Tracked work machine

Abstract

To provide a crawler type working machine capable of inhibiting a temporary increase in a turning radius at least at one of time of switching from a slow turn mode into a pivotal turn mode and time of switching from the pivotal turn mode into the slow turn mode.SOLUTION: In a bulldozer 1, when switching from a slow turn mode to a pivotal turn mode, a controller 100 causes an inner steering clutch 40IN to maintain engagement for a predetermined period (t3-t1) from a switching start point t1 at which the switching is started, meanwhile, when switching from the pivotal turn mode to the slow turn mode, the controller causes an inner steering brake 50IN to maintain braking operation for a predetermined period (t13-t11) from a switching start point t11 at which the switching is started.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

[0002] Conventionally, there is known a track-type work machine (e.g., a bulldozer) that includes left and right planetary gear mechanisms, left and right hydraulically driven steering clutches, left and right hydraulically driven steering brakes, and a swing motor (see Patent Document 1).

[0003] The left and right planetary gear mechanisms are disposed 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 between transmitting and cutting off 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 steering brakes brake the left and right output shafts. The swing motor rotates the left and right steering clutches so as to generate a rotation speed difference between the left and right output shafts.

[0004] The track-type working machine described in Patent Document 1 turns in a gentle turning mode by engaging the left and right steering clutches, releasing the left and right steering brakes, and driving the turning motor.

[0005] The track-type work machine described in Patent Document 1 turns in a pivot turn mode by releasing the inside steering clutch and applying the inside steering brake. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 53-27929 Summary of the Invention [Problem to be solved by the invention]

[0007] Incidentally, when switching from the gentle turning mode to the pivot turning mode, in order to prevent the inner steering brake from dragging, it is necessary to apply the inner steering brake after releasing the inner steering clutch. However, after the inner steering clutch is released, until the braking force is actually generated in the inner steering brake, the inner crawler is rotated together with the driving of the outer crawler, causing a straight-line phenomenon, and the turning radius becomes temporarily large.

[0008] Similarly, when switching from the pivot turn mode to the gentle turn mode, in order to prevent the inner steering brake from dragging, it is necessary to engage the inner steering clutch after releasing the inner steering brake. However, after the inner steering brake is released, until the inner steering clutch is actually engaged, the inner crawler is rotated together with the drive of the outer crawler, causing a straight-line phenomenon, and the turning radius becomes temporarily large.

[0009] An object of the present disclosure is to provide a track-type work machine that can suppress a temporary increase in turning radius when switching from a gentle turning mode to a pivot turning mode, and / or when switching from the pivot turning mode to the gentle turning mode. [Means for solving the problem]

[0010] A track-type work machine according to one aspect of the present disclosure includes left and right planetary gear mechanisms, left and right steering clutches, left and right steering brakes, a swing 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 steering clutches are rotatable about the input shaft and switch between transmission and interruption 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 steering brakes brake the left and right output shafts. The swing motor rotates the left and right steering clutches so as to generate a difference in rotation speed between the left and right output shafts. The controller controls the left and right steering clutches, the left and right steering brakes, and the swing motor to swing the track-type work machine in either a gentle swing mode or a pivot swing mode. The left and right steering clutches and the left and right steering brakes are each driven by a supply of hydraulic oil. In the gentle turning mode, the controller engages the left and right steering clutches and releases the left and right steering brakes, and drives the turning motor so that the rotation speed of the inner output shaft corresponding to the turning direction of the left and right output shafts is lower than the rotation speed of the outer output shaft opposite to the turning direction. In the pivot turning mode, the controller releases the inner steering clutch corresponding to the turning direction of the left and right steering clutches, brakes the inner steering brake corresponding to the turning direction of the left and right steering brakes, and drives the turning motor so that the rotation speed of the inner output shaft is lower than the rotation speed of the outer output shaft. When switching from the gentle turning mode to the pivot turning mode or when switching from the pivot turning mode to the gentle turning mode, the controller maintains the engagement of the inner steering clutch or the braking of the inner steering brake for a predetermined period from the start of switching. Effect of the Invention

[0011] According to the technology disclosed herein, it is possible to provide a track-type work machine that can suppress a temporary increase in turning radius when switching from a gentle turn mode to a pivot turn mode, and / or when switching from the pivot turn mode to the gentle turn mode. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view of a bulldozer according to an embodiment. [Diagram 2] FIG. 2 is a cross-sectional configuration diagram of a power transmission system of the bulldozer according to the embodiment. [Diagram 3] 1 is a schematic system configuration diagram of a power transmission system of a bulldozer according to an embodiment of the present invention. [Figure 4] 11 is a graph showing an example of a state of a bulldozer when switching from a gentle turn mode to a pivot turn mode. [Diagram 5] 11 is a graph showing an example of a state of a bulldozer when switching from a pivot turn mode to a gentle turn mode. [Figure 6] FIG. 4 is a schematic system configuration diagram of a power transmission system of a bulldozer according to a first modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] (Bulldozer 1 Configuration) Fig. 1 is a perspective view of a bulldozer 1 which is an example of a track-type working machine. Fig. 2 is a cross-sectional configuration diagram of a power transmission system of the bulldozer 1. Fig. 3 is a schematic system configuration diagram of the power transmission system of the bulldozer 1.

[0014] As shown in FIG. 1, the bulldozer 1 is equipped with left and right traveling gears 4L, 4R including left and right sprockets 2L, 2R and left and right tracks 3L, 3R, a blade 5 provided at the front of the vehicle, and a ripper device 6 provided at the rear of the vehicle.

[0015] The bulldozer 1 can perform work such as pushing earth with the blade 5 and work such as crushing and excavation with the ripper device 6 .

[0016] As shown in Figures 2 and 3, the bulldozer 1 has an engine 10, an engine power transmission unit 20, left and right planetary gear mechanisms 30L, 30R, left and right steering clutches 40L, 40R, left and right steering brakes 50L, 50R, left and right output shafts 60L, 60R, a swing motor 80, a motor power transmission unit 90, and a controller 100.

[0017] [Engine power transmission section] The engine power transmission unit 20 transmits power from the engine 10 to the left and right planetary gear mechanisms 30L, 30R. The engine power transmission unit 20 includes a power take-off device (power take-off) 21, a torque converter 22, a transmission 23, a pinion 24, a bevel gear 25, and an input shaft 26.

[0018] The power take-off device 21 transmits the power from the engine 10 to the torque converter 22. The torque converter 22 transmits the power of the engine 10 transmitted from the power take-off device 21 to the transmission 23 via a fluid. The transmission 23 has a plurality of speed stage clutches for changing the speed of the rotational power transmitted from the torque converter 22, and a direction stage clutch for switching between forward and reverse. The transmission 23 is connected to a pinion 24. The power from the transmission 23 is transmitted to an input shaft 26 via the pinion 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 synonymous with the left-right direction of the bulldozer 1.

[0019] [Planetary gear mechanism] The left and right planetary gear mechanisms 30L, 30R are disposed between the input shaft 26 and the left and right output shafts 60L, 60R. The left and right planetary gear mechanisms 30L, 30R include left and right ring gears 31L, 31R, left and right planetary gears 32L, 32R, left and right sun gears 33L, 33R, and left and right carriers 34L, 34R.

[0020] The left and right ring gears 31L, 31R are connected to the input shaft 26. The left and right planetary gears 32L, 32R are disposed inside the left and right ring gears 31L, 31R in a radial direction perpendicular to the axial direction of the input shaft 26. The left and right planetary gears 32L, 32R mesh with the left and right ring gears 31L, 31R and the left and right sun gears 33L, 33R. The left and right sun gears 33L, 33R are rotatably attached to the input shaft 26. The left and right sun gears 33L, 33R are disposed inside the left and right planetary gears 32L, 32R in the radial direction. The left and right sun gears 33L, 33R are connected to the left and right steering clutches 40L, 40R. The left and right sun gears 33L, 33R can be connected to and disconnected from a motor power transmission unit 90 (specifically, left and right clutch gears 91L, 91R described later) via left and right steering clutches 40L, 40R. The left and right carriers 34L, 34R are connected to the left and right planetary gears 32L, 32R and the left and right output shafts 60L, 60R.

[0021] [Steering clutch] The left and right steering clutches 40L, 40R are disposed between the left and right planetary gear mechanisms 30L, 30R and the motor power transmission unit 90. The left and right steering clutches 40L, 40R connect and disconnect the left and right sun gears 33L, 33R of the left and right planetary gear mechanisms 30L, 30R and the left and right clutch gears 91L, 91R of the motor power transmission unit 90.

[0022] The left and right steering clutches 40L, 40R are driven by the supply of hydraulic oil. The left and right steering clutches 40L, 40R are configured as wet multi-plate clutches that can be engaged and disengaged. In this embodiment, the left and right steering clutches 40L, 40R are positive type hydraulic clutches. The left and right steering clutches 40L, 40R are disengaged when hydraulic oil is not supplied, partially engaged when the hydraulic oil pressure supplied is less than a predetermined value, and fully engaged when the hydraulic oil pressure supplied is equal to or greater than a predetermined value.

[0023] The hydraulic 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 response to a clutch hydraulic pressure command input from the controller 100.

[0024] The left and right steering clutches 40L, 40R switch between transmitting and cutting off the 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.

[0025] 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 released, the left sun gear 33L enters a free rotating state, and the transmission of rotational power from the input shaft 26 to the left output shaft 60L is cut off. Similarly, the right steering clutch 40R switches between transmitting and cutting off the rotational power from the input shaft 26 to the right output shaft 60R depending on whether it is engaged or released.

[0026] Here, the left and right steering clutches 40L, 40R are rotatable about the input shaft 26. The left and right steering clutches 40L, 40R are rotated in opposite directions by the rotational power from the swing motor 80 transmitted via the motor power transmission unit 90.

[0027] For example, when the left and right steering clutches 40L, 40R are engaged and the left steering clutch 40L rotates forward while the right steering clutch 40R rotates reversely, the rotation speed of the left output shaft 60L becomes higher than the rotation speed of the right output shaft 60R, and the bulldozer 1 makes a gentle turn to the right.

[0028] In this specification, gentle turning means moving forward or backward like drawing an arc with a relatively large turning radius by generating a difference in rotation speed between the left and right output shafts 60L, 60R which rotate in the same direction.

[0029] In addition, when the left steering clutch 40L rotates forward while the right steering clutch 40R is in the engaged state, the right output shaft 60R stops rotating and the left output shaft 60L rotates, causing the bulldozer 1 to make a right pivot turn. However, when the bulldozer 1 makes a right pivot turn, the right steering brake 50R brakes the right output shaft 60R, as described later.

[0030] In this specification, pivot turning means turning around the track on the other side as an axis by rotating one of the left and right output shafts 60L, 60R while substantially or completely stopping the other.

[0031] As shown in FIG. 2, the right steering clutch 40R has a plurality of clutch plates 41, a plurality of clutch discs 42, and a clutch piston 43.

[0032] Each clutch plate 41 is attached to the right clutch gear 91R. Each clutch disc 42 is fixed to the right sun gear 33R. Each clutch plate 41 and each clutch disc 42 are arranged alternately in the axial direction.

[0033] When the clutch piston 43 moves leftward with the supply of hydraulic oil, the clutch plates 41 and the clutch discs 42 are pressed against each other, engaging the right steering clutch 40R. This brings the right sun gear 33R of the right planetary gear mechanism 30R and the right clutch gear 91R of the motor power transmission unit 90 into engagement.

[0034] On the other hand, when the clutch piston 43 moves to the right as the hydraulic oil is discharged, the clutch plates 41 and the clutch discs 42 separate from each other, and the right steering clutch 40R is released. As a result, the right sun gear 33R of the right planetary gear mechanism 30R and the right clutch gear 91R of the motor power transmission unit 90 separate from each other.

[0035] The left steering clutch 40L has a similar structure to the right steering clutch 40R.

[0036] [Steering brake] The left and right steering brakes 50L, 50R are driven by the supply of hydraulic oil. The left and right steering brakes 50L, 50R are configured by wet multi-plate clutches that can be engaged and disengaged. In this embodiment, the left and right steering brakes 50L, 50R are negative type hydraulic brakes. The left and right steering brakes 50L, 50R are fully engaged when no hydraulic oil is supplied, partially engaged when the hydraulic pressure of the supplied hydraulic oil is less than a predetermined value, and disengaged when the hydraulic pressure of the supplied hydraulic oil is equal to or greater than the predetermined value. When the left and right steering brakes 50L, 50R are engaged (fully engaged or partially engaged), a braking force is generated in the left and right steering brakes 50L, 50R.

[0037] The hydraulic pressure of the hydraulic oil supplied to the left and right steering brakes 50L, 50R is controlled by the left and right brake control valves 28L, 28R. The left and right brake control valves 28L, 28R are driven in response to a brake hydraulic pressure command input from the controller 100.

[0038] The left and right steering brakes 50L, 50R brake the rotation of the left and right output shafts 60L, 60R.

[0039] Specifically, when the left steering brake 50L is engaged, the rotation of the left output shaft 60L is braked, thereby reducing the rotation of the left sprocket 2L, while when the right steering brake 50R is engaged, the rotation of the right output shaft 60R is braked, thereby reducing the rotation of the right sprocket 2R.

[0040] As shown in FIG. 2, the right steering brake 50R includes a rotating member 51, a brake housing 52, a plurality of fixed plates 53, a plurality of brake discs 54, and a brake piston 55.

[0041] The rotating member 51 is fixed to the right output shaft 60L and rotates together with the right output shaft 60R. The brake housing 52 is fixed to the rotating member 51. Each fixed plate 53 is attached to the brake housing 52. Each brake disc 54 is fixed to the rotating member 51. Each fixed plate 53 and each brake disc 54 are arranged alternately in the axial direction.

[0042] When the brake piston 55 moves leftward as hydraulic oil is charged, the fixed plates 53 and the brake discs 54 separate, and the right steering brake 50R is released. On the other hand, when the brake piston 55 moves rightward as hydraulic oil is discharged, the fixed plates 53 and the brake discs 54 are pressed against each other, and a braking force is generated in the right steering brake 50R.

[0043] The left steering brake 50L has a similar configuration to the right steering brake 50R.

[0044] [Rotation motor] The swing motor 80 is driven by the power of the engine 10. The swing motor 80 rotates in either a forward rotation direction or a reverse rotation direction. The rotation direction and rotation speed of the swing motor 80 are controlled by the controller 100. The rotation speed of the swing motor 80 varies from 0% to 100% (maximum value) according to the power transmitted from the engine 10.

[0045] The rotational power of the swing motor 80 is transmitted to the left and right steering clutches 40L, 40R via the motor power transmission unit 90. The swing motor 80 rotates the left and right steering clutches 40L, 40R so that a difference in rotation speed occurs between the left and right output shafts 60L, 60R. For example, when the bulldozer 1 makes a gentle right turn, if the swing motor 80 reversely rotates the left and right steering clutches 40L, 40R, the rotation speed of the left output shaft 60L becomes higher than the rotation speed of the right output shaft 60R. Also, when the bulldozer 1 makes a right pivot turn, the swing motor 80 reversely rotates the left and right steering clutches 40L, 40R, but the right steering clutch 40R is released and the right steering brake 50R is braked, so that the right output shaft 60R does not rotate and only the left output shaft 60L rotates.

[0046] [Motor power transmission section] The motor power transmission unit 90 is disposed between the swing motor 80 and the left and right steering clutches 40L, 40R. The motor power transmission unit 90 transmits the rotational power of the swing motor 80 to the left and right steering clutches 40L, 40R.

[0047] The motor power transmission unit 90 includes left and right clutch gears 91L and 91R, a first transfer gear 92, a counter shaft 93, a second transfer gear 94, an idler gear 95, and a pinion gear 96.

[0048] The left and right clutch gears 91L, 91R can be engaged with and disengaged from the left and right sun gears 33L, 33R via the left and right steering clutches 40L, 40R. The left and right clutch gears 91L, 91R can rotate about the axial direction of the input shaft 26. The left clutch gear 91L meshes with an idler gear 95. The right clutch gear 91R is connected to the idler gear 95 via a first transfer gear 92, a counter shaft 93, and a second transfer gear 94. When the swing motor 80 rotates, the left and right clutch gears 91L, 91R rotate in opposite directions.

[0049] The idler gear 95 meshes with the left clutch gear 91L, the second transfer gear 94, and the pinion gear 96. The idler gear 95 is rotatable about the axial direction of the input shaft 26.

[0050] The pinion gear 96 meshes with the idler gear 95. The pinion gear 96 is rotatable about a pinion shaft 96a. The pinion gear 96 is rotated by the rotational power of the swing motor 80 transmitted via the pinion shaft 96a.

[0051] [controller] The controller 100 controls the rotation speed of the engine 10 and the speed stage clutch and direction stage clutch of the transmission 23 in order to travel the bulldozer 1.

[0052] The controller 100 controls the left and right steering clutches 40L, 40R, the left and right steering brakes 50L, 50R, and the turning motor 80 to cause the bulldozer 1 to travel in any one of a "straight mode," a "gentle turn mode," or a "pivot turn mode."

[0053] The controller 100 is connected to a steering lever 35 used for steering the bulldozer 1. The steering lever 35 can be operated in a left turning direction P2 and a right turning direction P3 with respect to a neutral position P1.

[0054] The controller 100 causes the bulldozer 1 to travel in any one of a "straight ahead mode," a "gentle turn mode," and a "pivot turn mode" according to the direction and amount of operation of the steering lever 35.

[0055] When the operation amount of the steering lever 35 is equal to or less than the first predetermined amount TH1, the controller 100 moves the bulldozer 1 straight in the straight-ahead mode. When the operation amount of the steering lever 35 is greater than the first predetermined amount TH1 and less than the second predetermined amount TH2, the controller 100 turns the bulldozer 1 in the gentle turn mode. When the operation amount of the steering lever 35 is equal to or greater than the second predetermined amount TH2, the controller 100 turns the bulldozer 1 in the pivot turn mode.

[0056] The second predetermined amount TH2 is greater than the first predetermined amount TH1. Each of the first and second predetermined amounts TH1 and TH2 can be set to a desired value. The first predetermined amount TH1 may be "0".

[0057] -Straight line mode In the straight ahead mode, the controller 100 controls the left and right clutch control valves 27L, 27R to fully engage the left and right steering clutches 40L, 40R.

[0058] In the straight ahead mode, the controller 100 controls the left and right brake control valves 28L, 28R to release the left and right steering brakes 50L, 50R.

[0059] In the straight ahead mode, the controller 100 stops the swing motor 80 .

[0060] - Gentle turning mode In the gentle turning mode, the controller 100 controls the left and right clutch control valves 27L, 27R to engage (typically, fully engage) the left and right steering clutches 40L, 40R.

[0061] In the gentle turning mode, the controller 100 controls the left and right brake control valves 28L, 28R to release the left and right steering brakes 50L, 50R.

[0062] In the gentle turning mode, the controller 100 controls the inner output shaft 60 as the operation amount of the steering lever 35 increases. IN The rotation speed of the outer output shaft is 60 OUT The rotation motor 80 is driven so that the rotation speed is lower than that of the rotation speed of the rotor 14.

[0063] Inner output shaft 60 IN The outer output shaft 60 is one of the left and right output shafts 60L and 60R that corresponds to the operation direction of the steering lever 35 (i.e., the turning direction). OUTThis refers to the output shaft, of the left and right output shafts 60L, 60R, that is opposite to the operating direction of the steering lever 35.

[0064] The controller 100 increases the rotation speed of the swing motor 80 as the amount of operation of the steering lever 35 increases. For example, the controller 100 may gradually increase the rotation speed of the swing motor 80 in proportion to the amount of operation of the steering lever 35, or may increase the rotation speed of the swing motor 80 in stages according to the amount of operation of the steering lever 35.

[0065] The rotation speed of the swing motor 80 when the amount of operation of the steering lever 35 is the second predetermined amount TH2 is not particularly limited as long as it is sufficiently high, but is preferably 90% or more, more preferably 95% or more, and particularly preferably 100% (maximum value).

[0066] -Pivot turn mode In the pivot turn mode, the controller 100 controls the left and right clutch control valves 27L, 27R to activate the inner steering clutch 40. IN release the outer steering clutch 40 OUT is engaged (typically fully engaged).

[0067] Inner steering clutch 40 IN The outer steering clutch 40 is one of the left and right steering clutches 40L and 40R that corresponds to the operation direction of the steering lever 35. OUT This refers to the steering clutch of the left and right steering clutches 40L, 40R that is opposite to the operating direction of the steering lever 35.

[0068] In the pivot turn mode, the controller 100 controls the left and right brake control valves 28L, 28R to apply the inside steering brake 50. IN Brake the outside steering brake 50 OUT Release it.

[0069] Inside steering brake 50 INThe outer steering brake 50 is one of the left and right steering brakes 50L and 50R that corresponds to the operation direction of the steering lever 35. OUT This refers to the steering brake of the left and right steering brakes 50L, 50R that is opposite to the operating direction of the steering lever 35.

[0070] In the pivot turning mode, the controller 100 maintains the rotation speed of the turning motor 80 at approximately the same level as the rotation speed in the gentle turning mode. The rotation speed of the turning motor 80 is not particularly limited as long as it is sufficiently high, but is preferably 90% or more, more preferably 95% or more, and particularly preferably 100%.

[0071] -Switching from gentle turning mode to point turning mode When switching from the gentle turning mode to the pivot turning mode, the controller 100 activates the inside steering brake 50 IN The inner steering clutch 40 is shifted from the released state to the braking state. IN from an engaged state to a released state.

[0072] FIG. 4 is a graph showing an example of the state of the bulldozer 1 when switching from the gentle turn mode to the pivot turn mode.

[0073] The controller 100 controls the inside steering brake 50 IN to transition from a released to an engaged state. IN Inner brake control valve for 28 IN The brake oil pressure command output to the brake control unit 3 is changed from the switching start point t1 to the switching completion point t4. The brake oil pressure indicated by the brake oil pressure command is changed from a maximum value before the switching start point t1 to a minimum value after the switching completion point t4. The switching from the gentle turning mode to the pivot turning mode starts at the switching start point t1 and is completed at the switching completion point t4.

[0074] Inside steering brake 50 INIn this case, the discharge of hydraulic oil starts at the switching start point t1, the brake piston 55 starts to move at the braking start point t3, and the movement of the brake piston 55 is completed at the switching completion point t4. Therefore, the inside steering brake 50 IN The braking force is not generated from the switching start point t1 to the braking start point t3, and gradually increases from the braking start point t3 to the switching completion point t4.

[0075] The controller 100 also controls the inner steering clutch 40 IN to transition from an engaged state to a disengaged state. IN Control valve for inner clutch 27 IN 4 does not show the timing at which the controller 100 starts to change the clutch oil pressure command, but the clutch oil pressure indicated by the clutch oil pressure command is changed to its minimum value at the clutch release point t2.

[0076] Inner steering clutch 40 IN At the clutch release point t2, the movement of the clutch piston 43 is completed. IN The clutch is engaged (including full engagement and partial engagement) up to the clutch release point t2, and then is released after the clutch release point t2.

[0077] Between the clutch release point t2 and the brake start point t3, the inner steering clutch 40 IN and inside steering brake 50 IN Therefore, the outer track 3 corresponding to the turning direction of the left and right tracks 3L, 3R is opened. OUT Driven by inner track 3 IN The accompanying rotation causes a straight-line phenomenon, and the turning radius temporarily becomes slightly larger.

[0078] As described above, when switching from the gentle turning mode to the pivot turning mode, the controller 100 controls the inner steering clutch 40 to rotate for a predetermined period (t3-t1) from the switching start point t1 at which the switching is started. IN Therefore, before the switching start point t1, the inner steering clutch 40 is kept engaged. IN Compared to releasing the inner steering clutch 40 IN and inside steering brake 50 IN Therefore, the period during which both the outer track 3 and the outer track 4 are open can be shortened. OUT Driven by inner track 3 IN This can prevent the turning radius from becoming larger due to the straight-line phenomenon caused by the entrainment of the rotor.

[0079] In addition, when switching from the gentle turning mode to the pivot turning mode, the controller 100 applies the inside steering brake 50 IN The inner steering clutch 40 is engaged before the braking start point t3 at which the braking force of IN Therefore, the inside steering brake 50 is released. IN This can prevent the drag phenomenon from occurring.

[0080] Switching from Pivot Turn Mode to Gently Turn Mode When switching from the pivot turning mode to the gentle turning mode, the controller 100 controls the inner steering clutch 40 IN from a disengaged state to an engaged state, and the inside steering brake 50 IN from a braked state to a released state.

[0081] FIG. 5 is a graph showing an example of the state of the bulldozer 1 when switching from the pivot turn mode to the gentle turn mode.

[0082] The controller 100 controls the inner steering clutch 40 IN In order to transition the inner steering clutch 40 from a disengaged state to an engaged state, IN Control valve for inner clutch 27 INThe clutch oil pressure command output to the clutch oil pressure control unit 10 is changed from the switching start point t11 ​​to the switching completion point t14. The clutch oil pressure indicated by the clutch oil pressure command is changed from a minimum value before the switching start point t11 ​​to a maximum value after the switching completion point t14. The switching from the pivot turn mode to the gentle turn mode starts at the switching start point t11 ​​and completes at the switching completion point t14.

[0083] Inner steering clutch 40 IN In this case, the filling of the hydraulic oil starts at the switching start point t11, the clutch piston 43 starts to move at the clutch engagement start point t13, and the movement of the clutch piston 43 is completed at the switching completion point t14. Therefore, the inner steering clutch 40 IN is released from the switching start point t11 ​​to the clutch engagement start point t13, and is gradually engaged from the clutch engagement start point t13 to the switching completion point t14.

[0084] The controller 100 also controls the inside steering brake 50 IN In order to transition the inside steering brake 50 from a braking state to a released state, IN Inner brake control valve for 28 IN 4 does not show the timing at which the controller 100 starts to change the brake oil pressure command, but the brake oil pressure indicated by the brake oil pressure command is changed to its maximum value at the brake release point t12.

[0085] Inside steering brake 50 IN At the brake release point t12, the movement of the brake piston 55 is completed. IN The brake generates braking force up to the brake release point t12, and then is released after the brake release point t12.

[0086] Between the brake release point t12 and the clutch engagement start point t13, the inner steering clutch 40 INand inside steering brake 50 IN Therefore, both the outer tracks 3 OUT Driven by inner track 3 IN Due to the phenomenon of the wheel rotating in a straight line, the turning radius temporarily becomes slightly larger.

[0087] As described above, when switching from the pivot turn mode to the gentle turn mode, the controller 100 controls the inside steering brake 50 to be in a predetermined period (t13-t11) from the switching start point t11 ​​at which the switching is started. IN Therefore, the inside steering brake 50 is maintained before the switching start point t11. IN Compared to releasing the inner steering clutch 40 IN and inside steering brake 50 IN Therefore, the period during which both the outer track 3 and the outer track 4 are open can be shortened. OUT Driven by inner track 3 IN This can prevent the turning radius from becoming larger due to the straight-line phenomenon caused by the entrainment of the rotor.

[0088] In addition, when switching from the pivot turning mode to the gentle turning mode, the controller 100 controls the inner steering clutch 40 IN The inside steering brake 50 begins to engage before the clutch engagement start point t13. IN Therefore, the inside steering brake 50 is released. IN This can prevent the drag phenomenon from occurring.

[0089] (Modification of the embodiment) The present invention is not limited to the above-described embodiments, and various modifications and alterations are possible without departing from the scope of the present invention.

[0090] (Variation 1) In the above embodiment, the controller 100 switches from the gentle turn mode to the pivot turn mode and from the gentle turn mode to the gentle turn mode in response to the amount of operation of the steering lever 35, but this is not limited to the above. The controller 100 may switch from the gentle turn mode to the pivot turn mode in response to the amount of operation of the steering lever 35 being greater than the first predetermined amount TH1 and receiving a pivot turn instruction from the operator. Furthermore, the controller 100 may switch from the pivot turn mode to the gentle turn mode in response to no longer receiving a pivot turn instruction from the operator during the pivot turn mode.

[0091] 6 is a schematic system configuration diagram of a power transmission system provided in a bulldozer 1a according to this modification. The bulldozer 1a has the same configuration as the bulldozer 1 according to the above embodiment, except that it is provided with a pivot turn button 36.

[0092] The pivot turn button 36 is connected to the controller 100. The pivot turn button 36 receives a pivot turn instruction from an operator. When the pivot turn button 36 is pressed by the operator, the pivot turn button 36 transmits the pivot turn instruction to the controller 100. The pivot turn button 36 may transmit the pivot turn instruction to the controller 100 while it is being pressed by the operator, or may continue to transmit the pivot turn instruction to the controller 100 until it is pressed again by the operator.

[0093] When the operation amount of the steering lever 35 is equal to or less than the first predetermined amount TH1, the controller 100 sets the travel mode of the bulldozer 1 to the straight ahead mode, as described in the above embodiment.

[0094] When the operation amount of the steering lever 35 is greater than the first predetermined amount TH1 and a pivot turn command has not been received, the controller 100 sets the travel mode of the bulldozer 1 to the gentle turn mode. The control by the controller 100 in the gentle turn mode is as described in the above embodiment.

[0095] When the operation amount of the steering lever 35 is greater than the first predetermined amount TH1 and a pivot turn command is received, the controller 100 sets the travel mode of the bulldozer 1 to the pivot turn mode. The control by the controller 100 in the pivot turn mode is as described in the above embodiment.

[0096] The control by the controller 100 when switching from the gentle turning mode to the yaw turning mode and when switching from the yaw turning mode to the gentle turning mode is as described in the above embodiment.

[0097] (Variation 2) In the above embodiment, the left and right steering clutches 40L, 40R are positive type hydraulic clutches, but they may be negative type hydraulic clutches.

[0098] (Variation 3) In the above embodiment, the left and right steering brakes 50L, 50R are negative type hydraulic brakes, but they may be positive type hydraulic clutches.

[0099] (Variation 4) In the above embodiment, the controller 100 executes control to suppress an increase in turning radius when switching from the gentle turn mode to the yaw turn mode and when switching from the yaw turn mode to the gentle turn mode, but the control may be executed only when switching in either one of the modes.

[0100] (Variation 5) In the above embodiment, the left and right output shafts 60L, 60R are connected to the left and right sprockets 2L, 2R, but left and right final reduction gears may be interposed between the left and right output shafts 60L, 60R and the left and right sprockets 2L, 2R.

[0101] (Variation 6) In the above embodiment, the controller 100 drives the swing motor 80 in the pivot turn mode, but this is not limited to the above. The controller 100 does not have to drive the swing motor 80 in the pivot turn mode. [Explanation of symbols]

[0102] 1. Bulldozer 10 Engine 20 Engine power transmission section 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 Swivel motor 90 Motor power transmission section 91L, 91R Left and right clutch gears 92 1st transfer gear 93 Secondary shaft 94 2nd transfer gear 95 Idle Gear 96 Pinion Gear 98 Fixing member 99 Swing motor 100 Controller

Claims

1. left and right planetary gear mechanisms disposed between the input shaft and the left and right output shafts; left and right steering clutches that are rotatable about the input shaft and switch between transmission and interruption 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 for braking the left and right output shafts; a rotation motor that rotates the left and right steering clutches so that a rotation speed difference is generated between the left and right output shafts; a controller that controls the left and right steering clutches, the left and right steering brakes, and the turning motor to turn the track-type working machine in either a gentle turning mode or a pivot turning mode; Equipped with the left and right steering clutches and the left and right steering brakes are driven by a supply of hydraulic oil, the controller, in the gentle turning mode, engages the left and right steering clutches, releases the left and right steering brakes, and drives the turning motor so that the rotation speed of an inner output shaft corresponding to a turning direction among the left and right output shafts is lower than the rotation speed of an outer output shaft opposite to the turning direction; the controller, in the pivot turn mode, releases an inner steering clutch of the left and right steering clutches corresponding to the turning direction, and applies an inner steering brake of the left and right steering brakes corresponding to the turning direction, The controller maintains the engagement of the inner steering clutch or the application of the inner steering brake for a predetermined period from the start of switching at least one of when switching from the gentle turning mode to the pivot turning mode and when switching from the pivot turning mode to the gentle turning mode. Tracked work machine.

2. When switching from the gentle turning mode to the pivot turning mode, the controller releases the inner steering clutch after the start of switching and before the braking force of the inner steering brake starts to be generated.

2. The track-type working machine according to claim 1.

3. The controller releases the inner steering brake when switching from the pivot turn mode to the gentle turn mode after the switching starts and before the inner steering clutch begins to engage.

3. A track-type working machine according to claim 1 or 2.

4. The controller drives the turning motor in the pivot turning mode.

4. A track-type working machine according to claim 1.

5. Each of the left and right planetary gear mechanisms is A ring gear connected to the input shaft; a sun gear rotatably attached to the input shaft and connected to the steering clutch; a planetary gear disposed between the ring gear and the sun gear; a carrier connected to the planetary gear and the output shaft; having 5. A track-type working machine according to claim 1.

6. left and right clutch gears that can be engaged with and disengaged from the sun gears of the left and right planetary gear mechanisms via the left and right steering clutches and that rotate in opposite directions to each other; an idler gear that transmits the rotational power of the swing motor to the left and right clutch gears; Equipped with 6. A track-type working machine according to claim 5.

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