31   b  determines whether lever operation aiming at operation of the work implement  1 A by the operator exists based on the operation signal input from the operator operation sensor  36 . The processing proceeds to a step S 404  if it is determined that lever operation exists. 
     In the step S 404 , the bucket display position deciding section  31   b  determines whether all of pressures generated in the three hydraulic cylinders (actuators)  5 ,  6 , and  7  are equal to or lower than a threshold set regarding each cylinder. If it is determined that the pressures of all cylinders  5 ,  6 , and  7  are equal to or lower than the respective thresholds, the velocity vector V of the tip of the bucket  10  (same as the velocity V in the step S 102  in  FIG.  8   ) is input from the work equipment velocity estimating section  29  in a step S 405 . Then, in the next step S 406 , the bucket display position deciding section  31   b  decides to change the display position of the bucket  10  from a reference position (to be described later) and decides the bucket display position after the change based on the velocity vector V in the step S 405 . The processing of this step S 406  will be described later. 
     The processing proceeds to a step S 407  if it is determined that lever operation does not exist in the step S 403  or if it is determined that at least one of the pressures of the three actuators  5 ,  6 , and  7  exceeds the threshold in the step S 404 . In the step S 407 , the bucket display position deciding section  31   b  does not execute the processing relating to change in the display position of the bucket  10 . That is, the display position of the bucket  10  in this case is the reference position. 
     Furthermore, the processing proceeds to a step S 408  if it is determined that the target surface distance is longer than the threshold in the step S 400 . In the step S 408 , the display mode deciding section  31   a  determines whether or not the current display mode is the enlargement mode based on the display mode signal. If it is determined that the current display mode is the enlargement mode here, the processing proceeds to a step S 409  and the display mode deciding section  31   a  outputs the display mode command to change the display mode to the overall mode to the display device  39 . Conversely, if it is determined that the current display mode is not the enlargement mode (that is, if the current display mode is the overall mode), the processing proceeds to a step S 410  and the display mode deciding section  31   a  outputs the display mode command to keep the overall mode to the display device  39 . 
     In  FIG.  20   , an example of displaying in the enlargement mode when the processing has proceeded to the step S 407  (when the bucket display position is not changed from the reference position) is shown. In  FIG.  21   , an example of displaying in the enlargement mode when the processing has proceeded to the step S 406  (when the bucket display position has been changed from the reference position) is shown. Point A to point I shown in  FIG.  20    and  FIG.  21    are points for explanation that are not displayed on the actual screen. Furthermore, arrow J shown in  FIG.  21    is an arrow for explanation that is not displayed on the actual screen. 
       FIG.  20    is the screen of the enlargement mode and is the case in which the bucket display position is not changed. When the bucket display position is not changed, the bucket display position deciding section  31   b  displays the bucket  10  in such a manner that the claw tip position corresponds with reference point E located at the center of the display part, and the target surface display position deciding section  31   c  displays the target surface  62  based on the position of the bucket  10 . 
     The processing of the step S 406  will be described.  FIG.  21    is the case in which the display mode is the enlargement mode and the bucket display position is changed. When the velocity vector V input in the step S 405  in  FIG.  19    is in the direction of arrow J in  FIG.  21   , the bucket display position deciding section  31   b  displays the bucket  10  in such a manner that the bucket tip position corresponds with the point existing in the direction of the vector that has reference point E as the initial point and is obtained by multiplying arrow J by a minus, i.e. point B in  FIG.  21   , and the target surface display position deciding section  31   c  displays the target surface  62  based on the position of the bucket  10 . Changing the display position of the bucket  10  in this manner makes it possible to present the target surface  62  existing in the direction in which the bucket  10  moves to the operator more widely. Although nine points of point A to point I are employed as the bucket display position in the example of  FIGS.  20  and  21   , all of these points do not necessarily need to be used as the bucket display position. For example, a format may be employed in which four points of point B, point H, point D, and point F existing in the upward, downward, left, and right directions with respect to reference point E are used as the bucket display position together with reference point E. 
     Due to configuring the guidance contents change section  31  in this manner, when lever operation exists and the pressures of the three actuators  5 ,  6 , and  7  are all equal to or lower than the threshold, the processing proceeds to the step S 406  and therefore the shape of the target surface  62  located in the direction in which the bucket  10  moves is displayed more widely. Furthermore, when the pressure of any actuator  5 ,  6 , or  7  is higher than the threshold, the processing proceeds to the step S 407  and therefore the bucket display position is kept at reference point E even when lever operation exists. Thus, for example, when the display position of the bucket  10  is not changed from reference point E even when lever operation is carried out in the case in which the thresholds of the pressures of the respective actuators  5 ,  6 , and  7  in the step S 404  are set to the relief pressures of the respective actuators  5 ,  6 , and  7 , the operator can intuitively grasp that the pressure of any of the actuators  5 ,  6 , and  7  has reached the relief pressure. 
     In the above-described example, the pressures of the three hydraulic cylinders  5 ,  6 , and  7  and the threshold are compared in the determination of the step S 404 . However, instead of this, the pressure of the specific hydraulic cylinder (for example, arm cylinder  6 ) and the threshold corresponding to it (for example, relief pressure) may be compared. When the hydraulic cylinder whose pressure is determined in the step S 404  is decided in advance as above, the operator can grasp that the hydraulic cylinder has reached the relief pressure (threshold) if the display position of the bucket  10  does not change from reference point E even when lever operation is carried out. 
     An example of displaying in the overall mode is shown in  FIG.  22   . In the overall mode, displaying is carried out in such a manner that the positions of the whole of the excavator and the target surface  62  are understood. Displaying in this manner allows the operator to easily grasp the positional relationship between the excavator  1  and the target surface  62 . 
     Modification Example 1 
     In the flow of  FIG.  19   , the display mode is switched according to whether the target surface distance is longer or shorter than one threshold in the step S 400 . However, two different thresholds may be set and the threshold in the case of switching to the enlargement mode may be set smaller than the threshold in the case of switching to the overall mode. Specifically, a first threshold and a second threshold smaller than the first threshold are set as the thresholds relating to the target surface distance and processing of a flowchart shown in  FIG.  23    is executed. The guidance contents change section  31  (controller  20 ) repeatedly carries out the flow of  FIG.  23    at a predetermined control cycle. 
     First, in a step S 500 , the display mode deciding section  31   a  determines whether or not the current displaying is in the overall mode based on the display mode signal. The processing proceeds to a step S 501  if it is determined that the current display mode is the overall mode. 
     In the step S 501 , the display mode deciding section  31   a  determines whether or not the target surface distance is equal to or shorter than the second threshold. If it is determined that the target surface distance is equal to or shorter than the second threshold, the processing proceeds to a step S 502  and the display mode deciding section  31   a  outputs the display mode command to change the display mode to the enlargement mode. If it is determined that the target surface distance is not equal to or shorter than the second threshold in the step S 501  (that is, if the target surface distance is longer than the second threshold), the processing proceeds to a step S 503  and the display mode deciding section  31   a  keeps the overall mode. 
     On the other hand, if it is determined that the current display mode is not the overall mode in the step S 500 , the processing proceeds to a step S 504  and the display mode deciding section  31   a  determines whether or not the target surface distance is equal to or longer than the first threshold. If it is determined that the target surface distance is equal to or longer than the first threshold, the processing proceeds to a step S 505  and the display mode deciding section  31   a  outputs the display mode command to change the display mode to the overall mode. If it is determined that the target surface distance is not equal to or longer than the first threshold in the step S 504  (that is, if the target surface distance is shorter than the first threshold), the processing proceeds to a step S 506  and the display mode deciding section  31   a  keeps the enlargement mode. 
     If the processing proceeds to the step S 502  or the step S 506  (that is, if the display mode is the enlargement mode), the controller  20  proceeds to the processing of the step S 403  in the flowchart shown in  FIG.  19   . On the other hand, if the processing proceeds to the step S 503  or the step S 505  (that is, if the display mode is the overall mode), the controller  20  ends the processing and waits until the next control cycle. 
     According to the flowchart shown in  FIG.  23   , change from the overall mode to the enlargement mode is carried out when the target surface distance has become equal to or shorter than the second threshold, and change from the enlargement mode to the overall mode is carried out when the target surface distance has become equal to or longer than the first threshold. This can prevent the occurrence of frequent switching between the enlargement mode and the overall mode and reduce annoyance given to the operator. 
     Modification Example 2 
     If it is determined that lever operation exists in the step S 403  in  FIG.  19   , a flowchart shown in  FIG.  24    may be started instead of the step S 404  in  FIG.  19   . 
     When the flow of  FIG.  24    is started, the velocity vector V of the bucket claw tip based on operator operation is input to the bucket display position deciding section  31   b  in a step S 600 . In the next step S 601 , the bucket display position deciding section  31   b  computes a display vector Vd according to the velocity vector V. The display vector Vd is the vector that is obtained by multiplying the velocity vector V by a minus and has reference point E as the initial point. 
     In a step S 602 , the pressure of the arm cylinder  6  (actuator pressure) is input from the actuator state sensor  37  to the bucket display position deciding section  31   b . In a step S 603 , the bucket display position deciding section  31   b  multiplies the display vector Vd computed in the step S 601  by a coefficient equal to or lower than 1 according to the actuator pressure acquired in the step S 602 . A correlation diagram between the actuator pressure and the coefficient is shown in  FIG.  25   . In the table of this diagram, the coefficient is set to monotonically decrease in response to increase in the actuator pressure. Specifically, when the actuator pressure is lower than a predetermined value P 1 , 1 is output as the coefficient. When this pressure is equal to or higher than the predetermined value P 1  and is lower than the relief pressure, a value that monotonically decreases toward 0 as this pressure increases is output as the coefficient. When this pressure is equal to or higher than the relief pressure, 0 is output as the coefficient. That is, when the actuator pressure is lower than P 1 , the display vector Vd becomes a vector that conforms to the magnitude of the velocity vector V because the coefficient is 1. When the actuator pressure is equal to or higher than P 1 , the magnitude of the display vector Vd becomes smaller as the pressure increases. 
     In a step S 604 , the bucket display position deciding section  31   b  decides the terminal point of the display vector Vd acquired in the step S 603  as the bucket display position and outputs the bucket display command corresponding to the position to the display device  39 . That is, the display vector Vd in the present modification example indicates the movement amount of the bucket display position from reference point E. For example, as shown in  FIG.  21   , when the terminal point of the display vector Vd in the step S 601  according to the velocity vector V is point B shown in  FIG.  21   , the terminal point of the display vector Vd in the step S 603  becomes any point on the line segment that links reference point E and point B and the claw tip of the bucket  10  is displayed at the terminal point thereof. For example, when the actuator pressure is an intermediate value between the relief pressure and P 1 , the coefficient becomes 0.5. Therefore, the magnitude of the display vector Vd becomes half the magnitude when the actuator pressure is lower than P 1  and the claw tip of the bucket  10  is displayed at the middle between reference point E and point B. Changing the bucket display position according to the magnitude of the actuator pressure in this manner allows the operator to intuitively grasp the magnitude of the load acting on the corresponding actuator (arm cylinder  6 ). 
     In the above description, the coefficient of the step S 603  is computed based on the pressure of the arm cylinder  6 . However, the coefficient may be decided based on the pressure of another hydraulic cylinder  5  or  7  or the coefficient may be decided from the pressures of plural hydraulic cylinders  5 ,  6 , and  7 . 
     Modification Example 3 
     In the flow of  FIG.  19   , the display mode is switched according to whether the target surface distance is longer or shorter than the threshold in the step S 400 . However, the display mode may be switched according to the direction of the perpendicular component Vbzsrf or Vazsrf with respect to the target surface  62  in the velocity vector Vb or Va generated due to operation of the boom  8  or the arm  9 . A flowchart in this case is shown in  FIG.  26   . The guidance contents change section  31  (controller  20 ) repeatedly carries out the flow of  FIG.  26    at a predetermined control cycle. 
     First, in a step S 700 , the display mode deciding section  31   a  determines whether the current display mode is the overall mode based on the display mode signal. The processing proceeds to a step S 701  if the current display mode is the overall mode. 
     In the step S 701 , the display mode deciding section  31   a  determines whether the target surface distance is equal to or shorter than a threshold. The threshold is a value for determining whether or not the bucket claw tip has come close to the target surface  62 . The processing proceeds to a step S 702  if the target surface distance is equal to or shorter than the threshold. 
     In the step S 702 , the display mode deciding section  31   a  determines whether the perpendicular component Vbzsrf or Vazsrf of the velocity vector Vb or Va generated due to operation of the boom  8  or the arm  9  is in such a direction as to come closer to the target surface  62 . The velocity vector Vb generated due to operation of the boom  8  is computed by the work equipment velocity estimating section  29  based on the dimension data of the boom  8  and the posture data thereof (boom angle signal) and the velocity of the boom cylinder  5 . The work equipment velocity estimating section  29  also computes the perpendicular component Vbzsrf of the velocity vector Vb with respect to the target surface  62 . Furthermore, the velocity vector Va generated due to operation of the arm  9  is also computed by the work equipment velocity estimating section  29  based on the dimension data of the boom  8  and the arm  9  and the posture data thereof (boom angle signal and arm angle signal) and the velocity of the arm cylinder  6 . The work equipment velocity estimating section  29  also computes the perpendicular component Vazsrf of the velocity vector Va with respect to the target surface  62 . The processing proceeds to a step S 703  if it is determined that the perpendicular component Vbzsrf or Vazsrf is in such a direction as to come closer to the target surface  62  (that is, negative direction) in the step S 702 . 
     In the step S 703 , the display mode deciding section  31   a  determines whether or not the pressures of the actuators (hydraulic cylinders)  5 ,  6 , and  7  are all equal to or lower than a threshold. The thresholds can be set to the same values as the step S 404  in  FIG.  19   . If it is determined that the actuator pressures are all equal to or lower than the threshold, the processing proceeds to a step S 704  and the display mode deciding section  31   a  outputs the display mode command to change the display mode to the enlargement mode to the display device  39 . 
     On the other hand, when it is determined that the target surface distance is not equal to or shorter than the threshold in the step S 701 , when it is determined that the perpendicular component Vbzsrf or Vazsrf is not in such a direction as to come closer to the target surface  62  in the step S 702 , or when it is determined that any of the actuator pressures is higher than the threshold in the step S 703 , the processing proceeds to a step S 705  and the display mode deciding section  31   a  keeps the display mode to the overall mode. 
     By the way, the processing proceeds to a step S 706  if it is determined that the current display mode is not the overall mode in the step S 700 . In the step S 706 , the display mode deciding section  31   a  determines whether the target surface distance is equal to or longer than a threshold. The threshold may be set to the same value as the step S 701  or may be set to a value larger than the value of the step S 701 . The processing proceeds to a step S 707  if the target surface distance is equal to or longer than the threshold. 
     In the step S 707 , the display mode deciding section  31   a  changes the display mode to the overall mode. If it is determined that the target surface distance is shorter than the threshold in the step S 706 , the processing proceeds to a step S 708  and the display mode deciding section  31   a  keeps the display mode to the enlargement mode. 
     When displaying is switched in this manner, change in the display mode in conformity to the work intention of the operator is enabled. For example, the case in which the processing proceeds to the step S 704  is when the operator is trying to bring the bucket  10  close to the target surface  62  and is the situation in which earth and sand that yield excavation resistance are absent on the upper side relative to the target surface  62 , that is, the situation in which finishing work is started. In such a case, it is preferable in terms of work to carry out displaying that allows the positional relationship between the bucket claw tip and the target surface  62  to be grasped in detail by making change from the overall mode to the enlargement mode. On the other hand, the case in which the processing proceeds to the step S 705  via the step S 703  is the state in which the operator is trying to bring the bucket  10  close to the target surface  62  but earth and sand that yield excavation resistance exist on the upper side of the target surface and the bucket  10  can not come sufficiently close to the target surface  62 . At such time, minute work like finishing work is not carried out and therefore it is better that the positional relationship between the whole of the excavator and the target surface  62  can be grasped. Furthermore, the case in which the processing proceeds to the step S 707  is the situation in which the distance between the bucket  10  and the target surface  62  is long and therefore it is better to make a transition from the enlargement mode to the overall mode. The case in which the processing proceeds to the step S 708  is the situation in which the distance between the bucket  10  and the target surface  62  is short and therefore it is better to keep the enlargement mode. 
     The determination of the direction of the perpendicular component in the step S 702  may be carried out by using the direction of the perpendicular component Vzsrf of the velocity vector V. 
     Furthermore, for the determination of whether or not lever operation exists in the step S 403  in  FIG.  19    and so forth, whether the pilot pressure (operation signal) is equal to or higher than a threshold may be used. Alternatively, the determination may be carried out by attaching potentiometer, encoder, and so forth to the operation device  15  and directly detecting the operation amount of the lever. 
     &lt;Others&gt; 
     The present invention is not limited to the above-described respective embodiments and various modification examples in such a range as not to depart from the gist thereof are included. For example, the present invention is not limited to what includes all configurations explained in the above-described respective embodiments, and what is obtained by deleting part of the configurations and what is obtained by replacing part of the configurations are also included. 
     In the step S 107  in  FIG.  8   , the pressure of the actuator  5 ,  6 , or  7  of the operation target and the threshold are compared. However, the pressure of the actuator  5 ,  6 , or  7  that is not the operation target and the threshold may be compared to carry out determination. Furthermore, the threshold may be made different for each of the actuators  5 ,  6 , and  7 . 
     In the above-described respective embodiments, the loads are selected as the states of the hydraulic cylinders (actuators)  5 ,  6 , and  7  and the pressures of the hydraulic cylinders  5 ,  6 , and  7  are detected for detecting the loads. However, the delivery pressure of the hydraulic pump  2  may be detected, and a rough tendency of the load acting on the respective hydraulic cylinders  5 ,  6 , and  7  may be grasped from the detected value and the result thereof may be reflected in the MG. 
     In the explanation of the above-described respective embodiments, as control lines and information lines, what are understood as necessary for the description of these embodiments are shown. However, all control lines and information lines relating to products are not necessarily shown. It may be thought that actually almost all configurations are mutually connected. 
     Regarding the respective configurations relating to the above-described controller  20 , functions and execution processing of these respective configurations, and so forth, part or all of them may be implemented by hardware (for example, logic that carries out the respective functions is designed with an integrated circuit, and so forth). Furthermore, as the configuration relating to the above-described controller  20 , a program (software) that is read out and executed by a calculation processing device (for example, CPU) to cause implementation of the respective functions relating to the configuration of the controller  20  may be employed. Data relating to this program can be stored in semiconductor memory (flash memory, SSD, and so forth), magnetic storing device (hard disk drive and so forth), recording medium (magnetic disc, optical disc, and so forth), and so forth, for example. 
     DESCRIPTION OF REFERENCE CHARACTERS 
     
         
           1 : Hydraulic excavator 
           1 A: Front work implement (work implement) 
           1 B: Machine body 
           2 : Hydraulic pump 
           5 : Boom cylinder (actuator) 
           6 : Arm cylinder (actuator) 
           7 : Bucket cylinder (actuator) 
           8 : Boom 
           9 : Arm 
           10 : Bucket 
           11 : Lower track structure 
           12 : Upper swing structure 
           13 : Travelling lever 
           14 : Operation lever 
           15 : Operation device 
           17 : GNSS antenna 
           20 : Controller (controller) 
           21 : Boom angle sensor 
           22 : Arm angle sensor 
           23 : Bucket angle sensor 
           24 : Machine body inclination angle sensor 
           25 : Boom cylinder pressure sensor 
           26 : Arm cylinder pressure sensor 
           27 : Bucket cylinder pressure sensor 
           28 : Work implement posture sensing section 
           29 : Work equipment velocity estimating section 
           30 : Target surface distance and work equipment angle calculating section (angle calculating section) 
           31 : Guidance contents change section 
           31   a : Display mode deciding section 
           31   b : Bucket display position deciding section 
           31   c : Target surface display position deciding section 
           34 : Work implement posture sensor 
           35 : Target surface setting device 
           36 : Operator operation sensor 
           37 : Actuator state sensor 
           38 : Informing device 
           39 : Display device 
           40 : Sound output device 
           62 : Target surface 
           391 : Light bar 
           392 : Warning message