Patent Publication Number: US-2023134225-A1

Title: Steering device and work machine

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National stage application of International Application No. PCT/JP2021/010959, filed on Mar. 18, 2021. This U.S. National stage application claims priority under 35 U.S.C. § 119(a) to Japanese Patent Application No. 2020-055999, filed in Japan on Mar. 26, 2020, the entire contents of which are hereby incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a steering device and a work machine. 
     BACKGROUND INFORMATION 
     As an articulated work machine, a configuration is disclosed in which the steering angle is changed by controlling the flow rate of oil supplied to a hydraulic actuator arranged over a front frame and a rear frame (for example, see Japanese Laid-open Patent Application Publication No. 2020-026230). In the work machine shown in Japanese Laid-open Patent Application Publication No. 2020-026230, the flow rate of oil supplied to the hydraulic actuator changes based on the operation angle of the joystick lever from a predetermined position with respect to the base member rotatably supported by the support section, and steering angle is changed. The change in steering angle is transmitted to the base member via the transmission mechanism, and the base member also rotates in response to the change in steering angle. When the joystick lever returns to a predetermined position with respect to the base member due to the rotation of the base member, the change of the steering angle is stopped and the stopped steering angle is maintained. 
     SUMMARY 
     However, in the configuration of Japanese Laid-open Patent Application Publication No. 2020-026230, backlash may occur in a gear, an intermediate shaft, or the like provided in the transmission mechanism, and the base member may be in a state of being movable in the rotational direction. In this case, when the operator operates the joystick lever, the base member also rotates together, which causes looseness and deteriorates the operation feeling. 
     An object of the present disclosure is to provide a work machine and a steering device capable of improving the operation feeling. 
     The work machine according to the first disclosure includes a body, a movement transmission mechanism, a support section, a movable section, an operating member, and an urging mechanism. The movement transmission mechanism transmits a movement of the body. The support section is installed with respect to the body. The movable section is movably supported with respect to the support section. The movable section is connected to the movement transmission mechanism. A movement of the body is input to the movable section. The operating member receives an operation to move with respect to the movable section. The urging mechanism adjusts a movement of the movable section with respect to the support section. 
     The steering device according to the second disclosure includes a support section, a movable section, an operating member, and an urging mechanism. The support section can be installed with respect to the body. The movable section is movably supported with respect to the support section. The movable section is connected to a movement transmission mechanism that transmits a movement of the body. The movement of the body is input to the movable section. The operating member receives an operation to move with respect to the movable section. The urging mechanism adjusts the movement of the movable section with respect to the support section. 
     According to the present disclosure, it is possible to provide a work machine and a steering device capable of improving the operation feeling. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a side view showing a wheel loader of an exemplary embodiment according to the present disclosure. 
         FIG.  2    is a side view showing the vicinity of a cab of  FIG.  1   . 
         FIG.  3    is a configuration diagram showing a steering system of  FIG.  1   . 
         FIG.  4    is a diagram showing a counterforce of a spring member with respect to a difference between a lever angle and a base plate angle. 
         FIG.  5 A  is a diagram showing an example of a correspondence relationship between a vehicle body frame angle and a base angle. 
         FIG.  5 B  is a diagram showing an example of a correspondence relationship between a vehicle body frame angle and a base angle. 
         FIG.  6    is a block diagram showing input/output and calculation of the controller of  FIG.  3   . 
         FIG.  7 A  is a diagram showing a map of  FIG.  6   . 
         FIG.  7 B  is a diagram showing a map of  FIG.  6   . 
         FIG.  7 C  is a diagram showing a map of  FIG.  6   . 
         FIG.  8 A  is a view for explaining a control operation of the wheel loader of  FIG.  1   . 
         FIG.  8 B  is a view for explaining a control operation of the wheel loader of  FIG.  1   . 
         FIG.  8 C  is a view for explaining a control operation of the wheel loader of  FIG.  1   . 
         FIG.  8 D  is a view for explaining the control operation of the wheel loader of  FIG.  1   . 
         FIG.  8 E  is a view for explaining the control operation of the wheel loader of  FIG.  1   . 
         FIG.  8 F  is a view for explaining the control operation of the wheel loader of  FIG.  1   . 
         FIG.  9    is a flow chart showing a control operation of the wheel loader of  FIG.  1   . 
         FIG.  10    is a configuration diagram showing a steering system of a wheel loader of another exemplary embodiment according to the present disclosure. 
         FIG.  11    is a block diagram showing input/output and calculation of a controller of  FIG.  10   . 
         FIG.  12 A  is a diagram showing an example of the map of  FIG.  11   . 
         FIG.  12 B  is a diagram showing an example of the map of  FIG.  11   . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A wheel loader as an example of a work vehicle according to the present disclosure will be described below with reference to the drawings. 
     First Embodiment 
     Hereinafter, a wheel loader  1  of a first embodiment according to the present disclosure will be described. 
     &lt;Configuration&gt; 
     (Overview of Wheel Loader Configuration) 
       FIG.  1    is a schematic view showing the configuration of the wheel loader  1  of the present embodiment. The wheel loader  1  of the present embodiment includes a vehicle body frame  2  (an example of a body), a work implement  3 , a pair of front tires  4 , a cab  5 , an engine room  6 , a pair of rear tires  7 , a steering system  8 , steering cylinders  9   a  and  9   b  (see  FIG.  3   ), and a transmission mechanism  10  (an example of a movement transmission mechanism) (see  FIG.  3   ). 
     In the following explanations, “front,” “rear,” “right,” “left,” “up,” and “down” indicate directions relative to a state of looking forward from the driver&#39;s seat. “Vehicle width direction” and “left-right direction” have the same meaning. In  FIG.  1   , “X” indicates the front-back direction and “Xf” is used to indicate the forward direction and “Xb” is used to indicate the backward direction. In addition, the left-right direction is indicated with “Y,” and “Yr is used to indicate the rightward direction and “Yl” is used to indicate the leftward direction in the following drawings. 
     The wheel loader  1  carries out work, such as earth and sand loading, by using the work implement  3 . 
     The vehicle body frame  2  is a so-called articulated type and includes a front frame  11 , a rear frame  12 , and a coupling shaft portion  13 . The front frame  11  is disposed in front of the rear frame  12 . The front frame  11  corresponds to an example of a second frame, and the rear frame  12  corresponds to an example of a first frame. The coupling shaft portion  13  is provided at the center in the vehicle width direction and couples the front frame  11  and the rear frame  12  so as to be swingable with each other. The front tires  4  as the pair are attached to the left and right sides of the front frame  11 . The rear tires  7  as the pair are attached to the left and right sides of the rear frame  12 . 
     The work implement  3  is driven by hydraulic fluid from a work implement pump (not shown). The work implement  3  includes a boom  14 , a bucket  15 , a lift cylinder  16 , and a bucket cylinder  17 . The boom  14  is attached to the front frame  11 . The bucket  15  is attached to the tip of the boom  14 . 
     The lift cylinder  16  and the bucket cylinder  17  are hydraulic cylinders. One end of the lift cylinder  16  is attached to the front frame  11 , and the other end of the lift cylinder  16  is attached to the boom  14 . The boom  14  swings up and down due to the expansion and contraction of the lift cylinder  16 . One end of the bucket cylinder  17  is attached to the front frame  11 , and the other end of the bucket cylinder  17  is attached to the bucket  15  via the bell crank  18 . The bucket  15  swings up and down due to the expansion and contraction of the bucket cylinder  17 . 
     The cab  5  is disposed on the rear frame  12 , and a joystick lever  41  for steering operation (see  FIG.  2    described later), a lever for operating the work implement  3 , various display devices are arranged inside the cab  5 . The engine room  6  is disposed behind the cab  5  and on the rear frame  12 , and houses the engine. 
       FIG.  2    is a partial side view of the cab  5 . An operator&#39;s seat  19  is provided in the cab  5  and a console box  20  is disposed to the side of the operator&#39;s seat. An arm rest  20   a  is disposed on the upper side of the console box  20 . The joystick lever  41  is disposed extending upward from the front end portion of the console box  20 . The joystick lever  41  corresponds to an example of an operating member. 
       FIG.  3    is a configuration view showing the steering system  8 . The steering system  8  changes the vehicle body frame angle of the front frame  11  with respect to the rear frame  12  by changing the flow rate of the oil supplied to the steering cylinders  9   a  and  9   b , and changes the traveling direction of the wheel loader  1 . 
     The pair of steering cylinders  9   a  and  9   b  are hydraulically driven. The pair of steering cylinders  9   a  and  9   b  are disposed side by side on the left and right sides in the vehicle width direction with the coupling shaft portion  13  interposed therebetween. The steering cylinder  9   a  is disposed on the left side of the coupling shaft portion  13 . The steering cylinder  9   b  is disposed on the right side of the coupling shaft portion  13 . One end of each of the steering cylinders  9   a  and  9   b  is attached to the front frame  11 , and the other end of each of the steering cylinders  9   a  and  9   b  is attached to the rear frame  12 . 
     When the steering cylinder  9   a  expands and the steering cylinder  9   b  contracts due to the hydraulic pressure from the steering system  8  described later, the actual vehicle body frame angle θs_real changes and the vehicle turns to the right. Further, when the steering cylinder  9   a  contracts and the steering cylinder  9   b  expands due to the hydraulic pressure from the steering system  8 , the actual vehicle body frame angle θs_real changes and the vehicle turns to the left. In this embodiment, the actual vehicle body frame angle θs_real when the front frame  11  and the rear frame  12  are arranged along the front-rear direction is set to zero, the right side is set to a positive value, and the left side is set to a negative value. 
     (Transmission Mechanism  10 ) 
     The transmission mechanism  10  transmits information about the vehicle body frame angle θs_real of the front frame  11  with respect to the rear frame  12  to the steering device  22  of the steering system  8 . The transmission mechanism  10  of the first embodiment mechanically transmits information on the vehicle body frame angle θs_real to the steering device  22 . 
     The transmission mechanism  10  is mechanically connected to the vehicle body frame  2  and is connected to the movable section  40  of the steering system  8  described later. The transmission mechanism  10  transmits information on the vehicle body frame angle θs_real to the transmission section  45  of the movable section  40 . The transmission mechanism  10  includes one or more components  10   a  including a gear, an universal joint, an intermediate shaft or the like. Backlash occurs in these components  10   a.    
     (Steering System  8 ) 
     The steering system  8  includes an adjustment mechanism  21 , a steering device  22 , a controller  23 , and a vehicle speed sensor  24 . The adjustment mechanism  21  adjusts the drive outputs of the steering cylinders  9   a  and  9   b . The steering device  22  includes a joystick lever  41  and the like, and an operator inputs the steering rotation instruction angle of the wheel loader  1  to the steering device  22 . The controller  23  instructs the adjustment mechanism  21  to adjust the drive outputs of the steering cylinders  9   a  and  9   b  based on the steering rotation instruction angle input to the steering device  22 . The vehicle speed sensor  24  detects the vehicle speed V of the wheel loader  1  and transmits the vehicle speed V to the controller  23  as a detection signal. 
     In  FIG.  3   , the transmission of signals based on electricity is shown by a dotted line, and the transmission based on hydraulic pressure is shown by a solid line. The detection by the sensor is indicated by a two-dot chain line. 
     (Adjustment Mechanism  21 ) 
     The adjustment mechanism  21  adjusts the flow rate of the oil supplied to the steering cylinders  9   a  and  9   b . The adjustment mechanism  21  includes a hydraulic valve  31 , a main pump  32 , an electromagnetic pilot valve  33 , and a pilot pump  34 . 
     The hydraulic valve  31  is a flow rate adjusting valve that adjusts the flow rate of oil supplied to the steering cylinders  9   a  and  9   b  according to the input pilot pressure. As the hydraulic valve  31 , for example, a spool valve is used. The main pump  32  supplies the hydraulic fluid for operating the steering cylinders  9   a  and  9   b  to the hydraulic valve  31 . 
     The hydraulic valve  31  includes a valve body (not shown) that can be moved to a left steering position, a neutral position, and a right steering position. When the valve body is disposed at the left steering position in the hydraulic valve  31 , the steering cylinder  9   a  contracts, the steering cylinder  9   b  expands, the actual vehicle body frame angle θs_real becomes small, and the body turns to the left. 
     When the valve body is disposed at the right steering position in the hydraulic valve  31 , the steering cylinder  9   b  contracts, the steering cylinder  9   a  expands, the actual vehicle body frame angle θs_real becomes large, and the body turns to the right. When the valve body is disposed at the neutral position in the hydraulic valve  31 , the actual vehicle body frame angle θs_real does not change. 
     The electromagnetic pilot valve  33  is a flow rate adjusting valve that adjusts the flow rate or pressure of the pilot hydraulic pressure supplied to the hydraulic valve  31  in response to a command from the controller  23 . The pilot pump  34  supplies the hydraulic fluid for operating the hydraulic valve  31  to the electromagnetic pilot valve  33 . The electromagnetic pilot valve  33  is, for example, a spool valve or the like, and is controlled according to a command from the controller  23 . 
     The electromagnetic pilot valve  33  includes a valve body (not shown) that can be moved to the left pilot position, the neutral position, and the right pilot position. When the valve body is disposed at the left pilot position in the electromagnetic pilot valve  33 , the hydraulic valve  31  is in the state of the left steering position. When the valve body is disposed at the right pilot position in the electromagnetic pilot valve  33 , the hydraulic valve  31  is in the state of the right steering position. When the valve body is disposed at the neutral position in the electromagnetic pilot valve  33 , the hydraulic valve  31  is in the state of the neutral position. 
     As described above, the hydraulic valve  31  is controlled by controlling the pilot pressure or the pilot flow rate from the electromagnetic pilot valve  33  in response to the command from the controller  23  and the steering cylinders  9   a  and  9   b  are controlled. 
     (Steering Device  22 ) 
     As shown in  FIG.  3   , the steering device  22  includes a joystick lever  41 , a support section  42 , a movable section  40 , an urging member  44 , a lever angle sensor  46 , a vehicle body frame angle sensor  47 , and an urging mechanism  50 . 
     (Support Section  42 ) 
     The support section  42  is fixed to the frame  20   f  of the console box  20 . The support section  42  may be a portion of the frame of the console box  20 . Fixing the support section  42  does not have to be limited to the console box  20 , and it is preferable that the support section  42  can be fixed with respect to the vehicle body frame  2 . Further, fixing the support section  42  to the vehicle body frame  2  may means not only directly fixing the support section  42  to the vehicle body frame  2 , but also indirectly fixing the support section  42  to the vehicle body frame  2  via the another member (console box  20  as in the example of the present embodiment). Further, fixing the support section  42  to the vehicle body frame  2  may mean a configuration that the support section  42  is fixed to the vehicle body frame  2  only when the operator operates another member. 
     (Movable Section  40 ) 
     The movable section  40  is connected to the transmission mechanism  10 , and the operation of the vehicle body frame  2  is input to the movable section  40  via the transmission mechanism  10  so that the movable section  40  moves with respect to the support section  42 . 
     The movable section  40  includes a base member  43  and a transmission section  45 . 
     The base member  43  is rotatably supported by the support section  42 . The base member  43  includes, for example, a shaft  43   a  as shown in  FIG.  3   , and the shaft  43   a  is rotatably supported by the support section  42 . As a result, the base member  43  is rotatable about the shaft  43   a  with respect to the support section  42 . Further, the base member  43  is configured to be rotatable with respect to the support section  42  by using the configuration that the support section  42  includes a shaft, a through hole is formed in the base member  43 , and the shaft of the support section  42  inserts the through hole of the base member  43 . 
     The transmission section  45  is connected to the base member  43 . A transmission mechanism  10  is connected to the transmission section  45 . Information on the actual vehicle body frame angle θs_real, which is the rotation angle of the front frame  11  with respect to the rear frame  12 , is mechanically input to the transmission section  45 . The transmission section  45  transmits the input information to the base member  43 . The transmission section  45  rotates or moves together with the rotation of the base member  43 . For example, the transmission section  45  includes a joint that rotates together with the base member  43 , the transmission mechanism  10  includes a joint, and the joints are connected to each other to form a universal joint, thereby transmitting information on the vehicle body frame angle θs_real from the transmission mechanism  10  to the base member  43  via the transmission section  45 . 
     The joystick lever  41  is rotatably disposed with respect to the base member  43  or the support section  42 . The joystick lever  41  is configured to be rotatable with respect to the base member  43  by, for example, forming a through hole at base end of the joystick lever  41  and inserting the shaft  43   a  into the through hole. Further, the joystick lever  41  is configured to be rotatable with respect to the support section  42  by forming a shaft at the support section  42  and inserting the shaft into a through hole at the base end section of the joystick lever  41 . 
     (Urging Member  44 ) 
     The urging member  44  is a spring member, and is interposed between the joystick lever  41  and the base member  43 . The urging member  44  urges the joystick lever  41  to the base reference position  43   b  (an example of a predetermined position) with respect to the base member  43 . The urging member  44  applies a counterforce to both the case where the joystick lever  41  is rotated to the right from the base reference position  43   b  and the case where the joystick lever  41  is rotated to the left from the base reference position  43   b . When the operator is not gripping the joystick lever  41 , the joystick lever  41  is positioned at the base reference position  43   b  by the urging force from the left and right rotation directions. 
     (Regulation Section  48 ) 
     The base member  43  is provided with a regulation section  48  that regulates the operation range of the joystick lever  41 . 
     The regulation section  48  includes contact sections  481  and  482 . The contact sections  481  and  482  regulate the rotation range of the joystick lever  41  with respect to the base member  43  within a predetermined angle range. When the longitudinal direction of the joystick lever  41  is disposed at the base reference position  43   b , the rotation angle of the joystick lever  41  with respect to the base member  43  is set to zero, and the case where the joystick lever  41  is rotated to the right with respect to the base member  43  is represented by a plus, and the case where the joystick lever  41  is rotated to the left with respect to the base member  43  is represented by a minus. The actual relative angle θr_real of the joystick lever  41  with respect to the base member  43  is shown in  FIG.  3   . 
     When the joystick lever  41  is rotated to the right direction Yr with respect to the base member  43  and the actual relative angle θr_real of the joystick lever  41  with respect to the base member  43  reaches θ1 (positive value), the joystick lever  41  abuts on the contact section  481  of the base member  43  and the joystick lever  41  cannot be rotated to the right any more. Further, when the joystick lever  41  is rotated to the left direction Yl with respect to the base member  43  and θr_real reaches θ1′ (negative value), the joystick lever  41  abuts on the contact section  482  of the base member  43  and the joystick lever  41  cannot be rotated to the left any more. That is, the joystick lever  41  is set to be rotatable with respect to the base member  43  within the range of angles θ1′ to θ1. The predetermined angles θ1′ and θ1 correspond to catch-up angles. Further, the predetermined angles θ1 and θ1′ are set to, for example, 10 degrees and −10 degrees. The absolute value of the predetermined angle θ1 and the absolute value of the predetermined angle θ1′ may be the same value or may be different. 
     Further, the joystick lever  41  is regulated by the support section  42  in addition to the base member  43 . The support section  42  includes a regulation section  49  with which the joystick lever  41  abuts, and the regulation section  49  includes a right side contact portion  491  and a left side contact portion  492 . The support section  42  regulates the base member  43  within a predetermined angle of θ2′ (negative value) to θ2 (positive value) with respect to the support reference position  42   b . The values of the predetermined angles θ2′ and θ2 are set to, for example, −20 degrees and 20 degrees. The absolute value of the predetermined angle θ2′ and the absolute value of the predetermined angle θ2 may have the same value or may be different. 
       FIG.  4    is a view showing a counterforce applied to an actual relative angle θr_real of the joystick lever  41  with respect to the base member  43 . In  FIG.  4   , the horizontal axis shows the actual relative angle θr_real of the joystick lever  41  with respect to the base member  43 , and the vertical axis shows the counterforce. A positive value on the horizontal axis (relative angle) indicates the case where the joystick lever  41  is rotated to the right with respect to the base member  43 , and a negative value on the horizontal axis (relative angle) indicates the case where the joystick lever  41  is rotated to the left with respect to the base member  43 . A positive value on the vertical axis (counterforce) indicates a case where a counterforce is applied in the left rotation direction, and a negative value on the vertical axis (counterforce) indicates a case where a counterforce is applied in the right rotation direction. 
     While the actual relative angle θr_real is from 0° to θ 1 or from 0° to θ 1′, a counterforce is applied by the spring characteristics of the urging member  44 . As the initial counterforce, that is, when the joystick lever  41  is operated from the base reference position  43   b , a counterforce of F 1  or more is applied. As the absolute value of the actual relative angle θr_real increases, the counterforce applied to the operation of the joystick lever  41  also increases. When the actual relative angle θr_real reaches θ1 or θ1′, the counterforce increases linearly. This is because the joystick lever  41  abuts on the contact sections  481  and  482  of the base member  43 . 
     (Lever Angle Sensor  46 ) 
     The lever angle sensor  46  is composed of, for example, a potentiometer, and detects the actual lever angle θi_real of the joystick lever  41  with respect to the support section  42  as the detection value θi_detect of the lever angle. 
     Here, the support reference position  42   b  of the joystick lever  41  with respect to the support section  42  is shown in  FIG.  3   . When the longitudinal direction of the joystick lever  41  is maintained at the support reference position  42   b , the actual vehicle body frame angle θs_real is controlled by the adjustment mechanism  21  so as to become 0° and the front frame  11  is disposed along the front-back direction with respect to the rear frame  12 . When the joystick lever  41  is disposed at the support reference position  42   b , the rotation angle of the joystick lever  41  with respect to the support section  42  is set to zero, and the case where the joystick lever  41  is rotated to the right with respect to the support section  42  is represented by a plus, and the case where the joystick lever  41  is rotated to the left with respect to the support section  42  is represented by a minus. The controller  23  performs the control so that the actual vehicle body frame angle θs_real becomes a value corresponding to the actual lever angle θi_real of the joystick lever  41  from the support reference position  42   b . The actual base angle of the base member  43  with respect to the support section  42  is θb_real. The actual base angle θb_real corresponds to the rotation angle of the base reference position  43   b  of the base member  43  from the support reference position  42   b . Further, when the base reference position  43   b  is disposed at the support reference position  42   b , the rotation angle of the base member  43  with respect to the support section  42  is set to zero, and the case where the base member  43  is rotated to the right with respect to the support section  42  is represented by a plus, and the case where the base member  43  is rotated to the left with respect to the support section  42  is represented by a minus. 
     (Vehicle Body Frame Angle Sensor  47 ) 
     The vehicle body frame angle sensor  47  detects the actual vehicle body frame angle θs_real as the detection value θs_detect of the vehicle body frame angle. The vehicle body frame angle sensor  47  is disposed in the vicinity of the coupling shaft portion  13  arranged between the steering cylinders  9   a  and  9   b , or on the transmission mechanism  10  or on the shaft  43   a  of the base member  43 . The vehicle body frame angle sensor  47  is composed of, for example, a potentiometer, and the detection value θs_detect of the detected vehicle body frame angle is sent to the controller  23  as a detection signal. 
     A cylinder stroke sensor for detecting the stroke of the cylinder may be provided in each of the steering cylinders  9   a  and  9   b , the detection values of these cylinder stroke sensors may be sent to the controller  23 , and the detection value θs_detect of the vehicle body frame angle may be detected. 
     Further, since the vehicle body frame angle θs_real and the base angle θb_real, which is the rotation angle of the base member with respect to the support section  42 , have a corresponding positional relationship by the transmission mechanism  10 , the vehicle body frame angle sensor  47  may be provided on the shaft  43   a  of the base member  43 . This is because the vehicle body frame angle can be detected by detecting the rotation angle of the base member  43  with respect to the support section  42 . 
       FIGS.  5 A and  5 B  show an example of the correspondence between the vehicle body frame angle θs_real and the base angle θb_real. In the examples of  FIGS.  5 A and  5 B , the base angle θb_real can have a width of 20° while the vehicle body frame angle θs_real has a width of ±40°. 
     In  FIG.  5 A , the base angle θb_real has a proportional relationship with the vehicle body frame angle θs_real, and as the vehicle body frame angle θs_real increases, the base angle θb_real also increases. 
     In  FIG.  5 B , the graph is a curve. In the case where the absolute value of the vehicle body frame angle θs_real is small, the change in the base angle θb_real when the vehicle body frame angle θs_real changes is large. As the absolute value of the vehicle body frame angle θs_real becomes large, the change in the base angle θb_real when the vehicle body frame angle θs_real changes is small. 
     Further, a damper, friction, or both a damper and friction may be provided between the joystick lever  41  and the support section  42 , or between the joystick lever  41  and the base member  43 . 
     (Urging Mechanism  50 ) 
     The urging mechanism  50  adjusts the movement of the movable section  40  with respect to the support section  42 . The urging mechanism  50  is a pressurization mechanism and suppresses loose movement that does not depend on the movement of the front frame  11 . The loose movement means that when backlash occurs in the transmission mechanism  10 , the base member  43  of the movable section  40  moves in the rotational direction together with the operation of the joystick lever  41  regardless of the movement of the front frame  11 . 
     In the present embodiment, the urging mechanism  50  urges the base member  43  toward either one of the rotation directions. As shown in  FIG.  3   , the urging mechanism  50  includes one or more spring members  50   a . One end of the spring member  50   a  is connected to the support section  42 , and the other end of the spring member  50   a  is connected to the base member  43 . In  FIG.  3   , the spring member  50   a  urges the base member  43  by, for example, attracting the base member  43  in the left rotation direction. Not limited to this, the spring member  50   a  may urge the base member  43  by pushing the base member  43  in the right rotation direction. The position of the spring member  50   a  is not limited, and it is sufficient that the base member  43  can be urged in either the right rotation direction or the left rotation direction. 
     The urging force of the base member  43  by the urging mechanism  50  is set to be larger than the urging force of the urging member  44 . For example, when backlash occurs in the transmission mechanism  10  and the base member  43  is in a state of being movable in the rotational direction, the base member  43  rotates due to the urging force of the urging member  44  accompanying the operation of the joystick lever  41  and looseness occurs. Therefore, by setting the urging force of the base member  43  by the urging mechanism  50  to be larger than the urging force of the urging member  44 , the base member  43  is not rotated by the urging force of the urging member  44  accompanying the operation of the joystick lever  41 . Since it is possible to suppress the occurrence of looseness. 
     (Controller  23 ) 
       FIG.  6    is a block diagram showing input/output and calculation of the controller  23 . 
     The controller  23  includes a processor and a storage device. The processor is, for example, a CPU (Central Processing Unit). Alternatively, the processor may be a processor different from the CPU. The processor executes a process for controlling the wheel loader  1  according to a program. The storage device includes a non-volatile memory, such as ROM (Read Only Memory), and a volatile memory, such as RAM (Random Access Memory). The storage device may include an auxiliary storage device, such as a hard disk or an SSD (Solid State Drive). A storage device is an example of a non-transitory recording medium that is readable by computer. The storage device stores programs and data for controlling the wheel loader. 
     The detection value θi_detect of the lever angle sensor  46 , the detection value θs_detect of the vehicle body frame angle sensor  47 , and the vehicle speed V_detect detected by the vehicle speed sensor  24  are input to the controller  23 . The controller  23  outputs the electromagnetic pilot valve control current output i based on these values, and controls the electromagnetic pilot valve  33 . 
     The controller  23  includes the functions of the following sections by executing the program while using the input detection value and the data stored in the storage device. 
     The controller  23  includes a target angle calculation section  91 , an actual steering angle calculation section  92 , a pulse/vehicle speed conversion section  93 , a difference calculation section  94 , and an output calculation section  95 . 
     The lever angle detection value θi_detect is input to the controller  23  from the lever angle sensor  46 , and the target angle calculation section  91  calculates the target angle θtarget using the map M 1 . Further, the detection value θs_detect of the steering angle is input to the controller  23  from the vehicle body frame angle sensor  47 , and the actual steering angle calculation section  92  calculates the actual steering angle θactual using the map M 2 . The detection value V_detect of the vehicle speed is input to the controller  23  from the vehicle speed sensor  24 . The pulse/vehicle speed conversion section  93  converts the input pulse to the vehicle speed and calculates the vehicle speed signal V. 
     The difference calculation section  94  calculates the difference θdiff between the target angle θtarget and the actual steering angle θactual. Then, the output calculation section  95  calculates the electromagnetic pilot valve control current output i from the difference diff and the vehicle speed signal V using the map M 3 , and outputs the electromagnetic pilot valve control current output i to the electromagnetic pilot valve  33 . The maps M 1  to M 3  are stored in the storage device of the controller  23 . 
       FIG.  7 A  is a diagram showing an example of the map M 1 .  FIG.  7 B  is a diagram showing an example of the map M 2 .  FIG.  7 C  is a diagram showing an example of the map M 3 . 
     An example of the map M 1  shown in  FIG.  7 A  shows a graph of the relationship between the detection value θi_detect of the lever angle and the target angle θtarget. In this example, the detection value θi_detect of the lever angle and the target angle θtarget have a proportional relationship. Using this map M 1 , the controller  23  calculates the target angle θtarget from the detection value θi_detect of the lever angle. The target angle θtarget indicates a target angle of the vehicle body frame angle. Further, in the map M 1  of  FIG.  7 A , θtarget=2×θi_detect, but the present disclosure is not limited to this. 
     An example of the map M 2  shown in  FIG.  7 B  shows a graph of the relationship between the detection value θs_detect of the steering angle and the actual steering angle θactual. In this example, the detection value θs_detect of the steering angle and the actual steering angle θactual have a proportional relationship. Using this map M 2 , the controller  23  calculates the actual steering angle θactual from the detection value θs_detect of the steering angle. The actual steering angle θactual indicates the actual angle of the vehicle body frame angle. Further, in the map M 2  of  FIG.  7 B , θactual=1×θs_detect, and the value of θactual and the value of θs_detect are equal to each other, but the present disclosure is not limited to this. 
     An example of the map M 3  of  FIG.  7 C  represents an example of a curve showing the value of the electromagnetic pilot valve control current output i with respect to the deviation angle θdiff. 
     The controller  23  stores curves showing the value of the electromagnetic pilot valve control current output i with respect to the difference angle θdiff for a plurality of vehicle speeds. In an example of the map M 3  shown in  FIG.  7 C , for example, a curve C 1  (solid line) when the vehicle speed is 10 km/h, a curve C 2  (dotted line) when the vehicle speed is 20 km/h, and a curve C 3  (one-dot chain line) when the vehicle speed is 30 km/h) are set. The faster the vehicle speed, the smaller the value of the electromagnetic pilot valve control current output i. As a result, as the vehicle speed becomes faster, the speed at which the actual vehicle body frame angle θs_real changes (which can also be called the angular velocity) becomes slower, and high-speed stability can be improved. Further, when the vehicle speed becomes slower, the speed at which the actual vehicle body frame angle θs_real changes (which can be said to be an angular velocity) becomes faster, and the operability at a low speed can be improved. When the vehicle speed V is between C 1 , C 2 , and C 3 , the electromagnetic pilot valve control current output i is determined by the interpolation calculation. 
     The controller  23  transmits a current to the electromagnetic pilot valve  33  based on  FIG.  7 C . 
     Although omitted in  FIG.  3   , the controller  23  may control the main pump  32 , the pilot pump  34 , and the like. 
     Further, the transmission/reception of signals between the controller  23  and the vehicle body frame angle sensor  47 , the lever angle sensor  46 , the vehicle speed sensor  24 , and the electromagnetic pilot valve  33  may be performed wirelessly or by wire. 
     Further, the maps M 1  to M 3  may be linear or non-linear as long as the output is uniquely determined with respect to the input. 
     &lt;Operation&gt; 
     The control operation of the wheel loader  1  of the present embodiment will be described below.  FIGS.  8 A to  8 F  are views showing the operation of the steering device  22  and the state of the vehicle body frame  2 .  FIG.  9    is a flow chart showing the operation of the wheel loader  1  of the present embodiment. 
     As shown in  FIG.  8 A , in the state (also referred to as an initial position) where the base reference position  43   b  of the base member  43  coincides with the support reference position  42   b  of the support section  42 , and the longitudinal direction of the joystick lever  41  also coincides with the support reference position  42   b , the actual lever angle θi_real by the joystick lever  41  is zero. 
     At this time, the electromagnetic pilot valve  33  is in the neutral position. In this case, the hydraulic valve  31  is also in the neutral position. Therefore, the oil of the left and right steering cylinders  9   a  and  9   b  is not supplied or discharged, and the actual vehicle body frame angle θs_real is maintained at zero. As described above, since the actual vehicle body frame angle θs_real is also zero, the base member  43  is also located at the initial position. 
     Then, the operator applies an operating force Fin to rotate the joystick lever  41  to the right from the support reference position  42   b . When the operating force Fin exceeds the initial urging force F 1  of the urging member  44 , the joystick lever  41  rotates to the right and the actual lever angle θi_real increases, as shown in  FIG.  8 B . Since the relative angle θr_real with the base member  43  increases as the joystick lever  41  is moved to the right, the counterforce applied by the urging member  44  increases as shown in  FIG.  4   . 
     In step S 10 , the lever angle sensor  46  detects the actual lever angle θi_real of the joystick lever  41  operated by the operator as the detection value θi_detect of the lever angle. 
     Next, in step S 20 , the vehicle body frame angle sensor  47  detects the actual vehicle body frame angle θs_real as the detection value θs_detect of the vehicle body frame angle. 
     At this time, the actual vehicle body frame angle θs_real is in a zero state due to the delay in the reaction of the left and right steering cylinders  9   a  and  9   b . Therefore, the detection value θs_detect of the vehicle body frame angle, which is the detection value by the vehicle body frame angle sensor  47 , is zero. Since the actual vehicle body frame angle θs_real is almost zero, the base member  43  also does not rotate. Therefore, as shown in  FIG.  8 B , in the state where the joystick lever  41  is rotated to the right, the joystick lever  41  is in the state where it rotates to the right with respect to the base reference position  43   b  of the base member  43 . Further, the joystick lever  41  is urged to return to the base reference position  43   b  (which can also be said to be the support reference position  42   b  in the state of  FIG.  8 B ) by the urging member  44 . 
     Next, in step S 30 , the controller  23  converts the detection value θi_detect of the detected lever angle into the target angle θtarget using the map M 1  shown in  FIG.  7 A . Further, the controller  23  converts the detection value θs_detect of the vehicle body frame angle into the actual steering angle θactual using the map M 2  shown in  FIG.  7 B . Further, the controller  23  calculates the difference between the target angle θtarget and the actual steering angle θactual to obtain the difference angle θdiff. 
     Next, in step S 40 , the controller  23  performs conversion from the detection signal V_detect by the vehicle speed sensor  24  to obtain the vehicle speed V. 
     Next, in step S 50 , the controller  23  determines the electromagnetic pilot valve control current output i from the stored map M 3  shown in  FIG.  7 C  using the difference angle θdiff and the vehicle speed V, and give a command to the electromagnetic pilot valve  33 . 
     Since the joystick lever  41  is rotated to the right, the electromagnetic pilot valve  33  is in the right pilot position, and the pilot pressure controlled by the electromagnetic pilot valve  33  is supplied to the hydraulic valve  31 . By supplying the pilot pressure, the hydraulic valve  31  is in the right steering position, and the main hydraulic pressure is supplied to the steering cylinders  9   a  and  9   b  so as to extend the steering cylinder  9   a  and contract the steering cylinder  9   b.    
     As a result, the actual vehicle body frame angle θs_real gradually increases, and the front frame  11  is directed to the right with respect to the rear frame  12 . 
     This change in the actual vehicle body frame angle θs_real is reflected in the angle of the base member  43  via the transmission mechanism  10 . 
     That is, as shown in  FIG.  8 C , the angle of the base member  43  also rotates at a position corresponding to the vehicle body frame angle θs_real. In this way, when the base member  43  rotates toward the rotation position of the joystick lever  41 , the deviation angle θr_real between the actual lever angle θi_real and the actual base angle θb_real becomes smaller as shown in  FIG.  8 C . Therefore, the urging force of the urging member  44  becomes smaller. 
     As shown in  FIG.  8 D , when the operator stops the joystick lever  41  at a predetermined actual lever angle θi_real=θa, the actual vehicle body frame angle θs_real gradually increases, so that the difference angle θdiff becomes smaller. 
     Then, as shown in  FIG.  8 E , when the actual vehicle body frame angle θs_real moves and the base angle θb_real becomes θa, the difference angle θdiff becomes zero. At this time, the electromagnetic pilot valve  33  is in the neutral position, and the hydraulic valve  31  is also in the neutral position. Therefore, oil is not supplied or discharged to the left and right steering cylinders  9   a  and  9   b , and the actual vehicle body frame angle θs_real is maintained at θc obtained by converting the rotation angle θa according to  FIG.  5 A . Further, as shown in  FIG.  8 E , the base member  43  also rotates to the right by θa, and the joystick lever  41  is located at the base reference position  43   b  of the base member  43 . 
     Next, the operator returns the joystick lever  41  from the right side position (θi_real=θa) toward the support reference position  42   b  (θi_real=zero). As shown in  FIG.  8 F , the joystick lever  41  is rotated to the left so that the joystick lever  41  is located at the support reference position  42   b.    
     Before returning the joystick lever  41  to the support reference position  42   b  with respect to the support section  42  (state shown in  FIG.  8 E ), the positional relationship between the joystick lever  41  and the base member  43  is the same as that in  FIG.  8 A . Therefore, when the joystick lever  41  is moved, the counterforce at the start of movement is the same as the counterforce at the start of movement from the initial position. That is, in the present embodiment, since the base member  43  rotates to a position corresponding to the actual vehicle body frame angle θs_real, the counterforce applied to the operation is determined according to the state of the electromagnetic pilot valve  33  (neutral position, right pilot position, and left pilot position) regardless of the position of the joystick lever  41 . 
     At this time, the actual vehicle body frame angle θs_real is in the state of  6   c  due to the delay in the reaction of the left and right steering cylinders  9   a  and  9   b . Further, since the actual base angle θb_real of the base member  43  is θa as well as the actual vehicle body frame angle θs_real, the urging member  44  urges the joystick lever  41  with respect to the base member  43  so that the joystick lever  41  is in the state of  FIG.  8 E . 
     Since the actual vehicle body frame angle θs_real is in the state of θc as described above, the difference angle θdiff decreases from zero and becomes negative. Then, the electromagnetic pilot valve  33  is in the left pilot position, the pilot pressure is supplied to the hydraulic valve  31 , and the hydraulic valve  31  is in the left steering position. As a result, hydraulic pressure is supplied so that the steering cylinder  9   b  expands and the steering cylinder  9   a  contracts. 
     Due to this supply of the hydraulic pressure, the actual vehicle body frame angle θs_real gradually decreases from the rotation angle θc. This change in the actual vehicle body frame angle θs_real is reflected in the base member  43  via the transmission mechanism  10 , and the base member  43  also rotates in the same manner as the change in the actual vehicle body frame angle θs_real. 
     Then, when the actual vehicle body frame angle θs_real becomes zero, the difference from the actual lever angle θi_real (=0) becomes zero. At this time, the electromagnetic pilot valve  33  is in the neutral position, and the hydraulic valve  31  is also in the neutral position. Therefore, oil is not supplied or discharged to the left and right steering cylinders  9   a  and  9   b , and the actual vehicle body frame angle θs_real is also maintained at zero. As a result, the front frame  11  is returned to the direction along the front-back direction with respect to the rear frame  12 . 
     Further, as the actual vehicle body frame angle θs_real decreases, the base member  43  rotates so that the actual base angle θb_real also becomes zero, and returns to the initial position (θb_real=0) as shown in  FIG.  8 A . 
     When the joystick lever  41  is rotated to the left side, the operation is the same as above and is omitted. 
     Second Embodiment 
     Next, the wheel loader  1 ? in a second embodiment of the present disclosure will be described. The wheel loader of the second embodiment has a different transmission mechanism configuration from the wheel loader  1  of the first embodiment. Therefore, this difference will be mainly explained. 
       FIG.  10    is a view showing the configuration of the steering system  8  and the transmission mechanism  10 ′ of the second embodiment. 
     The transmission mechanism  10 ′ of the second embodiment transmits information on the vehicle body frame angle θs_real to the base member  43  via electrical means. 
     The transmission mechanism  10 ′ of the second embodiment includes an electric motor  61  and an output gear  62  (an example of a motor drive transmission section). The electric motor  61  is driven based on a command from the controller  23 ′. The output gear  62  is fixed to the output shaft of the electric motor  61  and meshes with the gear of the transmission section  45 . For example, backlash may occur between the output gear  62  and the gear of the transmission section  45 . 
       FIG.  11    is a block diagram showing the configuration of the controller  23 ′ of the second embodiment. The controller  23 ′ shown in  FIG.  11    is further provided with a base angle calculation section  96  and a command current conversion section  97  as compared with the controller  23  of the first embodiment. The base angle calculation section  96  calculates the target angle θb_target of the base member  43  from the detection value θs_detect of the vehicle body frame angle sensor  47  using the map M 4 . 
       FIGS.  12 A and  12 B  are diagrams showing an example of the map M 4 . 
     An example of the map M 4  of each of  FIGS.  12 A and  12 B  shows an example of the correspondence between the detection value θs_detect of the steering angle and the target angle θb_target of the base member  43 . In the map M 4  of  FIGS.  12 A and  12 B , the vehicle body frame angle θs_real on the horizontal axis of  FIGS.  5 A and  5 B  is replaced with the detection steering angle θs_detect, and the base angle θb_real on the vertical axis is replaced with the target angle θb_target of the base member  43 . 
     The command current conversion section  97  converts the target angle θb_target calculated by the base angle calculation section  96  into a command current value im to the electric motor  61 , and transmits the command current value im to the electric motor  51 . The electric motor  51  rotates the base member  43  based on the command current value im, and the actual base angle θb_real of the base member  43  becomes the target angle θb_target. 
     In this way, the controller  23 ′ transmits the command current value im to the electric motor  61  so that the base angle θb_real of the base member  43  becomes the target angle θb_target of the base member  43  calculated based on the map M 4 . The command from the controller  23 ′ to the electric motor  51  may be performed with wired or wireless. 
     The wheel loader of the first embodiment includes a vehicle body frame  2 , a transmission mechanism  10 , a support section  42 , a movable section  40 , a joystick lever  41 , and an urging mechanism  50 . The wheel loader of the second embodiment includes a vehicle body frame  2 , a transmission mechanism  10 ′, a support section  42 , a movable section  40 , a joystick lever  41 , and an urging mechanism  50 . The transmission mechanism  10  transmit the movement of the vehicle body frame  2 . The transmission mechanism  10 ′ transmit the movement of the vehicle body frame  2 . The support section  42  is fixed with respect to the vehicle body frame  2 . The movable section  40  is movably supported with respect to the support section  42  and is connected to the transmission mechanism  10 , and the movement of the vehicle body frame  2  is input the movable section  40 . The movable section  40  is movably supported with respect to the support section  42  and is connected to the transmission mechanism  10 ′, and the movement of the vehicle body frame  2  is input the movable section  40 . The joystick lever  41  receives an operation to move with respect to the movable section  40 . The urging mechanism  50  adjusts the movement of the movable section  40  with respect to the support section  42 . 
     By adjusting the movement of the movable section  40  using the urging mechanism  50  in this way, even when backlash occurs in the transmission mechanisms  10  and  10 ′, it is possible to prevent the movable section  40  from moving with the operation of the joystick lever  41 . Therefore, it is possible to suppress the occurrence of looseness when the operator operates the joystick lever  41 . 
     The support section  42  is preferably fixed with respect to the vehicle body frame  2 , but may be installed at least on the vehicle body frame  2 . 
     In the wheel loader  1  of the first embodiment, the movable section  40  includes a base member  43  and a transmission section  45 . The base member  43  is rotatably supported by the support section  42 . The transmission section  45  is connected to the transmission mechanism  10  and the base member  43 , and transmits the movement of the vehicle body frame  2  to the base member  43 . The wheel loader  1  further includes an urging member  44 . The urging member  44  is interposed between the base member  43  and the joystick lever  41 , and urges the joystick lever  41  to the base reference position  43   b  with respect to the base member  43 . 
     By adjusting the movement of either the base member  43  or the transmission section  45  with respect to the support section  42 , it is possible to prevent the base member  43  from moving with the operation of the joystick lever  41  even when backlash occurs in the transmission mechanism  10 . 
     In the wheel loaders  1  of the first and second embodiments, the urging mechanism  50  is disposed between the support section  42  and the base member  43 , and urges the base member  43  in either of the rotatable directions. 
     By urging the base member  43  to either one of the rotation directions in this way even when backlash occurs in the transmission mechanisms  10  and  10 ′, it is possible to prevent the base member  43  from moving with the operation of the joystick lever  41   
     In the wheel loaders  1  of the first and second embodiments, the urging mechanism  50  includes a spring member  50   a  connected to the support section  42  and the movable section  40 . 
     By urging the movable section  40  with such a spring member  50   a , it is possible to prevent the base member  43  from moving with the operation of the joystick lever  41  even when backlash occurs in the transmission mechanisms  10  and  10 ′. 
     In the wheel loaders  1  of the first and second embodiments, the vehicle body frame  2  includes the rear frame  12  and the front frame  11 . The front frame  11  rotates with respect to the rear frame  12 . The transmission mechanism  10  transmits the rotational movement of the front frame  11  with respect to the rear frame  12  to the movable section  40 . The transmission mechanism  10 ′ transmits the rotational movement of the front frame  11  with respect to the rear frame  12  to the movable section  40 . 
     This makes it possible to improve the operation feeling in the articulated wheel loader  1 . 
     The wheel loader  1  of the second embodiment further includes a vehicle body frame angle sensor  47 . The vehicle body frame angle sensor  47  detects the rotation angle of the front frame  11  with respect to the rear frame  12 . The transmission mechanism  10 ′ includes the electric motor  61  and the output gear  62 . The output gear  62  transmits the output of the electric motor  61  to the movable section  40 . The wheel loader  1  further includes a controller  23 ′. The controller  23 ′ drives the electric motor  61  based on the detection value θs_detect of the vehicle body frame angle sensor  47 . 
     As a result, in the articulated wheel loader  1 , the rotation angle of the front frame  11  with respect to the rear frame  12  can be transmitted to the movable section  40  via the electric motor  61 . 
     The steering device  22  of each of the first and second embodiments includes a support section  42 , a movable section  40 , a joystick lever  41 , and an urging mechanism  50 . The support section  42  can be fixed with respect to the vehicle body frame  2 . The movable section  40  is movably supported with respect to the support section  42  and is connected to transmission mechanism  10  that transmit the movement of the vehicle body frame  2 . The movable section  40  is movably supported with respect to the support section  42  and is connected to transmission mechanism  10 ′ that transmit the movement of the vehicle body frame  2 . The operation of the vehicle body frame  2  is input to the movable section  40 . The joystick lever  41  receives an operation to move with respect to the movable section  40 . The urging mechanism  50  adjusts the movement of the movable section  40  with respect to the support section  42 . 
     By adjusting the movement of the movable section  40  with the urging mechanism  50  in this way, even when backlash occurs in the transmission mechanisms  10  and  10 ′, it is possible to prevent the movable section  40  from moving with the operation of the joystick lever  41 . Therefore, it is possible to suppress the occurrence of looseness when the operator operates the joystick lever  41 . 
     The support section  42  is preferably fixed with respect to the vehicle body frame  2 , but may be installed at least on the vehicle body frame  2 . 
     OTHER EMBODIMENTS 
     While an embodiment of the present disclosure has been explained above, the present disclosure is not limited to the above embodiments and various changes are possible within the scope of the present disclosure. 
     In the above first and second embodiments, the spring member  50   a  of the urging mechanism  50  is provided between the support section  42  and the base member  43 , but is not limited to this, and the spring member  50   a  may be provided between the transmission section  45  and the support section  42  or the vehicle body frame  2 . One end of the spring member  50   a  is fixed to the transmission section  45 . The other end of the spring member  50   a  may be fixed to the support section  42  or the vehicle body frame  2 . The other end of the spring member  50   a  is not only directly fixed to the support section  42  or the vehicle body frame  2  but also indirectly fixed to the support section  42  or the vehicle body frame  2  via another member. 
     In the above first and second embodiments, the lever angle sensor  46  for detecting the rotation angle of the joystick lever  41  with respect to the support section  42  is provided, but instead of the lever angle sensor  46 , a lever/vehicle body frame difference angle sensor  146  that detects an angle of the joystick lever  41  with respect to the base member  43  may be provided. 
     The actual relative angle θr_real of the joystick lever  41  with respect to the base member  43  corresponds to the difference between the actual lever angle θi_real of the joystick lever  41  with respect to the support section  42  and the actual base angle θb_real of the base member  43  with respect to the support section  42 . The actual base angle θb_real of the base member  43  corresponds to the vehicle body frame angle θs_real by the transmission mechanism  10 . 
     Therefore, the difference angle θdiff can be calculated from the angle of the joystick lever  41  with respect to the base member  43  and the electromagnetic pilot valve control current output i can be determined, and a command can be given to the electromagnetic pilot valve  33 . 
     In the wheel loaders  1  of the above first and second embodiments, the vehicle body frame angle sensor  47  that detects the vehicle body frame angle θs_real is provided, but a base member angle sensor that detects the rotation angle of the base member  43  may be provided instead of the vehicle body frame angle sensor  47 . 
     While in the above first and second embodiments, the amount of oil supplied from the hydraulic valve  31  to the steering cylinders  9   a  and  9   b  is controlled according to the pilot pressure input from the electromagnetic pilot valve  33 , the oil from the electromagnetic pilot valve  33  may be directly supplied to the steering cylinders  9   a  and  9   b  without going through the hydraulic valve  31 . That is, an electromagnetic main valve may be used instead of the electromagnetic pilot valve  33 . 
     In the above first and second embodiments, the range of the base member angle (angle scale) and the range of the lever angle (angle scale) are narrower than the range of the vehicle body frame angle (angle scale), but may be the same as the range of the vehicle body frame angle or may be larger than the range of the vehicle body frame angle. However, it is preferable that the range of the base plate angle (angle scale) and the range of the lever angle (angle scale) is narrower than the range of the vehicle body frame angle (angle scale) because the operator&#39;s operation range is narrow and it is easy to operate. 
     In the above first and second embodiments, the wheel loader  1  has been described as an example of the work vehicle, but an articulated dump truck, a motor grader, or the like may be used. 
     In the above first and second embodiments, only the joystick lever  41  has been described, but a steering wheel may be provided. A signal due to the rotation of the steering wheel is input to the controller  23 , and the electromagnetic pilot valve  33  is operated based on the rotation. 
     The work machine and the steering device of the present disclosure have an effect capable of improving the operation feeling, and are useful as a wheel loader or the like.