JPH0699842A - Traveling transmission structure of working vehicle - Google Patents

Abstract

PURPOSE:To improve operability at the gentle turning time by changeover-operating first changeover mechanism into the steep turning state from the gentle turning state by operating an operating lever over a specified position, returning second changeover mechanism into the gentle turning state by the return operation of the operating lever, and holding back the operation of the second changeover mechanism on the basis of the detection of the high speed travel state. CONSTITUTION:When a changeover lever 18 is operated into a gentle turn position, a second changeover valve 35 is changeover-operated by a solenoid 53 into a gentle turn position 35a of supplying operating oil to a gentle turning clutch 12. When the changeover lever 18 is operated into an ultra pivotal turn position, the second changeover valve 35 is switched into an ultra pivotal turn position 35b of supplying operating oil to the reversing clutch 30. When an operating lever 39 is operated into a second turn position L2 from a first turn position L1 on the left, for instance, the gentle turning speed becomes the maximum. In the case of desiring to make a small turn further to the left, the operating lever 39 is operated into a third turn position L3. When a second speed change lever 28 is detected to be in a high speed position by a limit switch 55, second changeover mechanism 53 is impeded so that the second changeover valve 35 is not changeover-operated into the ultra pivotal turn position 35b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a traveling power transmission structure for a work vehicle equipped with a pair of left and right traveling devices such as multi-wheel type or crawler type.

[0002]

2. Description of the Related Art As an example of a work vehicle as described above, there is a combine equipped with a pair of left and right traveling devices of a crawler type. An example of a traveling transmission structure and a turning structure of such a combine is disclosed in Japanese Unexamined Patent Publication No. 4-46871. Is disclosed in. In this structure, as shown in FIG. 2 of the publication, left and right side gears (12 in FIG. 2 of the publication) are engaged with a first transmission gear (7 in FIG. 2 of the publication). Then, the left and right traveling devices (4 in FIG. 2 of the above publication) are driven to rotate at the same speed, and the machine body goes straight.

As shown in FIGS. 2 and 3 of the publication, when the transmission shaft (24 in FIG. 3 of the publication) is slid to the left side of the drawing, the gears at both ends of the transmission shaft (see the publication). 11) in FIG. 3 is a gear (27 in FIG. 3 of the publication).
And the power from this transmission shaft is transmitted in reverse to the second transmission gear (9 in FIG. 2 of the above publication) (corresponding to the sudden turning mechanism). As a result, when the operation lever (34 in FIG. 1 of the publication) for turning operation is operated to a predetermined left position (L2 in FIG. 1 of the publication), as shown in FIG. 2 of the publication. The left side gear is slid to the left side gear, and through the clutch (RC in FIG. 2 of the above publication),
Reverse power is transmitted to the left traveling device. Therefore, the aircraft makes a super turning turn to the left (corresponding to a sharp turning state in which a large speed difference is given to the left and right traveling devices).

Next, the transmission shaft (24 in FIG. 3 of the above publication)
When is operated to slide to the right in the drawing, the gears (11 in FIG. 3 of the publication) at both ends of the transmission shaft directly engage with the second transmission gear (9 in FIG. 2 of the publication), The power from the transmission shaft is transmitted to the second transmission gear in a low speed normal rotation state (corresponding to a slow turning mechanism). As a result, when the operation lever for turning operation is operated to the predetermined left position as described above, the left side gear is slid as shown in FIG. 2 of the publication, and the low speed is applied to the left traveling device via the clutch. The normal rotation power of is transmitted. Therefore, the airframe gently turns to the left (corresponding to a gently turning state in which a small speed difference is given to the left and right traveling devices).

[0005]

In the above structure,
Select between the gentle turning state and the super turning state (steep turning state)
This is done by an operator slidingly operating a transmission shaft (24 in FIGS. 2 and 3 of the above publication) with a switching lever (corresponding to a switching operation tool). Then, the operator determines in advance which of the gentle turning state and the super-spinning turning state (a steep turning state) according to the state of the work place to travel, and operates the switching lever.

For example, in a state where the gentle turning state is selected, the operator operates the operation lever to a predetermined left position and tries to turn to the left. In this case, due to changes in the state of the work site, the aircraft may not turn at the turning radius expected by the operator, and the aircraft may not turn sufficiently to the left. In such a case, the operator needs to return the operation lever to the neutral position, stop the machine once, and operate the switching lever again from the gentle turning side to the super turning side (quick turning side). . Then, in this state, it is necessary to operate the operation lever again to the left predetermined position to turn the machine body to the left (super-turning), so there is room for improvement in terms of operability.
SUMMARY OF THE INVENTION It is an object of the present invention to improve operability in the case of a work vehicle of a type in which the gentle turning state and the sharp turning state are selected in advance as described above, when the body does not sufficiently turn in the gentle turning state. I am trying.

[0007]

A feature of the present invention is that the traveling power transmission structure of a work vehicle including a pair of left and right traveling devices as described above is provided with the following configuration. That is, a slow turning mechanism that gives a speed difference to the left and right traveling devices to turn the machine body to the right or left, and a speed difference larger than that of the slow turning mechanism to the left and right traveling devices to make the machine make a sharp turn to the right or left. A swivel mechanism and an operating lever for swivel operation that can be manually operated left and right. When the operation lever is operated from the neutral position to the right or left predetermined position, the slow turning mechanism operates, and when the operation lever is operated from the neutral position to the right or left predetermined position, the rapid turning mechanism is activated. A first switching mechanism that can switch between two states of a sudden turning state that operates, and a switching operation tool that can artificially selectively switch the first switching mechanism between a gentle turning state and a rapid turning state. When the operating lever is operated to exceed the predetermined position on the right or left with an operating force greater than the setting, the operation permitting mechanism that permits this operation and the operating lever in the state of switching the first switching mechanism to the gentle turning state are operated. When the first switching mechanism is operated to move beyond the predetermined position on the right or the left, the first switching mechanism is switched from the gentle turning state to the rapid turning state, and when the operation lever is returned to the predetermined position on the right or the left, the first switching mechanism is operated. A second switching mechanism for returning from the sudden turning state to the gentle turning state. Detecting means for detecting that the machine body is in a high-speed traveling state, and restraining means for restraining the operation of the second switching mechanism based on the detection by the detecting means.

[0008]

According to the structure of the present invention, the operator preliminarily selects either the gentle turning state or the sharp turning state by the switching operation tool in accordance with the state of the work place to travel. With this, when the gentle turning state is selected, when the operating lever is operated from the neutral position to the predetermined position on the right or left, the gentle turning mechanism is activated, and the body gently turns to the right or left. On the contrary, if the sudden turning state is selected, the rapid turning mechanism operates when the operating lever is operated from the neutral position to the predetermined position on the right or left, and the aircraft turns to the right or left. In this way, the state in which the operation lever is operated between the neutral position and the predetermined left and right positions is the normal state.

Then, when the gentle turning state is selected, it is assumed that the operating lever is operated to a predetermined left position, for example, and an attempt is made to turn left. In this case, if the machine body does not turn sufficiently within the turning radius expected by the operator, the operating lever is operated to the left with a slightly strong operating force, and the operating lever is operated to the left beyond the predetermined left position. As a result, the second switching mechanism switches the first switching mechanism from the gentle turning state to the sudden turning state, a speed difference larger than that in the gentle turning state is applied to the left and right traveling devices, and the body starts to make a sharp turn. The aircraft can be turned to the left with a desired turning radius. Then, when the operation lever is returned to the predetermined left position, the second switching mechanism returns the first switching mechanism from the sudden turning state to the first gently turning state. In the conventional structure of the above-mentioned publication, when the operator is holding the operation lever by hand and operating left and right to perform a turning operation in a state where the gentle turning state is selected, it is desirable to temporarily turn the body to a small size. Need to operate the switching lever (switching operation tool) from the gentle turning side to the sharp turning side. On the other hand, according to the present invention, the second switching mechanism automatically switches from the gentle turning state to the sharp turning state by simply slightly operating the operating lever which is held by hand from the beginning. It is not necessary to operate the switching lever (switching operation tool) unlike the conventional structure.

In a high-speed running state, when a sharp turning mechanism is used to give a large speed difference to the left and right running devices,
In some cases, the vehicle body may be swung to the outside by turning due to the centrifugal force, and the riding comfort may deteriorate. As a result, when traveling at high speeds, it is necessary to operate the switching lever (switching operation tool) to the gentle turning state side with a small turning radius in advance. You can operate it and make a sharp turn. In this case, when the switching lever (switching operation tool) is operated toward the gentle turning state during high-speed traveling, the second switching mechanism operates even if the operating lever is accidentally operated beyond the predetermined right or left position. Without doing so, the first switching mechanism remains held in the gentle turning state side without being operated in the sudden turning state side.

[0011]

As described above, in the working vehicle of the type in which the gentle turning state and the sharp turning state are selected in advance, when the body is desired to temporarily turn small in the gentle turning state, another switching operation is performed. Even if you do not operate the tool, you can switch to a sudden turning state by slightly operating the operating lever you have in your hand, and you can improve the operability when turning the work vehicle. It was Further, in the high-speed traveling state, even if the operation lever is largely operated, the switching operation from the gentle turning state to the sharp turning state is not automatically performed, so that the riding comfort does not deteriorate.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 4 shows a combine truck, which is an example of a work vehicle,
1 shows a structure inside a mission case 8 of a traveling system, in which power from an engine (not shown) is transmitted via a belt transmission mechanism (not shown) having a tension clutch, and a hydrostatic continuously variable transmission 1 The power from the output shaft 3 of the continuously variable transmission 1 is transmitted via the first transmission shaft 4 to the reaper (not shown) at the front of the machine body.

Power from the first transmission shaft 4 is transmitted to the second transmission shaft 11 via the first gear 9 and the second gear 10.
A shift gear 14 is slidably fitted to the second transmission shaft 11 by a spline structure, while a high speed gear 16, a medium speed gear 17, and a low speed gear 6 are fixed to a third transmission shaft 15 corresponding thereto. . With the above structure, the shift gear 14 is slid to engage the high-speed gear 7, the medium-speed gear 17, or the low-speed gear 6 that meshes with the high-speed gear 16, thereby shifting the forward rotation power for straight traveling into three stages of high, medium, and low. This normal rotation power can be applied to the first gear that meshes with the medium speed gear 17.
It is transmitted to the transmission gear 19. As described above, the shift gear 14, the high speed gear 7 and the like constitute the gear shift type transmission 13.

A right side gear 21R and a left side gear 21L are externally fitted to a support shaft 20 supporting the first transmission gear 19 so as to be rotatable relative to each other, and an input gear 23 of a left and right axle shaft 22 is a left and right side gear 21R, 21L is always occluded. As a result, the right or left side gear 21R, 2
1L is slid on the first transmission gear 19 to engage / separate the first transmission gear 19, and power transmission and transmission interruption operation are performed on the crawler type traveling device 24.
Side clutches 25R and 25L are formed between the left and right side gears 21R and 21L.

Next, a structure for driving one traveling device 24 in the reverse direction (for super-spot turning (steep turning)) will be described. As shown in FIG. 4, a third gear 37 that meshes with the high-speed gear 16 of the third transmission shaft 15 is externally fitted to the fourth transmission shaft 27 so as to be rotatable relative to the third gear 37 and the fourth transmission shaft 27. A hydraulic multi-plate reverse rotation clutch 30 (corresponding to a sudden turning mechanism) is provided between and. The second transmission gears 26R and 26L are bearing-supported at both left and right ends of the support shaft 20, and the fourth transmission gears 29 fixed to both ends of the fourth transmission shaft 27 have the second transmission gears 26R and 26L. Have bite each. As a result, the right side gear 21R or the left side gear 21L is connected to the right or left second transmission gear 26
When the reverse clutch 30 is engaged with the R and 26L engaged, the power from the high speed gear 16 is transmitted in reverse to the traveling device 24 while being decelerated to 1/2. And this is a super-spinning turning state (corresponding to a sudden turning state).

Next, a structure (for gentle turning) in which one traveling device 24 is driven in the normal direction at a lower speed than the other will be described.
As shown in FIG. 4, a small-diameter output gear 38 is fixed to the boss portion of the first transmission gear 19, and a large-diameter third transmission gear 40 is externally fitted to the fourth transmission shaft 27 so as to be rotatable relative to each other. Third
The transmission gear 40 meshes with the output gear 38. And
Between the third transmission gear 40 and the fourth transmission shaft 27, a hydraulic multi-plate type slow swing clutch 12 (corresponding to a slow swing mechanism) is provided. As a result, the right or left side gear 21R,
When the slow turning clutch 12 is engaged and operated in a state in which 21L is engaged with the right or left second transmission gears 26R, 26L, the forward drive power for straight traveling transmitted to the first transmission gear 19 is output gear 38, 3 transmission gear 40, slow swing clutch 12,
The fourth transmission shaft 27, the fourth transmission gear 29, and the right or left second
Through the transmission gears 26R, 26L, it is transmitted to the one traveling device 24 as the sufficiently reduced normal rotation power. And, this is a gentle turning state.

Next, the hydraulic oil supply structure for the hydraulic cylinders 31R, 31L for sliding the left and right side gears 21R, 21L, and the slow turning and reverse rotation clutches 12, 30 will be described. As shown in FIG. 3, the hydraulic oil from the pump 32 is passed through the first switching valve 33 to the left and right side gears 21.
The oil passages 34 from the side surfaces of the hydraulic cylinders 31R and 31L are supplied to the hydraulic cylinders 31R and 31L for the R and 21L, and the second switching valve 35 (corresponding to the first switching mechanism) for the slow turning and reverse clutches 12 and 30. )It is connected to the. Further, the oil passage 34 is connected to a variable relief valve 36 for the slow turning and reverse rotation clutches 12 and 30.

Next, the operation of the first switching valve 33, the second switching valve 35 and the variable relief valve 36 will be described. As shown in FIG. 3, a swing operation type switching lever 18 (corresponding to a switching operation tool) is provided in the control section of the machine body, and the operation position of the switching lever 18 is input to the control device 54. A solenoid 53 (corresponding to a second switching mechanism) for switching the valve 35 is provided. As a result, when the switching lever 18 is operated to the gentle turning position (wetland position), the solenoid 53
As a result, the second switching valve 35 is switched to the gently swiveling position 35a for supplying hydraulic oil to the slowly swiveling clutch 12, and when the switching lever 18 is operated to the super-spinning swivel position, the second switching valve 35 is operated by the solenoid 53. 35 is the reverse clutch 3
The operation is switched to the super-trust turning position 35b for supplying hydraulic oil to 0.

As shown in FIGS. 1 and 2, an operating arm 43 is swingably supported around a horizontal axis P1 of the control section of the machine body, and a lever base 44 is fixed to the operating arm 43. Then, the horizontal axis P2 at the upper end of the lever base portion 44
An operating lever 39 is swingably supported around the tongue piece 39a fixed downward to the operating lever 39, and a ball-type detent mechanism 45 fixed to a lever base 44 acts to move the lever base 44. On the other hand, the operation lever 39 is held in the posture shown by the solid line in FIG.

As shown in FIGS. 1 and 2, the operating arm 43
A pair of arms 48 and 49 are supported so as to freely swing around the horizontal axis P1 of the release wire 42, and the inner portion of the release wire 42 is connected to the one arm 48.
Is connected to the other arm 49. A tension spring 50 is connected across the pair of arms 48 and 49, and the other inner side of the release wire 42 is connected to the variable relief valve 36 as shown in FIG. The pin 43a fixed to the operation arm 43 is a pair of arms 4
The pin 43a and the first switching valve 33 are connected by the push-pull wire 41, as shown in FIGS. 1 and 3. Then, the position-fixed pin 51 is inserted between the pair of arms 48, 49.

With the above structure, first, the switching lever 18 shown in FIG.
It is assumed that 5 is operated to the gentle turning position 35a to select the gentle turning state. In this state, move the operating lever 39 to the neutral position N.
When it is operated to, the first switching valve 33 is also operated to the neutral position, the left and right hydraulic cylinders 31R and 31L contract, and the left and right side gears 21R and 21L are meshed with the first transmission gear 19. As a result, the normal rotation power transmitted to the first transmission gear 19 is transmitted to the left and right traveling devices 24, the left and right traveling devices 24 are driven at the same speed, and the machine body travels straight.

Next, when the operating lever 39 is operated from the neutral position N to the first turning position R1 on the right side or the first turning position L1 on the left side, only the first switching valve 33 is operated by the push-pull wire 41, and the hydraulic pressure is changed. The right or left side gear 21R, 2 engaged with the first transmission gear 19 via the right or left operating portion 46R, 46L by the cylinder 31R or 31L.
1L is separated from the first transmission gear 19 to the right or left second
It engages with the transmission gears 26R and 26L. In this case, since the holding action of the detent mechanism 45 of FIG. 1 is set to be sufficient, the operation lever 39 causes the horizontal axis P of the lever base portion 44 to move.
The operation lever 39 and the lever base 44 maintain the posture shown by the solid line in FIG.
One turn to the right first turning position R1 or the left first turning position L1.

As described above, when the operation lever 39 is operated, the one arm 48 or the other arm 49 is oscillated by the pin 43a and the inner of the release wire 42 is pulled, but the operation lever 39 is moved to the right. In the state of being operated to the first turning position R1 or the left first turning position L1 of
The variable relief valve 36 is still in the fully open state, and the slow swing clutch 12 is in the disengaged state. As a result, the transmission to the right or left traveling device 24 is cut off (transmission interruption state of the side clutch 25R or 25L), and the machine body gently turns to the right or left. The sequence valve 47 provided in the oil passage 34 of FIG. 3 applies the pressure required for the right or left side gear 21R, 21L to completely mesh with the right or left second transmission gear 26R, 26L. ,
This is for ensuring the hydraulic cylinders 31R and 31L.

Next, the operating lever 39 is moved from the right or left first turning position R1, L1 to the right or left second turning position R2, L.
When it is operated to 2 (corresponding to a predetermined position on the right or left), the inner of the release wire 42 is further pulled.
As a result, the right or left side gear 21R, 21L is engaged with the right or left second transmission gear 26R, 26L, and the second switching valve 35 is operated to the gentle turning position 35a,
The variable relief valve 36 is gradually operated from the fully opened state to the closed side. Therefore, the slow turning clutch 12 starts to act, and the right or left traveling device 24 is gradually driven to rotate at a low speed in the forward direction, so that the aircraft gently turns right or left. Then, at the right or left second turning position R2, L2 of the operating lever 39, the slow turning speed becomes maximum.

Next, it is assumed that the switching lever 18 is operated to the super-trust turning position and the second switching valve 35 is operated to the super-contact turning position 35b to select the super turning state. In this state, if the operation lever 39 is operated to the neutral position N, it goes straight as described above. If the operation lever 39 is operated from the neutral position N to the right or left first turning position R1, L1. In the same manner as described above, the transmission cutoff state of the right or left side clutch 25R, 25L appears.

Next, the operating lever 39 is moved from the right or left first turning position R1, L1 to the right or left second turning position R2, L.
When you move to 2, the right or left side gear 21R, 2
In the state where 1L is engaged with the right or left second transmission gears 26R, 26L, and the second switching valve 35 is operated to the super trust turning position 35b, the variable relief valve 36 is opened from the fully opened state as described above. It is gradually operated toward the closed side. This allows
The right or left traveling device 2 after the reverse clutch 30 starts to operate.
4 is gradually driven in the reverse direction, and the aircraft makes a super turning turn to the right or left. The reverse rotation speed becomes maximum at the right or left second turning position R2, L2 of the operating lever 39.

Next, a case will be described in which the airframe is temporarily turned to a small turn while the slow turn state is selected. As shown in FIGS. 1 and 2, the ring member 39b surrounding the detent mechanism 45 on the lever base 44 side is fixed to the tongue piece 39a on the operation lever 39 side.
The ring member 3 indicates that the lever 9 is bent laterally around the horizontal axis P2 from the posture shown by the solid line in FIG.
A limit switch 52 that contacts and separates from 9b and detects is fixed to the lever base 44. As shown in FIG. 3, a second gearshift lever 28 that performs a gearshift operation by sliding the shift gear 14 of the gearbox 13 (see FIG. 4) is provided in the control section of the aircraft, and this second gearshift lever 28 is provided. A limit switch 55 (corresponding to a high speed traveling state detecting means) for detecting that the vehicle is operated at a high speed position is provided. Further, a limit switch 56 for detecting that the switching lever 18 is operated at the wetland position is also provided.

With the structure described above, it is assumed that the switching lever 18 is operated to the gentle turning position and the second switching valve 35 is operated to the gentle turning position 35a as shown in FIG. 3 to select the gentle turning state. In this state, as shown in FIGS. 1 and 5,
For example, it is assumed that the operation lever 39 is operated to the left second turning position L2 around the horizontal axis P1. In this state, unexpectedly, if the aircraft does not turn sufficiently to the left, or if it is desired to turn to a smaller left, the hand holding the operating lever 39 is twisted slightly to the left, as shown in FIG. Detent mechanism 4
5 is removed from the tongue piece 39a on the operation lever 39 side, and the operation lever 39 is folded around the horizontal axis P2 with respect to the lever base 44 as shown by the chain double-dashed line in FIG. Operation (corresponding to the operation permission mechanism) (step S
1).

When the limit switch 52 detects such an operation, the second switching valve 35 is operated to the gentle turning position 35a (step S
2) An operation signal is transmitted from the control device 54 to the solenoid 53 shown in FIG. 3, and the second switching valve 35 is switched by the solenoid 53 from the gently swiveling position 35a to the super-spinning swiveling position 35b. As a result, the reverse rotation clutch 30 is turned on and the left traveling device 24 is reversely driven, and the super-spinning turning state is set (step S5). In this case, if the second shift lever 28 is operated to the high speed position, step S3
Then, the process returns to step S1 and the second switching valve 35 is never switched to the super-trusted turning position 35b (corresponding to the restraint prevention means).

Further, even when the switching lever 18 is operated to the wetland position and the second switching valve 35 is operated to the gentle turning position 35a, the process returns from step S4 to step S1 and the second switching valve 35 is switched to the supercritical state. There is no switching operation to the ground turning position 35b. This is because the super-infrastructure turning is performed by pushing the soil laterally by the traveling device 24 and a large amount of power is required. Therefore, forcibly performing the super-inclination turning in a wetland with large traveling resistance may cause an engine stop. Because there is. Therefore, when traveling through the wetland, the switching lever 18 is operated in advance to the wetland position so that only a gentle turn can be performed.

Then, when the operation lever 39 is returned to the left second turning position L2 from the state of operating the left third turning position L3, the operation lever 39 and the lever base 44 are returned to the straight state. (Step S6), the limit switch 52 detects that the control device 54 causes the solenoid 53 to
The operation signal is transmitted to the second switching valve 35 by the solenoid 53, and the second switching valve 35 is moved from the super-position turning position 35b to the gentle turning position 35a.
The operation is returned to (step S7).

Next, the first operation for shifting the continuously variable transmission 1
The shift lever 5 will be described. As shown in FIGS. 6 and 7, an operating member 57, which is L-shaped in side view, is swingably supported around a horizontal axis P3 of the control portion of the machine body. The operating member 57 and the continuously variable transmission 1 And are mechanically interlocked by a linkage mechanism 58. The first speed change lever 5 is swingably supported around the horizontal axis P3, and the first speed change lever 5 is inserted into the guide hole 57a of the operation member 57. A forward switch 59 and a reverse switch 60 are provided. And the friction plate 6
The gear 62 is pressed against the operation member 57 via the motor 1, and a motor 63 for rotating the gear 62 is provided.

With the above structure, when the first speed change lever 5 is operated to the forward side F or the reverse side R and the first speed change lever 5 reaches the end of the guide hole 57a, the first speed change lever 5 and At the same time, the operating member 57 is operated to the forward drive side F or the reverse drive side R, and the continuously variable transmission 1 is operated to shift. in this case,
When the first shift lever 5 contacts the forward or reverse switches 59 and 60, the motor 62 rotationally drives the gear 62 to the forward side F or the reverse side R to assist the shift operation of the first shift lever 5 and the operating member 57. The first shift lever 5 can be operated lightly. When it is detected by the limit switch 55 that the second gearshift lever 28 shown in FIG. 3 is operated to the high speed position, the motor 63 is simply driven and the gear 62 is simply rotationally driven. It As a result, the rotation of the gear 62 tends to be delayed with respect to the operation of the first speed change lever 5 and the operation member 57, and the gear 62 and the friction plate 61 serve as resistance and the operation of the first speed change lever 5 becomes heavy. . That is, the operation of the first speed change lever 5 is heavier when the second speed change lever 28 is operated at the high speed position than when the second speed change lever 28 is operated at the medium speed and low speed positions.

[Other Embodiments] In the above embodiments, the switching lever 18 is used to make a gentle turning state (a state in which one traveling device 24 is normally driven at a low speed) and a super-spinning state (one traveling device 24). Is a type in which a reverse drive is performed) (a sudden turning state), but a hydraulic side brake (not shown) may be provided instead of the reverse clutch 30 in FIG. . Thus, the fourth transmission shaft 27 of FIG.
When equipped with a side brake on the right side gear 21R
Alternatively, the left side gear 21L is separated from the first transmission gear 19 to be engaged with the right or left second transmission gears 26R and 26L, and the side brake is turned on and operated to brake one of the traveling devices 24 and transmit the signal. A ground turn (corresponding to a sharp turn state) can be performed. In this case, the switching lever 18 is operated to switch between a gentle turning state (a state in which one traveling device 24 is normally driven at a low speed) and a solid turning state (a state in which one traveling device 24 is braked).

It should be noted that reference numerals are given in the claims for convenience of comparison with the drawings, but the present invention is not limited to the configurations of the accompanying drawings by the entry.

[Brief description of drawings]

FIG. 1 is a front view near the operation lever.

[Fig. 2] Side view near the operating lever

FIG. 3 is a hydraulic circuit diagram of a hydraulic cylinder for a side gear, first and second switching valves, a variable relief valve, etc.

FIG. 4 is a schematic diagram showing a transmission structure of a traveling system in a mission case.

FIG. 5 is a diagram showing a flow of control at each operation position of a switching lever.

FIG. 6 is a side view near the first shift lever.

FIG. 7 is a plan view near the first shift lever.

[Explanation of symbols]

 12 Slow turning mechanism 18 Switching operation tool 24 Traveling device 30 Rapid turning mechanism 35 First switching mechanism 39 Operation lever 53 Second switching mechanism 55 Detection means N Neutral position of operation lever R2, L2 Right or left predetermined position of operation lever

Claims (1)

[Claims] 1. A traveling power transmission structure for a working vehicle comprising a pair of left and right traveling devices (24), the traveling power transmission structure for a working vehicle comprising the configurations described in [A] to [E] below. [A] A slow turning mechanism (12) that gives a speed difference to the left and right traveling devices (24) to turn the body to the right or left, and a speed difference that is larger than that of the slow turning mechanism (12). A sudden turning mechanism (30) for giving the device (24) a sudden turn to the right or left, and an operation lever (39) for turning operation that can be manually operated left and right. [A] When the operation lever (39) is operated from the neutral position (N) to the predetermined position (R2) or (L2) on the right or left, the gentle turning state in which the slow turning mechanism (12) operates, and When the operating lever (39) is operated from the neutral position (N) to the right or left predetermined position (R2), (L2), the sudden turning mechanism (30) is operated and the sudden turning state 2 is activated.
A first switching mechanism (35) capable of switching to a state, and a switching operation tool (18) capable of artificially selectively switching the first switching mechanism (35) between the gentle turning state and the sudden turning state. [C] When the operation lever (39) is operated to exceed the predetermined position (R2) or (L2) on the right or left with an operation force equal to or more than a setting, an operation permission mechanism that allows this operation, and the first
When the operation lever (39) is operated beyond the predetermined position (R2) or (L2) on the right or left while the switching mechanism (35) is being switched to the gentle turning state, the first switching mechanism ( 35) is switched from the gentle turning state to the sharp turning state, and when the operation lever (39) is returned to the right or left predetermined position (R2), (L2), the first switching mechanism (35). A second switching mechanism (53) for returning from the sudden turning state to the slowly turning state. [D] Detection means (55) for detecting that the aircraft is in a high-speed traveling state, and a restraining means for restraining the operation of the second switching mechanism (53) based on the detection by the detecting means (55).