JPH064386B2 - Agricultural tractor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a standard drive state in which power is transmitted to a front-wheel drive system which can be steerably operated at a drive speed substantially equal to a rear-wheel drive speed, and a rear-wheel drive mode. It has a clutch-type front wheel transmission that switches to a speed-increased drive state in which it is transmitted at a drive speed higher than the speed, and a steering wheel that allows the front-wheel transmission to be switched to the speed-increasing drive side by a steering operation over a set angle. And an agricultural tractor in which the front wheel transmission is linked with each other, and side brakes capable of independently braking the left and right rear wheels are provided.

[Conventional technology]

When turning in a general four-wheeled vehicle, the turning radius of the front wheels becomes larger than the turning radius of the rear wheels, so that a so-called inner / outer wheel difference occurs. Therefore, in order for the four-wheel drive vehicle to smoothly turn, it is preferable to make a difference in the drive speeds of the front and rear wheels, but in a normal four-wheel drive agricultural tractor, the drive speeds of the front and rear wheels are equal. The driving speed of the front wheels becomes slower than the driving speed suitable for the previous turning, and apparently the front wheels are braked and a resistance is generated between the front wheels and the ground.

Therefore, agricultural tractors equipped with the above-mentioned front wheel transmission have been put into practical use, and the front wheel transmission is positively pulled in the turning direction by switching the front wheel transmission to the speed-increasing drive side during turning. It is configured so that it can smoothly turn by going up and down.

[Problems to be solved by the invention]

In the case of an agricultural tractor equipped with side brakes that can independently brake the left and right rear wheels, it is possible to make a sharp turn by braking one of the rear wheels with this side brake. By using the front wheel speed-increasing effect of the above, it is expected that a sharp turning can be performed with a smaller turning radius, but the difference between the inner and outer wheels during a sharp turn using the side brake and the front wheel speed-increasing effect is It will be very large near the length of the wheel base.

Therefore, in the above cases, the conventional front wheel accelerating action alone is insufficient in speed, and as described above, the driving speed of the front wheels becomes slower than the turning speed of the front part of the airframe, and As a result, a resistance is generated between the front wheels and a sharp turn cannot be performed smoothly. Therefore, it is conceivable to add a speed increasing state suitable for a sharp turn using the conventional front wheel transmission and a steering operation for the front wheels and side brakes together, and to switch to three states, but the structure becomes complicated. In addition, it is difficult to put into practical use because the manufacturing cost is increased.

Here, the present invention focuses on the above-mentioned problem, and aims to configure so that a steep turn can be smoothly performed by using a steering operation of a front wheel and a side brake together while avoiding an extremely complicated structure. There is.

[Means for solving problems]

A characteristic configuration of the present invention is, in an agricultural tractor having a configuration as described above, a speed-increasing drive-side clutch of a front wheel transmission is a multi-plate friction clutch, and one of the rear wheels is braked by the side brake, and , A clutch pressure adjusting mechanism for lowering the operating pressure of the speed-increasing drive-side clutch below the set pressure by steering the steering handle at a set angle or more. The action and effect are as follows. It is as follows.

[Action]

When making a sharp turn using both the front wheel steering operation and the side brakes, the turning speed of the front part of the aircraft is faster than the driving speed of the front wheels, which is increased by the front wheel transmission compared to the rear wheels. Due to this difference in speed, resistance is generated between the front wheels and the ground. In this state, if the operating pressure of the speed-up drive side clutch in the front wheel transmission decreases, the speed-up drive side clutch becomes slippery, and the reverse drive force from the ground causes the speed-up drive side clutch to slip, further increasing the speed of the front wheels. It will be.

As described above, when the speed difference between the turning speed of the front part of the airframe and the driving speed of the front wheels becomes small, the resistance generated only between the front wheels and the ground decreases, and the speed-increasing drive-side clutch causes slippage. Resistance occurs. Since the increase in resistance generated in the speed-increasing drive side clutch is sufficiently smaller than the decrease in resistance generated between the front wheels and the ground, the speed-increasing action of the front wheels and the side brake are performed. The total resistance received by the aircraft during combined sharp turns is reduced.

〔The invention's effect〕

As described above, it is possible to reduce the resistance that occurs in a sharp turn using the front wheel speed increasing action and the side brakes together, and it is possible to perform a smooth sharp turn.

Also, in the above configuration, the front wheel transmission is not configured to be switchable in three stages, but the operating pressure of the speed-increasing drive-side clutch is dropped. Therefore, the structure is simpler than that of the three-stage switching structure. It is advantageous in terms of cost.

〔Example〕

Hereinafter, a four-wheel drive type agricultural tractor which is one of the embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 6, a pair of steerable left and right front wheels (1a),
(1b) and rear wheels (2a), (2b) drivably equipped with a lift arm (3) for connecting various working devices to a rear part of the machine body and a PTO shaft (4 for transmitting power to a front working device) ) Is provided to configure a four-wheel drive agricultural tractor.

The front wheel transmission (6) for the front wheels (1a), (1b) is provided under the mission case (5) at the rear of the fuselage. The detailed structure of this transmission is as shown in FIG. 5 and FIG. A first driven gear that is loosely fitted onto the front wheel output shaft (14) with respect to the first drive gear (8) that constantly receives the power branched from the auxiliary transmission (not shown) in the case (5). (9) is biting. A multi-plate hydraulic clutch, which serves as a speed-increasing drive-side clutch (12), is fitted onto the front wheel output shaft (14) by idling, and the clutch case (1
The second drive gear (11) fixed to 2a) meshes with the second drive gear (11) that constantly receives power from the auxiliary transmission like the first drive gear (8). .

Further, between the first driven gear (9) and the speed-up drive side clutch (12), a shift member (16) is slidably mounted on the front wheel output shaft (14) by a spline structure. .
Sliding this shift member (16) to move the first driven gear.
By engaging the occlusal part (9a) of (9), the power passes through the first drive / driven gears (8), (9), and the front wheels (1a), (1b) and the rear wheels (2
It is transmitted from the front wheel output shaft (14) to the front wheel differential mechanism (19) in a standard drive state where the speeds of a) and (2b) are substantially equal. On the contrary, the shift member (16) is engaged with the occlusal part (12c) of the sleeve (12b) of the speed-increasing drive-side clutch (12).
When the (12) is turned on and operated, the power is supplied to the second drive / driven gear (11,
13), the front wheels (1a), (1b) pass through the speed-increasing drive side clutch (12) and the front wheels (1a), (1b) are speeded up more than the rear wheels (2a), (2b). Transmitted.

Next, the steering wheel (32) and the left and right side brakes (7
The detailed structure of the linkage between a) and (7b) and the front wheel transmission (6) will be described in detail with reference to FIG.
a), (1b) The steering pitman arm (10) is mechanically linked and coupled, and the cam mechanism (15) provided in the pitman arm (10) and the shift member (6) of the front wheel transmission (6). An operation part (17) for sliding operation of (16) is interlockingly connected via a wire (18), and the operation part (17) is biased to a standard drive side (A) by a spring (20). . With the above configuration,
When the front wheels (1a), (1b) are steered beyond the set angle, the wire
The (18) is pulled and the operating portion (17) is operated to the speed-increasing drive side (B), that is, the shift member (16) is operated to the occlusal side of the sleeve (12b).

Furthermore, the clutch pressure adjusting mechanism (21) for adjusting the supply and discharge of hydraulic oil with respect to the speed increasing drive side clutch (12) in the front wheel transmission (6) during the steering operation as described above will be described in detail.
As shown in FIGS. 1 and 2, this clutch pressure adjustment mechanism
Reference numeral (21) is a spool type valve, and the pump port (23) and the drain port (2
4), a clutch port (25) communicating with the speed increasing drive side clutch (12) of the front wheel transmission (6), and a pressure reducing port (26) are provided. In a normal straight traveling state, the spool (27) is positioned by the urging force of the spring (28) in the state shown in FIG. 2, and the hydraulic oil from the speed-up drive side clutch (12) is drained and this is It is in a cut state.

An oscillating first operation arm (29) is arranged for the spool (27), and the first operation arm (29) and the cam mechanism (15) are interlocked via a wire (30). It is connected.
With this configuration, as described above, when the steering handlebar (32) is steered over the set angle, the wire (18) is pulled, and the shift member (16) is driven to accelerate through the operating portion (17). While engaging the sleeve (12b) of the side clutch (12),
(0) is also pulled and the first operation arm is moved as shown in FIG.
The spool (27) is pressed and operated by (29). In this state, the pump port (23) and the clutch port (25) communicate with each other, and the hydraulic oil is sent to the speed-increasing drive side clutch (12) through the oil passage (31), which enters the engagement state and increases the front wheel when turning. The fast state is revealed. The valve (33) provided in the oil passage (31) is a relief valve (33) for ensuring clutch pressure.

More specifically, the first operation arm as shown in FIG.
Swing-type second operation arm (34) with different arm length from (29)
And the wire (35) is attached. Then, as shown in FIG. 1, the other end of the wire (35) is connected to the left and right side brake pedals (36a) and (36b) with the inner side being one side brake pedal (36a) and the outer side being the other side brake pedal (36a). The inner side of the wire (35) is connected to the pedal (36b), and the inner side of the wire (35) is pulled only when one of the side brake pedals (36a) or (36b) is depressed. In addition, the left and right side brake pedals (36a),
The side brakes (7a), (7b) for the left and right rear wheels (2a), (2b) can be operated independently by (36b).

With the above configuration, one side brake pedal (36
When the steering handle (32) is steered over a set angle by depressing a) or (36b), both wires (30), (35) are pulled and the state shown in FIG. 4 is obtained. Since the first and second operation arms (29) and (34) have different arm lengths, the spool (27) is pushed further by the second operation arm (34) than in the state shown in FIG. 3, and the pump port ( 23), the clutch port (25) and the decompression port (26) are in communication with each other. The relief valve (33) is provided in the oil passage (37) from the pressure reducing port (26).
A relief valve (38) that opens at a lower pressure than is provided. As a result, the shift member (16) of the front wheel transmission (6) meshes with the sleeve (12b) of the speed increasing drive side clutch (12), and hydraulic oil is sent to the speed increasing drive side clutch (12). However, the operating pressure becomes a low pressure based on the relief valve (38).

Therefore, in the above state, the power is transmitted to the front wheels (1a), (1b) in the speed-up drive state via the speed-up drive side clutch (12). Compared to the front wheel (1
The driving speed of a) and (1b) is slow, and the reverse driving force is applied from the ground to the front wheels (1a),
When (1b) receives, the speed-up drive side clutch (12) slips, and the front wheels (1a), (1b) are further speeded up.

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]

The drawings show an embodiment of an agricultural tractor according to the present invention.
FIG. 1 is a schematic diagram showing the state of linkage between the front wheel transmission, the steering wheel and the clutch pressure adjusting mechanism, FIG. 2 is a schematic diagram of the clutch pressure adjusting mechanism, and FIG. 3 is a clutch pressure adjusting mechanism when only the steering wheel is operated. FIG. 4 shows the state of the clutch pressure adjusting mechanism when both the steering handle and the side brake pedal are operated, FIG.
FIG. 6 is a vertical 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) ... side brake, (12) ... speed-up drive side clutch, (21)… Clutch pressure adjustment mechanism, (32)… Control handle.

Claims (1)

[Claims] 1. A standard driving state in which power is transmitted to a front steering wheel (1a), (1b) which is freely steerable at a driving speed substantially equal to a rear wheel driving speed, and a driving speed higher than the rear wheel driving speed. Clutch-type front wheel transmission that switches to the transmitted speed-up drive state
(6) is provided, and the steering wheel (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 the steering operation over the set angle. An agricultural tractor equipped with side brakes (7a), (7b) capable of independently braking the left and right rear wheels (2a), (2b), respectively, which is a speed-increasing drive side of the front wheel transmission (6). The clutch (12) is a multi-plate friction clutch and the side brake
By braking one of the rear wheels (2a), (2b) by (7a), (7b) and steering the steering handle (32) at a set angle or more, the speed-increasing drive side clutch ( An agricultural tractor provided with a clutch pressure adjusting mechanism (21) for lowering the operating pressure of 12) below a set pressure.