JP2004237981A5 - - Google Patents

Description

Agricultural work equipment steering device

  The present invention relates to a steering device for an agricultural work machine provided with a pair of left and right crawler-type traveling devices.

As the steering device, for example, as disclosed in Patent Literature 1, a pair of left and right crawler-type traveling devices are each provided with a side clutch, and one traveling device with the side clutch disengaged. Slow turning drive means for driving at a speed lower than the operating speed of the other traveling apparatus in which the side clutch is not disengaged in the same direction as the other traveling apparatus, and rapid turning drive means for braking one traveling apparatus with the side clutch disengaged. When the steering operation tool is operated in the first operation area deviated to one of left and right from the neutral position, the side clutch of one of the traveling devices is disengaged, and the operation is performed in the subsequent second operation area. When the traveling device with the side clutch disengaged is decelerated by the gentle turning drive means and further operated in the third operation area, the side clutch is disengaged. The running device so as to brake by the brake mechanism, the steering operation member and the side clutch, the slow rotation drive means, and, that in conjunction with said braking means is proposed.
JP-A-7-47973

  The steering device has a turning function gradually increased as the operation amount of the steering operation tool increases, and is effective in performing a smooth turning of the body. The relevance has not yet been fully considered. That is, in an agricultural work machine such as a combine machine, there are two types of machine steering during work traveling: steering for causing the machine to follow a crop line, and steering for largely changing the direction of a machine on a ridge.

  Here, in the steering for causing the aircraft to follow the crop row, carelessly steering the fuselage may damage the crop or cause crop leakage, and do not deviate from the crop row. It is necessary to pay attention to the steering operation. Also, in the steering for turning the aircraft largely at the ridge, if the steering of the aircraft is slow, the turning space becomes large, so that it is necessary to quickly make a small turn.

  The main object of the present invention is to provide a steering device which can easily perform a steering operation required for such an agricultural work machine.

  [Structure, operation and effect of the invention according to claim 1]

(Structure) The steering device for an agricultural working machine according to the first aspect of the present invention includes a pair of left and right crawler-type traveling devices, and a single steering operation tool has an operation range from a neutral position to one of left and right turning directions, In a steering device of a farm work machine having a plurality of operation areas , so that the turning function becomes higher as the distance from the neutral position increases, one traveling device is moved in the same direction as the other traveling device and at a lower speed than the other traveling device. The slow turning operation area in which the decelerating drive is performed to perform the slow turning is set to be larger than other operation areas of the plurality of operation areas .

(Operation) According to the above configuration, in the work traveling in the field, by slightly operating the steering operation tool in one of the left and right turning directions from the neutral position, the aircraft body steering is started , and it follows the row of crops. For normal steering, operation in the gentle turning operation range is sufficient. In this case, since the gentle turning operation area is larger than the other operating areas, the airplane accidentally deviates from the gentle turning operation area during normal steering to follow the crop line. Is less likely to be steered unduly large.

(Effects) Therefore, according to the first aspect of the invention, by appropriately setting the area of the operation area, it is possible to appropriately perform the aircraft steering during the work traveling without performing excessive steering. At the same time, it was possible to accurately and easily perform a small turn such as turning on a ridge or turning on a road, thereby improving the steering operability as an agricultural work machine.

  [Structure, operation and effect of the invention according to claim 2]

(Structure) The steering apparatus for an agricultural work machine according to the second aspect of the present invention is the same as the first aspect, except that a brake operation area is provided outside the gentle turning operation area.

(Operation) According to the above configuration, it is possible to stop the braking of one traveling device in which the side clutch is disengaged, and to make sure that the vehicle body can make a small turn by driving only the other traveling device in which the side clutch is not disengaged.

(Effects) Therefore, according to the invention of claim 2, the steering characteristics of each operation area can be made different from each other, so that the above-mentioned effect of the invention of claim 1 can be obtained, and the smoother and more accurate body steering can be achieved. Will be able to do.

  FIG. 1 is a right side view of a combine, which is an example of an agricultural working machine to which the present invention is applied. This combine combines a cutting pre-processing unit 3 with a front part of a traveling machine body 2 having a pair of right and left crawler-type traveling devices 1L and 1R so as to be able to move up and down, and a threshing device 4 and a grain tank on the machine body. 5, engine 6, control unit 7, etc.

  Hereinafter, the transmission structure of the traveling devices 1L and 1R will be described with reference to FIGS. 2, 3, and 4. However, the description in the left-right direction in the description is based on the left-right direction of the airframe, and when viewed from the front. Are opposite to the left and right directions in FIG.

  The power of the engine 6 is transmitted to a hydrostatic continuously variable transmission (HST) 8 as a main transmission capable of switching between forward and reverse, and the transmission output thereof is transmitted to a transmission case 9. The power input to the transmission case 9 is transmitted to the first shaft 10 via gears G1 and G2, and then transmitted to the auxiliary transmission mechanism 11 via gears G3 and G4. Further, of the power taken out of the case from the first shaft 10, only the forward rotation power is transmitted to the mowing pre-processing unit 3 via the one-way clutch OC. The hydrostatic continuously variable transmission 8 is operated by a main transmission lever 29 provided in the control unit 7.

  The sub-transmission mechanism 11 performs three-stage gear shifting in a constant mesh manner. The sub-transmission mechanism 11 includes a small-diameter gear G5, a medium-diameter gear G6, and a large-diameter gear G7, which are loosely mounted on the second shaft 12, and the third shaft 13 The gears G8, G9, and G10 fixed on the second shaft 12 are always engaged with each other, and the two shift sleeves S1 and S2 provided on the second shaft 12 are shifted so that one of the three normally meshed gear pairs is shifted. The transmission is configured to perform a speed change transmission from the second shaft 12 to the third shaft 13.

  That is, as shown in FIGS. 5 and 6, the shift sleeves S1 and S2 are provided with a pair of shift forks 15a and 15b provided on a shifter 15 which slides along a support shaft 14 horizontally supported in a transmission case. The shift sleeves S1 and S2 are simultaneously shifted in the same direction as the shifter 15 slides. An operation arm 16a that engages with the shifter 15 is provided at the tip of a shift operation shaft 16 that is mounted in the transmission case 9 in a front and rear direction. The shifter 15 is configured to slide left and right by rotating the speed change operation shaft 16.

  Here, the shift sleeve S1 is directly spline-engaged with the second shaft 12 throughout the shift range, whereas the shift sleeve S2 is fitted with the boss portion of the gear G6 and the spline externally fitted on the second shaft 12. The shift can be performed over the spline collar 17 and the boss portion of the gear G7, and the three-speed shift is performed as follows.

  When the shifter 15 is in the low speed "L" position, as shown in FIG. 7, the shift sleeve S1 is engaged with the boss of the gear G5 over the second shaft 12, and the shift sleeve S2 is engaged with the boss of the gear G6. , And the power of the second shaft 12 is transmitted to the third shaft 13 at a low speed via the shift sleeve S1 and the gears G5 and G8. When the shifter 15 is at the medium speed "M" position, as shown in FIG. 8, the shift sleeve S1 is supported only on the second shaft 12, and the shift sleeve S2 is connected to the boss of the gear G6 and the spline collar. 17, the power of the second shaft 12 is transmitted to the third shaft 13 at an intermediate speed via the spline collar 17, the shift sleeve S2, and the gears G6, G9. When the shifter 15 is in the neutral "N" position, as shown in FIG. 9, the shift sleeve S1 is supported only by the second shaft 12, and the shift sleeve S2 is supported by the spline collar 17 only. And the power transmission from the second shaft 12 to the third shaft 13 is shut off. When the shifter 15 is at the high speed "H" position, as shown in FIG. 10, the shift sleeve S1 is supported only on the second shaft 12, and the shift sleeve S2 is connected to the boss of the gear G7 and the spline collar 17 as shown in FIG. And the power of the second shaft 12 is transmitted at high speed to the third shaft 13 via the spline collar 17, the shift sleeve S2, the gears G7 and G10.

  As shown in FIG. 6, the shifter 15 uses a ball detent 18 to reduce the low speed “L”, which is the harvesting speed of the lodging culm, the medium speed “M”, which is the standard harvesting speed, and the neutral “N”. , And at a high speed “H” which is a moving speed.

  The power transmitted to the third shaft 13 as described above is transmitted to the center gear G11 of the fourth shaft 19 via the central gear G9, and then to the left and right side clutches 20L, 20R, the axle gear 21L, The power is transmitted to the left and right traveling devices 1L and 1R via the 21R and the axles 22L and 22R.

  As shown in FIG. 4, the side clutches 20L and 20R are loosely fitted to the fourth shaft 19 and shift the side clutch gears 23L and 23R always engaged with the axle gears 21L and 21R to shift the center gear G11. The power transmission from the center gear G11 to the axles 22L, 22R is interrupted by engaging and disengaging the center internal teeth from the side, and means for shifting the side clutch gears 23L, 23R are described below. It is configured as follows.

  The fourth shaft 19 is configured as a stepped shaft having a large diameter at a central portion, and the side clutch gears 23L and 23R are externally fitted over a large diameter portion and a small diameter portion of the fourth shaft 19. It is always slid by the spring 24 toward the center gear G11 and held at the clutch engaged position. The pressure oil is supplied via oil passages a and b formed inside the fourth shaft 19, so that the side clutch gears 23L and 23R shift to the clutch disengagement position against the spring 24. It is supposed to be. When the side clutch gears 23L, 23R are shifted to the clutch disengagement position disengaged from the center gear G11, the oil passages a, b for supplying the pressure oil are changed to oil passages formed inside the fourth shaft 19. d.

  Further, the side clutch gears 23L and 23R are further shifted beyond the clutch disengagement position where the engagement with the center gear G11 is disengaged, so that the steering side gears loosely fitted to both end portions of the fourth shaft 19 are mounted. An occlusal connection can be made from the side to 25L and 25R. The steering side gears 25L, 25R are engaged with the gears 27L, 27R fixed to both end portions of the fifth shaft 26, and the gear G13 loosely fitted to the fifth shaft 26 is connected to the center gear G11. The gear G12 is engaged with a small-diameter gear G12 connected to the side and is interlocked with the gear G12.

  Between the gear G13 and the fifth shaft 26, there is provided a multi-plate clutch C which performs gentle turning. In this clutch C, the piston 32 is normally retracted and returned by the spring 31 incorporated therein, the clutch C is maintained in the disengaged state, and the pressure oil is supplied through the oil passage c formed inside the fifth shaft 26. As a result, the piston 32 is displaced against the spring 31 and is switched to the clutch engaged state.

  Further, one end of the fifth shaft 26 is supported by a side cover 33 attached to the right side surface of the transmission case 9, and a multi-plate type braking mechanism B for controlling pivoting is provided on the side cover 33. ing. In the braking mechanism B, the ring-shaped piston 34 advances into the case by applying hydraulic pressure to displace the pressing plate 35 against the interior spring 36, so that the fifth shaft 26 has a friction braking action. In addition, the braking is released by releasing the application of the hydraulic pressure and returning and retreating the pressing plate 35 by the internal spring 36, and the piston 34 is provided with the hydraulic pressure attached to the outer surface of the side cover 33. It is incorporated in block 37.

  FIG. 11 shows a hydraulic circuit diagram and a control system diagram for steering for operating the side clutches 20L and 20R, the clutch C, and the braking mechanism B. In the figure, V1 is a steering switching valve for selectively shifting the side clutch gears 23L, 23R of the side clutches 20L, 20R, and is neutralized by a solenoid SL1 disposed outside the transmission case 9. And, three positions of the forward and reverse are selected. V2 is a mode switching valve for selectively supplying pressure oil to either the clutch C or the braking mechanism B to switch the turning mode, and is normally urged to a pressure oil supply position to the clutch C, and the transmission case 9 Can be switched to the pressure oil supply position to the brake mechanism B by a solenoid SL2 disposed outside the valve.

  V3 in FIG. 11 is a sequence valve connected to an oil passage d formed inside the fourth shaft 19, and its operating pressure is determined by the side clutch gears 23L and 23R of the side clutches 20L and 20R. The pressure is set to shift to the clutch disengagement position and balance with the spring 24. A variable relief valve V4 is connected to the lower side of the sequence valve V3, communicates with a transmission case 9 also serving as a hydraulic oil tank, and an oil passage branched from between the sequence valve V3 and the variable relief valve V4. e is connected to the primary side of the mode switching valve V2.

  The solenoid SL1 for operating the steering switching valve V1 and the solenoid SL2 for operating the mode switching valve V2 are connected to a steering lever 42 as a steering operation tool provided on a handle tower 41 of the steering section 7 via a control device 43. The variable relief valve V4 is mechanically linked to a steering lever 42.

  As shown in FIGS. 12 and 13, a support shaft 45 is mounted on a bracket 44 attached to the upper right side (as viewed from the driver) of the handle tower 41 so as to be rotatable and guided about a fulcrum x in the front-rear direction. The steering lever 42 is mounted on a fulcrum bracket 46 provided at the rear end of the support shaft 45 so as to be swingable about a lateral fulcrum y, and the steering lever 42 is configured to be able to swing crosswise. A first operating arm 47 formed by bending a bar into an L shape is projected from the fulcrum fitting 46, and a second operating arm 48 made of a plate is projected from near the front end of the supporting shaft 45. The first operation arm 47 is linked to a potentiometer 49 attached to the handle tower 41 as described below so that the operation position of the steering lever 42 is electrically detected.

  That is, the operating lever 49a of the potentiometer 49 is urged to rotate in the clockwise direction in FIG. 12 by a built-in spring so as to always contact the first operating arm 47 from the side. Is operated in the left or right direction from the neutral position n, the operation lever 49a rotates following the first operation arm 47 while maintaining the contact state, so that the operation position of the steering lever 42 is changed to the potentiometer 49. Is continuously detected as a change in the output, and the detection signal is input to the control device 43.

  The second operation arm 48 is linked to a release wire 50 for operating the variable relief valve V4 as follows. That is, a pair of operating arms 51 and 52 are loosely fitted to the support shaft 45, and the two operating arms 51 and 52 are urged by the torsion spring 53 to swing toward each other and provided on the bracket 44. It is abutted and supported so as to sandwich the fixing pin 54. The free end of one operating arm 51 is connected to and supported by the end of the outer wire 50a of the release wire 50. The free end of the other operating arm 52 is connected to the end of the inner wire 50b of the release wire 50. Are connected and supported. Further, an operation pin 48a provided at the free end of the second operation arm 48 which is swung around the fulcrum x in the front-rear direction by the steering lever 42 is provided between the two operation arms 51 and 52.

  According to the above configuration, for example, in FIG. 12, when the steering lever 42 is swung from the neutral position n to the right turning direction (leftward in the drawing), the second operation arm 48 is swung counterclockwise in the drawing. The pin 48a contacts and swings one operating arm 51 counterclockwise. At this time, since the other operation arm 52 is prevented from swinging counterclockwise by contact with the fixing pin 54, the inner wire 50b of the release wire 50 is relatively pulled out from the outer wire 50a. Conversely, when the steering lever 42 is pivoted from the neutral position n to the left turning direction (rightward in the figure), the second operation arm 48 is pivoted clockwise in the figure, and the operation pin 48a is moved to the other operation arm. The contact 52 is swung clockwise. At this time, since one of the operating arms 51 is prevented from swinging clockwise by contact with the fixing pin 54, the inner wire 50b of the release wire 50 is pulled out from the outer wire 50a. That is, even if the steering lever 42 is swung from the neutral position n to the left turning direction or the right turning direction, the inner wire 50b of the release wire 50 is pulled out according to the operation amount, and the wire drawing amount is large. It is linked so that the operating pressure of the variable relief valve V4 becomes higher as much as possible.

  The steering switching valve V1 and the sequence valve V3 are incorporated in the hydraulic block 37, and the mode switching valve V2 and the variable relief valve V4 are incorporated in the side cover 33, and are formed inside the hydraulic block 37 and the side cover 33. The hydraulic circuit shown in FIG. 11 is formed by communicating with each other through the oil passages. The operation structure of the steering switching valve V1, the mode switching valve V2, and the variable relief valve V4 will be described below in detail with reference to FIGS.

  As shown in FIGS. 14 to 16, the steering switching valve V 1 is an operation in which a spool 61 slidably mounted in the front-rear direction on an upper part of a hydraulic block 37 is swinged from the outside via a support shaft 62. The solenoid SL1 is configured to engage with the arm 63 to perform a sliding operation, and the solenoid SL1 is linked to a lever 64 mounted on the outer end of the support shaft 62.

  According to the above configuration, when the steering lever 42 is at the neutral position n, the solenoid SL1 is in a non-energized state, the spool 61 is held at the neutral position by the return spring 65, and the pressure oil supplied from the pump port P is drained. It is returned to the mission case 9 via the flow path D. When the steering lever 42 is operated in the left turning direction, this is detected by a potentiometer 49, the solenoid SL1 is pushed and driven, the spool 61 is slid leftward in FIG. The oil is supplied to the left-turn side clutch 20L via the oil passage a. When the steering lever 42 is operated in the right turning direction, this is detected by the potentiometer 49, the solenoid SL1 is pulled, and the spool 61 is slid to the right in FIG. The supplied pressure oil is supplied to the right-turn side clutch 20R via the oil passage b.

  As shown in FIGS. 4 and 17, the mode switching valve V2 is provided with an operation arm which is swingably mounted on the upper part of the side cover 33 from the outside via a support shaft 67 and is provided with a spool 66 slidably in the front-rear direction. The solenoid SL2 is connected to a lever 70 mounted on the outer end of the support shaft 67 by interlocking connection with the lever 69 by pressing and contacting at 68.

  According to this structure, when the solenoid SL2 is in the non-energized state, the spool 66 is at the position shown in FIG. 17, and the lower oil passage e of the sequence valve V3 is connected to the oil passage c reaching the clutch C. . When the solenoid SL2 is energized and pulled, the lever 70 swings counterclockwise in FIG. 17, the spool 66 is switched against the spring 69, and the oil passage e reaches the braking mechanism B. It is configured to communicate with the oil passage f.

  As shown in FIG. 17, the variable relief valve V4 has a poppet 71 incorporated in the upper part of the side cover 33 so as to be movable in the front-rear direction, and urges the poppet 71 to a valve seat 72 to press the oil. A spring 73 for blocking the passage e from communicating with the drain flow path D, and a spring receiving member 74 for supporting the rear end of the spring 73, and the spring receiving member 74 is externally fitted to the support shaft 67. The relief pressure can be adjusted by abuttingly pressing and slidingly displacing with an operation arm 76 that is oscillated from the outside via a cylindrical support shaft 75, so that the relief pressure can be adjusted. The inner wire 50b of the release wire 50 is interlockingly connected to a lever 77 attached to the end. The lever 77 is oscillated and biased by a torsion spring 78 in a direction to separate the operation arm 76 from the spring receiving member 74. As shown in FIG. At this time, the relief pressure of the variable relief valve V4 is almost zero. As described above, when the steering lever 42 is swung left and right to pull the inner wire 50b of the release wire 50, the operation arm 76 is swung counterclockwise in FIG. The relief pressure of the variable relief valve V4 gradually increases as the member 74 is pushed in and displaced, and the swing amount of the steering lever 42 increases and the wire pulling amount increases.

  In addition, the vertical movement of the steering lever 42 which can be operated in a cross direction causes the cutting pre-processing unit 3 to move up and down. That is, as shown in FIGS. 12 and 13, a sensor 81 including a potentiometer or a switch for detecting the forward / backward swing of the steering lever 42 and a forward / backward swing of the steering lever 42 are provided on the left and right sides of the extension of the lateral fulcrum y. A torsion spring 82 is provided to urge the neutral n in the moving direction. When the sensor 81 detects that the steering lever 42 has been swung forward from the neutral n, the mowing pre-processing unit 3 is lowered. When the sensor 81 detects that it has been swung backward, the sensor 81 and a drive elevating mechanism (not shown) of the pre-cutting unit 3 are linked so as to raise the pre-cutting unit 3. I have.

  Reference numeral 83 in FIG. 2 denotes a stop and parking brake which is provided to act on the end of the third shaft 13, and is operated by depressing a pedal 84 provided at the foot of the control unit 7. The main clutch (not shown) provided in the transmission system from the engine 6 to the hydrostatic continuously variable transmission 8 is disengaged, and the brake 83 is braked. The parking brake can be applied by locking and holding the pedal 84 at the depressed position.

  The steering apparatus according to the present invention is configured as described above, and the steering operation will be described below.

  When the steering lever 42 is at the neutral position n, both the side clutches 20L and 20R are in the clutch engaged state, the left and right crawler traveling devices 1L and 1R are driven at a constant speed, and the body travels straight.

  When the steering lever 42 is swung from the neutral position n to the right or left, for example, to the right, this is detected by the potentiometer 49 and the solenoid SL1 is energized to drive the steering switching valve V1 to the right turning position. Then, the pressure oil is supplied through the oil passage b, and the right side clutch 20R is disengaged. In this case, while the steering lever 42 is in the first operation range Rc near the neutral position n, the relief pressure of the relief valve V4 is lower than the operating pressure of the sequence valve V3. 23R is displaced only to the clutch disengagement position, the right crawler traveling device 1R enters the idle state, and the airframe gently turns rightward by driving only the left crawler traveling device 1L.

When the steering lever 42 is operated beyond the first operation range Rc to the second operation range Rs, the relief pressure of the leaf valve V4 becomes larger than the operation pressure of the sequence valve V3, and therefore, the side clutch gear The 23R is greatly displaced beyond the clutch disengagement position, and is engaged with the steering side gear 25R as shown in FIG. In this case, while the steering lever 42 is in the second operation range Rs, the solenoid SL2 is in a non-energized state, and the pressure oil passing through the sequence valve V3 can be supplied to the clutch C. The hydraulic pressure applied to C is limited by the relief valve V4. Therefore, as the steering lever 42 in the second operation range Rs is closer to the neutral n side, the hydraulic pressure applied to the clutch C is lower, the torque transmitted through the clutch C is smaller, and the right crawler traveling device 1R is It is driven at a lower speed and with a smaller torque than the crawler traveling device 1L. Then, as the steering lever 42 in the second operation range Rs moves away from the neutral position n, the hydraulic pressure applied to the clutch C increases, and the torque transmitted to the right crawler traveling device 1R via the clutch C gradually increases. Eventually, the clutch C is completely engaged, and the right crawler traveling device 1R is driven at a low speed at a reduced speed at a predetermined ratio. Turning.

  When the steering lever 42 is operated beyond the second operation range Rs to reach the third operation range Rb, this is detected by the potentiometer 49 and the solenoid SL2 is energized to drive the mode switching valve V2 to switch the oil passage e. Is connected to the oil passage f, the pressure oil is supplied to the braking mechanism B, the oil passage c is communicated with the drain passage D, and the clutch C is disengaged. In this case, since the relief pressure has already been increased due to the large operation of the steering lever 42, the fifth shaft 26 is braked by the braking mechanism B, and In a state where the braking of the crawler traveling device 1R is stopped, only the left crawler traveling device 1L is driven, and the machine body makes a sharp turn to the right (a pivot turn).

  Needless to say, even when the steering lever 42 is operated in the left turning direction, similarly to the above, in the first operation range Lc, a gentle left turning is performed by disengaging only the left side clutch 20L. In the second operation region Ls, the clutch C is engaged to perform a left turn by decelerating the left crawler traveling device 1L, and in the third operation region Lb, the left crawler traveling device 1L is braked. Makes a sharp turn to the left.

  Here, as shown in FIG. 12, the sizes of the first operation areas Lc and Rc, the second operation areas Ls and Rs, and the third operation areas Lb and Rb are determined by disengaging the side clutch on the inside of the turn. The first operation range Lc, Rc, which turns only by the thrust of the outer crawler traveling device, is the smallest, and the third operation region Lb, which stops the braking of the crawler traveling device inside the turning and turns only by the thrust of the outer crawler traveling device. , Rb are the next smallest, and the second operation ranges Ls, Rs, which are the most frequently operated by the crawler traveling device inside the turning crawler running at a reduced speed and the crawling traveling device outside the turning not decelerated, are set to be the largest.

  The present invention can be implemented in the following forms.

  (1) As shown in FIG. 18, when the steering lever 42 is in the third operation range Lb, Rb, a spring compressed by the steering lever 42 is used as a means for imparting resistance to the operation of the steering lever 42. If the arrangement is made so as to recognize the presence of the third operation area Lb, Rb from the increased operation resistance, careless operation to the third operation area Lb, Rb is avoided. It becomes easier.

  (2) As shown in FIG. 19, the steering operation tool 42 can be configured to be rotationally operated by swinging the steering lever 42b by turning the steering handle 42a.

Right side view of the whole combine Front view showing transmission structure of traveling mission case Longitudinal front view showing the upper half of the transmission case Longitudinal front view showing the lower half of the transmission case Side view showing the operation structure of the auxiliary transmission mechanism Longitudinal front view of the shifter that operates the sub transmission mechanism Longitudinal front view of a main part showing a state where the sub-transmission mechanism is switched to a low speed. Longitudinal front view of a main part showing a state where the sub-transmission mechanism is switched to a medium speed. Longitudinal front view of a main part showing a state where the auxiliary transmission mechanism is switched to neutral. Longitudinal front view of a main part showing a state in which the subtransmission mechanism is switched at a high speed. Configuration diagram of steering hydraulic circuit and control system Front view of steering operation unit Side view of steering operation unit Side view showing the steering control unit Longitudinal side view showing the periphery of the steering switching valve Front view showing the operation unit of the steering switching valve Longitudinal side view showing the periphery of the mode switching valve and the variable relief valve Front view showing another embodiment of the steering operation unit Front view showing still another embodiment of the steering operation unit

Explanation of reference numerals

1L, 1R Traveling device 20L, 20R Side clutch 42 Steering operating tool 47 Operating member 49 Potentiometer 49a Operating lever C Clutch Lc, Rc First operating region Ls, Rs Second operating region Lb, Rb Third operating region

Claims (2)

Equipped with a pair of left and right crawler-type traveling devices, a single steering operation tool has a plurality of operation areas in an operation area from the neutral position to one of the left and right turning directions so that the turning function becomes higher as the distance from the neutral position increases. In the steering device of the formed agricultural work machine,
A gentle turning operation area in which one traveling device is driven in the same direction as the other traveling device and at a lower speed than the other traveling device to perform a gentle turning, Agricultural work equipment steering device that is also set large .   The steering device for an agricultural work machine according to claim 1, wherein a brake operation area is provided outside the gentle turning operation area.