Crawler-type work machine

Abstract

A crawler-type work machine is provided. A bulldozer (1) has a controller (100) that maintains engagement of an inner turning clutch (40 IN ) for a prescribed time (t3-t1) after a switching start time point (t1) from the start of switching from a gentle turning mode to a spot turning mode, and maintains braking of an inner turning brake (50 IN ) for a prescribed time (t13-t11) after a switching start time point (t11) from the start of switching from the spot turning mode to the gentle turning mode.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a track-type work machine. BACKGROUND

[0002] Conventionally, a track-type work machine (e.g., a bulldozer or the like) having a left and right planetary gear mechanism, left and right oil pressure driven turning clutches, left and right oil pressure driven turning brakes, and a turning motor is known (see Patent Document 1).

[0003] The left and right planetary gear mechanism is disposed between an input shaft and left and right output shafts. The left and right turning clutches are rotatable about the input shaft, and switch transmission and cutoff of rotational power by the left and right planetary gear mechanism from the input shaft to the left and right output shafts. The left and right turning brakes brake the left and right output shafts. The turning motor rotates the left and right turning clutches by causing a difference in the number of rotations of the left and right output shafts.

[0004] The track-type work machine described in Patent Document 1 engages the left and right turning clutches, releases the left and right turning brakes, and drives the turning motor, thereby turning in a gentle turning mode.

[0005] The track-type work machine described in Patent Document 1 releases the inner turning clutch, brakes the inner turning brake, thereby turning in a turning-in-place mode.

[0006] PRIOR ART DOCUMENTS

[0007] PATENT DOCUMENT

[0008] Patent Document 1: Japanese Patent Application Publication No. S53-27929 SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] However, in order to prevent the inner turning brake from exhibiting a drag phenomenon when switching from the gentle turning mode to the turning-in-place mode, it is necessary to brake the inner turning brake after releasing the inner turning clutch. However, during the period from when the inner turning clutch is released until the inner turning brake actually exerts a braking force, a straight-ahead phenomenon occurs due to the accompanying rotation of the inner track caused by the driving of the outer track, and the turning radius momentarily increases.

[0011] Similarly, in order to prevent the inner turning brake from exhibiting a drag phenomenon when switching from the turning-in-place mode to the gentle turning mode, it is necessary to engage the inner turning clutch after releasing the inner turning brake. However, during the period from when the inner turning brake is released until the inner turning clutch actually engages, a straight-ahead phenomenon occurs due to the accompanying rotation of the inner track caused by the driving of the outer track, and the turning radius momentarily increases.

[0012] The present disclosure aims to provide a track-type work machine that can suppress an instantaneous increase in a turning radius at least one of when switching from a gentle turning mode to a spot turning mode and when switching from the spot turning mode to the gentle turning mode.

[0013] Technical solution for solving the technical problem

[0014] One aspect of the track-type work machine of the present disclosure has: left and right planetary gear mechanisms, left and right turning clutches, left and right turning brakes, a turning motor, and a controller. The left and right planetary gear mechanisms are disposed between an input shaft and left and right output shafts. The left and right turning clutches are rotatable about the input shaft, and switch transmission and cutoff of rotational power from the input shaft to the left and right output shafts by the left and right planetary gear mechanisms. The left and right turning brakes brake the left and right output shafts. The turning motor rotates the left and right turning clutches by causing a difference in the number of revolutions of the left and right output shafts. The controller turns the track-type work machine in any of a gentle turning mode and a spot turning mode by controlling the left and right turning clutches, the left and right turning brakes, and the turning motor. The left and right turning clutches and the left and right turning brakes are each driven by supplying hydraulic oil. In the gentle turning mode, the controller engages the left and right turning clutches, releases the left and right turning brakes, and drives the turning motor so that the number of revolutions of an inner side output shaft corresponding to a turning direction is lower than that of an outer side output shaft opposite to the turning direction among the left and right output shafts. In the spot turning mode, the controller releases an inner side turning clutch corresponding to a turning direction among the left and right turning clutches, brakes an inner side turning brake corresponding to the turning direction among the left and right turning brakes, and drives the turning motor so that the number of revolutions of the inner side output shaft is lower than that of the outer side output shaft. The controller maintains engagement of the inner side turning clutch or braking of the inner side turning brake for a predetermined time from when switching starts at least one of when switching from the gentle turning mode to the spot turning mode and when switching from the spot turning mode to the gentle turning mode.

[0015] Effects of the invention

[0016] According to the technology of the present disclosure, a track-type work machine that can suppress an instantaneous increase in a turning radius at least one of when switching from a gentle turning mode to a spot turning mode and when switching from the spot turning mode to the gentle turning mode can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a perspective view of a bulldozer that is an embodiment.

[0018] Figure 2 is a structural sectional view of a power transmission system of the bulldozer that is an embodiment.

[0019] Figure 3 is a system configuration diagram of a power transmission system of a bulldozer that is an embodiment.

[0020] Figure 4 is a graph showing an example of a state of the bulldozer at the time of switching from the gentle turning mode to the spot turning mode.

[0021] Figure 5 is a graph showing an example of a state of the bulldozer at the time of switching from the spot turning mode to the gentle turning mode.

[0022] Figure 6 is a system configuration diagram of a power transmission system of a bulldozer that is a first modified example. DETAILED DESCRIPTION

[0023] (Structure of bulldozer 1)

[0024] Figure 1 is a perspective view of a bulldozer 1 that is an example of a crawler-type work machine. Figure 2 is a sectional view of a structure of a power transmission system of the bulldozer 1. Figure 3 is a system configuration diagram of a power transmission system of the bulldozer 1.

[0025] As shown in Figure 1 , the bulldozer 1 has left and right traveling devices 4L, 4R including left and right sprockets 2L, 2R and left and right tracks 3L, 3R, a dozer blade 5 provided at a front portion of the vehicle, and a ripper device 6 provided at a rear portion of the vehicle.

[0026] The bulldozer 1 can perform a dozing work or the like using the dozer blade 5 and perform a breaking and excavating work or the like using the ripper device 6.

[0027] As shown in Figure 2 and Figure 3 , the bulldozer 1 has an engine 10, an engine power transmission portion 20, left and right planetary gear mechanisms 30L, 30R, left and right turning clutches 40L, 40R, left and right turning brakes 50L, 50R, left and right output shafts 60L, 60R, a turning motor 80, a motor power transmission portion 90, and a controller 100.

[0028] [Engine power transmission portion]

[0029] The engine power transmission portion 20 transmits power from the engine 10 to the left and right planetary gear mechanisms 30L, 30R. The engine power transmission portion 20 includes a power take-off 21, a torque converter 22, a transmission 23, a pinion 24, a bevel gear 25, and an input shaft 26.

[0030] The power output device 21 transmits power from the engine 10 to the torque converter 22. The torque converter 22 transmits, via fluid, the power of the engine 10 transmitted from the power output device 21 to the transmission 23. The transmission 23 has a plurality of speed gear clutches for speed-shifting the rotational power transmitted from the torque converter 22, and a direction gear clutch for switching between forward and reverse. The transmission 23 is linked to a pinion gear 24. Power from the transmission 23 is transmitted to an input shaft 26 via the pinion gear 24 and a bevel gear 25. The input shaft 26 extends in the left-right direction. The axial direction of the input shaft 26 is the same as the left-right direction of the bulldozer 1.

[0031] [Planetary gear mechanism]

[0032] The left-right planetary gear mechanisms 30L, 30R are disposed between the input shaft 26 and left-right output shafts 60L, 60R. The left-right planetary gear mechanisms 30L, 30R have left-right ring gears 31L, 31R, left-right planetary gears 32L, 32R, left-right sun gears 33L, 33R, and left-right carriers 34L, 34R.

[0033] The left-right ring gears 31L, 31R are linked to the input shaft 26. The left-right planetary gears 32L, 32R are disposed inside the left-right ring gears 31L, 31R in a radial direction perpendicular to the axial direction of the input shaft 26. The left-right planetary gears 32L, 32R mesh with the left-right ring gears 31L, 31R and the left-right sun gears 33L, 33R. The left-right sun gears 33L, 33R are rotatably attached with respect to the input shaft 26. The left-right sun gears 33L, 33R are disposed inside the left-right planetary gears 32L, 32R in the radial direction. The left-right sun gears 33L, 33R are linked to left-right turning clutches 40L, 40R. The left-right sun gears 33L, 33R can be separated / coupled from the motor power transmission portion 90 (specifically, left-right clutch gears 91L, 91R described later) via the left-right turning clutches 40L, 40R. The left-right carriers 34L, 34R are linked to the left-right planetary gears 32L, 32R and the left-right output shafts 60L, 60R.

[0034] [Turning clutch]

[0035] The left-right turning clutches 40L, 40R are disposed between the left-right planetary gear mechanisms 30L, 30R and the motor power transmission portion 90. The left-right turning clutches 40L, 40R separate / couple the left-right sun gears 33L, 33R possessed by the left-right planetary gear mechanisms 30L, 30R and the left-right clutch gears 91L, 91R possessed by the motor power transmission portion 90.

[0036] The left and right steering clutches 40L, 40R are driven by supplying hydraulic oil. The left and right steering clutches 40L, 40R are constituted by wet-type multiple-plate clutches that can be engaged and disengaged. In the present embodiment, the left and right steering clutches 40L, 40R are active hydraulic clutches. The left and right steering clutches 40L, 40R are disengaged when no hydraulic oil is supplied, are partially engaged when the oil pressure of the supplied hydraulic oil is less than a prescribed value, and are fully engaged when the oil pressure of the supplied hydraulic oil is equal to or greater than the prescribed value.

[0037] The oil pressure of the hydraulic oil supplied to the left and right steering clutches 40L, 40R is controlled by the left and right clutch control valves 27L, 27R. The left and right clutch control valves 27L, 27R are driven in accordance with a clutch oil pressure command input from the controller 100.

[0038] The left and right steering clutches 40L, 40R switch the transmission and interruption of rotational power from the input shaft 26 to the left and right output shafts 60L, 60R by the left and right planetary gear mechanisms 30L, 30R.

[0039] Specifically, when the left steering clutch 40L is engaged, the rotation of the input shaft 26 is transmitted to the left output shaft 60L via the left ring gear 31L, the left planetary gear 32L, and the left carrier 34L. On the other hand, when the left steering clutch 40L is disengaged, the left sun gear 33L becomes in a free rotation state, and the transmission of rotational power from the input shaft 26 to the left output shaft 60L is interrupted. Similarly, the right steering clutch 40R switches the transmission and interruption of rotational power from the input shaft 26 to the right output shaft 60R in accordance with engagement and disengagement.

[0040] Here, the left and right steering clutches 40L, 40R can rotate with the input shaft 26 as a center. The left and right steering clutches 40L, 40R rotate in mutually opposite directions using rotational power from the turning motor 80 transmitted via the motor power transmission portion 90.

[0041] For example, when the left steering clutch 40L is rotating in the forward direction and the right steering clutch 40R is rotating in the reverse direction in a state in which the left and right steering clutches 40L, 40R are engaged, the number of revolutions of the left output shaft 60L is higher than the number of revolutions of the right output shaft 60R, and the bulldozer 1 turns to the right gently.

[0042] In the present specification, gentle turning refers to advancing or retreating by making the left and right output shafts 60L, 60R that are rotating in the same direction have a difference in the number of revolutions, and tracing a curve with a relatively large turning radius.

[0043] Furthermore, when the left steering clutch 40L is engaged and the right steering clutch 40R is disengaged, and the left steering clutch 40L rotates forward, the left output shaft 60L rotates as the rotation of the right output shaft 60R stops, causing the bulldozer 1 to turn to the right in place. However, when the bulldozer 1 is turning to the right in place, as described later, the right steering brake 50R brakes the right output shaft 60R.

[0044] In this manual, turning in place means turning around the track on the other side by rotating one of the left and right output shafts 60L and 60R and bringing the other shaft to a complete stop.

[0045] like Figure 2 As shown, the right-turn clutch 40R has: multiple clutch discs 41, multiple clutch plates 42, and a clutch piston 43.

[0046] Each clutch disc 41 is mounted on the right clutch gear 91R. Each clutch plate 42 is fixed to the right sun gear 33R. Each clutch disc 41 and each clutch plate 42 are alternately arranged in the axial direction.

[0047] When the clutch piston 43 moves to the left as the working oil is supplied, each clutch disc 41 presses against each clutch plate 42, and the right steering clutch 40R engages. As a result, the right sun gear 33R of the right planetary gear mechanism 30R engages with the right clutch gear 91R of the motor power transmission unit 90.

[0048] On the other hand, when the clutch piston 43 moves to the right as the working oil is discharged, each clutch disc 41 separates from each clutch plate 42, and the right steering clutch 40R is released. As a result, the right sun gear 33R of the right planetary gear mechanism 30R separates from the right clutch gear 91R of the motor power transmission unit 90.

[0049] It should be noted that the left-turn clutch 40L has the same structure as the right-turn clutch 40R.

[0050] [Steering brake]

[0051] The left and right steering brakes 50L and 50R are actuated by supplying hydraulic fluid. The left and right steering brakes 50L and 50R are composed of wet multi-plate clutches that can be engaged and disengaged. In this embodiment, the left and right steering brakes 50L and 50R are passive hydraulic brakes. The left and right steering brakes 50L and 50R are fully engaged when no hydraulic fluid is supplied, partially engaged when the hydraulic fluid pressure is insufficient, and released when the hydraulic fluid pressure is above the specified value. When the left and right steering brakes 50L and 50R are engaged (fully or partially engaged), they generate braking force.

[0052] The hydraulic pressure of the working fluid supplied to the left and right steering brakes 50L and 50R is controlled by the left and right brake control valves 28L and 28R. The left and right brake control valves 28L and 28R are driven according to the brake hydraulic pressure command input from the controller 100.

[0053] The left and right steering brakes 50L and 50R brake the rotation of the left and right output shafts 60L and 60R.

[0054] Specifically, when the left turn brake 50L is engaged, the rotation of the left output shaft 60L is braked, thereby reducing the rotation of the left sprocket 2L. On the other hand, when the right turn brake 50R is engaged, the rotation of the right output shaft 60R is braked, thereby reducing the rotation of the right sprocket 2R.

[0055] like Figure 2 As shown, the right turn brake 50R includes: a rotating component 51, a brake housing 52, multiple fixed plates 53, multiple brake discs 54, and a brake piston 55.

[0056] The rotating component 51 is fixed to the right output shaft 60R and rotates together with the right output shaft 60R. The brake housing 52 is fixed relative to the rotating component 51. Each fixing plate 53 is mounted on the brake housing 52. Each brake disc 54 is fixed to the rotating component 51. The fixing plates 53 and the brake discs 54 are alternately arranged in the axial direction.

[0057] As the brake piston 55 moves to the left as the working fluid is filled, the retaining plates 53 separate from the brake discs 54, and the right turn brake 50R is released. On the other hand, as the brake piston 55 moves to the right as the working fluid is discharged, the retaining plates 53 press against the brake discs 54, and the right turn brake 50R generates braking force.

[0058] It should be noted that the left turn brake 50L has the same structure as the right turn brake 50R.

[0059] [Turn Motor]

[0060] The turning motor 80 is driven by the power of the engine 10. The turning motor 80 rotates in any direction, either forward or reverse. The rotation direction and speed of the turning motor 80 are controlled by the controller 100. The speed of the turning motor 80 varies from 0% to 100% (maximum value) based on the power transmitted from the engine 10.

[0061] The rotational power of the turning motor 80 is transmitted to the left and right turning clutches 40L, 40R via the motor power transmission portion 90. The turning motor 80 rotates the left and right turning clutches 40L, 40R by causing the left and right output shafts 60L, 60R to have a difference in number of rotations. For example, when the turning motor 80 reversely rotates the left and right turning clutches 40L, 40R in the case where the bulldozer 1 is gently turning to the right, the number of rotations of the left output shaft 60L is higher than that of the right output shaft 60R. Also, in the case where the bulldozer 1 is turning in place to the right, the turning motor 80 reversely rotates the left and right turning clutches 40L, 40R, but the right turning clutch 40R is released and the right turning brake 50R is applied, so the right output shaft 60R does not rotate and only the left output shaft 60L rotates.

[0062] [MOTOR POWER TRANSMISSION PORTION]

[0063] The motor power transmission portion 90 is disposed between the turning motor 80 and the left and right turning clutches 40L, 40R. The motor power transmission portion 90 transmits the rotational power of the turning motor 80 to the left and right turning clutches 40L, 40R.

[0064] The motor power transmission portion 90 has left and right clutch gears 91L, 91R, a first transmission gear 92, a lay shaft 93, a second transmission gear 94, an idler gear 95, and a pinion gear 96.

[0065] The left and right clutch gears 91L, 91R are separable / couplable to the left and right sun gears 33L, 33R via the left and right turning clutches 40L, 40R. The left and right clutch gears 91L, 91R are rotatable about the axial direction of the input shaft 26. The left clutch gear 91L is engaged with the idler gear 95. The right clutch gear 91R is linked to the idler gear 95 via the first transmission gear 92, the lay shaft 93, and the second transmission gear 94. The left and right clutch gears 91L, 91R rotate in mutually opposite directions when the turning motor 80 rotates.

[0066] The idler gear 95 is engaged with the left clutch gear 91L, the second transmission gear 94, and the pinion gear 96. The idler gear 95 is rotatable about the axial direction of the input shaft 26.

[0067] The pinion gear 96 is engaged with the idler gear 95. The pinion gear 96 is rotatable about a pinion gear shaft 96a. The pinion gear 96 rotates by the rotational power of the turning motor 80 transmitted via the pinion gear shaft 96a.

[0068] [CONTROLLER]

[0069] The controller 100 controls the number of rotations of the engine 10, the speed range clutch, and the direction range clutch of the transmission 23 in order to cause the bulldozer 1 to travel.

[0070] The controller 100 causes the bulldozer 1 to travel in any of the "straight travel mode", the "gentle turning mode", and the "spinning turning mode" by controlling the left and right turning clutches 40L, 40R, the left and right turning brakes 50L, 50R, and the turning motor 80.

[0071] The controller 100 is connected to the steering lever 35 for a steering operation of the bulldozer 1. The steering lever 35 can be operated in the left turning direction P2 and the right turning direction P3 from the neutral position PI as a reference.

[0072] The controller 100 causes the bulldozer 1 to travel in any of the "straight travel mode", the "gentle turning mode", and the "spinning turning mode" according to the operation direction and the operation amount of the steering lever 35.

[0073] In a case where the operation amount of the steering lever 35 is equal to or smaller than a first prescribed amount TH1, the controller 100 causes the bulldozer 1 to travel straight in the straight travel mode. In a case where the operation amount of the steering lever 35 is larger than the first prescribed amount TH1 and smaller than a second prescribed amount TH2, the controller 100 causes the bulldozer 1 to turn in the gentle turning mode. In a case where the operation amount of the steering lever 35 is equal to or larger than the second prescribed amount TH2, the controller 100 causes the bulldozer 1 to turn in the spinning turning mode.

[0074] The second prescribed amount TH2 is larger than the first prescribed amount TH1. The first and second prescribed amounts TH1, TH2 can each be set to a desired value. The first prescribed amount TH1 can also be "0".

[0075] • Straight travel mode

[0076] In the straight travel mode, the controller 100 controls the left and right clutch control valves 27L, 27R so that the left and right turning clutches 40L, 40R are fully engaged.

[0077] In the straight travel mode, the controller 100 controls the left and right brake control valves 28L, 28R so that the left and right turning brakes 50L, 50R are released.

[0078] In the straight travel mode, the controller 100 stops the turning motor 80.

[0079] • Gentle turning mode

[0080] In the gentle turning mode, the controller 100 controls the left and right clutch control valves 27L, 27R so that the left and right turning clutches 40L, 40R are engaged (typically, fully engaged).

[0081] In the gentle turning mode, the controller 100 controls the left and right brake control valves 28L, 28R so that the left and right turning brakes 50L, 50R are released.

[0082] In the gentle turn mode, the controller 100 drives the turn motor 80 with a number of revolutions of the inner output shaft 60 IN being lower than a number of revolutions of the outer output shaft 60 OUT as the operation amount of the steering lever 35 increases.

[0083] The inner output shaft 60 IN is an output shaft corresponding to the operation direction (i.e., the turn direction) of the steering lever 35 among the left and right output shafts 60L, 60R. The outer output shaft 60 OUT is an output shaft opposite to the operation direction of the steering lever 35 among the left and right output shafts 60L, 60R.

[0084] The controller 100 increases the number of revolutions of the turn motor 80 as the operation amount of the steering lever 35 increases. For example, the controller 100 can gradually increase the number of revolutions of the turn motor 80 in proportion to the operation amount of the steering lever 35, or can increase the number of revolutions of the turn motor 80 in stages according to the operation amount of the steering lever 35.

[0085] The number of revolutions of the turn motor 80 when the operation amount of the steering lever 35 is the second prescribed amount TH2 is not particularly limited as long as it is high enough, but is preferably 90% or more, more preferably 95% or more, and particularly preferably 100% (the maximum value).

[0086] • The spin turn mode

[0087] In the spin turn mode, the controller 100 controls the left and right clutch control valves 27L, 27R to release the inner steering clutch 40 IN and to engage (typically, fully engage) the outer steering clutch 40 OUT .

[0088] The inner steering clutch 40 IN is a steering clutch corresponding to the operation direction of the steering lever 35 among the left and right steering clutches 40L, 40R. The outer steering clutch 40 OUT is a steering clutch opposite to the operation direction of the steering lever 35 among the left and right steering clutches 40L, 40R.

[0089] In the spin turn mode, the controller 100 controls the left and right brake control valves 28L, 28R to brake the inner steering brake 50 IN and to release the outer steering brake 50 OUT .

[0090] The inner steering brake 50 IN is a steering brake corresponding to the operation direction of the steering lever 35 among the left and right steering brakes 50L, 50R. The outer steering brake 50 OUTis the steering brake opposite to the steering brake corresponding to the operation direction of the steering lever 35 among the left and right steering brakes 50L, 50R.

[0091] In the spin mode, the controller 100 maintains the number of revolutions of the turning motor 80 to the same degree as that of the gentle turning mode. The number of revolutions of the turning motor 80 is not particularly limited as long as it is high enough, but is preferably 90% or more, more preferably 95% or more, and particularly preferably 100%.

[0092] • Switching from the gentle turning mode to the spin mode

[0093] The controller 100, at the time of switching from the gentle turning mode to the spin mode, moves the inner side steering brake 50 IN from the released state to the applied state, and moves the inner side steering clutch 40 IN from the engaged state to the released state.

[0094] Figure 4 is a graph showing an example of the state of the bulldozer 1 at the time of switching from the gentle turning mode to the spin mode.

[0095] The controller 100, in order to move the inner side steering brake 50 IN from the released state to the applied state, outputs a brake oil pressure command to the inner side brake control valve 28 IN corresponding to the inner side steering brake 50 IN . The brake oil pressure command output from the switching start time point tl to the switching completion time point t4 is changed. The brake oil pressure indicated by the brake oil pressure command is changed from the maximum value before the switching start time point tl to the minimum value after the switching completion time point t4. The switching from the gentle turning mode to the spin mode is started at the switching start time point tl and completed at the switching completion time point t4.

[0096] In the inner side steering brake 50 IN , at the switching start time point tl, the working oil starts to be discharged, at the brake application start time point t3, the brake piston 55 starts to move, and at the switching completion time point t4, the brake piston 55 completes the movement. Therefore, the brake force of the inner side steering brake 50 IN is not generated from the switching start time point tl to the brake application start time point t3, but gradually increases from the brake application start time point t3 to the switching completion time point t4.

[0097] In addition, the controller 100, in order to move the inner side steering clutch 40 IN from the engaged state to the released state, outputs a clutch oil pressure command to the inner side clutch control valve 27 IN corresponding to the inner side steering clutch 40 IN . The clutch oil pressure command output is changed. In the gentle turning mode, the clutch oil pressure command is set to the maximum value, and in the spin mode, the clutch oil pressure command is set to the minimum value.Figure 4 In this case, the timing at which the controller 100 starts changing the clutch oil pressure command is not illustrated, but the clutch oil pressure indicated by the clutch oil pressure command is changed to the minimum value at the clutch release timing point t2.

[0098] The inside turning clutch 40 IN In this case, the clutch piston 43 completes the movement at the clutch release timing point t2. Therefore, the inside turning clutch 40 IN is released after being engaged (including full engagement and partial engagement) up to the clutch release timing point t2.

[0099] During the clutch release timing point t2 to the brake application start timing point t3, the inside turning clutch 40 IN and the inside turning brake 50 IN are both released. Therefore, the straight-ahead phenomenon occurs due to the accompanying rotation of the inside track 3 OUT by the drive of the outside track 3 IN corresponding to the turning direction among the left and right tracks 3L, 3R, and the turning radius momentarily increases.

[0100] As described above, at the time of switching from the gradual turning mode to the spot turning mode, the controller 100 maintains the engagement of the inside turning clutch 40 IN for a predetermined time (t3-t1) after the switching start timing point t1 at which the switching starts. Therefore, compared to the case where the inside turning clutch 40 IN is released before the switching start timing point t1, the time to release both the inside turning clutch 40 IN and the inside turning brake 50 IN can be shortened. Therefore, the increase in the turning radius due to the straight-ahead phenomenon occurring due to the accompanying rotation of the inside track 3 OUT by the drive of the outside track 3 IN can be suppressed.

[0101] In addition, at the time of switching from the gradual turning mode to the spot turning mode, the controller 100 releases the inside turning clutch 40 IN before the brake application start timing point t3 at which the brake force of the inside turning brake 50 IN begins to be generated. Therefore, the occurrence of the dragging phenomenon of the inside turning brake 50 IN can be suppressed.

[0102] • Switching from the spot turning mode to the gradual turning mode

[0103] The controller 100 releases the inside turning clutch 40 INmoves from the released state to the engaged state, and turns the inside turning brake 50 IN moves from the braked state to the released state.

[0104] Figure 5 is a graph showing an example of the state of the bulldozer 1 at the time of switching from the spot turn mode to the gradual turn mode.

[0105] The controller 100 causes the inside turning clutch 40 IN moves from the released state to the engaged state, and turns the inside turning brake 50 IN The corresponding inside clutch control valve 27 IN The output clutch oil pressure command is changed from the switching start time point t11 to the switching completion time point t14. The clutch oil pressure indicated by the clutch oil pressure command is changed from the minimum value before the switching start time point t11 to the maximum value after the switching completion time point t14. The switching from the spot turn mode to the gradual turn mode is started at the switching start time point t11 and completed at the switching completion time point t14.

[0106] In the inside turning clutch 40 IN , the working oil starts to be filled at the switching start time point t11, the clutch piston 43 starts to move at the clutch engagement start time point t13, and the clutch piston 43 completes the movement at the switching completion time point t14. Therefore, the inside turning clutch 40 IN is released from the switching start time point t11 to the clutch engagement start time point t13 and gradually engaged from the clutch engagement start time point t13 to the switching completion time point t14.

[0107] In addition, the controller 100 causes the inside turning brake 50 IN moves from the braked state to the released state, and turns the inside turning brake 50 IN The corresponding inside brake control valve 28 IN The output brake oil pressure command is changed. In Figure 5 , the time at which the controller 100 starts to change the brake oil pressure command is not shown, but the brake oil pressure indicated by the brake oil pressure command is changed to the maximum value at the brake release time point t12.

[0108] In the inside turning brake 50 IN , the brake piston 55 completes the movement at the brake release time point t12. Therefore, the inside turning brake 50 IN generates the braking force until the brake release time point t12 and is released after the brake release time point t12.

[0109] From the brake release time t12 to the clutch engagement start time t13, the inner steering clutch 40 IN and inner steering brake 50 IN Both were released. Therefore, due to the outer track 3... OUT The inner track 3 is generated by the drive IN Due to the rotation caused by the straight-line phenomenon, the turning radius temporarily increases slightly.

[0110] As described above, when switching from the stationary turning mode to the smooth turning mode, the controller 100 maintains the inner steering brake 50 for a specified time (t13-t11) after the switching start time t11. IN Therefore, the inner steering brake 50 is engaged before the switching start time t11. IN Compared to the previous release, it can shorten the release time of the inner steering clutch by 40 degrees. IN and inner steering brake 50 IN The time for both parties. Therefore, it is possible to suppress the effect due to the outer track 3 OUT The inner track 3 driven by the drive IN The straight-line phenomenon caused by the rotation of the vehicle increases the turning radius.

[0111] Additionally, when switching from stationary turning mode to smooth turning mode, the controller 100 engages the inner steering clutch 40. IN The inner steering brake is engaged 50 degrees before the clutch engagement start time t13. IN Release. Therefore, it is able to suppress the inner steering brake 50. IN A dragging phenomenon occurred.

[0112] (Modifications of the implementation method)

[0113] This invention is not limited to the embodiments described above. Various modifications or variations can be made without departing from the scope of this invention.

[0114] (First variation)

[0115] In the above embodiments, the controller 100 switches from a smooth turning mode to a stationary turning mode and vice versa based on the amount of operation of the steering lever 35, but is not limited thereto. The controller 100 may also switch from a smooth turning mode to a stationary turning mode if the amount of operation of the steering lever 35 is greater than a first predetermined amount TH1 and a stationary turning instruction is received from the operator. Furthermore, the controller 100 may also switch from a stationary turning mode to a smooth turning mode if a stationary turning instruction is not received from the operator while in the stationary turning mode.

[0116] Here,Figure 6 is a system configuration diagram of a power transmission system that the bulldozer 1a of the present modification example has. The bulldozer 1a has the same structure as the bulldozer 1 of the above-described embodiment except for having the in-place turning button 36.

[0117] The in-place turning button 36 is connected to the controller 100. The in-place turning button 36 receives an in-place turning instruction from an operator. When the in-place turning button 36 is pressed by the operator, the in-place turning button 36 sends the in-place turning instruction to the controller 100. The in-place turning button 36 can send the in-place turning instruction to the controller 100 during being pressed by the operator, or can continuously send the in-place turning instruction to the controller 100 until being pressed again by the operator.

[0118] The controller 100, in a case where the operation amount of the travel lever 35 is equal to or smaller than the first prescribed amount TH1, causes the travel mode of the bulldozer 1 to be the straight travel mode as described in the above-described embodiment.

[0119] The controller 100, in a case where the operation amount of the travel lever 35 is larger than the first prescribed amount TH1 and the in-place turning instruction is not received, causes the travel mode of the bulldozer 1 to be the gentle turning mode. The control of the controller 100 in the gentle turning mode is as described in the above-described embodiment.

[0120] The controller 100, in a case where the operation amount of the travel lever 35 is larger than the first prescribed amount TH1 and the in-place turning instruction is received, causes the travel mode of the bulldozer 1 to be the in-place turning mode. The control of the controller 100 in the in-place turning mode is as described in the above-described embodiment.

[0121] The control of the controller 100 at the time of switching from the gentle turning mode to the in-place turning mode, and at the time of switching from the in-place turning mode to the gentle turning mode is as described in the above-described embodiment.

[0122] (Second Modification Example)

[0123] In the above-described embodiment, the left and right turning clutches 40L, 40R are active hydraulic clutches, but can be passive hydraulic clutches.

[0124] (Third Modification Example)

[0125] In the above-described embodiment, the left and right turning brakes 50L, 50R are passive hydraulic brakes, but can be active hydraulic brakes.

[0126] (Fourth Modification Example)

[0127] In the above-described embodiment, the controller 100 executes the control for suppressing the increase in the turning radius at the time of switching from the gradual turning mode to the spot turning mode and at the time of switching from the spot turning mode to the gradual turning mode, but can execute the control only at the time of switching on either side.

[0128] (Fifth Modification)

[0129] In the above-described embodiment, the left and right output shafts 60L, 60R are coupled to the left and right sprockets 2L, 2R, but there can be left and right final reduction devices between the left and right output shafts 60L, 60R and the left and right sprockets 2L, 2R.

[0130] (Sixth Modification)

[0131] In the above-described embodiment, the controller 100 drives the turning motor 80 in the spot turning mode, but is not limited thereto. The controller 100 can not drive the turning motor 80 in the spot turning mode.

[0132] Explanation of Reference Numerals

[0133] 1 bulldozer; 10 engine; 20 engine power transmission part; 26 input shaft; 30L, 30R left and right planetary gear mechanisms; 31L, 31R left and right ring gears; 32L, 32R left and right planetary gears; 33L, 33R left and right sun gears; 34L, 34R left and right carriers; 40L, 40R left and right steering clutches; 50L, 50R left and right steering brakes; 60L, 60R left and right output shafts; 80 turning motor; 90 motor power transmission part; 91L, 91R left and right clutch gears; 92 first drive gear; 93 countershaft; 94 second drive gear; 95 idler gear; 96 pinion gear; 98 fixed member; 99 turning motor; 100 controller.

Claims

1. A tracked operating machine, characterized in that, have: The left and right planetary gear mechanism is configured between the input shaft and the left and right output shafts; The left and right steering clutches are rotatable about the input shaft, and switch the transmission and disconnection of rotational power from the input shaft to the left and right output shafts by the left and right planetary gear mechanisms. Left and right steering brakes, which brake the left and right output shafts; A steering motor that causes a speed difference between the left and right output shafts, thereby rotating the left and right steering clutches; The controller enables the tracked work machinery to turn in any mode, including a smooth turning mode and a stationary turning mode, by controlling the left and right steering clutches, the left and right steering brakes, and the turning motor. The left and right steering clutches and the left and right steering brakes are each driven by the supply of working oil. In the smooth turning mode, the controller engages the left and right steering clutches and releases the left and right steering brakes, causing the inner output shaft (corresponding to the turning direction) to rotate at a lower speed than the outer output shaft (opposite to the turning direction), thus driving the turning motor. In the stationary turning mode, the controller releases the inner steering clutch corresponding to the turning direction among the left and right steering clutches, and engages the inner steering brake corresponding to the turning direction among the left and right steering brakes. When the controller switches from the smooth turning mode to the stationary turning mode, or at least one of the switches from the stationary turning mode to the smooth turning mode, it maintains the engagement of the inner steering clutch or the braking of the inner steering brake for a predetermined period of time after the start of the switch.

2. The tracked work machinery as described in claim 1, characterized in that, When the controller switches from the smooth turning mode to the stationary turning mode, it releases the inner steering clutch after the switch begins and before the inner steering brake begins to generate braking force.

3. The tracked work machinery as described in claim 1 or 2, characterized in that, When the controller switches from the stationary turning mode to the smooth turning mode, it releases the inner steering brake after the switch begins and before the inner steering clutch begins to engage.

4. The tracked work machinery as described in claim 1, characterized in that, In the stationary turning mode, the controller drives the turning motor.

5. The tracked work machinery as described in claim 1, characterized in that, Each of the left and right planetary gear mechanisms has: A gear ring, which is connected to the input shaft; The sun gear, which is rotatably mounted on the input shaft, is connected to the steering clutch; A planetary gear, disposed between the ring gear and the sun gear; Planetary carrier, which is connected to the planetary gears and the output shaft.

6. The tracked work machinery as described in claim 5, characterized in that, have: The left and right clutch gears can be disengaged / engaged from the sun gears of the left and right planetary gear mechanisms via the left and right steering clutches, and rotate in opposite directions. The idler gear transmits the rotational power of the turning motor to the left and right clutch gears.

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