KR102432272B1 - Transmission for tractor - Google Patents

Abstract

The present invention relates to a forward/backward transmission for a tractor, comprising: a main gear unit for changing the traveling speed of a tractor in multiple stages; a first hub coupled to the output shaft of the peripheral gear unit and provided to rotate with the output shaft; a forward gear and a reverse gear coupled to the output shafts of both sides of the first hub in an idling state, respectively; a first sleeve movably provided on the first hub and the forward and reverse gears to transmit the power of the output shaft to the forward gear or the reverse gear; a shift fork coupled to the first sleeve to linearly move the first sleeve; A shifting cylinder connected to the shift fork and automatically shifting the traveling direction of the tractor to forward or reverse by moving the shift fork when the vehicle speed is "0" during forward/backward shifting. .

Description

Transmission for tractor

The present invention relates to a forward/backward transmission for a tractor, and more particularly, to a forward/backward transmission for a tractor capable of automatically shifting forward/forward shifting of a transmission when the vehicle speed is “0”.

In general, a tractor is an agricultural work vehicle, structurally similar to a general vehicle, but is equipped with a powerful engine compared to a general vehicle, so it has good traction and is strong, so it is mainly used for farming. Various types of working machines can be selectively attached to the front, rear, or both of the front and rear of the body body for use as a furnace.

As such, a tractor mainly used for farming is equipped with a transmission for direction change and speed change, and the transmission of the tractor has a speed change from low speed to high speed or from high speed to low speed due to the characteristics of the tractor's work, and the forward and backward movement direction. Shifts are frequently required.

Such a conventional forward/backward transmission for a tractor has been disclosed in Korean Patent Registration No. 10-1006592, which will be described with reference to the accompanying drawings 1 and 2 .

As shown in FIG. 1, the conventional forward/reverse transmission for a tractor is provided with a frame 13 in which a front wheel 11 for steering and a rear wheel 12 for driving are installed in the tractor 10, and the frame 13 has an engine 20 and the transmission 30 are sequentially mounted from the front to the rear. In addition, the boarding driver 14 is mounted on the upper frame 13 on the rear side of the engine 20 , and the rear axle 40 for driving the rear wheel 12 is connected to the rear of the transmission 30 , and the transmission The PTO shaft 41 is extended from the PTO transmission unit at 30 to drive the work machine installed in the lift device 50 of the rear portion.

In addition, as shown in FIG. 2 , the transmission 30 includes a forward/backward transmission 31 and a forward/reverse transmission 31 for converting rotational power from the engine 20 into forward (forward rotation) and reverse (reverse rotation). ) at the output side of the main gear unit 32 that shifts the traveling speed of the tractor in 4 stages, and on the output side of the main gear unit 32, the secondary gear shifts the speed change of the main gear unit 32 to speeds of 2 to 4 steps. It consists of a final reduction unit 34 connected to the output shaft of the unit 33 and the auxiliary transmission unit 33 for final deceleration and changing the direction of transmission of power to the rear axle 40 . And, it includes a PTO (Power Take-Off) part 35 for receiving power from the main gear part 35 and withdrawing power to the working machine side.

In the tractor as above, the forward, neutral, and reverse are selected by operating the forward/reverse lever installed in the boarding driver 14, and the high-speed and low-speed (HIGH-LOW) shift levers of the auxiliary transmission unit 33 are operated. When a low speed is selected, the shift stage of the main gear unit 32 can be selected at a required speed by operating the main shift lever, and the shift is performed by an internal hydraulic clutch or a synchromesh mechanism according to this selection operation.

In the tractor having such a structure, the vehicle maintains a stopped state even if the driver places the forward/reverse lever in the neutral position and takes the foot off the clutch pedal. In such a state, since power is transmitted by the clutch, all gears and rotating shafts except for the forward/reverse driven shaft are rotated in the forward/reverse transmission. That is, the power of the engine is not transmitted to the forward/backward driven shaft, but the power of the engine is transmitted to the gear and the rotation shaft inside the forward/reverse transmission.

In this state, when the driver presses the clutch pedal to move the tractor forward or backward, the power transmitted by the clutch is cut off, but the gears and rotation shafts rotate by inertia because they have previously received the power of the engine.

In this state, if the driver places the forward/reverse lever at the forward or reverse position, the sleeve of the synchro mesh mechanism is engaged with the forward driven gear or reverse driven gear, and power is not transmitted by the clutch, but the rotational inertia of the gear and the rotation shaft As the forward and backward driven shaft rotates, a starting shock is generated. That is, the starting shock occurs the moment the driver steps on the clutch pedal and operates the forward/reverse lever. After such a starting shock occurs, the driver gently starts the tractor in a semi-clutch state.

However, this shifting process is performed by a synchronous mesh mechanism, which is a transmission mechanism, and there is a risk that parts such as an expensive synchronizer ring provided in the synchronous mesh mechanism may be damaged due to the starting shock that occurs frequently during shifting. When parts such as the niger ring are damaged, not only the synchro mesh mechanism but also the entire transmission must be replaced.

Republic of Korea Patent Publication No. 10-2012-0060482

Accordingly, the present invention has been devised to solve the problems of the prior art as described above, so that the forward or reverse shift of the transmission can be automatically shifted forward or backward when the vehicle speed is "0" without shifting to neutral. An object of the present invention is to provide a forward and backward transmission for a tractor.

A forward/backward transmission for a tractor according to the present invention for achieving the above object includes: a main gear unit for changing the traveling speed of the tractor in multiple stages; a first hub coupled to the output shaft of the peripheral gear unit and provided to rotate with the output shaft; a forward gear and a reverse gear coupled to the output shafts of both sides of the first hub in an idling state, respectively; a first sleeve movably provided on the first hub and the forward and reverse gears to transmit the power of the output shaft to the forward gear or the reverse gear; a shift fork coupled to the first sleeve to linearly move the first sleeve; and a shifting cylinder connected to the shift fork to automatically shift the moving direction of the tractor forward or backward by moving the shift fork when the vehicle speed is “0” during forward/backward shifting.

In addition, when the vehicle speed is “0”, the sleeve and the forward gear or the reverse gear have the same rotational speed, and the vehicle speed is sensed by a speed sensor to control the shifting cylinder.

In addition, the shifting cylinder includes a piston movably provided therein while connected with the shift fork; a spring provided between the piston and the shifting cylinder to move the shift fork in one direction; It may include a; is formed in the shifting cylinder opposite the spring to the hydraulic port for introducing the hydraulic pressure into and out of the shifting cylinder.

In addition, in the forward/reverse transmission device for a tractor of the present invention, the first gear unit coupled to the forward gear is fixedly provided while being rotatably provided in the peripheral gear unit, and the second gear is provided fixedly spaced apart from the first gear unit. a transmission shaft having a negative; an idle gear rotatably provided in a peripheral gear portion between the transmission shaft and the reverse gear and coupled to the second gear portion of the transmission shaft; a main shaft rotatably provided between the peripheral portion and the differential device; a second hub coupled to the main shaft and provided to rotate like the main shaft; a high-speed gear and a low-speed gear coupled to the main shafts of both sides of the second hub in an idling state, respectively; It may further include; a second sleeve provided to be movable on the second hub and the high and low speed gears to transmit power to the high speed gear or the low speed gear.

According to the forward/reverse gearbox for a tractor of the present invention, when the speed of the first sleeve and the forward gear or the reverse gear rotated together with the output shaft of the main gear unit is the same, that is, when the vehicle speed is "0", the forward/backward shift of the transmission is neutralized. Since it is possible to automatically shift forward or backward without shifting, it is possible to simplify the forward and backward transmission and to prevent damage to parts due to malfunction.

1 is a schematic diagram showing a power transmission structure of a general tractor.
Figure 2 is a power transmission system diagram of a general tractor.
3 is a cross-sectional configuration view showing the overall configuration of the forward/backward transmission for a tractor according to the present invention.
4 is an enlarged cross-sectional configuration view of a forward/backward transmission configured in the forward/backward transmission for a tractor according to the present invention.
5 is an operation diagram illustrating a forward shift state of a forward/reverse shift unit according to the present invention.
6 is an operation diagram illustrating a reverse shift state of the forward/reverse shift unit according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The terms used in the present invention are terms defined in consideration of the functions in the present invention, which may vary depending on the intention or custom of the user or operator, so the definitions of these terms correspond to the technical matters of the present invention and should be interpreted as a concept.

In addition, the embodiments of the present invention do not limit the scope of the present invention, but are merely exemplary matters of the constituent elements presented in the claims of the present invention, and are included in the technical spirit throughout the specification of the present invention and the scope of the claims. It is an embodiment including a substitutable component as an equivalent in the component.

In addition, optional terms in the examples below are used to distinguish one component from other components, and the components are not limited by the terms.

Accordingly, in describing the present invention, detailed descriptions of related known technologies that may unnecessarily obscure the gist of the present invention will be omitted.

3 to 6 are views showing a forward and backward transmission for a tractor according to the present invention and a forward and backward transmission configured therefor.

As shown in FIG. 3, the forward/backward transmission for a tractor according to the present invention includes a main gear unit 100 that is connected to the output side of an engine (not shown) and shifts the traveling speed of the tractor in four stages, and a main gear unit ( 100) connected to the output side of the forward/backward transmission unit 200 for switching the driving direction of the tractor to forward (forward rotation) or backward (reverse rotation) driving, and the main gear unit ( 100) includes a sub-transmission unit 300 for shifting the speed change to the speed of 2 to 4 steps.

And, on the output side of the auxiliary transmission unit 300, a differential device for transmitting power to the front and rear wheel drive shafts along with final deceleration is connected and provided, and PTO for receiving power from the main transmission unit 100 and drawing power to the working machine side (Power Take-Off) may include a unit (not shown).

In particular, in the present invention, considering that forward/reverse shifting is performed at a low speed stage, the forward/reverse shift unit 200 is connected to the output side of the main gear unit 100 behind the main gear unit 100, that is, when a malfunction occurs during the shifting process. There is also an advantage that can significantly reduce the damage of the device.

The main gear unit 100 is a transmission unit connected to the output side of the engine to change the traveling speed of the tractor in four stages. At the rear end thereof, as shown in FIG. 4 , the output shaft 110 from which the engine power is output is provided. is provided to protrude.

As shown in FIGS. 4 to 6 , the forward and backward transmission unit 200 is provided with a rear shaft 210 into which the output shaft 110 protruding from the rear of the main gear unit 100 is inserted, the output shaft 110 and the rear shaft 210 is provided to be integrally rotated by spline coupling or serration coupling (hereinafter referred to as "spline coupling").

This rear shaft 210 is provided in a state that surrounds the entire output shaft 110 protruding from the peripheral shaft 100, so that the output shaft 110 is protected by the rear shaft 210 as well as dispersing the load acting on the peripheral shaft 100 In case of damage due to a load, only the rear axle 210 needs to be replaced, so maintenance is simple and it has the advantage of transmitting a large amount of power.

On the other hand, the first hub 220 is spline-coupled to the outer surface of the rear shaft 210 as described above and is provided to rotate integrally. Gears 250 are respectively coupled to each other in an idling state.

And, on one side of the first hub 220, the forward gear 240, and the reverse gear 250, coupling protrusions 221, 241, and 251 in which a plurality of gear teeth protrude in a ring shape are respectively formed, and each coupling The protrusions 221, 241, and 251 are provided to have the same height.

Accordingly, the coupling protrusions 221 , 241 , and 251 of the first hub 220 , the forward gear 240 , and the reverse gear 250 are provided at the same height so that the first sleeve 230 to be described later is the first hub. 220 and the coupling protrusions 221 , 241 , and 251 of the forward gear 240 and the reverse gear 250 can be easily moved.

In addition, the first sleeve 230 is fitted on the outer circumferential surface of the first hub 220 , and the first sleeve 230 is provided on the inner circumferential surface of the first hub 220 , the forward gear 240 , and the reverse gear 250 . A gear-shaped coupling groove is formed corresponding to the coupling protrusions 221, 241, and 251 of the first sleeve ( 230 is movably provided on the coupling protrusions 221 , 241 , 251 of the first hub 220 and the forward and reverse gears 240 and 250 . Accordingly, the power of the output shaft 110 is transmitted to the forward gear 240 or the reverse gear 250 .

In particular, when the first sleeve 230 is formed to have the same width (left and right width) than the first hub 220, the first sleeve 230 is provided on the first hub 220 so that the neutral state is maintained. In the case where the first sleeve 230 is formed to have a greater width than the first hub 220 , the first sleeve 230 includes the first hub 220 and the forward gear 240 or the first hub 220 . ) and the reverse gear 250, so that it is possible to mechanically implement a shift structure in which only forward or reverse is possible without neutrality. Of course, even when the first hub 220 is formed to have a smaller width than the first sleeve 230, the forward and backward shift may be shifted only forward and backward without neutral.

Further, the movement of the first sleeve 230 as described above is performed by the shift fork 260 , and the shift fork 260 is automatically performed by the shifting cylinder 270 .

The shift fork 260 is provided in a state in which the forks (clamps) on both sides rotate about the hinge part, and grip the outer surface of the first sleeve 230 to move the first sleeve 230 in a straight line. At this time, since the shift fork 260 holding the first sleeve 230 is provided with a ball (not shown) as a medium between the first sleeve 230 and the first sleeve 230 , it does not interfere with the rotation of the first sleeve 230 . It is possible to smoothly move the first sleeve 230 .

The shifting cylinder 270 has a piston 273 movably provided therein, and a piston rod 274 passing through the shifting cylinder 270 is fixed to the shift fork 260 on the front side of the piston 273 . very well equipped Accordingly, as the piston rod 274 moves in and out of the shifting cylinder 270 , the shift fork 260 moves in a straight line.

And, a compression coil spring (hereinafter referred to as "spring") 272 is inserted between the rear surface of the piston 273 and the shifting cylinder 270, and the shifting cylinder 270 opposite to the spring 272 is provided. The front end of the piston 273 and the shifting cylinder 270 between the hydraulic pressure port 271 for entering and leaving is formed.

Accordingly, as the piston 273 and the piston rod 274 are moved forward by the tensile force of the spring 272 , the shift fork 260 is moved forward, that is, to the left as shown in FIG. 5 , and hydraulic pressure is applied to the hydraulic port 271 . When this is supplied, as the piston 273 and the piston rod 274 move backward, the shift fork 260 is moved backward, that is, to the right as shown in FIG. 6 .

Here, an air breather 274a connecting the inside and the outside of the shifting cylinder 270 having a spring 272 is formed on the piston rod 274 , and the piston by the air breather 274a is formed. When the 273 moves, the inside of the shifting cylinder 270 does not become a vacuum state, so that smooth operation can be induced.

On the other hand, as described above, the hydraulic pressure supplied to the hydraulic port 271 of the shifting cylinder 270 is controlled by an electronic control unit (ECU), and the ECU operates the shifting cylinder only when the vehicle speed is “0”. By supplying or recovering hydraulic pressure to the hydraulic port 271 of 270 and linear movement of the shift fork 260, the moving direction of the tractor can be automatically shifted forward or backward.

In this case, the case where the vehicle speed is “0” may include a state in which the tractor is stopped by the brake, but even when the tractor is stopped and the power is cut off by the clutch, the output shaft 110 receiving the engine power and the gear connected thereto They can be rotated by inertia.

Accordingly, in the present invention, when the vehicle speed is “0”, the rotational speed of the first sleeve 230 and the forward gear 240 or the reverse gear 250 is the same. Then, the vehicle speed is sensed by a speed sensor (not shown), and the ECU performs a control operation of supplying or recovering hydraulic pressure to the hydraulic port 271 of the shifting cylinder 270 according to the detection signal.

As shown in FIGS. 4 to 6 , the auxiliary transmission unit 300 is configured above the forward/reverse transmission unit 200 .

That is, the sub transmission unit 300 is integrally formed with the transmission shaft 310 rotatably provided at the rear of the main transmission unit 100 and the transmission shaft 310 to rotate like the transmission shaft 310 . On the other hand, the first gear unit 311 meshed with the forward gear 240 of the forward/reverse transmission unit 200 and the transmission shaft 310 spaced apart from the first gear unit 311 are integrally formed to form the transmission shaft 310 . ) and a second gear unit 312 that is rotated as in.

At this time, the first gear part 311 formed on the transmission shaft 310 is provided to have a larger diameter than the second gear part 312 , and the second gear part 312 is rotatable at the rear of the peripheral gear part 100 . The idle gear 320 is provided to be meshed with each other, and the reverse gear 250 on the rear shaft 210 is meshed with the lower portion of the idle gear 320 .

Accordingly, when the transmission shaft 310 is rotated, the first and second gear units 311 and 312 are simultaneously rotationally driven like the transmission shaft 310 , and the idle gear 320 is driven by the second gear unit 312 . is rotated and the reverse gear 250 meshed therewith is rotated on the rear shaft 210 in the opposite direction to the forward gear 240 .

And, the main shaft 330 is rotatably provided between the main shaft portion 100 and the differential device on the upper portion of the transmission shaft 310, and the second hub 340 is spline-coupled to the outer surface of the main shaft 330 to be integrally formed. It is provided to rotate, and the high-speed gear 360 and the low-speed gear 370 are respectively coupled to the main shafts 330 on both sides of the second hub 340 in an idling state.

In addition, on one side of the second hub 340 and the high-speed gear 360 and the low-speed gear 370, coupling protrusions 341, 361, 371 in which a plurality of gear teeth protrude in the form of a ring are formed, respectively, and each coupling The protrusions 341, 361 and 371 are provided to have the same height.

Accordingly, the coupling protrusions 341, 361, and 371 of the second hub 340 and the high-speed gear 360 and the low-speed gear 370 are provided at the same height so that the second sleeve 350 to be described later is the second hub. The coupling protrusions 341, 361, and 371 of the 340 and the high-speed gear 360 and the low-speed gear 370 can be easily moved.

In addition, a second sleeve 350 is fitted on the outer circumferential surface of the second hub 340 , and the second sleeve 350 has a second hub 340 , a high-speed gear 360 and a low-speed gear 370 on its inner circumferential surface. Since a gear-shaped coupling groove corresponding to the coupling protrusions 341, 361, 371 of ) 361 and 371 are movably provided. Accordingly, it is possible to rotate the main shaft 330 at a high speed or a low speed to drive the tractor at a high speed or a low speed.

And, the high-speed gear 360 and the low-speed gear 370 of the main shaft 330 are provided in a meshing state with the first gear part 311 and the second gear part 312 of the transmission shaft 310, and the main shaft ( An output gear 380 for transmitting power to the differential device is provided at the tip of the 330 to be rotated integrally by spline coupling with the main shaft 330, and the output gear 380 is provided to mesh with the gear provided in the differential device. do.

Meanwhile, the second sleeve 350 may include a separate shifting cylinder as in the aforementioned first sleeve 230 , and the separate shifting cylinder provided in the second sleeve 350 also has a vehicle speed of “0”. "It can be provided so that the shift is made only in the in state.

The operation relationship of the forward/reverse transmission device for a tractor as described above will be described.

First, when the tractor travels forward, the power transmitted from the engine by the clutch is transmitted, and the output shaft 110 of the main gear unit 100 provided at the rear of the clutch rotates, and the rear shaft 210 splined thereto is also It rotates like the output shaft 110 .

Then, the first hub 220 spline-coupled to the outer surface of the rear shaft 210 is rotated along with the rear shaft 210, and is moved forward by the shifting cylinder 270 as shown in FIG. ) and the first sleeve 230 spline-coupled to the coupling protrusions 221 and 241 of the forward gear 240, respectively, the first sleeve 230 and the forward gear 240 are also the same as the first hub 220. rotated

At this time, the piston 273 in the shifting cylinder 270 is moved forward in the shifting cylinder 270 by the spring 272, and the piston rod 274 connected to the piston 273 is the shifting cylinder. The shift fork 260 drawn out from the 270 and coupled to the first sleeve 230 is moved forward to engage the first sleeve 230 with the first hub 220 and the forward gear 240 . will do

On the other hand, when the forward gear 240 is rotated as described above, the first gear part 311 of the transmission shaft 310 meshed therewith is rotated interlockingly, and the transmission shaft 310 is rotated by the rotation of the first gear part 311 . ) and the second gear unit 312 are integrally rotated together.

In addition, when the first and second gear parts 311 and 312 of the transmission shaft 310 are rotated, the high-speed gear 360 of the main shaft 330 meshed with the first gear part 311 is rotated at the same time, 2 has a power transmission structure in which the idle gear 320 meshed with the gear unit 312 and the low speed gear 370 of the main shaft 330 are simultaneously rotated.

At this time, although the reverse gear 250 of the rear shaft 210 is also rotated by the rotation of the idle gear 320 , the reverse gear 250 is not connected to the first hub 220 by the first sleeve 230 . It idles on the rear shaft 210 , and the power of the output shaft 110 is output only through the forward gear 240 connected to the first hub 220 by the first sleeve 230 .

The power output in this way is transmitted to the first and second gear parts 311 and 312 of the transmission shaft 310 and the high-speed gear 360 and the low-speed gear 370 on the main shaft 330 meshed with each other, in this state When the second sleeve 350 coupled to the second hub 340 of the main shaft 330 is moved toward the high-speed gear 360 and connects the high-speed gear 360 with the second hub 340, the power is increased at high speed. It is transmitted to the main shaft 330 through the gear 360 so that the tractor travels at a high speed forward (power transmission state of No. ① in FIG. 4), or the second sleeve 350 is moved to the low speed gear 370 side to the low speed gear When 370 is connected to the second hub 340, power is transmitted to the main shaft 330 through the low-speed gear 370, and the tractor travels at a forward low speed (power transmission state of ② in FIG. 4).

Afterwards, when the tractor is driven backward, the ECU detects the vehicle speed between the first hub 220 and the reverse gear 250 through the speed sensor, and the vehicle speed is “0”, that is, the first hub 220 and the reverse gear 250 ), when the rotational speed becomes the same, hydraulic pressure is quickly supplied to the hydraulic port 271 of the shifting cylinder 270 as shown in FIG. 6 .

Then, the piston 273 is moved backward while compressing the spring 272 in the shifting cylinder 270 by the supplied hydraulic pressure, and the piston rod 274 is drawn into the shifting cylinder 270 and the shift fork 260 ) is moved backwards.

The first sleeve 230 is separated from the forward gear 240 by the backward movement of the shift fork 260 and is coupled to the coupling protrusions 221 and 251 of the first hub 220 and the reverse gear 250. get bitten

Accordingly, the power of the output shaft 110 of the main gear 100 is output through the reverse gear 250 rotated like the first hub 220 , and the power output through the reverse gear 250 is the power as described above. It is transmitted to the high-speed gear 360 and the low-speed gear 370 on the main shaft 330 through the transmission structure, respectively.

In this state, when the second sleeve 350 is moved toward the second hub 340 and the high-speed gear 360 to connect the high-speed gear 360 with the second hub 340 , power is transmitted through the high-speed gear 360 . It is transmitted to the main shaft 330 so that the tractor travels backward at high speed (the power transmission state of No. 3 in FIG. 4), or the second sleeve 350 is moved to the second hub 340 and the low speed gear 370 side and moves to a low speed When the gear 370 is connected to the second hub 340, power is transmitted to the main shaft 330 through the low-speed gear 370, so that the tractor travels backwards at low speed (power transmission state of No. ④ in FIG. 4).

Meanwhile, the movement with the second sleeve 350 as described above may also be performed while the vehicle speed is “0”, similarly to the movement of the first sleeve 230 .

Thereafter, when the tractor is to be driven forward again, the ECU withdraws and recovers the hydraulic pressure in the shifting cylinder 270 through the hydraulic port 271 while the vehicle speed is “0”. The piston 273, the piston rod 274, and the shift fork 260 are moved forward to engage the first sleeve 230 with the first hub 220 and the forward gear 240 so that the tractor can travel forward. do.

Although the present invention has been described in detail through specific examples, it is intended to describe the present invention in detail, and the present invention is not limited thereto, and by those of ordinary skill in the art within the technical spirit of the present invention. It is clear that the modification or improvement is possible.

All simple modifications and variations of the present invention fall within the scope of the present invention, and the specific protection scope of the present invention will be clarified by the appended claims.

100: peripheral part 110: output shaft
200: forward and backward transmission 210: rear axle
220: first hub 221: coupling protrusion
230: first sleeve 240: forward gear
241: coupling protrusion 250: reverse gear
251: coupling protrusion 260: shift fork
270: shifting cylinder 271: hydraulic port
272: spring 273: piston
274: piston rod 274a: air breather
300: auxiliary transmission 310: transmission shaft
311,312: gear unit 320: idle gear
330: main shaft 340: second hub
341: coupling protrusion 350: second sleeve
360: high-speed gear 361: coupling protrusion
370: low gear 371: coupling protrusion
380: output gear

Claims (4)

a peripheral gear shifting speed of the tractor in multiple stages;
a rear shaft coupled to the output shaft of the peripheral gear unit and provided to rotate integrally;
a first hub coupled to the rear shaft and provided to rotate like the rear shaft;
a forward gear and a reverse gear coupled to the output shafts of both sides of the first hub in an idling state, respectively;
a first sleeve movably provided on the first hub and the forward and reverse gears to transmit the power of the output shaft to the forward gear or the reverse gear;
a shift fork coupled to the first sleeve to linearly move the first sleeve;
a shifting cylinder connected to the shift fork and automatically shifting the moving direction of the tractor to forward or reverse by moving the shift fork when the vehicle speed is “0” during forward/backward shifting;
a piston rod provided to be in and out of the shifting cylinder to move the shift fork forward or backward;
A forward/backward transmission for a tractor including; an air breather that is formed on the piston rod and connects the inside and the outside of the shifting cylinder.
The method according to claim 1,
When the vehicle speed is “0”, the sleeve and the forward gear or the reverse gear have the same rotational speed, and the vehicle speed is sensed by a speed sensor to control the shifting cylinder.
The method according to claim 1 or 2,
The shifting cylinder includes: a piston provided movably therein while a piston rod is fixedly provided on one surface to move the shift fork forward or backward;
a spring provided between the piston and the shifting cylinder to move the shift fork in one direction;
A forward/backward transmission for a tractor comprising a; a hydraulic port formed on the shifting cylinder opposite the spring to allow hydraulic pressure to enter and exit the shifting cylinder.
The method according to claim 1,
a transmission shaft having a first gear portion that is rotatably provided in the peripheral gear portion while being fixedly coupled to the forward gear, and a second gear portion that is fixedly provided to be spaced apart from the first gear portion;
an idle gear rotatably provided in a peripheral gear portion between the transmission shaft and the reverse gear and coupled to the second gear portion of the transmission shaft;
a main shaft rotatably provided between the peripheral portion and the differential device;
a second hub coupled to the main shaft and provided to rotate like the main shaft;
a high-speed gear and a low-speed gear coupled to the main shafts of both sides of the second hub in an idling state, respectively;
A forward/backward transmission for a tractor comprising a second hub and a second sleeve movably provided on the high and low speed gears to transmit power to the high speed gear or the low speed gear.

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