JPS63287630A - Agricultural tractor - Google Patents

Abstract

PURPOSE:To less decrease resistance generated when a tractor performs a rapid turn and to enable the tractor to smoothly perform the rapid turn, by providing a clutch pressure adjusting mechanism which controls the working pressure in a speed increase driving side clutch to be decreased lower than the preset value. CONSTITUTION:A clutch pressure adjusting mechanism 21 is a valve of spool type providing a pump port 23 feeding working fluid from a pump 22, drain port 24, clutch port 25 communicating with a speed increase driving side clutch 12 in a front wheel transmission and a pressure reducing port 26. A control handle, if it is controlled to a preset angle or more, meshes with a sleeve of the speed increase driving side clutch 12 while controls also a wire 30 to be pulled, controlling a spool 27 to be adapted and pressed by the first control arm 29. Under this condition, the pump port 23 communicates with the clutch port 25 feeding the working fluid to the speed increase driving side clutch 12 through an oil path 31, and a tractor, when it performs a turn, realizes a front wheel speed increasing condition.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a transmission system for front wheels that can be freely steered, a standard drive state in which power is transmitted at a drive speed approximately equal to the rear wheel drive speed, and a rear wheel drive state. The front wheel transmission is equipped with a clutch-type front wheel transmission that can be switched to an accelerated drive state in which transmission is performed at a drive speed greater than the driving speed, and a steering handle is provided so that the front wheel transmission can be switched to an increased speed drive state by a steering operation that exceeds a set angle. The present invention relates to an agricultural tractor which is provided with a handbrake which is linked to the front wheel transmission and which is capable of independently braking the left and right rear wheels.

[Conventional technology]

When a general four-wheeled vehicle turns, the turning radius of the front wheels becomes larger than the turning radius of the rear wheels, resulting in what is called a difference between the inner and outer wheels. Therefore, in order for a four-wheel drive vehicle to turn smoothly, it is preferable to create a difference in the drive speed of the front and rear wheels, but in a normal four-wheel drive agricultural tractor, the drive speed of the front and rear wheels is the same. , the driving speed of the front wheels becomes slower than the driving speed suitable for the previous turn, and it appears that the front wheels are being braked and resistance is generated between the front wheels and the ground.

Therefore, agricultural tractors equipped with the aforementioned front wheel transmission have been put into practical use, and by switching the front wheel transmission to the speed-increasing drive side when turning, the front wheels can actively pull the machine in the direction of the turn. It is designed so that it can turn smoothly by moving forward.

[Problem that the invention seeks to solve]

Agricultural tractors equipped with hand brakes that can brake the left and right rear wheels independently can perform sharp turns by braking one of the rear wheels using the hand brake. By using the front wheel speed increase effect, it is expected that sharp turns can be made with an even smaller turning radius, but the difference between the inner and outer wheels when making a sharp turn using the handbrake and front wheel speed increase effect is It ends up being very large, close to the wheelbase length.

Therefore, in the above cases, the conventional front wheel speed increase effect alone is insufficient, and as mentioned earlier, the front wheel drive speed is slower than the turning speed of the front of the aircraft, causing the front wheel to touch the ground. Resistance is generated between the front wheels and it becomes impossible to make sharp turns smoothly. Therefore, it is conceivable to configure the conventional front wheel transmission to be able to switch between three states by adding a speed increasing state suitable for sharp turns using front wheel steering operation and a handbrake, but this would result in a more complicated structure. This also increases manufacturing costs, making it difficult to put it into practical use.

Here, the present invention focuses on the above-mentioned problem, and aims to provide a structure that allows smooth sharp turns using both front wheel steering operation and handbrake while avoiding extreme complexity of the structure. There is.

[Means for solving problems]

The characteristic configuration of the present invention is that, in the agricultural tractor having the above-mentioned configuration, the speed-increasing drive side clutch of the front wheel transmission is a multi-plate friction clutch, and the side brake applies braking to one rear wheel. , a clutch pressure adjustment mechanism is provided that lowers the operating pressure of the speed-increasing drive side clutch below the set pressure by operating the steering wheel beyond a set angle, and its functions and effects are as follows. That's right.

[For production]

When making a sharp turn using both the front wheel steering operation and the handbrake, the turning speed of the front of the aircraft is faster than the front wheel drive speed, which is increased faster than the rear wheels by the front wheel transmission. Because it is a vehicle, this speed difference causes resistance between the front wheels and the ground. In this state, when the operating pressure of the speed increasing drive side clutch in the front wheel transmission device decreases, the speed increasing drive side clutch becomes slippery, and the reverse driving force from the ground causes the speed increasing drive side clutch to slip and further speed up the front wheels. It turns out.

As described above, when the speed difference between the turning speed of the front part of the aircraft and the driving speed of the front wheels becomes smaller, the resistance that was generated only between the front wheels and the ground decreases, and the speed-increasing drive side clutch is caused by slipping. Resistance occurs. The increase in resistance generated by the speed-increasing drive side clutch is sufficiently smaller than the decrease in resistance that would have occurred between the front wheels and the ground, so the front wheel speed-increasing effect and the handbrake are reduced. When used in combination, the total amount of resistance the aircraft receives during sharp turns becomes smaller.

〔Effect of the invention〕

As described above, it is possible to reduce the resistance that occurs when making a sharp turn by using both the speed increasing action of the front wheels and the handbrake, making it possible to make a smooth sharp turn.

In addition, the above structure does not allow the front wheel transmission to be switched in three stages, but instead reduces the operating pressure of the clutch on the speed increasing drive side, so the structure is simpler and easier to manufacture than the three-stage switching structure. It is advantageous in terms of cost.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS A four-wheel drive agricultural tractor, which is one embodiment of the present invention, will be described below with reference to the drawings.

As shown in Figure 6, a pair of left and right front wheels (1a
), (1b) and the rear wheels (2a), (2b), and a lift arm (3) that connects various working devices to the rear of the machine so that they can be raised and lowered, and a PTO shaft that transmits power to the working devices. (4) is provided to constitute a four-wheel drive type agricultural tractor.

The front wheel (1a) is located at the bottom of the mission case (5) at the rear of the aircraft.
, (1b) is provided with a front wheel transmission (6), but to explain this configuration in detail, as shown in FIGS. 5 and 6, a sub-transmission (
The first driven gear (9), which is fitted loosely on the front export force shaft (14), engages with the first drive gear (8), which always receives the power branched from the (not shown). There is. A multi-disc hydraulic clutch as a speed-increasing drive side clutch (12) is fitted onto the front export power shaft (14) for free rotation, and a clutch case (12a) of the speed-increasing drive side clutch (12) is fitted onto the front output power shaft (14). The second driven gear (13), which is fixed, meshes with the second driving gear (11), which, like the first driving gear (8), always receives power from the auxiliary transmission.

Furthermore, the first driven gear (9) and the speed increasing drive side clutch (1
2), a shift member (16) is attached to the front export force shaft (14) with a spline structure so that it can be slid freely. By sliding this shift member (16) into engagement with the engagement portion (9a) of the first driven gear (9), the power is transferred to the first drive/driven gear (8), (9).
), the front wheels (1a), (1b) and the rear wheels (2a)
, (2b) are transmitted from the front export force shaft (14) to the front wheel differential mechanism (19) in a standard driving state in which the speeds of (2b) are approximately equal. Conversely, the shift member (16) is connected to the engaging portion (1) of the sleeve (12b) in the speed-increasing drive side clutch (12).
2c) and engages and operates the speed-increasing drive side clutch (12), the power is transferred to the second drive/driven gear (11), (1
3), through the speed-increasing drive side clutch (12), and then the front wheel (1a
) and (1b) are transmitted to the front export force shaft (14) in an accelerated drive state where the speed is increased more than that of the rear wheels (2a) and (2b).

Next, the linkage structure between the steering wheel (32), the left and right side brakes (7a), (7b), and the front wheel transmission (6) will be described in detail.As shown in FIG. 1, the steering wheel (32) and the front wheel (1a), (Lb) The steering pitman arm (10) is mechanically interlocked and connected, and the cam mechanism (1
5) and an operating section (17) for slidingly operating a shift member (16) of a front wheel transmission (6) are interlocked and connected via a wire (18), and the operating section (17) is connected to a spring (20). is biased towards the standard drive side (A).

With the above configuration, when the front wheels (1a) and (1b) are steered beyond the set angle, the wire (18) is pulled, and the operation part (17) is moved to the speed-increasing drive side (B), that is, the shift member (16 ) is operated toward the occlusal side of the sleeve (12b).

Furthermore, during the above steering operation, the front wheel transmission (6)
To explain in detail the clutch pressure adjustment mechanism (21) that adjusts the supply of hydraulic oil to the speed-increasing drive side clutch (12), as shown in FIGS. 1 and 2, this clutch pressure adjustment mechanism (2I) ) is a spool type valve, and the pump boat (22) is fed with hydraulic oil from the pump (22).
23), Dorenborg) (24), Front wheel transmission (6)
A clutch boat (25) and a pressure reducing boat (26) communicating with the speed increasing drive side clutch (12) are provided. In a normal straight-ahead state, the spool (27) is positioned as shown in Fig. 2 by the biasing force of the spring (28), and the hydraulic oil from the speed-increasing drive side clutch (12) is drained. It is in a cut state.

A swing-type first operating arm (29) is disposed with respect to the spool (27).
) and the cam mechanism (I5) are interlocked and connected via a wire (30). With this configuration, as described above, when the steering handle (32) is operated beyond the set angle, the wire (18) is pulled, and the shift member (16) is driven to increase the speed via the operation section (I7). Side clutch (12)
The wire (30) engages with the sleeve (12b) of the wire (30).
The first operating arm (
29), the spool (27) is brought into contact and pushed.

In this state, pump port (23) and clutch port (
25), and hydraulic oil is sent to the speed-increasing drive side clutch (12) through the oil passage (31), which is turned on and the front wheels are in a speed-increasing state when cornering. Oil road (3
The valve (33) provided in 1) is a relief valve (33) for securing clutch pressure.

More specifically, as shown in FIG. 2, a swingable second operating arm (34) having a different arm length from the first operating arm (29) is provided, and a wire (35) is attached thereto. The other end of the wire (35) is connected to the left and right handbrake pedals (36a) and (36) as shown in FIG.
For b), the inner side brake pedal is on one side (3).
6a), the outer is attached to the other side brake pedal (3).
6b), and is configured such that the inner wire (35) is pulled only when one of the handbrake pedals (36a) or (36b) is depressed. Furthermore, these left and right side brake pedals (3
6a), left and right rear wheels (2a) by (36b),
Handbrake (7a) for (2b), (7
b) can be operated independently.

With the above configuration, one side brake pedal (3
6a) or (36b) to operate the control handle (32).
) is steered beyond the set angle, both wires (30)
, (35) is pulled, resulting in the state shown in FIG. The first and second operating arms (29), (3
4) has different arm lengths, so the second operating arm (34)
Therefore, the spool (27) is further removed than the state shown in Fig. 3.
is pushed in, and the pump boat (23), clutch port (25), and pressure reduction port (26) are brought into communication. A relief valve (38) that opens at a lower pressure than the relief valve (33) is connected to the oil line (37) from the pressure reduction boat (26).
) is provided. This allows the front wheel transmission (6)
The shift member (16) engages with the sleeve (12b) of the speed increasing drive side clutch (12), and the speed increasing drive side clutch (12) engages with the sleeve (12b) of the speed increasing drive side clutch (12).
Hydraulic oil will be sent to 2), but its working pressure will be a low pressure based on the relief valve (38).

Therefore, in the above state, the power is transferred to the speed-up drive side clutch (12
) through the front wheels (1a), (1b) in an increased speed drive state.
However, the driving speed of the front wheels (Ia) and (1b) is slow compared to the turning speed of the front of the aircraft, so if the front wheels (1a) and (1b) receive reverse driving force from the ground, , the speed-increasing drive side clutch (12) slips,
The speed of the front wheels (1a) and (1b) is further increased.

Incidentally, although reference numerals are written in the claims section for convenient comparison with the drawings, the present invention is not limited to the structure shown in the accompanying drawings.

[Brief explanation of the drawing]

The drawings show an embodiment of the agricultural tractor according to the present invention.
The figure is a schematic diagram showing the linkage between the front wheel transmission, the steering wheel, and the clutch pressure adjustment mechanism. Figure 2 is a schematic diagram of the clutch pressure adjustment mechanism. Figure 3 is the clutch pressure adjustment mechanism when only the steering handle is operated. Figure 4 is a diagram showing the state of the clutch pressure adjustment mechanism when both the steering wheel and handbrake pedal are operated.
The figure is a longitudinal sectional side view of the front wheel transmission, and FIG. 6 is an overall side view of the agricultural tractor. (1a), (1b)...-front wheel, (2a),
(2b)...-Rear wheel, (6)...Front wheel transmission, (7a), (7b)...Handbrake, (12)... Speed increase Drive side clutch, (
21)...Clutch pressure adjustment mechanism, (32)...
...Control handle.

Claims (1)

[Claims] The transmission system for the front wheels (1a) and (1b), which can be freely steered, has a standard drive state in which power is transmitted at a drive speed approximately equal to the rear wheel drive speed, and an increased speed drive in which power is transmitted at a drive speed greater than the rear wheel drive speed. Clutch-type front wheel transmission (6
), and the steering handle (32) and the front wheel transmission (6) are linked so that the front wheel transmission (6) is switched to the speed-increasing drive side by a steering operation of a set angle or more, and , an agricultural tractor equipped with side brakes (7a) and (7b) capable of braking left and right rear wheels (2a) and (2b) independently, respectively, the speed-increasing drive side clutch ( 12) is a multi-disc friction clutch, one rear wheel (2a), (2b) is braked by the handbrake (7a), (7b), and the control handle (32) is rotated at a set angle or more. An agricultural tractor is provided with a clutch pressure adjustment mechanism (21) that lowers the operating pressure of the speed-increasing drive side clutch (12) from a set pressure by performing a steering operation.