JPH1178586A - Front wheel driving device for tractor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lock a front wheel so as to surely prevent the unexpected very slow speed traveling of a tractor and to return to traveling based on rear wheel driving by connecting (switching-ON) a hydraulic clutch while the tractor is parked in an engine stop state. SOLUTION: A hydraulic pump is not driven while a tractor is parked in an engine stop state, and thus no system pressure is applied to a cylinder chamber 96, a clutch plate 88 is switched ON by the repulsive force of an elastic body 98, a front wheel is so-called locked to prevent the idle running of the front wheel and the unexpected very slow speed traveling of the tractor is prevented. At this time, for a rear wheel, system pressure is applied to the cylinder chamber 96 by the hydraulic pump when the engine is started, a piston 84 is retreated against the elastic force of the elastic body 98 to cut off (disconnect) the clutch plate 88, and thus return is made to traveling based on only rear wheel driving.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a front wheel drive system for a tractor, and more particularly, to driving a front wheel by connecting and disconnecting a hydraulic clutch in a two-axis four-wheel agricultural tractor (so-called four-wheel drive). , Or a non-driving front wheel (so-called rear wheel driving).

[0002]

2. Description of the Related Art A front wheel drive device having a front wheel drive gear in a rear wheel drive transmission system and having a hydraulic clutch interlocked with the drive gear is known from Japanese Patent Publication No. Hei 7-100414 or the like. (The front wheels are driven substantially in synchronization with the rear wheels) and the speed increasing (the front wheels are driven to increase speed with respect to the rear wheels), and the constant speed hydraulic clutch is engaged (engaged). By driving the vehicle with four-wheel drive (so-called DT drive), the climbing force is increased, the traction force is increased, and the like, while the hydraulic clutch for speed increase is engaged with the steering (front wheel steering angle) to engage the clutch ( Contact), the small turning performance (so-called double speed drive) was improved.

[0003]

In a front wheel drive system in which a hydraulic clutch is incorporated in the front wheel drive train, when the tractor is parked with the engine stopped.
The hydraulic pump driven by the engine does not operate, so there is no hydraulic pressure to bring the hydraulic clutch into contact, the hydraulic clutch is in a disengaged state, and the front wheels are so-called free (free running) and are not locked. Therefore, there is a problem that the tractor may unexpectedly move at a very low speed (slow running).

In order to solve this problem, a parking brake is provided in the front wheel drive transmission system in the same manner as the rear wheel drive power transmission system (incidental).
However, there is a problem in that this increases the cost and lowers the transmission efficiency during normal running (during four-wheel drive and rear-wheel drive). Therefore, the present invention locks the front wheel by engaging (engaging) the hydraulic clutch when the tractor is parked with the engine stopped, thereby reliably preventing the tractor from running at an unexpectedly low speed, while maintaining the rear wheel. The main purpose is to be able to return to running by driving, and a secondary purpose is to also enable four-wheel drive (DT drive and double speed drive).

[0005]

SUMMARY OF THE INVENTION The present invention is directed to a front wheel drive system having a front wheel drive gear in a rear wheel drive transmission system and a hydraulic clutch interlocked with the drive gear. Has taken technical measures. That is, the front wheel drive device for a tractor according to the present invention includes an elastic body that brings the hydraulic clutch into a contact direction when the engine is stopped, and configures the hydraulic clutch in a disconnecting direction against the elastic body by a system pressure driven by the engine. (Claim 1).

[0006] By adopting such a configuration,
When the engine is stopped and the vehicle is parked, the front wheels are locked and unpredictable because the hydraulic clutch is in contact with the elastic body even when the hydraulic pump driven by the engine is not driven and no system pressure is generated. The tractor does not run at very low speed. On the other hand, when the engine is started from the parking state, the hydraulic pump is driven to generate a system pressure, so that the system can return to the rear wheel drive by disengaging the hydraulic clutch by the elastic body by this system pressure.

Here, the hydraulic clutch includes a hydraulic clutch for front-wheel constant speed (DT clutch) and a hydraulic clutch for double-speed front wheel (double-speed clutch) that can be mechanically engaged by an elastic body. In consideration of the gear ratio, it is advantageous in terms of efficiency to incorporate the clutch into a hydraulic clutch for constant velocity (which may be full constant velocity or substantially constant velocity).

In the present invention, the means for forming the hydraulic clutch in the disengagement direction slides and guides a boss portion of a hydraulic piston in the hydraulic clutch and forms a cylinder chamber when system pressure is supplied. (Claim 2). By adopting such a configuration, the switching between the front wheel lock and the rear wheel drive can be secured with a simple configuration in which the cylinder case is incorporated into the clutch pack of the hydraulic clutch.

Further, in the present invention, the hydraulic working area of the hydraulic piston is made larger than the hydraulic working area of the system pressure cylinder chamber, and the hydraulic clutch is brought into contact with the difference in the hydraulic working area so that the front wheels together with the rear wheels are moved. It is characterized by being drivable (claim 3). By adopting such a configuration, the DT drive and the double-speed drive can be performed while the front wheel lock described above is secured and parking can be reliably performed.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a tractor front wheel drive apparatus according to the present invention; FIG. The overall configuration of the transmission to which the present invention is applied (traveling transmission and PTO transmission) will be described with reference to FIG. 2, and the PTO transmission will be described with reference to FIG. 3 and FIG. The details of the front wheel drive device according to the present invention will be described with reference to FIG.

In FIG. 1, a tractor 1 has left and right front wheels 2.
A left and right front wheel 2 is a steering wheel that can be switched between a driving state and a non-driving state, and the left and right rear wheels 3 are driving wheels; A cabin 6 is mounted so as to surround the steering handle 4 and the driver's seat 5. Of course, a tractor without the cabin 6 may be used.

A tractor body 8 is formed by connecting a transmission case to a rear surface of the tractor engine 7 via a clutch housing. The tractor body 8 includes a traveling system transmission and a PTO system transmission shown in FIG. And a transmission including: A hydraulic lifting device 10 having left and right lift arms 9 is provided on the rear upper surface of the tractor body 8, and a work implement 12 shown as a rotary tiller in this example is mounted by a link mounting body 11 shown by a three-point link. And the working machine 12 is
It can be driven via the TO shaft 13.

In FIG. 2, a traveling system propulsion shaft 16 is intermittently connected to an engine crankshaft (output shaft) 14 via a traveling system main clutch 15, and a transmission gear group 17 on the propulsion shaft 16. The transmission shaft 19 having the transmission gear group 18 meshing with the transmission gear 19 constitutes a main transmission 20 as a traveling transmission capable of performing a four-speed shift in a synchronous occlusion system in the illustrated example.

A transmission shaft 23 of a shuttle transmission 22 is provided on the downstream side of the main transmission 20 (the exit side of the transmission shaft 19) via a hydraulic clutch 21 for inertia braking. Is the forward gear 24 and the reverse gear 2
5, the two gears 24, 25 can be freely turned on and off by a shifter 26. The output shaft of the shuttle transmission 22 also serves as the transmission shaft 28 of the auxiliary transmission 27. On this transmission shaft 28, the transmission gear 30 meshing with the reverse rotation gear 25 via the back gear 29 and the forward rotation transmission A gear 31 and a transmission gear 32 for high-speed sub-transmission are provided.

The counter shaft 33 of the auxiliary transmission 27 has a low-speed gear 34 that meshes with the gear 30 and a high-speed gear 35 that meshes with the gear 32, and has a shifter 36 that switches between the two gears 34, 35. Here, the subtransmission 27 can be shifted up and down. The counter shaft 33 has a cylindrical shaft configuration. A transmission shaft 37 is inserted into the counter shaft 33, and the transmission shaft 37 is connected to the rear wheel differential device 3 via a coupling 38.
9 drive shaft 40.

A creep transmission 41 is disposed below and in front of the auxiliary transmission 27.
Reference numeral 1 denotes a first creep speed change which is provided with a first creep shaft 42 and a second creep shaft 43 and is interlocked with the transmission shaft 37 via a gear on the first creep shaft 42; A second creep shift interlocking with the transmission shaft 37 via a gear on the creep second shaft is enabled by turning on and off the shifter.

A front wheel drive unit 44 according to the present invention is disposed in front of the creep transmission 41 and below the main transmission 20. The front wheel drive device 44 includes a clutch shaft 4 having a constant speed hydraulic clutch 45 and a speed increasing hydraulic clutch 46.
The clutch shaft 47 is interlocked with a gear 48 for driving the front and upper wheels of a transmission shaft 37, which is a rear-wheel drive transmission system, and a front wheel drive shaft 49 is provided below the clutch shaft 47. The front wheel drive shaft 49 is interlocked with the front and rear interlocking gear groups 50 and 51, and the front wheel drive shaft 49 is interlocked with the front wheel differential device via the propulsion shaft 52.

The main transmission 20, the shuttle transmission 22, the auxiliary transmission 27, and the creep transmission 41 constitute a traveling system transmission. The transmission is transmitted to the device 39, the left and right rear wheels 3 can be driven from the left and right yoke shafts of the rear wheel differential device 39 via the final reduction gear, and the left and right front wheels 2 are disconnected together with the hydraulic clutches 45 and 46. The non-drive state (drive of only the rear wheels) and the hydraulic clutches 45 and 46
, The front wheel drive state synchronized with the rear wheel 3 and the so-called double speed front wheel drive state in which the speed is higher than that of the rear wheel 3 are possible.

A PTO transmission 53 is provided on the front side of the rear wheel differential device 39. The PTO transmission 53 is connected and disconnected by an independent PTO clutch 54 which is directly connected to the engine (in the figure, directly connected to the crankshaft 14). Therefore, the traveling propulsion shaft 16 and the speed change shaft 28 are both coaxial with each other to form a cylindrical shaft, and the PTO propulsion shaft (input shaft) 55 is attached to these cylindrical shafts 16 and 28. Have been interpolated.

The output of the PTO transmission 53 is connected to a transmission shaft 57 via a coupling 56. The transmission shaft 57 is operatively connected to the PTO shaft 13 via a PTO reduction gear device 58. Is composed. Referring to FIG. 3 and FIG.
And the PTO transmission 53 will be described.

The independent PTO clutch 54 has a mounting coupling 57 for a clutch plate 56 on an input shaft 55 and a clutch housing 59 on an output shaft 58.
9 includes a hydraulic piston 61 that presses (clutches in) the clutch plate 56 by hydraulic pressure against the spring 60. The clutch housing 59 is provided with brake means 62, and the brake means 62
When 1 is returned by the spring 60 in the clutch disengagement direction, the brake means 62 acts in conjunction with this movement, and stops inertial idling at the time of switching from clutch engagement to disengagement. Provided.

Clutch output shaft (PTO shift input) 58
A drive gear 64 having an engaging portion 64A is engraved at the rear end, and a PTO speed change shaft 65 is installed coaxially with the clutch output shaft 58. The PTO speed change shaft 65 is connected to the PTO speed change shaft 65 via a coupling 56. The transmission shaft 57 is joined.
Outer splines 66A and 66B are formed on the PTO transmission shaft 65 so as to be divided into front and rear portions by a hollow portion 66C formed at an intermediate portion in the axial direction.
A shift gear 68 having inner splines 67A, 67B engaged with the gears A, 66B is fitted on the transmission shaft 65 so as to be slidable in the axial direction.

The shift gear 68 includes large and small gears 68A, 68B.
And the inner splines 67A, 67B
A hollow portion 67C is formed at an intermediate portion in the axial direction to partition the inner splines 67A and 67B forward and backward. A counter shaft 69 is provided in parallel with the PTO transmission shaft 65. The counter shaft 69 has a cylindrical structure, and is fitted around the differential drive shaft 40 so as to be relatively rotatable (slidable).

A transmission gear 70 meshing with the drive gear 64 and transmission gears 71, P
Transmission gear 72 for first-speed TO and gear 7 for reverse rotation of PTO
3 is formed with a gap in the axial direction from the front to the rear, and a reverse gear 73 is engaged with an idle gear 75 provided on a back shaft 74. Shift gear 6
8, a shift fork (not shown) is engaged, and reciprocatingly slides from one side in the axial direction of the speed change shaft 65 along the other side as indicated by an arrow X, so that the PTO 3rd speed (3P) and the PTO 2nd speed (2P) , Neutral (NP), PTO 1st speed (1P), PTO
The gears can be shifted in the reverse rotation (PR) order (including the reverse order), and the shift gear 68 can be turned on and off in an I-type shift pattern.

The PTO shift will be described in detail. The position of the shift gear 68 shown in FIG.
And the large gear 68A of the shift gear 68 is the reverse gear 7
3 through an idle gear 75,
When the PTO clutch 54 is engaged (engaged), the transmission shaft 65 is driven in reverse rotation via the drive gear 64 → gear 70 → gear 73 → gear 75 → gear 68A, and the PTO shaft 13 is driven via the reduction gear 58. It is driven in reverse rotation and is used, for example, when the work machine 12 is an up-cut rotary.

At the time of the reverse rotation of the PTO, the shift gear 68
3 and 4, a thrust force due to a corner force is acting rearward (rightward in the drawings).
8 is received by a wall such as a bearing, so that there is no shift-out. When the shift gear 68 is slid in the arrow X direction to the (IP) position, the large gear 68A of the shift gear 68
Meshes with the transmission gear 72 to achieve the first PTO speed, and at this time, the rear inner spline 67B of the shift gear 68
5 is engaged with the rear outer spline 66B and the shift gear 6
The front inner spline 67A of FIG.
6C and is not engaged, the shift gear 6
The thrust force 8 (acting to the left in the drawing) at this time is reduced, and shift-out is prevented.

Further, when the shift gear 68 is set to the (NP) position, the large and small gears 68A, 68B of the shift gear 68 do not mesh with any of the transmission gears 71, 72, so that the transmission gears 71, 7 are not engaged.
When the shift gear 68 is set to the (2P) position from this state, the small gear 68B of the shift gear 68 meshes with the transmission gear 71, and the shift gear 68
The front inner spline 67A of the transmission gear 65 meshes with the front outer spline 66A of the transmission shaft 65, and the rear inner spline 67A of the shift gear 68.
Since B is not engaged with the hollowed portion 66C of the speed change shaft 65, the thrust force (acting on the left side in the figure) of the shift gear 68 is reduced, thereby preventing a shift loss.

That is, in the I-type shift pattern, when the shift gear 68 is in the shift position at an intermediate position in the axial direction of the shift shaft 65, one of the front and rear splines of the inner and outer splines is in the biting state, so that the shift gear 68 is shifted. The dropout is prevented. Also, the shift gear 68
Is set to the (3P) position, the front inner spline 67A engages with the engaging portion 64A of the drive gear 64, and the output shaft 58 and the transmission shaft 6
5 is directly connected, and the PTO third speed is obtained. At this time, even if a thrust force on the left side of the figure acts on the shift gear 68, the drive gear 64 and the like act as a wall, so that there is no shift loss.

In the above-mentioned first to third speeds of the PTO, the PTO speed change shaft 65 is connected to the PT
It is obvious that the O-shaft 13 is driven, and on the condition that the pattern is an I-type shift pattern, the (PR), (IP), (NP),
(2P) and (3P) may be used. The details of the front wheel drive device 44 will be described with reference to FIG.
The clutch shaft 4 is rotatably supported on the front and rear walls of the transmission case by bearings 80 and 81 at the front and rear.
A constant speed clutch body 82 and a double speed clutch body 83 are fixedly fitted on the back 7 in a back-to-back manner.

Pistons 84 and 85 are slidably and oil-tightly fitted to both clutch bodies 82 and 83, respectively.
A and 51A are rotatably fitted on the clutch shaft 47 via bearings 86 and 87, and each clutch gear 50A,
Clutch bodies 82, 8 corresponding to the outer periphery of the boss of 51A
3, clutch plates 88 and 89 are interposed.

An interlocking gear 90 that meshes with the drive gear 48 is fitted and fixed (spline in the figure) to the clutch shaft 47, and a rotary joint 91 is provided at an end of the clutch shaft 47. Pressing oil passages 92 and 93 for the pistons 84 and 85 are connected to the oil passage distributing portion 91, and pressure oil from a hydraulic pump is supplied to the oil passages 92 and 93 by switching a control valve (not shown). By pressing each piston 84, 85, the clutch plates 88, 89 can be freely connected and disconnected by hydraulic pressure, and reference numeral 94 in FIG.

In the embodiment shown in FIG. 5, the piston 8
4 is oil-tightly inserted into a cylinder case 95 via a sealing material 84B such as an O-ring to form a cylinder chamber 96 of system pressure by the cylinder case 95. Is the oil passage 97 without the system pressure from the hydraulic pump passing through the control valve.
And can be supplied via the Internet.

Further, an elastic member 98 is provided between the clutch body 82 and the hydraulic piston 84 to urge the clutch plate 88 mechanically in the contact direction.
Although a coil spring is shown, a disc spring, a bamboo shoot spring, or the like can be adopted as the coil spring. The hydraulic pump is directly connected to the engine 7, and in the present embodiment, the hydraulic pump is connected to the PTO input shaft 55 shown in FIG.
Is driven by a hydraulic pump 99. The hydraulic pump 99 is a gear pump, and can supply hydraulic oil to the hydraulic elevating device 10 and various clutches 21, 54, 45, and 46.

In FIG. 2, the left and right yoke shafts (output shafts) of the rear wheel differential device 39 are interlocked with the rear wheel 3 via the final reduction gear, and the left and right yoke shafts or the left and right rear axles are used. It is equipped with a mechanical left and right independent brake, which can be used as a parking brake by allowing the left and right independent brakes to have a simultaneous brake function by making the pedal of the brake detachable with a connecting rod. ing.

The operation of the front wheel drive device 44 according to the present invention will be briefly described with reference to FIGS. 2 and 5. When the transmission of the traveling system is in a transmission state (means a shift state, 24 forward gears and 24 reverse gears are shown). The rear wheel 3 is driven via the rear wheel differential device 39, and the drive gear 48 on the transmission shaft 37, which is a rear wheel traveling transmission system, is used for the front wheel drive device 44.
Drives the clutch shaft 47 via the interlocking gear 90 (rotation)
doing.

In this state, the piston 8 of the hydraulic clutch 45 is
When the hydraulic oil is supplied to No. 4, the clutch plate 88 comes into contact,
The front wheel drive shaft 49 is transmitted to the front wheel differential device via the propulsion shaft 52 via the interlocking gear group 51, and the left and right front wheels 2 are synchronized with the rear wheel 3 to be driven by four wheels (DT drive). At this time, a cylinder chamber 96 is formed in the hydraulic clutch 45 via a cylinder case 95, and although system pressure is acting on the cylinder chamber 96, the hydraulic clutch 45 is formed by an area difference between the cylinder chamber 96 and the piston 84. Can be engaged (engaged) with the clutch, and here the forced 4WD is possible.

In the case of double speed drive, the hydraulic piston 8
The front wheel drive shaft 49 is driven to rotate at a double speed through the interlocking gear group 50 by applying hydraulic pressure to the front wheel 5, and it is detected that the turning angle (steering angle) of the front wheel 2 is turned,
By operating the hydraulic pressure on the hydraulic piston 85 in conjunction with this, the front wheel 2 is driven at double speed with respect to the rear wheel 3 to improve the small turning performance.

On the other hand, when the tractor 1 is parked with the engine 7 stopped, the hydraulic pump 99 is not driven, so that the cylinder body 96 does not act on the system pressure and the elastic body 98 is resilient. Clutch plate 88 by force
Is engaged, and the front wheels 2 (including the drive shaft 49, the propulsion shaft 52, etc., which is a front wheel transmission system) are so-called locked and the front wheels 2 are locked.
Is prevented, and the tractor 1 is prevented from running at an unexpectedly slow speed.

At this time, it is desirable that the parking brake described above is applied to the rear wheel 3. However, since the gears of the traveling system are engaged, the parking state of the tractor is not required even when the parking brake is applied. Is possible. When the engine 7 is started, the system pressure of the hydraulic pump 99 directly connected to the engine 7 acts on the cylinder chamber 96 to oppose the elastic force of the elastic body 98 and the piston 8
Since the clutch 4 is retracted and the clutch plate 88 is disengaged (disengaged), the running can be returned while only the rear wheel 3 is driven via the running transmission.

Although the elastic body 98 and the cylinder case 95 for guiding the piston boss portion 84A are incorporated in the constant-speed hydraulic clutch 45 in the drawing, they can also be incorporated in the double-speed hydraulic clutch 46. Taking into account (the gear ratio of the interlocking gear groups 50 and 51), it is more efficient to incorporate the clutch into the constant-speed hydraulic clutch 45.

[0041]

As described in detail above, according to the present invention, the front wheels can be reliably locked even when the engine is stopped, and the return to the rear wheel drive state, DT drive, etc., is also ensured.

[Brief description of the drawings]

FIG. 1 is a side view of a tractor equipped with a front wheel drive device according to the present invention.

FIG. 2 is an overall side view of a transmission including a PTO transmission equipped with a front wheel drive device according to the present invention;
It is partially expanded.

FIG. 3 is a side view of the PTO transmission.

FIG. 4 is a sectional view of a main part of FIG. 3;

FIG. 5 is a sectional view of a front wheel drive device according to the present invention.

[Explanation of symbols]

 2 front wheel 3 rear wheel 7 engine 8 tractor body 37 rear wheel traveling transmission system (transmission shaft) 44 front wheel drive device 45 constant speed hydraulic clutch 46 double speed hydraulic clutch 48 drive gear 95 cylinder case 98 elastic body

Claims (3)

[Claims] 1. A front wheel drive device comprising a front wheel drive gear in a rear wheel drive transmission system and a hydraulic clutch interlocked with the drive gear, comprising: an elastic body for bringing the hydraulic clutch into a contacting direction when the engine is stopped; A front wheel drive device for a tractor, wherein the hydraulic clutch is configured to be in a disengaged direction against the elastic body by a system pressure according to (1). The means for forming the hydraulic clutch in the disengagement direction is a cylinder case for slidingly guiding a boss portion of a hydraulic piston in the hydraulic clutch and forming a cylinder chamber when system pressure is supplied. The front wheel drive device for a tractor according to claim 1, wherein: 3. The hydraulic piston according to claim 1, wherein a hydraulic operating area of the hydraulic piston is larger than a hydraulic operating area of the cylinder chamber for system pressure, and the hydraulic clutch is brought into contact with the difference in the hydraulic operating area to drive the front wheels together with the rear wheels. The front wheel drive device for a tractor according to claim 1 or 2, wherein: