JP4443451B2 - Driving transmission structure of work vehicle - Google Patents

Description

  The present invention relates to a traveling transmission structure for a work vehicle, and more particularly, to a traveling transmission structure provided with a pair of hydrostatic continuously variable transmissions that individually drive a pair of left and right traveling apparatuses.

  Conventionally, as shown, for example, in Patent Document 1, the output of the engine 5 is transmitted to an input shaft 24 and a pair of hydrostatic continuously variable transmissions 21, from the input shaft 24 via gears G 1, G 2, G 3, The output from the motor shaft 21b of one hydrostatic continuously variable transmission 21 is transmitted to the axle 29 of the left crawler travel device 1 via the auxiliary transmission mechanism 25 and the gear mechanism 28. The travel of the combine so that the output from the motor shaft 22b of the other hydrostatic continuously variable transmission 22 is transmitted to the axle 33 of the crawler travel device 1 on the right side via the auxiliary transmission mechanism 30 and the gear mechanism 32. A transmission structure was developed.

  In the case of adopting this kind of traveling transmission structure, even if the hydrostatic continuously variable transmission of the left and right traveling device is operated to the same speed so as to travel straight, the driving load of the left and right traveling device If a situation in which there is a large difference occurs, a speed difference occurs between the two continuously variable transmissions due to this load difference, and it may be difficult to ensure straightness. In particular, when traveling at a high speed, even if the speed difference between the two continuously variable transmissions is relatively small, the influence of the speed difference tends to occur.

  For this reason, conventionally, as shown in Patent Document 1, the first intermediate shaft 26 linked to the axle 29 of the left traveling device 1 via the gear mechanism 28 and the axle 33 of the right traveling device 1 are geared. A straight traveling clutch 50 is provided between the first intermediate shaft 31 and the first intermediate shaft 31 that are linked via a mechanism 28. The continuously variable transmission 21 for left traveling and the continuously variable transmission 22 for right traveling are both in the same direction. Control means for engaging and operating the rectilinear clutch 50 when the same amount is operated, i.e., in the rectilinear operating state. That is, the first intermediate shafts 26 and 31 are integrated so that the axles 29 and 33 of the left and right traveling devices 1 are driven at the same speed so as to be straight.

JP 2004-34724 A (paragraphs [0021]-[0023], [0028], FIGS. 2, 3 and 4)

  When the above-described conventional technology is employed, it is necessary to provide an operation oil passage or a control oil passage for performing a switching operation and a switching control of the straight-ahead clutch, and there is a problem that the structure is complicated from this aspect.

  SUMMARY OF THE INVENTION An object of the present invention is to drive a working vehicle that can easily obtain a straight structure and a simple structure while shifting the left and right traveling devices by operating a hydrostatic continuously variable transmission. It is to provide a transmission structure.

In the traveling transmission structure for a work vehicle according to the first aspect of the invention, the engine is applied to the left traveling transmission system that transmits the engine output to the left traveling apparatus, and the right traveling transmission system that transmits the engine output to the right traveling apparatus. A hydrostatic continuously variable transmission that receives an output, and a planetary transmission that includes a carrier that receives an engine output;
In both the traveling transmission systems, the output of the hydrostatic continuously variable transmission is input to the sun gear of the planetary transmission and is output from the ring gear of the planetary transmission to the traveling device. Configured ,
When the hydrostatic continuously variable transmission is operated to shift to a set low speed position between the maximum speed position on the forward side and the neutral position, the planetary transmission stops the output and the traveling device Stopped, the travel device is driven backward on the side closer to the neutral position of the hydrostatic continuously variable transmission than the set low speed position, and the maximum speed of the hydrostatic continuously variable transmission from the set low speed position On the side close to the position, the traveling device is configured to be driven forward, and
The ratio between the power that is input from the engine to the planetary transmission and becomes the driving force of the traveling device and the power that is input from the hydrostatic continuously variable transmission to the planetary transmission and becomes the driving force of the traveling device is Changes with the shifting operation of the step transmission,
The higher the driving speed on the forward side from the neutral position to the maximum speed position of the hydrostatic continuously variable transmission, the greater the proportion of power that is input from the engine to the planetary transmission and becomes the driving force of the traveling device. Further, the gear ratio of the planetary transmission is set .

  That is, the planetary transmission carrier is driven by the engine output and the sun gear is driven by the output of the hydrostatic continuously variable transmission to operate the planetary gear, whereby the ring gear is rotated and output from the ring gear to the traveling device. Therefore, if the planetary transmission is set to a gear ratio appropriately set, when the hydrostatic continuously variable transmission is shifted, the driving force output from the ring gear shifts and the traveling device It is possible to drive at a variable speed. Further, the traveling device is driven by the power that is input from the engine to the planetary transmission device and becomes the driving force of the traveling device, and the power that is input from the hydrostatic continuously variable transmission to the planetary transmission device and becomes the driving force of the traveling device. Thus, even if the driving loads of the left and right traveling devices are different, the traveling device can be driven while it is difficult for a speed difference to occur between the two continuously variable transmissions. Further, the ratio between the power that is input from the engine to the planetary transmission and becomes the driving force of the traveling device and the power that is input from the hydrostatic continuously variable transmission to the planetary transmission and becomes the driving force of the traveling device is the hydrostatic pressure. As the output speed of the ring gear increases and the driving speed of the traveling device increases as the speed of the variable continuously variable transmission is changed, it is input from the engine to the planetary transmission and becomes the driving force of the traveling device. Even if the power ratio increases and the driving loads of the left and right traveling devices are different, the speed difference between the two continuously variable transmissions caused by this difference in load can be made less likely to occur or may not occur.

Therefore, according to the first aspect of the present invention, while the pair of hydrostatic continuously variable transmissions can change the driving speed of the left and right traveling devices individually and continuously, the steering operation of the aircraft can be performed. Even if a situation occurs in which the driving loads of the left and right traveling devices are different, a change in the traveling direction is less likely to occur due to a difference in speed between the left and right traveling devices, and the traveling speed change It is possible to exhibit excellent straightness so that it is less likely to occur at higher speeds.
In addition, the planetary gearbox is operated by the sun gear being rotated by the input from the continuously variable transmission, so that the special operation and control such as the operation oil path and the control oil path of the conventional linear clutch are performed. The structure can be omitted to simplify the structure, and can be advantageously obtained from an economic viewpoint.

According to the second aspect of the invention, in the configuration of the first aspect of the invention, when the hydrostatic continuously variable transmission is in a maximum speed state, the carrier and the ring gear of the planetary transmission are at the same rotational speed. The gear ratio of the planetary transmission is set so that the traveling device is driven only by the power that is input from the engine to the planetary transmission and becomes the driving force of the traveling device .

That is, when the hydrostatic continuously variable transmission is shifted to the maximum speed, the carrier and the ring gear of the planetary transmission are rotated at the same rotational speed, and the ring gear outputs the forward driving force. Therefore, even if the ratio of the power that is input from the engine to the planetary transmission and becomes the driving force of the traveling device becomes large and the driving loads of the left and right traveling devices are different, the two continuously variable transmissions caused by this load difference Ru can speed difference to drive the traveling device while so as not to occur at the maximum speed.

  Therefore, according to the second aspect of the invention, as the traveling speed is increased, even if a load difference between the left and right traveling devices occurs, a situation in which the traveling direction changes due to the difference in speed between the left and right traveling devices is less likely to occur. In addition, when traveling at the maximum speed, it is possible to exhibit excellent straightness so that the change in the traveling direction due to the load difference between the left and right traveling devices is least likely to occur.

Embodiments of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, in front of a body frame 3 of a self-propelled aircraft that is configured to be self-propelled by a pair of left and right crawler type traveling devices 1 and 1 and that includes a driving unit equipped with a driver seat 2. The base end side of the frame 11 of the pre-processing unit 10 is connected to the unit so as to be rotatable around a horizontal axis of the machine body, and the elevating cylinder 4 is interlocked with the pre-processing unit frame 11 so that the machine body of the machine frame 3 A threshing device 5 and a grain tank 6 are provided on the rear side to constitute a combine.

  This combine performs harvesting operations such as rice and wheat. When the elevating cylinder 4 is expanded and contracted, the elevating cylinder 4 swings the pre-processing unit frame 11 with respect to the body frame 3 to move up and down. The pre-processing unit 10 is raised and moved up and down to a lowering work state in which the lower end of the device 12 is located near the ground and a rising non-working state in which the pulling device 12 and the like are lifted off the ground. When the pre-processing unit 10 is moved down and the self-propelled vehicle is run, the pre-processing unit 10 causes the planted cereals to be processed by the plurality of pulling devices 12 arranged in the horizontal direction of the airframe as well as each pulling device. A clip conveying device that cuts the planted cereal from 12 with a clipper-shaped reaping device 13, and a clamping and conveying device that acts on the stock side of the reaped cereal from the reaping device 13, and a locking and conveying device that acts on the tip side It conveys to the machine body rear side with the conveying apparatus 14 with which it was equipped, and supplies it to the start end part of the threshing feed chain 5a of the threshing apparatus 5. The threshing device 5 supplies the tip side of the harvested cereal rice cake to the handling room (not shown) while squeezing and conveying the stock side of the harvested rice cake to the rear of the machine body by the threshing feed chain 5a. The grain tank 6 collects and stores the threshing grains from the threshing device 5.

  An engine 7 is provided below the driver's seat 2 of the self-propelled aircraft, and a transmission structure in which the driving force of the engine 7 is transmitted to the left and right traveling devices 1 and the preprocessing unit 10 is configured as shown in FIG.

  That is, the output from the output shaft 7 a of the engine 7 is transmitted to one end side of the intermediate shaft 21 via the transmission belt 20 and from the other end side of the intermediate shaft 21 to the traveling transmission shaft 24 via the gears 22 and 23. The engine output transmitted to the traveling transmission 24 is input from one end side of the traveling transmission shaft 24 to the left traveling transmission 30 and output from the output shaft 31 of the transmission 30. The left traveling device 1 is provided via an output shaft gear 32 provided with the output shaft 31 so as to be integrally rotatable, and an input gear 33 provided with the crawler drive shaft 1a of the left traveling device 1 so as to be integrally rotatable. The left traveling transmission system is configured to transmit to the crawler drive shaft 1a. The engine output transmitted to the traveling transmission shaft 24 is input to the right traveling transmission 30 from the other end of the traveling transmission shaft 24, and the output from the output shaft 31 of the transmission 30 is output to the output shaft 31. Are connected to the crawler drive shaft 1a of the right traveling device 1 via the output shaft gear 32 provided so as to be integrally rotatable, and the input gear 33 provided so that the crawler drive shaft 1a of the right traveling device 1 is integrally rotatable. A right traveling transmission system is configured to transmit.

  The engine output transmitted to the intermediate shaft 21 is provided with an intermediate shaft gear 25 connected to one end side of the intermediate shaft 21 and an input shaft 51 to which an input shaft gear 26 meshed with the intermediate shaft gear 25 is connected. The preprocessing transmission 50, the output shaft 52 of the transmission 50, and the transmission belt 15 attached to the input shaft 16 of the preprocessing unit 10 are transmitted to the input shaft 16 of the preprocessing unit 10 so as to be transmitted to the front shaft. A processing transmission system is configured.

  As shown in FIG. 2, both the left traveling transmission 30 provided in the left traveling transmission system and the right traveling transmission 30 provided in the right traveling transmission system are mounted on the traveling transmission shaft 24. A hydrostatic continuously variable transmission 35 including a hydraulic pump 36 and a planetary transmission 40 positioned inside a transmission case 41 connected to the hydrostatic continuously variable transmission 35 are provided.

  Both the continuously variable transmission 35 of the left traveling transmission 30 and the continuously variable transmission 35 of the right traveling transmission 30 are of an axial plunger type in which the traveling transmission shaft 24 is a pump shaft, and The variable displacement type hydraulic pump 36 and an axial plunger type hydraulic motor 37 connected to the hydraulic pump 36 via a drive circuit (not shown) are provided. The hydraulic pump 36 is driven by being input to the travel transmission shaft 24), and the hydraulic motor 37 is driven by the pressure oil from the hydraulic pump 36 and output from the motor shaft 38.

  One end side of the motor shaft 38 of each continuously variable transmission 35 is disposed inside the transmission case 41 and is connected to the sun gear 42 of the planetary transmission 40 so as to be integrally rotatable. By operating a speed change operation unit 39 formed of a swash plate operating shaft of the pump 36, the driving force from the engine 7 is converted into the driving force on the forward side and the reverse side and output from the motor shaft 38 to be output to the planetary transmission 40. The sun gear 42 is shifted forward or backward so that the sun gear 42 is rotationally driven forward or backward, or the output from the motor shaft 38 is stopped to drive the sun gear 42 of the planetary transmission 40. It becomes neutral to stop.

  Both the planetary transmission 40 of the left traveling transmission 30 and the planetary transmission 40 of the right traveling transmission 30 are supported by the sun gear 42 and the motor shaft 38 so as to be relatively rotatable. A planetary gear 44 that is rotatably supported via a support shaft at a plurality of locations in the rotation direction of the carrier 43 and that meshes with the sun gear 42, and a ring gear 45 that meshes with each planetary gear 44. Configured.

  In each planetary transmission 40, the carrier 43 is engaged with a transmission gear 24 a that the traveling transmission shaft 24 is provided so as to be integrally rotatable by an external gear portion provided all around the outer periphery of the carrier 43. The ring gear 45 is interlocked to the output shaft 31 so as to be integrally rotatable by a rotating shaft 46 extending from a side portion of the ring gear 45. Since the sun gear 42 is coupled to the motor shaft 38 so as to be integrally rotatable, each planetary transmission 40 is driven by the engine 43 from the traveling transmission shaft 24 to the carrier 43 so that the carrier 43 is rotated. The output from the motor shaft 38 of the step transmission 35 is input to the sun gear 42 and the sun gear 42 is rotationally driven, whereby each planetary gear 44 is operated, whereby the ring gear 45 is rotationally driven and rotated from the ring gear 45. Output to the output shaft 31 via the shaft 46.

  In both the left traveling gearbox 30 and the right traveling gearbox 30, the relationship between the speed state of the continuously variable transmission 35 and the driving speed (vehicle speed) of the traveling device 1, and the continuously variable transmission 35. Is operated in each speed state, the power ratio between the continuously variable transmission 35 and the planetary transmission 40, that is, the engine output is input from the traveling drive shaft 24 to the planetary transmission 40 and becomes the driving force of the traveling device 1. The planetary transmission 40 is operated so that the ratio between the power GD and the power HD input to the planetary transmission 40 from the continuously variable transmission 35 and serving as the driving force of the traveling device 1 is as shown in FIG. The gear ratio of the planetary transmission 40 is set.

  That is, when the continuously variable transmission 35 is operated to the forward speed maximum speed fm, the carrier 43 and the ring gear 45 of the planetary transmission 40 are rotationally driven at the same rotational speed, and the traveling drive shaft 24 The traveling device 1 is driven forward at the maximum speed FM only by the driving force transmitted to the planetary transmission 40, and the continuously variable transmission 35 is between the forward maximum speed fm and the neutral state n. Further, the continuously variable transmission 35 is connected to the set low speed fa on the forward side so that the output of the planetary transmission 40 is stopped and the traveling device 1 is stopped. When the speed change state is operated during the neutral state n, the continuously variable transmission 35 is further moved so that the planetary transmission 40 outputs the reverse drive force and the travel device 1 is driven backward. When operated to the neutral state n, the planet The speed device 40 outputs a driving force at the maximum speed on the reverse side, and the traveling device 1 is driven at the maximum speed RM on the reverse side only by the driving force transmitted from the continuously variable transmission 35 to the planetary transmission 40. It is set.

That is, when the self-propelled vehicle is driven, the shift operation unit 39 of the continuously variable transmission 35 of the left traveling transmission device 30 and the shift operation unit 39 of the continuously variable transmission 35 of the right traveling transmission device 30 are separately provided. By operating and shifting the two continuously variable transmissions 35 so as to be in the same speed state, both the left traveling device 1 and the right traveling device 1 are driven at the same drive speed to the forward side or the reverse side, respectively. The traveling machine travels straight forward or backward. When the two continuously variable transmissions 35 are shifted so as to be in different speed states, the left traveling device 1 and the right traveling device 1 are both driven forward or backward at different driving speeds, or the same. Even if the driving speed is one, one side is driven forward and the other side is driven backward, and the self-propelled aircraft turns.
Note that the hydraulic pump 70 shown in FIG. 2 supplies hydraulic oil to each continuously variable transmission 35.

  As shown in FIG. 2, the transmission 50 provided in the preprocessing transmission system includes a hydrostatic continuously variable transmission 55 having a hydraulic pump 56 mounted on the input shaft 51, and the hydrostatic continuously variable transmission. A planetary transmission 60 is located inside a mission case 61 connected to the device 55.

  The continuously variable transmission 55 is an axial plunger type, variable displacement type hydraulic pump 56, and an axial plunger type hydraulic motor connected to the hydraulic pump 56 via a drive circuit (not shown). 57 is provided. As shown in FIG. 2, the input shaft 51 is a pump shaft of the hydraulic pump 56, and one end side of the motor shaft 58 of the hydraulic motor 57 is located inside the mission case 61, and the planetary transmission 60. In the continuously variable transmission 55, the output of the engine 7 is input to the pump shaft (input shaft 51) to drive the hydraulic pump 56, and the hydraulic pump 56 is connected to the sun gear 62. The hydraulic motor 57 is driven by the pressure oil from the motor and the output from the motor shaft 58 is transmitted to the sun gear 62 of the planetary transmission 60.

  That is, the continuously variable transmission 55 converts the driving force from the engine 7 into the driving force on the forward rotation side and the reverse rotation side by operating the speed change operation unit 59 that is the swash plate operation shaft of the hydraulic pump 56. Output from the motor shaft 58 and the sun gear 62 of the planetary transmission 60 is driven to rotate in the forward rotation direction or the reverse rotation side so as to shift to the forward rotation side or the reverse rotation side. The output is stopped and the sun gear 62 of the planetary transmission 60 is stopped from being driven neutrally.

  As shown in FIG. 2, the planetary transmission 60 includes a carrier 63 that is rotatably supported by the sun gear 62 and the motor shaft 58 and is relatively rotatable with the sun gear 62, and the carrier 63. A planetary gear 64 that is rotatably supported via a support shaft at a plurality of locations in the circumferential direction 63 and meshes with the sun gear 62, and a ring gear 65 that meshes with each planetary gear 64. It is.

  The carrier 63 is meshed with a transmission gear 51a provided with the input shaft 51 so as to be integrally rotatable by an external gear portion provided all around the outer periphery of the carrier 63. The ring gear 65 is a ring gear 65. The output shaft 52 is interlocked with the output shaft 52 by a rotating shaft 66 extending from the side portion thereof. Since the sun gear 62 is connected to the motor shaft 58 so as to be integrally rotatable, the planetary transmission 60 receives the engine output from the input shaft 51 to the carrier 63, and the carrier 63 is driven to rotate, thereby continuously variable transmission. The output from the motor shaft 58 of the device 55 is input to the sun gear 62 and the sun gear 62 is rotationally driven, whereby each planetary gear 64 is operated, whereby the ring gear 65 is rotationally driven and the ring gear 65 rotates to the rotational shaft. The output is output to the output shaft 52 via 66.

The gear ratio of the planetary transmission 60 is set so that the planetary transmission 60 operates in a state where the relationship between the speed state of the continuously variable transmission 55 and the output speed of the planetary transmission 60 is as shown in FIG. .
That is, regardless of whether the continuously variable transmission 55 is shifted to the forward rotation side or the reverse rotation side, the planetary transmission device 60 outputs a positive rotation driving force that drives the preprocessing unit 10 in the normal rotation direction. Thus, when the continuously variable transmission 55 is operated to shift to the maximum rotational speed fm on the positive rotation side, the planetary transmission 60 is in a state of outputting the positive rotational driving force of the maximum speed UM. Further, when the continuously variable transmission 55 is shifted to the neutral state n, the planetary transmission 60 is further in a state of outputting a positive rotational driving force at a rotational speed UA that is ½ of the maximum speed fm. When the continuously variable transmission 55 is shifted to the reverse speed side maximum speed rm, the planetary transmission 60 is set in the output stop state.

  In other words, the preprocessing unit 10 is driven to shift by operating the speed change operation unit 59 of the continuously variable transmission 55, and when the continuously variable transmission 55 is shifted to the neutral state n, the preprocessing unit 10 moves to the maximum speed. The pre-processing unit 10 is driven at a higher speed as the speed change operation of the continuously variable transmission 55 from the neutral state n to the forward rotation side is increased. When the device 55 is shifted to a forward speed maximum speed fm, the pre-processing unit 10 is driven at the maximum speed. As the continuously variable transmission 55 is shifted from the neutral state n to the reverse rotation side to the high speed side, the pre-processing unit 10 is decelerated and driven, and the continuously variable transmission 55 is shifted to the maximum speed rm on the reverse rotation side. When the speed change operation is performed to the state, the preprocessing unit 10 stops.

[Another Example]
FIG. 5 shows the relationship between the speed state of the continuously variable transmission 35 and the driving speed (vehicle speed) of the traveling device 1 and the continuously variable transmission 35 in the traveling transmission 30 having another embodiment. Indicates the power ratio of the continuously variable transmission 35 and the planetary transmission 40 when operated in each speed state.

  In this transmission 30, when the continuously variable transmission 35 is operated to the forward speed maximum speed fm, the carrier 43 and the ring gear 45 of the planetary transmission 40 rotate at substantially the same rotational speed. The traveling device 1 is driven forward at the maximum speed FM by the driving force transmitted and transmitted from the traveling drive shaft 24 to the planetary transmission 40 and the driving force transmitted from the continuously variable transmission 35 to the planetary transmission 40. When the continuously variable transmission 35 is operated to a shift state at a set low speed fa between the maximum speed fm on the forward side and the neutral state n, the planetary transmission 40 stops outputting and travels. Further, when the continuously variable transmission 35 is operated to a shift state between the set low speed fa on the forward side and the neutral state n so that the device 1 is stopped, the planetary transmission 40 is driven on the reverse side. Output power and traveling device 1 goes backward Further, when the continuously variable transmission 35 is operated to the neutral state n so that the planetary transmission 40 is driven to the maximum speed on the reverse side, the traveling device 1 outputs the continuously variable transmission 35. The gear ratio of the planetary transmission 40 is set so that it is driven at the maximum speed RM on the reverse side only by the driving force transmitted to the planetary transmission 40.

  In addition to the transmission structure provided in the combine, the present invention can also be applied to the transmission structure provided in a working machine that harvests various crops such as carrots and onions. Accordingly, a combine, a work machine that harvests carrots and onions, and the like are collectively referred to as a work vehicle.

Side view of the entire combine Schematic diagram of transmission structure Explanatory drawing showing the relationship between continuously variable transmission and power ratio Explanatory drawing which shows the speed relationship of a continuously variable transmission and a planetary transmission. Explanatory drawing which shows the relationship between the continuously variable transmission and power ratio of the transmission provided with another embodiment.

Explanation of symbols

1 traveling device 35 hydrostatic continuously variable transmission 40 planetary transmission 42 sun gear 43 carrier 45 ring gear fm maximum speed of hydrostatic continuously variable transmission

Claims (2)

Hydrostatic continuously variable transmission and engine in which engine output is input to a left traveling transmission system that transmits engine output to the left traveling device, and a right traveling transmission system that transmits engine output to the right traveling device, and the engine A planetary gearbox including a carrier to which an output is input;
In both the traveling transmission systems, the output of the hydrostatic continuously variable transmission is input to the sun gear of the planetary transmission and is output from the ring gear of the planetary transmission to the traveling device. Configured ,
When the hydrostatic continuously variable transmission is operated to shift to a set low speed position between the maximum speed position on the forward side and the neutral position, the planetary transmission stops the output and the traveling device Stopped, the travel device is driven backward on the side closer to the neutral position of the hydrostatic continuously variable transmission than the set low speed position, and the maximum speed of the hydrostatic continuously variable transmission from the set low speed position On the side close to the position, the traveling device is configured to be driven forward, and
The ratio between the power that is input from the engine to the planetary transmission and becomes the driving force of the traveling device and the power that is input from the hydrostatic continuously variable transmission to the planetary transmission and becomes the driving force of the traveling device is Changes with the shifting operation of the step transmission,
The higher the driving speed on the forward side from the neutral position to the maximum speed position of the hydrostatic continuously variable transmission, the greater the proportion of power that is input from the engine to the planetary transmission and becomes the driving force of the traveling device. In addition, a traveling transmission structure for a work vehicle in which the gear ratio of the planetary transmission is set . When the hydrostatic continuously variable transmission is in the maximum speed state, the carrier of the planetary transmission and the ring gear rotate at the same rotational speed and are input from the engine to the planetary transmission and traveled. 2. The traveling transmission structure for a work vehicle according to claim 1, wherein a gear ratio of the planetary transmission is set so that the traveling device is driven only by power that is a driving force of the planetary gear.

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