Crawler-type construction machine

Abstract

In the bulldozer (1), the controller (110) causes the crawler-type construction machine to turn at one of a differential turning mode and a zero-radius 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). The controller (110) executes work oil amount control that, when the turning motor (80) is caused to turn, causes the work oil amount supplied from the hydraulic supply portion (100) to the turning motor (80) to decrease and the work oil amount supplied from the hydraulic supply portion (199) to the angle cylinder (8) and the lift cylinder (9) to increase when the angle cylinder (8) and the lift cylinder (9) are driven.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a crawler-type construction machine. BACKGROUND

[0002] Conventionally, a crawler-type construction machine (for example, a bulldozer or the like) provided with a left and right planetary gear mechanism, a left and right steering clutch of hydraulic drive type, a left and right steering brake of hydraulic drive type, and a steering motor is known (see Patent Literature 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 steering clutch is rotatable about the input shaft and switches transmission and cut-off of rotational power from the input shaft to the left and right output shafts by the left and right planetary gear mechanism. The left and right steering brakes brake the left and right output shafts. The steering motor rotates the left and right steering clutch in such a manner that the left and right output shafts generate a rotational speed difference.

[0004] The crawler-type construction machine described in Patent Literature 1 turns in a differential steering (slow swing) mode by engaging the left and right steering clutches, disengaging the left and right steering brakes, and driving the steering motor.

[0005] The crawler-type construction machine described in Patent Literature 1 turns in a spot steering mode by opening the inner side steering clutch and braking the inner side steering brake.

[0006] PRIOR ART DOCUMENTS

[0007] PATENT LITERATURE

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

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] The steering motor described in Patent Literature 1 is driven by hydraulic pressure discharged from a variable displacement hydraulic pump (hereinafter referred to as "steering motor pump") driven by power of an engine, but in Patent Literature 1, a case where the crawler-type construction machine is provided with a work device is not discussed.

[0011] Specifically, in a case where the steering motor is driven by the steering motor pump, power of the engine that can be distributed to the work device decreases, and thus the work performance of the work device can decrease.

[0012] An object of the present disclosure is to provide a crawler-type construction machine capable of suppressing a decrease in work performance of a work device.

[0013] SOLUTION TO PROBLEM

[0014] The track-type construction machine of one aspect of the present disclosure is provided with left and right planetary gear mechanisms, left and right steering clutches, left and right steering brakes, a steering motor, a work device hydraulic cylinder, a hydraulic supply portion, 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 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 steering brakes brake the left and right output shafts. The steering motor rotates the left and right steering clutches in a manner that causes the left and right output shafts to have a rotational speed difference. The work device hydraulic cylinder drives a work device mounted to a vehicle body. The hydraulic supply portion supplies working oil to the steering motor and the work device hydraulic cylinder. The controller causes the track-type construction machine to steer in one of a differential steering mode and a zero-radius steering mode by controlling the left and right steering clutches, the left and right steering brakes, and the steering motor. The controller executes working oil amount control that, when the work device hydraulic cylinder is driven with the steering motor being steered, reduces an amount of working oil supplied from the hydraulic supply portion to the steering motor and increases an amount of working oil supplied from the hydraulic supply portion to the work device hydraulic cylinder.

[0015] Effects of Invention

[0016] According to the technology of the present disclosure, it is possible to provide a track-type construction machine that can suppress a decrease in work device performance. BRIEF DESCRIPTION OF DRAWINGS

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

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

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

[0020] Figure 4 is a schematic system configuration view of the power transmission system of the bulldozer that is a modification example three. DETAILED DESCRIPTION

[0021] (External configuration of bulldozer 1)

[0022] Figure 1 is a perspective view of a bulldozer 1 that is an example of a track-type construction machine.

[0023] As shown in Figure 1 , the bulldozer 1 is provided with a vehicle body 2, a work device 3, and a left and right pair of track devices 1A.

[0024] The vehicle body 2 has a cab 4, an engine room 5, and a vehicle body frame (not shown). The cab 4 is disposed at the rear upper portion of the vehicle body 2. The engine room 5 is disposed in front of the cab 4.

[0025] The working device 3 is mounted to the vehicle body 2. The working device 3 has a blade 6, a frame 7, an angle cylinder 8, and a lift cylinder 9. The blade 6 is one example of the "working device" of the present disclosure. The blade 6 is disposed in front of the vehicle body 2. The blade 6 is supported by the frame 7. The front end of the frame 7 is rotatably mounted to the rear surface of the blade 6. The rear end of the frame 7 is rotatably supported to the side surface of the vehicle body 2.

[0026] The blade 6 is driven by the angle cylinder 8 and the lift cylinder 9. The angle cylinder 8 and the lift cylinder 9 are each one example of the "working device hydraulic cylinder" of the present disclosure.

[0027] The front end of the angle cylinder 8 is rotatably supported to the rear surface of the blade 6. The rear end of the angle cylinder 8 is rotatably supported to the side surface of the vehicle body 2. The angle cylinder 8 is extended and contracted by oil pressure, whereby the blade 6 is tilted in the front-rear direction.

[0028] The lower end of the lift cylinder 9 is rotatably supported to the upper surface of the frame 7. The intermediate portion of the lift cylinder 9 is rotatably supported to the side surface of the vehicle body 2. The lift cylinder 9 is extended and contracted by oil pressure, whereby the blade 6 is moved in the up-down direction.

[0029] The left and right pair of track devices 1A are traveling devices of the bulldozer 1. The left and right pair of track devices 1A are disposed in a manner of sandwiching the vehicle body 2.

[0030] The left and right pair of track devices 1A each have a track 2A, a drive wheel (sprocket) 3A, an idler wheel (pulley) 4A, and a track frame 5A.

[0031] The track 2A is configured in a ring shape (endless shape) and is wound around the drive wheel 3A and the idler wheel 4A. The track 2A is engaged with the drive wheel 3A and is rotated by the rotational drive of the drive wheel 3A.

[0032] The drive wheel 3A and the track frame 5A are each mounted to the side portion of the vehicle body 2. The drive wheel 3A is rotatably disposed in front of the track frame 5A. The idler wheel 4A is rotatably disposed at the front end portion of the track frame 5A.

[0033] (Internal structure of the bulldozer 1)

[0034] Figure 2 is a cross-sectional structure view of the power transmission system of the bulldozer 1. Figure 3 is a schematic system structure view of the power transmission system of the bulldozer 1.

[0035] As Figure 2 and Figure 3As shown, the bulldozer 1 has an engine 10, an engine power transmission portion 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 steering motor 80, a motor power transmission portion 90, a hydraulic pressure supply portion 100, and a controller 110.

[0036] [Engine power transmission portion]

[0037] 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 device (power output device) 21, a torque converter 22, a transmission 23, a pinion gear 24, a bevel gear 25, and an input shaft 26.

[0038] The power take-off device 21 distributes power of the engine 10 to the torque converter 22 and a variable displacement pump 101 described later. The torque converter 22 transmits power of the engine 10 transmitted from the power take-off device 21 to the transmission 23 via fluid. The transmission 23 has a plurality of speed stage clutches for speed-shifting the rotational power transmitted from the torque converter 22 and a direction stage clutch for switching forward and reverse. The transmission 23 is linked to the pinion gear 24. Power from the transmission 23 is transmitted to the input shaft 26 via the pinion gear 24 and the bevel gear 25. The input shaft 26 extends in the left and right directions. The axial direction of the input shaft 26 is synonymous with the left and right directions of the bulldozer 1.

[0039] [Planetary gear mechanism]

[0040] 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 have 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.

[0041] The left and right ring gears 31L, 31R are coupled 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 are engaged 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 with respect 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 coupled to the left and right steering clutches 40L, 40R. The left and right sun gears 33L, 33R can be decoupled or coupled to the motor power transmission portion 90 (specifically, the left and right clutch gears 91L, 91R described later) via the left and right steering clutches 40L, 40R. The left and right carriers 34L, 34R are coupled to the left and right planetary gears 32L, 32R and the left and right output shafts 60L, 60R.

[0042] [Steering clutch]

[0043] 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 portion 90. The left and right steering clutches 40L, 40R decouple or couple the left and right sun gears 33L, 33R possessed by the left and right planetary gear mechanisms 30L, 30R and the left and right clutch gears 91L, 91R possessed by the motor power transmission portion 90.

[0044] The left and right steering clutches 40L, 40R are driven by the supply of working oil. The left and right steering clutches 40L, 40R are constituted by wet-type multi-plate clutches that can be coupled and decoupled. In the present embodiment, the left and right steering clutches 40L, 40R are positive-type hydraulic clutches. The left and right steering clutches 40L, 40R are decoupled when working oil is not supplied, are partially coupled when the hydraulic pressure of the supplied working oil is less than a prescribed value, and are fully coupled when the hydraulic pressure of the supplied working oil is the prescribed value or more.

[0045] The hydraulic pressure of the working 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 hydraulic pressure command input from the controller 110.

[0046] The left and right steering clutches 40L, 40R switch the transmission and the cutoff of 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.

[0047] 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 planet carrier 34L. Conversely, when the left steering clutch 40L is disengaged, the left sun gear 33L becomes free-rotating, cutting off the transmission of rotational power from the input shaft 26 to the left output shaft 60L. Similarly, the right steering clutch 40R switches the transmission and disengagement of rotational power from the input shaft 26 to the right output shaft 60R depending on its engagement and disengagement.

[0048] Here, the left and right steering clutches 40L and 40R can rotate around the input shaft 26. The left and right steering clutches 40L and 40R rotate in opposite directions to each other by the rotational power from the steering motor 80 transmitted via the motor power transmission unit 90.

[0049] For example, when the left and right steering clutches 40L and 40R are engaged, when the left steering clutch 40L rotates forward and the right steering clutch 40R rotates in reverse, the speed of the left output shaft 60L becomes higher than the speed of the right output shaft 60R, and the bulldozer 1 turns to the right at differential speed.

[0050] In this manual, differential steering refers to the process of creating a speed difference between the left and right output shafts 60L and 60R, which rotate in the same direction, and then moving forward or backward in an arc with a relatively large turning radius.

[0051] Furthermore, with the left steering clutch 40L engaged and the right steering clutch 40R disengaged, when the left steering clutch 40L rotates forward, the rotation of the right output shaft 60R stops, and the left output shaft 60L rotates, 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.

[0052] In this specification, turning in place means turning around with the track on the other side as the axis by rotating one of the left and right output shafts 60L and 60R and bringing the other side to a substantial or complete stop.

[0053] like Figure 2 As shown, the right-turn clutch 40R has multiple clutch discs 41, multiple clutch plates 42, and a clutch piston 43.

[0054] Each clutch disc 41 is mounted on the right clutch gear 91R. Each clutch plate 42 is fixed to the right sun gear 33R. The clutch discs 41 and clutch plates 42 are alternately arranged in the axial direction.

[0055] When the clutch piston 43 moves to the right with the supply of working oil, the clutch discs 41 and 42 are pressed together, 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.

[0056] On the other hand, when the clutch piston 43 moves to the left along with the discharge of working oil, each clutch disc 41 and each clutch plate 42 disengages, and the right steering clutch 40R is disengaged. As a result, the right sun gear 33R of the right planetary gear mechanism 30R is separated from the right clutch gear 91R of the motor power transmission unit 90.

[0057] It should be noted that the left-turn clutch 40L has the same structure as the right-turn clutch 40R.

[0058] [Steering brake]

[0059] The left and right steering brakes 50L and 50R are driven by the supply of hydraulic fluid. The left and right steering brakes 50L and 50R are composed of wet multi-plate clutches capable of engagement and disengagement. In this embodiment, the left and right steering brakes 50L and 50R are negative-type 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 pressure of the supplied hydraulic fluid is less than a specified value, and disengaged when the hydraulic pressure of the supplied hydraulic fluid is above the specified value. When the left and right steering brakes 50L and 50R are engaged (fully or partially engaged), braking force is generated in the left and right steering brakes 50L and 50R.

[0060] The hydraulic pressure of the working oil 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 110.

[0061] The left and right steering brakes 50L and 50R brake the rotation of the left and right output shafts 60L and 60R.

[0062] 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.

[0063] like Figure 2 As shown, the right turn brake 50R has a rotating component 51, a brake housing 52, multiple fixed plates 53, multiple brake discs 54, and a brake piston 55.

[0064] 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 with respect to the rotating member 51. The respective fixed plates 53 are attached to the brake housing 52. The respective brake discs 54 are fixed to the rotating member 51. The respective fixed plates 53 and the respective brake discs 54 are alternately arranged in the axial direction.

[0065] When the brake piston 55 moves in the left direction in conjunction with the filling of the working oil, the respective fixed plates 53 are separated from the respective brake discs 54, and the right steering brake 50R is disengaged. On the other hand, when the brake piston 55 moves in the right direction in conjunction with the discharge of the working oil, the respective fixed plates 53 and the respective brake discs 54 are pressed and bonded, thereby generating a braking force in the right steering brake 50R.

[0066] Note that the left steering brake 50L has the same structure as the right steering brake 50R.

[0067] [Steering motor]

[0068] The steering motor 80 is driven by the power of the engine 10. The steering motor 80 rotates in one of a positive rotation direction and a reverse rotation direction. The rotation direction and the rotation speed of the steering motor 80 are controlled by the controller 110. The rotation speed of the steering motor 80 varies from 0% to 100% (maximum) depending on the power transmitted from the engine 10.

[0069] The rotational power of the steering motor 80 is transmitted to the left and right steering clutches 40L, 40R via the motor power transmission portion 90. The steering motor 80 rotates the left and right steering clutches 40L, 40R in such a manner that the left and right output shafts 60L, 60R generate a speed difference. For example, in the case where the bulldozer 1 is differentially steered to the right, the steering motor 80 rotates the left and right steering clutches 40L, 40R in such a manner that the rotation speed of the left output shaft 60L is higher than that of the right output shaft 60R. In addition, in the case where the bulldozer 1 is steered in place to the right, the steering motor 80 rotates the left and right steering clutches 40L, 40R in such a manner that the right output shaft 60R does not rotate and only the left output shaft 60L rotates.

[0070] [Motor power transmission portion]

[0071] The motor power transmission portion 90 is arranged between the steering motor 80 and the left and right steering clutches 40L, 40R. The motor power transmission portion 90 transmits the rotational power of the steering motor 80 to the left and right steering clutches 40L, 40R.

[0072] The motor power transmission portion 90 has left and right clutch gears 91L, 91R, a first transmission gear 92, a countershaft 93, a second transmission gear 94, an idler gear 95, and a pinion gear 96.

[0073] The left and right clutch gears 91L, 91R are able to be separated from or engaged with 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 are able to rotate 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 with the idler gear 95 via the first transmission gear 92, the lay shaft 93, and the second transmission gear 94. When the steering motor 80 rotates, the left and right clutch gears 91L, 91R rotate in opposite directions from each other.

[0074] 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 able to rotate about the axial direction of the input shaft 26.

[0075] The pinion gear 96 is engaged with the idler gear 95. The pinion gear 96 is able to rotate about the pinion gear shaft 96a. The pinion gear 96 rotates by the rotational power of the steering motor 80 transmitted via the pinion gear shaft 96a.

[0076] [Hydraulic Supply]

[0077] The hydraulic supply 100 supplies working oil to the angle cylinder 8, the lift cylinder 9, and the steering motor 80, respectively. The hydraulic supply 100 has a variable capacity pump 101 and a control valve 102.

[0078] The variable capacity pump 101 is an example of the "hydraulic pump" of the present disclosure. The variable capacity pump 101 is linked with the power take-off device 21. The variable capacity pump 101 is driven by the power of the engine 10 transmitted from the power take-off device 21.

[0079] The variable capacity pump 101 discharges working oil to the control valve 102. The discharge amount from the variable capacity pump 101 is changed according to the tilt angle of a swash plate provided in the variable capacity pump 101. The tilt angle of the swash plate is controlled by the controller 110.

[0080] The control valve 102 is connected with the variable capacity pump 101, the angle cylinder 8, the lift cylinder 9, and the steering motor 80 via pipes, respectively. The control valve 102 distributes the working oil discharged from the variable capacity pump 101 to the variable capacity pump 101, the angle cylinder 8, and the lift cylinder 9, respectively.

[0081] The amount of working oil supplied from the control valve 102 to the angle cylinder 8 is changed according to the position of an angle cylinder spool provided in the control valve 102. The amount of working oil supplied from the control valve 102 to the lift cylinder 9 is changed according to the position of a lift cylinder spool provided in the control valve 102. The amount of working oil supplied from the control valve 102 to the steering motor 80 is changed according to the position of a steering motor spool provided in the control valve 102. The positions of the angle cylinder spool, the lift cylinder spool, and the steering motor spool are each controlled by the controller 110.

[0082] [controller]

[0083] The controller 110 controls the rotation speed of the engine 10 and the speed stage clutches and the direction stage clutches of the transmission 23 in order to make the bulldozer 1 travel.

[0084] The controller 110 is connected to the work device lever 35 used in the driving operation of the blade 6. The work device lever 35 includes an angle lever for tilt operation of the blade 6 in the front-rear direction and a lift lever for lift operation of the blade 6 in the up-down direction. The controller 110 outputs control signals to the variable capacity pump 101 and the control valve 102 in accordance with the operation amount and the operation direction of the work device lever 35.

[0085] The controller 110 is connected to the steering lever 36 for the steering operation of the bulldozer 1. The controller 110 outputs control signals to the left-right clutch control valves 27L, 27R, the left-right brake control valves 28L, 28R, the variable capacity pump 101 and the control valve 102 in accordance with the operation amount of the steering lever 36.

[0086] The steering lever 36 is operable to the left steering direction P2 and the right steering direction P3 with the neutral position PI as a reference. The controller 110 controls the left-right steering clutches 40L, 40R, the left-right steering brakes 50L, 50R and the steering motor 80 in accordance with the operation direction and the operation amount of the steering lever 36, thereby making the bulldozer 1 travel in one of the "straight travel mode", the "differential steering mode" and the "in-place steering mode".

[0087] The controller 110 makes the bulldozer 1 travel straight in the straight travel mode when the operation amount of the steering lever 36 is equal to or smaller than a first prescribed amount TH1. The controller 110 makes the bulldozer 1 steer in the differential steering mode when the operation amount of the steering lever 36 is greater than the first prescribed amount TH1 and smaller than a second prescribed amount TH2. The controller 110 makes the bulldozer 2 steer in the in-place steering mode when the operation amount of the steering lever 36 is equal to or greater than the second prescribed amount TH2.

[0088] The second prescribed amount TH2 is greater than the first prescribed amount TH1. The first and second prescribed amounts TH1, TH2 can be set to desired values, respectively. The first prescribed amount TH1 can be "0".

[0089] • Straight travel mode

[0090] In the straight travel mode, the controller 110 controls the left-right clutch control valves 27L, 27R to make the left-right steering clutches 40L, 40R fully engaged.

[0091] In the straight travel mode, the controller 110 controls the left-right brake control valves 28L, 28R to make the left-right steering brakes 50L, 50R disengaged.

[0092] In the straight mode, the controller 110 stops the steering motor 80.

[0093] • Differential steering mode

[0094] In the differential steering mode, the controller 110 controls the left and right clutch control valves 27L, 27R so as to engage (typically, fully engage) the left and right steering clutches 40L, 40R.

[0095] In the differential steering mode, the controller 110 controls the left and right brake control valves 28L, 28R so as to disengage the left and right steering brakes 50L, 50R.

[0096] In the differential steering mode, the controller 110 drives the steering motor 80 in such a manner that the rotational speed of the inner output shaft 60 IN becomes lower than that of the outer output shaft 60 OUT as the operation amount of the steering lever 36 increases.

[0097] The inner output shaft 60 IN is the output shaft of the left and right output shafts 60L, 60R that corresponds to the operation direction (i.e., the steering direction) of the steering lever 36. The outer output shaft 60 OUT is the output shaft of the left and right output shafts 60L, 60R that is opposite to the operation direction of the steering lever 36.

[0098] The controller 110 increases the rotational speed of the steering motor 80 as the operation amount of the steering lever 36 increases. For example, the controller 110 can gradually increase the rotational speed of the steering motor 80 in proportion to the operation amount of the steering lever 36, or can increase the rotational speed of the steering motor 80 in stages according to the operation amount of the steering lever 36.

[0099] The rotational speed of the steering motor 80 when the operation amount of the steering lever 36 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).

[0100] • In-place steering mode

[0101] In the in-place steering mode, the controller 110 controls the left and right clutch control valves 27L, 27R so as to disengage the inner steering clutch 40 IN and engage (typically, fully engage) the outer steering clutch 40 OUT .

[0102] The inner steering clutch 40 IN is the steering clutch of the left and right steering clutches 40L, 40R that corresponds to the operation direction of the steering lever 36. The outer steering clutch 40 OUTis the steering clutch opposite to the steering lever 36 in the right and left steering clutches 40L, 40R.

[0103] In the spot turning mode, the controller 110 controls the right and left brake control valves 28L, 28R to turn off the inner side turning brake 50 IN brake, and turn on the outer side turning brake 50 OUT .

[0104] The inner side turning brake 50 IN is the turning brake corresponding to the steering direction of the steering lever 36 in the right and left turning brakes 50L, 50R. The outer side turning brake 50 OUT is the turning brake opposite to the steering direction of the steering lever 36 in the right and left turning brakes 50L, 50R.

[0105] In the spot turning mode, the controller 110 maintains the rotation speed of the steering motor 80 to the same degree as that in the differential steering mode. The rotation speed of the steering 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%.

[0106] • Work oil amount control in the spot turning mode

[0107] The controller 110 is connected to the low speed switch 37. The operator sets the low speed switch 37 to the on state when driving the blade 6 in the spot turning mode. The operator sets the low speed switch 37 to the off state when not driving the blade 6 in the spot turning mode.

[0108] The controller 110 rotates the steering motor 80 in the spot turning mode as described above. In this case, when the low speed switch 37 is in the on state, the controller 110 executes "work oil amount control" which reduces the work oil amount supplied from the hydraulic supply 100 to the steering motor 80 and increases the work oil amounts supplied from the hydraulic supply 100 to the angle cylinder 8 and the lift cylinder 9, respectively.

[0109] Specifically, the controller 110 controls the positions of the angle cylinder slide valve, the lift cylinder slide valve, and the steering motor slide valve, respectively, by outputting a control command to the control valve 102, thereby reducing the work oil amount supplied from the control valve 102 to the steering motor 80 and increasing the work oil amounts supplied from the control valve 102 to the angle cylinder 8 and the lift cylinder 9. The controller 110 controls the angle cylinder slide valve, the lift cylinder slide valve, and the steering motor slide valve to the positions set in advance, respectively, when executing the work oil amount control.

[0110] By such working oil amount control, the bulldozer 1 performs a swing at low speed, but the reduction in the performance (driving force and driving speed) of the blade 6 when the operator operates the working device lever 35 is suppressed.

[0111] The controller 110 can also make the amount of working oil supplied from the control valve 102 to the swing motor 80 "0". The closer the amount of working oil supplied from the control valve 102 to the swing motor 80 is to "0", the slower the swing speed of the bulldozer 1, and on the other hand, the performance of the working device 3 is further improved.

[0112] As described above, the controller 110 also rotates the swing motor 80 in the swing in the differential swing mode. However, in the present embodiment, the controller 110 does not perform working oil amount control during the swing in the differential swing mode. That is, the controller 110 does not reduce the amount of working oil supplied from the control valve 102 to the swing motor 80 even when the low speed switch 37 is in the on state in the swing in the differential swing mode. Thereby, the increase in the swing radius of the bulldozer 1 in the differential swing is suppressed.

[0113] (Modified Examples of the Embodiment)

[0114] The present application is not limited to the above embodiment, and various modifications or alterations can be made without departing from the scope of the present application.

[0115] (Modified Example 1)

[0116] In the above embodiment, the bulldozer 1 is described as an example of the track-type construction machine, but the present application can be widely applied to a track-type construction machine such as a hydraulic excavator having a track-type traveling device.

[0117] (Modified Example 2)

[0118] In the above embodiment, the blade 6 is described as an example of the working device, but the present application is not limited thereto. As the working device, for example, a ripper used in a breaking work or a digging work can be cited.

[0119] (Modified Example 3)

[0120] In the above embodiment, the hydraulic supply part 100 is provided with the variable capacity pump 101 and the control valve 102, but the present application is not limited thereto. For example, the hydraulic supply part 100 can be provided with a fixed displacement pump instead of the variable capacity pump 101. Figure 4As shown, the hydraulic supply part 100 can also have a steering motor hydraulic pump 103 that supplies working oil to the steering motor 80 and a work implement hydraulic pump 104 that supplies working oil to the angle cylinder 8 and the lift cylinder 9, respectively. In this case, the controller 110 can control the swash plate of the steering motor hydraulic pump 103 to decrease the amount of working oil supplied from the steering motor hydraulic pump 103 to the steering motor 80 and to increase the amount of working oil supplied from the work implement hydraulic pump 104 to the angle cylinder 8 and the lift cylinder 9 via the control valve 105, thereby performing the working oil amount control.

[0121] (Variant Four)

[0122] In the above embodiment, the controller 110 is configured not to perform the working oil amount control during steering in the differential steering mode, but can perform the working oil amount control during steering in the differential steering mode. In this case, although the steering radius of the bulldozer 1 becomes large in the differential steering, the decrease in the performance of the blade 6 can be suppressed even in the differential steering.

[0123] Note that the controller 110 can not perform the working oil amount control during steering in the in-place steering mode and perform the working oil amount control only during steering in the differential steering mode.

[0124] (Variant Five)

[0125] In the above embodiment, the controller 110 switches from the differential steering mode to the in-place steering mode when the operation amount of the steering lever 36 is equal to or greater than the second prescribed amount TH2, but is not limited thereto. The controller 110 can switch from the differential steering mode to the in-place steering mode when the operation amount of the steering lever 36 is greater than the first prescribed amount TH1 and the operator sets the in-place steering button to the on state.

[0126] (Variant Six)

[0127] In the above embodiment, the left and right steering clutches 40L, 40R are configured as positive-type hydraulic clutches, but can be negative-type hydraulic clutches.

[0128] (Variant Seven)

[0129] In the above embodiment, the left and right steering brakes 50L, 50R are configured as negative-type hydraulic brakes, but can be positive-type hydraulic brakes.

[0130] Explanation of Reference Numerals

[0131] 1 bulldozer

[0132] 10 engine

[0133] 20 engine power transmission part

[0134] 26 input shaft

[0135] 30L, 30R left planetary gear mechanism

[0136] 31L, 31R left ring gear

[0137] 32L, 32R left planet gears

[0138] 33L, 33R left sun gear

[0139] 34L, 34R left carrier

[0140] 40L, 40R left steering clutch

[0141] 50L, 50R left steering brake

[0142] 60L, 60R left output shaft

[0143] 80 steering motor

[0144] 90 motor power transmission portion

[0145] 100 hydraulic pressure supply portion

[0146] 110 controller

Claims

1. A track-type construction machine, characterized in that, Possess: left and right planetary gear mechanisms configured between an input shaft and left and right output shafts; left and right turning clutches capable of rotating around the input shaft, switching 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; left and right turning brakes that brake the left and right output shafts; a turning motor that rotates the left and right turning clutches in a manner that causes the left and right output shafts to have a rotational speed difference; a work device hydraulic cylinder that drives a work device mounted to a vehicle body; a hydraulic supply that supplies working oil to the turning motor and the work device hydraulic cylinder; a controller that causes the crawler-type construction machine to turn in one of a differential turning mode and a zero-radius turning mode by controlling the left and right turning clutches, the left and right turning brakes, and the turning motor; the controller executes working oil amount control that, when the work device hydraulic cylinder is driven with the turning motor turned, reduces an amount of working oil supplied from the hydraulic supply to the turning motor and increases an amount of working oil supplied from the hydraulic supply to the work device hydraulic cylinder, the controller does not execute the working oil amount control during turning in the differential turning mode and executes the working oil amount control during turning in the zero-radius turning mode.

2. The crawler-type construction machine according to claim 1, wherein the hydraulic supply has a hydraulic pump that is driven by power of an engine and discharges working oil, and a control valve that distributes the working oil discharged from the hydraulic pump to the turning motor and the work device hydraulic cylinder, the controller, when the work device hydraulic cylinder is driven with the turning motor turned, reduces an amount of working oil supplied from the control valve to the turning motor and increases an amount of working oil supplied from the control valve to the work device hydraulic cylinder, thereby executing the working oil amount control.

3. The crawler-type construction machine according to claim 1, wherein the hydraulic supply has a turning motor hydraulic pump that supplies working oil to the turning motor, and a work device hydraulic pump that supplies working oil to the work device hydraulic cylinder, the controller, when the work device hydraulic cylinder is driven with the turning motor turned, reduces an amount of working oil supplied from the turning motor hydraulic pump to the turning motor and increases an amount of working oil supplied from the work device hydraulic pump to the work device hydraulic cylinder, thereby executing the working oil amount control.

4. The crawler-type construction machine according to any one of claims 1 to 3, further comprising a low-speed switch, the controller executes the working oil amount control when the low-speed switch is in an on state. ​

Images