JPH11334396A - Transmission case structure of tractor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission case structure of a tractor, which is effective in constituting machine bodies with various specifications without changing basic constitution of a transmission case, by devising a method of unforcibly introducing a space case. SOLUTION: A space case 3c is disposed between a differential case 3b and a transmission case 3a accommodating a gear speed changing mechanism 11. A bevel pinion gear Gp is pivotally supported near a front end of the differential case 3b, while the space case 3c is disposed near the differential mechanism 17. Accordingly, a machine body bending moment caused by a machine body weight does not act on the space case 3c strongly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a transmission case structure for a tractor.

[0002]

2. Description of the Related Art A transmission case structure of a tractor is disclosed in, for example, Japanese Utility Model Laid-Open No.
As disclosed in Japanese Patent Publication No. 4904, there is known a vehicle in which a space case is interposed between a transmission case equipped with a gear transmission mechanism and a differential case.

[0003]

The introduction of the space case is used to increase the distance between the front and rear wheels (wheel base) and the number of gears without changing the basic structure of the transmission case. However, the conventional space case is disposed at a position relatively far away from the rear wheel differential mechanism, in other words, at a position at a large distance from the rear wheel. The stress had a large effect on the space case. Therefore, it is necessary to increase the strength of the space case itself and to increase the connection strength with the transmission case and the differential case.

The present invention has been made in view of such a point, and is designed so that the space case can be easily introduced. It is an object of the present invention to provide a tractor transmission case structure that is effective for configuring the tractor.

[0005]

Means for Solving the Problems [Structure, operation and effect of the invention according to claim 1]

(Structure) In the transmission case structure for a tractor according to the first aspect of the present invention, a space case is interposed between a transmission case having a gear transmission mechanism therein and a differential case, and a bevel pinion gear is provided near a front end of the differential case. It is characterized by being pivoted.

(Operation) According to the above configuration, the space case is disposed at a position very close to the front of the rear wheel differential mechanism, in other words, at a position at a small distance from the rear wheel.
The body bending moment based on the body weight acting on the space case is relatively small.

(Effects) Therefore, according to the first aspect of the present invention, it is not necessary to particularly set the strength of the space case itself and the connection strength between the space case, the transmission case, and the differential case, and the space case is made thick. It is not necessary to form a large number of reinforcing ribs, so that the mold for the space case is simple and easy to manufacture, and it is advantageous for cost reduction and weight reduction.

[Structure, operation and effect of the invention according to claim 2]

(Structure) According to a second aspect of the present invention, in the transmission case structure for a tractor according to the first aspect, the space case is provided with a shift operation shaft of the gear transmission mechanism.

(Operation / Effect) According to the above-described configuration, the strength of the case is reduced by forming the hole provided with the speed change operation shaft in the case. As described above, a large bending moment is generated in this space case. Does not work,
This is advantageous in equipping the gearshift operating shaft.

[Structure, operation and effect of the invention according to claim 3]

(Structure) According to a third aspect of the present invention, in the transmission case structure for a tractor according to the first or second aspect, a hydrostatic continuously variable transmission is connected to a front surface of the transmission case and the space is provided. An oil outlet for a charge pump in the hydrostatic continuously variable transmission is provided at a lower portion of the case.

(Operation / Effect) According to the above-described configuration, forming the opening in the case lowers the strength of the case. However, as described above, since a large bending moment does not act on this space case, the necessary space moment is required. An oil outlet having a size can be formed without a problem of a decrease in strength.

[0015]

FIG. 1 shows an overall side view of a tractor according to the present invention. This tractor has a main clutch housing 2 at the rear end of the engine 1 located at the front of the fuselage.
And the rear transmission case 3 located at the rear of the fuselage and the main clutch housing 2 are connected by a hollow housing 4 made of sheet metal to form a main body of the fuselage. A front axle case 7 that supports the front steering wheel 6 is supported in a freely rolling manner, and a rear wheel 8 is supported by the rear transmission case 3. In addition, a driver seat 9 is provided at the rear of the aircraft, and a lift arm 10 that is vertically oscillated by hydraulic drive is provided to lift and lower various working devices connected to the rear of the aircraft via a three-point link mechanism (not shown). Configured to operate.

FIG. 2 shows the internal structure of the rear transmission case 3 in detail. The rear transmission case 3 includes a transmission case 3a in which a gear transmission mechanism 11 as an auxiliary transmission mechanism is built, a differential case 3b that supports the rear wheel 8, and a transmission case 3b.
An axial plunger-type hydrostatic continuously variable transmission (HST) 12 is mounted as a main transmission on a front surface of the transmission case 3a. The hydrostatic continuously variable transmission 12 includes a variable displacement pump P and a constant displacement motor M built therein, and engine power is directly transmitted to a pump shaft 13. The pump P can change and adjust the discharge direction and discharge amount of the pressure oil to be discharged by changing the swash plate angle, and can continuously change the motor shaft 14 forward or backward to perform stepless forward and backward shifts. The swash plate angle of the pump P is changed by a shift pedal (not shown) operated by the right foot.

The motor shaft 14 is transmitted to the drive side shaft 15 of the gear transmission mechanism 11, where it is shifted to three stages and transmitted to the final transmission shaft 16, and via a bevel pinion gear Gp integrally formed at the end thereof. The power is transmitted to the differential mechanism 17 for driving the rear wheels. The gear transmission mechanism 11 includes a small-diameter gear G1, a medium-diameter gear G2, and a large-diameter gear G formed integrally with the drive-side shaft 15.
3 and a shift gear sG1 spline-mounted on the final transmission shaft 16. The shift gear sG1 is shifted, and its large-diameter gear G4, medium-diameter gear G5, and small-diameter gear G6 are connected to the small-diameter gear G1 and the medium-diameter gear. G2 and the large-diameter gear G3 are selectively engaged with each other, so that the final transmission shaft 16 is "low",
The gear is configured to shift to three steps of “medium” and “high”.

Here, the drive-side shaft 15 and the final transmission shaft 16 of the gear transmission mechanism 11 extend between a bearing wall 18 formed at the front and rear middle of the mission case 3a and a bearing wall 19 formed at the front end of the differential case 3b. Has been supported,
The space case 3c is formed in a simple short cylindrical shape.
An oil outlet 27 for inserting a filter is provided at a lower portion of the space case 3c, and lubricating oil in the case taken out through the filter from the oil outlet 27 is attached to a front portion of the hydrostatic continuously variable transmission 12. Hose 2 for charge pump 28
9 and is supplied to the hydraulic circuit of the hydrostatic continuously variable transmission 12.

As shown in FIG. 3, the shift gear sG1
Shift fork 21 is slidably supported along a support shaft 22 which is horizontally supported on the space case 3c, and a shift operation shaft 23 for shifting the shift fork 21 is provided on the left lateral side of the space case 3c. Is supported through. A shift operation arm 24 that engages with the boss portion 21a of the shift fork 21 is fixed to an inner end of the case of the shift operation shaft 23, and is slidably provided in sliding contact with the inner wall surface of the case. An operation lever 25 is externally fitted to the projecting portion of the operation shaft 23 and is connected to a pin. The operation lever 25 is operatively connected to a sub-transmission lever 26 provided on the side of the driver's seat 9.

The shift operation arm 24 is made of a plate material which is wide in the front and rear directions, and is arranged in three stages of shift positions "low", "medium",
The small diameter holes 31 are formed at a pitch corresponding to “high”, and the large diameter holes 32 are formed corresponding to the neutral position “N” between the small diameter holes 31. In addition, space case 3
A push-type switch 33 is attached to the outer wall surface of the case c, and a short-axis pusher 35 urged inward by a spring 34 inwardly against the operation portion 33a is attached to the case wall by a spring 34. And a steel ball 36 provided at the tip of the pusher 35 is disposed to face the small-diameter hole 31 and the large-diameter hole 32.

The switch 33 is used as a safety switch for allowing the engine to start only when the gear transmission mechanism 11 is in the neutral position.
Is in one of the shift positions, the steel ball 36 is engaged shallowly into the small-diameter hole 31 so that the operating portion 33a of the switch 33 is pushed in through the pusher 35, and the shift operating arm 24 is moved to any neutral position. At the position “N”, the steel ball 36 is deeply engaged in the large-diameter hole 32, whereby the pushing operation of the operation portion 33 a is released, and the operation state of the gear transmission mechanism 11 is detected by the switch 33. It has become.

The power of the final transmission shaft 16 is transmitted to a shift gear sG2 of the front wheel drive shaft 38 via an output gear G7 provided at the front end thereof, and the front wheel drive shaft 38 is driven by a hydrostatic continuously variable transmission ( HST) 12 and projected forward and transmitted to the front axle case 7 so that the front wheels 6 are driven at a speed synchronized with the rear wheels 8. The shift gear sG2 is configured so as to be able to engage and disengage with the output gear G7 by a forward and backward shift, and four-wheel drive is performed in an occlusal interlocking state shifted forward, and only the rear wheel 8 is engaged in an occlusal disengagement state shifted rearward. Performs two-wheel drive.

A hydrostatic continuously variable transmission (HST) 1
The second pump shaft 13 projects into the transmission case 3a, and a part of the engine power transmitted to the pump shaft 14 is transmitted to the PTO transmission mechanism 41 via the gears G8 and G9. The PTO transmission mechanism 41 includes an output shaft 4 having a small-diameter gear G10 and a large-diameter gear G11 integrally formed with the gear G9, and a gear G12 constantly engaged with the large-diameter gear G11.
2. Shift gears splined to this output shaft 42
G3, and the shift shaft sG3 is shifted forward to directly mesh with the small-diameter gear G10, thereby the output shaft 4
2 at low speed, shift gear sG3 backward and coaxially occlusally connect with gear G12 to output shaft 4
2 is driven at high speed. And
The transmission output is transmitted to the rear part of the differential case 3b via the intermediate shaft 43, and further reduced at G13 and G14 to the rear P.
The signal is output from the TO shaft 44. An output case 46 provided with a mid-PTO shaft 45 is attached to the bottom surface of the transmission case 3a. The output is output to the mid PTO shaft 45 via the gear G15 and the shift gear sG4. The mid PTO shaft 45 can be driven or stopped by shifting the shift gear sG4 to engage and disengage with the relay gear G15.

FIGS. 6 to 8 show the structure around the driver's seat 9. A pair of left and right fenders 52 are provided at the rear of the body and cover the left and right rear wheels 8 from the inside and above the body, and are connected to the rear end of the operation step 51. Brackets connected to the upper part of the rear case 3a of the rear transmission case 3 are provided. The left and right fenders 52 are connected by a horizontal stay 53a and a rear horizontal stay 54 connected to the upper part of the differential case 3b. A seat support 55 for supporting the driver's seat 9 so that the driver's seat 9 can be adjusted back and forth is mounted on the upper part of the bracket 53, and a tool box 56 is mounted between the bracket 53 and the rear lateral stay 54. Further, a front cover of the bracket 53 is provided with a central cover 57 for covering the foot below the seat, and a lateral cover 58 for closing a gap between the central cover 57 and the left and right fenders 52. That is, the bracket 53 functions as a common support member for connecting various members.

As shown in FIG. 10 and FIG. 11, a lever guide 62 integrally provided with an over fender portion 61 is put on the upper part of the left and right fenders 52 and is welded and fixed. The right lever guide 62 includes a lifting operation lever 63 for hydraulically swinging the lift arm 10 and a traveling mode switching lever 64 for operating the shift gear sG2 to select four-wheel drive or two-wheel drive. And the left lever guide 62 has a sub gear lever 26 for operating the shift gear sG1, a PTO gear lever 65 for operating the shift gear sG3, and a mid gear P for operating the shift gear sG4.
A mid PTO on / off lever 66 for operating or stopping the TO shaft 45 is inserted and guided.

[Brief description of the drawings]

FIG. 1 is an overall side view of a tractor.

FIG. 2 is a longitudinal sectional side view showing an internal configuration of a rear transmission case.

FIG. 3 is a longitudinal sectional side view of a front wheel transmission system.

FIG. 4 is a longitudinal sectional front view showing a speed change operation portion of the subtransmission mechanism.

FIG. 5 is a side view of the speed change operation arm.

FIG. 6 is a side view of the rear transmission case.

FIG. 7 is a front view around a driver seat.

FIG. 8 is a plan view around a driver seat.

FIG. 9 is a perspective view of the lower circumference of the driver's seat.

FIG. 10 is an exploded perspective view of a fender.

FIG. 11 is a longitudinal sectional front view of a lever guide portion.

[Explanation of symbols]

 Reference Signs List 3a Transmission case 3b Differential case 3c Space case 11 Gear transmission mechanism 12 Hydrostatic stepless transmission 23 Speed change operation shaft 27 Oil outlet 28 Charge pump Gp Bevel pinion gear

Claims (3)

[Claims] 1. A transmission case structure for a tractor, wherein a space case is interposed between a transmission case having a gear transmission mechanism therein and a differential case, and a bevel pinion gear is pivotally supported near a front end of the differential case. . 2. The tractor transmission case structure according to claim 1, wherein the space case is provided with a shift operation shaft of the gear transmission mechanism. 3. A hydrostatic stepless transmission is connected to a front surface of the transmission case, and an oil outlet for a charge pump in the hydrostatic stepless transmission is provided at a lower portion of the space case. Item 3. A transmission case structure for a tractor according to item 1 or 2.