JP2006130972A - Traveling power transmission for tractor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a traveling power transmission for tractor which enables a smooth turning to be performed without producing a shock in the speed variation or without damaging a vegetable field at the time of turning by changing the peripheral speed ratio continuously at a certain degree based on a turning radius by a handle operation when the machine frame is turned in a vicinity of the ridge. <P>SOLUTION: A center differential 5 is provided at the power branching section for a front wheel driving system 10 and a rear wheel driving system 11 of this traveling power transmission. By the center differential 5, the driving force from an engine E is transmitted to a front wheel differential 30 and a rear wheel differential 38, and front wheels 8 and rear wheels 9 on the right and the left are driven by the front and rear differentials 30 and 38 for this tractor. In the tractor, the center differential 5 is constituted of a limited slip differential having a differential-limiting function. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a traveling power transmission device for a tractor.

In recent years, tractors are equipped with a front wheel speed increasing device in the driving power transmission device to reduce headland at the shore, and when turning the body, the front wheel can be turned about twice as fast as the rear wheel, and a small turn can be made. This is known.
However, this front wheel speed increasing device switches the transmission gear by a hydraulic clutch regardless of the turning radius or wheel load when the steering wheel is turned, so that the front wheel is kept at a constant front and rear wheel speed ratio (circumferential speed ratio). Since the speed of the vehicle is increased, the load on the wheels is large, and the vehicle speed is increased to increase the speed of the front wheels.

In addition, the front wheel speed increasing device has a front / rear wheel speed ratio that is switched intermittently, so that a shock is generated at the time of switching, and the operator feels uncomfortable, and the electric / hydraulic control increases the number of parts. Was expensive.
Therefore, a center differential is provided in the power branching part of the front wheel drive system and rear wheel drive system of the traveling power transmission device, and torque is continuously distributed to the front and rear wheels by this center differential, continuously reducing the slip and side slip that occur during turning. Attempts have been made to control the front-rear wheel ratio, thereby enabling ideal turning with less change in vehicle speed and less shift shock during turning.

Further, when this center differential is adopted, a non-slip device using a one-way clutch is known to be installed in the center differential in order to prevent slipping of the vehicle due to idling of the front wheels (for example, patents) Reference 1).
JP-A-5-85213

The non-slip device described in Patent Document 1 is a vehicle that can prevent the vehicle from slipping by performing a center differential lock by the action of a one-way clutch when one or both of the front wheels idles when the vehicle moves forward. Can improve the running performance.
However, in this case, the center differential lock is not substantially activated when the vehicle is moving backward, and even when the vehicle is moving forward, the center differential lock is not activated when the rear wheel is idling. As a result, the vehicle slips. There is a problem that will be.

  In addition, if a non-slip device using a one-way clutch is added to the center differential, these devices will be increased in size, making it difficult to reduce the weight of the work vehicle transmission and make it difficult to reduce the cost.

  In order to solve the above problems, the present invention provides a center differential 5 at the power branching portion of the front wheel drive system 10 and the rear wheel drive system 11 of the traveling power transmission device, and the center differential 5 generates a driving force from the engine E. In the tractor that transmits to the front wheel differential 30 and the rear wheel differential 38 and drives the left and right front wheels 8 and the rear wheel 9 by the front and rear differentials 30 and 38, the center differential 5 is a limited slip differential having a differential limiting function. It is characterized by comprising.

  Further, the limited slip differential is characterized in that the differential limiting force of the front wheel 8 is more relaxed than the differential limiting force on the rear wheel 9 side.

  According to the present invention configured as described above, the peripheral speed ratio of the front wheels and the rear wheels is continuously changed to some extent based on the turning radius by the steering wheel operation by the limited slip differential during the turning of the aircraft at the shore. Thus, smooth turning is possible without causing a shift shock at the time of turning, and without damaging the field, as is the case with a conventional front wheel transmission.

In addition, even if one of the front and rear wheels or both front and rear wheels slip or slip, the limited slip differential can be increased by adding torque to the front or rear wheels on the low speed side. Can improve the running performance.
Further, if the limited slip differential is configured so that the differential limiting force on the front wheel side is less than the differential limiting force on the rear wheel side, the front wheel can easily obtain a speed ratio approximately twice as large as that of the rear wheel. Thus, even when the aircraft is turned slightly, it can be safely turned without increasing the vehicle speed.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a traveling power transmission device for an agricultural tractor. This tractor has a traveling drive system similar to a known one, a traveling transmission system 2 that is input from the engine E via the main clutch 1, a center differential 5 that is driven from the final gear 3 of the traveling transmission system 2, and A front-wheel drive system 10 and a rear-wheel drive system 11 drive the left and right front wheels 8 and rear wheels 9 from a front transmission shaft 6 and a rear transmission shaft 7 which are branched from the center differential 5.

Further, a PTO transmission system 12 having a PTO shaft 12a for driving a working machine such as a tillage device is driven by a drive shaft 13 that is directly connected to the main clutch 1 and extends rearward from the traveling transmission system 2.
In the traveling transmission system 2, a main transmission unit 16 including a main transmission gear group provided on the drive shaft 13 and the transmission shaft 15 performs four steps of high and low speeds, and forward / reverse transmission provided on the transmission shaft 15 and the first intermediate shaft 20. Forward / backward shifting is performed by the unit 19. Reference numeral 17 denotes a back shaft.

  Also, the second intermediate shaft 21 and the fourth intermediate shaft 23 are provided with an ultra-low speed clutch portion 26 comprising a meshing clutch mechanism, and a standard position for directly transmitting the rotation of the second intermediate shaft 21 to the fourth intermediate shaft 23, It is transmitted selectively to an ultra-low speed position transmitted to the fourth intermediate shaft 23 via the 3 intermediate shaft 22. Further, the fourth intermediate shaft 23 and the sub-transmission shaft 25 are provided with a sub-transmission unit 27 composed of a sub-variable gear group, and the rotation from the fourth intermediate shaft 23 is shifted in two steps, high and low. The power is transmitted from the final gear 3 to the diff ring gear 5a of the center differential 5.

The front wheel drive system 10 receives power from the front transmission shaft 6, and finally decelerates the pinion shaft 32 and the axle 33 by gear transmission from the front wheel transmission shafts 31, 31 that the front wheel differential 30 has on the left and right to drive the front wheels 8.
The axle 33 is configured to be rotatable about the pinion shaft 32 and is pivotally supported by a support case portion (not shown) that integrally includes a steering arm 35.

As a result, the left and right front wheels 8 are rotated about the pinion shaft 32 by the rotation of the respective steering arms 35 based on the steering operation, and the airframe can be steered.
In this embodiment, a differential lock releasing mechanism 50 that can automatically release the differential lock of the center differential 5 based on an increase in the steering amount is installed between the steering arm 35 and the center differential 5 with a configuration described later. is doing.

The rear wheel drive system 11 finally decelerates the axle 40 from the left and right differential shafts 39, 39 of the rear wheel differential 38 that is transmitted by the rear transmission shaft 7 of the center differential 5, and drives the rear wheel 9. To do.
The left and right differential shafts 39 are each provided with a brake mechanism 41 at the shaft end, and the left and right rear wheels 9 and 9 are braked simultaneously or alternatively by operating the brake mechanism 41 from the brake pedal of the control unit. can do.

Next, the center differential 5 installed between the front wheel drive system 10 and the rear wheel drive system 11 will be described. The center differential 5 in this embodiment employs a limited slip differential (differential limiting device) having a differential limiting function.
That is, the limited slip differential is constituted by a known mechanical limited slip differential as shown in, for example, Japanese Patent Application Laid-Open No. 7-293665. It is possible to generate a force to eliminate the rotation difference of the axle, and to limit the rotation difference between the front wheels 8 and the rear wheels 9 to prevent the transmission torque from being lowered.

  Further, the center differential 5 of the embodiment includes a braking portion (front braking portion) 36 on the front wheel transmission shaft 31 side and a braking portion (rear braking portion) 37 on the rear transmission shaft 7 side which are configured in a limited slip differential mechanism. The number of friction plates constituting each of the multi-plate clutch mechanisms is different, and the front braking portion 36 is provided smaller than the rear braking portion 37. As a result, the braking capacity of the front wheel transmission shaft 31 can be set smaller than the braking capacity on the rear transmission shaft 7 side, and the front wheel 8 and the rear wheel 9 have a peripheral speed ratio when turning with a small radius. The braking force is reduced with respect to the front wheel 8 side so as to allow even when the speed ratio of 8 is about twice that of the rear wheel 9.

  In constructing the limited slip differential type center differential 5, the tractor is operated between the center differential 5 and the steering arm 35 of the front wheel drive system 10 so that the left and right front wheels 8 are operated at a predetermined steering angle (front wheel breakage). A differential lock release operation mechanism 50 is provided that can automatically switch the center differential 5 from the differential lock state to the differential lock release state when the center differential 5 is rotated as described above.

The differential lock release operation mechanism 50 connects a differential lock member 51 provided in the center differential 5 and a steering arm 35 by configuring a link mechanism with an operating rod 52 and an operating piece 53.
An operating rod 52 that engages with the differential lock member 51 and an operating piece 53 that engages with the steering arm 35 are connected by a connecting pin 55, and a middle portion of the operating piece 53 has a front shaft 31 that houses the front wheel transmission shaft 31. It is rotatably supported by a support pin 56 protruding from the top.

  The steering arm 35 is provided integrally with the front wheel support case that is rotatably supported around the pinion shaft 32 of the transmission shaft case, and contact pieces 57 and 59 having different lengths are provided on the upper portion of the steering arm 35. Thus, the contact pieces 57 and 59 are selectively in contact with both end sides of the operating piece 52.

  With this configuration, when the front wheel 8 is rotated to the left or right beyond the predetermined front wheel turning angle by the steering operation by the steering operation, the contact piece 57 or the contact piece 59 is selected at both ends of the operating piece 53. The operating piece 53 is rotated around the support pin 56. As a result, the operating piece 53 pulls the operating rod 52 and moves the differential lock member 51 in the direction of the arrow, so that the differential lock state of the center differential 5 can be released.

As a result, during straight traveling where the steering wheel operation is not greatly performed, the center differential 5 maintains the differential lock state, and the front transmission shaft 6 and the rear transmission shaft 7 are fixed and rotated integrally, so that the peripheral speed ratio between the front wheels 8 and the rear wheels 9 is increased. It is possible to obtain a stable traction force when the aircraft is going straight.
Further, when turning the steering wheel with a large handle operation, the differential lock state of the center differential 5 can be automatically released, so that the differential limited turning using the center differential 5 can be smoothly performed.

As described above, the tractor in which the center differential 5 composed of the limited slip differential is installed at a location where the traveling transmission system 2 branches to the front wheel drive system 10 and the rear wheel drive system 11 is configured so that the front wheel The peripheral speed ratio between 8 and the rear wheel 9 can be controlled as follows.
That is, when the front wheel 8 is steered beyond a predetermined front wheel turning angle, the center differential 5 continuously moves to the front transmission shaft 6 and the rear transmission shaft 7 in accordance with a change in the required rotational speed associated with the front wheel cutting angle. Since the torque is distributed and the front wheels 8 and the rear wheels 9 are driven, it is possible to suppress slip and side slip of the front wheels 8 that are likely to occur when the aircraft is turning.

  Further, unlike the center differential with the conventional general differential mechanism, the center differential 5 of the limited slip differential system is adapted to change the required rotational speeds of the front wheels 8 and the rear wheels 9 according to the front wheel turning angle. Since the peripheral speed ratio can be changed during turning, even when the aircraft turns with a small turning radius, smooth turning with less turning shock and less change in vehicle speed is possible. Therefore, formation of a deep groove due to mud pushing of the front wheels 8 during turning is prevented, the field is not roughened, and the burden on the operator's driving operation can be reduced.

  Furthermore, when the left and right front wheels 8 or one of the front wheels 8 faces into the air due to unevenness of the ground or enters a non-resisting ground (sliding situation location) such as muddy, the front wheel 8 decreases in ground resistance. As a result of the idling, the front wheel transmission shaft 31 also idles and loses the driving force of the rear wheel 9 to deteriorate the running balance.

At this time, if the front wheel transmission shaft 31 tries to rotate more than the set circumferential speed ratio, the differential limiting mechanism in the center differential 5 is automatically operated to control the front wheel transmission shaft 31 to be braked and rotated within the set circumferential speed ratio. Therefore, the rear transmission shaft 7 is also kept rotating within the set peripheral speed ratio, and the rear wheel 9 can be driven to escape from the non-resistance ground and run through.
Further, since the center differential 5 acts in the same manner when the rear wheel 9 faces the non-resistance ground, in this case, the rear wheels 9 and the rear transmission shaft 7 are prevented from idling and the driving force of the front wheels 8 prevents the non-resistance ground. Can run through.

  At this time, the center differential 5 constituted by a limited slip differential mechanism is different from the front wheel 8 in that the number of friction plates is different between the front braking portion 36 on the front transmission shaft 6 side and the rear braking portion 37 on the rear transmission shaft 7 side. Even if one of the front and rear wheels 8, 9 or both front and rear wheels are idling or slipping because of the braking distribution structure in which the peripheral speed ratio with the rear wheel 9 is set to about 2 to 1. The limited slip differential can be increased by adding torque to the front wheel 8 or the rear wheel 9 on the low speed side, and the running ability in the field can be improved.

  Further, the limited slip differential relaxes the differential limiting force on the front wheel 8 side rather than the differential limiting force on the rear wheel 9 side, so that the front wheel 8 can easily obtain a speed ratio approximately twice as large as that of the rear wheel 9. Therefore, even when making a small turn, it is possible to turn safely without increasing the vehicle speed.

  Incidentally, the brake distribution structure of the front wheel transmission shaft 31 and the rear transmission shaft 7 configured as a limited slip differential is not limited to one in which the number of the friction plates is different, for example, the front braking portion 36 and the rear braking portion 37. Is composed of a single plate type brake plate or a belt brake type brake shoe, the set peripheral speed ratio can be determined by means such as changing the friction area, the braking pressure, or the like.

Further, as described above, the tractor including the traveling power transmission device and performing the turning control includes a front wheel drive adjusting device 60 on the front wheel drive system 10 side and a brake mechanism on the rear wheel drive system 11 side as shown by a dotted line in FIG. 61 can also be provided.
In this case, the front wheel drive adjustment device 60 is configured to mesh the drive gear 65 of the adjustment motor 62 that is operated so as to be capable of rotational adjustment from the control unit side with a gear 63 provided on the front transmission shaft 6.

  As a result, when the front wheel 8 tries to tow at a speed approximately twice the peripheral speed of the rear wheel 9 by the set peripheral speed ratio, the front wheel drive adjusting device 60 is operated from the control section side when the vehicle is turning, and the front transmission shaft 6 is moved. Since the speed can be increased or decreased, the peripheral speed of the front wheel 8 can be selected according to the field condition or the operator's preference, and the vehicle can turn at an arbitrary turning speed.

Further, the brake mechanism 61 is configured such that a braking portion 66 that is operated from the control portion side so as to be able to perform braking adjustment is provided in the middle portion of the rear transmission shaft 7.
As a result, when the front wheel 8 and the rear wheel 9 are rotated and pulled by the set peripheral speed ratio, an arbitrary braking force is applied to the rear transmission shaft 7 by operating the brake mechanism 61 and the rear wheel 9 is decelerated and rotated. Since the front wheel 8 can be rotated at an increased speed, the peripheral speed of the front wheel 8 and the rear wheel 9 can be selected according to the situation of the field or the operator's preference, and the vehicle can go straight and turn at an arbitrary speed.

It is a transmission block diagram of the traveling power transmission device of the tractor concerning this invention.

Explanation of symbols

2 Traveling transmission system 3 Final gear 5 Center differential 6 Front transmission shaft 7 Rear transmission shaft 8 Front wheel 9 Rear wheel 10 Front wheel drive system 11 Rear wheel drive system 30 Front wheel differential 36 Braking part (front braking part)
37 Braking part (rear braking part)
38 Rear wheel differential E engine

Claims (2)

  A center differential (5) is provided in the power branching portion of the front wheel drive system (10) and the rear wheel drive system (11) of the traveling power transmission device, and the driving force from the engine (E) is generated by the center differential (5). In the tractor that transmits to the differential (30) and the rear wheel differential (38) and drives the left and right front wheels (8) and the rear wheel (9) by the front and rear differentials (30) and (38), the center differential ( A traveling power transmission device for a tractor comprising 5) a limited slip differential having a differential limiting function. The traveling power transmission device for a tractor according to claim 1, wherein the limited slip differential is configured so that the differential limiting force of the front wheel (8) is less than the differential limiting force of the rear wheel (9).

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