JP5457792B2 - Control device for traveling transmission - Google Patents

Description

  The present invention relates to a control device for a travel transmission device, and more particularly to a control device for a travel transmission device that transmits power to a pair of left and right travel devices capable of turning.

  In a work vehicle using a crawler type traveling device such as a combine, turning has been realized by changing the speeds of the left and right traveling devices. As such a work vehicle, for example, a right and left traveling device, a first turning mechanism that turns the airframe by giving a speed difference to the right and left traveling devices, and the right and left traveling devices that make the first turn A second turning mechanism for turning the airframe with a larger speed difference than the mechanism, and a turning setting means capable of setting a first state in which the first turning mechanism is operated or a second state in which the second turning mechanism is operated; A steering operation tool (for example, a steering lever or a steering handle) that is operated artificially, and in the first state, as the steering operation tool is operated to the right or left from the straight position, the right and left The first turning mechanism is operated so that the speed difference of the left traveling device becomes large. In the second state, as the steering operation tool is operated to the right or left from the straight position, the right and left traveling are performed. Said second so that the speed difference of the device becomes large. There is work vehicle provided with a control means for operating the rotating mechanism (see Patent Document 1).

In this work vehicle, the steering operation tool is tilted in the direction in which it is desired to turn, thereby creating a speed difference corresponding to the amount of tilt for the left and right traveling devices, thereby realizing turning. In the first state, by transmitting power that slowed the running device of the orbiting inward side by the clutch, is realized turning. Further, in the second state, turning with a smaller turning radius is realized by applying a braking force to the traveling device on the turning direction side.

  In the work vehicle of Patent Document 1 described above, the operator switches between the first state and the second state by operating the turning setting means, but the first state and the second state are changed according to the operation amount of the steering operation tool. Work vehicles that switch between two states have also been proposed. In this work vehicle, when the operation amount of the steering operation tool is small, a turning state in which the traveling device is idled by disengaging a clutch provided in a transmission path to the traveling device on the inner side in the turning direction ( The first state in which the decelerated power is transmitted to the traveling device on the inner side in the turning direction as the operation amount of the steering operation tool increases thereafter. A transition is made to a second state in which a brake is applied to the traveling device on the inner side in the direction. When shifting from the idle state to the first state, the clutch is switched from the disengaged state to the engaged state by increasing the hydraulic pressure supplied to the clutch. Similarly, the brake is operated by hydraulic pressure.

JP 2009-096357 A

  FIG. 14 is a graph showing the relationship between the operation amount (tilt angle) of the steering operation tool and the hydraulic pressure in the latter working vehicle. FIG. 14A is a graph when the steering operation tool is operated at a predetermined operation speed. In this case, the hydraulic pressure of the clutch increases in accordance with the operation amount of the steering operation tool, and the state is shifted to the first state. Further, when the steering operation tool is further operated, the hydraulic pressure of the clutch decreases, the hydraulic pressure of the brake increases, and the state shifts to the second state.

  On the other hand, FIG. 14B shows a change in hydraulic pressure when the steering operation tool is operated at an operation speed equal to or higher than the predetermined operation speed. In this case, the operation amount of the steering operation tool reaches an amount corresponding to the second state before the clutch hydraulic pressure sufficiently increases, and at that time, the clutch hydraulic pressure decreases and the brake hydraulic pressure increases. . When the oil pressure is controlled in this way, the clutch is disengaged from the state where the clutch oil pressure is not sufficient, that is, from the half-clutch state, and braking by the brake is applied. At this time, since the traveling device on the inner side in the turning direction is not sufficiently decelerated, there is a possibility that an impact due to sudden braking may occur when shifting to the second state.

  In view of such a problem, an object of the present invention is to provide a control device for a travel transmission device for reducing the uncomfortable feeling when the speed difference between the left and right travel devices is changed during turning.

In order to solve the above problems, a control device for a travel transmission device according to claim 1 is a control device for a travel transmission device that transmits power to a pair of left and right travel devices. The control device is provided with a clutch that adjusts a transmission amount of power that is lower than that of the other travel device to the travel device, and a braking unit that applies a braking force to the one travel device. when steering operation member is switched operated from the first operating position to the second operation position that is, by increasing the transmission amount of the power by the clutch with an increase in the operation amount of the steering operation member, the steering When the direction operation member is switched from the second operation position to the third operation position, the transmission amount of the power by the clutch is gradually decreased as the operation amount of the steering operation member is increased, and the braking is performed. Braking force by means A control unit for masa, wherein, when the operation speed to the third operation position side from the second operating position of the steering operation member is less than the predetermined speed, the steering operation member The rate of increase in the amount of transmission of the power by the clutch is changed according to the rate of increase when the amount of operation is increased, and the steering operation member is operated from the second operation position to the third operation position side. If speed were predetermined speed or more, after said clutch is allowed to gradually increase the transmission amount of the power by the clutch by a predetermined rate of increase until the full transmission state, decreasing the transmission amount of the power by the clutch And the braking force by the braking means is gradually increased.

In this configuration, in accordance with the operation amount of the steering operation member is artificially operated state of the clutch and brake means has been configured to Setsu換Ru so. When the steering operation member is switched operated from the first operating position to the second operating position, by progressively entering Rimisao work the clutch, increasing the power transmitted to one of the traveling device, a steering operating member Is switched to the second operating position, the clutch is in a transmission state. At this time, since a lower speed power is transmitted to one traveling device than the other traveling device, a speed difference is generated between the traveling devices, and the vehicle can turn. On the other hand, the steering operation member when the switching operation to the third operation position from the second operating position is thereby gradually switching Rimisao operation of the clutch, to gradually increase the braking force of the brake means. As a result, the braking force acts on one of the traveling devices, and the vehicle can turn.

When the operation speed from the second operation position to the third operation position of the steering operation member is equal to or higher than the predetermined speed, the control unit does not follow the switching operation of the steering operation member, and the clutch After the power transmission amount is gradually increased until the complete transmission state is reached, the clutch power transmission amount is gradually decreased and the braking force by the braking means is gradually increased. As a result, even if the steering operation member is suddenly switched to the third operation position, the low speed power by the clutch is transmitted, that is, in the state where the speed of one traveling device is suppressed, Since the braking force is applied to the traveling device, the impact when the braking means is applied can be reduced.

In the control device for the travel transmission device according to claim 2, the control unit is configured such that an operation speed of the steering operation member from the second operation position to the third operation position is equal to or higher than the predetermined speed. Further, after gradually increasing the transmission amount of the power by the clutch at the predetermined increase rate until the clutch is in a complete transmission state, the transmission amount of the power by the clutch is gradually decreased and the braking is performed after a predetermined time has elapsed. The braking force by the means is gradually increased.

In general, a time lag occurs until the clutch is fully transmitted in response to a control signal from the control unit, and this time lag varies depending on individual differences and control environments (such as oil temperature if controlled by a hydraulic circuit). there is a possibility. For this reason, in this configuration, a standby time is provided after the control unit issues an instruction to bring the clutch into a complete transmission state. Thereby, the clutch can be surely brought into a complete transmission state without being affected by individual differences or the control environment.

In the control device for the travel transmission device according to claim 3, when the operation speed of the steering operation member from the second operation position to the third operation position is equal to or higher than the predetermined speed, the braking means The predetermined increase rate is set to be smaller than the increase rate at the time when the braking force is gradually increased.
In the control device of the traveling transmission apparatus constructed according to claim 4, wherein, when gradually increasing the braking force of said braking means, after increasing at a first rate, smaller than the first ratio of the Increase gradually at a rate of two.

  In this configuration, when the braking force of the braking means increases to some extent, the gradually increasing rate of the braking force is reduced. As a result, a braking force is gradually applied to one of the traveling devices, and the impact associated with the switching of the turning mode is further reduced.

It is a whole side view of a combine. It is a figure which shows the gear train of a transmission system. It is a vertical front view of a traveling transmission device. It is a vertical side view of a traveling transmission device. It is a longitudinal front view which shows the upper part of a driving | running | working transmission apparatus. It is a longitudinal front view which shows the lower part of a driving | running | working transmission apparatus. It is a vertical front view which shows the action | operation form in a driving subtransmission part. It is a vertical front view which shows a steering mechanism part. It is a circuit diagram which shows a hydraulic operation system. It is a block diagram which shows a control apparatus and an input / output device. It is a flowchart showing the flow of control of the control apparatus of this invention. It is a graph showing the relationship between the oil_pressure | hydraulic in embodiment and the operation amount of a steering lever. It is a graph showing the relationship between the oil_pressure | hydraulic in 1st another embodiment, and the operation amount of a steering operation tool. It is a graph showing the relationship between the hydraulic pressure in the prior art, and the operation amount of a steering control tool.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this embodiment, the traveling transmission device and its control device according to the present invention are mounted on a combine.

[Overall structure of the combine]
FIG. 1 is an overall side view of a combine equipped with a traveling transmission device 20 according to the present invention. As shown in the figure, this combine is composed of a pair of left and right crawler type traveling devices 1 (in particular, the left traveling device 1 is represented as 1L, and the right traveling device 1 is represented as 1R), and the driver's seat. And a pre-cutting processing unit 10 connected to the front part of the machine frame 3 of the traveling machine body. In addition, a threshing device 4 and a grain tank 5 are provided side by side in the lateral direction of the traveling machine body on the rear side of the machine body frame 3.

  An engine 6 (see FIG. 2) is provided below the driver seat 2, and a traveling transmission device 20 is provided at the front end of the body frame 3. The driving force output from the engine 6 is shifted by the traveling transmission device 20 and transmitted to the pair of left and right traveling devices 1. Thereby, the pair of left and right traveling devices 1 are driven, and the combine can travel.

  A hydraulic cylinder 12 (see FIG. 1) is connected to the pre-processing unit frame 11 (see FIG. 1) of the pre-cutting processing unit 10. The pre-cutting processing unit 10 is swung up and down with respect to the body frame 3 by the action of the hydraulic cylinder 12. That is, the pre-cutting processing unit 10 is moved up and down to a lowering work state in which the weeding tool 13 provided at the front end portion thereof is lowered near the ground, and an ascending non-working state in which the weeding tool 13 is raised from the ground. The

  When the pre-cutting processing unit 10 is in the descending work state and the traveling machine body is caused to travel, the pre-cutting processing unit 10 raises the planted culm with the weeding tool 13 and introduces it into the apparatus 14. In the pulling device 14, the planted culm to be lifted is cut by the clipper-shaped cutting device 15, and the cutting mash is transported to the rear side of the machine body by the transport device 16 and the threshing feed chain 4 a of the threshing device 4. To the beginning of The threshing device 4 sandwiches the stock side of the harvested cereal meal by the threshing feed chain 4a and conveys it to the rear of the runner, thereby supplying the tip side of the harvested grain meal to the handling room for threshing treatment. The grain tank 5 collects and stores the threshing grains from the threshing device 4.

[Configuration of transmission system]
FIG. 2 is a diagram showing a transmission gear train that guides the power output from the engine 6 to the traveling device 1 and the pre-cutting processing unit 10. FIG. 3 is a longitudinal front view of the travel transmission device 20, and FIG. 4 is a longitudinal side view of the travel transmission device 20.

  As shown in these figures, the upper end of the traveling transmission 20 is rotatably provided with a pump shaft 21 (described later) as an input shaft. On the other hand, a traveling case 20 is provided with a transmission case 22 at the lower end of the traveling transmission device 20. The transmission case 20 has a pair of left and right traveling drive shafts 1a (in particular, the left traveling drive shaft 1a is 1aL, The right travel drive shaft 1a is expressed as 1aR). The upper end of the mission case 22 accommodates a hydrostatic continuously variable transmission 23 (hereinafter referred to as HST23) as a traveling main transmission, and the traveling mission is located below the traveling body from the HST23. The part 30 is accommodated.

  FIG. 5 is a longitudinal front view of the upper end side of the traveling transmission device 20. As shown in FIGS. 2 to 5, the HST 23 includes an axial plunger type and variable displacement type hydraulic pump 24, and an axial plunger type hydraulic motor 25 driven by pressure oil from the hydraulic pump 24. ing. The pump shaft 21 described above is provided in the hydraulic pump 24.

FIG. 6 is a longitudinal front view of the lower end side of the traveling transmission device 20. As shown in FIGS. 2 to 6, the traveling mission unit 30 includes a traveling auxiliary transmission unit 32, a center gear 50, and a steering mechanism 51. Traveling auxiliary transmission section 32 includes an input gear 31 which bite into the motor shaft gear 27 provided to be rotatable in unison therewith the motor shaft 26 of HST23, and an output gear 33 to bite the center gear 50. The steering mechanism 51 is provided across the center gear 50 and the pair of left and right traveling drive shafts 1a.

  By configuring the traveling transmission device 20 in this manner, power is transmitted as follows. First, the driving force of the engine 6 is transmitted to the pump shaft 21 via a belt pulley 76 that is rotatably provided integrally with the pump shaft 21 so as to constitute the output shaft 6 a and the belt transmission mechanism 7.

  The driving force of the engine 6 input to the mission case 22 via the pump shaft 21 is input to the HST 23 and converted into a forward driving force or a backward driving force by the HST 23. Note that the HST 23 is configured to be able to perform a stepless shift on both the forward side and the reverse side.

  The output from the motor shaft 26 of the HST 23 is input to the input gear 31 of the traveling mission unit 30, and the driving force of the input gear 31 is shifted by the traveling sub-transmission unit 32 and transmitted to the center gear 50. The driving force of the center gear 50 is transmitted to the pair of left and right traveling drive shafts 1a by the steering mechanism 51, and the pair of left and right traveling devices 1 are driven.

  The traveling power transmission device 20 of the present embodiment is configured such that the steering mechanism 51 individually cuts or shifts the transmission with respect to the pair of left and right traveling drive shafts 1a to move the pair of left and right traveling devices 1 straightly and in a turning state. It can be switched to.

  As shown in FIGS. 2 to 4, the traveling transmission device 20 includes an input shaft 34 having an input gear 31 that can rotate integrally therewith. An output pulley 70 is rotatably provided at the end of the input shaft 34 that protrudes laterally outward from the transmission case 22. The driving force of the input shaft 34 is transmitted to the pre-cutting processing unit 10 through the output pulley 70.

[Travel auxiliary transmission section]
As shown in FIGS. 2 to 5, the traveling sub-transmission unit 32 includes a first transmission A for traveling that can be shifted in a plurality of stages and a second transmission B for traveling that can be shifted in a plurality of stages. Connected to and configured.

  The first transmission device A changes the occlusion state of the transmission gear in response to the operator's swinging operation with respect to the auxiliary transmission lever 81 (see FIG. 10) provided in the boarding driving unit having the driver's seat 2. It is constituted by a gear transmission mechanism capable of shifting.

  Specifically, in the first transmission device A (gear transmission mechanism), in accordance with the swing operation of the sub-shift lever 81, the shift gear 35 provided on the input shaft 34 so as to be integrally rotatable and shiftable is shifted, The object to be engaged with the shift gear 35 is selectively changed to the high speed gear 36 or the medium speed gear 37.

  On the other hand, the second transmission device B includes a clutch gear 39 that is supported by the intermediate transmission shaft 38 so as to be relatively rotatable and slidable, and a high-speed gear 41 that is supported at one end of the intermediate transmission shaft 38 so as to be relatively rotatable. ing. Further, on the intermediate transmission shaft 38 at the intermediate position between the clutch gear 39 and the high speed gear 41, the speed difference generated between the transmission upper side and the transmission lower side in accordance with the speed change operation is automatically reduced gradually to increase the power. A hydraulically operated friction clutch 42 having a number of friction plates for transmission is provided.

  As shown in FIG. 10, the boarding operation part is provided with a speed change lever 80 for speed changing the HST 23 for travel speed change, and a push button type operation button 82 is provided on the grip part 80 a of the speed change lever 80. Is provided. The operator can switch on / off by pressing the operation button 82, and in accordance with this operation, the sub-shift electromagnetic valve V 1 for sub-shift operation is operated by the hydraulic circuit in FIG. And the friction clutch 42 are switched to set the high speed side or the low speed side (details will be described later).

  As shown in FIGS. 5 and 7, the clutch gear 39 includes a cylinder portion 39a having a gear portion integrally formed on the outer peripheral side. A hydraulic piston 39b is housed in the cylinder portion 39a, and the hydraulic piston 39b is urged against the lateral side portion of the intermediate shaft first gear 40 by a pressing spring 39c.

  As shown in FIG. 7A, in a state in which the cylinder portion 39a and the hydraulic piston 39b are pressed against the lateral side portion of the intermediate shaft first gear 40, the gear portion on the outer peripheral side of the cylinder portion 39a is connected to the intermediate shaft first gear. It meshes with an internal gear portion 40 a formed on the lateral side of one gear 40 and meshes with the output shaft first gear 44 of the output shaft 45. At this time, the high-speed gear 41 supported on one end portion of the intermediate transmission shaft 38 and the friction clutch 42 provided between the intermediate transmission shaft 38 and the intermediate transmission shaft 38 are in a clutch disengaged state, and the rotation of the intermediate transmission shaft 38 is performed at a high speed. The gear 41 is configured not to be transmitted.

  When pressure oil is supplied to the cylinder portion 39a in this state, as shown in FIG. 7B, the cylinder portion 39a is moved from the lateral side portion of the intermediate shaft first gear 40 against the urging force of the pressing spring 39c. It moves to the side which leaves | separates and the meshing with the internal gear-like gear part 40a of the intermediate shaft 1st gear 40 is cancelled | released. At this time, the friction clutch 42 provided across the high-speed gear 41 and the intermediate transmission shaft 38 that are rotatably supported at one end of the intermediate transmission shaft 38 is switched from the cut-off state to the on-state by the hydraulic piston 42b. . Specifically, the case portion 42a of the friction clutch 42 is fixed to the intermediate transmission shaft 38, and as shown in FIG. 7B, the hydraulic piston 42b is moved away from the case portion 42a by the supplied pressure oil. It moves, and the friction plate of the friction clutch 42 supported between the high speed gears 41 is pressed, and it will be in a clutch engagement state. Thereby, the rotation of the intermediate transmission shaft 38 is transmitted to the high speed gear 41.

  As described above, in the traveling sub-transmission unit 32, the high speed gear 36 and the medium speed are obtained by performing the shift operation of the shift gear 35 provided on the input shaft 34 having the input gear 31 so that the input gear 31 can rotate integrally. The engagement with the gear 37 is changed. On the other hand, the clutch gear 39 supported by the intermediate transmission shaft 38 so as to be relatively rotatable and slidable is slidably operated by a cylinder portion 39a integrally formed therewith, and is engaged with and disengaged from the lateral side portion of the intermediate shaft first gear 40. Operated. On the other hand, the friction clutch 42 provided between the high-speed gear 41 and the intermediate transmission shaft 38 that are rotatably supported at one end of the intermediate transmission shaft 38 is switched between the on state and the off state by the hydraulic piston 42b. . As a result, the driving force of the input gear 31 shifted in three stages of high, medium, and low speed can be transmitted to the center gear 50 via the output gear 33.

  In the traveling auxiliary transmission unit 32 described above, the shift gear 35 is engaged with the high speed gear 36, the clutch gear 39 is engaged with the lateral side portion of the intermediate shaft first gear 40, and the friction clutch 42 is switched to the disengaged state. Then, a medium speed state is achieved as a cutting work speed suitable for a normal cutting work. At this time, the driving force of the input gear 31 includes the input shaft 34, the shift gear 35, the high speed gear 36, the intermediate shaft second gear 43, the intermediate transmission shaft 38, the intermediate shaft first gear 40, the clutch gear 39, and the output shaft first gear. 44, and transmitted to the output gear 33 via the output shaft 45.

  On the other hand, when the shift gear 35 is engaged with the high speed gear 36, the clutch gear 39 is disengaged from the lateral side portion of the intermediate shaft first gear 40, and the friction clutch 42 is switched to the engaged state. It becomes a high-speed state as a moving speed suitable for. At this time, the driving force of the input gear 31 includes the input shaft 34, the shift gear 35, the high speed gear 36, the intermediate shaft second gear 43, the intermediate transmission shaft 38, the friction clutch 42, the high speed gear 41, the output shaft second gear 46, and the output. It is transmitted to the output gear 33 via the shaft 45.

  On the other hand, when the shift gear 35 is engaged with the medium speed gear 37, the clutch gear 39 is engaged with the lateral side portion of the intermediate shaft first gear 40, and the friction clutch 42 is switched to the disengaged state, It becomes a low speed state as a low speed cutting work speed suitable for cutting. At this time, the driving force of the input gear 31 is output via the input shaft 34, the shift gear 35, the medium speed gear 37, the intermediate shaft first gear 40, the clutch gear 39, the output shaft first gear 44, and the output shaft 45. Is transmitted to.

  Further, when the shift gear 35 is engaged with the medium speed gear 37, the clutch gear 39 is disengaged from the lateral side of the intermediate shaft first gear 40, and the friction clutch 42 is switched to the engaged state, the normal cutting operation is performed. It becomes a medium speed state as a cutting work speed suitable for the above. At this time, the driving force of the input gear 31 includes the input shaft 34, the shift gear 35, the medium speed gear 37, the intermediate shaft first gear 40, the intermediate transmission shaft 38, the friction clutch 42, the high speed gear 41, the output shaft second gear 46, It is transmitted to the output gear 33 via the output shaft 45. This medium speed state is the same speed as the medium speed state when the shift gear 35 is engaged with the high speed gear 36 and the clutch gear 39 is engaged with the lateral side portion of the intermediate shaft first gear 40. In addition, a transmission ratio in the traveling auxiliary transmission unit 32 is set.

[Speed difference mitigation means]
In the second transmission device B, a speed difference mitigating means C provided for automatically reducing the speed difference generated between the transmission upper side and the transmission lower side in association with the speed change operation and performing power transmission is provided. A hydraulically operated friction clutch 42 is disposed on the intermediate transmission shaft 38 at an intermediate position between the clutch gear 39 and the high speed gear 41.

  The friction clutch 42 includes a case portion 42a that is externally fitted and fixed to the intermediate transmission shaft 38, and a high-speed gear 41 that is supported in a state in which only relative rotation with respect to the intermediate transmission shaft 38 is possible and movement in the axial direction is restricted. And a number of friction plates supported between the case portion 42a and the high speed gear 41, and hydraulic pressure capable of being pressed and urged toward the high speed gear 41 so as to sandwich the friction plates with the high speed gear 41. It is comprised with piston 42b.

  The clutch gear 39 is set to a tooth width that can maintain the occlusion state with the output shaft first gear 44 on the output shaft 45 side, regardless of whether the gear portion is shifted to either the high speed side or the low speed side. Has been.

  That is, in the second transmission device B, when performing a shifting operation to the high speed side, the clutch gear 39 is disengaged from the lateral side portion of the intermediate shaft first gear 40, and the friction clutch 42 is switched to the engaged state. When the hydraulic piston 42b presses the friction plate supported between the high speed gear 41 and the clutch is engaged by the supplied pressure oil, the transmission upper side and the transmission lower side are caused by slippage between the friction plates. It functions as the speed difference mitigating means C for automatically reducing the speed difference generated during the time period and performing power transmission.

  Further, in the second transmission device B, when the speed change operation is performed to the low speed side, a gradual decrease in the speed difference due to the slip of the friction plate cannot be expected, but the speed change from the state where the airframe is moving at a relatively high speed to the low speed is possible. Therefore, even if a shifting operation is performed during the movement of the aircraft, the clutch gear 39 interlocked with the traveling device 1 side continues to rotate in the same direction as the intermediate shaft first gear 40, and the relative speed difference is reduced. Therefore, it is easy to perform a shift operation with relatively little shift shock.

[Steering mechanism]
As shown in FIGS. 2, 3, 6, and 8, the steering mechanism 51 is for switching the pair of left and right traveling devices 1 between a straight traveling state, a large radius turning state, and a small radius turning state. . The steering mechanism 51 includes a pair of left and right steering clutch gears 52 (when it is particularly necessary to distinguish between them, the left steering clutch gear 52 is expressed as 52L, and the right steering clutch gear 52 is expressed as 52R), The hydraulic piston 52a integrally formed with the steering clutch gear 52 (in particular, when it is necessary to distinguish, the left hydraulic piston 52a is expressed as 52aL and the right hydraulic piston 52a is expressed as 52aR), the steering clutch gear 52 is A center gear 50 having an internal tooth portion to be engaged, a reduction gear 57 (an example of the clutch of the present invention) provided between a reduction gear 57 and an intermediate transmission shaft 58 meshed with a small diameter gear portion of the center gear 50, and an intermediate transmission shaft 58 Left and right transmission clutches 54 and 56 for intermittently operating the steering clutch gear 52 with respect to the steering clutch gear 52.

  In the steering mechanism 51, as shown in FIGS. 6 and 8, the pair of left and right steering clutch gears 52 are slid and operated by a hydraulic piston 52 a formed integrally with the steering clutch gear 52, and the internal teeth of the center gear 50 are The part is engaged and disengaged. The left transmission clutch 54 provided between the left steering clutch gear 52L and the left reduction gear 53 is switched between the on state and the off state by the hydraulic piston 54a. On the other hand, the right transmission clutch 56 provided between the right steering clutch gear 52R and the right transmission gear 55 is switched between the on state and the off state by the hydraulic piston 56a. A reduction transmission clutch 59 provided between the reduction gear 57 and the intermediate transmission shaft 58 meshed with the small-diameter gear portion of the center gear 50 is switched between the on state and the off state by the hydraulic piston 59a. Thereby, the pair of left and right traveling devices 1 can be switched to the above-described straight traveling state, large radius turning state, and small radius turning state.

  In other words, the steering mechanism 51 is operated to switch the pair of left and right steering clutch gears 52 so that one end of the steering clutch gear 52 is engaged with the internal gear of the center gear 50, and the left transmission clutch 54 and the right transmission clutch 56 are disconnected. When the operation is switched to the state, the driving force of the center gear 50 is transmitted to the left travel drive shaft 1aL via the left steering clutch gear 52L and the left travel drive gear 60. On the other hand, the driving force of the center gear 50 is transmitted to the right travel drive shaft 1aR via the right steering clutch gear 52R and the right travel drive gear 61. Thus, the steering mechanism 51 drives the pair of left and right traveling drive shafts 1a at the same drive speed, drives the pair of left and right traveling apparatuses 1 at the same drive speed in the same drive direction, and causes the traveling machine body to travel straight.

  On the other hand, during the turning steering, the steering mechanism 51 is operated as follows. In the following, the behavior in the case of a left turn will be described, but the right turn can be realized by operating left and right in reverse.

  First, the right steering clutch gear 52 </ b> R is switched to a state in which the right steering clutch gear 52 </ b> R is engaged with the inner tooth portion of the center gear 50, and the left steering clutch gear 52 </ b> L is switched to a state where it is disengaged from the inner gear portion of the center gear 50. At this time, the driving force of the center gear 50 is transmitted to the right travel drive shaft 1aR via the right steering clutch gear 52R meshed with the inner teeth of the center gear 50. On the other hand, the left traveling drive shaft 1aL corresponding to the left steering clutch gear 52L detached from the inner gear portion of the center gear 50 is in an idle state. As a result, the steering mechanism 51 drives the right traveling drive shaft 1aR and puts the left traveling drive shaft 1aL into the idle state. Therefore, only the right traveling device 1R is driven to move the traveling vehicle body with a large turning radius. It can be made to turn.

  Further, the right steering clutch gear 52R is switched to a state in which the right steering clutch gear 52R is engaged with the inner tooth portion of the center gear 50, and the left steering clutch gear 52L is switched to a state in which the left steering clutch gear 52L is detached from the inner gear portion of the center gear 50. The clutch 59 is switched to the engaged state, and the left transmission clutch 54 corresponding to the steering clutch gear 52 detached from the inner tooth portion of the center gear 50 is switched to the engaged state. At this time, the driving force of the center gear 50 is transmitted to the right travel drive shaft 1aR via the right steering clutch gear 52R meshed with the inner teeth of the center gear 50. Further, the driving force of the center gear 50 is transmitted to the intermediate transmission shaft 58 via the reduction gear 57 and the reduction transmission clutch 59, and further, the driving force of the intermediate transmission shaft 58 is separated from the inner tooth portion of the center gear 50. Is transmitted to the left steering clutch gear 52L separated from the internal teeth of the center gear 50 through the left intermediate shaft gear 62, the reduction gear 53, and the left transmission clutch 54 corresponding to the steering clutch gear 52L. Due to the transmitted driving force, the left steering clutch gear 52L is driven at a lower speed than the right steering clutch gear 52R, and this driving force is transmitted to the left travel drive shaft 1aL. As a result, the steering mechanism 51 drives the right travel drive shaft 1aR at the same drive speed as during straight travel, and drives the left travel drive shaft 1aL at a lower speed than during straight travel, thereby causing a pair of left and right travel Since the device 1 is driven at different driving speeds in the same driving direction, the traveling machine body can turn with a small turning radius.

  As shown in FIGS. 2, 3, 5 and 6, the steering mechanism 51 includes a hydraulically operated steering brake 64 (an example of the braking means of the present invention) provided at one end of the intermediate transmission shaft 58. . By actuating the steering brake 64 and applying a friction brake to the intermediate transmission shaft 58, the left traveling device 1L corresponding to the left steering clutch gear 52L that has been disengaged from the center gear 50 can be braked. . Thereby, the turning radius of the traveling machine body can be made smaller than the turning radius when the traveling device 1 inside the turning is driven to decelerate.

[Control form]
Next, the control mode of the traveling transmission device 20 will be described using the circuit diagram of the hydraulic operation system of FIG.

  As shown in FIG. 5, the traveling transmission device 20 is provided with a hydraulic pump 71 assembled to the transmission case 22 on the left side of the traveling machine body with respect to the main body having the hydraulic pump 24 and the hydraulic motor 25 of the HST 23. It has been.

  The hydraulic pump 71 is configured by a trochoid pump provided with a pump gear attached to the pump shaft 21. The hydraulic pump 71 includes an oil circuit inside the mission case 22 by a hydraulic circuit having a suction filter 73 (see FIG. 4) provided at the upper end of the mission case 22 and a suction oil passage formed in the mission case 22. The reservoir is connected to the operation valves of the hydraulic pistons 39b, 42b, 52a, 54a, 56a, 59a provided in the traveling mission unit 30. Thereby, the hydraulic pump 71 driven by the pump shaft 21 sucks the lubricating oil stored in the transmission case 22 and discharges the pressure oil, and the discharged pressure oil is discharged to the hydraulic pistons 39b, 42b, 52a. , 54a, 56a, 59a to switch the traveling mission unit 30.

  Further, a supply oil passage LL from a charge pump 72 provided separately from the hydraulic pump 71 is connected to a charge oil supply circuit of the HST 23. A relief valve V14 is provided in the supply oil passage LL.

  A discharge oil passage L from the hydraulic pump 71 branches into a first oil passage L1 and a second oil passage L2. In the first oil passage L1, a sub-shifting electromagnetic valve V1 for operating the traveling sub-transmission unit 32, a braking control solenoid valve V2 for controlling the turning braking state, and a pair of right and left are provided in the first oil passage L1. Steering solenoid valves V3 and V4 for operating the steering clutch gear 52 and the left and right transmission clutches 54 and 56 are provided. As shown in FIG. 10, the sub-transmission solenoid valve V <b> 1, the braking control solenoid valve V <b> 2, the steering solenoid valves V <b> 3 and V <b> 4, and a pressure regulation proportional solenoid control valve V <b> 9 described later are a control unit of the control device 100. It is configured to be controlled in response to a control signal from 100a.

  The control unit 100a receives an operation amount of the steering lever 83 detected by a potentiometer 83a (see FIG. 10) provided in the steering lever 83 (an example of the steering operation member of the present invention). It is configured. The controller 100a transmits a control signal based on the operation amount to control the hydraulic circuit.

  On the other hand, a pair of pilot operation valves V7 and V8 are connected in parallel to the second oil passage L2 via a sequence valve V12, and a seventh oil followed by pressure oil that has passed through the pilot operation valves V7 and V8. It is configured to be supplied to the path L7 and the eighth oil path L8. The pilot operation valve V7 is configured to operate with the pilot pressure supplied from the steering solenoid valve V4 that operates the left transmission clutch 54, and the pilot operation valve V8 operates the right transmission clutch 56. The pilot pressure supplied from the steering solenoid valve V3 is configured to operate.

  The seventh oil passage L7 connected to the pilot operation valve V7 is connected to supply pressure oil to both the left steering clutch gear 52 and the left transmission clutch 54. Note that the transmission clutch 54 is configured to be supplied with hydraulic pressure via the throttle S <b> 2, whereby the transmission clutch 54 operates more gently than the steering clutch gear 52. . Similarly, the eighth oil passage L8 connected to the pilot operation valve V8 is connected to supply pressure oil to both the right steering clutch gear 52 and the right transmission clutch 56. Note that the transmission clutch 56 is configured to be supplied with hydraulic pressure via the throttle S3, whereby the transmission clutch 56 operates more gently than the steering clutch gear 52. .

  The pressure oil that has passed through one of the pair of left and right steering clutch gears 52 is supplied to the subsequent ninth oil passage L9, and further supplied to the tenth oil passage L10 via the proportional electromagnetic control valve V9 for pressure adjustment. The The pressure oil supplied to the tenth oil passage L10 is supplied to the deceleration transmission clutch 59 or the steering brake by the brake switching valve V10 controlled by the pilot pressure of the brake control electromagnetic valve V2 for controlling the turning braking state. 64 is selectively supplied. A relief valve V13 is connected midway through the ninth oil passage L9.

The sub-transmission solenoid valve V1 provided in the first oil passage L1 is pressure oil supplied from the first oil passage L1 by the operation of the operation button 82 (see FIG. 10) provided in the grip portion 80a of the transmission lever 80. Between the state where the oil is supplied to the subsequent third oil passage L3 and the state where the oil is returned to the mission case 22 can be alternately switched.

  An open / close valve V5 is connected to the third oil passage L3. When the pressure oil is supplied to the third oil passage L3, the on-off valve V5 switches to a state in which the pressure oil is supplied to the cylinder portion 39a of the clutch gear 39 with the primary side pressure, and when the primary side pressure drops below a predetermined value, the return spring As a result, the cylinder portion 39a and the case portion 42a of the friction clutch 42 are switched to a state of opening to the drain side via the fifth oil passage L5.

  Further, a fourth oil passage L4 for supplying pressure oil to the oil chamber between the case portion 42a of the friction clutch 42 and the hydraulic piston 42b, which branches from the middle of the third oil passage L3, is provided. . The fourth oil passage L4 is provided with an accumulator 77, and the hydraulic pressure of the pressure set by the accumulator 77 is supplied to the hydraulic piston 42b of the friction clutch 42. Thus, since the pressure oil is supplied to the friction clutch 42 via the accumulator 77, even when the pressure oil is rapidly supplied in accordance with the switching operation of the sub-transmission solenoid valve V1, the accumulator. With the buffering effect of 77, it can be avoided that the friction plate of the friction clutch 42 is suddenly pressed.

  Between the accumulator 77 and the friction clutch 42 of the 4th oil path L4, the 6th oil path L6 which can unload the pressure of the 4th oil path L4 is connected. The sixth oil passage L6 is provided with a valve mechanism V6 that can release the open state and close the sixth oil passage L6. The valve mechanism V <b> 6 is provided with a throttle S <b> 1 at a location where an oil passage (see FIG. 5) formed inside the intermediate transmission shaft 38 is opened inside the transmission case 22. In the valve mechanism V6, when pressure oil is supplied to the clutch gear 39 and the cylinder portion 39a moves to the side away from the intermediate shaft first gear 40, the throttle S1 is closed by the cylinder portion 39a and the sixth oil passage L6 is opened. It switches to the state which canceled the state, and it is comprised so that the friction clutch 42 may be operated to the clutch engagement side with the pressure supplied from the accumulator 77 side. At this time, the fifth oil passage L5 is also closed by the on-off valve V5.

  The braking control solenoid valve V2 and the steering solenoid valves V3 and V4 are configured to be switched in accordance with the operation of the steering lever 83 (see FIG. 10) provided in the boarding operation section. Below, the operation position of the steering lever 83 and the control state with respect to each solenoid valve will be described.

(Straight running)
When the steering lever 83 is operated to the neutral position N, each solenoid valve is in the state shown in FIG. 9 by a control signal from the control unit 100a. At this time, one end of each of the left and right steering clutch gears 52R and 52L is engaged with the inner tooth portion of the center gear 50, and the left and right transmission clutches 54 and 56 are in a disconnected state. Thereby, the driving force of the center gear 50 is transmitted to the traveling device 1R via the steering clutch gear 52R, the traveling drive gear 61, and the traveling drive shaft 1aR. Similarly, the driving force of the center gear 50 is transmitted to the traveling device 1L via the steering clutch gear 52L, the traveling drive gear 60, and the traveling drive shaft 1aL. Thereby, the driving force of the same magnitude is transmitted to the left and right traveling devices 1R and 1L, and the airframe travels straight.

[First turning mode]
When the control unit 100a detects that the steering lever 83 is operated to the right turning position R1 (the first operation position of the present invention), the control unit 100a transmits a control signal so that the steering electromagnetic valve V3 is on the entry side. To do. Thereby, the hydraulic pressure is supplied to the pilot operation valve V8 via the steering solenoid valve V3 switched to the entry side. Further, the hydraulic pressure is supplied to the right steering clutch gear 52R and the right transmission clutch 56 via the pilot operation valve V8 operated to the entry side. Thus, the steering clutch gear 52R is operated in a direction away from the center gear 50, and the engagement between the steering clutch gear 52R and the internal gear portion of the center gear 50 is released. At this time, since the driving force is not transmitted to the travel drive gear 61, the right travel device 1R enters the idle state. The driving force of the center gear 50 is transmitted to the traveling device 1L via the clutch gear 52L, the traveling drive gear 62, and the traveling drive shaft 1aL. Therefore, the aircraft turns to the right.

  On the other hand, the control unit 100a that has detected that the steering lever 83 has been operated to the left turn position L1 (first operation position of the present invention) sends a control signal so that the steering solenoid valve V4 is on the entry side. Send. As a result, the hydraulic pressure is supplied to the pilot operation valve V7 through the steering solenoid valve V4 switched to the entry side. Further, hydraulic pressure is supplied to the left steering clutch gear 52L and the left transmission clutch 54 via the pilot operation valve V7 operated on the entry side. Thereby, the steering clutch gear 52L is operated in a direction away from the center gear 50, and the engagement between the steering clutch gear 52L and the internal gear portion of the center gear 50 is released. At this time, since the driving force of the center gear 50 is not transmitted to the travel drive gear 60, the left travel device 1L enters the idle state. The driving force of the center gear 50 is transmitted to the traveling device 1R via the steering clutch gear 52R, the traveling drive gear 61, and the traveling drive shaft 1aR. Therefore, the aircraft turns to the left.

[Second turning mode]
When the control unit 100a detects that the steering lever 83 has started an operation from the turning position R1 to the turning position R2 (the second operation position of the present invention) (or the turning position L1 to the turning position L2), From the control state of the first turning mode described above, an instruction current corresponding to the tilt angle of the steering lever 83 is supplied to the proportional electromagnetic control valve V9, and the clutch pressure of the deceleration transmission clutch 59 is increased. When the steering lever 83 reaches the turning position R2 (or L2), the clutch pressure of the reduction transmission clutch 59 becomes maximum, and the reduction transmission clutch 59 enters the transmission state. Thus, the driving force of the center gear 50 is applied to the clutch gear 52L (the clutch gear 52R at L2), the travel drive gear 60 (the travel drive gear 61 at L2), and the travel drive shaft 1aL (the travel drive shaft 1aR at L2). Is transmitted to the traveling device 1L (the traveling device 1R at L2), while the reduction gear 57, the reduction transmission clutch 59, the intermediate transmission shaft 58, the right intermediate shaft gear 63 (the left intermediate shaft gear 62 at L2), the deceleration Gear 55 (reduction gear 53 at L2), transmission clutch 56 (transmission clutch 54 at L2), steering clutch gear 52R (steering clutch gear 52L at L2), travel drive gear 61 (travel drive gear at L2) 60), it is transmitted to the travel device 1R (the travel device 1L at the time of L2) via the travel drive shaft 1aR (the travel drive shaft 1aL at the time of L2). As a result, the right traveling device 1R (left traveling device 1L at L2) is driven at a lower speed than the left traveling device 1L (right traveling device 1R at L2), and the fuselage is more than in the first turning mode. Turn right (left at L2) with a small turning radius.

[Third turn mode]
When the control unit 100a detects that the steering lever 83 is operated to the position of the turning position R3 (or L3) (the third operation position of the present invention), the control unit 100a starts braking control control from the control state of the second turning mode. A control signal is transmitted to the electromagnetic valve V2 so as to be opened to the brake switching valve V10 side. As a result, the pilot pressure from the first oil passage L1 acts on the brake switching valve V10 side and is switched to a state where the steering brake 64 acts. Since the steering brake 64 generates a braking force for the intermediate transmission shaft 58, the transmission from the intermediate transmission shaft 58 when the steering lever 83 is operated to the turning position R3 (or L3). Transmission to the clutch 56 (transmission clutch 54 at L3) is suppressed. As a result, braking force is generated on the right traveling device 1R (left traveling device 1L at L3), and the aircraft turns to the right (left at L3) with a smaller turning radius than in the second turning mode.

  In the transition process from the first turning mode to the second turning mode, the clutch pressure of the deceleration transmission clutch 59 gradually increases in accordance with the tilt angle (operation amount) of the steering lever 83, and the steering lever 83 is turned to the turning position R2 or L2. When operated, the maximum pressure is reached and the clutch is engaged. Further, in the process of transition from the second turning mode to the third turning mode, the hydraulic pressure supplied to the deceleration transmission clutch 59 is gradually supplied to the steering brake 64 side as the brake switching valve V10 is switched. The clutch pressure of the deceleration transmission clutch 59 decreases, and the braking force of the steering brake 64 increases.

  Hereinafter, the control flow of the control device of the present invention will be described with reference to FIGS. 11 and 12. In this example, it is assumed that a right turn is performed. First, the control unit 100a determines whether or not the operation speed of the steering lever 83 is equal to or higher than a predetermined speed (# 01). If the operation speed is less than the predetermined speed (No branch of # 01), the normal control described above is performed. Specifically, as the steering lever 83 is operated from the turning position R1 to the turning position R2, the current to the proportional electromagnetic control valve V9 increases, and the hydraulic pressure supplied to the deceleration transmission clutch 59 is changed. (# 02). When the steering lever 83 is switched from the turning position R2 to the turning position R3 (Yes branch at # 03), the brake switching valve V10 is switched, the hydraulic pressure of the deceleration transmission clutch 59 gradually decreases, and the steering brake 64 The oil pressure gradually increases (# 07).

  On the other hand, when the operation speed of the steering lever 83 is equal to or higher than the predetermined speed (Yes branch of # 01), the following control is performed. First, the hydraulic pressure supplied to the deceleration transmission clutch 59 is increased at a predetermined rate (# 04). In the present embodiment, as described above, the proportional electromagnetic control valve V9 is used to control the hydraulic pressure of the deceleration transmission clutch 59. Therefore, the control unit 100a sets the increase amount of the current (control signal) sent to the proportional electromagnetic control valve V9 to a predetermined value. Referring to FIG. 12, it can be seen that the steering lever 83 is suddenly operated from the turning position R2 to R3, while the clutch pressure of the speed reduction transmission clutch 59 increases more gradually.

  The pressure increase of the deceleration transmission clutch 59 is continued until the deceleration transmission clutch 59 is in a transmission state (loop from # 05 to # 04). The state where the deceleration transmission clutch 59 is in the transmission state corresponds to the second turning mode described above. In this embodiment, the transmission state of the speed reduction transmission clutch 59 is determined by the magnitude of the control signal to the proportional electromagnetic control valve V9, but it can also be determined by the hydraulic pressure supplied to the speed reduction transmission clutch 59 or the like.

  After the deceleration transmission clutch 59 enters the transmission state (Yes branch of # 05), the control unit 100a maintains that state for a predetermined time t, that is, waits for the next control (# 06). Although waiting for the predetermined time t is not indispensable, there is a possibility that the timing of the transmission state varies depending on the oil temperature, the individual difference of the apparatus, etc., so it is preferable to provide for the dispersion. In this case, the predetermined time t may be configured to be arbitrarily long or short.

Thereafter, the control unit 100a transmits a switching signal to the braking switching valve V10, and upon receiving the signal, the braking switching valve V10 is supplied with the hydraulic pressure supplied to the deceleration transmission clutch 59 to the steering brake 64 side. (The hydraulic pressure supplied to the deceleration transmission clutch 59 after the elapse of the predetermined time t begins to be supplied to the steering brake 64 side). As shown in FIG. 12, when the brake switching valve V <b> 10 is switched after the predetermined time t has elapsed after the deceleration transmission clutch 59 is in the transmission state, oil discharge from the deceleration transmission clutch 59 is started, and the deceleration transmission clutch 59. The oil pressure begins to drop. At the same time, the supply of oil to the steering brake 64 is started, the hydraulic pressure of the steering brake 64 increases, and the hydraulic pressure of the deceleration transmission clutch 59 and the hydraulic pressure of the steering brake 64 cross each other in the middle. When the switching valve V10 is completely switched, all the hydraulic pressure of the proportional electromagnetic control valve V9 is supplied to the steering brake 64, and the hydraulic pressure of the steering brake 64 increases to a predetermined pressure. This state corresponds to the third turning mode described above.

  Thus, in the present invention, even if the steering lever 83 is suddenly operated, the second turning mode is not delayed following the operation but shifted to the third turning mode. And then the third turning mode is entered. Therefore, the traveling device 1 inside the turning direction is sufficiently decelerated by the deceleration transmission clutch 59 before the steering brake 64 is operated. Thereby, the impact at the time of 3rd turning mode transfer can be relieved.

[First Embodiment]
In the present embodiment, the control for increasing the hydraulic pressure of the steering brake 64 is different from the above-described embodiment. FIG. 13 is a graph showing the relationship between the steering lever 83 and the hydraulic pressure in the embodiment. As is apparent from the figure, when shifting from the second turning mode to the third turning mode, the hydraulic pressure of the steering brake 64 increases at the first rate during the time t1, and thereafter during the time t2. Rising at a second rate smaller than the rate of 1. That is, time t2 is set to be longer than time t1. As described above, by increasing the hydraulic pressure of the steering brake 64 at the second rate, the timing at which the steering brake 64 is completely operated can be delayed. While the hydraulic pressure of the steering brake 64 is increasing, the steering brake 64 is in a slipping state, so that the braking force to the traveling device 1 on the inner side of the turning direction gradually increases, and the transition from the second turning mode to the third turning mode occurs. It is possible to reduce the discomfort of the operator. In this case, the second ratio may be arbitrarily changed with respect to the first ratio.

[Second Embodiment]
In the above-described embodiment, the turning direction and the turning radius can be operated by operating the steering lever 83. However, instead of the steering lever 83, a rotary steering handle may be used as the steering operation member. .

  INDUSTRIAL APPLICABILITY The present invention can be used for a control device for a traveling power transmission device for equipment including a pair of left and right traveling devices capable of turning, such as a combine, a tractor, and a construction machine.

R1, L1: Turning position (first operation position)
R2, L2: turning position (second operation position)
R3, L3: turning position (third operation position)
1, 1L, 1R: Traveling device 20: Traveling transmission device 59: Deceleration transmission clutch (clutch)
64: Steering brake (braking means)
83: Steering lever (steering member)
100: Control device 100a: Control unit t: Predetermined time

Claims (4)

A control device for a traveling transmission device that transmits power to a pair of left and right traveling devices,
The travel transmission device includes a clutch that adjusts the amount of power transmitted to one of the travel devices at a lower speed than the other travel device, and a braking unit that applies a braking force to the one travel device.
When the steering operation member that is artificially operated is switched from the first operation position to the second operation position, the control device increases the amount of power generated by the clutch as the operation amount of the steering operation member increases. It increased gradually the amount transferred, transmitted from the steering operation member is the second operating position when it is switched operation to the third operation position, of the power by the clutch with an increase in the operation amount of the steering operating member A controller for gradually decreasing the amount and gradually increasing the braking force by the braking means;
The control unit increases when the operation amount of the steering operation member increases when an operation speed of the steering operation member from the second operation position to the third operation position is less than a predetermined speed. Depending on the rate, change the rate of increase in the amount of power transmitted by the clutch,
And, when the operation speed from the second operating position of the steering operating member to the third operation position side was the predetermined speed or more, the a predetermined increase rate to said clutch is completely transmitting state after increasing the transmission amount of the power by the clutch, the control device of the traveling transmission apparatus for increasing the braking force by the braking means with gradually decreasing the transmission amount of the power by the clutch. When the operation speed from the second operation position to the third operation position side of the steering operation member is equal to or higher than the predetermined speed, the control unit performs the predetermined operation until the clutch is in a complete transmission state . after increasing the transmission amount of the power by the clutch by increasing rate, traveling transmission of claim 1, wherein the gradually increasing the braking force by the braking means with gradually decreasing the transmission amount of the power by the clutch after a predetermined time Control device for the device. When the operation speed from the second operation position to the third operation position side of the steering operation member is equal to or higher than the predetermined speed,
3. The control device for a travel transmission device according to claim 1 , wherein the predetermined increase rate is set to be smaller than an increase rate when the braking force is gradually increased by the braking means . The control unit, when gradually increasing the braking force of the braking means, gradually increases at a first rate, and then gradually increases at a second rate smaller than the first rate. The control device for the travel transmission device according to any one of the above.

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