JPH08337126A - Front wheel drive control device for four-wheel drive type agricultural tractor - Google Patents

Abstract

PURPOSE: To prevent selection of front wheels for a speed increase during a high-speed travel, and further prevent mud from being splashed during a turning steering operation in a wet field by providing a front wheel travel transmission system with a front wheel acceleration selector device allowing the selection of a speed increase only when the steering angles of right and left front wheels are equal to or above the preset values and at the same time, a travel speed is low. CONSTITUTION: When a rotary device is installed behind a tractor body for cultivating a field, a sub-transmission section 22, for example, is selected at a low speed mode for a low speed travel. In this case, a low speed detector 24 operates and an equal speed hydraulic clutch 35 is engaged, thereby rotating front wheels 5 at a peripheral speed approximately 1.05 times as large as the speed of rear wheels 6. In the case of turning at the end of the field, then, a steering handle is operated substantially toward a turning direction, and a left rear wheel brake 19, for example, is used to brake a left rear wheel 6 as a turning operation. In this case, a speed increase instruction is issued from a control circuit for engaging a speed increase hydraulic clutch 36. As a result, the front wheels 5 are accelerated at a peripheral speed approximately two times as large as the case of an equal speed, and a turning motion is quickly made within a small radius, using the left rear wheel 6 as a support point.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a front-wheel drive control device for a four-wheel drive agricultural tractor.

[0002]

2. Description of the Related Art Conventionally, a technique for increasing the peripheral speed of a front wheel when a four-wheel drive agricultural tractor makes a turn at the field end is known, for example, as disclosed in Japanese Patent Application Laid-Open No. Sho 54-12138.

[0003]

However, in the conventional front wheel drive control device, when the steering wheel is operated at a turning angle of, for example, 40 degrees or more, the speed of the front wheels is automatically switched with respect to that of the rear wheels. The switching operation to increase the speed is performed regardless of the traveling speed, whether the traveling speed is low or high.

Therefore, when performing work such as plowing and scraping in the field, the speed is always low, so there is no problem even if the front wheels are driven at an increased speed, and conversely the workability is improved by making a small turn. To do. However, when driving on the road (during high-speed driving), when the steering wheel reaches a sharp curve and the steering wheel is operated by a predetermined angle or more, if the front wheels are switched to speed-up, the front wheels suddenly start a sharp turn, and steering stability is impaired. ,Also,
There is a problem that not only an overload occurs in the transmission, the differential, the drive shaft, and the like, but also that the tires are worn out early.

In an agricultural tractor, the front wheels are
Because it is a steered wheel and is not covered with a fender to ensure forward visibility, a considerable amount of mud may jump up when the front wheels are driven at an increased speed during high-speed running. That is, when a small turn is performed by increasing the front wheel speed in a wet field or the like in a high-speed running state, a large amount of mud is flipped backward and left and right by the front wheel. Case), the mud was spread, and the mud was scattered outside from the headland, thereby contaminating the alleys around the field.

Therefore, in the present invention, it is determined when the traveling speed is low when working in a field or the like and the turning radius really needs to be reduced, and only at that time, the front wheels are automatically increased with respect to the rear wheels. In addition to increasing the speed, it prevents front wheels from switching to acceleration during high-speed driving, reduces muddy jumping up when turning in wetlands, and reduces power loss during small turns. That is the purpose.

[0007]

According to the present invention, the left and right front wheels 5 and 5 which can be steered by a steering handle 8 and can be driven by a front wheel traveling transmission system 25, and the traveling speed can be changed in a plurality of high and low stages. In a four-wheel drive agricultural tractor having left and right rear wheels 6 and 6 driven by a rear-wheel traveling transmission system M including a simple traveling transmission device 16 and a rear-wheel differential device 17, the above-mentioned object is achieved. In order to do so, the following technical measures are taken.

That is, according to the present invention, the front wheel traveling power transmission system 25 is branched from a rear wheel traveling power transmission system M between the traveling transmission 16 and the rear wheel differential device 17, and the front wheel traveling power transmission system 25 is provided. Drive rotation to the front wheels 5 and 5 is performed on the rear wheels 6 and 25.
6, a front wheel speed changeover device 30 that can be switched to a speed increase or substantially the same speed, a front wheel differential device 32 driven via the front wheel speed changeover device 30, and a drive rotation of the front wheels 5, 5 is cut off. The front wheel speed change-over switching device 30 switches from the substantially same speed to the speed increase only when the steering angle of the left and right front wheels 5, 5 is equal to or larger than the set angle and the traveling speed is low. It is characterized by the fact that it is configured to make a turning run, and by adopting such a configuration, it is approaching a sharp curve when traveling on the road etc. in a high speed running state for movement. As a result, it is possible to prevent the front wheels 5 from being accelerated when the steering wheel 8 is turned, and to ensure the steering stability without the front wheels 5 undergoing a sharp turning operation due to the speed increase switching during high-speed steering. be able to.

Further, when turning and steering in a wet field or the like,
Since the front wheel speed increase switching device 30 is configured to switch from substantially the same speed to the speed increase only when the traveling speed is low, the small wheel turning due to the acceleration of the front wheel 5 is not performed during the high speed traveling, and the muddy soil caused by the front wheel is prevented. It is possible to suppress the flip-up of the to within an allowable range. Further, since the front wheels 5 are driven to be accelerated only when the traveling speed is low, the power loss at the time of turning and steering can be suppressed to be small and the wear of the tire can be prevented.

Further, the front wheel drive transmission system 25 is provided with a clutch means 28 for connecting and disconnecting the drive rotation of the front wheel 5, so that four-wheel drive with high-speed restraint according to the work situation,
You can switch to rear-wheel drive.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the illustrated embodiment. FIG. 1 illustrates a four-wheel drive agricultural tractor, in which 1 is a tractor body, an engine 2, and an engine 2.
It is composed of a clutch housing 3, a transmission case 4, etc., and has left and right front wheels 5 and left and right rear wheels 6 that can be driven and rotated. Reference numeral 7 is a hood, and 8 is a steering handle, and as shown in FIG. 3, the left and right front wheels 5 can be steered from a steering gear box 9 on the tractor body 1 via a sector shaft 10, a pitman arm 11, a drag ring 12, and the like. .
Reference numeral 13 denotes a driver's seat, and reference numeral 14 denotes a hydraulic device for lifting and lowering the work implement.

As shown in FIG. 2, a transmission transmission system M such as a traveling transmission 16 and a rear wheel differential 17 interlocked with the engine 2 via a clutch 15 is built in the transmission case 4, and the rear wheels The differential device 17 is linked to each rear wheel 6 via a final reduction gear 18. Each rear wheel 6 is a rear wheel brake 19
The rear wheel brakes 19 can be operated simultaneously or independently by the interlocking / independent operation of the pair of left and right brake pedals 20 arranged in parallel on one side of the tractor body 1. ing.

The traveling transmission 16 has a main transmission section 21 and an auxiliary transmission section 22. The main transmission section 21 can change the traveling speed in multiple steps by a main transmission lever (not shown). The speed can be shifted between high and low speeds H and L by the sub-transmission lever 23. The sub transmission unit 22 is provided with a low speed detector 24 such as a limit switch for detecting the low speed side of the sub transmission lever 23, that is, a low vehicle speed.

Below the traveling transmission device 16, transmission shafts 26, 27 of a front wheel traveling transmission system 25 interlocking with the transmission device 16 are mounted in parallel, and clutch means 28 which can be manually operated between the transmission shafts 26, 27. Is provided. Here, the front wheel traveling transmission system 25 is provided to be branched from the rear wheel traveling transmission system between the traveling transmission 16 and the rear wheel differential device 17. That is, the gear is branched by step-contacting the shift gear 17B provided on the drive pinion shaft 17A of the rear wheel differential device 17 with the gear 26A provided on the transmission shaft 26.

Further, the transmission shaft 27 has a gear 27A, and the power take-out case 2 mounted on the lower abdomen of the transmission case 4 is used.
9 interlocks with a front wheel differential device 32 in a front axle case via a propulsion shaft 31 from a front wheel speed changeover device 30 in the front wheel axle 9, and interlocks with each front wheel 5 from the front wheel differential device 32 via a final reduction device 33. Can be increased or substantially equalized with respect to the rear wheel 6.

A front wheel speed changeover device 30 capable of changing the speed of the front wheels 5 to substantially the same speed as the front wheel 5 includes a planetary speed reducer 34 engaged with a gear 27A, a same speed hydraulic clutch 35 and a speed increasing hydraulic clutch 36. When the same-speed hydraulic clutch 35 is connected, the peripheral speed of the front wheel 5 is about 1.05 times that of the rear wheel 6, and when the speed-increasing hydraulic clutch 36 is connected, the peripheral speed of the front wheel 5 is about twice that at low speed. The two clutches 35, 3
By cutting 6 together, the front wheel 5 can be connected and disconnected.

That is, when the speed-increasing hydraulic clutch 36 is connected in conjunction with the turning operation of the steering handle 8, the front wheels 5 are driven to increase speed, and when the clutch 36 is disengaged and the clutch 35 is engaged, the front wheels 5 are substantially disengaged. It is assumed that they are driven at the same speed. FIG. 3 shows a control system, 37 is a hydraulic pump, 38 is a diversion valve, and 39 is a relief valve. Reference numeral 40 is a solenoid valve for three-position switching, which constitutes switching means for the hydraulic clutch 35 for same speed and the hydraulic clutch 36 for speed up, has solenoids 41 and 42, and is controlled by a control circuit 43.

Reference numeral 44 denotes a turning detector which detects when the steering angle of the handle 8 exceeds a certain level in association with the sector shaft 10. 45 is a one-brake detector, which releases the interlock of the left and right brake pedals 20 and operates it.
It is configured to detect as one-sided operation of the rear wheel brake 19. 46 is a switch. Reference numeral 47 denotes a high speed detector for detecting a high speed of the vehicle speed, which may detect the high speed of the auxiliary transmission unit 22 or may detect the high speed side of the multi-speed shift of the main transmission unit 21.

In this embodiment, the control circuit 43 comprises a low speed detector 24, a turning detector 44 and a one-brake detector 4.
5 is given to the solenoid 42 of the solenoid valve 40 at the time of all the detections, and the same speed command is given to the solenoid 41 when any of them is missing. At the time, a disconnection command is given to the solenoids 41 and 42.

That is, in conjunction with the turning operation of the steering wheel 8, only when the running speed is low, the speed is switched from substantially the same speed to the increased speed, and the front wheel 5 is driven at an increased speed via the hydraulic clutch 36 to perform the turning. When the speed is high, the vehicle is turned without driving the front wheels 5, or the front wheels 5 are driven at the same speed. Next, the operation of the above embodiment will be described. When a rotary device is mounted behind the tractor body 1 to perform tilling work in a field, for example, the sub-transmission unit 22 is driven at a low speed to run at low speed. At this time, the high-speed detector 47 does not work but the low-speed detector 24 works and the drainage 41 of the solenoid valve 40
Are excited, the same-speed hydraulic clutch 35 is connected, and the front wheel 5 rotates at a peripheral speed of about 1.05 times that of the rear wheel 6.

When turning at the end of the field, the steering wheel 8 is largely operated in the turning direction, and the brake pedal 20 in the turning direction, for example, in the case of turning in FIG. , Left rear wheel brake 19
As a result, the left rear wheel 6 is braked, and the vehicle turns one point using the brake as a fulcrum. At this time, in the present embodiment, the turning detector 44 and the one-brake detector 45 work, and the low-speed detector 24 has already been operated.
, The control circuit 43 outputs a speed-up command, the solenoid 42 is excited, and the solenoid valve 40 is switched.
The speed increasing hydraulic clutch 36 is connected. Accordingly, the front wheel 5 is driven at a peripheral speed approximately twice as high as that at the same speed, so that the front wheel 5 does not become a resistance to the rear wheel 6 and the left rear wheel 6 is used as a fulcrum. Can turn quickly with a small radius.
After turning, if the handle 8 is returned to the original state or the depression of the brake pedal 20 is released, the hydraulic clutch 35 for the same speed is connected again. That is, only when the steering angle of the steering wheel 8 is above a certain level and the traveling speed is low, the front wheels 5 can be switched from the substantially same speed to the rear wheels 6 to increase the driving speed so that the vehicle can turn.

That is, only when the traveling speed is low, the front wheels 5
Is driven at an increased speed, so that the power loss during turning steering can be reduced as described below,
Tire wear can be prevented. In order to understand such a peculiar effect, first, the relationship between the peripheral speeds of the front wheels and the rear wheels during a small turn will be described with reference to FIG.

As shown in FIG. 5, small turning (rapid turning)
In order to achieve this, the turning center of the airframe must be located near the sides of the rear wheels. At this time, since the distance from the turning center of the front wheel average peripheral speed vector is larger than the distance from the turning center of the rear wheel average peripheral speed vector, it is necessary to set the front wheel average peripheral speed larger than the rear wheel average peripheral speed. Nature occurs.

The relationship between the peripheral speeds is shown in FIG. 6. Ideally, as shown in FIG. 6 as an ideal ratio, the average front peripheral speed of the front wheels is gradually increased as the steering angle is increased. However, due to structural restrictions of the device, a two-stage switching type is adopted in which the steering speed is switched from approximately the same speed to the speed increase when the steering wheel is steered over a set angle.

In the example shown in FIG.
Although the front wheel average peripheral speed is set to be approximately twice as large as the rear wheel average peripheral speed when the vehicle is steered by more than °, the ideal ratio and the actual ratio greatly differ around the set angle, If the front-wheel speed-change switching device is speed-changed in a high-speed running state, an extremely large power loss occurs, and a great load is generated on the contact surfaces of the front wheels and the rear wheels, so that the tires are extremely worn.

Furthermore, in addition, when the front wheels are driven at a high speed when the steering wheel is steered over a set angle due to a sharp curve or the like when traveling on the road at a high speed, the missions, the diff, the drive shaft, etc. constituting the drive mechanism are driven. There may be a case where an overload occurs or a small turn at such a high speed causes uneven wear of the tire at an early stage, which requires replacement. Since the present invention is configured to drive the front wheels only at low speeds,
Even if the actual ratio between the front wheel average peripheral speed and the rear wheel average peripheral speed deviates from the ideal ratio, power loss and tire wear caused by driving the front wheel at increased speed during small turning can be kept within the allowable range. is there.

Also, when turning and steering in a wet field or the like,
Since the front wheel speed increase switching device 30 is configured to switch from substantially the same speed to the speed increase only when the traveling speed is low, the small wheel turning due to the acceleration of the front wheel 5 is not performed during the high speed traveling, and the muddy soil caused by the front wheel is prevented. It is possible to suppress the flip-up of the to within an allowable range. That is, when a small turn is performed by increasing the front wheel speed in a wet field or the like in a high-speed running state, a large amount of mud is flipped backward and left and right by the front wheel. In this case, mud is applied, and mud is scattered outside from the headland to soil alleys and the like around the field. However, according to the present invention, these can be prevented.

During plow work in the field, for example, the sub-transmission unit 22 is moved at a high speed to travel at a higher speed than during rotary work, but when turning, it is necessary to make a sharp turn with a small radius as described above. Therefore, at this time, since the low-speed detector 24 does not work, the switch 46 may be operated to provide a signal for low-speed detection to the control circuit 43. When the vehicle is traveling on the road, the vehicle travels at a high speed with a light load.
By disengaging both the speed increasing hydraulic clutch 36 and the rear wheel 6, only the rear wheels 6 can be driven independently to run at high speed, the tires of the front wheels 5 can be prevented from being worn, and unnecessary fuel consumption of the engine 2 can be prevented. During this high speed traveling, a sharp curve is approached and the steering wheel 8 is configured to make a turning traveling without driving the front wheels 5 whose steering angle is a certain value or more.

The detectors 24, 44, 4 of the embodiment are
5, 47 may be any of a contact type and a non-contact type.

[0030]

As described above in detail, according to the present invention, it is possible to secure a small turning movement in the field, to select four-wheel drive or rear-wheel drive while checking at high speed according to the work situation. Sometimes, it is possible to prevent the front wheels from being switched to a speed increase, to reduce splashing of mud during turning steering in a field, and to further reduce power loss during small turning.

[Brief description of drawings]

FIG. 1 is a side view of a tractor.

FIG. 2 is a configuration diagram of a traveling power system.

FIG. 3 is a block diagram of a control system.

FIG. 4 is a plan view of the tractor showing a turning operation.

FIG. 5 is a diagram showing a relationship between peripheral speeds of a front wheel and a rear wheel at the time of a small turn.

FIG. 6 is a diagram showing a steering angle, an ideal ratio, and an actual ratio.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tractor vehicle body 5 Front wheel 6 Rear wheel 8 Steering handle 16 Transmission 17 Rear wheel differential device 28 Clutch means 30 Front wheel speed increasing switching device 32 Front wheel differential device

Claims (3)

[Claims] 1. Left and right front wheels (5) (5) that can be steered by a steering handle (8) and can be driven by a front wheel traveling transmission system (25), and that can change the traveling speed in a plurality of high and low steps. Four-wheel drive agricultural machine having left and right rear wheels (6) (6) driven by a rear wheel transmission system (M) including a traveling transmission (16) and a rear wheel differential (17). In the tractor, the front wheel drive train (25) is connected to the travel transmission (1).
6) and the rear wheel differential device (17) are provided so as to be branched from a rear wheel traveling transmission system (M), and the front wheel traveling transmission system (2).
Drive rotation to the front wheels (5) and (5) for the rear wheel (6)
A front wheel speed increasing switching device (30) capable of speeding up or substantially the same speed as (6), a front wheel differential device (32) driven through the front wheel speed increasing switching device (30), and a front wheel. (5)
(5) clutch means (28) for connecting and disconnecting the drive rotation;
The front wheel speed increase switching device (30) switches from the substantially the same speed to the speed increase only when the steering angles of the left and right front wheels (5) (5) are equal to or more than the set angle and the traveling speed is low. A front-wheel drive control device for a four-wheel drive agricultural tractor, which is configured to rotate. The clutch means (28) for connecting and disconnecting the drive rotation of the front wheels (5) is provided with the front wheel speed increasing switching device (3).
The front wheel drive control device for the four-wheel drive agricultural tractor according to claim 1, wherein the front wheel drive control device is provided on the upstream side of 0). 3. The left and right front wheels (5) and (5) that can be steered by a steering handle (8) and can be driven by a front wheel traveling transmission system (25), and the traveling speed can be changed in a plurality of high and low stages. A four-wheel drive agricultural machine having left and right rear wheels (6) and (6) driven by a rear-wheel traveling transmission system (M) including a traveling transmission device (16) and a rear-wheel differential device (17). In the tractor, the front wheel drive transmission system (25) includes the travel transmission (1).
6) and the rear wheel differential device (17) are provided so as to be branched from a rear wheel traveling transmission system (M), and the front wheel traveling transmission system (2).
Drive rotation to the front wheels (5) and (5) for the rear wheel (6)
A front wheel speed increasing switching device (30) capable of speeding up or substantially the same speed as (6), and a front wheel differential device (32) driven via the front wheel speed increasing switching device (30). The front wheel speed-increasing switching device (30) is provided for the left and right front wheels (5) (5).
Only when the steering angle is equal to or greater than the set angle and the traveling speed is low, the vehicle is turned from the substantially same speed to the increased speed and the vehicle is turned. Further, the front wheel speed increasing switching device (30) is provided with a speed increasing device. A hydraulic clutch (36) and a hydraulic clutch (35) for the same speed are provided, and the drive rotation of the front wheels (5) and (5) is connected and disconnected by turning on and off the hydraulic clutches (35) and (36). A front wheel drive control device for a four-wheel drive agricultural tractor, characterized in that: