JPH05162554A - Four wheel drive type working vehicle - Google Patents

Abstract

PURPOSE:To dispense with space for slide operation of cam member and the like so as to make compact a changeover structure and a safety structure by internally fitting the changeover structure and safety structure by which a front wheel transmision is not operated to an acceleration condition side, in a fitting part between a control rod and a boss part of a shift fork. CONSTITUTION:A projection 20a is provided at a control rod 20 while a first and a second recesses 34a, 34b are provided at a boss part on the side of a shift fork 19. The boss part 34 is rotation operated by a first operation means 37 and thus the projection 20a is inserted into the first recess 34a. When front wheels are steered at a specified angle or more from a linear line position, under the above condition, due to the action of a cam mechanism, the rod 20 is slid to an acceleration condition side. In this case, since the projection 20a is inserted in the recess 34a, due to the engagement of the projection 20a with the recess 34a, the shift fork 19 is operated by slicling leftward together with the rod 20 and a front wheel transmission is changed over to the acceleration condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a sliding operation of a shift member in a standard condition in which front wheels and rear wheels are driven at substantially the same speed and in a speed increasing condition in which front wheels are driven at a higher speed than rear wheels. The present invention relates to a four-wheel drive work vehicle provided with a front wheel transmission that is selectively switchable in a front wheel transmission system.

[0002]

2. Description of the Related Art In an agricultural tractor, which is an example of a four-wheel drive type work vehicle, a front wheel steering operation system and a front wheel transmission are mechanically arranged as disclosed in, for example, Japanese Patent Application Laid-Open No. 2-245576. When the front wheels are steered from the straight ahead position over the set angle, the shift member of the front wheel transmission is slid to the speed-up state side in conjunction with this operation. is there. As a result, it is possible to smoothly make a small turning turn without roughening the ground due to the speed-up action of the front wheels. When equipped with the front wheel transmission as described above, when turning at high speed, if the front wheels are driven to increase speed, it will be in a dangerous state as it will turn sharply. It is necessary to have a switching structure that can be artificially switched in advance so that the transmission is not operated toward the speed increasing state. In the switching structure disclosed in the publication, the cam member (4 in FIG. 1 of the publication is operated by the operation of the steering operation system for the front wheels).
6) is rotated to operate the shift member (3 in FIG. 1 of the above publication).
The operation rod (42 in FIG. 1 of the publication) fitted with the shift fork 3) (48 in FIG. 1 of the publication) is slid to the speed-up state side by the cam member. And
By operating the cam member away from the operation rod, the front wheel transmission is prevented from being operated toward the speed increasing state.

[0003]

With the above-mentioned structure,
Since the switching structure operates so that the relatively large cam member is moved away from the operation rod, a large space is required between the position where the cam member contacts the operation rod and acts and the position where the cam member is separated from the operation rod. Therefore, there is room for improvement in terms of downsizing and downsizing of the switching structure in which the front wheel transmission is not operated to the speed increasing state. Also, when traveling at high speed, it is necessary to switch the front wheel transmission to a state in which it is not operated to the speed-up state side as described above. However, this switching operation may be forgotten. There is a case where the front wheel transmission is equipped with a safety structure for automatically switching to a state where it is not operated to the speed increasing state when operated to. Therefore, when the above-mentioned artificial switching structure is equipped with this safety structure, further downsizing and downsizing of the whole structure are required. It is an object of the present invention to reduce the size and size of a switching structure and a safety structure that bring a front wheel transmission to a state in which it is not operated toward the speed increasing state.

[0004]

A feature of the present invention is that the four-wheel drive type working vehicle as described above is configured as follows. That is, the front wheel and the rear wheel are driven at substantially the same speed, and the front wheel is driven at a higher speed than the rear wheel. The front wheel transmission is equipped in the transmission system to the front wheels, and the boss part on the shift fork side that slides the shift member is externally fitted to the operation rod, and when the front wheel is steered from the straight position over the set angle, it is linked to this operation. And a cam mechanism for sliding the operating rod to the speed increasing state side of the front wheel transmission, and an urging means for urging the shift fork toward the standard state side, and an outer surface of the operating rod or a boss portion of the shift fork. Provide a convex portion on one of the inner surfaces of
When this convex part enters, the first fork that slides the shift fork together with the operating rod to the speed-up state side, and when the convex part enters, the shift fork remains on the standard state side and the operating rod slides to the speed-up state side. The second concave portion is provided so as to be continuous with the other of the outer surface of the operation rod or the inner surface of the boss portion of the shift fork, and the convex portion enters the first concave portion and the convex portion enters the second concave portion. First operation means for switching and rotating the operation rod or the boss portion, and second operation means for rotating the operation rod or the boss portion to the linkage release position in conjunction with the operation to the high speed side of the traveling transmission. It is equipped with operating means.

[0005]

With the above-mentioned structure, for example, FIGS.
As shown in FIG. 3, the operation rod 20 is provided with a convex portion 20a, and the boss portion 34 on the shift fork 19 side is provided with the first and second concave portions 34a.
It is assumed that a and 34b are provided. Then, the first operating means 37
Thus, the boss portion 34 is rotated to insert the convex portion 20a into the first concave portion 34a (the front wheel transmission is in a standard state). In this state, when the front wheels are steered from the straight ahead position over the set angle, the operation rod 20 is slid to the speed increasing state side on the left side of the drawing by the action of the cam mechanism as shown in FIG.
In this case, since the convex portion 20a is inserted into the first concave portion 34a, the shift fork 19 together with the operating rod 20 is slid to the left side of the drawing by the engaging action of the convex portion 20a and the first concave portion 34a. As a result, the front wheel transmission is switched to the speed increasing state, and the front wheels are driven at a higher speed than the rear wheels. Next, from the state shown in FIG. 1, the boss portion 34 is rotated around the axis by the first operating means 37 to position the convex portion 20a in the second concave portion 34b as shown in FIG. With this arrangement, even if the front wheel is steered from the straight ahead position at a set angle or more as described above and the operation rod 20 is slid leftward in the plane of the drawing, the convex portion 20a moves in the second concave portion 34b in the left side of the sheet. The shift fork 19 is left by the urging force of the urging means 21, and the front wheel transmission device maintains the standard state.

Even when the front wheel transmission is switched to the speed increasing state by the first operating means 37 (the state shown in FIG. 1), the second operating means is operated when the traveling transmission is operated to the high speed side. As shown in FIG. 4, the operation rod 20 is rotated by 40 to insert the convex portion 20a into the second concave portion 34b. As a result, even if the front wheel is steered from the straight ahead position over the set angle and the operation rod 20 is slid leftward on the paper surface, the convex portion 20a moves leftward in the second concave portion 34b on the paper surface as described above. It only moves, the shift fork 19 is left by the urging force of the urging means 21, and the front wheel transmission device maintains the standard state.

In the conventional structure, the front wheel transmission is not operated to the speed-increasing state by sliding the cam member between the position where it is brought into contact with the operating rod and the position where it is separated from the operating rod. It constituted a switching structure.
On the other hand, in the present invention, the switching structure and the safety structure can be installed in the fitting portion between the operation rod, which is an existing member, and the boss portion on the shift fork side.

[0008]

As described above, the switching structure and the safety structure in which the front wheel transmission is not operated to the speed increasing state are provided in the fitting portion between the operation rod which is the existing member and the boss portion of the shift fork. By providing the interior, a space for sliding the cam member and the like is not required, and the switching structure and the safety structure can be made smaller and more compact.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 9, a four-wheel drive working vehicle, which is an example of a four-wheel drive type work vehicle, is provided with an engine 3 and a clutch 4 at the front of the machine supported by front wheels 1 and rear wheels 2, and a mission case 5 at the rear of the machine. A type of agricultural tractor. The power of the engine 3 is transmitted from the clutch 4 to the main transmission device (not shown) and the auxiliary transmission device (not shown) in the transmission case 5 via the first transmission shaft 6 and the second transmission shaft 11 shown in FIG. It is transmitted to the rear wheel 2 after being subjected to a speed change operation. And
The power branched from immediately before the differential device (not shown) of the rear wheel 2 is transmitted to the front wheel transmission 7 via the third transmission shaft 16 shown in FIG.
Is transmitted to the front wheels 1.

Next, the front wheel transmission 7 directly connected to the clutch 4 will be described. As shown in FIG. 6, the transmission shaft 16 is concentrically arranged on the third transmission shaft 16 so as to be relatively rotatable. The power from the standard gear 12 of the third transmission shaft 16 is applied to the first gear 13 and the second gear 14 (second transmission shaft 1
1 is relatively rotatable) to the speed-increasing gear 15 which is fitted to the speed change shaft 10 so as to be relatively rotatable. Speed change shaft 1
The shift member 18 has a spline structure for the shift shaft 10
Is externally fitted so as to be rotatable integrally with and slidable in the axial direction, and a multi-plate friction clutch 17 is provided between the transmission shaft 10 and the speed increasing gear 15.

In the above structure, when the shift member 18 is slid to engage the occlusal portion 18A of the shift member 18 with the occlusal portion 12A of the standard gear 12, the front wheel 1 and the rear wheel 2 are driven at substantially the same speed. Power is applied to the transmission shaft 10
Is transmitted to the front wheel 1 via the third gear 30 and the front wheel output shaft 8 (corresponding to the standard state). Shift member 18 in the opposite direction
When the friction clutch 17 is pressed in and out by the sliding member 18 by the shift member 18, the power is transmitted in a state in which the front wheel 1 is driven at a higher speed than the rear wheel 2 (corresponding to a speed-up state).

Next, the structure of the slide operation system of the shift member 18 will be described. As shown in FIG. 1, an operating rod 20 is arranged on the lateral side surface of the front wheel transmission 7 so as to be slidable in the axial direction and rotatable around the axial center.
A shift rod 33 is arranged concentrically with the operation rod 20 so as to be slidable in the axial direction, and a shift fork 19 for the shift member 18 of the front wheel transmission 7 is externally fitted to the shift rod 33 to shift. A spring 21 for urging the fork 19 and the shift rod 33 toward the standard gear 12 side.
(Corresponding to the biasing means) is provided. A spring 35 for urging the operating rod 20 toward the standard gear 12 side is also provided.

As shown in FIGS. 1 and 8, a boss portion 34 is fitted over both ends of the shift rod 33 and the operating rod 20 so as to be relatively rotatable. A first elongated hole 34a (corresponding to the first concave portion) along the circumferential direction of the boss portion 34 and a square second elongated hole 34b (corresponding to the second concave portion) along the axial direction are connected to form an opening. The operating rod 20 has the first pin 20
a (corresponding to the convex portion) is fixed, and the first pin 20a is the first
And the second elongated holes 34a and 34b. The boss portion 34 has a third elongated hole 34c formed along the circumferential direction thereof, and the pin 3 fixed to the shift rod 33 is formed.
3a is inserted in the third elongated hole 34c.

As shown in FIG. 7, front wheel support cases 23 are rotatably supported left and right at the left and right ends of the front axle case 22, and tie rods 24 are connected to the left and right front wheel support cases 23 so that the left tie rods are connected to each other. A hydraulic cylinder 25 for power steering is connected to the front wheel support case 23.

As shown in FIGS. 1, 2, and 7, the cam plate 27
In a (corresponding to a cam mechanism), a U-shaped bracket 27b is fixed to the lower side of the center of the cam hole 27a, and between the left side surface of the hood 26 (see FIG. 9) and the left front wheel 1, the front A cam plate 27 is swingably supported around a vertical axis P1 of the rear surface portion of the axle case 22 via a bracket 27b. Then, the operating rod 20 and the cam plate 27
Is connected via a linking rod 28 and a spring 29 for accommodation. The operation arm 31 is swingably supported around the vertical axis P2 of the rear surface portion of the front axle case 22,
The roller 31a of the operation arm 31 is inserted into the cam hole 27a of the cam plate 27, and the link rod 32 is connected between the left front wheel support case 23 and the tip of the operation arm 31.

The state shown in FIG. 1 is the first position of the operating rod 20.
The pin 20a is inserted into the first elongated hole 34a of the boss portion 34 (corresponding to the linkage position), and the front wheel 1 is operated to the straight-ahead position. Accordingly, the shift member 18 is engaged with the standard gear 12 by the biasing force of the spring 21, and the front wheel 1 and the rear wheel 2 are driven at substantially the same speed. From this state, the control handle 9 of FIG. 9 is operated to operate the hydraulic cylinder 2 of FIG.
It is assumed that the front wheel 1 is steered rightward from the straight-ahead position by 5 above the set angle. As a result, as shown in FIG. 2, the operation arm 31 is oscillated in the clockwise direction, and the cam plate 27 is oscillated in the counterclockwise direction by the action of the cam hole 27a and the roller 31a, so that the operation rod 20 is moved to the paper surface. It is operated to slide to the left.

In this case, the first pin 20 of the operating rod 20
Since a is inserted in the first elongated hole 34a of the boss portion 34, the engagement between the first pin 20a and the first elongated hole 34a causes the shift fork 19 and the shift rod 33 to move together with the operating rod 20 on the paper surface. It is operated to slide to the left. As a result, the shift member 18 presses and operates the friction clutch 17, and the front wheels 1 are driven at a higher speed than the rear wheels 2.

Next, as shown in FIG. 3 from the state of FIG.
The boss portion 34 is rotated around the axis to move the first pin 20a.
Is positioned within the second elongated hole 34b of the boss portion 34 (corresponding to the link release position). With this configuration, even if the front wheel 1 is steered from the straight-ahead position over the set angle and the operation rod 20 is slid leftward in the drawing as described above, the first pin 20a moves in the second elongated hole 34b. It only moves to the left on the paper surface, and the shift fork 19 is moved by the urging force of the spring 21.
And the shift rod 33 is left, and the shift member 18 is kept in the meshed state with the standard gear 12, and the front wheel 1 and the rear wheel 2 are maintained in a state of being driven at substantially the same speed.

Next, the structure for switching the front wheel 1 between high speed driving and non-high speed driving at the time of turning by rotating the boss portion 34 of FIG. 1 around the axis will be described. To do. As shown in FIGS. 1 and 8, the first operation arm 3 is provided around the horizontal axis P3 on the outer surface of the front wheel transmission 7.
6 is swingably supported, and a pin 34d fixed to the boss portion 34 is inserted into a forked end of the first operation arm 36. On the other hand, as shown in FIG. 9, a switching lever 37 (corresponding to the first operating means) is provided on the lower side of the steering handle 9, and the switching lever 37 and the first operating arm 36 are in the first linkage. It is interlockingly connected through the mechanism 38.

With the above structure, when the switching lever 37 is operated to the entry position (corresponding to the linkage position) as shown in FIG. 1, the first operation arm 36 is rocked clockwise in FIG. 8 and the boss portion 34 is moved. The operation rod 20 is rotated and operated.
The first pin 20a of is inserted into the first elongated hole 34a of the boss portion 34. This state is the state in which the front wheels 1 are driven at high speed during turning as described above. On the contrary, as shown in FIG. 3, the switching lever 35 is turned to the cut position (corresponding to the linkage release position).
8, the first operation arm 36 is oscillated counterclockwise in FIG. 8 and the boss portion 34 is rotated in the opposite direction, so that the first pin 20a of the operation rod 20 moves to the second length of the boss portion 34. It is inserted into the hole 34b. This state is a state in which the front wheels 1 are not driven at high speed during turning as described above.

Next, the structure for switching between the state in which the front wheels 1 are driven at high speed during turning and the state in which they are not driven at high speed, as described above, in conjunction with the shift operation for traveling will be described. The transmission case 5 shown in FIG. 9 is equipped with a main transmission (not shown) capable of shifting in multiple stages and an auxiliary transmission (not shown) capable of shifting between high and low stages. As shown in FIGS. 1 and 8, the horizontal axis P of the outer surface of the front wheel transmission device 7
A second operating arm 39 is swingably supported around the second arm 4, and the second pin 20b fixed to the operating rod 20 is the second pin.
It is inserted into the forked end of the operation arm 39. On the other hand, the control section of the machine body is provided with a sub-transmission lever 40 (corresponding to a second operating means) for the sub-transmission device. It is interlockingly connected via 41.

With the structure described above, if the sub-shift lever 40 is operated to the low speed position while the switching lever 37 is operated to the on position as shown in FIG. 1, the second operation arm 32 in FIG. Is oscillated counterclockwise and the operation rod 20 is rotatably operated.
The pin 20a is inserted into the first elongated hole 34a of the boss portion 34. If the switching lever 37 is operated to the cut position as shown in FIG. 3 in this state, the front wheels 1 are not driven at high speed during turning as described above.

Then, in the state of FIG. 1 (the state in which the switching lever 37 is operated to the on position), when the auxiliary transmission lever 40 is operated to the high speed position as shown in FIG. 4, the second operation arm 39 in FIG. Is oscillated in the clockwise direction and the operation rod 20 is rotated in the opposite direction.
The first pin 20a of is inserted into the second elongated hole 34b of the boss portion 34. As a result, even when the switching lever 37 is operated to the on position, the front wheels 1 are not driven at high speed during turning.

Further, as shown in FIG. 5, when the sub-shift lever 40 is operated to the high speed position while the switching lever 37 is operated to the cut position, the operation rod 2 is moved with respect to the boss portion 34.
9 is further rotated in the opposite direction, but since the second elongated hole 34b of the boss portion 34 has a square shape,
Even if operated as described above, the first pin 20 of the operation rod 20
There is no particular hindrance, as a is only in a state where it enters the inside of the second elongated hole 34b.

[Other Embodiment] In the above-mentioned embodiment, the first pin 2 is used.
0a is provided on the operation rod 20, and the first and second elongated holes 34
Although a and 34b are provided on the boss portion 34 on the shift fork 19 side, the relationship is reversed, and the first pin 20a is provided on the boss portion 34 on the shift fork 19 side, and the first and second elongated holes 34 are formed.
The operation rod 20 may be provided with a and 34b. When the operation rod 20 is provided with the first and second elongated holes 34a, 34b, instead of providing the penetrating first and second elongated holes 34a, 34b, a bottomed groove may be provided, This groove serves as a first recess and a second recess. In the above-described embodiment, the boss portion 34 is rotated by the operation of the switching lever 37, and the operation rod 20 is rotated by the operation of the auxiliary shift lever 40. However, this relationship is reversed. Alternatively, the operation rod 20 may be rotated by operating the switching lever 37, and the boss portion 34 may be rotated by operating the auxiliary shift lever 40.

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

[Brief description of drawings]

FIG. 1 is a shift member of a front wheel transmission, a shift fork,
Shows the linkage between the operating rod and the cam plate of the front wheel and the operating rod, with the switching lever in the on position and the auxiliary shift lever in the low speed position, and the boss and operating rod in the linked position. A plan view showing

FIG. 2 is a plan view showing a state in which the front wheel is steered over a set angle or more from the state shown in FIG. 1 and the operation rod is pulled to the friction clutch side.

FIG. 3 is a plan view showing a state in which a switching lever is operated to a cut position, a sub-transmission lever is operated to a low speed position, and a boss portion and an operation rod are operated to a linkage release position.

FIG. 4 is a plan view showing a state in which a switching lever is operated to an on position and a sub-transmission lever is operated to a high speed position, and a boss portion and an operation rod are operated to a linkage release position.

FIG. 5 is a plan view showing a state in which a switching lever is operated to a cut position, a sub-transmission lever is operated to a high speed position, and a boss portion and an operation rod are operated to a linkage release position.

FIG. 6 is a vertical sectional side view of the front wheel transmission.

FIG. 7 is a plan view of the vicinity of a cam plate that operates the front wheel transmission to an accelerating state when the front wheels are steered from a straight ahead position over a set angle.

FIG. 8 is an end portion of a control rod and a shift rod, a boss portion,
Perspective view of the vicinity of the first and second operation arms

FIG. 9: Side view of the entire agricultural tractor

[Explanation of symbols]

 1 front wheel 2 rear wheel 7 front wheel transmission 18 shift member 19 shift fork 20 operating rod 20a convex portion 21 biasing means 27 cam mechanism 34 boss portion 34a first concave portion 34b second concave portion 37 first operating means 40 second operating means

Claims (1)

[Claims] 1. A normal state in which a front wheel (1) and a rear wheel (2) are driven at substantially the same speed, and an increased state in which a front wheel (1) is driven at a higher speed than a rear wheel (2). , Shift members (18)
A shift fork (1) for slidingly operating the shift member (18) is provided with a front wheel transmission (7) which is selectively switchable by sliding operation of the shift wheel (18) in a transmission system to the front wheel (1).
When the boss portion (34) on the 9) side is fitted onto the operation rod (20) and the front wheel (1) is steered from a straight position to a set angle or more, the operation rod (2) is interlocked with this operation.
0) is provided with a cam mechanism (27) for sliding the front wheel transmission (7) to the speed increasing state side, and the shift fork (1) is provided.
9) is provided with an urging means (21) for urging the operation rod (20) toward the standard state, and a protrusion () is provided on one of the outer surface of the operation rod (20) or the inner surface of the boss (34) of the shift fork (19). 20a) is provided, and when the convex portion (20a) enters, the first concave portion (34a) that slides the shift fork (19) together with the operating rod (20) to the speed increasing state side, and the convex portion (20a). The second recess (34b) that slides the operating rod (20) toward the speed increasing state while leaving the shift fork (19) on the standard state side when the user enters the outer surface of the operating rod (20) or the shift fork (19). The boss (34) is connected to the other inner surface of the boss (34) so that the protrusion (20a) enters the first recess (34a) and the protrusion (20a) enters the second recess (34b). With the release position Over the operating rod (20) or the first operating means (3 boss portion (34) for operating switching rotation
7), and second operation means (40) for rotating the operation rod (20) or the boss portion (34) to the linkage release position in association with the operation of the traveling transmission to the high speed side. Four-wheel drive work vehicle.