JPH078619B2 - Tractor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an agricultural tractor, and more particularly to a constant four-wheel drive tractor in which front wheels and rear wheels are always driven by an engine.

2. Description of the Related Art Generally, a tractor is provided with a pair of left and right brake pedals that independently brake the left and right rear wheels, and one brake pedal brakes only one rear wheel to turn the rear wheel. It is possible to make a turn with a small turning radius around the center. Hereinafter, such a turn will be referred to as a sharp turn.

However, in a four-wheel drive tractor, in the case of performing the sharp turn, the drive system from the engine to the front wheels is disengaged by a clutch, and the front wheels are made to freely rotate at a rotation speed according to the turning. No. 52-50416. Further, a structure in which a clutch of a front-wheel-side power transmission system and a brake device provided separately for the left and right rear wheels are connected is shown in Japanese Patent Application No. 60-287174 filed by the present applicant. .

On the other hand, in a four-wheel drive vehicle, the power of the engine is dividedly transmitted to a front wheel drive shaft and a rear wheel drive shaft through a differential device at a constant ratio according to each axle load, and the drive force is effectively transmitted to the wheels. There is something I tried to tell.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In a four-wheel drive tractor, the present invention divides and transmits a driving force to a front-wheel drive shaft and a rear-wheel drive shaft via a differential device so that the tractor is always four-wheel drive. It is intended to improve its function by being driven by a car, and can be driven in an optimum drive mode according to each of them during agricultural work and traveling on public roads, and especially to make a smooth turn during a sharp turn. Is.

Therefore, according to the present invention, in the tractor of the four-wheel drive which is always provided with a pair of brake devices that can independently brake the left and right rear wheels, the output shaft of the engine is the tractor. Is connected to the front wheel drive shaft and the rear wheel drive shaft through a differential device arranged substantially in the center, and these two drive shafts are respectively connected through a front wheel side differential device and a rear wheel side differential device. The left and right front wheels and the rear wheels are connected to each other, and a differential lock device is provided in the central differential device.
When the differential of the central differential is locked between the pair of brake devices, the lock is released in response to the independent operation of either one of the pair of brake devices, Provide interlocking means that does not respond to simultaneous actuation of the braking device.

The tractor of the present invention is operated in a state in which the differential lock of the central differential device is released when traveling on a relatively flat public road, and the driving force from the engine is applied to the front and rear wheels via the central differential device. Will be distributed to. Therefore, even if there is a difference in the lengths of the turning trajectories between the front wheels and the rear wheels during turning, the rotational speeds of the front wheels and the rear wheels change according to this difference, so either one of the wheels does not slip The turning motion can be obtained.

At the time of work, the differential of the central differential device is locked, and operation is performed in a state where the front wheel drive shaft and the rear wheel drive shaft are directly connected. With this configuration, even if either the front wheel or the rear wheel is separated from the ground and runs idle on an uneven terrain, the driving force can be transmitted to the grounding wheel to continue traveling. However, as described above, when the rear wheel on one side is braked to make a sharp turn with the rear wheel as the center of turning, the turning locus of the rear wheel on the other side is inside the turning locus of the front wheel, The rolling distance of the front wheels is longer than the rolling distance of the rear wheels, so the rotation speed of the front wheels must be increased. In the present invention, when one of the braking devices is operated to make a sharp turn, the locking of the central actuating device is released by the interlocking means between the braking device and the differential lock device.
The central differential device differentially increases the rotation speed of the front wheels to a rotation speed corresponding to the turning, thereby enabling a smooth turning operation. The differential lock is released only when one of the brake devices is operated, and the lock is not released when both brake devices are operated to control the traveling of the tractor.

EXAMPLES Hereinafter, the present invention will be described with reference to illustrated examples. FIG. 1 is a side view showing an agricultural tractor to which the present invention is applied, which includes a pair of left and right front wheels 1 and rear wheels 2. An engine 3 is mounted on the front part of the vehicle body, and an output shaft 5 connected to a crankshaft of the engine 3 via a speed reducer 4 extends rearward. 6 is a seat, 7 is a steering wheel, and 8 is a brake pedal. One pair of left and right brake pedals 8 are provided. When the left brake pedal 8 is depressed, the left rear wheel 2 is braked, and when the right brake pedal 8 is depressed, the right rear wheel 2 is braked. Has become.

FIG. 2 is a plan view diagrammatically showing the wheel drive system of this tractor. As shown in FIG. 2 and FIG. 1, a central differential device 9 is provided between the front wheel 1 and the rear wheel 2. It is arranged. The central differential device 9 is a differential gear device including a differential gear box 10 (differential carrier), a small differential gear 11 (differential pinion), and a large differential gear 12 (differential side gear). Gearbox 10
The reduction gear 13 (ring gear) fixed to the output shaft 5
The reduction pinion 14 (drive pinion) fixed to is meshed. A front wheel drive shaft 15 and a rear wheel drive shaft 16 are connected to the front and rear differential gears 12, 12, respectively. It is adapted to be distributed to the rear wheel drive shaft 16. The power distributed to the front wheel drive shaft 15 is transmitted to the left and right front wheel shafts 18 and 1 via a front wheel differential device 17 composed of a similar differential gear device.
The power transmitted to 8 and distributed to the rear wheel drive shaft 16 is transmitted to the left and right rear wheels 20, 20 via the same rear wheel differential device 19. The front-wheel differential device 17 and the rear-wheel differential device 19 are the same as the differential device that is provided to give a differential to the left and right wheels in a normal four-wheel vehicle, and therefore detailed description thereof will be given. The description is omitted.

The central differential device 9 is provided with a differential lock device 21. That is, as shown in FIG. 3, a boss portion 22 is integrally provided on the end surface of the differential gear box 10 on the front wheel drive shaft 15 side, and the front wheel drive shaft 15 is adjacent to the boss portion 22 and has the same diameter. The cylindrical member 23 is fixed. Splines are engraved on the outer peripheral surfaces of the boss portion 22 and the columnar member 23, and a slider 24 is provided so as to be fitted in these splines and slidable in the axial direction. A circumferential groove 24a is provided on the circumferential surface of the slider 24, and the tip of the operating arm 25 is fitted into the groove 24a. Although the slider 24 can freely rotate with respect to the operating arm 25 together with the front wheel drive shaft 15, it moves to the left and right as the operating arm 25 swings, and engages only the column member 23 as shown in FIG. It is possible to slide from the position to the position where the cylindrical member 23 and the boss portion 22 are straddled to engage with each other. When the slider 24 is engaged only with the cylindrical member 23, the central differential device 9 functions, and the front wheel drive shaft 15 and the rear wheel drive shaft 16 can be differentially moved with respect to each other. That is, the central differential 9 is in the unlocked state. Slider 24 is cylindrical member 23 and boss
When it engages with the shaft 22, the central differential device 9 is locked, and the front wheel drive shaft 15 and the rear wheel drive shaft 16 are integrated via the central differential device 9.

For the reasons described above, this tractor is operated with the central differential unit 9 in the unlocked state while traveling on public roads.
During the agricultural work, the central differential unit 9 is operated in a locked state. Therefore, during the agricultural work, the front wheel drive shaft 15 and the rear wheel drive shaft 16 rotate at the same number of revolutions. In this state, for example, as shown in FIG. 5, the left rear wheel 2 is braked to bring the rear wheel 2 to the grounding point. When trying to make a sharp turn with 0 as the turning center, the turning radii r ₁ , r ₁ ′ of the front wheels 1, ₁ are larger than the turning radius r ₂ of the right rear wheel 2,
Further, since the rotation speed of the right rear wheel 2 becomes twice the rotation speed of the rear wheel drive shaft 16 due to the action of the rear wheel differential device 19, the rotation speed of the front wheel drive shaft 15 is the same as that of the rear wheel drive shaft 16. In this case, the number of rotations of the front wheel 1 becomes insufficient with respect to the length of the turning locus and the turning speed, and the front wheel 1 slips and a smooth turning motion cannot be obtained. Therefore, in the present invention, when the operating arm 25 is interlocked with the brake pedal 8 and the central differential device 9 is differentially locked and one of the left and right brake pedals 8 is depressed during the agricultural work, the central differential is generated via the operating arm 25. The lock of the device 9 is automatically released. Therefore, when making a sharp turn, the front wheel drive shaft 15 and the rear wheel drive shaft 16 are differentially moved, and
Rotate at the number of revolutions corresponding to each turning locus, and the engine power is transmitted not only to the rear wheels 2 but also to the front wheels 1, so that an extremely smooth turning motion can be obtained.

FIG. 4 shows a brake pedal 8 capable of realizing such an action.
An example of interlocking means between the operating arm 25 and the operating arm 25 is shown. In this example, the left and right brake pedals 8, 8 are connected at both ends by a connecting member 26 pivotally attached to the brake pedals 8, 8. Groove hole 27 extending left and right in the center of the connecting member 26
Is provided, and a shaft 28 is slidably provided through the slot 27. Below the connecting member 26, the connecting member 26
A guide member 29 is provided in the front-rear direction orthogonal to the shaft 28, and the shaft 28 is provided in a front-rear guide groove 30 provided in the guide member 29.
Has a lower end slidably engaged. In addition, the connecting member 26
A conductive contact piece 31 is fixed on the upper side adjacent to the central portion of the slot 27, and a conductive contact piece 32 slidably contacting the contact piece 31 is fixed to the shaft 28. The contact piece 31 is connected to the power source 35 via the conductor wire 33 and the changeover switch 34, and the contact piece 32 is the conductor wire.
It is connected to the solenoid 37 via 36. The operating arm
The solenoid 25 is connected to the movable piece 38 of the solenoid 37. When the solenoid 37 is not energized, it is engaged only with the cylindrical member 23 as shown by the solid line in FIG. 4 and as shown in FIG. You are in the unlocked position.

When the changeover switch 34 is turned on, the solenoid 37 is energized from the power source 35 through the changeover switch 34, the conductor 33, the contact piece 31, the contact piece 32 and the conductor 36, the movable piece 38 is attracted, and the operating arm 25 is moved to the position shown in FIG. The slider 24 is swung to the position shown by the broken line, and the slider 24 is slid to the position straddling the columnar member 23 and the boss portion 22, and the central operating device 9 is locked. As described above, the tractor is operated in such a state during the agricultural work. At this time, when the left brake pedal 8 is depressed to make a sharp turn to the left,
As shown by the chain line in FIG. 4, the connecting member 26 rotates about the right brake pedal 8, and the shaft 28 is guided by the slot 27 and the guide groove 30 to move relative to the connecting member 26.
The contact piece 31 and the contact piece 32 are separated from each other, and the power supply to the solenoid 37 is cut off. Therefore, the slider 24 is moved to the solid line position by the operating arm 25, the central differential 9 is unlocked, and the smooth turning motion is obtained as described above. When the left brake pedal 8 which has been stepped on is returned to its original position, the connecting member 26 returns to the solid line position again, so that the electrical connection to the solenoid 37 is restored and the slider 24 moves to the dotted line position to move to the central differential position. The device 9 is locked again. The same applies to the case of turning right.

When the left and right brake pedals 8, 8 are simultaneously depressed to brake the straight running of the tractor, the connecting member 26 moves forward in parallel, so the relative position of the contact piece 31 and the contact piece 32 does not change. Therefore, the solenoid 37 is kept energized and the central differential 9 is not unlocked. When traveling on public roads, the selector switch 34 is turned off to unlock the central differential device 9, so the operation of the brake pedals 8 and 8 and the differential lock device 2 are performed.
It becomes independent of the operation of 1.

Thus, when the differential of the central differential device 9 is locked between the differential lock device 21 and the pair of brake devices 8,8, one of the pair of brake devices 8,8 is locked. An interlocking mechanism is obtained in which the lock is released in response to the operation of one of the brakes alone and the brakes 8 and 8 are not operated simultaneously. It goes without saying that other interlocking means capable of achieving various purposes and functions may be provided between the differential lock device and the brake device.

As described above, according to the present invention, by locking or unlocking the differential of the differential device arranged in the center of the tractor, the tractor can be driven in a drive mode suitable for agricultural work and public road traveling. Can be driven by four wheels at all times,
In addition, during agricultural work, it is possible to extremely smoothly perform a sharp turn with a small turning radius centered on the rear wheel by turning the one rear wheel while driving both the front and rear wheels.

[Brief description of drawings]

FIG. 1 is a side view of an agricultural tractor to which the present invention is applied, FIG. 2 is a plan view diagrammatically showing a wheel drive system of the tractor, and FIG. 3 is a cutaway cross section of a central differential unit. 4 and 5 are drawings showing an example of interlocking means of the brake device and the differential lock device, and FIG. 5 is a diagram for explaining the behavior of the front wheels and the rear wheels during a sharp turn. 1 ... front wheel, 2 ... rear wheel, 3 ... engine, 4 ... reduction gear, 5 ... output shaft, 6 ... seat, 7 ... steering wheel, 8
...... Brake pedal, 9 ...... Central differential, 10 ...... Differential gear box, 11 ...... Differential small gear, 12 ...... Differential large gear, 13 ......
Large reduction gear, 14 …… Small reduction gear, 15 …… Front wheel drive shaft, 16
…… Rear wheel drive shaft, 17 …… Front wheel differential, 18 …… Front axle,
19 …… Rear wheel differential, 20 …… Rear axle, 21 …… Differential locking device, 22 …… Boss part, 23 …… Cylinder member, 24 …… Slider, 25 …… Working arm, 26 …… Coupling Material, 27 ... Slot, 28 ...
… Axis, 29 …… Guide member, 30 …… Guide groove, 31, 32 …… Contact piece, 33 …… Conductor, 34 …… Changeover switch, 35 …… Power supply, 36
...... Conductor, 37 ...... Solenoid, 38 ...... Movable piece.

Claims (1)

[Claims] 1. A brake system capable of independently braking each of the left and right rear wheels.
In a constant four-wheel drive tractor equipped with a pair of braking devices, an engine output shaft is connected to a front wheel drive shaft and a rear wheel drive shaft via a differential device arranged substantially in the center of the tractor. A drive shaft is connected to each of the left and right front wheels and rear wheels through a differential device on the front wheel side and a differential device on the rear wheel side, and a differential lock device is provided in the central differential device and Between the locking device and the pair of braking devices, when the differential of the central differential device is locked, the locking is performed in response to the independent operation of either one of the pair of braking devices. A tractor characterized by being provided with interlocking means that is released and does not respond to simultaneous actuation of both brake devices.